Method and apparatus for securing and/or identifying a link to a percutaneous probe

[0001] The present application claims priority to U.S. Provisional Application No. 60/325,975 filed Sep. 28, 2001 and incorporated herein in its entirety by reference.

[0002] The present invention relates generally to methods and apparatuses for securing and/or identifying a link to a percutaneous probe, such as an electrode used for electrical nerve stimulation. Electrical therapy has long been used in medicine to treat pain and other conditions. For example, transcutaneous electrical nerve stimulation (TENS) systems deliver electrical energy through electrode patches placed on the surface of a patient's skin to treat pain in the tissue beneath and around the location of the patches. One problem with TENS systems is that they may not provide patients with adequate relief. One approach to addressing this problem has been to deliver the electrical therapy percutaneously in a process termed “percutaneous neuromodulation therapy” (PNT) or “percutaneous electrical nerve stimulation” (PENS). This process can include inserting needle-like electrodes through the patient's skin to deliver electrical therapy more directly to the target nerves.

[0003] One method for applying percutaneous nerve stimulation is to insert acupuncture needles into the patient's skin and attach the needles to a wave form generator via cables and alligator clips to deliver percutaneous electrical currents. One drawback with this technique is that the acupuncture needles are typically exposed to the practitioner during insertion and removal. Accordingly, the practitioner can be exposed to blood-borne pathogens which might be present on the needle after the needle has been removed from the recipient.

[0004] The present invention is directed to methods and apparatuses for securing and/or identifying a link to a percutaneous probe. An apparatus in accordance with one aspect of the invention includes an electrical coupler having a coupling member configured to be removably positioned at least proximate to a percutaneous probe. The coupling member can also be coupleable to a therapeutic electrical signal emitter. The apparatus can further include a therapeutic signal transmission link coupled to the electrical coupling member and coupleable to a source of therapeutic electrical signals to transmit the therapeutic signals to the recipient. The device can still further include a status signal transmission link at least proximate to the therapeutic signal transmission link and coupleable to a status signal emitter. The status signal transmission link can be at least tamper-resistant and/or tamper-evident, and can be configured to transmit a status signal having a first characteristic value when the status signal transmission link is in a first condition, and transmit a status signal having a second characteristic value different than the first characteristic value when the status signal transmission link has been altered from the first condition to a second condition.

[0005] In a further aspect of the invention, the status signal transmission link can include an electrical conductor, such as a stainless steel or fibrous carbon conductor, and the apparatus can further comprise a sensor coupled to the signal transmission link. The sensor can include at least one of an electrical continuity sensor, an electrical resistance sensor, and an electrical impedance sensor.

[0006] In another aspect of the invention, the apparatus can include a memory device having a stored characteristic value and positioned at least proximate to the therapeutic signal transmission link. The status signal transmission link can be connected to the memory device and can be connectable to a sensor to transmit the stored characteristic value from the memory device to the sensor.

[0007] The invention is also directed to a method for assessing compatibility between a percutaneous signal emitter and an electrical coupler configured to transmit electrical signals to a percutaneous probe. The method can include transmitting a status signal along a tamper-resistant and/or tamper-evident status signal transmission link coupled to the electrical coupler. The method can further include receiving a value of a characteristic of the status signal transmission link based on the status signal, and comparing the value with a target value for the characteristic. When the value differs from the target value by at least a pre-selected amount, the method can further include providing an indication to a user. The indication can include disabling the transmission of therapeutic electrical signals.

[0017] The present disclosure describes methods and apparatuses for securing and/or identifying a link between a therapeutic signal emitter and an electrical coupler that is operatively coupled to a percutaneous probe, such as an electrode. Accordingly, the apparatus can include a tamper-evident and/or tamper-resistant link between the therapeutic signal emitter and the electrical coupler. As a result, the apparatus can provide a signal to the user to indicate when the link to the electrical coupler is missing, inappropriate, damaged, and/or severed.

