Influence of Vessel Distension and Myogenic Tone on Pulmonary Arterial Input Impedance. A Study using a Computer Model of Rabbit Lung

Publisher Website
Google Scholar
Abstract
A computer model of the pulmonary arterial (PA) bed of rabbit lungs was designed to test experimental observations of changes in PA input impedance and pulsatile hydraulic power (Wp) during increased PA pressure. The computer model was based on a simple 3-component analog representation of single vessels (i.e., resistance, inertance and compliance). Arterial vessels (16 generations), ranging from PA to 60 .mu.m diameter, were combined to calculate PA input impedance. Input impedance closely mimicked that observed experimentally. Both venous pressure elevation and arteriolar constriction reduced input impedance and Wp. By combining arteriolar constriction with increased myogenic tone of the larger arteries, Wp showed a minimum level at a certain PA pressure, dependent on the degree of arterial stiffening. Wp followed changes in arterial volume and resistance during simulated vasoconstriction. Wp dissipation in arterial vessels was calculated to approximately 50% of total input Wp at physiological pressure conditions, and could be reduced by one half after PA pressure increase from 20 to 50 cm H2O, despite a concurrent halving of arterial compliance. Arterial vessels smaller than 200 .mu.m diameter had negligible direct influence on PA input impedance.