Published ahead of print on August 29, 2007, doi:10.1164/rccm.200707-980OC
© 2007 American Thoracic Society doi: 10.1164/rccm.200707-980OC
Impaired Flow-mediated Dilation Is Associated with Low Pulmonary Function and Emphysema in Ex-smokersThe Emphysema and Cancer Action Project (EMCAP) Study1 Department of Medicine, College of Physicians and Surgeons, 2 Department of Epidemiology, Mailman School of Public Health, and 3 Department of Radiology, College of Physicians and Surgeons, Columbia University, New York, New York; and 4 Department of Biomedical Engineering and 5 School of Electrical and Computer Engineering, College of Engineering, Cornell University, Ithaca, New York Correspondence and requests for reprints should be addressed to R. Graham Barr, M.D., Dr.P.H., Presbyterian Hospital 9 East, Room 105, Columbia University Medical Center, 630 West 168th Street, New York, NY 10032. E-mail: rgb9{at}columbia.edu Rationale: Basic science research suggests a causal role for endothelial dysfunction in chronic obstructive pulmonary disease (COPD). Clinical studies examining endothelial function are lacking, particularly early in the disease. Flow-mediated dilation (FMD) is a physiologic measure of endothelial reactivity to endogenous nitric oxide. Objectives: We hypothesized that lower FMD among former smokers would be associated with lower post-bronchodilator FEV1, higher percentage of emphysema using computed tomography (CT) and lower diffusing capacity. Methods: We measured FMD, pulmonary function, and CT percentage of emphysema in a random sample of 107 cotinine-confirmed former smokers in the ongoing EMCAP study. FMD was defined as percentage change in the brachial artery diameter with reactive hyperemia. Generalized additive models were used to adjust for potential confounders and assess linearity. Measurements and Main Results: Mean age of participants was 71 ± 5 years, 46% were female, and pack-years averaged 48 ± 26. Mean FMD was 3.8 ± 3.1%; mean post-bronchodilator FEV1, 2.3 ± 0.8 L; and mean CT percentage of emphysema, 26 ± 10%. A 1 SD decrease in FMD was associated with a 132-ml (95% confidence interval, 16–248 ml; P = 0.03) decrement in post-bronchodilator FEV1 and a 2.6% (95% confidence interval, 0.5–4.7%; P = 0.02) increase in CT percentage of emphysema in fully adjusted models. These associations were linear across the spectrum from normality to disease, independent of smoking history, and also significant among participants without COPD. Associations with diffusing capacity were consistent but nonsignificant (P = 0.09). The FMD–FEV1 association was entirely attributable to percentage of emphysema. Conclusions: Impaired endothelial function, as measured by FMD, was associated with lower FEV1 and higher CT percentage of emphysema in former smokers early in COPD.
Key Words: pulmonary disease, chronic obstructive • bronchitis, chronic • pulmonary emphysema • endothelial dysfunction
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