Which type of blood sample is most appropriate for arterial blood gas analysis?

Which type of blood sample is most appropriate for arterial blood gas analysis?

• A. Venous blood
• B. Capillary blood
• C. Tissue fluid
• D. Arterial blood

Answer: (D)

Arterial blood gas analysis requires blood that truly reflects lung gas exchange. Arterial blood carries oxygen-rich blood and has the most accurate pH, PaO2, and PaCO2 values because it has just left the lungs before tissues extract gases. Venous blood has already delivered oxygen to tissues and picked up carbon dioxide, so its gas tensions and pH differ from arterial blood and don’t represent lung gas exchange. Capillary blood can vary depending on site and mix of arterial/venous blood, making it less reliable for ABG. Tissue fluid isn’t blood at all and won’t provide correct gas measurements. Therefore, arterial blood is the appropriate sample for arterial blood gas analysis.

Arterial blood gas analysis requires blood that truly reflects lung gas exchange. Arterial blood carries oxygen-rich blood and has the most accurate pH, PaO2, and PaCO2 values because it has just left the lungs before tissues extract gases. Venous blood has already delivered oxygen to tissues and picked up carbon dioxide, so its gas tensions and pH differ from arterial blood and don’t represent lung gas exchange. Capillary blood can vary depending on site and mix of arterial/venous blood, making it less reliable for ABG. Tissue fluid isn’t blood at all and won’t provide correct gas measurements. Therefore, arterial blood is the appropriate sample for arterial blood gas analysis.