SPHYGMOMANOMETER

instrument for measuring blood pressure. It consists of an inflatable rubber cuff, which is wrapped around the upper arm and which is connected to an apparatus that records pressure, usually in terms of the height of a column of mercury or on a dial. A blood pressure reading consists of two numbers, which typically may be recorded as x/y. The x is the systolic pressure, and y is the diastolic. Systole refers to the contraction period of the heart, when it forces blood from the heart into the circulating system, and diastole refers to the resting period, when the heart expands and receives another supply of blood. At each heartbeat, blood pressure is raised to the systolic level, and, between beats, it drops to the diastolic level. As the cuff is inflated with air, a stethoscope is placed against the skin at the crook of the arm. As the air is released, the first sound heard marks the systolic pressure; as the release continues, a dribbling noise is heard. This marks the diastolic pressure.