1984 Armstrong lecture. Hypoxic man: lessons from extreme altitude

Area of Science:

• Environmental Physiology
• High-Altitude Medicine
• Human Physiology

Background:

• Prolonged exposure to extreme altitudes presents significant physiological challenges.
• Understanding human adaptation to severe hypoxia is crucial for mountaineering and aerospace medicine.
• Previous research has explored responses to moderate altitude, but extreme conditions require further investigation.

Purpose of the Study:

• To investigate the physiological responses of humans to extreme prolonged hypoxia at high altitudes.
• To determine the limits of human tolerance to the low oxygen environment of Mount Everest.
• To gather data for future research on the effects of weightlessness on pulmonary function.

Main Methods:

• Physiological measurements were conducted at four distinct altitudes on Mount Everest, including the summit.
• Key parameters such as alveolar PCO2, arterial pH, arterial PO2, and maximum oxygen uptake were recorded.
• Data collection occurred during the American Medical Research Expedition in the fall of 1981.

Main Results:

• Humans tolerate extreme high-altitude hypoxia through a substantial increase in ventilation.
• Summit measurements revealed alveolar PCO2 of 7.5 mm Hg.
• Calculated arterial pH exceeded 7.7, arterial PO2 was below 30 mm Hg, and maximum oxygen uptake was approximately 1 L/min.

Conclusions:

• The human body compensates for extreme hypoxia at high altitudes primarily through hyperventilation.
• The physiological data provides critical insights into human endurance and adaptation limits.
• Findings inform future research, including studies on the effects of weightlessness on pulmonary function in space.