PF Ratio Calculator
Calculate PaO₂/FiO₂ ratio for ARDS assessment and respiratory evaluation
Blood Gas Parameters
Normal range: 75-100 mmHg (10-13.3 kPa) at sea level
Room air: 21% | Supplemental O₂: 24-100%
Quick FiO₂ Presets
PF Ratio Results
⚠️ Medical Disclaimer: This calculator is for educational purposes only. PF ratio results should be interpreted by qualified healthcare professionals in conjunction with clinical assessment. Always consult your doctor for medical decisions and ARDS management.
PF Ratio Classification
SOFA Respiratory Score
Quick Reference
PaO₂ from arterial blood gas
Room air FiO₂ = 21%
Used in ARDS diagnosis
Component of SOFA score
Understanding PF Ratio
What is PF Ratio?
The PF ratio (PaO₂/FiO₂ ratio) is the ratio of arterial oxygen partial pressure to fractional inspired oxygen. It's a key indicator of oxygenation efficiency and is used to assess the severity of acute respiratory distress syndrome (ARDS).
Components Explained
- •PaO₂: Partial pressure of oxygen in arterial blood
- •FiO₂: Fraction of inspired oxygen (21% = room air)
- •Ratio: Measures lung's ability to oxygenate blood
Clinical Applications
- ARDS Diagnosis: Essential criterion for ARDS classification
- SOFA Score: Respiratory component of organ failure assessment
- Ventilator Management: Guides oxygen therapy decisions
- Prognosis: Helps predict patient outcomes
- Research: Standardized measure for clinical studies
Normal Values: Healthy individuals breathing room air typically have PF ratios > 400 mmHg. Values below 300 mmHg indicate significant lung injury.
ARDS Classification (Berlin Definition)
| Severity | PF Ratio (mmHg) | Mortality Risk | Management |
|---|---|---|---|
| Mild ARDS | 200-300 | ~27% | Standard ventilation |
| Moderate ARDS | 100-200 | ~32% | Lung-protective ventilation |
| Severe ARDS | <100 | ~45% | Advanced therapies (ECMO, prone positioning) |