U.S. patent application number 13/445532 was filed with the patent office on 2012-08-02 for electrosurgical instrument and method of use.
This patent application is currently assigned to SurgRx, Inc.. Invention is credited to John H. Shadduck, Csaba Truckai.
Application Number | 20120197248 13/445532 |
Document ID | / |
Family ID | 46303336 |
Filed Date | 2012-08-02 |
United States Patent
Application |
20120197248 |
Kind Code |
A1 |
Truckai; Csaba ; et
al. |
August 2, 2012 |
ELECTROSURGICAL INSTRUMENT AND METHOD OF USE
Abstract
Embodiments of the invention provide an electrosurgical jaw
structure comprising first and second opposing jaws one or both of
which include 3D variable resistance bodies. The jaw structure can
be part of the working end of a surgical instrument. In one
embodiment, the jaws can comprise first and second energy-delivery
jaw surfaces having first and second 3D variable resistance bodies,
with the jaw surface configured to be coupled to an Rf source. The
3D variable resistance bodies can define different
temperature-resistance curves. The 3D bodies can be configured to
control ohmic heating of tissue by modulating the delivery of Rf
energy to tissue. Jaw structures having the 3D bodies can be used
to engage and produce high strength tissue welds in targeted tissue
including tissue volumes having varying tissue types. Such jaw
structures can be configured to simultaneously apply different
energy levels to each tissue type within the tissue volume.
Inventors: |
Truckai; Csaba; (Saratoga,
CA) ; Shadduck; John H.; (Menlo Park, CA) |
Assignee: |
SurgRx, Inc.
Redwood City
CA
|
Family ID: |
46303336 |
Appl. No.: |
13/445532 |
Filed: |
April 12, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12034407 |
Feb 20, 2008 |
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13445532 |
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10993413 |
Nov 18, 2004 |
7354440 |
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12034407 |
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10032867 |
Oct 22, 2001 |
6929644 |
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10993413 |
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10934755 |
Sep 3, 2004 |
7189233 |
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10032867 |
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60523567 |
Nov 19, 2003 |
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60563424 |
Apr 19, 2004 |
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60500746 |
Sep 4, 2003 |
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Current U.S.
Class: |
606/33 ;
606/41 |
Current CPC
Class: |
A61B 2018/00148
20130101; A61B 2018/1412 20130101; A61B 2018/0016 20130101; A61B
2018/00404 20130101; A61B 2018/00125 20130101; A61B 18/1445
20130101; A61B 2018/1455 20130101; A61B 2018/0063 20130101; A61B
18/1442 20130101; A61B 2018/00083 20130101; A61B 2018/00077
20130101; A61B 2018/00601 20130101 |
Class at
Publication: |
606/33 ;
606/41 |
International
Class: |
A61B 18/18 20060101
A61B018/18; A61B 18/14 20060101 A61B018/14 |
Claims
1. An electrosurgical jaw structure for applying Rf energy to
tissue, the structure comprising: first and second jaws defining
first and second tissue engagement surfaces, respectively, at least
one of the engagement surfaces including opposing polarity
conductor portions, the conductor portions configured to be coupled
to an Rf energy source; and a polymeric matrix portion positioned
within at least one tissue engagement surface, the matrix
configured to modulate at least one parameter of Rf energy
application, the at least one parameter including at least one of
voltage, current or impedance.
2. A jaw structure of claim 1, wherein the matrix is configured to
modulate Rf energy application from a conductor portion in the
engagement surface to adjacent tissue.
3. A jaw structure for applying energy to tissue, the structure
comprising: first and second jaw bodies extending along an axis and
defining first and second tissue-engaging surfaces, respectively;
at least one jaw body comprising a three dimensional matrix of a
temperature-responsive variable impedance material for impedance
matching with engaged tissue, the matrix configured to modulate
current density in the engaged tissue; and opposing polarity
conductor regions in the tissue-engaging surfaces, the regions
configured to be coupled to a voltage source for providing
contemporaneous current flow paths though engaged tissue.
4. The jaw structure of claim 3, wherein the first and second jaw
bodies comprise first and second temperature-responsive variable
impedance matrices, respectively, the first matrix configured to be
coupled to the voltage source in a first circuit and the second
matrix configured to be coupled to the voltage source in a second
circuit.
5. The jaw structure of claim 3, wherein the first circuit is a
series circuit and the second circuit is a parallel circuit.
6. An electrosurgical jaw structure for controlled application of
energy to tissue, the structure comprising: first and second jaw
bodies defining first and second tissue-engaging surfaces,
respectively, at least one of the jaw bodies comprising a
three-dimensional (3D) matrix of a temperature-responsive variable
impedance material for impedance matching with engaged tissue to
thereby provide contemporaneous current flow paths through engaged
tissue, the 3D matrix positioned within at least one of the jaw
bodies and configured to modulate current density in the engaged
tissue; and opposing polarity conductor regions positioned on at
least one of the tissue-engaging surfaces, the regions configured
to be coupled to a voltage source.
7. The electrosurgical jaw structure of claim 6, wherein the matrix
defines spaced apart current flow paths (a) between the opposing
polarity conductor regions proximate a tissue-engaging surface, and
(b) between the opposing polarity conductor regions at an interior
of at least one jaw body.
8. The electrosurgical jaw structure of claim 6, wherein a portion
of the first jaw body comprises a first 3D matrix of a
temperature-responsive variable impedance material and a portion of
the second jaw body comprises a second 3D matrix of a
temperature-responsive variable impedance material.
9. The electrosurgical jaw structure of claim 8, wherein the first
and second 3D matrices have different impedance
characteristics.
10. The electrosurgical jaw structure of claim 9, wherein the
different impedance characteristics include at least one of a
baseline impedance or a temperature impedance response.
11. The electrosurgical jaw structure of claim 8, wherein the first
and second matrices are coupled in parallel circuits with the
voltage source.
12. The electrosurgical jaw structure of claim 6, wherein the
matrix defines a positive temperature coefficient of impedance.
13. The electrosurgical jaw structure of claim 6, wherein the
matrix defines a negative temperature coefficient of impedance.
14. An electrosurgical jaw structure comprising: first and second
jaw bodies defining first and second energy-delivery surfaces, at
least one jaw body comprising first and second opposing polarity
portions; and a temperature-responsive variable impedance body
positioned intermediate the first and second opposing polarity
portions.
15. The electrosurgical instrument of claim 14, wherein a portion
of the variable impedance body is exposed on one of the first or
the second energy delivery surfaces.
16. An electrosurgical jaw structure for application of Rf energy
to tissue, the structure comprising: first and second tissue
engagement means defining first and second tissue engagement
surfaces, respectively; opposing polarity conductor means coupled
to the tissue engagement means, the conductor means configured to
be coupled to an Rf source means; and an Rf modulating means
portion coupled to at least one tissue engagement surface, the Rf
modulating means configured to modulate at least one parameter of
Rf energy application from a conductor means portion in an
engagement surface to the adjacent tissue, the parameter including
at least one of voltage, current or impedance.
17-27. (canceled)
Description
CROSS-REFERENCES TO RELATED ED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 10/993,413, No. 021447-000561US), filed Nov. 18, 2004, which
claimed the benefit of U.S. Provisional Application Nos. 60/523,567
(Docket No. 021447-000560US), filed Nov. 19, 2003, and of
60/563,424 (Docket No. 021447-002300US), filed Apr. 19, 2004; and
was a continuation-in-part of co-pending U.S. patent application
Ser. Nos. 10/032,867 (Docket No. 021447-000500US), filed Oct. 22,
2001; and of 10/934,755 (Docket No. 021447-000551US), filed Sep. 3,
2004, which claimed the benefit of U.S. Provisional Application No.
