Recent Journal Updates

DiabetologiaJun 6, 2026

Time-restricted eating versus dietetic guidance on glycaemic outcomes in adults at risk of type 2 diabetes: a non-inferiority randomised clinical trial

Clinical Context

We think this has broad domain relevance to Winter's Formula — PaCO2 Compensation.

DiabetologiaJun 5, 2026

MASLD, diabetes and PMOS across the female life stages

Clinical Context

We think this has broad domain relevance to Winter's Formula — PaCO2 Compensation.

British J Clinical PharmacologyMay 28, 2026

British National Formulary Guidance on prescribing in pregnancy: A descriptive cross‐sectional study

Clinical Context

We think this might be relevant to the clinical guidance for Winter's Formula — PaCO2 Compensation.

Winter's Formula

CO₂ Compensation Index

Chemical Input

Serum Bicarbonate (HCO₃⁻)

Quick Rule

The Expected PaCO₂ should roughly match the last two digits of the pH.

Compensation Tuner

Enter serum Bicarbonate to execute acid-base respiratory targeting.

Guidelines & Evidence

Verified

Last Review: 2026

When to Use

Any patient with confirmed Metabolic Acidosis (HCO₃⁻ < 22 mEq/L, pH < 7.35) who has an ABG available — apply before concluding the disorder is simple.

Determining whether the respiratory system is compensating appropriately, undercompensating, or overcompensating for the metabolic derangement.

Unmasking a superimposed respiratory acid-base disorder in any complex or mixed clinical picture.

Emergency medicine: DKA, lactic acidosis from septic shock, toxic ingestion (methanol, ethylene glycol, salicylates, isoniazid), uraemic acidosis, cardiac arrest.

ICU: ventilated patients — to set a rational PaCO₂ target that mirrors appropriate physiological compensation and avoid iatrogenic respiratory alkalosis or acidosis.

Post-intubation: verify that ventilator settings achieve the PaCO₂ that would be expected if the patient were breathing spontaneously with appropriate compensation.

Clinical Prerequisite

Winter's Formula applies exclusively to Metabolic Acidosis as the primary disorder. The primary disorder must be established first using pH, HCO₃⁻, and PaCO₂ together. Do not apply the formula in metabolic alkalosis, primary respiratory disorders, or without a concurrent ABG — a venous HCO₃⁻ alone is insufficient for interpreting PaCO₂.

Where It Should Not Be Applied

Metabolic Alkalosis: has its own compensation rule (PaCO₂ rises ~0.7 mmHg per 1 mEq/L rise in HCO₃⁻, max ~55 mmHg). Winter's Formula does not apply.

Primary Respiratory Acidosis or Alkalosis: these have separate renal compensation rules (acute and chronic variants).

Paediatric patients < 2 years: compensation physiology differs and paediatric-specific nomograms should be applied.

Chronic respiratory failure with known CO₂ retention: the baseline PaCO₂ is already abnormal and makes interpretation unreliable without a known true baseline.

Related Scores in Practice

In clinical practice, this assessment is frequently evaluated alongside other validated measures. Depending on the patient's presentation and specific diagnostic requirements, you may also need to utilize the Anion Gap Calculator, Urinary Anion Gap, Sodium Correction Rate, Abg Interpreter or the Anion Gap + Delta-Delta to formulate a comprehensive care plan.

Last Comprehensive Review: 2026

Related Nephrology Tools

KFRE — Kidney Failure Risk

Creatinine Clearance

Uric Acid & FEUA

UACR

Nephrology Calculators Internal Medicine Calculators Emergency Medicine Calculators

Have feedback about this calculator?Let us know.

Recent Journal Updates

DiabetologiaJun 6, 2026

Time-restricted eating versus dietetic guidance on glycaemic outcomes in adults at risk of type 2 diabetes: a non-inferiority randomised clinical trial

Clinical Context

We think this has broad domain relevance to Winter's Formula — PaCO2 Compensation.

DiabetologiaJun 5, 2026

MASLD, diabetes and PMOS across the female life stages

Clinical Context

We think this has broad domain relevance to Winter's Formula — PaCO2 Compensation.

British J Clinical PharmacologyMay 28, 2026

British National Formulary Guidance on prescribing in pregnancy: A descriptive cross‐sectional study

Clinical Context

We think this might be relevant to the clinical guidance for Winter's Formula — PaCO2 Compensation.

Winter's Formula

CO₂ Compensation Index

Chemical Input

Serum Bicarbonate (HCO₃⁻)

Quick Rule

The Expected PaCO₂ should roughly match the last two digits of the pH.

Compensation Tuner

Enter serum Bicarbonate to execute acid-base respiratory targeting.

Guidelines & Evidence

Verified

Last Review: 2026

When to Use

Any patient with confirmed Metabolic Acidosis (HCO₃⁻ < 22 mEq/L, pH < 7.35) who has an ABG available — apply before concluding the disorder is simple.

Determining whether the respiratory system is compensating appropriately, undercompensating, or overcompensating for the metabolic derangement.

Unmasking a superimposed respiratory acid-base disorder in any complex or mixed clinical picture.

Emergency medicine: DKA, lactic acidosis from septic shock, toxic ingestion (methanol, ethylene glycol, salicylates, isoniazid), uraemic acidosis, cardiac arrest.

ICU: ventilated patients — to set a rational PaCO₂ target that mirrors appropriate physiological compensation and avoid iatrogenic respiratory alkalosis or acidosis.

Post-intubation: verify that ventilator settings achieve the PaCO₂ that would be expected if the patient were breathing spontaneously with appropriate compensation.

Clinical Prerequisite

Where It Should Not Be Applied

Metabolic Alkalosis: has its own compensation rule (PaCO₂ rises ~0.7 mmHg per 1 mEq/L rise in HCO₃⁻, max ~55 mmHg). Winter's Formula does not apply.

Primary Respiratory Acidosis or Alkalosis: these have separate renal compensation rules (acute and chronic variants).

Paediatric patients < 2 years: compensation physiology differs and paediatric-specific nomograms should be applied.

Chronic respiratory failure with known CO₂ retention: the baseline PaCO₂ is already abnormal and makes interpretation unreliable without a known true baseline.

Related Scores in Practice

Last Comprehensive Review: 2026

Related Nephrology Tools

KFRE — Kidney Failure Risk

Creatinine Clearance

Uric Acid & FEUA

UACR

Nephrology Calculators Internal Medicine Calculators Emergency Medicine Calculators

Have feedback about this calculator?Let us know.