Cardiac rhythm management system with painless defibrillation lead impedance measurement
First Claim
1. A method of determining an impedance between first and second defibrillation electrodes, the method comprising:
- delivering a first current, for a first time period, from the first defibrillation electrode to the second defibrillation electrode;
delivering a second current, for a second time period, from the second defibrillation electrode to the first defibrillation electrode, wherein a first charge delivered from the first defibrillation electrode during the first time period is approximately equal in magnitude to a second charge delivered from the second defibrillation electrode during the second time period; and
measuring a voltage associated with the first and second defibrillation electrodes while at least one of the first and second currents is being delivered.
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Abstract
A cardiac rhythm management system includes a defibrillation lead impedance measurement system by which defibrillation lead impedance is measured using a test current source different from the defibrillation output supply. A resulting voltage is measured to determine the defibrillation lead impedance. Using low amplitude test currents (e.g., 10-20 milliamperes) avoids patient discomfort. Charge-balanced test currents avoids charge build-up that may interfere with sensing and avoids electrode degeneration. Different current amplitudes and resulting measured voltages provide a differential defibrillation lead impedance measurement for canceling undesired effects. Bidirectional test currents account for polarity effects on the defibrillation lead impedance measurement. A calibration/correction technique uses measurements of known resistances to correct a measurement of an unknown defibrillation lead impedance measurement.
29 Citations
28 Claims
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1. A method of determining an impedance between first and second defibrillation electrodes, the method comprising:
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delivering a first current, for a first time period, from the first defibrillation electrode to the second defibrillation electrode;
delivering a second current, for a second time period, from the second defibrillation electrode to the first defibrillation electrode, wherein a first charge delivered from the first defibrillation electrode during the first time period is approximately equal in magnitude to a second charge delivered from the second defibrillation electrode during the second time period; and
measuring a voltage associated with the first and second defibrillation electrodes while at least one of the first and second currents is being delivered. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of determining an impedance between first and second defibrillation electrodes, the method comprising:
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sourcing a first current, for a first time period, at the first defibrillation electrode;
sinking a second current, for a second time period, at the first defibrillation electrode, wherein a first charge sourced at the first defibrillation electrode during the first time period is approximately equal in magnitude to a second charge sunk at the first defibrillation electrode during the second time period; and
measuring a voltage associated with the first and second defibrillation electrodes while at least one of the first and second currents is being delivered.
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13. An apparatus for determining an impedance between first and second defibrillation electrodes, the apparatus comprising:
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means for delivering a first current, for a first time period, from the first defibrillation electrode to the second defibrillation electrode;
means for delivering a second current, for a second time period, from the second defibrillation electrode to the first defibrillation electrode, wherein a first charge delivered from the first defibrillation electrode during the first time period is approximately equal in magnitude to a second charge delivered from the second defibrillation electrode during the second time period; and
means for measuring a voltage associated with the first and second defibrillation electrodes while at least one of the first and second currents is being delivered.
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14. An apparatus for determining an impedance between first and second defibrillation electrodes, the apparatus comprising:
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a first current source/sink circuit coupled to the first defibrillation electrode;
a first voltage measurement circuit coupled to the first defibrillation electrode;
a second current source/sink circuit coupled to the second defibrillation electrode;
a controller, providing control signals to the first and second current source/sink circuits for sourcing a first charge at the first electrode and sinking a second charge at the first electrode, wherein the first and second charges are approximately equal in magnitude. - View Dependent Claims (15, 16, 17, 18, 19)
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20. An apparatus for determining an impedance between first and second defibrillation electrodes, the apparatus comprising:
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a first current source/sink circuit;
a first diode, coupling the first current source/sink circuit to the first defibrillation electrode;
a first voltage measurement circuit, coupled to the first defibrillation electrode through the first diode;
a second current source/sink circuit;
a second diode, coupling the second current source/sink circuit to the second defibrillation electrode; and
a second voltage measurement circuit, coupled to the second defibrillation electrode through the second diode. - View Dependent Claims (21, 22, 23)
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24. An apparatus for determining an impedance between first and second defibrillation electrodes, the apparatus comprising:
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a first diode, coupled to the first defibrillation electrode;
a second diode, coupled to the second defibrillation electrode;
a first current source/sink circuit;
a first voltage measurement circuit; and
a multiplexer circuit, coupling at least one of the first current source/sink circuit and the first voltage measurement circuit to each of the first and second defibrillation electrodes through the respective first and second diodes.
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25. An apparatus comprising:
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first and second defibrillation electrodes;
a first diode having an anode and a cathode, the cathode of the first diode coupled to the first defibrillation electrode;
a second diode having an anode and a cathode, the cathode of the second diode coupled to the second defibrillation electrode;
a first current source/sink circuit, coupled to the anode of the first diode;
a second current source/sink circuit, coupled to the anode of the second diode;
a controller, providing control signals to the first and second current source/sink circuits for sourcing a first charge at the first electrode and sinking a second charge at the first electrode, wherein the first and second charges are approximately equal in magnitude;
a first differential voltage measurement circuit, coupled to the anode of the first diode;
a first switching device, coupling the first defibrillation electrode to a ground node;
a second switching device, coupling the second defibrillation electrode to the ground node; and
a defibrillation output supply, coupled to the first defibrillation electrode through a third switching device, and coupled to the second defibrillation electrode through a fourth switching device. - View Dependent Claims (26, 27, 28)
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Specification