The main measurements of the pulse oximeter are pulse rate, oxygen saturation, and perfusion index (PI).
The pulse is the pulsation of the superficial artery. The pulse and heartbeat of a normal person are consistent.
The heart rate is the frequency of heartbeats, generally between 60-90 times per minute for most people. However, the heart rate can increase during exercise and stress.
The pulse rate is the number of pulses per minute.
Under normal circumstances, the pulse rate and heart rate are consistent. When atrial fibrillation or frequent premature contractions occur, the pulse rate is less than the heart rate.
Oxygen saturation (abbreviated as SO2) is one of the 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 (HbO2), reduced hemoglobin (Hb), carboxyhemoglobin (CoHb), and methemoglobin (MetHb). The one that makes a reversible combination with oxygen is reduced hemoglobin, and the ones that do not combine with oxygen are carboxyhemoglobin and methemoglobin).
Oxygen saturation is the percentage of the O2 capacity bound in the total blood volume to the total bindable O2 capacity.
The oxygen saturation of normal human arterial blood is 98%, and venous blood is 75%.
It is an important indicator reflecting the oxygen status in the body. It is generally believed that the normal value of oxygen saturation should not be less than 94%. Below 94% is considered oxygen deficient.
Perfusion Index (PI)
Usually, PI is a parameter that can reflect the limb perfusion status of the person being tested, indicating the accuracy of the machine’s detection, that is, it can still be detected under low perfusion and weak perfusion conditions.
Moreover, through the display of PI, it can also show the problems of the person’s own limb condition, that is, when low perfusion occurs, it indicates whether the person has its own reasons such as heart problems, shock, etc., and it can also reflect whether there are external factors such as cold weather, poor peripheral circulation, etc.
PI refers to the Perfusion Index (PI), the PI value reflects the pulsating blood flow situation, that is, it reflects the blood flow perfusion ability. The larger the pulsating blood flow, the more pulsating components, and the larger the PI value. Therefore, the measurement site (skin, nails, bones, etc.) and the patient’s own blood flow perfusion situation (the flow of arterial blood) will affect the PI value. Since the sympathetic nerves will affect the heart rate and arterial blood pressure (affecting the pulsating arterial blood flow), the body’s nervous regulation system or mental state will also indirectly affect the PI value. Therefore, under different anesthesia states, the PI value will also be different.