Effect of alveolar hypoxia on zonal distribution of pulmonary blood flow

Abstract

Redistribution of pulmonary blood flow was studied by means of the cardiogenic oscillations of expired gas tensions in six normal subjects after induction of alveolar hypoxia (13.5% O2 inspired). In three subjects the upper zones of the lungs were found to receive a considerably greater proportion of total pulmonary blood flow during hypoxia in both vertical and horizontal postures. Two subjects showed no redistribution in either position. The response of one subject was intermediate between these two groups. It is concluded that in some subjects there is no pulmonary vascular response to alveolar hypoxia, whereas in others there is a response consisting of preferential lower-zone vasoconstriction of greater or lesser magnitude. Earlier data on the effects of hypoxia on the pulmonary circulation are shown to be consistent with the operation of this mechanism. Submitted on July 16, 1962