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The effects of race, caucasian versus Chinese, on immittance audiometry norms Davies, Dreena 2003

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THE EFFECTS OF R A C E , C A U C A S I A N VERSUS CHINESE, ON IMMITTANCE AUDIOMETRY NORMS by D R E E N A DAVIES B.A. , The University of British Columbia, 1998 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF M A S T E R OF SCIENCE in THE F A C U L T Y OF G R A D U A T E STUDIES (School of Audiology and Speech Sciences) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH C O L U M B I A September 2003 © Dreena Davies, 2003 in presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver, Canada Date ^ L v V x \ ^ K ~ ~ x ZC^Cr*-, , DE-6 (2/88) Abstract This study examined racial differences between a group of normal hearing Caucasian and Chinese young adults on 5 tympanometric parameters. The goal of this study was to determine if the Chinese young adults had different low and multifrequency tympanometry results than the Caucasian young adults. There were a total of 40 subjects (and 80 ears) between the ages of 18 and 34 years, with 20 subjects (and 40 ears) per race group. Tympanometric data was gathered on a clinical immittance machine, the Virtual 310 equipped with an extended high frequency option. Two parameters—static admittance (SA) and tympanometric width (TW)—were measured at a standard low probe tone frequency of 226 Hz. The remaining 3 parameters—resonant frequency (RF), the frequency corresponding to an admittance phase angle of 45°, and SA up to 1200 Hz—could only be measured by multifrequency, multicomponent tympanometry. Findings indicated that all parameters except one (TW) showed a significant race effect. The parameter of SA up to 1200 Hz showed a significant race effect until 800 Hz. A significant measurement estimate effect (for negative vs. positive compensation and sweep pressure vs. sweep frequency) was found in all parameters except RF. Results from this study show that there is a significant race difference between Caucasian and Chinese adults on 4 tympanometric measures. The clinical implications of these findings are that audiologists should consider using race-based normative data when assessing patients with immittance audiometry. These findings suggest that further research into racial differences between other races should be initiated. Future research may also benefit from addressing racial differences in different age populations as well as determining the anatomic reasons for these differences. Table of Contents Abstract ii Table of Contents i i i List of Figures • . . . . . v i List of Tables.... viii Acknowledgements • - xvii C H A P T E R 1: I N T R O D U C T I O N 1 1.1 IMMITTANCE PRINCIPLES 4 1.2 TYMPANOMETRY REVIEW 8 1.2.1 Low Frequency Tympanometry 8 1.2.2 Multifrequency tympanometry 13 1.3 LITERATURE REVIEW 16 1.3.1 Low Frequency Tympanometry 16 1.3.2 Multifrequency Tympanometry 18 1.4 GOALS OF THIS STUDY 22 C H A P T E R 2: M E T H O D S 24 2.1 SUBJECTS 24 2.1.1 Inclusion and exclusion criteria 25 2.2 INSTRUMENTATION 26 2.3 PROCEDURE • 27 2.4 ANALYSIS OF DATA 31 C H A P T E R 3: R E S U L T S A N D DISCUSSION.. . . 32 3.1 STATIC ADMITTANCE 34 3.1.1 Procedure 34 3.1.2 Within-race group analysis—Caucasian 36 3.1.3 Within-race group analysis—Chinese 39 i i i 3.1.4 Between-race group analysis 40 3.2 TYMPANOMETRIC WIDTH 43 3.2.1 Procedure 43 3.2.2 Within-race group analysis—Caucasian 43 3.2.3 Within-race group analysis—Chinese 47 3.2.4 Between-race group analysis 48 3.3 STATIC ADMITTANCE UP TO 1200 Hz 50. 3.3.1 Procedure 50 3.3.2 Within-race group analysis—Caucasian ..50 3.3.3 Within-race group analysis—Chinese 54 3.3.4 Between-race group analysis 55 3.4 RESONANT FREQUENCY 61 3.4.1 Procedure 61 3.4.2 Within-race group analysis—Caucasian 62 3.4.3 Within-race group analysis—Chinese 67 3.4.4 Between-race group analysis 68 3.5 FREQUENCY CORRESPONDING TO A 45° PHASE ANGLE (F45°) 70 3.5.1 Procedure 70 3.5.2 Within-race group analysis—Caucasian 70 3.5.3 Within-race group analysis—Chinese 72 3.5.4 Between-race group analysis 73 C H A P T E R 4: G E N E R A L DISCUSSION 75 4.1 SUMMARY 75 4.2 LIMITATIONS • 75 4.3 SOURCES OF DIFFERENCES 78 4.4 CLINICAL IMPLICATIONS 79 4.5 FUTURE RESEARCH 83 R E F E R E N C E S 87 A P P E N D I C E S 98 iv APPENDIX I - A N O V A TABLES FOR STATIC ADMITTANCE (SA), TYMPANOMETRIC WIDTH (TW), RESONANT FREQUENCY (RF), AND THE FREQUENCY CORRESPONDING TO AN ADMITTANCE PHASE ANGLE OF 45° (F45°) 98 APPENDIX II - A N O V A TABLES OF S A UP TO 1200 H Z 102 APPENDIX III - TELEPHONE QUESTIONNAIRE 113 APPENDIX I V - VOCABULARY 114 v List of Figures FIGURE 1.1: Admittance terminology presented in polar and rectangular format. Bm=mass susceptance, Bs=stiffness susceptance; Btotai=total susceptance; G=conductance, 0=phase angle, | Y | =absolute admittance value: (Adapted from Van Camp, Margolis, Wilson, Creten, & Shanks, 1984) 5 FIGURE 1.2: Phase and vector rotation in admittance terminology. F45° corresponds to B = G; RF corresponds to B t = 0. (Margolis & Shanks, 1985) 7 FIGURE 1.3: Different SA values are obtained when using positive and negative tail compensation. (Figure from Shahnaz, 2000, with permission 12 FIGURE 1.4: TW is calculated by taking one half of the peak compensated static admittance (Y t m ) and drawing a hypothetical horizontal line which bisects the two values (in daPa) on the tympanogram. (Figure from Shahnaz, 2000, with permission) 13 FIGURE 1.5: A visual estimate of RF is made by finding the frequency at which the notch in the susceptance (B) tympanogram is equal to its positive or negative tail. (Figure from Shahnaz, 2000 with permission) 19 FIGURE 3.1: Box-and-whisker plot of static admittance (Y) at 226 Hz using positive (+) and negative (-) compensation for Caucasian and Chinese adults (collapsed genders) 42 FIGURE 3.2: A box-and-whisker plot of tympanometric width at 266 Hz using positive (+) and negative (-) compensation for Caucasian and Chinese adults (collapsed genders). No significant race differences were found on this variable. Please refer to page 43 for the definition of an outsider 49 vi FIGURE 3.3: Box-and-whisker plot showing SP recordings with positive compensation for race differences (between-subject factor) and estimate effects (within-subject factor) at probe tone frequencies up to 1200 Hz. Gender data is collapsed within each race group. Note that significant gender differences were found at 400 Hz and 500 Hz for Chinese females (figures 3.4-5 present individual gender by race data for 400 and 500 Hz). Please refer to page 43 the definition of outsider and outlier 59 FIGURE 3.4: Box-and-whisker plot showing SP recordings with negative compensation for race differences (between-subject factor) and estimate effects (within-subject factor) at probe tone frequencies up to 1200 Hz. Gender data is collapsed within each race group. Note that significant gender differences were found at 400 Hz and 500 Hz for Chinese females. Please refer to page 43 for the definition of outsider and outlier 60 FIGURE 3.5: Box-and-whisker plot showing individual race and gender effects at 400 and 500 Hz. Chinese subjects showed significant gender differences at these frequencies. Caucasian and Chinese females also showed significant race differences at these frequencies, while their male counterparts did not. Please refer to page 43 for the definition of outsider and outlier , : 61 FIGURE 3.6: Box-and-whisker plot showing a significant race effect for resonant frequency with race (collapsed genders) as a between-subject factor and estimate (SF+, SF-, SP+, SP-) as a within-subject factor. Please refer to page 43 for the definition of an outlier ' 69 FIGURE 3.7: Box-and-whisker plot showing F45° by gender and race (between-subject factors) and estimate (within-subject factor). Genders are not collapsed as significant gender differences were found in the Chinese adults. Please refer to page 43 for the definition of an outlier 74 vii List of Tables T A B L E 1.1: Mathematical relationships in admittance terminology between polar and rectangular notation 6 T A B L E 1.2: The effects of specific pathologies (relative to healthy ears) on four measurement parameters. Unknown effects are denoted with a question mark (?) 15 T A B L E 3.1: Results of static admittance (SA) at 226 Hz for the current study and other published normative studies. SA is reported for both positive (+) and negative (-) compensation. Values not reported are marked with —; M = male; F = female; C = combined genders; * = Shanks et al. (1993) reported median values 35 T A B L E 3.2: Procedural variables for measuring static admittance and tympanometric width at 226 Hz. Unreported variables are denoted by —; DNT = did not test 37 T A B L E 3.3: Results of static admittance (TW) at 226 Hz from the current study and other published normative studies. TW is reported for both positive (+) and negative (-) compensation. Values not reported are marked with —; M = male; F = female; C = combined genders 44 T A B L E 3.4: Descriptive statistics by race (collapsed genders) for static admittance (Y) up to 1200 Hz with both positive (+) and negative (-) compensation 51 T A B L E 3.5: Descriptive statistics from previous normative studies for static admittance (Y) up to 1200 Hz with positive (+) and negative (-) compensation 52 viii T A B L E 3.6: Procedural variables for the measurement of static admittance up to 1200 Hz. Unspecified variables are denoted by —; M/F = number of male and female subjects in the sample group 54 T A B L E 3.7: Descriptive statistics for Caucasian group by gender for static admittance (Y) up to 1200 Hz with both positive (+) and negative (-) compensation 56 T A B L E 3.8: Descriptive statistics for Chinese group by gender for static admittance (Y) up to 1200 Hz with both positive (+) and negative (-) compensation 57 T A B L E 3.9: Descriptive statistics for resonant frequency (RF), measured by sweep frequency (SF) with both positive (+) and negative (-) compensation for the current study as well as other published data. Shanks et al. (1993) reported median values (*); unreported values denoted by —; M = male; F = female; C = combined genders 63 T A B L E 3.10: Descriptive statistics for resonant frequency (RF), measured by sweep pressure (SP) with both positive (+) and negative (-) compensation for the current study as well as other published data; variables not tested are represented by —; M = male; F = female; C = combined genders 64 T A B L E 3.11: Procedural variables in the estimation of resonant frequency in published normative studies. Studies marked with ** also report F45° data; unspecified values are denoted by —; comp = method of compensation 67 T A B L E 3.12: Descriptive statistics for the frequency corresponding to an admittance phase angle of 45° (F45°) measured by sweep frequency (SF) and sweep pressure (SP) for both positive (+) and negative (-) compensation. Unreported values are denoted by —; M = male; F= female; C = combined genders 71 ix T A B L E 4.1: This table provides a summary of significant differences on each parameter tested. Within-race results refer to tests within each race group (C = Caucasian; A = Chinese); between-race results refer tests between race groups (M = male; F = female). When significant gender differences were found in within-race analysis, genders were analyzed separately in between-race measures. Significant differences are denoted by *; non-significant results are indicated by a blank space 76 T A B L E A l . l : Summary of A N O V A for Caucasian SA at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 98 T A B L E A1.2: Summary of A N O V A for Chinese SA at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 98 T A B L E A1.3: Summary of A N O V A for group differences between Caucasian and Chinese SA at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 98 T A B L E A1.4: Summary of A N O V A for Caucasian TW at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 99 T A B L E A1.5: Summary of A N O V A for Chinese TW at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 99 T A B L E A1.6: Summary of A N O V A for group differences between Caucasian and Chinese TW at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 99 x T A B L E A1.7: Summary of A N O V A for Caucasian RF at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (RF estimate: SP+, SP-, SF+, SF-) 100 T A B L E A1.8: Summary of A N O V A for Chinese RF at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (RF estimate: SP+, SP-, SF+, SF-) 100 T A B L E A1.9: Summary of A N O V A for group differences between Caucasian and Chinese TW at RF Hz with one between-subject factor (gender: male versus female) and one -within-subject factor (RF estimate: SP+, SP-, SF+, SF-) 100 T A B L E ALIO: Summary of A N O V A for Caucasian F45° at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (F45° estimate: SP+, S-, SF+, SF-) 101 T A B L E A 1.11: Summary of A N O V A for Chinese F45° at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (F45° estimate: SP+, S-, SF+, SF-) : 101 T A B L E A1.12: Summary of A N O V A for Caucasian female F45° with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (F45° estimate: SP+, S-, SF+, SF-) 101 T A B L E A1.13: Summary of A N O V A for Caucasian male F45° with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (F45° estimate: SP+, S-, SF+, SF-) .' 101 T A B L E A2.1: Summary of A N O V A for Caucasian SA at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 102 xi T A B L E A2.2: Summary of A N O V A for Chinese SA at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 102 T A B L E A2.3: Summary of A N O V A for group differences between Caucasian and Chinese SA at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 102 T A B L E A2.4: Summary of A N O V A for Caucasian SA at 315 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 103 T A B L E A2.5: Summary of A N O V A for Chinese SA at 315 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 103 T A B L E A2.6: Summary of A N O V A for group differences between Caucasian and Chinese SA at 315 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 103 T A B L E A2.7: Summary of A N O V A for Caucasian SA at 400 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 104 T A B L E A2.8: Summary of A N O V A for Chinese SA at 400 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 104 xii T A B L E A2.9: Summary of A N O V A for group differences between Caucasian and Chinese female SA at 400 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-) 104 T A B L E A2.10: Summary of A N O V A for group differences between Caucasian and Chinese male SA at 400 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-) 104 T A B L E A 2 . l l : Summary of A N O V A for Caucasian SA at 500 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 105 T A B L E A2.12: Summary of A N O V A for Chinese SA at 500 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 105 T A B L E A2.13: Summary of A N O V A for group differences between Caucasian and Chinese female SA at 500 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-) 105 T A B L E A2.14: Summary of A N O V A for group differences between Caucasian and Chinese male SA at 500 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-) 105 T A B L E A2.15: Summary of A N O V A for Caucasian SA at 630 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 106 T A B L E A2.16: Summary of A N O V A for Chinese SA at 630 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 106 xiii T A B L E A2.17: Summary of A N O V A for group differences between Caucasian and Chinese SA at 630 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-) 106 T A B L E A2.18: Summary of A N O V A for Caucasian SA at 710 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) . 107 T A B L E A2.19: Summary of A N O V A for Chinese SA at 710 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 107 T A B L E A2.20: Summary of A N O V A for group differences between Caucasian and Chinese SA at 710 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 107 T A B L E A2.21: Summary of A N O V A for Caucasian SA at 800 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 108 T A B L E A2.22: Summary of A N O V A for Chinese SA at 800 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 108 T A B L E A2.23: Summary of A N O V A for group differences between Caucasian and Chinese SA at 800 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 108 xiv T A B L E A2.24: Summary of A N O V A for Caucasian SA at 900 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 109 T A B L E A2.25: Summary of A N O V A for Chinese SA at 900 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) : 109 T A B L E A2.26: Summary of A N O V A for group differences between Caucasian and Chinese SA at 900 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 109 T A B L E A2.27: Summary of A N O V A for Caucasian SA at 1000 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 110 T A B L E A2.28: Summary of A N O V A for Chinese SA at 1000 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) .' 110 T A B L E A2.29: Summary of A N O V A for group differences between Caucasian and Chinese SA at 1000 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) 110 T A B L E A2.30: Summary of A N O V A for Caucasian SA at 1120 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) I l l T A B L E A2.31: Summary of A N O V A for Chinese SA at 1120 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) I l l xv T A B L E A2.32: Summary of A N O V A for group differences between Caucasian and Chinese SA at 1120 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-) I l l T A B L E A2.33: Summary of A N O V A for Caucasian SA at 1250 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y + , Y - ) 112 T A B L E A2.34: Summary of A N O V A for Chinese SA at 1250 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y + , Y - ) ; 112 T A B L E A2.35: Summary of A N O V A for group differences between Caucasian and Chinese SA at 1250 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y + , Y - ) 112 xvi Acknowledgements I would like to thank Dr. Navid Shahnaz, my thesis supervisor, for his enormous and unwavering support during the long process of completing this thesis. There were many moments where I stalled and felt stuck, but his knowledge, support, and encouragement kept me going towards the finished product. I would also like to thank my thesis committee, Dr. Carolyn Johnson and Sharon Adelman, for their contributions of time and their helpful comments and suggestions. I am grateful to the British Columbia Medical Services Foundation for providing me with a summer research scholarship, which helped my entire thesis experience by allowing me to concentrate much of my time and energy over the summer to this project. Finally, I would like to thank my family, friends, and my husband Mike for their support and encouragement, and also for lending an ear to my many complaints. This project could never have been completed alone, and I am grateful to everyone who helped me along the way. xvii Chapter 1: Introduction Tympanometry is a safe and quick method for assessing middle ear function. In this technique, a soft plastic probe is sealed in the outer ear. Sound is presented while the air pressure is changed within the ear canal. The sound pressure level monitored at the probe tip provides an index of the ease with which acoustic energy flows into the middle ear system, which is referred to as acoustic admittance. The resulting display is called a tympanogram, in which a normal ear has a bell-shaped curve with a single peak. Currently, tympanometry is usually conducted at a standard probe tone frequency of 226 Hz. At the low probe tone frequency used in standard tympanometry, the normal middle ear system is stiffness dominated, which means that stiffness contributes more to overall admittance than mass and the frictional element.1 Tympanometry performed using a standard low probe tone frequency has proven its validity in identifying a variety of middle ear disorders (e.g., effusion or abnormal air pressures within the middle ear cavity), tympanic membrane abnormalities (e.g., atrophic scarring, retraction, or perforation), and eustachian tube malfunction (Lilly, 1984). However, standard low frequency tympanometry often fails to distinguish normal middle ears from ears with pathologies that affect the ossicular chain (Browning, Swan, & Gatehouse, 1985; Colletti, 1975, 1976; Lil ly, 1984; Shahnaz & Polka, 1997). The development of multifrequency, multicomponent admittance devices has made it possible to record admittance across a wide range of frequencies and to measure the relative contribution of stiffness, mass, and frictional elements. These elements are represented by 1 These terms will be defined in the lmmittance Principles section 1 susceptance and conductance which are sub-components of an admittance tympanogram. To date, the advantage of multifrequency, multicomponent tympanometry over standard frequency tympanometry has been confirmed in detecting pathologies such as otosclerosis (Shahnaz & Polka, 1997, 2002) and ossicular discontinuity (Funasaka & Kumakawa, 1988; Hunter & Margolis, 1992; Lil ly, 1984; Valvik, Johnsen, & Laukli, 1994). One potentially useful parameter that can be derived from multifrequency, multicomponent tympanometry is an estimate of the middle ear resonant frequency, which is the frequency at which the middle ear vibrates most readily. It has been shown that an abnormality is most obvious when