NO168509B - DEVICE FOR CONNECTING AN ELECTRICAL KIT TO VARIOUS DEVICES - Google Patents

Description

The present invention relates to a device for connecting an electrode set to different devices, comprising a first electrode element to be attached to a patient's skin, a second electrode element to be attached to the patient's skin, means that create mutual relationships that enable selective connection of the electrode elements of a monitoring device, a stimulation device and a therapeutic device to produce the desired operation of any such device through these electrode elements, the monitoring device and the stimulation device, as well as the therapeutic device, which are otherwise separate and not connected to each other.

An emerging understanding of electrical signals that occur in the body and the application of electrical signals that are supplied to the body has created a need for the transmission of electrical energy. This transfer of electrical energy to and from a patient's body takes place using electrodes that are in contact with the patient's skin. These electrodes can generally be described as physiological electrodes.

Instruments or devices used together with physiological electrodes can be divided into three large groups, namely monitoring devices, stimulation devices and therapeutic devices. Examples of monitoring devices include cardioscopes, electrocardiographs, and electrocardiograms (for convenience called EKG as a term for all or any of these devices), for monitoring cardiac activity, and impedance pneumographs for monitoring respiratory functions. Therapeutic devices include electrosurgical units (ESUs) and a variety of radio frequency (RF) devices and other relatively high frequency devices used to reduce pain and promote healing. In the group of stimulators there are defibrillators (used to shock a patient to stop fibrillation, an asynchronous cardiac ventricular contraction or oscillating contractions) and other devices with direct current and low frequencies. The line between a therapeutic device and a stimulating device is not always clear, but in this description a therapeutic device shall be the term for an instrument where high-frequency signals are used (around 100 Hz and higher), while a stimulating device is defined as a device with direct current or low frequency signals (approximately 60 Hz and below).

In general, EKG electrodes are small conductive plates (of the order of 12.5 mm in size) that are electrically connected to the patient's skin by means of a saline gel. Each electrode has its own electrical lead to the electrocardiograph and a number of 3 - 7 electrodes (may be more for some diagnostic examinations) are used for cardiac monitoring. The electrodes are generally disposable so that they are thrown away after one use

.the wires are kept. New wires are usually connected to the wires with a snap connection. A number of problems are associated with ECG electrodes of this type. Firstly, the many individual wires will lead to the wires being constantly twisted together so that problems arise during storage and handling. With twisted together wires, it is also a problem to make the right connections even with color codes or similar attempts to •reduce the wrong connections. Also, movement of the leads leads to electrical signals, possibly a piezoelectric effect, which creates distortions in the ECG signal commonly referred to as motion or cable errors. Furthermore, voltage potentials between the electrodes can create a shift in the baselines of the ECG signals or recordings with an effect known as direct current shift, which in severe cases can prevent an ECG recording from being obtained. Variations in the DC displacement with time lead to a drift of the ECG baseline, further complicating the assessment of the ECG signals. Another problem associated with ECG electrodes is the presence of noise in the ECG recording, which is due to too high an impedance between the electrode and the patient's body. The presence of too high impedance is often due to the fact that the electrodes are too rigid to be able to form exactly to the part of the body where they are placed, so that the contact area between the electrode and the body is reduced, which increases the resistance or impedance (contact impedance) for the electrical circuit at this point.

In most ECG electrode designs, the snap mechanism for connecting the lead to the electrode sits just above the center of the electrode so that any stretch in the lead will tend to lift the electrode from the body and thus increase the impedance. Fluctuations in the tension of the wire will also vary the contact impedance at the interface between electrode and body by changing the pressure on the gel and thus forming a further source of error.

Ordinary defibrillators have a pair of plates that are equipped with handles that the operator of the defibrillator uses when the plates are pressed against the patient's body. A saline gel is placed on the plates before they are placed on the patient to form the desired separation surface between the plates and the patient's skin. As the plates are pressed against the patient's chest, a high-voltage pulse of defibrillating energy is delivered to the patient's body by operating discharge buttons in the plate's handle.

One of the most unfortunate features of conventional defibrillators is that the person operating the equipment is in the immediate vicinity of the discharge point. The risk of the person receiving a shock is therefore quite significant.

In terms of efficiency, a major disadvantage of the conventional defibrillator plates is that both plates are placed on the patient's chest. Experiments have shown that for the best results in defibrillation, it is desirable to have one of the defibrillation electrodes on the front of the body and the other on the back. This not only brings more current to the heart to increase the chances of a successful treatment (resuscitation by bringing the heart over from fibrillation to a life-sustaining rhythm), but also reduces local current densities, as experimental results show that this results in less myocardial damage. It is naturally difficult, if not impossible, in an emergency to prop up a patient so that one plate can be pressed against the chest and the other against the patient's back.

Another disadvantage of placing both plates on

the patient's chest is that a conducting path can be formed over the patient's skin from one plate to the other and thus reduce the energy that is carried through the body's tissues to the heart and it also increases the chances that the patient can be burned by the plates.

A further negative feature of conventional plates is that they are difficult to apply to a patient who is being prepared for surgery or who has a cardiopulmonary resuscitation (CPR) device attached to them. Another problem with conventional disc defibrillators is that the disc-to-skin impedance can be too high and thus result in energy loss and an increased risk of skin burns. A number of factors contribute to this undesirable high impedance, one of which is the stiffness of the plates, which prevents the plates from conforming sufficiently to the part of the body where they are placed. This problem can be overcome to some extent by pressure applied to the handles, but other factors such as insufficient area, less desirable contact metals and the use of poor quality gel make the impedance problem a concern. It should be pointed out that an insufficient plate area also produces less desirable patterns when it comes to the current density.

Finally, conventional disc defibrillators have the disadvantage

that when a patient begins to fibrillate, the plates must

if gel is applied, they can be put on the patient. The longer time it

goes between incipient fibrillation and the application of a defibrillating pulse, the greater the possibility that the patient will not have his heart function converted correctly.

Some of these problems with disc defibrillators have been at least partially solved by a disposable defibrillator electrode kit sold by Zenex Corporation under the name "BI-PAK". Although this device solves the problem of a front-back (anterior-posterior) placement of the electrodes, the impedance characteristics can be improved. In addition, the "BI-PAK" cannot connect the electrodes to a separate ECG or to an ESU.

In order to return the radio frequency (RF) energy that enters the body from an electrosurgical knife, an ESU return pad is normally placed under or attached to the patient with a wire that goes back to the ESU return clamp. Different shapes and sizes of these return pads have been used and a number of conductive materials have also been used.

As the RF currents that are introduced into the body during the electrosurgical operation are relatively large, there is a continuous problem of bringing the radiofrequency energy out of the patient's body without heating the pad and without burning the skin due to the current concentrations at the ESU pad . Patients are often burned despite the efforts made to rule this out. Such burns usually occur as a result of non-uniform current distribution in different areas of the ESU return pad, particularly at its outer circumference, which is referred to as an improper dispersion of the RF current. Another problem with prior art ESU return pads of which one does not seem to be aware is the existence of direct current or low frequency shocks that occur during electrosurgical operations. Some of this unwanted shock effect is probably due to leakage currents reaching the body through the ESU pad. However, it seems that some of the direct currents or the low frequency currents are directly due to the electrosurgical operations due to rectification of the RF signals during cutting of the tissues. With a continuous direct current path or low-frequency current path through the ESU return and lead back to the ESU unit, one seems to face an ever-present danger of the patient being exposed to shock from the unwanted direct current signals and low-frequency signals during an electrosurgical operation.

Apart from the problems associated with EKGs, defibrillators and ESU electrodes individually, significant problems are faced when more than one of these instruments is used at the same time. Thus, when a patient is monitored by an ECG, fibrillation may occur and it may be necessary to apply a defibrillating energy pulse to save the patient. Similarly, the patient's heart condition can often be monitored by an EKG during an electrosurgical operation. Furthermore, it may be necessary to defibrillate during the electrosurgical operation.

Pulses of defibrillating energy while ECG electrodes or an ESU return pad are connected to the patient can create burns under the electrodes or pad as well as cause damage to the ECG and ESU instruments. High-voltage protection circuits have been used to prevent this from happening. However, the recovery time for an ECG recording after applying a defibrillator signal is anywhere from a few seconds to over a minute. Lack of ECG recording from the time when the defibrillation took place is particularly serious because it is of the utmost importance to know whether the defibrillation shock is working as it should when it came to bringing the fibrillation to an end. ,Although high-voltage protective circuits protect the patient from burns and the ECG equipment from damage, it will therefore lead to an extension of the recovery time for the ECG recording.

The RF signals from the ESU equipment create further problems for the EKG equipment because these relatively high-energy. signals can cause burns under the ECG electrodes as well as significant disturbances in the ECG recording (especially at lower harmonic distortion). The filter circuit has been used to protect the ECG equipment against such RF influence, but the filters will often reduce the amplitude of the ECG recording so that it becomes difficult to analyse.

One of the main problems occurring today is that work has been carried out to isolate EKG equipment, ESU equipment and the defibrillator from each other in order to prevent the problems reproduced above. However, these attempts at isolation have made it impossible for the instruments to have a common reference so that further dangers arise due to potential differences between the instruments themselves.

