JP6552389B2 - Nerve stimulation system - Google Patents

Description

  The present invention relates to a nerve stimulation system and a control program therefor.

  Conventionally, a nerve stimulation system for reducing the heart rate of a patient is known (see, for example, Patent Document 1). The nerve stimulation system described in Patent Document 1 measures the heart rate of a patient, and when the measured heart rate is less than a predetermined minimum heart rate, the stimulation intensity to the parasympathetic nervous system is reduced.

Japanese Patent Application Publication No. 2008-541850

  If the lowest heart rate set in the neural stimulation system described in Patent Document 1 is inappropriately low, this neural stimulation system operates to maintain high stimulation intensity until reaching a predetermined lowest heart rate. This may place a burden on the living body.

  The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide a nerve stimulation system and a control program thereof that are less burdensome to a living body.

  One aspect of the present invention controls a nerve stimulation pulse applied to the nerve stimulation electrode connected to the nerve stimulation electrode, the heart rate measurement electrode, the nerve stimulation electrode, and the heart rate measurement electrode. A control unit, wherein the control unit acquires a heart rate during a period in which the nerve stimulation pulse is applied to the nerve stimulation electrode from the heart rate measurement electrode as a heart rate during stimulation, and the nerve stimulation The heart rate during the period when the nerve stimulation pulse is not applied to the electrodes is acquired from the heart rate measuring electrode as the non-stimulation heart rate, and a predetermined threshold is set for the stimulation heart rate and the non-stimulation heart rate. It is a nerve stimulation system characterized by determining whether there exists the above divergence.

The control unit acquires the non-stimulated heart rate as a first non-stimulated heart rate (A) immediately before the first timing at which application of the nerve stimulation pulse to the nerve stimulation electrode is started, and the first timing The non-stimulated heart rate is acquired as a second non-stimulated heart rate (B) immediately before the second timing at which the neural stimulation pulse starts to be applied to the nerve stimulation electrode after the duration of the nerve stimulation pulse in FIG. Then, after the first timing, within the duration of the nerve stimulation pulse, the stimulation heart rate is acquired as a first stimulation heart rate (C), and after the second timing, within the duration of the nerve stimulation pulse. When the heart rate during stimulation is acquired as the heart rate during second stimulation (D), and (A), (B), (C), and (D) satisfy the relationship shown in the following formula 1, It may be determined that
(B) / (A)> k (D) / (C) where k is a constant larger than 1 (equation 1)

  The control unit calculates a trend of the non-stimulated heart rate in a predetermined first period including a plurality of application durations of the nerve stimulation pulse as a non-stimulated trend, and determines the stimulation heart rate in the first period. When the trend is calculated as a trend at the time of stimulation, a cross-correlation coefficient between the trend at the time of non-stimulation and the trend at the time of stimulation is obtained by cross-correlation analysis, You may judge.

  The control unit calculates, as a non-stimulation variation, variation in each heart rate in a trend of the non-stimulation heart rate in a predetermined first period including a plurality of application durations of the nerve stimulation pulse, and calculates the variation in the first period. The variation of each heart rate in the trend of the heart rate at the time of stimulation is calculated as the variation at the time of stimulation, and it is determined that the deviation exists when the variation at the time of stimulation is smaller than a predetermined threshold with respect to the non-stimulation time variation. You may

  The control unit calculates a trend of the non-stimulation heart rate in a predetermined first period including a plurality of application durations of the nerve stimulation pulse as a non-stimulation trend, and the non-stimulation heart rate in the first period Calculating a rate of decrease in heart rate during stimulation with respect to the subject, calculating a trend of the rate of decrease in the first period as a rate of decrease rate, and cross-correlating the cross-correlation coefficient between the non-stimulated trend and the rate of decrease rate It may be determined that there is the divergence when the cross correlation coefficient is equal to or greater than a predetermined threshold.

  The control unit may change the intensity of the nerve stimulation pulse to be applied after the determination to an intensity lower than the intensity before the determination when it is determined that there is the divergence.

  Another aspect of the present invention is a control program for controlling a nerve stimulation system that electrically stimulates the vagus nerve by applying a nerve stimulation pulse, in a predetermined first period in which the nerve stimulation pulse is applied The heart rate is acquired as a stimulation heart rate, and the heart rate in a predetermined second period in which the nerve stimulation pulse is not applied is acquired as a non-stimulation heart rate, and the stimulation heart rate and the non-stimulation heart rate It is a control program characterized by determining whether or not there is a divergence greater than or equal to a predetermined threshold.

  ADVANTAGE OF THE INVENTION According to this invention, the nerve stimulation system with few burdens for a biological body and its control program can be provided.

1 is a schematic diagram of a nerve stimulation system according to a first embodiment of the present invention. It is a flowchart for demonstrating operation | movement of the control part of the same nerve stimulation system. It is a flowchart for demonstrating operation | movement of the control part of the same nerve stimulation system. It is a flowchart for demonstrating operation | movement of the control part of the same nerve stimulation system. It is a flowchart for demonstrating operation | movement of the control part of the same nerve stimulation system. It is a flowchart for demonstrating operation | movement of the control part of the nerve stimulation system of the modification of the embodiment. It is a graph which shows the heart rate and the heart rate reduction rate at the time of use of the nerve stimulation system of this modification. It is a graph which shows the heart rate and the heart rate reduction rate at the time of use of the nerve stimulation system of this modification. It is a flowchart for demonstrating operation | movement of the control part of the nerve stimulation system of 3rd Embodiment of this invention. It is a flowchart for demonstrating operation | movement of the control part of the nerve stimulation system of the modification of the embodiment. It is a flowchart for demonstrating operation | movement of the control part of the nerve stimulation system of 4th Embodiment of this invention.

First Embodiment
A first embodiment of the present invention will be described. FIG. 1 is a schematic view of a nerve stimulation system according to the present embodiment.
A nerve stimulation system 1 according to this embodiment shown in FIG. 1 is a medical system that electrically stimulates a patient's vagus nerve in order to treat tachycardia, myocardial infarction, chronic heart failure, and the like.
As shown in FIG. 1, the nerve stimulation system 1 includes a lead 2 and a control unit 10.
The lead 2 is a first electrode 3 (electrode for nerve stimulation) for applying a nerve stimulation pulse to a living body to stimulate the nerve, and a heart rate of a patient to which the nerve stimulation system 1 is to be attached. Two electrodes 4 (electrodes for heart rate measurement) and a covered wire 5 for connecting the first electrode 3 and the second electrode 4 to the control unit 10 are provided.

