Normative ranges of tympanometric measurements in cats

Abstract

Middle ear diseases are common in cats. The aim of this study was to determine the normative tympanometric data of cats. Tympanometry, which provides objective data in the examination of the middle ear in humans, can be used as a supplementary examination, especially in cats with middle ear diseases where the external ear canal is normal. In this study, 30 healthy ears belonging to 15 cats which were classified as ASA-I (American Society of Anesthesiologyist) were determined and evaluated according to equivalent ear canal volume (Vea), static acoustic admittance [Ytm (compliance)], tympanometric peak pressure (TPP) and gradient values under general anesthesia. Tympanometric measurements obtained from right and left ears were 0.61 ± 0.12 ml and 0.60 ± 0.12 ml Vea, 0.31 ± 0.11 ml and 0.31 ± 0.11 ml Ytm, -11.2 ± 26.9 daPa and -14.9 ± 29.2 daPa TPP, 0.19 ± 0.11 ml and 0.24 ± 0.18 ml gradient respectively.Tympanometry as a supplementary examination is an easy to perform test in healthy cats with consistent results. It has the advantages of being completed in a short time, easy evaluation and providing information about middle ear without advanced imaging techniques. Results of this study represents the normative tympanometric measurements of cats which can be helpful distinguishing normal and abnormal conditions. Further studies needed to present exact values of standart tympanometric measurements and to introduce other variables like acustic refleks, wideband and multifrequency tympanometric results. 1Department of Surgery, Faculty of Veterinary Medicine, Burdur Mehmet Akif Ersoy University, Burdur/TURKEY MAE Vet Fak Derg, 5 (3): 131134, 2020 DOI: 10.24880/maeuvfd.813073 Bu makaleye atıfta bulunmak için/ To cite this article: YS ŞİRİN, Ö ŞENGÖZ-ŞİRİN. Normative ranges of tympanometric measurements in cats. MAE Vet Fak Derg. 2020; 5 (3) :131-134. INTRODUCTION Impedance audiometry has two main components: tympanometry and stapedius reflex measurement (1). Tympanometry is one of the most frequently performed and important components of the basic audiological evaluation. Objective middle ear assessment can best be performed by tympanometry (2). It measures how the middle-ear system responds to sound energy and changes in atmospheric pressure. It provides an objective, physiological measure of the acoustic admittance of the middle ear with the aid of air pressure in a sealed ear canal (3). The permeability and resistance of the middle ear system is defined with tympanometry via measuring the response to a sound stimulus using a microphone while pressure is changed along the external ear canal (4). The purpose of tympanometry is to asses audition on the basis of an objective description of the integrity and compliance of the eardrum, the mobility of the ossicular chain, the function of middle ear muscles and their attachments, and the size of the external ear canal (3). Data can be obtained from a tympanometer are estimated volume of air in front of the probe (equivalent ear canal volume, Vea), maximum compliance (Ytm), pressure at which the middle ear system has the greatest absorption of sound energy (TPP) and gradient of the tympanogram curve (5). Qualitative and quantitative approaches have been used in the interpretation of 226-Hz tympanograms (6). Tympanograms can most simply be classified as types A, B, and C depending on the curve shape compared to 0 as the pressure is changed (2). Further classification according to the shape of the curve is also used widely, type A as normal and type B, C, AD and AS as abnormal. Quantitative analysis of tympanograms is prefered, especially when evaluating infants and children, for whom different age-based normative values are needed (6). Definitions within modified Jerger classifications of tympanogram is described according to middle ear compliance (Ytm in ml) and middle ear pressure (TPP in daPa) as: type A (Ytm ≥0.2; TPP above –100), C1 (Ytm ≥0.2; TPP below or equal to –100 and above –200), C2 (Ytm ≥0.2; TPP below or equal to –100 and above –400) and B (Ytm <0.2; TPP below or equal to –400). Clinicians usually combine A and C1 as normal (7). The aim of this study was to evaluate the usefulness and consistency of the 226Hz tympanometer and its values in healthy cats. However, there are early tympanometry articles with cats, according to the authors knowledge these are the first published in vivo normal tympanometry values. MATERIAL and METHODS Cats brought to Mehmet Akif Ersoy University Animal Hospital for elective surgery without ear problems were included in the study. The study was approved by the Ethics Commission of Mehmet Akif Ersoy University. Fifteen mixed breed male (n: 7) and female (n: 8) cats at the age between 12-24 months included in the study. All cats were clinically Research Article