Respiratory Emergency Medicine Renal Standard — widely used clinical tool for ABG interpretation

Winters' Formula for Metabolic Acidosis Compensation

Predicts the expected compensatory pCO₂ for a primary metabolic acidosis. A measured pCO₂ outside this range indicates a co-existing respiratory disorder.

Score interpretation

Appropriate Respiratory Compensation 0

Measured pCO₂ falls within the expected Winters' range (1.5 × HCO₃ + 8 ± 2 mmHg). Simple metabolic acidosis with adequate respiratory response.

→ Investigate and treat underlying cause: DKA, lactic acidosis, AKI, diarrhoea, renal tubular acidosis.

pCO₂ High — Co-existing Respiratory Acidosis 1

Measured pCO₂ above Winters' range. Inadequate respiratory compensation — concurrent respiratory acidosis.

→ Consider: COPD, neuromuscular weakness, sedation, respiratory fatigue. May indicate impending respiratory failure — assess ventilatory support need.

pCO₂ Low — Co-existing Respiratory Alkalosis 2

Measured pCO₂ below Winters' range. Excessive respiratory compensation — concurrent respiratory alkalosis.

→ Consider: sepsis, salicylate toxicity, anxiety, CNS disease, liver failure. Treat underlying cause.

Interpretation bands for the Winters' Formula. Apply clinical judgement and local guidance.

References

Winters RW. Terminology of acid-base disorders. Ann Intern Med. 1965;63(5):873–884.

Curated clinical cross-links plus same-class fallbacks.

Drugs

Pathways

Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.

Score interpretation

References

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