Patent Application
20250144418
The invention relates to a wearable electronic medical device for transcutaneous electrical stimulation of one or more nerves, i.e., neurostimulation.
There are many known technologies for delivering electrical stimulation. Implantable neurostimulation technologies require surgical implantation of stimulation leads, with a pulse generator that is either surgically implanted or connected externally to wire leads. Percutaneous neurostimulation technologies are less invasive, but still require the stimulation electrodes to pierce the skin. While these technologies can be effective in treating certain conditions, they are less desirable due to their invasiveness and because they can require the continued or routine attention of specialists, requiring doctor's office visits, phone calls, etc.
A neurostimulation system for applying transcutaneous electrical neurostimulation includes an electronic stimulator device or controller that controls the delivery of transcutaneous electrical neurostimulation signal via stimulation electrodes in contact with the subject's skin. The controller employs a novel circuit for modulating the electrical neurostimulation signal.
The neurostimulator system supplies constant current electrical stimulation pulses to at least one stimulation electrode to apply electrical stimulation to a subject. The system includes a power supply comprising a voltage rail and a ground. The system also includes a first constant current circuit configured to supply stimulation current from the voltage rail through the at least one stimulation electrode to ground. A controller is configured to control the constant current circuit. The first constant current circuit includes a first mirror circuit, a first current sink, and a first ground circuit. The first mirror circuit is configured to supply the constant current electrical stimulation pulses from the voltage rail to the at least one electrode. The first current sink is configured to control the constant current electrical stimulation pulses supplied to the at least one electrode from the mirror circuit in response to a first control voltage. The first ground circuit is configured to control a path to ground from the at least one stimulation electrode in response to a first ground control signal from the controller. The controller is configured to control the first control voltage to produce the constant current electrical stimulation pulses and to control the first ground control signal to establish the path to ground so that the constant current electrical stimulation pulses flow through the at least one stimulation electrode in a first direction to apply electrical stimulation to the subject.
According to one aspect, the controller can be configured to control the first control voltage to cause the first current sink so that the first mirror circuit produces the constant current stimulation pulses while isolating the subject from the voltage rail.
According to another aspect, alone or in combination with the preceding aspect, the first current sink and the current mirror can be electrically connected to one side of the at least one electrode, and the first ground circuit can be connected on an opposite side of the at least one electrode.
According to another aspect, alone or in combination with one or more of the preceding aspects, the first ground control signal can include the first control voltage, and the first ground circuit can include a current sink configured to control a path to ground from the at least one stimulation electrode in response to the first control voltage.
According to another aspect, alone or in combination with one or more of the preceding aspects, the first ground control signal can include a digital control signal, and the first ground circuit can include a MOSFET configured to control a path to ground from the at least one stimulation electrode in response to the digital control signal.
According to another aspect, alone or in combination with one or more of the preceding aspects, the system can include a second constant current circuit including a second mirror circuit configured to supply the constant current electrical stimulation pulses from the voltage rail to the at least one electrode. The second constant current circuit can also include a second current sink configured to control the constant current electrical stimulation pulses supplied to the at least one electrode from the mirror circuit in response to a second control voltage. The second constant current circuit can further include a second ground circuit configured to control a path to ground from the at least one stimulation electrode in response to a second ground control signal from the controller. The controller can be configured to control the second control voltage to produce the constant current electrical stimulation pulses and to control the second ground control signal establish the path to ground so that the constant current electrical stimulation pulses flow through the at least one stimulation electrode in a second direction, opposite the first direction, to apply electrical stimulation to the subject.
According to another aspect in combination with the preceding aspect, the first current sink and the first current mirror can be electrically connected to a first side of the at least one electrode, and the first ground circuit can be connected to a second side of the at least one electrode, opposite the first side. The second current sink and the second current mirror can be electrically connected to the second side of the at least one electrode, and the second ground circuit can be connected to the first side of the at least one electrode.
