GB2045088A

GB2045088A - Biomedical electrode

Info

Publication number: GB2045088A
Application number: GB8009454A
Authority: GB
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1979-03-21
Filing date: 1980-03-20
Publication date: 1980-10-29
Also published as: FR2451747A1; DE3010754A1; JPH0175408U; AU5662180A; AU538413B2; GB2045088B; FR2451747B1; IT8020791A0; IT1131006B; CA1152570A

Abstract

A dry, disposable biomedical electrode has a body conformable, electrically conductive interfacing member 11 with an adherent top surface and a lower body-contacting surface adapted for adherence to the skin, and a reusable body conformable, one-piece electrically conductive connector 21 (16, Figure 1, 31, Figure 8) with a flat electrical impulse distribution/receiving portion having an upper surface provided with means for connection to an electromedical device and a flat lower surface in electrical contact with member 11 to the top surface of which the connector 21 is releasably adherent. The top surface of member 11 maybe covered by a backing member 14 (Figure 3) of foamed material except for a circular area receiving connector 16. Alternatively part of the backing member 14A (Figure 5) may cover the top surface of connector 21 to prevent unwanted separation in use between connector 21 and member 11. The member 11 may be of plasticized natural gum or may have a woven or non-woven carrier 12 (Figure 2, 4) impregnated with, and having upper and lower surfaces of, electrically conductive adhesive 13. The connector may be of carbon impregnated polymeric material. <IMAGE>

Description

SPECIFICATION Biomedical electrode This invention relates to disposable electrodes, often termed "biomedical" electrodes, for establishing an electrical connection between the skin of the human anatomy and an electromedical apparatus, such as a high impedance electromyograph, electrocardiograph, electrical neurostimulator for pain relief, and the like. More particularly it relates to so called "dry" bioelectrodes which do not require the use of messy creams or gels to enhance conductivity between the skin and the electrode plate.

Avariety of disposable biomedical electrodes are known in the art. Generally, they comprise a metallic electrode plate adapted for connection to a lead wire which is, in turn, attached to the electromedical apparatus. Typically, a paste, cream, or gel which contains ionic material is relied upon to conduct the electric current and improve the electrical connection between the skin of the patient and the electrode plate. An adheive tape is commonly used to adhere the entire apparatus to the skin. Examples of electrodes of this general type are described in U.S.

Patents 3,587,565 and 3,805,769.

The conductve pastes, creams, or gels used in these prior art biomedical electrodes are unpleasant to use, sloppy, and often irritating to the skin particularly when the skin is cleaned and abraded prior to application of the electrode. Since these electrodes all contain water as the major ingredent to solvate the ions present and function as a medium through which the solvated ions migrate, they require elaborate packaging to prevent loss of water prior to use. Furthermore, they leave a residue on the skin after removal of the electrode which requires cleanup. A further disadvantage of the electrodes of the conductive paste, cream, and gel, types is that they develop an overpotential in defibrillation procedures unless the surface of the electrode plate is of expensive silver/silver chloride.

To overcome many of the problems associated with so called "wet" electrodes, biomedical electrodes having an integrally formed metal snap connector have been proposed which utilize "dry" conductive material. U.S. Patents 4,008,721 and 3,911,906 disclose biomedical electrodes utilizing adhesives impregnated with conductive particles.

These adhesives serve the dual purpose of enhancing conductivity with the skin and securing the electrode to the skin. Although avoiding the sloppiness and packaging problems associated with gels and pastes, such electrodes generally do not provide satisfactory electrical connection to the skin because the presence of the conductive filler results in a high signal-to-noise ratio and is deleterious to adhesion.

Generally, the use of nonhomogeneous conductive formulations in bio-electrodes had been found to give rise to noisy electrical signals. It is speculated that dispersed metal or salt particles in a binder matrix form a discontinuous, electrically conductive path which develops random, nonuniform electrical fields between particles which causes noise.

A Afurther disadvantage associated with most prior art disposable electrodes is their relatively high cost due to a large extent to the metal snap connector.

