Researchers have found a link between chronic obstructive pulmonary disease (COPD) and heart disease; however, a link is all they have found. In a previously funded grant, using a double blind, randomized experimental design, the investigators explored the effect of an acute dose of Kuvan or an antioxidant cocktail (1000mg of vitamin C, 600IU of vitamin E, and 600mg alpha-lipoic acid) on vascular health in patients with COPD. Consequently, the investigators found in separate experiments, that a single dose of both antioxidants and Kuvan transiently improves vascular health in patients with COPD. The current project is an attempt to expand on the investigator's previous findings and explore the effects of sub-chronic use of antioxidants and Kuvan on sustaining the improvements in vascular health in COPD.