What is a Blood Gas Analysis?

J.M. Willhite

A blood gas analysis is a diagnostic tool utilized for the identification and evaluation of certain conditions. Generally administered to evaluate the blood's oxygen absorption, the test may also be utilized to evaluate lung and kidney function. Commonly known as an arterial blood gas (ABG) analysis, this diagnostic test does carry some risk for complications and these should be discussed with a qualified health care provider prior to test administration.

A low blood oxygen level may require supplemental oxygen.
A low blood oxygen level may require supplemental oxygen.

The application of an arterial blood gas analysis is generally to measure gas levels in the blood, namely oxygen and carbon dioxide. The arterial blood sample may also be evaluated for blood pH (acid-base balance) levels and hemoglobin content. Levels of pH are indicative of the blood's acidity and may be interpreted to assess organ function. Hemoglobin is a protein-based substance found in red blood cells that serves as the body's main oxygen distributor and may be analyzed for its oxygen content.

A blood gas analysis is typically used to check oxygen levels.
A blood gas analysis is typically used to check oxygen levels.

Arterial blood is drawn from an artery, located in the wrist or arm, with a small needle that remains in place until a sufficient sample has been obtained. Once the needle is withdrawn, pressure is applied for a few minutes before a bandage is placed over the puncture site. Following the test, the individual may be monitored for a brief period of time for the potential development of any complications, including circulatory issues. Arterial blood draws differ from traditional blood draws that utilize the veins in that the arterial puncture may induce a momentary pulsating or cramping sensation.

Arterial blood is taken from an artery in the arm or wrist, rather than from a vein.
Arterial blood is taken from an artery in the arm or wrist, rather than from a vein.

The most frequent application of a blood gas analysis is for analyzing lung function and monitoring individuals who regularly receive respiratory, or oxygen, therapy. The test evaluates the efficiency of carbon dioxide filtration by the lungs, as well as, the circulation of oxygenated blood. As a means for evaluating lung function, ABG analysis results demonstrating elevated levels of carbon dioxide may be indicative of respiratory failure. Low levels of carbon dioxide often present with respiratory alkalosis, a condition induced by insufficient respiration, as often occurs with chronic hyperventilation or shortness of breath. Any abnormal ABG analysis results generally prompt additional testing for verification.

Individuals with suspected, diabetes-induced complications, such as ketoacidosis, may undergo a blood gas analysis to evaluate ketone levels in their bloodstream. If a person's blood oxygen levels are inadequate, he or she may develop a condition known as lactic acidosis. Triggering an accumulation of lactic acid in the blood stream, this condition may be detected by the presence of marked, insufficient oxygen levels and a high proportion of lactic acid. Metabolic and respiratory conditions, such as acidosis, may be detected during an ABG analysis due to the presence of a blood pH imbalance that may also be indicative of impaired or compromised kidney or lung function.

There are usually no preparatory measures necessary for an arterial blood gas analysis. Individuals on respiratory therapy may be given specialized instructions prior to test administration. Some individuals may develop bruising or a hematoma just under the puncture site. Risks associated with this diagnostic test may include infection, excessive bleeding, and lightheadedness.

In a cord blood gas test, the sample is transported to a lab, where it is tested to determine the dissolved gas level.
In a cord blood gas test, the sample is transported to a lab, where it is tested to determine the dissolved gas level.

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