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ROX Index Calculator (SpO2/FiO2/RR)
x402
ROX Index Calculator (SpO2/FiO2/RR) is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).
Calculates the ROX index as (SpO2% / FiO2) / respiratory rate per the Roca 2016 definition, returning the result rounded to two decimals.
Price / call$0.005
Success—
StatusUnknown
How this service works
ROX index as (SpO2 percent / FiO2) / respiratory rate in breaths/min (Roca 2016). Returns the index rounded to two decimals. Not a ventilation order. This is not the PaO2/FiO2 (P/F) ratio and not RSBI (respiratory rate / tidal volume).
Output
A single numeric ROX index value rounded to two decimal places, computed as (SpO2_percent / FiO2) / respiratory_rate. No interpretation, diagnosis, or ventilation order is included — the index alone is returned.
Example use cases
HFNC failure risk screening in ICU
“My patient is on high-flow nasal cannula with SpO2 of 92%, FiO2 of 0.6, and breathing at 35 breaths per minute — what's their ROX index?”
Serial ROX monitoring over a shift
“Track whether this patient is improving: their SpO2 is now 97%, FiO2 has been weaned to 0.35, and respiratory rate is 22 — compute the current ROX index.”
Respiratory triage in ED for COVID patient
“For a COVID patient in the ED with SpO2 95% on 40% oxygen (FiO2 0.40) and respiratory rate of 28, calculate their ROX index so I can assess intubation risk.”
Technical details
Endpoint
GEThttps://api.magentlab.com/api/calc/roxWhen to prefer
Use this endpoint when you need the Roca 2016 ROX index specifically — (SpO2/FiO2)/RR — distinct from the PaO2/FiO2 (P/F) ratio or RSBI (RR/tidal volume). Ideal for assessing HFNC success likelihood in clinical decision support agents or ICU monitoring workflows. Prefer this over manual calculation when integrating ROX scoring into automated pipelines.
Side effects
- Missing required parameter (spo2_percent, fio2, or respiratory_rate) returns a validation error
- FiO2 provided as percent (e.g. 40) instead of fraction (0.40) will produce a nonsensical result — no server-side correction
- Respiratory rate of 0 causes division-by-zero error
- SpO2 or FiO2 outside valid physiological range may be rejected or return unexpected output
- Payment not included or insufficient (x402) results in 402 Payment Required response
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"path": "/api/calc/rox",
"count": 2,
"items": [
{
"rox": 22.62,
"fio2": 0.21,
"formula": "rox",
"citation": {
"id": "roca-2016",
"doi": "10.1016/j.jcrc.2016.05.022",
"title": "Predicting success of high-flow nasal cannula in pneumonia patients with hypoxemic respiratory failure: The utility of the ROX index",
"source": "J Crit Care. 2016;35:200-205",
"authors": "Roca O, Messika J, Caralt B, García-de-Acilu M, Sztrymf B, Ricard JD, Masclans JR"
},
"disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
"spo2_percent": 95,
"respiratory_rate": 20,
"formula_expression": "rox = (spo2_percent / fio2) / respiratory_rate"
},
{
"rox": 22.62,
"fio2": 0.21,
"formula": "rox",
"citation": {
"id": "roca-2016",
"doi": "10.1016/j.jcrc.2016.05.022",
"title": "Predicting success of high-flow nasal cannula in pneumonia patients with hypoxemic respiratory failure: The utility of the ROX index",
"source": "J Crit Care. 2016;35:200-205",
"authors": "Roca O, Messika J, Caralt B, García-de-Acilu M, Sztrymf B, Ricard JD, Masclans JR"
},
"disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
"spo2_percent": 95,
"respiratory_rate": 20,
"formula_expression": "rox = (spo2_percent / fio2) / respiratory_rate"
}
]
}
}Tags
x402
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