Cardiovascular changes during isometric and dynamic exercise in chronic lung disease.

To compare circulatory changes during dynamic and isometric exercise in patients with chronic lung disease, vascular pressures and cardiac output were measured in pulmonary and systemic circulation. The patients, mainly chronic bronchitics, were divided according to pulmonary vascular resistance (PVR): six patients with PVR below 120 dyn.s.cm-5, and 17 with PVR above this value. Exercise was performed using the legs, in a supine position, at low load. Oxygen consumption increased, on average, from 270 ml/min at rest, to 340 ml/min during isometric exercise, and 585 ml/min during dynamic exercise. Isometric exercise produced an increase in systemic artery pressure similar to that of dynamic exercise, but other vascular changes were of much smaller magnitude: pulmonary artery pressure increased by 4 mmHg with isometric exercise, and by 14 mmHg during dynamic exercise, on average; for cardiac output, these changes were 0.8 and 3.3 l/min, respectively. The pressure/flow relationship in the pulmonary circulation was comparable for both types of exercise. Changes in filling pressures in relation to stroke volume were more marked in the group of patients with elevated pulmonary vascular resistance. Changes in wedge pressure and in right atrial pressure were remarkably parallel for patients with normal as well as with high pulmonary vascular resistance.

Respiratory and circulatory adaptation to isometric and dynamic exercise in chronic lung disease.

Changes at the beginning of isometric and dynamic low level exercise were studied in 23 patients with chronic lung disease. Ventilation, oxygen consumption and vascular pressures in systemic and pulmonary circulation were continuously monitored, and cardiac output was measured by thermodilution every minute. Circulatory changes took place suddenly at the beginning of isometric exercise and gradually during dynamic exercise. Ventilatory changes followed almost the same progressive pattern in both types of exercise. Ventilation increase in relation to oxygen uptake was slightly smaller during isometric exercise. Pulmonary artery pressure showed no further increase after the initial change, although ventilation was still rising.