Resting pulmonary diffusing capacity for CO and O2 at high altitude

Abstract

The possible increase of pulmonary diffusing capacity at high altitude is still controversial. During an expedition on Monte Rosa, Italy, experiments were performed on five male subjects, 27–44 years of age, at rest after a sojourn of 7–10 days at an elevation of 4,560 m, using two independent methods. Pulmonary diffusing capacity for CO (Dl_CO) was determined with the steady-state method at three levels of oxygenation with inspiratory O₂ pressures of 80, 150, and 400 mm Hg both at sea level and at altitude. The evaluation of the O₂ pressure diffusion gradients in hypoxia, obtained from the alveolar-arterial O₂ pressure gra dients and the arterio-alveolar CO₂ pressure gradients in hypoxia, permitted the estimation of the diffusing capacity for O₂ (DlO₀₂). There was no significant difference between sea level and high altitude in Dl_CO at the three levels of oxygenation, in the O₂ diffusion gradient and in DlCOCO₂ with hypoxia. alveolar-arterial O₂ pressure gradient; arterio-alveolar CO₂ pressure gradient; high altitude adaptation; acid-base balance of the blood Submitted on June 17, 1964