Respiratory muscle function in patients with cystic fibrosis

Respiratory muscle function in patients with cystic fibrosis (CF) can be assessed by measurement of maximal inspiratory pressure (Pi_max), maximal expiratory pressure (Pe_max), and pressure–time index of the respiratory muscles (PTI_mus). We investigated the differences in maximal respiratory pressures and PTI_mus between CF patients with no gross hyperinflation and healthy controls and described the effects of pulmonary function and nutrition impairment on respiratory muscle function in this group of CF patients. Forced expiratory volume in 1 sec (FEV₁), forced vital capacity (FVC) and maximal expiratory flow between 25% and 75% of VC (MEF_25–75), body mass index (BMI), upper arm muscle area (UAMA), Pi_max, Pe_max, and PTI_mus were assessed in 140 CF patients and in a control group of 140 healthy subjects matched for age and gender. Median Pi_max and Pe_max were significantly lower in CF patients compared to the controls [Pi_max = 74 (57–94) in CF vs. 84 (66–102) in controls, P = 0.009], [Pe_max = 71 (50–95) in CF vs. 84 (66–102) in controls, P < 0.001]. Median PTI_mus in CF patients compared to controls was significantly increased [PTI_mus = 0.110 (0.076–0.160) in CF vs. 0.094 (0.070–0.137) in controls, P = 0.049] and it was significantly higher in CF patients with impaired pulmonary function. In CF patients, PTI_mus was significantly negatively related to upper arm muscle area (r = 0.184, P = 0.031). These findings suggest that CF patients with no severe lung disease compared to healthy subjects exhibit impaired respiratory muscle function, while CF patients with impaired pulmonary function and nutrition indices exhibit higher PTI_mus values. Pediatr Pulmonol. 2013; 48:865–873. © 2012 Wiley Periodicals, Inc.