Protection apparatus for implantable medical device

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 09/844,621, filed Apr. 26, 2001, now allowed.

FIELD OF THE INVENTION

[0002] This invention relates generally to a method and apparatus for use with an electronic implantable medical device for protecting the device from physical and/or electrostatic discharge damage prior to medically implanting the device in a patient's body. Moreover, preferred embodiments of the invention afford the ability to functionally test the device without removing it from its sterilized shipping container prior to implantation.

BACKGROUND OF THE INVENTION

[0003] Many types of electronic medical devices are known which are intended for implantation in a patient's body. Although these devices vary widely in design, they typically include a housing containing electronic circuitry connected to two or more electrodes which extend exteriorly from the housing (or one or more electrodes when the housing is the other electrode). The circuitry can, for example, include a functional circuit (e.g., a pulse generator), a power supply circuit (e.g., rechargeable battery), and a transceiver for wirelessly communicating with an external controller. Implantable medical devices of this sort are useful in a variety of applications for stimulating muscle or nerve tissue and/or monitoring body parameters. See, for example, U.S. Pat. Nos. 6,164,284; 6,185,452; 6,208,894; 6,315,721; and 6,472,991; which primarily relate to such devices that are battery powered, each of which is incorporated by reference herein in their entirety. Also see, for example, U.S. Pat. Nos. 5,193,539; 5,193,540; 5,312,439; 5,324,316; and 5,405,367; which primarily relate to such devices that are RF powered, each of which is incorporated by reference herein in their entirety.

[0004] To minimize device failure and maximize device reliability, it is important that an electronic medical device be properly handled along the entire chain from manufacturing, through shipping and storage, and on to the medical procedure for implanting the device in a patient's body. For example, improper handling can subject the device to physical damage and/or component damage due to electrostatic discharge (ESD).

SUMMARY OF THE INVENTION

[0005] The present invention is directed to a method and apparatus for protecting an electronic implantable medical device prior to it being implanted in a patient's body. More particularly, a method and apparatus in accordance with the invention affords protection to the medical device from just after manufacture to just prior to implantation. Protection is afforded against electronic component damage due to electrostatic discharge and/or physical damage due to improper handling.

[0006] Embodiments of the invention are particularly valuable when used with small fragile medical devices which often comprise an electronic circuit housing having an axial dimension of less than 60 mm and a lateral dimension of less than 6 mm. The housing typically contains electronic circuitry which is electrically connected to first and second electrodes which extend exteriorly from the housing. See, for example, U.S. Pat. Nos. 6,164,284; 6,185,452; 6,208,894; 6,315,721; and 6,472,991; which primarily relate to such devices that are battery powered, each of which is incorporated by reference herein in their entirety. Also see, for example, U.S. Pat. Nos. 5,193,539; 5,193,540; 5,312,439; 5,324,316; and 5,405,367; which primarily relate to such devices that are RF powered, each of which is incorporated by reference herein in their entirety.

[0007] A preferred apparatus in accordance with the invention is comprised of a circuit board having first and second connective surfaces integral to the circuit board. The connective surfaces are configured using elastic O-rings to receive and releasably grasp the electrodes of a medical device housing to support the housing proximate to the surface of the circuit board. First and second conductive paths are formed on the circuit board extending between the first and second connective surfaces for shunting electrostatic discharge currents to prevent such currents from passing through the device's electronic circuitry. Preferably, the respective shunt paths include oppositely oriented diodes, preferably comprising diodes which emit visual light (i.e., LEDs) when current passes therethrough.

[0008] In accordance with the invention, a medical device is preferably mounted in the protective apparatus as a late step in the device manufacturing process. The protection apparatus/device combination is then placed into a shipping container. The combination remains engaged until the device is ready for medical implantation in a patient's body. The shipping container preferably includes a transparent window through which the light emitting diodes are visible.

[0009] In a preferred method in accordance with the invention, the medical device is sterilized, e.g., using steam or ethylene oxide (ETO), after being placed in the shipping container.

