Dose Determination Safety and Activity Study of Inhaled NX1011 to Treat Pulmonary Arterial Hypertension

Inclusion Criteria: * Patient must either: * meet the PAH diagnostic criteria at Screening (based on a documented history of diagnosis as outlined in the American College of Chest Physicians \[ACCP\] 2004 Evidence-Based Clinical Practices Guidelines)15; or * have elevated pulmonary pressure with a suspected PAH diagnosis based on a clinical referral at Screening for a RHC. * Patient must have PAH as defined by a mean pulmonary artery pressure (PAP) \> 25 mmHg. * Patient must have symptoms of pulmonary hypertension (PH) according to the World Health Organization (WHO) Functional Classification of Pulmonary Hypertension Class II through IV. * Patient must consent to, be able to tolerate, and have adequate venous and arterial access for Swan-Ganz catheterization (SGC) and an arterial line. Exclusion Criteria: * Clinically significant right-to-left intracardiac shunts based on Doppler echocardiography with bubble study. * History of pulmonary veno-occlusive disease or clinically significant aortic or mitral stenosis. * History of sustained ventricular tachycardia (VT-S) or ventricular fibrillation (VF) and cardiac arrest, or presence of atrial fibrillation. * Active cardiac disease meeting the following criteria: * Patient with elevated pulmonary capillary wedge pressures (PCWPs) \> 25 mmHg. * Patient with a history of myocardial infarction or coronary intervention within the last 60 days. * Patient with a history of pacemaker, cardiac defibrillator, or biventricular pacemaker insertion within 4 weeks of Baseline. * Patient who cannot be withdrawn from nitrate therapy.