The physiology of pressure breathing; a brief review of its present status

Barach, A.L.; Fenn, W.O.

Journal of Aviation Medicine 18(1): 73-87


ISSN/ISBN: 0095-991X
PMID: 20287794
Document Number: 3190
Pressure breathing is a device for increasing the altitude tolerance by increasing the pressure of the gases in the mask. This brings with it certain disadvantages, notably the discomfort of an extra tight mask, the difficulty of expiring against pressure, and the interference with the venous return. If the pressure in the mask does not exceed the ambient pressure by more than 10 to 15 mm. Hg, these difficulties are not serious, and the increased pressure of oxygen in the mask provides a gain in altitude tolerance which, on the average, is just what would be expected if the ambient pressure were increased a similar amount. The difficulty of expiring against continuous pressure can be avoided by the use of intermittent breathing devices which keep the pressure high on inspiration and low on expiration. This, however, usually results in hyperventilation which has an unfavorable effect on performance if the alveolar carbon dioxide tension falls below 25 mm. Hg. If this danger is avoided, intermittent pressure breathing is a useful method of gaining altitude. A discussion is included of the best criteria to be used for the measurement of the value of procedures like pressure breathing which are designed to improve the performance at altitude.

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The physiology of pressure breathing; a brief review of its present status