[0010] A significant feature of the invention allows the medical device to be functionally tested while in the shipping container. More particularly, exemplary medical devices include (1) transceivers which permit wireless communication of commands and data between an external controller and the device electronic circuitry and (2) battery charging circuits which extract energy from an external power source, e.g., via an alternating magnetic field, for charging a device battery. In accordance with the invention, a medical device can be functionally tested while still in the shipping container by transmitting a command or activation signal to the device. If the device is functioning properly, it will respond in a particular manner, as by outputting a sequence of pulses whose characteristics (e.g., frequency, pulse width, etc.) indicate proper operability. This output pulse sequence drives the protection apparatus LEDs which can be monitored to detect whether the device is operating within specifications. Additionally, the device battery can be charged while still in the shipping container by an external power source.

[0011] In a still further significant aspect of the present invention, a cutout is provided in the circuit board to permit a wire loop from an oscilloscope, pulse generator, or the like, to pass through and inductively measure/induce the electrical input/output characteristics of the medical device before implantation. A sealing pouch preferably has a conforming cutout to facilitate this test while maintaining the medical device in a sterilized environment. Alternatively and/or additionally, a photodiode may be placed on the circuit board to emit nonvisual radiation that may be sensed by an external detection apparatus to measure the electrical output characteristics of the medical device. Finally, the output characteristics of the medical device may be measured using external capacitively coupled plates and/or one or more coils.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 schematically depicts the structure of an exemplary electronic implantable medical device of the type intended for use with the present invention.

[0013]FIG. 2 is a block diagram generally representing the electronic circuitry typically employed in the exemplary medical device of FIG. 1.

[0014]FIG. 3 schematically depicts the exemplary medical device of FIG. 1 used in combination with a protection apparatus in accordance with the present invention.

[0015]FIG. 4 is an exploded isometric illustration depicting a protection apparatus in accordance with the present invention.

[0016]FIG. 5 is an isometric illustration depicting a protection apparatus in accordance with the present invention for accommodating a medical device to be protected.

[0017]FIG. 6 is an exploded isometric illustration depicting the manner of placing the protection apparatus and medical device into an exemplary shipping container.

[0018]FIG. 7 is an isometric view depicting the protection apparatus and medical device received in the exemplary shipping container and oriented so that the light emitting diodes (LEDs) of the apparatus are visible through a container transparent window.

[0019]FIG. 8 is a block schematic diagram depicting how the medical device is tested while in the exemplary shipping container.

[0020]FIGS. 9A and 9B show isometric views of the mounting of the medical device on a planar surface having a pair of connective surfaces for making electrical contact with the electrodes of the medical device and a pair of O-rings for retaining physical and electrical contact between the medical device's electrodes and the circuit board's connective surfaces.

[0021]FIGS. 10A and 10B show isometric views of the mounting of the medical device on a planar surface having a pair of connective surfaces for making electrical contact with the electrodes of the medical device and a single O-ring for retaining physical and electrical contact between the medical device's electrodes and the circuit board's connective surfaces.

[0022]FIG. 11 shows an isometric view of the circuit board and O-ring mounting apparatus of FIGS. 10A and 10B, additionally including a photodiode for emitting nonvisual radiation that can be externally monitored to test the functionality of the medical device, e.g., while it is still within a sterilized container, e.g., a pouch.

[0023]FIG. 12 shows a simplified schematic diagram of additional embodiments of the present invention that include the photodiode of FIG. 11 and/or a current loop path that may be used to emit an inductively coupled field to a loop connected to an oscilloscope probe or the like. Alternatively, a pulse generator of the like may be used to inductively emit a signal into the loop on the circuit board and thus verify the functionality of the sensor mode circuitry in the medical device.

[0024]FIGS. 13A and 13B show the presence of the current loop path described in reference to FIG. 12 with a cutout for allowing the oscilloscope probe loop to pass through.

[0025]FIGS. 14A, 14B, and <b>14</b>C respectively show top, side and bottom views corresponding to the embodiment of FIGS. 13A and 13B sealed within a sterile pouch having a compliant cutout formed thereon. Additionally, the use of an optional breakaway section is shown to remove the LED portion and thus improve the functionality of the current loop path (by removing interactions with the LED path).

