Biomed story songPulse oximetry
The Pulse in the Light
Tokyo, 1972. An engineer measuring blood with dye and light kept seeing a wobble in his signal with every heartbeat, and instead of filtering it out he used it to read oxygen in the blood.
A biomed story song. Diagrams are simplified to tell the story; it is not a service procedure.
The story behind it: Pulse oximetry
Takuo Aoyagi, an engineer at the Japanese medical company Nihon Kohden, was working in 1972 on an earpiece that used light and an injected dye to measure how much blood the heart pumps. The pulsing of arterial blood made his readings wobble with every heartbeat.
He realised that the pulsing part of the signal came only from arterial blood, so comparing how red and infrared light changed with each pulse could reveal how much oxygen that blood was carrying, with no needle. The first ear oximeter based on his idea appeared in the mid-1970s, and later fingertip probes made pulse oximetry a routine vital sign in hospitals.
Reviewed November 1, 2026. General information, not a service procedure: follow the manufacturer's instructions and your facility's policy.
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