Which variables are used in calculating the oxygen index (OI)?

Which variables are used in calculating the oxygen index (OI)?

• A. FiO2 and PaO2 only
• B. Paw, FiO2, PaO2
• C. PaO2, PaCO2
• D. Paw, FiO2, PaCO2

Answer: (B)

Oxygen index measures how effectively oxygenation is achieved given the current ventilator support. It combines the level of ventilatory support (mean airway pressure), the fraction of inspired oxygen (FiO2), and the arterial oxygen tension (PaO2). The formula is Paw × FiO2 × 100 divided by PaO2. Because of this, the correct variables are mean airway pressure, FiO2, and PaO2. PaCO2 isn’t included because the index focuses on oxygenation under the existing support, not on ventilation or CO2 removal. A higher OI indicates worse oxygenation for the given support level.

Oxygen index measures how effectively oxygenation is achieved given the current ventilator support. It combines the level of ventilatory support (mean airway pressure), the fraction of inspired oxygen (FiO2), and the arterial oxygen tension (PaO2). The formula is Paw × FiO2 × 100 divided by PaO2. Because of this, the correct variables are mean airway pressure, FiO2, and PaO2. PaCO2 isn’t included because the index focuses on oxygenation under the existing support, not on ventilation or CO2 removal. A higher OI indicates worse oxygenation for the given support level.