Repeated bouts of submaximal exercise are an important part of most pulmonary rehabilitation programmes. Patients with moderate-to-severe cystic fibrosis (CF) often demonstrate oxygen desaturation during submaximal exercise, which may limit their ability to participate in these programmes. This study examines whether arterial desaturation contributes to submaximal exercise limitation by testing whether supplemental O2 improves submaximal exercise capacity. Eight patients with CF (mean forced expiratory volume in one second 41% predicted) each underwent two submaximal exercise tests on a bicycle ergometer at 80% of maximal workload. The two tests were identical except for the addition of supplemental O2 (inspiratory O2 fraction 39%) during one of the tests. Exercise duration was significantly longer in the supplemental O2 study versus control (673 +/- 63 s versus 835 +/- 99 s). Arterial O2 saturation was also higher in the supplemental O2 study than the control exercise test (96 +/- 0.3% versus 86 +/- 1.5%). There was no statistical difference at end exercise between O2 consumption, minute ventilation and heart rate. There was a significant relationship between improvement in exercise capacity and the amount of desaturation during the control exercise test. Results indicate that supplemental oxygen improves submaximal exercise capacity in patients with moderate-to-severe cystic fibrosis. Oxygen therapy may be an important intervention to improve participation and maximise the benefits of pulmonary exercise rehabilitation programmes.
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