Noninvasive pulse oximetry utilizing skin reflectance photoplethysmography

The major concern in developing a sensor for reflectance pulse oximetry is the ability to measure large and stable photoplethysmograms from light which is backscattered from the skin. Utilizing a prototype optical reflectance sensor, locally heating the skin is shown to increase the pulsatile component of the reflected photoplethysmograms. Additional improvements to signal-to-noise ratio were achieved by increasing the active area of the photodetector and optimizing the separation distance between the light source and photodetector. The results from a series of in vivo studies to evaluate a prototype skin-reflectance pulse oximeter in humans are presented.