Implantable medical device and method of operating an implantable medical device

Abstract

The invention relates to an implantable medical device (1), comprising means (10) for capturing respiratory activity data (D) of a patient and / or calculating the respiratory activity data (D) of the patient based on at least one medical parameter (12) captured by the implantable medical device (1), and means (14) for triggering a storage of the captured and / or calculated respiratory activity data (D) of the patient in response to fulfillment of a predetermined triggering event (E), wherein the respiratory activity data (D) comprises a time series of the respiratory activity of the patient. The invention further relates to a computer-implemented method for operating an implantable medical device (1).

Description

[0001] Implantable medical device and method of operating an implantable medical device

[0002] The invention relates to an implantable medical device and to a computer-implemented method for operating an implantable medical device.

[0003] Implantable cardiac monitors have traditionally been utilized for syncope, detection of atrial fibrillation, and for diagnosis of palpitations. The future of ICMs includes the assessment, monitoring, and management of heart failure, and other chronic conditions that benefit from long-term monitoring. To support the management of HF, respiration is a key vital parameter, as lung function can be impacted by a failing heart and poor pulmonary function can also cause the failure of the heart, impact autonomic function or exacerbate existing HF.

[0004] Respiration rate throughout the day is also recognized as a predictive variable for HF and is utilized in worsening HF prediction algorithms in ICDs. Such a device uses daily trends in respiration rate as one variable to define an HF index value. When the HF index exceeds a programmed threshold, the likelihood of an HF decompensation event is declared.

[0005] ICMs can in principle measure respiration in multiple ways, and the method for measuring respiration is secondary to this concept. Methods include ECG amplitude modulation, heart rate modulation, impedance modulation, chest wall motion, and others.

[0006] Currently, no ICM measures respiration rate as this is an emerging field and a future indication for ICM implantation. While respiration rate is recognized as valuable, interpretation of the parameter is complicated by the measurement conditions and the unpredictable nature of respiration. Respiration behavior is impacted by exercise, talking, concentration, posture, and other factors, making the determination of a single respiration rate difficult or of limited clinical value. It is therefore an object of the present invention to provide an improved implantable medical device capable of effectively monitoring a respiration activity of a patient.

[0007] The object is solved by an implantable medical device having the features of claim 1.

[0008] Furthermore, the object is solved by a computer-implemented method for operating an implantable medical device having the features of claim 12.

[0009] Moreover, the object is solved by a computer program having the features of claim 13 and by a computer-readable data carrier having the features of claim 14 and a method for treating a patient with the implantable medical device having the features of claim 15.

[0010] Further developments and advantageous embodiments are defined in the dependent claims.

[0011] The present invention provides an implantable medical device, in particular a cardiac monitor and / or a neurostimulation device (e.g. a spinal cord stimulation device), comprising means for capturing respiratory activity data of a patient and / or calculating the respiratory activity data of the patient based on at least one medical parameter captured by the implantable medical device.

[0012] Moreover, the implantable medical device comprises means for triggering a storage of the captured and / or calculated respiratory activity data of the patient in response to fulfillment of a predetermined triggering event, wherein the respiratory activity data comprises a time series of the respiratory activity of the patient.

[0013] The present invention further provides a computer-implemented method for operating an implantable medical device, comprising capturing respiratory activity data of a patient and / or calculating the respiratory activity data of the patient based on at least one medical parameter captured by the implantable medical device. The method furthermore comprises triggering a storage of the captured and / or calculated respiratory activity data of the patient in response to fulfillment of a predetermined triggering event, wherein the respiratory activity data comprises a time series of the respiratory activity of the patient.

[0014] In addition, the present invention provides a computer program with program code to perform the method according to the present invention when the computer program is executed on a computer. Moreover, the present invention provides data carrier containing program code of a computer program for performing the method according to the present invention when the computer program is executed on a computer. Furthermore, the present invention provides a method for treating a patient with the implantable medical device of the present invention, wherein the implantable medical device is operated by the computer- implemented method of the present invention.

[0015] An idea of the present invention is to provide an implantable medical device capable of taking a snapshot of a respiratory activity of the patient. Having a time series or snapshot of the respiration activity enables a deeper assessment of the respiratory activity and also allows validation of the respiration activity via confirmation of the waveform, as well as allows offline analysis outside of the implant by a clinician, a more complicated processor / computer, or an Al system that can analyze the data for more meaningful physiologic parameters and indicators.

