The nasal cannula is MOST appropriately used in the prehospital setting:

• A. If long-term supplemental oxygen administration is required
• B. When the patient breathes primarily through his or her mouth
• C. When the patient cannot tolerate a nonrebreathing mask
• D. If the patient's nasopharynx is obstructed by secretions

Answer: (C)

The main idea is that nasal cannula delivers oxygen at low to moderate flow with a comfortable, nonrestrictive interface. It’s ideal when a patient needs supplemental oxygen but doesn’t require a high concentration or a tight seal around the mouth and nose.

In this scenario, the nasal cannula is the best choice when the patient cannot tolerate a nonrebreathing mask. A nonrebreathing mask can deliver higher FiO2 quickly, but its tight fit and feel can cause anxiety, claustrophobia, or discomfort for some patients. When that intolerance is present, you still want to provide oxygen, and a nasal cannula offers a tolerable, continuous delivery that maintains oxygenation during transport or evaluation.

Nasal cannula is less ideal if a very high FiO2 is needed, if there is significant nasal obstruction, or if the patient predominantly breathes through the mouth and cannot effectively draw oxygen through the nose. Those factors explain why other situations are not as suitable as this one.