Arterial blood is most commonly used to analyze which parameter?

• A. Hematology
• B. Organ function tests
• C. Blood gasses
• D. Blood chemistry

Answer: (C)

Measuring gas tensions and acid-base status requires arterial blood because it provides the most accurate snapshot of how well the lungs are exchanging gases and how the body's pH balance is being maintained. From an arterial sample you obtain pH, PaCO2, PaO2, bicarbonate, and base excess, along with oxygen saturation estimates. Venous blood has already delivered O2 to tissues and collected CO2, so its gas values differ and don’t reliably reflect lung function or acid-base status. Hematology focuses on cellular components and is typically performed on whole blood from a vein, while organ function tests and standard blood chemistry analyze enzymes, electrolytes, and metabolites in serum or plasma rather than gases. Therefore, arterial samples are used to analyze the blood gas status.