Non-Rebreather Mask

What FiO2 does a non-rebreather mask deliver?

A properly applied non-rebreather mask at 10–15 LPM oxygen flow delivers approximately 60–80% FiO2 (fraction of inspired oxygen) — significantly higher than a simple face mask (~40% at 6–10 LPM) or nasal cannula (~24–44% at 1–6 LPM). The actual FiO2 depends on the tightness of the mask seal, the patient's respiratory rate and tidal volume, and the oxygen flow rate. The NRB cannot deliver true 100% FiO2 due to mask seal limitations, but it provides the highest non-invasive oxygen concentration available.

When should a non-rebreather mask be used over a nasal cannula?

A non-rebreather mask is indicated when the patient requires high-concentration supplemental oxygen — typically SpO2 below 90% despite lower-flow supplemental oxygen, or when high-flow oxygen is immediately indicated (severe trauma, suspected CO poisoning, respiratory distress, post-cardiac arrest, hemorrhagic shock). A nasal cannula at 1–6 LPM is appropriate for mild to moderate hypoxia in a comfortable patient. The NRB is the choice when maximum non-invasive oxygen delivery is the priority.

What oxygen flow rate should I use with the NRB mask?

10–15 LPM is the standard flow rate for a non-rebreather mask. The minimum flow rate should be set high enough to keep the reservoir bag inflated — if the bag collapses during inspiration, the patient is inspiring room air through the bag, defeating the purpose of the NRB. At 10–15 LPM, the reservoir bag should remain partially inflated throughout the respiratory cycle. Higher flow rates may be needed for patients with high respiratory rates or large tidal volumes.

How long will a Size D oxygen cylinder last with an NRB mask at 15 LPM?

A Size D cylinder contains approximately 14.6 cubic feet (approximately 415 liters) of medical oxygen. At 15 LPM, a Size D cylinder will last approximately 27 minutes. At 10 LPM, approximately 41 minutes. This duration guide is important for prehospital planning — providers should calculate estimated transport time and ensure sufficient oxygen is available, or reduce flow to a clinically appropriate minimum once the patient is stabilized.

Can a non-rebreather mask be used on an unconscious patient?

The NRB mask requires the patient to be spontaneously breathing — it is a passive delivery system, not a ventilation tool. For an unconscious patient who is not breathing adequately, a bag valve mask (BVM) must be used to provide positive-pressure ventilation. An NRB can be used on a spontaneously breathing unconscious patient (e.g., deeply obtunded but maintaining adequate respiratory effort), but should be monitored closely for aspiration risk and the need to transition to BVM or advanced airway management.