Compensation of human variability in pulse oximetry
First Claim
1. A method for compensating for subject-specific variability in a pulse oximeter intended for non-invasively determining in in-vivo measurement the amount of at least two light-absorbing substances in the blood of a subject and provided with emitters for emitting radiation at a minimum of two different wavelengths and with a detector for transforming the radiation received into an electrical output signal, the method comprising the steps ofmeasuring a detector output signal when living tissue of the subject is present between the emitters and the detector in a sensor, wherein the detector output signal depends on the tissue,reading from a memory a nominal calibration comprising nominal extinction matrix Ekl0,reading from the memory nominal characteristics describing conditions under which the nominal calibration has been done, the nominal characteristics comprising:
- nominal values for a calculation defining tissue-induced correction to the nominal extinction matrix Ekl0 due to light transmission through living tissue,nominal values for a calculation defining temperature-induced corrections to the nominal extinction matrix Ekl0 due to wavelength shifts caused by changes in emitter temperatures,establishing values for both calculations for the sensor on the living tissue of the subject using the detector output signal,forming a subject-specific calibration by correcting the nominal extinction matrix Ekl0 with both calculations with the established values,solving hemoglobin fractions using the corrected nominal extinction matrix in a Lambert-Beer model.
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Accused Products
Abstract
Provided is a method of calibrating a pulse oximeter, in which the effects caused by tissue of a subject can be taken into account. A detector output signal is measured when living tissue of the subject is present between emitters and the detector in a sensor. Nominal calibration and nominal calibration characteristics are read from a memory, whereupon values for the same nominal characteristics for the sensor on living tissue of the subject are established using the detector output signal. Then, changes in the nominal calibration characteristics induced by the living tissue are calculated and a subject-specific calibration is formed by correcting the nominal calibration with the changes. Finally, the hemoglobin fractions are solved using the corrected nominal calibration.
27 Citations
6 Claims
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1. A method for compensating for subject-specific variability in a pulse oximeter intended for non-invasively determining in in-vivo measurement the amount of at least two light-absorbing substances in the blood of a subject and provided with emitters for emitting radiation at a minimum of two different wavelengths and with a detector for transforming the radiation received into an electrical output signal, the method comprising the steps of
measuring a detector output signal when living tissue of the subject is present between the emitters and the detector in a sensor, wherein the detector output signal depends on the tissue, reading from a memory a nominal calibration comprising nominal extinction matrix Ekl0, reading from the memory nominal characteristics describing conditions under which the nominal calibration has been done, the nominal characteristics comprising: -
nominal values for a calculation defining tissue-induced correction to the nominal extinction matrix Ekl0 due to light transmission through living tissue, nominal values for a calculation defining temperature-induced corrections to the nominal extinction matrix Ekl0 due to wavelength shifts caused by changes in emitter temperatures, establishing values for both calculations for the sensor on the living tissue of the subject using the detector output signal, forming a subject-specific calibration by correcting the nominal extinction matrix Ekl0 with both calculations with the established values, solving hemoglobin fractions using the corrected nominal extinction matrix in a Lambert-Beer model. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification