Patent Publication Number: US-2013253447-A1

Title: Needle placement system

Description:
TECHNICAL FIELD 
     This invention relates to systems, devices and methods for sensing and monitoring needle placement into an implanted medical device. 
     BACKGROUND 
     Various types of implanted medical devices, such as implanted drug pumps, are used to deliver controlled volumes of a therapeutic fluid substance (e.g. a drug) within a patient&#39;s body. These pumps generally have reservoirs that may be accessed through ports, which may be self-sealing and may provide a drug suspension or solution from the device. 
     After the medical device is implanted within a patient, it may be desirable to fill, refill, flush out, or change fluid in a reservoir or other portion of the device. Typically, this is accomplished by a health care provider (HCP), for example a clinician. The HCP typically locates the device access port by palpitating a patient&#39;s skin, as the access port typically protrudes from the infusion pump. The HCP then inserts a needle or similar device advancing through the patient&#39;s skin into the implanted device to dispense or remove the intended therapeutic fluid substance. 
     Because the implanted medical device cannot be directly viewed, care must be taken to ensure proper needle placement into the device before injecting a therapeutic substance. If the needle misses the device, the therapeutic substance may be dispensed in the patient&#39;s body resulting in delivery of an improper amount and at an improper location, with potentially adverse consequences for the patient. 
     SUMMARY OF THE INVENTION 
     The present invention provides, in one aspect, a needle detection system for determining needle position with respect to an implanted infusion device comprising:
         a hollow needle having a sharp distal end;   a needle electrode located at a first distance along the needle from the distal end;   a second electrode; and   a detector electrically coupled to the first and second electrode, the detector providing needle insertion position information when the needle is inserted in an implanted medical device.       

     The invention provides, in another aspect, a position-indicating needle comprising:
         a hollow needle having a sharp distal end;   a needle electrode located at a first distance along the needle from a distal end; and   a second electrode.       

     Still other aspects of the invention provide a method for detecting needle position with respect to an implanted infusion device, the method comprising:
         sensing changes in electrical characteristics as a needle electrode enters into an   implanted infusion device; and   determining whether the sensed changes in electrical characteristics are indicative of needle entry into the implanted infusion device.       

     Such needle, needle system and method have particular use when refilling, flushing or changing fluid in an implanted infusion device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a schematic illustration of an infusion system implanted in a patient. 
         FIG. 2  is a block diagram depicting components of an implanted infusion system of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of a portion of the implanted infusion device of  FIG. 1 . 
         FIG. 4  is a side view of a needle embodiment with a needle placement verification system. 
         FIG. 5A  is a side view, partially in section of another needle embodiment. 
         FIG. 5B  is a side view, partially in section of yet another needle embodiment. 
         FIG. 5C  is a perspective view of another needle embodiment. 
         FIG. 5D  shows a top, side and bottom view of  FIG. 5C . 
         FIGS. 6A-D  are schematic illustrations of various needle insertion stages into an implanted infusion device. 
         FIG. 7  is a schematic illustration of a needle integrity or calibration system. 
         FIG. 8  shows a typical signal response to needle entry into a septum of an implanted infusion device. 
         FIG. 9  is a flow diagram showing needle insertion detection in an implanted device in accordance with the teachings described herein. 
     
    
    
     The drawings are not to scale. Like numbers used in the figures refer to like components, steps and the like. However, the use of such numbers to label a component in a given figure is not intended to limit a component in another figure labeled with the same number. 
     DETAILED DESCRIPTION 
     The present disclosure describes systems, devices and methods that can be used to detect needle entry into an implanted infusion device. Such needle detection may be accomplished by monitoring changes in electrical characteristics such as changes in electrical resistance, impedance, current, voltage, frequency, or signal strength when a needle enters an implanted infusion device. 
       FIG. 1  shows an implanted infusion device  12  having two port assemblies  40 ,  40 ′ implanted in a patient. Infusion device  12  may include one, two, three, or any number of port assemblies. As shown in  FIG. 1 , a catheter  34  is connected to infusion device  12 . Distal portion  99  of catheter  34 , which may have one or more openings through which fluid may flow, is positioned at or near a target location of a patient to deliver fluid from infusion device  12  to the target location. The target location depicted in  FIG. 1  is the patient&#39;s intrathecal space surrounding the spinal canal. It will be understood, however, that any region of a patient&#39;s body may serve as a target location depending on the conditions, disease, or disorder to be treated. Port assemblies  40 ,  40 ′ can be accessed percutaneously by a needle (not shown in  FIG. 1 ), through which fluid may be delivered to infusion device  12 . 
