JP2009233024A - Vagus nerve stimulation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stimulate the vagus nerve without winding a stimulating electrode around the vagus nerve and without giving an uncomfortable feeling to a patient by adjusting the timing and strength to stimulate the vagus nerve. <P>SOLUTION: An electric stimulation is applied indirectly to the vagus nerve located in the vicinity of the phrenic nerve via the skin or nerve sheath using a stimulating electrode (a body surface electrode or a subcutaneous electrode). Nerve stimulating signals supplied to the stimulating electrode are controlled in such a way that the nerve stimulating signals are supplied to the stimulating electrode during a first period relating to respiration (an inhalation period) and not supplied to the stimulating electrode during a second period (an exhalation period). The stimulating strength of the nerve stimulating signals is determined by a nerve stimulating signal parameter. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vagus nerve stimulation system for performing electrical stimulation therapy to the vagus nerve, and more particularly to a vagus nerve stimulation system capable of stimulating the vagus nerve subcutaneously or indirectly from the body surface.

In recent years, lethal arrhythmia that causes myocardial infarction has become an important problem as a heart disease, but it is effective to apply electrical stimulation to the vagus nerve to prevent this fatal arrhythmia. It is known.
In other words, since the heart rate decreases when electrical stimulation to the vagus nerve is performed, the heart muscle oxygen consumption is decreased with the decrease in the heart rate, thereby preventing or improving myocardial oxygen deficiency. . This prevents the occurrence of myocardial ischemia and the accompanying fatal arrhythmia, which is said to be effective in the treatment and prevention of heart failure.

  In view of the fact that this electrical stimulation to the vagus nerve is effective in the treatment of heart disease, the present inventor has proposed a cardiac treatment device that prevents the occurrence of lethal arrhythmia by electrical stimulation of the vagus nerve. (See Patent Document 1). This proposal defines a permissible range of heart rate, and stimulates the vagus nerve when the heart rate exceeds this permissible range, and stimulates the vagus nerve when the heart rate falls below this permissible range. It is intended to stabilize the heart rate by performing cardiac stimulation rather than performing heartbeat.

JP 2004-173790 A

  However, in the heart treatment device described in Patent Document 1, a nerve electrode is directly wound around the vagus nerve of the neck and attached, but a high level of technology is required for attaching the nerve electrode to the vagus nerve. Become. For this reason, there is a possibility that the vagus nerve may be damaged in an intraoperative operation for attaching the nerve electrode, or the nerve electrode may mechanically press the vagus nerve even after the nerve electrode is attached, and the vagus nerve may be damaged. Furthermore, since various nerves pass through the cervical region, for example, the phrenic nerve (a nerve that controls the vertical movement of the diaphragm) running substantially parallel to the vagus nerve may be damaged. there were.

  In some cases, the nerve electrode must be replaced due to troubles caused by the electrode lead such as disconnection or unexpected infection. In such a case, removing and replacing the nerve electrode wound around the vagus nerve has a problem that it is forced to perform a considerably difficult work. For example, the electrode wound around the vagus nerve adheres firmly to the surrounding tissue and is very difficult to exchange.

  Therefore, there is a need for a method for stimulating the vagus nerve without requiring the troublesome task of wrapping the nerve electrode around the vagus nerve, and as one proposal, the vagus nerve is indirectly stimulated from the body surface or subcutaneous part. It is possible. However, on the other hand, since there are many parallel nerves in the vagus nerve, it is extremely difficult to give a necessary stimulus only to the vagus nerve without affecting those nerves.

  By the way, in the technique of Patent Document 1, a nerve electrode is wound around the vagus nerve of the cervix, and this vagus nerve runs vertically downward between the internal jugular vein in the carotid sheath and the common carotid artery. There is a nerve. In addition, as described above, the phrenic nerve that governs the movement of the diaphragm runs just outside the carotid sheath. Therefore, when the nerve electrode is placed subcutaneously or on the body surface and the vagus nerve is stimulated, there is a high possibility of stimulating not only the vagus nerve but also the phrenic nerve.

  In this way, when stimulating the vagus nerve, suddenly strong stimulation or continuous stimulation is applied to the phrenic nerve, which may cause breathing disturbance due to hiccups or strange diaphragm movement. appear. It goes without saying that this disorder of breathing gives the patient a sense of discomfort and discomfort. To eliminate this discomfort, it is only necessary to adjust the vagus nerve stimulation signal so that even if the phrenic nerve is stimulated during vagus nerve stimulation, breathing disturbance associated with hiccups or strange diaphragm movement does not occur. . In other words, considering the timing of stimulation to the vagus nerve, the diaphragm movement similar to normal breathing may be performed even if not only the vagus nerve but also the phrenic nerve is stimulated. For this reason, it is necessary to control the vagus nerve intermittently and to smoothly control the intensity thereof.

