title: Effect of lung volume on airway luminal area assessed by computed tomography in chronic obstructive pulmonary disease.
abstract: BACKGROUND
  Although airway luminal area (Ai) is affected by lung volume (LV), how is not precisely understood. We hypothesized that the effect of LV on Ai would differ by airway generation, lung lobe, and chronic obstructive pulmonary disease (COPD) severity.
  
  
  METHODS
  Sixty-seven subjects (15 at risk, 18, 20, and 14 for COPD stages 1, 2, and 3) underwent pulmonary function tests and computed tomography scans at full inspiration and expiration (at functional residual capacity). LV and eight selected identical airways were measured in the right lung. Ai was measured at the mid-portion of the 3(rd), the segmental bronchus, to 6(th) generation of the airways, leading to 32 measurements per subject.
  
  
  RESULTS
  The ratio of expiratory to inspiratory LV (LV E/I ratio) and Ai (Ai E/I ratio) was defined for evaluation of changes. The LV E/I ratio increased as COPD severity progressed. As the LV E/I ratio was smaller, the Ai E/I ratio was smaller at any generation among the subjects. Overall, the Ai E/I ratios were significantly smaller at the 5(th) (61.5%) and 6(th) generations (63.4%) and than at the 3(rd) generation (73.6%, p<0.001 for each), and also significantly lower in the lower lobe than in the upper or middle lobe (p<0.001 for each). And, the Ai E/I ratio decreased as COPD severity progressed only when the ratio was corrected by the LV E/I ratio (at risk v.s. stage 3 p<0.001, stage 1 v.s. stage 3 p<0.05).
  
  
  CONCLUSIONS
  From full inspiration to expiration, the airway luminal area shrinks more at the distal airways compared with the proximal airways and in the lower lobe compared with the other lobes. Generally, the airways shrink more as COPD severity progresses, but this phenomenon becomes apparent only when lung volume change from inspiration to expiration is taken into account.
authors.affiliation: First Department of Internal medicine, University of Toyama, Toyama, Japan.
authors.forename: Kenta
authors.initials: K
authors.lastname: Kambara
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: Kaoruko
authors.initials: K
authors.lastname: Shimizu
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: Hironi
authors.initials: H
authors.lastname: Makita
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Hasegawa
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: Katsura
authors.initials: K
authors.lastname: Nagai
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Konno
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Nishimura
mesh_terms: D000368:Aged; D045853:Exhalation; D005260:Female; D005652:Functional Residual Capacity; D006801:Humans; D001239:Inhalation; D008168:Lung / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology; D012129:Respiratory Function Tests; D012720:Severity of Illness Index; D013990:Tidal Volume; D014057:Tomography, X-Ray Computed