WO1997024155A1

WO1997024155A1 - Dispersive electrodes provided as a stack of like articles

Info

Publication number: WO1997024155A1
Application number: PCT/US1996/005633
Authority: WO
Inventors: Samuel G. Netherly
Original assignee: Minnesota Mining And Manufacturing Company
Priority date: 1995-12-29
Filing date: 1996-04-22
Publication date: 1997-07-10
Also published as: AU5567996A

Abstract

A stack (10) of at least two electrodes (12), each electrode (12) having a backing (16), a conductive layer (22) contacting that backing, and a field of conductive adhesive (28) contacting the conductive layer (22). The side of the backing (16) opposite the side contacting the conductive layer (22) has release properties (34) relative to the field of conductive adhesive (28) of the electrode (12) above it in the stack. The conductive layer (22) and/or the backing (16) has the property of resisting the passage of water vapor in order to retard the drying out of the field and conductive adhesive (28) directly below it. A field of skin adhesive (32) may advantageously be coated surrounding the conductive adhesive (28). A release liner (14) conveniently forms the bottom of the stack (10) of electrodes (12). This arrangement of electrodes (12) in a stack (10) allows the entire stack (10) to be packaged with little more than the packaging material conventionally required for each electrode (12) individually, but allows them to be conveniently kept and dispensed in the surgical suite.

Description

DISPERSIVE ELECTRODES PROVIDED AS A STACK OF LIKE ARTICLES

TECHNICAL FIELD The present invention relates generally to medical electrodes, and more particularly to dispersive electrodes which minimize packaging waste.

BACKGROUND

In order to minimize the risk of spreading infection within a hospital, many products intended for direct contact with a patient are disposed of after a single use One problem with using such disposable products is the volume of waste generated, not only by the product itself, but also by the packaging material the product may require A second problem is the cost of such packaging; the consumer must eventually pay both for the packaging material itself in its disposal

As will be described below, these two problems are particularly acute in the field of packaging for dispersive electrodes for electrosurgery. In electrosurgery, it is not a shaφ blade that does the cutting, but an intense electrical current The surgeon directs this current to exactly where it is required by wielding a cutting electrode, which because of its cylindrical shape and the way it is held in the hand is commonly called a "pencil". By activating controls which change the characteristics ofthe electrical current being sent to the pencil by an electrosurgical generator, the surgeon can use the pencil either to cut or to coagulate areas of bleeding This makes electrosurgery particularly convenient when surgery requiring extra control of blood loss is being performed

As in all situations where electrical current is flowing, in electrosurgery a complete circuit must be provided to and from the current source In this case, the current that enters the body at the pencil must leave it in another place and return to the generator It will readily be appreciated that when current enough to deliberately cut is brought to the body in one place, great care must be taken that unintentional damage is not also done at the location where that current is leaving the body. The task of collecting the return current safely is performed by a dispersive electrode.

A dispersive electrode performs this task by providing a large surface area through which the current can pass; the same current which was at cutting intensity when focused at the small surface area at the tip ofthe pencil is harmless when spread out over the large surface area ofthe dispersive electrode. Many popular dispersive electrodes also use a soft, water-bearing conductive adhesive to facilitate the transfer of current at the interface between the dispersive electrode and the body. For these reasons, the problems of packaging dispersive electrodes are particularly acute: these electrodes have a large surface area, and they are water-containing and must be protected by their packaging from dry-out. It is clear that the art requires a way to provide dispersive electrodes which minimizes the volume of packaging material required.

SUMMARY OF THE INVENTION The present invention solves the problems discussed above by providing dispersive electrodes as a stack of like articles. A stack of multiple electrodes can be packaged using only slightly more packaging material than is used for each electrode now. In the surgical suite, a stack can be unwrapped from its packaging material and individual electrodes can thereafter be peeled off the top ofthe stack and used whenever needed. Preferably, the electrodes are designed with configurations and materials which minimize the dry-out of their conductive adhesive while they wait unwrapped in the surgical suite before use.

