The main measures of the oximeter are pulse rate, blood oxygen saturation, and perfusion index (PI). Blood gen saturation (oxygen saturation SpO 2) is one of the important basic clinical data. Oxygen saturation is the percentage of the combined O2 volume to the total combined O2 volume in the total blood volume.

Principle of operation

The original blood oxygen saturation meter was developed by Millikan in the 1940s. It monitors the ratio of oxygen-carrying hemoglobin to oxygen-less hemoglobin. A typical oximerimeter comes with two light-emitting diodes. The two LEDs face the patient's site to be tested — usually the fingertip or earlobe. One diode releases a beam with a wavelength of 660 nm, and the other one releases either 905,910, or 940 nm. The absorption of both wavelengths by oxyhemoglobin varies greatly from that without oxygen. Using this property, the ratio of the two hemoglobins can be calculated. The process of testing usually does not require blood drawing from the patient. The usual oximetry can also show the patient's pulse. According to the Beer-Lambert law, the ratio R / IR is a function of arterial oxygen saturation (SaO 2), but because the biological tissue is a strong scattering, weak absorption, anisotropic complex optical system, not fully conform to the classical Beer-Lambert law, expressing the measurement between red and infrared light absorbance (R / IR value), and arterial oxygen saturation (SaO 2) mathematical model is difficult. The correspondence of R / IR and SEO 2, i. e., the calibration curve. Most pulse oximeter manufacturers use experimental methods to complete the pre-calibration of products.

Reason for the decreased folding saturation degree

Diseases of the respiratory and circulatory system, body autoregulation dysfunction caused by anesthesia, major surgery trauma, and other injuries caused by treatment and examination

Symptoms: dizziness, weakness, vomiting, severe cases, life-threatening.

Applicable to the crowd People with vascular disease (coronary heart disease, hypertension, hyperlipidemia, cerebral thrombosis) People with respiratory diseases (asthma, bronchitis, old chronic bronchitis, pulmonary heart disease, COPD) Older people over 60 years People who work more than 12 hours a day Extreme exercise and blood oxygen monitoring in alpine hypoxia Long-term alcoholics

Major component

A microprocessor, memory (EPROM and RAM), two digital-to-analog converters controlling the LED, a device that filters and enlarges the signal received by the photodiode, and an analog-to-digital converter that digitizes the received signal to the microprocessor. The LED was placed with the photodiode in small probes in contact with the patient's fingertip or earlobe. Pulse oximeter also generally includes small liquid crystal displays.