Oxygen supplementation during exercise in cystic fibrosis.

Fourteen female and 22 male patients with cystic fibrosis (CF), 8 to 29 yr of age, performed two progressive exercise tests to exhaustion on a cycle ergometer, breathing normoxic air (21% O2) for one test, and hyperoxic air (30% O2) for the other test. The order of gas administration was randomized. Minute ventilation (VE), oxygen uptake (VO2), end-tidal CO2 tension (PETCO2), work rate, oxyhemoglobin saturation (SAO2), and heart rate (HR) were measured throughout the tests. The SaO2 of 11 patients at peak exercise was 90% or less ("Low Sat" group). The SaO2 of 23 patients remained above 90% throughout the exercise ("High Sat" group). Hyperoxic air minimized desaturation during exercise in the Low Sat group to 2 +/- 2% compared to a decrease of 10 +/- 5% with normoxic air. The decrease in saturation was not significant for the High Sat group (1 +/- 1% for both 21% and 30% O2). Peak work rate and VO2 did not differ significantly between normoxic and hyperoxic conditions. However, VE and HR at peak exercise tended to be lower, and PETCO2 was higher during peak exercise with 30% O2 than 21% O2 for both groups. During submaximal exercise, O2 desaturation was diminished and HR was significantly lower with supplemental O2, specifically in the Low Sat group. VE was significantly lower for both groups during submaximal exercise with hyperoxic air. The results suggest that O2 supplementation minimizes O2 desaturation and enables patients with CF to exercise with reduced ventilatory and cardiovascular work.