Millikan oximeter

The Millikan oximeter was the first practical, portable oximeter, invented by the American physiologist Glenn Allan Millikan in 1940 to 1942 and generally acknowledged as the beginning of oximetry in physiology and clinical medicine; Millikan also introduced the word oximeter. In 1940 his former Cambridge advisor Lord Adrian asked him to help the Royal Air Force with a reliable breathing apparatus for pilots who lost consciousness in high-altitude dogfights, and Millikan built a device for monitoring the pilot's state in flight and presented it to the American Physiological Society in 1941. Integrated into the pilot's altitude mask and clasped to the earlobe, its earpiece held an incandescent light bulb, a set of red and green filters and a selenium barrier layer photocell, and it served as the primary sensor in the feedback loop of an oxygen supply system developed by Bendix Corporation. In 1942 it was found that the light it treated as green was largely invisible infrared light.