High Airway-To-Vessel Volume Ratio and Visual Bronchiectasis Are Associated With Exacerbations in COPD

The effects of the volume mismatch between the airway and lung vasculature on exacerbation in chronic obstructive pulmonary disease (COPD) is uncertain. We aimed to examine the association between an increased volume ratio of the airway to lung blood vessels (AVR) and exacerbations, regardless of visually assessed bronchiectasis (modified Reiff [mReiff] score) and extrapulmonary vasculature on computed tomography (CT), in patients with COPD during a 5-year follow-up period.

Participants were recruited from the Hokkaido COPD Cohort Study (original, N = 96) and Kyoto University cohort (validation, N = 130). CT-derived indices of the airway and vasculature, mReiff scores, and ratio of pulmonary artery diameter to aorta diameter (PA/Ao) were evaluated. The Kaplan-Meier method with log-rank tests was used to compare the high (highest quartile) and low (other quartiles) groups, while multivariable Cox proportional hazards models explored the factors associated with the time to first exacerbation.

The high AVR group showed a shorter time to first exacerbation than the low AVR group in analyses of both all patients and those without visual bronchiectasis. High AVR was significantly associated with exacerbations [Hazard ratio [95% confidence interval]: original, 3.85 [1.17, 12.6]; validation, 2.01 [1.15, 3.52]), irrespective of mReiff scores and PA/Ao in all patients. The lung-volume-corrected airway or blood vessel volumes did not correlate with the time to first exacerbation.

High AVR was associated with a shorter time to first exacerbation, complementary to mReiff score and PA/Ao, suggesting that AVR is a novel CT-derived predictor of exacerbation in COPD.