# Cole 1957 Pediatric Endotracheal Tube (ETT) Size Calculator

> Cole 1957 Pediatric Endotracheal Tube (ETT) Size Calculator is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Calculates the recommended uncuffed pediatric endotracheal tube internal diameter in millimetres using the Cole 1957 formula: age_years/4 + 4

## Facts

- Endpoint: GET https://api.magentlab.com/api/calc/pediatric_ett
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/cole-1957-pediatric-endotracheal-tube-ett-size-calculator-dc4d618d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_n1s9OrevIQD4pq0b9b1kW

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability cole-1957-pediatric-endotracheal-tube-ett-size-calculator-dc4d618d
```

Example prompt: What's the correct uncuffed endotracheal tube internal diameter for a 5-year-old child using the Cole formula?

## When to prefer this

Use this endpoint when you need a fast, authoritative, citation-backed arithmetic calculation of uncuffed pediatric ETT internal diameter by age (Cole 1957 formula, valid for ages 0.5–12 years). Prefer this over manual calculation to eliminate arithmetic errors in clinical workflows. Not suitable for neonatal tube sizing, cuffed tube selection, or length-based (Broselow tape) estimations.

## Known failure modes

- Age out of range (below 0.5 or above 12 years): formula is not validated for neonates or older adolescents
- Missing required age_years query parameter: returns a validation error
- Non-numeric or negative age input: returns a schema validation error
- Network/payment failure (x402 micropayment not fulfilled): request not processed

## How this service works

Cole 1957 uncuffed pediatric endotracheal tube internal diameter: age_years/4 + 4 millimetres. Deterministic published arithmetic with citation; not a device-selection order or length-based tape.

## Output

Returns the calculated uncuffed endotracheal tube internal diameter in millimetres computed as age_years/4 + 4, based on the Cole 1957 published formula. The result is a deterministic arithmetic output with a citation and does not represent a device order or length-based tape measurement.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "headers": {
     "type": "object",
     "additionalProperties": {
      "type": "string"
     }
    },
    "queryParams": {
     "type": "object",
     "required": [
      "age_years"
     ],
     "properties": {
      "age_years": {
       "type": "number",
       "description": "Age in years (0.5-12). Cole uncuffed ID (mm) = age/4 + 4. Not a neonatal-only formula."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "path": "/api/calc/pediatric_ett",
  "count": 2,
  "items": [
   {
    "formula": "cole_1957",
    "citation": {
     "id": "cole-1957",
     "doi": "10.1001/archpedi.1957.04030070084009",
     "title": "Pediatric formulas for the anesthesiologist",
     "source": "AMA Am J Dis Child. 1957;94(6):672-673",
     "authors": "Cole F"
    },
    "age_years": 4,
    "ett_id_mm": 5,
    "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.",
    "formula_expression": "ett_id_mm = age_years / 4 + 4"
   },
   {
    "formula": "cole_1957",
    "citation": {
     "id": "cole-1957",
     "doi": "10.1001/archpedi.1957.04030070084009",
     "title": "Pediatric formulas for the anesthesiologist",
     "source": "AMA Am J Dis Child. 1957;94(6):672-673",
     "authors": "Cole F"
    },
    "age_years": 4,
    "ett_id_mm": 5,
    "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.",
    "formula_expression": "ett_id_mm = age_years / 4 + 4"
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/cole-1957-pediatric-endotracheal-tube-ett-size-calculator-dc4d618d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.magentlab.com](https://www.zero.xyz/host/api.magentlab.com/llms.txt)