RESEARCH ARTICLE Open Access Determinants of exercise capacity in cystic fibrosis patients with mild-to-moderate lung disease Jean Pastré 1 , Anne Prévotat 1 , Catherine Tardif 2 , Carole Langlois 3 , Alain Duhamel 3 and Benoit Wallaert 1* Abstract Background: Adult patients with cystic fibrosis (CF) frequently have reduced exercise tolerance, which is multifactorial but mainly due to bronchial obstruction. The aim of this retrospective analysis was to determine the mechanisms responsible for exercise intolerance in patients with mild-to-moderate or severe disease. Methods: Cardiopulmonary exercise testing with blood gas analysis at peak exercise was performed in 102 patients aged 28 ± 11 years: 48 patients had severe lung disease (FEV 1 < 50%, group 1) and 54 had mild-to-moderate lung disease (FEV 1 ≥ 50%, group 2). VO 2 peak was measured and correlated with clinical, biological, and functional parameters. Results: VO 2 peak for all patients was 25 ± 9 mL/kg/min (65 ± 21% of the predicted value) and was < 84% of predicted in 82% of patients (100% of group 1, 65% of group 2). VO 2 peak was correlated with body mass index, C-reactive protein, FEV 1 , FVC, RV, DLCO, V E /VCO 2 peak, V D /V T , PaO 2 , PaCO 2 , P(A-a)O 2 , and breathing reserve. In multivariate analysis, FEV 1 and overall hyperventilation during exercise were independent determinants of exercise capacity (R 2 = 0.67). FEV 1 was the major significant predictor of VO 2 peak impairment in group 1, accounting for 31% of VO 2 peak alteration, whereas excessive overall hyperventilation (reduced or absent breathing reserve and V E /VCO 2 ) accounted for 41% of VO 2 alteration in group 2. Conclusion: Exercise limitation in adult patients with CF is largely dependent on FEV 1 in patients with severe lung disease and on the magnitude of the ventilatory response to exercise in patients with mild-to-moderate lung disease. Keywords: Cystic fibrosis, Cardiopulmonary exercise testing, Pulmonary function, Exercise Background Cystic fibrosis (CF) is characterized by deterioration of nutritional status and irreversible loss of lung function [1-3]. Patients with CF often experience exertional dys- pnea and have reduced maximal exercise capacity, which is an important predictor of mortality [4-7]. Regular exercise in these patients has been associated with improved aerobic exercise endurance and quality of life [4,8]. Physical exercise requires the cardiopulmonary system to deliver oxygen to muscles in sufficient quan- tity to generate energy through aerobic glycolysis. There are conflicting data on the precise mechanisms underlying exercise intolerance in CF, and a number of factors have been implicated [9], including poor nutri- tional status, peripheral muscle dysfunction [10,11], and especially, ventilatory limitation [12,13]. In other stud- ies, dysfunctional gas exchange has been shown to play a crucial role in limiting exercise performance [14-17]. Only a third of the variability in exercise capacity of CF patients can be explained by FEV 1 , demonstrating that resting pulmonary function tests (PFTs) alone are insufficient to explain the exercise limitation [1,9,13]. By comparison, cardiopulmonary exercise testing (CPET) offers a sensitive evaluation of potential physiological disturbances in cardiovascular, respiratory, peripheral, or neurosensory responses to a standardized exercise protocol [18]. Although it remains underutilized in CF [19], CPET could provide important exercise-related * Correspondence: benoit.wallaert@chru-lille.fr 1 Université Lille 2 et Clinique des Maladies Respiratoires, CRCM Hôpital Calmette, CHRU Lille, France Full list of author information is available at the end of the article © 2014 Pastré et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. Pastré et al. BMC Pulmonary Medicine 2014, 14:74 http://www.biomedcentral.com/1471-2466/14/74