FR2653023A1 - Improved electrode system intended for use in electrotherapy or ionophoresis - Google Patents

Abstract

The invention relates to an improved electrode system intended for use in electrotherapy or in ionophoresis, of the type comprising a member (4) for connecting to a voltage source (3) capable of delivering at least the desired current strength, a conducting surface (6) called the electrode, and a conducting connecting wire (5) connecting the said connecting and electrode members and attached to them. This electrode system is characterised in that it comprises at least one active element (11) mounted in series with the connecting wire (5) and suitable for limiting the strength of the current delivered to the electrode (6) to a predetermined threshold depending on the surface area of the said electrode, so that the current density of this electrode (6) corresponds to a value predetermined by the desired use.

Description

 The invention relates to an improved electrode system intended for use in electrotherapy or iontophoresis, of the type comprising a member for connection to a voltage source, a conductive surface known as an electrode and a conductive connecting wire connecting said connection member and electrode .

 Nowadays many medical and paramedical treatments use the ionization process to accelerate the migration of pharmaceutical products in the body. This method consists in passing a weak electric current between two parts of the body of a patient by means of electrodes applied judiciously on the body of this patient. The electrodes used are made of a deformable conductive material so as to obtain a distribution as uniform as possible over the entire surface of these electrodes. They are also connected to devices generally adapted to allow the simultaneous supply of several pairs of electrodes. These devices have, for this purpose, an adjustable current generator comprising a milliammeter for controlling the intensity of current delivered, by pair of electrodes.

 Controlling this intensity is, in fact, of primary importance because an increase in this intensity can be the cause of burns that are all the more dangerous as they can be painless when they are formed. However, the setpoint intensity must be systematically adapted as a function of the surface of the electrodes because the value to be taken into account, as regards the risk of burns, consists of the current density, that is to say l current intensity per unit area of the electrodes.

 For this purpose, and in order to deliver a current intensity which is a function of the surface of the electrodes, it is conventionally used, either of conversion tables, or of devices provided directly with graduation in milliamps per square centimeter. However, these solutions leave the risk of burns. Indeed, on the one hand, they do not make it possible to get rid of handling errors and in particular errors of connection or display of values not corresponding to the surface of the electrodes. In addition, they do not overcome the risk of burns due to improper placement of the electrodes resulting in partial detachment of the latter and therefore an increase in the current density. Finally, because the overall resistance of the human body varies during treatment, permanent monitoring is necessary during this treatment.

To overcome these drawbacks, it has been designed, as described in US Patents 3,918,459 and
EP 92015, devices provided with means for regulating the intensity of the current delivered, as a function of the surface of the electrodes. For this purpose, each pair of electrodes is associated with a resistance of determined value which is a function of the surface of these electrodes and intended to keep the current density below a given threshold. This resistor is connected to a third terminal provided on the connection plugs of the electrodes provided on the current generator, so as to form an integral part of a feedback circuit of this generator.

 Consequently, each pair of electrodes being associated with a resistor adapted so that the current density is less than a given threshold, such devices overcome the drawbacks of known conventional devices.

However, they require the use of current generators provided, for each pair of electrodes, with complex regulation electronics and therefore with a high cost price.

 The present invention aims to overcome this drawback and has the main objective of providing an electrode system designed to be able to be powered by a simple voltage source, and adapted to eliminate any risk of burns.

 Another objective is to provide an electrode system which makes it possible, with a minor additional cost, and for a required electrode area, to use a large number of electrodes with small unit areas.

 To this end, the invention relates to an improved electrode system intended for use in electrotherapy or in lonophoresis, of the type comprising a member for connection to a voltage source capable of delivering at least the desired current intensity, a surface conductive, called electrode, and a conductive connecting wire connecting said connection members and electrode and secured to them.

 According to the invention, this electrode system is characterized in that it comprises at least one active semiconductor element mounted in series on the connecting wire and adapted to limit the intensity of the current delivered to the electrode to a predetermined threshold. function of the surface of said electrode, so that the current density of this electrode corresponds to a value predetermined by the desired use.

