Blood pressure is one of the vital signs of the human body, blood pressure measurement needs to wind the cuff loosely and tightly, generally requires that the cuff under the cuff can be stuffed into 1 ~ – 2 fingers as appropriate, the purpose of doing so is to allow the cuff evenly in the arm to produce pressure. If the cuff is too loose and no pressure is generated, the cuff will swell and bulge, which is like a gas bag pressed against a blood vessel, requiring more pumping to block the arterial blood flow, and the blood pressure data measured will be high at this time. On the contrary, if the cuff is wound too tightly, the pressure is already generated without waiting for the pumping, and the blood pressure data measured at this time is on the low side, and the error between high and low is usually not more than 10 mmHg.