A patient is on 6 L/min of oxygen via nasal cannula. What is their FiO2?

A patient is on 6 L/min of oxygen via nasal cannula. What is their FiO2?

• A. 0.28
• B. 0.44
• C. 0.40
• D. 0.50

Answer: (B)

FiO2 is the fraction of inspired oxygen—the amount of oxygen the patient actually inhales. For a nasal cannula, a common rule of thumb is that FiO2 rises by about 4 percentage points for each liter per minute above room air (which is 21% O2). So at 6 L/min, you’d estimate 21% + (6 × 4%) = about 45% O2. In practice, the delivered FiO2 is often cited as around 0.44 for 6 L/min because real-world factors (mouth breathing, tubing, fit) cause slight variations and rounding. Therefore, the closest standard estimate is 0.44, since it best matches typical clinical values for this flow. The other options are outside the common range for a nasal cannula at this flow.

FiO2 is the fraction of inspired oxygen—the amount of oxygen the patient actually inhales. For a nasal cannula, a common rule of thumb is that FiO2 rises by about 4 percentage points for each liter per minute above room air (which is 21% O2). So at 6 L/min, you’d estimate 21% + (6 × 4%) = about 45% O2. In practice, the delivered FiO2 is often cited as around 0.44 for 6 L/min because real-world factors (mouth breathing, tubing, fit) cause slight variations and rounding. Therefore, the closest standard estimate is 0.44, since it best matches typical clinical values for this flow. The other options are outside the common range for a nasal cannula at this flow.