  The present invention has been made to solve the above-mentioned problems, and even when there is a trouble or infection caused by the electrode lead as described above, the nerve stimulation electrode can be easily removed and stray. An object of the present invention is to provide a vagus nerve stimulation system that minimizes the influence on nerves other than the nerve, particularly the influence on the phrenic nerve. Therefore, in the present invention, based on the movement of the diaphragm when the stimulation to the vagus nerve reaches the phrenic nerve, by adjusting the timing and intensity of stimulation of the vagus nerve, The vagus nerve can be stimulated even if direct contact between the nerve electrode and the vagus nerve is avoided.

  In order to solve the above problems and achieve the object of the present invention, the present invention provides an electrode for indirectly applying electrical stimulation to the vagus nerve located in the vicinity of the phrenic nerve, and connected to this electrode. A vagus nerve stimulation system including a stimulation device that generates a nerve stimulation signal for stimulating the vagus nerve. In this vagus nerve stimulation system, a first period for supplying a nerve stimulation signal to the electrode and a second period for not supplying the nerve stimulation signal to the electrode are set, and at least a part of the nerve stimulation signal is set in the first period. It is characterized in that the stimulation intensity increases gradually and / or gradually decreases with time. Here, “directly applying electrical stimulation” refers to stimulating the vagus nerve by placing an electrode outside the carotid artery sheath without directly winding the electrode around the vagus nerve. Examples of electrode placement include placing an electrode on the skin, placing an electrode between the skin and the cervical muscle, placing an electrode between the cervical and sternocleidomastoid muscles, and attaching the electrode directly to the carotid artery sheath. is there.

  Moreover, as a preferable form of this invention, the case where the electrode used for vagus nerve stimulation is a body surface electrode with which the body surface is mounted | worn, and the subcutaneous electrode implanted subcutaneously are considered. The stimulation device can be classified into an external stimulation device provided outside the body and an implantable stimulation device embedded in the body, depending on whether the body surface electrode or the subcutaneous electrode is used.

  Further, as a preferred form of the present invention, the nerve stimulation signal supplied to the nerve stimulation electrode is composed of a plurality of electrical pulses, and the gradual increase and / or decrease of the nerve stimulation signal is performed by this electric stimulation. This is done by adjusting the parameters of the target pulse.

  As the electrical pulse parameters, at least one of the period between pulses, the pulse width, the number of pulses, the pulse current, and the pulse voltage, or a plurality of combinations selected from these are considered. Some patterns of parameter adjustment include a method of changing an amplitude value of a pulse current or a pulse voltage, and a method of changing a pulse interval (the same for frequency).

  Further, in a preferred embodiment of the present invention, the gradual increase portion of the stimulation intensity applied to the electrode is made in a predetermined period after the start of the first period, and the gradual decrease portion of the stimulation intensity applied to the electrode in the first period is The predetermined period before the end of the first period is set.

  Furthermore, in a preferred embodiment of the present invention, a sensor for detecting motion is provided, and at least one of the first period and the second period is adjusted based on the sensor output. Here, an acceleration sensor or a body motion sensor is used as a sensor for detecting motion.

  In a preferred embodiment of the present invention, when these sensors detect movement, in addition to performing control to shorten the second period, control is performed to further shorten the first period as necessary. .

Further, as a preferred form of the present invention, a means for detecting respiration is provided, and when respiration is detected, the start of the first period is delayed. Here, detection of respiration is performed based on measurement of impedance of the chest.
Further, as a preferred embodiment of the present invention, the vagus nerve is stimulated after the generation of the nerve stimulation signal or before the nerve stimulation signal is generated, or the vagus nerve is stimulated in the near future. Informing means for informing this is provided. The notification means may be an alarm (buzzer) that emits an audible sound or a visible indicator that can be visually confirmed by the patient.

  Furthermore, as a preferred embodiment of the present invention, there is provided a heart rate measuring means for measuring a heart rate (or a heart beat interval measuring means for measuring a heart beat interval), and the output of the heart rate measuring means falls below a predetermined value. Control is performed so as to stop the generation of the nerve stimulation signal when it exceeds a predetermined value in the case of a heartbeat interval. The heart rate (or heart rate interval) is measured based on the output of a pulse wave sensor arranged in the vicinity of the electrode to which the nerve stimulation signal is supplied. As this pulse wave sensor, a pressure sensor is usually used. Usually, as will be described later, the stimulation electrode for stimulating the vagus nerve and the pulse wave sensor for detecting pulsation are integrally attached to the body surface (in the case of a body surface electrode) or applied to the subcutaneous tissue. Attached (for subcutaneous electrodes). Instead of the above-described pulse wave sensor, heart rate information can also be obtained using electrocardiogram information.

