Blood gases, venous

Alphabetical Test listing

Blood gases, venous-201

Blood gases, venous
  • pH
  • PCO2
  • PO2
  • HCO3
  • Base excess
  • Osaturation

Blood gas testing is used to evaluate respiratory diseases, conditions that affect the lungs, determine the effectiveness of oxygen therapy, and provide information about the body's acid / base balance, which can reveal important clues about lung and kidney function and the body's general metabolic state.

Heparin whole blood, venous

Blood gas syringe

2.0 mL

Warning: Should be collected at a hospital site

Expel all air from the sample



Blood gas syringe



The tube should be fully filled, unopened, and must arrive at AHL Central lab within one (1)hour of collection.


Do not open, and do not spin


Dk green Sodium heparin (Na hep), no gel


Time sensitive

Refrigerated - 30 minutes

  • Vacutainer collection tubes submitted for venous blood gas analysis cannot be sent through the Pneumatic tube system (PTS)
  • Clotted specimens
  • Insufficient quantity 
  • Incorrect anticoagulant (anything other than lithium heparin) or contaminated
  • Specimens that do not meet transportation and storage requirements
  • Specimen that has been exposed to air or contains air bubbles
  • Specimen received in a plasma separator (PST) tube
  • Improper labels (unlabeled or mislabeled)
  • Leaking container resulting in compromised specimen
  • Quantity not sufficient (QNS)
AHL - Chemistry: C
1 day

Ion selective electrodes


Venous blood gas reference ranges


Reference range

pH, venous


pCO2, venous

41-51 mmHg 

pO2, venous

34-50 mmHg (0-<1 day)

34-40 mmHg (1 day - >1 mo)

35-40 mmHg (≥1 mo)

HCO3, venous

22-29 mmol/L

Base excess

-2.0 - 3.0 

O2 saturation, venous

40.0-70.0 % (<1 day)

70-75 % (≥1 day)


Blood gasmeasurements determine the acidity (pH) of the blood, and how much oxygen and carbon dioxide the blood contains. The pH of the blood depends on the relationship of the components of the bicarbonate buffer system – bicarbonate and carbonic acid. Carbonic acid is proportional to the dissolved carbon in the blood (0.03 × pCO2).

The plasma bicarbonate concentration is controlled mainly by the kidneys and is affected by the end products of metabolism of cells. It is referred to as the metabolic component. pCO2 is controlled by the rate of excretion of CO2 by the lungs. It is referred to as the respiratory component.

A low pH (acidosis) may be due to a fall in the HCO3- (metabolic acidosis) or a rise in pCO2 (respiratory acidosis). The body responds to a change in one component by producing a similar change in the other. This is called compensation, and is usually incomplete.

Vacutainer tubes are not anaerobic and it can result in an elevated pO2 if not handled properly