Influence of blood pulsation on diagnostic volume in pulse oximetry and photoplethysmography measurements

Recent advances in the development of ultra-compact semiconductor lasers and technology of printed flexible hybrid electronics have opened broad perspectives for the design of new pulse oximetry and photoplethysmography devices. Conceptual design of optical diagnostic devices requires careful selection of various technical parameters, including spectral range, polarization and intensity of incident light, actual size, geometry, and sensitivity of the detector, and mutual position of source and detector on the surface of skin. In current study utilizing a unified Monte Carlo computational tool we explore the variations of diagnostic volume due to arterial blood pulsation for the typical transmitted and back-scattered probing configurations at human finger. The results of computational studies show that the variations of diagnostic volumes due to arterial pulse wave are notably (up to 45%) different in visible and near-infrared spectral ranges both in transmitted and back-scattered probing geometries. While these variations are acceptable for relative measurements in pulse oximetry and/or photoplethysmography, for the absolute measurements an alignment normalization of diagnostic volume is required, and can be done by computational approach utilized in frame of current study.