Lung function assessment
Participants attended Perth Children’s Hospital for lung function
assessment. Respiratory mechanics were assessed using the TremoFlo C-100
(Thorasys Inc. Montreal, Canada). Spectral oscillometry was performed
across 5-37Hz and intrabreath oscillometry was performed using a single
10Hz frequency. Spirometry was performed using the using the Medisoft
Hypair or BodyBox 5500 (Medisoft Corporation, Sorinnes, Belgium). All
tests were carried out according to American Thoracic Society/European
Respiratory Society (ATS/ERS) guidelines.1,28,29
Spirometry outcomes were expressed as z-scores according to the Global
Lung Function Initiative equations.30 Spectral
oscillometry outcomes including respiratory resistance at 5Hz
(Rrs5), resonant frequency (Fres), area under the
reactance curve (AX) and respiratory system reactance at 5Hz
(Xrs5) were expressed as z-scores according to the
reference equations published by Calogero et al (6-12 year
data,31) and Oostveen et al , (16-23 year data,32). Rrs5-20, and intra-breath
oscillometry measures were expressed as raw values and absolute
difference.33
Oscillometry and spirometry were performed before and after
administration of 400µg salbutamol via a spacer. A bronchodilator
response by spirometry was defined according to ATS/ERS guidelines as an
increase of ≥200mls and 12% in FEV1 or FVC29 (the 200ml rule was omitted for children ≤12
years). A bronchodilator response by spectral oscillometry was defined
according to ERS guidelines as a change of ≤−40% in
Rrs5, ≥50% in Xrs5 or ≤−80% in AX
across all age groups.1