Expected pCO₂ in metabolic acidosis.
Expected pCO₂ = (1.5 × HCO₃) + 8 ± 2. Used ONLY in metabolic acidosis. If measured pCO₂ is within the expected range: simple metabolic acidosis with appropriate compensation. Below range: concurrent respiratory alkalosis. Above range: concurrent respiratory acidosis. This is critical for identifying mixed acid-base disorders.