U.S. patent application number 13/007839 was filed with the patent office on 2011-05-12 for system and method for providing even heat distribution and cooling return pads.
This patent application is currently assigned to TYCO Healthcare Group LP. Invention is credited to James E. Dunning, Peter Gadsby, David Gresback, Kyle R. Rick.
Application Number | 20110112525 13/007839 |
Document ID | / |
Family ID | 39591313 |
Filed Date | 2011-05-12 |
United States Patent
Application |
20110112525 |
Kind Code |
A1 |
Dunning; James E. ; et
al. |
May 12, 2011 |
System and Method for Providing Even Heat Distribution and Cooling
Return Pads
Abstract
A return pad for use with an electrosurgical system is
disclosed. The return pad includes a conductive layer, a contact
layer configured to engage a patient's skin and an intermediate
layer disposed between the conductive layer and the contact layer.
The intermediate layer is adapted to distribute energy.
Inventors: |
Dunning; James E.; (Boulder,
CO) ; Rick; Kyle R.; (Boulder, CO) ; Gresback;
David; (Minneapolis, MN) ; Gadsby; Peter;
(Broomfield, CO) |
Assignee: |
TYCO Healthcare Group LP
Boulder
CO
|
Family ID: |
39591313 |
Appl. No.: |
13/007839 |
Filed: |
January 17, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11732277 |
Apr 3, 2007 |
|
|
|
13007839 |
|
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Current U.S.
Class: |
606/34 |
Current CPC
Class: |
A61B 2018/00011
20130101; A61B 2018/00047 20130101; A61B 2018/00023 20130101; A61B
18/16 20130101; A61F 2007/0075 20130101; A61B 2018/00005
20130101 |
Class at
Publication: |
606/34 |
International
Class: |
A61B 18/16 20060101
A61B018/16 |
Claims
1. A return pad for use with an electrosurgical system, comprising:
a conductive layer; a contact layer in contact with the conductive
layer, disposed directly on the conductive layer and configured to
engage and adhesively attach to patient skin; and a cooling section
in contact with the conductive layer, disposed directly on the
conductive layer and configured to reduce the temperature of at
least one of the contact layer and the conductive layer; wherein
the conductive layer separates the cooling layer from the contact
layer thereby preventing direct contact therebetween.
2. The return pad according to claim 1, wherein the cooling section
is configured to absorb thermal energy generated in the return
pad.
3. The return pad according to claim 1, wherein the cooling section
is configured to absorb thermal energy from the conductive layer
and the contact layer.
4. The return pad according to claim 1, wherein the cooling section
includes a passive cooling device.
5. The return pad according to claim 1, wherein the cooling section
includes a Peltier cooling device.
6. The return pad according to claim 1, wherein the cooling section
includes a chemical layer.
7. The return pad according to claim 1, further including a backing
layer disposed on the cooling section and adapted to allow heat to
dissipate therethrough.
8. The return pad according to claim 1, wherein the cooling section
further includes: an intermediate layer in contact with the
conductive layer, disposed directly on the conductive layer and
constructed from a material that distributes energy; and a cooling
device in contact with the intermediate layer, disposed directly on
the intermediate layer.
9. The return pad according to claim 8, wherein the cooling device
is selected from a group consisting of an active cooling device and
a passive cooling device.
10. The return pad according to claim 8, wherein the intermediate
layer is selected from a group consisting of a dielectric layer and
a carbon layer.
11. The return pad according to claim 1, wherein at least a portion
of the cooling section includes at least one cooling chamber
configured to allow fluid to flow therethrough.
12. A return pad cooling system for electrosurgical surgery
comprising: a return pad including: a conductive layer; a contact
layer in contact with the conductive layer, disposed directly on
the conductive layer and configured to engage and adhesively attach
to patient skin; a cooling section in contact with the conductive
layer, disposed directly on the conductive layer and configured to
reduce the temperature of at least one of the contact layer and the
conductive layer, the cooling section including one or more cooling
chambers configured to allow fluid to flow therethrough; wherein
the conductive layer separates the cooling layer from the contact
layer thereby preventing direct contact therebetween, and a cooling
system that supplies cooling fluid to the cooling chamber.
13. The cooling system according to claim 12, wherein the cooling
system includes a pump that circulates cooling fluid through the
cooling chamber.
14. The cooling system according to claim 12, where the cooling
section further includes an intermediate layer disposed on the
conductive layer and configured to distribute energy.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a continuation application of
U.S. patent application Ser. No. 11/732,277 entitled "SYSTEM AND
METHOD FOR PROVIDING EVEN HEAT DISTRIBUTION AND COOLING RETURN
PADS" filed by James E. Dunning et al. on Apr. 3, 2007, the entire
contents of which are hereby incorporated by reference herein.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure is directed to electrosurgical
apparatus, methods and systems, and, in particular, to an
electrosurgical return pad that provides even heat and current
distribution and cooling.
[0004] 2. Background of Related Art
[0005] During monopolar electrosurgery, a source or active
electrode delivers energy, such as radio frequency energy, from an
electrosurgical generator to the patient and a return pad carries
the current back to the electrosurgical generator. The source
electrode is typically placed at the surgical site and high density
current flows from the source electrode to create the desired
surgical effect of cutting and/or coagulating tissue. In tissue
ablation, another form of electrosurgery, the source electrode or
electrodes are typically placed in or adjacent the target tissue
and high density current flows through the target tissue thereby
destroying the target tissue. The patient return pad is placed at a
distance from the source electrode and may be in the form of a pad
adhesively adhered to the patient.
[0006] The return pad typically has a large patient contact surface
area to minimize heating at that return pad site. The larger the
contact area between the return pad and patient skin, the lower the
current density and the lower the intensity of the heat. The size
of return pads is based on assumptions of the maximum current seen
in surgery and the duty cycle (e.g., the percentage of time the
generator is on) during the procedure. The first types of return
pads were in the form of large metal plates covered with conductive
jelly. Later, adhesive electrodes were developed with a single
metal foil covered with contact layer formed of conductive jelly,
conductive adhesive or conductive hydrogel.
