GB2240928A

GB2240928A - Skin contact electrode

Info

Publication number: GB2240928A
Application number: GB9003802A
Authority: GB
Inventors: R John Bertram Derrick Rush
Original assignee: POLYMEDICAL Ltd
Current assignee: POLYMEDICAL Ltd
Priority date: 1990-02-20
Filing date: 1990-02-20
Publication date: 1991-08-21
Also published as: GB9003802D0

Abstract

A semidisposable skin contact electrode, for example an ecg electrode, is made up of a reusable header (e.g. Fig. 5) and a disposable electrolyte interface member (e.g. Fig. 4). The individual reusable header consists of an electrolyte contacting means 12 such as a silver/silver chloride reference electrode, a flexible non electrical mounting 11, and an electrical connecting means such as a stud 13 (or wire 15) which is electrically connected to the electrolyte contacting means. The disposable interface member consists of a quantity of non liquid electrolyte 4 mounted over a proportion of the area of a flexible and open celled foam or mesh material 10, such that when the disposable interface member is placed in physical contact with the header the electrolyte contacting means makes electrical contact with the electrolyte of the disposable interface member. The disposable interface member is placed in contact with the skin of a person so that the electrolyte is also in contact and electrical signals arising from the body are transmitted through the electrolyte to the header and its electrical connection. The electrolyte may be adhesive so as to maintain the physical and electrical contact between the electrolyte and the skin and between the electrolyte and the header. That part of the mesh or open celled foam of the disposable interface member which is free of electrolyte is of assistance in handling the disposable interface member during placement and removal. <IMAGE>

Description

SKIN CONTACT ELECTRODE This invention relates to electrodes, particularly, though not exclusively, to skin contact electrodes for use on the human body.

Skin contact electrodes are used extensively in the assessment of clinical condition, for example in the monitoring of cardiac condition. The electrodes are placed in contact with a human body and the electrical signals which result may be examined. A large proportion of the electrodes used are self adhesive disposable electrodes having single patient use. Where large numbers of patients are to be examined the cost of providing a number of electrodes for each patient can be considerable even though the cost of each individual electrode may be low.

The applicants have realised that a reduced cost may be incurred by retaining part of the electrode for multiple use and using this part in conjunction with a disposable skincontacting part.

Accordingly the present invention provides an adhesive skin-contacting electrode comprising a disposable skincontacting body and a re-usable header part, the disposable skin-contacting body having a skin-contacting surface and a header-contacting surface and electrolyte means providing an electrically conductive path from skin-contacting surface to header-contacting surface.

In use the re-usable header part should not contact the skin so as to reduce the risk of cross contamination between patients. This may be achieved by making the disposable skin-contacting body as large or larger than the re-usable header in lateral extent.

Conveniently the skin-contacting body may comprise a piece of non-fluid electrolyte, such as a gelled aqueous electrolyte or solid polymeric electrolyte, extending from a skin-contacting surface to a header-contacting surface. This piece of non-fluid electrolyte may be carried by a flexible mount for handling or may indeed form the whole of the skincontacting part.

In an alternative construction the skin-contacting body may comprise a porous body either carrying a liquid electrolyte, or into which a liquid electrolyte may be introduced, so that the electrolyte means providing an electrically conductive path from skin-contacting surface to header-contacting surface comprises liquid electrolyte retained in the porosity of the skin-contacting part.

Further features of the invention will become apparent in the following description and from the claims.

The following description illustrates the invention by way of example only and with reference to the drawings in which: Fig. 1 shows a first form of skin-contacting body in accordance with the invention, Fig. 2 shows a second form of skin-contacting body in accordance with the invention, Fig. 3 shows a third form of skin-contacting body in accordance with the invention, Fig. 4 shows a fourth form of skin-contacting body in accordance with the invention, Fig. 5 shows a first form of reusable header in accordance with the invention, Figs. 6 & 7 show alternative forms of header in accordance with the invention, Fig. 8 shows yet a further form of header in accordance with the invention, Fig. 9 shows yet a further form of header in accordance with the invention.

Figure 1 shows a disposable adhesive skin contact pad.

It comprises a flexible annular substrate 1 which is coated on the front side with an adhesive 2 suitable for contact with the skin. Suitable materials for the substrate 1 include: i) plastic foam, e.g. 8104-800 foam from DRG Kwikseal, The Woodside Estate, Dunstable, Beds LU5 4TP; ii) microporous tape, such as Dupont Sontara polyester 7002 800 from the same suppliers; iii) flexible paper, such as Medifix 7000 from the same suppliers; iv) thin plastic sheet either perforated or otherwise; or v) woven or non-woven cloth.