Since the connector is permanently attached to the electrode it must be discarded after one use along with the electrode.

The biomedical electrode according to the present invention offers several advantages over the previously described biomedical electrodes. The present electrode by virtue of its dry conductive material eliminates messy gels, creams or pastes. Also, the biomedical electrode of the present invention may be manufactured at a lower cost because the rigid snap fastener which is an integral part of the prior art electrode has been eliminated and a flexible reusable connector provided instead.

According to the present invention, there is provided a biomedical electrode comprising a body conformable, electrically-conductive extensible interfacing member having an adherent top surface and a lower body contacting surface adapted for adherence to the skin. For connecting the electrode to an electromedical device there is provided a one-piece body conformable electrically conductive connector having a substantially flat electrical impulse distribution/receiving portion which has a lower surface releasable adherant to the top surface of the interfacing member. The upper surface of the connector has means for connection to the electromedical device. A backing member is preferable adhered to the upper surface of the interfacing member to enhance the mechanical integrity of the electrode.The backing member may releasably overlay a substantial portion of the connector to hold it in place on the interfacing member in which case lateral access for connection with the electromedical device is provided or the backing may have a hole therethrough allowing the entire surface of the connector to be exposed.

A better understanding of the present invention will be obtained with reference to the following drawing wherein: Figure 1 is a perspective view of the biomedical electrode of the present invention.

Figure 2 is an enlarged cross-sectional view of the biomedical electrode of Figure 1 through line 2-2.

Figure 3 is a perspective view of the interfacing member and attached backing of the biomedical electrode of the present invention.

Figure 4 is a cross-sectional view of the biomedical electrode of Figure 3 through line 4-4.

Figure 5 is a perspective view of alternative embodiment of the electrode of the present invention.

Figure 6 is a fragmented side view of the biomedical electrode of Figure 5.

Figure 7 is an end view of the biomedical electrode of Figure 6.

Figure 8 is a side view of a second alternative embodiment of the electrode of the present invention.

Referring to the drawing wherein like reference characters designate like or corresponding elements and referring particularly to Figure 1,the biomedical electrode 10 is comprised of a one piece electrically conductive reusable connector 16 and a body con formable, electrically conductive interfacing member 11 having a top surface and a lower body contacting surface adapted for adherence to the skin.

Interfacing member 11 preferably exhibit-extensibilitywhich is similarto skin. Extensibility is used herein to mean the ability to respond to a force by stretching in any direction in a manner which is similar to human skin. Skin is a very extensible material which stretches 20% to 30% during normal activities and up to 50%- if needed. Skin is also resilient which allows it to return to an unstretched condition when stress is removed. The preferred interfacing member 11 is comprised of a carrier portion 12, coated with an electrically conductive adhesive 13. Carrier portion 12 may be comprised of a mat of separate fibers bonded together, e.g. a nonwoven web, which is body conformable and extensible. The fibers may be polyester, nylon or a cellulosic derivative, e.g., rayon, paper, etc.Carrier portion 12 may also be of a woven structure if the weave allows for the needed extensibility and adhesive impregnation. The ability of a woven or nonwoven structure to allow for impregnation of the conductive adhesive enables the adhesive 13 to conduct the electrical impulse evenly throughout the interfacing member 11. It has been unexpectedly found carrier portion 12 may be made of a film, such as cellophane, for certain types of electrode, e.g., receiving electrode. The preferred material for carrier portion 12 is Crystex" paper tissue, manufactured by Crystal Paper Co., Middletown, Ohio.

Carrier portion 12 imparts a measure of mechanical strength to the construction and may be omitted if the conductive adhesive layer 13 has sufficient strength and extensibility to maintain integrity during use. One group of adhesives which have been found to exhibit this integrity is plasticized natural gums, e.g., karaya, carageenen, guar.

Adhesive 13 not only should be electrically conductive but should exhibit sufficient tack to releasable adhere to both the skin and reusable connector 16.

