System including implantable medical device configured for transmission mode optical sensing

Abstract

An example system includes an implantable medical device (IMD) includes a housing configured for implantation within a patient; a detector on or within the housing, the detector configured to detect light emitted by a light source outside of the patient; and processing circuitry configured to determine a physiological characteristic of the patient based on the detected light.

Description

Atty Ref. No.: A0010862 WOO 1SYSTEM INCLUDING IMPLANTABLE MEDICAL DEVICE CONFIGURED FOR TRANSMISSION MODE OPTICAL SENSING

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 750,066, filed January 27, 2025, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] This disclosure generally relates to sensing patient parameters, and more particularly optically sensing, via an implantable medical device.BACKGROUND

[0003] Various implantable medical devices (IMDs) have been clinically implanted or proposed for therapeutically treating or monitoring one or more conditions of a patient. Such devices may be adapted to monitor or treat conditions or functions relating to heart, muscle, nerve, brain, stomach, endocrine organs or other organs and their related functions. Advances in design and manufacture of miniaturized electronic and sensing devices have enabled development of implantable devices capable of therapeutic as well as diagnostic functions such as pacemakers, cardioverters, defibrillators, biochemical sensors, implantable loop recorders, and pressure sensors, among others. Such devices may be associated with leads that position electrodes or sensors at a desired location or may be leadless with electrodes and / or sensors integrated into the device housing. These devices may have the ability to wirelessly transmit data either to another device implanted in the patient or to another instrument located externally of the patient, or both.SUMMARY

[0004] In general, this disclosure is directed to systems, devices, and techniques for measuring and / or determining a physiological characteristic of a patient based on light detected via transmission mode sensing using an implantable medical device (IMD). In particular, methods and devices disclosed herein are directed to emitting light by a light source of an external device, detecting, by a detector of an IMD, light emitted from the light source, and determining a physiological characteristic, such as blood pressure, based, at least, on the detected light.Atly Ref. No.: A0010862 WOO 1

[0005] In some examples, determining a physiological characteristic, such as blood pressure, based on detected light that is emitted by a light source external to a patient instead of a light source of an IMD may reduce the power used by an IMD to determine the physiological characteristic, as emitting light via a light source requires power. Since the light source emitting the light to be detected is positioned in an external device that is a separate device than the IMD, power may be conserved in the IMD.

[0006] In some examples, the light source being external to the patient may enable greater magnitude of signal strength, greater sampling frequency, greater duty cycles, and / or greater wavelength variations of light emitted as an external device may be less restricted by limited power capacity and limited space than an IMD. In some examples, increasing the magnitude of signal strength, increasing sampling frequency, increasing duty cycles, and / or increasing wavelength variations of the emitted light that is detected by a detector of the IMD may improve the accuracy of the determination of the blood pressure or other physiological characteristic based on detected optical signals.

[0007] In some examples systems described herein, each of an IMD and external device may respectively include at least one light source and at least one detector, where a detector of the IMD may be configured to detect light emitted by a light source of the external device and a detector of the external device may be configured to detect light emitted by a light source of the IMD. In some examples, a detector of the IMD being configured to detect light emitted by a light source of the external device and a detector of the external device being configured to detect light emitted by a light source of the IMD may enable a detection system to operate in four modes, transmission mode from IMD to external device, transmission mode from external device to IMD, reflection mode from IMD to IMD, and reflection mode from external device to external device, which may enable improved signal strength of light detected by respective detectors, e.g., by selection over time of various modes based on an evaluation of signal strength, which may enable improved accuracy of blood pressure determinations based on detected light.

[0008] In one example, this disclosure describes a system comprising: an implantable medical device (IMD) comprising: a housing configured for implantation within a patient; a detector on or within the housing, the detector configured to detect light emitted by a light source outside of the patient; and processing circuitry configured to determine a physiological characteristic of the patient based on the detected light.Atty Ref. No.: A0010862 WOO 1

[0009] In another example, this disclosure describes a method of determining a physiological characteristic of a patient, the method comprising: emitting light by a light source of an external device positioned external to the patient; detecting, by a detector of an implantable medical device (IMD), the light emitted by the light source; and determining, by processing circuitry and based, at least, on the detected light, the physiological characteristic of the patient.

[0010] This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the apparatus and methods described in detail within the accompanying drawings and description below. The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.BRIEF DESCRIPTION OF DRAWINGS

[0011] FIGS. 1 A-1B are conceptual drawings illustrating an example medical system in conjunction with a patient, according to various examples described in this disclosure.

[0012] FIG. 2 is a functional schematic diagram of an example implantable medical device (IMD), according to various examples described in this disclosure.

[0013] FIG. 3 is a conceptual perspective schematic diagram of an example IMD of FIG. 2, according to various examples described in this disclosure.

[0014] FIG. 4A is a block diagram illustrating the example IMD of FIGS. 1-3.

[0015] FIG. 4B is a block diagram illustrating the example external device of FIGS.1A-1B.

[0016] FIG. 5 is an example of a conceptual cross-sectional side-view of an example IMD of FIGS. 1-4, according to various examples described in this disclosure.

[0017] FIG. 6 is an example of a conceptual cross-sectional side-view of an example IMD and example external device of FIGS. 1-4, according to various examples described in this disclosure.

[0018] FIG. 7 is an example of a conceptual cross-sectional side-view of an example IMD and example external device of FIGS. 1-4, according to various examples described in this disclosure.Atly Ref. No.: A0010862 WOO 1

[0019] FIG. 8 is a flow diagram of an example method of determining a physiological characteristic of a patient, according to various examples described in this disclosure.

[0020] In the figures, use of a same reference number or a same reference number with a letter extension may be used to indicate a same or corresponding device or element when used in a same drawing or in different drawings. In addition, unless otherwise indicated, devices and / or other objects such as a patient, an implantable medical device, or an electrical device such as an electrical coil, are not necessarily illustrated to scale relative to each other and / or relative to an actual example of the item being illustrated. In particular, various drawings provided with this disclosure illustrate a “patient” represented by a human-shaped outline and are not to be considered drawn to scale relative to an actual human patient or with respect to other objects illustrated in the same figure unless otherwise specifically indicated in the figure for example by dimensional indicators, or for example as otherwise described in the text of the disclosureDETAILED DESCRIPTION

[0021] A variety of types of medical devices sense physiological signals or parameters of a patient. An implantable medical device (IMD) may include an optical sensor configured to sense optical signals from which processing circuitry of a system including the IMD may determine physiological signal values or parameter values. The optical sensor may be integrated with a housing of the IMD. The optical sensor may comprise a detector configured to detect light, such as light emitted by a light source. Example IMDs that may be configured to sense optical signals that may be used to monitor physiological signals or parameters include pacemakers and implantable cardioverter-defibrillators, which may be coupled to intravascular or extravascular leads, as well as pacemakers with housings configured for implantation within the patient, which may be leadless. An example of pacemaker configured for intracardiac implantation is the Micra™ Transcatheter Pacing System, available from Medtronic, Inc. Some IMDs that do not provide therapy, e.g., implantable patient monitors, may be configured to sense optical signals that may be used to monitor physiological signals or parameters. One example of such an IMD is the Reveal LINQ™ and LINQ II™ Insertable Cardiac Monitors (ICMs), available from Medtronic, Inc., which may be inserted subcutaneously. Such IMDs may facilitate relatively longer-term monitoring of patients during normal daily activities, andAtty Ref. No.: A0010862 WOO 1may periodically transmit collected data to a network service, such as the Medtronic Carelink™ Network.

[0022] Limited power capacity of IMDs due to the limited size of an IMD and the duration of time an IMD is intended to be implanted in the patient may limit a magnitude of signal strength, sampling frequency, duty cycle, and / or wavelength variations of light emitted by light sources of an IMD to be detected by a detector of the optical sensor of the IMD.

[0023] In some examples of the techniques described herein, a system may include an IMD including an optical sensor that includes a detector configured to detect light emitted by a light source positioned external to a patient, and processing circuitry configured to determine blood pressure based on the detect light. In some examples, determining blood pressure based on detected light that is emitted by a light source external to a patient may reduce the power used by an IMD as a light source is external to the IMD.

[0024] In some examples, the light source being external to the patient may enable greater magnitude of signal strength, greater sampling frequency, greater duty cycles, and / or greater wavelength variations of light emitted by a light source external to the patient as an external device may be less restricted by limited power capacity and device size than an IMD. In some examples, increasing the magnitude of signal strength, increasing sampling frequency, increasing duty cycles, and / or increasing wavelength variations of the emitted light that is detected by a detector of the IMD may improve the accuracy of the determination of the blood pressure based on detected optical signals.

