Abstract:
Injection training devices comprising elements for repeatable and accurate simulation of parenteral injection for training individuals in the administration of one or more medications are provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of U.S. Provisional Application No. 61/365,178, titled “A device that simulates the action of a pre-filled medicine syringe used to teach patients how to operate an actual pre-filled medicine syringe.”, filed Jul. 16, 2010, the disclosure of which is incorporated herein by reference in its entirety. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     NOT APPLICABLE 
     REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
     NOT APPLICABLE 
     BACKGROUND 
     The present invention relates to parenteral injection training devices including devices that simulate an injection time or a resistance of a filled injection device or syringe. 
     Many people take medications one or more times a day to maintain or improve their health. Often, these medications must be delivered by injection or parenterally, that is, taken into the body or administered in a manner other than through the digestive tract. 
     If medications are not taken in the proper manner, individual health may be jeopardized. For example, failure to take a complete injection for treatment of diabetes can result in severe health consequences, including death. Non-compliance with a prescribed dose regimen includes patients who fail to properly inject their medication or only inject a portion of their medication. 
     Further, failure to properly inject medications, particularly in the elderly and the aging population, can result in billions of dollars of unnecessary health care costs because expensive medications can be wasted in the process. That is, an incomplete injection, often leaves expensive or necessary medication in a syringe that is disposed of in the garbage. 
     An injection (often referred to as a “shot” is an infusion method of putting fluid into the body, usually with a hollow needle and a syringe which is pierced through the skin to a sufficient depth for the material to be forced into the body. An injection follows a parenteral route of administration; that is, administered other than through the digestive tract. 
     Some medications must be delivered into the body parenterally. It is common for manufacturer&#39;s of such medications to provide medication for injection in pre-filled syringes. Common syringes, whether pre-filled, or filled by the patient, manual or auto-injection, typically utilize a hollow needle for delivering a liquid medication from the syringe into the body. Theses medications are typically stored in a cylinder having a hollow needle connected to a cylindrical reservoir and having a plunger for forcing the liquid medication from the reservoir, through the needle, into the body. 
     When force is applied to the plunger by mechanical means, such as in an auto-injection syringe or manually, by the person administering the injection, the medicine is forced through the needle into the body. There is a resistance caused by the liquid medicine being forced through a needle. The magnitude of the resistance dictates the time that it takes to force all the medicine through the needle and complete the injection. 
     An auto-injector is a medical device designed to deliver a single dose of a particular, typically life-saving, drug but may be provided for many kinds of drugs. 
     Most auto-injectors operate as spring-loaded syringes. By design, auto-injectors are easy to use and are intended for self-administration by patients, or administration by untrained personnel. The site of injection depends on the drug loaded, but administration typically is into the arm, thigh or the buttocks. These injectors were initially designed to overcome the hesitation associated with self-administration of a needle-based drug delivery device. 
     An auto-injector typically keeps the needle tip shielded prior to injection and also may have a safety mechanism to prevent accidental firing (injection). Injection depth can be adjustable or fixed and a function for needle shield removal may be incorporated. By pressing a button, the syringe needle is automatically inserted and the drug is delivered. Once the injection is completed some auto injectors have visual indication to confirm that the full dose has been delivered. Auto-injectors may contain glass syringes, this can make them fragile and contamination can occur. More recently, companies have been making auto-injectors syringes using plastic to prevent this issue. 
     Patients require training in the operation of a an auto-injector or manual syringe. Known methods of training patients include using an actual auto-injector or manual syringe. These methods are impractical and undesirable because patients would receive multiple or unnecessary injections. While it is possible to use a known injection device without the medication or without a needle, such a simulation would not accurately replicate an actual injection. For example, without liquid medication in the injection device, the patient would inject too quickly because there is no liquid present to resist the force applied to a plunger. Thus, in such a case, a patient would be trained to believe that the injection process is much faster than an actual injection and may, in actual practice, pull the needle out of their skin too early thus receiving an inadequate dose of medication. 
     Some known training devices simply remove liquid medicine from the actual injection device in order to use the empty unit as an injection trainer. As mentioned above, this approach does not accurately simulate the duration or the force required in an actual injection. 
