Question 1

What is Winter's formula?

Accepted Answer

Winter's formula predicts the expected pCO2 in a primary metabolic acidosis: **pCO2 ≈ 1.5 × HCO3 + 8 ± 2**. If the measured pCO2 is higher, there is a coexisting respiratory acidosis; if lower, a coexisting respiratory alkalosis. It is the most commonly tested compensation formula in medicine.

Question 2

How do I tell acute from chronic respiratory acidosis?

Accepted Answer

In acute respiratory acidosis, HCO3 rises about 1 mEq/L for every 10 mmHg rise in pCO2 above 40. In chronic respiratory acidosis (sustained over days), the renal response brings HCO3 up about 4 mEq/L per 10 mmHg. A patient with pCO2 of 60: HCO3 ~26 = acute, HCO3 ~32 = chronic, HCO3 in between = acute-on-chronic.

Question 3

What does the delta ratio tell me?

Accepted Answer

Delta ratio = (corrected anion gap − 12) / (24 − HCO3). Less than 1 implies a coexisting non-anion-gap metabolic acidosis. Between 1 and 2 implies a pure high-anion-gap metabolic acidosis. Greater than 2 implies a coexisting metabolic alkalosis. It is the standard tool for spotting mixed acid-base disorders that the primary acid-base interpretation alone would miss.

Question 4

Why correct the anion gap for albumin?

Accepted Answer

The anion gap is the sum of unmeasured anions, of which albumin is the largest contributor. In hypoalbuminemia, the "normal" gap drifts downward, so a gap of 12 in a patient with albumin of 2 is actually meaningfully elevated. Correction: add 2.5 × (4 − albumin in g/dL) to the calculated AG.

Question 5

Can compensation overshoot the normal range?

Accepted Answer

No. The body partially compensates a primary disturbance but does not over-correct the pH back into the normal range. If the pH is fully normal in the setting of abnormal pCO2 and HCO3, there is almost certainly a second, opposite disturbance occurring — not "perfect compensation."

Question 6

Does this tool interpret oxygenation?

Accepted Answer

No — it focuses on acid-base only. Oxygenation (P/F ratio, A-a gradient) is calculated separately and is part of a different clinical question (gas exchange / shunt physiology) than acid-base balance.

ABG Interpreter (with compensation check)

References

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