title: Reference values of impulse oscillometric lung function indices in adults of advanced age.
abstract: BACKGROUND
  Impulse oscillometry (IOS) is a non-demanding lung function test. Its diagnostic use may be particularly useful in patients of advanced age with physical or mental limitations unable to perform spirometry. Only few reference equations are available for Caucasians, none of them covering the old age. Here, we provide reference equations up to advanced age and compare them with currently available equations.
  
  
  METHODS
  IOS was performed in a population-based sample of 1990 subjects, aged 45-91 years, from KORA cohorts (Augsburg, Germany). From those, 397 never-smoking, lung healthy subjects with normal spirometry were identified and sex-specific quantile regression models with age, height and body weight as predictors for respiratory system impedance, resistance, reactance, and other parameters of IOS applied.
  
  
  RESULTS
  Women (n = 243) showed higher resistance values than men (n = 154), while reactance at low frequencies (up to 20 Hz) was lower (p<0.05). A significant age dependency was observed for the difference between resistance values at 5 Hz and 20 Hz (R5-R20), the integrated area of low-frequency reactance (AX), and resonant frequency (Fres) in both sexes whereas reactance at 5 Hz (X5) was age dependent only in females. In the healthy subjects (n = 397), mean differences between observed values and predictions for resistance (5 Hz and 20 Hz) and reactance (5 Hz) ranged between -1% and 5% when using the present model. In contrast, differences based on the currently applied equations (Vogel & Smidt 1994) ranged between -34% and 76%. Regarding our equations the indices were beyond the limits of normal in 8.1% to 18.6% of the entire KORA cohort (n = 1990), and in 0.7% to 9.4% with the currently applied equations.
  
  
  CONCLUSIONS
  Our study provides up-to-date reference equations for IOS in Caucasians aged 45 to 85 years. We suggest the use of the present equations particularly in advanced age in order to detect airway dysfunction.
authors.affiliation: Institute of Epidemiology I, Helmholtz Zentrum München, Munich, Germany. schulz@helmholtz-muenchen.de
authors.forename: Holger
authors.initials: H
authors.lastname: Schulz
authors.forename: Claudia
authors.initials: C
authors.lastname: Flexeder
authors.forename: Jürgen
authors.initials: J
authors.lastname: Behr
authors.forename: Margit
authors.initials: M
authors.lastname: Heier
authors.forename: Rolf
authors.initials: R
authors.lastname: Holle
authors.forename: Rudolf M
authors.initials: RM
authors.lastname: Huber
authors.forename: Rudolf A
authors.initials: RA
authors.lastname: Jörres
authors.forename: Dennis
authors.initials: D
authors.lastname: Nowak
authors.forename: Annette
authors.initials: A
authors.lastname: Peters
authors.forename: H-Erich
authors.initials: HE
authors.lastname: Wichmann
authors.forename: Joachim
authors.initials: J
authors.lastname: Heinrich
authors.forename: Stefan
authors.initials: S
authors.lastname: Karrasch
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009991:Oscillometry / Q000379:methods*; D012015:Reference Standards; D012129:Respiratory Function Tests