[0016] The advantages of the respiration snapshot are that significant diagnostic information is conveyed in the time series data of respiration or a surrogate respiration measure. Simple statistics such as mean minimum and maximum are not sufficient to convey the complexity of respiration.

[0017] Another advantage is that the time series data can be used for post-processing within the implant to determine critical features of the patient's health or current respiratory state in a manner that is compatible with a low power implant. The time series data may also be transmitted to a server or a cloud-based application for detailed analysis and extraction of features, classification of respiratory waveform, determination of respiratory disorder, or diagnosis of health condition in an offline server, connected peripheral, or cloud computer.

[0018] Performing this time series data collection in an implant with a means to communicate the data to the outside further confers the advantage of minimal required patient compliance while achieving continuous monitoring of respiration. Currently, there is no viable alternative to achieve continuous monitoring of respiration with this fidelity in an implantable device with no user interaction.

[0019] According to an aspect of the invention, the time series of the respiratory activity of the patient comprises a continuous waveform of a predetermined duration, and wherein the respiratory activity data is stored in the implantable medical device to be later transmitted for analysis offline or analyzed in real-time and stored on the implantable medical device.

[0020] By capturing a continuous waveform of a predetermined duration of a respiratory signal, more information can be extracted. In order to distinguish a false peak from an actual peak of a breathing cycle the snapshot of the breathing morphology is required.

[0021] According to a further aspect of the invention, the at least one medical parameter captured by the implantable medical device used for calculating the respiratory activity data of the patient comprises a thoracic impedance, an amplitude variation of an ECG and / or timevarying properties of the ECG. Thus, even implantable medical devices not fitted with an accelerometer are configured to produce respiratory activity data of the patient.

[0022] According to a further aspect of the invention, the means for capturing the respiratory activity data of the patient is an accelerometer or means for communicating with an accelerometer, wherein the captured respiratory activity data, in particular for an implantable cardiac monitor, is a chest wall motion. The chest wall motion data advantageously provides accurate respiration data of the patient, which then may be subject to further analysis. According to a further aspect of the invention, the means for capturing the respiratory activity data of the patient is configured to capture an impedance (e.g. of a chest cavity) measured between two electrodes of the implantable medical device or two electrodes on the surface of the patient body. This alternative measuring method also provides accurate respiration data of the patient that can then be used in downstream evaluation.

[0023] According to a further aspect of the invention, the means for capturing the respiratory activity data of the patient is configured to measure the time series of the respiratory activity of the patient with a sample rate between 0.5 Hz and 1 kHz, in particular with a sample rate between 1 Hz and 32 Hz. Said sample rate yields sufficient data points to identify relevant events in the respiratory signal of the patient. The sample rate may further be chosen to adequately sample the data with respect to the slew rate of the signal. Further, the sample rate be oversampled initially as the device provides data to more than one feature, and subsequently resampled to the chosen respiration sample rate.

[0024] According to a further aspect of the invention, the means for capturing the respiratory activity data of the patient is configured to record the time series of the respiratory activity of the patient on a periodic basis based on an amount of time elapsed, a time of day or due to a predefined triggering event. The periodic measurement thus provides typical patient medical data in which normal and / or abnormal respiration patterns may be observed.

[0025] According to a further aspect of the invention, the predefined triggering event is a change in body position or posture and / or establishing a resting posture such as no significant body motion or physical activity for at least a predetermined time period. This indicates the patient is at rest and in a steady state.

[0026] According to a further aspect of the invention, the predefined triggering event comprises motion sensor inputs, ECG inputs, impedance inputs, sleep status indicators, or triggers from peripheral or external devices, in particular a wearable sensor and / or an outside server or cloud-based system, wherein the ECG inputs comprise ECG amplitude modulation, ECG frequency modulation and / or autonomic nervous system indicators. The event can thus be triggered by a wide range of sensors thus providing flexibility in data sources for event triggering.

[0027] According to a further aspect of the invention, the predefined triggering event occurs based on a geolocation of the patient, an incline angle of the patient, a status of the patient as determined by additional user data based on the patient's lifestyle and habits, or risk factors.

[0028] An example would be triggering a respiration measurement when a patient is in a region with low air quality index or a location where cigarette smoking or environmental smoke is common, conditions which might trigger asthma or exacerbation of COPD. Another example would be triggering a respiration measurement on patients taking CNS depressants / opioids for chronic pain management, because such medications can dampen human respiratory function, they cause significant health consequences.

[0029] According to a further aspect of the invention, the predefined triggering event occurs based on a measurement of a connected altimeter, depth sensor or pressure sensor.

