ROX–Heart Rate Index Calculator

Calculates a heart-rate-adjusted ROX index from oxygen saturation, inspired oxygen, respiratory rate and heart rate. Includes field guidance, formula provenance, interpretation and Learn More content.

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ROX–Heart Rate Index
Clinical Decision Tool

Calculates a heart-rate-adjusted ROX index from oxygen saturation, inspired oxygen, respiratory rate and heart rate.

Use a contemporaneous saturation.
Enter as a fraction, not a percentage.
Count or measure contemporaneously.
Use a contemporaneous heart rate.
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Clinical Decision Support Only

MediCalc calculators are intended to support qualified healthcare professionals and must not replace professional clinical judgement. Do not enter patient-identifiable information into Saved Progress.

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Learn More About ROX–Heart Rate Index
MedicalC Knowledge Hub

ROX–Heart Rate Index: Clinical Guide

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Calculates a heart-rate-adjusted ROX index from oxygen saturation, inspired oxygen, respiratory rate and heart rate.

Overview

Calculates a heart-rate-adjusted ROX index from oxygen saturation, inspired oxygen, respiratory rate and heart rate.

Clinical Significance

Exploratory heart-rate-adjusted ROX measure intended to contextualise high-flow nasal oxygen response. Thresholds are population- and time-point dependent.

How It Is Calculated

  • ROX–HR = [(SpO₂/FiO₂)/RR] ÷ (HR/100).

Interpretation

  • Exploratory heart-rate-adjusted ROX measure intended to contextualise high-flow nasal oxygen response. Thresholds are population- and time-point dependent.

Worked Example

Enter a clinically consistent set of values in the displayed units. MedicalC applies: ROX–HR = [(SpO₂/FiO₂)/RR] ÷ (HR/100).

Limitations

  • This tool does not establish a diagnosis or mandate treatment.
  • Published cut-offs may vary between cohorts and measurement methods.
  • Calculation precision cannot compensate for poor source data.

Clinical Pearls

  • Trend the result over time where clinically appropriate.
  • Record the source values and units alongside the calculated result.

Common Mistakes

  • Using the wrong unit.
  • Combining measurements obtained at different times.
  • Applying a research-derived threshold as a universal treatment trigger.

Frequently Asked Questions

What does this calculator provide?

Calculates a heart-rate-adjusted ROX index from oxygen saturation, inspired oxygen, respiratory rate and heart rate.

Can this result be used alone?

No. It must be interpreted with clinical context and appropriate investigations.

What equation is used?

ROX–HR = [(SpO₂/FiO₂)/RR] ÷ (HR/100).

What is the main limitation?

The result depends on valid inputs and may not be calibrated for every population or setting.

References

  1. Goh KJ et al. Early prediction of high-flow nasal cannula therapy outcomes using a modified ROX index incorporating heart rate. J Intensive Care. 2020. — Formula, physiological or validation reference.

Reviewed by: MedicalC Clinical Editorial Team
Last reviewed: July 2026

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Reviewed by: MedicalC Clinical Editorial Team Last reviewed: July 2026

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Clinical Disclaimer

MedicalC calculators and clinical tools are intended to support healthcare professionals. They do not replace clinical judgement, individual patient assessment, local guidance or specialist advice.

Results should always be interpreted in the context of the patient’s history, examination, investigations, current clinical condition and applicable professional guidance.

Reviewed by: MedicalC Clinical Editorial Team Last reviewed: July 2026
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