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Clinical application of the Interacoustics REFLWIN system wideband reflectance machine in the assessment… Kenny, Stéfane Pascal Van Neste 2011

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CLINICAL APPLICATION OF THE INTERACOUSTICS REFLWIN SYSTEM WIDEBAND ENERGY REFLECTANCE MACHINE IN THE ASSESSMENT OF THE EUSTACHIAN TUBE  by  STÉFANE PASCAL VAN NESTE KENNY B.Sc., The University of Victoria, 2007  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Audiology and Speech Sciences)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver)  OCTOBER 2011  © Stéfane Pascal Van Neste Kenny, 2011  Abstract Objective: Eustachian tube function remains an area of middle ear analysis in which suitable clinical tests are lacking. Eustachian tube malfunction has been linked to pathology of the middle ear such as otitis media with effusion. Wideband reflectance (WBR) is a new clinical technique which determines the ratio of sound energy that enters the middle ear to that which reflects back into the ear canal. This technique could provide information regarding Eustachian tube function that other tympanometric measures do not. Design: Measures of WBR were taken in 50 Chinese and Caucasian young adult subjects before and after performing Valsalva and Toynbee manoeuvres. Subjects were students or affiliates of the University of British Columbia. Data were analysed based on static and dynamic power absorbance measures, power absorbance tympanograms, 226 Hz tympanograms and 1000 Hz tympanograms provided by the Interacoustics REFLWIN wideband reflectance system. Baseline measurements were compared between gender and ethnicity. Similarities to measurements using other clinical WBR devices were also analysed. Finally, comparisons were made on each variable between baseline and post-manoeuvre state. Results: Baseline results were comparable with previous wideband reflectance research in this subject population. Notable differences were observed between the current study and a previous version of the same device. Differences between the current system and the Mimosa Acoustics system were minimal. For both the Valsalva and Toynbee manoeuvres significant shifts in middle ear pressure were indicated by changes in tympanometric peak pressure and power absorbance tympanogram peak pressure.  ii  However, dynamic power absorbance did not differ between baseline and either manoeuvre state. Conclusion: The current version of the Interacoustics REFLWIN system provides comparable estimates of WBR to the other major clinical system available on the market. The measures of wideband reflectance did not offer information regarding Eustachian tube function in addition to that already provided by measures of tympanometry following physical manoeuvres. However, the equivalent performance of wideband reflectance to tympanometry shows that it can be used to evaluate Eustachian tube function in the same manner as tympanometry. There is still a need to devise a clinical test to accurately distinguish between healthy and pathological Eustachian tubes.  iii  Preface  This study was approved by the University of British Columbia Clinical Research Ethics Board as part of a larger study entitled “The Effects of Race, Caucasian Versus East Asian, on Middle Ear Function and Hearing Sensitivity Norms.”  iv  Table of Contents  Abstract ........................................................................................................................................... ii Preface ............................................................................................................................................ iv Table of Contents ............................................................................................................................ v List of Tables................................................................................................................................. viii List of Figures ................................................................................................................................ xii List of Abbreviations................................................................................................................... xviii Acknowledgments ......................................................................................................................... xix Dedication ...................................................................................................................................... xx Introduction ..................................................................................................................................... 1 Eustachian Tube Tests................................................................................................................. 4 Manometric Tests ........................................................................................................................ 4 Equalization of static pressures. .............................................................................................. 4 Forced opening test. ................................................................................................................ 6 Radiographic and Clearance Tests .............................................................................................. 8 Sonotubometry .......................................................................................................................... 10 Tympanometry .......................................................................................................................... 14 Wideband Reflectance .............................................................................................................. 19 Wideband Reflectance Systems ................................................................................................ 25 Gender and Ethnic Effects in Middle Ear Analysis .................................................................. 28 Goals of the Study ..................................................................................................................... 30 Methods ......................................................................................................................................... 33 Participants ................................................................................................................................ 33 Intrumentation ........................................................................................................................... 34 Procedure................................................................................................................................... 35 Data Analysis. ........................................................................................................................... 36 Results ........................................................................................................................................... 39 Baseline Comparisons of Static and Dynamic Energy Reflectance and Power Absorption in Caucasian and Chinese Subjects ............................................................................................... 39 Baseline static energy reflectance. ........................................................................................ 39 Baseline static power absorbance. ......................................................................................... 40 v  Baseline dynamic power absorbance. ................................................................................... 43 Baseline power absorbance tympanometry. .......................................................................... 47 Baseline 226 Hz tympanometry. ........................................................................................... 50 Baseline 1000 Hz tympanometry. ......................................................................................... 52 Comparison between static and dynamic baseline measurements. ....................................... 54 Comparison of the Current Study’s Baseline Measurements to those of a previous version of REFLWIN and the Mimosa Acoustics RMS-system in Caucasian and Chinese Subjects ....... 57 Static power absorbance. ....................................................................................................... 57 Dynamic power absorbance. ................................................................................................. 63 Comparisons between Baseline and the Valsalva Manouevre in Caucasian and Chinese Subjects ..................................................................................................................................... 66 Valsalva manoeuvre dynamic power absorbance. ................................................................ 66 Valsalva manoeuvre power absorbance tympanometry. ....................................................... 68 Valsalva manoeuvre 226 Hz tympanometry. ........................................................................ 73 Comparisons of Baseline to Toynbee’s Manouevre in Caucasian and Chinese Subjects ......... 76 Toynbee manoeuvre dynamic power absorbance. ................................................................ 76 Toynbee manoeuvre power absorbance tympanometry. ....................................................... 78 Toynbee manoeuvre 226 Hz tympanometry. ........................................................................ 82 Toynbee manoeuvre 1000 Hz tympanometry. ...................................................................... 83 Discussion ..................................................................................................................................... 85 Baseline Measures ..................................................................................................................... 86 Static power absorbance. ....................................................................................................... 86 Dynamic power absorbance. ................................................................................................. 93 Comparison between Static and Dynamic measurement modes. .......................................... 98 System Comparisons ............................................................................................................... 100 Valsalva’s Manoeuvre ............................................................................................................. 103 Dynamic power absorbance. ............................................................................................... 103 Power absorbance tympanometry. ...................................................................................... 105 226 Hz tympanometry. ........................................................................................................ 106 1000 Hz tympanometry. ...................................................................................................... 107 Toynbee’s Manoeuvre ............................................................................................................. 107 Dynamic power absorbance. ............................................................................................... 107 Power absorbance tympanometry. ...................................................................................... 109 vi  226 Hz tympanometry. ........................................................................................................ 112 1000 Hz tympanometry. ...................................................................................................... 113 Comparison between Toynbee Manoeuvre and Valsalva Manoeuvre .................................... 113 Clinical Application of Wideband Energy Reflectance in the Evaluation of Eustachian Tube Function .................................................................................................................................. 115 Limitations of the Current Study and Directions for Future Research.................................... 116 Conclusion .................................................................................................................................. 118 Bibliography................................................................................................................................ 122 Appendix I - Descriptive Statistics Tables .................................................................................. 129 Appendix II - Consent From for Normal Hearing Subjects ........................................................ 148  vii  List of Tables  Table A1. Static energy reflectance descriptive statistics for the baseline condition. Statistics include mean energy reflectance, maximum energy reflectance, minimum energy reflectance and standard deviation taken at ambient pressure for four gender/ethnicity combinations. ....................................................................................... 129 Table A2. Static power absorbance descriptive statistics from the baseline condition for the four gender/ethnicity combinations. Measures include mean power absorbance, minimum power absorbance, maximum power absorbance and standard deviation. ... 130 Table A3. Dynamic power absorbance descriptive statistics for four gender/ethnicity combinations. Measures include mean power absorbance, maximum power absorbance, minimum power absorbance and standard deviation..................................................... 131 Table A4. Descriptive statistics for the baseline power absorbance tympanograms. Statistics are displayed for both peak pressure and peak power absorbance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak power absorbance include mean power absorbance, minimum power absorbance, maximum power absorbance and the standard deviation. ........................................................................................................................ 132 Table A5. Descriptive statistics for the 226 Hz tympanograms in the baseline condition. Statistics are displayed for both tympanometric peak pressure and peak compensated static admittance. Measures for tympanometric peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak compensated static admittance include mean admittance, minimum admittance, maximum admittance and the standard deviation. ......................................................... 133  viii  Table A6. Descriptive statistics for the 1000 Hz tympanograms in the baseline condition. Statistics are displayed for both tympanometric peak pressure and peak compensated static admittance. Measures for tympanometric peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak compensated static admittance include mean admittance, minimum admittance, maximum admittance and the standard deviation. ..................................... 134 Table A7. Static energy reflectance descriptive statistics from Shaw (2009) taken using the Interacoustics device. Statistics include mean energy reflectance, maximum energy reflectance, minimum energy reflectance and standard deviation taken at ambient pressure for four gender/ethnicity combinations............................................................ 135 Table A8. Static energy reflectance descriptive statistics from Shaw (2009) taken using the Mimosa Inc. device. Statistics include mean energy reflectance, maximum energy reflectance, minimum energy reflectance and standard deviation taken at ambient pressure for four gender/ethnicity combinations............................................................ 136 Table A9. Static power absorbance descriptive statistics from Shaw (2009) taken using the Interacoustics device. Statistics include mean power absorbance, maximum power absorbance, minimum power absorbance and standard deviation taken at ambient pressure for four gender/ethnicity combinations............................................................ 137 Table A10. Static power absorbance descriptive statistics from Shaw (2009) taken using the Mimosa Inc. device. Statistics include mean power absorbance, maximum power absorbance, minimum power absorbance and standard deviation taken at ambient pressure for four gender/ethnicity combinations............................................................ 138 Table A11. Dynamic power absorbance descriptive statistics from Shaw (2009) taken using the Interacoustics device. Statistics include mean power absorbance, maximum  ix  power absorbance, minimum power absorbance and standard deviation taken at ambient pressure for four gender/ethnicity combinations............................................................ 139 Table A12. Dynamic power absorbance descriptive statistics for four gender/ethnicity combinations taken following the Valsalva manoeuvre. Measures include mean power absorbance, maximum power absorbance, minimum power absorbance and standard deviation. ........................................................................................................................ 140 Table A13. Descriptive statistics for the Valsalva manoeuvre power absorbance tympanograms. Statistics are displayed for both peak pressure and peak power absorbance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak power absorbance include mean power absorbance, minimum power absorbance, maximum power absorbance and the standard deviation.......................................................................... 141 Table A14. Descriptive statistics for the Valsalva manouevre 226 Hz tympanograms. Statistics are displayed for both tympanometric peak pressure and peak compensated static admittance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak compensated static admittance include mean admittance, minimum admittance, maximum admittance and the standard deviation. ......................................................... 142 Table A15. Descriptive statistics for the Valsalva manouevre 1000 Hz tympanograms. Statistics are displayed for both tympanometric peak pressure and peak compensated static admittance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and t the standard deviation. Measures for peak compensated static admittance include mean admittance, minimum admittance, maximum admittance and the standard deviation. ......................................................... 143  x  Table A16. Dynamic power absorbance descriptive statistics for four gender/ethnicity combinations taken following the Toynbee manoeuvre. Measures include mean power absorbance, maximum power absorbance, minimum power absorbance and standard deviation. ........................................................................................................................ 144 Table A17. Descriptive statistics for the Toynbee manouevre power absorbance tympanograms. Statistics are displayed for both peak pressure and peak power absorbance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak power absorbance include mean power absorbance, minimum power absorbance, maximum power absorbance and the standard deviation.......................................................................... 145 Table A18. Descriptive statistics for the Toynbee manouevre 226 Hz tympanograms. Statistics are displayed for both tympanometric peak pressure and peak compensated static admittance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak compensated static admittance include mean admittance, minimum admittance, maximum admittance and the standard deviation. ......................................................... 146 Table A19. Descriptive statistics for the Toynbee manouevre 1000 Hz tympanograms. Statistics are displayed for both tympanometric peak pressure and peak compensated static admittance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak compensated static admittance include mean admittance, minimum admittance, maximum admittance and the standard deviation. ......................................................... 147  xi  List of Figures  Figure 1.1. Wideband energy reflectance across frequency in normal Caucasian and Chinese subjects. Error bars denote the 95th percent confidence interval. Reproduced with permission from Shahnaz and Bork (2006). ............................................................. 22 Figure 3.1. Baseline energy reflectance across frequency averaged across all subjects. The shaded area indicates the 90% range of data at each frequency. ............................... 40 Figure 3.2. Baseline static power absorbance averaged across all subjects. The shaded area denotes the 90% range of data at each frequency. .................................................... 41 Figure 3.3. Frequency, gender, ethnicity interaction: static power absorbance displayed across frequency. Genders are displayed in separate panes. Error bars denote the 95th percent confidence interval. .............................................................................................. 42 Figure 3.4. Frequency, gender, ethnicity interaction: static power absorbance displayed across frequency. Ethnic groups are displayed in separate panes. Error bars denote the 95th percent confidence interval. ....................................................................................... 43 Figure 3.5. Baseline dynamic power absorbance measured at tympanometric peak pressure averaged across all subjects. The shaded area denotes the 90% range of the data at each frequency. ............................................................................................................. 44 Figure 3.6. Frequency/gender interaction. Dynamic power absorbance measured at tympanometric peak pressure is displayed across frequency. Error bars denote the 95th percent confidence interval at each frequency.................................................................. 46 Figure 3.7. Frequency/ethnicity interaction. Dynamic power absorbance measured at tympanometric peak pressure across frequency. The error bars denote the 95th percent confidence interval at each frequency. ............................................................................. 47  xii  Figure 3 8. Average baseline peak pressure of the power absorbance tympanogram in Caucasian females, Caucasian males, Chinese females and Chinese males. Error bars denote the 95th percent confident interval of each mean. ................................................. 48 Figure 3.9. Average baseline peak power absorbance from the power absorbance tympanogram from each of the four subject groups. The error bars denote the 95th percent confidence interval. .............................................................................................. 49 Figure 3.10. Average baseline peak compensated static admittance (Ytm) of the 226 Hz tympanogram for each of the four subject groups. Error bars denote the 95th percent confidence interval............................................................................................................ 51 Figure 3.11. Baseline 226 Hz tympanogram peak compensated static admittance in Chinese and Caucasian subjects. The boxed area represents the 25-75% range while the bars denote the entire range of measurement. .................................................................. 52 Figure 3 12. Average baseline peak compensated static admittance (Ytm) for the four subject groups. Error bars denote the 95th percent confidence interval. .......................... 53 Figure 3.13. Peak static admittance on the 1000 Hz tympanogram in male and female subjects. The boxed area represents the 25-75% range while the bars denote the entire range of measurement. ...................................................................................................... 54 Figure 3.14. Estimates of baseline power absorbance taken using the static and dynamic modes of measurement in Chinese and Caucasian subjects. Error bars denote the 95% confidence intervals. ......................................................................................................... 56 Figure 3.15. Mean static power absorbance measurements in young adult Caucasian and Chinese subjects taking using an older version of the Interacoustics REFLWIN device (Shaw, 2009). The grey shaded area represents the 90% range of the data. ................... 58  xiii  Figure 3.16. Comparison of static power absorbance measurements across frequency from the current study to those taken in a previous study using an older version of the Interacoustics REFLWIN device. Error bars denote the 95th percent confidence interval. Ethnic groups are displayed in separate panels. ............................................................... 60 Figure 3.17. Mean static power absorbance measurements in young adult Caucasian and Chinese subjects taking using the Mimosa Acoustics RMS System (Shaw, 2009). The grey shaded area represents the 90% range of the data. ............................................ 61 Figure 3.18. Comparison of static power absorbance measurements across frequency from the current study to those taken in a previous study using the Mimosa Inc device. Error bars denote the 95th percent confidence interval. Ethnic groups are displayed in separate panels. ................................................................................................................. 63 Figure 3.19. Average dynamic power absorbance measurements in Caucasian and Chinese young adult subjects taken using the older version of the Interacoustics REFLWIN system (Shaw, 2009). The grey shaded area represents the 90% range of the data.................................................................................................................................... 64 Figure 3.20. Comparison of dynamic power absorbance measurements across frequency from the current study to those taken in a previous study using an older version of the Interacoustics REFLWIN device. Error bars denote the 95th percent confidence interval. .......................................................................................................................................... 65 Figure 3.21. Dynamic power absorbance measured at tympanometric peak pressure following the Valsalva manoeuvre. The shaded area denotes the 90% range for each frequency. ......................................................................................................................... 66 Figure 3.22. Dynamic power absorbance before and after performing a Valsalva’s manoeuvre. Error bars denote the 95th percent confidence interval. ............................... 68  xiv  Figure 3.23. Average peak pressure of the power absorbance tympanogram in four subject groups following performance of the Valsalva manoeuvre. Error bars denote the 95th percent confidence interval of the mean. ................................................................... 69 Figure 3.24. Peak pressure of the power absorbance tympanogram before and after performing the Valsalva’s manoeuvre. The boxed area represents the 25-75% range while the error bars denote the entire range of measurement. .......................................... 70 Figure 3.25. Average peak power absorbance of the power absorbance tympanogram measured following performance of the Valsalva manoeuvre. Error bars denote the 95th percent confidence interval. .............................................................................................. 71 Figure 3.26. Peak power absorbance of the power absorbance tympanogram before and after performing the Valsalva’s manoeuvre. The boxed areas represent the 25-75% range while the bars denote the entire range of measurement. ................................................... 72 Figure 3.27. Average peak compensated static admittance (Ytm) following performance of the Valsalva manoeuvre by four subject groups. Error bars denote the 95th percent confidence interval............................................................................................................ 73 Figure 3.28. Average peak compensated static admittance (Ytm) of the 1000 Hz tympanogram following performance of the Valsalva manoeuvre in four subject groups. Error bars denote the 95 percent confidence interval. ...................................................... 75 Figure 3.29. Dynamic power absorbance measured at tympanometric peak pressure averaged across all subjects following the performance of the Toynbee manoeuvre. The shaded area denotes the 90% range at each frequency. .................................................... 76 Figure 3.30. Dynamic power absorbance before and after performing the Toynbee manoeuvre. Error bars denote the 95th percent confidence interval. Genders are displayed in separate panels.............................................................................................. 77  xv  Figure 3.31. Mean peak pressure of the power absorbance tympanogram following performance of the Toynbee manoeuvre by four subject groups. Error bars denote the 95 percent confidence interval. .............................................................................................. 78 Figure 3.32. Peak pressure of the power absorbance tympanogram before and after performing the Toynbee manoeuvre in male and female subjects. The boxed areas represent the 25-75% range while the bars denote the entire range of measurement....... 80 Figure 3.33. Peak power absorbance of the power absorbance tympanogram in four subject groups following performance of the Toynbee manoeuvre. Error bars denote the 95 percent confidence interval. ......................................................................................... 81 Figure 3.34. Average peak compensated static admittance (Ytm) of the 226 Hz tympanogram following performance of the Toynbee maneovure in four subject groups. Error bars denote the 95 percent confidence interval. ...................................................... 82 Figure 3.35. Average peak compensated static admittance of the 1000 Hz tympanogram following performance of the Toynbee manoeuvre by four subject groups. Error bars denote the 95 percent confidence interval. ....................................................................... 84 Figure 4.1. Static wideband energy reflectance measures in normal adult subjects. Results from the current study are compared to those reported by Feeney and Sanford (2004) [N=40], Sanford and Feeney (2008) [N=21], Keefe et al. (1993) [N=10], and Voss and Allen (1994) [N=10] in equivalent populations. The grey shaded area represents the 95th percent confidence interval of the data from the current study. ......... 