Use to detect mixed disorders.
Metabolic acidosis
Expected PaCO₂ = 1.5 × HCO₃ + 8 ± 2 (Winters)
Metabolic alkalosis
Expected PaCO₂ ≈ 0.7 × ΔHCO₃ above 24
Acute respiratory acidosis
HCO₃ rises 1 per 10 ↑PaCO₂
Chronic respiratory acidosis
HCO₃ rises 3.5 per 10 ↑PaCO₂
Acute respiratory alkalosis
HCO₃ falls 2 per 10 ↓PaCO₂
Chronic respiratory alkalosis
HCO₃ falls 5 per 10 ↓PaCO₂