the probe tone frequency approaches resonant frequency (Margolis & Shanks, 1991; Shanks, 1984). The greatest impact of middle ear pathology on static admittance is at frequencies close to the resonant frequency (Liden, Harford, & Hallen, 1974; Shahnaz & Polka, 2002). In order to effectively use both standard and multifrequency tympanometry in clinical practice, all sources of subject variability that can affect the outcome of measurement should be taken into consideration. These sources of variability, such as age, gender, and race have been addressed to some extent with standard low frequency tympanometry. Several researchers have shown age (DeChiccis, Todd, & Nozzia, 2000; Hanks & Rose, 1993; Roup, Wiley, Safady, & Stoppenbach, 1999; Wiley, Cruishanks, Nondahl, Tweed, Klein & Klein, 1996) and gender (Roup et a l , 1998; Wan & Wong, 2002; Wiley et al., 1996) effects, while others have not (Margolis & Heller, 1987). The most relevant published data to date on the effect of race on standard tympanometry is from Wan and Wong (2002). They collected low frequency data on Chinese young adults and compared it to non-Hispanic Caucasian adult normative data collected by Roup et al. (1998). They found that Chinese adults had 2 significantly different results and suggested that these differences could be caused by anatomic variations between the two races. The results of previous research in multifrequency tympanometry have been ambiguous on the effects of age and gender, with some studies showing an age effect (Hanks & Rose, 1993; Wiley et al., 1999), some showing a gender effect (Wiley et al., 1999), and some showing no effects (Holte, 1996; Margolis & Goycoolea, 1993). There has been no research yet on the effects of race on multifrequency tympanometry. It is important to note that all normative standard and multifrequency tympanometry data to date has either been based on Caucasian data, or the race of the participants has not been specified. The goal of the present project is to determine if there are differences between Chinese and Caucasian young adults in standard and multifrequency tympanometry. Two parameters Of low frequency tympanometry—static admittance and tympanometric width— will be compared with three parameters derived from multifrequency tympanometry: middle ear resonant frequency, the frequency corresponding to a phase angle of 45°, and static admittance derived at multiple frequencies (up to 1200 Hz). If race-based differences in these parameters are found, they could impact the diagnosis of middle ear pathology in Chinese adults. Differences found between these two races will also prompt further research into the differences between other racial groups. If it is possible to find an underlying mechano-acoustic difference between the middle ears of these two races, this may provide insight into why certain middle ear diseases are more prevalent in specific race groups. For example, research has shown that American Indians and Inuits have higher incidences of otitis media (Klein, 1978; Northern & Downs, 2002). Preliminary research into the prevalence of otitis 3 media in Chinese and Caucasian children has shown that Chinese children in Hong Kong have a similar or lesser prevalence of otitis media than their Caucasian counterparts in North America (Rushton, Tong, Yue, Wormald, van Hasselt, 1997; Tong, Yue, Ku, Lo, van Hasselt, 2000). In order to better understand the topics that will be discussed in this study, some basic physical principles of immittance audiometry will be reviewed. Following this, the underlying principles of tympanometry as an immittance measurement will be reviewed. The third section is a review of studies on both standard and multifrequency tympanometry, with an emphasis on the subject variables of age, gender, and race. The final section will outline the goals of this study. /./ Immittance Principles Tympanometry is a form of immittance audiometry. Immittance audiometry is an estimate of energy flow into the middle ear system that can be measured in either impedance, or its reciprocal admittance. Impedance measures the opposition of a system to energy flow and is denoted by the symbol Z and measured in acoustic ohms. Admittance measures the ease of energy flow into a system and is represented by the symbol Y and measured in acoustic millimho (mmho). Some immittance systems are capable of measuring both impedance and admittance; however, currently available instruments typically measure admittance. Admittance will be used exclusively in this study. The elements of mass, stiffness, and friction determine the admittance of a system. Admittance is comprised of the subcomponents of susceptance (mass and stiffness) and conductance (friction). The admittance offered by the mass elements in the middle ear is 2 Appendix IV has a review of vocabulary items and their abbreviations. 4 called mass susceptance is denoted by B m (referred to as mass reactance, X m , in impedance terminology). The admittance offered by stiffness elements in the middle ear is referred to as stiffness susceptance and is denoted by the symbol B s . Stiffness is the inverse of compliance, and the equivalent of B s in impedance terminology is called compliant reactance (-X c ) . Total susceptance (referred to as B t ) is the sum value of the mass and stiffness elements. When represented graphically, B s is on the positive Y-axis and B m is on the negative Y-axis. If B t is a positive number, the middle ear system is stiffness-dominated; if B t is a negative number this tells us that the middle ear is a mass-dominated system. The final variable of admittance is friction, referred to as conductance and denoted by G (or resistance, R, in impedance terminology), and this variable is responsible for the absorption and dissipation of acoustic energy. Conductance is always a positive value and is represented on the X-axis (Fig. 1.1). POLAR RECTANGULAR CONDUCTANCE (C) Bs+ B , T t^otal —1.5 mmho G - 1.5 mralios Figure 1.1: Admittance terminology presented in polar and rectangular format. Bm=mass susceptance, Bs=stiffness susceptance; Btotal=total susceptance; G=conductance, 0=phase angle, | Y | =absolute admittance value. (Adapted from Van Camp, Margolis, Wilson, Creten, & Shanks, 1984) 5 In mathematical terms susceptance and conductance can be expressed in either rectangular or polar format. It is important to remember that | Y | is a vector sum of both susceptance and conductance. In rectangular notation this relationship is expressed by: Y = G + j B t (1) The j in this formula is equal toV-T , which means that susceptance and conductance cannot be added algebraically because they are vectors that operate in different directions (Shahnaz & Polka, 1997). Polar notation expresses | Y | as a phase angle and magnitude, where the phase angle (0y; represented by 0x in impedance terminology) represents the angle between the | Y | vector and the X-axis and magnitude refers to the length of the vector (see Fig. 1). This relationship is: Y < 0y (2) Polar and rectangular notations are related to each other by the following conversion formulas (Table 1.1): Admittance Y ] Y | < 0y (polar notation) Y = G + j B t (rectangular notation) G = | Y | cos 0y B = | Y | sin 0y l tm — tm + B t m Tan 0y = B / G 0y = arctan ( B / G ) Table 1.1 : Mathematical relationships in admittance terminology between polar and rectangular notation. 6 In a normal ear, there is a specific relationship between admittance variables and frequency: Conductance values are independent of frequency, B m is directly proportional to frequency, and B s is inversely proportional to frequency. This means that as the frequency of the probe tone increases, B t moves from a positive stiffness- dominated value, through 0°, to a negative mass-dominated value. When the | Y | vector is between 0° and 90° the middle ear system is stiffness controlled; when the vector moves between 0° and -90° the system is mass dominated. At low probe tone frequencies the | Y | vector is between 45° and 90° and B > G (Fig. 2). As the frequency increases, susceptance decreases, and B and G become equal to each other at 45°. This is referred to as the frequency corresponding to a phase angle of 45° (F45°). An additional increase in frequency makes B < G and the vector moves between 45° and 0° degrees! -90° 0 1 2 3 4 5 CONDUCTANCE (G) mmho Figure 1.2 : Phase and vector rotation in admittance terminology. F45° corresponds to B = G; resonant frequency corresponds to B t= 0. (Margolis & Shanks, 1985) 7 An important concept to return to is resonant frequency. The point where B s and B m are equal to one another (or the point where B t = 0 mmhos) is referred to as the resonant frequency of the middle ear. When B t is at, or very close to 0, G is the only component that is contributing to the admittance of the system. The resonant frequency of the middle ear may be shifted higher or lower by various pathologies (Shanks & Shelton, 1991). Mass loading pathologies (i.e., ossicular discontinuity) shift resonant frequency to a lower value, while pathologies caused by abnormal stiffness (i.e., otosclerosis) shift resonant frequency to higher values. These shifts are caused by the relationship between resonant frequency and certain mechanical characteristics of the middle ear, such that resonant frequency is directly proportional to the stiffness of the middle ear system and is inversely proportional to the mass of the middle ear system. This translates into a higher resonant frequency in a stiffness dominated middle ear, and a lower resonant frequency in a mass dominated middle ear transmission system. 1.2 Tympanometry Review 1.2.1 Low Frequency Tympanometry The principle behind the earliest acoustic immittance instruments was to present sound to the ear and measure the reflected sound energy in the ear canal. The clinical application of tympanometry uses this principle to gain information on the status and function of the middle ear. A tympanogram is a graphical representation of the admittance of the middle ear as a function of the ear canal air pressure. It is recorded with a pressure change in the ear canal in the presence of a probe tone. 8 Tympanograms are measured by sealing the ear canal with a soft plastic probe tip. This probe tip is connected to an admittance meter and has three basic components. The first is a tube attached to an air pump used to change the pressure in the ear canal; the second is a small loudspeaker, attached to a signal generator, which produces the probe tone; and the last is a small microphone which measures the reflected probe tone in the ear canal and converts it to an electrical signal used to measure the acoustic admittance. The probe tone is kept at a constant sound pressure level (SPL) by an automatic gain control (AGC) circuit. The measured SPL in the ear canal is directly proportional to the voltage at the microphone output. This means that if the SPL output of the microphone is too low, the A G C circuit increases the voltage to maintain a constant probe tone SPL in the ear canal (Margolis & Shanks, 1985). The reverse occurs when the SPL level is too high and the A G C circuit decreases the voltage to decrease the probe tone SPL. Any change in voltage (in response to an SPL change in the ear canal) is directly proportional to the admittance magnitude at the tip of the probe (Shahnaz, 1996). In a normal tympanogram the admittance of the middle ear reaches a maximum level close to ambient air pressure and decreases as air pressure becomes more positive or negative. The probe tip of the admittance meter is remote from the plane of the tympanic membrane, and as a result, admittance measured at the tip of the probe reflects both the admittance of the ear canal and the middle ear. The dimensions of the ear canal may vary depending on the depth of insertion of the probe and individual variation in size. These variations can produce substantial differences in the admittance of the ear canal and, as a result, affect the joint admittance (admittance at the measurement plane). 9 To reach an estimate of only the admittance of the middle ear, it is necessary to subtract the admittance due to the ear canal from the overall admittance value (Margolis & Hunter, 2000). This can be done by placing the eardrum under enough tension (by high positive or negative pressure) to drive the admittance of the middle ear system towards infinity. The admittance measured under one of these conditions provides an estimate of ear canal volume alone. This value can then be subtracted from the joint admittance estimate, which leaves an estimate of the tympanic membrane and middle ear. This value is referred to as peak compensated acoustic admittance ( Y t m ; ANSI 1987). The notation SA can also be used for peak compensated static admittance, and these two terms will be used interchangeably in this study. Clinical immittance machines use this method to estimate static admittance. It is important to note that it is not mathematically correct to subtract the peak from the tail value of an admittance tympanogram. This is because vector quantities such as admittance cannot be added or subtracted unless the phase angles are identical (Margolis & Shanks, 1985). The correct procedure is to transform admittance from its polar format (admittance magnitude and corresponding phase angle) into rectangular format (susceptance and conductance), apply compensation (correction for the ear canal volume) to its rectangular components, and then transform them back to polar notation (please refer to the Methods section for a more detailed explanation). As mentioned above, clinical machines do not use the most accurate method to estimate static admittance. A major reason for this is the time-consuming and labour intensive process necessary to mathematically derive static admittance values. Unfortunately, 10 until this mathematical procedure is built into clinical machines the majority of clinicians will use less accurate estimates of static admittance when evaluating tympanometric results. The term compensated refers to the subtraction of the ear canal admittance from the joint admittance estimate. Compensation in a clinical setting is typically achieved by subtracting the admittance at the positive or negative tail of the tympanogram (see Fig. 3). The tail of the tympanogram is the most positive or negative value measured. Compensated static admittance is usually higher when the negative tail is used to estimate ear canal volume (Shanks & Lil ly, 1981). This variation is due to an inherent asymmetry in the tympanogram, which causes volume estimates at negative pressures to be lesser than estimates at positive pressures (Margolis & Smith, 1977). The negative tail offers a more accurate estimate of ear canal volume (Shanks & Lil ly, 1981); however, the positive tail offers less variability in test-retest measures (Hanks & Mortenson, 1997; Holte, 1996; Margolis & Goycoolea, 1993; Shahnaz & Polka, 1997). Different ear canal pressures may be used to estimate ear canal volume, and typically more extreme pressure values result in lower ear canal volume estimates (Margolis & Hunter, 2001). Several features from standard low probe tone frequency (226 Hz) tympanometry are used to evaluate the function of the middle ear system, and this study will focus on two of them. As explained above, static admittance (or peak compensated acoustic admittance) is calculated by subtracting the admittance of the ear canal from the measured total admittance. Tympanometric width (TW), or the sharpness of the tympanometric peak, can be indicative of middle ear pathology (Fiellau-Nikolajsen, 1983; Haughton, 1977; Nozza, Bluestone, & Kardatze, 1992; Paradise, Smith, & Bluestone, ,1976). It is measured by taking one half of the static admittance value, and drawing a hypothetical horizontal line which bisects two 11 £ c o E 1.50 -p 1.25 •• a 1.00 •-£ E 0.75 •-0.50 •-0.25 •-0.0 --500 226 Hz Tympanogram Peak Ytm (1-00mmho) >/\i negative compensation: 1.00 - 0.40 = 0.60: negative tail (0.40 mmho) positive compensation: 1.00 - 0.5. = 0.50 mmho positive tail (0.50 mmho) -400 -300 -200 -100 0 100 Air Pressure (daPa) 200 300 400 Figure 1.3: Different static admittance (SA) values are obtained when using positive and negative tail compensation. (Figure from Shahnaz, 2000, with permission) 500 values (in daPa) on the tympanogram (see F ig . 4). It is possible for pathologic conditions to either widen or narrow the T W . Eardrum abnormalities, such as atrophic scarring and tympanosclerotic plaques, may cause a decrease in T W ; however, the only middle ear disorder noted to decrease T W is ossicular fixation (Ivey, 1975; Shahnaz & Polka, 1997; Shanks, 1984). Nozza et al. (1992) found that middle ear effusion can create a wider T W . He calculated T W for two groups of pre-myringotomy children and correlated these results with surgical findings of effusion. Results indicated that children with surgically confirmed effusion had larger tympanometric widths than those without fluid. Nozza concluded that T W alone should not be used to diagnose effusion, as there is an overlapping distribution of T W between the two groups. 12 226 Hz Tympanogram Figure 1.4: Tympanometric width (TW) is calculated by taking one half of the peak compensated static admittance (Y t m ) and drawing a hypothetical horizontal line which bisects the two values (in daPa) on the tympanogram. (Figure from Shahnaz, 2000, with permission) 1.2.2 Multifrequency tympanometry The selection of a low frequency probe tone (220 or 226 Hz) was not necessarily made for its diagnostic value but was primarily made for ease in calibration (Margolis & Shanks, 1995). Multifrequency multicomponent tympanometry allows tympanograms to be recorded at multiple frequencies (226-2000 Hz) and with multiple components (susceptance . and conductance). The low frequency tympanogram from a normal ear shows a single peak, while tympanograms recorded at higher frequencies may show multiple peaks. The multifrequency tympanometry parameters measured in this study are resonant frequency, F45°, and static admittance (up to 1200 Hz). Static admittance can be measured above 1200 Hz; however, previous data has only been reported up to 1200 Hz by Shanks et al. (1993) and up to 1000 Hz by Shahnaz & Polka (2002). Also, static admittance at higher frequencies is more subject to artifact (Shahnaz & Polka, 2002). 13 Several researchers have studied the effects of different pathologies on multifrequency static admittance and resonant frequency (Colletti, 1975, 1976, 1977; Li l ly , 1973; Margolis & Goycoolea, 1993; Shahnaz & Polka, 1997, 2002; Valvik et al., 1994). Lil ly (1973) found that resonant frequency was higher in ears with otosclerosis (a stiffness loading pathology) than in normal ears. He suggested two methods for the differential diagnosis of otosclerosis: (1) measure static admittance at a probe tone frequency close to the resonant frequency of a normal ear, or (2) measure the resonant frequency of the pathologic ear. Colletti (1977) found that patients with ossicular fixation (otosclerosis) had an increase in resonant frequency compared to a healthy ear, due to an increase of stiffness in the middle ear transmission system. He also noted that patients with ossicular discontinuity had a decrease in resonant frequency relative to a normal ear, caused by a decrease in stiffness or an increase in mass in the middle ear system. Margolis & Goycoolea (1993) found similar results and reported that a higher resonant frequency was consistent with abnormal stiffness of the middle ear (e.g., otosclerosis), and a lower resonant frequency was associated with eardrum abnormalities, ossicular discontinuity, and mass loading lesions. There has been limited research on F45°, and all research has been focused on the relationship between F45° and otosclerosis. Shanks, Wilson, and Palmer (1987) suggested that F45° might be a better tool than RF for the differential diagnosis of otosclerosis. Shahnaz and Polka (1997, 2002) found F45° to be the best single measure to distinguish otosclerotic from healthy ears. Table 1.2 shows the effects of certain pathologies on both low and multiple frequency tympanometric parameters. 14 Pathology Parameter Ossicular Fixation Effusion Ossicular Discontinuity Static Admittance Lower Lower / Flat Higher Tympanometric Width Narrower Wider Normal Resonant Frequency Higher Lower Lower F45° ' Higher 7 ? Table 1.2: The effects of specific pathologies (relative to healthy ears) on four measurement parameters. Unknown effects are denoted with a question mark (?). Many variables can affect the results of multifrequency tympanometry. Variables that will be discussed here are recording method, pressure direction, pressure range, and compensation method. Multifrequency tympanometry can be recorded by two methods. In the sweep frequency (SF) method, pressure is held constant while frequency is swept across multiple frequencies. The sweep pressure (SP) method holds frequency constant while the pressure is swept across a given range. Consecutive SP recordings can temporarily change the mechanical properties of the middle ear (Osguthorpe & Lam, 1981; Vanpeperstraete, Creten, & Van Camp, 1979), so SF recordings should be done first. However, the SF method results in higher estimates of resonant frequency (Margolis & Goycoolea, 1993; Shahnaz & Polka, 1997). This finding is probably related to the effects of the rate of pressure change (Creten & Van Camp, 1974, Shanks & Wilson, 1986) and multiple pressure sweeps (Osputhorpe & Lam, 1981; Vanpeperstraete et al., 1979). Using a faster rate of pressure change combined with multiple pressure sweeps can increase the static admittance and decrease the resonance frequency of the middle ear (Margolis & Goycoolea, 1993). Pressure direction can also affect the results of multifrequency tympanometry, and positive to negative pressure sweeps show less complex tympanometric shapes (Kobesell et al., 1998) than the reverse pressure direction. The measured pressure range has a similar effect in multifrequency measures to low frequency tympanometry, and more extreme 15 pressure values can result in lower ear canal volume estimates. Negative compensation has been previously shown to yield higher estimates of resonant frequency than positive compensation (Hanks & Mortenson, 1997; Holte, 1996; Margolis & Goycoolea, 1993; Shahnaz & Polka, 1997) although both compensation methods will be used in this study. 