Effects of breathing a normoxic helium mixture on exercise tolerance of patients with cystic fibrosis.
Breathing helium-oxygen (He-O2) mixtures of 20.9% O2/79.1% 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-O2 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-O2. 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-O2. The He-O2 mixture significantly increased (P < 0.05) forced expiratory volume in 1 sec (FEV1) 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 (FEF25-75%) were unchanged by breathing He-O2. Ventilation and oxygen uptake at matched submaximal power outputs were not increased while breathing He-O2, nor were peak exercise ventilation (VEpeak) or peak exercise oxygen uptake (VO2peak). Estimated hemoglobin saturation and total exercise time were also unchanged during He-O2 breathing. However, there was a trend for the subjects with the better FEV1 to increase VO2peak. Increases in VO2peak when breathing He-O2 and air were correlated (r = 0.67, P < 0.05) with the percent of predicted FEV1 values. Still, in the 11 patients as a group, breathing He-O2 did not significantly improve VO2peak, VEpeak, or exercise tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)
Martin
D
D
Department of Physical Therapy, University of Florida, Gainesville.
Day
J
J
Ward
G
G
Carter
E
E
Chesrown
S
S
D000293:Adolescent; D000328:Adult; D003550:Cystic Fibrosis / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D004338:Drug Combinations; D005080:Exercise Test / Q000187:drug effects; D017079:Exercise Tolerance / Q000187:drug effects*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006371:Helium / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D008297:Male; D010100:Oxygen / Q000494:pharmacology / Q000627:therapeutic use*; D010101:Oxygen Consumption / Q000187:drug effects; D012119:Respiration / Q000187:drug effects; D012129:Respiratory Function Tests; D012138:Respiratory Therapy; D012720:Severity of Illness Index
D004338:Drug Combinations; D007773:Lactates; D006371:Helium; D019344:Lactic Acid; D010100:Oxygen