WO2001017423A2

WO2001017423A2 - Biomedical electrode including a strip of ionically-conductive adhesive

Info

Publication number: WO2001017423A2
Application number: PCT/US2000/023137
Authority: WO
Inventors: Paul Weidenhaupt; Frank Otte; Nico Loutis
Original assignee: 3M Innovative Properties Company
Priority date: 1999-09-10
Filing date: 2000-08-23
Publication date: 2001-03-15
Also published as: GB9921377D0; WO2001017423A3

Abstract

A biomedical electrode comprises a connector stud (1) anchored in a rectangular patch of adhesive-coated backing material (2) which is used to secure the electrode to the skin of a patient. The connector stud (1), which is located in a pierced opening in the backing material (2), has a head portion (3) to which an electrical lead of an electromedical monitoring/diagnostic system can be attached, and an electrode plate (4) which, when the biomedical electrode is in use, is placed in electrical communication with the skin of the patient. A strip of ionically-conductive adhesive (9) extends across the backing material and over the electrode plate (4), and a strip of scrim material (10) is located adjacent the adhesive coating on the backing material, underneath the adhesive strip (9). The two strips (9, 10) have the same width, less than the diameter of the electrode plate (4) so that the latter contacts the adhesive coating on the backing material. A non-adhesive tab (8) is formed on one edge of the patch of backing material, adjacent a corner of the patch, for use in handling the electrode.

Description

BIOMEDICAL ELECTRODE INCLUDING A STRIP OF IONICALLY-

CONDUCTΓVE ADHESIVE

The present invention relates to biomedical electrodes, that is electrodes which can be attached to the skin of a patient to establish an electrical connection between the skin and an electromedical monitoring/diagnostic/therapeutic system. The invention relates more especially, but not exclusively, to ECG electrodes for use in a part of a system for monitoring and/or diagnosing cardiac function and is likewise applicable to electrodes for use in electroencephalograph (EEG) systems. ECG monitoring systems are well known and are used in a variety of health care situations. Such systems require the use of electrodes which are attached to the skin, at selected points of the body, to enable electrical signals (indicative of cardiac function) to be fed to an electrocardiograph. The electrodes, which are conventionally attached to the skin by an adhesive, are required to make good electrical contact with the skin and to be constructed to permit the easy attachment of electrical leads from the electrocardiograph. It is also desirable that the electrodes should be easy to remove from the protective liner material with which they are normally provided and from the skin of a patient, after use, without leaving any adhesive or other residues.

One known type of ECG electrode comprises a connector stud having a head portion to which electrical leads can be attached, and an electrode plate through which contact is made to the skin. The stud is located in a patch of backing material, with the electrode plate positioned on one side of the material and the head portion on the other. The side of the backing material on which the electrode plate is positioned is coated with a pressure-sensitive adhesive, enabling the ECG electrode to be securely attached to the skin and an electrical contact to be formed between the skin and the electrode plate.

Electrodes of that general type are described in U.S. Patent Nos. 3,993,049, 4,273,135, and 4,580,339. Each of those documents also describes the provision of an additional layer of conductive material to improve the connection between the electrode plate and the skin of the patient. In one of the electrodes described in U.S. Patent No. 3,993,049, that additional layer comprises a circular patch of non-woven fibrous material, impregnated with an adhesive-electrolyte material, which covers most of the pressure- sensitive adhesive and the whole of the electrode plate of the stud. In the electrode described in U.S. Patent No. 4,273,135, the additional layer comprises a conductive material which coats the electrode plate; and in the electrode described in U.S. Patent No. 4,580,339, the additional layer comprises an adhesive conductive polymer strip which covers most of the pressure-sensitive adhesive and the whole of the electrode plate. WO 98/02089 describes a biomedical electrode in which a strip of ionically- conductive adhesive extends across the adhesive-coated side of the backing material and over the electrode plate of the stud to improve the electrical connection between the electrode plate and the skin. To ensure good adhesion of the ionically-conductive adhesive to the backing material, a parallel strip of scrim material is located between the pressure-sensitive and ionically-conductive adhesives. The construction of this electrode facilitates its manufacture and enables it to be produced in a manner that is highly cost effective.

