An arterial blood gas (ABG) test measures the acidity (pH) and the levels of oxygen and carbon dioxide in the blood. This test is used to check how well your lungs are able to move oxygen into the blood and remove carbon dioxide from the blood.
As blood passes through your lungs, oxygen moves into the blood while carbon dioxide moves out of the blood into the lungs.
What to Expect
The clinical staff will draw blood from an artery (most blood for medical testing is taken from a vein). Arterial blood is used because the oxygen and carbon dioxide levels can be measured before they enter body tissues. When blood is taken from a vein, the blood has already passed through the body's tissues, so the oxygen is used up and carbon dioxide is produced.
A sample of blood from an artery is usually taken from the inside of the wrist (radial artery), but it can also be collected from an artery in the groin (femoral artery) or on the inside of the arm above the elbow crease (brachial artery).
Collecting blood from an artery is more complicated than collecting it from a vein because the arteries are deeper and are protected by nerves. A local anesthetic is sometimes used for this procedure.
Why It Is Done
An arterial blood gas (ABG) test is done to:
- Check for severe breathing problems and lung diseases, such as asthma, cystic fibrosis, or chronic obstructive pulmonary disease.
- See how well treatment for lung diseases is working.
- Find out if you need extra oxygen or help with breathing
- Find out if you are receiving the right amount of oxygen when you are using oxygen in the hospital.
- Measure the acid-base level in the blood of people who have heart failure, kidney failure, uncontrolled diabetes, sleep disorders, severe infections, or after a drug overdose