[0026]FIG. 15 is a block schematic diagram depicting how the medical device is tested while in the shipping container includes one or more of the following techniques: sensing of nonvisual radiation from the photodiode using a photodetector and a transconductance amplifier, use of an inductively coupled current loop path (with an optional breakaway section to electrically detach the LEDs), capacitive sensing of the circuitry, inductive sensing of the circuitry (without the current loop path and cutout), and/or one or more switches, e.g., a single pole double throw (SPDT) switch, to selectively connect the medical device's electrodes to the LEDs and/or the inductively coupled current loop.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Attention is initially directed to FIG. 1 which schematically depicts an electronic implantable medical device <b>20</b>. The device <b>20</b> is intended to be representative of a wide range of known electronic devices designed to be medically implanted in a patient's body for a variety of applications. For example only, such devices can be controlled to selectively stimulate muscle and nerve tissue and/or monitor and report various body parameters. The exemplary device <b>20</b> is depicted as comprising an elongate housing <b>22</b> defined by a peripheral wall <b>24</b> enclosing an interior volume <b>26</b>. The housing <b>22</b> can be variously shaped but, for simplicity herein, it will be assumed to be cylindrical. Typically such implantable medical devices are small in size, e.g., preferably having an axial dimension of less than 60 mm and a lateral dimension of less than 6 mm, and relatively fragile structurally. See, for example, U.S. Pat. Nos. 6,164,284; 6,185,452; 6,208,894; 6,315,721; and 6,472,991; which primarily relate to such devices that are battery powered, each of which is incorporated by reference herein in their entirety. Also see, for example, U.S. Pat. Nos. 5,193,539; 5,193,540; 5,312,439; 5,324,316; and 5,405,367, which primarily relate to such devices that are RF powered, each of which is incorporated by reference herein in their entirety. Reasonable care must be exercised in handling the devices <b>20</b> to prevent physical damage.

[0028] The exemplary device <b>20</b> is depicted as containing electronic circuitry <b>30</b> within the interior volume <b>26</b>. The circuitry <b>30</b> is connected between first and second electrodes <b>32</b>, <b>34</b> which extend exteriorly from the housing <b>22</b>. The circuitry <b>30</b> typically includes sensitive electronic components which can be permanently damaged by high currents which can be caused, for example, by electrostatic discharge (ESD). Accordingly, as with many other electronic devices, it is advisable to exercise appropriate care to avoid discharging high currents through the circuitry <b>30</b>. The present invention is primarily directed to a method and apparatus as depicted in FIGS. <b>3</b>-<b>15</b>, for protecting the device <b>20</b>, from damage while being shipped, stored, and handled between a late manufacturing stage and up to the time it is implanted in a patient's body.

[0029]FIG. 2 is a block diagram which generally depicts the functional components of typical electronic circuitry <b>30</b> employed in an implantable medical device <b>20</b>. More particularly, the electronic circuitry <b>30</b> is shown as comprising a power supply <b>38</b> which may include a rechargeable battery or a capacitor (not shown). A charging circuit <b>40</b> is connected to the power supply <b>38</b> for deriving energy from an external power source to charge the battery. For example only, the charging circuit <b>40</b> can respond to an alternating, e.g., amplitude modulated or frequency modulated, magnetic field or RF field to supply a charging current to the power supply <b>38</b>. The power supply <b>38</b> is depicted as supplying an operating voltage to a transceiver circuitry <b>42</b> and a pulse generator <b>44</b>. The transceiver circuitry <b>42</b> is configured to communicate with an external controller (not shown) employing a suitable form of wireless communication via path <b>43</b>, typically radio communication. Commands and data can be supplied via path <b>43</b> from the external controller to the transceiver circuitry <b>42</b> for controlling or programming the pulse generator <b>44</b>. The pulse generator <b>44</b> can in turn provide data to the transceiver circuit <b>42</b> via path <b>45</b> for communication to the external controller.

[0030] It should be understood that FIG. 2 is intended to only very generally depict the functionality of the electronic circuitry <b>30</b> contained in the device <b>20</b>. The method and apparatus of the invention to be described herein, is useful in combination with a wide variety of medical devices <b>20</b>, e.g., muscle stimulators, neural stimulators, physiological sensors, pacemakers, etc.

