{
  "slug": "abg-interpretation",
  "title": "ABG Interpretation Aid",
  "heading": "Arterial Blood Gas Interpretation Aid",
  "category": "fitness-health",
  "url": "https://www.revenuelab.fyi/toolbox/abg-interpretation",
  "summary": "Step through pH, CO2, and bicarbonate to a likely acid-base pattern.",
  "description": "Interpreting an arterial blood gas systematically avoids missing mixed disorders. This tool applies the standard sequence: check pH for acidemia or alkalemia, check pCO2 and HCO3 to see which is driving the primary disturbance, then apply Winter's formula to check whether respiratory compensation for a metabolic acidosis is appropriate, inadequate, or excessive (suggesting a second, superimposed process). It also flags likely primary respiratory acidosis or alkalosis based on pCO2 direction relative to pH. This is a structured educational aid, not a replacement for full clinical correlation — the same numbers can represent very different underlying physiology depending on history (renal failure, diabetic ketoacidosis, opioid overdose, sepsis, salicylate toxicity, and more all produce distinct but sometimes overlapping ABG patterns). Anion gap, lactate, and the clinical context are essential companions to this reading, and any ambiguous or mixed pattern should go to a clinician for full interpretation. This tool is for education and workflow support only — not medical advice. Always verify results with a clinician and use clinical judgment alongside your institution's protocols.",
  "formula": "Winter's formula expected pCO2 = 1.5 × HCO3 + 8 (± 2), used to check respiratory compensation for metabolic acidosis.",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=abg-interpretation",
  "inputs": [
    {
      "id": "ph",
      "label": "pH",
      "kind": "number",
      "hint": null,
      "default": 7.28,
      "unit": null,
      "min": 6.6,
      "max": 7.8
    },
    {
      "id": "pco2",
      "label": "pCO2",
      "kind": "number",
      "hint": null,
      "default": 30,
      "unit": "mmHg",
      "min": 10,
      "max": 100
    },
    {
      "id": "hco3",
      "label": "Bicarbonate (HCO3)",
      "kind": "number",
      "hint": null,
      "default": 14,
      "unit": "mEq/L",
      "min": 2,
      "max": 45
    }
  ],
  "outputs": [
    {
      "id": "primary",
      "label": "Likely primary disorder",
      "format": "raw",
      "hint": null,
      "primary": true
    },
    {
      "id": "expectedPco2",
      "label": "Expected pCO2 (Winter's formula)",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "compensation",
      "label": "Compensation assessment",
      "format": "raw",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "pH: 7.28",
      "pCO2: 30 mmHg",
      "Bicarbonate (HCO3): 14 mEq/L"
    ],
    "outputs": [
      "Likely primary disorder: Primary metabolic acidosis",
      "Expected pCO2 (Winter's formula): 29",
      "Compensation assessment: Appropriate respiratory compensation"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter ph.",
      "Enter pco2 (mmHg).",
      "Enter bicarbonate (hco3) (mEq/L).",
      "Read your likely primary disorder on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "ph": 6.6,
        "pco2": 18,
        "hco3": 8
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "ph": 7.28,
        "pco2": 30,
        "hco3": 14
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "ph": 7.8,
        "pco2": 48,
        "hco3": 22
      }
    }
  ],
  "limitations": [
    "Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass.",
    "Results do not account for medical conditions, medication, or pregnancy.",
    "Use this as a directional reference, not a diagnosis — talk to a clinician before acting on it."
  ],
  "faq": [
    {
      "q": "What's the standard order to read an ABG?",
      "a": "Check pH first to establish acidemia versus alkalemia, then look at pCO2 and HCO3 to see which one moved in the direction that would explain the pH — that's your primary process. Then check whether the other value moved in the expected compensatory direction and by the expected amount, using formulas like Winter's for metabolic acidosis."
    },
    {
      "q": "What does it mean if compensation is 'better' or 'worse' than expected?",
      "a": "If the actual pCO2 is lower than Winter's formula predicts, there's likely an additional primary respiratory alkalosis on top of the metabolic acidosis (common in sepsis or salicylate toxicity). If pCO2 is higher than predicted, there's likely a superimposed respiratory acidosis, meaning the patient cannot compensate adequately, often due to fatigue or a separate lung process."
    },
    {
      "q": "Should I calculate anion gap too?",
      "a": "Yes, always, alongside this tool. Anion gap tells you whether a metabolic acidosis is due to unmeasured acids (ketoacidosis, lactic acidosis, toxic alcohols, renal failure) versus a non-gap process (diarrhea, renal tubular acidosis, saline-induced). This ABG aid does not calculate anion gap — pair it with a dedicated anion gap tool."
    },
    {
      "q": "Can this replace a clinician's interpretation?",
      "a": "No. This structured walkthrough teaches the pattern-recognition steps, but real patients frequently have mixed or evolving disorders that require full clinical context, trend over time, and lab correlation (lactate, ketones, toxicology) that a single ABG snapshot cannot capture."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/osmolar-gap",
    "https://www.revenuelab.fyi/toolbox/delta-gap-ratio",
    "https://www.revenuelab.fyi/toolbox/winters-formula"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — ABG Interpretation Aid (https://www.revenuelab.fyi/toolbox/abg-interpretation)"
}