🧪 Acid-Base Compensation Predictor
Predict the expected compensation for a primary acid-base disorder; deviation from the expected value suggests a coexisting second disorder.
Compensation never overcorrects — values beyond the expected range mean a mixed disorder.
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When to use
Identify mixed acid-base disorders on a blood gas by comparing measured with expected compensation.
How it works
Metabolic acidosis: expected PaCO₂ = 1.5·HCO₃ + 8 (Winter's). Metabolic alkalosis: 0.7·HCO₃ + 21. Acute/chronic respiratory acidosis & alkalosis use fixed HCO₃ change per 10 mmHg PaCO₂.
Key points
- Compensation never overcorrects — values beyond the expected range mean a mixed disorder.
- Always interpret with pH and the anion gap.
- Winter's formula carries ± 2 mmHg uncertainty.
References
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.
| Primary disorder | Metabolic acidosis |
|---|---|
| HCO₃⁻ (for metabolic disorders) | 12 mmol/L |
| PaCO₂ (for respiratory disorders) | 60 mmHg |
→Expected PaCO₂26.0mmHg
- Rule：Winter's formula; ± 2 mmHg
| Primary disorder | Chronic respiratory alkalosis |
|---|---|
| HCO₃⁻ (for metabolic disorders) | 12 mmol/L |
| PaCO₂ (for respiratory disorders) | 60 mmHg |
→Expected HCO₃⁻32.0mmol/L
- Rule：Chronic: HCO₃ ↓ 4 per 10 ↓ PaCO₂
Frequently asked questions
- What is Acid-Base Compensation Predictor?
- Predict the expected compensation for a primary acid-base disorder; deviation from the expected value suggests a coexisting second disorder.
- How is Acid-Base Compensation Predictor calculated? What is the core formula?
- Metabolic acidosis: expected PaCO₂ = 1.5·HCO₃ + 8 (Winter's). Metabolic alkalosis: 0.7·HCO₃ + 21. Acute/chronic respiratory acidosis & alkalosis use fixed HCO₃ change per 10 mmHg PaCO₂.
- When is Acid-Base Compensation Predictor used?
- Identify mixed acid-base disorders on a blood gas by comparing measured with expected compensation.
- What are the key clinical points for Acid-Base Compensation Predictor?
- Compensation never overcorrects — values beyond the expected range mean a mixed disorder. Always interpret with pH and the anion gap. Winter's formula carries ± 2 mmHg uncertainty.
- What are the limits and cautions when using Acid-Base Compensation Predictor?
- 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 Acid-Base Compensation Predictor calculated in practice? Can you show a worked example?
- Inputs: Primary disorder Metabolic acidosis, HCO₃⁻ (for metabolic disorders) 12 mmol/L, PaCO₂ (for respiratory disorders) 60 mmHg → Result: Expected PaCO₂ 26.0 mmHg（Rule: Winter's formula; ± 2 mmHg） Inputs: Primary disorder Chronic respiratory alkalosis, HCO₃⁻ (for metabolic disorders) 12 mmol/L, PaCO₂ (for respiratory disorders) 60 mmHg → Result: Expected HCO₃⁻ 32.0 mmol/L（Rule: Chronic: HCO₃ ↓ 4 per 10 ↓ PaCO₂）