In a nasal cannula, how far does the tubing typically extend into the nostrils?

• A. About 5 centimeters
• B. Beyond the nostrils into the nasal cavity
• C. About 1 centimeter
• D. About 10 centimeters

Answer: (C)

The idea is to place the nasal cannula prongs just inside the nostrils, resting in the nasal vestibule. This shallow position delivers oxygen effectively to the nasal mucosa while minimizing irritation or injury to the nasal tissues. If the prongs go too deep, they irritate the mucosa, can cause dryness or nosebleeds, and are uncomfortable. If they sit too shallow, gas can leak around the nostrils and FiO2 delivery becomes less reliable. So the best fit is a light, comfortable placement that stays at the entrance of the nostrils rather than extending deep into the nasal cavity.