DD158612A1 - DEVICE FOR STIMULATING PERIPHERAL NERVES - Google Patents

Abstract

The invention relates to a medical device that can be used in particular for the determination of manifest and latent phases of neuromuscular blockade during surgical procedures. The aim of the invention is to obtain reliable information about the condition of the patient during anesthesia. The invention has for its object to expand the scope of the return of muscle activity. The device includes a feed unit and stimulation electrodes. In between, an oscillator, a frequency divider, a time regulator and a power stage are connected in series, wherein the frequency divider can provide current pulses with corresponding supraphysiological frequencies and both the feed unit and the oscillator are connected to a high voltage switch unit, which in turn is coupled to the power stage , D.Geraet can be fed with a dry battery or a rechargeable battery. The ball-shaped electrodes are arranged outside the housing, each coupled to a transition piece. The transition pieces are arranged in the wall of the housing in Schraubenhuelsen, which are limited to each other movable.

Description

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Apparatus for stimulating peripheral nerves Field of application of the invention

The invention relates to a medical device for stimulating peripheral nerves, which is particularly suitable for determining manifest and latent phases of neuromuscular blockade and has a feed unit and a stimulation electrode. Bas device according to the invention is particularly advantageously applicable to surgical and operational procedures when the Stimulation of a muscle innervierendan nerve by means of the contraction of the muscle causing current pulses is made.

Characteristic of the known technical solutions

In surgical and operational procedures, the use of general anesthesia of the patient is widespread. For anesthesia, appropriate medicines are used, in addition to other muscles relaxing the muscles of the body, the so-called curare, which by forcing the relaxation of the skeletal musculature significantly facilitate the interventions to be made in the body cavities. "The curar are drugs of very effective action, but not of paralysis only the skeletal muscles, but also the muscles of the respiratory system, d, h, the diaphragm are suitable. The curars produce their effect on the striated musculature, d. h, they act at the points where the stimulus is transferred from the nerve to the muscle. "The essence of their action is that on the neuromuscular end plate the depolarization of the nerve which has become free of the nerve and the action potential of the nerve

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Muscle-inducing acetylcholine is prevented and thus the contraction of the muscle is excluded and the muscle assumes the state of balancing. This condition is called neuromuscular blockade,

It is obvious that by using vital physiological functions of paralyzing drugs, their action is very carefully controlled with possible maximum reliability. For the determination of the action of the curar, the use of various devices for stimulating peripheral nerves has been known in medical practice for about 20 years. The work of these devices is based on the stimulation of a muscle innervating nerve and the detection of the resulting under the action of the stimulus contraction of the muscles. The most common stimulators are suitable for producing two types of stimuli. One of these types is the so-called "twich" stimulus, which consists of a simple single stimulus. The other type of stimuli consists of a so-called "tetanizing" series of pulses generated within 5 to 10 seconds, whereby the pulses are characterized by a relatively low repetition frequency. At the same time, another device was developed, which generates pulse trains consisting of four pulses (so-called "train of four") with a repetition frequency of 2 Hz. The known devices for stimulating peripheral nerves have a common drawback: they are only suitable in a very narrow range of changes in the neuromuscular blockade characteristic muscle contractions to provide reliable information about the condition of the patient.

The organism realizes the transmission of the neuromuscular stimuli, as well as other vital functions in one

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pretty high reserve. The relaxation of the muscles required for the surgical procedures can only be achieved in such a way that all reserves of the transmission capacity of the musculature are blocked. The reserve, the so-called latent curarization, amounts to 75% of the transmission capacity. The remaining and about 25% share is called manifest curare. The control of this area is very void during the operation, because the doctor on the one hand gain information about the muscle sonus, on the other hand, can observe the pharmacodynamics of the drug. After the completion of the surgical singing riff, the muscle activity in the patient should be secured again with the highest possible level. This is necessary to secure the respiratory reserves, to maintain the occupancy and the circulation. As a result, testing becomes necessary not only for the manifestation of curvature but also for the reserve (the latent curarization).