1.3 Literature review 1.3.1 Low Frequency Tympanometry The American Speech-Language-Hearing Association (1990) recommends normative middle ear screening values for adults based on the data of Margolis and Heller (1987). This data was gathered using low probe tone frequency, and the subjects were males and females between 19 - 69 years of age. Margolis and Heller did not find significant differences across age and gender and combined these variables when establishing normative criteria. However, other reports of normative data have shown variations in both age and gender. Aging effects have been noted in standard low frequency tympanometry. De Chicchis et al. (2000) looked at static admittance and ear canal volume changes from infancy to childhood (ages 6 months to 5 years) and found that both of these variables increased with age. Hanks and Rose (1993) looked at the standard low frequency variables of static admittance, ear canal volume, and tympanometric peak pressure in children aged 6 to 15 years and found no significant changes over this time period. Wiley et al. (1996) studied standard low frequency tympanometry in older adults (ages 48 - 90 years). They found that the older adults had lower static admittance values, higher ear canal volume values, and lower tympanometric width values as compared to the Margolis and Heller published data. Roup et al. (1998) controlled the variable of age by studying young adults aged 20 to 30 16 years. Relative to the Margolis and Heller data, differences in mean ear canal volume (significantly higher values) and mean tympanometric width values (significantly smaller) were found. These results provide evidence of an age effect in low frequency tympanometry; however, this effect is minimal within small age groups (i.e. there is no age effect in a group of 20 to 30-year-old adults). Gender has also been found to affect immittance audiometry results. Margolis and Heller did not find a significant gender effect in their research, and collapsed their male and female data together. However, collapsing their results across genders may have decreased the sensitivity of their normative data. Several low frequency tympanometry studies have demonstrated a gender effect, with males having a larger mean peak static admittance and ear canal volume, and smaller tympanometric width than females (Roup et al., 1998; Wan & Wong, 2002; Wiley et al., 1996). The dependency of norms on age and gender has already been addressed in standard low frequency tympanometry. Limited research has been conducted on the effects of race on low frequency tympanometry variables; many studies do not even indicate which racial population was studied. Robinson and Allen (1984) and Robinson, Allen, and Root (1988) looked at the prevalence of otitis media in African-American children and found that it was less prevalent than in Caucasian children. They analyzed their data by comparing tympanometric shapes from the two races (Jerger, 1970; Paradise et al., 1976). Results from both studies showed that African-American children had a significantly lower incidence of failure on screening by tympanometric shapes than Caucasian children. The authors attributed their results to physiological differences in the middle ear of African-Americans, and suggested that these children had larger mastoid pneumatic cells that allowed the ear to 17 drain more readily. Klein (1978) reported that American Indian and Inuit groups show a higher incidence of otitis media; Northern & Downs (2002) has subsequently reported that this is due to a physical difference in the eustachian tube of these races. Wan and Wong (2002) used low probe tone frequency tympanometry to compare norms in Chinese young adults (aged 19 - 34) to the non-Hispanic Caucasian norms established by Roup et al. (1998). They found that Chinese subjects had smaller peak static admittance, larger peak tympanometric width, more positive tympanometric peak pressure, and a smaller 90% range than the Roup et al. subjects. The only gender difference found in the Chinese subjects was on the variable of ear canal volume, which was significantly smaller in females. Compared to Roup et al., the Chinese males had significantly lower mean peak static admittance and ear canal volume values than the Caucasian males, and tympanometric peak pressure was more positive and tympanometric width were significantly smaller across gender in the Chinese subjects. Wan and Wong suggested that these middle ear differences could be caused by anatomic variations in the eustachian tube of the Chinese subjects. 1.3.2 Multifrequency Tympanometry Low frequency tympanometry has produced variable results in identifying mass r loading pathologies of the middle ear (e.g., otitis media), and measuring only at a low probe frequency might limit the sensitivity of the compensated immittance measures. These issues have been addressed by the use of multifrequency tympanometry, which has gained clinical acceptance due to its superiority in detecting pathologies of the ossicular chain. 18 Multifrequency tympanometry measures different variables (resonant frequency, F45°, and static admittance up to 1200 Hz) than standard low frequency tympanometry. An important parameter derived from multifrequency tympanometry is resonant frequency. Resonant frequency is measured by recording susceptance and conductance tympanograms using multiple frequencies (typically 250-2000 Hz). Using this data, resonant frequency can be derived by finding the frequency at which compensated susceptance equals zero (this can also be done visually by noting when the notch on the susceptance tympanogram equals the volume estimate value, i.e., positive or negative tail; see Fig. 4). Right 900 Hz Tympanogram 6.00 5.00 4.00 O J= E E i U 3.00 C ra 2.00 < 0.0 PS Is i iiiii:!!::::: 4 TStSTiT?!]:: i I" • i 1 vj?.:::::::::: 500 -400 -300 -200 -100 0 100 200 300 400 500 Air Pressure (daPa) Figure 1.5: A visual estimate of resonant frequency is made by finding the frequency at which the notch in the susceptance (B) tympanogram is equal to its positive or negative tail. (Figure from Shahnaz, 2000 with permission). Margolis and Goycoola (1993) collected normative data on 56 normal ears using eight measures of resonant frequency. They estimated resonant frequency with four different methods: (1) using positive compensation, (2) using negative compensation, (3) using a volume estimate derived by a hypothetical line connecting the positive and negative tails, and (4) by finding the lowest frequency at which the admittance tympanogram notched. Each of these four methods of resonant frequency estimation were measured using two recording 19 methods—sweep frequency (SF) and sweep pressure (SP)—which resulted in eight different estimates of resonant frequency. The SP method is the traditional way to record a . tympanogram, meaning that the ear canal air pressure is continuously changed while the probe tone frequency is held constant. To obtain multifrequency information, multiple sweeps of frequency are run using different probe tone frequencies. With the SF method, ear canal pressure is altered in discrete pressure intervals. At each successive pressure setting, a series of probe tones is presented. Data is obtained at multiple frequencies with a single negative to positive (or positive to negative) pressure change, which is slower and takes longer to collect than a single SP recording. Margolis and Goycoolea found that estimates of resonant frequency were higher when negative tail compensation was used, but they recommended using positive tail compensation as it has better test-retest reliability. They also noted that resonant frequency was lower when calculated from SP recordings, and suggested that this recording method be used to detect pathologies associated with an abnormally high resonant frequency (e.g., otosclerosis). Sweep frequency recordings produced higher estimates of resonant frequency and should be used in detecting pathologies associated with an abnormally low resonant frequency (e.g., ossicular discontinuity, effusion). This study contributed to more widespread use of multifrequency tympanometry in clinical practice by providing norms for resonant frequency. However, comparable data from pathologic groups are needed to develop the most effective diagnostic criteria. Another application of multifrequency, multicomponent tympanometry is F45°. From a plot of admittance components recorded at multiple frequencies between 226 and 2000 Hz, the frequency at which the compensated conductance (G) becomes equal to 20 compensated susceptance (B) can be determined. This value corresponds to a 45° phase angle when admittance is expressed in polar notation (G = B at 45°). This value may provide more accurate information than resonant frequency with respect to distinguishing healthy ears from pathologic ears (Shahnaz & Polka, 1997; Shanks et al., 1987). Confounding variables in multifrequency tympanometry include age, gender, and race. Margolis and Goycoolea looked at subjects from a wide age range (19 to 48 years) and did not examine any gender effects; they collapsed their data across these variables when establishing normative values. Other research has demonstrated age and gender effects on resonant frequency. Normative multifrequency data has been obtained over a wide age range, from infants (Holte, Margolis, & Cavanaugh, 1991) to elderly adults (Holte, 1996; Wiley et al., 1999). Resonant frequency in school-aged children (Hanks & Rose, 1993) was found to be lower than in the adults tested by Margolis and Goycoolea. Wiley et al. (1999) measured resonant frequency with multifrequency tympanometry in a group of older adults and found that their resonant frequencies were lower than the Margolis and Goycoolea young adults. Holte (1996) replicated this study with older male subjects and found no ageing effects to resonant frequency. It seems that there is not yet a definitive answer to the effects of age on resonant frequency. Comparing resonant frequency across genders has given mixed results. Wiley et al. (1999) found that older females showed a higher resonant frequency than older males. They felt that this result was consistent with the findings that women have lower static admittance than both younger (Roup et al., 1998) and older (Wiley et al., 1996) males, and that lower static admittance means a stiffer middle ear transmission system and a resulting higher 21 resonant frequency. However, Margolis and Goycoolea found the opposite result in their study and reported no gender differences. Again, there is no definitive answer to effect of gender differences on resonant frequency. Multifrequency tympanometry has not yet been applied to the question of normative values for different racial populations. This is an important issue to investigate in the increasing multicultural society of North America. Currently the tympanograms from individuals of different races are being assessed based on Caucasian norms (or norms of an unspecified race). If the middle ear system of different racial groups (e.g., Chinese) behave differently than those of Caucasian individuals, there is a possibility of misdiagnosis. Further research into this area is necessary to determine if different normative values should be established for individual races. Further research in the areas of age and gender is also necessary to determine if these variables impact multifrequency tympanometry results. 1.4 Goals of this study The purpose of this.study is to investigate any differences between a group of Chinese and Caucasian young adults in terms of immittance audiometry results. Results will be compared to Wan and Wong's (2002) low frequency tympanometry findings. New findings on multifrequency tympanometric values, specifically resonant frequency, F45°, and static admittance up to 1200 Hz will be reported. Findings from this study could indicate a need for further research in establishing normative data for different racial groups. Research to date on racial differences in immittance audiometry has left many gaps. Only a limited number of races have been studied (African-American, Chinese, American Indian, and Inuit), and all information has been gathered using low frequency tympanometry. These, as well as 22 other factors have motivated the present study. Shahnaz (2001) found a subgroup of Chinese subjects to have different immittance results than a randomly chosen group of Caucasian participants. This finding provided a starting point, in terms of the two racial groups being studied, for the present research. Another contributing factor is the increasing multicultural society currently found in Canada and the large East Asian population in Vancouver. As the population becomes more diverse, we will need different norms to correctly identify middle ear pathology in patients of different racial backgrounds. The specific research questions that this study will address are: Does the Chinese race have different low probe tone frequency immittance audiometry norms than the Caucasian race? Does the Chinese race have different high frequency tympanometry results than the Caucasian race? Low frequency probe tone variables that will be measured are static admittance and tympanometric width. Multifrequency tympanometric variables will be static admittance (up to 1200 Hz), resonance frequency, and F45°. It is expected that results from this study will replicate Wan and Wong's (2002) results in terms of low frequency tympanometric values. The multifrequency variables are expected to show a higher resonant frequency and F45° value in the Chinese subjects than the Caucasian group. These changes may be due to the smaller average body size of Chinese individuals (Wan & Wong, 2002), and their correspondingly smaller middle ear cavity (Huang, Rosowski, & Peake, 2000). 23 Chapter 2: Methods This chapter provides details of the subjects, instrumentation, and procedures used in this study. First, subject characteristics and inclusion and exclusion criteria are discussed. This is followed by an overview of the instrumentation used in this research. Finally, the mathematical procedures and formulas used to calculate each parameter are described and explained. 2.1 Subjects Subjects ranged in age from 18 to 33 years (grand mean = 26 years; mean Caucasian = 27; Chinese = 25; female = 27; male = 25). There were 20 subjects per group (10 male, 10 female) for a total of 40 subjects and 80.ears in the study. A total of four subjects (four ears) were excluded: two ears did not meet the pure tone threshold criteria and two ears did not meet the transient otoacoustic emission (TEOAE) criteria. Both ears of these four subjects were excluded. The sample size in this study is smaller than other published studies in Caucasian (Roup et al., 1998) and Chinese (Wan & Wong, 2002) adults, but still will be compared to'previously established norms. Posters placed both on and off the U B C campus were used to recruit subjects for this study. Participants recruited from U B C do not necessarily represent the level of education of the parent population of the community; however, this variable does not affect middle ear measurement values. Subjects were divided into two racial groups. Participants in the Chinese group were primarily Han ethnic descendants of immigrants from Mainland China, Hong Kong, and Taiwan without traceable foreign descent (i.e., both grandparents and parents must be from 24 Mainland China, Hong Kong, or Taiwan). This definition is based on the racial group studied by Wan and Wong (2002) which established norms in a similar group. The Caucasian group was defined based on the detailed classification of race by Statistic Canada (2002). Based on this definition the Caucasian group is non-Hispanic, non-Aboriginal, non-Arab/West Arab, non-Black, and non-East/South/South-East Asian, with white or light skin and of European descent. Subjects were placed in the appropriate group based on their self-reported racial classification. Each race group included an equal number of subjects from each gender. 2.1.1 Inclusion and exclusion criteria To be included in this study, subjects were required to meet several criteria: 1. Subjects had pure tone audiometric thresholds lower than 25 dB H L at octave frequencies between 250-8000 Hz. None of the subjects had an air bone gap of greater then 10 dB at any frequency. 2. No subjects in either group had otoscopic evidence of gross eardrum abnormalities or excessive cerumen documented by otoscopic examination. 3. A l l subjects passed T E O A E testing. A pass consisted of a greater than 3 dB signal to noise ratio in three frequency bands. TEOAEs were performed to verify normal hearing status. TEOAEs provide a screening for normal cochlear and middle ear function in that they are very sensitive to cochlear hearing loss of 30 dB H L or more (Bonfils & Uziel, 1989; Collet, Gartner, Moulin, Kauffman, Distant, & Morgon, 1989; Kemp et al., 1988), and are also quite sensitive to conductive impairment (Koivunen, Uhari, Laitakari, Alho, & Luotonen, 2000; Owens, McCoy, Lonsbury-25 Martin, & Martin, 1992). Therefore, TEOAEs were performed to further verify normal hearing status. 4. No subjects in either group had a history of head trauma or recurrent otitis media. 2.2 Instrumentation Otoscopy was conducted using a Welch-Allyn clinical otoscope with disposable probe tips. Pure tone audiometry was conducted using a Madsen audiometer with N O A H software, calibrated according to ANSI standards (re: S3.6.1987). Hearing levels were tested in a sound attenuating booth with EAR-3A insert earphones. TEOAEs were tested using a clinical ILO-92 Analyzer (Otodynamics Ltd., Hatfield, England) calibrated based on the operations manual of the manufacturer. TEOAEs have been proven to be a non-invasive and risk free procedure for newborns (NTH, 1993), young children, and adults (Robinette & Glattke, 2002). In this procedure a miniature microphone with a hypoallergenic probe tip was inserted into the subject's ear. A series of click-like sounds were delivered to each ear at a level of 80 dB pe (heard at about 50dB HL), which is similar in loudness to average conversational speech. The emitted sound echoed back from the cochlea was collected and averaged by a computer. A commercially available clinical middle ear analyzer which is routinely used to test newborns, children, and adults was used for this study. The Virtual digital immittance instrument (model 310) equipped with an extended high frequency option was used to perform tympanometry. Before each data collection, the Virtual system was calibrated using three standard cavities (0.5, 2.0, and 5.0 cm3) according to the operation manual provided by 26 the manufacturer. With this device, admittance tympanograms were automatically displayed, and a display of tympanometric data in rectangular or polar format was readily accessible. 2.3 Procedure Potential subjects contacted the investigator regarding eligibility for this study. A brief telephone questionnaire was presented for the purpose of determining racial eligibility and any history of head trauma or middle ear problems (see appendix III). Testing took place at the School of Audiology & Speech Sciences in room 226 of the James Mather building on the University of British Columbia campus. First, each subject's ears were examined using a clinical otoscope to rule out any excessive cerumen, discharge, or gross tympanic membrane abnormalities. Second, pure tone audiometry was performed in a standard sound booth using a 10 dB H L down, 5 dB H L up bracketing technique. Subjects were asked to respond behaviourally by pressing a button to the softest tone they could hear. TEOAEs were run from a computer in a quiet room. Results from this test provided information about the status of the cochlea and the middle ear. The total test time varied between 5 to 10 minutes per subject. TEOAEs were tested following pure tone audiometry so as not to bias the pure tone test with prior knowledge of cochlear or middle ear status. The presence or absence of TEOAEs was interpreted according to the study by Vohr, White, Maxon, and Hohnson (1993). The T E O A E measurements were considered technically unreliable when the stimulus level in the closed ear canal was less than 71 dB pe. Each of the three frequency bands, 1 to 2, 2 to 3, and 3 to 4 KHz, was estimated separately. TEOAEs were considered to be present in one band when the amplitude of the emission was greater than, or equal to, 3 dB relative to the noise (> 3 dB signal-to-noise ratio). 