Patent Publication Number: US-2020297584-A1

Title: System and Method for External Steering of Nasogastric Tube During Its Placement

Description:
BACKGROUND OF THE INVENTION 
     Physicians and other health care providers frequently use catheters to treat patients. Known catheters include a tube which is inserted into the human body. Certain catheters are inserted through the patient&#39;s nose or mouth for treating the gastrointestinal tract. These catheters, sometimes referred to as enteral catheters, typically include feeding tubes. The feeding tube lies in the stomach or intestines, and a feeding bag delivers liquid nutrient, liquid medicine or a combination of the two to the patient. 
     Other types of catheters are inserted into the patient&#39;s veins or arteries for treating the cardiovascular system. These catheters include, among others, the central venous catheter, peripheral venous catheter and the peripherally inserted central catheter (PICC). These catheters include a relatively small tube that passes through the patient&#39;s veins or arteries. The health care provider uses these catheters to provide patients with injections of medications, drugs, fluids, nutrients, or blood products over a period of time, typically several weeks or more. 
     When using these known catheters, it is important to place the end of the catheter at the proper location within the human body. Erroneous placement of the catheter tip may injure or harm the patient. For example, if the health care provider erroneously places an enteral catheter into the patient&#39;s lungs, liquid may be introduced into the lungs with harmful results. If the health care provider erroneously places a catheter into the wrong cavity of the cardiovascular system, the patient may experience infection or a harmful blockage. 
     While advancements have been made in the development of a signal generator placement control device for use in conjunction with electronic catheter guidance systems, there is still a risk of erroneous placement of a catheter by a health care provider, even when using a catheter guidance system. For instance, when a nasogastric (NG) tube is placed through the nasal cavity, the intent is for the NG tube to traverse through the esophagus, then down into the stomach, and into the small bowel, if desired. As the tube travels down the throat, the anatomy splits into the trachea and esophagus at the oropharynx. NG tubes can be misplaced into the trachea at this split, which can result in pneumonia, a pneumothorax, or even death. In addition, it is often challenging for health care providers to position the NG tube within the desired location in the gastrointestinal system, as the flexible nature of the NG tube makes manipulation of the tube into precise locations difficult. 
     Accordingly, there is a need for a system and method to overcome each of these disadvantages. 
     SUMMARY OF THE INVENTION 
     Objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In one particular embodiment, the present invention is directed to a tubing assembly. The tubing assembly includes a catheter and a steering apparatus. The catheter has a proximal end and a distal end and extends in a longitudinal direction, where the proximal end and the distal end define a lumen therebetween. The steering apparatus includes an electrical connection having a distal end and a proximal end as well as a sheath having a proximal end and a distal end, where the sheath includes an electroactive polymer layer. The proximal end of the sheath is coupled to the distal end of the electrical connection, and the steering apparatus is located within the lumen of the catheter. Further, activation of the electroactive polymer layer results in a change in dimension of the sheath, where the change in dimension initiates a change in a direction in which the catheter travels within a body. 
     In one embodiment, the electroactive polymer layer can be an ionic electroactive polymer or an electric electroactive polymer. 
     In another embodiment, the sheath can include at least one insulating layer. For example, the sheath can include a first insulating layer and a second insulting layer, where the electroactive polymer layer can be disposed therebetween. Further, the insulating layer can include polyamide, polyethylene, polypropylene, poly-L-lysine, poly-D-lysine, polyethylene glycol, polyvinyl alcohol, polyvinyl acetate, polymethyl methacrylate, or a combination thereof. 
     In still another embodiment, the electrical connection can be configured to deliver an electrical signal from a power source to the electroactive polymer layer to initiate the change in dimension. 
     In yet another embodiment, the change in dimension of the sheath can result in the catheter changing in direction by an angle ranging from about 1° to about 180° relative to the longitudinal direction in which the catheter extends. 
     In one more embodiment, the proximal end of the electrical connection can be coupled to a controller coupler, where the controller coupler can be configured for connection to a power source. 
     In an additional embodiment, the electrical connection can include a wire. 
     In another embodiment, the tubing assembly can further include a signal generating assembly. The signal generating assembly can include an elongated wire assembly having a proximal end and a distal end and a signal generator, where the signal generator can be coupled to the distal end of the elongated wire assembly. Further, the elongated wire assembly can extend through a lumen of the sheath, and the signal generator can be positioned adjacent the distal end of the sheath towards the distal end of the catheter. In addition, the signal generator can be a magnetic field generator. 