     Infusion device  12  may be any device capable of delivering fluid to a patient. For example, infusion device  12  may be an access port, e.g. a vascular access port, through which a solution or therapeutic substance from a needle may be delivered through a catheter to a patient, or may be a device having a reservoir (shown in  FIG. 2 ) for holding solutions containing a therapeutic substance to be delivered over a period of time, such as devices with fixed or variable rate pumps, programmable pumps, or the like. Infusion devices having a reservoir will generally include a port assembly to allow for filling the reservoir. 
     Port assemblies  40 ,  40 ′, shown in  FIG. 1 , may for example respectively be a catheter access port and a fill port. As described in further detail below, fill port assembly  40  provides access to a reservoir  32  that retains a therapeutic substance. Exemplary devices having a catheter access port and a fill port include Medtronic&#39;s SYNCHROMED™ implanted infusion device, DePuy&#39;s CODMAN™ 3000 and OMT&#39;s LENUS PRO™ or other such implantable medical devices. Other exemplary implantable I.V. infusion port devices include Smiths Medical&#39;s PORT-A-CATHT™ and P.A.S PORT™, and Bard Medical&#39;s POWERPORT™. Any currently known or future developed implanted infusion device can also be used. 
     In some embodiments, multiple catheters may be coupled to infusion device  12  to target the same or different tissue sites within a patient. Thus, although a single catheter  34  is shown in  FIG. 1 , in other embodiments, infusion device  12  may include multiple catheters or catheter  34  may define multiple lumens for delivering different therapeutic substances or for delivering a therapeutic substance to different tissue sites within patient. Accordingly, in some embodiments, infusion device  12  may include a plurality of reservoirs for storing more than one type of therapeutic substance, with each such reservoir typically having its own access port. For ease of description, an infusion device  12  including a single reservoir is primarily discussed herein. 
       FIG. 2  shows a block diagram depicting systems and components in a representative system  10  that includes an implanted infusion device  12 . Implanted infusion device  12  further includes a refill port  40 , septum  42 , chamber  44 , reservoir  32 , a pressure sensor  14 , a detector  39 , an indicator  16  and a power supply  48 . Also depicted in  FIG. 2  is a syringe assembly  18  including a needle  20  useful for percutaneously interfacing with the implanted infusion device  12 . In general, infusion device  12  shown in  FIG. 2  includes a housing  30  that typically will surround reservoir  32 . Reservoir  32  may contain a therapeutic substance to be delivered to the patient, for example, via a catheter  34 . 
     The therapeutic substance can be any infusion agent, product, or substance intended to have a therapeutic effect such as pharmaceutical compositions, genetic materials, biologics, and others (e.g., insulin, saline solution, fluoroscopy agents, antibiotics or the like). A pump, metering device, flow regulator or combination thereof can be provided for dictating the therapeutic substance flow from reservoir  32  in a desired fashion. The pump/metering device can assume a variety of forms, and device  12  can further include a propellant chamber associated with reservoir  32  for exerting a constant, positive pressure onto the contained therapeutic substance to ensure delivery to the outlet catheter  34 . In other embodiments, the pump/metering device can be eliminated, especially where gravity, osmotic pressure or other driving forces may be used to deliver the therapeutic substance to the patient. 
       FIG. 3  is a simplified, cross-sectional view of a portion of system  10  and infusion device  12 , housing  30 , reservoir  32 , and port assembly  40 . In general, port assembly  40  is formed in an opening  70  of housing  30  such that port assembly  40  is exteriorly accessible relative to housing  30 . Septum  42  may be disposed across port chamber  44  (referenced generally) defined by a wall of port assembly  40 , such that septum  42  seals the opening  70  relative to the port chamber  44 /reservoir  32 . 
     Septum  42  can be made from any suitable sealing material or materials and may be electrically conducting or non-conducting. Typically, septum  42  may be made of an elastomeric material, for example, silicone rubber that is electrically non-conducting, able to be pierced or otherwise penetrated by a needle  20  and compatible with the therapeutic substance to be contained within reservoir  32 . In various embodiments, port assembly  40  further includes a septum plug  74  used to retain septum  42  while providing a fluid-tight seal. Septum plug  74  defines the port chamber  44  to include drain holes  78  that allow fluids delivered to port chamber  44  to pass into reservoir  32 . In some embodiments, a valve can be provided to further control liquid flow from port chamber  44  to reservoir  32 . As a point of reference, relative to an arrangement of port assembly  40 , septum  42  defines a first or exterior side and a second or interior side  82 . Exterior side  80  is exposed relative to opening  70  of housing  30 , whereas interior side  82  defines a portion of port chamber  44 . While  FIG. 3  is described with regard to a fill port assembly  40 , it will be understood the components described with regard to  FIG. 3  can be readily applied or adapted to the catheter access port assembly  40 ′. 