[0025] FIGS. 1A-1B are conceptual drawings illustrating an example system 10 in conjunction with a patient 12, according to various examples described in this disclosure. The systems, devices, and methods described in this disclosure may include example optical sensors included with IMD 14, as illustrated and described with respect to FIGS.1 A-1B. For purposes of this description, knowledge of cardiovascular anatomy and functionality is presumed, and details are omitted except to the extent necessary or desirable to explain the context of the techniques of this disclosure. As shown in FIG. 1 A, system 10 includes IMD 14 including optical sensor 62, implanted at or near the site of a heart 18 of a patient 12. As shown in FIG. IB, system 10 includes IMD 14 including optical sensor 62, implanted at or near a limb of a patient 12. In some examples, system 10 may further include an external device 16. In some examples, external device 16 may beAtly Ref. No.: A0010862 WOO 1positioned near a site of IMD 14, e.g., over IMD and, in some cases, against or on the patient’s skin. In some examples, system 10 may further include computing device 24. In some examples, system 10 may further include external device 16 and computing device 24. The computing device 24 may be external to patient 12. In some examples, the functionality ascribed herein to external device 16 and computing device 24 may be embodied in a single device.

[0026] Example techniques disclosed herein may be used with IMD 14, which may be in wireless communication with at least one of external device 16, computing device 24, and other devices not pictured in FIGS. 1 A-1B. In some examples, IMD 14 is implanted outside of a thoracic cavity of patient 12 (e.g., subcutaneously in the pectoral location illustrated in FIGS. 1 A-1B). IMD 14 may be positioned near the sternum near or just below the level of the heart of patient 12, e.g., at least partially within the cardiac silhouette. In some examples, IMD 14 may include a plurality of electrodes 48 (FIGS. 2-4) and may be configured to sense a cardiac electrogram (EGM) via the plurality of electrodes, as well as other physiological signals and / or parameters, such as blood pressure, via optical sensor 62. In some examples, IMD 14 may include at least one detector 64A (FIGS. 5-7) configured to detect light emitted by a light source outside of patient 12 and processing circuitry of system 10 may be configured to determine blood pressure of patient 12 based on the detected light. In some examples, IMD 14 may further include at least one light source 63 A (FIG. 7) configured to emit light. In some examples, IMD 14 takes the form of the LINQ™ or LINQ II™ ICM, or another ICM similar to, e.g., a version or modification of, the LINQ™ or LINQ II™ ICM. Although described primarily in the context of examples in which IMD 14 is an ICM, in various examples, IMD 14 may represent a blood pressure monitor, cardiac monitor, a defibrillator, a cardiac resynchronization pacer / defibrillator, a pacemaker, an implantable pressure sensor, a neurostimulator, or any other implantable or external medical device.

[0027] In some examples, IMD 14 is defined by a length L, a width W and thickness or depth D and is in the form of an elongated rectangular prism wherein the length L is much larger than the width W, which in turn is larger than the depth D, as illustrated in FIG. 3 below. In one example, the geometry of the IMD 14 - in particular a width W greater than the depth D - is selected to allow IMD 14 to be inserted under the skin of the patient using a minimally invasive procedure and to remain in the desired orientationAtly Ref. No.: A0010862 WOO 1during insert. For example, IMD 14 may include a radial asymmetry (notably, a rectangular shape) along the longitudinal axis that maintains the device in the proper orientation following insertion. For example, in one example the spacing between electrode 48A and electrode 48B may range from 30 millimeters (mm) to 55mm, 35mm to 55mm, and from 40mm to 55mm and may be any range or individual spacing from 25mm to 60mm. In another example the spacing between electrode 48A and electrode 48B may range from 15mm to 30mm, 17mm to 28mm, and from 20mm to 28mm and may be any range or individual spacing from 12mm to 30mm. In addition, IMD 14 may have a length L that ranges from 30mm to about 70mm. In other embodiments, the length L may range from 40mm to 60mm, 45mm to 60mm and may be any length or range of lengths between about 30mm and about 70mm. In some examples, IMD 14 may have a length L that ranges from 15mm to about 35mm, or from 20mm to 30mm, 22mm to 30mm and may be any length or range of lengths between about 15mm and about 35mm. In addition, the width W of a major surface of IMD 14, e.g., insulative cover 76 in the example shown, may range from 3mm to 10mm and may be any single or range of widths between 3mm and 10mm, or may range from 1.5mm to 5mm and may be any single or range of width between 1.5mm and 5mm. The thickness of depth D of IMD 14 may range from 2mm to 9mm, or from 1.5mm to 4.5mm. In other embodiments, the depth D of IMD 14 may range from 2mm to 5mm and may be any single or range of depths from 2mm to 9mm, or may range from 1mm to 2.5mm and may be any single or range of depts from 1mm to 4.5mm. In addition, IMD 14 according to an example of the present invention has a geometry and size designed for ease of implant and patient comfort. Examples of IMD 14 described in this disclosure may have a volume of 3 cubic centimeters (cm) or less, 1.5 cubic cm or less or any volume between 3 and 1.5 cubic centimeters, or may have a volume of 1.5 cubic centimeters (cm) or less, 0.75 cubic cm or less or any volume between 1.5 and 0.75 cubic centimeters.

[0028] IMD 14 may be configured to communicate with external device 16 and / or computing device 24. In some examples, IMD 14 may communicate via near-field communication technologies (e.g., inductive coupling, NFC or other communication technologies operable at ranges less than 10-20 cm) and far-field communication technologies (e.g., RF telemetry according to the 802.11 or Bluetooth® specification sets,Atty Ref. No.: A0010862 WOO 1or other communication technologies operable at ranges greater than near-field communication technologies).

[0029] External device 16 may include at least one light source 63B (FIGS. 6-7) that is configured to emit light to be detected by detector 64A (FIGS. 5-7) of IMD 14. In some examples, light source 63B may be a photo emitter such as a light emitting diode (LED), a laser such as a vertical cavity surface emitting laser (VCSEL), or any suitable light source. In some examples, light source 63B may be configured to emit light signal belonging to a particular wavelength spectrum. Some examples of a particular wavelength spectrum may be an amber wavelength spectrum, a green wavelength spectrum, yellow wavelength spectrum, blue wavelength spectrum, red wavelength spectrum, an infrared wavelength spectrum, or any other suitable wavelength spectrum. In some examples, external device 16 may be a wearable patch, such as an adhesive patch, a wearable garment, handheld light emitting component, smartphone, or any other light emitting component. In some examples, external device 16 may be positioned on or near skin of patient 12. In some examples, such as when external device 16 is adhesive patch, external device 16 may be positioned on skin of patient 12. In some examples, external device 16 may be positioned near IMD 14 to help enable IMD 14 to detect the light emitted by the light source of external device 16. In some examples, external device 16 may include at least one detector 64B (FIG. 7) configured detect light emitted by a respective light source 63 A (FIG. 7) of IMD 14.

[0030] In some examples, external device 16 may include one or more light sources 63B (FIGS. 6-7) that transmit light into the tissue creating a transmission mode sensor rather than reflection mode sensor (e.g., light source is in IMD 14). In some examples, both IMD 14 and external device 16 may have one or more light sources and may measure physiological characteristics of a plurality of different tissue volumes based on location of external device 16 and light source selection on external device 16 or IMD 14. In some examples, external device 16 may block ambient light (e.g., light from a different light source external to optical sensor) that may interfere with measurements of light detected by optical sensor 62. In some examples, ambient light may contribute to noise or reduce the effective dynamic range of detector 64 A and external device 16 emitting light and blocking ambient light may increase the received light signal to noise ratio by reducing noise factors.Atty Ref. No.: A0010862 WOO 1

[0031] External device 16 may be configured to communicate with IMD 14 and / or computing device 24. In some examples, external device 16 may communicate via near-field communication technologies (e.g., inductive coupling, NFC or other communication technologies operable at ranges less than 10-20 cm) and far-field communication technologies (e.g., RF telemetry according to the 802.11 or Bluetooth® specification sets, or other communication technologies operable at ranges greater than near-field communication technologies).

[0032] Computing device 24 may be a computing device with a display viewable by the user and an interface for providing input to external device 16 (i.e., a user input mechanism). In some examples, computing device 24 may include a memory and a user interface. In some examples, computing device 24 may be a notebook computer, tablet computer, workstation, one or more servers, smartphone, cellular phone, personal digital assistant, or another computing device that may run an application that enables the computing device 24 to interact with IMD 14 and / or external device 16. Computing device 24 is configured to communicate with IMD 14 and / or external device 16 and, optionally, another computing device (not illustrated in FIGS. 1 A-1B), via wireless communication. Computing device 24, for example, may communicate via near-field communication technologies (e.g., inductive coupling, NFC or other communication technologies operable at ranges less than 10-20 cm) and far-field communication technologies (e.g., RF telemetry according to the 802.11 or Bluetooth® specification sets, or other communication technologies operable at ranges greater than near-field communication technologies).

