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We have examined the effects of prolonged periods of hypoxia produced at high altitudes on the latency of the auditory brain-stem evoked response (ABER) in 9 subjects at around sea level, 3,500 m, and 4,370 m. Following an ascent from 1,300 m to 3,500 m over 24 h, the mean blood O2 saturation fell to 86.5 +/- 1.2% (+/- S.E.M.) and was associated with a mean prolongation of latency of wave V of the ABER of 0.34 +/- 0.10 ms (p = 0.011 two-tailed paired t-test). Using the stimulus-level/response latency relation determined at around sea-level for each subject, this prolongation of wave V corresponded to a mean reduction in sensitivity of 9.1 dB +/- 1.6 dB. Over a period of 72 h, blood O2 saturation improved slightly (mean 88.1% +/- 1.8%) and mean wave V latency returned to control values. A second rapid ascent to 4,370 m reduced blood O2 to below prerecovery levels (82.5% +/- 1.7%), but in this case there were no significant changes in auditory sensitivity (p = 0.79 two-tailed paired t-test). These data show that mild hypoxia results in an initial decrease in auditory sensitivity. However, the recovery of sensitivity with more prolonged exposure suggests that the auditory system can compensate for chronic mild hypoxia.

Type

Journal article

Journal

Aviat Space Environ Med

Publication Date

12/1992

Volume

63

Pages

1093 - 1097

Keywords

Adult, Altitude, Altitude Sickness, Auditory Threshold, Brain Stem, Evoked Potentials, Auditory, Brain Stem, Female, Humans, Hypoxia, Male, Oxygen, Reaction Time