A blood test performed using blood from a vein to determine the pH, pCO2, pO2, and bicarbonate level is called what?

• A. ABG
• B. A-line
• C. Chest tube
• D. VBG

Answer: (D)

This item tests understanding of arterial versus venous blood gas testing. When the blood sample is drawn from a vein, the test that results is a venous blood gas. Venous samples are used to assess acid-base status and CO2 levels, and can provide pH, pCO2, and bicarbonate reliably enough for trend, though pO2 from venous blood is not as accurate for determining oxygenation as arterial samples. In contrast, an arterial blood gas uses arterial blood (often from an arterial line) to give precise pO2 and other gas measurements, which is why arterial testing is preferred when exact oxygenation status is needed. The other options relate to arterial access or procedures (arterial line) or are not used for gas analysis from blood.