Patent Publication Number: US-2021187309-A1

Title: Transcutaneous energy transfer system including alarm

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/951,230, filed Dec. 20, 2019, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure generally relates to a transcutaneous energy transfer system that includes an alarm and an implantable device that is implantable within a patient. 
     BACKGROUND 
     Transcutaneous energy transfer (TET) systems are used to supply power to devices such as pumps implanted within a human body. A magnetic field generated by a transmitting coil outside the body can transmit power across a cutaneous (skin) barrier to a magnetic receiving coil implanted within the body. The receiving coil can then transfer the received power to the implanted pump or other implantable devices and to one or more power sources (e.g., batteries) implanted within the body to charge the power source. Such systems efficiently generate and wirelessly transmit a sufficient amount of energy to power one or more implanted devices while maintaining the system&#39;s efficiency and overall convenience of user. 
     TET systems can be utilized, e.g., with ventricular assist devices (VADs) that include implantable blood pumps that are used when a patient&#39;s heart is unable to provide adequate circulation to the patient&#39;s body, thereby leading to heart failure. Such patients may use a VAD while awaiting a heart transplant or for longer periods of time. Further, some patients may use a VAD while recovering from heart surgery. Such VADs typically include implanted power sources that can be charged, e.g., by a TET system. 
     SUMMARY 
     The techniques of this disclosure generally relate to various embodiments of a transcutaneous energy transfer system and a method of using such system. The system can include one or more controllers that are adapted to provide a charging alarm to at least one of a patient, caregiver, or clinician that indicates that charging of an internal power source of the system that is implanted within the patient&#39;s body should commence. Such charging of the internal power source should resume before the power source is depleted and an implantable device such as a blood pump that is electrically connected to the internal power source ceases to operate. 
     In one example, aspects of this disclosure relate to a transcutaneous energy transfer system that includes an internal component adapted to be disposed within a body of a patient. The internal component includes an internal coil, an internal power source electrically connected to the internal coil and adapted to receive power from the internal coil, an implantable device electrically connected to the internal power source, and internal circuitry including an internal transceiver adapted to send and receive signals representative of one or more parameters relating to operation of the internal component. The system also includes an external component adapted to be disposed outside the body of the patient. The external component includes an external coil, an external power source electrically connected to the external coil, and external circuitry electrically connected to the external power source and the external coil. The external circuitry includes an external transceiver and an external controller, where the external transceiver is adapted to communicate with the internal transceiver and send and receive the signals representative of the one or more parameters relating to operation of the internal component. Further, the external controller is electrically connected to the external transceiver and adapted to determine whether the internal coil is electromagnetically disconnected from the external coil. If the internal coil is electromagnetically disconnected from the external coil, then the external controller is adapted to determine a reconnection time threshold based upon at least one of a power transfer efficiency value between the internal coil and the external coil, a charge state of the internal power source, or a power consumption value of the implantable device; and output a charging alarm if a time interval when the internal coil is electromagnetically disconnected from the external coil exceeds the reconnection time threshold. 
     In another example, aspects of this disclosure related to a ventricular assist device that includes a transcutaneous energy transfer system. The transcutaneous energy transfer system includes an internal component adapted to be disposed within a body of a patient. The internal component includes an internal coil, an internal power source electrically connected to the internal coil and adapted to receive power from the internal coil, an implantable device electrically connected to the internal power source, and internal circuitry including an internal transceiver adapted to send and receive signals representative of one or more parameters relating to operation of the internal component. The system also includes an external component adapted to be disposed outside the body of the patient. The external component includes an external coil, an external power source electrically connected to the external coil, and external circuitry electrically connected to the external power source and the external coil. The external circuitry includes an external transceiver and an external controller, where the external transceiver is adapted to communicate with the internal transceiver and send and receive the signals representative of the one or more parameters relating to operation of the internal component. Further, the external controller is electrically connected to the external transceiver and adapted to determine whether the internal coil is electromagnetically disconnected from the external coil. If the internal coil is electromagnetically disconnected from the external coil, then the external controller is adapted to determine a reconnection time threshold based upon at least one of a power transfer efficiency value between the internal coil and the external coil, a charge state of the internal power source, or a power consumption value of the implantable device; and output a charging alarm if a time interval when the internal coil is electromagnetically disconnected from the external coil exceeds the reconnection time threshold. 