[0031] Attention is now directed to FIG. 3 which depicts an electronic protection circuit <b>60</b> externally connected between the device electrodes <b>32</b>, <b>34</b>. The protection circuit <b>60</b> is comprised of first and second shunt paths <b>62</b>, <b>64</b> which each include a unidirectional current device, e.g., a diode. Shunt path <b>62</b> contains diode <b>66</b> oriented from electrode <b>32</b> to electrode <b>34</b>. Shunt path <b>64</b> contains diode <b>68</b> which is oppositely oriented, i.e., from electrode <b>34</b> to electrode <b>32</b>. The shunt paths <b>62</b> and <b>64</b> operate to shunt current spikes which can be caused, for example, by electrostatic discharge around electronic circuitry <b>30</b>. Thus, the shunt paths limit excessive currents and voltage rise across the medical device <b>20</b>.

[0032] As will be discussed hereinafter, the diodes <b>66</b>, <b>68</b> preferably have an audible or light generator associated therewith to indicate current therethrough. More specifically, preferred embodiments of the invention are preferably implemented with light emitting diodes (LEDs). As will be understood hereinafter, it is preferable for the respective LEDs to produce light of different colors so that the direction of current flow between electrodes <b>32</b> and <b>34</b> can be readily determined by an observer.

[0033]FIG. 4 depicts a preferred implementation of a protection apparatus <b>70</b> in accordance with the present invention tailored for use with the exemplary cylindrical medical device <b>20</b>. The apparatus <b>70</b> is comprised of a substrate or circuit board <b>72</b> having an upper surface <b>74</b> and a lower surface <b>76</b>.

[0034] First and second spring contact clips <b>80</b>, <b>82</b> are provided for mounting on the circuit board <b>72</b>. Each clip is essentially comprised of a cradle portion <b>84</b> including spaced first and second resilient arms <b>86</b>, <b>88</b>. The arms <b>86</b>, <b>88</b>, together with end finger <b>90</b>, define a cradle for releasably retaining an electrode <b>32</b>, <b>34</b> of device <b>20</b>. The cradle portion <b>84</b> is cantilevered by a shank portion <b>92</b> which extends to spaced contact fingers <b>94</b>, <b>96</b> and to a post <b>98</b>. The clips <b>80</b>, <b>82</b> can be inexpensively formed by a stamping and bending operation.

[0035] The circuit board <b>72</b> has shunt path <b>62</b> formed on upper surface <b>74</b> depicted as including path portion <b>100</b> and path portion <b>102</b>. Path portion <b>100</b> is comprised of a longitudinal leg <b>104</b> and a lateral leg <b>106</b>. Similarly, path portion <b>102</b> is comprised of a longitudinal leg <b>108</b> and a lateral leg <b>110</b>. The clips <b>80</b> and <b>82</b> are respectively mounted onto the board <b>72</b> with the posts <b>98</b> extending into and electrically contacting through plated apertures <b>114</b> and <b>116</b> in path legs <b>104</b> and <b>108</b>. The through plated apertures extend and are electrically connected to a second shunt path <b>64</b> formed on the opposite lower surface <b>76</b> of circuit board <b>72</b>. The shunt path <b>64</b> on the surface <b>76</b> can be shaped identically to the shunt path <b>62</b> on upper surface <b>74</b> depicted in FIG. 4. The post <b>98</b> of clip <b>80</b> extending through the aperture <b>114</b> electrically interconnects the first ends of shunt paths <b>62</b> and <b>64</b>. Similarly, the post <b>98</b> of clip <b>82</b> extending through aperture <b>116</b> electrically interconnects the second ends of shunt paths <b>62</b> and <b>64</b>. Each shunt path includes a diode as depicted in FIG. 4. More particularly, note that LED <b>120</b> is configured to be surface mounted across legs <b>106</b> and <b>110</b> of shunt path <b>62</b> on board surface <b>74</b>. Similarly, LED <b>122</b> is intended for corresponding surface mounting in shunt path <b>64</b> on board surface <b>76</b>. Alternatively, LEDs <b>120</b>,<b>122</b> may be mounted on the same surface of the circuit board <b>72</b>.

