Apparatus and methods for providing electrical stimulation

An apparatus is disclosed for providing electrical stimulation to a subject from a stimulation unit using a transmission line and a plurality of electrodes. The apparatus may include a plurality of discrete nodes, each adapted to connect to the transmission line for receiving the electrical stimulation and to connect with at least one pair of the plurality of electrodes. Related methods are also described.

COPYRIGHT STATEMENT

A portion of the disclosure of this document contains material subject to copyright protection. No objection is made to the facsimile reproduction of the patent document or this disclosure as it appears in the Patent and Trademark Office files or records, but any and all rights in the copyright(s) are otherwise reserved.

TECHNICAL FIELD

The present disclosure relates to the physical therapy arts and, more particularly, to apparatus and methods for providing therapy with electrical stimulation and related methods.

BACKGROUND OF THE INVENTION

Various types of physical therapy, including rehabilitative exercise, may employ externally applied, transcutaneous stimulation in the course of treating a subject. Typically, the stimulation comprises discrete electrical pulses generated by an external stimulator, and travel through associated wires to one or more electrode pairs placed on the skin adjacent a target location. In the case of exercise therapy, the electricity passing through the skin causes the targeted muscle fibers to activate or contract, even without voluntary control by the subject. Accordingly, such stimulation is frequently used in situations where the subject is incapacitated or otherwise unable to control function of the muscles, such as in the event of an injury to the brain or associated portion of the nervous system.

Despite the past use of electrical stimulation for providing therapy, certain limitations in the application of this technology and the results produced remain. For one, a pair of electrodes is typically associated with a single stimulation channel providing the electrical pulses to the targeted location. Thus, to simultaneously or even sequentially provide stimulation to different muscle groups or otherwise in a distributed fashion, pairs of electrodes must each be connected to a different channel of a stimulation source using individual wire for transmitting the pulses. Thus, for example, to stimulate three different muscle groups, three pairs of electrodes would be used, with each pair having an individual wire for transmitting the stimulation pulses from a three channel stimulator (and, to make the wires universal, they are typically made longer than necessary to reach a given body part). Aside from greatly increasing the cost and complexity, such wires may easily become tangled or damaged during the exercise movement.

In typical applications, the stimulation pulses delivered from the source are also infinitesimally small compared to the inter-pulse interval. For example, a given pulse may be active for less than 1,000 milliseconds for every 20,000 milliseconds of time that passes. Thus, there is a substantial amount of unused potential of the stimulation device while it waits to deliver the next pulse.

Accordingly, a need is identified for apparatus and methods that provide an improvement in delivering electrical stimulation to a subject in an efficient and effective manner. In particular, the apparatus would use a single transmission line per channel connected to serially arranged nodes, each associated with an electrode pair, to minimize the number of wires required. This would potentially allow for the application of stimulation to an unprecedented number of channels without significantly adding to the complexity or cost. Moreover, the apparatus would be capable of maximizing the potential of the stimulation device, which further enhances efficiency and reduces cost. Overall, a significant improvement over known past approaches would be realized.

SUMMARY OF THE INVENTION

One aspect of the disclosure is an apparatus for providing electrical stimulation to a subject from a stimulation unit using a transmission line and a plurality of electrodes. The apparatus comprises a plurality of discrete nodes, each adapted to connect to the transmission line for receiving the electrical stimulation and to connect with at least one pair of the plurality of electrodes.

In one embodiment, the nodes are serially connected to the transmission line. Thus, a first node is adapted to be connected to the stimulation unit by a first segment of the transmission line, and further adapted to be connected to a second segment of the transmission line. A second node is adapted to be connected to the second segment of the transmission line, and this succession may be repeated.

A first end of the first segment of the transmission line may be connected to the stimulation unit, and the first node provided with a first receptacle for connecting with a second end of the first segment. The second node includes a first receptacle for connecting with a second end of a second segment. Each node may further include an indicator indicating the provision of stimulation from the unit to the node.

A first node may include a circuit adapted for receiving the stimulation from the stimulation unit. The circuit may be adapted to receive a pulse train of stimulation and output only pulses intended for the corresponding node. Alternatively or additionally, the circuit may be adapted to activate the first node while a second node remains inactive.

The subject may have a plurality of different muscle groups in need of stimulation. In such case, a first node is arranged to stimulate a first of the muscle groups and a second node being arranged to stimulate a second one of the muscle groups. A garment adapted to be worn by the subject may also incorporate the plurality of nodes.

Another aspect of the disclosure relates to an apparatus for providing electrical stimulation from a stimulation unit to a subject using a plurality of electrodes. The apparatus comprises a plurality of nodes for receiving the stimulation associated with a pair of electrodes. Each adjacent node is connected by at least one transmission line. At least a first node of the plurality of nodes comprises a circuit adapted to operate in one of a first mode to allow stimulation pulses to pass to the subject donning the electrodes and a blocking mode to block pulses intended for other nodes. Preferably, the plurality of nodes are connected to each other and the stimulation unit in a daisy chain.

Still another aspect of the disclosure pertains to an improvement in a system for providing neuromuscular electrical stimulation as the result of a stimulation signal provided from stimulation unit to a plurality of pairs of electrodes positioned on a skin surface of a human subject. The improvement comprises at least one node associated with a transmission line and each electrode pair, said node adapted for receiving and processing the stimulation signal from the stimulation unit.

The improvement may further include a plurality of discrete nodes connected to the transmission line in a daisy chain. At least the first node may include a circuit adapted to operate in one of a first mode to receive a pulse train of stimulation from the stimulation unit in which every ithpulse is intended for the ithnode, or a second mode to receive a pulse train for activating a selected node to provide the stimulation while another node remains inactive.

The transmission line may comprise a first segment having a first end connected to the stimulation unit and a second end removably connected in a first receptacle on the first node, and further including a second segment having a first end connected in a second receptacle on the first node. The second segment may include a second end for removably connecting with a second receptacle on a second node.

Preferably, the stimulation unit includes a first output channel for connecting with the plurality of discrete nodes and further including a second output channel for connecting with a second plurality of discrete nodes. Each node in the second plurality of discrete nodes may be associated with at least two electrodes.

Yet another aspect of the disclosure relates to an apparatus for providing electrical stimulation to a subject using a plurality of electrodes. The apparatus comprises a plurality of nodes, each node adapted to connect to at least one pair of the plurality of electrodes and provide stimulation to the subject using the electrodes, and a stimulation unit for providing a first train of stimulation pulses in which every ithpulse is intended for the ithnode.

Preferably, the nodes are connected by a single transmission line in a daisy chain. Besides the first train, the stimulation unit may be adapted for providing a second train of stimulation pulses in which every pulse is intended for a selected node. Each node may include a pulse gating circuit adapted to output a selected pulse from the first train of stimulation pulses.

A further aspect of the disclosure pertains to a kit for forming an apparatus for providing electrical stimulation to a subject from a stimulation unit using a transmission line and a plurality of electrodes. The kit comprises a plurality of nodes, each including at least one receptacle adapted to connect to the transmission line, and a plurality of electrode pairs, each for connecting to one of the plurality of nodes. A related aspect comprises a computer-implemented method for providing stimulation for a subject using a stimulation unit, including programming the stimulation unit to operate in combination with the kit.

Related methods disclosed include a method for forming an apparatus for providing electrical stimulation to a subject from a stimulation unit using a first transmission line and a plurality of electrodes. The method comprises connecting a plurality of discrete nodes to the first transmission line, each node adapted for connecting to at least one pair of electrodes. The connecting step may comprise positioning a first removable connector of the transmission line in a first receptacle of a first node. The connecting step may further comprise connecting a second removable connector of the transmission line in a second receptacle of a first node; and connecting a third removable connector of the transmission line in a first receptacle of a second node. The method may further include the step of providing the nodes on a garment. The step of programming the stimulation unit to provide a pulse train in which every ithpulse is intended for the ithnode may also form part of the method, as may the step of programming the stimulation unit to provide a pulse train in which a group of sequential pulses are intended for a selected node.

