Abstract:
A patient monitoring device incorporates a receiver capable of single-antenna or multi-antenna operation. Multi-antenna operation permits the monitoring device to take advantage of spatial diversity for improved communication with an implantable medical device in the presence of fading. However, the small size of many patient monitoring devices can make the incorporation of multiple antennas difficult. To permit spatial diversity operation, a base station includes at least a second antenna that can be coupled to the patient monitoring device. Alternatively, the base station may have one or more high quality antennas that are used by patient monitoring device instead of the antenna in the patient monitoring device when the patient monitoring device is coupled to the base station.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to implantable medical devices and, more particularly, patient monitoring devices for communication with implantable medical devices.  
         BACKGROUND  
         [0002]    Implantable medical devices typically include a wireless telemetry link that permits communication between the implanted medical device and an external programmer or patient monitoring device. The wireless telemetry link may permit the transmission of commands from a programmer or patient monitoring device to the implantable medical device, e.g., to program new features or functionality into the implantable medical device. Also, the wireless telemetry link may permit the programmer or monitoring device to interrogate the implantable medical device to obtain stored operational information and sensed physiological parameters.  
           [0003]    A transceiver and antenna typically are located within a housing associated with the implantable medical device. Conventional programmers and patient monitoring devices incorporate a transceiver head that is placed in close proximity to the implantable medical device for programming and interrogation. The transceiver head may be coupled to the programmer or monitoring device via a cord. More recently, telemetry systems for implantable medical devices have eliminated the need for a transceiver head in the programmer or monitoring device. Instead, various wireless communication techniques have been implemented to permit increased transmission distances between the implantable medical device and the programmer or patient monitoring device.  
           [0004]    Improved wireless communication techniques may permit the implantable medical device to be located several meters from the programmer or monitoring device, providing the patient with increased mobility during programming and interrogation. In some cases, a patient monitoring device may be placed within the home of a patient, and configured to monitor the implantable medical device by wireless telemetry during the course of the patient&#39;s daily routine. In addition, some patient monitors may take the form of portable devices that can be carried with the patient, e.g., much like a personal digital assistant (PDA) or cell phone.  
         SUMMARY  
         [0005]    In general, the invention is directed to a patient monitoring device having a receiver capable of both single-antenna and multi-antenna operation. Multi-antenna operation permits the monitoring device to take advantage of spatial diversity for improved communication with an implantable medical device in the presence of fading. However, the small size of many patient monitoring devices can make the incorporation of multiple antennas difficult. To permit spatial diversity operation, the invention provides a base station having a second antenna that can be coupled to the patient monitoring device. Alternatively, the base station may have one or more high quality antennas that are used by patient monitoring device instead of the antenna in the patient monitoring device when the patient monitoring device is coupled to the base station.  
           [0006]    The patient monitoring device may provide multi-antenna operation when it is coupled to the base station, and single-antenna operation when it is not coupled to the base station. Alternatively, the patient monitoring device may use a high quality antenna provided in the base station when it is coupled to the base station. The base station may take the form of a docking station, platform, cradle or the like that receives the patient monitoring device and couples an antenna to the patient monitoring device, e.g., for spatial diversity or increased antenna quality. The patient monitoring device may provide an adaptable receiver and transmitter capable of operating in either the single-antenna or multi-antenna mode. In this manner, the invention can achieve spatial diversity without consuming additional space within the monitoring device for a second antenna.  
           [0007]    In one embodiment, the invention provides a system comprising an implantable medical device, a base station having a first antenna, and a monitoring device having a second antenna, wherein the monitoring device receives wireless signals from the implantable medical device via both the first antenna and the second antenna when the monitoring device is coupled to the base station.  
           [0008]    In another embodiment, the invention provides a monitoring device for monitoring an implanted medical device, the device comprising a first antenna, a wireless receiver coupled to the first antenna to process signals received from the implanted medical device via the first antenna, and a terminal to couple the receiver to a second antenna associated with a base station to process signals received from the implanted medical device via the second antenna.  
