U.S. patent number 3,901,218 [Application Number 05/409,884] was granted by the patent office on 1975-08-26 for disposable electrode.
Invention is credited to Martin Buchalter.
United States Patent |
3,901,218 |
Buchalter |
August 26, 1975 |
Disposable electrode
Abstract
The disposable medical electrode includes a disk formed of a
semi-rigid plastic material having a recessed embossment located
centrally thereof. A metallic electrical contact is mounted on the
disk centrally of the embossment and has portions thereof located
on both sides of the disk. An absorbent pad positioned in the
recessed embossment has absorbed therein an electrically conductive
gel for forming an electrical contact between the patient on whom
the electrode is positioned and the electrical contact thereby to
permit electrical signals from the patient to be detected with the
electrode by appropriate electrical equipment connected thereto.
The disk has an adhesive applied thereto for firmly securing the
electrode to the patient's skin.
Inventors: |
Buchalter; Martin (Parsippany,
NJ) |
Family
ID: |
23622370 |
Appl.
No.: |
05/409,884 |
Filed: |
October 26, 1973 |
Current U.S.
Class: |
600/392; 600/394;
600/397 |
Current CPC
Class: |
A61B
5/25 (20210101) |
Current International
Class: |
A61B
5/0408 (20060101); A61B 005/04 () |
Field of
Search: |
;128/2.6E,2.1E,DIG.4,417,418,404,172.1,410,411 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Cohen; Lee S.
Attorney, Agent or Firm: Eslinger; Lewis H. Sinderbrand;
Alvin
Claims
What is claimed is:
1. A disposable medical electrode comprising a disk of hard
semi-rigid material having a recessed embossment formed centrally
thereof and opening towards the side of the disk to be secured to a
patient and a flat peripheral flange completely surrounding the
embossment for securing the disk to the patient, a metallic
electrical contact mounted on said disk centrally of said recessed
embossment and having portions thereof located on opposite sides of
said embossment, and an absorbent pad positioned in and
substantially filling said recessed embossment, said pad being in
electrical contact with said metallic electrical contact and having
absorbed therein an electrically conductive gel; said flat
peripheral flange having a flat outer surface surrounding said
recess on said one side of the disk, said flat surface having an
adhesive coating thereon; and a carrier sheet formed of a plastic
sheet material having a release coating thereon engaged and
releasably secured to the entire flat surface of said peripheral
flange on said one side of the disk, covering the recess and pad
therein and sealing said recess about the entire periphery thereof
on said one side of the disk whereby the pad and gel in the recess
are protected and sealed therein with a vapor barrier on all sides
thereof formed by said disk and carrier sheet to prevent
evaporation of gel in the recess prior to use of the disk, said
adhesive coating on the flat surface of said peripheral flange
serving to adhere the disk to the patient when in use.
2. The electrode as defined in claim 1 wherein said absorbent pad
is a sponge.
3. The electrode as defined in claim 2 wherein said disk is
circular in plan and said recessed embossment is generally
cylindrical in shape having an open end opening towards said one
side of said disk.
4. The electrode as defined in claim 2 wherein said electrical
contact member comprises a two section contact having a first
section located in said recessed embossment on said one side of
said disk including an extension pin extending through said disk to
the opposite side thereof and a second section located on the
opposite side of said disk including a female extension receiving
said extension pin in mating engagement to form an electrical
connection therebetween, said absorbent pad and gel therein being
positioned in contact with said first section of said contact
member to provide electrical communication therebetween.
5. The electrode as defined in claim 2 wherein said disk is
circular in plan and said recessed embossment is generally square
in plan, having an open end opening towards said one side of said
disk.
6. The electrode as defined in claim 1 wheein said release coating
is a silicone release coating.