In one aspect, the invention provides a stack of at least two electrodes, each electrode having a backing, a conductive layer contacting that backing, and a field of conductive adhesive contacting the conductive layer. In currently preferred embodiments, the side ofthe backing opposite the side contacting the conductive layer on at least one ofthe electrodes has release properties relative to the field of conductive adhesive ofthe electrode above it in the stack. This can either be because the backing has been coated or laminated with a release layer, or because the material chosen for the backing has release properties relative to the conductive adhesive as a natural property. In presently preferred embodiments, the conductive layer has the property of resisting the passage of water vapor. This retards the drying out ofthe field of conductive adhesive directly below it. It may in other embodiments be convenient for the backing to have the property of resisting the passage of water vapor. Conveniently, the field of conductive adhesive on the electrode on the bottom ofthe stack contacts a disposable release liner to protect the conductive adhesive. It is most convenient if that release liner also resists the passage of water vapor.

In presently preferred embodiments, a field of hydrophobic, skin- compatible adhesive is coated on the backing surrounding the conductive adhesive. This helps to hold the electrode in firm contact with the body ofthe patient, and also retards the loss of water through the edge ofthe field of conductive adhesive.

In a second aspect, the invention provides a method of preparing a plurality of electrodes for shipping and handling prior to use, comprising the step of providing a stack ofthe plurality of electrodes, each electrode comprising a backing; a conductive layer adjacent to the backing; and a field of conductive adhesive adjacent to the conductive layer, the field of conductive adhesive on one ofthe electrodes being releasably adhered to the backing ofthe electrode below it in the stack. Presently preferred embodiments ofthe method have the further step of adhering a release liner to the field of conductive adhesive ofthe bottom electrode in the stack. Other preferred embodiments have the further step of sealing the entire stack of electrodes within a package.

BRIEF DESCRIPTION OF THE DRAWING The present invention will be further described with reference to the accompanying drawing wherein like reference numerals refer to like parts in the several views, and wherein:

Figure 1 is a perspective view of a stack of electrodes according to one presently preferred embodiment ofthe present invention,

Figure 2 is a bottom view of one ofthe electrodes from the stack of electrodes of Figure 1 , and

Figure 3 is a side cross-section view ofthe stack of Figure 1. DETAILED DESCRIPTION Referring now to Figure 1, a perspective view of a stack of electrodes 10 according to one presently preferred embodiment ofthe present is illustrated. The stack of electrodes 10 in this view includes four individual electrodes 12 which are releasably adhered together as will be described with more particularity below. The stack 10 is conveniently provided with a release liner 14 adhered to the bottom electrode 12 in the stack 10. The topmost electrode 12 in the stack 10 has backing 16. Extending from under backing 16 are tabs 18 and 20, which extend from conductive layers 22 and 24, the outlines of which are seen through the conformable backing 16 These tabs serve to connect the electrodes 12 to e.g. an electrosurgical generator. A tab support 26 is conveniently present to provide additional physical support for Ihe tabs 18 and 20 of conductive layers 22 and 24.

Referring now to Figure 2, a bottom view of one ofthe electrodes 12 of Figure 1 , seen in isolation, is illustrated It is more readily seen in this view how the conductive layers 22 and 24 are provided side-by-side. It is known to workers in this field that the conductive layer of a dispersive electrode can be made of a single piece, but that it is frequently convenient to provide the conductive layer as two adjacent sections as shown in Figure 2 This arrangement is cooperative with circuitry in many conventional electrosurgical generators which monitor the quality ofthe electrical contact between the electrode 12 and the body ofthe patient. This monitoring typically involves analysing the impedance to a test current though the body ofthe patient between the two conduction layers 22 and 24 One such monitoring system is known as "REM"-type, for "Return Electrode Monitoring".

