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Original Research: Copd |

Effect of Emphysema on CT Scan Measures of Airway Dimensions in SmokersEmphysema Effect on CT Scan Measures of Airways

Alejandro A. Diaz, MD; MeiLan K. Han, MD; Carolyn E. Come, MD, MPH; Raúl San José Estépar, PhD; James C. Ross, MS; Victor Kim, MD; Mark T. Dransfield, MD; Douglas Curran-Everett, PhD; Joyce D. Schroeder, MD; David A. Lynch, MD; Juerg Tschirren, PhD; Edwin K. Silverman, MD, PhD; George R. Washko, MD
Author and Funding Information

From the Division of Pulmonary and Critical Care Medicine (Drs Diaz, Come, and Washko), Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA; Department of Pulmonary Diseases (Dr Diaz), Pontificia Universidad Católica de Chile, Santiago, Chile; University of Michigan School of Medicine (Dr Han), Ann Arbor, MI; Surgical Planning Laboratory (Dr San José Estépar and Mr Ross), Laboratory of Mathematics in Imaging, Department of Radiology, Brigham and Women’s Hospital, Boston, MA; School of Medicine (Dr Kim), Temple University, Philadelphia, PA; Division of Pulmonary, Allergy, and Critical Care Medicine (Dr Dransfield), The University of Alabama at Birmingham, Birmingham, AL; Division of Biostatistics and Bioinformatics (Dr Curran-Everett), National Jewish Health, Denver, CO; Department of Biostatistics and Informatics (Dr Curran-Everett), Colorado School of Public Health, Denver, CO; Division of Radiology (Drs Schroeder and Lynch), National Jewish Health, University of Colorado, School of Medicine, Denver, CO; VIDA Diagnostics, Inc (Dr Tschirren), Coralville, IA; and Channing Laboratory (Dr Silverman), Brigham and Women’s Hospital, Boston, MA.

Correspondence to: Alejandro A. Diaz, MD, Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women’s Hospital, 75 Francis St, Boston, MA, 02115; e-mail: ADiaz6@partners.org


Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.

Funding/Support: The COPDGene Study is funded by National Institutes of Health (NIH) [Grants U01 HL089897 and U01 HL089856]. This work is supported by the NIH [Grants K23 HL093351 (to Dr Han), T32 HL007633-26 (to Dr Come), K25 HL104085 (to Dr San José Estépar), K23 HL094696-01A2 (to Dr Kim), and K23 HL089353 (to Dr Washko)].


Chest. 2013;143(3):687-693. doi:10.1378/chest.12-0039
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Background:  In CT scans of smokers with COPD, the subsegmental airway wall area percent (WA%) is greater and more strongly correlated with FEV1 % predicted than WA% obtained in the segmental airways. Because emphysema is linked to loss of airway tethering and may limit airway expansion, increases in WA% may be related to emphysema and not solely to remodeling. We aimed to first determine whether the stronger association of subsegmental vs segmental WA% with FEV1 % predicted is mitigated by emphysema and, second, to assess the relationships among emphysema, WA%, and total bronchial area (TBA).

Methods:  We analyzed CT scan segmental and subsegmental WA% (WA% = 100 × wall area/TBA) of six bronchial paths and corresponding lobar emphysema, lung function, and clinical data in 983 smokers with COPD.

Results:  Compared with segmental WA%, the subsegmental WA% had a greater effect on FEV1% predicted (−0.8% to −1.7% vs −1.9% to −2.6% per 1-unit increase in WA%, respectively; P < .05 for most bronchial paths). After adjusting for emphysema, the association between subsegmental WA% and FEV1 % predicted was weakened in two bronchial paths. Increases in WA% between bronchial segments correlated directly with emphysema in all bronchial paths (P < .05). In multivariate regression models, emphysema was directly related to subsegmental WA% in most bronchial paths and inversely related to subsegmental TBA in all bronchial paths.

Conclusion:  The greater effect of subsegmental WA% on airflow obstruction is mitigated by emphysema. Part of the emphysema effect might be due to loss of airway tethering, leading to a reduction in TBA and an increase in WA%.

Trial registry:  ClinicalTrials.gov; No.: NCT00608764; URL: www.clinicaltrials.gov

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