What is the oxygen flow rate and FiO2 for a partial rebreather mask?

• A. 12-15 LPM 70-90%
• B. 6-8 LPM 30-50%
• C. 4-6 LPM 25-35%
• D. 9-10 LPM 40-60%

Answer: (D)

Partial rebreather masks sit between a simple mask and a nonrebreather, using a reservoir bag to recycle some exhaled air and boost the amount of oxygen delivered without reaching the highest FiO2. With enough flow to keep the bag partially inflated, you typically get more oxygen than a simple mask but not the near-maximal FiO2 of a nonrebreather. That’s why a flow around 9–10 L/min is used to maintain bag inflation and supply moderate oxygen, yielding an FiO2 in roughly the 40–60% range. If the flow is much higher, you approach the conditions of a nonrebreather with higher FiO2; if it’s much lower, FiO2 drops toward the lower end. So the combination of about 9–10 L/min and 40–60% FiO2 best matches a partial rebreather mask.