OXYGEN DIVING-INDUCED MIDDLE-EAR UNDER-AERATION

Middle ear negative pressure and effusions have been described after o xygen diving. The prevalence, dynamics and pathophysiology of this phe nomenon are not clear, and were hence investigated in the present stud y. Thirty-four oxygen divers with normal otoscopic and tympanometric e valuation participated in the study. The subjects' symptoms were docum ented, and pneumatic otoscopy and tympanometry were repeated immediate ly after the completion of a 3 h, 15 feet oxygen dive, and 7 h later o n awakening from the night's sleep. Most divers had positive otoscopic findings the morning after the dive, all of which cleared within 4 h of rising. A significant decrease was observed in average middle ear c ompliance (p = 0.0463, one way ANOVA), and an increase was found in th e number of ears with tympanic compliance less than 0.3 ml (p = 0.0001 , Kruskal-Wallis non-parametric ANOVA). In addition, 14.7% of the ears had type C, and 27.9% type B tympanograms the morning after the dive (p = 0.0001 chi(2)). The generalized nature of oxygen-induced middle e ar under-aeration, combined with the dynamics of the symptoms and sign s observed, make middle ear barotrauma, tympanic cavity oxygen absorpt ion, and middle ear epithelial oxygen toxicity all unlikely explanatio ns. The observed phenomenon and its dynamics might stem from a reversi ble derangement in a middle ear chemoreceptor reflex arch, which has r ecently been suggested as regulating middle ear aeration.