     Novel injection training devices that can be reusable and can accurately simulate an injection time or resistance and methods of training for improving patient compliance in parenteral administration of liquid medications are disclosed herein. 
     SUMMARY OF THE INVENTION 
     In one aspect of the invention an apparatus can comprise a first gear. The gear can have a first set of gear teeth, an inside surface and a central aperture. The apparatus can have a first stationary drum element and a second stationary drum element that mates with the first stationary drum element and the first gear to form an assembly. The assembly can include a cavity formed between the first and second drum elements and the inside surface of the first gear. The cavity can be substantially filled with a damping grease. The device can also comprise a second gear having a second set of gear teeth. The first and second sets of gear teeth can be fitted to articulate with each other. The device can include an assembly carrier. The carrier comprising one or more supports for mounting the assembly, wherein the one or more supports prevent rotation of the stationary drum elements while said first gear rotates thereby engaging the first set of gear teeth with the second set of gear teeth at a predetermined speed. 
     In one embodiment of the invention, the first gear can be substantially circular. 
     In another embodiment of the invention, the second gear can be substantially linear. 
     In some embodiments of the invention, the damping grease comprises silicone. 
     In other embodiments of the invention, the damping grease can comprise dimethylpolysiloxane. 
     In certain embodiments of the invention, the damping grease can have a viscosity between about 900,000 cps and about 1,100,000 cps at 25 degrees C. 
     In other embodiments of the invention, the gear can have eighteen circumferential teeth located about twenty degrees apart. 
     In yet other embodiments of the invention, the assembly carrier can be actuated by at least one spring element. 
     In some embodiments of the invention, the at least one spring element can be stainless steel. 
     In certain embodiments of the invention, actuating the carrier can produce at least one audible user alert sound. 
     In certain embodiments of the invention, actuating the carrier can produce a first and a second audible user alert. The first alert can indicate that a simulated injection has started. The second alert can indicate that the simulated injection is complete. 
     In some embodiments of the invention, the first alert and the second alert can occur at a predetermined time interval. 
     In some embodiments, the predetermined time interval can be between about 5 seconds and about 15 seconds. 
     In yet other embodiments the predetermined time interval can be between 3 seconds and 15 minutes. 
     In another aspect of the invention a method can comprise the steps of: (a) actuating a carrier assembly; the carrier assembly comprising one or more supports for mounting a drum assembly, the drum assembly having a first gear; (b) generating a first user alert sound; (c) rotating the first gear about the drum assembly from an initial position to a final position in a predetermined time; and (d) generating a second user alert sound. 
     In certain embodiments of this aspect of the invention, the method can further including the step of (e) reloading, wherein the first gear is moved from the final position to the initial position by application of a reset force. 
     In certain embodiments of the invention, the reset force can be between about 13N and about 18N. 
     In yet other embodiments of the invention, the method can comprise the further steps of (a) actuating the carrier assembly; the carrier assembly can comprise one or more supports for mounting a drum assembly, the drum assembly can have a first gear (b) generating the first user alert sound (c) rotating the first gear about the drum assembly from the initial position to the final position in the predetermined time; and (d) generating the second user alert sound. 
     In some embodiments of the invention, the predetermined time can be between about 3 seconds and about 30 seconds. 
     In other embodiments of the invention, the predetermined time can be between about 5 seconds and about 15 seconds. 
     In another aspect of the invention, an apparatus can comprise a first gear having a first set of gear teeth, an inside surface and a central aperture. A first stationary drum element and a second stationary drum element that mates with the first stationary drum element and the first gear form an assembly. The assembly can include a cavity formed between the first and second drum elements and the inside surface of the first gear. The cavity can be substantially filled with a damping grease. A second gear can have a second set of gear teeth. The first and second sets of gear teeth can be fitted to articulate with each other. An assembly carrier can comprise one or more supports for mounting the assembly on a syringe housing. The one or more supports can prevent rotation of the stationary drum elements while the first gear rotates and can thereby engage the first set of gear teeth with the second set of gear teeth. 
     In one embodiment of this aspect of the invention, the first gear can be substantially circular. 
