Variability of the tympanogram due to eustachian tube closing failure.

Tympanometry is generally considered a reliable measure of middle ear status. Nevertheless are abnormal tympanograms not uncommonly recorded in ears showing no signs of pathology. Recent studies have demonstrated that sniff-induced negative middle ear pressure can be a pathogenetic factor in the development of middle ear disease. It has also been shown that sniff-induced negative middle ear pressure per se, does not necessarily imply malfunction of the eustachian tube, since many normal individuals can evacuate their middle ears by sniffing. The purpose of this paper is to demonstrate that sniffing can produce a shift in the tympanometric pattern, and it is suggested that this mechanism can explain the occurrence of abnormal tympanograms in otherwise healthy ears. Sniffing may also explain the pronounced day-to-day variability seen in tympanometry.