title: Effect of emphysema on CT scan measures of airway dimensions in smokers.
abstract: BACKGROUND
  In CT scans of smokers with COPD, the subsegmental airway wall area percent (WA%) is greater and more strongly correlated with FEV1 % predicted than WA% obtained in the segmental airways. Because emphysema is linked to loss of airway tethering and may limit airway expansion, increases in WA% may be related to emphysema and not solely to remodeling. We aimed to first determine whether the stronger association of subsegmental vs segmental WA% with FEV1 % predicted is mitigated by emphysema and, second, to assess the relationships among emphysema, WA%, and total bronchial area (TBA).
  
  
  METHODS
  We analyzed CT scan segmental and subsegmental WA% (WA% = 100 × wall area/TBA) of six bronchial paths and corresponding lobar emphysema, lung function, and clinical data in 983 smokers with COPD.
  
  
  RESULTS
  Compared with segmental WA%, the subsegmental WA% had a greater effect on FEV1% predicted (-0.8% to -1.7% vs -1.9% to -2.6% per 1-unit increase in WA%, respectively; P < .05 for most bronchial paths). After adjusting for emphysema, the association between subsegmental WA% and FEV1 % predicted was weakened in two bronchial paths. Increases in WA% between bronchial segments correlated directly with emphysema in all bronchial paths (P < .05). In multivariate regression models, emphysema was directly related to subsegmental WA% in most bronchial paths and inversely related to subsegmental TBA in all bronchial paths.
  
  
  CONCLUSIONS
  The greater effect of subsegmental WA% on airflow obstruction is mitigated by emphysema. Part of the emphysema effect might be due to loss of airway tethering, leading to a reduction in TBA and an increase in WA%.
authors: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA; Department of Pulmonary Diseases, Pontificia Universidad Católica de Chile, Santiago, Chile. Electronic address: ADiaz6@partners.org.
authors: Alejandro A
authors: AA
authors: Diaz
authors: University of Michigan School of Medicine, Ann Arbor, MI.
authors: MeiLan K
authors: MK
authors: Han
authors: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
authors: Carolyn E
authors: CE
authors: Come
authors: Surgical Planning Laboratory, Laboratory of Mathematics in Imaging, Department of Radiology, Brigham and Women's Hospital, Boston, MA.
authors: Raúl
authors: R
authors: San José Estépar
authors: Surgical Planning Laboratory, Laboratory of Mathematics in Imaging, Department of Radiology, Brigham and Women's Hospital, Boston, MA.
authors: James C
authors: JC
authors: Ross
authors: School of Medicine, Temple University, Philadelphia, PA.
authors: Victor
authors: V
authors: Kim
authors: Division of Pulmonary, Allergy, and Critical Care Medicine, The University of Alabama at Birmingham, Birmingham, AL.
authors: Mark T
authors: MT
authors: Dransfield
authors: Division of Biostatistics and Bioinformatics, National Jewish Health, Denver, CO; Department of Biostatistics and Informatics, Colorado School of Public Health, Denver, CO.
authors: Douglas
authors: D
authors: Curran-Everett
authors: Division of Radiology, National Jewish Health, University of Colorado, School of Medicine, Denver, CO.
authors: Joyce D
authors: JD
authors: Schroeder
authors: Division of Radiology, National Jewish Health, University of Colorado, School of Medicine, Denver, CO.
authors: David A
authors: DA
authors: Lynch
authors: VIDA Diagnostics, Inc, Coralville, IA.
authors: Juerg
authors: J
authors: Tschirren
authors: Channing Laboratory (Dr Silverman), Brigham and Women's Hospital, Boston, MA.
authors: Edwin K
authors: EK
authors: Silverman
authors: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
authors: George R
authors: GR
authors: Washko
mesh_terms: D000328:Adult; D056151:Airway Remodeling / Q000502:physiology; D001995:Bronchography; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011656:Pulmonary Emphysema / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D012044:Regression Analysis; D012907:Smoking / Q000009:adverse effects / Q000503:physiopathology; D014057:Tomography, X-Ray Computed