     In another example, aspects of this disclosure relate to a method of outputting a charging alarm for a transcutaneous energy transfer system, including determining whether an internal coil of an internal component of the transcutaneous energy transfer system is electromagnetically disconnected from an external coil of an external component of the system. If the internal coil is electromagnetically disconnected from the external coil, then the method includes determining a reconnection time threshold based upon at least one of a power transfer efficiency value between the internal coil and the external coil, a charge state of an internal power source of the internal component that is electrically connected to the internal coil, or a power consumption value of an implantable device of the internal component that is electrically connected to the internal power source. The method further includes outputting the charging alarm if a time interval when the internal coil is disconnected from the external coil exceeds the reconnection time threshold. 
     The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view of one embodiment of a transcutaneous energy transfer system. 
         FIG. 2  is a schematic front view of an external component of the transcutaneous energy transfer system of  FIG. 1 . 
         FIG. 3  is a schematic front view of an internal component of the transcutaneous energy transfer system of  FIG. 1  disposed within a body of a patient. 
         FIG. 4  is a flowchart of one embodiment of a method outputting a charging alarm for a transcutaneous energy transfer system. 
     
    
    
     DETAILED DESCRIPTION 
     The techniques of this disclosure generally relate to various embodiments of a transcutaneous energy transfer system and a method of using such system. The system can include one or more controllers that are adapted to provide a charging alarm to at least one of a patient, caregiver, or clinician that indicates that charging of an internal power source of the system that is implanted within the patient&#39;s body should commence. Such charging of the internal power source should resume before the power source is depleted and an implantable device such as a blood pump that is electrically connected to the internal power source ceases to operate. 
     Patients that have implantable devices such as ventricular assist devices (VADs) or left ventricular assist devices (LVADs) may receive notifications from such devices that power sources such as batteries contained within the devices are nearing depletion or are depleted. Upon receiving such notifications, the patient can recharge the power sources using any suitable technique or techniques, e.g., a transcutaneous energy transfer (TET) system. Notifications that are provided by a controller or other electronic component disposed within the implantable device may, however, be difficult for the patient to hear or detect. Further, external components that are associated with the implantable device may be disposed in a location where alarms provided by such external components can be difficult if not impossible for the patient to detect. 
     One or more embodiments of a TET system described herein can provide one or more alarms or notifications to at least one of a patient, caregiver, or clinician associated with the patient that indicate the critical need to initiate recharging of the implantable device before the implanted power source is depleted, thereby potentially leading to diminished capabilities of the implantable device. 
       FIG. 1  schematically illustrates a TET system  10 . The system  10  includes an internal component  12  adapted to be disposed within a body  2  of a patient and an external component  14  adapted to be disposed outside the body of the patient. The internal component  12  includes an internal coil  16 , an internal power source  18  electrically connected to the internal coil and adapted to receive power from the internal coil, and an implantable device  20  electrically connected to the internal power source. The internal component  12  also includes internal circuitry  22  that includes an internal transceiver  24  adapted to send and receive signals representative of one or more parameters relating to operation of the internal component. 
     Further, the external component  14  includes an external coil  26 , an external power source  30  electrically connected to the external coil, and external circuitry  36  electrically connected to the external power source and external coil. The external circuitry  36  includes an external transceiver  28  and an external controller  32 . The external transceiver  28  is adapted to communicate with the internal transceiver  24  and send and receive the signals representative of one or more parameters relating to operation of the internal component  12 . Further, the external controller  32  is electrically connected to the external transceiver  28 . As is further described herein, the external controller  32  is adapted to determine whether the internal coil  16  is electromagnetically disconnected from the external coil  26 . If the internal coil  16  is electromagnetically disconnected from the external coil  26 , then the external controller  32  is adapted to determine a reconnection time threshold based upon at least one of a power transfer efficiency value between the internal coil and the external coil, a charge state of the internal power source  18 , or a power consumption value of the implantable device  20 . Further, the external controller  32  is also adapted to output a charging alarm if a time interval when the internal coil  16  is electromagnetically disconnected from the external coil  26  exceeds the reconnection time threshold. 
