Health

A-a Gradient (Alveolar-Arterial O₂)

Calculate the alveolar-arterial O₂ gradient to distinguish hypoxemia causes. PAO₂ = FiO₂×(P_atm−47) − PaCO₂/0.8; A-a = PAO₂ − PaO₂. Normal ≈ (Age+10)/4. Elevated → V/Q mismatch, shunt, diffusion impairment. Derived from StatPearls, LITFL, Cornell PICU, and Martin 1999. Not medical advice.

json· JSON resultOpen tool

Quick start

Call this tool from your code in three languages.

cURL

curl -X POST 'https://api.elysiatools.com/en/api/tools/a-a-gradient-calculator' \
  -H 'Content-Type: application/json' \
  -d '{"pao2":55,"paco2":32,"fio2":"0.21","age":60,"patm":0,"decimalPlaces":1}'

API reference

Send a POST request with your inputs as JSON. File parameters require a separate upload first.

Endpoint

HTTP

POST https://api.elysiatools.com/en/api/tools/a-a-gradient-calculator

Parameters

Name	Type	Required	Description
pao2	number	Yes	Arterial partial pressure of oxygen (mmHg) from ABG.
paco2	number	Yes	Arterial partial pressure of CO₂ (mmHg) from ABG.
fio2	select	Yes	—
age	number	Yes	Patient age (years), used for age-adjusted normal A-a gradient.
patm	number	No	Atmospheric pressure (mmHg). Default 760 at sea level. Lower at altitude (e.g. Denver ~630).

MCP integration

Add this tool to your Model Context Protocol server so AI agents can list and call it.

Server configuration

Add this block to your MCP client configuration:

mcp.json

{
  "mcpServers": {
    "elysiatools-a-a-gradient-calculator": {
      "name": "a-a-gradient-calculator",
      "description": "Calculate the alveolar-arterial O₂ gradient to distinguish hypoxemia causes. PAO₂ = FiO₂×(P_atm−47) − PaCO₂/0.8; A-a = PAO₂ − PaO₂. Normal ≈ (Age+10)/4. Elevated → V/Q mismatch, shunt, diffusion impairment. Derived from StatPearls, LITFL, Cornell PICU, and Martin 1999. Not medical advice.",
      "baseUrl": "https://api.elysiatools.com/mcp/sse?toolId=a-a-gradient-calculator",
      "command": "",
      "args": [],
      "env": {},
      "isActive": true,
      "type": "sse"
    }
  }
}

List available tools

After connecting to the SSE endpoint, list the exposed tools:

tools/list

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list"
}

Call this tool

Invoke the tool by its id, passing arguments built from its parameters:

tools/call

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/call",
  "params": {
    "name": "a-a-gradient-calculator",
    "arguments": {
  "pao2": 55,
  "paco2": 32,
  "fio2": "0.21",
  "age": 60,
  "patm": 0,
  "decimalPlaces": 1
}
  }
}

Chain multiple tools in one session with a comma-separated toolId list, e.g. /mcp/sse?toolId=png-to-webp,jpg-to-webp,gif-to-webp (max 20).

Questions or issues? Contact [email protected]

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