Dynamic bioimpedance range adjustment for medical devices

Abstract

The present disclosure relates to apparatuses, systems, and techniques for dynamically adjusting a bioimpedance measurement range. An example apparatus includes a plurality of electrodes. The apparatus also includes sensing circuitry configured to sense bioimpedance and processing circuitry. The processing circuitry is configured to apply an excitation signal to the sensing circuitry and, based on the application of the excitation signal, determine a sensed bioimpedance value within a bioimpedance measurement range. The processing circuitry is also configured to determine whether the sensed bioimpedance value is within a predetermined portion of the bioimpedance measurement range for a predetermined period of time and, based on the sensed bioimpedance value being within the predetermined portion of the bioimpedance measurement range for the predetermined period of time, adjust the excitation signal.

Description

Technical Field

[0001] The present disclosure relates generally to medical device systems, and more particularly to medical device systems configured to monitor patient parameters. Background Art

[0002] Some types of medical devices can be used to monitor one or more physiological parameters of a patient. Such medical devices may include, or may be part of, a system that includes sensors that detect signals associated with such physiological parameters. Values ​​determined based on such signals can be used to help detect changes in a patient's condition, assess the efficacy of treatment, or generally evaluate the patient's health. Summary of the Invention

[0003] In general, the present disclosure relates to devices, systems, and techniques for collecting bioimpedance values ​​of a patient using a medical device. Bioimpedance values ​​(e.g., BioZ values) are an effective way to monitor patient parameters. In some examples, bioimpedance values ​​can effectively monitor a patient's heart failure condition. For example, bioimpedance values ​​can be used to calculate a heart failure score and monitor disease progression. However, if the patient's actual bioimpedance value is outside the bioimpedance measurement range of the medical device used to sense the patient's bioimpedance, such as above the upper boundary limit of the bioimpedance measurement range or below the lower boundary limit of the bioimpedance measurement range, the measurement result may be inaccurate, and the clinician analyzing the measurement result may be less able to monitor the progression of heart failure and less able to determine the effectiveness of medical, pharmaceutical, or other treatments.

[0004] According to the technology disclosed herein, the bioimpedance measurement range of a medical device can be dynamically changed to reduce the occurrence of erroneous measurement results. In some examples, the medical device can periodically determine whether the measured bioimpedance value is within a predetermined portion (e.g., the bottom portion or the top portion) of the bioimpedance measurement range for a predetermined period of time (e.g., two or three days). Based on the measured bioimpedance value being within the predetermined portion of the bioimpedance measurement range for a predetermined period of time, the medical device can adjust an excitation signal, such as a current or voltage applied to a sensing circuit system for sensing bioimpedance. Adjusting the excitation signal applied to the sensing circuit system can change the upper limit of the bioimpedance measurement range, thereby dynamically changing the bioimpedance measurement range of the device. The adjustment of the excitation signal can be performed in a manner that expands the bioimpedance measurement range and thereby moves the measured bioimpedance value toward the center of the adjusted bioimpedance measurement range. In this way, the medical device can more accurately measure the bioimpedance value, thereby allowing clinicians, for example, to more accurately track the progression of heart failure in patients.

[0005] In some examples, a device includes: a plurality of electrodes; a sensing circuit system configured to sense bioimpedance; and a processing circuit system configured to: apply an excitation signal to the plurality of electrodes via the sensing circuit system; determine a sensed bioimpedance value within a bioimpedance measurement range based on the application of the excitation signal; determine whether the sensed bioimpedance value is within a predetermined portion of the bioimpedance measurement range for a predetermined time period; and adjust the excitation signal based on the sensed bioimpedance value being within the predetermined portion of the bioimpedance measurement range for a predetermined time period, wherein adjusting the excitation signal adjusts the bioimpedance measurement range.

[0006] In some examples, a method includes: applying, by a processing circuit system, an excitation signal to a plurality of electrodes via a sensing circuit system; determining, by the processing circuit system and based on the application of the excitation signal, a sensed bioimpedance value within a bioimpedance measurement range; determining, by the processing circuit system, whether the sensed bioimpedance value is within a predetermined portion of the bioimpedance measurement range for a predetermined time period; and adjusting the excitation signal based on the sensed bioimpedance value being within the predetermined portion of the bioimpedance measurement range for the predetermined time period, wherein adjusting the excitation signal adjusts the bioimpedance measurement range.

[0007] In some examples, a non-transitory computer-readable medium includes instructions for causing one or more processors to: apply an excitation signal to a plurality of electrodes via a sensing circuit system; determine a sensed bioimpedance value within a bioimpedance measurement range based on the application of the excitation signal; determine whether the sensed bioimpedance value is within a predetermined portion of the bioimpedance measurement range for a predetermined time period; and adjust the excitation signal based on the sensed bioimpedance value being within the predetermined portion of the bioimpedance measurement range for the predetermined time period, wherein adjusting the excitation signal adjusts the bioimpedance measurement range.

[0008] This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to be an exclusive or exhaustive explanation of the systems, devices, and methods described in detail in the following figures and the specification. Further details of one or more examples of the disclosure are set forth in the accompanying drawings and the following detailed description. Additional features, objects, and advantages will be apparent from the description and drawings, as well as from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 An environment illustrating an exemplary medical device system in conjunction with a patient, in accordance with one or more techniques of the present disclosure.

[0010] Figure 2 is a diagram illustrating one or more techniques described herein. Figure 1Conceptual diagram of an exemplary configuration of an implantable medical device (IMD) of a medical device system.

[0011] Figure 3 is a diagram illustrating one or more techniques described herein. Figure 1 and Figure 2 Functional block diagram of an exemplary configuration of an IMD.

[0012] Figure 4A and Figure 4B is to illustrate that one or more techniques described herein may be substantially similar to Figures 1 to 3 Block diagrams of two additional exemplary IMDs that may include one or more additional features.

[0013] Figure 5 is a diagram showing one or more techniques according to the present disclosure Figure 1 A block diagram of an exemplary configuration of components of an external device.

[0014] Figure 6 is a block diagram illustrating an exemplary system according to one or more techniques described herein, the system including an access point, a network, an external computing device such as a server, and one or more other computing devices that can be coupled to a server via the network. Figure 1 to 4 IMDs, external devices, and processing circuit systems.

[0015] Figure 7 is a flow chart illustrating an example of dynamically adjusting a bioimpedance measurement range according to one or more techniques of this disclosure.

[0016] Figure 8 is a flow chart illustrating another example of dynamically adjusting a bioimpedance measurement range according to one or more techniques of this disclosure.

[0017] Like reference numerals represent like elements throughout the specification and drawings. DETAILED DESCRIPTION

[0018] The present disclosure describes techniques for dynamically adjusting the bioimpedance measurement range of a medical device. For example, measuring bioimpedance values ​​is an effective way to determine the fluid content of a patient's body and to determine the patient's respiratory activity. For example, the DC component of the measured bioimpedance can indicate the fluid content within the patient's body, and the relatively small AC component of the measured bioimpedance can indicate the patient's respiratory activity. Both the patient's body fluid content and respiration can be used individually or together as part of the calculation of a heart failure score, which can provide clinicians with a way to track the progression of heart failure in patients.

[0019] Bioimpedance can be measured by applying an excitation signal, such as a current or voltage, to sensing circuitry in an implantable medical device (IMD); delivering the excitation signal (such as a current or voltage) via a plurality of electrodes coupled to the sensing circuitry; and measuring the other of the resulting current or voltage. Processing circuitry in IMD 10 may determine a bioimpedance value based on the delivered excitation signal and the measured voltage or current.

[0020] Bioimpedance values ​​can be transmitted to an external device periodically (such as daily) and can be used by a clinician to monitor the progression of heart failure in a patient. A given excitation signal (such as a current or voltage) establishes a corresponding bioimpedance measurement range for which the IMD can measure the patient's bioimpedance values. When the IMD is implanted, the clinician can determine an appropriate excitation signal to accurately measure the patient's bioimpedance. For example, the clinician can attempt to select an excitation current or voltage that places the measured bioimpedance at or near the center of the bioimpedance measurement range.

