Tympanometric measures in ears with negative middle ear pressure, and tests of some common assumptions

Abstract

Objective: To test the assumptions concerning the compensation of middle ear pressure (MEP) in using peak Y_tm and the tympanogram asymmetry phenomenon, and to address the variability and reliability of 226 Hz tympanometry under negative MEP. Design: (1) Repeated measures in normal ears with experimentally-induced negative MEP; (2) Retrospective analysis of clinical data from ears with negative MEP. Study sample: Experimental data: 57 adult ears. Clinical data: 200 adult ears. Results: Mean peak Y_tm significantly increased (˜ 0.10 mmhos) under negative MEPs (> − 190 daPa). TW increased, up to ˜50 daPa, for MEP ≤ − 130 daPa. V_ea decreased when MEP ≤ − 190 daPa. With increasing negative MEP, peak Y_tm and tympanogram gradient tended to decrease. The within-subject variation of all measures and difference between normal and negative MEP were small. Conclusions: The tympanometry procedure increases peak Y_tm in ears with low to moderate negative MEP, and decreases gradient and V_ea with high negative MEP. This is referred to as hypercorrection of the admittance and should be accounted for in clinical norms. Results imply that tympanogram asymmetry is due to divergent effects of air pressure on the middle ear. The variability of tympanometry does not increase and reliability not decrease under negative MEP.

Key Words::

• Tympanometry
• acoustic immittance
• acoustic admittance
• middle ear
• negative middle ear pressure

Acknowledgements

We thank the Evelyn Hendren Cassat Speech-Language-Hearing Clinic of Wichita State University for their support, and Kayla R Eldridge for her assistance in the collection of data from patients’ clinical records.

Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for writing and content of the paper.