Which device is described as accurately measuring the oxygen and carbon dioxide levels in the blood?

• A. Pulse oximeter
• B. Capnograph
• C. Arterial blood gas analyzer
• D. Stethoscope

Answer: (A)

Accurate assessment of both oxygen and carbon dioxide in the blood comes from arterial blood gas analysis. An arterial blood gas analyzer analyzes arterial blood to provide the partial pressures of oxygen and carbon dioxide (pO2 and pCO2), along with pH and bicarbonate, giving a true snapshot of oxygenation and ventilation. Pulse oximetry estimates how much oxygen is bound to hemoglobin (SpO2) but does not measure CO2. A capnograph measures CO2 in exhaled gas, not in the bloodstream. A stethoscope is used for auscultation, not gas measurements. Therefore, the arterial blood gas analyzer is the device that accurately measures both oxygen and carbon dioxide levels in the blood.