Table 3.

Linear compensation formulas for the four primary acid-base disorders

Acid-Base Disorder	Compensation Equation
Metabolic acidosis	PCO2=1.54×[HCO3–]+8.36±2.2 ↓ΔPCO2=1.1×↓Δ[HCO3–]
Metabolic alkalosis	PCO2=0.7×[HCO3–]+20±5 ↑ΔPCO2=0.75×↑Δ[HCO3–]
Acute respiratory acidosis	↑Δ[HCO3–]=0.1×↑ΔPCO2
Chronic respiratory acidosis	↑Δ[HCO3–]=0.35×↑ΔPCO2
Acute respiratory alkalosis	↓Δ[HCO3–]=0.2×↓ΔPCO2
Chronic respiratory alkalosis	[HCO3–]=0.41×PCO2+9.1 ↓Δ[HCO3–]=0.41×↓ΔPCO2

Equations are written in terms of the independent variable that is altered by the primary acid-base disorder. The coefficient represents the slope of each respective linear equation. PCO₂, carbon dioxide partial pressure (mm Hg); [HCO₃^–], bicarbonate concentration (mM) (1,2,38–42).