[0007] One issue with these adhesive electrodes was that current
flow from the active electrode concentrates at the leading edge,
the edge of the return pad closest to the active electrode, causing
a heating imbalance across the return pad. This phenomenon, known
as "Leading Edge Effect" can cause tissue change or injury if the
skin under the leading edge portion of the return pad is heated
beyond the point where circulation of blood can cool the skin.
SUMMARY
[0008] The present disclosure relates to an electrosurgical return
pad. The return pad, for use in performing electrosurgical
procedures, includes a conductive layer, a contact layer configured
to engage a patient's skin and an intermediate layer disposed
between the conductive layer and the adhesive layer. The
intermediate layer is adapted to distribute energy.
[0009] The intermediate layer is constructed from a material that
may include a dielectric layer, a carbon layer, evaporative layer
or any combination thereof. The material of the intermediate layer
may be silk screened or printed onto the conductive layer, or
vice-versa. Intermediate layer and the conductive layer may be
joined by a conductive adhesive, such as a hydrogel. The impedance
of the material may be configured to be substantially uniform or
the impedance may decrease away from a leading edge of the return
pad.
[0010] The contact layer may include a plurality of contact layer
sections and an insulating barrier between each of the plurality of
contact layer sections.
[0011] The conductive layer may be is disposed on a portion of the
intermediate section and may be spaced away from the leading edge
of the intermediate layer. A backing layer may be at least
partially disposed on the conductive layer.
[0012] Intermediate layer may include a cooling device selected
from an active cooling device and a passive cooling device.
Alternatively, intermediate layer may include at least one cooling
chamber configured to allow fluid to flow therethrough.
[0013] In yet another embodiment of the present disclosure return
pad is disclosed that includes a conductive layer and a contact
layer. The contact layer is disposed on the conductive layer and is
configured to engage patient skin. A cooling section may be
disposed on the conductive layer and configured to reduce the
temperature of at least one of the contact layer and the conductive
layer.
[0014] The cooling section may include a heat exchanger, an
evaporative material, a passive cooling device, a Peltier cooling
device and/or a heat exchanger. A backing layer may be disposed on
the cooling section and may be adapted to allow heat to dissipate
therethrough. Alternatively, cooling section may include at least
one cooling chamber configured to allow fluid to flow
therethrough.
[0015] Cooling section may further include an intermediate layer
disposed on the conductive layer and constructed from a material
that distributes energy. The cooling section may also include a
cooling device disposed on the intermediate layer that may consist
of an active cooling device, a passive cooling device and/or may
include an evaporative material. A backing material may be at least
partially disposed on the cooling device. The intermediate layer
may be a dielectric layer and/or a carbon layer.
[0016] In yet another embodiment of the present disclosure a return
pad is disclosed that includes a cooling system for electrosurgical
surgery having a return pad and a cooling system for supplying
cooling fluid. The return pad includes a conductive layer, a
contact layer disposed on the conductive layer and configured to
engage patient skin and a cooling section. The cooling section may
be disposed on the conductive layer and configured to reduce the
temperature of the contact layer and/or the conductive layer. The
cooling section may include one or more cooling chambers configured
to allow fluid to flow therethrough. The cooling system is
configured to supply cooling fluid to the cooling chamber and may
include a pump that circulates cooling fluid through the cooling
chamber. Cooling section may also include an intermediate layer
disposed on the conductive layer that is configured to distribute
energy.
[0017] In yet another embodiment of the present disclosure a method
for performing electrosurgery is disclosed and includes the steps
of: providing an electrosurgical return pad including a conductive
layer, a contact layer configured to engage patient skin and an
intermediate layer disposed between the conductive layer and the
contact layer. The intermediate layer is adapted to distribute
energy. The method also includes the steps of: placing the
electrosurgical return pad in contact with patient skin; generating
electrosurgical energy via an electrosurgical generator; and
supplying the electrosurgical energy to the patient via an active
electrode. The intermediate layer may include a dielectric layer, a
carbon layer and/or an evaporative layer.
[0018] The method for performing monopolar surgery may include a
cooling device and further include the step of enabling the cooling
device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above and other aspects and features of the present
disclosure will become more apparent in light of the following
detailed description when taken in conjunction with the
accompanying drawings in which:
[0020] FIG. 1A is a schematic illustration of a monopolar
electrosurgical system with a return pad;
[0021] FIG. 1B is a detail of the leading edge of the return pad of
FIG. 1;
[0022] FIG. 2A is a cross-sectional view of one envisioned
construction of a return pad with an intermediate layer of the
present disclosure;
[0023] FIG. 2B is a cross-sectional detail of the leading edge of
the return pad of FIG. 2;
[0024] FIG. 3A is a cross-sectional view of yet another embodiment
of a return pad having an intermediate layer disposed between a
conductive layer and a first contact layer;
[0025] FIG. 3B is a cross-sectional detail of the leading edge of
the return pad of FIG. 3;
[0026] FIG. 3C is a top view of yet another embodiment of the
return pad of FIGS. 3A-3B with an insulating barrier between the
conductive gel portions;
[0027] FIG. 4A is a cross-sectional view of yet another embodiment
of a return pad with an intermediate layer;
[0028] FIG. 4B is a cross sectional detail of the leading edge of
the return pad of FIG. 4;
[0029] FIG. 4C is a top view of yet another embodiment of the
return pad of FIGS. 4A-4B with an insulating barrier between the
conductive gel portions;
[0030] FIG. 5 is a cross-sectional view of a return pad with a
plurality of contact layers;
[0031] FIG. 6A is a cross sectional view of a return pad with a
passive cooling layer;
[0032] FIG. 6B-6D illustrate various embodiments of passive cooling
layers;
[0033] FIG. 7 is a top view of a return pad with an active cooling
system;
[0034] FIG. 8 is a top view of the return pad of FIG. 7 with an
even heat distribution layer;
[0035] FIG. 9 is a cross-sectional view of yet another embodiment
of an active cooling system with an intermediate layer;
[0036] FIG. 10A is a cross-sectional view of yet another embodiment
of a return pad with a heating layer;
[0037] FIG. 10B is a top view of the return pad of FIG. 10A wherein
the heating layer utilizes an electric heater; and
[0038] FIG. 10C is a cross-sectional view of a return pad with the
heating layer disposed in at least a portion of the contact
layer.
