Signal processing apparatus and method
First Claim
1. A method of determining an indication of blood oxygen saturation comprising the steps of:
- transmitting light of at least first and second wavelengths through body tissue carrying blood to a light-sensitive detector to generate first and second measured intensity signals;
filtering at least one of said first and second intensity signals with an adaptive canceler to provide at least one output signal; and
calculating oxygen saturation based upon said at least one output signal.
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Accused Products
Abstract
A signal processor which acquires a first signal, including a first desired signal portion and a first undesired signal portion, and a second signal, including a second desired signal portion and a second undesired signal portion, wherein the first and second desired signal portions are correlated. The signals may be acquired by propagating energy through a medium and measuring an attenuated signal after transmission or reflection. Alternatively, the signals may be acquired by measuring energy generated by the medium. A processor generates a noise reference signal which is a combination of only the undesired signal portions and is correlated to both the first and second undesired signal portions. The noise reference signal is then used to remove the undesired portion of each of the first and second measured signals via an adaptive noise canceler, preferably of the joint process estimator type. The processor may be employed in conjunction with an adaptive noise canceler in physiological monitors wherein the know properties of energy attenuation through a medium are used to determine physiological characteristics of the medium. Many physiological conditions, such as the pulse of a patient or the concentration of a constituent in a medium, can be determined from the desired portion of the signal after undesired signal portions, such as those caused by erratic motion, are removed.
560 Citations
44 Claims
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1. A method of determining an indication of blood oxygen saturation comprising the steps of:
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transmitting light of at least first and second wavelengths through body tissue carrying blood to a light-sensitive detector to generate first and second measured intensity signals;
filtering at least one of said first and second intensity signals with an adaptive canceler to provide at least one output signal; and
calculating oxygen saturation based upon said at least one output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
multiplying at least one of said first and second intensity signals by a predetermined constant and subtracting the result from the other of said first and second intensity signals to provide a reference signal; and
filtering at least one of said first and second intensity signals based upon said reference signal.
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11. The method of claim 5, wherein said step of filtering at least one of said first and second intensity signals with an adaptive canceler comprises the steps of:
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multiplying at least one of the digital representations of said first and second intensity signals by a predetermined constant and subtracting the result from the other of said first and second intensity signals to provide a reference signal; and
adaptively filtering at least one of the digital representations of said first and second intensity signals based upon said reference signal.
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12. The method of claim 11, further comprising the step of filtering said first and second signals with a predetermined filter prior to filtering at least one of said first and second intensity signals with an adaptive canceler.
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13. The method of claim 5, where said adaptive canceler is a dynamic multiple notch filter.
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14. The method of claim 13, wherein said adaptive canceler adjusts its transfer function in accordance with a predetermined algorithm.
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15. The method of claim 14, wherein said predetermined algorithm is a least-squares algorithm.
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16. A pulse oximeter which measures the oxygen saturation of blood in body tissue, said pulse oximeter comprising:
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a light emitter adapted to emit light of at least first and second wavelengths;
a light detector responsive to light from said light emitter which has passed through body tissue having blood, said light detector providing intensity signals;
an adaptive filter responsive to said intensity signals to provide at least one filtered signal; and
a oxygen saturation module responsive to at least said filtered signal to calculate oxygen saturation of said blood. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A pulse oximeter which measures the oxygen saturation of blood in body tissue, said pulse oximeter comprising:
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a light emitter adapted to emit light of at least first and second wavelengths;
a light detector responsive to light from said light emitter which has passed through body tissue having blood, said light detector providing intensity signals;
a digital to analog converter which digitizes the intensity signals from said light detector;
a multiple notch filter responsive to said intensity signals after conversion with said digital to analog converter to provide at least one filtered signal; and
an oxygen saturation module responsive to at least said filtered signal to calculate oxygen saturation of said blood. - View Dependent Claims (27)
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28. A pulse oximeter which measures the oxygen saturation of blood in body tissue, said pulse oximeter comprising:
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a light emitter adapted to emit light of at least first and second wavelengths;
a light detector responsive to light from said light emitter which has passed through body tissue having blood, said light detector providing intensity signals having desired and undesired signal portions;
an analog to digital converter which digitizes the intensity signals from said light detector;
an adaptive signal processor responsive to that operates to process said intensity signals to adaptively filter said intensity signals to provide processed intensity signals; and
an oxygen saturation module routine responsive to at least one signal said processed intensity signals to calculate oxygen saturation of said blood. - View Dependent Claims (29, 30, 31, 32)
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- 33. A method for determining oxygen saturation of blood in body tissue, the method comprising the steps of:
- 39. A pulse oximeter comprising:
Specification