Around some portion of the periphery of the annular substrate the adhesive coating on the front may be either omitted or covered so as to form an area 3 which is not adhesive to the skin, which portion may be used in the manual placement or removal of the disposable pad from the skin, or from the carrier on which the disposable substrate is supplied, or from the header with which the disposable skin contact pad is used. The profile of the area 3 may be extended or delineated so as to expedite this function.

The open region in the substrate 1 in figure 1 is filled with a layer of gelled electrolyte 4, such as Promeon RG-63B, from Medtronic Inc, 6700 Shingle Creek Parkway, Brooklyn Center, MN 55430. The electrolyte 4 need not be the same thickness as the substrate and need not be coplanar with either the front or rear surfaces of the substrate. In order to maintain the integrity of the disposable construction the piece of gelled electrolyte 4 must be attached to the substrate 1. In figure 1 the electrolyte pad 4 is adherent to a third component 5 which is an annulus of material which is adherent to the rear of the substrate 1.In order that the disposable skin contact pad may be used the rear of the disposable skin contact pad must be brought into contact with the front face of the header, and for this purpose some portion of the rear of the disposable skin contact pad is coated with adhesive 6. If the disposable skin contact pad is larger in area than the surface of the header with which it is in intimate contact, a means of indicating the desired relative location of the disposable skin contact pad with respect to the header may be incorporated in the rear of the disposable skin contact pad. This may be done visually with a printed line 7; a printed area, some other indicia, or by making the mounting ring 5 sufficiently large, adhesive on its rear surface and visually distinguishable from the substrate 1.

Figure 2 shows a second possible embodiment of the disposable skin contact pad, which is intended for use with a liquid electrolyte which is either pre-encapsulated on the pad or applied by the end user. The disposable skin contact pad consists of an annular substrate 1 which is coated with a medical grade of adhesive 2 on the front, skin-contacting, surface. A piece of porous material 8 is located over the aperture in the substrate 1 for the purpose of retaining the electrolyte in that region. The support 8 may be made of open celled foam or other material through which the electrolyte may permeate. The support 8 is attached to the substrate 1 either by direct adhesion as in figure 2 or via a third component such as a ring 5 as in figure 1 or a disc of thin laminar porous material similarly located.The rear of the disposable skin contact pad is coated with an adhesive which is partly covered with a thin non-adhesive layer 9, leaving an aperture 22. The portion of the adhesive on the rear of the disposable skin contact pad which remains exposed may be used to stick the disposable skin contact pad to the header. If the non-adhesive area is visually distinguishable from the adhesive area, for example by using coloured covering material or coloured adhesive, it will serve as a guide in locating the disposable skin contact pad on the header.

Figures 3 and 4 show further embodiments of the disposable skin contact pad. In both of these designs the substrate material 1 in figures 1 and 2, which is adhesive to the subject skin, is omitted. In figure 3 the disposable skin contact pad consists only of a piece of non-fluid electrolyte 4 such as a gelled aqueous electrolyte or a solid polymeric electrolyte material. In both figures 3 and 4 the piece of electrolyte 4 is itself adhesive to the skin and the material of the header and is of sufficient area to remain in contact with both surfaces for the time period required. A suitable such electrolyte comprises Promeon RG-63B or Promeon 3110 NDO from Meditronic Inc. 6700 Shingle Creek Parkway, Brooklyn Center, MN 55430.Figure 4 shows a modification in which a piece of thin open mesh material 10 is mounted on the rear of the electrolyte pad 4, to enable the electrolyte 4 to be handled more easily, for example in removal from the header after use.

Figure 5 shows a possible embodiment of the header in a relatively simple form. It consists of a substrate 11, contact pad 12 and a stud 13 by which external connection to the header may be made. A suitable stud, when used in conjunction with the correct rivet, would be part number BS 53052 from TRW Ltd. The substrate 11 need not be electrically conducting but the contact pad 12 and the connecting stud 13 need to be solid materials which conduct electrically. The substrate 11 may be rigid provided its area is such that the lack of conformability does not inhibit the adhesion of the disposable skin contact pad to the body.