The problem to which the present invention is directed is that of enabling the cost of manufacturing an electrode of this type to be reduced still further without detracting from the reliability and convenience of the electrode when in use.

The present invention provides a biomedical electrode comprising:

(a) a backing material coated on one side with a pressure-sensitive adhesive, the backing material having a thickness of less than 0.2 mm;

(b) a connector stud located in the backing material, the stud having an electrode plate located on one side of the backing material for electrical connection to the skin of a patient and, on the other side of the backing material, a head portion to which an electrical connector can be attached; and

(c) a strip of ionically-conductive adhesive extending across the adhesive-coated side of the backing material and over the electrode plate of the stud; wherein the electrode plate is in contact with the pressure-sensitive adhesive and is adhered thereby to the backing material.

The present invention further provides a biomedical electrode comprising:

(a) a backing material coated on one side with a pressure-sensitive adhesive;

(b) a connector stud located in the backing material, the stud having an electrode plate located on one side of the backing material for electrical connection to the skin of a patient and, on the other side of the backing material, a head portion to which an electrical connector can be attached; (c) a strip of ionically-conductive adhesive extending across the adhesive-coated side of the backing material and over the electrode plate of the stud; and

(d) a parallel strip of scrim material located between the ionically-conductive and pressure-sensitive adhesives; the scrim material extending between the pressure-sensitive adhesive and the electrode plate of the stud, and having a width such that the electrode plate extends beyond at least one edge of the scrim material into contact with the pressure- sensitive adhesive, and is adhered thereby to the backing material.

In accordance with another aspect of the invention, there is provided a biomedical electrode comprising: (a) a backing material coated on one side with a pressure-sensitive adhesive;

(d) a non-adhesive tab positioned on the periphery of the backing material to facilitate the handling of the electrode, the location of the tab being such that a user will peel the backing material from a surface to which it is adhered in a direction inclined at less than 90° to the adjacent edge of the conductive adhesive strip.

By way of example only, embodiments of the invention will be described with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view, from above, of an ECG electrode in accordance with the invention;

Fig. 2 is an enlarged view from below of the electrode; Fig. 3 is a greatly enlarged, diagrammatic, end view of the electrode, in the direction of the arrow LU in Fig. 1;

Fig. 4 shows a greatly enlarged, diagrammatic, vertical cross-section through the electrode, taken on a line mid-way between the two ends of the electrode as seen in Fig. 3;

Fig. 5 is a perspective view of the connector stud of the electrode of Fig. 1; Fig. 6 illustrates, schematically, a process for the production of electrodes as shown in Figs. 1 to 4;

Fig. 7 illustrates, schematically, the insertion of connector studs into backing material in the process illustrated in Fig. 6; and Fig. 8 illustrates apparatus for carrying out the process illustrated in Fig. 7.

The ECG electrode shown in Figs. 1 to 4 comprises a connector stud 1 positioned in an opening in the centre of a generally rectangular patch of non-conductive backing material 2. The connector stud 1, shown separately in Fig. 5, is a one-piece moulded component comprising: a rounded head portion 3; a circular electrode plate 4 at the base of the stud; an outwardly projecting circular flange 5 which extends completely around the head portion 3 at the base of the latter; and, between the electrode plate 4 and the flange 5, a smooth stem portion 6. The backing material 2 is held in the space between the electrode plate 4 and the flange 5 of the stud 1, so that the electrode plate 4 is located on one side of the backing material, and the flange 5 and head portion 3 are located on the other. As will be described in greater detail below, the opening in the backing material (in which the stud 1 is located) is preferably a pierced opening but it could, alternatively, be a punched opening.

