title: Reference values for within-breath pulmonary impedance parameters in asymptomatic elderly.
abstract: BACKGROUND
  A new application for the forced oscillation technique (FOT) has been described by Dellaca et al. using sinusoidal pressure variations at 5 Hz to detect expiratory flow limitation by measuring the within-breath reactance [termed difference between inspiratory and expiratory X5 (DX5)]. Few studies have been performed on respiratory phase differences in the elderly.
  
  
  OBJECTIVE
  Our aim was to present reference values for within-breath impedance measurements and to examine how the earlier mentioned method performs in a study population of asymptomatic elderly.
  
  
  METHODS
  An age- and sex-stratified random sample was drawn from the elderly population of Bergen, Norway. Among the healthy non-smoking responders from a postal questionnaire study, 148 were selected to perform FOT measurements using an impulse oscillometry system (IOS). Seventy five of these participants had a normal spirometry and were able to perform at least two valid FOT measurements. Predictive equations for men and women were created for FOT parameters by linear multiple regression analysis. DX5 was calculated from the within-breath variation of reactance at 5 Hz.
  
  
  CONCLUSIONS
  This study presents reference values for whole-breath and within-breath impedance parameters in asymptomatic elderly aged >70 years using the IOS method. We found higher resistance measurements than what is reported in previous studies and significantly larger frequency dependence.
authors: Department of Thoracic Medicine, Haukeland University Hospital, Bergen, Norway. bernt.bogvald.aarli@helse-bergen.no
authors: Bernt Bøgvald
authors: BB
authors: Aarli
authors: Tomas Mikal Lind
authors: TM
authors: Eagan
authors: Ivar
authors: I
authors: Ellingsen
authors: Per Sigvald
authors: PS
authors: Bakke
authors: Jon Andrew
authors: JA
authors: Hardie
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000403:Airway Resistance / Q000502:physiology*; D017097:Electric Impedance; D045853:Exhalation / Q000502:physiology; D005260:Female; D005540:Forced Expiratory Flow Rates / Q000502:physiology*; D006801:Humans; D001239:Inhalation / Q000502:physiology; D016014:Linear Models; D008297:Male; D009991:Oscillometry / Q000379:methods* / Q000592:standards*; D011237:Predictive Value of Tests; D012016:Reference Values; D015203:Reproducibility of Results; D012129:Respiratory Function Tests / Q000592:standards; D013147:Spirometry