Charging system for rechargeable implantable stimulation system

Abstract

A charging device for an implantable pulse generator includes a charging coil and a controller. The controller is configured to track a net consumed thermal energy of the charging device and modulate a charging duty cycle of the charging device based on the net consumed thermal energy to limit heat generated by the charging device. The charging device is configured to charge the implantable material based on the modulated charging duty cycle by providing a voltage to the charging coil.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 442,731, filed February 1, 2023. The above-referenced provisional application is incorporated herein by reference. Background Art

[0003] A neurostimulation system is disclosed that includes a rechargeable implantable pulse generator and an external charging device. The system also includes a thermal regulation method for controlling the external charging device using duty cycle modulation and net thermal energy tracking to safely charge the implantable medical device by limiting the heat generated by the charging device.

[0004] Over the past fifteen years, treatments with neurostimulation systems have become increasingly common. These neurostimulation systems typically have a neurostimulation component (e.g., a pulse generator) and one or more interface components. The pulse generator can be an implantable pulse generator (IPG) or an external pulse generator (EPG). The interface component can include a charging device (CD). For example, the charging device can be capable of wirelessly charging the IPG and sending or receiving data from the IPG or the interface component.

[0005] While neurostimulation systems have been widely implemented to treat a variety of conditions, there are still many implementation issues that need to be addressed. For example, a charging device may operate in a non-optimal manner or may pose a safety risk when it is subjected to excessive temperatures, which may be caused by a combination of the environment in which it is used and the heat generated by the charging device itself. Therefore, it would be advantageous to design methods, systems, and devices for monitoring and regulating the temperature of a charging device while it is in use in order to ensure optimal safety and efficacy. The need to monitor and regulate neurostimulation systems may be particularly important given the impact they may have on patient health and the patient safety risks associated with these systems. Summary of the Invention

[0006] A neurostimulation system is disclosed that includes a rechargeable implantable pulse generator and an external charging device. The system also includes a thermal regulation method for controlling the external charging device using duty cycle modulation and net thermal energy tracking to safely charge the implantable medical device. Furthermore, an embodiment is disclosed in which the thermal regulation method operates without the need for a thermal sensor.

[0007] The disclosed implantable neurostimulation system can be used for sacral nerve stimulation (SNM) to treat overactive bladder (OAB). The implantable components of the rechargeable SNM system include a rechargeable implantable pulse generator (IPG) and leads. The typical locations of the IPG and leads in the body are as follows: Figure 1 shown.

[0008] The external charging device (CD) disclosed herein may include a heat regulation method. The CD may also include a battery, a circuit for generating an electromagnetic field to charge the IPG, a controller and device for facilitating the operation of the CD, and a storage device for a control system for the method and other data. The method or control system for the CD may include a duty cycle modulation scheme so that the CD can operate under a desired heat generation limit. The method or control system may also include tracking the net consumed heat energy in heat units so that the desired heat generation limit is determined as a function of the net consumed heat energy.

[0009] In one embodiment, the charging circuitry in the CD includes a charging coil, and when charging the IPG, the CD generates a voltage or current in the coil of a magnitude to drive the charging process, such that the IPG rectified charging voltage is maintained within its desired operating range. In one embodiment, the CD controller monitors and measures the power drawn from the battery and determines the operating duty cycle so that the heat generation rate by the CD is maintained below applicable operating thermal limits. In other words, the measurement and resulting adjustment of heat generated by the CD is based on the battery voltage and current (i.e., the power generated). Thus, regardless of the inductive coupling conditions with the IPG, the CD output is duty-cycle modulated to maintain the CD's heat generation rate level below a preferred operating level or target. Alternatively, the power drawn can be pre-characterized using a lookup table, and the values ​​in the lookup table can be used in place of or in addition to measuring the CD battery power drawn.

[0010] The disclosed method controls the charging operation based on the heat generated by the CD, rather than the heat generated by the IPG and / or the heat delivered to the patient. The method does not require the use of a temperature sensor for sensing the temperature of the device or for sensing the temperature of the patient.

