Measuring process for blood gas analysis sensors
First Claim
1. A method of determining the level of oxygenation of arterial blood SaO2 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 resultant 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, Ω
i which can be calculated as ##EQU3## for each wavelength pair i=a,b of different frequencies;
d) calculating at least one attenuation ratio LAj through said tissue for at least one wavelength where LAj can be calculated as;
LAj =ln (light intensity received/light intensity emitted);
e) obtaining calibration data of SaO2 v. Ω
i for at least one frequency for each said LAj ;
f) computing the level of oxygenation depending by comparing measured data with the calibration data.
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Abstract
The invention relates to a measuring process, the purpose of which is to increase the measuring accuracy of pulse oxymeters and comparable optical devices which are used in vivo to ascertain oxygen saturation of arterial blood. The measuring process according to the invention is provided for the purpose of ascertaining oxygenation of arterial blood in tissue by evaluating the differential light attenuation at several wavelengths. It is characterized by the fact that light attentuation of at least one wavelength is determined in order to choose those calibration curves of several variables (Ω1, Ω2. . . .) produced by different wavelength pairings with a minimized error in order to generate an output signal for the arterial blood oxygenation.
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Citations
16 Claims
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1. A method of determining the level of oxygenation of arterial blood SaO2 in tissue in vivo considering optical tissue properties by pulse oximetry, comprising the steps of:
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a) emitting light through said tissue at a plurality of wavelengths at different instants of time, and different resultant 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, Ω
i which can be calculated as ##EQU3## for each wavelength pair i=a,b of different frequencies;
d) calculating at least one attenuation ratio LAj through said tissue for at least one wavelength where LAj can be calculated as;
LAj =ln (light intensity received/light intensity emitted);e) obtaining calibration data of SaO2 v. Ω
i for at least one frequency for each said LAj ;f) computing the level of oxygenation depending by comparing measured data with the calibration data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification