Patent Description:
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's nose or mouth for treating the digestive or 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.

When using such 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's trachea, lungs, or other anatomical regions of the respiratory system or airway rather than through the esophagus and to the stomach to reach the desired location in the digestive tract for delivering nutrients or medicine, liquid may be introduced into the lungs with harmful, and even fatal, consequences. In particular, the esophagus of the digestive tract and the trachea of the respiratory system are in close proximity to each other and are blind to the health care provider during catheter placement, which creates a dangerous risk for erroneous catheter placement.

In some cases, health care providers use X-ray machines to gather information about the location of the catheters within the body. There are several disadvantages with using X-ray machines. For example, X-ray machines are relatively large and heavy, consume a relatively large amount of energy and may expose the patient to a relatively high degree of radiation. Also, these machines are typically not readily accessible for use because, due to their size, they are usually installed in a special X-ray room. This room can be far away from the patient's room. Therefore, health care providers may find it inconvenient to use these machines for their catheter procedures. In addition, using X-ray technology is expensive and is a time-consuming task that can create unnecessary delays in delivering critical nutrients to the patient. <CIT> discloses stimulating one or more esophageal muscle contractions to evoke motion and/or restore function in one or more organs located distal to the lower esophageal sphincter.

Accordingly, there is a need to overcome each of these disadvantages.

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 having a proximal end and a distal end and extending in a longitudinal direction, wherein the proximal end and the distal end define a lumen therebetween, and wherein the catheter is configured for placement within a digestive tract of a patient; a stimulation electrode assembly, wherein the stimulation electrode assembly is configured to deliver an electrical stimulation to tissue; and an electrical connection for delivering a stimulation waveform to the stimulation electrode assembly.

In another embodiment, the stimulation electrode assembly can include an anode and a cathode, wherein the anode and the cathode are disposed on an outer wall of the distal end of the catheter.

In still another embodiment, the stimulation electrode assembly can include a first electrode disposed on an outer wall of the catheter and a second electrode configured for placement on a surface of skin.

In yet another embodiment, the tubing assembly can also include a recording electrode assembly. The recording electrode assembly can include an active recording electrode, an inactive recording electrode, and a reference electrode. Further, the active recording electrode, the inactive recording electrode, and the reference electrode can be disposed on an outer wall of the distal end of the catheter. Alternatively, the active recording electrode, the inactive recording electrode, and the reference electrode can be configured for placement on a surface of skin.

In one more embodiment, the recording electrode assembly can be configured to monitor for electrical activity elicited by the tissue in response to the stimulation waveform and communicate the electrical activity elicited by the tissue to a processor in real-time.

In an additional embodiment, the stimulation electrode assembly can be configured for a wired connection or a wireless connection to the processor. Further, the wired connection can include a wire or a printed conduit.

In another particular embodiment, the present invention is directed to a catheter guidance system. The catheter guidance system includes (a) a processor; (b) a power source; (c) a stimulator; and (d) a tubing assembly. Further, the tubing assembly includes a catheter having a proximal end and a distal end and extending in a longitudinal direction, wherein the proximal end and the distal end define a lumen therebetween; a stimulation electrode assembly, wherein the stimulation electrode assembly is configured to deliver an electrical stimulation to tissue; and a recording electrode assembly, wherein the recording electrode assembly is configured to monitor for electrical activity elicited by the tissue in response to the stimulation waveform, further wherein the recording electrode assembly communicates the electrical activity elicited by the tissue to the processor in real-time; wherein the catheter guidance system alerts a user as to correct placement of the catheter in a digestive tract of a patient or alerts the user as to incorrect placement of the catheter in a respiratory tract of the patient.

In one embodiment, the system can also include a display device, wherein the display device is coupled to the processor and displays a graph of the electrical activity elicited by the tissue and communicated to the processor by the recording electrode assembly.

In still another embodiment, the system can also include a memory device storing instructions which, when executed by the processor, cause the processor to (i) interpret the electrical activity elicited by the tissue and communicated by the recording electrode assembly and (ii) cause the catheter guidance system to alert the user as to correct placement of the catheter in the digestive tract of the patient or alert the user as to incorrect placement of the catheter in the respiratory tract of the patient based on the interpretation of the electrical activity elicited by the tissue.

In yet another embodiment, the stimulation electrode assembly can include an anode and a cathode, wherein the anode and the cathode are disposed on an outer wall of the distal end of the catheter.

In one more embodiment, the stimulation electrode assembly can include first electrode disposed on an outer wall of the catheter and a second electrode configured for placement on a surface of skin.

In an additional embodiment, the recording electrode assembly can include an active recording electrode, an inactive recording electrode, and a reference electrode. Further, the active recording electrode, the inactive recording electrode, and the reference electrode can be disposed on an outer wall of the distal end of the catheter. Alternatively, the active recording electrode, the inactive recording electrode, and the reference electrode can be configured for placement on a surface of skin.

As used herein, the terms "about," "approximately," or "generally," when used to modify a value, indicates that the value can be raised or lowered by <NUM>% and remain within the disclosed embodiment. Further, when a plurality of ranges are provided, any combination of a minimum value and a maximum value described in the plurality of ranges are contemplated by the present invention. For example, if ranges of "from about <NUM>% to about <NUM>%" and "from about <NUM>% to about <NUM>%" are described, a range of "from about <NUM>% to about <NUM>%" or a range of "from about <NUM>% to about <NUM>%" are also contemplated by the present invention.

Generally speaking, the present invention is directed to a tubing assembly that includes a catheter having a proximal end and a distal end and extending in a longitudinal direction, where the proximal end and the distal end define a lumen therebetween. Further, the catheter is configured for placement within a digestive tract of a patient. The tubing assembly also includes a stimulation electrode assembly that is configured to deliver an electrical stimulation to tissue (e.g., esophageal tissue such as striated muscle or tissue in the trachea such as cartilage, connective tissue, and the trachealis muscle), as well as an electrical connection for delivering a stimulation waveform to the stimulation electrode assembly. A catheter guidance system and method for accurately placing a catheter in the digestive tract are also provided.

