sphygmomanometer

This device measures blood pressure. An inflatable cuff is wrapped around the upper arm and inflated. This squeezes a large artery in the arm, stopping the blood flow for a moment. Blood pressure is measured as air is let out of the cuff and blood flows through the artery again. Listening with a stethoscope over the artery allows a doctor or nurse to hear the first pulse as the blood flows through. This is the systolic pressure. The diastolic pressure is noted when the sounds stop.