According to another aspect, alone or in combination with one or more of the preceding aspects, the first ground control signal can include the first control voltage, and the first ground circuit can include a current sink configured to control a path to ground from the at least one stimulation electrode in response to the first control voltage. The second ground control signal can include the second control voltage, and the second ground circuit can include a current sink configured to control a path to ground from the at least one stimulation electrode in response to the second control voltage.
According to another aspect, alone or in combination with one or more of the preceding aspects, the first ground control signal can include a first digital control signal, and the first ground circuit can include a MOSFET configured to control a path to ground from the at least one stimulation electrode in response to the first digital control signal. The second ground control signal can include a second digital control signal, and the second ground circuit can include a MOSFET configured to control a path to ground from the at least one stimulation electrode in response to the second digital control signal.
According to another aspect, alone or in combination with one or more of the preceding aspects, the controller can be configured to enforce a control regimen in which the second control voltage is held at zero while the first control voltage is modulated to provide the constant current electrical stimulation pulses. The controller can also be configured to enforce a control regimen in which the first control voltage is held at zero while the second control voltage is modulated to provide the constant current electrical stimulation pulses.
According to another aspect, alone or in combination with one or more of the preceding aspects, the system can include a wearable upon which the controller and the one or more stimulation electrodes are mounted.
The system 10 is configured to apply electrical stimulation signals to one or more nerves of the subject through the skin according to a prescribed neurostimulation method. While these methods can vary widely, they all entail varying or modulating the applied electrical neurostimulation signal, a process referred to herein as neuromodulation. To do so, a neurostimulation circuit 20 embedded in the controller 12 includes a constant current source that is controlled to produce the neuromodulation signal. The neurostimulation circuit 20 is capable of high voltage biphasic output applied across a load which, in the neurostimulation setting, includes the stimulated tissue. To accomplish this, three distinct and often contradictory requirements must be managed: 1) minimizing current fluctuation, 2) managing a high rail voltage, and 3) ensuring charge balance in the bi-phasic waveform.
For neuromodulation, a biphasic signal is preferred so as to avoid charge build up in the subject, thus making the therapy more comfortable and avoiding redux reactions affecting the electrodes 14. It is common for microcontrollers to have built in digital to analog converters (DACs) that allow for an adjustable amplitude voltage output. The problem with this output is that the current flow is limited to one direction. A common solution to adapt this direct current (DC) signal to alternating current (AC) is to utilize solid state switches to alternate the direction of current flow through the output. This is a standard circuit known as an H-bridge, which is shown in
As shown in
Constant current output is important for neuromodulation so that therapy is not affected by potential impedance variations, as are commonly encountered during any real-world subject use. Circuits configured to vary the stimulation voltage in order to maintain a constant stimulation current are sometimes used. A limitation, however, of these circuits is that the current output is limited to one direction of current flow. If this varied voltage constant current neurostimulation signal is applied via an H-bridge (see,
There are standard circuits that can create a biphasic and adjustable amplitude constant current using DC signals. One example is the Howland current pump 40 shown in
The problem with this constant current circuit is that neuromodulation requires a high voltage output. The constant current source current pump 40 is directly powered from the op-amp 42, and high voltage capable op-amps are very difficult to design.
It is possible to isolate the current source from the load and provide the high voltage required to maintain the current separately from the op-amp. An example of such an isolated high-voltage circuit is shown in
The system 10 implements a neurostimulation circuit that produces a controlled waveform implementing all neurostimulation requirements while utilizing a single high voltage power rail.
The neurostimulation circuit 100 includes two constant current circuits 102 configured to apply a constant current stimulation signal through the load RLoad, i.e., the electrode 14 and the stimulated tissue. A first one of the constant current circuits 102a is configured to apply a constant current stimulation signal IStim1 supplied by the rail voltage VRail in a first direction through the load RLoad, i.e., left-to-right as viewed in
The constant current circuits 102 combine several simple component circuits in a novel way to create a simple and effective solution to the problems outlined above.
Utilizing the current sink 110 alone would connect the subject directly to a high voltage power supply, i.e. VRail. Additionally, utilizing the current sink 110 alone would also make it difficult to reverse the current flow through the load RLoad due, for example, to the rise and fall times of the transistors Q3 and Q4, which affect the switching speed of the circuits.
