Can a Non-Rebreather Mask (NRBM) be connected to an oxygen concentrator with a 10 L/min output for a patient requiring 8 L/min of oxygen flow?

Non-Rebreather Mask Should Not Be Connected to a 10 L/min Oxygen Concentrator

A non-rebreather mask (NRBM) should not be connected to an oxygen concentrator with a maximum output of 10 L/min for a patient requiring 8 L/min of oxygen flow, as NRBMs require a minimum flow rate of 15 L/min to function properly and avoid carbon dioxide rebreathing. 1

Why NRBMs Require Higher Flow Rates

• NRBMs are designed to deliver high oxygen concentrations (60-90%) but require a minimum flow rate of 15 L/min to function safely and effectively 1
• Using an NRBM with insufficient flow (below 15 L/min) creates a significant risk of carbon dioxide rebreathing and potential carbon dioxide narcosis 2
• When oxygen flow to an NRBM is lower than the patient's minute ventilation, the risk of carbon dioxide rebreathing dramatically increases, especially in patients with chronic obstructive pulmonary disease and low tidal volumes 2

Appropriate Oxygen Delivery Options for a 10 L/min Concentrator

• Simple face masks are more appropriate for oxygen concentrators with 10 L/min capacity, delivering 40-60% oxygen concentration 1
• Venturi masks provide precise oxygen concentration control and can be used with flow rates appropriate to the specific Venturi setting 1
• Nasal cannulae should be considered as the first choice of delivery device for patients requiring home oxygen therapy at flow rates of 4 L/min or less 3

Clinical Decision Algorithm for This Scenario

1. For this patient requiring 8 L/min:

   • Use a simple face mask at 8-10 L/min with the oxygen concentrator 1, 3
   • This will deliver approximately 40-60% oxygen concentration 1

2. If higher oxygen concentration is essential:

   • Consider using oxygen cylinders that can deliver the required 15 L/min flow rate for the NRBM 1
   • Compressed oxygen cylinders (H cylinders) can meet short-term oxygen needs but are logistically difficult to maintain for many patients 3

3. If precise oxygen concentration control is needed:

   • Use a Venturi mask at the appropriate flow rate for the desired concentration 1, 3

Safety Considerations and Evidence

• A case report documented carbon dioxide narcosis in a COPD patient when an NRBM was inappropriately used with only 4 L/min of oxygen flow 2
• Research comparing oxygen delivery devices found that NRBMs perform poorly at low flow rates, with higher inspired CO2 levels and less efficient CO2 clearance 4
• Even with a tightly fitted NRBM and 15 L/min flow, the average inspired oxygen fraction achievable is approximately 0.97 (97%), not 100% 5
• Oxygen concentrators are reliable and useful alternatives to piped-in oxygen or cylinders, but only for patients requiring flows of up to 4 L/min 6

Alternative Approaches

• For patients requiring medium-concentration oxygen (40-60%), a simple face mask at 5-10 L/min is appropriate 1, 3
• High-flow nasal cannula (HFNC) may be considered as an alternative to NRBM in appropriate clinical settings, as it has shown better oxygenation and patient satisfaction in some studies 7
• For patients with chronic respiratory conditions requiring home oxygen, oxygen concentrators should be used to deliver long-term oxygen therapy at flow rates of 4 L/min or less 3

Remember that using an NRBM with insufficient flow is not just a matter of reduced efficacy but presents a serious safety risk of carbon dioxide rebreathing and potential respiratory deterioration 2.