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A blood gas test or blood gas analysis tests blood to measure blood gas tension values and blood pH.It also measures 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. [44]
Arterial blood carbon dioxide tension. P a CO 2 – Partial pressure of carbon dioxide at sea level in arterial blood is between 35 and 45 mmHg (4.7 and 6.0 kPa). [9] Venous blood carbon dioxide tension. P v CO 2 – Partial pressure of carbon dioxide at sea level in venous blood is between 40 and 50 mmHg (5.33 and 6.67 kPa). [9]
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.
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.
Venous blood with an oxygen concentration of 15 mL/100 mL would therefore lead to typical values of the a-vO 2 diff at rest of around 5 mL/100 mL. During intense exercise, however, the a-vO 2 diff can increase to as much as 16 mL/100 mL due to the working muscles extracting far more oxygen from the blood than they do at rest. [citation needed]
Venous blood is typically colder than arterial blood, [1] and has a lower oxygen content and pH. It also has lower concentrations of glucose and other nutrients and has higher concentrations of urea and other waste products. The difference in the oxygen content of arterial blood and venous blood is known as the arteriovenous oxygen difference.
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 ...