Stretch Reflexes from the Main Pulmonary Artery to the Systemic Circulation

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Abstract
In open-chest dogs, the greater and lesser circulations were perfused by a system of pumps and oxygenator. All blood was drained from the right heart and from the left atrium. in most experiments, there was no dissection around the pulmonary hila, the aorta, or the pulmonary artery. A 30-ml. balloon (Foley catheter) was inserted into the pulmonary artery through a stab wound in the wall of the right ventricle. Pressures were recorded in the pulmonary-artery balloon and in a femoral artery. In other experiments, the main pulmonary artery was distended with blood at known pressures after hydraulic isolation with ligatures and snares. When the main pulmonary artery was distended proximal to its bifurcation, constriction of the systemic arteries occurred. This phenomenon was abolished by local anesthesia of the wall of the main pulmonary artery, by interrupting conduction in the vagi, by a sympatholytic drug, and by reflex systemic hypotension elicited by multiple small pulmonary emboli. The pressor reflex from the pulmonary artery to the systemic circulation was not influenced by changes of pulmonary blood flow or by inflation of other balloons in various chambers of the heart. Limitations inherent in the experimental procedure did not permit us to assign physiological significance to the phenomenon.