The disclosure also relates to a method for providing electrical stimulation to a subject using a plurality of electrodes. The method comprises providing a plurality of nodes, each node adapted to connect to at least one pair of the plurality of electrodes, and providing a first train of stimulation pulses in which every ithpulse is intended for the ithnode. The method may further include the step of providing a second train of stimulation pulses in which every pulse is intended for a selected node.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment relates to an active distributed electrode array (ADEA) system10for electrical stimulation therapy and, neuromuscular electrical stimulation, in particular. The system10includes a stimulation unit12having at least one output that, using other components described herein, may be shared to provide essentially an unlimited number of virtual stimulation channels with intelligently controlled coordinated simulation patterns. This allows for use in high channel count applications without the added cost and complexity of a rigidly defined high channel count NMES unit. The system10further allows virtual stimulation channels to be added and/or removed as needed by the therapist to form a low-cost network of stimulation nodes using a minimal set of wires and simulation that is controlled automatically by the stimulation unit12.

As shown inFIG. 1, the stimulation unit12is adapted to output stimulation pulses to at least one, and preferably a plurality of discrete stimulation nodes14(i.e., virtual channels) associated with each output channel, rather than to a single electrode pair. Each node14, is in turn, associated with a pair of electrodes16a,16b, for applying the stimulation to a particular location, such as the skin surface adjacent a muscle or muscle group of a human subject in need of therapy (e.g., assisted exercise or rehabilitation, including possibly pain management). As illustrated, these electrodes16a,16bmay be discrete and thus comprise separate flat pads of a flexible material, and may be associated with suitable fasteners (adhesives, straps, bands, etc., not shown) for attachment to the skin surface. Four nodes14are shown inFIG. 1for purposes of illustration, but is should be appreciated that any number could be used. In the illustrated embodiment, the node14is connected to a surface of the electrode pad opposite the surface for applying the stimulation to the skin surface of the subject, but it should be appreciated that the node could be a separate structure as well.

The nodes14may be connected together and to the stimulation unit12using suitable a transmission line18, which may comprise multiple wires and thus be adapted to provide not only the simulation pulses, but also communication signals. Preferably, the connection is made in a daisy-chain fashion, such that a single transmission line18connects the stimulation unit12to each successive node14in the chain. Thus, for example,FIG. 2shows that the line18includes a first segment18afor connecting the node14with the stimulation unit12, and a second segment18bfor connecting to the next successive node (e.g., A2, if node14inFIG. 2is A1).

As should be appreciated, segments of transmission line18may be added for connecting additional nodes14to the array. Regardless of the number of segments or precise form used, the use of a single, external transmission line18from the stimulation unit12to the nodes14associated with a particular channel is advantageous because the number of wires that must be managed is greatly reduced (usually, two per channel). This not only greatly simplifies the set up process, but also reduces the potential for damage as the result of the exercise movement.

Referring to the block diagram inFIG. 3, the node14is shown as being connected to a simulation unit12via a port A (which as should be appreciated corresponds to virtual channels A1-A4in the illustrated embodiments). This port A may provide the nodes14with power, communication, and access to the stimulation output channel of the unit12. Preferably, there are two stimulation channels delivered through different ports A and B to distinct arrays of discrete nodes14arranged in tandem (seeFIGS. 7 and 8), but more or fewer may be used depending on the particular application.

The connection of the segments18a,18bto the node14is made in a releasable fashion. For example, in the illustrated embodiment, the node14comprises a housing14a(which is optional), and releasability is achieved using suitable receptacles14bon the housing14a. These receptacles14bmay take the form of a conventional telephone (RJ-11) jack, for associating with suitable connectors on the corresponding ends of the segments18a,18b. By using common connectors releasably attached in this manner, the nodes14may be added or removed along the transmission line18with ease.

Suitable lines19also connect each node14to the electrodes16a,16bfor providing the stimulation pulses. This connection may also be established using releasable connectors19a(e.g., pins for positioning in jacks associated with pigtail leads) to allow for the removal and replacement of the electrodes16a,16b, if necessary or desired. The node14is shown inFIGS. 2 and 2aas being carried by one of the electrodes16a,16bin the pair, but this is entirely optional. Each node14may also associate with an indicator20for providing a signal indicating an active condition (i.e., the stimulation current is reaching the node and/or flowing to the electrodes16a,16b), as well as possibly indicating the stimulation intensity (e.g., as a function of current).