60/500,746 (Docket No. 021447-000550US), filed on Sep. 4, 2003, the
full disclosures of which are incorporated herein by reference.
[0002] This application is also related to but does not claim the
benefit of co-pending U.S. patent application Ser. Nos. 10/351,449
(Docket No. 021447-000540US), filed Jan. 22, 2003, and of
10/993,210 (Docket No. 021447-002310US), filed Nov. 18, 2004 (now
U.S. Pat. No. 7,309,849), each of which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0003] Embodiments of the invention relate to medical devices and
methods and more particularly relate to an electrosurgical jaw
structure with at least one impedance matching three-dimensional
body within a jaw for causing controlled ohmic heating of engaged
tissue, together with multiple circuitry components for
intraoperative control of voltage applied to the engaged
tissue.
[0004] Radiofrequency (Rf) energy has been employed for surgical
applications for the last 80 or more years. More recently, Rf and
other energy sources such as ultrasound and lasers have been
developed to coagulate, seal or join together tissues volumes in
open and laparoscopic surgeries. Particular surgical applications
relate to sealing blood vessels which contain considerable fluid
pressure therein. In general, no instrument working ends using any
energy source have proven reliable in creating a "tissue weld" or
"tissue fusion" that has very high strength immediately
post-treatment. For this reason, the commercially available
instruments, typically powered by Rf or ultrasound, are mostly
limited to use in sealing small blood vessels and tissues masses
with microvasculature therein. Current Rf devices fail to provide
seals with substantial strength in various tissues and anatomical
structures including anatomic structures having walls with
irregular or thick fibrous content, in bundles of disparate
anatomic structures, in substantially thick anatomic structures, or
in tissues with thick fascia layers (e.g., large diameter blood
vessels).
[0005] In a basic bi-polar Rf jaw arrangement, each face of
opposing first and second jaws comprises an electrode and Rf
current flows across the captured tissue between the opposing
polarity electrodes. Such prior art Rf jaws that engage opposing
sides of tissue typically cannot cause uniform thermal effects in
the tissue--whether the captured tissue is thin or substantially
thick. As Rf energy density in tissue increases, the tissue surface
becomes desiccated and resistant to additional ohmic heating.
Localized tissue desiccation and charring can occur almost
instantly as tissue impedance rises, which then can result in a
non-uniform seal in the tissue. Currently available Rf jaws can
cause further undesirable effects by propagating Rf density
laterally from the engaged tissue thus causing unwanted collateral
thermal injury or damage.
[0006] The commercially available Rf sealing instruments typically
adopt a "power adjustment" approach to attempt to control Rf flux
in tissue wherein a system controller rapidly adjusts the level of
total power delivered to the jaws' electrodes in response to
feedback circuitry coupled to the electrodes that measures tissue
impedance or electrode temperature. Another approach used consists
of jaws designs that provide spaced apart of offset electrodes
wherein the opposing polarity electrode portions are spaced apart
by an insulator material--which may cause current to flow within an
extended path through captured tissue rather that simply between
opposing electrode surfaces of the first and second jaws.
Electrosurgical grasping instruments having jaws with
electrically-isolated electrode arrangements in cooperating jaws
faces were proposed by Yates et al. in U.S. Pat. Nos. 5,403,312;
5,735,848; and 5,833,690. However, a need exists for
electrosurgical instruments which can reliably create high strength
seals in one or more anatomical structures including anatomic
structures having walls with irregular or thick fibrous content, in
bundles of disparate anatomic structures, in substantially thick
anatomic structures, or in tissues with thick fascia layers such as
larger arteries and veins.
BRIEF SUMMARY OF THE INVENTION
[0007] Embodiments of the invention provide novel electrosurgical
systems, structures and methods to deliver energy to targeted
tissue volumes in a controlled manner to thermally weld or seal
targeted tissue. Embodiments of the system allow for a "one-step"
welding-transecting procedure wherein the surgeon can
contemporaneously (i) engage tissue within a jaw structure (ii)
apply Rf energy to the tissue, and (iii) transect the tissue.
[0008] In various embodiments, the invention provides an
electrosurgical system having a jaw structure that is configured to
apply different energy levels across the jaws' engagement surfaces
using "smart" materials that modulate the delivery of energy to
tissue, without the need for complex feedback circuitry coupled to
thermocouples or other sensors in the jaw structure. These
materials can include positive temperature coefficient of
resistance (PTC) materials which are used to construct
three-dimensional (3D) temperature-responsive variable resistance
bodies integral to or carried by the jaw structure. Specific
embodiments provide an electrosurgical jaw structure having 3D
temperature-responsive variable resistance bodies (which can also
be variable impedance bodies as is described herein). Jaw
structures having these temperature responsive variable impedance
bodies can be used to modulate the delivery of Rf energy to create
high strength thermal welds or seals in targeted tissues. Such jaw
structure can also be used to engage and weld tissue bundles having
varying tissue types, (e.g., fat, blood vessels, fascia, etc.). In
specific embodiments, jaw structures having 3D
temperature-responsive variable resistance bodies can be configured
to simultaneously apply different energy levels to each different
tissue type.
[0009] Many embodiments of the invention provide an electrosurgical
jaw structure comprising first and second opposing jaws one or both
of which include 3D variable resistance bodies. The jaw structure
can be part of the working end of a number surgical instruments
known in the art such as surgical forceps or scissors. In one
embodiment, the electrosurgical jaws can comprise first and second
energy-delivery jaw surfaces having first and second variable
resistance bodies, with the jaw surface configured to be coupled in
series to an Rf source. The Rf source can utilize the first and
second variable resistance bodies to control Rf energy parameters
such as voltage and current within engaged tissue. In another
embodiment, the electrosurgical jaws can comprise first and second
3D variable resistance bodies or matrices that define different
temperature-resistance curves. The 3D variable resistance bodies
can be configured to control ohmic heating of tissue by modulating
the delivery of Rf energy to tissue. The bodies can be selected
based on their resistance curves (e.g., as is shown in FIGS. 4A and
4B) in order to produce a desired level of control of ohmic
heating.
[0010] Another embodiment provides and electrosurgical jaw
structure comprising first and second jaw bodies defining first and
second tissue-engaging surfaces, respectively. At least one of the
jaw bodies comprises a three-dimensional (3D) matrix of a
temperature-responsive variable impedance material for impedance
matching with engaged tissue to thereby provide contemporaneous
current flow paths through engaged tissue. The 3D matrix is
positioned within at least one of the jaw bodies and is configured
to modulate current density in the engaged tissue. Also at least
one of the tissue engaging surfaces includes opposing polarity
conductor regions positioned on the at least one surface. The
regions are configured to be coupled to a voltage source such as an
Rf source. Also, the 3D matrix can include first and second
matrices having different impedance characteristics such as
baseline impedance or a temperature impedance response.
[0011] Yet another embodiment of the electrosurgical jaw structure
comprises first and second jaw bodies defining first and second
energy-delivery surfaces with at least one jaw body comprising
first and second opposing polarity portions. A
temperature-responsive variable impedance body is positioned
intermediate the first and second opposing polarity portions. Also,
a portion of the variable impedance body can be exposed on one of
the first or the second energy delivery surfaces.
[0012] In an exemplary embodiment of a method for using a jaw
structure having 3D variable impedance bodies, the jaw structure is
used to engage tissue and apply Rf energy to the engaged tissue T
to cause ohmic heating therein. After the tissue is elevated in
temperature, heat is conducted from the engaged tissue back to the
variable impedance bodies to thereby elevate temperatures in at
least the surfaces region of the body. When the temperature of the
matrix material adjacent the ohmically heated tissue is elevated to
a selected temperature, the resistance of the matrix material
increases significantly. Current flow can be reduced accordingly or
even terminated so as to precisely control energy densities in the
engaged tissue. In this way, the matrices can be used to produce
more uniform heating of tissue and in turn, more uniform welds.
