# Altitude-adjusted PERC Altitude-adjusted PERC Status: LIVE Price: $0.005 USDC `GET /api/calc/perc_altitude` HTML: https://magentlab.com/docs/perc-altitude Markdown: https://magentlab.com/docs/perc-altitude.md Not a medical device. Not a diagnosis, dose, or listing recommendation. ## What it computes Apply the Madsen 2019 altitude-adjusted eight-factor pulmonary embolism rule-out criteria (hypoxia as O2 sat <90% at ~4980 ft) and return whether all eight are met (PERC-negative). ## When to use When an agent already has a low pretest probability of PE, as in Kline, and the encounter is at altitude as studied by Madsen (chest pain and/or SOB at ~4980 ft), and needs a published altitude-adjusted PERC-negative result from caller-assigned findings. ## When not to use - Not a medical device. - Not a PE diagnosis and not sea-level PERC (that is perc). Not a D-dimer protocol. - Only for patients who already have a low pretest probability of pulmonary embolism, as in Kline. Madsen studied chest pain and/or SOB at altitude. magent does not assign pretest probability. - The caller assigns age, pulse, SaO2, and the five clinical flags. magent does not measure vitals or examine the patient. ## Formula ``` PERC-negative iff age < 50 and pulse < 100 bpm and SaO2 ≥ 90% and no unilateral leg swelling and no hemoptysis and no recent trauma or surgery and no prior PE or DVT and no hormone use ``` ## Citation [Impact of altitude-adjusted hypoxia on the Pulmonary Embolism Rule-out Criteria.](https://doi.org/10.1016/j.ajem.2018.05.050) Madsen T, Jedick R, Teeples T, Carlson M, Steenblik J Am J Emerg Med. 2019;37(2):281-285 (Epub 2018 May 24) DOI: [10.1016/j.ajem.2018.05.050](https://doi.org/10.1016/j.ajem.2018.05.050) ## Worked example ### All eight criteria met at SaO2 90 Given: `age=40, estrogen_use=false, heart_rate_bpm=80, hemoptysis=false, prior_vte=false, recent_surgery_or_trauma=false, spo2_percent=90, unilateral_leg_swelling=false` 1. Age 40 < 50; pulse 80 < 100; SaO2 90 ≥ 90 (meets altitude-adjusted hypoxia; would fail sea-level PERC >94) 2. Five harmful findings absent 3. PERC-negative ### Age 50 fails the age criterion Given: `age=50, estrogen_use=false, heart_rate_bpm=80, hemoptysis=false, prior_vte=false, recent_surgery_or_trauma=false, spo2_percent=90, unilateral_leg_swelling=false` 1. Age 50 is not < 50 2. PERC-negative is false ## Also searched as - altitude-adjusted PERC - Madsen PERC - PERC altitude - altitude PERC rule - hypoxia-adjusted PERC - PERC 4980 ft - altitude-adjusted pulmonary embolism rule-out ## Parameters - `age` (integer, required): Age in years (18-120). Criterion met when age < 50; 50 does not meet. - `heart_rate_bpm` (integer, required): Pulse in beats per minute (integer 30-220). Criterion met when pulse < 100; 100 does not meet. - `spo2_percent` (number, required): Oxygen saturation percent (50-100). Criterion met when SaO2 ≥ 90; 89.9 does not meet. Madsen 2019 altitude adjustment, not sea-level PERC >94. - `unilateral_leg_swelling` (boolean, required): Unilateral leg swelling. true or false as assigned by the caller. Criterion met when false. - `hemoptysis` (boolean, required): Hemoptysis. true or false as assigned by the caller. Criterion met when false. - `recent_surgery_or_trauma` (boolean, required): Recent trauma or surgery. true or false as assigned by the caller. Criterion met when false. - `prior_vte` (boolean, required): Prior PE or DVT. true or false as assigned by the caller. Criterion met when false. - `estrogen_use` (boolean, required): Hormone or exogenous estrogen use. true or false as assigned by the caller. Criterion met when false. ## Bulk (POST) POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement. Method: `POST /api/calc/perc_altitude` Max items: 25 Price: unit_amount + extra_item_amount * (n - 1) (unit 5000 atomic, extra 2000 atomic) Status: PREVIEW - 1 to 25 items. Each item uses the same keys as the GET query parameters. - POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows. - 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": [ { "age": "40", "estrogen_use": "false", "heart_rate_bpm": "80", "hemoptysis": "false", "prior_vte": "false", "recent_surgery_or_trauma": "false", "spo2_percent": "90", "unilateral_leg_swelling": "false" }, { "age": "40", "estrogen_use": "false", "heart_rate_bpm": "80", "hemoptysis": "false", "prior_vte": "false", "recent_surgery_or_trauma": "false", "spo2_percent": "90", "unilateral_leg_swelling": "false" } ] } ``` Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/perc-altitude Example 200: ```json { "count": 2, "path": "/api/calc/perc_altitude", "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": "Madsen T, Jedick R, Teeples T, Carlson M, Steenblik J", "doi": "10.1016/j.ajem.2018.05.050", "id": "madsen-2019", "pmid": "29848460", "source": "Am J Emerg Med. 2019;37(2):281-285 (Epub 2018 May 24)", "title": "Impact of altitude-adjusted hypoxia on the Pulmonary Embolism Rule-out Criteria." }, "formula": "perc_altitude", "formula_expression": "PERC-negative iff age < 50 and pulse < 100 bpm and SaO2 ≥ 90% and no unilateral leg swelling and no hemoptysis and no recent trauma or surgery and no prior PE or DVT and no hormone use", "criteria": [ { "value": 40, "factor": "age_lt_50", "met": true }, { "value": 80, "factor": "pulse_lt_100", "met": true }, { "value": 90.0, "factor": "sao2_ge_90", "met": true }, { "factor": "no_unilateral_leg_swelling", "met": true }, { "factor": "no_hemoptysis", "met": true }, { "factor": "no_recent_surgery_or_trauma", "met": true }, { "factor": "no_prior_vte", "met": true }, { "factor": "no_estrogen_use", "met": true } ], "perc_negative": true }, { "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": "Madsen T, Jedick R, Teeples T, Carlson M, Steenblik J", "doi": "10.1016/j.ajem.2018.05.050", "id": "madsen-2019", "pmid": "29848460", "source": "Am J Emerg Med. 2019;37(2):281-285 (Epub 2018 May 24)", "title": "Impact of altitude-adjusted hypoxia on the Pulmonary Embolism Rule-out Criteria." }, "formula": "perc_altitude", "formula_expression": "PERC-negative iff age < 50 and pulse < 100 bpm and SaO2 ≥ 90% and no unilateral leg swelling and no hemoptysis and no recent trauma or surgery and no prior PE or DVT and no hormone use", "criteria": [ { "value": 40, "factor": "age_lt_50", "met": true }, { "value": 80, "factor": "pulse_lt_100", "met": true }, { "value": 90.0, "factor": "sao2_ge_90", "met": true }, { "factor": "no_unilateral_leg_swelling", "met": true }, { "factor": "no_hemoptysis", "met": true }, { "factor": "no_recent_surgery_or_trauma", "met": true }, { "factor": "no_prior_vte", "met": true }, { "factor": "no_estrogen_use", "met": true } ], "perc_negative": true } ] } ``` ## Response fields - `formula` (string): perc_altitude - `formula_expression` (string): Eight Kline factors with Madsen 2019 SaO2 ≥ 90% hypoxia threshold - `perc_negative` (boolean): true only when all eight criteria are met. Not a diagnosis. - `criteria` (array): Per-factor rows with factor, met, and value when numeric - `citation` (object): Madsen 2019 Am J Emerg Med 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": "Madsen T, Jedick R, Teeples T, Carlson M, Steenblik J", "doi": "10.1016/j.ajem.2018.05.050", "id": "madsen-2019", "pmid": "29848460", "source": "Am J Emerg Med. 2019;37(2):281-285 (Epub 2018 May 24)", "title": "Impact of altitude-adjusted hypoxia on the Pulmonary Embolism Rule-out Criteria." }, "formula": "perc_altitude", "formula_expression": "PERC-negative iff age < 50 and pulse < 100 bpm and SaO2 ≥ 90% and no unilateral leg swelling and no hemoptysis and no recent trauma or surgery and no prior PE or DVT and no hormone use", "criteria": [ { "value": 40, "factor": "age_lt_50", "met": true }, { "value": 80, "factor": "pulse_lt_100", "met": true }, { "value": 90.0, "factor": "sao2_ge_90", "met": true }, { "factor": "no_unilateral_leg_swelling", "met": true }, { "factor": "no_hemoptysis", "met": true }, { "factor": "no_recent_surgery_or_trauma", "met": true }, { "factor": "no_prior_vte", "met": true }, { "factor": "no_estrogen_use", "met": true } ], "perc_negative": true } ``` ## Errors - HTTP 400 `invalid_perc_altitude`: Altitude-adjusted PERC needs age, heart_rate_bpm, spo2_percent, and the five Kline flags (Madsen 2019). Returned before settlement; you are not charged. - HTTP 400 `invalid_age`: age must be an integer from 18 to 120 Returned before settlement; you are not charged. - HTTP 400 `invalid_heart_rate`: heart_rate_bpm must be an integer from 30 to 220 Returned before settlement; you are not charged. - HTTP 400 `invalid_spo2`: spo2_percent must be a number from 50 to 100. Returned before settlement; you are not charged. - HTTP 400 `invalid_flag`: boolean clinical flags must be true or false 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 - [PERC rule](https://magentlab.com/docs/perc) — Apply the Kline 2004 eight-factor pulmonary embolism rule-out criteria and return whether all eight are met (PERC-negative). - [Wells PE](https://magentlab.com/docs/wells-pe) — Compute the Wells pulmonary-embolism probability score and return three-tier and two-tier bands. ## Payment Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, 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 accepts[0] (exact, EIP-3009) with validBefore = now + maxTimeoutSeconds (600 seconds), or accepts[1] (batch-settlement deposit/voucher) on product GET. Ping and POST {items} stay exact. Magent retries transient facilitator 429/5xx before answering. - Retry the same URL with PAYMENT-SIGNATURE (base64 JSON of accepted and payload). Magent attaches canonical extensions.bazaar on CDP verify/settle; echoing 402 bazaar is optional. - Success is HTTP 200 JSON plus PAYMENT-RESPONSE. exact settles before the tool. batch-settlement verifies (and deposit-settles) before the tool and commits the charge after HTTP 2xx. HTTP 503: retry the same PAYMENT-SIGNATURE. Mint a new exact 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. - offered `batch-settlement` on eip155:8453: Payment-channel vouchers claimed later in batches. Exact stays accepts[0]. Same-path POST {items} is still exact. extra.assetTransferMethod=eip3009 extra.paymentFlow=authorization. - 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. Same-path POST {items} is still scheme exact: one EIP-3009 authorization for GET unit plus $0.002 per extra item. 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 - HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged. HTTP 402 never includes the tool JSON. - exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. 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.