Low-flow oxygen is delivered at 1 to 6 L/min and up to 24-44% O2. Which device is commonly used for this delivery?

• A. Nonrebreather Mask
• B. Nasal Cannula
• C. Bag Valve Mask
• D. Continuous Positive Airway Pressure

Answer: (B)

Low-flow oxygen therapy delivers a modest amount of oxygen that mixes with ambient air, so the FiO2 you get depends on the flow rate and how the patient is breathing. At flow rates of about 1–6 L/min, the device that is most commonly used is the nasal cannula because it sits in the nostrils and reliably delivers oxygen within that lower range, yielding roughly 24–44% O2 depending on flow and whether the patient breathes through the nose or mouth. It’s comfortable for ongoing use, allows talking and eating, and is well suited for routine, non-emergency support.

Other devices are better suited for higher oxygen needs or different situations: a nonrebreather mask can provide much higher FiO2 but requires higher flow and is used for patients needing rapid, substantial oxygen delivery; a bag-valve mask is primarily for active ventilation rather than steady supplemental oxygen; CPAP provides continuous airway pressure and can deliver oxygen as part of ventilatory support, not simply the low-flow, ambient-mixing delivery described here.