Exercise in pulmonary vascular diseases

Abstract

Pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension are the most common diseases of pulmonary vasculature. The physiological derangements of pulmonary hypertension result in characteristic abnormalities observed during dynamic exercise and often lead to dyspnoea and exercise intolerance. Impaired cardiac function results in reduced aerobic capacity, low anaerobic threshold and reduced value of the relationship between oxygen uptake and work rate (ΔV′O 2 /ΔWR). Both high physiologic dead space and chemosensitivity contribute to elevated ratio of minute ventilation to CO 2 output (V′ E /V′CO 2 ) during exercise testing. Consequently, resting hypocapnia with low end-tidal PCO 2 throughout exercise is typically observed and is related to the severity of disease. Exertional hypoxaemia is also a variable but frequent finding during exercise, which can be related to ventilation-perfusion heterogeneity, low mixed venous O 2 content from impaired cardiac output and right-to-left shunting through a patent foramen ovale. Even in the absence of significant resting airflow obstruction, dynamic hyperinflation can occur in pulmonary vascular diseases, which contributes to exertional dyspnoea and exercise intolerance. Peripheral muscle dysfunction is another common component of exercise pathophysiology in these conditions.