 The main advantage of the invention therefore lies in the fact that each electrode system has a fully autonomous regulation system unlike the devices described in US Patents 3,918,459 and EP 92015 for which the resistances associated with the electrodes are an integral part of the feedback from the constant current power system.

 Consequently, no control electronics are required at the level of the current generator because each electrode equipped with its active semiconductor element behaves like a stable current generator and adapted to the surface of this electrode of which it forms an integral part.

 Thus, one can directly connect the electrodes to a simple battery or a conventional current source. The maximum power supplied to the patient will be constant up to an easily calculable limit and dependent only on the maximum voltage available.

 In addition, to treat large areas, one can use in parallel, without significantly increasing the cost of installation, a large number of electrodes of small areas regulated independently and arranged judiciously. Thus, the risk of burns due to partial detachment of an electrode is almost eliminated since the intensity of current delivered to each of the electrodes is low.

 In addition, this electrode system allows several patients to be treated simultaneously, even with different surface / intensity electrodes connected to the same current source. Indeed, an error in the choice of electrodes (different surfaces for the same patient) has no influence because it is the electrode (positive or negative) of lower surface which determines the intensity of maximum current delivered.

 Furthermore, it should be noted that when two electrodes (positive or negative) of the same surface are used for treatment, it is only necessary to use one electrode system in accordance with the invention, the other electrode can be classic. In this case, however, and according to another characteristic of the invention, the electrode system preferably comprises a diode mounted in series with the active element and adapted to avoid any connection error.

 According to another characteristic of the invention, each electrode system can be provided with two active elements in series mounted in opposition, allowing the use of faradaic currents.

 Finally, each active element preferably consists of a field effect transistor mounted so that the source and the gate are in short circuit.

Other characteristics, objects and advantages of the invention will emerge from the detailed description which follows with reference to the appended drawings which show by way of nonlimiting example a preferred embodiment as well as an example of application. On these drawings which form an integral part of the present description
FIG. 1 is a longitudinal section of a connection plug of an electrode incorporating a regulation system according to the invention,
FIG. 2 is a simplified diagram of an ionization device comprising an electrode system according to the invention,
FIG. 3 is a graph representing the power dissipated as a function of the resistance of the body for different intensities and voltages,
FIG. 4 is a schematic top view of a form of preferred electrode according to the invention,
- Figure 5 is a sectional view illustrating the use of a device according to the invention with a transdermal device.

 As shown in FIG. 2, the invention relates to electrode systems 1, 2 intended to be supplied by a current generator 3 and each comprising a member 4 for connection to said generator, a conductive surface called electrode 6, and a conductive connecting wire 5 connecting said connection members and electrode. Each electrode 6 is made, in a conventional manner, of a deformable conductive material, such as tin or conductive plastic rubber, adapted to allow a uniform distribution of the current over the entire surface of this electrode.

 In addition, and as shown in FIG. 4, each electrode 6 preferably has an elliptical shape, and the conductive wire 5 is secured to this electrode 6 towards the center of the latter and so that the conductor / electrode contact area is linear and located substantially on the axis of the focal points of the ellipse.

 This specific shape in fact makes it possible to obtain equipotential lines having the shape of ellipses centered on the linear contact area between conductor and electrode, and, by the same token, a decreasing current density from the center of the electrode towards the periphery of this one. Thus, the risk of possible burns resulting from improper positioning of the electrode and detachment of the edges thereof is reduced.

 It should be noted that by elliptical shape, we also mean a circular shape, because a circle corresponds to the particular case of an ellipse whose two foci are combined. In this case, the conductor / electrode contact is reduced to a point contact.

 As shown in Figures 1 and 2, each electrode system has its own autonomous regulation device. This regulation device, as shown in FIG. 1, is integrated inside the connection member 4.

 To this end, this connection member 4 consists of a banana plug comprising a pin 7 provided with a threaded rear end 7a, and a longitudinal sleeve 8 which is screwed or fitted onto this threaded end 7a.

 Inside this sleeve 8 is placed a metal reinforcing plate 9 provided towards its rear end with a sleeve 9a for shrinking the connecting wire 5.