With the present invention, a single pair of electrode elements can be used for selective conduction of electrical energy between a patient's body and a monitoring device, a stimulation device and a therapeutic device. (Although the definitions reproduced above are appropriate for this description, it should be pointed out that the physiological electrode system described here can also be used for equipment that cannot be classified directly. In impedance cardiography, signals are used in the "therapeutic" frequency range for recording physiological changes that are important for monitoring.) Each of the aforementioned instruments can be connected to the patient's body through the electrode elements alone or in combination with one or more of the other instruments by means of an appropriate connection device. Protective features are built into the physiological electrode system to reduce or eliminate the risk of harming a patient and of damaging one of the instruments.

According to the invention, the means initially mentioned are characterized by the fact that they include:

a) a first connecting plug means,

a first electrically conductive wire connected therebetween

first electrode element and this first connection plug means, and a second electrically conductive line connected between the second electrode element and the first connection plug means and at least one of the following

cables:

b) a therapeutic device cable with one end to be connected to the therapeutic device,

a therapeutic device electrode coupling which is attached to the other end of the therapeutic device cable and thus designed to bring this first connection together

part plug means in a second connection plug means in this therapeutic apparatus cable between one end and

the electrode coupling,

c) a stimulation device cable having a first end, which is designed to be connected to the stimulation device;

a stimulator electrode connector which is attached to the other end of the stimulator's cable, and is so designed as to produce the engagement of the first or second connector plug means, and a third connector plug means in the stimulator's

cable between the first end and the electrode coupling,

d) a monitoring device cable that can be connected to the monitoring device at one end, and

a monitoring device electrode connector attached to

the other end of the monitoring device's cable and intended to be assembled with any of the electrical connection plugs, the device comprising

additional protective means which are linked to said means for the mutual relationship to enable selective, desired combinations of the monitoring device, the stimulation device and the therapeutic device can be connected to the patient at the same time only through said first and second electrode elements, where the protective means is appropriately selected from components comprising capacitive coupling devices which are incorporated in this therapeutic device's electrode coupling and connect this second connecting wire to the supply lines of the therapeutic device cable, which are capable of forming a return path for the therapeutic device's signals to protect the therapeutic device against energy pulses from the stimulation device and to protect the patient from shock currents,

a low pass filter included in said second connector plug means,

a high voltage protection circuit included in this third connecting plug means, and/or

a high-voltage protection circuit and/or a low-pass filter, which is included in this monitor electrode connection.

Further distinguishing features will appear from the patent claims, as well as from the following description.

For the sake of illustration and to facilitate the explanation, the remainder of this description will relate to an EKG (monitoring device), a defibrillator (stimulation device) and an ESU (therapeutic device). A single pair of electrode elements is attached to the patient's body for ECG monitoring and defibrillation of the patient and to form a return path for RF energy introduced into the patient's body during electrosurgery.

It is advantageous if the electrode elements are part of an electrode set that can be thrown away after use and which includes the electrode elements, a connecting plug and a pair of wires (the term "wires" used here should indicate an ability to conduct electric current and not that such current is conducted at any one time), where each of the wires extends from the plug to an associated electrode element. The plug is standardized for connection to the EKG, ESU or the defibrillator, or to any combination of these. The coupling plug can e.g. have four contacts where two of the contacts each have their own first end of the respective wires that are connected. The other two contacts are electrically coupled to form a DC fault finding circuit for the ESU equipment as described in more detail below. Capacitive coupling, e.g. one or more capacitors, may also be connected from one or both of the leads to the bridged or shorted contacts to form a path for the return of RF signals to the ESU equipment.

The electrode elements must be able to satisfy the different requirements for monitoring electrodes, stimulation electrodes and therapeutic electrodes. Thus, for ECG monitoring, when the electrode elements are attached to the body, the impedance between the electrode elements and the patient's skin must be as low as possible to prevent unwanted attenuation of the ECG signals. Since the most effective way of reducing noise in the ECG recording is to have a high input impedance at the ECG equipment with a low impedance at the interface between the electrode element and the body, a reduction in the element-to-skin impedance will also lead to a reduction of disturbances. An important feature of the ECG electrode is that the polarization of the electrode material with a high-energy electrical signal, e.g. a defibrillator pulse, must return quickly to enable recovery of the ECG recording. This recovery time must be as short as possible to achieve as continuous monitoring of the heart as possible. Furthermore, the shifting direct current potentials between the electrode elements must be minimal and as stable as possible.

When it comes to the processing of the ESU signals, at least one of the electrode elements must have such a size and format that a desired current distribution is obtained, thereby reducing heating and the risk of the patient being burned due to an unwanted current concentration in a small area. As such a concentration area would normally lie at the circumference of the electrode, the desired RF dispersion is a prominent factor when it comes to the circumference of the electrode element. The use of both electrode elements for RF return helps with the dispersion of RF currents and further reduces the risk of burns.

Finally, the electrode elements must have a size and shape as well as sufficiently low electrode element-to-housing impedance when attached to the patient that optimizes the transfer of a desired pattern of stimulating energy to the patient's body while minimizing the risk of skin burns. When it comes to the high energies used in defibrillation, the electrode elements must be able to conduct such stimulating high energy signals as well as high ESU energy or other therapeutic signals without this affecting any of the other desired properties of the electrode elements.

In order to achieve all these properties, circular electrode elements can be used, each of which has an electrically conductive plate of sufficiently small thickness that the conductive plate can largely adapt to the area of the patient's body where it is to be attached. The conductive plate can be made entirely of a suitable conductive material or it can have a layer of the desired conductive material applied or coated on another conductive base metal or even a non-conductive or partially conductive carrier. In all cases, an outside of the conductive plate is made of the desired conductive metal. An electrically conductive medium, e.g.

a saline gel is placed between the outside of the desired conductive metal and the patient's skin to improve the transfer of electrical energy between the patient and the conductive plate.

A chloride of the desired conductive metal is placed between the conductive metal and the patient's skin by e.g. applying a layer of the chloride directly to the metal or by introducing the chloride into the conductive medium. A suitable binder e.g. a binder layer on a supporting device made of foam plastic is used to attach the electrode element to the patient.

Although any conductive metal and its chloride can be used, it has been shown that tin and tin chloride are particularly suitable when it comes to satisfying the many requirements for these multi-function electrode elements. In a preferred embodiment described below, the conductive plate can therefore be made entirely of tin, e.g. tin foil, or because tin has been applied is a conductive base plate, e.g. brass, or with a layer of tin on a non-conductive substrate, e.g. of plastic material. The stannous chloride can be applied directly to the tin surface, e.g. by spraying on a thin layer or the stannous chloride can be in the conductive medium. However constructed, the novel use of metal-metal chloride for defibrillation and ESU return has been made possible by the discovery of the highly advantageous features of the tin-tin chloride electrode element. Not only does the tin-tin chloride electrode element exhibit highly advantageous features for the multi-function electrode, but the electrode element has also demonstrated superior properties for single functions such as ECG monitoring. In addition to the highly desirable working properties, the tin-tin chloride electrode element is highly resistant to corrosion which easily occurs in the presence of saline gel and this design therefore has a much longer life during storage for electrodes to be discarded

use.

Although the electrode elements could be connected directly to the instruments as indicated above, the desired option is to be able to utilize a disposable electrode set with wires running from the electrode elements to the connector plug. This connection plug can be made for direct connection to the desired instrument, but the preferred solution is to use a separate cable with a suitable connection device for connection to the plug at one end and with electrical connection to the desired instrument or instruments at the other end. These cables can then be relatively permanent so that only the electrode sets are replaced with each use.

For the ECG cable, one end has a connecting device for an ECG monitor for connecting the cable to the ECG device or instrument. An ECG electrode coupler at the other end of the cable is designed to mate with the connector plug on the disposable electrode set. A pair of wires extend from the ECG monitor coupler to the ECG electrode coupler to connect the electrode elements directly to appropriate ECG inputs.

As most ECG instruments require a minimum of 3 inputs, connecting the electrode elements directly to two of the inputs will not produce a suitable recording. For that reason, it is necessary to have a simulation circuit for the body's tissue impedance so that the EKG equipment thinks it is receiving three inputs from the body. This simulation circuit for the body

> tissue impedance can take any convenient form from a simple resistor to a multiple resistance-capacitance circuit. Although this simulation circuit for the body's tissue impe-

dans can be placed at any convenient place in the cable, it has been found particularly advantageous to place it in the EKG electrode connector with a third wire running from the circuit to a third input of the EKG equipment.

To prevent high-frequency interference, e.g. from RF signals used in electrosurgery, a low-pass filter is placed in the cable. In the same way to protect the ECG equipment against high-energy signals, e.g. a defibrillator pulse,

a high-voltage protective circuit is used in the cable. Finally, to further reduce the risk of RF burns at the ECG electrode elements, an RF choke filter circuit may be incorporated into the cable. Although all of these circuits may be placed in convenient places in the cable, the low-pass filter, the high-voltage protection circuit and the RF choke filter circuit are preferably placed in the EKG electrode's connection device.

By placing all signal attenuation elements at the end of the cable away from the ECG instrument, a further advantage is achieved. This additional benefit is a significant reduction and virtually elimination of errors due to cable movement. It is believed that this very significant reduction in cable movement error is achieved as a result of the piezoelectrically generated signals being diverted across the impedance of the EKG electrode connector rather than across the impedance of the EKG equipment itself.