     The internal component  12  of the system  10  can include any suitable elements or components that are disposed within the body  2  of the patient. One or more components of the internal component  12  can be disposed within a housing  52  ( FIG. 3 ) as is described, e.g., in U.S. Patent Publication No. 2015/0290373 A1 to Rudser et al. and entitled TRANSCUTANEOUS ENERGY TRANSFER SYSTEMS. In one or more embodiments, one or more of the elements of the internal component  12  can be disposed independently from the housing  52  within the body  2  of the patient. For example, in one or more embodiments, one or more of the internal coil  16 , the power source  18 , the transceiver  24 , and optional controller  34  can be disposed within the housing  52 , and the implantable device  20  can be disposed outside of the housing independent from the other components but electrically connected to one or more of such components disposed within the housing. 
     As mentioned herein, the internal component  12  includes the internal coil  16  that is electrically connected to the power source  18  using any suitable technique or techniques. The internal coil  16  can include any suitable coil or device that can be electromagnetically connected (e.g., inductively connected) to the external coil  26  through an electromagnetic field to transfer energy or power wirelessly therebetween. 
     Electrically connected to the internal coil  16  is the internal power source  18 . The internal power source  18  is adapted to receive power from the internal coil  16 . The internal power source  18  can include any suitable power source or combination of power sources. In one or more embodiments, the internal power source  18  can include a lithium-ion cell/battery housed within a titanium or medical-grade plastic casing. In one or more embodiments, the internal power source  18  can include any suitable storage capacity. In one or more embodiments, the internal power source  18  is adapted to store any suitable charge needed for the system to operate as desired. 
     The internal power source  18  is electrically connected to the implantable device  20  to power the device. The internal power source  18  is also electrically connected to the internal circuitry  22  using any suitable technique or techniques. In one or more embodiments, energy received at the internal coil  16  is stored in the internal power source  18 , provided to the implantable device  20 , or both, via the internal circuitry  22 . In one or more embodiments, energy stored at the internal power source  18  can be provided to the implantable device  20  via the internal circuitry  22 . 
     Electrically connected to the internal power source  18  is the implantable device  20 . The implantable device  20  can include any suitable implantable device, e.g., an implantable blood pump. In one or more embodiments, the implantable device  20  can include a pump such as for use in pumping blood as a ventricular assist device (VAD″, for example. The implantable device  20  can include controlling circuitry to control, for example, a pump. 
     The implantable device  20  receives power from internal power source  18 , the internal coil  16 , or both. The implantable device  20  can have any suitable power requirements. Such power requirements can depend upon the nature of the device and may vary during operation of such device. For example, in one or more embodiments, systems for use with a typical VAD can be adapted to transmit at least 5 watts, at least 10 watts, at least 15 watts, or at least 20 watts of continuous power to the device  20 . 
     The internal component  12  also includes internal circuitry  22 . Such circuitry  22  can be electrically connected to at least one of the primary coil  16 , the internal power source  18 , or the implantable device  20  using any suitable technique or techniques. Further, such circuitry  22  can include any suitable device or components. For example, in one or more embodiments, internal circuitry  22  can include at least one of control circuitry (e.g., optional controller  34 ), RF telemetry (e.g., transceiver  24 ), voltage regulator circuitry, or power source selection circuitry as is described, e.g., in U.S. Patent Publication No. 2015/0290373 A1. In one or more embodiments, internal circuitry  22  can also include an optional controller  34  electrically connected to at least one of the transceiver  24 , power source  18 , or device  20 . The controller  34  can include any suitable controller or controllers, e.g., controller  32  of external component  14  as is further described herein. 
     The transceiver  24  can include any suitable transceiver or transceivers that are adapted to send and receive signals representative of one or more parameters relating to operation of the internal component  12 . The one or more parameters can include any suitable information regarding the internal component  12 , e.g., charge state of the internal power source  18 , operation state of the implanted device  20 , operation state of the internal coil  16 , thermal state of the internal component, etc. 
     The external component  14  of system  10  is adapted to be disposed outside the body  2  of the patient and can include any suitable devices or components for providing energy to the internal component  12 . One or more of the devices or components of the external component  14  can be disposed within a housing  46 . In one or more embodiments, one or more devices or components of the external component  14  can be disposed outside of or on the housing  46 . 
