Patient device for bidirectional data communication with an implant

This invention relates generally to a system comprising an implantable electrical medical device such as a cardiac pacemaker, together with an external device that provides a bidirectional telemetric link to the implantable medical device. This invention relates in particular to the functionality of such an external patient device.

The patient device comprises:

• a receiver
• a memory operatively connected to said receiver, said memory being configured to store code identifying a specific implant (implant's identification code (IID))
• a timer and
• a control unit operatively connected to said receiver, said memory and said timer.

In a system comprising one or more implantable medical devices (IP) and one or more patient devices (PD, also referred to as external device), an implantable medical device and patient device may include transceivers that facilitate bidirectional communications between the devices for home monitoring purposes. For wireless communication in such environment the MICS (Medical Implant Communications Service) frequency band is reserved.

In a system for bidirectional communication each patient device should be assigned to a single implant to prevent multiple patient devices from attempting communication with a single implant. This is particularly important in an area where multiple patient devices are in close proximity (e.g., in a nursing home), and so competition between patient devices may result in failed communications due to interference.

If unidirectional telemetry (i.e. telemetry from implant to patient device) is used, then such assignment is not necessary, as unidirectional telemetry does not require or provide for acknowledgements.

In order to follow the MICS regulations as defined by the FCC and ETSI, when communications are to be established, it is necessary for the patient device to scan the MICS band, to find the Least Interfered-with Channel (LIC), and then to transmit a beacon signal to the implant. Subsequently, the implant must search the band to find the channel on which the patient device is transmitting, and only then may the implant use that channel to transmit its data to the patient device. If periodic communications are desired, time synchrony of the implant and patient device is needed in order to prevent either unnecessary emission by the patient device on the MICS band, or unnecessary receiver activity (thus power consumption by the implant) outside of the time of interest. Therefore, timing information is exchanged between the implant and patient device during their communications.

Presently, assignment is achieved manually by addressing the patient device via the internet and transmitting an implant identification code to the patient device to thus assign the patient device to the implant specified by the implant identification code.

It is an object of the present invention to facilitate assignment of implants or patient devices to each other in an environment as illustrated above.

According to the present invention the object of the invention is achieved by a patient device that can be at least in an unpaired state or in a paired state, wherein in its paired state the patent device is paired to a specific implant specified by an implant's identification code that is stored in said memory of the patent device. The control unit is adapted to control automatic pairing of the patient device to a specific implant upon receiving a data packet containing an implant's identification code when the patient device is in its unpaired state with no valid implant identification code stored in said memory prior to receiving said data packet containing said implant identification code.

The control unit tentatively pairs the patient device to an implant identified by the implant's identification code contained in said data packet by storing said implant's identification code in said memory.

When the patient device eventually is tentatively paired to a specific implant, the control unit will

• either cancel tentative pairing to said implant by deleting said implant's identification code in said memory, if no further data communication is occurring within a predetermined period of time after first receiving said data packet containing the implant's identification code leading to tentative pairing,
• or maintain a paired state by keeping said implant's identification code in said memory if further data communication is occurring within a predetermined first period of time after first receiving said data packet containing the implant's identification code leading to tentative pairing.

The pairing thus automatically achieved is called "soft pairing" for the purpose of this description. Another type of pairing preferably provided by the patient device is "hard pairing". Whereas a soft paired patient device will return to its unpaired state when no communication between said patient device and the implant the patient device is paired to takes place within a predetermined period of time (that is longer than the period of time for cancelling tentative pairing), no such time limit is applicable to hard paired patient devices.

The invention is based on the concept, that a patient device is unambiguously assigned and thus paired to a specific implant identified by its implant identification code. Additionally, an implant does not store assignment information relating to a specific patient device other than the patient device's identification code for mirroring purposes when responding to a data packet originating from the patient device.. A patient device can be assigned to no implant or a single implant, but never simultaneously to multiple implants. Thus, the patient device can either be in an unpaired state where it is not assigned to any specific implant or in some paired state wherein the patient device is assigned to a single specific implant. In particular, two paired states are provided, namely a soft paired state resulting from automatic pairing and a manually induced hard paired state. The hard paired state is preferably achieved using a programmer for directly programming a specific implant's identification code IID into the patient device's memory. Hard pairing can also be achieved by sending a pairing message to the patient device over the telephone, the internet, or other means.

