Which oxygen delivery device is most appropriate for moderate to high oxygen needs?

• A. Nasal cannula at 2-6 L/min
• B. Simple face mask at 5-8 L/min
• C. Venturi mask at 4-12 L/min
• D. Nonrebreather mask at 12-15 L/min (correct)

Answer: (D)

When oxygen needs are high, you want a device that delivers the highest possible oxygen concentration with minimal room air mixing. The nonrebreather mask fits that requirement because it provides a reservoir of oxygen and has one-way valves that prevent inhaling exhaled air, delivering a very high FiO2 as long as the flow is high enough to keep the bag inflated. At flows of 12–15 L/min, the patient can receive near-ambient oxygen concentrations, often around 80–100%, depending on fit and breathing pattern.

Nasal cannulas deliver only low to moderate oxygen levels, up to roughly 40–45% at the upper flow limit, making them unsuitable for moderate to high needs. Simple face masks can provide moderate FiO2 (roughly 40–60%) but are less reliable because the mask’s fit and bag inflation affect the actual oxygen delivered. Venturi masks offer precise, fixed FiO2 but typically max out around the upper 50–60% range and require specific adapters and proper flow to maintain the intended concentration.

So, for moderate to high oxygen requirements, the nonrebreather mask is the best choice because it can supply the highest concentration of oxygen when used with appropriate flow to keep the reservoir filled.