Abstract: Non-invasive oximetry wherein red and infrared light from light sources energized at different frequencies is applied to arterial blood-containing tissue of a living subject. The red and infrared light coming from this tissue is sensed in order to obtain frequency-muliplexed information as to the absorption of said light by said tissue, the information being processed in order to derive therefrom a measure of percent oxygen saturation of said blood. The processing includes filtering for separating information represented by red light absorption from information represented by infrared light absorption. In particular, both notch and bandpass filters are used, and AM detectors provide for further separating such information into DC and AC components.

Abstract: A sensor for placement against the tissue of a living subject for the purpose of measuring a physiological quantity. The sensor includes a rigid housing having a recess chamber formed therein. A light source and sensor is mounted in a flexible mounting pad secured to the housing. The flexible mounting pad allows the light source and sensor to move independently of each other and conforms to the adjacent tissue.