Which statement correctly describes a nonrebreather mask with a good seal delivering high oxygen?

Which statement correctly describes a nonrebreather mask with a good seal delivering high oxygen?

• A. Delivers up to 95% O2 at about 15 L/min
• B. Delivers exactly 100% O2
• C. Delivers less than 50% O2 at 6 L/min
• D. Does not require a seal

Answer: (A)

Nonrebreather masks deliver very high concentrations of oxygen by using a reservoir and one-way valves that minimize room air entrainment when the seal is tight and the flow is high. With about 10–15 liters per minute and a good seal, the patient can breathe in oxygen-rich air that approaches about 95% O2. It isn’t exactly 100% because some room air can still mix in during inhalation and a perfect, completely closed system isn’t achieved. At lower flow rates or with a poor seal, the FiO2 drops because more ambient air is drawn in. The seal is essential; without it, entrainment of room air reduces the oxygen concentration significantly.

Nonrebreather masks deliver very high concentrations of oxygen by using a reservoir and one-way valves that minimize room air entrainment when the seal is tight and the flow is high. With about 10–15 liters per minute and a good seal, the patient can breathe in oxygen-rich air that approaches about 95% O2. It isn’t exactly 100% because some room air can still mix in during inhalation and a perfect, completely closed system isn’t achieved. At lower flow rates or with a poor seal, the FiO2 drops because more ambient air is drawn in. The seal is essential; without it, entrainment of room air reduces the oxygen concentration significantly.