Prior to applying a nonrebreathing mask to a patient, you must ensure that the:

• A. Reservoir bag is fully inflated.
• B. One-way valve is sealed.
• C. Patient has reduced tidal volume.
• D. Flow rate is set at 6 L/min.

Answer: (A)

Nonrebreathing masks supply oxygen from a reservoir to avoid drawing in room air, and they rely on one-way valves to prevent rebreathing of exhaled air. Because of this setup, the reservoir bag must be fully inflated before placing the mask so the patient has an immediate oxygen reservoir to draw from during inspiration. If the bag isn’t inflated, the patient may inhale room air or exhaled air, reducing the delivered oxygen concentration. The other options don’t fit: you don’t “seal” a one-way valve, tidal volume isn’t something you pre-check in this way, and a flow rate of 6 L/min is typically too low to keep the bag expanded and deliver high FiO2.