Do Phosphodiesterase 5A Inhibitors Improve Exercise Capacity in Patients With Chronic Obstructive Pulmonary Disease (COPD) and Pulmonary Hypertension?

Inclusion Criteria: * COPD * Forced expiratory volume in 1 second (FEV1) \<80% (FEV1/FVC \<0.70) * Right ventricular systolic pressure (RVSP) \> 30 mmHg or Pulmonary Acceleration time \<120 ms Exclusion Criteria: * Pulmonary stenosis or echo left ventricular outflow tract obstruction * Left ventricular ejection fraction \< 45% * Patients taking nitrates, nicorandil or doxazosin. * Drug contraindications: * Systolic Blood Pressure \<90 mmHg * recent stroke * unstable angina * past history of non arteritic anterior ischaemic optic neuropathy