Pulse oximeters are devices which measure person’s oxygen saturation (SO2) and HR. Its reading of SpO2 (peripheral oxygen saturation) is not always identical to the reading of SaO2 (arterial oxygen saturation) from arterial blood gas analysis, but the two are correlated well enough that the safe, convenient, noninvasive, inexpensive pulse oximetry method is valuable for measuring oxygen saturation in clinical use.
The oximetry is essential in any type of setting:
Emergency rooms, operating rooms, intensive care, sports medicine, aerospace medicine, paediatrics, outpatient medicine.
Most of the oxygen (O2) is transported in the blood by hemoglobin molecules, which are like cars with 4 seats for “special passengers” (the O2 molecules coming in through breathing) inside special “containers”, the red blood cells.
When red blood cells reach the pulmonary alveoli, the O2 molecules try to get into these “cars”, occupying at least 95 percent of the available “seats” in the time it takes for just one breath: technically this means that 95% of the hemoglobin is saturated with oxygen (denoted by SpO2 = 95%).