[0021] If the patient subsequently loses or gains weight, the measured bioimpedance value may change. For example, muscle tissue is more conductive than fat tissue. Muscle tissue may have an impedance ranging from 200 ohms to 2000 ohms, while fat tissue may have an impedance ranging from 1500 ohms to 5000 ohms. Therefore, if the patient gains or loses weight, the tissue contacting the electrodes used to sense the patient's bioimpedance value may change, causing the measured bioimpedance value to change for reasons unrelated to the patient's condition being monitored by the IMD. The measured bioimpedance value may also change if the patient's health changes significantly. Furthermore, the measured bioimpedance value may also change if the IMD migrates within the patient's body, causing the IMD's electrodes used to sense the patient's bioimpedance value to contact different tissue within the patient's body. These types of changes can shift the measured bioimpedance value from the center of the bioimpedance measurement range toward the top or bottom of the bioimpedance measurement range, or even move the patient's actual bioimpedance value outside the lower or upper limits of the bioimpedance measurement range. For example, if the patient's actual bioimpedance value is 3000 ohms and the top of the bioimpedance measurement range is 2500 ohms, the IMD will measure the bioimpedance value as 2500 ohms. In this case, because the patient's actual bioimpedance value is outside the bioimpedance measurement range, the IMD may not accurately measure the DC component of the bioimpedance that indicates fluid retention or the relatively small AC component of the bioimpedance signal that represents respiratory activity. Therefore, fixed lower and upper limits of the bioimpedance measurement range may work well initially but become less effective over time.

[0022] If the lower or upper limit of the bioimpedance measurement range is incorrect (e.g., the patient's actual bioimpedance value is outside the bioimpedance measurement range or at the top or bottom of the bioimpedance measurement range), the measured bioimpedance value may not be equal to the patient's actual bioimpedance value. Therefore, the measured bioimpedance value may not be useful to a clinician monitoring a patient's health or condition, such as the progression of a patient's heart failure. According to the techniques of the present disclosure, a device such as an IMD or one or more implanted or external devices can be used to measure a patient's bioimpedance value. The lower and / or upper limit of the device's bioimpedance measurement range can be dynamically adjusted by adjusting an excitation signal (such as current or voltage) to change the bioimpedance measurement range so that the measured patient's bioimpedance value is closer to the center of the bioimpedance measurement range than the originally measured bioimpedance value was. In this way, the IMD can measure the patient's bioimpedance value relatively accurately, even after the patient gains or loses weight, the patient's health condition changes significantly, or the IMD migrates within the patient's body. In some examples, the bioimpedance measurement range can be adjusted automatically (e.g., without intervention by a clinician or patient).

[0023] Figure 1 The environment of an exemplary medical device system 2 incorporating a patient 4 according to one or more techniques of the present disclosure is shown. Although the techniques described herein are generally described in the context of an insertable cardiac monitor, the techniques of the present disclosure can be implemented in any implantable medical device configured to measure bioimpedance, such as a pacemaker and / or defibrillator, or a neurostimulator, which can be coupled to electrodes via leads. The exemplary techniques can be used with an IMD 10 that can be coupled to an external device 12 and Figure 1 The processing circuit system 14 is used to wirelessly communicate with at least one of the other devices not shown in the figure. Figure 1 10 and external device 12, but may be processing circuitry of IMD 10 and / or processing circuitry of external device 12. In general, the techniques of this disclosure may be performed by one or more devices of a system, such as processing circuitry 14 of one or more devices that include sensors that provide signals, or processing circuitry of one or more devices that do not include sensors but still analyze signals using the techniques described herein. For example, another external device ( Figure 1 10 and / or external device 12 via a network.

[0024] In some examples, IMD 10 may be implanted outside of the chest of patient 4 (e.g., subcutaneously). Figure 1The IMD 10 can be positioned near the sternum of the patient 4 near or just below the heart level, e.g., at least partially within the outline of the heart. In some examples, the IMD 10 utilizes the LINQ TM In the form of an insertable cardiac monitor (ICM).

[0025] Clinicians sometimes diagnose patients with medical conditions based on one or more observed physiological signals collected by physiological sensors, such as electrodes, optical sensors, chemical sensors, temperature sensors, acoustic sensors, and motion sensors. In some cases, clinicians apply non-invasive sensors to patients to sense one or more physiological signals while the patient is at a medical appointment in a clinic. However, in some examples, physiological markers of the patient's condition (e.g., irregular heartbeat and long-term breathing trends) are rare or difficult to observe within a relatively short period of time. Therefore, in these examples, the clinician may not be able to observe the physiological markers needed to diagnose a patient with a medical condition while monitoring one or more of the patient's physiological signals during the medical appointment. Figure 1 In the example shown, IMD 10 is implanted in patient 4 to continuously record one or more physiological signals, such as bioimpedance, of patient 4 over an extended period of time.

[0026] In some examples, IMD 10 includes a plurality of electrodes. The plurality of electrodes are configured to detect signals that enable, for example, processing circuitry 14 of IMD 10 to determine current values ​​of additional parameters associated with cardiac and / or pulmonary function of patient 4. For example, the plurality of electrodes may be configured to measure bioimpedance values ​​of patient 4. In some examples, the plurality of electrodes of IMD 10 are configured to detect signals indicative of the electrical potential of tissue surrounding IMD 10. Furthermore, in some examples, IMD 10 may additionally or alternatively include one or more optical sensors, accelerometers, temperature sensors, chemical sensors, light sensors, or pressure sensors. Such sensors may detect one or more physiological parameters indicative of the patient's condition.

[0027] The external device 12 may be a handheld computing device having a display viewable by a user and an interface for providing input to the external device 12 (i.e., a user input mechanism). For example, the external device 12 may include a small display screen (e.g., a liquid crystal display (LCD) or a light emitting diode (LED) display) that presents information to the user. In addition, the external device 12 may include a touch screen display, a keypad, buttons, a peripheral pointing device, voice activation, or another input mechanism that allows the user to navigate through the user interface of the external device 12 and provide input. If the external device 12 includes buttons and a keypad, the buttons may be dedicated to performing a specific function (e.g., a power button), the buttons and keypad may be soft keys that change function depending on the part of the user interface currently being viewed by the user, or any combination thereof.

[0028] In other examples, the external device 12 may be a separate application within a larger workstation or another multi-function device rather than a dedicated computing device. For example, the multi-function device may be a laptop computer, a tablet computer, a workstation, one or more servers, a cellular phone, a personal digital assistant, or another computing device that can run an application that enables the computing device to operate as a security device.

[0029] When external device 12 is configured for use by a clinician, it can be used to transmit instructions to IMD 10 and receive measurements, such as sensed bioimpedance values. Example instructions may include a request to set the electrode combination for sensing and any other information that can be programmed into IMD 10. The clinician can also configure and store operating parameters of IMD 10 within IMD 10 with the assistance of external device 12. In some examples, external device 12 helps the clinician configure IMD 10 by providing a system for identifying potentially beneficial operating parameter values.

[0030] Regardless of whether external device 12 is configured for clinician or patient use, external device 12 is configured to communicate with IMD 10 via wireless communication, and optionally with another computing device ( Figure 1 For example, the external device 12 may communicate via a near field communication technology (e.g., inductive coupling, NFC, or other communication technology that can operate at a range of less than 10 cm to 20 cm) and a far field communication technology (e.g., according to 802.11 or RF telemetry based on a standard set or other communication technology that can operate at a range greater than near field communication technology.

[0031] In some examples, processing circuitry 14 may include one or more processors configured to implement instructions for functions and / or processes executed within IMD 10. For example, processing circuitry 14 may be capable of processing instructions stored in a memory device. Processing circuitry 14 may include, for example, a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or equivalent discrete or integrated logic circuitry, or a combination of any of the foregoing. Thus, processing circuitry 14 may include any suitable structure, whether hardware, software, firmware, or any combination thereof, to perform the functions of processing circuitry 14 described herein.

[0032] Processing circuitry 14 may represent processing circuitry located within any combination of IMD 10 and external device 12. In some examples, processing circuitry 14 may be located entirely within the housing of IMD 10. In other examples, processing circuitry 14 may be located entirely within the housing of external device 12. In other examples, processing circuitry 14 may be located within any combination of IMD 10, external device 12, and the like. Figure 1 Thus, techniques and capabilities attributed herein to processing circuitry 14 may be attributed to IMD 10, external device 12, and any combination of another device or groups of devices not shown. Figure 1 Any combination of other devices not shown.

