ARDS Severity Index (PaO₂/FiO₂): Explanation and Clinical Context The ARDS Severity Index uses the ratio of arterial oxygen partial pressure (PaO₂) to fractional inspired oxygen (FiO₂) to stratify patients with acute respiratory distress syndrome according to severity.
A PaO₂/FiO₂ ratio >300 mmHg indicates no ARDS; 201-300 mmHg indicates mild ARDS; 101-200 mmHg indicates moderate ARDS; < 100 mmHg indicates severe ARDS.
This index helps clinicians in risk stratification, guiding mechanical ventilation strategies, and prognostication.
Reference:
Ranieri VM, Rubenfeld GD, Thompson BT, et al. Acute respiratory distress syndrome: The Berlin Definition. JAMA. 2012;307(23):2526-2533. doi:10.1001/jama.2012.5669