The preferred adhesive 13 is comprised of 75:25 butyl acrylate-acrylic acid copolymer neutralized to 95 mole percent with methyl diethanolamine to which 20 parts/100 parts copolymer and 30 parts/100 parts copolymer of a water soluble plasticizer and a water soluble tackifier respectively are added as described in U.S. Patent 3,065,770. The resultant adhesive composition preferably is coated onto both sides of said carrier scrim 12 at 9.2 micrograms/cm2 (dry basis) to form the interfacing member 11.

It is contemplated that other polymeric adhesive such as those disclosed in U.S. Patents 4,125,110, 4,066,078,4,067,342, 3,911,906,4,054,714 and 3,994,302 may be utilized in interfacing members of the present invention.

Optionally attached to the top surface of interfacing member 11 is a backing member 14 which in the embodiment of Figures 1-4 has a hole 15 therethrough which allows access to the top surface of the interfacing member 11. The backing member 14 acts to maintain the integrity of the interfacing member 11 by covering all of its surface except the hole 15 when the biomedical electrode 10 is positioned on the wearer. Backing member 14 must exhibit sufficient extensibility to be compliant with interfacing member 11 after electrode 10 is placed on the wearer. The preferred material for backing member 14 is a vinyl foam tape sold under the trade name of Microfoam Tape, 3M Company, St. Paul, Minnesota 55101.Other suitable materials include a compressed polyurethane foam sold under the trade name of Scott Felt, Scott Foam Division, Scott Paper Company, Eddystone, Pennsylvania or a closed cell polyethylene foam, sold under the trade name of Volara, Voltex Corporation, Lawrence, Massachusetts.

Backing member 14 may be omitted resulting in a biomedical electrode constituted ofthe interfacing member 11 and body conformable reusable connector 16 (discussed below). With this alternative construction, it is preferable that connector 16 cover the entire top surface of interfacing member 11 because of the increased likelihood that foreign matter will adhere to the top surface of the interfacing member 11.

For the present invention, a reusable body conformable, one-piece electrically conductive connector 16 connects the interfacing member 11 to the electro-medical device. Reusable connector 16 is comprised of a substantially flat electrical impulse distribution/receiving portion having a flat lower surface adapted to fit within hole 15 of backing member 14 in electrical contact with the interfacing member 11. Connector 16 also is provided with an upper surface having an adapter 18 for connection to the connector lead of the electromedical device (not shown). The connector is preferably made of a carbon impregnated silicone rubber, SE 7600, General Electric Company, Waterford, New York.Other suitable carbon impregnated polymeric materials include plasticized polyvinyl chloride, epichlorohydrin rubber, polyurethane molding compound, polytetrafluoroethylene and a polymer of ethyienepropylene-diene (e.g. EPDM rubber).

Referring to Figure 4, an optional release liner 17 may be attached to the lower surface of the interfacing member 11 in order to preserve its adhesive character until ready for use. Such release liners are well known to the art.

To use the biomedical electrode assembly of the present invention, the release liner 17 is removed and the electrode is placed on the desired surface of the skin. Prior to placing the electrode to the skin, the skin or the lower surface of the interfacing member 11 may be wetted with water to optimize the adherence and conductivity of the adhesive. The connector, which has been previously attached to the lead of the electromedical device, is then releasably adhered to the upper surface of the interfacing member 11 through hole 15. When the monitoring or stimulation is complete the connector is removed and preserved while the disposable portion constituted by the interfacing member 11 and the attached backing 14 may be discarded.

Referring to Figures 5 through 8, alternative embodiment 20 and 30 may be made without department from the spirit of the present invention.

The alternative embodiments 20 and 30 are also comprised of an optional release liner 17, an interfacing member 11 and an optional backing member 14A. Connectors 21 and 31 of embodiments 20 and 30 respectively likewise comprise a one piece construction having means for connection with an external electromedical device 18 and a flat electrical impulse distribution/receiving portion for electrical contact with interfacing member 11.

