Detecting seizures based on heartbeat data

Information

  • Patent Grant
  • 9585611
  • Patent Number
    9,585,611
  • Date Filed
    Friday, April 25, 2014
    10 years ago
  • Date Issued
    Tuesday, March 7, 2017
    7 years ago
Abstract
A method includes receiving heartbeat data of a patient and receiving activity data of the patient. The activity data includes one or more activity values that are related to an activity level of the patient and that are measured independently of the heartbeat data. The method further includes determining a value of a weighting factor based on the activity data. The method also includes determining modified heartbeat data by applying the weighting factor to at least a portion of the heartbeat data. The method also includes detecting a seizure event based on the modified heartbeat data.
Description
RELATED APPLICATION

This application is related to U.S. patent application Ser. No. 14/262,508, entitled “Cranial Nerve Stimulation To Treat Depression During Sleep,” filed contemporaneously herewith, which is hereby incorporated by reference as though fully set forth herein.


FIELD OF THE DISCLOSURE

The present disclosure is generally related to detecting seizures based on heartbeat data.


BACKGROUND

Advances in technology have led to the development of medical devices that can be implanted within a living organism, such as a human, to provide treatment or monitoring. For example, a medical device may detect when a seizure occurs in a patient. Early detection of a seizure may allow appropriate responsive action to be taken. Such actions may include sending an alert signal to the patient or a caregiver, initiating a treatment therapy, or taking remedial action such as making the patient and/or an environment around the patient safe. One way to detect seizures is by monitoring a heartbeat of the patient to determine whether the heartbeat increases beyond a threshold. However, other factors can also cause the heartbeat to increase beyond the threshold. Thus, seizure detection based on a heartbeat may be subject to a significant number of false positives.


SUMMARY

A medical device monitoring and/or providing therapy to a patient may detect and respond to seizures based on patient heartbeat data and based on patient activity data (including patient state data). The medical device may use a seizure detection algorithm that is capable of distinguishing between pathological changes in the detected heartbeat, which may indicate a seizure, and non-pathological changes in the detected heartbeat. The non-pathological changes may correspond to normal physiological functioning as opposed to a seizure. The non-pathological changes may be difficult to distinguish from the pathological changes based solely on information associated with the heartbeat.


For example, the patient's heartbeat may increase when a seizure event occurs (e.g., a pathological change). However, the patient's heartbeat may also change when the patient engages in a state of physical activity (such as running, jumping, exercising, swimming, etc.) or the patient assumes a state or changes to or from a state (such as initiating running, awaking from sleep, going to sleep, changing from healthy to sick, etc.). Other external factors may also cause the patient's heartbeat to increase. For example, a change in temperature may contribute to an increase in the patient's heartbeat. It may become difficult for the medical device to determine whether an increase in the patient's heartbeat is due to a seizure, physical activity, or other external factors.


To address such concerns, the medical device may account for the physical activity and/or other external factors when determining whether or not a seizure event is indicated by heartbeat data. For example, the medical device may use an algorithm that detects whether or not a seizure event is present based on a background heart rate and a foreground heart rate. The foreground heart rate may correspond to a rate at which the patient's heart is beating at a present time, which can be the most-recent heart rate value obtained from the patient or be an average of several recent heart rate values that are adjacent to and include the most-recent heart rate value. The background heart rate may be a function of the foreground heart rate and a previously-determined background heart rate. For example, the algorithm may be expressed as BGn=λ*BGn-1+(1−λ)*FGn, where BGn is the background heart rate at the present time (n), BGn-1 is the previously-determined background heart rate, FGn is the foreground heart rate at the present time (n), and λ is a weighting factor. The previously-determined background heart rate may correspond to an average heart rate during a moving period of time or time window (e.g., an average heart rate during a moving five minute time window that remains immediately prior to the present time), with the period of time or time window being selected to capture a sufficient number of stable heart beats to provide an average heart rate value that is representative of the patient's heart rate and not heavily influenced by any extremely-high or low single heart beat or grouping of heart beats. When a ratio of the foreground heart rate and the background heart rate at the present time exceeds a seizure detection threshold, the medical device may determine that a seizure event is present.


A value of the weighting factor may be based on physical activity and/or other external factors that affect heart rate. The weighting factor may be zero, one, or between zero and one. As can be appreciated, when the weighting factor is set at a high value that is at or close to one, the calculation of the background heart rate will be heavily influenced by the value of the previously determined-background heart rate, thus providing a background heart rate that is greatly dependent on a window of time corresponding to the time period assigned when determining the previously-determined heart rate. As can also be appreciated, when the weighting factor is set at a low value that is at or close to zero, the calculation of the background heart rate will be heavily influenced by the value of the foreground heart rate, thus providing a background heart rate that is greatly dependent on an instant heart rate or recently-measured heart rate values. As can be further appreciated, when the weighting factor is set at a middle value that is at or close to 0.5, the calculation of the background heart rate will be equally influenced by the values of the previously-determined heart rate and the foreground heart rate, thus providing a background heart rate that is balanced in its dependence on previously-measured heart rate values and recently-measured heart rate values. As an illustrative non-limiting example, the value of the weighting factor may be approximately equal to 0.95 when the patient is in an idle state (e.g., sleep), which would provide a background heart rate that heavily depends (e.g., 95% dependence) on the previously-determined background heart rate and lightly depends (e.g., 5% dependence) on the foreground heart rate. When the patient is undergoing physical activity such as running on a treadmill, or the patient is subject to external factors that affect heart rate, the value of the weighting factor may be set to a lesser value than with the idle state, which will generate a background heart rate that is more dependent on the foreground heart rate than the previously-determined background heart rate, and/or generate a background heart rate that is based on a balancing of the foreground heart rate and the previously-determined heart rate. For example, when the value of the weighting factor is reduced from 0.95 to 0.50 when the patient leaves an idle state to undergo a particular physical activity, the background heart rate can be 50% dependent on the previously-determined background heart rate and 50% dependent on the foreground heart rate, thereby providing a background heart rate that accounts for a recent change in the heart rate due to the physical activity and accounts for the more-stable and longer-measured heart rate that was observed before the recent change in heart rate.


Thus, physical activity and/or external factors may be used alone or in combination to determine the background heart rate by changing the value of the weighting factor based on the physical activity and/or external factors that affect heart rate. As a result, when the background heart rate is compared to the foreground heart rate to determine whether a seizure event is occurring, physical activity and/or external factors are taken into account.


