Figure 1

Results of an exercise test in a 16-year-old patient with cystic fibrosis and a forced expiratory volume in 1 s of 57% predicted. Forced vital capacity (FVC) was 65% predicted. The test was maximal since respiratory exchange ratio at peak exercise was 1.12 and rating of perceived exertion was 10 on a Borg CR10 scale. The data indicate deconditioning. a) Peak oxygen uptake (V′O2peak) (76% predicted) and peak work rate (Wpeak) (88% predicted) were slightly reduced. b) The Δheart rate/Δoxygen uptake (V′O2) slope was below the predicted maximal slope of 51.5 beats·L−1 and peak heart rate (179 beats·min−1) was in the normal range (92% predicted) indicating normal cardiac function. Arterial oxygen saturation measured by pulse oximetry (SpO2) decreased from 98% at rest to 94% at peak exercise, which still reflects a normal response (maximum normal drop in SpO2 is 4%). c) There was a normal response in tidal volume (VT) and respiratory frequency (fR) with exercise. d) The Δminute ventilation (V′E)/Δcarbon dioxide production (V′CO2) slope was within the normal range (it should be <28.6) and V′E reached 82% of the predicted maximal voluntary ventilation (MVV). Based on this test, the patient started individualised exercise intervention adding 2 h of vigorous activities per week to his routine. Within 7 months, V′O2peak had increased to 91% predicted without significant changes in lung function. At the re-test, however, there were some signs of respiratory limitation (drop in SpO2 of 5% and V′E exceeding estimated MVV).