Sphygmomanometer

A sphygmomanometer is an inflatable cuff used to measure blood pressure. It is placed around the upper arm, at roughly the same vertical height as the heart in a sitting person, and attached to a manometer. The cuff is inflated until the artery is completely occluded. Listening with a stethoscope to the brachial artery at the elbow, the examiner slowly releases the pressure in the cuff. When bloodflow barely begins again in the artery, a "whooshing" or pounding sound is heard (see Korotkoff sounds). The pressure is noted at which this sound began. This is the systolic blood pressure. The cuff pressure is further released until the sound can no longer be heard. This is the diastolic blood pressure. The peak pressure in the arteries during the cardiac cycle is the systolic pressure, and the lowest pressure (at the resting phase of the cardiac cycle) is the diastolic pressure.