Cardiovascular artifact filter
First Claim
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1. For suppressing cardiovascular artifact from a respiration signal derived from a patient, a filtering device comprising:
- heat beat detecting means for detecting heart beats of the patient;
processing means for determining the heart rate of the patient in response to the detected heart beats; and
filtering means operable for sampling the respiration signal in proportion to the heart rate and producing a filtered respiration signal as follows;
space="preserve" listing-type="equation">Filtered Respiration Signal=S.sub.(t) +(K.sub.1 +K.sub.2)Z.sup.-1.sub.(t-1) +(K.sub.3 +K.sub.4)Z.sup.-2.sub.(t-1)where;
S.sub.(t) is the respiration signal currently being sampled;
space="preserve" listing-type="equation">Z.sup.-1.sub.(t) =S.sub.(t) +K.sub.1 Z.sup.-1.sub.(t-1) +K.sub.3 Z.sup.-2.sub.(t-1)
space="preserve" listing-type="equation">Z.sup.-2.sub.(t) =Z.sup.1.sub.(t-1) ;
andK1, K2, K3, and K4 are constants.
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Abstract
For suppressing cardiovascular artifact from a respiration signal derived from a patient'"'"'s transthoracic impedance, an adaptive filtering device determines the patient'"'"'s heart rate, converts the respiration signal from an analog to digital representation at a rate proportional to the heart rate, and then filters the digital respiration signal such that that portion of the respiration signal having a frequency content at or above the heart rate is most greatly attenuated.
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Citations
5 Claims
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1. For suppressing cardiovascular artifact from a respiration signal derived from a patient, a filtering device comprising:
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heat beat detecting means for detecting heart beats of the patient; processing means for determining the heart rate of the patient in response to the detected heart beats; and filtering means operable for sampling the respiration signal in proportion to the heart rate and producing a filtered respiration signal as follows;
space="preserve" listing-type="equation">Filtered Respiration Signal=S.sub.(t) +(K.sub.1 +K.sub.2)Z.sup.-1.sub.(t-1) +(K.sub.3 +K.sub.4)Z.sup.-2.sub.(t-1)where; S.sub.(t) is the respiration signal currently being sampled;
space="preserve" listing-type="equation">Z.sup.-1.sub.(t) =S.sub.(t) +K.sub.1 Z.sup.-1.sub.(t-1) +K.sub.3 Z.sup.-2.sub.(t-1)
space="preserve" listing-type="equation">Z.sup.-2.sub.(t) =Z.sup.1.sub.(t-1) ;and K1, K2, K3, and K4 are constants. - View Dependent Claims (2, 3, 4, 5)
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Specification