Which instrument is used to measure blood pressure?

The sphygmomanometer is the instrument specifically designed to measure blood pressure. It consists of an inflatable cuff that is wrapped around the arm, a measuring unit that displays the blood pressure reading, and a way to inflate (either a manual bulb or an electronic system). When the cuff is inflated, it temporarily stops blood flow in the artery. As the air is gradually released, the pressure in the cuff decreases, and the person measuring listens for the sound of the blood flowing back through the artery using a stethoscope or observes the pressure reading on the device. The readings indicate systolic and diastolic blood pressure, which are vital signs indicating the health of the cardiovascular system.

In contrast, the stethoscope is an instrument used to listen to internal sounds of a patient’s body, often used in conjunction with a sphygmomanometer, but it does not measure blood pressure by itself. The thermometer measures body temperature and is unrelated to blood pressure measurement. The pulse oximeter is designed to measure the oxygen saturation of a person's blood, providing another important health metric, but it does not measure blood pressure. Therefore, the correct choice, relating specifically to blood pressure measurement, is the sphygmomanometer.