What is a no rebreather (non-rebreather) mask used for in medical treatment?

What is a Non-Rebreather Mask?

A non-rebreather mask (NRB) is a high-concentration oxygen delivery device consisting of a face mask with an attached reservoir bag and one-way valves that delivers 60-90% oxygen when used with the required flow rate of 15 L/min. 1

Core Design and Mechanism

The NRB mask operates through a specific valve system that prevents rebreathing of exhaled air:

• A one-way valve sits between the mask and reservoir bag, allowing oxygen to flow from the bag into the mask during inspiration while preventing exhaled air from entering the reservoir 1
• The nonrebreathing outlet valve must function properly at oxygen flows up to 30 L/min to maintain safety 1
• Standard NRB designs include safety vents that typically deliver 60-80% oxygen concentration 1

Critical Flow Rate Requirements

NRB masks absolutely require oxygen flow rates of 15 L/min to function safely and effectively 1, 2. This is non-negotiable for proper function:

• Flow rates below 15 L/min create serious safety hazards, including inadequate oxygenation and dangerous CO2 rebreathing 3
• When oxygen flow is lower than the patient's minute ventilation (typically 6-10 L/min), CO2 rebreathing risk dramatically increases, especially in patients with COPD and low tidal volumes 3
• A documented case report describes CO2 narcosis requiring intubation when a NRB was inappropriately used at only 4 L/min 3

Clinical Applications

NRB masks are designed for specific emergency situations:

• Most suitable for trauma and emergency situations requiring immediate high-concentration oxygen delivery 1
• Recommended for acute cluster headache attacks at 12-15 L/min flow 1
• Appropriate for pregnant women with major trauma or severe hypoxemia 1

Critical Safety Precautions and Common Pitfalls

Do not connect NRB masks to oxygen concentrators with maximum output of 10 L/min—use simple face masks or nasal cannulae instead 1, 4. This is a common and dangerous error:

• Simple face masks deliver 40-60% oxygen at 5-10 L/min and are appropriate for standard concentrators 1, 4
• For patients requiring precise oxygen titration, use Venturi masks instead of NRB 1
• Patients with COPD and hypoxic ventilatory drive are more safely managed using nasal cannula at 1-2 L/min or simple face mask at 5 L/min rather than NRB 3

When Higher Concentrations Are Needed

If you need to deliver near-100% oxygen using a NRB:

• Use a three-valve mask (valve replacing the safety vent in the mask body) rather than standard two-valve design 5
• Ensure oxygen flow at 15 L/min 5
• Fit the mask tightly to the face to achieve inspired oxygen fraction up to 0.97 5