US20160175037A1 - End-effector assembly including a pressure-sensitive layer disposed on an electrode - Google Patents

Abstract

An end-effector assembly includes first and second jaw members disposed in opposing relation relative to one another, at least one of the jaw members moveable from an open position to a closed position for grasping tissue therebetween. First and second conductive plates are disposed on opposing surfaces of corresponding first and second jaw members. First and second compressible membranes are configured to electrically connect corresponding first and second conductive plates to a surgical field when subjected to a compression bias.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• The present application is a continuation application of U.S. patent application Ser. No. 13/926,491 filed Jun. 25, 2013, now U.S. Pat. No. 9,271,783, which claims priority to U.S. Provisional Application No. 61/672,344 filed Jul. 17, 2012, the entire contents of each of which are incorporated herein by reference.
BACKGROUND
• The present disclosure relates to a surgery. More particularly, the present disclosure relates to an electrosurgical forceps that includes self-aligning jaws.
TECHNICAL FIELD
• Electrosurgical forceps utilize both mechanical clamping action and electrical energy to affect hemostasis by heating tissue and blood vessels to coagulate, cauterize and/or seal tissue. As an alternative to open forceps for use with open surgical procedures, many modern surgeons use endoscopes and endoscopic instruments for remotely accessing organs through smaller, puncture-like incisions. As a direct result thereof, patients tend to benefit from less scarring and reduced healing time.
• Endoscopic instruments are inserted into the patient through a cannula, or port, which has been made with a trocar. Typical sizes for cannulas range from three millimeters to twelve millimeters. Smaller cannulas are usually preferred, which, as can be appreciated, ultimately presents a design challenge to instrument manufacturers who must find ways to make endoscopic instruments that fit through the smaller cannulas.
• Many endoscopic surgical procedures require cutting or ligating blood vessels or vascular tissue. Due to the inherent spatial considerations of the surgical cavity, in addition to the occurrence of fluid in the surgical field, surgeons often have difficulty suturing vessels or performing other traditional methods of controlling bleeding, e.g., clamping and/or tying-off transected blood vessels. By utilizing an endoscopic electrosurgical forceps, a surgeon can either cauterize, coagulate/desiccate and/or simply reduce or slow bleeding simply by controlling the intensity, frequency and duration of the electrosurgical energy applied through the jaw members to the tissue. Most small blood vessels, i.e., in the range below two millimeters in diameter, can often be closed using standard electrosurgical instruments and techniques. However, if a larger vessel is ligated, it may be necessary for the surgeon to convert the endoscopic procedure into an open-surgical procedure and thereby abandon the benefits of endoscopic surgery. Alternatively, the surgeon can seal the larger vessel or tissue. Typically, after a vessel or tissue is sealed, the surgeon advances a knife to sever the sealed tissue disposed between the opposing jaw members.
SUMMARY
• In accordance with the present disclosure, an end-effector assembly of a surgical forceps is provided. An end-effector assembly includes first and second jaw members disposed in opposing relation relative to one another, at least one of the jaw members being moveable from an open position to a closed position for grasping tissue therebetween. First and second conductive plate are disposed on opposing surfaces of corresponding first and second jaw members. First and second compressible membranes are configured to electrically connect corresponding first and second conducive plates to a surgical field when subjected to a compression bias.
• The first and second compressible membranes electrically connect corresponding first and second conductive plates through the portions of the first and second compressible membranes adjacent the applied compression bias.
• In one aspect, the electrical connection formed between the first and second conductive plates through the corresponding first and second compressible membranes is a capacitive connection. The capacitance of the compressible membranes is configured to vary in magnitude in response to the applied compression bias.
• In another aspect, the electrical connection formed between the first and second conductive plates through the first and second compressible membranes is a resistive connection. The resistance of the resistive connection through each of the compressible membranes is responsive to the applied compression bias.
• In another aspect, the first and second compressible membranes each include a plurality of switching mechanisms formed on opposing surfaces thereof, each of the plurality of switching mechanisms being responsive to an applied compression bias. Each of the plurality of switching mechanism forms a low-resistance connection in response to the applied compression bias.
• In yet another aspect, the first and second compressible membranes each include one or more pairs of electrically conductive parallel plates, wherein in an uncompressed condition the parallel plates are separated by a non-conductive fluid and form a high-resistance pathway through the compressible membranes and in a compressed condition the parallel plates connect and form a low-resistance pathway though the compressible membranes. At least one of the one or more pairs of electrically conductive parallel plates connects to the conductive plate of one of the jaw members and the corresponding electrically conductive parallel plate connects to an outer surface of a respective compressible membrane of the jaw member. The non-conductive fluid viscosity may be related to the temperature of the compressible membrane. The non-conductive fluid viscosity may be indirectly proportional to the temperature of the compressible membrane.
• In yet another aspect, one or both of the first and second compressible membranes includes a compressible material embedded with a plurality of conductive particles. The distance between the conductive particles may be responsive to an applied compression bias and/or the resistance of the compressible material may be responsive to the distance between conductive particles. Alternatively, the capacitance of the compressible material may be responsive to the distance between conductive particles.
BRIEF DESCRIPTION OF THE DRAWINGS
• Various embodiments of the subject instrument are described herein with reference to the drawings wherein:
• FIG. 1 is a top, perspective view of an alternate embodiment of an endoscopic forceps, including a housing, a handle assembly, a shaft and an end-effector assembly;
