Changes in alveolar and arterial gas tensions as related to altitude and age

¹ Department of Anatomy and Physiology, Indiana University, Bloomington, Indiana

In the summer of 1962 at the White Mountain Research Station the early phases of altitude acclimatization were studied in six of the surviving eight members of the 1935 expedition to the Chilean Andes; they were from 58 to 71 years of age. Alveolar and arterial Po₂ and Pco₂ were determined for each man a few hours after arrival at 3,093 m and at 3,800 and 4,343 m over the next few days. The effects of age were superimposed on the classical responses to high altitude. The arterial and alveolar Pco₂ values showed no significant gradient; the alveolar Pco₂ was found to be lower for a given altitude than 27 years before. For example, their average alveolar Pco₂ at 4,700 m in 1935 was 27.7 mm Hg as opposed to 25.1 mm Hg at 4,343 m in 1962. The case of Hall was exceptional: his alveolar Pco₂ ranged from 21 to 24 mm Hg regardless of altitude for his sojourn of 22 days. In 1935 these six men had a mean A-a Po₂ gradient of +3.0 mm Hg at 4,700 m, while in 1962 the gradient over the three altitudes was +12.4 mm Hg. These findings would likely be explained partially by age changes in the pulmonary ventilation-perfusion ratio.

Submitted on February 19, 1963