The principle of blood pressure measurement is mainly based on the turbulence that can be created by blood flow through narrow arterial ducts. Blood pressure is the pressure of blood flow against the walls of an arterial pipe. Blood pressure falls off very little in larger arteries, and brachial artery blood pressure is generally measured in the upper arm to represent arterial blood pressure. The brachial artery measurement point, the heart, and the sphygmomanometer should be kept at the same level when measuring blood pressure. The cuff is attached to the upper arm and inflated inward. When the cuff airbag pressure is higher than the systolic pressure, completely blocking the brachial artery, the brachial artery pulsation disappears, and the stethoscope placed at the brachial artery does not hear a sound. Continue to inflate the cuff so that the mercury column rises 20-30 mmHg and then slowly relax the airbag. When the pressure of the airbag decreases and is equal to or slightly lower than the systolic pressure, the blood flow suddenly flows into the compressed and narrowed blood vessels, generating turbulence, and the first sound of blood flow can be heard, and at this time, the mercury column reading is the systolic pressure. The airbag pressure continues to decrease, the pressure is equal to or slightly lower than the diastolic pressure, the airbag will not cause pressure on the blood vessel wall, the blood flow is completely smooth, can not hear the sound of blood flow, this time the reading for the diastolic pressure. In addition, it is recommended to take a 15-minute break before measuring blood pressure, and not to drink coffee or strong tea, etc., in order to minimize the influencing factors of blood pressure and make the measurement of blood pressure more accurate. For specific methods and details of blood pressure measurement, consult a medical professional.