27 Tympanometry was performed on each subject who met the above inclusion criteria. To begin immittance testing a standard 226 Hz tympanogram was recorded. Next, tympanograms were obtained at higher probe tone frequencies using both the sweep frequency and sweep pressure recording methods. Sweep pressure recording was not conducted before sweep frequency recording because it has been reported that consecutive sweep pressure recordings appear to temporarily change the mechanical properties of the middle ear system (Osguthorpe & Lam, 1981; Vanpeperstraete et al., 1979), thus affecting the results of sweep frequency recording. In the sweep frequency procedure, admittance magnitude is measured while air pressure in the external ear canal is decreased from +250 daPa to -300 daPa in discrete 9 daPa steps. At each step the probe tone frequency was swept through a series of probe tones progressing from low to high frequencies. Two sweep frequency tympanograms were recorded: the first swept through a series of probe tones between 250 - 1000 Hz, and the second through a series of probe tones between 1000 - 2000 Hz. In each series, the frequency was changed in one-sixth octave steps. A total of twenty probe tone frequencies were used. In the sweep pressure method, the air pressure of the external ear canal was decreased continuously from +250 daPa to -300 daPa (positive to negative) at a rate of 125 daPa/sec while the probe tone frequency was held constant. This procedure was repeated for multiple probe tone frequencies ranging from 250 - 2000 Hz progressing from low to high frequencies. Twenty tympanograms were recorded, with one at each of the same frequencies used in the sweep frequency recording. A descending pressure direction (positive to negative) was used for both sweep frequency and pressure tympanograms because it results in fewer irregular tympanograms 28 compared to the ascending direction of pressure change (Margolis, Van Camp, Wilson, & Creten, 1985; Wilson, Shanks, & Kaplan, 1984). The left ear of each subject was tested first. Estimates of static admittance (SA), tympanometric width (TW), resonant frequency (RE) and the frequency corresponding to a phase angle of 45° (F45°) were derived from this data. A total of eight estimates of RF and F45° were made, with two of the estimates using each of the two recording methods, and two estimates using each compensation method. Any subjects with abnormal results in any of the above tests were recommended to visit the appropriate health care professional. The Virtual system is capable of providing the above data in two formats: as a visual display of tympanometric data, and in a numerical format. This study uses the numerical format calculation method used by Shahnaz and Polka (2002). Each of the above four measures (SA, TW, RF, F45°) was derived for each recording method and frequency from numerical values stored in a text format by the Virtual machine; i.e., the data were recorded in an uncompensated admittance polar format (magnitude and its corresponding phase angle) as a function of air pressure. The following equations were used at multiple probe tone frequencies to derive susceptance and conductance (the rectangular components) from the polar format: B = | Y | sin 4 (3) G = | Y | cos <|> (4) Following this, positive (+250 daPa) and negative (-300 daPa) compensation were applied to correct for ear canal admittance for both susceptance and conductance. The pressure point corresponding to the maximum admittance value was determined at the lowest 29 probe tone frequency for each recording method ( 2 5 0 Hz for SF, 2 2 6 Hz for SP) and applied to all other probe tone frequencies. Compensated susceptance and conductance were obtained by the following formulas: Btm — Bpeak - B e c (5) G t m = Gpeak - G e c (6) Note that the t m refers to measurements at the plane of the tympanic membrane, and that e c refers to the positive ( + 2 5 0 daPa) or negative ( -300 daPa) reactance component for ear canal volume. Finally, the compensated susceptance and conductance were converted back to polar format (as compensated phase angle and admittance) by the following formula: Y,m =^Glm2+Btm2 (7) ^ = a r c t a n | ^ (8) lm Shahnaz and Polka ( 2 0 0 2 ) derived this method of calculation to increase the accuracy of each measure, as vector quantities such as admittance cannot be added or subtracted unless the phase angles of the admittance parameters are identical (Margolis & Shanks, 1985) . As noted above, SA and TW are typically measured from a standard 2 2 6 Hz probe tone.. The middle ear is stiffness dominated at this low frequency, and any change in admittance value causes little error. However, this error can become considerable at higher frequencies when admittance vectors are added or subtracted. As a result, at higher probe 3 0 tone frequencies it is necessary to apply compensation to the rectangular components of susceptance and conductance, and then transform the data back to polar notation. This ensures that only admittance vectors that are represented in a rectangular format are added or subtracted (Margolis & Hunter, 1999; Shanks, Wilson, & Cambron, 1993). This method also calculates compensated conductance. Previous research has suggested that cerumen and the soft tissue in the deepest one third of the ear canal can contribute to acoustic conductance and must be compensated for (Feldman, 1976, Van Camp et al., 1986). 2.4 Analysis of data A repeated measures analysis of variance (ANOVA) was used to compare tympanometric variables across race and gender groups. An alpha level of 0.05 was used in all statistics. Descriptive statistics are provided for all tympanometric values for both racial groups. Gender was used as a between-subject factor, and estimate method (e.g., positive or negative compensation, sweep pressure, or sweep frequency) as a within-subject factor for the within-race repeated measures A N O V A . If no gender differences were found within each race group, all data was collapsed together for the group analysis between races. If significant gender differences were found in either race group, races were compared on a gender specific basis. A between-race group analysis for was also completed. For this analysis, race was the between-subject factor and estimate the within-subject factor. 31 Chapter 3: Results and Discussion A total of five tympanometric measures were examined in this stud The results from the standard low frequency variables of static admittance and tympanometric width will be examined first, followed by three variables that can only be derived from multifrequency, multicomponent tympanometry: static admittance up to 1200 Hz, resonant frequency, and F45°. There are a total of four measures of resonant frequency and F45°, with two estimates of ear canal compensation (positive and negative) derived from data obtained using two different recording methods (sweep frequency and sweep pressure). Each admittance (Y) tympanogram recorded in this study was broken down into its rectangular components, susceptance (B) and conductance (G). As discussed earlier (see Chapter 2, Methods), these components were transformed from polar to rectangular format. The rectangular components were then corrected for the effects of ear canal volume and changed back to polar notation. This mathematical method allows admittance tympanograms to be reported with a high degree of accuracy. In almost all other published data, with the exception of Shanks et al. (1993) and Shahnaz & Polka (2002), static admittance has been computed manually or automatically from admittance tympanogram graphs, which may result in significant error especially at higher probe tone frequencies. Only admittance values are reported in this study. This is done for two reasons. First, the admittance values from this study accurately reflect the effects of compensated susceptance and conductance due to the mathematical method of estimation. Second, in clinical practice, static admittance is the most commonly used variable for the differential diagnosis of middle-ear pathology. In the interests of time, clinical audiologists rarely analyze the subcomponents of 32 tympanograms. Therefore, to increase the clinical applicability of these results, only Y values will be discussed. Gender differences were examined in each race group for each variable. This analysis was done for three reasons. First, it allowed us to investigate whether the gender differences within each race group were significant. It also allowed the current data to be compared to previous research that has separated genders (e.g., Margolis & Heller, 1987; Roup et al., 1998; Wan & Wong, 2000; Wiley et al., 1996, 1999). Finally, this method of analysis allowed genders to be collapsed together (when the effect of race is being investigated) if no significant differences were found. The results and discussion of these variables are organized into five sections: (1) static admittance at a standard probe tone frequency of 226 Hz, (2) tympanometric width at a standard probe tone frequency of 266 Hz, (3) static admittance up to 1200 Hz, (4) resonant frequency, and (5) the frequency corresponding to an admittance phase angle of 45° (F45°). Each section is divided in to three smaller subsections, presented as follows. The first part reviews the procedure and measurement method of each variable. This is followed by a statistical analysis and discussion of the results found for each measure. A table reporting the mean, standard deviation, and 90% range for each race group and gender is presented for individual variables. This data is compared to, and discussed in relation to published normative values. The final part is a group analysis, where differences between the Caucasian and Chinese adults are statistically analyzed and discussed. 33 3.1 Static Admittance 3.1.1 Procedure As discussed earlier, peak compensated static admittance (SA) describes the height of the tympanogram measured at the plane of the tympanic membrane (Fowler & Shanks, 2002). The term peak refers to the highest admittance value of the tympanogram, while the term compensated tells us that the measurement was taken at the plane of the tympanic membrane and that the acoustic admittance of the ear canal has been subtracted. Compensation can be achieved by subtracting the admittance peak value from admittance at the positive or negative tail of the tympanogram. SA was calculated by applying compensation to admittance rectangular components and deriving compensated admittance from these values. A total of two measures were derived using sweep pressure recording, one with positive and one with negative compensation. Table 3.1 provides a summary of descriptive statistics for each race and gender group, as well as a comparison to other published studies. Both sweep pressure (SP) and sweep frequency (SF) tympanograms were recorded, but only data obtained from SP recordings was analyzed. This was done to increase the clinical relevance of these results. In a clinical setting, time is an important factor. If norms are established for each frequency up to 1200 Hz, it is much faster to run one SP recording at an optimum higher probe tone frequency and compare that to normative data than it is to run a SF recording of an entire frequency range of 250-2000 Hz. 34 SA + compensation - compensation Investigator Mean (mmho) SD (mmho) 90% Range (mmho) Mean (mmho) SD (mmho) 90% Range (mmho) Current Study (Caucasian) M 0.70 0.34 0.24-1.46 0.76 0.36 0.32-1.59 F 0.74 0.52 0.34-2.49 0.81 0.54 0.40-2.61 C 0.72 0.43 0.34-1.55 0.79 0.46 0.39-1.69 Current Study (Chinese) M 0.58 0.34 0.22-1.47 0.63 0.33 0.24-1.51 F 0.43 0.28 0.14-1.22 0.47 0.28 0.17-1.17 C 0.50 0.32 0.19-1.23 0.55 0.31 0.20-1.19 Wan & Wong (2002) (Chinese) M 0.58 0.29 0.30-1.10 - - . . . F 0.52 0.28 0.20-1.30 - - -C 0.55 0.28 0.20-1.10 - - -Roup et al. (1998) (Non-Hispanic Caucasian) M 0.87 0.46 0.30-1.80 - - -F 0.58 0.27 0.30-1.12 - • - — C 0.72 0.40 0.30-1.19 - - — . Margolis & Heller (1987) M 0.77 0.37 v, - - - -F 0.65 0.21 - - - -C 0.72 0.32 0.27-1.38 - -Wiley et al. (1996) 0.66 - 0.20-1.50 - - -Holte (1996) 0.84 0.53 0.30-1.80 0.86 0.55 0.30-1.90 Shahnaz & Polka (1997) - - - 0.85 0.47 0.40-1.60 Shahnaz & Polka (2002) 0.65 0.31 0.30-1.70 0.74 0.31 0.39-1.26 Margolis & Goycoolea (1993) 0.79 0.37 0.30-1.70 0.88 0.37 0.40-1.70 Shanks et al. (1993) 0.40 - - - - — Table 3.1: Results of static admittance (SA) at 226 Hz from the current study and other published normative studies. SA is reported for both positive (+) and negative (-) compensation. Values not reported are marked with --; M = male; F = female; C = combined genders. Shanks et al. (1993) reported median values. 35 3.1.2 Within-race group analysis—Caucasian Combined static admittance values (both genders collapsed together) with positive compensation in this study are comparable to normative data reported by Roup et al. (1993) and Margolis & Heller (1987). The mean static admittance results for Caucasian adults in this study (0.72 mmho) are identical to both Roup et al. and Margolis and Heller. However, the standard deviation and 90% range of the current study (0.43; 0.34 - 1.55 mmho) is larger than those found by Roup et al. (0.40 mmho; 0.30 - 1.19 mmho) and Margolis and Heller (0.32 mmho; 0.27 - 1.38 mmho). The 90% ranges of these studies have similar lower cut-off values; however, the current study has considerably higher high cut-off values, indicating that some subjects in the current study have higher static admittance values. A 90% range is composed of the values between the 5 t h and 95 t h percentiles of a given range. Ninety percent ranges provide important information for differential diagnosis. A low cut-off value (or 5 t h percentile) could indicate a stiffening pathology such as otosclerosis (Shahnaz & Polka, 1997, 2002), while a high cut-off value (95 t h percentile) could suggest a loose ossicular chain and a possible diagnosis of ossicular discontinuity (Margolis & Heller, 1999). It is interesting that the results from these studies are so similar, because each study used different instruments and procedural variables (Table 3.2 lists these variables for several published normative studies). One major difference between the current study and Roup et al. and Margolis and Heller is the method of calculation. SA was automatically derived from the measurement machine by both Roup et al. and Margolis and Heller, while the current study computed admittance from its rectangular components of susceptance and conductance. This > mathematical method of computing admittance accounts for compensated conductance, 36 Investigator Machine #of subjects (ears) Age M/F Pump speed (daPa/sec) Pressure range (daPa) Compensation SA TW Current study Virtual 310 40 (80) 18-34 20/20 125 +250 to -300 +, - +, -Wan & Wong (2002) GSI-33 100 (200) 19-34 50/50 600/200 +200 to ? + + Roup et al. (1998) GS 37 102 20-30 51/51 600/200 +200 to -300 + + Margolis & Heller (1987) Welch Allyn MicroTymp 87 19-61 49/38 200 +200 to -300 + + Wiley et al. (1996) GSI 37 2147 48-92 825/ 1322 600/200 +200 to ? + + Holte (1996) Virtual 310 144 20-90+ Male 75-100 +250 to -300 +, - — Shahnaz & Polka (1997) Virtual 36 (68) 20-43 — 125 +250 to -300 - -Shahnaz & Polka (2002) Virtual 36 20-43 — 125 +250 to -300 +, - DNT Shahnaz (2001) Virtual 36 (68) 20-43 ~ 125 +250 to -300 +, - +, -Margolis & Goycoolea (1993) Virtual 28(56) 19-48 250 +400 to -500 +, - + Shanks et al (1993) Virtual 26 20-40 Male — +200 to -350 + DNT Table 3.2: Procedural variables for measuring static admittance and tympanometric width at 226 Hz. Unreported variables are denoted by --; DNT = did not test. which gives a more accurate admittance value. However, at lower probe tone frequencies (e.g., 226 Hz) the admittance phasor (vector) is very close to susceptance, which means that the amount of error in calculating compensated admittance from an admittance tympanogram is negligible. Another difference amoung the three studies is the pump speed. Roup et al. and Margolis and Heller both used a faster pump speed than the current study, which can cause increased static admittance values (Margolis & Heller, 1987). Roup et al.'s pump speed was 600/200 daPa/s, meaning that the speed was 600 daPa/s at the extreme pressures and 200 37 daPa/s near the peak; Margolis and Heller used a pump speed of 200 daPa/s. This study uses a constant pump speed of 125 daPa/s. The factor of pump speed did not appear to increase the mean or 90% range of the current project, as it shows higher cut-off values than both previous studies. Subject variables such as age and race must also be taken into account. Roup et al. specified the race of their subjects (non-Hispanic Caucasian), but Margolis and Heller made no reference to race in their sample population. The age range of Roup et al.'s subjects is comparable to the present study (20 - 30 years versus 18-34 years), while Margolis and Heller looked at a much broader age spectrum (19 - 61 years). Each of these three studies specified the gender of their subjects and reported both collapsed and separate gender results. A final subject variable is the sample size of the study. Both Roup et al. and Margolis and Heller had a larger sample size than the current study (87, 102, and 40 subjects respectively). Positive compensation is generally preferred due to the inherent asymmetry found in tympanograms. SA values are typically higher with negative compensation but show more reliable test-retest values with positive compensation (Margolis & Smith, 1977). This trend is observed in the current data. Few studies have reported results with negative compensation, but the current results are similar to those that have (Holte, 1996; Margolis & Goycoolea, 1993; Shahnaz & Polka, 1997, 2002). The mean SA value of this study is slightly lower (0.79 mmho) than that of Holte (1996) and Shahnaz & Polka (1997) with values of 0.86 and 0.85 mmho, respectively. The 90% ranges of these three studies are comparable. To investigate the effect of gender a repeated measures A N O V A was conducted with gender as a between-subject variable and estimate method (positive [+] or negative [-] 38 compensation) as a within-subject factor. The main effect of gender was not significant [F (1, 38) = 0.1 l,p = 0.74]. However, Caucasian females show a slightly higher SA than males. These findings are in contrast to Roup et al.'s results, which show a statistically significant difference between genders, with males having a larger SA than females. These differences could be caused by the procedural variables discussed above, or by the smaller sample size of the current study. The effect of estimate was significant [F (1, 38) = 42.68, p = 0.00] indicating that the method of measurement (Y+, Y-) significantly affects the results of SA at 226 Hz. There was no interaction between gender and estimate [F (1, 38) = 0.54, p = 0.47], meaning gender effects are not evident with each method of estimation. Table A l . l in Appendix I has a complete A N O V A summary of this variable. 3.1.3 Within-race group analysis—Chinese Chinese adults in this study have comparable SA values to those found by Wan and Wong (2002). It is important to remember that Wan and Wong only reported positive compensation values. The mean value for combined genders is very close, with Wan and Wong having a slightly larger value (0.55 mmho) than the current study (0.50 mmho). The 90% ranges are also very comparable, with the current study having a slightly larger range (0.19 - 1.23 mmho versus 0.20 - 1.10 mmho). The current study has lower 5 t h percentile and higher 95 t h percentile values than those reported by Wan and Wong, indicating a larger range of "normal" static admittance values. Wan and Wong also used a different machine and larger sample size, both of which could contribute to these differences. Negative compensation results from the current study show a similar pattern to Caucasian results, with slightly higher mean values than obtained with positive compensation (i.e., the current study 39 has a negative compensation mean of 0.55 mmho and 90% range of 0.20 - 1.19 mmho). Table 3.2 compares descriptive results from the current study to other published norms. Patterns in gender differences were investigated with a repeated measure A N O V A (same factors as Caucasian analysis). There was not a significant main effect of gender [F (1, 38) = 2.59, p = 0.12] or interaction between estimate and gender [F (1, 38) = 0.80, p = 0.79]. The main effect of estimate (Y+, Y-) was significant [ F ( l , 38) = 31.38, p = 0.00] indicating that the estimate method significantly affects the results of static admittance at 226 Hz. Table A 1.2 in Appendix I reports complete A N O V A results. Chinese males show higher SA values than Chinese females in the current study, which is consistent with the trend in Wan and Wong's findings (their gender differences were also not significant). Chinese females in the current study have a lower SA (by 0.09 mmho) than Wan and Wong show, while males show the same mean SA, with a larger 90% range (0.22 - 1.47 mmho and 0.30 - 1.10 mmho respectively). 