Circuits and Methods for Using a High Impedance, Thin, Coin-Cell Type Battery in an Implantable Electroacupuncture Device

• US 20140214128A1
• Filed: 02/18/2013
• Published: 07/31/2014
• Est. Priority Date: 03/12/2012
• Status: Active Grant

• Current Assignee: Valencia Bioscience, Inc.
• Original Assignee: Valencia Technologies Corporation
• Inventors: Peterson, David K. L., Greiner, Jeffrey H.
• Granted Patent: US 9,089,716 B2
• Time in Patent Office: Days
• US Class Current: 607/59
• CPC Class Codes: A61H 2201/5005 for controlling frequency distribution, modulation or interference of a driving signal
• CPC Class Codes: A61H 2201/5035 Several programs selectable
• CPC Class Codes: A61H 2201/5038 freely programmable by the user
• CPC Class Codes: A61H 2201/5097 wireless
• CPC Class Codes: A61H 39/002 Using electric currents electrotherapy A61N1/32
• CPC Class Codes: A61N 1/36117 for treating hypertension
• CPC Class Codes: A61N 1/36125 Details of circuitry or electric components
• CPC Class Codes: A61N 1/36175 Pulse width or duty cycle
• CPC Class Codes: A61N 1/37205 Microstimulators, e.g. implantable through a cannula
• CPC Class Codes: A61N 1/3756 Casings with electrodes thereon, e.g. leadless stimulators
• CPC Class Codes: A61N 1/3758 Packaging of the components within the casing
• CPC Class Codes: A61N 1/378 Electrical supply
• CPC Class Codes: A61N 1/3782 producing a voltage above the power source level

Abstract

An implantable electroacupuncture device (IEAD) treats a disease or medical condition of a patient through application of stimulation pulses applied at a specified acupoint or other target tissue location. In a preferred implementation, the IEAD is an implantable, coin-sized, self-contained, leadless electroacupuncture device having at least two electrodes attached to an outside surface of its housing. The device generates stimulation pulses in accordance with a specified stimulation regimen. Power management circuitry within the device allows a primary battery, having a high internal impedance, to be used to power the device. The stimulation regimen generates stimulation pulses during a stimulation session of duration T3 minutes applied every T4 minutes. The duty cycle, or ratio T3/T4, is very low, no greater than 0.05. The low duty cycle and careful power management allow the IEAD to perform its intended function for several years.

Claims

1. An Implantable ElectroAcupuncture Device (IEAD) for treating a specified medical condition of a patient through application of electroacupuncture (EA) stimulation pulses applied substantially at or near a specified acupoint, its underlying nerves, or other target tissue location, comprising:

a small IEAD housing having an electrode configuration thereon that includes at least two electrodes/arrays, the longest linear dimension of the small IEAD housing being no greater than about 25 mm, wherein at least one of said at least two electrodes/arrays comprises a central electrode/array located substantially in the center of a first surface of the IEAD housing, and wherein at least another of said at least two electrodes/arrays comprises a circumferential electrode/array located substantially around and at least 5 mm distant from the center of the central electrode/array, wherein the first surface of the IEAD housing when implanted is adapted to face inwardly into the patient'"'"'s tissue at or near the specified target tissue location;

pulse generation circuitry located within the IEAD housing and electrically coupled to the at least two electrodes/arrays, wherein said pulse generation circuitry is adapted to deliver stimulation pulses to the patient'"'"'s body tissue at or near the target tissue location in accordance with a specified stimulation regimen, said stimulation regimen defining the duration and rate at which a stimulation session is applied to the patient, said stimulation regimen requiring that the stimulation session have a duration of T3 minutes and a rate of occurrence of once every T4 minutes, wherein the ratio of T3/T4 is no greater than 0.05, and wherein during each stimulation session EA stimulation pulses having one or more specified widths and amplitudes are generated at one or more specified rates;

a primary battery contained within the IEAD housing and electrically coupled to the pulse generation circuitry that provides operating power for the pulse generation circuitry, said primary battery having a nominal output voltage of 3 volts, and an internal impedance greater than 5 ohms; and

a sensor contained within the IEAD housing responsive to operating commands wirelessly communicated to the IEAD from a non-implanted location, said operating commands allowing limited external control of the IEAD.

2. The IEAD of claim 1 wherein the circumferential electrode/array comprises an anode electrode/array and the central electrode/array comprises a cathode electrode/array.

3. The IEAD of claim 1 wherein the circumferential electrode/array comprises a cathode electrode/array and the central electrode/array comprises an anode electrode/array.

4. The IEAD of claim 1 wherein the small IEAD housing is coin-shaped having a diameter no greater than about 25 mm and a thickness of no greater than about 2.5 mm.

