High-flow nasal cannula response and escalation risk
ROX Index Calculator for HFNC Monitoring
Calculate the ROX index to help estimate whether a patient on high-flow nasal cannula appears to be stabilizing or may be trending toward failure. The ROX index combines SpO₂, FiO₂, and respiratory rate into one fast bedside number.
Use this page alongside our P/F ratio and oxygenation index tool, A–a Gradient calculator, Causes of Hypoxemia, and the ABG Analyzer for a broader oxygenation and escalation picture.
Calculator inputs
Enter FiO₂ as a percentage (e.g. 50).
What the ROX index helps you do
Track HFNC response
The ROX index helps estimate whether a patient on high-flow nasal cannula appears to be stabilizing or may be failing support.
Frame escalation risk
It is most useful when combined with work of breathing, oxygen requirement, trajectory, and the overall clinical picture.
Results
How to think about the ROX index
The ROX index is a quick bedside way to combine oxygenation and respiratory effort into one number. Higher values are generally more reassuring. Lower values can suggest that a patient on HFNC is struggling and may need closer monitoring or escalation.
It should never replace clinical judgment. Work of breathing, mental status, trajectory, secretion burden, and blood gas data still matter.
How this fits into the PulmTools oxygenation cluster
- • Use ROX for HFNC response monitoring
- • Use P/F Ratio & Oxygenation Index for oxygenation severity and ARDS context
- • Use A–a Gradient to help distinguish causes of hypoxemia
- • Use ABG Analyzer to interpret the broader gas exchange picture
- • Read Causes of Hypoxemia to frame the differential