Winters' formula

Winters' formula,[1] named for Dr. R.W. Winters,[2] is a formula used to evaluate respiratory compensation when analyzing acid–base disorders and a metabolic acidosis is present.[3][4] It can be given as

${\displaystyle P_{CO_{2}}=(1.5\times HCO_{3}^{-})+8\pm 2}$,

where HCO3⁻ is given in units of mEq/L and pCO₂ will be in units of mmHg.

Winters' formula gives an expected value for the patient's P_CO2; the patient's actual (measured) P_CO2 is then compared to this:

• If the two values correspond, respiratory compensation is considered to be adequate.
• If the measured P_CO2 is higher than the calculated value, there is also a secondary respiratory acidosis or mixed acid base disorder.
• If the measured P_CO2 is lower than the calculated value, there is also a secondary respiratory alkalosis or mixed acid base disorder.