# Cerebral perfusion pressure CPP Status: LIVE Price: $0.005 USDC `GET /api/calc/cpp` HTML: https://magentlab.com/docs/cpp Markdown: https://magentlab.com/docs/cpp.md Not a medical device. Not a diagnosis, dose, or listing recommendation. ## What it computes Compute cerebral perfusion pressure as MAP minus ICP in mm Hg and flag whether CPP is at least 70 mm Hg per Rosner 1995. ## When to use When an agent has caller-supplied MAP and ICP in mm Hg and needs the published CPP identity and the Rosner 1995 minimum-CPP-of-70 flag, not a monitor reading or a treatment order. ## When not to use - Not a medical device. Not a treatment protocol. - map_mm_hg and icp_mm_hg are caller-supplied. magent does not measure MAP or ICP and is not an invasive monitor. - cpp_ge_70 is the Rosner 1995 protocol minimum CPP of at least 70 mm Hg. It is not a later target. - CPP may be negative when ICP exceeds MAP. That is not a validation error. ## Formula ``` cpp_mm_hg = map_mm_hg - icp_mm_hg ``` ## Citation [Cerebral perfusion pressure: management protocol and clinical results](https://doi.org/10.3171/jns.1995.83.6.0949) Rosner MJ, Rosner SD, Johnson AH J Neurosurg. 1995;83(6):949-962 DOI: [10.3171/jns.1995.83.6.0949](https://doi.org/10.3171/jns.1995.83.6.0949) ## Worked example ### MAP 90, ICP 10 Given: `icp_mm_hg=10, map_mm_hg=90` 1. cpp_mm_hg = 90 − 10 = 80 → 80.0 2. 80.0 ≥ 70 → cpp_ge_70 true ## Also searched as - cerebral perfusion pressure - CPP - MAP minus ICP - cerebral perfusion - Rosner CPP - intracranial pressure CPP - CPP mm Hg ## Parameters - `map_mm_hg` (number, required): Mean arterial pressure in mm Hg (30-180). Caller-supplied; magent does not measure MAP. - `icp_mm_hg` (number, required): Intracranial pressure in mm Hg (0-100). Caller-supplied; magent does not measure ICP. ICP may exceed MAP. ## 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/cpp` 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": [ { "icp_mm_hg": "10", "map_mm_hg": "90" }, { "icp_mm_hg": "10", "map_mm_hg": "90" } ] } ``` Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/cpp Example 200: ```json { "count": 2, "path": "/api/calc/cpp", "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": "Rosner MJ, Rosner SD, Johnson AH", "doi": "10.3171/jns.1995.83.6.0949", "id": "rosner-1995", "pmid": "7490638", "source": "J Neurosurg. 1995;83(6):949-962", "title": "Cerebral perfusion pressure: management protocol and clinical results" }, "formula": "cpp", "formula_expression": "cpp_mm_hg = map_mm_hg - icp_mm_hg", "cpp_ge_70": true, "cpp_mm_hg": 80.0, "icp_mm_hg": 10.0, "map_mm_hg": 90.0 }, { "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": "Rosner MJ, Rosner SD, Johnson AH", "doi": "10.3171/jns.1995.83.6.0949", "id": "rosner-1995", "pmid": "7490638", "source": "J Neurosurg. 1995;83(6):949-962", "title": "Cerebral perfusion pressure: management protocol and clinical results" }, "formula": "cpp", "formula_expression": "cpp_mm_hg = map_mm_hg - icp_mm_hg", "cpp_ge_70": true, "cpp_mm_hg": 80.0, "icp_mm_hg": 10.0, "map_mm_hg": 90.0 } ] } ``` ## Response fields - `formula` (string): cpp - `formula_expression` (string): Exact expression used - `map_mm_hg` (number): Mean arterial pressure used, mm Hg - `icp_mm_hg` (number): Intracranial pressure used, mm Hg - `cpp_mm_hg` (number): Cerebral perfusion pressure in mm Hg, 1 decimal - `cpp_ge_70` (boolean): true iff CPP is at least 70 mm Hg (Rosner 1995 protocol minimum). Not a later target. - `citation` (object): Rosner 1995 J Neurosurg 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": "Rosner MJ, Rosner SD, Johnson AH", "doi": "10.3171/jns.1995.83.6.0949", "id": "rosner-1995", "pmid": "7490638", "source": "J Neurosurg. 1995;83(6):949-962", "title": "Cerebral perfusion pressure: management protocol and clinical results" }, "formula": "cpp", "formula_expression": "cpp_mm_hg = map_mm_hg - icp_mm_hg", "cpp_ge_70": true, "cpp_mm_hg": 80.0, "icp_mm_hg": 10.0, "map_mm_hg": 90.0 } ``` ## Errors - HTTP 400 `invalid_map_mm_hg`: map_mm_hg must be a number from 30 to 180. Returned before settlement; you are not charged. - HTTP 400 `invalid_icp_mm_hg`: icp_mm_hg must be a number from 0 to 100 (Rosner 1995 CPP). 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 - [Glasgow Coma Scale](https://magentlab.com/docs/gcs) — Compute the Glasgow Coma Scale as the sum of caller-assigned eye, verbal, and motor integers. The 1974 or 1976 edition is required. ## 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.