We read with interest the comparison of spatially matched airways which reveals thinner airway walls in COPD than in controls by Smith et al. 1 While we find these results interesting, we wonder about the approach taken.

First, grouping airway segments from the five prespecified paths in one given generation number (table E1) would dismiss regional differences in airway structure.2 For example, RB1 is very likely different from right lower lobe bronchus (RLL) proximal to RB7 in the 3rd generation while RB1 subsegments are …