Cardiac cycle synchronized sampling of impedance signal
First Claim
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1. A cardiac rhythm management device, comprising:
- a sensor for obtaining a signal indicative of an action of a heart;
an impedance measurement circuit adapted to measure transthoracic impedance;
means for processing the signal indicative of the action of the heart to sample the transthoracic impedance at sampling intervals commenced by fiducial markers in the signal indicative of the action of the heart, the sampling of the impedance signal removing the component of a stroke volume of the heart from the signal and thereby providing ventilation information; and
a therapy circuit for generating and delivering cardiac rhythm management therapy to a patient.
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Abstract
A cardiac rhythm management device for obtaining transthoracic impedance. The device comprises a sensor for obtaining a signal indicative of an action of a heart, an impedance measurement circuit adapted to measure transthoracic impedance and a processor for utilizing the signal indicative of the action of the heart to sample the transthoracic impedance at sampling intervals commenced by fiducial markers in the signal indicative of the action of the heart, where the sampling of the impedance signal removes the component of a stroke volume of the heart from the signal and thereby provides lung ventilation information.
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Citations
45 Claims
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1. A cardiac rhythm management device, comprising:
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a sensor for obtaining a signal indicative of an action of a heart; an impedance measurement circuit adapted to measure transthoracic impedance; means for processing the signal indicative of the action of the heart to sample the transthoracic impedance at sampling intervals commenced by fiducial markers in the signal indicative of the action of the heart, the sampling of the impedance signal removing the component of a stroke volume of the heart from the signal and thereby providing ventilation information; and a therapy circuit for generating and delivering cardiac rhythm management therapy to a patient. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A cardiac rhythm management system comprising:
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at least one endocardial lead adapted to be coupled to a plurality of locations in a thorax of a patient, wherein the at least one endocardial lead includes at least one electrode; and a cardiac rhythm management device coupled to the at least one endocardial lead, wherein the cardiac rhythm management device includes; an exciter adapted to deliver a pulsed current stimulus to an endocardial lead; a signal processor programmed to detect fiducial markers in a signal indicative of the action of the heart, and wherein the signal processor also includes a receiver adapted to obtain transthoracic impedance information responsive to the pulsed current stimulus; a sampling element coupled to the receiver and adapted to cause the receiver to obtain transthoracic impedance in response to an occurrence of a fiducial marker; and a housing for the cardiac rhythm management device, an outer surface of the housing further comprising a housing electrode, wherein the housing electrode is coupled to the exciter. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of measuring transthoracic impedance, the method comprising:
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detecting fiducial markers in a signal indicative of an action of a heart; applying a predetermined pulsed current stimulus across a thorax region of a patient in a predetermined time relationship to an occurrence of a fiducial marker; sampling a voltage across the thorax region while applying the predetermined pulsed current stimulus, such that a component of the voltage from a stroke volume of the heart is substantially constant; and calculating an impedance from the sampled voltage and the current stimulus. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A cardiac rhythm management system comprising:
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a plurality of endocardial leads adapted to be coupled to a plurality of locations in a thorax of a patient, wherein each of the plurality of endocardial leads includes at least one stimulus-applying electrode; and a cardiac rhythm management device coupled to the plurality of endocardial leads, wherein the cardiac rhythm management device includes; a housing for the cardiac rhythm management device, an outer surface of the housing further comprising a further electrode; an exciter, coupled to the electrodes and adapted to deliver a pulsed current stimulus from the endocardial lead electrodes to the housing electrode; a signal processor in communication with the electrodes and programmed to detect fiducial markers in a signal indicative of an action of a heart, and wherein the signal processor also includes a receiver adapted to obtain transthoracic impedance information responsive to the current stimulus; and means for sampling the transthoracic impedance in response to the occurrence of a fiducial marker in the signal indicative of the action of the heart. - View Dependent Claims (33, 34)
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35. A method of treating lung ventilation disorders, the method comprising:
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detecting fiducial markers in a signal indicative of an action of a heart; applying a predetermined pulsed current stimulus across a thorax region of a patient in a predetermined time relationship to the fiducial markers; sampling a voltage across the thorax region while applying the predetermined current stimulus; calculating impedance from the sampled voltage and the current stimulus; determining respiratory activity from the calculated impedance; determining if the respiratory activity falls below a predetermined level; and providing a therapy for stimulating breathing activity if the respiratory activity falls below the predetermined level. - View Dependent Claims (36, 37, 38, 39, 40)
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41. A method of measuring a transthoracic impedance, the method comprising:
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detecting fiducial markers in a signal indicative of the action of the heart; a step of applying a predetermined pulsed current stimulus across a thorax region of a patient in a fixed relationship to the occurrence of a fiducial marker; sampling a voltage across the thorax region when applying the predetermined pulsed current stimulus, such that a component of the voltage from a stroke volume of the heart is substantially constant; and calculating an impedance from the measured voltage and the predetermined pulsed current stimulus. - View Dependent Claims (42, 43, 44, 45)
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Specification