Compared with mercury sphygmomanometer, electronic sphygmomanometer has the characteristics of portability and high accuracy. It is an indispensable daily product for patients with hypertension and many middle-aged and elderly people.

Electronic sphygmomanometer is a kind of medical equipment which uses modern electronic technology and the principle of indirect blood pressure measurement to measure blood pressure. At present, most of the home electronic sphygmomanometers on the market use oscillographic method to measure blood pressure. This method is simple, relatively reliable and easy to be realized by electronic circuit. Electronic sphygmomanometer can be divided into arm type and wrist type. Its technology has experienced the development of the first generation, the second generation (arm type) and the third generation (wrist type). Electronic sphygmomanometer has become the main tool for home blood pressure measurement, and is increasingly used in hospitals and other medical institutions.

Circuit structure and working principle of medical electronic sphygmomanometer

Many people (including medical staff) think that electronic sphygmomanometer is not as accurate as mercury sphygmomanometer, because the readings are different. In fact, this is a misunderstanding. Any sphygmomanometer’s repeated pressure measurement is not the same, because the human body’s blood pressure is not relatively fixed like weight or height, but constantly changing. People’s blood pressure rises when they are excited, nervous, exercising, drinking, bathing and smoking. Electronic sphygmomanometer, objective sphygmomanometer.

The electronic sphygmomanometer consists of balloon, cuff, measurement and display panel. Balloon and cuff are exactly the same as mercury sphygmomanometer. The measurement and display part is composed of pressure sensor, LCD display, IC and battery. The internal circuit structure is shown in the figure below.

Circuit structure and working principle of medical electronic sphygmomanometer

The principle of electronic sphygmomanometer is working principle. The sphygmomanometer can be divided into direct type and indirect type. The working principle of the two kinds of sphygmomanometers is different. The direct type uses a pressure sensor to directly measure the pressure change; The working principle of the indirect type is to control the pressure applied to the measured part from the outside, and judge the result of the control and the related information of the generation and disappearance of Coriolis sound. The former can be continuously tested for both arteries and veins, while the latter can only measure arterial systolic and diastolic blood pressure. Indirect measurement methods are divided into auscultation and oscillometry

1) Auscultation, also known as Coriolis sound method, is the gold standard of blood pressure measurement. Coriolis sound method itself is realized and put forward by auscultation method. It takes the external pressure corresponding to the first sound of the audible sound as the systolic pressure, which is equivalent to the highest blood pressure formed by the systolic pressure of the heart in the brachial artery; Diastolic blood pressure (DBP) is recorded when there is no aphasia, which is equivalent to the lowest blood pressure formed in the brachial artery of the heart.

2) The process of blood pressure measurement by oscillometry is the same as that by Kirschner’s method. The cuff is pressurized to block the blood flow of brachial artery, and then slowly decompressed, during which the voice and pressure pulse will come out of the arm. Kirschner’s method is to recognize the voice coming from the arm by hand, and judge the systolic and diastolic blood pressure. The oscillographic method relies on the instrument to identify the small pulses transmitted from the arm to the cuff, and make a difference, so as to get the blood pressure value.

It must be pointed out that in terms of measurement principle, there is no more accurate problem between the two methods, but at present, most blood pressure monitors and automatic electronic sphygmomanometers use oscillographic method to measure blood pressure.


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