In a particular embodiment, a method includes receiving heartbeat data of a patient and receiving activity data of the patient. The activity data can provide one or more activity values that are related to an activity level of the patient and that are independent of the heartbeat data. The method further includes determining a value of a weighting factor based on the activity data. The method also includes determining modified heartbeat data by applying the weighting factor to at least a portion of the heartbeat data. The method also includes detecting a seizure event based on the modified heartbeat data.


In another particular embodiment, a medical device includes a first interface to receive heartbeat data of a patient and a second interface to receive activity data of the patient. The activity data includes one or more activity values that are related to an activity level of the patient and that are measured independently of the heartbeat data. The medical device also includes a processor to determine a value of weighting factor based on the activity data. The processor determines modified heartbeat data by applying the weighting factor to at least a portion of the heartbeat data. The processor also detects a seizure event based on the modified heartbeat data.


In another particular embodiment, a non-transitory computer readable medium stores instructions that are executable be a processor to cause the processor perform operations. The operations include receiving heartbeat data of a patient and receiving activity data of the patient. The activity data includes one or more activity values that are related to an activity level of the patient and that are measured independently of the heartbeat data. The operations further include determining a value of a weighting factor based on the activity data and determining modified heartbeat data by applying the weighting factor to at least a portion of the heartbeat data. The operations also include detecting a seizure event based on the modified heartbeat data.


The features, functions, and advantages that have been described can be achieved independently in various embodiments or may be combined in yet other embodiments, further details of which are disclosed with reference to the following description and drawings.





BRIEF DESCRIPTION OF THE DRAWINGS


FIG. 1 is a particular illustrative embodiment of a diagram illustrating heartbeat data modification based on activity data;



FIG. 2 is a particular embodiment of a system that is operable to detect a seizure event based on heartbeat data and activity data;



FIG. 3 is a block diagram of a particular embodiment of a medical device in communication with a patient that is operable to detect a seizure event based on heartbeat data and activity data; and



FIG. 4 is a flow chart of a particular embodiment of a method of detecting a seizure event based on heartbeat data and activity data.





DETAILED DESCRIPTION


FIG. 1 is a particular illustrative embodiment of a diagram 100 illustrating heartbeat data modification based on physical activity. The diagram 100 includes a first trace 110 illustrating an electrocardiogram of a patient, a second trace 120 illustrating a background heart rate of the patient which is derived from the first trace 110 and calculated using a fixed weighting factor, a third trace 130 illustrating a foreground heart rate of the patient which is derived from the first trace 110, and a fourth trace 140 illustrating a modified background heart rate of the patient which is derived from the first trace 110 and calculated using a weighting factor and adjusted based on activity data. The four traces 110, 120, 130, and 140 of diagram 100 are aligned with each other to provide identical x-axis representation of time and to provide similar y-axis representations of magnitude of the measured or calculated parameter.


The electrocardiogram illustrated in the first trace 110 may include a plurality of R waves. For example, the electrocardiogram may include a first R wave 102 and a second R wave 104. A time between respective points on the first R wave 102 and the second R wave 104 is an R-R interval. The first R wave 102 and the second R wave 104 may correspond to a first and second heartbeat, respectively, and the R-R interval may correspond to an amount of time that elapses between consecutive heartbeats (e.g., a heartbeat rate, also referred to as a “heart rate”).


A faster heartbeat may result in a shorter R-R interval between consecutive heartbeats (e.g., R waves). For example, a third R wave 106 and a fourth wave 108 may have a shorter R-R interval than the R-R interval between the first and second R waves 102, 104. Thus, the patient's heart is beating at a faster rate at a time corresponding to the third and fourth R waves 106, 108 as opposed to a time corresponding to the first and second R waves 102, 104. As illustrated by the first trace 110, an increased rate of the patient's heartbeat (e.g., shorter R-R intervals) may be indicative of a seizure event. For example, the seizure event may begin at a critical time (Ta) when the rate of the patient's heartbeat exceeds a threshold level.


The background heart rate of the patient illustrated in the second trace 120 may be expressed as BGR=0.95*BGn-1+0.05*FGn, where BGR is a reference background heart rate at the present time (n), BGn-1 is the previously-determined background heart rate, and FGn is the foreground heart rate at the present time (n). The previously-determined background heart rate may be generated by taking an electrocardiogram over a particular time span and performing an infinite impulse response (IIR) operation on the electrocardiogram. For example, the previously-determined background heart rate may correspond to an IIR operation on an electrocardiogram spanning a five minute time period before the present time (n). In another example, the previously-determined background heart rate may correspond to an IIR operation on an electrocardiogram spanning a time period determined by a number of heart beats before the present time (n).


The foreground heart rate (FGn) at the present time (n) is illustrated in the third trace 130. The foreground heart rate may be generated by taking an electrocardiogram over a time span corresponding to a most recent R-R interval. For example, the foreground heart rate may correspond to a current heart rate. When the current heart rate increases, a magnitude of the foreground heart rate increases. When the current heart rate decreases, the magnitude of the foreground heart rate decreases.


Referring back to the exemplary embodiment represented with second trace 120, ninety-five percent of the reference background heart rate is based on a heart rate spanning over a previous five minute period (e.g., the previously-determined background heart rate) and five percent of the reference background heart rate is based on the foreground heart rate illustrated in the third trace 130. Thus, when determining the reference background heart rate, the previously-determined background heart rate is weighted at a fixed rate (e.g., 0.95) and the foreground heart rate is weighted at a fixed rate (e.g., 0.05). When comparing the foreground heart rate illustrated in the third trace 130 to the reference background heart rate illustrated in the second trace 120, a ratio of the foreground heart rate and the reference background heart rate may be calculated, and the ratio may be compared to a seizure threshold and, when the threshold is exceeded, detect the occurrence of a seizure event at the critical time (Tc).


However, if the increased heart rate at the critical time (Ta) is associated with a physical activity of the patient as opposed to a seizure, then using the reference background heart rate in the second trace 120 may result in a false detection of a seizure event. For example, volitional motion or other non-seizure activity may increase heart rate, and the dominance of the previously-determined background heart rate (when, e.g., weighted at 95%) in the calculation of the reference background heart rate and/or the ratio may result in a false indication of a seizure event. To reduce the likelihood of detecting a false seizure event, the modified background heart rate illustrated in the fourth trace 140 may be used along with the foreground heart rate illustrated in the third trace 130 to detect whether a seizure event is present.


For example, the modified background heart rate may factor in an activity level of the patient to account for the increased heart rate. The modified background heart rate may be expressed as BGM=λ*BGn-1+(1−λ)*FGn, where BGM is the modified background heart rate at the present time (n), BGn-1 is the previously-determined background heart rate, FGn is the foreground heart rate at the present time (n), and λ is a weighting factor.


