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(12) United States Patent
(10) Patent No.:
Wham et al. (54) VESSEL SEALING SYSTEM (71) Applicant: COVIDIEN AG, Neuhausen am Rheinfall (CH)
See application file for complete search history. (56)
Subject to any disclaimer, the term of this
patent is extended or adjusted under 35 U.S.C. 154(b) by 315 days.
U.S. PATENT DOCUMENTS 371,664 A 10, 1887 Brannan et al.
This patent is Subject to a terminal dis-
(21) Appl. No.: 14/072,342 (22) Filed:
*Jun. 28, 2016
(2013.01); A61B 2017/2945 (2013.01); A61 B 2018/0063 (2013.01); A61B 2018/00404 (2013.01); (Continued) (58) Field of Classification Search
James H. Orszulak, Nederland, CO (US)
US 9,375,271 B2
(45) Date of Patent:
FOREIGN PATENT DOCUMENTS
Nov. 5, 2013
Prior Publication Data
US 2014/OO58385 A1
Feb. 27, 2014
Related U.S. Application Data
(63) Continuation of application No. 13/652.932, filed on continuation of application No. 12/057,557, filed on (Continued) (51) Int. Cl. A6 IB 8/4 A6 IB 8/8
(Continued) OTHER PUBLICATIONS
U.S. Appl. No. 08/926,869, filed Sep. 10, 1997, Chandler. U.S. Appl. No. 08/177,950, filed Oct. 23, 1998, Frazier. U.S. Appl. No. 09/387,883, filed Sep. 1, 1999, Schmaltz. U.S. Appl. No. 09/591.328, filed Jun. 9, 2000, Ryan. U.S. Appl. No. 12/336,970, filed Dec. 17, 2008, Sremeich.
Oct. 16, 2012, now Pat. No. 8,591,506, which is a Mar. 28, 2008, now Pat. No. 8,287,528, which is a
Primary Examiner – Michael Peffley (57)
An electroSurgical system is disclosed. The electroSurgical system includes an electroSurgical generator adapted to Sup ply electroSurgical energy to tissue. The electroSurgical gen erator includes impedance sensing circuitry which measures impedance of tissue, a microprocessor configured to deter mine whether a tissue reaction has occurred as a function of a
minimum impedance value and a predetermined rise in impedance, wherein tissue reaction corresponds to a boiling
point of tissue fluid, and an electrosurgical instrument includ ing at least one active electrode adapted to apply electroSur
gical energy to tissue.
7 Claims, 17 Drawing Sheets
US 9,375,271 B2 Page 2 Related U.S. Application Data continuation of application No. 10/626,390, filed on Jul. 24, 2003, now Pat. No. 7,364,577, which is a continuation-in-part of application No. 10/073,761, filed on Feb. 11, 2002, now Pat. No. 6,796,981, which is a continuation-in-part of application No. 09/408, 944, filed on Sep. 30, 1999, now Pat. No. 6,398,779. (60) Provisional application No. 60/105,417, filed on Oct. 23, 1998.
(51) Int. Cl. A6 IB A61B A61B A61B
8/2 7/12 7/29 18/00
(2006.01) (2006.01) (2006.01) (2006.01)
(52) U.S. Cl. CPC .................. A61 B2018/00601 (2013.01); A61B
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EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP GB GB GB GB JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP JP
WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO WO
WO O2/080785 WO O2/080786 WO O2/080793 WO O2/080794 WO O2/080795 WO O2/080796 WO O2/080797 WO O2/080798 WO O2/080799 WO O2/O81 170 WO O2/O85218 WO O2/O94746 WOO3,061500 WO 03/068046 WOO3,O90630 WOO3,096880 WOO3/101311 WO 2004/028585 WO 2004/032776 WO 2004/O32777 WO 2004/052221 WO 2004/073488 WO 2004/073490 WO 2004/073753 WO 2004/082495 WO 2004/083797 WO 2004/098383 WO 2004,103 156 WO 2005/004734 WO 2005/004.735 WO 2005/009255 WO 2005/O11049 WO 2005/030071 WO 2005/048.809 WO 2005/05O151 WO 2005,110264 WO 2006/021269 WO 2008/OO8457 WO 2008/04.0483 WO 2008.045348 WO 2008.045350 WO 2008, 112147 WO 2009/005850 WO 2009/032623 WO 2009/039.179 WO 2009/0395.10 WO 2009/124097 WO 2010/104753 WO 2011/O18154
Michael Choti, Abdominoperineal Resection with the LigaSureVes
& OTHER PUBLICATIONS
sel Sealing System and LigaSure Atlas 20 cm Open Instrument':
Innovations That Work, Jun. 2003.
8, 1999 8, 1999
Chung et al., "Clinical Experience of Sutureless Closed Hemor rhoidectomy with LigaSure” Diseases of the Colon & Rectum vol.
5431 p. 361, ISSN: 0007-1447.
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WO WO WO
WOOO,53112 WOOO. 59392 WO 01 00114
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Koyle et al., “Laparoscopic Palomo Varicocele Ligation in Children and Adolescents' Pediatric EndoSurgery & Innovative Techniques, vol. 6, No. 1, 2002.
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LigaSure Vessel Sealing System, the Seal of Confidence in General, Gynecologic, Urologic, and Laparaoscopic Surgery; Sales/Product Literature; Apr. 2002. Joseph Ortenberg “LigaSure System Used in Laparoscopic 1st and 2nd Stage Orchiopexy” Innovations That Work, Nov. 2002. Sigel et al. “The Mechanism of Blood Vessel Closure by High Fre quency Electrocoagulation” Surgery Gynecology & Obstetrics, Oct. 1965 pp. 823-831. Sampayan et al. “Multilayer Ultra-High Gradient Insulator Technol ogy” Discharges and Electrical Insulation in Vacuum, 1998. Nether lands Aug. 17-21, 1998; vol. 2, pp. 740-743. Paul G. Horgan, “A Novel Technique for Parenchymal Division Dur ing Hepatectomy” The American Journal of Surgery, vol. 181, No. 3, Apr. 2001 pp. 236-237. Benaron et al., “Optical Time-of-Flight and Absorbance Imaging of Biologic Media'. Science, American Association for the Advance ment of Science, Washington, DC, vol. 259, Mar. 5, 1993, pp. 1463 1466.