[0033] Figure 1 The medical device system 2 is an example of a system for measuring bioimpedance values ​​in accordance with one or more techniques of the present disclosure. In some examples, the processing circuit system 14 may include an EGM analysis circuit system configured to determine one or more parameters of an EGM signal of the patient 4. In one example, the EGM signal is sensed via multiple electrodes of the IMD 10. An EGM is a signal that is measured by electrodes implanted in the body (typically within the heart itself) that represents the electrical activity of the heart. For example, a cardiac EGM may include, among other events, a P wave (depolarization of the atria), an R wave (depolarization of the ventricles), and a T wave (repolarization of the ventricles). Information related to the aforementioned events, such as the time to separate one or more events, can be used for a variety of purposes, such as determining whether an arrhythmia is occurring and / or predicting whether an arrhythmia is likely to occur. The cardiac signal analysis circuit system, which may be implemented as part of the processing circuit system 14, may perform signal processing techniques to extract information indicative of one or more parameters of the cardiac signal.

[0034] In some examples, IMD 10 includes one or more accelerometers. The accelerometers of IMD 10 can collect accelerometer signals reflecting a measure of motion of patient 4. In some cases, the accelerometers can collect three-axis accelerometer signals indicating movement of patient 4 within a three-dimensional Cartesian space. For example, the accelerometer signals can include a vertical-axis accelerometer signal vector, a transverse-axis accelerometer signal vector, and a frontal-axis accelerometer signal vector. The vertical-axis accelerometer signal vector can represent an acceleration of patient 4 along the vertical axis, the transverse-axis accelerometer signal vector can represent an acceleration of patient 4 along the transverse axis, and the frontal-axis accelerometer signal vector can represent an acceleration of patient 4 along the frontal axis. In some cases, the vertical axis extends substantially along the torso of patient 4 from the neck of patient 4 to the waist of patient 4, the transverse axis extends across the chest of patient 4 perpendicular to the vertical axis, and the frontal axis extends outward from and through the chest of patient 4, the frontal axis being perpendicular to both the vertical and transverse axes.

[0035] In some examples, processing circuitry 14 may be configured to identify that IMD 10 has flipped from a previous position (e.g., rotated to face another direction) based on the accelerometer signal. For example, multiple electrodes of IMD 10 may not be anchored to surrounding tissue, and IMD 10 may migrate within patient 4's body. In some cases, IMD 10 may flip. Processing circuitry 14 may analyze the accelerometer signal and determine that IMD 10 has flipped by determining that accelerometer data in the accelerometer signal has reversed in one axis. In some examples, processing circuitry 14 may determine whether the measured bioimpedance value is within a predetermined portion of the bioimpedance measurement range based on determining that IMD 10 has flipped. In some examples, processing circuitry 14 may continuously monitor the accelerometer signal. In other examples, processing circuitry 14 may periodically monitor the accelerometer signal.

[0036] While in one example, IMD 10 takes the form of an ICM, in other examples, IMD 10 takes the form of any combination of an implantable cardioverter-defibrillator (ICD) with intravascular or extravascular leads, a pacemaker, a cardiac resynchronization therapy device (CRT-D), a neuromodulation device, a left ventricular assist device (LVAD), an implantable sensor, an orthopedic device, or a drug pump, as examples. Bioimpedance values ​​of patient 4 can be measured using one or more of the aforementioned devices.

[0037] Figure 2 is a demonstration of one or more techniques described herein Figure 1 A conceptual diagram of an exemplary configuration of an IMD 10 of a medical device system 2 is shown. Figure 2In the example shown, IMD 10 may include a leadless, subcutaneously implantable monitoring device having a housing 15, a proximal electrode 16A, and a distal electrode 16B. Housing 15 may further include a first major surface 18, a second major surface 20, a proximal end 22, and a distal end 24. In some examples, IMD 10 may include one or more additional electrodes 16C, 16D located on one or both major surfaces 18, 20 of IMD 10. Housing 15 encloses the electronic circuitry located within IMD 10 and protects the circuitry contained therein from fluids such as bodily fluids. In some examples, electrical feedthroughs provide electrical connection of electrodes 16A to 16D and antenna 26 to the circuitry within housing 15. In some examples, electrode 16B may be formed from an uninsulated portion of conductive housing 15.

[0038] exist Figure 2 In the example shown, IMD 10 is defined by a length L, a width W, and a thickness or depth D. In this example, IMD 10 is in the form of an elongated rectangular prism, wherein length L is significantly greater than width W, and wherein width W is greater than depth D. However, other configurations of IMD 10 are contemplated, such as those in which the relative proportions of length L, width W, and depth D are similar to those of FIG. Figure 2 In some examples, the geometry of IMD 10, such as width W being greater than depth D, may be selected to allow IMD 10 to be inserted under the patient's skin using a minimally invasive procedure and maintained in a desired orientation during insertion. Additionally, IMD 10 may include radial asymmetry (e.g., a rectangular shape) along the longitudinal axis of IMD 10, which may help maintain the device in a desired orientation after implantation.

[0039] In some examples, the spacing between proximal electrode 16A and distal electrode 16B can be in a range of about 30 to 55 mm, about 35 to 55 mm, or about 40 to 55 mm, or more generally, about 25 to 60 mm. In general, IMD 10 can have a length L of about 20 to 30 mm, about 40 to 60 mm, or about 45 to 60 mm. In some examples, the width W of major surface 18 can be in a range of about 3 to 10 mm, and can be any single width or range of widths between about 3 and 10 mm. In some examples, the depth D of IMD 10 can be in a range of about 2 to 9 mm. In other examples, the depth D of IMD 10 can be in a range of about 2 to 5 mm, and can be any single depth or range of depths between about 2 and 9 mm. In any such examples, IMD 10 is compact enough to be implanted in the subcutaneous space of patient 4 in the pectoral region.

[0040] According to examples of the present disclosure, IMD 10 can have a geometry and size designed for ease of implantation and patient comfort. Examples of IMD 10 described in the present disclosure can have a volume of 3 cubic centimeters (cm 3 ) or smaller, 1.5cm 3 or smaller or any volume therebetween. In addition, Figure 2 In the example shown, the proximal end 22 and the distal end 24 are rounded to reduce discomfort and irritation to surrounding tissue once implanted under the skin of the patient 4 .

[0041] exist Figure 2 In the example shown, when IMD 10 is inserted into patient 4, first major surface 18 of IMD 10 faces outward toward the skin, while second major surface 20 faces inward toward the muscle tissue of patient 4. Thus, first major surface 18 and second major surface 20 can face in a direction along the sagittal axis of patient 4 (see FIG. Figure 1 ) and due to the size of IMD 10, this orientation can be generally maintained when implanted.

[0042] When IMD 10 is subcutaneously implanted in patient 4, proximal electrode 16A and distal electrode 16B may be used to sense cardiac EGM signals (e.g., ECG signals). In some examples, the processing circuitry of IMD 10 may also determine whether patient 4's cardiac ECG signals indicate an arrhythmia or other abnormality, which the processing circuitry of IMD 10 may assess when determining whether patient 4's medical condition (e.g., heart failure, sleep apnea, or COPD) has changed. The cardiac ECG signals may be stored in a memory of IMD 10, and data derived from the cardiac ECG signals may be transmitted to another device, such as external device 12, via integrated antenna 26. In some examples, IMD 10 may also use one or both of electrodes 16A and 16B to sense bioimpedance values ​​during bioimpedance measurements performed by IMD 10. In some examples, such sensed bioimpedance values ​​may be stored in a memory of IMD 10 and may be transmitted to another device, such as external device 12, via integrated antenna 26. In some examples, the sensed bioimpedance values ​​may be transmitted to another device periodically, such as daily. The sensed impedance values ​​detected by IMD 10 may reflect impedance values ​​associated with contact between electrodes 16A, 16B and target tissue of patient 4. Additionally, in some examples, the communication circuitry of IMD 10 may utilize electrodes 16A, 16B for tissue conductance communication (TCC) communication with external device 12 or another device.

