WO2016005053A1

WO2016005053A1 - Method and device for monitoring a treatment of the human or animal body

Info

Publication number: WO2016005053A1
Application number: PCT/EP2015/001396
Authority: WO
Inventors: Azad KHEDER
Original assignee: Signus Medizintechnik Gmbh
Priority date: 2014-07-09
Filing date: 2015-07-09
Publication date: 2016-01-14
Also published as: DE102015006914A1

Abstract

A method for monitoring a treatment of the human or animal body, in which current pulses with a predetermined pulse width are deposited into the body in the region of a nerve cord and voltage signals triggered by the current pulses are measured in the region of a muscle connected to the nerve cord, wherein, in a preliminary step, at least one criterion of voltage signals which are still measurable in response to the current pulses is established and the amplitude of the current pulses is regulated in such a way during the course of the treatment that the voltage signals obtained in response approximately satisfy the criterion.

Description

METHOD AND DEVICE FOR MONITORING TREATMENT AM

HUMAN OR ANIMAL BODY

The invention relates to a method for monitoring a treatment on the human or animal body in which electrical current pulses of predetermined pulse width and predetermined frequency are deposited in the body in the region of a nerve cord and measured in the region of a muscle connected to the nerve cord by the current pulses triggered electrical voltage signals become.

In the operation on the human or animal body, it must be prevented that the nervous system is damaged more than absolutely necessary. This is especially important in spine surgery. In this area, numerous nerves from the spinal canal penetrate to the muscles, which must be protected during surgery. For this purpose, it is possible to exploit the fact that current impulses are transmitted to the muscles to be enervated via the nerve cords and a voltage response to the current impulses is measured in the area of the enervated muscles can. Corresponding current pulses can also be deposited by an external device in the body, the amplitude of the current pulses needed to trigger a measurable voltage signal on the enervated muscle at a known current pulse width, a measure of the distance of the place of landfill of the current pulse to the nerve. This knowledge is exploited in methods described for example in US 8,050,769 B2 for monitoring a surgical treatment. In this known method, a current pulse sequence with pulses of increasing amplitude in the area of the wound or in the surgical field is continuously deposited in the course of the surgical treatment. If the current required to generate a given voltage response of about 100 ν in the region of the muscle falls below a predetermined limit of 10 mA, the surgeon is advised that he is in the nerve branch with the instrument with which he deposits the current pulses in the human body approaches. If the current required to produce the critical voltage of about 100 μV falls below 4 mA, another warning signal is triggered to inform the operator that there is now an immediate risk of nerve damage.

Although a helpful warning of the surgeon can be made with this known method, it has been shown that the monitoring can simultaneously lead to a disability of the operation. In view of these problems in the prior art, the object of the invention is to enable disability-free monitoring of a treatment on the human or animal body.

In procedural terms, the object is achieved by a development of the known method, which is characterized essentially in that in a preparatory step, a criterion of still responding to current pulses measurable voltage signals is determined and in the course of treatment, the amplitude of the current pulses is regulated so that in response thereto received voltage signals approximately meets the criterion.

Within the scope of the invention, electrodes for signal derivation, as used in electromyography, can be used. Both the use of dipolar needle electrodes and the use of monopolar electrodes is possible. Furthermore, surface electroforming arrangements as described in US Pat. No. 8,050,769 B2 can be used. Within the scope of the invention, fine wire electrodes are particularly preferably used.

The signal derivation and processing including filtering can be done as in known methods of electromyography. The signal derivation and processing in this method is described, for example, in the "EMG Primer, a Practical Introduction to Kinesiological Electromyography, Peter Konrad, Verse 1.0, September 2005". Content of this document is hereby incorporated by reference into this description in terms of signal derivation and signal processing.

During signal propagation along the muscle fiber, as described in the cited document, a depolarization repolarization cycle takes place. This causes a depolarization wave propagating along the muscle fiber. When electromyography measures a signal as a potential difference between two electrodes placed along the muscle fiber, a bipolar signal is obtained which depends on the distance between the electrodes and the potentials of all the muscle fibers excited within the detectable motor unit. Such signals are examples of current pulses triggered by voltage signals in the context of this invention.

