title: Reference values for respiratory system impedance using impulse oscillometry in healthy preschool children.
abstract: OBJECTIVE
  The normal values for lung resistance and lung capacity of children, as determined by impulse oscillometry (IOS), are different for children of different ethnicities. However, reference values there is no available reference value for Korean preschool children have yet to be determined. The aim of the present study was to determine the normal ranges of IOS parameters in Korean preschool children.
  
  
  METHODS
  A total of 133 healthy Korean preschool children were selected from 639 children (aged 3 to 6 years) who attended kindergarten in Seongnam, Gyeonggi province, Korea. Healthy children were defined according to the European Respiratory Society (ERS) criteria. All subjects underwent lung function tests using IOS. The relationships between IOS value (respiratory resistance (Rrs) and reactance (Xrs) at 5 and 10 Hz and resonance frequency (RF)) and age, height, and weight were analyzed by simple linear and multiple linear regression analyses.
  
  
  RESULTS
  The IOS success rate was 89.5%, yielding data on 119 children. Linear regression identified height as the best predictor of Rrs and Xrs. Using stepwise multiple linear regressions based on age, height, and weight, we determined regression equations and coefficients of determination (R(2)) for boys (Rrs(5)=1.934-0.009×Height, R(2)=12.1%; Xrs(5)=0.774+0.006×Height-0.002×Age, R(2)=20.2% and for girls (Rrs(5)=2.201-0.012×Height, R(2)=18.2%; Xrs(5)=-0.674+0.004×Height, R(2)=10.5%).
  
  
  CONCLUSIONS
  This study provides reference values for IOS measurements of normal Korean preschool children. These provide a basis for the diagnosis and monitoring of preschool children with a variety of respiratory diseases.
authors.affiliation: Department of Pediatrics, CHA Bundang Medical Center, CHA University, Seongnam, Gyeonggi-do, Korea.
authors.forename: Jye Hae
authors.initials: JH
authors.lastname: Park
authors.forename: Jung Won
authors.initials: JW
authors.lastname: Yoon
authors.forename: Youn Ho
authors.initials: YH
authors.lastname: Shin
authors.forename: Hye Mi
authors.initials: HM
authors.lastname: Jee
authors.forename: Young Sun
authors.initials: YS
authors.lastname: Wee
authors.forename: Sun Jung
authors.initials: SJ
authors.lastname: Chang
authors.forename: Jung Hwa
authors.initials: JH
authors.lastname: Sim
authors.forename: Hye Yung
authors.initials: HY
authors.lastname: Yum
authors.forename: Man Yong
authors.initials: MY
authors.lastname: Han