3.1.4 Between-race group analysis As there were no statistical differences between genders in each race group, gender data was pooled together for each race to examine group differences. A repeated measures A N O V A was conducted, with one between-subject variable (race: Caucasian, Chinese) and one within-subject variable (SA estimate: Y+, Y-). Table A1.3 in Appendix I provides an ' A N O V A summary table. Significant main effects of race [F (1, 78) = 7.03, p = 0.01] and estimate [F (1, 78) = 75.33, p = 0.00) were found. There was no interaction effect between race and estimate [F (1, 78) = 1.61, p = 0.21]. The main effect of race indicates that Caucasian adults have significantly higher mean static admittance values at 266 Hz than their 40 Chinese counterparts. The Chinese group also has a smaller 90% range than the Caucasian adults (0.19 - 1.23 mmho versus 0.34 - 1.55 mmho). These results are consistent with those of Wan and Wong, who reported a significantly lower mean SA in their Chinese subjects as compared to Roup et al.'s non-Hispanic Caucasian adults. The main effect of estimate indicates that the method of measuring SA (e.g., positive or negative compensation) significantly impacts the results. It is essential for clinicians to be aware of this finding so they use the correct norms (e.g., the norms representing the method of compensation used by their immittance machine) when assessing patients. The clinical implications of these findings are important in terms of both gender and race differences. Results of static admittance at 226 Hz did not find any gender differences, which implies that males and females can be diagnosed by the same normative values. The knowledge that male and female ears are the same in low frequency tympanometry can help the clinical audiologist assess the middle ear status of both genders more accurately. Race differences were significant for this variable, with Chinese adults having significantly lower static admittance values than Caucasian adults. Lower static admittance indicates less middle ear compliance. Lower compliance translates into an increased contribution of stiffness to the middle ear transmission system. This lower static compliance can result in misdiagnosis in a clinical setting. If a Chinese adult were to have a static admittance of 0.20 mmho (which is within the 90% range of both the current study and Wan and Wong, 2002), they would be considered "abnormal" by A S H A norms (as mentioned earlier, A S H A has adopted Margolis and Heller's, 1987, norms). The end result of this situation would be the misdiagnosis of a "normal" Chinese ear as "abnormal" based on Caucasian standards. 41 Race differences between Caucasian and Chinese subjects are shown in a box-and-whisker plot in Fig. 3.1. The SYSTAT software manual (1998) describes the central box in the plot as the midrange, or middle 50 percent of the distribution (values from the 25 t h to 75 t h percentile). The middle line in the box represents the median value. The lower whisker shows the range of observed values that fall within the range of the 50 t h to 75 t h percentile minus 1.5 times the midrange. This is referred to as the lower inner fence. The upper whisker shows observed values within the 25 t h to 50 t h percentile plus 1.5 times the midrange. This is referred to as the upper inner fence. The circles represent outliers, which are defined as values greater than either: (1) the 25 t h to 50 t h percentile plus 3 times the midrange (called the upper outer fence), or (2) the 50 t h to 75 t h percentile minus 3 times the midrange (called the lower outer fence). The whiskers extend only to observed values, while the fences do not necessarily correspond to observed values. This means that the whiskers do not necessarily extend all the way to the inner fences. Asterisks represent values that lie between the inner and outer fences. They will be referred to as outsiders in the current study. R A C E E3 C a u c a s i a n D C h i n e s e * Outs ider o Out l ie r u v+ v-Estimate Figure 3.1:' Box-and-whisker plot of static admittance (Y) at 226 Hz using positive (+) and negative (-) ' compensation for Caucasian and Chinese adults (collapsed genders). 42 3.2 Tympanometric width 3.2.1 Procedure Tympanometric width (TW) refers to the width of the tympanogram (in daPa) measured at one half of the compensated static admittance. After transforming admittance values from polar notation to rectangular format and compensating for the effects of ear canal on susceptance and conductance, the compensated admittance was recalculated at different pressure points. TW was calculated by taking one half of the peak admittance at 226 Hz, and drawing a hypothetical horizontal line which bisects the two values (in daPa) on the tympanogram. The magnitude points corresponding to the positive and negative values were noted. The absolute values of the pressure of each of these points were added together to derive the TW. If there were two identical pressure values for any one point, the earlier value was taken; if there were three identical points, the middle value was taken; if there were four identical points, the first value of the middle two points was taken. This procedure was used to, calculate TW for positive and negative compensation for sweep pressure recordings for Y tympanograms. Descriptive statistics are provided for each race group in Table 3.3. 3.2.2 Within-race group analysis—Caucasian The results of tympanometric width obtained using positive compensation on Caucasian adults (collapsed genders) in this study are not closely comparable to other published data using the same mode of compensation, with the exception of Shahnaz (2001). 43 TW + compensation - compensation Investigator Mean (daPa) SD (daPa) 90% Range (daPa) Mean (daPa) SD (daPa) 90% Range (daPa) Current Study (Caucasian) M 88.7 24.0 . 52.4-149.2 101.9 30.1 65.8-1643 F 89.7 28.2 33.8-153.9 106.6 36.6 33.6-177.7 C 87.9 24.0 47.2-148.8 101.4 28.9 52.4-150.4 Current Study (Chinese) M 91.9 25.8 52.4-162.6 106.9 31.6 52.4-164.2 F 89.0 30.8 29.6-153.9 107.1 45.6 29.1-196.5 C 90.5 28.1 51.9-153.9 107.0 37.6 47.2-177.9 Wan & Wong (2002) (Chinese) M' 88.3 34.1 45.0-174.5 - - -F 94.2 29.2 45.3-144.8 - - -C 91.2 31.8 45.0-159.3 - - — Roup et al. (1998) (Non-Hispanic Caucasian) M 59.8 17.3 35.0-87.0 - - -F 73.9 17.2 45.0-107.0 - - -C 66.9 18.6 32.8-95.0 - - - -Margolis & Heller (1987) M 79.1 21.1 - - - -F 73.8 15.0 - - - — C 76.8 18.8 51.0-114.0 - - — Wiley et al. (1996) 75.0 31.0 35.0-125.0 - - -Holte (1996) • 83.7 31.4 37.6-141.0 - - -Shahnaz & Polka (1997) - - - 84.0 27.0 48.0-134.0 Shahnaz (2001) 79.6 27.9 29.9-125.3 94.6 35.5 39.3-155.1 Margolis & Goycoolea (1993) 106.0 43.0 42.0-183.0 - — — Table 3.3: Results of static admittance (TW) at 226 Hz from the current study and other published normative studies. TW is reported for both positive (+) and negative (-) compensation. Values not reported are marked with - ; M = male; F = female; C = combined genders. 44 The present study found a/mean of 87.9 daPa and a 90% range of 47.5 - 148.8 daPa. These results are very similar to those found by Shahnaz, who reported a mean of 79.6 daPa and a 90% range of 29.9 - 125.3 daPa. Shahnaz used an identical instrument and procedural variables to the current study; however, he did not specify the racial background of his subjects. Results from the current study are higher than those reported by Roup et al. (1998), who found a mean of 66.9 daPa and a 90% range of 32.8 - 95.0 daPa, Margolis and Heller (1987) with a mean of 76.8 daPa and a 90% range of 51.0 -114.0 daPa, and Wiley et al. (1996) who found a mean of 75.0 and a 90% range of 35.0 - 125.0. These differences are most likely attributed to procedural and subject differences between the studies (see Table 3.1 on page 38 for a list of procedural variables). Wiley et al. studied older adults between the ages of 48 - 90 years, Margolis and Heller used an age range of 19 - 61 years, and Roup et al.'s subjects are the closest age to the current study at 20 - 30 years. Both Roup et al. and Margolis and Heller used faster pump speeds (600/200 and 200 daPa/s respectively) than the present study (125 daPa/s). Previous research has shown that faster rates of pressure change may result in higher estimates of static admittance (Cretan & Van Camp, 1974; Koebsell & Margolis, 1985), which produces a narrower tympanometric width. Holte (1996) found a more similar TW to the present results with a mean of 83.7 daPa and a 90% range of 37.6 -141.0 daPa; her study used a pump speed of 75 to 100 daPa/s. Table 3.3 provides a more detailed comparison of the current study to published normative studies. Shahnaz (2001) is the only study to date to mathematically calculate TW from negative compensation. His study used the same measurement device and parameters as the present study and found comparable results. The present study found a mean of 101.4 daPa and a 90% range of 52.4 - 150.4 daPa, while Shahnaz found a mean of 94.6 daPa and a 90% 45 range of 39.3 - 155.1 daPa. Shahnaz and Polka (1997) used an automatic calculation of TW from the Virtual 310 and found a mean of 84.0 daPa and a 90% range of 48.0 - 134 daPa. This lower mean value may be caused by the different methods used to derive TW, as the current study takes compensated conductance into account, which the automatic calculation does not. The larger sample size used by Shahnaz and Polka may also have contributed to the discrepancy in results. Caucasian males and females in the current study show similar TWs, with females having a marginally larger mean value than males (89.7 daPa and 88.7 daPa, respectively) and a larger 90% range (33.8 - 153.9 daPa versus 52.4 - 149 daPa). This larger 90% range indicates that females have slightly more variability in their static admittance values. A repeated measures A N O V A analysis with gender as a between-subject factor and TW as a within-subject factor was conducted to investigate these differences (complete A N O V A tables for this variable are in Table A1.4 in Appendix I). There was not a significant gender effect [F (1,38) = 0.83, p = 0.37] or interaction between gender and estimate [F (1, 38) = 0.37, p = 0.55]. Estimate effects were significant [ F ( l , 38) = 13.81,/? = 0.00], indicating that the measurement method (e.g., using positive or negative compensation) significantly affects the results of this parameter. The trends in these results are not comparable to those of Roup et al., who found that females had statistically greater mean TW values; (73.9 daPa) than males (59.8 daPa), as well as a larger 90% range than males (45.0 - 107.7 daPa versus 35.0 - 87.0 daPa). Wiley et al. found the same trend in their data; however, the differences were not significant. Margolis and Heller reported males and females to have similar values (79.1 daPa and 73.8 daPa, respectively), but their mean values were lower than the current data. These differences could be caused in part by procedural variables, since the current 46 study uses a different measurement system, calculation method, pump speed (slower), pressure range (i.e., positive compensation is measured at 250 daPa versus 200 daPa by Roup et al. and Margolis & Heller), and sample size (smaller) than those studies. 3.2.3 Within-race group analysis—Chinese Positive compensation results of tympanometric width of Chinese adults in this study are comparable to Wan and Wong's (2002) results. This study found a mean TW of 90.5 daPa and a 90% range of 51.9 - 153.9 daPa, while Wan and Wong reported a mean value of 91.2 daPa with a 90% range of 45.0 - 159.3 daPa. It is interesting to note that these values are so similar to Wan and Wong's data despite the fact that they used a different measurement machine, a larger sample size, and a smaller pressure range (they measured positive compensation at +200 daPa instead of the +250 daPa in the current study). However, the age range and racial characteristics of their subjects are identical to those in the present study. Chinese male and female TWs are very similar, with males showing marginally greater mean values than females (91.9 versus 89.0 daPa; difference of 2.80 daPa) but females having a larger 90% range (29.6 - 153.9 daPa versus 52.4 - 152.6 daPa). A mixed model of A N O V A (with identical parameters to those described above) was conducted to investigate gender differences. No significant gender differences [F (1,38) = 0.17, p = 0.90] or interactions between estimate and gender [F (1, 38) = 0.16, p = 0.69] were found. A significant estimate effect was noted [F (1, 38) = 19.11, p = 0.00], again indicating that measurement method (Y+, Y-) impacts TW values. Wan and Wong's results show the reverse gender trend, with females having larger values than males (94.2 daPa and 88.3 daPa 47 respectively; difference of 5.90 daPa). Wan and Wong's females show a smaller 90% range than the current study (45.3 - 144.8 daPa 29.6 - 153.9 daPa), while males have a more similar range (45.0 - 174.5 daPa versus 52.4 - 162.6 daPa). Complete A N V O A tables can be found in Table A 1.5 in Appendix I. 3.2.4 Between-race group analysis A group analysis was conducted to investigate differences in tympanometric width between Caucasian and Chinese subjects. No gender differences were found in either race group, so genders were pooled together for this analysis. A repeated measures A N O V A was conducted, with one between-subject variable (race: Caucasian versus Chinese) and one within-subject variable (estimate: Y+ versus Y-). No significant race differences [F (1, 78) = 0.44, p = 0.51] or interactions between race and estimate [F (1, 78) = 0.35, p = 0.55] were found. These results indicate that there are no race differences on the variable of tympanometric width. There are also no interaction effects, which tell us that race effects are not evident with each method of estimation. A significant estimate effect was noted [F (1, 78) = 33-44, p = 0.00], indicating that the method of estimate affects the results (refer to Table A1.7 in Appendix I for A N O V A summary tables). This has similar clinical implications to those discussed earlier in terms of SA, indicating a need for clinicians to be diligent about the normative data used in their workplace. Assessing patients on a machine with different parameters than the normative results can result in the misdiagnosis of a normal TW as abnormal. For example, if a clinical machine was calculating TW by negative compensation but the clinician was using positive compensation norms, a client could be incorrectly assessed as having an abnormal TW (e.g., a TW of 50.0 daPa is within the 90% 48 range for negative compensation; however, this value is just outside of the 90% range for positive compensation). The data from the current study shows a trend that Chinese adults (collapsed genders) have larger mean TWs than their Caucasian (collapsed genders) counterparts, but this difference is not statistically significant, (see Fig. 3.2). This same trend was reported by Wan and Wong, who found their Chinese subjects to have a significantly higher mean TW than the non-Hispanic Caucasian adults tested by Roup et al. Both groups in the current study show similar 90% ranges, with the Caucasian adults having slightly lower 5 t h and 95 t h percentile values than the Chinese data (47.2 - 148.8 daPa and 51.9 -153.9 daPa respectively). These differences in cut-off values suggest that Caucasian adults have higher static admittance values, which results in a narrower tympanometric peak and a correspondingly lower TW value. 200 0 Caucasian • Chinese * Outsider Y+ Y-E s t i m a t e Figure 3.2: A box-and-whisker plot of tympanometric width at 266 Hz using positive (+) and negative (-) compensation for Caucasian and Chinese adults (collapsed genders). No significant race differences were found on this variable. Please refer to page 43 for the definition of an outsider. 49 3.3 Static Admittance up to 1200 Hz 3.3.1 Procedure Static admittance up to 1200 Hz was measured from both race groups for sweep pressure recordings using both negative and positive ear canal compensation. Compensation was applied to admittance rectangular components and compensated admittance was derived from these values. SA derived by this mathematical method represents the contributions of both compensated susceptance and conductance. This parameter was measured and derived in the same manner as static admittance at 266 Hz (see page 35). The descriptive statistics for this measure compared to other published data are shown in Tables 3.4-3.5. 3.3.2 Within-race group analysis—Caucasian Positive compensation results for static admittance up to 1200 Hz from this study are not comparable to previously reported data. The mean SA values found in the current study are smaller across the entire frequency range than those found by Shahnaz and Polka (2002), and larger than those found by Shanks et al. (1993). The only exception to this trend in Shahnaz and Polka's data is at 226 Hz, where the mean and 90% ranges are correspondingly smaller. For example, at 630 Hz the current study found a mean SA of 2.25 mmho and a 90% range of 0.96 - 4.36 mmho; at the same frequency Shahnaz and Polka found a mean of 3.07 mmho and a 90% range of 1.14 - 5.64 mmho. The main difference between these two studies is in subject variables, such as sample size, race, and age. Shahnaz and Polka used 68 ears (36 subjects), a larger age range (20 - 43 years) and did not specify the race of their subjects. As their study was conducted in Canada, it can probably be assumed that the majority of the subjects were Caucasian; however, some subjects may have been from 50 ~ cu ON O 00 r -CN CO i n i n T f CO vo CO CN VO CO VO CN T f CO 0 0 ^ y > o S » 2 —H r H CN CO T f i n i n 4 4 4 CO 1 o CN 6 CO r H T f 4 i n CN VO 00 0 0 CN q ov q vo r H d d d d d d d d r H r ^ r H • A1 r-H co CO T f CO >n oo r - q vo CN o CO q Ov Ov 00 00 CO oo hinese) d d d d r-H r H i—i d d d hinese) CS es -g <u s i n i n i n 00 r H O vo CO T f CN Ov r -o r H —H i n 0 0 o CN o u s i d d r H r-H i—1 r H CN CN CN CN CN r i resent Stud * 2 /—N O CO CN 1 CV r H 00 00 7—H 1 r-H CO r H CN CN CO CO m q CO 1 CO T f CN m 4 • vo T f r-H i n i n i CO T f VO CO i n i OV T f H 00 i n i m r -T f 0 0 CN r-~ T f i o ov T f CN T f 1 m q resent Stud d d d d d d d d d d PH + >< 'o' o 1 CN CO CO T f T f m vo oo q OV CN vo CO CO CO 00 q m r ^ vo ov d d d d d d a "o cs -g CU H r H IT) Ov T f Ov i n CN CO vq r-H 0 0 r--Ov OV —H r ^ . 1 o VO o s i d d d T-H T-H r H r-H CN CN CN CN 2 ON vq <—i T f 00 CN T f i n CO CN VO T f T f T f T f r -r -4 CO i n 4 CN o 4 m 00 CO m o 4 T f l> CO OV CO 4 T f 4 i n r H r - vo 00 H OV .—i q CN r-H ov q r H r H 4 q d d d d d d r-H r ^ r H r H r H i Q i vo T f Ov VO CO oo CO q CO r H CN CN i n r-H r -ov vo oo CO 00 vo d d d *—< r H H r—1 d d d d casian) S o es -3 V a Os VO r n 1—I T l ; 00 00 r H CO OV T f OV i n —H m 0 0 T f r -co CO CN casian) s i d r H -H -H CN CN CN CN CN CN CN* (Cau< m i n 00 vo r -vq CN m VO CO CO 00 T f r ->n -H CO CN r H r -CN T f (Cau< 2 r H CN CO T f T f 4 4 T f 4 T f 4 Study 1 T f CO 1 T f 4 VO CN VO OV OV OV q CN CN m CO CN CN q Study d d d d d d Present + o 1 CO T f VO VO 00 OV OV o t-H OV r-H CO OV OV T f Ov T f OV vo' ov Present t/J 1 d d d d r H i—1 H d d d d S S cs - g CU H CN r -o r H 00 T f 00 C-; wo CN CO T f r-m i n 0 0 m r-H i n o T f SI d 1—1 1—I r-H CN CN CN CN CN CN CN u a cu 3 a" cu u to N 33 vo CN CN N a i-H rO N S3 © © N © © in N 33 © VO s 33 © i-H N 33 © © N 33 © © ov N 33 © © © i-H N 33 © CN i-H i—1 S 33 © i n CN ON ON cs cs .2 JS a S o NO d u-> ON d IT) O Ti- ro NO "1 00 T t 00 o in CN in o o Tt in NO ro 00 o o o ro in T t o o 00 o CN CN in O s 33 NO CN N 33 ON co CO ir, s X NO N X oo NO X ON 1 > s X T f o ON N X s n © ro N 35 co T t CN X © o CN CL. 3 C o c ID e o _> *-t-» CS 60 O a II-g CN o o o N cs ! * cu w S cs £ u £ j £ S o w ON o «1 c s S s w> ^ S o" cs JS u s ^ s o w ON o O 1 0% u a cu 3 « NO CN in in CO o d CN ON T t I -H ON d o q in i o o CN . m CN ON U 1 IT) r -ON NO NO O 00 u-> I U 0 IT) CO T t CO NO T t 0 0 ro ^O CN CO T t CN O CN CN oo CN CO o o CN o q CO o T t CO T t CN CO d o uo CN ^O d oo 0 0 T t I r-r— d CO ro in ON. d T t NO U O Ti-ro 0 0 ro ro T t o NO CO IT) NO r -NO I CN 0 0 0 0 r -NO I U O CN in NO S3 NO CN CN O NO N 35 i n CO CN o IT) T t o T t m CN N X o NO T t U 0 r-o N S3 o CO NO O m T t co co 133 T t T t uo N S3 o o 00 IT) T t 00 CO N 33 © o ON CN m c-ON N 33 o o o > o Ou o c B 1 -a n o 3 > s u O c 3 O '> 6 o o Q iK ro 3 CS H 52 different racial backgrounds. The present study uses a smaller sample size (40 ears per race group) and age range (18-34 years), as well as subjects from specific race groups. Shanks et al. (1993) recorded median values, and with the exception of 1243 Hz the current data shows larger values. Their study used a smaller sample size, a larger age range, and exclusively male subjects, and the investigators did not specify the race of the participants. Results from negative compensation show an identical trend and are not comparable to previous data. Again, the mean SA values from the current study are smaller than the results from Shahnaz and Polka and larger than those from Shanks et al. The exception to this trend is again at 266 Hz, where the current results are slightly larger than Shahnaz and Polka's findings (0.79 mmho versus 0.76 mmho). The 90% ranges in Shahnaz and Polka's results are larger for all frequencies than the current findings (i.e. at 900 Hz, the 90% ranges are 1.70 - 6.16 mmho and 1.12 - 4.05 mmho, respectively). The 5 t h percentile values from the current study are smaller than those from Shahnaz and Polka, while the 95 t h percentile values are larger in Shahnaz and Polka's findings. It is important to note that each of the three studies have used different intermediate frequencies (i.e., the current study uses 315 Hz, Shahnaz and Polka used 355 Hz, and Shanks et al. used 339 Hz), which make the results difficult to compare precisely. Neither Shahnaz and Polka nor Shanks et al. specified the gender of their subjects; therefore a gender comparison is not possible. The same issues of sample size and race discussed above may have affected these results. Table 3.6 provides a more detailed list of procedural variables for each of these studies. 