[0018] Many specific details of certain embodiments of the invention are set forth in the following description and in FIGS. 1-9 to provide a thorough understanding of these embodiments. One skilled in the art, however, will understand that the present invention may have additional embodiments, and that the invention may be practiced without several of the details described below.

[0019] FIG. 1 is a partially schematic isometric illustration of an apparatus 10 in accordance with an embodiment of the invention. In one aspect of this embodiment, the apparatus 10 can include a control device 30 having a therapeutic signal emitter 32 configured to transmit therapeutic electrical signals along a therapeutic signal transmission link 34. The therapeutic signal transmission link 34 can include a plurality of electrical conductors, each connected to an electrical coupler 50 via a coupler cable 57. The electrical couplers 50 can be removably supported on a flexible support member 20. Accordingly, the support member 20 can include a plurality of support sites 22, each configured to support one of the electrical couplers 50. The electrical couplers 50 can be removed from the support member 20 and attached to percutaneous probes for delivering electrical therapy to a recipient, as described in greater detail below with reference to FIG. 2. Further details of embodiments of the support member 20 are included in U.S. patent application Ser. No. 09/751,382 titled “Apparatus and Method for Coupling Therapeutic and/or Monitoring Equipment to a Patient,” filed Dec. 29, 2000 and incorporated herein by reference. Further details of embodiments of the control device 30 are included in the U.S. Provisional Application No. 60/325,725 titled “Method and Apparatus for Controlling Percutaneous Electrical Signals,” filed Sep. 28, 2001 and incorporated herein by reference.

[0020] The apparatus 10 can further include a status signal transmission link 40 (shown in dashed lines in FIG. 1) connected between the support member 20 and the control device 30 to transmit status signals to and from the control device 30. The status signal transmission link 40 can be bundled together with the therapeutic signal transmission link 34 in a support member cable 21 to provide a compact link between the support member 20 and the control device 30.

[0021] The control device 30 can include status signal emitter 31 and a status signal sensor 33, both operatively coupled to the status signal transmission link 40. The status signal emitter 31 can direct status signals along the status signal transmission link 40, and the status signal sensor 33 can detect characteristics of the status signal transmission link 40 based upon the signals transmitted along the signal transmission link 40 by the status signal emitter 31. For example, the status signal transmission link 40 can include an electrical conductor and the status signal emitter 31 can transmit an electrical signal along the status signal transmission link 40. The status signal sensor 33 can detect a resistance, impedance and/or other electrical characteristic of the status signal transmission link 40, based on the electrical signal transmitted along the status signal transmission link 40. The status signal sensor 33 (and/or other components of the control device 30) can compare the measured value of the characteristic to an expected value and, if the measured value differs from the expected value by more than a pre-selected margin, the status signal sensor 32 (or other components) can provide an indication that the status signal transmission link 40 is missing or has been severed or damaged.

[0022] In one embodiment, the indication can include interrupting and/or preventing the therapeutic signal emitter 32 from transmitting therapeutic signals to the electrical couplers 50. In other embodiments, the indication can include a visual indication, such as an indicator light, display or sound. In any of these embodiments, the apparatus 10 can warn the user and/or restrict the user from using the apparatus 10 when it detects a damaged or missing status signal transmission link 40.

[0023] FIG. 2 is a partially schematic, isometric illustration of the support member 20 placed upon a recipient's back in accordance with an embodiment of the invention. In one aspect of this embodiment, the support member 20 can include ten support sites 22, each removably carrying an electrical coupler 50 (one of which is shown in FIG. 2), and each aligned with an electrode assembly 60 removably positioned on the recipient's back. In other embodiments, the support member 20 can carry more or fewer electrical couplers 50, and/or the support member 20 can be configured to contact portions of the body other than the back. In any of the foregoing embodiments, the electrical couplers 50 can each be removed from the corresponding support site 22 and connected to the corresponding electrode assembly 60 to (a) insert a percutaneous probe from the electrode assembly 60 into the recipient in a shielded manner, and (b) provide electrical contact with the percutaneous probe, as described in greater detail below with reference to FIGS. 3-5.

