THE EFFECT OF ACUTE-HYPOXIA ON THE LATENCY OF THE HUMAN AUDITORY BRAIN-STEM EVOKED-RESPONSE

Recent studies have shown a decrease in the amplitude and an increase in the threshold of the cat's auditory brainstem evoked response (ABER) during severe hypoxia (PaO2 of 20 to 30 Torr). In this study we have examined the effects of euoxia (end tidal PO2 100 Torr) and mild hypoxia (end tidal PO2 of 45 to 50 Torr) on the latency of the ABER in 6 human subjects. Hypoxia resulted in a blood O2 saturation of between 75 to 85% and caused a significant prolongation of the latency of wave V of the ABER by 0. 185 +/- 0.045 ms (Mean +/- S.D; p < 0.01). The prolongation of the ABER during severe hypoxia has previously been attributed to a change in peripheral sensitivity. Using the stimulus level/response latency relationship obtained for each subject under normal breathing conditions, the change in latency produced by mild hypoxia can be interpreted as a mean shift in auditory sensitivity of 5.1 +/- 3.4 dB. These results suggest that the auditory system is sensitive to much smaller changes in blood O2 saturation than previously thought. auditory sensitivity.