Patent Publication Number: US-2009226328-A1

Title: Remote Data Monitor For Heart Pump System

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/522,874, entitled “REMOTE DATA MONITOR FOR HEART PUMP SYSTEM,” filed on Nov. 16, 2004, which is incorporated by reference. 
    
    
     BACKGROUND 
     The invention relates generally to heart pump systems and, more specifically, to a remote monitor for such pumps. 
     Implantable blood pump systems are generally employed either to completely replace a human heart that is not functioning properly, or to boost blood circulation in patients whose heart still functions but is not pumping blood at an adequate rate. Known implantable blood pump systems are primarily used as a “bridge to transplant.” In other words, existing blood pump system applications are mainly temporary fixes, intended to keep a patient alive until a donor is available. However, the shortage of human organ donors, coupled with improvements in blood pump reliability make long-term, or even permanent blood pump implementations a reality. 
     Despite this need, existing implantable pump systems have not been satisfactory for long term use. Known systems of the continuous flow type are designed primarily for use in a hospital setting. These systems typically include the implanted pump device, a power source such as a rechargeable battery, a motor controller for operating the pump motor, and an external operator console. While some existing implantable pump systems allow for operation while decoupled from the operator console, operating these systems “stand-alone” can be a risky endeavor. This is due, at least in part, to the lack of an adequate user interface when the system is decoupled from the console. 
     Moreover, prior blood pump systems are not conducive to long-term use outside an institutional setting. Known systems often require a large, fixed operator console for the system to function. While prior art operator consoles may be cart mounted to be wheeled about the hospital, at home use of known systems is difficult at best. Other problems of prior pump systems that have limited their mobility and use to relatively short times are related to motor controller size and shape limitations. 
     Thus, there is a need for a pump control system that addresses the shortcomings associated with the prior art. 
     SUMMARY 
     In accordance with certain teachings of the present disclosure, a pump control system includes a controller module for controlling a pump, such as an implantable blood pump. A remote monitor is adapted to communicate with the controller module via a wireless communications medium, such as a low-power radio frequency link. The remote monitor provides a user interface similar or identical to the controller module, providing a user the ability to remotely monitor the pump&#39;s performance and to respond to alarms. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a block diagram of a pump system in accordance with teachings of the present disclosure. 
         FIG. 2  illustrates an exemplary implantable heart pump in accordance with an embodiment of the system disclosed herein. 
     