[0011] In one embodiment, a method of operating a rechargeable system for providing neurostimulation to a patient is disclosed herein. The system includes a charging device (CD) and an implantable pulse generator (IPG), and the method includes the following steps: tracking, by a controller, a heat counter, wherein the heat counter is a value indicating a net consumed thermal energy of the CD based on an operating power of the CD and a charge duty cycle of the CD; modulating, by the controller, the charge duty cycle based on the heat counter to limit heat generated by the CD; and charging the IPG based on the modulated charge duty cycle.

[0012] In one embodiment, a method of operating a charging device (CD) for an implantable pulse generator (IPG) is disclosed herein. The method includes the steps of tracking, by a controller, a net consumed thermal energy of the CD, modulating, by the controller, a charging duty cycle based on the net consumed thermal energy to limit heat generated by the CD, and controlling charging of the IPG based on the modulated charging duty cycle.

[0013] In one embodiment, a charging device (CD) for an implantable pulse generator (IPG) is disclosed herein. The CD includes a charging coil, a battery, and a controller configured to control functions of the CD, wherein the controller is configured to track the net thermal energy consumed by the CD; modulate a charging duty cycle of the CD based on the net thermal energy consumed to limit heat generated by the CD; and direct current to be supplied to the charging coil to charge the IPG based on the modulated charging duty cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 An example of a neurostimulation system with implantable stimulation leads and an implantable pulse generator is shown.

[0015] Figure 2 An exemplary neurostimulation system including a rechargeable implantable pulse generator and a charging device is schematically illustrated.

[0016] Figure 3 An example of an external charging device when not in use is shown.

[0017] Figure 4 An example of an external charging device held in a charging position relative to the IPG is shown.

[0018] Figure 5 A flow chart illustrating one embodiment of a process for regulating heat generation of a neural stimulation system is shown.

[0019] Figure 6 A functional block diagram of a method for operating thermal regulation of a charging device is shown.

[0020] Figure 7 is a schematic diagram of the charging device and implantable pulse generator. DETAILED DESCRIPTION

[0021] Figure 1 An example of a neurostimulation system 100 is shown having an implantable stimulation lead 20 and an implantable pulse generator 10 configured to stimulate one or more nerves 30. Typical locations of the IPG 10 and the lead 20 with electrodes 40 within the body are as follows: Figure 1 An exemplary embodiment is shown in FIG.

[0022] Figure 2 An exemplary neurostimulation system 100 is schematically shown and includes a rechargeable implantable pulse generator 10 and a charging device 50. In one embodiment, the rechargeable implantable pulse generator (IPG) 10 is a rechargeable implantable device that provides electrical pulses to stimulate target sacral nerves.

[0023] In one embodiment, neurostimulation system 100 includes lead 20. In one embodiment, lead 20 is a serrated lead that also includes a plurality of electrode contacts 40 for carrying stimulation pulses. In one embodiment, the distal tip of lead 20 is implanted through a suitable foramen near the S3 sacral nerve, with the proximal end of lead 20 connected to IPG 10. In one embodiment, the serrations on lead 20 facilitate securing lead 20 just posterior to the sacral foramen.

[0024] In one embodiment, neurostimulation system 100 includes a remote control (RC) 70. In one embodiment, RC 70 is a non-rechargeable battery-powered device that communicates with IPG 10 using radio frequency (RF) signals. In one embodiment, RC 70 allows the subject to check and adjust the stimulation level, to check the status of the IPG 10 battery charge level, and to turn stimulation on or off.

[0025] In one embodiment, the neurostimulation system 100 includes a charging device (CD) 50. In one embodiment, the CD 50 is an external portable device powered by a rechargeable battery. The CD 50 can be configured to charge the IPG 10 transcutaneously via electromagnetic induction. In one embodiment, Figure 3 As shown, the external CD 50 is compatible with a base 51 that is configured to connect to a wall outlet and can be used to recharge the external CD 50. The CD 50 can be attached to the patient's skin using an adhesive or can be attached using a strap 53 (e.g., Figure 4 as shown) or held in place by an adhesive patch.