53 Investigator Machine #of subjects (ears) Age M/F Pump speed (daPa/s) Pressure range (daPa) COMPENS ATION Current Study Virtual 40 (80) 18-34 20/20 125 +250 to -300 + and -Shanks et al (1993) Virtual 26 20-40 Male — +200 to -350 + arid -Shahnaz & Polka (2002) Virtual 36 20-43 — 125 +250 to -300 + and -Table 3.6: Procedural variables for the measurement of static admittance up to 1200 Hz. Unspecified variables are denoted by - ; M/F = number of male and female subjects in the sample group. To determine whether gender differences are significant, a separate repeated measures A N O V A was preformed for each probe tone frequency with gender as a between-subject variable and SA estimate (Y+, Y-) as a within-subject factor. There were no significant gender effects at any frequency (see Appendix II for A N O V A results at each frequency); however, the gender differences in the current study do show an interesting trend. Between 500 Hz and 800 Hz, males have a higher mean SA than females while at all other frequencies females show higher mean values than males. Gender differences at each frequency are reported in Table 3.7. 3.3.3 Within-race group analysis—Chinese There is no research to date that has examined static admittance up to 1200 Hz in Chinese adults. A repeated measures A N O V A was performed to determine if gender differences in this group are significant (the same parameters used above). Significant differences were found at two frequencies: 400 Hz [F (1, 38) = 5.03, p = 0.03] and 500 Hz [F (1, 38) = 5.18, p = 0.03]. Although only two frequencies show significant differences, this group has a different pattern in terms of gender differences as males always show higher 54 SA than females (regardless of the probe tone frequency). This is opposite to the Caucasian group, where females had higher SA values at most frequencies. The 90% range for males is also larger. Table 3.8 reports values at each frequency for male and female Chinese subjects; Appendix II reports complete A N O V A results at each frequency. 3.3.4 Between-race group analysis A group analysis between Caucasian and Chinese adults was conducted to determine if there were differences due to race in static admittance up to 1200 Hz. Gender differences were noted between Chinese males and females at 400 and 500 Hz; these frequencies were analyzed independently for each gender. A l l other frequencies were examined with collapsed genders in each race group. A repeated measures A N O V A was conducted to examine race differences with one between-subject variable (race: Caucasian, Chinese) and one within subject variable (SA estimate: Y+, Y-). Results for race effects at 226 Hz [F (1, 38) = 7.03, p = 0.01], 315 Hz [F (1, 38) = 5.85, p = 0.02], 630 Hz [F (1, 38) = 5.97, p = 0.02], 710 Hz [F (1, 38) = 4.64, p = 0.03], and 800 Hz [F (1, 38) = 4.14, p = 0.05] were significant. Estimate effects were significant at all frequencies except 900 and 1000 Hz. This finding emphasizes the importance of using normative values appropriate for the parameters of the clinical immittance machine (e.g., compensation method). The use of inappropriate norms can result in the misdiagnosis of static admittance at higher frequencies. Results at 400 and 500 Hz were analyzed separately for each gender using a repeated measures A N O V A . For both male and female groups, the between-subject variable was race and the within-subject variable was measurement method (Y+, Y-) . Results for 400 Hz show a significant race effect for females [F (1, 38) = 6.57, p = 0.01], but not for males [F (1, 38) = 55 Present study (Caucasian) Frequency Y+ Y -Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) 226 Hz M 0.70 0.34 0.24-1.46 0.76 0.36 0.32-1.59 F 0.74 0.52 0.34-2.49 0.81 0.54 0.40-2.61 315 Hz M 1.09 0.54 0.44-3.60 1.14 0.58 0.44-2.45 F 1.11 0.78 0.35-3.60 1.18 0.80 0.44-3.76 400 Hz M 1.40 0.62 0.54-2.74 1.49 0.66 0.64-2.94 F 1.41 1.03 0.32-4.60 1.46 1.05 0.32-4.75 500 Hz M 1.81 0.82 0.72-3.35 1.95 0.88 0.71-3.58 F 1.75 1.16 0.47-5.04 1.82 1.17 0.43-5.13 630 Hz M 2.37 1.12 0.96-4.36 2.49 1.18 0.86-4.44 F 2.13 1.10 0.42-5.05 2.14 1.08 0.61-5.09 710 Hz M 2.63 1.23 1.00-4.83 2.75 1.26 1.02-4.76 F 2.23 1.14 0.61-5.12 2.23 1.15 0.52-5.05 800 Hz M 2.66 1.16 1.07-4.80 2.76 1.20 0.99-4.99 F 2.50 1.14 1.04-4.74 2.42 1.10 1.01-4.52 900 Hz M 2.56 0.93 1.22-4.15 2.53 0.93 1.12-4.02 F 2.58 1.08 1.02-4.25 2.48 1.03 0.98-4.02 1000 Hz M 2.55 1.06 1.15-3.94 2.48 0.76 1.20-3.77 F 2.62 1.06 1.07-4.55 2.49 0.96 1.04-4.15 1120 Hz M 2.41 0.76 1.23-3.61 2.60 1.11 1.02-4.81 F 2.31 0.65 1.27-3.29 2.41 0.98 0.99-4.48 1250 Hz M 2.24 0.70 1.02-3.49 2.15 0.57 1.17-4.47 F 2.56 1.16 0.91,-5.52 2.30 0.93 1.00-4.47 Table 3.7: Descriptive statistics for the Caucasian group by gender for static admittance (Y) up to 1200 Hz with both positive (+) and negative (-) compensation. 56 Present stuc y (Chinese) Frequency Y+ Y -Mean (mmho) SD (mmho) 90% range (mmho) Mean (mmho) SD (mmho) 90% range (mmho) 226 Hz M 0.58 0.34 0.22-1.47 0.63 0.33 0.24-1.51 F 0.43 0.28 0.14-1.22 0.47 0.28 0.17-1.17 315 Hz M 0.92 0.42 0.43-1.88 0.96 0.42 0.43-1.96 F 0.67 0.42 0.25-1.92 0.75 0.43 0.29-1.80 400 Hz M 1.12 0.59 0.49-2.28 1.19 0.56 0.56-2.27 F 0.75 0.41 0.30-1.93 0.83 0.45 0.38-2.23 500 Hz M 1.52 0.87 0.44-3.20 1.62 0.85 0.65-3.20 F 0.99 0.54 0.41-2.53 1.11 0.60 0.46-3.00 630 Hz M 1.85 1.23 0.41-4.66 1.94 1.16 0.76-4.55 F 1.40 0.90 0.57-4.42 1.54 0.95 0.63-4.85 710 Hz M 2.05 1.47 0.40-5.54 3.12 1.41 0.77-5.34 F 1.58 1.07 0.71-5.36 1.71 1.09 0.82-5.58 800 Hz M 2.25 1.61 0.45-6.19 2.31 1.52 0.78-6.15 F 1.68 1.02 0.76-5.17 1.83 1.01 0.96-5.23 900 Hz M 2.57 1.58 0.54-6.47 2.29 1.23 0.81-4.55 F 1.81 0.91 0.77-4.50 1.93 0.86 1.00-4.55 1000 Hz M 2.31 1.27 0.76-5.60 2.30 1.17 0.96-5.33 F 1.90 0.84 0.94-4.19 2.01 0.78 1.18-4.07 1120 Hz M 2.24 1.13 0.80-5.03 2.21 1.04 0.93-4.84 F 1.91 0.78 1.07-4.00 1.95 0.69 1.13-3.74 1250 Hz M 2.22 1.11 0.62-5.08 2.13 0.98 0.84-4.81 F 1.91 0.78 1.07-3.98 1.91 0.64 1.19-3.50 Table 3.8: Descriptive statistics for the Chinese group by gender and race for static admittance (Y) up to 1200 Hz with both positive (+) and negative (-) compensation. 57 2.38,p = 0.13]. Females also show a significant race difference at 500 Hz [F (1, 38) = 6.46, p = 0.02], while again males do not [F (1, 38) =1.30, p = 0.26]. Figs. 3.3-3.4 show box-and-whisker plots for multiple frequency static admittance for positive and negative compensation; Fig. 3.5 shows individual race and gender effects at 400 and 500 Hz. Appendix II has complete A N O V A tables for each race and frequency. Although only frequencies below 900 Hz show significant race differences, almost all frequencies follow the trend of Caucasian adults showing larger mean values than Chinese adults. This trend is also evident in estimate method (Y+, Y-). Ninety percent ranges show a large amount of variability between the races and measurement methods. This could be caused by the relatively small sample size of the current study. These findings have similar implications for differential diagnosis as those at 226 Hz, in that Chinese adults may be incorrectly assessed (by Caucasian norms) with abnormal static admittance values, when in fact their middle ear transmission system is completely normal. The fact that significant differences were found up to 900 Hz is also important. If a clinician were to run just one multiple frequency tympanogram, it would probably be below 900 Hz. For example, research has shown that the optimal frequency for the differential diagnosis of otosclerosis is 630 Hz (Shahnaz & Polka, 2002). Vanhuyse, Creten, and Van Camp (1975) developed a model that predicted the shapes of susceptance and conductance tympanograms at 678 Hz in normal and pathologic ears, and this model has generated a large amount of information on this particular frequency. For reasons such as these it is clinically relevant to be aware that Caucasian and Chinese ears differ significantly in this frequency range. 58 • C a u c a s i a n • C h i n e s e * Outs ider o Outlier 226 315 400 500 630 710 800 900 1000 1120 1250 Probe Tone Frequency (Hz) Figure 3.3: Box-and-whisker plot showing SP recordings with positive compensation for race differences (between-subject factor) and estimate effects (within-subject factor) at probe tone frequencies up to 1200 Hz. Gender data is collapsed within each race group. Note that significant gender differences were found at 400 Hz and 500 Hz for Chinese females (figures 3.4-5 present individual gender by race data for 400 and 500 Hz). Please refer to page 43 for the definitions of outsider and outlier. 59 o "I CD o d -i—< -I—; E < • Caucasian D Chinese * Outsider o Outlier 2 2 6 3 1 5 4 0 0 5QD 630 7 1 0 BOO 90D 1 0 0 0 1 1 2 0 1 2 5 0 Probe Tone Frequency (Hz) Figure 3 .4: Box-and-whisker plot showing SP recordings with negative compensation for race differences (between-subject factor) and estimate effects (within-subject factor) at probe tone frequencies up to 1200 Hz. Gender data is collapsed within each race group. Note that significant gender differences were found at 400 Hz and 500 Hz for Chinese females. Please refer to page 43 for the definition of outsider and outlier. 60 0 Caucasian Female • Caucasian Male H Chinese Female • Chinese Male * Outsider o Outlier 400, S P * 400, S P - 500, SP+ 500, S P -Frequency (Hz) and Estimation Method Figure 3.5: Box-and-whisker plot showing individual race and gender effects at 400 and 500 Hz. Chinese subjects showed significant gender differences at these frequencies. Caucasian and Chinese females also showed significant race differences at these frequencies, while their male counterparts did not. Please refer to page 43 for the definition of outsider and outlier. 3.4 Resonant Frequency 3.4.1 Procedure This is the frequency at which the mass and stiffness elements in the middle ear are equal and the total reactance is zero (Margolis & Hunter, 1999). Total susceptance is the algebraic sum of the mass and the stiffness elements in the middle ear. It is possible to estimate RF from the susceptance component at the frequency at which compensated susceptance equals zero. RF was calculated by first transforming admittance from polar 61 format into its rectangular components. The rectangular components of susceptance and conductance were then compensated for the effects of ear canal volume, and the frequency at which the compensated susceptance value was closest to zero was considered the resonant frequency. If two frequencies had compensated values that were equidistant from zero, the earlier frequency was taken. RF was measured for sweep frequency and sweep pressure recordings with both negative and positive compensation for a total of four measures. Descriptive statistics and a comparison to other published studies are provided in Tables 3.9-3.10. 3.4.2 Within-race group analysis—Caucasian Positive compensation results from sweep frequency recordings (SF+) show that Caucasian adults have similar resonant frequencies to previously reported data. The mean RF for SF+ is 985 Hz, which is very close to that found by Shahnaz (2001) who reported a mean of 955 Hz. The 90% ranges of these two studies are also comparable. Other published studies report mean values as high as 1135 Hz (Margolis & Goycoolea, 1993) and as low as 817 Hz (Shanks et al., 1993). The current study and Shahnaz (2001) share identical instrumentation and procedural variables, which could account for the similar results. Sweep frequency recordings with negative compensation (SF-) show a similar trend, with the results from the current study agreeing with other published data. The mean value of 1133 Hz from the current study is almost identical to Shahnaz's mean of 1124 Hz, with similar 90% ranges (805 - 1590 Hz and 710 - 1600 Hz respectively). Again, the current study falls in the middle of published values, with the highest value (1315 Hz) found by Margolis and Goycoolea and the lowest (1001 Hz) by Holte. 62 SF + compensation - compensation Investigator Mean (Hz) SD (Hz) 90% Range (Hz) Mean (Hz) SD (Hz) 90% Range (Hz) Current Study (Chinese) M 1084 168 805-1400 1377 298 905-1800 F 1105 158 900-1400 1444 283 1120-2000 C 1094 161 900-1400 1411 289 1000-1990 Current Study (Caucasian) M 997 157 715-1250 1168 225 805-1600 F 973 138 572-1120 1098 212 577-1400 C 985 146 714-1250 1133 219 805-1590 Margolis & Goycoolea (1993) 1135 306 800-2000 1315 377 710-2000 Hanks & Rose (1993) 1003 216 650-1400 - - ~ Shanks et al. (1993) 817* - 565-1130 1100 * — 678-1243 Valvik et al. (1994) 1049 261 650-1500 - ~ — Holte(1996) 905 184 630-1250 1001 257 710-1400 Hanks & Mortenson (1997) 908 188 650-1300 1318 308 900-1750 Shahnaz & Polka (1997) 894 166 630-1120 1043 290 710-1400 Wiley et al. (1999) M 826 146 ~ 993 259 — F 898 189 -- 1076 297 — C 866 175 - 1039 283 ~ Shahnaz (2000) 955 206 612-1347 1124 309 710-1600 Table 3.9: Descriptive statistics for resonant frequency (RF), measured by sweep frequency (SF) with both positive (+) and negative (-) compensation for the current study as well as other published data. Shanks et al. (1993) reported median values (*); unreported values denoted by - ; M = male; F = female; C = combined genders. 63 SP + compensation - compensation Investigator Mean (Hz) SD (Hz) 90% Range (Hz) Mean (Hz) SD (Hz) 90% Range (Hz) Current Study (Chinese) M 990 148 810-1250 1141 243 810-1780 F 1032 133 805-1250 1214 202 715-1600 C 1011 141 800-1250 1177 223 • 800-1600 Current Study -(Caucasian) M 905 132 710-1244 1036 195 800-1393 F 881 134 634-1120 1036 225 715-1590 C 893 132 710-1120 1035 - 208 800-1400 Margolis & Goycoolea (1993) 990 290 630-1400 1132 337 710-2000 Hanks & Rose (1993) - ~ - - - — Shanks et al. (1993) - ~ - - ~ — VaMk et al. (1994) ~ ~ - ~ - — Holte (1996) -- - ~ - ~ — Hanks & Mortenson (1997) — — ~ — — — Shahnaz & Polka (1997) 615 148 400-870 508 127 355-686 Wiley et al. (1999) M ~ ~ ~ - - — F -- -- ~ - . - -C - - ~ - - -Shahnaz (2000) 841 168 560-1120 974 253 630-1250 Table 3.10: Descriptive statistics for resonant frequency (RF),-measured by sweep pressure (SP) with both positive (+) and negative (-) compensation for the current study as well as other published data; unreported variables denoted by - M = male; F = female; C = combined genders. There are fewer published studies to compare results from sweep pressure recordings with positive (SP+) and negative (SP-) compensation. With SP+, the present study found a mean of 893 Hz and a 90% of 710-1120 Hz, which is comparable with two of the other three normative studies. These results are again closest to those of Shahnaz (2001), who found a mean of 841 Hz and a 90% range of 560 - 1120 Hz, and slightly lower than Margolis and Goycoolea with a mean of 990 Hz and a 90% range of 630 - 1400 Hz. SP- results for the present study show a similar trend, again being most similar to Shahnaz (2001) and slightly lower than Margolis and Goycoolea. It is important to examine the differences in results obtained using sweep frequency versus sweep pressure recordings. Margolis and Goycoolea (1993) reported differences in estimates of resonant frequency when using different recording methods. They found that resonant frequency values were lower when derived from sweep pressure recordings, and attributed these differences to the faster rate of pressure change used in this recording method. Faster rates of pressure change can produce a lower estimate of resonant frequency, as they show higher compensated susceptance values (Shanks & Wilson, 1986) and deeper notches (Creten & Van Camp, 1975). Another reason for this difference is the number of tympanometric sweeps that must be rim in order to gather information across a large frequency range. Research has shown that multiple consecutive tympanometric sweeps may produce higher admittance values, which can result in an earlier notch in the susceptance tympanogram and in turn produce a lower resonant frequency value (Osguthorpe & Lam, 1981; Vanpeperstraete et al., 1979; Wilson et al., 1984). The current data follows this trend, and sweep frequency estimates of resonant frequency are higher than sweep pressure estimates. 65 A repeated measures A N O V A was run to investigate gender differences with respect to resonant frequency, with gender as the between-subject variable and RF estimates (SF+, SF-, SP+, SP-) as the within-subject variable. No significant gender [F (1, 38) = 0.34, p = 0.57], within-subject (estimate) [F (1, 38) = 1.31, p = 0.26], or gender-estimate interactions [F (1, 38) = 0.61, p = 0.44] were noted. Complete A N O V A results are in Table A1.7 of Appendix I. No estimate effect implies that RF values are not significantly affected by the measurement method (SF+, SF-, SP+, SP-). This finding is in contrast to Shahnaz and Polka (1997) and Margolis and Goycoolea (1993), who both reported an estimate effect in resonant frequency. Gender trends reveal that Caucasian males have higher RFs than females, with the exception of SP recordings in which they show the same mean. Male 90% ranges are also larger for each recording method except SP. Wiley et al. (1999) showed the opposite trend in SF recordings, with females having higher RF values than males. Their study differed from the current one in several procedural variables (e.g. method of RF estimation), as well as the subject variables of age (they studied older adults between 48 - 90 years). They defined the race of their subjects as non-Hispanic white, which is comparable to the current study. They also used a different method of RF estimation, which was not clearly explained in their article; it appears that they analyzed the data in a numerical format, but it is unclear exactly how they derived their R F values. Table 3.11 provides a detailed review of the procedural variables in the measurement of RF between the current study and other normative research. As no gender differences were found in this analysis, data were collapsed together for the group analysis of race. 66 Investigator Machine #of subjects (ears) Age M/F Pump speed Pressure range (daPa) MC Method of RF estimation Current Study** Virtual 40 (80) 18-34 20/20 125 daPa/s +250 to -300 + and - Mathematically Margolis & Goycoolea (1993) Virtual 28 (56) 19-48 250 daPa/s +400 to -500 + (+250 daPa), -(-500 daPa) Visually; by Y, B, G Hanks & Rose (1993) GSI 33 90 6-15 — 50 daPa/s +200 to -400 + Automatically Shanks et al (1993) Virtual 26 20-40 Male — +200 to -350 + and - Mathematically Valvik et al. (1994) GSI 33 100 — 53/57 — +200 to ? + Automatically Holte (1996) Virtual 136 20-90+ — 75-100 daPa/s +250 to -300 + and - Visually Hanks & Mortenson (1997) GSI 33 53 (106) 18-25 50 daPa/s +200 to -400 + Automatically Shahnaz & Polka (1997)** Virtual 36 (68) 20-43 125 daPa/s +250 to -300 + and - Mathematically Wiley et al. (1999) Virtual 404 48-90 — — +250 to -300 + and - Own formula; visually Shahnaz (2001)** Virtual 36 20-43 — 125 daPa/s +250 to -300 + and - Mathematically Table 3.11: Procedural variables in the estimation of resonant frequency in published normative studies. Studies marked with ** also report F45° data; unspecified values are denoted by - ; MC = method of compensation. 3.4.3 Within-race group analysis—Chinese There has been no research to date investigating resonant frequency in Chinese adults, or in any other specified race group. A repeated measures A N O V A was used to examine gender effects in this race group. The same variables described above were used. Gender [F (1, 38) = 0.90, p = 0.35], estimate [F (91, 38) = 2.40, p = 0.13], and gender-estimate interactions [F (1, 38) = 0.44, p = 0.51] were not significant. Chinese adults show the opposite gender trend to Caucasian adults, with females having higher resonant frequency values than males. Both groups show similar 90% ranges. The lack of gender 67 effect allows this data to be collapsed together for group analysis. No significant estimate effect implies that measurement method does not affect RF values. See A1.8 in Appendix I for complete A N O V A results. 3.4.4 Between-race group analysis A repeated measures A N O V A was conducted to determine if there were race differences between the two groups. Neither race group showed a gender effect, so gender data was collapsed within Caucasian and Chinese groups. Race (Caucasian versus Chinese) was the between-subject factor and estimate (SF+, SF-, SP+, SP-) was the within-subject factor. A significant race effect was found on the variable of resonant frequency [F (1, 78) = 19.27, p - 0.00]. Figure 3.4 shows a box-and-whisker plot of these results. Chinese adults show a significantly higher mean RF than Caucasian adults. This higher resonant frequency could be caused by increased stiffness in the Chinese group as was evident in their lower static admittance value. This lower static admittance value causes a notch in the susceptance tympanogram at a higher frequency, which in turn causes a higher resonant frequency. Since race effects were found to be significant, it is important for clinicians to use different norms when assessing the resonant frequency of Chinese and Caucasian patients. There was not a significant effect for estimate [F (1, 78) =3.75, p = 0.06) or race-estimate interaction [F (1, 78) = 0.26, p = 0.61]. This finding is not consistent with Shahnaz (2001) who reported a main effect of estimate (measurement method). He found that resonant frequency was significantly higher for negative compensation in each recording method (SF and SP). The current study uses identical instrumentation and procedures to Shahnaz; however, Shahnaz's sample size was larger than the present study (104 ears versus 68 80 ears). The current findings have unclear clinical implications. They imply that measurement method does not affect RF values; however, previous research contradicts this. Perhaps the best way for the clinician to deal with these incongruent findings is to be cautious and assume that there is an estimate effect. Further research into this question is necessary before drawing conclusions. A complete A N O V A summary is in Table A 1.9 in Appendix I. 2400 400 S F + S F - S P + S P -RF Estimation Method 0 Caucaisan • Chinese * Outsider Figure 3.6: Box-and-whisker plot showing a significant race effect for resonant frequency with race (collapsed genders) as a between-subject factor and estimate (SF+, SF-, SP+, SP-) as a within-subject factor. Please refer to page 43 for the definition of an outsider. 