The Effect of Inhaled Nitric Oxide on Pulmonary Gas-exchange 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 individuals 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 individuals with mild COPD, 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.

Inclusion Criteria: * Twenty participants with mild COPD (forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) below the lower limit of normal (\ pack-years) will be recruited. Twenty participants with moderate COPD (FEV1/ FVC below the lower limit of normal (\ pack-years) will also be recruited. Additionally, 40 healthy individuals with be recruited. * Participants will be free of any known significant cardiovascular, metabolic or neuromuscular disease. Participants with COPD will have global initiative for chronic obstructive lung disease (GOLD) Stage 1 mild COPD (FEV1/FVC ratio \