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Health care PCB:How does intelligent wearable medical equipment monitor heart rate?

Article source:Medical Technology NetworkEditor:Sun&Lynn Mobile phone view
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Popularity:41Dated :03-20-2020 10:08【big well Small

    As an important medium of intelligent medical treatment, the explosive growth of intelligent bracelet in recent days has increasingly narrowed the direct distance between health-grade and medical-grade medical devices. Heart rate monitoring, which was originally a professional diagnosis, has also moved from hospitals to families. Health care PCBSo intelligent bracelet monitoring heart rate is unreliable? What principle does it use to carry out such professional work?

    1:PPG PhotoPlethysmoGraphy (Photoplethysmography), which is the most widely used working principle in intelligent bracelets, is simply to convert light reflection into electrical signals according to pulsating changes of light transmittance in blood, and then convert into heart rate using certain algorithms.

智能可穿戴医疗设备是如何监测心率的

    It is based on the principle that when a light beam with a fixed wavelength irradiates the skin surface, the light beam will transmit the light to the photoelectric receiver through transmission or reflection. During this process, the light intensity detected by the detector will be weakened due to attenuation caused by absorption by skin muscle and blood. The absorption of light by skin, muscle tissue, etc. remains constant throughout the blood circulation, but the blood volume in the skin changes pulsatively under the action of the heart. When the heart contracts, the peripheral blood volume is the largest, the light absorption is the largest, and the detected light intensity is the smallest. When the heart relaxes, on the other hand, the detected light intensity is the largest, making the light intensity received by the light receiver fluctuate accordingly.

    The reason why most smart bracelet LED lamps on the market are green is that the absorption rate of green light in red blood is the largest, and the data can be judged most accurately by green light detection. When a person's exercise is in a relatively stable state, his heart rate is relatively stable. As long as the pulse strength of the heart at different times is detected, the corresponding heart rate can be calculated through the algorithm.

智能可穿戴医疗设备是如何监测心率的

    However, this is only limited to sit down, sleep, walk and run when the exercise is relatively stable. If the heart rate is high and low in the case of accelerating, decelerating and playing basketball, it is difficult to calculate the accurate heart rate by this method. In addition, the light absorption rate of sweat is not fixed due to a large amount of sweat on the skin during vigorous exercise, which will also affect the measurement accuracy. However, considering that most users of smart bracelets do not need to detect the heart rate during strenuous exercise as a health management parameter most of the time, this defect is unnecessary.

    2. ECG signal measurement is similar to ECG (electrocardiogram). This method uses potential difference of human body to detect heart rate, which is similar to ECG in hospital. The tissues and body fluids around the heart can conduct electricity, so the human body can be seen as a volume conductor with three dimensions of length, width and thickness. The heart is like a power supply. Every heartbeat, the action of myocardial cells will cause tiny electrode changes on the human body surface. After capturing these electrode changes, the frequency of heart rate beat can be restored through the algorithm. At present, only a few smart bracelets and watches on the market use this principle to work.

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