It needs to be accompanied by a stethoscope and readings are taken on the basis of auscultation.
The examinee sits with the upper arm exposed and straightened, with the elbow at the same level as the heart. After confirming that the stethoscope is free of mercury leakage, the air cuff is wrapped around the upper arm evenly and tightly against the skin, with the lower edge about 2.5 cm from the elbow socket.After the examiner has palpated the brachial artery pulsation, the body part of the stethoscope is placed over the pulsation.
Inflate the cuff, inflate and auscultate at the same time, when the brachial artery pulsation disappears, then raise 30mmHg. slowly deflate (2～6mmHg/s), and read with both eyes looking at the surface of the mercury column. The first loud tapping sound heard is the systolic blood pressure, then the sound gradually decreases and becomes softer, and finally the blood pressure value when the sound disappears or is significantly weakened is the diastolic blood pressure.
If you do not know how to use a mercury column sphygmomanometer, you can choose a verified and qualified electronic sphygmomanometer (BHS, AAMI, ESH) or go to the hospital for checkup.