     In certain embodiments of the invention, the second gear can comprise a plunger. 
     In some embodiments of the invention, the second gear can be substantially linear. 
     In certain embodiments of the invention, the damping grease can comprise a polymeric material. 
     In certain embodiments of the invention, the polymeric material can comprise dimethylpolysiloxane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts an isometric exploded view of an injection training device according to one embodiment of the present invention. 
         FIGS. 2A through 2E  depict several views of a barrel element included in the injection training device of  FIG. 1 . 
         FIG. 3  depicts an isometric view of an interlock element included in the injection training device of  FIG. 1 . 
         FIGS. 4A through 4C  depict several views of a carrier element included in the injection training device of  FIG. 1 . 
         FIG. 5  depicts an isometric view of a plunger element included in the injection training device of  FIG. 1 . 
         FIGS. 6A and 6B  depict several views of a drum and gear assembly included in the injection training device of  FIG. 1 . 
         FIGS. 7A and 7B  depicts several views of cap and stem elements included in the injection training device of  FIG. 1 . 
         FIGS. 8A and 8B  depict several views of another embodiment of the present invention comprising various elements included therein. 
         FIG. 9  depicts test results of average delivery time vs. actuation cycle by sample number for an embodiment of the present invention. 
         FIG. 10  depicts test results of trigger button actuation force vs. sample number for an embodiment of the present invention. 
         FIG. 11  depicts test results of average reset force vs. actuation cycle by sample number for an embodiment of the present invention. 
         FIGS. 12A and 12B  depict test results of reset force vs. reset speed for two samples of an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the terms medicine or medication refers to any material that can be injected into the human body. The terms medicine or medication may be singular or plural and are used interchangeably herein. 
     As used herein, the terms syringe or injector refer to any device capable of injecting a medicine into the human body. 
     As shown in  FIG. 1 , injection simulator assembly  100  in accordance with one embodiment of the present invention includes a top case  1  and a bottom case  2 . The top and bottom cases include apertures  1 A and  2 A and can mate through the use of interlocking tabs  2 C and slots (not shown) located on the perimeter of both the top case and bottom case, respectively. Top case  1  includes a second aperture  1 B for mounting trigger button  3 . 
     Top case  1  and bottom case  2  can be snapped together to lock the assembly and form an enclosure for holding and locating the internal components of the device as described below. When the case is assembled, apertures  1 A and  2 A are aligned such that an indicator can be viewed through the assembled case as will be discussed below. The top and bottom cases can include ribs  1 C and other internal means (not shown), that can be utilized to trap components within the case when the top and bottom cases are snapped together. The top case comprises a rear wall  2 E for closure of the assembly and for containing spring element  8  as discussed below. 
     Components of the present invention can be fabricated from polymers or other structural materials which will be known to one skilled in the art of manufacturing. Like-wise, snap fit designs of many types and manufacturing processes such as, for example, injection molding, compression molding, casting, or machining are well known to those skilled in the art of polymer component manufacturing. 
     In this embodiment, a trigger button  3  is mounted to top case  1 . Trigger button  3  includes aperture  3 A and latch attachment  7  which is mounted to substantially perpendicular to trigger button  3  by screws  14 . Trigger button  3  is mounted to top case  1  such that when assembled, trigger button  3  can be depressed in the direction of bottom case  2  wherein the latch attachment  7  can lock or can release the injection simulator. 
     Trigger button  3  and latch attachment  7  can be fabricated from a polymer or other structural material well known in the arts, by for example, injection molding. Screws  14  can be fabricated using materials and manufacturing processes that are well known in the art of manufacturing, such as steel. 
     As shown in  FIGS. 2A-2E , nose barrel  6  can be mounted within top case  1  and bottom case  2 . In this embodiment, nose barrel  6  is cylindrically shaped. The nose barrel comprises a front end and a back end, apertures  6 A,  6 B,  6 C,  6 D, and tabs  6 E,  6 F,  6 G. Nose barrel  6  includes flange  6 H and a contoured nose circularly disposed around the perimeter of the front end  61 . 
