Patent Publication Number: US-2021183269-A1

Title: Physiological training system

Description:
RELATED APPLICATIONS 
     This application is division of U.S. application Ser. No. 15/452,945 filed Mar. 8, 2017, which claims the benefit of U.S. Provisional Application No. 62/305,066 filed on Mar. 8, 2016, each of which are fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to simulated physiological structures for use as medical training aids. More particularly, the present disclosure relates to an anatomically correct modular airway simulation manikin developed to provide more realistic training when practicing medical procedures. 
     BACKGROUND 
     While it is desirable to train students in patient care protocols before allowing contact with real patients, textbooks and other reading materials lack the important benefit to students and medical personnel obtained from “hands-on” practice or experience. Thus, the use of physiological structures for training students and providing skill training for practicing medical personnel has become widespread. Although cadavers have traditionally been beneficially employed for this purpose, cadavers are not always readily available and are not well suited for all types of training. Instead, practice in the use of skills, techniques and various medical instruments for patient care education is often taught using simulated physiological structures or trainers, such as a manikin. 
     The need for such simulated physiological structures should not be underestimated, because they can provide valuable training that will lead to more effective treatment for patients. In particular, training in administering emergency trauma care on a manikin, which includes the practice of procedures that are usually performed on a person who has experienced some form of severe and often life-threatening trauma, is particularly beneficial. Such procedures may aid in the treatment or diagnosis of a condition, or may provide immediate lifesaving care until more complete medical treatment is available. The procedures may include intubation, clearing a blocked airway and/or draining accumulations of fluid from internal organs. While appearing to be simple procedures, if these procedures are performed improperly, the result can worsen the patient&#39;s condition, placing the patient in an even greater peril of death. By their nature, trauma care procedures are usually performed under emergency conditions in which the person administering the care is under time-related stress. It is therefore useful to provide training methods and apparatuses to fully prepare students and medical personnel in these procedures, so that they can be performed without delay, under stressful conditions. 
     Another reason why the use of a simulated physiological structure is desirable, is that while anatomy follows general rules, variations based on sex, age, height, weight, and various types of trauma experienced by the patient are common. As such, a student cannot be simply provided a one-size-fits-all set of directions for performing a given medical procedure. The use of a simulated physiological structure enables students to apply their knowledge of anatomy to determine the proper position for executing a medical procedure. 
     However, because the materials commonly selected for the construction of conventional simulated physiological structures are typically durable plastics and rubbers that do not closely mimic human tissue, these simulated physiological structures generally sacrifice realism and fidelity for durability and ease in manufacturing. Conventional simulated physiological structures also fail to emulate other significant aspects of a human patient, such as mass, biomechanics, and variations in anatomical structure. The result is that conventional simulated physiological structures are more doll-like than human-like and are thus incapable of providing an accurate teaching experience. 
     The inattention to realism in the anatomical construction is a detriment to the training of medical professionals since these factors must be accounted for and adapted to when performing certain medical procedures. Accordingly, these simulated physiological structures are only able to provide a generalized overview in learning the sequential order of steps required to perform medical procedures, thereby creating the false impression that the medical procedure is a routine procedure that does not require adaptation to patient-specific factors. Moreover the design of conventional simulated physiological structures fails to provide the critical tactile and sensory information that informs medical professionals of adjustments and responses required to successfully perform certain medical procedures. The result is often that conventional simulated physiological structures enforce negative training that can lead to serious complications and injuries when such negative training is used in the real-world environment. 
     Accordingly, the applicants of the present disclosure have identified a need for non-biologic simulation manikin systems with a high degree of anatomical fidelity not found in conventional simulation trainers so as to provide superior experiential training for medical personnel. Moreover, the applicants of the present disclosure have identified a need for modularity, so that certain portions of the simulation manikin can be quickly and easily replaced with different pathological scenarios to provide a plurality of differences which may be seen among actual patients. 
     SUMMARY OF THE DISCLOSURE 
     Embodiments of the present disclosure meet the need for a sensor-ready, modular, anatomically accurate physiological training system with a higher degree of anatomical fidelity than conventional simulation manikins. The physiological training system&#39;s unique modular design further enhances its medical training value and utility through the easy replacement and interchanging of components, which both multiplies the number of training scenarios that the physiological training system can facilitate, and extends the life of the physiological training system by permitting easy repair rather than replacement of the entire unit. 
     One embodiment of the present disclosure provides a modular physiological training system including a torso, a rear skull portion, an airway assembly, and a front skull portion. The torso assembly can represent a portion of a torso of a patient. The rear skull portion can be operably coupled to the torso assembly, and can represent a rear portion of a patient&#39;s skull. The airway assembly can represent an airway of the patient. The front skull portion can include one or more coupling mechanisms, and can represent a front portion of the patient&#39;s skull. The torso assembly and the rear skull portion can be configured to receive a portion of the airway assembly. The one or more coupling mechanisms of the front skull portion can be configured to operably coupled the front skull portion to the airway assembly, and a front skull portion to the rear skull portion. 
     The physiological training system&#39;s superior anatomical accuracy and realism enhance its training value and utility relative to conventional simulators by introducing users to a more complete simulation of the many variables that must be accounted for during the performance of medical procedures, thereby reducing the potential for negative training that results from the less complete simulations of other, less realistic training devices. The physiological training system&#39;s attention to replicating the physical appearance, tissue properties (such as hardness), mass distribution, biomechanics, and the interaction of different anatomical systems (skeletal muscles, airway organs and tissues, bone structure, etc.) of a real patient enables users to develop more refined and informed technique and decision-making before performing real-world medical procedures, such as intubation. 
     For example, one embodiment of the present disclosure provides an airway assembly for a physiological training system configured to model the look and feel of human anatomy during a medical training procedure. The airway assembly can include an airway assembly subsystem and a cradle assembly. The airway assembly subsystem can be constructed of a first silicone material and can be configured to represent a portion of an airway of a human. The cradle assembly can be constructed of a second silicone material, can be operably coupled to the airway assembly, and can be configured to represent the muscle and other tissue in the neck of a human, so as to provide additional weight and additional resistance to mechanical deformation during the medical training procedure. 
     The physiological training system can be sensorized, for example by using conformable carbon nanotube sensor technology, or other sensor technologies, to gather stress force measurements induced during training simulations. Certain educational metrics can then be applied to the sensor-derived information, thereby providing enhanced evaluation of a user&#39;s performance of intubation techniques and skills. The sensor-collected data can give educators objective, quantifiable, and meaningful assessment data superior to subjective observations, thereby improving the educator&#39;s ability to guide users toward best practices. The result can be a superior training platform which better prepares medical professionals for the successful performance of various airway management procedures, such as intubation, of patients. 
     For example, one embodiment of the present disclosure provides a physiological training system with sensorized organs configured to sense the magnitude and position of external forces applied to the organ during a medical training procedure. The physiological training system can include an organ and one or more sensing elements. The organ can be constructed of a silicone material and modeled after human anatomy to represent at least a portion of an organ of the patient. The one or more sensing elements can be operably coupled to the organ and can be configured to detect both the magnitude and relative position of an external force applied to the sensing element. Each sensing element can include a first layer constructed of a high resistance elastomeric material, a second layer constructed of a nonconductive elastomeric material, and a third layer constructed of a high electrical resistance elastomeric material, such that when an external force is applied to the sensing element, the first and third layers converge to an electrically conductive position. 
     The summary above is not intended to describe each illustrated embodiment or every implementation of the present disclosure. The figures and the detailed description that follow more particularly exemplify these embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure can be more completely understood in consideration of the following detailed description of various embodiments of the disclosure, in connection with the accompanying drawings, in which: 
         FIG. 1  is a perspective view depicting a physiological training system in accordance with an embodiment of the disclosure. 
         FIG. 2A  is a perspective view depicting an assembled airway assembly in accordance with an embodiment of the disclosure. 
         FIG. 2B  is a perspective view depicting an exploded airway assembly in accordance with an embodiment of the disclosure. 
         FIG. 3  is a perspective view depicting an airway in accordance with an embodiment of the disclosure. 
         FIG. 4  is a perspective view depicting a portion of a tongue in accordance with an embodiment of the disclosure. 
         FIG. 5  is a perspective view depicting a trachea in accordance with an embodiment of the disclosure. 
         FIG. 6  is a perspective view depicting an epiglottis and vocal cord in accordance with an embodiment of the disclosure. 
