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Conventional and multi-frequency tympanometric norms for Caucasian and Chinese school-aged children Bosaghzadeh, Vahideh 2011

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 Conventional and Multi-Frequency Tympanometric Norms for Caucasian and Chinese School-Aged Children by VAHIDEH BOSAGHZADEH B.A., The Fatemieh University of Medical Sciences, 2003    A THESIS SUBMITTED IN PARTIAL FUFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Audiology and Speech Sciences)   THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) November, 2011    © Vahideh Bosaghzadeh 2011 ii   Abstract Objectives: The present study used tympanometric parameters to evaluate application of the current norms in Caucasian and Chinese school-aged children.  The goals of this study were 1) to establish normative tympanometric data for school-aged children; 2) to determine whether the results vary significantly between Caucasian and Chinese children, male and female children, and children and adults; and 3) to compare normal paediatric tympanometric data with tympanometric data obtained from children with middle-ear pathology. Design: Tympanometry was measured in 98 subjects with normal middle-ear function with an average age of 5.8 years.  There were a total of 66 participants who had abnormal middle-ear condition with a mean age of six years.  Control group subjects were recruited from elementary schools in the Greater Vancouver area.  Subjects with middle-ear effusion (MEE) were consisted of two groups.  Those with confirmed middle- ear effusion (21 subjects) classified as ―OTL confirmed‖ and those who recruited at elementary schools (eight subjects) were classified as ―not OTL confirmed‖.  Statistical analysis (mixed-model ANOVA) was performed for effects of gender, ethnicity (Caucasian versus Chinese), age (child versus adult), and middle-ear condition. Conventional 226-Hz and multi-frequency tympanometry performed using GSI- Tympstar tympanometer (v. 2).  . Results: Vanhuyse patterns were single peak (1B1G) at 226-Hz probe-tone frequency, but more complex patterns (e.g. 1B3G) were observed at higher probe-tone frequencies. Chinese school-aged children had lower Vea and Ytm, wider TW, and higher RF values than did Caucasian school-aged children.  Diseased group tympanometric data was significantly different from normal group data.  Statistical comparison of the area under receiver operating characteristic curve (AUROC) plots revealed that Ytm at 678-Hz had better test performance in distinguishing normal middle-ear status from MEE than did Ytm at other probe-tone frequencies (226-, and 1000-Hz).  The results showed that Ytm from a 678-Hz probe-tone frequency, TW, and RF had the highest sensitivity, highest specificity, and statistically higher test performance in identification of MEE. Conclusions: A preliminary set of normative tympanometric data revealed significant differences between Caucasian and Chinese school-aged children and also between children and adults.  Therefore, application of ethnic-specific criteria changes sensitivity or specificity of tympanometry in clinics. iii  Preface Ethical approval for this study was obtained from the Clinical Research Ethics Board of the University of British Columbia (UBC CREB # H03-70209). iv  Table of Contents Abstract ............................................................................................................................... ii Preface ............................................................................................................................... iii Table of Contents ............................................................................................................... iv List of Tables .................................................................................................................... vii List of Figures ................................................................................................................... xv Acknowledgements .......................................................................................................... xix 1 Introduction ...................................................................................................................... 1 1.1 General Introduction ................................................................................................. 1 1.2 Etiology of Otitis Media ............................................................................................ 3 1.2.1 Physiology of the Eustachian Tube .................................................................... 3 1.2.2 Role of Eustachian Tube in Otitis Media with Effusion .................................... 6 1.3 Clinical Issues Related to Otitis Media with Effusion .............................................. 7 1.4 Effect of Ethnicity and OME Prevalence .................................................................. 9 1.5 Tympanometry ........................................................................................................ 11 1.6 Principles of Tympanometry ................................................................................ 17 1.7 Conventional 226-Hz Tympanometry ..................................................................... 22 1.8 Multi-Frequency Tympanometry—MFT ................................................................ 26 1.9 Goals ........................................................................................................................ 34 2 Materials and Methods ................................................................................................... 37 2.1 Ethics Approval ....................................................................................................... 37 2.2 Experiment 1: Control Group .................................................................................. 37 2.2.1 Description of Subjects ..................................................................................... 37 2.2.2 Instrumentation............................................................................................... 40 2.2.3 Procedure .......................................................................................................... 41 2.3 Experiment 2: Diseased Group ............................................................................... 43 2.3.1 Subjects ............................................................................................................. 43 2.3.2 Instrumentation ................................................................................................. 44 2.3.3 Procedure .......................................................................................................... 45 2.4 Statistical Analyses ................................................................................................. 46 2.4.1 Diseased Group Subjects (group with abnormal middle ear condition) ........... 47 v  3 Results ............................................................................................................................ 49 3.1 Descriptive Analysis of Tympanometric Shapes .................................................... 49 3.2 Control Group Tympanometric Data Using Conventional 226-Hz Tympanometry .............................................................................................................. 52 3.2.1 Equivalent Ear-Canal Volume (Vea) ................................................................ 52 3.2.2  Compensated Static Admittance (Ytm) ........................................................... 53 3.2.3 Tympanometric Width (TW) ............................................................................ 54 3.2.4 Tympanometric Peak Pressure (TPP) ............................................................... 54 3.3 Control group Tympanometric Data Using Multi-Frequency Tympanometry (MFT)  ....................................................................................................................................... 54 3.3.1 Static Admittance (Ytm) from Rectangular Components (Btm, Gtm) ............. 55 3.3.2 Resonant Frequency (RF) ................................................................................. 60 3.4 Paediatric vs. Adult Tympanometric Data Using Conventional 226-Hz Tympanometry .............................................................................................................. 60 3.4.1 Equivalent Ear-Canal Volume (Vea) ................................................................ 60 3.4.2 Compensated Static Admittance (Ytm) ............................................................ 62 3.4.3 Tympanometric Width ...................................................................................... 68 3.4.4 Tympanometric Peak Pressure (TPP) ............................................................... 70 3.5 Paediatric vs. Adult Tympanometric Data using Multi-Frequency Tympanometry (MFT) ............................................................................................................................ 71 3.5.1 Ytm from Rectangular Components (Btm and Gtm) ....................................... 71 3.5.2 Resonant Frequency (RF) ................................................................................. 75 3.6  Diseased Group Tympanometric Data Analyzed by Middle-Ear Condition Using Conventional 226-Hz Tympanometry ........................................................................... 78 3.6.1 Equivalent Ear-Canal Volume (Vea) ................................................................ 78 3.6.2 Peak-Compensated Static Admittance (Ytm) ................................................... 80 3.6.3 Tympanometric Width (TW) ............................................................................ 82 3.7 Diseased Group Tympanometric Data Analyzed by Middle-Ear Condition Using Multi-Frequency tympanometry (MFT)........................................................................ 83 3.7.1 Ytm Obtained from Rectangular Components ................................................. 83 3.7.2 Resonant Frequency (RF) ................................................................................. 91 3.8 Test Performance of Tympanometric Parameters in Distinguishing Ears with MEE from Normal Ears .......................................................................................................... 92 vi  4 Discussion .................................................................................................................... 101 4.1 Comparison of Results .......................................................................................... 101 4.1.1 Tympanometric Shapes .................................................................................. 101 4.1.2 Equivalent Ear-Canal Volume (Vea) .............................................................. 106 4.1.3 Static Admittance (Ytm) ................................................................................. 109 4.1.4 Tympanometric Width (TW) .......................................................................... 116 4.1.5 Tympanometric Peak Pressure (TPP) ............................................................. 117 4.1.6 Resonant Frequency (RF) ............................................................................... 118 4.2 Variation of Tympanometric Values with Age ..................................................... 121 4.2.1 Equivalent Ear-Canal Volume ........................................................................ 121 4.2.2 Static Admittance ........................................................................................... 122 4.2.3 Tympanometric Width .................................................................................... 123 4.2.4 Tympanometric Peak Pressure ....................................................................... 124 4.2.5 Resonant Frequency ....................................................................................... 125 4.3 Diseased Group ..................................................................................................... 125 4.3.1 Equivalent Ear Canal Volume ........................................................................ 125 4.3.2 Static Admittance ........................................................................................... 126 4.3.3 Tympanometric Width .................................................................................... 131 4.3.4 Resonant Frequency ....................................................................................... 132 4.4 Test Performance ................................................................................................... 132 4.5 Clinical Implications ............................................................................................. 137 4.6 Research Limitations ............................................................................................. 138 4.7 Future Research ..................................................................................................... 139 References ....................................................................................................................... 141 Appendix 1 ...................................................................................................................... 154       vii  List of Tables Table 1.1: List of important acronyms ............................................................................... 2 Table 1.2: Selected studies investigating prevalence of OM in different ethnicities in children. ............................................................................................................................ 16 Table 1.3:  Mathematical relationship between polar and rectangular notation in admittance terminology (Adapted from Shahnaz, 2000.) ................................................. 21 Table 2.1: Distribution of normal subjects in the control group ............................... 38 Table 3.1: Proportion of different Vanhuyse tympanometric configurations, expressed as a percentage, across different probe-tone frequencies among normal Caucasian and Chinese school-aged children. .......................................................................................... 50 Table 3.2:  Mean, SD, and 90% range (5 th–95th percentile) for distance between the two outermost peaks in daPa obtained from the susceptance (B) tympanogram.  The maximum number of peaks (maxima) and troughs (minima) obtained from susceptance (B) and conductance (G) tympanograms in normal Caucasian and Chinese school-aged children using a 678-Hz probe-tone frequency is also reported. ...................................... 51 Table 3.3: Mean, standard deviation (SD), and 90% range for ear-canal volume (Vea) at +250 daPa in school-aged children (current study) and young adults (Shahnaz & Bork, 2008), (M: male; F: female; O: overall [combined male and female]). ............................ 61 Table 3.4: Mean, standard deviation (SD), and 90% range for static admittance (Ytm) from positive compensation at +250 daPa in school-aged children (current study) and young adults (Shahnaz & Davies, 2006), (M: male; F: female; O: overall [combined male and female]). ..................................................................................................................... 63 viii  Table 3.5: Mean, standard deviation (SD), and 90% range for static admittance (Ytm) from positive compensation at +250 daPa, using rectangular components at 226-Hz probe-tone frequency, in school-aged children (current study) and young adults (Shahnaz & Bork, 2008), (M: male; F: female; O: overall [combined male and female]). .............. 65 Table 3.7: Mean, standard deviation (SD), and 90% range for TPP in Caucasian and Chinese young adults (Shahnaz & Davies, 2006) and school-aged children (M: male; F: female; O: overall [combined male and female]). ............................................................ 70 Table 3.8: Mean, standard deviation (SD), and 90% range for static admittance (Ytm) from positive compensation at +250 daPa, using rectangular components at 678-Hz probe-tone frequency, in school-aged children (current study) and young adults (Shahnaz & Bork, 2008), (M: male; F: female; O: overall [combined male and female]). .............. 72 Table 3.9: Mean, standard deviation (SD), and 90% range for static admittance (Ytm) from positive compensation at +250 daPa, using rectangular components at 1000-Hz probe-tone frequency, in school-aged children (current study) and young adults (Shahnaz & Bork, 2008), (M: male; F: female; O: overall [combined male and female]). .............. 73 Table 3.11: AUROC, sensitivity, specificity, and 95% CI for variables analysed using ROC.  ( AUROC: Area under ROC; SE: Sensitivity; SP: Specificity; 95% CI: 95% confidence interval; Ytm-YaP: positively compensated static admittance obtained from Ya tympanogram; Ytm-YaN: negatively compensated static admittance obtained from Ya tympanogram; Ytm-BGP: positively compensated static admittance obtained from rectangular components; Ytm-BGN: negatively compensated static admittance obtained from rectangular components). ......................................................................................... 94 ix  Table 3.12: Summary of comparison between different tympanometric tests.  (AUROC: Area under ROC; 95% CI: 95% confidence interval; Ytm-YaP: positively compensated static admittance obtained from automatic static admittance tympanogram; Ytm-YaN: negatively compensated static admittance obtained from automatic static admittance tympanogram; Ytm-BGP: positively compensated static admittance obtained from rectangular components; Ytm-BGN: negatively compensated static admittance obtained from rectangular components). ......................................................................................... 98 Table 3.13: AUROC, sensitivity, specificity, and 95% CI for variables in the group consisting of normal ears as well as OTL confirmed ears, using ROC (AUROC: Area under ROC; 95% CI: 95% confidence interval; SE: Sensitivity; SP: Specificity;  Ytm- YaP: positively compensated static admittance obtained from automatic static admittance tympanogram; Ytm-YaN: negatively compensated static admittance obtained from automatic static admittance tympanogram; Ytm-BGP: positively compensated static admittance obtained from rectangular components; Ytm-BGN: negatively compensated static admittance obtained from rectangular components). .............................................. 99 Table 4.1: Tympanometric results in selected studies in paediatric Caucasian and Chinese populations at standard 226 Hz probe-tone frequency for variables of Vea (ear- canal volume); Ytm (compensated static admittance), TW: (tympanometric width), N: (number of ears), and TPP: (tympanometric peak pressure from admittance tympanogram). ................................................................................................................ 114 Table 4.2: Procedures used in selected tympanometric studies in paediatric Caucasian and Chinese populations ................................................................................................. 115 x  Table 4.3: Descriptive RF values obtained by sweep-frequency (SF) and sweep-pressure (SP) recording methods, between the current study and Hanks and Rose (1993). ......... 120 Table 4.4: Tympanometric pass and fail criteria from different studies.  Vea: equivalent ear-canal volume; Ytm: compensated static admittance, TW: tympanometric width and TPP: tympanometric peak pressure from admittance tympanogram. ............................. 136 Table A1.1: Mean, SD, and 90% range (5 th–95th percentile) for ear-canal volume (Vea) obtained from uncompensated admittance (Ya) using positive tail (Vea+) in normal Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]) ........................................................................................................... 154 Table A1.2: Mean, SD, and 90% range (5th–95th percentile) for ear-canal volume (Vea) obtained from uncompensated admittance (Ya) using negative tail (Vea−) in normal Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]). .......................................................................................................... 154 Table A1.3: Mean, SD, and 90% range (5th–95th percentile) for compensated static admittance (Ytm) obtained from uncompensated admittance (Ya) using positive compensation (Ytm+), in normal Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]). ...................................................... 155 Table A1.4: Mean, SD, and 90% range (5th–95th percentile) for compensated static admittance (Ytm) obtained from uncompensated admittance (Ya), using negative compensation (Ytm−), in normal Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]). ...................................................... 156 xi  Table A1.5: Mean, standard deviation (SD), and 90% range values for TW (obtained from Y tympanogram at 226-Hz) for Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]). ............................................ 156 Table A1.6: Mean, standard deviation (SD), and 90% range values for TPP (obtained from Y tympanogram at 226-Hz) for Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]). ............................................ 157 Table A1.7: Mean, SD, and 90% range (5th–95th percentile) for ear-canal volume (Vea) obtained from uncompensated susceptance (Ba) using positive tail (Vea +) in normal Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]). .......................................................................................................... 157 Table A1.8: Mean, SD, and 90% range (5th–95th percentile) for ear-canal volume (Vea) obtained from uncompensated susceptance (Ba), using negative tail (Vea−) in normal Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]). .......................................................................................................... 158 Table A1.9: Mean, standard deviation (SD), and 90% range for compensated susceptance (Btm), conductance (Gtm), and admittance (Ytm) obtained from positive compensation using 226-Hz probe-tone frequency (M: male; F: female; O: overall [combined male and female]). .......................................................................................................................... 159 Table A1.10: Mean, standard deviation (SD), and 90% range for compensated susceptance (Btm), conductance (Gtm), and admittance (Ytm) obtained from negative compensation using 226-Hz probe-tone frequency (M: male; F: female; O: overall [combined male and female]). ........................................................................................ 160 xii  Table A1.11: Mean, standard deviation (SD), and 90% range for compensated susceptance (Btm), conductance (Gtm), and admittance (Ytm) obtained from positive compensation using 678-Hz probe-tone frequency (M: male; F: female; O: overall [combined male and female]). ........................................................................................ 161 Table A1.12: Mean, standard deviation (SD), and 90% range for compensated susceptance (Btm), conductance (Gtm), and admittance (Ytm) obtained from negative compensation using 678-Hz probe-tone frequency (M: male; F: female; O: overall [combined male and female]). ........................................................................................ 162 Table A1.13: Mean, standard deviation (SD), and 90% range for compensated susceptance (Btm), conductance (Gtm), and admittance (Ytm) obtained from positive compensation using 1000-Hz probe-tone frequency (M: male; F: female; O: overall [combined male and female]). ........................................................................................ 163 Table A1.14: Mean, standard deviation (SD), and 90% range for compensated susceptance (Btm), conductance (Gtm), and admittance (Ytm) obtained from negative compensation using 1000-Hz probe-tone frequency (M: male; F: female; O: overall [combined male and female]). ........................................................................................ 164 Table A1.15: Mean, standard deviation (SD), and 90%  range values of resonant frequency (RF) for Caucasian and Chinese school-aged children using sweep-frequency (SF) and sweep-pressure (SP) recording methods (M: male; F: female; O: overall [combined male and female]). ........................................................................................ 165 Table A1.16: Summary of ANOVA for Ytm from Ya using 226-Hz Conventional Tympanometry ................................................................................................................ 166 Table A1.17: Summary of ANOVA for Ytm from Ya at 678-Hz using MFT .............. 167 xiii  Table A1.18: Summary of ANOVA for Ytm from Ya at 1000-Hz using MFT ............ 168 Table A1.19: Summary of ANOVA for Ytm at 226-Hz from rectangular components- MFT ................................................................................................................................ 169 Table A1.20: Summary of ANOVA for Vea from 226-Hz Conventional Tympanometry  ......................................................................................................................................... 170 Table A1.21: Summary of ANOVA for Ytm from Ya using 226-Hz Conventional Tympanometry ................................................................................................................ 170 Table A1.22: Summary of ANOVA for Ytm form rectangular components at 226-Hz- MFT ................................................................................................................................ 171 Table A1.23: Summary of ANOVA for Ytm form rectangular components at 678-Hz- MFT ................................................................................................................................ 172 Table A1.24: Summary of ANOVA for Ytm form rectangular components at 1000-Hz- MFT ................................................................................................................................ 173 Table A1.25: Summary of ANOVA for TW from 226-Hz Conventional Tympanometry  ......................................................................................................................................... 173 Table A1.26: Summary of ANOVA for TPP from 226-Hz Conventional Tympanometry  ......................................................................................................................................... 174 Table A1.27: Summary of ANOVA for RF from MFT ................................................. 174 Table A1.28: Summary of ANOVA for Vea from Ya using 226-Hz Conventional Tympanometry ................................................................................................................ 175 Table A1.29: Summary of ANOVA for Ytm at 678-Hz from rectangular components- MFT ................................................................................................................................ 175 xiv  Table A1.30: Summary of ANOVA for Ytm from Ya using 226-Hz Conventional Tympanometry ................................................................................................................ 176 Table A1.31: Summary of ANOVA for Ytm from Ya using 678-Hz MFT .................. 176 Table A1.32: Summary of ANOVA for Ytm from Ya using 1000-Hz MFT ................ 176 Table A1.33: Summary of ANOVA for Ytm from rectangular components at 226-Hz- MFT ................................................................................................................................ 177 Table A1.34: Summary of ANOVA for Ytm from rectangular components at 678-Hz- MFT ................................................................................................................................ 177 Table A1.35: Summary of ANOVA for Ytm from rectangular components at 1000-Hz- MFT ................................................................................................................................ 178 Table A1.36: Summary of ANOVA for TW from 226-Hz Conventional Tympanometry  ......................................................................................................................................... 179 Table A1.37: Summary of ANOVA for RF from MFT ................................................. 179            xv  List of Figures  Figure 1.1: Left—impedance terminology [Xm: mass reactance; Xs: stiffness reactance; |Z|: absolute impedance magnitude; Øz: impedance phase angle].  Right—admittance terminology [Bm: mass susceptance; Bc: stiffness susceptance; |Y|: absolute admittance magnitude; Øy: admittance phase angle] (Adapted from Shahnaz, 2000). ...................... 18 Figure 1.2: The admittance terminology [Bm: mass susceptance; Bs: stiffness susceptance; Ba: total susceptance is algebraic sum of Bm and Bs; |Y|: absolute admittance magnitude; φ: admittance phase angle]. j is equal to √−1in complex number notation and indicates that conductance and susceptance cannot be combined by simple addition because they are vectors that operate in different directions (Shahnaz, 2008) ... 20 Figure 1.3: Vanhuyse Model showing four normal tympanometric patterns: (A) 1B1G, (B) 3B1G, (C) 3B3G, and (D) 5B3G (Adapted from Fowler & Shanks, 2002). .............. 28 . .......................................................................................................................................... 28 Figure 1.4: Estimation of resonant frequency (RF) from the uncompensated susceptance (Ba) tympanogram using a Virtual 310 middle-ear analyzer (Adapted from Shahnaz, 2008). ................................................................................................................................ 30 Figure 1.5:  GSI-Tympstar sweep frequency recording of ΔB and ΔG (in mmho) using positive compensation.  When ΔB is positive, the system is stiffness dominated; if it is negative, the system is mass dominated.  The crossing of ΔB with ΔG corresponds to an admittance phase angle of 45 °.  When ΔB is zero, the system is at resonance  (Adapted from Shahnaz, 2007). ........................................................................................................ 31 xvi  Figure 3.1: Interaction between ethnicity (Caucasian versus Chinese), gender (male versus female), and compensation (positive compensation versus negative compensation) in school-aged children using 678-Hz probe-tone frequency. .......................................... 56 Figure 3.2: Variations of Btm (compensated susceptance), Gtm (compensated conductance), and Ytm (compensated admittance) values as a function of compensation (positive vs.  negative) method between Caucasian and Chinese school-aged children using 678-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval. ...... 58 Figure 3.3: Interaction between Btm (compensated susceptance), Gtm (compensated conductance), and Ytm (compensated admittance), ethnicity (Caucasian versus Chinese) and age (adults versus children) using 226-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval. ................................................................................................... 67 Figure 3.4: Interaction between Btm (compensated susceptance), Gtm (compensated conductance), and Ytm (compensated admittance), gender (male versus female) and age (adults versus children) using 226-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval. ........................................................................................................... 68 Figure 3.5:  Interaction between gender (male versus female) and ethnicity (Caucasian versus Chinese) between children and adults for resonant frequency.  Vertical bars denote 0.95 confidence interval. ................................................................................................... 77 Figure 3.6: Variation in ear-canal volume (Vea) obtained from positive and negative tails as a function of middle-ear condition using a 226-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval. ....................................................................................... 79 Figure 3.7: Interaction between Btm (compensated susceptance), Gtm (compensated conductance), Ytm (compensated admittance), compensation (positive versus negative), xvii  and middle-ear condition using 226-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval ............................................................................................................ 82 Figure 3.8: Variation of static admittance (Ytm from Ya) obtained from positive and negative compensations as a function of middle-ear condition using a 678-Hz probe-tone frequency.  Vertical bars denote an 0.95 confidence interval. .......................................... 84 Figure 3.9: Interaction between Btm (compensated susceptance), Gtm (compensated conductance), Ytm (compensated admittance), compensation (positive versus negative), and middle-ear condition using a 678-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval. ................................................................................................... 