Patent Description:
Implantable neurostimulator devices are devices that generate and deliver electrical stimuli to body nerves and tissues for the therapy of various biological disorders, such as pacemakers to treat cardiac arrhythmia, defibrillators to treat cardiac fibrillation, cochlear stimulators to treat deafness, retinal stimulators to treat blindness, muscle stimulators to produce coordinated limb movement, spinal cord stimulators to treat chronic pain, cortical and deep brain stimulators to treat motor and psychological disorders, and other neural stimulators to treat urinary incontinence, sleep apnea, shoulder subluxation, etc. The description that follows will generally focus on the use of the invention within a Deep Brain Stimulation (DBS) or Spinal Cord Stimulation (SCS) system, such as that disclosed in <CIT> and <CIT>. However, the present invention may find applicability with any implantable neurostimulator device system.

A DBS or SCS system typically includes an Implantable Pulse Generator (IPG) <NUM> shown in <FIG>. The IPG <NUM> includes a biocompatible device case <NUM> that holds the circuitry and a battery <NUM> for providing power for the IPG to function. The IPG <NUM> is coupled to tissue-stimulating electrodes <NUM> via one or more electrode leads that form an electrode array. For example, one or more percutaneous leads <NUM> can be used having electrodes <NUM> carried on a flexible body. In another example, a paddle lead <NUM> provides electrodes <NUM> positioned on one of its generally flat surfaces. Lead wires within the leads are coupled to the electrodes <NUM> and to proximal contacts <NUM> insertable into lead connectors <NUM> fixed in a header <NUM> on the IPG <NUM>, which header can comprise an epoxy for example. Once inserted, the proximal contacts <NUM> connect to header contacts <NUM> within the lead connectors <NUM>, which are in turn coupled by feedthrough pins <NUM> through a case feedthrough <NUM> to stimulation circuitry <NUM> within the case <NUM>. The number and type of leads, and the number of electrodes on such leads, can vary depending on the application. The conductive case <NUM> can also comprise an electrode.

In a SCS application, as is useful to alleviate chronic back pain for example, the electrode lead(s) are typically implanted in the spinal column proximate to the dura in a patient's spinal cord, preferably spanning left and right of the patient's spinal column. The proximal contacts <NUM> are tunneled through the patient's tissue to a distant location such as the buttocks where the IPG case <NUM> is implanted, at which point they are coupled to the lead connectors <NUM>. In a DBS application, as is useful in the treatment of tremor in Parkinson's disease for example, the IPG <NUM> is typically implanted under the patient's clavicle (collarbone). Percutaneous leads <NUM> are tunneled through and under the neck and the scalp where the electrodes <NUM> are implanted through holes drilled in the skull and positioned for example in the subthalamic nucleus (STN) and the pedunculopontine nucleus (PPN) in each brain hemisphere.

IPG <NUM> can include an antenna 34a allowing it to communicate bi-directionally with a number of external devices discussed subsequently. Antenna 34a as shown comprises a conductive coil within the case <NUM>, although the coil antenna 34a can also appear in the header <NUM>. When antenna 34a is configured as a coil, communication with external devices preferably occurs using near-field magnetic induction. IPG <NUM> may also include a Radio-Frequency (RF) antenna 34b. In <FIG>, RF antenna 34b is shown within the header <NUM>, but it may also be within the case <NUM>. RF antenna 34b may comprise a patch, slot, or wire, and may operate as a monopole or dipole. RF antenna 34b preferably communicates using far-field electromagnetic waves, and may operate in accordance with any number of known RF communication standards, such as Bluetooth, Zigbee, WiFi, MICS, and the like. IPG <NUM> can also include functionally-similar devices that are not fully implantable in the patient. For example, the IPG <NUM> can comprise an External Trial Stimulator (ETS), having leads implantable in the patient but connected to a circuitry portion that is external to the patient. When an ETS is used, stimulation can be tried on a prospective implant patient without going so far as to implant the IPG's case <NUM>. ETS devices are explained further in <CIT>.

Stimulation in IPG <NUM> is typically provided by pulses, as described in the above-referenced '<NUM> Publication. Pulses can be formed by stimulation circuitry <NUM> in the IPG, again as described in the '<NUM> Publication. Stimulation circuitry <NUM> can comprise a part of, or can communicate with, the IPG's control circuitry <NUM>. The control circuitry <NUM> can comprise a microcontroller, microprocessor, Field Programmable Grid Array, Programmable Logic Device, Digital Signal Processor or like devices. In one example, control circuitry <NUM> can comprise or include an MSP430 microcontroller device, manufactured by Texas Instruments, Inc. Control circuitry <NUM> may also be based on well-known ARM microcontroller technology. Control circuitry <NUM> may include a central processing unit capable of executing instructions, with such instructions stored in volatile or non-volatile memory within the control circuitry. Control circuitry <NUM> may also include, operate in conjunction with, or be embedded within, an Application Specific Integrated Circuit (ASIC), such as described in <CIT>, <CIT>, <CIT>, or <CIT>. The control circuitry <NUM> may comprise an integrated circuit with a monocrystalline substrate, or may comprise any number of such integrated circuits. Control circuitry <NUM> may also be included as part of a System-on-Chip (SoC) or a System-on-Module (SoM) which may incorporate memory devices and other digital interfaces.

IPG <NUM> may also include a magnetic field sensor <NUM>, such as a Hall effect sensor. Magnetic field sensor <NUM> can also comprise other devices or circuits in the IPG, for example as taught in <NUM>,<NUM>,<NUM> and <CIT>. Use of the magnetic field sensor <NUM> in an IPG <NUM> is explained further below.

<FIG> shows various external devices that can wirelessly communicate with the IPG <NUM>, including a patient hand-held remote controller (RC) <NUM> and a clinician programmer (CP) <NUM>. Both of devices <NUM> and <NUM> can be used to wirelessly transmit information, such as a stimulation program, to the IPG <NUM>-that is, to program stimulation circuitry <NUM> to produce stimulation (e.g., pulses) with a desired amplitude and timing. Both devices <NUM> and <NUM> may also be used to adjust one or more stimulation parameters of a stimulation program that the IPG <NUM> is currently executing, to update software in these devices, or to place the IPG into different operational modes as discussed further below. Devices <NUM> and <NUM> may also wirelessly receive information from the IPG <NUM>, such as various status information, etc..