           [0009]    In a further embodiment, the invention provides a method comprising receiving wireless signals from an implantable medical device via both a first antenna associated with a monitoring device and a second antenna associated with a base station when the monitoring device is coupled to the base station, and receiving the wireless signals via only the first antenna when the monitoring device is not coupled to the base station.  
           [0010]    In yet another embodiment, the invention provides a monitoring device for monitoring an implanted medical device, the monitoring device comprising a wireless receiver to receive signals transmitted by a transmitter, wherein the receiver receives the signals via a first antenna and a second antenna when the monitoring device is coupled to a second device and receives signals via only the first antenna when the monitoring device is not coupled to the second device.  
           [0011]    In another embodiment, the invention provides a base station comprising an antenna, and a terminal to connect the antenna to a monitoring device for monitoring an implantable medical device when the monitoring device is coupled to the base station.  
           [0012]    The invention includes various aspects. For example, the invention may permit spatial diversity operation in a patient monitoring device without the need to incorporate an additional antenna in the device. Instead, the patient monitoring device may provide single-antenna operation when it is not coupled to the base station and multi-antenna operation when it is coupled to the base station. Alternatively, the patient monitoring device may use a high quality antenna provided in the base station instead of the device antenna.  
           [0013]    When the patient monitoring device is not coupled to the base station, the patient is more likely to carry the monitoring device in closer proximity to the implantable medical device. In this case, single-antenna operation may be sufficient. When the patient monitoring device is not carried by the patient and, hence, may be further away from the implantable medical device, placing the patient monitoring device in the base station provides improved communication via spatial diversity techniques or via a higher quality antenna. In this manner, the invention may improve overall reliability of communication between the patient monitoring device and the implantable medical device.  
           [0014]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other aspects of the invention will be apparent from the description and drawings, and from the claims. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0015]    [0015]FIG. 1 is a block diagram illustrating a system including a patient monitoring device capable of multi-antenna operation in accordance with the invention.  
         [0016]    [0016]FIG. 2 is a block diagram illustrating a patient monitoring device and a base station in accordance with the invention.  
         [0017]    [0017]FIG. 3 is a block diagram illustrating connection of a patient monitoring device and a base station in accordance with an embodiment of the invention.  
         [0018]    [0018]FIG. 4 is a block diagram illustrating connection of a patient monitoring device and a base station in accordance with another embodiment of the invention.  
         [0019]    [0019]FIG. 5 is a block diagram illustrating spatial diversity circuitry associated with a patient monitoring device.  
         [0020]    [0020]FIG. 6 is a flow diagram illustrating a process for selection of single-antenna or multi-antenna operation in a patient monitoring device.  
         [0021]    [0021]FIG. 7 is a block diagram illustrating connection of a patient monitoring device and a base station in accordance with an added embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0022]    [0022]FIG. 1 is a block diagram illustrating a system  10  including a patient monitoring device  12  capable of multi-antenna operation in accordance with an embodiment of the invention. As shown in FIG. 1, system  10  may include monitoring device  12 , an implantable medical device (“IMD”)  14 , and a base station  16 . IMD  14  transmits signals via antenna  18  to patient monitoring device  12 . Monitoring device  12  includes an antenna  20 . Base station  16  includes an antenna  22 . Monitoring device  12  may be used independently of base station  16  or coupled to the base station.  
         [0023]    In accordance with the invention, monitoring device  12  is configured for single-antenna operation or multi-antenna operation. In particular, monitoring device  12  uses antenna  20  for communication with IMD  14  when the monitoring device is not coupled to base station  16 . When monitoring device  12  is coupled to base station  16 , however, the monitoring device uses not only antenna  20 , but also antenna  22  provided in base station  16 . In this manner, monitoring device  12  can take advantage of spatial diversity to communicate with IMD  14  when the monitoring device is coupled to base station  16 .  
