Biomedical electrode

Abstract: A biomedical electrode comprises a flexible electrode plate (1) which conforms to the skin surface of a living body, and an electrically conductive adhesive layer (2) which fixes the electrode plate on the skin surface and transmits an electric signal from the living body to said electrode plate. A non-contact area (A) to which said conductive adhesive layer is not substantially bonded is formed on the electrode plate, and an electrically conductive tongue (4) for connecting a terminal which takes said electric signal from the living body to a biomedical diagnostic appaatus is provided on the non-contact area by forming a cut (3) in the non-contact area.

Description: The present invention relates to a biomedical electrode for taking out or receiving an electric signal generated from a living body. The term "biomedical electrode" as used hereinafter means an electrode for establishing an electrical connection between the skin of a living body and an electro-medical apparatus. Various electrodes which are adhered and secured to the skin surface of a patient have been developed as a biomedical electrode to a cardiomotile electric current and potential. In such electrodes, an electrically conductive cream or paste is interposed between the electrode and the skin surface of the living body to improve electrical contact. On the other hand, a substantially circular disposable biomedical electrode has been developed from the standpoint of the convenience of its application to the skin. This biomedical electrode comprises an electrically conductive electrode plate of metal foil having provided on one side thereof an electrically conductive adhesive layer. This conventional disposable biomedical electrode is designed to have a tab on the edges of the electrically conductive plate so as to connect it to a biomedical diagnostic apparatus. This conventional biomedical electrode is advantageous in its attachment to body and its handling, and avoiding the necessity of cleaning the skin surface, as compared with the use of electrically conductive cream or paste. The use of the elctrically conductive cream or paste involves various disadvantages in complication of its application, poor adhesion to the skin when sweating, and contamination of the skin surface. Further, the conventional biomedical electrode is arranged to have the tab on the edges of the electrically conductive electrode plate, so that when a lead wire terminal such as a clip or the like which connects to the biomedical diagnostic apparatus is coupled to the tab, stress is exerted. Such stress is also applied to the marginal edge of the electrically conductive adhesive layer to lift the biomedical electrode by means of the terminal and so involve cleavage stress between the skin surface and the adhesive layer after connection. For this reason, the conductive adhesive layer is lifted beyond the tab or peeled therefrom to result in lack of stability of electric signal due to poor adhesion. This is also the prominent phenomenon when the biomedical electrode is used in monitoring for a long period of time. The electrically conductive electrode plate comprises silver/silver chloride, nickel, tin, chromium or the like, which is a non-polarizable material and an expensive material. Considering reduction in production cost which is an important factor as a ready and disposable biomedical electrode, a formation of the tab which extends beyond the edges of the electrode plate is not considered to be satisfactory from the standpoints of complication of production and decrease in yield. There is also known from WO-A-81/01646 a biomedical electrode according to the preamble of Claims 1 and 3. In such an arrangement the tongue for connecting the terminal does not extend beyond the edges of the electrode plate, but needs to be lifted up out of the plane of the electrode plate for connection of the terminal, which can be inconvenient. It is accordingly an object of the invention to provide an improved biomedical electrode, wherein the connection of the terminal is facilitated. This object is achieved by the characterising features of Claim 1 or 3. The invention is illustrated by way of example in the accompanying drawings, in which: Figures 1 and 2 are sectional views of a biomedical electrode according to the present invention. Figure 1 is a sectional view showing an embodiment of the biomedical electrode according to the present invention. An electrically conductive adhesive layer 2 is provided on the entire circumferential area of a flexible electrode plate 1 which conforms to the skin surface of a living body. An electrically conductive tongue 4 which can connect to a biomedical diagnostic apparatus is formed by a cut 3 of substantially U-shaped configuration in the electrode plate 1 corresponding to a non-contact area formed at the center portion of the electrode plate. A member 6 which is non-tacky to the flexible electrode plate 1 is interpositioned between the center portion of the plate 1 and the electrically conductive adhesive layer 2, and forms the non-contact area. The member 6 is formed of a foamed elastomer in a compressed state. The electrically conductive tongue 4 is readily raised and lifted away from the electrode plate 1 having the cut 3 by the rebound stress of the elastomer, thereby facilitating the connection of the lead wire terminal. By using a thick elastomer having a thickness of 0.5mm to ten-odd mm as the non-tacky member 6, the compressive stress caused when the member 6 is interposed between the electrode plate 1 and the adhesive layer 2 is released by the cut, and the tongue 4 is automatically raised by the rebound stress to facilitate connection of the lead wire terminal. Figure 2 is a sectional view showing a further embodiment of the biomedical electrode according to the present invention. The non-tacky member 6 is formed of a thick non-elastomer instead of the elastomer as shown in Fig. 1. The electrically conductive adhesive layer 2 corresponding to the portion of the member 6, is caused to protrude to the skin contact side so that the member 6 serves to raise the tongue 4 upright when the biomedical electrode is applied to the skin. The electrode plate 1 functions as a medium for transmitting the electric signal taken from the skin surface through the adhesive layer 2 to the biomedical diagnostic apparatus. Examples of the plate 1 are sheet-like material of a metal such as copper, tin, nickel, aluminum or silver; and a sheet-like material having an electroconductivity such as a plastic film, paper, a woven fabric or a non-woven fabric, each having a metallic thin layer provided thereon by electroless plating, vacuum deposition or laminating. The electrode plate is produced by appropriately selecting material having a flexibility sufficient to conform to the skin to which the plate is applied. As shown in Fig. 1, an electrically insulating layer 1' is laminated to a conductive layer 1'' on the side opposite to the electrically conductive layer 2, thereby preventing noise derived from the contact when the biomedical electrode is applied to the skin, and the electric signal is taken out therefrom. If desired, functional materials such as woven fabrics, non-woven fabrics, net-like materials, foamed articles or synthetic films can be provided on the electrically insulating layer 1' according to the purpose. This is particularly effective to prevent the ends of the cut formed on the electrode plate 1 from tearing. The electrically conductive adhesive layer 2 disposed on the electrode plate 1 is a flexible layer for transmitting the electric signal received from the skin to which the biomedical electrode is applied, to the biomedical diagnostic apparatus. The adhesive layer 2 is formed of a material having an electroconductivity. Materials for the adhesive layer are polysaccharide such as Karaya gum; semisynthetic high polymer such as various cellulose; and a synthetic high polymer such as polyacrylic acid (or its salt), polyacrylic ester derivative, homopolymer or copolymer of polyvinyl alcohol or other hydrophilic polymer. For the purpose of further improving the electroconductivity of high polymers, electrically conductive materials such as various metal powders, carbon, water and electrolyte such as KCℓ or NaCℓ can be added thereto. Further, the electrically conductive material can be used in combination with conventional materials having no electroconductivity. Although the electrically conductive adhesive layer 2 composed of the high polymer can be applied on the electrode plate 1 directly, a reinforcing sheet which does not inhibit the electroconductivity of the layer 2 can be interpositioned between the plate 1 and the layer 2 to improve a shape retention property thereof and avoid contamination such as an adhesive residue on the skin. Examples of this reinforcing sheet are paper, woven or non-woven fabric, various plastic films and meshes, and metal foil. The reinforcing sheet can be also used by providing through holes if it lacks the electroconductivity. As already mentioned, the member 6 is non-tacky to the electrically conductive tongue 4. By simply using a thick non-elastomer as the non-tacky member 6, as shown in Fig. 2, the electrically conductive tongue 4 can be made upright through the cut 3 by stress when it is applied to the skin surface. As described above, the biomedical electrode according to the present invention is designed to form the electrically conductive tongue in the inside region of the electrode plate for connecting to the biomedical diagnostic apparatus by utilizing the cut, and the electrically conductive tongue is easily connected to the lead wire terminal, when it is attached thereto, by automatic raising of the tongue through the cut resulting in simpler operation required for the connection as compared with the known biomedical electrodes. Further, since the electrically conductive adhesive layer does not rise from the surface of the living body after connection, and the weight load after connection to the lead wire terminal is applied to the entire biomedical electrode, poor adhesion due to the local load and instability of the electric signal resulting therefrom, can be improved. The biomedical electrode of the present invention has the advantages that since the electrically conductive tongue for connection is disposed in the inside region of the electrode plate through the cut, the expensive material for the electrode plate can be used without loss, compact packing is possible, and the bulk thereof for storage can be reduced.