87 Figure 3.10: Variation in static admittance (Ytm from Ya) obtained from positive and negative compensations as a function of middle-ear condition using a 1000-Hz probe- tone frequency.  Vertical bars denote 0.95confidence interval. ........................................ 88 Figure 3.11: Variation of Btm (compensated susceptance), Gtm (compensated conductance), and Ytm (compensated admittance) as a function of middle-ear condition using 1000-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval. .... 89 Figure 3.12: Interaction between Btm (compensated susceptance), Gtm (compensated conductance), Ytm (compensated admittance), compensation (positive versus negative) and middle-ear condition, using a 1000-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval. ................................................................................................... 90 Figure 3.13: Variation of resonant frequency (RF) as a function of middle-ear condition. Vertical bars denote 0.95confidence interval. ................................................................... 92 Figure 3.14: Compares performance of Ytm_BGN_678 (static admittance obtained from susceptance and conductance components using negative compensation) with xviii  Ytm_BGP_678 (static admittance obtained from susceptance and conductance components using positive compensation). ...................................................................... 95 Figure 3.15: Distribution of Ytm_BGN_678 (static admittance obtained from susceptance and conductance components using negative compensation) between a group of normal middle-ears, and a group of ear with MEE. ..................................................... 96 Figure 3.16: Compares performance of Ytm_BGN_678 (static admittance obtained from susceptance and conductance components using negative compensation) with RF (resonant frequency obtained from SF and SP methods) and TW (tympanometric width).  ........................................................................................................................................... 96 Figure 4.1: Variation of acoustic admittance (Ya) as a function of probe-tone frequency (adapted from Margolis & Shanks, 1991). ...................................................................... 134     xix  Acknowledgements  First and foremost I would like to offer my deep and sincere gratitude to my supervisor, Dr. Navid Shahnaz. His patience during my difficult moments has been of great value for me. I attribute the level of my Masters degree to his encouragement and effort and without his support this thesis would not have been completed. His understanding, encouraging and personal guidance have provided a good basis for the present thesis.  I would also like to show my gratitude to my thesis committee Dr. Tony Herman, Dr. Susan Small, and Dr. David Stapells for their detailed review, constructive comments and excellent advice during the preparation and presentation of this thesis.  I owe my loving thanks to my husband Majid Mirabadi, my son Hamed Mirabadi, and my daughter Zahra Mirabadi. They have lost a lot due to my research. Without their encouragement and understanding it would have been impossible for me to finish this work.  Finally, I would like to thank my parents who share my happiness and never showed less than absolute confidence in me.  1  1 Introduction 1.1 General Introduction   About 91% of children have at least one episode of middle-ear infection during their first two years of life (Casselbrant, Mandel, Kurs-Lasky, Rockette, & Bluestone, 1995). Research shows that the prevalence of middle-ear infection has grown due to the increase in allergies among children as well as the increased use of child-care facilities (Lanphear, Byrd, Auinger, & Hall, 1997).  If untreated, middle-ear infections may prevent natural development of speech, language and cognition in young children (Brown, 1994). Undetected middle-ear infection might also result in reduced academic achievement (ASHA, 1997).  Even unilateral conductive hearing loss can disrupt normal development of binaural processing in the higher auditory processing pathways (Haggard & Hughes, 1988).  Accurate diagnosis of middle-ear problems might result in earlier identification of middle-ear effusion, which in turn allows better management, which minimizes the complications of middle-ear effusion. The term otitis media (OM as is shown in table 1.1) is a general term that is used to refer to middle-ear conditions that involve the presence of fluid within the middle-ear cavity (Sagraves, Maish & Kameshka, 1992).  This condition may include otitis media with effusion (OME) as well as acute otitis media (AOM).  OME is a condition where the fluid is behind the eardrum with no signs of an active infection.  In contrast, AOM is accompanied by a rapid onset of infection that is followed by active discharge of fluid from the ear, which might or might not be followed with inflammation.  Research shows that OME occurs most commonly in children who are less than six years old (Thrasher & 2  Allen, 2005).  Mora et al. (2002) stated that 80% of children experience at least one episode of OME. Table 1.1: List of important acronyms  OM OME MFT Vea Ya Ytm Btm Gtm TW TPP RF SF SP ROC AUROC Otitis media Otitis media with effusion Multi-frequency tympanometry Equivalent ear canal volume Uncompensated static admittance Compensated static admittance (static admittance) Compensated susceptance Compensated conductance Tympanometric width Tympanometric peak pressure Resonant frequency Sweep frequency Sweep pressure Receiver operating characteristic curve Area under receiver operating characteristic curve    3  1.2 Etiology of Otitis Media  There are many factors causing OM in young children.  Some of these factors may include infection (viral or bacterial), anatomical factors, and Eustachian-tube dysfunction.  However, among all these factors, Eustachian-tube dysfunction is the most important factor in all age groups (Bluestone, 1996).  There are some risk factors that contribute to the incidence of OM, such as ethnicity, breastfeeding, smoking, and daycare attendance (Bluestone, 1996).  Paradise et al. (1997) concluded that the number of days a child experienced middle-ear effusion varied directly  with the number of smokers and the number  of other children to whom infants were exposed, and whether they were at home  or in daycare settings.  These authors also suggested that the period of experiencing OM is inversely related to breastfeeding.  Although the incidence of OM has increased dramatically during recent decades due to daycare attendance (Bluestone, 1996) and viral and bacterial infections, Eustachian-tube dysfunction is still the most important contributing factor in development of middle-ear diseases.  Other studies (e.g. Sade, 1966) suggested that OM resulted from mucous-membrane (rather than Eustachian-tube) involvement due to allergies or infection.    1.2.1 Physiology of the Eustachian Tube  The Eustachian tube is an organ which connects the middle-ear cavity to the nasopharyngeal cavity.  The tube consists of mucosa, cartilage, soft tissue, muscles, and a superior bony support.  The Eustachian tube has three major physiological 4  responsibilities: ventilation and gas regulation of the middle-ear cavity, protection from nasopharyngeal sound pressure and secretions, and clearance of middle-ear secretions (Bluestone, 1996). Pressure regulation and middle-ear ventilation are the primary functions of the Eustachian tube.  A normal Eustachian tube opens by active contraction of the tensor veli palatini muscle during swallowing and regulates the pressure in the middle-ear.  The middle-ear cavity is surrounded by a mucous membrane, and there is an exchange of gases between the mucosa and the middle-ear space.  Therefore, changes in the pressure of the middle-ear may lead into abnormal functioning of this system.  Kitajiri, Sando, and Takahara (1987) indicated that the Eustachian tube and its surrounding structures continue to develop until 19 years of age and, therefore, even in children with normal middle-ears, the Eustachian tube is not as good as an adult Eustachian tube in terms of its function. Any obstruction or failure of the opening mechanism of the Eustachian tube can impair the pressure-regulation job of the tube.  The obstructions can be caused by inflammation as a result of infection or allergy.  Obstruction can also happen in the middle-ear due to cholesteatoma or polyps.  In addition, opening mechanism failer may happen in children who have cleft palate (Bylander, Tjernstrom, & Ivarsson, 1983) but is more likely to occur in children with middle-ear disease (Bluestone, Paradise, & Beery, 1972). The Eustachian tube also has a protective function.  A normal Eustachian tube is made of a cartilaginous portion (the nasopharyngeal portion) and a bony portion, and there is a narrow section which is called the isthmus.  In rest position, the Eustachian tube 5  is closed.  During swallowing, the nasopharyngeal portion of the tube opens, and liquids can enter the tube; however, this does not happen due to the protective function of the tube.  The isthmus prevents liquids from entering the middle-ear cavity.  Studies show that in children who have had otitis media, liquids may enter the middle-ear cavity (Bluestone, Paradise, & Beery, 1972), which may be related to the functional and anatomical changes in a Eustachian tube with OM. The protective function of the Eustachian tube may be interrupted for several reasons.  The first is abnormal patency of the Eustachian tube (called palates tube), in which the tube is open most of the time.  This may be due to the loss of the supportive tissue surrounding the tube as a result of weight loss, or it may be due to abnormal tube geometry (Bluestone, 1996).  As a result, unwanted secretions such as nasopharyngeal secretions can enter the middle-ear cavity and cause ear infections.  Patients with Down’s syndrome have patent Eustachian tubes (Sadler-Kimes, Siegel, & Todhunter, 1989). Normally, children up to seven years of age have shorter tubes than adults (Sadler-Kimes, Siegel, & Todhunter, 1989).  A short Eustachian tube can negatively affect the protective characteristics of the tube. Studies report that children with cleft palate or Down’s syndrome have even shorter Eustachian tubes than do normal children (Bluestone, 1996). Another phenomenon that can affect Eustachian-tube function is abnormal gas pressure. When the pressure balance between the middle-ear and the environment is interrupted, high negative pressure will develop in the middle-ear.  The negative pressure will then result in aspiration of nasopharyngeal secretions into the middle-ear (Bluestone, 1996).   The Eustachian tube also has a clearance function.  Clearance of secretions from the middle-ear is done by the mucociliary system of the middle-ear as well as by the 6  pumping action of the Eustachian tube.  Ciliated cells are located in the middle-ear and are more active as they get closer to the opening of the Eustachian tube.  Using these mechanisms, the secretions are drained into the nasopharyngeal cavity. Many conditions may affect the clearance function of the Eustachian tube.  The most important factors are passive smoking and impairment of ciliary function.  It has been shown that people who have ciliary dysmobility in their respiratory system suffer from chronic middle-ear effusion (Shikowitz, Ilardi, & Gero, 1988).  In addition, these authors suggested that when the opening mechanism is not active enough, the pumping action of the tube is also ineffective (Nozoe, Okazaki, Ayani, & Kumazawa, 1984). Finally, Eustahcian tube dysfunction will affect the tympanogram’s shape. Eustachian tube dysfunction in school-aged children will result in abnormal tympanograms which will also predict possible presence of OME in this population in the future. 1.2.2 Role of Eustachian Tube in Otitis Media with Effusion  When the Eustachian tube does not open regularly, there is no exchange of pressure with the environment, therefore, middle-ear pressure will not be regulated.  As a consequence, the oxygen in the middle ear space will be absorbed by the cells, and middle-ear pressure becomes negative.  Then, the negative pressure extracts a sterile fluid from the cells, which accumulates behind the eardrum.  Tubal opening is possible in a middle-ear with effusion, so nasopharyngeal secretions that may contain bacteria can enter the middle-ear and cause an acute bacterial infection (Bluestone, 1996).  Obstruction of the Eustachian tube can cause negative middle-ear pressure, retraction of the tympanic membrane, and hearing loss (Bluestone, 1996).  The 7  obstruction may be because of an inflammation or a failure in the opening mechanism of the tube.  Depending on how acute the conditions is, and whether it is chronic or not, middle-ear effusion will eventually drain into the nasopharyngeal cavity (Bluestone, 1996).  1.3 Clinical Issues Related to Otitis Media with Effusion    Gravel and Ruben (1996) suggested that temporary hearing loss as a result of OM may lead to auditory deprivation.  A frequent complication associated with OM is a fluctuating mild to moderate conductive hearing loss (Roberts et al., 2002).  This could be particularly disturbing during two periods of a child’s life.  First, during the first 12 to 18 months of life, in which children learn to listen and understand before they begin to talk.  OM may disrupt this important listening and learning period, which will have serious consequences for speech and language development, as well as cognitive performance later in life (Petinou, Schwartz, Gravel, & Raphael, 2001; Roland et al., 1989).  Second, during the first year of elementary school, OM and associated conductive hearing loss can disrupt academic performance and impair the child’s ability to cope with various stresses imposed by the school setting (Fria, Cantekin, & Eichler, 1985; Lous, 1995; Paradise, 1981).  On the other hand, some studies have reported that OM has no lasting effects on children’s development (e.g., Paradise et al., 2000). Several studies found permanent peripheral damage following chronic episodes of OM using extended high-frequency audiometry.  Margolis et al. (2000) confirmed the findings of previous reports that children who have recovered from chronic OM have significantly poorer hearing in extended high frequencies compared with children without 8  significant OM histories.  They stated that extended high-frequency hearing losses that occur in children with OM histories are strongly frequency dependent, suggesting an impact on the base of the cochlea.  The results of other studies also support the hypothesis that OM-related extended high-frequency hearing losses are cochlear in origin (Margolis, Saly, & Hunter, 2000).  An extended high-frequency hearing loss caused by OME, may affect a child’s performance.  Recent studies showed that extended high frequencies and extended bandwidth in hearing aids play an important role in improving sound quality (Ricketts, Ditt-Berner, & Johnson, 2008), music quality (Moore & Tan, 2003), speech perception (Pittman, 2008; Stelmachowicz,  Lewis,  Choi, & Hoover, 2007) spatial awareness ( Kidd, Arbogast, Mason, & Gallun, 2005; and loudness perception (Soeta, & Nakagawa, 2008). In addition, other studies demonstrated deficits in central auditory processing (CAP) in children who had had OME using standard CAP tests.  Some longitudinal studies suggest that CAP deficits are more obvious when the test is completed shortly after the OME episode (Hall, Grose, and Pillsbury, 1995).  These studies reported that it is possible that the auditory system plasticity compensates for the developing auditory system deficit.  In a study on school-aged children, Gravel et al. (2006) found that audiometric and physiologic results were significantly affected by OME in early childhood; however, functional auditory processes such as those that were examined using speech-in-noise tests were not related to early childhood OME.  Because Gravel et al. used the auditory brainstem response in this study, they reported that the latency of wave V was significantly associated with early childhood OME.  Therefore, they suggest that OME and hearing loss affect the physiology of the auditory system at the level of the 9  auditory brainstem.  Tucci, Cant, and Durham, (2001) studied animal models with induced conductive hearing loss and reported that conductive hearing loss may decrease the central auditory system’s neural activity in the ipsilateral cochlear nucleus, contralateral inferior colliculus, and in the nuclei of the superior olivary complex, bilaterally.  For example, unilateral conductive hearing loss that occurs in either childhood or adulthood may impair binaural hearing both during and after the hearing loss; recovery from the impairment can take place by training over a period of several months after restoration of normal peripheral function (Moore et al., 1999).  Moreover, Hartley and Moore (2003) reported that middle-ear effusion not only attenuates sound amplitude but also distorts the timing of the cochlear microphonic (CM) responses in gerbils. Therefore, children who have had multiple episodes of OME in the first few years of life may have poorer sound detection in noisy environments, which is caused by reduced binaural unmasking (Hogan and Moore, 2003).  Binaural unmasking is a reduction in the ability of masking noise heard with both ears to mask another sound heard by one ear only.  Research shows that children who had OME in one or both ears for more than about 50% of the first five years had reduced binaural unmasking (Hogan and Moore, 2003).  1.4 Effect of Ethnicity and OME Prevalence  The epidemiology of asymptomatic OME has not been documented in school- aged children in Canada.   It may not even be possible to determine the true incidence of OME, because the pathology is asymptomatic by definition.  Prevalence of a disease is defined as the total number of cases of the disease in a population in a given period of 10  time; however, the point prevalence of a disease is defined as the total number of cases of the disease in a population at a specific time (e.g. on a specific day) and is mostly used for chronic conditions.  The point prevalence of OME varies dramatically among studies and ranges between 1% (Ogisi, 1988) and 31.3% (Holmquist, Fadala, & Qattan, 1987). The striking difference between these estimates is probably due to divergent methods of documenting OM, definitions of the disease, observation intervals, prevalence windows, environmental factors, and subject characteristics.  The point prevalence of OME for school-aged children in various countries is shown in Table 1.1.  Of particular interest to this study is the effect of ethnicity.  The low prevalence of OM reported in studies involving populations of African extraction (e.g., Jamaica, in Jadusingh et al., 1998; Nigeria, in Ogisi, 1988) and Chinese (e.g., Hong Kong, in Tong, Yue, Ku, Lo, & van Hasselt, 2000) ethnic groups could be attributed to differences of mechano-acoustical properties of the middle-ear and/or anatomical variations in Eustachian tube.  Doyle (1977) has suggested that differences in the dimensions and angle of the bony Eustachian tube produce a more efficient Eustachian tube in in populations with dark skin color. This issue has not been fully investigated in the Chinese ethnic group. There is no published research investigating multi-frequency tympanometry (MFT) parameters in children aged five to seven years. There has been preliminary research on the prevalence of OM between a group of Chinese children in Hong Kong and a group of their Caucasian counterparts in North America (Tong, Yue, Ku, Lo, & van Hasselt, 2000).  Results show that Chinese children in Hong Kong have a similar or lesser prevalence of OM than do their Caucasian counterparts in North America. Different studies show different 11  results regarding the effect of age and most of them are based on adult populations.  1.5 Tympanometry  The frequency of OM and its consequences, particularly in childhood, have motivated researchers to seek out the most efficient clinical strategies and accurate norms for early diagnosis and management of this condition.  Tympanometry is a safe and objective tool in diagnosis of middle-ear diseases.  Tympanometric values can be affected by age, gender, and ethnicity.  Wan and Wong (2002) found ethnic differences between groups of Chinese and Caucasian young adults.  They suggest that body size and mechano-acoustical factors are important differences between the two groups.  In a study conducted by Shahnaz and Davies, (2006), the effect of ethnicity on the conventional 226-Hz tympanometry and MFT variables was investigated between a group of Chinese and Caucasian young adults.  They concluded that body size played a crucial factor in the observed differences between the Caucasian group and Chinese groups at a standard probe-tone frequency of 226-Hz as well as at higher frequencies of 678-Hz and1000-Hz. The American Speech-Language-Hearing Association (ASHA; 1997) recommends normative middle-ear screening values for school-aged children based on the data of Nozza, Bluestone, Kardatzke, and Bachman (1992).  These data were gathered using low probe-tone frequency for male and female subjects between one and 12 years of age.  However, the distribution of ethnicity in their normative data was not mentioned.  Limited research has been conducted on the effects of ethnicity on low- 12  frequency tympanometric variables; many studies do not indicate which ethnicity was studied.  Robinson and Allen (1984) and Robinson, Allen, and Root (1988) investigated the prevalence of OM in African-American children and found that it was less prevalent than in Caucasian children.  They analyzed their data by comparing tympanometric shapes between the two ethnicities (Jerger, 1970; Paradise et al, 1976).  Results from both studies showed that African-American children had a significantly lower incidence of referral in screening than Caucasian children, and that this difference varied with tympanometric shape.  The authors attributed their results to physiological differences between the middle-ears of African Americans and those of Caucasians, and suggested that the African-American children had larger mastoid pneumatic cells that allowed the ear to drain more readily.  Klein (1978) reported that First nations and Inuit ethnicities show a higher incidence of OM; it has subsequently been discovered that this is because of a physical difference in the Eustachian tubes of people of these ethnicities (Northern & Downs, 2002).   Previous research has demonstrated a high prevalence of OM in specific ethnic populations as shown in table 1.1.  The prevalence of hearing loss mostly due to OM among school-aged First Nations (FN) children in Canada has been reported to vary between 4 and 30% (e.g Ayukawa, Lejeune, & Proulx, 2004). Comparatively, this rate is much lower (2.63%) among school-aged children in general (Lundeen, 1991).  It has also been shown that First Nations children in Canada are hospitalized for OM six times more often than other children (Thomson, 1994).  The World Health Organization and the Ciba Foundation found a high prevalence of OM in Inuit, Native Americans, and Australian Aborigines (WHO & Ciba Foundation, 1996).  They provided evidence that the Eustachian tubes of people in these groups may 13  be larger in diameter or of lower resistance (semi-patulous) than those of people in other ethnic groups; this physiological difference may allow easier reflux of nasopharyngeal secretions into the middle-ear (Bluestone, 1998).  Daly (1997) also concluded that a combination of innate predisposition (i.e. a decreased ability to produce antibodies against common OM pathogens, differences in Eustachian-tube anatomy and function) and early exposure to risk factors (i.e. childcare, bottle-feeding) probably resulted in earlier onset of OM in this group. Wan and Wong (2002) used low probe-tone frequency tympanometry to compare norms in Chinese young adults (aged 19 to 34) to the non-Hispanic Caucasian norms established by Roup et al. (1998).  Wan and Wong suggested that these middle- ear differences could be caused by anatomic variations between the Eustachian tubes of the two groups.  Their findings revealed a statistically significant difference in the mechano-acoustical properties of the middle-ear between the two groups.  In another study, conducted by Shahnaz and Davies (2006) on young Chinese and Caucasian adults, the Chinese group had statistically higher middle-ear resonant frequencies than did their Caucasian counterparts, regardless of gender.  Shahnaz and Davies suggested that these variations are a reflection of differences in average middle-ear size, because Chinese are typically smaller in body-size indices than Caucasians (Huang, Rosowski, & Peake, 2000).  The effect of ethnicity on the normative data obtained in school-aged children, however, has not been addressed.  This issue is of particular importance since these tests are commonly used for screening of OM in school-aged children.  Current screening norms are not ethnic specific and may increase misdiagnosis of this commonly occurring disease. 14  Moreover, multi-frequency tympanometry has not yet been applied to the question of normative values for different ethnical populations. Multi-frequency tympanometry applies different probe-tone frequencies (e.g. 226-, 678-, and 1000-Hz) to test middle-ear charactristics.  There are no conclusive data regarding the effects of age, gender, or ethnicity on multi-frequency tympanometry variables.  Therefore, further research is needed to address the impact of these issues on normative data of school-aged children.  Driscoll et al., (2008) used standard tympanometry to test Chinese school-aged children whose age range was between six and 15 years old.  They compared the results of their study with the criteria proposed by ASHA (1997) for audiological screening, and by Shahnaz and Davies (2006) for adults.  Driscoll et al. (2008) recommended ethnic-specific criteria for audiological evaluation of Chinese school-aged children.  In another recent investigation, by Wong et al. (2008), researchers used standard tympanometry, which uses 226-Hz probe-tone frequency to show the tympanometric differences between the two ethnic groups (Caucasian and Chinese) and explored the prevalence of OME in Chinese and Caucasian school-aged children (6–15 years old).  They stated that Chinese school-aged children had a lower peak static admittance (Ytm) limit and wider tympanometric width (TW) values than did Caucasian children.  Wong et al. (2008) also concluded that ASHA (1997) guidelines for identifying ears for referral with respect to Chinese school-aged children may therefore not be adequately sensitive or specific.  They recommended that to increase the accuracy of tympanometry in Chinese school-aged children, the criteria in their study (i.e., peak Ytm lower limit <0.2 mmho and Vec upper limit >1.5 cm 3 ) 15  should be considered in addition to ASHA (1997) tympanometric screening guidelines. However, so far, the issue has not been addressed with regard to MFT. Current study addresses the application of MFT in school-aged children in both Caucasian and Chinese ethnicities. 16  Table 1.2: Selected studies investigating prevalence of OM in different ethnicities in children.   Study Sample Size Age Method of OM Documentation Ethnicity Point Estimate of Prevalence Holmquist et al., 1987 893 6–12 Tympanometry, Otoscopy Middle East- Kuwait 31.3% El-Sayed and Zakzouk, 1995 4124 1–8 Tympanometry Middle East- Saudi Arabia 13.8% Saim et al., 1997 1097 5–6 Tympanometry, otoscopy, acoustic reflex Southeast Asia- Malaysia 13.8% Marchiso et al., 1998 3413 5–7 Tympanometry, otoscopy Caucasian- Italy 14.2% Schilder et al., 1993 1004 5–8 Tympanometry Caucasian- The Netherlands 9.5% Williamson et al., 1994 856 5–8 Tympanometry Caucasian- UK 6–20% Apostolopoulos et al., 1997 5121 6–12 Tympanometry, otoscopy, acoustic reflex Caucasian- Greece 6.5% Lous & Fiellau- Nikolajsen, 1981 387 7 Tympanometry Caucasian- Sweden 26% Lyn et al., 1998 2202 5–7 Tympanometry, pure-tone audiometry African descend- Jamaica 1.9% Tong et al., 2000 6000 6–7 Tympanometry, pure-tone audiometry East Asian- Hong Kong 2.2% Ogisi, 1988 407 5–6 Tympanometry African descend- Nigeria 1%  17   1.6 Principles of Tympanometry  Immittance refers to the relationship between air volume in the ear canal and the characteristics of the middle-ear (e.g. impedance, admittance, and their components). This generic term refers to acoustic impedance, acoustic admittance, and all of their components.  Acoustic impedance is the reciprocal of acoustic admittance, and it refers to the amount of opposition that is offered by a system to the flow of acoustic energy. Acoustic admittance defines how easily the acoustic energy can get through the middle-  ear system.  Currently available immittance instruments typically measure admittance.   There are two important reasons for measuring admittance.  First, ear-canal volume between the probe tip and the tympanic membrane does not affect the shape of admittance tympanograms, but simply shifts the baseline; however, the shape of impedance tympanograms is greatly affected by ear-canal volume (Shanks and Lilly 1981). Second, the shape of admittance tympanograms is more susceptible to changes in middle-ear condition than is that of impedance tympanograms; therefore, they render themselves open to better classification of tympanometric shapes (Fowler & Shanks, 2002) Acoustic admittance has three main components.  These variables are mass, compliance, and friction or resistance.  The admittance offered by the acoustic-mass elements of the middle-ear system is called mass susceptance.  Mass susceptance is denoted as Bm and is also called mass reactance or positive reactance (Xm in impedance terminology).  The second element of acoustic admittance is compliant susceptance, which is the reciprocal of stiffness (Xc in impedance terminology); it is denoted as Bc. 18  Compliant susceptance refers to the admittance that is offered by the stiffness characteristics of the middle-ear system.  Total susceptance, Btotal  (Bt), is the sum of Bm and Bc:                                    Btotal (admittance) = Bm+ Bc                                                                            (1)                              Xtotal (impedance) = Xm + Xc    The third variable of the admittance system is called acoustic conductance, which refers to the amount of energy that is dissipated by the friction of the middle-ear system and is denoted by Ga (Figure 1.1).  Acoustic millimho (mmho) is the unit that we apply to all of these variables.     Figure 1.1: Left—impedance terminology [Xm: mass reactance; Xs: stiffness reactance; |Z|: absolute impedance magnitude; Øz: impedance phase angle].  Right—admittance terminology [Bm: mass susceptance; Bc: stiffness susceptance; |Y|: absolute admittance magnitude; Øy: admittance phase angle] (Adapted from Shahnaz, 2000).   In order to better understand multi-frequency and multi-component tympanometry it is important to know how the relation between admittance components varies as a function of frequency in the normal middle-ear system.  Acoustic conductance varies 19  with frequency variation.  The variation of conductance (G) with frequency can be understood as a variation of reactance (Xa) with frequency (see Equation 2).                                                            Ga = -   __Ra____                                                                            Ra 2 + Xa 2  (2)     However, compliance and mass susceptance are also frequency dependent.  Mass susceptance is directly proportional to frequency, and compliance susceptance is inversely proportional to frequency.  As frequency increases, total susceptance progresses from positive values (stiffness-controlled) toward zero (resonance) to negative values (mass-controlled).  Resonance of the middle-ear system occurs when compliant and mass susceptances are equal.  Using tympanometry, the resonant frequency of the normal adult ear has been reported to be as low as 630-Hz and rise as high as 2000-Hz, depending on compliant and mass susceptance (Margolis & Goycoolea, 1993).   The admittance vector rotates as a function of probe-tone frequency in a normal ear.  When the admittance vector lies between 0° and 90° (i.e., at frequencies below resonance), the system is stiffness-controlled, and when the admittance vector lies between 0° and −90° (i.e., at frequencies above resonance), the system is mass- controlled.  At lower frequencies, susceptance becomes larger than conductance (B>G) and the admittance vector lies between 45° and 90°.  As we increase the frequency, susceptance (B) decreases and conductance (G) increases.  