Implantable stimulation device having synchronous sampling for a respiration sensor
First Claim
1. An implantable cardiac device for delivering electrical stimulation to the heart, the device comprising:
- a sensing circuit adapted to detect a heart signal indicative of electrical activity of the heart;
an impedance sensor adapted to measure a body parameter that is indicative of the ventilation and cardiac activity of the patient and provide an unfiltered impedance signal indicative thereof; and
a processor which receives the unfiltered impedance signal and the heart signal, wherein the processor is adapted to use the heart signal and the impedance signal to control the delivery of therapeutic stimulation to the heart, wherein the processor is further adapted to trigger the minute ventilation sensor to measure the body parameter indicative of the ventilation and cardiac activity during intervals of time selected so that the contribution to the impedance signal resulting from the action of the heart can be discounted so as to allow the processor to develop a minute ventilation parameter from the unfiltered impedance signal.
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Accused Products
Abstract
An implantable cardiac device that is adapted to periodically measure a body parameter, such as transthoracic impedance, at time periods selected so that the body parameter is primarily indicative of the respiration of the patient. In this way, a ventilation parameter, such as minute ventilation, can be reconstructed from the signals without requiring filtering of the sampled signals. In one embodiment, the implantable cardiac device measures transthoracic impedance during each quiescent period of the heart and thereby obtains a plurality of transthoracic impedance data points which are then used to reconstruct a ventilation signal. As the transthoracic impedance data points are obtained during the quiescent period, the contribution of the heart to the resulting transthoracic impedance measurement can be ignored and the resulting measurements are indicative of the action of the heart. In another embodiment, the implantable cardiac device obtains transthoracic impedance signals during the zero crossings of the measured impedance signal. As the transthoracic signal is measured during the zero crossing of the measured impedance signal, the heart component of the signal is filtered out.
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Citations
42 Claims
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1. An implantable cardiac device for delivering electrical stimulation to the heart, the device comprising:
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a sensing circuit adapted to detect a heart signal indicative of electrical activity of the heart;
an impedance sensor adapted to measure a body parameter that is indicative of the ventilation and cardiac activity of the patient and provide an unfiltered impedance signal indicative thereof; and
a processor which receives the unfiltered impedance signal and the heart signal, wherein the processor is adapted to use the heart signal and the impedance signal to control the delivery of therapeutic stimulation to the heart, wherein the processor is further adapted to trigger the minute ventilation sensor to measure the body parameter indicative of the ventilation and cardiac activity during intervals of time selected so that the contribution to the impedance signal resulting from the action of the heart can be discounted so as to allow the processor to develop a minute ventilation parameter from the unfiltered impedance signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An implantable cardiac device for delivering electrical stimulation to the heart of a patient, the device comprising:
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means for stimulating the heart of a patient;
sensing means for providing a signal indicative of the function of the heart;
ventilation means for measuring a body parameter indicative of the patient'"'"'s ventilation and for providing a parameter signal indicative thereof;
processing means for processing the parameter signal from the ventilation means to develop a ventilation parameter, wherein the processing means induces the ventilation means to measure the body parameter during time periods when the contribution of the heart to the body parameter can be discounted so that the ventilation parameter can be developed by the processing means without filtering to remove the contribution of the heart to the ventilation parameter. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An implantable cardiac device, comprising:
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a sensor adapted to obtain a heart signal indicative of the action of the heart;
an impedance measurement circuit that obtains transthoracic impedance measurements; and
a control unit that receives the heart signal and triggers the impedance measurement circuit to obtain the impedance measurements during a time period selected based on the heart signal so that the contribution to the impedance measurement due to the activity of the heart is negligible so that the impedance measurement is primarily indicative of the respiration of the patient, the control unit further programmed to control stimulation therapy based on the impedance measurement. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30)
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31. A method of obtaining a ventilation parameter for an implantable cardiac device which can be used to provide therapeutic stimulation to the heart of the patient, the method comprising:
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obtaining a heart signal indicative of the electrical function of the heart;
evaluating the heart signal so as to determine a quiescent time period;
periodically measuring the transthoracic impedance of the patient during the quiescent time period, wherein the quiescent time period is selected so that the contribution of the heart to resulting impedance measurement is reduced such that an impedance measurement indicative of the patient'"'"'s ventilation can be obtained with reduced filtering of the sampled measurement; and
processing the periodically obtained impedance measurements to produce a ventilation parameter that can be used to vary the delivery of therapeutic stimulation to the heart of the patient. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38)
determining the occurrence of an R-wave; and
measuring a delay period following the occurrence of the R-wave, wherein the delay period is selected so that the quiescent time period corresponds to the delay period following the occurrence of the R-wave.
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34. The method of claim 31, wherein periodically measuring the transthoracic impedance of the patient comprises sending a impedance measurement waveform from the lead implanted to a case electrode within the body of the patient.
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35. The method of claim 34, wherein periodically measuring the transthoracic impedance measurement comprises obtaining at least four impedance measurements during each ventilation cycle of the patient.
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36. The method of claim 35, wherein processing the periodically obtained impedance measurements to obtain the ventilation parameter comprises mathematically reconstructing a ventilation signal corresponding to the ventilation of the patient.
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37. The method of claim 36, wherein processing the periodically obtained impedance measurement further comprises producing a minute ventilation parameter from the ventilation signal.
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38. The method of claim 37, further comprising adjusting the delivery of therapeutic stimulation to the heart based at least in part on the minute ventilation parameter.
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39. A method of obtaining a ventilation parameter for an implantable cardiac device which can be used to provide therapeutic stimulation to the heart of the patient, the method comprising:
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obtaining a heart signal indicative of the function of the heart;
evaluating the heart signal so as to determine the frequency of the heart signal and the corresponding period;
periodically measuring the transthoracic impedance of the patient at a selected interval during each period of the heart signal such that the resulting transthoracic impedance measurements are indicative of the patient'"'"'s ventilation activity; and
processing the periodically obtained transthoracic impedance measurements so as to obtain a curve that corresponds to the component of the transthoracic impedance that is the result of the patient'"'"'s ventilation activity without filtering the heart component of the transthoracic impedance measurements. - View Dependent Claims (40, 41, 42)
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Specification