One common symptom of patients with covid-19 is “decreased blood oxygen content”. Blood oxygen content, as a major vital sign, is an important physiological parameter reflecting respiratory and circulatory functions, but its concept and importance are little known. Xinhua Sports had previously interviewed relevant experts to launch scientific popular article how important is blood oxygen content? Listen to what experts say. This time, Xinhua Sports continued to discuss the principle of detecting blood oxygen saturation by smart wearable devices.
△ can provide respiratory humidification therapeutic apparatus with high oxygen concentration and rapid improvement of blood oxygen. Xinhua Net hair
The first thing to explain is, why choose smart wearable devices to detect blood oxygen saturation instead of medical devices? In our daily life, there are several major scenes that may require blood oxygen saturation detection: first, when engaging in outdoor sports such as mountaineering. We know that the higher the altitude, the thinner the air, the lower the blood oxygen saturation of human body. When you are engaged in outdoor activities in high altitude areas, monitoring blood oxygen saturation can assess the physical condition in real time, thus adjusting the current exercise intensity to cope with the changing environment.
△The guides of Tibet Lhasa Himalayan Mountaineering Guide School are climbing Mount Everest. Xinhua News Agency issued (taken by Tairen Sangzhu)
II. Drinking. For every unit of alcohol completely decomposed, the human body needs three units of oxygen. Therefore, hypoxia is one of the important manifestations of drunkenness. However, people who have been drinking for a long time have formed a certain tolerance to alcohol and hypoxia, which is basically imperceptible when they are slightly drunk. Such people need to pay more attention to monitoring blood oxygen changes when drinking.
Third, carry out high-intensity mental work. Brain oxygen consumption accounts for 20% of the total body oxygen uptake. When performing high-intensity mental work, brain oxygen consumption will inevitably rise. However, the human body can take in limited oxygen, consume more and consume less, which will not only cause dizziness, fatigue, slow response and other problems, but also cause harm to the brain. People who study or work for a long time every day need to strengthen the monitoring of their blood oxygen saturation.
It can be seen from the above scenes that people need to monitor their blood oxygen saturation in specific activities and sports, and have the demand of “convenience” and “immediacy. Although compared with professional medical equipment, smart wearable devices such as sports bracelets are slightly inferior in data accuracy, they are better than “dynamic tracking” and “real-time feedback”, so they are more suitable for sports enthusiasts.
Then, according to what principle does the smart wearable device detect blood oxygen saturation?
The oxygen we need for metabolism enters the body through the respiratory system, combines with hemoglobin in blood red blood cells to oxyhemoglobin, and then sends it to various tissue cells of the human body. Therefore, blood hemoglobin is the key to accurately detect blood oxygen saturation. On the other hand, the oxygen level contained in hemoglobin will affect the absorption of red light and infrared light by blood. Specifically, oxygen-saturated hemoglobin will absorb more infrared light, while hemoglobin without oxygen will absorb more red light.
△The bright color in the figure indicates that the oxygen-saturated hemoglobin will absorb more infrared light.
△The darker color in the figure indicates that hemoglobin without oxygen will absorb more red light.
Generally, smart wearable devices, such as smart wristbands or watches, use photoelectric sensor to make optical measurements based on the principle that the absorption of light from arterial blood changes with arterial pulse. Two luminotron are installed in the sports watch to emit red light and infrared light respectively, and a photodetector is installed to convert the detected red light and infrared light passing through arterial blood vessels into electrical signals to obtain a set of data. According to these data, using the background algorithm, the sports watch can calculate the estimated value of the user’s blood oxygen saturation.
It can also be seen from this that the calculation result is not an absolutely accurate value, but an estimated value. So will this value lose its guiding significance?
According to the medical definition, under normal circumstances, the oxygen saturation of human arterial blood is about 95%-100%, and that of venous blood is about 75%. Generally, arterial blood oxygen less than 94% is insufficient oxygen supply, and less than 90% can be defined as hypoxemia.
Because blood oxygen saturation is evaluated according to interval values, the blood oxygen saturation detected by wearing devices such as sports watches can still help people effectively judge their physical condition.
For example, when climbing above 3000 meters above sea level, when the heart rate is not more than 100, the blood oxygen saturation is greater than 90% is normal; between 80% and 90% belong to mild hypoxia, should reduce activities, appropriate rest; Between 70% and 80% belong to moderate hypoxia, should be appropriate oxygen inhalation, take anti-hypoxia drugs; less than 70% is a severe hypoxia. All activities should be stopped and medical treatment should be timely.
At present, there are many wearable devices with blood oxygen detection function on the market. Huawei, Xiaomi, Jiaming, Suunto and other smart wearable device manufacturers have launched a variety of products. After you understand the principle of blood oxygen saturation detection of smart wearable devices, you can judge whether there is any purchase need according to your actual situation. (Wang Jianbing)