A value of the weighting factor may be based on activity data. In a particular embodiment, the activity data includes accelerometer data, body temperature data, electromyography data, respiration data, perspiration data, impedance data, or a combination thereof. The activity data may include data obtained from an electroencephalography (EEG) sensor, an electrooculography (EOG) sensor, an electrocardiography (ECG) sensor, an electromyography (EMG) sensor, an accelerometer, or a combination thereof, as disclosed in contemporaneously-filed U.S. patent application Ser. No. 14/262,508, entitled “Cranial Nerve Stimulation To Treat Depression During Sleep,” which is hereby incorporated by reference as though fully set forth herein. In another particular embodiment, the activity data may correspond to one or more activity values that are related to an activity level of the patient. The activity values may be measured independently of the heart rate of the patient (e.g., measured independently of heartbeat data). The activity values may also be based on a state of the patient or a change of patient state, e.g., based on an activity state, a sleep state, or a change in the patient activity or sleep state. The activity values may also be related to measurements corresponding patient temperature, patient muscle activity, breathing rate, a skin response such as sweating, or combinations thereof. For example, activity data measured with an accelerometer may have a first activity value associated with running, activity data measured with a respiration sensor may have a second activity value associated with walking, activity data measured with an EEG sensor may have a third activity value associated with sleeping, etc. With regard to sleeping, the activity value may correspond to a sleep state of the patient so as to increase or decrease the weighting factor when the patient is in a sleep state that, for example, exhibits reduced or increased body movements, when the patient transitions from one sleep state to another sleep state, when the patient moves or changes positions during sleep, and/or when the patient awakes from sleep, as disclosed in contemporaneously-filed U.S. patent application Ser. No. 14/262,508, entitled “Cranial Nerve Stimulation To Treat Depression During Sleep,” which is hereby incorporated by reference as though fully set forth herein. The value of the weighting factor may decrease as an activity level of the patient increases. As a non-limiting example, the value of the weighting factor may be approximately 0.95 when the activity corresponds to sleeping or to a sleep state, 0.75 when the activity corresponds to walking, and 0.50 when the activity corresponds to running. As the weighting factor decreases, the modified background heart rate becomes more dependent on the foreground heart rate (e.g., more dependent on a current heart rate of the patient) and less dependent on the previously-determined background heart rate. Thus, the modified background heart rate updates more quickly than the reference background heart rate when the patient is engages in activities that cause an immediate or foreseeable increase in heart rate.


The modified background heart rate may become increasingly similar to the foreground heart rate as the value of the weighting factor decreases. For example, the third trace 130 (e.g., the foreground heart rate) may become increasingly similar to the fourth trace 140 (e.g., the modified background heart rate) as the value of the weighting factor approaches zero. As a result, when comparing the foreground heart rate illustrated in the third trace 130 to the modified background heart rate illustrated in the fourth trace 140, a ratio of the foreground heart rate and the modified background heart rate may not exceed the seizure threshold at the critical time (Tc) when the increased heart rate is based on patient activity. Thus, using the modified background heart rate to detect a seizure event may yield fewer false positives.


Referring to FIG. 2, a system 200 that is operable to detect a seizure event based on heartbeat data and activity data is shown. The system 200 includes a patient-contacting medical device 202, which can be, for example, an implantable medical device or an external device fixed to the surface of a patient's skin. The medical device 202 includes a processor 206 that is coupled to a memory 204 and can also be coupled directly or wirelessly to a therapy delivery unit 212, which may be part of the medical device 202 (as illustrated in FIG. 2) or located external to the medical device 202.


The medical device 202 includes a first interface 208 that is coupled to receive heartbeat data 220 of a patient. The heartbeat data 220 may be generated from an electrode implanted within, or externally coupled to, the patient. The heartbeat data 220 of the patient may include electrocardiogram data. For example, the heartbeat data 220 may correspond to the electrocardiogram illustrated in the first trace 110 of FIG. 1. In a particular embodiment, the heartbeat data 220 is a numeric value indicating a most recent R-R interval or a signal corresponding to an electrocardiogram data trace. The first interface 208 may be configured to provide the heartbeat data 220 to the processor 206.


The medical device also includes a second interface 210 that is coupled to receive activity data 230 of the patient. The activity data 230 may be generated from a component (such as an accelerometer) within the medical device 202 (not shown in FIG. 2) or an external device such as an electrode implanted within, or externally coupled to, the patient as illustrated in FIG. 2. In a particular embodiment, the activity data 230 includes accelerometer data, body temperature data, electromyography data, perspiration data, impedance data, or a combination thereof. The activity data 230 may include one or more activity values that are related to an activity level of the patient. For example, a first activity value may be associated with running, a second activity value may be associated with walking, a third activity value may be associated with sleeping, etc. The activity values may be measured independently of the heartbeat data 220. In a particular embodiment, the activity data is a numeric value or signal indicating a measurement that is associated with the activity level of the patient. The second interface 210 may be configured to provide the activity data 230 to the processor 206.


The processor 206 may be configured to receive the heartbeat data 220 from the first interface 208 and to receive the activity data 230 from the second interface 210. The processor 206 may perform an IIR operation on the heartbeat data 220 (e.g., perform an IIR operation on the electrocardiogram data) to generate a background heart rate for spanning over a time period (e.g., a five minute time period). The processor 206 may also be configured to determine a value of a weighting factor based on the activity data 230.


The processor 206 may further be configured to determine modified heartbeat data by applying the weighting factor to at least a portion of the heartbeat data. Determining the modified heartbeat data may include determining a background heart rate based on a previously-determined background heart rate, a most recent R-R interval, and the weighting factor. Determining the modified heartbeat data may also include determining a foreground heart rate based on a most recent R-R interval. For example, the modified heartbeat data may correspond to the modified background heart rate illustrated in the fourth trace 140 of FIG. 1 and may be expressed as BGM=λ*BGn-1+(1−λ)*FGn, where BGM is the modified heartbeat data (e.g., the modified background heart rate), BGn-1 is a previously-determined background heart rate, FGn is a foreground heart rate at the present time (n), and λ is the weighting factor determined based on the activity data 230. Thus, the modified heartbeat data may be determined as a sum of a first value and a second value. The first value (λ*BGn-1) may be the weighting factor times the previously-determined background heart rate, and the second value ((1−λ)*FGn) may be one minus the weighting factor times the most recent R-R interval (e.g., the foreground heart rate).


