Which mask is specifically designed to not allow room air to mix with the oxygen delivered?

The nonrebreathing mask is designed to provide a high concentration of oxygen to the patient while minimizing the mixing of room air with the oxygen being delivered. This mask features a one-way valve that prevents exhaled air from entering the oxygen reservoir bag and directly obstructs room air from mixing with the oxygen supply. As a result, patients receive a more concentrated dose of oxygen, which is crucial in situations requiring high-flow oxygen therapy, such as severe respiratory distress or hypoxia.

In contrast, other options, like the simple mask and partial rebreathing mask, allow varying degrees of room air mixing with the oxygen supply. The simple mask can deliver a moderate concentration of oxygen but does not have mechanisms to prevent air mixing effectively. The partial rebreathing mask, while it can provide higher oxygen concentrations than a simple mask, still allows some room air to mix with oxygen because it incorporates features that permit exhaled air to return to the reservoir bag. The nasal cannula provides a low flow of supplemental oxygen and is even less effective at preventing the mixing of room air, making it unsuitable for situations requiring high concentrations of oxygen.