In addition to a stimulation electrode assembly, the tubing assembly contemplated by the present invention can also include a recording electrode assembly. The recording electrode assembly is configured to monitor for electrical activity elicited by the tissue in response to the stimulation waveform and communicate the electrical activity elicited by the tissue to a processor in real-time. For example, if the electrical activity elicited by the tissue in response to a stimulation waveform (e.g., a monophasic or biphasic square wave pulse) is in the form of one or more evoked potentials, then it can be confirmed that the catheter has been placed or inserted into the digestive tract. Meanwhile, if the electrical activity elicited by the tissue is not in the form of one or more evoked potentials, then it can be confirmed that the catheter is not placed in the digestive tract. Alternatively, if the electrical activity elicited by the tissue is monitored by measuring the impedance of the tissue in response to a stimulation waveform (e.g., an electrical noise signal, a single frequency waveform, multiple frequency waveforms superimposed on top of one another, etc.), a first level of impedance can indicate that the catheter is placed in the digestive tract, while a second level of impedance can indicated that the catheter is not placed in the digestive tract. The present inventors have found that the tubing assembly, catheter guidance system, and method described in more detail herein allow for the electrical activity elicited by tissue in response to a stimulation waveform delivered by the stimulation electrode assembly and captured in real-time via the recording electrode assembly can be used to determine if the distal end of the catheter is accurately placed within the digestive tract (e.g., the epiglottis, esophagus, stomach, intestines, etc.) rather than erroneously placed within the respiratory system (e.g., the trachea, bronchi, lungs, etc.), where such placement could be harmful and even fatal to a patient. Further, the present inventors have found that because the recording electrode assembly can obtain measurements and communicate those measurements to processor and ultimately a display device or other communication device (e.g., a phone, pager, etc.) in real time, the correct placement of the catheter can be confirmed within seconds of a catheter placement procedure, which can save valuable time, resources, and cost while at the same time limit patient risk in the event of the erroneous placement of the catheter.

Specifically, the present inventors have found that capturing and monitoring electrical activity elicited by tissue at a distal end of a catheter in response to a stimulation waveform in real-time, where the catheter is to be placed in a predetermined location along the digestive tract (e.g., esophagus, stomach, intestines, etc.), which is facilitated by the stimulation electrode assembly and the recording electrode assembly of the catheter guidance system of the present invention, allows for the efficient and accurate placement of the catheter within the digestive tract at a low cost. For instance, the recording electrode assembly of the tubing assembly can capture data associated with electrical activity elicited by tissue in response to stimulation in the form an electrical pulse waveform or random noise signal waveform within the catheter as it is being directed by a health care provider in to the body of a patient, where the recorded electrical activity (e.g., in the form of evoked potentials, impedance of tissue measured between electrical contacts, etc.) can then be transmitted to a display device via a processor. The health care provider can then view the electrical activity elicited by the tissue on the display device to determine if the catheter has been accurately placed in the digestive tract or erroneously placed in an anatomical region of the respiratory system (e.g., the trachea, bronchi, lungs, etc.). Alternatively or additionally, a memory device that can include machine readable instructions and one or more computer programs (which, for example, may include a plurality of algorithms) can be used by the processor to process the data from the recording electrode assembly, where the display device can then indicate the catheter information to the health care provider in the form of a signal as to whether the catheter is accurately placed in the digestive tract or erroneously placed within, for instance, a portion of the respiratory system. For example, a green check mark or the word "Yes" can be displayed on the screen to indicate accurate placement of the catheter within the digestive or gastrointestinal tract, while a red circle with a diagonal line through it, an "X", or the word "No" can be displayed on the screen for erroneous placement, such as placement within the respiratory system.

The various features of the catheter guidance system are discussed in detail below.

Referring now to the drawings, in an embodiment illustrated in <FIG>, the catheter guidance system <NUM> contemplated by the present invention includes: (a) an apparatus <NUM> having a housing <NUM> which supports a controller or processor <NUM> and a display device <NUM>; (b) a power cord <NUM> that couples the apparatus <NUM> to a power source <NUM>; (c) a printer <NUM> coupled to the apparatus <NUM> for printing out paper having graphics which indicate catheter location information; (d) an optional non-invasive movable receiver-transmitter or transceiver <NUM> electronically coupled to the processor <NUM> by a wire, cable, signal data connection or signal carrier <NUM>; and (e) an invasive electronic catheter unit <NUM> in communication with and operatively coupled to the apparatus <NUM> by a wire, cable, cord or electrical extension <NUM>, which, in turn, is operatively coupled to the processor <NUM>, where the electronic catheter unit <NUM> includes a tubing assembly <NUM> that includes a catheter <NUM>; a stimulation electrode assembly <NUM>; a recording electrode assembly <NUM>; a stimulator <NUM>; and an optional signal generator <NUM> when the system <NUM> includes the optional non-invasive movable receiver-transmitter or transceiver <NUM>.

As best illustrated in <FIG>, the system <NUM>, in one embodiment, includes: (a) a plurality of input devices <NUM> for providing input signals to the system <NUM> such as one or more control buttons <NUM>, a touch screen <NUM>, and the optional transceiver <NUM>; (b) a stimulation electrode assembly <NUM>; (c) a recording electrode assembly <NUM> that can continuously capture electrical activity elicited by tissue near the catheter <NUM> of the tubing assembly <NUM> in real-time; (d) a stimulator <NUM> which sends electrical signals in the form of a waveform via the stimulation electrode assembly <NUM>; (e) an optional signal generator <NUM> which produces or generates electronic signals that are received by the transceiver <NUM>; (f) a memory device <NUM> including machine readable instructions and one or more computer programs (which, for example, may include a plurality of algorithms <NUM>) which are used by the processor <NUM> to process the electrical activity data captured by the recording electrode assembly <NUM> as well as to process the signal data produced by the signal generator <NUM> and transmitted by the transceiver <NUM> if present; (g) a data acquisition system <NUM>; (h) a signal amplifier <NUM>; and (i) a plurality of output devices <NUM> such as the display device <NUM> and the printer <NUM> which indicate the catheter information to the health care provider, such as in the form of a graph <NUM> (see <FIG>). The display device <NUM> 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 <NUM> can store instructions which, when executed by the processor <NUM>, cause the processor <NUM> to (i) interpret catheter <NUM> location and/or position information as determined and communicated by the recording electrode assembly <NUM> based on the tissue's response to stimulation delivered from the stimulator <NUM> via the stimulation electrode assembly <NUM> and the optional signal generating assembly <NUM> (including the signal generator <NUM> and the non-invasive transceiver <NUM>), and (ii) cause the processor <NUM> to then instruct the system <NUM> to alert the health care provider either via the display device <NUM>, auditory signals, etc. as to the accurate or inaccurate placement of the catheter <NUM>.

