Maximum flow rate for nasal cannula?

• A. 2-4 L/min
• B. 6 L/min
• C. 8 L/min
• D. 1 L/min

Answer: (B)

A standard nasal cannula delivers oxygen best up to about 6 liters per minute. The device is designed to mix supplied oxygen with room air as you breathe through your nose, so increasing flow raises the oxygen concentration only up to a point, with 6 L/min being the practical ceiling for most adults. Beyond that, the FiO2 benefit plateaus and patient comfort can suffer, so higher oxygen concentrations are provided with other devices like a simple mask or a non-rebreather, or with high-flow systems when available. At 6 L/min, the FiO2 is typically in the roughly mid-40s percent range. Flows of 1 L/min or 2–4 L/min are valid but do not represent the maximum capability of a nasal cannula, and 8 L/min exceeds what a standard cannula can reliably deliver.