When susceptance becomes equal to conductance (B=G), the admittance phase angle is 45°.  With further increases in frequency, conductance becomes larger than susceptance (B<G).  At or near resonance, total susceptance approaches zero (Figure 1.2).  20      Figure 1.2: The admittance terminology [Bm: mass susceptance; Bs: stiffness susceptance; Ba: total susceptance is algebraic sum of Bm and Bs; |Y|: absolute admittance magnitude; φ: admittance phase angle]. j is equal to √−1in complex number notation and indicates that conductance and susceptance cannot be combined by simple addition because they are vectors that operate in different directions (Shahnaz, 2008)  A system’s admittance (|Y|) is a quantity which is a vector sum of conductance (G) and total susceptance (Bt).  Mathematically, admittance can be expressed in rectangular notation or in polar notation.  In rectangular notation, admittance is expressed as the sum of its conductance (G) and susceptance (Bt) elements.  Thus, acoustic admittance in rectangular notation can be expressed as Equation 3: 21                                                          Y = G + jBt                                                                                         (3) j is an imaginary number mathematically equal to  in complex number notation and indicates that conductance and susceptance cannot be combined by a simple arithmetical addition because they are vector quantities  that operate in different directions.  Subscript t stands for total susceptance.  In polar notation, admittance is expressed by the two components of magnitude and phase angle.  The angle between the admittance vector and the horizontal axis is denoted by the phase angle, y.  Therefore, acoustic admittance in polar notation can be shown as Equation 4 (Table 1.2):                                                     |Y| ∠ y                                                             (4)   Table 1.3:  Mathematical relationship between polar and rectangular notation in admittance terminology (Adapted from Shahnaz, 2000.)  Acoustic Admittance Ya  𝑌𝑎  < 𝜑𝑌𝑎  (Polar Notation) 𝐺𝑎 + 𝑗𝐵𝑎 (Rectangular Notation) 𝐺𝑎 =  𝑌𝑎   × 𝐶𝑜𝑠 𝜑𝑌𝑎 𝐵𝑎 =  𝑌𝑎   × 𝑆𝑖𝑛 𝜑𝑌𝑎 𝑌𝑎 =  𝐺𝑎2 + 𝐵𝑎2 𝜑𝑌𝑎 = tan −1 𝐵𝑎 𝐺𝑎   22    1.7 Conventional 226-Hz Tympanometry  Tympanometry can be used as a safe and quick method for assessment of middle-ear function.  226-Hz is usually used as the standard probe-tone frequency for tympanometry.  This frequency was chosen partly at random (Terkildsen and Scott-Nielsen, 1960), and partly because the time microphones were nonlinear at higher probe-tone frequencies.  Four diagnostic parameters contribute to conventional 226-Hz tympanometry: equivalent ear-canal volume (Vea), compensated static admittance (Ytm), tympanometric width (TW), and tympanometric peak pressure (TPP).  Vea can be used in screening and diagnosis of middle-ear diseases.  It is defined as the amount of air volume between the probe tip and the tympanic membrane.  The measured volume of the ear canal may vary depending on the depth of insertion of the probe tip, the dimensions of the ear canal, the amount of cerumen, and the pathologies of the middle-ear.  Based on the findings by Shanks et al. (1992), the current ASHA clinical high cut-off value for normal Vea in children, calculated from a Y-226 Hz tympanogram is >1.0  mmho which indicates perforation or pressure-equalization (PE) tube patency. Driscoll et al. (2008), in their study on Chinese school-aged children, proposed a high cut-off value of 1.07 mmho for Vea, which is very close to the ASHA (1997) value for Vea (>1.0 mmho). Compensated static admittance (Ytm) is another parameter that is widely used in diagnostic processes.  This variable is derived from Ya (peak static admittance from Y tympanogram), which includes both ear-canal admittance and admittance corresponding 23  to the middle-ear.  In order to obtain middle-ear admittance alone, the peak admittance is subtracted from the tail admittance; this is called compensated static admittance.  It has been proven that Ytm can be a useful clinical tool for indication of middle-ear pathologies (Nozza, Bluestone, Kardatzke, & Bachman, 1992).  For example, in the presence of middle-ear pathologies, static admittance may increase, decrease, becomes extremely negative in terms of pressure, or becomes notched (Wiley & Fowler, 1997). ASHA-recommended norms in children suggest a clinical low cut-off value of 0.3 mmho for Ytm, calculated from a Y-226 Hz tympanogram, for separating ears with effusion from those without (ASHA, 1997).  Driscoll et al. (2008), however, propose a lower low cut-off value of 0.22 mmho for Ytm in Chinese school-aged children.  Such discrepancies between the Ytm values from different studies reveal the need for further investigation to see whether current ASHA norms can be used in the population of Chinese children. The third parameter is tympanometric width, which has been used as a diagnostic parameter in clinical settings.  Tympanometric width (in daPa) is measured at half of the height from the peak to the tail (Wiley & Fowler, 1997).  Since OME widens the tympanometric width, it has a great diagnostic value for diagnosis of OME (Nozza et al., 1994).  Nozza, Bluestone, Kardatzke, & Bachman (1994), suggested a clinical high cut- off value of 275 daPa for TW calculated from Y-226 Hz tympanogram for separating ears with effusion from those without effusion in children.  ASHA (1997) suggests a high cut- off value of 200 daPa for diagnosis of middle-ear pathologies.  However, Driscoll et al., (2008) proposed a high cut-off value of 144 daPa in Chinese children, which is lower than the limit proposed by ASHA (1997).  Since, current available guidelines are not 24  based on the Chinese population; further research is required to develop clinical norms for Chinese children.  Finally, TPP is the fourth parameter is the pressure at which the admittance tympanogram reaches its peak value (Wiley & Fowler, 1997).  In the presence of middle- ear pathologies, TPP may become negative (e.g. −200).  However, research shows that even in children with normal middle-ear function, TPP may be negative (Lindholdt, 1980).  Therefore, it is believed that TPP is not a good indication of middle-ear pathology for clinical use (Roush & Tait, 1985).  There are few studies on conventional 226-Hz tympanometry which show the effect of age on the normative data for children.  De Chiccis et al. (2000) concluded that static admittance and ear-canal volume increased from infancy to childhood (six months to five years).  Hanks and Rose (1993) tested school age children aged six to 15 years old and found no significant change in standard tympanometric parameters such as static admittance, ear-canal volume, and tympanometric peak pressure. Another variable that can affect the tympanometric results is gender.  In the adult population, some studies, such as Margolis and Heller (1987), did not find any gender differences; however, several other studies notice a gender effect (Wan & Wong, 2002; Roup et al (1998).; 1996; Shahnaz & Davies, 2006).  For example, Shahnaz and Davies, (2006) reported that the Vea was significantly smaller in the Caucasian female group than in the Caucasian male group.  Moreover, they stated that in 25  their Chinese adult subjects static admittance was larger in males than in females and TPP was lower in females than in males. The effect of ethnicity on normative values obtained using conventional 226-Hz tympanometry in adult and child populations has been investigated in several studies. Wan and Wong (2002) conducted a study in the Chinese adult population, age range 19– 34.  They found that compared to the Caucasian norms reported by Roup et al. (1998), Chinese subjects had smaller static admittance, wider TW, and more positive peak pressure.  In the child population, the most recent normative study, by Wong et al. (2008), tested 278 Southern Chinese schoolchildren aged 6–15 years old and showed that there are differences between the normative data of Chinese children and normative values obtained from Western populations.  In particular, they mentioned that Peak Ytm values were lower and TW values wider in the Chinese pediatric samples.  Driscoll et al. (2008) mentioned that Tong (1999), in a doctoral dissertation, found that up to 48% of children of Chinese ethnicity who failed their tympanometry, based on the ASHA (Caucasian) pass/fail criterion (ASHA, 1997) were misdiagnosed.  On the other hand, the most commonly used immittance guidelines and referral criteria for the pediatric population are based on normative studies on Caucasian children. Tympanometry conducted using 226-Hz probe-tone frequency has proven valid in identifying different middle-ear disorders (Shanks and Lilly, 1981). However, several studies have shown that conventional 226-Hz tympanometry often cannot distinguish normal-hearing middle-ears from ears with pathologies that affect the ossicular chain (Colletti, 1976; Shahnaz & Polka, 1997).  It can also fail to distinguish middle-ears with pathologies in 26  newborn infants and infants below six months of age (Holte, Margolis, & Cavanaugh, 1991; Hunter & Margolis, 1992; Margolis, Bass-Ringdahl, Hanks, Holte, & Zapala, 2003; Paradise, Smith, & Bluestone, 1976).  In addition, the standard 226-Hz tympanogram does not have the ability to detect sequelae and subtle mechano-acoustical changes in middle-ear mechanics following OM (Margolis, Hunter, & Giebnik, 1994; Vlachou, Ferekidis, Tsakanikos, Apostolopoulos, and Adamopoulos, 1999).  1.8 Multi-Frequency Tympanometry—MFT  Another way of measuring middle-ear function is through multi- frequency, multi-component admittance devices.  MFT has made it possible to record admittance across a wide range of frequencies and to measure the relative contributions of stiffness, mass, and frictional elements.  Four potentially useful parameters that can be derived from MFT for diagnostic purposes are tympanometric configuration (Vanhuyse Pattern), resonant frequency (RF), frequency corresponding to admittance phase angle of 45 degree (F45°), Vea, and static admittance (Ytm) at multiple frequencies.  In this section, the MFT parameters will be defined first, and then research relevant to the purpose of this study will be reviewed. Earlier studies of multi-frequency tympanometry revealed that tympanograms at high frequencies have a more complex pattern compared to lowfrequency tympanograms.   In 1976, researchers explored multi-frequency tympanometry in patients with various middle-ear pathologies (Colletti, 1976).   Colletti reported that tympanometric patterns were different among patients with ossicular chain 27  fixations, ossicular chain discontinuities, and normal middle-ears, as probe frequency was changed from 200 to 2000 Hz. One of the models that were developed for multi-frequency tympanometric patterns was the Vanhuyse pattern (Vanhuyse et al., 1975).  The Vanhuyse model categorizes the tympanograms based on the number of peaks or extrema on the B (susceptance) and G (conductance) tympanograms and predicts four tympanometric patterns at 678 Hz.   For example, the 1B1G pattern has one peak on the B tympanogram and one peak on the G tympanogram; 3B3G has two peaks (―maxima‖) and one trough (a ―minimum‖) on the B and the G tympanograms (Figure 1.4).   Shahnaz (2000) showed that the transition between different Vanhuyse patterns can be shifted to higher or lower probe-tone frequencies depending on the nature of the middle-ear pathology (Shahnaz, 2000). The first normal pattern in the Vanhuyse model is called 1B1G (Figure 1.4). In this pattern, there is one peak on each of susceptance (B) and conductance (G) tympanograms.   The admittance tympanogram also has only one peak.  The 1BIG pattern occurs when the middle-ear system is stiffness-dominated and the absolute value of acoustic reactance is greater than the acoustic resistance.  This pattern occurs between admittance phase angles of 45 o  and 90 o .  The 1B1G pattern is usually seen in ears with a normal middle-ear function. The second normal pattern is 3B1G.  In this pattern, we have two peaks on the susceptance tympanogram and only one peak on the conductance tympanogram.   Again, the admittance tympanogram is single peaked.  This pattern occurs between admittance phase angles of 0 o  and 45 o .  In this pattern, the middle- 28  ear system is either stiffness dominated (y > 0o) or at resonance (y = 0o).  The admittance tympanogram in this case is usually single peaked; however, it can also be notched (Margolis et al., 1985).  If the notch on the susceptance tympanogram stays above either the positive or the negative tail, the middle-ear system is stiffness dominated; however, if it falls below one of the tails, the middle-ear system becomes mass dominated.    Figure 1.3: Vanhuyse Model showing four normal tympanometric patterns: (A) 1B1G, (B) 3B1G, (C) 3B3G, and (D) 5B3G (Adapted from Fowler & Shanks, 2002).  .   Based on the Vanhuyse model, the third pattern is 3B3G (Figure 1.4).  In this pattern, we have one notch on each of the susceptance and conductance tympanograms; 29  in other words, two peaks and one notch on each tympanogram.  The admittance tympanogram also has two peaks and one notch.  With the 3B3G pattern, the middle-ear is mass-dominated, and the admittance phase angle falls between 0 o  and -45 o .  The final pattern is 5B3G, in which there are three peaks and two notches on the susceptance tympanogram and two peaks and one notch on the conductance tympanogram.  The admittance tympanogram has two peaks and one notch.  In the 5B3G pattern, the admittance phase angle falls between -45 o and -90 o , and the system is also mass dominated. Vanhuyse et al. suggested normative data for tympanometric patterns at a 678-Hz probe-tone frequency in the adult population.  Vanhuyse et al. (1975) suggested that the normal distance between the outermost peaks should be 75 daPa for 3B1G and 3B3G tympanograms and 100 daPa for 5B3G tympanograms to be considered within standard limits (Vanhuyse et al., 1975).  Also, the maxima of the G tympanogram should be within the outermost maxima of the B tympanogram and the total number of peaks and troughs should not exceed 5 for B and 3 for G.   However, we do not have specific norms for tympanometric patterns at high probe-tone frequencies in school-aged children. Resonant frequency (RF) can be estimated from compensated susceptance. Using the Vanhuyse model, RF is the frequency at which the notch in the susceptance tympanograms becomes equal to the positive tail (positive compensation) or negative tail (negative compensation).  RF can be measured either by plotting the susceptance tympanogram at various probe-tone frequencies (e.g, using Virtual 310 middle-ear analyzer, GSI-33 or Tympstar) or by plotting peak–compensated B (Bpeak – Btail), also called delta B (Δ B), as a function of probe-tone frequency (e.g., using GSI-33 or 30  Tympstar).  Figure 1.5 shows a plot of B and G tympanograms as a function of air pressure obtained from a Virtual 310 middle-ear analyzer.   Whenever the notch value on the susceptance tympanogram becomes equal to a positive tail (positive compensation) or negative tail (negative compensation), the total susceptance becomes zero, and the system is at resonant frequency (see Figure 1.5).   Figure 1.6 shows a plot of delta B and G as a function of probe-tone frequency obtained using GSI-Tympstar.  When delta B crosses the zero line (0 mmho), the system is at resonance.            Figure 1.4: Estimation of resonant frequency (RF) from the uncompensated susceptance (Ba) tympanogram using a Virtual 310 middle-ear analyzer (Adapted from Shahnaz, 2008).  Another parameter that can be estimated from multi-frequency tympanometry is the admittance phase angle of 45°.  This is the angle at which compensated susceptance is equal to compensated conductance.  Some findings suggest that the frequency corresponding to an admittance phase angle of 45° may be a better index than resonant 31  frequency with respect to distinguishing healthy ears from otosclerotic ears (Shanks, Wilson, & Palmer, 1987; Shahnaz & Polka, 1997; Shahnaz et al. 2009).  -14 -12 -10 -8 -6 -4 -2 0 2 4 6 250 450 650 850 1050 1250 1450 1650 1850 Frequency-Hz im m it ta n c e  -  m m h o Delta B Delta G mmho  G    Figure 1.5:  GSI-Tympstar sweep frequency recording of ΔB and ΔG (in mmho) using positive compensation.  When ΔB is positive, the system is stiffness dominated; if it is negative, the system is mass dominated.  The crossing of ΔB with ΔG corresponds to an admittance phase angle of 45 °.  When ΔB is zero, the system is at resonance  (Adapted from Shahnaz, 2007).   Recent research showed the advantage of MFT over conventional 226- Hz tympanometry in detecting pathologies such as otosclerosis (Shahnaz & Polka, 1997, 2002; Shahnaz & Davis 2006; Margolis, 1992).  The Vanhuyse model describes the complex patterns of tympanograms as frequency increases in both normal and abnormal middle-ears (Margolis, Van Camp, Wilson, & Creten, 1985). However, the frequency at which each of these patterns may occur can shift with the 32  presence of different middle-ear pathologies (Shahnaz, 2001).  In middle-ear pathologies such as otosclerosis, the resonant frequency is shifted towards higher frequencies. Therefore, the frequency at which the notch occurs on the B and G tympanograms will also shift towards higher probe-tone frequencies.   Resonant frequency (RF) is a useful diagnostic parameter, as many middle-ear pathologies greatly affect tympanometric patterns around the resonant frequency (Liden, Harford, & Hallen, 1974; Margolis & Shanks, 1991; Shanks, 1984).  Margolis and Goycoolea (1993) did not find any inter-aural or gender differences for conventional tympanometric parameters of static acoustic admittance, tympanometric width, and tympanometric peak pressure or for multi-frequency tympanometric parameters of the resonant frequency.  They also reported that as probe frequency increases, tympanometric patterns progress consistently with the Vanhuyse model.  Resonant frequency may be estimated using two recording methods: sweep pressure (SP) and sweep frequency (SF).  In the SP method, frequency is held constant while the pressure is changing, and in the SF method, frequency is changing while the pressure is constant.  Margolis and Goycoolea also suggested that the SP method is a more appropriate method for measuring RF than the SF method. Vea measurements can also be done through MFT.  B tympanograms can provide useful information regarding Vea.  The most commonly used method for estimating ear- canal volume was proposed by Terkildsen and Thomsen (1959).  They suggested the use of high positive pressure (200 daPa, 1 daPa = 10 Pa) during the measurement, which could drive the admittance of the middle-ear toward zero.  The resulting tympanogram- tail admittance measured at the probe tip can be attributed, assuming that the canal walls 33  are rigid, mainly to the air trapped in the ear canal itself.  The Vea estimated from the tail is always greater than the actual ear-canal volume because of residual vibration of the middle-ear (Shanks & Lilly, 1981).  Shanks and Lilly (1981) reported that in adults the volume of trapped air is more accurately estimated from the susceptance (B) tail than from the admittance (Y) tail.  The researchers stated that by calculating Vea from B, the conductance value will be equal to zero (G = 0) and estimated that Vea is closer to the real volume of the ear canal.  However, by calculating Vea from Y, the magnitude of the conductance value will also be included (G > 0), and the estimated Vea will not reflect the true volume of the ear canal.  Shanks and Lilly (1981) also reported that Vea is more accurately estimated from the negative tail at – 400 daPa than from the positive tail at +400 daPa, because with changing ear-canal pressure, changes in ear-canal volume are minimal (0.18 ml) at – 400 daPa; therefore, the error is smallest if we estimate Vea to be at – 400 daPa.  In adults, Shanks and Lilly reported that the difference in estimation of Vea from admittance and from susceptance is small at 226-Hz, but increases to approximately 9% at 660-Hz due to decrease in reactance by increasing probe-tone frequency.  Selection of these probe-tone frequencies for estimation of Vea is based on previous research (e.g. Shanks and Lilly, 1981).  The common clinical procedure is to estimate Vea from the 226-Hz probe-tone frequency.  Shanks and Lilly (1981) reported that estimation of Vea from 678-Hz is more accurate compared with from 226-Hz. However, they stated that, clinically, estimation of Vea from the 678-Hz probe-tone frequency does not reflect the actual size of the ear canal, since conductance is not zero at this frequency.  The authors suggested that as the probe-tone frequency increases towards the middle-ear’s resonant frequency (800-1200-Hz), reactance is less affected by middle- 34  ear changes (as probe frequency increases, reactance decreases), which results in more accurate estimation of Vea.  Threfore, in the current study, Vea was calculated from 226- and 1000-Hz. Middle-ear admittance is often calculated using the baseline method by subtracting the tail admittance (positive or negative) from the peak admittance. However, middle-ear admittance may be more accurately estimated by compensating for the susceptance and conductance components at either the positive or negative tail.  The difference between admittance derived from the baseline method and admittance derived from the compensation of the rectangular components is negligible for adults, owing to the small value of conductance at the tails, especially with a 226-Hz probe-tone (Shanks & Lilly, 1981); this difference becomes great for young infants, owing to the large value of conductance at the tails, especially for a 1000-Hz probe-tone (see e.g. Kei et al., 2007).  Consequently, in order to establish normative tympanometric data, especially at higher probe-tone frequencies, it is necessary to investigate the variations of admittance and its two rectangular components, susceptance and conductance, at both negative and positive tails as a function of age.  To the best of our knowledge, such a study has not yet been published.  1.9 Goals  Tympanometric measurements can be potetially related to all sources of subject variability such as age, gender, and ethnic origin.  However, we have limited research data on the effect of ethnicity on standard and muti-frequency parameters. 35  This is a very important issue to investigate because of limited normative data across ethnicities and age groups in today’s multicultural society. Research has shown that middle-ear characteristics are different between Caucasian and Chinese young adults; however, this issue has not been addressed in school-aged children.  It is important to explore whether there are any differences in the middle-ear characteristics of Caucasian and Chinese school-aged children because current screening norms for this population are based on Caucasian norms, and OM is more common at this age. The purpose of this study is to investigate any differences between groups of Chinese and Caucasian school-aged children using standard and multi-frequency tympanometry. Findings from this study could indicate a need for further research to establish normative data for different ethnic groups.  Research to date on differences in middle-ear analysis techniques by patient ethnicity has left many gaps.  Only a limited number of ethnicities have been studied (African American, First nations, and Eskim), and all information has been gathered using conventional 226-Hz tympanometry.  These factors, as well as other factors such as possible need for age-specific normative MFT data and the increasingly multicultural (e.g. Canadian) societies have motivated the present study.  As the population becomes more diverse, we may need different norms to correctly identify middle-ear pathology in patients of different ethnic backgrounds.       The goal of this research was to explore the differences in mechano-acoustical properties of the middle-ear between two groups, of Chinese and Caucasian school-aged children respectively.  This will hopefully allow accurate differentiation of children with normal ears from children with ears affected by middle-ear problems in both these ethnic 36  groups.  The results of this study were compared to Shahnaz and Bork’s (2008) study of Caucasian and Chinese adults, and ASHA’s (1997) tympanometric norms for Caucasian children of the same age range in order to explore whether these norms are comparable and explore potential sources for these differences.  Previous studies on school-aged children only reported on conventional 226-Hz tympanometric results; however, this study is examining MFT parameters as well as conventional 226-Hz tympanometric parameters.  For this purpose we will compare the normal results from healthy ears to the abnormal results obtained from ears with OME in both ethnicities. The following hypothesis was proposed: 1.  Tympanometric patterns and parameters are generated by school-aged children with healthy middle-ear status differ as a function of ear, gender, or ethnicity. 2.  The conventional and MF tympanometric values obtained from school- aged children differ from the normative adult data found by Shahnaz and Davies (2006). 3.  The normative pediatric data can safely be applied to the tympanometric patterns and parameters of children with middle-ear pathology, specifically, middle-ear effusion and negative middle-ear pressure in both Caucasian and Chinese school-aged children.     37  2 Materials and Methods 2.1 Ethics Approval  Ethics approval was obtained at the University of British Columbia the Office of Research Services prior to testing.  This approval was required for testing at BC Children’s hospital and at the elementary schools.  The ethics provisions were also approved by each school district before commencement of data collection.  The ethics approval certificates (included in a package) were sent to the schools to obtain their permission.  Consent forms, along with an invitation letter and a brief case-history report, were prepared for each student, to be signed and filled in by the parent.  All of the personal information in this study was kept confidential.  The term school-aged children in the present study refer to children between 5 to 7 years old.  A sample of what was sent to schools is included in the appendix.  2.2 Experiment 1: Control Group 2.2.1 Description of Subjects  The control group consisted of 98 participants (176 ears).  There were 55 participants (30 male and 25 female) in the Caucasian control group, and 43 participants (29 male, 14 female) in the Chinese control group (Table 2.1).  The mean age was 5.62 years old (five to seven years, standard deviation = 0.61) for the Caucasian control group, and 5.95 years old (five to seven years) for the Chinese control group.  Thirty-three ears in the Chinese group and 21 ears in the Caucasian group were excluded from the study, because they either had missing data or did not meet the inclusion criteria listed below. 38     Table 2.1: Distribution of normal subjects in the control group  Subjects  n = subjects             n = ears Caucasian male     30             50 Caucasian female     25              46 Chinese male     29              54 Chinese female     14              26   In the present study the following inclusion and exclusion criteria were used:  All participants had to meet a modified version of the American Speech- Language-Hearing Association (ASHA; 1997) screening criteria for normal auditory function and middle-ear status that has been explained below: 1. All subjects had to pass a transient-evoked otoacoustic-emission (TEOAE) screening with specific passing criteria.  A pass was considered to be a result showing at least a 3 dB signal-to-noise ratio (S/N) at 1 and 1.5 kHz and a 6 dB S/N at 2, 3, and 4 kHz, in at least four out of the five frequency bands.  This stopping criterion was chosen since it has been shown to have a reasonable test performance for detecting hearing loss in a large sample of newborns (Norton et al., 2000). 39  3.   All subjects were required to have normal tympanometric peak pressure (< 150 daPa) at 226 Hz using a positive to negative pressure direction (Jerger, 1970; Silman et al., 1992).             4.   All subjects were required to have no sign of outer or middle-ear pathology during otoscopy             5.  All subjects were required to have no evidence of a syndrome or developmental delay and no reported history of head trauma or hospitalization for an illness.         6.    Students could be in either kindergarten or Grade One. Subjects for the control group were recruited from different elementary schools in the cities of Richmond and Vancouver, within the Greater Vancouver area.  The elementary schools were: William Cook Elementary School, Mitchell Elementary School, Richmond Christian Elementary School and Maple Lane Elementary School in Richmond, and Lord Kitchener and Bayview Elementary Schools in Vancouver. Students were chosen from kindergarten and Grade One classes.  After obtaining the school board’s permission, a package containing ethics approval, school board permission, a letter from the school principal, a case history form, and consent forms was taken to the schools and distributed among students to get parents’ permission.  Children who brought their signed consent forms back participated in this study.  In each school, between 15 and 20% of the consent forms were signed by the parents and returned. Ethnicity was determined in the parental report.  40   2.2.2 Instrumentation  For otoscopy, a Welch-Allen clinical otoscope was used.  To perform pure tone audiometry, a Maico MA 40 portable audiometer was used.  All instruments were calibrated according to ANSI standards (ANSI, 1989).  In addition, the audiologist performed a listening check each day before testing.  For testing children who were referred to the UBC School of Audiology and Speech Sciences (SASS), a GSI 61 diagnostic audiometer was used.  TDH-39 supra-aural headphones were used as receivers for screening audiometry at schools.  At SASS, an insert ear phone and a bone vibrator were also used to conduct hearing tests.  Testing was performed in a quiet room (S/N> 3 dB) at each school and in a soundproof booth at SASS. Transient evoked otoacoustic emissions (TEOAEs) were tested using a laptop computer equipped with ILO 292 software (v. 6) which was calibrated prior to testing.  A GSI-Tympstar tympanometer (v. 2) was used for tympanometry.  Before each data-collection session, the GSI system was calibrated using three standard cavities (0.5, 2.0, and 5.0 cm 3 ), in accordance with the operation manual provided by the manufacturer. The system had the ability to measure Admittance (Y), Susceptance (B) and Conductance (G) at 226, 678 and 1,000 Hz probe-tones.  This system also allowed for multifrequency tympanometry, which was useful for determining resonant frequency. This machine had enough memory to save up to 28 tests at the same time, which gave us the possibility of switching between recorded tests.  Different probe-tip sizes were available for TEOAEs and tympanometry depending on the size of the ear canal. 41   2.2.3 Procedure  A series of tests were performed prior to subject inclusion.  Otoscopic examination was performed to make sure that the child had a healthy outer ear and the ear canal was not occluded with ear wax.  Air conduction thresholds were obtainned at 20 dB HL for 1000, 2000, and 4000-Hz, following the ASHA (1990) screening protocol.  Thresholds were also obtained at 20 dB HL for 500-Hz.  Each signal was presented three times, and children raised their hands when they heard the signal.  Environmental noise was not measured prior to testing; however, periodic listening checks were performed to make sure that the sound was audible at all frequencies to the audiologist.  In addition to ASHA screening protocols other tests such as TEOAE, conventional 226-Hz tympanometry, and MFT were also performed. TEOAEs were tested following audiometric testing.  TEOAE was performed to assure normal cochlear (sensory) function and middle-ear function.  To obtain TEOAEs, a soft probe tip is inserted into the ear canal.  The stimulus level was adjusted at 84±3 dBSPL, and a non-linear click repeating 50 times per second in a 20 ms time window was introduced into the ear canal.  The emissions were recorded for 1, 1.5, 2, 3, and 4 kHz.  In order for a click to be considered present, the signal-to-noise ratio had to be at +3 dB at 1 and 1.5 kHz and 6 dB at 2000–4000-Hz, and the reproducibility had to be 70%.  If the child did not pass the test, the test was repeated one more time with a deeper probe fit. All of the tips were disinfected after being used. Conventional 226-Hz tympanometry was conducted following otoacoustic emission (OAE) testing.  