Health care providers can use the system <NUM> in a variety of catheter applications. In one example illustrated in <FIG>, the system <NUM> is used in an enteral application. Here, a portion of the electronic catheter unit <NUM> is placed through an orifice <NUM> of the patient, such as the patient's nose or mouth. The distal end or tip <NUM> of the electronic catheter unit <NUM> can ultimately by positioned in the stomach <NUM>. As the health care provider advances the catheter <NUM> of the electronic catheter unit <NUM> towards the patient's stomach <NUM>, the stimulator <NUM> can be activated to deliver a stimulation waveform to the stimulation electrode assembly <NUM> while the recording electrode assembly <NUM> can continuously monitor for electrical activity elicited by tissue near the distal end <NUM> of the catheter <NUM> where at least one electrode in the stimulation electrode assembly <NUM> is positioned as the catheter <NUM> is inserted by the health care provider, as shown in <FIG> and <FIG>. The stimulation electrode assembly <NUM> and the recording electrode assembly <NUM> can each include a plurality of electrodes as will be discussed in more detail with respect to <FIG> and <FIG>, where it is to be understood that one or more of the electrodes in the recording electrode assembly <NUM> and/or a surface electrode 46c of the stimulation electrode assembly <NUM> can be present on a surface of skin <NUM> such that the stimulation and/or recording of electrical activity can be achieved transcutaneously. The display device <NUM> and/or the printer <NUM> can indicate information related to the location of the portion of the electronic catheter unit <NUM> within the body <NUM> based on the electrical activity data acquired by the recording electrode assembly <NUM>, as well as information related to the shape of the pathway taken by the catheter unit <NUM> if the system includes a signal generating assembly <NUM> that utilizes the signal generator <NUM> and the associated non-invasive transceiver <NUM>. It should be appreciated that the system <NUM> need not indicate the exact location or path of the catheter unit <NUM> to provide assistance to the health care provider.

Referring to <FIG>, in one embodiment, the electronic catheter unit <NUM> includes a tubing assembly <NUM>, which includes the catheter <NUM>, at least a portion of the stimulation electrode assembly <NUM>, and optionally at least a portion of the recording electrode assembly <NUM>. The catheter <NUM> includes a lumen <NUM> defined between a proximal end <NUM> and a distal end <NUM> to define a catheter body <NUM>, where the catheter <NUM> can generally extend in the longitudinal direction L. Further, in one embodiment, at least a portion of the stimulation electrode assembly <NUM> and at least a portion of the recording electrode assembly <NUM> can be disposed on an outer wall <NUM> of the catheter, at a distal end <NUM> of the catheter <NUM> or tip <NUM> of the electronic catheter unit <NUM>, as shown in <FIG>. However, it is also to be understood that a portion of the stimulation electrode assembly <NUM> and all or a portion of the recording electrode assembly <NUM> can be positioned on a surface of skin <NUM> so long as the stimulation waveform delivered to an area of tissue by the stimulation electrode assembly <NUM> can reach the area of tissue at levels sufficient to elicit an electrical response and the electrical activity elicited by tissue in response to the stimulation waveform can be adequately recorded by the recording electrode assembly <NUM>.

In one embodiment, for instance, a surface electrode 46c of the stimulation electrode assembly <NUM> and one or more electrodes of the recording electrode assembly <NUM> can be located on a surface of skin <NUM>. The surface electrode 46c can be used when the electrical stimulation waveform is delivered by the stimulation electrode assembly <NUM> in monopolar fashion, while a cathode 46a and an anode 46b disposed on an outer wall <NUM> of the catheter <NUM> can be used in the electrical stimulation waveform delivered by the stimulation electrode assembly <NUM> is delivered in bipolar fashion. Further, the recording electrode assembly <NUM> can include an active recording electrode 48a, an inactive recording electrode 48b, and a reference electrode 46c, each of which can also be disposed on the outer wall <NUM> of the catheter anywhere along its length or can be disposed on a surface of skin <NUM>. Further, as shown in <FIG> and <FIG>, when any of the electrodes or located on the outer wall <NUM> of the catheter <NUM>, the electrodes (e.g., the stimulation electrode assembly <NUM> and/or recording electrode assembly <NUM>) can be electrically connected to the apparatus <NUM> via an electrode electrical connection <NUM>, which can be in the form of a wire or printed conduit. However, it is also to be understood that the connection can be wireless. Moreover, when any of the electrodes are located on a surface of skin <NUM> for transcutaneous stimulation and/or recording, the electrodes (e.g., the stimulation electrode assembly <NUM> and/or recording electrode assembly <NUM>) can be electrically connected to the apparatus <NUM> via a wire <NUM>. However, it is also to be understood that the connection can be wireless.

Referring to <FIG> and <FIG>, the stimulation electrode assembly <NUM> can be disposed on the outer wall <NUM> of the catheter <NUM> at distal end <NUM> of the catheter <NUM>, while the recording electrode assembly <NUM> can also be disposed at the distal end <NUM> or can be disposed anywhere along the length of the catheter <NUM> between the proximal end <NUM> and the distal end <NUM>. In any event, the cathode 46a and the anode 46b of the stimulation electrode assembly <NUM> and the active recording electrode 48a, the inactive recording electrode 48b, and the reference electrode 48c of the recording electrode assembly <NUM> can each have a width W ranging from about <NUM> millimeters to about <NUM> millimeters, such as from about <NUM> millimeters to about <NUM> millimeters, such as from about <NUM> millimeters to about <NUM> millimeters and can encircle all or a portion of the catheter wall <NUM> in the form of a ring, a stent-like embodiment, an expandable balloon, etc. In addition, the cathode 46a and the anode 46b can be separated by a distance D1 ranging from about <NUM> millimeter to about <NUM> millimeters, such as from about <NUM> millimeters to about <NUM> millimeters, such as from about <NUM> millimeters to about <NUM> millimeters. Moreover, the stimulation electrode assembly <NUM> and the recording electrode assembly can be separated by a distance D2 ranging from about <NUM> millimeters to about <NUM> millimeters, such as from about <NUM> millimeters to about <NUM> millimeters, such as from about <NUM> millimeters to about <NUM> millimeters. Lastly, the active recording electrode 48a and the reference electrode 48c as well as the inactive recording electrode 48b and the reference electrode 48c, can be separated by a distance D3 ranging from about <NUM> millimeter to about <NUM> millimeters, such as from about <NUM> millimeters to about <NUM> millimeters, such as from about <NUM> millimeters to about <NUM> millimeters.

In addition, the components of the stimulation electrode assembly <NUM>, the recording electrode assembly <NUM>, and any other electrical components can be formed from MRI compatible materials such that the catheter guidance system <NUM> can be used in patients undergoing MRI or other diagnostic testing where magnetic components cannot be used. For instance, carbon or any other non-magnetic materials can be used.

