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1. The influence of the length and width of the blood pressure cuff on blood pressure measurement


According to the principle of measuring blood pressure with a cuff sphygmomanometer, the selection of the cuff should be: the ratio of the length of the cuff balloon to the circumference of the upper arm is 0.8, and the ratio of the width to the circumference of the upper arm is 0.4. In real life, we use the same size cuff to measure the blood pressure of different ages, different weight, and different parts (upper and lower limbs). Now most of the sphygmomanometer cuff airbags we use are about 24cm in length and 12cm in width. It is suitable for measuring the blood pressure of those whose upper arm circumference is 30cm. Using such a cuff to measure the circumference of the upper arm less than 30cm (children, thin people), the measured blood pressure is lower than the actual blood pressure, and the measurement of the circumference of the upper arm is greater than 30cm (obese people, thighs), the measured blood pressure is higher than actual blood pressure. The larger the circumference distance of 30cm, the larger the measured error.


This is because when the same disposable cuff acts on a thin person, a smaller amount of inflation in the air bag (the pressure in the cuff) can block the arterial blood flow, and the blood pressure measured at this time is lower than normal; Obese people require more inflation (pressure in the cuff), which results in higher blood pressure.


2. The influence of tightness and position of blood pressure cuff on blood pressure measurement


When measuring blood pressure, the tightness of the BP cuff should be appropriate, just enough to insert an index finger, and the position of the cuff should be 2-3cm away from the elbow fossa. If the cuff is too tight, the measured blood pressure value is lower than the actual blood pressure; if the cuff is too loose, the measured blood pressure value is too high. The principle is that when the air bag is too tight, a small amount of inflation (pressure in the cuff) can block the arterial blood flow, so the measured blood pressure is low. On the contrary, when the air bag is too loose, the air bag is inflated more than normal, and the measured blood pressure is higher than the actual blood pressure.


When the position of the BP cuff is too low, covering the elbow joint, the measured blood pressure value is higher than the actual blood pressure. This is because the position is low, and the balloon that actually compresses the brachial artery is narrowed. At this time, more inflation is required to block the arterial blood flow, and the measured blood pressure is higher than the actual blood pressure.


3. The influence of the air in the blood pressure cuff is not exhausted on the blood pressure measurement


If the air in the cuff is not exhausted, there is still air left in the cuff, and the measured blood pressure value is higher than normal. According to the principle of sphygmomanometer, the tightness of the blood pressure cuff should be enough to fit a finger. This is the standard. When there is air remaining in the cuff, the cuff should be tied to the upper arm. air in the cuff), the cuff is too loose. The blood pressure measured at this time was high.

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