In response to the activity data 230 indicating an increased activity level of the patient, the processor 206 is configured to determine the value of the weighting factor such that an effect of prior heartbeat data (BGn-1) on the modified heartbeat data is decreased. As a non-limiting example, the value of the weighting factor may be approximately 0.95 when the activity corresponds to sleeping or a sleep state, 0.75 when the activity corresponds to walking, and 0.50 when the activity corresponds to running Thus, the value of the weighting factor decreases as the activity level of the patient increases. As can be appreciated, the calculation of modified background heart rate and the weighting factor can be modified to provide the same operation described above, but configured so that the value of the weighting factor increases as the activity level of the patient increases.


The processor 206 may also be configured to detect an indication of noise in the heartbeat data 220. Noise may be detected via patterns in an electrocardiogram, such as the electrocardiogram illustrated in the first trace 110 of FIG. 1. For example, noise may be present if the detected heartbeat falls below a lower threshold or rises above an upper threshold. In a particular embodiment, the lower threshold is about 35 beats per minute (bpm) and the upper threshold is about 180 bpm. As another example, noise may be present if a beat-to-beat variability rises above an upper threshold or falls below a lower threshold. In a particular embodiment, the upper threshold may be about 115 percent and the lower threshold is about 65 percent.


In response to the detected noise in the heartbeat data 220 increasing, the processor 206 may determine the value of the weighting factor such that an effect of prior heartbeat data (BGn-1) on the modified heartbeat data is decreased. For example, in response to the detected noise in the heartbeat data 220 increasing, the processor 206 may lower the value of the weighting factor so that the modified heartbeat data is more dependent on the foreground heart rate. In response to the detected noise in the heartbeat data decreasing, the processor 206 may determine the value of the weighting factor such that the effect of the prior heartbeat data (BGn-1) on the modified heartbeat data is increased. For example, in response to the detected noise in the heartbeat data 220 decreasing, the processor 206 may raise the value of the weighting factor so that the modified heartbeat data is more dependent on the previously-determined background heart rate (BGn-1).


The processor 206 may further be configured to detect a seizure event based on the modified heartbeat data. For example, the processor 206 may compare a ratio of the foreground heart rate and the modified background heart rate (e.g., the modified heartbeat data) to a seizure detection threshold. When the ratio exceeds the seizure detection threshold, the processor 206 may determine that a seizure event is present. When the ratio is below the seizure detection threshold, the processor 206 may determine that no seizure event is present. As explained with respect to FIG. 3, in response to detecting the seizure event, the processor 206 may be configured, for example, to provide a notification that a seizure is detected, to initiate a recording of the seizure event, and/or to cause the therapy delivery unit 212 to apply stimulation to tissue of the patient.


The memory 204 may include tangible, non-transitory, computer-readable media (e.g., one or more computer memory devices). The processor 206 may be implemented using a single-chip processor or using multiple processors. The memory 204 may include various memory devices, such as registers, cache, volatile memory, and non-volatile memory. For example, the memory 204 can include cache that is accessible by the processor 206 to rapidly retrieve and store data. As a non-limiting example, the memory 204 may store information corresponding to the previously-determined background heart rate (BGn-1) and/or weighting factor values for different activities. In a particular embodiment, a look-up table, an algorithm, or a combination thereof, is stored in the memory 204 to determine the weighting factor values based on the activity data 230, the detected noise in the heartbeat data 220, or a combination thereof. Examples of computer-readable media that the memory 204 may use include, but are not limited to: magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROM disks; magneto-optical media; and specially configured hardware devices such as application-specific integrated circuits (ASICs), programmable logic devices (PLDs), and ROM and RAM devices.


The memory 204 may also store instructions that are executable by the processor 206 to implement various functions. To illustrate, the instructions may be executable by the processor 206 to cause the processor to perform operations including receiving the heartbeat data 220 and receiving the activity data 230. The operations may also include determining the value of the weighting factor based on the activity data 230 and determining modified heartbeat data by applying the weighting factor to at least a portion of the heartbeat data 220. The instructions may also be executable by the processor 206 to cause the processor to detect the seizure event based on the modified heartbeat data. In a particular embodiment, the instructions are executable by the processor 206 to detect R waves in an electrocardiogram, R-R intervals in an electrocardiogram, noise in the heartbeat data 220, other information descriptive of a heartbeat, or a combination thereof.


Additionally or in the alternative, the medical device 202 may include dedicated hardware implementations, such as application specific integrated circuits, programmable logic arrays and other hardware devices, to implement one or more functions of the processor 206. Accordingly, the present disclosure encompasses software, firmware, and hardware implementations.


When the heartbeat data 220 is received as an electrocardiogram trace, the processor 206, or an application-specific integrated circuit (ASIC), may perform an IIR operation on an electrocardiogram trace to detect R waves and R-R intervals. The processor 206 (or ASIC) may determine a foreground heart rate by monitoring the timing between the most recent R waves in the electrocardiogram. The processor 206 may also determine the modified background heart rate based on prior heartbeat data stored in the memory 204, the foreground heart rate, and the weighting factor. For example, the prior heartbeat data may be based on heartbeat data 220 received during a five minute window prior to the heartbeat data 220 associated with the foreground heart rate. Activity data 230 associated with patient may be provided to the processor 206 via the second interface 210 to determine the value of the weighting factor.


The processor 206 may detect whether a seizure event is present based on the heartbeat data 220 and the activity data 230. For example, the processor 206 may compare the ratio of the foreground heart rate and the modified background heart rate to the seizure detection threshold to determine whether the seizure event is present. In response to detecting the seizure event, the processor 206 may, for example, send a signal to provide a notification that a seizure is detected, to initiate a recording of the seizure event, and/or to the therapy delivery unit 212 to cause the therapy delivery unit 212 to stimulate a tissue of the patient.


Referring to FIG. 3, a block diagram of a particular embodiment of implantable medical device 202 within a patient is shown. The medical device 202 includes the memory 204, the processor 206, the first interface 208, the second interface 210, the therapy delivery unit 212, a heartbeat sensor 320, and an activity sensor 330.


The medical device 202 may be adapted to be surgically implanted in a patient 306 to detect a seizure event based on activity data 230 and heartbeat data 220, to provide therapy, to monitor one or more conditions, for another purpose, or any combination thereof. In a particular embodiment, the medical device 202 may be coupled to one or more electrodes 308 and may be adapted to deliver electrical stimulus to tissue 304 of the patient 306 via the electrodes 308. In a particular embodiment, the medical device 202 is an implantable nerve stimulation device. Examples of the implantable nerve stimulation device may include an implantable cranial nerve stimulation device, an implantable spinal cord stimulation device, etc. The electrodes 308 may be coupled to the medical device 202 and may be positioned proximate to or coupled to a nerve, such as a cranial nerve (e.g., the trigeminal nerve, the hypoglossal nerve, the vagus nerve or a branch of the vagus nerve).


