Patent Publication Number: US-7715913-B1

Title: External defibrillator with training mode and method of use

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   
       
       
         
           This application claims the benefit of U.S. provisional application Ser. no. 60/543,142 filed Feb. 10, 2004, which is incorporated herein. 
         
       
     
  

   Aspects of this invention relate generally to external defibrillator training, and more specifically to external defibrillators usable in a training mode and to a method for training a user to operate an external defibrillator. 
   Abnormal heart activity, such as ventricular fibrillation, may be returned to a normal sinus rhythm by applying an electric current to the heart using an external defibrillator. External defibrillators may be manual, automatic or semi-automatic. It is desirable to teach operators of all types of external defibrillators to use actual defibrillation equipment, in a realistic training environment that simulates and approximates actual defibrillator use procedures and conditions. 
   Modern external defibrillators may incorporate a training mode in addition to a therapy mode in order to provide an in situ training opportunity to potential users. In the therapy mode, electrotherapy is delivered from the defibrillator through medical electrodes attached to living subjects. In the training mode, electrotherapy is simulated—the training electrodes are attached to a training apparatus, such as a mannequin, and are not electrically connected to the defibrillator. Examples of external defibrillators having both therapy modes and training modes are provided in U.S. Pat. No. 5,611,815, and in U.S. Pat. No. 5,662,690, the specifications of which are incorporated herein by reference. 
   Interactive training modes of known defibrillators guide an operator through the defibrillation process without feedback from the training electrodes. Instead, the operational state changes in the defibrillator are simulated based on other inputs, such as elapsed time, detecting the insertion of a training electrode into an electrode interface, manipulation of the defibrillator controls by the user, or by signals generated by a remote device operated by the training supervisor. Interactive training generally begins with the operator being instructed to call emergency medical services, expose the chest, open and place one or more non-conductive training electrodes onto a particular position on a mannequin. The operator&#39;s proper electrode placement and positioning generally triggers an operational state change in the training mode of the defibrillator—the defibrillator operator, for example, next being instructed that the defibrillator is analyzing, and not to touch the patient. Actual medical electrodes, however, are often internally electrically conductive, to allow for communication with the defibrillator about electrode state or handling prior to patient placement, and may be packaged in containers and/or disposed on release liners, which must be successfully removed by a defibrillator operator prior to patient placement. 
   Several types of sensing systems have been developed to indicate proper positioning of training electrodes on mannequins. For example, conductive adapter strips for use with mannequins are described in U.S. Pat. No. 5,993,219. In another example, conductive objects are embedded in mannequins. In a further example, U.S. Pat. No. 5,137,458 describes mannequins fitted with Hall-effect sensors to detect magnetic fields produced by permanent magnets in training electrodes. Mannequins adapted for training electrode placement and detection, however, are expensive, complex, and/or impractical for many training applications and locations. 
   There is therefore a need for an external defibrillator having a training mode, and a method of operating an external defibrillator in the training mode, which interactively guides a defibrillator operator through pre-patient-placement electrode handling steps in a way that more closely approximates actual defibrillator procedures and conditions, and which may be used with more realistic training electrodes. There is also a need for a simple, low-cost, realistic training apparatus and method for use with an external defibrillator that allows for verification of proper electrode placement, but that does not require a mannequin. 
   According to one aspect of the present invention, an external defibrillator is selectably usable in one of a therapy mode and a training mode. When in the training mode, the defibrillator has a plurality of training state notifications. The defibrillator is adapted for electrical coupling with an electrode arrangeable on a release liner. The electrode is electrically conductive and configured for placement on a subject. The defibrillator includes an energy source; an electrode interface responsive to the electrode; an energy delivery system operable to selectively deliver electrical energy from the energy source to the electrode via the electrode interface; a state identifier, identifying, when the electrode is electrically coupled to the electrode interface, a degree of electrical connectivity along an electrical path including the electrode; a controller, operative in the training mode, prior to placement of the electrode on the subject, to advance the external defibrillator from a first training state to a second training state when the state identifier identifies a predetermined degree of electrical conductivity along the electrical path; and a user interface, operative in the training mode to issue a training state notification indicating that the external defibrillator has advanced from the first training state to the second training state. 