The invention is based on the finding that the problems occurring in the prior art are essentially due to the fact that the current pulses used for monitoring are regularly above the depolarization threshold, so that the current pulses leading to a voltage signal cause a muscle contraction. This hinders the operation. In the known methods, a high detection threshold for the voltage signals is set to ensure that a reproducible voltage response can be detected.

In contrast, in methods according to the invention, a criterion, such as a detection level, which is regularly below the depolarization threshold is determined for each operation and each patient individually, so that the current pulses used for monitoring, whose amplitude is always controlled so that the voltage signal is approximately the criterion, in particular the detection level, do not lead to muscle contraction. As a result, a trouble-free monitoring of the operation or the treatment of the human or animal body can be ensured. In this case, the criterion may also represent a time profile of the voltage signal, such as an increase or decrease of the voltage signal that can be measured in response to the current pulse.

The time advance of the voltage signals can be measured with sufficient accuracy if the voltage signals are measured at a frequency or the waveform is scanned or scanned at such a frequency which is greater than the frequency of the current pulses, in particular at least ten times the current pulse frequency ,

Additionally or alternatively, the criterion to be met by the voltage signals may be a detection level of voltage signals still measurable in response to current pulses.

In the method according to the invention, the detection level is between 50 pV and 150 pV, depending on the circumstances of the individual case. This detection level can be dependent from the distance of the place where the current pulses are deposited, from the nerve supplying the muscle equipped with the measuring arrangement, with current pulses having an amplitude of 2 to 100 mA as square pulses and whose pulse width is between 10 ps and 300 ps is located. In preferred methods, the pulse width is between 150 ps and 250 ps, more preferably about 200 ps. The pulses are preferably deposited at a frequency which can be used to ensure that a period of time passes between the individual current pulse sequences within which the response to the current pulses completely dissipates.

In the method according to the invention, the detection level is usually less than 00 pV. Thus, the depolarization threshold is not reached. There is no muscle contraction.

On the other hand, an association between the distance between the point of deposition of the current pulses and the nerve on the one hand and the current intensity of the current pulses which lead to a voltage signal with the detection level can be determined with the aid of empirical investigations. It can then be determined that a dangerous approach of the instrument with which the current pulses are deposited takes place on the nerve when, in order to obtain the detection level, current pulses with an amplitude which falls below a predetermined limit are deposited. Therefore, in a preferred embodiment of the invention, it is provided that a first warning signal is triggered when the amplitude of the current pulses required to obtain the detection level falls below a predetermined limit, possibly determined by empirical methods. As the instrument depositing the current pulses approaches the nerve, the level required to obtain the detection level decreases

Amplitude of the current pulses continues. A safe avoidance of the damage of nerve tracts while preventing an unnecessary impairment of the surgeon can be achieved when a second warning signal is triggered as soon as the required to obtain the detection level amplitude of the current pulse falls below a second predetermined limit, the second predetermined limit is less than the first preset limit.

With the use of such monitoring methods, the surgeon can easily be active in the area between the first threshold and the second threshold, if he takes special care there.

To obtain the detection level, an average value of the voltage signals triggered by the current pulses and the average deviation of the voltage signals from the mean value are expediently determined, the detection level being defined as the level at which the average deviation falls below a predetermined limit value. The limit can be set to 50 percent of the detection level, preferably to 30 percent of the detection level. Thus, when the detection level is about 80V, it can be defined as the detection level when the mean deviation thereof is less than 40V.

In a particularly preferred embodiment of the invention, to obtain the detection level, the spontaneous activity of the muscle is measured without stimulation with current pulses and the detection level to a level of spontaneous activity, which is usually about 30 to 60 μ \ by a predetermined amount, preferably 30 to 50 V, exceeding value.

