Composition of Alveolar Air and Rate of Pulmonary Ventilation During Long Exposure to High Altitude

Alveolar gas pressures and resting pulmonary ventilation were repeatedly measured as four subjects were continuously exposed to increasing altitude in a low pressure chamber during a thirty-five day period. Average alveolar carbon dioxide and oxygen pressures correspond closely with the data of other observers up to 18,000 feet. Above this point the alveolar sub p CO2 values of our subjects were lower. Alveolar sub p O2 values were also slightly lower than those reported by Helmholz et al. The respiratory quotients of our partially acclimatized subjects were lower than those of the subjects of short term exposures. The values reported herein are probably more representative of the equilibrium state at any given altitude. In terms of ambient conditions, pulmonary ventilation was found to increase with increasing altitude. In terms of standard conditions, however, ventilation remained nearly constant at the altitudes studied. This indicates that roughly the same number of molecules of oxygen were taken into the lungs during inspiration at altitude as at sea level.