   The predetermined degree of electrical conductivity may be an impedance level, of between about 2000 ohms and 15K ohms, indicating that the electrode was removed from the release liner, or may alternatively indicate that the electrode was removed from a package containing the electrodes and release liner. The training state notification may be a voice message or visual prompt, instructing the user of subsequent actions to be taken. When the electrode is a training electrode, the training electrode includes a conductive attachment layer, and a conductive metal layer, such as tin foil, in communication therewith, having a void therein that provides a nonconductive region. The electrical path is through the conductive attachment layer and the release liner. When the training electrode is attached, the defibrillator is not operable in the therapy mode. 
   According to another aspect of the present invention, a method for training a user to operate an external defibrillator, usable in a therapy or training mode, includes an energy source; an electrode interface responsive to an electrode arrangeable on a release liner and configured for placement on a subject; and an energy delivery system operable to selectively deliver electrical energy from the energy source to the electrode via the electrode interface. The method includes: when the electrode is coupled to the electrode interface, receiving an input signal from the electrode, prior to placement of the electrode on the subject; based on the input signal, identifying a degree of electrical connectivity along an electrical path including the electrode; based on the determined degree of electrical conductivity, advancing the external defibrillator from a first training state to a second training state; and issuing a training state notification indicating advancement from the first training state to the second training state. A computer-readable storage medium may be encoded with a computer program which, when loaded into a processor, is operative to perform the method. 
   According to a still further aspect of the present invention, a method for making a training apparatus for use with an external defibrillator, the external defibrillator responsive to a first electrode and a second electrode, includes: providing a transparent layer having a first electrode attachment region defining an opening sized to receive the first electrode; disposing a signal conductor proximate the first electrode attachment region, the signal conductor having a transfer path, the transfer path operable to provide communication between the first electrode and the second electrode, when the first electrode and the second electrode are disposed on the training apparatus; and providing a two-dimensional representation of an anterior portion of a defibrillation subject, identifiable through the transparent layer, having the first electrode attachment region arranged thereon in a manner that defines a preferred placement area of the first electrode on the defibrillation subject. A second electrode attachment region may be defined to receive the second electrode. When the first and second electrodes are arranged in their respective attachment regions, in such a manner that the transfer path is operating, the external defibrillator is operable to detect a connection state between the first and second electrodes and the training apparatus. 
   According to a further additional aspect of the present invention, a method for performing defibrillator training includes: providing an automatic external defibrillator training device; providing a pair of training electrodes in electrical communication with the training device; sensing an impedance between the pair of training electrodes; and advancing a training rescue based on the sensed impedance. The method may further include changing an operational mode of the defibrillator to a training mode based on the sensing step, and providing a defibrillator training apparatus with electrically coupled depictions of the proper position of each of the training electrodes. 

   
     In the drawings: 
       FIG. 1  is a schematic representation of an external defibrillator usable in connection with aspects of the present invention. 
       FIG. 2  illustrates a plan view of a training electrode usable in connection with aspects of the present invention. 
       FIG. 3  is a perspective view of the training electrode shown in  FIG. 2 , mounted on a release liner and ready for storage in an electrode package. 
       FIG. 4  is a flowchart of a method for training an operator to use the external defibrillator represented in  FIG. 1 . 
       FIG. 5  is a layered perspective view of a training apparatus in accordance with aspects of the present invention. 
       FIG. 6  is a plan view of one configuration of a certain layer of the training apparatus shown in  FIG. 5 . 
       FIG. 7  is a plan view of another configuration of the layer shown in  FIG. 6 . 
       FIG. 8  is a plan view of another layer of the training apparatus shown in  FIG. 5 . 
   

   Turning now to the drawings, wherein like numerals designate like components,  FIG. 1  is a schematic representation of an external defibrillator  10 , suitable for use with aspects of the present invention. External defibrillator  10  may be automatic, semi-automatic, or manual, such as Philips Heartstart HS1. During normal operation, energy delivery system  12 , under the control of controller  18 , selectably provides actual or simulated voltage or current pulses using well-known methods and techniques to an electrode interface  17 , via energy delivery system  12 . Electrode interface  17  is detachably connectable to one or more electrodes  14 , using, for example, a connector associated with electrode  14  or packaging (discussed further below) therefore. Defibrillator  10  is preferably adapted to use a variety of electrodes  14 , including both treatment and training electrodes. Electrodes  14  are connected to defibrillation subjects  15 , such as living persons or training apparatuses. 
   Energy delivery system  12  includes elements such as charging circuit  26 , one or more capacitors  24 , and an energy storage medium  22  (for example, a battery). Energy delivery system  12  also includes elements (not shown) such as electrical connectors, housings, signal conductors, or switches, to allow selectable connection of an energy source to electrode interface  17  by a controller  18 . 