[0026] In one embodiment, the neurostimulation system 100 includes a clinician programmer (CP) 60, which may be embodied as a tablet computer used by a clinician to program the neurostimulation system 100. In one embodiment, the CP 60 communicates wirelessly with the IPG 10.

[0027] In one embodiment, the neurostimulation system 100 is designed to work in conjunction with an external testing system 200. The external testing system 200 can be used to screen patients for SNM therapy before the neurostimulation system 100 is permanently implanted. In one embodiment, the external testing system 200 includes an external pulse generator (EPG) 80 that is connected to the lead 20 instead of the IPG 10 and interfaces with the RC 70 and CP 60 in a manner similar to the IPG 10.

[0028] To implant the IPG 10, a set of surgical tools 90 may be required. The set of surgical tools 90 may include a bore needle with a needle stylet, a directional introducer, an introducer sheath and dilator, a lead stylet (with a straight or curved tip), a torque wrench, a tunneling tool, a needle stimulation cable, and a lead stimulation cable.

[0029] Figure 3 An example of an external charging device 50 is shown when not in use. In one embodiment, the CD 50 is an external portable accessory to the SNM system. Figure 3 In the figure, the charging device 50 is placed on the charging base 51, which can be used to charge the charging device 50.

[0030] Figure 4 Shown relative to IPG 10 ( Figure 4 An example of an external charging device 50 (not shown) held in a recharging position. In one embodiment, the CD 50 allows the patient to wirelessly recharge the IPG 10 via electromagnetic induction. When the CD 50 is placed on the patient's skin above the IPG 10, the CD 50 will begin to charge the IPG 10 battery. Figure 4 As shown, a strap 53 or carrier may be used to hold the charging device or charger 50 in place while the IPG 10 is being charged. Figure 4 It shows how the strap 53 can be used to place or adhere the CD 50 to a person's skin while the IPG 10 is being recharged.

[0031] Charging the IPG 10 typically takes about an hour, depending on the depth of the IPG 10 and how the CD 50 is positioned relative to the IPG 10. For efficient charging, the CD 50 should be placed directly on the correct location of the IPG 10, which provides optimal alignment between the CD 50 and the IPG 10. When the alignment between the CD 50 and the IPG 10 is less than ideal, charging efficiency is low, thereby generating heat in the charging device. To ensure safe charging of deep implants, or when the CD 50 and IPG 10 are misaligned, it is necessary to operate the CD 50 in a manner that regulates the heat generated in the charging device.

[0032] In one embodiment, the thermal restriction operating curve W OHL is defined so that the operation of the CD does not cause the heat generated by charging the IPG to exceed the thermal limit operating curve W OHL Control of heat generation may be achieved using a controller (ie, a processor) within the CD. The controller may be configured to execute instructions stored in a memory device located within the CD.

[0033] Caloric restriction operating curve W OHL Can vary depending on the state of the CD. For example, the thermally limited operating curve W OHL is determined so that when the CD is known to cool, it allows for increased heat generation wattage W hi On the contrary, when the CD is likely to get hot (i.e., when the thermal energy is close to the maximum J max When the operation switches to the reduced heat generation wattage limit W lo In one embodiment, J max 、W hi and W lo Determined by empirical characterization.

[0034] The CD thermal regulation method includes using an internal counter to track the amount of net thermal energy J drawn from the CD battery. In one embodiment, the counter increments J to a value measuring thermal energy in millijoules that is stored internally in non-volatile / non-transitory memory within the CD.

[0035] In one embodiment, a counter is incremented by J to track the net energy consumed when the CD's battery generates power (i.e., CD power). In one embodiment, the counter can be decremented by J to model the cooling down of the device in inactive mode. In one embodiment, the inactive mode can include a power-off mode and a charging base powered mode.