Olsson et al. “Radical Cystectomy in Females' Current Surgical Techniques in Urology, vol. 14, Issue 3, 2001. Palazzo et al. “Randomized clinical trial of Ligasure versus open haemorrhoidectomy' British Journal of Surgery 2002, 89, 154-157. Levyet al. “Randomized Trial of Suture Versus Electrosurgical Bipo lar Vessel Sealing in Vaginal Hysterectomy Obstetrics & Gynecol ogy, vol. 102, No. 1, Jul. 2003. “Reducing Needlestick Injuries in the Operating Room' Sales/Prod uct Literature 2001.
Bergdahl et al. “Studies on Coagulation and the Development of an Automatic Computerized Bipolar Coagulator J.Neurosurg, vol. 75. Jul. 1991, pp. 148-151. Strasberg et al. “A Phase I Study of the LigaSure Vessel Sealing System in Hepatic Surgery Section of HPB Surger, Washington University School of Medicine, St. Louis MO, Presented at AHPBA, Feb. 2001.
Sayfan et al. “Sutureless Closed Hemorrhoidectomy: A New Tech nique” Annals of Surgery vol. 234 No. 1 Jul. 2001; pp. 21-24. Levyet al., “Update on Hysterectomy New Technologies and Tech niques' OBG Management, Feb. 2003. Dulemba et al. “Use of a Bipolar Electrothermal Vessel Sealer in Laparoscopically Assisted Vaginal Hysterectomy” Sales/Product Literature; Jan. 2004.
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US 9,375,271 B2 1. VESSEL SEALING SYSTEM CROSS REFERENCE TO RELATED APPLICATIONS
The present application is a continuation of U.S. patent application Ser. No. 13/652.932, entitled “Vessel Sealing System”, by Robert Wham et al., now U.S. Pat. No. 8,591, 506, which is a continuation of U.S. patent application Ser. No. 12/057,557 entitled “Vessel Sealing System”, by Robert
Wham et al., now U.S. Pat. No. 8,287,528, which is a con
tinuation of U.S. patent application Ser. No. 10/626,390 also entitled “Vessel Sealing System', by Robert Wham et al., now U.S. Pat. No. 7,364,577, which is a continuation-in-part application of U.S. patent application Ser. No. 10/073,761 also entitled “Vessel Sealing System', by Robert Wham et al., now U.S. Pat. No. 6,796,981, which is a continuation-in-part of U.S. patent application Ser. No. 09/408,944 also entitled “Vessel Sealing System', by Robert Wham et al., now U.S. Pat. No. 6,398,779, and which claims priority to U.S. Provi sional Patent Application Ser. No. 60/105,417 filed on Oct. 23, 1998. The disclosure of each Patent Application is incor porated by reference herein in its entirety. FIELD
This invention relates generally to medical instruments and, in particular, to generators that provide radio frequency (RF) energy useful in sealing tissue and vessels during elec troSurgical and other procedures. ElectroSurgical generators are employed by Surgeons to cut and coagulate the tissue of a patient.
It has been well established that a measurement of the
electrical impedance of tissue provides an indication of the state of desiccation of the tissue, and this observation has been
High frequency electrical power, which may be also referred to as radio frequency (RF) power or energy, is pro duced by the electroSurgical generator and applied to the tissue by an electroSurgical tool. Both monopolar and bipolar configurations are commonly used during electroSurgical procedures. ElectroSurgical techniques can be used to seal Small diam eter blood vessels and vascular bundles. Another application of electroSurgical techniques is in tissue fusion wherein two layers of tissue are grasped and clamped together by a Suitable electroSurgical tool while the electroSurgical RF energy is applied. The two layers of tissue are then fused together. At this point it is significant to note that the process of coagulating Small vessels is fundamentally different than ves sel sealing or tissue fusion. For the purposes herein the term coagulation can be defined as a process of desiccating tissue wherein the tissue cells are ruptured and dried. Vessel sealing or tissue fusion can both be defined as desiccating tissue by the process of liquefying the collagen in the tissue so that it crosslinks and reforms into a fused mass. Thus, the coagula tion of small vessels if generally sufficient to close them, however, larger vessels normally need to be sealed to assure permanent closure. However, and as employed herein, the term “electrosurgi cal desiccation' is intended to encompass any tissue desicca tion procedure, including electroSurgical coagulation, desic cation, Vessel sealing, and tissue fusion. One of the problems that can arise from electrosurgical desiccation is undesirable tissue damage due to thermal effects, wherein otherwise healthy tissue surrounding the tis Sue to which the electroSurgical energy is being applied is thermally damaged by an effect known in the art as “thermal
2 spread’. During the occurrence of thermal spread excess heat from the operative site can be directly conducted to the adja cent tissue, and/or the release of steam from the tissue being treated at the operative site can result in damage to the Sur rounding tissue. It can be appreciated that it would be desirable to provide an electroSurgical generator that limited the possibility of the occurrence of thermal spread. Another problem that can arise with conventional electro Surgical techniques is a buildup of eschar on the electroSur gical tool or instrument. Eschar is a deposit that forms on working Surface(s) of the tool, and results from tissue that is electrosurgically desiccated and then charred. One result of the buildup of eschar is a reduction in the effectiveness of the Surgical tool. The buildup of escharon the electroSurgical tool can be reduced if less heat is developed at the operative site.