[0043] exist Figure 2In the example shown, proximal electrode 16A is in close proximity to proximal end 22, and distal electrode 16B is in close proximity to distal end 24 of IMD 10. In this example, distal electrode 16B is not limited to a flat, outward-facing surface, but rather may extend from first major surface 18 around rounded edge 28 or end surface 30 and in a three-dimensional curved configuration onto second major surface 20. As shown, proximal electrode 16A is located on first major surface 18 and is substantially flat and outward-facing. However, in other examples not shown here, both proximal electrode 16A and distal electrode 16B may be configured similarly to Figure 2 The proximal electrode 16A shown in FIG, or both may be configured similarly to Figure 2 16B is shown in FIG. In some examples, additional electrodes 16C and 16D may be positioned on one or both of first major surface 18 and second major surface 20, such that a total of four electrodes are included on IMD 10. Any of electrodes 16A-16D may be formed from a biocompatible conductive material. For example, any of electrodes 16A-16D may be formed from stainless steel, titanium, platinum, iridium, or alloys thereof. Additionally, the electrodes of IMD 10 may be coated with materials such as titanium nitride or fractal titanium nitride, although other suitable materials and coatings for such electrodes may also be used.

[0044] exist Figure 2 In the example shown, the proximal end 22 of the IMD 10 includes a head assembly 32 having one or more of a proximal electrode 16A, an integrated antenna 26, an anti-migration protrusion 34, and a suture hole 36. The integrated antenna 26 is located on the same major surface (e.g., the first major surface 18) as the proximal electrode 16A and can be an integral part of the head assembly 32. In other examples, the integrated antenna 26 can be formed on a major surface opposite the proximal electrode 16A, or in other examples, the integrated antenna can be incorporated into the housing 15 of the IMD 10. The antenna 26 can be configured to transmit or receive electromagnetic signals for communication. For example, the antenna 26 can be configured to transmit or receive electromagnetic signals for communication via inductive coupling, electromagnetic coupling, tissue conductance, near field communication (NFC), radio frequency identification (RFID), Antenna 26 may be coupled to communication circuitry of IMD 10 that may drive antenna 26 to transmit signals to external device 12, and may transmit signals received from external device 12 to processing circuitry of IMD 10 via the communication circuitry.

[0045] In some examples, IMD 10 may include several features that hold IMD 10 in place once subcutaneously implanted in patient 4, so as to reduce the chance of IMD 10 migrating within the body of patient 4. For example, Figure 2 As shown, housing 15 may include anti-migration protrusions 34 positioned adjacent integrated antenna 26. Anti-migration protrusions 34 may include a plurality of bumps or projections extending away from first major surface 18 and may help prevent longitudinal movement of IMD 10 after implantation in patient 4. In other examples, anti-migration protrusions 34 may be located on a major surface opposite proximal electrode 16A and / or integrated antenna 26. Additionally, Figure 2 In the example shown, head assembly 32 includes suture holes 36 that provide another means of securing IMD 10 to the patient to prevent movement after insertion. In the example shown, suture holes 36 are located near proximal electrode 16A. In some examples, head assembly 32 may include a molded head assembly made of a polymer or plastic material that may be integrated with or separate from the main portion of IMD 10.

[0046] Electrodes 16A and 16B may be used to sense cardiac ECG signals, as described above. In some examples, additional electrodes 16C and 16D may be used in addition to or in place of electrodes 16A and 16B to sense subcutaneous tissue bioimpedance. In some examples, the processing circuitry of IMD 10 may determine a bioimpedance value for patient 4 based on signals received from at least two of electrodes 16A to 16D. For example, the processing circuitry of IMD 10 may generate an excitation signal, such as a current signal or a voltage signal, deliver the signal via two or more selected electrodes from electrodes 16A to 16D, and measure the other of the resulting current or voltage. The processing circuitry of IMD 10 may determine a bioimpedance value based on the delivered excitation signal and the measured voltage or current.

[0047] exist Figure 2 In the example shown in , IMD 10 includes a light emitter 38, a proximal light detector 40A, and a distal light detector 40B located on housing 15 of IMD 10. Light detector 40A can be located at a distance S from light emitter 38, while distal light detector 40B is located at a distance S+N from light emitter 38. In other examples, IMD 10 can include only one of light detectors 40A, 40B, or can include additional light emitters and / or additional light detectors. Although light emitter 38 and light detectors 40A, 40B are described herein as being located on housing 15 of IMD 10, in other examples, one or more of light emitter 38 and light detectors 40A, 40B can be located on the housing of another type of IMD within patient 4, such as a transvenous, subcutaneous, or extravascular pacemaker or ICD, or connected to such a device via leads.

[0048] like Figure 2, light emitter 38 can be positioned on head assembly 32, although in other examples, one or both of light detectors 40A, 40B can additionally or alternatively be positioned on head assembly 32. In some examples, light emitter 38 can be positioned on an intermediate portion of IMD 10, such as part of the path between proximal end 22 and distal end 24. Although light emitter 38 and light detectors 40A, 40B are shown as being located on first major surface 18, light emitter 38 and light detectors 40A, 40B can alternatively be located on second major surface 20. In some examples, the IMD can be implanted such that light emitters 38 and light detectors 40A, 40B face inward, toward the muscles of patient 4, when IMD 10 is implanted, which can help minimize interference from background light outside the body of patient 4. Light detectors 40A, 40B can include glass or sapphire windows, such as those described below with reference to FIG. Figure 4B As described, it may be positioned beneath a portion of housing 15 of IMD 10 that is made of glass or sapphire or other transparent or translucent material.

[0049] In some examples, IMD 10 may include one or more additional sensors, such as one or more accelerometers ( Figure 2 4). Such an accelerometer may be a 3D accelerometer configured to generate a signal indicative of one or more types of movement of the patient, such as whole-body movement of the patient (e.g., exercise), patient posture, movement associated with a heartbeat, or coughing, rales or other breathing abnormalities, or movement of IMD 10 within the body of patient 4. One or more of the parameters monitored by IMD 10 (e.g., bioimpedance, ECG) may fluctuate in response to changes in one or more of these types of movement. For example, a change in a parameter value may sometimes be attributed to increased patient movement (e.g., exercise or other physical movement compared to immobility) or to a change in the patient's posture, and not necessarily to a change in the medical condition. Thus, in some methods of identifying or tracking a medical condition of patient 4, it may be advantageous to consider such fluctuations when determining whether a change in a parameter indicates a change in the medical condition. Additionally, data within an accelerometer signal reversal may indicate that IMD 10 has flipped. Based on determining that IMD 10 has migrated or turned within the body of patient 4, it may be advantageous to determine whether the measured bioimpedance value is within a predetermined portion of the bioimpedance measurement range because the tissue contactable by electrodes 16A-16D may change as IMD 10 migrates or turns.

[0050] Figure 3 is a diagram illustrating one or more techniques described herein. Figure 1 and Figure 2FIG. 1 is a functional block diagram of an exemplary configuration of IMD 10. In the illustrated example, IMD 10 includes electrodes 16, antenna 26, processing circuitry 50, sensing circuitry 52, communication circuitry 54, storage 56, switching circuitry 58, sensors 62 including motion sensor 42 (which may be an accelerometer), and power supply 64. Although FIG. Figure 3 Not shown, but sensor 62 may include Figure 2 The light detector 40 is provided.

[0051] Processing circuitry 50 may include fixed-function circuitry and / or programmable processing circuitry. Processing circuitry 50 may include any one or more of a microprocessor, a controller, a DSP, an ASIC, an FPGA, or equivalent discrete or analog logic circuitry. In some examples, processing circuitry 50 may 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 50 herein may be embodied in software, firmware, hardware, or any combination thereof. In some examples, one or more techniques of the present disclosure may be performed by processing circuitry 50.

