Hematocrit-corrected Pulmonary Vascular Resistance.

Abstract

The diagnosis and evaluation of severity of pulmonary vascular disease rests on the invasive determination of a pulmonary vascular resistance (PVR). It is often overlooked that PVR is linearly related to the viscosity of the blood, which in turn is curvilinearly related to hematocrit. We propose a correction diagram for patients with anemia or with polycythemia. Based on a distensibility model of the pulmonary circulation, we show that magnitude of hematocrit correction of PVR is increased in proportion to pulmonary artery wedge pressure (PAWP) and the measured levels of PVR or hematocrit, and decreased in case of preserved resistive vessel distensibility and absence of pulmonary hypertension. We also demonstrate that hematocrit correction of PVR is independent of the absolute levels of pulmonary artery pressure or cardiac output. A PVR of 1.5 Wood units (WU) at a hematocrit of 20 % and a high-normal PAWP becomes 4.1 WU at a hematocrit of 45 % and 10.8 WU at a hematocrit of 80 %. A review of reported hemo...