69 3.5 Frequency corresponding to a 45 °phase angle (F45 °) 3.5.1 Procedure F45° was estimated as the lowest frequency at which peak conductance became equal to or larger than peak susceptance (Shahnaz & Polka, 1997). F45° was calculated in a numerical format by finding the lowest frequency at which compensated susceptance and conductance were closest or equal to each another. This procedure was measured with both positive and negative compensation for both the sweep frequency and pressure methods. Table 3.11 (p. 68) compares procedural variables in the measurement of F45° across several studies. Descriptive statistics for this variable and a comparison to other normative studies are provided in Table 3.12. 3.5.2 Within-race group analysis—Caucasian Mean F45° values and 90% range for both SF and SP recordings are very similar to those found by Shahnaz (2001). The largest difference noted is in the SF- recording, where the current study has a mean of 749 Hz and Shahnaz reports a mean of 706 Hz. It is interesting to note that Shahnaz and Polka (1997) found substantially lower mean values (i.e., SF- value of 615 Hz) and smaller 90% ranges (400 - 870 Hz versus 500-1000 Hz in the current study). However, in Shahnaz and Polka's study F45° values were determined visually by comparing compensated susceptance to uncompensated conductance tympanograms at different probe tone frequencies. This estimate does not reflect the contributions of compensated conductance. The current study uses the same measurement instrument and methods as Shahnaz (2001). 70 SP - compensation 90% Range (Hz) 453-800 564-1114 500-1000 403-800 355-800. 357-800 355-686 417-800 SP - compensation C A B ON T t i/-> T t SO CN CN ro ON CN r-CN T t CO SP - compensation Mean (Hz) o i n NO ON NO r~ ON o r -00 o NO OO NO i n 00 00 m oo o i n CN ON i n SP + compensation 90% Range (Hz) 315-706 453-800 315-800 357-706 355-560 355-630 355-768 SP + compensation C A 3-o tN ON ON NO fN CN ON ON. m 0 0 i ON CN i—i SP + compensation Mean (Hz) T t O i n co NO 00 NO m ro ON T t o 00 T t NO 00 T t i m SF || - compensation || 90% Range (Hz) 630-1000 560-1120 | 564-1120 503-1000 405-900 J 500-1000 400-870 450-1000 SF || - compensation || / — - N C A S »—H T t 00 IT) ^ CN i n NO y—( r->n 00 i n 00 T t 00 r-SF || - compensation || Mean (Hz) CN CN 00 IT) ON 0 0 ON i n 00 T t NO (-» T t CO r-ON T t m NO NO o o SF || + compensation 90% Range (Hz) 362-800 453-900 453-895 405-800 319-796 400-800 l i 400-900 SF || + compensation C A S T t 0 0 CN CN NO CN r- i i 00 T t SF || + compensation Mean (Hz) ON -o NO tN ON NO »—i m NO o o NO NO o NO CO o NO l i T t o NO Investigator % U fe O CS Shahnaz (2000) Investigator Current Study (Chinese) Current Study (Caucasian) Shahnaz & Poll (1997) Shahnaz (2000) Gender differences were examined by a repeated measures A N O V A test, with gender as the between-subject variable and estimate (SF+, SF-, SP+, SP-) as the within-subject variable. Gender [F (1, 38) = 0.30, p = 0.59] and gender-estimate interactions [F (1, 38) = . 46.65, p = 0.00] were not significant, but there was a significant effect of estimate [F (1, 38) = 46.64, p = 0.00]. Table A L I O in Appendix I has complete A N O V A results. This estimate effect indicates that the method of measurement significantly affects F45° values. This finding stresses the importance of procedural variables (e.g., recording method, positive or negative compensation) in the normative values clinicians are using. Males show marginally higher F45° values than females, although there is no previous research that has examined gender differences on this variable. 3.5.3 Within-race group analysis—Chinese A repeated measure A N O V A analysis was run to determine if significant gender differences exist on the variable of F45° in Chinese adults. Gender differences were found to be significant [F (1,38)=9.85, /?=0.00]. This finding indicates that gender specific norms should be established for this race group. Estimate [F (1, 38) = 3.11, p - 0.09] and gender-estimate interactions [F (1, 38) = 3.11,/? = 0.09] were not significant, meaning that method of measurement has no significant effect on F45° values. Chinese adults show the opposite gender trend to their Caucasian counterparts, with females having higher mean F45° values than males. There is no literature with which to compare these results. Complete A N O V A results can be found in Table A l . 11 in Appendix I. 72 3.5,4 Between-race group analysis As a significant gender effect was found in Chinese adults, gender data cannot be collapsed together for a group analysis. Instead, females and males were compared separately across race groups. A repeated measures A N O V A was conducted with a between-subject factor of race (e.g., Caucasian female and Chinese female) and a within-subject factor of measurement method (SF+, SF-, SP+, SP-). A significant race effect and race-estimate interaction was found for female subjects ([F (1,38) = 19.25, p = 0.00]; [F (1, 38) = 6.16, p = 0.01]) but not for males ([F (1,38) = 0.82, p = 0.37]; [F (1, 38) = 0.35, p = 0.56]). While this finding appears to indicate a need for gender-specific race-based norms, it is important to remember that the current study has a relatively small sample size (40 ears per race group). This finding should be replicated in a larger sample size before generalizations are made. A significant estimate effect was also found for both groups (females [F (1, 38) = 8.98, p = 0.01], males [F (1, 38) =27.44, p = 0.00]. This estimate effect was also noted by Shahnaz (2001). He reported that measurement methods impacted F45° values, with negative compensation for each recording method producing higher F45° values. Figure 3.5 shows box-and-whisker plots for gender and race differences for the variable of F45°; Tables A 1.12-1.13 in Appendix I report complete A N O V A results. 73 1200 T 1 1 r 1100-1000-N 900-800-700-600-500-400-3 0 0 -u c cr I \ SF+ SF- SP+ SP-F45 Estimation Method 0 Caucasian Female n Caucasian Male a Chinese Female • Chinese Male * Outsider Figure 3 .7 : Box-and-whisker plot showing F45° by gender and race (between-subject factors) and estimate (within-subject factor). Genders are not collapsed as significant gender differences were found in the Chinese adults. Please refer to page 43 for the definition of an outsider. 74 Chapter 4: General Discussion 4.1 Summary This project was initiated to examine racial differences in immittance audiometry between a group of Caucasian and Chinese normal hearing adults. The two main goals of the project were to determine if: (1) the Chinese race has different standard low probe tone frequency immittance audiometry norms than the Caucasian race, and (2) the Chinese race has different multifrequency tympanometry results than the Caucasian race. These goals were addressed by examining five tympanometric measures in 40 Caucasian and 40 Chinese middle ears. Two of these measures—static admittance at 226 Hz and tympanometric width—were obtained using standard low probe tone frequency tympanometry. The remaining three variables—static admittance up to 1200 Hz, resonant frequency, and the frequency corresponding to a phase angle of 45°— can only be measured using multifrequency, multicomponent tympanometry. A l l of these parameters except one (tympanometric width) showed a significant race effect. The parameter of static admittance up to 1200 Hz showed a race effect until 800 Hz; frequencies above this did not exhibit significant effects. Table 4.1 summarizes the statistical findings of the project. 4.2 Limitations The current study has several limitations which should be taken into account before these findings can be generalized. The first limitation is the small sample size of the study. Each race group was comprised of only 20 subjects (or 40 ears). This is a small size compared to other immittance audiometry studies. For example, Wan and Wong (2002) had 75 Group results Within-race Group Results Between-races Gender Estimate Gender* Estimate Race Estimate Race* Estimate C A C A C A M F M F M F SA @226 Hz * * * * * TW @ 266 Hz * * * SA 315 Hz * * * 400 Hz * * * * 500 Hz * * * * * 630 Hz * * * * * * 710 Hz * * * * * 800 Hz * * * * * * * * 900 Hz * 1000 Hz * * 1120 Hz * * * * * 1250 Hz * * * * * RF * * F45° * * * * Table 4.1: This table provides a summary of significant differences on each parameter tested. Within-race results refer to tests within each race group (C = Caucasian; A = Chinese); between-race results refer tests between race groups (M = male; F = female). When significant gender differences were found in within-race analysis, genders were analyzed separately in between-race measures. Significant differences are denoted by *; non-significant results are indicated by a blank space. 100 Chinese subjects (and 200 ears), while Roup et al. (1998) used one ear each of 102 non-Hispanic Caucasian participants. These studies used over 100 ears for a single race, while the current study used a total of 80 ears for two races. Sample size plays an important role in research, and in order to generalize results to the majority of a specific population a large sample of that population must be tested. This research should be replicated with a 76 substantially larger sample size (at least 100 ears per race group) before the results can be clinically implemented as normative data. Another limitation of this study is the assumption that each subject's two ears can be treated separately. This study made the supposition that each subject could be treated as two individual ears. Several previous studies have made this same assumption (Hanks & Mortenson, 1997; Hanks & Rose, 1993; Margolis & Goycoolea, 1993; Shahnaz & Polka, 1997, 2002; Wan & Wong, 2002; Wiley et al., 1996) while others have not and only used one ear per subject (Holte, 1996; Roup et a l , 1998; Shanks et al., 1993). It is interesting to note that Holte (1996) gathered data from both ears of 136 subjects, but only reported right ear findings. Wan and Wong (2002) recorded tympanograms from both ears of their subjects, compared the results from left and right ears, determined that there was no statistical difference between the ears, and combined all data from two ears. Results from the Chinese adults in the current study were compared to Wan and Wong's (2002) findings, and found to be very similar on the standard low frequency (226 Hz) parameters of static admittance and tympanometric width. Wan and Wong state that their normative values encompass only a Southern Chinese population and suggest that their results be verified in a Northern Chinese group. Chinese participants in the present study were from Mainland China, Hong Kong, and Taiwan, and represent a more heterogeneous population than tested by Wan and Wong. 77 4.3 Sources of Differences Another shortcoming in the current study is the unknown sources of differences between the race groups. These sources of variability can be subdivided into two categories: (1) unmeasured audiological variables, and (2) physiological differences. Information on several immittance variables were collected but not analyzed. This was done to keep the current research within the scope of a Master's thesis. One of the variables not analyzed was tympanometric peak pressure (TPP), which is the pressure corresponding to the peak of a tympanogram. TPP may be used as an indirect measure of middle ear pressure (e.g., a highly negative TPP-may be observed with eustachian tube dysfunction). However, TPP measures have a high variability across both normal and pathologic ears (Wiley & Stoppenbach, 2002) and lack the diagnostic specificity of other tympanometric measures (Shanks et a l , 1988; Wiley & Smith, 1995). Wan and Wong (2002) reported significantly more positive TPP in their Chinese subjects than Roup et al.'s Caucasian group. If this finding is replicated in the current study, it could indicate that a more positive TPP is related to better aeration of the middle ear (Wan & Wong, 2002). This in turn may be caused by anatomic differences, such as better functioning eustachian tubes or larger pneumatic mastoid cells. Another possible source of difference between Chinese and Caucasian middle ears is the anatomic variable of body size. Typically, Chinese adults have a smaller body size than their Caucasian counterparts (Wan & Wong, 2002). Animal studies have shown that the size of specific middle ear structures—such as the area of the tympanic membrane, stapes footplate, and middle ear cavity—are closely related to body size (Huang et al., 2000; Rosowski, 1994). Huang et al. (2000) found that smaller body size correlates with lower 7.8 middle ear compliance in animal models. The current study shows a similar finding. Chinese middle ears had lower compliance and higher resonant frequency than Caucasian middle ears. Is this finding related to body size? The answer to this question would have to be obtained through advanced imaging techniques or post-mortem analysis. However, determining the anatomic reasons for these race differences is outside of the scope of this research. 4.4 Clinical Implications The clinical implications of this research can be divided into general and specific implications. General implications address how multifrequency tympanometry fits into the field of clinical audiology, and will be discussed first. A discussion of specific implications, such as how findings from this study can be clinically implemented, will follow. There is currently little clinical use of multifrequency tympanometry. This is for two reasons. First, multifrequency tympanometry is more time consuming—it takes more time to run one sweep frequency or several sweep pressure recordings than it does to run a standard 226 Hz tympanogram. The second reason is that the underlying physical principles of immittance audiometry are not well understood by the clinical audiology community. This lack of understanding translates into uncertainty of what multifrequency variables, such as resonant frequency and F45°, actually measure. There is also confusion about what these values translate into in clinical practice. Every audiologist knows that static admittance is a measure of the admittance of the middle ear transmission system, but fewer audiologists know that resonant frequency occurs when susceptance equals zero and conductance is the only component contributing to the total admittance of the middle ear. 79 It has been shown that standard low probe tone tympanometry often fails to distinguish normal middle ears from ears with lesions that affect the ossicular chain, such as otosclerosis, ossicular discontinuity, or fixation of one or more of the ossicles (Colletti, 1975, 1976; Lil ly, 1984). Previous research has shown that resonant frequency, F45°, and high frequency static admittance are more effective indicators of pathologies that affect the ossicular chain, such as otosclerosis (Colletti, 1976; Hunter & Margolis, 1992; Shahnaz & Polka, 1997, 2002) and ossicular discontinuity (Colletti, 1976). Although evidence exists to prove the clinical utility of multifrequency tympanometry in differential diagnosis, it is still not widely used in the field of clinical audiology. Resonant frequency can be established either visually or numerically, as it was calculated in this study. To visually determine the resonant frequency, a clinician must determine the frequency at which the notch on a susceptance tympanogram becomes equal to the positive or negative tail of the tympanogram (see figure 1.5 on p. 19). The main benefit of the visual method is that it is easy and very time efficient. It is a somewhat more time consuming process to establish a more accurate estimate of resonant frequency using the numerical values of rectangular components. The clinician must first determine the peak and tail values df susceptance and conductance tympanograms at several different frequencies. They must then transform these polar values into rectangular format (using equations 3 and 4, p. 30) apply a compensation formula (equations 5 and 6, p. 31) and then transform these values back to polar notation (formulas 7 and 8, p. 31). This must be repeated at several different frequencies to determine resonant frequency. The time required for this process is not feasible for a fully booked clinical audiologist. However, there is an advantage to mathematically determining resonant frequency. This method produces a more consistent 80 and accurate estimate of resonant frequency. It is an objective method that is not affected by human error (e.g., difficulty visually determining the frequency at which the susceptance notch equals the applicable tail). If resonant frequency falls close to two frequencies, this method will tell the clinician at which frequency the notch is closest to zero. While the mathematical method of calculation produces a more numerically accurate estimate of resonant frequency, it is also important to look at its effects on static admittance and F45°. The current study takes compensated conductance into account, which can produce a more mathematically correct static admittance or F45° value. Shahnaz and Polka (2002) found that otosclerosis may affect the conductance (and not stiffness) element of the middle ear at higher probe tone frequencies. This finding indicates that taking compensated conductance into account may improve the diagnostic value of both standard (static admittance at 226 Hz) and multifrequency (static admittance up to 1200 Hz, F45°) parameters. A potential time saving solution to the mathematical calculation of standard and multifrequency parameters does exist. This can be accomplished by creating a macro template on a spreadsheet that automatically calculates compensated susceptance and conductance values. This template could easily be created in a spreadsheet program (such as Excel), and it would drastically reduce the time necessary for the calculation of multifrequency variables. If such a template existed, the audiologist would only have to determine the peak and tail values of B and G tympanograms. How this is accomplished depends on the clinical machine, but typically involves moving a cursor to the three desired points (peak, negative and positive tail) and recording the values. These values would then be entered into the appropriate spots in the template, and compensated susceptance and 81 conductance values would be calculated. From these values, resonant frequency could be determined as the frequency at which compensated susceptance equals zero, and F45° as the frequency at which compensated susceptance equals compensated conductance. Static admittance could also be calculated in a more mathematically correct manner. Another solution to the time consuming nature of these calculations is to have the appropriate formulas written into the software of clinical immittance machines. If this were to occur, no additional calculations would be necessary. However, immittance machine manufacturers will not invest time and money into developing software not typically used in a clinic. In summary, despite the diagnostic advantage of multifrequency over standard low probe tone frequency tympanometry it has not become a routine test due to the following reasons. First, many clinicians do not understand the diagnostic value of multifrequency tympanometry. Second, it is currently a complex procedure to calculate multifrequency tympanometry measures. Therefore, multifrequency tympanometry is not used due to lack of understanding and time-consuming calculations. Since multifrequency tympanometry is not commonly used, immittance companies will not invest money to create software that automatically calculates multifrequency parameters. The solution to this problem is to promote the widespread use of multifrequency tympanometry in clinical settings, and to objectively prove the advantages of multifrequency over standard low probe tone frequency tympanometry in diagnosing different middle ear pathologies. This study also has specific clinical implications for the five tympanometric measures: (1) Static admittance at 226 Hz showed significant race and estimate effects, (2) Tympanometric width at 226 Hz showed significant estimate effects, (3) Multifrequency 82 static admittance showed significant race and estimate effects up to 800 Hz, (4) Resonant frequency showed significant race effects, and (5) F45° values showed gender and race (females only) effects as well as estimate effects for both genders. Significant race effects demonstrate a need for race specific norms when assessing Caucasian and Chinese adults. Significant estimate effects prove that the method of measurement (e.g., Y+, Y - , SF+, SF-, SP+, SP-) affects the results of tympanometric measures, and therefore clinicians should use normative values that match the procedure that their immittance machine uses. This estimate effect is very important information for clinical audiologists. Research studies use very specific measurement parameters (e.g., pressure direction, compensation method, pressure range) that are typically not used in a clinic. For example, most clinical immittance machines use a negative-to-positive pressure direction, while most research studies use a positive-to-negative direction. A positive-to-negative pressure direction should be used with multifrequency tympanograms to minimize the occurrence of multipeaked tympanograms (Margolis & Shanks, 1985). However, if clinicians use a negative-to-positive pressure direction, their findings will not be comparable to normative data obtained with positive-to-negative pressure direction. The danger of clinicians not being aware of the significant effect of estimate is that they will use inappropriate norms in the differential diagnosis of middle ear pathology. This may ultimately result in the patient being incorrectly diagnosed. 