Variability of intra-breath oscillometry in children with cystic fibrosis

Abstract

Objectives Intra-breath oscillometry (IB-OSC) has shown promise in detecting changes in early cystic fibrosis (CF) lung disease in children. Establishing clinical utility requires understanding long-term variability. Our aim was to define long-term variability of IB-OSC indices in children with CF. Methods Routine IB-OSC measurements were performed with children as part of the ongoing Early Life Origins (ELO) study at the Queensland Children’s Hospital (Australia) using the tremoflo C-100 device (10 Hz sinusoidwaveform; Thorasys, CA). Eligible children for this analysis had ≥3 stable clinic visits: defined as no change in respiratory symptoms within the preceding 2 weeks. IB-OSC indices examined included resistance and reactance at end-expiration and end-inspiration (ReE, ReI, XeE, XeI), and the tidal change for both (ReE-eI [ΔR], XeE-eI [ΔX]. Long-term variability was calculated as standard deviation between vists (SDbv) and coefficient of variation (CoV). Kruskal-Wallis test assessed between-visit differences. Results A total of 195 measurements met inclusion criteria from 65 children (46% female, median (25th–75th %) age 9.4 (6.9–12.7) years). Results expressed as median (25th–75th %) are shown in the below table. There were no statistically significant differences between visits for any indices. SDbv was highest for ReE and ReI whilst CoV was highest for XeE and XeI, with the latter potentially reflecting the proximity of reactance values to zero in CoV calculations. Conclusion Our preliminary findings have defined long-term repeatability of IB-OSC indices, performed when stable, in children with CF. Ongoing work will determine appropriate cut-offs to detect clinically significant changes in lung disease over time. Grant support Cystic Fibrosis Foundation (USA) and Child Health Foundation (AUS). [Formula presented]