Which oxygen delivery device provides FiO2 approximately 70–100%?

Which oxygen delivery device provides FiO2 approximately 70–100%?

• A. Nasal cannula 24–44%
• B. Simple face mask 40–60%
• C. Partial rebreather mask 60–90%
• D. Non-rebreather mask 70–100%

Answer: (D)

The key idea is that the amount of oxygen a patient inhales (FiO2) depends on how much room air mixes with the delivered oxygen. A non-rebreather mask uses one-way valves and a reservoir bag filled with oxygen. When the patient inhales, the one-way valves prevent room air from entering through the exhalation ports, so most of the air drawn in comes from the oxygen-filled reservoir. With a proper flow, the bag stays inflated and the inspired gas is nearly pure oxygen, giving FiO2 in the range of about 70–100%. In contrast, a nasal cannula delivers oxygen directly into the nose, but room air mixes with it during inhalation, typically yielding around 24–44% FiO2. A simple face mask covers the nose and mouth but also leaks around edges, so the FiO2 is usually about 40–60%. A partial rebreather mask has a reservoir and vents that allow some exhaled air to mix back in, providing roughly 60–90% FiO2 depending on flow and mask fit, but not as consistently high as a true non-rebreather with a full, well-filling reservoir. So, when the goal is the highest possible FiO2 from a standard device, the non-rebreather mask best delivers approximately 70–100% FiO2.

The key idea is that the amount of oxygen a patient inhales (FiO2) depends on how much room air mixes with the delivered oxygen. A non-rebreather mask uses one-way valves and a reservoir bag filled with oxygen. When the patient inhales, the one-way valves prevent room air from entering through the exhalation ports, so most of the air drawn in comes from the oxygen-filled reservoir. With a proper flow, the bag stays inflated and the inspired gas is nearly pure oxygen, giving FiO2 in the range of about 70–100%.

In contrast, a nasal cannula delivers oxygen directly into the nose, but room air mixes with it during inhalation, typically yielding around 24–44% FiO2. A simple face mask covers the nose and mouth but also leaks around edges, so the FiO2 is usually about 40–60%. A partial rebreather mask has a reservoir and vents that allow some exhaled air to mix back in, providing roughly 60–90% FiO2 depending on flow and mask fit, but not as consistently high as a true non-rebreather with a full, well-filling reservoir.

So, when the goal is the highest possible FiO2 from a standard device, the non-rebreather mask best delivers approximately 70–100% FiO2.