The Effect of Acute Hypoxia on the Latency of the Human Auditory Brainstem Evoked Response

Abstract

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 (P_aO₂ of 20 to 30Torr). 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.

Key Words:

• mild hypoxia
• auditory sensitivity