🫁 Winter's Formula (Respiratory Compensation)
Calculate the expected PaCO₂ for a metabolic acidosis with Winter's formula.
Clinical takeaway
Measured > expected → added respiratory acidosis.
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When to use
Detect a concomitant primary respiratory disorder in metabolic acidosis.
How it works
Expected PaCO₂ = 1.5 × HCO₃ + 8 ± 2 mmHg.
Key points
- Measured > expected → added respiratory acidosis.
- Measured < expected → added respiratory alkalosis.
- Apply only to a primary metabolic acidosis.
References
Decision support for licensed clinicians only; not a substitute for clinical judgement, diagnosis or local protocols.
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Bicarbonate (HCO₃⁻) | 12 mmol/L |
|---|---|
| Measured PaCO₂ (optional) | 26 mmHg |
→Expected PaCO₂26mmHg
- Expected PaCO₂：24.0–28.0 mmHg (1.5·HCO₃ + 8 ± 2)
- Interpretation：Measured PaCO₂ within expected range → appropriate respiratory compensation.
Frequently asked questions
- What is Winter's Formula (Respiratory Compensation)?
- Calculate the expected PaCO₂ for a metabolic acidosis with Winter's formula.
- How is Winter's Formula (Respiratory Compensation) calculated? What is the core formula?
- Expected PaCO₂ = 1.5 × HCO₃ + 8 ± 2 mmHg.
- When is Winter's Formula (Respiratory Compensation) used?
- Detect a concomitant primary respiratory disorder in metabolic acidosis.
- What are the key clinical points for Winter's Formula (Respiratory Compensation)?
- Measured > expected → added respiratory acidosis. Measured < expected → added respiratory alkalosis. Apply only to a primary metabolic acidosis.
- What are the limits and cautions when using Winter's Formula (Respiratory Compensation)?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- How is Winter's Formula (Respiratory Compensation) calculated in practice? Can you show a worked example?
- Inputs: Bicarbonate (HCO₃⁻) 12 mmol/L, Measured PaCO₂ (optional) 26 mmHg → Result: Expected PaCO₂ 26 mmHg（Expected PaCO₂: 24.0–28.0 mmHg (1.5·HCO₃ + 8 ± 2), Interpretation: Measured PaCO₂ within expected range → appropriate respiratory compensation.）