Patent EP0522674A2 successfully refreshed from Google Patents.
EP0522674A2
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EP
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Oximeter for reliable clinical determination of blood oxygen saturation in a fetus
Assignee: University of New Mexico
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Filing: 1992-07-10
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Granted: —
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Expires: 2012-07-10
Abstract
Abstract With the crude instrumentation now in use to continuously monitor the status of the fetus at delivery, the obstetrician and labor room staff not only over-recognize the possibility of fetal distress with the resultant rise in operative deliveries, but at times do not identify fetal distress which may result in preventable fetal neurological harm. The invention, which addresses these two basic problems, comprises a method and apparatus for non-invasive determination of blood oxygen saturation in the fetus. The apparatus includes a multiple frequency light source which is coupled to an optical fiber. The output of the fiber is used to illuminate blood containing tissue of the fetus. In the preferred embodiment, the reflected light is transmitted back to the apparatus where the light intensities are simultaneously detected at multiple frequencies. The resulting spectrum is then analyzed for determination of oxygen saturation. The analysis method uses multivariate calibration techniques that compensate for nonlinear spectral response, model interfering spectral responses and detect outlier data with high sensitivity.
Inventors
- 👤 Mark R. Robinson
- 👤 Kenneth J. Ward
- 👤 David M. Haaland
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 11:35
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/145; A61B5/1455; A61B5/1464; A61B5/14542; G; G01; G01N; G01N21/00; G01N21/17; G01N21/25; G01N21/31; A61B5/1495; G01N2201/00; G01N2201/12; G01N2201/129
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
386 words
A method of determining non-invasively and in vivo the blood oxygen level in a mammal, said method comprising the steps of: a. simultaneously generating a plurality of different wavelengths of light, said wavelengths being in the range of 500 nm to 1,000 nm; b. irradiating in vivo and non-invasively blood containing tissue having an unknown blood oxygen level during the diastolic portion of the cardiac cycle of said mammal with said wavelengths of light, so that there is differential attenuation of at least some of said wavelengths by said blood containing tissue as a function of said wavelengths, said differential attenuation causing intensity variations of said wavelengths incident from said blood containing tissue as a function of said wavelengths, said tissue and said unknown blood oxygen level; c. simultaneously measuring said intensity variations from said blood containing tissue during said diastolic portion to obtain a diastolic set of intensity variations v. wavelengths; d. irradiating in vivo and non-invasively said blood containing tissue during the systolic portion of said cardiac cycle of said mammal with said wavelengths of light, so that there is attenuation of at least some of said wavelengths by said blood containing tissue as a function of said wavelengths, said differential attenuation causing intensity variations of said wavelengths incident from said blood containing tissue as a function of said wavelengths, said tissue and said unknown blood oxygen level; e. simultaneously measuring said intensity variations from said blood containing tissue during said systolic portion to obtain a systolic set of intensity variations v. wavelengths; and f. calculating the value of said unknown blood oxygen level in said blood containing tissue from said measured intensity variations during said diastolic portion and said systolic portion of said cardiac cycle utilizing an algorithm and a calibration model, said algorithm being a multivariate algorithm using 3 or more variables and being capable of modeling at least some nonlinearities over the entire clinically observed range of blood oxygen levels, said model being constructed from a set of calibration samples in which the blood oxygen levels are known, and being a function of said known oxygen levels and the intensity variations v. wavelengths obtained from irradiating said set of calibration samples with a plurality of different wavelengths of light, said wavelengths being in the range of 500 nm to 1,000 nm.
Claim 2
Dependent Claim
34 words
The method as set forth in claim 1, further including the step of determining whether said intensity variations v. wavelengths from said blood containing tissue having an unknown blood oxygen level represent an outlier.
Claim 3
Dependent Claim
36 words
The method as set forth in claim 1, further including the step of pretreatment of said measured intensity variations, said pretreatment including centering, scaling, normalizing, taking first or higher order derivatives, smoothing, Fourier transforming or linearization.
Claim 4
Dependent Claim
28 words
The method as set forth in claim 1, wherein said algorithm is selected from the group including PLS, PCR, CLS, Q-matrix method, cross correlation, Kalman filtering and MLR.
Claim 5
Dependent Claim
37 words
The method as set forth in claim 1, wherein said algorithm has decreased sensitivity to noise by signal averaging the effects of intensity variations v. wavelengths when there are more intensities than independent sources of spectral variation.
