title: Respiratory impedance and bronchodilator response in healthy Italian preschool children.
abstract: OBJECTIVE
  To define normal values for respiratory resistance (R(rs)) and reactance (X(rs)) and bronchodilator response (BDR) in a population of healthy Italian preschool children using a commercially available forced oscillation device.
  
  
  METHODS
  R(rs) and X(rs) were measured in kindergartens in Viterbo, Italy. Regression analysis was performed taking into account height, weight, age, gender, and reference equations calculated. The coefficient of repeatability (CR) between two tests performed 15 min apart was calculated in a subset of children. BDR was assessed by repeating the measurements 15 min after the administration of 200 µg of inhaled salbutamol and calculated as an absolute change in R(rs) and X(rs) at 8 Hz, as a percent change in baseline, and as a change in Z-score calculated from the reference equations.
  
  
  RESULTS
  Lung function was attempted in 175 healthy children and successful in 163 (81 male, median age 4.8, range 2.9-6.1 years). R(rs) and X(rs) at 6, 8, and 10 Hz were related to height but not other variables. The CR was 1.53 hPa s L(-1) for R(rs8) and 0.91 hPa s L(-1) for X(rs8). The 5th percentile for absolute R(rs8) BDR was -3.16 hPa s L(-1), whereas the 95th percentile for absolute X(rs8) BDR was 2.25 hPa s L(-1). These cut-off values corresponded to a change in the Z-score of -1.88 and 2.48, respectively.
  
  
  CONCLUSIONS
  We have established reference equations for R(rs) and X(rs) in healthy Italian preschool children using forced oscillations. We recommend a change in Z-score of -1.88 for R(rs8) and 2.48 for X(rs8) as cut-off values for a positive BDR.
authors.affiliation: Section of Respiratory Medicine, Department of Paediatrics, University of Florence, Anna Meyer University Hospital for Children, Florence, Italy. c.calogero@meyer.it
authors.forename: C
authors.initials: C
authors.lastname: Calogero
authors.forename: N
authors.initials: N
authors.lastname: Parri
authors.forename: A
authors.initials: A
authors.lastname: Baccini
authors.forename: B
authors.initials: B
authors.lastname: Cuomo
authors.forename: M
authors.initials: M
authors.lastname: Palumbo
authors.forename: E
authors.initials: E
authors.lastname: Novembre
authors.forename: P
authors.initials: P
authors.lastname: Morello
authors.forename: C
authors.initials: C
authors.lastname: Azzari
authors.forename: M
authors.initials: M
authors.lastname: de Martino
authors.forename: P D
authors.initials: PD
authors.lastname: Sly
authors.forename: E
authors.initials: E
authors.lastname: Lombardi
mesh_terms: D000403:Airway Resistance / Q000187:drug effects / Q000502:physiology*; D000420:Albuterol / Q000008:administration & dosage; D001827:Body Height / Q000502:physiology; D001993:Bronchodilator Agents / Q000008:administration & dosage; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007558:Italy; D008297:Male; D012016:Reference Values; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*
chemical_list: D001993:Bronchodilator Agents; D000420:Albuterol