Pulse Oximeter

A pulse oximeter is the device used in pulse oximetry, a noninvasive method for monitoring the oxygen saturation of a patient's blood, and its readings, called peripheral oxygen saturation or SpO2, are typically accurate to within two percent of a direct arterial blood oxygen measurement. The device passes two wavelengths of light through the tissue, usually a fingertip, to a photodetector, and by tracking how the light absorption changes with each heartbeat it distinguishes oxygenated from deoxygenated hemoglobin and calculates the percentage of blood oxygen saturation. The Japanese bioengineers Takuo Aoyagi and Michio Kishi developed the first pulse oximeter in 1972 at the Japanese medical equipment maker Nihon Kohden, working out the ratio of red to infrared light absorption in the pulsating blood at the measurement site.