Effect of negative-pressure inflation of the lung on pulmonary vascular resistance

Abstract

Pulmonary vascular resistance was studied as a function of both transpulmonary pressure and lung volume, using excised dog lungs inflated by lowering pleural pressure and perfused with fresh, heparinized dog blood. The absolute magnitude of the vascular pressures was kept constant. Measurements were taken under static conditions. In all cases, resistance was found to be lowest at approximately half maximal lung volume and showed a progressive rise on either further inflation or further deflation. Also, the course of resistance as a function of transpulmonary pressure was found to vary significantly according to inflation history, especially inflation vs. deflation, but was found to be relatively constant when plotted against lung volume. It is thus concluded that pulmonary vascular resistance is volume-dependent rather than pressure-dependent when inflation is accomplished by lowering the pressure around the lung. Submitted on September 19, 1960