         FIG. 7  is a perspective view with hidden lines depicting an airway in accordance with an embodiment of the disclosure. 
         FIG. 8  is a cutaway perspective view with hidden lines depicting a portion of a torso assembly having a chest rise mechanism in accordance with an embodiment of the disclosure. 
         FIG. 9  is a perspective view of a bifurcated connector in accordance with an embodiment of the disclosure. 
         FIG. 10  is a perspective view of an epigastric acoustic gurglar in accordance with an embodiment of the disclosure. 
         FIG. 11A  is a perspective view of an airway cradle in accordance with an embodiment of the disclosure. 
         FIG. 11B  is a perspective view of an airway operably coupled to an airway cradle in accordance with an embodiment of the disclosure. 
         FIG. 12A  is a perspective view of a muzzle in accordance with an embodiment of the disclosure. 
         FIG. 12B  is a left side view of the muzzle of  FIG. 12A . 
         FIG. 12C  is a detailed view of a portion of the muzzle of  FIG. 12B . 
         FIG. 12D  is a top view of the muzzle of  FIG. 12A . 
         FIG. 12E  is a detailed view of a portion of the muzzle of  FIG. 12D . 
         FIG. 13  is a profile view of a jaw assembly in accordance with an embodiment of the disclosure. 
         FIG. 14  is a perspective view of a torso assembly in accordance with an embodiment of the disclosure. 
         FIG. 15  is a partial perspective view of a torso assembly showing hidden lines in accordance with an embodiment of the disclosure. 
         FIG. 16  is a perspective view of a baseplate in accordance with an embodiment of the disclosure. 
         FIG. 17  is a perspective view of an exploded skull assembly in accordance with an embodiment of the disclosure. 
         FIG. 18A  is a perspective view of an assembled spine assembly in accordance with an embodiment of the disclosure. 
         FIG. 18B  is a perspective view of an exploded spine assembly in accordance with an embodiment of the disclosure. 
         FIG. 19  is a schematic view depicting a medical procedure being performed on a sensorized embodiment of a physiological training system in accordance the disclosure. 
         FIGS. 20A-B  are schematic views depicting the measurement of a resistance across sensing elements in accordance with embodiments of the disclosure. 
         FIG. 21A  is a partial cross sectional view depicting a sensing element embedded within a tube or balloon in accordance with an embodiment of the disclosure. 
         FIG. 21B  is a profile view depicting a sensing element operably coupled to a tube or balloon in accordance with an embodiment of the disclosure. 
         FIG. 22  is a sensing element operably coupled to a piston mechanism in accordance with an embodiment of the disclosure. 
         FIG. 23  is a cross-sectional view depicting a fluid-filled bubble comprising a sensing element in accordance with an embodiment of the disclosure. 
         FIG. 24  is a cross-sectional view depicting a fluid-filled blister comprising a sensing element in accordance with an embodiment of the disclosure. 
         FIG. 25  is an exploded view depicting a sensing element in accordance with an embodiment of the disclosure. 
         FIG. 26  is a perspective view depicting a plurality of sensing elements configured to cover a portion of a physiological training system in accordance with an embodiment of the disclosure. 
         FIGS. 27A-D  are schematic views depicting a method of determining a position of an external force on a sensing element, in accordance with an embodiment of the disclosure. 
         FIG. 28  is a perspective view of a physiological training system having a truncated torso in accordance with an embodiment of the disclosure. 
         FIGS. 29A-E  depict a process of removal and replacement of various interchangeable components of the physiological training system, in accordance with an embodiment of the disclosure. 
     
    
    
     While embodiments of the disclosure are amenable to various modifications and alternative forms, specifics thereof are shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims. 
     DETAILED DESCRIPTION 
     I. Overview 
     Referring to  FIG. 1 , a physiological training system  100 , alternatively referred to as a manikin training system or Airway Intubation Training Manikin (AITM), is depicted in accordance with an embodiment of the disclosure. In some embodiments, the various components of the physiological training system  100  can be designed to balance close replication of real human anatomy, the needs of manufacturing facilities, and a degree of modularity necessary to enable the removal and replacement of certain components of the physiological training system  100 . In one embodiment, the physiological training system  100  can be constructed to resemble portions of a head, chest, torso, and arms of a human body. In other embodiments, the physiological training system  100  can additionally or in the alternative be constructed to resemble other portions of a human body. The modulus, color, thickness, tear strength, hardness, and toughness of the materials for each physiological training system  100  component can contribute to the anatomical correctness of the overall manikin system to provide a realistic training experience. 
     In one embodiment, the physiological training system  100  has two primary assemblies, including an airway assembly  102 , and a torso assembly  104 . Further, several of the physiological training system  100  components can be designed to enable modularity. For example, as depicted in  FIG. 1 , different airway assemblies  102 A-C, each having its own characteristics, can be operably coupled to the torso assembly  104  to provide some of the variations likely to occur among actual patients. Moreover, the interchange of different airway assemblies  102 A-C can be performed relatively quickly and without the use of tools. Thus, although the torso assembly  104  can, in some embodiments, remain the same, various interchangeable airway assemblies  102 A-C can present variations, for example, based on sex, age, height, weight, various types of trauma, pathological conditions and combinations of the foregoing. 
     Both the airway assembly  102  and the torso assembly  104  can be comprised of numerous modular parts designed to promote accurate biomechanics and force application requirements relevant to performing certain medical procedures, including articulation of the head, neck positioning, jaw movement, tongue movement, and movement of the epiglottis, vallecula, arytenoids, and vocal cords, among other things. Each component can additionally be configured to accurately interact with a full range of medical tools, including but not limited to, MACINTOSH and MILLER laryngoscopes, endotracheal tubes with balloon cuffs, stylets, oropharyngeal airways, bougies, and bag valve masks. 
     Additionally, the various components of the physiological training system  100  can be configured to provide accurate behavior in the movements and articulation of the head and neck positioning, BVM mask sealing, jaw opening, tongue displacement, epiglottis lifting, vallecular forces, arytenoids and cord deflection, and endotracheal tube balloon compliance. 
     II. The Airway Assembly 
     Referring to  FIG. 2A , an airway assembly  102  is depicted in accordance with an embodiment of the disclosure. In one embodiment, the airway assembly  102  can include an airway  106 , a muzzle  108 , teeth  110 , a jaw  112 , jaw brackets  114 , jaw pads  116 , and an airway cradle  118  (as depicted in  FIG. 11B ). 
     Referring to  FIG. 2B , an exploded view of an airway assembly  102  is depicted in accordance with an embodiment of the disclosure. In one embodiment, the muzzle  108  can serve as a foundation or base from which the airway assembly  102  can be constructed. Further, in one embodiment, the muzzle  108  can include a coupling mechanism configured to interchangeably and operably couple the airway assembly  102  to the torso assembly  104  (discussed more in connection with  FIGS. 12A-E ). 
     The upper teeth  110 A can be coupled to a bottom side of muzzle  108 , for example by one or more fasteners or adhesive. In another embodiment, the upper teeth  110 A can include one or more slots  122  configured to mate with one or more posts of the muzzle  108 , thereby enabling different sets of upper teeth  110 A to be interchangeably installed and/or removed from the airway assembly  102 , quickly, and without the use of tools. In other embodiments, other coupling and/or locking mechanisms can be used to selectively couple the upper teeth  110 A to the muzzle  108 . 
     A pair of jaw brackets  114  can be coupled to opposing lateral sides of the muzzle  108 , for example by one or more fasteners or adhesive. In one embodiment, the muzzle  108  includes grooves  124  configured to mate with a portion of each jaw bracket  114 , thereby strengthening the coupling between the jaw brackets  114  and the muzzle  108 . 
     A jaw pad  116  can be coupled to each jaw bracket  114 , for example by adhesive or interference fitting. Each jaw pad  116  can have a slot  126  defined therein. A pair of pins  120  can be employed to couple the jaw  112  to the slot  126  defined in each jaw pad  116 . In some embodiments, the pair of pins  120  can be inserted and removed without the use of tools, thereby easing the removal and replacement of the jaw  112 . 