  According to the present invention, when stimulating the vagus nerve, the timing of the vagus nerve and the intensity of the stimulation are adjusted so that the influence on the respiratory motion of the patient is reduced. Even in the case of the phrenic nerve, strange diaphragm movements (occurrence of “hiccups”, etc.) can be suppressed as much as possible, and discomfort and discomfort given to the patient can be removed. Therefore, the troublesome work of wrapping the nerve stimulation electrode around the vagus nerve as in the past can be avoided, and the vagus nerve can be stimulated simply by attaching the stimulation electrode to the body surface or subcutaneously.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the overall configuration of the first embodiment of the present invention.
The present embodiment is configured by a vagus nerve stimulation apparatus 100 and a body surface electrode (or subcutaneous electrode) 200 having a built-in pulse wave sensor 201. The pulse wave sensor 201 is usually a pressure sensor, and detects fluctuations (pulsations) in the internal pressure of the carotid artery.

  The vagus nerve stimulation apparatus 100 includes a pulse wave detection means 10 that detects pulsation from the pulse wave sensor 201 and an exercise level that detects a signal from the exercise sensor 20 that detects whether the body is in motion. Detection means 21 is provided. The motion sensor 20 is a sensor that is attached to the patient's body and detects the motion state of the patient. For example, the motion sensor 20 is the same as an acceleration sensor or a vibration sensor used in a pacemaker.

  The pulse wave detection means 10 is connected to a heart rate measurement means 11 that measures a heart rate from pulsation, and the heart rate measurement means 11 is connected to one input terminal of the heart rate limit value comparison means 13. The heart rate limit value storage means 12 is connected to the other input terminal of the heart rate limit value comparison means 13.

  Further, the exercise level detection means 21 is connected to the first period selection means 22 and the second period selection means 23. Here, the first period is a period in which the nerve stimulation signal is supplied to the body surface electrode (or subcutaneous electrode) 200, and the second period is a period in which the nerve stimulation signal is not supplied. The first period selection means 22 is a means for determining (selecting) the first period based on the patient's exercise level detected by the exercise level detection means 21, and the second period selection means 23 is similarly detected by the patient's exercise. This is means for determining (selecting) the second period based on the level.

  The first period selection unit 22 is connected to the first period timer 24, and the second period selection unit 23 is connected to the second period timer 25. Then, the first period selected by the first period selecting means 22 is loaded into the first period timer 24, and similarly, the second period selected by the second period selecting means 23 is loaded into the second period timer 25. . The second period timer 25 is connected to the first period timer 24, and the reset and start of the count of the first period timer 24 are determined by a signal from the second period timer 25. On the other hand, the output of the first period timer 24 is configured to be sent to the second period timer 25, and the count of the second period timer 25 is reset and started by the output of the first period timer 24.

  Further, the exercise level detection means 21 is connected to the nerve stimulation signal parameter adjustment means 27. The nerve stimulation signal parameter adjusting means 27 is a means for adjusting the type and intensity of a nerve stimulation signal parameter, which will be described later, according to the patient's movement level detected by the movement level detection means 21. The nerve stimulation signal parameter adjusting means 27 is connected to the nerve stimulation signal generating means 26. The nerve stimulation signal generating means 26 is connected to the first period timer 24 and the heart rate limit value comparing means 13 described above. A start / stop signal for controlling the start and stop of the operation is supplied from the first period timer 24 to the nerve stimulation signal generating means 26. The heart rate limit value comparing means 13 is supplied with an on / off signal for determining whether or not to enter the operating state to the nerve stimulation signal generating means 26.

  The nerve stimulation signal generating means 26 is activated only when there is a signal from the heart rate limit value comparing means 13, that is, when the measured heart rate is larger than the limit value, and otherwise (the measured heart rate is When it is smaller than the limit value), it is controlled so as to be inactive. The nerve stimulation signal is supplied to the body surface electrode (or subcutaneous electrode) only when the nerve stimulation signal generating means 26 is in the operating state and only during the period counted by the first period timer 24. Yes. The stimulation intensity of the nerve stimulation signal is controlled based on the signal supplied from the nerve stimulation signal parameter adjusting means 27 to the nerve stimulation signal generating means 26 so that the stimulation intensity is optimal for the patient's condition at that time. Is done.