utilized in Some electroSurgical generators to automatically terminate the generation of electroSurgical power based on a measurement of tissue impedance. At least two techniques for determining an optimal amount of desiccation are known by those skilled in this art. One technique sets a threshold impedance, and terminates electro Surgical power when the measured tissue impedance crosses the threshold. A second technique terminates the generation of electroSurgical power based on dynamic variations in the tissue impedance. A discussion of the dynamic variations of tissue impedance can be found in a publication entitled “Automatically Con trolled Bipolar Electrocoagulation”, Neurosurgical Review, 7:2-3, pp. 187-190, 1984, by Vallfors and Bergdahl. FIG. 2 of this publication depicts the impedance as a function of time during the heating of a tissue, and the authors reported that the impedance value of tissue was observed to be near to a mini mum value at the moment of coagulation. Based on this observation, the authors suggest a micro-computer technique for monitoring the minimum impedance and Subsequently terminating the output power to avoid charring the tissue. Another publication by the same authors, “Studies on Coagulation and the Development of an Automatic Comput erized Bipolar Coagulator, Journal of Neurosurgery, 75:1, pp. 148-151, July 1991, discusses the impedance behavior of tissue and its application to electroSurgical vessel sealing, and reports that the impedance has a minimum value at the moment of coagulation. The following U.S. Patents are also of interest in this area. U.S. Pat. No. 5,540.684, Hassler, Jr. addresses the problem associated with turning off the RF energy output automati cally after the tissue impedance has fallen from a predeter mined maximum, Subsequently risen from a predetermined minimum and then reached a particular threshold. A storage device records maximum and minimum impedance values, and a circuit determines the threshold. U.S. Pat. No. 5,472,
443, Cordis et al., discusses a variation of tissue impedance with temperature, wherein the impedance is shown to fall, and then to rise, as the temperature is increased. FIG. 2 of this patent shows a relatively lower temperature Region A where salts contained in body fluids are believed to dissociate, thereby decreasing the electrical impedance. A relatively next higher temperature Region B is where the water in the tissue boils away, causing the impedance to rise. The next relatively higher temperature Region C is where the tissue becomes charred, which results in a slight lowering of the electrical impedance. U.S. Pat. No. 4,191,188, Belt et al., discloses the use of two timers whose duty cycles are simultaneously and
US 9,375,271 B2 3 proportionately adjusted so that high frequency signal bursts are constantly centered about the peak power point, regard less of duty cycle variations. Also of interest is U.S. Pat. No. 5,827,271, Buysse et al., “Energy Delivery System for Vessel Sealing, which employs a Surgical tool capable of grasping a tissue and applying an appropriate amount of closure force to the tissue, and for then conducting electroSurgical energy to the tissue concurrently with the application of the closure force. FIG. 2 of this patent, shown herein as FIG. 1 for depicting the prior art, illustrates a set of power curves which represent the electroSurgical power delivered to the tissue as a function of the tissue imped ance. At low impedances, the electroSurgical power is increased by rapidly increasing the output current. The increase in electroSurgical power is terminated when a first impedance breakpoint, labeled as 1, is reached (e.g. <20 ohms). Next, the electroSurgical power is held approximately constant until proteins in the vessels and other tissues have melted. The impedance at which this segment ends varies in accordance with the magnitude of the RMS power. For example, where the maximum RMS power is approximately 125 Watts, the segment (B) ends at about 128 ohms. When a lower power is used (e.g., 75 Watts), the segment (C) may end at an impedance value of 256 ohms. Next, the output power is
4 An accommodation for overvoltage clamping is also desir able. In this regard, conventional overVoltage techniques use a means of clamping or clipping the excess overvoltage using avalanche devices Such as diodes, Zener diodes and transorbs
lowered to less than one half the maximum value, and the
lower power delivery is terminated when a second impedance breakpoint is reached (2.048x103 ohms). Alternatives to using the impedance for determining the second breakpoint are the use of I-V phase angle, or the magnitude of the output Based on the foregoing it should be evident that electro surgery requires the controlled application of RF energy to an operative tissue site. To achieve Successful clinical results during Surgery, the electroSurgical generator should produce a controlled output RF signal having an amplitude and wave shape that is applied to the tissue within predetermined oper ating levels. However, problems can arise during electroSur gery when rapid desiccation of tissue occurs resulting in excess RF levels being applied to the tissue. These excess levels produce less than desirable tissue effects, which can increase thermal spread, or can cause tissue charring and may shred and disintegrate tissue. It would be desirable to provide a system with more controlled output to improve vessel seal ing and reduce damage to Surrounding tissue. The factors that affect vessel sealing include the Surgical instrument utilized, as well as the generator for applying RF energy to the instru ment jaws. It has been recognized that the gap between the instrument jaws and the pressure of the jaws against the tissue affect tissue sealing because of their impact on current flow. For example, insufficient pressure oran excessive gap will not Supply sufficient energy to the tissue and could result in an inadequate seal. However, it has also been recognized that the application of RF energy also affects the seal. For example, pulsing of RF energy will improve the seal. This is because the tissue loses moisture as it desiccates and by stopping or significantly lowering the output the generator between pulses, this allows Some moisture to return to the tissue for the application of next RF pulse. It has also been recognized by the inventors that varying each pulse dependent on certain parameters is also advantageous in providing an improved seal. Thus, it would be advantageous to provide a vessel sealing system which better controls RF energy and which can be varied at the outset of the procedure to accommodate different tissue structures, and which can further be varied during the proce dure itself to accommodate changes in the tissue as it desic Cates.