For the purpose of performing the curarization, the patient is intravenously administered a corresponding drug, which very quickly leads to complete paralyzing of all muscles of the body, since it causes the blockade of all muscle receptors of the acetylcholine and therefore excludes the suppuration of the nerve impulses. Later, the sites of action are gradually depleted of the remedy and the possibility of muscle activity. In this case, the manifest curarisation remains for a long time and the conditions of the operation are good. The return of muscle activity is controlled by various pacemakers. In the case of stimulation made by the known single pulses or "tetanizing" pulse series of low repetition frequency, the beginning of the muscle activity can only be about 90%.

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value <3 _ΘΓ neuromuscular block. This implies that under the action of the stimuli, a relatively small amount of the acetylcholine has become free and similar amounts can be observed also in the normal physiological conditions. The traditional methods allow the examination of this process to about 75% neuromuscular blockade, because at this blockade value, the contraction of the muscles under the action of both the Binzelimpulse, and the "tetansaerenden" pulse series low frequency takes the usual value and the doctor the process This means that from the 100% range of neuromuscular capacity only a proportion of about 15 to 20 % can be tested by means of the known devices and methods.

' Object of the invention

The object of the invention is to obtain more reliable information about the condition of the patient during anesthesia.

Explanation of the essence of the invention

The invention has for its object to develop such a device for stimulating peripheral nerves, which can significantly expand the range of observation of the return of muscle activity, in comparison with the known solutions, d. h, it should ensure the possibility of observing the beginning of the return of muscle activity from the 95% (instead of 90%) value of the neuromuscular blockade and the pursuit of the V

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reduce the neuromuscular blockade to 36%, possibly 30%.

The development of the invention is based on a proven physiological fact: when the stimulation by means of impulses of so-called supraphysiological, d. H. even reaching frequencies reaching 400 Hz, advantageously at a frequency of 100, 200 or 400 Hz, the acetylcholine frees itself from the nerve endings in a well-defined manner: initially in a larger amount, later, under the action of repetitive stimuli in one The said process is currently controlled only under normal conditions, d, h, under conditions when drugs do not prevent the transmission of neuromuscular stimuli. Normally, the muscle responds to the supraphysiological stimuli with a regular zontraction, although the amount of acetylcholine decreases with the repetition of the stimuli. This follows from the fact that the transmission of the neuromuscular stimuli is also realized with a high reserve, i. H. a small amount of the acetylcholine is sufficient to cause the depolarization required for activity. If a portion of the reserve is blocked by a curare, muscle fatigue occurs as the amount of acetylcholine decreases. Fatigue has a very characteristic consequence: the large amplitude of muscle contraction at the beginning of stimuli diminishes under the influence of successive stimuli. So, the well-known stimuli devices that use traditional stimulus parameters are not expected to contract the responses of the muscles in the under 7% range of neuromuscular blockade

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Create shapes and processes. According to our knowledge, the application of the supraphysiological frequencies makes it possible to induce the different muscle contractions in this area, and thus to increase the safety of the patient to whom a curare has been applied «

The stated object has been achieved by devising a device for stimulating peripheral nerves, in particular for determining manifest and latent phases of the neuromuscular blockage, which has a feed unit and a stimulation electrode, according to the invention between the feed unit and the stimulation electrodes the oscillator connected to the supply unit, a pulse in a frequency range from 25 to 400 Hz and radio frequency pulses advantageously provided with a frequency divider delivering 25 kHz, a time regulator supplying a current pulse series at least within a time range of 2 seconds, and a power stage connected to the stimulation electrodes , the supply unit and the oscillator are coupled to a high voltage switch unit and the outputs of the high voltage switch unit are supplied to the power stage.

The time controller is advantageously provided with a unit for producing at least 0.1 sec. Lasting current pulses. The oscillator has a unijunction transistor.

In an advantageous embodiment of the device according to the invention is a coupled to the frequency divider unit for regulating the frequency of the current pulses, and a

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connected to the power stage, the power of the current pulses regulating unit available. In another advantageous embodiment, a starter switch is used together with the time controller and the power stage is designed as a current generator output exhibiting speed regulator circuit.

Different from the previous practice is expedient to arrange the electrode outside the housing of the device by means of appropriate transition pieces. The transition pieces can be made as inflexible, straight or curved rods, which are fastened in the housing and in the rotated position.