In this technique, a probe was sealed in the outer ear canal. Sound was presented while the air pressure in the ear canal was changed at 200 daPa/sec 42  pump speed.  The sound pressure level monitored at the probe tip showed how easily acoustic energy flows into the middle-ear system, which is referred to as acoustic admittance (Y).  Because the tail values (positive and negative) were subtracted form the peak value, the term compensated (Ytm) was used.  The results were displayed as a tympanogram, which in a normal ear is a bell-shaped curve with a single peak.  Ear-canal volume (Vea) was measured using conventional 226-Hz tympanometry since it has been shown that it can accurately estimate the actual volume of ear canal (Lilly and Shanks, 1981). Following a conventional 226-Hz tympanogram, tympanograms were obtained at 678- Hz and 1000-Hz for Ya, Ba, and Ga using sweep-pressure recording.  Finally, resonant frequency (RF) was obtained using sweep-frequency and sweep-pressure recording procedures.  In the sweep-frequency procedure, the probe-tone frequency was swept through a series of probe-tones from low to high frequencies with a 50 Hz interval (250 to 2000-Hz).  This was done at extreme positive pressure (+200 daPa) and at a pressure corresponding to the peak for Ba.  The corresponding values at the peak were automatically subtracted from the positive tail value (compensated susceptance or B) and were plotted as a function of the probe-tone frequency. In the sweep-pressure method, the air pressure of the external ear canal was decreased continuously in a positive to negative pressure direction at different probe-tone frequencies for both Ba and Ga.  After testing, all the peaks were labeled, and the results were printed out.  Then the numeric values were transferred onto a Microsoft Excel (version: 14.0.4760.1000) spreadsheet for further calculations. First, the peak (or notch in the case of multi-peak tympanograms) was subtracted from 43  the positive (+200 daPa) and negative (−400) tail on the Ba/Ga tympanograms.  Then, Ytm was derived from the rectangular components of susceptance and conductance using the following equation:    (5) 2.3 Experiment 2: Diseased Group  2.3.1 Subjects     Subjects with abnormal middle ear condition were chosen based on tympanogram abnormality.  The abnormal tympanograms included those with a mild negative pressure (150–200 daPa), those with a high negative pressure (> −200 daPa), and those with middle-ear effusion (MEE) or flat configuration.  There were a total of 66 subjects (93 ears: 56 males), in the diseased group.  The group with mild negative pressure consisted of 24 subjects (33 ears), whose peak pressure ranged from −150 daPa to −200 daPa.  There were 14 subjects (20 ears) in the group with severe negative pressure (defined as > −200 daPa.  The third sub-group consisted of 20 subjects (40 ears) with MEE.  The age range of the children was five to seven years old with a mean age range of six years.  In all groups, age and ethnicity were reported by parents using questionnaires.    Participants with abnormal middle ear condition were recruited from two sources: some were recruited through elementary schools (the ―not OTL confirmed‖ group; see below) and consisted of subjects with negative middle-ear pressure, either mild or severe, or with MEE.  These subjects were initially recruited as control subjects but were found 44  to have abnormal middle-ear status at the time of testing.  There were 12 ears in this group with MEE.  The other group of diseased group participants was recruited through the Division of Pediatric Otolaryngology at British Columbia Children's Hospital (BCCH) and is called ―OTL confirmed‖ in the present study.  This group consisted of 21 subjects with MEE (28 ears).              2.3.2 Instrumentation  Diseased-group subjects recruited through elementary schools: Identical instrumentation to that described for control group subjects was used to test audiological thresholds, gathering TEOAE and tympanometric data for subjects recruited through their elementary school. Diseased group subjects recruited through BCCH: Audiological thresholds were measured using a GSI 61 audiometer at the BCCH audiology department.  The same instrumentation mentioned in the control group section for gathering TEOAE and tympanometric data was used to gather data from diseased group subjects tested at BCCH.  45  2.3.3 Procedure Otoscopy was performed to rule out gross abnormalities of the external ear and tympanic membrane.  TEOAE and tympanometric data were gathered for all diseased group subjects using the same procedure described for control group subjects.  The static admittance, TPP, and TW of the tympanograms were taken into consideration in order to categorize the tympanograms.  For example, tympanograms with TW greater than 200 daPa were classified as flat.  High frequency (678-Hz & 1000-Hz) tympanograms were also used to help interpret the 226-Hz tympanograms. Diseased group subjects recruited through elementary schools: An identical procedure to what has been described for the control subjects was performed for the subjects tested at their elementary schools.  However, diseased group subjects did not have normal hearing thresholds, so they were not able to respond to two presentations of a tonal stimulus in at least one of the four tested frequencies.  Middle-ear conditions were determined using a battery of test results, including elevated air conduction thresholds, absent otoacoustic emissions, and abnormal immittance results using 226-, 678-, and 1000-Hz probe-tones. Diseased-g Group subjects recruited through BCCH: Air and bone conduction thresholds were obtained, with good reliability, at 500, 1000, 2000, and 4000-Hz by a registered audiologist at the BCCH audiology department.  A bone conduction test was performed in cases of elevated air conduction thresholds, absent otoacoustic emissions, and abnormal impedance results, to make sure the type of hearing loss was conductive. Pneumatic otoscopy and video otomicroscopy were conducted by a pediatric otolaryngologist to confirm the presence of middle-ear pathology.  The results were then 46  sent to an otologist to review the video-otomicroscopy results to confirm the diagnosis of MEE.  2.4 Statistical Analyses  A mixed-model analysis of variance (ANOVA) was used in this study to analyze tympanometric data in the normal group and the group with abnormal middle ear condition.    The mixed-model analysis of variance (ANOVA) was also used to compare children’s data from the present study to adult data from Shahnaz and Bork (2008).   Results of descriptive analysis of tympanometric shapes are reported in this section.  Equivalent ear-canal volume (Vea), static admittance (Ytm), tympanometric width (TW), tympanometric peak pressure (TPP), and resonant frequency (RF) were tested using standard 226-Hz and multi-frequency tympanometry (MFT). According to Van Camp et al. (1986), under standard conditions a 1 cm 3 cavity has a susceptance of 1 mmho.  In this paper both units are used, since 1 cm 3  is considered to be equal to 1 mmho.  The variables mentioned above, were tested by ethnicity, gender, ear, and age (each at two levels) as between-subject factors, and by compensation method (positive versus negative compensation) and recording method (SF vs. SP), where applicable as within-subject factors.  Factor of ear was chosen as the between-subject factor because each ear may be affected by a pathology independent of the other ear, and even in normal ears, tympanometric results may be different between the right and the left ears.  The Greenhouse Geisser (1959) approach was performed to confirm the significant interactions.  Any main factor and interaction equal to or below the alpha level 47  (≤ 0.05) were considered significant.  The Post-hoc HSD Tukey test was performed for significant main effects and interactions to identify differences between factors.  2.4.1 Diseased Group Subjects (group with abnormal middle ear condition)  Normative peadiatric tympanometric data were compared with tympanometric data from the diseased groups on the factor of middle-ear condition (normal, mild negative middle-ear pressure, severe negative middle-ear pressure, and MEE) as the between-subject factor.  Post-hoc analyses were performed to confirm the significant differences that existed between the normative and diseased group data. Signal detection theory (SDT) was used in the current study to provide measure for analyzing decision making in the presence of uncertainty.  In the present study there were four possible outcomes based on SDT: 1) hit: subjects with middle ear pathology that were truly identified as diseased 2) miss: subjects with middle ear pathology that were identified as normal 3) false positive: subjects with normal middle ears that were identified as having middle ear pathology and 4) true negative: subjects with normal middle ears that were identified as normal (not having middle ear pathology). Receiver operating characteristic (ROC) curves were measured using MedCalc for Windows, v. 9.0 (MedCalc Software, Mariakerke, Belgium) to statistically compare the diagnostic performance of MFT (Phi-coefficient analysis; Siegel & Castellan, 1988).  The ROC curve was plotted with the false positive rate on the horizontal axis and the hit rate on the vertical axis. The software automatically measured the area under the curve (AUROC), with a 95% confidence interval (CI) for this area at each probe-tone frequency and each testing parameter.  Sensitivity (the ability of the test to distinguish true positives), and 48  specificity (the ability of the test to distinguish true negatives) of the test were also calculated automatically using the software. The area under the curve was interpreted as the area that lies between 0.5 and 1. The first number, 0.5, indicated that the test did not have the ability to distinguish between the two groups, and as a result, the curve coincided with or became close to the diagonal line.  However, 1 indicated perfect separation between two groups, where the curve reached the upper left corner of the plot.  The 95% CI was the interval in which AUROC lay with 95% confidence.  The P-value showed whether the AUROC was different from 0.5.  If the P-value was less than 0.05, it was concluded that the test did not have the ability to distinguish between the two groups. AUROCs were also used to compare the performance of two separate variables or parameters for the same sample of patients.  The correlation between the areas was taken into account to test how close the AUROCs were and whether they were statistically different.  Comparison of AUROC of 2 or more correlated ROC curves was based on a non-parametric statistical approach of DeLong and DeLong (1988) and Hanley and McNeil (1982).        49  3 Results 3.1 Descriptive Analysis of Tympanometric Shapes  Table 3.1 shows the distribution of Vanhuyse patterns at 226-, 678-, and 1000-Hz among Caucasian and Chinese school-aged children.  The most complex patterns were observed at 1000-Hz.  At a 226-Hz probe-tone frequency, the most dominant pattern in both Caucasian and Chinese groups was 1B1G pattern accounting for almost 100% of Vanhuyse patterns.  This pattern is consistent with stiffness dominated middle-ear system with admittance phase angle of greater than 45 degree.  At 678-Hz probe-tone frequency, more complex patterns started to emerge.  While the dominant pattern at 678-Hz in both the Caucasian and Chinese groups was the 1B1G pattern, the 3B1G pattern accounted for 12–23% of the patterns.  At 678-Hz, the lowest proportion of the 3B1G pattern was observed in the Chinese female (12.5%).  At the 1000-Hz probe-tone frequency, the 3B1G pattern was the most dominant pattern in the Caucasian group and accounted for roughly 66% of the observed patterns.  In contrast, it accounted for less than 50% of the observed patterns in the Chinese group.  Overall, as the probe-tone frequency increased, the proportion of single-peak patterns (1B1G) decreased and the proportion of multi-peak patterns increased.  For example, the 1B1G pattern decreased by a ratio of 6.8 in Caucasian males, 3.9 in Caucasian females, 2.8 in Chinese males, and 2.1 in Chinese females as the probe-tone frequency increased from 226-Hz to 1000-Hz.  However, the proportion of 3B1G patterns increased as the probe-tone frequency increased by a ratio of 64.58 in Caucasian males, 28.3 in Caucasian females, 24 in Chinese males, and 45.8 in Chinese females from 226- Hz to 1000-Hz. 50  Table 3.1: Proportion of different Vanhuyse tympanometric configurations, expressed as a percentage, across different probe-tone frequencies among normal Caucasian and Chinese school-aged children.  Proportion of different tympanometric configurations  AGE (mean)  GENDER  N=ears  1B1G  3B1G  3B3G  5B3G  OTHER  Total Caucasian male—226-Hz 5.38 M 50 100 0 0 0 0 100 Caucasian female—226-Hz 5.38 F 46 97.69 2.22 0 0 0 100 Chinese male—226-Hz 5.59 M 54 97.82 2.18 0 0 0 100 Chinese female—226-Hz 5.49 F 26 100 0 0 0 0 100 Caucasian male—678-Hz 5:38 M 50 74.47 23.40 2.13 0 0 100 Caucasian female—678-Hz 5.38 F 46 78.00 20.00 2.00 0 0 100 Chinese male—678-Hz 5.59 M 54 74.47 23.4 2.13 0 0 100 Chinese female—678-Hz 5.49 F 26 87.5 12.5 0 0 0 100 Caucasian male—1000-Hz 5.38 M 50 14.89 65.95 8.51 4.25 6.40 100 Caucasian female—1000-Hz 5.38 F 46 25.58 65.11 4.65 0 4.65 100 Chinese male—1000-Hz 5.59 M 54 32 48 16 2 2 100 Chinese female—1000-Hz 5.49 F 26 45.83 45.01 4.16 0 5 100 51  Consistent with Vanhuyse tympanometric model for adults at a 660-Hz probe- tone frequency, tympanograms at 678-Hz were further analyzed for these school-aged children (Table 3.2).  Similar to the model proposed by Vanhuyse et al. (1975), the number of peaks (maxima) and troughs (minima) was calculated for both susceptance (B) and conductance tympanograms (G).  The distance between the two outermost peaks in daPa was calculated for susceptance tympanograms.  Descriptive analysis showed that the mean distance between the two outer most peaks was smaller in the Caucasian than in the Chinese group.  Moreover, the maximum number of peaks did not exceed 5 for B and 3 for G in either ethnicity.  The two outermost maxima on the conductance were always within the two outermost maxima on the susceptance tympanograms.  Table 3.2:  Mean, SD, and 90% range (5 th–95th percentile) for distance between the two outermost peaks in daPa obtained from the susceptance (B) tympanogram.  The maximum number of peaks (maxima) and troughs (minima) obtained from susceptance (B) and conductance (G) tympanograms in normal Caucasian and Chinese school-aged children using a 678-Hz probe-tone frequency is also reported.  678-Hz Mean SD 90% range Maximum number of peaks Caucasian males 119.57 44.44 51–195 5B3G Caucasian females 109.09 38.40 41–159 3B3G Chinese males  122.11 34.76 72–180 3B3G Chinese females 125.42 43.59 50–180 3B1G      52  3.2 Control Group Tympanometric Data Using Conventional 226-Hz Tympanometry  Mean, standard deviation (SD), and 90% range (5 th  to 95 th  percentiles) for Caucasians and Chinese children were calculated and summarized in Appendix A.  The ANOVA tables are summarized in the Appendix, and the data in boldface show significant findings. 3.2.1 Equivalent Ear-Canal Volume (Vea)  Descriptive analysis revealed that in Caucasians and Chinese children at 226-Hz, positive tail values were larger than negative tail values.   It also showed that Vea values were larger in males compared to females at both probe-tone frequencies and in both ethnicities. At 226-Hz probe tone frequency, results of the mixed model ANOVA revealed that the effect of gender [F (1, 165) = 5.69, p = 0.018] and tail [F (1, 165) = 265.92, p = 0.000] were significant. The Vea was significantly higher in the male group and significantly lower for the negative tail.   The interaction between tail and gender [F (1, 165) = 7.38, p = 0.007] was significant indicating that Vea tail values varied differently between males and females.  The interaction between tail, gender, and ethnicity [F (1, 165) = 7.77, p = 0.005] was also significant, indicating that male and female tail values vary differently between Caucasian and Chinese school-aged children.  However, the post hoc test did not reveal any significant findings between male and female in either ethnicity   at either tail.  53  3.2.2  Compensated Static Admittance (Ytm)  Descriptive analysis showed that overall, Ytm values obtained from negative compensation were larger compared to Ytm values obtained from positive compensation. Descriptive analysis also revealed that Ytm values were larger in males compared to females in both ethnicities.  The results demonstrated that Ytm values were larger in Caucasians compared to Chinese regardless of compensation method (+ or –) use. Results of mixed-model ANOVA for peak-compensated Ytm at 226-Hz revealed that only the main effect of ethnicity [F (1, 164) = 11.27, p = 0.000] was. Results of mixed-model ANOVA for compensated Ytm calculated from rectangular components revealed that at 226-Hz, the effects of ethnicity [F (1, 163) = 26.42, p = 0.000] and compensation [F (1, 163) = 31.93, p = 0.000] were significant indicating that Ytm was significantly larger in Caucasians than Chinese and by using negative compensation than positive compensation in school-aged children. The interaction between compensation (positive vs. negative tail) and component (Y, B, and G) was significant [F (2, 326) = 150.91, p = 0.000] indicating that different components may vary differently between different compensation methods.  The results also revealed that the interaction between component and ethnicity was significant [F (2, 326) = 9.24, p = 0.000] indicating that Caucasian and Chinese children may vary differently across different components.  After the G-G correction method was applied, the interactions remained significant. The post-hoc Tukey HSD test was performed, and the results showed that in both ethnicities, Btm and Gtm values were significantly smaller for positive compensation than for negative compensation.  Moreover, post-hoc results indicated that regardless of 54  the compensation method used, Caucasians had significantly larger Btm, Gtm, and Ytm values than their Chinese counterparts.  3.2.3 Tympanometric Width (TW)  Descriptive analysis showed that Chinese TW values were wider than Caucasian TW values. The mixed model ANOVA for TW showed that only the effect of ethnicity [F (1, 160) = 5.97, p = 0.015] was significant, indicating that the Chinese children had wider TW compared to the Caucasian children.  3.2.4 Tympanometric Peak Pressure (TPP)  Descriptive analysis and the mixed model ANOVA did not show variation between male and female children or between the two ethnicities.  3.3 Control group Tympanometric Data Using Multi-Frequency Tympanometry (MFT)  Mean, standard deviation (SD), and 90% range (5 th  to 95 th  percentiles) for Caucasians and Chinese children were calculated and summarized in Appendix A.  The ANOVA tables are summarized in the Appendix, and the data in boldface show significant findings.   55   3.3.1 Static Admittance (Ytm) from Rectangular Components (Btm, Gtm)  Descriptive analysis revealed that at all probe-tone frequencies ( 678-, and 1000- Hz) Ytm values are larger in Caucasian than in Chinese school-aged children, regardless of the compensation method used (+ or – compensation). At 678-Hz, mixed-model ANOVA for peak compensated Ytm revealed that the effects of ethnicity [F (1, 168) = 13.12, p = 0.000] and compensation method [F (1, 167) = 358.74, p = 0.000] were significant indicating that Ytm in Caucasian school-aged children was significantly larger than Chinese school-aged chilren and Ytm obtained from negative tail was significantly larger than Ytm obtained from positive tail. Moreover, the interaction between compensation, ethnicity, and gender [F (1, 168) = 5.43, p = 0.020] was significant, indicating that Caucasian and Chinese male and female children may vary differently between the two compensation methods.  In order to further investigate the significance of this interaction, a post-hoc Tukey HSD test was performed. The results revealed that Ytm values using negative compensation were significantly larger than Ytm values obtained from positive compensation as is shown in Figure 3.1 in both males and females and Caucasian and Chinese school-aged children.  Moreover, results also revealed that regardless of compensation method used, Ytm from Ya at 678- Hz did not vary significantly between Caucasian and Chinese children or between males and females. 56   Figure 3.1: Interaction between ethnicity (Caucasian versus Chinese), gender (male versus female), and compensation (positive compensation versus negative compensation) in school-aged children using 678-Hz probe-tone frequency.  Mixed-model ANOVA at 678-Hz for Ytm from rectangular components revealed that the effects of ethnicity [F (1, 162) = 13.83, p = 0.000] and compensation [F (1, 162) = 232.89, p = 0.000] were significant indicating that Ytm in Caucasian school-aged children was significantly larger than Ytm in Chinese school-aged chilren and Ytm obtained from negative tail was significantly larger than Ytm obtained from positive tail. There were significant interactions between compensation and gender [F (1, 162) = 7.17, p = 0.008], indicating that male and female children vary differently between positive and negative compensation; the interaction between compensation and component was also significant [F (2, 324) = 246.23, p = 0.000], indicating that the differences between positive and negative compensation were different across the components.  The interaction between component and gender [F (2, 324) = 5.38, p = 0.005] was significant, 57  indicating that male and female children vary differently across different components, and finally, the interaction between component and ethnicity [F (2, 324) = 4.74, p = 0.009] was significant, indicating that Caucasian and Chinese children may vary differently across different components.  Following G-G correction, the interactions remained significant. Post-hoc Tukey HSD test results indicated that the difference between male and female was not significant, regardless of which compensation was used.  The results also revealed that Btm and Ytm obtained from the negative compensation were significantly larger than Btm and Ytm obtained from the positive compensation.  Gtm values were not significantly different between positive and negative compensation as is shown in Figure 3.2.  The results also revealed that both genders had larger values for negative compensation than for positive compensation.  However, post-hoc results did not show a statistical difference between males and females across any individual components (Y, B, or G).  Results also indicated that Gtm and Ytm values were significantly larger in Caucasians than in Chinese; however, Btm differences between the two ethnic groups were not significant. 58   Figure 3.2: Variations of Btm (compensated susceptance), Gtm (compensated conductance), and Ytm (compensated admittance) values as a function of compensation (positive vs.  negative) method between Caucasian and Chinese school-aged children using 678-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval.  At 1000-Hz, mixed-model ANOVA for peak-compensated Ytm revealed that the effects of ethnicity [F (1, 163) = 3.98, p = 0.047], and compensation [F (1, 163) = 664.40, p = 0.000] were significant indicating that Ytm in Caucasian school-aged children was significantly larger than Ytm in Chinese school-aged chilren and Ytm obtained from negative compensation was significantly larger than Ytm obtained from positive compensation.  The interaction between compensation and gender [F (1, 163) = 4.26, p = 0.040] was significant, indicating that male and female Ytm values may vary differently between compensation methods.  The interaction between compensation and ethnicity [F (1, 163) = 5.98, p = 0.015] was also significant, indicating that Caucasian and Chinese 59  children may vary differently between compensation methods.  The post-hoc test did not reveal any significant findings between male and female in either ethnicity at either tail. The data from Ytm, Btm, and Gtm (rectangular components) at 1000-Hz was also analyzed using mixed-model ANOVA.  The results revealed that the main effects of ethnicity [F (1, 164) = 12.80, p = 0.000] and compensation [F (1, 164) = 200.47, p = 0.000] were significant indicating that Ytm in Caucasian school-aged children was significantly larger than Ytm in Chinese school-aged chilren and Ytm obtained from negative compensation was significantly larger than Ytm obtained from positive compensation..   The interaction between component and gender [F (2, 328) = 3.23, p = 0.040] was significant, indicating that male and female children may vary differently across components; the interaction between component and ethnicity [F (2, 328) = 5.85, p = 0.003] was significant, indicating that Caucasian and Chinese children may vary differently across components; and the interaction between compensation and component [F (2, 328) = 106.21, p = 0.000] was significant, indicating that positive and negative tail values may vary differently across components. After G-G correction, the interaction between component and gender was no longer significant; however, all other interactions remained significant. The post-hoc HSD test indicated that Gtm and Ytm values were significantly larger in Caucasians than in Chinese, while Btm values were not significantly different between the two ethnicities.  The test also revealed that all negatively compensated component values (Btm, Gtm, Ytm) were significantly larger than positively compensated component values.  60     3.3.2 Resonant Frequency (RF)     Descriptive analysis showed that regardless of recording method (SF vs. SP), females had higher RF compared to males.  Results also indicated that Chinese children had higher RFS compared to Caucasian children. Results of mixed-model ANOVA revealed that main effects of gender [F (1, 163) = 7.91, p = 0.005] and ethnicity [F (1, 163) = 7.24, p = 0.007] were significant.  The results indicated that RF was higher in females than males and in Chinese than Caucasians.  3.4 Paediatric vs. Adult Tympanometric Data Using Conventional 226-Hz Tympanometry  3.4.1 Equivalent Ear-Canal Volume (Vea)   Vea data from the Y tympanogram at 226-Hz (positive tail only) were analyzed, since estimation of Vea from positive tail is the most commonly used method in clinics. The mean, SD, and 90% range of Vea in children were compared with Vea values for adults in Table 3.3. 61  Table 3.3: Mean, standard deviation (SD), and 90% range for ear-canal volume (Vea) at +250 daPa in school-aged children (current study) and young adults (Shahnaz & Bork, 2008), (M: male; F: female; O: overall [combined male and female]).   Vea+ (+250 daPa) Mean (mmho) SD (mmho) 90% range (mmho) Current Study Caucasians (age = 5–7 years) M (n = 50) 0.89 0.21 0.60–1.20 F (n = 46)  0.76 0.14 0.60–1.00 O (n = 96) 0.83 0.19 0.60–1.20 Current Study Chinese (age = 5–7 years) M (n = 54) 0.79 0.16 0.60–1.04 F (n = 26) 0.75 0.12 0.60–0.90 O (n = 80) 0.78 0.15 0.60–1.00 Shahnaz and Bork (2008) Caucasians (age = 18–33 years) M (n = 24) 1.45 0.38 1.00–2.07 F (n = 23) 1.28 0.22 1.00–1.69 O (n = 47) 1.34 0.35 0.95–1.85 Shahnaz and Bork (2008) Chinese (age = 18–33 years) M (n = 24) 1.32 0.25 1.00–1.69 F (n = 26) 1.06 0.25 0.70–1.55 O (n = 50) 1.16 0.31 0.70–0.80  The mixed-model ANOVA at 226-Hz revealed that the main factors of ethnicity [F (1, 264) = 17.68, p = 0.000], gender [F (1, 264) = 29.00, p = 0.000] and age (child vs adult) [F (1, 264) = 305.65, p = 0.000] were significant indicating that ear-canal volume was significantly larger in Caucasians than Chinese, in males than females, and in adults than school-aged children.  The interaction between ethnicity and age [F (1, 264) = 5.40, p = 0.020] was significant, indicating that Caucasian and Chinese ear-canal volume varied differently between children and adults, and the interaction between gender and age [F (1, 264) = 5.67, p = 0.017] was significant, indicating that male and female ear- 62  canal volume varied differently between children and adults.  After the application of the G-G correction method, significant interactions remained significant.  A post-hoc Tukey HSD test was performed to further investigate the significant interactions.  The analysis showed that in both ethnicities, adults had significantly larger Vea compared to children.  Moreover, Caucasian adults had larger ear-canal volumes compared to Chinese adults.  There was not a significant Vea difference in children between Caucasian and Chinese groups.  Result of post-hoc testing also revealed that adult males had larger ear-canal volumes compared to adult females; however, there was not a significant Vea difference among male and female children.    3.4.2 Compensated Static Admittance (Ytm)  Ytm results from the Ya tympanogram at 226-Hz were explored for the effect of age, ethnicity, and gender, using positive tail compensation because this method is the most commonly used method in clinics.  Descriptive values for Adult and school-aged children are summarized in Table 3.4.  Descriptive statistical analysis showed that mean and 90% range of Ytm were larger in adults compared to children, leading to different cut-offs between adults and children.  Moreover, Caucasians had larger Ytm values compared to Chinese; therefore, Ytm cut offs were different between the two ethnicities.   63  Table 3.4: Mean, standard deviation (SD), and 90% range for static admittance (Ytm) from positive compensation at +250 daPa in school-aged children (current study) and young adults (Shahnaz & Davies, 2006), (M: male; F: female; O: overall [combined male and female]).  Ytm+ (+250 daPa) Mean (mmho) SD (mmho) 90% range (mmho) Current Study Caucasians (age = 5–7 years ) M (n = 50) 0.51 0.26 0.24–1.08 F (n = 46)  0.48 0.23 0.22–1.02 O (n = 96) 0.49 0.24 0.20–1.10 Current Study Chinese (age = 5–7 years) M (n = 54) 0.38 0.16 0.20–0.74 F (n = 26) 0.32 0.11 0.20–0.50 O (n = 80) 0.36 0.14 0.20–0.61 Shahnaz and Bork (2008) Caucasians (age = 18–33 years) M (n = 24) 0.79 0.33 0.30–1.38 F (n = 23) 0.75 0.41 0.30–1.70 O (n = 47) 0.77 0.37 0.30–1.60 Shahnaz and Bork (2008) Chinese (age = 18–33 years) M (n = 24) 0.58 0.35 0.20–1.31 F (n = 26) 0.40 0.24 0.17–1.10 O (n = 50) 0.47 0.29 0.20–1.30  The mixed-model ANOVA results for peak-compensated Ytm revealed significant effects of ethnicity [F (1, 261) = 37.09, p = 0.000], gender [F (1, 261) = 21.74, p = 0.000] and age (child vs. adult) [F (1, 261) = 49.53, p = 0.000] indicating that indicating that peak-compensated Ytm was significantly larger in Caucasians than Chinese, in males than females, and in adults than school-aged children.  Results also revealed significant interaction between gender and age [F (1, 261) = 9.73, p = 0.000], indicating that male and female static-admittance values varied differently between children and adults.  Tukey HSD analysis revealed that adult males had significantly 64  larger Ytm compared to adult females.  The results also showed that adult males had significantly larger values compared to male and female children.  65  Table 3.5: Mean, standard deviation (SD), and 90% range for static admittance (Ytm) from positive compensation at +250 daPa, using rectangular components at 226-Hz probe-tone frequency, in school-aged children (current study) and young adults (Shahnaz & Bork, 2008), (M: male; F: female; O: overall [combined male and female]). 226-Hz            Btm+              Gtm+              Ytm+ Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) Current Study Caucasians (age = 5–7 years) M (n = 50) 0.53 0.24 0.25–0.97 0.32 0.16 0.15–0.63 0.63 0.28 0.32–1.21 F (n = 46)  0.51 0.23 0.27–1.01 0.30 0.14 0.14–0.53 0.60 0.25 0.31–1.84 O (n = 96) 0.52 0.24 0.26–1.01 0.31 0.15 0.15–0.60 0.61 0.27 0.31–1.27 Current Study Chinese (age = 5–7 years) M (n = 54) 0.39 0.16 0.20–0.73 0.23 0.09 0.10–0.39 0.45 0.17 0.23–0.85 F (n = 26) 0.36 0.15 0.20–0.60 0.19 0.06 1.11–0.30 0.41 0.15 0.25–0.65 O (n = 80) 0.38 0.15 0.20–0.72 0.22 0.08 0.10–0.36 0.44 0.16 0.23–0.84 Shahnaz and Bork (2008) Caucasians (age = 18–33 years) M (n = 24) 0.81 0.39 0.33–1.26 0.46 0.23 0.21–0.89 0.94 0.45 0.40–1.54 F (n = 23) 0.65 0.22 0.31–1.08 0.37 0.11 0.23–0.55 0.74 0.26 0.36–1.23 O (n = 47) 0.73 0.32 0.33–1.22 0.42 0.18 0.21–0.81 0.83 0.37 0.37–1.46 Shahnaz and Bork (2008) Chinese (age = 18–33 years) M (n = 24) 0.60 0.27 0.26–1.06 0.39 0.19 0.14–0.64 0.73 0.33 0.29–1.18 F (n = 26) 0.34 0.16 0.14–0.64 0.22 0.11 0.10–0.41 0.41 0.19 0.17–0.76 M (n = 50) 0.46 0.25 0.16–0.90 0.29 0.17 0.10–0.56 0.55 0.30 0.19–1.08  M (n = 24) 0.60 0.27 0.26–1.06 0.39 0.19 0.14–0.64 0.73 0.33 0.29–1.18 F (n = 26) 0.34 0.16 0.14–0.64 0.22 0.11 0.10–0.41 0.41 0.19 0.17–0.76 M (n = 50) 0.46 0.25 0.16–0.90 0.29 0.17 0.10–0.56 0.55 0.30 0.19–1.08 66  The mixed-model ANOVA for Ytm from rectangular components revealed that using 226-Hz probe-tone frequency, factors of ethnicity [F (1, 262) = 45.40, p = 0.000], gender [F (1, 262) = 19.04, p = 0.000] and age (child vs. adult); F (1, 262) = 13.43, p = 0.000) were significant indicating that indicating that Ytm was significantly larger in Caucasians than Chinese, in males than females, and in adults than school-aged children.. The interaction between gender and age [F (1, 262) = 10.38, p = 0.001] was significant, indicating that children and adults varied differently by gender, and the interaction between component and ethnicity [F (2, 524) = 30.50, p = 0.000] was significant, indicating that Caucasian and Chinese children varied differently across different components.  