[0036] Because the CD internal heat generation rate due to the charging process is a fraction of the CD power generated by the CD battery, the latter is measured (CD peak power: W peak) is an appropriate means for adjusting the former. By adjusting the duty cycle D, the average power of CD W = D × W peak ≤W OHL , the CD can regulate the heat generation rate to keep the CD temperature within acceptable operating levels. As shown in the above equation, it should be noted that W OHL is the upper limit condition, so the average operating power of CD can be equal to or lower than the operating heat generation limit W OHL .

[0037] The disclosed method measures the voltage and current output by the CD battery and uses the voltage and current to calculate W peak To limit the CD average power W. Alternatively, voltage and power measurements can also be performed during the coil power generation phase. Alternatively, the method uses a lookup table to determine the power W based on one or both of the voltage or current produced by the CD battery. peak .

[0038] CD heat generation limit W OHL As a function of the heat unit counter value J is determined as follows (Table 1).

[0039]

[0040] Table 1

[0041] Table 1 shows exemplary operating heat generation limits for charging equipment as a function of net consumed thermal energy.

[0042] When the heat counter is greater than or equal to J max When the operating heat generation limit W OHL Will be set to the reduction amount W lo If there is sufficient charge C in the battery CD (e.g., the remaining energy capacity in the battery measured in mAh), then W lo =W lo,charged The controller can also be configured to check whether the charge C of CD is less than a set minimum charge value C depleted , so that if the battery CD is less than the set minimum C depleted , then W lo =W lo,depleted This depleted operation heat generation limit is even lower than normal charging (i.e. W lo,depleted <W lo,charged ), so that the CD's battery is protected at a lower state of charge.

[0043] In one embodiment, when the CD is off or powered by the charging base (ie, when the IPG is not charging), the accumulated heat units J are decremented at a preset rate as a function of the value of the heat unit counter, as shown in Table 2 below.

[0044]

[0045] Table 2

[0046] Table 2 discloses exemplary charging device thermal decay rates and corresponding thermal unit ranges in the counter.

[0047] At high intermediate calorie counter value J lim1 To the maximum calorie counter value J max Within the preset range, the calorimeter will rapid So, when the CD is at the hotter end of the heat counter range (such as after a long full charge session), the heat counter will decrease rapidly at the set time rate.

[0048] At low intermediate calorie counter value J lim2 To high intermediate calorie counter value J lim1 Within the preset range of , the decreasing rate of the calorie counter J over time will be set as a function of J. Depending on the design of CD, this function can be a linear function or a nonlinear function.

[0049] Below the low intermediate heat counter value J lim2 The decreasing rate of the heat counter over time will be set to J slow At lower heat counter values, the heat will dissipate more slowly because the difference between the temperature of the CD and the surroundings or environment is smaller. Therefore, the heat decay rate of the CD will be set within the above setting range, where J rapid >f(J)>J slow .

[0050] Figure 5 The flow chart shown provides a graphical representation of the control system. Figure 5 is a flow chart illustrating how to maintain an operational thermal limit for a charging device according to an exemplary embodiment of a control system. Figure 5 The flow chart shown also shows the operating thermal limits within different thermal unit ranges.

[0051] At 501, when a charging session is initiated, the CD will OHL =W lo The W lo The limit may be the lowest set thermally limited operating curve for which the device is designed.

[0052] At 502, the heat unit counter is to track the heat unit counter J indicating the accumulated heat energy of the charging session. If the charger is initiated before the tracked heat energy J has completely decreased to 0, the baseline heat energy J0 can start from 0, a set baseline number, or a non-baseline number. When charging is first initiated, the controller will set J=J0. At this step, the tracking of the heat unit counter J can also include the heat unit counter J n The sum of the values ​​represents the peak power of the CD at time (or increment) n+1 weighted by the charging duty cycle of the CD, so that J=J0+∑J n , where n can be a different time or number of increments set by the controller in time increments (or any set increments) n+1 to track, collect and / or sum the heat counter J at time (or number of increments) n. Since the heat counter J depends on the modulated duty cycle of the CD, the value of J will vary. At higher duty cycles, larger heat counters are added, while lower duty cycles will result in smaller heat counters being added to the previously tracked heat counters.

