Distribution of vascular resistance in the isolated perfused dog lung.

Publisher Website
Google Scholar
Abstract
The vascular waterfall effect was used to measure the pressure falls due to arterial, "capillary," and venous resistances during perfusion of excised, liquid-filled, and air-filled dog lungs. The venous pressure drop was estimated in the situation where, theoretically, the pressure within the venous end of the capillary equalled that just outside it. At each rate of perfusion, the left atrial pressure, when this occurred, was shown by a sharp change in the relationship between the pulmonary arterial and left atrial pressures. Pericapillary pressure as that to which the pulmonary arterial pressure fell when flow was stopped was estimated. Thus, the end-capillary to left atrial pressure difference was obtained. The arterial pressure difference was similarly assessed by reversing the direction of perfusion. The total resistive pressure drop across the lungs was the same with forward as with reverse perfusion. Venous and arterial pressure differences increased with perfusion rate in liquid-filled but not significantly in air-filled lungs. In air-filled lungs that portion of the total pressure drop due to the capillaries predominated and increased at faster flow rates and with larger numbers of capillaries in the waterfall state.