History of Pulse Oximeters

Long before the discovery of pulse oximetry, arterial blood gases were the prime diagnostic tests to measure the saturation of oxygen in patients. In most cases, anesthetists rely on the physical appearance of the patient to detect hypoxemia (low blood oxygen) associated to the administration of anesthesia. Back then, the mortality rates were higher compared after the development of the device that was a radical innovation in the field of respiratory care.

The beginning of pulse oximetry can be traced back to the late 1800s when Karl von Vierordt, a German physician innovated tools that monitor blood circulation and attempted to use light to measure blood saturation. Ludwig Nicolai used this idea in 1931 and measured transmission of red light through a hand.

By the 1930s, researchers have started using spectrophotometers to gauge light transmission through the skin. In 1935, Karl Matthes introduced the “ear oximeter” or ear oxygen meter that used two wavelengths of light. It wasn’t until the Second World War when the value of oximetry became pronounced due to the dangers of hypoxia (low oxygenation of body tissues) in pilots. In 1949, Earl Wood mathematically developed the ear oximeter by adding the idea of a pneumatic cuff and modifying previous ear oximeters. The oximeter underwent through a lot of modifications over the years but it only became available to the clinical setting when the Hewlett-Packard Company brought it to the market.

The current pulse oximeter came to being when Japanese bioengineers Takuo Aoyagi and Michio Kishi at Nihon Koden calculated the ratio of red to infrared light absorption that was transmitted through an earpiece. Primarily, it was Takuo Aoyagi who noticed the pulsating changes in light absorption and related this to the density of blood in the site. The resulting device became the pioneer of modern pulse oximetry. In the 1980s, the device became commercially available and continuously developed by companies for respiratory therapists and anesthesiologists. Later, it became applicable in almost every clinical setting including the neonatal intensive care units. The first finger pulse oximeter made its first appearance on the market in 1995.

Today, a number of manufacturers are producing a wide array of pulse oximeters with digital displays and alarms that are assured of better accuracy in reading the oxygen saturation of the blood.