[0013] In various embodiments of methods of the invention, the
targeted volume of tissue can be uniformly elevated to the
temperature needed to denature proteins therein in order to create
a more effective "weld" in tissue. To create a "weld" in tissue,
collagen, elastin and other protein molecules within an engaged
tissue volume can be denatured by breaking the inter- and
intra-molecular hydrogen bonds--followed by re-crosslinking on
thermal relaxation to create a fused-together tissue mass. It can
be easily understood that ohmic heating in tissue--if not
uniform--can at best create localized spots of truly "welded"
tissue. Such a non-uniformly denatured tissue volume still is
"coagulated" and will prevent blood flow in small vasculature that
contains little pressure. However, such non-uniformly denatured
tissue may not create a seal with significant strength (e.g. leak
strength), for example in 2 mm. to 10 mm. arteries that contain
high pressures.
[0014] Various embodiments of system and methods of the invention
relate to creating thermal "welds" or "fusion" within native tissue
volumes. The alternative terms of tissue "welding" and tissue
"fusion" are used interchangeably herein to describe thermal
treatments of a targeted tissue volume that result in a
substantially uniform fused-together tissue mass, for example in
welding blood vessels that exhibit substantial burst strength
immediately post-treatment. The strength of such welds is desirable
(i) for permanently sealing blood vessels in vessel transection
procedures, (ii) for welding organ margins in resection procedures,
(iii) for welding other anatomic ducts wherein permanent closure is
required, and also (iv) for vessel anastamosis, vessel closure or
other procedures that join together anatomic structures or portions
thereof. The welding or fusion of tissue as disclosed herein is to
be distinguished from "coagulation", "sealing", "hemostasis" and
other similar descriptive terms that generally relate to the
collapse and occlusion of blood flow within small blood vessels or
vascularized tissue. For example, any surface application of
thermal energy can cause coagulation or hemostasis--but does not
fall into the category of "welding" as the term is used herein.
Such surface coagulation does not create a weld that provides any
substantial strength in the affected tissue.
[0015] At the molecular level, the phenomena of truly "welding"
tissue as disclosed herein may not be fully understood. However,
the authors have identified the parameters at which tissue welding
can be accomplished. An effective "weld" as disclosed herein
results from the thermally-induced denaturation of collagen,
elastin and other protein molecules in a targeted tissue volume to
create a transient liquid or gel-like proteinaceous amalgam. In one
embodiment of a method the invention, this can be achieved by
delivering energy to target tissue to provide a selected energy
density in the targeted tissue to cause hydrothermal breakdown of
intra- and intermolecular hydrogen crosslinks in collagen and other
proteins. The denatured amalgam is maintained at a selected level
of hydration--without desiccation--for a selected time interval
which can be very brief. The targeted tissue volume is maintained
under a selected very high level of mechanical compression to
insure that the unwound strands of the denatured proteins are in
close proximity to allow their intertwining and entanglement. Upon
thermal relaxation, the intermixed amalgam results in "protein
entanglement" as re-crosslinking or renaturation occurs to thereby
cause a uniform fused-together mass.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a perspective view of an exemplary surgical
instrument with and a jaw structure carrying variable resistance
matrix bodies for tissue welding corresponding to the invention,
the matrix bodies coupled to an Rf source via series and parallel
circuits for modulating ohmic heating in engaged tissue.
[0017] FIG. 2 is a graphic representation of opposing jaws engaging
a tissue bundle comprising large blood vessels, fatty tissue and
small blood vessels embedded in the fat.
[0018] FIG. 3 is a schematic sectional view of the jaw structure of
FIG. 1 taken along line 3-3 of FIG. 1 showing the variable
impedance matrices in each jaw together with the series and
parallel circuits.
[0019] FIG. 4A is a diagram of the temperature-resistance curves of
exemplary variable resistance matrix bodies as in FIG. 3.
[0020] FIG. 4B is a diagram similar to that of FIG. 4A illustrating
alternative temperature-resistance curves of variable impedance
matrix bodies.
[0021] FIG. 5 is a block diagram of the series and parallel
electrical circuit components of the working end of FIG. 3.
[0022] FIG. 6 is a sectional schematic view of the variable
impedance matrix bodies showing potential current flow paths in the
engaged tissue and the matrix bodies.
[0023] FIG. 7 is a perspective view of an alternative instrument
with and a jaw structure carrying variable impedance matrix bodies
together with blade means for transecting tissue.
[0024] FIG. 8 is a sectional view of the jaw structure of FIG. 7
taken along line 8-8 of FIG. 7 showing the variable impedance
matrices in each jaw together blade means.
[0025] FIG. 9 is a sectional schematic view of the jaw structure of
FIGS. 7-8 that illustrates potential current flow paths in the
engaged tissue and the matrix bodies.
[0026] FIG. 10A is a sectional view of the jaw structure of FIGS.
7-8 illustrating an initial step in a method of the invention
wherein Rf current flow paths cross the engaged tissue to cause
ohmic heating therein.
[0027] FIG. 10B is a sectional view of the jaw structure of FIG.
10A depicting a subsequent step in a method of the invention with
modulated Rf current flow paths in the engaged tissue.
[0028] FIG. 10C is another sectional view similar to FIGS. 10A-10B
depicting a step in a method of the invention wherein Rf current
flow paths within an interior of a variable impedance matrix
prevent sparking at a jaw engagement surface.
[0029] FIG. 10D is another view similar to FIGS. 10A-10C depicting
a step in a method of the invention wherein Rf current flow paths
occur in different axial regions of the jaws depending on local jaw
compression.
[0030] FIG. 11 is a perspective view of an alternative
high-compression jaw structure carrying 3D variable impedance
matrix bodies that is adapted for one-step tissue welding and
transection corresponding to the invention, the matrix bodies
coupled to an Rf source via series and parallel circuits.
[0031] FIG. 12 is a schematic sectional view of the jaw structure
of FIG. 11 taken along line 12-12 of FIG. 11 showing the variable
impedance matrices in each jaw together with the series and
parallel circuits.
[0032] FIG. 13 is an enlarged sectional view of a portion the jaw
structure of FIGS. 11-12 showing the potential current paths in
engaged tissue and the variable impedance 3D matrix bodies during
operation.
[0033] FIGS. 14A-14C are schematic sectional views of the jaw
structure of FIGS. 11-13 with elongate jaws progressively engaging,
welding and transecting a tissue bundle.
[0034] FIG. 15 is a sectional perspective view of a portion an
alternative jaw structure with capacitive components combined with
variable impedance matrix bodies.
[0035] FIG. 16 is a sectional view of a portion an alternative jaw
structure with negative temperature coefficient components combined
with capacitive and variable impedance matrix bodies.
DETAILED DESCRIPTION OF THE INVENTION
[0036] Various embodiments of the invention provide systems and
methods to deliver energy to targeted tissue volumes in a
controlled manner to thermally weld or seal targeted tissue.
Specific embodiments provide a system including an electrosurgical
jaw structure configured to contemporaneously (i) engage tissue
between paired jaws, (ii) deliver energy to the tissue, and (iii)
optionally, transect the tissue to provide a "one-step"
welding-transecting procedure. Embodiments of the invention also
provide an electrosurgical jaw structure that can engage and weld
tissue bundles, defined herein as bundles of disparate tissue types
(e.g., fat, blood vessels, fascia, etc.). For the welding of tissue
bundles, the jaw surfaces can apply different energy levels to each
different tissue type simultaneously. Related embodiments provide
an electrosurgical system that can apply different energy levels
across the jaws engagement surfaces using "smart" materials without
the need for complex feedback circuitry coupled to thermocouples or
other sensors in the jaw structure.