The heartbeat sensor 320 may be configured to detect (e.g., sense) a heartbeat of the patient 306. For example, the heartbeat sensor 320 may be coupled to a nerve via the electrodes 308 to detect the heartbeat of the patient 306. In a particular embodiment, the heartbeat sensor 320 is an electrocardiogram (ESG) sensor. For example, based on the detected heartbeat, the heartbeat sensor 320 may generate electrocardiogram data and provide the electrocardiogram data to the processor 206. The electrocardiogram data may correspond to the electrocardiogram data illustrated by the first trace 110 of FIG. 1 and may indicate R waves and R-R intervals of the detected heartbeat. The activity sensor 330 may be configured to detect an activity level of the patient 306. For example, the activity sensor 330 may be coupled to a nerve via the electrodes 308 to detect an activity level of the patient 308. Alternatively, the activity sensor 330 may include a device that detects other indications of activity, such as an amount of perspiration, a body temperature, breathing rate, etc.


As explained with reference to FIG. 2, the medical device 202 may include the therapy delivery unit 212 that is configured to control generation of treatment stimulus provided to the electrodes 308 to provide an electrical stimulus to the tissue 304. In another particular embodiment, the medical device 202 is an implantable drug pump. In another particular embodiment, the medical device 202 is an implantable sensor. Examples of an implantable sensor may include an electrocardiogram (ESG) sensor, an electromyogram (EEG) sensor, etc. Note that the term “patient” is used broadly to include any organism and is not intended to imply that the patient 306 is human; although the patient 306 is a human patient in one embodiment.



FIG. 4 is a flow chart of a particular embodiment of a method 400 of detecting a seizure event based on heartbeat data and activity data. For example, the method 400 may be performed by a medical device and the components thereof, such as the medical device 202, the memory 204, the processor 206, the first interface 208, the second interface 210, the therapy delivery unit 212 of FIGS. 2 and 3, or any combination thereof. The method 400 may be performed while monitoring for a seizure event in a patient, such as the patient 306 of FIG. 3.


The method 400 may include receiving heartbeat data of a patient, at 402. For example, in FIG. 2, the first interface 208 may be coupled to receive the heartbeat data 220 of a patient, such as the patient 306 of FIG. 3. The heartbeat data 220 of the patient 306 may include electrocardiogram data (e.g., an electrocardiogram trace). For example, the heartbeat data 220 may correspond to the electrocardiogram illustrated in the first trace 110 of FIG. 1. The first interface 208 may provide the heartbeat data 220 to the processor 206.


Activity data of the patient may be received, at 404. For example, in FIG. 2, the second interface 210 may be coupled to receive the activity data 230. The activity data 230 may include one or more activity values that are related to an activity level of the patient 306 and that are measured independently of the heartbeat data 220. In a particular embodiment, the activity data 230 includes accelerometer data, body temperature data, electromyography data, perspiration data, impedance data, or a combination thereof. In a particular embodiment, the activity data 230 may be detected (e.g., sensed) by the activity sensor 330. Additionally or alternatively, the activity data 230 may be received wirelessly from one or more external sensors (not shown). The second interface 210 may provide the activity data 230 to the processor 206.


A value of a weighting factor may be determined based on the activity data, at 406. For example, in FIG. 2, the processor 206 may determine the value of the weighting factor such that an effect of prior heartbeat data on the modified heartbeat data is decreased in response to the activity data 230 indicating an increased activity level of the patient 306.


Modified heartbeat data may be determined by applying the weighting factor to at least a portion of the heartbeat data, at 408. For example, the processor 206 of FIG. 2 may determine the modified heartbeat data based on an algorithm, such as BGM=λ*BGn-1+(1−λ)*FGn, where BGM is the modified heartbeat data (e.g., the modified background heart rate), BGn-1 is a previously-determined background heart rate, FGn is a foreground heart rate at the present time (n), and λ is the weighting factor determined based on the activity data. Thus, the modified heartbeat data may be determined as a sum of a first value and a second value. The first value (λ*BGn-1) may be the weighting factor time the previously-determined background heart rate and the second value ((1−λ)*FGn-1) may be one minus the weighting factor times the most recent R-R interval (e.g., the foreground heart rate).


A seizure event may be detected based on the modified heartbeat data, at 410. For example, the processor 206 of FIG. 2 may compare a ratio of the foreground heart rate and the modified background heart rate (e.g., the modified heartbeat data) to a seizure detection threshold. When the ratio exceeds the seizure detection threshold, the processor 206 may determine that a seizure event is present. When the ratio is below the seizure detection threshold, the processor 206 may determine that there is no seizure event present.


In a particular embodiment, the method 400 may include detecting an indication of noise in the heartbeat data. For example, the processor 206 of FIG. 2 may detect an indication of noise in the heartbeat data 220. The weighting factor may be further determined based on the indication of noise in the heartbeat data. For example, in response to the detected noise in the heartbeat data 220 increasing, the processor 206 may determine the value of the weighting factor such that an effect of prior heartbeat data on the modified heartbeat data is decreased. Thus, in response to the detected noise in the heartbeat data 220 increasing, the processor 206 may lower the value of the weighting factor so that the modified heartbeat data is more dependent on the foreground heart rate. Alternatively, in response to the detected noise in the heartbeat data decreasing, the processor 206 may determine the value of the weighting factor such that the effect of the prior heartbeat data on the modified heartbeat data is increased. Thus, in response to the detected noise in the heartbeat data 220 decreasing, the processor 206 may raise the value of the weighting factor so that the modified heartbeat data is more dependent on the previously-determined background heart rate.


In a particular embodiment, the method 400 may include causing stimulation to be applied to tissue of the patient in response to detecting the seizure event. For example, the therapy delivery unit 212 of FIG. 3 may control generation of treatment stimulus provided to the electrodes 308 to provide an electrical stimulus to the tissue 304 in response to the processor 206 detecting the seizure event. In another particular embodiment, the method 400 may include generating a report regarding the detection of a seizure event, and may include the initiation of a recording of a detected seizure event.


The illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The illustrations are not intended to serve as a complete description of all of the elements and features of apparatus and systems that utilize the structures or methods described herein. Many other embodiments may be apparent to those of skill in the art upon reviewing the disclosure. Other embodiments may be utilized and derived from the disclosure, such that structural and logical substitutions and changes may be made without departing from the scope of the disclosure. For example, method steps may be performed in a different order than is shown in the figures or one or more method steps may be omitted. Accordingly, the disclosure and the figures are to be regarded as illustrative rather than restrictive.