At least one, and preferably all of the nodes14are “intelligent” and thus may be adapted to receive and process the stimulation pulses received from the stimulation unit12. For example, the nodes14may process and selectively output the stimulation pulses intended only for an electrode pair16a,16bfor a particular operation (e.g., stimulating a muscle group), while blocking pulses intended for the other electrodes/muscle groups. To achieve this goal, each node14may include a pulse selection circuit22and a pulse gating circuit24, which work together to provide certain predetermined operating modes.

The pulse gating circuit24serves as the interface between the stimulation unit12and the electrodes16a,16bconnected to each node14. In a pass-through mode, the gating circuit24allows stimulation pulses from the unit12to pass to the subject donning the electrodes when certain amplitude and width specifications are met. In blocking mode, the gating circuit24blocks pulses intended for other nodes14.

The pulse selection circuit22in turn is responsible for communicating with the stimulator12, monitoring the stimulation pulse train on a pulse-by-pulse basis, enabling the pulse gating circuit (such as via an enable line26), indicating node activity (such as via the stimulation indicator20, which is shown inFIG. 3as comprising a light-emitting diode), and allowing for the selection of a particular virtual channel via a selector switch (not shown). A suitable controller associated with each node14may be used to perform these functions, or alternatively an application specific integrated circuit (ASIC) may be used.

The pulse gating circuit24may comprise a discrete transistor-based circuit or a TRIAC, but other arrangements may be possible as well. For example,FIGS. 4 and 5present schematic diagram for two possible alternative applications for forming the pulse gating circuit24for each stimulation node14of the system10. The block L represents the load (i.e., the electrodes16a,16bconnected by tissue), and transistors Q control current flow through the load L when the stimulation unit12generates a pulse on the “A” stimulation bus. Current flow (shown as dashed line C in this example) proceeds from the A(+) stimulation output through the transistor Q, load L, and diode D before returning to the unit12via the A (−) bus. This flow may be reversed to pass the second phase when two events occur: (1) the pulse selection circuit22withdraws the enable (+) line and asserts the enable (−) line, and (2) the stimulator12switches the polarity of the A(+) and A(−) bus in preparation for generating the second phase of the stimulation pulse.

InFIG. 5, the shunt circuit28comprises an extra transistor that is placed in parallel with the electrodes (i.e., load L). This circuit28is intended to prevent an unintended muscle contraction caused by leakage current through the gating circuit24(i.e., a pulse that is not fully blocked when the gating circuit is disabled). This provides a path for the leakage current to flow that bypasses the electrodes. The transistor of shunt circuit26would be enabled whenever both legs of the gating circuit24are disabled. Alternatively, two relays (not shown) could be used in place of transistors Q inFIG. 4. The relay coil would be excited by the pulse selection circuit22.

A timing diagram illustrating one possible embodiment of the monitoring and triggering tasks of the pulse selection circuit22is shown inFIG. 6. Pulses P of the interlaced pulse train T are shown for virtual channels A1and A2. Trigger events are shown on the falling edges of each stimulation pulse P, and may cause a microcontroller interrupt, such that the interrupt service routine determines if the output of the pulse gate circuit24of a particular node14should be enabled (such as by counting the pulses and enabling for pulses which are intended to be output using the particular electrodes16a,16b). To enable a pulse P to the particular virtual channel, the enable signal E may be set high during the inter-pulse interval before the pulse to be output and return to the disabled state during the inter-pulse interval following the desired pulse output. The output to the A1electrodes16a,16bare shown, indicating that the A1pulse passes and the A2pulses are blocked.

Alternative arrangements may also be used to control the gating circuit24. For instance, a microcontroller associated with each node14could use an error-checking scheme to determine the inter-phase interval (i.e., the period between anodic and cathodic pulses for the same channel) from the inter-pulse interval (i.e., the period between successive pulses for different channels), and then disable the node if an error is detected. Alternative approaches could be the use of pulse width to evaluate which pulses should be outputted using the electrodes associated with a node14, or an asynchronous clocking scheme in which the nodes and stimulation unit12employ synchronized clock rates to output pulses during a particular window of time. Yet another alternative approach could be for the controller (stimulation unit12) to send a command during the interpulse interval to enable the desired channel prior to outputting a pulse.

