What aspect of a nonrebreather mask helps in delivering high concentrations of oxygen?

The correct answer is the oxygen reservoir bag, which plays a crucial role in delivering high concentrations of oxygen to a patient. When oxygen is supplied to the mask, the reservoir bag fills with oxygen, allowing for a reserve of concentrated oxygen to be available during inhalation. This design ensures that as the patient breathes in, they receive a much higher concentration of oxygen compared to other delivery methods, effectively providing supplemental oxygen for patients in respiratory distress or those who are critically ill.

The presence of the one-way valve is important as it prevents exhaled air from entering the reservoir bag and ensures that the patient inhales primarily the oxygen stored in the bag. Although the inflatable nature of the mask contributes to its overall effectiveness in providing a secure fit, it is the reservoir that is key to achieving high oxygen concentrations. The size of the mask can influence the comfort and fit but does not fundamentally enhance the oxygen delivery capabilities compared to the function of the reservoir bag.