In addition to the invasive test in the hospital, most of the blood oxygen test or pulse oximeter to carry out, and the principle of the oximeter is through the red LED + infrared LED emission of specific wavelengths of light, and then by the equipment to receive the reflected or projected light, the finger clip type oximeter used by the projected, and smart watches and smart bracelets such as the wrist device, taking into account the transmittance and the watch band The smartwatch and smart bracelet wrist devices, considering the transmittance and strap reasons, naturally not good to use the projected type, so they all use the reflective type.
But there are still differences in the accuracy of the two, we take Apple's Apple Watch as an example, we can see when we look at the parameters, Apple's heart rate monitoring function is over the U.S. FDA certification, but its oxygen saturation monitoring is not certified, and most of the smart wearable devices this function has not been certified by the FDA. This can also be seen in the domestic devices, such as Huawei's Watch GT 3 Pro ECG ECG analysis through the national NMPA Class II medical device certification, but through the certification of the wrist oximeter is almost nothing, even if there is also unrelated to smart wearable devices. You can see the smart wearable device program, to reach the medical level of blood oxygen measurement is still difficult.
In contrast, the transmissive finger-clip oximeters have a large number of FDA-approved and NMPA-approved, and the accuracy is generally able to reach ±2% or less. This is because these finger-clip oximeters tend to completely wrap around the test site to avoid interference from other external factors, such as light, wearing looseness, and skin thickness. These certified oximeters can be used in hospitals, while other OTC oximeters, especially smart wearable devices, are still mainly used for general health and exercise scenarios and are not suitable for patients, which is why such devices are noted in the product interface that their oximetry data is not intended for diagnostic or medical use