As best illustrated in <FIG>, in one embodiment, such as when a wired connection (e.g., a connection via a physical electrode electrical connection <NUM> as opposed to a wireless connection, which is also contemplated by the present invention, where the stimulation electrode assembly <NUM> and/or the recording electrode assembly <NUM> include a battery or other source of power) electrically connects the stimulation electrode assembly <NUM> and the recording electrode assembly <NUM> to the processor <NUM>, the tubing assembly <NUM> can also include (a) a tube or an electrical tubular insulator <NUM>; (b) a mid-connector or union device <NUM> which receives the tubular insulator <NUM>; (c) a multi-port connector or y-port connector <NUM> attachable to the union device <NUM>; (d) a catheter <NUM>, such as a feeding tube, connected to the y-port connector <NUM>; and (e) a distal end or tip <NUM> of the catheter <NUM>, where at least a portion of the stimulation electrode assembly <NUM> and optionally the recording electrode assembly <NUM> can be located on an outer wall <NUM> of the catheter <NUM> at the distal end or tip <NUM> or where the recording electrode assembly <NUM> can be located anywhere upstream along the length of the catheter <NUM>. Components (a) through (c) can also be used to electrically connect the optional signal generator <NUM> via wire assembly <NUM> as discussed in more detail below.

In one embodiment, the tubular insulator <NUM> includes a tube having a proximal end <NUM> attachable to an attachment member or neck <NUM> of a controller coupler or electrical connector <NUM> and a distal end <NUM> receivable by the union device <NUM>; and an internal diameter which is substantially equal to or greater than an external diameter of a wire assembly <NUM> and the electrode electrical connection <NUM>, which can serve as the hard wired electrical connection between the portions of the stimulation electrode assembly <NUM> and the recording electrode assembly <NUM> present on the outer wall <NUM> of the catheter <NUM> signal generator <NUM> and the processor <NUM>, so as to slide over the electrical electrode connection <NUM> and the wire assembly <NUM>. In another embodiment, the tubular insulator <NUM> may fit relatively tightly over the electrical electrode connection <NUM> and the wire assembly <NUM>.

As best illustrated in <FIG>, in one embodiment, the union device <NUM> includes: (a) a proximal end <NUM>; (b) a distal end <NUM>; (c) a position adjuster, extender or elongated neck <NUM> positioned between the proximal end <NUM> and the distal end <NUM>; (d) a grasp or gripping member <NUM> positioned adjacent to the distal end <NUM> so as to assist users in grasping and manipulating the union device <NUM>; and (e) an insert <NUM> positioned adjacent to the gripping member <NUM> which is received by the y-port connector <NUM>. When assembled, the proximal end <NUM> of the union device <NUM> is coupled to the distal end <NUM> of the tubular insulator <NUM>.

In one embodiment, the multi-port or y-port connector <NUM> includes: (a) a body <NUM>; (b) a liquid delivery branch, medicine delivery branch or medicine branch <NUM> attached to the body <NUM> for distributing drugs, medicine or other medicinal liquids to the patient; (c) a nutrient delivery branch or feeding branch <NUM> attached to the body <NUM> and sized to receive the insert <NUM> of the union device <NUM>; (d) a catheter or feeding tube connection branch <NUM> attached to the catheter <NUM>; (e) a flexible or movable arm <NUM> attached to the body <NUM>; and (f) a flexible or movable arm <NUM> attached to the body <NUM>. In an alternative embodiment, y-port connector <NUM> includes additional branches for administering various nutrients or medicines to the body <NUM>. In another alternative embodiment, the y-port connector <NUM> includes only a feeding branch <NUM> and a connection branch <NUM>. The arm <NUM> has a stopper <NUM>, and the arm <NUM> has a stopper <NUM>. The stoppers <NUM> and <NUM> are sized to prevent fluid from passing through the branches <NUM> and <NUM> after such branches <NUM> and <NUM> are plugged with stoppers <NUM> and <NUM>, respectively. In addition, the arm <NUM> includes a fastener <NUM> which secures a tube-size adapter <NUM> to the arm <NUM>. The tube-size adapter <NUM> enables fluid delivery tubes (not shown) having various diameters to connect to the feeding branch <NUM> of the y-port connector <NUM>.

As illustrated in <FIG>, in one embodiment, the catheter <NUM> includes a feeding tube or catheter <NUM> with a body <NUM> having a proximal end <NUM> attached to the catheter connection branch <NUM> of the y-port connector <NUM> and a distal end <NUM>. The proximal end <NUM> is insertable into the catheter connection branch <NUM> of the y-port connector <NUM> so as to bring the catheter <NUM> into fluid communication with the y-port connector <NUM>.

As also shown in <FIG>, in one embodiment, the end member, bolus or tip <NUM> is attached to the distal end <NUM> of the catheter <NUM>. The tip <NUM> includes a body <NUM> having a collar <NUM> and an end member <NUM>. The body <NUM> defines a passage <NUM> and an opening <NUM>. The opening <NUM> is positioned between the collar <NUM> and the end member <NUM>. A portion <NUM> of the end member <NUM> can have a rounded shape. The shape of the passage <NUM> and opening <NUM> of the tip <NUM> is configured to facilitate the flow of fluid from the catheter <NUM> into the patient's body while decreasing the likelihood that the opening <NUM> will become clogged.

The tubular connector <NUM>, union device <NUM>, y-port connector <NUM>, catheter <NUM>, and tip <NUM> can be made from any suitable polymer or plastic material including, but not limited to, polyamide, polyethylene, polypropylene, polyurethane, silicone and polyacrylonitrile.

Turning now to the specifics of the connection of the stimulation electrode assembly <NUM>, the recording electrode assembly <NUM> (in some embodiments), and the optional signal generator <NUM> to the system <NUM>, and referring to <FIG>, <FIG>, and <FIG>, a controller coupler or an electrical connector <NUM> can be operatively connected to the electrical extension <NUM> and an electrode electrical connection <NUM> can be operatively coupled to the electrical connector <NUM> to form a wired connection between the electrode assemblies and the processor <NUM> and any other electrical components of the system <NUM>. In addition, an elongated wire assembly <NUM> can be operatively coupled to the electrical connector <NUM> to form a wired connection between the signal generator <NUM> and the processor <NUM>, although it is to be understood that all of the electrical connections can be wireless. Further, a wire or elongated stiffener <NUM> can be attached to the connector <NUM> and can serve as a support for the wire assembly <NUM> when it is inserted into the body <NUM> of the catheter <NUM>. Additionally, the tubular insulator <NUM> described above can cover a portion <NUM> of the wire assembly <NUM> and the electrode electrical connection <NUM> positioned adjacent to the connector <NUM>. In any event, the electrical connector or controller coupler <NUM> can provide the electrical connection between the apparatus <NUM> and the stimulation electrode assembly <NUM> as well as the recording electrode assembly <NUM> when the assemblies are hard wired to the catheter guidance system <NUM> via the electrode electrical connection <NUM>.