[0024] FIG. 3 is an exploded isometric view of an embodiment of the electrode assembly 60 described above with reference to FIG. 2. The electrode assembly 60 can include a housing 61, which can in turn include a base 62 that rests on the recipient's skin, an adhesive pad 64 to adhere the base 62 to the skin, and a sleeve 66 received in the base 62. The base 62 can include a skin engaging surface and a casing. For example, the skin engaging surface can be an annular lip 65 and the casing can be a tube 63 projecting from the lip 64 at a desired angle. A slider 67 can fit in the sleeve 66 to support a percutaneous probe 68 (such as a sharpened electrode) for movement relative to the base 62 into and out of the recipient.

[0025] In operation, the slider 67 can slide downwardly and upwardly within the sleeve 66 to insert and retract the probe 68. In one aspect of this embodiment, the slider 67 and the sleeve 66 can rotate as a unit to selected positions relative to the base 62. In a further aspect of this embodiment, the slider 67, the sleeve 66, and the base 62 can all be coaxial with a central axis 69 of the housing 61, and the probe 68 can be offset or eccentric relative to the central axis 69. Accordingly, when the slider 67 and the sleeve 66 are rotated together as a unit relative to the base 62, the probe 68 orbits about the central axis 69 to a new position relative to the patient's skin surface. In an alternate embodiment, the probe 68 can be aligned on the central axis 69, and/or the sleeve 66 can be fixed relative to the base 62, for example, when it is not necessary to orbit the probe 68 about the central axis 69.

[0026] FIG. 4 is an exploded top isometric view of an electrical coupler 50 that engages the slider 67 (FIG. 3) and moves the slider 67 and the probe 68 (FIG. 3) into the recipient. The electrical coupler 50 can include a plunger 51 that releasably engages the slider 67 and translates the slider 67 axially within the sleeve 66 (FIG. 3). The electrical coupler 50 can further include an electrical coupling member 52 supported by a support body 53. In one embodiment, the electrical coupling member 52 can be biased into direct contact with the probe 68 by a spring 55 to make electrical contact with the probe 68. Alternatively, the coupling member 52 can transmit electrical signals to the probe 68 without making direct contact with the probe 68, for example, via an intermediate dielectric material. In either embodiment, the coupling member 52 can be connected to the therapeutic signal link 34, housed within the coupler cable 57. The coupler cable 57 can pass through a cap 56 and a grommet 54 into the electrical coupler 50.

[0027] In one embodiment, the status signal transmission link 40 also can extend into electrical coupler 50. In one aspect of this embodiment, the status signal transmission link 40 can form a loop that terminates in the support body 53 proximate to the coupling member 52. In other embodiments, the status signal transmission link 40 can form a loop that terminates in other portions of the electrical coupler 50. In still further embodiments, the status signal transmission link 40 can form a loop that terminates at the support member 20 (FIG. 1) without being operatively coupled to the electrical coupler 50.

[0028] FIG. 5 is a partially exploded isometric view of an embodiment of the electrical coupler 50 positioned to actuate the probe 68 of the electrode assembly 60. In one aspect of this embodiment, the slider 67 carrying the probe 68 can include a guide member 72 positioned for sequential movement in a transverse groove 70 and an axial groove 71 of the housing 61. The slider 67 can further include a receiving portion positioned to receive the electrical coupler 50 so that the coupling member 52 of the electrical coupler 50 makes electrical contact with an elbow portion 73 of the probe 68. The electrical coupler 50 can then be rotated and driven axially downwardly to insert the probe 68 into the recipient. When the probe 68 has been inserted, the user or practitioner can deliver therapeutic electrical signals to the recipient via the probe 68 by operating the control unit 30 (FIG. 1). Further details of embodiments of the electrical coupler 50 and the electrode assembly 60 are included in pending U.S. patent application Ser. Nos. 09/452,477 titled “Percutaneous Electrical Therapy System With Electrode Entry Angle Control,” filed Dec. 1, 1999, and 09/666,931 titled “Method and Apparatus for Repositioning a Percutaneous Probe,” filed Sep. 21, 2000, both incorporated herein in their entireties by reference.

