THE EFFECT OF ACETYLCHOLINE ON THE HUMAN PULMONARY CIRCULATION UNDER NORMAL AND HYPOXIC CONDITIONS1

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Abstract
Acetylcholine was infused at the rate of 0.5 mg/ minute into the pulmonary artery of 8 human subjects under normal and hypoxic conditions. The drug caused a fall in pulmonary arterial pressure which was more evident after hypoxia had produced pulmonary hypertension. The fall in pressure was not associated with a reduction in cardiac output, and there was no change in the pulmonary wedge pressure, heart rate, systemic blood pressure, or central blood volume. Results suggest that acetylcholine dilated the pulmonary vessels. The enhanced effect during hypoxia was believed to be due to an increased vascular tone.