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     Turning to the figures, and in particular to  FIG. 1 , a ventricle assist device (VAD) system  10  in accordance with an embodiment of the present invention is illustrated. The VAD system  10  includes components designed to be implanted within a human body and components external to the body. The components of the system  10  that are implantable include a pump  12  and a flow sensor  14 . The external components include a portable controller module  16  and a remote monitor module  18 . The implanted components are connected to the controller module  16  via a percutaneous cable. The controller module  16  may be mounted to a support device, such as a user&#39;s belt  23  or to a vest worn by the user, for example. Additional components of a VAD system are shown and described in U.S. Pat. No. 6,183,412, which is incorporated by reference. 
     The controller module  16  includes a processor, such as a microcontroller  80 , which in one embodiment of the invention is a model PIC16C77 microcontroller manufactured by Microchip Technology. The microcontroller  80  includes a multiple channel analogue to digital (A/D) converter, which receives indications of motor parameters from the motor controller  84 . Thus, the controller module  16  may monitor parameters such as instantaneous motor current, the DC component or mean value of the motor current, and motor speed. 
     The embodiment shown in  FIG. 1  further includes an integral flow meter  86 . At least one flow sensor  14  is implanted down stream of the pump  12 . Alternately, a flow sensor  14  may be integrated with the pump  12 . The flow meter  86  is coupled between the implanted flow sensor  14  and the microcontroller  80 . The flow meter  86  receives data from the flow sensor  14  and outputs flow rate date to the microcontroller  80 , allowing the system to monitor instantaneous flow rate. 
     The VAD System  10  may incorporate an implantable continuous-flow blood pump, such as the various embodiments of axial flow pumps disclosed in U.S. Pat. No. 5,527,159 or in U.S. Pat. No. 5,947,892, both of which are incorporated herein by reference in their entirety. An example of a blood pump suitable for use in an embodiment of the invention is illustrated in  FIG. 2 . The exemplary pump  12  includes a pump housing  32 , a diffuser  34 , a flow straightener  36 , and a brushless DC motor  38 , which includes a stator  40  and a rotor  42 . The housing  32  includes a flow tube  44  having a blood flow path  46  therethrough, a blood inlet  48 , and a blood outlet  50 . 
     The stator  40  is attached to the pump housing  32 , is preferably located outside the flow tube  44 , and has a stator field winding  52  for producing a stator magnetic field. In one embodiment, the stator  40  includes three stator windings and may be three phase “Y” or “Delta” wound. The rotor  42  is located within the flow tube  44  for rotation in response to the stator magnetic field, and includes an inducer  58  and an impeller  60 . Excitation current is applied to the stator windings  52  to generate a rotating magnetic field. A plurality of magnets  62  are coupled to the rotor  42 . The magnets  62 , and thus the rotor  42 , follow the rotating magnetic field to produce rotary motion. 
     The remote data monitor (RDM)  18  is a small portable handheld device that includes a processing device  112  and a user interface  110  that effectively replicates the user interface  111  of the controller module  16  remotely via a wireless communication link  120 . In an exemplary embodiment, the wireless link  120  is a low-power radio frequency (RF) link usable over a maximum distance of approximately 300 feet (100 meters) using the system&#39;s standard antenna configuration. While in use, the device provides the user with the ability to remotely monitor the VAD pump&#39;s  12  performance and to respond to alarms. The pump controller  16  and remote monitor(s)  18  may be programmed via the clinical data acquisition system or the remote monitor  18  may be programmed telemetrically by the pump controller  16 , for example. 
     The wireless link  120  includes antennas, which my suitably comprise simple monopoles. The system&#39;s antennas maybe constructed from ferrite rods or with traces on the system&#39;s internal printed circuit board. Integral antennas may be used exclusively, or external antennas may be employed for increased range capability, or a combination of integral and external antennas may be used. 
     The integrity of the link  120  will be continuously verified while the device is in operation. In the event that the remote monitor  18  is located too far from the VAD controller  16 , the RF link becomes “noisy” or unusable, or if the monitor&#39;s  18  batteries are low, the VAD controller  16  will continue to function and alarm normally. More specifically, in exemplary implementations, the remote monitor  18  periodically transmits status information back to the pump controller  16  to conform proper link operation. The remote monitor  18  may monitor and display received signal strength information, and the pump controller  16  can increase or decrease its transmitter output power proportional to the signal strength reported back from the remote monitor  18 . 
     The carrier may be angle modulated (i.e. frequency modulated (FM) or phase modulated (PM)) to minimize the effects of external noise induced errors. Alternatively, the carrier may be amplitude modulated (AM) to maximize battery life. Forward error correction techniques may be used to maximize the integrity of the communication link. Spread spectrum techniques are used to further minimize externally induced noise from compromising the communication link between the pump controller and corresponding remote monitor. The receiver may request that a transmission be retransmitted in the event of an error. In typical installations, transmissions are within the US and European ISM (i.e. Industrial, Scientific, Medical) band. 
     Multiple controller  16  and remote monitor  18  pairs may be used in close proximity to one another. Each pump controller  16  and corresponding remote monitor  18  may communicate on a designated frequency or frequency pair or on the same frequency or frequency pair. Transmitted data packets contain the address of the intended remote monitor  16 . Each pump controller  16  first “listens” to confirm if another pump controller  16  is transmitting. In the event there is no other transmission, the pump controller  16  may begin transmitting and, conversely, in the event another transmission is “heard” the pump controller  16  will wait for the channel to be clear. In other implementations, one pump controller  16  may broadcast to several remote monitors  16  (e.g. one with the patient, one with the caregiver). 
     The data transmitted between the pump controller  16  and remote monitor  18  may be encoded such that the remote monitor  18  only responds to data transmitted with a unique address or to transmissions containing the correct address. A hardware or software based correlator may be used to identify the address. 
     In certain embodiments, the remote monitor  18  is approximately 3 inches wide by 2 inches high by 1 inch thick, weighs less than 5 oz., includes a wrist-strap such that it may be worn by the caregiver or patient on the wrist, and includes a combination belt clip/tilt stand for use on the patient&#39;s or caregiver&#39;s belt or nightstand. The device  18  may be powered from an internal rechargeable battery to be completely portable or it may be plugged into the ac mains using an optional power adapter. Additionally, the device  18  may be plugged into an automotive power outlet for continuous operation while on long trips in an automobile or airplane. The device  18  will support simultaneous charging of the internal battery while monitoring the VAD controller  16  (e.g. at night while patient and parent/caregiver are sleeping). 
     The remote monitor&#39;s  18  user interface is identical to the VAD controller  18  interface and includes a tricolor light emitting diode (LED) backlit graphic liquid crystal display (LCD) to display multi-lingual diagnostic and emergency messages, a sealed two-button keypad with tactile feedback and rim-embossing to silence alarms and scroll through diagnostic message displays, three bicolor LEDs indicating individual battery status and fail-safe mode operation, two distinct, variable pitch, variable loudness audible enunciators, and an optional audible voice output for diagnostic and emergency alarms. 
     The backlit LCD can indicate functional pump information to the patient and/or caregiver, and in exemplary embodiments, the backlight utilizes multiple colors to convey functional and alarm information to the patient and caregiver (e.g. green=normal, yellow-diagnostic alarm, red=emergency alarm). 
     The audible alarms may be elicited through piezo buzzer enunciators. The variable loudness audible enunciators maybe be operated such that the pitch and/or volume changes proportionally to the length of time that the alarm is activated. The audible voice output may be elicited through a voice coil type speaker element. A natural language speech synthesizer may be employed, including a phoneme based speech synthesizer enabling audible speech to be generated in a multiplicity of languages. Further, the natural language voice&#39;s pitch and cadence may be programmed to simulate a male or female adult voice based on the patient or caregiver&#39;s preference. Still further, the natural language voice output&#39;s pitch and cadence may be programmed to simulate a less-intimidating child&#39;s voice for pediatric cases. A motor with integral eccentric may be enabled to vibrate during any alarming condition to help in alerting the patient or caregiver. 
     Optionally, in pediatric applications, a wireless audio channel may be added to integrate the functionality of a commercial “baby monitor” into the system. A transmitter with a microphone or other sound detecting device transmits audio signals to a receiver integrated into the remote monitor  18 , which further includes an output device such as a speaker. This minimizes the number of different systems the parent or caregiver must use and manage. This function would also include a volume control to allow the parent or caregiver to set the device&#39;s output to the desired audio level. 
     The above description of exemplary embodiments of the invention are made by way of example and not for purposes of limitation. Many variations may be made to the embodiments and methods disclosed herein without departing from the scope and spirit of the present invention. The present invention is intended to be limited only by the scope and spirit of the following claims.