• FIG. 2 is a top, perspective view of an endoscopic forceps shown in an open configuration and including a housing, a handle assembly, a shaft and an end-effector assembly for use with the present disclosure;
• FIG. 3 is a top, perspective view of an open surgical forceps, including a handle assembly, first and second shafts and an end-effector assembly for use with the present disclosure;
• FIG. 4 is an enlarged, side, perspective view of the end-effector assembly ofFIG. 1;
• FIG. 5A is a front, cross-sectional view of the jaw members in an open configuration in accordance with one embodiment of the present disclosure;
• FIG. 5B is a front, cross-sectional view of the jaw members ofFIG. 5A, disposed in a closed configuration;
• FIG. 6A is a side, cross-sectional view of a portion of the jaw members disposed in a closed configuration with a compressible membrane in accordance with one aspect of the present disclosure;
• FIG. 6B is a side, cross-sectional view of a portion of the jaw members disposed in a closed configuration with a compressible membrane with tissue positioned between the jaw members;
• FIG. 7 is an electrical circuit schematic that approximates the electrical circuit formed by the end effector ofFIG. 6B;
• FIG. 8 is an electrical circuit schematic that approximates the electrical circuit formed by the end effector ofFIG. 6B including the compressed and uncompressed portions of the compressible membrane;
• FIG. 9 is a side, cross-sectional view of a portion of a jaw member with another aspect of a compressible member of the present disclosure, with tissue positioned between the jaw members;
• FIG. 10 is a side, cross-sectional view of a portion of a jaw member with yet another aspect of a compressible member of the present disclosure, with tissue positioned between the jaw members;
• FIG. 11 is a side, cross-sectional view of a portion of a jaw member with yet another aspect of a compressible member including a plurality of switches formed in the compressible membranes; and
• FIG. 12 is a side, cross-sectional view of a portion of a jaw member with yet another aspect of the compressible member including a plurality of parallel plates formed in each of the compressible membranes.
DETAILED DESCRIPTION
• Detailed embodiments of the present disclosure are described herein; however, it is to be understood that the disclosed embodiments are merely exemplary and may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present disclosure in virtually any appropriately detailed structure. In the drawings and in the descriptions which follow, the term “proximal”, as is traditional, will refer to the end of theforceps10 which is closer to the user, while the term “distal” will refer to the end which is further from the user.
• In the present disclosure, conventional electrosurgical conducting surfaces are covered with a compressible membrane. The compressible membrane prevents and/or minimizes leakage current by eliminating direct contact between the electrosurgical conductive surfaces and the surgical field. Application of a compression bias to the compressible membrane alters a mechanical property and/or an electrical property of the compressible membrane thereby forming an electrical connection between the electrosurgical conductive surfaces and the surgical field through the compressible membrane.
• Turning now toFIG. 1, an alternate embodiment of anendoscopic forceps10 is shown that includes ahousing20, ahandle assembly30, a rotatingassembly80, atrigger assembly70 and an end-effector assembly100.Forceps10 further includes ashaft12 having adistal end16 configured to mechanically engage end-effector assembly100 and aproximal end16 that mechanically engageshousing20.Forceps10 also includeselectrosurgical cable310 that connectsforceps10 to a generator (not explicitly shown).Cable310 has sufficient length to extend throughshaft12 in order to provide electrical energy to at least one of thejaw members110 and120 of end-effector assembly100.
• Handleassembly30 includes fixedhandle50 and amoveable handle40. Fixedhandle50 is integrally associated withhousing20 and handle40 is moveable relative to fixedhandle50. Rotatingassembly80 is integrally associated withhousing20 and is rotatable approximately 180 degrees in either direction about a longitudinal axis “A” defined throughshaft12. Thehousing20 includes two halves that house the internal working components of theforceps10.
• Turning now toFIG. 2, an endoscopicsurgical forceps10′ is shown for use with various surgical procedures and generally includes ahousing20′, ahandle assembly30′, a rotatingassembly80′, aknife trigger assembly70′ and an end-effector assembly100′ which mutually cooperate to grasp, seal and divide tubular vessels and vascular tissue.
• Forceps10′ includes ashaft12′ that has adistal end16′ dimensioned to mechanically engage the end-effector assembly100′ and aproximal end14′ that mechanically engages thehousing20′. Theproximal end14′ ofshaft12′ is received within thehousing20′.Forceps10′ also includes anelectrosurgical cable310′ that connects theforceps10′ to a source of electrosurgical energy, e.g., a generator (not explicitly shown). Handleassembly30′ includes twomovable handles30a′ and30b′ disposed on opposite sides ofhousing20′.Handles30a′ and30b′ are movable relative to one another to actuate the end-effector assembly100′.
• Rotatingassembly80′ is mechanically coupled tohousing20′ and is rotatable approximately 90′ degrees in either direction about a longitudinal axis “A′” defined throughshaft12′. Rotatingassembly80′, when rotated, rotatesshaft12′, which, in turn, rotates end-effector assembly100′. Such a configuration allows end-effector assembly100′ to be rotated approximately 90′ degrees in either direction with respect tohousing20′. Details relating to the inner-working components offorceps10′ are disclosed in commonly-owned U.S. Pat. No. 7,789,878, the entire contents of which is incorporated by reference herein.
• Referring now toFIG. 3, another alternate embodiment of aforceps10″ for use with open surgical procedures is shown.Forceps10″ includes end-effector assembly100″ that attaches todistal ends16″ and26″ ofshafts12″ and20″, respectively. The end-effector assembly100″ includes a pair of opposingjaw members110″ and120″ which are pivotably connected about apivot pin65 and that are movable relative to one another to grasp tissue therebetween.
• Eachshaft12″ and20″ includes a handle15″ and17″, disposed at the proximal end thereof which each define a finger hole15a″ and17a″, respectively, therethrough for receiving a finger of the user. As can be appreciated, finger holes15a″ and17a″ facilitate movement of theshafts12″ and20″ relative to one another which, in turn, pivot thejaw members110″ and120″ from an open position wherein thejaw members110″ and120″ are disposed in spaced relation relative to one another to a clamping or closed position wherein thejaw members110″ and120″ cooperate to grasp tissue therebetween. End-effector assembly100″ is configured in a similar manner to the end-effector assembly ofFIGS. 1 and 2 above.
