Oxygenation Index (OI)
Independent clinical validation: pending
Two independent clinical validators will be named here once review is complete.
How it is calculated
OI = (MAP × FiO₂ × 100) ÷ PaO₂, where MAP is mean airway pressure in cmH₂O, FiO₂ is the inspired-oxygen fraction (0.21–1.0), and PaO₂ is arterial oxygen tension in mmHg; the result is a unitless index displayed to one decimal. The explicit ×100 factor compensates for FiO₂ being entered as a fraction, so this equals the PALICC table rendering MAP × FiO₂% ÷ PaO₂ (Slaughter 2025). Bands are matched against the raw unrounded value using the PALICC-2 (2023) two-tier scheme: OI < 4 is below the invasive-ventilation oxygenation criterion, 4 ≤ OI < 16 is mild–moderate, and OI ≥ 16 is severe.
Limitations and notes
OI is the mean airway pressure times FiO₂ times 100, divided by the arterial oxygen tension (PaO₂) — higher OI means a worse oxygenation defect. It requires an arterial line (for the PaO₂) and is defined only on positive-pressure ventilation, where a mean airway pressure exists (conventional IMV or HFOV); it is undefined for spontaneous breathing, nasal cannula, or standard non-invasive masks. Interpretation bands here are the PALICC-2 (2023) two-tier scheme for invasively ventilated children: the oxygenation criterion is OI ≥ 4 and severe is OI ≥ 16. PALICC 2015 used a three-tier scheme — mild (4 ≤ OI < 8), moderate (8 ≤ OI < 16), severe (OI ≥ 16) — and PALICC-2 collapsed the two lower tiers into mild–moderate while leaving the OI severe cutoff (≥ 16) unchanged; this implementation applies the PALICC-2 (2023) edition. The ×100 factor exactly compensates for FiO₂ being a fraction; the PALICC table rendering MAP × FiO₂% / PaO₂ gives the same number — applying both or neither is a 100× error. [NEEDS SOURCE]: the map_awp (5–50 cmH₂O) and pao2 (10–700 mmHg) numeric limits are engineering input-validation bounds, not values from a specific publication. OI classifies a physiologic defect; it is not an individual-patient outcome prediction.
Accepted input ranges
- Mean airway pressure (MAP) — 5–50 cmH2O
- Fraction of inspired oxygen (FiO₂) — 0.21–1 fraction
- Arterial oxygen tension (PaO₂) — 10–700 mmHg
References
- Emeriaud G, López-Fernández YM, Iyer NP, et al; Second Pediatric Acute Lung Injury Consensus Conference (PALICC-2) of the 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;24(2):143–168.PMID 36661420DOI 10.1097/PCC.0000000000003147
- Pediatric Acute Lung Injury Consensus Conference Group. Pediatric acute respiratory distress syndrome: consensus recommendations from the Pediatric Acute Lung Injury Consensus Conference. Pediatr Crit Care Med. 2015;16(5):428–439.PMID 25647235DOI 10.1097/PCC.0000000000000350
- Khemani RG, Smith LS, Zimmerman JJ, Erickson S; Pediatric Acute Lung Injury Consensus Conference Group. Pediatric acute respiratory distress syndrome: definition, incidence, and epidemiology: proceedings from the Pediatric Acute Lung Injury Consensus Conference. Pediatr Crit Care Med. 2015;16(5 Suppl 1):S23–S40.PMID 26035358DOI 10.1097/PCC.0000000000000432
- Slaughter J, Sites J, Ballard H, Bauer J, Schadler A, Severyn N. Comparison of the oxygenation index and the oxygen saturation index as clinical indicators for neonatal ECMO. Front Pediatr. 2025;13:1586985.PMID 40630719DOI 10.3389/fped.2025.1586985
Version and changelog
v1.0.0 · Respiratory
- 2026-07-25 v1.0.0 — Initial release: OI split out from the former OI/OSI score, with PALICC-2 (2023) two-tier severity bands.