To combat this, each constant current circuit 102 also includes an inverse current mirror circuit 112. The mirror circuit 112 isolates the subject from the high voltage rail VRail. Combining both the current sinks 110 and the mirror circuit 112 provides a novel circuit that enables precise control of current flow with a high maximum voltage, while isolating the subject from the high voltage rail VRail. The neurostimulation circuit 100 utilizes two of these constant current circuits 102 that can selectively open/close a path to ground in order to generate and maintain the same current flow in both directions through the load RLoad. Implementing two constant current circuits 102 as shown in
Referring to
Referring to
As shown in
Noting that the neurostimulation circuit 100 implements two constant current circuits 102a, 102b configured to apply stimulation current in opposite directions through the load, it can be seen that when one constant current circuit is supplying stimulation current to the load, the other constant current circuit supplies no current. Thus, the controller 12 is configured so that when the first control voltage Vin1 is non-zero, meaning that the first constant current circuit 102a is supplying the stimulation current IStim1, the second control voltage Vin2 is zero. Conversely, the controller 12 is configured so that when the second control voltage Vin2 is non-zero, meaning that the first constant current circuit 102b is supplying the stimulation current IStim2, the first control voltage Vin1 is zero.
Given that the controller 12 is configured so that, during stimulation operation, one control voltage is non-zero and the other is zero, the operation of the constant current circuits 102a, 102b can be seen. When the controller 12 utilizes the first constant current circuit 102a to supply the stimulation current IStim1, Vin1 is non-zero and Vin2 is zero. Thus, current sink circuit 110a generates a stimulation voltage VStim1, supplied from the rail voltage VRail, to produce the desired stimulation current IStim1 through the load RLoad, as dictated by the first control voltage Vin1. At the same time, current sink 110d, being controlled by the first control voltage Vin1, provides a path to ground for the stimulation current IStim1. Also at the same time, while stimulation current is being supplied by the first constant current circuit 102a, because the second control voltage Vin2 is by definition zero, current sink circuit 110b leaves its path to ground open, and current sink circuit 110c produces zero stimulation voltage.
Conversely, when the controller 12 utilizes the second constant current circuit 102b to supply the stimulation current IStim2, Vin2 is non-zero and Vin1 is zero. Thus, current sink circuit 110c generates a stimulation voltage VStim2, supplied from the rail voltage VRail, to produce the desired stimulation current IStim2 through the load RLoad, as dictated by the second control voltage Vin2. At the same time, current sink 110b, being controlled by the second control voltage Vin2, provides a path to ground for the stimulation current IStim2. Also at the same time, while stimulation current is being supplied by the second constant current circuit 102b, because the first control voltage Vin is by definition zero, current sink circuit 110d leaves its path to ground open, and current sink circuit 110a produces zero stimulation voltage.
In the neurostimulation circuit 100, the amplitude of voltages Vin1 and Vin2 control the current supply flowing from the rail VRail through the load RLoad. RLoad includes the electrode 14 and the tissue of the subject upon which the electrode is positioned. RLoad can therefore fluctuate from session to session, and even during the same session due, for example, to the electrode 14 shifting and/or subject sweating. Advantageously, the neurostimulation circuit 100 can maintain a constant current flow through the load RLoad, even when the load fluctuates.
A modification to the neurostimulation circuit 100 is shown in
Thus, for example, in
Conversely, to establish a current pulse IStim2 through the load RLoad, the controller 12 adjusts the control second voltage Vin2 to a non-zero voltage in order to apply a second stimulation voltage VStim2 from the rail voltage VRail sufficient to produce the second current pulse IStim2 through the load RLoad. At the same time, the controller 12 commands IO1 to digital 1, closing the path to ground through MOSFET M1. Additionally, the controller 12 controls the first control voltage Vin1 to zero and commands IO2 to digital 0, opening the path to ground through MOSFET M2.