  Further, in the vagus nerve stimulation apparatus 100 of the present embodiment example, an indicator 28 is connected to the nerve stimulation signal generating means 26. The indicator 28 may emit an alarm such as a buzzer, or may be visually informed such as blinking of a light emitting diode. In any case, the nerve stimulation signal for stimulating the vagus nerve is supplied to the body surface electrode (or subcutaneous electrode), or will be supplied soon, or the supply of the nerve stimulation signal is It is for informing the patient of how long it will be finished.

  FIG. 2 shows the structure of a body surface electrode (or subcutaneous electrode) 200 for stimulating the vagus nerve 202. As described above, the vagus nerve 202 is a nerve that runs vertically downward between the internal jugular vein in the carotid sheath and the common carotid artery. It has already been explained that the phrenic nerve that governs the movement of the diaphragm coexists immediately outside the carotid sheath. As shown in FIG. 2, the body surface electrode 200 includes a pair of stimulation electrodes 2a and 2b arranged on the upper portion of the carotid artery sheath 4 through the skin, and a pulse for detecting pulsation of the carotid artery between the pair of electrodes. The wave sensor 3 is arranged. As described above, this pulse wave sensor is a kind of pressure sensor. In this embodiment, the pulse wave sensor 3 and the stimulation electrodes 2 a and 2 b are formed integrally with the fixing member 5. In the case of the body surface electrode, the surface of the stimulation electrodes 2a and 2b is coated with an adhesive gel for increasing the conductivity with the skin, and the fixing member 5 is adhered to the surface of the body with an adhesive or a double-sided tape. It has come to be attached. In the case where the stimulation electrode 2 is an implantable subcutaneous electrode, the structure is fixed by being tied to a portion near the carotid artery sheath using a thread (not shown) in the subcutaneous portion.

  FIG. 3 shows the state of the nerve stimulation signal supplied to the body surface electrode (or subcutaneous electrode). The horizontal axis is time, and the pulsed nerve stimulation signal is generated in the first period as described above. In the second period, no nerve stimulation signal is issued. FIGS. 4A and 4B are diagrams illustrating an example of controlling the stimulation intensity of the nerve stimulation signal pulse generated in the first period. As an example, as shown in FIG. 4 (a), the amplitude of the stimulation signal pulse is gradually increased for a while from the start of the first period, and then the amplitude of the stimulation signal pulse is kept constant, and then the first period. Control is performed so that the amplitude of the stimulation signal pulse gradually decreases after the end of the period.

FIG. 4B shows an example in which the stimulation intensity is gradually increased and decreased by controlling the frequency of the nerve stimulation signal pulse generated in the first period. As shown in FIG. 4 (b), the frequency of the stimulation signal pulse is increased for a while from the beginning of the first period, and a predetermined period of time is allowed to remain at a high frequency near the center of the first period. After that, the frequency is lowered for a while.
Even if the amplitude control of FIG. 4A or the frequency control of FIG. 4B is used, a strong stimulation signal is gradually weakened at first without adding a strong stimulation signal to the vagus nerve. After that, the original weak stimulus signal is gradually used, and the stimulus signal is stopped at the end of the first period.

  By controlling the stimulation intensity of the nerve stimulation signal in this way, even if this nerve stimulation signal reaches the phrenic nerve, the diaphragm slowly contracts in the portion where the stimulation intensity in the initial period of the first period is gradually increased. As a result, inspiration is performed, the diaphragm maintains its contraction in the part where the stimulation intensity is maintained, and exhalation due to the slow relaxation of the diaphragm is performed in the part where the stimulation intensity at the end of the first period is gradually reduced, Breathing is performed by smooth diaphragm movement. In addition, as described above, the selection of the first period and the second period according to the detection of the exercise level and the adjustment of the type and intensity of the parameters of the nerve stimulation signal are also performed, so that the patient can get a little uncomfortable during exercise Neural stimulation treatment can be performed. In addition, the indicator allows the patient to know that the nerve stimulation signal has been delivered, will be delivered soon, or how long the nerve stimulation signal delivery will end. By performing breathing in accordance with the indicator, it is possible to perform a vagus nerve stimulation treatment without a sense of incongruity.

