SPHERIC-1. Sildenafil and Pulmonary HypERtension In COPD

Although pulmonary hypertension (PH) is a quite frequent complication of advanced pulmonary diseases, and it is an independent prognostic factor, until now no evidence-based treatment approach exists for those patients. This study will address if the drug sildenafil can lower pulmonary vascular resistance in patients with significant pulmonary hypertension (high blood pressure in the lungs) associated to chronic obstructive pulmonary disease (COPD). It will see if this treatment can improve effort capacity, quality of life without causing a deterioration in pulmonary gas exchange (mainly arterial oxygenation). Patients 18 years of age and older with moderate COPD and pulmonary hypertension (mean pulmonary arterial pressure \>30 mmHg) may be eligible for this study. Participants are randomly assigned to receive sildenafil or placebo (pill with no drug) for 16 weeks. Before starting treatment (baseline), and a the end of the study, the patients have a comprehensive assessment including: * a chest x-ray and CT scan (only at baseline); * pulmonary function tests to measure how much air the patient can breathe in and out, and the capacity of diffusion of gases; * arterial blood gases analysis (for safety reason this examination is performed at baseline, before the randomization after one hour from the administration of a tablet (20 mg) of sildenafil, and every month) * an echocardiogram (heart ultrasound) (only at baseline); * a 6-minute walk test to measure exercise capacity; * a quality-of-life assessment (SF-36 questionnaire) * a right heart catheterization to evaluate the severity of hypertension At the end of the 16-week period, patients may opt to continue to receive sildenafil and monitoring in an open-label phase of the study for up to 1 year.