Within‐breath changes in respiratory system impedance in children with cystic fibrosis

Abstract

Background The aim of this study was to assess within‐breath respiratory system impedance by the forced oscillation technique (FOT) in children with cystic fibrosis (CF) and relate it to the underlying lung disease. Methods Thirty‐three children with CF (median [range] age 12.0 [6‐17] years) underwent FOT at 8 Hz during tidal breathing, multiple breath nitrogen washout (LCI), spirometry (FEV1), body plethysmography (RV/TLC), and magnetic resonance imaging (MRI). FOT outcomes included: mean inspiratory, expiratory, and whole breath resistance (R8INSP, R8EXP, R8TOT) and reactance (X8INSP, X8EXP, X8TOT), and the differences between X8INSP and X8EXP (ΔX8). Morphological changes were evaluated by MRI using CF‐specific morphological scores. Spearman correlation was performed to examine the correlation between FOT indices and other parameters. Results FEV1 was negatively correlated with R8EXP (r = −0.52, P = 0.002) and ΔX8 (r = −0.55, P = 0.001), and positively correlated with and X8EXP (r = 0.56, P < 0.001). RV/TLC was positively correlated with R8EXP (r = 0.43, P = 0.013), and ΔX8 (r = 0.54, P = 0.001) and negatively correlated with X8EXP (r = −0.54, P = 0.001). We found poor correlation between FOT parameters and LCI and no correlation between FOT parameters and MRI scores. Conclusion In children with CF, changes in within‐breath FOT parameters are consistent with peripheral obstruction and dynamic airway compression, while they are not associated with ventilation heterogeneities and morphological alterations.

Forced Oscillation Technique for Monitoring the Respiratory Status of Children with Cystic Fibrosis: A Systematic Review

“…A limitation of this study, however, was that at the time of BAL collection, the studied children were clinically stable and therefore these findings did not provide an insight into the correlation of FOT parameters with the clinical symptoms and disease exacerbations. No relation was found between FOT values and MRI CF morphological scores as evaluated by Zannin et al [18] indicating that FOT should not be used as a substitute for imaging studies.…”

“…Xrs5 correlated with FEV1 at a significant level only when raw data were considered. Furthermore, Zannin et al [18] studied the relationship of FOT values with spirometry. They also studied the within-breath changes in respiratory impedance with spirometric indices.…”

Oscillometry of the respiratory system: a translational opportunity not to be missed

“…For these reasons, oscillometry has been increasingly used in children, including CF patients ( 137 , 138 ). The findings using oscillometry in CF have been variable with studies in children showing that oscillometry has low sensitivity detecting disease in preschoolers ( 139 ) whereas within breath assessment of impedance suggested peripheral obstruction ( 140 ). In fact, oscillometry was the tool that made it possible to demonstrate a lung phenotype in mice with a CFTR mutation ( 60 ).…”

Pediatric pulmonology year in review 2019: Physiology

“…These results demonstrate that IOS can identify differences in lung function between asthmatic and non‐asthmatic children and that within‐breath changes in IOS measurements can be useful in differentiating the two groups without needing to use a bronchodilator challenge. Zannin et al 9 studied within‐breath changes in IOS measurements in children with CF. R8 and X8, which reflect small airways function, correlated with FEV1 and residual volume/total lung capacity, but there was poor correlation between IOS measurements and both lung clearance index (LCI) and chest magnetic resonance imaging (MRI) scores.…”