[0052] Sensing circuitry 52 and communication circuitry 54 may be selectively coupled to electrodes 16A-16D via switching circuitry 58, as controlled by processing circuitry 50. Sensing circuitry 52 may monitor signals from electrodes 16A-16D to monitor electrical activity of the heart (e.g., to generate an ECG) and / or bioimpedance, which is indicative of at least some aspects of fluid retention and breathing patterns of patient 4. Sensing circuitry 52 may also monitor signals from sensors 62, which may include motion sensor 42 (which may be an accelerometer) and any additional light detectors that may be positioned on IMD 10. In some examples, sensing circuitry 52 may include one or more filters and amplifiers for filtering and amplifying signals received from one or more of electrodes 16A-16D and / or motion sensor 42 (which may be an accelerometer).

[0053] Communication circuitry 54 may include any suitable hardware, firmware, software, or any combination thereof, for communicating with another device, such as external device 12 or another IMD or sensor, such as a pressure sensing device. Under the control of processing circuitry 50, communication circuitry 54 may receive downlink telemetry from external device 12 or another device, and transmit uplink telemetry to the device, via an internal or external antenna, such as antenna 26. Additionally, processing circuitry 50 may communicate with an external device (e.g., external device 12) and a computer network, such as the Medtronic ® ® developed by Medtronic, plc, Dublin, Ireland. The network communicates with networked computing devices.

[0054] A clinician or other user may retrieve data from IMD 10 using external device 12 or by using another local or networked computing device configured to communicate with processing circuitry 50 via communication circuitry 54. A clinician may also program parameters of IMD 10 using external device 12 or another local or networked computing device.

[0055] In some examples, storage device 56 includes computer-readable instructions that, when executed by processing circuitry 50, cause IMD 10 and processing circuitry 50 to perform the various functions attributed herein to IMD 10 and processing circuitry 50. Storage device 56 may comprise any volatile, nonvolatile, magnetic, optical, or electrical media, such as random access memory (RAM), read-only memory (ROM), nonvolatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other digital media.

[0056] Power supply 64 is configured to deliver operating power to the components of IMD 10. Power supply 64 may include a battery and a power generation circuit for generating the operating power. In some examples, the battery is rechargeable to allow for long-term operation. In some examples, recharging is achieved through proximal inductive interaction between an external charger and an inductive charging coil within external device 12. Power supply 64 may include any one or more of a variety of different battery types, such as nickel-cadmium batteries and lithium-ion batteries. Non-rechargeable batteries may be selected to last for several years, while rechargeable batteries may be inductively charged from an external device, for example, on a daily or weekly basis.

[0057] Figure 4A and Figure 4B shows that one or more techniques described herein may be substantially similar to Figures 1 to 3 The IMD 10 but may include one or more additional features of two additional exemplary IMDs. Figure 4A and Figure 4B Components may not necessarily be drawn to scale but may be exaggerated to show details. Figure 4A is a block diagram of a top view of an exemplary configuration of IMD 10A. Figure 4B is a block diagram of a side view of an exemplary IMD 10B, which may include insulating layers as described below.

[0058] Figure 4A It is shown that it can be basically similar to Figure 1 A conceptual diagram of another exemplary IMD 10 is shown in FIG. Figures 1 to 3 In addition to the components shown, Figure 4A The example of the IMD 10 shown may also include a body portion 72 and an attachment plate 74. The attachment plate 74 may be configured to mechanically couple the head assembly 32 to the body portion 72 of the IMD 10A. The body portion 72 of the IMD 10A may be configured to receive Figure 3 One or more of the internal components of IMD 10 are shown, such as one or more of processing circuitry 50, sensing circuitry 52, communication circuitry 54, memory device 56, switching circuitry 58, internal components of sensor 62, and power supply 64. In some examples, body portion 72 may be formed from one or more of titanium, ceramic, or any other suitable biocompatible material.

[0059] Figure 4B is shown to include substantially similar Figure 1 A conceptual diagram of an exemplary IMD 10B is shown with reference to components of the IMD 10. Figure 1-3 In addition to the components shown in Figure 4B The example IMD 10B shown in FIGURE 1 may also include a wafer-level insulating cover 76 that can help insulate electrical signals transmitted between electrodes 16A-16D and / or photodetectors 40A, 40B on housing 15B and processing circuitry 50. In some examples, insulating cover 76 can be positioned over open housing 15 to form a housing for the components of IMD 10B. One or more components of IMD 10B (e.g., antenna 26, light emitter 38, photodetectors 40A, 40B, processing circuitry 50, sensing circuitry 52, communication circuitry 54, switching circuitry 58, and / or power supply 64) can be formed on the bottom side of insulating cover 76, for example, using flip-chip technology. Insulating cover 76 can be flipped over onto housing 15B. When flipped over and placed onto housing 15B, the components of IMD 10B formed on the bottom side of insulating cover 76 can be positioned within gap 78 defined by housing 15B.

[0060] Insulating cover 76 can be configured so as not to interfere with the operation of IMD 10B. For example, one or more of electrodes 16A-16D can be formed or placed above or on top of insulating cover 76 and electrically connected to switching circuitry 58 via one or more through-holes (not shown) formed through insulating cover 76. Insulating cover 76 can be formed from sapphire (i.e., corundum), glass, parylene, and / or any other suitable insulating material. Sapphire can have a transmittance greater than 80% for wavelengths in the range of approximately 300 nm to approximately 4000 nm and can have a relatively flat profile. In varying conditions, varying transmittance at different wavelengths can be compensated for, for example, by using ratiometric methods. In some examples, insulating cover 76 can have a thickness of approximately 300 microns to approximately 600 microns. Housing 15B can be formed from titanium or any other suitable material (e.g., a biocompatible material) and can have a thickness of approximately 200 microns to approximately 500 microns. These materials and dimensions are examples only, and other materials and thicknesses are possible with the devices of the present disclosure.

[0061] Figure 5 is a block diagram illustrating an exemplary configuration of components of the external device 12 according to one or more techniques of this disclosure. Figure 5 In the example shown, external device 12 includes processing circuitry 80 , communication circuitry 82 , storage 84 , user interface 86 , and power supply 88 .

[0062] In one example, processing circuitry 80 may include one or more processors configured to implement functional and / or process instructions for execution within external device 12. For example, processing circuitry 80 may be capable of processing instructions stored in storage device 84. Processing circuitry 80 may include, for example, a microprocessor, a DSP, an ASIC, an FPGA, or equivalent discrete or integrated logic circuitry, or a combination of any of the foregoing devices or circuitry. Thus, processing circuitry 80 may include any suitable structure, whether hardware, software, firmware, or any combination thereof, to perform the functions of processing circuitry 80 described herein. In some examples, processing circuitry 80 may perform one or more of the techniques of the present disclosure.

[0063] Communications circuitry 82 may include any suitable hardware, firmware, software, or any combination thereof, for communicating with another device, such as IMD 10. Under the control of processing circuitry 80, communications circuitry 82 may receive downlink telemetry from, and send uplink telemetry to, IMD 10 or another device.

[0064] Storage device 84 may be configured to store information on external device 12 during operation. Storage device 84 may include a computer-readable storage medium or a computer-readable storage device. In some examples, storage device 84 includes one or more of short-term memory or long-term memory. Storage device 84 may include, for example, RAM, dynamic random access memory (DRAM), static random access memory (SRAM), a magnetic disk, an optical disk, flash memory, or various forms of electrically programmable memory (EPROM) or EEPROM. In some examples, storage device 84 is used to store data indicating instructions executed by processing circuit system 80. Storage device 84 may be used by software or applications running on external device 12 to temporarily store information during program execution.

[0065] The data exchanged between external device 12 and IMD 10 may include operating parameters. External device 12 may transmit data including computer-readable instructions that, when implemented by IMD 10, may control IMD 10 to change one or more operating parameters and / or export collected data. For example, processing circuitry 80 may transmit instructions to IMD 10 requesting IMD 10 to export collected data (e.g., data corresponding to one or more of an ECG signal, a bioimpedance value, or an accelerometer signal) to external device 12. External device 12 may, in turn, receive the collected data from IMD 10 and store the collected data in storage device 84. Additionally or alternatively, processing circuitry 80 may export instructions to IMD 10 requesting IMD 10 to update one or more operating parameters of IMD 10.

