From the Guidelines
A non-rebreather (NRB) mask delivers oxygen at concentrations between 60% and 90% when used at a flow rate of 15 L/min. The delivered oxygen concentration is variable and will depend on the mask fit and the patient’s breathing pattern 1.
Key Considerations
- The mask fit is crucial to prevent room air entrainment, which would dilute the oxygen concentration.
- The oxygen flow rate should be set at 15 L/min to achieve the desired oxygen concentration.
- The reservoir bag should remain at least partially inflated during respiration to ensure optimal performance.
- NRB masks are most suitable for trauma and emergency use in patients in whom carbon dioxide retention is unlikely 1.
Important Factors
- Patient's respiratory pattern: the actual delivered oxygen percentage may vary based on the patient's breathing pattern.
- Mask fit: a tight seal against the face is necessary to prevent room air entrainment.
- Reservoir bag inflation: the bag should remain at least partially inflated during respiration to ensure optimal performance. The high oxygen concentration delivered by the NRB mask makes it an ideal choice for emergency situations where patients require high concentrations of oxygen, such as severe hypoxemia 1.
From the Research
Percent Oxygen Delivered by a Non-Rebreather Mask
- The percentage of oxygen delivered by a non-rebreather (NRB) mask can vary depending on the oxygen flow rate and the specific design of the mask.
- A study published in 2018 2 found that a non-rebreather mask delivered a mean FeO2 of 81% (95% CI 78% to 83%) at a flush rate oxygen flow of 40 to 60 L/min.
- Another study published in 2024 3 found that a non-rebreather mask delivered a mean FeO2 of 78% (95% CI 74% to 83%) at a flush rate oxygen flow from a portable tank.
- A simulation-based study published in 2022 4 found that a non-rebreather mask delivered an FIO2 range of 0.93-1.00 at oxygen flow rates of 1-15 L/min and flush.
Comparison to Other Oxygen Masks
- The non-rebreather mask has been compared to other oxygen masks in terms of oxygen delivery.
- A study published in 1998 5 found that a Tusk mask delivered a higher PaO2 than a non-rebreather mask in both normal subjects and patients with interstitial lung disease.
- The simulation-based study published in 2022 4 found that the non-rebreather mask delivered the highest FIO2 among the masks tested, followed by the partial rebreather mask and the simple mask.
Factors Affecting Oxygen Delivery
- The oxygen flow rate and the design of the mask can affect the percentage of oxygen delivered by a non-rebreather mask.
- A study published in 1991 6 found that oxygen flow rates less than 5 L/min can lead to rebreathing and excessive respiratory work during oxygen therapy with a Hudson mask.
- The study published in 2024 3 found that preoxygenation using a non-rebreather mask at 25 L/min from a portable tank was inferior to bag-valve-mask at flush rate.