title: Respiratory impedance and bronchodilator responsiveness in healthy children aged 2-13 years.
abstract: BACKGROUND
  The forced oscillation technique (FOT) can be used in children as young as 2 years of age and in those unable to perform routine spirometry. There is limited information on changes in FOT outcomes in healthy children beyond the preschool years and the level of bronchodilator responsiveness (BDR) in healthy children. We aimed to create reference ranges for respiratory impedance outcomes collated from multiple centers. Outcomes included respiratory system resistance (R(rs)) and reactance (X(rs)), resonant frequency (Fres), frequency dependence of R(rs) (Fdep), and the area under the reactance curve (AX). We also aimed to define the physiological effects of bronchodilators in a large population of healthy children using the FOT.
  
  
  METHODS
  Respiratory impedance was measured in 760 healthy children, aged 2-13 years, from Australia and Italy. Stepwise linear regression identified anthropometric predictors of transformed R(rs) and X(rs) at 6, 8, and 10 Hz, Fres, Fdep, and AX. Bronchodilator response (BDR) was assessed in 508 children after 200 µg of inhaled salbutamol.
  
  
  RESULTS
  Regression analysis showed that R(rs), X(rs), and AX outcomes were dependent on height and sex. The BDR cut-offs by absolute change in R(rs8), X(rs8), and AX were -2.74 hPa s L(-1), 1.93 hPa s L(-1), and -33 hPa s L(-1), respectively. These corresponded to relative and Z-score changes of -32%; -1.85 for R(rs8), 65%; 1.95 for X(rs8), and -82%; -2.04 for AX.
  
  
  CONCLUSIONS
  We have established generalizable reference ranges for respiratory impedance and defined cut-offs for a positive bronchodilator response using the FOT in healthy children.
authors.affiliation: Unit of Respiratory Medicine, Department of Paediatrics, University of Florence, Anna Meyer University Hospital for Children, Florence, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Calogero
authors.forename: Shannon J
authors.initials: SJ
authors.lastname: Simpson
authors.forename: Enrico
authors.initials: E
authors.lastname: Lombardi
authors.forename: Niccolò
authors.initials: N
authors.lastname: Parri
authors.forename: Barbara
authors.initials: B
authors.lastname: Cuomo
authors.forename: Massimo
authors.initials: M
authors.lastname: Palumbo
authors.forename: Maurizio
authors.initials: M
authors.lastname: de Martino
authors.forename: Claire
authors.initials: C
authors.lastname: Shackleton
authors.forename: Maureen
authors.initials: M
authors.lastname: Verheggen
authors.forename: Tania
authors.initials: T
authors.lastname: Gavidia
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Franklin
authors.forename: Merci M H
authors.initials: MM
authors.lastname: Kusel
authors.forename: Judy
authors.initials: J
authors.lastname: Park
authors.forename: Peter D
authors.initials: PD
authors.lastname: Sly
authors.forename: Graham L
authors.initials: GL
authors.lastname: Hall
mesh_terms: D000293:Adolescent; D000403:Airway Resistance / Q000187:drug effects / Q000502:physiology*; D000420:Albuterol / Q000494:pharmacology; D001315:Australia; D001980:Bronchi / Q000187:drug effects / Q000502:physiology*; D001993:Bronchodilator Agents / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D017097:Electric Impedance; D005260:Female; D006801:Humans; D007558:Italy; D016014:Linear Models; D008168:Lung / Q000187:drug effects / Q000502:physiology; D008171:Lung Diseases / Q000175:diagnosis*; D008297:Male; D012016:Reference Values; D012129:Respiratory Function Tests / Q000379:methods
chemical_list: D001993:Bronchodilator Agents; D000420:Albuterol