[0033] Computing device 24 may be used to configure operational parameters for IMD 14 and / or external device 16. Computing device 24 may be used to retrieve data from IMD 14 and / or external device 16. The retrieved data may include values of physiological parameters measured by IMD 14, indications of blood pressure detected by IMD 14, and physiological signals recorded by IMD 14, e.g., from optical sensor 62. For example, computing device 24 may retrieve value of the detected light recorded by IMD 14 and / or external device 16, e.g., due processing circuitry of system 10 determining to determine blood pressure of patient 12 based on a particular trigger, such as magnitude of detected light satisfying a sampling threshold or receiving an indication that at least one light source, such as 63B is emitting light to be detected. In some examples, one or moreAtly Ref. No.: A0010862 WOO 1remote computing devices may interact with IMD 14 and / or external device 16 in a manner similar to computing device 24, e.g., to program IMD 14 and / or external device 16 and / or retrieve data from IMD 14 and / or external device 16, via a network.

[0034] In various examples, IMD 14 may include one or more additional sensor circuits configured to sense a particular physiological or neurological parameter associated with patient 12, or may comprise a plurality of sensor circuits, which may be located at various and / or different positions relative to patient 12 and / or relative to each other and may be configured to sense one or more physiological parameters associated with patient 12.

[0035] For example, IMD 14 may include a sensor operable to sense a body temperature of patient 12 in a location of the IMD 14, or at the location of the patient where a temperature sensor coupled by a lead to IMD 14 is located. In another example, IMD 14 may include a sensor configured to sense motion, such as steps taken by patient 12 and / or a position or a change of posture of patient 12. In various examples, IMD 14 may include a sensor that is configured to detect breaths taken by patient 12. In various examples, IMD 14 may include a sensor configured to detect heartbeats or heart rhythm of patient 12.

[0036] In various examples, IMD 14 includes optical sensor 62 that is configured to measure one or more physiological parameters of patient 12, such as systemic blood pressure of patient 12, an oxygenation of blood of patient 12, and / or blood movement within tissue and / or vasculature of patient 12 which may be indicative of pulse pressure waveforms. In some examples, e.g., as illustrated in FIGS. 3 and 5-7, IMD 14 may include a housing 20 comprising an optical window 75 and an optical sensor 62 within housing 20. In some examples, the optical sensor 62 includes one or more detectors 64A configured to detect light 406 A emitted by a light source outside of patient 12 after the light interacts with the tissue 402 of the patient. In some examples, the optical sensor 62 includes one or more detectors 64A configured to detect light 406A emitted by a light source outside of patient 12 after the light interacts with the arterial / arteriole pulse wave 404 of the patient 12. In some examples, the optical sensor 62 of IMD 14 may further include one or more light sources 63A configured to emit light 406B to the optical window 75 towards tissue of patient 12, e.g., a photo emitter such as a light emitting diode (LED), a laser such as a vertical cavity surface emitting laser (VCSEL), or any suitable light source.Aty Ref. No.: A0010862 WOO 1

[0037] Processing circuitry of IMD 14, external device 16, and / or computing device 24 may be configured to determine a physiological characteristic (e.g., a physiological signal or parameter, such as blood pressure and / or generate an arterial pulse pressure waveform) of patient 12 based on light 406A (e.g., light that is emitted by a light source 63B and passes into tissue 402 and interacts with tissue 402 that may include an arterial / arteriole pulse wave 404, such as through absorption and scattering) detected by at least one detector 64A of IMD 14. In some examples, processing circuitry of IMD 14, external device 16, and / or computing device 24 may be configured to determine a physiological characteristic (e.g., a physiological signal or parameter, such as blood pressure and / or generate an arterial pulse pressure waveform) of patient 12 based on light 406A (e.g., light that is emitted by a light source 63B of external device 16 and passes into tissue 402 and interacts with tissue 402 that may include an arterial / arteriole pulse wave 404, such as through absorption and scattering) detected by at least one detector 64A of IMD 14 and light 406B (e.g., light that is emitted by light source 63 A and passes into tissue 402 and interacts with tissue 402 that may include an arterial / arteriole pulse wave 404, such as through absorption and scattering) respectively detected by at least one detector 64B of external device 16.

[0038] In some examples, determining blood pressure based on detected light 406A that is emitted by a light source 63B external to patient 12 may reduce the power used by IMD 14 to determine blood pressure as power used to emit light is from the external device 16 as light source 63B is external to the IMD 14. In some examples, having light sources 63 A, 63B, and detectors 64A, 64B respectively positioned in IMD 14 and external device 16 may enable system 10 to operate in four modes, transmission mode from IMD 14 to external device 16, transmission mode from external device 16 to IMD 14, reflection mode from IMD 14 to IMD 14, and reflection mode from external device 16 to external device 16 which may enable improved detected signal strength. In some examples, system 10 being configured to operate in some or all of the four modes may enable improved detected signal strength by selecting the optical vector detected by respective detectors 64A, 64B with at least one of the highest signal to noise ratio, highest signal strength, or most prominent waveform morphology features of interest. In some examples, multiple modes may be used simultaneously such that the detectors are capturing light from both transmission mode and reflection mode sources in parallel. In some examples, multipleAtty Ref. No.: A0010862 WOO 1modes may be used sequentially, and the sensed waveforms are post-processed to generate a high-fidelity synthetic, reconstructed signal generated from a combination of waveforms.

[0039] In some examples, system 10 being configured to operate in some or all of the four modes, such as in the fashions described above, may enable improve accuracy blood pressure determinations based on detected optical signals. In some examples, increasing the magnitude of signal strength, increasing sampling frequency, increasing duty cycles, and / or increasing wavelength variations of optical sensing light that is detected by detectors 64A and / or 64B may improve the accuracy of a physiological characteristic such as blood pressure determined by IMD 14, external device 16, computing device 24, or other devices such as a server, based on light detected by respective detectors 64A and / or 64B.

[0040] In some examples, one or more of the sensors comprising IMD 14 may be implanted within patient 12, that is, implanted below at least the skin level of the patient. In various examples, IMD 14 may be configured to sense one or more physiological parameters associated with patient 12, and to transmit data corresponding to the sensed physiological parameter or parameters to the external device 16 or computing device 24, as represented by the lightning bolt coupling IMD 14 to the computing device 24, the lightning bolt coupling external device 16 to the computing device 24, and the lightning bolt coupling IMD 14 to the external device 16.

[0041] Transmission of data between IMD 14, external device 16 and / or computing device 24 in various examples may be performed via wireless transmission, using for example any of the formats for wireless communication described above. In various examples, IMD 14 may communicate wirelessly to an external device (e.g., an instrument or instruments) other than or in addition to external device 24, such as a transceiver or an access point that provides a wireless communication link between IMD 14 and a network. Examples of communication techniques used by any of the devices described above with respect to FIGS. 1 A-1B may include radiofrequency (RF) telemetry, which may be an RF link established via Bluetooth®, Wi-Fi, Near Field Communication (NFC), or medical implant communication service (MICS).

[0042] In some examples, system 10 may include more or fewer components than depicted in FIGS. 1A-1B. For example, in some examples, system 10 may include multiple additional HMDs, such as implantable pacemaker devices or other IMDs,Aty Ref. No.: A0010862 WOO 1implanted within patient 12. In these examples, IMD 14 may function as a hub device for the other IMDs. For example, the additional IMDs may be configured to communicate with the IMD 14, which would then communicate to the computing device 24, such as a user’s smartphone, via a low-energy telemetry protocol. IMD 14 may provide a theoretically infinite energy capacity, in that IMD 14 may not need to be replaced or otherwise removed. Accordingly, IMD 14 may provide the ability to more-frequently telemeter information, as well as more-active titration of therapies.

[0043] For the remainder of the disclosure, a general reference to a medical device system may refer collectively to include any examples of system 10, a general reference to IMD 14 may refer collectively to include any examples of IMD 14, a general reference to sensor circuits may refer collectively to include any examples of sensor circuits of IMD 14, a general reference to an external device may refer collectively to any examples of external device 16, and a general reference to an computing device may refer collectively to any examples of computing device 24.