  The control unit 10 includes a housing 11, a power supply unit 12 serving as a power source for the nerve stimulation system 1, an operation unit 13 for an operator to set the intensity and application period of the nerve stimulation pulse, and the nerve stimulation system 1. And a control unit 14 for controlling the whole.

  The control unit 14 receives power supply from the power supply unit 12 and outputs a nerve stimulation pulse to the lead 2 in accordance with a predetermined input operation to the operation unit 13.

  The control unit 14 of the present embodiment includes a stimulus intensity adjustment unit 15 and a pulse generation unit 20.

  The stimulation intensity adjustment unit 15 includes a heart rate measurement unit 16, a storage unit 17, a change amount calculation unit 18, and a comparison unit 19.

  The heart rate measurement unit 16 acquires the heart rate of the patient to which the second electrode 4 of the lead 2 is attached from the second electrode 4. The heart rate measurement unit 16 can, for example, A / D convert information capable of specifying a patient's heart rate and output the information to the storage unit 17.

  The storage unit 17 can store the heart rate information acquired from the second electrode 4 by the heart rate measuring unit 16 as information associated with the presence / absence of application of a nerve stimulation pulse and the acquisition time of the heart rate. In this specification, information on the heart rate acquired during the period (first period) during which the nerve stimulation pulse is applied is referred to as “stimulation heart rate”, and the period during which no nerve stimulation pulse is applied. Information on the heart rate acquired in the (second period) is referred to as “non-stimulated heart rate”.

  The variation calculation unit 18 acquires the following information (A), (B), (C), and (D) from the storage unit 17.

(A) First non-stimulation heart rate: non-stimulation heart rate (bpm) obtained from the second electrode 4 immediately before the first timing to start applying a nerve stimulation pulse to the nerve stimulation electrode
(B) Second unstimulated heart rate: acquired from the second electrode 4 immediately before the second timing when the nerve stimulation pulse starts to be applied to the nerve stimulation electrode after the duration of the nerve stimulation pulse at the first timing has elapsed. Heart rate without stimulation (bpm)
(C) Heart rate during first stimulation: Heart rate during stimulation (bpm) obtained from the second electrode 4 within the duration of the neural stimulation pulse after the first timing
(D) Heart rate during second stimulation: Heart rate during stimulation (bpm) obtained from the second electrode 4 within the duration of the neural stimulation pulse after the second timing

For example, the first timing is an arbitrary timing, and the second timing is a timing immediately after the first timing.
It should be noted that the first timing and the second timing are not limited to those in the time series and immediately after that. That is, the timing of the start of application of the nth time (n is a natural number) after the timing defined as the first timing may be the second timing.

  The change amount calculation unit 18 changes (differences) the heart rate per cycle when one cycle is from the start of the non-stimulation period immediately before the start of application of the nerve stimulation pulse to the end of the duration of the nerve stimulation pulse. Are calculated for non-stimulation and stimulation, respectively. Note that n is 1 when the second timing is immediately after the first timing.

The change amount rb of the heart rate per one cycle during non-stimulation is calculated by the following (Expression 1).
rb = {(B)-(A)} / n (Equation 1)

The amount of change rc of the heart rate per cycle at the time of stimulation is calculated by the following (Formula 2).
rc = {(D) − (C)} / n (Equation 2)

When the comparison unit 19 satisfies any of the relationships shown in the following (Expression 3) and (Expression 4), there is a difference between the heart rate change rb during non-stimulation and the heart rate change rc during stimulation. It is determined that
(Rc / rb) <0.5 (Equation 3)
2 <(rc / rb) (Equation 4)

  Note that the magnitude of rc / rb is not affected by the value of n.

The comparison unit 19 transmits, to the pulse generation unit 20, a control signal for reducing the intensity of the nerve stimulation pulse, when any of the relationships shown in the above (Equation 3) and (Equation 4) is satisfied.
Note that the comparison unit 19 does not transmit a control signal to the pulse generation unit 20 in a state in which neither of (Equation 3) and (Equation 4) is satisfied.

The pulse generator 20 generates a predetermined nerve stimulation pulse and outputs the nerve stimulation pulse to the first electrode 3. The intensity of the nerve stimulation pulse generated by the pulse generation unit 20 can be changed by input to the operation unit 13 and transmission of a control signal from the comparison unit 19.
For example, as an example of changing the intensity of the nerve stimulation pulse by the input to the operation unit 13, the operator of the nerve stimulation system 1 inputs an appropriate nerve stimulation intensity in consideration of the past test results and the like.
Further, as an example of changing the intensity of the nerve stimulation pulse by transmitting the control signal from the comparison unit 19, the pulse generation unit 20 generates a pulse when the pulse generation unit 20 receives a control signal for reducing the intensity of the nerve stimulation pulse. Any one of the frequency, pulse width, current and voltage of the neural stimulation pulse generated by the unit 20 is changed.
As an example, when the pulse generator 20 receives a control signal for reducing the intensity of the nerve stimulation pulse, the pulse generator 20 first decreases the frequency if the frequency of the nerve stimulation pulse can be decreased. Also, the pulse generator 20 shortens the pulse width when the frequency is at the lower limit. In addition, the pulse generation unit 20 reduces the current and the voltage when the frequency is at the lower limit and the pulse width is at the lower limit.
Thereby, when receiving the control signal, the pulse generating unit 20 makes the intensity of the nerve stimulation pulse generated after receiving the control signal weaker than the intensity of the nerve stimulation pulse generated before receiving the control signal.

  The control unit 14 of the present embodiment including the above-described stimulation intensity adjustment unit 15 and the pulse generation unit 20 may be, for example, a computer having an input / output unit, a calculation unit, and a storage unit. In this case, the control unit 14 operates in accordance with the control program stored in the storage unit in order to operate the computer as the stimulation intensity adjustment unit 15 and the pulse generation unit 20 described above.