Clinician programmer (CP) <NUM> is described further in <CIT>, and can comprise a computing device <NUM>, such as a desktop, laptop, notebook computer, tablet, mobile smart phone, or Personal Data Assistant (PDA)-type mobile computing device, etc. In <FIG>, computing device <NUM> is shown as a laptop computer that includes typical computer user interface means such as a screen <NUM>, a mouse, a keyboard, speakers, a stylus, a printer, etc., not all of which are shown for convenience. Also shown in <FIG> are accessory devices for the CP <NUM> that are usually specific to its operation as a stimulation controller, such as a communication "wand" <NUM> coupleable to suitable ports on the computing device <NUM>, such as USB ports <NUM> for example.

The antenna used in the CP <NUM> to communicate with the IPG <NUM> can depend on the type of antennas included in the IPG. If the patient's IPG <NUM> includes a coil antenna 34a, wand <NUM> can likewise include a coil antenna 70a to establish near-field magnetic-induction communications at small distances. In this instance, the wand <NUM> may be affixed in close proximity to the patient, such as by placing the wand in a belt or holster wearable by the patient and proximate to the patient's IPG <NUM>. If the IPG <NUM> includes an RF antenna 34b, the wand <NUM>, the computing device <NUM>, or both, can likewise include an RF antenna 70b to establish communication at larger distances.

To program stimulation programs or parameters for the IPG <NUM>, or to otherwise control the IPG <NUM>, the clinician interfaces with a clinician programmer graphical user interface (GUI) <NUM> provided on the display <NUM> of the computing device <NUM>. As one skilled in the art understands, the GUI <NUM> can be rendered by execution of clinician programmer software <NUM> stored in the computing device <NUM>, which software may be stored in the device's non-volatile memory <NUM>. Execution of the clinician programmer software <NUM> in the computing device <NUM> can be facilitated by control circuitry <NUM> such as one or more microprocessors, microcomputers, FPGAs, DSPs, other digital logic structures, etc., which are capable of executing programs in a computing device, and which may comprise their own memories. For example, control circuitry <NUM> can comprise an i5 processor manufactured by Intel Corp, as described at https://www. com/ content/ www/ us/ en/ products/ processors/ core/ i5-processors. Such control circuitry <NUM>, in addition to executing the clinician programmer software <NUM> and rendering the GUI <NUM>, can also enable communications via antennas 70a or 70b to communicate stimulation parameters chosen through the GUI <NUM> to the patient's IPG <NUM>.

Remote controller (RC) <NUM> can be as described in <CIT> for example, and may comprise a controller dedicated to work with the IPG <NUM>. RC <NUM> may also comprise a general purpose mobile electronics device such as a mobile phone which has been programmed with a Medical Device Application (MDA) allowing it to work as a wireless controller for the IPG <NUM>, as described in <CIT>. Like the CP <NUM>, RC <NUM> includes a graphical user interface including a display <NUM> and means for entering commands or selections, such as buttons <NUM> or selectable graphical elements rendered on the display. The RC <NUM>'s graphical user interface also enables a patient to adjust stimulation parameters, although it may have limited functionality when compared to the more-powerful CP <NUM> described above. The RC <NUM> can have one or more antennas capable of communicating with the IPG <NUM>. For example, the RC <NUM> can have a near-field magnetic-induction coil antenna 54a capable of wirelessly communicating with the coil antenna 34a in the IPG <NUM>. The RC <NUM> can also have a far-field RF antenna 54b capable of wirelessly communicating with the RF antenna 34b in the IPG <NUM>. The RC <NUM> includes control circuitry <NUM> which may be similar to the control circuitry in the CP <NUM>, and which includes memory for storing software and the like. The RC <NUM> typically has a battery (not shown) to provide operating power, and such battery is usually rechargeable (similar to a cell phone).

The IPG <NUM>, RC <NUM>, and CP <NUM>, as well as communicating with each other, can communicate with a network <NUM>. Network <NUM> can comprise a WiFi gateway and the Internet for example, and communication between the devices can occur using the network <NUM> as an intermediary. A server <NUM> can be connected to the network, which can for example be used to send stimulation programs or other useful information (e.g., software updates) to the various devices in the system.

<FIG> further shows a permanent bar magnet <NUM> in the communication system for the IPG <NUM>. Use and function of the bar magnet <NUM> is described further below.

A method is disclosed for controlling an implantable medical device (IMD), which may comprise: receiving at the IMD a first instruction to cause the IMD to enter a protective mode, wherein in the protective mode the IMD is enabled to execute one or more protective measures to protect the IMD from a first field produced by equipment; while in the protective mode, receiving at the IMD a second instruction to cause the IMD to enter a pairing mode, wherein the pairing mode enables the IMD to pair for communications with an external device; while in the protective mode and the pairing mode, receiving at the IMD, from a first external device, a third instruction to cause the IMD and the first external device to pair for communications; and while in the protective mode, receiving at the IMD, from the first external device, a fourth instruction to cause the IMD to exit the protective mode.

In one example, the first instruction is received at the IMD from a second external device paired for communications with the IMD, wherein the second external device is different from the first external device. In one example, the second instruction comprises a second magnetic field. In one example, the second magnetic field is produced by an external magnet. In one example, the second magnetic field comprises a DC magnetic field. In one example, the second magnetic field is effective to cause the IMD to enter the pairing mode when the second magnetic field is received at the IMD for a first duration. In one example, the first duration is between a minimum duration and a maximum duration. In one example, the IMD is programmed with the minimum duration and the maximum duration. In one example, the first field comprises an AC magnetic field produced by the equipment. In one example, the method further comprises, while in the protective mode, receiving at the IMD a fifth instruction from the equipment to cause the IMD to execute the one or more protective measures. In one example, the fifth instruction comprises a third magnetic field. In one example, the third magnetic field is produced by the equipment. In one example, the third magnetic field comprises a DC magnetic field produced by a magnet in the equipment. In one example, the third magnetic field is effective to cause the IMD to execute the one or more protective measures when the third magnetic field is received at the IMD for a second duration. In one example, the third magnetic field is effective to cause the IMD to stop executing the one or more protective measures when the third magnetic field is not received at the IMD for a third duration. In one example, the method further comprises periodically broadcasting pairing data from the IMD when the IMD is in the pairing mode. In one example, the protective mode comprises a Magnetic Resonance Imaging (MRI) mode, and wherein the equipment comprises an MRI machine.