DETAILED DESCRIPTION
[0039] Embodiments of the presently-disclosed electrosurgical
return electrode (return pad) and method of using the same are
described below with reference to the accompanying drawing figures
wherein like reference numerals identify similar or identical
elements. In the following description, well-known functions or
constructions are not described in detail to avoid obscuring the
disclosure in unnecessary detail. In addition, terms such as
"above", "below", "forward", "rearward", etc. refer to the
orientation of the figures or the direction of components and are
simply used for convenience of description.
[0040] Heat Distribution
[0041] Referring initially to FIG. 1A, a schematic illustration of
a monopolar electrosurgical system 100 is shown. The
electrosurgical system 100 generally includes a return pad 200, an
electrosurgical generator 110, a surgical instrument 116 (e.g., an
active electrode) and a return electrode monitor (REM) 112. In FIG.
1A and in the figures hereinbelow, return pad 200 is illustrated in
contact with patient tissue "T". Generally, electrosurgical energy
is supplied to the active electrode 116 by the generator 110
through a supply cable 114 to treat tissue (e.g., cut, coagulate,
blend, etc.). The return pad 200 acts as a return path for energy
delivered by the active electrode 116 to patient tissue "T". Energy
returns back to the electrosurgical generator 110 via a return
cable 118.
[0042] While FIGS. 1A-9 depict cross-sections of return pads 200,
300, 400, 500, 600, 600a-d, 700 and 800, it is within the scope of
the disclosure for the return pads to have any suitable regular or
irregular shape.
[0043] In the embodiments illustrated in FIGS. 1A and 1B, return
pad 200 is formed of a conductive layer 210 engaged on the top with
an insulating layer 212 and on the bottom with a contact layer 215.
Conductive layer 210 connects to generator 110 by return cable 118
in any suitable manner.
[0044] Contact layer 215 is formed of a gel or adhesive configured
to couple to patient tissue "T" and can be made from, but is not
limited to, a polyhesive adhesive, conductive hydrogel, a Z-axis
adhesive or a water-insoluble, hydrophilic, pressure-sensitive
adhesive. The portion of the contact layer 215 in contact with a
patient tissue "T" is a patient-contacting surface 216 that is
configured to ensure an optimal contact area between the return pad
200 and the patient tissue "T". In addition, contact layer 215
provides ionic conductive contact with the skin to transfer energy
out of the body.
[0045] A leading edge 205 of the return pad 200 is that portion of
the return pad 200 positioned closest to the active electrode 116.
Leading edge 205 is defined in this disclosure not as a single
point but as a general portion of the return pad 200 positioned
closest to the active electrode 116.
[0046] In use, the current applied by the active electrode 116
travels through various tissue paths between the active electrode
116 and the return pad 200. The amount of current supplied by the
active electrode 116 is typically equal to the amount of current
received by the return pad 200. The only difference between the
active electrode 116 and the return pad 200 is the amount of area
in which the current is conducted. Concentration of electrons at
the active electrode 116 is high due to the small surface area of
the active electrode 116, which results in high current density and
generation of heat, while the large surface area of the return pad
200 disperses the same current over the large contacting surface
216 resulting in a low current density and little production of
heat.
[0047] Electric charge passing between the active electrode 116 and
the return pad 200 will travel along various paths in patient
tissue "T" and will seek the path with the lowest impedance. With
reference to FIGS. 1A-4, three tissue paths (TP1), (TP2) and (TP3)
are provided for illustrating tissue paths with varying impedances.
However, any number of suitable paths may be utilized for
conducting current through tissue "T".
[0048] Tissue path one (TP1) is a path in patient tissue "T"
between the active electrode 116 and the leading edge 205 of return
pad 200. Tissue path two (TP2) and tissue path three (TP3) are
paths in patient tissue "T" between the active electrode 116 and a
portion of the return pad 200 away from the leading edge 205 of the
return pad 200.
[0049] The total impedance of a given pathway between the active
electrode 116 and the return cable 118, through the return pad 200,
is determined by combining the impedance of the tissue pathway and
the impedance of the various layers of the return pad 200. As
illustrated in FIG. 1B, the impedance of the first path equals the
sum of the impedance of the first tissue path (TP1), the impedance
of the first adhesive path (AP1) through the contact layer 215 and
the impedance of the first conductive path (CP1) through the
conductive layer 220. Similarly, the impedance of the second path
equals the sum of the impedance of the second tissue path (TP2),
the impedance of the second adhesive path (AP2) and the impedance
of the second conductive path (CP2). Finally, impedance of the
third path equals the sum of the impedance of the third tissue path
(TP3), the impedance of the third adhesive path (AP3) and the
impedance of the third conductive path (CP3).
[0050] In comparing the impedance of the various portions of the
three illustrative current pathways, the impedance of adhesive
paths (AP1), (AP2) and (AP3) and the impedance of conductive paths
(CP1), (CP2) and (CP3) are substantially the same regardless of the
tissue path selected. In addition, the impedance of adhesive path
(AP1), (AP2) and AP3 and the impedance of a conductive path (CP1),
(CP2) and (CP3) are generally small in comparison to the impedance
of a tissue path (TP1), (TP3) and (TP3) and are therefore
negligible with respect to the impedance of each respective tissue
path (TP1), (TP2) and (TP3). Therefore, the current density at any
point on the contacting surface 216 is generally dependant on the
impedance of the tissue path.
[0051] As illustrated by perpendicular "P" drawn from first tissue
path (TP1) in FIG. 1B, the lengths of the second and third tissue
paths (TP2) and (TP3) are longer than first tissue path (TP1) by
lengths of (TP2') and (TP3'), respectively. This additional length
(TP2') and (TP3') in tissue adds additional impedance to second and
third tissue paths (TP2) and (TP3), thus resulting in a higher
current density at the leading edge 205 and a reduction in current
density away from leading edge 205.
[0052] This phenomenon, known as "Leading Edge Effect," results in
the concentration of energy and heat at the leading edge 205 of the
return pad 200 and heating imbalance across the return pad 200.
Leading Edge Effect may result in serious injury to skin under the
leading edge 205 if patient tissue "T" is heated beyond the point
where circulation of blood can cool the tissue.