So as to limit the operating levels. In these techniques the excess energy, as well as the forward conduction energy, is absorbed by the protection device and inefficiently dissipated in the form of heat. More advanced prior art techniques actively clamp only the excess energy using a predetermined comparator reference value, but still absorb and dissipate the excess energy in the form of heat. U.S. Pat. No. 5,594,636 discloses a system for AC to AC power conversion using Switched commutation. This system addresses overVoltage conditions which occur during Switched commutation by incorporating an active output volt age sensing and clamping using an active clamp Voltage regu lator which energizes to limit the output. The active clamp Switches in a resistive load to dissipate the excess energy caused by the overvoltage condition. Other patents in this area include U.S. Pat. No. 5,500,616, which discloses an overvoltage clamp circuit, and U.S. Pat. No. 5,596,466, which discloses an isolated half-bridge power module. Both of these patents identify output overvoltage limiting for all power devices, and overvoltage limit protec tion is provided for power devices by using proportionately scaled Zeners to monitor and track the output off voltage of each device to prevent power device failure. The Zener device is circuit configured such that it provides feedback to the gate of the power device. When Zeneravalanche occurs the power device partially turns on, absorbing the excess overvoltage energy in conjunction with the connective load. Reference can also be had to U.S. Pat. No. 4,646,222 for disclosing an inverter incorporating overvoltage clamping. Overvoltage clamping is provided by using diode clamping devices referenced to DC power sources. The DC power Sources provide a predetermined reference Voltage to clamp the overvoltage condition, absorbing the excess energy through clamp diodes which dissipate the excess Voltage in the form of heat.
It would be advantageous as to provide an electroSurgical generator having improved overvoltage limit and transient energy Suppression. SUMMARY
The foregoing and other problems are overcome by meth ods and apparatus in accordance with embodiments disclosed herein. 50
An electroSurgical generator includes a controlling data processor that executes Software algorithms providing a num ber of new and useful features. These features preferably include the generation of an initial pulse, that is a low power pulse of RF energy that is used to sense at least one electrical characteristic of the tissue prior to starting an electroSurgical desiccation cycle. Such as a tissue sealing cycle. The sensed electrical characteristic is then used as an input into the deter mination of initial sealing parameters, thereby making the sealing procedure adaptive to the characteristics of the tissue to be sealed. Another feature preferably provided measures the time required for the tissue to begin desiccating, prefer ably by observing an electrical transient at the beginning of an RF energy pulse, to determine and/or modify further seal parameters. Another preferable feature performs a tissue tem perature control function by adjusting the duty cycle of the RF energy pulses applied to the tissue, thereby avoiding the prob lems that can result from excessive tissue heating. A further preferable feature controllably decreases the RF pulse volt
US 9,375,271 B2 5 age with each pulse of RF energy so that as the tissue desic cates and shrinks (thereby reducing the spacing between the Surgical tool electrodes), arcing between the electrodes is avoided, as is the tissue destruction that may result from uncontrolled arcing. Preferably a Seal Intensity operator con trol is provided that enables the operator to control the sealing of tissue by varying parameters other than simply the RF power.
The system disclosed herein preferably further provides a unique method for overvoltage limiting and transient energy Suppression. An electroSurgical system uses dynamic, real time automatic detuning of the RF energy delivered to the tissue of interest. More specifically, this technique automati cally limits excess output RF Voltages by dynamically chang ing the tuning in a resonant Source of RF electroSurgical energy, and by altering the shape of the RF Source signal used to develop the output RF signal. The inventive technique limits the excess output transient RF energy by a resonant detuning of the generator. This occurs in a manner which does not clip or significantly distort the generated RF output signal used in a clinical environment for electroSurgical applica
BRIEF DESCRIPTION OF THE DRAWINGS 15
The above set forth and other features of the invention are
made more apparent in the ensuing Detailed Description when read in conjunction with the attached Drawings, wherein:
A method for electroSurgically sealing a tissue, in accor dance with this disclosure, preferably includes the steps of (A) applying an initial pulse of RF energy to the tissue, the pulse having characteristics selected so as not to appreciably heat the tissue; (B) measuring a value of at least one electrical characteristic of the tissue in response to the applied first pulse: (C) in accordance with the measured at least one elec trical characteristic, determining an initial set of pulse param eters for use during a first RF energy pulse that is applied to the tissue; and (D) varying the pulse parameters of subsequent RF energy pulses individually in accordance with at least one characteristic of an electrical transient that occurs at the
The at least one characteristic that controls the variation of
The step of determining an initial set of pulse parameters preferably includes a step of using the measured value of at least one electrical characteristic of the tissue to readout the
initial set of pulse parameters from an entry in a lookup table. The step of determining an initial set of pulse parameters may also preferably include a step of reading out the initial set of pulse parameters from an entry in one of a plurality of lookup tables, where the lookup table is selected either manu ally or automatically, based on the electroSurgical instrument or tool that is being used. The method also preferably includes a step of modifying predetermined ones of the pulse parameters in accordance with a control input from an operator. The predetermined ones of the pulse parameters that are modified include a pulse power, a pulse starting Voltage level, a pulse Voltage decay scale factor, and a pulse dwell time.
FIG. 1A is a graph that plots output power versus tissue impedance (Z) in ohms, in accordance with the operation of a prior art electroSurgical generator, FIG. 1B is a graph that plots output power versus imped ance in ohms, in accordance with the operation of an electro Surgical generator that is an aspect of this disclosure; FIG. 2 is a simplified block diagram of an electroSurgical system that can be used to practice the teachings of this disclosure;
beginning of each individual Subsequent RF energy pulse. The method terminates the generation of subsequent RF energy pulses based upon a reduction in the output Voltage or upon a determination that the electrical transient is absent. the pulse parameters is preferably a width of the electrical transient that occurs at the beginning of each Subsequent RF energy pulse. The initial set of pulse parameters include a magnitude of a starting power and a magnitude of a starting Voltage, and the pulse parameters that are varied include a pulse duty cycle and a pulse amplitude. Preferably, the sub sequent RF energy pulses are each reduced in amplitude by a controlled amount from a previous RF energy pulse, thereby compensating for a decrease in the spacing between the Sur gical tool electrodes due to desiccation of the tissue between
6 Preferably a circuit is coupled to the output of the electro Surgical generator for protecting the output against an over Voltage condition, and includes a Suppressor that detunes a tuned resonant circuit at the output for reducing a magnitude of a Voltage appearing at the output. In accordance with this aspect of the disclosure, the circuit has a capacitance network in parallel with an inductance that forms a portion of the output stage of the generator. A Voltage actuated Switch, Such as a transorb, couples an additional capacitance across the network upon an occurrence of an overvoltage condition, thereby detuning the resonant network and reducing the mag nitude of the Voltage output.