     The lower teeth  110 B can be operably coupled to the jaw  112 , for example, by one or more fasteners or adhesive. In another embodiment, the lower teeth  110 B can include one or more pins configured to couple with one or more aperture  128  defined in the jaw  112 . In other embodiments, other coupling and/or locking mechanisms can be used to selectively couple the lower teeth  110 B to the jaw  112 . In one embodiment, the jaw  112  can further define a recessed mounting surface  130  configured to accept the lower teeth  110 B, thereby strengthening the coupling between the lower teeth  110 B and the jaw  112 . 
     The airway  106  can be operably coupled to the airway cradle  118  (as depicted in  FIG. 11B ). Alternatively, the airway cradle  118  can be integrally molded into or onto a portion of the airway  106 . Airway cradle  118  can provide additional weight and can provide certain restrictions to movement so that the airway  106  more accurately models the human anatomy. 
     The airway  106  can be operably coupled to the muzzle  108  through, for example, an interference fit. For example, in one embodiment, a portion of airway  106  can be inserted into a cavity defined in the muzzle  108 . In other embodiments, the airway  106  can be overmolded onto the muzzle  108 . 
     In one embodiment, various pathological configurations can be interchanged through removal and replacement of different components of the airway assembly  106 . For example, in one embodiment, jaw  112  and upper and lower teeth  110 A/B can be easily interchanged without the use of tools to provide for a variety of pathological configurations resembling the different characteristics common among actual patients. 
     A. The Airway 
     Referring to  FIG. 3 , an airway  106  is depicted in accordance with an embodiment of the disclosure. In one embodiment, airway  106  is configured to accurately replicate the movements, distortions, and appearance of the human airway environment during various medical procedures, thereby enabling a higher level of instructional value by accurately imitating human physiology. 
     The airway  106  can be a single piece comprised of eight or more anatomical features. In some embodiments, the eight or more anatomical features can be divided into two categories based upon how they are constructed, referred to herein as “specialized” anatomical features and the “general” anatomical features. In one embodiment, the specialized anatomical features can include a tongue  130 , a trachea  132 , an epiglottis  134 , and vocal cords  136 . The specialized anatomical features can have unique defining physical properties achieved through the use of unique compositions of material blends and construction procedures. The general anatomical features can include an oral cavity  138 , a nasal cavity  140 , an esophagus  142 , and arytenoids  144 . In one embodiment, the general anatomical features do not require specialized material blends and construction procedures. 
     1. Construction of Specialized Anatomical Features 
     Referring to  FIG. 4 , a portion of a tongue  130  is depicted in accordance with an embodiment of the disclosure. In various medical procedures, such as intubation, a precise understanding of how to properly displace the tongue  130  is necessary to make the epiglottis  134  accessible. Learning the proper technique is therefore dependent upon a realistic, anatomically correct tongue  130 . In one embodiment, tongue  130  includes an outer shell  146  and an interior filling  148 . The outer shell  146  and interior filling  148  can be made from two different material blends, for example a Primary Silicone Rubber (PSR) having a first hardness and modulus of elasticity, and a silicone gel having a second hardness and modulus of elasticity. In one embodiment, the PSR can be PlatSil Gel100 having a hardness of approximately 33 Shore 00, a tensile strength of approximately 154 psi, a maximum elongation of approximately 1275%, a tear strength of approximately 56 ppi, a density of approximately 1.1, and a viscosity of approximately 22000 cP. In one embodiment, the silicone gel can be P7616-195 gel having a density of approximately 0.98, and a viscosity of approximately 1200 cP. Other materials are also contemplated. These materials, when working in conjunction, can provide a highly realistic simulation of a human tongue. 
     In some embodiments, the outer shell  146  of the tongue  130  is formed by injecting PSR into a traditional cavity mold and corresponding pickout core. The cavity mold can create the contours of the exterior surface of the outer shell  146  of tongue  130 , while the pickout core can serve to create a void or cavity, which can ultimately be filled with an interior filling  148 . For example, once the outer shell  146  has cured, the pickout core can be removed and the silicone gel filling can be poured into the cavity of the PSR outer shell  148 . In one embodiment, a volume of PSR can be injected into the cavity mold, thereby forming the outer shell  146  of tongue  130 . After removal of the pickout core, a volume of silicone gel can be injected into the cavity to form the interior filling  148  of tongue  130 . In some embodiments, the interior cavity can then be sealed, thereby trapping the silicone gel within the outer shell  146  of tongue  130 . In other embodiments, the various steps described herein can be performed in an alternative order. 
     In one embodiment, an additional thin layer of silicone  147  having a greater durometer than the PSR can be affixed to the outer shell  146 , after the outer shell  146  has cured. For example, silicone having a hardness of approximately 20 Shore A, a tensile strength of approximately 1015 psi, a maximum elongation of approximately 800%, a tear strength of approximately 115 ppi, a density of approximately 1.10, and/or a viscosity of approximately 15,000 cP can be used. Other materials are also contemplated. In some embodiments, the additional thin layer of silicone  147  increases the strength of the tongue  130  during certain medical procedures, while retaining a realistic feeling. Accordingly, the additional thin layer of silicone  147  can extend the usable life of tongue  130 , without significantly affecting its performance during the practice of medical procedures. 
     Referring to  FIG. 5 , a trachea  132  is depicted in accordance with an embodiment of the disclosure. In various medical procedures, it is necessary to have an understanding of how to distinguish between the esophagus  142  and the trachea  132  using either sight or feel. The proper technique can therefore depend upon realistic characteristics such as the presence of tracheal cartilage. To facilitate this, in one embodiment, the trachea  132  can be constructed of a rubber (hereinafter, the “cartilage rubber”) with a greater durometer than the PSR. For example, in one embodiment, the cartilage rubber can have a hardness of approximately 80 Shore A, a tensile strength of approximately 1100 psi, a maximum elongation of approximately 75%, a tear strength of approximately 75 ppi, a density of approximately 1.02, and/or a viscosity of approximately 90,000 cP, thereby having a hardness, texture, and feel similar to that of human cartilage. Other materials are also contemplated. In one embodiment, the trachea  132  can include representations of human thyroid cartilage, median cricothyroid cartilage, cricoid cartilage, and annular (intercartilginous) ligaments between tracheal cartilages. 
     Referring to  FIG. 6 , an epiglottis  134  is depicted in accordance with an embodiment of the disclosure. In various medical procedures, for example in intubation, mastery of techniques to manipulate the epiglottis  134  so as to expose the opening of the trachea  132  is required. Accordingly, learning the proper technique can be dependent upon a biomechanically accurate epiglottis  134 . In order to improve biomechanical accuracy, in one embodiment, the epiglottis  134  can be comprised of silicone rubber (hereinafter, the “epiglottic silicone rubber”) with a greater durometer than the PSR. For example, in one embodiment, the epiglottic silicone rubber can have a hardness of approximately 20 Shore A, a tensile strength of approximately 1015 psi, a maximum elongation of approximately 800%, a tear strength of approximately 115 ppi, a density of approximately 1.10, and/or a viscosity of approximately 15,000 cP. Other materials are also contemplated. 
     In one embodiment, the epiglottis  134  can be formed by injecting epiglottic silicone rubber into a cavity within an airway pickout core. The airway pickout core can then be placed within an airway cavity mold, and secured in position, before the epiglottic silicone rubber has cured, such that the uncured epiglottic silicone rubber can intermingle and/or fuse with the PSR and/or other components of the airway  106  during construction. 
     With continued reference to  FIG. 6 , vocal cords  136  are depicted in accordance with an embodiment of the disclosure. In various medical procedures it is necessary to visually identify the vocal cords, which often have a distinct coloration. Accordingly, in order to enhance visual distinction of the vocal cords  136 , a silicone rubber having a coloring agent (hereinafter, the “vocal cord silicone rubber”) can be used to construct the vocal cords  136 . For example, in one embodiment, the vocal cord silicone rubber can have a white or pale color. In one embodiment, the vocal cords can be constructed of colored PSR or of a material with mechanical properties substantially similar to the PSR. In another embodiment, the vocal cords can be constructed of a material having a hardness of approximately 80 Shore A, a tensile strength of approximately 1100 psi, a maximum elongation of approximately 75%, a tear strength of approximately 75 ppi, a density of approximately 1.02, and/or a viscosity of approximately 90,000 cP. Other materials are also contemplated. 
     In one embodiment, the vocal cords  136  can be formed by injecting the vocal cord material into a cavity within an airway pickout core. The airway pickout core can then be placed within an airway cavity mold, and secured in position, before the vocal cord silicone rubber has cured, such that the uncured vocal cord silicone rubber can intermingle and/or fuse with the PSR and/or other components of the airway  106  during construction. 