87 Figure 4.2. Static power absorbance measures in healthy subjects. The mean static power absorbance from the current study is compared to the 95% range of the normative data from the Interacoustic REFLWIN system, based on the study by Lui et al. (2008). Error bars denote the 95 percent confidence interval of the mean. .................................. 89  xvi  Figure 4.3. Dynamic power absorbance measures in healthy subjects. The mean dynamic power absorbance from the current study is compared to the 95% range of the normative data from the Interacoustic REFLWIN system, based on the study by Lui et al. (2008). Error bars denote the 95 percent confidence interval of the mean...................... 90 Figure 4.4. Baseline static and dynamic power absorbance across frequency. The lighter shaded region represents the 90% range of the static measurement while the darker shaded area represents the 90% range of the dynamic measurement. .............................. 99 Figure 4.5. Adjusted post-Valsalva manoeuvre dynamic power absorbance compared to baseline static power absorbance. The post-Valsalva manoeuvre data was adjusted by subtracting the difference between baseline static and dynamic power absorbance. ..... 105 Figure 4.6. Adjusted post-Toynbee manoeuvre dynamic power absorbance compared to baseline static power absorbance. The post-Toynbee manoeuvre data was adjusted by subtracting the difference between baseline static and dynamic power absorbance. ..... 109  xvii  List of Abbreviations  OME – Otitis Media with Effusion. SOM – Serous Otitis Media COM – Chronic Otitis Media Ya - Uncompensated Static Admittance Ytm – Peak Compensated Static Admittance TPP – Tympanometric Peak Pressure Vea – Equivalent Ear Canal Volume TW – Tympanometric Width WBR – Wideband Reflectance PA – Power Absorbance ER – Energy Reflectance  xviii  Acknowledgments  I would like to extend my thanks to Dr. Valter Ciocca, Dr. David Stapells and Alison Beers for helpful comments and for donating their time to participate on my committee. I would also like to thank Jacqie Wong for her outstanding assistance in subject recruitment and database work. Furthermore I would like to thank all my friends and family for their constant support and encouragement. Finally, and most importantly, I would like to thank Dr. Navid Shahnaz for agreeing to take me on as a thesis candidate and mentoring and guiding me through the process as my supervisor. I am deeply indebted to his support and patience throughout this process.  xix  Dedication  I dedicate this work to my parents, Richard and Jocelyne, and my sister Erin. Their unwavering support has always been a source of strength and inspiration. I could not have reached where I am today without their wisdom and guidance.  xx  Introduction  Middle ear analysis is a critical component of the audiological test battery. As test stimuli must be transmitted through the middle ear before stimulating the inner ear, audiological results are dependent on middle ear integrity and audiological status will be impacted by middle ear pathology. Otoacoustic emissions are particularly affected since both the stimulus and the elicited auditory response must pass through the middle ear before results can be measured The middle ear is comprised of the tympanic membrane and the tympanic cavity, which contains the three smallest bones in the human body, the malleus, incus and stapes, collectively referred to as the ossicles (Yost, 2007). The ossicles are connected in series within the middle ear cavity. The head of the malleus is attached to the tympanic membrane, the footplate of the stapes is connected to the round window of the cochlea, and the incus joins the two. Vibration of the tympanic membrane causes the bones to move together producing a complex frequency-dependant motion at the round window, which compensates for the loss of energy that would occur if sound were to pass directly from the air filled middle ear to the fluid filled cochlea (Yost, 2007). In the posterior-superior direction, the tympanic cavity narrows into a passage called the aditus ad antrum. The aditus ad antrum is terminated by the antrum of the mastoid bone which connects a series of air filled cavities, called the mastoid air cells to the middle ear (Voss, Horton, Woodbury and Sheffield, 2008). The superior-anterior wall of the middle ear cavity contains an opening to the Eustachian tube which connects the middle ear space with the rhinopharynx (Bluestone and Doyle, 1988; Bluestone, 1983). In adults this tube lies at an angle of 45° to the horizontal and runs for an average 1  length of 31-38 mm. In young infants this tube is significantly less angled, lying only 10° from the horizontal plain (do we know the typical length of a child’s ET?) (Bluestone and Doyle, 1988). The Eustachian tube is comprised of two distinct regions. The osseus or bony region of the Eustachian tube, contained within the temporal bone of the skull is continuous with the anterior-superior wall of the middle ear. The inferior fibrocartilaginous portion of the Eustachian tube is comprised of cartilaginous tissue and connected to the osseus region by fibrous bands(Bluestone and Doyle, 1988). The interior mucosal lining of the tube is continuous with those of the nasopharynx and middle ear (Bluestone and Doyle, 1988). When at rest, the Eustachian tube lies closed. It is actively opened in association with yawning, swallowing, sneezing and, in some individuals, certain movements of the mandible (Bluestone and Doyle, 1988; Marais and Armstrong, 1999; Finkelstein, Talmi, Rubel and Zohar , 1988). This opening is achieved by the action of three muscles attached to the fibrocartilaginous portion of the tube. On the inferior side lie the levator veli palatine and salpingopharyngeus muscles while on the lateral side lies the tensor veli palatine muscle. The relative importance of these muscles is unclear, although it is thought that the levator veli palatine and tensor veli platatine muscles contribute more to the opening of the tube than does the salpingopharyngeus muscle (Marais and Armstrong, 1999). A fourth muscle, the tensor tympani, is also associated with the Eustachian tube, but is not thought to play a role in opening the tube (Bluestone and Doyle, 1988). The Eustachian tube is theorized to play three main roles with respect to the middle ear: ventilation of the middle ear space, protection of the middle ear from nasopharyngeal secretions and pressures, and drainage of secretions produced by the middle ear into the nasopharynx (Bluestone, 1983; Bluestone and Doyle, 1988;  2  Bluestone, Paradise, Beery and Wittel, 1972; Holmquist and Olen, 1980; Straetemans, van Heerbeek, Schilder, Feuth, Rijkers, and Zielhuis, 2005; Van der Avoort, van Heerbeek, Zielhuis and Cremers, 2005). Air and gas absorption also occurs across the lining of the middle ear at a rate of ~1 mL/24 hours (Bluestone, 1983). This has recently been shown to be bidirectional and a major contributor to the regulation of middle ear pressure. It is therefore possible that the Eustachian tube plays a minor role in ventilation of the middle ear unless pathology impairs the gas exchange function of the middle ear lining (Bunne, Magnuson, Falk and Hellstrom, 2000). Pathology that affects any component of the middle ear can impair its overall function of sound transmission to the cochlea. Examples of such pathologies include the presence of fluid in the middle ear cavity, ossification of the bones in the middle ear, perforation of the tympanic membrane and disarticulation of the ossicular joints (Allen, Jeng, and Levitt, 2005). Eustachian tube dysfunction has been linked to the development of middle ear pathology (Harford, 1973; Miller 1965; Perlman, 1939; Williams, 1975), such as negative pressure (Bluestone and Doyle, 1988; Bunne et al., 2000a; Bunne, Falk, Magnuson and Hellstrom, 2000; Grimmer and Poe, 2005; Harford, 1973) and Otitis Media with Effusion (OME) (Bunne et al., 2000a; Bunne et al., 2000b; Grimmer and Poe, 2005; Stenstrom, Bylander-Groth and Ingvarsson, 1991; Straetemans et al., 2005). Poor Eustachian tube function can also impair successful recovery from middle ear surgery (Harford, 1973; Miller, 1965; Uzun, Cayé-Thomasen, Andersen and Tos, 2004; Williams 1975). Unfortunately, few middle ear pathologies show visible signs on the tympanic membrane, and even then they usually only appear at the most severe stages. Early detection of abnormal middle ear status is desirable in order to facilitate pathology management and minimize the effects of decreased hearing.  3  Eustachian Tube Tests  Eustachian tube evaluation is one area of middle ear analysis in need of further development. Four categories of tests have been developed to define Eustachian tube function: Manometric tests, Radiographic and Clearance tests, Sonometric tests, and Impedance tests. Each category will be discussed below. Manometric Tests  Equalization of static pressures.  Manometric tests are some of the earliest developed methods to define Eustachian tube function. Subjects are required to equalize static pressures applied to the middle ear. These techniques were first described by Flisberg, Ingelstedt and Ortegren (1963), where pressure was introduced to the middle ear through a tympanic membrane defect such as a perforation or a surgical incision. A manometer was connected through a nylon tube to a cuff sealed in the external ear canal creating a closed system comprised of both the external and middle ear. Pressure of the middle ear could be directly altered by applying air to or removing air from the system. Once a negative middle ear pressure had been established, subjects were instructed to swallow repeatedly. Flisberg and colleagues (1963) were able to chart a stepwise reduction in negative middle ear pressure with each swallow, as air passed through the Eustachian tube to equalize pressure on either side. Miller (1965) further developed this technique. In addition to negative pressure, Miller also introduced positive pressure to the middle ear and monitored its reduction as subjects swallowed repeatedly. Healthy control subjects were compared to those 4  suffering from chronic otitis media, and Miller (1965) categorized his subjects into three groups according to tubal function: those whose Eustachian tubes opened to both positive and negative middle ear pressure, those whose Eustachian tubes opened to positive middle ear pressure but not negative middle ear pressure, and those whose Eustachian tubes opened to neither positive nor negative pressure. Elner, Ingelstedt and Ivarsson (1971) categorized Eustachian tube function of normal hearing, healthy subjects into four groups. The majority of their 102 subjects (71%) were classified into group I, able to fully equalize both positive and negative middle ear pressures with ambient pressure. Group II subjects (21%) were only partially able to equalize positive and negative middle ear pressures. Group III subjects (2%) were only able to equalize positive pressures, not negative pressures, while group IV subjects (5%) could equalize neither positive nor negative pressures. The authors concluded that there exists variability in Eustachian tube function among otologically healthy subjects. The equalization method has been consistent across test sessions and is therefore considered a sufficiently reliable method of assessing Eustachian tube function (Van Heerbeek, Ingels, Snik and Zielhuis, 2001). The majority of healthy subjects tested using the equalization technique fall into the highest category of Eustachian tube function (Elner et al., 1971). Additionally, an age-linked improvement in tubal function has been demonstrated (Bylander, Tjernstrom and Ivarsson, 1983; Bylander and Tjernstrom, 1983). Adult tubal function is significantly better than children’s tubal function (Bylander et al., 1983). Furthermore, older children show improved Eustachian tube function compared to younger children (Bylander et al., 1983). A longitudinal study by  5  Bylander and Tjernstrom (1983) revealed improvement in individual children over the span of three years. Poor equalization ability exists in subjects with middle ear pathology such as otitis media with effusion (Bunne et al., 2000b; Stenstrom et al., 1991; Van Heerbeek et al., 2001) and retraction-type middle ear disease (Bunne et al., 2000b). Considerable variability also exists among subjects with middle ear pathology (Bunne et al., 2000a; Bunne et al., 2000b; Falk and Magnuson, 1984; Stenstrom et al., 1991). Some authors have attributed the observed differences in equalization ability to fluctuations in middle ear status over the course of the pathology (Bunne et al., 2000b); however considerable variability is also observed in normal subjects (Stenstrom et al., 1991). The intrinsic variability limits the prognostic value of the equalization technique and renders it incapable of predicting the presence or course of disease within individual subjects. In addition, the technique is of limited clinical use because in order to directly manipulate middle ear pressure, subjects must have a tympanic membrane defect such as a perforation or ventilation tubes, or the subject must be placed within a pressurized chamber. Forced opening test.  The forced opening test is another type of manometric test that provides a continuous recording of middle ear pressure. Middle ear pressure is steadily increased by an external source and the test determines the pressure at which the Eustachian tube is forced open. This is referred to as the opening pressure (Pol). Eustachian tube opening is indicated by a sudden drop in middle ear pressure, associated with air escaping from the middle ear through the suddenly opened Eustachian tube. Once the Eustachian tube 6  opens, the external pressure device is removed which allows middle ear pressure to decrease. The pressure will continue to decrease until the Eustachian tube closes and a plateau is reached. The pressure value of this plateau is referred to as the closing pressure (Pcl) (Bunne et al., 2000a; Bunne et al., 2000b; Bylander et al., 1983; Bylander and Tjernstrom, 1983; Falk and Magnuson, 1984; Stenstrom et al., 1991). Pol is thought to represent the total closing forces of the Eustachian tube including luminal forces (attributes of the wall of the Eustachian tube) and extra-luminal forces (attributes of the tissue surrounding the Eustachian tube) while Pcl is thought to represent only the extraluminal forces. The pressure difference between the two values is thought to reflect the contributions of luminal forces (Bylander et al., 1983). The reliability of the forced opening test is questionable. A significant drop in Pol (Van Heerbeek et al., 2001) and Pcl (Groth, Ivarsson and Tjernstrom 1982) has been observed between two consecutive measurements in healthy adult subjects. Groth et al. (1982) noted that measurements stabilized after three to four measurements, and the values of Pol and Pcl did not drop further with subsequent measurements. They concluded that initial pressure changes occurred due to altered surface tension of the mucosal lining after Eustachian tube opening. Initial measures of Eustachian tube opening are more representative of tubal function in its natural state compared to repeated forced opening pressure measures. A study by Bylander et al. (1983) demonstrated higher Pcl in children classified as having poor Eustachian tube function by the equalization method compared to healthy controls.. However, no such finding was apparent in their adult subjects. Additionally, no change in Eustachian tube function was seen over time in children, contrary to the results seen in the equalization method (Bylander and Tjernstrom, 1983). 7  Similar to the equalization method, the forced opening test has been associated with significant variability between measurements within the same subject (Bunne et al., 2000a; Bunne et al., 2000b; Falk and Magnuson, 1984; Stenstrom et al., 1991; Van Heerbeek et al., 2001), which has led to accusations of questionable test reliability (Bunne et al., 2000b; Stenstrom et al., 1991; Van Heerbeek et al., 2001). Additionally and similar to the equalization method, the forced opening test requires that the subject either have a tympanic membrane perforation through which pressure can be introduced or be placed in a pressurized chamber. The former limits the test population while the latter is expensive, unpleasant and is not practical for use in a clinical setting. Radiographic and Clearance Tests  Eustachian tube drainage and protective functions have been evaluated using radiographic techniques (Bluestone et al., 1972) and clearance tests (Prasad, Hegde, Prasad and Meyappan, 2009). These techniques make use of radiopaque media and imaging technology as well as other visualization techniques to demonstrate the transition of (or lack thereof) fluids through the Eustachian tube. Bluestone et al. (1972) used this technique to evaluate both the drainage and protective functions of the Eustachian tube in young children with cleft palate before and after surgical palate repair. To evaluate the drainage function, radiopaque media was introduced into the middle ear and its progress through the Eustachian tube was monitored. The protective function of the Eustachian tube was evaluated by introducing the radiopaque media to the nasopharynx and monitoring whether it was able to progress through the Eustachian tube and into the middle ear. Pre-palate repair, the protective function of the Eustachian tube was poor. Following palate repair, slightly over half 8  (55%) of the subjects demonstrated normal protective Eustachian tube function. Eustachian tube clearance was observed in subjects both pre- and post-palate repair. Prior to palate repair, however, the clearance function depended on the subject’s physical position and the viscosity of the fluid; following palate repair, subjects were able to clear the fluid from the middle ear regardless of their position and fluid viscosity. The authors concluded that a functional Eustachian tube obstruction can exist in children who have the ability to clear fluid from the middle ear but demonstrate a blockage to retrograde flow; they concluded that in these cases the Eustachian tube lacks sufficient stiffness. Prasad et al. (2009) used a similar technique to evaluate Eustachian tube function in 86 patients with Chronic Otitis Media by applying a methylene blue dye to the middle ear through a tympanic membrane perforation. The blue liquid was easily viewed using a sinoscope and subjects were not exposed to the radiation used in imaging techniques. Eustachian tube function was classified based on the time interval between the application of the dye the middle ear and the time at which is first appeared in the nasopharyngeal opening of the Eustachian tube. Normal function was defined as an interval of less than ten minutes, while intervals between ten and twenty minutes signified partial Eustachian tube dysfunction. Intervals greater than twenty minutes were considered to represent gross Eustachian tube dysfunction. Prasad et al. concluded that of their 86 subjects with Chronic Otitis Media, 67 were classified as having normal Eustachian tube function, 16 with partial dysfunction, and only 3 with gross dysfunction. Prasad et al. (2009) also employed a less invasive technique to evaluate Eustachian tube clearance function. This Saccharin Test involved placing a small saccharin tablet in the middle ear near the opening to the Eustachian tube. This tablet  9  dissolved in mucosal layer of the middle ear and was transmitted in solution through the Eustachian tube. Since saccharin is an artificial sweetener, subjects were able to taste the substance when it reached the back of the throat. The authors measured the time interval from tablet insertion to subjects first reporting tasting the saccharin; this was termed the saccharin perception time. Time interval classifications of normal function as well as partial and gross dysfunction were identical to those used in the methylene blue dye test. Of their 86 subjects, 64 patients were classified as having normal Eustachian tube function, while 19 and 3 patients demonstrated partial and gross dysfunction, respectively. Results of the two methods correlated well to each other; Prasad et al. concluded that the less invasive Saccharin Test was sufficient to determine Eustachian tube function. The abovementioned radiographic and clearance techniques are of limited utility in a clinical setting. Similar to the manometric tests, these techniques require that a tympanic membrane perforation be present. Furthermore, the older radiographic imaging techniques expose the patient to radiation. Finally, tests like the Methylene Blue Dye test and the Saccharin test require a significant amount of time as the dye or sweetener moves through the Eustachian tube. In pathological cases this can take upwards of 20 minutes, and is not practical for clinical or screening purposes. Sonotubometry  The principle behind sonotubometry dates back to Politzer in the 1800s. He noticed that the perceived loudness of a tuning fork held to the nose increased during the act of swallowing (Perlman, 1939). Modern day techniques have taken this principle and used advanced microphone technology to directly measure increases in sound pressure 10  level during the act of swallowing in order to detect Eustachian tube openings. The experimental set up consists of two components: a sound source inserted into one nostril and a sensitive microphone placed in the external ear canal. A constant sound pressure level is introduced into the nasopharynx via the sound source and a baseline recording determined in the external canal. Upon swallowing, a sharp spike in the recorded sound level is measured when the Eustachian tube opens (Perlman, 1939; Virtanen, 1978). Typically an increase of at least 5 dB is needed for a positive result to be registered (Virtanen, 1978). A test session will usually consist of multiple openings measured consecutively as the Eustachian tube does not open with every swallow (Van der Avoort et al., 2005). Results are interpreted based on the assumption that when an increase in sound is detected in the external auditory canal, air is simultaneously passing through the Eustachian tube (Holmquist and Olen, 1980). Other methods of opening the Eustachian tube during sonotubometry testing, such as yawning or performing the Valsalva manoeuvre have been considered; however swallowing, either with water or saliva alone, produces the largest number of openings (Di Martino, Thaden, Antweiler, Reineke, Westhofen, Beckschebe, Vorlander and Vary, 2007). Previous methods of Eustachian tube analysis have been criticized for being non-physiological tests of Eustachian tube function. Sonotubometry avoids this critique by using natural methods to induce Eustachian tube openings at ambient pressure (Di Martino et al., 2007; Van der Avoort et al., 2005). The act of swallowing produces a broad spectrum noise with significant variability at and below 2000 Hz. This noise is shaped by the resonance of the nasal and oral cavities. This noise will combine with the noise source placed in the nasal cavity, confounding detection of a signal increase due solely to the opening of the Eustachain 11  tube. Above 7000 Hz, the noise created by the act of swallowing contains minimal energy, typically no more than 30 dB SPL (Virtanen, 1978). Thus most sonotubometry studies have focused on the use of high frequency probe tones. High frequency pure tones, however, can easily produce standing wave patterns in the external ear canal, as the presence of the recording microphone closes off the canal allowing reflected sound to propagate back towards the ear drum. These standing wave patterns can result in measurement error if the recording microphone is located at an antinodein the pattern. As a result it has been suggested that high-frequency narrow-band noise be used as a test signal (Van der Avoort, van Heerbeek, Zielhuis, and Cremers, 2006). By using a band of noise as opposed to a pure-tone signal the researchers ensure that even if the microphone is located in a null for a portion of the signal it will not be in a null for all frequency components of the test tone. Sonotubometry has been able to demonstrate tubal openings in a large proportion of healthy subjects. Van der Avoort et al. (2006) were able to measure tubal openings in 91.6% of adult subjects and in a follow-up study demonstrated tubal openings in 82% of children aged 6 – 8 years (Van der Avoort, van Heerbeek, Snik, Zielhuis and Cremers, 2007). Subjects with middle ear pathology, on the other hand, show a reduced number of tubal openings in comparison to control subjects. Virtanen (1978) reported measurements on 12 subjects with upper respiratory tract infections and 14 subjects with negative middle ear pressure (ranging from 31-140 mm H2O) none of whom displayed positive results on sonotubometry. Van der Avoort, van Heerbeek, Admiraal, Zielhuis and Cremers (2008) showed that only 57% of children with a cleft palate produced positive sonotubometry results compared to 82% of healthy controls. Children with OME perform significantly worse than control subjects but show no difference after 12  treatment of the disease with ventilation tubes (Van der Avoort, van Heerbeek, Zielhuis and Cremers, 2009). Sonotubometry results have shown good test-retest reliability. Between two test sessions, Virtanen (1978) reported changes of only 0-1 dB in the measured sound increase for most subjects. Likewise, 64% of adult subjects in the Van der Avoort et al. (2006) studies showed identical numbers of openings between two test sessions. However, significant test-retest variability has been observed within subjects, even healthy populations. A few of Virtanen’s (1978) subjects showed measured sound increase differences of more than 11 dB between sessions. Likewise some of the Van der Avoort et al. (2006) subjects demonstrated a difference of as many as 5 openings between test sessions. Research comparing sonotubometry to other tests of Eustachian tube function has produced mixed results. Jonathan, Chalmers and Wong (1986) compared sonotubometry to the Toynbee manoeuvre measured using tympanometry. They found no difference between the two techniques in healthy adult subjects. A correlation was seen between results on sonotubometry and high negative middle ear pressure (measured by tympanometry) in subjects with the common cold. However, even subjects with severe negative middle ear pressure showed a number of positive sonotubometry results (Virtanen and Marttila, 1982). Additionally, sonotubometry results do not always agree with the results produced by the equalization test (Iwano, Ushiro, Yukawa, Doi, Kinoshita, Hamada and Kumazawa, 1993). There are limitations that have kept sonotubometry from becoming a well-used clinical test of Eustachian tube function. The above-mentioned problems with variability and reproducibility make it difficult to determine a standard range of performance for control subjects. Additionally, there is significant results distribution overlap between disease group and control subjects, where 13  a considerable number of subjects are classified as having normal tubal function despite the presence of middle ear pathology (Van der Avoort et al., 2008). Based on their comparison of sonotubometry with the equalization test, Iwano et al. (1993) suggested that the discrepancy can be at least partially accounted for by measuring the duration of tubal opening. They noted that the duration of tubal opening in subjects with positive results on both tests was significantly longer than those who showed tubal openings to only sonotubometry. It is possible that the Eustachian tube openings in the latter group are long enough to permit the transmission of the test signal but not long enough to allow proper equalization of middle ear pressure. This could account for the large number of positive results seen in disease group subjects by Van der Avoort et al. (2005) and challenges the utility of sonotubometry as a clinical technique for assessment of Eustachian tube function. Tympanometry  While the historical manometric tests provided considerable insight into Eustachian tube function, they required a tympanic membrane defect to be present and were therefore unsuitable for clinical use. The advent of tympanometry allowed convenient testing of middle ear properties across an intact ear drum (Holmquist, 1969). Conventional tympanometry is based on measurements of the acoustic admittance (the ease with which sound energy flows into a system) of a test signal as pressure is varied in the external ear canal (Fowler and Shanks, 2002). Typically a 226 Hz probe tone is used in the measurement (Harford, 1973). Admittance is graphed as a function of pressure to form the tympanogram. Admittance is complex value comprised of two components: acoustic conductance (the ease of which sound enters a resistive element) and acoustic  14  susceptance (the ease of which sound enters a compliant or mass element) (Fowler and Shanks, 2002). These two components may also be recorded separately on modern tympanometers. For routine use, however, the focus has remained on admittance measurements as opposed to measures of conductance and susceptance. There are four variables considered in the measurement of a tympanogram: peak compensated static acoustic admittance (Ytm), tympanometric peak pressure (TPP), tympanometric width (TW) and equivalent ear canal volume (Vea). Vea is the acoustic estimate of the volume of air medial to the probe tip. In a healthy ear this volume of air is bounded by the tympanic membrane, resulting in an estimate of the volume of the external ear canal. If a perforation is present in the tympanic membrane, the air present in the middle ear cavity is continuous with that of the external ear canal and the estimate combines the volume of the two (Fowler and Shanks, 2002). The measurement of Vea is then used in the calculation of Ytm. The system directly measures the admittance of the probe tone through the entire system medial to the probe. However, we are truly interested in the admittance of the tympanic membrane and middle ear system, not the combination of the admittance of sound through the volume of air present in the external ear canal and the middle ear system. Thus the calculated admittance of the external ear canal is subtracted from the overall estimate of admittance to produce the Ytm, an estimate of only the middle ear system (Fowler and Shanks, 2002). This value can be visualized on the tympanogram as the vertical distance between the peak admittance and the tail of the measurement (Fowler and Shanks, 2002). The TPP is the pressure at which the peak of the recording occurs and represents the point of highest admittance. In healthy ears this typically occurs around ambient pressure (Fowler and Shanks, 2002). This point occurs when the pressures on both sides of the tympanic membrane are equal 15  and thus will shift with the build up of pressure in the middle ear (Harford, 1973).  