• Referring now toFIG. 4, end-effector assembly100 is described with reference to the end-effector assembly100 show inFIG. 1. It is understood that all of the above end effector assemblies and forceps include similar designs and may be configured to accomplish the same purpose. End-effector assembly100 may be configured for mechanical attachment at thedistal end16 ofshaft12 offorceps10. End-effector assembly100 includes a pair of opposingjaw members110 and120. Handleassembly30 of forceps10 (seeFIG. 1) ultimately connects to a respective drive assembly (not shown) which, together, mechanically cooperate to impart movement of thejaw members110 and120 from a first, open position wherein thejaw members110 and120 are disposed in spaced relation relative to one another, to a second, clamping or closed position wherein thejaw members110 and120 cooperate to grasp tissue therebetween. Details relating to the working components of the handle assembly and drive assembly offorceps10 are disclosed in above-mentioned U.S. Pat. No. 7,789,878.
• With reference to the example embodiment of an end-effector assembly100 shown inFIG. 4, opposingjaw members110 and120 are pivotably connected aboutpivot103.Jaw members110 and120 include electrically conductive sealing surfaces112 and122 that are dimensioned to securely engage tissue when clamped therebetween. A longitudinally-orientedknife channel115 is defined betweenjaw members110 and120 for reciprocation of aknife185 therethrough.Knife channel115 is defined bychannels115aand115b(see, e.g.,FIGS. 5A-5B) disposed in the sealing surfaces112 and122, respectively. Alternatively,knife channel115 may be defined completely within one of the sealing surfaces112 and122. Further,forceps10 may be provided without the knife assembly and, accordingly, the sealing surfaces112 and122 would be configured without theknife channel115 defined therethrough. At least one of thejaw members110,120 may include an electrically insulative stop member (or members)750 configured to control the gap distance between sealingsurfaces112 and122 ofjaw members110 and120, respectively.
• Features ofjaw members110 and120 will now be described with reference toFIGS. 5A-5B and 6A-6B.FIG. 5A showsjaw members110 and120 disposed in a first, spaced-apart position. Sealing surface or opposingsurface112 ofjaw member110 has a generally concave shape. Sealing surface or opposingsurface122 ofjaw member120 has a generally convex shape. More specifically, sealingsurface112 defines an inward radial portion from oppositelongitudinal sides118aand118bof sealingsurface112 having a radius “r” from acenter point119 of sealingsurface112. Opposing sealingsurface122 defines an outwardly protruding convex portion extending from oppositelongitudinal sides128aand128bof sealingsurface122 and having a radius “r” which is substantially equal to the radius “r” of the radial portion defined withinjaw member110. Accordingly, opposingsurface112 and opposingsurface122 have complementary and, preferably non-linear shapes such that when thejaw members110 and120 are moved into the second, or closed position, the concave radial portion ofjaw member110 and the convex radial portion ofjaw member120 fit together, as shown inFIG. 5B.
• These complementary-shaped opposingsurfaces112 and122 ofFIGS. 5A-5B align thejaw members110 and120 as described hereinbelow. For example, as shown inFIG. 5A, due to the inherent splay which results when two surfaces connected about a pivot come together,jaw members110 and120 may be offset from one another as thejaw members110 and120 move to and from open and closed positions. For example, as shown inFIG. 5A,jaw member110 is offset relative tojaw member120. Asjaw members110 and120 move to the position shown inFIG. 5B,jaw member110 is forced into alignment withjaw member120, so that the complementary opposingsurfaces112 and122 fit together.
• Further, the self-aligning feature of the above-described complementary-shaped opposingsurfaces112 and122 ensures alignment ofknife channels115aand115basjaw members110 and120 move from an open to a closed position. The alignment ofknife channels115aand115b, as shown inFIG. 5B, allows knife blade of knife185 (seeFIG. 4) to more easily translate throughknife channel115 to cut tissue disposed betweenjaw members110 and120. Additionally, the complementary concave and convex sealing surfaces112 and122, respectively, provide a larger seal width as compared to linear sealing surfaces having the same overall width. On the other hand, the complementary concave and convex sealing surfaces112 and122, respectively, allowjaw members110 and120 to be constructed with an overall smaller width, while maintaining an equal seal width as compared to jaw members having linear sealing surfaces.
• The vessel sealing instruments illustrated inFIGS. 1-3, with end effectors similar to the end effectors illustrated inFIGS. 4, and 5A-5B, are three examples of a family of surgical instruments used for tissue fusion. Other tissue fusion devices may not include a cutting apparatus, may be configured to spot fuse tissue of particular tissue (e.g., fusing nerve tissue) or may be configured to perform tissue fusion along a resection line.
• Normally, tissue fusion cannot be performed in a surgical field with electrically conductive fluid. In use, a clinician must be aware of fluid in the surgical field, as an electrosurgical generator (not explicitly shown) will normally detect such conditions and will fail to perform, or even start, the electrosurgical energy delivery algorithm if the surgical instrument detects contact with electrically conductive fluid.
• Other electrosurgical instruments that normally perform electrosurgical procedures in a fluid-filled surgical field (e.g., prostantectomy's, fibroid removals in the uteruses and urinary bladder ablations) typical favor instruments based on an ablative electrosurgical algorithm.
• One aspect of the present disclosure positions acompressible membrane312,322 in the conventional jaw arrangement of the end effectors provided inFIGS. 1-4 and 5A-5B thereby minimizing (and possibly eliminating) leakage currents due to the presence of electrically conductive fluids in the surgical field or leakage currents due to contact with tissue adjacent the target tissue.FIGS. 6A and 6B illustrate a partial cross-section of a portion of anend effector assembly200 with opposingjaw members210 and220 according to one aspect of the present disclosure. Eachjaw member210,220 includes ajaw housing216,226 that houses a jawconductive plate212,222 that each connect to opposing potentials of a source of electrosurgical energy (e.g., electrosurgical generator, not explicitly shown).
