Which type of mask allows a patient to rebreathe about one-third of their exhaled air?

The partial rebreather mask is designed to allow a patient to inhale a mixture of ambient air and a portion of their exhaled air. It typically has a reservoir bag that captures some of the exhaled air, which contains carbon dioxide, and a small amount of oxygen. When the patient inhales, this allows them to rebreathe some of that exhaled air along with fresh oxygen. It is often utilized for patients who require a higher concentration of oxygen but are still able to maintain some level of carbon dioxide in the mixture, which is beneficial for their respiratory drive. This mechanism enhances their oxygen delivery while ensuring they do not breathe entirely pure oxygen, which could lead to oxygen toxicity over prolonged periods.

In contrast, other options, such as a nasal cannula or a non-rebreather mask, have different functions. A nasal cannula delivers a constant flow of oxygen without allowing for any rebreathing of exhaled air, while a non-rebreather mask is designed to prevent the inhalation of exhaled air completely. The simple face mask, while it can deliver oxygen, also does not provide the rebreathe capability found in the partial rebreather mask. Thus, the partial rebreather mask is specifically intended