To deliver 80% oxygen continuously in a noninvasive manner, which delivery system should be selected?

• A. Nasal cannula
• B. Nonrebreather mask
• C. Venturi mask
• D. Simple face mask

Answer: (A)

To deliver a high concentration of oxygen noninvasively, you need a device that minimizes admission of room air and provides a reservoir of oxygen. The nonrebreather mask fits this requirement because it has a reservoir bag and one-way valves that prevent exhaled gas from diluting the oxygen in the mask. With an adequate flow (usually around 12–15 L/min) and a good seal, it can deliver very high FiO2, approaching 80–100%, which is suitable for delivering 80% oxygen continuously without intubation.

A nasal cannula, by contrast, delivers relatively low FiO2—typically about 24–40% at standard flows—and room air mixes in, making 80% oxygen unreliable. A Venturi mask is designed for precise, fixed FiO2 but generally tops out around 50–60% depending on the adapter, not 80%. A simple face mask can provide more than a nasal cannula but usually only about 40–60% and still not reliably reach 80%.

So for continuous noninvasive delivery of 80% oxygen, the nonrebreather mask is the best-fitting option.