Which oxygen delivery device is appropriate for a patient who is hypoxic and breathing spontaneously but can tolerate a device and needs a higher oxygen concentration than a nasal cannula?

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

Answer: (B)

Delivering the highest possible oxygen concentration to a spontaneously breathing patient who needs more than a nasal cannula can provide points to the nonrebreather mask. This device has a reservoir bag that fills with oxygen and one-way valves at the exhalation ports, which prevents most room air from diluting the inspiratory gas. When the patient inhales, they draw gas primarily from that reservoir, so the delivered FiO2 can be very high—approaching 80–100% with proper flow and a well-sealed fit. That makes it the best option when someone is hypoxic and you need a high concentration of oxygen quickly while they continue to breathe on their own.

A nasal cannula supplies a relatively low fraction of inspired oxygen, typically up to about 44% at higher flow rates, so it’s not enough for significant hypoxemia. A simple face mask can deliver more than a nasal cannula, but its FiO2 is variable and generally lower than a nonrebreather, depending on breathing pattern and fit. A Venturi mask provides a precise, moderate FiO2 (often in the 24–50% range) but cannot reliably deliver very high concentrations like a nonrebreather mask, though it’s valuable when precise oxygen levels are needed.