BLOOD FLOW THROUGH EACH LUNG IN MAN DURING UNILATERAL HYPOXIA 1

Abstract

Effects of pulmonary unilateral hypoxia upon the distribution of pulmonary blood flow through each lung were studied in 6 normal subjects. The techniques of bronchospirometry, cardiac catheterization and arterial cannulation were combined to obtain blood and gas samples for the determination of data permitting the application of the Fick principle to the measurement of total pulmonary blood flow and of unilateral blood flow through one lung breathing a mixture of 25% O2 in N2. Estimation of blood flow through the contralateral lung breathing room air or a hypoxic mixture was obtained by difference. Validity of the method is discussed in detail. During unilateral breathing of 10% O2 in N2, the total blood flow, the distribution of blood flow through each lung, and the pulmonary arterial pressures remained unchanged, while the arterial blood O2 saturation was on an average reduced to 91%. It is concluded that under these conditions (1) the unilateral hypoxic stimulus does not act upon either the lung, the postarteriolar segments of the pulmonary vascular bed, to increase pulmonary vascular resistance to blood flow and (2) that the weak arterial hypoxemic stimulus is not capable of increasing total cardiac output or causing pulmonary hypertension.