[0030] Low oxygen environments would be another important application where respiration monitoring and the properties of breathing are important to maintain proper oxygen and carbon dioxide balance in the blood. In these cases, respiration as triggered by an altimeter or depth sensor or pressure sensor would be appropriate while providing respiration waveforms and ECG waveforms in combination with other sensors to provide an overall risk and status of the patient.

[0031] The herein described features of the implantable medical device are also disclosed for the computer-implemented method for operating an implantable medical device and vice versa.

[0032] For a more complete understanding of the present invention and advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings. The invention is explained in more detail below using exemplary embodiments, which are specified in the schematic figures of the drawings, in which: Fig. 1 shows a diagram of an implantable medical device according to a preferred embodiment of the invention;

[0033] Fig. 2 shows a flowchart of a computer-implemented method for operating an implantable medical device according to the preferred embodiment of the invention;

[0034] Fig. 3 - 7 show graphs of respiratory activity data of a patient according to the preferred embodiment of the invention; and

[0035] Fig. 8 shows various implantation locations of the implantable medical device according to the preferred embodiment of the invention.

[0036] The implantable medical device 1 shown in Fig. 1 comprises means 10 for capturing respiratory activity data D of a patient and / or calculating the respiratory activity data D of the patient based on at least one medical parameter 12 captured by the implantable medical device 1. The implantable medical device 1 may be a cardiac monitor (e.g. a loop recorder) and / or a neurostimulation device (e.g. a spinal cord stimulation device).

[0037] Furthermore, the implantable medical device 1 comprises means 14 for triggering a storage of the captured and / or calculated respiratory activity data D of the patient in response to fulfillment of a predetermined triggering event E, wherein the respiratory activity data D comprises a time series of the respiratory activity of the patient.

[0038] The time series of the respiratory activity of the patient comprises a continuous waveform of a predetermined duration. The respiratory activity data D is preferably stored in the implantable medical device 1 to be later transmitted for analysis offline or alternatively analyzed in real-time and stored on the implantable medical device 1.

[0039] The at least one medical parameter 12 captured by the implantable medical device 1 used for calculating the respiratory activity data D of the patient comprises a thoracic impedance, an amplitude variation of an ECG and / or time-varying properties of the ECG. Moreover, the means 10 for capturing the respiratory activity data D of the patient is an accelerometer 18 or alternatively a means for communicating with an accelerometer 18, wherein the captured respiratory activity data D, in particular for an implantable cardiac monitor, is a chest wall motion.

[0040] Furthermore alternatively, the means 10 for capturing the respiratory activity data D of the patient may be configured to capture an impedance (e.g. of a chest cavity) measured between two electrodes of the implantable medical device 1 or two electrodes on the surface of the patient body.

[0041] The means 10 for capturing the respiratory activity data D of the patient is further configured to measure the time series of the respiratory activity of the patient with a sample rate between 0.5 Hz and 1 kHz, in particular with a sample rate between 1 Hz and 32 Hz.

[0042] The means 10 for capturing the respiratory activity data D of the patient is configured to record the time series of the respiratory activity of the patient on a periodic basis based on an amount of time elapsed, a time of day or due to a predefined triggering event E.

[0043] The predefined triggering event E is a change in body position or posture and / or establishing a resting posture such as no motion and / or no physical activity for at least a predetermined time period. The predefined triggering event E comprises motion sensor inputs, ECG inputs, impedance inputs, sleep status indicators, or triggers from peripheral or external devices, in particular a wearable sensor and / or an outside server or cloud-based system, wherein the ECG inputs comprise ECG amplitude modulation, ECG frequency modulation and / or autonomic nervous system indicators.

[0044] Alternatively, or in addition, the predefined triggering event E may occur based on a geolocation of the patient, an incline angle of the patient, a status of the patient as determined by additional user data based on the patient's lifestyle and habits, or risk factors. The predefined triggering event E may also occur based on a measurement of a connected altimeter, depth sensor or pressure sensor. Fig. 2 shows a flowchart of a computer-implemented method for operating an implantable medical device 1 according to the preferred embodiment of the invention.

[0045] The method comprises capturing Sla respiratory activity data D of a patient and / or calculating Sib the respiratory activity data D of the patient based on at least one medical parameter 12 captured by the implantable medical device 1.

[0046] An addition, the method comprises triggering S2 a storage of the captured and / or calculated respiratory activity data D of the patient in response to fulfillment of a predetermined triggering event E, wherein the respiratory activity data D comprises a time series of the respiratory activity of the patient.