Moreover, although specific embodiments have been illustrated and described herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar results may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the description.


The Abstract of the Disclosure is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, the claimed subject matter may be directed to less than all of the features of any of the disclosed embodiments.

Claims
  • 1. A method comprising: receiving heartbeat data of a patient;receiving activity data of the patient, wherein the activity data includes an activity value related to an activity level of the patient that is measured independently of the heartbeat data;determining one of a plurality of activity value ranges to which the activity value belongs;determining a weighting factor based on the determined activity value range, each of the plurality of activity value ranges associated with a different one of a plurality of predetermined weighting factors;determining modified heartbeat data by applying the weighting factor to at least a portion of the heartbeat data; anddetecting a seizure event based on the modified heartbeat data.
  • 2. The method of claim 1, wherein determining the modified heartbeat data includes determining a background (BG) heart rate based on a previously-determined BG heart rate, a most recent R-R interval, and the weighting factor.
  • 3. The method of claim 2, wherein the BG heart rate is determined as a sum of a first value and a second value, wherein the first value is the weighting factor times the previously-determined BG heart rate and the second value is one minus the weighting factor times the most recent R-R interval.
  • 4. The method of claim 2, wherein determining the modified heartbeat data further includes determining a foreground (FG) heart rate based on one or more R-R intervals of the heartbeat data.
  • 5. The method of claim 4, wherein detecting the seizure event comprises comparing a ratio of the FG heart rate and the BG heart rate to a seizure detection threshold.
  • 6. The method of claim 1, wherein the heartbeat data of the patient includes electrocardiogram data.
  • 7. The method of claim 6, wherein the electrocardiogram data indicates a timing related to a plurality of R-waves.
  • 8. The method of claim 1, further comprising detecting an indication of noise in the heartbeat data, wherein the weighting factor is determined further based on the indication of noise in the heartbeat data.
  • 9. The method of claim 8, wherein: in response to detecting an increase in the noise in the heartbeat data, the value of the weighting factor is determined such that an effect of prior heartbeat data on the modified heartbeat data is decreased; andin response to detecting a decrease in the noise in the heartbeat data, the value of the weighting factor is determined such that the effect of the prior heartbeat data on the modified heartbeat data is increased.
  • 10. The method of claim 1, further comprising causing, in response to the detection of the seizure event, initiating at least one of a stimulation to tissue of the patient, a reporting of the occurrence of the seizure event, and a recording of the seizure event.
  • 11. The method of claim 1, wherein the activity data includes accelerometer data, body temperature data, electromyography data, perspiration data, impedance data, or a combination thereof.
  • 12. The method of claim 1, wherein in response to the activity data indicating an increased activity level of the patient, the value of the weighting factor is determined such that an effect of prior heartbeat data on the modified heartbeat data is decreased.
  • 13. A medical device comprising: a first interface to receive heartbeat data of a patient;a second interface to receive activity data of the patient, wherein the activity data includes an activity value related to an activity level of the patient that is measured independently of the heartbeat data; anda processor configured to: determine one of a plurality of activity value ranges to which the activity value belongs;determine a weighting factor based on the determined activity value range, each of the plurality of activity value ranges associated with a different one of a plurality of predetermined weighting factors;determine modified heartbeat data by applying the weighting factor to at least a portion of the heartbeat data; anddetect a seizure event based on the modified heartbeat data.
  • 14. The medical device of claim 13, wherein determining the modified heartbeat data includes determining a background (BG) heart rate based on a previously-determined BG heart rate, a most recent R-R interval, and the weighting factor.
  • 15. The medical device of claim 14, wherein the BG heart rate is determined as a sum of a first value and a second value, wherein the first value is the weighting factor times the previously-determined BG heart rate and the second value is one minus the weighting factor times the most recent R-R interval.
  • 16. The medical device of claim 14, wherein determining the modified heartbeat data further includes determining a foreground (FG) heart rate based on one or more R-R intervals of the heartbeat data, wherein the seizure event is detected by comparing a ratio of the FG heart rate and the BG heart rate to a seizure detection threshold.
  • 17. The medical device of claim 13, wherein the processor is configured to detect an indication of noise in the heartbeat data, wherein in response to the noise in the heartbeat data increasing, the processor determines the value of the weighting factor such that an effect of prior heartbeat data on the modified heartbeat data is decreased, and wherein, in response to the noise in the heartbeat data decreasing, the processor determines the value of the weighting factor such that the effect of the prior heartbeat data on the modified heartbeat data is increased.