[0037] It has been found that very high compression of engaged
tissue in combination with controlled Rf energy delivery is
desirable for welding the engaged tissue volume. Additionally, it
has been found that ohmic heating and dehydration of tissue in the
process of closing the jaw structure greatly assists in the
ultimate compression of tissue (particularly tissue bundles) to the
desired thickness of a membrane. With the engaged tissue in
membrane thickness in a controlled gap between the engagement
surfaces of the jaw structure, e.g., from about 0.001'' to about
0.05'', the method for controlling ohmic heating in tissue can be
optimized (as described below).
[0038] FIG. 1 illustrates an embodiment of a system 80 for the
application of energy to tissue energy to thermally weld or seal
targeted tissue. The system can comprise a surgical instrument 90,
a voltage source 150A and controller 150B. Instrument 90 can be a
forcep-type instrument as shown in the figure, as well any number
of surgical instruments known in the art, including e.g., a
scissors, clamps and various minimally invasive surgical
instruments known in the art. Surgical instrument 90 includes a
working end or electrosurgical jaw structure 100A. Jaw structure
100A is coupled to voltage source 150A and controller 150B for
controlling one or more energy delivery parameters, such as the
duration of energy delivery (FIG. 3). In preferred embodiments,
voltage source 150A is an Rf generator known in the art and the
energy delivery parameters are one or more Rf parameters (e.g.,
power, frequency, duty cycle, total delivered energy, etc.). In
these and related embodiments, system 80 is an electrosurgical
system for delivering energy to tissue.
[0039] In most embodiments, jaw structure 100A comprises first
(lower) jaw element 112A and second (upper) jaw element 112E that
close or approximate about axis 115 that is straight or curved.
Also, the jaw elements can be of any curved or straight shape
suitable for open and/or endoscopic surgeries with a scissors-type
actions or with one or more can mechanisms as is known in the art.
The jaws also can carry a sliding cutting blade as will be
described below.
[0040] Referring now to FIG. 2, a discussion of the electrosurgical
functionality of embodiments of system 80 will now be presented. In
FIG. 2, the opposing jaws 112A and 112B are depicted schematically
as engaging a tissue bundle T of differentiated tissue types--which
is a common occurrence in open and endoscopic surgeries. FIG. 2
depicts a longitudinal sectional view of jaws 112A and 112B and an
engaged tissue bundle T that contains, for example, insulative fat
118, large blood vessels 120 and smaller embedded blood vessels
122. The gap between the jaws is not-to-scale, and in an actual jaw
structure, the compressed tissue bundle T could be reduced to the
thickness of a thin membrane. In an actual procedure, the tissue
bundle would likely also contain one or more of fascia, ligamentous
tissues and other tissues that could exhibit a wide range of
hydration levels, electrolyte levels etc. which in turn, could
locally alter tissue impedance, compressibility etc. For
convenience, only three tissue types with three impedance levels
are shown in FIG. 2; however this figure is only exemplary, and the
jaws can be used to engage any number of tissue types (e.g.,
dermal, muscle, cartilage, etc.) having a variety of physical
properties (e.g. hydration, electrolyte concentrations, etc.). As
indicated graphically by the micro-currents MC in FIG. 2,
embodiments of the electrosurgical jaw structures of system 80 can
be configured to contemporaneously modulate energy densities/energy
delivery across the various tissue types in the bundle T according
to the impedance of one or more of the engaged tissue types and/or
engaged regions within the bundle. Further, embodiments of the jaw
structures can be configured to continuously modulate energy
densities/energy delivery to each tissue type as the engaged tissue
types or regions dynamically changes in hydration, impedance,
conductivity and/or geometry. As energy is delivered, the tissue
will shrink as it dehydrates.
[0041] FIG. 3 illustrates the tissue-engaging surfaces 124A and
124B of jaws 112A and 112B. In various embodiments, the jaws can
each include or be coupled to a three-dimensional (3D)
temperature-responsive variable resistance body. In many
embodiments, the 3D temperature responsive variable resistance body
can be carried by the jaws. The lower jaw 112A carries variable
impedance body indicated at 125, also at times referred to herein
as a positive temperature coefficient of resistance (PTC) body or
matrix. The term resistance refers to the electrical resistance of
the body or matrix when its is subjected to a DC current. The body
or matrix also has an impedance when subject to an alternating
current, such as Rf current, as is used in various embodiments of
invention. In either case, the resistance or impedance of the body
or matrix varies as a function of its temperature. For ease of
discussion, the temperature varying electrical properties of the
PTC materials/bodies described herein will be described in terms of
the material's resistance as a function of temperature; however,
the material will also have an impedance that varies with
temperature in AC current scenarios. Thus while the PTC bodies
described herein are referred to as variable resistance bodies,
they also act as variable impedance bodies in AC current scenarios
such as Rf current as is used in various embodiments of invention.
Also, by the term three-dimensional, it is meant for example, that
variable impedance body 125 defines an axial dimension X and a
cross-axial dimension Y about the tissue-engaging surface, as well
as defining a substantial depth dimension Z that is orthogonal to
the plane of the tissue-engaging surface 124A. In other words, the
variable resistance body or matrix 125 has a selected thickness
dimension in various embodiments to provide a multiplicity of
varied local current flow paths through the matrix as it
dynamically responds to adjacent ohmically heated tissue, as is
discussed herein. The upper jaw 112B in one embodiment shown in
FIG. 3 carries variable impedance body 130 that again can have any
suitable depth dimension. Further description of PTC materials
(including polymer PTC compositions), their properties and methods
of manufacture may be found in Ser. No. 10/993,210 (Docket No.
021447-002310US), filed Nov. 18, 2004 (now U.S. Pat. No.
7,309,849), which is fully incorporated by reference herein.
[0042] Still referring to FIG. 3, it can be seen that lower jaw
112A can have a structural component or body 132A that is of a
suitable electrical conductor material so that it functions as an
electrode--that is indicated for convenience with a negative
polarity (-). Similarly, the upper jaw 112B has structural
component or body 132B that is has the same polarity (-) as the
lower jaw body. An electrically conductive member or electrode 140
is provided within variable impedance matrix 125 either at the
tissue-engaging surface 124A or proximate the surface as depicted
in FIG. 3. Both jaws optionally can have an insulative coating
indicated at 142 at the exterior of lower jaw 112A. Coating 142 can
positioned over all or portion of jaw 112A.
[0043] In a preferred embodiment shown in FIGS. 2 and 3, the
variable impedance matrices 125 and 130 in lower jaw 112A and upper
jaw 112B comprise a polyethylene or a medical grade silicone
polymer that is doped with conductive particles (e.g., carbon)
using doping methods known in the art. The use of such
temperature-responsive variable impedance materials is described
for related uses in co-pending U.S. patent application Ser. No.
10/351,449 filed Jan. 22, 2003 (Docket No. 021447-000540US)
entitled Electrosurgical Instrument and Method of Use; Ser. No.
10/032,867 filed Oct. 22, 2001 (Docket No. SRX-011) entitled
Electrosurgical Jaw Structure for Controlled Energy Delivery, and
in Ser. No. 10/993,210 (Docket No. 021447-002310US), filed Nov. 18,
2004 (now U.S. Pat. No. 7,309,849), entitled Polymers Compositions
Exhibiting Highly Nonlinear PTC Effects And Methods Of Fabrication,
all of which are incorporated herein by reference. Polymer positive
temperature coefficient materials are known in the field of
overcurrent protection devices that will trip and become resistive
when a selected trip current and temperature are exceeded.
