Updated July 2026 · 7 min read
Part of the ICU Emergencies Hub — browse every related guide in one place.
In the sickest hypoxemic patients — severe ARDS, right heart failure, pulmonary hypertension — a class of inhaled drugs can buy oxygenation when the ventilator alone is not enough. Inhaled nitric oxide (iNO) and inhaled epoprostenol (a prostacyclin, often known by the brand Flolan or Veletri) are delivered as a continuous gas or mist directly into the breathing circuit. Because they are inhaled, they act mainly where air is actually reaching, dilating blood vessels next to open, ventilated alveoli and steering blood toward the parts of the lung doing the gas exchange. They are rescue therapies, not cures, and the nurse managing them has to understand two things above all: how they help, and why they can never be turned off abruptly.
In severe lung injury, blood flows through areas of lung that are collapsed or filled with fluid and not exchanging gas, so it returns to the body still poorly oxygenated — a mismatch between ventilation and perfusion. An inhaled vasodilator can only reach alveoli that air is reaching, so it selectively opens the vessels beside ventilated lung. Blood is preferentially routed to those good units, and away from the dead zones, and oxygenation improves without the systemic blood-pressure drop you would get from an IV vasodilator hitting the whole body. The same pulmonary-vessel dilation lowers the pressure the right ventricle has to pump against, which is why these agents are also used in acute right heart failure and pulmonary hypertension.
| Inhaled nitric oxide (iNO) | Inhaled epoprostenol | |
|---|---|---|
| Form | Medical gas blended into the circuit via a dedicated delivery system | Prostacyclin mist delivered by continuous nebulization into the circuit |
| Main uses | Severe hypoxemia, pulmonary hypertension, RV failure, neonatal PPHN | Similar indications; often chosen for lower cost and simpler equipment |
| Special monitoring | Methemoglobin and NO2 (a toxic byproduct) levels; dose is measured in ppm | Platelet effects and circuit/equipment issues; can gum up filters |
| Onset / offset | Fast on, fast off — which is exactly why abrupt loss is dangerous | Short-acting — same rebound concern on interruption |
Both are short-acting by design, which is what makes them titratable — and also what makes any unplanned interruption an emergency. The evidence that they improve survival is limited; they reliably improve the oxygenation number and can stabilize a failing right heart, which is often enough to bridge a patient through the worst window.
Inhaled nitric oxide and inhaled epoprostenol are rescue therapies that open the blood vessels of ventilated lung, improving oxygenation and unloading a struggling right ventricle without dropping the systemic blood pressure. They work only where they are continuously delivered, and their short action means an interruption is not a minor inconvenience — it can rebound the patient into a crisis. Keep the circuit intact, protect delivery through every transport and suction, follow the drug-specific monitoring, and never let one of these agents stop abruptly. Managed carefully, they can be the bridge that carries a profoundly hypoxemic patient through their worst day.
Related: Prone positioning in ARDS · PEEP titration · ECMO basics · Mechanical ventilation basics
Educational content for licensed clinicians. Always follow your facility's protocol and provider orders. Not medical advice.
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