• Compressible membranes312,233 cover the outward facing portion of respective jawconductive plates212,222. In one aspect, thecompressible membranes312,322 completely cover the outward surfaces of respective jawconductive plates212,222 thereby preventing any direct contact between the jawconductive plates212,222 and tissue “T” and/or fluid in the surgical field. Eachcompressible membrane312,322 connects to the source of electrosurgical energy through the respective jawconductive plate212,222.
• Thecompressible membranes312,322 include one or more properties, features and/or other aspects that provide a change in impedance and/or resistance when compressed. The change may be due to (or related to) a physical change in structure. For example, an applied compression bias, due to the tissue “T” positioned between thejaw members210,220, may deform the shape of thecompressible membranes312,322 wherein the deformation results in a change in impedance and/or resistance. Alternatively, the change may be due to the applied compression bias, which may not result in a dimensional/physical change in thecompressible membranes312,322. For example, the tissue “T” positioned between thejaw members210,220 may not substantially deform thecompressible membrane312,322 although the applied compression bias (due to the tissue “T”) may change the impendence and/or resistance of thecompressible membrane312,322 at the location of the compression bias (at the tissue “T”).
• A change in the physical structure of thecompressible membranes312,322 may be due to compression of thecompressible membranes312,322 or due to redistribution of the material in the compressible membranes (Seecompressible membranes412,422,512,522). For example, the compression bias may reduce the thickness of thecompressible membrane312,322 in the area where the compression bias is applied, while the thickness of the remaining portion of the compressible membranes (312,322) remains substantially unchanged. Alternatively, the applied compression bias may result in a redistribution of the material that forms the compressible membrane. As such, the thickness of thecompressible membrane312,322 may be reduced in the area where the compression bias is applied while the thickness of the remaining portion of thecompressible membrane312,322 may increase.
• Acompressible membrane312,322 that changes structure may conform to the contours (e.g., shape) of the tissue “T”. The varying contours and thickness of the tissue “T” may result in an impedance geometry that is related to the geometry of the tissue “T”.
• In another aspect of the present disclosure, the applied compression bias generated by compressing the tissue “T” between thejaw members210,220 may change the impedance of thecompressible membrane312,322 without changing the shape, structure or distribution of material of thecompressible membrane312,322.
• As illustrated inFIG. 6A, the thickness of thecompressible membranes312,322 in an uncompressed condition is substantially uniform along the length of thejaw members210 and220. While not explicitly shown, the thickness of thecompressible membranes312,322 may also be substantially uniform along the width of thejaw members210,220. Further, each of thecompressible membranes312,322 may include a compressible membrane formed on each side ofrespective knife channels115a,115b(SeeFIGS. 4, 5A and 5B). Thecompressible membranes312,322 in an uncompressed condition form a high-impedance barrier between the surgical field and the jawconductive plates212,222 as discussed in more detail hereinbelow.
• As illustrated inFIG. 6B, at least a portion of eachcompressible membrane312 and322 is compressed by tissue “T” positioned between thejaw members210 and220. Theuncompressed portions312a-312band322a-322bof thecompressible membranes312 and322 maintain a high-impedance barrier and thecompressed portions312cand322cof thecompressible membranes312 and322 form an area of variable impedance. The impedance in theuncompressed portions312a-312band322a-322bis much higher than the tissue goal impedance within thecompressed portions312c,322c(e.g., the tissue goal impedance is the combined impedance of the impedance of thecompressed portions312cand322cand the impedance of the tissue at any point in time during the sealing procedure).
• The variable and varying impedance of thecompressed portions312cand322calong the length and width of the tissue “T” steers electrical currents to low impedance pathways through tissue “T”. As such, the current density pattern formed in the tissue “T” may be related to the impedance of the tissue “T” and the amount of compression and/or the amount of compression bias applied to thecompressible membrane312,322 along each point of the tissue “T”.
• In one aspect of the disclosure, thecompressible membranes312,322 form a variable capacitor. In an uncompressed condition, the capacitance of thecompressible membranes312,322 is very low. In a compressed condition, thecompressible membranes312,322 have a higher capacitance and can act much like a capacitor. A capacitor is formed by positioning two parallel conductive surfaces in parallel and separated by a dielectric. Assuming that the dielectric constant remains the same, the capacitance of a capacitor increases as the distance between the surfaces decreases. The variability of capacitance is represented as:
• $\begin{array}{cc}C={\varepsilon }_r{\varepsilon }_0\frac{A}{d}& \left(1\right)\end{array}$
• where,
• C is the capacitance between two parallel conductive plates (in farads), A is the area of overlap between the two parallel plates measured in square meters, ∈_ris the relative static permittivity of the membrane between plates, ∈_ois the permittivity of free space (where ∈_o=8.854×10⁻¹²F/m) and d is the separation between the plates, measured in meters. As shown inEquation 1, capacitance is directly proportional to the surface area of the conductive plates or sheets.
• The starting impedance (hereinafter, “Z_start”) for tissue in a surgical procedure is typically very low and almost entirely resistive (as opposed to capacitive or inductive). For example, Z_startmay be less than about 50 ohms.
• The goal impedance (hereinafter, “Z_goal”) for tissue in a surgical procedure is typically at least 10 to 100 times greater than Z_startand only partly resistive. For example, Z_goalmay be as much as 5000 ohms.
• The frequency of RF energy in a surgical procedure may be in the range of 100 kHz to 1000 kHz, with a typical frequency of about 472 kHz generating AC currents in the range from a few milliamps to several amps (as much as 5 amps).
• The arrangement of the opposingjaws210 and220, and in particular the jawconductive plates212 and222 and thecompressible membranes312 and322, form an electrical circuit through tissue, as illustrated in the first approximation circuit ofFIG. 7.
