Author(s)

C. P. Hersh, G. R. Washko, R. S. Estepar, S. Lutz, P. J. Friedman, M. L. K. Han, J. E. Hokanson, P. F. Judy, D. A. Lynch, B. J. Make, N. Marchetti, J. D. Newell, F. C. Sciurba, J. D. Crapo, E. K. Silverman, COPDGene Investigators

ISBN

1465-993X

Publication year

2013

Periodical

Respiratory Research

Periodical Number

Volume

14

Pages

Author Address

Hersh, CP Brigham & Womens Hosp, Channing Div Network Med, 181 Longwood Ave, Boston, MA 02115 USA Brigham & Womens Hosp, Channing Div Network Med, Boston, MA 02115 USA Harvard Univ, Sch Med, Boston, MA 02115 USA Brigham & Womens Hosp, Div Pulm & Crit Care Med, Boston, MA 02115 USA Colorado Sch Publ Hlth, Dept Biostat, Aurora, CO USA Colorado Sch Publ Hlth, Dept Epidemiol, Aurora, CO USA Univ Calif San Diego, Dept Radiol, San Diego, CA 92103 USA Univ Michigan Hlth Syst, Div Pulm & Crit Care Med, Ann Arbor, MI USA Brigham & Womens Hosp, Dept Radiol, Boston, MA 02115 USA Natl Jewish Hlth, Dept Radiol, Denver, CO USA Natl Jewish Hlth, Div Pulm & Crit Care Med, Denver, CO USA Temple Univ, Sect Pulm & Crit Care Med, Philadelphia, PA 19122 USA Univ Iowa, Dept Radiol, Iowa City, IA 52242 USA Univ Pittsburgh, Div Pulm Allergy & Crit Care Med, Pittsburgh, PA USA

Full version

Background: Gas trapping quantified on chest CT scans has been proposed as a surrogate for small airway disease in COPD. We sought to determine if measurements using paired inspiratory and expiratory CT scans may be better able to separate gas trapping due to emphysema from gas trapping due to small airway disease.
Methods: Smokers with and without COPD from the COPDGene Study underwent inspiratory and expiratory chest CT scans. Emphysema was quantified by the percent of lung with attenuation < -950HU on inspiratory CT. Four gas trapping measures were defined: (1) Exp-856, the percent of lung < -856HU on expiratory imaging; (2) E/I MLA, the ratio of expiratory to inspiratory mean lung attenuation; (3) RVC856-950, the difference between expiratory and inspiratory lung volumes with attenuation between -856 and -950 HU; and (4) Residuals from the regression of Exp-856 on percent emphysema. Results: In 8517 subjects with complete data, Exp(-856) was highly correlated with emphysema. The measures based on paired inspiratory and expiratory CT scans were less strongly correlated with emphysema. Exp(-856), E/I MLA and RVC856-950 were predictive of spirometry, exercise capacity and quality of life in all subjects and in subjects without emphysema. In subjects with severe emphysema, E/I MLA and RVC856-950 showed the highest correlations with clinical variables. Conclusions: Quantitative measures based on paired inspiratory and expiratory chest CT scans can be used as markers of small airway disease in smokers with and without COPD, but this will require that future studies acquire both inspiratory and expiratory CT scans.