DE1539104A1 - Device for monitoring neuromuscular blockage - Google Patents

Description

DR. EULE DR. BERG DIPL.-ING. STAPF

PATENTANWÄLTE 8MONCHENa ₁ HILBUKSTRASSEZO 1539104

Dr. Owl Dr. Barg Pipl.-Ing. Stopf 8 MOncrnn 7. HilblMtroH · 20

Dr. Expl.

Your sign Unfw sign date

December 21, 1965

Lawyer file no . 13 601

THE WELLCOME FOUNDATION LIMITED I83-I93 Euston Road, London NW 1 England

"Device for Monitoring Neuromuscular Blocking"

This invention relates to a portable monitoring device for neuromuscular blocking, or more precisely, to a portable device for applying electrical Stimulation signals to a patient for the determination of Type and degree of neuromuscular existing in the patient Blocking.

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Surgery is often required to be relaxed or paralyzed because of the voluntary muscles in the area where the surgeon is working. That way, it won't be able to contract or move while the surgeon is working. This effect is achieved by the administration of an agent causing the neuromuscular blockage, or muscle relaxant, as these substances are often called. Such substances are succinylcholine, decamethonium, hexabiscarbocholine, D-tubocurarine or gallamine. These substances work by preventing electrical impulses running along the fibers of the motor nerves during normal body function from activating the corresponding muscles. Normally, when impulses transmitted along the nerve fibers reach the synapse between the nerve fiber and the ilic muscle, a chemical vehicle is released ₃ that causes depolarization of the muscle endplate membrane, which in turn actuates the muscle. In the following process, the chemical carrier is removed and repolarization occurs. Neuromuscular blocking agents are usually classified as depolarization or non-depolarization agents based on whether they cause prolonged depolarization of the muscular endplate membrane or prevent depolarization from occurring.

In the course of an operation it is often necessary to change the Art Know the neuromuscular blockage present and its extent. Then, if necessary, a muscle relaxation

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drugs are administered to increase the blockage, or the patient can be stimulated to the muscle relaxant drug by administering a drug of opposite effect to that to counteract. This is done either during the actual surgery or for relief recovery in the postoperative period. As an antidote commonly used physostigmine, eserin and edrophonium. The choice and use of antidotes depends, however on the type and degree of blockage present. In In some cases that have been reported, the use of antidotes had the opposite effect and was prolonged or increased neuromuscular blockage. This can have serious consequences.

It is an object of the present invention to provide a portable to provide electrical apparatus for determining the type and degree of blockage present in a patient. The device can be used to precisely track the time to administer more muscle relaxant drug or continue the time to administer an antidote to determine, and it monitors the subsequent occurrence Effect. Likewise, the device can be used as an aid in deciding how much muscle relaxant or antidote to administer.

The principle of the invention is explained below. if a motor in its normal state Nerve through a small, artificially created electrical

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Impulse is stimulated, it lets the corresponding muscle itself pull together. When all the motor nerve pasers become one given muscle are completely blocked, then - the nerve irritation does not result in muscle contraction. With a partial neuromuscular blockage, little muscle effects occur. Surgeons work within the area between partial and complete blockage. Thus normal, natural response is reduced to a level that is convenient for the patient is not dangerous, but allows the surgeon to work on the relaxed muscle. This stage of relaxation can be monitored for artificial stimuli by observing muscle irritability.

It is assumed that a suitable nerve, such as the ulnar nerve in the wrist and forearm, is stimulated, and that the corresponding muscle, the adductor pollicis, is observed. When a single, short-lasting electrical impulse is applied, the muscle spasms and fingers that are just relaxed are instantly bent upwards into a typical spasm. In the absence of neuromuscular obstruction, severe spasms occur, and partial blockages result in less spasms. One skilled in the art of anesthesia can assess the degree of blockage present from the degree of cramping.

