JP5738687B2 - Nerve stimulator and method of operating neurostimulator - Google Patents

Description

  The present invention relates to a nerve stimulation apparatus and a method for operating the nerve stimulation apparatus.

  Conventionally, an apparatus for treating arrhythmia by suppressing an increase in heart rate and sympathetic excitement by applying electrical stimulation to the vagus nerve via an electrode connected to the vagus nerve (for example, (See Patent Documents 1 and 2.) In Patent Documents 1 and 2, an increase in heart rate is more strongly suppressed by increasing the intensity of stimulation or increasing the frequency.

Japanese Patent No. 4563785 Japanese Patent No. 4252826

  However, the heart rate suppression effect may decrease as the device continues to stimulate the vagus nerve. This includes the factors on the living body side where the vagus nerve becomes dull with respect to the stimulus and the living body does not respond sufficiently to the stimulus, and the contact impedance of the electrode due to the displacement of the electrode and the fibrosis of the nerve tissue. There is a factor on the electrode side in which the stimulation voltage decreases due to the increase.

  In other words, in the case of the devices of Patent Documents 1 and 2, when the heart rate suppression effect is reduced due to factors on the living body side, stimulation is not performed even if the stimulation is further strengthened, even though the heart rate suppression effect is not obtained. There is a problem that the battery is exhausted and an excessive load is applied to the vagus nerve.

  The present invention has been made in view of the above-described circumstances, and can eliminate waste of electric power and an excessive load on nerves by omitting stimulation enhancement that does not contribute to improvement of therapeutic effect. And it aims at providing the operating method of a nerve stimulating device.

In order to achieve the above object, the present invention provides the following means.
The present invention includes a nerve stimulation unit that outputs an electric pulse between a pair of electrodes connected to a nerve that controls the heart, an impedance measurement unit that measures impedance between the electrodes, and a heart rate measurement unit that measures a heart rate A heart rate change amount calculating unit that calculates a rate of decrease in the heart rate measured by the heart rate measuring unit before and after the electrical pulse is output by the nerve stimulation unit, and an impedance measured by the impedance measuring unit. And a control unit that controls the nerve stimulation unit to increase the energy of the electric pulse when the decrease rate calculated by the heart rate change amount calculation unit decreases. A stimulator is provided.

According to the present invention, the electrical pulse output from the nerve stimulation unit is supplied to the nerve via the electrode, so that the nerve can be excited and the function of the heart can be improved.
In this case, the impedance measuring unit measures the impedance between the pair of electrodes to which the electric pulse is applied, and the control unit increases the energy of the electric pulse when the measured value increases. That is, when the electrical pulse actually supplied to the nerve becomes weak, the electrical pulse is enhanced. As a result, it is possible to omit an increase in stimulation that does not contribute to the improvement of the therapeutic effect, and to prevent waste of power and an excessive load on the nerve.

In the above invention, a heart rate measurement unit that measures a heart rate, and a heart rate change that calculates a rate of decrease in the heart rate measured by the heart rate measurement unit before and after the electrical pulse is output by the nerve stimulation unit. A volume calculation unit, and the control unit controls the nerve stimulation unit to increase the energy of the electric pulse when the rate of decrease calculated by the heart rate change amount calculation unit decreases. and, since the stimulation decreases regulatory effect an increase in impedance of the heart by electrical pulses by a factor between the electrodes applied to the nerve by the control unit when the cause is enhanced more reliably the load on the nerve stimulation It is possible to keep adjusting the heart rate to a certain level while preventing it.

In the above invention, the control unit maintains the energy of the electric pulse when the impedance is not increased and when the amount of change in the heart rate does not decrease even when the impedance is increased. The nerve stimulation unit may be controlled so as to output the next electric pulse as it is.
By doing so, the intensity of stimulation is maintained without being increased except when the effect of adjusting the heartbeat is weakened due to an increase in inter-electrode impedance. Thereby, unnecessary enhancement of stimulation can be omitted more reliably.

  In the above invention, the control unit may increase the energy of the electric pulse by increasing at least one of the voltage, width, frequency, and output period of the electric pulse.

The present invention is also a method for operating a nerve stimulation apparatus that outputs an electric pulse between a pair of electrodes connected to a nerve that controls the heart, and measures the impedance between the electrodes and outputs the electric pulse. A method of operating a nerve stimulation apparatus that calculates a rate of decrease in heart rate before and after, increases the measured impedance , and controls to increase the energy of the electric pulse when the calculated rate of decrease decreases I will provide a.

