FiO2 refers to which of the following?

FiO2 refers to which of the following?

• A. Fraction of inspired air
• B. Fraction of expired air
• C. Partial pressure of oxygen in arterial blood
• D. Total inspired air volume

Answer: (A)

FiO2 is the fraction of inspired oxygen in the gas the patient breathes. It’s a dimensionless ratio (often shown as 0.21 for room air or 21%), representing how much of the inhaled gas is oxygen. This is about the oxygen concentration in the inspired mixture, not the air the patient exhales, not the partial pressure of oxygen in arterial blood (that’s PaO2), and not the total amount or volume of air the patient inspires. In practice, FiO2 increases with supplemental oxygen delivery devices, allowing clinicians to adjust the oxygen level the patient receives.

FiO2 is the fraction of inspired oxygen in the gas the patient breathes. It’s a dimensionless ratio (often shown as 0.21 for room air or 21%), representing how much of the inhaled gas is oxygen. This is about the oxygen concentration in the inspired mixture, not the air the patient exhales, not the partial pressure of oxygen in arterial blood (that’s PaO2), and not the total amount or volume of air the patient inspires. In practice, FiO2 increases with supplemental oxygen delivery devices, allowing clinicians to adjust the oxygen level the patient receives.