Pressure chamber tympanometry in diving candidates

The currently recommended examination for diving fitness ascertains middle ear autoinflation ability only under surface pressure conditions. The purpose of our study was to document and quantify middle ear pressure equalization failure during simulated dives among diving candidates who had otherwise met the otologic criteria for diving fitness. Forty-two candidates for regular naval diving activity were included in the study. Tympanograms of both ears at 1 and 1.1 absolute atmospheres (ATA) were taken inside a pressure chamber with the subjects in two positions: seated and supine. At a pressure of 1 ATA, type A tympanograms were found in all 84 ears examined. At a pressure of 1.1 ATA, with subjects in the upright position, 19 (22.9%) of the ears had type C and 2 (2.4%) type B tympanograms, while with subjects recumbent during descent, 6 of the ears (7.2%) had type C and 7 (8.4%) type B. Our results suggest that successful autoinflation at surface ambient pressure does not necessarily reflect middle ear pressure equalization ability during descent in a dive.