If the substrate 11 is large and rigid it will prevent the disposable skin contact pad from conforming to the curvature of the subject's skin and so prevent adhesion. The substrate 11 can be made of a flexible material such as a rubber or plastic, in which case the area of adhesive contact between the header and the rear of the disposable skin contact pad may be larger than would otherwise be the case. The substrate 11 may also have an extension 14 which falls outside the area of adhesion between the header and the disposable skin contact pad, which will assist in mounting and removal of the disposable skin contact pad on the header and of the combined unit on the subjects skin. The electrolyte' contact pad 12 is in surface contact with the electrolyte when in use.This pad 12 may be of simple metallic material such as silver, tin, aluminium or carbon or carbon composite, or may comprise an inert material such as nylon surface coated with such materials, or may be in the form of a reference electrode.

This latter arrangement may be obtained either by coating an inert material with the components of a reference electrode, or by suitable surface treatment of the solid metallic material from which the pad 12 is made. A suitable component would be a silver chloride coated rivet, part number PC 53460 from TRW Ltd, Controls and Fasteners Group, 180 State Road, Westminster, Mass, U.S.A.

Figure 6 and 7 show alternative embodiments of the header in which the wire connection is built in permanently to the header. The header has a substrate 11 and an electrolyte contact pad 12 as before, and may have an extension tab 14 as in figure 5. An electrically conducting insulated wire 15, which may be metallic or otherwise is connected to the rear of the pad 12 permanently so as to be an integral part of the header. A cover 19, which may also be a label is fixed over the back of the header. In Figure 6 the other end of the wire 15 is fitted with a device 16 such as a plug or socket which will enable it to be connected to a monitor either directly or via a multiway cable capable of terminating several headers (not shown). In Figure 7 the multiway cable 17 is made part of the non-disposable unit by having several wire connected headers connected permanently to it.

A further embodiment of the header is shown in Figure 8, in which the external connection 13 to the header is offset from the electrolyte contact pad 12. The purpose of the offset connection is to enable a press connection between the header and the wire to be made, with the unit in contact with the subject skin, without applying pressure to the subject.

The substrate 11 is extended laterally as shown and supports an electrical connection 18 between the rear of the contact pad 12 and the external connection 13. The external connection may be in the form of a simple metallic tab or may be more complex such as a press stud as shown. An insulating cover material 19 may cover part of the rear of the header.

Figure 9 shows a further embodiment of the wire connected header similar to those described in Figures 6 and 7. This device incorporates a buffer amplifier 20 in the header itself in close proximity to the rear of the contact pad 12. The operation of such a buffer amplifier requires that the built in connection should be a multiway cable 21 rather than a single connecting wire 15 as in Figure 6.

A suitable amplifier is AD548JN or OPA1l1AM from RS Components Ltd, P.O. Box 99, Corby, Northants NN17 9RS.

The disposable skin-contacting bodies described above may be supplied encapsulated on a suitable carrier, or even supported on a suitable material such as a release paper.

The low cost of the disposable skin-contacting body in relation to the re-usable header part can result in great savings in costs compared with the conventional skin-contact electrodes in which the entire body of electrolyte and contact is thrown away.

Claims

1. An adhesive skin contact electrode comprising a disposable skin-contacting body and a re-usable header part, the disposable skin-contacting body having a skin-contacting surface and a header-contacting surface and electrolyte means providing an electrically conductive path from skin-contacting surface to header-contacting surface.

2. An adhesive skin-contacting electrode as claimed in claim 1 in which the disposable skin-contacting body comprises a piece of non-fluid electrolyte extending from a skincontacting surface to a header-contacting surface.

3. An adhesive skin-contacting electrode as claimed in claim 2 in which the electrolyte has adhesive properties sufficient to retain the disposable skin-contacting body to skin and to the header.

4. An adhesive skin-contacting electrode as claimed in claim 2 or claim 3 in which the piece of non-fluid electrolyte is supported on a flexible carrier.

5. An adhesive skin-contacting electrode as claimed in claim 1 comprising a porous medium impregnated with, or capable of impregnation with, a liquid electrolyte, the electrolyte means providing an electrically conductive path from skin-contacting surface to header-contacting surface comprising the liquid electrolyte in the porosity of the porous medium.

6. An adhesive skin contact electrode as claimed in any preceding claim comprising a disposable skin-contacting body having an electrolyte-carrying region, the disposable skincontacting body bearing indicia to assist placement of the re-usable header part against the disposable-skin-contacting body so that a contact in the header part may make electrical contact with the electrolyte-carrying region.

7. An adhesive skin contact electrode as claimed in any preceding claim in which the re-usable header part comprises a contact to make electrical contact with the electrolyte means of the disposable skin-contacting body, the header means also comprising electrical connection means in electrical contact with the contact means and for the connection of the adhesive skin contact electrode to monitoring apparatus.

