Effect of hypobaric hypoxia on auditory sensitivity.

Introduction: Previous studies on the effect of hypobaric hypoxia on auditory sensitivity are not readily interpretable, in most cases because the potential effect of ambient pressure on stimulus level was not considered. In this study, auditory sensitivity to 1, 8, 12, and 16 kHz tones was compared between conditions of hypoxia and normoxia at the same simulated altitude (3700 m).

Method: In the hypoxic condition, the partial pressure of oxygen in the inspired air was allowed to decrease with increasing altitude. In the normoxic condition, the partial pressure of oxygen was maintained at a level equivalent to that experienced at mean sea level (MSL). This comparison also controlled for any effect resulting from physiological consequences of hypobaria other than hypoxia (such as a change in middle-ear impedance).

Results: A small (2.57 dB) reduction in sensitivity across the frequency range tested was observed.

Conclusion: A reduction in sensitivity of this magnitude would not be expected to have a large impact on the effectiveness of information transfer via the auditory modality.