Diagnosis and management of eustachian tube malfunction

The eustachian tube is an essential part of the pressure regulating system of the middle ear. The physiologic function of the tube is to equalize the middle ear pressure with that of the atmosphere, and at the same time make the middle ear independent of the nasopharyngeal environment with its loud sounds, extensive respiratory pressure changes, and potentially harmful bacterial flora. Thus, the protective closing action is essential in the normal physiology of the eustachian tube, and lack of protection is central in tubal malfunction. We have come to consider eustachian tube closing failure and the subsequent induction of negative middle ear pressure as an important causative factor in the development of chronic ear disease, for example, persistent middle ear effusion and manifest retraction of the tympanic membrane. Here, the patient's behavior may be of more importance than the simple tubal mechanics. In the presence of tubal closing failure, if the patient sniffs habitually, the middle ear cavity will be evacuated repeatedly. This constitutes a repetitive barotrauma which may have secondary effects. As a result of the negative pressure the tympanic membrane retracts, and increased transudation and secretion of fluid may give rise to effusion. Tubal closing failure also implies reduced protection against ascending infection with increased susceptibility to acute otitis media. Repeated sniff-induced barotrauma and repeated purulent infection may together be responsible for the development of manifest structural lesions seen in chronic ear disease. Is it possible to determine the function of the eustachian tube? This question is crucial since it is difficult or impossible to give normative values for tubal function tests. The variability of tubal responses with time has been found to be considerable. Thus, the result of a test represents only one specific moment in time, having little prognostic value. Tubal function is a continuous and composite variable that cannot be "determined" according to a static scheme. Our knowledge of eustachian tube physiology is still fragmentary, and continued study is necessary in order to learn more. Presently, tubal function tests have little value from the clinical viewpoint. When a tympanoplastic procedure is considered, the need for surgery should be determined by the clinical judgment based on the otomicroscopic findings and the hearing. In the case of a central perforation of the eardrum the prognosis for hearing is good, irrespective of results obtained in tubal function tests.(ABSTRACT TRUNCATED AT 400 WORDS)