What does FiO2 stand for?

FiO2 stands for Fraction of Inspired Oxygen; it is a fraction of the amount of oxygen a patient is inhaling produced by an oxygen device such as a nasal cannula or mask. Different devices deliver different amounts of oxygen to the patient.

With a nasal cannula, it is assumed that the patient's oxygen intake increases 4 percent for every liter of oxygen that flows through the cannula.

• No extra oxygen gives a FiO2 of 0.20.
• 1 liter per minute of oxygen gives a FiO2 of 0.24.
• 2 liters per minute of oxygen gives a FiO2 of 0.28.
• 3 liters per minute of oxygen gives a FiO2 of 0.32.
• 4 liters per minute of oxygen gives a FiO2 of 0.36.
• 5 liters per minute of oxygen gives a FiO2 of 0.40.
• 6 liters per minute of oxygen gives a FiO2 of 0.44.

Using a Venturi mask, which mixes air from the room with the oxygen, provides an accurate and constant FiO2 unlike the nasal cannula. It is often used when doctors are worried about carbon dioxide retention.

• 4 liters per minute of oxygen gives a FiO2 of 0.24 to 0.28.
• 6 liters per minute of oxygen gives a FiO2 of 0.31.
• 8 liters per minute of oxygen gives a FiO2 of 0.35 to 0.40.