     2. Construction of General Anatomical Features 
     Integration of the general anatomical features into the final airway can be achieved by first constructing the four specialized anatomical features and then pre-loading them within a traditional cavity mold and pickout core assembly. The cavity mold can create the contours of the exterior surface of the airway  106 , while the airway pickout core can create the contours of the interior surface. Additionally, the airway pickout core can have spaces, concavities, grooves, and other topographical features which, in conjunction with the cavity mold, hold the primary anatomical features in place. The airway pickout core can be comprised of a plurality of parts, which can be anchored together with a plurality of pins. Given the complicated shape of the interior surface of the airway  106 , the removal of a single-piece airway pickout core can be difficult without damaging the airway  106 . By making the airway pickout core a multi-piece unit, the parts can be separated and removed through the oral cavity  138  and the open ends of the trachea  132  and esophagus  142 . 
     Referring to  FIG. 7 , in one embodiment, the airway pickout core can be shaped so as to enable esophagus necking  150  to form within the esophageal lumen  152  of esophagus  142 . The esophagus necking  150 , sometimes in combination with other features, such as an epigastric acoustic gurgler as described below, enables a tactile indicator of the unsuccessful performance of certain medical procedures. For example, when intubation tools are placed down the esophagus  142  and then pulled back up, the esophagus necking  150  can be configured to generate suction upon the intubation tools. Further, in some embodiments, the airway  106  can include a nasal passage added to the upper airway  106 , to enable certain medical procedures, such as nasal intubation. 
     In addition to the airway pickout core, the specialized anatomical features can be positioned within the cavity mold. For example, in one embodiment, the tongue  130 , trachea  132 , epiglottis  134 , and vocal cords  136  are placed within the airway cavity mold, in conjunction with the pickout core assembly. In some embodiments, the specialized anatomical features can be held in position by at least one of the airway cavity mold, the pickout core assembly, and/or one or more positioning locks. 
     PSR can then be injected into the airway cavity mold, thereby enveloping the cartilage rubber of the trachea  132 , and fusing with the tongue  130 , epiglottis  134 , vocal cords  136 , and other specialized anatomical features, without a homogeneous intermingling of the various types of rubbers, such that each of the anatomical features retains its desired characteristics. In one embodiment, the PSR can be PlatSil Gel100 having a hardness of approximately 33 Shore 00, a tensile strength of approximately 154 psi, a maximum elongation of approximately 1275%, a tear strength of approximately 56 ppi, a density of approximately 1.1, and a viscosity of approximately 22000 cP. 
     In one embodiment, a volume of PSR can be injected into the airway cavity mold. Accordingly, the PSR fills the space around the airway pickout core, thereby forming the general anatomical features and bonding to the specialized anatomical features. After the PSR is injected into the airway cavity mold, and cures, the airway cavity mold can be opened. The airway  106 , which contains the airway pickout core can then be removed. In other embodiments, the various steps described herein can be performed in an alternative order. 
     B. Chest Rise Mechanism 
     Referring to  FIG. 8 , a portion of a physiological training system  100  including a chest rise mechanism is depicted in accordance with an embodiment of the disclosure. In one embodiment, physiological training system  100  includes one or more balloons  154 , in fluid communication with the airway  106  and configured to at least partially inflate upon the flow of fluid, such as air, into the one or more balloons  154 . For example, in one embodiment, the physiological training system  100  includes two balloons  154 , representing a right and left lung. The one or more balloons  154  can be positioned between a lung shelf  158  and right and left lung plates  156 A/B, which can be positioned proximal to an exterior surface  160  of the torso assembly  104 . In one embodiment, the right and left lung plates  156 A/B can be coupled to a sternum  162 , positioned between the right and left lung plates  156 A/B, by way of silicone rubber enveloping the sternum  162 . In one embodiment, the sternum  162  and lung shelf  158  are operably coupled to a medial brace  163 . 
     Collectively, these components, including the one or more balloons  154  positioned between the lung shelf  158  and right and left lung plates  156 A/B can enable the chest of the physiological training system  100  to rise and fall, thereby more accurately simulating the characteristics of an actual patient. The thickness and durometer of the exterior surface  160  of the torso assembly  104 , combined with the durometer of the flexure material for the right and left lung plates  156 A/B can determine the pressure required for the chest to rise. 
     With some medical procedures, chest rise can serve as an indicator that the medical procedure has been performed successfully. For example, a chest rise can represent successful intubation of an airway, as opposed to improper intubation of the esophagus  142 , which can carry mortal risks, such as pulmonary aspiration and anoxia. By achieving air pressure driven chest rise, the physiological training system  100  can provide a more accurate and lifelike simulation of the physiological responses occurring in a patient, thereby enabling students and medical personnel to observe the physiological training system  100  and determine whether medical procedure has been successfully performed. 
     Students and medical personnel may also use the rate at which the air pressure increases as a tactile indicator of the successful performance of a medical procedure. In some medical procedures, the rate at which air pressure increases may indicate whether only one lung has been intubated, as opposed to both lungs, or otherwise recognizing improper intubation, such as when the endotracheal tube is incorrectly inserted into the esophagus  142  instead of the trachea  132 . 
     Referring to  FIG. 9 , a bifurcated connector  164  configured to connect the trachea  132  to the lungs or balloons  154  is depicted in accordance with an embodiment of the disclosure. The bifurcated connector  164  can have a main stem  166  that branches into a right stem  168 A and left stem  168 B. In one embodiment, the main stem  166  can be operably coupled to the trachea  132 , while the right stem  168 A and left stem  168 B can respectively be operably coupled to a pair of balloons  154 . In one embodiment, the split between the right stem  168 A and left stem  168 B is positioned at an anatomically accurate distance from the upper airway  106 , such that the right stem  168 A has a more vertical orientation and a larger diameter than the left stem  168 B. These features of the bifurcated connector  164  allow physiological training system  100  to replicate common errors of intubation practice. Specifically, the difference in the structure of the right and left stems of the bifurcated connector  164  replicate the difference in structure of a human&#39;s right and left main bronchus which make it significantly more likely for medical tools placed too far down the airway to divert into the right bronchus, so as to access only a single lung, when access of both lungs is desired. In some cases, accessing only a single lung during a medical procedure can severely reduce the availability of oxygen to a patient, which can carry mortal risks during performance of the procedure. 
     C. Epigastric Gurgler 
     Referring to  FIG. 10 , an epigastric acoustic gurgler  170  is depicted in accordance with an embodiment of the disclosure. In one embodiment, the epigastric acoustic gurgler  170  can include an esophagus connection  172 , a check valve  174  and an acoustic gurgler  176 . When installed in a physiological training system  100 , the esophagus connection  172  can be in fluid communication with the esophagus  142 , so that the check valve  174  and an acoustic gurgler  176  can replicate the sounds and tactile indicators of a patient&#39;s stomach. In some embodiments, the epigastric acoustic gurgler  170  can be operably coupled to the medial brace  163 . 
     During the performance of certain medical procedures, when a medical tool, such as an endotracheal tube, is placed in the esophagus  142  instead of the trachea  132 , air flows into the stomach (i.e., the epigastric acoustic gurgler  170 ) instead of into the lungs (i.e., balloons  154 ). The epigastric acoustic gurgler  170  replicates the sounds of this event. Check valve  174 , in conjunction with esophageal necking  150  generates suction on the medical tools similar to what would be experienced with an actual patient. 
     D. Airway Cradle 
     Referring to  FIG. 11A , an airway cradle  118  is depicted in accordance with an embodiment of the disclosure. Referring to  FIG. 11B , an airway  106  positioned within an airway cradle  118  is depicted in accordance with an embodiment of the disclosure. A human airway is surrounded by muscle tissue which affects the way in which the airway can be moved and distorted. In one embodiment, the physiological training system  100  replicates this tissue with an airway cradle  118 . The airway cradle  118  can secure the position of the lower end of the airway  106  inside of the neck and torso. The airway cradle  118  can also provide added weight, physical restriction and mobility, and visual representation of the muscle surrounding the airway  106 . 