[0053] FIG. 2A is a cross-sectional view of a first embodiment of
the present disclosure. Return pad 300 for providing, among other
advantages, even heat distribution is formed of a conductive layer
310, an insulating layer 312 disposed on conductive layer 310, and
an intermediate layer 320 placed between conductive layer 310 and
contact layer 315. In one embodiment, intermediate layer 320 is
formed of a thin dielectric material, such as, for example, a
polyimide film sold under the trademark Kapton.TM. or a
biaxially-oriented polyethylene terephthalate polyester film sold
under the trademark Mylar.TM.. In other embodiments, intermediate
layer 320 may also be formed of a semi-conductive material, such
as, for example, carbon, silicon, or germanium.
[0054] Intermediate layer 320 forms a low impedance connection with
conductive layer 310 and contact layer 315. Low impedance
connection may be formed by printing or silk screening the
intermediate layer 320 on conductive layer 310. Alternatively,
conductive layer 310 may be printed or silk screened on
intermediate layer 320. Low impedance connection may be formed by
bonding conductive layer 310 and intermediate layer 320 with a
suitable conductive adhesive or gel. Such conductive adhesive or
gel can be made from, but is not limited to, a polyhesive adhesive,
conductive hydrogel, a Z-axis adhesive or a water-insoluble,
hydrophilic, pressure-sensitive adhesive. Contact layer 315 forms a
low impedance connection with intermediate layer 320.
[0055] With additional reference to FIG. 2B, the total impedance
for a given pathway between the active electrode (not explicitly
shown) and a return cable 318, through the return pad 300, includes
the respective sum of the impedance of the tissue path (TP1), (TP2)
and (TP3), the impedance of the adhesive paths (AP1), (AP2) and
(AP3), the impedance of the conductive paths (CP1), (CP2) and (CP3)
and the impedance of the intermediate path (IP1), (IP2) and (IP3).
The additional impedance of the intermediate layer 320 evenly
distributes the current flow through the return pad 300, thus
reducing the current density at the leading edge 305 of return pad
300 or leading edge 305 of contact layer 315.
[0056] Intermediate layer 320 may also conduct heat generated by
the current flowing through patient tissue "T" and the return pad
300. Areas of higher current density may generate hot spots on the
return pad 300. Intermediate layer 320 evenly distributes energy,
i.e. heat and/or current, thus lowering the temperature of hot
spots on the return pad 300.
[0057] The impedance of the intermediate layer 320 may not be
uniform. Intermediate layer 320 may have greater impedance at
leading edge 305 of return pad 300 and the impedance of the
intermediate layer 320 may be reduced away from the leading edge
305. For example, the impedance of the first intermediate path
(IP1) may be greater than the impedance of the second intermediate
path (IP2), and the impedance of the third intermediate path (IP3)
may be less than the impedance of first and second intermediate
paths (IP1) and (IP2). Reduction in impedance of the intermediate
layer 320 away from leading edge 305 may be gradual, linear or
non-linear. The change in impedance may be accomplished by changing
the material type, material density, material construction or any
other suitable method or means for varying material impedance.
[0058] The varying impedance of the intermediate layer 320 may
offset the difference in impedance of the various tissue pathways
(TP1), (TP2) and (TP3). As discussed hereinabove, the perpendicular
"P" from the first tissue pathway (TP1) illustrates the additional
impedance lengths of the second and third tissue pathway (TP2') and
(TP3'). Varying the impedance of the intermediate layer 320 may
equalize the impedance of the three illustrative pathways. For
example, the impedance of the first and third illustrative pathways
will be substantially the same if the sum of the impedance in
tissue of (TP3') and the impedance of the third intermediate path
(IP3) equal the impedance of the first intermediate path (IP1).
Similarly, the impedance of the first and second illustrative
pathways will be equal if the sum of the impedance in tissue of
(TP2') and the impedance of the second intermediate path (IP2)
equal the impedance of the first intermediate path (IP1).
[0059] Referring now to FIGS. 3A and 3B, a return pad 350 for
providing, among other advantages, even heat distribution is shown
and includes a conductive layer 310, an intermediate layer 320 and
contact layer 315 larger than conductive layer 310. Return cable
318 connects to conductive layer 310. Insulating layer 312 is
disposed upon at least a portion of the conductive layer 310 and
the intermediate layer 320. Reduction in the size of the conductive
layer 310 relative to intermediate layer 320 and contact layer 315
increases the impedance of current pathways away from the
conductive layer 310.
[0060] With reference to FIGS. 2A and 3A, reducing the size of the
conductive layer 310, as illustrated in FIG. 3B, does not change
the impedance of the second intermediate path (IP2) because the
pathway in the two embodiments is unchanged. The reduction of the
size of the conductive layer 310 increases the impedance of the
first intermediate path (IP1) because the conductive layer is
spaced a distance away from the leading edge 305 while the
impedance of the third intermediate path (TP3) is slightly
increased.
[0061] The size and placement of the conductive layer 310, relative
to the intermediate layer 320 and contact layer 315, impacts the
impedance of the various current pathways. Positioning conductive
layer 310 substantially in the middle of the intermediate layer 320
and contact layer 315 effectively increases the impedance of the
pathways at the edges of the return pad 350. As illustrated in
FIGS. 4A and 4B, positioning conductive layer 410 away from the
leading edge 405, increases the impedance of the pathways at the
leading edge 405 of the return pad 400, thus further reducing the
current density at the leading edge 405 of return pad 400.
[0062] Referring back to FIG. 3A, decreasing the size of the
conductive layer 310 also increases the current density, and may
result in the generation of heat at the connection between the
intermediate layer 320 and the conductive layer 310.
[0063] Conductive layers 310, 410 may be formed as a single layer
or may be formed as a plurality of sections separated by a barrier
330, 430, as illustrated in FIGS. 3A-3C and 4A-4C. Barrier 330, 430
may be formed from a conductive material or alternatively, as
described hereinbelow, barrier 330, 430 may be formed from a
non-conductive or insulating material.
