A reservoir mask with CLOSED exhalation ports is classified as which type?

• A. Partial rebreather
• B. Simple mask
• C. Nasal cannula
• D. Non-rebreather

Answer: (D)

Delivering near-maximum oxygen concentration with a mask depends on a reservoir bag and one-way valve system that prevents the patient’s exhaled gas from entering the oxygen reservoir. A reservoir mask with closed exhalation ports uses that valve arrangement so the air the patient inhales comes predominantly from the reservoir, not from recently exhaled gas. Exhaled gas escapes through the ports to the atmosphere, while the reservoir remains filled with oxygen, delivering the highest FiO2 among common bedside devices. This setup distinguishes it from a simple mask (no reservoir), a nasal cannula (low FiO2 with no reservoir), and a partial rebreather (some rebreathed gas in the reservoir).