     The airway cradle  118  can be a single component composed of silicone rubber. For example, in one embodiment, the airway cradle can have a hardness of approximately 33 Shore 00, a tensile strength of approximately 154 psi, a maximum elongation of approximately 1275%, a tear strength of approximately 56 ppi, a density of approximately 1.1, and a viscosity of approximately 22000 cP. In another embodiment, the airway cradle can have a hardness of approximately 20-24 Shore A, a tensile strength of approximately 1015 psi, a maximum elongation of approximately 800%, a tear strength of approximately 115 ppi, a density of approximately 1.10, and/or a viscosity of approximately 15,000 cP. Other materials are also contemplated. The airway cradle can be formed using a traditional cavity mold. 
     E. Muzzle 
     Referring to  FIGS. 12 -A-E a muzzle  108  is depicted in accordance with an embodiment of the disclosure. In one embodiment, muzzle  108  can serve as the foundation or base on which other components of the airway assembly  102  are operably coupled. The shape of the muzzle  108  can be defined to represent the bone and cartilage of the nasal region of the human anatomy. In one embodiment, the muzzle  108  can be constructed of, for example, a plastic high-density polyethylene (HDPE) or other material that provides a rigid structure. For example, in one embodiment, the muzzle material can have a hardness of approximately 70 Shore D, a tensile strength of approximately 3916 psi, and/or a density of approximately 0.96. Other materials are also contemplated. 
     In one embodiment, muzzle  108  can include a coupling and/or locking mechanism, such as a slotted groove  178 , configured to interchangeably and operably couple the muzzle  108  (and associated airway assembly  102 ) to the torso assembly  104 . In one embodiment, the slotted groove  178  can be operably coupled to the skull  188 , for example, by a quick release mechanism  202  in the front portion of a skull  188 A of the torso assembly  104  (as depicted in  FIG. 18 ). In one embodiment, a pin in the front skull portion  188 A can be actuated between an open position by the quick release mechanism  202 , in which the pin freely slides into and out of the slotted groove  178 , and a locked position, in which the pin  202  is biased against a surface of the muzzle  108 , thereby creating a friction interference fit to impede removal of muzzle  108  from the pin  202 . 
     F. Jaw Assembly 
     Referring to  FIG. 13 , a jaw assembly  180  is depicted in accordance with an embodiment of the disclosure. In some medical procedures, precise manipulation of a patient&#39;s jaw can be required to properly perform the procedure. For example, intubation may require the use of tools, such as a bag valve mask, and is therefore dependent upon an anatomically and biomechanically accurate jaw. To facilitate the anatomically and biomechanically accurate jaw, in one embodiment, the jaw assembly  180  can include a jaw bone  112 , a pair of jaw brackets  114 , a pair of jaw pads  116 , and a pair of jaw pins  120 . In some embodiments, the jaw assembly can further include upper and lower sets of teeth  110 A/B (as depicted in  FIGS. 2A /B). 
     In one embodiment, jaw bone  112  can be a single component, constructed of a plastic high-density polyethylene (HDPE) or other material that provides a rigid structure. For example, in one embodiment, the jaw bone material can have a hardness of approximately 70 Shore D, a tensile strength of approximately 3916 psi, and/or a density of approximately 0.96. Other materials are also contemplated. 
     The jaw brackets  114  can be comprised of two single piece components, and can be mirror images of one another. In one embodiment, the jaw brackets  114  can be constructed of a rigid lightweight metal, such as aluminum. The jaw brackets  114  can be operably coupled the jaw assembly  180  to the muzzle  108 . The jaw pads can include two single piece components, and can be constructed of a rubber different from that of the jaw bone. For example, in one embodiment, the jaw pads can have a hardness of approximately 35 Shore A, a tensile strength of approximately 1390 psi, a maximum elongation of approximately 852%, a tear strength of approximately 146 ppi, and/or a density of approximately 1.14. Other materials are also contemplated. The jaw pads  116  can be affixed to jaw brackets  114  via an interference fit within an aperture  182  defined within each jaw bracket  114 . 
     The jaw pins  120  can be inserted into the mandibular condyle of the jaw bone  112  and extend inwards. In one embodiment, the jaw pins  120  can be inserted and removed without the use of tools, thereby easing the removal and replacement of the jaw assembly  180 . In one embodiment, each jaw pad  116  can define a slot  122 , into which jaw pin  120  can at least partially be inserted. The jaw pin  120  can accordingly be unable to both pivot and traverse along slot  122 , thereby enabling anatomically accurate opening, jaw thrust, and increased resistance when the jaw assembly  180  is being manipulated. In one embodiment, the width of slot  122  can narrow towards one end, such that an increased resistance can be felt as jaw bone  112  is pulled forward. 
     During certain medical procedures, for example intubation, the teeth of a patient can be damaged. For this reason, the physiological training system  100  can include a set of anatomically correct teeth  110 A/B. With additional reference to  FIGS. 2A /B, Upper teeth  110 A can be coupled to a bottom side of muzzle  108 , for example by one or more fasteners or adhesive. In another embodiment, upper teeth  110 A can include a one or more slots  122  configured to mate with one or more posts of muzzle  108 , thereby enabling different sets of upper teeth  110 A to be interchangeably installed and/or removed from the airway assembly  102 , quickly, and without the use of tools. In other embodiments, other coupling and/or locking mechanisms can be used to selectively couple the upper teeth  110 A to the muzzle  108 . 
     The lower teeth  110 B can be operably coupled to the jaw  112 , for example, by one or more fasteners or adhesive. In another embodiment, the lower teeth  110 B can include one or more pins configured to couple with one or more aperture  128  defined in the jaw  112 . In other embodiments, other coupling and/or locking mechanisms can be used to selectively couple the lower teeth  110 B to the jaw  112 . In one embodiment, the jaw  112  can further define a recessed mounting surface  130  configured to accept the lower teeth  110 B, thereby strengthening the coupling between the lower teeth  110 B and the jaw  112 . In one embodiment, the teeth  110 A/B are formed using a traditional cavity mold. In one embodiment, the teeth  110 A/B are constructed from an acrylic material. 
     III. Torso Assembly 
     Referring to  FIG. 14 , a torso assembly  104  is depicted in accordance with an embodiment of the disclosure. In one embodiment, the torso assembly  104  can include a torso body  186 , a skull  188 , a spine  190 , and face skin  192 , configured to provide neck articulation and proportionally distributed, simulated body mass, similar to that of an actual patient. 
     In one embodiment, torso body  186  can provide the majority of the weight of the physiological training system  100 . In one embodiment, the construction materials and components can be distributed such that that weight distribution is anatomically accurate to that of an actual human patient. The torso body  186  can be configured to at least partially house or contain the airway assembly  102 . In one embodiment, the torso body  186  is over molded over a rear portion of the skull  188 B. The torso body  186  can be composed of silicone using a traditional cavity mold, and coated with a skin layer of PSR. For example, in one embodiment, the torso material can have a hardness of approximately 20 Shore A, a tensile strength of approximately 1015 psi, a maximum elongation of approximately 800%, a tear strength of approximately 115 ppi, a density of approximately 1.10, and/or a viscosity of approximately 15,000 cP. In one embodiment, the exterior skin layer can have a hardness of approximately 33 Shore 00, a tensile strength of approximately 154 psi, a maximum elongation of approximately 1275%, a tear strength of approximately 56 ppi, a density of approximately 1.1, and a viscosity of approximately 22,000 cP. Other materials are also contemplated. 
     The face skin  192  can be configured to provide visual and tissue fidelity and also provide a resistance to movement of the jaw assembly  180 . In one embodiment, the tissue fidelity can enable medical devices or tools, such as a bag valve mask (BVM) to interact with the physiological training system  100  as they would on an actual patient. For example, BVM sealing can occur due to the nature of the skin materials and accurate internal structural bone anatomy with adequate subcutaneous tissue. 
     In one embodiment, the face skin  192  can be removable so that different pathologies and appearances can be introduced to the simulation experience. For example, the face skin  192  and torso body  186  can be shaped and sized so as to represent a man, a woman, an adolescent, a young child, or an infant. Additionally, the face skin  192  and torso body  186  can be configured to represent different ethnicities, including different hair and skin colors, as well as distinguishing physiological aspects which may be present among different ethnicities. Further, the face skin  192  can be configured to present pathologies including but not limited to burns, blunt force trauma, and lacerations. 
     In one embodiment, the face skin  192  can stretch over a portion of torso body  186  and skull  188 , thereby creating a friction fitting with the face skin  192  to hold the face skin  192  and a fixed position relative to the torso body  186 . A portion of the face skin  192  proximal to the neck can include one or more snaps configured to interlock with snaps  194  positioned on torso body  186 , thereby further holding the face skin  192  in a fixed position relative to the torso body  186 . 