[0053] At step 503, the controller will check whether the unit heat counter J is greater than or equal to J max When the heat counter J is greater than or equal to J max When the operating heat generation limit W OHL Will be set to the reduction amount W lo , that is, the controller will modulate the charging duty cycle so that the target operating heat generation limit at step 504 is W lo The controller can also be configured to check whether the charge C of CD is less than a set minimum charge value C depleted , so that if the battery CD is less than the set minimum charge value C depleted , then at step 504 W lo =W lo,depleted This depleted operation heat generation limit is even lower than normal charging (i.e. W lo,depleted <W lo,charged ), so that the battery of CD is protected at a lower state of charge to prevent damage. If sufficient charge C is contained in the battery of CD, then at step 504 W lo =W lo,charged After step 504, the controller will return to step 502 and continue to track the heat counter J after a period of time (or number of increments) n at 502. Generally, when the heat counter J reaches or exceeds J max The device will operate continuously within the high thermal operating range, where W OHL Will be set to the reduction amount W lo , until the charging session is completed. It should be noted that W OHLis the upper limit condition, so the actual operating power of the CD can be equal to or lower than the operating heat generation limit W OHL .

[0054] At step 505, if the heat counter J ≥ J max is not true, the controller will check whether J <J min If condition J <J min If true, it means that the CD is currently in a lower temperature operating range and has a higher heat capacity, so that at step 506, W OHL Can be equal to enhanced charging W hi In W OHL =W hi When J <J min Is true, CD is just allowed its maximum operating power.After step 506, controller will return to step 502, and continues to track heat counter J after a period of time (or increment number) n.

[0055] At step 507, if the condition J≥J max and J <J min If neither is true, the operating heat generation limit W OHL Will be limited to W hi and W lo At this step, W OHL is determined as a function of the heat unit counter value J such that W OHL =f(J), where f(J) can be linear or nonlinear. In an exemplary embodiment, f(J) can be W hi and W lo In one exemplary embodiment, f(J) may be numerically retrieved by the controller from a lookup table stored in a memory of the CD.

[0056] At step 508, the controller can be configured to check whether the CD is still charging the IPG. If the CD is no longer charging the IPG, then at step 509, the controller will begin decrementing the calorie counter J per unit time (or increment) based on the amount set in Table 2. If the CD is on, step 502 will be repeated and continue to track the calorie counter J after a period of time (or number of increments) n.

[0057] Figure 6 A functional block diagram of a controller of a CD illustrating the operation of a method for thermal regulation of a charging device is shown. Figure 6As shown, the duty cycle of the CD can also be varied due to temperature feedback from the IPG. For example, if the temperature set point associated with the IPG is exceeded, the duty cycle of the CD can be adjusted to prevent the IPG from exceeding the temperature limit. A temperature sensor can be used to monitor the temperature of the IPG in a conventional manner. In contrast, as described herein, by monitoring the thermal energy drawn from the CD battery, the heat generated by the CD can be controlled without the use of any temperature sensors. As shown in dashed lines, the IPG temperature block can be omitted and the thermal regulation of the CD need not be fully controlled. As shown in FIG. Figure 6 As shown, the IPG telemetry block 601 sends the coil on / off status (i.e., coil duty cycle or charging duty cycle) to the thermal unit counter block 602 so that the controller can calculate and track J to evaluate which thermal limit condition to implement in block 603. The thermal limit condition will be converted by the control block 604 into a corresponding duty cycle limit that matches the thermal limit condition set in block 603. The control block 604 will command the duty cycle modulator block 605 so that the duty cycle limit will never exceed the set amount corresponding to the operating heat generation limit set at block 603.

[0058] Figure 7 A simplified schematic diagram of a charging device 50 and an IPG 10 being charged is shown. CD 50 may include memory 54, a power source 55, electronic circuitry 56 configured to power a charging coil 57, and a controller 58 configured to control the electronic circuitry. Power source 55 may be a battery or a power module that receives power from an external source. Memory 54 may be any data storage device, such as volatile memory (e.g., random access memory (RAM)) or non-volatile memory. Controller 58 includes a processor. Memory 54 may be part of controller 58 and located within controller 58 (e.g., a cache).