Claims: A biomedical electrode comprising a flexible electrode plate (1) capable of conforming to a skin surface of a living body, an electrically conductive adhesive layer (2) capable of fixing the plate to the skin surface and transmitting an electric signal from the living body to said plate (1), a non-contact area to which said conductive adhesive layer (2) is not substantially bonded being formed on the electrode plate (1) by a non-tacky member (6) interposed between said electrode plate (1) and said electrically conductive adhesive layer (2), said non-tacky member (6) being non-adherent to said electrode plate (1), and an electrically conductive tongue (4) for connecting a terminal which takes said electric signal from the living body to a biomedical diagnostic apparatus being formed by a cut (3) in the electrode plate (1) in the non-contact area characterised in that said non-tacky member (6) is made of a foamed elastomer which, before formation of said cut (3), is in a compressed state, and upon formation of said cut (3), enables the automatic raising of said electrically conductive tongue (4) by the rebound stress of the elastomer. A biomedical electrode as claimed in Claim 1, wherein the elastomer has a thickness of 0.5mm to ten-odd mm. A biomedical electrode comprising a flexible electrode plate (1) capable of conforming to a skin surface of a living body, an electrically conductive adhesive layer (2) capable of fixing the plate to the skin surface and transmitting an electric signal from the living body to said plate (1), a non-contact area to which said conductive adhesive layer (2) is not substantially bonded being formed on the electrode plate (1) by a non-tacky member (6) interposed between said electrode plate (1) and said electrically conductive adhesive layer (2), said non-tacky member (6) being non-adherent to said electrode plate (1), and an electrically conductive tongue (4) for connecting a terminal which takes said electric signal from the living body to a biomedical diagnostic apparatus being formed by a cut (3) in the electrode plate (1) in the non-contact area characterised in that said non-tacky member (6) is formed of a thick non-elastomer such that part of said electrically conductive adhesive layer surface which is located in the region of said non-contact area and which is to face the skin surface is caused to protrude away from the remaining part of the said adhesive layer surface, whereby said conductive tongue (4) is caused to be raised automatically when the biomedical electrode is attached to the skin surface. A biomedical electrode as claimed in any preceding claim wherein said electrode plate (1) comprises a laminate of an electrically conductive layer (1'') and an electrically insulating layer (1') and said electrically conductive adhesive layer (2) is formed on the side of said electrically conductive layer (1''). A biomedical electrode as claimed in Claim 4, wherein said electrically insulating layer (1') is a laminate of plastic film and functional material.

Inventors: NOMURA YOICHI, TAKAHASHI HISANORI, WADA SHINTARO, NOMURA, YOICHI NITTO ELECTRIC INDUSTRIAL CO.LTD., TAKAHASHI, HISANORI NITTO ELECT.INDUSTRIAL CO.LTD., WADA, SHINTARO NITTO ELECTRIC INDUSTRIAL CO.LTD.
Applicants: NITTO DENKO CORP, NITTO DENKO CORPORATION
Application year: 1985
Main classification: A61B5
IPC codes: A61B5