     The face skin  192  can be composed of softened silicone and be produced using a traditional cavity mold. For example, in one embodiment, the face material can have a hardness of approximately 10 Shore A, a tensile strength of approximately 1015 psi, a maximum elongation of approximately 800%, a tear strength of approximately 115 ppi, a density of approximately 1.10, and/or a viscosity of approximately 15,000 cP. In one embodiment, the face material can have a hardness of approximately 33 Shore 00, a tensile strength of approximately 154 psi, a maximum elongation of approximately 1275%, a tear strength of approximately 56 ppi, a density of approximately 1.1, and a viscosity of approximately 22,000 cP. Other materials are also contemplated. 
     Referring to  FIG. 15 , a portion of the torso body  186  is depicted in accordance with an embodiment of the disclosure. In one embodiment, a portion of the torso body  186  can be filled with a foam material in order to improve neck movement. For example, in one embodiment, the torso body  186  can define a void  195  from an area proximal to the base of the skull  188  to an area proximal to the clavicle region, having a trapezoidal shape, which can be filled with foam. The foam can enable a student or medical personnel to position the head using a force similar to what is required when dealing with an anesthetized patient. In one embodiment, the foam can have a hardness of approximately 35 Shore A, a tensile strength of approximately 1200-1800 psi, a maximum elongation of approximately 800%, a tear strength of approximately 185 ppi, a density of approximately 1.10, and/or a viscosity of approximately 3,500 cP. Other materials are also contemplated. 
     Referring to  FIG. 16 , a baseplate  196 , which can be operably coupled to, and/or seal off one end of torso body  186 , as depicted in accordance with an embodiment of the disclosure. For example, in one embodiment, baseplate  196  can be shaped and sized to mate with the open-ended cross section of torso body  186 . Baseplate  196  can be operably coupled to torso body  186  by one or more latches  198 , which can selectively couple to a corresponding latch receiver in torso body  186 , for example in the arms of torso body  186 . Baseplate thereby enables easy access to components within the interior of the torso body  186 , while ensuring that pressure generated by the inflation of the lung balloons  154  and other components, press against interior components of the torso body  186 , and not through the bottom of the torso body  186 . 
     Referring to  FIG. 17 , a front portion  188 A and a rear portion  188 B of the skull are depicted in accordance with an embodiment of the disclosure. The front portion  188 A of the skull can be a simplified representation of a human skull, for example retaining features such as eye sockets. 
     In one embodiment, the airway assembly  102  is attached to the torso assembly  104  at several points. For example, front portion  188 A can include one or more pins  202  configured to be operably coupled to one or more slotted grooves  178  of muzzle  108 . In one embodiment, the pin  202  of the front skull portion  188 A can be actuated between an open position, in which a pin  202  freely slides into and out of the slotted groove  178 , and a locked position, in which the pin  202  is biased against a surface of the muzzle  108 , thereby creating a friction interference fit to impede removal of muzzle  108  from the pin  202 . In one embodiment, pin  202  can be biased to the locked position. 
     The rear portion  188 B of the skull can be over molded into the torso body  186 . The rear portion  188 B can have a quick release mechanism  203  that operably couples a pin  204  on the rear portion  188 B, thereby enabling modularity through the ease of removing and replacing the front portion  188 A of the skull from the rest of the torso assembly  104 . 
     In one embodiment, front portion  188 A and rear portion  188 B can be constructed of HDPE using a traditional cavity mold. For example, in one embodiment, the skull material can have a hardness of approximately 70 Shore D, a tensile strength of approximately 3916 psi, a maximum elongation of approximately 600%, and/or a density of approximately 0.96. Other materials are also contemplated. In one embodiment the front portion  188 A can weigh approximately 0.944 lbs, and the rear portion  188 B can weigh approximately 1.261 lbs. 
     Referring to  FIGS. 18A and 18B , a spine  190  is depicted in accordance with an embodiment of the disclosure. The spine  190  can be configured to regulate the motion of portions of the torso assembly  104  and the airway assembly  102 , in a manner that replicates the movement of an actual patient. In one embodiment, the spine can be composed of a corrugated steel pressure hose  206  configured with steel ball joints  208 ,  210  at the C3 and C7 vertebral positions. Lower spine anchor  212  can be operably coupled and/or embedded within torso body  186 , while skull anchor  214  can be operably coupled rear portion  188 B of the skull. Spine  190  can enable proper head and neck motions, with the desired ruggedness necessary in the training environment, thereby enabling a student or medical practitioner to practice various medical procedures in different neck positions. Accordingly, when the head is moved, the airway will correspondingly move with it. 
     IV. Sensors 
     Referring to  FIG. 19 , a sensing element  216  configured to be operably coupled to or embedded within physiological training system  100 , is depicted in accordance with an embodiment of the disclosure. In one embodiment, the sensing element  216  is configured to provide a measurement of stress, elongation, pressure, or load applied to or placed upon the a portion of the physiological training system and sensing element  216 , thereby providing an objective standard by which to evaluate the performance of a medical procedure performed by a student or medical personnel. In one embodiment, a plurality of sensing elements  216  can be utilized to evaluate performance of a medical procedure training event, including one or more sensing elements  216  positioned in a tool  300  used in conjunction with or inserted into the physiological training system  100 . 
     For example, in one embodiment, one or more sensing elements  216  can be positioned in the teeth  110 , upper palate, the back of the throat, and/or in the trachea  132  of the physiological training system  100 . The one or more sensing elements  216  can be incorporated into the material of the physiological training system  100 , with minimal rigid components attached thereto, such that the sensing elements  216  are blended into the physiological training system, thereby preserving the biomechanical realism of the physiological training system  100 . 
     The one or more sensing elements  216 , either alone or in combination, can sense at least one of a magnitude of an applied force or pressure, and/or a location of an applied force or pressure to portions of the physiological training system  100 . In one embodiment, sensing elements  216  can be incorporated into the physiological training system  100  in layers configured to provide increased sensing capabilities. For example, in one embodiment, orthogonal rows of sensing elements  216  can be included in a portion of the physiological training system  100 , thereby enabling measurement of both the magnitude and location of an applied force. In one embodiment, a first layer of sensors  216  can be configured to measure forces in a first range of magnitudes, and a second layer of sensors  216  can be configured to measure forces and a second range of magnitudes. In some embodiments, the first and second range of magnitudes can be overlapping, while in other embodiments, the first and second range of magnitudes can be mutually exclusive. 
     Referring to  FIGS. 20A and 20B , a sensing element  216  is depicted in accordance with an embodiment of the disclosure. In one embodiment, the sensing element  216  includes a piezoresistive elastomeric body  218  configured to measure elongation along at least one axis. In one embodiment, the sensing element  216  is configured to elongate along multiple axes. Piezoresistivity is the change in electrical resistivity under stress or strain can be defined by the following formula: 
       ρσ=(Δρ/ρ)/ε
 
     wherein 
     ρ=original resistivity; 
     Δρ=change in resistivity; and 
     ε=elongation. 
     Accordingly, when a voltage, for example from a battery  220 , is applied to the sensing element  216 , and a stress or strain is applied to the sensing element  216 , as the elastomer body  218  elongates the electrical resistance of the material changes, and the resulting change in resistance can be measured in the change in current, for example from an ammeter  222 , through the sensing element  216 . In one embodiment Ohm&#39;s Law (ΔI=V/ΔR) can be used to determine a change in resistance. A lookup table or other correspondence between the change in resistance and the corresponding stress or strain applied to the sensing element can be established as a reference to correlate the change in resistance with an elongation and/or applied force. In one embodiment, the sensing element  216  can have a sheet resistance of 10 3  Ω/sq or less. 
     In one embodiment, the sensing element  216  is constructed of an elastomeric body  218  composed of a combination of elastomer and conductive nanotubes  224 , thereby forming an electrically conductive path along at least one axis between a plurality of wires or electrodes  226 . In one embodiment, the elastomeric body  218  can contain from between 0.2% to 8% by total weight of conductive nanotubes  224 . In one embodiment, the conductive nanotubes  224  are from about 3% to 5% by total weight of the elastomeric body  218 . 