FIG. 3 is a perspective view of one embodiment of a sur gical instrument having bipolar forceps that are suitable for practicing this disclosure; FIG. 4 is an enlarged, perspective view of a distal end of the bipolar forceps shown in FIG. 3; FIG.5 is a perspective view of an embodiment of a surgical instrument having forceps that are Suitable for use in an endoscopic Surgical procedure utilizing the electroSurgical system disclosed herein; FIG. 6A is a simplified block diagram of a presently pre ferred embodiment of the power control circuit of the elec troSurgical generator of FIG. 2; FIG. 6B depicts the organization of a seal parameter lookup table (LUT) shown in FIG. 6A: FIGS. 7A and 7B illustrate a presently preferred electro surgical generator output waveform of RMS current vs. time for implementing at least the first pulse of the pulsed opera tion mode that is an aspect of this disclosure; FIG. 8 depicts a full set of electrosurgical RF pulses in accordance with this disclosure, and illustrates the Voltage, current and power characteristics of the pulses, as well as the response of the tissue impedance to the applied RF pulses; FIG.9A illustrates a Seal Intensity control that forms a part of this disclosure, while FIGS. 9B and 9C show a preferred variation in certain parameters from the seal parameter LUT based on different Seal Intensity settings; FIG. 10 is a simplified block diagram of a circuit for achieving an overvoltage limiting and transient energy Sup pression energy function; FIG. 11 is a waveform diagram illustrating the effect of the operation of the circuit in FIG. 10; FIG. 12 is a logic flow diagram that illustrates a method in accordance with the system disclosed herein; FIG. 13 is a more detailed logic flow diagram that illus trates a method in accordance with the system disclosed herein;
FIG. 14 is a chart illustrating a fixed number of pulses determined from the measured impedance and the RMS cur rent pulse width:
US 9,375,271 B2 8
7 FIG. 15 illustrates a Seal Intensity control that forms a part
16 and 18. These end effectors members 6A can be referred to
of this disclosure; and
FIG. 16 is a logic flow diagram that illustrates another method in accordance with the system disclosed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
An electroSurgical system 1, which can be used to practice this invention, is shown in FIG. 2. The system 1 can be used for sealing vessels 3 and other tissues of a patient, including ducts, veins, arteries and vascular tissue. The system 1 includes an electro-Surgical generator 2 and a Surgical tool, also referred to herein as a Surgical instrument 4. The Surgical instrument 4 is illustrated by way of example, and as will become apparent from the discussion below, other instru ments can be utilized. The electroSurgical generator 2, which is of most interest to the teachings herein, includes several interconnected Sub-units, including an RF drive circuit 2A, a power control circuit 2B, a variable D.C. power supply 2C and an output amplifier 2D. The Surgical instrument 4 is electrically connected to the electroSurgical generator 2 using a plug 5 for receiving controlled electroSurgical power there from. The Surgical instrument 4 has some type of end effector member 6, Such as a forceps or hemostat, capable of grasping and holding the vessels and tissues of the patient. The member 6, also referred to simply as end effector 6, is assumed, in this embodiment, to be capable of applying and maintaining a relatively constant level of pressure on the vessel 3. The member 6 is provided in the form of bipolar electro Surgical forceps using two generally opposing electrodes dis posed on inner opposing surfaces of the member 6, and which are both electrically coupled to the output of the electrosur gical generator 2. During use, different electric potentials are applied to each electrode. In that tissue is an electrical con ductor, when the forceps are utilized to clamp or grasp the vessel 3 therebetween, the electrical energy output from the electroSurgical generator 2 is transferred through the inter vening tissue. Both open Surgical procedures and endoscopic Surgical procedures can be performed with Suitably adapted Surgical instruments 4. It should also be noted that the mem ber 6 could be monopolar forceps that utilize one active electrode, with the other (return) electrode or pad being attached externally to the patient, or a combination of bipolar and monopolar forceps. By way of further explanation, FIG.3 is a perspective view of one embodiment of the Surgical instrument 4 having a bipolar end effector implemented as forceps 6A while FIG. 4 is an enlarged, perspective view of a distal end of the bipolar forceps 6A shown in FIG. 3. Referring now to FIGS. 3 and 4, a bipolar surgical instru ment 4 for use with open Surgical procedures includes a mechanical forceps 20 and an electrode assembly 21. In the drawings and in the description which follows, the term “proximal, as is traditional, refers to the end of the instru
both of the end effectors 22, 24 can be movable.
As is best seen in FIG. 4, end effector 24 includes an upper or first jaw member 44 which has an inner facing Surface and a plurality of mechanical interfaces disposed thereon which are dimensioned to releasable engage a portion of an elec trode assembly 21, which may be disposable. Preferably, the mechanical interfaces include Sockets 41 which are disposed at least partially through the inner facing Surface of jaw mem ber 44 and which are dimensioned to receive a complimentary detent attached to an upper electrode 21A of the disposable electrode assembly 21. The upper electrode 21A is disposed across from a corresponding lower electrode 21B. The end effector 22 includes a second or lower jaw member 42 which has an inner facing Surface which opposes the inner facing surface of the first jaw member 44. Preferably, shaft members 12 and 14 of the mechanical forceps 20 are designed to transmit a particular desired force to the opposing inner facing Surfaces of the jaw members 22 and 24 when clamped. In particular, since the shaft members 12 and 14 effectively act together in a spring-like manner (i.e., bending that behaves like a spring), the length, width, height and deflection of the shaft members 12 and 14 directly impacts the overall transmitted force imposed on opposing jaw members 42 and 44. Preferably, jaw members 22 and 24 are more rigid than the shaft members 12 and 14 and the strain energy stored in the shaft members 12 and 14 provides a constant closure force between the jaw members 42 and 44. Each shaft member 12 and 14 also includes a ratchet por tion 32 and 34. Preferably, each ratchet, e.g., 32, extends from the proximal end of its respective shaft member 12 towards the other ratchet 34 in a generally vertically aligned manner such that the inner facing surfaces of each ratchet 32 and 34 abut one another when the end effectors 22 and 24 are moved
from the open position to the closed position. Each ratchet 32 and 34 includes a plurality of flanges which project from the inner facing surface of each ratchet 32 and 34 such that the ratchets 32 and 34 can interlock in at least one position. In the embodiment shown in FIG.3, the ratchets 32 and 34 interlock
at several different positions. Preferably, each ratchet position holds a specific, i.e., constant, strain energy in the shaft mem bers 12 and 14 which, in turn, transmits a specific force to the end effectors 22 and 24 and, thus, to the electrodes 21A and
21B. Also, preferably a stop is provided on one or both of the end effectors 22, 24 to maintain a preferred gap between the 55
ment 4 which is closer to the user, while the term “distal refers to the end which is further from the user.
