Arterial Blood Gases

Arterial blood gases, called ABGs, are a series of bloodmeasurements that are ordered as a single test. This test isused mainly to check lung function and acid levels in the body.

Who is a candidate for the test?

Any time there is a question about breathing problems,oxygen and carbon dioxide exchange, or acid levels in the body, this testcan be helpful. Examples include:

people with shortness of breathdue to lung problems

people with rapid breathing due to heart or blood conditions

people who are unconscious

people who are suspected of having too much or too little acid in thebody, such as someone with kidney failure

people on artificial breathing machines calledventilators.ABGs are done regularly to assure that the machines are set correctly.

How is the test performed?

A blood sample from an artery is needed to do this test.In most cases, an artery on the palm side of the wrist is used to get theblood. Sometimes, an artery in the groin or other area may be used.The skin over the artery is cleaned first. Next, a small needle is insertedthrough the skin and into the artery. The needle is usually hooked up toa syringe. Blood flows into the syringe once the needle is put into theartery. Pressure is applied over the area after the blood is collected toprevent bleeding. The blood is then sent to the lab for analysis.

What is involved in preparation for the test?

Most of the time, there is no preparation needed for this test.A doctor will give any instructions if needed.

What do the test results mean?

There are several values that are measured in an ABG.Each of the values has a set range that is considered to be withinhealthy limits. If anyof the main values becomes severely abnormal, the person may die.

pH Level

The pH is one of the main parts of this test. This is ameasure of the level of acid in the blood. Acid levels may be too high with:

kidney failure or damage

certain cases of uncontrolled diabetes

exposure to certain toxic substances, such as a drug overdose

shock, which may occur from heart failure, serious infections, ormassive blood or fluid loss

breathing troubles, such as lung infections,asthma, emphysema,or not breathing fast enough

certain medicines

Acid levels may be too low from:

dehydration

certain types of kidney problems

breathing too fast, such as when a person has apanic disorder

excessive vomiting

salt imbalances,which may result from a hormone problem in the body

certain medicines

If the pH is abnormal, the other parts of the test can helpfind out the reason. For example, if the acid level in the body is toohigh, it could be from breathing or metabolism problems. It is crucialto know what is causing the high acid level so that the best treatment canbe chosen. If the acid level is too high because of a breathingproblem, the person may need extra oxygen or even a ventilator.If the acid level is too high from metabolism problems, a personmay need to be hooked up to a blood-filtering machine or may needantibiotics or other medicines.

Oxygen and Carbon Dioxide Levels

Other parts of the test are the oxygen andcarbon dioxide levels in the blood. The job of the lungs is to takein oxygen and get rid of carbon dioxide. If some type of breathingor respiratory problem is present, these values will be abnormal.The oxygen level can also be used to check if a person is gettingenough oxygen or whether they need extra oxygen.

Bicarbonate Level

The part of the test that measures the bicarbonate levelin the blood will determine whether there is a metabolism problem.

Other minor parts of the test may bemonitored by a doctor in certain situations.

The doctor must look at the pH, breathing, and metabolicparts of the test as a whole. This allows the doctor to sort out differentproblems in a person’s body.