A non-claimed method for controlling an implantable medical device (IMD) is disclosed, which may comprise: receiving at the IMD a first instruction to cause the IMD to enter a protective mode, wherein in the protective mode the IMD is enabled to execute one or more protective measures to protect the IMD from a first field produced by equipment; while in the protective mode, detecting the presence of the equipment and thereafter executing the one or more protective measures; while in the protective mode, detecting the absence of the equipment and thereafter stopping the execution of the one or more protective measures; and receiving at the IMD a second instruction to cause the IMD to exit the protective mode.

In one example, the IMD is programmed with a first duration, wherein equipment is detected at a first time and wherein the one or more protective measures are executed the first duration after the first time. In one example, the IMD is programmed with a second duration, wherein the absence of the equipment is detected at a second time and wherein the one or more protective measures are stopped the second duration after the second time. In one example, the presence of the equipment is detected by detecting the first field produced by the equipment. In one example, the first field comprises an AC magnetic field. In one example, the presence of the equipment is detected by detecting a second magnetic field produced by the equipment. In one example, the second magnetic field comprises a DC magnetic field. In one example, the DC magnetic field is produced by a DC magnet in the equipment. In one example, the IMD comprises an implantable stimulation device configured to provide stimulation to a patient's tissue, and wherein entering the protective mode causes the stimulation to stop. In one example, exiting the protective mode causes the stimulation to begin. In one example, the IMD comprises an implantable stimulation device configured to provide normal stimulation or conditional stimulation to a patient's tissue, and wherein entering the protective mode causes the normal stimulation to stop and conditional stimulation to begin. In one example, exiting the protective mode causes the conditional stimulation to stop and the normal stimulation to begin. In one example, the IMD comprises an implantable stimulation device with stimulation circuitry configured to provide normal stimulation to a patient's tissue, wherein the one or more protective measures comprise one or more of the following: disabling the stimulation circuitry; starting conditional stimulation; increasing a power supply voltage of the stimulation circuitry; and/or opening switches in the stimulation circuitry. In one example, the method further comprises disabling telemetry at the IMD upon executing the one or more protective measures. In one example, the method further comprises enabling telemetry upon stopping the execution of the one or more protective measures. In one example, detecting the presence of the equipment does not comprise receiving wireless data telemetry from the equipment. In one example, exiting the protective mode causes the IMD to reset. In one example, the first and second instructions are received from one or more external devices. In one example, the protective mode comprises a Magnetic Resonance Imaging (MRI) mode, and wherein the equipment comprises an MRI machine.

A non-claimed method for pairing an implantable medical device (IMD) for communications with an external device, wherein the IMD is configured to provide therapy to a patient. The method may comprise in order: (a) receiving at the IMD a DC magnetic field from an external magnet; (b) determining at the IMD whether the DC magnetic field is received for a duration, wherein the duration is programmed in memory in the IMD; (c) when the DC magnetic field is received for the duration, resetting the IMD, wherein the reset causes the IMD to stop providing the therapy; (d) if the DC magnetic field is received for longer than the duration, holding the IMD in reset; (e) determining at the IMD whether the DC magnetic field is no longer received at the IMD; and (f) when the DC magnetic field is no longer received, causing the IMD to enter a pairing mode, wherein the pairing mode enables the IMD to pair for communications with the external device.

In one example, the method further comprises in step (f), causing the IMD to start providing the therapy when the DC magnetic field is no longer received. In one example, the method further comprises, prior to step (a), operating the IMD in a normal mode, wherein in the normal mode the IMD provides the therapy. In one example, the method further comprising in step (f), periodically broadcasting pairing data from the IMD when the IMD is in the pairing mode. In one example, the external magnet comprises a permanent bar magnet. In one example, the method further comprising in step (e), exiting reset upon determining at the IMD that the DC magnetic field is no longer received at the IMD. In one example, the therapy comprises measurements taken by the IMD. In one example, the IMD comprises an implantable stimulation device (ISD), and wherein the therapy comprises stimulation provided to a tissue of a patient.

A patient having an implanted IPG may from time to time need to undergo a medical procedure involving the use of high magnetic fields. For example, an IPG patient may require medical imaging using a Magnetic Resonance Imaging (MRI) machine <NUM> (<FIG>). As is known, an MRI machine <NUM> includes a high-powered DC magnet <NUM> (<FIG>) capable of producing a DC magnetic field with strengths of up to several Tesla. This DC magnetic field by itself is not usually harmful to the IPG <NUM>, nor does it present a particular safety issue for the IPG patient. However, when an MRI machine is turned on, AC magnetic fields are produced, which can potentially harm the IPG <NUM> or the patient. Briefly, AC magnetic fields can induce currents in the IPG <NUM>, and in particular in the IPG's leads, which can cause current to be injected into the IPG via the electrode connections. Such current injection can harm the IPG <NUM>'s circuitry, and can also produce uncontrolled stimulation in the patient's tissue.

As a result, it is known to place an IPG <NUM> into an MRI mode prior to the patient receiving an MRI scan. As explained further below, the IPG can be placed wirelessly into an MRI mode using an external device, such as the patient remote controller <NUM> described earlier (<FIG>). Even though a patient may have the ability to place his IPG <NUM> into MRI mode via his RC <NUM>, often times a clinician will enter this mode on the patient's behalf in advance of the patient receiving an MRI scan, such as by using the patient's RC <NUM> or the clinician's CP <NUM>.

When placed in the MRI mode, the IPG <NUM>'s control circuitry <NUM> can take one or more MRI protective measures to mitigate the potentially deleterious effects of the MRI scan. For example, in MRI mode, the control circuitry <NUM> may disable the stimulation circuitry <NUM> from providing stimulation to the patient, although this isn't always the case. In other examples, entering the MRI mode can allow the IPG <NUM> to provide MRI-conditional stimulation which may differ from normal stimulation otherwise provided when the IPG <NUM> is operating in a normal mode. Additionally or alternatively, when in the MRI mode, the control circuitry <NUM> may increase one or more voltages within the IPG <NUM> to prevent unwanted current induction into the IPG. For example, the control circuity <NUM> may increase the power supply voltage for the stimulation circuitry <NUM>-typically known as the compliance voltage-to a maximum value (e.g., 18V). See, e.g., <CIT> and PCT (Int'l) <CIT> (discussing the compliance voltage and its adjustment in an IPG). The IPG may also modify or suspend other operations in MRI mode. For example, the control circuitry <NUM> may open passive charge recovery switches in the stimulation circuitry <NUM>. These switches are connected to the electrodes, and when closed will passively couple charge to an AC ground. See, e.g., <CIT> and <CIT> (discussing passive charge recovery switches). Because these switches can potentially create a path for MRI-injected electrode currents, they are opened during MRI mode. Further prior art is known from <CIT>.