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Let us now assume that a series of continuous, artificial impulses are applied to the nerve. if If the frequency of the impulses is low, the cramp occurs, and then the muscle relaxes again and the pingers return to their relaxed position until another impulse makes them tense again. However, when the pulse frequency is increased, the frequency decreases accordingly Cramping too. This can continue to a point at which the cramps occur so quickly that after a spasm and before the muscle has time to relax another spasm occurs again. That way it remains the muscle in its contracted state. This phenomenon is known as tetanus, and the muscles of the fingers and hands remain in a contracted state with the fingers in are characteristically curved.

The frequency of the pulses used to cause tetanus changes something from patient to patient. However, it is usually included about 20 pulses per second. If the frequency of the tetanus-causing impulses is increased, the effects will still persist Tetanus. This state remains when the impulses fail get so fast that not just the next * impulse before relaxation of the muscle arrives, but it arrives before the nerves / muscle synaps · »I have recovered and the impulse from the Nerve for heating the muscle. This means that the next impulse arrives in the refractory recovery period. The recovery time is about 2 milliseconds, so the tetanus frequency

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should not be greater than 500 pulses per second. Each impulse corresponds to a certain electrical input energy, and the higher the frequency, the greater the solubility of tissue reactions such as reddening or burning. . Little progress has been made in the use of the higher frequency that causes tetanus, and although the frequency range of 20 - 500 pulses to generate of tetanus, the preferred range is lower. It is chosen slightly higher than the minimum value, the tetanus instead of rapid convulsions guaranteed. A preferred frequency range for tetanus is 25-250 pulses per second, and the range of 25 pulses per second is preferred. In particular, a frequency value in the vicinity of 30 pulses per Second preferred.

The frequency of cramping pulses, hereinafter referred to as the cramping rate, is less than 20 pulses per second, but a pulse rate of one pulse per hour or less would still produce cramping. For continuous monitoring during an operation a pulse Β © should be frequently applied that changes in the patient ENFC so fast "* covers expectant &si" as determined on zutreten fjögisiiißn · Accordingly wirö oils Verkramgjfniigs frequency mm fsll by how often OCE Anästeslearzt or surgeon Me Blocking to Monitor®

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wishes. Without the use of a special monitoring device in conjunction with this pulse delivery device, rapid cramping cannot be great interpreted accurately, and so will cramp frequencies of usually less than one cramp applied per second.

There is a further restriction on the preferred cramping frequency for the following reasons. One of the symptoms of non-depolarization block is when a seizure rate is applied, followed by a tetanus rate for a few seconds, and then reapplied to the seizure rate. Then the extent of the cramping effects immediately after the tetanus is greater than the cramping effects immediately before the tetanus. This phenomenon is known as post-tetanus relief (P.Τ · Ρ.). The post-tetanus period for which PTP can be observed is approximately 20 seconds. Therefore, at least two convulsive pulses should be used in the 20 second post-tetanus period, one to monitor the PTF and one to confirm it. Preferably at least 3 to 7 pulses should be applied so that PTF can be clearly observed and confirmed. Therefore, the cramping rate should be greater than one pulse per 10 seconds and preferably between one pulse per second and one pulse per 7 seconds. 009811/0682

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Another feature for non-depolarization blocking is that initially tetanus is sustained insignificantly, leaving a slight recovery from the tetanus state occurs even when a tetanus frequency is still applied. This is called the Wedenzky escapement known, and a tetanus frequency should be used for at least two seconds to monitor them. With depolarization blocking, tetanus is well sustained and the relaxation is eased not observed.

From the above discussion it can be seen that for easy interpretation and constant monitoring of neuromuscular blockage, an electrical stimulus device should be able to continuously deliver single pulses at a rate of one pulse per second and one pulse per seven seconds (cramping rate). Furthermore, a switching device should be provided through which an alternating current frequency between 25 and 250 pulses per second, and preferably between 25 and 50 pulses per second, and again preferably a frequency of about 30 pulses per second (tetanus frequency) can generate, which for a Duration of two to ten seconds can be applied.

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The following invention provides an electrical Apparatus created that output these types of signals supplies. The accompanying drawing shows a pulse generator circuit, which was created to deliver these required series of impulses.