Claim 6
Dependent Claim
44 words
The method as set forth in claim 1, further including the step of determining the difference between said diastolic set of intensity variations v. wavelengths from said blood containing tissue and said systolic set of intensity variations v. wavelengths from said blood containing tissue.
Claim 7
Dependent Claim
37 words
The method as set forth in claim 6, wherein said determination of said diastolic portion and said systolic portion of said cardiac cycle is accomplished by concurrently measuring the electrical activity of the heart of said mammal.
Claim 8
Dependent Claim
44 words
The method as set forth in claim 6, wherein said light incident on said blood containing tissue is partially absorbed by said tissue and partially diffusely reflected from said tissue, and wherein at least a portion of said reflected light is subsequently simultaneously measured.
Claim 9
Dependent Claim
18 words
The method as set forth in claim 8, wherein said blood containing tissue is that of a fetus.
Claim 10
Dependent Claim
21 words
The method as set forth in claim 9, wherein the measurement of fetal oxygen level is made through the chorio-amniotic membrane.
Claim 11
Dependent Claim
28 words
The method as set forth in claim 1, further including the step of determining whether any of said calibration samples from said set of samples is an outlier.
Claim 12
Independent Claim
238 words
A method of determining invasively and in vivo the oxygen level in a sample of blood, said method comprising the steps of: a. generating a plurality of different wavelengths of light, said wavelengths being in the range of 500 nm to 1,000 nm; b. irradiating said sample with said wavelengths of light so that there is differential attenuation of at least some of said wavelengths by said sample as a function of said wavelengths, said differential attenuation causing intensity variations of said wavelengths incident from said sample as a function of said wavelengths and said unknown blood oxygen level; c. measuring said intensity variations from said sample to obtain a set of intensity variations v. wavelengths; d. calculating the value of said unknown blood oxygen level in said sample from said measured intensity variations v. wavelengths utilizing an algorithm and a calibration model, said algorithm being a multivariate algorithm using 3 or more variables and being capable of modeling at least some nonlinearities over a blood oxygen level range corresponding to oxygen saturations of 30% to 100%, said model being constructed from a set of calibration samples in which the blood oxygen levels are known and being a function of said known blood oxygen levels and intensity variations v. wavelengths obtained from irradiating said set of calibration samples with a plurality of different wavelengths of light, said wavelengths being in the range of 500 nm to 1,000 nm.
Claim 13
Dependent Claim
355 words
An oximeter for accurately and precisely determining the blood oxygen level in a mammal at all levels, including levels corresponding to oxygen saturations of 75% or less, said oximeter comprising: a. means for simultaneously generating a plurality of different wavelengths of light, said wavelengths being in the range of 500 nm to 1,000 nm; b. means for directing at least a portion all of said wavelengths of light to a section of blood continuing tissue of a mammal having an unknown oxygen level, said means for directing including means for coupling to said mammal; c. means for simultaneously collecting at least a portion of said wavelengths of light which are directed from said blood containing tissue to said means for collecting, said means for collecting including said coupling means; d. means, connected to said means for collecting, for simultaneously measuring the intensity of each of said wavelengths collected by said means for collecting; e. means, coupled to said means for measuring, for storing said measured intensity variations v. wavelengths; f. means for storing a calibration model, said model being generated by a multivariate algorithm using 3 or more variables and which is capable of modeling at least some nonlinearities resulting from irradiation of a set of calibration samples in which the blood oxygen levels are known and which span the range of variation of all factors influencing the spectra that are expected to be found in said blood containing tissue, said model being a function of said known blood oxygen levels from said set of calibration samples and the intensity variations v. wavelengths obtained from irradiating said calibration samples with wavelengths of light in the range of 500 nm to 1,000 nm; g. means for storing said multivariate algorithm which utilizes said calibration model and said stored intensity variations v. wavelengths for determination of said unknown blood oxygen level; h. a microprocessor, coupled to said means for storing said calibration model, said means for storing said multi-variate algorithm and said means for storing said intensity variations v. wavelengths, for calculating said unknown blood oxygen level; and i. means for indicating said calculated blood oxygen level.
Claim 14
Dependent Claim
51 words
The oximeter as set forth in claim 13, further including means for determining which of said intensity variations v. wavelengths correspond to the maximum (systolic) and minimum (diastolic) expansion of the vascular system of said mammal and means for determining the differences between said systolic and diastolic intensity variations v. wavelengths.
References Cited (Backward Citations)
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