In the above SL invention, if the impedance is not increased, and, if the heart rate decrease rate of even the impedance has increased is not reduced, the electrical pulses following electrical pulses while maintaining the energy of the It is good also as controlling to output.
In the above invention, at least one of the voltage, width, frequency, and output period of the electric pulse may be increased.

  According to the present invention, it is possible to prevent waste of electric power and an excessive load on a nerve by omitting an increase in stimulation that does not contribute to improvement of a therapeutic effect.

1 is an overall configuration diagram of a nerve stimulation apparatus according to an embodiment of the present invention. It is a whole block diagram which shows the modification of the nerve stimulation apparatus of FIG. (A) It is a figure explaining the specification of the stimulation pulse which the nerve stimulation part of the nerve stimulation apparatus of FIG. 1 outputs, and the change of the heart rate by (b) this stimulation pulse being supplied to a vagus nerve. It is a flowchart explaining the operating method of the nerve stimulation apparatus of FIG. FIG. 5 is a flowchart showing a continuation of the flowchart of FIG. 4. FIG.

Hereinafter, a nerve stimulation apparatus 1 according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a nerve stimulation apparatus 1 according to this embodiment includes a main body 2 arranged outside a patient's body, a nerve electrode 3 connected to the main body 2 via a lead (not shown), and a heartbeat. And an electrode 4.
The nerve electrode 3 is, for example, a cuff type wound around the side surface of the vagus nerve, and is embedded in the body and connected to the vagus nerve. The nerve electrode 3 includes a pair of an anode 3a and a cathode 3b.

  The heartbeat electrode 4 is connected to the body surface of the patient and detects the heartbeat of the patient. The heartbeat electrode 4 may be connected to any position on the patient's body as long as the heartbeat can be detected. For example, the heartbeat electrode 4 may be implanted in the body and directly connected to the heart, or may be provided on the same lead as the nerve electrode 3 and connected to a blood vessel existing in the vicinity of the vagus nerve. Further, as shown in FIG. 2, the heartbeat electrode 4 is used in common with the nerve electrode 3, and the switching unit 15 switches between supply of a stimulation pulse, measurement of interelectrode impedance, and measurement of the heart rate, which will be described later. It may be broken.

  The main body 2 includes a nerve stimulation unit 5 that outputs a stimulation pulse (electric pulse) to the nerve electrode 3, a heart rate measurement unit 6 that measures a heart rate based on the heart rate detected by the heart electrode 4, An impedance measuring unit 7 that measures impedance, a heart rate measuring unit 6, a storage unit 8 that stores measurement values obtained by the impedance measuring unit 7, and a heart rate that calculates a heart rate decrease measured by the heart rate measuring unit 6 A decrease amount calculation unit (heart rate change amount calculation unit) 9, a control unit 10 that controls operations of the units 5, 6, 7, and 9, and a battery 11 are provided.

  The main body 2 includes, for example, a resin or metal housing, and the nerve stimulation unit 5, the heart rate measurement unit 6, the impedance measurement unit 7, the storage unit 8, the heart rate reduction calculation unit 9, the control unit 10, and the battery 11 are Housed in a housing. The main body 2 includes a display unit 13 and an operation input unit 14 as a user interface 12 for an operator to operate the main body 2 on the outside of the casing.

  The nerve stimulation unit 5 generates a stimulation pulse, and outputs the generated stimulation pulse between the electrodes 3a and 3b of the nerve electrode 3, thereby supplying the stimulation pulse to a region sandwiched between the electrodes 3a and 3b of the vagus nerve. To do. As shown in FIG. 3A, the nerve stimulation unit 5 stops outputting a stimulation pulse after a predetermined output period T1 in which a stimulation pulse having a predetermined voltage V1, a width W1, and a frequency F1 is repeatedly output. The predetermined rest period Toff is one cycle, and this cycle is repeated. The nerve stimulation unit 5 can set the voltage V1 to about 0 to 20 V, the width W1 to 0 to 1 millisecond, and the frequency F1 to 5 to 20 Hz for each parameter of the stimulation pulse. In the nerve stimulation unit 5, for example, the voltage V1 is set to 5 V, the width W1 is set to 100 μsec, the frequency F1 is set to 10 Hz, and the output time T1 is set to 10 seconds as initial values of the parameters of the stimulation pulse.