With the present invention, ECG monitoring can therefore be achieved with a simple cable which overcomes the "crow's nest" problems with the previously known many ECG leads. In addition, the EKG instrument is protected against high-frequency disturbances and possible harmful high-energy signals. Furthermore, the possibility of RF burns at the electrode elements can be reduced. By using the ECG cable together with the electrode elements according to the invention, noise disturbances can be further reduced, shifting DC potentials and drift can be reduced and the recovery time for an ECG recording after the application of a defibrillator pulse can be brought to a minimum, all while get a stronger ECG recording signal.

When it comes to the defibrillator cable, there are two variants. In one of these, the usual defibrillator plates have been replaced. In the second, there is an adaptation device which enables the use of defibrillator plates together with the electrode elements according to the invention.

By using the flat disposable electrode elements

according to the invention, a desired front-to-back placement of the defibrillator electrodes can easily be achieved. This enables more current to be applied to the heart with a strong increase in the chances of a successful defibrillation. At the same time, the presence of smaller and more uniform current densities throughout the heart will greatly reduce the risk of myocardial damage. In addition to this, the time that elapses between the start of fibrillation and the application of a defibrillating pulse will be reduced to a minimum since the electrode elements are already in place before fibrillation begins.

The fact that the electrode elements are already in place also enables the defibrillation of patients who are covered for surgery or who have CPR equipment attached to them. A particularly suitable placement of the electrodes is to have the front electrode placed at the lung tip (apex) or at the left leg, while the back electrode or posterior electrode is placed on the right arm. This placement of the electrode element will not only give very good defibrillation results, but the placement of the front electrode element at the apex of the lung means that this element will be on a part of the body that does not normally have hair and the placement of the posterior electrode pulls this away from the uneven spinal area thereby reducing problems caused by impedance between electrode and skin and difficulties in bonding the electrode element correctly to the skin. Furthermore, the placement of the front electrode at the apex of the lung will keep this electrode away from interfering with cardiopulmonary resuscitation (CPR) attempts that may be performed on the patient. This means that ECG monitoring of the heart can continue without interruption and that the electrode elements can remain in position for immediate defibrillation should the heart begin to fibrillate.

In the first version of the defibrillator cable is

it used a coupling device for a defibrillator instrument to replace the connection between the usual plates and the defibrillator. A pair of wires in the defibrillator cable extend from the connector for the defibrillator instrument to a defibrillator electrode coupler through which the defibrillator outputs can be connected directly to the electrode elements. A discharge control unit is placed in the defibrillator cable, preferably close to the end of the cable facing the defibrillator instrument. The discharge control has four button-operated switches connected to the defibrillator through another pair of wires. All four button switches must be pressed down for a pulse of defibrillating energy to be sent to the patient through the defibrillator cable. By placing the discharge control unit in the defibrillator cable, the defibrillation control will be located at a distance from the patient to protect the operator from electric shock.

An ECG output coupler is located at the discharge control unit. This ECG output coupler is intended for connection with the ECG electrode coupler on an ECG cable so that an ECG instrument can be connected to the electrode elements through the defibrillator cable. The ECG output coupler is connected to the wires in the defibrillator cable through a high-voltage protection circuit. An impedance matching circuit can be connected between the high voltage protection circuit and the ECG output coupler to improve the ECG signal and reduce interference. This circuit is particularly important in conditions where the ECG signal is not only reproduced on a local instrument, but also sent to a central unit, e.g. a main hospital for a paramedic system.

Although the most logical use of the defibrillator cable is to use the multi-function electrode set described above so that the electrode elements can be used for ECG monitoring and are already in place if defibrillation becomes necessary, electrode elements only for ECG monitoring can be manufactured at less cost .

One has thus arrived at an option where a pair of EKG electrodes can be used for monitoring through the defibrillator cable. A separate sleeve for ECG electrodes is arranged in the defibrillator's electrode coupler. To prevent ECG electrodes (which cannot handle defibrillator pulses or ESU return signals) from being incorrectly connected to the other sleeves, the ECG electrode plug is designed to fit only the ECG sleeve. It should be mentioned here that these ECG electrodes can be used with the ECG cable if only ECG monitoring is required.

An additional pair of wires extends from the ECG-only sleeve to the ECG output connector side at the high-voltage protection circuit in the discharge control unit. If an impedance matching circuit is used, the connection is between the high voltage protection circuit and the impedance matching circuit.

In the case of the defibrillator cable in the design with adaptation for discs, an adaptation unit is attached to the end of the defibrillator cable facing from the defibrillator electrode couplers. The fitting unit includes a pair of conductive plates onto which standard defibrillator plates can be placed. An insulating part between these plates prevents accidental short-circuiting of the defibrillator plates. The conductive plates are connected to the defibrillator's electrode coupler, which is the same as the defibrillator electrode coupler that was used in the version with a control unit for the discharge, and the connection is made with a pair of wires. A push-button control for a switch sticks up through each of the conductive plates so that when the plates are in the correct position, the push-button controls will be able to close the switches in a battery-operated direct current circuit to initiate an audible alarm buzzer. Sound from the buzzer indicates to the person carrying out the treatment that a correct conductive circuit is complete for applying a defibrillator pulse to the patient by operating the discharge controls on the normal plates. The buzzer also serves to warn other staff so that they pull away from the patient's area.

An ECG cable may be permanently attached to the fitting unit with a suitable body tissue impedance simulation circuit for this ECG circuit located in the fitting unit. An ECG monitor connector is found at the other end of the ECG cable. Alternatively, a plug or coupling device for interaction with an ECG electrode coupler may be provided. A high-voltage protective circuit is placed between the simulation circuit for the body's tissue impedance and the wires that extend to the defibrillator's electrode couplers. A further ECG output coupler is also placed in the adaptation unit and connected between the high-voltage protection circuit and the simulation circuit for the body's tissue impedance. The wires leading from the ECG-only sleeve, in the defibrillator electrode couplers, are also connected between the high-voltage protection circuit and the body tissue impedance simulation circuit.

With both variants of the defibrillator cable, the control unit for the defibrillator's discharge is located at a distance from the patient with optimal safety for the person carrying out the treatment. In addition to this, the electrode element structure with relatively large size, flexibility and metal-metal chloride, especially tin-tin chloride, in the form of a conductive plate will lead to reduced impedance between the electrode element and the skin and a better distribution of the current density. Also, the fact that the electrodes are already in place will save valuable time when applying a defibrillation pulse to the patient should fibrillation occur. Furthermore, the use of disposable electrodes will enable precise control of the type of gel used, as gels that are not specially prepared for defibrillation can affect the defibrillation operation.

An ESU cable has a pair of wires extending from an ESU instrument coupler to an ESU electrode coupler. These conductors extend to the shorted or shorted contacts in the plug of the disposable electrode set to form a DC fault finding circuit. A direct voltage source, e.g. a battery in the ESU instrument, carries a signal over the wires to put the ESU instrument into operation. The debugger thus ensures that the ESU electrode coupler and the connector plug on the disposable electrode set are properly assembled to form a return path for ESU RF energy before the ESU instrument can be put into use.

Capacitive coupling between the wires and the contacts

in the ESU electrode coupler which works together with the other two contacts in the connector plug, forms a path for RF signals from the electrode elements to the wires. This capacitive coupling preferably takes the form of a first capacitor which is connected from one of the contacts to one of the wires, a second capacitor which is connected from the second contact to the other wire and a third capacitor which is connected between the two wires. This capacitive coupling actually forms a high-pass filter that prevents direct current and low-frequency currents from passing to or from the ESU instruments. By thus using high-power capacitors, the ESU equipment can be completely protected against direct current signals with high energy, e.g. defibrillator pulses. In addition, the capacitive coupling will protect the patient against low-frequency currents and direct currents that are potentially capable of producing fibrillation. These low-frequency currents and direct currents can either be leakage currents from the ESU equipment or currents resulting from the rectification of RF currents during the electrosurgical operation.

Instead of using the disposable electrode set with its two electrode elements, the ESU cable can be used only for FSU return current. For this purpose, a simple RF return pad constructed in the same way as the electrode elements described above can be used, although a cheaper return pad of a suitable conductive material, e.g. aluminium, can be used instead of the metal-metal chloride design which is particularly suitable for defibrillation and ECG use. A wire extends from the pad or electrode element to a contact in a connector plug that has two other contacts jumpered or shorted for the fault finding circuit. Capacitive coupling is available with the ESU electrode coupler for capacitive coupling of the wire to the wires in the ESU cable. As an alternative or as a supplement, this capacitive coupling can be achieved in the coupling plug with a capacitor connected between the wire and the bridged contacts. Although a single wire described here constitutes an operational system, in the preferred embodiment described here, an additional wire is used between the return pad and the connector plug so that the ESU cable takes the form described in connection with two electrode elements . However, the coupling plug and the ESU electrode coupler are designed in such a way that this coupling plug can only be assembled with a coupling device where it is determined that defibrillator pulses or ECG signals must pass because the ESU return pulse cannot function for defibrillation or ECG monitoring.

