# ROX index ROX index Status: LIVE Price: $0.005 USDC `GET /api/calc/rox` HTML: https://magentlab.com/docs/rox Markdown: https://magentlab.com/docs/rox.md Not a medical device. Not a diagnosis, dose, or listing recommendation. ## What it computes Compute the ROX index as pulse-oximetry SpO2 percent divided by inspired oxygen fraction, then divided by respiratory rate. ## When to use When an agent needs (SpO2/FiO2)/respiratory_rate and must not invent HFNC success or failure, a PaO2/FiO2 ratio, or RSBI. ## When not to use - Not a diagnosis and not a ventilation order. - Magent does not apply the 4.88 12-hour HFNC success/failure cutoff; that threshold is time-contextual in Roca 2016. - This is not the PaO2/FiO2 (P/F) ratio. - This is not RSBI (respiratory rate divided by tidal volume). ## Formula ``` rox = (spo2_percent / fio2) / respiratory_rate ``` ## Citation [Predicting success of high-flow nasal cannula in pneumonia patients with hypoxemic respiratory failure: The utility of the ROX index](https://doi.org/10.1016/j.jcrc.2016.05.022) Roca O, Messika J, Caralt B, García-de-Acilu M, Sztrymf B, Ricard JD, Masclans JR J Crit Care. 2016;35:200-205 DOI: [10.1016/j.jcrc.2016.05.022](https://doi.org/10.1016/j.jcrc.2016.05.022) ## Worked example ### SpO2 95, FiO2 0.21, RR 20 Given: `fio2=0.21, respiratory_rate=20, spo2_percent=95` 1. rox = (95 / 0.21) / 20 = 22.619… → 22.62 ### SpO2 95, FiO2 1.0, RR 20 Given: `fio2=1.0, respiratory_rate=20, spo2_percent=95` 1. rox = (95 / 1.0) / 20 = 4.75 ## Also searched as - ROX index - Roca ROX - SpO2/FiO2 over respiratory rate - HFNC ROX index - respiratory rate oxygenation - SpO2 FiO2 RR index - ROX HFNC ## Parameters - `spo2_percent` (number, required): Pulse-oximetry SpO2 as a percent (50-100). - `fio2` (number, required): Inspired oxygen as a fraction (0.21-1.0), not a percent. Required. - `respiratory_rate` (integer, required): Respiratory rate in breaths/min (integer 4-80). ## Bulk (POST) POST the same path with a JSON items array. Price is n times the GET unit. Invalid items return HTTP 400 before settlement. Method: `POST /api/calc/rox` Max items: 25 Price: unit_amount * n (unit 5000 atomic) Status: PREVIEW - 1 to 25 items. Each item uses the same keys as the GET query parameters. - The first invalid item fails the whole request (index in the 400 JSON). You are not charged. - HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row. - Catalog misses (empty matches, found=false) stay paid 200s inside that slot. - x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items. Example request: ```json { "items": [ { "fio2": "0.21", "respiratory_rate": "20", "spo2_percent": "95" }, { "fio2": "0.21", "respiratory_rate": "20", "spo2_percent": "95" } ] } ``` Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/rox Example 200: ```json { "count": 2, "path": "/api/calc/rox", "items": [ { "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.", "citation": { "authors": "Roca O, Messika J, Caralt B, García-de-Acilu M, Sztrymf B, Ricard JD, Masclans JR", "doi": "10.1016/j.jcrc.2016.05.022", "id": "roca-2016", "source": "J Crit Care. 2016;35:200-205", "title": "Predicting success of high-flow nasal cannula in pneumonia patients with hypoxemic respiratory failure: The utility of the ROX index" }, "formula": "rox", "formula_expression": "rox = (spo2_percent / fio2) / respiratory_rate", "fio2": 0.21, "respiratory_rate": 20, "rox": 22.62, "spo2_percent": 95.0 }, { "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.", "citation": { "authors": "Roca O, Messika J, Caralt B, García-de-Acilu M, Sztrymf B, Ricard JD, Masclans JR", "doi": "10.1016/j.jcrc.2016.05.022", "id": "roca-2016", "source": "J Crit Care. 2016;35:200-205", "title": "Predicting success of high-flow nasal cannula in pneumonia patients with hypoxemic respiratory failure: The utility of the ROX index" }, "formula": "rox", "formula_expression": "rox = (spo2_percent / fio2) / respiratory_rate", "fio2": 0.21, "respiratory_rate": 20, "rox": 22.62, "spo2_percent": 95.0 } ] } ``` ## Response fields - `formula` (string): rox - `formula_expression` (string): Exact expression used - `spo2_percent` (number): SpO2 percent used - `fio2` (number): Inspired oxygen fraction used - `respiratory_rate` (integer): Respiratory rate used, breaths/min - `rox` (number): (SpO2 