On a nonrebreather mask, the reservoir bag should be filled

• A. Prior To Being Placed On The Patient's Face
• B. After Being Placed On The Patient's Face
• C. During The Patient's Transport
• D. Never

Answer: (A)

The key idea is that the reservoir bag of a nonrebreather mask must be prefilled so the patient starts off inhaling high-concentration oxygen immediately. The bag stores oxygen and feeds it to the patient during each breath through a one-way valve, preventing inhalation of exhaled air. If you put the mask on with an empty bag, the first breaths will pull in room air until the bag fills, lowering the oxygen concentration delivered and delaying adequate oxygenation. Once the mask is on, you want a flow rate high enough (about 10–15 L/min) to keep the bag inflated during inspiration and maintain a high FiO2. Filling during transport or never filling would not provide the immediate, high-oxygen delivery the patient needs.