In any case, the system10may be configured to operate in two possible modes: (i) pulse sharing; and (ii) channel phasing. In pulse sharing mode, the unit will configure a plurality of virtual channels (e.g., A1-A4) to be active and then output an interlaced pulse train T of stimulation provided by stimulation unit12in which every ithpulse is intended for the ithnode14. Thus, as shown inFIG. 7, the nodes14will parse the pulse train T to selectively output only the pulses intended for the particular node14(i.e., output every 4thpulse). In this mode, the stimulation unit12may be used to simultaneously activate multiple muscle groups using a single channel and thus form a distributed array.

In channel phasing mode, the unit10may activate a selected virtual channel (A1, A2, or A3) while other channels (e.g., A4) are inactive. The unit12may then be used to output a traditional stimulation pulse train T. The pulses are delivered by only the electrodes16a,16bassociated with the active virtual channel. This mode of operation is shown schematically inFIG. 8. These modes may be used in combination such that the stimulation unit12essentially has an unlimited number of channels for a given transmission line18.

As can be best understood with reference toFIG. 9, use of these aspects of the system10together (which is optional) may provide several advantages. At the top of this figure, a traditional electrical stimulation pulse train M to a single electrode pair is shown. Stimulation pulses are infinitesimally small compared to the inter-pulse interval (e.g., less than or equal to 1000 ms active per every period greater than or equal to 20,000 ms). The shaded region R indicates the unused potential of the stimulation device as it waits to deliver the next pulse. With the present system10, the stimulation unit10may output the interlaced pulse train N as shown, which includes pulses for virtual channels A1-A4. All connected stimulation nodes14receive the interlaced pulse train N and either output the pulses to the connected electrode pair16a,16bor block pulses intended for other nodes/virtual channels.

The modular nature of the system10allows for selected components to be provided as a kit. For example, the kit may comprise a plurality of nodes14and electrode pairs16a,16b, both adapted for connecting to the associated transmission line18,19. The kit may be provided for use by product developers for use in a particular stimulation application. The components of the system10or the kit could also be incorporated into a stimulation garment30(shown as a shirt inFIG. 10as one example, but the garment may also comprise a sleeve, band, pant, or the like, depending on the particular need of the subject).

The stimulation unit12may be programmed to provide the stimulation patterns desired for each electrode or group of electrodes to meet the individual needs of the patient. This programming may be done, for example, by using a software application for designing a particular stimulation regimen, including the ability to program the different virtual channels simultaneously (seeFIG. 11, a screen shot from an application for designing stimulation regimens;FIG. 12, which is a pattern generator application; andFIG. 13, which is a program for designing the display output on a stimulation unit12). Alternatively or additionally, pre-programmed stimulation paradigms may be provided, and at power-up the stimulation unit12may evaluate the connected nodes14and automatically bypass those not in use. In this case, the array size would be easily scalable by the end user (a physical therapist or even a patient) by simply adding or removing nodes14to the particular stimulation channel(s).

As should also be appreciated, the modular nature of the nodes14allows for their positioning in a stimulation array that may be distributed among several different muscle groups. For example, different nodes14may be associated with the subject's quadriceps, gluteals, and hamstrings. In this manner, a complete stimulation solution may be provided using a single stimulation channel. The nodes14need not be limited to a particular body part or region of the body, but may extend over multiple body parts (e.g., the chest, shoulder, and arm; the back or abdomen and legs, etc.).

To further facilitate the portability of the system10and concomitant ease of use, the stimulation unit12preferably comprises a portable, hand-held battery operated device. For example, the unit12may take the form of the CK200 device available from customKYnetics, Inc. of Versailles, Ky. Certain features of this unit12are described in U.S. patent application Ser. Nos. 12/164,554 and 60/937,633, the disclosures of which are incorporated herein by reference.

The foregoing descriptions of various embodiments of the invention are provided for purposes of illustration and not intended to be exhaustive or limiting. Modifications or variations are also possible in light of the above teachings. The embodiments described above were chosen to provide the best application to thereby enable one of ordinary skill in the art to utilize the disclosed inventions in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention.