Patent ID: 6226540
Filing Date: 2001-05-01
Classification: A61B,G01N

Abstract:
A method of determining the level of oxygenation of arterial blood SaO.sub.2 in tissue in vivo considering optical tissue properties by pulse oximetry, comprising the steps of:a) emitting light through said tissue at a plurality of wavelengths at different instants of time, and different blood flow;b) measuring said light received passing through said tissue at said plurality of wavelengths at said instants of time;c) calculating a plurality of ratios of differential attenuation vs. time, .OMEGA..sub.i corresponding to ##EQU4##for each wavelength pair i=a,b of different frequencies, wherein at least one wavelength pairing is selected based on optical tissue parameters, sufficient wavelength pairings and calibration curves of SaO2 v. .OMEGA..sub.i have been empirically made such that the calibration curves are chosen for .OMEGA..sub.i depending on optical tissue parameters to minimize error in producing an output signal indicative of level of arterial oxygenation;d) calculating at least one attenuation ratio LA.sub.j through said tissue for at least one wavelength, where LA.sub.j corresponds to:LA.sub.j =ln (light intensity received/light intensity emitted);using calibration data of SaO.sub.2 v. .OMEGA..sub.i for at least one said LA.sub.j ; andf) computing the level of oxygenation by comparing measured data with the calibration data.