Thoracic or intracardiac impedance detection with automatic vector selection
First Claim
1. A method comprising:
- measuring a first impedance signal between at least first and second electrodes, which define a first electrode configuration, in a subject'"'"'s thorax;
extracting a first cardiac stroke signal from the first impedance signal;
extracting a first respiration signal from the first impedance signal;
extracting a first cardiac amplitude measurement from the first cardiac stroke signal;
extracting a first respiration amplitude measurement from the first cardiac stroke signal;
computing a first comparative measurement between the first cardiac amplitude measurement and the first respiration amplitude measurement;
measuring a second impedance signal between at least third and fourth electrodes, which define a second electrode configuration, in a subject'"'"'s thorax, wherein at least one of the third and fourth electrodes is a different electrode from at least one of the first and second electrodes;
extracting a second cardiac stroke signal from the second impedance signal;
extracting a second respiration signal from the second impedance signal;
extracting a second cardiac amplitude measurement from the second cardiac stroke signal;
extracting a second respiration amplitude measurement from the second cardiac stroke signal;
computing a second comparative measurement between the second cardiac amplitude measurement and the second respiration amplitude measurement; and
using the first and second comparative measurements as a basis for selecting one of the first and second electrode configurations for subsequent extraction of at least one of the respiration and cardiac stroke signals.
1 Assignment
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Accused Products
Abstract
This document discusses, among other things, a cardiac function management device or other implantable medical device that includes a test mode and a diagnostic mode. During a test mode, the device cycles through various electrode configurations for collecting thoracic impedance data. At least one figure of merit is calculated from the impedance data for each such electrode configuration. In one example, only non-arrhythmic beats are used for computing the figure of merit. A particular electrode configuration is automatically selected using the figure of merit. During a diagnostic mode, the device collects impedance data using the selected electrode configuration. In one example, the figure of merit includes a ratio of a cardiac stroke amplitude and a respiration amplitude. Other examples of the figure of merit are also described.
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Citations
41 Claims
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1. A method comprising:
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measuring a first impedance signal between at least first and second electrodes, which define a first electrode configuration, in a subject'"'"'s thorax;
extracting a first cardiac stroke signal from the first impedance signal;
extracting a first respiration signal from the first impedance signal;
extracting a first cardiac amplitude measurement from the first cardiac stroke signal;
extracting a first respiration amplitude measurement from the first cardiac stroke signal;
computing a first comparative measurement between the first cardiac amplitude measurement and the first respiration amplitude measurement;
measuring a second impedance signal between at least third and fourth electrodes, which define a second electrode configuration, in a subject'"'"'s thorax, wherein at least one of the third and fourth electrodes is a different electrode from at least one of the first and second electrodes;
extracting a second cardiac stroke signal from the second impedance signal;
extracting a second respiration signal from the second impedance signal;
extracting a second cardiac amplitude measurement from the second cardiac stroke signal;
extracting a second respiration amplitude measurement from the second cardiac stroke signal;
computing a second comparative measurement between the second cardiac amplitude measurement and the second respiration amplitude measurement; and
using the first and second comparative measurements as a basis for selecting one of the first and second electrode configurations for subsequent extraction of at least one of the respiration and cardiac stroke signals. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method comprising:
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measuring a first impedance signal between at least first and second electrodes, which define a first electrode configuration, in a subject'"'"'s thorax;
extracting a first cardiac stroke signal from the first impedance signal;
extracting a first respiration signal from the first impedance signal;
extracting a first cardiac amplitude measurement from the first cardiac stroke signal;
extracting a first respiration amplitude measurement from the first cardiac stroke signal;
computing a first ratio by dividing the first respiration amplitude measurement by the first cardiac amplitude measurement;
measuring a second impedance signal between at least third and fourth electrodes, which define a second electrode configuration, in a subject'"'"'s thorax, wherein at least one of the third and fourth electrodes is a different electrode from at least one of the first and second electrodes;
extracting a second cardiac stroke signal from the second impedance signal;
extracting a second respiration signal from the second impedance signal;
extracting a second cardiac amplitude measurement from the second cardiac stroke signal;
extracting a second respiration amplitude measurement from the second cardiac stroke signal;
computing a second ratio by dividing the second respiration amplitude measurement by the second cardiac amplitude measurement; and
selecting the first electrode configuration for subsequent extraction of the respiration signal if the first ratio exceeds the second ratio. - View Dependent Claims (9, 10)
