IEEE transactions on bio-medical engineering
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A bivariate version of Andrews plots is introduced for naturally paired multivariate data. The bivariate Andrews plots are space curves, and are particularly effective for revealing patterns and clusters when depicted dynamically. Projections of the bivariate Andrews plots recover the familiar univariate Andrews plots.
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IEEE Trans Biomed Eng · Dec 1991
Simple photon diffusion analysis of the effects of multiple scattering on pulse oximetry.
Photon diffusion theory is used to derive analytical expressions that relate the ac-dc intensity ratios measured by transmission-mode and reflectance-mode pulse oximeters to arterial oxygen saturation (SaO2). The effects of multiple scattering are examined by comparing the results of the photon diffusion analysis with those obtained using an analysis based on the Beer-Lambert law which neglects scattering. ⋯ After evaluating the relationship between SaO2 and the red/IR ac-dc ratio (R) under a variety of physiological conditions, we conclude that, for oximeters utilizing fixed calibration curves based on measurements obtained from normal subjects, errors introduced by interfering variables should be less than a few percent when SaO2 exceeds 70%. Predicted errors at lower oxygen saturation values are substantially greater because R is much more sensitive to interfering variables in this measurement range.