Acute Effect of Sildenafil on Exercise Tolerance and Functional Capacity in COPD, IPF and Post Pneumonectomy Patients

* Pulmonary diseases are increasingly important causes of morbidity and mortality in the modern world. * Sildenafil, an orally administered a phosphodiesterase type 5 (PDE-5) inhibitor, targets the nitric oxide (NO) pathway. The drug was first approved for the treatment of Pulmonary Arterial Hypertension (PAH) in 2005. * The aim of the suggested study is to examine the acute effect of oral intake of sildenafil on exercise tolerance and functional capacity in Chronic Obstructive Pulmonary Disease (COPD), Idiopathic pulmonary fibrosis (IPF) and post Pneumonectomy patients. * The investigators hypothesize that oral ingestion of sildenafil prior the exercise may enhance exercise tolerance and improve function in COPD, IPF and post Pneumonectomy patients. * Patients and Methods: Sixty chronic lung disease patients males and females (aged 30 to 90 years) 20 COPD (GOLD III-IV) \[9, 39\] , 20 IPF and 20 post Pneumonectomy patients will be recruit to this study. * All subjects will carried out two maximal cardiopulmonary exercise tests (CPET) on bicycle ergometer in different days; 60 min after intake of placebo and 60 min after intake of 100 mg sildenafil (Pfizer, Sandwich, UK), in random order. * In first meeting prior exercise test at rest standard pulmonary function test, diffusion of CO, TLC and RV will be measured. In addition, Doppler Echocardiography and blood samples for NT-proBNP will be taken prior and post each CPET. * After 15-20 minute of passive recovery post exercise test all patients will perform 3 short functional tests including 6 minute walk test to assess functional capacity.