Alternate Names: Arterial blood gas analysis

How Performed: The test is performed by collecting a sample of blood from an artery. Using a small needle, the sample may be collected from the radial artery in the wrist, the femoral artery in the groin, or the brachial artery in the arm. After the blood is drawn, pressure must be applied to the puncture site for at least 5 minutes to completely stop the bleeding. The test must be sent to the laboratory for analysis immediately, or the accuracy of the results cannot be guaranteed.

How To Prepare: There is no special preparation. If the person receiving the test is on oxygen, the oxygen concentration must remain constant for 20 minutes preceding the test. If the test is to be taken without oxygen, the oxygen must be turned off for 20 minutes before the sample is taken to ensure accurate test results.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child’s age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:

• infant test or procedure preparation (birth to 1 year)
• toddler test or procedure preparation (1 to 3 years)
• preschooler test or procedure preparation (3 to 6 years)
• schoolage test or procedure preparation (6 to 12 years)
• adolescent test or procedure preparation (12 to 18 years)

How It Feels: A needle is inserted through the skin into the artery. There may be brief cramping or throbbing at the puncture site. The needle is withdrawn after the sample is collected. Pressure will be applied over the site for 5 to 10 minutes to prevent bleeding, and then a dressing will be applied over the puncture site. The site will be observed for signs of bleeding or impairment of the circulation.

Risks: Risks of blood gas are related to arterial stick. In general, there is a very low risk when the procedure is done correctly. There may be bleeding or bruising at the puncture site, or delayed bleeding from the site. Circulation impairment at the area of the puncture may occur but very rarely does.

Why Performed: The test is used to evaluate respiratory diseases and conditions that affect the lungs. It is used to determine the effectiveness of oxygen therapy. The acid-base component of the test also gives information on how well the kidneys are functioning.

Normal Values: Values at sea level:

• partial pressure of oxygen (PaO2) - 75 to 100 mm Hg
• partial pressure of carbon dioxide (PaCO2) - 35 to 45 mm Hg
• pH - 7.35 to 7.45
• oxygen saturation (SaO2) - 94% to 100%
• bicarbonate - (HCO3) - 22 to 26 mEq/liter

Abnormal Results: Abnormal results may indicate respiratory, metabolic, or renal diseases. Results may also be abnormal in trauma, particularly with head or neck injuries that may affect breathing.

Cost:

Special Considerations: Notify the health care provider if there is bleeding, bruising, numbness, tingling, or discoloration at the puncture site.