  When the stimulation pulse is supplied to the vagus nerve via the nerve electrode 3, as shown in FIG. 3 (b), the heart rate temporarily decreases with the start of the supply of the stimulation pulse, and the heart rate with the stop of the supply of the stimulation pulse. The number rises. Here, even if a stimulation pulse in which each parameter is set to the same value is output from the nerve stimulation unit 5, it is caused by blunting of the vagus nerve with respect to the stimulation pulse or a change in the contact state between the nerve electrode 3 and the vagus nerve. The heart rate reduction amounts D and D ′ may decrease with time, that is, the heart rate suppression effect by the stimulation pulse may be weakened.

  The heart rate measuring unit 6 calculates the heart rate from the reciprocal of the time interval of the heart beat detected by the heartbeat electrode 4. The heart rate measuring unit 6 outputs the calculated heart rate to the storage unit 8.

  The impedance measuring unit 7 applies a voltage between the electrodes 3a and 3b of the nerve electrode 3, measures a drop amount of the applied voltage, and based on the measured drop amount, impedance (hereinafter referred to as an electrode) between the electrodes 3a and 3b. R1 is calculated. The interelectrode impedance R1 includes the contact impedance between the nerve electrode 3 and the vagus nerve, and the impedance of a tissue such as the vagus nerve or body fluid disposed between the electrodes 3a and 3b. Therefore, it is measured by the impedance measuring unit 7 when the connection position or contact state of the electrodes 3a and 3b is changed, or when fibrosis of the vagus nerve or attachment of body fluid occurs between the electrodes 3a and 3b. The interelectrode impedance R1 can gradually increase. The impedance measuring unit 7 outputs the calculated interelectrode impedance R1 to the storage unit 8.

  The storage unit 8 chronologically stores the heart rate H1, H2, the interelectrode impedance R1, and the heart rate reduction rate D1 input from the heart rate measurement unit 6, impedance measurement unit 7, and heart rate reduction amount calculation unit (described later) 9, respectively. Remember me. The storage unit 8 also stores an initial value R0 (described later) of the interelectrode impedance and an initial value D0 (described later) of the heart rate reduction rate.

  The heart rate reduction amount calculation unit 9 reads out the heart rate H1 immediately before the stimulation pulse is output from the nerve stimulation unit 5 and the heart rate H2 immediately before the stimulation pulse is stopped from the storage unit 8, and these heart rates The amount of heart rate reduction (change amount) is calculated from H1 and H2. That is, the heart rate decrease amount calculation unit 9 calculates the amount of heart rate decrease due to stimulation of the vagus nerve by the stimulation pulse. In the present embodiment, the heart rate reduction rate D1 = (H1−H2) / H1 is calculated as the heart rate reduction amount. The heart rate reduction amount calculation unit 9 outputs the calculated heart rate reduction rate D1 to the control unit 10.

  The control unit 10 causes the impedance measurement unit 7 and the heart rate reduction amount calculation unit 9 to calculate the inter-electrode impedance R1 and the heart rate reduction rate D1 for each cycle of the stimulation pulse output, and calculates these values R1, Based on D1, the pulse voltage V1 of the stimulation pulse to be generated next by the nerve stimulation unit 5 is determined.

  Specifically, the control unit 10 sets the stimulation pulse voltage V1 to a predetermined value when the interelectrode impedance R1 increases from the initial value R0 and the heart rate reduction rate D1 decreases from the initial value D0. A value V1 + α that is larger by α is set. That is, when the heart rate suppression effect by the stimulation pulse is reduced due to the increase in the interelectrode impedance R1, the control unit 10 increases the energy of the stimulation pulse to be output next.

  On the other hand, when the interelectrode impedance R1 has not increased, and when the heart rate reduction rate D1 has not decreased even though the interelectrode impedance R1 has increased, the control unit 10 determines the voltage of the current stimulation pulse. The next stimulation pulse is output while maintaining it. That is, when the heart rate reduction rate D1 decreases even though the interelectrode impedance R1 is not increased, the response to the stimulation pulse of the vagus nerve is saturated, and therefore the stimulation pulse is further increased. Maintain the current stimulation pulse intensity without. If the heart rate reduction rate D1 does not decrease even though the interelectrode impedance R1 increases, the heart rate suppression effect is sufficiently exhibited by the current stimulation pulse intensity. To maintain.