[0044] FIG. 2 is a functional schematic diagram of IMD 14, and FIG. 3 is a conceptual perspective schematic diagram of IMD 14, according to various examples described in this disclosure. IMD 14 may be a leadless, subcutaneously implantable monitoring device including proximal electrode 48B located at proximal end 222, distal electrode 48A located at distal end 220 (collectively “electrodes 48”), optical sensor(s) 62, integrated antenna 226, electrical circuitry 200 and power source 202. In particular, electrical circuitry 200 is coupled to proximal electrode 48B and distal electrode 48A to sense cardiac signals and monitor events. Electrical circuitry 200 may also connected to transmit and receive communications via integrated antenna 226. Powersource 202 provides power to electrical circuitry 200, as well as to any other components that require power. Power source 202 may include one or more energy storage devices, such as one or more rechargeable or non-rechargeable batteries. In some examples, electrical circuitry 200 includes processing circuitry 50 and a storage device, such as memory 56, as shown in FIG. 4A, the memory 56 being operatively coupled to the processing circuitry 50 and configured to store data and / or instructions.

[0045] In the example shown in FIG. 2, electrical circuitry 200 may receive raw EGM or EMG (electromyography) signals monitored by proximal electrode 48B and distal electrode 48A and raw optical signals monitored by optical sensor(s) 62. ElectricalAtty Ref. No.: A0010862 WOO 1circuitry 200 may include components / modules for converting the raw EGM signal to a processed EGM signal that can be analyzed to detect sense events and for converting the raw optical signals to calibrated processed optical signal(s) that can be analyzed to detect sense events. Although not shown, electrical circuitry 200 may include any discrete and / or integrated electronic circuit components that implement analog and / or digital circuits capable of producing the functions described for analyzing optical signal(s) to determine a health condition status of a patient. For example, the electrical circuitry 200 may include analog circuits, e.g., pre-amplification circuits, filtering circuits, and / or other analog signal conditioning circuits. The modules may also include digital circuits, e.g., digital filters, combinational or sequential logic circuits, state machines, integrated circuits, a processor (shared, dedicated, or group) that executes one or more software or firmware programs, memory devices, or any other suitable components or combination thereof that provide the described functionality.

[0046] In one example, electrical circuitry 200 includes a sensing unit for monitoring the EGM signal detected by the respective proximal and distal electrodes 48A and 48B and light signals received by the optical sensor(s) 62, respectively. In one example, electrical circuitry 200 includes processing circuitry 50 that is utilized to receive information regarding sensed events and implements one or more algorithms for determining a health condition status of a patient. In addition, the analog voltage signals received from electrodes 48A and 48B may be passed to analog-to-digital (A / D) converters included in the electrical circuitry 200 and stored in a memory unit (not shown) included as part of electrical circuitry 200 for subsequent analysis with firmware executed by the processor included as part of electrical circuitry 200.

[0047] In the examples shown in FIGS. 2-3, IMD 14 may include container 15 and an insulative cover 76. In some examples, insulative cover 76 may include optical window 75. In some examples, optical window 75 may be formed of the same material as insulative cover 76. In some examples, optical window 75 may be a portion of insulative cover 76. Electrode 48A and electrode 48B may be formed or placed on an outer surface of cover 76. Electrical circuitry 200 may be formed or placed on an inner surface of cover 76, or within container 15. In some examples, antenna 226 is formed or placed on the inner surface of cover 76. In other examples, antenna 226 is formed or placed on the outer surface of cover 76, and in other examples, antenna 226 may be formed or placed at leastAtty Ref. No.: A0010862 WOO 1partially on the inner surface and partially on the outer surface of cover 76. In some examples, insulative cover 76 may be positioned over an open container 15 such that container 15 and cover 76 form housing 20 and enclose electrical circuitry 200 (and in some cases antenna 226) and protect the circuitries from fluids such as body fluids. For example, housing 20 may be a hermetically-sealed housing configured for subcutaneous implantation within the patient, wherein at least the power source 202, memory, and processing circuitry 50 are within the hermetically-sealed case, and in some examples, optical sensor(s) 62 are within the hermetically-sealed case.

[0048] Electrical circuitry 200 may be formed on the inner side of insulative cover 76, such as by using flip-chip or wire bond integrated circuit packaging technology. Insulative cover 76 may be flipped onto a container 15. When flipped and placed onto container 15, the components of IMD 14 formed on the inner side of insulative cover 76 may be positioned in a gap defined by container 15. Electrodes 48 and antenna 226 (when placed or formed on the outer surface of cover 76) may be electrically connected to sensing circuitry 52 and communication circuitry 54A(FIG. 4A), respectively, e.g., through one or more vias formed through insulative cover 76. Insulative cover 76 may be formed of sapphire (i.e., corundum), glass, and / or any other suitable insulating material. Container 15 may be formed from any suitable material configured to house electrical circuitry 200, support and mate with cover 76 to isolate electrical circuitry 200 from contact with tissue and / or fluids of patient 12, and to be implantable within patient 12. In some examples, container 15 may house power source 202 (e.g., a battery). In some examples, container 15 may also be electrically conductive. For example, container 15 may be formed from titanium or any other suitable material (e.g., a biocompatible material). Electrodes 48 may be formed from any of stainless steel, titanium, platinum, iridium, or alloys thereof. In addition, electrodes 48 may be coated with a material such as titanium nitride or fractal titanium nitride, although other suitable materials and coatings for such electrodes may be used.

[0049] FIG. 4A is a block diagram illustrating an example of IMD 14 of FIGS. 1-3. FIG. 4B is a block diagram illustrating an example of external device 16 of FIGS. 1A-1B. FIGS. 4A-4B are described with reference to FIGS. 5-8. FIG. 5 is a conceptual cross-sectional side-view of an example system including IMD 14 that includes detector 64 A configured receive light 406 A from a light source outside of patient 12 in a firstAtly Ref. No.: A0010862 WOO 1configuration. FIG. 6 is a conceptual cross-sectional side-view of an example system including IMD 14 that includes detector 64 A configured to detect light 406 A emitted from light source 63B of external device 16 in a second configuration. FIG. 7 is a conceptual cross-sectional side-view of an example system including example IMD 14 including detector(s) 64A and light source(s) 63 A and external device 16 including detector(s) 64B and light source(s) 63B, the detector(s) 64A configured to detect light 406A emitted from light source(s) 63B, and the detector(s) 64B configured to detect light 406A emitted from light source(s) 63 A in a third configuration.

[0050] As shown in FIG. 4 A, IMD 14 may include processing circuitry 50 A, memory 56A, one or more sensor(s) 61, which may include one or more optical sensor(s) 62, sensing circuitry 52A coupled to sensors 61 and electrodes 48 (e.g., electrodes 48A and 48B), power source 202A, and communication circuitry 54A. Power source 202A provides operational power for processing circuitry 50A, sensing circuitry 52A, sensor(s) 61, communication circuitry 54A, and memory 56 A. As used herein, “sensors” may refer to any sensors described herein, including electrodes 48 and optical sensor 62.

[0051] Processing circuitry 50A may include fixed function circuitry and / or programmable processing circuitry. Processing circuitry 50Amay include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, processing circuitry 50Amay include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processing circuitry 50A herein may be embodied as software, firmware, hardware or any combination thereof.

[0052] Sensing circuitry 52A may be coupled to electrodes 48 to sense electrical signals of the heart of patient 12, for example by selecting electrodes 48 and polarity, used to sense an ECG as controlled by processing circuitry 50A. In some examples, sensing circuitry 52A may sense the ECG from electrodes 48 in order to facilitate monitoring the electrical activity of the heart. In some examples, electrodes 48 may be configured to sense other electrogram signals of patient 12, and / or impedance of tissue fluid proximate the electrodes 48. In some examples, sensing circuitry 52Amay monitor signals fromAtty Ref. No.: A0010862 WOO 1sensors 61, which may include one or more accelerometers (e.g., 3-axis accelerometers), pressure sensors, temperature sensors, heart sound sensors (e.g., microphones or accelerometers), optical sensors 62, or other sensors.

[0053] In some examples, sensing circuitry 52A may include one or more filters and amplifiers for filtering and amplifying signals received from electrodes 48 and / or sensors 61. In some examples, sensing circuitry 52 A may sense or detect physiological parameters, such as heart rate, blood pressure, respiration, and other physiological parameters associated with a patient. Sensing circuitry 52A and processing circuitry 50A may store ECG data and / or other physiological parameter data in memory 56A.