Mechanical forceps 20 includes first and second members 9 and 11 which each have an elongated shaft 12 and 14, respectively. Shafts 12 and 14 each include a proximal end and a distal end. Each proximal end of each shaft portion 12,
collectively as bipolar forceps. Preferably, shaft portions 12 and 14 are affixed to one another at a point proximate the end effectors 22 and 24 about a pivot 25. As such, movement of the handles 16 and 18 imparts movement of the end effectors 22 and 24 from an open position, wherein the end effectors 22 and 24 are dis posed in spaced relation relative to one another, to a clamping or closed position, wherein the end effectors 22 and 24 coop erate to grasp the tubular vessel 3 therebetween. Either one or
In some cases it may be preferable to include other mecha nisms to control and/or limit the movement of the jaw mem bers 42 and 44 relative to one another. For example, a ratchet and pawl system could be utilized to segment the movement of the two handles into discrete units which, in turn, impart discrete movement to the jaw members 42 and 44 relative to
14 includes a handle member 16 and 18 attached thereto to
allow a user to effect movement of the two shaft portions 12 and 14 relative to one another. Extending from the distal end of each shaft portion 12 and 14 are end effectors 22 and 24, respectively. The end effectors 22 and 24 are movable relative to one another in response to movement of handle members
FIG. 5 is a perspective view of an embodiment of the Surgical instrument 4 having end effector members or forceps 63 that are suitable for an endoscopic surgical procedure. The end effector member 63 is depicted as sealing the tubular vessel 3 through a cannula assembly 48.
US 9,375,271 B2 The Surgical instrument 4 for use with endoscopic Surgical procedures includes a drive rod assembly 50 which is coupled to a handle assembly 54. The drive rod assembly 50 includes an elongated hollow shaft portion 52 having a proximal end and a distal end. An end effector assembly 63 is attached to the distal end of shaft 52 and includes a pair of opposing jaw members. Preferably, handle assembly 54 is attached to the proximal end of shaft 52 and includes an activator 56 for imparting movement of the forceps jaw members of end effector member 63 from an open position, wherein the jaw members are disposed in spaced relation relative to one another, to a clamping or closed position, wherein the jaw members cooperate to grasp tissue therebetween. Activator 56 includes a movable handle 58 having an aper ture 60 defined therein for receiving at least one of the opera tor's fingers and a fixed handle 62 having an aperture 64 defined therein for receiving an operators thumb. Movable handle 58 is selectively moveable from a first position relative to fixed handle 62 to a second position in the fixed handle 62 to close the jaw members. Preferably, fixed handle 62 includes a channel 66 which extends proximally for receiving a ratchet 68 which is coupled to movable handle 58. This structure allows for progressive closure of the end effector assembly, as well as a locking engagement of the opposing jaw members. In some cases it may be preferable to include
least the ADC block 78 can be an internal block of the feed
other mechanisms to control and/or limit the movement of
handle 58 relative to handle 62 such as, e.g., hydraulic, semi hydraulic and/or gearing systems. As with instrument 4, a stop can also be provided to maintain a preferred gap between the jaw members.
The handle 62 includes handle sections 62a and 62b, and is
generally hollow such that a cavity is formed therein for housing various internal components. For example, the cavity can house a PC board which connects the electrosurgical energy being transmitted from the electroSurgical generator 2 to each jaw member, via connector 5. More particularly, elec troSurgical energy generated from the electroSurgical genera tor 2 is transmitted to the handle PC board by a cable 5A. The PC board diverts the electrosurgical energy from the genera tor into two different electrical potentials which are transmit ted to each jaw member by a separate terminal clip. The handle 62 may also house circuitry that communicates with the generator 2, for example, identifying characteristics of the electroSurgical tool 4 for use by the electroSurgical generator 2, where the electroSurgical generator 2 may select a particu lar seal parameterlookup table based on those characteristics (as described below). Preferably, a lost motion mechanism is positioned between each of the handle sections 62a and 62b for maintaining a predetermined or maximum clamping force for sealing tissue between the jaw members. Having thus described two exemplary and non-limiting embodiments of Surgical instruments 4 that can be employed with the electroSurgical generator 2, a description will now be provided of various aspects of the inventive electroSurgical generator 2. FIG. 6A is a block diagram that illustrates the power con trol circuit 2B of FIG. 2 in greater detail. The power control circuit 2B includes a suitably programmed data processor 70 that is preferably implemented as one or more microcontrol ler devices. In a most preferred embodiment there are two principal microcontrollers, referred to as a main microcon
microcontrollers are capable of communicating using shared data that is stored and retrieved from a shared read/write
back microcontroller 70B, and need not be a separate, exter nal component. It should be further noted that the same ana log signals can be digitized and read into the master microcontroller 70A, thereby providing redundancy. The master microcontroller 70A controls the state (on/off) of the high Voltage (e.g., 190V max) power Supply as a safety pre caution, controls the front panel display(s), Such as a Seal Intensity display, described below and shown in FIG.9A, and also receives various input Switch closures, such as a Seal Intensity selected by an operator. It is noted that in a preferred embodiment of the electro surgical generator 2 a third (waveform) microcontroller 70C is employed to generate the desired 470 kHz, sinusoidal wave form thatforms the basis of the RF pulses applied to the tissue to be sealed, such as the vessel 3 (FIG. 2). The waveform microcontroller 70C is controlled by the feedback microcon troller 70B and is programmed thereby. An output signal line from the feedback microcontroller 70B is coupled to a Reset input of the waveform microcontroller 70C to essentially turn the waveform microcontroller 70C on and off to provide the pulsed RF signal in accordance with an aspect of this disclo Sure. This particular arrangement is, of course, not to be viewed in a limiting sense upon the practice of this system, as those skilled in the art may derive a number of methods and circuits for generating the desired RF pulses in accordance with the teachings found herein. As an overview, the software algorithms executed by the data processor 70 provide the following features. First, and referring now also to the preferred waveform depicted in FIGS. 7A and 7B, a low power initial pulse of RF energy is used to sense at least one electrical characteristic of the tissue
