How does a blood oximeter work?

Aguilera

How does a blood oximeter work? [Copy link]

The oximeter uses non-invasive infrared technology to measure the oxygen content in the fingers, toes, and ears, which are the most common places to measure blood oxygen. The more accurate name for the measurement object is blood oxygen saturation, or SpO2, and the test results are expressed in digital form, mainly showing the ratio of total oxygen saturation under actual oxygen content, generally expressed as a percentage. The typical blood oxygen saturation of a healthy human body is 90-100%, but the lowest can be as low as 60%. The blood oxygen saturation of the human body depends on many factors, the most important of which is that the patient's body has a relatively poor blood supply capacity, and the HbO2 reading will decrease.

Working Principle:
By driving a red LED (660nm) and an infrared LED (910nm) in sequence, the blue line indicates the sensing curve of the receiving tube to reduced hemoglobin when hemoglobin does not carry oxygen molecules. From the curve, it can be seen that the absorption of reduced hemoglobin to 660nm red light is relatively strong, while the absorption of 910nm infrared light is relatively weak. The red line indicates the sensing curve of the receiving tube to oxygenated hemoglobin when hemoglobin carries oxygen molecules in red blood cells. The absorption of 660nm red light is relatively weak, and the absorption of 910nm infrared light is relatively strong.

When measuring blood oxygen, the difference in the absorption of light of different wavelengths by reduced hemoglobin and oxygenated hemoglobin is detected, and the measured data difference is the most basic data for measuring blood oxygen saturation. In blood oxygen testing, the two most common wavelengths are 660nm and 910nm. In fact, to achieve higher accuracy, in addition to the two wavelengths, more wavelengths must be added, even up to 8 wavelengths. The main reason is that in addition to reduced hemoglobin and oxygenated hemoglobin, human hemoglobin also has other hemoglobins. The one we often see is carbon oxyhemoglobin. More wavelengths are conducive to better accuracy.

QWE4562009

The ratio of receiving part of the red light component/red light + infrared light is SPO2?

alan000345

So this is how it is detected, no wonder it is so fast.