In order to perform a blood gas analysis (BGA), we express a small amount of blood from the fingertip. The test will measure the amount of carbon dioxide and oxygen contained in the blood as well as the pH of the blood.
The blood gas analysis is used, for example, for monitoring the course of pulmonary diseases such as asthma and can also be used in other acute respiratory problems. It also is useful to detect other diseases since not only the lungs affect the composition of the blood gases. In simple terms, gas exchange in the body is described as follows:
The "outer breathing" brings the inhaled oxygen (O2) through the pulmonary alveoli into the blood that flows through the lungs. In return, the carbon dioxide (CO2) from the blood is passed through the pulmonary alveoli and exhaled.
The oxygenated blood (arterial blood) is distributed by the heart to the body by way of arteries. The body cells absorb oxygen and give off the carbon dioxide into the blood ("internal respiration"). The now deoxygenated blood (venous blood) is transported through the veins back through the heart into the lungs and the carbon dioxide is exhaled.
Thus heart disease also affects the composition of the blood gases. But even "harmless" diseases such as a gastrointestinal disease can cause a loss of fluids. The BGA can therefore also be used to assess the severity of fluid loss or an impending ketoacidosis.The electrolytes (blood salts) can also be determinated using the BGA, allowing changes to be detected early on, especially in gastrointestinal infections.