Which instrument is used to measure blood pressure?

• A. Stethoscope
• B. Oximeter
• C. Thermometer
• D. Sphygmomanometer

Answer: (D)

Measuring blood pressure relies on quantifying the force of blood against the arterial walls using a cuff and a readout device—the sphygmomanometer. This instrument directly measures cuff pressure, which corresponds to the arterial pressure inside the arm. In the classic auscultatory method, you inflate the cuff and then deflate it while listening with a stethoscope for the Korotkoff sounds; the first sound marks the systolic pressure and the disappearance of sound marks the diastolic pressure. The stethoscope helps you hear those sounds, but the actual numerical pressure comes from the sphygmomanometer. Other devices mentioned have different functions: an oximeter measures oxygen saturation, and a thermometer measures body temperature.