Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a ground electrode pad
for electrosurgical procedures, and more particularly to a
pad known as a counter-electrode to be used as a ground
electrode in close contact with the body of a patient
undergoing surgery by means of an electro-surgical unit.
In an electro-surgical unit, a high frequency
current of 100 RHz or higher, for example, 500 to 2,000 KHz,
is passed between a blade electrode of the electro-surgical
unit and a counter-electrode or ground pad which is in close
contact at a suitable position (e.g. back or thigh) of the
human anatomy to perform a surgical operation at the tip
portion of said blade el~ctrode. Accordingly, the counter-
electrode is required to be closely contacted with the human
body at a relatively large area so as to have small electric
lS resistance. A counter-electrode frequently used these days
employ~ a lead plate which is clo~ely contacted with the
human body with gauze containing phy~iological saltous water
interposed therebetween. This method, while it is less
expen~ive ~ince repeated use of the lead plate i8 possible,
is liable to cause irregularity in current density
distribution. In addition, the gauze will be dried during
a prolonged operation to further aggravate the distribution
irregularity of the current density to such an extent that
burning frequently occurs on the skin on account of local
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current oascage. Quite recently, in place of a repeatedly
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used lead plate, there is used a so-called dry-type counter-
electrode consicting mainly of a disposable metal foil for
hygienic purpose~. This counter-electrode comprises
aluminum foil attached to a carrier layer containing
cushioning material such as sponge therebetween, which
counter-electrode i~ to be closely contacted with a human
body by adhesive ~ealed on marginal portions of said carrier
paper. One example of such a counter-electrode is disclosed
in Japanese published utility model application No.
97989/1974. This counter-electrode can be easily handled
because no saltous water is used and it is also advantageous
from a hygienic as well as an economic standpoint. But, a
relatively large contact area is required to make its size
relatively larger and therefore it is difficult to apply it
to an infant. Further, a dry system counter-electrode will
cause a local increase of current density due to perspiration.
Another disadvantage resides in the inability of the specific
~tructure of the counter-electrode plate (foil) to be closely
contacted with a human body on its entire surface. To
describe in more detail, when the foil is pressed in con-
formity with the contours of a human body, a large number of
creases are inevitably formed. Formation of creases means
formation of concave-convex structures, and sharp convex
port~ons thereof are closely contacted locally with the skin,
a~ a re~ult of which the current density is increased to
cause, together with the aforesaid problem of perspiration,
a local concentration of current density-generation of burns
to great disadvantage. In fact, on account of this problem,
thi~ type of pad is prohibited for use in the U.S.A.
Another type of counter-electrode which takes the
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place of the aforesaid type of electrode and is now popularlyused
in the U.S.A. is the so-called wet type counter-electrode. This
electrode comprises a soft foamed resin body containing a jelly
of an aqueous electrolyte solution attached to a carrying sheet
similarly as described above so as to be readily contoured to a
human body, as disclosed by, for example, U.S. Patent 3,848,600.
This electrode is well contacted with a human body and is readily
applicable on those with hairy skins. It is also advantageous in
having a relatively small extent of distribution irregularity of
current density. During prolonged use, however, the aqueous jelly
may become dry and thereby cause burns to a patient.
The object of the present invention is to provide a novel
improved disposable ground pad which has overcome allthe drawbacks
of the product of the prior art described above.
According to the pre~ent invention, there is pro~ided a
ground electrode pad for an electro-surgical unit, comprising
~ a) a flexible, electrically conductive cloth body, at least
10% of which con6i6ts of first electrically conductive fibers;
~ b) a self-adhering adhesive layer of from 0.1 to 0.5 mm in
th~ckness coated on a surface of said cloth body, said layer
having second electrically conductive fiberæ of from 0~5 to 5 mm
in length dispersed therein to render said layer electrically
conductive; and
tc~ a metal terminal secured to said cloth body in elec-
trical contacting relationship therewith.
The pad of the present invention can be ideally con-
toured to the human body to completely avoid irregularity of
current density distribution, since the conductive woven
fabric being excellent in flexibility is directly contacted
with the human body by means of a self-adhering adhesive
layer having electroconductivity. Further, due to the
absence of such a substance as water, it can be stored with-
out caring about the growth of mold or evaporation. Accord-
ingly, the present pad is simple in structure and very easy
to handle. In addition, there is no change in physical
properties on prolonged use thereof and therefore it can be
used stably for a long time. Another advantage of the
present pad is that it can be used when placed under the
body of a patient during a surgical operation.
The present invention may be best understood with
reference to the accompanying drawings, which are shown for
illustration of the preferred embodiment of the present in-
vention.