The operation flow of the control unit 14 of the nerve stimulation system 1 of the present embodiment will be described. 2 to 5 are flowcharts for explaining the operation of the control unit 14 of the nerve stimulation system 1 of the present embodiment.
The control unit 14 of the nerve stimulation system 1 starts operating when an input operation for performing nerve stimulation treatment is performed on the operation unit 13.
First, the control unit 14 resets the counter (see step S1, FIG. 2). In step S1, the value of a variable t increasing corresponding to the elapsed time after the control unit 14 starts operation and a variable m increasing corresponding to the number of repetitions of the application timing of the nerve stimulation pulse are set to zero.
Step S1 is complete | finished now and it progresses to step S2.

Step S2 is a step of acquiring a heart rate.
In step S2, the heart rate measurement unit 16 measures the heart rate using the second electrode 4 (electrode for heart rate acquisition). The heart rate measurement unit 16 stores the measured heart rate value (bpm).
Step S2 is complete | finished now and it progresses to step S3.

Step S3 is a step of switching the start and stop of stimulation using a nerve stimulation pulse.
In step S3, first, the control unit 14 compares the heart rate acquired by the heart rate measuring unit 16 in the above step S2 with the bradycardia threshold preset in the nerve stimulation system 1 (step S101, FIG. 3). In step S101, for example, the control unit 14 determines whether or not the heart rate acquired in step S2 is less than the bradycardia threshold.
If it is determined in step S101 that the heart rate is lower than the bradycardia threshold (Yes), the process proceeds to step S102.
If it is determined in step S101 that the heart rate is equal to or greater than the bradycardia threshold (No), the process proceeds to step S104.

Step S102 is a step of determining whether or not it is during application of a nerve stimulation pulse or the application start timing of a nerve stimulation pulse.
If it is determined in step S102 that the nerve stimulation pulse is being applied or that it is the application start timing of the nerve stimulation pulse (Yes), the process proceeds to step S103.
If it is determined in step S102 that the application of the nerve stimulation pulse is not in progress or the application start timing of the nerve stimulation pulse is not (No), step S3 ends and the process proceeds to step S4.

Step S103 is a step in which the application of the nerve stimulation pulse after the determination in step S102 is stopped or attenuated.
In step S103, when the nerve stimulation pulse is being applied, the intensity of the nerve stimulation pulse is reduced or the application is stopped. In step S103, when it is the application start timing of the nerve stimulation pulse, the application of the nerve stimulation pulse is not started, or the application of the nerve stimulation pulse is started with the intensity reduced.
Step S103 is ended now and it progresses to Step S4.

Step S104 is a step of determining whether or not it is a stimulation start timing.
When it is the stimulation start timing (Yes) at the time of execution of step S104, it progresses to step S105.
When it is not the stimulation start timing (No) at the time of execution of step S104, it progresses to step S106.

Step S105 is a step of starting output of a nerve stimulation pulse.
In step S105, the control unit 14 outputs the nerve stimulation pulse having the intensity designated by the input operation to the operation unit 13 or the intensity attenuated in the above step S103 to the first electrode 3 (neural stimulation electrode).
The nerve stimulation started by step S105 is continued until the time of execution of above-mentioned step S103 or the following step S107.
Step S105 is ended here, and it progresses to Step S4.

Step S106 is a step of determining whether or not it is a stimulation end timing.
If it is the stimulation end timing (Yes) at the time of execution of step S106, the process proceeds to step S107.
If it is not the stimulation end timing (No) at the time of execution of step S106, the process proceeds to step S4.

Step S107 is a step in which the control unit 14 stops the output of the nerve stimulation pulse.
In step S107, the output of the nerve stimulation pulse from the pulse generation unit 20 is stopped. Note that when the output of the nerve stimulation pulse is stopped in step S107, information on the intensity of the nerve stimulation pulse output last is stored. The intensity stored at this time can be used to set the intensity of the nerve stimulation pulse when the output of the nerve stimulation pulse is resumed (step S105 above).
Step S107 is ended now and it progresses to Step S4.

Step S4 is a step of determining whether or not a nerve stimulation pulse is being applied.
In step S4, if nerve stimulation has been started in step S105, the process proceeds to step S5. If nerve stimulation has been stopped in step S103 or step S107, the process proceeds to step S6.

Step S5 is a step of storing that neural stimulation is in progress.
In step S5, 1 is substituted for a variable (in-stimulus flag P) indicating whether or not neural stimulation is in progress. The initial value of the stimulating flag P is 0.
Step S5 is completed here, and it progresses to step S7.

Step S6 is a step of storing that neural stimulation is not in progress.
In step S6, 0 is substituted for a variable (in-stimulus flag P) indicating whether or not neural stimulation is in progress.
Step S6 is ended here, and it progresses to step S7.

Step S7 is a step of storing heart rate information.
In step S7, the heart rate acquired in step S2 is stored in association with the value of the variable t and the in-stimulation flag P.
Step S7 is ended here, and it progresses to step S8.

Step S8 is a step of determining whether or not it is the non-stimulation heart rate storage timing.
For example, in the series of operations from step S1 to step S15, the non-stimulated heart rate storage timing is set to the stimulating flag P in step S5 after 0 is substituted in the stimulating flag P in step S6. This is the timing set in the period until 1 is substituted.
If it is the non-stimulation heart rate storage timing at the time of execution of step S8 (Yes), the process proceeds to step S9, and if it is not the non-stimulation heart rate storage timing at the time of step S8 (No), the process proceeds to step S10.

Step S9 is a step of internally storing the heart rate saved in step S7 as a non-stimulated heart rate.
In step S9, the information on the heart rate stored in step S7 is read out, associated with the variable m and the value of the in-stimulation flag P, and saved as the non-stimulus heart rate.
After the non-stimulated heart rate is stored in step S9, the stored non-stimulated heart rate information is used to determine whether or not the stimulation intensity has decreased from steps S201 to S204 described later (see FIG. 4). Used to process execution.
Step S9 is ended here, and it progresses to step S13.

Step S10 is a step of determining whether or not it is a stimulation heart rate storage timing.
For example, in the series of operations from step S1 to step S15, the stimulation heart rate storage timing is set to 0 in the stimulation flag P in step S6 after 1 is substituted in the stimulation flag P in step S5. It is the timing set to the period until it is substituted.
If it is the stimulation heart rate storage timing at the time of execution of step S10 (Yes), the process proceeds to step S11. If it is not the stimulation heart rate storage timing at the time of execution of step S10 (No), the process proceeds to step S13.

