Alveolar-arterial oxygen gradient in Andean natives at high altitude

Abstract

The A-a Do₂ (alveolar-arterial oxygen tension difference) was determined at three levels of oxygenation in three groups of subjects: 1) normal persons at sea level, 2) normal Andean natives at high altitude, 3) Andean natives with chronic mountain sickness. The values of A-a Do₂ in the Andean natives were uniformly higher than in normal sea-level residents at all levels of oxygenation. These findings were accentuated in patients with chronic mountain sickness. It is concluded that there is no decrease in diffusion barrier for oxygen, and there may be increased veno-arterial shunting in the lung and wider distribution of ventilation-perfusion ratios in the high-altitude residents than in normal subjects at sea level; and that part, at least, of the condition of chronic mountain sickness is an accentuation of these changes. tissue hypoxia; acclimatization; chronic mountain sickness; secondary polycythemia; pulmonary O₂ diffusion barrier; pulmonary veno-arterial shunt; pulmonary ventilation perfusion ratio Submitted on April 3, 1963