Study to determine if inhaled nitric oxide (iNO) given through a special delivery device (INOpulse® DS) is safe and efficacious in treating Pulmonary Arterial Hypertension (PAH). Medical literature and clinical experience suggests that iNO at pulsed doses of 0.013 to 0.1 mg/kg per hour for 1 month to 2+ years appears safe and suggests efficacy for the treatment of pulmonary hypertension.