4.5 Future Research Results from the current study raised several unanswered questions. The question of racial differences in immittance audiometry would benefit from additional research. First, i 83 the current study should be replicated with a larger sample size to confirm the race differences found in static admittance at 226 Hz, static admittance up to 800 Hz, resonant frequency, and F45°. Second, because the current research shows a race difference, this brings up the possibility that differences may exist between other races. It would be interesting to test both completely different races (e.g., African-American) as well as other Asian races (e.g., Japanese) to see if differences exist. The results of other Asian races would be especially interesting, as they could either follow a similar pattern to the Chinese results (e.g., lower static admittance, higher resonant frequency and F45° than Caucasian group), or they could show a totally different pattern relative to Caucasian ears. Third, this research should be replicated in different age groups. Both children and adults would benefit from this research. Application of the same protocol at younger ages (pre-school and school aged children) could determine if there are race differences in this population. Otitis media is more prevalent in this age group (Northern & Downs, 2002), and any information which could aid in the differential diagnosis of otitis media would have implications in the assessment and treatment of children, as well as with the costs associated with this disorder. A point estimate of the prevalence of otitis media in different race groups in this population could also help confirm if the Chinese race is less prone to otitis media, as was reported from preliminary results by Tong et al. (2000). Adults outside of the age range of the current study would also benefit from further research into the question of race-based normative values. For example, an older Chinese adult with low static admittance may be diagnosed with a stiffening pathology when it is possible that his or her static admittance 84 values are within the normal range for the Chinese race. It is impossible to know if older adults follow the same trend as younger adults without further research. Fourth, the contribution of conductance to static admittance (standard and multifrequency) and F45° would benefit from further research. There is no data to date comparing the current method of calculation (e.g., visual resonant frequency) with the mathematically accurate method (e.g., numerical resonant frequency) used in this research. It is essential to initiate a test performance analysis to gather statistical evidence on the clinical utility of different calculation methods of tympanometric variables on differential diagnosis. Another interesting test performance analysis would be the relationship between race-specific norms (e.g., Chinese adults) and various confirmed pathologies. For example, do stiffening pathologies such as otosclerosis produce the same changes in the middle ear transmission system of Chinese adults as in Caucasian adults? Or would a Chinese (or an African-American) middle ear react differently to ossicular discontinuity than a Caucasian middle ear? The answers to these questions may provide clinical audiologists with new information for differential diagnosis. 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Baltimore, M D : Lippincott Williams & Wilkins. 97 Appendices Appendix I - ANOVA tables for Static Admittance (SA), tympanometric width (TW), resonant frequency (RF), and the frequency corresponding to an admittance phase angle of 45 °(F45 °) SA at 226 Hz Source SS df MS F P Gender 4.35E-02 1 4.35E-02 0.11 0.74 Error 15.27 38 0.402 - -SA 8.22E-02 1 8.22E-02 42.68 0.00 SA*Gender 1.05E-03 1 1.05E-03 0.54 0.47 Error 7.32E-02 38 1.93E-03 - ~ Table Al.l—Summary of ANOVA for Caucasian static admittance at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Gender .0.50 1 0.50 2.59 0.12 Error 7.25 38 1.91 - -SA 4.56E-02 1 4.56E-02 31.38 0.00 SA*Gender 1.09E-04 1 1.09E-04 0.80 0.79 Error 5.52E-02 38 1.45E-03 - — Table A 1.2—Summary of ANOVA for Chinese static admittance at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Race 2.08 1 2.08 7.03 0.01 Error 23.06 78 0.30 - -SA 0.13 1 0.13 75.33 0.00 SA*Race 2.68E-03 1 2.68E-03 1.61 0.21 Error 0.13 78 1.66E-03 - — Table A 1.3—Summary of ANOVA for group differences between Caucasian and Chinese static admittance at 226 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-). 98 TW at 226 Hz Source SS df MS F P Gender 959.11 1 959.11 0.83 0.37 Error 43926.00 38 1155.95 — --TW 3642.30 1 3642.30 13.81 0.00 TW*Gender 98.12 1 98.12 0.37 0.55 Error 5.52E-02 38 1.45E-03 — — Table A 1.4—Summary of ANOVA for Caucasian tympanometric width at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (TW estimate: Y+, Y-). Source SS df MS F P Gender 32.77 1 32.77 0.17 0.90 Error 74854.23 38 1969.85 - -TW 5481.36 1 5481.36 19.11 0.00 TW*Gender 45.91 1 45.91 0.16 0.69 Error 10902.41 38 286.91 . ~ ~ Table A 1.5—Summary of ANOVA for Chinese tympanometric width at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (TW estimate: Y+, Y-). Source SS df MS F P Race 671.58 1 671.58 0.44 0.51 Error 119772.12 78 1535.54 - — TW 9030.03 1 9030.03 33.44 0.00 TW*Race 93.64 1 93.64 0.35 0.55 Error 21066.22 78 270.08 - — Table A1.6—Summary of ANOVA for group differences between Caucasian and Chinese tympanometric width at 226 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-). 99 RF Source SS df MS F P Gender 34810.00 1 34810.00 0.34 0.57 Error 3921080.00 38 103186.32 -- -RF 15488.00 1 15488.00 1.31 0.26 RF*Gender 7200.00 1 7200.00 0.61 0.44 Error 448662.00 38 11806.90 -- — Table A 1.7—Summary of ANOVA for Caucasian static admittance at resonant frequency with one between-subject factor (gender: male versus female) and one within-subject factor (RF estimate: SP+, SP-, SF+, SF-). Source SS df MS F P Gender 104040.00 1 104040.00 0.90 0.35 Error 4398747.50 38 115756:51 - — RF 45904.50 1 45904.50 2.40 0.13 RF*Gender 8450.00 1 8450.00 0.44 0.51 Error 727675.50 38 19149.36 ~ ~ Table A 1.8—Summary of ANOVA for Chinese static admittance at resonant frequency with one between-subject factor (gender: male versus female) and one within-subject factor (RF estimate: SP+, SP-, SF+, SF-). Source SS df MS F P Race 2089811.25 1 2089811.25 19.27 0.00 Error 8458677.50 78 108444.58 - -RF 57360.25 1 57360.25 3.75 0.06 RF*Race 4032.25 1 4032.25 0.26 0.61 Error 1191987.50 78 15281.89 - — Table A 1.9—Summary of ANOVA for group differences between Caucasian and Chinese resonant frequency with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (RF estimate: SP+, SP-, SF+, SF-). 100 F45° Source SS df MS F P Gender 15015.63 -1 15015.63 0.30 0.59 Error 1926106.88 38 50687.02 -- ~ F45° 187884.50 , 1 187884.50 46.65 0.00 F45° * Gender 7381.13 1 7381.13 1.83 0.18 Error 153044.38 38 4027.48 - -Table ALIO—Summary of A N O V A for Caucasian F45° with one between-subject factor (gender: male versus female) and one within-subject factor (F45° estimate: SP+, SP-, SF+, SF-). Source SS df MS F P .Gender 402503.91 1 402503.91 9.85 0.00 Error 1552319.69 38 40850.52 - ~ F45° 26507.53 1 26507.53 3.11 0.09 F45° * Gender 13000.78 1 13000.78 1.53 0.22 Error 323455.44 38 8511.99 - ~ Table A l . l 1—Summary of A N O V A for Chinese F45° with one between-subject factor (gender: male versus female) and one within-subject factor (F45° estimate: SP+, SP-, SF+, SF-). Source SS df MS F P Race 899250.16 1 899250.16 19.25 0.00 Error 1775454.69 38 46722.49 -F45° 80701.53 1 80701.53 8.98 0.01 F45° * Race 55361.28 1 55361.28 6.16 0.02 Error. 341520.94 38 , 8987.39 - — Table A l . 12—Summary of A N O V A for Caucasian and Chinese female F45° with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (F45° estimate: SP+, SP-, SF+, SF-). Source SS df MS F P Race 36602.50 1 36602.50 0.82 0.37 Error 1702971.88 38 44815.05 -- -F45° 97461.13 1 97461.13 • 27.44 0.00 F45° Race 1250.00 1 1250.00 0.35 0.56 Error 134978.88 38 3552.08 - — Table A 1.13—Summary of A N O V A for Caucasian and Chinese males F45° with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (F45° estimate: SP+, SP-, SF+,SF-). 101 Appendix II - ANOVA tables ofSA up to 1200 Hz SA at 226 Hz Source SS df MS F P Gender 4.35E-02 1 4.35E-02 0.11 0.74 Error 15.27 38 0.402 -- -SA 8.22E-02 1 8.22E-02 ' 42.68 0.00 SA*Gender 1.05E-03 1 1.05E-03 0,54 0.47 Error 7.32E-02 38 1.93E-03 ~ --Table A2.1—Summary of ANOVA for Caucasian static admittance at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Gender 0.50 1 0.50 2.59 0.12 Error 7.25 38 1.91 ~ ~ SA 4.56E-02 1 4.56E-02 31.38 0.00 SA*Gender 1.09E-04 1 1.09E-04 0.80 0.79. Error 5.52E-02 38 1.45E-03 - — Table A2.2—Summary of ANOVA for Chinese static admittance at 226 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Race 2.08 1 2.08 7.03 0.01 Error 23.06 78 0.30 - -SA 0.13 1 0.13 75.33 0.00 SA*Race 2.68E-03 1 2.68E-03 1.61 0.21 Error 0.13 78 1.66E-03 ~ ~ Table A2.3—Summary of ANOVA for group differences between Caucasian and Chinese static admittance at 226 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-). 102 SA at 315 Hz Source SS df MS F P Gender 1.19E-02 1 1.19E-02 0.1 0.91 Error 35.47 38 0.933 - -SA 7.25E-02 1 7.25E-02 21.10 0.00 SA*Gender 2.12E-03 1 2.12E-03 0.62 0.44 Error 0.13 38 3.44E-03 - — Table A2.4—Summary of ANOVA for Caucasian static admittance at 315 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Gender 1.09 1 1.09 3.11 0.09 Error 13.36 38 0.35 - -SA 7.28E-02 1 7.28E-02 14.86 0.00 SA*Gender 4.95E-03 ' 1 4.95E-03 1.01 0.32 Error 0.19 38 4.90E-03 - -Table A2.5—Summary of ANOVA for Chinese static admittance at 315 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Race 3.75 1 3.75 5.85 0.02 Error 49.94 78 0.64 - -SA 0.15 1 0.15 35.00 0.00 SA*Race 9.21E-08 1 9.21E-08 0.00 1.00 Error 0.32 78 4.15E-03 - ~ Table A2.6—Summary of ANOVA for group differences between Caucasian and Chinese static admittance at 315 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Yr). 103 SA at 400 Hz Source SS df MS F P Gender 2.95E-03 1 2.95E-03 0.00 0.97 Error 56.32 38 1.48 - -SA 9.83E-02 1 9.83E-02 37.18 0.00 SA*Gender 5.92E-03 1 5.92E-03 2.24 1.43 Error 0.10 38 2.64E-02 -- — Table A2.7—Summary of ANOVA for Caucasian static admittance at 400 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Gender 2.60 1 2.60 5.03 0.03 Error 19.67 38 0.52 - ~ SA 0.11 1 0.11 42.26 0.00 SA*Gender 2.06E-03 1 2.06E-03 0.78 0.38 Error 0.10 38 2.64E-03 — — Table A2.8—Summary of ANOVA for Chinese static admittance at 400 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P P Race 8.30 1 8.30 6.57 0.01 Error 48.01 38 1.26 SA 9.49E-02 1 9.49E-02 46.26 0.00 SA*Race 5.10E-03 1 5.10E-03 ' 2.49 0.12 1 Error 7.79E-02 38 2.05E-03 Table A2.9—Summary of ANOVA for group differences between Caucasian and Chinese FEMALES static admittance at 400 Hz with one between-subject factor (race: Caucasian females versus Chinese females) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Race 1.75 1 1.75 2.38 0.13 Error 27.98 38 0.74 SA 0.12 1 0.12 35.66 0.00 SA*Race 2.59E-03 1 2.59E-03 0.80 0.38 Error 0.12 38 3.23E-03 Table A2.10—Summary of ANOVA for group differences between Caucasian and Chinese MALES static admittance at 400 Hz with one between-subject factor (race: Caucasian males versus Chinese males) and one within-subject factor (SA estimate: Y+, Y-). 104 SA at 500 Hz Source SS df MS F P Gender 0.18 1 0.18 0.9 0.77 Error 78.84 38 2.08 -- ~ SA 0.22 1 0.22 25.78 0.00 SA*Gender . 2.62E-02 1 2.62E-02 3.08 0.09 Error 0.32 38 8.52E-03 ~ --Table A2.11—Summary of ANOVA for Caucasian static admittance at 500 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Gender 5.48 1 5.48 5.18 0.03 Error 40.23 38 1.06 - -SA 0.25 1 0.25 41.25 0.00 SA*Gender 9.53E-04 1 9.53E-04 0.16 0.69 Error 0.23 38 5.94E-03 ~ — Table A2.12—Summary of ANOVA for Chinese static admittance at 500 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Race 10.84 1 10.84 6.46 0.02 Error 63.79 38 1.68 SA 0.17 1 0.17 35.68 0.00 SA*Race 1.20E-02 1 1.20E-02 2.47 0.13 Error 0.19 38 4.86E-03 Table A2.13—Summary of ANOVA for group differences between Caucasian and Chinese FEMALE static admittance at 500 Hz with one between-subject factor (race: Caucasian female versus Chinese female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Race 1.89 1 1.89 1.30 0.26 Error 55.28 38 1.46 SA .30 1 0.30 31.20 0.00 SA*Race 6.95E-03 1 6.95E-03 0.72 0.40 Error 0.37 38 9.60E-03 Table A2.14—Summary of ANOVA for group differences between Caucasian and Chinese M A L E static admittance at 500 Hz with one between-subject factor (race: Caucasian male versus Chinese male) and one within-subject factor (SA estimate: Y+, Y-). 105 SA at 630 Hz Source SS df MS F P Gender 1.76 .1 1.76 0.70 0.41 Error 95.07 , 38 2.50 - --SA 8.92E-02 1 8.92E-02 6.60 0.01 SA*Gender 5.77E-02 1 5.68E-02 4.26 0.05 Error 0.51 38 1.35E-02 -- ~ Table A2.15—Sumrnary of ANOVA for Caucasian static admittance at 630 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Gender 3.60 1 3.60 1.59 0.22 Error 86.25 38 2.27 - — SA 0.27 1 0.27 24.45 0.00 SA*Gender 1.05E-02 1 1.05E-02 0,96 0.33 Error 0.42 38 1.09E-02 - — Table A2.16—Summary of ANOVA for Chinese static admittance at 630 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Race 14.29 1 14.29 5.97 0.02 Error 186.69 78 2.39 ~ — SA 0.33 1 0.33 26.01 0.00 SA*Race 2.38E-02 1 2.38E-02 , 1.86 0.18 Error 1.00 78 1.28E-02 ~ --Table A2.17—Summary of ANOVA for group differences between Caucasian and Chinese static admittance at 630 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-). 106 SA at 710 Hz Source SS df MS F P Gender 4.21 1 4.21 1.48 0.23 Error 107.85 38 2.84 -- — SA . 6.23E-02 1 6.23E-02 4.34 0.04 SA*Gender 6.22E-02 1 6.22E-02 4.33 0.04 Error 0.55 38 1.44E-02 ~ . — Table A2.18—Summary of ANOVA for Caucasian static admittance at 710 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Gender 3.87 1 3.87 1.20 0.28 Error 122.41 38 3.22 - -SA 0.22 1 0.22 24.96 0.00 SA*Gender 1.24E-02 1 1.24E-02 1.44 0.24 Error 0.33 38 8.66E-03 ~ ~ Table A2.19—Summary of ANOVA for Chinese static admittance at 710 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Race 14.17 1 14.17 4.64 . 0.03 Error 238.34 78 3.06 - ~ SA 0.26 1 0.26 20.97 0.00 SA*Race 2.32E-02 1 2.32E-02 1.91 0.17 Error 0.95 78 1.22E-02 — ~ Table A2.20—Summary of ANOVA for group differences between Caucasian and Chinese static admittance at 710 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-). 107 SA at 800 Hz Source SS df MS F P Gender 1.32 1 1.32 0.51 0.48 Error 99.43 38 2.62 -- ~ SA 9.67E-03 1 9.67E-03 0.58 0.45 SA*Gender 0.12 1 0.12 7.28 0.01 Error 0.63 38 1.66E-02 -- -Table A2.21—Summary of ANOVA for Caucasian static admittance at 800 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Gender 5.51 1 5.51 1.59 0.22 Error 131.67 38 3.47 - — SA 0.21 1 0.21 18.87 0.00 SA*Gender 4.04E-02 1 4.04E-02 3.71 0.06 Error 0.41 38 1.09E-02 - — Table A2.22—Summary of ANOVA for Chinese static admittance at 800 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Race 12.65 1 12.66 4.14 0.045 Error 237.93 78 3.05 - -SA 0.15 1 0.15 9.83 0.00 SA*Race 6.30E-02 1 6.30E-02 4.07 0.048 Error 1.21 78 1.55E-02 ~ — Table A2.23—Summary of ANOVA for group differences between Caucasian and Chinese static admittance at 800 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-). 108 SA at 900 Hz Source SS df MS F P Gender 5.66E-03 1 5.66E-03 0.00 0.96 Error 74.39 38 1.96 - -SA 7.80E-02 1 7.80E-02 4.90 0.03 SA*Gender 1.89E-02 1 1.89E-02 1.19 0.28 Error 0.61 38 1.59E-02 - — Table A2.24—Summary of ANOVA for Caucasian static admittance at 900 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Gender 6.21 1 6.21 2.61 0.12 Error 90.44 38 2.38 - -SA 0.14 1 0.14 0.34 0.57 SA*Gender 0.85 1 0.85 2.09 0.16 Error 15.46 . 38 0.41 ~ — Table A2.25—Summary of ANOVA for Chinese static admittance at 900 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Race 5.97 1 5.97 2.72 0.10 Error 171.05 78 2.19 ~ -SA 0.21 1 0.21 0.97 0.33 SA*Race 4.05E-03 1 4.05E-03 0.02 0.89 Error 16.94 78 0.22 - — Table A2.26—Summary of ANOVA for group differences between Caucasian and Chinese static admittance at 900 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-). 109 SA at 1 0 0 0 Hz Source SS df MS F P Gender 3.12E-02 1 3.12E-02 0.02 0.89 Error 62.39 38 1.64 - --SA 0.19 1 0.19 9.83 0.00 SA*Gender 2.33E-02 1 2.33E-02 1.18 0.28 Error 0.75 38 1.97E-02 ~ — Table A2.27—Summary of ANOVA for Caucasian static admittance at 1000 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Gender 2.50 1 2.50 1.17 0.29 Error 80.84 38 2.13 - ~ SA 4.04E-02 1 4.04E-02 3.44 0.07 SA*Gender 7.26E-02 1 7.26E-02 6.19 0.02 Error 0.45 38 1.17E-02 ~ • — Table A2.28—Summary of ANOVA for Chinese static admittance at 1000 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Race 6.51 1 6.51 3.49 0.07 Error 145.77 78 1.87 - -SA . 2.87E-02 1 2.87E-02 1.73 0.19 SA*Race 0.21 1 .21 12.42 0.00 Error 1.29 78 1.66E-02 - — Table A2.29—Summary of ANOVA for group differences between Caucasian and Chinese static admittance at 1000 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-). 110 SA at 1120 Hz Source SS df M S F P Gender 0.43 1 0.43 0.27 0.60 E r r o r 59.60 38 1.57 ~ S A 0.39 1 .39 12.52 0.00 S A * G e n d e r 5.35E-02 1 5.35E-02 1.73 0.20 E r r o r 1.18 38 3.09E-02 -- — Table A2.30—Summary of ANOVA for Caucasian static admittance at 1120 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df M S F P Gender 1.75 1 1.75 1.02 0.32 E r r o r 65.27 38 1.72 ~ ~ . S A 9.41E-04 1 9.41E-04 0.07 0.79 S A * G e n d e r 2.18E-02 1 . 2.18E-02 1.70 0.20 E r r o r 0.49' 38 1.28E-02 - — Table A2.31—Summary of ANOVA for Chinese static admittance at 1120 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df M S F P Race 5.20 1 5.20 3.19 0.08 E r r o r 127.04 78 1.63 - — S A 0.18 1 0.18 7.86 0.01 S A * R a c e 0.21 1 0.21 9.578 0.00 E r r o r .1.74 78 2.23E-02 - ~ Table A2.32—Summary of ANOVA for group differences between Caucasian and Chinese static admittance at 1120 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-). I l l SA at 1250 Hz Source SS df MS F P Gender 1.09 1 1.09 0.76 0.39 Error 54.97 38 1.45 ~ --SA 0.61 1 0.61 10.25 0.00 SA*Gender 0.13 1 0.13 2.20 0.15 Error 2.267 38 5.96E-02 — — Table A2.33—Summary of ANOVA for Caucasian static admittance at 1250 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Gender 1.39 1 1.39 0.88 0.36 Error 60.29 38 1.59 - ~ SA 3.31E-02 1 3.31E-02 1.94 0.17 SA*Gender 3.95E-02 1 3.95E-02 2.32 0.14 Error 0.65 38 1.70E-02 ~ — Table A2.34—Summary of ANOVA for Chinese static admittance at 1250 Hz with one between-subject factor (gender: male versus female) and one within-subject factor (SA estimate: Y+, Y-). Source SS df MS F P Race 2.99 1 2.99 1.98 0.16 Error 117.74 78 1.51 ~ ~ SA .46 1 .46 11.74 0.00 SA*Race .18 1 .18 4.55 0.04 Error 3.08 78 3.95E-02 - — Table A2.35—Summary of ANOVA for group differences between Caucasian and Chinese static admittance at 1250 Hz with one between-subject factor (race: Caucasian versus Chinese) and one within-subject factor (SA estimate: Y+, Y-). 112 Appendix III - Telephone Questionnaire Before you are invited to participate in this research study, I must first ask you some questions to determine if you are eligible for participation. Age/ Gender: Are you between the ages of 18-34? What is your gender? Racial Background: (must answer yes to one question) 1 Are^you a Chinese descendant (Han ethnic) of immigrants from Mainland China, Taiwan, or Hong Kong without traceable foreign descent? Are you a white/Caucasian (non-Hispanic, non-Aboriginal, non-Arab/West Arab, non-Black, and non-East/South/South-East Asian, with white or light skin)? Ears / Hearing: (must answer yes, no, no) Do you have normal hearing (to the best of your knowledge)? Do you have a history of middle ear problems (recurrent ear infections, surgery, or fluid in your ears)? Have you ever had a major head trauma? 113 Appendix IV- Vocabulary Abbreviation Vocabulary Item A G C Automatic gain control B Susceptance (admittance) B m Mass susceptance (admittance) B s Stiffness susceptance (admittance) B t Total susceptance (admittance) F45° Frequency corresponding to an admittance phase angle of 45° G Conductance (admittance) H L Hearing level kHz Kilohertz R Resistance (impedance) RF Resonant frequency TW Tympanometric width TEOAE Transient evoked otoacoustic emission SA Static admittance SF Sweep frequency SP Sweep pressure SPL Sound pressure level X m Mass reactance (impedance) -Xc Compliant reactance (impedance) Y Admittance Ytm Peak compensated acoustic admittance Z Impedance 0y Admittance phase angle 

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