Blood gases
Alternative names:
arterial blood gas analysis
How the test is 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 for the test:
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:
How the test will feel:
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 The needle is withdrawn after the sample is collected.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.
Why the test is 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.
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