[0044] Various embodiments of the temperature-responsive variable
resistance materials described herein can be fabricated from a
non-conductive polymer that exhibits two phases and geometries that
define greater and lesser conductive states. The first phase is a
crystalline or semi-crystalline state where the polymer molecules
form long chains and are arranged in a more ordered architecture.
When the temperature of the material is elevated, the polymer
molecules maintain the crystalline architecture or structure--but
eventually transition to an at least partly amorphous phase from
the crystalline state. In the amorphous state, the molecules are
aligned more randomly, and there may be a slight change in actual
material geometry. The non-conductive polymer is combined with a
dispersed, highly conductive particles, e.g., carbon nanoparticles
to form a matrix. In the crystalline phase of the polymer, the
carbon particles are packed into the crystalline boundaries and
form many conductive paths across and through the matrix material.
In this low temperature crystalline state, the polymer-carbon
matrix is engineered to have a low resistance. FIG. 4A illustrates
the positively-sloped resistance-temperature curve 130M of an
exemplary variable resistance matrix 130 of FIG. 3. Note that the
curves in FIGS. 4A and 4B can also be expressed in terms of
resistivity (which accounts for effects from the length and/or
thickness of the material as is known in the art) and will
generally have the same shape.
[0045] In an embodiment of a method of the invention using an
electrosurgical jaw structure, jaw structure 100A of FIG. 3 is used
to engage tissue and apply Rf energy to the engaged tissue T to
cause ohmic heating therein. After the tissue is elevated in
temperature, heat is conducted from the engaged tissue T back to
the variable resistance matrices 125 and 130 to thereby elevate
temperatures in at least surfaces region of the matrices 125 and
130. Details of the actual method of using the matrices to provide
high temperature and low temperature process limits are described
below. As long as the temperature increase in the matrix portion
adjacent the ohmically heated tissue does not cause a phase change
in the polymer, current can flow unimpeded through the matrix. When
the temperature of the matrix material is elevated to a selected
temperature, called a switching range herein, the temperature will
cause a phase change in the polymer (see FIG. 4A). The crystalline
structure of the polymer will disappear, the polymer volume may
expand slightly and the carbon chains that allow for conduction
across the matrix will be broken--an extraordinary increase in
resistance. The polymer-carbon matrix can define a resistance
measured in milliohms or ohms before the phase change. After the
phase change, the matrix' resistance can be measured in megaohms.
Current flow can be reduced accordingly or terminated. In this way,
embodiments using variable resistance matrices can be used to
precisely control energy densities in the engaged tissue. Such
control in turn allows for one or more of the following: 1) more
uniform heating and/or temperature distribution of the engaged
tissue; 2) a more uniform thermal affect in the engaged tissue; 3)
more uniform welds in the engaged tissue; 4) more precise control
of energy delivery parameters (e.g., rate and total energy
delivered); 5) reduced and incidence of tissue charring and/or
desiccation; and 6) reduced thermal injury/effect to non-target
tissue.
[0046] The process described above is reversible so that when a
portion of a matrix falls in temperature, the polymer component
will return to its crystalline structure and the matrix volume will
return to its original state. The conductive carbon particles will
reform into conductive paths within the interstices of the
crystalline polymer architecture. The exact same conductive paths
appear not to reform themselves after first use of the matrix, and
for this reason the polymer matrices of the invention may be
temperature cycled several times in the fabrication process which
appears to cause the material to have substantially resettable
conductive paths. In the fabrication process, the matrix can also
be treated in various processes (e.g., gamma, UV irradiation etc.)
to cross-link the polymer or co-polymers of the matrix.
[0047] Referring again to FIG. 3, various embodiments of polymer
matrix 125 can comprise at least two differentiated regions 144 and
145 that have different temperature impedance responses so as to
have different temperature-impedance curves as illustrated in FIG.
4B. The regions 144a and 144b (collectively 144) at the center of
the lower jaw and the laterally-outward edge of the jaw are
comprised of a highly conductive matrix that will only terminate
current flow therethrough at a high temperature, for example
between 100.degree. C. and 200.degree. C. as shown in FIG. 4B.
These regions 144, effectively function as the opposing polarity
conductive electrodes as the regions 144 are in contact with the
central first polarity conductor 140 and the second polarity jaw
body 132A. The lower jaw's matrix region 145 can be configured to
provide a plurality of slightly different regions 145a and 145b
that have somewhat different base resistances and/or switching
ranges as shown in FIG. 4B for reasons described below. Further,
one or both of regions 144 and 145 of matrix 135 can be positioned
intermediate opposing polarity conductor portions 140 and 132A.
[0048] In various embodiments, matrices 130 and 140 can have
impedance characteristics chosen so as to yield a selectable
relationship between the impedance characteristics of the two
matrices. Such impedance characteristics can include without
limitation, baseline impedance and temperature impedance response
including one or more of the slope, shape and switching range of
the temperature impedance response curve. For example, in one
embodiment, the matrix 130 can be have a higher or lower base
resistance and/or a steeper or flatter response curve vs. matrix
140. In one embodiment, matrix region 145 can have a base
resistance that is somewhat higher than that of matrix 130 in the
upper jaw 112B. Further the relationship between impedance
characteristics of matrices 130 and 140 can be configured to
enhance the ability of the matrices to modulate the delivery of
energy to tissue, including the ability of the matrices to modulate
or control one or more of tissue current density, tissue
temperature and peak tissue temperature.
[0049] A discussion will now be presented of the manner in which
matrices 125 and 130 can operate to modulate energy delivery in
tissue. In various embodiments, the jaw structure 100A can be
configured to utilize the two differently performing matrices 125
and 130 (e.g., as illustrated in FIG. 3) in combination with the
series and parallel circuitry of FIG. 5 to provide effective high
and low process limits for temperatures and energy densities in the
engaged tissue T. It has been found that such dynamic energy and
temperature controls are desirable for creating uniform thermal
effects in tissue to denature tissue proteins and to create high
strength welds. In one embodiment as in FIG. 3, the matrix 130 in
upper jaw 112B is configured to exhibit unique
temperature-impedance characteristics represented by the
positively-sloped curve 130M of FIG. 4B. This matrix 130 maintains
a relatively low base resistance over a selected base temperature
range with a dramatically increases resistance above a selected
narrow temperature range (switching range) that can be any
1.degree. to 10.degree. range between about 50.degree. C. and
200.degree. C., and more preferably between about 70.degree. C. and
120.degree. C. In comparison, the matrix region 145 in lower jaw
112A is designed to have an impedance-resistance curve exhibiting a
higher initial base resistance (see FIG. 4B). The matrix region 145
provides this higher base resistance over a similar temperature
range as matrix 130. The matrix 145 and its temperature-impedance
curves (145a, 145b) in FIG. 4B again exhibits a dramatically
increasing resistance above its selected switching range, which can
fall in the range described previously with reference to matrix
130.
[0050] Referring now to FIG. 6, a discussion will be presented of
the self-modulating properties of various embodiments of jaw
structure 100A. FIG. 6 graphically depicts the manner in which the
jaw structure 100A of FIGS. 1 and 3 can self-modulate current flow
among multiple paths--depending on the temperature of the engaged
tissue and other electrical conduction parameters of the tissue to
which the matrices 125 and 130 respond. FIG. 6 again depicts a
sectional view of the jaws 112A and 112B as in FIG. 3 engaging
tissue T in phantom view. In FIG. 6, the tissue thickness is not to
scale to allow a graphic representation of potential current paths.
