Inspiratory Muscle Strength and Endurance in Children and Adolescents with Cystic Fibrosis

BACKGROUND: Pulmonary changes that occur in cystic fibrosis may influence inspiratory muscle strength and endurance. We evaluated inspiratory muscle strength and endurance in children and adolescents with cystic fibrosis in comparison with healthy subjects. METHODS: This is a cross-sectional observational study with subjects with cystic fibrosis and paired healthy individuals, age 6-18 y. Spirometry, impulse oscillometry, plethysmography, manovacuometry, and a protocol of inspiratory muscle endurance were performed. RESULTS: Subjects with cystic fibrosis (n = 34) had higher maximum percent-of-predicted inspiratory pressure (P-Imax) than healthy (n = 68) subjects (118.5 +/- 25.8% vs 105.8 +/- 18.0%) and no significant difference in endurance (60.9 +/- 13.3% vs 65.3 +/- 12.3%). When restricting the analysis to subjects without Pseudomonas aeruginosa colonization and with FEV1 > 80%, P-Imax values were significantly higher, and inspiratory muscle endurance was lower, in comparison with the control group. P-Imax correlated significantly with FVC (r = 0.44, P = .02) and FEV1 (r = 0.41, P = .02), whereas endurance correlated better with total airway resistance (r = 0.35, P = .045) and with central airway resistance (r = 0.48, P = .004). CONCLUSIONS: Children and adolescents with cystic fibrosis with no colonization by P. aeruginosa and normal lung function present increased inspiratory muscle strength and decreased endurance compared with healthy individuals, indicating that changes in the respiratory muscle function seem to be distinctly associated with pulmonary involvement. Strength was related to pulmonary function parameters, whereas endurance was associated with airway resistance.