Which statement about nasal cannula oxygen delivery is true when delivering 6 L/min?

• A. Approximately 24%.
• B. Approximately 35%.
• C. Approximately 44%.
• D. Approximately 52%.

Answer: (C)

Understanding how FiO2 from a nasal cannula changes with flow helps you estimate the oxygen concentration delivered. With a nasal cannula, the room air baseline is about 21% oxygen. A common rule of thumb is that the FiO2 increases by roughly 4 percentage points for each additional liter per minute of flow, up to about 6 L/min. So for 6 L/min, the estimate is 21% + (6 × 4%) ≈ 45%, which is typically rounded to about 44–45%. That’s why the statement around 44% is the best fit. Real-world factors like mouth breathing or how well the cannula fits can cause slight variation, but 44% is the standard expectation at this flow.