[0054] Communication circuitry 54A may include any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as external device 16, computing device 24 (FIGS. 1 A-1B), another networked computing device, or another IMD or sensor. Under the control of processing circuitry 50A, communication circuitry 54A may receive downlink telemetry from, as well as send uplink telemetry to external device 16, computing device 24 or another device with the aid of an internal or external antenna, e.g., antenna 226. In addition, processing circuitry 50A may communicate with a networked computing device via external device 16 or computing device 24 and a computer network, such as the Medtronic CareLink® Network. Antenna 226 and communication circuitry 54A may be configured to transmit and / or receive signals via inductive coupling, electromagnetic coupling, Near Field Communication (NFC), Radio Frequency (RF) communication, Bluetooth®, Wi-Fi, or other proprietary or non-proprietary wireless communication schemes. Communication antenna 226 may telemeter data at a high frequency, such as around 2.4 gigahertz (GHz).

[0055] In some examples, memory 56A includes computer-readable instructions that, when executed by processing circuitry 50A, cause IMD 14 and processing circuitry 50A to perform various functions attributed to IMD 14 and processing circuitry 50A herein. Memory 56A may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random-access memory (RAM), dynamic RAM (DRAM), static RAM (SRAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other digital media. Memory 56A may store, as examples, programmed values for one or more operational parameters of IMD 14 and / or data collected by IMD 14, e.g., posture, heart rate, activity level,Atly Ref. No.: A0010862 WOO 1respiration rate, oxygen saturation, blood pressure, and other parameters, as well as digitized versions of physiological signals, e.g., optical signals or ECG signals, sensed by IMD 14, for transmission to another device using communication circuitry 54A. In some examples, memory 56A is used to store program instructions for execution by processing circuitry 50A. Memory 56A may be used by software or applications running on processing circuitry 50A and / or sensing circuitry 52A to temporarily store information during program execution.

[0056] In the illustrated example, IMD 14 includes processing circuitry 50A and an associated memory 56A, sensing circuitry 52A, one or more sensors 61, and the communication circuitry 54A coupled to antenna 226 as described above. However, IMD 14 need not include all of these components, or may include additional components.

[0057] Sensing circuitry 52A may additionally be coupled to optical sensor 62 to sense a physiological characteristic, signal, or parameter, of patient 12, e.g., a blood pressure, an oxygenation of arterial blood, perfusion and oxygenation of tissue, a heart rate, a respiration rate, a movement, or any suitable physiological characteristic. Optical sensor 62 may include at least one detector 64 configured to receive light originating from at least one light source outside of patient 12 and passing through tissue 402 and / or arterial / arteriole pulse wave 404 (FIGS. 5-7). In some examples, optical sensor 62 may include at least one detector 64 configured to receive light originating from at least one light source 63B in an external device 16 positioned outside of patient 12 and passing through tissue 402 and / or arterial / arteriole pulse wave 404 (FIGS. 6-7).

[0058] In some examples, optical sensor 62 may further include at least one light source 63 A configured to emit light signals. In some examples, light source 63 A may be configured to emit light signal belonging to a particular wavelength spectrum. Some examples of a particular wavelength spectrum may be an amber wavelength spectrum, a green wavelength spectrum, yellow wavelength spectrum, blue wavelength spectrum, red wavelength spectrum, an infrared wavelength spectrum, or any other suitable wavelength spectrum. Detector 64A may be configured to receive optical signals of the corresponding particular wavelength spectrum, such as corresponding to a wavelength spectrum of light emitted from a respective light source 63B of external device 16, e.g., facilitated by filtering and / or or detector material selection.Atly Ref. No.: A0010862 WOO 1

[0059] Optical sensor 62 may also include one or more masking(s) 66A. In some examples, blocking light comprises reflecting the light, absorbing the light, or attenuating some or all of the light. In some examples, it may be preferable to absorb the light intended to be blocked, rather than to reflect the light, to prevent that light from being backscattered by tissue 402 towards detector 64A. In some examples, masking 66A may also be configured, such as being coated with a particular coating, to spectrally filter light, e.g., to block some wavelengths of light more than others. In some examples, masking may comprise other spectral filters, e.g., infrared filter(s), visible filter(s), ultraviolet filter(s), or any number of filters configured to absorb any suitable spectral band.

[0060] Sensing circuitry 52A and / or processing circuitry 50A may be configured to control operation of optical sensor 62, e.g., to determine parameters of light source 63 A such as brightness level and / or pulsing emission of the light, and parameters of detector 64A such as gain. In some examples, detector 64A may be a photodetector. In some examples, optical sensor 62 may be a photoplethysmography (PPG) sensor, an oxygenation sensor, a blood pressure sensor, a heart rate sensor, or any suitable optical sensor configured to detect a physiological characteristic and / or parameter of patient 12.

[0061] As shown in FIG. 4B, external device 16 may include processing circuitry 50B, memory 56B, at least one light source 63B, power source 202B, and communication circuitry 54 A. In some examples, external device 16 may further include at least one detector 64B sensing circuitry 52B coupled to detector 64B. Power source 202B may provide operational power for one or more of processing circuitry 50B, light source 63B, detector 64B, sensing circuitry 52B, communication circuitry 54B, and / or memory 56B.

[0062] Processing circuitry 50B may include fixed function circuitry and / or programmable processing circuitry. Processing circuitry 50B may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, processing circuitry 50Amay include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processing circuitry 50B herein may be embodied as software, firmware, hardware or any combination thereof.Atty Ref. No.: A0010862 WOO 1

[0063] Sensing circuitry 52B may be coupled to detector 64B to sense optical signal detected by detector(s) 64B. In some examples, sensing circuitry 52Amay include one or more filters and amplifiers for filtering and amplifying signals received from detector(s) 64B. In some examples, sensing circuitry 52B may sense or detect physiological parameters, such as blood pressure, and / or generate arterial pulse pressure waveform associated with a patient. Sensing circuitry 52B and processing circuitry 50B may store optical signal data, arterial pulse pressure waveform data, and / or blood pressure data in memory 56B.

[0064] Communication circuitry 54B may include any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as IMD 14, computing device 24 (FIGS. 1 A-1B), another networked computing device, or another IMD or sensor. Under the control of processing circuitry 50B, communication circuitry 54B may receive downlink telemetry from, as well as send uplink telemetry to IMD 14, computing device 24 or another device with the aid of an internal or external antenna. In addition, processing circuitry 50B may communicate with a networked computing device via IMD 14 or computing device 24 and a computer network, such as the Medtronic CareLink® Network. Communication circuitry 54B may be configured to transmit and / or receive signals via inductive coupling, electromagnetic coupling, Near Field Communication (NFC), Radio Frequency (RF) communication, Bluetooth®, Wi-Fi, or other proprietary or non-proprietary wireless communication schemes. External device 16 may include a communication antenna that may telemeter data at a high frequency, such as around 2.4 gigahertz (GHz).

[0065] In some examples, light source 63B may be a photo emitter such as a light emitting diode (LED), a laser such as a vertical cavity surface emitting laser (VCSEL), or any suitable light source. In some examples, light source 63B may be configured to emit light signal belonging to a particular wavelength spectrum. Some examples of a particular wavelength spectrum may be an amber wavelength spectrum, a green wavelength spectrum, yellow wavelength spectrum, blue wavelength spectrum, red wavelength spectrum, an infrared wavelength spectrum, or any other suitable wavelength spectrum.

[0066] In some examples, memory 56B includes computer-readable instructions that, when executed by processing circuitry 50B, cause external device 16 and processing circuitry 50B to perform various functions attributed to external device 16 and processingAtly Ref. No.: A0010862 WOO 1circuitry 50B herein. Memory 56B may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random-access memory (RAM), dynamic RAM (DRAM), static RAM (SRAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other digital media. Memory 56B may store, as examples, programmed values for one or more operational parameters of external device 16 and / or data collected by external device, e.g., detected optical signals, blood pressure, and other parameters, as well as digitized versions of physiological signals, e.g., optical signals sensed by detector 64B, for transmission to another device using communication circuitry 54B. In some examples, memory 56B is used to store program instructions for execution by processing circuitry 50B. Memory 56B may be used by software or applications running on processing circuitry 50B and / or sensing circuitry 52B to temporarily store information during program execution.

[0067] In the illustrated example, external device 16 includes processing circuitry 50B and an associated memory 56B, sensing circuitry 52B, light source(s) 63B, detector(s) 64B, the communication circuitry 54B as described above. However, external device 16 need not include all of these components, or may include additional components. In some examples, external device 16 may include light source(s) 63B but may not include detector(s) 64B. In some examples, external device 16 may include light source(s) 63B and include detector(s) 64B.

