Body Mass Index, A Silent Determinant of Eustachian Tube Function

Background: The body mass index (BMI) is the metric currently in use for defining anthropometric height/weight characteristics in adults and for categorizing them into groups. It is a convinient indicator of body fat and it correlates sufficiently well with direct measures of total body fat. Eustachian tube (ET) is a fibrocartilagenous structure consisting of two parts: the first solidly connected with the temporal bone, close to the tympanic cavity; the second soft, partly ligamentous, partly cartilaginous, directed towards the nasopharynx. ET functions to protect the middle ear against nasopharyngeal pressure variations, ascending secretions, and microorganisms. Change in BMI with resultant change in adipocyte tissue around the tube (Ostmann's fat) can affect the normal ET function that would manifest in the change in tympanometric parameters. Aim: The aim of this study was to determine the effects of body mass index on tympanometric parameters. Materials and Methods: This is a descriptive community based cross sectional study conducted on adult population aged (18-60 years) in Kano metropolis, northwestern Nigeria. Participants with no history of chronic ear disease, ear surgery or active upper respiratory tract infection were selected using simple random sampling technique. A total of eighty (80) participants and hundred and sixty (160) ears were examined. Each participant had detailed otoscopy, nasal endoscopy, throat examinations, Rinne’s and Webar tests and tympanometry. Each participant had weight and height measured and BMI calculated. Findings were recorded and analyzed. Results: The mean height of the participants was 1.62±0.11M while the mean weight of the participants was 55.96±10.78kg. There was statistically significant difference between the tympanometric parameters of the right and left ears p<0.05. There was statistically significant difference between the tympanometric parameters of male and female participants p<0.05. Tympanometric peak pressure (TPP) was found to be more positive in participants with lower BMI and (ECV) was found to be higher in participants with higher BMI. Discussion: This study found ECV was higher for the right ears compared with the left ears. TPP was also found to be more positive in the right ears compared to the left, however, no statistically significant difference was found in the static compliance (SC) of the right and left. TPP, ECV and SC were all found to be higher in male participants than in female participants. TPP was found to be more positive in participants with lower BMI and more negative as the BMI was increasing, similarly ECV was found to be increasing as the BMI was increasig, with statistically significant correlation. Conclusion: This study established statistically significant relationship between tympametric parameters of the right and left side, with parameters on the right side showing statistically higher values. A statistically significant relationship was equally established between tympanometric parameters of the male and female participants, affirming the effect of genger on tympanometric parameters. BMI was found to have statistically significant relationship with tympanometric parameters, with participant with higher BMI showing more negative TPP and lower SC, signifying higher risk of developing eustachian tube dysfunction (ETD) among overweight and obesse individulas.