🫁 SpO₂/FiO₂ (S/F) Ratio
UseWhen to use: ARDS / hypoxemic respiratory failure triage without arterial blood gas.
StrataTeaching maps ≈235↔P/F 200 and ≈315↔P/F 300; prefer ABG when possible.
LimitsWhen not to use: SpO₂ >97% (flat portion of dissociation curve). · Pitfall: entering FiO₂ as % without conversion when >1. · Not a solo Berlin definition.
SourceRice TW et al. S/F vs P/F
This-shift next steps
After scoring: open the scene pack, peer scores, and the matching pathway. Local reference — no HIS write.
Paste the link in Slack, Teams, X, or LinkedIn — the preview image comes from this page’s Open Graph card.
Methodology · worked example, guidelines & full notes
SpO₂÷FiO₂.
When to use
When to use: ARDS / hypoxemic respiratory failure triage without arterial blood gas.
How it works
S/F = SpO₂ / FiO₂ (fraction).
Key points
- SpO₂÷FiO₂.
- ≈235 / ≈315 cues.
- Next: P/F if ABG.
References
- Rice TW et al. S/F vs P/F
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| SpO₂ | 92 % |
|---|---|
| FiO₂ | 0.40 fraction (0–1) or % |
→S/F230
- FiO₂ used：0.40
- Cue：<235 — roughly aligns with P/F <200 (moderate–severe ARDS cue)
Verification & sources · governance
FAQ
Frequently asked questions
- Does SpO₂/FiO₂ (S/F) Ratio upload patient data? Where is it calculated?
- Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.
- How is SpO₂/FiO₂ (S/F) Ratio calculated in practice? Can you show a worked example?
- Inputs: SpO₂ 92 %, FiO₂ 0.40 fraction (0–1) or % → Result: S/F 230（FiO₂ used: 0.40, Cue: <235 — roughly aligns with P/F <200 (moderate–severe ARDS cue)）