Exercise pathophysiology in patients with chronic mountain sickness exercise in chronic mountain sickness

ABSTRACT: BACKGROUND:Chronic mountain sickness is characterized by a combination of excessive erythrocytosis, severe hypoxemia and pulmonary hypertension, all of which affect exercise capacity. METHODS:Thirteen chronic mountain sickness patients and 15 healthy highlander and 15 newcomer lowlander controls were investigated at an altitude of 4350m (Cerro de Pasco). All of them underwent measurements of lung diffusing capacity for nitric oxide and carbon monoxide at rest, echocardiography for estimation of mean pulmonary arterial pressure and cardiac output at rest and at exercise, and an incremental cycle ergometer cardiopulmonary exercise test. RESULTS:The chronic mountain sickness patients, the healthy highlanders and the newcomer lowlanders reached a similar maximal oxygen uptake, at 32±1, 32±2 and 33±2 ml.min(-1).kg(-1) respectively, mean ± SE, p=0.8, with ventilatory equivalents for CO(2) versus end-tidal PCO(2), measured at the anaerobic threshold, of 0.9±0.1, 1.2±0.1 and 1.4±0.1 mmHg(-1), p<0.001, arterial O(2) content of 26±1, 21±2 and 16±1 ml.dl(-1), p<0.001, diffusing capacity for carbon monoxide corrected for alveolar volume of 155±4, 150±5 and 120±3% predicted, p<0.001, with diffusing capacity for nitric oxide and carbon monoxide ratios of 4.7±0.1 at sea-level decreased to 3.6±0.1, 3.7±0.1 and 3.9±0.1, p<0.05 and a maximal exercise mean pulmonary arterial pressure at 56±4, 42±3, and 31±2 mmHg, p<0.001. CONCLUSIONS:The aerobic exercise capacity of chronic mountain sickness patients is preserved in spite of severe pulmonary hypertension and relative hypoventilation, probably by a combination of increased oxygen carrying capacity of the blood and lung diffusion, the latter being predominantly due to an increased capillary blood volume.JOURNAL ARTICLESCOPUS: ar.jinfo:eu-repo/semantics/publishe