Effect of acceleration on the distribution of pulmonary blood flow

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Abstract
The distribution of pulmonary blood flow has been measured during increased positive (+Gz) acceleration. Macroaggregated albumin labeled with iodine 131 was injected intravenously during centrifugal acceleration, by the method described by Wagner and co-workers. The particles embolize the pulmonary vascular bed in proportion to flow and can be subsequently detected by scintillation scanning of the lung. One study was done in one subject in one of the five following conditions: supine, seated, +2 Gz, +3 Gz, and +4 Gz. The results show a progressively smaller reduction in upper zone perfusion with increasing acceleration agreeing with hydrostatic principles. Flow increased in the base up to +2 Gz but thereafter becomes fixed, suggesting that the vessels were then maximally dilated. The gas exchange consequences of these changes of perfusion are discussed indicating that there must also be ventilatory changes. lung; perfusion; iodine 131; acceleration Submitted on January 18, 1965