Airway dimensions in COPD: relationships with clinical variables.

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.