5. The IEAD of claim 1 wherein the pulse generation circuitry includes:

a boost converter circuit that boosts the nominal voltage of the primary battery to an output voltage V_OUT that is at least three times the nominal battery voltage;

means for selectively turning the boost converter circuit OFF and ON to limit the amount of current that may be drawn from the primary battery; and

an output circuit powered by V_OUT that generates the stimulation pulses as defined by the specified stimulation regimen.

6. The IEAD of claim 5 wherein the stimulation pulses generated by the pulse generation circuit and delivered through the at least two electrodes/arrays into a load at the target tissue location comprise current pulses having a current amplitude of no less than about 1 milliampere (mA) and no greater than about 25 mA.

7. The IEAD of claim 5 wherein the primary battery has sufficient capacity to power the pulse generation circuitry in accordance with the specified stimulation regimen for a minimum of 2 years.

8. The IEAD of claim 5 wherein the means for selectively turning the boost converter circuit OFF and ON comprises a control circuit configured to generate a digital signal that modulates the boost converter circuit between an OFF state and an ON state, with the ON state comprising no more than about 2% of the time that the IEAD is operating.

9. The IEAD of claim 5 wherein the means for selectively turning the boost converter circuit OFF and ON comprises a boost converter circuit having a shut down feature which automatically places the boost converter circuit in an OFF state whenever the battery voltage falls below a set minimum value, wherein the set minimum value of the battery below which the boost converter is placed in an OFF state comprises a voltage that is sufficiently high to continue to power other digital processing circuits within the pulse generation circuitry even when the boost converter is turned OFF.

10. The IEAD of claim 5 wherein the pulse generation circuitry further includes means for reducing leading edge transient signals that may be present in the stimulation pulses generated by the pulse generation circuitry.

11. The IEAD of claim 10 wherein the output circuit of the pulse generation circuitry includes a programmable current source, and wherein the means for reducing leading edge transient signals comprises connecting a cascode circuit at the input of the programmable current source.

12. The IEAD of claim 11 wherein the pulse generation circuitry further includes means for kick starting the programmable current source when low amplitude stimulation pulses are generated, wherein such kick starting eliminates or reduces undesired delays in the leading edge of the stimulation pulses generated by the pulse generation circuitry.

13. An implantable electroacupuncture device (IEAD) adapted to generate and apply electrical stimulus pulses to a target tissue location of a patient when the IEAD is implanted at or near the target tissue location, the IEAD comprising:

a thin, disc-shaped, hermetically-sealed case having a front side, a back side, and an edge side, the edge side joining the front side to the back side around the perimeter of the sealed case, the front and back sides having a longest linear dimension D2 that is no greater than about 25 mm, and the edge side defining an overall thickness or width W2 of the disc-shaped case to be no greater than about 2.5 mm;

at least one anodic electrode and at least one cathodic electrode secured to an outside surface of the thin, disc-shaped hermetically-sealed case in a symmetrical configuration, wherein at least one electrode comprises a central electrode located substantially in the center of the front side of the disc-shaped case, and wherein at least another electrode comprises a circumferential electrode located around and at least 5 mm distant from the closest point of the central electrode;

electronic circuitry housed within the thin, disc-shaped, hermetically sealed case that causes electrical stimulus pulses to be generated and applied to the at least one cathodic electrode and the at least one anodic electrode in accordance with a prescribed stimulation regime;

feed-through means for electrically connecting the electronic circuitry on the inside of the hermetically sealed case to the at least two electrodes on the outside of the hermetically sealed case; and

a thin, coin-cell type primary battery on the inside of the thin, disc-shaped, hermetically sealed case connected to the electronic circuitry that provides operating power for the electronic circuitry, the coin-cell primary battery having a nominal output voltage of V_BAT volts, where V_BAT ranges from as low 2.2 volts to as high as 3.6 volts;

wherein the primary battery has an internal impedance greater than 5 ohms; and

wherein the electronic circuitry includes power management circuitry that limits the amount of instantaneous current that can be drawn from the battery; and

wherein the prescribed stimulation regime causes electrical stimulus pulses to be generated and applied only during a stimulation session having a duration of T3 minutes, wherein T3 is at least 10 minutes, and wherein the time interval between stimulation sessions is T4 minutes, and wherein the ratio of T3/T4 is no greater than 0.05.