     As shown in  FIG. 3 , interlock  4 , having tabs  4 A,  4 B can be snap mounted to barrel  6  near the front end of the barrel by disposing tabs  4 A and  4 B within apertures  6 A and  6 B. 
     As shown in  FIG. 1 , inner lock  5 , having tabs  5 A,  5 B can be slideably mounted on barrel  6  by a utilizing a split ring snap configuration such that tabs  5 A,  5 B abut tabs  4 A,  4 B respectively. Inner lock  5  is mounted to barrel such that it is substantially perpendicular to the longitudinal axis of the barrel wherein the inner lock mates in proximity to trigger button aperture  3 A. 
     When top case  1  and bottom case  2  are mated, barrel  6  can be mounted longitudinally within the mated case halves, such that flange  6 H is trapped, while tabs  6 E and  6 F lockably engage top case  1  and tab  6 G lockably engages bottom case  2 . It is important to recognize that when barrel  6 , inner lock  5  and interlock  4  are mated and assembled with top case  1  and bottom case  2 , barrel  6  is stationary while interlock  4  and inner lock  5  are slidably mounted. As discussed below, this feature allows for the training device to be triggered only when the interlock  4  is depressed by a user. 
     A plurality of geometries, barrel configurations, and individual component configurations are contemplated within the scope of the present invention. For example, the barrel  6  can be rectangular or the trigger button  3  can be square. 
     As depicted in  FIGS. 4A-4C , carrier  10  comprises cavity  10 A, flange  10 B, and tabs  10 C,  10 D, and  10 E. Carrier  10  includes a forward end  10 F and a rearward end  10 G. The carrier can be cylindrical and generally U shaped. The rearward end  10 G includes a cavity for containing an inner spring element  9  when it is mated with spring cap  12  as shown in  FIG. 1 . 
     The assembly of spring cap  12  with the rearward end  10 G creates a cavity for containing inner spring element  9  and an outer diameter for engaging outer spring element  8 . Flange  10 B and tabs  10 C,  10 D and  10 E engage features in barrel  6  and trigger button  3  such that the carrier is slideably mounted within the closed case (i.e. when top and bottom cases  1  and  2  are in an assembled position). 
     Carrier  10  has mounting arms  10 F for mounting damping gear assembly  13  as discussed below. 
     Carrier  10  can be molded or fabricated from any suitable durable structural material, for example, a polymeric material. Suitable materials and manufacturing methods will be well known to those skilled in the art of manufacturing engineering polymers. 
     In this particular embodiment, as shown in  FIG. 5 , plunger  11  comprises front section  11 A, central section  11 B, gear track section  11 C and a rear section  11 D. As shown in  FIG. 5 , the front section  11 A can be tapered and includes an internal feature to simulate the appearance of a hypodermic needle  11 E. The central section  11 B can be a color, such as yellow, for indicating to the user that the device has been triggered and the simulated injection is complete  11 F. During operation, the plunger  11  can translate within the top and bottom case from a first locked and loaded position to a second released injected position wherein section  11 B is visible to the user as discussed above. 
     The gear track section  11 C of plunger  11  accommodates mounting damping gear assembly  13  ( FIGS. 6A-6B ). Assembly  14  is mounted to carrier  10  by mounting arms  10 F. 
     As shown in  FIGS. 6A-6B , in this particular embodiment, damping gear assembly  14  comprises a substantial circular gear  20  having a central aperture, a first stationary drum  24 , a second stationary drum  28  and a damping fluid or grease  32 . In this embodiment the circular gear comprises  18  circumferential teeth  21  located about 20 degrees apart. The circumferential gear teeth  21  are designed to mate with gear teeth  11 G located along a portion of gear track section  11 C ( FIG. 5 ). This feature allows the gear assembly to disengage from the gear track and contact flange  11 D to create an audible sound when an injection cycle is complete. 
     The first and second stationary drums fit together within the central aperture of gear  20  to create a cavity that can be filled with damping grease  32 . The gear is free to rotate around the stationary drums. The damping grease in the cavity between the stationary drums and the gear defines a consistent coefficient of friction between the moving parts of the damping gear assembly. This novel mechanism results in a controllable, smooth, predictable and repeatable motion of the device when moving between a first locked and loaded position and a second released injected position. 