[0047] Fig. 3 to 7 show graphs of respiratory activity data D of a patient according to the preferred embodiment of the invention.

[0048] In the case where the patient has regular and continuous normal respiratory activity as shown in graph 100 of Fig. 3, there are multiple peaks within a given amount of time and these peaks are detected using, for instance, a threshold value. Such a threshold is shown in 120, where the peaks 105, 110, and 115 are appropriately detected. In this case, a mean respiration rate can be determined and are representative of the patient’s respiratory state.

[0049] In a different scenario, as shown in graph 200 of Fig. 4, the respiratory peaks have different amplitudes and change over time, and there are also pauses between the respiratory peaks which are diagnostically important. A simple threshold as shown in 230 would be insufficient and not representative of the breathing status as peaks 205, 215 and 220 would be detected while peak 210 would not. In this case, the pause is only detected as the lack of a peak and could not be discriminated from the peak 210 which is simply below the threshold 230.

[0050] Taking the mean respiration rate over this period would erroneously consist of three peaks over the time period of the snapshot and this mean would be well below the actual mean during the time where breathing was present. The pause in breathing and the variations in amplitude would be lost information. Without a snapshot and time course of this data proper diagnosis could not be achieved.

[0051] Another example of this is shown in Graph 300 of Fig. 5 where a general higher threshold shown as 340 is able to detect certain types of respiration activity, i.e. peaks 305, 330 but a more aggressive threshold shown as 350 is necessary to detect additional lower amplitude respiratory activity, i.e. peaks 310, 315, 320. While simple implants may be able to implement a single-tier threshold system for detection of respiratory peaks multiple levels may be required or a more complex analysis may be required to fully determine inhalation and exhalation and therefore measure and report a proper statistic for respiration rate, number of pauses, inhalation to expiration ratio, relative tidal volume, regularity, depth, and other relevant parameters.

[0052] The time series data may be used as a confirmatory measure to validate statistics such as minimum, maximum, and mean. As shown in graph 400 of Fig. 6 mean and ranges of respiration data per day can be provided over time and these are provided by existing solutions. However, a time series would resolve exactly what led to the mean respiration rate or range of respirations visible in the data and provide much greater diagnostic power to determine the health of the patient.

[0053] The daily index shown in graph 400 indicates normal or abnormal breathing. A plurality of indices are plotted over time such as several days. The index in this case denotes amplitude of the respiration rate pattern but it could also stand for variability depending on what is considered the most important indicator of normal and abnormal breathing rate patterns.

[0054] The area 405 shows a normal respiratory function, whereas the area 410 shows abnormal respiratory function. The line 420 indicates a threshold of a breathing rate of e.g. 18 breaths per minute. A reason for the increased breathing rate in the area 410 could be some fluid in the lungs which was later drained off be taking a specific drug to this effect, which then resulted in a more normal breathing rate. Furthermore, determining signal minima and maxima in order to determine peak and trough points of a waveform might be complicated by waveform morphology as shown in graph 500 of Fig. 7. Here a false peak 505, 510 compared to an actual peak 515 or false trough 520 compared to an actual trough 525 can be detected due to the shape, and signal thresholding determines erroneous results. However, offline analysis using more sophisticated morphology matching algorithms and those assessing flat line portions or low slope portions of the waveform are used to accurately identify respiration parameters. In these cases, a respiration snapshot is critical to enable accurate analysis.

[0055] Fig. 8 shows various implantation locations of the implantable medical device 1 according to the preferred embodiment of the invention.

[0056] The implantable medical device 1 measures respiration as a continuous quantity. Respiration could be measured using thoracic impedance, amplitude variation of ECG, time-varying properties of ECG such as rate, or other methods. In particular, for an implantable cardiac monitor, chest wall motion as measured via an accelerometer 18 is particularly apt.

[0057] In this case, a device placed under the skin and above the sternum or rib cage as shown in Fig. 8 with device locations shown as 10, 20, or 30 is preferable. These locations also provide the ability to detect cardiac activity. If no cardiac activity is desired contralateral locations on the right side of the chest are also appropriate. Lateral locations under the arm or on the side of the rib cage would in this case also be appropriate.

