Which oxygen delivery device can achieve the highest FiO2 range under typical use?

Which oxygen delivery device can achieve the highest FiO2 range under typical use?

• A. Nasal cannula 24–44%
• B. Simple face mask 40–60%
• C. Non-rebreather mask 70–100%
• D. Venturi mask 24–50%

Answer: (C)

Delivering the highest fraction of inspired oxygen (FiO2) depends on how much ambient room air is entrained during inhalation. The non-rebreather mask uses a reservoir bag and one-way valves that mostly prevent room air from diluting the inhaled gas. When the flow is enough to keep the bag inflated, the patient inhales mainly oxygen from the bag, yielding FiO2 that can reach near 100% under ideal conditions. In typical use, this translates to roughly 70–100% FiO2, making it capable of delivering the highest oxygen concentration among common devices. By comparison, a nasal cannula delivers oxygen through prongs and relies on a continuous influx of room air around the prongs, so FiO2 increases only modestly with flow and usually tops out around 24–44%. A simple face mask covers the nose and mouth but can leak and doesn’t seal well, limiting FiO2 to about 40–60% in many patients. A Venturi mask provides a precise, fixed FiO2 by mixing air with oxygen, but its maximum is generally in the 24–50% range, not designed for very high concentrations.

Delivering the highest fraction of inspired oxygen (FiO2) depends on how much ambient room air is entrained during inhalation. The non-rebreather mask uses a reservoir bag and one-way valves that mostly prevent room air from diluting the inhaled gas. When the flow is enough to keep the bag inflated, the patient inhales mainly oxygen from the bag, yielding FiO2 that can reach near 100% under ideal conditions. In typical use, this translates to roughly 70–100% FiO2, making it capable of delivering the highest oxygen concentration among common devices.

By comparison, a nasal cannula delivers oxygen through prongs and relies on a continuous influx of room air around the prongs, so FiO2 increases only modestly with flow and usually tops out around 24–44%. A simple face mask covers the nose and mouth but can leak and doesn’t seal well, limiting FiO2 to about 40–60% in many patients. A Venturi mask provides a precise, fixed FiO2 by mixing air with oxygen, but its maximum is generally in the 24–50% range, not designed for very high concentrations.