The person whose blood pressure is to be measured should refrain from smoking, alcohol, coffee, and the intake of foods that cause excitement and stimulation within half an hour before the blood pressure measurement. If the person has just exercised, he or she should sit and rest for at least ten minutes in a quiet environment to calm down and relax, otherwise the activity or tension will lead to a high value. After turning on the sphygmomanometer, turn on the switch to see if the mercury column is at the “0” scale, if not, it should be calibrated, otherwise it will affect the measured value. Turn the balloon switch off, press the cuff with one hand and inflate the cuff with the other hand to see if the mercury column rises or if there is a break in the mercury. If it does not rise or there is a gap, it means that the sphygmomanometer has a leak, or the amount of mercury has decreased, so the sphygmomanometer can no longer be used to measure. When it is hot, the cuffs should be pulled up to reveal most of the upper arm, and it is best to take off the sleeves. When it is cold, reduce the amount of clothing on the measuring arm as much as possible without affecting the warmth, so as not to overload the blood pressure with too much clothing. When measuring blood pressure, the person being measured can be in a sitting or supine position with the upper extremities straight and the elbows at the same level as the heart and slightly outwardly extended. After expelling the gas from the cuff by squeezing the cuff, the central part of the cuff bag with the rubber tube is aligned with the elbow fossa and the cuff is wrapped flatly around the upper arm. The lower end of the cuff is 2-3 cm above the elbow fossa, and the tightness is such that a finger can be placed inside. When measuring, the chest piece of the stethoscope, the stethoscope, should be placed at the brachial artery in the elbow fossa, and should not be tucked inside the cuff for convenience, as this will make the measured blood pressure higher than it actually is. Put on the stethoscope, close the balloon switch, inflate the cuff until the pulsating sound of the brachial artery disappears, and then inflate it again so that the mercury column continues to rise by 20-30 mm Hg. Keep your eyes level with the mercury column scale, open the balloon switch, and deflate the air evenly and slowly at a rate of 4 mm Hg per second, not too fast. During the fall of the mercury column, the scale represented when the first clear beating sound is heard is the systolic blood pressure of the subject. The next beat will be heard all the time, and when the beat suddenly becomes weak or disappears from hearing, the scale indicated is the diastolic blood pressure. If the blood pressure value is too abnormal during the measurement, or if the person does not hear it clearly, the gas in the cuff should be drained first, and the mercury column should be lowered to the “0” scale again, and then a second measurement should be taken after a few moments. Generally, no more than two consecutive measurements should be taken, and the lowest result obtained should prevail. After the measurement, remove the cuff, squeeze to drain the air, turn off the balloon switch, fold it and put it in the box. Be sure not to forget to tilt the lid of the sphygmomanometer 45° to the right so that the mercury is completely returned to the tank, then close the switch on the mercury tank and close the lid. If the mercury is not returned to the tank, it will cause the mercury column to break the next time it is used, and the mercury will evaporate very quickly. Some mercury sphygmomanometers now have clear instructions that they can be used without reflux, and this will have to be treated specifically according to the manufacturer’s product instructions.