Respiratory compensation is the physiologic mechanism that occurs in an attempt to normalize metabolic acidosis. Winter’s formula can be used to help determine if there is adequate respiratory compensation or if there is another underlying acid-base disturbance (Burger & Schaller, 2023).
 

• Winter’s formula gives an expected value for the patient’s expected PCO₂.
• Winter's Formula is primarily used in metabolic acidosis and uses the patient's bicarbonate level (HCO₃^-) to help calculate what the appropriate respiratory compensation should be.
• If the patient’s actual (measured) PCO₂ is the same as the expected value, then respiratory compensation is considered adequate. This may be present in a patient with chronic obstructive pulmonary disease (COPD) who has a chronically elevated CO₂ and whose kidneys have compensated so that the pH remains normal.  
• If PCO₂ is higher than the calculated value, there is also a secondary respiratory acidosis or mixed acid-base disorder. This may be present in a patient that has both poor perfusion and hypoventilation, for example, a patient with cardiac arrest.
• If the measured PCO₂ is lower than the calculated value, there is a secondary respiratory alkalosis or mixed acid base disorder. This may be present in a patient with diabetic ketoacidosis (DKA) who is hyperventilating to compensate for the severe metabolic acidosis associated with DKA. 

References:

Albert, M. S., Dell, R. B., & Winters, R. W. (1967). Quantitative displacement of acid-base equilibrium in metabolic acidosis. Annals of internal medicine, 66(2), 312–322. https://doi.org/10.7326/0003-4819-66-2-312

Burger, M., & Schaller, D. (2023, July 17). Metabolic acidosis. STAT PEARLS. https://www.ncbi.nlm.nih.gov/books/NBK482146/

More Resources
Blog	Blog	Pocket Card
Anion Gap Acidosis: How Do I Calculate It? How Do I Interpret It?	Delta Ratio	Arterial Blood Gas Analysis Pocket Card