When the electrode is in use, the bottom surface of the electrode plate 4 of the stud is placed in electrical communication with the skin of a patient and the stud 1 will then provide an electrical connection between the patient's skin and the head portion 3 of the stud, to which one lead of an electromedical monitoring/diagnostic system is connected. To enable the connector stud 1 to be held in contact with the patient's skin, the backing material 2 in which the stud is positioned is provided with an adhesive coating 7 (Figs. 3 and 4). The stud 1 is preferably formed from a plastics material, for example a glass-filled copolymer of acrylonitrile, butadiene and styrene (ABS), provided with a coating of an electrically-conductive material, for example silver/silver chloride. It may, however, be formed of any other material known to be suitable for the connector studs of biomedical electrodes, for example stainless steel or aluminum. In a specific embodiment, the diameter of the electrode plate 4 is 10.3 mm; the maximum transverse dimension of the head portion 3 is 3.8 mm; the diameter of the flange 5 is 6.1 mm; the diameter of the stem 6 is 2.5 mm; the height of the stud 1 is 6.0 mm and the height of the stem 6 is 1.1 mm. Generally, the diameter of the flange 5 is preferably at least 1.5 (more preferably 1.6) times the maximum transverse dimension of the rounded head portion 3, to assist in retaining the stud 1 in the backing material 2. A process by which a connector stud 1 having a flange 5 of that size can be inserted into the backing material 2, will be described below.

The backing material 2 comprises any suitable material that is thin enough to conform readily to the surface to which it is to be adhered. Generally, for that purpose, the backing material is less than 0.2 mm thick. Preferably the backing material is a polymeric film material, for example a polyethylene film or a polyethylene vinyl acetate film, but it could alternatively be a polyester non- woven material or a cellulose rayon non-woven material or a synthetic foam material. The backing may be transparent or opaque, and may carry printed information. The rectangular patch measures about 30 mm x 35 mm and, along one of the longer sides, has an extension 8 with a curved edge. The adhesive coating 7 on the backing material is a pressure-sensitive adhesive, preferably one that is biocompatible with mammalian skin.

Extending across the middle of the patch of backing material, parallel to the side with the extension 8, is a strip 9 of an ionically-conductive adhesive. The strip 9 extends from one edge of the patch of backing material to the opposite edge, over the bottom surface of the electrode plate 4 of the stud 1. To ensure good adhesion of the strip 9 to the backing material 2, a strip 10 of scrim material is located between the adhesive strip 9 and the pressure-sensitive adhesive 7. In the region of the stud 1, the scrim material 10 is positioned on the other side of the electrode plate 4 to the adhesive strip 9 (i.e. immediately adjacent the pressure-sensitive adhesive 7).

As can be seen from Figs. 3 and 4, the strips (9, 10) of adhesive and scrim material ionically-conductive adhesive are substantially coextensive and have a width that is less than the diameter of the electrode plate 4 of the stud 1. The electrode plate 4 thus extends into contact with the pressure-sensitive adhesive 7 on both sides of the strip of scrim material. In one embodiment, in which the diameter of the electrode plate 4 is 10.3 mm, the width of the strips 9, 10 is 6.35 mm with a tolerance of about ± 2 mm. It will be understood that, in the case mentioned above in which the backing material 2 of the electrode is transparent, the strip of scrim material 10 and the outer portions of the electrode plate 4 will be visible through the backing (not illustrated). The adhesive coatings 7, 9 on the backing material 2 are protected during storage until use by a removable liner 11 which may be formed from any suitable material, for example a siliconized polyester film having a thickness of about 0.1 mm. The liner material 11 extends over the extension 8 but the extended portion 13 is separated from the generally rectangular main portion by a cut 12. The extended portion 13 of the liner material 11 is intended to remain in place when the rectangular main portion is removed, to form a non-adhesive tab that can assist in removing the electrode from the liner material and also in applying the electrode to, and removing it from, the skin of a patient. Alternatively, as mentioned below, the tab could be formed by an adhesive-free portion of the backing material 2 in which case the portion 13 of the liner material can be omitted. The pressure-sensitive adhesive 7 on the electrode backing material 2 can be any appropriate pressure-sensitive adhesive known to be suitable for use on biomedical electrodes. Suitable adhesives include acrylate ester adhesives, and more particularly acrylate ester copolymer adhesives. Such adhesives are generally described in U.S. Patent Nos. 2,973,826; Re 24,906; Re 33,353; 3,389,827; 4,112,213; 4,310,509; 4,323,557; 4,732,808; 4,917,928; 4,917,929; and European Patent Publication 0051935.