After the patient has received their MRI scan, the IPG <NUM> preferably exits the MRI mode and assumes operation in a normal mode, including the provision of normal stimulation. Normally, the MRI mode can be exited as it was entered-though use of the patient's RC <NUM> or another external device with which the IPG is paired. However, experience teaches that not all patients will have their RCs <NUM> readily available after their MRI scan, and thus are at risk of being unable to exit the MRI mode. This could occur for any number of reasons. A patient may not be accustomed to using their RC, may not often carry it, may not keep it charged, or their RC may simply be broken. If the patient's IPG <NUM> was placed into MRI mode by the clinician, the chances increase that the patient will be reliant on the clinician to control such modes, meaning that the patient will likely not have their RC <NUM> at the end of the MRI scan, and instead will need to rely on the clinician to exit this mode. A patient may also need an MRI scan on an emergency basis, and may not have access to their RC <NUM> at the time of the scan. Regardless of the reason for the patient not having their RC <NUM>, the inability to exit MRI mode can be a substantial problem. As noted above, normal stimulation is usually suspended upon entering the MRI mode, and if a patient cannot exit such mode, they will be unable to receive such therapy. Even if MRI-conditional stimulation is provided to the patient while the IPG <NUM> is in the MRI mode, such stimulation may not be optimal when compared to normal stimulation.

The above problems can be addressed by programming an IPG <NUM> appropriately, and by modifying the manner in which the IPG <NUM> operates in different modes. In accordance with the disclosed techniques, another external device, and in particular another RC <NUM>' which may not have been previously paired to the IPG <NUM>, can be used to take the IPG <NUM> out of MRI mode, and to resume operation in a normal mode.

<FIG> shows a communication environment of an improved IPG <NUM>, including various external devices that can be implicated in the practice of the disclosed techniques. Such external devices include the patient RC <NUM>. The RC <NUM>'s control circuitry <NUM> can include or communicate with memory <NUM> that stores an ID code (RC1) for the RC <NUM>. This ID code may be stored with other credentials or certificates that allow the RC <NUM> to communicate with various IPGs such as IPG <NUM>. The RC's control circuitry <NUM> can also include a memory <NUM> that stores the ID codes (and other credentials and certificates) for IPGs with which the RC <NUM> has previously been paired for communications. In this example, it is assumed that RC <NUM> has previously been paired with IPG <NUM>, and thus stores that IPG's ID code (IPG1). Notice that the IPG's control circuitry <NUM> can have similar memories <NUM> and <NUM> that respectively store the IPG's ID code (IPG1), and the ID code of previous RCs with which it has been paired (such as RC1). Again, the ID codes stored in memories <NUM> and <NUM> may be stored with other credentials or certificates as necessary to communicate with external devices such as RC <NUM>. RC <NUM>'s GUI can include an option that allows the user to review IPGs to which it is currently paired ("IPG communications"), which can populate information stored in memory <NUM>. RC's GUI can further include an option to allow RC <NUM> to be paired with a new IPG ("IPG pairing"), which when selected can cause the RC <NUM> to scan for new IPGs, as explained further below.

In the example shown, an "IPG modes" portion of the RC <NUM>'s GUI can allow the patient (or clinician) to cause the IPG <NUM> to enter different operational modes. For example, the RC <NUM> can include a selectable option to enter the IPG <NUM> into the MRI mode described previously, or to exit that mode, as explained further below. A user may also use the RC <NUM> to select other IPG <NUM> operational modes (Mode <NUM>, Mode <NUM>, etc.), although such other modes are not relevant to the present disclosure. In some examples, the RC can include a selectable option to allow the IPG <NUM> to operate in its normal mode, although mode logic <NUM> in the IPG <NUM> may also cause the IPG to operate in the normal mode automatically, as explained further below.

Relevant external devices in the system can include another RC <NUM>' which has not been previously paired to the IPG <NUM>. RC <NUM>' stores its ID code (RC2) in its memory <NUM>, but notice that its memory <NUM> is blank because this RC <NUM>' has not been previously paired with another IPG (or at least in this example has not been previously paired with IPG <NUM>). As explained further below, RC <NUM>' can be used to cause the IPG <NUM> to exit MRI mode (after an MRI scan), which is especially useful if the patient does not have access to RC <NUM> already paired to the IPG <NUM>. In this example, it is assumed for simplicity that RC <NUM>' comprises a remote controller similar or identical to remote controller <NUM>. However, RC <NUM>' could comprise any new device in the communication system, such as the clinician programmer <NUM>, or another external device capable of communicating with the IPG <NUM>.

Also relevant in the communication environment of <FIG> is bar magnet <NUM>. Bar magnet <NUM> is provided to the patient upon implantation of IPG <NUM>, and can be used by the patient to cause a "reset" of the IPG <NUM>. For example, if the patient is experiencing severe side effects or problems related to the stimulation therapy that the IPG <NUM> is providing, the patient can place the bar magnet <NUM> proximate to the IPG <NUM> to cause it to enter a reset mode. In the reset mode, the IPG <NUM>'s control circuitry <NUM> can suspend the delivery of stimulation to the patient, as discussed further below. Reset can also suspend telemetry and otherwise operate the IPG <NUM> in a low power state. Bar magnet <NUM> can also have other functions in the system, and in particular can be used to pair RCs with the IPG <NUM>, again as discussed further below.

<FIG> also shows the basic circuitry in the IPG <NUM> that is implicated by the disclosed techniques. IPG <NUM> includes the control circuitry <NUM> mentioned earlier, although when used with the disclosed techniques this control circuitry <NUM> is programmed in a unique manner. In particular, mode logic <NUM> within the control circuitry <NUM> is programmed to place the IPG <NUM> into different modes and under certain conditions as explained further below. Such modes include a normal mode, which comprises the basic mode in which the IPG <NUM> is active and providing normal stimulation to the patient; the MRI mode discussed above (which may cause normal stimulation to cease, or which can be used to provide MRI-conditional stimulation); and a pairing mode used for pairing the IPG <NUM> for communications with an external device. The mode logic <NUM> can also issue certain control signals which may be associated with one of more of these modes. For example, when in the normal mode, a normal stimulation control signal indicates whether normal stimulation can commence. An IPG reset control signal, as well as resetting the IPG, can cause the IPG to operate in the pairing mode, although this depends on whether or not the IPG is currently in the MRI mode, as explained further below. An MRI protective measure control signal can indicate when certain MRI protective measures such as those mentioned above should be executed, and as explained further below, this control signal is issued at certain times during the MRI mode. An MRI-conditional stimulation control signal indicates when MRI-conditional stimulation can issue when the IPG is in the MRI mode. A telemetry enable/disable control signal can be used to enable or disable the IPG <NUM> to communicate with external devices to which it is paired. Mode logic <NUM> may also place the IPG <NUM> into other various modes, but those modes are not relevant to discuss here.