7. A disposable medical electrode comprising, in combination, a
circular support disk formed of a semi-rigid hard plastic material,
said disk having an embossed recess formed at a central portion of
the disk opening towards one side of said disk whereby the opposite
side of said disk has a raised central portion formed therein, said
disk having an aperture therein at the center of said recess and a
flat peripheral flange completely surrounding the embossment for
securing the disk to the patient; a two-piece electrical contact
member secured to said raised central portion of the disk including
a first contact piece located in said recess on said one side of
the disk including an extension pin extending through said
apertures and a second contact piece located on the opposite side
of said disk including a female extension member receiving and
mating with said extension member of said first contact piece to
form an electrical connection therebetween; and an absorbent sponge
positioned in said recess in contact with said first contact piece,
said sponge having absorbed therein an electrically conductive gel
whereby, when said one side of the electrode is secured to a
patient with said sponge in contact with the patient's skin, an
electrical connection is formed between the skin and said second
contact piece thereby to permit electrical signals from the patient
to be detected; said flat peripheral flange having a flat outer
surface surrounding said recess on said one side of the disk, said
flat surface having an adhesive coating thereon; a carrier sheet
formed of a plastic sheet material having a silicone release
coating thereon engaged and releasably secured to said adhesive
coating on the entire flat surface of said peripheral flange, said
carrier sheet extending across the entire recess and covering said
recess and sponge therein thereby sealing said recess about the
entire periphery thereof on said one side of the disk whereby the
pad and gel in the recess are protected and sealed therein with a
vapor barrier formed on all sides thereof by said disk and carrier
sheet to prevent evaporation of gel in the recess prior to use of
the disk, said adhesive coating on the flat surface of said
peripheral flange serving to adhere the disk to the patient when
the disk is in use.
8. The electrode as defined in claim 7 wherein said embossed recess
is generally circular in plan.
9. The electrode as defined in claim 7 wherein said embossed recess
is square in plan.
Description
The present invention relates to medical electrodes, and more
particularly to pre-wet or pre-gelled disposable medical electrodes
designed for use in short or long term applications.
The use of disposable metal electrodes for monitoring a patient,
taking electrocardiograms and other medical diagnostic information
has recently developed in connection with expanded technology which
permits such diagnostic procedures and monitoring to take place at
remote locations, in the home, ambulance, emergency room of a
hospital, an intensive care unit, etc. Pre-wet or pre-gelled
disposable electrodes have also been found to be more convenient to
transport to remote locations than conventional electrodes and can
be discarded immediately after use so that no special storage
facilities are required in the physician's bag or ambulance. Such
pre-wet electrodes, whether used in the hospital itself or at a
remote location, eliminate the need to apply an electrode gel,
paste or solution to the electrode or patient prior to placing the
electrodes on the patient. Moreover, by the use of disposable
electrodes, the diagnostic unit can be immediately reused on
successive patients without the electrodes being sterilized or
otherwise cleaned for use on the new patient, since disposable
electrodes can simply be discarded and new ones used in place
thereof.
Previously proposed disposable electrodes have been supplied in
many forms. Typically, the electrodes are formed as a relatively
large diameter disk of foamed plastic material or adhesive tape
having a hard rigid plastic receptacle mounted at the center
thereof for containing an absorbent electrode pad. This pad
normally is secured to the plastic receptacle by an adhesive or the
like and contains an electrically conductive gel or fluid absorbed
therein, and it is positioned in contact with a metallic electrode
which extends through the disk. The connector is then used to
electrically connect the electrode to the diagnostic or monitoring
unit, for example to an ECG, an ECG monitor or the like. The
absorbent pad or sponge in the hard rigid disk mounted on the
electrode provides the electrical connection between the skin of
the patient and the electrical connector.
Typically, disposable electrodes of this type, i.e. formed of a
sponge or foamed plastic disk or as a disk of adhesive tape, are
supplied on a sheet of paper, with the side of the electrode
containing the sponge contact being adhesively secured to a carrier
sheet and with the sponge contact exposed through an aperture in
the carrier sheet. A rigid plastic cap member is usually secured to
the disk of the electrode in order to protect the gel in the sponge
against deterioration and to prevent evaporation of the gel
absorbed therein until the electrode is used. Accordingly, it will
be appreciated that such previously proposed disposable electrodes
are relatively expensive to manufacture, requiring numerous
components and are relatively difficult and expensive to assemble,
particularly because of the provision of a special disk to hold the
absorbent pad or sponge and the consequential need for a cover cap
to protect the sponge and gel.
Another type of previously proposed disposable electrode simply
consists of the foamed plastic disk, with a metallic connector
extending therethrough. The metallic connector is then placed
directly in contact with the patient's skin when the electrode is
used. Not only is the metallic electrode in contact with the skin
in this manner irritating and uncomfortable for the patient, but
also the quality of signals detected, because of the typically poor
contact and conductivity between the metal contact of the
electrodes and the skin, is sometimes unacceptable. This type of
electrode sometimes has a porous paper disk pre-wetted with a
conductive gel covering the metallic electrode. However, the paper
disk has insufficient thickness to absorb or hold enough
electrolytic gel so that uniform or sufficient contact with both
the skin of the patient and the surface of the electrode is not
provided.