If the electrodes are designed in the form of spheres, the device according to the invention can be used to particular advantage. The fulfillment of the safety of the operation and the patient serving regulations is greatly facilitated if the feed unit is provided with a battery. But it is also possible to use a rechargeable battery.

The transition pieces are arranged in the wall of the housing at a distance of at least 20 mm from each other. The transition pieces are arranged in the wall of the housing in screw sleeves, wherein the transition pieces in the screw sleeves are limited to each other movable.

The housing of the device is designed as an elongated sheath with a vascular cross-section whose maximum width is 55 nm and maximum height is 50 mm. On the housing are an indicator for signaling the operation of the electrodes and an indicator for tracking; voltage

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Level of the dining unit arranged. The starter switch is provided behind the indicators and next to it the actuating unit of the power regulating actuator with a dial,

The height of the housing is smaller with the indicators than with the starter switch.

The device according to the invention helps the physician in the surgical interventions to make the stimulation of certain peripheral nerves easily and reliably. Its construction can be designed such that it can be used in a housing which satisfies ergonomic and aesthetic requirements. The housing can be made with small dimensions. The device thus represents an easily portable and manageable medical instrument.

Ausführungsbe ispiel

The stimulation device according to the invention will be explained in more detail below with reference to an embodiment with reference to the accompanying drawings. Show it:

1 shows the block diagram of the device according to the invention,

2 shows the circuit arrangement of an embodiment of the device according to the invention,

3 is a side view of a provided with ball electrodes embodiment of the device according to the invention,

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4 shows the top view of the device according to FIG. 3, FIG. 5 shows the front view of the device according to FIG. 3,

6 shows the characteristic distances between the movably clamped electrodes,

Fig. 7 eräts part of the side view of an embodiment provided with flat electrodes ^G of the invention and

Fig. 8 shows a part of the side view of an embodiment of the device according to the invention, which is provided with electrodes arranged at the end of a flexible conductor.

For the power supply of the device according to the invention (FIG. 1), a storage unit 1 is provided, which is connected on the one hand to an oscillator 2, on the other hand to a high-voltage switch unit 5. The oscillator 2 supplies high-frequency pulses to a frequency divider 3, which supplies pulses with an adjustable frequency in the range from 25 to 400 Hz to the time controller 10. The frequency divider 3 is advantageously connected to an actuator 6 for regulating the value of the frequency. The time controller 10 is coupled to a starter switch 9. The time controller 10 and the high-voltage switch unit 5 are supplied to a power stage 4, which is advantageously also connected to an actuator 7 for regulating the power of the current pulses _e The outputs of the power stage 4 are provided for feeding electrodes 8. From the circuit arrangement of the device according to the invention (Fig. 2) it can be seen that the oscillator 2 is a unijunction transistor

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20 contains that a potentiometer forms the actuator 7 and the stable value of the AusgangsesignaIs the power stage 4 · secures. This solution offers the possibility of supplying current pulses to the electrodes 8 whose value is independent of the external conditions, in particular the resistance of the skin of the patient to be controlled.

The high-voltage switch unit 5 converts the signals obtained from the frequency divider 3 into the necessary high-voltage signals. It includes (Figure 2) transistors 21, 22, a transformer 23, and rectifiers 24, 25. At the output, the power stage provides a DC signal. The time controller 10 is constructed with integrated circuits 26 and 27. "Of these, the first is for setting greater than 2 sec. Time duration, and the second for setting the duration of the individual pulses. The actuator 6 causes the simultaneous supply of the supply voltage to the supply unit 1 and to the output of the frequency divider 3 · The device further includes indicators 11 and 12, which are powered by operational amplifier. The indicator 11 signals the reduction of the supply voltage (the battery voltage) below a certain value. In this case, he sends a torn off light signal; the indicator 12 ensures a signal on the open state of the fed by the starter switch 9 integrated circuit 26 "

The device according to the invention is advantageously provided with spherical electrodes 8 (FIGS. 3, 4, 5 and 6), which are connected to the device by means of corresponding transition pieces 14. The transition pieces 14 are formed from inflexible elements, serve for their clamping corresponding screw sleeves. The screw sleeves 15 allow the relative movement of the spherical electrodes 8 to a distance

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D from each other. In this area, the electrodes 8 can be arranged in any position along the circular lines of Fig. 6. The distance of the transition pieces 14 is in the axis of the screw sleeves 15 1 · The distance D is generally against 90 mm, where d = 2 mm, L = 25 mm · Obviously, other values can be selected according to the requirements.

