What mode of oxygen delivery would likely reverse the symptoms of a patient with an O2 saturation of 84%?

A non-rebreather mask is specifically designed to deliver a high concentration of oxygen, making it the most effective option for rapidly increasing the oxygen saturation in patients with significantly low levels, such as 84%. This type of mask has a reservoir bag that stores oxygen and is equipped with one-way valves that prevent exhaled air from entering the bag. When a patient inhales through a non-rebreather mask, they receive almost pure oxygen, which can quickly help to elevate their oxygen saturation levels.

In cases where a patient presents with critically low oxygen saturation, such as in respiratory distress or severe hypoxemia, the non-rebreather mask is a critical intervention. It allows for the delivery of 10-15 liters of oxygen per minute, effectively meeting the immediate needs of the patient while waiting for further assessment and treatment.

Other options, like a simple face mask or nasal cannula, would not provide the high concentration of oxygen required in this situation. A Venturi mask can regulate oxygen delivery but is typically used for patients who need a precise dosage rather than immediate high flow to correct dangerous hypoxemia. Hence, the choice of a non-rebreather mask is appropriate and aligns with the urgent need to reverse the low oxygen saturation.