Signal processing apparatus and method
First Claim
1. A physiological monitoring apparatus comprising:
- means for acquiring a first signal comprising a first desired signal portion and a first undesired signal portion and a second signal comprising a second desired signal portion and a second undesired signal portion;
an adaptive canceler having a reference input for receiving a reference signal and a signal input for receiving said first and said second signals, wherein said adaptive canceler generates an output signal which approximates said first desired signal portion and said second desired portion; and
a processor responsive to the output of said adaptive canceler to calculate a physiological parameter.
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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 sodium and measuring an attenuated signal after transmission or reflection. Alternatively, the signals may be acquired by measuring energy generated by the medium. A processor of the present invention 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 of the present invention may be employed in conjunction with an adaptive noise canceler in physiological monitors wherein the known 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 notion, are removed.
1266 Citations
30 Claims
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1. A physiological monitoring apparatus comprising:
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means for acquiring a first signal comprising a first desired signal portion and a first undesired signal portion and a second signal comprising a second desired signal portion and a second undesired signal portion;
an adaptive canceler having a reference input for receiving a reference signal and a signal input for receiving said first and said second signals, wherein said adaptive canceler generates an output signal which approximates said first desired signal portion and said second desired portion; and
a processor responsive to the output of said adaptive canceler to calculate a physiological parameter. - View Dependent Claims (2, 3)
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4. A pulse oximeter comprising:
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at least first and second light emitting devices;
at least one light detector configured to receive light attenuated by transmission through a living tissue with arterial pulsing blood, the light detector acquiring a first signal based on the first light emitting device comprising a first desired signal portion and a first undesired signal portion and a second signal based on the second light emitting device comprising a second desired signal portion and a second undesired signal portion;
an adaptive filter which filters the first and the second signals through use of an estimate of the first or the second undesired signal portion, wherein the adaptive filter generates an output signal which approximates the first desired signal portion and the second desired signal portion; and
a processor responsive to the output of the adaptive filter to calculate oxygen saturation. - View Dependent Claims (5, 6, 7, 8)
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9. A pulse oximeter comprising:
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at least first and second light emitting devices;
at least one light detector configured to receive light attenuated by transmission through a living tissue with arterial blood, the light detector generating a first signal based on the first light emitting device and a second signal based on the second light emitting device;
a filter responsive to signals representing the first and second signals to filter the first and the second signals, wherein the filter adjusts its transfer function in response to changes in at least one of the first and the second signals and in response to an evaluation of an error to optimize at least one of a first and a second filtered output signals; and
a processor calculator responsive to the first and the second filtered output signals to calculate oxygen saturation. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method of calculating 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;
adaptively filtering representations of the first and second measured intensity signals to provide first and second filtered signals; and
calculating oxygen saturation based upon the first and second filtered signals. - View Dependent Claims (16, 17, 18, 19)
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20. A method of calculating 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 signals;
filtering the first and the second signals, wherein the filtering comprises adjusting a filter transfer function in response to changes in at least one of the first and the second signals and in response to an evaluation of an error, and wherein the filtering optimizes at least one of a first and a second filtered output signal; and
calculating oxygen saturation based upon the first and the second filtered output signals. - View Dependent Claims (21, 22, 23, 24, 25)
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26. A pulse oximeter comprising:
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a light emitter adapted to emit light of at least first and second wavelengths;
at least one light detector configured to receive light attenuated by transmission through a living tissue with arterial pulsing blood, the light detector acquiring a first signal based on the first wavelength and a second signal based on the second wavelength;
an analog to digital converter that digitizes the first and the second signals to produce digitized first and second signals;
an adaptive signal processor responsive to the first and the second digitized signals to filter the first and the second digitized signals, to produce adaptively filtered first and second signals; and
a processor responsive to the adaptively filtered first and second signals to calculate oxygen saturation. - View Dependent Claims (27, 28, 29, 30)
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Specification