Pulse Oximeter Working Principle

The basic principle of oxygen saturation detection Oxygen is to maintain the basis of human life, the heart's contraction and relaxation make the body's blood flow through the lungs, a certain amount of reduced hemoglobin (HbR) and oxygen in the lungs combined oxygen And hemoglobin (HbO2), and another about 2% dissolved in the plasma oxygen. The blood is delivered through the arteries to the capillaries, which are then released in the capillaries to maintain the metabolism of the tissue cells. SpO2 is the percentage of oxygen-bound oxygenated hemoglobin (HbO2) in the blood that accounts for the total amount of hemoglobin (Hb) that is bound, ie, the concentration of blood oxygen in the bloodstream, which is an important physiological parameter. The functional oxygen saturation HbO2 concentration and HbO2 Hb concentration ratio, different from the percentage of oxyhemoglobin. Therefore, monitoring of arterial oxygen saturation (SaO2) can assess pulmonary oxygenation and hemoglobin oxygen carrying capacity

Function and Principle Pulse Oximetry SPO2 refers to the percentage of blood oxygen and blood oxygen capacity. SPO2 has been recognized as a noninvasive, responsive, safe and reliable continuous monitoring indicator. It is currently used extensively in anesthesia, surgery and PACU and ICU. According to the spectroscopic properties of HbO2 and Hb in the red and infrared regions, it can be seen that the absorption of HbO2 and Hb in the red region (600-700 nm) is very different. The degree of light absorption and the light scattering The degree depends greatly on the oxygen saturation; and in the infrared spectral region (800 ~ 1000nm), the absorption difference is large, the degree of light absorption and the degree of light scattering mainly hemoglobin content, so the content of HbO2 and Hb different absorption The spectra are also different, so blood in the blood oxygen saturation meter can accurately reflect the blood oxygen saturation according to the contents of HbO2 and Hb, whether arterial or venous blood. 〕: The ratio of the blood reflectance near 660nm and around 900nm (ρ660 / 900) most sensitively reflects changes in oxygen saturation. The clinical general oximeter (such as the Baxter saturation meter) also uses this ratio as a variable . In the photoconductive route, in addition to arterial hemoglobin to absorb light, other tissues (such as skin, soft tissue, venous blood, and capillary blood) can also absorb light. However, when the incident light passes through the finger or earlobe, the light can be absorbed by pulsatile blood and other tissues at the same time, but the light intensity absorbed by both is different. The light intensity (AC) absorbed by pulsating arterial blood changes with the change of arterial pressure wave And change. While the light intensity (DC) absorbed by other tissues does not change with the pulsation and the time, whereby the light absorption ratio R at two wavelengths can be calculated. R = (AC660 / DC660) / (AC940 / DC940). R and SPO2 was negatively correlated, according to the R value, the SPO2 value can be drawn from the standard curve.