When using inventive method, it is possible to obtain a particularly small detection level when the voltage signals are amplified by a carrier frequency amplifier whose carrier frequency corresponds to the frequency of the current pulses. In a carrier frequency amplifier or lock-in amplifier or phase-sensitive rectifier, the measurement signal is multiplied by a signal of a predetermined frequency and then integrated into a low-pass filter. This determines the cross-correlation between the measurement and reference signals for a fixed phase shift. The cross-correlation for signals of different frequency is about zero. Therefore, the carrier frequency amplifier does not provide an output signal when the frequency of the reference signal is different from that of the measurement signal. Only for equal frequencies does the cross-correlation provide a finite value and the carrier frequency amplifier thus gives a finite output signal. By selecting the appropriate frequency, in this case the frequency of the current pulses, it is thus possible to filter out the corresponding component from the measurement signal. As a result, the signal-to-noise ratio of the measurement signal can be significantly improved. In the method according to the invention, it is thus possible to determine a reproducible detection level even with very low voltage signals.

According to another aspect of the invention, which is considered to be independently protectable independently of the above-described embodiments of the invention, a time interval between the dumping of the current pulses and the measurement of the voltage signals is set. This can be done for example with a so-called boxcarintegrator.

This aspect of the invention is based on the idea that between the deposit of current pulses and the detection of voltage signals in response to a transmission distance between the place of deposit of the current pulses and the location of the voltage detection corresponding transmission time elapses and the detection sensitivity can be increased upon detection of the voltage signals if a measurement takes place only after a predetermined time interval after depositing the current pulses, the time interval between the dumping of the current pulses and the detection of the voltage pulses being voltage signals corresponds to the transmission time and the length of the detection interval can correspond approximately to the time length of the current pulses.

With such a method, the detection sensitivity in the detection of the voltage signals generated in response to the current pulses can be increased so that a reliable voltage signal detection before reaching the Depolarisationsschwelle can still be done if a detection level of, for example, 30 to 150 μν, preferably 30 to 50 μν fixed becomes.

However, it has proven to be particularly advantageous, even if in this embodiment a detection level is determined in a preparatory step and a reaction to the dumping of current pulses is not accepted until the detection level has been reached. For this purpose, also in this embodiment of the invention in a preparatory step, the spontaneous activity of the muscle can be determined. The detection level may then be set to a value exceeding the level of the spontaneous activity by a predetermined amount.

In particular, in the last-described embodiment of the invention, it has proved to be expedient if in the monitoring method a first pulse sequence of successive current pulses having a first current pulse having an amplitude having the first predetermined limit, a second current pulse having a current amplitude having the second predetermined limit and at least a third current pulse having an amplitude exceeding the second limit is deposited, wherein an enable signal is generated when none of the current pulses results in a voltage signal responsive thereto, wherein the first pulse train is repeated when the enable signal is to be generated.

By this embodiment of the invention, a safe continuation of the operation can already be signaled when current pulse trains are generated with only three current pulses, the third current pulse to protect the release may even have an amplitude that is above the second threshold.

According to a further embodiment of the invention, it has proven to be expedient to accelerate the detection of an operating situation in which increased attention is required when a second pulse train is generated in which alternately a first current pulse having a first predetermined limit amplitude and a second current pulse having a second predetermined limit amplitude is generated, wherein the first warning signal is generated and the second pulse train is repeated when only in response to the first current pulse, a voltage signal is measured. In this embodiment of the invention, therefore, an operating situation in which increased Attention is required, proven with only two current pulses having current pulse trains.

According to a further preferred embodiment of the invention, a particularly critical operation situation can be monitored at high speed if a third pulse train is generated in response to the detection of a voltage signal in response to a current pulse having a second limit amplitude, alternating current pulses of different amplitudes, which are each below the second limit, are generated, wherein only when a current pulse having an amplitude corresponding to the second limit value is generated again, when in response to no current pulse of the third pulse train, a voltage signal can be detected.

This method allows a particularly dynamic monitoring of a critical operation situation with only two current pulses having current pulse trains. If after completion of the third pulse train, that is, when in response to no current pulse of the third pulse train, a voltage signal is detected and no voltage signal when depositing a current pulse with a second threshold corresponding pulse height is detected, the method can continue with the first or second pulse train become.

In all embodiments of the invention, the current pulses are deposited at a frequency of 25 Hz or less, preferably 23 Hz or less, in particular 10 to 15 Hz, more preferably 13 Hz.

