Arterial Blood Gases


A blood test to identify the levels of certain gases that are indicators of lung and kidney function.

Parts of the Body Involved

Blood and an artery in the wrist, arm, or groin

The Arteries

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Reasons for Procedure

This test determines the amount of oxygen and carbon dioxide dissolved in the blood, as well as the acid/base status. Oxygen and carbon dioxide levels are indicators of lung function. The acid/base status provides information on how well the lungs and kidneys are functioning.

This test helps evaluate respiratory problems, such as asthma, and other conditions that affect the lungs. It also helps evaluate metabolic problems that affect acid-base status. If you are undergoing oxygen therapy, this test will determine whether or not the therapy is effective.

Risk Factors for Complications During the Procedure

There are no risk factors associated with arterial blood gases.

What to Expect

Prior to Procedure

If the blood is going to be taken from an artery in the arm, an Allen test will be done to evaluate blood circulation. The Allen test involves pressing the radial and ulnar arteries in the wrist, which causes the palm to turn white. When the arteries are released, the skin turns pink and flushes. Failure to flush within five seconds indicates decreased blood flow, and another site for puncture will need to be selected.



Description of the Procedure

The puncture site is swabbed clean. The needle is inserted into the selected artery, and blood is withdrawn. The needle is then removed.

After Procedure

The puncture site should be compressed for a minimum of five minutes to stop the bleeding. If you have recently taken aspirin or other blood-thinning medications, it will take longer for the bleeding to stop. Once blood flow has stopped, a bandage will be placed on the puncture site, and should not be removed for at least 30-60 minutes.

How Long Will It Take?

About 15 minutes, including preparation, blood draw, and compression.

Will It Hurt?

There may be some discomfort during insertion of the needle.

Possible Complications

Complications from an arterial blood draw are fairly rare. They include:

  • Persistent bleeding
  • Bruising
  • Impaired circulation
  • Injury to the artery

Average Hospital Stay

Hospital stay is not required.

Postoperative Care

Keep the puncture site clean and protected until it heals.


Based on the test results, which should be available quickly, your doctor can assess your lung and kidney function. Normal results are:

TestNormal Results
Partial pressure of oxygen (PaO2)75-100 mm HG
Partial pressure of carbon dioxide (PaCO2)35-45 mm HG
Oxygen saturation (SaO2)94-100%
Bicarbonate (HCO3)22-26 mEq/liter

Abnormal results may indicate respiratory, metabolic, or kidney problems or disease.

Call Your Doctor If Any of the Following Occurs

  • Signs of infection, including fever and chills
  • Numbness
  • Excessive bleeding
  • Weakness of an extremity
  • Tingling
  • Bruising


American Association for Respiratory Care

National Heart, Lung, and Blood Institute


BC Health Guide

Health Canada


American Association for Respiratory Care website. Available at: .

Last reviewed March 2008 by Jill D Landis, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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