Effects of Progressive Vascular Occlusion on Slope and Intercept of the Pulmonary Artery Pressure-Flow Relationship

Abstract

Pulmonary hemodynamics may be described by mean pulmonary arterial pressure (PAP)-cardiac output (CO) plots. The slope of the PAP-CO relationship may define the incremental resistance (IR), and the extrapolated pressure intercept (P_I), the effective outflow pressure. The authors investigated the effects of progressive pulmonary vascular occlusion on the IR and P_I of the PAP-CO plot.

Nine experimental and nine time control dogs were studied. In the former group, PAP-CO plots were obtained in three conditions: (1) Baseline, (2) following occlusion of the right pulmonary artery, and (3) following occlusion of the right pulmonary artery and blood flow to the left upper lobe. Following progressive occlusion, there was a corresponding increase in the IR of the PAP-CO plot, from 1.95 to 3.62 to 5.16 mmHg.1^-1.min (all P < 0.05). In contrast to the increase in IR, P_I remained constant. Over the same interval, there were no changes in IR or P_I in the time control group.

These findings indicate that changes in the slope of the PAP-CO plot correspond to changes in the number of parallel vascular units.

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