Effects of Unilateral Pulmonary Artery or Vein Disten-sion with a Balloon on the Pulmonary and Femoral Arterial Pressures in Anesthetized Dogs

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Abstract
Unilateral pulmonary artery or vein was distended by a balloon in closed and open chest anesthetized dogs. A part of the experiments was performed under perfusion of unilateral lung in situ. Persistent elevation in the pulmonary arterial pressure is always observed during distension of unilateral pulmonary artery as well as a pulmonary vein. Transient fall in the femoral arterial pressure is often observed at the initial stage. Following it, persistent slight decrease during the distension and rebounded rise after release of the distension are sometimes observed. The increase in the mean pulmonary arterial pressure correlated with degree of distension of the pulmonary vascular wall. The maximal change in the mean pulmonary arterial pressure is about 6 mm. Hg or about 37% increase in arterial distension and about 3 mm. Hg or about 22% increase in venous distension. The fall in the femoral arterial pressure correlates with changes in the intraluminal pressure of the inflated balloon. The maximal change of the transient hypotension is about 6% decrease in arterial distension and about 19% decrease in venous distension. The maximal change of the following persistent hypotension is about 3% decrease in arterial distension and about 12% decrease in venous distension. The cardiac output shows about 9% reduction. The pulmonary hypertension is concluded to be due to pulmonary vasoconstriction elicited by stimulation of stretch receptors in the pulmonary artery and vein. Participation of the vagal and sympathetic pathways is not proved. The changes in the femoral arterial pressure are also concluded to be due to both decrease in vascular tone and decrease of the cardiac output.