     In another particular embodiment, the present invention is directed to a catheter guidance system. The system includes a controller, a power source, a tubing assembly, and a non-invasive movable receiver-transmitter or transceiver in communication with the tubing assembly, where the tubing assembly and the non-invasive movable receiver-transmitter or transceiver are electronically coupled to the controller. The tubing assembly includes a catheter and a signal generating assembly. The catheter includes a proximal end and a distal end and extends in a longitudinal direction, where the proximal end and the distal end define a lumen therebetween; and a steering apparatus, where the steering apparatus includes an electrical connection having a distal end and a proximal end and a sheath having a proximal end and a distal end and comprising an electroactive polymer layer, where the proximal end of the sheath is coupled to the distal end of the electrical connection, where the steering apparatus is located within the lumen of the catheter, where activation of the electroactive polymer layer from the power source via the electrical connection results in a change in dimension of the sheath, where the change in dimension initiates a change in direction in which the catheter travels within a body. 
     In one more embodiment of the present invention, a method for steering a catheter during placement of the catheter inside a body of a patient is provided. The method includes inserting a distal end of a tubing assembly into an orifice of the body, where the tubing assembly also has a proximal end and includes the catheter, where the catheter has a proximal end and a distal end and extends in a longitudinal direction, where the proximal end and the distal end define a lumen therebetween; and a steering apparatus, wherein the steering apparatus comprises an electrical connection having a distal end and a proximal end and a sheath having a proximal end and a distal end and comprising an electroactive polymer layer, where the proximal end of the sheath is coupled to the distal end of the electrical connection, where the steering apparatus is located within the lumen of the catheter. The method also includes connecting the tubing assembly to a power source; and delivering an electrical signal from the power source to the steering apparatus via the electrical connection to activate the electroactive polymer layer, where activating the electroactive polymer layer changes a dimension of the sheath, where the change in dimension changes a direction in which the catheter travels within the body. 
     In one embodiment, the orifice can be a nose or mouth. 
     In another embodiment, the change in dimension of the sheath can result in the catheter changing in direction by an angle ranging from about 1° to about 180° relative to the longitudinal direction in which the catheter extends. 
     In still another embodiment, the electroactive polymer layer can include an ionic electroactive polymer or an electric electroactive polymer. 
     In yet another embodiment, the method can include activating the electroactive polymer layer as the catheter reaches an area near the patient&#39;s epiglottis so that the catheter is steered towards the esophagus rather than the trachea. 
     In one more embodiment, the method can include activating the electroactive polymer layer as the catheter reaches an area near the patient&#39;s pylorus to facilitate duodenal or jejunal placement of the catheter. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  is a perspective view of the catheter position guidance system illustrating the display device, electronic catheter unit and hand-held transceiver being used to position a catheter within a patient in one embodiment of the present invention. 
         FIG. 2  is schematic block diagram of the electronic configuration of the catheter position guidance system illustrating the processor, memory device, signal generator, input devices and output devices in one embodiment of the present invention. 
         FIG. 3  is a top or plan view of the electronic catheter unit and the display device illustrating an enteral application involving a catheter inserted into a human body and indication of catheter information on the display device. 
         FIG. 4  is a top or plan view of the electronic catheter unit and the display device illustrating a parenteral application involving a catheter inserted into a human body and indication of catheter information on the display device. 
         FIG. 5  is a perspective view of the electronic catheter unit illustrating the tubing assembly and the signal generator being received by and housed in the tubing assembly in one embodiment of the present invention. 
         FIG. 6  is a perspective view of the distal end of the electronic catheter unit illustrating the steering apparatus in one embodiment of the present invention. 
         FIG. 7  is a cross-sectional view of the distal end of the electronic catheter unit of illustrating the steering apparatus in one embodiment of the present invention. 
         FIG. 8  is a perspective view of the signal generator illustrating the tubular insulator housing a portion of the wire assembly in one embodiment of the present invention. 
         FIG. 9  is a top or plan view of the of the electronic catheter unit illustrating an enteral application involving insertion of a catheter into a human body and the steering of the catheter down the esophagus upon activation of the steering apparatus in one embodiment of the present invention. 
         FIG. 10  is a top or plan view of the of the electronic catheter unit illustrating an enteral application involving insertion of a catheter into a human body and the steering of the catheter from the esophagus and into the stomach upon activation of the steering apparatus in one embodiment of the present invention. 
         FIG. 11  is a top or plan view of the of the electronic catheter unit illustrating an enteral application involving insertion of a catheter into a human body and the steering of the catheter from the stomach towards the pylorus upon activation of the steering apparatus in one embodiment of the present invention. 
         FIG. 12  is a top or plan view of the of the electronic catheter unit illustrating an enteral application involving insertion of a catheter into a human body and the steering of the catheter from the pylorus to the duodenum upon activation of the steering apparatus in one embodiment of the present invention. 
