Acute pulmonary artery hypertension produced by distention of the main pulmonary artery in the conscious dog.

In order to delineate further the function of the main pulmonary artery as a receptor site, a specially designed Laks triple-lumen balloon catheter was inserted transvenously and positioned in the main pulmonary artery. In six conscious nonsedated dogs, inflation of a balloon in the main pulmonary artery produced acute reversible pulmonary arterial hypertension; the pressure beyond the balloon increased from a mean of 21/6 mm Hg to 43/14 mm Hg (P less than 0,001). This observed pulmonary hypertension occurred at an amount of balloon inflation which produced an increase in right ventricular systolic pressure (P less than 0.001), but no significant change occurred in cardiac output (P greater than 0.05) or right ventricular end-diastolic pressure (P greater than 0.1). Left atrial and pulmonary artery wedge pressures did not change or decreased slightly (P greater than 0.1 and P greater than 0.1, respectively). The calculated pulmonary vascular resistance increased (P less than 0.001), while the calculated systemic vascular resistance did not chang (P greater than 0.04). Therefore, we postulate that distention of the main pulmonary artery in the conscious dog reflexly produces constriction of pulmonary arterioles, and possibly venules, due to excitation of receptors probably located in the wall of the pulmonary artery or possibly the right side of the heart, or both.