Oxygenation Index
Oxygenation index integrates FiO₂, mean airway pressure, and PaO₂ to quantify oxygenation efficiency. Higher OI indicates more severe hypoxemia.
Results
Oxygenation index
14.4
Mild impairment
Clinical interpretation:
- Use OI to track ARDS progression and response to ventilation strategies.
- OI ≥ 25 commonly used as threshold for considering advanced therapies (e.g., prone positioning, ECMO consult).
How to Use This Calculator
Gather ventilator data
Record current FiO₂ (%) and mean airway pressure from the ventilator or MAP calculator.
Use latest arterial blood gas
Enter PaO₂ (mmHg) from ABG obtained while on the specified ventilator settings.
Trend OI over time
Monitor OI changes after adjusting ventilator settings, proning, or introducing rescue therapies.
Formula
OI = (FiO₂ × MAP × 100) ÷ PaO₂.
FiO₂ expressed as decimal (e.g., 0.6). Multiply by 100 to convert to percentage-based formula.
Frequently Asked Questions
How often should I calculate OI?
In severe ARDS, reassess with each ABG or major ventilator change (e.g., every 4–6 hours).
Is OI better than PaO₂/FiO₂ ratio?
OI incorporates ventilator pressure (MAP) and may correlate more closely with lung stress than PaO₂/FiO₂ alone.
What about pediatric thresholds?
Similar cutoffs apply; OI ≥ 40 often triggers ECMO consideration in pediatric ARDS.
Does higher MAP always increase OI?
Yes mathematically. However, increased MAP may also improve PaO₂, potentially stabilizing OI; interpret dynamically.
Can I use kPa for PaO₂?
Convert kPa to mmHg (1 kPa ≈ 7.5 mmHg) before entering to maintain consistent units.