Relationship of emphysema and airway disease assessed by CT to exercise capacity in COPD

Diaz, Alejandro A.; Bartholmai, Brian; San José Estépar, Raúl; Ross, James; Matsuoka, Shin; Yamashiro, Tsuneo; Hatabu, Hiroto; Reilly, John J.; Silverman, Edwin K.; Washko, George R.

doi:10.1016/j.rmed.2010.02.023

« Previous Next »Respiratory Medicine
Volume 104, Issue 8 , Pages 1145-1151, August 2010

Relationship of emphysema and airway disease assessed by CT to exercise capacity in COPD

Alejandro A. Diaz
- Pulmonary and Critical Care Medicine Division, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston MA, USA
- Department of Pulmonary Diseases, Pontificia Universidad Católica de Chile, Chile
- Corresponding author at: Pulmonary and Critical Care Medicine Division, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston MA, USA. Tel.: +1 617 732 5187; fax: +1 617 732 7421.
Brian Bartholmai
- Department of Radiology, Mayo Clinic, Rochester MI, USA
Raúl San José Estépar
- Surgical Planning Laboratory, Laboratory of Mathematics in Imaging, Department of Radiology, Brigham and Women's Hospital, Boston MA, USA
James Ross
- Surgical Planning Laboratory, Laboratory of Mathematics in Imaging, Department of Radiology, Brigham and Women's Hospital, Boston MA, USA
Shin Matsuoka
- Department of Radiology, Brigham and Women's Hospital, Boston MA, USA
Tsuneo Yamashiro
- Department of Radiology, Brigham and Women's Hospital, Boston MA, USA
Hiroto Hatabu
- Department of Radiology, Brigham and Women's Hospital, Boston MA, USA
John J. Reilly
- Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburg, Pittsburg PA, USA
Edwin K. Silverman
- Pulmonary and Critical Care Medicine Division, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston MA, USA
- Channing Laboratory, Brigham and Women's Hospital, Boston MA, USA
George R. Washko
- Pulmonary and Critical Care Medicine Division, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston MA, USA

Received 6 December 2009; accepted 23 February 2010. published online 12 April 2010.

Summary

Objective

To assess the association of emphysema and airway disease assessed by volumetric computed tomography (CT) with exercise capacity in subjects with chronic obstructive pulmonary disease (COPD).

Methods

We studied 93 subjects with COPD (Forced Expiratory Volume in 1 s [FEV₁] %predicted mean ± SD 57.1 ± 24.3%, female gender = 40) enrolled in the Lung Tissue Research Consortium. Emphysema was defined as percentage of low attenuation areas less than a threshold of −950 Hounsfield units (%LAA-950) on CT scan. The wall area percentage (WA%) of the 3rd to 6th generations of the apical bronchus of right upper lobe (RB1) were analyzed. The 6-min walk distance (6MWD) test was used as a measure of exercise capacity.

Results

The 6MWD was inversely associated with %LAA-950 (r = −0.53, p < 0.0001) and with the WA% of 6th generation of RB1 only (r = −0.28, p = 0.009). In a multivariate regression model including CT indices of emphysema and airway disease that were adjusted for demographic and physiologic variables as well as brand of CT scanner, only the %LAA-950 remained significantly associated with exercise performance. Holding other covariates fixed, this model showed that a 10% increase of CT emphysema reduced the distance walked in 6 min 28.6 m (95% Confidence Interval = −51.2, −6.0, p = 0.01).

Conclusion

These results suggest that the extent of emphysema but not airway disease measured by volumetric CT contributes independently to exercise limitation in subjects with COPD.

Keywords: COPD, CT, Emphysema, Airways, 6-min walk test