[0066] A user, such as a clinician or patient 4, can interact with external device 12 via user interface 86. User interface 86 includes a display (not shown), such as an LCD or LED display or other type of screen, which processing circuitry 80 can utilize to present information related to IMD 10 (e.g., EGM signals obtained from at least one electrode or at least one electrode combination or bioimpedance values). In addition, user interface 86 may include an input mechanism for receiving input from the user. The input mechanism may include, for example, any one or more of a button, a keypad (e.g., an alphanumeric keypad), a peripheral pointing device, a touch screen, or another input mechanism that allows a user to navigate through a user interface presented by processing circuitry 80 of external device 12 and provide input. In other examples, user interface 86 also includes an audio circuitry for providing auditory notifications, instructions, or other sounds to patient 4, receiving voice commands from patient 4, or both. Storage device 84 may include instructions for operating user interface 86 and for managing power supply 88.

[0067] The power supply 88 is configured to deliver operating power to the components of the external device 12. The power supply 88 may include a battery and a power generation circuit system for generating the operating power. In some examples, the battery is rechargeable to allow for long-term operation. Recharging can be achieved by electrically coupling the power supply 88 to a bracket or plug connected to an alternating current (AC) outlet. In addition, recharging can be achieved through proximal inductive interaction between an external charger and an inductive charging coil within the external device 12. In other examples, conventional batteries (e.g., nickel-cadmium or lithium-ion batteries) can be used. In addition, the external device 12 can be directly coupled to an AC power outlet for operation.

[0068] Figure 6 is a block diagram illustrating an example system including access point 90, network 92, an external computing device such as server 94, and one or more other computing devices 100A through 100N that may be coupled to IMD 10, external device 12, and processing circuitry 14 via network 92, in accordance with one or more techniques described herein. In this example, IMD 10 may communicate with external device 12 via a first wireless connection and with access point 90 via a second wireless connection using communication circuitry 54. Figure 6 In the example of , access point 90 , external device 12 , server 94 , and computing devices 100A to 100N are interconnected and can communicate with each other via network 92 .

[0069] Access point 90 may include a device that is connected to network 92 via any of a variety of connections, such as a telephone dial-up, a digital subscriber line (DSL), or a cable modem connection. In other examples, access point 90 may be coupled to network 92 via different forms of connection, including a wired connection or a wireless connection. In some examples, access point 90 may be a user device that can be co-located with the patient, such as a tablet computer or a smartphone. As described above, IMD 10 may be configured to transmit data, such as any one or a combination of EGM signals, bioimpedance values, or accelerometer signals, to external device 12. In addition, access point 90 may interrogate IMD 10, for example periodically or in response to a command from the patient or network 92, to retrieve parameter values ​​determined by processing circuitry 50 of IMD 10 or other operational or patient data from IMD 10. Access point 90 may then transmit the retrieved data to server 94 via network 92.

[0070] In some cases, server 94 may be configured to provide a secure storage site for data (such as bioimpedance values ​​or heart failure scores) that has been collected from IMD 10 and / or external device 12. In some cases, server 94 may compile the data in a web page or other document for viewing by trained professionals (such as clinicians) via computing devices 100A-100N. Figure 6 One or more aspects of the illustrated system may be similar to the Medtronic system developed by Medtronic plc, Dublin, Ireland. It is implemented using the general network technologies and functions provided by the network.

[0071] Server 94 may include a processing circuit system 96. Processing circuit system 96 may include fixed-function circuit systems and / or programmable processing circuit systems. Processing circuit system 96 may include any one or more of a microprocessor, a controller, a DSP, an ASIC, an FPGA, or an equivalent discrete or analog logic circuit system. In some examples, processing circuit system 96 may 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 circuit systems. The functions attributed to processing circuit system 96 herein may be embodied as software, firmware, hardware, or any combination thereof. In some examples, processing circuit system 96 may perform one or more techniques described herein. In some examples, processing circuit system 96 may determine a heart failure score based on the bioimpedance value sensed by IMD 10.

[0072] Server 94 may include memory 98. Memory 98 includes computer-readable instructions that, when executed by processing circuitry 96, cause IMD 10 and processing circuitry 96 to perform the various functions attributed herein to IMD 10 and processing circuitry 96. Memory 98 may include any volatile, nonvolatile, magnetic, optical, or electronic medium, such as RAM, ROM, NVRAM, EEPROM, flash memory, or any other digital medium.

[0073] In some examples, one or more of computing devices 100A-100N (e.g., device 100A) can be a tablet or other smart device located at a clinician's location, through which the clinician can program IMD 10, receive alerts from the IMD, and / or query the IMD. For example, the clinician can access data corresponding to, for example, bioimpedance values, EGM signals, and / or accelerometer signals collected by IMD 10 via device 100A while patient 4 is between clinician visits to check the status of a medical condition, such as heart failure. In some examples, the clinician can enter instructions for a medical intervention for patient 4 into an app in device 100A, such as based on the status of the patient's condition determined by IMD 10, external device 12, processing circuitry 14, or any combination thereof, or based on other patient data known to the clinician. Device 100A can then transmit the instructions for the medical intervention to another computing device (e.g., device 100B) located at patient 4 or a caregiver of patient 4 among computing devices 100A-100N. For example, such instructions for medical intervention may include instructions to change medication dosage, timing, or selection, instructions to schedule a clinician visit, or instructions to seek medical attention. In another example, device 100B may generate an alert to patient 4 based on the status of patient 4's medical condition determined by IMD 10, which may enable patient 4 to proactively seek medical attention before receiving instructions for medical intervention. In this way, patient 4 may be empowered to take action as needed to address his or her medical condition, which may help improve clinical outcomes for patient 4.

[0074] Figure 7 is a flow chart illustrating an example of dynamically adjusting an impedance measurement range according to one or more techniques of this disclosure. Figure 7 The examples focus on processing circuitry 50 of IMD 10 performing one or more of the techniques of this disclosure. However, processing circuitry 14, processing circuitry 50, processing circuitry 80, processing circuitry 96, or any combination thereof may perform one or more of the techniques of this disclosure.

[0075] The processing circuit system 50 may apply an excitation signal (110) to the sensing circuit system 52. For example, the processing circuit system 50 may apply an excitation current or an excitation voltage to the sensing circuit system 52. The excitation signal may be associated with a bioimpedance measurement range within which the bioimpedance value of the patient 4 may be sensed or measured. For example, the bioimpedance measurement range may be from 1000 ohms to 3000 ohms. The processing circuit system 50 may determine a sensed bioimpedance value (112). For example, the sensing circuit system 52 may deliver an excitation signal (e.g., a current or a voltage) via one or more of the electrodes 16A to 16D, and the processing circuit system 50 may measure the other of the resulting current or voltage. The processing circuit system 50 may determine whether the sensed bioimpedance value is within a predetermined portion of the bioimpedance measurement range for a predetermined period of time (114). For example, the processing circuit system 50 may determine whether the sensed bioimpedance value is at the top or bottom of the bioimpedance measurement range for a number of days, such as two or three days. In some examples, the predetermined portion of the bioimpedance measurement range can be a percentage of the range, such as the top 10% to 25% of the bioimpedance measurement range or the bottom 10% to 25% of the bioimpedance measurement range. In some examples, the predetermined portion of the bioimpedance measurement range can be a number of ohms, such as within 200 ohms of the upper limit of the bioimpedance measurement range or within 200 ohms of the lower limit of the bioimpedance measurement range. In some examples, the processing circuit system 50 can periodically (such as daily) determine whether the sensed bioimpedance value is within the predetermined portion of the bioimpedance measurement range for a predetermined period of time. In some examples, the processing circuit system 50 is configured to automatically (e.g., without intervention by a clinician or patient) determine whether the sensed bioimpedance value is within the predetermined portion of the bioimpedance measurement range for a predetermined period of time.

[0076] If the sensed bioimpedance value is within a predetermined portion of the bioimpedance measurement range for a predetermined period of time ( Figure 7 If the excitation current is increased (the "yes" path in the example), processing circuit system 50 may adjust the excitation signal (116). For example, by increasing the excitation current, the bioimpedance measurement range may become smaller by reducing the upper limit of the bioimpedance measurement range. By decreasing the excitation current, the bioimpedance measurement range may become larger by increasing the upper limit of the bioimpedance measurement range. Processing circuit system 50 may apply the adjusted excitation signal to sensing circuit system 52 (110).