The interaction between component and gender [F (2, 524) = 7.45, p = 0.000] was significant, indicating that male and female children varied differently across different components, and the interaction between component and age [F (2, 524) = 13.90, p = 0.000] was also significant, indicating that adults and children varied differently across different components.  Finally, the interaction between component, ethnicity, and age [F (2, 524) = 4.65, p = 0.009] was significant, indicating that children and adults varied differently between ethnicities and across different components, and the interaction between component, gender, and age [F (2, 524) = 7.25, p = 0.000] was significant, indicating that component values varied differently between genders and between children and adults.  After G-G correction was performed, the interactions remained significant. A post-hoc Tukey HSD test was performed. Post-hoc results indicated that Caucasians have significantly larger component values than their Chinese counterparts as is shown in Figure 3.3.  The results indicated that, in the Caucasian group, Ytm and Btm 67  were significantly larger in adults compared to in children.  However, in the Chinese group, there was not a significant difference between children and adults across component values.  The results also revealed that the difference between children and adults’ component values in the female group was not significantly different.    However, Ytm and Btm values were significantly larger in adults compared to children in the male group as is shown in Figure 3.4.  Figure 3.3: Interaction between Btm (compensated susceptance), Gtm (compensated conductance), and Ytm (compensated admittance), ethnicity (Caucasian versus Chinese) and age (adults versus children) using 226-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval.   68   Figure 3.4: Interaction between Btm (compensated susceptance), Gtm (compensated conductance), and Ytm (compensated admittance), gender (male versus female) and age (adults versus children) using 226-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval.               3.4.3 Tympanometric Width  Mean, SD, and 90% range of TW were compared between the two age groups. Descriptive analysis showed that in the Caucasian group children had wider TW values compared to adults.  In the Chinese group there was an overlap between the adult and child TW data.  Overall, Chinese TW values were wider than Caucasian TW values (Table 3.6).    69  Table 3.6: Mean, standard deviation (SD), and 90% range for TW in Caucasian and Chinese young adults (Shahnaz & Davies, 2006) and school-aged children (M: male; F: female; O: overall [combined male and female]).  TW ( daPa) Mean  SD  90% range Current Study- Caucasians (age = 5–7 years) M (n = 50) 111.96 32.46 62.50–153.75 F (n = 46)  104.20 25.72 75.00–149.25 O (n = 96) 108.17 29.46 67.25–65.00 Current Study- Chinese (age = 5–7 years) M (n = 54) 120.94 32.96 75.00–167.00 F (n = 26) 118.80 27.66 82.00–173.00 O (n = 80) 120.26 31.20 75.00–170.00 Shahnaz and Bork (2008) Caucasians (age = 18–33 years) M (n = 24) 78.75 17.83 55.75–109.25 F (n = 23) 92.00 27 61.00–133.00 O (n = 47) 85.00 25.23 57.50–124.00 Shahnaz and Bork (2008) Chinese (age = 18–33 years) M (n = 24) 107.50 71.85 41.50–247.25 F (n = 26) 127.69 48.67 70.00–217.50 O (n = 50) 117.85 61.45 49.53–60.00   Group analysis using mixed-model ANOVA for TW revealed that there were significant effects of age [F (1, 257) = 6.73, p = 0.009] and ethnicity [F (1, 257) = 20.98, p = 0.000] indicating that TW was wider in children than adults and in Chinese than Caucasians.  The interaction between age and ethnicity [F (1, 257) = 4.50, p = 0.034] was significant, indicating that TW in Caucasian and Chinese groups varies differently between children and adults.  The interaction between age and gender [F (1, 257) = 5.14, p = 0.024] was also significant, indicating that TW in children and adults varied differently among males and females. The Tukey HSD test indicated that in the female group there was not a significant difference between children’s and adults’ TW values; however, in the male group, 70  children had significantly larger TW values compared to adults.  Moreover, Caucasian adults’ TW values were significantly wider than those of Caucasian children, while in the Chinese group, TW was not significantly different between children and adults.  Finally, Chinese had wider TW than Caucasians in the adult group only.   3.4.4 Tympanometric Peak Pressure (TPP)  The adult mean, SD, and 90% range data are summarized in Table 3.7. Comparing adult data to the data obtained from children in the current study revealed that TPP values are more positive in adults than in children and that as a result, the cut-offs are different between the two age groups. Table 3.7: Mean, standard deviation (SD), and 90% range for TPP in Caucasian and Chinese young adults (Shahnaz & Davies, 2006) and school-aged children (M: male; F: female; O: overall [combined male and female]).  TPP Mean (mmho) SD (mmho) 90% range (mmho) Current Study Caucasians (age = 5–7 years) M (n = 50) −17.24 36.63 -80.00–27.00 F (n = 46)  −18.26 29.61 −81.25–10.00 O (n = 96) −17.74 33.24 −86.5–15.00 Current Study Chinese (age = 5–7 years) M (n = 54) −19.34 34.40 −76.00–11.00 F (n = 26) −7.12 33.83 −48.75–22.50 O (n = 80) −15.32 34.49 −65.50–20.50 Shahnaz and Bork (2008) Caucasians (age = 18–33 years) M (n = 24) 0.63 5.58 −22.00–14.0 F (n = 23) 1.00 9.00 −24.00–5.00 O (n = 47) 0.00 8.07 −16.75–5.00 71  Shahnaz and Bork (2008) Chinese (age = 18–33 years) M (n = 24) 0.73 15.3 −37.80–28.0 F (n = 26) −4.04 7.49 −15.00–5.00 O (n = 50) −4.29 10.78 −16.75–15.00  The mixed-model ANOVA revealed a significant effect of age [F (1, 263) = 14.41, p = 0.000] indicating that adults had significantly more positive TPP values than children.  3.5 Paediatric vs. Adult Tympanometric Data using Multi-Frequency Tympanometry (MFT) 3.5.1 Ytm from Rectangular Components (Btm and Gtm)  Ytm obtained from rectangular components (Btm and Gtm) for the positive tail (positive compensation) was compared between children and adults at 678-, and 1000-Hz probe-tone frequencies.  Overall, descriptive statistics revealed larger Ytm, Btm, and Gtm values in Caucasians compared to Chinese at the these probe-tone frequencies.  These differences were larger for Ytm and smaller for Gtm.  Ytm, Btm, and Gtm were larger for adults compared to school-aged children, regardless of ethnicity as it is summarized in Tables 3.8, and 3.9).  72  Table 3.8: Mean, standard deviation (SD), and 90% range for static admittance (Ytm) from positive compensation at +250 daPa, using rectangular components at 678-Hz probe-tone frequency, in school-aged children (current study) and young adults (Shahnaz & Bork, 2008), (M: male; F: female; O: overall [combined male and female]).  678-Hz            Btm+              Gtm+              Ytm+ Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) Current Study Caucasians (age = 5–7 years) M (n = 50) 0.62 0.81 −0.33–1.89 1.79 1.04 0.71–3.13 2.00 1.15 0.79–3.50 F (n = 46)  0.86 0.59 −0.04–1.79 1.69 1.28 0.66–3.71 1.99 1.26 0.83–4.00 O (n = 96) 0.74 0.72 −0.29–1.88 1.74 1.16 0.65–3.62 2.00 1.20 0.77–3.96 Current Study Chinese (age = 5–7 years) M (n = 54) 0.51 0.44 0.03–1.30 1.38 0.95 0.56–3.54 1.53 0.96 0.73–3.89 F (n = 26) 0.62 0.31 0.10–1.07 1.08 0.49 0.56–1.98 1.27 0.51 0.72–2.13 O (n = 80) 0.55 0.40 0.05–1.22 1.28 0.84 0.55–2.69 1.44 0.85 0.72–2.97 Shahnaz and Bork (2008) Caucasians (age = 18–33 years) M (n = 24) 0.57 0.67 −0.30–1.32 1.93 0.94 0.69–3.36 2.12 0.95 0.86–3.89 F (n = 23) 0.65 0.49 −0.03–1.57 1.59 0.76 0.60–2.57 1.76 0.81 0.62–2.74 O (n = 47) 0.61 0.58 −0.13–1.55 1.75 0.86 0.65–3.28 1.93 0.89 0.80–3.75 Shahnaz and Bork (2008) Chinese (age = 18–33 years)  M (n = 24) 0.42 0.69 −0.31–1.49 1.92 1.05 0.64–3.63 2.07 1.07 0.71–3.64 F (n = 26) 0.37 0.43 −0.30–1.19 0.99 0.57 0.32–1.96 1.11 0.61 0.38–2.27 M (n = 50) 0.39 0.55 −0.32–1.37 1.40 0.93 0.35–3.08 1.57 0.97 0.41–3.27 73  Table 3.9: Mean, standard deviation (SD), and 90% range for static admittance (Ytm) from positive compensation at +250 daPa, using rectangular components at 1000-Hz probe-tone frequency, in school-aged children (current study) and young adults (Shahnaz & Bork, 2008), (M: male; F: female; O: overall [combined male and female]).   1000-Hz            Btm+              Gtm+              Ytm+ Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) Current Study Caucasians (age = 5–7 years ) M (n = 50) −0.76 1.20 −3.16–0.61 3.08 1.77 1.14–6.57 3.31 1.91 1.16–6.98 F (n = 46)  −0.20 1.52 −2.49–1.13 2.75 1.62 1.09–4.78 3.14 1.62 1.21–6.27 O (n = 96) −0.49 1.39 −3.00–0.99 2.92 1.70 1.14–5.93 3.23 1.77 1.17–6.79 Current Study Chinese (age = 5–7 years) M (n = 54) −0.60 1.39 −3.37–0.76 2.02 1.41 0.71–5.29 2.43 1.56 0.88–6.39 F (n = 26) 0.05 1.11 −0.71–1.19 2.24 1.24 0.85–4.19 2.42 1.37 0.93–4.44 O (n = 80) −0.38 1.34 −3.20–0.97 2.09 1.36 0.78–4.52 2.43 1.49 0.89–6.23 Shahnaz and Bork (2008) Caucasians (age = 18–33 years) M (n = 24) −0.54 1.64 −3.70–1.33 2.95 1.47 0.91–5.25 3.34 1.60 1.30–5.36 F (n = 23) −0.41 1.07 −2.27-1.19 3.10 1.68 1.12–6.26 3.16 1.85 0.95–6.81 O (n = 47) −0.47 1.35 −3.52–1.33 3.03 1.57 0.94–6.24 3.25 1.72 1.15–6.76 Shahnaz and Bork (2008) Chinese (age = 18–33 years) M (n = 24) −1.04 1.21 −2.72–0.44 2.24 1.53 0.73–5.45 2.87 1.55 1.12–5.70 F (n = 26) −0.26 0.60 −1.23–0.34 1.53 1.09 0.39–3.48 1.62 1.14 0.39–3.59 M (n = 50) −0.61 0.99 −2.34-0.41 1.92 1.36 0.43–4.55 2.18 1.47 0.44–5.49 74   The mixed-model ANOVA at 678-Hz for Ytm from rectangular components revealed that factors of ethnicity [F (1, 260) = 14.37, p = 0.000] and gender [F (1, 260) = 6.41, p = 0.011] were significant indicating that Ytm was larger in Caucasians than in Chinese and in males than in females.  The interaction between component and ethnicity [F (2, 520) = 3.72, p = 0.024] was significant, indicating that Caucasian and Chinese children varied differently across different components. The interaction between component and gender [F (2, 520) = 14.62, p = 0.000] was significant indicating that male and female children varied differently across different components; the interaction between component and age [F (2, 520) = 3.75, p = 0.023] was also significant, indicating that adults and children varied differently across different components. Post-hoc results indicated that Ytm values were significantly larger in Caucasians than Chinese.  The results did not show a significant variation of components between the genders or the age groups. The mixed-model ANOVA for Ytm from rectangular components revealed that using a 1000-Hz probe-tone frequency, the factor of ethnicity [F (1, 262) = 24.81, p = 0.000] was significant indicating that Caucasians had larger Ytm than Chinese.  The interaction between component and gender [F (2, 524) = 7.19, p = 0.000] was significant, indicating that male and female children varied differently across different components, and the interaction between component and ethnicity [F (2, 524) = 8.52, p = 0.000] was also significant, indicating that Caucasians and Chinese varied differently across different components.  After G-G correction, significant interactions remained significant. 75  Post-hoc testing revealed that Caucasians had significantly larger Ytm and Gtm compared to their Chinese counterparts.  Post-hoc testing did not show a significant difference between the genders.  3.5.2 Resonant Frequency (RF)  RF data were explored for the effect of age in this study; mean, SD, and 90% range data for adults are summarized in Table 3.10.  Comparing the data between adults and children revealed that Caucasian adults have higher mean RF values than Caucasian children and the cut-offs are different between the two age groups.  However, Chinese children have higher RF values compared to Chinese adults, and as a result the cut-offs are different between the two age groups (Table 3.10).  Moreover, in both ethnicities, female mean RF values are higher than male mean RF values, except for Caucasian adults, where male mean RF values are higher than female mean RF values. 76   Table 3.10: Mean, SD, and 90% range of RF for Caucasian and Chinese adults, adapted from Shahnaz and Bork (2008).  (M: male; F: female; O: overall [combined male and female]).  Mixed-model ANOVA on RF revealed that the effect of gender [F (1, 268) = 8.55, p = 0.003] was significant, and the interactions between ethnicity and gender [F (1, RF—SF (Hz) +compensation  Mean (Hz)  SD (Hz) 90% Range Current Study Caucasians (age = 5−7 years) GSI-Tympstar M (n = 50) 834 169 500−1050 F (n = 46)  932 217 663−700 O (n = 96) 881 199 575−1250 Current Study Chinese (age = 5−7 years) GSI-Tympstar M (n = 54) 910 262 600−1400 F (n = 26) 1006 291 613−1438 O (n = 80) 942 274 600−1400 Shahnaz and Bork (2008) Caucasians (age = 18−33 years) GSI-Tympstar M (n = 24) 911 175 642−1120 F (n = 23) 907 108 719−1108 O (n = 47) 893 182 670−1120 Shahnaz and Bork (2008) Chinese (age = 18−33 years) GSI-Tympstar M (n = 24) 927 258 642−1250 F (n = 26) 947 114 758−1090 O (n = 50) 921 221 630−710 77  268) = 4.21, p = 0.041], and ethnicity, gender, and age [F (1, 268) = 3.97, p = 0.047] were also significant.  The results indicated that Caucasian and Chinese male and female resonant frequency values varied differently between children and adults.  After G-G correction, the interactions remained significant.  Post-hoc testing revealed that Chinese females (adults and children) had higher resonant frequencies than Caucasian male children as is shown in Figure 3.5.   Figure 3.5:  Interaction between gender (male versus female) and ethnicity (Caucasian versus Chinese) between children and adults for resonant frequency.  Vertical bars denote 0.95 confidence interval.  78    3.6  Diseased Group Tympanometric Data Analyzed by Middle-Ear Condition Using Conventional 226-Hz Tympanometry   The diseased group data were analyzed and compared to the control group data. Ethnic-specific test-performance analyses (Chinese only and Caucasian only) were performed in addition to analyses where data from all ethnic groups were combined. Although normative paediatric data reveal a significant effect of ethnicity for most tympanometric variables, using ethnic-specific normative data did not improve the test performance of any tympanometric variables in identifying MEE.  To perform the group analysis, the data from all ethnicities and genders were combined and a mixed-model ANOVA was conducted to discover the differences between the control group and the diseased group.  The ANOVA tables are summarized in the Appendix A, and the data in boldface show significant findings.  3.6.1 Equivalent Ear-Canal Volume (Vea)   The mixed-model ANOVA for Vea revealed that the interaction between tail and middle-ear condition [F (4, 266) = 33.22, p = 0.000] was significant, indicating that the Vea values (positive and negative) varied differently across middle-ear conditions.  After G-G correction was performed, the interaction remained significant. A Tukey HSD test was performed to further investigate the significant interaction. The results as is demonstrated in Figure 3.6 indicated that Vea obtained from the positive tail was significantly different from Vea obtained from the negative tail in the normal 79  group only; in all other middle-ear conditions, the factor of tail was not significant.  In the normal group, Vea obtained from the positive tail was significantly larger than Vea obtained from the negative tail.   Figure 3.6: Variation in ear-canal volume (Vea) obtained from positive and negative tails as a function of middle-ear condition using a 226-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval.  Moreover, using the positive tail, Vea values were not significantly different between the normal group, the group with mild negative pressure, the group with severe negative pressure, and the OTL confirmed group.  Vea value was significantly larger in the not OTL confirmed group than in the other groups.  However, using the negative tail, Vea values were significantly smaller in the normal group, the group with mild negative pressure, and the group with severe negative pressure than in the not OTL confirmed and OTL confirmed groups. 80  3.6.2 Peak-Compensated Static Admittance (Ytm)  At 226-Hz, mixed-model ANOVA for peak-compensated Ytm revealed that only the main effect of middle-ear condition [F (4, 265) = 12.71, p = 0.000] was significant, indicating that Ytm values varied differently between middle-ear conditions. The mixed-model ANOVA for Ytm from rectangular components using 226-Hz probe-tone frequency also showed that the main effect of middle-ear condition [F (4, 259) = 20.12, p = 0.000] was significant indicating that Ytm values varied differently between middle-ear conditions.  There was a significant interaction between compensation methods and middle-ear condition [F (4, 259) = 9.34, p = 0.000], indicating that Ytm varied differently between middle-ear conditions across compensation methods. Interaction between component (Ytm, Btm, Gtm) and middle-ear condition [F (8, 518) = 15.29, p = 0.000] was also significant, indicating that component values varied differently between different middle-ear conditions, and the interaction between component and compensation [F (2, 518) = 17.34, p = 0.000] was significant, indicating that component values varied differently between positive and negative compensation methods.  Finally, the interaction between compensation, component, and middle-ear condition [F (8, 518) = 5.14, p = 0.000] was also significant, indicating that component values varied differently between compensation methods and across middle-ear conditions.  After G-G correction was performed, all interactions remained significant. A post-hoc Tukey test was performed for the highest order of interactions. Results revealed that Btm obtained from negative compensation was significantly larger compared to the Btm obtained from positive compensation in the normal group.  In other groups, Btm did not vary significantly between the two compensation methods.  Gtm 81  obtained from positive compensation was significantly larger compared to the Gtm obtained from negative compensation in the normal group and the group with severe negative pressure.  In other groups Gtm did not vary significantly different between the two compensation methods.  Ytm obtained from negative compensation was significantly larger compared to the Ytm obtained from positive compensation in normal group.  In other groups, Ytm did not vary significantly between the two compensation methods. Results from positive tail analysis revealed that Btm and Gtm decreased significantly from the group with severe negative pressure to the non–OTL confirmed; however, there was not a significant difference between the Btm and Gtm values among other middle-ear conditions as is shown in Figure 3.7.  Overall, Btm decreased significantly by a ratio of 3.7, and Gtm decreased significantly by a ratio of 2.8 from the normal group to the not OTL confirmed group.  Ytm values decreased significantly from the group with mild negative pressure to the group with severe negative pressure, and from the group with severe negative pressure to the not OTL confirmed group.  Ytm values decreased significantly from the normal group to the not OTL confirmed group, by a ratio of 2.4. Negative-tail results (Figure 3.7) showed that Btm and Ytm values decreased significantly from the group with mild negative pressure to the group with severe negative pressure and from the group with severe negative pressure to the not OTL confirmed group.  The differences between other middle-ear conditions were not significant.  Btm and Ytm values decreased by the ratios of 5.7 and 4.2 from the normal group to the OTL confirmed group.  Gtm values decreased significantly from the group 82  with mild negative pressure to the group with severe negative pressure and also decreased significantly, by a ratio of 2.75, from the normal group to the not OTL confirmed group.     Figure 3.7: Interaction between Btm (compensated susceptance), Gtm (compensated conductance), Ytm (compensated admittance), compensation (positive versus negative), and middle-ear condition using 226- Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval.   3.6.3 Tympanometric Width (TW)   TW values were obtained from the Y tympanogram at 226-Hz.  The mixed-model ANOVA revealed that the effect of middle-ear condition [F (4, 255) = 275.88, p = 0.000] was significant.  Overall, the results showed that TW widens as the middle-ear pathology 83  progresses towards MEE, by a ratio of 3.2 from the normal group to not OTL confirmed group.  3.7 Diseased Group Tympanometric Data Analyzed by Middle-Ear Condition Using Multi-Frequency tympanometry (MFT)   3.7.1 Ytm Obtained from Rectangular Components  The peak-compensated Ytm and compensated Ytm from rectangular components data were analyzed at 678-, and 1000-Hz.  At 678-Hz, mixed-model ANOVA for peak- compensated Ytm revealed that the main effects of middle-ear condition [F (4, 268) = 17.16, p = 0.000] and compensation [F (4, 268) = 52.47, p = 0.000] were significant. The interaction between compensation and middle-ear condition [F (4, 268) = 22.24, p = 0.000] was also significant, indicating that Ytm from Ya varied differently between the compensation methods (positive vs. negative) across middle-ear conditions.  After G-G correction was performed, the interaction remained significant. The Tukey HSD test revealed that only in the normal group and the group with mild negative pressure was Ytm obtained from negative compensation was significantly larger than Ytm obtained from positive compensation as is demonftrated in Figure 3.8.  In other groups, there was not a significant difference between Ytm obtained from positive compensation and Ytm obtained from negative compensation.  The post-hoc results also indicated that Ytm obtained from negative compensation decreased significantly from one group to the next group (as the middle-ear condition progressed towards MEE); however, Ytm was not significantly different between the OTL confirmed and not OTL confirmed groups.  Moreover, the results indicated that Ytm obtained from positive 84  compensation was significantly smaller in the not OTL confirmed group compared to the other groups; however, it did not vary significantly among other middle-ear conditions (see Figure 3.8).    Figure 3.8: Variation of static admittance (Ytm from Ya) obtained from positive and negative compensations as a function of middle-ear condition using a 678-Hz probe-tone frequency.  Vertical bars denote an 0.95 confidence interval.   At 678-Hz the mixed-model ANOVA for Ytm from rectangular components revealed that the main factors of middle-ear condition [F (4, 260) = 20.34, p = 0.000] and compensation [F (1, 260) = 19.38, p = 0.000] were significant.  There was a significant interaction between compensation and middle-ear condition [F (4, 260) = 15.77, p = 0.000], indicating that Ytm varied differently between compensation methods across 85  different middle-ear conditions.  Interaction between component (Ytm, Btm, Gtm), and middle-ear condition [F (8, 520) = 3.25, p = 0.001] was also significant, indicating that Ytm, Btm, and Gtm varied differently between different middle-ear conditions; furthermore, interaction between component and compensation [F (2, 520) = 129.03, p = 0.000] was significant, indicating that component values varied differently between compensation methods.  Finally, interaction between compensation, component, and middle-ear condition [F (8, 520) = 4.26, p = 0.000] was significant, indicating that component values varied differently between compensation methods across middle-ear conditions.  After G-G correction was performed, all interactions remained significant.  Post-hoc examination confirmed that the Btm values obtained from positive compensation were significantly smaller than the Btm values obtained from negative compensation in all groups of middle-ear condition.  There was no significant difference between Gtm values obtained from positive vs. negative compensation across the middle- ear condition groups, except for the group with severe negative pressure, where Gtm values were larger using positive compensation than using negative compensation. Moreover, there was no significant difference between the Ytm values obtained from positive and negative compensation across the middle-ear condition groups except for the normal group, where Ytm values were larger using negative compensation than using positive compensation. Post-hoc analysis revealed that Btm values were smaller than Gtm and Ytm values for positive compensation as demonstrated in Figure 3.9.  Btm decreased significantly from the group with mild negative pressure to the group with severe negative pressure and from the group with severe negative pressure to the not OTL 86  confirmed group.  Btm values also decreased, with a ratio of 3.6, from the normal group to the not OTL confirmed group.  Gtm and Ytm values decreased significantly from the normal group to the not OTL confirmed group.  There was a significant decrease from the group with mild negative pressure to the group with severe negative pressure and another from the group with severe negative pressure to the not OTL confirmed group.  However, the differences between the other middle-ear condition groups were not significant.  Gtm and Ytm decreased by a ratio of 6.2 and 4.3 from the normal group to the not–OTL confirmed.  Using negative compensation, Btm, Gtm, and Ytm values decreased significantly from the normal group to the not OTL confirmed group, by ratios of 5.12, 5.5 and 6.1, respectively.  The three component values decreased significantly from one group to the next group; however, Btm, Gtm, and Ytm did not vary significantly differently between the not OTL confirmed and OTL confirmed groups (see Figure 3.9).  87    Figure 3.9: Interaction between Btm (compensated susceptance), Gtm (compensated conductance), Ytm (compensated admittance), compensation (positive versus negative), and middle-ear condition using a 678- Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval.   At 1000-Hz, mixed-model ANOVA for peak-compensated Ytm revealed that the main effects of middle-ear condition [F (4, 262) = 5.64, p = 0.000] and compensation [F (1, 262) = 411.76, p = 0.000] were significant.  The interaction between compensation and middle-ear condition [F (4, 262) = 92.25, p = 0.000] was also significant, indicating that Ytm from Ya varied differently between the compensation methods (positive vs. negative) across middle-ear conditions.  After the G-G correction method was performed, the interaction remained significant. The post-hoc Tukey HSD test revealed that in the normal group, the group with mild negative pressure, and the OTL confirmed group, Ytm obtained from negative 88  compensation was significantly larger compared to Ytm obtained from positive compensation as is shown in Figure 3.10.  In the group with severe negative pressure there was not a significant difference between Ytm obtained from positive compensation and Ytm obtained from negative compensation.  The post-hoc results indicated that Ytm from negative compensation decreased significantly from normal group to OTL confirmed and  not OTL confirmed groups as is shown in Figure 3.11.  However, Ytm from positive compensation was significantly larger in OTL confirmed group compared to the normal group.  Figure 3.10: Variation in static admittance (Ytm from Ya) obtained from positive and negative compensations as a function of middle-ear condition using a 1000-Hz probe-tone frequency.  Vertical bars denote 0.95confidence interval.   89   Figure 3.11: Variation of Btm (compensated susceptance), Gtm (compensated conductance), and Ytm (compensated admittance) as a function of middle-ear condition using 1000-Hz probe-tone frequency. Vertical bars denote 0.95 confidence interval.   At 1000-Hz, the mixed-model ANOVA for Ytm from rectangular components revealed that the main effects of middle-ear condition [F (4, 263) = 13.42, p = 0.000] and compensation [F (1, 263) = 25.20, p = 0.000] were significant.  There was a significant interaction between compensation and middle-ear condition [F (4, 263) = 17.26, p = 0.000], indicating that Ytm varied differently between compensation methods across components (Ytm, Btm, Gtm).  Interaction between component and middle-ear condition [F (8, 526) = 9.60, p = 0.000] was also significant, indicating that component values varied differently across middle-ear conditions.  Finally, interaction between component and compensation [F (2, 256) = 55.59, p = 0.000] was also significant, indicating that 90  component values varied differently between compensation methods.  Following G-G correction, significant interactions remained significant.    Figure 3.12: Interaction between Btm (compensated susceptance), Gtm (compensated conductance), Ytm (compensated admittance), compensation (positive versus negative) and middle-ear condition, using a 1000-Hz probe-tone frequency.  Vertical bars denote 0.95 confidence interval.  Post-hoc results indicated that values obtained from negative compensation were larger than values obtained from positive compensation.  Post-hoc results also confirmed that Btm values obtained from positive compensation were significantly smaller than Btm values obtained from negative compensation.  Gtm and Ytm values were larger using positive compensation than negative compensation.  The results indicated that only in the normal group and the group with mild negative pressure, values obtained from negative compensation were significantly larger than positively compensated values.  However, in 91  the other groups, there was not a significant difference between positively and negatively compensated values.  Moreover, the results revealed that Btm and Ytm values did not vary significantly across middle-ear conditions; however, Gtm values decreased significantly from the group with severe negative pressure to the not OTL confirmed and OTL confirmed groups as is shown in Figure 3.12. 3.7.2 Resonant Frequency (RF)   In order to obtain RF, both SF and SP recording methods were used.  Mixed- model ANOVA results showed that the main factor of middle-ear condition [F (4, 254) = 63.73, p = 0.000] was significant as is shown in Figure 3.13.  Post hoc results indicated that RF was significantly different among the normal group, the group with mild negative pressure, the group with severe negative pressure, the not OTL confirmed group, and the OTL confirmed group.  RF values decreased significantly from the group with severe negative pressure to the not OTL confirmed group, with a ratio of 3.6.     92    Figure 3.13: Variation of resonant frequency (RF) as a function of middle-ear condition.  Vertical bars denote 0.95confidence interval.    3.8 Test Performance of Tympanometric Parameters in Distinguishing Ears with MEE from Normal Ears        Area under ROC (AUROC) plots, along with the corresponding 95% CI and a pairwise comparison between tympanometric variables were performed automatically using MedCalc statistical software (MedCalc Software).  Data from children of all ethnicities were combined for ROC analyses.  Analysis was performed for all variables using 226-, 678-, and 1000-Hz probe-tone frequencies, TW, and RF. Using ROC analysis, a comparison was performed between Ytm values obtained from the Ya tympanogram and Ytm values obtained from rectangular components to 93  investigate their test performance in distinguishing normal ears from ears with MEE (see Table 3.26).  The results revealed that using positive compensation, at a 226-Hz probe- tone frequency there was not a statistically significant difference between Ytm from Ya and Ytm from rectangular components.  However, using negative compensation at 226- Hz, Ytm from Ya was superior compared to Ytm from rectangular components, indicating that Ytm from Ya had a better test performance in distinguishing normal ears from ears with MEE.  At 678-Hz probe-tone frequency, there was not a statistically significant difference between Ytm obtained from rectangular components compared to Ytm obtained from Ya under either compensation method.  Results indicate that at 678- Hz, Ytm from rectangular components and Ytm from Ya had the same test performance in distinguishing normal ears from ears with MEE.  