Using FiO2 estimation FiO2 ≈ 0.21 + 0.04 × L/min, what is FiO2 at 0 L/min?

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Multiple Choice

Using FiO2 estimation FiO2 ≈ 0.21 + 0.04 × L/min, what is FiO2 at 0 L/min?

FiO2 estimation with a nasal cannula starts from a baseline room air of 21% (0.21) at zero flow, and then increases by about 4 percentage points for each liter per minute of flow. At 0 L/min there is no extra oxygen delivered, so FiO2 remains 0.21. Plugging in 0 for flow confirms this: 0.21 + 0.04 × 0 = 0.21. The other values would require some positive flow (for example, 0.25 corresponds to about 1 L/min, and so on).

FiO2 estimation with a nasal cannula starts from a baseline room air of 21% (0.21) at zero flow, and then increases by about 4 percentage points for each liter per minute of flow. At 0 L/min there is no extra oxygen delivered, so FiO2 remains 0.21. Plugging in 0 for flow confirms this: 0.21 + 0.04 × 0 = 0.21. The other values would require some positive flow (for example, 0.25 corresponds to about 1 L/min, and so on).

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