In yet another form of previously proposed disposable electrodes,
the electrode is formed simply as a paper disk having a metallic
connector extending therethrough. Electrodes of this type suffer
from the same disadvantages as the above discussed electrodes and,
moreover, the paper disk is readily and easily torn or damaged
during handling, particularly when it is pulled from the adhesive
carrier sheet on which the electrode is supplied to the physician.
Still further, all of the previously proposed disposable electrodes
are formed with a relatively large diameter so that it is not
possible to simultaneously place six chest electrodes across a
patient's chest as is required in recently developed three channel
electrocardiogram equipment or with conventional 10 lead equipment
where all of the leads are simultaneously connected to the patient
but sequentially read.
Accordingly, it is apparent that although a variety of previously
proposed disposable electrodes have been used in the past, such
electrodes have not been entirely satisfactory in use even though a
substantial demand for such electrodes is evident in the medical
field.
Accordingly, it is an object of the present invention to provide a
disposable electrode which has substantial strength and yet is
inexpensive to manufacture.
Another object of the present invention is to provide a disposable
medical electrode which is relatively simple in construction and
durable in use.
Another object of the present invention is to provide a relatively
inexpensive yet durable disposable medical electrode which is
highly suitable for use in monitoring a patient's condition.
Yet another object of the invention is to provide a disposable
electrode which is of relatively small dimensions to permit use
with conventional ten lead electrocardiogram equipment and/or with
the three channel EKG equipment.
In accordance with one aspect of the present invention, the
disposable metal electrode provided thereby includes a circular
support disk defining the electrode which is formed of a semi-rigid
hard plastic material. The disk has an integrally formed embossed
recess at its central portion, which recess may be generally
cylindrical or square in shape. The recess opens towards one side
of the disk so that the opposite side of the disk has a raised
central portion formed therein. The disk has an aperture formed
therein at the center of the recess and a two-piece electrical
contact member is secured to the raised central portion of the disk
and includes a first contact piece located within the recess on one
side of the disk. This first contact piece includes an extension
pin which extends through the aperture in the electrode disk into
engagement with a second contact piece located on the opposite side
of the disk. This second electrode includes a female extension
which receives and mates with the extension member of the first
contact piece in order to form an electrical connection
therebetween.
An absorbent pad of a sponge or sponge-like material is positioned
in the embossed recess of the disk in contact with the first
electrical contact piece and is preferably held there snugly by a
friction fit. The sponge has absorbed therein an electrically
conductive gel so that when the electrode is secured to a patient,
with the sponge in contact with the patient's skin, an electrical
connection is formed between the skin and the second contact piece
thereby to permit electrical signals from the patient to be
detected. Accordingly, the disposable electrode of the present
invention is formed from a minimum of inexpensively manufactured
parts.
The above, and other objects, features and advantages of the
present invention will be apparent in the following detailed
description of an illustrative embodiment thereof, which is to be
read in connection with the accompanying drawings, wherein:
FIG. 1 is a partial plan view of a patient having a plurality of
disposable electrodes constructed in accordance with the present
invention adhered to his chest for the purpose of patient
monitoring;
FIG. 2 is a perspective view of a disposable electrode constructed
in accordance with one embodiment of the present invention and an
electrical connector which connects the electrode to the diagnostic
device;
FIG. 3 is a perspective view of a disposable electrode constructed
in accordance with another embodiment of the invention;
FIG. 4 is a sectional view of a disposable medical electrode of the
present invention, taken along line 4--4 of FIG. 2 prior to
application of the electrode to the patient; and
FIG. 5 is a sectional view similar to FIG. 4 showing the electrode
as mounted on a carrier sheet.
Referring to the drawing in detail, and initially to FIG. 1
thereof, it will be seen that disposable electrodes 10, constructed
in accordance with the present invention, are adapted to be placed
on the chest wall of a patient 12, in order to detect or monitor
electrical signals formed in the body or to apply electrical
impulses to the body, such as in muscle stimulation or electrical
nerve block techniques. Typically, the electrodes of the present
invention are used to monitor a patient's condition in a hospital
room or in intensive care, or to monitor stress in a patient or
subject during exercise and the like or to take an
electrocardiogram from a patient in the conventional manner or to
provide electrical impulses to the body. Thus, the electrodes are
connected through a plurality of electrical conductors or leads 14
to a plug cable 16 of conventional construction from which the
signals can be supplied to the diagnostic unit or device to a
telephone line or the like for transmission to the hospital or main
diagnostic apparatus, computer, etc. As a result, the technician,
nurse or physician is able to monitor the patient's condition or
record the patient's electrocardiogram, even though the display
device or electrocardiogram machine itself is not present with the
patient.
