Oxygen saturation in adult cystic fibrosis patients during exercise at high altitude

The objective of this study was to determine the frequency and severity of decreased arterial oxy‐hemoglobin saturation during exercise in adults with cystic fibrosis at 1,500 m above sea level. A convenience sample of 50 adults with cystic fibrosis who did not have hypoxemia (oxygen saturation, < 90%) at rest were evaluated. Spirometry was performed according to American Thoracic Society standards, and maximal exercise tests were performed on an electronically braked cycle ergometer using a ramp protocol individualized for each patient. Pulse oximetry was measured every 2 min. When exercising at high altitude, 45 of 50 patients had a decrease in arterial oxy‐hemoglobin saturation from baseline to some degree. In 29 patients, oxy‐hemoglobin saturation fell below 90%; in 14 patients, it fell below 85%; and in 4 patients, it fell below 80%. Oxy‐hemoglobin saturation decreased to < 90% in 12 of 14 patients with severe pulmonary disease (FEV 1  < 40% predicted), in 15 of 26 patients with moderate disease (40% less than or equal to FEV 1  < 70% predicted), in 2 of 6 patients with mild disease (70% less than or equal to FEV 1  < 90% predicted), and in 0 of 4 with normal pulmonary function (FEV 1 greater than or equal to 90%). Percent predicted FEV 1 (r = 0.57; P  < 0.0001) and FEV 1 /FVC ratio (r = 0.52; P  < 0.0001) most highly correlated with arterial oxy‐hemoglobin saturation at peak exercise. We conclude that at 1,500 m above sea level, adult CF patients with obstructive airways disease are at significant risk for decreased arterial oxy‐hemoglobin saturation during exercise. A supervised exercise test should be considered prior to recommending an exercise program for such patients. Pediatr Pulmonol. 2001; 32:437–441. © 2001 Wiley‐Liss, Inc.