         FIG. 13  is a top or plan view of the of the electronic catheter unit illustrating an enteral application involving insertion of a catheter into a human body and the steering of the catheter from the duodenum to the jejunum upon activation of the steering apparatus in one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     Generally speaking, the present invention is directed to a tubing assembly for use in conjunction with electronic catheter guidance systems. The tubing assembly includes a catheter and a steering apparatus. The catheter has a proximal end and a distal end that define a lumen therebetween and extends in a longitudinal direction. The steering apparatus includes an electrical connection and a sheath. Further, the sheath includes an electroactive polymer layer, and the sheath&#39;s proximal end is coupled to the distal end of the electrical connection, where the steering apparatus is located within the lumen of the catheter. Activation of the electroactive polymer layer results in a change in dimension of the sheath, which initiates a change in a direction in which the catheter travels within a patient&#39;s body to assist in accurate placement of the catheter at a desired location. A catheter guidance system and a method for steering a catheter during its placement inside a body are also provided. Because of the specific components of the tubing assembly, catheter guidance system, and their methods of use, the present inventor has found that the placement of a catheter with a patient&#39;s gastrointestinal tract or any other anatomical location can be precisely controlled when the electroactive polymer layer is activated. 
     For instance, a health care provider can use the tubing assembly and catheter guidance system of the present invention to manipulate the placement of a catheter from outside the body. Such manipulation is facilitated by the electroactive polymer layer that forms at least a part of the sheath of the steering apparatus of the tubing assembly, where the polymer or polymers in the electroactive polymer layer can exhibit a change in dimension (e.g., a change in size, shape, and/or diameter) when exposed to an electric field, where the electric field can be applied from a power source in the form of a voltage or current via an electrical connection between the power source and the electroactive polymer layer. Because of the change in dimension of the steering apparatus due to the changes to the electroactive polymer layer, the catheter, which surrounds the steering apparatus (i.e., the steering apparatus is disposed within the lumen of the catheter), can bend in a desired direction such that the catheter can be accurately placed in a specific anatomical region. 
     For example, a catheter extending in a longitudinal direction L can change its direction of travel by an angle θ ranging from about 1° to about 180°, such as from about 5° to about 160°, such as from about 10° to about 90°, or any ranges therebetween, relative to the longitudinal direction L in which the catheter extends in response to the activation and resulting change in dimension of the electroactive polymer layer in the sheath of the steering apparatus, where the steering apparatus can be positioned or disposed within the catheter&#39;s lumen. Further, the length L 1  of the sheath component of the steering apparatus relative to the overall length of the catheter can be relatively small, such as from about 0.5 inches (about 12.5 millimeters) to about 10 inches (about 250 millimeters), such as from about 1 inch (about 25 millimeters) to about 8 inches (about 200 millimeters), such as from about 2 inches (about 50 millimeters) to about 6 inches (about 150 millimeters), or any ranges therebetween. Nevertheless, despite the relatively short length of the sheath with respect to the overall catheter length, activation of the electroactive polymer layer is sufficient to adjust or alter the direction in which the catheter was traveling prior to activation. 
     The various components of the tubing assembly and catheter guidance system of the present invention are discussed in more detail below. 
     Referring now to the drawings, in an embodiment illustrated in  FIGS. 1 and 2 , the catheter position guidance system or catheter guidance system  2  can include: (a) an apparatus  10  having a housing  18  which supports a controller or processor  20  and a display device  22 ; (b) a non-invasive movable receiver-transmitter or transceiver  32  electronically coupled to the processor  20  by a wire, cable, signal data connection or signal carrier  62 ; (c) a power cord  27  that couples the apparatus  10  to a power source  25  (e.g., a power supply or battery); (d) a printer  28  coupled to the apparatus  10  for printing out paper having graphics which indicate catheter location information; and (e) an invasive electronic catheter unit  12  including a catheter  50 , signal generator  58 , and steering apparatus  79  in communication with the transceiver  32  and operatively coupled to the apparatus  10  by a wire, cable, cord or electrical extension  34 , which, in turn, is operatively coupled to the processor  20 , where it is also to be understood that the connection can be wireless (not shown). It should also be appreciated that the transceiver  32  can include a device which has a separate signal receiver and signal transmitter. The transceiver  32  can also include a single device which functions so as to receive and transmit signals. 
