Physiologic Effects of Exposure to Increased Oxygen Tension at 5 Psia.

A PREVIOUS STUDY lo reported the effect on man of exposure to an atmosphere consisting primarily of oxygen at reduced total pressure (190 mm. Hg). Arterial desaturation was found in two of eight test subjects at the conclusion of 17 days, suggesting the possibility of atelectasis being present. This was not cordlrmed by either x-ray or vital capacity data. Atelectasis had been noted, however, at oxygen partial pressures of 418 man. Hg during the course of a seven-day experiment. 8 Since it has been proposed that future manned spacecraft missions utilize an oxygen atmosphere at a total pressure of 5 psia (258 ram. Hg), it was desirable to amplify the results of previous studies with experiments in the anticipated atmosphere. The purpose of the experiments reported here was to observe the possible development of pulmonary atelectasis utilizing arterial and alveolar oxygen and carbon dioxide partial pressures, vital capacity, posterior-anterior chest x-ray, and clinical examination as indicators. Psychomotor performance was included to determine the gross effect of atelectasis (if present) on the functional capability of the test subjects.