Step S11 is a step of internally storing the heart rate saved in step S7 as the heart rate during stimulation.
In step S11, the information on the heart rate stored in step S7 is read out, associated with the value of the variable m and the value of the in-stimulation flag P, and saved as a stimulation heart rate.
After the stimulation heart rate is stored in step S11, the stored information on the stimulation heart rate is used for determination and execution of stimulation intensity reduction including steps from step S201 to step S204 described later. .
Step S11 is ended here, and it progresses to step S12.

  Step S12 is a step of increasing the value of the variable m by one. When step S12 ends, the process proceeds to step S13.

Step S13 is a step of comparing the non-stimulated heart rate stored in step S9 with the stimulated heart rate stored in step S11.
In step S13, if the non-stimulated heart rate is equal to the stimulated heart rate, the process proceeds to step S14. If the non-stimulated heart rate is not equal to the stimulated heart rate, the process proceeds to step S15.

Step S14 is a step of increasing the stimulation intensity or notifying the user.
In step S14, for example, the intensity of the nerve stimulation pulse is increased in response to the determination that the non-stimulation heart rate and the stimulation heart rate are equal in step S13. In step S14, the user is notified by, for example, displaying a message prompting the user to intensify the intensity of the nerve stimulation pulse.
Step S14 is ended here, and it progresses to step S15.

  Step S15 is a step of increasing the value of the variable t by one. When step S15 ends, the process proceeds to step S2, and the process from step S2 to step S15 is repeated.

A flow of processing for judging and executing stimulation intensity reduction using the non-stimulation heart rate stored in step S9 and the information on stimulation heart rate stored in step S11 (from step S201 to step S204) ) Will be described with reference to FIG.
Step S201 is a step of calculating the amount of change rb between the first non-stimulated heart rate and the second non-stimulated heart rate.
In step S201, using the value of the variable m, the non-stimulation heart rate (m-1, P) immediately before the first timing m-1 is acquired as the first non-stimulation heart rate. In step S201, the non-stimulation heart rate (m, P) immediately before the second timing m is acquired as the second non-stimulation heart rate using the value of the variable m. Further, in step S201, a change amount rb (see the above formula 1) between the first non-stimulated heart rate and the second non-stimulated heart rate is calculated.
In addition, step S201 is not performed, when the information of the heart rate at the time of non-stimulation is insufficient (in the case of m = 0).
Step S201 is ended here, and it progresses to step S202.

Step S202 is a step of calculating a change amount rc between the first stimulation heart rate and the second stimulation heart rate.
In step S202, using the value of the variable m, the stimulation heart rate (m-1, P) immediately after the first timing m-1 is acquired as the heart rate during the first stimulation. Further, in step S202, using the value of the variable m, a stimulation heart rate (m, P) immediately after the second timing m is acquired as the second stimulation heart rate. Further, in step S202, a change amount rc (see the above formula 2) between the first stimulation heart rate and the second stimulation heart rate is calculated.
Note that step S202 is not executed when information on the heart rate during stimulation is insufficient (when m = 0).
Step S202 is ended here, and it progresses to step S203.

Step S203 is a step of comparing the change amount rb calculated in step S201 with the change amount rc calculated in step S202.
If (rc / rb) is within a predetermined range (0.5 ≦ rc / rb ≦ 2) when step S203 is executed, the process returns to step S9.
If 0.5 ≦ rc / rb ≦ 2 is not satisfied during the execution of step S203, the process proceeds to step S204. That is, in step S203, when either (formula 3) or (formula 4) is satisfied, the process proceeds to step S204.

Step S204 is a step of reducing the intensity of the nerve stimulation pulse.
In step S204, first, the control unit 14 determines whether it is necessary to rapidly reduce the intensity of the nerve stimulation pulse (step S301, see FIG. 5).
The determination as to whether or not the intensity of the nerve stimulation pulse needs to be rapidly reduced is, for example, based on whether or not the value of (rc / rb) deviates from the range in step S203 above by a predetermined threshold or more. It will be.
If it is determined in step S301 that the intensity of the nerve stimulation pulse needs to be rapidly reduced, the process proceeds to step S302. If it is determined in step S301 that it is not necessary to rapidly weaken the intensity of the nerve stimulation pulse, the process proceeds to step S303.

Step S302 is a step of rapidly reducing the intensity of the nerve stimulation pulse.
In step S302, the current value or the voltage value is lowered among the conditions (current, voltage, frequency, pulse width) which define the intensity of the nerve stimulation pulse. That is, in step S302, a control signal for changing the current value or the voltage value to a low value is transmitted to the pulse generation unit 20.
At this point, step S302 ends, and the process proceeds to step S304.

Step S303 is a step of gently reducing the intensity of the nerve stimulation pulse.
In step S303, the frequency is lowered among the conditions (current, voltage, frequency, pulse width) for defining the intensity of the nerve stimulation pulse. That is, in step S303, a control signal for changing the frequency to a low value is transmitted to the pulse generator 20.
Step S303 is ended here, and it progresses to step S304.

Step S304 is a step of determining whether or not it is necessary to additionally weaken the intensity of the nerve stimulation pulse.
In step S304, for example, when the current value or the voltage value reaches the lower limit value in step S302 described above, and when the frequency reaches the lower limit value in step S303 described above, other conditions are changed to change nerve stimulation. In order to further weaken the intensity of the pulse, one of executable steps of step S305 (reduction of current value or voltage value), step S306 (reduction of pulse width), and step S307 (reduction of frequency) is performed. . Steps S305, S306, and S307 may be executed in any order.
When step S305, step S306 and step S307 are finished, step S304 is executed again.
When the current value or the voltage value does not reach the lower limit value in the above step S302, and when the frequency does not reach the lower limit value in the above step S303, it is not necessary to additionally weaken the neurostimulation pulse intensity. And step S204 ends.

The operation of the nerve stimulation system 1 of the present embodiment will be described.
When a nerve stimulation pulse is applied to a living body to lower the heart rate, if the nerve stimulation pulse strength is within an appropriate range, the nerve stimulation pulse strength and the heart rate reduction rate are correlated. However, the higher the intensity of the nerve stimulation pulse, the lower the heart rate will not be.

  When the heart rate is lowered by nerve stimulation pulse, the homeostasis of the patient causes an action to increase the heart rate, and the heart rate is below the lower limit heart rate at which the action of nerve stimulation pulse and homeostasis antagonize Is hard to fall. Since the lower limit heart rate varies depending on individual differences among patients, the environment, etc., it is difficult to grasp the lower limit heart rate before the start of use of the nerve stimulation system 1.

