Winter’s Formula Calculation: Expected pCO2 = 1.5 * HCO3- + 8 +/- 2

When to use Winter’s Formula

Winter formula is used during times of metabolic acidosis, metabolic acidosis is when both pH < 7.35 and HCO3- < 22 on an arterial blood gas.

What is the purpose of the Winters formula

Is the respiratory system properly compensating for the metabolic acidosis.

HCO3− mEq/L
pCO2 in mmHg

If measured and calculated values correspond, respiratory compensation is considered to be adequate. How ever if something else is going on there is improper compensation.

  • PCO2 is greater than the calculated value, there is also a primary respiratory acidosis.
  • PCO2 is less than the calculated value, there is also a primary respiratory alkalosis.
  • Winters Formula

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