In the case of the ESU cable intended for use with the disposable electrode set with a pair of electrode elements, an ESU cable coupler is located in the ESU cable between the ESU instrument coupler and the ESU electrode coupler. This ESU cable coupler has a pin arrangement similar to the connector plug so that an EKG electrode coupler or a defibrillator electrode coupler can be assembled with it. A second pair of wires extends from this plug part in the ESU cable coupler to the two unbridged contacts in the ESU electrode coupler. A low-pass filter preferably located in the ESU cable coupler is connected to this second pair of wires to prevent RF signals from passing to an EKG unit or defibrillator connected to the ESU cable coupler. To be able to use all three types of instruments together with the single pair of electrodes, a defibrillator can be connected to the ESU cable coupler and an EKG unit can be connected to the discharge control unit or adapter in the defibrillator cable.

With the connection options available with the present invention, a common reference has been obtained for all instruments that are connected to the electrode elements. This common reference reduces the problems of dangerous leakage between the instruments and also forms a basis for the reduction of disturbances at one instrument due to the output of another instrument. With this invention, a physiological electrode system has therefore been arrived at where a single pair of disposable electrode elements can be connected simultaneously to several instruments for performing several different functions. The invention not only provides opportunities for many functions, but also provides improvements in each of these functions whether they are performed by means of the multi-function arrangement or whether they are connected for separate use.

These and other purposes, advantages and features of the invention will be apparent from the following and by way of illustration and not as limitation, examples of embodiments of the invention are shown in the drawings. Fig. 1 schematically shows a preferred embodiment of the invention with three instruments simultaneously connected to provide several functions through a single pair of electrode elements. Fig. 2 shows in more detail the electrode elements which are connected in a preferred embodiment for a disposable electrode set. Fig. 3 schematically shows the pin device for the connection plug in the disposable electrode set in fig. 2. Fig. 4 shows one of the electrode elements in fig. 2 on an enlarged scale and with the parts pulled apart. Fig. 5 schematically shows a preferred embodiment of an ECG cable. Fig. 6 schematically shows the ECG cable in fig. 5 with certain features of this shown in more detail. Fig. 7 schematically shows a connection core for the EKG cable in fig. 5 and 6. Fig. 8 schematically shows another embodiment of the ECG cable in fig. 5. Fig. 9 shows a connection core for the ECG cable of fig. 8. Fig. 10 schematically shows a preferred embodiment

form of a defibrillator cable.

Fig. 11 shows in more detail the defibrillator cable in fig. 10. Fig. 12 shows a connection core for the defibrillator cable in fig. 10 and 11. Fig. 13 schematically shows the structure of the pin device in the connection plug for the ECG electrodes shown in fig. 12. Fig. 14 schematically shows another embodiment of the defibrillator cable. Fig. 15 shows in more detail the defibrillator cable in fig. 14. Fig. 16 shows a connection core for the defibrillator cable in fig. 14 and 15. Fig. 17 is a four-part representation of a conventional and the new placement of the defibrillator electrodes. Fig. 18 schematically shows a single pair of electrode elements which are simultaneously connected to a defibrillator and an EKG unit. Fig. 19 shows in more detail the system shown in fig. 18. Fig. 20 schematically shows the pin location in the connection plug for the electrode set shown in fig. 18 and 19. Fig. 21 schematically shows a preferred embodiment of an ESU cable. Fig. 22 shows in more detail and schematically the ESU cable in fig. 21. Fig. 23 schematically shows a preferred embodiment for an ESU return pad set which is thrown away after use. Fig. 24 shows a connector core for the disposable ESU return pad set of Fig. 23 and the ESU cable in fig. 21 and 22. Fig. 25 schematically shows the pin location in the connector plug for the ESU return pad set in fig. 22 and 23. Fig. 26 schematically shows an ESU unit and an ECG unit which are simultaneously connected to a pair of electrode elements. Fig. 27 shows in more detail the system in fig. 26. Fig. 28 shows in more detail the system shown in fig. 1-.

A preferred embodiment of a physiological electrode system which is made according to the invention is shown in fig. 1. A single pair of electrode elements 31 and 33 are simultaneously connected to an EKG instrument or device 35, a defibrillator instrument or device 37 and an ESU instrument or device 39. Naturally, these instruments can be of any type devices for monitoring, stimulation and therapy as explained above.

The electrode elements 31 and 33 may be of any type of suitable electrodes placed on a patient's body, but in this preferred embodiment these electrode elements are single-use elements arranged in an electrode set which is discarded after use. In this preferred embodiment, electrode element 31 is approximately 8 cm in diameter and electrode element 33 is approximately 12 cm in diameter, but any suitable size of electrodes may be used. The connecting device includes wires 41 and 43, a connecting plug 45, an ESU cable 47, a defibrillator cable 49 and an ECG cable 51. Details of this connecting device and of the protection circuits and measures that enable the simultaneous connection of several instruments to a single pairs of electrode elements to be able to perform a plurality of functions will be reviewed in the following.

A disposable electrode set 53 is shown in more detail in fig. 2. The disposable electrode set includes the electrode elements 31 and 33, the wires 41 and 43 and the connection plug 45. The connection plug 45 is a standardized plug that can be connected to the ESU cable 47 or the defibrillator cable 49 or the ECG cable 51. Although the connection plug 45 can be constructed with two or three contacts for certain applications in order to achieve the desired multiple functions, the plug 45 should have four contacts.

Although the plug 45 may be of any suitable type of connector plug, in this preferred embodiment the connector plug 45 has the structure shown with projecting insulating caps 55 in which there are conductive pins or contacts 57. The conductive pins or pins 57 may either solid male pins or hollow female pins. These pins can be arranged in suitable patterns to exclude unwanted interventions between coupling plugs and other coupling devices. E.g. is as shown in fig. 3 the two outer pins 59 and-61 female pins while the two inner pins 6 3

and 65 are male taps. In order for the plug to be able to be inserted into a coupling device, the coupling device must have male pins at the outer contacts and female pins at the inner contacts. The electrode set 53 is intended for all types of functions so that the EKG unit, the defibrillator or the ESU unit can be connected to the electrode elements 31 and 33 individually or in different combinations as long as the connection device on the cable has the correct pin arrangement.

In fig. 2 it will be seen that the coupling plug 45 is of a construction which is easy to assemble and consists of two housing parts 66 and 67. Although any design can of course be used, this construction forms a complete coupling plug which is nonetheless easy to assemble .

A preferred arrangement or construction of the electrode elements 31 and 33 is shown in fig. 4. Although different shapes of the electrodes can be used, it has been found that the circular or round shape shown here offers certain advantages which are explained in more detail below. It should also be pointed out that the description of the circular electrode element shown in fig. 4 too

is designated as the electrode element 33 for the sake of illustration, relates to the preferred embodiment of all electrode elements discussed in this description.

A circular base 67 made of foam has a layer of adhesive (glue) 69 on one side and forms the bottom or basis for the electrode element. The base 67 is preferably made of plastic foam, but it may be made of any suitable insulating material which is relatively rigid but has a certain degree of flexibility. Marking or labels can be attached to the side of the substrate 67 which faces from the adhesive layer 69, but this marking must not be so dimensioned or be placed in such a way that it can affect the flexibility of the electrode element.

An electrically conductive plate 71 is then attached to the adhesive layer 69 on the substrate 67. The conductive plate 71 preferably has a circular shape with a desired electrically conductive metal on at least one side. A chloride of the conducting metal is placed between the metal and the patient's skin, e.g. by spraying a layer 72 on the conductive metal surface.

Although it is possible that other metal-metal chloride combinations can be used successfully (silver-silver chloride has been used for ECG electrodes), an important feature of the invention is the discovery that the tin-tin chloride combination provides unexpectedly strong advantages over other types of materials. (It is possible that alloys formed mainly of tin would also provide some or all of the desired properties when used in conjunction with stannous chloride). Measurements have thus shown that the tin-tin chloride electrode element will provide a very low impedance between the electrode element and the patient's skin. This result is particularly interesting when it comes to ECG monitoring and defibrillation. In addition to this, the tin-tin chloride electrode element will conduct high-energy currents produced by defibrillation without apparent deterioration while at the same time very rapidly reversing the polarization that occurs at these high energy levels. In reality, recovery of an ECG recording after the application of a defibrillation pulse is almost instantaneous, which is a marked improvement over previously known ECG recovery times. Measurements to date have shown that the direct current displacement produced by the use of tin-tin chloride electrode elements is well within the accepted limits and can be compared with existing devices or is superior to these. However, it is very important that these measurements also show that the direct current displacement potential, which results from the use of tin-tin chloride electrode elements, was very stable so that one only had

a very small drift of the ECG recording.

The construction of the electrically conductive plate 71 can be carried out in many different ways. E.g. could the plate 71 be entirely made of tin, e.g. tin foil, or it can be a tin coating on a substrate. This substrate can be another conductive metal, e.g. brass, or it can be a non-conductive material such as plastic.

In the preferred embodiment described here, a tin foil is used.

In order to create an electrical connection between the conductive plate 71 and the wire 43, one must have an electrical connection between the plate 71 and the wires 73 in the wire 43 where the insulation has been removed. Any way can be used, but in this preferred embodiment it has been found that the end of the wire 43 and the wires 73 can be attached to the adhesive layer 69 before the tin plate 71 is placed so that when the plate 71 is in place on the adhesive layer 69, you will have a good electrical connection between the wires 73 and the tin plate 71.

