Safe-mode implantable medical devices

• US 20070021785A1
• Filed: 07/21/2005
• Published: 01/25/2007
• Est. Priority Date: 07/21/2005
• Status: Active Grant

• Current Assignee: Flint Hills Scientific, LLC, LivaNova USA, Inc. (LivaNova Plc)
• Original Assignee: Cyberonics, Inc
• Inventors: Inman, Dana Michael, Armstrong, Randolph, Armstrong, Scott
• Granted Patent: US 8,165,693 B2
• Time in Patent Office: Days
• US Class Current: 607/2
• CPC Class Codes: A61N 1/36082 Cognitive or psychiatric applications, e.g. dementia or Alzheimer's disease
• CPC Class Codes: A61N 1/36114 Cardiac control, e.g. by vagal stimulation stimulating the heart A61N1/362
• CPC Class Codes: A61N 1/36142 for improving safety
• CPC Class Codes: A61N 1/36146 specified by the stimulation parameters
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents

Abstract

A method, system, and apparatus for implementing a safe mode operation of an implantable medical system using impedance adjustment(s) are provided. A first impedance is provided to a lead. An indication of a possibility of a coupled energy is received. Based upon said indication, a second impedance associated with the lead to reduce the coupled energy is provided.

Claims

1. An implantable medical device (IMD) for operating in a modified impedance mode, comprising:

a stimulation unit to provide an electrical stimulation signal through a lead operatively coupled to said IMD; and

a controller comprising

a signal detection unit to receive an indication selected from the group consisting of an indication of the presence of a coupled energy on said lead and an indication of the future presence of a coupled energy on said lead, and

an impedance unit to modify an impedance of said lead based upon said indication received by said signal detection unit.

2. The implantable medical device of claim 1, wherein said signal detection unit comprises at least one of:

a frequency count unit to perform at least one of a frequency division and a frequency count to determine whether said coupled energy is present on said lead;

a bandpass filter comprising at least one of a highpass filter and a lowpass filter to determine whether said coupled energy is present on said lead;

an envelope comparator circuit to determine whether said coupled energy is present on said lead;

a signal threshold detector to determine whether said coupled energy is present on said lead; and

a thermal sensor to determine whether said coupled energy is present on said lead.

3. The implantable medical device of claim 1, wherein said impedance unit comprises:

at least one of a capacitive impedance, an inductive impedance, a resistive impedance, a short-circuit, an open circuit; and

a switching network capable of switching at least one of said capacitive impedance, inductive impedance, resistive impedance, said open circuit, and said short circuit to modify said impedance of said lead.

4. The implantable medical device of claim 1, wherein said impedance unit comprises:

a plurality of capacitive impedances positioned in at least one of a series arrangement and a parallel arrangement;

a plurality of inductive impedances positioned in at least one of a series arrangement and a parallel arrangement;

a plurality of resistive impedances positioned in at least one of a series arrangement and a parallel arrangement; and

a switching network capable of switching at least one of said capacitive impedances, inductive impedances, and resistive impedances to modify said impedance of said lead.

5. The implantable medical device of claim 4, wherein said capacitive impedances, inductive impedances, resistive impedances are arranged in a parallel form with each other.

6. The implantable medical device of claim 4, wherein said switching network comprising:

a plurality of switches to switch between at least one of said capacitive impedances, inductive impedances, and resistive impedances to modify said impedance of said lead; and

a switch controller to control the switching of said switches.

7. The implantable medical device of claim 1, further comprising an active cancellation unit capable of actively reducing said coupled energy.

8. The implantable medical device of claim 7, wherein said active cancellation unit comprises a controlled current source.

9. The implantable medical device of claim 1, wherein said signal detection unit comprises circuitry to receive a signal from an external source indicating a future coupled energy.

10. The implantable medical device of claim 1, wherein said impedance unit comprises an active cancellation unit.

11. The implantable medical device of claim 10, wherein said active cancellation unit comprises a current signal for providing a zero current in the presence of said coupled energy.

12. A medical device system for providing a stimulation signal to a patient, comprising:

an electrode coupled to a tissue in a patient'"'"'s body;

a lead operatively coupled to said electrode, said lead to carry a stimulation signal to said electrode; and

a signal generator operatively coupled to said lead, said signal generator to provide said stimulation signal to said tissue through said lead, said signal generator comprising;

a stimulation unit to provide said stimulation signal through said lead, and

a controller to receive an indication selected from the group consisting of an indication of the presence of a coupled energy and an indication of the future presence of a coupled energy, said controller to also modify an impedance of said lead set based upon said indication.

13. The medical device system of claim 12, wherein said medical device system further comprises:

a plurality of capacitive impedances positioned in at least one of a series arrangement and a parallel arrangement;

a plurality of inductive impedances positioned in at least one of a series arrangement and a parallel arrangement;

a plurality of resistive impedances positioned in at least one of a series arrangement and a parallel arrangement; and

a switching network capable of switching at least one of said capacitive impedances, inductive impedances, and resistive impedances.

14. The medical device system of claim 12, wherein said tissue is at least one of a right vagus nerve, a left vagus nerve, and another cranial nerve.

15. The medical device system of claim 12, wherein said electrical stimulation signal is used to treat a condition selected from the group consisting of depression, epilepsy, and bulimia.

16. The medical device system of claim 12 wherein said controller comprises:

a signal detection unit to receive an indication selected from the group consisting of the presence of a coupled energy on said lead and an indication of the future presence of a coupled energy on said lead, and

an impedance unit to modify an impedance of said lead based upon said indication received by said signal detection unit.

17. The medical device system of claim 16, wherein said signal detection unit comprises circuitry to receive a signal from an external source indicating a future coupled energy.

18. The implantable medical device of claim 12, wherein said signal generator further comprises an active cancellation unit.

19. The implantable medical device of claim 18, wherein said active cancellation unit comprises a current signal for providing a zero current in the presence of said coupled energy.

20. A computer readable program storage device encoded with instructions that, when executed by a computer, performs a method for reducing coupled energy on a lead associated with an implantable medical device (IMD), comprising:

providing a first impedance to said lead;

receiving an indication of a possibility of said coupled energy; and

providing a second impedance associated with said lead to reduce said coupled energy based upon said indication.

21. A medical device system for providing a therapy to a patient, comprising:

an electrode coupled to a portion of a tissue in a patient'"'"'s body;

a lead operatively coupled to said electrode, said lead to carry a stimulation signal to said electrode; and

a signal generator operatively coupled to said lead and comprising

a stimulation unit to provide a stimulation signal to said tissue through said lead, and

an impedance unit to modify an impedance of said lead based upon a command from an external source.

22. The medical device system of claim 21, wherein said impedance unit comprises an active cancellation unit.

23. The implantable medical device of claim 22, wherein said active cancellation unit comprises a current signal for providing a zero current in the presence of said coupled energy.

24. The implantable medical device of claim 21, wherein said impedance unit comprises:

at least one of a capacitive impedance, an inductive impedance, a resistive impedance, a short-circuit, an open circuit; and

a switching network capable of switching at least one of said capacitive impedance, inductive impedance, resistive impedance, said open circuit, and said short circuit to modify said impedance of said lead.