Your result shows the expected pCO2 range if the lungs are appropriately compensating for a primary metabolic acidosis. Compare this expected range with the patient's actual measured pCO2 from the arterial blood gas (ABG). If the actual pCO2 falls within the expected range (calculated value +/- 2 mmHg), respiratory compensation is appropriate — the patient has a simple metabolic acidosis with intact compensatory hyperventilation.

If the actual pCO2 is lower than the expected range, the patient has a concurrent respiratory alkalosis in addition to the metabolic acidosis. This pattern is seen in conditions like sepsis, salicylate toxicity, or anxiety-driven hyperventilation superimposed on metabolic acidosis. If the actual pCO2 is higher than the expected range, the patient has a concurrent respiratory acidosis — the lungs are not compensating adequately. This occurs in patients with underlying lung disease (COPD, neuromuscular weakness) or respiratory fatigue, and may indicate impending respiratory failure requiring ventilatory support.

Use Winter's formula as part of a systematic approach to acid-base analysis whenever a primary metabolic acidosis has been identified (low pH with low serum bicarbonate). It is one of the essential steps in the classic acid-base interpretation algorithm: identify the primary disorder, assess compensation, calculate the anion gap, and compute the delta-delta if an anion gap is elevated.

This calculation is most commonly performed in the emergency department and ICU when interpreting arterial blood gases in patients with metabolic acidosis from conditions such as diabetic ketoacidosis (DKA), lactic acidosis, renal failure, toxic ingestions (methanol, ethylene glycol), or severe diarrhea. It is also a fundamental teaching tool in medical education for understanding respiratory compensation physiology.

Winter's formula applies only to primary metabolic acidosis. It should not be used to assess compensation in metabolic alkalosis, respiratory acidosis, or respiratory alkalosis — each of these has different compensation formulas. Applying Winter's formula to the wrong primary disorder will yield misleading results.

The formula also assumes that the patient's respiratory system is capable of mounting a normal compensatory response. In patients with pre-existing lung disease (COPD, restrictive lung disease, neuromuscular disorders), the respiratory compensation may be blunted even without a true concurrent respiratory acidosis. Additionally, compensation takes time — full respiratory compensation for metabolic acidosis typically develops within 12–24 hours. In acute metabolic acidosis, the actual pCO2 may not yet have reached its expected compensatory level, and repeated assessment may be needed.