Patients with chronic obstructive pulmonary disease (COPD) suffer from impaired exercise capacity and quality-of-life, largely related to shortness of breath. Many of the therapies currently available for COPD are aimed at improving these factors. Exercise capacity is limited in part by high blood pressure in the blood vessels in the lungs. Sildenafil, also known as Viagra, is an FDA-approved therapy for male erectile dysfunction. One of its effects is to relax (or open) the lung vessels, thereby lowering the blood pressure in the lungs. We hypothesize that sildenafil will result in an improvement in exercise capacity, quality-of-life, and shortness of breath.~Enrolled subjects will receive sildenafil or placebo for 4 weeks followed by exercise tests, breathing tests, and administration of quality-of-life questionnaires. Subjects will then receive placebo or sildenafil (whichever one they did not receive for the first 4 weeks) for another 4 weeks, followed by the same testing.
The purpose of this study is to determine if sildenafil improves the exercise capacity and lung function of patients with chronic obstructive pulmonary disease.