Blood oxygen saturation is measured by directing infrared light through the blood vessels in the finger.

A pulse oximeter is an indispensable device for: for people on home oxygen therapy people with asthma and chronic obstructive pulmonary disease for patients with heart failure in people with dyspnoea on a different background irreplaceable during shifts in hospital emergency departments and admission rooms an important element of ambulance and medical transport teams equipment necessary at work in every department, especially in pulmonology, internal medicine, cardiology, and geriatrics useful in nursing homes, hospices, retirement homes