The ionically-conductive adhesive 9 on the electrode backing material 7 can be any appropriate ionically-conductive adhesive known to be suitable for use on biomedical electrodes. Ionically-conductive adhesives useful in connection with biomedical electrodes are described in U.S. Patent Nos. 4,524,087; 4,539,996; 4,848,353; 5,133,356; 5,225,473; 5,276,079; 5,338,490; 5,362,420; 5,385,679; and WO95/20634 and WO94/12585.

The strip of ionically-conductive adhesive 9 may be coated, either in a flood coating or in a pattern coating, onto the backing material 2 and then cured. If a pattern coating is employed, the process disclosed in PCT Patent Publication W096/15715 can be used. Alternatively, as described below, the adhesive may be pre-cured and a strip of the pre-cured adhesive may be laminated to the backing material.

The scrim material used for the strip 10 should have a tensile strength that is high enough, having regard to the width of the strip, to ensure that it will not break during the manufacture of the electrode. One suitable material for use in the manufacturing process described below is a cellulosic tissue material with a basis weight of 15 lbs/3000 sq. ft. (24.2 gm/m²), available from Crystal Tissue of Middletown, Ohio, USA. The electrode illustrated in Figs. 1 to 4 is particularly adapted to manufacture at high speed and in a cost-effective manner, as will be described below, and is also reliable and convenient when in use. The film backing material 2 of the electrode will conform readily to the contours of that part of the patient's body to which it is secured when in use, which assists in achieving good adhesion to the skin. On the other hand, despite the comparative thinness of the backing material 2, good anchorage of the electrode stud 1 is ensured: first by the shaping of the stud and, in particular, the provision of the enlarged flange 5 on one side of the backing material and, second, by the contact between the electrode plate 4 and the pressure-sensitive adhesive 7 outside the edges of the scrim material 10. Adhesion of the electrode to the patient's skin is further assisted by the comparatively large areas of pressure-sensitive adhesive 7 that are available on the backing material 2, since the pressure-sensitive adhesive typically adheres better to the skin than the ionically-conductive adhesive 9. In that way, the risk of the electrode plate 4 lifting away from the skin, when the electrode is in use, can be reduced. In addition, the electrode construction illustrated in Figs. 1 to 4 enables cost savings to be achieved by virtue of the reduced width of the strips 9, 10 of ionically- conductive adhesive and scrim material. Previously, in the case of ECG electrodes employing an ionically-conductive medium to ensure adequate electrical contact between the electrode plate and the skin of the patient, it has been generally accepted that the ionically-conductive medium should cover at least the whole of the electrode plate. In the case of the electrode construction illustrated in Figs. 1 to 4, however, it has unexpectedly been found possible to maintain the reliability and functionality of the electrode even when the strip 9 of ionically-conductive adhesive does not entirely cover the electrode plate 4. The use of a narrower strip 9 of ionically-conductive adhesive permits the use of a narrower strip 10 of scrim material also. From the point of view of economy, the strips of ionically-conductive adhesive 9 and scrim material 10 should be as narrow as possible consistent with maintaining the reliability and functionality of the electrode. If, however, it is desired to increase the width of the strip 9 of ionically-conductive adhesive then it is not always necessary to increase the width of the scrim material also: in some cases, good results can be achieved using a strip 10 of scrim material that is narrower than the strip 9 of adhesive material, especially if the edges of the strips closest to the tab 8 are aligned to reduce the risk of the adhesive strip 9 delaminating when the electrode is removed from the patient's skin. In that way, the economic advantage resulting from the use of as little scrim material as possible can be retained. In the event that the ionically-conductive adhesive 9 adheres sufficiently well to the pressure-sensitive adhesive 7 without the scrim material 10, the latter can be omitted completely. In that case, the whole area of the upper surface of the electrode plate 4 will be available to contact the pressure-sensitive adhesive 7.

The non-conductive backing material 2 of the electrode can be any appropriate material and, although a comparatively thin material is preferred, it is also possible for a thicker material to be used, for example a 1 mm thick synthetic foam material as described in WO 98/02089. The patch of backing material can also have any other appropriate shape, for example round or oval.

The form and location of the non-adhesive tab 8 of the electrode shown in Figs. 1 to 4 is particularly advantageous. As described above, the tab 8 is formed by an extended portion of the backing material 2 together with a separated extension 13 of the electrode liner material 11. The tab 8 is used when the electrode is being handled i.e. when the liner material is being removed or when the electrode is being adhered to, or removed from, the skin of a patient. The outer edge of the tab 8 is curved so that the main body of the tab (i.e. the portion that will be held by the user) is positioned adjacent a corner of the rectangular patch of backing material 2. As a result, when the electrode is removed from a surface, be it the liner material 11 or the skin of a patient, the user will tend to peel away the backing material in a direction inclined at less than 90° to the adjacent edge of the strip 9 of ionically-conductive adhesive and, preferably, in a direction that lies more generally along the line of that strip of adhesive than at right angles to it. The possibility of the adhesive strip 9 delaminating during this procedure is, as a consequence, greatly reduced. A similar advantage can be achieved by locating the tab 8 adjacent a corner on any one of the other sides of the patch of backing material 2. Alternatively, if the patch of backing material is non-rectangular, a similar advantage can be achieved by locating the tab 8 in a position that encourages the user to peel the backing material from a surface in a direction not at right angles to the edges of the conductive adhesive strip. It will be appreciated that the particular shape of the tab 8 as shown in Figs. 1 and 2 is less important than its location and that any other shape could be employed. It is not necessary, for example, for the non-adhesive tab 8 to extend the whole length of one side of the rectangular patch of backing material or for the tab to have a curved outer edge. If desired, the tab 8 could be distinctively marked (e.g. coloured) for example by printing on the backing material 2 or, if the backing material is transparent, by printing on the extension 13 of the liner material 11.

A process for producing electrodes as shown in Figs. 1 to 4 will now be described with reference to Fig. 6. The process is similar to that described in WO98/02089 and comprises the following steps:

(i) A continuous strip of electrode backing material 19, coated with a pressure- sensitive adhesive 22 on one side, is fed through a laminating station 20 in which a continuous strip of scrim material 26 is laminated to the adhesive, in a location corresponding to the intended location of the scrim in the finished electrode.

(ii) The backing material 19 is then fed to a stud insertion station 21, described in greater detail below, in which spaced connector studs are anchored in the scrim material. (iii) The backing material 19 is then fed to a laminating station 23 in which a strip 24 of pre-cured ionically-conductive adhesive laminated to the liner material 25 for the finished product is applied over the scrim material and the line of connector studs.

(iv) The final laminated assembly, comprising backing material, scrim, connector studs, adhesives, and liner material is then fed to a cutting station 29, in which the liner material only is cut along a line corresponding to the line 12 in the finished product and the laminated assembly is cut into individual electrodes.

The waste material is then removed, as indicated at 30.

The process described above can, if required, be carried out in such a way that two, or more, rows of electrodes are produced simultaneously across the width of the backing material 19.

The manner in which the connector studs are inserted into the backing material in the station 21 of Fig. 6 will now be described with reference to Figs. 7 and 8. The backing material 19, with the pressure-sensitive adhesive 22 and the strip of scrim material 26, passes over a piercing head 31 comprising a piercing tool 32 surrounded by a tubular sleeve 33. The adhesive-coated side of the backing material is uppermost as seen in Fig. 7 (i.e. it is the side remote from the piercing head 31). In steps (a) and (b), the piercing tool 32 is pushed through the backing material 19, the pressure-sensitive adhesive 22 and the scrim 26. In step (c), the sleeve 33 is pushed through the pierced opening 34 in the backing material and holds it open while the piercing tool is withdrawn. Advantageously, the comparatively narrow strip of scrim 26 is severed when the pierced opening is formed, thereby eliminating the effects of any elongation differences in the scrim and backing material which might occur during the process of Fig. 6 and cause the backing material of the completed electrode to wrinkle.