 The actual regulation device is disposed on this plate 9. It includes a printed circuit 10, for example soldered with tin on the plate 9, on the rear end of which the stripped end Sa of the connecting wire 5 is welded .

 On this printed circuit are arranged two field effect transistors ll in series, mounted in opposition. As shown in Figure 2 each of these field effect transistors 11 is further mounted so that the source and the gate are in short circuit, the gate-source potential being constant.

 As shown in FIG. 3, this electrode system provided with an autonomous regulation system specific to each electrode has the advantage of making it possible, by a judicious choice of the characteristics of the field effect transistors 11, to limit the power maximum supplied to the patient at an easily calculable limit depending only on the maximum available voltage.

 In addition to conventional applications in the fields of electrotherapy or iontophoresis, these electrode systems, by their design, can also be used in combination with transdermal devices.

 Conventionally, the transdermal devices 12 firstly comprise a lower layer 13 consisting of a protective film to be removed before application, an adhesive layer, and a membrane. On this membrane is, moreover, secured a film 14 delimiting a housing for the treatment product 15 in gel or liquid.

 Currently, although these transdermal devices are used more and more, they have the major drawback of allowing only a slow and partial diffusion of the drug product.

 The combination of an electrode-e system according to the invention and a transdermal device 12 overcomes this drawback.

 As shown in FIG. 5, the transdermal device 12 includes, in view of this association and in 5US of the elements 13 and 15 cited above, an impermeable upper film 16 delimiting a pocket of shape adapted to accommodate an electrode 6 making it possible to activate the diffusion of the drug product. In addition, unlike conventional devices, the aforementioned film 14 is a film allowing the passage of current.

Such an association of an electrode system according to the invention and of a transdermal device 12 can therefore consist in producing a device comprising
- a fixed, autonomous and portable voltage source (not shown),
a transdermal device 12 as described above,
- two electrodes 6, of which:
at least one is of suitable shape to be accommodated in the pocket delimited by the film 16,
at least one includes the autonomous regulation system described above.

Claims (8)

 1 / - Improved electrode system intended for use in electrotherapy or iontophoresis, of the type comprising a connection member (4) to a voltage source (3) capable of delivering at least the desired current intensity, a surface conductive (6), said electrode, and a conductive connecting wire (5) connecting said connection members and electrode and secured to them, said electrode system being characterized in that it comprises at least one semi-element active conductor (11) mounted in series on the connecting wire (5) and adapted to limit the intensity of the current delivered to the electrode (6) to a predetermined threshold depending on the surface of said electrode, so that the density current of this electrode (6) corresponds to a value predetermined by the desired use.  2 / - electrode system according to ia claim 1 characterized in that it comprises a diode mounted in series with the active element (11) and adapted to avoid connection errors.  3 / - electrode system according to claim 1 characterized in that it comprises two active elements (11) in series, mounted in opposition.  4 / - electrode system according to one of claims 1 to 3 characterized in that each active element consists of a field effect transistor (11) mounted so that the source and the gate are in short- circuit.  5 / - electrode system according to claim 4 characterized in that each field effect transistor (11) is mounted so that the gate-source potential is constant.  6 / - electrode system according to one of the preceding claims comprising a connection member (4) of the banana plug type provided with a connection pin (7) and an insulating sleeve (8), characterized in that the active element (s) (11) are integrated inside said sleeve.  7 / - electrode system according to one of the preceding claims, characterized in that the electrode (6) has an elliptical shape, and in that the conductive connecting wire (5) is secured to said electrode towards the center of the latter and so that the conductor (5) / electrode (6) contact area is linear and located substantially on the axis of the focal points of the ellipse.  8 / - Device associating an electrode system with a transdermal device (12) comprising a lower layer (13) capable of being applied to the body of a patient and an upper film (14) delimiting a housing for a treatment product (15), characterized in that it comprises  - a fixed, autonomous and portable voltage source,  - a transdermal device (12) provided with a film (14) permeable to the passage of a current, and comprising an upper film (16) delimiting a pocket with the film (14),  - two electrode systems including  at least one of said systems comprises an electrode (6) of a shape adapted to be housed in the pocket of the transdermal device,  at least one of said systems conforms to one of the preceding claims.