     As best illustrated in  FIG. 2 , the catheter position guidance system  2 , in one embodiment, includes: (a) a plurality of input devices  17  for providing input signals to the system  2  such as one or more control buttons  29 , a touch screen  31  and the transceiver  32 ; (b) a signal generating assembly  16  which produces or generates electronic signals that are received by the transceiver  32 ; (d) a steering apparatus  79  that receives one or more electronic signals from a power source via the processor  20  or other suitable means; (d) a memory device  21  including machine readable instructions and one or more computer programs (which, for example, may include a plurality of algorithms  23 ) which are used by the processor  20  to instruct the steering apparatus  79  to change direction as well as to process the signal data produced by the signal generating assembly  16  and transmitted by the transceiver  32 ; and (e) a plurality of output devices  19  such as the display device  22  and the printer  28  which indicate the catheter information to the health care provider. For instance, the display device  22  and/or the printer  28  can display graphics  37  that help the user in guiding the catheter tip  60  to a desired location within the human body. The display device  22  may be any suitable display mechanism including, but not limited to, a liquid crystal display (LCD), light-emitting diode (LED) display, cathode-ray tube display (CRT) or plasma screen. 
     In one particular embodiment, the memory device  21  can store instructions which, when executed by the processor  20 , cause the processor  20  to (i) interpret catheter  50  location and/or position information as determined and communicated by the signal generating assembly  16  and the non-invasive transceiver  32 , and (ii) cause the processor  20  to then instruct the steering apparatus  79  to change direction based on such location and/or position information so that the catheter  50  is steered or guided via the system  2  to a desired anatomical region. 
     Health care providers can use the system  2  in a variety of catheter applications. In one example illustrated in  FIG. 3 , the system  2  is used in an enteral application. Here, a portion  70  of the electronic catheter unit  12  is placed through the patient&#39;s nose or mouth  72 . The distal end or tip  60  of the unit  12  is positioned in the stomach  74 , where the distal end or tip  60  of the unit  12  is steered or guided into position via the steering apparatus  79 . The health care provider places the transceiver  32  over the chest area  76  of a body  78 . The display device  22  and/or the printer  28  can indicate information related to the location of the portion  70  of the electronic catheter unit  12  within the body  78 , as well as information related to the shape of the pathway taken by the catheter unit  12 . It should be appreciated that the system  2  need not indicate the exact location or path of the catheter unit  12  to provide assistance to the health care provider. 
     In another example illustrated in  FIG. 4 , a portion  71  of the electronic catheter unit  12  is introduced into the patient&#39;s body  78  through a vein or artery  73  leading to the heart  75 . Similar to the enteral example, the system  2  assists the health care provider in guiding the portion  71  of the unit  12  in the patient&#39;s vein or artery  73  to a desired cavity in the heart  75  in preparation for parenteral feeding. 
     Referring to  FIG. 5 , in one embodiment, the electronic catheter unit  12  includes a tubing assembly  14  that includes a catheter  50  housing the steering apparatus  79  and signal generating assembly  16 . The various components of the electronic catheter unit  12  are discussed in more detail below. 
     As best illustrated in  FIGS. 1 and 5-7 , in one embodiment, the tubing assembly  14  includes: (a) a tube or an electrical tubular insulator  40 ; (b) a mid-connector or union device  42  which receives the tubular insulator  40 ; (c) a connector  44  attachable to the union device  42  or attachable directly to the tube or electrical insulator  40  without the requirement of the union device  42 , where the connector  44  can be a multi-port connector, a y-port connector, or a single port connector; (d) a catheter  50 , such as a feeding tube, connected to the connector  44 ; (e) a catheter end, bolus or tip  60  attached to the distal end of the catheter  50 ; and (f) a steering apparatus  79  containing an electroactive polymer layer  82  that can adjust the direction in which the catheter  50  travels upon activation. 
     In one embodiment, the tubular insulator  40  includes a tube having: (a) a proximal end  100  attachable to an attachment member or neck  108  of the electronic catheter unit  12 ; (b) a distal end  102  receivable by the union device  42 ; (c) an internal diameter which is substantially equal to or greater than an external diameter of a wire assembly  38  (see  FIGS. 1 and 8 ) described below so as to slide over the wire assembly  38 ; and (d) an external diameter. In another embodiment, the tubular insulator  40  may fit relatively tightly over the wire assembly  38  so as to be secured to the wire assembly  38 . 
     In one embodiment, the union device  42  includes: (a) a proximal end  116 ; (b) a distal end  118 ; (c) a position adjuster, extender or elongated neck  120  positioned between the proximal end  116  and the distal end  118 ; (d) a grasp or gripping member  122  positioned adjacent to the distal end  118  so as to assist users in grasping and manipulating the union device  42 ; and (e) an insert  124  positioned adjacent to the gripping member  122  which is received by the y-port connector  44 . When assembled, the proximal end  116  of the union device  42  is coupled to the distal end  102  of the tubular insulator  40 . 
