Blood gas analysis is also called arterial blood gases, or ABGs. This test allows your doctor to assess and manage, if needed, the status of your lung and kidney function and check for acid-base and electrolyte balances. It also helps determine the amount of oxygen your body is receiving.
Features
ABGs are routinely performed on critically ill patients, those on ventilators (breathing machines), those going into surgery or those whose electrolytes are out of balance. The blood sample used for this test is drawn from an artery that contains oxygen-rich blood. A small sample via a needle puncture will be collected from an artery either in the wrist, groin or arm.
Function
The test measures pH of the blood, which indicates if it is acidic or alkalinic. It also measures the amounts of carbon dioxide, which reveals function of the lungs, and bicarbonate, which shows function of the kidneys. ABGs also measure the amount of oxygen in the arteries.
Normal Values
The following measurements, from MedlinePlus, a service from the National Library of Health and the National Institutes of Health, indicate normal laboratory values for arterial blood gases:
PaO2, which stands for partial pressure* of oxygen, is 75 to 100 mmHg.**
PaCO2, or partial pressure of carbon dioxide, is 35 to 45 mmHg.
HCO3, which is bicarbonate, should be 22 to 26 mEq/L.**
The pH should be between 7.35 and 7.45.
*The term "partial pressure" is defined as "the pressure that one component of a mixture of gases would exert if it were alone in a container" by the American Heritage Dictionary.
**The abbreviation mmHg stands for millimeters of mercury, and mEq/L is milliequivalents per liter.
Abnormal Results
An increase or decrease of each value of this test can mean a variety of things. For example, increased carbon dioxide means reduced breathing, such as if you had a head injury or if you received too much sedating medication, while a reduction would indicate a hyperventilating state. Increased bicarbonate levels might occur if you are vomiting a lot, or the levels may decrease if you are having chronic diarrhea. From differences of pH, your doctor may determine dysfunctions of the lungs or kidneys or other metabolic disorders.
Considerations
If you take either aspirin or anticoagulants, which thin the blood, tell your doctor prior to the test, due to the risk of bleeding from the puncture site. Also, if you experience bleeding after the puncture, bruising or a numbing sensation, notify the health care provider.
References
- "Mosby's Manual of Diagnostic and Laboratory Results"; Kathleen Deska Pagana, Ph.D., R.N.; Timothy J.Pagana, M.D., FACS; 2006
- Dictionary.com
- MedlinePlus: Blood Gases