Subsequently, in steps (d) to (g), a connector stud 35 is placed (head portion first) into the end of the tubular sleeve 33 and is held in place, with the flange 5 of the stud engaging the end of the sleeve, as the latter is withdrawn through the opening 34. The stud is then released, in step (h) when it has reached the position in which the edges of the pierced opening are located in the space 6 (Fig. 5) between the electrode plate 4 and the flange 5 of the stud. The backing material then passes to the station 23 of Fig. 6.

To prevent the connector studs 35 slipping too far into the tubular sleeve 33, the electrode plate 4 of each stud should have a diameter greater than that of the sleeve. To enable the backing material 19 to lie flat around the stem 6 of each stud, the stem 6 should have as small a diameter as possible, preferably not more than 0.75 times that of the flange 5.

Advantageously, the process illustrated in Fig. 7 is carried out continuously in the manner illustrated in Fig. 8. The backing material 19 and pressure-sensitive adhesive 22, with scrim 26, passes over a continuously-driven insertion wheel 40 containing a plurality of radially-located piercing tools 32 and surrounding tubular sleeves 33. The piercing tools and sleeves 32, 33 are cam driven so that they each move uniformly in and out of the insertion wheel 40 in the manner illustrated in Fig. 7. The backing material 19 is initially held against the insertion wheel 40 by a first belt 41 while the pierced openings are being formed. Connector studs 1 to be placed on the ends of the sleeves 33 are then fed into position at 42 and held in place by a second belt 43 as the sleeves are withdrawn to locate the studs in the backing material 19 which is then removed as indicated at 44.

The stud insertion process described above with reference to Figs. 7 and 8 is also described in WO 98/02089, referred to above. A pre-cured conductive adhesive for use in step (iii) of the process described above with reference to Fig. 6 can be prepared according to the following procedure. A precursor is prepared, having the following formulation (by weight): 18.61% acrylic acid; 0.05% 2,2-dimethoxy-2-phenyl acetophenone; 0.09% 4-(2-hydroxyethoxy)phenyl-(2- hydroxy-2-methylpropyl)ketone; 0.04% methylene bis(acrylamine); 41.39% glycerine; 21.35% deionized water; 0.09% guar gum; 16.53% NAOH (50% sol); 1.85% potassium chloride. The precursor can be prepared in the following manner: A kettle equipped with overhead stirrer and a cooling jacket is charged with the acrylic acid, 2,2-demethoxy-2- phenyl acetophenone, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-methylpropyl)ketone, methylene bis(acrylamide), glycerin, guar gum, and a proportion of the deionized water. To the well stirred solution is charged the 50% aqueous NAOH portion-wise maintaining the batch temperature below 38°C. The hydroxide line is rinsed with deionized water and stirred, and the potassium chloride is then added as a 25% aqueous solution (preferably warmed to a temperature of about 80 - 90°F (26 to 32°C)) to yield a coater-ready precursor. The precursor is coated onto a siliconized polyester liner at 0.33 mm thick, overlaminated with a siliconized polyester liner, and passed through a curing chamber consisting of banks of fluorescent "black" lights, exposing the material to an intensity of 1.0 mW/sqcm and a total dose of 315 mJ/sqcm. Following removal of one of the polyester liners, the cured conductive adhesive so prepared is ready for use together with the final product liner in the laminating station 23 of Fig. 6.

To facilitate the handling of the cured adhesive and, if necessary, enable it to be transported from the location in which it is cured, a scrim material may be located on the liner material onto which the adhesive precursor is coated. Following curing, the scrim material (which is additional to the scrim material 26 of step (i) of the process of Fig. 6) will be embedded substantially in the middle of the adhesive layer.

