The pulse oximeter works by measuring the absorption of radiation of two different wavelengths - red and infrared - by red blood cells in the capillaries, The measured signal consists of two components: a constant and a variable (pulsating) component. The variable component describes the absorbance of the pulsed arterial blood. From the measurement, the degree of hemoglobin saturation with oxygen is calculated The pulse oximeter also measures the heart rate. 
 
The pulse oximeter is a small device for the rapid measurement of vital signs such as pulse. The correct oxygen saturation level should be between 94 and 99%.
During the test, it is important to remember that the pulse rate should not be tested after physical exertion or in a state of emotional distress. The average heart rate is age-dependent. The pulse oximeter test is best performed in a sitting position, without having performed much physical exertion beforehand.
The pulse oximeter is a device that should be found in every home.
It is intended, mainly for people who have difficulty breathing, people with chronic lung diseases, in asthma, in hypoxia emergencies, in cardiovascular diseases, in heavy physical exertion and in many other cases, as well as for daily health monitoring.