  • 18. The medical device of claim 13, wherein the processor, in response to the detection of the seizure event, provides a signal to at least one of stimulation device disposed to provide stimulation to tissue of the patient, a signal indicating the occurrence of the seizure event, and a signal initiating the recording of the seizure event.
  • 19. The medical device of claim 13, wherein activity data includes accelerometer data, body temperature data, electromyography data, perspiration data, impedance data, or a combination thereof.
  • 20. The medical device of claim 13, wherein, in response to the activity data indicating an increased activity level of the patient, the processor determines the value of the weighting factor such that an effect of prior heartbeat data on the modified heartbeat data is decreased.
  • 21. A non-transitory computer-readable medium storing instructions that are executable by a processor to cause the processor to perform operations including: receiving heartbeat data of a patient;receiving activity data of the patient, wherein the activity data includes an activity value related to an activity level of the patient that is measured independently of the heartbeat data;determining one of a plurality of activity value ranges to which the activity value belongs;determining a weighting factor based on the determined activity value range, each of the plurality of activity value ranges associated with a different one of a plurality of predetermined weighting factors;determining modified heartbeat data by applying the weighting factor to at least a portion of the heartbeat data; anddetecting a seizure event based on the modified heartbeat data.
US Referenced Citations (211)
Number Name Date Kind
4702254 Zabara Oct 1987 A
4867164 Zabara Sep 1989 A
4920979 Bullara May 1990 A
4979511 Terry, Jr. Dec 1990 A
5012411 Policastro et al. Apr 1991 A
5025807 Zabara Jun 1991 A
5081987 Nigam Jan 1992 A
5137020 Wayne et al. Aug 1992 A
5154172 Terry, Jr. et al. Oct 1992 A
5179950 Stanislaw Jan 1993 A
5186170 Varrichio et al. Feb 1993 A
5188104 Wernicke et al. Feb 1993 A
5205285 Baker, Jr. Apr 1993 A
5215086 Terry, Jr. et al. Jun 1993 A
5215089 Baker, Jr. Jun 1993 A
5222494 Baker, Jr. Jun 1993 A
5231988 Wernicke et al. Aug 1993 A
5235980 Varrichio et al. Aug 1993 A
5237991 Baker, Jr. et al. Aug 1993 A
5263480 Wernicke et al. Nov 1993 A
5269302 Swartz et al. Dec 1993 A
5269303 Wernicke et al. Dec 1993 A
5299569 Wernicke et al. Apr 1994 A
5304206 Baker, Jr. et al. Apr 1994 A
5330507 Schwartz Jul 1994 A
5330515 Rutecki et al. Jul 1994 A
5335657 Terry Aug 1994 A
5458625 Kendall Oct 1995 A
5522862 Testerman et al. Jun 1996 A
5531778 Maschino et al. Jul 1996 A
5540730 Terry, Jr. et al. Jul 1996 A
5540734 Zabara Jul 1996 A
5571150 Wernicke et al. Nov 1996 A
5601435 Quy Feb 1997 A
5611350 John Mar 1997 A
5690681 Geddes et al. Nov 1997 A
5690688 Noren et al. Nov 1997 A
5700282 Zabara Dec 1997 A
5707400 Terry, Jr. et al. Jan 1998 A
5720771 Snell Feb 1998 A
5743860 Hively et al. Apr 1998 A
5814092 King Sep 1998 A
5913882 King Jun 1999 A
5916239 Geddes et al. Jun 1999 A
5928272 Adkins et al. Jul 1999 A
5995868 Dorfmeister et al. Nov 1999 A
6016449 Fischell et al. Jan 2000 A
6018682 Rise Jan 2000 A
6041258 Cigaina et al. Mar 2000 A
6061593 Fischell et al. May 2000 A
6073048 Kieval et al. Jun 2000 A
6104956 Naritoku et al. Aug 2000 A
6205359 Boveja Mar 2001 B1
6208894 Schulman et al. Mar 2001 B1
6208902 Boveja Mar 2001 B1
6221908 Kilgard et al. Apr 2001 B1
6240316 Richmond et al. May 2001 B1
6269270 Boveja Jul 2001 B1
6304775 Iasemidis et al. Oct 2001 B1
6324421 Stadler et al. Nov 2001 B1
6337997 Rise Jan 2002 B1
6339725 Naritoku et al. Jan 2002 B1
6341236 Osorio et al. Jan 2002 B1
6356788 Boveja Mar 2002 B2
6366814 Boveja et al. Apr 2002 B1
6459936 Fischell et al. Oct 2002 B2
6473639 Fischell et al. Oct 2002 B1
6473644 Terry, Jr. et al. Oct 2002 B1
6484132 Hively et al. Nov 2002 B1
6505074 Boveja et al. Jan 2003 B2
6549804 Osorio et al. Apr 2003 B1
6556868 Naritoku et al. Apr 2003 B2
6564102 Boveja May 2003 B1
6587719 Barrett et al. Jul 2003 B1
6587727 Osorio et al. Jul 2003 B2
6600956 Maschino et al. Jul 2003 B2
6606523 Jenkins Aug 2003 B1
6609025 Barrett et al. Aug 2003 B2
6610713 Tracey Aug 2003 B2
6611715 Boveja Aug 2003 B1
6615081 Boveja Sep 2003 B1
6615085 Boveja Sep 2003 B1
6622038 Barrett et al. Sep 2003 B2
6622041 Terry, Jr. et al. Sep 2003 B2
6622047 Barrett et al. Sep 2003 B2
6658294 Zadeh et al. Dec 2003 B1
6662052 Sarwal et al. Dec 2003 B1
6668191 Boveja Dec 2003 B1
6671555 Gielen et al. Dec 2003 B2
6671556 Osorio et al. Dec 2003 B2
6681003 Linder et al. Jan 2004 B2
6684104 Gordon et al. Jan 2004 B2
6684105 Cohen et al. Jan 2004 B2
6708064 Rezai Mar 2004 B2
6721603 Zabara et al. Apr 2004 B2
6760626 Boveja Jul 2004 B1
6764498 Mische Jul 2004 B2
6768969 Nikitin et al. Jul 2004 B1
6819956 DiLorenzo Nov 2004 B2
6904390 Nikitin et al. Jun 2005 B2
6920357 Osorio et al. Jul 2005 B2
6922592 Thompson et al. Jul 2005 B2
6934580 Osorio et al. Aug 2005 B1
6944501 Pless Sep 2005 B1
6959215 Gliner et al. Oct 2005 B2
6961618 Osorio et al. Nov 2005 B2
7006872 Gielen et al. Feb 2006 B2
7043305 KenKnight et al. May 2006 B2
7050856 Stypulkowski May 2006 B2
7054792 Frei et al. May 2006 B2
7076288 Skinner Jul 2006 B2
7079977 Osorio et al. Jul 2006 B2
7134996 Bardy Nov 2006 B2
7146211 Frei et al. Dec 2006 B2
7149572 Frei et al. Dec 2006 B2
7149581 Goedeke Dec 2006 B2
7156808 Quy Jan 2007 B2
7156809 Quy Jan 2007 B2
7164941 Misczynski et al. Jan 2007 B2
