Common airway variants and chronic obstructive pulmonary disease

Abstract

Background: COPD is the third-leading cause of death globally but susceptibility to COPD, beyond cigarette smoking, is incompletely understood. Small autopsy series suggest that variant branching of lower lobe segmental airways is common, yet its functional consequences are unexplored. We tested the association of variant airway branching on chest CT with COPD, regional airflow, and particle deposition in a general population sample. Methods: Lower lobe segmental airway branch patterns were ascertained on full-lung scans among 3169 participants ages 54-94 years. COPD was defined by standard spirometric criteria. Results were adjusted for age, gender, height, weight, race-ethnicity, smoking status and pack-years. Computational fluid dynamics analysis was used to model regional airflow and particle deposition. Results: Segmental airway branch variants were observed in 26.5% (95%CI:24.9-27.8%) of participants. The most common airway variants were presence of an accessory sub-superior segmental airway (16.0%) and absence of the right medial-basal airway (6.1%). The prevalence of COPD was 49% higher among smokers and never-smokers with an accessory sub-superior segmental airway compared to participants with standard anatomy (95%CI:13-97%;p=0.005) and 86% higher among smokers lacking the right medial-basal airway compared to smokers with standard anatomy (95%CI:22-284%;p=0.004). The first variant was associated with lower regional airflow whereas the second was associated with increased particle deposition. Conclusions: Common airway variants were associated with COPD and with altered regional airflow or particle deposition. These findings suggest an anatomical basis for COPD susceptibility among smokers and never-smokers.