Pulse Oximetry

Pulse oximetry is sometimes referred to as the fifth vital sign; it is a quick and non-invasive monitoring technique that measures the oxygen saturation in the blood by shining light at specific wavelengths through tissue, most commonly the fingernail bed. Deoxygenated and oxygenated hemoglobin absorb light at different wavelengths, 660 nm, and 940 nm, respectively. The absorbed light is processed by a proprietary algorithm in the pulse oximeter to display a saturation value. In most developed countries, pulse oximetry is the standard of care to use pulse oximetry to monitor oxygen saturation for patients receiving anesthesia.

Pulse oximetry is also used in emergency departments, hospital wards, and ambulances to assess blood oxygenation in patients with respiratory difficulties or to monitor the potential respiratory depressant effects of pain medications. Since the widespread use of pulse oximetry in hospitals was instituted, the incidence of unrecognized oxygen desaturation has decreased significantly.

In addition to hospital-grade pulse oximeters, newer and much smaller consumer-grade models are rapidly gaining popularity in sports, private aviation, mountain climbing, and other recreational activity communities. Because of the size and cost of consumer-grade models, many patients with chronic respiratory illnesses purchase these devices to monitor their oxygen saturation or to titrate their medications or oxygen flow at home. Of note, the Food and Drug Administration has not evaluated most consumer-grade devices regarding their reliability to diagnose or treat diseases.