[0029] In any of the foregoing embodiments, a feature of the electrode assembly 60 and the electrical coupler 50 in that they can be operated together to insert the probe 68 into the recipient without exposing the sharp end of the probe 68 to the practitioner or others who may be in the vicinity. Accordingly, the electrode assembly 60 and the electrical coupler 50 can reduce the likelihood for inadvertently pricking the practitioner and others with the probe 68, and can accordingly reduce the likelihood for transmitting blood-borne pathogens and/or other potentially harmful agents.

[0030] FIG. 6 is a partially schematic view of a portion of the apparatus 10 described above with reference to FIGS. 1-5. For purpose of illustration, only two of the ten electrode couplers 50 shown in FIG. 1 are shown in FIG. 6. Each electrical coupler 50 can be connected to the therapeutic signal emitter 32 via the therapeutic signal link 34. Accordingly, the therapeutic signal link 34 can include a plurality of electrical conductors 35 (two are shown in FIG. 6), each of which is connected to one of the electrical couplers 50, and each of which is electrically isolated from the other in the support member cable 21. In one aspect of this embodiment, each electrical conductor 35 can include a tamper-resistant and/or damage-resistant material. For example, each electrical conductor 35 can include a stainless steel wire or other conductor which is difficult to sever. In other embodiments, the electrical conductors 35 can include other materials that are also damage-resistant and/or tamper-resistant.

[0031] In a further aspect of this embodiment, the status signal transmission link 40 can include a loop that extends to two of the electrical couplers 50. For example, the status signal transmission link 40 can include an electrically conductive wire that extends from the status signal emitter 31, along the support member cable 21, out to one of the electrical couplers 50, back to the support member 20, out to the other electrical coupler 50, and back along the support member cable 21 to the status signal emitter 31 and/or electrical ground. Accordingly, the status signal transmission link 40 can form a normally closed, complete electrical circuit having a known characteristic, such as an impedance or resistance.

[0032] In operation, the status signal emitter 31 can direct a small current flow along the status signal transmission link 40, and the status signal sensor 33 can measure or detect the characteristic of the status signal transmission link 40 and compare the measured characteristic to an expected characteristic. If the measured characteristic differs from the expected characteristic by more than a pre-selected amount, the status signal sensor 33 can interrupt and/or prevent the transmission of therapeutic electrical signals along the therapeutic signal link 34. For example, if the status signal sensor 33 detects a break in the continuity of the normally closed circuit (indicating, for example, that the status signal transmission link 40 is missing or has been severed), or a substantial change in the impedance or resistance of the status signal transmission link 40 (indicating, for example, that the status signal transmission link 40 has been severed and reconnected), then the status signal sensor 33 can direct that the therapeutic signal emitter 32 be disabled from transmitting therapeutic signals along the therapeutic signal link 34.

[0033] In one embodiment, the status signal transmission link 40 can include a stainless steel wire or other conductor, which as described above, is both electrically conductive and resistant to severing. Stainless steel wire segments are also generally difficult to electrically reconnect without substantially altering the impedance of the circuit formed by the stainless steel wire. For example, stainless steel wires typically cannot be reconnected using conventional solder techniques, and twisting together the ends of a severed stainless steel wire will typically increase the impedance of the wire. Accordingly, reconnecting the status signal transmission link 40 (a) can be physically difficult and (b) can be difficult to do without altering the impedance of the status signal transmission link 40. As a result, the measured impedance of the signal transmission link 40 can indicate when the link 40 has been cut and reconnected.

[0034] In other embodiments, the status signal transmission link 40 can include other materials which are also (a) difficult to electrically reconnect and/or (b) difficult to reconnect without measurably altering the circuit impedance. Such materials include carbon fiber, which is (a) physically difficult to reconnect due to its fibrous structure, and (b) is difficult to reconnect without altering the overall impedance of the status signal transmission link. Other suitable materials include Kevlar® fiber with a conductive coating, and/or a plastic film or filament with a thin metal coating. In still further embodiments, the status signal transmission link 40 can include other materials that also resist being severed, change impedance when severed and reconnected, and/or are physically difficult to reconnect after being severed.