Further, in one embodiment and referring to <FIG> and <FIG>, the catheter body <NUM> can have a plurality of markings <NUM> uniformly spaced along its external surface that can be used in conjunction with the stimulation electrode assembly <NUM> and the recording electrode assembly <NUM> to determine accurate placement of the catheter <NUM> and/or to determine the appropriate time during which to deliver the stimulation waveform from the stimulator <NUM> via the stimulation electrode assembly <NUM> and to initiate recording of the electrical activity elicited by tissue near the esophagus <NUM> of a patient via the recording electrode assembly <NUM>. These markings <NUM> can function as placement markers which assist the user in assessing the depth that the catheter <NUM> is placed within the patient's body <NUM>. For instance, when the stimulation electrode assembly <NUM> is located at the distal end <NUM> of the catheter <NUM>, the markings <NUM> can be present from the distal end <NUM> of the electronic catheter unit <NUM> or the distal end <NUM> of the catheter <NUM> to a point <NUM> on the catheter <NUM> that spans a distance that can correspond with the average distance between the trachea <NUM> and nostril <NUM> in a typical patient. As the catheter <NUM> is being inserted into the body <NUM> via the nostril <NUM>, once the markings <NUM> are no longer visible outside the body <NUM>, the user can be alerted to start delivering an electrical stimulation waveform from the stimulator <NUM> via the stimulating electrode assembly <NUM> and to start monitoring the graphs <NUM> on the display device <NUM> to observe the data recorded by the recording electrode assembly <NUM> related to the electrical activity elicited by tissue in response to the stimulation or to start monitoring for a visual indication, auditory indication, or both that the catheter <NUM> has be inserted into the correct (e.g., digestive tract) or incorrect location (e.g., respiratory tract). For example, if the lack of an appearance of an evoked potential is shown on the display device <NUM> in response to the delivery of stimulation waveform to tissue near the distal end <NUM> or if an impedance versus time plot exhibits certain characteristics once the markings <NUM> are no longer visible outside the body <NUM>, then the user will be able to determine that the catheter <NUM> has been improperly inserted into the trachea <NUM> instead of the esophagus <NUM>, and the catheter <NUM> can be immediately retracted. In an alternative embodiment, these markings <NUM> can assist the user in measuring the flow or distribution of liquid to or from the patient.

Now that the specific components of the catheter guidance system <NUM> have been discussed in detail, a method of using the catheter guidance system <NUM> of the present invention in order to verify the accurate placement of a catheter <NUM> used for enteral feeding in the digestive tract is discussed in more detail below with reference to <FIG>.

Generally, the method for determining if the catheter <NUM> is accurately placed within a digestive tract (e.g., the esophagus of a body <NUM> of a patient includes inserting a distal end of the tubing assembly <NUM> (e.g., the distal end <NUM> of the catheter <NUM> or tip <NUM> of the electronic catheter unit <NUM>) into an orifice <NUM> of the body <NUM>, such as a nostril <NUM> of the patient's nose. As described above, the tubing assembly <NUM> can include the catheter <NUM>, at least a portion of the stimulation electrode assembly <NUM> (part of which can be placed transcutaneously on a surface of skin <NUM>), the recording electrode assembly <NUM> (or, alternatively all or a portion of the recording electrode assembly <NUM> can be placed transcutaneously on a surface of skin <NUM>) and the optional signal generator <NUM>. Once the tubing assembly <NUM> is inserted into the orifice <NUM> of the body <NUM>, the stimulation electrode assembly <NUM>, the recording electrode assembly <NUM>, and the optional signal generator <NUM> can be electrically connected to a processor <NUM> via a wired connection, such as the electrode electrical connection <NUM> and the wire assembly <NUM>, although a wireless connection is also contemplated by the present invention such that no electrode electrical connection <NUM>, wire assembly, <NUM> or controller coupler <NUM> is required.

Next, the stimulation electrode assembly <NUM> is activated, such as by providing power to stimulator <NUM> connected to the stimulation electrode assembly <NUM>, and the stimulation electrode assembly <NUM> then begins to deliver a stimulation waveform to tissue near the distal end <NUM> of the catheter/the tip or distal end <NUM> of the electronic catheter unit <NUM> via the stimulation electrode assembly <NUM>. At the same time, the recording electrode assembly <NUM> can be activated to begin to record the electrical activity (e.g., muscle activity or twitches in the form of action potentials, impedance measurements, etc.) elicited by the tissue in response to the stimulation waveform. The recording electrode assembly <NUM> then communicates with the processor <NUM> via the wired connection (e.g., connection <NUM>) or the wireless connection to deliver the acquired electrical activity data to the processor <NUM> in real-time.

The stimulation waveform can have various features depending on the electrical activity to be monitored. For instance, when monitoring for electrical muscle activity in response to stimulation, where the muscle activity is in the form of evoked potentials, indicating activation of muscle tissue associated with the presence of the distal end <NUM> of the electronic catheter unit <NUM> in the esophagus <NUM>, which contains striated muscle, or where there is insufficient activation of muscle tissue, indicating that the distal end <NUM> of the electronic catheter unit <NUM> has been inserted into the trachea, which contains cartilage such that no evoked potential is present, the stimulation waveform can be a constant-current or constant voltage square waveform (monophasic or biphasic). For instance, the stimulation waveform can have a stimulation amplitude ranging from greater than <NUM> volt to less than <NUM> volts, such as from about <NUM> volts to about <NUM> volts, such as from about <NUM> volts to about <NUM> volts, such as from <NUM> volts to about <NUM> volts. Alternatively, the stimulation waveform can have a stimulation waveform of less than <NUM> milliamps, such as from about <NUM> milliamps to about <NUM> milliamps, such as from about <NUM> milliamp to about <NUM> milliamps, such as from about <NUM> milliamps to about <NUM> milliamps. Further, the stimulation waveform can have a frequency ranging from about <NUM> hertz to about <NUM> hertz, such as from about <NUM> hertz to about <NUM> hertz, such as from about <NUM> hertz to about <NUM> hertz. In addition, the stimulation waveform can have a pulse width of less than <NUM> milliseconds, such as from about <NUM> milliseconds to about <NUM> milliseconds, such as from about <NUM> millisecond to about <NUM> milliseconds, such as from about <NUM> milliseconds to about <NUM> milliseconds.