     Although not depicted in  FIG. 3 , infusion device  12  may also include components such as safety valves, flow regulators and other components that may enhance the implanted infusion device&#39;s operation. Such components include those described in, for example, U.S. Pat. Nos. 6,203,523 and 6,048,328, both to Haller et al. both of which are incorporated herein by reference. 
     After infusion device  12  is implanted within patient, reservoir  32  can conveniently be accessed percutaneously to refill, flush or change the therapeutic substance stored within reservoir  32 . For example, reservoir  32  may be refilled every few weeks or every few months, depending upon the capacity of reservoir  32  and the desirable agent delivery rate for a patient. 
     The disclosed needle system assists a HCP in obtaining the accurate needle placement within the appropriate chamber or other portion of an implanted medical device, and not in the patient&#39;s tissue, before fluid is dispensed. 
     Needle  20  may be any instrument that may be used to pierce through a patient&#39;s tissue to enter septum  42  and deliver a therapeutic substance into device  12 . After needle  20  passes through septum  42 , a therapeutic substance may be released from syringe  18  through the distal end of needle  20  into reservoir  32 . Percutaneous direct fluid delivery to a patient may also be accomplished by introducing needle  20  or another medical instrument through catheter access port assembly  40 ′. Catheter access port assembly  40 ′ provides a sealed structure through which fluid may directly flow to catheter  34 , thereby effectively bypassing reservoir  32 . 
     An embodiment of a needle device  19 , shown in  FIG. 4  includes needle  20 , connected to a syringe  18  that contains a therapeutic substance  24  in fluid form. The syringe  18  includes a fluid-containing vessel or barrel  23  that receives and retains therapeutic substance  24 . A plunger  25  may be inserted into syringe  18  to deliver therapeutic substance  24 . The needle  20  is connected to the syringe  18  via a hub  21 . Hub  21  may, for example, be a LUER connection or the like. Hub  21  may be formed from metal or polymer materials such as acrylonitrile butadiene styrene (ABS), polystyrene, polyvinyl chloride, polysulfone or other suitable material. 
     Needle  20  may be, for example, a conventional hypodermic or infusion needle, or another instrument that may be capable of piercing through a patient&#39;s tissue and entering an implanted infusion device  12 , and delivering therapeutic substance into reservoir  32 . Needle  20  desirably is made from a conductive material such as a metal or a metallic alloy. In other embodiments a non-conducting needle may be made conductive by coating with suitable conductive material such as a metal, alloy, carbon black, conductive polymer or other conductive material. Exemplary conductive coatings include thin film conductive traces, conductive foils, and conductive deposits formed using thin-film deposition techniques such as vapor deposition, metal plating, PVD sputter deposition and the like. Suitable conductive materials include, for example, aluminum, copper, gold, silver, nickel, iron, stainless steel, nitinol, composite conductive polymers and the like. Needle  20  may be removably coupled to hub  21  and may be designed for either single use or reuse. Exemplary needles include non-coring Huber needles, standard 22 gauge; angled non-coring Huber type needle, 22 gauge or 20-25 gauge; straight non-coring Huber type needle, 20-25 gauge; angled and straight safety non-coring Huber type needles, 20-25 gauge; non-coring infusion sets for I.V. port access such as Bard Wing Infusion set by Bard Medical or the like. 
     Referring to  FIG. 4 , needle  20 , which may be an electrically conducting needle, may be covered by insulating layer  22  along the entire needle length. Insulating layer  22  is then covered by a conductive layer  27 . Conductive layer  27  extends to the bottom of a over insulating layer  22 . A second insulating layer  28 , which covers the top of conductive layer  27 , extends toward hub  21  and stops above a, creating electrode  26 . In other embodiments, the needle may be a non-conducting needle that is made conductive at designated sections on the needle (as described below). These conductive sections serve as electrodes. 
