Tympanometric measurements in conscious sheep - a diagnostic tool for pre-clinical middle ear implant studies

Abstract

Objective: To investigate and establish the use of tympanometry in conscious sheep to provide a means of objective assessment of tympanic membrane integrity, middle ear ventilation and functioning of the Eustachian tube (ET). Design: After conditioning the sheep for four weeks, tympanometric measurements at 226 Hz were carried out weekly for 13 weeks. Before measurements, the external ear canal had been cleaned. Resultant curves were classified according to human reference values. Study Sample: Tests were performed on 12 female blackface sheep. Results: After cleaning of the external ear canal under otoscopic control, tympanic membranes were intact with no evidence of acute or chronic middle ear inflammation, middle ear effusion or retraction. Cleaning ensured valid, objective and reproducible measurements. As the majority of normal tympanograms were notched without the appearance of any malformation, an additional tympanogram type (A_N) was introduced. The notched appearance can most likely be explained by the anatomy of the middle ear of the sheep and the test frequency that was used. Conclusion: The current study demonstrated how tympanometry can be used to evaluate treatment modalities for middle ear and ET function in conscious sheep. This provided a large animal model for further human research in otology.

Key Words:

• Animal studies
• medical audiology
• middle ear
• anatomy
• physiology

Acknowledgements

The authors would like to thank Christopher F. Halpin (Department of Audiology in the Massachusetts Eye and Ear infirmary), Frank Mösker (Otometrics), Jasmin Bohlmann, Felicitas Miller, Ines Linke and Odett Kaiser (Department of Otorhinolaryngology) for valuable comments and technical assistance, as well as the central animal facility for the support during the experiments.

Declaration of interest

The authors declare that they have no conflict of interest.

The study was supported by the Federal Ministry of Education and Research Bundesministerium for Bildung und Forschung (BMBF), being a part of REMEDIS sub-project C3 (FKZ03IS2081E).