         [0024]    As further shown in FIG. 1, base station  16  may be coupled to a host computer  23  that provides access to a network  26 . Alternatively, base station  16  may be coupled directly to an access point  24  that provides to network  26 . Network  26  may be a local area network, wide area network or global computer network, such as the World Wide Web, and provides communication between monitoring device  12  and one or more network clients  28 . Monitoring device  12  or an application running on host computer  23  may gather and forward data obtained from IMD  14  to the clients  28 . Clients  28  may be associated with monitoring physicians and may run automated applications to process information received from monitoring device  12  via network  26 .  
         [0025]    Base station  16  may serve multiple purposes. In addition to providing a second antenna for spatial diversity, base station  16  may operate as a docking station to permit wired or wireless communication of monitoring device  12  with host computer  23  or network access point  24 . In some embodiments, base station  16  may facilitate synchronization of data stored within monitoring device  12  with data stored by host computer  23  or one or more of clients  28 . In this sense, base station  16  may operate much like a “synch” cradle used with many conventional PDAs. Also, base station  16  may serve to charge a rechargeable battery within monitoring device  12  when the monitoring device is coupled to, e.g., docked within, the base station.  
         [0026]    Monitoring device  12  may be used with a variety of different IMDs  14  including a cardiac stimulator, a neuro stimulator, a drug delivery device, and a physiological sensor device. One example of an implantable medical device  14  is a pacemaker. Another example of an implantable medical device is a pacemaker-cardioverter-defibrillator (“PCD”). Other examples include an implantable brain stimulator, an implantable gastric system stimulator, an implantable nerve stimulator or muscle stimulator, an implantable lower colon, an implantable drug or beneficial agent dispenser or pump, an implantable cardiac signal loop or other type of recorder or monitor, an implantable gene therapy delivery device, an implantable incontinence prevention or monitoring device, an implantable insulin pump or monitoring device, and so on. IMD  14  may continuously collect operational information and physiological information. The physiological information may include heart rate, heart rate variability, blood glucose levels, oxygen saturation, partial pressure of oxygen in the blood, blood pressure, baro-reflex measures, electrogram morphologies, lung wetness, and the like.  
         [0027]    Antenna  20  of monitoring device  12  is coupled to a wireless receiver to process signals received from IMD  14 . In addition, antenna  20  may be coupled to a wireless transmitter. Accordingly, monitoring device  12  may be designed for one-way or two-way communication with IMD  14 . A transmitter may be used by monitoring device  12  to program IMD  14 . Also, in accordance with the invention, monitoring device  12  may provide either single-antenna or multiple-antenna operation. In this manner, monitoring device  12  may be configured to provide a spatial diversity mode in which the receiver processes signals received via both antenna  20  and antenna  22 .  
         [0028]    Monitoring device  12  may take a variety of forms. For example, monitoring device  12  may be a dedicated monitoring device. Alternatively, monitoring device  12  may be integrated with other device functionality. In particular, monitoring device  12  may be integrated with a cell phone, a PDA, or the like. The monitoring device  12  may receive wireless signals from IMD  14  via only antenna  20  when it is not coupled to base station  16 . Additionally, the monitoring device  12  may receive signals from IMD  14  via both antenna  20  and antenna  22  when it is coupled to base station  16 .  
         [0029]    [0029]FIG. 2 is a block diagram illustrating a patient monitoring device  12  and a base station  16  in accordance with one embodiment of the invention. As shown in FIG. 2, base station  16  may define a cradle, platform or other support to receive monitoring device  12  and provide engagement between contact terminals associated with the base station and the monitoring device. In particular, monitoring device  12  may include a contact terminal to couple the receiver to a second antenna  22  provided in base station  16 . Base station  16  may include a reciprocal terminal that engages the contact terminal in monitoring device  12  to couple antenna  22  to the monitoring device. Alternatively, in other embodiments, antenna  22  of base station  16  may be coupled to monitoring device  12  via a cable.  