     In one embodiment, the multi-port or y-port connector  44  includes: (a) a body  140 ; (b) a liquid delivery branch, medicine delivery branch or medicine branch  142  attached to the body  140  for distributing drugs, medicine or other medicinal liquids to the patient; (c) a nutrient delivery branch or feeding branch  144  attached to the body  140  and sized to receive the insert  124  of the union device  42 ; (d) a catheter or feeding tube connection branch  146  attached to the catheter  50 ; (e) a flexible or movable arm  148  attached to the body  140 ; and (f) a flexible or moveable arm  150  attached to the body  140 . In an alternative embodiment, y-port connector  44  includes additional branches for administering various nutrients or medicines to the body  78 . In another alternative embodiment, the y-port connector  44  includes only a feeding branch  144  and a connection branch  146 . The arm  148  has a stopper  152 , and the arm  150  has a stopper  154 . The stoppers  152  and  154  are sized to prevent fluid from passing through the branches  142  and  144  after such branches  142  and  144  are plugged with stoppers  152  and  154 , respectively. In addition, the arm  150  can include a fastener  155  which secures a tube-size adapter  156  to the arm  150 . The tube-size adapter  156  enables fluid delivery tubes (not shown) having various diameters to connect to the feeding branch  144  of the y-port connector  44 . 
     As illustrated in  FIGS. 5-6 , in one embodiment, the catheter  50  includes a feeding tube with a body  160  having: (a) a proximal end  162  attached to the catheter connection branch  146  of the y-port connector  44 ; and (b) a distal end  164 . The proximal end  162  is insertable into the catheter connection branch  146  of the y-port connector  44  so as to bring the catheter  50  into fluid communication with the y-port connector  44 . In one embodiment, the end member, bolus or tip  60  of the catheter  50  is attached to the distal end  164  of the catheter  50 . The tip  60  includes a body  172  having a collar  174  and an end member  176 . The body  172  defines a passage  178  and an opening  180 . The opening  180  is positioned between the collar  174  and the end member  176 . A portion  177  of the end member  176  can have a rounded shape. The shape of the passage  178  and opening  180  of the tip  60  is configured to facilitate the flow of fluid from the catheter  50  into the patient&#39;s body while decreasing the likelihood that the opening  180  will become clogged. 
     The tubular connector  40 , union device  42 , y-port connector  44 , catheter  50 , and tip  60  can be made from any suitable polymer or plastic material including, but not limited to polyamide, polyethylene, polypropylene, polyurethane, silicone, polyacrylonitrile, poly-L-lysine, poly-D-lysine, polyethylene glycol, polyvinyl alcohol, polyvinyl acetate, polymethyl methacrylate, or a combination thereof. 
     Further, as illustrated in  FIGS. 5-7 , the tubing assembly  14  also includes a steering apparatus  79  that can include a sheath  80  or tubing containing one or more polymeric layers  81 ,  82 , and  83  as well as an electrical connection  84 . Although a sheath  80  is described in detail below, it is to be understood that the steering apparatus  79  can also be in the form of a coating, wrap, or any other substrate configured for activation of one or more electroactive polymers via an electrical signal delivered via an electrical connection  84  that can be wired (shown) or wireless connection (not shown). For example, the steering apparatus  79  can include a sheath  80  defining a proximal end  85  and a distal end  86  to define an opening or lumen  98  therebetween and can also include an electroactive polymer layer  82 . Additionally, in some embodiments, the sheath  80  can include an outer layer  81  that surrounds an outer surface of the electroactive polymer layer  82 , where the outer layer  81  helps to insulate the body  78  from any effects of the electroactive polymer layer  82  when it is activated via the electrical connection  84  at the proximal end  85  of the sheath  80 . In addition, in some embodiments, the sheath  80  can include an inner layer  83  that surrounds an inner surface of the electroactive polymer layer  82 , where the inner layer  83  can insulate the wire assembly  38  and signal generator  58  (discussed in more detail below) from the electroactive polymer layer  82  when the electroactive polymer layer  82  is activated to reduce any interference between the electrical and/or electromagnetic signals associated with each of the individual components. Although any suitable insulating material can be used, in some embodiments, the outer layer  81  and/or the inner layer  83  can include polyamide, polyethylene, polypropylene, poly-L-lysine, poly-D-lysine, polyethylene glycol, polyvinyl alcohol, polyvinyl acetate, polymethyl methacrylate, or a combination thereof. Further, as shown, the proximal end  103  of the electrical connection  84  portion of the steering apparatus  79  is connected to a controller coupler or an electrical connection  36  that is connected to the electrical extension  34 , while the distal end  105  of the electrical connection  84  is connected to the proximal end  85  of the sheath  80  of the steering apparatus  79 . 