     The external coil  26  of the external component  14  can include any suitable coil or coils, e.g., the same coil described herein regarding internal coil  16 . In one or more embodiments, the external coil  26  can be disposed within a housing  44  as is further described herein. The external coil  26  can be of flexible or rigid construction and may have a size determined for optimal coupling to the internal coil. In one or more embodiments, the external coil  26  may be incorporated into a far-field wireless transmission network where the internal coil  16  is equipped to receive sufficient energy in this modality to affect the recharge of the implantable power source  18 . 
     The external component  14  can further include one or more external power sources that are electrically connected to the external coil  26  and external circuitry  36 . For example, the external component  14  can include external power source  30  that is electrically connected to the external coil  26  and external circuitry  36 . In one or more embodiments, the external power source  30  can include a rechargeable battery. The external power source  30  can include any suitable power source or sources, e.g., the same power sources described herein regarding internal power source  18 . In one or more embodiments, the external component  14  can also include a building power source  38  (such as AC power, or converted DC power, supplied from an electrical outlet in a building). In one or more embodiments, the external power source such as building power source  38  can include an AC to DC power converter. The external power sources  30 ,  38  can supply any suitable input voltage, e.g., at least about 20V and no greater than about 250V. 
     The external circuitry  36  of the external component  14  is electrically connected to the external power source  30 ,  38  and the external coil  26 . Such circuitry  36  can include any suitable elements or components, e.g., the same elements or components described herein regarding internal circuity  22  of internal component  12 . The external circuitry  36  includes the transceiver  28  and the external controller  32 . 
     The external transceiver  28  of the external component  14  is adapted to communicate with the internal transceiver  24  and send and receive the signals representative of the one or more parameters relating to operation of the internal component. In one or more embodiments, the external transceiver  28  can be adapted to send and receive signals representative of one or more parameters relating to operation of the external component. The external transceiver  28  can include any suitable transceiver or transceivers, e.g., the same transceivers described herein regarding internal transceiver  24 . 
     Electrically connected to the external transceiver  28  is the external controller  32 . The external controller  32  can include any suitable controller or controllers. In one or more embodiments, the external controller  32  can include one or more processors, memory, input devices, output devices, sensors, power sources, etc. 
     Further, the external controller  32  can includes data storage that allows for access to processing programs or routines and one or more other types of data that may be employed to carry out the exemplary techniques, processes, and algorithms of the present disclosure. For example, processing programs or routines may include programs or routines for performing computational mathematics, matrix mathematics, Fourier transforms, compression algorithms, calibration algorithms, image construction algorithms, inversion algorithms, signal processing algorithms, normalizing algorithms, deconvolution algorithms, averaging algorithms, standardization algorithms, comparison algorithms, vector mathematics, analyzing optical sensor data, analyzing laser singulation settings, controlling an emitting device, detecting substrate surface defects, or any other processing required to implement one or more embodiments as described herein. 
     In one or more embodiments, the external controller  32  can utilize one or more computer programs executed on programmable computers, such as computers that include, for example, processing capabilities (e.g., microcontrollers, programmable logic devices, etc.), data storage (e.g., volatile or non-volatile memory and/or storage elements), input devices, and output devices. Program code and/or logic described herein may be applied to input data to perform functionality described herein and generate desired output information. The output information may be applied as input to one or more other devices and/or processes as described herein or as would be applied in a known fashion. 
     The programs used to implement the processes described herein may be provided using any programmable language, e.g., a high-level procedural and/or object orientated programming language that is suitable for communicating with a computer system. Any such programs may, for example, be stored on any suitable device, e.g., a storage media, readable by a general or special purpose program, computer or a processor apparatus for configuring and operating the computer when the suitable device is read for performing the procedures described herein. 
     In view of the above, it will be readily apparent that the functionality as described in one or more embodiments according to the present disclosure may be implemented in any manner as would be known to one skilled in the art. As such, the computer language, the computer system, or any other software/hardware that is to be used to implement the processes described herein shall not be limiting on the scope of the systems, processes or programs (e.g., the functionality provided by such systems, processes or programs) described herein. 
