Cardiac cycle synchronized sampling of impedance signal
First Claim
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1. A cardiac management system comprising:
- an implantable device, including;
a memory circuit;
an intrinsic cardiac signal sensor;
an impedance measurement circuit configured for generating a sampled transthoracic impedance signal; and
a processor, coupled to the intrinsic cardiac signal sensor and the impedance measurement circuit, the processor configured to;
initiate sampling of a transthoracic impedance signal substantially at an instance of a fiducial marker in a sensed intrinsic cardiac signal, the sampling to attenuate or remove a cardiac stroke component from the transthoracic impedance signal and to preserve a respiratory component of the transthoracic impedance signal; and
measure a time interval between successive occurrences of the fiducial marker indicative of a cardiac cycle and to store a value in the memory circuit representative of the sampled measured transthoracic impedance in correspondence with an indication of the measured time interval; and
determine lung information using the sampled measured transthoracic impedance in correspondence with an indication of the measured time interval.
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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.
255 Citations
26 Claims
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1. A cardiac management system comprising:
an implantable device, including; a memory circuit; an intrinsic cardiac signal sensor; an impedance measurement circuit configured for generating a sampled transthoracic impedance signal; and a processor, coupled to the intrinsic cardiac signal sensor and the impedance measurement circuit, the processor configured to; initiate sampling of a transthoracic impedance signal substantially at an instance of a fiducial marker in a sensed intrinsic cardiac signal, the sampling to attenuate or remove a cardiac stroke component from the transthoracic impedance signal and to preserve a respiratory component of the transthoracic impedance signal; and measure a time interval between successive occurrences of the fiducial marker indicative of a cardiac cycle and to store a value in the memory circuit representative of the sampled measured transthoracic impedance in correspondence with an indication of the measured time interval; and determine lung information using the sampled measured transthoracic impedance in correspondence with an indication of the measured time interval. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of measuring transthoracic impedance with an implantable medical device, the method comprising:
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sensing an intrinsic cardiac signal; generating a transthoracic impedance signal; sampling the transthoracic impedance signal substantially at an instance of a fiducial marker in the sensed intrinsic cardiac signal, wherein the sampling removes a cardiac stroke component from the transthoracic impedance signal and preserves a respiratory component of the transthoracic impedance signal; measuring a time interval between successive occurrences of the fiducial marker indicative of a cardiac cycle; storing a value representative of the sampled measured transthoracic impedance in correspondence with an indication of the measured time interval; and determining lung information using the sampled measured transthoracic impedance in correspondence with an indication of the measured time interval. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification