Flat biomedical electrode with reuseable lead wire

A biomedical electrode (10) adapted to be applied to a body (34). The electrode (10) has a backing material (16), preferably foam, having an aperture (20). A protective web (12) at least partially secured to the backing material (16) covers the aperture (20). A removeable liner (18) is positioned between the protective web (12) and the backing material (16). An electrically conductive adhesive (28) is positioned adjacent the backing material (16) on the opposite side from the protective web (12). A second removeable release liner (30) is positioned adjacent the electrically conductive adhesive (28) opposite from the backing material (16). A lead wire (22) having a conductive portion (24) is insertable under the protective web (12) to be secured there upon the removal of the release liner (18), by the protective web (12) and the electrically conductive adhesive (28). A bottom release liner (30) may be removed and the biomedical electrode (10) may be secured to a body (34). The conductive portion (24) of the lead wire (22) should be silver or silver plated and preferably subjected to chloride treatment.

BACKGROUND OF THE INVENTION 
The present invention relates generally to biomedical electrodes. 
Biomedical electrodes are useful for both stimulation and body monitoring 
functions. Stimulation uses of biomedical electrodes include 
transcutaneous electronic nerve stimulation (TENS) for the treatment of 
pain and neuromuscular stimulation (NMS) as, for example, treatment for 
scoliosis. Body monitoring uses for biomedical electrodes include 
electrocardiogram (ECG) for monitoring heart activity. 
Among biomedical electrodes in existence are those of Phipps et al, 
Cartmell and Larimore. Phipps et al in U.S. Pat. No. 3,170,459 discloses a 
biomedical instrumentation electrode constructed from multiple plies of 
discs made from a relatively inflexible material, i.e., cork. The 
electrode utilizes a conductive gel to establish contact with the body. 
Cartmell in U.S. Pat. No. 4,543,958 discloses a medical electrode 
assembly. The electrode has a flexible, dimensionally stable substrate 
which is striped with an electrically conductive paint. The electrode is 
then clamped into a bulky cable connector. Larimore in U.S. Pat. No. 
4,458,696 (assigned to Minnesota Mining and Manufacturing Company) 
discloses a TENS electrode with a raised structure to permit entry of an 
attachment to a tubular electrical conductor. 
These electrodes suffer from several deficiencies including that all are 
"high profile" electrodes and that the electrodes do not "conform" well to 
the body. 
For monitoring electrodes electrical currents passing through the 
electrodes are relatively low so that excellent electrical conductivity in 
the electrode is required for proper performance, i.e., the ability of the 
biomedical electrode to pick up and transmit electrical signals obtained 
from the body. In most instances, good electrical performance requires 
that silver be utilized as a conductive element in the electrode in order 
to promote the proper conductivity, however, silver is an extremely 
expensive ingredient, the use of silver in disposable biomedical 
electrodes makes monitoring body functions a costly endeavor. 
SUMMARY OF THE INVENTION 
The present invention provides a biomedical electrode which is (1) flat and 
conformable to the body, (2) has excellent performance required of 
monitoring electrodes, (3) has a disposable body contacting portion with a 
reuseable electrical lead wire, and (4) is cost effective because the only 
silver utilized in the electrode is utilized in the reuseable lead wire. 
The present invention provides a biomedical electrode which is adapted to 
be applied to a body. A backing material is utilized having an aperture a 
protective web is at least partially secured to the top side of the 
backing material covering the aperture. A first removeable release liner 
is positioned between the protective web and the backing material. An 
electrically conductive adhesive is positioned adjacent the bottom side of 
the backing material covering the aperture in the back material. A second 
removeable release liner is positioned adjacent the electrically 
conductive adhesive opposite from the backing material. A lead wire is 
adapted to be positioned from the top side of the backing material within 
the apertures so as to be adhered by the electrically conductive adhesive. 
This provides a biomedical electrode in which the second removeable liner 
may be removed and the biomedical electrode may be applied to the body 
with the electrically conductive adhesive. The first removeable release 
liner may then be removed and the lead wire may be positioned with the 
electrically conductive end of the lead wire within the aperture and 
secured by the protective web. In a preferred embodiment, the lead wire is 
formed with a flattened disc of electrically conductive material and, in 
one embodiment the flattened disc is silver plated and, in a still another 
embodiment, has been subjected to chloride treatment. In one embodiment, 
the backing material is a foam material most preferably a polyethylene 
foam. In another embodiment, a pressure sensitive adhesive helps to hold 
the protective web to the backing material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 illustrate the basic construction of the biomedical electrode 
10 of the present invention. A protective web 12 is applied by a pressure 
sensitive adhesive 14 to a backing material 16. A removeable release liner 
18 is positioned between the protective web 12 and its associated pressure 
sensitive adhesive 14 and backing material 16. Backing material 16 
contains an aperature 20 which the protective web covers. An electrical 
lead wire 22 having a conductive portion 24 and an insulative portion 26 
is insertable into the biomedical electrode with the conductive portion 24 
of lead wire 22 positioning itself within aperture of backing material 16. 