• The first approximation circuit is a series circuit that includes the capacitance of the first jawcompressible membrane312,C_(comp)1, the resistance of the tissue “T”, R_tissue, and the capacitance of the second jaw compressible membrane322C_(comp)2 connected in series to the electrosurgical generator “AC”. From the perspective of the electrosurgical generator “AC”, the capacitors are directly in series. Assuming thatC_(comp)1 is approximately equal toC_(comp)2, the mathematical model of the generator load impedance of this circuit is as follows:
• $\begin{array}{cc}{Z}_{\mathrm{load}}=Z_{C\left(\mathrm{comp}\right)1,C\left(\mathrm{comp2}\right)}+R_{\left(\mathrm{tissue}\right)}& \left(2\right)\\ Z_{\mathrm{load}}=\frac{1}{j\omega \frac{C_{\left(\mathrm{comp}\right)1}*C_{\left(\mathrm{comp}\right)2}}{C_{\left(\mathrm{comp}\right)1}+C_{\left(\mathrm{comp}\right)2}}}+R_{\left(\mathrm{tissue}\right)}& \left(3\right)\\ Z_{\mathrm{load}}=\frac{1}{j\omega \frac{C_{\left(\mathrm{comp}\right)}}{2}}+R_{\left(\mathrm{tissue}\right)}& \left(4\right)\end{array}$
• Since the normal process for tissue fusion begins with a low tissue impedance, it is desirable for the impedance due to thecompressible membrane312 and322 (when compressed) to also be as low as possible and ideally about equal to or slightly greater than the tissue impedance.
• $\begin{array}{cc}{R}_{\mathrm{tissue}}=Z_{\mathrm{start}}\ge Z_{C\left(\mathrm{comp}\right)}& \left(5\right)\\ \frac{1}{j\omega \frac{C_{\left(\mathrm{comp}\right)}}{2}}\le Z_{\mathrm{start}}& \left(6\right)\\ \frac{1}{j{\mathrm{\omega Z}}_{\mathrm{start}}}\le \frac{C_{\left(\mathrm{comp}\right)}}{2}& \left(7\right)\end{array}$
• This leads to a minimum value of the compressedcompressible membrane312 and322 capacitance, C_(comp), which is determined by the following equation:
• $\begin{array}{cc}{C}_{\mathrm{comp}}\ge \frac{2}{j{\mathrm{\omega Z}}_{\mathrm{start}}}& \left(8\right)\end{array}$
• A second approximation circuit illustrated inFIG. 8, accounts for additional areas of thecompressible membrane312 and322. In the second approximation circuit the capacitance of thecompressible membrane312 and322 represents the area of the plates of the capacitor and is related to the combined capacitance of theuncompressed portions312a-312b,322a-322band thecompressed portions312c,322cas well as the distance between the plates (e.g., thickness of thecompressible membrane312,322).
• The capacitance of thecompressed portion312c,322cof thecompressible membrane312 and322 (e.g., in the area of the tissue) is affected by the compression bias while the capacitance of theuncompressed portions312a-312band322a-322b(e.g., the area outside of the tissue “T”) of thecompressible membrane312a-312band322a-322bis not affected by the compression bias. As such, the capacitance ofuncompressed portions312a-312band322a-322b(C_uncomp3 andC_uncomp4, respectively) of thecompressible membrane312,322 with respect to thecompressed portion312c,322c(C_(comp)1 andC_(comp)2, respectively) of thecompressible membrane312 and322 may be represented as follows:
• $\begin{array}{cc}{Z}_{\mathrm{load}}=\frac{Z_{\mathrm{uncomp}}*\left(Z_{\mathrm{comp}}+R_{\mathrm{tissue}}\right)}{Z_{\mathrm{uncomp}}+\left(Z_{\mathrm{comp}}+R_{\mathrm{tissue}}\right)}& \left(9\right)\end{array}$
• Where Z_uncompis a series capacitive circuit modeled as:
• $\begin{array}{cc}{Z}_{\mathrm{uncomp}}=\frac{1}{j\omega *\frac{C_{\mathrm{uncomp3}}*C_{\mathrm{uncomp3}}}{C_{\mathrm{uncomp3}}+C_{\mathrm{uncomp3}}}}& \left(10\right)\end{array}$
• Again,C_uncomp3 is substantially equal toC_uncomp4 thereby reducing equation 9 as follows:
• $\begin{array}{cc}\frac{1}{j\omega *\frac{{\mathrm{<figure-callout\; label="C\; uncomp"\; filenames="US20160175037A1-20160623-D00006.png,US20160175037A1-20160623-D00007.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{uncomp}}}{2}}=Z_{\mathrm{uncomp}}& \left(11\right)\end{array}$
• At the tissue goal impedance, Z_goal, Z_compis a negligible factor compared to R_tissue, therefore, the circuit reduces to two parallel impedances, Z_uncompand R_tissue. As discussed hereinabove, the uncompressed membrane impedance is much higher than the goal impedance of the tissue by at least a factor of 10 although higher ratios are clearly acceptable and/or desirable.
• $\begin{array}{cc}\frac{1}{j\omega *\frac{{\mathrm{<figure-callout\; label="C\; uncomp"\; filenames="US20160175037A1-20160623-D00006.png,US20160175037A1-20160623-D00007.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{uncomp}}}{2}}=Z_{\mathrm{uncomp}}\ge 10*Z_{\mathrm{goal}}& \left(12\right)\\ C_{\mathrm{uncomp}}\le \frac{1}{\mathrm{j\omega }*5*Z_{\mathrm{goal}}}& \left(13\right)\end{array}$
• As can be appreciated, increasing the amount of tissue “T” positioned between thejaw members210 and220 decreases the amount (e.g., total surface area) of theuncompressed portion312a-312band322a-322bof thecompressible membrane312 and322 thereby reducing the capacitance of the compressed portion of thecompressible membrane312,322. As a result, more current is steered into the tissue “T” as long as the maximum capacitance for the uncompressed area is maintained.
• As discussed hereinabove, other material properties may be exploited to practice the fundamentals of the present disclosure.FIGS. 9-11 illustrate additional embodiments of the present disclosure.
• FIG. 9 illustrates a partial cross-section of an end effector assembly400 that includes opposing jaw members410 and420. Each jaw member410,420 include a jawconductive plate212,222 andcompressible membranes412,422. The jawconductive plates212,222 connect to opposing potentials of a source of electrosurgical energy (e.g., electrosurgical generator, not explicitly shown) and provide electrosurgical energy to the correspondingcompressible membrane412,422 attached thereto.
• Compressible membranes412 and422, instead of having a variable capacitance, as discussed hereinabove with respect toFIGS. 7 and 8, each include an array of conductive particles “CP” embedded through-out each of thecompressible membranes412 and422. Compression of thecompressible membranes412 and422 decreases the distance between the conductive particles “CP” thereby changing the conductive properties of thecompressible membranes412 and422.
• In one embodiment, the conductivity of thecompressible membrane412,422 is related to the percentage of the compression. For example, as a portion of thecompressible membrane412,422 is compressed, the distance between conductive particles “CP” decreases and the compressed portion of thecompressible material412,422 becomes more conductive. The percentage of compression may range from about 0% compression (e.g., uncompressed) to 90% compression, wherein the thickness at 90% compression is about 1/9^ththe thickness at 0% compression. The compression percentage is related to the conductivity of thecompressible membrane412,422 wherein the conductivity decreases with an increase in the compression percentage.
