Impaired flow-mediated dilation is associated with low pulmonary function and emphysema in ex-smokers: the Emphysema and Cancer Action Project (EMCAP) Study.
BACKGROUND
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.


OBJECTIVE
We hypothesized that lower FMD among former smokers would be associated with lower post-bronchodilator FEV(1), 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.


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 FEV(1), 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 FEV(1) 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-FEV(1) association was entirely attributable to percentage of emphysema.


CONCLUSIONS
Impaired endothelial function, as measured by FMD, was associated with lower FEV(1) and higher CT percentage of emphysema in former smokers early in COPD.
Barr
R Graham
RG
Dr.P.H., Presbyterian Hospital 9 East, Room 105, Columbia University Medical Center, 630 West 168th Street, New York, NY 10032, USA. rgb9@columbia.edu
Mesia-Vela
Sonia
S
Austin
John H M
JH
Basner
Robert C
RC
Keller
Brad M
BM
Reeves
Anthony P
AP
Shimbo
Daichi
D
Stevenson
Lori
L
D000368:Aged; D001783:Blood Flow Velocity / Q000502:physiology*; D001916:Brachial Artery / Q000503:physiopathology*; D002318:Cardiovascular Diseases / Q000150:complications / Q000503:physiopathology*; D015331:Cohort Studies; D004730:Endothelium, Vascular / Q000503:physiopathology*; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D011656:Pulmonary Emphysema / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D011673:Pulsatile Flow / Q000502:physiology; D012143:Respiratory Physiological Phenomena; D012907:Smoking / Q000009:adverse effects; D014664:Vasodilation / Q000502:physiology