In Figs. 3, 4 and 5, an expedient embodiment of the housing 13 can be seen. The cross section of the housing 13 is vascular. At one end, the housing 13 has a narrower part. The height of the housing 13 expediently exceeds the value h = 50 mm and the vertical width does not exceed the value of 55 mm. The vascular form training represents an ergonomically advantageous solution, the indicators 11 and 12 (with inscriptions Batt and STM) can be arranged in the vicinity of the electrodes 8. An appropriate part of the starter switch 9 (labeled STAHT) and the Anstellorgans 7 (labeled mA) is on the one, larger cross-section having part of the housing 13. By means of the knob of the actuator 7, the intensity of the current pulses in a range of 0 to 20 mA are selected. The device can be easily held in the hand, and the operation is made only with the fingers of the holding hand.

The device according to the invention can, for. Example, arranged at the ends of the inflexible elements flat electrodes 16 (Fig. 7) or with arranged at the end of a resilient transition piece 14 (a compliant conductor) and point contact ensuring electrodes 17 are provided, as shown in FIG.

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Under the upper part of the housing 13, the electronic units of the device can be arranged and at the same time a chamber made of plastic for battery or accumulator is provided. The electrodes 8 are expediently prepared from chromed metal pieces.

The device according to the invention operates as follows:

By pressing the starter switch 9, in the integrated circuit 26 (eg, in the monostable multivibrator of HEF 4528 B type) of the timing controller 10, the measurement of a certain period of time, e.g. B, started 3 seconds. The unijunction transistor (ζ B. of TIS 43 type) of the oscillator 2 generates basic signals of 100 kHz frequency, which are divided by means of the frequency divider. The frequency divider 3 contains z. B, the integrated circuit of HSF 4040. A 12-bit prepared dividing chain of the frequency divider 3 provides at the output pulse signals in the frequency range of 25 to 400 Hz and at the same time ensures signals of 25 kHz frequency of the high-voltage switch unit.

The high-voltage switch unit 5 contains z. B »consists of a two-transistor (of BG 182 and BC 212 type) and in push-pull realized drive circuit whose voltages of the secondary side of the transformer according to an equation is 150 V. The signal of the frequency divider 3 is supplied to the integrated circuit 27 (eg, a monostable multivibrator of HEF 4528 3 type) by the setting member 6, which is suitable for producing pulses (quadrilateral signals), e.g. B. 0.2 ms forming width is provided. The integrated circuit 26 ensures the generation of the pulses during the

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agreed on time duration (if necessary 3 sec.); the amplitude of the pulses is regulated by means of a zener diode (eg of the LM 324 type) present at the output of the time regulator 10. In the power level 4 z. For example, a high-voltage transistor of BF 259 type ift may be applied to a power generator circuit. The base of the transistor is an output of an operational amplifier, for. B. supplied by IM 324 type. This amplifier ensures the fixed value of the electrodes 8 supplied current pulses, the fixed value by means of the actuator 7, z. B. a potentiometer,

The operational amplifier ensures further display possibilities (of the indicator 12), and the possibility of controlling the value of the supply voltage. When using a battery, it is important to signal the reduction of the voltage. When the voltage of the battery drops to the value 5 _} 4 7, the indicator 11 emits a broken-off light signal. In a proper training, the power consumption of the 'device makes about 50 mA, d, h, with simple batteries, the device can be applied for about 10 hours.

The device according to the invention is used as follows;

In the operational procedures, the distance between the electrodes 8 of the device is adjusted appropriately and fixed the position by means of the screw sleeves 15. It is expedient to select the spherical electrodes, since the balls always touch with the same skin surfaces. On the device, the desired frequency of the stimuli is set and turned on the device.