In order to eventually receive a data packet originating from an implant and containing an implant identification code, the control unit preferably is adapted to cause the patient device's receiver to periodically or continuously scan or monitor a predetermined wireless communication frequency band or a predetermined channel within said wireless communication frequency band, respectively, for incoming data packets containing an implant's identification code.

Such scanning of a plurality of channels of a wireless communication frequency band may be performed to determine a least used channel within said frequency band and to thereupon send a request data packet using said channel thus determined in order to induce an implant receiving said request data packet to send a response data packet containing said implant's identification code IID.

Therefore, in a preferred embodiment, the control unit is adapted to cause the patient device's receiver to periodically or continuously scan all channels of a predetermined wireless communication frequency band for incoming data packets containing an implant's identification code when the patient device is in its unpaired state.

As a result of pairing, a dedicated channel within said wireless communication frequency band may be determined for future communication between the patient device and the implant the patient device is paired to. Therefore, in particular if the patient device already is in its paired state, it is preferred that the control unit be adapted to cause the patient device's receiver to periodically or continuously monitor a predetermined channel in said wireless communication frequency band for incoming data packets containing an implant's identification code IID.

In a particularly preferred embodiment the patient device's receiver is part of a transceiver, and the control unit is adapted to cause the patient device's transceiver to:

• Periodically or continuously scan a predetermined data transmission band for a least used channel
• Send an outgoing data packet containing the patient device's identification code using said least used channel, and
• Wait for an incoming data packet in response to said outgoing data packet that contains said patient device's identification code (EID) and an implant identification code (IID).

In order to prevent the patient device from being fooled by data packets sent out by other patient devices, the control unit preferably is adapted to discriminate data packets originating from an implant from data packets originating from other devices. The control unit can be adapted to evaluate a predetermined bit or bits of an incoming data packet in order to determine whether the data originates from an implant or not. In a preferred embodiment, the control unit is adapted to reject pairing when determination of the incoming data packets origin indicates that said incoming data packet does not originate from an implant. Thus, automatic soft pairing can only be induced by an implant itself.

In order to prevent a patient device from pairing itself to an implant that is already in communication with another patient device, the control unit preferably is adapted to cease pairing when the patient device receives an incoming data packet containing a specific patient device identification code (EID) other than the patient device's own patient device identification code EID. Thus, the control unit is adapted only to allow pairing when the patient device receives an incoming data packet containing an unspecific patient device identification code (EID). Said unspecific patient device identification code number (EID) preferably is the number zero. Thus, the patient device will only pair in response to reception of a data packet originating from an implant that contains a specific implant identification code IID along with a patient device identification code EID that either is0 or the receiving patient device's own identification code.

Preferably, means are additionally provided to let the patient device return to its unpaired state. Such means can be a user actuatable means for setting the patient device in its unpaired state, preferably a reset button operatively connected to the control unit, said control unit being adapted to delete said implant's identification code in said memory in response to pressing the reset button. In addition or as an alternative, the patient device can be adapted to reset to its unpaired state by a reset message from a programmer or a customer service centre, communicated via, for example, the telephone or the internet.

In addition or as an alternative, the control unit can be adapted to automatically reset the patient device from its soft paired state to its unpaired state if for a second predetermined period of time (the time for soft pairing to expire) no further incoming data packet containing the stored implant identification code is received, said second period of time being longer than said first period of time (the time for tentative pairing to expire).

Setting the patient device in its unpaired state is preferably achieved by storing an unspecific implant identification code, e.g. IID=0, in the patient device's memory at an address reserved for the implant identification code (IID).

