Signal processing apparatus
DCFirst Claim
1. In a signal processor for processing at least two measured signals S1 and S2 each containing a primary signal portion s and a secondary signal portion n, said signals S1 and S2 being in accordance with the following relationship:
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space="preserve" listing-type="equation">S.sub.1 =s.sub.1 +n.sub.1
space="preserve" listing-type="equation">S.sub.2 =s.sub.2 +n.sub.2where s1 and s2, and n1 and n2 are related by;
s1 =ra s2 and n1 =rv n2and where ra and rv are coefficients,a method comprising the steps of;
determining a value for the coefficient ra which minimizes correlation between s1 and n1 ;
calculating the blood oxygen saturation from said value of ra ; and
displaying the blood oxygen saturation on a display.
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Abstract
The present invention involves method and apparatus for analyzing two measured signals that are modeled as containing primary and secondary portions. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, the present invention involves utilizing a transformation which evaluates a plurality of possible signal coefficients in order to find appropriate coefficients. Alternatively, the present invention involves using statistical functions or Fourier transform and windowing techniques to determine the coefficients relating to two measured signals. Use of this invention is described in particular detail with respect to blood oximetry measurements.
1534 Citations
23 Claims
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1. In a signal processor for processing at least two measured signals S1 and S2 each containing a primary signal portion s and a secondary signal portion n, said signals S1 and S2 being in accordance with the following relationship:
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space="preserve" listing-type="equation">S.sub.1 =s.sub.1 +n.sub.1
space="preserve" listing-type="equation">S.sub.2 =s.sub.2 +n.sub.2where s1 and s2, and n1 and n2 are related by; s1 =ra s2 and n1 =rv n2 and where ra and rv are coefficients, a method comprising the steps of; determining a value for the coefficient ra which minimizes correlation between s1 and n1 ; calculating the blood oxygen saturation from said value of ra ; and displaying the blood oxygen saturation on a display.
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2. In a signal processor for processing at least first and second measured signals S1 and S2 each containing a primary signal portion s and a secondary signal portion n, said signals S1 and S2 being in accordance with the following relationship:
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space="preserve" listing-type="equation">S.sub.1 =s.sub.1 +n.sub.1
space="preserve" listing-type="equation">S.sub.2 =s.sub.2 +n.sub.2where s1 and s2, and n1 and n2 are related by; s1 =ra s2 and n1 =rv n2 and where ra and rv are coefficients, a method comprising the steps of; determining a value for the coefficient ra which minimizes correlation between s1 and n1 ; and processing at least one of the first and second signals using the determined value for ra to significantly reduce n from at least one of the first or second measured signal to form a clean signal. - View Dependent Claims (3, 4, 5, 6, 7)
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8. A physiological monitor comprising:
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a first input configured to receive a first measured signal S1 having a primary portion, s1, and a secondary portion n1 ; a second input configured to received a second measured signal S2 having a primary portion s2 and a secondary portion n2, said first and said second measured signals S1 and S2 being in accordance with the following relationship;
space="preserve" listing-type="equation">S.sub.1 =s.sub.1 +n.sub.1
space="preserve" listing-type="equation">S.sub.2 =s.sub.2 +n.sub.2where s1 and s2, and n1 and n2 are related by; s1 =ra s2 and n1 =rv n2 and where ra and rv are coefficients; a transform module responsive to said first and said second measured signals and responsive to a plurality of possible values for ra to provide at least one power curve as an output; an extremum calculation module responsive to said at least one power curve to select a value for ra which minimizes the correlation between s and n, and to calculate from said value for ra a corresponding saturation value as an output; and a display module responsive to the saturation value output of said extremum calculation module to display said saturation value.
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9. In a signal processor for processing at least firs and second measured signals, each containing a primary signal portion and a secondary signal portion, said first and second signals substantially adhering to a predefined signal model, a method comprising the steps of:
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sampling said first and second signals over a period to obtain a first series of data points representing said first signal over said period and a second series of data points representing said second signal over said period; transforming said first series of data points into a first transformed series of points having at least a frequency component and a magnitude component and transforming said second series of data points into a second transformed series of points having at least a frequency component and a magnitude component; comparing said first and second transformed series of points to obtain a third series of comparison values having a magnitude component and at least a frequency component; selecting at least one of said comparison values that has a magnitude within a selected threshold; and from said selected at least one comparison value, determining a resulting value consistent with the predefined signal model. - View Dependent Claims (10, 11, 12, 13)
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14. In a signal processor for processing at least first and second measured signals, each containing a primary signal portion and a secondary signal portion, said first and second signals substantially adhering to a signal model for blood constituent saturation, a method comprising the steps of:
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sampling said first and second signals over a period to obtain a first series of data points representing said first signal over said period and a second series of data points representing said second signal over said period; transforming said first and second series of data points from time domain to frequency domain to obtain a first transformed series of points and a second transformed series of points, said first and second transformed series of points having a magnitude component and at least a frequency component; determining a series of ratios of magnitudes with respect to frequency of ones of said first transformed series of points to ones of said second transformed series of points; selecting at least one of the ratios from said series of ratios that has a magnitude within a selected threshold; and from said selected at least one of the ratios, determining a resulting value consistent with the signal model. - View Dependent Claims (15, 16, 17, 18, 19)
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20. In a signal processor for processing at least first and second measured signals, each containing a primary signal portion and a secondary signal portion, said first and second signals substantially adhering to a signal model, a method comprising the steps of:
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sampling said first and second signals over a period to obtain a first series of data points representing said first signal over said period and a second series of data points representing said second signal over said period; performing a fast saturation transform with said first and second series of data points to obtain a series of transformed data points in said frequency domain; determining a selected saturation value from said series of transformed data points. - View Dependent Claims (21, 22, 23)
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Specification