14. The IEAD of claim 13 wherein the electronic circuitry includes:

a boost converter circuit (U1) that boosts the battery voltage V_BAT to an output voltage V_OUT, where V_OUT is at least 3 times V_BAT and no more than 8 times V_BAT;

a microcontroller circuit (U2) powered by VBAT that controls the operation of the electronic circuitry so that the stimulus pulses are generated at a specified amplitude in accordance with the prescribed stimulation regime;

a programmable current source circuit (U3) that sets the amplitude of the current in the stimulus pulses to a desired level;

a sensor circuit (U4) adapted to receive external commands from an external control device that provide operating commands or parameters for the microcontroller circuit, the operating commands including ON/OFF commands, and the operating parameters including defining the time T3, the time T4, and the stimulus amplitude;

an electronic switch (U5), controlled by the microcontroller circuit, that switchably applies the programmed current to the at least one cathodic electrode and the at least one anodic electrode so that when the IEAD is implanted in the patient such switching is adapted to cause the programmed current to flow through the patient'"'"'s body tissue at or near the specified target tissue location.

15. The IEAD of claim 14 wherein the microcontroller circuit includes means for controlling the operation of the boost converter circuit in a way that limits the amount of instantaneous current that can be drawn from the battery, thereby preventing the battery voltage V_BAT from dropping to values that would prevent the electronic circuitry from operating.

16. The IEAD of claim 15 wherein the means for controlling the operation of the boost converter circuit in a way that limits the amount of instantaneous current that can be drawn from the battery comprises duty-cycle modulating the boost converter circuit with a digital control signal that causes the boost converter circuit to switch between an ON state for a short time and to an OFF state for a long time, the ratio of the ON time to the OFF time being less than 0.02.

17. The IEAD of claim 14 wherein the boost converter circuit automatically shuts down whenever the battery voltage V_BAT drops below a fixed threshold, wherein the battery voltage below the fixed threshold is still sufficiently high to permit operation of the microcontroller circuit, and wherein the automatic shutting down of the boost converter circuit significantly decreases the current being drawn from the battery, whereby due to the high internal resistance of the battery the battery voltage increases when the boost converter circuit shuts down and decreases when the boost converter circuit is ON, thereby causing the boost converter circuit to automatically switch between an ON state and an OFF state, which switching limits the amount of current that can be drawn from the battery.

18. The IEAD of claim 17 wherein the nominal battery voltage is 3 volts, and the fixed threshold below which the boost converter circuit shuts down is 2.5 volts.

19. The IEAD of claim 17 wherein the electronic circuitry further includes means for kick starting the programmable current source when the stimulus current amplitude is less than about 2 mA, which kick starting has the effect of driving the programmable current source directly from the microcontroller circuit at the beginning of the stimulus pulse, which action shortens a delay associated with starting the operation of the programmable current source at low current amplitudes by at least a factor of about 5.

20. The IEAD of claim 17 wherein the electronic circuitry further includes a cascode circuit (Q1) connected to the input terminal of the programmable current source circuit (U3), which cascode circuit is adapted to significantly reduce the input capacitance looking into the cascode circuit over the capacitance that is seen looking into the input terminal of the programmable current source, wherein transient signals appearing at the leading edge of the stimulus pulse are significantly reduced.

21. A method of operating an implantable electroacupuncture device (IEAD) powered only by a thin, coin-cell type battery having an internal impedance greater than 5 ohms, over a period of at least 2 years, the IEAD being adapted to generate stimulus pulses during a stimulation session, the method comprising:

powering pulse generation circuitry within the IEAD with the coin-cell type battery,

limiting the duration of stimulation sessions during which stimulus pulses are generated to a time period that has a duty cycle of less than 0.05, where the duty cycle is the ratio of T3 to T4, where T3 is the duration of the stimulation session, and where T4 is the time interval between stimulation sessions;

boosting the battery voltage from the coin-cell type battery using a boost converter circuit by a factor of at least 4 in order to provide sufficient operating power to generate current stimulus pulses of up to 25 mA during a stimulation session; and

limiting the instantaneous current that can be drawn from the coin-cell type battery to prevent the battery voltage, V_BAT, from dropping below safe operating levels.

22. The method of operating an IEAD of claim 21 wherein limiting the instantaneous current that can be drawn from the coin-cell type battery comprises duty-cycle modulating the boost converter circuit so that it switches between an ON state and an OFF state, with the ON state having a duration of no more than 2% of the duration of the OFF state.

23. The method of operating an IEAD of claim 22 wherein duty-cycle modulating the boost converter circuit comprises using a boost converter circuit that automatically shuts down when the battery voltage drops below a prescribed threshold, which shutting down of the boost converter circuit immediately causes the instantaneous current drawn from the battery to decrease, which decrease in instantaneous battery current causes the battery voltage to begin to increase, whereby the battery voltage is not allowed to drop below levels that would prevent the proper operation of the IEAD.