Finally, using negative compensation at a 1000-Hz probe-tone frequency, Ytm from rectangular components had a better test performance in distinguishing normal ears from ears with MEE than Ytm from Ya as is shown in Table 3.11.     94    Table 3.11: AUROC, sensitivity, specificity, and 95% CI for variables analysed using ROC.  ( AUROC: Area under ROC; SE: Sensitivity; SP: Specificity; 95% CI: 95% confidence interval; Ytm-YaP: positively compensated static admittance obtained from Ya tympanogram; Ytm-YaN: negatively compensated static admittance obtained from Ya tympanogram; Ytm-BGP: positively compensated static admittance obtained from rectangular components; Ytm-BGN: negatively compensated static admittance obtained from rectangular components).   AUROC SE SP 95% CI Ytm-YaP (from Y tymp—226-Hz) 0.89 78 88 0.84-0.93 Ytm-YaN (from Y tymp—226-Hz) 0.95 83 97 0.91-0.97 Ytm-BGP-226-Hz 0.84 76 79 0.80-0.90 Ytm-BGN-226-Hz 0.92 84 94 0.88-0.96 Ytm-YaP (from Y tymp—678-Hz) 0.90 82 85 0.85-0.93 Ytm-YaN (from Y tymp—678-Hz) 0.96 90 97 0.92-0.98 Ytm-BGP—678-Hz 0.92 82 98 0.88-0.95 Ytm-BGN—678-Hz 0.98 92 98 0.95-0.99 Ytm-YaP (from Y tymp—1000-Hz) 0.83 92 66 0.77-0.88 Ytm-YaN (from Y tymp—1000-Hz) 0.56 59 63 0.49-0.62 Ytm-BGP—1-kHz 0.86 80 99 0.81-0.90 Ytm-BGN—1-kHz 0.90 88 98 0.86-0.94 RF-SF 0.96 94 97 0.92-0.98 RF-SP 0.96 94 99 0.92-0.98 TW 0.96 93 99 0.93-0.98  Using ROC analysis, a comparison was also performed between Ytm values obtained from the positive compensation and Ytm values obtained from negative 95  compensation to investigate their test performance in distinguishing normal ears from ears with MEE.  Results revealed that Ytm (form both Ya and rectangular components) was larger using negative compensation than Ytm from positive compensation at 226-, 678-, and 1000-Hz probe-tone frequencies.  Since Ytm obtained from negative compensation at 678-Hz had the largest AUROC (sensitivity of 92% and specificity of 98%), it was chosen for further analysis as is shown in Figure 3.14.  The dual plot in Figure 3.15 shows the distribution of negatively compensated Ytm at 678-Hz between normal ears and ears with MEE.  The horizontal line (maximum of the Youden index) shows the cut off for best sensitivity and specificity.    Figure 3.14: Compares performance of Ytm_BGN_678 (static admittance obtained from susceptance and conductance components using negative compensation) with Ytm_BGP_678 (static admittance obtained from susceptance and conductance components using positive compensation).  96    Figure 3.15: Distribution of Ytm_BGN_678 (static admittance obtained from susceptance and conductance components using negative compensation) between a group of normal middle-ears, and a group of ear with MEE.    Figure 3.16: Compares performance of Ytm_BGN_678 (static admittance obtained from susceptance and conductance components using negative compensation) with RF (resonant frequency obtained from SF and SP methods) and TW (tympanometric width).  Ytm at 678-Hz obtained from rectangular components was statistically compared with Ytm from Ya at 226-Hz, Ytm from rectangular components at 1000-Hz, RF, and 97  TW.  AUROC plots and corresponding 95% CI, along with pairwise comparison of AUROC between Ytm obtained from negative compensation and other variables, is summarized in Table 3.12.  The analysis showed that Ytm from negative compensation at 678-Hz was superior to Ytm from positive compensation at 678-Hz.  It also showed that Ytm from negative compensation at 678-Hz was superior to Ytm obtained from Ya at 226-Hz and Ytm from rectangular components at 1000-Hz.  Pairwise comparison of the ROC plots revealed that Ytm from rectangular components obtained from negative tail at 678-Hz probe-tone frequency, RF, and TW were not statistically different and have essentially similar performances in distinguishing normal middle-ears from ears with MEE.            98  Table 3.12: Summary of comparison between different tympanometric tests.  (AUROC: Area under ROC; 95% CI: 95% confidence interval; Ytm-YaP: positively compensated static admittance obtained from automatic static admittance tympanogram; Ytm-YaN: negatively compensated static admittance obtained from automatic static admittance tympanogram; Ytm-BGP: positively compensated static admittance obtained from rectangular components; Ytm-BGN: negatively compensated static admittance obtained from rectangular components).   Difference between AUROCs p 95% CI Ytm-BGN-226-Hz vs. Ytm-YaN-226-Hz  0.02 0.18 −0.01–0.05 Ytm-BGP-226-Hz vs. Ytm-YaP-226-Hz  0.05 0.01 0.01–0.09 Ytm-BGN-678-Hz vs. Ytm-YaN-678-Hz  0.02 0.08 0.00–0.03 Ytm-BGP-678-Hz vs. Ytm-YaP-678-Hz  0.02 0.21 −0.01–0.06 Ytm-BGN-1-kHz vs. Ytm-YaN-1-kHz  0.35 0.00 0.25–0.44 Ytm-BGP-1-kHz vs. Ytm-YaP-1-kHz  0.03 0.43 −0.04–0.09 Ytm-YaP-226-Hz vs. Ytm-YaN-226-Hz  0.56 0.00 0.03–0.09 Ytm-BGN-226-Hz vs. Ytm-BGP-226-Hz 0.08 0.00 0.04–0.12 Ytm-YaP-678-Hz vs. Ytm-YaN-678-Hz  0.60 0.00 0.02–0.01 Ytm-BGN-678 Hz vs. Ytm-BGP-678 Hz 0.05 0.00 0.02–0.08 Ytm-YaP-1-kHz vs. Ytm-YaN-1-kHz  0.26 0.00 0.18–0.35 Ytm-BGN-1-kHz vs. Ytm-BGP-1-kHz 0.04 0.04 0.00–0.08 Ytm-BGN-678 Hz vs. Ytm-YaP-226 Hz 0.89 0.00 0.04–0.12 Ytm-BGN-678 Hz vs. Ytm-YaN-226 Hz 0.03 0.03 0.00–0.05 Ytm-BGN-678 Hz vs. Ytm-BGN-1-kHz  0.72 0.00 0.04–0.10 Ytm-BGN-678 Hz vs. Ytm-BGP-1kHz  0.11 0.00 0.07–0.16 Ytm-BGN-678 Hz vs. RF-SF 0.02 0.38 −0.01–0.04 Ytm-BGN-678 Hz vs. RF-SP 0.02 0.34 −0.01–0.04 Ytm-BGN-678 Hz vs. TW 0.02 0.54 −0.03–0.06  99  The foregoing analysis was performed based on the combined data from the OTL confirmed group and the not OTL confirmed group.  Since the not OTL confirmed group was determined using tympanometric protocols stated earlier in the methods section, this group would not truly reflect the performance of the tympanometric variables.  For further analysis, the not OTL confirmed group was excluded from analysis and the OTL confirmed group, along with the normal group, was analyzed using Ytm obtained from rectangular components at 678-Hz, RF, and TW to evaluate performance of acoustic immittance variables in ears with otologically documented MEE (OTL confirmed).  Table 3.13: AUROC, sensitivity, specificity, and 95% CI for variables in the group consisting of normal ears as well as OTL confirmed ears, using ROC (AUROC: Area under ROC; 95% CI: 95% confidence interval; SE: Sensitivity; SP: Specificity;  Ytm- YaP: positively compensated static admittance obtained from automatic static admittance tympanogram; Ytm-YaN: negatively compensated static admittance obtained from automatic static admittance tympanogram; Ytm-BGP: positively compensated static admittance obtained from rectangular components; Ytm-BGN: negatively compensated static admittance obtained from rectangular components).   Normal and OTL confirmed  AUROC SE SP 95% CI Ytm from YaP—678-Hz 0.91 81 95 0.86–0.95 Ytm from YaN—678-Hz 0.97 96 97 0.94–0.99 Ytm-BGP-678-Hz 0.95 85 98 0.90–0.97 Ytm-BGN-678-Hz 0.98 93 98 0.96–0.99 RF-SF 0.99 100 97 0.97–0.99 RF-SP 0.99 100 99 0.97–0.99 TW 100 100 99 0.98–1.00  100  Consistent with previous findings with all MEE (OTL confirmed  and Not OTL confirmed), AUROC comparison of the ROC plots revealed that Ytm from 678-Hz, TW, and RF had better overall test performance in distinguishing normal middle-ears from ears with MEE compared to other variables.  The results showed that there was not statistically significant difference between the two previous analyses.              101  4 Discussion  In this study, 176 healthy ears were tested in the control group, and 93 ears with varying degrees of middle-ear pathology were tested in the diseased group.   The primary goal of the study was 1) to investigate whether standard and multi-frequency tympanometric parameters differ significantly among Caucasian and Chinese male and female children and also to compare these tympanometric parameters between children with healthy middle-ears and those with varying degrees of middle-ear pathology and 2) to provide age- and ethnicity-specific normative data to use as a guideline in clinical practice.  The goals were met by testing multiple tympanometric parameters using conventional as well as MFT.  In this chapter the following will be discussed: (i) findings from the study (ii) potential sources to explore observed differences (iii) clinical implications of the findings and suggested normative data for clinical practice, and (iv) limitations of the study and potential areas for further research will be discussed.  4.1 Comparison of Results  4.1.1 Tympanometric Shapes   The distribution of Vanhuyse patterns at 226-Hz was mostly 1B1G for normal 6 year-old children, across both ethnicities.  This pattern is consistent with what we expect from a normal adult ear.  Based on the Vanhuyse model, the 1B1G pattern is most likely to appear when the middle-ear is stiffness dominated.  As has been shown previously by Cai (2010), the distribution of Vanhuyse patterns at 226-Hz was exclusively 3B1G (44%) and 3B3G (56%) during the first month, with no occurrences of 1B1G.  However, by the sixth month, her study showed that complex patterns diminished and almost all (98%) 102  tympanograms showed a 1B1G pattern.  In a study of newborn intensive care–unit (NICU) and three-week-old infants, Shahnaz et al. (2008) reported a high proportion of 5B3G (55%), 3B3G (24%), and 3B1G (12%) patterns, with a very small proportion of 1B1G (3%) in their NICU infants at a standard 226-Hz probe-tone frequency.  They also reported that there were no occurrences of 5B3G in their three-week-old infants, and the proportion of 1B1G patterns was much higher (13%).  Calandruccio et al. (2006) performed a study on a group of zero-to-two-year-old infants as well as a group of adults. Using the 226-Hz probe-tone frequency, they found that, as infants become older, the proportion of 1B1G tympanograms increases.  Comparing the current study to Shahnaz et al. (2008) shows that in young babies there is a high proportion of multi-peak tympanograms, but as the present study shows, in five-to-seven-year-old children there is a great proportion (100% in Caucasian males and 98% in Caucasian females) of single- peak tympanograms.  This is similar to the findings of Calandruccio et al. (2006) for adults.  Comparing the proportion of different Vanhuyse patterns among these studies with current study’s findings indicates that there may be maturational effects.  This conclusion is based on the fact that as age increases, proportion of single-peak tympanograms also increases.  Vanhuyse et al. (1975) used a 678-Hz probe-tone frequency to characterize B/G patterns in normal-hearing adults; correspondingly, a 678-Hz probe-tone frequency was also used to classify B/G patterns in normal-hearing children in the current study. Compared with a 226-Hz probe-tone frequency, at 678-Hz a greater variety of B/G patterns were observed.  The predominant pattern was still 1B1G (e.g. 78% in Caucasian females); however, other patterns, such as 3B1G and 3B3G also occured.  The proportion 103  of different B/G tympanometric patterns was essentially similar between the two ethnicities; however, Chinese female subjects had a larger proportion (100%) of 1B1G tympanometric patterns compared to Caucasians (87.5%).  A higher percentage of 1B1G patterns in the Chinese female group is an indication of a stiffness- dominated system ( > 45).  This finding may be related to the different characteristics of the Chinese middle- ear and specifically is likely due to the differences in the size of the ear canal and the middle-ear.  It has been shown that body size correlates to the size of the ear canal and middle-ear (Wan & Wong, 2002).  Therefore, Chinese middle-ears may be stiffer (due to smaller size) resulting in a less complex (1B1G) tympanometric shape at this frequency compared to Caucasians.  Calandruccio et al. (2006) found a higher proportion of 1B1G (more than 90%) than other tymp patterns in all age groups (including adults) using a 630-Hz probe-tone frequency as compared to using 678-Hz probe-tone frequency.  This difference may be due to the different probe-tones used (630 vs. 678-Hz), or it may be related to the age difference between the subjects in the two studies. The results of the current study for children at 678-Hz are comparable to the model proposed by Vanhuyse et al. (1975) for adults.  Vanhuyse et al. reported four normal B/G tympanometric patterns in adults, recorded at 678-Hz; these were 1B1G, 3B1G, 3B3G, and 5B3G.  The findings of the present study in children are consistent with the findings of Vanhuyse et al. (1975) in adults.  The four tympanometric patterns observed by Vanhuyse et al. (1975) in adults were present in the current study in 6 year- old children.  Shahnaz (2001) also reported on the distribution of Vanhuyse patterns in adult subjects.  Consistent with the findings of the current study in school-aged children, Shahnaz (2001) reported that in adults Vanhuyse patterns change in an orderly way from 104  1B1G to 5B3G as probe-tone frequency is increased. At 678-Hz, Shahnaz found zero 3B3G patterns in adults.  In the present study, at 678-Hz the distribution of 3B3G was almost 2% in school-aged children.  Therefore, there was not a large difference in distribution of 3B3G patterns between the present study and Shahnaz (2001).  At a 226- Hz probe-tone frequency, consistent with the findings of Shahnaz (2001) for adults, the current study found 1B1G patterns to be a dominant pattern. As in Vanhuyse et al. (1975), the distance between the two outer most peaks (in daPa) was calculated for susceptance tympanograms at a 678-Hz probe-tone frequency for 3B1G, 3B3G and 5B3G patterns.  The results of the current study indicate that the maximum number of peaks did not exceed 3B3G in either ethnicity and that only one child had the 5B3G pattern.  The two outermost maxima on the conductance tympanogram were always within the two outermost maxima on the susceptance tympanogram, which is consistent with the findings of Vanhuyse et al. (1975) for adults. These finding can also be compared to the findings of Van de Heyning et al. (1982) which quantified the number of extrema and the pressure interval between the outermost extrema to define abnormal notching in adults.  In the present study, at 678-Hz only one normal ear with a 5B pattern was found, and, therefore, in contrast to adults at 678-Hz, it is very unlikely that in school-aged children the maximum number of peaks exceeds 3B3G.  The high cut-off value of the 90% range of the pressure interval between the outermost extrema from 3B patterns in the present study (160 daPa for Caucasians and 137 daPa  for Chinese) was wider than the norms that were proposed by Van de Heyning et al. (1982) ( > 75 daPa ).  This difference between the studies may be due to the age difference between the subject groups. 105  Using the 1000-Hz probe-tone frequency, the proportion of 1B1G patterns decreased dramatically, while the proportion of other multi-peak patterns greatly increased.  The proportion of 3B1G patterns was dramatically higher than that of 1B1G patterns, except for the Chinese female group, where the proportion of both patterns was the same (45.83%).  As mentioned earlier, this may be due to the stiffer middle-ears of Chinese female subjects as a result of the size of the middle-ear, which could potentially be smaller in Chinese females (smaller volume offers lower compliance, which might contribute to this increased stiffness).  Overall, at 1000-Hz in Caucasians, the dominant pattern was 3B1G.  Calandruccio et al. (2006) found similar results for their Caucasian adult participants.   They reported that infants and toddlers tend to have equal distribution between 1B1G and 3B1G patterns, whereas adults have predominately 3B1G (80%) tympanograms.   Shahnaz et al. (2008) and Cai (2010) also reported more 1B1G patterns using 1000-Hz in their infants.  Consistent with the previous findings of Calandruccio et al. (2006) and Shahnaz (2000) in adults, the proportion of multi-peak patterns in the children in the current study increased as probe-tone frequency increased; this may be due to greater contribution of mass elements in school-aged children by increasing probe- tone frequency.  Figure 4.1 shows that in adults as we increase the probe-tone frequency, the middle-ear system becomes more mass dominated and more multi-peak patterns appear (Margolis and Shanks, 1991).  As mentioned earlier, there are not many studies evaluating the shape of tympanograms in pre-school and school-aged children at higher probe-tone frequencies. As a result, there are not enough data to compare the distribution of tympanogram shapes in this population.  Overall, the results of the current study are close to findings of other 106  studies in the adult population, indicating that Vanhuyse tympanometric patterns in school-aged children become more adult-like by the age of five to seven years. Distribution of Vanhuyse patterns was almost the same between Caucasian and Chinese children.  However, at higher probe-tone frequencies in Chinese female children distribution of single-peak patterns was still higher than multi-peak patterns which may also be contributed to the more stiffness dominated middle-ear system of Chinese female children.  The distance between the maxima was wider in Chinese children compared to Caucasian children which was expected due to smaller Ytm in Chinese children.  4.1.2 Equivalent Ear-Canal Volume (Vea)  Vea refers to the volume of the air between the probe tip and the tympanic membrane.  Factors such as the depth of insertion of the probe tip, the dimensions of the ear canal, and the amount of volume occupied by cerumen may greatly affect ear-canal volume (Lilly & Shanks, 1981).  In the current study, ears with cerumen were refered for cerumen management before testing.  Mean and 90% range of Vea and some other tympanometric values are compared to those given in other published studies in Table 4.1 below.  ASHA normative values for school-aged children are based on Nozza et al. (1992).  Vea values were calculated from positive and negative tails in the current study; however, since the effect of tail was not significant in the analysis and most studies used the positive tail in their procedure (for better test-retest reliability), only the positive tail values will be discussed.  The procedures (e.g. depth of probe-tip insertion) used in different studies less likely affect Vea estimation.   Location of probe-tipe was the same 107  among all participants.  The discrepancies observed within the current study are most likely due to the age range, sample size, and potentially due to ethnic differences.  Effect of ethnicity: The mean Vea value obtained from the Ya tympanogram for Caucasians in this study was 0.83 (mmho) at 226-Hz using the positive tail.  Mean Vea value in this study for Caucasians was 0.71 (mmho) at 226-Hz using the negative tail.  In the present study, the low cut offs were used if the probe tip was blocked by cerumen or the ear-canal wall, while the high cut-offs were used to distinguish eardrum perforation or patency of the pressure-equalization (PE) tube.  Vea is larger at the positive tail since positive pressure pushes the eardrum towards the middle-ear and the volume of the ear- canal increases.  Applying negative pressure has the opposite effect.  Negative pressure pulls the eardrum towards the ear-canal and decreases the volume of the ear canal. Moreover, the acoustic resistance of the middle-ear system is higher for negative than for positive pressure, and, therefore, middle-ear impedance is higher when negative pressure is introduced to the ear canal (Van Camp et al., 1986; Shanks & Lilly, 1981).  At 226 Hz, the Vea value is close to what Haapaniemi (1996) found in his sample of Caucasian school-aged children (0.80 cc) using the positive tail.  The age range in Haapaniemi (1996) was six to 15 years old.  Nozza et al. (1992), in their study on 3-to-16-year-old Caucasian children, reported a mean value of 0.90 cc for Vea (see Table 4.1).  The low cut-off values of the 90% range of Vea from Nozza et al. (1992) are the same as those (0.60 mmho) of the current study for Caucasian Vea; however, Nozza et al.’s high cut-off values are higher (1.40 cc) than those of Caucasians in the current study (1.20 mmho). The mild discrepancy between these values and those in the present study can be related to the different age groups used in each study and/or to the depth of probe-tip insertion, 108  since deeper insertion results in a smaller Vea value.  The ear-canal volume increases with age (see e.g. Haapaniemi, 1996); therefore, it is to be expected that larger mean values would be seen in Nozza et al. (1992) compared to the current study because the age range in their study was higher compared to the current study. The mean Vea value for Chinese school-aged children in the current study was 0.78 (mmho) at 226-Hz using the positive tail, and 0.68 (mmho) using the negative tail. The differences observed between the two tails are consistent with those in the Caucasian groups.  At 226-Hz, mean Vea and 90% range of the Chinese school-aged children are similar to the Vea values of Driscoll et al, (2008), who reported a mean Vea of 0.85 cm 3 and a 90% range of 0.61 to 1.07 cm 3  for Chinese children ranging between six and 13 years in age.  The current study’s mean Vea value was also compared with Wong et al. (2008), who studied a sample of 278 Chinese school-aged children between six and 15 years of age.  Wong et al. divided their sample into subgroups of ages 6–9, 10–12, and 13–15.  They reported that their mean Vea for the youngest age group (6 to 9 years) was 0.98 cm 3 .  The low cut-off values of the 90% range (0.60–1.50 cm3) of Vea from Wong et al. are the same as the Vea low cut-off values of the current study; however, their high cut-off values are higher than those of the current study.  The pressure point was the same for both studies (+200 daPa).  The difference between the values may be due to a different age range and/or depth of probe tip insertion between the studies. The results from the present study indicated that Caucasian ear-canal volume was larger compared to Chinese ear-canal volume in school-aged children, which may be related to the overall smaller body size of Chinese school-aged children compared to Caucasian school-aged children.  This finding is consistent with the findings of Shahnaz 109  and Bork (2008) in adults and also with the findings of Wong et al. (2008) in Chinese children. Effect of Gender: The Vea data from Ya in the current study showed that male school-aged children had larger ear-canal volumes compared to female school-aged children, which may be related to the smaller body size of females.  Also, consistent with adult data by Shahnaz and Davies (2006), in the present study, the gender difference was larger in Caucasian subjects and smaller in Chinese subjects.  Wong et al (2008) stated that because the gender difference was not large (0.08 cm 3 ), they did not recommend gender-specific norms for Chinese school-aged children.  The findings of the current study are also in agreement with Haapaniemi (1996) that reported no gender difference in ear-canal volume among Caucasian subjects.  4.1.3 Static Admittance (Ytm)  Clinically, static admittance has been used to differentiate between normal middle-ears and middle-ears with different pathological conditions.  For example, abnormally low static admittance values represent high-impedance pathologies such as otosclerosis, and abnormally high static admittance values represent low-impedance pathology such as ossicular discontinuity.  Ytm values in the current study were calculated from positive and negative tails.  However, for comparison with other studies only, values obtained from positive tail (positive compensation) will be discussed, since most studies have used positive compensation due to better test-retest reliability (Margolis & Goycoolea, 1993).  In addition to the compensation method used, pump speed directly affects static admittance in older children and adults.  In adults, it has been 110  shown that faster pump speeds can increase Ytm values (Margolis & Heller, 1987). Subject age also plays an important role in Ytm discrepancies observed between the current study and other studies.  In Shahnaz et al. (2008), admittance magnitude using a 1000-Hz probe-tone frequency was compared between three-week-old infants and adults. Shahnaz et al. found that Ytm was significantly higher for adults than for infants.  Holte et al. (1991) proposed that developmental expansion of the middle-ear cavity has been a contributing factor to increase in admittance magnitude with age. The current study is the only study to have calculated Ytm from positive and negative compensations using both Ya (baseline compensation) and rectangular components at 226-, 678-, and 1000-Hz probe-tone frequencies in school-aged children. Since, Ytm is clinically an important diagnostic tool; further research using different probe-tone frequencies is required.  4.1.3.1 Peak Compensated Static Admittance   Effect of ethnicity:  Mean Ytm value in this study for Caucasians was 0.49 (mmho) at 226-Hz, 1.49 (mmho) at 678-Hz, and 1.25 (mmho) at 1000-Hz using positive compensation and 0.60 (mmho) at 226-Hz, 2.13 (mmho) at 678-Hz, and 2.44 (mmho) at 1000-Hz using negative compensation.  High and low cut-off values of 90% range for this value are close to what Haapaniemi (1996) found in his sample of Caucasian school- aged children (0.50 mmho).  Nozza et al. (1992) reported a mean value of 0.78 mmho for Ytm using 226-Hz probe-tone frequency.  Their low and high cut-off values of Ytm are higher than those in the current study.  The discrepancy between these values can be related to the age of the studied population.  Static admittance increases with age 111  (Haapaniemi, 1996; Calandruccio et al., 2006; Shahnaz et al., 2008), therefore, Nozza et al.’s reported mean value should be larger compared to the current study’s mean value, as they had a wider and older age range.  At 678-Hz and 1000-Hz, there are no published data in school-aged children to which to compare the results of this study. The mean Ytm value in this study for Chinese school-aged children was 0.36 (mmho) at 226-Hz, 1.00 (mmho) at 678-Hz, and 1.01 (mmho) at 1000-Hz using positive compensation, and 0.38 (mmho) at 226-Hz, 1.59 (mmho) at 678-Hz, and 1.92 (mmho) at 1000-Hz using negative compensation.  Compared to the Ytm values of Caucasians in the current study, all Chinese Ytm values are lower, indicating a significant effect of ethnicity.  At a 226-Hz probe-tone frequency, the findings of the current study’s mean Ytm are comparable with those of Wong et al. (2008)’s six-to-nine-year-old age group. Wong et al. reported that the mean Ytm for this group was 0.42 cm 3 .  The low cut-off Ytm value from Wong et al. (2008) is the same as that of the current study; however, their high cut-off value is higher than the high cut-off value of the current study.  The present study’s Ytm findings are also close to the Ytm values of Driscoll et al. (2008), who reported a mean Ytm of 0.45 cm 3 for Chinese children ranging between six and 13 years of age.  Again, in both studies, the difference between the values may be due to the wider, older age range used in the Driscoll study.  At 1000-Hz, there was no published data in Chinese school-aged children to compare the results with. Results from the present study indicated that effect of ethnicity was significant at 226-Hz, 678-Hz, and 1000-Hz probe-tone frequencies.  In the present study, Caucasian Ytm was larger than Chinese Ytm at all three probe-tone frequencies.  Caucasian static admittance from other studies (Haapaniemi, 1996; Hanks & Rose, 1993; Nozza et al., 112  1992) was also larger compared to Chinese static admittance in school-aged children (from the current study), which may be due to the overall smaller body size of Chinese school-aged children compared to Caucasian school-aged children.  This difference between Caucasian and Chinese Ytm (Caucasian Ytm > Chinese Ytm) data at 226-Hz has also been reported by Wong et al. (2008); however, there are no studies on school-aged children to compare 678 and 1000-Hz data for Ytm. Ytm was also calculated from rectangular components in the current study. Results indicated that effect of ethnicity was significant at 226-Hz, 678-Hz, and 1000-Hz probe-tone frequencies.  Results also showed that Ytm from rectangular components was larger in Caucasian than in Chinese school-aged children, which is consistent with Ytm from Ya results (in the current study).  At 226-Hz, the difference was due to larger susceptance and conductance components in Caucasian children; however, at 678- and 1000-Hz, it was due to larger conductance values in Caucasian children. Effect of Gender: At 226-Hz, the Ytm data from Ya showed that Ytm for Caucasian and Chinese school-aged children did not vary between male and female. Wong et al. (2008) and Haapaniemi (1996) also reported no significant effect of gender in their results on Chinese and Caucasian school-aged children.  In the current study, the effect of gender was also not significant at 678- and 1000-Hz probe-tone frequencies. There are no other studies on the effect of gender at 678 and 1000-Hz to compare the results with. At 226-, 678-, and 1000-Hz probe-tone frequencies, Ytm data from rectangular components in the current study showed that Ytm for Caucasian and Chinese school-aged children did not vary between male and female.  The current study is the first study 113  reporting gender-specific Ytm from rectangular components in Caucasian and Chinese school-aged children.  Evaluation of Ba (susceptance) and Ga (conductance) at higher frequencies is especially important because it offers information on the relative contribution of mass and stiffness to the admittance tympanogram, which helps in identification of the probable cause of middle-ear disorder (Wiley & Fowler, 1997). Moreover, computing static admittance from rectangular components is mathematically more accurate, especially at higher frequencies.  As mentioned earlier, at low frequencies (e.g. 226-Hz), the admittance vector is very close to susceptance, which means that the difference between Ytm from Ya and Ytm from rectangular components is negligible. However, at higher frequencies (e.g., 678-Hz and 1000-Hz), the difference between admittance vector and susceptance becomes larger, and estimation of Ytm from rectangular components is more accurate (Shanks and Shohet, 2010).  114  Table 4.1: Tympanometric results in selected studies in paediatric Caucasian and Chinese populations at standard 226 Hz probe-tone frequency for variables of Vea (ear-canal volume); Ytm (compensated static admittance), TW: (tympanometric width), N: (number of ears), and TPP: (tympanometric peak pressure from admittance tympanogram). 226-Hz Age (years) N   Ethnicity Variable Vea Ytm+ TW TPP Current study:                          Mean                               90% range 5–7 96 Caucasian 0.83 0.60–1.20 0.49 0.20–1.10 108.17 67.25–152.75 −17.74 −86.50–15.00 Current study:                          Mean                               90% range 5–7 80 Chinese 0.78 0.60–1.00 0.36 0.20–0.61 120.26 75.00–170 −15.32 −65.50–20.25 Wong et al. (2008):                    Mean                                   90% range 6–15     556 Chinese 0.98 0.60–1.50 0.42 0.20–0.70 118 70–205 −9.8 −95–30 Driscoll et al. (2008):                 Mean                                      90% range 6–13 154 subjects Chinese 0.85 0.61–1.07 0.45 0.22–0.73 103 57–144 −12 -62–22 Li et al. (2006):                          Mean                              90% range 6–13 538 Chinese 1.03 0.68–1.46 0.58 0.26–1.13 112 62–156 −25 -85–+10 Haapaniemi (1996):                 Mean                                       90% range 6–9 476 Caucasian 0.40–0.90  0.20–1.00      −110–15 Hanks and Rose (1993):              Mean                                          90% range 6–15 316 Caucasian 1.00 0.60–1.50 0.70 0.30–1.50  −7 −65–20 Nozza et al. (1992):                    Mean                                        90% range 3–16 130 Caucasian 0.90 0.60–1.40 0.78 0.40–1.39 104 60–168 −34 -207–15 Shahnaz and Bork (2008):          Mean                                          90% range 18–34 47 subjects Caucasian 1.00 95–1.85 0.77 0.30–1.60  85 57.50–124.00 0.00 −16.75–5.00  Shahnaz and Bork (2008):          Mean                                           90% range 18–34 50 subjects Chinese 1.16 0.70–0.8 0.47 0.20–1.30 117.85 49.53–60.00 −4.29 −16.75–15.00   115  Table 4.2: Procedures used in selected tympanometric studies in paediatric Caucasian and Chinese populations 226-Hz Age (years) N (ears)  Ethnicity Variable Machine Pump speed (daPa/s) Pressure range Compensation Current study  5–7 96 Caucasian GSI- Tympstar  200  +200 to −400  +200, −400 Current study  5–7 80 Chinese GSI- Tympstar  200   +200 to −400  +200, −400 Wong et al. (2008)  6–15 278 subjects Chinese GSI-33  600/200  +200 to −400   +200 Driscoll et al. (2008)   6–13 154 Chinese Madsen Zodiac 901  400  +200 to −400   +200  Li et al. (2006)   6–13 269 Chinese Madsen Zodiac 901  400  +200 to −400  +200  Haapaniemi (1996)  6–9 476 subjects Caucasian   600/200   +200 to −400    +200   Hanks and Rose (1993)  6–15 316 subjects Caucasian GSI-33  50  +200 to −400 +200  Nozza et al. (1992)  3–16 130 Caucasian       GSI-33 600/200  +400 to −600 +300  Shahnaz and Bork (2008)  18–34 47 Caucasian GSI- Tympstar   200      Shahnaz and Bork (2008)  18–34 50 Chinese GSI- Tympstar  200       116  4.1.4 Tympanometric Width (TW)  Tympanometric width is the sharpness of the tympanometric peak, which is clinically used for identification of middle-ear pathologies. Different middle-ear pathologies may widen or sharpen the TW.  