Age-related upper limits of normal for maximum upright exercise pulmonary haemodynamics

Abstract

The exercise definition of pulmonary hypertension was eliminated from the pulmonary hypertension guidelines in part due to uncertainty of the upper limits of normal (ULNs) for exercise haemodynamics in subjects >50 years old. The present study, therefore, evaluated the pulmonary haemodynamic responses to maximum upright incremental cycling exercise in consecutive subjects who underwent an invasive cardiopulmonary exercise testing for unexplained exertional intolerance, deemed normal based on preserved exercise capacity and normal resting supine haemodynamics. Subjects aged >50 years old (n=41) were compared with subjects <50 years old (n=25). ULNs were calculated as mean+2SD. Peak exercise mean pulmonary arterial pressure was not different for subjects >50 and <50 years old (23±5 versus 22±4 mmHg, p=0.22), with ULN of 33 and 30 mmHg, respectively. Peak cardiac output was lower in older subjects (median (interquartile range): 12.1 (9.4-14.2) versus 16.2 (13.8-19.2) L min-1, p<0.001). Peak pulmonary vascular resistance was higher in older subjects compared with younger subjects (mean±SD: 1.20±0.45 versus 0.82±0.26 Wood units, p<0.001), with ULN of 2.10 and 1.34 Wood units, respectively. We observed that subjects >50 and <50 years old have different pulmonary vascular responses to exercise. Older subjects have higher pulmonary vascular resistance at peak exercise, resulting in different exercise haemodynamics ULNs compared with the younger population.