8. An adhesive skin contact electrode as claimed in claim 7 in which the electrical contact and electrical connection means are separated laterally so that the electrical connection means will not overlie an adhesive skin-contact area on the disposable skin-contacting body when in use.

9. An adhesive skin contact electrode az: claimed in claim 7 or claim 8 in which the connection means comprise a wire terminating in a connecting device remote from the contact means.

10. An adhesive skin contact electrode as claimed in any of claims 7 to 9 in which the re-usable header part comprises a buffer amplifier and carries a multiple cable for supplying electrical power to the buffer amplifier and for transmitting the resultant signal from the re-usable header part.

11. An assembly of adhesive skin contact electrodes as claimed in any of claims 7 to 10 permanently connected to a multiple cable.

12. A skin-contacting body for use in an adhesive skin contact electrode as claimed in any preceding claim.

13. A re-usable header part for use in an adhesive skin contact electrode as claimed in any of claims 1 to 11.

14. A skin-contacting body, substantially as described with reference to Fig.l, Fig.2, Fig.3 or Fig.4.

15. A re-usable header part, substantially as described with reference to Fig.5, Fig.6, Fig.8 or Fig.9.

16. An assembly of header parts, substantially as described with reference to Fig. 7.

Amendments to the claims have been filed as follows 1) A disposable interface member for skin contact electrodes which consist of a sheet of electrolyte, which is either gelled or polymerised or otherwise formulated to render it a viscoelastic and adhesive solid, said sheet of electrolyte being mounted on a continous sheet of a woven or nonwoven mesh which mas be regular or otherwise and of larger area than the sheet of electrolyte, such that the said mesh extends beyond some or all of the periphery of the electrolyte, so that the said mesh will enable the interface member to be handled without touching said electrolyte, and said electrolyte being mounted on said mesh such that said electrolyte impregnates said mesh to an extent that said electrolyte is capable of forming when in use, an electrically conductive path from its first major surface which may be placed in intimate contact with the skin to its second and opposite surface which may concurrently be placed in intimate contact with a reusable electrical contact device.

2) A disposable interface member which consists of a continuous sheet of open celled foam which is impregnated over part of its total area with an electrolyte, such that said foam will enable said disposable interface member to be handled without touching said electrolyte, and in which said electrolyte is an adhesive gelled liquid, such that said electrolyte forms a multiplicity of continuous paths between the two surfaces of said open celled foam, and thereby forms an electrical connection between said two surfaces over substantially all of the area of said open celled foam which is impregnated with said electrolyte, so that said electrolyte will form an electrical connection between, and adher to both the skin and an electrical contact device when said disposable interface member is placed between and in intimate contact with both said skin and said electrical contact device.

3) A disposable interface member as claimed in claims 1 or 2 which is mounted individually and separately or packaged individualy and separately and may be supplied independently of the contact electrode with which it is intended to be used.

4) An adhesive skin contact electrode in which the re-usable header part comprises a contact to make electrical contact with the electrolyte of the skin contact body, the said header means also comprising a buffer amplifier in close proximity to the said electrolyte contact means and with electrical connection between said contact means and the input of said buffer amplifier, and electrical connection means in electrical contact with the output of the buffer amplifier and for the connection of that output to monitoring apparatus.

5) An adhesive skin contact assembly comprising a multiplicity of headers each of which is connected electrically by an individual cable to a multiple cable which terminates in a means for making electrical contact between each header and monitoring apparatus, and in which each said header comprises a contact to make electrical contact with the electrolyte means of the disposable skin contact body and connection means to the individual cable of each header.

6) An adhesive skin contact assembly as in claim 5 in which each header also includes a buffer amplifier the input of which is connected electrically to the disposable skin contact body electrolyte contact means, and the output of which is connected electrically to the individual output cable of each header.

7. An adhesive skin contact electrode as claimed in any preceding claim in which the re-usable header part comprises a contact to make electrical contact with the electrolyte means of the disposable skin-contacting body; the header means also comprising electrical connection means in electrical contact with the contact means and for the connection of the adhesive skin contact electrode to monitoring apparatus.

9. An adhesive skin contact electrode as claimed in claim 7 or claim 8 in which the connection means comprise a wire terminating in a connecting device remote from the contact means.

14. A skin-contacting body, substantially as described with reference to Fig.1, Fig.2, Fig.3 or Fig.4.