     As mentioned above, the solid components of the present invention can be manufactured using materials and molding methods known to one of skill in the art of manufacturing. The damping grease  32  can be a dimethylpolysiloxane comprising inorganic fillers. One such grease is ASA DG302, manufactured by Asahi of Tokyo, Japan. The speed of the injection device can be modified to suit the needs of a user by, for example, the use of different materials, different gears, different fluids or greases, or different spring elements. 
     Inner spring element  9  can be mounted on plunger rear section  11 D. As explained above, inner spring element can be contained in a longitudinal direction along the long axis of the device between plunger flange  11 H and carrier  10 . The assembly of spring cap  12  with the rearward end  10 G ( FIG. 1 ) creates a cavity for containing inner spring element  9  and an outer diameter for holding outer spring element  8  which can be mounted longitudinally between the spring cap  12  and carrier  10  assembly and rear the rear wall  1 E of the top cap when assembled. 
     Spring elements  8  and  9  may be metallic or non-metallic. A preferred material is stainless steel, however, selection of the material and spring element design will depend on the forces required for each spring to function in accordance with a particular design. The spring elements may be designed to provide more force or less force, thus allowing for a multitude of designs for simulating different injection times and resistances while allowing for reuse and ease of reloading. 
     As shown in  FIGS. 7A-7B , cap  15  includes stem element  16 . Cap  15  can include grippers  15 A. The grippers and the cap geometry are fitted to frictionally mount to the end of the device to protect the mechanism and simulate the look and feel of an actual auto-injection syringe. Further, the stem element is sized such that when the device is discharged, the stem element can be used to push the plunger back into a locked and loaded position to reset the device for reuse. 
     The geometry depicted in this embodiment of the present invention is one of many configurations that can utilize the invention disclosed herein. For example, it is contemplated that the gear track can be substantially linear, circular or spiral for use in various embodiments of the invention. 
     In operation, a user can remove the cap. The user can observe thorough the apertures in the top and bottom cases that the device is in a loaded or ready position, that is, the device has been reset using the cap to move the plunger into a locked or loaded position. In this loaded position, both spring elements  8  and  9  are compressed, and the damping gear assembly  13  engages a portion of the teeth on the plunger track. When the user depresses the interlock against a potential injection site, such as and arm or thigh, the trigger button can be depressed by the user. If the interlock is not depressed, the training device will remain locked and pressing the trigger will not initiate a training cycle. This feature prevents accidental “injection” and closely simulates actual auto-injectors that are commonly used in the industry. 
     When the user depresses the trigger button, the spring elements are released and are thus free to act against the plunger or carrier. Depressing the trigger button creates an audible click or snapping sound that can alert a user that the injection process has been initiated. The user can also see movement of the plunger through the apertures in the top and bottom cases. 
     Because the drum assembly is stationary and has a substantially constant frictional resistance, the spring forces cause the plunger to move in the direction of the interlock and the gear to rotate along the track on the carrier. When the gear rotates beyond the carrier track teeth, the resistance decreases such that the spring forces acting on the plunger causes the gear to contact the plunger flange, thus creating a second audible click which indicates that the injection process has been completed. 
     As discussed above, the user can also see that a colored, for example, a yellow portion of the plunger is now visible through the apertures in the top and bottom cases. Thus, the user can confirm both audibly or visually when the simulated injection has started and when it has completed. 
     The time between the start of the simulated or training injection and the completion of the injection can be modified to cover a range of injection times. The injection time required will depend on the specific medication injected and the medical specifications required for such an injection. Using the training device, the user can repeat the process as often as necessary until the user is trained before administration of medication with an actual syringe or auto-injector. It is contemplated that the injection time can be between about 1 second and about 15 minutes. 
     In this way, a patient will have less of a tendency to inject a medication too quickly, too slowly or not completely, all of which can be dangerous or costly to the patient. For example, removal of a syringe before completion of the actual injection may cause the patient to receive a lower dosage than necessary and waste medicine that may remain in the syringe or may squirt out of the syringe but not into the body. 