   Controller  18 , which may be a processor, is illustrated functionally, and is responsive to various additional elements of defibrillator  10 , including an operator interface  19 , a memory  30 , computer programs  31 , a mode selector  32 , and a state identifier  34 . 
   Controller  18  receives input and provides output through operator interface  19 , which, functionally, includes an input element  20  and an output element  28 . Internal arrangements of input element  20  and output element  28  are well-known, and may include buttons or other actuators, displays, microphones, speakers, keypads, switches, status indicators, light-emitting diodes, temperature sensors, status measurement units, or other devices or ports, digital or analog, or any combination thereof. 
   Controller  18  is also responsive to memory  30 , such as a removable data card, for storing digital and/or analog information. Memory  30  may be any local or remote computer-readable storage medium, now known or later developed, capable of storing data, including but not limited to a digital memory, a hard disk drive, a videocassette recorder tape, all types of compact disks and digital videodisks, a magnetic tape, or other local or networked storage means. 
   Controller  18  is further responsive to a state identifier  34 , which may perform and/or direct periodic monitoring of various elements or systems of defibrillator  10 , either automatically or in response to an operator&#39;s action. Internal arrangements of state identifier  34  are well known, and may include elements that characterize electrical or other communication paths, such as paths (discussed further below) internal to electrode(s)  14 , or discriminate other operating conditions of defibrillator  10 . State identifier  34  may perform in well known manners in conjunction with other elements of defibrillator  10 , such as memory  30 , controller  18 , computer programs  31 , mode selector  32 , and operator interface  19 . State identifier  34 , for example, may operate in a manner set forth in U.S. Patent Application Publication No. US 2003/0055478, the disclosure of which is incorporated herein by reference. 
   Defibrillator  10  is preferably operable in at least two different modes—a treatment mode and training mode—selectable via mode selector  32 . Mode selector  32  may be any suitable device or technique for changing the operational mode of defibrillator  10 , such devices, techniques and operating principles thereof being well known. For example, insertion of a predetermined battery may cause defibrillator  10  to enter the training mode, or the training electrodes may be coded in a way that is differentiable and identifiable by the external defibrillator. 
   In the treatment mode, currents are delivered through electrodes  14 , such as medical electrodes, attached to living subjects. In the training mode, actual or simulated currents are delivered through electrodes  14 , such as training electrodes  200  (shown in  FIG. 2  and discussed further below), attached to a training apparatus (a training apparatus in accordance with further aspects of the present invention is shown in  FIG. 5  and discussed further below). Once defibrillator  10  has entered the training mode, it is preferable that the external defibrillator is not operable in the therapy mode, and the operator may receive a notification, such as a voice prompt or other indicator, via operator interface  19 , that defibrillator  10  is in the training mode. 
   One or more computer programs  31 , alone or in combination with hardware or firmware, when loaded into a processor such as controller  18 , are operative to control external defibrillator  10  in both therapy and training modes. Computer programs  31  may be stored in a memory, for example, memory  30 . One skilled in the art may, using well known procedures and algorithms, select or implement instructions in software, hardware, firmware or a combination thereof, which effect operation and/or control of defibrillator  10  in the treatment and training modes. 
   In accordance with one aspect of the present invention, when defibrillator  10  is in the training mode, a training electrode, such as electrode  200  illustrated in plan view in  FIG. 2 , is electrically coupled and/or responsive to electrode interface  17 . The training electrode is also preferably arranged in series with respect to defibrillator  10  with a resistive device  207 , such as a resistor, having an impedance of approximately 1k ohms. Resistor  207  facilitates identification of electrode  200  as a training electrode, and not a therapy electrode, by raising the real component of the complex impedance level of the electrode above patient impedance levels, which are approximately 25-500 Ohms. Identification of electrode  200  as a training electrode may be important to prevent accidental shocking through electrode  200 . Communication between electrode  200  and defibrillator  10  may occur via one or more communication paths such as a lead wire  206 . This provides a safety feature. If the pads are mislabeled or not labeled, the defibrillator will not administer a high voltage shock. 
   As shown, electrode  200  is oval-shaped, although any suitable shape or combination of shapes is possible, such as a generally rectangular shape having curved edges. Electrode  200  preferably has a top side  202  (an edge thereof is shown), a bottom side  204 , and an inner layer  203 . 
