Blood pressure measurement with a mercury sphygmomanometer requires the use of a qualified instrument, the adoption of an appropriate body position, and the correct reading of blood pressure readings. Instrument: A qualified bench-top mercury sphygmomanometer approved and regularly calibrated by the national metrology department. Measurement position: sitting or lying position is acceptable. The sitting position requires the preparation of a table and a chair with a backrest that is suitable for the patient’s arm height; the lying position requires the preparation of a treatment bed where the patient’s elbow can be abducted. The upper arm is exposed and the cuff is tied at the same level as the heart. Measurement process: Turn on the sphygmomanometer switch and observe whether the level of the mercury column is flush with the 0 point. The middle of the cuff is placed on the upper arm, with the edge of the cuff above the elbow fossa. The cuff is loosened and tightened enough to fit 2 fingers. The brachial artery is palpated and the stethoscope body piece is placed on the brachial artery. Determine the blood pressure reading: Observe the height of the rising mercury column and raise it by 20-30 mmHg after the pressure in the balloon has reached the disappearance of the brachial artery pulsation, then deflate slowly and evenly at a rate of 2-4 mmHg per second, while looking horizontally at the convex surface of the mercury column. During the deflation process, when the first brachial artery beat is heard, the vertical height of the convex surface of the mercury column is the systolic pressure. As the mercury column descends, the sound suddenly becomes smaller and eventually disappears, and the value shown in the column is the diastolic pressure. The blood pressure value is recorded by rapidly deflating to zero with a tail number of 2. Regardless of the position used for measurement, the balloon should be positioned at the same height as the level of the right atrium when measuring blood pressure.