EFFECTS OF BREATHING A NORMOXIC HELIUM MIXTURE ON EXERCISE TOLERANCE OF PATIENTS WITH CYSTIC-FIBROSIS

Breathing helium-oxygen (He-O-2) mixtures of 20.9% O-2/79.1% He has been shown to increase exercise ventilation and peak oxygen uptake in healthy subjects. The improved exercise performance is thought to be due to the reduced density of He-O-2 compared to air and the resulting increases in ventilation. Patients with cystic fibrosis (CF) frequently have abnormal pulmonary function test results, low exercise ventilations and diminished exercise tolerance. This led to the hypothesis that in CF the exercise tolerance of patients might improve when breathing He-O-2. To test this hypothesis, 11 patients with CF or mild to severe airway obstruction performed spirometry and progressive maximal exercise tests while breathing air or He-O-2. The He-O-2 mixture significantly increased (P < 0.05) forced expiratory volume in 1 sec (FEV(1)) by 8.2%, peak expired flow by 39%, and maximal voluntary ventilation (MVV) by 17.9% compared to air, while forced vital capacity (FVC) and forced mid-expiratory flow rate (FEF(25-75%)) were unchanged by breathing He-O-2. Ventilation and oxygen uptake at matched submaximal power outputs were not increased while breathing He-O-2, nor were peak exercise ventilation (V-Epeak) or peak exercise oxygen uptake (V-O2peak). Estimated hemoglobin saturation and total exercise time were also unchanged during He-O-2 breathing. However, there was a trend for the subjects with the better FEV(1) to increase V-O2peak. Increases in V-O2peak when breathing He-O-2 and air were correlated (r = 0.67, P < 0.05) with the percent of predicted FEV(1) values. Still, in the 11 patients as a group, breathing He-O-2 did not significantly improve V-O2peak, V-Epeak, or exercise tolerance. Therefore He-O-2 is unlikely to have additional benefits to patients with CF who use an exercise program to help optimize their health status. Pediatr Pulmonol. 1994; 18:206-210. (C) 1994 Wiley-Liss, Inc.