LIVE

PaO2/FiO2 ratio

Compute the PaO2/FiO2 ratio as arterial PO2 in mm Hg divided by inspired oxygen fraction.

LIVE $0.005 USDC GET /api/calc/pf_ratio

Markdown: /docs/pf-ratio.md · Canonical: https://magentlab.com/docs/pf-ratio

Not a medical device. Not a diagnosis, dose, or listing recommendation.

What it computes

Compute the PaO2/FiO2 ratio as arterial PO2 in mm Hg divided by inspired oxygen fraction.

When to use

When an agent needs PaO2 divided by FiO2 and must not invent ARDS severity bands or the oxygenation index.

When not to use

• Not a diagnosis. Magent does not apply ARDS severity cutoffs.
• This is not the oxygenation index (FiO2 × MAP × 100 / PaO2).
• FiO2 is required as a fraction (0.21–1.0), not a percent, and is not defaulted to room air.

Formula

pf_ratio = pao2_mm_hg / fio2

Citation

Title

Pulmonary response to major injury

Authors

Horovitz JH, Carrico CJ, Shires GT

Source

Arch Surg. 1974;108(3):349-355

DOI

10.1001/archsurg.1974.01350270079014

Worked example

Also searched as

• P/F ratio
• PaO2 over FiO2
• PaO2/FiO2
• PaO2 FiO2 ratio
• PF ratio
• arterial PaO2 FiO2

Try

Opens the live endpoint. Unpaid browser requests show the paywall; agents should send Accept: application/json.

/api/calc/pf_ratio?pao2_mm_hg=95&fio2=0.21

Full URL: https://api.magentlab.com/api/calc/pf_ratio?pao2_mm_hg=95&fio2=0.21

Call

Expect HTTP 402 until you retry with PAYMENT-SIGNATURE. Incomplete query params return HTTP 400 before any quote or charge.

curl -i -H "Accept: application/json" "https://api.magentlab.com/api/calc/pf_ratio?pao2_mm_hg=95&fio2=0.21"

Parameters

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.

POST /api/calc/pf_ratio Max 25 unit_amount * n 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 (fixture)

{
  "items": [
    {
      "fio2": "0.21",
      "pao2_mm_hg": "95"
    },
    {
      "fio2": "0.21",
      "pao2_mm_hg": "95"
    }
  ]
}

Open bulk paywall →

Opens a two-item fixture on the API host. Unpaid browsers get the same MetaMask paywall as GET; Pay retries POST with those items.

Example 200 (fixture)

{
  "count": 2,
  "path": "/api/calc/pf_ratio",
  "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": "Horovitz JH, Carrico CJ, Shires GT",
        "doi": "10.1001/archsurg.1974.01350270079014",
        "id": "horovitz-1974",
        "source": "Arch Surg. 1974;108(3):349-355",
        "title": "Pulmonary response to major injury"
      },
      "formula": "pf_ratio",
      "formula_expression": "pf_ratio = pao2_mm_hg / fio2",
      "fio2": 0.21,
      "pao2_mm_hg": 95.0,
      "pf_ratio": 452.4
    },
    {
      "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": "Horovitz JH, Carrico CJ, Shires GT",
        "doi": "10.1001/archsurg.1974.01350270079014",
        "id": "horovitz-1974",
        "source": "Arch Surg. 1974;108(3):349-355",
        "title": "Pulmonary response to major injury"
      },
      "formula": "pf_ratio",
      "formula_expression": "pf_ratio = pao2_mm_hg / fio2",
      "fio2": 0.21,
      "pao2_mm_hg": 95.0,
      "pf_ratio": 452.4
    }
  ]
}

Response

Example JSON

Machine form of the same example. Frozen fixture. Not a live lookup.

{
  "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": "Horovitz JH, Carrico CJ, Shires GT",
    "doi": "10.1001/archsurg.1974.01350270079014",
    "id": "horovitz-1974",
    "source": "Arch Surg. 1974;108(3):349-355",
    "title": "Pulmonary response to major injury"
  },
  "formula": "pf_ratio",
  "formula_expression": "pf_ratio = pao2_mm_hg / fio2",
  "fio2": 0.21,
  "pao2_mm_hg": 95.0,
  "pf_ratio": 452.4
}

Client errors (HTTP 400)

Invalid params return 400 without charge. Shared HTTP 402 and 503 meanings: Payments.

Related tools

• A-a O2 gradient — Compute the alveolar–arterial oxygen gradient from arterial blood-gas values using the simplified ideal alveolar-gas equation.
• Oxygenation index — Compute the oxygenation index from inspired oxygen fraction, mean airway pressure in cm H2O, and arterial PO2.

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. Unpaid valid requests return HTTP 402 with a base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote: retry the same PAYMENT-SIGNATURE. Full handshake and shared payment errors: Payments. Stdio MCP: /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.