• The change in conductivity of thecompressible membrane412,422 may be directly proportional to the compression percentage (e.g., related to the change in thickness). This relationship may be a linear or a non-linear relationship with respect to the compression percentage.
• The conductivity of thecompressible membrane412,422 may be related to a change in the spacing between the conductive particles “CP” or related to a change in the distribution of the conductive particles “CP”. The relationship therebetween may be a linear, a non-linear or any combination thereof.
• The cross-sections illustrated inFIGS. 9 and 10 exposes a particular distribution of conductive particles “CP” formed in thecompressible membranes412,422. The particular distributions are exemplary as any suitable particle distribution may be used. Theuncompressed portions412a-412band422a-422bof thecompressible membrane412 and422, respectively, illustrate evenly distributed conductive particles “CP” with substantially uniform spacing between columns and/or rows.
• InFIG. 9, a varying compression bias is applied to thecompressible membranes412,422 in the area adjacent tissue “T” wherein the force of the compression bias is related to the thickness of the tissue “T” positioned between thecompressible membranes412,422. As the compression bias applied by the tissue “T” increases, the spacing between the rows of the conductive particles “CP”, within thecompressible membranes412,422, is reduced while the spacing between the columns of conductive particles “CP” remains unchanged. In other words, under compression the arrangement of the conductive particles “CP” remains substantially the same with respect to the spacing between columns with the only change in the arrangement of the conductive particles “CP” being a decrease in the spacing between rows. In this particular embodiment, applying a compression bias to thecompressible membrane412,422 does not redistribute the conductive particles “CP” but merely changes the spacing therebetween.
• In a further embodiment, at least one of thecompressible membranes412,422 exhibits resilient properties wherein a substantial portion of thecompressible membrane412,422 returns to its original shape (e.g., thickness and/or material distribution) after the compression bias is removed.
• FIG. 10 illustrates another embodiment of the present disclosure wherein a varying compression bias applied by the tissue “T” results in a redistribution of the conductive particles “CP”. As illustrated in the cross-section ofFIG. 10, a particular distribution of conductive particles “CP” is formed in thecompressible membranes412,422 of an end effector assembly500. The end effector assembly includes opposing jaw members510 and520 each jaw member510,520 including a jawconductive plate212,222 and acompressible membrane512,522. The jawconductive plates212,222 each connect to opposing potentials of a source of electrosurgical energy (e.g., electrosurgical generator, not explicitly shown) and provide electrosurgical energy to the correspondingcompressible membrane512,522 attached thereto.
• Theuncompressed portions512a-512band522a-522bof thecompressible membranes512 and522, respectively, illustrate evenly distributed conductive particles “CP” with substantially uniform spacing between columns and between rows. As a compression bias is applied to thecompressible membranes412,422 (e.g., in the area adjacent tissue “T”) the spacing between conductive particles “CP” within thecompressible membranes512,522 is reduced with respect to the spacing between rows of conductive particles “CP” and with respect to the spacing between columns of conductive particles “CP”. In other words, applying a compression bias to thecompressible membrane512,522 changes the spacing between the conductive particles “CP” in thecompressed portion512c,522cof thecompressible membranes512,522 by redistributing and/or repositioning the conductive particles “CP”. As such, the change in the conductive property of thecompressible membranes512,522 may be due to the change in the distance between conductive particles “CP” (due to the applied compression bias), may be due to the redistribution of the conductive particles “CP” or both.
• In one embodiment, thecompressible membranes512,522 includes a gel-like material that is repositionable within thecompressible membranes512,522. The varying compression bias, applied to thecompressible membranes512,522 by compressing the tissue “T”, repositions the gel-like material within thecompressible membranes512,522. Repositioning of the gel-like material may change one or more material properties, such as, for example, the repositioning may decrease the capacitance and/or the resistance of in the vicinity of the applied compression bias (e.g., in the area adjacent tissue “T”). The repositioning of the gel-like material may also increasing the capacitance and/or the resistance of theuncompressed portions512a-512band522a-522bof thecompressible membranes512,522 in the vicinity away from the applied compression bias. Alternatively, repositioning the gel-like material may increase the conductive properties of thecompressible membranes512,522 in the vicinity of the applied compression bias while the repositioned material may decrease the conductive properties in the vicinity of theuncompressed portion512a-512band522a-522b.
• FIG. 11 illustrates another embodiment of the present disclosure in which the cross-section exposes a plurality of switchingmechanisms640 embedded in or near the opposing surfaces of one or bothcompressible membranes612,622. The end effector assembly600 includes opposing jaw members610 and620 that each include a jawconductive plate212,222 and acompressible membrane612,622. The jawconductive plates212 and222 connects to opposing potentials of a source of electrosurgical energy (e.g., electrosurgical generator, not explicitly shown), and provides electrosurgical energy to each of the correspondingcompressible membrane612,622 attached thereto.
• Thecompressible membranes612,622 may include a plurality ofswitches640 formed on, or below, one or moreopposing surfaces612d,622d.Switches640, in the absence of an applied compression bias, form a high-resistance pathway (e.g., form an open connection) through thecompressible membranes612,622. As such, the uncompressed portions612a-612band622a-622bof the respectivecompressible membrane612,622 form a high-resistance and/or low conduction pathway between the jawconductive plates212 and222.
• The application of a compression bias (e.g., positioning of tissue “T” between the compressible membranes612,622) engagesindividual switches640 thereby forming a plurality of low resistance connections with tissue “T” and the portions of thecompressible membranes612,622 receiving the compression bias. As such, thecompressed portions612c,622cform a low-resistance and/or a highly conductive pathway between the jawconductive plates212,222 through thecompressed portions612cand622cof thecompressible membranes612 and622 and the tissue “T” positioned therebetween.