On the other hand, when monitoring for changes in impedance in tissue based on the presence of the catheter <NUM> in the esophagus <NUM> or trachea <NUM>, the stimulation waveform can be in the form of a noise signal having a frequency ranging from greater than <NUM> hertz to about <NUM> kilohertz, such as from about <NUM> kilohertz to about <NUM> kilohertz, such as from about <NUM> kilohertz to about <NUM> kilohertz, such as from about <NUM> kilohertz to about <NUM> kilohertz, and with the same stimulation amplitudes as described above. Because the impedance of esophageal tissue and tissue in the trachea have distinct characteristics, it can then be determined if the distal end <NUM> of the catheter <NUM>/the distal end or tip <NUM> of the electronic catheter unit <NUM> is positioned in the esophagus or trachea.

In addition, a display device <NUM> can be coupled to the processor <NUM> and displays the electrical activity data communicated to the processor <NUM> by the recording electrode assembly <NUM> for a health care provider to use during the catheter insertion procedure, where the data may first pass through an amplifier <NUM> to amplify the frequencies of interest and through a data acquisition system <NUM> to digitize the recorded signals. The data can then be presented on the display device <NUM>, where differences in the responses recorded by the recording electrode assembly <NUM> in response to the stimulation waveforms delivered by the stimulation electrode assembly <NUM> associated with catheter insertion into the digestive tract and into the respiratory tract can be easily identified by the health care provider via the graphs <NUM> on the display device <NUM>. Alternatively or additionally, the memory device <NUM> can store instructions which, when executed by the processor <NUM>, cause the processor <NUM> to interpret catheter <NUM> location and/or position information as determined and communicated by the optional signal generating assembly <NUM> and the non-invasive transceiver <NUM> and cause the processor <NUM> to then instruct the system <NUM> to alert the health care provider either via the display device <NUM>, auditory signals, etc. as to the accurate or inaccurate placement of the catheter <NUM>.

Specifically, when the electrical stimulation is in the form of a square-wave pulsed waveform, the appearance of evoked potentials on an amplitude versus time graph <NUM> that can be shown on the display device <NUM> can indicate placement of the catheter <NUM> in the digestive tract, where the evoked potentials are associated with activation of the muscle in the esophagus <NUM> near the distal end <NUM> of the electronic catheter unit <NUM>. Meanwhile, the lack of appearance of such evoked potentials upon delivery of the square-wave pulsed waveform on an amplitude versus time graph <NUM> shown on the display device <NUM> can indicate erroneous placement of the catheter in the respiratory system (e.g., the trachea <NUM>, bronchi <NUM>, lungs <NUM>, etc., or other anatomical region of the respiratory tract of the patient) at which time the insertion procedure should be stopped immediately and the tubing assembly <NUM> be removed from the respiratory tract to avoid potential harm to the patient. Further, in order for such information to be displayed or otherwise communicated by the display device <NUM>, a memory device <NUM> stores instructions which, when executed by the processor <NUM>, cause the processor <NUM> to (i) interpret the data communicated by the recording electrode assembly <NUM> and (ii) cause the display device <NUM> to communicate whether or not the catheter <NUM> is accurately placed within the digestive tract of the patient based on the interpretation of the electrical activity data.

Alternatively, when the electrical stimulation is in the form of a noise signal, a single frequency waveform, or multiple frequencies and one or more of the electrical contacts forming the stimulation electrode assembly or the recording electrode assembly <NUM> are utilized to measure the impedance of the tissue being contacted, the impedance measurements shown on an impedance versus time graph <NUM> on the display device <NUM> can indicate accurate placement of the catheter <NUM> in the digestive tract (e.g., the esophagus <NUM>) or erroneous placement in the respiratory system (e.g., the trachea <NUM>, bronchi <NUM>, lungs <NUM>, etc., or other anatomical region of the respiratory tract of the patient) at which time the insertion procedure should be stopped immediately and the tubing assembly <NUM> be removed from the respiratory tract to avoid potential harm to the patient. Further, in order for such information to be displayed or otherwise communicated by the display device <NUM>, a memory device <NUM> stores instructions which, when executed by the processor <NUM>, cause the processor <NUM> to (i) interpret the data communicated by the recording electrode assembly <NUM> and (ii) cause the display device <NUM> to communicate whether or not the catheter <NUM> is accurately placed within the digestive tract of the patient based on the interpretation of the electrical activity data.

The present inventors have found that the distinctions between the electrical activity elicited by tissue (e.g., electrical activity elicited by muscle in the esophagus versus electrical activity elicited by cartilage and/or muscle in the trachea) propagating from the opening <NUM> at the distal end <NUM> of the electronic catheter unit <NUM> and catheter <NUM> when the distal end or tip <NUM> of the electronic catheter unit <NUM> or catheter <NUM> is placed within the digestive tract or respiratory system are allow for an efficient and possibly life-saving determination of accurate enteral feeding catheter <NUM> placement in the digestive tract, where erroneously placing the catheter in the respiratory system would deliver fluid into the lungs, which can have fatal consequences.

For instance, as shown in <FIG>, when the distal end or tip <NUM> of the electronic catheter unit <NUM> and catheter <NUM> is inserted into the nostril <NUM> of the patient and is advanced through the nasal cavity <NUM>, past the nasopharynx <NUM>, and into the esophagus <NUM> just past the epiglottis <NUM>, as the recording electrode assembly <NUM> is continuously receiving, recording, and/or processing electrical activity elicited by tissue near the distal end <NUM> of the electronic catheter unit <NUM> and catheter <NUM> where the stimulation electrode assembly <NUM> is positioned or disposed, the amplitude versus time spectrogram graph <NUM> (Fig. 7B-7I) displayed or otherwise communicated by the processor <NUM>, such as via the display device <NUM>, may show the presence of evoked potentials as the distal end or tip <NUM> of the electronic catheter unit <NUM> or catheter <NUM> travels into the digestive tract and not into the respiratory system, so long as the stimulation waveform amplitude is above a certain threshold. For instance, the stimulation amplitude of <NUM> volt in <FIG> was insufficient to elicit an evoked potential by the muscle in the esophagus <NUM> in response to the stimulation waveform, although the stimulation amplitudes of <NUM> volts (<FIG>), <NUM> volts (<FIG>), <NUM> volts (<FIG>), <NUM> volts (<FIG>), <NUM> volts, reversed polarity (<FIG>), and <NUM> volts, reversed polarity (<FIG>) were sufficient to elicit evoked potentials from the muscle in the esophagus.