A porous foam disc 75 is then placed over the conductive tin plate 71. The porous foam disc 75 has tabs or ears 77 protruding from the circumference as an aid when placing the disc 75 in the construction. The porous foam in the disc 75 is designed to absorb and hold an electrically conductive medium such as e.g. a saline gel so that a good conducting path is obtained between the tin plate 71 and the patient's skin. Any suitable type of conductive medium or gel can be used if it satisfies the requirements set due to the various functions to be performed by means of the electrode elements. However, one must be particularly careful when choosing a conductive medium or gel so that it gives the desired results when defibrillation pulses with high energy are applied.

It is explained that the stannous chloride can be attached to the tin plate 71 by spraying a layer 72 of stannous chloride onto the plate. This layer need not cover the entire surface of the plate 71, but could be collected in a smaller selected area or in a number of selected areas. Another possibility, however, is to introduce the stannous chloride directly into the conductive medium so that it is not necessary to attach the stannous chloride to the conductive plate 71.

A retaining ring 79 is then placed over the porous foam which contains or will contain the conductive medium. The ring 79 can be made of any suitable material, but for the easiest possible manufacture it is made of the same foam material as the substrate 67 in the case of the preferred embodiment. The ring 79 is attached to the adhesive layer 69 on the base 67 above the tabs or ears 77 to hold the foam disc 75 in place. It should be pointed out that other methods for fixing the foam disk 75 in place can be used and that the protruding tabs 77 are only examples of the assembly method used in this preferred example. Furthermore, it should be pointed out that the ring 79 will normally be somewhat thicker than the substrate 67 as it forms a "pond" for the gel that is absorbed in the porous foam in the disk 75. An adhesive layer 81 is found on the upper side of the ring 79.

Finally, a sealing cover 83 is placed on the adhesive layer 81 on the ring 79. The purpose of the cover 83 is to form a largely airtight or hermetic seal which will prevent the gel in the disc 75 from drying out. This cover may be of any suitable material, but a thin rigid transparent plastic is used in the preferred embodiment shown here. In use, the cover 83 is removed from the electrode element and the electrode element is then attached to the patient using the adhesive layer 81 on the ring 79.

Among the advantages of the circular electrode element is the uniform flexibility so that the electrode element and the conductive plate 71 can be precisely adapted to the shape of the part of the body where the electrode element is placed. By precisely adapting the electrode and the conductive plate to the shape of the body, the largest possible conductive area is achieved, which reduces the contact impedance between the electrode element and the patient's skin. The low impedance is particularly important for ECG monitoring and defibrillation. In the case of the ESU, the circular design of the electrode element and conductive plate 71 provides the most uniform current distribution for RF dispersion. The flexibility of the electrode for adaptation to the shape of the part of the body where the element is placed also contributes to a uniform contact area which counteracts current concentrations that would otherwise lead to RF burns.

A schematic representation of a preferred embodiment of the ECG cable 51 can be found in fig. 5. The cable 51 is a shielded cable with an ECG monitor connector 85 at one end. The ECG monitor connector 85 is intended to be assembled with the input jack of a standard ECG instrument. The ECG input jack is designed to receive three or

multiple ECG inputs.

At the other end of the ECG cable 51 there is that

an ECG electrode coupler 87. This ECG electrode coupler 87 may be of any suitable design for connection to the connector plug 45, but it is preferred that the ECG electrode coupler 87 be of a standard shape that can also be used with the ESU cable 47 and the defibrillation cable 49. The preferred form shown here is a rectangular box with sufficient space inside to accommodate the various circuits contained in the various electrode couplers on the various cables. A sleeve 89 protrudes from the housing for the coupler 87 and must fit the plug 45.

Fig. 6 shows part of a connection core for the cable in fig. 5 where the cable is shown in more detail. As can be seen, there are three wires 91, 93 and 95 extending from the ECG monitor coupler 85 to the ECG electrode coupler 87. A body tissue impedance simulation circuit 97 is built into the coupler 87 along with a high voltage protection circuit 99. The body tissue impedance simulation circuit 97 enables application of an EKG unit which normally requires three or more inputs with only the two electrode elements 31 and 33. The high voltage protection circuit 99 is built in to protect the EKG unit against signals with a high energy level e.g. the defibrillator pulses. In addition, a low-pass filter 101 is placed in the coupler 87 together with the simulation circuit 97 for the body's tissue impedance and the high-voltage protection circuit 99. The low-pass filter 101 serves to reduce the influence of RF signals, e.g. those produced by an electrosurgical unit (ESU) and other relatively high signals that can distort the ECG recording and make analysis difficult.

In the more detailed connection diagram in fig. 7 it can be seen that the wires 91 and 93 are connected directly from the two inputs on the EKG unit 35 (these inputs are denoted by A and C) to the contacts in the sleeve 89 (fig. 6) which will result in the inputs A and C being connected to the electrode elements 31 and 33. The body tissue impedance simulation circuit 97, connected to the third ECG input B by a lead 95, is represented by a simple resistor 103. Although a simple resistance may be satisfactory under certain conditions, the body tissue impedance simulation circuit 97 may tissue impedance also includes circuits with multiple resistors or resistance-capacitance circuits. The actual structure of the simulation circuit 97 for the body's tissue impedance is such that it will apparently act as three inputs at the EKG unit instead of the two inputs received in reality. Each of the inputs B or C can be a reference or ground conductor for the ECG unit.

The low-pass filter 101 is illustrated as a capacitor 105 and a resistor 107 connected in parallel between the lines 91 and 93. This circuit is only to be considered as an example and any low-pass filter circuit can be used.

The high voltage protection circuit 99 is illustratively shown as a pair of series resistors 109 and 111 connected in leads 91 and 93. Again, the high voltage resistor circuit 99 may take any suitable form, although a pair of series resistors 109 and 111 normally will be sufficient to provide the desired protection.

To further ensure that conductive paths are formed for the RF signals, e.g. when only small ECG electrodes are connected to the cable 51 which increases the risk of RF burns at these electrodes, an RF choke filter 113 can be added to the coupler 87 as shown in fig. 8. As shown in fig. 9, the choke filter 113 includes, for example, choke coils 115, 117, 119 and 121 and a capacitance 123. Of course, this particular circuit is also only to be considered as an example and any suitable RF choke filter device can be used.

Another variant of the circuits that can be used is the addition of oppositely polarized diodes 125 and 127 connected between wires 91 and 93 in the low-pass filter 101. The diodes 125 and 127 help with filtering relatively high frequencies that would distort or interfere with the EKG the record, e.g. "shot" noise. Although circuits 97, 99, and 101 could be located anywhere in cable 51, placing these circuits in coupler 87 will not only simplify fabrication, but also greatly assist in reducing motion errors by having all signal attenuation located itself at the electrode end of the cable. Errors due to movement of the cables while receiving ECG signals from a patient are largely dissipated across the impedances at this end of the cable with the result that very little effect of the errors is perceived by the ECG instrument itself. Diodes 125 and 127 also help protect the ECG unit from defibrillation pulses by generally shorting leads 91 and 93 through the high voltage protection circuit 99.

The defibrillator cable 49 is shown schematically in fig. 10. A defibrillator instrument coupler 129 is placed at one end of the cable 49 while a defibrillator electrode coupler 131 sits at the other end of the cable. The defibrillator electrode coupler 131 has a sleeve 133 which should work together with the connecting plug 45. The coupler 131 is also provided with another sleeve 135 which should work together with the connecting plug for a pair of ECG electrodes in the event that it is desired to use the cables 49 only for ECG monitoring without defibrillation option until a connecting plug 45 is inserted into the sleeve 133 and the electrode elements 31 and 33 are attached to the patient.

A control unit 137 for defibrillator discharge is placed in the cable 49. The discharge control 137 has four push buttons 139, 141, 143 and 145 - all of which must be pressed in to be able to conduct a defibrillating pulse through the cable 49 to the electrode elements 31 and 33 on the patient. An ECG output terminal 147 has a plug portion corresponding to the connector plug 45 for cooperation with the sleeve 89 of the ECG electrode coupler to provide ECG monitoring through the cable 49. Separate cable portions 149 and 151 extend from the discharge control 137 to the instrument coupler 129. The cable portion 149 contains wires to carry the defibrillating current while the cable part 151 has wires for a discharge control circuit.

On the partial coupling core of fig. 11 you want

see more details of the cable 49. Thus, it can be seen that the cable part 151 contains wires 153 and 155 which are connected in series through switches 157, 159, 161 and 163 corresponding respectively to the operating buttons 139, 141, 143 and 145. Furthermore, it can be seen that the cable part 149 contains wires 165 and 167 which continue through the discharge control 137 to thereby extend from the defibrillator instrument coupler 129 to the sleeve 133 of the defibrillator electrode coupler 131. A high-voltage protection circuit 169 is connected between the ECG output terminal 147 and the leads 165 and 167. Another pair of electrical leads 171 and 173 connect the ECG-only sleeve 135 in the connector 131 to the ECG output terminal 147. The leads 171

and 173 is connected to the terminal 147 on the plug side of the high-voltage protection circuit 169 so that this high-voltage protection circuit also protects an instrument connected to the wires 171 and 173 against the defibrillation energy in the wires 165 and 167.

