Distribution of pulmonary perfusion in erect man.

Abstract

Xe133 was used to measure regional pulmonary perfusion per alveolus in 6 erect subjects. At FRC [functional residual capacity], 3 lung zones could be defined in relation to flow distribution. Flow appeared to be absent in the uppermost 2.9 cm of the lung (zone 1), then increased rapidly down the lung (zone 2) until 15-20 cm from the top, where the rate of increase in flow became less (zone 3). If the top of zone 2 is taken to represent mean pulmonary arterial pressure (Pa), and the top of zone 3 is taken to represent pulmonary venous pressure (Pv), a close correspondence is found with directly measured vascular pressures. Xe133 data have been used to predict that Pa rises and Pv falls at full inspiration, and that Pv must rise sharply at RV. These predictions have been confirmed by direct measurement in one normal subject. Regional distribution of inspired gas was studied both during inspiration of Xe133 and after room-air inspiration following intravenous injection of Xe . These 2 techniques yielded similar results.