This is a pilot study of a new use of Epoprostenol via inhalation (Epoprostenol is approved for intravenous use). The purpose of this study is to administered inhaled Epoprostenol and intravenous Phenylephrine to improve arterial oxygen tension during one-lung anesthesia either with volatile anesthesia (Sevoflurane) or with intravenous anesthesia (Propofol).