In the drawings:
Fig. 1 shows a perspective view of one preferred
embodiment of the pad according to the present invention;
Fig. 2 is a longitudinal cross-sectional view of
said embodiment;
Fig. 3 through Fig.6 are perspective views of other
preferred embodiments of the pad according to the present
inve~tion, having metal terminals at different positions
secured to the conductive cloth; and
Fig. 7 is a longitudinal cross-sectional view of
still another embodiment of the pad according to the present
invention, having a water repellent covering layer provlded
on the conductive cloth on the side opposite to the adhesive
layer.
Referring to the preferred embodiment shown in Fig.
1 and Fig. 2, a conductive woven fabric 1 is coated with a
self-adhering layer to form a composite principal body
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of the pad. For the purpose of the invention, the woven
fabric is required to be flexible so as to be sufficiently
contourable to the human body. It is also required to have
substantial conductivity. Thus, the conductive cloth of the
invention is generally constituted of yarns or mixed yarns
comprising conductive fibers such as carbon fibers, graphite
fibers or metallic fibers. The content of such conductive
fibers in the conductive cloth is required to be at least
10 ~, preferably 20 % or higher. ~he conductive cloth is
preferably a woven fabric with a flexible texture such as
provided by a plain weave or leno weave. The thickness of
the conductive cloth is not particularly limited, but it is
generally preferred to fall within the range from 0.1 to
1 mm. One example of the fabric 1 is a woven fabric of mixed
yarns comprising carbon fibers or graphite fibers as known
under the trade marks such as Sonel (Union Carbide Co.,
U.S.A.), Carbolon (Nihon Carbon, Co., Japan), Thermolon
(Tokai Carbon Co., Ltd., Japan), Torayca (Toray Industries
Inc., Japan) or Tientex (Nitto Boseki Co., Ltd., Japan).
Such a conductive woven fabric is cut in a size of 1~ x 15
cm, for example, with its corner edges rounded off for use.
Another example of the fabric 1 is a conductive woven fabric
of mixed yarns comprising metallic fibers and synthetic
fibers. For example, there may be mentioned stainless steel
fiber, high nickel alloy fiber, tantalum fiber, tungsten
fiber, molybdenum fiber, etc. As commercially available
fibers, there is Naslon (trade mark: Nippon Yakin Kogyo Co.,
Ltd., Japan). Such a metallic fiber is required to be inert
to the adhesive as hereinafter described and to the storage
environment such as air or humidity, and can be suitably
selected depending on the chemical and physical properties
thereof such as electrical resistance. Furthermore, there
may also be used an unwoven fabric having combined these
carbon fibers and metallic fibers with conductive synthet;c
resin materials.
The self-adhering adhesive layer 2 is exemplified
by a pressure-sensitive adhesive layer. Preferably, the
adhesive layer contains conductive materials, for example,
3 to 20 % of carbon fibers with lengths of 0.5 to 5 mm
dispersed therein. But, in place of the pressure sensitive
adhesive, a tacky adhesive may also be used. The adhesive
layer 2 is coated, preferably with a thickness of from 0.1
to 0.5 mm, uniformly on the entire surface of the aforesaid
flexible woven fabric 1 and is self-adhering in nature to be
lS excellently contoured to the human body, whereby there occurs
no local concentration of the current density distribution.
In place of the aforesaid carbon fibers which may be provided
for imparting conductivity to the adhesive, there may alsc
be used carbon particles, short fibers or fine flakes of
metals.
In Fig. 1, at the central portion of the woven
fabric 1, there is also provided a metal piece 3 secured
fixedly thereon by caulking and having a lead wire 4
soldered there-to so as to be electrically connectable to
an electro-surgical unit (not shown). At least one surface
of the metal piece 3 should have a surface area large enough
to establish a favorable electrical connection to the con-
ductive woven fabric, but such a large area as will inhibit
excellent contouring to the human body should be avoided.
Figs. 3 through 6 show other embodiments of the pad
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according to the preQent invention, wherein one metal
terminal or two metal terminals are provided at different
positions of the conductive cloth. In Fig. 5, two metal
terminals 3 and 3' are provided for the purpose of safety.
Namely, according to this embodiment, when one terminal 3
happens to suffer from some inconvenience such as an
accidental electrical disconnection, the other terminal 3'
can serve to aompensate for such a defect.
In another preferred embodiment of the pad accord-
ing to the present invention, a backing or covering layer 5
is provided on the surface of the conductive oloth l on the
opposite side of the adhesive layer 2. Such a baoking is
desirably made of a flexible, water repellent material, for
example, a polyurethane foam.
lS As the result of measurement when the above-
described pad i8 connected to a human body by means of an
electro-surgical unit, the electrical resistance is found to
be as low as 20 ohm at a high frequency of 100 KHz or higher,
ordinarily 500 to 2,000 KHz, to prove that the present pad
can be a counter-electrode with sufficiently low electrical
resistance. Furthermore, at frequencies lower than I00 KHz,
the ground pad of the present invention is found to have a
high impedance. This characteristic wi}l avoid troubles
encountered in the pad of the prior art when the frequency
is lowered accidentally.
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