Respiratory · LIVE

Predicted six-minute walk distance

Predicted 6MWD

Compute Enright 1998 predicted six-minute walk distance and lower limit of normal from sex, age, height, and weight using the Table 3 height/weight equations.

LIVE $0.005 USDC GET /api/calc/6mwd

Markdown: /docs/6mwd.md · Canonical: https://magentlab.com/docs/6mwd

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

What it computes

Compute Enright 1998 predicted six-minute walk distance and lower limit of normal from sex, age, height, and weight using the Table 3 height/weight equations.

When to use

When an agent needs the published predicted 6MWD and LLN and must not time the walk, apply the BMI alternate equations, or invent an 80% or 400 m class.

When not to use

• Not a medical device. Enright 1998 derived the equations in healthy adults aged 40-80. magent does not time the walk.
• Table 3 height/weight equations only. Does not apply the BMI alternate equations.
• Does not assign an 80% predicted or 400 m cutoff. Those are not Enright 1998 output bands.
• Height 50-250 cm and weight 1-500 kg are magent clamps via Params; age 40-80 is the paper derivation range.

Formula

male: 6MWD_m = 7.57 × height_cm − 5.02 × age − 1.76 × weight_kg − 309; female: 6MWD_m = 2.11 × height_cm − 2.29 × weight_kg − 5.78 × age + 667; LLN_m = predicted_m − 153 (male) or predicted_m − 139 (female)

Citation

Title

Reference equations for the six-minute walk in healthy adults

Authors

Enright PL, Sherrill DL

Source

Am J Respir Crit Care Med. 1998;158(5 Pt 1):1384-1387

DOI

10.1164/ajrccm.158.5.9710086

Worked example

Also searched as

• six minute walk
• 6MWD
• six-minute walk distance
• predicted 6MWD
• Enright six-minute walk
• 6 minute walk test
• six minute walk distance
• 6MWT predicted

Try

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

/api/calc/6mwd?sex=male&age=50&height_cm=170&weight_kg=70

Full URL: https://api.magentlab.com/api/calc/6mwd?sex=male&age=50&height_cm=170&weight_kg=70

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/6mwd?sex=male&age=50&height_cm=170&weight_kg=70"

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/6mwd 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": "50",
      "height_cm": "170",
      "sex": "male",
      "weight_kg": "70"
    },
    {
      "age": "50",
      "height_cm": "170",
      "sex": "male",
      "weight_kg": "70"
    }
  ]
}

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/6mwd",
  "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": "Enright PL, Sherrill DL",
        "doi": "10.1164/ajrccm.158.5.9710086",
        "id": "enright-1998",
        "pmid": "9817683",
        "source": "Am J Respir Crit Care Med. 1998;158(5 Pt 1):1384-1387",
        "title": "Reference equations for the six-minute walk in healthy adults"
      },
      "formula": "enright_1998",
      "formula_expression": "male: 6MWD_m = 7.57 × height_cm − 5.02 × age − 1.76 × weight_kg − 309; female: 6MWD_m = 2.11 × height_cm − 2.29 × weight_kg − 5.78 × age + 667; LLN_m = predicted_m − 153 (male) or predicted_m − 139 (female)",
      "age_years": 50,
      "sex": "male",
      "weight_kg": 70.0,
      "height_cm": 170.0,
      "lln_m": 450.7,
      "predicted_m": 603.7
    },
    {
      "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": "Enright PL, Sherrill DL",
        "doi": "10.1164/ajrccm.158.5.9710086",
        "id": "enright-1998",
        "pmid": "9817683",
        "source": "Am J Respir Crit Care Med. 1998;158(5 Pt 1):1384-1387",
        "title": "Reference equations for the six-minute walk in healthy adults"
      },
      "formula": "enright_1998",
      "formula_expression": "male: 6MWD_m = 7.57 × height_cm − 5.02 × age − 1.76 × weight_kg − 309; female: 6MWD_m = 2.11 × height_cm − 2.29 × weight_kg − 5.78 × age + 667; LLN_m = predicted_m − 153 (male) or predicted_m − 139 (female)",
      "age_years": 50,
      "sex": "male",
      "weight_kg": 70.0,
      "height_cm": 170.0,
      "lln_m": 450.7,
      "predicted_m": 603.7
    }
  ]
}

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": "Enright PL, Sherrill DL",
    "doi": "10.1164/ajrccm.158.5.9710086",
    "id": "enright-1998",
    "pmid": "9817683",
    "source": "Am J Respir Crit Care Med. 1998;158(5 Pt 1):1384-1387",
    "title": "Reference equations for the six-minute walk in healthy adults"
  },
  "formula": "enright_1998",
  "formula_expression": "male: 6MWD_m = 7.57 × height_cm − 5.02 × age − 1.76 × weight_kg − 309; female: 6MWD_m = 2.11 × height_cm − 2.29 × weight_kg − 5.78 × age + 667; LLN_m = predicted_m − 153 (male) or predicted_m − 139 (female)",
  "age_years": 50,
  "sex": "male",
  "weight_kg": 70.0,
  "height_cm": 170.0,
  "lln_m": 450.7,
  "predicted_m": 603.7
}

Client errors (HTTP 400)

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

Related tools

• BODE — Sum Celli 2004 BODE points from BMI, FEV1 percent predicted, MMRC dyspnea, and 6-minute walk distance.
• mMRC — Return the Mahler 1988 modified Medical Research Council (mMRC) dyspnea grade 0-4 from a caller-assigned integer, with the published grade wording.
• Peak expiratory flow — Compute Nunn and Gregg 1989 predicted peak expiratory flow in L/min from age, sex, and height.

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. 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.