Auditory and vestibular function in human subjects exposed to oxygen at two atmospheres absolute

Abstract

Experiments were conducted to test the hypothesis that intermittent exposure to oxygen at two atmospheres absolute (2 ATA) could delay the onset of pulmonary toxicity. This paper reports effects of 2 ATA O2 (total exposure time of 14.1–19.3 h) upon the auditory and vestibular systems of five diver volunteers and effects of a normoxic N2O2 mix on a sixth. Immediately after exposure four subjects had increased acuity by air conduction in the mid-frequency range. Bone conduction sensitivity increased for all six subjects. Middie-ear reflexes were depressed or absent with only partial recovery one month after the experiment for the O2-breathing subjects, but were more sensitive after exposure for the subject breathing N2O2. Middle-ear pressures grew markedly more variable for O2 subjects up to 72 h postexposure, implying decreased eustachian tube function from oxygen. Vestibular systems of four O2-exposed subjects and the N2O2 subject were markedly suppressed to caloric stimulation after exposure, implying pressure as the contributory cause. Operational application may be found in possibly sensitizing certain frequencies to improve the listener's ability to detect signals in noise. [Work supported by CIC, NRMC. and COMSUBDEVGRU ONE.]