For example, middle-ear effusion can widen TW (Nozza et al., 1994); however, an ossicular fixation may decrease TW (Shahnaz & Polka, 1997). Effect of Ethnicity: Mean TW value in the present study for Caucasians was 108 daPa and for Chinese was 120 daPa.  Analysis of TW values from peak Ytm in the current study indicated significant (p < 0.05) ethnic differences between the values.  As mentioned in the introduction section, the TW is calculated from peak compensated admittance (Ytm) value; therefore, coming down from the peak by a smaller number should result in a narrower TW, while coming down by a bigger number should result in a wider TW.  However, the current study showed that although in Chinese children Ytm was smaller compared with Caucasians, the Chinese children’s TW was wider compared with Caucasians.  Consistent with the findings of previous studies (e.g. Koebsell & Margolis, 1986; Wong et al., 2008), the current study shows that there is a moderate correlation between TW and Ytm.  Different systematic and anatomical characteristics (e.g: body mass index ) of Caucasian and Chinese children’s ear systems may account for different TW values in these populations. Nozza et al. (1994) reported a mean value of 216 daPa in their study on Caucasian children.  Their 90% range was 84 to 394 daPa, which is higher than the 90% range from the current study.  The mean (118 daPa) and high cut-off value (90% range) of Wong et al. (2008) are lower and higher than the mean and high cut-off value (90% range) of the 117  current study.  This discrepancy is expected since the current study’s age range is younger than that of Wong et al.  Chinese school-aged children had wider TW values compared to Caucasian school-aged children.  Some studies, such as Wong et al. (2008), suggest that peak Ytm and TW are related to each other because TW is calculated from the Ytm tympanogram.  In the present study, we had a reduced peak Ytm for the Chinese group; therefore, it is not unexpected to have a wider TW for this group.  Wong et al. (2008) stated that the TW difference between Caucasian and Chinese was 10 to 20 daPa. Effect of Gender: No significant effect of gender was found in the current study for TW values, which is consistent with the findings of Wong et al. (2008) in Chinese school-aged children.  4.1.5 Tympanometric Peak Pressure (TPP)  TPP is clinically used to indicate middle-ear pressure.  In the presence of middle- ear pathologies such as MEE, middle-ear pressure is abnormally negative (e.g. −250 dPa), and in the presence of pathologies such as acute otitis media, middle-ear pressure is abnormally positive (Ostergard & Carter, 1981).  Because middle-ear pressure fluctuates greatly in children, it is no longer considered as an indication of middle-ear pathology (Margolis & Heller, 1987; Nozza et al., 1994; Paradise et al., 1976).  Presence of high negative pressure in children, however, may be a sign of MEE and should be monitored accordingly (Antonio et al., 2002). Effect of Ethnicity: Mean TPP values were −18 daPa in Caucasian and −15 daPa in Chinese school-aged children.  Nozza et al. (1992) reported a mean value of −34 daPa in Caucasian children.  The high cut-off value of their 90% range is similar to that of the 118  present study; however, their low cut-off value was smaller than the low cut-offs of the current study.  The results of the present study did not reveal a significant TPP difference between Caucasian and Chinese school-aged children.  The findings are in agreement with the findings of Wong et al. (2008) among Chinese school-aged children. Effect of Gender: No gender differences were found for the effect of TPP in the current study.  This finding is consistent with the findings of Wong et al. (2008) in Chinese school-aged children.  4.1.6 Resonant Frequency (RF)  Resonant frequency is applied clinically to diagnose middle-ear pathologies. Research has shown that RF has a high test performance in reflecting middle-ear pathologies such as MEE (Abou-Elhamd et al., 2006) and ossicular chain fixation (Shahnaz & Polka, 1997; Shahnaz et al. 2009).  RF is abnormally low in low-impedance middle-ear pathologies (e.g. ossicular chain discontinuity) and abnormally high in high- impedance pathologies (e.g. ossicular chain fixation). Effect of Ethnicity: Mean RF data from the present study is 881-Hz in Caucasian and 942-Hz in Chinese school-aged children using the SF recording method.  Using the SP recording method, mean RF data from the present study is 886-Hz in Caucasians and 979-Hz in Chinese school-aged children.  Consistent with the findings of Shahnaz and Davies (2006), the effect of ethnicity was significant for RF in this study.  The results showed that Chinese school-aged children had significantly higher resonant frequencies compared to Caucasian school-aged children.  This finding may be due to the potentially smaller middle-ear cavity in the Chinese children, or it may be due to a stiffer middle-ear 119  system in the Chinese children.  Hanks and Rose (1993) had the closest age range to the present study.  They investigated RF in nine-to-15-year-old Caucasian school-aged children (see Table 4.4).  Some of the observed discrepancies between the two studies are likely due to the wider age range or larger sample size used by Hanks and Rose.  The low cut-off of the 90% range (in Caucasians) from the current study is quite similar to that in Hanks and Rose (1993), and the high cut-off is noticeably higher in Hanks and Rose (1993).  The age range in Hanks and Rose (1993) was nine to 15 years old, whereas it was five to seven years old in the current study.  Therefore, considering the fact that younger children have smaller ears and resonant frequency is higher in ears with smaller size, resonant frequency should have been higher in the current study compared to Hanks and Rose (1993).  To the best of our knowledge, there is no other published data on the effect of ethnicity on RF in school-aged children. Effect of Gender:  Consistent with the findings of Shahnaz and Davies (2006) the effect of gender was also significant for RF values.  The results of this study showed that females had higher mean RF values compared to males in both ethnicities (see results). This finding is likely due to the smaller size of the ear canal or middle-ear in the females compared to the males, since a smaller volume results in a higher middle-ear resonant frequency.  However, Hanks and Rose (1993) did not find any significant effects of gender in their study, although their sample size was larger than the current sample size, therefore, more research is required to see wether gender differences for RF are present in school-aged children or not. Effect of recording method: There was no significant effect of recording method in the present study.  However, Shahnaz and Polka (1997) and Margolis and Goycoolea, 120  Table 4.3: Descriptive RF values obtained by sweep-frequency (SF) and sweep-pressure (SP) recording methods, between the current study and Hanks and Rose (1993).  RF Age (year) Ethnicity SF SP Mean SD 90% range Mean SD 90% range Current study (n = 96) 5–7 Caucasian 881  199 575–1250 886 181 650–1200 Current study (n = 80) 5–7 Chinese 942 247 600–1400 979 267 600–1400 Current study (n = 146) 5–7 Combined 908 237 600–1330 928 229 625–1350 Hanks and Rose (1993) (n = 90) 6–15 Caucasian 1003  216  650–1400 --  -- --  121  (1993) reported a significant difference between recording methods, with higher estimates of resonant frequency observed for the SF than for the SP recording method in adults.  Discrepancy between the studies here is likely due to different age ranges.  4.2 Variation of Tympanometric Values with Age 4.2.1 Equivalent Ear-Canal Volume 4.2.1.1 Equivalent Ear-Canal Volume from Ya    The current study showed that the gender difference is more pronounced in adults than in children.  The appearance of gender differences at older ages may be due to Vea changes (e.g. size) that occur after maturation due to further changes in body-size indices (Shahnaz and Davies, 2006).  To date there has been no published literature on the effect of maturation on tympanometric variables between Chinese and Caucasians.  Comparison between the current study’s results and Shahnaz and Bork’s (2008) study on adults clearly shows the maturational changes in ear-canal volume.  The results of the present study showed that Vea increased from 0.83 mmho in children to 1.00 mmho  in adults in Caucasians and from 0.78 mmho in children to 1.16 mmho in adults in Chinese.  Haapaniemi (1996) found that as the age of Caucasian children increased from six to 15 years, their Vea increased from 0.65 to 1.00 mmho.  Finding the effect of age is also in agreement with the findings of Wong et al. (2008).  In their study, Wong et al (2008) reported that Vea values in Chinese children  aged six to seven years were significantly lower (0.44 mmho) than older children (aged eight years and above) and adults, and they attributed these changes to growth in the osseous portion of the external ear-canal.  As also mentioned by Wong et al. (2008), these findings may be consistent with the findings of Eby and Nadol (1986), who reported two phases of mastoid growth: 122  first, from birth to seven years, and second, from seven years to 15 years.  According to this explanation, children between 8 and 15 years of age may have similar Vea to adults. 4.2.2 Static Admittance  The results of the current study showed that adult males had significantly larger static admittance compared to adult females.  Adult males also had significantly larger static admittance compared to male and female children which is again due to larger size of the middle-ear in adult males.  Although Wong et al. (2008) found a significant effect of gender between the two ethnic groups; they did not suggest separate norms for males and females.  Comparison between the current study’s results and Shahnaz and Bork (2008) clearly shows the maturational changes in static admittance.  The results of the present study show that Ytm increased from 0.49 to 0.77 mmho  in Caucasian and from 0.36 to 0.47 mmho in Chinese groups.  This effect can be associated with changing in physical dimensions, and also with increase in the efficiency of the middle-ear system with aging (Haapaniemi 1996; Margolis & Heller, 1987).  This finding on the effect of age is also in agreement with findings of Wong et al. (2008) in school-aged children. Significant changes with age were also observed for static admittance obtained from rectangular components.  In general, the findings of the present study show that at lower frequencies such as 226-Hz, Ytm value is mostly attributable to the value of Btm (i.e., the middle-ear is stiffness dominated); however, at higher frequencies such as 678- Hz and 1000-Hz, Ytm is mostly attributable to the value of Gtm (and so the middle-ear is at resonance or shifting to a mass dominated system).  Moreover, at higher probe-tone frequencies, we are approaching the resonant frequency, in the vicinity of which susceptance becomes smaller and conductance contributes more toward admittance; 123  therefore, at RF, static admittance becomes equal to G.  The results also revealed that at 226-Hz and 678-Hz there was no significant difference between female children’s and female adult’s Ytm values; in their male counterparts, however, Ytm values were significantly larger in adults compared to children.  The results are likely due to larger ear canal and middle-ear cavity in adult’s male.  Greater Body Mass Index (BMI) of the male group is probably responsible for the more pronounced differences in males compared to females (Shahnaz, 2008).  A comparison between static admittance obtained from rectangular components in the current study to that in Shahnaz and Bork (2008) on adults shows a significant effect of age at 226-Hz in the Caucasian population only.  Increase in Ytm in adults is due to increase in Btm; this effect can be associated with change in physical dimensions and increase in the efficiency of the middle-ear system with aging (Haapaniemi, 1996; Margolis & Heller, 1987).  There was no significant effect of age at 678- or 1000-Hz probe-tone frequencies for either ethnicity. 4.2.3 Tympanometric Width  Results also indicated that in the female group there was not a significant difference between child and adult TW values; however, in the male group children had significantly wider TW values compared to adults.  In agreement with the findings of the present study, Wong et al. (2008) also found no significant effect of gender for the variable of TW.   Overall TW values changed from 109 daPa (in children) to 85 daPa (in adults) in Caucasians and from 120 daPa (in children) to 118 daPa (in adults) in Chinese.  A comparison between the TW values in this study and those in Shahnaz and Bork (2008) 124  reveals that in the Chinese group (as compared with the Caucasians), although there is a slight decrease in TW values (2–3 daPa decrease in mean values), TW does not change dramatically with age, which may be attributed to the anatomic and systematic characteristics of the ear in East Asian peoples.  DeChicchis et al. (2000) reported a systematic increase in peak Ytm and decrease in TW with increasing age from six months to five years of age, attributing the differences to anatomical and physiological changes in the developing ear.   4.2.4 Tympanometric Peak Pressure  There were no significant effects of ethnicity and gender for the variable of TPP in the current study, which is consistent with the findings of Wong et al. (2008).  TPP values changed from −18 daPa in Caucasian children (in the current study) to 0 daPa in Caucasian adults (Shahnaz & Bork, 2008) and from −15 daPa in the Chinese children (current study) to −4 daPa in Chinese adults (Shahnaz & Bork, 2008).  Results showed that adults had significantly higher (more positive) TPP values than did children. Bylander et al. (1981) suggested that TPP differences between children and adults are related to anatomical differences (e.g. shorter or longer Eustachian tube) in the Eustachian tube between children and adults.  They reported that these anatomical differences end by the age of seven.  It was also shown in other studies, such as Wong et al. (2008) on Chinese subjects and Haapaniemi (1996) on Caucasians, that TPP tends to increase by age and becomes more positive, which may be related to the higher efficiency of the Eustachian tube in adults, which makes them less prone to OM compared to children. 125  4.2.5 Resonant Frequency  Resonant frequencies obtained with the SF recording method were compared to the RF values obtained with a similar recording method in Shahnaz and Bork (2008). Chinese females (adults and children) had significantly higher resonant frequencies than Caucasian male children.   Although not statistically significant (p = 0.064), in Chinese adult, males had lower RF than females.   RF data from the present study were also compared with RF data from Shahnaz and Bork, 2008; to investigate whether there is a significant effect of age.  Analysis indicated no significant effect of age.  Hanks and Rose (1993) reported no significant effect of age in their study, which is consistent with the findings of the current study. Hanks and Rose (1993) stated that the maturity of the middle-ear between six and 15 years of age has no significant effect on RF values.  4.3 Diseased Group 4.3.1 Equivalent Ear Canal Volume  The Vea data were explored to find the differences among middle-ear conditions. The information was gathered from Ya and Ba tympanogram tails (positive and negative) at 226-Hz probe-tone frequency. At 226-Hz, results showed no significant effects of middle-ear condition or tail values (positive versus negative tail), which indicates that Vea did not vary differently between middle-ear conditions and tails.  Mean Vea value in ears with MEE was 0.83 mmho using the positive tail and 0.86 mmho using the negative tail, which is within the 90% range of control-group Vea in the current study for both Caucasian and Chinese 126  children.  One important finding of the current study is that in the control group there was a difference (larger Vea by application of positive pressure) between positive and negative tails, which was diminished in the diseased–middle-ear condition.  In normal middle-ear condition this issue may be due to the movement of the eardrum and the higher resistance at negative pressures, which results in smaller Vea.  However, in cases of negative middle-ear pressure and MEE, the movement of the ear drum is restricted and may even mask the effect of resistance, and therefore diminishes the difference between the two compensation methods.    It has been hypothesized that if middle-ear impedance is infinitely high, the ear canal will act as a hard-wall cavity, and then the immittance measured in the plane of the probe can be attributed entirely to the ear canal.  In agreement with the current results, research (e.g. Shanks and Lilly, 1981) has shown that an extreme negative or positive pressure cannot drive the impedance of the middle-ear to infinity and as a result middle-ear contributes to the measurements of ear-canal volume. The finding implies that measurement of Vea is affected by middle-ear conditions.  For example, research showed that OME affects RECD values in children (Martin, Westwood and Bamford, 1996).  4.3.2 Static Admittance 4.3.2.1 Peak Compensated Static Admittance  At 226-Hz, results of the current study revealed that only the main effect of middle-ear condition was significant, indicating that static admittance obtained from Ya- tympanogram values varied differently among middle-ear conditions.  Mean Ytm in ears with MEE was 0.14 mmho using the positive tail and 0.09 mmho using the negative tail, 127  both of which are lower than the low cut-off values of the 90% range of Ytm in the current study for both normal Caucasian and normal Chinese school-aged children.  The results indicate that middle-ear fluid greatly reduces the admittance of the middle-ear. Consistent with these findings, Nozza et al. (1994) also reported reduced static admittance in the presence of fluid in the middle-ear cavity, using 226-Hz standard tympanometry. The results of the current study revealed that at a 678-Hz probe-tone frequency, Ytm obtained from negative compensation was larger than Ytm obtained from positive compensation in the diseased group.  Mean Ytm in ears with MEE was 0.26 mmho using the positive tail and 0.30 mmho using the negative tail, both of which are lower than the low cut-off values of the 90% range of Ytm in the current study for both normal Caucasian and normal Chinese school-aged children.  A possible explanation for these findings is that as middle-ear pathology progresses towards MEE, Ytm decreases, as has already been reported by other studies (e.g. Nozza et al., 1994) using a 226-Hz probe- tone frequency.  However, the current study is the only study that reports variations of Ytm as a function of middle-ear fluid in school-aged children using a 678-Hz probe-tone frequency.  The estimation of Ytm from a 678-Hz probe-tone frequency in clinical practice is important, because it could potentially provide higher sensitivity for detection of MEE in school-aged children.  High prevalence of MEE in this population and early intervention for children with MEE require the most sensitive diagnostic test battery available.  Although other variables (e.g. Ytm at 226-Hz) are successfully being used in clinical settings, Ytm from 678-Hz should certainly be included in the test battery.  At a 1000-Hz probe-tone frequency, mean Ytm in ears with MEE was 0.08 mmho using the 128  positive tail and 2.22 mmho using the negative tail, both of which are lower than the low cut-off values of the 90% range of Ytm for both the Chinese group and the Caucasian group of children.  Results also indicated that regardless of compensation method, Ytm decreased significantly as middle-ear condition progressed towards MEE, which is consistent with what we expect.  At a 1000-Hz probe-tone frequency, the findings of the current study show that variation of Ytm from negative compensation is greater than variation of Ytm from positive compensation as a function of middle-ear condition, which means that Ytm from negative compensation is more affected (decreased) by MEE.  In normal ears Ytm from negative compensation is larger than Ytm from positive compensation which is caused by an increase in the resistive element at the eardrum by introducing negative pressure into the ear-canal.  Presence of middle-ear effusion and /or negative pressure may mask the effect of the resistive element and affect (decrease) Ytm from negative compensation more than Ytm from positive compensation.  This factor may account for greater variation of Ytm from negative compensation in ears with MEE than Ytm from positive compensation. Moreover, earlier studies have shown that the effect of middle-ear pathology is more pronounced closer to the resonant frequency of the middle-ear; therefore, higher probe-tone frequencies such as 678- and 1000-Hz may provide more diagnostic information or more sensitivity in separating normal ears from ears with MEE.  4.3.2.2 Static Admittance Obtained from Rectangular Components  At 226-Hz, Ytm varied differently across middle-ear conditions.  Mean Ytm in ears with MEE was 0.25 mmho using the positive tail and 0.19 mmho using the negative 129  tail, both of which are lower than the low cut-off values of the 90% range of Ytm in the current study for both normal Caucasian and normal Chinese school-aged children.  In the normal group, smaller values for positive compensation were obtained than for negative compensation, which is expected because the resistive element at the negative tail of the tympanogram is higher than that at the positive tail (Margolis & Smith, 1977). In other groups, Ytm did not vary significantly between the two compensation methods. Again in the diseased condition, the difference between positive and negative compensation diminishes, which may be due to restricted eardrum movement in this condition. Using positive compensation, Ytm values decreased significantly from the normal group to the not OTL confirmed group, by a ratio of 2.4, and using the negative tail Ytm values decreased significantly as well, by a ratio of 4.2.  In other words, the current findings suggest that the Ytm decreases by a larger factor for negative compensation than for positive compensation which may have clinical implications.  For example, negative compensation may better distinguish ears with MEE than does positive compensation. At 678-Hz, Ytm varied differently between compensation methods across different middle-ear conditions.  Mean Ytm values in ears with MEE were 0.50 mmho using the positive tail and 0.40 mmho using the negative tail, both of which were lower than the low cut-off values of the 90% range of Ytm in the current study for both normal Caucasian and normal Chinese school-aged children. The difference between Ytm values obtained from positive compensation and Ytm values obtained from negative compensation across different middle-ear conditions was not significant.  Using positive compensation, Ytm values decreased significantly 130  from the normal group to the not OTL confirmed group (by a ratio of 4.3) and using negative compensation, Ytm values decreased by a ratio of 6.1.  The greater variation (decrease) of Ytm using negative compensation accounts for its better ability to show MEE compared to Ytm from positive compensation.  To investigate this issue further, ROC (Receiver operating characteristic) curve analysis was performed, which will be discussed later in this chapter. At 1000-Hz, Ytm varied differently between compensation methods across different middle-ear conditions.  Mean Ytm in ears with MEE was 1.08 mmho using the positive tail and 0.89 mmho using the negative tail.  These values were lower than the low cut-off values of the 90% range of Ytm for normal Caucasian and normal Chinese school-aged children for both compensation methods.  The only exception was that in Chinese children the mean value for ears with MEE at positive compensation was the same as the low cut-off value of the 90% range of Ytm for normal Chinese children. Ytm values decreased significantly from the normal group to the not OTL confirmed group by a ratio of 2.75 using positive compensation and by a ratio of 2.06 using negative compensation. The following patterns of change in Ytm and its rectangular components revealed that in current study at the lower probe-tone frequency of 226-Hz, susceptance mostly contributed to the value of static admittance at both positive and negative compensations in both normal ears and ears with middle-ear pathologies such as MEE.  As we increase the probe-tone frequency, conductance becomes the main contributor to Ytm (φ  45o). In the current study, at a 678-Hz probe-tone frequency for both positive and negative compensations, conductance was the main contributor to Ytm in the normal group. 131  Therefore, reduction in conductance accounts for significant reduction of Ytm.  Recall that conductance (Ga) is consisted of resistance (Ra) and reactance (Xa).  Since, conductance (not resistance) is frequency dependent, increase in probe-tone frequency will increase the contribution of conductance.  Middle-ear resistance may decrease due to accumulation of fluid and restriction of eardrum movement in ears with MEE, and therefore decreases conductance.  At 678-Hz, reduction in conductance was better shown by using negative compensation.  Because resistance is larger close to 1000-Hz (Allen, Jeng, and Levitt, 2005), it can be affected by MEE to a greater extent.  Finally, at 1000- Hz probe-tone frequency, reduction in Ytm due to the reduction in conductance occurred by using either compensations.  As a result, higher probe-tone frequencies (678- and 1000-Hz) that are closer to the RF of middle-ear (Ga is maximum) may better reflect the mechano-acoustical changes of ear system due to the presence of MEE. 4.3.3 Tympanometric Width  Mean TW in ears with MEE was 372 daPa using a 226-Hz probe-tone frequency, which is wider than the high cut-off value of the 90% range of TW for both Caucasian and Chinese school-aged children with MEE.  Overall, the results showed that TW widens as the middle-ear pathology progresses towards MEE, with a ratio of 3.2 from the normal group to the not OTL confirmed group, which is consistent with the reduction of static admittance as the middle-ear pathology progresses.  This finding is consistent with what has been reported in the literature (Nozza et al., 1992).  132   4.3.4 Resonant Frequency  Mean RF in ears with MEE was 301-Hz using the SF method and 277-Hz using the SP method, both of which are lower than the low cut-off values of the 90% range of RF in the current study for both normal Caucasian and normal Chinese school-aged children. Results revealed that RF values dropped significantly from the normal group to the not OTL confirmed and OTL confirmed groups.  Moreover, RF values did not vary differently between recording methods (SF vs. SP) across middle-ear conditions.  RF values decreased significantly from the normal group to the not OTL confirmed group, with a ratio of 3.5.  Reduction in resonant frequency is expected, because the tympanogram is most likely flat in nature; therefore, RF becomes zero or close to zero as the pathology progresses towards MEE.  Abou-Elhamd et al. (2006) also found similar results.  They stated that their mean RF value was 428 +/− 159 Hz for patients with otitis media with effusion, which is in agreement with the findings of the current study.  4.4 Test Performance  The overall test performance of Ytm was objectively evaluated using ROC analysis across the three probe-tone frequencies.  The results revealed that at 226-Hz using negative compensation, Ytm from Ya had a better test performance in distinguishing normal ears from ears with MEE than did Ytm obtained from rectangular components.  At 678-Hz, performance of Ytm from Ya and Ytm from rectangular components was the same using both compensation methods and finally, at 1000-Hz, 133  Ytm from rectangular components had a better test performance (statistically larger AUROC) in distinguishing normal ears from ears with MEE using negative compensation.  This finding is consistent with prior literature regarding calculation of Ytm from its rectangular components, particularly at higher frequencies.  Admittance (Ya) is a vector sum of the components Ba and Ga, and varies both in magnitude and phase angle depending on the probe-tone frequency as shown in Figure 4.1.  At low probe-tone frequencies like 226-Hz, the admittance vector is very close to susceptance; therefore, estimation of Ytm from Ya should not result in a large error, which is in accord with the findings of the present study (Figure 4.1).  As we increase probe-tone frequency, the difference between the admittance vector and susceptance increases, and measurement of Ytm from rectangular components (rather than directly from the admittance tympanogram) becomes necessary to avoid a large error.  The current study also showed that at 1000-Hz, estimation of Ytm from rectangular components can better distinguish healthy ears from ears with MEE than can Ytm from Ya.  Mathematical calculation of Ytm from its rectangular components has been previously examined in the literature; however, in the current study implications for distinguishing MEE in clinical settings are discussed.      134   Figure 4.1: Variation of acoustic admittance (Ya) as a function of probe-tone frequency (adapted from Margolis & Shanks, 1991).  Another important finding of the present study is that among the three probe-tone frequencies used in this study, 678-Hz has the best performance in distinguishing MEE in children population.  Moreover, ROC analysis in the present study revealed that performance of Ytm at 678-Hz, TW, and RF were not statistically different in distinguishing normal middle-ears from ears with MEE in school-aged children (AUROCs were not statistically different).  Therefore, each of thses variables can be used in clinical settings to increase the performance of test battery for distinguishing MEE in school-aged children.  High sensitivity of TW and RF has previously been shown in the literature (Nozza et al., 1994; Abou-Elhamd, 2006), however, this is the first study that reports high performance of Ytm at 678-Hz in identification of MEE.  Further research is needed in this area to investigate the reliability of these tests in school-aged children. Depending on the type of clinical setting and the purpose of testing, each of these 135  variables (RF, TW, and Ytm) can be used in screening and diagnosis of MEE in school- aged children.  The 90% ranges for the four tympanometric parameters (Vea, Ytm, TW, TPP, and RF) reflect the normative values obtained in the present study (see Table 4.1).  ASHA normative values were applied to the present study for normal group data.   Application of current ASHA norms for TW (> 200 daPa) showed high specificity in the current study’s normal group.  Therefore, ASHA high cut-off value for TW can safely be used in Chinese and Caucasian school-aged children for identification of MEE.  However, nine normal Chinese subjects (11%) from current study failed to meet ASHA normative values for Vea (> 1.00 mmho).  Moreover, application of ASHA normative values for Ytm (< 0.3 mmho) results in high rates of false positives in normal subjects of the current study, particularly in the Chinese children (21.25% of normal subjects failed).  Therefore, the low cut-off value of the 90% range for Ytm ( < 0.2 mmho) from the current study is recommended twhen testing both Chinese and Caucasian school-aged children.  Norms suggested by the current study are also consistent with those recommended by Shahnaz and Davies’s (2006) suggested norms for adults. Moreover, Ytm and TW norms introduced by Driscoll et al., (2008) for Chinese school-aged children (six to 13 years old) were applied to the current study’s normal- and diseased-group data.  Application of their Ytm (0.22–0.73 mmho) and TW (57–144 daPa) norms to the current study’s normal Ytm and TW data revealed a high rate of false positives.  For example, 20% of the normal subjects from the current study failed using the Driscoll et al.’s (2008) Ytm norms and 19% of these subjects failed under Driscoll et al.’s TW norms.  