• FIG. 12 illustrates another embodiment of the present disclosure in which the cross-section exposes a plurality ofswitches740 each including aninner plate740aand a correspondingouter plate740bpositioned in thecompressible membranes712 and722 and separated by anon-conductive fluid74. Theinner plates740aindividually connect to the respective jawconductive plate212,222 and theouter plates740bindividually connect to the opposingsurfaces712dand722dof the respectivecompressible membranes712 and722. In an uncompressed condition, eachinner plate740aandouter plate740bpair is separated by the non-conductive fluid thereby forming a high-resistance and/or low conduction pathway through thecompressible membranes712,722. The application of a compression bias compresses thecompressible membrane612,622 thereby moving theinner plates740aand/or theouter plates740btoward one another in the vicinity of the applied compression bias (e.g., adjacent the tissue “T”). Moving theupper plates740aand thelower plates740btoward one another forces the non-conductive fluid74 from between the individual pairs of upper andlower plates740aand740band at least a portion of the upper andlower plates740aand740bform an electrical connection therebetween.
• The compression bias generated by compressing tissue “T” must overcome the fluid pressure formed within thecompressible membranes712,722 to displace the non-conductive fluid74 from between theparallel plates740aand749b. Displacing thenon-conductive fluid74 and forcing theparallel plates740aand740btogether forms a low-resistance and/or highly conductive pathway between the jawconductive plates212 and222 through thecompressible membranes612,622 and the tissue “T”.
• Various aspects described in the present disclosure effectively “steer” or “direct” current to the portions of the compressible membranes where the tissue applies a compression bias between thejaw members210,220 thereby reducing, if not eliminating, stray current paths that are not through tissue “T” Eliminating and/or reducing stray currents reduces the overall energy requirements of the electrosurgical generator, improves electrosurgical generator efficiently and increases patient safety.
• The compressible membranes described herein may include a fluid with viscous properties that facilitate the deformation of the compressible membranes adjacent tissue “T”. In one embodiment, the viscosity of the fluid in the compressible membrane is indirectly proportional to temperature (e.g., an increase in temperature decrease the viscosity of the fluid). As such, heat generated in tissue “T” conducts to a portion of the compressible membrane adjacent the tissue “T” thereby lowering the viscosity of the fluid in the compressible membrane. Lowering the viscosity of the fluid adjacent the tissue “T” may provide additional compression of the compressible membrane.
• Fluid in the compressible membrane may be configured to expand as temperature increases. Expansion of the fluid in the compressible membrane increases the pressure applied to the tissue “T” positioned between. At the initiation of a seal cycle, the temperature of the compressible membrane is at a minimum. As the sealing cycle is performed, the temperature of the compressible membrane increases thereby resulting in an expansion of the fluid that forms the compressible membrane. The expansion results in an increase in the pressure applied to tissue “T” and binding of the collegen/elastin is performed under the higher pressures. The tissue “T”, as it continues to heat, eventual shrinks thus reducing the pressure applied by thejaw members210,220. As such, the pressure profile may be used to determine the completion of the seal cycle.
• In some embodiments, the compressible membranes described herein may include a rheopectic fluid wherein the viscosity increases when subjected to the compression bias. Rheopectic fluids show a time-dependent change in viscosity wherein the longer the fluid undergoes a shearing force, the higher its viscosity. Application of a compression bias to a compressible membrane containing a rheopectic fluid increases the viscosity of the fluid. Fluid may be displaced by the placement of tissue “T” between thejaw members210,220 (e.g., fluid moves away from the tissue “T” where the pressure is applied) thereby expanding other areas of the jaw members thus resulting in an increased compression bias being applied to the displaced fluid. The rheopectic nature of the fluid would result in an increase in viscosity and possible partial or full solidification of at least a portion of the rheopectic fluid.
• In some embodiments, compressible membrane provides a minimum separation distanced (e.g., gap) between thejaw members210,220 thereby preventing closure therebetween and preventing pre-mature cutting of the tissue “T”. Embodiments that include a rheopectic fluid may form a minimum gap by “setting” (e.g., increasing of viscosity) a portion of the rheopectic fluid to a semi-solid or solid state.
• Various aspects of the compressible membranes described in the present disclosure electrically insulate and/or isolate the electrically conductive portions of the jaw members (e.g., the jawconductive plates212,222) from the surgical field. The compressible membranes described herein may be applied to other types of electrosurgical instruments. For example, an electrosurgical pencil may include a compressible membrane according to the present disclosure wherein the surgical pencil only conducts after a suitable amount of pressure is applied to the patient by the electrosurgical pencil. The electrical isolation, connection and switching mechanisms described herein, as applied to the various tissue sealing devices, tissue sealing technologies and electrosurgical devices, enables the devices to be utilized in a field flooded with fluid and/or saline, such as, for example, procedures associated with the uterus, bladder, kidneys and prostate.
• In addition, steering the electrosurgical currents to the applied compression bias as discussed hereinabove, enables an electrosurgical generator to utilize algorithms associated with vessel sealing in a surgical field flooded with fluid and/or saline. In the generator, alarms related to excess fluid and/or excess leakage currents may be bypassed and/or eliminated and clinician may not to include the step of clearing fluids from the surgical field prior to performing an electrosurgical tissue sealing procedure, thereby reducing the time of such surgical procedures.
• From the foregoing and with reference to the various figure drawings, those skilled in the art will appreciate that certain modifications can also be made to the present disclosure without departing from the scope of the same. 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. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims (14)