     The techniques described in this disclosure, including those attributed to the systems, or various constituent components, may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, various aspects of the techniques may be implemented by the external controller  32 , which may use one or more processors such as, e.g., one or more microprocessors, DSPs, ASICs, FPGAs, CPLDs, microcontrollers, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components, image processing devices, or other devices. The term “processing apparatus,” “processor,” or “processing circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry. Additionally, the use of the word “processor” may not be limited to the use of a single processor but is intended to connote that at least one processor may be used to perform the exemplary techniques and processes described herein. 
     Such hardware, software, and/or firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. In addition, any of the described components may be implemented together or separately as discrete but interoperable logic devices. Depiction of different features, e.g., using block diagrams, etc., is intended to highlight different functional aspects and does not necessarily imply that such features must be realized by separate hardware or software components. Rather, functionality may be performed by separate hardware or software components, or integrated within common or separate hardware or software components. 
     When implemented in software, the functionality ascribed to the systems, devices and techniques described in this disclosure may be embodied as instructions on a computer-readable medium such as RAM, ROM, NVRAM, EEPROM, FLASH memory, magnetic data storage media, optical data storage media, or the like. The instructions may be executed by the external controller  32  to support one or more aspects of the functionality described in this disclosure. 
     The external circuitry  36  can further include any additional devices or components. For example, the external circuitry  36  can include at least one power source selection circuitry, drive circuitry, or a user interface. The power source selection circuitry is adapted to select an external power source (e.g., power source  30 , building power source  38 ) from which to provide power to the external coil  26  and other components of the external circuitry  36 . The drive circuit is adapted to drive the external coil  26  such that energy is transferred from the external coil to the internal coil  16  through an electromagnetic field. In one or more embodiments, the external circuitry  36  can also include a coupling detection circuit  33  that is adapted to provide an indication of whether the external coil  26  is electromagnetically coupled to the internal coil  16 . 
     The system  10  may optionally include a clinical monitor  40  for collecting system parameters (e.g., implanted battery life, charge stored in implanted battery, alarms, pump data, patient health data, etc.) to be monitored, such as by the patient or by a hospital clinical staff. The clinical monitor  40  can include a memory, internal or external, for storing the collected parameters, as well as for logging an event history of the patient (e.g., a low flow condition, a no-flow or suction condition, an interrupt, etc.). The clinical monitor  40  can further be connected to and receive/transmit information to and from units other than the TET system, such as to and from the patient&#39;s watch or smartphone, or to and from a hospital computer database. The clinical monitor  40  can also be powered by its own dedicated power source or battery  42 . 
     In some examples, the clinical monitor  40 , aside from receiving and monitoring data from the other components of the TET system  10 , can deliver set points or parameters (e.g., a flow rate) pertaining to the desired operation of the system  10 . Such set points may be communicated to the external circuitry  36 , internal circuitry  22 , or both as an instruction for operating the system  10 , and thereby utilized in setting further parameters of the system&#39;s operation, such as a pulse width and/or frequency for driving the wireless energy transmission to power the implanted device  20 . 
       FIG. 2  illustrates a schematic view of an exemplary arrangement of the external component  14  of the system  10 , and  FIG. 3  illustrates a schematic view of an exemplary arrangement of the internal component  12  of the system implanted within the patient. 
     The external component  14  can include the housing  46  and the external coil  26 . In one or more embodiments, the external coil  26  can be disposed in a separate housing  44  from the housing  46 . The housing  46  can be disposed in any suitable location relative to the patient&#39;s body  2 , e.g., around the patient&#39;s hip (e.g., in a pocket of the patient&#39;s clothing, mounted to a belt of the patient, etc.), and the external coil  26  can be located in any suitable location relative to the patient&#39;s body, e.g., on the patient&#39;s chest and secured in place by a garment worn by the patient, such as a sling or vest. The housing  46  of the external component and external coil  26  are further connected to each other by a wire  48 . Also shown in  FIG. 2  is the clinical monitor  40 , which can be worn, e.g., on the patient&#39;s wrist. In other examples, the clinical monitor  40  can be located elsewhere, such as in the housing  46 , or in the patient&#39;s smartphone, or not on the patient altogether. 
     In the embodiment illustrated in  FIG. 2 , the external power source  30  and external circuitry  36  can be disposed in the housing  46 . In one or more embodiments, the external power source  30  can be disposed in a separate housing (e.g., separately mounted to the outside of the patient) and wired to the external circuitry  36  disposed within the housing  46 . 