Although not absolutely required, it is preferred that lead wire 22 have 
an insulative portion 26 such that when the conductive portion of lead 
wire 22 is positioned within aperture 20 and covered with protective web 
12 only the insulated portion 26 of lead wire 22 is exposed. An 
electrically conductive adhesive 28 is located on the backing material 16 
below aperature 20. The electrically conductive adhesive 28 positioned in 
this manner will contact the conductive portion 24 of lead wire 22 when 
the lead wire is inserted into aperature 20. A second removeable release 
liner 30 is positioned below electrically conductive adhesive 28 to be 
removed before the biomedical electrode 10 is applied to the body. It is 
only necessary that electrically conductive adhesive 28 be positioned 
under apperature 20 in backing material 16. Electrically conductive 
adhesive 28, of course, could cover the entire surface area of backing 
material 16. If this were the case, no other adhesive in the biomedical 
electrode would be required. However, since electrically conductive 
adhesives may be more expensive than other adhesives. In a preferred 
embodiment, electrically conductive adhesive 28 covers only the general 
area of backing material 16 which is under aperture 20. Another pressure 
sensitive adhesive 32 is then applied to the remainder of the surface area 
of backing material 16 to enable the biomedical electrode to be secured to 
the body when it is utilized. Alternatively pressure sensitive adhesive 32 
could be applied to the entire surface area of backing material 16 and the 
portion under aperature 20 would be removed when aperature 20 was cut into 
backing material 16. 
Although shown in generally rectangular shape, biomedical electrode 10 by 
appropropriate sizing or trimming of backing material 16 may be any 
appropriate shape desired in order to conform or be located in any 
particular spot on the body. Aperture 20 is shown circular in nature and 
central within backing member 16 neither is absolutely required. Aperture 
20 could, for example, be elongated to more appropriately conform to the 
conductive portion 24 of lead wire 22 and need not be centrally located 
within the backing material 16. As illustrated, protective web 12 covers 
generally only the area of backing material 16 over aperature 20. In other 
embodiments, protective web 12 could, of course, cover more of the surface 
area of backing material 16 fir the entire surface area of backing 
material 16, if desired. 
In a preferred embodiment, protective web 12 is electrically insulative to 
confine the electrical signals used in the biomedical electrode 10 to the 
lead wire 22 or to the body. In a preferred embodiment, protective web 12 
is approximately 2 mils (0.51 millimeters) thick and is preferably 
constructed from polyester film. Pressure sensitive adhesive 14 is 
preferably an acrylate adhesive. Release liner 18, which is removeable, 
facilitates the lifting of protective web 12 away from backing material 16 
in order that lead wire 22 may be inserted and protective web 12 
subsequently reapplied securing a conductive portion 24 of lead wire 22 
and the biomedical electrode 10. In a preferred embodiment, release liner 
18 is a Polyslick material as manufactured by James River Corporation, H. 
P. Smith Division, Bedford Park, Ill. 
Backing material 16 may be constructed from any generally flat, body 
comformable, flexible material. In a preferred embodiment, backing 
material 16 is a foam material, and in a more preferred embodiment is a 
polyethylene foam, for example, a 0.030 inches thick polyethylene foam. 
Lead wire 22 maybe copper wire whose insulative portion 26 is insulated 
with any suitable insulation, as for example, rubber or plastic. The 
conductive portion 24 of lead wire 22 maybe a flat crimped on conductor 
plate 30. Conductor plate 30 is flat which facilitates the biomedical 
electrode 10 being of low profile, flat and conformable to the body. In 
most preferred embodiments of the biomedical electrode 10, the conductive 
portion 24 of lead wire 22 must be silver or silver plated and preferably 
have a chloride treatment. Conductive adhesive 28 operates to secure the 
biomedical electrode 10 to the body and to provide through electrical 
conductivity from the body to the biomedical electrode. It is preferred 
that conductive adhesive 28 have better cohesion than adhesion in order to 
facilitate the ease with which the biomedical electrode 10 may be removed 
from the body. In a preferred embodiment, conductive adhesive 28 is a 
conductive adhesive as described in U.S. Pat. No. 4,554,924, Engel, 
Conductive Adhesive and Biomedical Electrode, which is hereby incorporated 
by reference. Removeable release liner 30 may also be Polyslick liner. 
Pressure sensitive adhesive 32 is also an acrylate adhesive. 
FIG. 3 illustrates the biomedical electrode 10 having been applied to a 
body 34. Lead wire 22 is shown being secured in the biomedical electrode 
10 by protective web 12, its associated pressure sensitive adhesive 14 
(not shown) and the electrically conductive adhesive 28 (not shown) to 
which it contacts. Backing material 16 is secured to the body with 
electrically conductive adhesive 28 (not shown) and pressure sensitive 
adhesive 32 (not shown). When this particular use of the biomedical 
electrode has been completed, protective web 12 may be pulled back 
releasing lead wire 22 from the biomedical electrode 10 allowing the reuse 
of lead wire 22 and another biomedical electrode 10. Since there are no 
silver components to the biomedical electrode except for the silver 
plating or silver containment of conductive portion 24 lead wire 22 and 
since the lead wire 22 may be reused many times, an economical biomedical 
electrode 10 is provided. Biomedical electrode is flatter and more 
conformable to the body contours and body movement than prior art 
electrodes. The biomedical electrode 10 relies on adhesive contact with a 
flat electrical conductor as opposed to rubber connector strips or snaps. 
The biomedical electrode 10 has a very low profile which makes it suitable 
to be worn under tight clothing and to be comfortable when slept upon or 
when leaned against, as for example, when sitting in a chair. The 
biomedical electrode 10 may be trimmed to virtually any size or shape to 
allow flexibility and adaptability in placement and location upon the 
body. 
Thus, it can be seen that there has been shown and described a novel, flat, 
biomedical electrode with a reuseable lead wire. It is to be recognized 
and understood, however, the various changes, modifications and 
substitutions in the form and of the details of the present invention can 
be made by those skilled in the art without departing from the scope of 
the invention as defined by the following claims.