[0064] In yet another embodiment of the present disclosure, as
illustrated in FIGS. 3C and 4C, contact layer 315 includes a
plurality of contact layer sections 315a-d, 415a-d formed as a
plurality of concentric rings or rows. FIG. 3C illustrates a
concentric or substantially circular return pad 350c, and FIG. 4C
illustrates a rectangular shaped return pad 400c. Return pads 350c
and 400c may be formed from any suitable shape, e.g., oblong, oval,
hexagonal, or polygonal.
[0065] More particularly, FIG. 3C illustrates the return pad 350 of
FIG. 3B with the various portions of the contact layer 315
separated by barriers 330 formed of a non-conductive or insulating
material. Contact layer 315 includes a center contact portion 315e,
a first contact ring 315b, a second contact ring 315c, and an outer
contact ring 315d with a barrier 330 between the adjacent
portions.
[0066] FIG. 4C illustrates the return pad 400 of FIG. 4B with
various portions of the contact layer separated by barriers 430
formed of an insulating material. Contact layer 415 includes a
first contact row 415a, a second contact row 415b, a third contact
row 415e and an outer contact row 415d with a barrier 330 between
the adjacent portions.
[0067] Barriers 330, 430 electrically isolate concentric rings
315a-d and rows 415a-d, respectively, thereby preventing current
flow between rings 315a-d or rows 415a-d. Current enters the
portion of the intermediate layer 320 above each concentric rings
a-d or rows 415a-d. The current paths in contact layer 315 are
substantially perpendicular to patient tissue "T" and the impedance
of the intermediate paths will be different for each concentric
ring 315a-d or rows 415a-d with the impedance of the pathways
increasing as the distance away from the conductive layer 310
increases.
[0068] With reference to FIGS. 4A and 4B, leading edge 405 of
return pad 400 is positioned closest to the active electrode (not
explicitly shown) and conductive layer 410 is positioned away from
leading edge 405. Current following the first tissue path (TP1)
travels through outer contact row 415d, as illustrated by first
contact path (AP1), and enters intermediate layer 415 toward the
leading edge 405. Current travels across a substantial portion of
the length of intermediate layer 415 as illustrated by first
intermediate path (IP1), before entering conductive layer 410.
Current following the third tissue path (TP3) travels through first
contact row 415A, as illustrated by third adhesive path (AP3), and
enters intermediate layer 415 in close proximity to conductive
layer 410. Current must only travel across the width of
intermediate layer 420 before entering conductive layer 410. For
both examples, current takes a substantially similar path through
conductive layer 410, as illustrated by conductive path CP.
[0069] In one embodiment, the intermediate layer 420 may be formed
of material with impedance properties substantially similar to the
impedance properties of patient tissue "T". Matching the impedance
properties of the intermediate layer 420 to patient tissue "T"
results in substantially similar impedance for any given path
between the active electrode (not shown) and return cable 418
through the return pad 400.
[0070] With reference to FIGS. 3A, 3B, 4A and 4B, backing layer 312
and 412, respectively, is disposed upon at least a portion of
conductive layer and intermediate layer.
[0071] FIG. 5 illustrates yet another embodiment of the present
disclosure having a return pad 500 that provides, among other
advantages, even heat and current distribution and is formed of a
first contact layer 515 having a first side adapted to couple to
patient tissue "T" and a second side adapted to couple to a first
side of intermediate layer 520. A second contact layer 525 engages
second side of intermediate layer 520 to conductive layer 510.
First and second contact layer can be made from, but is not limited
to, a polyhesive adhesive, conductive hydrogel, a Z-axis adhesive
or a water-insoluble, hydrophilic, pressure-sensitive adhesive.
Insulating layer 512 is disposed upon the top portion of conductive
layer 510 and return cable 518 connects to conductive layer
510.
[0072] Return Pad Cooling
[0073] With reference to FIG. 6A, a cooled return pad 600a is shown
and includes a contact layer 615, a conductive layer 610, a cooling
layer 635 and a backing layer 640. Return cable 618 connects to
conductive layer 610, which is formed of a suitable metal foil,
dielectric material or dielectric/metal material combination.
Cooling layer 635 and conductive layer 610 are configured in
thermal communication such that energy, e.g., heat, is distributed
and/or dissipated. Distribution and/or dissipation (herein referred
to as distribution) of energy includes the transfer of energy
between patient skin and/or the layers of the return pad 600a, the
transfer of energy from the return pad to the surrounding area 642
and/or the transfer of energy between conductive layer 610 and
cooling layer 635. Cooling layer 635 may be formed of an
electrically non-conductive material and/or may be electrically
isolated from conductive layer 610.
[0074] Cooling layer 635 may employ passive or active cooling
techniques. Passive cooling requires backing layer 640 to be formed
from a breathable material that allows heat to dissipate from
cooling layer 635 into surrounding area 642. Active cooling may
require backing layer 640 to be formed of impervious material to
facilitate circulation of a cooling air or fluid. Backing layer 640
may form an air-tight or liquid-tight seal with conductive layer
610 or other portion of return pad 600a.
[0075] FIGS. 6B-6E illustrates several constructions of a cooled
return pad with passive cooling. FIG. 6B illustrates cooled return
pad 600b with a backing layer 640, contact layer 615, conductive
layer 610, a return cable 618 connected to conductive layer 610 and
a heat exchanger 636 as the cooling layer. Heat exchanger 636 may
include a plurality of fins 636a to aid in the dissipation of heat.
Heat exchanger 636 may be formed of any heat conducting material
provided heat exchanger 636 is electrically isolated from
conductive layer 610. Heat exchanger 636 may be formed of a heat
conducting insulator, such as, for example a ceramic or dielectric
material. Backing layer 640 is disposed on or otherwise integrated
with heat exchanger 636 and is formed of highly permeable material
that allows heat to dissipate or exchange with surrounding area
642.
[0076] FIG. 6C shows yet another embodiment of the present
disclosure having the cooling layer as an evaporative layer 637.