         [0030]    In the example of FIG. 2, monitoring device  12  includes antenna  20 , a display screen  32  and user input media such as an array of buttons  34 . Base station  16  includes antenna  22 , and a cradle-like receptacle to receive monitoring device  12  and facilitate engagement of reciprocal contact terminals in the monitoring device and the base station. Base station  16  may be coupled to a source of power via a power cord (not shown in FIG. 2). In addition, base station  16  may include communication links to host computer  23  or access point  24 . FIG. 2 depicts antenna  22  is shown as protruding from base station  16 . In other embodiments, however, antenna  22  could be a dedicated, free-standing antenna that is coupled to base station  16  via a cable. Alternatively, antenna  22  could be integrated with a power cord associated with base station  16 , or embedded within the housing of the base station.  
         [0031]    In some embodiments, base station  16  may further include radio circuitry to process wireless signals received via antenna  22 . In other words, base station  12  may provide some of the circuitry necessary to process one of the spatial diversity channels involved in transmitting or receiving signals via multiple antennas  20 ,  22 . In this manner, base station  16  may further reduce the size, power consumption and complexity of monitoring device  12 . Alternatively, such circuitry may be provided in monitoring device  12 , with base station  16  providing a simple electrical pass-through from antenna  22  and the monitoring device.  
         [0032]    In accordance with the invention, a monitoring device  12  that is capable of single-antenna or multi-antenna communication can provide more reliable communication between IMD  14  and the monitoring device. Monitoring device  12  can take advantage of spatial diversity without the need to incorporate an additional antenna in the monitoring device. Instead, monitoring device  12  cooperates with its own base station  16  to provide spatial diversity, thereby reducing the size, cost and complexity of the monitoring device. The space required for the second antenna  22 , and perhaps radio circuitry for processing signals received and transmitted by the second antenna, can be provided by base station  16 .  
         [0033]    [0033]FIG. 3 is a block diagram illustrating connection of patient monitoring device  12  and base station  16  in accordance with an embodiment of the invention. As shown in FIG. 3, monitoring device  12  includes transmitter/receiver (TX/RX) circuitry  36  to process signals received and transmitted by antenna  20  in monitoring device  12  and antenna  22  in base station  16 . In particular, TX/RX  36  may be coupled to antenna  20  and a terminal  38 . In addition, TX/RX  36  may be coupled to a modem  41  that modulates and demodulates signals transmitted and received via antenna  20  or both antennas  20 ,  22 .  
         [0034]    When monitoring device  12  rests in or on base station  16 , terminal  38  contacts a terminal  40  in base station  16 . Terminal  40  may be coupled to antenna  22  or, alternatively, radio circuitry with base station  16  that processes signals transmitted and received by antenna  22 . Additional terminals  42 ,  44  may be provided on monitoring device  12  and base station  16 , respectively, for exchange of data and battery charging current.  
         [0035]    Monitoring device  12  processes signals exchanged with IMD  14 . TX/RX  46  in monitoring device  12  may include a spatial diversity receiver and transmitter to process signals received and transmitted via antenna  20 ,  22 . In other embodiments, monitoring device  12  may not include a transmitter and instead serves only to gather data from IMD  14 . When monitoring device  12  is not coupled to base station  12 , it receives signals via antenna  20 . When monitoring device  12  is coupled to base station  12 , however, it receives signals via both antennas  20 ,  22 . Accordingly, TX/RX  44  may provide an auto-detection feature that automatically detects the connection of antenna  22  via contact terminals  38 ,  40 .  
