Is it practical for smart watches to measure blood oxygen?

A common symptom of patients with new coronary pneumonia is "decreased blood oxygen content". As a vital sign, blood oxygen content is an important physiological parameter reflecting respiratory and circulatory functions, but its concept and importance are little known. This time, we will continue to discuss the principle of blood oxygen saturation detection by smart wearable devices.

The first thing to explain is why choose smart wearable devices to detect blood oxygen saturation, rather than medical devices? In our daily life, there are several scenarios that may require blood oxygen saturation detection:

1. When engaging in outdoor sports such as mountaineering. We know that the higher the altitude, the thinner the air, and the lower the oxygen saturation of the human body. When you are engaged in outdoor activities at high altitudes, monitoring blood oxygen saturation can evaluate your physical condition in real time, so as to adjust the current exercise intensity to cope with the changing environment.

Second, drinking. The human body needs three units of oxygen to completely break down one unit of alcohol. Therefore, hypoxia is one of the important manifestations of drunkenness. However, long-term alcoholics have developed a certain tolerance to alcohol and hypoxia, and they are basically undetectable when they are slightly drunk. Such people need to pay more attention to monitoring blood oxygen changes when drinking.

3. Carry out high-intensity mental work. The oxygen consumption of the brain accounts for 20% of the oxygen consumption of the whole body. During high-intensity mental work, the oxygen consumption of the brain will inevitably increase. The human body can take in limited oxygen, and the consumption of more and less intake will not only cause dizziness, fatigue, unresponsiveness and other problems, but also cause damage 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 scenarios that people need to monitor their own blood oxygen saturation during specific activities and sports, and have the needs of "convenience" and "immediacy". Although compared with professional medical equipment, smart wearable devices such as sports bracelets are slightly inferior in data accuracy, but they are better than "dynamic tracking" and "real-time feedback", so they are more suitable for sports enthusiasts.

So, what is the principle of smart wearable devices to detect blood oxygen saturation?

The oxygen needed for our metabolism enters the body through the respiratory system, combines with the hemoglobin in the red blood cells to form oxyhemoglobin, and then transports it to the cells of various parts of the human body. Therefore, blood hemoglobin is the key to accurately detect blood oxygen saturation. On the other hand, the level of oxygen contained in hemoglobin affects the absorption of red and infrared light by the blood. Specifically, oxygen-saturated hemoglobin absorbs more infrared light, and oxygen-free hemoglobin absorbs more red light.

Usually, Smart SpO2 Watch such as smart bracelets or watches use photoelectric sensors to perform optical measurements based on the principle that the amount of light absorbed by arterial blood changes with the pulse of the arteries. There are two light-emitting tubes installed in the sports watch, which emit red light and infrared light respectively, and a photodetector is installed to convert the detected red light and infrared light through the arterial blood vessels into electrical signals to obtain a set of data. Based on this data, using a background algorithm, the sports watch is able to calculate an estimate of the user's blood oxygen saturation.

It can also be seen that the calculated result is not an absolutely accurate value, but an estimated value. So will this value lose its guiding significance?

According to the medical definition, the oxygen saturation of human arterial blood is about 95%-100% under normal circumstances, and the oxygen saturation 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 based on interval values, blood oxygen saturation detected by wearable devices such as sports watches can still help people effectively judge their physical condition.

For example, when mountaineering at an altitude of 3000 meters or more, if the heart rate does not exceed 100, it is normal for the blood oxygen saturation to be greater than 90%; between 80% and 90% is mild hypoxia, and activities should be reduced. , Proper rest; between 70%-80% is moderate hypoxia, appropriate amount of oxygen should be inhaled, and anti-hypoxia drugs should be taken; less than 70% is severe hypoxia, all activities should be stopped, and medical treatment should be timely.

After understanding the principle of blood oxygen saturation detection of smart wearable devices, you can judge whether you need to purchase according to your own actual situation.