Abstract:
An electrode configuration for surface electrical stimulation to treat chronic and acute pain electrically re-routes current through one of a variety of possible switching means to selectively use a set of electrodes in different modes, for example, in a cross current mode or a longitudinal current mode.

Description:
CROSS REFERENCE TO RELATED CASES  
       [0001]     This application claims priority of U.S. Provisional Patent Application Ser. No. 60/599,012, filed Aug. 6, 2004, the entire specification of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention is generally related to surface electrical stimulation and, more particularly, is related to a system that uses a switchable and programmable electrode configuration during sequential stimulation  
       BACKGROUND OF THE INVENTION  
       [0003]     Surface Electrical Stimulation (also referred to as Transcutaneous Electrical Nerve Stimulation therapy or “TENS” or Neuromuscular Electrical Stimulation, “NMES”) delivers electrical pulses across the skin for various purposes. One of the main indications for Surface Electrical Stimulation (SES) is the relief of acute or chronic pain. Another type of SES (with different parameter sets and electrode configurations) is Neuromuscular Electrical Stimulation (NMES) and is used primarily but not exclusively for disuse atrophy, and or maintenance of range of motion (ROM). Other examples of Surface Electrical Stimulation are, but should not be limited to, Transcutaneous Electrical Nerve Stimulation (TENS), Neuromuscular Electrical Stimulation (NMES), Interferential Stimulation, Diadynamic Stimulation, High Volt Galvanic Stimulation (HVGS), Electro-Magnetic and Pulsed Electro-Magnetic Field Stimulation (EMF &amp; PEMF) and Micro-current Stimulation. SES can also be utilized to effect the healing of various types of tissue, such as, bone, cartilage, connective tissue, etc.  
         [0004]     It has been shown that sequential stimulation (stimulation of different modes or types of stimulation in a sequence) is of benefit and may provide advantages over the use of single modes of stimulation in isolation. One beneficial sequence is first using Interferential stimulation (true interferential rather than pre-modulated) to provide pain control and “quiet” the system followed by Neuromuscular Electrical Stimulation (muscle stimulation) for “working” the muscle or muscle rehabilitation.  
         [0005]     The use of “true interferential” rather than pre-modulated interferential can have some significant benefits. True interferential produces an additive effect to the amplitude where the two circuits cross and allows deeper penetration of higher amplitude signals with less surface stimulation and potential discomfort (see e.g.  FIG. 1 ). This can produce greater levels of stimulation and more effective pain control to deeper structures with less potential patient discomfort.  
         [0006]      FIG. 2  shows a diagram of the current intensity. The depth of modulation can vary from 0 to 100%, depending on the direction of the currents. When two circuits intersect at 90 degrees, the maximum resultant amplitude (i) and the deepest level of modulation is halfway between the two circuits (45 degrees diagonally).  
         [0007]     True interferential current is used with other forms of electrical stimulation in a treatment pattern or sequence. The interferential current typically has a base medium frequency alternating current between 500-20,000 Hz. An interferential current is set up between two circuits that are arranged in a cross pattern (see e.g.  FIG. 1 ). Where the circuits superimpose, the resultant beat frequency will be the difference between the frequencies of the two circuits and the amplitude will be additive and greater than either circuit alone. The range of the beat frequency achieved is usually between 1-250 beats per minute. Multiple levels of stimulation can be treated depending on the electrode pairing combination and modulation pattern selected. The range of output can be from 0-100 volts per circuit, depending on the patient&#39;s needs. The amplitude can be modulated in the respective circuits to increase the area of targeted stimulation. This type of current (interferential) provides improved directional control, decreased accommodation/habituation and depth of penetration in comparison to other types of standard surface stimulation systems. This can also apply to standard implantable stimulation systems and their accompanying surgical leads.  
         [0008]     The inventor has determined that compliance with instructions to manually change electrode configuration is very low. Consequently, manufacturers of devices capable of sequential styles of stimulation have historically used pre-modulated interferential which does not require a change in configuration, but at the same time does not give the full benefit of true interferential stimulation.  
         [0009]     Thus, there is a need in the industry for improvements in apparatus and methods for applying electrical stimulation.  
       SUMMARY OF THE INVENTION  
       [0010]     It is to be understood that both the following summary and the detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Neither the summary nor the description that follows is intended to define or limit the scope of the invention to the particular features mentioned in the summary or in the description.  
         [0011]     In an embodiment, a switchable and programmable electrode configuration is applied during a process of sequential stimulation (a process of stimulation that includes more than one type or sequence of electrical stimulation). Previously, patients were required to manually change the electrode configuration (but not necessarily the electrode placement) from a cross pattern to a longitudinal pattern, which is inconvenient. In preferred embodiments, the switchable configuration disclosed herein allows switching of electrodes between a plurality of predetermined connection patterns, such as, for example, between a longitudinal pattern and a cross pattern.  