[0036]FIG. 5 shows the medical device <b>20</b> accommodated in the clips <b>80</b> and <b>82</b> and with the LEDs <b>120</b>, <b>122</b> being mounted on opposite surfaces <b>74</b> and <b>76</b> of circuit board <b>72</b>. In accordance with the invention, the device <b>20</b> is mounted into the clips <b>80</b>, <b>82</b> in a late stage of the manufacturing process of device <b>20</b>. Thereafter, the mated protection apparatus <b>70</b> and medical device <b>20</b> are placed in a shipping container <b>140</b>, as depicted in FIG. 6. Shipping container <b>140</b> can be inexpensively formed of molded plastic, and preferably includes a cavity <b>142</b> shaped and dimensioned to accommodate the mated protection apparatus <b>70</b> and medical device <b>20</b>. In placing the mated combination in the cavity, circuit board <b>72</b> should be oriented so that the LEDs <b>120</b> and <b>122</b> face upwardly. A transparent sheet <b>150</b> covers the cavity <b>142</b>, to define a window through which the LEDs <b>120</b> and <b>122</b> are visible as depicted in FIG. 7.

[0037] It is intended that the protection apparatus <b>70</b> and medical device <b>20</b> remain mated together in the shipping container <b>140</b> for the full duration of its shelf life from the manufacturing stage to just prior to medically implanting the device <b>20</b> in a patient's body. After the mated protection apparatus and medical device <b>20</b> are placed into the shipping container <b>140</b> and the cavity <b>142</b> sealed by transparent sheet <b>150</b>, the device <b>20</b> is preferably sterilized using a known gas, e.g., ethylene oxide (ETO), or steam process. For its entire life between manufacturing and implantation, the protection apparatus <b>70</b> will protect the medical device from electronic component damage attributable to electrostatic discharge (ESD). Moreover, the apparatus <b>70</b> protects device <b>20</b> against physical damage because it is firmly retained by spring clips <b>80</b>, <b>82</b> mounted on the substantially rigid circuit board <b>72</b>.

[0038] In accordance with the present invention, the device <b>20</b> is preferably functionally tested while still in its shipping container <b>140</b>. More particularly, as depicted in FIG. 8, an external power source <b>160</b> is able to charge the onboard device battery via the aforementioned charging circuit <b>40</b> by generating an appropriate field, e.g., alternating magnetic field, in close proximity to the device <b>20</b>. The power source <b>160</b> can be similar or identical to the power source normally used to charge the battery after the device is implanted in a patient's body. Similarly, an external controller <b>164</b> can be used to provide commands and receive data from the medical device <b>20</b> while it is still contained within the shipping container <b>140</b>. In a particularly useful procedure, the controller <b>164</b> is able to wirelessly communicate a command or activation signal to the device <b>20</b>, e.g., via an RF signal. The controller <b>164</b> can be similar or identical to a controller utilized by the patient or by a medical practitioner to program the device <b>20</b> after implantation in the patient's body. The procedure depicted in FIG. 8 contemplates that the controller <b>164</b> provides an activation signal to the medical device <b>20</b> while it is still in the shipping container <b>140</b>. The electronic circuitry of the device <b>20</b> is designed to respond to the activation signal to cause pulse generator <b>44</b> to output a known pulse sequence between electrodes <b>32</b> and <b>34</b>. This pulse sequence will cause LEDs <b>120</b> and <b>122</b> to illuminate in accordance with a pattern having known characteristics (e.g., frequency, pulse width, etc.). The activity of the LEDs <b>120</b> and <b>122</b> can be monitored by monitor <b>168</b> to determine whether the device <b>20</b> is operating properly. For example, if the device <b>20</b> is configured to generate monophasic pulses, one LED will “brightly” light during generation of each pulse and the other LED will “dimly” light during recharge of the pulse generator <b>44</b>. Alternatively, if the device <b>20</b> is configured to generate a biphasic pulse, the intensity of the light emitted from each LED will be approximately the same.

[0039] Thus, it will be appreciated that the protection apparatus <b>70</b> in accordance with the present invention offers both electrical and physical protection of the device <b>20</b> during shipping and handling, and facilitates the testing of the device prior to it being medically implanted in a patient's body.