     Regardless of the particular arrangement of the steering apparatus  79 , whether it be in the form of a sheath  80  as described above or as a coating, wrap, etc., the steering apparatus  79  contains an electroactive polymer layer  82  or other electroactive polymer component that can adjust the direction in which the catheter  50  travels upon activation of the electroactive polymer or polymers contained therein. Although any suitable electroactive polymer or combination thereof can be used in the steering apparatus  79  contemplated by the present invention, in some embodiments, the electroactive polymer can be an ionic electroactive polymer such as a conductive polymer, an ionomeric polymer-metal composite (IPMC), or carbon nanotubes (CNT). For example, the conductive polymer can include polypyrrole, poly(3,4-ethylenedioxythiophene), polythiophene, polyaniline, poly-p-phenylene-sulphide, polyacetylene, polyisoprene, polybutadiene, or a combination thereof. Meanwhile, the IPMC can include perfluorosulphonate, perfluorocarboxylate, or a combination thereof. In other embodiments, the electroactive polymer can be an electric electroactive polymer. For instance, in one embodiment, the electric electroactive polymer can be a piezoelectric polymer, such as polyvinylidene fluoride (PVDF) or a copolymer thereof. In another embodiment, the electric electroactive copolymer can be an electro-statically stricted polymer (ESSP), such as polyurethane, silicone, fluorosilicone, fluorodastomer, polybutadiene, isoprene natural rubber latex, polyacrylonitrile, or a combination thereof. In other embodiments, the electric electroactive polymer can be an electrorestrictive graft elastomer, an electro-viscoelastic elastomer, a liquid crystal elastomer, or a combination thereof. 
     Referring specifically to  FIGS. 6-7 , when the steering apparatus  79  includes a sheath  80 , the sheath can span a length L 1  in the longitudinal direction L in which the tubing assembly  14  and catheter  50  extend ranging from about 0.5 inches (about 12.5 millimeters) to about 10 inches (about 250 millimeters), such as from about 1 inch (about 25 millimeters) to about 8 inches (about 200 millimeters), such as from about 2 inches (about 50 millimeters) to about 6 inches (about 150 millimeters), or any ranges therebetween. In addition, the sheath  80  can have a diameter D 4  that is less than the diameter D 3  of the catheter  50  so that the sheath  80  can fit within the lumen  101  of the catheter  50 . Meanwhile, the lumen  98  of the sheath  80  has a diameter D 1  that is large enough to contain the elongated wire assembly  38  component of a signal generating assembly  16 , discussed in more detail below, which has a diameter of D 2 . 
     As shown in  FIG. 6 , in some embodiments, the diameter D 1  of the lumen  98  of the sheath  80  can be generally the same as the diameter D 2  of the elongated wire assembly  38 , which can provide additional stiffness or rigidity to the elongated wire assembly  38 , which can, in turn, allow for more precise control in moving the tubing assembly  14  that includes the catheter  50  to the desired location within the body  78 . As shown in  FIG. 7 , in other embodiments, the diameter D 1  of the lumen  98  of the sheath  80  can be larger than the diameter D 2  of the elongated wire assembly  38  to provide a space within the lumen  98 , which may help to attenuate the electrical signals associated with the electroactive polymer layer  82  upon activation and reduce interference with the signals traveling through the elongated wire assembly  38 , which allow for tracking of the catheter tip  60  via the signal generator  58  component of a signal generating assembly  16 , which is discussed in more detail below. 
     As shown in  FIGS. 1, 5, and 8 , in one embodiment, the catheter guidance system  2  and tubing assembly  14  can also include an invasive signal generating assembly  16 . The signal generating assembly  16  can include: (a) the controller coupler or an electrical connector  36  discussed above and connected to the electrical extension  34 ; (b) an elongated wire assembly  38  connected to the controller coupler or electrical connector  36 ; (c) a wire or elongated stiffener  39  attached to the controller coupler or electrical connector  36  and serving as a support for the wire assembly  38 ; (d) a signal generator or magnetic field generator  58  coupled to the distal end of the wire assembly  38 ; and (e) a suitable fastener attaching the distal end of the elongated stiffener  39  to the magnetic field generator  58 . Referring to  FIG. 8 , the tubular insulator  40  described above covers a portion  41  of the wire assembly  38  positioned adjacent to the controller coupler  36 , and it is to be understood that the signal generating assembly  16  can be considered a component of the tubing assembly  14  described above. 
