Pulmonary disease severity and peripheral muscle function as limiting factors for exercise capacity in adult patients with cystic fibrosis

BACKGROUND: Although there is some evidence that the progression of lung disease associated with protein malnutrition and metabolic impairments contribute to muscle mass atrophy and dysfunction, the causes of exercise limitation in patients with Cystic Fibrosis (CF) are still poor understood.

OBJECTIVE: The primary aim of this study was to characterize the functional aspects of CF adult patients. Secondarily, we aimed to evaluate the association between pulmonary function, nutritional status and functional capacity variables.

METHODS: In a cross-sectional study, twenty-one adult patients with CF underwent spirometry, whole-body plethysmography, carbon dioxide diffusion capacity, bioelectrical impedance analysis, cardiopulmonary exercise testing(CPET), six-minute walk test (6MWT) and quadriceps maximal isometric strength and endurance. According to data distribution (Shapiro-Wilk test), statistical analysis used Student's t-test or Mann-Whitney test for comparisons, and Pearson's test for correlations. The significance level was set at 5%.

RESULTS: The patients presented with reduced peak VO $_{2}$ , distance in the 6MWT (6MWD), fat-free mass, peripheral and respiratory muscle strength, and quadriceps endurance. There were associations between pulmonary function variables and the results of exercise tests (CPET and 6MWD), as well as between static hyperinflation and CPET variables, and peripheral muscle function (force and endurance) and 6MWD.

CONCLUSIONS: Adult patients with CF have impaired exercise tolerance, nutritional status, and peripheral muscles' strength and endurance. There are associations between exercise capacity, pulmonary function and skeletal muscles' performance in these patients.