Objectives: Exercise testing in patients with cystic fibrosis (CF) has become an important tool in assessing disease severity and predicting overall outcome. The reproducibility of maximal exercise testing was examined in adult subjects with stable CF.
Methods: Nine subjects with CF underwent a total of three maximal exercise tests carried out under identical circumstances over a 28-day period. Oxygen uptake (VO2), minute ventilation (VE), respiratory frequency (f), heart rate (HR), and arterial oxygen saturation (SaO2) were measured at rest, at end exercise, and at 40% and 70% of maximum workload.
Results: There were no significant differences in these measurements among the three tests. Reproducibility of exercise performance was assessed using the coefficient of variation. The mean within-subject coefficient of variation for test variables at end exercise are as follows: VO2, 6.9%; VE, 6.2%; f, 5.8%; IIR, 3.0%; and SaO2, 1.1%. The mean within-subject coefficient of variation for test variables at 40% and 70% of maximal work rates are as follows: VO2, 5.2% and 4.6%; SaO2, 0.3% and 0.9%; HR, 4.0% and 3%; VE, 5.7% and 6.5%; and f, 5.8% and 7.2%, respectively.
Conclusions: Variables measured during clinical cycle ergometer exercise testing in adult patients with stable CF are reproducible. No learning effect was found on repeated testing.