[0077] For example, the processing circuit system 50 can change the current or voltage to adjust the bioimpedance measurement range. In some examples, the processing circuit system 50 can determine the adjusted excitation signal based on the sensed bioimpedance value. For example, the excitation signal value required to place the sensed bioimpedance value at the center of the adjusted bioimpedance measurement range for a given bioimpedance value can be determined in a laboratory environment. A lookup table can be stored in the storage device 56, and the lookup table can include multiple excitation signal values ​​that are to be applied to different sensed bioimpedance values ​​to change the adjusted bioimpedance measurement range so that the sensed bioimpedance value can be located at or toward the center of the adjusted bioimpedance measurement range. Alternatively, the processing circuit system 50 can use a formula to determine the adjusted excitation signal based on the sensed bioimpedance value.

[0078] In some examples, processing circuitry 50 may adjust the bioimpedance measurement range so that the measured bioimpedance value is closer to the center of the adjusted bioimpedance measurement range than it was in the bioimpedance measurement range before the adjustment. In some examples, the measured bioimpedance value may not be within a predetermined portion of the adjusted bioimpedance measurement range that corresponds to a predetermined portion of the bioimpedance measurement range before the adjustment. For example, the measured bioimpedance value may not be within the top x% or bottom y% or the top x ohms or bottom y ohms of the adjusted bioimpedance measurement range.

[0079] If the sensed bioimpedance value is not within a predetermined portion of the bioimpedance measurement range for a predetermined period of time ( Figure 7 If the “no” path is not reached, processing circuitry 50 may not adjust the excitation signal and may apply the same excitation signal to sensing circuitry 52 the next time processing circuitry 50 attempts to determine a sensed bioimpedance value (110).

[0080] Figure 8 is a flow chart illustrating another example of dynamically adjusting an impedance measurement range according to one or more techniques of this disclosure. Figure 8 The example technique can be used with Figure 7 The techniques of the examples may be used together or individually. Figure 8 The examples focus on processing circuitry 50 of IMD 10 performing one or more of the techniques of this disclosure. However, processing circuitry 14, processing circuitry 50, processing circuitry 80, processing circuitry 96, or any combination thereof may perform one or more of the techniques of this disclosure.

[0081] Processing circuitry 50 may apply an excitation signal (120) to sensing circuitry 52. ​​For example, processing circuitry 50 may apply an excitation current or an excitation voltage to sensing circuitry 52. ​​The excitation signal may be associated with a bioimpedance measurement range within which bioimpedance values ​​of patient 4 may be measured. Processing circuitry 50 may determine a sensed bioimpedance value (122). For example, sensing circuitry 52 may deliver an excitation signal (e.g., a current or a voltage) via one or more of electrodes 16A to 16D, and processing circuitry 50 may measure the other of the resulting current or voltage.

[0082] Processing circuitry 50 may determine whether IMD 10 has flipped (124). For example, processing circuitry 50 may continuously or periodically monitor the signal from the accelerometer to determine whether IMD 10 has flipped. A reversal of the data in the accelerometer signal may indicate that IMD 10 has flipped. In this case, electrodes 16A-16D may contact different tissue than before IMD 10 flipped, which may cause the sensed bioimpedance value to change. If IMD 10 has not flipped ("No" path from block 124), processing circuitry 50 may not adjust the excitation signal and may apply the same excitation signal to sensing circuitry 52 the next time processing circuitry 50 attempts to determine the sensed bioimpedance value (110).

[0083] If IMD 10 has flipped ("yes" path from block 124), processing circuitry 50 may determine whether the sensed bioimpedance value is within a predetermined portion of the bioimpedance measurement range based on determining that IMD 10 has flipped (126). For example, processing circuitry 50 may determine whether the sensed bioimpedance value is at the top or bottom of the bioimpedance measurement range. In some examples, the predetermined portion of the bioimpedance measurement range may be a percentage of the range or a number of ohms, such as top x% or bottom y% or top x ohms or bottom y ohms. In some examples, x may be equal to y. In other examples, x may not be equal to y.

[0084] If the sensed bioimpedance value is within the predetermined portion of the bioimpedance measurement range ("Yes" path from block 126), processing circuitry 50 may adjust the excitation signal (128). For example, by increasing the excitation current, the bioimpedance measurement range may become smaller and the top of the bioimpedance measurement range may drop. By decreasing the excitation current, the bioimpedance measurement range may become larger and the top of the bioimpedance measurement range may rise. Processing circuitry 50 may apply the adjusted excitation signal to sensing circuitry 52 (120).

[0085] For example, the processing circuit system 50 can change the current or voltage to adjust the bioimpedance measurement range. In some examples, the processing circuit system 50 can determine the adjusted excitation signal based on the sensed bioimpedance value, as described above with respect to Figure 7 discussed.

[0086] In some examples, processing circuitry 50 may adjust the bioimpedance measurement range so that the measured bioimpedance value is closer to the center of the adjusted bioimpedance measurement range than it was in the bioimpedance measurement range before the adjustment. In some examples, the measured bioimpedance value may not be in a predetermined portion of the adjusted bioimpedance measurement range that corresponds to a predetermined portion of the bioimpedance measurement range before the adjustment, as described above with respect to Figure 7 If the sensed bioimpedance value is not within the predetermined portion of the bioimpedance measurement range (“NO” path from block 126 ), processing circuitry 50 may not adjust the excitation signal and may apply the same excitation signal to sensing circuitry 52 the next time processing circuitry 50 attempts to determine a sensed bioimpedance value ( 110 ).

[0087] This disclosure includes the following non-limiting examples.

[0088] Example 1. A device comprising: a plurality of electrodes; a sensing circuit system configured to sense bioimpedance; and a processing circuit system configured to: apply an excitation signal to the plurality of electrodes via the sensing circuit system; determine a sensed bioimpedance value within a bioimpedance measurement range based on the application of the excitation signal; determine whether the sensed bioimpedance value remains within a predetermined portion of the bioimpedance measurement range for a predetermined time period; and adjust the excitation signal based on whether the sensed bioimpedance value remains within the predetermined portion of the bioimpedance measurement range for a predetermined time period, wherein adjusting the excitation signal adjusts the bioimpedance measurement range.

[0089] Embodiment 2. The device of embodiment 1, wherein the predetermined portion of the bioimpedance measurement range is at least one of an upper boundary limit of the bioimpedance measurement range or a lower boundary limit of the bioimpedance measurement range.

[0090] Example 3. An apparatus according to Example 1 or Example 2, wherein the sensed bioimpedance value is within the adjusted bioimpedance measurement range and is not within a predetermined portion of the adjusted bioimpedance measurement range, and wherein the predetermined portion of the adjusted bioimpedance measurement range is at least one of the top of the adjusted bioimpedance measurement range or the bottom of the adjusted bioimpedance measurement range.

[0091] Embodiment 4. The apparatus of any combination of embodiments 1 to 3, wherein the sensed bioimpedance value is closer to the center of the adjusted bioimpedance measurement range than the sensed bioimpedance value is to the center of the bioimpedance measurement range.

[0092] Embodiment 5. The apparatus of any combination of Embodiments 1 to 4, wherein the processing circuitry is configured to adjust the excitation signal by determining an adjusted excitation signal based on the sensed bioimpedance value.

[0093] Example 6. The device according to any combination of Examples 1 to 5, further comprising an accelerometer, wherein the processing circuit system is further configured to: determine whether the device has been flipped over based on a signal from the accelerometer; and based on determining that the device has been flipped over, determine whether the sensed bioimpedance value is within the predetermined portion of the bioimpedance measurement range.

[0094] Embodiment 7 The device of any combination of Embodiments 1 to 6, further comprising a communication circuit system configured to transmit the sensed bioimpedance value to an external device.

[0095] Embodiment 8. The apparatus of any combination of Embodiments 1 to 7, wherein the processing circuitry is configured to periodically determine whether the sensed bioimpedance value is within the predetermined portion of the bioimpedance measurement range.

[0096] Embodiment 9. The device of embodiment 8, wherein the periodicity is daily.

[0097] Embodiment 10. The apparatus of any combination of Embodiments 1 to 9, wherein the processing circuitry is configured to automatically determine whether the sensed bioimpedance value is within the predetermined portion of the bioimpedance measurement range.

