LATE-BREAKING ABSTRACT: Functional and clinical correlations of daily physical activity in patients with pulmonary arterial hypertension

Abstract

Background: PAH patients exhibit reduced daily physical activity (DPA)1 but the physiological and clinical correlations of DPA in PAH are unknown. Aims and objectives: To investigate: i) the association of DPA with baseline clinical and physiological characteristics and ii) cardiac output (CO) and quadriceps oxygen saturation (Q%StO2) responses during DPA in PAH patients. Methods: A cross-sectional study of 13 stable PAH outpatients who undertook: 1) a preliminary incremental treadmill test with measurement of movement intensity by triaxial accelerometer (MoveMonitor®), 2) 7-day monitoring of DPA, 3) individualized cardiopulmonary treadmill testing corresponding to each patient's mean movement intensity of DPA with real-time measurements of CO (PhysioFlow®) and Q%StO2 (NIRO 200NX®). Results: There was moderately strong positive correlation between movement intensity of treadmill-reproduced DPA and changes in Q%StO2 from rest (r=.619, p=0.02). Moderately strong negative correlations were identified with NT-proBNP (r=-.622, p=0.02), CO during treadmill-reproduced DPA (r=-.650, p=0.02) and also, with changes in CO (r=-.699, p=0.01) and heart rate (r=-.738, p=0.004) from rest. No correlations were identified between quality of life (CAMPHOR, emPHasis-10), WHO FC, 6MWD, TLCO and peak VO2. Conclusions: Greater levels of DPA are associated with enhanced locomotor muscle oxygen saturation and milder changes in central hemodynamic responses. Thus, preserved limb muscle oxygen supply and utilisation may be an important determinant of DPA in PAH patients. 1. Pugh, M.E. et al. Physical Activity Limitation as Measured by Accelerometry in Pulmonary Arterial Hypertension. Chest 2012;142:1391-1398.