[0040] It is important that medical devices intended for implantation in a patient's body be biocompatible, i.e., that they employ materials which do not produce deleterious effects on the living tissue. This requirement dictates a choice of appropriate biocompatible materials. In order to avoid compromising biocompatibility, it is preferable that the contact clips <b>80</b>, <b>82</b> which physically contact the electrodes <b>32</b>, <b>34</b> of the device <b>20</b> also be formed of an appropriate biocompatible material, e.g., platinum.

[0041]FIGS. 9A and 9B show isometric views of the mounting of the medical device <b>20</b> on a planar surface <b>200</b> having a pair of connective surfaces <b>202</b>, <b>204</b> for making electrical contact with the electrodes <b>32</b>, <b>34</b> of the medical device <b>20</b> and a pair of O-rings <b>206</b>, <b>208</b> (preferably formed from medical grade silicone) for physically retaining and maintaining electrical contact between the medical device's electrodes <b>32</b>, <b>34</b> and the circuit board's connective surfaces <b>202</b>, <b>204</b>. In this embodiment, the use of O-rings <b>206</b>, <b>208</b> functionally replace the previously described use of clips <b>80</b>, <b>82</b> while further minimizing any potential for damage to protective gloves worn by medical practitioners when working with the sterilized and packaged medical device <b>20</b>. The O-rings <b>206</b>, <b>208</b> are easily rolled onto the ends of the circuit board <b>72</b> until they hold the medical device <b>20</b> into contact with the connective surfaces <b>202</b>, <b>204</b>. Since the package must be subject to high temperatures for sterilization purposes, the planar surface <b>20</b>, e.g., circuit board <b>72</b>, is formed of polyimide or like material that can withstand the temperatures associated with sterilization. The connective surfaces are preferably formed from a biocompatible material, e.g., platinum or gold plated nickel on copper to provide a surface that will minimize electrical resistance to the medical device's electrodes while maintaining biocompatible safety should the gold or platinum slough off onto the electrodes <b>32</b>, <b>34</b>. FIG. 9B, in particular, shows two optional means that may be used to stabilize the position of the medical device <b>20</b> on the connective surfaces. In this example, connective surface <b>202</b>′ is shown with a recess, e.g., a concave portion, and connective surface <b>204</b>′ is shown with a notched portion, each of which are exemplary of optional techniques for stabilizing the medical device's position. Clearly, each of these techniques could be used on both ends of the medical device and the use of different techniques for each electrode is primarily for illustrative purposes to minimize the number of provided figures.

[0042]FIGS. 10A and 10B (a variation of that already shown and described in relation to FIGS. 9A and 9B) show isometric views of the mounting of the medical device <b>20</b> on a planar surface <b>200</b> having a pair of connective surfaces <b>202</b>, <b>204</b> for making electrical contact with the electrodes <b>32</b>, <b>34</b> of the medical device <b>20</b> with a single O-ring <b>210</b> for retaining physical and electrical contact between the medical device's electrodes and the circuit board's connective surfaces <b>202</b>, <b>204</b>. In this embodiment, the circuit board <b>72</b> is formed with a pair of opposing retaining lips <b>212</b>, <b>214</b> for retaining/capturing opposing ends of the O-ring <b>210</b>. In operation, the O-ring <b>210</b> is typically initially captured by the two retaining lips <b>212</b>, <b>214</b> and when the medical device <b>20</b> is available it is slipped between the O-ring <b>210</b> and the circuit board <b>72</b> from the outside end <b>216</b> of the circuit board <b>72</b> until its electrodes <b>32</b>, <b>34</b> line up with the connective surfaces <b>202</b>, <b>204</b>. Due to the relatively large size of the connective surfaces <b>202</b>, <b>204</b> to the electrodes <b>32</b>, <b>34</b>, this positioning is easily performed. Optionally, a stop may be placed on connective surface <b>204</b> at location <b>218</b> to block further inner movement of the medical device <b>20</b> during insertion into the protection apparatus <b>70</b>′ (see FIG. 10A). Alternatively, the medical device <b>20</b> may be placed on the circuit board <b>72</b> and the single O-ring <b>210</b> may be stretched and captured between the two retaining lips <b>212</b>, <b>214</b>. Functionally, e.g., as pertaining to protection and test features, the apparatus described in relation to FIGS. 9A, 9B, <b>10</b>A, and <b>10</b>B performs as previously described in relation to FIGS. 4 and 5.