     The position of electrode  26  may, as shown in  FIG. 4 , be at a distance b from the distal end of needle, i.e. the needle tip and have a length a such that when the tip of needle  20  is fully inserted into reservoir  32 , electrode  26  is enveloped by septum  42 . It should be understood that the position and length of electrode  26  is dictated by the device used. The length a of electrode  26  may be, for example, less than the depth of a septum. This way, electrode  26 , when fully inserted in reservoir  32  will be completely enveloped by septum  42  and no electrode portion will be exposed in the tissue or in the reservoir. For example, electrode  26  may be positioned about 0.2 to about 0.3 inches from the distal tip of needle  20  with the length of the electrode about 0.05 to about 0.15 inches. 
     Depending on the electrical conducting characteristic of septum  42 , for example, if non-conducting, septum  42  insulates electrode  26  and blocks current to a return electrode resulting in higher resistance or higher impedance compared to the resistance or impedance when electrode  26  is not enveloped by septum  42 . Exemplary needle insulating materials include titanium dioxide, polytetrafluoroethylene (PTFE), PARYLENE™ polymers, AMC141-18 polymers from Advanced Materials Coatings, nylon and other polyamides and the like. 
     The needle electrode  26  may be electrically coupled to wire  46  via hub  21 , which in turn is electrically coupled to detector  50 . In some embodiments, a return electrode or ground pad  45  is separately provided and electrically coupled to the detector  50  by cables or wires  48 . The return electrode  45  may be a surface electrode, for example, a standard ECG pads, such as the Conmed Suretrace ECG electrode. The surface electrode such as the ECG pad may be placed at a desirable position on a patient and the surface electrode returns the current or other electrical characteristic distributed from the needle electrode to the detector through the cables or wires to complete the electrical circuit. In other embodiments, a standard electrically conductive needle may be separately inserted into a patient&#39;s skin a small distance from the needle  20  to serve as a return electrode. In still other embodiments, needle  20  may include an additional electrode on the needle  20  which may serve as a return electrode. 
     Detector  50  may include a signal adjustment  51  and a display  53 . Signal adjustment  51  may regulate the applied voltage, applied frequency, allowable current or other signal between wires  46  and  48 . Detector  50  may receive multiple electrical signals and may compute, display or store information based on such signals. Detector  50  may also provide an audible, tactile, visual or other indication or cue to the user to show needle status or location within the body tissue or within various components of an implanted infusion device, such as a septum. If desired, the detected electrical characteristics may be outputted wireless from detector  50 . 
     As shown in  FIG. 5A , multiple needle electrodes may be provided on a non-conducting needle  60  in a multilayered configuration. Conductive layers  61 ,  63 , &amp;  65  may be deposited in an alternating arrangement with insulating layers  62 ,  64  &amp;  66 . The insulating layers  62 ,  64  &amp;  66  may be disposed on each conductive layer  61 ,  63 , &amp;  65  such that a designated section or sections of the underlying conductive layer are partially or fully exposed. The partially or fully exposed sections serve as electrodes  61 ,  63 , &amp;  65 . It will be understood that a variety of other methods for forming a needle with multiple electrodes may be used and that the needle used to form the multiple electrodes may be a conductive or non-conductive needle. 
       FIG. 5B  shows a further embodiment with multiple electrodes arranged at different depths along the needle. Such a multiple electrode needle  70  includes a non-conducting needle  71  that is made conductive by providing conductive strips or traces  72 ,  74  along the needle sides as opposed to conductive layers along the entire needle circumference. Conductive strips  72 ,  74  are covered by insulating layers  73 ,  75 . Uninsulated sections  72 ,  74  act as electrodes and are electrically coupled to detector  50 . In some embodiments, where the needle is a conductive needle, the needle tip may also serve as an electrode. It will be understood that additional electrodes at varying depths may be created as described here. 
       FIGS. 5C  &amp; D show yet another embodiment where electrodes  72 ,  74  are provided as strips  72 ,  74  and at different depths and where a single insulating layer  73  is disposed on each conductive strip  72 ,  74  such that designated section or sections of the underlying conductive strips  72 ,  74  are partially or fully exposed to form the electrodes. 
     When a multiple electrode needle is used, the needle system may measure changes in electrical characteristics such as changes in electrical resistance (when direct current is used), impedance (when alternating current is used), current, voltage, frequency, or signal strength between multiple needle electrodes or between each electrode and a separate return electrode. While  FIGS. 5A-D  depict two or three electrodes, depending on the required needle placement resolution, additional electrodes may be included on the needle with or without a separately provided return electrode. 
