What factors affect the accuracy of pulse oximeter readings?

When we use pulse oximeters for home use to understand our health, we all hope to get accurate results. But in fact, many people may find that the values ​​measured at different times and in different states are different, and sometimes the measurement results are confusing. This is because the accuracy of pulse oximeter readings does not depend entirely on the instrument itself, but is affected by a combination of factors from multiple aspects. From the quality and age of the equipment itself, to the user's personal physical condition, behavioral habits, and the surrounding environmental conditions, each link may have an effect on the final measurement results.

Equipment factors

Equipment quality

The quality of handheld pulse oximeters on the market varies. Some cheap, rough-made, no-name oximeters have poor accuracy and stability of core components such as internal sensors and circuit boards. It's like if you buy a cheap plastic toy watch, it will definitely not be as accurate as a professional mechanical watch. Good oximeters, such as those from big brands that have undergone strict quality testing and certification, are more guaranteed in terms of accuracy.

Equipment aging

Even a pulse oximeter of good quality will become "ineffective" after a long time of use. Generally speaking, after a few years of use, the sensor sensitivity of the oximeter will decrease and the battery performance will also deteriorate. This is like our mobile phones. After a long time of use, the battery life is not good and the camera photos are not so clear. When the oximeter ages, the measured blood oxygen saturation and pulse rate values ​​may be biased.

User's own factors

Physical condition

Anemia: People with anemia have lower hemoglobin content in their blood than normal people. Hemoglobin is the "small truck" responsible for transporting oxygen. The less "truck", the less oxygen transported. At this time, although the pulse oximeter can measure the blood oxygen saturation, because of the low hemoglobin itself, this value may not truly reflect the actual amount of oxygen obtained by the body tissue.

Poor peripheral circulation: For example, people with Raynaud's disease and diabetic peripheral vascular disease have poor blood circulation in their limbs. The fingertip pulse oximeter mainly obtains data by detecting the blood in the fingers, toes and other parts. When the blood circulation in these places is poor, the blood flow is not smooth, and it is difficult for the oximeter to measure accurately, and the measured value may be low.

Limb activity

If you keep moving your fingers or shaking your limbs greatly during measurement, the reading of the oximeter will be unstable. Because it needs stable light to penetrate the skin and tissue to detect the oxygen content in the blood during measurement, limb activity will interfere with the normal detection of light, causing the measurement results to fluctuate, sometimes high and sometimes low, and you don’t know which value is accurate.

Skin condition

Nails: Applying thick nail polish, especially dark nail polish, such as black and dark blue, is like covering your fingers with a layer of "shading cloth". It is difficult for light to penetrate this layer of "cloth" to detect blood, which will affect the measurement results and make the readings low. There are also people who have done nail art stickers, which will also affect the measurement.

Skin color: People with darker skin color, the pigment in the skin will absorb some light, which will also interfere with the detection of the oximeter. However, some advanced oximeters now use algorithms to minimize this effect, but there may still be some errors.

Environmental factors

Temperature

In a cold environment, peripheral blood vessels will contract to reduce heat loss. At this time, the blood flow in the fingers, toes and other parts will decrease, just like a water pipe becomes thinner and the water flow becomes smaller. The signal detected by the oximeter becomes weaker and the measurement result may be inaccurate. On the contrary, too high a temperature, such as measuring in a very hot sauna, may also affect the accuracy of the measurement.

Light

Strong external light, such as direct sunlight or surgical shadowless light, will interfere with the light detection emitted by the oximeter itself. Imagine that it is difficult to see the content on the mobile phone screen under the sun. The same is true for the oximeter. The strong external light will make it "unclear" the oxygen situation in the blood, thereby affecting the accuracy of the reading.

Electromagnetic Interference

There are many electronic devices in hospitals, such as MRI machines and CT machines, which generate strong electromagnetic fields when working. If a pulse oximeter is used in such an environment, these electromagnetic fields may interfere with the electronic components inside the oximeter, resulting in inaccurate measurement results. Similarly, similar problems may occur when measuring near strong electromagnetic sources such as large motors and substations.