Relationship of airway dimensions with airflow limitation or lung volumes in chronic obstructive pulmonary disease (COPD)

Abstract

We have recently developed new software to obtain longitudinal images and accurate short axis images of airways with an inner diameter > 2 mm located anywhere in the lung, using curved multiplanar reconstruction. Using this software, we demonstrated in patients with COPD that FEV1 (%predicted) was highly correlated with airway dimensions and the correlation coefficients improved as the airway became smaller in size (3). In this study, our aims are to further confirm the significant relationship between airway dimensions and airflow limitation in larger number of subjects, and to examine the relationship of airway dimensions with lung volumes in 95 patients with COPD (stage 0, 10; stage I, 23; stage II, 35; stage III, 24; stage IV, 3). We analyzed the airway dimensions from the 3rd to the 6th generations of the apical bronchus (B1) of the right upper lobe and the anterior basal bronchus (B8) of the right lower lobe. Lung volumes were measured by the helium closed circuit method. Both airway luminal area (Ai) and wall area percent (WA%) of all the generations, except a few, from the two bronchi were significantly correlated with RV and RV/TLC, but not with TLC or FRC. More importantly, the correlation coefficients (r) between airway dimensions and RV/TLC improved as the airways became smaller in size from the 3rd to 6th generations in both bronchi (r = –0.483, –0482, –0.553, –0.624 for Ai of B8; r = 0.316, 0.380, 0.499, 0.551 for WA% of B8). These findings provide further evidence that distal (small) airways rather than proximal (large) airways are the determinants for airflow limitation in COPD.