  The battery 11 is a primary battery, and supplies power for operating these components 5 to 10 and 12 to 14. Note that a rechargeable secondary battery may be used as the battery 11, and power may be supplied by an AC adapter or the like instead of the battery 11.

  The display unit 13 is a liquid crystal display, an LED (light emitting diode) display, or the like, and calculates stimulation pulse parameters V1, W1, F1, T1, heart rate H1, H2 measured by the heart rate measurement unit 6, and heart rate decrease amount. The heart rate reduction rate D1 calculated by the unit 9 is displayed. By observing these numerical values displayed on the display unit 13, the operator can confirm the current specification of the stimulation pulse, the therapeutic effect of tachycardia due to the stimulation pulse, and the like.

  The operation input unit 14 is a switch, a touch panel, or the like. The operator operates the operation input unit 14 to set initial values of the stimulation pulse parameters V1, W1, F1, T1, and the like, and instructs the control unit 10 in the main body 2 to start and end the nerve stimulation. Can be entered.

Next, the operation of the nerve stimulation apparatus 1 configured as described above will be described with reference to the flowcharts of FIGS. 4 and 5.
The nerve stimulation apparatus 1 starts to operate when an instruction to start nerve stimulation is input to the operation input unit 14 by the operator (step S1).

  At this time, the nerve stimulation apparatus 1 initially sets the initial value D0 of the heart rate reduction rate to zero. Further, the nerve stimulation apparatus 1 measures the interelectrode impedance, and stores the measured value in the storage unit 8 as the initial value R0 of the interelectrode impedance. The initial value R0 is measured not immediately after the nerve electrode 3 is implanted into the body but at a time when the contact state between the nerve electrode 3 and the vagus nerve is stabilized, for example, about two weeks to one month after implantation. It is preferable.

  Next, the nerve stimulation apparatus 1 measures and stores the interelectrode impedance R1 and the heart rate H1 (steps S2 and S3), and then starts outputting stimulation pulses by the nerve stimulation unit 5 (step S4). The nerve stimulation apparatus 1 measures the heart rate H2 again (step S6) immediately before stopping the supply of the stimulation pulse (step S5), and then stops the stimulation pulse (step S7). Then, the nerve stimulation apparatus 1 calculates the heart rate reduction rate D1 from the heart rates H1 and H2 before and after the output of the stimulation pulse (step S8).

  The nerve stimulation apparatus 1 determines a change of the interelectrode impedance R1 with respect to the initial value R0 (step S9), and if the interelectrode impedance R1 has increased (YES in step S9), the change of the heart rate reduction rate D1 is further increased. (Step S10), if the heart rate reduction rate D1 has decreased (YES in step S10), the pulse voltage of the stimulation pulse is changed to a value larger by αV, for example, 1V (step S11). On the other hand, when the inter-electrode impedance R1 has not increased (NO in step S9) and the heart rate reduction rate D1 has not decreased (NO in step S10), the nerve stimulation apparatus 1 sets the stimulation pulse. Is maintained as it is.

  Next, the neurostimulator 1 updates the initial value D0 by storing the current heart rate reduction rate D1 as the initial value D0 in the storage unit 8 (step S12), and then leaves a rest period Toff (step S13). ) The above steps (steps S2 to S12) are repeated until an instruction to stop nerve stimulation is input to the operation input unit 14 by the operator (step S14). At this time, when the inter-electrode impedance R1 increases (YES in step S9) and the heart rate reduction rate D1 decreases (YES in step S10), the nerve stimulation device 1 keeps the heart rate reduction rate D1 constant. Until it becomes (NO in Step S10), that is, until the heart rate suppression effect appears sufficiently, the voltage V1 of the stimulation pulse is increased by α (Step S11).

  Thus, according to this embodiment, every time a stimulation pulse is supplied to the vagus nerve, it is determined whether or not the interelectrode impedance R1 is increased, and the heart rate reduction rate D1 is increased by the increase in the interelectrode impedance R1. If so, increase the energy of the stimulation pulse. Thereby, even if the contact state of the nerve electrode 3 and the vagus nerve changes, the intensity of the stimulation pulse actually supplied to the vagus nerve can be kept constant.