     As illustrated in  FIG. 3 , the internal component  12  can include the internal coil  16  disposed within a housing  50 , the implantable device  20 , and internal circuitry  22  disposed within housing  52  and electrically connected to the internal coil and the implantable device. In one or more embodiments, each of the circuitry  22 , the implantable medical device  20 , and the internal coil  16  can be disposed in a separate housing and dispersed throughout the patient&#39;s body  2  to accommodate the anatomy of the patient. For instance, in the embodiment illustrated in  FIG. 3 , the internal circuitry  22  is disposed within the housing  52  and mounted in the patient&#39;s chest. In one or more embodiments, the housing  50  of the internal coil  16  can be mounted to the patient&#39;s rib, back, or abdomen. 
     The internal coil  16  is electrically connected to the internal component  12  by a first cable  54 , and the implantable device  20  is electrically connected to the internal circuitry by a second cable  56 . 
     The internal coil  16  is disposed within the housing  50  and is adapted to be electromagnetically connected to the external coil  26 . For example, the internal coil  16  can be adapted to be inductively coupled to the primary coil  26 . Positioning of the internal coil  16  within the patient can be done in such a manner that makes mounting the external coil  26  in proximity to the secondary coil easy for the patient. For instance, the internal coil  16  can be positioned close to the skin of the patient. Moreover, the external coil  26  can be positioned close to a relatively flat part of the patient&#39;s body  2  to make mounting the external coil easier. In the embodiment illustrated in  FIG. 3 , the internal coil  16  is positioned close to the front of the patient&#39;s chest such that mounting the external coil  26  to the patient&#39;s chest places the external coil proximate the internal coil. In those examples where the housing  50  is mounted to the patient&#39;s rib, back, or abdomen, the external coil  26  can similarly be located close to the patient&#39;s skin, such that the internal coil  16  can be mounted in close proximity. 
     Any suitable technique or techniques can be utilized to output a charging alarm for the transcutaneous energy system  10  of  FIGS. 1-3 . For example,  FIG. 4  is a flowchart of one embodiment of a method  100  of providing an alarm or alarms to the patient. Although the method  100  is described regarding the transcutaneous energy transfer system  10  of  FIGS. 1-3 , such method can be utilized with any suitable transcutaneous energy transfer system. 
     The external controller  32  can be adapted to perform the method  100 . In one or more embodiments, the internal controller  34  can be adapted to perform the method  100 . Further, in one or more embodiments, both the external controller  32  and the internal controller  34  can be adapted to perform the method  100 . 
     At  102 , the external controller  32  is adapted to determine whether the internal coil  16  is electromagnetically disconnected from the external coil  26 . Any suitable technique or techniques can be utilized to make this determination. For example, in one or more embodiments, the external circuitry  36  can include coupling detection circuitry  33  that is adapted to determine whether the internal and external coils  16 ,  26  are electromagnetically connected and the degree of such connection. In one or more embodiments, such coupling detection circuitry can receive information from a voltage detector indicating an amount of voltage in the external coil  26 , and may determine connection between the coils  16 ,  26  based on the detected voltage. In one or more embodiments, the coupling detection circuitry  33  can receive telemetry signals from the internal circuitry  22  that indicates a current, Voltage, or other measure indicating coupling efficiency between the coils  16 ,  26 . The coupling detection circuitry  33  can then determine an electromagnetic connection between the coils  16 ,  26  based on the telemetry signals (except in those examples where telemetry signals are not being received). The coupling detection circuitry  33  can also be adapted to aid the patient in properly aligning the coils  16 ,  26  as is further described in U.S. Patent Publication No. 2015/0290373 A1. 
     If the system  10  determines that the internal coil  16  is electromagnetically disconnected from the external coil  26 , then the external controller  32  is further adapted to determine a reconnection time threshold at  104 . As used herein, the term “reconnection time threshold” refers to a time value at which an alarm will be provided to the patient if the coils  16 ,  26  are not electromagnetically reconnected or coupled. The reconnection time threshold can be based upon the reconnection time, which is an interval calculated for both close and far states, where information such as the last known charging state of the internal power source  18 , the age of the power source, the number of charging cycles encountered by the power source, and current implantable medical device power consumption rate are used to calculate a safe maximum duration before charging of the power source  18  should be reinitiated. As used herein, the term “close state” means a state where the external component  14  can determine that it is in proximity to the patient, e.g., by maintaining a regular communication link to the internal controller  34  via the internal transceiver  24  and the external transceiver  28 . Further, the term “far state” refers to a state where the external component  14  can determine that it is not in proximity to the patient via the absence of a regular communication link between the internal component  12  and the external component. 