[0058] Reference Signs

[0059] 1 implantable medical device

[0060] 10 means for capturing respiratory activity data

[0061] 12 medical parameter

[0062] 14 means for triggering a storage

[0063] 18 accelerometer

[0064] 100, 200, 300, 400, 500 graph

[0065] 105, 110, 115 peak

[0066] 120, 230, 420, 550 threshold

[0067] 205, 210, 215, 220 peak

[0068] 305, 310, 315, 320, 330 peak

[0069] 340, 350 threshold

[0070] 405, 410 area

[0071] 505, 510 false peak

[0072] 515 actual peak

[0073] 520 false trough

[0074] 525 actual trough

[0075] D respiratory activity data

[0076] E triggering event

[0077] Sla - S2 method steps

Claims

Claims1. Implantable medical device (1), comprising: means (10) for capturing respiratory activity data (D) of a patient and / or calculating the respiratory activity data (D) of the patient based on at least one medical parameter (12) captured by the implantable medical device (1); and means (14) for triggering a storage of the captured and / or calculated respiratory activity data (D) of the patient in response to fulfillment of a predetermined triggering event (E), wherein the respiratory activity data (D) comprises a time series of the respiratory activity of the patient; wherein the implantable medical device (1) is a cardiac monitor and / or a neurostimulation device.

2. Implantable medical device of claim 1, wherein the time series related to the respiratory activity of the patient comprises a continuous waveform of a predetermined duration, and wherein the respiratory activity data (D) is stored in the implantable medical device (1) to be later transmitted for analysis offline or analyzed in real-time and stored on the implantable medical device (1).

3. Implantable medical device of claim 1 or 2, wherein the at least one medical parameter (12) captured by the implantable medical device (1) used for calculating the respiratory activity data (D) of the patient comprises an impedance, an amplitude variation of an ECG and / or time-varying properties of the ECG.

4. Implantable medical device of any one of the preceding claims, wherein the means (10) for capturing the respiratory activity data (D) of the patient is an accelerometer (18) or means for communicating with an accelerometer (18), wherein the captured respiratory activity data (D), in particular for an implantable cardiac monitor, is a chest wall motion.

5. Implantable medical device of any one of claims 1 to 4, wherein the means (10) for capturing the respiratory activity data (D) of the patient is configured to capture animpedance measured between two electrodes of the implantable medical device (1) or two electrodes on the surface of the patient body.

6. Implantable medical device of any one of the preceding claims, wherein the means (10) for capturing the respiratory activity data (D) of the patient is configured to measure the time series related to respiratory activity of the patient with a sample rate between 0.5 Hz and 1 kHz, in particular with a sample rate between 1 Hz and 32 Hz.

7. Implantable medical device of any one of the preceding claims, wherein the means (10) for capturing the respiratory activity data (D) of the patient is configured to record the time series related to the respiratory activity of the patient on a periodic basis based on an amount of time elapsed, a time of day or due to a predefined triggering event (E).

8. Implantable medical device of any one of claim 7, wherein the predefined triggering event (E) is a change in body position or posture and / or establishing a resting posture such as no physical activity for at least a predetermined time period.

9. Implantable medical device of claim 7 or 8, wherein the predefined triggering event (E) comprises motion sensor inputs, ECG inputs, impedance inputs, sleep status indicators, or triggers from peripheral or external devices, in particular a wearable sensor and / or an outside server or cloud-based system, wherein the ECG inputs comprise ECG amplitude modulation, ECG frequency modulation and / or autonomic nervous system indicators.

10. Implantable medical device of any one of claims 7 to 9, wherein the predefined triggering event (E) occurs based on a geolocation of the patient, an incline angle of the patient, a status of the patient as determined by additional user data based on the patient's lifestyle and habits, or risk factors.

11. Implantable medical device of any one of claims 7 to 10, wherein the predefined triggering event (E) occurs based on a measurement of a connected altimeter, depth sensor or pressure sensor.

12. Computer-implemented method for operating an implantable medical device (1), comprising the steps of: capturing (SI a) respiratory activity data (D) of a patient and / or calculating (Sib) the respiratory activity data (D) of the patient based on at least one medical parameter (12) captured by the implantable medical device (1); and triggering (S2) a storage of the captured and / or calculated respiratory activity data (D) of the patient in response to fulfillment of a predetermined triggering event (E), wherein the respiratory activity data (D) comprises a time series of the respiratory activity of the patient; wherein the implantable medical device (1) is a cardiac monitor and / or a neurostimulation device.

13. Computer program with program code to perform the method of claim 12 when the computer program is executed on a computer.

14. Computer-readable data carrier containing program code of a computer program for performing the method of claim 12 when the computer program is executed on a computer.

15. Method for treating a patient with the implantable medical device (1) of any one of claims 1 to 11, wherein the implantable medical device (1) is operated by the computer-implemented method of claim 12.

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