[0043] FIGS. <b>3</b>-<b>8</b>, <b>10</b>A and <b>10</b>B, primarily show a protection apparatus whose output drivers may also be functionally tested (generally in response to received communication signals) by visually (or automatically, see monitor <b>168</b> in FIG. 8) monitoring the response of its LEDs <b>120</b> and <b>122</b> when the medical device <b>20</b> is commanded to generate stimulation pulses. While this is an effective functional test, its capability to measure actual performance characteristics, e.g., the milliamp output, of the medical device <b>20</b> is limited. Accordingly, FIGS. <b>11</b>-<b>15</b> are primarily directed to alternative embodiments that additionally provide the capability to measure, albeit, indirectly the performance characteristics of the medical device <b>20</b> prior to implantation. The requirement to indirectly measure these characteristics is dictated by the requirement that the medical device <b>20</b> be maintained within a sterile package before implantation. The description of various techniques follows, including (1) the use of a photodiode and associated photodetector (and transconductance amplifier) to provide a relatively linear measurement of the output of the medical device, (2), the use of an inductive current loop with an associated cutout in the circuit board of the protection apparatus to accept a receiving inductive pickup loop, e.g., connected to an oscilloscope or the like, to measure the output of the medical device, (3) the use of an inductive current loop with an associated cutout in the circuit board of the protection apparatus to accept a transmitting inductive current loop driven by an external pulse generator or the like to provide an input signal, e.g., a simulated neuro-muscular signal, and thus allow the sense circuitry of the medical device to be tested, etc. These techniques may be used in various combinations but what is significant is that they all provide test/measurement capabilities while the medical device is still within its sterile delivery package, e.g., a pouch.

[0044]FIG. 11 shows an isometric view of circuit board <b>72</b> and O-ring mounting apparatus of FIGS. 10A and 10B, additionally including a photodiode <b>220</b> (also see FIG. 12) for emitting nonvisual, e.g., ultraviolet or infrared, radiation (light) that can be externally monitored to test the functionality of the medical device <b>20</b>, e.g., while it is still within a sterilized delivery package, e.g., a pouch. As shown in FIG. 15, an external monitor/generator <b>222</b> may include a photodetector <b>224</b> that is sensitive to nonvisual radiation <b>226</b> emitted by the photodiode <b>220</b>. When the photodetector <b>224</b> is used in combination with a transconductance amplifier <b>228</b> or the like, the nonvisual radiation <b>226</b> which was generated in an essentially linear relationship with the current passed through the photodiode <b>224</b> is converted to an output signal <b>230</b> which essentially linearly corresponds to the output of the medical device <b>20</b> through its electrodes <b>32</b>, <b>34</b>. This output signal <b>230</b> may then be measured with an oscilloscope, automated test equipment, or the like, to confirm that the medical device <b>20</b> is performing within specifications (before implantation).

[0045]FIGS. 13A and 13B show the presence of a current loop path <b>232</b> (also shown in FIG. 12) with a cutout <b>234</b> for allowing an inductive pickup loop <b>236</b>, e.g., an oscilloscope probe loop, to pass through and thus inductively measure the current being passed between electrodes <b>32</b>, <b>34</b> of the medical device <b>20</b> (via connective surfaces <b>202</b>, <b>204</b> and feedthrough/back side connection path <b>238</b>. Optionally, a resistor element <b>240</b>, e.g., on the order of 250 ohms, is used to simulate body tissue and to avoid/limit interactions with LEDs <b>120</b>, <b>122</b>. Also, see FIG. 15 where photodiode <b>220</b> is essentially replaced by a short circuit and monitor/generator <b>222</b> measures/detects the operation of medical device <b>20</b> through inductive pickup loop <b>236</b>.

[0046]FIGS. 14A, 14B, and <b>14</b>C respectively show top, side and bottom views of the embodiment of FIGS. 13A and 13B sealed within a sterile pouch <b>242</b> having a compliant, and thus somewhat smaller cutout <b>244</b> formed thereon. Inductive pickup loop <b>236</b> may thus pass through sterile pouch cutout <b>244</b> which in turn is within cutout <b>234</b>, without breaking the sterile seal of pouch <b>242</b>.