Two fields 28 and 30 of conductive adhesive are coated on top of the conductive layers 22 and 24 and serve to transfer the current from electrosurgical procedures from the body ofthe patient. Many compositions suitable for use for the two fields 28 and 30 of conductive adhesive are transparent, or at least translucent, and have been depicted that way for convenience in providing an explanatory drawing. A layer of skin adhesive 32 is coated on backing 16 in order to adhere the conductive layers 22 and 24 to the backing, and to help adhere the electrode 12 to the skin during use Many compositions suitable for use for the skin adhesive 32 are transparent, or at least translucent, and have been depicted that way for convenience in providing an explanatory drawing

In order to facilitate removing an electrode 12 from the stack 10 with the fingers, it may be convenient to provide a lift tab 33 adhered to the skin adhesive 32 along one edge ofthe electrode Many different thin films of polymeric material will be suitable for forming the lift tab 33, provided that the material adheres well to the skin adhesive 32.

Referring now to Figure 3, a cross-sectional view of stack 10, taken along section lines 3-3 in Figure 1, is illustrated Four similar electrodes 12a - 12d are stacked, one on the other, resting on the release liner 14 Like materials in each ofthe four electrodes 12a - 12b are cross-hatched similarly for clarity in this Figure An optional release layer 34 (labeled 34a - 34d, respectively) is depicted as being laminated to the upper surface of each backing 16 In the alternative, release layer 34 can be coated or adhered to backing 16 As a further alternative, a separate release layer may be rendered unnecessary if the material chosen for the backing has as a natural property release characteristics relative to the conductive adhesive

Backing Backing 12 can be electrically insulative, and preferably is very conformable to the human body Many material may be used for this purpose, as will be apparent to those skilled in the art In one presently preferred embodiment, a closed-cell foam is considered particularly suitable, one such material is commercially available as Volara foam from Voltek, Inc of Massachusetts The backing has a thickness ranging from about 0 75 mm (0 03 inch) to about 1 5 mm (0 06 inch), and preferably 1 0 mm (0 04 inch)

Conductive layer

For the depicted application as a dispersive electrode for electrosurgery, the conductive layer 22 and 24 ofthe electrode 12 is conveniently made from thin aluminum laminated to polyethylene terephthalate (PET) film The PET film is conveniently approximately 0 05 mm (0 002 inch) thick, and the aluminum layer conveniently ranges in thickness between about 0 0075 mm (0 0003 inch) to about 0 025 mm (0 001 inch) and preferably 0 012 mm (0 0005 inch) For diagnostic applications, where non-polarizability is a consideration, the conductive layer is conveniently formed from an electrically non-conductive sheet of plastic coated with silver/silver chloride on the surface adjacent the conductive adhesive Such a coating is conveniently accomplished by use of a silver/silver chloride ink, one suitable ink is commercially available as R-301 from Ercon of Waltham, MA. Alternatively, the conductive layer can be constructed from materials disclosed in PCT publications WO 94/26950 and WO 95/20350 As a further alternative, the conductive layer can be constructed from graphite materials as disclosed in U S Patent 5,215,087

Conductive adhesive

Nonlimiting examples of conductive adhesives useful in connection with the present invention include those compositions disclosed in U S Patent Nos 4,524,087 (Engel), 4,539,996 (Engel), 4,848,353 (Engel), 5,225,473 (Duan), 5,276,079 (Duan et al), 5,338,490 (Dietz et al), 5,362,420 (Itoh et al), 5,385,679 (Uy et al), 5,133,356 (Bryan et al), copending and coassigned applications PCT Publication Nos WO 95/20634 and WO 94/12585, and PCT Patent Application Serial Nos US95/17079 (Docket No 51537PCT6A), US95/16993 (Docket No 51290PCT8A), and US95/16996 (Docket No 48381PCT1A)

