Which statement about oxygen delivery settings for nasal cannula versus simple mask is correct?

• A. Nasal cannula 1-6 L/min; humidification is recommended only below 2 L/min.
• B. Nasal cannula 1-6 L/min with humidification recommended above 4 L/min; Simple mask 5-8 L/min with FiO2 roughly 0.4-0.6.
• C. Simple mask requires less flow than nasal cannula.
• D. Nonrebreather mask is for lower oxygen needs.

Answer: (D)

The main idea is matching oxygen delivery devices to how much oxygen the patient needs. Nasal cannula delivers a relatively low to moderate FiO2 at flows of about 1–6 L/min, and humidification is commonly used when flows are higher to prevent drying of the mucosa. A simple face mask delivers a higher FiO2 than a nasal cannula and requires a minimum flow around 5 L/min to be effective, with typical FiO2 roughly 40–60% if well-fitted. The nonrebreather mask, on the other hand, is designed for the highest oxygen needs among basic devices and requires high flow (roughly 10–15 L/min) to fill the reservoir and maintain a high FiO2, often up to around 85–90% in ideal conditions.

The statement that a nonrebreather mask is for lower oxygen needs is not correct—it is used when the patient requires very high oxygen delivery. The other options contain elements that aren’t universally accurate (for example, humidification practices and exact FiO2 ranges can vary with fit and device design), but the core point is that nonrebreather masks are chosen for high oxygen needs, not low.