The  final value of interest, TW describes the width of the tympanogram in the vicinity of the peak. It corresponds to the width in pressure measured at half the distance between the peak and the tail (Fowler and Shanks, 2002). The simplest applications of tympanometry in Eustachian tube evaluation have come from estimates of middle ear pressure derived from the TPP. It was proposed that tympanometry could be used for long-term monitoring of Eustachian tube function (Harford, 1973) and that consistent negative or positive pressure in the middle ear is indicative of Eustachian tube dysfunction (Holmquist and Olen, 1980). Attempts have been made, however to develop more quantitative measurements of Eustachian tube function. These attempts have involved subjects actively exercising the Eustachian tube while tympanometric recordings are made. Typically an initial baseline tympanogram is measured, a manoeuvre performed, and then a follow-up tympanogram measured. Some researchers also measure a third and final tympanogram after subjects clear their ears by swallowing multiple times (Jonathan et al., 1986). One of the manoeuvres typically used is the Valsalva manoeuvre. The subject uses his or her fingers to occlude the nostrils by manually pressing on the outside of the nose. With mouth closed the subject blows air outwards. As both nostrils and the mouth are obstructed, pressure is developed in the rhinopharynx. Once sufficient pressure has built up, the Eustachian tube will be forced open allowing the pressure to be transmitted to the middle ear (Stenstrom et al., 1991). A second manoeuvre, the Toynbee manoeuvre, has also been used in a similar manner. In this manoeuvre the nostrils are again occluded by the subject. The subject is then asked to swallow. The opening of the  16  Eustachian tube typically draws air out of the middle ear due to the development of negative pressure in the rhinopharynx during swallowing. As a result negative pressure is usually developed in the middle ear (Uzun et al., 2004).  However, this is not always  the case. Elner et al. (1971) showed that the pressure developed in the nasopharynx is actually biphasic in nature, with a positive peak followed by a negative deflection. They note that usually the Eustachian tube opens during the negative phase, developing the standard negative pressure expected from a Toynbee manoeuvre. However, in some subjects the Eustachian tube may open during the positive phase. Thus it is possible to see positive pressure developed by the manoeuvre as well (Williams, 1975). The magnitude of pressure developed during the manoeuvres can vary considerably between subjects. As such, typical criteria for positive manoeuvres have been changes in middle ear pressures of at least 10 daPa (Jonathan et al., 1986). The previous manoeuvres are designed to evaluate the patency of the Eustachian tube. Successful transmission of pressure to the middle ear indicates that the tube is open and unobstructed (Inglestedt and Ortegren, 1963). The Eustachian tube also protects the middle ear from nasopharyngeal pressures (Bluestone and Doyle, 1988), and as a result researchers have sought to use tympanometry to evaluate this protective function. This is done using the Sniff test (Bunne et al., 2000a). A baseline tympanogram is measured following which the subject is asked to sniff multiple times. The post-manoeuvre middle ear pressure is recorded by a follow-up tympanogram. If a decrease in middle ear pressure is observed, the protective function of the Eustachian tube is considered deficient (Straetemans et al., 2005). This change in pressure indicates that the Eustachian tube failed to remain closed against the nasopharyngeal pressures (Bunne et al., 2000b). 17  An alternative use of tympanometry in the assessment of Eustachian tube function was developed by Williams (1975). Her swallow test used the tympanometer to change the pressure in the external ear canal to a static positive or negative value after which the subject would be required to swallow. The addition of positive pressure pushes the tympanic membrane inwards which increases the resting pressure in the middle ear and in turn exerts mechanical pressure on the opening of the Eustachian tube. When the subject swallows, air is expected to be forced through the tube resulting in a negative shift in the peak of a subsequent tympanogram. Conversely, negative pressure applied to the external ear canal draws the tympanic membrane outwards, decreasing the resting pressure in the middle ear. Upon swallowing, more air is allowed into the middle ear cavity, resulting in a positive shift in the peak of a subsequent tympanogram. A shift of around 15-20 mm H2O was considered typical of healthy Eustachian tubes while smaller shifts were indicators of Eustachian tube dysfunction. A few subjects demonstrated significantly larger shifts (25-30 mm H2O). These subjects had previously had perforations which had since healed over and thus it was impossible to determine if the greater shift was attributed to either an overly compliant Eustachian tube or to a more compliant tympanic membrane resulting in greater pressure differentials in the middle ear. Williams (1975) also noticed a tendency for the amplitude of the tympanogram to increase after the manoeuvre. Seifert, Seidemann and Givens (1979) followed up on this observation and suggested that the criteria for a positive result should be either a shift in the tympanometric peak of 5 mm H2O or more or an increase in tympanogram amplitude of 5% or more. It was also demonstrated that shifts in the tympanometric peak were more easily produced by using more extreme levels of ear canal pressure around +/- 400 18  mm H2O (Siefert et al., 1979). Unfortunately, even this test was subject to considerable variability. Furthermore, inexplicable shifts opposite to the expected direction were observed in some subjects (Schuchmans and Joachims, 1985). The only way the test was able to pass the majority of healthy subjects was by adopting an extremely lenient set of criteria. As a result, the prognostic value of the test has been questioned and the technique thought to merely represent an interesting group level phenomenon with no bearing at the individual level (Schuchmans and Joachims, 1985).  Wideband Reflectance  Another technique for evaluating the middle ear status is wideband energy reflectance (WBR). Pressure reflectance [R(ω)] is the ratio of a forward moving pressure (Pi) wave to the reflected pressure wave (Pr), related by the following equation (Voss and Allen, 1994): 𝑅(𝜔) =  𝑃𝑟 𝑃𝑖  Equation (1)  The magnitude of this ratio, squared gives energy reflectance (ER). ER is a number that varies from 0, indicating all energy has been absorbed by the middle ear space to 1, indicating all energy has been reflected by the middle ear space (Shahnaz and Bork, 2006). The measurement is actually obtained by measuring the input impedance (Z[k]) of a given frequency (k) at the entrance of the ear canal and calculating ER from this value. Input impedance is related to the pressure reflection coefficient R[k] by the following equation (Keefe, Ling and Bulen, 1992): 𝑍[𝑘] = 𝑍𝑐 [𝑘](1 + 𝑅[𝑘])/(1 − 𝑅[𝑘])  Equation (2) 19  Zc[k] represents the characteristic impedance of the entrance to the tube and is related to the cross-sectional area of the ear canal (A), the density of air (ρ) and the speed of sound through it (c) (Keefe, Ling and Bulen, 1992): 𝑍𝑐 = 𝜌𝑐/𝐴  Equation (3)  The area of the ear canal may be estimated by an average of the ear canal area for the human ear or it may be calculated acoustically. The average human ear canal area has proven to be the most robust estimate of true ear canal area and the small individual differences between the estimate and true area do not grossly affect the measurements (Voss et al., 2008). Small, frequency dependant viscothermal losses through the external canal wall also exist, but do not drastically affect the calculation in adults and older children (Keefe, 1984). It should be noted that this does not hold true for infants and very young children whose ear canals are much more compliant (Keefe et al. 1993). Given the above, pressure reflectance can be calculated through a rearrangement of Equation (2) (Keefe et al., 1992): 𝑅[𝑘] = (𝑍[𝑘] − 𝑧𝑐 [𝑘])/(𝑍[𝑘] + 𝑧𝑐 [𝑘])  Equation (4)  In order to measure the input impedance of an unknown system (in other words the human ear), one must first know the Thevenin parameters (source impedance and pressure) of the probe assembly. Thus the system must first be calibrated using a set of two tubes. These tubes are composed of plastic, closed at one end and are of known length, diameter and thickness. The probe assembly is inserted into the open end of the tube and the test signal delivered. In order to determine two complex quantities (source impedance and pressure) two tubes are necessary. The known parameters of the tubes allow the calculation of the Thevenin parameters, which are in turn compared to a model 20  of the system using a χ2 statistic to ensure accurate measurement. The Thevenin parameters are then stored and used in the calculation of the unknown system (Keefe et al., 1992). WBR has a number of potential advantages over conventional tympanometry. The technique measures over a large range of frequencies (typically 250 Hz to 10,000 Hz). It is also very fast, taking only a couple of seconds to perform. Additionally, the magnitude of the ER does not depend on the distance between the probe tip and the eardrum and so the location of the probe in the ear canal is not as critical as it is in tympanometry (Voss et al., 2008). Finally, wideband reflectance can be run at ambient pressure and does not require pressurization of the ear canal (Shahnaz, Longridge, and Bell, 2009). It is, however, possible to run a pressurized WBR measurement (or reflectance tympanogram) by varying the pressure in a manner identical to tympanometry (Keefe and Levi, 1996). At ambient pressures healthy adults show a pattern of high reflectance in the low frequencies which decreases to a minimum between 1000 Hz and 4000 Hz before increasing again at high frequencies (Shahnaz and Bork, 2006). Figure 1.1 demonstrates this pattern in normal Caucasian and Chinese subjects.  21  Figure 1.1. Wideband energy reflectance across frequency in normal Caucasian and Chinese subjects. Error bars denote the 95th percent confidence interval. Reproduced with permission from Shahnaz and Bork (2006).  Pressurized measurements show a similar pattern with minima around 1500 Hz to 3500 Hz. However, as pressure increases, an increase in low frequency reflectance is observed consistent with increased stiffness of the middle ear due to pressurization (Margolis, Saly and Keefe, 1999). In very young infants, below the age of 6 months, a decrease in low frequency reflectance has been demonstrated in ambient pressure measurements (Sanford and Feeney, 2008), which then approaches adult-like values over the first few years of life (Keefe, Bulen, Arehart and Burns, 1993). This has been attributed to developmental differences in the infant ear canal, eardrum and middle ear, and primarily to the  22  significant ear canal wall vibrations that occur in the more compliant ears of young children (Keefe et al., 1993).  One of the most appealing features of WBR is its potential to differentiate between different types of middle ear pathology. Conventional techniques such as 226 Hz probe tone tympanometry often fail to distinguish normal middle ears from ears with pathology affecting the ossicular chain (Shahnaz and Davies, 2006). In contrast, research into WBR has demonstrated that the technique is significantly more sensitive to these pathologies (Shahnaz, Bork, Polka, Longridge, Bell and Westerberg, 2009). Moreover, the patterns of reflectance vary depending on the status of the middle ear and thus different pathologies result in different patterns of reflectance. Generally, a stiffening pathology will result in increased reflectance over a specific frequency range. For example, otosclerotic ears demonstrate significantly increased reflectance between 400 Hz and 1000 Hz (Shahnaz et al., 2009). Ears with negative middle ear pressure demonstrate increased reflectance below 2000 Hz and even higher frequencies may be affected as the severity of the pressure increases (Beers, Shahnaz, Westerberg and Kozak, 2010). Ears with OME show even more reflectance across a broad range of frequencies (Allen et al., 2005; Beers et al, 2010). In contrast, ears with loosening pathology demonstrate patterns of decreased reflectance. Perforated eardrums result in reflectance patterns with significant decreases in reflectance compared to healthy controls across nearly all frequencies, with the largest decreases in reflectance below 1.5 kHz (Allen et al., 2005). Work with cadavers has demonstrated a significant notch in the reflectance pattern between 561 Hz and 841 Hz when a discontinuity is introduced to the ossicular chain. This notch disappears upon surgical repair of the defect (Feeney, Grant  23  and Mills, 2009). A similar notch is observed after surgical intervention for otosclerosis. The insertion of a prosthetic stapes requires the severing of the annular ligament resulting in decreased stiffness of the middle ear post surgery (Shahnaz, Longridge and Bell, 2009). Feeney, Grant and Marryott (2003) also demonstrated a low frequency notch between 500 Hz and 600 Hz in two subjects with hypermobile tympanic membranes arising from healed perforations. Voss, Merchant and Horton (in press) suggest that wideband reflectance may offer a powerful tool, used in conjunction with conventional measures of tympanometry, to aid in identifying middle ear pathology. It is important to note that the technique is not confounded by pathology located in the cochlea. Ears with sensorineural hearing loss are indistinguishable from normal controls, indicating that damage to the cochlea does not impact the measurement of reflectance (Feeney et al., 2003).  When evaluating a new clinical technique, one must also question its reliability. Voss and Allen (1994) noted significant between-subject variability in their measurements in healthy young adults. However, Vander Werff, Prieve and Georgantas (2007) showed that the variability between subjects is much smaller than the changes introduced by middle ear pathology. Furthermore they evaluated test-retest reliability by performing multiple readings while removing the probe assembly between measurements (Vander Werff et al., 2007). The test-retest reliability was excellent in adult subjects and more than adequate in most infant subjects. Beers et al. (2010) also evaluated the testretest reliability in a subset of their subjects in order to determine the proportion of the observed differences attributed to reinsertion compared to the proportion of the observed differences attributed to middle ear effusion in their disease group subjects. The  24  difference following reinsertion was insignificant compared to the large change in reflectance introduced by the presence of effusion in the middle ear. The largest variability was attributed to poor fit of the probe in the ear canal and could be minimized through proper insertion technique.  The above results demonstrate the potential use of WBR in the analysis of the middle ear. The technique is sensitive to middle ear pathology, uninfluenced by inner ear pathology and reliable in both children and adults. However, more work is needed to fully verify this technique’s utility. To date no one has evaluated the application of pressurized measurements of reflectance in assessing Eustachian tube function. As mentioned previously, even the application of small amounts of pressure to the middle ear can have an effect on patterns of reflectance. Beers et al. (2010) noted significant increases in energy reflectance between 400 Hz and 1800 Hz with the presence of even mild negative middle ear pressure in their pediatric subjects. This suggests that wideband reflectance could be used to monitor potential changes in middle ear pressure by comparing patterns of reflectance. This may allow us to evaluate Eustachian tube function by measuring energy reflectance before and after subjects perform physical manoeuvres that exercise the tube. A corresponding change from baseline after a subject performs a manoeuvre could potentially provide information regarding the function and patency of the Eustachian tube. Wideband Reflectance Systems  Currently there is only one wideband reflectance system commercially available. This system, the Mimosa Acoustics RMS system, is a lap-top based system capable of  25  measuring wideband reflectance and ambient pressure from 250 Hz to 8000 Hz. These measurements can be plotted in terms of energy reflectance, or power absorbance (Shaw, 2009). A new WBR machine (the REFLWIN Interacoustics [Eclipse system-v.1]) has been developed which has the ability to measure energy reflectance at both ambient pressure (static mode) and with changing pressure (dynamic mode). The system’s static mode displays two variables following a measurement. ER is plotted as a function of frequency between 250 Hz and 8000 Hz. The second variable is power absorption (PA) which can also be plotted as a function of frequency. In addition to energy reflectance and power absorbance, the system offers measures of impedance, phase angle and sound pressure level. Dynamic mode offers five measurements. The pressure sweep may allow such dynamic measures to provide information that is not given by static measures alone. For example, a pathology could have an effect at the pressure extremes while providing no effect closer to ambient pressure. Following a measurement, a 3-dimensional graph is generated plotting ER as a function of frequency and pressure. Additionally the system provides a graph of power absorption plotted as a function of frequency. This is similar to the static measurement except that it is taken at tympanometric peak pressure as opposed to ambient pressure. Peak power absorbance is calculated at a given pressure (p) from (Liu, Sanford, Ellison, Fitzpatrick, Gorga and Keefe, 2008): < 𝐸𝐴(𝑝) >  1  𝑁𝑓  ∑𝑖(1 − |𝑅(𝑓𝑖 , 𝑝|2 )  Equation (5)  where Nf is the number of frequency bands centered at frequency band fi from 380 Hz to 2000 Hz. The bandpass TPP (p̂) is then determined from the pressure bin with the  26  maximum power absorbance (pk) and the size of the pressure sampling (Δp) through the following equation (Liu et al., 2008): p� = pk + ∆p  ak−1 −ak+1  2(ak−1 −2ak +ak+1 )  Equation (6)  Where ak-1, ak and ak+1 are the power absorbances at pk- Δp, pk and pk+ Δp. Dynamic power absorbance is displayed at this pressure point. The third analysis provided is power absorption tympanometry. This measure produces a graph of average absorption as a function of pressure. Finally, for the fourth and fifth measurement variables the system extracts 226 Hz and 1000 Hz tympanograms from the data by compiling data points from a single frequency of interest across the pressure range of the system. The value of this dynamic evaluation has yet to be determined. Margolis et al. (1999) have provided information on the change in pattern in the absence of pathology; however, little information has been acquired from ears with known pathology. If measurement of ER across pressure improves the sensitivity and specificity of the technique in comparison to measurement at ambient pressure, it may be worth introducing pressure into the ear canal in order to increase the measurement’s clinical utility. In addition to the different measurement techniques provided by the wideband reflectance systems, differences in the size and structure of the outer and middle ears between genders or ethnic groups have the potential to impact middle ear analysis. For example, increases to the size of the skull have been demonstrated to alter both the size and compliance of the middle ear cavity (Huang, Rosowski and Peak, 2000). The next section will review current reports on the effects of these variables on middle ear measurements.  27  Gender and Ethnic Effects in Middle Ear Analysis  Differences in the size and structure of the outer and middle ears between genders could have an effect on middle ear analysis. Previous work with conventional techniques has demonstrated an effect of gender on measurement variables. Roup, Wiley, Safady and Stoppenbach (1998) showed significant differences between Caucasian males and females on the conventional tympanometric measures of Peak Ytm, Vea and TW. Peak Ytm and Vea were higher in males than females while TW was higher in females than males. These findings were reproduced in a study by Shahnaz and Bork (2006b). Measures of middle ear resistance also differ between males and females with males demonstrating higher resistance below 1000 Hz and lower resistance between 2000 Hz and 4000 Hz. Additionally, reactance measurements are more positive below 1500 Hz in males (Margolis et al., 1999). Shahnaz and Bork (2006a) measured normalized admittance across a broad range and frequencies and demonstrated significantly higher admittance in males between 1781 Hz and 2367 Hz. WBR has not shown such straightforward effects. Hunter, Tubaugh, Jackson and Propes (2008) found no difference between genders in their ambient pressure measurements of children. Looking at adult data, main effects for gender in the Shahnaz and Bork (2006) study of ambient pressure measurements were not significant either.  There is, however, possible variation in WBR measurements between members of different ethnic groups. Such effects have previously been demonstrated. The multifrequency tympanometry measure of static admittance has been shown to be higher in Caucasian subjects as opposed to Chinese subjects up to 1200 Hz (Shahnaz and 28  Davies, 2006). Furthermore, ambient pressure WBR measurements have revealed that Caucasian subjects have consistently lower ER values between 469 Hz and 1500 Hz compared to Chinese subjects while the Chinese subjects had consistently lower ER values between 3891 Hz and 6000 Hz (Shahnaz and Bork, 2006). Such differences exist even at young ages with Chinese children demonstrating lower ER between 1250 Hz and 2500 Hz compared to Caucasian children; Caucasian children showed lower ER between 2500 Hz and 5000 Hz compared to Chinese children (Beers et al., 2010). Small variations in anatomy and physiology between ethnicities likely underlie these observations. Specifically, it is thought that differences in body size may account for the differences in measurements (Shahnaz and Davies, 2006). It is not known whether external and middle ear volumes increase as body size increases (Shahnaz and Bork, 2006). However, a study of the middle ears in exotic cat species has demonstrated that the compliance of the middle ear cavity increases with body size while the frequency at which the reflectance minimum occurs decreases with body size (Huang, Rosowski and Peake, 2000). Sound energy is also absorbed by various components in the middle ear such as the tympanic membrane, ligaments of the ossicles and mastoid air cells (Rosowski, 1991). Therefore, differences in the composition of these components could also contribute to differences in middle ear measurements. Such differences can have clinical implications as well. Consistent differences suggest that using homogenous normative data for all ethnic groups is inappropriate (Wan and Wong, 2002). The use of ethnic specific normative data could also enhance the sensitivity of clinical tests for middle ear pathology. Shahnaz and Bork (2006) demonstrated that ER below 1000 Hz is the most sensitive frequency range for detecting otosclerosis with Chinese and Caucasian subjects show differing 95th percentile ranges at this frequency. They argue that the use  29  of mixed group normative data could result in an otosclerotic ear from one ethnic group being contained within the normal range of the mixed group data where it would fall outside the normal range under the appropriate ethnic-specific normative data. As a result the mixed group normative data would label the otosclerotic ear as normal while the ethnic-specific normative data would correctly identify the pathology. Variations in middle ear function may also shed light on differences in disease prevalence between ethnic groups, particularly differences in the prevalence of otitis media with effusion. . Williamson, Dunleavey, Bain and Robinson (1994) reported a point prevalence for OME of 17% for Caucasian children at the age of 5 in Southwest Hampshire, Britain. In comparison, the point prevalence for a comparable group of Chinese children in Hong Kong was only 2.2% (Tong, Yue, Ku, Lo and van Hasselt, 2000). Tympanometric peak pressure has been demonstrated to be consistently higher in Chinese subjects (Wan and Wong, 2002). A difference in the functionality of the Eustachian tube between ethnic groups could underlie the difference in resting pressure and directly affect the development and recovery from OME in these populations. Goals of the Study  The current study has the following goals: (i) to compare the effectiveness of the REFLWIN Interacoustics (Eclipse System-v.1) dynamic WBR measures in healthy young adult Caucasian and Chinese subjects to equivalent measurements taken at ambient pressure. Previous reports in the literature have focused largely on measurements at ambient pressure. Dynamic WBR measurements retain the potential to provide an increase in the sensitivity of the analysis. If the dynamic measurement cannot provide an advantage over ambient pressure measurements, then there is little reason to  30  subject patients to pressurized measurements; (ii) to compare baseline static and dynamic measures of wideband reflectance to previous evaluations of an equivalent population. The REFLWIN system is still under development. It is important to demonstrate that the system provides equivalent estimates of wideband reflectance to other commercially available systems. If these systems offer substantially different estimates of wideband reflectance, then it prevents the comparison of measurements taken with competing devices. Furthermore, this would question the validity of the calculation itself and throw doubt on its usefulness in assessing the middle ear; (iii) to determine if WBR can be used to evaluate Eustachian tube function in normal hearing young adults. A need remains to devise a simple and efficient test of Eustachian tube function that can be used in a clinical setting. As wideband reflectance has been shown to be more sensitive than conventional tympanometry to many middle ear pathologies (Shahnaz et al., 2009), it may also serve to improve upon the current tympanometric methods of evaluating Eustachian tube function; and (iv) to evaluate any potential gender and ethnic effects present in Eustachian tube assessment using WBR. Ethnic effects have been noted both in tympanometric measures (Shahnaz and Davies, 2006) as well as early reports of wideband reflectance (Shahnaz and Bork, 2006). Variation in the parameters used to evaluate the middle ear can have a direct impact on its interpretation. If enough difference exists between the two populations and a homogenous normative data set is used, there is the risk of classifying a normal subject as having pathology or, even worse, classifying an ear with pathology as normal. The use of ethnic-specific normative data could help to avoid such risks. However, such differences must be well documented before implementing such procedures. Additionally, there have been differences observed in the prevalence of middle ear pathology between ethnic groups (Williamson  31  et al., 1994; Tong et al., 2000). A difference in the function of the Eustachian tube could underlie such an observation.  32  Methods  Participants Participants for this study were recruited via posters placed around the University of British Columbia campus. A total of 50 young adults were recruited for the study (30 females, 20 males). These groups were equally distributed between two ethnic groups (Caucasian and Chinese), resulting in four total subject groups: 15 Chinese females, 10 Chinese males, 15 Caucasian females and 10 Caucasian males. Ethnicity was determined based on self-report. The Chinese group was comprised of Canadian and Chinese born individuals whose parents were from mainland China, Hong Kong or Taiwan and who had no traceable foreign decent. The Caucasian group was defined based on the classification of race by Statistics Canada (2006) which defines the group as non-Chinese, non South/East/West Asian, non-Aboriginal, non-Arab, non-Black, nonFilipino and non-Hispanic individuals with white or light pigmentation of the skin and of European decent. Subjects were given a small honorarium for their participation in this study. In order to qualify for the study, subjects needed to meet the following conditions: (i) no history of middle ear disease or surgery; (ii) no history of head trauma; (iii) no history of exposure to excessive noise or use of ototoxic drugs; (iv) present no gross eardrum abnormalities or excessive cerumen as documented by otoscopic examination; (v) present pure-tone air conduction audiometric thresholds of 20 dB HL or lower between 250 and 8000 Hz including the 3000 and 6000 Hz inter-octave frequencies; (vi) display broadband noise elicited acoustic reflexes at 85 dB HL; (vii) have normal 226 Hz tympanograms based on ethnic-specific norms documented by  33  Shahnaz and Bork (2008) and (viii) pass Distortion-Product Otoacoustic Emission (DPOAE) screening. A pass consisted of emissions present at least 3 dB above 2 standard deviations above the noise floor for four test frequencies between 1500 Hz and 4000 Hz after a minimum of four sweeps. In addition, the measured emission amplitude needed to be at least -3 dB SPL. Intrumentation WBR measurements were taken using the REFLWIN Interacoustics (Build Version 2.60500) WBR machine, a PC-based system capable of performing both static (at ambient pressure) and dynamic (with introduced pressure changes) measures of energy reflectance. The system was calibrated by determining the Thevenin parameters of a set of two tubes of known length and diameter before each subject. Conventional 226 Hz probe tone tympanometry and Multi-Frequency Tympanometry were run using the Grason-Stadler Inc. Tympstar Version 2 calibrated using standard cavities as directed by the operator’s manual in accordance with American National Standards Institute (ANSI) standards. Distortion product otoacoustic emissions were measured using either the Otodynamics Echoport ILO292 USB-I system or the Intelligent Hearing System’s SmartOAE system (version 4.54). A third device, the Otodynamics Otoport DP+TE portable screener, was used to test a small number of subjects due to equipment malfunction partway through the study. Pure-tone air conduction audiometry was run in a sound-treated booth using the Grason-Stadler Inc. Model 61 Audiometer under Etymotic Research (ER) 3A Insert earphones also calibrated in accordance with ANSI standards (re: S3.6.1996).  