As already explained above, it has proven to be particularly expedient in methods according to the invention if the current pulses are deposited by means of a surgical instrument, such as a scalpel, a cannula, or the like. As can be seen from the above explanation of methods according to the invention, a device for carrying out such methods has an arrangement for depositing current pulses of predetermined amplitude, frequency and pulse width in the human or animal body, an electrode arrangement for detecting voltage signals triggered by the current pulses, a device for determining a criterion such as a detection level of voltage signals still detectable in response to the current pulses, and a controller for controlling the amplitude of the current pulses in response to the voltage signals received thereon, such that the voltage signals approximately meet the criterion, in particular approximately the detection level. The device may include means for generating visual and / or audible warning signals when the amplitude of the current pulses falls below a predetermined threshold to thereby alert the operator to an improper approach to a nerve.

In a preferred embodiment of the invention, a carrier frequency amplifier is provided for amplifying the voltage signals, wherein the carrier frequency is predetermined by the frequency of the current pulses.

In addition or as an alternative to a carrier frequency amplifier, a device according to the invention can have a voltage signal detection device in the form of a box-coarse integrator, with which a measurement of voltage signals takes place only within a predetermined, in particular selectable time window after deposit of the current signal.

In a particularly preferred embodiment of the invention, devices according to the invention have an adjustment facility via which the surgeon can set the location of the operation and the location of the voltage signal detection, so that within the device, the transmission time between landfill of the current pulses and their detection can be calculated. Thus, the settings of the voltage signal detection device with respect to the time window within which the voltage signals are to be detected, can be easily specified.

The invention will be explained in more detail with reference to the drawing, to which reference is made with respect to all essential to the invention and in the description not further highlighted details. In the drawing shows:

1 shows a schematic representation of a first current pulse sequence,

Fig. 2 is a schematic representation of a second current pulse train and

Fig. 3 is a schematic representation of a third current pulse train.

The first current pulse sequence shown in FIG. 1 comprises a first current pulse having an amplitude of 6 mA corresponding to the second limit value, a second current pulse having an amplitude corresponding to the first limit value of 10 mA, a third current pulse having an amplitude of 11 mA and three successive current pulses with an amplitude of 20 mA each. If none of these current pulses causes a voltage response, it can be safely assumed that the current impulse deposition occurs at a sufficient distance from the monitored nerve path. In this case, a voltage response is only accepted if a detection level is reached. The level of detection is determined in the embodiment of the invention explained with reference to the drawing, in which First, the spontaneous activity of the muscle is measured without stimulation with current impulses and the detection level is set to a value exceeding the level of the spontaneous activity by 30 to 50 μν.

In the second current pulse sequence shown in FIG. 2, a first current pulse having an amplitude corresponding to the first limit value and a second current pulse having an amplitude corresponding to the second limit value are generated alternately. The first warning signal is triggered when a voltage response can only be detected when the second current pulse is deposited.

The third current pulse sequence shown in FIG. 3 is triggered when in the case of the second current pulse sequence illustrated in FIG. 2, a voltage response is also obtained in response to a current pulse having an amplitude corresponding to the second limit value. Then alternating current pulses of 2 or 4 mA are generated, each having an amplitude below the second threshold. Only when a voltage signal can not be detected on any of these pulses with an amplitude of 2 mA and 4 mA, again a current pulse is deposited with a corresponding to the second threshold amplitude of 6 mA. Although no voltage signal can be detected on this current pulse, the dumping of current pulses takes place automatically according to the second current pulse sequence shown in FIG. Even if no signal can be detected in response to this current pulse sequence, the dumping of current pulses takes place in accordance with the first current pulse sequence.

Claims

claims

1. A method for monitoring a treatment on the human or animal body, wherein in the region of a nerve strand current pulses of predetermined pulse width deposited in the body and measured in the region of a nerve-related muscle by the current pulses triggered voltage signals, characterized in that a preparatory step, at least one criterion of voltage pulses which can still be measured in response to current pulses is determined, and in the course of the treatment the amplitude of the current pulses is regulated so that the voltage signals received in response to this satisfy the criterion.

