Neha Patil (Editor)

Winter's formula

Updated on
Edit
Like
Comment
Share on FacebookTweet on TwitterShare on LinkedInShare on Reddit

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

P C O 2 = ( 1.5 × H C O 3 − ) + 8 ± 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 PCO2; the patient's actual (measured) PCO2 is then compared to this:

  • If the two values correspond, respiratory compensation is considered to be adequate.
  • If the measured PCO2 is higher than the calculated value, there is also a primary respiratory acidosis.
  • If the measured PCO2 is lower than the calculated value, there is also a primary respiratory alkalosis.

    • Alkalosis

    Note that Winters' formula pertains to settings of metabolic acidosis.

    To calculate the expected pCO2 in the setting of metabolic alkalosis, the following equations are used:

  • pCO2 = 0.7 [HCO3] + 21 mmHg +/- 5

    • References

    Winter's formula Wikipedia
    (Text) CC BY-SA