[0098] Embodiment 11. A method comprising: applying, by processing circuitry, an excitation signal to a plurality of electrodes via sensing circuitry; determining, by the processing circuitry and based on the applying of the excitation signal, a sensed bioimpedance value within a bioimpedance measurement range; determining, by the processing circuitry, whether the sensed bioimpedance value remains within a predetermined portion of the bioimpedance measurement range for a predetermined period of time; and adjusting the excitation signal based on the sensed bioimpedance value remaining within the predetermined portion of the bioimpedance measurement range for the predetermined period of time.

[0099] The excitation signal is adjusted to adjust the bioimpedance measurement range.

[0100] Embodiment 12. The method of embodiment 11, wherein the predetermined portion of the bioimpedance measurement range is at least one of an upper boundary limit of the bioimpedance measurement range or a lower boundary limit of the bioimpedance measurement range.

[0101] Example 13. A method according to Example 11 or Example 12, wherein the sensed bioimpedance value is within the adjusted bioimpedance measurement range and is not within a predetermined portion of the adjusted bioimpedance measurement range, and wherein the predetermined portion of the adjusted bioimpedance measurement range is at least one of the top of the adjusted bioimpedance measurement range or the bottom of the adjusted bioimpedance measurement range.

[0102] Embodiment 14. The method of any combination of Embodiments 11 to 13, wherein the sensed bioimpedance value is closer to the center of the adjusted bioimpedance measurement range than the sensed bioimpedance value is to the center of the bioimpedance measurement range.

[0103] Embodiment 15. The method of any combination of Embodiments 11 to 14, wherein adjusting the excitation signal comprises determining an adjusted excitation signal based on the sensed bioimpedance value.

[0104] Example 16. The method according to any combination of Examples 11 to 15 further includes: determining by the processing circuit system whether the device has been flipped over based on a signal from the accelerometer; and based on determining that the device has been flipped over, determining by the processing circuit system whether the sensed bioimpedance value is within the predetermined portion of the bioimpedance measurement range.

[0105] Embodiment 17 The method according to any combination of Embodiments 11 to 16, further comprising transmitting the sensed bioimpedance value to an external device.

[0106] Embodiment 18 The method of any combination of Embodiments 11 to 17, wherein the determining whether the sensed bioimpedance value is within the predetermined portion of the bioimpedance measurement range is performed periodically.

[0107] Embodiment 19. The method of any combination of Embodiments 11 to 18, wherein the determining whether the sensed bioimpedance value is within the predetermined portion of the bioimpedance measurement range is automatic.

[0108] Embodiment 20. A non-transitory computer-readable medium comprising instructions for causing one or more processors to: apply an excitation signal to a plurality of electrodes via a sensing circuit system; determine a sensed bioimpedance value within a bioimpedance measurement range based on the application of the excitation signal; determine whether the sensed bioimpedance value remains within a predetermined portion of the bioimpedance measurement range for a predetermined period of time; and adjust the excitation signal based on whether the sensed bioimpedance value remains within the predetermined portion of the bioimpedance measurement range for a predetermined period of time, wherein adjusting the excitation signal adjusts the bioimpedance measurement range.

[0109] The techniques described in this disclosure may be implemented, at least in part, in the form of hardware, software, firmware, or any combination thereof. For example, various aspects of these techniques may be implemented in one or more processors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic QRS circuit systems, as well as any combination of such components, which are embodied in external devices (such as clinician or patient programmers, simulators, or other devices). The terms "processor" and "processing circuit system" may generally refer to any of the aforementioned logic circuit systems, alone or in combination with other logic circuit systems, or any other equivalent circuit system, alone or in combination with other digital or analog circuit systems.

[0110] For various aspects implemented in software, at least some of the functionality attributed to the systems and devices described in this disclosure may be embodied as instructions on a computer-readable storage medium, such as RAM, DRAM, SRAM, magnetic disk, optical disk, flash memory, or various forms of EPROM or EEPROM. The instructions may be executed to support one or more aspects of the functionality described in this disclosure.

[0111] In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules. Describing different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be implemented by separate hardware or software components. Instead, the functionality associated with one or more modules or units may be performed by separate hardware or software components, or integrated within common or separate hardware or software components. In addition, the technology may be fully implemented in one or more circuits or logic elements. The technology disclosed herein may be implemented in various devices or apparatuses, including an IMD, an external programmer, a combination of an IMD and an external programmer, an integrated circuit (IC) or a set of ICs and / or discrete circuitry resident in the IMD and / or external programmer.

[0112] Various examples have been described. These and other embodiments are within the scope of the following claims.

Claims

1. A medical device comprising: Multiple electrodes; sensing circuitry configured to sense bioimpedance; as well as processing circuitry configured to: applying an excitation signal to the plurality of electrodes via the sensing circuit system; determining a sensed bioimpedance value within a bioimpedance measurement range based on said applying of said excitation signal; determining whether the sensed bioimpedance value is within a predetermined portion of the bioimpedance measurement range for a predetermined period of time; as well as adjusting the excitation signal based on the sensed bioimpedance value being within the predetermined portion of the bioimpedance measurement range for the predetermined period of time, The excitation signal is adjusted to adjust the bioimpedance measurement range. 2 . The apparatus according to claim 1 , wherein the predetermined portion of the bioimpedance measurement range is at least one of an upper boundary limit of the bioimpedance measurement range or a lower boundary limit of the bioimpedance measurement range.

3. The apparatus of claim 1 , wherein the sensed bioimpedance value is within the adjusted bioimpedance measurement range and is not within a predetermined portion of the adjusted bioimpedance measurement range, and wherein the predetermined portion of the adjusted bioimpedance measurement range is at least one of a top portion of the adjusted bioimpedance measurement range or a bottom portion of the adjusted bioimpedance measurement range. 4 . The apparatus of claim 1 , wherein the sensed bioimpedance value is closer to a center of the adjusted bioimpedance measurement range than the sensed bioimpedance value is to a center of the bioimpedance measurement range. 5 . The apparatus of claim 1 , wherein the processing circuitry is configured to adjust the excitation signal by determining an adjusted excitation signal based on the sensed bioimpedance value.

6. The apparatus of claim 1 , further comprising an accelerometer, wherein the processing circuitry is further configured to: determining whether the device has been flipped over based on a signal from the accelerometer; and Based on determining that the device has been flipped over, a determination is made as to whether the sensed bioimpedance value is within the predetermined portion of the bioimpedance measurement range. 7 . The device of claim 1 , further comprising communication circuitry configured to transmit the sensed bioimpedance value to an external device.

8. The apparatus of claim 1, wherein the processing circuitry is configured to periodically determine whether the sensed bioimpedance value is within the predetermined portion of the bioimpedance measurement range.

9. The apparatus of claim 8, wherein the periodicity is daily.

10. The apparatus of claim 1, wherein the processing circuitry is configured to automatically determine whether the sensed bioimpedance value is within the predetermined portion of the bioimpedance measurement range.

11. A method for adjusting a bioimpedance measurement range, the method comprising: applying, by the processing circuitry, an excitation signal to the plurality of electrodes via the sensing circuitry; determining, by the processing circuitry and based on the applying of the excitation signal, a sensed bioimpedance value within the bioimpedance measurement range; determining, by the processing circuitry, whether the sensed bioimpedance value is within a predetermined portion of the bioimpedance measurement range for a predetermined period of time; as well as The excitation signal is adjusted based on the sensed bioimpedance value being within the predetermined portion of the bioimpedance measurement range for the predetermined period of time, wherein adjusting the excitation signal adjusts the bioimpedance measurement range.

12. A non-transitory computer-readable medium comprising instructions for causing one or more processors to: applying an excitation signal to the plurality of electrodes via the sensing circuit system; determining a sensed bioimpedance value within a bioimpedance measurement range based on said applying of said excitation signal; determining whether the sensed bioimpedance value is within a predetermined portion of the bioimpedance measurement range for a predetermined period of time; as well as The excitation signal is adjusted based on the sensed bioimpedance value being within the predetermined portion of the bioimpedance measurement range for the predetermined period of time, wherein adjusting the excitation signal adjusts the bioimpedance measurement range.

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