Next, the operation of the embodiment of the present invention will be described based on the flowchart of FIG.
When the processing is started, first, nerve stimulation signal parameters are initialized in the nerve stimulation signal parameter adjusting means 27 shown in FIG. 1 (step S1). As an initial set value, a parameter of a nerve stimulation signal supplied at rest is selected. Here, as a parameter of the nerve stimulation signal, a period (or frequency) between pulses of the nerve stimulation signal pulse, a pulse width, the number of pulses, a pulse current, a pulse voltage, and the like can be considered. In step S1, it is determined which of these parameters is specifically used, which two (or a plurality of) parameters are used to control stimulation of the vagus nerve, and the like. For example, as some patterns, a method of changing the amplitude value of the pulse current or pulse voltage (the method of FIG. 4A) or a method of changing the pulse interval (the same for the frequency) (the method of FIG. 4B). ) And the like.

  Next, the first period selection means 22 loads the initial value of the first period into the first period timer 24 (step S2). As described above, this first period is a period during which a nerve stimulation signal is supplied to the vagus nerve. If this nerve stimulation signal reaches the phrenic nerve, it corresponds to one breathing time. Usually, the initial value setting for this first period is set to the resting breathing time when not exercising. For example, when a patient who breathes 10 times per minute at rest is a wearing subject, the time for one breath is 6 seconds. Therefore, these 6 seconds are loaded as the initial value of the first period timer 24.

  Subsequently, the second period selection means 23 loads the initial value of the second period into the second period timer 25 (step S3). This second period is a period during which no nerve stimulation signal is supplied to the vagus nerve, and if set to an integral multiple of the time set as the first period, the patient can breathe spontaneously during this period and there is little discomfort . If the second period is set to be long, the effect of the vagus nerve stimulation treatment is reduced, and if it is too short, the patient's breathing may be disturbed. Therefore, it is desirable to set it to several times the first period.

  When the initial first period and the second period are set in steps S2 and S3, the period is notified to the indicator 28 shown in FIG. 1 as the notification means (step S4). Here, what is important is the first period in which the nerve stimulation signal is supplied to the vagus nerve, and the notification by the indicator 28 is performed immediately before or just after the period starts. As the indicator 28, a visual indicator in which light is blinked by a light emitting means such as an LED, or an indicator by a sound that emits a buzzer sound by a sounding means such as a speaker can be used.

  Next, the first period timer 24 starts counting the first period, and a start signal is supplied to the nerve stimulation signal generation means 26. The nerve stimulation signal generation means 26 is adjusted by the nerve stimulation signal parameter adjustment means 27. Based on the parameters of the neural stimulation signal, a neural stimulation signal is generated for the stimulation electrode (step S6). Note that the nerve stimulation signal is generated only when an ON signal permitting stimulation of the vagus nerve is supplied from the heart rate limit value comparison means 13 to the nerve stimulation signal generation means 26. This will be described in the next step S7 and subsequent steps.

As described above, the result of the heart rate measurement by the heart rate measuring means 11 has an influence on the generation of the nerve stimulation signal in step S6. In the following steps, processing related to heart rate measurement will be described.
First, based on the pulsation signal from the pulse wave sensor 201 provided in the body surface electrode (or subcutaneous electrode) 200, the heart rate is measured by the heart rate measuring means 11 (step S7). Subsequently, the heart rate limit value comparison unit 13 compares the measured heart rate with the lower limit value stored in the heart rate limit value storage unit 12 (step S8). Here, the heart rate stored as the lower limit value is set by the doctor based on the physical condition of the patient, but usually 40 to 50 which is slightly smaller than the heart rate at rest. Set to about times. The vagus nerve stimulation reduces the heart rate, but if the heart rate falls below this lower limit, the patient may be dizzy, so the lower limit of the heart rate when stimulating the vagus nerve in advance If the heart rate becomes lower than the lower limit value, control is performed so as not to stimulate the vagus nerve.

  If it is determined in step S8 that the measured heart rate is greater than the lower limit value stored in the heart rate limit value storage unit 12, that is, if it is determined that the vagus nerve may be stimulated, Subsequently, it is determined whether or not the first period timer 24 has timed out (step S9). That is, it is determined whether or not the first period timer 24 is counting the first period (intake period) set in step S2. If during the first period, the first period timer 24 has not timed out, the process returns to step S8, and if it is determined that the first period timer 24 has timed out, the generation of the neural stimulation signal is stopped (step). S10). In step S10, generation of the nerve stimulation signal is stopped, but control may be performed so that the stimulation intensity of the nerve stimulation signal is weakened.