Cooled return pad 600c includes evaporative layer 637 formed of a
liquid or semi-liquid material with highly evaporative properties,
such as, for example, alcohol or water, or alcohol or water-based
gel. Evaporative layer 637 absorbs heat from conductive layer 610
and heat is removed from cooled return pad 600c by evaporation,
i.e. vaporization or evaporation of the evaporative material in
evaporative layer 637. Top surface 610a of conductive layer 610 may
form ridges or fins 610b to increase the area of contact surface
between conductive layer 610 and evaporative layer 637. Backing
layer 640 is permeable to air. Alternatively, backing layer 640 may
be permeable to air and impermeable to the material forming the
evaporative layer 637. Backing layer 640 contains evaporative layer
637 between backing layer 640 and conductive layer 610 while
allowing the vaporized gas to remove the heat. Backing layer 640
may be formed of a cloth or fabric treated with thermo-mechanically
expanded polytetrafluoroethylene (PTFE) or other Fluoropolymer,
such as the fabric treatment commonly sold over the trademark
Gore-Tex.TM. or other porous hydrophobic materials or coating.
[0077] FIG. 6D shows yet another embodiment of the present
disclosure having the cooling layer of the cooled return pad 600d
composed of one or more Peltier devices 638, a well known device in
the art that operates as a heat pump. In one embodiment, Peltier
device 638 is formed by sandwiching a series array of small p and n
type Bismuth Telluride cubes 638c between two metallized ceramic
plates 638a and 638b that connect the cubes in series and applying
a DC current, supplied from a DC power supply 638D, thereto. When a
DC current is applied to the series array of small Bismuth
Tellurite cubes 638c, heat moves from one side of the Peltier
device 638 to the other. The cold side "C" cools the conductive
layer 610 and the contact layer 610 and the hot side "H" exchanges
heat with the surrounding air 642. Peltier device 638 may also
include a heat sink 638d to improve the cooling effect. Backing
layer 640 is disposed on Peltier device 638 and is formed of highly
permeable material that allows heat to dissipate or exchange with
surrounding air 642.
[0078] FIG. 6E illustrates another embodiment of the present
disclosure having a cooled return pad 600e with even heat
distribution. More particularly, return pad 600e includes an
intermediate layer 620, as illustrated in FIGS. 1-5 and disclosed
hereinabove, and a cooling layer 635 as illustrated in FIGS. 6A-6D
and 7-9 and discussed herein. Intermediate layer 620 provides even
current and hence even heat distribution and dissipation of energy
and cooling layer 635 removes heat from the return pad 600e.
[0079] Cooled return pad 600e includes a backing layer 640, a
cooling layer 635, a conductive layer 610, an intermediate layer
620 and a contact layer 615. Conductive layer 610 is disposed
between intermediate layer 620 and cooling layer 635. Intermediate
layer 620 is disposed between conductive layer 610 and contact
layer 615. Backing layer 640 is disposed upon at least a portion of
cooling layer 635 and allows heat to dissipate or exchange with the
surrounding air 642.
[0080] While FIGS. 6B-6E illustrate various passive techniques of
cooling a return pad, other suitable techniques of passive cooling
may be used. Moreover, a passive cooling technique may be combined
with one or more active cooling techniques as disclosed below.
[0081] With reference to FIG. 7, cooled return pad 700 includes a
contact layer 715, a conductive layer 710, a return cable 718
connected to conductive layer 710 and a backing layer 735. Backing
layer 735 and conductive layer 710 form a cooling chamber 735a for
circulating cooling fluid therewithin. Cooling chamber 735a may be
further defined by dimples 735b on backing layer 735. Dimples 735b
are configured as spacers between contact conductive layer 710
backing layer 735 and provide cooling chamber with support and
dimension. Edge 735c provides a seal between the layers forming the
cooling chamber 735a and contains cooling fluid within cooling
chamber 735a. Seal may be formed mechanically, i.e. clamping,
crimping, etc., or by bonding, i.e. adhesive, ultrasonic bonding,
etc, or by other suitable sealing techniques.
[0082] Alternatively, dimples 735b may be formed by point or spot
welding the layers that from the cooling chamber 735a. Cooling
chamber 735a defines one or more fluid pathway "FP". Pump 740d
supplies cooling fluid to inflow tube 740a, cooling fluid
circulates through cooling chamber and outflow tube 740b returns
cooling fluid to cooling system 740.
[0083] Cooling chamber 735a may also be defined by one or more
channels formed in the backing layer 735 and/or conductive layer
710. Cooling chamber may be a single channel or chamber or may
comprise a plurality of channels or chambers.
[0084] Cooling fluid may be purified water, distilled water or
saline, although any suitable fluid, including air, may be used.
Cooling system may also include a cooling module 740c, such as a
refrigeration system, one or more Peltier device, vortex cooling
device, heat exchanger, ice, etc. While FIG. 7 illustrates an
active cooling technique for a return pad 700, other suitable
active cooling techniques art may be utilized to accomplish the
same purpose.
[0085] FIG. 8 shows a cooled return pad 800 that includes an
intermediate layer 820 to provide even heat distribution as
disclosed hereinabove. While many different variations and
combinations are envisioned, FIG. 8 illustrates a particular
embodiment with the even heat distribution pad, illustrated in
FIGS. 4A and 4B and disclosed hereinabove, incorporated into the
cooled return pad 700 illustrated by FIG. 7 and described
hereinabove.
[0086] Return pad 800 includes a contact layer 815, a conductive
layer 810, an intermediate layer 820, and a cooling layer 835.
Conductive layer 810 is disposed on intermediate layer 820.
Alternatively, conductive layer 810 may be disposed on only a
portion of intermediate layer 820. As discussed hereinabove, the
size and placement of the conductive layer 810 relative to the
leading edge 805 of the pad 800 effects the impedance of the
various current paths. Dimples 835b contact conductive layer 810
and/or intermediate layer 820 and provide cooling chamber with
support and dimension and define various fluid pathways "FP" in
cooling chamber 835a. Pump 840d supplies cooling fluid to inflow
tube 840a and outflow tube 840b returns cooling fluid to cooling
system 840. Cooling module 840a may include a refrigeration system,
a Peltier device, a vortex cooling device, a heat exchanger, ice,
etc.
[0087] As disclosed hereinabove, intermediate layer 820 reduces the
current density at the leading edge 805 of cooled return pad 800,
dissipates energy and/or conveys heat from hot spots thus providing
even heat distribution across the cooled return pad 800. Even
distribution of heat across the cooled return pad 800 enables
cooling system 840 to more efficiently remove heat and reduce the
temperature of cooled return pad 800.