     Generally, the controller coupler  36  contains circuitry that enables it to transmit electrical signals (e.g., current and/or voltage) from the apparatus  10  (e.g., the processor or controller  20 ) through the electrical connection  84  of the steering apparatus  79  to activate the electroactive polymers in the sheath  80  to guide the movement of the catheter  50  within the tubing assembly  14  as it passes through various regions of the body  78 . Various methods of steering the tubing assembly  14  to a desired location are discussed in more detail below with respect to  FIGS. 9-13 . In addition, the same controller coupler  36  can transmit electrical current from the apparatus  10  to the signal generator or magnetic field generator  58  described below to aid in the tracking and/or visualization of the catheter  50  as it is being placed within the body  78 . 
     In one embodiment, the signal generator or magnetic field generator  58  is formed through a plurality of spirals or coils of wire. As the apparatus  10  transmits electrical current through the wires, the current travels in a circular path defined by the coils. This circular motion of current produces an electromagnetic field, B field or electromagnetic radiation. Further, it should be appreciated that the signal generator  58  can include any alternate suitable mechanism or device which generates or produces magnetic energy or a magnetic field. In one embodiment, the magnetic field generator  58  includes a magnet such as a permanent magnet, resistive magnet or superconducting magnet. 
     In operation, when the apparatus  10  sends electrical current to the coils, the coils transmit a signal or electromagnetic field capable of being detected by the non-invasive transceiver  32 . The transceiver  32  then detects the electromagnetic field or signal generated by the signal generator  58  inside the body  78 . The processor  20  then causes the display device  22  and/or the printer  28  to produce graphics  37  which assist the health care provider in catheter placement procedure. 
     Further, although not shown, in an alternative embodiment, it is to be understood that the invasive signal generating assembly  16  including the signal generator  58  can be incorporated directly into tubing assembly  14 , for example, by embedding the coils of the signal generator  58  into a wall of the catheter  50 . 
     Methods of using the various assemblies and components described above for accurately placing a catheter  50  in a desired anatomical region in, for example, a gastrointestinal tract of a of a patient are now described in detail with respect to  FIGS. 9-13 , although it is to be understood that the tubing assembly  14  and other components can be used for placing a catheter in an area outside of the gastrointestinal tract as well. 
     Generally, a method, such as a computer-implemented method, for steering a catheter  50  during placement of the catheter  50  inside a body  78  of a patient according the present invention, and referring to  FIGS. 1, 3, and 9-13 , includes inserting a distal end  126  of a tubing assembly  14  into an orifice (e.g., the nose  72 ) of the body  78 . The tubing assembly  14  also has a proximal end  128 , which can also be described as the proximal end of the catheter  50 , located outside the body  78  and towards the apparatus  10  that can include a controller or processor  20 , where the apparatus  10  is connected to the tubing assembly  14  via an electrical extension  34  (e.g., a wire, cable, cord, wireless connection, etc.). Further, the tubing assembly  14  includes the catheter  50 , and the steering apparatus  79  is contained within the lumen  101  of the catheter  50  towards the distal end or tip  60  of the catheter, where the tubing assembly  14  containing the catheter  50  and steering apparatus  79  extends in the longitudinal direction L. 
     Once the distal end  126  of the tubing assembly  14  is inserted into an orifice of the body  78 , such as one of the nostrils  87  of the nose  72 , various components of the tubing assembly  14  can be connected to the power source  25  such as via the controller coupler  36 . For instance, the steering apparatus  79  can be connected to the power source  25  via the electrical extension  34  through the controller coupler  36  and through the electrical connection  84  of the steering apparatus  79 . The electrical connection  84  can then be in contact with the electroactive polymer layer  82  of the sheath  80  so that the electroactive polymer layer  82  can be activated as needed via an electrical signal sent by the power source (e.g., current, voltage, etc.) to initiate a change in dimension (e.g., size, shape, diameter, etc.) of the sheath  80 , which, in turn, results in the bending or angling of the catheter  50  in a desired direction to guide or steer the catheter  50  to a desired location. Further, although a physical electrical connection between the power source  25  and the steering apparatus  79  via the electrical extension  34  and the electrical connection  84  are described above, it is also to be understood that wireless connections are contemplated by the present invention. 
     Referring to  FIGS. 9-13 , the change in dimension of the sheath results in the catheter changing in direction by an angle θ ranging from about 1° to about 180°, such as from about 5° to about 160°, such as from about 10° to about 90°, or any ranges therebetween, relative to the longitudinal direction L in which the catheter  50  extends. 
     Referring to  FIG. 9 , in one particular embodiment, the electroactive polymer layer  82  can be activated as the catheter  50  of an enteral feeding tube system in the form of an electronic catheter unit  12  reaches an area near the patient&#39;s epiglottis  90  so that the catheter  50  is steered towards the back of the throat  97 , enabling the catheter  50  to be properly inserted into the esophagus  91  rather than the trachea  92  after the catheter  50  passes through the nasal cavity  88  and nasopharynx  89 . As shown, the catheter  50  can bend in the direction of the arrow as a result of the activation of the electroactive polymer layer  82  of the steering apparatus  79 . 
