Time constant of inspiratory muscle relaxation in cystic fibrosis

• Published in: Pediatric research Vol. 77; no. 4; pp. 541 - 545
• Main Authors: Dassios, Theodore, Kaditis, Athanasios, Katelari, Anna, Chrousos, George, Doudounakis, Stavros, Dimitriou, Gabriel
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.04.2015
• Subjects: 692/699/1785; Adolescent; Adult; Case-Control Studies; Child; Cross-Sectional Studies; Cystic Fibrosis - physiopathology; Female; Forced Expiratory Volume - physiology; Humans; Inhalation - physiology; Male; Medicine & Public Health; Muscle Relaxation - physiology; Pediatric Surgery; Pediatrics; Respiratory Muscles - physiopathology; Spirometry; Time Factors; translational-investigation; Vital Capacity; Young Adult
• ISSN: 0031-3998; 1530-0447; 1530-0447
• DOI: 10.1038/pr.2015.2

Background: Patients with cystic fibrosis (CF) are at increased risk of inspiratory muscle fatigue and respiratory failure. The time constant ( τ ) of the inspiratory muscle relaxation is a simple bedside test of muscle fatigue. We have compared patients with CF and healthy controls regarding τ and hypothesized that it is negatively associated with severity of lower airway obstruction. Methods: For this cross-sectional study, τ after maximal inspiration and spirometric indices (forced expiratory volume in 1 s (FEV 1 ) and forced vital capacity (FVC)) were measured. Results: Fifty-three CF patients (median age 14 y (interquartile range: 11–19.5)) and 53 age- and sex-matched healthy control subjects (14 y (11–19.5)) were recruited. Application of a general linear model revealed that health status (CF vs. non-CF) had a significant effect on τ ( P < 0.001), but age group and the interaction of age group with health status did not have significant effects on τ ( P = 0.10 and P = 0.71, respectively). Participants with CF had significantly higher τ (253 (188–406)) than control subjects (117 (81–185)) ( P < 0.001) and τ was negatively related to FEV 1 ( r = −0.205; P = 0.031) and FVC ( r = −0.294; P = 0.002). Conclusion: Patients with CF have higher τ than healthy controls but the correlation of τ with expiratory flow function is modest.