   As is well-known, top side  202  may include an insulating, supportive, or protective cover (not shown), which may be flexible, and which may graphically indicate a proper placement of electrode  200  on a subject. 
   Bottom side  204  is preferably defined by a conductive attachment layer, such as a gel or adhesive layer, having an approximate thickness of about 0.020-0.040 inch (0.05-0.10 centimeter). A suitable conductive attachment layer is a hydrogel. A suitable hydrogel product is commercially available from Katecho, Inc. part number KM30G. 
   Internally, electrode  200  includes a conductive foil layer  203 , interposed between top side  202  and bottom side  204 . Conductive foil layer  203  preferably has an opening therein, such as a hole  208 , of about 3.81 centimeters in diameter. Hole  208  may be cut, stamped or punched from conductive foil layer  203  using well-known methods and techniques. Hole  208  operates to provide a high level of pad-to-pad or pad-to-liner impedance when electrode  200  is disposed on one or either slide of the release liner. With two electrodes present, the gels make contact through the hole in the center of the liner. 
   In accordance with further aspects of the present invention, defibrillator  10  preferably operates in the training mode prior to placement of one or more training electrodes, such as electrodes  200 , on a training subject.  FIG. 3  is a perspective view of electrode  200  arranged on release liner  304 , including optional further packaging  308 . 
   Optional packaging  308  may comprise a housing having an electrical interface  360  for connection of electrodes, such as electrodes  200 , to defibrillator  10 . A cartridge identifier  380  may also be included in packaging  308 , to facilitate identification of training electrodes by defibrillator  10 . Package  308  may be implemented in any suitable manner. 
   Release liner  304  may be constructed of one or more layers of a nonconductive, non-stick material such as silicon-coated paper, polyester, polypropylene, polyethylene, and/or other non-stick material, in a manner well understood in the art. Release liner  304  preferably has an opening therein, such as a hole  322 , of about 1.27 centimeters in diameter. Hole  322  may be cut, stamped or punched from release liner  304  using well-known methods and techniques. Examples of various release liner configurations adaptable for use in connection with aspects of the present invention are shown in U.S. Patent Application Publication US2003/005 5478, the specification of which is incorporated herein by reference. 
   Electrode  200  is preferably positioned on release liner  304  in such a manner that, when defibrillator  10  is electrically coupled to electrode  200 , defibrillator  10  can characterize and/or identify a degree of electrical connectivity (for example, perform an impedance measurement to measure an impedance level) along an electrical path that includes electrode  200 . It will be appreciated that the manner of electrically coupling electrode  200  to release liner  304  and/or defibrillator  10  may determine a number of characterizable electrical paths that include electrode  200 . 
   As shown, bottom side  204  of electrode  200  is arranged on release liner  304 , in such a manner that hole  208  (not visible) and the conductive attachment layer are disposed over hole  322 . Lead wire  206 , connected in series with resistor  207 , is attachable to optional rigid electrode package  308 . Electrical coupling between defibrillator  10  and electrode  200  may occur via connector  360 , or, if package  308  is absent, via any other suitable connector. 
   One electrical path having an identifiable degree of electrical connectivity is created when the conductive attachment layer of electrode  200  is in contact with hole  322  in release liner  304 , and electrode  200  is electrically coupled to defibrillator  10 . In practice, the electrical path may include a second electrode (not shown, including the same elements as electrode  200 ), also arranged on release liner  304  in such a manner that its hole  208  and its conductive attachment layer are disposed over hole  322 , such that the conductive attachment layers of both electrodes are in contact via hole  322 . It will be appreciated that any arrangement of one or more electrodes on release liner  304  is possible, which allows defibrillator  10  to characterize a degree of electrical connectivity along an electrical path including one or more of the electrodes. 
   When package  308  is used, another electrical path having an identifiable degree of electrical connectivity may be created when electrode  200  (disposed on release liner  304 ) is stored in package  308 , and package  308  is electrically coupled to defibrillator  10 . 