  When it is determined in step S8 that the heart rate is smaller than the lower limit value (NO in step S8), the heart rate limit value comparison unit 13 causes the nerve stimulation signal generation unit 26 to stop its operation. Supply an off signal for Then, upon receiving this off signal, the nerve stimulation signal generating means 26 stops generating the nerve stimulation signal (step S11) and waits for the first period timer 24 to time out (step S12). After the nerve stimulation signal is stopped in step S10 or after the first period timer 24 is timed out in step S12, the second period timer 25 starts counting (step S13). Then, it waits for the second period timer 25 to finish counting (time out) (step S14). When the second period timer 25 times out, the process proceeds to the next step (A) (see FIG. 6).

  Next, the operations of the motion sensor 20 and the motion level detection means 21 will be described with reference to FIG. First, the motion level of the patient is detected by the motion sensor 20 and the motion level detection means 21 (step S15). As the patient exercises, their breathing time decreases and diaphragm contraction increases. Assuming that the nerve stimulation signal by the nerve stimulation signal parameter reaches the phrenic nerve during exercise during the first period, the second period, and the resting period. Spontaneous breathing exercises coexist, resulting in irregular diaphragm movements and patient discomfort. Therefore, during exercise, the first period and the second period in which the respiratory time is short and the diaphragm contraction is strong so that the patient does not feel discomfort even if the nerve stimulation signal reaches the phrenic nerve There will be a need to adjust the neural stimulation signal parameters.

  First, the first period selection means 22 selects a first period corresponding to the detected exercise level, and this is loaded into the first period timer 24 (step S16). The nerve stimulation signal parameter adjustment means 27 receives the signal from the movement level detection means 21, and adjusts the nerve stimulation signal parameters such as the pulse current and pulse voltage of the nerve stimulation signal pulse described above to parameters corresponding to the movement level. Is supplied to the nerve stimulation signal generating means 26 (step S17). Subsequently, a second period corresponding to the exercise level is selected by the second period selecting means 23, and this is loaded into the second period timer 25 (step S18), and the process returns to step S4 (see FIG. 5B). Then, based on the first period, the second period, and the nerve stimulation signal parameter corresponding to the newly set exercise level, the loop process from step S4 to step S18 shown in FIGS. 5 and 6 is repeated.

FIG. 7 is a block diagram showing a second embodiment of the vagus nerve stimulation system of the present invention.
The same blocks as those in the first embodiment shown in FIG.
The difference from the first embodiment shown in FIG. 1 is that an electrocardiogram signal from the electrocardiogram / chest impedance measurement electrode 30 is used as means for measuring the heart rate. That is, in the first embodiment shown in FIG. 1, the pulse rate sensor 201 provided in the body surface electrode (or subcutaneous electrode) 200 detects the pulsation of the carotid artery and measures the heart rate. In the second embodiment, the R wave is detected from the electrocardiogram using the R wave detecting means 33 and the heart rate is derived.

  Here, the R wave is a waveform having the largest amplitude among the waveforms appearing on the electrocardiogram for each heartbeat. Usually, the waveform that appears on the electrocardiogram for each heartbeat is largely composed of five waves, P, Q, R, S, and T waves, and the most prominent among them is the R wave (also called QRS wave). It appears when the ventricle contracts.

In addition, the chest impedance is measured from the electrocardiogram / chest impedance measurement electrode 30 used when measuring the electrocardiogram, and the presence or absence of breathing is detected from the measured chest impedance. Here, the operation of the chest impedance and impedance measuring means 31 and the respiration detecting means 32 will be described.
First, the chest impedance is an impedance measured by passing a weak current through the chest through the electrocardiogram / chest impedance measurement electrode 30. This chest impedance is known to change as air enters and leaves the lungs. If the chest impedance in the state of exhaling is the baseline, the chest impedance decreases from the baseline during inspiration. During exhalation, the chest impedance reverses and increases and returns to the baseline again.

  Therefore, by measuring the chest impedance by the impedance measuring means 31, the respiration detecting means 32 can detect the presence or absence of respiration, and a threshold value slightly smaller than the baseline of the chest impedance is set in advance and measured. When the chest impedance is smaller than this threshold, it is determined that respiration is being performed, and when it is greater than the threshold, it is determined that respiration has ended. The respiration detection means 32 is connected to the first period timer 24, and the start and reset of the first period timer 24 are controlled by the output of the respiration detection means 32, and the respiration detection means 32 is a second period timer. 25, and the output of the second period timer 25 is supplied to the respiration detection means 32.

