🫁 ROX Index (HFNC Outcome)
Predict high-flow nasal cannula success with the ROX index in acute hypoxaemic respiratory failure.
Clinical takeaway
Assess at ~2, 6 and 12 hours of HFNC.
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When to use
Monitor response to HFNC and flag impending failure.
How it works
ROX = (SpO₂% / FiO₂) / respiratory rate. ≥ 4.88 predicts success; < 3.85 suggests failure.
Key points
- Assess at ~2, 6 and 12 hours of HFNC.
- Persistently low values warrant considering intubation.
- Combines oxygenation and respiratory drive in one number.
References
Decision support for licensed clinicians only; not a substitute for clinical judgement, diagnosis or local protocols.
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 | 94 % |
|---|---|
| FiO₂ | 0.5 fraction |
| Respiratory rate | 24 /min |
→ROX index7.83
- Interpretation：≥ 4.88 — lower risk of HFNC failure.
- Formula：(SpO₂% / FiO₂) / respiratory rate
Frequently asked questions
- What is ROX Index (HFNC Outcome)?
- Predict high-flow nasal cannula success with the ROX index in acute hypoxaemic respiratory failure.
- How is ROX Index (HFNC Outcome) calculated? What is the core formula?
- ROX = (SpO₂% / FiO₂) / respiratory rate. ≥ 4.88 predicts success; < 3.85 suggests failure.
- When is ROX Index (HFNC Outcome) used?
- Monitor response to HFNC and flag impending failure.
- What are the key clinical points for ROX Index (HFNC Outcome)?
- Assess at ~2, 6 and 12 hours of HFNC. Persistently low values warrant considering intubation. Combines oxygenation and respiratory drive in one number.
- What are the limits and cautions when using ROX Index (HFNC Outcome)?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- How is ROX Index (HFNC Outcome) calculated in practice? Can you show a worked example?
- Inputs: SpO₂ 94 %, FiO₂ 0.5 fraction, Respiratory rate 24 /min → Result: ROX index 7.83（Interpretation: ≥ 4.88 — lower risk of HFNC failure., Formula: (SpO₂% / FiO₂) / respiratory rate）