Small-Airway Loss in COPD Accounts for Increased Resistance

A new definition of emphysema may be needed to reflect the involvement of small airways beyond the simple absence of obvious fibrosis. Permanent enlargement of the distal airspaces may serve only as a structural biomarker that is a secondary result of small-airway inflammation and destruction.

This study was supported by grants from the U.S. National Heart, Lung, and Blood Institute; the Canadian Institute of Health Research–Thoracic Imaging Network of Canada; the Canadian Collaborative Innovative Research Fund; GlaxoSmithKline; and the Lavin Family Supporting Foundation. Three of the authors have received grants, honorarium, service contracts, or travel reimbursement from GSK. The Lavin Family Foundation has provided grants to one author and research support to the institution of another. Dr. Mitzner is on grant review panels for and receives travel expenses from the National Institutes of Health. Further disclosures are available at nejm.org.