2. The method according to claim 1, characterized in that a criterion represents a time course of the voltage signal.

3. The method according to claim 1, characterized in that the voltage signals are measured at a frequency which is greater than the frequency of the current pulses, in particular at least 10 times the current pulse frequency.

4. The method according to any one of the preceding claims, characterized in that a criterion is a detection level of in response to current pulses still measurable voltage signals.

5. The method according to claim 4, characterized in that a first warning signal is triggered when the required to obtain the detection level amplitude of the current pulse falls below a first predetermined limit.

6. The method of claim 4 or 5, characterized in that a second warning signal is triggered when the required to obtain the detection level amplitude of the current pulses falls below a second predetermined limit, wherein the second predetermined limit is smaller than the first predetermined limit.

7. Method according to one of the preceding claims 4 to 6, characterized in that to obtain the detection level, an average value of the voltage signals triggered by the current pulses and the average deviation of the voltage signals from the mean value is true, wherein the detection level is determined as the level at which the mean deviation falls below a predetermined limit.

8. The method according to any one of the preceding claims, characterized in that to obtain the detection level, the spontaneous activity of the muscle measured without stimulation with current pulses and the detection level is set to a level of spontaneous activity by a predetermined amount, preferably 30 to 50 pV, exceeding value ,

9. The method according to any one of the preceding claims 4 to 8, characterized in that the voltage signals are amplified by a carrier frequency amplifier whose carrier frequency corresponds to the frequency of the current pulses.

10. The method according to any one of the preceding claims, characterized in that the current pulses by means of a surgical instrument, such as a scalpel, a cannula, or the like are deposited.

11. A method, in particular according to one of the preceding claims, characterized in that a time interval between the landfill of the current pulses and the measurement of the voltage signals is set.

12. The method according to claim 1 1, characterized in that the voltage signals are measured only in a predetermined time window after depositing the current pulses.

13. A method, in particular according to one of the preceding claims, characterized in that in a first pulse sequence of successive current pulses, a first Stromimmpüls having the first predetermined limit having amplitude, a second current pulse having a second predetermined limit amplitude and a third current pulse is deposited with an amplitude exceeding the second threshold and an enable signal is generated when none of the current pulses results in a voltage signal responsive thereto, wherein the first pulse train is repeated when the enable signal is to be generated.

14. The method according to any one of the preceding claims, characterized in that in a second pulse train alternately a first current pulse having a first predetermined limit having amplitude and a second current pulse having the second predetermined limit having amplitude is generated, wherein the first warning signal generated and the second pulse train is repeated if only in response to the first current pulse, a voltage signal is measured.

15. The method according to any one of the preceding claims, characterized in that a third pulse train is generated in response to the detection of a voltage signal in response to a current pulse having an amplitude having the second limit, at the alternating current pulses of different amplitudes, each below the second threshold are generated, in which case again a current pulse is generated with an amplitude corresponding to the second limit value, if a voltage signal is detected in response to no current pulse of the third pulse train.

16. An apparatus for carrying out a method according to any one of the preceding claims.

17. The apparatus of claim 16 with an arrangement for depositing current pulses predetermined amplitude, frequency and pulse width in a human or animal body, an electrode assembly for detecting triggered by the current pulses voltage signals, means for determining criteria of the voltage signals, in particular a detection level of still in response to the current pulses detectable voltage signals and a control device for regulating the amplitude of the current pulses in response to the voltage signals received in response thereto, such that the voltage signals meet approximately the criteria.

18. The apparatus according to claim 17, characterized by a device for generating optical and / or acoustic warning signals when the regulated amplitude of the current pulses falls below a predetermined limit.

19. The apparatus of claim 17 or 18, characterized by a carrier frequency amplifier for amplifying the voltage signals, wherein the carrier frequency is predetermined by the frequency of the current pulses.

20. Device according to one of claims 17 to 19, characterized in that the arrangement for depositing the current pulses comprises a surgical instrument equipped with an electrode assembly, such as a scalpel, a cannula, or the like.

21. Device according to one of claims 16 to 20 with a Spannungssignalnachweisein- direction, with which a measurement of voltage signals only within a predetermined, in particular selectable time window after depositing the current signal takes place.