   Referring now to  FIGS. 1-3 , during normal operation in the training mode, defibrillator  10  guides an operator through a training sequence that simulates operation of defibrillator  10  in the treatment mode. In accordance with one aspect of the present invention, when electrode interface  17  is electrically coupled to a training electrode such as electrode  200 , and the training electrode is disposed on a release liner, such as release liner  304 , but prior to the operator&#39;s placement of the training electrode on a training subject, defibrillator  10  is operative in a first training state. One possible first training state is waiting for the operator to remove the electrode from the release liner; another possible first training state is waiting for the operator to remove the electrode from other packaging, such as container  308 . Defibrillator  10  advances from the first training state to a second training state when a predetermined degree of electrical connectivity or variability in the electrical conductivity occurs along an electrical path including the electrode. One example of the second training state is waiting for the operator to remove the electrode from a package, which causes a detectable change in pad-to-pad impedance. Another example of a second or third training state is waiting for the operator to remove one or more pads from the release liner. A further training state is to wait until the user properly places the electrode(s) onto a training apparatus. The operator of defibrillator  10  is notified by operator interface that defibrillator  10  has changed training states—a voice prompt, for example, may acknowledge the removal of one or more electrodes  200  from release liner  304 , and/or instruct the operator to place the removed electrode(s) onto a training apparatus. Other prompts, such as blinking light(s) or text written to a display may also serve to notify the operator that defibrillator  10  has changed training states. 
   Training state advancement is preferably performed or coordinated by controller  18 , and state identifier  34  preferably identifies the predetermined degree of electrical connectivity—by obtaining an impedance measurement along the electrical path, for example. The identified impedance may indicate that the operator has removed the training electrode from the release liner, and/or removed the release liner from any optional packaging. For example, in the case of two electrodes  200  attached to a common release liner  304 , with the conductive attachment layers  204  of the electrodes in electrical contact via opening  322 , an electrical current traveling through the conductive attachment layers would encounter a predetermined impedance associated with opening  322 . An impedance in a range greater than about 2000 ohms, but less than about 15 Kohms indicates that one or both electrodes  200  remain on release liner  304 , and no training state advancement occurs. An impedance indicating that one or both electrodes  200  have been removed from release liner  304  (for example, the impedance approaches infinity), triggers controller  18  to advance defibrillator  10  from the first training state to the second training state. 
   The removal of one or more electrodes  200  from any optional packaging may be detected by measuring small changes in electrode-to-electrode impedance. Upon handling the electrode pads, the pad-to-pad impedance experiences changes larger than the noise floor. The device monitors, identifies, and enhances these pad-to-pad impedance changes in order to detect when the pads have been removed from their package. When these impedance changes are detected, the defibrillator advances to the next training state or to the next training prompt. 
   In accordance with another aspect of the present invention, with continuing reference to  FIGS. 1-3 , a flowchart of a method for training an operator to use a defibrillator, such as defibrillator  10 , is shown in  FIG. 4 . After beginning at block  400 , at step  402 , an external defibrillator, such as defibrillator  10 , operable in both treatment and training modes and responsive to an electrode, such as electrode  200  coupled to electrode interface  17  and arranged on a release liner, such as release liner  304 , is provided. The method continues at step  404 , where an input signal is received from the electrode, prior to placement of the electrode on a subject such as a training apparatus. At step  406 , a degree of electrical connectivity is determined along an electrical path that includes the electrode. For example, an impedance that indicates whether the conductive attachment layer of electrode  200  is in contact with opening  322  may be measured. Based on the determined degree of electrical connectivity, the external defibrillator may advance from a first training state (for example, waiting for an operator to remove the electrode from the release liner) to a second training state (for example, waiting for the operator to place the electrode on the training apparatus), at step  408 . At step  410 , a training state notification—a voice prompt, for example—is issued to the operator, indicating that the defibrillator advanced from the first training state to the second training state. 
   After a defibrillator operating in the training mode in accordance with above-described aspects of the present invention reaches a state where training electrodes coupled thereto have been removed from packaging and/or release liners, the training electrodes may be applied to a training apparatus. 
   In accordance with a further aspect of the present invention,  FIG. 5  is a layered perspective view of a training apparatus  500  particularly useful with defibrillator  10  (shown in  FIG. 1 ), and one or more training electrodes  200  (shown in  FIG. 2 ). Apparatus  500  may, however, be adapted for use with any type of defibrillator or training electrodes. 