percent / FiO2) / respiratory rate, 2 decimals - `citation` (object): Roca 2016 citation - `disclaimer` (string): Not-a-device notice ## Example JSON Frozen fixture. Not a live lookup. ```json { "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.", "citation": { "authors": "Roca O, Messika J, Caralt B, García-de-Acilu M, Sztrymf B, Ricard JD, Masclans JR", "doi": "10.1016/j.jcrc.2016.05.022", "id": "roca-2016", "source": "J Crit Care. 2016;35:200-205", "title": "Predicting success of high-flow nasal cannula in pneumonia patients with hypoxemic respiratory failure: The utility of the ROX index" }, "formula": "rox", "formula_expression": "rox = (spo2_percent / fio2) / respiratory_rate", "fio2": 0.21, "respiratory_rate": 20, "rox": 22.62, "spo2_percent": 95.0 } ``` ## Errors - HTTP 400 `invalid_spo2`: spo2_percent must be a number from 50 to 100. Returned before settlement; you are not charged. - HTTP 400 `invalid_fio2`: fio2 must be a fraction from 0.21 to 1.0. Returned before settlement; you are not charged. - HTTP 400 `invalid_respiratory_rate`: respiratory_rate must be an integer from 4 to 80. Returned before settlement; you are not charged. - HTTP 400 `invalid_items`: POST body must be a JSON object with only an items array Returned before settlement; you are not charged. - HTTP 400 `invalid_item_count`: items must be an array of 1 to 25 objects Returned before settlement; you are not charged. - HTTP 400 `invalid_item`: each items entry must be a JSON object Returned before settlement; you are not charged. Shared HTTP 402 and 503: https://magentlab.com/docs/payments ## Related tools - [PaO2/FiO2 ratio](https://magentlab.com/docs/pf-ratio) — Compute the PaO2/FiO2 ratio as arterial PO2 in mm Hg divided by inspired oxygen fraction. - [Rapid shallow breathing index](https://magentlab.com/docs/rsbi) — Compute the Yang and Tobin rapid shallow breathing index as respiratory rate in breaths/min divided by tidal volume in liters. ## Payment Required query parameters must be present and valid. Invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s. - GET the tool with Accept: application/json (do not send Accept: text/html unless you want the human paywall). - HTTP 402 means you have not paid. Decode the base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote. - Sign EIP-3009 (scheme exact, assetTransferMethod eip3009) with validBefore = now + accepts[0].maxTimeoutSeconds (600 seconds). That window starts when you sign and must cover wallet confirmation plus CDP verify and settle. Magent retries transient facilitator 429/5xx before answering. Do not send upto or batch-settlement payloads; magent does not offer those schemes. - Retry the same URL with PAYMENT-SIGNATURE (base64 JSON echoing accepted, payload, and extensions when present). - Success is HTTP 200 JSON plus PAYMENT-RESPONSE. Settlement happens before the tool runs. HTTP 503 settlement_uncertain or settle_failed: retry the same PAYMENT-SIGNATURE. Mint a new nonce only after a new HTTP 402. - offered `exact` on eip155:8453: Fixed-price USDC on Base. The buyer authorizes the advertised amount (EIP-3009). magent settles before the tool runs (paymentFlow upfront). extra.assetTransferMethod=eip3009 extra.paymentFlow=upfront. - not offered `upto`: Not offered. Usage-based: buyer authorizes a ceiling, seller settles the actual amount after work. Reserved for a future metered tool. Not for current calculators or code search. - not offered `batch-settlement`: Not offered. Payment-channel vouchers claimed later in batches. Not the same as POST {items} bulk (that is still exact). Same-path POST {items} is still scheme exact: one EIP-3009 authorization for n times the GET unit. That is not x402 batch-settlement (payment channels / vouchers). Shared HTTP 402 and 503 table: https://magentlab.com/docs/payments Stdio MCP (one process per host): https://magentlab.com/docs/mcp ## Guarantees - Invalid query parameters return HTTP 400 before settlement. You are not charged. - Settlement finishes before the tool executes (paymentFlow upfront). Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE. - HTTP 402 is unpaid only. Do not sign a second authorization because of a 503. - Execution is timeout-bounded and concurrency-capped. - Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.