The adequate and healthy percentage of blood oxygen is considered to be between 95% and 100%. Therefore, when saturation is below 90% Hypoxemia occurs, that is, the level of blood oxygen below normal.
And one of its characteristic symptoms is difficulty breathing. Furthermore, when a percentage lower than 80 is given, it is considered Severe Hypoxemia.
It is measured with a device by placing it on the index finger of the hand.