     In another embodiment of the invention, as shown in  FIGS. 8A-8B , the simulation device may be adapted to simulate a manual injection rather than an automated injection. 
     In this embodiment of the present invention, injection simulator  200  comprises syringe body  204 . The body includes cavity  208  adapted to accept plunger  212 . The body can include a tapered region  216  to accept a simulated needle  220 . The plunger  212  has a top end  224  having an injection tab and a bottom end  228  adapted to fit the body. The plunger comprises a linear gear track  232  disposed along a portion of the plunger. 
     Injection training device  200  includes housing  240 . Damping gear assembly  244  is mounted within the housing an can be connected to syringe body flange  248 . The housing can be a separate component or molded with the body as one or more pieces. As shown in  FIG. 8A-8B , in this particular embodiment, damping gear assembly  244  comprises a substantial circular gear  250  having a central aperture, a first stationary drum, a second stationary drum and a damping fluid or grease substantially similar to damping assembly  13  as described above in another embodiment of the present invention and depicted in  FIGS. 1 ,  6 A and  6 B. The circular gear teeth  228 , are designed to mate with linear gear track  232 . 
     The first and second stationary drums fit together within the central aperture of circular gear  244  to create a cavity that can be filled with a damping grease. The circular gear is free to rotate about the stationary drums. The damping grease in the cavity between the stationary drums and the circular gear defines a consistent coefficient of friction between the moving parts of the damping gear assembly. This mechanism results in a smooth, predictable and repeatable motion of the device when moving between a first pre-injection position and a second post-injection position. 
     As mentioned above, the components can be manufactured using materials and manufacturing methods known to one of skill in the art of manufacturing. The damping grease can be a dimethylpolysiloxane comprising inorganic fillers. 
     The speed of the injection device or the resistance of the plunger to an injection force can be modified to suit the needs of a user by, for example, the use of different gear sizes, different fluids or greases, or different plunger materials. 
     In practice, when the user depresses the plunger, the plunger moves within the syringe body. The damping gear assembly controls the rate of motion and acts to inform or train the user as to the look and feel of an actual injection. Because the device may be reset by pulling the plunger in the opposite direction of the injection direction, the user can practice injection at a predetermined rate until the user is trained. 
     For the purpose of patient training and compliance, this device is far superior to using an actual syringe because an actual empty syringe does not provide resistance similar to an actual injection. Further, many syringes are designed for one time use so that the plunger components may wear out after one or more injections and would fail to provide accurate simulation of an injection in which a fluid usually fills all or part of the syringe body. 
     Ease and consistency of use are important factors in achieving patient compliance, particularly for very old or very young patients who may not have sufficient strength to operate a training device. 
       FIG. 9  depicts a graphical plot of the average delivery time for one particular embodiment of the present invention, that is, the time between the start of the simulated injection and the end of the injection. Ten rounds of testing were performed, each round having ten actuation cycles. The range of average delivery times was between about 4 seconds and about 11 seconds. The average delivery time can be designed to meet a range of delivery time requirements, depending on the needs of a particular user. 
       FIG. 10  depicts the average button actuation force vs. actuation cycle. It can be seen that between test “firings” 56-100 the force required to actuate the device was in the range of 3-5 N. This level of force represents an easily achieved and repeatable level of force for many types of patients. 
       FIG. 11  depicts the average reset for vs. actuation cycle for ten rounds of testing in which ten actuations were performed for each round. The reset force was generally in the range of 20-24 N as shown in the graph. 
     As shown in  FIGS. 12 and 12A , the compressive load is plotted for resetting the device at 2 different speeds. Two rounds of testing were conducted on individual samples at 0.167 inches/second and at 0.083 inches/second, respectively ( FIGS. 12A and 12B ). The mean reset force under these conditions was about 18N at 0.167 inches/second and 16N at 0.083 inches/second. Again, the results indicate that the training device reset force is consistent, repeatable and manageable for a wide range of patients. As expected, resetting the device at a faster rate requires slightly more force. 
     As will also be appreciated, a significant benefit of the present invention includes the repeatability of the device for training patients to inject one or more medicines and the ability to change the design to accommodate different injection speeds. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the disclosure herein.