  In the nerve stimulation system 1 of the present embodiment, it is suggested that the lower limit heart rate of the patient is reached by applying the nerve stimulation pulse when the above equation 3 or 4 is satisfied. The intensity of the nerve stimulation pulse should be reduced because it is inappropriately high and may be burdensome to the living being.

  The nerve stimulation system 1 of the present embodiment satisfies the judgment condition in step S203 based on the heart rate of the patient (non-stimulation heart rate, stimulation heart rate) by the flow from step S201 to step S204 described above. Decrease the stimulus intensity setting when there is not. This series of steps can prevent the continuous application of an inappropriately strong nerve stimulation pulse to the patient.

In addition, if the heart rate is controlled to be constant regardless of the daily fluctuation of the heart rate, the heart rate is forcibly lowered during a high heart rate within the daily fluctuation range, which places a burden on the living body. In a time zone where the heart rate is high within the range of the daily fluctuation, the heart rate can be increased according to the height, so that the heart rate does not burden the living body even if there is a daily fluctuation. desirable.
In the neural stimulation system 1 of the present modification, the comparator 19 transmits a control signal for reducing the stimulation intensity to the pulse generator 20 when the above equation 3 or 4 is satisfied. It is possible to prevent continuous application of high intensity nerve stimulation pulses.

  As described above, according to the nerve stimulation system 1 of the present embodiment, the burden on the living body can be reduced when reducing the heart rate.

(Modification)
A modification of the first embodiment will be described. FIG. 6 is a flowchart for explaining the operation of the control unit of the nerve stimulation system of the present modification.
The comparison unit 19 (see FIG. 1) of the nerve stimulation system 1 of the present modification determines the presence or absence of divergence based on a criterion different from that of the first embodiment.
That is, in this modification, even if the above (Expression 3) or (Expression 4) is satisfied, there is no difference when the following (Expression 5) and (Expression 6) are satisfied simultaneously. It is judged.

−0.05 × (A) <rb <0.05 × (A) (Equation 5)
−0.05 × (C) <rc <0.05 × (C) (Equation 6)
In the present modification, when the above (Equation 5) and (Equation 6) are satisfied, the comparison unit 19 determines that there is no divergence regardless of the value of rc / rb. That is, when the above (Equation 5) and (Equation 6) are satisfied, a control signal for reducing the intensity of the nerve stimulation pulse is not transmitted.

The operation of the control unit 14 in the present modification will be described along the flowchart shown in FIG.
In this modification, instead of the flow from step S201 to step S204 described above, the flow from step S401 to step S405 is executed.

Steps S401 and S402 are the same as steps S201 and S202 described above. In step S401 and step S402, as in the first embodiment, the non-stimulated heart rate information stored in step S9 and the stimulated heart rate information stored in step S11 are referred to.
After the end of step S401 and step S402, it progresses to step S403.

Step S403 is a step which makes the same comparison as the above-mentioned step S203 and makes a judgment.
If (rc / rb) is within the predetermined range (0.5 ≦ rc / rb ≦ 2) when step S403 is executed, step S403 ends.
If 0.5 ≦ rc / rb ≦ 2 is not established at the time of execution of step S403, the process proceeds to step S404. That is, in step S403, in a state in which either (formula 3) or (formula 4) above is satisfied, the process proceeds to step S404.

Step S404 is a step of judging whether the above (formula 5) and (formula 6) are satisfied.
In step S404, when the above (formula 5) and (formula 6) are both satisfied, step S404 ends.
In step S404, when at least one of the above (formula 5) and (formula 6) is not satisfied, the process proceeds to step S405.

Step S405 is a step of reducing the intensity of the nerve stimulation pulse.
In step S405, the flow from step S301 to step S307 is executed, and at least one of the conditions (current, voltage, frequency, pulse width) that defines the intensity of the nerve stimulation pulse is changed as described above.
Step S405 ends here.

Variations in heart rate when using the nerve stimulation system 1 of the present modification will be described with reference to FIGS.
FIG. 7 and FIG. 8 are graphs showing the heart rate during non-stimulation (HR during non-stimulation), the heart rate during stimulation (HR during stimulation), and the heart rate reduction rate in time series (horizontal axis), respectively.
FIG. 7 shows the case where the transmission of the control signal by the comparison unit 19 of this modification is not always performed. FIG. 8 shows a case where the comparison unit 19 transmits a control signal to the pulse generation unit 20 based on the above-described reference.

  As shown in FIG. 7, when no control signal is sent, the time-series fluctuation of the heart rate during non-stimulation does not correlate with the time-series fluctuation of the heart rate during stimulation, and the heart rate reduction rate is large. There are fluctuations. On the other hand, as shown in FIG. 8, when the control signal is transmitted, there is a correlation between the heart rate at the time of non-stimulation and the heart rate at the time of stimulation, and the heart rate decrease rate is stably changed. There is.

  In this modification, there is no difference between the amount of change between heart rates during non-stimulation and the amount of change between heart rates during nerve stimulation when both (Equation 5) and (Equation 6) above are satisfied. The nerve stimulation intensity can be maintained as it is. For this reason, according to the nerve stimulation system 1 of the present modification, it is possible to reduce the burden on the living body and stabilize the rate of decrease in the heart rate.

Second Embodiment
A second embodiment of the present invention will be described. In the following embodiments, the same components as those disclosed in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and redundant descriptions are omitted. Further, in each of the following embodiments, components corresponding to the components disclosed in the first embodiment described above are shown in FIG. 1 with different characters after the reference in each embodiment.

  The nerve stimulation system 1A of the present embodiment includes a change amount calculation unit 18A and a comparison unit 19A having configurations different from those of the change amount calculation unit 18 and the comparison unit 19 disclosed in the first embodiment. The configuration other than the change amount calculation unit 18A and the comparison unit 19A in the nerve stimulation system 1A may be the same as that in the first embodiment described above.

  As in the first embodiment, the change amount calculation unit 18A of the nerve stimulation system 1A of the present embodiment has the first unstimulated heart rate (A), the second unstimulated heart rate (B), and the first Information on the stimulation heart rate (C) and the second stimulation heart rate (D) is acquired from the storage unit 17.

