Winter's formula helps to determine whether the compensation by other body system is adequate or not in case of metabolic acidosis. It helps to calculate expected PCO2 (arterial partial pressure of carbon dioxide) in metabolic acidosis.

The formula utilized in this calculation includes:

• Expected PCO2 = [(1.5*HCO3) + 8] (range ± 2)

If the patients actual measured PCO2 is greater than expected then it indicates that the respiratory system is not able to completely compensate for metabolic acidosis and both respiratory and metabolic acidosis are present simultaneously. However, if patients actual measured PCO2 is less than expected then it indicates that respiratory alkalosis is present in addition to metabolic acidosis.

Data the user will need:

• Bicarbonate (HCO3) in mmol/L or mEq/L

Abbreviations used:

• PCO2= Arterial partial pressure of carbon dioxide
• HCO3= Bicarbonate

Interpretation:

The user needs to enter all value of HCO3 which is then used in the formula given below

• Expected PCO2 = [(1.5*HCO3) + 8] (range ± 2)

References:

1. http://acidbase.homestead.com/ABG_Analysis_Rev_2.0.pdf (A synopsis)
2. http://webapps.acep.org/sa/Syllabi/SA-30.pdf (Scientific assembly)