34  Procedure The testing procedure began by obtaining informed consent from each subject. Following this, a case history was completed followed by a screening procedure to ensure the subject met the study’s inclusion criteria. Both ears were tested for each subject. First, otoscopy was performed to ensure that the ear canal was free of excessive wax and debris. Admittance tympanograms were measured using a 226 Hz probe tone. Following this, susceptance and conductance tympanograms were recordedwith a 226 Hz probe tone. Next, multi-frequency tympanometry was performed to determine the resonant frequency of the ear. This was done twice, once using the sweep frequency method (pressure held constant while frequency was swept from 200 to 2000 Hz) and once using the sweep pressure method (frequency held constant while pressure was swept from +200 to – 200 daPa). The acoustic reflex was tested by presenting a broadband noise stimulus at an intensity of 85 dB HL. Subjects were then seated in a soundproof booth and air conduction audiometric thresholds determined at one octave intervals from 250 to 8000 Hz as well as at 3000 Hz and 6000 Hz. Finally, distortionproduct otoacoustic emissions were measured in each ear. Once subjects had met the inclusion criteria, the main study protocol was employed to evaluate the Eustachian tube using wideband energy reflectance. Subjects were first evaluated in their natural state using both static and dynamic pressure readings. Subjects were then asked to perform the Valsalva manoeuvre by plugging their nose and blowing with mouth closed until they felt pressure had been introduced into their ears. Subjects were instructed to sit still and avoid swallowing while a dynamic WBR measurement was performed. Once a satisfactory measurement had been recorded subjects were allowed to equalize the pressure in their ears by yawning or swallowing. If they desired, subjects were allowed a  35  small glass of water to aid in this process. Once the effects of the previous test had been cleared, subjects were asked to perform the Toynbee manoeuvre by plugging their nose and swallowing four times to establish pressure in the middle ear space. The use of four swallows was selected based on the findings of Jonathan et al. (1986). They noted that the Eustachian tube does not open to every swallow. They suggested that two openings out of five could be considered normal. The selection of four swallows per manoeuvre was made to ensure that at least one Eustachian tube opening occurred for each subject. Dynamic WBR was once again performed in this state. The sequence in which the manoeuvres were performed was reversed every second subject to counterbalance any potential order effects. In addition to the wideband reflectance patterns, the system also provides 226 Hz and 1000 Hz tympanograms. Admittance is related to the reflectance function [R(f)] by the following equation (Liu, Sanford, Ellison, Fitzpatrick, Gorga and Keefe, 2008): 𝑌(𝑓) = 𝑍𝑐−1  1−𝑅(𝑓)  1+𝑅(𝑓)  Equation (7)  This function is applied at individual frequencies across the pressure range of the system in order to produce the desired tympanograms. The system provides uncompensated static admittance (Ya) when the data is extracted from the measurements. This was manually converted into positively compensated peak static admittance (Ytm) by subtracting the admittance value at the positive tail (located at +200 daPa) from the uncompensated static admittance (Ya). Data Analysis There is a set relationship between static energy reflectance and static power absorbance patterns. Power absorbance is the reverse of energy reflectance and can be 36  calculated by subtracting the estimate of energy reflectance at a given frequency from 1. Due to this relationship we would expect the two patterns to mirror each other. Allen et al. (2005) suggest that power absorbance is more easily interpreted as it is the absorbed power that will in turn determine the sensitivity of the ear. As such, power absorbance was selected for analysis. Static power absorbance was analysed using a 2x2x16 mixed model ANOVA with gender and ethnicity as between-subject factors and frequency as a within-subject factor. Individual frequencies were averaged into one-third octave bands providing a final within-subject factor with 16 levels. A similar analysis using a 2x2x16 mixed model ANOVA was performed to analyse baseline dynamic power absorbance, again with gender and ethnicity as between-subject factors and frequency as a withinsubject factor. Baseline power absorbance tympanograms were evaluated on two variables: peak pressure and peak power absorbance. Both of these analyses were 2x2 ANOVAs with gender and ethnicity as between-subject factors. Equivalent analyses were performed for the extracted 226 Hz and 1000 Hz tympanograms. Each was evaluated on the basis of tympanometric peak pressure and positively compensated peak static admittance, again with 2x2 ANOVAs where gender and ethnicity were the between-subject factors. Following the baseline analyses, static and dynamic power absorbance measures were compared to equivalent measures from a study conducted by a previous student at the University of British Columbia using two clinical devices (Shaw, 2009). The first set was obtained using a previous version of the Interacoustics REFLWIN system while the second was obtained using the Mimosa Acoustics RMS-system. The procedures in the previous study were identical to the current study’s baseline measurements. Wideband reflectance measurements were obtained on Caucasian and Chinese young adult subjects. 37  For the dataset obtained using the older version of the REFLWIN Interacoustics software both static and dynamic measurements were conducted by the previous study. For the dataset obtained using the Mimosa Acoustics RMS-system only static measurements were produced as the system does not offer dynamic measurements. These comparisons were analysed using 2x2x2x15 mixed-model ANOVAs where gender, ethnicity and system were between-subject factors and frequency was a within-subject factor. One less frequency band was analysed in this portion of the study as the measurements from the previous study did not include the 8000 Hz frequency band. Finally, analyses were performed comparing baseline measures of dynamic power absorbance, power absorbance tympanogram peak pressure, power absorbance tympanogram peak power absorbance, 226 Hz tympanometric peak pressure, 226 Hz peak compensated static admittance (Ytm)1000 Hz tympanometric peak pressure and 1000 Hz peak compensated static admittance (Ytm) to the same measures following both the Valsalva and Toynbee manoeuvres. The dynamic power absorbance analyses were performed using 2x2x2x16 mixed-model ANOVAs with gender and ethnicity as between-subject factors and condition (baseline vs either Valsalva or Toynbee manoeuvre) and frequency as within-subject factors. The remaining variables were analysed as 2x2x2 mixed-model ANOVAs with gender and ethnicity as between-subject factors and condition as a within-subject factor. For all analyses an alpha level of 0.05 was used in order to assess statistical significance. Due to the large number of repeated measures, the Greenhouse and Geisser (1959) approach was used to compensate for violations of the sphericity assumption, which could lead to inflated Type I error in all analyses containing the frequency factor.  38  Results  The results of the study are divided into the following four sections: Baseline comparisons of Static and Dynamic Power Absorbance in Caucasian and Chinese Subjects; Comparison of the Current Study’s Baseline Measurements to those of the study by Shaw (2009); Comparisons of Baseline to Valsalva’s Manouevre in Caucasian and Chinese Subjects,; Comparisons of Baseline to Toynbee’s Manouevre in Caucasian and Chinese Subjects.  Baseline Comparisons of Static and Dynamic Energy Reflectance and Power Absorption in Caucasian and Chinese Subjects Baseline static energy reflectance.  Figure 3.1 displays the baseline static energy reflectance across all groups. The descriptive statistics including mean energy reflectance, maximum energy reflectance, minimum energy reflectance and the standard deviation for the sixteen frequency bands measured (250 Hz, 315 Hz, 400 Hz, 500 Hz, 630 Hz, 800 Hz, 1000 Hz, 1250 Hz, 1600 Hz, 2000 Hz, 2500 Hz, 3150 Hz, 4000 Hz, 5000 Hz, 6300 Hz, 8000 Hz) in Caucasian males, Caucasian females, Chinese males and Chinese females are contained in Appendix 1.  39  Energy Reflectance  1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 8  6.3  5  4  3.15  2.5  2  1.6  1.25  1  0.8  0.63  0.5  0.4  0.315  0.25  Frequency (kHz)  Figure 3.1. Baseline energy reflectance across frequency averaged across all subjects. The shaded area indicates the 90% range of data at each frequency.  Baseline static power absorbance.  Figure 3.2 displays the baseline static power absorbance across all groups. The descriptive statistics including mean power absorbance as well as minimum power absorbance, maximum power absorbance and the standard deviation for the sixteen frequency bands measured (250 Hz, 315 Hz, 400 Hz, 500 Hz, 630 Hz, 800 Hz, 1000 Hz, 1250 Hz, 1600 Hz, 2000 Hz, 2500 Hz, 3150 Hz, 4000 Hz, 5000 Hz, 6300 Hz, 8000 Hz) for Caucasian males, Caucasian females, Chinese males and Chinese females are contained within Appendix 1.  40  1.20  Power Absorbance  1.00 0.80 0.60 0.40 0.20  8  6.3  5  4  3.15  2.5  2  1.6  1.25  1  0.8  0.63  0.5  0.4  0.315  0.25  0.00  Frequency (kHz)  Figure 3.2. Baseline static power absorbance averaged across all subjects. The shaded area denotes the 90% range of data at each frequency.  The main effects of gender [F(1,87)=0.190, p=0.66] and ethnicity [F(1,87)=0.527, P=0.47] were not significant. The main effect of frequency [F(3.47,301.85)=361.774, p<0.000] was significant. This indicates that power absorbance varied across frequency bands. The interaction between gender and ethnicity [F(1,87)=6.005, p=0.016] was significant, demonstrating that overall static power absorbance differed between Caucasian males, Caucasian females, Chinese males and Chinese females. Additionally the interaction between frequency and gender [F(3.47,301.85)=2.567, p=0.046] and the interaction between frequency and ethnicity [F(3.47,301.85)=3.528, p<0.011] were significant. This demonstrates that the variation of power absorbance across frequency differed between males and females and also differed between Chinese and Caucasian subjects. Finally, the higher-order interaction of frequency, gender and ethnicity [F(3.47,301.85)=3.288, p<0.016] was also significant, indicating that the variation of power absorbance across frequency differed between gender/ethnicity combinations. A 41  Greenhouse-Geisser correction was performed to ward against inflated Type 1 error due to repeated measures. Following correction, all measures remained significant. The frequency, gender, and ethnicity interaction was further explored using the Tukey’s HSD post-hoc method. Caucasian females differed significantly from Chinese females from 5000 Hz – 8000 Hz. (figure 3.3) with Chinese females giving higher measures of power absorbance at these frequencies. Meanwhile Chinese females differed significantly from Chinese males at 4000 Hz and 5000 Hz (figure 3.4) with Chinese females showing higher power absorbance than the Chinese male subjects in these frequency bands. Chinese males also differed significantly from Caucasian females at 8000 Hz with Chinese males producing higher power absorbance. Caucasian males did not differ from any of the other gender/ethnicity combinations at any frequency band. 1.0 0.9 0.8  Power Absorbance  0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 -0.1 0.25  0.4  0.63  1.0  1.6  Frequency (kHz)  Female  2.5  4.0  6.3  0.25  0.4  0.63  1.0  1.6  2.5  4.0  6.3  Frequency (kHz)  Male  Caucasian Chinese  Figure 3.3. Frequency, gender, ethnicity interaction: static power absorbance displayed across frequency. Genders are displayed in separate panes. Error bars denote the 95th percent confidence interval.  42  1.0 0.9 0.8  Power Absorption  0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 -0.1 0.25  0.4  0.63  1.0  1.6  2.5  4.0  6.3  Frequency (kHz)  Caucasian  0.25  0.4  0.63  1.0  1.6  2.5  4.0  6.3  Frequency (kHz)  Chinese  Female Male  Figure 3.4. Frequency, gender, ethnicity interaction: static power absorbance displayed across frequency. Ethnic groups are displayed in separate panes. Error bars denote the 95th percent confidence interval.  Baseline dynamic power absorbance.  Figure 3.5 displays the baseline dynamic power absorbance measured at tympanometric peak pressure averaged across all subjects. The descriptive statistics for Caucasian females, Caucasian males, Chinese females and Chinese males determined across the sixteen frequency bands (250 Hz, 315 Hz, 400 Hz, 500 Hz, 630 Hz, 800 Hz, 1000 Hz, 1250 Hz, 1600 Hz, 2000 Hz, 2500 Hz, 3150 Hz, 4000 Hz, 5000 Hz, 6300 Hz, 8000 Hz) are contained in Appendix 1.  43  1.20  Power Absorbance  1.00 0.80 0.60 0.40 0.20  8  6.3  5  4  3.15  2.5  2  1.6  1.25  1  0.8  0.63  0.5  0.4  0.315  0.25  0.00  Frequency (kHz)  Figure 3.5. Baseline dynamic power absorbance measured at tympanometric peak pressure averaged across all subjects. The shaded area denotes the 90% range of the data at each frequency.  The main effect of gender [F(1,87)=0.061, p=0.805] was not significant while the main effects of ethnicity [F(1,87)=4.390, p=0.039] and frequency [F(3.76,327.22)=362.927, p<0.000] were significant. This revealed that overall dynamic power absorbance differed between ethnic groups. Additionally, across all subjects dynamic power absorbance differed between frequency bands. Further analysis revealed a significant interaction between gender and ethnicity [F(1,87)=12.570, p=0.001], demonstrating that overall dynamic power absorbance differed between Caucasian males, Caucasian females, Chinese males and Chinese females. Finally, the interaction between frequency and gender [F(3.76,327.22)=3.786, p<0.006] and between frequency and ethnicity [F(3.76,327.22)=10.369, p<0.000] were significant, while the three-way interactions between gender, ethnicity and frequency failed to reach significance  44  [F(3.76,327.22)=1.573, p=0.185]. Following a Greenhouse-Geisser correction for inflated type 1 error due to repeated measures both the interaction between frequency and gender as well as the interaction between frequency and ethnicity remained significant, indicating that the pattern of dynamic power absorbance across frequency differed between Caucasian and Chinese subjects in addition to differing between male and female subjects. A Tukey’s HSD post-hoc analysis was performed to further explore the frequency/gender interaction. As demonstrated in figure 3.6, dynamic power absorbance differed between male and female subjects at 5000 Hz, with female subjects having higher power absorbance than male subjects in this frequency region. They did not differ significantly in any of the remaining frequency bands.  45  0.9 0.8  Power Absorption  0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.25  0.4  0.63  1.0  1.6  2.5  4.0  6.3  Frequency (kHz) Female Male  Figure 3.6. Frequency/gender interaction. Dynamic power absorbance measured at tympanometric peak pressure is displayed across frequency. Error bars denote the 95th percent confidence interval at each frequency.  The frequency/ethnicity interaction was also explored using the Tukey’s HSD post-hoc method. This comparison is displayed in figure 3.7. The post-hoc analysis indicated that Caucasian subjects demonstrated significantly higher power absorbance from 800 Hz to 1250 Hz compared to their Chinese counterparts. At higher frequencies, Chinese subjects demonstrated significantly higher power absorbance from 5000 Hz to 8000 Hz compared to Caucasian subjects.  46  0.9 0.8  Power Absorption  0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.25  0.4  0.63  1.0  1.6  2.5  4.0  6.3  Frequency (kHz) Caucasian Chinese  Figure 3.7. Frequency/ethnicity interaction. Dynamic power absorbance measured at tympanometric peak pressure across frequency. The error bars denote the 95th percent confidence interval at each frequency.  Baseline power absorbance tympanometry.  Peak pressure. The power absorption tympanogram extracted from the dynamic power absorbance measure for each subject was analyzed in terms of peak pressure and peak power absorbance. Figure 3.8 displays the average peak pressure obtained from the power absorbance tympanogram for each of the four subject groups. The descriptive statistics for peak pressure of the power absorbance tympanogram from the baseline condition for all four gender/ethnicity combinations are contained in Appendix I. These  47  statistics include mean pressure, minimum pressure, maximum pressure and the standard deviation. -10  Peak Presure (daPa)  -15  -20  -25  Caucasian Females Caucasian Males Chinese Females Chinese Males  -30  -35  Figure 3 8. Average baseline peak pressure of the power absorbance tympanogram in Caucasian females, Caucasian males, Chinese females and Chinese males. Error bars denote the 95th percent confident interval of each mean.  Neither the main effects of gender [F(1,87)=0.5173, p=0.475] nor ethnicity [F(1,87)=0.0449, p=0.833] were significant, indicating that the peak pressure of the power absorbance tympanogram did not differ between genders or between Caucasian and Chinese subjects. Furthermore, the interaction between gender and ethnicity [F(1,87)=0.0611, p=0.805] was not significant, indicating the peak pressure did not differ between Caucasian males, Caucasian females, Chinese males or Chinese females either.  48  Peak power absorbance. The average peak power absorbance from each of the 4 subject groups is displayed in figure 3.9. The descriptive statistics from the peak power absorbance of the power absorbance tympanogram from the baseline condition for all four gender/ethnicity combinations are contained in Appendix I. The measures displayed include mean power absorbance, minimum power absorbance, maximum power absorbance and the standard deviation. 0.65  Peak Power Absorbance  0.6 0.55 Caucasian Females 0.5  Caucasian Males  0.45  Chinese Females Chinese Males  0.4 0.35 0.3  Figure 3.9. Average baseline peak power absorbance from the power absorbance tympanogram from each of the four subject groups. The error bars denote the 95th percent confidence interval.  Again, neither the main effect of gender [F(1,87)=0.5137, p=0.475] nor ethnicity [F(1,87)=0.0449, p=0.833] was significant. Additionally, the interaction between gender and ethnicity [F(1,87)=0.0611, p=0.805] failed to reach significance. These results indicate that the peak power absorbance of the power absorbance tympanogram did not 49  differ between genders, between Caucasian and Chinese subjects, or between any of Caucasian males, Caucasian females, Chinese males or Chinese females.  Baseline 226 Hz tympanometry.  Tympanometric peak pressure is an indirect measurement of middle ear pressure (Fowler and Shanks, 2002). It is expected that the tympanometric peak pressures of the 226 Hz and 1000 Hz tympanograms and the peak pressure of the power absorbance tympanogram should be the same as they are all derived from a single measurement (Liu et al., 2008). Comparison of the peak power absorbance and 226 Hz and 1000 Hz tympanometric peak pressures from the current study confirms that they are identical. As a result the pressure corresponding to the peak power absorbance of the power absorbance tympanogram was chosen to be reported in the results section. The other two variables are excluded from the manuscript as their discussion is redundant. Peak Compensated Static admittance (Ytm). The 226 Hz tympanogram extracted from the dynamic power absorbance measurement was analyzed in terms of peak compensated static admittance (Ytm). Figure 3.10 displays the average baseline Ytm for Caucasian females, Caucasian males, Chinese females and Chinese males. The descriptive statistics for the 226 Hz tympanogram from the baseline condition are contained within Appendix I. These statistics include mean admittance, minimum admittance, maximum admittance and the standard deviation.  50  1.8 1.6 1.4 Ytm (mmho)  1.2  Caucasian Females  1  Caucasian Males  0.8  Chinese Females  0.6  Chinese Males  0.4 0.2 0  Figure 3.10. Average baseline peak compensated static admittance (Ytm) of the 226 Hz tympanogram for each of the four subject groups. Error bars denote the 95th percent confidence interval.  The main effect of gender [F(1,80)=1.306, p=0.257] was not significant, indicating that peak compensated static admittance did not differ between male and female subjects. In contrast, the effect of ethnicity [F(1,80)=21.407, p<0.001] was significant, showing that peak compensated static admittance differed between Caucasian and Chinese subjects. Figure 3.11 demonstrates that Chinese subjects produced lower peak compensated static admittances than Caucasian subjects did. Finally, the interaction between gender and ethnicity [F(1,80)=1.193, p=0.278] did not reach significance, indicating that peak compensated static admittance did not differ between Caucasian males, Caucasian females, Chinese males or Chinese females.  51  1.0 0.9 0.8 0.7  Ytm  0.6 0.5 0.4 0.3 0.2 0.1 0.0 Chinese  Caucasian Ethnicity  Median 25%-75% Non-Outlier Range  Figure 3.11. Baseline 226 Hz tympanogram peak compensated static admittance in Chinese and Caucasian subjects. The boxed area represents the 25-75% range while the bars denote the entire range of measurement.  Baseline 1000 Hz tympanometry.  Peak Compensated Static Admittance (Ytm). The 1000 Hz tympanogram extracted from the dynamic power absorbance measure was analyzed in terms of peak compensated static admittance. Figure 3.12 displays the average baseline Ytm for Caucasian females, Caucasian males, Chinese females and Chinese males. The descriptive statistics for the 1000 Hz tympanogram are contained within Appendix I. These statistics include mean admittance, minimum admittance, maximum admittance and the standard deviation.  52  1.8 1.6 1.4 Ytm (mmho)  1.2  Caucasian Females  1  Caucasian Males  0.8  Chinese Females  0.6  Chinese Males  0.4 0.2 0  Figure 3 12. Average baseline peak compensated static admittance (Ytm) for the four subject groups. Error bars denote the 95th percent confidence interval.  The main effect of gender [F(1,80)=5.912, p=0.017] was significant, indicating that the peak compensated static admittance of the 1000 Hz tympanogram differed between male and female subjects, with female subjects demonstrating higher values. The main effect of ethnicity [F(1,80)=4.675, p=0.034] was also significant, demonstrating that the peak compensated static admittance also differed between Chinese and Caucasian subjects. Figure 3.13 demonstrates this relationship; Caucasian subjects showed significantly higher peak compensated static admittance at the 1000 Hz probe tone frequency compared to their Chinese counterparts.  53  3.5 3.0 2.5  Ytm  2.0 1.5 1.0 0.5 0.0 -0.5 Chinese  Caucasian Ethnicity  Median 25%-75% Non-Outlier Range  Figure 3.13. Peak static admittance on the 1000 Hz tympanogram in male and female subjects. The boxed area represents the 25-75% range while the bars denote the entire range of measurement.  Finally, the interaction between gender and ethnicity [F(1,80)=0.018, p=0.895) was not significant, indicating that Caucasian males, Caucasian females, Chinese males and Chinese females did not differ on the measure of peak compensated static admittance. Comparison between static and dynamic baseline measurements.  Baseline measurements of static and dynamic power absorbance were also compared to each other. The main effect of measurement type [F(1, 87) = 128.851, p<0.001] was significant indicating that estimates of baseline power absorbance differed between static and dynamic measurement modes. Additionally, the interaction between measurement type and frequency [F(15, 1305)=47.941, p<0.001] was significant,  54  showing that the difference in power absorbance estimates between measurement types varied by frequency. Finally, the higher order interaction between measurement type, frequency and ethnicity [F(15, 1305)=5.782, p<0.001] was also significant, indicating that the pattern of variation in power absorbance between measurement types across frequency differed between Chinese and Caucasian subjects. Following a GreenhouseGeisser adjustment for inflated type 1 error, all interactions remained significant. Tukey’s HSD post-hoc analysis was performed to determine which frequency bands differed. Figure 3.14 demonstrates that Caucasian subjects produced significantly lower estimates of power absorbance using the static measurement mode from 250 to 2500 Hz as well as higher estimates of power absorbance using the static measurement mode from 4000 to 5000 Hz. Chinese subjects also showed lower estimates of power absorbance using the static mode of measurement at low frequencies, but for a reduced range of frequencies from 500 to 2500 Hz. They did not produce a difference in estimates at higher frequencies.  55  0.9 0.8 0.7  Power Absorbance  0.6 0.5 0.4 0.3 0.2 0.1 0.0 -0.1 0.25 0.4 0.63 1.0 1.6 2.5 4.0 6.3  0.25 0.4 0.63 1.0 1.6 2.5 4.0 6.3  Frequency (kHz)  Frequency (kHz)  Caucasian  Chinese  Static Dynamic  Figure 3.14. Estimates of baseline power absorbance taken using the static and dynamic modes of measurement in Chinese and Caucasian subjects. Error bars denote the 95% confidence intervals.  56  Comparison of the Current Study’s Baseline Measurements to those of a previous version of REFLWIN and the Mimosa Acoustics RMS-system in Caucasian and Chinese Subjects  The baseline results of the current study were compared to the results of a previous version of the REFLWIN system by using a 2x2x2x15 mixed-model ANOVA with gender, ethnicity and database being the between subject factors and frequency being the within subject factor. An identical analysis was performed to compare the results of the current study to measurements made using the Mimosa Acoustics RMSsystem. The results are discussed below. Static power absorbance.  Comparison between measurements taken with the previous version of the REFLWIN system and the current study. The average static power absorbance and 90% range of the power absorbance measurements across 15 frequency bands (250 Hz, 315 Hz, 400 Hz, 500 Hz, 630 Hz, 800 Hz, 1000 Hz, 1250 Hz, 1600 Hz, 2000 Hz, 2500 Hz, 3150 Hz, 4000 Hz, 5000 Hz, 6300 Hz) taken using the previous version of the Interacoustics REFLWIN system are displayed in figure 3.15. The descriptive statistics for the baseline static power absorbance measurements taken using the previous version of the Interacoustics REFLWIN device are displayed Appendix I. These statistics include the mean power absorbance, minimum power absorbance, maximum power absorbance and the standard deviation and are displayed across the  57  Power Absorbance  1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0  Frequency (kHz) 90% Range  Mean Static Power Absorbance  Figure 3.15. Mean static power absorbance measurements in young adult Caucasian and Chinese subjects taking using an older version of the Interacoustics REFLWIN device (Shaw, 2009). The grey shaded area represents the 90% range of the data.  The main effect of system [F(1,197)=80.18, p<0.000] was significant, indicating that power absorbance differed between the two studies. Additionally, the interaction between frequency and system [F(3.22,634.73)=29.98, p<0.000] was significant, indicating that the variation between studies differed from frequency band to frequency band. The three-way interaction between frequency, gender and system [F(3.22,634.73)=0.20, p=0.907] was not significant showing that the variation between the two estimates of power absorbance across frequency did not differ between male and female subjects. However, the three-way interaction between frequency, ethnicity and system [F(3.22,634.73)=3.18, p<0.021] was significant, showing that this pattern of variation differed between Caucasian and Chinese subjects. All significant results  58  remained significant following a Greehouse-Geisser correction. The frequency, ethnicity, database interaction was further explored using the Tukey’s HSD post-hoc method, the results of which are displayed in figure 3.16. The analysis revealed that Caucasian subjects from the current study had significantly lower power absorbance than their counterparts measured using the older version of the software from 250 Hz – 1600 Hz. Additionally, they showed higher power absorbance at 4000 Hz. Like the Caucasian subjects, Chinese subjects from the current study produced significantly lower estimates of power absorbance from 250 Hz – 1600 Hz, however they did not differ significantly from subjects measured using the older version at 4000 Hz.  59  0.9 0.8  Power Absorbance  0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 -0.1 0.25 0.4 0.63 1.0  1.6  2.5  4.0  6.3  Frequency (kHz)  Caucasian  0.25 0.4 0.63 1.0  1.6  2.5  4.0  6.3  Frequency (kHz)  Chinese  JS Interacoustics SK Interacoustics  Figure 3.16. Comparison of static power absorbance measurements across frequency from the current study to those taken in a previous study using an older version of the Interacoustics REFLWIN device. Error bars denote the 95th percent confidence interval. Ethnic groups are displayed in separate panels.  