     Any suitable technique or techniques can be utilized to determine the reconnection time threshold. In one or more embodiments, the reconnection time threshold can be based upon at least one of a power transfer efficiency value between the internal coil  16  and the external coil  26 , a charge state of the internal power source  18 , or a power consumption value of the implantable device  20 . Further, the reconnection time threshold can be based upon a time period for the patient to retrieve the external component  14  and electromagnetically connect the external coil  26  to the internal coil  16 . Any suitable technique or techniques can be utilized to determine such time period. In one or more embodiments, the reconnection time threshold can also be based upon a charging history of the internal power source  18 . Any suitable technique or techniques can be utilized to determine the charging history of the internal power source  18 . In addition, the state of charge of the external component  14  may be considered. In the case of low charge level of the external power source  30 , where a connection to line (AC) power may be required, the reconnection time threshold may have an additional safety factor applied to allow for time to locate and connect to an electrical outlet. 
     Any suitable technique or techniques can be utilized to determine the power transfer efficiency value between the internal coil  16  and the external coil  26 , e.g., one or more of the techniques described in U.S. patent application Ser. No. XX/XXX,XXX, entitled INTEGRITY MONITORING FOR A TRANSCUTANEOUS ENERGY SYSTEM (Atty Docket No. 21819D-612P; MDT No. A0002106US01). In one or more embodiments, a wireless power transfer efficiency value measured over the predetermined period of time corresponds to a long term moving average. In one or more embodiments, the long term moving average indicates whether performance is degrading due to at least one non-alignment factor between the internal coil and external coil. In one or more embodiments, the at least one non-alignment factor includes at least one of increased fat thickness of a person in which the implantable power device is implanted and degradation of at least one material characteristics of the implantable power device. For example, increased fat thickness of a person may be caused by an increase in fatty tissue or subcutaneous fluid accumulation where the increased fat thickness may result in increased distance between the implanted coil and the skin surface. In one or more embodiments, the at least one non-alignment factor includes at least one characteristic of a person that causes the distance between the implanted coil and the skin surface (or external coil) to increase. 
     In one or more embodiments, the existence of the far state can be used to trigger an arbitrary time safety factor to be incorporated in setting the alarm. For example, if the system is determined to be in the far state the assumption could be set in the system to assume, e.g., at least  20  minutes will be required to reconnect the external charging system to couple to the internal coil  16 . Additionally, location information derived from connectivity systems (e.g., Bluetooth®, WiFi, cellular based GPS) can be monitored and recorded to derive a projected physical distance, and from that, modulate the predicted time required to reacquire an external system for charging. 
     Further, any suitable technique or techniques can be utilized to determine a charge state of the internal power source  18 . For example, a charge level of the internal power source  18  can be determined using any suitable technique or techniques by the internal controller  34 . Such information can be transmitted to the external component  14  via the transceiver  24  of the internal component  12  and the transceiver  28  of the external component. Further, other information regarding the internal power source  18  can be determined by the internal controller  34 . For example, the internal controller  34  can determine a charge capacity value of the internal power source  18 . Further, the internal controller  34  can determine the number of charging cycles encountered by the internal power source  18  and compare that to a charge cycle threshold. In embodiments where the external power source  30  includes a rechargeable battery, the reconnection time threshold can also be based upon a charge state of the rechargeable battery. Any suitable technique or techniques can be utilized to determine this charge state. 
     Any suitable technique or techniques can be utilized to determine a power consumption value or values of the internal power source  18 . As used herein, the term “power consumption value” the rate of discharge of the internal power source  18  as determined by the power level used to drive the implantable electronics and pump system. For example, a pump system configured to deliver 8 Watts of power to the LVAD system will consume internal stored energy faster than a system configured to deliver 5 Watts of power. This setting (or potential range of settings) is known to the external component  14  at the time of coil decoupling and will be used to compute the appropriate recharge time. One or more embodiments of techniques for determining power consumption trends of an implantable device such as a blood pump are described in U.S. patent application Ser. No. 16/248,888, entitled EARLY WARNING OF LVAD THROMBUS FORMATION, can be utilized to determine the power consumption value or values of the internal power source  18 . 