The mode logic <NUM> is responsive, at least, to the magnetic field sensor <NUM> in the IPG <NUM>, and to commands that are received at the IPG's antenna 34a and/or 34b. Magnetic fields received by the magnetic field sensor <NUM> and commands received at the IPG's antenna may be generally considered as "instructions," because either can inform the mode logic <NUM> how to operate. Although not shown, one skilled will understand that the IPG <NUM> would include demodulation circuitry to convert telemetry received at the antenna 34a/b into digital information understandable by the mode logic <NUM>. As noted earlier and as relevant to external communications, IPG <NUM>'s control circuitry <NUM> can include or communicate with memory <NUM> that stores an ID code (IPG1) for the IPG <NUM>, and memory <NUM> that stores ID codes for previously-paired RCs, as well as other necessary credentials or certificates.

Also included in the control circuitry <NUM> is timer circuitry <NUM>. The timer <NUM> is useful to determine whether certain durations have run. Such durations are programmable in memory, and include a normal pairing duration (<NUM>), a detect field onset duration (<NUM>), a detect field offset duration (<NUM>), and a MRI pairing duration (<NUM>), which can have minimum and maximum values. These durations are described further below.

<FIG> discuss different IPG modes, how such modes and entered and exited, and how such modes function in the IPG <NUM>. <FIG> shows a reset/pairing mode, which, as controlled by mode logic <NUM>, combines the processes of placing the IPG <NUM> into reset followed by placing the IPG in a pairing mode that allows the IPG to establish communications with an external device. In <FIG>, the reset/paring mode shows operation to pair the IPG with an RC <NUM>, although pairing with another external device, such as the CP <NUM>, would occur similarly.

The reset/pairing mode is discussed chronologically, and at t0 it is assumed that the IPG <NUM> is operating in a normal mode. In the normal mode, the IPG <NUM> is controlled (by mode logic <NUM>) to provide normal stimulation. Normal telemetry is also enabled in the normal mode, as are other IPG functions not relevant to mention here. When normal telemetry is enabled, the IPG <NUM> can freely communicate with external devices, such as RC <NUM>, with which the IPG <NUM> has already been paired, exchanging previously stored credentials or certificates as necessary. Preferably, to save power in the IPG <NUM>, normal telemetry is enabled by periodically powering the antennas 34a or 34b in the IPG <NUM> and any associated communication circuitry (e.g., modulation and demodulation circuitry) during short listening windows (e.g., <NUM>) which are issued and at a period of about <NUM>-<NUM> seconds. How normal telemetry occurs with a paired RC can depend on the type of connection to be established and the communication standard that governs that connection. For example, if Bluetooth or Bluetooth Low Energy (BLE) is used for the connection, the IPG <NUM> can listen for a broadcast from RC <NUM> during each of the listening windows. Upon receiving proper credentials from RC <NUM> (such as the RC's ID code RC1, stored in the IPG's memory <NUM>), a communication session can be established, at which time the IPG <NUM> can continuously power its antenna 34a or 34b and associated communication circuitry until the end of the communication session. Communication sessions can also be governed by communication intervals that also involve periodic powering of the telemetry circuitry. For example, when BLE communications are used, the connection interval can be in the range of <NUM> to <NUM>.

At time t1, bar magnet <NUM> is placed over (or proximate to) the IPG <NUM>. The magnetic field sensor <NUM> in the IPG <NUM> detects the magnetic field produced by the bar magnet <NUM>, and provides information to the mode logic <NUM> that a magnetic field is present. The mode logic <NUM> monitors the output of the sensor <NUM> to determine whether a magnetic field is consistently detected for a time period, such as <NUM> seconds or more. This time period, called the normal pairing duration, can be programmed in memory <NUM> (<FIG>), and can be monitored by the timer <NUM> (<FIG>). Requiring the presence of a continuous magnetic field for a time period is preferred to ensure that the IPG <NUM> isn't inadvertently placed into the reset/pairing mode by a transient magnetic field to which the patient might be exposed.

If the bar magnet <NUM> is present for the time period, the mode logic <NUM> issues a reset at time t2. Different functions in the IPG <NUM> can be affected upon reset, but significantly here the reset disables the stimulation circuitry <NUM> and thus normal stimulation is stopped. In this respect, the bar magnet <NUM> acts as a safety device by providing the patient a means for stopping stimulation on an emergency basis. For example, if the stimulation being provided by the IPG <NUM> is proving problematic for the patient, and the patient is not able to quickly remedy the situation using their RC <NUM>, the bar magnet <NUM> provides a quick and safe means of easily stopping stimulation. In this regard, note that if the magnetic field is present and detected by the magnetic field sensor <NUM> for longer than the two-second time period, the mode logic <NUM> will hold the IPG in reset (from t2 to t3) until the bar magnet <NUM> is removed. Therefore, a patient experiencing problems can simply keep the bar magnet <NUM> continually proximate to the IPG to keep it in reset, and to prevent potentially problematic stimulation from re-occurring. (In this circumstance, the IPG patient would normally promptly make an appointment to see his clinician to attempt to rectify the problem). Use of a bar magnet <NUM> to cause a reset, and the actions that can occur in the IPG <NUM> when such a reset is issued, are discussed further in <CIT>.

At time t3, the bar magnet <NUM> is removed from the IPG, and thus sensor <NUM> stops detecting its magnetic field. The mode logic <NUM> then, once the reset procedure is completed (which may take a few seconds) causes the IPG <NUM> to exit reset. Upon exiting reset, the mode logic <NUM> again enables normal stimulation, and as is most significant here also preferably automatically causes the IPG to enter the pairing mode. Other conditions not mentioned here may also need to occur before automatically entering the pairing mode.