As seen in FIG. 2, the electrode 10 of the present invention
includes a main disk 18 which is formed of a semirigid relatively
hard plastic sheet material. This material may, for example, be
formed of polyvinylchloride, polyethylene, or other conveniently
available thermoformable plastic material which have some
flexibility, so as to permit the disk to conform to the contours of
the patient's body on which it is placed, and yet are also
relatively hard so that they are not torn or damaged when used and
handled. Such plastic materials preferably form a vapor barrier to
prevent drying or evaporation of the gel in the electrode during
storage or use. Drying of such gel is a principal problem with
previously proposed electrodes requiring special caps or seals
which are avoided by the present invention.
Disk 18 preferably has a diameter of approximately 11/2 inches and
has a central embossment 20 formed therein which, as seen in FIG.
3, opens towards one side 22 of disk 18. The use of a small
diameter for the disk 18 has several important advantages including
that it permits a hard plastic material to be used so as to form a
vapor barrier with the small size being such as to be able to
accommodate body curvature at the point of application of the
electrode by slight flexing of the disk. In addition, the small
size of the electrodes permit a plurality of the electrodes (e.g.
five or six) to be simultaneously placed across the chest wall of
the patient in order to permit a conventional ten lead ECG to be
taken or to allow use of recently developed three channel ECG
machines. Moreover, the electrode is light in weight and can flex
with body movements so that it is relatively comfortable on the
skin and to the touch.
The embossments 20 can be formed in a generally cylindrical
configuration as seen in FIG. 3, or in a square configuration as
shown in FIG. 4. The square embodiment is advantageous since it
provides a greater surface area for the recess and therefore the
absorbent sponge therein for a given diameter or maximum side
dimension. In either case, the embossment 20 is formed in any
convenient manner, such as for example, by thermoforming the sheet
material of which the disks 18 are formed. By this construction, a
central recess 24 is provided having an annular flange 26 extending
thereabout. The recess 24 is located substantially coaxially with
the disk 18, and has an aperture 28 formed therein at its
center.
Aperture 28, which may be preformed during the thermoforming
operation or die cut after that operation, permits the mounting of
a two-piece metal electrical connector member 30 on the disk 18.
Connector 30 includes a first connector piece 32 which consists of
an annular disk 34 having a male extension 36 extending therefrom
in a generally friction tight relation through the aperture 28. A
second connector piece 38 is located on the opposite side of the
disk 18 from connector piece 34 and has a female extension 40 which
receives the extension 36 of connector piece 32 in mating
engagement. In this manner the two contact pieces are in a snap
fitting relationship, so that they essentially clamp themselves
onto the disk 18 at the center thereof in a rigid mating
relationship with the disk 18 sandwiched therebetween. Moreover,
the contact pieces, as seen in FIG. 4, form a seal with each other
and with disk 18 to prevent or limit evaporation of the gel in the
electrode's recess 24 through opening 28 or through the stems of
the contact pieces themselves.
The recess or cavity 24 provides a retention pocket for an
absorbent pad 46 which may be formed of a natural or synthetic
sponge material. The sponge substantially fills the recess 24 as
seen in FIG. 3, and may be cut in a slightly larger diameter than
that of recess 24 so as to be frictionally held in the recess. In
that case, the sponge will bulge slightly, as shown in FIG. 3, out
of recess 24. However, when placed on the body the bulge will
insure proper contact of the sponge with the skin. Moreover, the
securement of the disk to the patient's skin by the adhesive on the
disk, as described hereinafter, will urge the sponge into recess 24
so that it also is in contact with connector 30.
In addition, sponge 46 has absorbed therein an electrically
conductive gel material which is commercially available and well
known in the art, such as for example, hydroxyethyl cellulose or
any of the cellulose products with 1/2 to 5% sodium potassium or
calicum chloride or combinations thereof, plus a suitable
preservative and a umectant. In another embodiment a chloride-free
electrically conductive gel may also be used in sponge 46, such as
for example, Spectra 360 Electrode gel sold by Parker
Laboratories.