[0068] External device 16 may also include one or more light absorber(s) 66B configured to block light, such as ambient light 6 (FIG. 6). In some examples, light absorber(s) 66B may be a masking. In some examples, blocking light comprises reflecting the light, absorbing the light, or attenuating some or all of the light. In some examples, it may be preferable to absorb the light intended to be blocked, rather than to reflect the light or let light pass through, to prevent that light from being backscattered by tissue 402 towards detector 64A. In some examples, masking 66 may also be configured, such as being coated with a particular coating, to spectrally filter light, e.g., to block some wavelengths of light more than others. In some examples, masking 66 may comprise other spectral filters, e.g., infrared filter(s), visible filter(s), ultraviolet filter(s), or any number of filters configured to absorb any suitable spectral band.Aty Ref. No.: A0010862 WOO 1

[0069] Sensing circuitry 52B and / or processing circuitry 50B may be configured to control parameters of light source(s) 63B such as brightness level and / or pulsing emission of the light, and / or control parameters of detector(s) 64B such as gain. In some examples, detector 64B may be a photodetector.

[0070] In the examples shown in FIGS. 5-7, IMD 14 is implanted within patent 12 and is in contact with tissue 402. Tissue 402 includes blood vessels, such as arterioles having relatively high dynamic (highly variable) optical absorbance through the cardiac cycle, and tissue structures that do not have relatively high dynamic optical absorbance through the cardiac cycle. Tissue 402 may include an arterial / arteriole pulse wave 404 pulse through the tissue.

[0071] In some examples, optical window 75 may comprise sapphire to transmit light from light source 63 A into tissue 402 and / or to detect light within tissue 402 at detector 64A. In some examples, optical window 75 may comprise a single crystal sapphire, glass, or polymer.

[0072] In some examples light transmission from light source 63 into optical window 75 may result in some emitted light 406 from light source 63 being reflected light 408. In some examples, ambient light 6 (e.g., light from a different light source external to optical sensor 62) from within the ambient environment may enter tissue 402 and be detected by detector 64A. In some examples, ambient light may interfere with measurements of light 406A, such as light 406A emitted by light source 63B through optical window 75 to tissue 402 and received from tissue 402 by detector 64 A.

[0073] In some examples, external device 16 may include a light absorber 66B configured to absorb a portion of the ambient light 6 and / or reflected light. In some examples, light absorber 66B may comprise absorptive masking. In some examples, light absorber 66B blocking ambient light 6 may increase a signal to noise ratio of light 406A, 406B respectively detected by detectors 64A, 6B. In some examples, light absorber 66B may reduce internal reflections and / or may reduce ambient light transmission and interference with detector(s) 64A of IMD 14 and / or detector(s) 64B of external device. In some examples, the X-direction, as shown in FIGS. 5-7, may be referred to as a planar direction, and the Y-direction, as shown in FIGS. 5-7, may be referred to as a vertical direction. In some examples, light absorber 66B may be positioned adjacent to light source 63B and / or detector 64B in the planar direction.Atty Ref. No.: A0010862 WOO 1

[0074] Processing circuitry of IMD 14, external device 16 or computing device 24 may be configured to determine blood pressure of patient 12 based on light 406 A (e.g., light that is emitted by light source 63B and passes into tissue 402 and interacts with tissue 402, such as through absorption and scattering) detected by detector(s) 64A. In some examples, processing circuitry of IMD 14, external device 16, and / or computing device 24 may be configured to determine blood pressure of patient 12 based on light 406 A (e.g., light that is emitted by light source 63B of external device 16 and passes into tissue 402 and interacts with tissue 402 that may include an arterial / arteriole pulse wave 404, such as through absorption and scattering) detected by at least one detector 64A of IMD 14 and light 406B (e.g., light that is emitted by light source 63 A and passes into tissue 402 and interacts with tissue 402 that may include an arterial / arteriole pulse wave 404, such as through absorption and scattering) respectively detected by at least one detector 64B of external device 16.

[0075] In some examples, light source(s) 63 A and / or 63B may comprise a plurality of light sources. In other examples, light source(s) 63 A and / or 63B may comprise a single light source, e.g., an LED. In some examples, light source(s) 63 A and / or 63B may be configured to emit light within a substantially large solid angle, e.g., a Lambertian or substantially Lambertian light source. In other examples, light source(s) 63 A and / or 63B may be configured to emit light within particular range of angles and in a particular angular direction, e.g., a conical solid angle having an apex angle between 20 degrees and 180 degrees and directed at any suitable angle, e.g., from zero degrees (substantially normal, or perpendicular, to the outer surface of insulative cover 76) to 90 degrees (substantially parallel to the outer surface of insulative cover 76, e.g., a glancing angle along the outer surface of insulative cover 76). In some examples, light source(s) 63 A and / or 63B may include, or be used in conjunction with, beam forming and / or shaping optics, such as lenses, diffraction gratings, holographic optical elements, or the like. In some examples, light source 63 may include a coherent light source, e.g., temporally and / or spatially coherent, such as a laser, a VCSEL, or the like, which may have a divergence angle of less than or equal to 20 degrees.

[0076] In some examples, detector(s) 64A and / or 64B may comprise a single detecting element, e.g., a relatively large area photodiode. In some examples, detector(s) 64 A and / or 64B may comprise an array in one or two dimensions of a plurality of detectors. InAtly Ref. No.: A0010862 WOO 1some examples, detector(s) 64A and / or 64B may be a photodetector. In some examples, optical window 75 includes top side 77A and bottom side 77B, the top side 77A being positioned adjacent to tissue 402 when IMD 14 is implanted and bottom side 77B being positioned to optical sensor 62. In some examples, top side 77A is on an opposite side of optical window 75 compared to bottom side 77B.

[0077] In some examples, processing circuitry of system 10 may refer to one or more of processing circuitry 50A of IMD 14, processing circuitry 50B of external device 16, processing circuitry 26 of computing device 24, and / or additional processing circuitry in other computing devices not shown in the Figures, such as a server.

[0078] FIG. 5 is a conceptual cross-sectional side-view of an example system including IMD 14 that includes detector 64 A configured receive light 406 A from a light source outside of patient 12. In some examples, processing circuitry of at least one of IMD 14, external device, or computing device 24 may be configured to determine blood pressure of the patient based on the detected light 406A. In some examples, light 406A from a light source outside of patient 12 may include sunlight.

[0079] FIG. 6 is a conceptual cross-sectional side-view of an example system including IMD 14 that includes detector 64 A configured to detect light 406 A emitted from light source 63B of external device 16. In some examples, IMD 14 may include at least one detector 64A configured to detect light 406A emitted by a light source 63B of external device 16. In some examples, processing circuitry of system 10 may be configured to determine blood pressure of patient 12 based on the detected light 406 A. In some examples, external device 16 may further include light absorber 66B, such as a masking, configured to block ambient light 6. In some examples, light absorber 66B may reflect ambient light.

[0080] In some examples, processing circuitry of system 10 may be configured to determine whether one or more features of the detected light 406A during a period of time satisfy a sampling threshold. In some examples, in response to determining light 406A satisfies a sampling threshold (e.g., satisfying a sampling threshold may indicate the detected light 406A is sufficient for an accurate determination of blood pressure or indicate light source 63B is powered on and sufficient transmitting light 406A to detector 64 A to accurately determine blood pressure) processing circuitry of system 10 may be configured to determine blood pressure of the patient based on the detected light 406AAty Ref. No.: A0010862 WOO 1during the period of time. In some examples, the one or more features of the detected light may include one or more of a power, wavelength, or frequency of the detected light. In some examples, processing circuitry of system 10 may be configured to receive a communication signal indicating that light source 63B is emitting light 406A to be detected. In some examples, external device 16 may transmit a communication signal indicating that light source 63B is emitting light 406A. In some examples, in response to receiving the communication signal indicating that light source 63B is emitting light 406 A, processing circuitry of system 10 may be configured to determine blood pressure of the patient based on the detected light 406A. In some examples, by determining blood pressure in response to receiving the communication signal indicating that light source 63B is emitting light 406A, system 10 may conserve power be determining blood pressure during times when the light received by detector 64A is more likely to be sufficient to produce more accurate blood pressure measurements. In some examples, IMD 14 may be configured to generate an arterial pressure waveform based on detected light 406A and processing circuitry of system 10 may be configured to determine blood pressure of the patient based on the detected arterial pressure waveform.

[0081] In some examples, processing circuitry of system 10 may be configured to determine blood pressure of patient 12 based on the detected light 406 A. In some examples, determining blood pressure based on detected light 406A that is emitted by light source 63B may reduce the power used by IMD 14 as the power used to emit light from light source 63B is provided by external device 16. In some examples, light source 63B being in external device 16 that is external to patient 12 may enable greater magnitude of signal strength, greater sampling frequency, greater duty cycles, and / or greater wavelength variations of light 406 A as external device 16 may be less restricted by limited power capacity than IMD 14. In some examples, increasing the magnitude of signal strength, increasing sampling frequency, increasing duty cycles, and / or increasing wavelength variations of the emitted light that is detected by a detector of the IMD may improve the accuracy of the determination of blood pressure based on detected light 406A.