Then, the start and reset of the first period timer 24 can be controlled by the relationship between the respiration detection by the respiration detection means 32 and the output of the second period timer 25 to delay the start of the first period. That is, if it is determined by the respiration detecting means 32 that the respiration is being performed after the second period when the vagus nerve is not stimulated (after the time-out of the second period timer 25), the respiration is terminated. Wait for the first period (neural stimulation) to begin. As a result, the nerve stimulation signal is supplied after waiting for the spontaneous breathing to end. Therefore, even if the nerve stimulation signal reaches the phrenic nerve, it does not interfere with the spontaneous breathing.
The block configuration and operation other than those described above are the same as those in the first embodiment shown in FIG.

  Next, the operation of the second embodiment of the present invention shown in FIG. 7 will be described based on FIG. 8 and FIG. However, the operations from step S1 to step S13 in FIG. 8 are substantially the same as the operations from step S1 to step S13 used in the description of the operation of the first embodiment shown in FIG. Is omitted.

  The different operations of the first embodiment (explained based on FIGS. 1 to 6) and the second embodiment are the heart rate detection operation (step S7 in FIG. 5) and the respiratory detection means using the chest impedance. 32. As already described, the heart rate detection operation does not need to be described again because only the R wave detection means from the electrocardiogram is used in place of the pulse wave sensor 201. Hereinafter, respiration detection will be described based on the flowchart shown in FIG.

  First, when the count of the second period timer 25 in step S13 in FIG. 8 is started, the process proceeds to (A) in FIG. 9 as the next step. Then, it is determined whether or not the second period timer 25 has timed out (step S14). After the second period has been counted (timed out), it is determined whether or not the respiration is detected by the respiration detection means 32 of FIG. 7 (step S20).

  If respiration is detected in step S20, that is, if the measured chest impedance is smaller than the threshold value, it is subsequently determined whether or not the detected respiration has ended (step S21). Here, the end of breathing means that the measured chest impedance exceeds the threshold value. Only when it is confirmed that the breathing has ended, the first period for performing nerve stimulation is started. Steps S15 to S18 in FIG. 9 are the same as the flow described in FIG.

As described above, the first embodiment and the second embodiment of the present invention both have a lower heart rate than the lower limit of a value that is slightly smaller than the resting heart rate. When the value falls below the value, stimulation of the vagus nerve is stopped. Further, according to the exercise level obtained from the motion sensor 20, a first period in which nerve stimulation is performed and a second period in which nerve stimulation is not performed are set, and nerve stimulation signal parameters are adjusted.
In particular, in the second embodiment of the present invention, since the heart rate is measured based on the electrocardiogram information, the electrocardiogram / thoracic impedance measurement electrode 30 used when taking the electrocardiogram information is used to detect respiration from the change in the chest impedance. The presence or absence is detected, and the timing of nerve stimulation is adjusted according to the state of this breathing.

As described above, in the embodiment of the present invention, when stimulating the vagus nerve, the timing for stimulating the vagus nerve and the intensity of the stimulation are adjusted in accordance with the patient's exercise level and breathing. Even if the stimulation to the phrenic nerve passes through the neighborhood, it is possible to suppress strange diaphragm movement (occurrence of "hiccup" etc.) as much as possible, and without disturbing spontaneous breathing during exercise, It is possible to perform vagus nerve stimulation treatment with less discomfort.
Therefore, unlike the prior art, there is no need to perform a troublesome work for stimulating the vagus nerve without affecting the phrenic nerve, such as winding the nerve stimulation electrode directly around the vagus nerve.
The vagus nerve stimulation system of the present invention can be used not only for the prevention and treatment of lethal arrhythmia and heart failure, but also with other multiple treatments that involve stimulation of the cervical vagus nerve (epileptic, depression, anxiety, Alzheimer's disease, It can be used for migraine).

  Although the vagus nerve stimulation system of the present invention has been described based on the illustrated embodiment, the present invention is not limited to the above-described embodiment, and departs from the gist of the present invention described in the claims. It goes without saying that the present invention extends to other application examples and modifications as long as it is not.