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11. A method comprising:
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measuring a first impedance signal between at least first and second electrodes, which define a first electrode configuration, in a subject'"'"'s thorax;
extracting a first cardiac stroke signal from the first impedance signal;
extracting a first respiration signal from the first impedance signal;
extracting a first cardiac amplitude measurement from the first cardiac stroke signal;
extracting a first respiration amplitude measurement from the first cardiac stroke signal;
computing a first ratio by dividing the first cardiac amplitude measurement by the first respiration amplitude measurement;
measuring a second impedance signal between at least third and fourth electrodes, which define a second electrode configuration, in a subject'"'"'s thorax, wherein at least one of the third and fourth electrodes is a different electrode from at least one of the first and second electrodes;
extracting a second cardiac stroke signal from the second impedance signal;
extracting a second respiration signal from the second impedance signal;
extracting a second cardiac amplitude measurement from the second cardiac stroke signal;
extracting a second respiration amplitude measurement from the second cardiac stroke signal;
computing a second ratio by dividing the second cardiac amplitude measurement by the second respiration amplitude measurement; and
selecting the first electrode configuration for subsequent extraction of the cardiac signal if the first ratio exceeds the second ratio. - View Dependent Claims (12, 13)
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14. A method comprising:
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measuring impedance signals in a subject'"'"'s thorax using different corresponding electrode configurations;
extracting, from each of the impedance signals, a cardiac stroke signal and a corresponding respiration signal obtained using the same electrode configuration as the corresponding cardiac stroke signal;
computing ratios between amplitudes of each cardiac stroke signal and the corresponding respiration signal; and
selecting a particular one of the electrode configurations for subsequently measuring an impedance signal to obtain at least one of an respiration signal and a cardiac stroke signal impedance-derived respiration, the selecting the particular one of the electrode configurations determined using values of the ratios relative to at least one of each other and a predefined threshold value. - View Dependent Claims (15, 16)
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17. A system comprising:
an implantable medical device (IMD), the IMD comprising;
an impedance detector circuit, including inputs configured to receive impedance signals from different electrode configurations in a subject'"'"'s thorax;
a cardiac stroke signal filter circuit, coupled to the impedance detector circuit to receive the impedance signals and extract therefrom corresponding cardiac stroke signals;
a respiration signal filter circuit, coupled to the impedance detector circuit to receive the impedance signals and to extract therefrom corresponding respiration signals;
a cardiac stroke amplitude measurement circuit, coupled to the cardiac stroke signal filter circuit to receive the cardiac stroke signals and to extract therefrom corresponding cardiac stroke amplitudes;
a respiration amplitude measurement circuit, coupled to the respiration signal filter circuit to receive the respiration signals and to extract therefrom corresponding respiration amplitudes; and
a processor circuit, including instructions executable or otherwise interpretable to compute comparative measurement between each cardiac stroke amplitude and each corresponding respiration amplitude from the same electrode configuration, and based on relative values of the comparative measurement associated with each electrode configuration to select a particular electrode configuration for use in obtaining at least one of a cardiac stroke signal and a respiration signal for use in a diagnostic or therapeutic algorithm. - View Dependent Claims (18, 19, 20, 21)
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22. A method comprising:
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measuring a first impedance signal between at least first and second electrodes, which define a first electrode configuration, in a subject'"'"'s thorax;
calculating a first figure of merit using the first impedance signal;
measuring a second impedance signal between at least third and fourth electrodes, which define a second electrode configuration, in a subject'"'"'s thorax, wherein at least one of the third and fourth electrodes is a different electrode from at least one of the first and second electrodes;
calculating a second figure of merit using the second impedance signal; and
using values of the first and second figures of merit as a basis for automatically selecting one of the first and second electrode configurations for subsequent diagnostic extraction of one of the first and second impedance signals. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A system comprising:
an implantable medical device (IMD), the IMD comprising;
an impedance detector circuit, including inputs configured to receive impedance signals from different electrode configurations in a subject'"'"'s thorax; and
a processor circuit, including instructions executable or otherwise interpretable to a compute at least one figure of merit from each of the different electrode configurations, and using values of the figure of merit from the different electrode configurations for automatically selecting a particular electrode configuration for use in subsequently obtaining diagnostic impedance data. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41)
Specification