title: Airway dimensions in COPD: relationships with clinical variables.
abstract: BACKGROUND
  COPD patients have varying degrees of airways disease and emphysema. CT scanning can differentiate these pathological subtypes. We evaluated airway dimensions and emphysema severity with low dose CT scanning in COPD patients to determine relationships with clinical features of the disease.
  
  
  METHODS
  Fifty six patients with COPD had a low dose thoracic CT scan. Airways were analysed using novel software as either proximal (1st and 2nd generation) or distal (3rd to 6th generation); the extent of emphysema was assessed as the percentage of pixels less than -950 Hounsfield units. CT measures were related to clinical features of COPD.
  
  
  RESULTS
  Thicker walls in the proximal airways were associated with clinical features that may represent a bronchitic phenotype (MRC Bronchitis Score; β = 0.20, p = 0.003, Frequent Exacerbations; β = 0.14, p = 0.017, Total St George's Score; β = 0.50, p = 0.001 and body mass index [BMI]; β = 0.26, p = 0.049); these associations were independent of emphysema. BMI was negatively correlated with the degree of emphysema (β = -0.41, p = 0.001). Airway wall thickness was negatively correlated with CT measured emphysema for both proximal and more distal airways (r = -0.30, p = 0.025 and r = -0.32, p = 0.015).
  
  
  CONCLUSIONS
  CT measured airway dimensions are associated with several clinical measures of COPD; these are related to a bronchitic phenotype and the effect is independent of emphysema.
authors.affiliation: MRC Centre for Inflammation Research, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Grant
authors.initials: G
authors.lastname: Mair
authors.forename: John
authors.initials: J
authors.lastname: Maclay
authors.forename: Joy J
authors.initials: JJ
authors.lastname: Miller
authors.forename: David
authors.initials: D
authors.lastname: McAllister
authors.forename: Martin
authors.initials: M
authors.lastname: Connell
authors.forename: John T
authors.initials: JT
authors.lastname: Murchison
authors.forename: William
authors.initials: W
authors.lastname: MacNee
mesh_terms: D000368:Aged; D000402:Airway Obstruction / Q000000981:diagnostic imaging* / Q000503:physiopathology; D015992:Body Mass Index; D001991:Bronchitis / Q000000981:diagnostic imaging* / Q000235:genetics / Q000503:physiopathology; D004646:Emphysema / Q000000981:diagnostic imaging* / Q000235:genetics / Q000503:physiopathology; D005260:Female; D005541:Forced Expiratory Volume / Q000235:genetics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging / Q000235:genetics / Q000503:physiopathology*; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging* / Q000235:genetics / Q000503:physiopathology; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D014057:Tomography, X-Ray Computed