The main measurement indicators of the oximeter are pulse rate, oxygen saturation, and perfusion index (PI).
1. Measurement index of oximeter: pulse rate
Pulse is the pulsation of the superficial arteries. A normal person's pulse and heartbeat are the same. Heart rate is the frequency at which the heart beats. The average person is between 60--90 times per minute. However, when people exercise and are nervous, their heart rate will increase. Pulse rate is the number of pulses per minute. Normally the pulse rate and heart rate are the same. The pulse rate is lower than the heart rate during atrial fibrillation or frequent premature contractions.
2. Measurement index of the oximeter: oxygen saturation
Pulse SPO2 is one of the most important basic data in clinical medicine. The oxygen consumed by the human body mainly comes from the oxygen carried by hemoglobin (there are four types of hemoglobin in normal blood: oxyhemoglobin, reduced hemoglobin, carboxyhemoglobin, and methemoglobin. Among them, reduced hemoglobin is reversibly bound to oxygen, and carboxyhemoglobin and methemoglobin are not bound to oxygen.)
Usually, the oxygen content in the blood refers to the percentage of the hemoglobin combined with oxygen in the blood to the total hemoglobin. The physical quantity of blood oxygen saturation is used to describe the change of the oxygen content in the blood. Oxygen saturation refers to the percentage of bound O2 volume in the total blood volume of the total bound O2 volume. The oxygen saturation of normal human arterial blood is 98% and that of venous blood is 75%. It is an important indicator to reflect the oxygen status in the body. It is generally believed that the normal value of blood oxygen saturation should not be lower than 94%, and below 94% is regarded as insufficient oxygen supply.
3. Measurement index of oximeter: perfusion index (PI)
Usually PI is used as a parameter index, which can reflect the limb perfusion status of the tested person, indicating the detection accuracy of the oximeter machine. That is, it can still be detected under the conditions of low perfusion and weak perfusion. Moreover, through the display of PI, it can also indicate the subject's own limb condition, that is, when low perfusion occurs, it indicates whether the subject has its own causes, such as heart problems, shock, etc., and can also reflect Whether there are external factors, such as cold weather, poor peripheral circulation, etc., can be judged by the above conditions.
PI refers to the blood perfusion index, and the PI value reflects the pulsatile blood flow, that is, the blood perfusion ability. The greater the pulsatile blood flow, the greater the pulsatile component and the greater the PI value. Therefore, both the measurement site (skin, nails, bones, etc.) and the patient's own blood perfusion (arterial blood flow) will affect the PI value. Since sympathetic nerves affect heart rate and arterial blood pressure (affecting pulsatile arterial blood flow), the body's neuromodulatory system or mental state also indirectly affects PI values. Therefore, under different anesthesia states, the PI value will also be different.