In use, the working end 100A of FIG. 6 can be configured to have
the ability to modulate current flow among multiple different paths
through the tissue T as well as through the matrices 125 and 130.
Current and voltage in the tissue T is modulated after the tissue
is ohmically heated--and thereafter heat from the tissue T is
transferred by passive conduction to adjacent regions of matrices
125 and 130. While there will exist a multiplicity of potential
current paths in the engaged tissue and matrices, FIG. 6
illustrates four different flow paths, P1 through P4, that provide
a means for a self-modulating energy control system used by various
embodiments of the invention. These paths are exemplary, and other
paths not shown are equally applicable. Energy levels in each flow
path are dynamic during Rf energy delivery to tissue, which will be
described in more detail below. In FIG. 6, flow paths P1 indicates
potential Rf microcurrent flows directly through tissue T between
first polarity electrode 140 and conductive region 145 and the low
resistance matrix 130 of upper jaw 112B that overlies the
(opposing) second polarity jaw body 132B. It can be understood that
these current paths P1 provide initial rapid ohmic heating of
tissue. Flow paths P2 indicate Rf current flow through tissue T
between the highly conductive regions 144a and 144b that are
laterally spaced apart in the lower jaw that are in contact with
first polarity conductor 140 and second polarity jaw body 132A,
respectively.
[0051] In various embodiments, working end 100A can be configured
to use potential current flow paths indicated at P3 and P4, to
modulate ohmic heating in engaged tissue as its conductive
parameters (e.g., impedance, temperature, hydration, etc.) are
dynamic during energy application. Potential flow paths P3
represent potential microcurrent paths through a region of tissue
between spaced apart surface portions of matrix 125 that engage
such a tissue region. Potential current flow paths P4 are at an
interior of the jaw and the 3D matrix 125 wherein current can flow
generally from electrode 140 across the matrix region 145 to the
interior of the opposing polarity jaw body 132A. A more detailed
step-by-step description of current flow modulation is provided
below in the text accompanying FIGS. 10A-10D.
[0052] For clarity of explanation, FIG. 6 depicts the principles of
the working end in a basic forceps-type jaw structure 100A of FIGS.
1 and 3. However it should be appreciated that matrices 125 and 135
can be configured to be used in any number of surgical instruments
known in the art. For example, the same variable resistance
matrices 125 and 130 can be provided in embodiments of a jaw
structure indicated at 100B in FIGS. 7 and 8 that carry a blade or
other cutting means for transecting the welded tissue. Further, the
same variable impedance matrices 125 and 130 can be carried in a
one-step jaw structure that is described below (see FIGS. 11-12)
wherein jaw closing, Rf energy delivery and tissue transection
occur in a single operation.
[0053] Referring now referring to FIGS. 7 and 8, a forceps-type
instrument is shown with a detachable cartridge 154 that carries a
thin flexible blade member 155 that can be pushed by thumb slider
156 when the jaws are locked in a closed position. Such a blade
cartridge was disclosed in co-pending U.S. patent application Ser.
No. 10/443,974, filed May 22, 2003 (Docket No. SRX-017A) entitled
Electrosurgical Working End with Replaceable Cartridges which is
incorporated herein by this reference.
[0054] FIG. 8 illustrates a cross section of the upper and lower
jaws 112A and 112B with a central blade slot 160 for receiving the
slidable, flexible blade member 155. On either side of the blade
slot 160, the jaw bodies carry variable resistance matrices 125'
and 130' that are similar (or identical) to the matrices depicted
in FIG. 3. In the exemplary embodiment of FIG. 8, the lower jaw
112B has a matrix 125' that is simplified in that electrode 140 is
exposed in the center of the jaw's engagement surface 124A with a
portion of the 3D matrix 125' extending laterally on either side of
blade slot 160 as well as within the interior of the jaw. As can be
seen in FIG. 7, matrix extends in a "U"-shape around the end of
blade slot 160 to allow welding of engaged tissue around the end of
a welded and transected tissue region. In various embodiment blade
member 155 can comprise other surgical cutting means known in the
art.
[0055] In various embodiments, the working end 100B of FIGS. 7-8
functions to modulate Rf energy application to tissue in between
multiple potential paths as described above and depicted in FIG. 6.
FIG. 9 illustrates the working end 100B of FIGS. 7-8 and again
graphically depicts the potential Rf current paths in tissue and
across regions of the variable resistance matrices. The current
paths P1, P2 and P3 again represent potential paths in the engaged
tissue T. In FIG. 9, the current paths P4 represent paths within
the interior regions of matrix 125' between first polarity (+)
surface conductor 140 and a second polarity (-) region of jaw body
132A.
[0056] Referring now to FIGS. 10A-10D, a discussion will now be
presented of various methods of utilizing temperature responsive
variable resistance matrices for Rf modulation in tissue welding
and other electrosurgical applications (e.g., cut, coagulation,
etc.) FIGS. 10A-10D graphically illustrate the sequential energy
delivery phases in a method of the invention. In FIGS. 10A-10D, the
opposing jaws 112A and 112B are depicted engaging a tissue bundle
T, and Rf energy application to tissue is modulated by matrices 125
and 130 between various paths P1-P4 in the tissue to create a
uniform temperature without desiccation or charring to provide an
effective high strength weld. FIGS. 10A-10D illustrate a basic jaw
structure 100C similar to that of FIG. 1 without a blade member,
but it should be appreciated that a jaw 100B with a reciprocal
blade as in FIGS. 7-8 would create a weld by the same means of
energy application and modulation. For clarity of explanation, the
engagement surface 124A of FIGS. 10A-10D has the central conductive
member or electrode 140 exposed in the surface (cf. FIGS. 7-9).
[0057] Now turning to FIG. 10A, an initial energy application step
is illustrated wherein tissue bundle T is engaged as the jaws apply
compression and the surgeon applies Rf energy to the tissue. At
initiation of Rf energy application, FIG. 10A illustrates that
current flows are substantially through the tissue between the
first polarity conductor 140 and the opposing matrix 130 and
laterally-outward upper jaw 132B as well to the second polarity
lower jaw body 132A, that is in paths P1 and P2 as depicted in
FIGS. 3 and 9. Thus, FIG. 10A depicts current flow that causes very
high energy densities and very rapid ohmic heating in the engaged
tissue T. In this initial phase of Rf energy application to the jaw
structure 100C and to the engaged tissue T, the matrices 125 and
130 are, in effect, in a stand-by mode and are not yet operating to
modulate flow paths of the microcurrents in the tissue. The matrix
130 in the upper jaw at ambient room temperature has a low base
resistance (see FIG. 4B) and allows a multiplicity of conductive
flow paths all across and through the matrix 130 to the second
polarity jaw body 132B from the first polarity conductor 140 in the
lower jaw through the tissue T.
[0058] In FIG. 10A, the ohmically heated tissue causes conductive
heat transfer to the matrices 125 and 130 to heat at least the
surface regions of both matrices. At the same time (see FIG. 10B)
the ohmically heated tissue T dehydrates, changes its geometry by
shrinking and exhibits an increased impedance. In this phase of
energy application, the variable resistance matrix 130 responds
according to its selected temperature-resistance curve (see FIG.
4B) wherein the material regulates and modulates flow paths P1 of
microcurrents therethrough. For example, the switching range of
matrix 130 can be between about 60.degree. C. to 120.degree. C. and
is more preferably in the 70.degree. C. to 90.degree. C., range.
During and following this phase, the impedance of tissue regions
will be substantially matched by the induced impedance of adjacent
regions of matrix 130, to thereby modulate current flow in paths P1
between the jaws. In this way, matrix 130 acts as an impedance
matching 3D body.
