Arterz’aZ Blood Gases dzlrhzg Presswe Bred thing at Simzcla ted High Altitudes1

R ECENT ADVANCES in aircraft design have made possible attainment of altitudes in which man is unable to live, even while breathing pure oxygen. This difficulty has been overcome by the development of pressurized cabins and, to some extent, by the use of pressure-breathing equipment. The latter effectively increases alveolar oxygen tension; however, there has been some uncertainty as to whether, in the presence of the unusually high intrapulmonary pressure increment, the expected increase of arterial oxygen saturation actually occurs. Likewise, there is uncertainty as to whether carbon dioxide exchange and acid-base equilibrium remain within normal or reasonable limits. To test these points we have studied the oxygen saturation, carbon dioxide content and PH of the arterial blood of young men during pressure breathing at rest, at simulated high altitudes in a low-pressure chamber.