Approximate FiO2 delivered by a nasal cannula at 5 L/min.

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Multiple Choice

Approximate FiO2 delivered by a nasal cannula at 5 L/min.

The main idea is how oxygen concentration from a nasal cannula scales with flow. For nasal cannulas, a common estimation is FiO2 ≈ 0.21 + 0.04 × (flow in L/min), up to about 6 L/min. Starting from room air (21% O2) and adding roughly 4 percentage points for each liter per minute of flow, at 5 L/min you get 0.21 + 0.20 ≈ 0.41, or about 41% O2. That’s the closest approximate value among typical options. Remember this is an estimate—the actual FiO2 can vary with mouth breathing, cannula fit, and patient breathing pattern.

The main idea is how oxygen concentration from a nasal cannula scales with flow. For nasal cannulas, a common estimation is FiO2 ≈ 0.21 + 0.04 × (flow in L/min), up to about 6 L/min. Starting from room air (21% O2) and adding roughly 4 percentage points for each liter per minute of flow, at 5 L/min you get 0.21 + 0.20 ≈ 0.41, or about 41% O2. That’s the closest approximate value among typical options. Remember this is an estimate—the actual FiO2 can vary with mouth breathing, cannula fit, and patient breathing pattern.

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