Clinical and functional determinants of exercise limitation in adult patients with cystic fibrosis

Abstract

Exercise tolerance is reduced in adult patients with cystic fibrosis (CF). The aim of this retrospective analysis was to determine the mechanisms of this limitation.

Patients and methods

Cardiopulmonary exercise testing (CPET) with peak exercise blood gas was performed in 102 patients (Sex Ratio M/F=0.51) aged 28+/-11 years old (FEV1<50%: 48 patients; FEV1 between 50 and 80%: 22; FEV1>80%: 32). VO2 peak was correlated with clinical, biological and functional parameters.

Results

VO2 peak was decreased (<84%) in 85% of patients (25+/-9 ml/kg or 65+/-21% predicted) and was correlated with Body Mass Index (r = 0.26), CRP (r = -0.34), FEV1 (r = 0.71), FVC (r = 0.69), RV (r = -0.63) and DLCO (r = 0.56). Upon exercise parameters, VO2 peak was correlated with VE/VO2 at ventilatory threshold, peak VD/VT, peak PaO2, PaCO2 and P(A-a)O2, and ventilatory reserve (r= -0.50 respectively, -0.64, 0.54, 0.64, -0.54 and 0.37). In multivariate analysis, FEV1 was the most predictive parameter of VO2 peak impairment, accounting for 48% of VO2 peak alteration. Reduced or absent ventilatory reserve and excessive hyperventilation (VE/VO2 threshold) accounted for respectively 10 and 8% of VO2 peak alteration. Peak VD/VT and P(A-a)O2 explained only 1% each of the VO2 peak value.

Conclusion

Limiting aerobic capacity in adult patients with cystic fibrosis is correlated with nutritional status, inflammation and lung function. This limitation is largely dependent, not only on FEV1, but also on the importance of ventilatory response to exercise. CPET is useful for a better management of CF patients.