7167743 Heruth et al. Jan 2007 B2
7167750 Knudson et al. Jan 2007 B2
7171271 Koh et al. Jan 2007 B2
7188053 Nikitin et al. Mar 2007 B2
7228167 Kara et al. Jun 2007 B2
7231254 DiLorenzo Jun 2007 B2
7236831 Firlik et al. Jun 2007 B2
7242983 Frei et al. Jul 2007 B2
7254439 Misczynski et al. Aug 2007 B2
7263467 Sackellares et al. Aug 2007 B2
7265676 Gordon et al. Sep 2007 B2
7277758 DiLorenzo Oct 2007 B2
7280867 Frei et al. Oct 2007 B2
7282030 Frei et al. Oct 2007 B2
7292890 Whitehurst et al. Nov 2007 B2
7295881 Cohen et al. Nov 2007 B2
7305268 Gliner et al. Dec 2007 B2
7321837 Osorio et al. Jan 2008 B2
7324850 Persen et al. Jan 2008 B2
7324851 DiLorenzo Jan 2008 B1
7340302 Falkenberg et al. Mar 2008 B1
7353064 Gliner et al. Apr 2008 B2
7366572 Heruth et al. Apr 2008 B2
7373199 Sackellares et al. May 2008 B2
7389144 Osorio et al. Jun 2008 B1
7401008 Frei et al. Jul 2008 B2
7403820 DiLorenzo Jul 2008 B2
7483747 Gliner et al. Jan 2009 B2
7894890 Sun et al. Feb 2011 B2
20020072782 Osorio et al. Jun 2002 A1
20020099417 Naritoku et al. Jul 2002 A1
20020151939 Rezai Oct 2002 A1
20020188214 Misczynski et al. Dec 2002 A1
20040122484 Hatlestad et al. Jun 2004 A1
20040122485 Stahmann et al. Jun 2004 A1
20040133119 Osorio et al. Jul 2004 A1
20040138647 Osorio et al. Jul 2004 A1
20040138711 Osorio et al. Jul 2004 A1
20040158119 Osorio et al. Aug 2004 A1
20040199212 Fischell et al. Oct 2004 A1
20050124901 Misczynski et al. Jun 2005 A1
20050143786 Boveja Jun 2005 A1
20050148893 Misczynski et al. Jul 2005 A1
20050148895 Misczynski et al. Jul 2005 A1
20050154425 Boveja et al. Jul 2005 A1
20050177192 Rezai et al. Aug 2005 A1
20050187590 Boveja et al. Aug 2005 A1
20050187796 Rosenfeld et al. Aug 2005 A1
20050192644 Boveja et al. Sep 2005 A1
20050197590 Osorio et al. Sep 2005 A1
20050277998 Tracey et al. Dec 2005 A1
20060009815 Boveja et al. Jan 2006 A1
20060155495 Osorio et al. Jul 2006 A1
20060167497 Armstrong et al. Jul 2006 A1
20060173493 Armstrong et al. Aug 2006 A1
20060224191 Dilorenzo Oct 2006 A1
20060241697 Libbus et al. Oct 2006 A1
20060241725 Libbus et al. Oct 2006 A1
20060293720 DiLorenzo Dec 2006 A1
20070027486 Armstrong Feb 2007 A1
20070088404 Wyler et al. Apr 2007 A1
20070100278 Frei et al. May 2007 A1
20070100392 Maschino et al. May 2007 A1
20070123758 Miesel et al. May 2007 A1
20070208212 DiLorenzo Sep 2007 A1
20070213785 Osorio et al. Sep 2007 A1
20070233192 Craig Oct 2007 A1
20070239210 Libbus et al. Oct 2007 A1
20070244407 Osorio Oct 2007 A1
20070282177 Pilz Dec 2007 A1
20080033508 Frei et al. Feb 2008 A1
20080064934 Frei et al. Mar 2008 A1
20080071327 Miesel et al. Mar 2008 A1
20080081941 Tononi Apr 2008 A1
20080103548 Fowler et al. May 2008 A1
20080119900 DiLorenzo May 2008 A1
20080195166 Sun et al. Aug 2008 A1
20080208285 Fowler et al. Aug 2008 A1
20080234598 Snyder et al. Sep 2008 A1
20080234785 Nakayama et al. Sep 2008 A1
20080269631 Denison et al. Oct 2008 A1
20080319281 Aarts Dec 2008 A1
20090198145 Chow Aug 2009 A1
20100087701 Berka et al. Apr 2010 A1
20110029044 Hyde et al. Feb 2011 A1
20110112381 Sun et al. May 2011 A1
20110270096 Osorio Nov 2011 A1
20110270346 Frei et al. Nov 2011 A1
20110295083 Doelling et al. Dec 2011 A1
20120116183 Osorio May 2012 A1
20120277605 Colborn Nov 2012 A1
20120277618 Giftakis et al. Nov 2012 A1
Foreign Referenced Citations (3)
Number Date Country
2030565 Mar 2009 EP
2007072425 Jun 2007 WO
2013056099 Apr 2013 WO
Non-Patent Literature Citations (13)
Entry
Borovikova, L.V. et al., “Vagus Nerve Stimulation Attenuates the Systemic Inflammatory Response to Endotoxin,” Letters to Nature, Nature, vol. 405, May 25, 2000, pp. 458-462.
Chakravarthy, N. et al., “Controlling Synchronization in a Neuron-Level Population Model,” International Journal of Neural Systems, vol. 17, No. 2, 2007, pp. 123-138.
Chen, C. et al., “Vagal Efferent Fiber Stimulation Ameliorates Pulmonary Microvascular Endothelial Cell Injury by Downregulating Inflammatory Responses,” Inflammation, vol. 36, No. 6, Dec. 2013, pp. 1567-1575.
Dodrill, C.B. et al., “Effects of Vagal Nerve Stimulation on Cognition and Quality of Life in Epilepsy,” Epilepsy & Behavior, vol. 2, Issue 1, 2001, pp. 46-53.
Frei, M.G. et al., “Left Vagus Nerve Stimulation with the Neurocybernetic Prosthesis Has Complex Effects on Heart Rate and on Its Variability in Humans,” Epilepsia, vol. 42, No. 8, 2001, pp. 1007-1016.
Iasemidis, L.D. et al., “Spatiotemporal Transition to Epileptic Seizures: A Nonlinear Dynamical Analysis of Scalp and Intracranial EEG Recordings,” Spatiotemporal Models in Biological and Artificial Systems, IOS Press, 1997, pp. 81-88.
Jaseja, H., “Vagal Nerve Stimulation Technique: Enhancing Its Efficacy and Acceptability by Augmentation with Auto Activation and Deactivation Mode of Operation,” Medical Hypotheses, vol. 63, Issue 1, 2004, pp. 76-79.
Kucera, M., “‘Active Air’ Inhalation Therapy: Autonomic Regulation Mechanisms with Use of Heart Rate Variability Analysis,” Explore! vol. 16, No. 2, 2007, 3 pages.
Malow, B.A. et al., “Vagus Nerve Stimulation Reduces Daytime Sleepiness in Epilepsy Patients,” Neurology, vol. 57, Issue 5, 2001, pp. 879-884.
Valdes-Cruz, A. et al., “Chronic Stimulation of the Cat Vagus Nerve Effect on Sleep and Behavior,” Progress in Neuro-Psychopharmacology & Biological Psychiatry, vol. 26, Issue 1, 2002, pp. 113-118.
Zabara, J., “Neuroinhibition in the Regulation of Emesis,” Space Life Sciences, vol. 3, Issue 3, 1972 pp. 282-292.
International Application No. PCT/US2015/024960, “PCT Search Report and Written Opinion”, dated Jun. 17, 2015, Rijswijk and Munich.
International Application No. PCT/us2015/024879, PCT Search Report and Written Opinion dated Jun. 25, 2015, 13 pages.
Related Publications (1)
Number Date Country
20150305666 A1 Oct 2015 US