Quick Review Cards for Medical Laboratory Science

Blood Gas Parameters Clinical Chemistry Review 125

REFERENCE RANGE

PARAMETER MEASUREMENT OF: DERIVATION (ARTERIAL BLOOD)

pH [H+] pH electrode on blood gas analyzer 7.35–7.45

PCO 2 Partial pressure of CO 2 PCO 2 electrode on blood gas analyzer 35–45 mm Hg

PO 2 Partial pressure of O 2 PO 2 electrode on blood gas analyzer 80–100 mm Hg

HCO– 3 Bicarbonate Calculated value on blood gas analyzer 22–26 mmol/L

Total CO 2 Bicarbonate + carbonic acid Calculated value on blood gas analyzer 23–27 mmol/L

Base excess* Metabolic component of acid-base status. Calculated value on blood gas analyzer –2 to +2 mEq/L

Difference between titratable bicarbonate

of sample & that of normal blood sample

Oxygen saturation Amount of oxygenated hemoglobin Measured by oximeter 94%–100%

*Negative values indicate base deficit.