Pulse oximeters are very simple to use devices where you just have to put your finger and wait for the measurement. Its purpose is to measure the oxygen saturation in the blood.
The normal blood oxygen level is 75 to 100 millimeters of mercury (mm Hg), although below 90 it is already considered low. It is indicative of hypoxemia, that is, a deficit of oxygen in the blood. It is very important to monitor these values in people with heart disease or chronic obstructive pulmonary diseases such as bronchial asthma.
During the COVID-19 pandemic, it has been used a lot because a deficit of oxygen in the blood in a healthy patient is an indicator of a primary infection with respiratory symptoms.