Respiratory · LIVE

Predicted peak expiratory flow (Nunn and Gregg)

Peak expiratory flow

Compute Nunn and Gregg 1989 predicted peak expiratory flow in L/min from age, sex, and height.

LIVE $0.005 USDC GET /api/calc/peak_expiratory_flow

Markdown: /docs/peak-expiratory-flow.md · Canonical: https://magentlab.com/docs/peak-expiratory-flow

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

What it computes

Compute Nunn and Gregg 1989 predicted peak expiratory flow in L/min from age, sex, and height.

When to use

When an agent needs the published adult predicted PEF and must not invent a personal-best or action-plan zone.

When not to use

• Not a personal-best, asthma action-plan zone, or diagnosis of obstruction. Predicted PEF is for adults aged 15-85 as enrolled.
• Does not apply pediatric equations. Does not convert a measured PEF to percent predicted unless the agent supplies the measured value separately.

Formula

ln(PEF_l_min) = a*ln(age) + b*age + c/height_cm + d; male a=0.544 b=-0.0151 c=-74.7 d=5.48; female a=0.376 b=-0.0120 c=-58.8 d=5.63

Citation

Title

New regression equations for predicting peak expiratory flow in adults

Authors

Nunn AJ, Gregg I

Source

BMJ. 1989;298(6680):1068-1070

DOI

10.1136/bmj.298.6680.1068

Worked example

Also searched as

• predicted PEF
• peak expiratory flow
• Nunn Gregg PEF
• expected peak flow
• PEFR predicted

Try

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

/api/calc/peak_expiratory_flow?age=40&sex=male&height_cm=175

Full URL: https://api.magentlab.com/api/calc/peak_expiratory_flow?age=40&sex=male&height_cm=175

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/peak_expiratory_flow?age=40&sex=male&height_cm=175"

Parameters

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.

POST /api/calc/peak_expiratory_flow Max 25 unit_amount + extra_item_amount * (n - 1) extra $0.002 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 (fixture)

{
  "items": [
    {
      "age": "40",
      "height_cm": "175",
      "sex": "male"
    },
    {
      "age": "40",
      "height_cm": "175",
      "sex": "male"
    }
  ]
}

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/peak_expiratory_flow",
  "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": "Nunn AJ, Gregg I",
        "doi": "10.1136/bmj.298.6680.1068",
        "id": "nunn-gregg-1989",
        "source": "BMJ. 1989;298(6680):1068-1070",
        "title": "New regression equations for predicting peak expiratory flow in adults"
      },
      "formula": "nunn_gregg_1989",
      "formula_expression": "ln(PEF_l_min) = a*ln(age) + b*age + c/height_cm + d; male a=0.544 b=-0.0151 c=-74.7 d=5.48; female a=0.376 b=-0.0120 c=-58.8 d=5.63",
      "age_years": 40,
      "sex": "male",
      "height_cm": 175.0,
      "predicted_pef_l_min": 636.0
    },
    {
      "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": "Nunn AJ, Gregg I",
        "doi": "10.1136/bmj.298.6680.1068",
        "id": "nunn-gregg-1989",
        "source": "BMJ. 1989;298(6680):1068-1070",
        "title": "New regression equations for predicting peak expiratory flow in adults"
      },
      "formula": "nunn_gregg_1989",
      "formula_expression": "ln(PEF_l_min) = a*ln(age) + b*age + c/height_cm + d; male a=0.544 b=-0.0151 c=-74.7 d=5.48; female a=0.376 b=-0.0120 c=-58.8 d=5.63",
      "age_years": 40,
      "sex": "male",
      "height_cm": 175.0,
      "predicted_pef_l_min": 636.0
    }
  ]
}

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": "Nunn AJ, Gregg I",
    "doi": "10.1136/bmj.298.6680.1068",
    "id": "nunn-gregg-1989",
    "source": "BMJ. 1989;298(6680):1068-1070",
    "title": "New regression equations for predicting peak expiratory flow in adults"
  },
  "formula": "nunn_gregg_1989",
  "formula_expression": "ln(PEF_l_min) = a*ln(age) + b*age + c/height_cm + d; male a=0.544 b=-0.0151 c=-74.7 d=5.48; female a=0.376 b=-0.0120 c=-58.8 d=5.63",
  "age_years": 40,
  "sex": "male",
  "height_cm": 175.0,
  "predicted_pef_l_min": 636.0
}

Client errors (HTTP 400)

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

Related tools

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• ROX index — Compute the ROX index as pulse-oximetry SpO2 percent divided by inspired oxygen fraction, then divided by respiratory rate.

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. 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

• HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged.
• 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.