Multivariate analysis of mean (95% confidence interval) differences in structural CT changes (emphysema. airway wall thickening and gas trapping) according to classification of airflow limitation correcting for age, height, BMI, packyears and respiratory symptoms.

The group FEV1/FVC >70% was used as reference. # p<0.001 Log950% =  log-transformed percentage of voxels below HU -950. E/I-ratio% =  expiratory mean lung density in HU divided by the inspiratory mean lung density in HU expressed as a percentage. Pi10 =  the square root of wall area for a theoretical airway with 10 mm lumen perimeter.