What FiO2 range does a simple face mask deliver?

What FiO2 range does a simple face mask deliver?

• A. 0.25-0.40
• B. 0.60-0.80
• C. 0.35-0.50
• D. 0.10-0.20

Answer: (C)

A simple face mask delivers a moderate concentration of oxygen because there’s no reservoir to hold pure oxygen between breaths, so inspired air is a mix of oxygen and surrounding room air. With typical flow rates around 5–6 L/min, this produces an FiO2 in roughly the mid-30s to about 50%. That’s why the 0.35–0.50 range is the best match. Higher ranges (around 0.60–0.80) come from devices with reservoirs or tighter seals (like non-rebreathers or high-flow systems), while much lower ranges (0.10–0.20) are more characteristic of a nasal cannula at low flow. The 0.25–0.40 range is possible but less representative of a simple mask’s typical performance, hence the 0.35–0.50 range is the most appropriate choice.

A simple face mask delivers a moderate concentration of oxygen because there’s no reservoir to hold pure oxygen between breaths, so inspired air is a mix of oxygen and surrounding room air. With typical flow rates around 5–6 L/min, this produces an FiO2 in roughly the mid-30s to about 50%. That’s why the 0.35–0.50 range is the best match. Higher ranges (around 0.60–0.80) come from devices with reservoirs or tighter seals (like non-rebreathers or high-flow systems), while much lower ranges (0.10–0.20) are more characteristic of a nasal cannula at low flow. The 0.25–0.40 range is possible but less representative of a simple mask’s typical performance, hence the 0.35–0.50 range is the most appropriate choice.