Studies on the physiopathology of experimental pulmonary embolism. 1. Pulmonary and systemic hemodynamics

Abstract

The purpose of this study on 25 closed-chest, anesthetized dogs, which were subjected to catheterization of the pulmonary arteries and veins, was to contribute to the question of the nature of the pulmonary and systemic hemodynamic changes that occur with pulmonary embolization. By balloon occlusion of a lobar artery of the left lung a slight but statistically significant increase in the pulmonary arterial pressure and in the pulmonary resistance was obtained. As with a simple mechanism of obstruction a similar rise in pressure was obtained—sometimes of lesser degree, sometimes completely absent. Only by occluding a main branch of the pulmonary artery, we came to the conclusion that the hypertension which we have shown must also be based on the occurrence of a reflex factor. Inflation of the balloon led to no modification of either the pulmonary venous pressure or the systemic blood pressure. By successively injecting a suspension of barium sulfate and iron perchloride distal to the inflated balloon, we obtained a further and much more severe increase in the pulmonary arterial pressure, without a rise in the venous pressure, and with an increase in the pulmonary vascular resistance. Having ascertained also by histologic examination that the embolization could not be extended beyond the area of injection, and so could not reduce the pulmonary vascular bed, we confirmed that also for this remarkable hypertension in the lesser circulation the intervention of a refiex mechanism must be accepted. Together with the embolism, a severe systemic arterial hypotension was obtained which was sometimes fatal. We also have discussed the possibility of a reflex factor in the pathogenesis of this phenomenon.