Expected PaCO₂ for respiratory compensation of a metabolic acidosis
Serum bicarbonate (mEq/L)
Measured PaCO₂ (mmHg) — optional
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Evidence
Original publication
Albert MS, Dell RB, Winters RW. Quantitative displacement of acid-base equilibrium in metabolic acidosis. In sustained metabolic acidosis the respiratory response fell along the line PaCO₂ ≈ 1.5·[HCO₃⁻] + 8, within roughly ± 2 mmHg.
Annals of Internal Medicine, 1967
Open source
Guideline
Winter's formula is standard in acid-base teaching and practice: a measured PaCO₂ above the predicted range indicates a superimposed respiratory acidosis, and one below it a superimposed respiratory alkalosis. It applies to a simple metabolic acidosis, not to acute changes still evolving.
Last reviewed: 2026-09
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