Heritage of the tissue-bed oximeter

The pulse oximeter is well established in clinical medicine as a monitor of the efficacy of the cardiorespiratory system. The principle of this device represents the end of a long evolutionary line of noninvasive instruments designed to measure the redness of blood i.e. oxygen saturation. This historical note describes the many ingenious devices that are the heritage of the pulse oximeter, which was described by Nakajima et al. (1979) and Yoshiya et al. (1980).