In the pairing mode, the IPG <NUM> attempts to pair with an external device. During the pairing mode, the IPG <NUM> will periodically broadcast pairing (advertising) data. To save power, such pairing data may be periodically broadcast during transmission windows, such as every <NUM> seconds. In one example, the pairing data can comprise the IPG's ID code or serial number ("IPG1," memory <NUM>), which the RC <NUM> may recognize (if stored in memory <NUM>). The pairing data can also comprise additional data necessary for authentication, which may be necessary to allow the IPG <NUM> to be paired with a previously-unknown external device. In this regard, the pairing data may depend on the type of connection to be established and the communication standard that govern that connection. For example, if Bluetooth or BLE is used, that standard will dictate the particulars of the pairing data to be broadcast by the IPG <NUM>. During pairing mode, the IPG <NUM> can still receive communications from external devices that were previously paired to the IPG, and should this occur, the pairing mode is exited at the IPG.

At time t4, it is assumed that an external device, such as RC <NUM>, is present (i.e., proximate to the IPG <NUM>) and able to pair with the IPG <NUM>. The user selects the IPG pairing mode at the GUI of the external device (e.g., RC <NUM>) to scan for available IPGs, and selects the option to connect with IPG <NUM>. At this point, RC <NUM> receives the pairing data being broadcast from IPG <NUM>. If the pairing data includes IPG data already known to the RC <NUM>, such as the IPG <NUM>'s ID code (IPG1) stored in RC <NUM>'s memory <NUM>, pairing and connection with IPG <NUM> can be simplified. For example, if RC <NUM> and IPG <NUM> were previously paired (as is assumed here), each device would know that fact, as each has stored the other's ID codes and other certificates and credentials (see memories <NUM> and <NUM>, <FIG>). If the pairing data does not include IPG data already known to the RC <NUM>, additional authentication data may be required to allow the devices to pair. For example, the user may need to enter a password or PIN for the IPG <NUM> in the GUI of the RC <NUM>, or authentication can occur automatically through the exchange of secure keys at part of an authentication procedure. Again, the particulars of the pairing data and the data exchanged to allow the RC <NUM> to connect to a new IPG <NUM> may differ depending on the communication standard used, which can vary in different implementations.

It is preferred that the IPG not operate in the pairing mode indefinitely. In this regard, a pairing mode duration may be set and stored with the IPG's control circuitry <NUM> and/or mode logic <NUM>. This pairing mode duration is preferably long enough to give the user of the external device (e.g., RC <NUM>) time to complete the pairing procedure using the RC's GUI as just explained. In one example, the pairing mode duration may be about <NUM> minutes. After expiration of the pairing mode duration, the mode logic <NUM> preferably cusses the IPG to revert to operation in its normal mode. Details concerning this pairing mode duration are omitted from the Figures for simplicity.

Once the IPG <NUM> and RC <NUM> are paired and connected at time t4, the mode logic <NUM> in the IPG's control circuitry <NUM> can cause the IPG exit the pairing mode, and to automatically enter the normal mode. Normal stimulation started at t3 thus can continue, and normal telemetry can be enabled with the now-paired RC <NUM>. Although not shown, both the IPG and the external device (e.g., RC <NUM>), can store information relevant to the device with which its now paired, e.g., by storing relevant information about the other device in memories <NUM> and <NUM> (<FIG>), and this may be especially useful to do if this is the first time that the IPG and external device are being paired.

<FIG> shows the MRI mode. At time t10, the IPG <NUM> is operating in the normal mode, and is providing normal stimulation. Normal telemetry is also enabled with RC <NUM>, to which the IPG <NUM> is currently paired. At time t11, the IPG <NUM> is placed in MRI mode, which occurs using the GUI of paired RC <NUM>, as explained earlier. This causes RC <NUM> to transmit an MRI mode instruction to the IPG <NUM>, which is received at the IPG's antenna 34a or 34b. At this point, normal stimulation is stopped. Additionally, if the IPG <NUM> is capable of providing MRI-conditional stimulation as described earlier, such conditional stimulation can be commenced. As noted earlier, MRI mode is entered in advance of the patient receiving an MRI scan. The delay between entering the MRI mode (t11) and the beginning of the MRI scan (t12) can comprise anywhere between a few minutes or a number of days.

At time t12, it is assumed that the patient is proximate to the MRI machine <NUM> and is getting ready to have their MRI scan taken. At this point, the magnetic field sensor <NUM> in the IPG <NUM> will detect the presence of the large DC magnet <NUM> in the MRI machine. As such, the IPG <NUM> detects the MRI machine <NUM> without receiving wireless data from the medical equipment. Note in this example that the magnetic field sensor <NUM> is unable to differentiate between a magnetic field produced by the bar magnet <NUM> (<FIG>) and the magnetic field produced by the MRI magnet <NUM>. This is however not problematic, because the mode logic <NUM> in the IPG <NUM> will assess the duration of such fields, and make informed determinations as necessary to operate the IPG in a proper mode, as explained further below.

The mode logic <NUM> will also enter modes conditionally depending on the IPG's current operating mode. For example, at time t12, the mode logic <NUM> will not issue a reset when the IPG <NUM> is in the MRI mode, even if the magnetic field (from magnet <NUM>) is present for more than <NUM> seconds. Compare <FIG>, where the mode logic <NUM> issues a reset when the IPG <NUM> is in a normal mode. When a magnet is sensed in MRI mode, it is preferred to not issue a reset (compare t2, <FIG>), as this could hamper the IPG <NUM>'s ability to provide MRI protective measures, as described next. Note that the magnetic field sensor <NUM> will detect the MRI magnet <NUM> at time t12 when the patient is merely proximate to the MRI machine <NUM>, such as when the patient is in the room containing the MRI machine <NUM>, or is laying in the MRI's machine's bed. In short, the MRI machine may not yet be operating when the MRI magnet <NUM> is detected at time t12.

When the IPG <NUM> is in the MRI mode, the mode logic <NUM> will assess whether any magnetic field (presumably, but not necessarily, from the MRI magnet <NUM>) is sensed by magnetic field sensor <NUM> for a time period, such as <NUM> (X) seconds. This time period, called the detect field onset duration, can be programmed in memory <NUM> (<FIG>), and can be monitored by the timer <NUM> (<FIG>). This time period is preferably long for a couple of reasons: first, to ensure that the MRI magnet <NUM> is continuously detected (as opposed to transient magnetic fields); second, to differentiate detection of the MRI from the bar magnet <NUM> which can also be used during MRI mode, as explained further below with reference to <FIG>.

