Cognitive performance during short acclimation to severe hypoxia

Exposure to high altitudes requires acclimation or acclimatization, to prevent the negative effects of severe hypoxia. Among several methods, short acclimation with intermittent exposure to severe hypoxia in a hypobaric chamber triggers efficient physiological pre-adaptation mechanisms (11-13). However, we have little knowledge about the cognitive repercussions of such an acclimation protocol.

Four mountaineers were tested daily in the course of a short acclimation protocol (5 d). After their SaO2 (arterial oxyhemoglogin saturation) were recorded, they carried out a choice reaction time task (Manikin test) twice every day; first at ground level (250 m, control sessions), second at the highest altitude of the day (D1 = 5000 m, D2 = 5500 m, D3 = 6000 m, D4 = 6500 m, D5 = 7000 m).

High altitude SaO2 level decreased during the first 3 d, then stabilized around 72-73%. Despite a slight and transient increase at the highest altitude relative to the ground level in D4, the error rate remained low throughout the protocol. Further, response time to the Manikin task did not show significant changes among the days during the acute stage of hypoxia relative to ground level up to 7000 m.

On the whole, it seems that a short acclimation protocol based on intermittent exposure to simulated high altitudes triggered adaptive processes without major impairment in a choice reaction time task during the acute stages of severe hypoxia.