First of all, Oxygen is required for every part of the body. Hemoglobin within the body helps in carrying oxygen to different parts of the body.
There are 2 kinds of hemoglobin: Oxygenated and Deoxygenated hemoglobin:
Now more oxygenated hemoglobin means more saturation level.
You could look at the below table to clarify!
Now coming on to how the oximeter checks oxygen level.
When we put the finger inside the oximeter, There are two rays that come out of the top cover of the oximeter. One Ray is Red Light with wavelength (650nm) and another ray is infrared light with wavelength (950nm). When the rays are passed, oxygenated and deoxygenated hemoglobin absorbs some amount of light rays. Subsequently, photodetectors at the lower part of the oximeter keep the check on the ratio of absorption of red light and infrared light.
After calculating the ratio of absorption of these rays by oxygenated and deoxygenated hemoglobin, it converts this ratio into spo2 reading which is visible on the screen of the oximeter.
A little information in detail, if you want to go deeper into this study.
Believe me, after reading this, you will learn a lot today!
So, talking about the ideal ratio of the oxygenated hemoglobin should be as follows:
The above table simply means that the oxygenated hemoglobin should adsorb less red light and more infrared light to get an ideal (100% spo2).
Whereas; for ...
Here, the graph says that if deoxygenated hemoglobin absorbs more red light and less infrared light, then this gives a 0% spo2 level.
In all to provide a summarize concept, plz look at below chart
Hence, if the graph is more towards the oxygenated hemoglobin then the spo2 level increases. However, it decreases when the line graph moves towards deoxygenated hemoglobin line.
Hope your invested time gave you some knowledge out of it,
Thanks for reading :)