A tubular sleeve, similar to the sleeve 33 of Fig. 7, can also be used when it is required to insert a stud of the type shown in Fig. 5 into a punched (rather than pierced) hole in electrode backing material 2 and will facilitate the location of the stud in the hole, despite the comparatively large diameter of the flange 5 of the stud 1. When the stud is in position in the backing material, the comparatively large diameter of the flange 5, in combination with the contact between the electrode plate and the pressure-sensitive adhesive 7 again ensures that the stud will be well anchored in the backing material 2. It will be appreciated that, although a continuous process as illustrated in Figs. 7 and 8 is preferred in that it enables a fast production rate to be achieved (and the cost of producing electrodes to be reduced), it is not essential since the same process could be carried out intermittently.

It will also be appreciated that the process could be used to produce electrodes having a different form from that shown in Figs. 1 to 4. For example, the overall shape of the connector studs 1 could be varied, as could the shape of the patches of backing material 2.

As a further alternative, the backing material 19 supplied to the laminating station 20 can be strip coated with the pressure-sensitive adhesive so that it has an adhesive-free margin along the side at which the tab 8 will be located in the final product. In that case, the liner material 13 for the tab is omitted. The strip coating of the pressure- sensitive adhesive can be applied to a full width of backing material which is then slit into suitable widths for the process of Fig. 6. Advantageously, the width of backing material used in the process of Fig. 6 allows two electrodes to be formed side-by-side, in which case there would be an adhesive-free margin along each edge (typically about 5.0 mm wide) with a band of pressure-sensitive adhesive (about 60.5 mm wide between. In that case, the full width of backing material would be strip coated with several parallel pressure-sensitive adhesive bands, each 60.5 mm wide, separated by adhesive free bands having a width of 10 mm, with 5.0 mm wide adhesive-free margins along each edge of the material. The full-width material would then be slit longitudinally at the mid-point of each adhesive free band.

Example

An electrode as illustrated in Figs. 1 to 4 was assembled in the manner described with reference to Figs. 6 to 8. The backing material 2 was a low density polyethylene film having a thickness of 0.1 mm and measured approximately 30 mm x 35 mm. The tab 8, positioned along one of the longer sides of the backing material had a maximum width of about 8.0 mm. The backing material was coated with an acrylate ester copolymer adhesive.

The stud 1 was formed from a glass-filled ABS copolymer coated with silver and had an electrode plate approximately 10.3 mm in diameter. The scrim material was a cellulosic tissue material as specified above, and the ionically-conductive adhesive was prepared as described in detail above. Both strips had a width of 6.35 mm and the strip of scrim material was measured as having a tensile strength of 10+ 2N. The electrical characteristics of the electrode were measured and found to comply with ANSI/AAMI/EC 12/1991.

An alternative embodiment to the electrode shown in Fig. 1 to 4 is an electrode comprising two pieces for the connector stud 1, a stud piece and an eyelet piece. In that case, the insertion of the connector stud in the backing material of the electrode can be carried out as described with reference to Fig. 12 of WO98/02089.

Suitably-shaped and sized electrodes of the general type shown in Figs. 1 to 4, can be also used in association with EEG systems. Likewise, biomedical electrodes of the present invention can be connected electrically and mechanically to electrosurgical generators or cardiac stimulation devices to provide dispersive electrode connection or cardiac stimulation electrode connection, respectively. Electrosurgical generators are commonly available and known to those skilled in the art, such as devices marketed by Birtcher Medical Systems, Inc. of Irvine, California, USA; Aspen Surgical Systems, Inc. of Utica, New York, USA; and Valleylab, Inc. of Boulder, Colorado, USA. Cardiac stimulation devices for cardioversion, external pacing, and defibrillation are commonly available and known to those skilled in the art, such as devices marketed by Hewlett- Packard Corporation of McMinnville, Oregon, USA, Zoll Medical Corporation of Newton, Massachusetts, USA and Physiocontrol Corporation of Redmond, Washington, USA.

Claims

1. A biomedical electrode comprising:

(b) a connector stud located in the backing material, the stud having an electrode plate located on one side of the backing material for electrical connection to the skin of a patient and, on the other side of the backing material, a head portion to which an electrical connector can be attached; and (c) a strip of ionically-conductive adhesive extending across the adhesive- coated side of the backing material and over the electrode plate of the stud; wherein the electrode plate is in contact with the pressure-sensitive adhesive and is adhered thereby to the backing material.