The object of the invention also is achieved by a data packet for use in wireless communication between a patient device and an implant, wherein the data packet contains an implant identification code (IID), a patient device identification code (EID) and an identifier of data packet origin. Said identifier of data packet origin preferably is a single origin identifier bit which in its first state, 0 or 1, characterizes a data packet originating from an implant and in its second state, 1 or 0, respectively, characterizes a data packet originating from a patient device.

Messages sent out by an implant may have different levels of priority. Preferably three levels of priority are provided: low, medium and high.

According to a preferred embodiment of the invention, the state of pairing results in treating different kind of messages differently depending on a message's priority as follows:

• high-priority messages do not require acknowledgements from the patient device, and thus are unidirectional communications from an implant to any nearby patient device. The patient device will always accept a high priority message from any implant regardless of the state of pairing of the patient device. This is achieved by making the patient device's control unit sensitive to a priority indicator contained in an incoming data packet.
• If the patient device is in its hard paired state it will communicate in a bidirectional manner only with the implant that said patient device is assigned to, although even a hard paired patient device will also accept high-priority unidirectional data from any implant, as indicated above.
• If the patient device is in its soft paired state it will communicate only with the implant that said patient device is assigned to if an incoming data packet contains data characterizing the incoming message as being a low priority (periodic, bidirectional) message. A soft paired patient device is adapted to communicate with any implant for either medium-priority (bidirectional) or high-priority (unidirectional) messages.

Thus, a preferred patient device will accept:

• routine or low-priority messages if the data packet containing the message contains an implant identification code (IID) corresponding to the IID that is stored in the patient device's memory, that is if said routine or low-priority message origins from an implant that the patient device is paired to.
• medium-priority messages containing any implant identification code as long as the patient device is in it's soft paired state or is hard paired to the specific implant that said medium-priority message origins from.
• any high-priority messages from any implant.

For this purpose, a data packet according to the invention preferably contains a priority indicator.

Accepting a message received by means of an incoming data packet preferably includes storing and forwarding said message to a further device like a central service centre.

Preferably, the patient device is adapted so that it can be interrogated to determine the implant identification code (IID) stored in the patient device's memory and which characterizes the implant that the patient device is paired to. The IID may be, for example, the implant's serial code.

It is a major advantage of a patient device according to the invention, that said pairing is performed by the patient device alone, that is, no action or storing of information is required to be performed by the implant. All pairing means are incorporated into the patient device. This is important, as it allows any implant to pair with any unpaired patient device, and thus to communicate information to the user.

Further preferred embodiments become apparent from the following detailed

description of the invention.

The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein:

• FIG. 1 shows a system comprising an implantable pacemaker, a patient device and a programmer, the patient device being represented by a schematic block diagram showing the main features of the patient device being of importance with respect to a preferred embodiment of the invention.
• FIG. 2 is a state diagram of the patient device illustrating the functional behaviour of the patient device.

The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims.

In Figure 1, a patient device 10 is depicted in an environment also comprising an implant 12 and a programmer 14.

Patient device 10 is a patient device comprising - among other features of no particular interest for the present invention - a patient device transceiver eTRX, connected to an antenna 20 and to a patient device control unit eCTRL. Control unit eCTRL is connected to a timer 22 and to a patient device memory eMEM. Memory eMEM comprises program or instruction data defining an assignment procedure to be carried out by the control unit CTRL and the patient device during pairing of patient device 10 to an implant. Memory eMEM also comprises dedicated address space for storing an implant identification code IID.

Control unit eCTRL further is connected to a patient device read only memory eROM comprising the patient devices identification code EID (external device ID).

The implant also comprises a memory iMEM, that preferably is a read only memory ROM for storing an implant identification code IID, a control unit iCTRL connected to said implant's memory iMEM and a transceiver iTRX for bidirectional data communication with said patient device 10.

The tranceiver eTRX of the patient device and of the implant iTRX are both adapted to operate in the MICS band, a wireless communication frequency band reserved for medical implant communications services.

