Propagation of Blood Flow Pulse in the Normal Human Pulmonary Arterial System

We studied a number of dynamic events associated with the pulsatile flow of blood in the pulmonary arterial system of six healthy men in the supine position. We used the nitrous oxide-body plethysmograph method to record the pulmonary capillary blood flow pulse and the phonocardiogram to determine the time of opening and closing of the pulmonary valve. The pattern of right ventricular ejection was modified by administration of atropine and isoproterenol and by exercise. The time of conduction of the flow pulse from the pulmonary valve to the lung capillaries averaged 120 msec. Acceleration of capillary blood during systole averaged 8.2 ml/sec/msec. The fraction of stroke volume which distended the pulmonary arterial system during systole averaged 67.2%. The peak flow rate averaged 186 ml/sec. Tachycardia resulted in a decrease in the fraction of the stroke volume stored in the arterial tree during systole. Isoproterenol and exercise resulted in an increase in average capillary blood acceleration. Conduction time is accounted for by pulmonary arterial distensibility, which also allows storage of the ejected blood during systole, which in turn helps to maintain continuity of blood flow in the capillaries. Despite these modifying effects of the pulmonary arterial system upon the flow wave, changes in the pattern of inflow pulse were detectable in the capillary flow pulse. ADDITIONAL