         [0012]     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     Many aspects of the invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views:  
         [0014]      FIG. 1  is a perspective drawing showing an interferential pattern area;  
         [0015]      FIG. 2  is a drawing of an interferential current density pattern;  
         [0016]      FIG. 3  is a drawing of a true interferential current stimulation electrode configuration;  
         [0017]      FIG. 4  is a drawing of an electrode configuration for pre-modulated interferential current stimulation using a longitudinal pattern appropriate for NMES;  
         [0018]      FIG. 5  is a schematic drawing of an embodiment of the invention;  
         [0019]      FIG. 6  is a schematic drawing of an embodiment of the invention;  
         [0020]      FIG. 7  is a perspective drawing of electrode placement for pain control around the knee; and  
         [0021]      FIG. 8  is a perspective drawing of electrode placement for muscle maintenance near the knee. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     This disclosure provides and discloses exemplary embodiments. In particular, the specification discloses one or more embodiments that incorporate the features of the invention. The embodiment(s) described, and references in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, persons skilled in the art may effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.  
         [0023]     Embodiments may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g. a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); hardware memory in PDAs, mobile telephones, and other portable devices; magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical, or other forms of propagated signals (e.g. carrier waves, infrared signals, digital signals, analog signals, etc.), and others. Further, firmware, software, routines, instructions, may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers or other devices executing the firmware, software, routines, instructions, etc.  
         [0024]     An exemplary, preferred embodiment includes starting with a first portion of a treatment protocol with 15-30 minutes of true interferential stimulation, which requires a cross pattern of at least two circuits.  FIG. 1  shows an interferential pattern area  102  formed at the cross pattern intersection of electrodes  104  and  104 ′ defining a first circuit  105  and electrodes  106  and  106 ′ defining a second circuit  107 .  FIG. 2  shows the interferential current pattern generated by the arrangement of  FIG. 1 .  FIG. 3  shows electrodes  104  and  104 ′ and  106  and  106 ′ applied across the spinal area. A second treatment protocol, for example, NMES, is then applied. This protocol requires a longitudinal placement of electrodes along the length of the target muscle. Referring to  FIG. 4 , an exemplary placement is shown with a first circuit using electrodes  104  and  106 , and a second circuit using electrodes  104 ′ and  106 ′.  
         [0025]      FIGS. 5 and 6  demonstrate an exemplary embodiment of the invention that uses a mechanical (hardware) switch or relay to re-route the current from two of the electrodes (one from each channel). As shown in  FIGS. 5 and 6 , a device  500  incorporates a first channel circuit  502  and a second channel circuit  504 . Outputs  508  and  510  of circuit  502  are connected respectively to electrode  104 ′ and to an input  516  of switch  506 .  
         [0026]     Input  516  of switch  506  is selectively connected to one of outputs A and B associated with input  516 , depending on the state of switch  506 . Outputs A and B are connected to electrodes  106 ′ and  104  respectively. Second channel circuit  504  has outputs  512  and  514 , connected respectively to input  518  of switch  506  and to electrode  106 . Input  518  of switch  506  is connected either to electrode  104  or to electrode  106 ′, depending on the state of switch  506 .  
         [0027]     In this embodiment, switch  506  is shown schematically as a double pole, double throw switch. However, it will be understood that the scope of the invention is not limited to any particular type of switch. The functionality of switch  506  can be implemented either as a mechanical switch, a solid state or electronic switch, or in any other known manner that produces similar results in terms of the application of electrical stimulation in the desired patterns.  
         [0028]     As can be seen, when switch  506  is in the first state (inputs connected to the A outputs), as shown in  FIG. 5 , a longitudinal pattern electrode configuration is provided. In a second state of switch  506 , as shown in  FIG. 6 , a cross pattern electrode configuration is provided.  
         [0029]     Other desirable embodiments utilize electronic circuitry to switch the electrode configuration and have the advantage of smaller size, but provide similar functionality. The electronic circuitry may vary the state of the electrode connections under control of an automatic program or processor to provide an appropriate automated sequence of stimulation. Switch  506  has a control means  520  for actuating the switch. Control means  520  may be any desired mechanism for controlling the state of the switch or switch equivalent used in the circuit. For example, without limitation, control means  520  may be a manual activation by a user or clinician, a timer, an electronic control, or a microprocessor control responding to a program for applying a predetermined sequence of stimulations.  
         [0030]     A switchable and programmable electrode configuration will greatly benefit patients suffering from pain and muscle dysfunction by increasing their compliance to the prescribed protocol while obtaining the added benefits of true interferential stimulation.  
         [0031]     Another use for a switchable electrode configuration is for incorporation into garments that include multiple electrodes (garment not shown). One such garment is provided for the knee to activate surface electrical stimulation surrounding a joint or area of pain (see  FIG. 7 ), and then switch to a different configuration that would facilitate patterned or reciprocal stimulation of the agonist (Quadriceps) and antagonist (Hamstrings) muscle groups (see  FIG. 8 ).  
         [0032]     While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.