title: Reference values of impulse oscillometry and its utility in the diagnosis of asthma in young Korean children.
abstract: OBJECTIVE
  The aims of this study were (1) to determine the reference values for impulse oscillometry (IOS) and (2) to apply them to the evaluation of asthma in the general population of young Korean children.
  
  
  METHODS
  We performed a questionnaire survey and IOS measurements in 390 children aged 3-7 years in Seoul and Gyeonggi province, Korea, from July to August 2010. IOS measurements included respiratory resistance (Rrs) and respiratory reactance (Xrs) at 5, 10, 15, 20, 25, and 35 Hz, respiratory impedance (Zrs), and resonance frequency (RF) before and 15 min after inhalation of 200 μg salbutamol. To determine the reference values for IOS, 161 children defined as healthy controls were assessed.
  
  
  RESULTS
  The IOS measurements were presented as means and standard deviations. The reference equations for IOS variables were determined by multiple linear regression analysis taking into account their height, weight, and age (R5 = 2.242 - 0.008 × height (cm) - 0.005 × age (months), coefficients of determination (R(2)) = 0.213). Height had the greatest correlation with IOS variables, similar to previous studies. Positive airway obstruction was defined as R5 greater than the 95th percentile of predicted R5 from the reference equation. There was a higher percentage of children with positive airway obstruction in children with asthma than in healthy controls (27.3% vs. 6.2%). Multivariate logistic regression analysis indicated that positive airway obstruction was a significant risk factor for the diagnosis of asthma (adjusted odds ratio (aOR), 6.245; 95% confidence interval (CI), 2.270-17.175).
  
  
  CONCLUSIONS
  This study provided reference values for IOS in young Korean children and applied the reference values to evaluate children with asthma. We suggest the 95th percentile of predicted R5 as a cut-off value for positive airway obstruction, which may increase the risk for diagnosis of asthma.
authors.affiliation: Childhood Asthma Atopy Center, Asan Medical Center, Department of Pediatrics, Ulsan University College of Medicine, Seoul, Korea.
authors.forename: Jung-Yong
authors.initials: JY
authors.lastname: Lee
authors.forename: Ju-Hee
authors.initials: JH
authors.lastname: Seo
authors.forename: Hyung Young
authors.initials: HY
authors.lastname: Kim
authors.forename: Young Ho
authors.initials: YH
authors.lastname: Jung
authors.forename: Ji-Won
authors.initials: JW
authors.lastname: Kwon
authors.forename: Byoung-Ju
authors.initials: BJ
authors.lastname: Kim
authors.forename: Hyo Bin
authors.initials: HB
authors.lastname: Kim
authors.forename: So-Yeon
authors.initials: SY
authors.lastname: Lee
authors.forename: Gwang Cheon
authors.initials: GC
authors.lastname: Jang
authors.forename: Dae Jin
authors.initials: DJ
authors.lastname: Song
authors.forename: Woo Kyung
authors.initials: WK
authors.lastname: Kim
authors.forename: Jung Yeon
authors.initials: JY
authors.lastname: Shim
authors.forename: Ha-Jung
authors.initials: HJ
authors.lastname: Kim
authors.forename: Yee-Jin
authors.initials: YJ
authors.lastname: Shin
authors.forename: Jung-Won
authors.initials: JW
authors.lastname: Park
authors.forename: Sang-Heon
authors.initials: SH
authors.lastname: Cho
authors.forename: Joo-Shil
authors.initials: JS
authors.lastname: Lee
authors.forename: Soo-Jong
authors.initials: SJ
authors.lastname: Hong
mesh_terms: D001249:Asthma / Q000175:diagnosis*; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D009991:Oscillometry / Q000379:methods* / Q000592:standards; D012016:Reference Values; D056910:Republic of Korea; D012189:Retrospective Studies; D011795:Surveys and Questionnaires