Which instrument is used to measure blood pressure by determining systolic and diastolic pressure?

The sphygmomanometer is the instrument specifically designed to measure blood pressure, which includes both systolic and diastolic pressure readings. It works by inflating a cuff around the patient's arm, which temporarily occludes blood flow in the brachial artery. As the cuff pressure is gradually released, the healthcare provider listens with a stethoscope for the sounds of blood flow – specifically, the first appearance of sound indicates the systolic pressure, while the point at which the sounds disappear corresponds to the diastolic pressure.

In contrast, other instruments listed serve completely different purposes. A glucometer measures blood glucose levels, a stethoscope is primarily a listening device used in conjunction with other instruments (like the sphygmomanometer) to assess internal sounds, and a thermometer measures body temperature. Therefore, while they are all important in clinical practice, only the sphygmomanometer is equipped to directly measure blood pressure.