[0082] In some examples, a blood pressure transmission mode sensor, such as cuff or clip, squeezes an emitter and detector together, such as on an earlobe or fingertip, which slows down the peripheral blood volume that may result in reduction of venous oscillations and inaccurate blood pressure determinations. In examples of a blood pressureAtly Ref. No.: A0010862 WOO 1transmission mode sensor that squeezes an emitter and detector together, such as cuff or clip, if the applied pressure affects the blood flow the applied pressure leads to inaccurate readings. In some examples, external device 16, as shown in FIGS. 6-7, may be configured as an adhesive patch, wearable garment, or substantially planar or conformable device to be positioned on top or above a surface of skin of patient 12. In some examples, unlike a cuff or clip, external device 16 being configured in such as fashion may not put substantial mechanical force or pressure on patient 12 which may slow down the peripheral blood volume that may result in reduction of venous oscillations and inaccurate blood pressure determinations. In some examples, determining blood pressure based on light 406A and / or 406B transmitted through tissue 402 with minimal to no mechanical force or pressure exerted by external device 16 on patient 12 may enable more accurate determinations of blood pressure based on detected light 406A and / or 406B.

[0083] In some examples, at least one detector 64A may sample varying wavelengths of light 406A and IMD 14 and provide feedback, via communication circuitry 54A, of the detected light 406A at various wavelengths. Processing circuitry of system 10 may be configured to determine or select a particular wavelength for light source 63B to emit light based on the feedback of the light at various wavelengths. For example, processing circuitry of system 10 may be configured to determine a particular wavelength, based on the feedback, that has the greatest signal strength or signal to noise ratio and cause at least one light source 63B to emit light at that particular wavelength which may improve accuracy of blood pressure determinations.

[0084] In some examples, as shown in FIG. 6, IMD 14 and external device 16 operating to determine blood pressure based on transmission mode sensing may enable light 406A to interact with different tissue volumes 402 than a reflectance mode sensor, which may improve detected signal strength or signal to noise ratio of detected light 406A, which improves the accuracy of determining blood pressure based on detected light 406A.

[0085] FIG. 7 is a conceptual cross-sectional side-view of an example system 10 including IMD 14 that includes detector(s) 64 A and light source(s) 63 A and external device 16 that includes detector(s) 64B and light source(s) 63B. The detector(s) 64Amay be configured to respectively detect light 406 A emitted from light source(s) 63B. The detector(s) 64B may be configured to detect light 406B emitted from light source(s) 63 A.Atty Ref. No.: A0010862 WOO 1In some examples, processing circuitry of system 10 may be configured to determine blood pressure of patient 12 based on light 406 A and light 406B.

[0086] IMD 14 may further include communication circuitry 54Aand external device 16 may further include communication circuitry 54B that are configured to communicate with each other. In some examples, IMD communication circuitry 54A is configured to transmit an IMD communication signal to external device communication circuitry 54B indicating that at least one IMD light source 63 A is emitting or will emit light 406B for a first particular period of time. In some examples, external device communication circuitry 54B is configured to transmit an external device communication signal to IMD communication circuitry 54A indicating that at least one external device light source 63B is emitting or will emit light 406A for a second particular period of time. In some examples, in response to external device communication circuitry 54B receiving the IMD communication signal and the IMD communication circuitry 54A receiving the external device communication signal, processing circuitry of system 10 may be configured to determine blood pressure based on the light 406A detected by IMD detector(s) 64A during the second particular period of time and light 406B detected by the external device detector 64B during the first particular period of time.

[0087] In some examples, processing circuitry of IMD 14, external device 16, and / or computing device 24 may be configured to determine blood pressure of patient 12 based on light 406A (e.g., light that is emitted by light source 63B of external device 16 and passes into tissue 402 and interacts with tissue 402 that may include an arterial / arteriole pulse wave 404, such as through absorption and scattering) detected by at least one detector 64A of IMD 14 and light 406B (e.g., light that is emitted by light source 63 A and passes into tissue 402 and interacts with tissue 402 that may include an arterial / arteriole pulse wave 404, such as through absorption and scattering) respectively detected by at least one detector 64B of external device 16.

[0088] In some examples, having light sources 63 A, 63B, and detectors 64A, 64B respectively positioned in IMD 14 and external device 16 may enable system 10 to operate in four modes, transmission mode from IMD 14 to external device 16, transmission mode from external device to IMD 14, reflection mode from IMD 14 to IMD 14, and reflection mode from external device 16 to external device 16 which may enable greater signal strength detected by respective detectors 64A, 64B which may enable improve accuracyAty Ref. No.: A0010862 WOO 1blood pressure determinations based on detected optical signals. In some examples, increasing the magnitude of signal strength, increasing sampling frequency, increasing duty cycles, and / or increasing wavelength variations of optical sensing light that is detected by detectors 64A and / or 64B may improve the accuracy of a physiological characteristic such as blood pressure determined by IMD 14, external device 16, computing device 24, or other devices such as a server, based on light detected by respective detectors 64 A and / or 64B.

[0089] In some examples, such as prior to external device 16 being placed on over patient 12, IMD 14 may emit light via at least one light source 63A to indicate a location of the IMD 14 in patient 12. In some examples, emitting light to indicate a location of IMD 14 may help external device 16 be positioned at location near IMD 14 to enable a more direct path between light sources 63 A, 63B and detectors 64A, 64B of IMD 14 and / or external device 16 to improve signal quality of optical signals received by respective detectors 64 A, 64B.

[0090] FIG. 8 is a flow diagram of an example method of determining a physiological characteristic of a patient, according to various examples described in this disclosure. Although the example technique of FIGS. 1 A-1B is described with respect to system 10, IMD 14, external device 16, and computing device 24 of FIGS. 1-8, the example technique of FIG. 8 may be performed using any system including an implantable medical device, external device, and / or computing device.

[0091] Light source 63B of external device 16 may emit light 406A towards a tissue 402 of patient 12 (802). For example, processing circuitry 50B may cause light source 63B to emit broadband light or light having a specific wavelength band, e.g., IR light. The light may include optical sensing light (e.g., light that is emitted by a light source 63B passes into tissue 402 and interacts with tissue 402, such as through absorption and scattering) that interacts with tissue 402 of patient 12.

[0092] Detector 64A of IMD 14 may detect the light 406A (e.g., light that is emitted by a light source 63B of external device 16 and passes into tissue 402 and interacts with tissue 402, such as through absorption and scattering) (804). Sensing circuitry 52A and / or processing circuitry 50A may receive a signal indicative of the detected light 406A from detector 64A. At least one or more of sensing circuitry and / or processing circuitryAtty Ref. No.: A0010862 WOO 1respectively of external device 16, IMD 14, and / or computing device 24 may determine a physiological characteristic of patient 12 based, at least, on the detected light (806).

[0093] The techniques described in this disclosure may be implemented, at least in part, in hardware, software, firmware or any combination thereof. For example, various aspects of the described techniques may be implemented within one or more processors or processing circuitry, including one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components. The term “processor” or “processing circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry. A control unit including hardware may also perform one or more of the techniques of this disclosure.

[0094] Such hardware, software, and firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. In addition, any of the described units, circuits or components may be implemented together or separately as discrete but interoperable logic devices. Depiction of different features as circuits or units is intended to highlight different functional aspects and does not necessarily imply that such circuits or units must be realized by separate hardware or software components. Rather, functionality associated with one or more circuits or units may be performed by separate hardware or software components or integrated within common or separate hardware or software components.

[0095] The techniques described in this disclosure may also be embodied or encoded in a computer-readable medium, such as a computer-readable storage medium, containing instructions that may be described as non-transitory media. Instructions embedded or encoded in a computer-readable storage medium may cause a programmable processor, or other processor, to perform the method, e.g., when the instructions are executed. Computer readable storage media may include random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), flash memory, a hard disk, a CD-ROM, a floppy disk, a cassette, magnetic media, optical media, or other computer readable media.

[0096] Various aspects of the techniques may enable the following examples.Atly Ref. No.: A0010862 WOO 1

[0097] Example 1 : A system includes an implantable medical device (IMD) includes a housing configured for implantation within a patient; a detector on or within the housing, the detector configured to detect light emitted by a light source outside of the patient; and processing circuitry configured to determine a physiological characteristic of the patient based on the detected light.

[0098] Example 2: The system of example 1 further comprising an external device comprising the light source.

[0099] Example 3: The system of any of examples 1-2, wherein the processing circuitry is further configured to determine whether one or more features of the detected light during a period of time satisfy a sampling threshold; and in response to a determination that the one or more features of the detected light satisfy the sampling threshold, determine the physiological characteristic of the patient based on the detected light during the period of time.