  After acquiring the above (A), (B), (C), and (D), the change amount calculation unit 18A calculates the values of (B) / (A) and (D) / (C). (B) / (A) shows the rate of change in heart rate during non-stimulation, and (D) / (C) shows the rate of change in heart rate during stimulation.

The comparison unit 19A compares the change rates calculated by the change amount calculation unit 18A, and determines whether or not there is a difference between the change rates.
That is, when the above (A), (B), (C), and (D) satisfy the relationship shown in the following equation 7, the comparison unit 19A determines that there is the deviation.

(B) / (A)> k (D) / (C) where k is a constant larger than 1 (equation 7)
Here, the constant k is a value set in advance in consideration of the age, sex and the like of the patient to whom the nerve stimulation system 1 is applied.

  Satisfying Equation 7 above indicates that the rate of change in the heart rate during stimulation is too small than the rate of change in the heart rate during non-stimulation, and the intensity of the nerve stimulation pulse is inappropriately high Suggests that.

When it is determined that there is a difference between the change rates, the comparison unit 19A sends a control signal for increasing (D) / (C) to the pulse generation unit in order to eliminate the state that satisfies the above expression 1. Send to 20.
If it is determined that the change rates do not deviate, the comparison unit 19A does not transmit the control signal to the pulse generation unit 20.

  The nerve stimulation system 1A of the present embodiment can also reduce the burden on the living body when reducing the heart rate, as in the first embodiment.

Third Embodiment
A third embodiment of the present invention will be described. FIG. 9 is a flowchart for explaining the operation of the control unit of the nerve stimulation system of the present embodiment.
The nerve stimulation system 1B (see FIG. 1) of the present embodiment includes a change amount calculation unit 18B and a comparison unit 19B having different configurations from the change amount calculation unit 18 and the comparison unit 19 disclosed in the first embodiment. doing. The configuration other than the change amount calculation unit 18B and the comparison unit 19B in the nerve stimulation system 1B may be the same as that in the first embodiment described above.

Operation | movement of the control part 14 of the nerve stimulation system 1B of this embodiment is demonstrated along the flowchart shown in FIG.
In this embodiment, after the heart rate is stored in step S7 (see FIG. 2) in the first embodiment, the following flow from step S501 to step S503 is executed.

Step S501 is a step in which cross-correlation analysis is performed using heart rate trend information.
In step S501, first, the variation calculation unit 18B of the nerve stimulation system 1B determines the trend of the non-stimulation heart rate in a predetermined first period T (t <T <t + s) including a plurality of application durations of nerve stimulation pulses. Calculated as a non-stimulated trend fb (T). For example, the constant s in the first period T described above is a value previously defined such that the first period T includes at least three or more application durations.
Furthermore, the nerve stimulation system 1B calculates the trend of the heart rate during stimulation in the first period as the trend fc (T) during stimulation. The non-stimulation trend fb (T) and the stimulation trend fc (T) are both stored in the storage unit 17.
Furthermore, after the non-stimulation trend fb (T) and the stimulation trend fc (T) are stored in the storage unit 17 in step S501, the change amount calculation unit 18B generates the non-stimulation trend fb (T) and the stimulation time The cross correlation coefficient with the trend fc (T) is acquired by cross correlation analysis.
Step S501 is completed here, and it progresses to step S502.

Step S502 is a step in which the process branches based on the cross-correlation coefficient acquired in step S502.
In step S502, when the cross correlation coefficient is smaller than 1 by a predetermined threshold value (for example, in the present embodiment, the cross correlation coefficient is less than 0.4), there is a difference in the heart rate change rate And the comparison unit 19B determines that the process proceeds to step S403.
In step S502, when the cross correlation coefficient has a value closer to 1 than the predetermined threshold (for example, in the present embodiment, the cross correlation coefficient is 0.4 or more), step S502 ends.

Step S503 is a step of weakening the stimulation intensity setting value to weaken the nerve stimulation pulse.
In step S503, the control signal for weakening the nerve stimulation pulse is transmitted to the pulse generation unit 20 by executing the steps S301 to S307.
Step S503 ends here.

As described above, the nerve stimulation system 1B according to the present embodiment reduces the influence of heart rate variation by comparing the non-stimulation trend fb (T) with the stimulation trend fc (T) to thereby obtain a nerve stimulation pulse. The strength of the can be adjusted.
As a result, in the nerve stimulation system 1B according to the present embodiment as well as the first embodiment, the burden on the living body can be reduced when the heart rate is lowered.

(Modification)
A modified example of the third embodiment will be described. FIG. 10 is a flowchart for explaining the operation of the control unit of the nerve stimulation system of the present modification.
In the present modification, the control unit 14 selects whether to decrease the intensity of the nerve stimulation pulse suddenly or gently according to the value of the cross-correlation coefficient, and defines a condition (current) that defines the intensity of the nerve stimulation pulse. , Voltage, frequency, pulse width) based on the selection according to the value of the cross correlation coefficient.

The operation of the control unit 14 in the present modification will be described along the flowchart shown in FIG.
First, in step S7 disclosed in the first embodiment, step S601 for performing cross-correlation analysis is executed in the same manner as in step S501.

  After step S601, the values of the cross-correlation coefficients are compared under the same judgment condition as that of step S502 described above (step S602). If it is determined in step S602 that the cross correlation coefficient is smaller than 1 by more than a predetermined threshold (in the present modification, the cross correlation coefficient is less than 0.4), the process proceeds to step S603. If it is determined in step S602 that the cross correlation coefficient has a value closer to 1 than the predetermined threshold (in the present modification, the cross correlation coefficient is 0.4 or more), the process proceeds to step S604.

Step S603 is a step of reducing the current value or voltage value among the conditions (current, voltage, frequency, pulse width) that define the intensity of the nerve stimulation pulse. The current value or the voltage value is a condition in which the intensity of the nerve stimulation pulse can be rapidly changed among the above conditions.
Step S603 ends here.

  Step S604 is a step of comparing the value of the cross correlation coefficient with the threshold using a threshold different from the above step S602 (0.7 in this modification). If it is determined in step S604 that the cross correlation coefficient is smaller than 1 by more than a predetermined threshold (in this modification, the cross correlation coefficient is less than 0.7), the process proceeds to step S605. If it is determined in step S604 that the cross correlation coefficient has a value closer to 1 than the predetermined threshold (in the present modification, the cross correlation coefficient is 0.7 or more), step S604 ends.

