When testing for the carbon dioxide level as bicarbonate in the blood, the person's blood is removed using venipucture, and is placed within a machine to detect the level of CO2 within the blood. This level is necessary for evaluating the body's acid-base homeostasis.
An Overview of Carbon Dioxide
Carbon dioxide (CO2) is an odorless gas formed as the byproduct of respiration in which oxygen is inhaled. Whereas oxygen is mainly distributed in the body within the red blood cells, carbon dioxide is found within the serum and is released from the lungs into the air.
Since it is not within the red blood cells, the carbon dioxide is converted to bicarbonate. If too much of this is located within the body, then body's acid-base balance can be affected. The acid-base balance is controlled by the components of the circulatory and respiratory system. The acid-base balance of the body ensures that the internal environment is maintained at a fairly neutral pH.
Why Is The Test Ordered
The CO2 levels in blood test results is obtained after a physician has ordered routine blood work. The test is performed on blood that is drawn to test the level of electrolytes in the body.
In other instances, CO2 levels in blood are tested to check that systems involved in normal acid base balance are working effectively. The body is only able to function at a narrow pH range and in some cases, death may occur if the balance is not properly regulated
A third reason why a physician might want to order CO2 blood level testing is to monitor any medication that might affect the body's homeostasis. It can also be used to confirm the diagnosis of a particular illness or disease.
How is The Test Performed
When testing for bicarbonate levels in the blood, the person's blood is removed from the arm in the process known as venipuncture. Venipuncture is the process where blood is drawn from the forearm right above the elbow. The laboratory technician taking the blood sample will first clean the skin above the area.
A torniquet is then applied to upper arm so the veins are more visible, and a hypodermic needle is inserted. The sample is collected within a vial and sent to the laboratory to be tested. After the blood has been drawn, it is placed within a machine called a blood gas analyzer that measures the level of blood gases contained within the body.
Blood Test Results
The CO2 levels in blood test results will only tell the physician what the level of bicarbonates is within the blood. Further tests will be necessary to determine exactly what's causing an abnormal blood level. Usually the level of carbon dioxide in the form of bicarbonate is about twenty to thirty milliequivalents per liter.
However kidney, heart, and lung disease and certain medications such as salicylates, found in aspirin, can all contribute to abnormal results in the blood serum if taken at toxic levels. If the level is abnormal, then treatment of the underlying cause of the acid-base malfunction will most likely bring the bicarbonate level back within normal range.
Print Source: Davidson, Stanley & C. Haslett. 2002. "Davidson’s Principles and Practice of Medicine." Churchill Livingstone, Edinburgh.
Print Source: Cotran R, Kumar V, and Robbins, SL. 1999. Robbins Pathologic Basis of Disease, 6th Ed. W.B. Saunders Company, Philadelphia.
Web Source: Lab Tests Online, American Association For Clinical Chemistry. "Bicarbonate: The Test." 2010. Available: http://www.labtestsonline.org.uk/understanding/analytes/co2/test.html