troller 70A and a feedback microcontroller 70B. These two
memory 72. A control program for the data processor 70 is stored in a program memory 74, and includes Software rou
10 tines and algorithms for controlling the overall operation of the electroSurgical generator 2. In general, the feedback microcontroller 70B has a digital output bus coupled to an input of a digital to analog converter (DAC) block 76 which outputs an analog signal. This is a system control Voltage (SCV), which is applied to the variable DC power supply 2C to control the magnitude of the Voltage and current of output RF pulses. An analog to digital converter (ADC) block 78 receives analog inputs and Sources a digital input bus of the feedback microcontroller 70B. Using the ADC block 78 the microcon troller 70B is apprised of the value of the actual output voltage and the actual output current, thereby closing the feedback loop with the SCV signal. The values of the output voltage and current can be used for determining tissue impedance, power and energy delivery for the overall, general control of the applied RF energy waveform. It should be noted that at
prior to starting the seal cycle. Second, the sensed electrical characteristic of the tissue is used as an input into the deter mination of the initial sealing parameters, thereby making the sealing procedure adaptive to the characteristics of the tissue to be sealed. Third, the technique measures the time required for the tissue to begin desiccating, preferably by observing an electrical transient, to determine and/or modify further seal parameters. Fourth, the technique performs a tissue tempera ture control function by adjusting the duty cycle of RF pulses applied to the tissue, thereby avoiding excessive tissue heat ing and the problems that arise from excessive tissue heating. This is preferably accomplished by using at least one calcu lated seal parameter related to the time required for the tissue to begin desiccating. Fifth, the technique controllably changes the RF pulse voltage with each pulse of RF energy DEL as the tissue desiccates and shrinks (thereby reducing the pacing between the Surgical instrument electrodes), arc ing between the instrument electrodes (e.g. 21A and 21B of
US 9,375,271 B2 11 FIG. 4) is avoided, as is the tissue destruction that may result from Such uncontrolled arcing This is also preferably accom plished by using at least one calculated seal parameter that is related to the time required for the tissue to begin desiccating. Sixth, the above-mentioned Seal Intensity front panel control (FIG.9A) enables the operator to control the sealing of tissue by varying parameters other than simply the RF power. These various aspects of this disclosure are now described in further detail.
Referring now also to the logic flow diagram of FIG. 13, the impedance sensing feature is implemented at the beginning of the seal cycle, wherein the electroSurgical generator 2 senses at least one electrical characteristic of the tissue, for example, impedance, I-V phase rotation, or the output current, by using a short burst of RF energy (FIG. 13, Steps A and B). The electrical characteristic of the tissue may be measured at any frequency or power level, but preferably is performed at the same frequency as the intended working frequency (e.g., 470 kHz). In a most preferred case the short burst of RF energy (preferably less than about 200 millisecond, and more pref erably about 100 millisecond) is a 470 kHz, sine wave with approximately 5 W of power. The initial pulse RF power is made low, and the pulse time is made as short as possible, to
enable an initial tissue electrical characteristic measurement
to be made without excessively heating the tissue. In a most preferred embodiment the electrical characteris tic sensed is the tissue impedance which is employed to determine an initial set of parameters that are input to the sealing algorithm, and which are used to control the selection of sealing parameters, including the starting power, current and voltage (FIG. 13, Step C). Other sealing parameters may include duty cycle and pulse width. Generally, if the sensed impedance is in the lower ranges, then the initial power and starting Voltage are made relatively lower, the assumption being that the tissue will desiccate faster and require less energy. If the sensed impedance is in the higher ranges, the initial power and starting Voltage are made relatively higher, the assumption being that the tissue will desiccate slower and require more energy. In other embodiments at least one of any other tissue elec trical characteristic, for example, the Voltage or current, can be used to set the parameters. These initial parameters are preferably modified in accordance with the setting of the Seal Intensity control input (FIG. 13, Step D), as will be described
moisture in the tissue, the current falls. Reference in this
regard can be had to the circled areas designated as 'A' in the It waveform of FIG. 8. The actual width of the resulting electrical transient, preferably a current transient 'A', is an important factor in determining what type and amount of tissue is between the jaws (electrodes) of the Surgical instru ment 4 (measured from “Full Power RF Start” to “Pulse Low and Stable'.) The actual current transient or pulse width is also employed to determine the changes to, or the values of the parameters of the pulse duty cycle (“Dwell Time') and to the change of the pulse Voltage, as well as other parameters. This parameter can also be used to determine whether the tissue seal has been completed, or if the Surgical instrument 4 has shorted.
in further detail below.