Step S605 is a step of decreasing the frequency among the conditions (current, voltage, frequency, pulse width) defining the intensity of the nerve stimulation pulse. The frequency is a condition that can change the intensity of the nerve stimulation pulse more slowly than the current and voltage.
Step S605 is ended here.

Similarly to the second embodiment, the nerve stimulation system 1B of the present modification can also reduce the burden on the living body when the heart rate is lowered.
Furthermore, in the present modification, the control unit 14 determines whether it is necessary to rapidly reduce the intensity of the nerve stimulation pulse or to gradually decrease the intensity of the nerve stimulation pulse from the magnitude of the value of the cross correlation coefficient. Since the judgment can be made automatically, it is possible to change the intensity of the nerve stimulation pulse to an appropriate intensity using the information on the trend of the heart rate.

Fourth Embodiment
A fourth embodiment of the present invention will be described. FIG. 11 is a flowchart for explaining the operation of the control unit of the nerve stimulation system of the present embodiment.
The nerve stimulation system 1C of the present embodiment includes a change amount calculation unit 18C and a comparison unit 19C which are different in configuration from the change amount calculation unit 18 and the comparison unit 19 disclosed in the first embodiment. The configuration other than the change amount calculation unit 18C and the comparison unit 19C in the nerve stimulation system 1C may be the same as that in the first embodiment described above.

The control unit 14C of the neural stimulation system 1C of the present embodiment executes the following flow from step S701 to step S703 (see FIG. 11).
Step S701 is a step of calculating variation in the trend of the heart rate.
In step S701, the change amount calculation unit 18C of the control unit 14C selects each heartbeat in the non-stimulation trend fb (T) in a predetermined first period T (t <T <t + s) including a plurality of application durations of nerve stimulation pulses. The variation of the number is calculated as the non-stimulation variation vb (T). Furthermore, the variation calculation unit 18C calculates the variation in each heart rate in the stimulation trend fc (T) in the first period as the stimulation variation vc (T). The non-stimulation variation vb (T) and the stimulation variation vc (T) are both stored in the storage unit 17.
Step S701 is ended here, and it progresses to step S702.

Step S702 is a step for branching the process by comparing the variations stored in step S701.
In step S702, a change in the heart rate occurs when the comparison at the time of stimulation vc (T) is smaller than the predetermined threshold (5 in the present embodiment) with respect to the non-stimulation time variation vb (T). It is determined that there is a divergence in the rate, and the process proceeds to step S703.
If the stimulation time variation vc (T) with respect to the non-stimulation time variation vb (T) is equal to or greater than the predetermined threshold (5 in this embodiment) in step S702, the process returns to step S7 and proceeds to step S8.
Step S703 is a step of reducing the stimulation intensity setting value in order to reduce the intensity of the neural stimulation pulse.
In step S703, the control signal for reducing the intensity of the nerve stimulation pulse is transmitted to the pulse generation unit 20 by executing the steps from step S301 to step S307.

  In the present embodiment, when the stimulation variation vc (T) is smaller than the non-stimulation variation vb (T) by exceeding the predetermined threshold, the action and homeostasis of lowering the heart rate by the influence of the nerve stimulation pulse This means that the variation in heart rate is reduced by strongly antagonizing the action of raising the heart rate. That is, when the stimulation variation vc (T) is smaller than the non-stimulation variation vb (T) by exceeding the predetermined threshold, it is preferable to weaken the nerve stimulation pulse to reduce the burden on the patient. The nerve stimulation system 1C according to this embodiment compares the non-stimulation variation vb (T) with the stimulation variation vc (T) to determine whether the intensity of the nerve stimulation pulse is in an inappropriately high state. It can be determined. As a result, the nerve stimulation system 1C according to the present embodiment can perform nerve stimulation by a nerve stimulation pulse with an intensity that is less harmful to the living body.

Fifth Embodiment
A fifth embodiment of the present invention will be described.
The nerve stimulation system 1D of the present embodiment includes a change amount calculation unit 18D and a comparison unit 19D that are different in configuration from the change amount calculation unit 18 and the comparison unit 19 disclosed in the first embodiment. The configuration other than the change amount calculation unit 18D and the comparison unit 19D in the nerve stimulation system 1D may be the same as that in the first embodiment described above.

The change amount calculation unit 18D calculates the trend of the non-stimulation heart rate in the predetermined first period T (t <T <t + s) including a plurality of application durations of the nerve stimulation pulse as the non-stimulation trend fb (T). . Furthermore, the change amount calculation unit 18D calculates the rate of decrease in the heart rate during stimulation with respect to the heart rate during non-stimulation in the first period T, and calculates the trend of the rate of decrease in the first period as the rate of decrease trend fbc (T). . The non-stimulus trend fb (T) and the decrease rate trend fbc (T) are stored in the storage unit 17.
After that, the change amount calculation unit 18D acquires the cross correlation coefficient between the non-stimulation trend fb (T) and the decrease rate trend fbc (T) by cross correlation analysis.

  The comparison unit 19D determines that there is a deviation in the rate of change of the heart rate when the cross-correlation coefficient acquired by the change amount calculation unit 18D is close to 1 (for example, the cross-correlation coefficient is 0.7 or more). A control signal for weakening the nerve stimulation pulse is transmitted to the pulse generator 20.

  In the neural stimulation system 1D of the present embodiment, the cross correlation coefficient between the non-stimulation trend and the reduction rate trend is acquired, and the non-stimulation trend and the reduction rate trend are compared with each other, The nerve stimulation pulse can be weakened by detecting a state in which the nerve stimulation pulse has such a high intensity that the change in heart rate at the time of stimulation does not follow the change. As a result, the nerve stimulation system 1D according to the present embodiment can perform nerve stimulation by a nerve stimulation pulse with an intensity that is less harmful to the living body. Further, since the comparison unit 19D makes a determination using the decrease rate trend, even when the value of the decrease rate of the heart rate shows an abnormal value due to the influence of noise or the like, the determination can be made with high accuracy.

As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.
For example, in each of the above-described embodiments and modifications thereof, a signal for prompting a user to change a setting for reducing the intensity of the nerve stimulation pulse, instead of automatically changing the intensity of the nerve stimulation pulse. The control unit may output.
Moreover, it is possible to combine and comprise the component shown in the above-mentioned each embodiment and each modification suitably.

