Circulatory response to repeated exercise in patients with chronic lung disease

The pulmonary and systemic circulatory response to repeated exercise has been studied in 24 patients with chronic lung disease, mainly chronic bronchitis. The exercise consisted of supine bicycling at a constant low load (from loadless pedalling to 30 W) for 10 min with a 20 min rest period between exercises. Cardiac output was similar during the first (E1) and the second (E2) exercise periods, as well as pulmonary vascular resistance. Systemic arterial pressure, however, was lower during E2 than during E1, and this difference was significantly correlated with lung function (VC% predicted, FEV1 and FEV1% predicted) and blood gases at rest and during exercise. The patients with PaO2 below 65 mm Hg showed a larger increase in systemic arterial pressure during E1 and a smaller increase during E2 than the others. The larger increase might be due to a vasoconstrictor effect of hypoxemia and/or of the functional residual capacity increase observed in such patients with exercise. Whatever the mechanism involved, these results show that the systemic circulation is modified in patients with chronic lung disease. Results after some intervention have to be interpreted with caution if the protocol includes two exercise periods.