     Any suitable technique or techniques can be utilized to combine, e.g., the values of power transfer efficiency between the internal coil and the external coil, a charge state of the internal power source, or a power consumption value of the implantable device and calculated a reconnection time threshold. For example, weighting can be applied to each of these values, and a reconnection time threshold can be calculated based upon these weighted values. 
     In one or more embodiments, the reconnection time threshold can include a far state reconnection time threshold and a close state reconnection time threshold. Any suitable technique or techniques can be utilized to determine the far state reconnection time threshold. In one or more embodiments, the far state reconnection time threshold can be determined based upon loss of communication between the external transceiver  28  and the internal transceiver  24 . Further, the close state reconnection time threshold can be determined using any suitable technique or techniques. In one or more embodiments, the close state reconnection time threshold can be determined based upon maintained communication between the external transceiver  28  and the internal transceiver  24 . 
     The external controller  32  can also be adapted to deactivate the charging alarm when the external coil  26  is electromagnetically reconnected with the internal coil  16 . Further, in one or more embodiments, the external controller  32  can also be adapted to deactivate the charging alarm based upon a user input. Any suitable technique or techniques can be utilized to provide the user input. For example, in one or more embodiments, the external component  14  can include a display or keypad that can be utilized by the patient to provide the user input to the external controller  32  to deactivate the charging alarm. Further, in one or more embodiments, the external controller  32  can also be adapted to deactivate the charging alarm based upon a caregiver or clinician input. Any suitable technique or techniques can be utilized to provide the caregiver or clinician input to the external controller  32 . For example, a clinician can provide input to the clinical monitor  40  that can then be transmitted to the transceiver  28  of the external component  14  using any suitable technique or techniques. 
     The charging alarm that is output by the external controller  32  can include any suitable alarm or alarms. In one or more embodiments, the charging alarm includes an audible alarm that can be heard by the patient to warn the patient that the external coil  26  should be electromagnetically connected to the internal coil  16  to provide power to the internal power source  18 . In one or more embodiments, the charging alarm can include a voice recording that provides information to the patient, e.g., regarding the charge state of the internal power source  18 . Further, in one or more embodiments, the charging alarm can include a vibratory alarm that provides a tactile notification to the patient that the internal power source  18  should be charged. In one or more embodiments, the external controller  32  can be adapted to transmit via the external transceiver  28  the charging alarm to at least one of a caregiver or a clinician. Further, in one or more embodiments, the external controller  32  can be adapted to transmit via the external transceiver  28  the charging alarm to a smart phone of the user of the system. The user can include the patient, a caregiver or a clinician. The external controller  32  can also adopt industry-standard broadcast techniques to communicate with all compatible devices within local range in an emergency mode operation. 
     At  104  of  FIG. 4 , an expected reconnection time for either the close state or the far state can be calculated using any suitable technique or techniques. A wait loop can then be initiated at  114  and the time interval can be evaluated at  106  using any suitable technique or techniques. If the time interval evaluated at  106  does not exceed the reconnection time threshold, then the wait loop is reinitiated at  114 , and the time interval continues to be evaluated at  106 . If, however, the reconnection time threshold is met at  106 , then a charging alarm can be output at either  108  or  110  depending upon whether the close reconnection time threshold or the far reconnection time threshold has been met. For example, if the close reconnection time threshold has been met at  106 , then the charging alarm for the close reconnection state can be provided by the external controller  32  at  108 . Further, if the far reconnection time threshold has been met at  106 , then the charging alarm for the far reconnection state can be provided at  110 . 
     At  112 , the external controller  32  can be adapted to determine whether the internal power source  18  is in a charge state. If the internal power source is in a charge state, then the method  100  returns to the coil connection state at  102 . Although not shown, the external controller  32  can be adapted to deactivate the charging alarm at  112  if the internal power source  18  is in a charge state. If, however, the internal power source  18  is not being charged at  112 , then the method  100  returns to the time evaluation state at  106 . 
     It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device. 
     In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer). 
     Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.