Audiometric survey and endoscopic study of the external auditory canal were performed on a group of 31 professional divers, all of whom had experienced frequent exposure to dysbaric conditions.
The results are as follows.
1) Over 40% had exostosis of the external auditory canal. There was no relationship between the incidence of the exostosis and the length of their occupational career as a diver. Many of the divers had hearing loss whether they had exostosis or not.
2) Over 70% had sensorineural hearing loss, taking into account hearing loss due to aging. Most had no experience of inner ear barotrauma on descent, causing sudden a shift in hearing threshold. Deafness was related to the length of their occupational career as a diver.
In conclusion, we speculate that repetitive small changes in barometric pressure on the outer ear influences the pressure on the middle ear and further on that of the perilymph, finally damaging the inner ear auditory system.