If the magnetic field sensor <NUM> detects a magnetic field for this time period, at time t13, the IPG <NUM> automatically starts executing MRI protective measures. These MRI protective measures were discussed previously, and can include: disabling normal stimulation, or providing MRI-conditional stimulation (although this may also preferably have occurred earlier at time t11); increasing voltages within the IPG <NUM>, such as the compliance voltage; opening passive charge recovery switches; etc. As noted earlier, because some of these MRI protective measures involve use of the IPG's stimulation circuitry <NUM>, it is preferred that no reset issues in the MRI mode (between t12 and t13) as this may disable the stimulation circuitry.

Note that the MRI protective measures are preferably automatically executed by mode logic <NUM> at t13 (after <NUM>) even is the MRI machine <NUM> is not yet on and producing an AC magnetic field. As noted earlier, it is these AC magnetic fields that are of potential concern, as they can cause AC current injection into the IPG <NUM>. In this regard, note that the time period between the detection of the MRI's DC magnetic <NUM> (t12), and the start of AC magnetic fields by the MRI machine (at t14) would normally be significantly longer than <NUM> seconds, because it will normally take longer than this to get the patient situated in the MRI machine <NUM> before the MRI machine is turned on. As such, the MRI protective measures are executed in the IPG <NUM> in advance of the potentially-harmful AC magnetic fields. At time t13, normal telemetry is also preferably disabled, although this could also have occurred earlier in the MRI mode. Disabling normal telemetry causes the IPG <NUM> to stop issuing listening windows, which prevents the IPG <NUM> from communicating with its current-paired RC <NUM>.

At time t14, it is assumed that the MRI machine <NUM> is now operating and is producing an AC magnetic field, although as just noted the IPG <NUM> has likely already began executing MRI protective measures at time t13. At time t15, the AC magnetic fields have ceased and the MRI machine <NUM> is still off, and thus the patient's MRI scan is complete. (Note that the IPG's magnetic field sensor <NUM> does not in this example sense the presence or termination of the AC magnetic fields, although that is possible in other embodiments). Even after the MRI machine <NUM> is turned off at time t15, the patient is still proximate the MRI machine <NUM>, and so the magnetic field sensor <NUM> continues to sense the MRI machine's DC magnet <NUM>.

At time t16, it is assumed that the patient is no longer proximate to the MRI machine <NUM>, and therefore that magnetic field sensor <NUM> is no longer sensing the presence of the MRI machine's magnet <NUM>. At this point, mode logic <NUM> assesses whether magnetic fields have consistently ceased for a time period, such as <NUM> (Y) seconds. This time period, called the detect field offset duration, can be programmed in memory <NUM> (<FIG>), and can be monitored by the timer <NUM> (<FIG>). If so, at time t17, MRI protective measures are stopped, and normal telemetry is once again enabled. Preferably, the duration that the DC magnetic field is detected (X=<NUM>) to enter the MRI protective measures (at t13) is different from the duration that the DC magnetic field is not detected (Y=<NUM>) when determining when to stop the MRI protective measures (at t17).

Even though the IPG <NUM> and mode logic <NUM> can be fairly confident at this point that the patient's MRI needs are over, the IPG <NUM> is still operating in the MRI mode, and it is preferred to affirmatively exit this mode once it is clear that MRI intervention is no longer a concern. Because normal telemetry is now enabled (t17), the MRI mode can be exited using the RC <NUM> with which the IPG <NUM> is paired, and this occurs at time t18. As shown, the patient (or clinician) can select the MRI modes menu in the GUI, and can select to exit the MRI mode. This causes RC <NUM> to transmit an exit MRI mode instruction to the IPG <NUM>, which is received at the IPG's antenna 34a or 34b. At this point, mode logic <NUM> can cause the IPG <NUM> to enter the normal mode, which can automatically cause normal stimulation to begin (and cause any MRI-condition stimulation to stop).

Although not shown in <FIG>, exiting the MRI mode at time t18 can also include resetting the IPG. In this example, when the IPG receives the exit mode instruction at t18, the mode logic <NUM> issues a reset. As explained earlier, this causes stimulation to stop (momentarily), and the pairing mode to begin (when stimulation commences again). Even though the user had just used the RC <NUM>'s GUI to send the exit MRI mode instruction, the user will thus have to use the RC <NUM>'s GUI again re-pair with the IPG so that the pairing mode can be exited, and the normal mode entered, as described earlier. While incorporating a reset with exiting the MRI mode is not strictly required, this can be sensible to ensure that the IPG returns to a normal state after experiencing the MRI environment.

As noted earlier, a potential problem with operation as described thus far can occur if the patient does not have his RC <NUM> at time t18 and so is unable to exit the MRI mode. In this circumstance it may be necessary to use a new external device that is not paired with the IPG <NUM>. The mode logic <NUM> is thus programmed to allow the IPG <NUM> to be paired to a new external device while in the MRI mode, as shown in <FIG>. In <FIG>, it is assumed that this new external device comprises RC <NUM>', although again another type of external device could be used as well.

As was the case earlier (<FIG>), bar magnet <NUM> can be used as the means for pairing in the pairing mode. However, as <FIG> explains, modifications to the programming are made to allow the mode logic <NUM> to differentiate magnetic fields detected by the magnetic field sensor <NUM> when in the MRI mode. Such differentiation occurs through sensing the length of time that such magnetic fields are detected by the magnetic field sensor <NUM>. As noted earlier with respect to <FIG>, detection of a magnetic field for <NUM> or more signals the mode logic to being executing MRI protective measures (t13, <FIG>), the assumption being that the magnetic field in this circumstance must be caused by the MRI magnet <NUM>. By contrast, detection of a magnetic field for a significantly shorter duration will signal the mode logic <NUM> to enter the pairing mode (t20, <FIG>), the assumption being that the magnetic field in this circumstance is caused by the bar magnet <NUM>. Distinguishing the magnetic fields in this manner is important to allowing the mode logic <NUM> to take appropriate steps when magnetic fields are detected in the MRI mode. The pairing mode preferably comprises a sub-mode with the MRI mode, as shown in <FIG>.

<FIG> starts with t17 (<FIG>), with the IPG <NUM> in the MRI mode. It is assumed here that that t17 occurs after the patient's MRI scan and after MRI protective measures have ceased. However, it may also be the case at time t17 that the patient's MRI scan never occurred (e.g., it was canceled). In short, the IPG <NUM> may have been placed in the MRI mode (t11, <FIG>), but steps shown at times t12-<NUM> (<FIG>) never occurred.

