Study of PAH Subjects With LTOT Use That Have Demonstrated Improved Exercise Tolerance With the Use of Inhaled Nitric

Inclusion Criteria: 1. Signed Informed Consent Form prior to the initiation of any study mandated procedures or assessments 2. Subjects must be enrolled in the PULSE PAH-004 clinical trial and must have been on LTOT and on open-label treatment with iNO 75 mcg/kg IBW/hr for at least 4 months 3. Subjects must have achieved ≥ 30 meter improvement in 6MWD after 4, 8 or 12 months of open-label treatment with iNO 75 mcg/kg IBW/hr as compared to either their PULSE PAH-004 Week 2 end of Run-in OR End of Study (EOS)in PULSE-PAH-004. 4. Subjects are willing and considered in the judgement of the Investigator able to use the INOpulse device continuously for up to 24 hours per day 5. Female subjects of childbearing potential must have a negative pregnancy test (serum or urine) at randomization. All female subjects must use an effective method of birth control to avoid pregnancy. Exclusion Criteria: 1. Subjects with episodes of worsening of PAH in the last 30 days prior to PULSE PAH-007 Baseline/Randomization 2. Subjects that experience Pulmonary Rebound in PULSE-PAH-004 3. Change in dose or types of PAH specific therapies in the last 30 days prior to Baseline/Randomization 4. Subjects who require treatment with riociguat 5. Subjects who early discontinued drug/device usage due to withdrawal of consent or an adverse event requiring termination from treatment in PULSE PAH-004 6. Women who are pregnant 7. The concurrent use of the INOpulse device with a continuous airway pressure (CPAP), Bilevel Positive Airway Pressure (BiPAP, or any other positive pressure device.