1984 Armstrong lecture. Hypoxic man: lessons from extreme altitude.

Physiological responses to extreme prolonged hypoxia were studied during the American Medical Research Expedition to Mount Everest in the fall of 1981. Measurements were carried out at four sites on the mountain, including the summit. The results show that man can tolerate the extreme hypoxia of these great altitudes only by an enormous increase in ventilation. Alveolar PCO2 on the summit was 7.5 mm Hg, the arterial pH and PO2 were calculated to be over 7.7 and less than 30 mm Hg, respectively, and maximum oxygen uptake was about 1 L X min-1. Our experimental program is now moving to Spacelab IV to study the effects of weightlessness on pulmonary function in 1985 or early 1986.