Blood pressure is the force per unit area that blood places on the inside wall of a blood vessel and is measured in millimetres of mercury

Blood pressure is the force per unit area that blood places on the inside wall of a blood vessel and is measured in millimetres of mercury (mm Hg). Sphygmomanometer is the device used to measure arterial blood pressure. Firstly, a cuff is wrapped around the arm such that when inflated , it completely compresses the brachial artery against the muscles of the humerus, temporarily stopping the blood flow. After that air is gradually released from the cuff in the meanwhile a health-care practitioner places a stethoscope just distal to the compressed artery and listens for blood flow. Once the first pulsation is heard through the stethoscope, the sphygmomanometer is read. The reading on the dial at this time is the systolic blood pressure. The health-care practitioner continue to listen to artery pulsations, and when the pulsations stop, the sphygmomanometer is read again for measurement of diastolic blood pressure.