Comparison between the Mimosa Acoustics RMS-system measurements and the current study. The average static power absorbance and 90% range of the power absorbance measurements across 15 frequency bands (250 Hz, 315 Hz, 400 Hz, 500 Hz, 630 Hz, 800 Hz, 1000 Hz, 1250 Hz, 1600 Hz, 2000 Hz, 2500 Hz, 3150 Hz, 4000 Hz, 5000 Hz, 6300  60  Hz) taken using the previous version of the Interacoustics REFLWIN system are displayed in figure 3.17. The descriptive statistics for the measurements taken using the Mimosa Acoustics RMS-system are displayed in Appendix I for Caucasian females, Caucasian males, Chinese females and Chinese males.Again, these statistics include mean power absorbance, minimum power absorbance, maximum power absorbance and  Power Absorbance  the standard deviation. 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0  Frequency (kHz) 90% Range  Average Static Power Absorbance  Figure 3.17. Mean static power absorbance measurements in young adult Caucasian and Chinese subjects taking using the Mimosa Acoustics RMS System (Shaw, 2009). The grey shaded area represents the 90% range of the data.  The main effect of system [F(1, 195)=6.297, p=0.013] was significant, demonstrating that the estimates of power absorbance from the current study were different from those produced by the Mimosa device. Additionally, the interaction between frequency and system [F(3.05, 595.46)=7.862, p<0.000] was significant, showing that the differences between the two systems differed across the frequency range. The interaction between  61  frequency, gender and system [F(3.05, 595.46)=0.345, p=0.796] was not significant. This means that the variation in power absorbance measures between the two devices did not differ between male subjects or between female subjects in the two studies. Finally, the interaction between frequency, ethnicity and system [F(3.05, 595.46)=2.805, p<0.038] was significant, indicating that the patterns of variation in power absorbance across frequency from the two devices differed within Caucasian subjects from each study as well as within Chinese subjects from each study. Greenhouse-Geisser corrections were applied to account for inflated type 1 error, and all significant effects remained significant post-correction. The frequency, ethnicity, system interaction was further explored using the Tukey’s HSD post-hoc analysis method. Figure 3.18 displays the results of this analysis. The results indicated that Caucasian subjects measured using the current version of the Interacoustics device differed significantly from those measured using the Mimosa device at 5000 Hz. Figure 3.18 shows that Caucasian subjects measured using the Interacoustics device produced higher estimates of power absorbance at this frequency. Chinese subjects measured using each device did not differ significantly at any frequency.  62  0.9 0.8  Power Absorbance  0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 -0.1 0.25  0.4  0.63  1.0  1.6  2.5  Frequency (kHz)  Caucasian  4.0  6.3  0.25  0.4  0.63  1.0  1.6  2.5  4.0  6.3  Frequency (kHz)  Chinese  JS Mimosa SK Interacoustics  Figure 3.18. Comparison of static power absorbance measurements across frequency from the current study to those taken in a previous study using the Mimosa Inc device. Error bars denote the 95th percent confidence interval. Ethnic groups are displayed in separate panels.  Dynamic power absorbance.  The final variable compared between systems was dynamic power absorbance. The average baseline dynamic power absorbance from subjects tested using the older version of the Interacoustics REFLWIN system is displayed in figure 3.19. The descriptive statistics for dynamic power absorbance for these subjects tested are contained in Appendix I. These statistics include mean power absorbance, minimum power absorbance, maximum power absorbance and the standard deviation for Caucasian females, Caucasian males, Chinese females and Chinese males. No comparisons could be made to the Mimosa device as it is currently only capable of performing measurements at ambient pressure.  63  Power Absorbance  1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0  Frequency (kHz) 90% Range  Mean Dynamic Power Absorbance  Figure 3.19. Average dynamic power absorbance measurements in Caucasian and Chinese young adult subjects taken using the older version of the Interacoustics REFLWIN system (Shaw, 2009). The grey shaded area represents the 90% range of the data.  The main effect of system [F(1,196)=11.66, p=0.001] was significant, indicating that the two systems produced differing estimates of dynamic power absorbance. The interaction between frequency and system [F(3.22, 631.87)=7.34, p<0.000] was also significant, showing that the difference between systems varied from frequency to frequency. Neither the interaction between frequency, gender and system [F(3.22, 631.87)=0.35, p=0.807] or the interaction between frequency, ethnicity and system [F(3.22, 631.87)=0.72, p=0.550] was significant, indicating that while estimates of dynamic power absorbance differed between systems and across frequency, the patterns of variation across frequency did not differ between male subjects from each study, between female subjects from each study, between Caucasian subjects from each study or  64  between Chinese subjects from each study. Following Greenhouse-Geisser correction, the frequency, system interaction remained significant. It was further explored using the Tukey’s HSD post-hoc analysis method. This analysis revealed that the two systems differed from 250 Hz – 630 Hz as well as at 4000 Hz. Figure 3.20 demonstrates that subjects from the current study produced significantly lower estimates of dynamic power absorbance from 250 Hz – 630 Hz, but produced higher estimates of dynamic power absorbance at 4000 Hz compared to their counterparts measured using the previous version of the software. 0.9 0.8  Power Absorbance  0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.25  0.4  0.63  1.0  1.6  2.5  4.0  6.3  Frequency (kHz) JS Interacoustics SK Interacoustics  Figure 3.20. Comparison of dynamic power absorbance measurements across frequency from the current study to those taken in a previous study using an older version of the Interacoustics REFLWIN device. Error bars denote the 95th percent confidence interval.  65  Comparisons between Baseline and the Valsalva Manouevre in Caucasian and Chinese Subjects Valsalva manoeuvre dynamic power absorbance.  The dynamic power absorbance measured at tympanometric peak pressure following the performance of the Valsalva manoeuvre is displayed in figure 3.21. The descriptive statistics for measurements taken in this condition across the sixteen frequency bands (250 Hz, 315 Hz, 400 Hz, 500 Hz, 630 Hz, 800 Hz, 1000 Hz, 1250 Hz, 1600 Hz, 2000 Hz, 2500 Hz, 3150 Hz, 4000 Hz, 5000 Hz, 6300 Hz, 8000 Hz) are displayed in Appendix 1 for Caucasian females, Caucasian males, Chinese females and Chinese males. 1.20  Power Absorbance  1.00 0.80 0.60 0.40 0.20  8  6.3  5  4  3.15  2.5  2  1.6  1.25  1  0.8  0.63  0.5  0.4  0.315  0.25  0.00  Frequency (kHz)  Figure 3.21. Dynamic power absorbance measured at tympanometric peak pressure following the Valsalva manoeuvre. The shaded area denotes the 90% range for each frequency.  66  The main effect of condition [F(1, 87)=8.468, p=0.005] was significant, indicating that the estimates of dynamic power absorbance differed between the Valsalva’s manoeuvre and baseline. The interaction between condition and frequency [F(2.48, 215.85)=2.312, p=0.089] was not significant following Greenhouse-Geisser correction,indicating that the differences between baseline and valsalva’s manoeuvre did not vary from frequency band to frequency band. The interactions between condition, frequency and gender [F(2.48, 215.85)=0.374, p=0.733], condition, frequency and ethnicity [F(2.48, 215.85)=0.597, p=0.586] and condition, frequency, gender and ethnicity [F(2.48, 215.85)=0.430, p=0.695] were not significant. This indicates that the variation between conditions did not differ between male and female subjects, Caucasian and Chinese subjects, or between any of the individual gender / ethnicity combinations. GeisserFigure 3.22 demonstrates that while there was a trend towards lower power absorbance following the Valsalva’s manoeuvre, there was not enough separation to provide statistically significant results.  67  0.9 0.8  Power Absorbance  0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.25  0.4  0.63  1.0  1.6  2.5  4.0  6.3  Frequency (kHz) Baseline Valsalva  Figure 3.22. Dynamic power absorbance before and after performing a Valsalva’s manoeuvre. Error bars denote the 95th percent confidence interval.  Valsalva manoeuvre power absorbance tympanometry.  Peak pressure. The average peak pressure of the power absorbance tympanogram following performance of the Valsalva manoeuvre is dislayed in figure 3.23 for each of the four subject groups. The descriptive statistics for the power absorbance tympanogram peak pressure from the post-Valsalva’s manoeuvre condition are contained in Appendix I. The statistics include the mean pressure, minimum pressure, maximum pressure and the standard deviation.  68  120  Peak Pressure (daPa)  100 80 Caucasian Females 60  Caucasian Males  40  Chinese Females Chinese Males  20 0 -20  Figure 3.23. Average peak pressure of the power absorbance tympanogram in four subject groups following performance of the Valsalva manoeuvre. Error bars denote the 95th percent confidence interval of the mean.  The main effect of condition [F(1,87)=47.600, p<0.000] was significant. This indicates that the peak pressure was significantly different following a Valsalva’s manoeuvre compared to baseline. Figure 3.24 shows that the peak pressure was higher (or more positive) following the Valsalva’s manoeuvre compared to baseline.  69  250 200  Pressure (daPa)  150 100 50 0 -50 -100 -150 Baseline  Valsalva  Median 25%-75% Non-Outlier Range  Figure 3.24. Peak pressure of the power absorbance tympanogram before and after performing the Valsalva’s manoeuvre. The boxed area represents the 25-75% range while the error bars denote the entire range of measurement.  The interactions between condition and gender [F(1, 87)=1.732, p=0.192], condition and ethnicity [F(1,87)=1.114, p=0.294] and condition, gender and ethnicity [F(1, 87)=0.456, p=0.501] were not significant. While the overall peak pressure was higher in the Valsalva condition, the magnitude of this variation did not differ between male and female subjects, between Caucasian and Chinese subjects or between Caucasian males, Caucasian females, Chinese males or Chinese females.  Peak power absorbance. The average peak power absorbance of the power absorbance tympanogram measured following performance of the Valsalva manoeuvre is displayed in figure 3.25  70  for Caucasian females, Caucasian males, Chinese females and Chinese males. The descriptive statistics for the peak power absorbance of the power absorbance tympanogram from the Valsalva manoeuvre condition are contained in Appendix I. These statistics include the mean power absorbance, minimum power absorbance, maximum power absorbance and the standard deviation. 0.65  Peak Power Absorbance  0.6 0.55 Caucasian Females 0.5  Caucasian Males  0.45  Chinese Females Chinese Males  0.4 0.35 0.3  Figure 3.25. Average peak power absorbance of the power absorbance tympanogram measured following performance of the Valsalva manoeuvre. Error bars denote the 95th percent confidence interval.  The main effect of condition [F(1, 87)=7.147, p=0.009] was significant, indicating that peak power absorbance was significantly different following the Valsalva’s manoeuvre in comparison to the baseline condition. Figure 3.26 demonstrates that peak power absorbance was significantly lower following the Valsalva’s manoeuvre.  71  0.8  0.7  Power Absorbance  0.6  0.5  0.4  0.3  0.2  0.1 Baseline  Valsalva  Median 25%-75% Non-Outlier Range  Figure 3.26. Peak power absorbance of the power absorbance tympanogram before and after performing the Valsalva’s manoeuvre. The boxed areas represent the 25-75% range while the bars denote the entire range of measurement.  The interactions between condition and gender [F(1, 87)=0.852, p=0.359], condition and ethnicity [F(1, 87)=0.489, p=0.486] and condition, gender and ethnicity [F(1, 87)=0.610, p=0.437] were not significant. This indicates that while overall peak power absorbance was lower following the Valsalva’s manoeuvre, the magnitude of this variation did not differ between male and female subjects, between Caucasian and Chinese subjects or between Caucasian males, Caucasian females, Chinese males and Chinese females.  72  Valsalva manoeuvre 226 Hz tympanometry. Peak Compensated Static admittance (Ytm). Figure 3.27 displays the average peak compensated static admittance of the 226 Hz tympanogram following performance of the Valsalva manoeuvre. The descriptive statistics for the 226 Hz tympanogram from the Valsalva’s manoeuvre condition are displayed in Appendix I. These statistics include mean admittance, minimum admittance, maximum admittance and the standard deviation for Caucasian females, Caucasian males, Chinese females and Chinese males. 0.7 0.6  Ytm (mmho)  0.5 Caucasian Females 0.4  Caucasian Males  0.3  Chinese Females Chinese Males  0.2 0.1 0  Figure 3.27. Average peak compensated static admittance (Ytm) following performance of the Valsalva manoeuvre by four subject groups. Error bars denote the 95th percent confidence interval.  73  The main effect of condition [F(1, 80)=1.375, p=0.244] was not significant. This indicates that the overall peak compensated static admittance was the same before and after performing Valsalva’s manoeuvre. Additionally, the interactions between condition and gender [F(1, 80)=1.445, p=0.233], between condition and ethnicity [F(1, 80)=1.379, p=0.244] and between condition, gender and ethnicity [F(1, 80)=1.447, p=0.232] were not significant. The difference in the peak compensated static admittance between the two conditions did not differ between male and female subjects, between Caucasian and Chinese subjects or between Caucasian females, Caucasian males, Chinese females and Chinese males.  Valsalva manoeuvre 1000 Hz tympanometry. Peak Compensated Static admittance (Ytm). The average peak compensated static admittance of the 1000 Hz tympanogram from the Valsalva manoeuvre condition is displayed in figure 3.28. The descriptive statistics for the post-Valsalva manoeuvre condition are contained in Appendix I. These statistics include the mean admittance, minimum admittance, maximum admittance and the standard deviation for Caucasian females, Caucasian males, Chinese females and Chinese males.  74  6 5  Ytm (mmho)  4 3 2 1  Caucasian Females Caucasian Males Chinese Females Chinese Males  0 -1 -2  Figure 3.28. Average peak compensated static admittance (Ytm) of the 1000 Hz tympanogram following performance of the Valsalva manoeuvre in four subject groups. Error bars denote the 95 percent confidence interval.  The main effect of condition [F(1, 81)=1.730, p=0.192] was not significant. This indicates that the overall peak compensated static admittance was not different after subjects had performed Valsalva’s manoeuvre. Additionally, the interactions between condition and gender [F(1, 81)=1.757, p=0.189], between condition and ethnicity [F(1, 81)=1.123, p=0.293] and between condition, gender and ethnicity [F(1, 81)=1.334, p=0.252] were not significant. The peak compensated static admittance of the 1000 Hz tympanogram did not differ between male and female subjects, between Caucasian and Chinese subjects or between any of the four individual gender / ethnicity combinations before and after Valsalva’s manoeuvre.  75  Comparisons of Baseline to Toynbee’s Manouevre in Caucasian and Chinese Subjects Toynbee manoeuvre dynamic power absorbance.  The dynamic power absorbance measured at tympanometric peak pressure following the performance of the Toynbee manoeuvre is displayed in figure 3.29. The descriptive statistics for Caucasian females, Caucasian males, Chinese females and Chinese males are displayed in Appendix 1. 1.20  Power Absorbance  1.00 0.80 0.60 0.40 0.20  8  6.3  5  4  3.15  2.5  2  1.6  1.25  1  0.8  0.63  0.5  0.4  0.315  0.25  0.00  Frequency (kHz)  Figure 3.29. Dynamic power absorbance measured at tympanometric peak pressure averaged across all subjects following the performance of the Toynbee manoeuvre. The shaded area denotes the 90% range at each frequency.  The main effect of condition [F(1, 87)=2.729, p=0.102] was not significant. This indicates that overall dynamic power absorbance did not differ after performing the 76  Toynbee manoeuvre. However, the interaction between condition and frequency [F(2.85, 248.3)=2.371, p=0.074] was not significant following Greenhouse-Geisser correction, indicating that the variation in dynamic power absorbance did not vary from frequency band to frequency band. The interaction between condition, frequency and ethnicity [F(2.85, 248.3)=0.317, p=0.803] was not significant, showing that the magnitude of variation across frequency did not differ between Caucasian and Chinese subjects. Finally, the interaction between condition, frequency and gender [F(2.85, 248.3)=2.261, p=0.085] was not significant nor was the four-way interaction between condition, frequency, gender and ethnicity [F(2.85, 248.3)=0.554, p=0.637] following GreenhouseGeisser correction. GeisserFigure 3.30 demonstrates that there was a trend towards male subjects showing lower dynamic power absorbance at high frequencies following the Toynbee manoeuvre; however this failed to reach statistical significance. 0.9 0.8  Power Absorbance  0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.25  0.4  0.63  1.0  1.6  2.5  Frequency (kHz)  Female  4.0  6.3  0.25  0.4  0.63  1.0  1.6  2.5  4.0  6.3  Frequency (kHz)  Male  Baseline Toynbee  Figure 3.30. Dynamic power absorbance before and after performing the Toynbee manoeuvre. Error bars denote the 95th percent confidence interval. Genders are displayed in separate panels.  77  Toynbee manoeuvre power absorbance tympanometry.  Peak pressure. The average peak pressure of the power absorbance tympanogram measured following performance of the Toynbee manoeuvre by Caucasian female, Caucasian male, Chinese female and Chinese male subjects is displayed in figure 3.31. The descriptive statistics for these measurements are contained in Appendix I. These statistics include the mean pressure, minimum pressure, maximum pressure and the standard deviation. 0 -20  Peak Pressure (daPa)  -40 -60  Caucasian Females  -80  Caucasian Males  -100  Chinese Females  -120  Chinese Males  -140 -160 -180  Figure 3.31. Mean peak pressure of the power absorbance tympanogram following performance of the Toynbee manoeuvre by four subject groups. Error bars denote the 95 percent confidence interval.  78  The main effect of condition [F(1, 87)=34.059, p<0.000] was significant, indicating that the peak pressure of the power absorbance tympanogram differed following the performance of the Toynbee manoeuvre. Additionally, the interaction between condition and gender [F(1, 87)=5.690, p=0.0192] was significant. This indicates that the magnitude of this pressure change differed between male and female subjects. The interaction between condition and ethnicity [F(1, 87)=9.212, p=0.003] was also significant, indicating that the magnitude of the pressure change between conditions differed between Caucasian and Chinese subjects. Finally, the threeway interaction between condition, gender and ethnicity [F(1, 87)=9.447, p=0.003] was significant. This indicates that peak pressure differed between individual gender / ethnicity combinations. Chinese males produced a significantly more negative shift in pressure following the Toynbee manoeuvre than Chinese females. It can also be seen in figure 3.32 that Chinese males produced a larger shift in the negative direction than Caucasian males did. The other gender / ethnicity combinations did not differ significantly in the shift following the Toynbee manoeuvre.  79  100  50  Pressure (daPa)  0  -50  -100  -150  -200  -250 Female  Male Gender  Baseline Toynbee  Figure 3.32. Peak pressure of the power absorbance tympanogram before and after performing the Toynbee manoeuvre in male and female subjects. The boxed areas represent the 25-75% range while the bars denote the entire range of measurement.  Peak power absorbance. The average peak power absorbance of the power absorbance tympanogram following performance of the Toynbee manoeuvre is displayed in figure 3.33. The descriptive statistics for the peak power absorbance in this condition are contained in Appendix I. These statistics include mean power absorbance, minimum power absorbance, maximum power absorbance and the standard deviation for Caucasian males, Caucasian females, Chinese males and Chinese females.  80  0.7 0.65 Peak Power Absorbance  0.6 0.55 0.5 0.45 0.4  Caucasian Females Caucasian Males Chinese Females Chinese Males  0.35 0.3 0.25 0.2  Figure 3.33. Peak power absorbance of the power absorbance tympanogram in four subject groups following performance of the Toynbee manoeuvre. Error bars denote the 95 percent confidence interval.  The main effect of condition [F(1, 87)=0.961, p=0.330] was not significant, indicating that peak power absorbance did not change following the performance of a Toynbee manoeuvre. Additionally, the interaction between condition and gender [F(1, 87)=0.298, p=0.586] was not significant, indicating that the lack of change between conditions was identical between male and female subjects. The interaction between condition and ethnicity [F(1, 87)=0.075, p=0.784] was not significant. As was the case with genders, the lack of change between conditions was true for both Caucasian and Chinese subjects. Finally, the interaction between condition, gender and ethnicity [F(1, 87)=0.270, p=0.605] was not significant, showing that the lack of change between conditions was true for each of the four gender / ethnicity combinations.  81  Toynbee manoeuvre 226 Hz tympanometry.  Peak Compensated Static admittance (Ytm). The average peak compensated static admittance of the 226 Hz tympanogram obtained following performance of the Toynbee manoeuvre is displayed in figure 3.34 for all four subject groups. The descriptive statistics from this condition are contained in Appendix I. These the statistics include mean admittance, minimum admittance, maximum admittance and the standard deviation for Caucasian females, Caucasian males, Chinese females and Chinese males. 0.8 0.7  Ytm (mmho)  0.6 0.5 0.4  Caucasian Females Caucasian Males Chinese Females Chinese Males  0.3 0.2  Figure 3.34. Average peak compensated static admittance (Ytm) of the 226 Hz tympanogram following performance of the Toynbee maneovure in four subject groups. Error bars denote the 95 percent confidence interval.  The main effect of condition [F(1, 80)=1.545, p=0.218] was not significant, indicating that the overall peak compensated static admittance did not change after the Toynbee manoeuvre had  82  been performed. Additionally, the interactions between condition and gender [F(1,80)=1.492, p=0.226], between condition and ethnicity [F(1, 80)=1.524, p=0.221] and between condition, gender and ethnicity [F(1, 80)=1.487, p=0.226] were not significant. This indicates that the lack of change in peak compensated static admittance after performing the Toynbee manoeuvre was true for both male and female subjects, both Caucasian and Chinese subjects and for Caucasian males, Caucasian females, Chinese males and Chinese females.  Toynbee manoeuvre 1000 Hz tympanometry.  Peak Compensated Static admittance (Ytm). The average peak compensated static admittance of the 1000 Hz tympanogram following performance of the Toynbee manoeuvre is displayed in figure 3.35. The descriptive statistics for this condition are displayed in Appendix I. These statistics include mean admittance, minimum admittance, maximum admittance and the standard deviation for Caucasian females, Caucasian males, Chinese females and Chinese males.  83  2 1.8 1.6  Ytm (mmho)  1.4 1.2 1 0.8  Caucasian Females Caucasian Males Chinese Females Chinese Males  0.6 0.4 0.2 0  Figure 3.35. Average peak compensated static admittance of the 1000 Hz tympanogram following performance of the Toynbee manoeuvre by four subject groups. Error bars denote the 95 percent confidence interval.  The main effect of condition [F(1, 81)=1.512, p=0.222] was not significant. This indicates that the overall peak compensated static admittance of the 1000 Hz tympanogram did not change after subjects performed the Toynbee manoeuvre. Additionally, the interactions between condition and gender [F(1, 81)=1.586, p=0.211], between condition and ethnicity [F(1, 81)=1.431, p=0.235] and between condition, gender and ethnicity [F(1, 81)=1.625, p=0.206] were not significant. This reveals that the lack of change in the peak compensated static admittance of the 1000 Hz tympanogram was true for both male and female subjects, for both Caucasian and Chinese subjects and for Caucasian females, Caucasian males, Chinese females and Chinese males.  84  Discussion This study evaluated both static and dynamic wideband reflectance (WBR) measures in normal hearing subjects. Subjects were divided into groups based on gender and ethnicity, with Caucasian and Chinese subjects comprising the two ethnic groups. Static measurements were evaluated on two components: energy reflectance and power absorbance. Dynamic measurements provided four graphical extractions: dynamic power absorbance, power absorbance tympanometry, 226 Hz tympanometry and 1000 Hz tympanometry. These baseline measures were then compared to the databases of a previous study (Shaw, 2009) which was performed using both a different clinical device as well as a previous version of the Interacoustics REFLWIN system. The REFLWIN system measurements were compared in terms of static and dynamic power absorbance. The comparisons between the current study baselines and the Mimosa system were done only in terms of static measures as the Mimosa device is not capable of performing dynamic measures. Finally, subjects also performed the Valsalva and Toynbee manoeuvres, following which dynamic measurements of wideband reflectance were performed. The difference between each manoeuvre and baseline measurements were analyzed on the same baseline dynamic measurement variables. The discussion section is divided into six sections: baseline measures, system comparisons, Valsalva’s manoeuvre, Toynbee’s manoeuvre, comparison between the Valsalva and Toynbee manoeuvre and clinical application of wideband energy reflectance in the evaluation of Eustachian tube function. The first section, baseline measures, discusses the conclusions drawn from the static and dynamic measures taken on subjects in their natural state and evaluates potential sources of variability introduced by ethnicity and gender. The second section, device comparisons, contains two subsections in which the current version of the  85  Interacoustics REFLWIN system is compared to the Mimosa Acoustics system and the older version of the RELFWIN system respectively. The next two sections, Valsalva’s Manoeuvre and Toynbee’s Manoeuvre, describe the conclusions drawn regarding Eustachian tube function from each manoeuvre and potential sources of variability such as gender and ethnicity. These sections are followed by a discussion comparing the information provided by the two manoeuvres. Finally a discussion is presented supplying the current conclusions regarding the usefulness of wideband energy reflectance in evaluating the status of the Eustachian tube. Baseline Measures Static power absorbance. Baseline static power absorbance measurements produce estimates of power absorbance across sixteen frequency bands. At low frequencies subjects had very low estimates of power absorbance which increased in the mid-frequencies before dropping again to low estimates at high frequencies. Two maxima were observed. The first occurred around 1500 Hz while the second, larger maximum, was found around 4000 Hz. This indicates that the middle ear was most capable of absorbing sound energy in the mid-frequencies and that less of the highest and lowest frequency energy was transmitted through the tympanic membrane. Previous studies of wideband energy reflectance have typically reported static measurements in terms of energy reflectance, not power absorbance (Feeney and Sanford, 2004; Keefe et al.,1993; Sanford and Feeney, 2008; and Voss and Allen, 1994). Figure 4.1 compares the current findings (reported in energy reflectance) to the findings of previous published research evaluating wideband energy reflectance in normal adult subjects.  86  1.20  Current Study 95% Confidence Interval  0.80  Keefe et al. (1993)  0.60  Sanford and Feeney (2008)  0.40  Feeney and Sanford (2004)  0.20  Voss and Allen (1994)  0.00  Current Study 250 315 397 500 630 794 1000 1260 1587 2000 2520 3175 4000 5040 6350 8000  Energy Reflectance  1.00  Frequency (Hz)  Figure 4.1. Static wideband energy reflectance measures in normal adult subjects. Results from the current study are compared to those reported by Feeney and Sanford (2004) [N=40], Sanford and Feeney (2008) [N=21], Keefe et al. (1993) [N=10], and Voss and Allen (1994) [N=10] in equivalent populations. The grey shaded area represents the 95th percent confidence interval of the data from the current study.  As demonstrated by the figure, the baseline results from the current study are comparable with other reports of energy reflectance in the literature. At low frequencies, estimates of energy reflectance are high. These estimates decrease as frequency increases, reaching a minimum around 4000 Hz. Then energy reflectance rises towards 1 again at the highest frequencies. Early studies tended to report their results in terms of energy reflectance and not power absorbance. 