Breathe Easier With Tadalafil Therapy for Dyspnea in COPD-PH

The investigators will study whether the drug tadalafil improves shortness of breath in 126 Veterans with Chronic Obstructive Pulmonary Disease (COPD) and high blood pressure in the lungs. The investigators will also assess whether tadalafil improves quality of life, home daily physical activity, exercise endurance, the frequency of acute flares of COPD, blood pressure in the lungs, and lung function. Veterans who enroll in the trial will be allocated by chance to either active tadalafil or an inactive identical capsule (placebo). Neither the Veteran nor the investigator will know whether the Veteran is taking tadalafil or placebo. Veterans will be followed closely in clinic or by telephone at 1, 2, 3, 4, 5, and 6 months, with attention to side effects and safety. At 1,3, and 6 months the investigators will repeat the questionnaires and testing of blood pressures in the lung and lung function. The investigators anticipate that the results of this study will determine whether tadalafil improves shortness of breath when added to usual medications for COPD.