[0035] In yet further embodiments, the status signal transmission link 40 can conduct signals other than electrical signals. For example, the status signal transmission link 40 can include an optical fiber that transmits optical signals. The status signal emitter 31 can accordingly emit optical signals, and the status signal sensor 33 can accordingly detect changes in the characteristics of the status signal transmission link 40 by detecting changes in the signal transmitted along the link 40 when the link 40 is severed or severed and reconnected. In other embodiments, the status signal transmission link 40 can act as a wave guide and the status signal sensor 33 can detect signals reflected from discontinuities or breaks in the status signal transmission link 40, for example, using time domain reflectometry (TDR). In still further embodiments, the signal transmission link 40, the status signal emitter 31, and the status signal sensor 33 can have other arrangements.

[0036] One feature of the foregoing embodiments described above with reference to FIGS. 1-6 is that the status signal transmission link 40 can operate together with the status signal emitter 31 and the status signal sensor 33 to detect a break in the support member cable 21 and/or the coupler cable 57. An advantage of this arrangement is that the practitioner can be alerted to damage in either one of these cables and can correct the damage before administering therapy to the recipient and, in particular, before inserting the percutaneous probes 68 into the recipient.

[0037] Another feature of the foregoing embodiments described above with reference to FIGS. 1-6 is that the status signal sensor 33 can detect when the support member cable 21 and/or the coupler cables 57 have been severed and reconnected. For example, if a user were to sever one of the coupler cables 57 (including the conductor 35 and the signal transmission link 40), reconnect the severed ends of the signal transmission link 40 to each other, and connect the electrical conductor 35 to a device other than the electrical coupler 50 (such as an unprotected acupuncture needle), the status signal sensor 33 can detect this event and can halt the transmission of therapeutic electrical signals. Accordingly, this arrangement can detect when a user connects the control device 30 to percutaneous probes that lack the electrical coupler 50 originally attached to coupler cable 57. An advantage of this arrangement is that it can prevent or at least discourage the use of percutaneous probes that may not have the same safety features as embodiments of the electrode assembly 60 and the electrical coupler 50 described above. As a result, this arrangement can protect both patients and practitioners from potentially unsafe percutaneous therapy practices.

[0038] In other embodiments, the apparatus 10 can have other arrangements that include a tamper-resistant and/or tamper-evident status signal transmission link 40. For example, in one embodiment shown in FIG. 7, an apparatus 710 can include a support member 720 that removably supports a plurality of electrical couplers 750 in a manner generally similar to that described above with reference to FIG. 1. The support member 720 can be connected to a support member cable 721 that houses a corresponding plurality of electrical conductors 735, each connected to a corresponding one of the electrical couplers 750 via a corresponding plurality of coupler cables 757. The apparatus 710 can further include a status signal transmission link 740 that extends through the support member cable 721, along each coupler cable 757 in a series arrangement, and back along the support member cable 721. Accordingly, the status signal transmission link 740 can provide tamper-resistant and/or tamper-evident characteristics for each of the coupler cables 757 and the electrical couplers 750.

[0039] FIG. 8 is a partially schematic illustration of an apparatus 810 having a plurality of status signal transmission links in accordance with another embodiment of the invention. In one aspect of this embodiment, the apparatus 810 can include a support member 820 that supports a plurality of electrical couplers 850 (four of which are identified in FIG. 8 as electrical couplers 850a-d) in a manner generally similar to that described above with reference to FIG. 1. The apparatus 810 can further include a corresponding plurality of coupler cables 857 (shown as couple cables 857a-d), each of which houses a corresponding electrical conductor 835 (shown as electrical conductors 835a-d). Each coupler cable 857 can also house a corresponding status signal transmission link 840 (shown as status signal transmission links 840a-d). Each status signal transmission link 840 can be separately connected to an individual status signal emitter and status signal sensor (not shown in FIG. 8). Accordingly, in the event of a fault with one of he coupler cables 857 or electrical couplers 850 an embodiment of the arrangement shown in FIG. 8 can narrow the location of the fault.

