Oxygenation Index
All calculations should be independently verified prior to clinical use. These calculators are intended to supplement, not replace, clinical judgment.
Calculate the oxygenation index (OI) from FiO2, mean airway pressure, and PaO2. OI is used to assess severity of respiratory failure and ECMO candidacy in pediatric patients.
The oxygenation index combines the inspired oxygen requirement, the degree of ventilatory support, and the resulting arterial oxygenation into a single measure of respiratory failure severity:
FiO2 is entered as a percentage (21–100); the formula treats it as such without further conversion. MAP is mean airway pressure from the ventilator in cmH2O. PaO2 is the arterial partial pressure of oxygen in torr from a blood gas drawn during stable ventilation.
Unlike the P/F ratio (PaO2/FiO2), OI incorporates mean airway pressure and therefore accounts for the ventilatory cost of achieving a given level of oxygenation. A higher OI indicates more severe disease.
Clinical severity is based on the oxygen index ≥ 4 hr after the initial diagnosis of PARDS. and ECMO threshold reference:
| OI | Interpretation |
|---|---|
| Normal range | |
| Mild / moderate respiratory failure | |
| Severe respiratory failure | |
| Critical respiratory failure; ECMO candidacy threshold in many pediatric centres (Ortiz et al. 1987) |
The OI > 40 threshold for ECMO candidacy was established in the paediatric literature by Ortiz et al. (1987) and remains in common use, though individual centre thresholds and patient factors should always guide clinical decision-making.
References
- Ortiz RM, Cilley RE, Bartlett RH. Extracorporeal membrane oxygenation in pediatric respiratory failure. Pediatr Clin North Am. 1987;34(1):39–46.
- Trachsel D, McCrindle BW, Nakagawa S, Bohn D. Oxygenation index predicts outcome in children with acute hypoxemic respiratory failure. Am J Respir Crit Care Med. 2005;172(2):206–211.
- Flori HR, Glidden DV, Rutherford GW, Matthay MA. Pediatric acute lung injury: prospective evaluation of risk factors associated with mortality. Am J Respir Crit Care Med. 2005;171(9):995–1001.
- Emeriaud G, López-Fernández YM, Iyer NP, et al; Second Pediatric Acute Lung Injury Consensus Conference (PALICC-2) Group on behalf of the Pediatric Acute Lung Injury and Sepsis Investigators (PALISI) Network. Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2). Pediatr Crit Care Med. 2023 Feb 1;24(2):143-168.