Release liner

Release liner 14 can be any construction suitable for protecting the conductive adhesive and/or the skin adhesive on electrode 12 at the bottom ofthe stack 10 One suitable liner is a 0 05 mm (0 002 inch) thick sheet of biaxially oriented polypropylene liner, commercially available as Daubert 1-2 BOPPL-164Z from Daubert Co of Dixon, IL Package

It may be convenient to provide some packaging for the entire stack 10 to protect it from dust or the like during shipping A paper/polyethylene/aluminum foil/low density polyethylene laminate, adapted to be heat sealed to itself along the margins, has been found to be suitable for the puφose. In particular, the product commercially available from Cooper Flexible Packaging, Inc of Bensenville, IL, is considered particularly suitable

Skin adhesive Nonlimiting examples of skin adhesives 32 useful in connection with the present invention 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, 1 12,213, 4,310,509, 4,323,557, 4,732,808, 4,917,928, 4,917,929, and European Patent Publication 0 051 935

Various modifications and alterations ofthe present invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not limited to the illustrative embodiments set forth herein In particular it will be perceived that other types of medical electrodes such as diagnostic electrodes or stimulating electrodes such as are used for defibrillation or Transcutaneous Electrical Nerve Stimulation (TENS) could also be provided in a stack and this is considered to be within the scope ofthe present invention The claims follow

Claims

What is claimed is:

1. A stack of at least two electrodes, each electrode comprising: a backing having a release surface a conductive layer contacting the backing, and a field of conductive adhesive contacting the conductive layer, wherein the field of conductive adhesive of one electrode contacts the release surface ofthe backing of a second electrode.

2. The stack of at least two electrodes according to claim 1, wherein the side ofthe backing opposite the side laminated to the conductive layer on at least one ofthe electrodes has release properties relative to the field of conductive adhesive ofthe electrode above it in the stack.

3 The stack of at least two electrodes according to claim 2, further comprising a release layer contacting the backing on the side ofthe backing opposite the side contacting the conductive layer, the release layer having release properties relative to the conductive adhesive ofthe electrode above it in the stack.

4 The stack of at least two electrodes according to claim 1, wherein the conductive layer resists the passage of water vapor away from the field of conductive adhesive.

5. The stack of at least two electrodes according to claim 1, further comprising a disposable release liner adhered to the field of conductive adhesive on the electrode on the bottom ofthe stack.

6 The stack of at least two electrodes according to claim 5, the disposable release liner resists the passage of water vapor away from the field of conductive adhesive.

7 The stack of at least two electrodes according to claim 1, further comprising a field of hydrophobic, skin-compatible adhesive is coated on the backing surrounding the field of conductive adhesive

8 The stack of at least two electrodes according to claim 7, further comprising a lift tab adhered to the field of hydrophobic, skin-compatible adhesive

9 A method of preparing a plurality of electrodes for shipping and handling prior to use, comprising the steps of providing a stack ofthe plurality of electrodes, each electrode comprising a backing, a conductive layer adjacent to the backing, and a field of conductive adhesive adjacent to the conductive layer, the field of conductive adhesive on one ofthe electrodes being releasably adhered to the backing ofthe electrode below it in the stack

10 The method according to claim 9, wherein the side ofthe backing opposite the side contacting the conductive layer on at least one ofthe electrodes has release properties relative to the field of conductive adhesive ofthe electrode above it in the stack

1 1 The method according to claim 10, further comprising a release layer laminated to the backing on the side ofthe backing opposite the side contacting the conductive layer, the release layer having release properties relative to the conductive adhesive ofthe electrode above it in the stack

12 The method according to claim 10, wherein the conductive layer resists the passage of water vapor away from the field of conductive adhesive

13. The method according to claim 9, further comprising the step of adhering a release liner to the field of conductive adhesive ofthe bottom electrode in the stack.

14. The method according to claim 13, further comprising the step sealing the entire stack of electrodes within a package.