     In one embodiment, the conductive nanotubes  224  are substantially homogenously mixed or combined with an elastomer to form the elastomeric body  218 . The conductive nanotubes  224  can be substantially aligned, such that the longitudinal axis of each nanotube  224  is oriented in the same direction, or the conductive nanotubes  224  can be unaligned, such that the direction of the longitudinal axis of each nanotube  224  is oriented randomly. In one embodiment, the conductive nanotubes  224  can be at least one of single-walled or multi-walled rolled graphene sheet carbon nanotubes (CNTs). For example, in one embodiment, the conductive nanotubes  224  are multi-wall carbon nanotubes, and are approximately 4 nm in diameter by 1 micron or less in length. 
     The elastomer within the elastomeric body  218  can be, for example, an epoxy resin, a silicone resin, a thermoset resin, and ethylenically unsaturated elastomeric resin, a thermoplastic polymer, or a natural rubber. For example, in one embodiment, the elastomer can be a two part, platinum cured liquid silicone rubber. In one embodiment, the elastomeric body  218  can be constructed of a carbon nanotube doped polydimethylsiloxane elastomer. The molecular structure of the elastomer can be imagined as a “spaghetti and meatball” structure, with the meatballs signifying covalent cross-link bonds between individual molecular chains. The elasticity is derived from the ability of the long chains to reconfigure themselves to distribute applied stress. The covalent cross linkages aid the elastomer in returning to its original configuration when the stress is removed. As a result of this extreme flexibility, elastomers can reversibly extend (e.g., retain their elasticity) at least once, and preferably repeatedly without inelastic deformation occurring. 
     In one embodiment, the elastomer can have an elastic range of between 5% to 500% elongation. In one embodiment, the elastomer has a hardness of between 10 and 60 Asker C and an elastic elongation capability of at least 200% elongation. In one embodiment, the elastomeric body  218  has a modulus of elasticity of within 40% of the surface (e.g. the airway assembly  102  and/or torso assembly  104 ) to which it is operably coupled. 
     The sensing element  216  can be coupled to one or more voltage supplies  220  and/or processors  222  (including an ammeter) by a plurality of electrodes  226 . In one embodiment, the electrodes  226  can be in the form of wires for a wire mesh embedded within the elastomeric body  218 . In another embodiment, the electrodes  226  can be an electrically conductive flexible cloth  226  that is either adhered to or embedded within the elastomeric body  218 . For example, in one embodiment, the flexible cloth  226  is at least one of stitched to, adhered to and/or embedded within elastomeric body  218 . In some embodiments, the use of a flexible electrode  226  can reduce drift to maintain the accuracy of sensing element  216  over time, as the connection point between the electrodes  226  and the elastomeric body  218  can degrade with more rigid electrodes. The physiological training system  100  can also include wireless communication between the voltage meter reading the sensing element  216  output and the processor  222 . 
     Referring to  FIGS. 21A and 21B , a sensing element  216  configured to sense a dimensional change in any elastic tube or balloon  228  is depicted in accordance with an embodiment of the disclosure. For example, the sensing element  216  can be at least one of adhered to an outer surface of an elastic tube or balloon  228 , or embedded within the elastic tube or balloon, such that when a change in pressure is experienced surrounding the elastic tube or balloon  228  relative to a quantity of fluid contained within the elastic tube or balloon  228 , the dimensional change of the elastic tube or balloon  228  and the sensing element  216  operably coupled thereto, will affect a change in measurable electrical resistance of the sensing element  216 . 
     In one embodiment, the elastic tube or balloon  228  can be constructed of group of polymers consisting of polyurethanes, polyetherurethanes, polyesterurethanes, silicone, thermoplastic elastomer (C-flex), polyether-amide thermoplastic elastomer (Pebax), fluoroelastomers, fluorosilicone elastomer, styrene-butadiene rubber, butadiene-styrene rubber, polyisoprene, neoprene (polychloroprene), polyether-ether-ketone (PEEK), ethylene-propylene elastomer, chlorosulfonated polyethylene elastomer, butyl rubber, polysulfide elastomer, polyacrylate elastomer, nitrite rubber, a family of elastomers composed of styrene, ethylene, propylene, aliphatic polycarbonate polyurethane, polymers augmented with antioxidants, polymers augmented with image enhancing materials, polymers having a proton (HI) core, polymers augmented with protons (H+), butadiene and isoprene (Kraton) and polyester thermoplastic elastomer (Hytrel), polyethylene, PLA, PGA, and PLEA. 
     The tube or balloon can be part of a tool or device  300  or treatment utilized in a variety of medical procedures in which the tube or balloon  228  or any expandable device is used to create pressure, increase volume restrictions, deliver materials, remove materials, stabilize organs, and the like. Non-limiting examples of such procedures include at least treatment of vascular occlusions, gastric insertions, spinal stabilization, aneurism stabilization, drug delivery implants, joint stabilization, bone stabilization, organ stabilization, delivery of medical devices, infusion devices, penile implants, bladder control devices, intestinal controls, urethral implants, orthopedic implants and the like. 
     Referring to  FIG. 22 , a sensing element  216  operably coupled to piston mechanism  230 , such that the sensing element  216  can be configured to sense a change in pressure, as depicted in accordance with an embodiment of the disclosure. The piston mechanism  230  can include a housing  232  defining a tubular fluid chamber  234  containing fluid therein, and a piston  236  operably coupled to a pressure application surface  238 . The piston  236  can be movable proximal to the first end of the tubular fluid chamber  232  and in contact with the fluid, and can be configured to shift relative to the housing  230  when an external pressure is applied to the pressure application surface  238 , thereby affecting a change in fluid pressure. The sensing element  216 , which can be in the form of a piezoresistive membrane, can be in contact with the fluid, and can be configured to change in electrical resistance one deformed by pressure changes in the fluid. 
     Referring to  FIG. 23 , a sensing element  216  comprising at least a portion of fluid-filled bubble  240 , configured to sense a change in pressure, is depicted in accordance with an embodiment of the disclosure. For example, an elastic membrane  242  can form a sealed pocket containing a quantity of fluid, wherein at least a portion of the elastic membrane  242  includes a sensing element  216 , in the form of a piezoresistive structure. Accordingly, a change in pressure fluid surrounding the elastic membrane  242  relative to the quantity of fluid contained within the sealed pocket of the elastic membrane  242  will affect a dimensional change of the elastic membrane  242  and the sensing element  216 , thereby affecting a change in a measurable electrical resistance of the sensing element  216 . 
     Referring to  FIG. 24 , a sensing element  216  comprising at least a portion of a fluid-filled blister  244  affixed to a solid surface  246 , configured to sense a change in pressure, is depicted in accordance with an embodiment of the disclosure. For example, an elastic membrane  248  can be affixed to a solid support base  246 , such that the elastic membrane  248  forms a sealed pocket  244  with the solid support base  246  to contain a quantity of fluid, wherein at least a portion of the elastic membrane  248  includes a sensing element  216 , in the form of a piezoresistive structure. Accordingly, a change in pressure fluid surrounding the elastic membrane  248  relative to the quantity of fluid contained within the sealed pocket  244  of the elastic membrane  248  will affect a dimensional change of the elastic membrane  248  and the sensing element  216 , thereby affecting a change in a measurable electrical resistance of the sensing element  216 . 
     Referring to  FIG. 25 , a sensing element  216 ′ configured to detect both the magnitude and the relative position of an external force applied to the sensing element  216 ′ is depicted in accordance with an embodiment of the disclosure. In one embodiment, the use of a single sensing element  216 ′ enables the position of an external force to be determined without a need to overlap multiple sensors, thereby significantly reducing the number of electrodes  226  required. 
     In one embodiment, sensing element  216 ′ can include three layers  250 ,  252 ,  254 . First layer  250  can be constructed of a low electrical resistance elastomeric material, and can have a single electrical coupling  256 , in which an electrode  226  can be connected. For example, in one embodiment, first layer  250  can be a silver (Ag) coated nylon fabric. In another embodiment, first layer  250  can be a carbon nanotube doped elastomer. 
     Second layer  252 , can be positioned between the first layer  250  and third layer  254 , and can be constructed of a nonconductive elastomeric material. Second layer  252  can serve as a selectively penetrable insulator, for the selective electrical insulation of first layer  250  from third layer  254 . For example, in one embodiment, second layer  252  can be constructed of a screen or woven elastomeric material. In another embodiment, second layer  252  can be constructed of a porous or perforated material. 