[0047] Ideally, however, the LEDs <b>120</b>,<b>122</b> are not present when the current loop path <b>232</b> is used. Accordingly, an optional breakaway portion path <b>246</b> may be implemented on the circuit board <b>72</b> to permanently disconnect the LEDs <b>120</b>,<b>122</b> when they are no longer needed. Thus, in this mode the LEDs <b>120</b>,<b>122</b> would be used as an initial “go/no go” test and then, as a final before implantation test, the LEDs <b>120</b>,<b>122</b> would be disconnected via breakaway portion path <b>246</b> before final measurement testing via current loop path <b>232</b>. Alternatively, a single pole double throw (SPDT) switch <b>248</b> could be used to alternatively enable LEDs <b>120</b>,<b>122</b> or current loop path <b>232</b> (see FIG. 15). Such a switch could either be a discrete device soldered to the circuit board <b>72</b> or could be one or more metallic appendages that extend from the circuit board <b>72</b> to form one or more electrical switches to create the functional equivalent of switch <b>248</b>.

[0048] As an additional alternative (see FIG. 15), a pair of capacitive plates <b>250</b>, <b>252</b> coupled to the monitor/generator <b>222</b> could be used to detect operation of the medical device <b>20</b>. Alternatively, capacitive plates <b>250</b>, <b>252</b> could be replaced with one or more coils or a surrounding coil to similarly detect operation of the medical device <b>20</b>. In such a case, element <b>240</b> may be replaced with an inductor. Since such alternatives would tend to block passage of an RF signal into the medical device (needed for RF powered stimulators), this alternative is best used with a battery powered stimulator.

[0049] Finally, the previously referenced implantable medical devices (see, for example, U.S. Pat. Nos. 6,164,284; 6,185,452; 6,208,894; 6,315,721; and 6,472,991) may also be able to operate as a sensor and thus sense neuro-muscular signals via its electrodes <b>32</b>, <b>34</b>. To test functionality of such devices operating as a sensor, one must provide an electrical signal to electrodes <b>32</b>, <b>34</b> and communicate (typically via an RF signal) with the medical device <b>20</b> to confirm proper detection of the input voltage signal. In this mode (see FIG. 15), the monitor/generator <b>222</b> operates as a pulse generator and puts out various programmable frequency and amplitude signals through pickup loop <b>236</b> which is inductively provided through current loop path <b>232</b> to electrodes <b>32</b>, <b>34</b> of the medical device <b>20</b>. In response, medical device <b>20</b> communicates with controller <b>164</b> to determine functionality of the medical device <b>20</b>. Optionally, controller <b>164</b> may communicate with monitor/generator <b>222</b> (shown as a dashed path) to coordinate comparisons of the expected and actual received signals.

[0050] Although a specific embodiment of the invention has been described, it is recognized that variations and modifications will readily occur to those skilled in the art coming within the intended spirit and scope of the present invention as defined by the appended claims. For example, while the aforedescribed apparatus <b>70</b> shown in FIG. 4 is particularly suited for use with the exemplary small, cylindrical device of FIG. 1, the present invention includes the use of the aforedescribed protection circuitry with other differently shaped medical devices having two or more electrodes. In such cases, the mounting means would be adjusted accordingly to accommodate the particular device. In particular, the O-ring embodiments of FIGS. 9A, 9B, <b>10</b>A, <b>10</b>B, <b>11</b>, <b>13</b>A, <b>13</b>B, <b>14</b>A, <b>14</b>B and <b>14</b>C are particularly adapt at retaining non-cylindrical, e.g., square, triangular, hexagonal, etc., shaped medical devices in the protection apparatus of the present invention. Additionally, it should be noted that while current loop path <b>232</b> is shown graphically as a single loop (see, e.g., FIG. 13A), this is primarily to simplify the graphical depiction of this path and embodiments are intended to also include multi-looped paths. Advantageously, multi-looped embodiments will facilitate transmission and/or reception of inductively radiated signals. Finally, it is noted that a negative capacity preamp, i.e., an amplifier having a capacitor for negative feedback, could be used within the monitor/generator to pickup an electrostatic signal from the medical device and/or the medical device/protection apparatus combination and thus detect/monitor the operation of the medical device.