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An arterial blood gas (ABG) test, or arterial blood gas analysis (ABGA) measures the amounts of arterial gases, such as oxygen and carbon dioxide.An ABG test requires that a small volume of blood be drawn from the radial artery with a syringe and a thin needle, [1] but sometimes the femoral artery in the groin or another site is used.
A blood gas test or blood gas analysis tests blood to measure blood gas tension values, it also measures blood pH, and the level and base excess of bicarbonate.The source of the blood is reflected in the name of each test; arterial blood gases come from arteries, venous blood gases come from veins and capillary blood gases come from capillaries. [1]
Acid–base and blood gases are among the few blood constituents that exhibit substantial difference between arterial and venous values. [6] Still, pH, bicarbonate and base excess show a high level of inter-method reliability between arterial and venous tests, so arterial and venous values are roughly equivalent for these.
This helps to determine the degree of any problems with how the lungs transfer oxygen to the blood. [5] A sample of arterial blood is collected for this test. [6] With a normal P a O 2 of 60–100 mmHg and an oxygen content of F I O 2 of 0.21 of room air, a normal P a O 2 /F I O 2 ratio ranges between 300 and 500 mmHg.
Base excess is defined as the amount of strong acid that must be added to each liter of fully oxygenated blood to return the pH to 7.40 at a temperature of 37°C and a pCO 2 of 40 mmHg (5.3 kPa). [2] A base deficit (i.e., a negative base excess) can be correspondingly defined by the amount of strong base that must be added.
Blood gas tension refers to the partial pressure of gases in blood. [1] There are several significant purposes for measuring gas tension. [ 2 ] The most common gas tensions measured are oxygen tension (P x O 2 ), carbon dioxide tension (P x CO 2 ) and carbon monoxide tension (P x CO). [ 3 ]
Using the fact that each gram of hemoglobin can carry 1.34 mL of O2, the oxygen content of the blood (either arterial or venous) can be estimated by the following formula: = [] ( /) + PO2 is the partial pressure of oxygen and reflects the amount of oxygen gas dissolved in the blood. The term 0.0032 * P02 in the equation is very small and ...
However even though the partial pressure of oxygen is about equilibrated between the pulmonary capillaries and the alveolar gas, this equilibrium is not maintained as blood travels further through pulmonary circulation. As a rule, PAO 2 is always higher than P a O 2 by at least 5–10 mmHg, even in a healthy person with normal ventilation and ...