[0088] Seal along edge 835c is formed between conductive layer 810
and backing layer 835, and between intermediate layer 820 and
backing layer 835. Cooling chamber 835a, formed between backing
layer 835 and at least a portion of conductive layer 810 and a
portion of intermediate layer 820, is configured to allow fluid to
flow therethrough. Seal along edge 835c may be formed mechanically,
i.e. clamping, crimping, etc., or by bonding, i.e. adhesive,
ultrasonic bonding, etc, or by other suitable sealing technique.
Cooling chamber 835a may be formed over intermediate layer,
conductive layer or both.
[0089] FIG. 9 illustrates an electrosurgical system 900 including
an electrosurgical generator 810, an active electrode 816, a cooled
return pad 800 and a cooling fluid supply system 840.
Electrosurgical generator 810 supplies electrosurgical energy to
active electrode 816 through supply cable 814 and return pads 800
returns electrosurgical energy to electrosurgical generator 810
through return cable 818. Return cable 818 may also supply power DC
power from the electrosurgical generator to cooling device in the
return pads 800.
[0090] Cooling supply system 840 includes a cooling supply tube 841
that connects to a cooling supply 840c, a cooling return tube 842
that connects to the cooling return 840e and a pump 840d. In one
embodiment, pump 840d supplies cooling fluid to the cooled return
pads 800 through cooling supply 840 and cooling fluid supply tube
841. Cooling fluid from the return pad 800 then returns to cooling
system 840 through cooling fluid return tube 842 and cooling return
840e. Cooling supply system 840 may use any suitable supply for the
cooling fluid, such as, for example, a saline drip bag or potable
water supply. Cooling supply system 840 may circulate fluid thus
relying on the ambient temperature to cool the fluid or cooling
system supply 840 may include a variety of mechanism that are
designed to cool the fluid, such as, for example, a refrigeration
unit, a Peltier device, a heat exchanger, etc.
[0091] In use, a clinician connects supply cable 814 of
electrosurgical return pad 800 to electrosurgical generator 810 and
places return pad 800 in contact with patient "P" skin. Cooling
device on return pad 800 may be connected to an energy supply such
as, for example, an electrical energy source (not shown) or a
cooling fluid supply system 840. An active cooling layer or device
on return pad 800 may be enabled by providing electrical power or
cooling fluid flow. A passive cooling device or layer may be
enabled by exposing the device or layer to ambient air.
Electrosurgical generator 810 generates electrosurgical energy and
supplies the electrosurgical energy to the patient via an active
electrode 816.
[0092] Return pad 800 in electrosurgical system 900 may include one
or more the above identified features in any of the embodiments of
the present disclosure.
[0093] In yet another embodiment, cooling supply system 840 may
include one or more chemicals that actively cool the return pads
800 in which the one or more chemicals may react to cool the return
pads 800. For example, cooling supply tube 841 may include two
lumens and may supply two fluids that create an endothermic
reaction when released and combine in the cooling chamber. Cooling
supply system may use other suitable methods of chemical cooling
the return pad 800.
[0094] Return Pad Heating
[0095] FIGS. 10A-10C illustrate other embodiments of the present
disclosure having heated return pads 1000, 1010. Heated return pads
1000, 1010 are configured in such a manner that the return pads are
heated either prior to or after applying the return pad to a
patient.
[0096] With reference to FIG. 10A, heated return pad 1000 includes
a heating layer 913 for heating at least a portion of the return
pad 1000. As discussed hereinbelow, heating layer 913 may be an
active heating layer, e.g., an electric heating means, or heating
layer 913 may be a passive heating layer, e.g., one or more
materials that create an exothermal chemical reaction. One purpose
of the heating layer 913 is to preheat at least a portion of the
contact layer 915 to a temperature similar to the temperature of
patient's skin, typically between about 30.degree. C. and
35.degree. C., thus eliminating or reducing patient discomfort that
may be associated with adhering a cold return pad 1000 to patient's
skin.
[0097] Heated return pad 1000 also includes a contact layer 915, a
conductive layer 910, and a backing layer 912. A cable 918 connects
to conductive layer 910 and, in some embodiments, may connect to
heating layer 913. The composition and function of contact layer
915, conductive layer 910, and backing layer 912 are described
hereinabove. Heating layer 913, as described hereinbelow may be
incorporated into any of the embodiments described herein or any
combination of embodiments.
[0098] Heating layer 913 may be in thermal communication with
contact layer 915 through conductive layer 910, as illustrated in
FIG. 10A. Conductive layer 910 thermally conducts heat energy
generated by the heating layer 913 from heating layer 913 to
contact layer 915. Alternatively, at least a portion of heating
layer 913 may be in direct contact with the contact layer 915 and
thereby directly heat contact layer 915. In yet another embodiment,
such as is illustrated in FIG. 10C, heating layer 913 may be at
least partially positioned within contact layer 915 or the
functionality of the heating layer 913 may be incorporated into
contact layer 915.
[0099] FIG. 10B is a top view of the return pad 1000 of FIG. 10A
(shown disposed within the active heating layer 913) and includes
an electric heater element 913a and a substrate 913b. Electric
heater element 913a may be disposed on substrate 913b or heater
element 913a may be disposed between two substrates. One example of
a suitable heater is a thermofoil heater manufactured by Minco
under the trademark Kapton.TM.. Substrate 913b may electrically
insulate heater element 913a from conductive layer 910 while
allowing heat energy to transfer from heating layer 913 to
conductive layer 910.
[0100] Cable 918 is configured to supply electric current to heater
element 913a from the electrosurgical generator or other suitable
power source. Heater element 913a may also be a resistive-type
heater and may be powered with AC or DC current. For example,
heater element 913a may be powered by the electrosurgical generator
110 with a frequency of about 500 kHz, 120 VAC or 50 VDC.
[0101] Various types of heaters could be used for the heating layer
913 provided the heater is sufficiently thin and insertable into
return pad 1000 and/or sufficiently flexible as to not add an
appreciable amount of stiffness to the return pad 1000. Heater
element 913a (when disposed within the heater) may be formed from a
single element, as illustrated in FIG. 10B, or heater may be formed
with several heater elements arranged in parallel. For example, the
thermofoil heater manufactured by Minco under the trademark
Kapton.TM. has a suitable thickness of approximately 7 mils.