The pulse generator comprises a relaxation oscillator circuit which comprises an npn transistor Tr ₁ and a pnp transistor Tr _2. The collector of the npn transistor Tr ₁ is connected to the base of Tr ₂ via a resistor Ry. The base of Tr. Is connected to a collector of Tr _{2 via a capacitor C 1 and a resistor R.} The primary winding of a step-up transformer T is connected between the emitter of Tr ₁ and the collector of Tr _2. The base Tr ₁ is also connected to the positive terminal of a weak DC voltage source B via one of the resistors R ₁ and R _2. There is a two-position switch Sw ₂ in the circuit. Through this, the two resistors R ₁ and R ₂ can be optionally switched into the circuit. The emitter of the pnp-Transletor Tr ₂ ^is connected directly to the positive terminal of B. The negative connection of B is connected to the emitter _{via an on and off switch Sw 1} , whereby the switch puts the current source in the circuit.

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Connected in series between the capacitor _C1 and the collector of Tr ₂ connected resistance and also a switched parallel to the primary winding of T and parallel to Tr ^ emitter-T ^ -Kollektor link capacitor C ₂ are inserted into the circuit to external voltages to belittle. The resistor R ₇ between the The collector of Tr ₁ and the base of Tr ₂ are included in the circuit so that the circuit characteristics are changed, but it is not an essential component.

_{A resistor R 11} and a gas tube G are connected in series in parallel with the secondary winding of T. Likewise, parallel to the secondary winding of T and parallel to R ^ and G is a voltage regulator or variable resistor RV. switched. The final output pulse is taken from the voltage regulator via Rg and fed to _{two terminals or electrodes E 1} and E _2.

The following shows how the circuit works. When SW _{1 is turned} "on", a potential difference is applied across the base-Eaitter junction of transistor Tr ₁ and across the primary winding of T. A current begins to flow in the primary winding of T, the capacitors C. and C ₂ begin to charge, and turning on Tr ₁ turns on Tr ₂ ,

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which in turn feeds the primary winding T. The build-up of an impulse in the primary winding of T induces a voltage in the secondary winding, and a potential difference appears _{across E 1 and Ep.} Until the transformer T saturates or the current in the primary winding reaches equilibrium, a current continues to be induced in the secondary winding. However, as soon as the magnetic flux in T ceases to change, a reverse EIiK is induced according to Lenz's law. This reverse electromotive force creates a potential at the base of the npn translator Tr ₁ of such a polarity that it is opened and therefore the transistor Tr _{2 is} opened. The capacitors C ₁ and Cp are also discharged until the _{polarity at the base of the transistor Sr 1 is} such that the transistor switches back to the on-state and the whole cycle repeats itself. The circuit thus begins to oscillate, and a series of pulses _{results as the output signal at E 1 and Ep.}

The gas tubes selected are of such a construction that they ignite at the peak value of each pulse and thereby indicate that the device is delivering a signal of a predetermined value. The top of the "on" area is cut off slightly due to the presence of the gas tube. However, the flickering indicates to the observer that the device is working. '009811 / 0882'-

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Many changes can be made to the circuitry described above and shown in the accompanying drawings be made without departing from the essence of the invention. Below are two groups of components given for the production of such Device can be used.

The preferred circuit contains the following components:

npn transistor T pnp transistor T resistor R ₁ resistor Rp resistor R-, capacitor C ₁ capacitor C ₂ battery B resistor R ₁ ^ resistor Rg gas tube G transformer T

Resistance R ₇ potentiometer RV.,

2N-'35 (SYLVania)

2N 3215 (Delco)

3.3 KOhm + 5 % {\ Watt)

■ 0.5 MOhm (1/4 watt) 100 Ohm (IM watt) 20 microfarads, 15 volts (electrolytic capacitor) 3 microfarads, 20 volts (electrolytic capacitors)

3 volts (2xEveryready No 1050, l | V)

47 KOhm (IM-Watt) 10 KOhm + 5 % (1/4 Watt) H-II6-303 neon lamp

Merit part no. A 2932, transmission ratio = χ 30 20 KOhm +5 % (1/2 V / att) 50 KOhm POT Ciarostat

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This choice of components results in the following output at E ₁ and E ₂ assuming a skin resistance of 1 KOhm between E. and E ₂ :

Output voltage 0-30 volts Output current 1 m.A.