87  Comparing between energy reflectance and power absorbance we can see the direct relationship between the two. At the lowest and highest frequencies energy reflectance is high while power absorbance is low. Over the mid-frequency range, where estimates of energy reflectance decrease, corresponding estimates of power absorbance increase. Additionally, the reflectance pattern minima at 1500 Hz and 4000 Hz are mirrored by the power absorbance maxima at the same frequencies. It should be noted that Shahnaz and Bork (2006) noted two minima in their energy reflectance patterns only for Caucasian subjects while the Chinese subjects in their study demonstrated only a single minimum around 4 kHz. The current study observed the dual maxima pattern for both ethnic groups and thus contrasts with the previous study in this regard. Average baseline measurements were also compared to the normative data displayed on the REFLWIN system when measurements are taken. This data is based on the report published by Liu et al. (2008). Figure 4.2 demonstrates this comparison for the static measurement mode.  88  8.0  6.3  5.0  4.0  3.15  2.5  2.0  1.6  1.25  1.0  0.8  0.63  0.5  0.4  0.315  0.25  Power Absorbance  1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0  Frequency (kHz) REFLWIN 95% Range  Mean Static Power Absorbance  Figure 4.2. Static power absorbance measures in healthy subjects. The mean static power absorbance from the current study is compared to the 95% range of the normative data from the Interacoustic REFLWIN system, based on the study by Lui et al. (2008). Error bars denote the 95 percent confidence interval of the mean.  The figure demonstrates that the mean and 95 percent confidence interval of the mean fall well within the range of the normative data provided by the system. Estimates of power absorbance are low at very low and high frequencies with an increase to two distinct maxima in the midfrequency range. It is important for measurements in normal subjects to agree with the provided normative data. This data is intended to be used to visually determine whether an ear might contain pathology. If measurements in confirmed, healthy young subjects fall out of the range of the normative data then it could not be used for this purpose. At most frequencies the dynamic power absorbance measures also agree with the normative data provided by the REFLWIN system (figure 4.3).  89  Power Absorbance  1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0  Frequency (kHz) REFLWIN 95% Range  Mean Dynamic Power Absorbance  Figure 4.3. Dynamic power absorbance measures in healthy subjects. The mean dynamic power absorbance from the current study is compared to the 95% range of the normative data from the Interacoustic REFLWIN system, based on the study by Lui et al. (2008). Error bars denote the 95 percent confidence interval of the mean.  There is one frequency where the average dynamic power absorbance from the current study provides higher estimates of power absorbance than the normative data (6300 Hz).  This may be  due to a difference in probe assembly between the current version of the system and that used by Liu et al. (2008) to provide the normative data. Communication with the manufacturer has indicated that a correction was made to correct faulty wiring in the probe assembly that was causing a decrease in the click stimulus at high frequencies (Interacoustics Inc, personal communication, June 23, 2011). This decreased power would have directly affected the incident power entering the external ear canal and ultimately altered the measurement of power absorbance, resulting in lower estimates of power absorbance at high frequencies. It also interesting to note the difference in the 95 percent range of the normative data between static and 90  dynamic measurement modes. The data in the dynamic condition are more uniform in nature than that of the static condition. In particular the maxima are more distinct and there is less variability at the low end of the range around 1000 Hz. This could arise due to a difference between true middle ear resting pressure and the ambient pressure measurement point of the static measurement mode. The presence of a pressure differential could result in lower estimates of power absorbance at these frequencies, resulting in the larger variability at the low end of the 95 percent range. Since the dynamic measurement mode estimates power absorbance at tympanometric peak pressure it may account for this effect, reducing the variability in the 95 percent range at these frequencies. Despite observing dual maxima patterns in both ethnic groups, there were significant differences between Chinese and Caucasian power absorbance measurements. Chinese females produced higher estimates of power absorbance than Caucasian females at 5000 Hz. Chinese females also produced higher estimates of power absorbance than Chinese males from 4000 – 5000 Hz. Shahnaz and Bork (2006) compared measurements of static energy reflectance in Chinese and Caucasian subjects, but did not observe a significant interaction between frequency, gender and ethnicity. Only their frequency by ethnicity interaction was significant. They reported Caucasian subjects differing significantly from Chinese subjects from 469 – 1500 Hz as well as from 3891 – 6000 Hz. In the low frequencies they noted that Caucasian subjects produced significantly lower energy reflectance than their counterparts while at the high frequencies the Chinese subjects produced lower energy reflectance. Their high frequency observations are consistent with the current study where Chinese females also showed higher power absorbance than Caucasian females (5000 Hz). At low frequencies, however, the current study did not observe a difference between Caucasian and Chinese subjects, in contrast to the  91  observations of Shahnaz and Bork (2006). Shahnaz and Bork (2006) measured wideband energy reflectance using the Mimosa Acoustics RMS system as opposed to the Interacoustics REFLWIN system. Differences in the calibration procedure, the manner in which energy reflectance is calculated by the software or in the physical structure of the probe assembly could underlie this difference. Alternatively, the observation could be rooted in differences in testing technique such as insertion depth of the probe tip or in determining what constitutes a proper versus loose fit. These techniques depend on examiner experience and are not standardized, thereby allowing a potential source of variability into the measurements. Shahnaz and Bork (2006) also reported differences between Caucasian and Chinese subjects on static wideband reflectance measures. They proposed that a difference in body size between ethnicities could in part play a role in observed differences in middle ear measurements. An increase in the size of the middle ear cavity has been demonstrated to decrease energy reflectance below 1000 Hz (Voss et al., 2008). Huang et al. (2000) performed numerous middle ear measurements on twelve different species of exotic cat. As skull size increased, so did the size of the middle ear cavity. Additionally they reported an increase in the compliance of the middle ear cavity as skull size increased. Caucasian individuals are on average taller than Chinese individuals and this could possibly translate to larger middle ear cavities. Shahnaz and Bork (2006) cautioned any direct conclusions, however, as it is impossible to make claims regarding differences in middle ear cavity volumes without taking direct body size indices. This caution remains valid in the current study as such indices were not taken. Size of the middle ear cavity is not the only possible explanation for the observed differences. Small variations in the thickness of the tympanic membrane and the mobility of the ear canal walls could also play a role (Keefe et al., 1993). One final factor could be the associated increase in the mass of the conductive system  92  with increases in body size (Shahnaz, 2008). The effect of such an increase would affect various frequencies of sound differently, lending support to the observation that only certain frequencies differed between ethnic groups.  Dynamic power absorbance. Power absorbance. Like static power absorbance, one of the four graphs produced by a dynamic power absorbance measurement is an estimate of power absorbance across sixteen frequency bands. This differs from the static power absorbance estimate in that the system determines the pressure at which peak absorbance is obtain collapsed across frequency and then provides the estimate of power absorbance across frequency at this pressure point. The observed baseline measurement produced a pattern nearly identical to that of the static measurement: low estimates of power absorbance at very low and very high frequencies with increasing absorbance at mid-frequencies. Even the maxima were identical, with two being observed: the first around 1500 Hz and the second larger maxima around 4000 Hz. Unlike static power absorbance, however, the frequency by gender by ethnicity interaction was not significant for dynamic power absorbance. The lower order interaction between frequency and ethnicity was significant. Figure 3.7 demonstrates that Caucasians produced significantly higher absorbance from 800 – 1250 Hz while Chinese subjects produced significantly higher absorbance at 5000 Hz & 8000 Hz. Shahnaz and Bork (2006) also noted significantly lower estimates of energy reflectance for Caucasian subjects from 469 – 1500 Hz. Based on the relationship between PA and ER it is evident that the current study agrees with this observation. The middle ears of Caucasian subjects absorb a significantly larger  93  proportion of sound energy at these frequencies than Chinese subjects. The high frequency finding also agrees with the Shahnaz and Bork (2006) report which demonstrated significantly lower energy reflectance in Chinese subjects from 3891 – 6000 Hz. It was also observed that female subjects produced higher estimates of power absorbance at 5000 Hz than their male counterparts (figure 3.6). Shahnaz and Bork (2006) also reported a significant frequency by gender interaction for their measures of static energy reflectance; however, they did not specify the frequencies at which these differences occurred. The degree to which the two studies agree cannot be determined, but both studies reported a difference in power absorbance and energy reflectance patterns across frequencies between male and female subjects. It should be noted that the dynamic measurement revealed a difference between ethnicities at low frequencies which was not elucidated by the static measurements. Such a finding could be explained by the difference in resting pressure noted by Shahnaz and Davies (2006) between Caucasian and Chinese subjects. They observed that Caucasian subjects had a more negative resting pressure than their Chinese counterparts. The ambient pressure measurement of the current study static measure could have been sufficiently far off the resting pressure for Caucasian subjects to abolish the difference between ethnicities. The dynamic measure may have accounted for this difference in resting pressures, thereby revealing the effect of ethnicity. The benefits of a dynamic measurement might also become more apparent in pathological states where the reported resting pressure point could vary considerably from ambient pressure. In such a scenario the dynamic measurement might provide an indication of the difference between the way sound enters the pathological middle ear at optimal external ear canal pressure versus the way it enters the pathological middle ear at ambient pressure. 94  Power absorbance tympanometry. Power absorbance tympanometry collapses power absorbance across frequency and graphs the resultant power absorbances across the pressure range. The mean peak pressure across all four groups was -24.74 daPa while the mean peak power absorbance was 0.52. No differences were found between any of the groups, either for the pressure at which the peak absorbance occurred or the magnitude of the peak absorbance. By collapsing power absorbance across frequency a less detailed view of energy transmission into the middle ear results compared to the information provided through energy reflectance and power absorbance measurements. As such, it appears that power absorbance tympanometry is not a sensitive indicator of differences that exist between ethnic groups. Collapsing measures across frequencies conceals frequency-specific differences between ethnic groups, which are small in comparison to the large variations seen in the power absorbance patterns. Diagnostically power absorbance tympanometry retains the potential to indicate pathology in the same manner as tympanometry: drastic departures from the expected normal values could indicate pathology. For example, extreme shifts in peak pressure may occur in the presence of middle ear pressure. This would need to be explored by comparing measurements in subjects with confirmed pathology to determine normative data for these measures. 226 Hz tympanometry. The REFLWIN system extracts a 226 Hz tympanogram from the dynamic power absorbance measure. The average tympanometric peak pressure for all four groups combined was -26.36 daPa while the average peak compensated static admittance was 0.44 mmho. Chinese subjects produced significantly lower estimates of peak compensated static admittance  95  with an average peak compensated static admittance of 0.36 mmho compared to the 0.56 mmho average produced by Caucasian subjects. These findings are comparable to those of Shahnaz and Davies (2006) who reported average peak compensated static admittances of 0.79 mmho and 0.58 mmho for Caucasian and Chinese subjects, respectively. Shahnaz and Bork (2008) also reported significantly lower peak compensated static admittance in Chinese subjects compared to Caucasian subjects. Previous research has also demonstrated smaller ear canal volume for Chinese subjects compared to Caucasian subjects (Shahnaz and Davies, 2006; Shahnaz and Bork, 2008). Huang et al. (2000) showed that as skull size increased, so did the size of the middle ear cavity. Additionally they noted an increase in the compliance of the middle ear cavity as skull size increased. Caucasian individuals are on average taller than Chinese individuals and this could possibly translate to larger middle ear cavities. As previously mentioned, Shahnaz and Bork (2006) caution any direct conclusions without measuring body size indices. That said, differences in the size of these structures could affect absorption of sound energy into the middle ear represented by peak compensated static admittance. The size of the outer and middle ears is not the only possible explanation for the observed differences. Small variations in the thickness of the tympanic membrane and the mobility of the ear canal walls could also play a role (Keefe et al., 1993). A final factor could be the associated increase in the mass of the conductive system with increases in body size (Shahnaz, 2008). In contrast, tympanometric peak pressures published by Shahnaz and Davies (2006) were considerably closer to 0 daPa than those reported here. Investigations of ethnic effects on TPP have yielded mixed results in past studies: Shahnaz and Davies (2006) reported a significant effect of ethnicity, where TPP was more positive among Chinese subjects in compared to Caucasian subjects. However, Shahnaz and Bork (2008) investigated TPP using two clinical  96  tympanometers (the Grason-Stadler Inc.-33 and the Virtual 310 system) and did not find a significant effect of ethnicity using either device; the current study also did not find a significant effect of ethnicity.  Neither of the previous studies by Shahnaz and Bork (2006, 2008) found a  significant effect of gender on tympanometric peak pressure, which was replicated in the current study. Tympanometric peak pressure is the pressure value measured at the point of greatest admittance. The admittance peak is expected to occur when the pressure in the external canal is equal to that of the middle ear, thereby allowing the greatest movement of the tympanic membrane. TPP is an indirect estimate of middle ear pressure. A difference in middle ear pressure could be related to Eustachian tube function, as the Eustachian tube plays a role in maintaining this pressure. However, no significant differences were measured between genders or ethnicities in the current study, no further conclusions can be drawn regarding Eustachian tube function between these groups. 1000 Hz tympanogram. The 1000 Hz tympanogram is extracted by the REFLWIN system in the same manner as the 226 Hz tympanogram. As was the case for the 226 Hz tympanogram there were significant effects for peak compensated static admittance. Chinese subjects produced significantly lower estimates of peak compensated static admittance with a mean Ytm of 0.72 mmho compared to the mean Ytm of 1.12 mmho found in Caucasian subjects. Previous work with multi-frequency tympanometry has revealed lower SA at 1000 Hz in Chinese subjects (Shahnaz and Davies, 2006). However, this effect was only significant within female subjects. The equivalent comparison between male subjects was non-significant. The current study collapsed data across gender as there were no significant differences between Caucasian females, Caucasian males, Chinese females or Chinese males specifically. As mentioned for the 226 Hz tympanogram, 97  such differences could relate to anatomical differences between the ethnic groups. Size and mass of the tympanic membrane and conductive system should impact the transmission of the 1000 Hz probe tone in a similar manner to the 226 Hz probe tone.  Comparison between Static and Dynamic measurement modes. Baseline measures of power absorbance were compared between static and dynamic measurement modes. Significantly lower estimates of power absorbance were produced in both Caucasian and Chinese subjects at low frequencies while measuring at ambient pressure compared to measurement at tympanometric peak pressure. Additionally, Caucasian subjects demonstrated slightly higher estimates of power absorbance using the static method of measurement from 4000 to 5000 Hz. These observations are consistent with the measurements reported by Liu et al. (2008), who also demonstrated lower estimates of power absorbance at low frequencies and higher estimates at high frequencies when measuring at ambient pressure. They postulated that this difference could arise due to a residual positive pressure present in the external ear canal in the ambient measurement state. This pressure would arise due to the compression of air that occurs when the probe tip is inserted into the ear. They note that this impact would not affect clinical use of the measurements as these effects would be shared by both healthy and pathological ears. The difference in these effects between Chinese and Caucasian subjects could be related to differences in the resting pressure of the middle ear between ethnic groups. Chinese individuals have been demonstrated to show higher (more positive) tympanometric peak pressure compared to their Caucasian counterparts (Shahnaz and Davies, 2006). A more positive middle ear pressure would result in closer agreement between the pressures in the outer and middle ears when the positive pressure in the external canal is 98  introduced due to insertion of the probe tip. As such, the ambient pressure measurement would be closer to tympanometric peak pressure and should result in fewer differences compared to the dynamic measurement which occurs at tympanometric peak pressure, consistent with the current observations. There is a noticeable difference between the 90% ranges of the baseline static and dynamic power absorbance measurements (Figure 4.4). 1.20  Power Absorbance  1.00 0.80  Dynamic 90% Range  0.60  Static 90% Range  0.40  Baseline Dynamic Power Absorbance  0.20  Baseline Static Power Absorbance 8  6.3  5  4  3.15  2.5  2  1.6  1.25  1  0.8  0.63  0.5  0.4  0.315  0.25  0.00  Frequency (kHz)  Figure 4.4. Baseline static and dynamic power absorbance across frequency. The lighter shaded region represents the 90% range of the static measurement while the darker shaded area represents the 90% range of the dynamic measurement.  The above figure demonstrates that the 90% range of the dynamic measurement is significantly higher than that of the static measurements in the low to mid frequency region. The lower bound  99  data also reveal that the lower bound of the 90% range for the static measurements is significantly lower than that of the dynamic measurements in the same region. This suggests that the normative region for each measure differs. As a result the implication is that in clinical practice it would be appropriate to use separate sets of normative data for each measurement.  System Comparisons Baseline static and dynamic power absorbance measurements taken in the current study were compared to the same measurements taken using an older version of the REFLWIN device and the Mimosa Acoustics RMS system. Static power absorbance estimates in Caucasian and Chinese subjects were significantly lower using the current version of the software from 250 – 1600 Hz compared to measurements from the older version of the REFLWIN system. Additionally, for Caucasian subjects only, estimates of static power absorbance were higher at 4000 Hz in the current version of the software. The Mimosa Acoustics system differed from the current version of the REFLWIN system only at 5000 Hz in Caucasian subjects where the current version of REFLWIN produced higher estimates of power absorbance. Finally the two versions of the REFLWIN system differed from 250 – 630 Hz and again at 4000 Hz on measures of dynamic power absorbance with the current version producing lower estimates of power absorbance at lower frequencies and higher estimates at 4000 Hz. There are a few explanations as to why such differences were observed. One of the changes between the older and current versions of the REFLWIN system was an upgrade to the probe assembly. Changes in this structure could account for the differences in measurement. However, the manufacturer states that the only changes made to the probe assembly were to  100  correct faulty wiring which was causing a decrease in the magnitude of the click stimulus at high frequencies (Interacoustics Inc, personal communication, June 23, 2011). It seems unlikely that this change would result in the low frequency differences that were observed. A more likely explanation lies in the compression of the volume of air in the middle ear that occurs when the probe is inserted. Liu et al. (2008) also noted higher estimates of power absorbance at low frequencies and lower estimates of power absorbance at high frequencies in their comparison of dynamic to static measures of power absorbance. They conducted their study using a prototype version of the REFLWIN system. They suggested that the insertion of the probe tip into the ear compressed the volume of air present in the external ear canal. This resulted in a positive pressure remaining in the canal during the ambient pressure measurements. In contrast the dynamic measurement would extract the power absorbance measurement at tympanometric peak pressure (usually at or near 0 daPa). The existence of positive pressure in the canal during ambient pressure measurements would be expected to decrease power absorbance at low frequencies and increase power absorbance around 4000 Hz (Liu et al., 2008). They suggested that this difference could be countered by having the device manually set the pressure to 0 daPa in the ear canal prior to ambient pressure measurements. Such a change has been implemented in the newer version of the REFLWIN system (Doug Keefe, personal communication, June 27, 2011). The pattern observed in the current study indicates the presence of a potential positive pressure effect. The current version of the REFLWIN system produced a pattern similar to that observed by Liu et al. (2008) with lower power absorbance produced by the current version at low frequencies and higher power absorbance around 4000 Hz. This suggests that the ear canal pressure was more positive in subjects measured in the current system compared to those of the previous study.  101  The differences observed between the current and older versions of the REFLWIN system were also observed by Shaw (2009) when comparing between the older version of the REFLWIN system and the Mimosa system. The latest version now provides much more comparable estimates of power absorbance to those produced by the Mimosa system. The remaining differences between the current version of the REFLWIN system and the Mimosa Acoustics system could be attributed to differences in the calibration of the devices, the estimation of ear canal area or differences in the type of probe tip used to seal the ear canal. The Mimosa Acoustics system uses a four-chamber calibration technique in comparison to the twotube system of the REFLWIN device. Keefe et al. (1992) have demonstrated that two tubes are sufficient to determine all Thevenin parameters used in the calculation of energy reflectance, although they admit that the use of more than two tubes could result in more robust estimates. Alternatively differences could arise in the manner in which ear canal area is estimated by the two systems. The REFLWIN system uses an average estimate of the human ear canal diameter in all calculations of energy reflectance. In contrast the Mimosa Acoustics system determines ear canal area by using an ear canal diameter associated with the size of probe tip used in the measurement (Shaw, 2009). The probe tip size is selected by the clinician to best fit each subject’s ear and then indicated in the user interface of the computer system. A difference in the ear canal area estimated by the system would in turn result in differing estimates of energy reflectance. Finally, the probe tips also differ between the devices. The REFLWIN system uses different sized rubber tips to seal the ear canal, allowing the manipulation of the ear canal pressure. In contrast the Mimosa Acoustics system, which does not offer pressurized measurements, uses foam tips. Ideally wideband reflectance systems produced by different manufacturers should produce comparable estimates. This facilitates comparison between older  102  and new measurements taken on different machines. These situations often arise when subjects transfer from clinic to clinic or are referred on for further evaluation at another center. If the different devices produce comparable baseline estimates, then clinicians can confidently state that any observed changes are attributable to changes in the state of the middle ear as opposed to differences between measuring devices. Valsalva’s Manoeuvre Dynamic power absorbance. Dynamic power absorbance was measured after subjects had performed a Valsalva manoeuvre. This measurement was compared to the baseline measures that had been performed prior to the manoeuvre. While the main effect of condition was significant indicating a difference in power absorbance between the baseline and test conditions, post hoc analyses failed to identify any specific frequency bands as different following the physical manoeuvre. As can be seen in Figure 3.22, there was a trend towards lower power absorbance following the manoeuvre across a broad range of frequencies; however the effect was not large enough to reach statistical significance. A larger difference had been predicted prior to the onset of the study as the Valsalva manoeuvre typically introduces significant positive pressure into the middle ear (Stenstrom et al., 1991). Such positive pressure was indeed achieved in the current study as indicated by the large shift in the peak pressures noted in the power absorbance tympanogram (figure 3.23). However, the introduction of such positive pressure does not seem to have significantly altered the flow of sound energy into the middle ear. A possible explanation for the lack of effect lies in the way this measurement is taken. The REFLWIN system extracts the dynamic power absorbance graph by charting power absorbance across frequency at the pressure corresponding to the peak power absorbance of the power absorbance tympanogram. 103  For healthy subjects we would expect the baseline measurement to be fairly close to ambient pressure. For the Valsalva manoeuvre condition we would expect the measurement to be extracted a positive pressure. However, this pressure point is the point at which the greatest amount of sound energy is able to enter the middle ear as tympanometric peak pressure is the point at which the tympanic membrane moves most easily. By selecting this point, the system is essentially negating the effect of pressure build up in the middle ear cavity and this likely resulted in similar estimates of power absorbance. Future studies could choose to evaluate this effect using static measurements instead of dynamic ones. By measuring at ambient pressure regardless of middle ear pressure this confound could be avoided. To explore this potential the difference between baseline static and dynamic power absorbance measures was calculated and the average post-Valsalva dynamic power absorbance adjusted by this value (Figure 4.5).  104  0.80  Power Absorbance  0.70 0.60 0.50 0.40 0.30  Adjusted Valsalva  0.20  Static Baseline  0.10 0.00  Frequency (kHz)  Figure 4.5. Adjusted post-Valsalva manoeuvre dynamic power absorbance compared to baseline static power absorbance. The post-Valsalva manoeuvre data was adjusted by subtracting the difference between baseline static and dynamic power absorbance.  The adjusted data displayed is also nearly identical to the original results obtained using the dynamic measurement. However, this ex post facto method of adjustment is insufficient as the effects of the positive middle ear pressure have been reduced by the method of measurement. As such, this attempt also likely to underestimate the effect of positive pressure that could have been viewed by running the measurements in static mode. Power absorbance tympanometry. As previously mentioned, a significant positive shift in the peak pressure of the power absorbance tympanogram was noted after the Valsalva manoeuvre had been performed. Such a pressure change had been expected as previous investigations of the Valsalva manoeuvre have reported significant increases in middle ear pressure post-manoeuvre (Stenstrom et al., 1991).  