In any event, at time t17 in <FIG> and during the MRI mode, normal telemetry is enabled and thus IPG <NUM> is able to communicate with RC <NUM> to which it is currently paired. However, RC <NUM> is not present in this example (as occurred at t18 in <FIG>), and instead the IPG <NUM> will be paired with a new RC <NUM>'. As noted above, such pairing occurs using bar magnet <NUM>, which at time t19 is brought proximate to the IPG <NUM> to commence the pairing mode. At t19, the bar magnet <NUM> starts to be sensed by the IPG's magnetic field sensor <NUM>, and mode logic <NUM> determines the duration that this magnetic field is present. As noted above, when in the MRI mode, the mode logic will take certain actions-such as initiating MRI protective measures, t13, <FIG>-if the magnetic field is detected for a relatively long time (≥ <NUM>). It is not desired in <FIG> that such MRI protective measures are (again) executed at time t19. To ensure this, the user is instructed to hold the bar magnet <NUM> proximate to the IPG <NUM> for a time period between <NUM> and <NUM> seconds, and then to remove the bar magnet. Notice that this time period is easy for the user to estimate; its minimum value is suitably long to differentiate from transient fields; and its maximum value is significantly shorter than the duration necessary to start MRI protective measures (e.g., <NUM>). In short, by controlling the time period during which the bar magnet <NUM> is proximate to the IPG <NUM>, the user can cause the mode logic <NUM> to enter the pairing mode without taking other actions such as executing MRI protective measures.

At time t20, the bar magnet <NUM> is removed and no longer sensed. If the mode logic <NUM> determines that the magnetic field was present for the specified time period (<NUM> ≤ t ≤ <NUM>), the pairing mode is entered. This time period, called the MRI pairing duration, can be programmed in memory <NUM> (<FIG>), including both its minimum (e.g., <NUM>) and maximum (e.g., <NUM>) values. Like other durations programmed in the IPG, this duration can be monitored by the timer <NUM> (<FIG>). Thus, the IPG <NUM> can periodically broadcast pairing data during transmission windows. Note when entering the pairing mode from the MRI mode, the mode logic <NUM> will preferably not issue a reset. (Compare, <FIG>, when in normal mode, a reset precedes entry into the pairing mode). As noted earlier, a reset would stop stimulation and telemetry as well, and is unnecessary in the context of <FIG>.

At time t21, it is assumed that new RC <NUM>' is present (i.e., proximate to the IPG <NUM>) and able to pair with the IPG <NUM>. The user selects the IPG pairing mode at the GUI of RC <NUM>' to scan for available IPGs. At this point, RC <NUM>' receives the pairing data being broadcast from IPG <NUM>, and the user can then select the option to connect with the IPG <NUM>. As noted earlier, the pairing data and authentication data exchanged during the pairing process may differ depending on the communication standard used (e.g., Bluetooth).

Once the IPG <NUM> and RC <NUM>' are paired and connected at time t21, the mode logic <NUM> in the IPG's control circuitry <NUM> can exit the pairing mode. However, the IPG <NUM> is still in the MRI mode. Again, it is preferred for safety that this mode be affirmatively exited by the patient or clinician. Thus, and similarly to what was described earlier (t18, <FIG>), the user at time t22 can use the GUI of RC <NUM>' to exit the MRI mode. This causes RC <NUM>' to transmit an exit MRI mode instruction to the IPG <NUM>, which is received at the IPG's antenna 34a or 34b. At this point, mode logic <NUM> can cause the IPG <NUM> to enter the normal mode, which can automatically cause normal stimulation to begin (and cause any MRI-condition stimulation to stop).

At this point the IPG <NUM> is paired to RC <NUM>', which probably does not belong to the patient. If and when the patient relocates his RC <NUM>, the IPG <NUM> can once again be paired to RC <NUM> using the normal pairing procedure described earlier (<FIG>). As noted earlier, this can be facilitated because the RC50 and IPG <NUM> would have stored information about the other (see <FIG>, memories <NUM>, <NUM>).

<FIG> summarize how the mode logic <NUM> operates upon detecting, or ceasing detecting, a magnetic field in the different circumstances summarized earlier, and also describes the actions that the mode logic <NUM> can take, which depends upon the current mode in which the IPG is operating. When in the normal mode, if a magnetic field is sensed on for <NUM> (A) second or more (and then the field is sensed off), it is assumed that the sensed field is coming from bar magnet <NUM> (<FIG>). The IPG <NUM> is reset (t2, <FIG>), and then preferably automatically enters the pairing mode (t3, <FIG>), thus allowing the IPG <NUM> to be paired or reconnected to the patient's RC <NUM> or any other relevant external device (such as RC <NUM>').

When operating in the MRI mode, the actions taken depend on how long the magnetic field is sensed. If a magnetic field is sensed for <NUM> (B) second or more, it is assumed that the sensed field is coming from magnet <NUM> in the MRI machine <NUM> (<FIG>). The IPG <NUM> assumes that an MRI scan will begin shortly, and will start executing MRI protective measures, and will also disable telemetry (t13, <FIG>). Afterwards, when the magnetic field is not sensed for <NUM> seconds (C), it is assumed that the MRI magnet <NUM> has been removed and is no longer proximate to the IPG. At this point, MRI protective measures can be stopped, and telemetry enabled (t17, <FIG>).

By contrast, if a magnetic field is sensed for a shorter time between <NUM> (D) and <NUM> (E) seconds when in the MRI mode, it is assumed that the sensed field is coming from bar magnet <NUM>, and that the pairing mode should commence (t20, <FIG>). Note that, preferably, D and E are greater than A, and D and E are less than B and/or C.

Claim 1:
A method for controlling an implantable medical device, IMD, comprising:
receiving at the IMD a first instruction to cause the IMD to enter a protective mode, wherein in the protective mode the IMD is enabled to execute one or more protective measures to protect the IMD from a first field produced by equipment;
while in the protective mode, receiving at the IMD a second instruction to cause the IMD to enter a pairing mode, wherein the pairing mode enables the IMD to pair for communications with an external device;
while in the protective mode and the pairing mode, receiving at the IMD, from a first external device, a third instruction to cause the IMD and the first external device to pair for communications; and
while in the protective mode, receiving at the IMD, from the first external device, a fourth instruction to cause the IMD to exit the protective mode.