Claims

1. A method of operating a rechargeable system for providing neurostimulation to a patient, the system comprising a charging device (CD) and an implantable pulse generator (IPG), the method comprising the steps of: tracking a heat counter by a controller, wherein the heat counter indicates a value of net consumed heat energy of the CD based on an operating power of the CD and a charging duty cycle of the CD; modulating, by the controller, the charging duty cycle based on the heat counter to limit heat generated by the CD; as well as The IPG is charged based on the modulated charging duty cycle.

2. The method according to claim 1, wherein Modulating the charge duty cycle to limit heat generated by the CD is based on the operating power of the CD weighted by the charge duty cycle of the CD, rather than on the sensed temperature or the temperature of the patient.

3. The method according to claim 1, wherein Modulating the charging duty cycle includes limiting the average operating power of the CD over a period of time to a power level that is equal to or lower than a thermally limited operating curve.

4. The method according to claim 3, wherein: The caloric restriction operating curve depends on the caloric counter.

5. The method according to claim 4, wherein When the calorie counter is below a predetermined first value, the calorie limit operating curve is at an increasing value; and Wherein when the calorie counter is above a predetermined second value, the calorie restriction operating curve is at a reduced value.

6. The method according to claim 5, wherein: The value of the reduction also depends on the current state of charge of the battery used to power the CD.

7. The method according to claim 4, wherein: When the CD is not charging the IPG, the calorie counter decreases over time.

8. A method of operating a charging device (CD) for an implantable pulse generator (IPG), the method comprising the steps of: Tracking, by a controller, the net consumed heat energy of the CD; modulating, by the controller, a charging duty cycle based on the net consumed thermal energy to limit heat generated by the CD; as well as The controller controls charging of the IPG based on a modulated charging duty cycle.

9. The method according to claim 8, wherein Modulating the charge duty cycle to limit heat generated by the CD is based on the operating power of the CD weighted by the charge duty cycle of the CD, rather than on the sensed temperature or the temperature of the patient.

10. The method according to claim 8, wherein The step of modulating the charging duty cycle limits the average operating power of the CD over a period of time to a power level at or below a thermally limited operating curve.

11. The method according to claim 10, wherein: The thermal limit operation curve depends on a thermal counter, wherein the thermal counter is a value indicating the net consumed thermal energy of the CD based on the operating power of the CD and the charging duty cycle of the CD.

12. The method according to claim 11, wherein When the calorie counter is below a predetermined first value, the calorie limit operating curve is at an increasing value; and Wherein when the calorie counter is above a predetermined second value, the calorie restriction operating curve is at a reduced value.

13. The method according to claim 12, wherein: The value of the reduction also depends on the current state of charge of the battery used to power the CD.

14. The method according to claim 4, wherein When the CD is not charging the IPG, the calorie counter decreases over time.

15. A charging device (CD) for an implantable pulse generator (IPG), wherein: The CD includes: Charging coil; Battery; Controller; Wherein, the controller is configured as follows: Tracking the net consumed heat energy of the CD; and modulating a charging duty cycle of the CD based on the net consumed thermal energy to limit heat generated by the CD; Current is directed to the charging coil to charge the IPG based on a modulated charging duty cycle.

16. The apparatus according to claim 15, wherein The CD does not include a temperature sensor.

17. The apparatus according to claim 15, wherein The controller is configured to track the net consumed thermal energy by monitoring power drawn from the battery of the charging device.

18. The apparatus according to claim 15, wherein The controller is configured to track net consumed thermal energy of the CD using a lapse rate when the CD is not charging the IPG.

19. The apparatus according to claim 15, wherein The controller is configured to modulate a charging duty cycle of the CD by varying an average power of the CD to one of at least three different power levels.

20. The apparatus according to claim 19, wherein When the battery voltage of the CD is lower than the set charge value, the average power level of the CD is low.

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