For higher concentrations of oxygen, which device is appropriate?

• A. Nasal cannula
• B. Venturi mask
• C. Simple face mask
• D. Non-rebreather mask

Answer: (D)

When you need a high concentration of oxygen, you want a delivery method that minimizes dilution with room air. The non-rebreather mask achieves this best because it has a reservoir bag that fills with oxygen and one-way valves that prevent inhaled air from coming back through the exhalation ports. With the bag kept inflated and a high flow (typically about 10–15 L/min), the patient can receive nearly pure oxygen, approaching 100% FiO2.

Other common devices deliver lower and more variable FiO2. A nasal cannula reaches only up to about 40% oxygen; a simple face mask usually provides roughly 40–60% depending on fit and flow; a Venturi mask can deliver precise but more moderate oxygen levels, typically in the 24–50% range depending on the adapter. Therefore, for higher oxygen concentrations, the non-rebreather mask is the appropriate choice.