[0040] FIG. 9 is a partially schematic illustration of an apparatus 910 that includes a support member 920 having a support member cable 921 with an identity device 980 in accordance with another embodiment of the invention. In one aspect of this embodiment, the identity device 980 can include an integrated circuit chip that stores a pre-selected, unique identifier, such as a serial number. For example, the serial number can be the same for all support member cables 921 that are pre-determined to be compatible with a corresponding control device 930. Suitable identity devices 980 are manufactured by Maxim Integrated Products of Sunnyvale, Calif. and Dallas Semiconductor of Dallas, Tex. In other embodiments, the identity device 980 can have other configurations. In any of these embodiments, the identity device 980 can be coupled to a sensor 933 with a status signal transmission link 940. If the sensor 933 recognizes the identity of the identity device 980 as acceptable, the sensor 933 can allow a therapeutic signal emitter 932 to transmit electrical therapeutic signals to one or more electrical couplers 950 along a therapeutic signal link 934, in a manner generally similar to that described above. Alternatively, if the sensor 933 determines that the identity device 980 is missing or is not an appropriate device, the sensor 933 can interrupt and/or prevent signals from being transmitted from the therapeutic signal emitter 932.

[0041] In one aspect of the foregoing embodiments, the sensor 933 can check for both an identifier (such as a code or serial number) and an impedance of the status signal transmission link 940. In another aspect of these embodiments, at least one of these security features can be selectively deactivated. For example, the capability of the sensor 933 to check impedance can be deactivated when it is unnecessary, undesirable or uneconomical to include this feature. This feature can be selectively reactivated when appropriate.

[0042] In any of the foregoing embodiments, the identifier provided by the identity device 980 can be correlated with the type of support member 920. For example, one identifier can be correlated with a clavicular support member, and another identifier can be correlated with a lumbar support member. In other embodiments, the identifier can be correlated with other types of support members.

[0043] In an alternate arrangement, the apparatus 910 can include another identity device 980a positioned in an electrical coupler 950, in addition to or in lieu of the identity device 980 described above. The identity device 980a can be coupled to the sensor 933 with a status signal transmission link 940a. Accordingly, the sensor 933 can determine whether the identity device 980 is acceptable, unacceptable or missing. In other embodiments, the apparatus 910 can include identity devices having other locations, such as in the support member 920 or in coupler cables 957 connected between the support member 920 and the electrical couplers 950.

[0044] In any of the embodiments described above with reference to FIG. 9, a feature of these arrangements is that the sensor 933 can determine when an unauthorized percutaneous therapy device (such as a support member cable or electrical coupler) has been attached to the controller 930, by determining that the identity device 980 or 980a is missing or is an inappropriate device. As described above with reference to FIGS. 1-8, an advantage of this arrangement is that it can prevent practitioners from using the controller 930 with electrode assemblies and electrode couplers that lack the safety features described above with reference to FIGS. 2-5.

[0045] Nevertheless, it may be possible for a practitioner to circumvent the tamper-resistant and/or tamper-evident features of any of the foregoing devices described above with reference to FIGS. 1-9, despite the clear disincentives to do so. For example, a practitioner can severe the tamper-resistant and/or tamper-evident status signal transmission link coupled between a first (or original) electrical coupler and a status signal emitter and/or status signal sensor, provide a second (or replacement) electrical coupler in place of the first electrical coupler, and couple the status signal transmission link to the replacement electrical coupler. When the status signal transmission link includes an electrical conductor, the practitioner can reconnect the severed electrical conductor to the replacement electrical conductor by welding, brazing, melting, reflowing, crimping (for example, with a specialized tool) or otherwise processing the conductor to reestablish the connection between the status signal transmission link and the replacement electrical coupler without measurably altering the impedance of the circuit that includes the transmission link. In other embodiments, the practitioner may circumvent the status signal transmission link in other manners.

[0046] From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.