105  This effect, however, was only true between conditions and did not differ between gender or ethnic groups. Thus there seems to have been no difference in the amount of pressure introduced into the middle ear by the manoeuvre between subject groups as indicated by the power absorbance tympanogram pressure shift. Previous research has generally considered shifts of at least 10 daPa to be indicative of a successful manoeuvre (Jonathan et al., 1986). Such shifts were achieved by the majority subjects in the current study, with 66 out of 91 ears achieving at least this 10 daPa shift. This provides a specificity of 0.73 for the 10 daPa cut-off criterion. The decrease in specificity from 1.0 can be explained by a large variation in pressure change. Some subjects very easily transmitted pressure to the middle ear via the Valsalva manoeuvre, while others reported difficulty doing so. Unlike peak pressure, a significant decrease in peak absorbance was noted following the Valsalva’s manoeuvre (figure 3.24). This indicates a reduction in the amount of sound energy across frequency that was able to enter the middle ear once the pressure had been introduced to the middle ear. There were no differences between genders or ethnic groups for this variable. 226 Hz tympanometry. There was no difference in the peak compensated static admittance of the 226 Hz tympanogram before and after subjects performed the Valsalva manoeuvre. The average peak compensated SA in the baseline condition was 0.44 while the average peak compensated SA post-manoeuvre was 1.40. The difference between values did not reach significance. This indicates that the introduction of pressure into the middle ear did not drastically alter the transmission of the 226 Hz probe tone into the middle ear.  106  1000 Hz tympanometry. There was no difference between the peak compensated static admittance of the 1000 Hz tympanogram between the baseline and Valsalva manoeuvre conditions. The average peak compensated SA in the baseline condition was 1.23 mmho while the average peak compensated SA in the Valsalva condition was 4.31 mmho. However, there was considerable variability on this measure, especially in the Valsalva manoeuvre condition as indicated by the standard deviation. The variability at baseline was considerably less than post-manoeuvre suggesting that the introduction of positive pressure has an unpredictable effect on the peak compensated SA, resulting in great variation in the magnitude of the change.  Toynbee’s Manoeuvre Dynamic power absorbance. Dynamic power absorbance was also measured after subjects had performed a Toynbee manoeuvre. Again, this measurement was compared to the baseline measures that had been performed prior to the manoeuvre. There was no significant difference in dynamic power absorbance between the baseline and the Toynbee manoeuvre conditions. Figure 3.30 demonstrates that there was a trend towards lower power absorbance at high frequencies postmanoeuvre in male subjects only. However, as this did not reach statistical significance we cannot draw conclusions. The Toynbee manoeuvre typically produces a biphasic pressure wave in the middle ear with a positive pressure deflection followed by a negative deflection (Elner et al., 1971). As WBR is measured following the manoeuvre, we would expect a negative pressure to be introduced into the ear. This shift in pressure was observed in the current study by the  107  change in the peak pressure of the power absorbance tympanogram but the pressure did not significantly alter the dynamic power absorbance measure. This lack of effect may have occurred for the same reason discussed for the lack of effect observed following the Valsalva manoeuvre. Following the Toynbee manoeuvre we would expect the system to extract the dynamic power absorbance measurement at tympanometric peak pressure which is expected to be negative. This corresponds to the pressure point at which the greatest amount of sound energy is able to enter the middle ear. As was mentioned before, by selecting this point the system is essentially negating the effect of pressure build up in the middle ear cavity which could result in the near identical estimates of power absorbance. As was the case with the Valsalva manoeuvre analysis, an adjustment was attempted for the Toynbee manoeuvre by subtracting the baseline static power absorbance from dynamic power absorbance and applying this correction to the post-Toynbee manoeuvre data. Figure 4.6 displays the results.  108  0.80  Power Absorbance  0.70 0.60 0.50 0.40 0.30  Adjusted Toynbee  0.20  Static Baseline  0.10 0.00  Frequency (kHz)  Figure 4.6. Adjusted post-Toynbee manoeuvre dynamic power absorbance compared to baseline static power absorbance. The post-Toynbee manoeuvre data was adjusted by subtracting the difference between baseline static and dynamic power absorbance.  As was the case in the Valsalva manoeuvre analysis, the post-adjustment data is qualitatively similar to the original dynamic power absorbance data and little difference is observed between baseline and post-manoeuvre power absorbance curves. Again, since the original data was gathered using the dynamic mode, the effect of the negative pressure is not represented in the adjusted data. As a result the analysis likely underestimates any effects that could be observed by running the original measurements in static mode. Power absorbance tympanometry. There was a significant change in the peak pressure of the power absorbance tympanogram after the Toynbee manoeuvre had been performed. The average peak pressure across all groups in the baseline condition was -24.74 daPa while it was -64.55 daPa in the 109  Toynbee manoeuvre condition. Such a shift in peak pressure is consistent with previous observations of middle ear pressure following the Toynbee manoeuvre. Both Uzun et al. (2004) and Elner et al. (1971) recorded significant negative shifts in middle ear pressure after their subjects had performed the Toynbee manoeuvre. The magnitude of this pressure shift differed between various gender and ethnic groups. Chinese males in particular produced a much larger negative shift than their counterparts. They produced statistically larger shifts than both Chinese females and Caucasian males. The larger negative shifts in middle ear pressure in Chinese subjects following the Toynbee manoeuvre could potentially be related to differences in Eustachian tube function. Since the Toynbee manoeuvre functions in a physiological manner, the natural variations in Eustachian tube function should be portrayed in the results. If the Eustachian tubes of Chinese subjects are more easily convey pressure changes between the middle ear cavity and the rhinopharynx, as indicated by the greater shift in peak pressure, this could in turn play a role in the observed differences in the prevalence of middle ear pathology such as otitis media with effusion (Williams et al., 1994; Tong et al., 2000). Since the Eustachian tubes in Chinese subjects demonstrate an increased patency, they could in turn provide better protection by more easily eliminating extreme pressure and transporting secretions as well as by demonstrating an increased resistance to obstruction. As with the Valsalva manoeuvre, previous researchers have generally considered a shift of at least 10 daPa to indicate a successful Toynbee manoeuvre (Jonathan et al., 1986). Such shifts were achieved by the majority of subjects in the current study with 75 of 91 ears reaching the cut-off. This provides a specificity of 0.82. As was observed with the Valsalva manoeuvre, there was significant variability in the pressure introduced to the middle ear by the Toynbee manoeuvre. Some subjects very easily transmitted pressure to the middle ear while others reported difficulty doing  110  so. This may explain why not all subjects were able to reach the designated criterion for a significant shift. Peak power absorbance, on the other hand, did not differ between the baseline and Toynbee manoeuvre conditions. The baseline mean power absorbance was 0.52 while the Toynbee manoeuvre mean power absorbance was 0.51. The introduction of negative pressure to the middle ear space does not seem to have drastically altered the transfer of sound energy into the middle ear, at least at peak pressure. It is possible that the negative pressure could have introduced changes at off-peak pressures; however this aspect of the tymanogram was not explored in the current study. The lack of difference was true for both genders and for both Caucasian and Chinese subjects. This contrasts with the results of the Valsalva manoeuvre where a significant reduction was observed post-manoeuvre. It is unclear why the presence of positive pressure would have an impact while the presence of negative pressure did not. Beers et al. (2010) reported significant impact on low frequency energy reflectance from 400 Hz to 1800 Hz with the introduction of negative pressure. They attributed this change to an increase in the stiffness of the middle ear system. As such we might expect the presence of negative pressure to reduce the amount of energy entering the middle ear cavity. There are a few possible explanations as to why this was not the case. First, the power absorbance tympanogram is created by averaging absorbance across a broad range of frequencies from 380 Hz to 2000 Hz (Liu et al., 2008). This averaging could potentially mask changes that were evident only at a smaller subset of frequencies. However, given that no individual frequencies were significant in the dynamic power absorbance measurement this explanation is unlikely. It is also possible that the amount of negative pressure introduced to the middle ear by the current subjects was not sufficiently large enough to affect the dynamic power absorbance measures. Beers et al. (2010)  111  defined mild negative pressure ranging from -100 to -199 daPa. This is considerably more negative than the average shift produced by the current subjects after performing the Toynbee manoeuvre. It is also possible that the great variability present in the magnitude of the pressure that introduced into the middle ear cavity by the manoeuvre underlies the lack of observed effect. While the shift was at least 10 daPa in 75 out of 91 ears, some subjects barely made this criterion while others greatly exceeded it. Additionally, due to the biphasic nature of the pressure wave created by the Toynbee manoeuvre, it is possible to introduce positive pressure into the middle ear rather than negative pressure if the Eustachian tube opens during the positive part of the pressure fluctuation. The observed result combines the effects of all individual subjects, regardless of whether or not they introduced positive or negative pressure into the middle ear (Elner et al., 1971). Future studies employing this technique may wish to restrict their analysis to subjects who introduce negative pressure only.  226 Hz tympanometry. The current data did not demonstrate a significant difference in the peak compensated static admittance of the 226 Hz tympanogram compared between baseline and Toynbee manoeuvre conditions. The mean peak compensated SA across all subjects was 0.44 mmho in the baseline condition and 1.31mmho in the Toynbee manoeuvre condition. This lack of difference was true for both genders and both Chinese and Caucasian subjects. This finding indicates that the transmission of the 226 Hz probe tone into the middle ear was not significantly impacted by the presence of negative pressure. As was discussed for power absorbance tympanometry, it is possible that off-peak effects were created by the negative pressure, but this aspect of the tympanogram was not evaluated in the current study. 112  1000 Hz tympanometry. There was no significant difference in the peak compensated static admittance of the 1000 Hz tympanogram between conditions. The mean peak compensated static admittance across all subjects was 1.23 mmho in the baseline condition and 4.59 mmho in the Toynbee manoeuvre condition As was the case with the Valsalva manoeuvre, significant variability was present in the peak compensated static admittance of the 1000 Hz tympanogram post-manoeuvre (table 3.12). This is demonstrated by the particularly large standard deviations listed in the descriptive statistics. Thus it seems that the introduction of pressure into the middle ear has an unpredictable effect on the transmission of the 1000 Hz probe tone. It is possible that the peak compensated static admittance is dependent on the magnitude of the pressure shift and alters significantly with small changes in this magnitude.  Comparison between Toynbee Manoeuvre and Valsalva Manoeuvre Both the Toynbee manoeuvre and Valsalva manoeuvre performed as expected in the current study. The Valsalva manoeuvre shifted the middle ear pressure in the positive direction as Stenstrom et al. (1991) described while the Toynbee manoeuvre shifted the middle ear pressure in the negative direction as indicated by Elner et al. (1971). These effects were confirmed by the shifting of peak pressure of the power absorbance tympanogram. Subjects were successfully able to alter middle ear pressure by exercising the Eustachian tube. Significant variability was noted in magnitude of the pressure shift for both post-Valsalva and post-Toynbee manoeuvre data. In contrast, significantly less variability was present in the baseline data. This  113  is consistent with previous observations of variability in Valsalva and Toynbee manoeuvre recordings (Bunne et al., 2000a; Williams, 1975). Anecdotal evidence from data collection reveals that while some subjects were able to apply pressure to the ears via the manoeuvres with great ease, others reported significant difficulty in manipulating the middle ear pressure through either manoeuvre. This variability in subject ability to perform the required manoeuvres is the reason researchers have had difficulty in devising a simple and effective test of Eustachian tube function. Neither manoeuvre drastically altered the dynamic power absorbance measures compared to baseline, despite confirmed pressure changes in the middle ear cavity. For the manoeuvre conditions we would expect the system to extract dynamic power absorbance at a negative tympanometric peak pressure for the Toynbee manoeuvre or a positive tympanometric peak pressure for the Valsalva manoeuvre. However, regardless of negative or positive pressure, the system selects the pressure point at which the greatest amount of sound energy is able to enter the middle ear as tympanometric peak pressure is the point at which the tympanic membrane moves most easily. By selecting this point, the system is essentially negating the effect of pressure build up in the middle ear cavity and this likely resulted in similar estimates of power absorbance. Finally, differences between Caucasian and Chinese subjects were noted following the Toynbee manoeuvre but were not present in the Valsalva manoeuvre data. Specifically, there were significant differences in the amount of negative pressure introduced to the middle ear following the Toynbee manoeuvre with Chinese subjects producing larger negative shifts than their Caucasian counterparts. One reason why no ethnic effects were present in the postValsalva manoeuvre data may be due to the comparative mechanisms by which the manoeuvres operate. The Valsalva manoeuvre is a non-physiological act. Pressure is accumulated in the  114  rhinopharynx when a subject closes his or her nose and blows with force. When sufficient pressure builds up it overcomes the closing forces of the Eustachian tube and the pressure is transmitted to the middle ear cavity. On the other hand, the Toynbee manoeuvre acts in a physiological manner. The Eustachian tube is opened by natural mechanisms when the subject swallows. It is possible that differences in Eustachian tube function related to ethnicity are overshadowed by the non-physiological nature of the Valsalva manoeuvre, whereas the natural motions of the Toynbee manoeuvre preserve these differences. It is also possible that not all subject properly performed the manoeuvres correctly, which could also have impacted the measurement of any ethnic differences.  Clinical Application of Wideband Energy Reflectance in the Evaluation of Eustachian Tube Function A number of wideband reflectance variables were evaluated for their potential use in the assessment of Eustachian tube function. All variables were evaluated following alteration of the subjects’ middle ear pressure using the Valsalva manoeuvre and the Toynbee manoeuvre. Dynamic power absorbance was not significantly altered from baseline measurements after either of the physical manoeuvres. Additionally, neither peak compensated static admittance of the 226 Hz and 1000 Hz tympanograms nor the peak power absorbance of the power absorbance tympanogram were altered following either of the manoeuvres. As such, these variables fail to provide significant information that could be used to distinguish pathological ears from normal ears. In contrast, the pressure corresponding to the peak power absorbance of the power absorbance tympanogram was significantly altered following the physical manoeuvres. Previous research has suggested a cut-off criterion for normal ears as a change of at least 10 daPa 115  (Jonathan et al., 1986). Using this criterion, the current data has revealed specificities of 0.73 and 0.82 for the Valsalva and Toynbee manoeuvres, respectively. As previously mentioned, the Toynbee manoeuvre provides insight into the physiological functioning of the Eustachian tube while the Valsalva manoeuvre is non-physiological in nature. As such the Toynbee manoeuvre provides a more likely candidate for evaluation of Eustachian tube function as its physiological state is of great interest to clinicians. The Toynbee manoeuvre’s candidacy for this test is further augmented by the stronger specificity indicated by the current measures. At this point, however, measures of wideband reflectance fail to reveal any information regarding Eustachian tube function that is not provided by conventional tympanometry measures. There is one aspect of wideband reflectance measurements that continues to have potential use as a test of Eustachian tube function. Evaluation using static measures of power absorbance could provide information that is not present in dynamic measures, due to the manner in which the REFLWIN system extracts dynamic power absorbance from the bandpass tympanometric peak pressure from 380 Hz to 2000 Hz. Future studies will need to assess this potential before wideband reflectance is completely ruled out as a method for assessing Eustachian tube function.  Limitations of the Current Study and Directions for Future Research There were a few limitations to the current study. Body size indices were not taken, and therefore it is impossible to conclude whether body size and middle ear cavity volume truly differed between the test groups. The extent of pressure change was not monitored when subjects performed the Valsalva and Toynbee manoeuvres. Some subjects perform the manoeuvres very easily while others did not produce a measureable effect. We cannot account for the individual effort each subject applied to performing the manoeuvres or the ability of the 116  subjects to perform the manoeuvres correctly. It was sometimes also difficult to maintain a seal in the external ear canal with the probe tip after subjects had performed the physical manoeuvres. Care had to be taken to physically hold the probe in place for some subjects. Finally, the current study did not evaluate the three dimensional pattern of reflectance across pressure, an option provided by the REFLWIN system. Future studies may wish to investigate this feature more thoroughly. It may provide a potential avenue for information regarding baseline reflectance patterns as well as changes following the Valsalva and Toynbee manoeuvres that measurement of dynamic power absorbance at tympanometric peak pressure does not. Finally, future researchers may also wish to consider evaluating post-manoeuvre states using static energy reflectance as opposed to dynamic measures. Evaluating energy reflectance at 0 daPa may provide information that comparisons at tympanometric peak pressure do not.  117  Conclusion The current study had four main goals: (i) to compare the effectiveness of the REFLWIN Interacoustics (Eclipse System-v.1) dynamic WBR measures in healthy young adult Caucasian and Chinese subjects to equivalent measurements taken at ambient pressure; (ii) to compare baseline static and dynamic measures of wideband reflectance to previous evaluations of an equivalent population; (iii) to determine if WBR can be used to evaluate Eustachian tube function in normal hearing young adults through the performance of the Valsalva and Toynbee manoeuvres; and (iv) to evaluate any potential gender and ethnic effects present in Eustachian tube assessment using WBR. There were differences between dynamic and static measurements of wideband reflectance in healthy subjects. Static measurements produced significantly lower estimates of power absorbance at low frequencies in both Caucasian and Chinese subjects. Caucasian subjects also demonstrated slightly higher estimates of power absorbance at high frequencies using the static measurement mode. The differences may have arisen due to the introduction of positive pressure into the ear canal during static measurement that arises due to compression of the air in the external ear canal when the probe tip is inserted (Liu et al., 2008). Such an effect is not present in dynamic measurement mode as the pressure in the external ear canal is actively altered during the measurement. There yet remains a potential advantage for dynamic measurements in the evaluation of middle ear pathology where the disease process may significantly alter the state of the middle ear cavity and conductive system. The dynamic measurements could in these circumstances offer an increase in the sensitivity and specificity of wideband reflectance to the detection of these pathologies.  118  Significant differences were observed in estimates of power absorbance between the current version of the REFLWIN system, the older version of the system and the Mimosa Acoustics RMS system. Lower estimates of power absorbance were observed at low frequencies in the current version of the system compared to the older version while higher estimates were present at high frequencies. These differences are likely related to the compression of the volume of air in the external ear canal that occurs when the probe is inserted. The resultant positive pressure resulted in decreases in power absorbance at low frequencies and increases in power absorbance around 4000 Hz (Liu et al., 2008). The observations in the current study were consistent with a positive pressure effect being present in the current version of the software which resulted in the lower estimates of power absorbance at low frequencies. The differences observed between the current version of the REFLWIN device and the Mimosa Acoustics RMSsystem could be due to differences in the calibration procedure, differences in the estimation of ear canal area or differences in the probe tip used to seal the external ear canal.  The study was successful in using wideband reflectance to evaluate Eustachian tube function through the performance of the Valsalva and Toynbee manoeuvres. The shifts in middle ear pressure indicated by the movement of the tympanometric peak pressures demonstrated that the subjects’ Eustachian tubes were patent and able to transport air between the middle ear and rhinopharynx. Unfortunately the technique did not reveal anything more about Eustachian tube function than previous attempts using tympanometry. Only the shifts in pressure were significantly different after pressure had been introduced into the middle ear by the manoeuvres. Estimates of dynamic power absorbance remained nearly identical before and after each manoeuvre. It is possible that the estimation of dynamic power absorbance at  119  tympanometric peak pressure was responsible for this lack of difference. By measuring power absorbance at tympanometric peak pressure we afford the tympanic membrane the greatest amount of mobility resulting in the greatest admittance of sound energy possible under the circumstances. This could offset the impact of extreme pressure in the middle ear. As such, it remains possible that the technique could convey information regarding Eustachian tube function by reporting on pressure points other than peak pressure. Perhaps static measures of wideband reflectance are more suited to this analysis as they would provide estimates at 0 daPa regardless of the magnitude of shift produced by the physical manoeuvres.  Finally, a number of gender and ethnic differences were revealed in this study. Chinese and Caucasian subjects produced significantly different baseline estimates of static and dynamic power absorbance. Chinese females produced higher estimates of energy reflectance and lower estimates of power absorbance than Caucasian females at 5000 Hz. Caucasian subjects demonstrated higher estimates of dynamic power absorbance from 800-1000 Hz while Chinese subjects had higher estimates at 5000 Hz. The peak static admittance of the 1000 Hz tympanogram was also lower in Chinese subjects. These findings were consistent with previous investigations of middle ear measures in these population groups (Shahnaz and Bork, 2006; Shahnaz and Bork, 2008; Shahnaz and Davies, 2006). Chinese females also produced lower estimates of energy reflectance and higher estimates of power absorbance than Chinese males from 4000 – 5000 Hz. Female subjects also produced lower estimates of dynamic power absorbance at 5000 Hz. Male subjects demonstrated lower peak static admittance on the 1000 Hz tympanogram in the baseline condition. These differences may have occurred due to differences in body size (Shahnaz and Bork, 2006; Huang et al., 2000), differences in tympanic  120  membrane and ear canal properties (Keefe et al., 1993) or differences in the conductive mechanism (Shahnaz, 2008).  Gender and ethnic effects were also present in the post-Toynbee  manoeuvre data. Chinese male subjects produced greater shifts in pressure than Caucasian male subjects in the peak pressure of the power absorbance tympanogram. Chinese males also produced a larger shift than Chinese females on the power absorbance tympanogram peak pressure. 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Burlington, MA: Elsevier Inc.  128  Appendix I - Descriptive Statistics Tables  Table A1. Static energy reflectance descriptive statistics for the baseline condition. Statistics include mean energy reflectance, maximum energy reflectance, minimum energy reflectance and standard deviation taken at ambient pressure for four gender/ethnicity combinations.  Freq. (Hz) Mean  250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000  0.90 0.90 0.85 0.79 0.65 0.57 0.45 0.37 0.42 0.41 0.40 0.31 0.26 0.46 0.62 0.71  Caucasian Female Min. Max. SD  0.80 0.76 0.69 0.61 0.45 0.30 0.22 0.10 0.21 0.17 0.07 0.01 0.01 0.17 0.35 0.42  0.98 1.00 0.97 0.95 0.87 0.83 0.73 0.66 0.70 0.59 0.67 0.51 0.56 0.73 0.76 0.86  0.05 0.06 0.07 0.08 0.11 0.13 0.15 0.15 0.13 0.11 0.12 0.12 0.14 0.16 0.12 0.11  Mean  0.89 0.88 0.82 0.75 0.60 0.54 0.45 0.38 0.42 0.41 0.39 0.26 0.24 0.41 0.58 0.60  Caucasian Male Min. Max. SD  0.77 0.75 0.70 0.60 0.43 0.34 0.22 0.20 0.26 0.19 0.19 0.02 0.02 0.11 0.24 0.21  0.97 0.98 0.93 0.88 0.79 0.79 0.71 0.61 0.70 0.65 0.63 0.54 0.40 0.70 0.73 0.78  0.05 0.05 0.06 0.07 0.09 0.11 0.13 0.13 0.13 0.13 0.16 0.16 0.13 0.15 0.15 0.17  Mean  0.92 0.92 0.87 0.81 0.67 0.59 0.51 0.43 0.47 0.41 0.37 0.21 0.15 0.29 0.49 0.59  Chinese Female Min. Max. SD  0.84 0.82 0.75 0.62 0.40 0.27 0.30 0.22 0.19 0.25 0.07 0.02 0.01 0.04 0.16 0.34  0.98 0.99 0.97 0.93 0.84 0.80 0.69 0.62 0.71 0.64 0.62 0.37 0.50 0.72 0.66 0.75  0.04 0.05 0.06 0.08 0.10 0.13 0.11 0.11 0.12 0.11 0.13 0.11 0.10 0.17 0.13 0.11  Mean  Chinese Male Min. Max.  SD  0.91 0.91 0.86 0.80 0.67 0.61 0.50 0.45 0.48 0.41 0.39 0.33 0.33 0.48 0.61 0.58  0.86 0.82 0.73 0.58 0.40 0.36 0.28 0.31 0.28 0.13 0.04 0.02 0.01 0.19 0.35 0.30  0.03 0.05 0.06 0.09 0.12 0.12 0.13 0.09 0.11 0.16 0.21 0.21 0.17 0.16 0.15 0.15  0.97 0.99 0.95 0.93 0.84 0.80 0.68 0.63 0.70 0.73 0.82 0.77 0.69 0.86 0.91 0.81  129  Table A2. Static power absorbance descriptive statistics from the baseline condition for the four gender/ethnicity combinations. Measures include mean power absorbance, minimum power absorbance, maximum power absorbance and standard deviation.  Freq. (Hz) Mean  250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000  0.10 0.10 0.15 0.21 0.33 0.42 0.54 0.63 0.57 0.59 0.59 0.69 0.73 0.53 0.37 0.29  Caucasian Female Min. Max. SD  0.01 0.01 0.03 0.05 0.11 0.16 0.27 0.34 0.30 0.41 0.32 0.49 0.43 0.27 0.23 0.14  0.20 0.24 0.31 0.39 0.53 0.69 0.77 0.90 0.78 0.83 0.92 0.99 0.97 0.82 0.64 0.58  0.05 0.06 0.07 0.08 0.11 0.13 0.14 0.15 0.13 0.11 0.12 0.12 0.14 0.15 0.11 0.11  Mean  0.11 0.12 0.18 0.25 0.38 0.46 0.54 0.62 0.58 0.59 0.60 0.74 0.76 0.57 0.41 0.40  Caucasian Male Min. Max. SD  0.03 0.02 0.07 0.12 0.20 0.21 0.29 0.39 0.30 0.35 0.36 0.46 0.59 0.29 0.26 0.22  0.23 0.25 0.30 0.39 0.56 0.65 0.78 0.80 0.74 0.81 0.81 0.97 0.98 0.88 0.76 0.78  0.05 0.05 0.06 0.07 0.09 0.10 0.13 0.13 0.13 0.13 0.16 0.16 0.13 0.15 0.15 0.17  Mean  0.08 0.08 0.13 0.19 0.31 0.40 0.49 0.57 0.53 0.59 0.62 0.79 0.84 0.70 0.50 0.41  Chinese Female Min. Max. SD  0.02 0.01 0.03 0.07 0.14 0.20 0.30 0.38 0.28 0.36 0.37 0.62 0.49 0.28 0.34 0.25  0.15 0.18 0.25 0.37 0.57 0.73 0.70 0.77 0.80 0.74 0.92 0.98 0.98 0.96 0.83 0.66  0.04 0.05 0.06 0.08 0.10 0.13 0.11 0.11 0.12 0.11 0.13 0.11 0.10 0.17 0.12 0.10  Mean  Chinese Male Min. Max.  