15 January 1996 Phase delays in reflectance pulse oximetry: a Monte Carlo study
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Abstract
In pulse oximetry, the red and infrared intensity fluctuations are often assumed to have the same form. However, we observed strong phase delays between these signals during measurements on the forehead of some of our subjects when no pressure was applied onto the probe, which practically disappeared when pressure was applied on the probe. The signals obtained at different distances from the light source were transformed into fluctuations in the absorption and reduced scattering coefficient by means of results from Monte Carlo simulations. The changes in the reduced scattering coefficient appeared to be inverted when no pressure was applied onto the probe. Although the calculated relation between the red and infrared fluctuations in the absorption coefficient was sometimes free of hysteresis, the ratio between the fluctuations still depend on pressure on the probe, and on the chosen optical properties of the medium.
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Reindert Graaff, A. C. M. Dassel, W. G. Zijlstra, Frits F. M. de Mul, Jan G. Aarnoudse, "Phase delays in reflectance pulse oximetry: a Monte Carlo study", Proc. SPIE 2628, Optical and Imaging Techniques for Biomonitoring, (15 January 1996); doi: 10.1117/12.230004; https://doi.org/10.1117/12.230004
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