ABG Interpretation Practice
Classify each value, determine the primary disorder, and assess compensation status.
Case ABG Values
pH
7.41
PaCO2
40
mmHg
HCO3-
24
mEq/L
PaO2
90
mmHg
Normal Reference Ranges
pH7.35 to 7.45
PaCO235 to 45 mmHg
HCO3-22 to 26 mEq/L
PaO280 to 100 mmHg
Compensation Formulas
Metabolic AcidosisWinter's: PaCO2 = 1.5 × HCO3- + 8 ±2
Metabolic AlkalosisPaCO2 = 0.7 × (HCO3- − 24) + 40 ±5
Resp AcidosisHCO3- ↑ 3.5 per 10 mmHg CO2 (chronic)
Resp AlkalosisHCO3- ↓ 5 per 10 mmHg CO2 (chronic)
Classification Grid
Click each cell to classify the value as Acidic, Normal, or Alkaline.
Acidic
Normal
Alkaline
pH
< 7.35
7.35 to 7.45
> 7.45
PaCO2
> 45
35 to 45
< 35
HCO3-
< 22
22 to 26
> 26
Note: For PaCO2, elevated is acidic and decreased is alkaline (inverse of pH direction).