1-20. (canceled)

21. A bipolar end effector, comprising:

first and second opposing jaw members, at least one of the jaw members configured to move between an open position and a closed position for grasping tissue between the jaw members, each of the first and second jaw members including an electrically conductive tissue sealing surface disposed thereon; and

a first membrane disposed on the tissue sealing surface of the first jaw member and a second membrane disposed on the tissue sealing surface of the second jaw member, the tissue sealing surfaces configured to connect the first and second membranes to a source of electrosurgical energy, each of the first and second membranes configured to compress such that an outer surface portion of each of the first and second membranes conforms to the contour of tissue grasped between the first and second jaw members upon movement of at least one of the jaw members to the closed position,

wherein compression of the first and second membranes causes the first and second membranes to direct electrosurgical energy from the tissue sealing surfaces to the tissue grasped between the first and second jaw members.

22. The bipolar end effector according toclaim 21, wherein the first and second membranes completely cover the corresponding tissue sealing surface of the first and second jaw members.

23. The bipolar end effector according toclaim 21, further comprising at least one switching device disposed within the outer surface portion of at least one of the first or second membranes.

24. The bipolar end effector according toclaim 23, wherein the at least one switching device is configured to direct electrosurgical energy from the tissue sealing surfaces away from an uncompressed portion of the first and second membranes and through a compressed portion of the first and second membranes to the tissue grasped between the first and second jaw members.

25. The bipolar end effector according toclaim 21, wherein the first and second membranes include a plurality of conductive particles disposed therein, the first and second membranes configured to transition between an uncompressed condition such that the plurality of conductive particles are separated by a distance and a compressed condition such that the distance is decreased.

26. The bipolar end effector according toclaim 21, further comprising a pair of electrically conductive parallel plates disposed within at least one of the first or second membranes.

27. The bipolar end effector according toclaim 26, wherein the first and second membranes include a non-conductive fluid disposed therein, the first and second membranes configured to transition between an uncompressed condition such that the non-conductive fluid is disposed between the pair of electrically conductive parallel plates and a compressed condition such that the non-conductive fluid is displaced from between the pair of electrically conductive parallel plates.

28. The bipolar end effector according toclaim 27, wherein a viscosity of the non-conductive fluid is related to a temperature of the first and second membranes.

29. The bipolar end effector according toclaim 27, wherein a viscosity of the non-conductive fluid is indirectly proportional to a temperature of the first and second membranes.

30. A bipolar end effector, comprising:

first and second opposing jaw members, at least one of the jaw members moveable from an open position to a closed position for grasping tissue between the jaw members, each of the first and second jaw members including an electrically conductive tissue sealing surface disposed thereon;

a first membrane disposed on the tissue sealing surface of the first jaw member and a second membrane disposed on the tissue sealing surface of the second jaw member, the tissue sealing surfaces configured to connect the first and second membranes to a source of electrosurgical energy; and

a switching device disposed within at least one of the first or second membranes, the at least one switching device configured to direct electrosurgical energy from the tissue sealing surfaces away from an uncompressed portion of the first and second membranes and through a compressed portion of the first and second membranes to the tissue grasped between the first and second jaw members.

31. The bipolar end effector according toclaim 30, wherein an outer surface portion of each of the first and second membranes is configured to compress to conform to the contour of tissue grasped between the first and second jaw members upon movement of at least one of the jaw members to the closed position.

32. The bipolar end effector according toclaim 30, wherein the first and second membranes completely cover the corresponding tissue sealing surface of the first and second jaw members.

33. A bipolar end effector, comprising:

first and second opposing jaw members, at least one of the jaw members configured to move between an open position and a closed position for grasping tissue between the jaw members, each of the first and second jaw members including an electrically conductive tissue sealing surface disposed thereon; and

a first membrane completely covering the tissue sealing surface of the first jaw member and a second membrane completely covering the tissue sealing surface of the second jaw member, the tissue sealing surfaces configured to connect the first and second membranes to a source of electrosurgical energy, each of the first and second membranes configured to compress such that an outer surface portion of each of the first and second membranes conforms to the contour of tissue grasped between the first and second jaw members upon movement of at least one of the jaw members to the closed position,

wherein the first and second membranes are configured to direct electrosurgical energy from the tissue sealing surfaces away from an uncompressed portion of the first and second membranes and through a compressed portion of the first and second membranes to the tissue grasped between the first and second jaw members.

Images