SD  0.08 0.09 0.14 0.20 0.31 0.38 0.49 0.55 0.52 0.59 0.61 0.67 0.66 0.51 0.39 0.42  0.01 0.00 0.04 0.07 0.15 0.20 0.32 0.37 0.30 0.27 0.18 0.22 0.30 0.13 0.08 0.19  0.04 0.05 0.06 0.09 0.12 0.12 0.13 0.09 0.11 0.16 0.21 0.20 0.17 0.16 0.15 0.15  0.13 0.18 0.27 0.41 0.58 0.64 0.72 0.69 0.72 0.87 0.94 0.98 0.98 0.78 0.65 0.70  130  Table A3. Dynamic power absorbance descriptive statistics for four gender/ethnicity combinations. Measures include mean power absorbance, maximum power absorbance, minimum power absorbance and standard deviation. Freq. (Hz) Mean  250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000  0.13 0.14 0.20 0.28 0.43 0.55 0.69 0.72 0.65 0.67 0.67 0.70 0.69 0.48 0.35 0.27  Caucasian Female Min. Max. SD  0.07 0.05 0.10 0.14 0.24 0.30 0.37 0.48 0.43 0.45 0.41 0.48 0.46 0.25 0.17 0.09  0.23 0.29 0.34 0.44 0.63 0.76 0.93 0.89 0.90 0.94 0.96 0.97 0.89 0.80 0.65 0.45  0.04 0.05 0.06 0.08 0.10 0.14 0.14 0.10 0.12 0.13 0.14 0.13 0.12 0.15 0.12 0.10  Mean  0.17 0.20 0.27 0.37 0.51 0.62 0.72 0.75 0.70 0.69 0.70 0.77 0.70 0.49 0.36 0.37  Caucasian Male Min. Max. SD  0.12 0.12 0.17 0.21 0.33 0.42 0.53 0.55 0.52 0.52 0.52 0.51 0.40 0.18 0.22 0.22  0.25 0.27 0.36 0.56 0.73 0.89 0.87 0.88 0.87 0.92 0.94 0.96 0.97 0.89 0.73 0.75  0.04 0.05 0.06 0.09 0.11 0.13 0.11 0.09 0.10 0.11 0.14 0.14 0.15 0.17 0.14 0.16  Mean  0.10 0.12 0.17 0.25 0.38 0.48 0.61 0.66 0.60 0.64 0.70 0.82 0.84 0.68 0.47 0.39  Chinese Female Min. Max. SD  0.05 0.05 0.09 0.14 0.25 0.33 0.47 0.52 0.46 0.44 0.51 0.57 0.57 0.40 0.29 0.22  0.19 0.24 0.31 0.46 0.61 0.72 0.78 0.82 0.83 0.91 0.96 0.99 0.97 0.96 0.79 0.63  0.04 0.05 0.06 0.08 0.09 0.11 0.10 0.08 0.09 0.11 0.12 0.10 0.09 0.16 0.13 0.11  Mean  Chinese Male Min. Max.  SD  0.10 0.11 0.17 0.25 0.38 0.45 0.57 0.64 0.62 0.65 0.63 0.70 0.67 0.50 0.37 0.40  0.03 0.01 0.06 0.09 0.17 0.24 0.38 0.45 0.32 0.26 0.20 0.23 0.30 0.14 0.11 0.19  0.05 0.07 0.09 0.14 0.16 0.15 0.13 0.11 0.14 0.16 0.20 0.20 0.17 0.17 0.14 0.13  0.20 0.26 0.39 0.61 0.82 0.76 0.78 0.90 0.88 0.85 0.94 0.96 0.99 0.78 0.60 0.67  131  Table A4. Descriptive statistics for the baseline power absorbance tympanograms. Statistics are displayed for both peak pressure and peak power absorbance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak power absorbance include mean power absorbance, minimum power absorbance, maximum power absorbance and the standard deviation. Variable  Peak Pressure (daPa)  Peak Power Absorbance (PA)  Caucasian Female Mean  Min.  -25.60  -55.00  0.53  0.32  Max.  Caucasian Male  SD  Mean  Min.  5.00  14.53  -24.41  -50.00  0.69  0.09  0.59  0.45  Max.  Chinese Female SD  Mean  Min.  0.00  10.29  -25.69  0.77  0.09  0.48  Chinese Male  Max.  SD  Mean  Min.  Max.  SD  -40.00  5.00  9.61  -23.25  -60.00  -5.00  12.17  0.37  0.63  0.08  0.47  0.32  0.63  0.09  132  Table A5. Descriptive statistics for the 226 Hz tympanograms in the baseline condition. Statistics are displayed for both tympanometric peak pressure and peak compensated static admittance. Measures for tympanometric peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak compensated static admittance include mean admittance, minimum admittance, maximum admittance and the standard deviation. Variable  Caucasian Female Mean  226 Hz Tympanometric Peak Pressure (daPa)  226 Hz Peak Compensated Static Admittance (mmho)  Min.  Max.  Caucasian Male SD  Mean  Min.  Max.  Chinese Female SD  Mean  Min.  Max.  Chinese Male SD  Mean  Min.  Max.  SD  -24.80  -62.50  20.00  18.04  -26.32  -52.50  -2.50  10.20  -24.83  -47.50  75.00  21.66  -29.50  -90.00  -12.50  17.56  0.51  0.15  0.84  0.19  0.60  0.27  1,21  0.24  0.36  0.07  0.60  0.13  0.36  0.05  0.73  0.18  133  Table A6. Descriptive statistics for the 1000 Hz tympanograms in the baseline condition. Statistics are displayed for both tympanometric peak pressure and peak compensated static admittance. Measures for tympanometric peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak compensated static admittance include mean admittance, minimum admittance, maximum admittance and the standard deviation. Variable  Caucasian Female Mean  Tympanometric Peak Pressure (daPa)  Peak Compensated Static Admittance (mmho)  Min.  Max.  Caucasian Male SD  Mean  Min.  Max.  Chinese Female SD  Mean  Min.  Max.  Chinese Male SD  Mean  Min.  Max.  SD  -16.50  -52.50  22.50  17.56  -24.71  -82.50  42.50  17.99  -19.74  -62.50  12.50  14.61  -20.00  -57.5  7.5  14.82  1.35  0.50  2.95  0.69  0.88  -0.97  2.40  0.77  0.93  0.03  2.01  0.51  0.50  -2.30  1.87  1.12  134  Table A7. Static energy reflectance descriptive statistics from Shaw (2009) taken using the Interacoustics device. Statistics include mean energy reflectance, maximum energy reflectance, minimum energy reflectance and standard deviation taken at ambient pressure for four gender/ethnicity combinations.  Freq. (Hz) Mean  250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300  0.84 0.81 0.78 0.71 0.60 0.53 0.42 0.33 0.38 0.39 0.36 0.28 0.34 0.46 0.62  Caucasian Female Min. Max. SD  0.08 0.10 0.17 0.28 0.36 0.22 0.17 0.16 0.22 0.20 0.11 0.02 0.04 0.06 0.29  0.96 0.94 0.92 0.86 0.78 0.72 0.60 0.52 0.54 0.65 0.84 0.85 0.73 0.70 0.83  0.21 0.20 0.18 0.15 0.13 0.15 0.13 0.10 0.09 0.11 0.17 0.18 0.18 0.17 0.15  Mean  0.88 0.84 0.80 0.71 0.58 0.52 0.42 0.32 0.35 0.31 0.29 0.25 0.31 0.48 0.65  Caucasian Male Min. Max. SD  0.46 0.49 0.51 0.47 0.20 0.13 0.12 0.17 0.17 0.11 0.07 0.01 0.01 0.09 0.20  0.97 0.95 0.95 0.90 0.82 0.75 0.59 0.52 0.49 0.48 0.49 0.56 0.71 0.91 0.94  0.09 0.09 0.09 0.11 0.15 0.16 0.13 0.09 0.09 0.11 0.12 0.15 0.19 0.20 0.15  Mean  0.87 0.84 0.80 0.72 0.60 0.54 0.43 0.35 0.40 0.37 0.33 0.28 0.35 0.44 0.55  Chinese Female Min. Max. SD  0.71 0.65 0.59 0.49 0.39 0.28 0.17 0.15 0.20 0.15 0.03 0.05 0.06 0.11 0.28  0.96 0.95 0.93 0.89 0.80 0.74 0.62 0.56 0.57 0.54 0.61 0.53 0.70 0.82 0.83  0.07 0.09 0.10 0.11 0.12 0.13 0.12 0.11 0.11 0.11 0.13 0.12 0.16 0.19 0.16  Mean  Chinese Male Min. Max.  SD  0.88 0.84 0.79 0.71 0.58 0.53 0.45 0.35 0.37 0.38 0.38 0.30 0.34 0.42 0.57  0.79 0.75 0.68 0.55 0.39 0.26 0.19 0.13 0.17 0.11 0.17 0.12 0.04 0.08 0.23  0.05 0.06 0.08 0.10 0.11 0.11 0.10 0.10 0.10 0.10 0.11 0.13 0.21 0.24 0.19  0.94 0.92 0.90 0.85 0.74 0.67 0.59 0.52 0.53 0.62 0.65 0.51 0.72 0.87 1.00  135  Table A8. Static energy reflectance descriptive statistics from Shaw (2009) taken using the Mimosa Inc. device. Statistics include mean energy reflectance, maximum energy reflectance, minimum energy reflectance and standard deviation taken at ambient pressure for four gender/ethnicity combinations. Freq. (Hz) Mean  250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300  0.90 0.86 0.80 0.71 0.59 0.48 0.38 0.33 0.34 0.33 0.29 0.27 0.34 0.55 0.69  Caucasian Female Min. Max. SD  0.64 0.58 0.51 0.25 0.12 0.13 0.04 0.11 0.13 0.08 0.05 0.01 0.11 0.06 0.13  1.00 0.96 0.94 0.90 0.83 0.72 0.68 0.65 0.57 0.51 0.46 0.53 0.79 1.02 1.08  0.07 0.08 0.11 0.15 0.19 0.18 0.15 0.13 0.10 0.11 0.10 0.10 0.16 0.22 0.22  Mean  0.90 0.86 0.80 0.70 0.58 0.49 0.44 0.37 0.36 0.33 0.30 0.30 0.40 0.60 0.73  Caucasian Male Min. Max. SD  0.82 0.76 0.66 0.55 0.29 0.14 0.17 0.21 0.12 0.07 0.01 0.01 0.04 0.08 0.42  0.96 0.93 0.90 0.86 0.78 0.66 0.59 0.61 0.57 0.55 0.55 0.50 0.68 0.86 0.97  0.04 0.05 0.06 0.09 0.12 0.13 0.09 0.11 0.12 0.13 0.14 0.14 0.17 0.20 0.16  Mean  0.92 0.88 0.84 0.78 0.69 0.59 0.48 0.45 0.41 0.38 0.31 0.25 0.25 0.34 0.47  Chinese Female Min. Max. SD  0.81 0.79 0.73 0.62 0.45 0.30 0.20 0.11 0.11 0.09 0.04 0.03 0.04 0.07 0.02  0.99 0.96 0.93 0.88 0.83 0.78 0.72 0.68 0.64 0.58 0.51 0.54 0.70 0.78 0.83  0.04 0.05 0.05 0.07 0.10 0.12 0.13 0.13 0.14 0.12 0.12 0.14 0.18 0.20 0.20  Mean  Chinese Male Min. Max.  SD  0.92 0.88 0.84 0.77 0.68 0.57 0.48 0.41 0.36 0.34 0.31 0.27 0.33 0.46 0.55  0.86 0.81 0.76 0.66 0.53 0.35 0.23 0.11 0.07 0.06 0.01 0.09 0.08 0.05 0.17  0.04 0.04 0.05 0.07 0.09 0.12 0.12 0.14 0.13 0.13 0.12 0.09 0.14 0.21 0.19  0.98 0.96 0.91 0.86 0.80 0.72 0.66 0.60 0.54 0.54 0.45 0.41 0.63 1.00 0.93  136  Table A9. Static power absorbance descriptive statistics from Shaw (2009) taken using the Interacoustics device. Statistics include mean power absorbance, maximum power absorbance, minimum power absorbance and standard deviation taken at ambient pressure for four gender/ethnicity combinations.  Freq. (Hz) Mean  250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300  0.23 0.21 0.29 0.40 0.54 0.64 0.73 0.76 0.70 0.67 0.70 0.73 0.64 0.49 0.33  Caucasian Female Min. Max. SD  0.11 0.09 0.13 0.18 0.28 0.42 0.60 0.64 0.58 0.47 0.41 0.41 0.39 0.22 0.14  0.44 0.39 0.57 0.78 0.87 0.91 0.90 0.87 0.83 0.86 0.96 0.97 0.92 0.93 0.56  0.09 0.08 0.11 0.16 0.18 0.17 0.09 0.05 0.06 0.10 0.13 0.13 0.15 0.15 0.11  Mean  0.24 0.22 0.31 0.42 0.56 0.63 0.70 0.75 0.69 0.69 0.69 0.69 0.59 0.43 0.32  Caucasian Male Min. Max. SD  0.12 0.12 0.14 0.23 0.34 0.43 0.57 0.60 0.54 0.47 0.45 0.47 0.28 0.16 0.08  0.39 0.37 0.47 0.65 0.84 0.89 0.82 0.87 0.88 0.90 0.91 0.94 0.99 0.87 0.63  0.07 0.06 0.09 0.10 0.13 0.11 0.08 0.07 0.08 0.10 0.12 0.14 0.19 0.18 0.14  Mean  0.17 0.16 0.21 0.30 0.42 0.50 0.62 0.68 0.65 0.66 0.69 0.75 0.73 0.64 0.47  Chinese Female Min. Max. SD  0.08 0.08 0.10 0.16 0.27 0.32 0.45 0.50 0.51 0.52 0.49 0.50 0.41 0.24 0.18  0.29 0.27 0.35 0.44 0.59 0.76 0.88 0.84 0.85 0.85 0.88 0.96 0.94 0.86 0.72  0.06 0.05 0.08 0.09 0.10 0.11 0.11 0.09 0.09 0.08 0.09 0.11 0.16 0.17 0.13  Mean  Chinese Male Min. Max.  SD  0.23 0.22 0.27 0.36 0.47 0.53 0.63 0.72 0.70 0.69 0.72 0.75 0.67 0.56 0.49  0.10 0.09 0.13 0.20 0.30 0.37 0.49 0.55 0.57 0.40 0.42 0.38 0.40 0.30 0.18  0.17 0.17 0.16 0.16 0.15 0.15 0.13 0.10 0.09 0.12 0.14 0.14 0.16 0.17 0.19  1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  137  Table A10. Static power absorbance descriptive statistics from Shaw (2009) taken using the Mimosa Inc. device. Statistics include mean power absorbance, maximum power absorbance, minimum power absorbance and standard deviation taken at ambient pressure for four gender/ethnicity combinations.  Freq. (Hz) Mean  250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300  0.10 0.15 0.20 0.29 0.40 0.51 0.61 0.67 0.65 0.66 0.71 0.73 0.67 0.46 0.32  Caucasian Female Min. Max. SD  0.00 0.04 0.06 0.10 0.17 0.28 0.32 0.35 0.43 0.49 0.54 0.47 0.21 -0.02 -0.08  0.36 0.42 0.49 0.75 0.88 0.87 0.96 0.89 0.87 0.92 0.95 0.99 0.89 0.94 0.87  0.07 0.09 0.11 0.16 0.19 0.18 0.16 0.13 0.10 0.11 0.10 0.11 0.16 0.23 0.22  Mean  0.11 0.15 0.20 0.30 0.42 0.50 0.56 0.63 0.63 0.66 0.69 0.71 0.62 0.42 0.28  Caucasian Male Min. Max. SD  0.04 0.07 0.10 0.14 0.22 0.34 0.41 0.39 0.43 0.45 0.45 0.50 0.32 0.14 0.03  0.18 0.24 0.34 0.45 0.65 0.86 0.83 0.79 0.87 0.93 0.99 0.99 0.96 0.92 0.58  0.04 0.05 0.06 0.08 0.11 0.13 0.10 0.11 0.11 0.13 0.14 0.15 0.17 0.20 0.17  Mean  0.09 0.12 0.16 0.23 0.32 0.42 0.52 0.56 0.59 0.62 0.69 0.74 0.75 0.65 0.52  Chinese Female Min. Max. SD  0.03 0.05 0.08 0.12 0.17 0.22 0.28 0.32 0.38 0.42 0.49 0.46 0.30 0.22 0.17  0.19 0.21 0.27 0.38 0.55 0.70 0.80 0.89 0.89 0.91 0.96 0.97 0.96 0.93 0.98  0.04 0.04 0.05 0.07 0.10 0.12 0.13 0.13 0.14 0.12 0.12 0.15 0.18 0.21 0.20  Mean  Chinese Male Min. Max.  SD  0.08 0.12 0.16 0.22 0.32 0.42 0.52 0.57 0.63 0.66 0.70 0.75 0.69 0.55 0.45  0.02 0.04 0.09 0.14 0.20 0.28 0.33 0.40 0.46 0.46 0.55 0.59 0.37 0.00 0.07  0.03 0.04 0.04 0.06 0.09 0.12 0.13 0.13 0.13 0.12 0.12 0.10 0.15 0.19 0.18  0.14 0.19 0.24 0.34 0.47 0.65 0.77 0.89 0.93 0.94 0.99 0.96 0.92 0.95 0.83  138  Table A11. Dynamic power absorbance descriptive statistics from Shaw (2009) taken using the Interacoustics device. Statistics include mean power absorbance, maximum power absorbance, minimum power absorbance and standard deviation taken at ambient pressure for four gender/ethnicity combinations.  Freq. (Hz) Mean  250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300  0.23 0.21 0.29 0.40 0.54 0.64 0.73 0.76 0.70 0.67 0.70 0.73 0.64 0.49 0.33  Caucasian Female Min. Max. SD  0.11 0.09 0.13 0.18 0.28 0.42 0.60 0.64 0.58 0.47 0.41 0.41 0.39 0.22 0.14  0.44 0.39 0.57 0.78 0.87 0.91 0.90 0.87 0.83 0.86 0.96 0.97 0.92 0.93 0.56  0.09 0.08 0.11 0.16 0.18 0.17 0.09 0.05 0.06 0.10 0.13 0.13 0.15 0.15 0.11  Mean  0.24 0.22 0.31 0.42 0.56 0.63 0.70 0.75 0.69 0.69 0.69 0.69 0.59 0.43 0.32  Caucasian Male Min. Max. SD  0.12 0.12 0.14 0.23 0.34 0.43 0.57 0.60 0.54 0.47 0.45 0.47 0.28 0.16 0.08  0.39 0.37 0.47 0.65 0.84 0.89 0.82 0.87 0.88 0.90 0.91 0.94 0.99 0.87 0.63  0.07 0.06 0.09 0.10 0.13 0.11 0.08 0.07 0.08 0.10 0.12 0.14 0.19 0.18 0.14  Mean  0.17 0.16 0.21 0.30 0.42 0.50 0.62 0.68 0.65 0.66 0.69 0.75 0.73 0.64 0.47  Chinese Female Min. Max. SD  0.08 0.08 0.10 0.16 0.27 0.32 0.45 0.50 0.51 0.52 0.49 0.50 0.41 0.24 0.18  0.29 0.27 0.35 0.44 0.59 0.76 0.88 0.84 0.85 0.85 0.88 0.96 0.94 0.86 0.72  0.06 0.05 0.08 0.09 0.10 0.11 0.11 0.09 0.09 0.08 0.09 0.11 0.16 0.17 0.13  Mean  Chinese Male Min. Max.  SD  0.20 0.19 0.25 0.34 0.45 0.51 0.62 0.71 0.69 0.68 0.71 0.74 0.66 0.54 0.47  0.10 0.09 0.13 0.20 0.30 0.37 0.49 0.55 0.57 0.40 0.42 0.38 0.40 0.30 0.18  0.08 0.07 0.08 0.10 0.11 0.12 0.11 0.08 0.07 0.11 0.13 0.13 0.15 0.15 0.16  0.40 0.37 0.46 0.58 0.71 0.84 0.88 0.85 0.85 0.92 0.95 0.97 0.88 0.86 0.75  139  Table A12. Dynamic power absorbance descriptive statistics for four gender/ethnicity combinations taken following the Valsalva manoeuvre. Measures include mean power absorbance, maximum power absorbance, minimum power absorbance and standard deviation.  Freq. (Hz) Mean  250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000  0.12 0.13 0.19 0.26 0.41 0.53 0.68 0.69 0.62 0.64 0.67 0.71 0.70 0.50 0.36 0.27  Caucasian Female Min. Max. SD  0.03 0.02 0.05 0.07 0.19 0.23 0.34 0.44 0.41 0.44 0.41 0.46 0.48 0.22 0.19 0.11  0.19 0.23 0.30 0.42 0.66 0.79 0.88 0.86 0.87 0.91 0.94 0.90 0.96 0.93 0.65 0.79  0.04 0.05 0.06 0.09 0.11 0.14 0.16 0.11 0.12 0.13 0.15 0.12 0.14 0.19 0.13 0.14  Mean  0.15 0.17 0.23 0.32 0.44 0.54 0.64 0.69 0.64 0.63 0.63 0.70 0.67 0.47 0.35 0.35  Caucasian Male Min. Max. SD  0.02 0.01 0.02 0.02 0.01 0.01 0.01 0.02 0.03 0.05 0.05 0.04 0.07 0.14 0.10 0.17  0.23 0.26 0.35 0.47 0.64 0.78 0.84 0.85 0.90 0.92 0.90 0.93 0.96 0.88 0.75 0.77  0.06 0.07 0.09 0.12 0.16 0.18 0.20 0.19 0.19 0.19 0.21 0.22 0.21 0.19 0.16 0.18  Mean  0.10 0.11 0.16 0.24 0.37 0.46 0.59 0.62 0.57 0.60 0.66 0.78 0.82 0.69 0.50 0.41  Chinese Female Min. Max. SD  0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.11 0.22 0.33 0.38 0.29 0.22  0.22 0.26 0.31 0.48 0.66 0.74 0.77 0.80 0.84 0.94 0.97 1.00 0.97 0.96 0.88 0.62  0.05 0.07 0.08 0.11 0.14 0.16 0.16 0.16 0.16 0.18 0.17 0.17 0.15 0.16 0.15 0.10  Mean  Chinese Male Min. Max.  SD  0.09 0.10 0.15 0.23 0.35 0.42 0.56 0.63 0.59 0.61 0.60 0.64 0.63 0.47 0.39 0.40  0.01 0.00 0.01 0.02 0.15 0.18 0.29 0.38 0.29 0.26 0.19 0.23 0.25 0.12 0.12 0.11  0.06 0.08 0.11 0.15 0.17 0.16 0.15 0.14 0.18 0.21 0.22 0.22 0.21 0.22 0.18 0.18  0.24 0.31 0.44 0.64 0.79 0.70 0.83 0.91 0.90 0.93 0.98 1.00 0.99 0.88 0.79 0.71  140  Table A13. Descriptive statistics for the Valsalva manoeuvre power absorbance tympanograms. Statistics are displayed for both peak pressure and peak power absorbance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak power absorbance include mean power absorbance, minimum power absorbance, maximum power absorbance and the standard deviation. Variable  Caucasian Female Mean  Min.  Max.  Caucasian Male SD  Mean  Min.  Max.  Chinese Female SD  Mean  Min.  Max.  Chinese Male SD  Mean  Min.  Max.  SD  Peak Pressure (daPa)  23.60  -55.00  200.00  68.73  57.65  -50.00  200.00  96.58  17.24  -135.00  200.00  76.07  30.25  -50.00  200.00  78.98  Peak Power Absorbance (PA)  0.51  0.31  0.69  0.10  0.52  0.02  0.72  0.16  0.46  0.00  0.64  0.13  0.45  0.23  0.65  0.11  141  Table A14. Descriptive statistics for the Valsalva manouevre 226 Hz tympanograms. Statistics are displayed for both tympanometric peak pressure and peak compensated static admittance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak compensated static admittance include mean admittance, minimum admittance, maximum admittance and the standard deviation. Variable  Caucasian Female Mean  Min.  Max.  Caucasian Male SD  Mean  Min.  Max.  Chinese Female SD  Mean  Min.  Max.  Chinese Male SD  Mean  Min.  Max.  SD  Tympanometric Peak Pressure (daPa)  17.60  -87.50  200.00  71.66  43.68  -52.50  200.00  91.50  5.52  -300.00  200.00  94.83  -6.25  -300.00  200.00  103.85  Peak Compensated Static Admittance (mmho)  0.45  0.00  0.81  0.19  0.44  0.00  86.21  0.34  0.37  0.00  1.41  0.28  0.36  0.00  1.40  0.31  142  Table A15. Descriptive statistics for the Valsalva manouevre 1000 Hz tympanograms. Statistics are displayed for both tympanometric peak pressure and peak compensated static admittance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and t the standard deviation. Measures for peak compensated static admittance include mean admittance, minimum admittance, maximum admittance and the standard deviation. Variable  Caucasian Female Mean  Min.  Max.  Caucasian Male SD  Mean  Min.  Max.  Chinese Female SD  Mean  Min.  Max.  Chinese Male SD  Mean  Min.  Max.  SD  Tympanometric Peak Pressure (daPa)  16.50  -300.00  200.00  96.49  51.91  -47.50  200.00  81.67  24.14  -295.00  200.00  97.76  19.87  -300.00  200.00  107.49  Peak Static Admittance (mmho)  1.01  0.00  3.33  0.86  0.90  -0.50  266.01  0.78  1.18  -0.65  12.79  2.30  1.87  -2.72  29.21  6.52  143  Table A16. Dynamic power absorbance descriptive statistics for four gender/ethnicity combinations taken following the Toynbee manoeuvre. Measures include mean power absorbance, maximum power absorbance, minimum power absorbance and standard deviation.  Freq. (Hz) Mean  250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000  0.13 0.15 0.21 0.31 0.45 0.56 0.68 0.69 0.62 0.63 0.64 0.70 0.69 0.49 0.35 0.25  Caucasian Female Min. Max. SD  0.06 0.05 0.10 0.13 0.24 0.30 0.35 0.46 0.40 0.44 0.38 0.31 0.23 0.12 0.17 0.10  0.27 0.36 0.45 0.62 0.79 0.82 0.93 0.80 0.74 0.81 0.90 0.99 0.99 0.89 0.56 0.42  0.06 0.07 0.09 0.12 0.15 0.16 0.13 0.09 0.09 0.10 0.14 0.17 0.18 0.18 0.11 0.09  Mean  0.16 0.19 0.26 0.36 0.50 0.60 0.68 0.71 0.67 0.66 0.66 0.70 0.64 0.45 0.34 0.33  Caucasian Male Min. Max. SD  0.01 0.02 0.02 0.01 0.01 0.01 0.00 0.02 0.02 0.00 0.01 0.01 0.01 0.01 0.03 0.17  0.24 0.30 0.39 0.49 0.71 0.87 0.90 0.90 0.95 0.97 0.87 0.94 0.96 0.88 0.74 0.72  0.05 0.07 0.08 0.12 0.16 0.19 0.20 0.20 0.21 0.22 0.21 0.22 0.23 0.21 0.17 0.17  Mean  0.10 0.11 0.17 0.26 0.38 0.48 0.59 0.63 0.58 0.63 0.70 0.82 0.86 0.72 0.50 0.41  Chinese Female Min. Max. SD  0.01 0.01 0.04 0.10 0.24 0.31 0.32 0.35 0.34 0.41 0.52 0.57 0.70 0.36 0.28 0.22  0.22 0.26 0.33 0.44 0.59 0.70 0.80 0.81 0.74 0.84 0.99 0.99 0.97 0.96 0.74 0.62  0.05 0.06 0.07 0.09 0.10 0.11 0.12 0.10 0.09 0.11 0.13 0.10 0.07 0.16 0.13 0.10  Mean  Chinese Male Min. Max.  SD  0.10 0.12 0.18 0.27 0.39 0.44 0.54 0.62 0.60 0.65 0.61 0.63 0.60 0.44 0.36 0.37  0.01 0.01 0.01 0.09 0.18 0.19 0.25 0.35 0.30 0.24 0.18 0.22 0.31 0.12 0.11 0.13  0.06 0.08 0.11 0.14 0.15 0.14 0.14 0.13 0.16 0.19 0.19 0.19 0.18 0.20 0.15 0.16  0.21 0.31 0.44 0.66 0.78 0.67 0.79 0.87 0.92 0.96 0.93 0.93 0.98 0.78 0.60 0.67  144  Table A17. Descriptive statistics for the Toynbee manouevre power absorbance tympanograms. Statistics are displayed for both peak pressure and peak power absorbance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak power absorbance include mean power absorbance, minimum power absorbance, maximum power absorbance and the standard deviation. Variable  PAT Peak Pressure (daPa)  PAT Peak Power Absorbance (PA)  Caucasian Female  Caucasian Male  Chinese Female  Chinese Male  Mean  Min.  Max.  SD  Mean  Min.  Max.  SD  Mean  Min.  Max.  SD  Mean  Min.  Max.  SD  -49.40  -125.00  25.00  42.21  -38.82  -160.00  150.00  68.80  -48.97  -155.00  200.00  67.37  -121.00  -300.00  -25.00  73.08  0.53  0.32  0.70  0.09  0.57  0.01  0.77  0.17  0.47  0.29  0.62  0.09  0.47  0.29  0.63  0.09  145  Table A18. Descriptive statistics for the Toynbee manouevre 226 Hz tympanograms. Statistics are displayed for both tympanometric peak pressure and peak compensated static admittance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak compensated static admittance include mean admittance, minimum admittance, maximum admittance and the standard deviation. Variable  Caucasian Female Mean  Tympanometric Peak Pressure (daPa)  Peak Static Admittance (mmho)  Min.  Max.  Caucasian Male SD  Mean  Min.  Max.  Chinese Female SD  Mean  Min.  Max.  Chinese Male SD  Mean  Min.  Max.  SD  -49.40  -117.50  27.50  40.82  -63.68  -222.50  -2.50  61.66  -72.24  -290.00  17.50  60.54  -113.00  -300.00  60.00  82.91  0.54  0.17  0.89  0.20  0.62  0.17  73.99  0.25  0.38  0.05  0.69  0.15  0.37  0.05  0.84  0.22  146  Table A19. Descriptive statistics for the Toynbee manouevre 1000 Hz tympanograms. Statistics are displayed for both tympanometric peak pressure and peak compensated static admittance. Measures for peak pressure include mean pressure, minimum pressure, maximum pressure and the standard deviation. Measures for peak compensated static admittance include mean admittance, minimum admittance, maximum admittance and the standard deviation. Variable  Caucasian Female Mean  1000 Hz Tympanometric Peak Pressure (daPa)  1000 Hz Peak Compensated Static Admittance (mmho)  Min.  Max.  Caucasian Male SD  Mean  Min.  Max.  Chinese Female SD  Mean  Min.  Max.  Chinese Male SD  Mean  Min.  Max.  SD  -40.60  -112.50  30.00  38.73  -58.97  -190.00  17.50  62.11  -66.98  -295.00  22.50  66.66  -115.00  -300.00  -2.50  78.26  0.97  -3.68  3.36  1.37  1.38  -0.50  290.23  0.78  1.09  0.31  5.11  0.88  0.57  -2.54  1.71  0.98  147  Appendix II - Consent From for Normal Hearing Subjects  THE UNIVERSITY OF BRITISH COLUMBIA  Consent Form  School of Audiology & Speech Sciences Faculty of Medicine  Project Title  2177 Wesbrook Mall, Friedman Bldg.  The Effects of Race, Caucasian Versus East Asian, on Middle Ear Function and Hearing Sensitivity Norms  Principal Investigator  Co-Investigator  Dr. Navid Shahnaz  Stefane Kenny  Assistant Professor  Graduate Student  School of Audiology & Speech Sciences  School of Audiology & Speech Sciences  Co-Investigator Dr. Susan Small Assistant Professor School of Audiology & Speech Sciences  148  Purpose  This project will evaluate the effectiveness of new middle ear analysis techniques for assessing middle ear function in different ethnic groups. These new procedures are a variation of a test procedure that is used frequently to detect middle ear and Eustachian tube problems in clinics which is called tympanometry. Multi-frequency tympanometry is a modification of this technique that assesses the function of the middle ear across much wider frequency range, therefore, providing a more detailed picture of your middle ear. Wide band reflectance is a new middle ear analysis technique and poses no risks or danger to your ear or hearing. The project will also incorporate a new and safe way to assess the middle-ear function. Wideband reflectance tympanometry is a well established technique used throughout the hearing research community for measurements of the middle-ear function. This method is also a safe procedure and poses no risks or danger to your ear or hearing. A moderate intensity (very similar to the intensity of normal conversational speech) chirp like sound will be presented and the amount of reflection and absorption of the sound is measured automatically within 2-3 seconds. Your height, weight, and skull dimensions will also be measured. The purpose of this project is 1) to investigate the effects of race, Caucasian versus Chinese, on hearing sensitivity, middle ear and Eustachian tube function as measured by immittance audiometry, wide band reflectance tympanometry, and real ear to coupler difference (RECD), and 2) to establish race dependent guidelines and protocols for extended high frequency hearing sensitivity, multifrequency tympanometry, wide band reflectance tympanometry and RECD. Results from this study will help us determine if there are differences in the hearing sensitivity and middle ear and Eustachian tube function of subjects from different ethnic backgrounds. If differences are found, this will lead to a better diagnosis of middle ear problems in individuals with different ethnic origin. You are invited to participate in this research.  Study Procedures  As a subject for this study, you will attend one session about 1-1.5 hour in duration. All appointments will be scheduled at your convenience. Testing will be carried out in Room B-28 in the basement of the Woodward Instructional Resources Centre or School of Audiology and Speech Sciences located on UBC campus. In order to be included in this study you should be a Caucasian or East Asian young adult between the ages of 18-34, with a normal hearing system as assessed by the following tests. You should also be free of any history of head trauma and middle ear infection. You have been invited to participate in this study because you meet the above criteria  149  Before the test procedures are conducted, your hearing will be tested using conventional and extended high frequencies and your eardrum and ear canal will be inspected. Four tests will be done in this study: 1) Transient otoacoustic emissions, 2) Wide band reflectance Tympanometry, 3) Multifrequency tympanometry (MFT); and 4) Real Ear to Coupler Difference. In the first three tests, a small earphone will be placed into the entrance of your ear canal using a soft and delicate plastic or sponge tip. It is designed not to cause any allergic reactions. The presence of the earphone may be a bit uncomfortable to some subject, but not painful. The earphone and the attached tip pose no risks or danger to your ear or hearing and have been used extensively in testing newborns, children, and adults. The first test, transient-evoked otoacoustic emissions, is commonly used in clinics to detect hearing loss. A click sound will be presented through the small earphone placed at the entrance of your ear canal. The level of sound is the same as normal talking. Echoes to the sound come back out of your ear. These echoes are measured by a computer. This test will give us information about your middle and inner ear. It will take 2-3 minutes in each ear.  The second test, multi-frequency tympanometry, presents a pure tone while the air pressure in the ear canal is changed. We will test at the frequencies of speech. You will be tested on two commercially available systems to also check for test-retest-reliability of the systems. It will take about 8 minutes in each ear.  The third test involves a test called the Real Ear to Coupler Difference. In this test, the same soft tip as in tympanometry remains in your ear, while a small, narrow tube is inserted alongside the tip in your ear canal. The tube is soft and will not cause you any pain. Some adults report a tickling sensation when the tube is in their ear. You will then hear a series of tones that increase in pitch. The tube will help measure the amount of sound close to your eardrum. The test time varies between 2-4 minutes per each ear.  The fourth test, wide band reflectance tympanometry, presents chirping sounds to the ear while the air pressure in the ear canal is changed. This helps us see how well the middle ear reacts to sounds that span the human speech range. This test will take about 2-3 seconds for each ear. This test will be conducted four times to assess your middle-ear as well as your Eustachian tube function. Eustachian tube is also part of your middle-ear system and is responsible to equate the pressure within the middle-ear to the atmospheric pressure. During Eustachian tube assessment we would like to know whether the pressure within the middle ear can be changed by a given activity such as swallowing or blowing your nose while your mouth and nose are closed. These tests are routinely being conducted in clinics to assess Eustachian tube function in children and adults.  150  You may withdraw from this study at any time and without providing any reasons for your decision. Should you decide to withdraw from this study all the data collected before your withdrawal will be discarded permanently from our database. Withdrawal will in no way jeopardize your present or future clinical care. Risks There are no known or anticipated side effects of the above procedures. All tests completed in this study are routine, non-invasive, clinical procedures that are used on newborns, children, and adults. However, some people may experience slight discomfort during the test procedures. Adequate breaks will be provided if this occurs. Confidentiality Your identity will be coded using a code known only to the researchers, and all information that is collected from you will remain confidential. Only group results or coded individual results will be given in any reports about the study. Coded results only (no personal information) will be kept in computer files on a password protected hard drive. Your confidentiality will be respected. No information that discloses your identity will be released or published without your specific consent to the disclosure. However, research records and medical records identifying you may be inspected in the presence of the Investigator or his designate by representatives of Health Canada, and the UBC Research Ethics Board for the purpose of monitoring the research. However, no records that identify you by name or initials will be allowed to leave the Investigators’ offices.  Reimbursement You will be paid an honorarium of $10 for your participation in this research. Your participation in this study is entirely voluntary; should you withdraw from the study at any point you will still receive the $10 honorarium. Compensation for Injury Signing this consent form in no way limits your legal rights against the sponsor, investigators, or anyone else.  151  Consent: I, _________________________, have read the above study consent form and I consent to participate in this study undertaken by Dr. Navid Shahnaz at the School of Audiology & Speech Sciences at UBC. The researcher assures me that my participation in this experiment is completely voluntary and that I may withdraw from this research at any time without consequences.  If I have any question or desire further information with respect to this study, I may contact Dr. Navid Shahnaz. If I have any concerns about my treatment or rights as a research subject, I may contact the Research Subject Information Line at the University of British Columbia Office of Research Services. I have received a signed and dated copy of this consent form for my records.  ____________________________ Subject name (please print)  Subject signature  __________________________  ______________________________  Witness name (please print)  Witness signature  __________________________  ______________________________  Name of principal/co-investigator (please print)  Co/Investigator signature  Date  Date  Date  152  

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