       FIGS. 6A-D  show various needle insertion stages and the expected condition of various electrical circuits as the needle is inserted into an implanted infusion device  12 . In some embodiments, needle position may be determined with reasonable precision by simply monitoring the available circuits to determine if they are open or closed. It should be understood that by “open circuit” is meant an intact circuit but for the presence of the non-conducting material that resists or impedes current flow and not a circuit with a physical, actual gap or broken connection (disconnected wires). An open circuit for the purposes of this disclosure would result in higher impedance, whereas a circuit that has a gap or disconnected wires would result in infinite or unmeasurable impedance. 
     Greater precision may be obtained by monitoring a factor such as resistance (when direct current is employed) or impedance (when alternating current is employed), as doing so can indicate the extent to which any particular electrode has advanced along the needle insertion path through a zone in which the surrounding material (e.g. air, skin, percutaneous tissue, septum or reservoir fluid) changes to another material. Characteristic resistance values for subcutaneous tissue, the electrode(s) and their insulating sections, the septum, and the therapeutic substance may be measured to help determine needle position under various conditions. In one desirable embodiment, the highest resistance is obtained when the needle is correctly located in the septum. This can help the user of the needle, typically a HCP, detect when the distal end of needle  60  properly projects through the septum  42 . As shown in  FIG. 6D , for example, multiple electrodes may be spaced along the needle length such that when the distal tip of needle  60  reaches the bottom of reservoir  32  and electrode  61  is also in reservoir  32 , electrode  63  is enveloped by septum  42  and electrode  65  is in the patient&#39;s tissue. 
     Detector  50  may, for example, continuously indicate a high current flow, or low resistance or impedance value while the distal end of the needle is advanced through the patient&#39;s skin on its way into the reservoir  32  via septum  42  (see  FIG. 6B ). When the distal end of the needle and its electrode  61  enters into a non-conducting septum  42  (see  FIG. 6C ), the current flowing between electrode  61  and ground pad decreases while resistance or impedance increases. The increase indicates to the user that electrode  61  has entered septum  42 . The user then may further advance the needle into device  12  until the indicated resistance or impedance decreases sufficiently to indicate that the needle is properly positioned within reservoir  32  to permit therapeutic substance delivery. It will be understood that impedance between electrodes  61  and  63 ,  61  and  65  or  63  and  65  may also be measured as opposed to between individual needle electrodes  61 ,  63  or  65  and the ground pad. 
     It should be understood that while the needle has been described as conductive and as passing through a non-conductive septum of an implanted infusion device, the respective electrical properties of the needle and particular implanted infusion device component may be altered, e.g. reversed with respect to one another. For example, the needle may be uninsulated along all or most of its length, and may indicate its position by interacting with an electrically conductive implanted infusion device or component thereof. 
       FIG. 7  shows a needle being inserted into a refill bottle. Needle placement into a refill bottle may serve as an initial system integrity check or for calibration of the needle system. For example, needle insertion until all the electrodes are immersed into a saline solution or the therapeutic substance maybe used as a check to confirm that all circuits are complete or that electrical characteristics such as voltage, resistance, impedance, current, frequency or signal strength values have expected or appropriate values in each circuit. If the system appears intact, the syringe can be filled and the needle used to deliver the syringe contents to a reservoir or catheter. 
       FIG. 8  shows an exemplary impedance profile associated with needle insertion through septum  42  into reservoir  32 . The impedance profile shown in  FIG. 8  was obtained by inserting a modified HUBER™ needle into the septum of SYNCHROMED™ II pump (Medtronic, Inc.) placed subcutaneously (SubQ) in sheep. The needle modification involved coating the entire needle length with an insulating material (PARYLENE™ polymer) except for a 0.1″ wide band beginning 0.2″ from the distal end of the needle to provide a single electrode. Proper insertion depth is indicated by the zone A in  FIG. 8 . 
       FIG. 9  shows a flow diagram illustrating a method for monitoring and detecting needle insertion into a septum. The method includes inserting a needle into a patient in an attempt to access an implanted infusion device ( 100 ) and monitoring changes in electrical characteristics ( 110 ). A determination may then be made as to whether the monitored information is indicative of needle insertion through a septum ( 120 ). If the monitored information is indicative of proper needle insertion into the reservoir or other component of the infusion device a cue may be generated ( 130 ) to alert the user of successful needle placement. The cue may take any form such as a visual, audible or tactile cue. The user may then proceed to deliver fluid into the reservoir or catheter via the needle ( 140 ). If information monitored is indicative of incorrect or insufficient needle insertion, no cue or a different cue may be generated ( 150 ), allowing the user to again attempt to insert the needle or reposition the needle ( 100 ) before fluid delivery.