Severity of Ventilation Impairment (PF ratio)
What is the PF ratio?
- PaO2/FiO2 is the ratio of arterial oxygen partial pressure to fractional inspired oxygen – aka the Carrico or Horrowitz index and the PF ratio.
- It is a widely used clinical indicator of hypoxaemia, at sea level, it is normally > 500mmHg.
- Mild – PF ratio 200-300mmHg
- Moderate – PF ratio 100-200mmHg
- Severe – PF ratio <100mmHg