Oximeter for reliable clinical determination of blood oxygen saturation in a fetus
First Claim
1. A quantitative analysis instrument for noninvasive measurement of blood oxygen saturation in a fetus, said instrument comprising:
- a. a source of at least four different wavelengths of light, at least some of said wavelengths being in the range from 500 to 1000 nm;
b. optical means for introducing said wavelengths into said fetus and for collecting at least a portion of said wavelengths that are reflected back from said fetus;
c. a device for positioning said optical means relative to said fetus, whereby at least a portion of said wavelengths are introduced into said fetus and said portion of said reflected wavelengths are collected;
d. at least one detector positioned relative to said optical means for measuring the spectral intensities of said reflected wavelengths during the diastolic portion of the cardiac cycle of said fetus, to obtain a diastolic set of spectral intensities v. wavelengths, and for measuring the spectral intensities of said reflected wavelengths during the systolic portion of said cardiac cycle, to obtain a systolic set of spectral intensities v. wavelengths;
e. electronics including a microprocessor and memory means for, (i) storing said diastolic set of spectral intensifies v. wavelengths and said systolic set of spectral intensities v. wavelengths;
(ii) processing said diastolic and systolic sets of spectral intensities to determine a measure of change between said diastolic and systolic sets to obtain a third set of spectral intensifies v. wavelengths, and (iii) processing said third set of spectral intensifies v. wavelengths to determine a measure of oxygen saturation, said memory means including a multivariate algorithm and a multivariate calibration model, said algorithm using at least three variables; and
f. means, for indicating said determined measure of oxygen saturation.
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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.
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Citations
14 Claims
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1. A quantitative analysis instrument for noninvasive measurement of blood oxygen saturation in a fetus, said instrument comprising:
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a. a source of at least four different wavelengths of light, at least some of said wavelengths being in the range from 500 to 1000 nm; b. optical means for introducing said wavelengths into said fetus and for collecting at least a portion of said wavelengths that are reflected back from said fetus; c. a device for positioning said optical means relative to said fetus, whereby at least a portion of said wavelengths are introduced into said fetus and said portion of said reflected wavelengths are collected; d. at least one detector positioned relative to said optical means for measuring the spectral intensities of said reflected wavelengths during the diastolic portion of the cardiac cycle of said fetus, to obtain a diastolic set of spectral intensities v. wavelengths, and for measuring the spectral intensities of said reflected wavelengths during the systolic portion of said cardiac cycle, to obtain a systolic set of spectral intensities v. wavelengths; e. electronics including a microprocessor and memory means for, (i) storing said diastolic set of spectral intensifies v. wavelengths and said systolic set of spectral intensities v. wavelengths;
(ii) processing said diastolic and systolic sets of spectral intensities to determine a measure of change between said diastolic and systolic sets to obtain a third set of spectral intensifies v. wavelengths, and (iii) processing said third set of spectral intensifies v. wavelengths to determine a measure of oxygen saturation, said memory means including a multivariate algorithm and a multivariate calibration model, said algorithm using at least three variables; andf. means, for indicating said determined measure of oxygen saturation. - View Dependent Claims (2, 3, 4, 5)
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6. A method for noninvasive measurement of blood oxygen saturation in a fetus, said method comprising the steps of:
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a. generating at least four different wavelengths of light, some of said wavelengths being in the range from 500 to 1000 nm; b. irradiating said fetus with said wavelengths and collecting a portion of said wavelengths that are reflected back from said fetus; c. measuring the spectral intensities of said reflected wavelengths during the diastolic portion of the cardiac cycle of said fetus, to obtain a diastolic set of spectral intensities v. wavelengths, and measuring the spectral intensities of said reflected wavelengths during the systolic portion of said cardiac cycle, to obtain a systolic set of spectral intensities v. wavelengths; and d. determining a third set of spectral intensities v. wavelengths from said diastolic and systolic sets of spectral intensities, and determining a measure of oxygen saturation from said third set of spectral intensities v. wavelengths utilizing a multivariate algorithm and a multivariate calibration model, said algorithm using at least three variables. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14)
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Specification