Cramp frequency one every four seconds' £ O ₅ 5 sec.

/ "when R _{2 is switched} into the circuit_7

Tetanus rate 29 pulses per second (range

between 25 and ² IO) / "if FL is switched into the circuit 7

Duration of the impulses approx. Two milliseconds The following other components can be used:

npn transistor Tr ₁ 2 N 335 pnp transistor Tr ₂ 2 N 166 Capacitor C ₁ 20 microfarads Resistance R ₁ 5.1 KOhm Resistance R ₂ 330. KOhm Resistance R » is missing Capacitor G ₂ 15 microfarads Gas pipe G NE 51 H

The other components remain the same as before.

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This circuit delivers a higher frequency both for spasms as well as for tetanus and also a higher output voltage. This is less than satisfactory but this circuit is supposed to show again circuit modified by changing the components can be. Any further changes can of course be made by an electronics engineer who is familiar with this technology getting produced.

Flat electrodes can be used, but preferably needle-like electrodes, such as those of the standard 25-gauge metal needle type, should be used will.

Devices of the type described above are not new per se; rather, it is assumed that a small, portable, simple device is new. The DC voltage source B should deliver a voltage below 12 V and this prevents damage to the main devices and high voltages and high currents. This is special important when used in operating theaters where highly flammable gases are present. By using a compact device can be made of transistors; and a small dry cell battery can be made be used in a compact design.

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In this way the present invention provides one portable neuromuscular obstruction monitor in a compact design. This includes a dry battery with an output voltage greater than O up to 12V, a transistorized oscillator circuit that converts the battery's DC energy into a series of electrical pulses with two fixed frequencies. The first fixed frequency is in Range from one pulse per second to one pulse per ten seconds, and the second fixed frequency is located in the range of 25 to 250 pulses per second. The device further includes switching means by which each of these two frequencies is selected and maintained can be a step-up transformer, as well as a Voltage divider on the step-up side of the transformer. The device further includes a pair of Connections to which the output pulses from the device are applied via the voltage divider.

Patent claims:

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Claims (1)

Claims ι ί 1) ^ portable and carried out in more compact construction device for monitoring the neuromuscular block, characterized by a dry battery produces a voltage from zero to twelve volts, a transistorized oscillator circuit for converting ψ of the DC power of the battery in a series of electrical pulses having two fixed frequencies, the first fixed frequency being in the range of one pulse per second to one pulse per ten seconds and the second fixed frequency being in the range of 25 to 250 pulses per second, and switching means so that any of the frequencies can be selected and maintained Step-up transformer and a voltage divider on the step-up voltage side of the transformer, and a pair of terminals through which the output pulses from the voltage divider are taken. 2e) Device according to claim 1, characterized in that that the first fixed frequency is in the range of one pulse per second to one pulse per seven seconds and the second frequency is in the range of 25 to 50 pulses per second. 009811/06 82 -I ₇ - - 17 - 3.) Device according to claim 1 or 2, characterized in that that the battery is a 3 volt dry battery. 4.) Device according to claim!, Characterized in that the battery is a 3 volt! Dry battery, the first fixed frequency is in the range of one pulse per second to one pulse per seven seconds and the second fixed frequency is in the range of 25 to 50 pulses per second, and the transformer and the voltage divider are chosen so that the voltage of the output pulse is between zero and thirty VoI ^- ^ β 5.) Device according to claim 4 »characterized in that the first frequency is approximately one pulse per four Seconds and the second frequency is about 30 pulses per second. 6.) Device according to one of claims 1 to 5 »thereby characterized in that it also includes a gas tube to indicate the operation of the device. 7.) Device for monitoring the neuromuscular blockage according to one of claims 1 to 6, characterized characterized in that the oscillator circuit is a 0098U / 06Ö2 - 18 - npn transistor, a pnp transistor »resistors R ₁ and Ro and a capacitor C, which are connected in the manner shown in the accompanying drawing * 8.) Neuromuscular Blocking Monitoring Device, as essentially described above and in ■ the drawing was shown · 009811/0682