Measuring principle of pulse oximeter

In addition to heart rate, blood pressure, respiratory rate and temperature, pulse oximetry (PO) is considered to be the fifth most important health indicator. Hemoglobin (Hb) is an important component of blood cells. It is responsible for transporting oxygen from the lungs to other tissues in the body. The amount of oxygen contained in hemoglobin at any time is called oxygen saturation. Oxygen saturation is expressed as a percentage, which is the ratio of the oxygen content of hemoglobin to the oxygen carrying capacity of hemoglobin. Blood oxygen saturation is an important physiological parameter that reflects whether the human respiratory function and oxygen content are normal. It is an important physiological parameter that shows whether the various tissues of our body are healthy. Severe hypoxia will directly lead to tragedies such as suffocation, shock and death. In developed countries such as Europe and the United States, people attach great importance to the monitoring of blood oxygenation, and the oximeter has a very high penetration rate.

Based on changes in light absorption during arterial pulse. Two light sources located in the visible red light spectrum (660 nanometers) and the infrared spectrum (940 nanometers) alternately illuminate the area to be tested (generally fingertips or earlobe). The amount of light absorbed during these pulsations is related to the oxygen content in the blood. The microprocessor calculates the ratio of the two spectra absorbed, and compares the result with the saturation value table stored in the memory to obtain the hemorrhagic oxygen saturation.

A typical oximeter sensor has a pair of LEDs that face a photodiode through the translucent part of the patient's body (usually the fingertip or earlobe). One of the LEDs is red and the wavelength is 660nm; the other is infrared and the wavelength is 940nm. The percentage of blood oxygen is calculated based on measuring the light of these two wavelengths with different absorption rates passing through the body.

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Susan F.//SMC Editor