2. A biomedical electrode as claimed in claim 1, in which the backing material is substantially rectangular in shape and the strip of ionically-conductive adhesive extends across the backing material substantially parallel to two opposed sides of the backing material.

3. A biomedical electrode comprising:

(a) a backing material coated on one side with a pressure-sensitive adhesive;

(b) a connector stud located in the backing material, the stud having an electrode plate located on one side of the backing material for electrical connection to the skin of a patient and, on the other side of the backing material, a head portion to which an electrical connector can be attached;

(c) a strip of ionically-conductive adhesive extending across the adhesive- coated side of the backing material and over the electrode plate of the stud; and

(d) a parallel strip of scrim material located between the ionically-conductive and pressure-sensitive adhesives; the scrim material extending between the pressure- sensitive adhesive and the electrode plate of the stud, and having a width such that the electrode plate extends beyond at least one edge of the scrim material into contact with the pressure-sensitive adhesive, and is adhered thereby to the backing material.

4. A biomedical electrode as claimed in claim 3, in which the electrode plate extends beyond both edges of the scrim material into contact with the pressure sensitive adhesive.

5. A biomedical electrode as claimed in claim 3 or claim 4, in which the width of the strip of scrim material is substantially the same as the width of the strip of ionically- conductive adhesive.

6. A biomedical electrode as claimed in anyone of claims 3 to 5, in which the connector stud is located in a pierced hole in the backing material, the scrim material being fractured at the location of the pierced hole.

7. A biomedical electrode as claimed in any one of claims 3 to 6, in which the backing material is substantially rectangular in shape and the strips of scrim material and ionically-conductive adhesive extend across the backing material substantially parallel to two opposed sides of the backing material.

8. A biomedical electrode as claimed in claim 7, in which the backing material has a non-adhesive portion at one of the said two opposed sides to facilitate the handling of the electrode.

9. A biomedical electrode as claimed in claim 8, in which the non-adhesive portion comprises a tab positioned adjacent a corner of the backing material.

10. A biomedical electrode as claimed in claim 8 or claim 9, in which the non- adhesive portion is formed by an extension of the backing material with the coating of pressure-sensitive adhesive, the pressure-sensitive adhesive on the extension being covered by a liner material.

11. A biomedical electrode comprising:

(a) a backing material coated on one side with a pressure-sensitive adhesive; (b) a connector stud located in the backing material, the stud having an electrode plate located on one side of the backing material for electrical connection to the skin of a patient and, on the other side of the backing material, a head portion to which an electrical connector can be attached; (c) a strip of ionically-conductive adhesive extending across the adhesive- coated side of the backing material and over the electrode plate of the stud; and

12. A biomedical electrode as claimed in claim 11, in which the backing material is substantially rectangular in shape, and the non-adhesive tab is positioned adjacent a corner of the backing material.

13. A biomedical electrode as claimed in claim 12, in which the conductive adhesive strip extends substantially parallel to two opposed sides of the backing material, and the non-adhesive tab is positioned adjacent a corner on one of those sides.

14. A biomedical electrode as claimed in any one of claims 11 to 13, in which the non-adhesive tab is formed by an extension of the backing material with the coating of pressure-sensitive adhesive, the pressure-sensitive adhesive on the tab being covered by a liner material.

15. A biomedical electrode as claimed in any one of claims 3 to 14, in which the backing material is a polymeric film material.

16. A biomedical electrode as claimed in any one of claims 3 to 15, in which the backing material has a thickness of less than 0.2 mm.

17. A biomedical electrode as claimed in any one of the preceding claims, in which the ionically-conductive adhesive is in the form of a pre-cured strip which is laminated in position.

18. A biomedical electrode as claimed in any one of the preceding claims, in which the adhesive-carrying side of the backing material is covered by a removable liner.

19. A biomedical electrode as claimed in any one of the preceding claims, in which the connector stud is a one-piece stud.

20. A biomedical electrode substantially as described herein with reference to, and as shown in, Figs. 1 to 4 of the accompanying drawings.