Therefore, application of the low cut-off value for Ytm and high cut-off 136  value for TW from the current study is more appropriate for young (five to seven years old) Chinese children than Driscoll et al’s norms.  Driscoll et al.’s norms were also applied to the current study’s diseased (OTL confirmed) data to evaluate the sensitivity of Ytm and TW norms in this population.  The results showed that by using the lower cut- off value of Ytm from Driscoll et al., six subjects (out of 27) with MEE received false negatives.  However, Driscoll et al.,’s high cut-off for TW had 100% sensitivity in identification of subjects with MEE.  Therefore, by using Driscoll et al.’s (2008) normative data, there will be a considerable number of misses for Ytm and the possibility of over-referrals (false positives) for TW in Chinese school-aged children.   Table 4.4: Tympanometric pass and fail criteria from different studies.  Vea: equivalent ear-canal volume; Ytm: compensated static admittance, TW: tympanometric width and TPP: tympanometric peak pressure from admittance tympanogram.        226-Hz    Age (years)     Vea  (mmho)    Ytm  (mmho)   TW  (daPa)         TPP (daPa) Current study, Caucasians 5-7 > 1.20 < 0.20 > 153 −86-15 Current study, Chinese 5-7 > 1.00 < 0.20 > 170 −65.50–20.25    ASHA (1997): Nozza et al.,1992,1994 Shanks et al., 1992  1-7 1-7   > 1.00  < 0.30  > 200     Driscoll et al. (2008) 6-15  0.22–0.73 57–144 −62–22  Acoustic immittance data on 27 ears of 18 children in the OTL confirmed group was compared with normal group data to evaluate the immittance variable’s test 137  performance in identification of ears with MEE.  The analysis showed that TW and RF (both SF and SP) had the highest sensitivity (100%) and specificity, while Ytm from Ya at 678-Hz had slightly lower sensitivity and specificity in identification of ears with MEE.  Then, test performance of tympanometric variables was evaluated by combining the not OTL confirmed group and the OTL confirmed group and were compared to the normal group.  In this analyses also similar tympanometric variables of RF, TW, and Ytm at 678-Hz had the highest sensitivity and specificity in identification of MEE.  However, in the later group, sensitivity of RF (94%), TW (93%), and Ytm (90%) were slightly less than the OTL confirmed group in the present study. Nozza et al., (1994) reported that TW had the best test performance (sensitivity and specificity above 80%) in identification of MEE in their study.   Slight changes in test performance of tympanometric variables may be due to the differences in prevalence of the subjects and the disease from one group to another group (Nozza et al., 1992).  4.5 Clinical Implications  The current study investigated five tympanometric variables (Vea, Ytm, TW, TPP, and RF) in Caucasian and Chinese school-aged children.  Among the studied variables in the present study, TPP is not recommended for identification of MEE due to its high variability.  The current study does not recommend gender specific norms for Ytm in school-aged children, because the difference between the genders was not very large (< 0.06 mmho).  The present research recommends measurement of individual RECDs in children with OME rather than averaged RECDs. 138  Test performance of Ytm and TW in identification of MEE was examined and compared with the results of ASHA (1997) and of Driscoll et al. (2008).  Based on the results, we recommend that the cut-off of 0.2 be used for Ytm at 226-Hz in school-aged children from both ethnicities. In addition, it is suggested that Ytm at 678-Hz using negative compensation provides more accurate information regarding MEE in school- aged children (Chinese and Caucasian) due to its high sensitivity and specificity in identification of MEE in this population.  Therefore, use of Ytm from 678-Hz tympanometry (from negative tail) in addition to conventional 226-Hz tympanometry for identification of school-aged children with MEE is highly recomended.  TW norms performed well in identifying MEE in Chinese school-aged children and therefore can be used in clinical settings.  Although application of TW and Ytm for detection of MEE is common to the current study, ASHA (1997), and Driscoll et al. (2008) study, the findings from the present study supports RF as also a valuable tool for identification of MEE.  Overall, application of MFT for detection of school-aged children with MEE is highly recommended.  4.6 Research Limitations   One limitation of the current study was recruitment of Chinese children for the diseased group.  Although a large population of Chinese-Canadians and Chinese immigrants live in the greater Vancouver area, during the data-collection period, the majority of diseased group subjects who were referred to BC Children’s Hospital or recruited through elementary schools consisted of Caucasians and other ethnicities rather than Chinese.  Studying pathological middle-ear conditions in a larger population of 139  Chinese children may better reflect tympanometric differences in the middle-ear system as compared to Caucasian children.  This issue was more prominent in the MEE group. There were 12 ears (two Chinese, nine Caucasian, and one mixed) with MEE in the not OTL confirmed group and 28 ears (two Chinese, 13 Caucasian, 10 other ethnicities, and one unknown) with MEE in the OTL confirmed group.  Moreover, the prevalence of MEE was different between the two ethnicities.  Prevalence of a disease is specifically important when two different groups with a disease are being compared since prevalence affects the predictive values and test performance of the variables (Nozza et al., 1992). Although predictive values have not been discussed in the current study, they provide valuable information about the performance of a test.  Therefore, consideration of prevalence of a disease and also the predictive values may better reflect the actual test performance of the variables in identification of MEE in the Chinese population (and also Caucasian population). Another limitation of this study arises in the possibility that a disproportionate number of parents who had concerns about their child’s hearing signed the consent form and therefore that a higher proportion of these kids may have had hearing or ME problems and so may not be a true representation of the population at that age. Therefore, adjustments should be made by sending a more detailed case history form to parents or talking to them before testing to obtain a more detailed background of the child’s health. 4.7 Future Research  This study used tympanometry in a group of children with MEE.  Future research may be of benefit by taking a larger-scale approach to recruitment of Chinese school- 140  aged children to further investigate the performance of tympanometric variables in detection of MEE in this population.  Vriables with high test performance from the present study (e.g. RF and Ytm at 678-Hz) can be used in a larger sample of children for future research.  This method may provide additional benefit in determining optimal clinical norms for Chinese school-aged children.  In the present study application of current ASHA (1997) guidelines were tested in Chinese children.  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Williamson IG, Dunleavey J, Bain J, Robinson D (1994)  The natural history of otitis media with effusion--a three-year study of the incidence and prevalence of abnormal tympanograms in four South West Hampshire infant and first schools. J Laryngol Otol. 108: 930-4.   154    Appendix 1  Table A1.1: Mean, SD, and 90% range (5 th–95th percentile) for ear-canal volume (Vea) obtained from uncompensated admittance (Ya) using positive tail (Vea+) in normal Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]) .  Caucasian Chinese Frequency Vea+ (+250 daPa) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range 226 Hz M 0.89 0.21 0.60–1.20 0.79 0.16 0.60– 1.04 F 0.76 0.14    0.60–1.00 0.75 0.12 0.60–0.90 O 0.83 0.19 0.60–1.20 0.78 0.15 0.60–1.00 1000 Hz M 4.15 0.86 2.82–5.62 3.83 0.76 2.84–5.35 F 3.65 0.55 3.02–4.75 3.60 0.59 2.67–4.55 O 3.91 0.77 2.96–5.47 3.76 0.72 2.68–5.08  Table A1.2: Mean, SD, and 90% range (5th–95th percentile) for ear-canal volume (Vea) obtained from uncompensated admittance (Ya) using negative tail (Vea−) in normal Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]).   Caucasian Chinese Frequency Vea− (−400 daPa) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range 226 Hz M 0.73 0.23 0.50–1.10 0.89 0.16 0.50–0.97 F 0.68 0.13 0.46–0.89 0.65 0.11 0.50–0.80 O 0.71 0.19 0.48–1.10 0.68 0.15 0.50–0.95 1000 Hz M 2.89 0.50 2.14–3.71 2.85 0.48 2.10–3.72 155  F 2.57 0.63 2.03–3.24 3.47 2.04 2.74–0.53 O 2.73 0.58 2.05–3.68 2.82 0.50 2.06–3.72  Table A1.3: Mean, SD, and 90% range (5th–95th percentile) for compensated static admittance (Ytm) obtained from uncompensated admittance (Ya) using positive compensation (Ytm+), in normal Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]).   Caucasian Chinese Frequency Y+ Y+ Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range 226 Hz M 0.51 0.26 0.24–1.08 0.38 0.16 0.20–0.74 F 0.48 0.23 0.22–1.02 0.32 0.11 0.20–0.50 O 0.49 0.24 0.2–1.10 0.36 0.14 0.20–0.61 678 Hz M 1.48 0.97 0.23–2.99 1.03 0.77 0.28–2.87 F 1.49 1.03 0.55–3.31 0.95 0.47 0.37–1.73 O 1.49 0.99 0.39–3.23 1.00 0.68 0.33–2.22 1000 Hz M 1.21 1.37 −0.40–3.38 0.88 1.08 −0.31–2.66 F 1.28 1.02 −0.02–3.09 1.29 0.73 0.29–2.41 O 1.25 1.21 −0.30–3.16 1.01 1.00 −0.25–2.49 156  Table A1.4: Mean, SD, and 90% range (5th–95th percentile) for compensated static admittance (Ytm) obtained from uncompensated admittance (Ya), using negative compensation (Ytm−), in normal Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]).   Caucasian Chinese Frequency Y− Y− Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range 226 Hz M 0.64 0.29 0.30–1.24 0.36 0.96 0.25–0.81 F 0.55 0.22 0.31–1.04 0.43 0.13 0.26–0.62 O 0.60 0.26 0.30–1.12 0.38 0.80 0.25–0.80 678 Hz M 2.24 1.04 1.09–3.74 1.59 0.89 0.83–3.61 F 2.01 1.19 0.92–3.83 1.59 0.78 0.85–3.26 O 2.13 1.11 0.98–3.82 1.59 0.85 0.80–3.54 1000 Hz M 2.50 1.42 1.14–5.23 2.37 1.01 0.85–4.03 F 1.86 1.26 0.60–4.11 2.06 0.81 0.94–3.54 O 2.44 1.24 0.90–4.47 1.92 1.14 0.79–3.96   Table A1.5: Mean, standard deviation (SD), and 90% range values for TW (obtained from Y tympanogram at 226-Hz) for Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]).   Caucasian Chinese TW (daPa) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range 226 Hz M 111.96 32.46   62.50–153.75 120.94 32.96 75.00–167.00 F 104.20 25.72 75.00–149.25   118.80    27.66 82.00–173.00 O 108.17 29.46 67.25–65.00 120.26 31.20 75.00–170.00  157  Table A1.6: Mean, standard deviation (SD), and 90% range values for TPP (obtained from Y tympanogram at 226-Hz) for Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]).    Caucasian Chinese TPP (daPa) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range 226 Hz M -17.24 36.63 −80.00–27.00 -19.34 34.40 −76.00–11.00 F -18.26 29.61 −81.25–10.00 -7.12 33.83 −48.75–22.50 O -17.74 33.24 −86.5–15.00 -15.32 34.49 −65.50–20.50  Table A1.7: Mean, SD, and 90% range (5th–95th percentile) for ear-canal volume (Vea) obtained from uncompensated susceptance (Ba) using positive tail (Vea +) in normal Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]).   Caucasian Chinese Frequency Vea+ (+250 daPa) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range 226 Hz M 0.86 0.20 0.63–1.19 0.77 0.16 0.56–1.05 F 0.76 0.12 0.55–0.97 0.74 0.12 0.52–0.89 O 0.82 0.17 0.59–1.15 0.76 0.15 0.55–1.00 1000 Hz M 3.94 0.75 2.76–5.01 3.67 0.77 2.55–5.16 F 3.47 0.64 2.79–4.17 3.48 0.55 2.59–4.34 O 3.71 0.74 2.78–4.96 3.61 0.71 2.56–5.02 158    Table A1.8: Mean, SD, and 90% range (5th–95th percentile) for ear-canal volume (Vea) obtained from uncompensated susceptance (Ba), using negative tail (Vea−) in normal Caucasian and Chinese school-aged children (M: male; F: female; O: overall [combined male and female]).  Caucasian Chinese Frequency Vea− (−400 daPa) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range 226 Hz M 0.70 0.25 0.31–1.10 0.68 0.23 0.47–0.94 F 0.66 0.13 0.46–0.80 0.61 0.11 0.45–0.79 O 0.68 0.20 0.44–1.04 0.66 0.20 0.46–0.92 1000 Hz M 2.79 0.48 2.06–3.58 2.70 0.51 1.90–3.61 F 2.52 0.52 1.90–3.06 2.61 0.48 1.94–3.33 O 2.67 0.51 1.98–3.57 2.67 0.50 1.90–3.60 159   Table A1.9: Mean, standard deviation (SD), and 90% range for compensated susceptance (Btm), conductance (Gtm), and admittance (Ytm) obtained from positive compensation using 226-Hz probe-tone frequency (M: male; F: female; O: overall [combined male and female]).               226-Hz Btm+ Gtm+ Ytm+ Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho)  Caucasians  M 0.53 0.24 0.25–0.97 0.32 0.16 0.15–0.63 0.63 0.28 0.32–1.21 F 0.51 0.23 0.27–1.01 0.30 0.14 0.14–0.53 0.60 0.25 0.31–1.84 O 0.52 0.24 0.26–1.01 0.31 0.15 0.15–0.60 0.61 0.27 0.31–1.27  Chinese M 0.39 0.16 0.20–0.73 0.23 0.09 0.10–0.39 0.45 0.17 0.23–0.85 F 0.36 0.15 0.20–0.60 0.19 0.06 1.11–0.30 0.41 0.15 0.25–0.65 O 0.38 0.15 0.20–0.72 0.22 0.08 0.10–0.36 0.44 0.16 0.23–0.84 160    Table A1.10: Mean, standard deviation (SD), and 90% range for compensated susceptance (Btm), conductance (Gtm), and admittance (Ytm) obtained from negative compensation using 226-Hz probe-tone frequency (M: male; F: female; O: overall [combined male and female]).                  226-Hz            Btm-              Gtm-              Ytm- Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho)  C  M 0.69 0.30 0.32–1.30 0.30 0.25 0.09–0.63 0.77 0.36 0.36–1.45 F 0.60 0.23 0.32–1.07 0.25 0.19 0.06–0.58 0.66 0.26 0.35–1.27 O 0.65 0.27 0.32–1.29 0.28 0.22 0.08–0.63 0.72 0.32 0.35–1.37  A M 0.39 0.16 0.20–0.73 0.23 0.09 0.10–0.39 0.45 0.17 0.23–0.85 F 0.36 0.15 0.20–0.60 0.19 0.06 0.11–0.30 0.41 0.15 0.25–0.65 O 0.49 0.16 0.29–0.81 0.18 0.09 0.07–0.35 0.53 0.17 0.31–0.88 161  Table A1.11: Mean, standard deviation (SD), and 90% range for compensated susceptance (Btm), conductance (Gtm), and admittance (Ytm) obtained from positive compensation using 678-Hz probe-tone frequency (M: male; F: female; O: overall [combined male and female]).  678-Hz            Btm+              Gtm+              Ytm+ Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho)  C  M 0.62 0.81 -0.33-1.89 1.79 1.04 0.71-3.13 2.00 1.15 0.79-3.50 F 0.86 0.59 -0.04-1.79 1.69 1.28 0.66-3.71 1.99 1.26 0.83-4.00 O 0.74 0.72 -0.29-1.88 1.74 1.16 0.65-3.62 2.00 1.20 0.77-3.96  A M 0.51 0.44 0.03-1.30 1.38 0.95 0.56-3.54 1.53 0.96 0.73-3.89 F 0.62 0.31 0.10-1.07 1.08 0.49 0.56-1.98 1.27 0.51 0.72-2.13 O 0.55 0.40 0.05-1.22 1.28 0.84 0.55-2.69 1.44 0.85 0.72-2.97      162  Table A1.12: Mean, standard deviation (SD), and 90% range for compensated susceptance (Btm), conductance (Gtm), and admittance (Ytm) obtained from negative compensation using 678-Hz probe-tone frequency (M: male; F: female; O: overall [combined male and female]).                   678-Hz            Btm-              Gtm-              Ytm- Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho)  C  M 1.38 0.82 0.48–2.71 1.87 1.09 0.68–3.37 2.43 1.16 1.30–3.94 F 1.46 0.65 0.57–2.41 1.60 1.22 0.61–3.39 2.27 1.21 1.06–4.04 O 1.42 0.74 0.51–2.57 1.74 1.15 0.62–3.39 2.35 1.18 1.16–4.03  A M 1.12 0.57 0.27–2.12 1.39 0.93 0.64–3.46 1.85 0.97 1.01–4.24 F 1.14 0.32 0.87–1.77 0.98 0.53 0.42–2.00 1.53 0.52 0.99–2.59 O 1.13 0.50 0.39–1.89 1.26 0.84 0.51–2.69 1.75 0.87 1.00–3.39 163  Table A1.13: Mean, standard deviation (SD), and 90% range for compensated susceptance (Btm), conductance (Gtm), and admittance (Ytm) obtained from positive compensation using 1000-Hz probe-tone frequency (M: male; F: female; O: overall [combined male and female]).                          1000-Hz Btm+ Gtm+ Ytm+ Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho)  C  M −0.76 1.20 −3.16–0.61 3.08 1.77 1.14–6.57 3.31 1.91 1.16–6.98 F −0.20 1.52 −2.49–1.13 2.75 1.62 1.09–4.78 3.14 1.62 1.21–6.27 O −0.49 1.39 −3.00–0.99 2.92 1.70 1.14–5.93 3.23 1.77 1.17–6.79  A M −0.60 1.39 −3.37–0.76 2.02 1.41 0.71–5.29 2.43 1.56 0.88–6.39 F 0.05 1.11 −0.71–1.19 2.24 1.24 0.85–4.19 2.42 1.37 0.93–4.44 O −0.38 1.34 −3.20–0.97 2.09 1.36 0.78–4.52 2.43 1.49 0.89–6.23 164   Table A1.14: Mean, standard deviation (SD), and 90% range for compensated susceptance (Btm), conductance (Gtm), and admittance (Ytm) obtained from negative compensation using 1000-Hz probe-tone frequency (M: male; F: female; O: overall [combined male and female]).  1000-Hz            Btm−              Gtm−              Ytm- Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho)  C  M 0.35 1.07 −1.08–1.71 3.40 1.85 1.24–6.95 3.60 1.81 1.52–7.01 F 0.80 1.31 −1.87–2.16 3.00 1.32 1.29–4.76 3.34 1.37 1.47–6.03 O 0.57 1.20 −1.45–2.02 3.21 1.62 1.28–6.39 3.47 1.61 1.49–6.65  A M 0.32 1.57 −3.11–1.88 2.23 1.51 0.84–5.68 2.71 1.55 1.09–6.43 F 0.85 0.84 0.12–1.69 2.31 1.32 0.84–4.62 2.65 1.19 1.37–4.67 O 0.48 1.40 −2.65–1.88 2.25 1.45 0.83–5.35 2.69 1.45 0.83–5.35 165  Table A1.15: Mean, standard deviation (SD), and 90%  range values of resonant frequency (RF) for Caucasian and Chinese school-aged children using sweep-frequency (SF) and sweep-pressure (SP) recording methods (M: male; F: female; O: overall [combined male and female]).   Caucasian Chinese  RF (Hz) Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range SF M 834 169 500–1050 910 262 600–1400 F 932 217 663–700 1006 291 613–1438 O 881 199 575–1250 942 274 600–1400 SP M 843 180 600–1100 968 274 660–1490 F 932 174 700–1290 1002 258 610–1380 O 886 182 650–1200 979 267 600–1465             166  Table A1.16: Summary of ANOVA for Ytm from Ya using 226-Hz Conventional Tympanometry                       Ytm from Ya using 226-Hz Conventional Tympanometry SS Degree Of Freedom MS F p Intercept 65.70605 1 65.70605 300.6985 0.000000 {1}Ear 0.03355 1 0.03355 0.1535 0.695681 {2}Gender 0.05163 1 0.05163 0.2363 0.627541 {3}Ethnicity 2.46286 1 2.46286 11.2711 0.000979 Ear*Gender 0.09030 1 0.09030 0.4133 0.521220 Ear*Ethnicity 0.02417 1 0.02417 0.1106 0.739897 Gender*Ethnicity 0.08355 1 0.08355 0.3824 0.537204 Ear*Gender*Ethnicity 0.12161 1 0.12161 0.5565 0.456730 Error 35.83587 164 0.21851 {4}Compensation 0.37476 1 0.37476 2.4719 0.117822 Compensation*Ear 0.04981 1 0.04981 0.3285 0.567306 Compensation*Gender 0.01930 1 0.01930 0.1273 0.721682 Compensation*Ethnicity 0.07346 1 0.07346 0.4845 0.487362 Compensation*Ear*Gender 0.05736 1 0.05736 0.3784 0.539328 Compensation*Ear*Ethnicity 0.07628 1 0.07628 0.5032 0.479120 Compensation*Gender*Ethnicity 0.17849 1 0.17849 1.1773 0.279493 4*1*2*3 0.11242 1 0.11242 0.7415 0.390426 Error 24.86313 164 0.15160 167      Table A1.17: Summary of ANOVA for Ytm from Ya at 678-Hz using MFT  Ytm from Ya at 678-Hz  using MFT SS Degree Of Freedom MS F p Intercept 773.1519 1 773.1519 461.4275 0.000000 {1}Ear 2.6727 1 2.6727 1.5951 0.208347 {2}Gender 0.4983 1 0.4983 0.2974 0.586233 {3}Ethnicity 21.9990 1 21.9990 13.1293 0.000385 Ear*Gender 0.5962 1 0.5962 0.3558 0.551654 Ear*Ethnicity 1.8293 1 1.8293 1.0918 0.297585 Gender*Ethnicity 0.1194 1 0.1194 0.0712 0.789857 Ear*Gender*Ethnicity 1.3109 1 1.3109 0.7824 0.377684 Error 281.4950 168 1.6756 {4}Compensation 30.7888 1 30.7888 358.7491 0.000000 Compensation*Ear 0.0022 1 0.0022 0.0259 0.872225 Compensation*Gender 0.1342 1 0.1342 1.5635 0.212891 Compensation*Ethnicity 0.0418 1 0.0418 0.4876 0.485957 Compensation*Ear*Gender 0.1141 1 0.1141 1.3294 0.250546 Compensation*Ear*Ethnicity 0.3280 1 0.3280 3.8222 0.052237 Compensation*Gender*Ethnicity 0.4665 1 0.4665 5.4359 0.020914 4*1*2*3 0.0410 1 0.0410 0.4776 0.490462 Error 14.4182 168 0.0858                  168      Table A1.18: Summary of ANOVA for Ytm from Ya at 1000-Hz using MFT  Ytm from Ya at 1000-Hz  using MFT SS Degree Of Freedom MS F p Intercept 868.0992 1 868.0992 334.7919 0.000000 {1}Ear 0.3607 1 0.3607 0.1391 0.709672 {2}Gender 1.1927 1 1.1927 0.4600 0.498603 {3}Ethnicity 10.3324 1 10.3324 3.9848 0.047577 Ear*Gender 0.0643 1 0.0643 0.0248 0.875021 Ear*Ethnicity 0.0141 1 0.0141 0.0054 0.941400 Gender*Ethnicity 1.2612 1 1.2612 0.4864 0.486528 Ear*Gender*Ethnicity 0.0018 1 0.0018 0.0007 0.979013 Error 422.6511 163 2.5930 {4}Compensation 83.7007 1 83.7007 664.4060 0.000000 Compensation*Ear 0.0795 1 0.0795 0.6310 0.428129 Compensation*Gender 0.5369 1 0.5369 4.2615 0.040571 Compensation*Ethnicity 0.7540 1 0.7540 5.9854 0.015488 Compensation*Ear*Gender 0.0187 1 0.0187 0.1480 0.700911 Compensation*Ear*Ethnicity 0.0164 1 0.0164 0.1302 0.718698 Compensation*Gender*Ethnicity 0.1327 1 0.1327 1.0537 0.306176 4*1*2*3 0.0262 1 0.0262 0.2083 0.648678 Error 20.5345 163 0.1260                   169  Table A1.19: Summary of ANOVA for Ytm at 226-Hz from rectangular components- MFT  Ytm at 226-Hz from rectangular components-MFT SS Degree Of Freedom MS F p Intercept 177.1714 1 177.1714 912.0845 0.000000 {1}Ear 0.1035 1 0.1035 0.5329 0.466447 {2}Gender 0.6640 1 0.6640 3.4184 0.066285 {3}Ethnicity 5.1329 1 5.1329 26.4244 0.000001 Ear*Gender 0.0093 1 0.0093 0.0480 0.826829 Ear*Ethnicity 0.0813 1 0.0813 0.4186 0.518544 Gender*Ethnicity 0.0104 1 0.0104 0.0534 0.817586 Ear*Gender*Ethnicity 0.0001 1 0.0001 0.0004 0.983791 Error 31.6626 163 0.1942 {4}Compensation 0.8982 1 0.8982 31.9325 0.000000 Error 4.5850 163 0.0281 {5}Component 18.3373 2 9.1686 580.5276 0.000000 Component*Ear 0.0067 2 0.0034 0.2126 0.808608 Component*Gender 0.0244 2 0.0122 0.7714 0.463225 Component*Ethnicity 0.2920 2 0.1460 9.2436 0.000125 Component*Ear*Gender 0.0019 2 0.0009 0.0590 0.942688 Component*Ear*Ethnicity 0.0183 2 0.0091 0.5781 0.561562 Component*Gender*Ethnicity 0.0007 2 0.0004 0.0224 0.977850 Error 5.1487 326 0.0158 Compensation*Component 1.1293 2 0.5647 150.9055 0.000000 Compensation*Component*Ear 0.0130 2 0.0065 1.7377 0.177555 Compensation*Component*Gender 0.0209 2 0.0105 2.7938 0.062654 Compensation*Component*Ethnicity 0.0028 2 0.0014 0.3757 0.687107 Error 1.2198 326 0.0037         170     Table A1.20: Summary of ANOVA for Vea from 226-Hz Conventional Tympanometry  Vea from 226-Hz Conventional Tympanometry SS Degree Of Freedom MS F p Intercept 261.1999 1 261.1999 5721.402 0.000000 Ethnicity 0.8071 1 0.8071 17.679 0.000036 Gender 1.3243 1 1.3243 29.008 0.000000 Child vs Adult 13.9538 1 13.9538 305.649 0.000000 Ethnicity*Gender 0.0001 1 0.0001 0.003 0.958598 Ethnicity*Child vs Adult 0.2465 1 0.2465 5.399 0.020913 Gender*Child vs Adult 0.2591 1 0.2591 5.675 0.017915 Ethnicity*Gender*Child vs Adult 0.1130 1 0.1130 2.476 0.116816 Error 12.0524 264 0.0457   Table A1.21: Summary of ANOVA for Ytm from Ya using 226-Hz Conventional Tympanometry  Ytm from Ya using 226-Hz Conventional Tympanometry SS Degree Of Freedom MS F p Intercept 65.77723 1 65.77723 1316.532 0.000000 Ethnicity 1.85312 1 1.85312 37.090 0.000000 Gender 1.08642 1 1.08642 21.745 0.000005 Child vs Adult 2.47482 1 2.47482 49.533 0.000000 Ethnicity*Gender 0.11426 1 0.11426 2.287 0.131687 Ethnicity*Child vs Adult 0.07153 1 0.07153 1.432 0.232569 Ethnicity*Child vs Adult 0.48618 1 0.48618 9.731 0.002015 Ethnicity*Gender*Child vs Adult 0.06664 1 0.06664 1.334 0.249196 Error 13.04021 261 0.04996           171        Table A1.22: Summary of ANOVA for Ytm form rectangular components at 226-Hz- MFT  Ytm form rectangular components at 226- Hz-MFT SS Degree Of Freedom MS F p Intercept 166.3319 1 166.3319 1354.192 0.000000 {1}Ethnicity 5.5763 1 5.5763 45.399 0.000000 {2}Gender 2.3382 1 2.3382 19.037 0.000018 {3}Child vs. Adult 3.8607 1 3.8607 31.432 0.000000 Ethnicity*Gender 0.1495 1 0.1495 1.217 0.270931 Ethnicity*Child vs. Adult 0.2404 1 0.2404 1.957 0.163029 Gender*Child vs. Adult 1.2740 1 1.2740 10.373 0.001440 Ethnicity*Gender*Child vs. Adult 0.1214 1 0.1214 0.989 0.320963 Error 32.1808 262 0.1228 {4}Component 11.5429 2 5.7714 759.455 0.000000 Component*Ethnicity 0.4636 2 0.2318 30.504 0.000000 Component*Gender 0.1132 2 0.0566 7.450 0.000645 Component*Child vs. Adult 0.2113 2 0.1057 13.904 0.000001 Component*Ethnicity*Gender 0.0047 2 0.0023 0.307 0.735734 Component*Ethnicity*Child vs. Adult 0.0707 2 0.0354 4.652 0.009942 Component*Gender*Child vs. Adult 0.1102 2 0.0551 7.249 0.000785 4*1*2*3 0.0072 2 0.0036 0.474 0.622876 Error 3.9821 524 0.0076                172   Table A1.23: Summary of ANOVA for Ytm form rectangular components at 678-Hz- MFT  Ytm form rectangular components at 678-Hz- MFT SS Degree Of Freedom MS F p Intercept 1164.257 1 1164.257 730.6946 0.000000 {1}Ethnicity 22.902 1 22.902 14.3734 0.000186 {2}Gender 10.226 1 10.226 6.4180 0.011885 {3}Child vs. Adult 0.033 1 0.033 0.0204 0.886494 Ethnicity*Gender 4.484 1 4.484 2.8142 0.094637 Ethnicity*Child vs. Adult 0.862 1 0.862 0.5412 0.462617 Gender*Child vs. Adult 6.109 1 6.109 3.8341 0.051289 Ethnicity*Gender*Child vs. Adult 0.625 1 0.625 0.3922 0.531686 Error 414.273 260 1.593 {4}Component  179.743 2 89.872 266.8538 0.000000 Component*Ethnicity 2.506 2 1.253 3.7200 0.024882 Component*Gender 9.853 2 4.926 14.6278 0.000001 Component*Child vs. Adult 2.532 2 1.266 3.7597 0.023926 Component*Ethnicity*Gender 0.799 2 0.400 1.1869 0.305990 Component*Ethnicity*Child vs. Adult 0.738 2 0.369 1.0952 0.335256 Component*Gender*Child vs. Adult 1.053 2 0.527 1.5638 0.210332 4*1*2*3 0.310 2 0.155 0.4600 0.631525 Error 175.127 520 0.337                     173     Table A1.24: Summary of ANOVA for Ytm form rectangular components at 1000-Hz- MFT  Ytm form rectangular components at 1000-Hz- MFT SS Degree Of Freedom MS F p Intercept 1841.095 1 1841.095 708.1994 0.000000 {1}Ethnicity 64.507 1 64.507 24.8135 0.000001 {2}Gender 0.150 1 0.150 0.0579 0.810108 {3}Child vs. Adult 1.646 1 1.646 0.6330 0.426976 Ethnicity*Gender 0.552 1 0.552 0.2124 0.645314 Ethnicity*Child vs. Adult 3.657 1 3.657 1.4067 0.236676 Gender*Child vs. Adult 5.968 1 5.968 2.2958 0.130926 Ethnicity*Gender*Child vs. Adult 6.185 1 6.185 2.3791 0.124173 Error 681.117 262 2.600 {4}Component 1543.539 2 771.769 386.8681 0.000000 Component*Ethnicity 34.015 2 17.007 8.5253 0.000227 Component*Gender 28.718 2 14.359 7.1977 0.000825 Component*Child vs. Adult 0.793 2 0.397 0.1988 0.819752 Component*Ethnicity*Gender 5.375 2 2.688 1.3473 0.260851 Component*Ethnicity*Child vs. Adult 0.252 2 0.126 0.0631 0.938899 Component*Gender*Child vs. Adult 1.692 2 0.846 0.4242 0.654521 4*1*2*3 9.773 2 4.886 2.4495 0.087327 Error 1045.336 524 1.995     Table A1.25: Summary of ANOVA for TW from 226-Hz Conventional Tympanometry  TW from 226-Hz Conventional Tympanometry SS Degree Of Freedom MS F p Intercept 2766415 1 2766415 2019.205 0.000000 Ethnicity 28732 1 28732 20.972 0.000007 Gender 2095 1 2095 1.529 0.217392 Child vs Adult 9229 1 9229 6.736 0.009992 Ethnicity*Gender 570 1 570 0.416 0.519380 Ethnicity*Child vs Adult 6163 1 6163 4.498 0.034889 Gender*Child vs Adult 7048 1 7048 5.145 0.024148 Ethnicity*Gender*Child vs Adult 5 1 5 0.004 0.951837 Error 352103 257 1370 174     Table A1.26: Summary of ANOVA for TPP from 226-Hz Conventional Tympanometry  TPP from 226-Hz Conventional Tympanometry SS Degree Of Freedom MS F p Intercept 18361.4 1 18361.35 23.85813 0.000002 Ethnicity 6.0 1 6.04 0.00785 0.929457 Gender 561.9 1 561.91 0.73013 0.393619 Child vs Adult 11095.7 1 11095.70 14.41738 0.000182 Ethnicity*Gender 758.9 1 758.90 0.98609 0.321613 Ethnicity*Child vs Adult 1416.6 1 1416.65 1.84074 0.176027 Gender*Child vs Adult 394.5 1 394.48 0.51258 0.474660 Ethnicity*Gender*Child vs Adult 572.0 1 571.99 0.74322 0.389416 Error 202406.3 263 769.61   Table A1.27: Summary of ANOVA for RF from MFT  RF from MFT SS Degree Of Freedom MS F p Intercept 206132811 1 206132811 4109.768 0.000000 Ethnicity 78881 1 78881 1.573 0.210908 Gender 428949 1 428949 8.552 0.003746 Child vs Adult 32 1 32 0.001 0.979944 Ethnicity*Gender 211438 1 211438 4.216 0.041026 Ethnicity*Child vs Adult 81157 1 81157 1.618 0.204464 Gender*Child vs Adult 11463 1 11463 0.229 0.632989 Ethnicity*Gender*Child vs Adult 199205 1 199205 3.972 0.047286 Error 13442022 268 50157              175  Table A1.28: Summary of ANOVA for Vea from Ya using 226-Hz Conventional Tympanometry  Vea from Ya using 226-Hz Conventional Tympanometry                 SS Degree Of Freedom MS F Intercept 157.9648 1 157.9648 1994.320 Middle ear condition 0.7259 4 0.1815 2.291 Error 21.0692 266 0.0792 Tail 0.0049 1 0.0049 1.250 Tail*Middle ear condition 0.5237 4 0.1309 33.222 Error 1.0483 266 0.0039  Table A1.29: Summary of ANOVA for Ytm at 678-Hz from rectangular components- MFT Ytm at 678-Hz from rectangular components- MFT SS Degree Of Freedom MS F p Intercept 1896.150 1 1896.150 512.7002 0.000000 {1}Ear 2.480 1 2.480 0.6707 0.414020 {2}Gender 3.693 1 3.693 0.9986 0.319133 {3}Ethnicity 51.164 1 51.164 13.8343 0.000275 Ear*Gender 0.162 1 0.162 0.0437 0.834718 Ear*Ethnicity 0.000 1 0.000 0.0000 0.994909 Gender*Ethnicity 1.403 1 1.403 0.3793 0.538823 Ear*Gender*Ethnicity 0.012 1 0.012 0.0032 0.955187 Error 599.134 162 3.698 {4}Compensation 21.481 1 21.481 232.8923 0.000000 Compensation*Ear 0.024 1 0.024 0.2593 0.611274 Compensation*Gender 0.662 1 0.662 7.1779 0.008143 {5}Component 124.118 2 62.059 91.8354 0.000000 Component*Ear 0.372 2 0.186 0.2755 0.759397 Component*Gender 7.272 2 3.636 5.3807 0.005025 Component*Ethnicity 6.410 2 3.205 4.7427 0.009329 Component*Ear*Gender 0.892 2 0.446 0.6599 0.517620 Component*Ear*Ethnicity 0.039 2 0.019 0.0288 0.971646 Component*Gender*Ethnicity 0.027 2 0.013 0.0199 0.980341 Error 218.947 324 0.676 Compensation*Component 15.606 2 7.803 246.2316 0.000000 Compensation*Component*Ear 0.016 2 0.008 0.2554 0.774742 Compensation*Component*Gender 0.023 2 0.012 0.3670 0.693079 Compensation*Component*Ethnicity 0.016 2 0.008 0.2583 0.772515 Error 10.268 324 0.032  176   Table A1.30: Summary of ANOVA for Ytm from Ya using 226-Hz Conventional Tympanometry  Ytm from Ya using 226-Hz Conventional Tympanometry  SS Degree Of Freedom MS F Intercept 22.93660 1 22.93660 136.0727 Middle ear condition 8.57099 4 2.14275 12.7120 Error 44.66876 265 0.16856 Compensation*Middle ear condition 0.00162 1 0.00162 0.0166 Compensation*Middle ear condition 0.29638 4 0.07409 0.7571 Error 25.93389 265 0.09786   Table A1.31: Summary of ANOVA for Ytm from Ya using 678-Hz MFT  Ytm from Ya using 678-Hz MFT SS Degree Of Freedom MS F Intercept 193.5304 1 193.5304 121.0479 Middle ear condition 109.7665 4 27.4416 17.1640 Error 428.4761 268 1.5988 Compenation 4.2725 1 4.2725 52.4743 Compenation*Middle ear condition 7.2441 4 1.8110 22.2430 Error 21.8206 268 0.0814     Table A1.32: Summary of ANOVA for Ytm from Ya using 1000-Hz MFT  Ytm from Ya using 1000-Hz MFT SS Degree Of Freedom MS F Intercept 347.8464 1 347.8464 106.8571 Middle ear condition 73.5479 4 18.3870 5.6484 Error 852.8748 262 3.2552 Compensation 64.9355 1 64.9355 411.7688 Compensation*Middle ear condition 58.1918 4 14.5480 92.2515 Error 41.3171 262 0.1577  177   Table A1.33: Summary of ANOVA for Ytm from rectangular components at 226-Hz- MFT  Ytm from rectangular components at 226-Hz- MFT SS Degree Of Freedom MS F Intercept 68.49229 1 68.49229 339.3516 Middle ear condition 16.24401 4 4.06100 20.1206 Error 52.27470 259 0.20183 Compensation*Middle ear condition 0.83508 4 0.20877 9.3482 Error 5.78412 259 0.02233 Compensation 6.38614 2 3.19307 152.6134 Compensation*Middle ear condition 2.56034 8 0.32004 15.2965 Error 10.83791 518 0.02092 Compensation*Component 0.27138 2 0.13569 17.3456 Compensation*Component*Middle ear condition 0.32219 8 0.04027 5.1483 Error 4.05215 518 0.00782   Table A1.34: Summary of ANOVA for Ytm from rectangular components at 678-Hz- MFT Ytm from rectangular components at 678-Hz- MFT SS Degree Of Freedom MS F Intercept 513.2437 1 513.2437 145.9294 Middle ear condition 286.1253 4 71.5313 20.3383 Error 914.4377 260 3.5171 Compensation 1.9368 1 1.9368 19.3777 Compensation*Middle ear condition 6.3045 4 1.5761 15.7694 Error 25.9867 260 0.0999 Componant 46.0736 2 23.0368 39.9376 Componant*Middle ear condition 15.0170 8 1.8771 3.2543 Error 299.9460 520 0.5768 Compensation*Componant 9.1116 2 4.5558 129.0384 Compensation*Componant*Middle ear condition 1.2057 8 0.1507 4.2689 Error 18.3590 520 0.0353        178   Table A1.35: Summary of ANOVA for Ytm from rectangular components at 1000-Hz- MFT  Ytm from rectangular components at 1000-Hz- MFT SS Degree Of Freedom MS F Intercept 1395.306 1 1395.306 195.0642 Middle ear condition 384.034 4 96.008 13.4220 Error 1881.255 263 7.153 Compensation 6.702 1 6.702 25.1993 Compensation*Middle ear condition 18.365 4 4.591 17.2623 Error 69.948 263 0.266 Component 456.960 2 228.480 58.1289 Component*Middle ear condition 301.974 8 37.747 9.6034 Error 2067.482 526 3.931 Compensation*Component 14.617 2 7.309 55.5944 Compensation*Component*Middle ear condition 1.428 8 0.179 1.3580 Error 69.149 526 0.131                           179    Table A1.36: Summary of ANOVA for TW from 226-Hz Conventional Tympanometry  TW from 226-Hz Conventional Tympanometry            SS Degree Of Freedom MS F Intercept  6319629 1 6319629 3199.508 Middle ear condition 2179682 4 544921 275.883 Error 503673 255 1975     Table A1.37: Summary of ANOVA for RF from MFT  RF from MFT SS Degree Of Freedom MS F Intercept 76095500 1 76095500 813.3682 Middle ear condition 23851934 4 5962983 63.7370 Error 23763232 254 93556 SF vs. SP 15447 1 15447 0.6802 SF vs. SP*Middle ear condition 53981 4 13495 0.5942 Error 5768422 254 22710  

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