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A-a Gradient Calculator (Alveolar-Arterial Oxygen Gradient)
x402
A-a Gradient Calculator (Alveolar-Arterial Oxygen Gradient) is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).
Computes the alveolar–arterial oxygen gradient using the simplified alveolar gas equation given FiO2, barometric pressure, PaCO2, PaO2, and respiratory quotient
Price / call$0.005
Success—
StatusUnknown
How this service works
Alveolar–arterial oxygen gradient from FiO2, barometric pressure, PaCO2, PaO2, and RQ using the simplified alveolar-gas equation (PH2O 47 mm Hg). Deterministic published arithmetic with citation; not a diagnosis.
Output
Returns the computed alveolar oxygen tension (PAO2), the A-a gradient in mm Hg (PAO2 − PaO2), and interpretive reference context including citation to the published formula. All values are deterministic arithmetic; no diagnosis is rendered.
Example use cases
ICU blood gas interpretation
“My ICU patient is on 50% oxygen (FiO2 0.50), their PaCO2 is 35 mm Hg and PaO2 is 65 mm Hg at sea level — what is the A-a gradient?”
High-altitude hypoxemia workup
“Can you compute the A-a oxygen gradient for someone at altitude where barometric pressure is 620 mm Hg, breathing room air, with a PaCO2 of 32 and a PaO2 of 58?”
Post-op respiratory monitoring
“Post-surgical patient is breathing 40% O2 (FiO2 0.40), PaCO2 is 45 mm Hg, PaO2 is 90 mm Hg, barometric pressure 760 — calculate their alveolar-arterial oxygen gradient.”
Technical details
Endpoint
GEThttps://api.magentlab.com/api/calc/aa_gradientWhen to prefer
Use this endpoint when you need a fast, deterministic, citeable A-a gradient computation from raw arterial blood gas values. Prefer it over manual calculation or LLM arithmetic to avoid rounding errors and to get a traceable citation. It is ideal for clinical decision-support pipelines, EHR automation, and educational tools that require reproducible pulmonary physiology math.
Side effects
- PaCO2 or PaO2 out of accepted range (8–80 and 20–700 mm Hg respectively) returns a validation error
- FiO2 outside 0.21–1.0 range rejected
- Barometric pressure outside 500–800 mm Hg range rejected
- RQ outside 0.7–1.0 range rejected
- Missing required parameters (paco2_mm_hg or pao2_mm_hg) returns 400 error
- Payment not settled via x402 returns 402 Payment Required
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"path": "/api/calc/aa_gradient",
"count": 2,
"items": [
{
"rq": 0.8,
"fio2": 0.21,
"formula": "aa_gradient",
"citation": {
"id": "riley-cournand-1949",
"doi": "10.1152/jappl.1949.1.12.825",
"title": "\"Ideal\" alveolar air and the analysis of ventilation-perfusion relationships in the lungs",
"source": "J Appl Physiol. 1949;1(12):825-847",
"authors": "Riley RL, Cournand A"
},
"pb_mm_hg": 760,
"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.",
"pao2_mm_hg": 95,
"paco2_mm_hg": 40,
"aa_gradient_mm_hg": 4.7,
"water_vapor_mm_hg": 47,
"formula_expression": "PAO2_mm_hg = fio2 * (pb_mm_hg - 47) - paco2_mm_hg / rq; aa_gradient_mm_hg = PAO2_mm_hg - pao2_mm_hg",
"pao2_alveolar_mm_hg": 99.7
},
{
"rq": 0.8,
"fio2": 0.21,
"formula": "aa_gradient",
"citation": {
"id": "riley-cournand-1949",
"doi": "10.1152/jappl.1949.1.12.825",
"title": "\"Ideal\" alveolar air and the analysis of ventilation-perfusion relationships in the lungs",
"source": "J Appl Physiol. 1949;1(12):825-847",
"authors": "Riley RL, Cournand A"
},
"pb_mm_hg": 760,
"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.",
"pao2_mm_hg": 95,
"paco2_mm_hg": 40,
"aa_gradient_mm_hg": 4.7,
"water_vapor_mm_hg": 47,
"formula_expression": "PAO2_mm_hg = fio2 * (pb_mm_hg - 47) - paco2_mm_hg / rq; aa_gradient_mm_hg = PAO2_mm_hg - pao2_mm_hg",
"pao2_alveolar_mm_hg": 99.7
}
]
}
}Tags
x402
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