In the more detailed connection core in fig. 12 shows further details of the defibrillation cable 49. It can thus be seen that the high-voltage protection circuit 169 includes a pair of large series resistors 175 and 177 and a capacitance 179 connected across the wires. It should again be pointed out that this is only an illustrative circuit and that any other high-voltage circuit pattern can be used. It is also seen that an impedance matching circuit including a resistor 181 and oppositely biased diodes 183 and 185 is connected across the ECG output terminal 147. • Although this impedance matching circuit can be used with any ECG device, it is particularly suitable for use on remote places and in emergency situations when the ECG recording is sent to a central unit or a hospital using telemetry. Leads 171 and 173 from the ECG-only sleeve 135 are connected between this impedance matching circuit and the high voltage protection circuit 169.

A disposable set of ECG electrodes 187 and 189 and an ECG electrode connector plug 191 is schematically shown in fig. 12. The plug 191 is intended to cooperate with the sleeve 135, which only applies to the ECG, but sits in the defibrillator's electrode couplers 131. The plug 191 and the sleeve 135 are specially shaped so that the coupling plug 191 cannot work together with e.g. the sleeve 133 since the ECG electrodes 187 and 189 cannot handle the defibrillation energy from the leads 165 and 167. To prevent the ECG electrodes 187 and 189 from being connected to the leads 165 and 167, fig. 13 that although the EKG connection plug 191 has female pins 193 and 195 in the outer insulating sheaths 55 to enable connection to the plug 45, a female pin 194 is placed in one of the inner sheaths 55. In this way, the plug 191 cannot be assembled with the sleeve 133 which will also have a female pin in the inner contact or sheath position, thereby preventing any possibility of defibrillation energies being conducted to the EKG electrodes 187

and 189.

The ECG electrodes 187 and 189 can be ordinary ECG electrodes, specially designed ECG electrodes or smaller versions of the electrode element shown in fig. 4. E.g. could the EKG electrodes be constructed in the same way as the element in fig. 4, but have a diameter of around 4 cm. Such a pair of electrode elements has been found to be very satisfactory for ECG use. In addition to the other advantages discussed above, such an ECG electrode will have the further advantage that the wire 43 comes out on the side of the electrode element. The normal EKG electrodes of the snap type have the snap device directly above the center of the electrode so that stretching the wire up to the snap device will change the gel pressure and in the ECG recording this will lead to errors due to movement of the electrode. When the wire exits the side of the electrode element, most of these errors will be eliminated. This reduction of errors due to the electrode element also applies to the electrode elements 31 and 33.

A final note regarding the structure of the defibrillator cable 49 is that a shorting bridging conductor 196 can be placed in the defibrillator's instrument coupler 129 to regulate the applied energy for defibrillation of adults or children or for internal defibrillation energies.

A variant of the defibrillator coupler 49 is shown schematically in fig. 14 where a plate transition 197 is placed at one end of the cable 49 and with the defibrillator electrode coupler 131 still at the other end of the cable 49. Instead of describing each of the elements of this variant of the cables 49, the same or similar parts have the same reference numbers to facilitate the overview.

The plate transition 197 has a pair of conductive plates 199 and 201 which are intended to receive ordinary defibrillator plates and they form a continuous electrically conductive path. The conductive plates 199 and 201 are separated by an insulating part 203 to prevent accidental short-circuiting of the defibrillator plates. Push-button switches 205 and 207 project from the conductive plates 199 and 201. When both push-buttons 205 and 207 are depressed by the defibrillator plates, an audible alert is produced to indicate to the operator that a proper defibrillation connection has been made and to alert others by the staff so that they can pull away from the area surrounding the patient.

An ECG cable 209 is shown permanently attached to the plate transition 197 in this preferred embodiment (although alternatively a plug or connector could be provided for external connection through an ECG cable 51) and an ECG monitor coupler 211 is provided at the end of this cable 209. An ECG output terminal 213 is also provided on the plate transition 197 for connection to another ECG instrument or for connection to a telemetry unit for transmission of the ECG signals to a central unit or a hospital.

Further details of the defibrillator cable 49 with the plate transition 197 are shown in fig. 15. In this figure you can see that the push buttons 205 and 207 close the associated switches 215 and 217 when the buttons are pressed down. This makes the circuit a suitable energy source, e.g. a 9 volt DC battery 219 which activates a buzzer 221. The ECG cable 209 has three wires extending from the ECG monitor coupler 211 to a body tissue impedance simulation circuit 223 and this circuit is located in the plate junction 197. The body tissue impedance simulation circuit 223 is coupled to the main wires 165 and 167 through a high voltage protection circuit 225. The ECG output terminal 213 is connected between the body tissue impedance simulation circuit 223 and the high voltage protection circuit 225 as this coupler will fit with the ECG electrode coupler on an ECG cable where the body tissue impedance simulation circuit is already present. The wires 171 and 173 from the ECG-only sleeve 135 in the coupler 131 are also connected between the body tissue impedance simulation circuit 223 and the high-voltage protection circuit 225.

The more detailed connection core in fig. 16 is a further explanation of the defibrillator cable 49. Thus, the common defibrillator plates 227 and 229 are shown schematically and they are to be brought into contact with the conductive plates 199 and 201. The plates 277 and 229 have handles 231 and 233 with associated control means 235 and 237 for defibrillation discharge. Placing the defibrillator plates 227 and 229 on the plates 199 and 201 will depress the buttons 205 and 207 so that the buzzer 221 will sound. Defibrillation can then be performed by pressing the control buttons 235 and 237 for the discharge, whereby a defibrillating pulse is sent through the wires 165 and 167 to the electrode elements

> 31 and 33.

The high voltage protection circuit 225 is shown including series resistors 239 and 241 together with a spark gap device 243 connected across the resistors. However, any suitable type of high voltage protection circuit will be acceptable.

The impedance simulation circuit 223 is represented by the resistor 245. The permanent ECG cable 209 is also provided with a low pass filter circuit including the resistor 247, the capacitance 249 and oppositely biased diodes 251 and 253.

With one or another variant of the defibrillator cable 49 which is reproduced in fig. 10 and 14 you get improved defibrillator effect. Among the improved features are better current density distribution due to sufficient electrode area (electrode elements 31 and 33 are about 8 cm and 12 cm in diameter), sufficient flexibility in the electrode elements to optimize the size of the available area against the patient's skin and the reduction of the impedance between the electrode element and the skin. Other advantages are that the electrodes 31 and 33 can be placed on the patient in advance and connected to the defibrillator in advance so that a defibrillator pulse can be delivered to the patient very shortly after fibrillation has occurred. The use of disposable electrodes also provides better control with the conductive medium or the gel used and, as the control device for the discharge is located at a good distance from the patient, you get better protection for the person carrying out the treatment or other staff.

Perhaps one of the most prominent advantages of the present invention for defibrillation is that it enables the use of a new lung tip-posterior placement of the electrodes. The four schematic representations on fig. 17 shows the advantages of this placement. In fig. 17A, the heart 255 is shown in its normal position lying between the lungs 257 and 259. It is immediately clear from this sketch that there are difficulties in delivering sufficient defibrillation energy to the heart with the usual sternum-lung apex location of the defibrillation plates 261 and 263 From the schematic representation in fig. 17B the problem of getting sufficient defibrillation energy to the heart is clear. Not only is there a significant loss of energy directly between the plates 261 and 263, but most of the current that reaches the heart is directed only through part of this. It is therefore not only difficult to get the energy to the heart, but the current that does not reach the heart is concentrated in a relatively small area of it and thereby increases the risk of myocardial damage.

Fig. 17C shows the new lung tip-posterior placement that is used in conjunction with the present invention. It can be seen here that the smaller electrode element 31 is placed at the tip of the lung or at the left branch. It is immediately clear that this location offers two advantages. One is that the electrode is out of the way of any cardiopulmonary resuscitation attempts that may need to be performed on the patient. The second is that the electrode is located in an area of the body that is generally free of hair, so that the problems with attaching the electrode and conducting current are reduced to a minimum. With the large electrode element 33 placed on the back of the right arm, this electrode is also in an area of the body that is generally without hair and it does not affect any treatments that may have to be carried out from the front of the patient and the electrode is also in good condition distance from the uneven spine area. Fig.

17D shows dramatically how this placement of the electrode elements 31 and 33 results in the majority of the defibrillation energy being conducted throughout the volume of the heart with very negligible interference from the lungs. This greater concentration of energy in the heart not only increases the chances of a successful defibrillation, but due to the distribution of this defibrillation energy throughout the heart, the risk of myocardial damage will be greatly reduced.

Fig. 18 and 19 show the combination of the cables 49 and 51 so that both ECG monitoring and defibrillation functions are obtained through the single pair of electrode elements 31 and 33. When the ECG electrode coupler 87 is assembled with the ECG output terminal 147 on the control unit 137 for the defibrillator discharge, the operation of the ECG unit 35 will be as if the coupler 87 were connected directly to the coupling plug 45. The only difference is that an additional high voltage protection circuit 169 is provided for further protection of the ECG unit 35 against the high energy discharge pulses from the defibrillator 37. Further explanation of the details of these circuits would be repetitive, but it should be noted that discharge control switches 157, 159, 161 and 163 are shown schematically in fig. 19 as a simple box 265 which can be referred to as the discharge control circuit.