On the other hand, as shown in <FIG> and <FIG>, when the distal end or tip <NUM> of the catheter <NUM> is inserted into the nostril <NUM> of the patient and is advanced through the nasal cavity <NUM>, past the nasopharynx <NUM>, and into the trachea <NUM> just past the epiglottis <NUM>, and then into the bronchi <NUM> or lungs <NUM>, as the recording electrode assembly <NUM> is continuously receiving, recording, and/or processing electrical activity elicited by tissue near the distal end <NUM> of the electronic catheter unit <NUM> and catheter <NUM> where the stimulation electrode assembly <NUM> is positioned or disposed, the amplitude versus time spectrogram graph <NUM> (<FIG>) displayed or otherwise communicated by the processor <NUM>, such as via the display device <NUM>, may show the absence of evoked potentials as the distal end or tip <NUM> of the electronic catheter unit <NUM> or catheter <NUM> travels into the digestive tract and not into the respiratory system, so long as the stimulation waveform amplitude is above a certain threshold. For instance, the stimulation amplitude of <NUM> volts in <FIG> was insufficient to elicit an evoked potential in response to the stimulation waveform, although the stimulation amplitudes of <NUM> volts (<FIG>), <NUM> volts (<FIG>), <NUM> volts (<FIG>), <NUM> volts (<FIG>), <NUM> volts, reversed polarity (<FIG>), and <NUM> volts, reversed polarity (<FIG>) were sufficient to elicit evoked potentials from the muscle in the esophagus. This indicates that the catheter <NUM> in <FIG> is not placed in the esophagus <NUM> and is instead being inserted into the trachea <NUM>. At this point, the health care provider can be alerted to remove the tubing assembly <NUM> from the respiratory system and start a new procedure to accurately place the distal end or tip <NUM> of the electronic catheter unit <NUM> or catheter <NUM> into the digestive tract for enteral feeding.

The present inventors have also found that the distinctions between the impedance measurements of tissue collected by the various electrical electrodes on the catheter (e.g., impedance data collected from electrodes placed in the esophagus versus impedance data collected from electrodes placed in the trachea) allow for an efficient and possibly life-saving determination of accurate enteral feeding catheter <NUM> placement in the digestive tract, where erroneously placing the catheter in the respiratory system would deliver fluid into the lungs, which can have fatal consequences.

Specifically, <FIG> is a graphical view of the impedance of tissue measured at an electrical contact (e.g., any of the electrodes that are part of the stimulation electrode assembly <NUM> or the recording electrode assembly <NUM>) when placed on the electronic catheter unit <NUM> or the catheter <NUM> at various frequencies as the electronic catheter unit <NUM> and catheter <NUM> of <FIG> is inserted past the epiglottis in real-time, where the characteristics of the impedance values measured are in response to a noise signal that is generated by the stimulator and delivered through the contacts onto the catheter and are indicative of the placement of the catheter within the esophagus. As shown, the impedance values (in Ohms) over a range of frequencies ranging from greater than <NUM> hertz to about <NUM>,<NUM> hertz show an impedance signature indicative of various peaks and valleys characteristic of esophageal tissue. Although <FIG> shows the impedance values measured when a noise signal is delivered to the tissue, it is also to be understood that that impedance can be measured at a single frequency (e.g., <NUM> kilohertz, <NUM> kilohertz, <NUM> kilohertz, <NUM> kilohertz, etc.), or can be measured when multiple frequencies are superimposed and delivered as one waveform (e.g., multiple sine waves delivered from the stimulator <NUM>).

Meanwhile, <FIG> is a graphical view of the impedance measured at an electrical contact (e.g., any of the electrodes that are part of the stimulation electrode assembly <NUM> or the recording electrode assembly <NUM>) when placed on the electronic catheter unit <NUM> or the catheter <NUM> at various frequencies as the electronic catheter unit <NUM> and catheter <NUM> of <FIG> is inserted past the epiglottis in real-time, where the characteristics of the impedance values measured are in response to a noise signal that is generated by the stimulator and delivered through the contacts onto the catheter and are indicative of erroneous placement of the catheter in the trachea. As shown, the impedance values (in Ohms) over a range of frequencies ranging from greater than <NUM> hertz to about <NUM>,<NUM> hertz show an impedance signature indicative of tracheal tissue (e.g. exponentially decaying impedance values with increasing frequencies). Although <FIG> shows the impedance values measured when a noise signal is delivered to the tissue, it is also to be understood that that impedance can be measured at a single frequency (e.g., <NUM> kilohertz, <NUM> kilohertz, <NUM> kilohertz, <NUM> kilohertz, etc.), or can be measured when multiple frequencies are superimposed and delivered as one waveform (e.g., multiple sine waves delivered from the stimulator <NUM>).

For instance, in one particular embodiment, utilizing a waveform having a stimulation frequency of <NUM> hertz, the impedance values at various electrical contacts (e.g., any of the electrodes in the stimulation electrode assembly <NUM> or recording electrode assembly <NUM>) made with tissue (e.g., esophageal tissue or tracheal tissue) can vary depending on the location of the catheter <NUM>. When the catheter <NUM> is inserted in the esophagus and the impedance value is determined between the cathode 46a and the anode 46b of the stimulation electrode assembly <NUM>, for instance, the impedance can be between <NUM> ohms and <NUM> ohms. Further, when the impedance value is determined between the active recording electrode 48a and the reference electrode 48c of the recording electrode assembly <NUM>, the impedance can be between <NUM> ohms and <NUM> ohms. Further, when the impedance value is determined between the inactive recording electrode 48b and the reference electrode 48c, the impedance can be between <NUM> ohms and <NUM> ohms. In addition, when the impedance value is determined between the active recording electrode 48a and the inactive recording electrode 48b, the impedance can be between about <NUM> ohms and <NUM> ohms. Thus, regardless of the particular electrical contacts used when determining the impedance of tissue in the esophagus (e.g., epithelium, muscle, etc.), the impedance of the esophageal tissue is generally consistent.

On the other hand, when the catheter <NUM> is inserted in the trachea and the impedance value is determined between either between the cathode 46a and the anode 46b of the stimulation electrode assembly <NUM>, between the active recording electrode 48a and the reference electrode 48c of the recording electrode assembly <NUM>, between the inactive recording electrode 48b and the reference electrode 48c, or between the active recording electrode 48a and the inactive recording electrode 48b, the impedance is around <NUM> ohms and is intermittent. This illustrates that the impedance signature collected from electrodes placed in the esophagus is distinct from the impedance signature collected from electrodes placed in the trachea, such that impedance measurements in response to a stimulation waveform can be utilized to determine the proper placement of a catheter in the respiratory tract. Without intending to be limited by any particular theory, the present inventors have found that the impedance signature of tissue in the trachea is minimal or exponentially decaying due to lack of contact with excitable tissue since the trachea is rigid due to the presence of cartilaginous tissue. Meanwhile, the impedance of esophageal tissue is generally consistent and has increased values due to the excitability of tissue in the esophagus (e.g., muscle capable of contracting).