     Third layer  254  can be constructed of a high electrical resistance elastomeric material, and can have, in one embodiment, three electrical couplings  258 A,  258 B and  258 C. For example, in one embodiment, third layer  254  can be constructed of an epoxy resin, a silicone resin, a thermoset resin, and ethylenically unsaturated elastomeric resin, a thermoplastic polymer, or a natural rubber doped with conductive nanotubes from between 0.2% to 8% by total weight. In one embodiment, the third layer  254  can be constructed of a carbon nanotube doped polydimethylsiloxane elastomer. 
     Referring to  FIG. 26 , a plurality of sensing elements  216 ′ can be combined to create a portion of skin, or other organ, configured to cover or be embedded within a portion of physiological training system  100 . In one embodiment, the first layer  250  is positioned on the exterior surface  160  of the torso assembly  104 , so that the electrodes  226  associated with the third layer  254  can be retained below the exterior surface  160 . In one embodiment, the first layer  256  of each of the plurality of sensing elements  216 ′ can be in electrical communication with one another, thereby alleviating the need to electrically couple an electrode  226  to each first layer  256 . In another embodiment, the third layer  254  is positioned on the exterior surface  160  of the torso assembly  104 . 
     Referring again to  FIG. 25 , when an external force is applied to either of the first layer  250  or the third layer  254 , the external force will cause layers  250  and  254  to converge. If the external force is of a sufficient magnitude, the convergence will enable first layer  250  to make electrical contact with third layer  254  through the insulating second layer  252 . 
     In one embodiment, a voltage from a power source can be applied across the electrical couplings of the first layer  250  and the third layer  254 . For example, in one embodiment, a voltage can be applied to any one of electrical couplings  258 A-C of third layer  254 , while electrical coupling  256  of the first layer  250  can serve as a ground, thereby completing the electrical circuit when first layer  250  is in electrical communication with third layer  254 . 
     In one embodiment, the magnitude of the external force can be determined by a measured resistance between electrical couplings  258 A-C and electrical coupling  256 , wherein a lower measured resistance is an indication of a larger magnitude force. A lookup table or other correspondence between resistance and deformation can be established as a reference to correlate the resistance with an applied force magnitude. In some embodiments, the thickness and/or compressibility of second layer  252  can be selected based on a desired magnitude range of the external forces to be detected. For example, a very thin and/or highly compressible second layer  252  can be used to insulate first layer  250  from third layer  254  when measuring small external forces, while a thicker and/or rigid second layer  254  can be used to insulate first layer  250  from third layer  254  when measuring external forces a large magnitude. 
     Referring to  FIGS. 27A-27D , a method of determining the position of the external force is depicted in accordance with an embodiment of the disclosure. For example, in one embodiment, the position of an applied external force can be determined through a process of triangulation. An electrical resistance between electrical coupling  258 A and electrical coupling  258 B can be established as a baseline for understanding the electrical resistance of third layer  254 . When an external force is applied to sensing element  216 ′, and a voltage applied through third layer  254  is electrically grounded to electrical coupling  256  of the first layer  250 , the electricity will naturally follow a path of least resistance. 
     If the voltage is applied sequentially through the electrical couplings  258 A-C in a predefined pattern, a unique resistance should be detectable for each electrical coupling  258 A-C. For example, if a voltage is applied to electrical coupling  258 A, the electricity will follow the path of least resistance between electrical coupling  258 A and the point of contact  260  between third layer  254  and first layer  250 . The resistance  262 A in this electrical circuit can then be measured. As the voltage is sequentially applied through electrical couplings  258 B and  258 C, the corresponding resistances  262 B and  262 C can be measured. The resistances  262 A-C can then be used to determine the relative distance of the point of contact  260  from each of the electrical couplings  258 A-C. 
     Although third layer  254  is depicted as having a triangular shape with three electrical couplings, other shapes, such as a circle, oval, rhombus, or other polygons are envisioned. Other shapes may have greater or fewer electrical couplings. In one embodiment, third layer  254  can be different in shape than first layer  250  and second layer  252 . For example, first layer  250  and second layer  252  can be continuous sheets of fabric, while third layer  254  can be a plurality of triangles or other shapes. 
     Other examples of sensing elements  216  can be found in U.S. Pat. No. 8,850,897 (filed Feb. 16, 2012); U.S. Pat. No. 8,746,075 (filed Aug. 30, 2012); U.S. Patent Publ. No. 2014/0272870 (filed Aug. 30, 2013); U.S. Patent Publ. No. 2015/0177079 (filed Dec. 20, 2013); U.S. Patent Publ. No. 2014/0305226 (filed Apr. 28, 2014); and U.S. Patent Publ. No. 2015/0044656 (filed Sep. 23, 2014), the disclosures of which are hereby incorporated by reference herein. 
     V. Operation 
     In operation, the several components of the physiological training system  100  can be designed to enable modularity. For example, different airway assemblies  102 , each having its own characteristics, can be operably coupled to the torso assembly  104  to provide some variations likely to occur among actual patients. Moreover, the interchange of different airway assemblies can be performed relatively quickly and without the use of tools. Thus, although the torso assembly  104  can, in some embodiments, remain the same, various interchangeable airway assemblies  102  can present variations, based on sex, age, height, weight, various types of trauma, pathological conditions and combinations of the foregoing. 
     For example, in one embodiment, the airway assembly  102  and/or torso assembly  104  can be shaped and sized so as to represent a male or female, an adult, an adolescent, a young child, or a neonatal patient. Additionally, the airway assembly  102  and/or torso assembly  104  can be configured to represent different ethnicities, including different hair and skin colors, as well as one or more physiological aspects characteristic of a particular ethnicity. 
     In some embodiments, the physiological training system  100  can include a chest and upper torso of a patient (such as that depicted in  FIGS. 1 and 15 ). In other embodiments, the physiological training system  100  can be an abridged model, including only the shoulders and upper chest region of a torso (such as that depicted in  FIG. 28 ). In such embodiments, portions of the various organs, for example the lung balloons  154  and/or the epigastric acoustical gurgler  170  can extend from a base of the torso assembly  104 . Embodiments of the present disclosure can be mounted to a base  199  for stability during use. 
     Referring to  FIGS. 29A-E , a method of interchanging the airway assembly  102  is depicted in accordance with an embodiment of the disclosure. Removal of the airway assembly  102  from the torso  186  can begin with removal of the face skin  192 . In one embodiment, the face skin  192  can include one or more neck straps  193  that secure behind the neck portion of torso  186 . The neck straps  193  can be unsecured or loosened. Snaps  194  between the face skin  192  and the torso  186  can be uncoupled. With the neck straps  193  and snaps  194  uncoupled, the face skin  192  can be removed from the torso  186 , thereby exposing the front portion of the skull  188 A and the airway assembly  102 . 
     The skull front portion  188 A can be removed from skull rear portion  188 B by pressing on quick release mechanism  203 , thereby releasing pin  204 . The skull front portion  188 A can then be separated from the skull rear portion  188 B. The skull front portion  188 A can be separated from the airway assembly  102  by pressing on a quick release mechanism  202 , thereby releasing a connection between a pin located in the skull front portion  188 A with a slotted groove  178  defined in the muzzle  108 . The front skull portion  188 A can then be slidably released from the muzzle  108  and the airway assembly  102 . 
     The airway assembly  102  can then be removed from the torso  186  by lifting a portion of the airway assembly  102  proximal to the rear skull portion  188 B. In one embodiment, a friction fitting can be created between lower portions of the airway assembly  102  and the torso  186 . Additionally, various connections between the airway assembly  102  and other components within the torso  186 , such as lung balloons  154  and epigastric acoustic gurgler  170 , can be uncoupled before the airway assembly  102  is removed. 
     The airway assembly  102  can be installed in the torso  186  by reversing the various steps of the above procedure. It should be understood that the individual steps used in the methods of the present teachings may be performed in any order and/or simultaneously, as long as the teaching remains operable. Furthermore, it should be understood that the apparatus and methods of the present teachings can include any number, or all, of the described embodiments, as long as the teaching remains operable. 
     Persons of ordinary skill in the relevant arts will recognize that embodiments may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted. Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended. Furthermore, it is intended also to include features of a claim in any other independent claim even if this claim is not directly made dependent to the independent claim. 
     Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein. 
     For purposes of interpreting the claims, it is expressly intended that the provisions of Section 112, sixth paragraph of 35 U.S.C. are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim.