CT metrics of airway disease and emphysema in severe COPD

Background CT scan measures of emphysema and airwaydisease have been correlated with lung function in cohorts of subjects with a range of COPD severity. The contribution of CT scan-assessed airwaydisease to objective measures of lung function and respiratory symptoms such as dyspnea in severe emphysema is less clear. Methods Using data from 338 subjects in the National Emphysema Treatment Trial (NETT) Genetics Ancillary Study, densitometric measures of emphysema using a threshold of −950 Hounsfield units (%LAA-950) and airwaywall phenotypes of the wall thickness (WT) and the square root of wall area (SRWA) of a 10-mm luminal perimeter airwaywere calculated for each subject. Linear regression analysis was performed for outcome variables FEV 1 and percent predicted value of FEV 1 with CT scan measures of emphysema and airwaydisease. Results In univariate analysis, there were significant negative correlations between %LAA-950 and both the WT ( r = −0.28, p = 0.0001) and SRWA ( r = −0.19, p = 0.0008). Airwaywall thickness was weakly but significantly correlated with postbronchodilator FEV 1 % predicted (R = −0.12, p = 0.02). Multivariate analysis showed significant associations between either WT or SRWA (β = −5.2, p = 0.009; β = −2.6, p = 0.008, respectively) and %LAA-950 (β = −10.6, p = 0.03) with the postbronchodilator FEV 1 % predicted. Male subjects exhibited significantly thicker airwaywall phenotypes (p = 0.007 for WT and p = 0.0006 for SRWA). Conclusions Airwaydisease and emphysema detected by CT scanning are inversely related in patients with severe COPD. Airwaywall phenotypes were influenced by gender and associated with lung function in subjects with severe emphysema.