Measurement of blood pressure:
Blood pressure is usually measured by an instrument called sphygmomanometer; it consists of a mercury manometer. Cuff and hand pump. The cuff is tied around the cubical fossa of the individual then the hand pump is pressed so that air is inflated in the cuff. When the cuff is fully inflated, air pressure is more than blood pressure. So blood flow in the brachial artery is completely obstructed. Now the hand pump is slowly released until the time the appearance of the first sound is heard (by means of a stethoscope put in the cubital fossa*. The manometer reading is now noted this regarding the systolic pressure.
Later the hand pump is slowly released until the time that the sound becomes louder and louder. Later it stops the manometric reading is noted when the sound disappears. This reading is the diastolic blood pressure.