[0102] In yet another embodiment, as illustrated in FIG. 10C,
heating element 913b is at least partially disposed in at least a
portion of contact layer 915a and performs the function of the
heating layer 913 in FIGS. 10A and 10B. Conductive layer 910 is
disposed between the backing layer 912 and the contact layer
915.
[0103] Again with reference to FIG. 10A, other technologies may be
employed to perform the same or similar functions as heating layer
913. For example, a chemical, exothermic pack (not shown) may be
used to generate a sufficient amount of energy to heat the contact
layer 915 to a target temperature. Exothermic pack may be manually
activated, automatically activated when connected to the
electrosurgical generator or activated when the return pad is
removed from the packaging.
[0104] In operation of one embodiment, heating layer 913 pre-heats
the contact layer 915 prior to the application of the return pad
1000 to a patient's skin. The contact layer 915 is pre-heated to a
temperature about equal to, or slightly less than, the surface
temperature of skin to prevent patient discomfort that may be
experienced when the contact layer 915, at room temperature, or
approximately 22.degree. C., is placed on skin at the body
temperature, or approximately 35.degree. C.
[0105] Heating layer 913 is capable of providing a sufficient
amount of energy to heat contact layer 915 to a target temperature.
The target temperature may vary based on the specific application
and use. For example, the target temperature may range from
30.degree. C. to 35.degree. C. for application and use on a human
and the upper limit may be as high as 39.degree. C. for
veterinarian use.
[0106] The energy delivered by the heating layer 913, e.g., the
rate of power delivered and/or the total amount of energy
delivered, may be specifically matched to the size and/or volume of
contact layer 915. For example, to heat and maintain a 3.times.3
inch return pad at a target temperature may require a lower rate of
energy delivery and less total energy than what may be required to
heat and maintain a 4.times.4 inch return pad.
[0107] The rate of power delivery and/or the total amount of energy
delivered can be easily calculated if the energy source is
chemical, such as, for example, an exothermic pack. The exothermic
pack may only last for a few minutes and may provide a sufficient
amount of heat energy to heat the contact layer 915 to the target
temperature. The heating capacity of the exothermic pack may be
varied to match the size and/or volume of the contact layer
915.
[0108] A heating layer 913 that receives energy from an electrical
energy source may require one or more safety features to ensure
that the temperature of the contact layer 915 does not exceed a
target temperature. For example, with reference to FIGS. 10B and
10C, temperature sensor 914b may be used to measure the temperature
of the return pad. An electrical energy source, e.g., the
electrosurgical generator 110, then controls the current to heating
layer 913 to maintain return pad 1000 at a target temperature.
[0109] Various safety measures may be employed to insure that
heating layer 913 does not overheat heated return pad 1000. For
example, one or more devices 914c may be incorporated in or
associated with heating element 913a to interrupt or limit the
current supplied to the heating element 913b. Device 914a may be a
current limiting fuse, a thermal cut-off device, a timer-type
device or any suitable device that may be incorporated into the
circuit and/or system to prevent the return pad 1000 from exceeding
the target temperature range.
[0110] Other safety measures may be incorporated into the
electrosurgical generator 110. For example, electrosurgical
generator 110 may employ existing circuitry to measure the
temperature of the return pad or to measure the amount of current
supplied to the heating element 913a. Electrosurgical generator 110
may terminate the supply of current when a predetermined
temperature is obtained or after a predetermined amount of energy
is supplied to the return pad 1000. Alternatively, new hardware
and/or new software may be incorporated into the electrosurgical
generator 110 to detect when a return pad 1000 is initially
connected to the electrosurgical generator. Connecting the return
pad 1000 may cause the electrosurgical generator 110 to
automatically heat the return pad 1000 for a predetermined period
of time or until a predetermined amount of energy is delivered to
the return pad 1000. The predetermined period of time and
predetermined amount of energy may be determined by the clinician
or electrosurgical generator 110 may be configured to automatically
determine or calculate the period of time based on the size and/or
type of return pad.
[0111] Current supplied to the heating element 913a may be
terminated when the electrosurgical generator 110 detects that the
return pad 1000 is in contact with tissue. The return electrode
monitor (REM) 112, or any other suitable contact quality system,
may be used to determine when the return pad 1000 is in contact
with patient tissue.
[0112] In use, return pad 1000 is connected to the electrosurgical
generator 110. Electrosurgical generator 110 automatically switches
power to heater element 913a and supplies a low level current.
Current is limited to an amount that will heat the return pad 1000
to a target temperature without resulting in an over-temperature
condition. At least periodically, the REM 112 may be activated to
determine if the return pad 1000 is applied to patient. After
contact current to the heater element 913a is switched off, the
return pad 1000 is enabled and the system is ready for activation.
If temperature sensor 913b is present, temperature at the return
pad 1000 may be measured and the current to the heater element 913a
may be automatically adjusted by the electrosurgical generator 110
to maintain return pad 1000 at a target temperature. Safety devices
914c, if present, may disable the current flow if the return pad
1000 exceeds a maximum temperature.
[0113] In an alternative application, a heating layer, such as
heating layer 913, may be employed on the back of a return
electrode that could be used for patient heating. Typically,
patients are kept warm with blankets and/or water or air flow
heating systems. According to an embodiment of the disclosure, a
large surface area pad, constructed with a backing layer, a
thermofoil heater(s), and an adhesive hydrogel could provide a low
profile solution to patient heating. The adhesive hydrogel may
provide a uniform and comfortable contact area. Temperature sensing
devices, such as thermistors or thermocouples, may be included in
such a system to regulate temperature and ensure that the pad does
not get too warm.
[0114] While several embodiments of the disclosure have been shown
in the drawings, it is not intended that the disclosure be limited
thereto, as it is intended that the disclosure be as broad in scope
as the art will allow and that the specification be read likewise.
For example, the return pad may include a plurality of electrodes
or may include a plurality of novel intermediate layers. Therefore,
the above description should not be construed as limiting, but
merely as exemplifications of various embodiments. Those skilled in
the art will envision many other possible variations that are
within the scope and spirit of the disclosure as defined by the
claims appended hereto.
* * * * *