Physiological Factors Influencing Pulmonary Artery Pressure During Separate Perfusion of the Systemic and Pulmonary Circulations in the Dog

¹ From the Institute for Medical Research and the Departments of Surgery and Medicine, Cedars of Lebanon Hospital, Los Angeles, California

An open-chest dog preparation is described in which the systemic circulation is perfused by a heart-lung machine and the lesser circulation is perfused by a pump-reservoir circuit. In this preparation there is no connection between the two circulations other than the bronchial flow; the flow in the pulmonary vessels is known and controlled at all times. The influence of physiological variables on pulmonary artery pressure was investigated and the results of earlier investigations were confirmed with reference to pressure-flow relationships, the effect of changes in pulmonary ventilation (in part), the inhalation of CO₂, pulmonary air embolism, the lack of effect of changes of systemic arterial pressure. Increases of systemic venous pressure caused simultaneous increases of pulmonary arterial pressure.