[0100] Example 4: The system of example 3, wherein the one or more features of the detected light includes a power of the detected light.

[0101] Example 5: The system of any of examples 1-2, wherein the processing circuitry is further configured to receive a communication signal indicating that the light source is emitting light to be detected; and in response to receiving the communication signal, determine the physiological characteristic of the patient based on the detected light.

[0102] Example 6: The system of any of examples 1-2, wherein the processing circuitry is further configured to receive a communication signal indicating that the light source is emitting or will emit light for a particular period of time; and in response to receiving the communication signal, determine the physiological characteristic of the patient based on the detected light during the particular period of time.

[0103] Example 7: The system of any of examples 1-6, wherein the IMD is configured to generate an arterial pressure waveform based on the detected light, and the processing circuitry is further configured to determine the physiological characteristic of the patient based on the arterial pressure waveform.

[0104] Example 8: The system of any of examples 2-7, wherein the detector of the IMD is an IMD detector, and the light source of the external device is an external device light source, wherein the IMD further comprises an IMD light source configured to emit light, wherein the external device further comprises an external device detector to detectAtty Ref. No.: A0010862 WOO 1light emitted by the IMD light source, and wherein the processing circuitry is further configured to determine the physiological characteristic based on the light detected by the IMD detector and the light detected by the external device detector.

[0105] Example 9: The system of example 8, wherein the IMD further comprises IMD communication circuitry and the external device further comprises external device communication circuitry, wherein the IMD communication circuitry is configured to transmit an IMD communication signal to the external device communication circuitry indicating that the IMD light source is emitting or will emit light for a first particular period of time, wherein the external device communication circuitry is configured to transmit an external device communication signal to the IMD communication circuitry indicating that the external device light source is emitting or will emit light for a second particular period of time, and wherein in response to the external device communication circuitry receiving the IMD communication signal and the IMD communication circuitry receiving the external device communication signal, the processing circuitry is further configured to determine the physiological characteristic based on the light detected by the IMD detector during the second particular period of time and the light detected by the external device detector during the first particular period of time.

[0106] Example 10: The system of any of examples 2-9, wherein the external device is an adhesive patch configured to be positioned on skin of the patient.

[0107] Example 11 : The system of any of examples 2-10, wherein the external device further comprises a light absorber positioned adjacent the light source, the light absorber being configured to absorb ambient light.

[0108] Example 12: The system of any of examples 1-11, wherein the processing circuitry is positioned in at least one of the IMD, the external device, or another computing device.

[0109] Example 13: The system of any of examples 1-12, wherein the physiological characteristic is a blood pressure of the patient.

[0110] Example 14: A method of determining a physiological characteristic of a patient includes emitting light by a light source of an external device positioned external to the patient; detecting, by a detector of an implantable medical device (IMD), the light emitted by the light source; and determining, by processing circuitry and based, at least, on the detected light, the physiological characteristic of the patient.Atly Ref. No.: A0010862 WOO 1

[0111] Example 15: The method of example 14 further includes determining whether one or more features of the detected light during a period of time satisfy a sampling threshold; and in response to a determination that the one or more features of the detected light satisfy the sampling threshold, determining the physiological characteristic of the patient based on the detected light during the period of time.

[0112] Example 16: The method of example 15, wherein the one or more features of the detected light includes a power of the detected light.

[0113] Example 17: The method of example 14 further includes receiving a communication signal indicating that the light source is emitting light to be detected; and in response to receiving the communication signal, determining the physiological characteristic of the patient based on the detected light.

[0114] Example 18: The method of example 14 further includes receiving a communication signal indicating that the light source is emitting or will emit light for a particular period of time; and in response to receiving the communication signal, determining the physiological characteristic of the patient based on the detected light during the particular period of time.

[0115] Example 19: The method of any of examples 14-18, wherein the detector of the IMD is an IMD detector, and the light source of the external device is an external device light source, the method further includes emitting light by an IMD light source; detecting, by an external device detector, light emitted by the IMD light source; and determining the physiological characteristic of the patient based on the light detected by the IMD detector and the light detected by the external device detector.

[0116] Example 20: The method of example 19 further includes transmitting, via IMD communication circuitry, an IMD communication signal to the external device indicating that the IMD light source is emitting or will emit light for a first particular period of time; transmitting, via external device communication circuitry, an external device communication signal to the IMD indicating that the external device light source is emitting or will emit light for a second particular period of time; and in response to the external device receiving the IMD communication signal and the IMD receiving the external device communication signal, determining the physiological characteristic based on the light detected by the IMD detector during the second particular period of time and the light detected by the external device detector during the first particular period of time.Aty Ref. No.: A0010862 WOO 1

[0117] Example 21 : The method of any of examples 14-20, wherein the external device is an adhesive patch configured to be positioned on skin of the patient.

[0118] Example 22: The method of any of examples 14-21, wherein the physiological characteristic is a blood pressure of the patient.

[0119] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. Atly Ref. No.: A0010862 WOO 1WHAT IS CLAIMED IS:

1. A system comprising:an implantable medical device (IMD) comprising:a housing configured for implantation within a patient;a detector on or within the housing, the detector configured to detect light emitted by a light source outside of the patient; andprocessing circuitry configured to determine a physiological characteristic of the patient based on the detected light.

2. The system of claim 1 further comprising an external device comprising the light source.

3. The system of any of claims 1-2, wherein the processing circuitry is further configured to determine whether one or more features of the detected light during a period of time satisfy a sampling threshold; andin response to a determination that the one or more features of the detected light satisfy the sampling threshold, determine the physiological characteristic of the patient based on the detected light during the period of time.

4. The system of claim 3, wherein the one or more features of the detected light includes a power of the detected light.

5. The system of any of claims 1-2, wherein the processing circuitry is further configured to receive a communication signal indicating that the light source is emitting light to be detected; andin response to receiving the communication signal, determine the physiological characteristic of the patient based on the detected light.

6. The system of any of claims 1-2, wherein the processing circuitry is further configured to receive a communication signal indicating that the light source is emitting or will emit light for a particular period of time; andAtly Ref. No.: A0010862 WOO 1in response to receiving the communication signal, determine the physiological characteristic of the patient based on the detected light during the particular period of time.

7. The system of any of claims 1-6, wherein the IMD is configured to generate an arterial pressure waveform based on the detected light, andthe processing circuitry is further configured to determine the physiological characteristic of the patient based on the arterial pressure waveform.

8. The system of any of claims 2-7, wherein the detector of the IMD is an IMD detector, and the light source of the external device is an external device light source,wherein the IMD further comprises an IMD light source configured to emit light, wherein the external device further comprises an external device detector to detect light emitted by the IMD light source, andwherein the processing circuitry is further configured to determine the physiological characteristic based on the light detected by the IMD detector and the light detected by the external device detector.

9. The system of claim 8, wherein the IMD further comprises IMD communication circuitry and the external device further comprises external device communication circuitry, wherein the IMD communication circuitry is configured to transmit an IMD communication signal to the external device communication circuitry indicating that the IMD light source is emitting or will emit light for a first particular period of time, wherein the external device communication circuitry is configured to transmit an external device communication signal to the IMD communication circuitry indicating that the external device light source is emitting or will emit light for a second particular period of time, andwherein in response to the external device communication circuitry receiving the IMD communication signal and the IMD communication circuitry receiving the external device communication signal, the processing circuitry is further configured to determine the physiological characteristic based on the light detected by the IMD detector during the second particular period of time and the light detected by the external device detector during the first particular period of time.Atty Ref. No.: A0010862 WOO 110. The system of any of claims 2-9, wherein the external device is an adhesive patch configured to be positioned on skin of the patient.

11. The system of any of claims 2-10, wherein the external device further comprises a light absorber positioned adjacent the light source, the light absorber being configured to absorb ambient light.

12. The system of any of claims 2-11, wherein the processing circuitry is positioned in at least one of the IMD, the external device, or another computing device.

13. The system of any of claims 1-12, wherein the physiological characteristic is a blood pressure of the patient.

14. A method of determining a physiological characteristic of a patient, the method comprising:emitting light by a light source of an external device positioned external to the patient;detecting, by a detector of an implantable medical device (IMD), the light emitted by the light source; anddetermining, by processing circuitry and based, at least, on the detected light, the physiological characteristic of the patient.

15. The method of claim 14 further comprising:determining whether one or more features of the detected light during a period of time satisfy a sampling threshold; andin response to a determination that the one or more features of the detected light satisfy the sampling threshold, determining the physiological characteristic of the patient based on the detected light during the period of time.

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