A real world environment may comprise a plurality of patient devices and implants. Therefore, any patient device in such environment shall be assigned to its specific single implant or to no implant at all. Assigning a patient device to an implant is called pairing for the purpose of this description.

Patient device 10 may be in different states of pairing. Patient device 10 may be unpaired, can be soft paired or can be permanently paired (hard paired) to a specific implant. Soft pairing of a patient device to an implant results from automatic pairing, whereas hard pairing of a patient device to an implant results from manual pairing, e. g. via programmer 14.

When in its soft paired state, patient device 10 will return to its unpaired state if for a predetermined period of time no data communication has occurred with the implant that patient device 10 is paired to. For a hard paired patient device, no such period of time is applicable, thus a hard paired patient device is permanently paired to a specific implant.

When patient device 10 is in its unpaired state, patient device 10 also is in a search mode wherein patient device 10 carries out a protocol for automatic pairing. As long as patient device 10 is paired to its specific implant, patient device 10 may be either in a wait mode as long as no data communication is going on with the implant patient device 10 is assigned (paired) to, or in a communication mode during data communication between patient device 10 and the implant patient device 10 is paired to.

As long as patient device 10 is unpaired and therefore is in its search mode, control unit eCTRL causes the patient devices transceiver eTRX to periodically scan the MICS band in order to determine a least used channel. This is called listen before talk. Thereafter, patient device 10 will use said least used channel to send out a data packet containing the patient device's identification code EID and an unspecific implant identification code IID as is stored in memory eMEM. Since, when in its search mode patient device 10 is in its unpaired state, no or an unspecific implant identification code is stored in said memory eMEM. In said data packet, an origin identifier bit is set in order to mark the data packet as originating from a patient device.

An implant like implant 12 scanning all channels of the MICS bend eventually may receive a data packet originating from patient device 10. If said data packet contains a specific implant identification code IID that does not correspond to the receiving implant's implant identification code IID, then the receiving implant will not respond to such data packet. On the other hand, if the data packet received by the implant contains an unspecific implant identification code IID (e. g. IID = 0), the implant will respond to said data packet by sending out a data packet containing the patient device identification code EID as received with said incoming data packet, its implant identification code IID and a origin identifier bit set as to mark a data packet originating from an implant.

If patient device 10 receives such data packet originating from an implant containing the patient device's own identification code EID, such data packet causes patient device 10 to enter its tentatively paired mode and to store the implant identification code IID received with said data package in memory eMEM.

Patient device 10 thereupon will send out a further data packet with its own identification code EID being the specific patient device identification code as stored in patient device's eROM and the origin identifier bit set to "patient device". Thereafter, patient device 10 will wait for a predetermined first period of time for a response data packet from the specific implant patient device 10 is tentatively paired to. If during said predetermined period of time a response data packet is received from the implant the patient device is tentatively paired to, and said response data packet contains the patient device's own identification code, then patient device 10 will enter its soft paired state.

The patient device will stay in its soft paired state as long as a data communication periodically occurs with the implant to which the patient device is paired, and as long as no manual reset of the patient device to its unpaired state occurs.

If for another predetermined period of time, being longer than said first period of time that the patient device will wait until leaving its tentatively paired state no data communication between the patient device and the implant it is paired to occurs, the soft paired state is cancelled and the patient device returns into its unpaired state. This is controlled by timer and control unit eCTRL, and is performed by storing an unspecific implant identification code IID, e.g. IID=0, into memory eMEM of patient device 10.

At any time patient device 10 may be manually reset by pressing reset button RESET, or via other means, e.g., a physician programmer or via the internet.

For further details of the patient device's behaviour with respect to pairing please refer to the state diagram in Figure 2.

Although an exemplary embodiment of the present invention has been shown and described, it should be apparent to those of ordinary skill that a number of changes and modifications to the invention may be made without departing from the spirit and scope of the invention. This invention can readily be adapted to such devices by following the present teachings. All such changes, modifications and alterations should therefore be recognized as falling within the scope of the present invention.