From the above, it will be appreciated that the neurostimulation circuits 100 of
The neurostimulation circuit 100 can be implemented in the neurostimulation system 10 to apply electrical stimulation via the stimulation electrodes 14, which apply the electrical stimulation transcutaneously, according to a proscribed treatment regimen. The neurostimulation circuit can be used to energize the stimulation electrodes in any system, apparatus, or method that implements a neurostimulation treatment or therapy. Implementation of the neurostimulation circuit 100 is not limited to any particular neurostimulation system, apparatus, or method. The neurostimulation circuit 100 can be applied to any system, apparatus, or method for applying electrical neurostimulation. Moreover, implementation of the neurostimulation circuit 100 is not limited to transcutaneous electrical neurostimulation systems, apparatuses, and methods. The neurostimulation circuit can, for example, be implemented in percutaneous electrical neurostimulation systems, apparatuses, and methods.
In one example implementation, the neurostimulation circuit 100 can be implemented in an electronic medical device, a system including the medical device, and a method for using the medical device, configured to apply transcutaneous electrical stimulation to peripheral nerves. According to one specific example, the neurostimulation circuit 100 can be implemented in a system, apparatus, or method for stimulating the tibial nerve (transcutaneous tibial nerve stimulation “TTNS”) to treat medical conditions associated with pelvic floor dysfunction, e.g., over-active bladder (OAB). In a TTNS implementation, a system including an electronic medical device can implement the neurostimulation circuit 100 to apply electrical stimulation near the medial malleolus, which activates both sensory and motor fibers in the nerve. The activation of the sensory fibers of the tibial nerve helps to treat the urge-related symptoms of OAB. The activation of the motor fibers can, however, cause unwanted side effects, such as toe twitch or spasm.
As another example, the system can be used to apply electrical stimulation to the tibial nerve to treat sexual dysfunction. In this manner, it is believed that tibial nerve stimulation could be used to treat genital arousal aspects of female sexual interest/arousal disorder by improving pelvic blood flow.
As another example, the system can be applied to the wrist area to provide stimulation to the ulnar nerve and/or median nerve for pain management in carpal tunnel syndrome, hypertension management, and nerve conduction study/nerve injury diagnosis for median/ulnar nerve neuropathy, etc.
The system and/or the device employed by the system can have a variety of implementations. According to one implementation, the electronic medical device (i.e., the electrodes, control unit, wiring, etc.) can be fixed to a garment that is worn by the subject. The garment can be tight or snug-fitting so as to maintain sufficient contact between the subject's skin and can be configured to position the electrodes at locations specific to the peripheral nerves being stimulated. For example, to stimulate peripheral nerves in the area of the foot or ankle, such as the tibial nerve near the medial malleolus as described above, the garment can be in the form of a sock, ankle brace, strap, sleeve, or other like structure. For stimulating peripheral nerves on the leg, the garment can be a brace, strap, or sleeve sized appropriately for lower leg, knee, or upper leg positioning. For knee or ankle positioning, the garment can be configured, e.g., with openings, slots, or interconnected sections, to allow for bending with the joint while maintaining electrode positioning and contact.
Similarly, for stimulating peripheral nerves on the hand, the garment can be in the form of a glove, mitten, hand brace, or sleeve. For stimulating peripheral nerves on the arm, the garment can be a tight/snug fitting brace, strap, or sleeve (e.g., neoprene) that is sized appropriately for lower arm (forearm/wrist), elbow, or upper arm positioning. For wrist and/or elbow positioning, the sleeve can be configured, e.g., via openings, slots, or interconnected sections, to allow for bending with the joint while maintaining electrode positioning and contact.
In keeping with the above, it will be appreciated that the manner in which the electronic medical device can be secured or supported on the subject can vary. It will also be appreciated that the manner in which the electronic medical device is supported is not critical, as long as contact between the electrodes and the subject's skin is maintained, the positions of the electrode on the subject are maintained, and that the aforementioned are achieved in a manner that is comfortable to the subject.
Various examples of the disclosure have been described. These and other examples are within the scope of the following claims.
This application claims the benefit of U.S. Provisional Application Ser. No. 63/595,821, filed on Nov. 3, 2023. This application is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63595821 | Nov 2023 | US |