Connectors 21 and 31 differ from connector 16 of electrode 10 in that they are elongated rather than circular. It has been found that in certain use situations movements of the patient may cause the connector 16 of embodiment 10 to become separated from interfacing member 11. By overlaying a portion of backing 14A on the top surface of connectoe 21 or 31 this problem is substantially eliminated.

In order to facilitate the placement of connector 21 or 31, an additional double sided release liner (not shown) may be placed between a portion of the backing member 14 and the interfacing member 11.

This double sided release liner may then be removed and connector 21 or 31 positioned on interfacing member 11 as shown in Figure 5 or 8. Backing member 14A is then positioned so as to releasably adhere to at least a portion of the top surface of connector 21 or 31 and interfacing member 11 so as to insure electrical contact between connector 21 or 31 and interfacing member 11. It is contemplated that electrode 20 can be supplied as shown in Figure 5 and the connector may be removed if desired after the initial use for a later reuse.

Claims

1. A dry biomedical electrode for establishing electrical contact between the epidermal layer of the skin of a mammal and an external electromedical device wherein the electrode is characterized by: a a body conformable, electrically conductive interfacing member having an adherent top surface and a lower body contacting surface adapted for adherence to the skin; a backing member attached to said top surface of said interfacing member, said backing member having a hole therethrough providing access to said interfacing member for electrical contact; and at least one body conformable, one-piece electrically conductive connector having a substantially flat electrical impulse distribution/receiving portion having a flat lower surface adapted to fit within said hole of said backing member in electrical contact with said interface member and an upper surface having a means for connection to said electro-medical device, said connector being releasably adherent to said top surface of said interfacing member.

2. A dry biomedical electrode in accordance with Claim 1 wherein said interfacing member is a plasticized natural gum.

3. A dry biomedical electrode in accordance with Claim 1 wherein said interfacing member is comprised of a carrier portion having an electrically conductive adhesive coating said top surface and said lower body contacting surface.

4. A dry biomedical electrode in accordance with Claim 3 wherein said carrier portion is a nonwoven web.

5. A dry biomedical electrode in accordance with Claim 3 wherein said carrier portion is a cellophane film.

6. A dry biomedical electrode for establishing electrical contact between the epidermal layer of the skin of a mammal and an external electromedical device wherein: a body conformable, electrically conductive interfacing member having an adherent top surface and a lower body contacting surface adapted for adherence to the skin; and at least one body conformable, one-piece electrically conductive connector having a substantially flat electrical impulse distribution/receiving portion having a flat lower surface adapted for electrical contact with said interfacing member and an upper surface having means for connection to said electromedical device, said connector being releasably adherent to said top surface of said interfacing member.

7. The dry biomedical electrode in accordance with Claim 6 wherein said connctor consists of a carbon impregnated polymeric material selected from a group consisting of silicone rubber, plasticised polyvinyl chloride, epichlorohydrin rubber, polytetrafluoroethylene, or a polymer of ethylenepropylene diene.

8. A dry biomedical electrode in accordance with Claim 6 wherein said interfacing member is comprised of a carrier portion having an electrically conductive adhesive coating said top surface and said lower body contacting surface.

9. A dry biomedical electrode in accordance with Claim 6 wherein a backing member is releasably adhered to said connector and at least a portion of said top surface of said interfacing member.

10. A dry biomedical electrode for establishing electrical contact between the epidermal layer of the skin of a mammal and an external electromedical device wherein: a body conformable, electrically conductive interfacing member having an adherent top surface and a lower body contacting surface adapted for adherence to the skin; at least one body conformable, one-piece electrically conductive connector having a substantially flat electrical impulse distribution/receiving portion having a flat lower surface adapted for electrical contact with said interfacing member and an upper surface having means for connection to said electromedical device, said connector being releasably adherent to said top surface of said interfacing member; and a backing member releasable adherable to said connector and at least a portion of said top surface of said interfacing member whereby said connector is retained in electrical contact with interfacing member.

11. A biomedical electrode substantially as described herein with reference to and as illustrated by Figures 1 to 4; Figures 5 to 7; or Figures 8 of the accompanying drawings.