Peripheral endothelial dysfunction is associated with gas exchange inefficiency in smokers

AIMS: To assess the cross-sectional association between exercise capacity, gas exchange efficiency and endothelial function, as measured by flow-mediated dilation (FMD) and nitroglycerin-mediated dilation (NMD) of the brachial artery, in a large-scale population-based survey. METHODS: The study population was comprised of 1416 volunteers 25 to 85 years old. Oxygen uptake at anaerobic threshold (VO(2)@AT), peak exercise (peakVO(2)) and ventilatory efficiency (VE vs. VCO(2 )slope and VE/VCO(2)@AT) were assessed on a breath-by-breath basis during incremental symptom-limited cardiopulmonary exercise. FMD and NMD measurements at rest were performed using standardised ultrasound techniques. RESULTS: Multivariable logistic regression analyses revealed a significant association between FMD and ventilatory efficiency in current smokers but not in ex-smokers or non-smokers. There was no association between FMD and VO(2)@AT or peak VO(2). In current smokers, for each one millimetre decrement in FMD, VE/VCO(2)@AT improved by -3.6 (95% CI -6.8, -0.4) in the overall population [VE vs. VCO(2 )slope -3.9 (-7.1, -0.6)]. These results remained robust after adjusting for all major influencing factors. Neither exercise capacity nor ventilatory efficiency was significantly associated with NMD. CONCLUSION: In current smokers, FMD is significantly associated with ventilatory efficiency. This result may be interpreted as a potential clinical link between smoking and early pulmonary vasculopathy due to smoking.