[0059] In addition to impedance matching, matrix 130 can also
operate to prevent or significantly reduce the possibility of arcs
or sparks at the interface of jaw surfaces 124A and 124E with the
engaged tissue since, current flow will be eliminated before
excessive high temperatures are reached about any region of the
tissue-jaw interfaces. The prevention of such arcs eliminates the
possibility of unwanted tissue charring. In this way, matrix 130
provides a means for not only preventing or reducing arcing, but
also for reducing or preventing tissue charring and/or other
unwanted thermal injury to tissue. This in turn, reduces thermal
injury or damage to collateral tissue outside the target tissue
region.
[0060] During the initial energy application phase illustrated in
FIGS. 10A and 10B, the ohmically heated tissue also will conduct
heat back to matrix 125 in the lower jaw 112A to elevate the lower
matrix above its selected switching range, for example in the
70.degree. C. to 90.degree. C., range. Still referring to FIG. 10A,
as the thickness of tissue T is reduced by compression and
ohmic-induced dehydration, the increased impedance of the tissue
will first prevent microcurrent flows in paths P1 as the upper
jaw's matrix 130 is masked. At this point, there will remain the
possibility of microcurrent flows in paths P2 between the electrode
140 and the laterally-outward jaw body portion 132A.
[0061] Now referring to FIG. 10B, it can be seen that the
dehydrated tissue T typically will be compressed to a thin membrane
which can increase its impedance in the most direct paths of
current (P1 and P2) between the opposing polarity body portions.
With the tissue in this condition, the reduction or termination of
ohmic heating will cause slight cooling of the tissue and
re-hydration of the tissue can occur due to inward fluid migration.
In this state, the lower matrix 125 will respond by cooling and
then by causing microcurrent flows in paths P3 as indicated in FIG.
10B. Of particular interest, the increase in ohmic heating is then
localized is these lateral regions of the engaged tissue while the
tissue impedance still masks the upper jaw matrix 130. During this
regulated phase of Rf energy application, the engaged tissue may
hydrate to allow current flows in paths P1 and P2 to cause
additional ohmic tissue heating. Thus, it can be understood how the
temperature responsive matrices will self-modulate ohmic energy
densities in the tissue between the various potential flow
paths.
[0062] FIG. 10C indicates another potential flow path P4 that can
come into play if any voltage occurs that could cause an are at the
jaw-tissue interface. In effect, the energy can be dissipated by
energy flows in the paths indicated at P4 between the first
polarity conductor 140 and the second polarity lower jaw body 132A
directly through the lower matrix 125 at the jaw's interior.
[0063] FIGS. 10A-10C indicate generally how the
temperature-responsive matrices 125 and 130, at the tissue-engaging
surfaces 124A and 124B, will modulate ohmic heating in the engaged
adjacent tissue T. It should be appreciated that the energy
modulation also occurs about very localized regions of the engaged
tissue T that is made up of different tissue types as discussed in
the text accompanying FIG. 2. Thus as any local region of tissue
impedance changes during ohmic heating, the local adjacent region
of matrix 130 in the initial phase will move to an impedance
matching level.
[0064] Further, as described above, the tissue dimension and
geometry between the engagement surfaces 124A and 125B of the jaws
is dynamic and shrinking during ohmic heating of the tissue T.
Thus, the local dynamics of ohmic heating in tissue along the axial
length of the jaw can be significant. FIG. 10D illustrates the
pivoting jaw structure 100C as applying higher compression to more
proximal tissue regions and the jaws close and the tissue
dehydrates and shrinks during energy delivery. It can be understood
that ohmic heating is thus modulated by matrices 125 and 130 in the
jaws' engagement surfaces to provide locally independent energy
densities in discrete tissue regions depending on local tissue
temperature and impedance--as well as tissue geometry.
[0065] It has been found that the system described above can be
operated with a pre-set duration of Rf energy delivery, wherein
energy flow and tissue heating is self-regulated by matrices 125
and 130 to effectively provide high and low process limits for the
selected duration of energy application. Depending on selected
power levels and selected matrix parameters, duration of energy
application to create an effective weld can range between about 1
second and 20 seconds, and more preferably is between about 3
second and 15 seconds.
[0066] Referring now to FIGS. 11 and 12, another embodiment of jaw
structure 200 is illustrated that carries cooperating variable
resistance matrices as descried above. The upper and lower jaws
212A and 212B have respective engagement surfaces 224A and 224B
that carry cooperating variable resistance matrices 125 and 130 as
in the previous embodiments of FIGS. 3, 6, 8 and 9. The jaw
embodiment of FIGS. 11 and 12 differs in that it is adapted for
"one-step" welding and transection of the engaged tissue.
[0067] In FIGS. 11 and 12, of jaw structure 200 has an
opening-closing mechanism that is capable of applying very high
compressive forces on tissue on the basis of cam mechanisms with a
reciprocating "I"-beam member 240, wherein jaw closing occurs
contemporaneous with Rf energy delivery. Further, the slidable
"I"-beam member 240 and the exterior jaw surfaces provide cam
surfaces (i) for moving the jaw assembly to the (second) closed
position to apply very high compressive forces, and (ii) for moving
the jaws toward the (first) open position to apply substantially
high opening forces for dissecting tissue. This feature allows the
surgeon to insert the tip of the closed jaws into a dissectable
tissue plane--and thereafter open the jaws to apply such dissecting
forces against tissues. Many prior art instruments are
spring-loaded toward the open position and may not be useful for
dissecting tissue.
[0068] In the embodiment illustrated in FIGS. 11 and 12, the
reciprocating "I"-beam member 240 is actuatable from the handle
(not shown) of the instrument by any suitable mechanism, such as a
lever arm, that is coupled to a proximal end of member 240. The
distal end portion 242 of reciprocating "I"-beam member 240 carries
first (lower) and second (upper) continuous laterally-extending
flange elements 244A and 244B that are coupled by an intermediate
transverse element 245. The flange elements 244A and 244B slide in
a recessed slot portion 246 in each of the upper and lower jaws
(see FIG. 12) to close the jaws and wherein the sliding contact of
the lateral edges of flanges 244A and 244B and the side of the
recessed slot 246 function to prevent lateral flexing of the jaws.
The transverse element 245 and blade edge 250 slide within channels
252 (collectively) in the paired first and second jaws 212A and
212B to thereby open and close the jaws. The transverse element 245
is adapted to transect tissue captured between the jaws with a
sharp leading blade edge 250 (FIG. 11). In the embodiment, the
"I"-beam 240 also is adapted to provide electrosurgical
functionality as it transects tissue and has a polarity that
matches that of the jaw bodies 232A and 232B which it slidably
contacts. The jaw structure of 200 of FIGS. 11 and 12 is described
in more complete detail in co-pending U.S. patent application Ser.
No. 10/079,728 filed Feb. 19, 2002 (Docket No. SRX-004A) entitled
Electrosurgical Systems and Techniques for Sealing Tissue, and U.S.
patent application Ser. No. 10/340,144 filed Jan. 10, 2003 (Docket
No. 021447-000520US) entitled Jaw Structure for Electrosurgical
Instrument and Method of Use, which are incorporated herein by this
reference.
[0069] Still referring to FIGS. 11 and 12, the first and second
jaws 212A and 212E close about an engagement plane 255 wherein the
tissue-engaging surface layers 224A and 224B that contact and
deliver energy to engaged tissue T as described above. The jaws can
have any suitable length with teeth or serrations 256 for gripping
tissue (FIG. 11). One preferred embodiment of FIG. 11 provides such
teeth 156 at an inner portion of the jaws along channels 248 thus
allowing for substantially smooth engagement surface layers 224A
and 224B laterally outward of the tissue-gripping elements. The
axial length of jaws 212A and 212B indicated at can be any suitable
length depending on the anatomic structure targeted for transection
and sealing and typically will range from about 10 mm. to 50 mm.