         [0036]    [0036]FIG. 4 is a block diagram illustrating connection of patient monitoring device  12  and base station  16  in accordance with another embodiment of the invention. FIG. 4 conforms substantially to FIG. 3 but illustrates incorporation of TX/RX circuitry within base station  16  to process signals for antenna  22 . In particular, first TX/RX circuitry  36 A is provided in monitoring device  12  to process signals for antenna  20 , and second TX/RX circuitry  36 B is provided in base station  16  to process signals for antenna  22 . TX/RX circuitry  36 A,  36 B may perform filtering, amplification, upconversion or downconversion of signals transmitted or received by antennas  20 ,  22 , respectively. Accordingly, each of TX/RX circuitry  36 A,  36 B may be coupled to modem  41 . However, TX/RX circuitry  36 B is coupled to modem  41  via terminals  38 ,  40  upon coupling of monitoring device  12  with base station  16 .  
         [0037]    [0037]FIG. 5 is a block diagram illustrating spatial diversity circuitry associated with a patient monitoring device  12 . As shown in FIG. 5, monitoring device may include separate channels for processing signals transmitted or received by antennas  20 ,  22  to spatial diversity. One channel includes radio frequency (RF) circuitry  46 A and analog-to-digital (ADC)/digital-to-analog (DAC) circuitry  48 A to process signals for antenna  20 . A second channel includes RF circuitry  46 B and ADC/DAC circuitry  48 B to process signals for antenna  22 . RF circuitry  46 A,  46 B may include conventional filtering, amplification, downconversion, and upconversion circuitry to process signals transmitted and received by antennas  20 ,  22 , respectively. Also, ADC/DAC circuitry  48 A,  48 B converts digital signals generated by modem  41  into analog signals for transmission on antennas  20 ,  22 , and converts analog signals received by antennas  20 ,  22  to digital signals for demodulation by modem  41 .  
         [0038]    [0038]FIG. 6 is a flow diagram illustrating a process for selection of single-antenna or multi-antenna operation in a patient monitoring device. As shown in FIG. 6, if monitoring device  12  is in an operating mode that supports receive/transmit (RX/TX) diversity ( 50 ). If RX/TX diversity is not supported, monitoring device  12  processes signals received and transmitted by a single antenna ( 58 ). If RX/TX diversity is supported, however, monitoring device  12  determines whether it is coupled to base station  16  ( 60 ). Monitoring device  12  may detect whether it is coupled to base station  16  by sensing signals on one or more contact terminals that engage contact terminals on the base station. If monitoring device  12  is coupled to base station  16 , the monitoring device processes signals received and transmitted by multiple antennas ( 62 ). In other words, monitoring device  12  provides spatial diversity when it is coupled to base station  16 . In this case, monitoring device may offer enhanced communication with IMD  14 .  
         [0039]    [0039]FIG. 7 is a block diagram illustrating connection of a patient monitoring device and a base station in accordance with an added embodiment of the invention. The example of FIG. 7 conforms substantially to that of FIG. 3. Instead of providing spatial diversity operation, however, patient monitoring device  12  includes a switch  58  that permits operation using either antenna  20  associated with the patient monitoring device, or antenna  22  associated with base station  16 . Antenna  22  of base station  16  may be a higher quality antenna relative to antenna  20  of patient monitoring device  12 . For example, antenna  22  may have larger or more favorable dimensions, or be made of more favorable materials, than antenna  20  due to size, space, complexity or cost limitations associated with patient monitoring device  12 .  
         [0040]    Switch  58  may be configured to select one of antennas  20 ,  22  for used by RX/TX circuitry  36 . If patient monitoring device  12  is not coupled to base station  16 , switch  58  selects antenna  20 . On the other hand, if patient monitoring device  12  is coupled to base station  16 , switch  58  selects the higher quality antenna  22  for enhanced communication with IMD  14 . In other words, in the exemplary embodiment of FIG. 7, patient monitoring device  12  may be configured to use antenna  22  instead of antenna  20  when antenna  22  is available for use. As a further alternative, antenna  22  may incorporate two more antennas for spatial diversity operation. In this case, switch  58  may couple multiple antennas from base station  16  to RX/TX circuitry  36 , enabling spatial diversity communication by patient monitoring device  12  when it is coupled to base station  16 .  
         [0041]    Various embodiments of the invention have been described. These and other embodiments are within the scope of the following claims.