Nitric Oxide on Dyspnea and Exercise Tolerance in COPD

Chronic Obstructive Pulmonary Disease (COPD) is a lung disorder commonly caused by smoking, which makes breathing more difficult. When COPD patients exercise, they are not efficient breathers and this leads to serious breathing difficulties, which often causes these patients to stop exercise at low intensities. Even though patients with a mild form of COPD have relatively well preserved lung function, they still have inefficient breathing during exercise. The investigators think that these patients have problems exchanging fresh gas (i.e., oxygen) into the blood stream because of poor lung blood vessel function. The investigators will test whether inhaled medications, specifically nitric oxide, can improve lung blood vessel function and decrease breathing difficulties during exercise. With this research, the investigators will understand more about breathing efficiency and lung blood vessel function in mild COPD patients, and find out whether improving lung blood vessel function helps COPD patients breathe easier and exercise longer. Understanding the reasons behind the feeling of difficult breathing may lead to more effective therapy and improved quality of life in COPD patients.