Controlling noise sources during telemetry

• US 20030045913A1
• Filed: 09/06/2001
• Published: 03/06/2003
• Est. Priority Date: 09/06/2001
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Ericksen, James H., House, Chris T., .Stroebel, John C, Huelskamp, Paul J., Peichel, David J., Pape, Forrest C.M.
• Granted Patent: US 6,701,188 B2
• Time in Patent Office: Days
• US Class Current: 607/60
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: A61N 1/3975 Power supply A61N1/378 takes precedence
• CPC Class Codes: A61N 1/3981 High voltage charging circuitry

Abstract

The invention presents techniques for reducing the interference to telemetry from an implanted medical device caused by a source of controllable noise. In the context of an implanted system that includes a defibrillator system and a telemetry system, for example, the invention reduces the interference by suspending energy storage during telemetry. The invention further provides for suspending energy storage operation gradually rather than abruptly, by gradually reducing the duty cycle of a clock that controls the energy storage.

Claims

1. A method comprising:

suspending storing energy in an energy storage device in an implanted defibrillator; and

initiating a telemetry communication upon suspending the energy storage.

2. The method of claim 1, wherein suspending storing energy in an energy storage device includes gradually reducing the amount of energy delivered to the energy storage device.

3. The method of claim 1, wherein suspending storing energy in an energy storage device includes reducing a duty cycle of a clock that controls delivery of energy to the energy storage device.

4. The method of claim 3, wherein reducing a duty cycle of a clock includes reducing the duty cycle to zero.

5. The method of claim 1, further comprising resuming storing energy in the energy storage device upon completion of the telemetry communication.

6. The method of claim 5, wherein resuming storing energy in the energy storage device comprises increasing a duty cycle of a clock that controls delivery of energy to the energy storage device.

7. The method of claim 1, further comprising resuming storing energy in the energy storage device upon expiration of a time limit.

8. The method of claim 1, wherein suspending storing energy in an energy storage device includes reducing a frequency of a clock that controls delivery of energy to the energy storage device.

9. The method of claim 1, wherein initiating the telemetry communication includes transmitting a radio frequency message.

10. The method of claim 9, further comprising:

listening for a second radio frequency message upon suspending

storing energy in the energy storage device;

maintaining the suspension upon receiving the second radio frequency message; and

terminating the telemetry communication and resuming storing energy in the energy storage device when the second radio frequency message is not received within a time period.

11. The method of claim 10, wherein maintaining the suspension comprises maintaining the duty cycle at zero.

12. A method comprising:

reducing a duty cycle of a clock that controls a charging circuit in an implantable medical device over a period of time; and

when the duty cycle has been reduced to a predetermined level, transmitting a radio frequency message from the device.

13. The method of claim 12, wherein the predetermined level is zero.

14. The method of claim 12, wherein reducing a duty cycle of a clock comprises reducing a duty cycle of a clock that controls storage of energy in an energy storage device.

15. The method of claim 12, wherein reducing a duty cycle of a clock comprises reducing a duty cycle of a clock that controls storage of energy in an energy storage device in an implanted defibrillator.

16. The method of claim 12, further comprising receiving a radio frequency message when the duty cycle has been reduced to a predetermined level.

17. The method of claim 12, wherein reducing the duty cycle comprises reducing the duty cycle by a predetermined amount per switching period.

18. The method of claim 12, further comprising increasing the duty cycle of the clock when transmission is completed.

19. The method of claim 18, wherein increasing the duty cycle comprises increasing the duty cycle by a predetermined amount per switching period.

20. The method of claim 12, further comprising:

increasing the duty cycle of the clock;

transmitting a message while the duty cycle of the clock is increased.

21. The method of claim 12, further comprising:

listening for a second radio frequency message when the duty cycle is the predetermined level; and

maintaining the duty cycle at the predetermined level when a second message is received, otherwise increasing the duty cycle of the clock.

22. A method, comprising:

charging a capacitor in an implanted defibrillator reducing the duty cycle of a clock that controls a switch that charges the capacitor; and

transmitting a radio frequency message when the duty cycle has been reduced to a predetermined level.

23. The method of claim 22, wherein transmitting a radio frequency message when the duty cycle has been reduced to a predetermined level comprises transmitting a radio frequency message when the duty cycle has been reduced to zero.

24. The method of claim 22, wherein reducing the duty cycle comprises reducing the duty cycle by a predetermined amount per switching period.

25. A medical device comprising:

a transceiver;

a charging circuit; and

a controller that disables the charging circuit prior to initiating a telemetry communication via the transceiver.

26. The device of claim 25, wherein the charging circuit comprises a switch to control a supply of energy in response to a duty cycle of a charge clock.

27. The device of claim 26, wherein the controller disables the charging circuit by reducing a duty cycle of the charge clock.

28. The device of claim 25, further comprising a defibrillation electrode coupled to a capacitor.

29. The device of claim 25, wherein the charging circuit comprises an inductive element coupled to a capacitor via a switch controlled by a signal having a duty cycle, and further wherein the controller controls the duty cycle to disable the charging circuit.

30. A device comprising:

telemetry means for transmitting and receiving radio frequency messages;

arrhythmia management means, comprising a capacitor in proximity to the telemetry means;

charging means for charging the capacitor with a switched charging circuit;

controller means for disabling the charging means when the telemetry means transmits a radio frequency message.

31. The device of claim 30, further comprising clock means, coupled to the switched charging circuit, for activating and deactivating a switch to deliver charge to the capacitor.

32. The device of claim 31, wherein the clock means activates and deactivates the switch once every switching period, wherein the duty cycle of the clock means comprises the ratio of the time of activation to the time of deactivation, and wherein the controller means disables the charging means by reducing the duty cycle of the clock means.

33. The device of claim 30, wherein the controller means enables the charging means when the telemetry means completes transmission of the radio frequency message.