The jaw assembly can apply very high compression over much longer
lengths, for example up to about 200 mm., for resecting and sealing
organs such as a lung or liver. Other embodiments of the invention
provide jaw assemblies configured for use with surgical instruments
known in the art used in micro-surgeries. In these and related
embodiments the jaw length can be about 5.0 mm or less.
[0070] In FIGS. 11 and 12, it can be seen that the lower jaw 212A
has a variable resistance matrix 125 that has an edge portion 258
that (optionally) extends laterally over the outer edge of the jaw
body 232A. This matrix feature has been found useful in modulating
Rf energy density in the margin of the treated tissue to create
distinct region between welded tissue and unaffected tissue. Also,
the upper jaw's matrix 130 is positioned to extend slightly outward
(dimension 262) from the upper jaw body 232B. FIG. 13 illustrates
that the jaw structure 200 of FIGS. 11 and 12 provides the
multiplicity of flow paths P1-P4 as described previously in FIGS.
10A-10D. In all other electrosurgical aspects, the jaw structure
200 and variable resistance matrices of FIGS. 11 and 12 function as
described above with reference to FIGS. 3, 6, 8, 9 and 10A-10D.
[0071] Of particular interest, FIGS. 14A-14C graphically illustrate
the one-step sealing and transection method of the invention. When
using elongated jaws in a small diameter instrument, the issue of
jaw flexure when clamping thick tissue bundles typically creates
difficulties for both sealing and transection. The jaw structure
200 of FIGS. 11 and 12 solve such problems by applying Rf energy
contemporaneously with jaw closure. Initial Rf energy delivery will
begin to dehydrate the engaged tissue T thus making it possible to
compress the tissue to a thin membrane. At the same time, the
matrices 125 and 130 will modulate Rf ohmic heating axially along
the length of the jaws to thereby insure that thin treated tissue
regions in the proximal jaw are not being ohmically heated while
more distal regions of the engaged tissue are receiving maximal
ohmic heating. All the while, each tissue region containing a
different tissue type will receive the optimal Rf energy density
based on impedance matching with the adjacent region of a variable
impedance matrix.
[0072] In FIGS. 14A-14C, the jaws 212A and 212B are shown with a
greatly exaggerated flex characteristics to illustrate, in effect,
a method of the invention. The "I"-beam 240 can compress the tissue
T dramatically as it is progressively welded. Thus a very small jaw
structure 200 in a 5 mm. diameter device can chomp down on, weld
and transect very thick tissue bundles, that are initially up to
1/2 inch or more. The highest ohmic heating progresses in a "front"
across the tissue and is automatically modulated by the variable
impedance matrices 125 and 130 and series-parallel circuitry as
described above. The jaw structure 200 further allows the surgeon
tactile feedback of the tissue welding process as the advancement
of the "I"-beam" 240 indicates that the tissue is welded. This
inventive method for welding tissue can be most accurately
summarized as the microscale modulation of ohmic active heating in
engaged tissue as depicted in FIGS. 10A-10D combined with the
progressive macroscale application of ohmic heating as in FIGS.
14A-14C as the blade 245 transects the engaged tissue. The one-step
welding and transecting functionality is provided by the high
compression "I"-beam for jaw closure and tissue transection
together with the cooperating variable impedance component 125 and
130 of the jaw structure.
[0073] Now turning to FIG. 15, an alternative embodiment of jaw
structure 300A is shown that carries the same variable impedance
matrices 125 and 130 as in FIGS. 11 and 12. The upper and lower
jaws 212A and 212B carry matrices 125 and 130 that function largely
as in the previous embodiments of FIGS. 11-13. The jaw structure
300A differs in that the opposing engagement surfaces 224A and 224B
and optionally the exterior of the jaw bodies is covered with a
capacitive coating of a suitable thin polymeric material layer
(e.g., silicone) indicated at 310. The polymer layer can be
deposited on, and bonded to, the engagement surfaces 224A and 224B
by any suitable means and have a thickness ranging from about 0.05
microns to 10 microns. It has been found that such a capacitive
coating in combination with a polymeric-based variable impedance
material as in matrices 125 and 130 is useful in enhancing the
matrices' non-stick characteristics. In effect, the exterior
capacitive coating layer comprises a second energy-modulating
composition that complements the energy-modulating characteristics
of the variable impedance matrix composition already described
above. Thus, an embodiment of the invention comprises an
electrosurgical working end that carries an energy-modulating body
intermediate first and second polarity conductors in
tissue-engaging surface portions of the system, wherein the
energy-modulating body comprises a capacitive surface portion
overlying a 3D variable impedance interior portion that
collectively control an Rf energy parameter (current, voltage)
applied across the tissue-engaging surface portions of the system.
In operation, the actual Rf application across the tissue-engaging
surfaces can be described as capacitive coupling. In operation, the
jaw structure 300A provides Rf energy modulation through paths
P1-P4 generally as described above.
[0074] Still referring to FIG. 15, the jaw structure 300A also
carries another optional alternative feature that comprises a
capacitive layer 315 at an interior of the jaw body intermediate
the matrix 125 and jaw body 232A. Further, the lateral portion of
the variable impedance matrix 125 is covered by electrical
insulator 316. The capacitive layer 315 can comprise a low
durometer polymer known in the art and it can be understood that
voltage levels and slight compression of the capacitive layer 315
can cause capacitive coupling between the interior of variable
impedance matrix 125 and jaw body 232A to provide a current path P4
between first polarity electrode 140 and second polarity the jaw
body 232A.
[0075] FIG. 16 illustrates an embodiment of an alternative jaw
structure 300B that carries a capacitive layer 310 about its
engagement surfaces and jaw exterior as in FIG. 15. The alternative
jaw structure 300B of FIG. 16 is similar to the previously
described forceps jaw of FIGS. 8 and 9, with like reference
numerals. The capacitive layer 310 is depicted as a transparent
layer about the entire jaws surface, except for the blade slot 160.
The jaw structure differs in that the interior of the jaws carries
a negative temperature coefficient matrix 322 intermediate the
matrix 125 and the jaw body 232A. It can be easily understood that
upon the variable impedance matrix 125 reaching a switching
temperature at which the matrix reduces of terminates current flow,
the negative temperature coefficient matrix 322 has a complementary
switching temperature at which it allows current flow therethrough.
In effect, the current path P4 then is facilitated by the use of a
positive temperature coefficient variable impedance matrix body 125
exposed at the engagement surface between opposing polarity
conductor portions (to respond to ohmically-heated tissue
temperature) together with a corresponding negative temperature
coefficient variable impedance matrix body portion 322 at an
interior of the jaw to short excess voltages away from the
engagement surfaces to eliminate the potential of arcs and tissue
char. It should be appreciated that these capacitive features and
negative temperature coefficient bodies can be provided in any of
the various jaw embodiments described above.
[0076] The foregoing description of various embodiments of the
invention has been presented for purposes of illustration and
description. It is not intended to limit the invention to the
precise forms disclosed. Many modifications, variations and
refinements will be apparent to practitioners skilled in the art.
Further, elements or acts from one embodiment can be readily
recombined with one or more elements or acts from other embodiments
to form numerous additional embodiments. Also, elements or acts
from one embodiment can be readily substituted with elements or
acts of another embodiment. Hence, the scope of the present
invention is not limited to the specifics of the exemplary
embodiment, but is instead limited solely by the appended
claims.
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