The relationship of pulmonary vascular resistance and compliance to pulmonary artery wedge pressure during submaximal exercise in healthy older adults

Abstract

The resistive and pulsatile components of right ventricular afterload [pulmonary vascular resistance (Rp) and compliance (Cp)] are related by an inverse hyperbolic function, expressed as their product known as RpCp-time. The RpCp-time exhibits a narrow range, but may be altered by the pulmonary artery wedge pressure (PAWP). Elucidating the determinants of RpCp-time should improve the understanding of the physiologic behaviour of the pulmonary arterial systolic, diastolic, and mean pressure (PASP, PADP, mPAP) in response to perturbations. We examined the effect of exercise in 28 healthy non-athletic adults (55 ± 6 years) who underwent right heart catheterization to assess hemodynamics and calculate Rp and Cp. Measurements were made at rest and during two consecutive 8–10 min stages of cycle-ergometry, at targeted heart-rates of 100 bpm (Light) and 120 bpm (Moderate). Cardiac output increased progressively during exercise. PASP, PADP, mPAP and PAWP increased at Light exercise, without further rise at Moderate exercise. RpCp-time decreased at Light exercise (0.39 ± 0.08 to 0.25 ± 0.08, P < 0.001) without further change at Moderate exercise, and the decrease in RpCp-time was related to changes in PAWP (r^2 = 0.26, P < 0.001). Changes in each of PASP (r^2 = 0.43, P < 0.001), PADP (r^2 = 0.47, P < 0.001), and mPAP (r^2 = 0.50, P < 0.001) were linearly correlated with changes in PAWP, but were not significantly related to changes in cardiac output. In healthy adults exercise is associated with decreases in Cp and a resultant decline in RpCp-time, indicating increased pulsatile right ventricular afterload. Changes in RpCp-time, PASP, PADP and mPAP were systematically related to increases in PAWP.

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