[Various individual features of human adaptation to altitude].

Two groups of young healthy men--natives of lowlands who for one year lived and worked in chronic hypoxia (Group 1 at an altitude of 1680 m with PO2 = 120 mm Hg and Group 2 at an altitude of 3650 with PO2 = 90 mm Hg) were examined. It was found that after this prolonged exposure the subjects showed a higher sensitivity of the respiration system to hypoxia, an enhanced lung ventilation and circulation, a lower gas exchange and physical work capacity. The concentration of lactic acid at rest in the Group 2 subjects was 47% higher than in the Group 1 subjects. The lactate/pyruvate ratio in the Group 2 subjects increased by 46% thus indicating an enhanced rate of anaerobic processes. A higher deficiency of buffer bases, a lower concentration of bicarbonates in blood at rest and during exercise tests of the Group 2 subjects pointed to metabolic acidosis. The subjects with a higher rate of anaerobic metabolism in a low PO2 environment displayed a diminished sensitivity of the hypoxic stimulation of respiration, an increased tolerance to the very low PAO2 and a reduced work capacity in chronic hypoxia.