title: Ventilation heterogeneity in the acinar and conductive zones of the normal ageing lung.
abstract: BACKGROUND
  Small airways function studies in lung disease have used three promising multiple breath washout (MBW) derived indices: indices of ventilation heterogeneity in the acinar (S(acin)) and conductive (S(cond)) lung zones, and the lung clearance index (LCI). Since peripheral lung structure is known to change with age, ventilation heterogeneity is expected to be affected too. However, the age dependence of the MBW indices of ventilation heterogeneity in the normal lung is unknown.
  
  
  OBJECTIVE
  The authors systematically investigated S(acin), S(cond) or LCI as a function of age, testing also the robustness of these relationships across two laboratories.
  
  
  METHODS
  MBW tests were performed by never-smokers (50% men) in the age range 25-65 years, with data gathered across two laboratories (n=120 and n=60). For comparison with the literature, the phase III slopes from classical single breath washout tests were also acquired in one group (n=120).
  
  
  RESULTS
  All three MBW indices consistently increased with age, representing a steady worsening of ventilation heterogeneity in the age range 25-65. Age explained 7-16% of the variability in S(acin) and S(cond) and 36% of the variability in LCI. There was a small but significant gender difference only for S(acin). Classical single breath washout phase III slopes also showed age dependencies, with gender effects depending on the normalisation method used.
  
  
  CONCLUSIONS
  With respect to the clinical response, age is a small but consistent effect that needs to be factored in when using the MBW indices for the detection of small airways abnormality in disease.
authors.affiliation: Respiratory Division, University Hospital UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium. sylvia.verbanck@uzbrussel.be
authors.forename: Sylvia
authors.initials: S
authors.lastname: Verbanck
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Thompson
authors.forename: Daniel
authors.initials: D
authors.lastname: Schuermans
authors.forename: Harpal
authors.initials: H
authors.lastname: Kalsi
authors.forename: Martyn
authors.initials: M
authors.lastname: Biddiscombe
authors.forename: Chris
authors.initials: C
authors.lastname: Stuart-Andrews
authors.forename: Shane
authors.initials: S
authors.lastname: Hanon
authors.forename: Alain
authors.initials: A
authors.lastname: Van Muylem
authors.forename: Manuel
authors.initials: M
authors.lastname: Paiva
authors.forename: Walter
authors.initials: W
authors.lastname: Vincken
authors.forename: Omar
authors.initials: O
authors.lastname: Usmani
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011650:Pulmonary Alveoli / Q000502:physiology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D012044:Regression Analysis; D012129:Respiratory Function Tests