Effects of unilateral pulmonary artery or vein distension with a balloon on the pulmonary and femoral arterial pressures in anesthetized dogs.

performed under perfusion of unilateral lung in situ. During the distension, persistent elevation of the pulmonary arterial pressure was always observed. The rise correlated with degree of distension of the pulmonary vascular wall. Transient systemic hypotension was often observed at the initial stage. Following it, persistent slight hypotension was sometimes observed during the distension. The transient hypotension correlated with changes of the intraluminal pressure of the balloon. The cardiac output and the instantaneous aortic flow showed slight decrease. It is concluded that the observed pulmonary hypertension is due to pulmonary vasoconstriction, and that the observed systemic hypotension is due to both systemic vasodilatation and decrease of the cardiac output.