How to measure peripheral pulmonary vascular mechanics

Abstract

Pulmonary hypertension (PH) is initially a disease of the small, peripheral resistance arteries. Changes in these vessels are best assessed by measurement of pulmonary artery pressure at several levels of flow to generate multi-point pressure-flow curves. This approach is superior to the traditional single-point measurement of pulmonary vascular resistance (PVR) because it allows a flow-independent definition of the resistive properties of that portion of the pulmonary vascular bed and also provides information on its distensibility. In animal models, multi-point pressure-flow curves can be obtained using an isolated, ventilated, perfused lung system. Clinically, cardiopulmonary exercise testing (CPET) with non-invasive echocardiography is feasible and provides realistic values of the resistance and peripheral compliance. Together, these values can be used to better understand and screen for PH and exercise-induced PH.

Fig. 1

Multi-point pressure-flow curves in isolated, ventilated, perfused lungs from healthy control (○: PAP, □ LAP) and chronically hypoxic (△: PAP, □: LAP) mouse lungs with best fits to (1) shown in solid (CTL) and dashed (HPH) lines. Note that HPH lungs have increased pressure at all flow rates due to remodeling of small, peripheral arteries.

Fig. 2

Multi-point pressure-flow curves for two representative healthy human subjects during CPET with echocardiography showing a wide range of normal pressure-flow relationships and goodness-of-fit to linear and curvilinear (1) shapes.