     Referring to  FIGS. 10 and 11 , in another particular embodiment, the electroactive polymer layer  82  can be activated as the catheter  50  of the electronic catheter unit  12  reaches an area near the end of the patient&#39;s esophagus  91  so that the catheter  50  is steered towards the pylorus  94  once it enters the stomach  74 , enabling the catheter  50  to be properly inserted into the desired location in the gastrointestinal tract. As shown, the catheter  50  can bend in the direction of the arrows in  FIGS. 10 and 11  as a result of the activation of the electroactive polymer layer  82  of the steering apparatus  79 . 
     Meanwhile, referring to  FIGS. 12 and 13 , in other embodiments, the electroactive polymer layer  82  can be activated as the catheter  50  of the electronic catheter unit  12  reaches an area near pylorus  94  after it enters the stomach  74  so that the catheter  50  is properly inserted into the desired location (e.g., the duodenum  95  in  FIG. 12  or the jejunum  96  in  FIG. 13  in the gastrointestinal tract. As shown, the catheter  50  can bend in the direction of the arrows in  FIGS. 12 and 13  to reach the desired locations at the duodenum  95  or the jejunum  96  depending on where the heath care provider has decided to place the catheter  50  for providing nutrition and/or medicine to the patient as a result of the activation of the electroactive polymer layer  82  of the steering apparatus  79 . 
     Further, it should be understood that a method of guiding or steering the placement of the catheter  50  with the steering apparatus  79  as described above with respect to  FIGS. 9-13  can be also involve the use of the signal generating assembly  16  including the signal generator  58 , where its placement can be controlled to assist in the health care provider in tracking the location of the tubing assembly  14  and steering apparatus  79 . In the embodiments best illustrated in  FIGS. 1 and 5 , the union device  42  assists in maintaining the position of the signal generator  58  at or near the tip  60  of the catheter  50 . The use of the union device  42 , in one such embodiment, reduces the likelihood that the signal generator  58  might protrude through the tip  60  or stop substantially short of the tip  60 . Therefore, the union device  42  functions as a generator placement control device. In one embodiment, this placement and control function of the union device  42  is adjustable to conform to catheters  50  that have different lengths. 
     In one example, the method of controlling the placement of the signal generator  58  includes first step of determining the length of the catheter  50 . Next, prior to placing the catheter  50  into the human body  78  for enteral or parenteral feeding in conjunction with the steering apparatus  79 , the health care provider or an assembler can place the signal generator  58  at a desired location within the catheter  50 . In one particular embodiment, the sheath  80  of the steering apparatus  79  surrounds the wire assembly  38 , while the signal generator  58  is located adjacent the steering apparatus  79  at a distal end  86  of the sheath  80 , as shown in  FIG. 7 . Finally, after proper placement of these components is confirmed, the health care provider or the assembler locks this placement by fastening the tubular insulator  40  to the union device  42  using a suitable adhesive. 
     Once the position of the steering apparatus  79  and signal generator  58  has been properly set, the health care provider places the transceiver  32  on the patient&#39;s chest area  76  and inserts the tubing assembly  14  of the electronic catheter unit  12  including the catheter  50  into the body  78 . While doing so, the display device  22  displays graphics  37  that help the user in guiding the catheter tip  60  to a desired location within the human body  78 . Once the catheter  50  is placed in the desired location via the aid of the steering apparatus  79  and the signal generating assembly  16  described in detail above, the health care provider can remove the steering apparatus  79  and signal generating assembly  16  including the wire assembly  38  and signal generator  58  while the position of the catheter  50  is maintained. The health care provider can then attach medicine and/or nutritional delivery tubes to the y-port connector  44  for introducing fluids into the body  78  for medical treatment. 
     It should be appreciated that the tubing assembly, electronic catheter unit and catheter position guidance system of the present invention can be used in a variety of catheter procedures and applications. These procedures may involve the treatment of the gastrointestinal tract, cardiovascular system or other portions of the human body. These procedures may involve treatment of humans by physicians, physician assistants, nurses or other health care providers. In addition, these procedures may involve treatment of other mammals and animals by veterinarians, researchers and others. 
     The present invention, in one embodiment, includes a tubing assembly and signal generator for an electronic catheter unit of a catheter position guidance system. The tubing assembly and signal generator are used in conjunction with other components of the system to assist the user in performing a catheter placement procedure. The tubing assembly has a position controller which enables the system to be used with catheters of variable lengths. Therefore, the tubing assembly and the position controller, used in conjunction with the catheter position guidance system of the present invention, provide an enhancement in medical treatment. 
     Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.