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The Working Principle of Oximeter

The oximeter uses non-invasive measurement infrared technology to measure the oxygen content in the fingers, toes, and ears. This is the most common place to measure the oxygen content in the blood oxygen.

The measurement object is more accurately called the blood oxygen saturation, or SpO2, The results of the test are expressed in digital form. The main display is the ratio of total oxygen saturation under actual oxygen content. It is generally expressed as a percentage.

The typical blood oxygen saturation of the human body is 90-100%, but the lowest can also be over. To 60%. The blood oxygen saturation of the human body depends on many factors. The most important factor is the poor blood supply capacity of the patient’s body and the reading of HbO2 will decrease.

The working principle of oximeter

By driving a red LED (660nm) and an infrared LED (910nm) in turn, the blue line indicates the sensitivity curve of the receiving tube to reduced hemoglobin when hemoglobin does not carry a hundred molecules of oxygen. From the graph, you can see the reduced hemoglobin pair The absorption of 660nm red light is relatively strong, while the absorption length of 910nm infrared light is relatively weak. The red line represents the induction curve of the hemoglobin and the red blood cell with oxygen molecules in the receiving tube to the oxygenated hemoglobin, the absorption channel of 660nm red light is relatively weak, and the absorption of 910nm infrared light is relatively strong.

When measuring blood oxygen, reducing hemoglobin and aerobic hemoglobin, by detecting the difference between the two kinds of light absorption of different wavelengths, the measured data difference is the most basic data for measuring blood oxygen saturation. In the blood oxygen test, the two most common wavelengths of 660nm and 910nm, in fact, to achieve higher accuracy, in addition to the two wavelengths, there are even up to 8 wavelengths. The main reason is that the human hemoglobin is not only reduced In addition to hemoglobin and oxyhemoglobin, but there are also other hemoglobins. We often see carbon-weighted oxyhemoglobin. More wavelengths will help you make better accuracy.

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