Background: Luminal narrowing is a hallmark feature of airway remodeling in COPD, but current measures focus on airway wall remodeling. Quantification of the natural increase in cumulative cross-sectional area along the length of the human airway tree can facilitate assessment of airway narrowing.
Methods: We analysed the airway trees of 7641 subjects enrolled in the multicenter COPDGene cohort. Airway luminal tapering was assessed by estimating the slope of the change in cumulative cross-sectional area along the length of the airway tree over successive generations (T-Slope). We performed multivariable regression analyses to test the associations between T-Slope and lung function, St. George's Respiratory Questionnaire (SGRQ), modified Medical Research Council (mMRC) dyspnea score, 6-minute walk distance (6 MWD), FEV1 change, exacerbations, and all-cause mortality after adjusting for demographics, %CT emphysema, and total airway count.
Results: The T-Slope decreased with increasing COPD severity: 2.69 (0.70) in nonsmokers and 2.33 (0.70), 2.11 (0.65), 1.78 (0.58), 1.60 (0.53), and 1.57 (0.52) in GOLD stages 0 through 4 respectively (Jonckheere-Terpstra p=0.04). On multivariable analyses, the T-Slope was independently associated with FEV1 (β=0.13 L, 95% CI 0.10 to 0.15, p<0.001), 6MWD (β=15.0 m, 95%CI 10.8 to 19.2, p<0.001), change in FEV1 (β=-4.50 ml·year-1, 95% CI -7.32 to -1.67; p=0.001), exacerbations (IRR=0.78, 95% CI 0.73 to 0.83, p<0.001), and mortality (HR=0.79, 95% CI 0.72 to 0.86, p<0.001).
Conclusion: T-Slope is a measure of airway luminal remodeling and is associated with respiratory morbidity and mortality.
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