When this combination is used, the electrode elements 31 and 33 can be attached to a patient for monitoring that person with a separate ECG instrument 35. If the defibrillator 37 is of the type that has an ECG unit built in for monitoring through the defibrillation plates, monitoring will naturally be able to find location without the use of any separate ECG unit 35 and cable 51. Even with such a unit, however, it may be necessary to have a separate ECG unit or there may be a need to send the ECG signals to a remote location, e.g. . a central hospital. The last condition is particularly linked to emergency situations, e.g. such where a paramedic medical team must be in operation. The possibilities for connecting a separate ECG unit or a telemetry unit to the electrodes 31 and 33 through the ECG output coupler 147 is therefore very significant as well as extremely valuable in those cases where the defibrillator does not have a built-in ECG monitor.

If the ECG recording should indicate that the patient has started fibrillation, the electrode elements 31 and 33 are already in place for defibrillation and these electrodes are already connected to the defibrillator through the cable 49. A defibrillating pulse can thus be applied to the patient approximately as soon as it is seen that fibrillation has occurred, which increases the chance of successful treatment for the patient. Furthermore, the effect of the conductive gel on the skin will increase the conductivity (and thus reduce the impedance) between the electrode element and the patient's body during a first period after the electrode element has been put in place. By having the electrode elements placed on the patient in advance, the transfer of defibrillating energy to the patient will therefore be improved. At the same time, you get virtually continuous ECG monitoring through the electrode elements 31 and 33 with loss of ECG recording for only a very short time during application of the defibrillation pulse. This combination is therefore of great use in paramedical use, in emergency rooms, in operating theaters and in intensive care. The combination is of course also of great importance for other types of situations, e.g. when a stimulating signal of another type is applied to the body and it is desirable to monitor the heart to be sure that the stimulation does not cause cardiac problems.

In some situations it may be desirable to have only ECG monitoring and defibrillation options and in this case the connector plug 45 may have the pins arranged as shown in fig. 20. From this schematic representation it will be seen that the outer sheaths 55 are provided with female pins 267 and 269 corresponding to pins 59 and 61 on the main plug 45. However, the two middle pins contain solid non-conductive plugs 271 and 273.

An ESU cable 47<*> is shown in fig. 21 and 22. Marked reference numbers are used to identify this cable which does not include a cable coupler which is included in the ESU cable 47 as explained in more detail below. The ESU cable 47' has an ESU instrument coupler 275 at one end for connecting the cable to the ESU device. At the other end of the cable 47' is an ESU electrode coupler 277. The ESU electrode coupler 277 has the same standardized rectangular box used in the ECG and defibrillator electrode couplers 1 87 and 131.

As shown in fig. 22, the ESU cable 47' includes a pair of wires 279 and 281 extending from the ESU instrument coupler 275 to contacts 283 and 285 of the ESU electrode coupler 277. Contacts 283 and 285 are capacitively coupled to another pair of contacts 287 and 289 of the coupler 287, e.g. with capacitances 291, 293 and 295. Although in this preferred embodiment two contacts 287 and 289 are used, a single contact 287 could be used as explained in detail below. If a single contact 287 was used, the capacitive coupling would preferably extend to both leads 279 and 281 although only a single lead 279 could be used in some cases.

In certain circumstances, the purchaser may only need or desire an ESU return pad to return the RF current to the ESU instrument. For such a situation, a simple ESU return pad 297 can be arranged. Although any suitable type of conductive pad could be used, in this preferred embodiment an electrode element is constructed in accordance with the description of FIG. 4 with the exception that the element has a conductive plate, e.g. of aluminum instead of the described tin-tin chloride structure. For ease of manufacture, the ESU pad 297 may be identical to the electrode element 33 in other ways. As explained above, there are many advantages associated with the special ESU return cushion according to the invention, but certain features of the invention can also be used together with other types of return cushions.

The ESU pad 297 is connected to a connector plug 299 by one or more wires. In this preferred embodiment, two wires 301 and 303 are used. The plug 299 is largely the same as the plug 45, but with different locations of the pins (fig. 25).

Regarding the connection diagram in fig. 24, one will see that the wires 301 and 303 are connected to contacts 305 and 307 in the connection plug 299. Two other contacts 309 and 311 in the plug 299 are electrically connected together or short-circuited with a short-circuit rail 313.

When the plug 299 is assembled with the ESU electrode coupler 277, the leads 301 and 303 and thus the ESU return pad 297 are capacitively coupled to the leads 279 and 281 with the capacitances 291, 293 and 295. In reality, the capacitive coupling for the RF return path could be achieved with a single wire 301 and a single wire 279 which are capacitively coupled by means of one or more of the capacitances 291, 293 or 295. For some ESU instruments this system would allow

taken out completely.

However, most ESU devices have a DC fault detection circuit to ensure that an RF return path is established before the ESU can be energized. Thus, the preferred embodiment described here uses two leads 279 and 281 to provide a DC fault detection circuit. This direct current fault finding loop is terminated by means of the jumper 313 when the contact 283 is electrically connected to the contact 309 and the contact 285 is electrically connected to the contact 311. This fault finding device for the line can of course be used with a single line 301 which is capacitively connected to the lines 279 and 281. However, as a further margin of safety, in the preferred embodiment another wire 303 is used.

The capacitive coupling between the wires 301 and

301 for the ESU return pad and wires 279 and 281 is extremely important because of its isolation from DC and low frequency AC. The most prominent feature of this isolation is the protection it provides for the patient against low frequency or direct current leakage from the ESU unit and from low frequency and direct current signals that are returned to the ESU unit as a result of rectification of the RF signals during the electrosurgical operation. In addition, the insulation in the capacitive coupling will also protect the ESU instrument against direct current with high energy and low-frequency signals with high energy, e.g. defibrillation pulses. In addition to the capacitive coupling formed with the capacitances 291, 293 and 295, additional capacitive coupling can be obtained on the side where the coupling plug 299 is located, e.g. with a capacitance coupled from one or both (with capacitive isolation) of leads 301 and 303 to the jumper 313. In practice, all capacitive coupling may reside in the coupling plug 229, but safety and profitability considerations mean that at least some of this capacitive coupling is placed in the ESU electrode coupler 277.

As the ESU return pad 297 would not be sufficient for ECG monitoring or defibrillation, it is necessary to ensure that the connecting plug 299 cannot be assembled with a connecting device intended for ECG or defibrillation. In this preferred embodiment, this is achieved by means of the pin device shown in fig.

25 with male pins 317 and 319 corresponding to contacts 309

and 311 and female pins 321 and 323 corresponding to contacts 305 and 307.

Fig. 26 and 27 show the combination of an EKG unit 35 and an ESU unit 39 where you get both EKG monitoring and

RF return to the ESU unit. The basic electrode set 53 is used in this preferred embodiment instead of the simple ESU return pad. The same type of ESU instrument coupler 275 is used together with the cable 4 7 as with the cable 47'. An ESU electrode coupler 325 instead of the ESU electrode coupler 277 is used for assembly with the connector plug 45. Also, an ESU cable coupler 327 is added for connecting the ECG cable 51 to the ESU cable 47. An ECG output terminal or connector plug 329 with the same pin device as the plug 45 is placed on the coupler 327 for assembly with an EKG electrode coupler 87.

In fig. 27, it will be seen that the ECG electrode coupler 87 has the matching circuit 97 for the body tissue impedance, the high-voltage protection circuit 99 and the low-pass filter 101 for the ECG cable 51. In addition, the ESU cable coupler 327 has another low-pass filter 331 associated with the ECG output coupler 329 to further protect The ECG unit against RF energy and subharmonic influence. One will also see that a short-circuiting jumper 333 corresponding to the jumper 313 in the plug 29 9

i is arranged in the plug 45. Although the shorting jumper 333 stands over the two middle contacts instead of the . two outer contacts as in the plug 299 have the same function, namely to form a fault finding loop for the wires 279 and 281 when the plug 45 and the coupler 325 34 are assembled. The same

> capacitive coupling can be used in the coupler 325 in the same way as in the coupler 277. In both cases, one should be aware that the use of the capacitances 291, 293 and 295 is only

an illustration and that various other capacitor combinations can be used.

In order to provide a current path for the ECG signals and possible other electrical signals passing through the ECG output coupler 329, an additional pair of wires 335 and 337 are provided in the cable 47 between the couplers 325 and 327. The wires 335 and 337 are connected to the connectors in the coupler 335 which is electrically connected to the contacts in the plug 4 5 while this is connected to the electrode elements 31 and 33 when the plug 45 and the coupler 325 are assembled. At the other end, leads 335 and 337 are connected to the ECG output terminal 329 through low-pass filter 331.

With the combination in fig. 26 and 27 it is possible to achieve continuous ECG monitoring during an electrosurgical operation using the same electrode elements which form an RF return path. As the ECG signals are obtained through the same electrode elements that form the RF return path, the risk of RF burns occurring under the small ECG electrodes will be eliminated. The large electrode element 33 is also largely the same as the ESU return pad 297, which works very effectively on its own. If desired, the capacitive coupling in the coupler 325 or the plug 45 can therefore be such that it only uses the electrode 33 for the RF return. In the preferred embodiment described here, however, both electrode elements 33 and 31 are used as RF return, which gives an even better RF spread and further reduces the risk of RF combustion. The addition of the electrode element 31 therefore not only enables the use of a separate ECG unit 35 together with the ESU unit 39, but also provides a very efficient RF return system for the ESU unit.