  In addition, when the response to the stimulation pulse of the vagus nerve is saturated and the heart rate suppression effect is reduced, the stimulation pulse is not further increased. Thereby, the energy of the stimulation pulse is not unnecessarily increased in spite of not contributing to the therapeutic effect, and it is possible to prevent the battery 11 from being wasted and an excessive load applied to the vagus nerve.

  In the present embodiment, the stimulation pulse voltage V1 is increased in order to increase the stimulation pulse energy. Instead, the stimulation pulse width W1, frequency F1, or output period T1 is increased. Alternatively, a plurality of these parameters V1, W1, F1, and T1 may be increased.

Moreover, in this embodiment, when the interelectrode impedance R1 increases, a notification unit that notifies the operator of that fact, for example, a lamp that lights a warning lamp or a speaker that emits a warning sound may be provided. .
By doing in this way, the patient can recognize the poor connection of the nerve electrode 3 at an early stage.

  In this embodiment, the case of stimulating the vagus nerve has been described. However, the sympathetic nerve that controls the heart or the parasympathetic nerve other than the vagus nerve may be stimulated. In the case of stimulating the sympathetic nerve, a heart rate increase calculation unit (heart rate change amount calculation unit) that calculates an increase amount of the heart rate before and after the output of the stimulation pulse is provided instead of the heart rate decrease amount calculation unit 9. When the calculated increase amount decreases, the energy of the stimulation pulse may be increased. Moreover, it is good also as stimulating nerves other than a sympathetic nerve and a parasympathetic nerve.

  In this way, nerves other than the vagus nerve also gradually slow down with respect to the stimulus due to repeated stimulation, or the contact state of the electrode changes, so that the therapeutic effect on the treatment target organ over time Can weaken. At this time, it is determined whether there is a factor that reduces the therapeutic effect due to stimulation on the nerve side or on the electrode side, and the stimulation is increased only when there is a factor on the electrode side. It is possible to prevent waste of load and power.

DESCRIPTION OF SYMBOLS 1 Neural stimulation apparatus 2 Main body 3 Neural electrode 4 Heart rate electrode 5 Neural stimulation part 6 Heart rate measurement part 7 Impedance measurement part 8 Memory | storage part 9 Heart rate fall amount calculation part (heart rate change amount calculation part)
DESCRIPTION OF SYMBOLS 10 Control part 11 Battery 12 User interface 13 Display part 14 Operation input part 15 Switching part

Claims (6)

A nerve stimulation unit that outputs an electric pulse between a pair of electrodes connected to a nerve that controls the heart;
An impedance measuring unit for measuring the impedance between the electrodes;
A heart rate measuring unit for measuring heart rate;
A heart rate change amount calculation unit that calculates a rate of decrease in the heart rate measured by the heart rate measurement unit before and after the electrical pulse is output by the nerve stimulation unit;
When the impedance measured by the impedance measurement unit increases and the rate of decrease calculated by the heart rate change amount calculation unit decreases, the nerve stimulation unit increases the energy of the electric pulse. A nerve stimulation apparatus comprising: a control unit that controls When the impedance has not increased, and when the rate of decrease in the heart rate does not decrease even when the impedance has increased, the control unit performs the next electric pulse while maintaining the energy of the electric pulse. nerve stimulation apparatus according to claim 1 for controlling the neural stimulation portion to output. Wherein the control unit is, the voltage of the electrical pulse, width, nerve stimulation apparatus according to claim 1 or claim 2 to increase at least one of the frequency and the output period. A method of operating a nerve stimulation device that outputs an electrical pulse between a pair of electrodes connected to a nerve that controls the heart,
Measuring the impedance between the electrodes,
Calculate the rate of decrease in heart rate before and after outputting the electrical pulse,
A method of operating a nerve stimulation apparatus for controlling to increase the energy of the electric pulse when the measured impedance increases and the calculated decrease rate decreases . When the impedance does not increase, and when the rate of decrease in the heart rate does not decrease even if the impedance increases, control is performed to output the next electric pulse while maintaining the energy of the electric pulse. The operation method of the nerve stimulating device according to claim 4 . The operation method of the nerve stimulation apparatus according to claim 4 or 5, wherein at least one of a voltage, a width, a frequency, and an output period of the electric pulse is increased.

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