INFLUENCE OF HIGH ALTITUDE ENVIRONMENT ON BRAIN FUNCTION

Abstract

Acute and subacute altitude exposure tests were performed on 38 members of Himaraya expeditions in a laboratory with low atmospheric pressure, and EEG changes and reactions of physiological acute adaptation were examined in order to obtain informations that will prove of help in preventing hypobaropathy and in health management in high mountain climbing.Meanwhile, EEG during climbing Mt. Everest were recorded and analyzed using power spectrum to compare with the results of above-mentioned tests. An inquiry was also made into the effct of a long-term sojourn at altitudes on brain function which has remained almost unclarified so far.1. Acute exposure to the altitude up to 4, 000m was attended with little change in EEG pattern, while at the altitude around 6, 000m slow waves were observed on EEG in all subjects, suggesting marked depression of brain function.2. EEG changes caused by long-term exposure to altitudes (Mt. Everest climbing) were marked primarily by slowing of alpha waves with a subsequent appearance of slow waves. However, these changes varied grossly in severity with different indivisuals, depending upon the physiological compensatory function of the whole boby.3. A follow-up EEG study demonstrated that a conspicuous delta-bursts occurred on activated hyperventilation following a long stay in altitudes, suggesting that the effects of long-term exposure to high altitude on brain function may persist for a certain period of time.4. Hypoxic symptoms observed in high altitude environment were attributable to the disruption of various physiological compensatory functions and EEG could serve as an index for the evaluation of impairment of brain function.5. It may be concluded that it is difficult to evaluate an aptitude for climbing high mountains only from these results.