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After the indicator 11 lights up (it emits green light), which follows the activation of the device after about 5 seconds, the device is ready to work, to generate the stimuli. By means of the disc of the Anstellorgans 7, the required current can be adjusted: a 0 mA stepwise increasing current is used to stimulate a peripheral nerve of the examined muscle. A _r zt selected generally the ulnar nerve, d to the investigations. h, the motor nerve of the little finger. To test muscular activity, it is convenient to use twice that current value at which the movement of the little finger had been induced. The movement generally follows, depending on the Αχ-znei, in the range of 2 to 3 niA. After setting the required current, the AniAJB switch 9 should be printed so that a pulse train with a duration of 3 s and a frequency of 25 to 400 Hz is generated. After this time, the lighting of the indicator 12 starts, and when it emits red light, the starter switch 9 remains ineffective. The examinations are repeated every 4 to 8 hints. It is expedient to moisten the surface of the skin with a solution of NaCl before stimulation, and thus to reduce the resistance of the skin.

The device according to the invention can be designed as a portable and lightweight medical instrument, which ensures the complete fulfillment of the safety regulations to be observed during surgical and operational procedures and is suitable for the reliable control of the neuromuscular blockade.

Claims (14)

229348 3 -15- 14.8.1981 59 136/16 Claim for invention A device for stimulating peripheral nerves, in particular for determining manifest and latent phases of neuromuscular blockade, which has a feed unit, and a stimulation electrode, characterized in that between the feed unit (1) and the stimulation electrodes (8) one from a the supply unit (1) connected to the oscillator (2), a pulse in a frequency range of 25 to 400 Hz and radio frequency pulses advantageously with a frequency of 25 kHz delivering frequency divider (3) »at least within 2 sec. A Stromimpuisenserie supplying time regulator (10 ) and a connected to the stimulation electrodes power stage (4) existing series circuit is provided, wherein a high-voltage switch unit (5) both with the feed unit (1) and with the oscillator 2. Apparatus according to item 1, characterized in that the time controller (10) is provided with an organ for the production of current pulses with at least 0.1 ms amount of time. (2), and the outputs of the high voltage switch unit (5) are coupled to the power stage (4). 3. Device according to item 1 or 2, characterized in that the oscillator (2) has a unijunction transistor (20). 229346 3 -16- · 14.8.1981 59 136/16 4 ·. Device according to one of the items 1 to 3 », characterized in that the frequency divider (3) is an actuator (6) for regulating the frequency of the current pulses and the power stage (4) an actuator (7) is switched to regulate the power of the current pulses. 5. Device according to one of the items 1 to 4, characterized in that the time controller (10) with a starter switch (9) is connected. 6, device according to item 4 or 5 », characterized in that the power stage (4) comprises a current regulator circuit designed as a current generator, and the power regulating actuator (7) comprises a potentiometer in the range of 0 to 20 mA. having. Device according to one of the items 1 to 6, characterized in that it comprises a housing (13) and the electrodes (8) are arranged outside the housing (13), each coupled to a transition piece (14). 8. Device according to one of the points 1 to 7 »characterized in that a rigid curved rod is provided as a transition piece (14), which is rotatably mounted in the housing (13) and fastened in the rotated position. 9. Apparatus according to item 8, characterized in that the electrodes (8) are spherical in shape · Device according to one of the points 7 to 9 », characterized in that the transition pieces (14) in the wall of the 229346 3 -17- 14.8.1981 59 136/16 11. Apparatus according to item 9 or 10, characterized in that the transition piece (14) in the wall of the housing in a screw sleeve (15) is arranged, wherein the transition pieces (14) in the screw sleeves (15) are limited to each other movable · 12. An apparatus according to any one of items 1 to 11, characterized in that a dry battery or an accumulator is provided as a feed unit (1). 13. Apparatus according to item 12, characterized in that the housing (13) is formed as an elongate sheath with a vessel-shaped cross-section whose maximum width is 35 mm / uad maximum height (h) 50 mm, from which an indicator (12) for signaling the operation of the electrodes (12), an indicator (11) for tracking the voltage level of the feed unit (1) is arranged and the starter switch (9) behind the indicators (11, 12) and next to the actuating unit of the power regulating actuator (7) is provided with a dial, 14. Apparatus according to item 13, characterized in that the height (h) of the housing (13) in the indicators (11, 12) is smaller than in the starter switch (9). Uffe JfcJeiien drawings