On the basis of the previous review is

it is now possible to better understand the multiple function system in fig. 1 and which is shown in more detail in the schematic diagram in fig. 28. A further detail found in this diagram is that the low pass filter 331 in the ESU cable coupler 327 is illustrated as a capacitance 339 and a resistance 341 connected in parallel between the wires 335 and

337. Important features of this circuit are that the capacitance 339 largely isolates the EKG unit from the ESU unit's RF signals or any other relatively high-frequency influence and the resistance 341 forms a compensation for the direct current shift while also contributing to the filter function.

It should also be pointed out that the numbers 291, 293 and 295 are used as references for the capacitances in the coupler 325 to show that they correspond to the capacitances in the coupler 277 even if the actual connections differ somewhat. The capacitance 295 is primarily a safety detail to ensure that the lines 279 and 281 are mostly short-circuited for RF signals, although the capacitances 291 and 293 would normally provide sufficient coupling for the RF signals. The contacts in the coupler 325 and the plug 45 do not have their own references, even though they correspond to the contacts 283, 285, 287 and 289 in the coupler 277 (fig. 24) and the contacts 305, 307, 309 and 311 in the plug 299 (fig. 24). With reference to fig. 3 it will be seen that the contacts 305 and 309 are in reality male pins 6 3 and 65 and between these there is the jumper 333. In addition, the contacts 307 and 311 correspond to the female pins 59 and 61.

By using the cables 47, 49 and 51, the EKG unit 35, the defibrillator 37 and the ESU unit 39 can be connected to the electrode elements 31 and 33 at the same time so that the many functions are performed with the help of a single pair of electrode elements. Not only do you have many functions, but an improved physiological effect of the electrode system is achieved for each of the functions if you make use of all the features described here.

The importance of this multifunctional possibility with the simple pair of electrode elements 31 and 33 can be illustrated with an example. In an emergency, a paramedic would place the electrode elements 31 and 33 on the patient for ECG monitoring using an ECG cable 51 and a defibrillation cable 49 as shown in FIG. 18. If fibrillation of the patient's heart is observed, a defibrillating pulse of energy can be applied by depressing buttons 139, 141, 143 and 145 on the discharge control device. At the same time,

the ECG monitoring is virtually uninterrupted.

The patient is then taken to a hospital. If surgery is required, the patient is taken to the emergency room where the plug 45 can be released from the coupler 131 in the physician's system and then reassembled with a coupler 325

in the system of fig. 1. The same electrode elements 31 and 33 that the doctor put in place will thus enable ECG monitoring, a return path for RF energy from the electrosurgical unit ESU and the possibility of immediate defibrillation if necessary.

After the surgical intervention, the patient can be taken to the post for intensive monitoring where a system of cables 49 and 51 as shown in fig. 18 can be connected to the electrode elements 31 and 33 for ECG monitoring. A defibrillator would not normally be connected to each individual patient, but if the onset of fibrillation could be detected, a defibrillator can be quickly connected to the coupler 129 for applying a defibrillating pulse to the patient. As an alternative, defibrillation cables 49 with plate transitions 197 can be used so that the defibrillating discharge could be carried out using ordinary plates without the need to attach a coupler 129 to the defibrillator.

In the same way, in an operating theatre, the system in fig. 1, the patient is connected for electrosurgery. After a surgical operation, the patient is transferred to the system shown in fig. 18 by intensive monitoring as described above.

If, as in another example, electrosurgery

does not affect the cardiovascular structure and ECG monitoring was only a safety measure, the system of fig.

26 is used. If fibrillation unexpectedly occurred, one could

defibrillator is quickly connected to the ESU cable coupler 327 for applying a defibrillating pulse through the electrode elements 31 and 33.

In addition to the possibility of several functions through a single pair of electrode elements, the invention also aims at separately connecting each of the instruments to the aforementioned pair of electrode elements. Each of the electrode elements itself constitutes a new and improved form of physiological electrode and the electrode elements are combined into a new electrode set for single use. In addition, special and new cables are used to connect the electrode set to the various instruments. For that reason, this invention not only relates to the unique system, but it also relates to a number of new and distinctive subsystems and components for the physiological electrode system. Some of the special features of these sub-parts of the system can also be used together with other devices that are not directly part of the physiological electrode system. Finally, the invention includes certain alternative or partially modified variants.

Although the preferred embodiments described here use the features shown and described, many of the new features of the invention can be used alone without being included in the collection of features described here and still this will fall within the spirit and scope of protection of the invention . Although certain alternative and modified solutions or features have been described, it will also be understood that various modifications, changes and variations can be made in the arrangement, use of and details in the construction of the elements shown here without thereby deviating from the invention spirit and scope.

Claims (8)

1. Device for connecting an electrode set to different devices, comprising: a first electrode element (31) to be attached to a patient's skin, a second electrode element (33) to be attached to the patient's skin, means that produce mutual relationships that provide possibility of selective connection of the electrode elements to a monitoring device (35), a stimulation device (37) and a therapeutic device (39) to produce the desired operation of any such device through these electrode elements, the monitoring device and the stimulation device, as well as the therapeutic the device, which are otherwise separate and not connected to each other, characterized in that said means comprise: a) a first connecting plug means (45), a first electrically conductive wire (41) connected between the first electrode element and this first connecting plug means, and a second electrically conductive wire (43) connected between the second electrode element and the first connecting plug means and at least one of the following cables: b) a therapeutic device cable (47) with one end (275) to be connected to the therapeutic device, a therapeutic device electrode coupling (325) which is attached to the other end of the therapeutic device cable and thus designed to bring together this first connecting plug means in a second connecting plug means (327) in this therapeutic device cable between one end and the electrode coupling, c ) a stimulation device cable (49) having a first end (129, 197) which is designed to be connected to the stimulation device, a stimulation device electrode coupling (131) which is attached to the second end of the stimulation device cable, and is thus designed , that it produces the engagement of the first or second connecting plug means, and a third connecting plug means (147, 213) in the stimulation device cable between the first end and the electrode coupling, d) a monitoring device cable (51) which with one end (85) can connected to the monitor, and a monitor electrode connector (87) attached to the other end of the monitor cable and intended to be assembled with any of the electrical connection plugs, the device comprising additional protection means which are linked to said means for the mutual relationship to enable selective, desired combinations of the monitoring device, the stimulation device and the the therapeutic device at the same time can be connected to the patient only through said first and second electrode elements, where the protective means is suitably selected from components comprising capacitive coupling devices (293, 295) which are incorporated in this therapeutic device's electrode coupling and connect this second connecting wire (43 ) to the supply lines (281, 279) in the therapeutic device cable, which are capable of forming a return path for the therapeutic device signals to protect the therapeutic device against energy pulses from the stimulation device and to protect the patient against shock currents, a low-pass filter ( 331) which is included in this second connection plug means, a high-voltage protection circuit (169) included in this third connection plug means, and/or a high-voltage protection circuit (99) and/or a low-pass filter (101), which is included in this monitoring device electrode coupling. 2. Device as stated in claim 1, characterized in that each of these electrode elements is for single use and comprises: an electrically conductive plate (71) which is sufficiently thin to have enough flexibility that the conductive plate largely corresponds to the area of the patient's body where the plate is placed, an electrically conductive medium which is arranged between this conductive plate and the patient's skin, in order to improve the electrical energy transfer between the patient and the conductive plate, an outer surface of this conductive plate being formed of an electrically conductive metal , a chloride (72) of the electrically conductive metal being intended to be between this metal and the skin of the patient, as well as an adhesive (81) for releasably connecting the disposable electrode elements to the patient. 3. Device as specified in claim 2, characterized in that the electrically conductive metal is tin and that the chloride is tin(II) chloride. 4. Device as stated in claim 1, characterized in that the monitoring device is an EKG unit (35) and that said means for mutual relationships also includes a body tissue impedance simulation circuit (97), to enable these first and second electrode elements (31, 33) in said ECG from the patient supplies input information, which normally requires the use of a minimum of three separate electrodes. 5. Device as set forth in claim 1, characterized in that the stimulation device is a defibrillator (37) and that this means of interrelationship also comprises a defibrillator discharge control device (137, 235, 237), which enables an operator to send a impulse of the defibrillating energy to the patient through the defibrillator cable (49) when desired. 6. Device as stated in claim 5, characterized in that the control device for the defibrillator's discharge comprises a discharge control module (137) which is placed in the defibrillator cable. 7. Device as stated in claim 5, characterized in that there is a plate adapter (paddle adapter) (197) to enable the use of these two electrode elements (31, 33) for defibrillation with a defibrillator (37) with ordinary defibrillation plates, this adapter has a pair of electrically conductive plates (199, 201) with which the defibrillator plates must be placed in contact, and where the first end of this defibrillator cable (49) is connected to the adapter and not the defibrillator, in order to receive defibrillation impulses from the conductive plates. 8. Device as stated in claim 1, characterized in that the therapeutic device is an electrosurgical instrument (ESU) (39) and that the connecting plug means (45, 299) comprises electrically conductive devices (333, 313), to connect the ends of the connecting wires (279, 281) with each other, when this plug means includes this ESU connecting unit (325, 277) and thereby enables the passage of a string fault test direct current through this conductive wire, to indicate that a path for the return of RF the signal to said ESU is fully completed, before said ESU can be made functional.