Generally, the ratio of the impedance collected in the trachea to the impedance collected in the esophagus can be at least about <NUM>;<NUM>, such as from about <NUM>:<NUM> to about <NUM>:<NUM>, such as from about <NUM>:<NUM> to <NUM>:<NUM>, such as from about <NUM>:<NUM> to about <NUM>:<NUM>.

Moreover, as an alternative or in addition to recording the electrical activity elicited in response to the delivery of stimulation waveform, the health care provider can also verify accurate placement of the catheter <NUM> in the esophagus <NUM> rather than the trachea <NUM> by observing for the presence or absence of a plurality of markings <NUM> uniformly spaced along the external surface of the catheter <NUM>. As described above, such markings <NUM> can be used in conjunction with the stimulation electrode assembly <NUM> and the recording electrode assembly <NUM> to determine accurate placement of the catheter <NUM>. These markings <NUM> can function as placement markers which assist the user in assessing the depth that the catheter <NUM> is placed within the body <NUM>. For instance, when the recording electrode assembly <NUM> is located at the distal end <NUM> of the electronic catheter unit <NUM> or catheter <NUM>, the markings <NUM> can be present from the distal end <NUM> of the catheter <NUM> to a point <NUM> on the catheter <NUM> that spans a distance that can correspond with the average distance between the trachea <NUM> and nostril <NUM> in a typical patient. As the catheter <NUM> is being inserted into the body <NUM> via the nostril <NUM>, once the markings <NUM> are no longer visible outside the body <NUM>, the health care provider can be alerted to start monitoring the graphs <NUM> on the display device <NUM> to observe the amplitude or impedance versus time plotted from electrical activity data measured by the recording electrode assembly <NUM> in response to stimulation delivered by the stimulation electrode assembly <NUM> or to start monitoring for a visual indication, auditory indication, or both that the catheter <NUM> has be inserted into the correct (e.g., digestive tract) or incorrect location (e.g., respiratory tract). For example, if there is a lack of an evoked potential on an amplitude versus time spectrogram shown on the display device <NUM> is present once the markings <NUM> are no longer visible outside the body <NUM>, then the user will be able to determine that the catheter <NUM> has been improperly inserted into the trachea <NUM> instead of the esophagus <NUM>, and the catheter <NUM> should be immediately retracted.

Regardless of the particular method by which proper placement of the catheter <NUM> is determined, once the distal end or tip <NUM> of the electronic catheter unit <NUM> or catheter <NUM> has been accurately placed within the desired location in the digestive tract, the health care provider can then attach medicine and nutritional delivery tubes to the y-port connector <NUM> for introducing fluids into the body (e.g., digestive tract) for medical treatment.

Moreover, in conjunction with the stimulation electrode assembly <NUM> and the recording electrode assembly <NUM> described herein, the system <NUM> also contemplates the use of an optional signal generator <NUM> and associated transceiver <NUM> that can be used to track the position of the distal end <NUM> of the catheter <NUM> as it is being inserted into the patient's body <NUM>. In one embodiment, the signal generator <NUM>, which is located at the distal end <NUM> of the electronic catheter unit <NUM> and can be connected to the apparatus <NUM> via the controller coupler/electrical connected <NUM> and the wire assembly <NUM> (see <FIG>, <FIG>, and <FIG>), can be formed through a plurality of spirals or coils of wires. Further, the apparatus <NUM> can be configured to transmit electrical current through the wires such that the current travels in a circular path defined by the coils. This circular motion of current produces an electromagnetic field. In operation, when the apparatus <NUM> sends electrical current to the coils of the signal generator <NUM>, the coils then transmit a signal or electromagnetic field capable of being detected by the non-invasive transceiver <NUM>. The transceiver <NUM> then detects the electromagnetic field or signal generated by the signal generator <NUM> inside the patient's body <NUM> and the system <NUM> analyzes the resulting information to cause the display device <NUM> and the printer <NUM> to produce additional graphics <NUM> which can assist the health care provider in a catheter placement procedure in conjunction with electrical activity data acquired by the recording electrode assembly <NUM>. For instance, the system <NUM> can include a memory device <NUM> including machine readable instructions and one or more computer programs (which, for example, may include a plurality of algorithms <NUM>) which are used by the processor <NUM> to process the signal data produced by the signal generator and transmitted by the transceiver <NUM>, after which the processed data is displayed in graphical format on the display device <NUM> corresponding to the location of the distal end <NUM> of the catheter <NUM> within the patient's body <NUM>. In one particular embodiment, the transceiver <NUM> can be used to determine the distance the signal generator <NUM> is from the transceiver <NUM> and its dept in the patient's body <NUM> can communicate with the display device <NUM> via the processor <NUM> to show a reference image of a non-subject body and an image of the signal generator <NUM> located on the display device <NUM> with the reference image.

It should also 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 digestive or gastrointestinal tract 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.

Claim 1:
A tubing assembly (<NUM>) comprising:
a catheter (<NUM>) having a proximal end (<NUM>) and a distal end (<NUM>) and extending in a longitudinal direction, wherein the proximal end (<NUM>) and the distal end (<NUM>) define a lumen (<NUM>) therebetween, and wherein the catheter (<NUM>) is configured for placement within a digestive tract of a patient;
a stimulation electrode assembly (<NUM>), wherein the stimulation electrode assembly (<NUM>) is configured to deliver an electrical stimulation to tissue;
an electrical connection for delivering a stimulation waveform to the stimulation electrode assembly (<NUM>); and
a recording electrode assembly (<NUM>),
characterized in that the recording electrode assembly (<NUM>) is configured to:
(i) monitor for electrical activity elicited by the tissue in response to the stimulation waveform and communicate the electrical activity elicited by the tissue to a processor (<NUM>) in real-time, wherein if the electrical activity elicited by the tissue is in the form of one or more evoked potentials, then it is confirmed that the catheter (<NUM>) is placed in the digestive tract, and if the electrical activity elicited by the tissue is not in the form of one or more evoked potentials, then the catheter (<NUM>) is not placed in the digestive tract; or
(ii) monitor for electrical activity elicited by the tissue by measuring an impedance level of tissue via one or more electrical contacts in the stimulation electrode assembly (<NUM>) or the recording electrode assembly (<NUM>), wherein a first level of impedance indicates that the catheter (<NUM>) is placed in the digestive tract and a second level of impedance indicates that the catheter (<NUM>) is not placed in the digestive tract; and
communicate the electrical activity elicited by the tissue to a processor (<NUM>) in real-time.