It is a block block diagram which shows the example of 1st embodiment of this invention. It is an example of the body surface electrode or subcutaneous electrode used for the example of 1st embodiment of this invention. It is a figure which shows the relationship between a 1st period, a 2nd period, and a nerve stimulation signal. It is an example which changes the intensity | strength of the nerve stimulation performed in a 1st period, (a) is an example which changes the amplitude of the electric current or voltage of a nerve stimulation pulse, (b) is an example which changes the frequency of a nerve stimulation pulse. . It is a flowchart for demonstrating operation | movement of the example of 1st embodiment of this invention. It is a continuation of the flowchart for demonstrating operation | movement of the example of 1st embodiment of this invention. It is a block block diagram which shows the example of 2nd embodiment of this invention. It is a flowchart for demonstrating the operation | movement of the 2nd embodiment of this invention. It is a continuation of the flowchart for demonstrating operation | movement of the 2nd embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Vagus nerve stimulation apparatus, 2a, 2b, 200 ... Body surface electrode (stimulation electrode) 3, 201 ... Pulse wave sensor, 10 ... Pulse wave detection means, 11 ... Heart rate Measuring means, 12 ... heart rate limit value storage means, 13 ... heart rate limit value comparison means, 20 ... motion sensor, 21 ... exercise level detection means, 22 ... first period selection means , 23 ... second period selection means, 24 ... first period timer, 25 ... second period timer, 26 ... nerve stimulation signal generation means, 27 ... nerve stimulation signal parameter adjustment means, 28 ... Indicator, 30 ... Electrocardiogram / chest impedance measurement electrode, 31 ... Impedance detection means, 32 ... Respiration detection means

Claims (18)

An electrode that indirectly provides electrical stimulation to the vagus nerve located in the vicinity of the phrenic nerve;
A vagus nerve stimulation system comprising a stimulation device that generates a nerve stimulation signal for stimulating the vagus nerve by connecting to the electrode,
A first period for supplying the nerve stimulation signal to the electrode and a second period for not supplying the nerve stimulation signal to the electrode are set,
In the first period, the stimulation intensity of at least a part of the nerve stimulation signal gradually increases and / or decreases with time.   The vagus nerve stimulation system according to claim 1, wherein the electrode is a body surface electrode attached to a body surface, and the stimulation device is an extracorporeal stimulation device provided outside the body.   The vagus nerve stimulation system according to claim 1, wherein the electrode is a subcutaneous electrode implanted under the skin, and the stimulation device is an implantation type stimulation device implanted in a body.   The vagus nerve stimulation system according to any one of claims 1 to 3, wherein the nerve stimulation signal includes a plurality of electrical pulses.   5. The vagus nerve stimulation system according to claim 4, wherein the gradual increase and / or decrease of the neural stimulation signal is performed by adjusting various parameters of the electrical pulse.   The parameter is at least one of a period or frequency, a pulse width, a pulse number, a pulse current, and a pulse voltage of the electrical pulse, or a plurality of combinations selected from these. 5. The vagus nerve stimulation system according to 5.   The vagus nerve stimulation system according to claim 5, wherein the adjustment of the parameter is performed by changing an amplitude value of the pulse current or pulse voltage.   The vagus nerve stimulation system according to claim 5, wherein the adjustment of the parameter is performed by changing the pulse interval or the frequency.   The portion of the stimulation intensity of the nerve stimulation signal applied to the electrode in the first period is a predetermined period after the start of the first period, and is applied to the electrode in the first period. The vagus nerve stimulation system according to any one of claims 1 to 8, wherein the portion of the stimulation intensity of the nerve stimulation signal gradually decreases during a predetermined period before the end of the first period.   Furthermore, a sensor for detecting movement is provided, and at least one of the first period and the second period is adjusted based on the sensor output. The vagus nerve stimulation system described.   The vagus nerve stimulation system according to claim 10, wherein the second period is shortened when the sensor detects movement.   The vagus nerve stimulation system according to claim 11, wherein the first period is further shortened when the sensor detects movement.   The vagus nerve according to any one of claims 1 to 12, further comprising respiration detection means for detecting respiration, wherein when the respiration detection means detects respiration, the start of the first period is delayed. Stimulation system.   The vagus nerve stimulation system according to claim 13, wherein the respiration detection means is performed by measuring chest impedance.   2. The information processing apparatus according to claim 1, further comprising notification means for informing that the stimulation of the vagus nerve has been performed or is performed after the generation of the nerve stimulation signal or prior to the generation of the nerve stimulation signal. The vagus nerve stimulation system in any one of -14.   2. The method according to claim 1, further comprising heart rate measuring means for measuring a heart rate, wherein the generation of the nerve stimulation signal is stopped when the heart rate measured by the heart rate measuring means falls below a predetermined value. The vagus nerve stimulation system according to any one of -15.   The heart rate measurement by the heart rate measuring means is made based on an output of a pulse wave sensor arranged in the vicinity of an electrode to which the nerve stimulation signal is supplied. Vagus nerve stimulation system.   The vagus nerve stimulation system according to claim 16, wherein the heart rate is measured by the heart rate measuring means based on electrocardiogram information.

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