Respiratory Muscle Function in Children and Adolescents with Cystic Fibrosis in the Era of CFTR Modulator Therapies.

: The objective of this study was to analyze respiratory muscle function in children and adolescents with cystic fibrosis (CF) treated with Elexacaftor/Tezacaftor/Ivacaftor (ETI) compared to healthy individuals, based on the hypothesis that CFTR modulators may improve respiratory muscle strength. : A descriptive, observational, cross-sectional study was conducted with patients with CF treated with ETI aged 6-18 years. Lung function, maximal expiratory and inspiratory pressures (MIP and MEP), diet quality (KIDMED), and physical activity levels (PAQ) were assessed. The student's -test or the Mann-Whitney U-test was used to compare differences between groups. The effect size was calculated with Cohen's d. Significance level was set as a -value < 0.05. : A total of 48 children and adolescents (60.4% male) were analyzed in this study (24 healthy and 24 with CF). The participants with CF had mild pulmonary involvement. No significant differences were found in respiratory muscle strength between groups (MEP = 0.440, MIP = 0.206). Patients with CF showed lower KIDMED ( = 0.022) and PAQ ( = 0.010) scores. However, the MIP and MEP values observed in CF participants were higher than those reported in previous studies conducted before the introduction of ETI modulators. : Children and adolescents with CF treated with ETI showed respiratory muscle strength comparable to that of healthy controls. Despite differences in lifestyle factors, these findings may reflect a positive impact of CFTR modulators on respiratory muscle function, although further longitudinal and controlled studies are needed.