The Hepatopulmonary syndrome (HPS) results from intrapulmonary microvascular dilatation that impairs arterial oxygenation in the setting of cirrhosis or portal hypertension. As many as 10-20% of cirrhotics being evaluated for orthotopic liver transplantation (OLT) have advanced HPS and mortality is greater in those with HPS than in those without HPS. Currently, OLT is the only effective treatment, although post-operative mortality in HPS is increased relative to cirrhotic patients without HPS, with a one-year survival of between 68-80 %. Therefore, an effective medical therapy for advanced HPS could improve both pre-operative and post-operative mortality.