1,1A, 1B, 1C, 1D Neural stimulation system 2 Lead 3 First electrode (electrode for nerve stimulation)
4 Second electrode (electrode for heart rate measurement)
DESCRIPTION OF SYMBOLS 5 Covered wire 10 Control unit 11 Housing | casing 12 Power supply part 13 Operation part 14, 14C Control part 15 Stimulus intensity adjustment part 16 Heart rate measurement part 17 Storage part 18, 18A, 18B, 18C, 18D Change amount calculation part 19, 19A, 19B, 19C, 19D Comparison unit 20 Pulse generation unit

Claims (4)

A nerve stimulation electrode,
Heart rate measurement electrodes,
A controller for controlling a nerve stimulation pulse applied to the nerve stimulation electrode connected to the nerve stimulation electrode and the heart rate measurement electrode;
Equipped with
The control unit
The heart rate in a predetermined first period in which the nerve stimulation pulse is applied to the nerve stimulation electrode is acquired from the heart rate measurement electrode as a stimulation heart rate,
The heart rate in a predetermined second period in which the nerve stimulation pulse is not applied to the nerve stimulation electrode is acquired from the heart rate measurement electrode as a non-stimulation heart rate,
A controller for determining whether or not there is a difference between the heart rate during stimulation and the heart rate during non-stimulation ,
Immediately before the first timing to start applying the nerve stimulation pulse to the nerve stimulation electrode, the non-stimulation heart rate is acquired as a first non-stimulation heart rate (A),
After the elapse of the duration of the nerve stimulation pulse at the first timing, the non-stimulation heart rate is set to the second non-stimulation heart rate immediately before the second timing when the nerve stimulation pulse starts to be applied to the nerve stimulation electrode ( B) get as
After the first timing, the stimulation heart rate is acquired as a first stimulation heart rate (C) within the duration of the nerve stimulation pulse,
After the second timing, the stimulation heart rate is acquired as a second stimulation heart rate (D) within the duration of the nerve stimulation pulse,
When the (A), (B), (C), (D) satisfy the relationship shown in the following Formula 1 or Formula 2, it is determined that there is the difference
A neural stimulation system characterized by
{(B)-(A)} / {(D)-(C)} <0.5 (Formula 1)
2 <{(B)-(A)} / {(D)-(C)} (Expression 2) A nerve stimulation electrode,
Heart rate measurement electrodes,
A controller for controlling a nerve stimulation pulse applied to the nerve stimulation electrode connected to the nerve stimulation electrode and the heart rate measurement electrode;
Equipped with
The control unit
The heart rate in a predetermined first period in which the nerve stimulation pulse is applied to the nerve stimulation electrode is acquired from the heart rate measurement electrode as a stimulation heart rate,
The heart rate in a predetermined second period in which the nerve stimulation pulse is not applied to the nerve stimulation electrode is acquired from the heart rate measurement electrode as a non-stimulation heart rate,
A controller for determining whether or not there is a difference between the heart rate during stimulation and the heart rate during non-stimulation ,
Immediately before the first timing to start applying the nerve stimulation pulse to the nerve stimulation electrode, the non-stimulation heart rate is acquired as a first non-stimulation heart rate (A),
After the elapse of the duration of the nerve stimulation pulse at the first timing, the non-stimulation heart rate is set to the second non-stimulation heart rate immediately before the second timing when the nerve stimulation pulse starts to be applied to the nerve stimulation electrode ( B) get as
After the first timing, the stimulation heart rate is acquired as a first stimulation heart rate (C) within the duration of the nerve stimulation pulse,
After the second timing, the stimulation heart rate is acquired as a second stimulation heart rate (D) within the duration of the nerve stimulation pulse,
When the (A), (B), (C), and (D) satisfy the relationship shown in the following formula 1, it is determined that there is the deviation.
A neural stimulation system characterized by
(B) / (A)> k (D) / (C) where k is a constant greater than 1 (Equation 1) A nerve stimulation electrode,
Heart rate measurement electrodes,
A controller for controlling a nerve stimulation pulse applied to the nerve stimulation electrode connected to the nerve stimulation electrode and the heart rate measurement electrode;
Equipped with
The control unit
The heart rate in a predetermined first period in which the nerve stimulation pulse is applied to the nerve stimulation electrode is acquired from the heart rate measurement electrode as a stimulation heart rate,
The heart rate in a predetermined second period in which the nerve stimulation pulse is not applied to the nerve stimulation electrode is acquired from the heart rate measurement electrode as a non-stimulation heart rate,
A controller for determining whether or not there is a difference between the heart rate during stimulation and the heart rate during non-stimulation ,
The variation of each heart rate in the trend of the non-stimulation heart rate in a predetermined first period including a plurality of application durations of the nerve stimulation pulse is calculated as the non-stimulation time variation,
The fluctuation of each heart rate in the trend of the heart rate during stimulation in the first period is calculated as the variation during stimulation,
It is determined that there is the deviation when the variation at the time of stimulation is smaller than a predetermined threshold with respect to the variation at the time of non-stimulation.
A neural stimulation system characterized by A nerve stimulation electrode,
Heart rate measurement electrodes,
A controller for controlling a nerve stimulation pulse applied to the nerve stimulation electrode connected to the nerve stimulation electrode and the heart rate measurement electrode;
Equipped with
The control unit
The heart rate in a predetermined first period in which the nerve stimulation pulse is applied to the nerve stimulation electrode is acquired from the heart rate measurement electrode as a stimulation heart rate,
The heart rate in a predetermined second period in which the nerve stimulation pulse is not applied to the nerve stimulation electrode is acquired from the heart rate measurement electrode as a non-stimulation heart rate,
A controller for determining whether or not there is a difference between the heart rate during stimulation and the heart rate during non-stimulation ,
Calculating a trend of the non-stimulated heart rate in a predetermined first period including a plurality of application durations of the nerve stimulation pulse as a non-stimulated trend,
The reduction rate of the stimulation heart rate to the non-stimulation heart rate in the first period is calculated, and the trend of the reduction rate in the first period is calculated as the reduction rate trend.
Obtain a cross-correlation coefficient between the non-stimulus trend and the decline rate trend by cross-correlation analysis,
It is determined that the deviation is present when the cross correlation coefficient is greater than or equal to a predetermined threshold value
A neural stimulation system characterized by

Images