A patient who breathes through his or her mouth is least likely to benefit from which oxygen delivery method?

A patient who breathes through their mouth is least likely to benefit from the nasal cannula because this method delivers oxygen through two small prongs that are inserted into the nostrils. Effective oxygen delivery through a nasal cannula relies on the patient's ability to breathe through their nose, as oxygen is delivered directly into the nasal passages and is primarily intended for patients who can maintain nasal breathing.

In contrast, other methods such as the simple face mask, non-rebreather mask, and biphasic positive airway pressure provide oxygen directly over the mouth and nose, making them suitable for mouth breathers. The face mask covers both the mouth and nose to ensure inhalation of oxygen, the non-rebreather mask creates a seal around the mouth and nose to provide high concentrations of oxygen, and biphasic positive airway pressure supports breathing during both inhalation and exhalation. Therefore, for a mouth-breathing patient, those options would be more beneficial.