Ace the Airwaves: 2026 RRT-NPS Neonatal/Pediatric Practice Test - Breathe Easy and Rise to the Top!

The key idea is recognizing when to use inhaled nitric oxide based on how severely oxygenation is failing despite ventilation. Oxygenation index (OI) quantifies this failure and is calculated as (mean airway pressure x FiO2 x 100) divided by PaO2. A higher OI means worse oxygenation relative to the support being given, which in PPHN reflects significant pulmonary hypertension and right-to-left shunting.

Inhaled nitric oxide is a selective pulmonary vasodilator that improves blood flow to ventilated portions of the lung, lowers pulmonary vascular resistance, and helps reduce shunting, often improving PaO2 without causing systemic hypotension. Because of this mechanism, a threshold around greater than 25 is commonly used to initiate iNO therapy in PPHN. Values higher than that (30, 40, etc.) indicate more severe disease, and some protocols may consider iNO at those levels as well, but >25 is the standard trigger in many guidelines.

So, the correct threshold is when OI is greater than 25, because it signals significant oxygenation impairment due to PPHN that can be mitigated by selective pulmonary vasodilation with inhaled nitric oxide.