Many people may think that it is easy to measure blood pressure, but only a small percentage of people can measure blood pressure in a standardized way. So how can blood pressure be measured correctly? First of all, the person being measured needs to pay attention to the following matters: 1. Do not make any position changes within 5 minutes before the examination, rest quietly and relax mentally. Avoid cold, force, pain, fatigue, eating, smoking and drinking coffee within 30 minutes before the measurement, and empty the bladder. 2, body position: the measured person to take a sitting position, preferably in a reclining chair; bare the right upper arm, elbow placed at the same level as the heart. If peripheral vascular disease is suspected, blood pressure should be measured on both arms at the first visit. In special cases, blood pressure can be measured in the prone or standing position, and in the elderly, diabetic patients and those with frequent postural hypotension, standing blood pressure should also be measured. The standing blood pressure measurement should be taken 2 minutes after the prone position is changed to the standing position. 3, the requirements of the measurement environment: (1) the examination room temperature is appropriate, the ideal room temperature should be about 21 degrees Celsius. (2) Quiet without noise. Measurers need to pay attention to: 1, the choice of sphygmomanometer: before the current mercury column sphygmomanometer is not eliminated can choose to meet the measurement standards of the mercury column sphygmomanometer for measurement. If you use a mechanical barometer or an electronic sphygmomanometer that conforms to international standards (BHS and AAMI), you need to calibrate the values measured at the same time as the mercury column sphygmomanometer. Check the sphygmomanometer, that is, close the airbag valve, pressurized inflatable, such as the mercury column does not rise or there is a gap, it means that the leakage or the amount of mercury is insufficient, the sphygmomanometer can not be used. 2, the cuff binding: the cuff tied to the upper arm of the person being measured, cuff tightness to accommodate two fingers is appropriate. The lower edge of the cuff should be 2.5 cm from the elbow bend. the cuff is at the same level as the heart. In sitting position, the brachial artery is level with the fourth rib cartilage, and in supine position, the brachial artery is level with the mid-axillary line and slightly abducted when extended. 3.Place the chest piece of the stethoscope at the brachial artery in the elbow fossa and fix it with slight pressure. Regardless of the position of the subject, the sphygmomanometer should be placed at the level of the heart. 4.The cuff size should be appropriate and the cuff air bag should wrap at least 80% of the upper arm. Most people’s arm circumference of 25-35cm, it is appropriate to use 13-15cm wide, 30-35cm long airbag cuff specifications, obese or large arm circumference should use a large size cuff, children with a smaller cuff. 5, measurement of rapid inflation, the pressure in the balloon should reach the radial artery pulsation disappeared, at this time the pressure in the cuff is greater than the systolic pressure of the heart, blood flow is blocked, and then rise 30mmHg, and then slowly deflate at a constant rate (2 ~ 6mmHg / sec). Look at the scale indicated by the mercury column with both eyes level. The rate of deflation is slower when the heart rate is slower. Get the diastolic blood pressure reading and then deflate quickly to zero. 6.Listen carefully to the Koch sound during deflation and observe the vertical height of the convex surface of the mercury column in the Ⅰst and Ⅴth phases of the Koch sound. The systolic pressure reading is taken from the first phase of the Koch sound, and the diastolic pressure reading is taken from the fifth phase of the Koch sound (disappearing sound). In children, pregnant women, severe anemia, incomplete aortic valve closure, or those with non-disappearing Koch’s sound, the diastolic pressure is set at the Ⅳth phase of Koch’s sound (the change of sound). 7, blood pressure units expressed in millimeters of mercury (mmHg), millimeters of mercury and kilopascal (kPa) conversion relationship, 1 mmHg = 0.133kPa. 8, the first measurement should be repeated after 2 minutes apart, take the average of the two readings recorded. If the difference between the systolic or diastolic readings of the 2 measurements is >5mmHg, measure again after 2 minutes apart and then take the average of the 3 readings.