Is a Blood Gas Test?
A blood gas test measures the amount of oxygen and carbon dioxide
in the blood. It may also be used to determine the pH of the blood, or how
acidic it is. The test is commonly known as a blood gas analysis or arterial
blood gas (ABG) test.
Your red blood cells transport oxygen and carbon dioxide throughout
your body. These are known as blood gases. As blood passes through your lungs,
oxygen flows into the blood while carbon dioxide flows out of the blood into
the lungs. The blood gas test can determine how well your lungs are able
to move oxygen into the blood and remove carbon dioxide from the blood.
Imbalances in the oxygen, carbon dioxide, and pH levels of your
blood can indicate the presence of certain medical conditions. These may
- kidney failure
- heart failure
- uncontrolled diabetes
- chemical poisoning
- a drug overdose
Your doctor may order a blood gas test when you’re showing
symptoms of any of these conditions. The test requires the collection of a
small amount of blood from an artery. It’s a safe and simple procedure that
only takes a few minutes to complete.
Is a Blood Gas Test Done?
A blood gas test provides a precise measurement of the oxygen and
carbon dioxide levels in your body. This can help your doctor determine how
well your lungs and kidneys are working.
Your doctor may order a blood gas test if you’re showing symptoms
of an oxygen, carbon dioxide, or pH imbalance. The symptoms can include:
- shortness of breath
- difficulty breathing
These symptoms may be signs of certain medical conditions,
including asthma and chronic
obstructive pulmonary disease (COPD).
Your doctor may also order a blood gas test if they suspect you’re
experiencing any of the following conditions:
- lung disease
- kidney disease
- metabolic disease
- head or neck injuries that affect breathing
Identifying imbalances in your pH and blood gas levels can also help
your doctor monitor treatment for certain conditions, such as lung and kidney
A blood gas test is often ordered along with other tests, such a blood glucose test
to check blood sugar levels and a creatinine blood test
to evaluate kidney function.
Are the Risks of a Blood Gas Test?
Since a blood gas test doesn’t require a large sample of blood,
it’s considered a low-risk procedure. However, you should always tell your doctor
about existing medical conditions that may make you bleed more than expected. You
should also tell them if you’re taking any over-the-counter or prescription medications,
such as blood thinners, that may affect your bleeding.
Possible side effects associated with the blood gas test include:
- bleeding or bruising at the puncture site
- feeling faint
- blood accumulating under the skin
- infection at the puncture site
Tell your doctor if you experience unexpected or prolonged side
Is a Blood Gas Test Performed?
A blood gas test requires the collection of a small sample of
blood. This blood can be obtained from an artery in your wrist, arm, or groin.
A technician called a phlebotomist will first sterilize the
injection site with an antiseptic. Once they find an artery, they’ll insert a
needle into the artery and draw blood. You might feel a slight prick when the
needle goes in, but the test itself isn’t painful. After the needle is removed,
the technician will put a bandage over the puncture wound.
The blood sample will then be analyzed by a portable machine or
in an on-site laboratory. The sample must be analyzed within 10 minutes of the
procedure to ensure an accurate test result.
the Results of a Blood Gas Test
The results of a blood gas test can help your doctor diagnose
various diseases or determine how well treatments are working for certain
conditions, including lung diseases. The test measures:
- Arterial blood pH measures the amount of
hydrogen ions in blood. A pH of less than 7.0 is called acidic, and a pH greater
than 7.0 is called basic, or alkaline. A lower blood pH may indicate that your
blood is more acidic and has higher carbon dioxide levels. A higher blood pH
may indicate that your blood is more basic and has a higher bicarbonate level.
- Bicarbonate is a chemical that helps prevent the
pH of blood from becoming too acidic or too basic.
- Partial pressure of oxygen is a measure of the
pressure of oxygen dissolved in the blood. It determines how well oxygen is
able to flow from the lungs into the blood.
- Partial pressure of carbon dioxide is a measure of
the pressure of carbon dioxide dissolved in the blood. It determines how well
carbon dioxide is able to flow out of the body.
- Oxygen saturation is a measure of the amount of
oxygen being carried by the hemoglobin in the red blood cells.
In general, normal values include:
- arterial blood pH: 7.38 to 7.42
- bicarbonate: 22 to 28 milliequivalents per liter
- partial pressure of oxygen: 75 to 100 mm Hg
- partial pressure of carbon dioxide: 38 to 42 mm Hg
- oxygen saturation: 94 to 100 percent
Your blood oxygen levels may be lower if you live above sea level.
Abnormal results can be signs of certain medical conditions, including
the ones in following table:
Normal and abnormal ranges can vary depending on the lab because
some use different measurements or methods to analyze blood samples. You should
always meet with your doctor to discuss your test results in more detail. They’ll
be able to tell you if you need more testing and if you’ll need any treatment.