Which device delivers high-concentration oxygen with a reservoir?

• A. Nasal Cannula
• B. Venturi Mask
• C. Nonrebreather Mask
• D. Simple Face Mask

Answer: (C)

Understanding how oxygen delivery devices control the amount of oxygen a patient inhales. The nonrebreather mask is designed to deliver high-concentration oxygen because it uses a reservoir bag that fills with oxygen from the supply, plus one-way valves at the mask edges that prevent room air or exhaled air from diluting the inflow. When the reservoir stays filled and the flow is sufficient, most of the inhaled air comes from that oxygen-rich reservoir, achieving a high FiO2 quickly. The other devices don’t use a reservoir: a nasal cannula delivers lower concentrations with no bag, a simple face mask provides moderate FiO2 without a reservoir, and a Venturi mask gives fixed concentrations through a Venturi system but without a reservoir bag, so it doesn’t achieve the same high oxygen concentration.