   With reference to  FIG. 5 , and also to  FIGS. 1-3 , apparatus  500  includes a transparent first layer  502 . Layer  502  may be, for example, polyester or another clear material or coating of any suitable thickness in the range of about 0.001 to 0.010 inch (0.0025-0.25 cm) that allows for detachment of the conductive attachment layer of electrode  200 . As shown, layer  502  (and subsequent layers, discussed further below) is rectangular, although any geometric shape is possible. Layer  502  preferably includes one or more, electrode attachment regions  504 ,  506  and  508 , such as openings sized to receive electrodes  200 . Three electrode attachment regions  504 ,  506  and  508  are shown, although in practice either one, two or three openings would be placed via die-cutting, punching, cutting, stamping or another suitable method or technique. Electrode attachment regions  504  and  506  are preferably located in areas (discussed further below) approximating proper placement of electrodes on the anterior torso of an adult defibrillation subject (also discussed further below), and electrode attachment region  508  is preferably located in an area approximating proper placement of an electrode on the anterior torso of a child defibrillation subject. Electrode attachment regions may be smaller or larger than the size of electrodes adapted for attachment thereto. 
   A second layer  510  is a two-dimensional representation of an anterior portion of a defibrillation subject, either an adult&#39;s torso or a child&#39;s torso, identifiable through transparent first layer  502 . Layer  510  may be a printable paper or label.  FIG. 6  is an example of second layer  510  having an adult&#39;s torso shown thereon. The adult&#39;s torso may be life-sized, or another size.  FIG. 7  is an example of second layer  510  having a torso shown thereon with an electrode attachment region  508  in the center of the sternum. The torso may be life-sized, or another size. Layer  510  also preferably includes openings therein, sized and positioned similarly to openings  504 ,  506  and  508  in layer  502 . As shown in  FIG. 6 , openings  504  and  506  are arranged in the sternum and apex positions, respectively, of the adult&#39;s torso, and the apex position may be graphically indicated to wrap around the torso.  FIG. 7  illustrates opening  508  arranged in approximately the middle of the torso. 
   Referring again to  FIG. 5 , and to  FIGS. 1-3  as necessary, a third layer  512  is a signal conductor. Layer  512  operates to provide a communication path, such as an electrical path, between two electrodes, such as electrodes  200 , when they are properly positioned in electrode attachment regions  504  and  506 , or  508  and  518  (discussed further below). When electrodes  200  are properly placed on appropriate electrode attachment regions, defibrillator  10  may detect a predetermined degree of impedance (for example, an impedance associated with opening  208 ) across the electrical path between the electrodes—and may interact with the operator of defibrillator  10  in the training mode based on the impedance detection in accordance with well-known methods and techniques. 
   Layer  512  may be pure grade tin or another conductive material that does not corrode in the presence of the conductive attachment layer of electrode  200 , and may be exposed through attachment regions/openings  504 ,  506  and  508 . As shown, layer  512  is co-extensive with layer  510  and  514  (discussed further below), but may have a different configuration, such as a smaller length or width that still extends from one electrode attachment region to another. Alternatively, signal conduction may occur via networked individual conductors within or about electrode attachment regions  504  and  506 , or  508  and  518  (discussed further below). If layer  510  represents an adult&#39;s torso, and both electrode attachment regions  504  and  506  are formed on layer  502 , then layer  512  may be laminated on one side (for example, on the side opposite layer  502 ), with polyester or another suitable material. If layer  510  represents a child&#39;s torso, then layer  512  may additionally be folded (for example, in half), so that a conductive side is positioned in two directions—one direction facing layer  502 , and another direction facing a fourth layer  514 . Layer  512  is foldable or bendable in a way that minimizes the number of folds through the signal conductor. 
   Fourth layer  514  protects third layer  512 . When layer  510  represents an adult&#39;s torso, layer  514  may be a plain paper layer, or another non-conductive material, and may serve as the back of apparatus  500 . It may also be printed to show the two-dimensional representation of the adult back or posterior view for times when posterior electrode placement training is requisite, as illustrated in FIG.  8 . When layer  510  represents a child&#39;s torso, layer  514  is preferably a two-dimensional representation of a posterior view of the child&#39;s torso, identifiable through a transparent fifth layer  516 , which is configured and constructed in the same manner as layer  502 , including an electrode attachment region  518  that may be offset from electrode attachment region  508 . 
   The embodiment(s) depicted and described herein are meant to be illustrative in nature, and it will be understood that various training apparatuses, methods, systems and defibrillators may be designed using the principles set forth herein, and used for various commercial and consumer applications. For example, it will be appreciated that aspects of the present invention are not limited to any specific embodiments of computer programs or signal processing methods, and that multiple storage media, controllers/processors and configurations of such devices are possible. Moreover, the methods described herein may be implemented by computer software, firmware, hardware (e.g., application-specific integrated circuits), or any combination thereof.