Finger-clip oximeter, blood oxygen watch, blood oxygen app... Which one is more reliable? We did a scientific evaluation and doctors gave us professional advice. Save it now!

The Year of the Rabbit is getting closer and closer. After a period of "sheep sheep", recently, in addition to various medicines and masks, blood oximeters must be added to everyone's "New Year must-buy" list. Many people have placed orders online for a week and are still waiting in line for delivery... If you can't buy a blood oximeter, many smart watches and bracelets with blood oxygen detection functions have become everyone's second choice, and even mobile phone apps and mini-programs that can measure blood oxygen have appeared. So are the above products that can self-test blood oxygen saturation at home reliable? Metropolis Express and Science Popularization China have jointly conducted a scientific evaluation for everyone, full of dry goods, don't miss it!

【one】

Science TIME

How much do you know about the indicators and detection principles of the blood oximeter that everyone is scrambling for?

①What is human blood oxygen saturation?

Oxygen enters the human blood through the respiratory system and combines with hemoglobin in the blood to form oxygenated hemoglobin, which is then transported to the tissues and cells of various parts of the human body. What we usually call blood oxygen saturation refers to the blood oxygen saturation of the arteries. During the test, the principle of different absorption rates of hemoglobin and oxygenated hemoglobin at different electromagnetic wavelengths is used to measure the absorption rates of two beams of light with different wavelengths, and the ratio of oxygenated hemoglobin to hemoglobin is calculated.

②Why does COVID-19 cause hypoxia?

The new coronavirus infection causes hypoxia because the coronavirus enters the lungs and attacks the alveolar epithelial cells, causing diffuse alveolar damage and a large amount of inflammatory exudate. The lungs show varying degrees of consolidation, which affects the gas exchange function of the lungs, and oxygen cannot enter the blood, causing hypoxia.

③When do you need to test your blood oxygen at home?

If you have symptoms of hypoxia after COVID-19 infection, you can test your blood oxygen regularly. Symptoms of hypoxia include rapid heartbeat, rapid breathing, chest tightness, shortness of breath, poor appetite, fatigue, and poor spirits.

④ What should we pay attention to when the blood sample data is low? What should we do if the data is too low?

Normally, oxygen saturation should be 95% or above. If it is below 90%, there is definitely hypoxia, which should be taken seriously and medical attention should be sought as soon as possible. If medical attention cannot be sought immediately, measures should be taken to relieve hypoxia, check whether the patient has airway obstruction, and turn the patient over and pat the back to promote sputum drainage.

丨Experts of this issue丨

Li Qian

Zhejiang Provincial People's Hospital

Deputy Director of Emergency Medicine

●Understand the principle

Finger-clip oximeter, smart watch, sports bracelet, mobile phone APP, blood oxygen measurement applet

The working principle of these product tests is the same. They use a technology called photoplethysmography, or PPG for short.

By emitting low-intensity infrared light, mainly 660nm red LED and 880nm infrared LED, the hemoglobin (special protein that transports oxygen in red blood cells) in human blood is observed and monitored to absorb infrared light in oxygenated and non-oxygenated states. There will be different reflection results, and the human body's blood oxygen saturation is calculated through the light reflection from subcutaneous blood vessels.

Finger clip oximeter - There is an LED light that emits low-intensity infrared light and a corresponding sensing photodiode. When we put our fingers in place, the low-intensity infrared light is emitted through the fingers and received by the photodiode, which is converted into an electrical signal. By analyzing the electrical signal, the corresponding blood oxygen saturation is determined.

Smart watches and wristbands are different from finger-clip oximeters because they use a "reflective" method. The LED light that emits and the photodiode that receives the signal are designed on the same plane, and the current blood oxygen saturation is determined by monitoring the signal reflected back by the LED light penetrating the wrist tissue.

The flash of the mobile phone emits light, illuminating the finger, and the camera collects light data and measures the blood oxygen saturation through calculation. The working principle is similar to that of finger-clip oximeters, watches, and bracelets. However, due to the different performance of different mobile phone cameras, the accuracy of blood oxygen saturation is not accurate.

【two】

Product reliability evaluation

Experiments are the proof

In order to verify the products available to consumers on the market, we prepared home finger-clip oximeters, smart watches, smart bracelets, mobile phone apps, and WeChat mini-programs. Next, we will do a real-life test, using them under the same conditions to see if the blood oxygen saturation values ​​they measure are accurate.

Experiment 1

Real person test

Three experimenters used the above four methods to test blood oxygen saturation and made statistical tables.

From the overall data, the three test data of the two finger-clip oximeters are basically consistent. The most accurate one is the finger-clip oximeter, after all, it is a professional medical device. It is difficult to ensure that the wrist and the dial are tightly fitted when we wear smart bracelets and watches. In addition, PPG measurement is more susceptible to interference from light, movement and skin color absorption rate, so the blood oxygen value measured by such products cannot remain the same every time. The three experimenters of the WeChat applet conducted multiple tests, and the data obtained were all the same, which makes people doubt the accuracy and is not recommended.

Experiment 2

Testing other items

Recently, many netizens have posted their own blood oxygen measuring devices, which can measure the blood oxygen saturation of all kinds of strange things, questioning the scientific nature of blood oxygen testing. Let's test this.

We prepare items of different materials and colors, and test them with different products to see if the problem can be detected.

All three devices have measured data a few times, but in most cases they cannot be detected normally.

●Hard-core interpretation·√Key points

The most accurate one is the clip-on blood oximeter , which is a professional medical device after all. However, you should be careful when purchasing it. Many cheap blood oximeters only cost a few dozen dollars, but their quality is questionable. You should identify big brands and buy products that meet national standards .

Although devices such as smart watches and sports bracelets have disadvantages compared to medical oximeters in terms of measurement location and have a certain gap in measurement accuracy , the gap is gradually narrowing with the upgrade of optical sensor hardware and the iteration of algorithms. Moreover, these products are very convenient to use because they are worn all the time and monitored in real time .

Mobile apps and mini-programs are almost free to use, but their test results are relatively inaccurate .

The above methods of self-testing blood oxygen at home are actually for reference only. Users should combine their own physical conditions. Once the value is too low, they should seek medical attention immediately.

I wish you all a healthy New Year!

Producer: Science Popularization China

Contractor: Metropolis Express

Planning: Han Xiaojuan, Teng Jinyao

Editor: Li Xue, Jin Jingxin