Although previously proposed electrodes use silver or silver plated
contact members, or nickel contact members with a non-chloride gel
to prevent corrosion of the nickel, applicant has found that a
nickel or brass-nickel plated contact can be used in the electrode
with a chloride or low chloride type gel while avoiding corrosion
or rust in the contact.
By the provision of the absorbing gel in sponge 46 an electrical
connection is made between the outer surface 48 of the sponge
(which is placed in contact with the body) and the electrical
connector member 30 so that electrical signals from the patient can
be detected and supplied to the electrocardiogram by proper
connection with the connector 30.
For example, as illustrated in FIG. 2, a commercially available
wire lead 50 is provided which has an annular connector member 52
having a central aperture 54 therein which is adapted to receive
the extension 40 of electrode 10. In the embodiment of the wire
electrode 50 illustrated in the drawing, a pair of wire contacts 56
extend along opposite sides of the opening 54 so as to snap over
the enlargement 44 at the top of the electrode 10, thereby to
insure proper electrical contact between the contact extension 40
and connector 52. The opposite end of the wire lead 50 can be
provided with a male plug 58, for insertion in the plug cable
system 16 so that the signals detected by the various leads can be
sent over a common line 60 to the electrocardiogram at the hospital
through a telephone line or the like.
The electrodes 10 of the present invention are typically supplied
with a plurality of the electrodes adhesively secured to a carrier
or support sheet 62 by a pressure sensitive adhesive or the like
which is medically inactive and which will not effect the patient.
The carrier sheet preferably is formed from a polyethylene silicone
coated release paper such as is available from the H. P. Smith
Division of Philips Petroleum. Such paper sheet is either
impregnated with polyethylene or laminated to a polyethylene sheet
and then coated with a silicone release coating on one side
thereof. This release coating, or the under side of the electrodes
10 surrounding the recesses therein, then have an adhesive layer 63
applied thereto in any convenient manner so as to secure the
electrodes to the carrier sheet, as seen in FIG. 5. Carrier sheet
62 thus closes the opened end of recess 24 and thus forms a vapor
barrier so as to protect the gel in sponge 46 from deterioration or
evaporation in the air.
When it is desired to use the electrode 10, the electrode or
electrodes are simply peeled from the carrier sheet 62 and applied
to the patient's body. It is noted that the same adhesive which
secures the electrode to the carrier sheet serves to firmly adhere
the electrode in position on the patient. The adhesive layer 63
which is used between the electrode and the carrier sheet can be
any of the commercially available pressure sensitive adhesives
which are FDA approved for application to the body.
It is noted that the carrier 62 can also be formed of a plastic
sheet material, or alternatively, can be formed of paper, treated,
in either case, with a silicon layer on the side to which the
electrode is adhered to permit removal of the electrode from the
sheet. However, it is preferred that a plastic or plastic
impregnated sheet material be utilized because it has additional
strength over paper and because it forms a vapor barrier which will
limit or even prevent evaporation of the gel in the electrode
during storage.
Accordingly, it is seen that a relatively simply constructed
electrode, having a minimum of elements, is provided which will be
relatively durable in use. By forming the electrode of a
semi-rigid, but hard plastic material, the electrode will not be
damaged or torn during handling or removal from the carrier sheet.
In addition, since the electrode is a semi-rigid and hard plastic
material, it can be embossed to form the integral recess 24 therein
so as to provide a carrier and support pocket for the electrode
sponge 46. This material thus forms an integral vapor barrier in
the electrode to limit or prevent evaporation of the gel through
the electrode material. This is in contradistinction to previously
proposed disposable electrodes wherein a separate hard plastic ring
or cavity member is secured to a sponge or foam plastic material
and closed by a hard plastic cap in order to support the electrode
sponge in the electrode during storage and to limit evaporation of
the gel. Accordingly, the present invention provides an inexpensive
method of manufacturing electrodes using gel carrier sponges by
eliminating the rings and caps required in the prior art while at
the same time retaining the use and advantages of the sponge
carrier as compared to the prior art devices in which no carrier or
only a flat paper disk is used for the gel.
Although an illustrative embodiment of the present invention has
been described herein with reference to the accompanying drawing,
it is to be understood that the invention is not limited to that
precise embodiment and that various changes and modifications may
be effected therein by one skilled in the art without departing
from the scope or spirit of this invention.
* * * * *