Referring again to FIG. 13, Step C, the sensed impedance is employed to determine which set of values are used from a seal parameterlookup table (LUT) 80 (see FIGS.6A and 6B). The seal parameter look up table may one of a plurality that are stored in the generator or accessible to the generator. Furthermore, the seal parameter table may be selected manu ally or automatically, based on, for example, the electroSur gical tool or instrument being employed. The specific values read from the seal parameter LUT 80 (FIG. 6B) are then adjusted based on the Seal Intensity front panel setting 82 (FIG. 13, Step D), as is shown more clearly in FIGS. 9A and 9B. In a preferred, but not limiting embodiment, the values read from the seal parameter LUT 80 comprise the power, the maximum Voltage, starting Voltage, minimum Voltage, Volt age decay, Voltage ramp, maximum RF on time, maximum cool scale factor, pulse minimum, pulse dwell time, pulse off time, current and the desired pulse width. In a preferred, but not limiting embodiment, the seal parameter values adjusted by the Seal Intensity front panel setting 82 (FIGS. 9A and 9B) comprise the power, starting Voltage, Voltage decay, and pulse
12 FIG. 1B is a graph that plots output power versus imped ance in ohms for the disclosed electroSurgical generator. The plot labeled “Intensity Bar 1 shows the electrosurgical gen erator power output versus impedance when the “VLOW' setting 82A (FIG.9A) of the Seal Intensity front panel setting 82 is selected. The plot labeled Intensity Bar 2 shows the power output of the electroSurgical generator when the “LOW setting 82B of the Seal Intensity front panel setting 82 is selected. The plot labeled Intensity Bars 3, 4, 5, shows the power output of the electroSurgical generator when the “MED82C, “HIGH 82D or “VHIGH 82E Seal Intensity front panel settings 82 are selected. The Seal Intensity front panel settings 82 adjust the seal parameter values as shown in FIG.9B. These values may be adjusted depending on instru ment used, tissue characteristics or Surgical intent. Discussing this aspect of the disclosure now in further detail, and referring as well to FIGS. 7A, 7B and 8, the selected Seal Parameter Table, adjusted by the Seal Intensity front panel settings is then utilized by the RF energy genera tion system and an initial RF Sealing pulse is then started. As each pulse of RF energy is applied to the tissue, the current initially rises to a maximum (Pulse Peak) and then, as the tissue desiccates and the impedance rises due to loss of
As an alternative to directly measuring the pulse width, the rate of change of an electrical characteristic (for example current, Voltage, impedance, etc.) of the transient 'A' (shown in FIG. 7B) may be measured periodically (indicated by the reference number 90 shown in FIG. 7B) over the time the transient occurs. The rate of change of the electrical charac teristic may be proportional to the width. At 95 of the transient 'A', defined by the relationship: Aisde/dt
where defdt is the change in the electrical characteristic over time. This rate of change may then be used to provide an indication of the width of the transient 'A' in determining the type and amount of tissue that is between the jaws (elec trodes) of the Surgical instrument 4, as well as the Subsequent pulse duty cycle (“Dwell Time'), the amount of subsequent pulse Voltage reduction, as well as other parameters. Referring to FIG. 13, Step E, a subsequent RF energy pulse is applied to the tissue, and the pulse width of the leading edge current transient is measured (FIG. 13, Step F). A determina tion is made if the current transient is present. If it is, control passes via connector 'a' to Step H, otherwise control passes via connector “b' to Step K. Assuming that the current transient is present, and referring to FIG. 13, Step H, if the current transient pulse is wide, for example, approximately in the range of 500-1000 ms, then one can assume the presence of a large amount of tissue, or tissue that requires more RF energy to desiccate. Thus, the Dwell Time is increased, and an increase or Small reduction is
made in the amplitude of the next RF pulse (see the Vrms
US 9,375,271 B2 13 waveform in FIG. 8, and FIG. 13, Step I). If the current transient pulse is narrow, for example, about 250 ms or less (indicating that the tissue impedance rapidly rose), then one can assume a small amount of tissue, or a tissue type that requires little RF energy to desiccate is present. Other ranges of current transient pulse widths can also be used. The rela tionship between the current transient pulse width and the tissue characteristics may be empirically derived. In this case the Dwell Time can be made shorter, and a larger reduction in the amplitude of the next RF pulse can be made as well (FIG. 13, Step J). If a current pulse is not observed at FIG. 13, Step G, it may
14 Maximum RF On Time or MAX Pulse Time is preferably preprogrammed to some value that cannot be readily changed. The RF pulse is terminated automatically if the Pulse Peak is reached but the Pulse Peak-X % value is not
be assumed that either the instrument 4 has shorted, the tissue
has not yet begun to desiccate, or that the tissue has been fully desiccated and, thus, the seal cycle is complete. The determi nation of which of the above has occurred is preferably made by observing the tissue impedance at FIG. 13, Steps Kand M. If the impedance is less than a low threshold value (THRESH), then a shorted instrument 4 is assumed (FIG. 13, Step L), while if the impedance is greater than a high threshold value (THRESH), then a complete tissue seal is assumed (FIG. 13, Step N). If the tissue impedance is otherwise found to be between the high and low threshold values, a determination is made as to whether the Max RF On Time has been exceeded. If the
are defined as follows.
Max RF On Time has been exceeded, it is assumed that the
seal cannot be successfully completed for Some reason and the sealing procedure is terminated. If the Max RF On Time has not been exceeded then it is assumed that the tissue has not
yet received enough RF energy to start desiccation, and the seal cycle continues (connector 'c'). After the actual pulse width measurement has been com pleted, the Dwell Time is determined based on the actual pulse width and on the Dwell Time field in the seal parameter LUT 80 (see FIG. 6B.) The RF pulse is continued until the Dwell Time has elapsed, effectively determining the total time that RF energy is delivered for that pulse. The RF pulse is then turned off or reduced to a very low level for an amount of time specified by the Pulse Off field. This low level allows
Some moisture to return to the tissue. Based on the initial Desired Pulse Width field of the Seal
parameter LUT 80 for the first pulse, or, for subsequent pulses, the actual pulse width of the previous pulse, the desired Voltage limit kept constant or adjusted based on the Voltage Decay and Voltage Ramp fields. The desired voltage limit is kept constant or raised during the pulse if the actual pulse width is greater than the Desired Pulse Width field (or last actual) pulse width), and is kept constant or lowered if the actual pulse width is less than the Desired Pulse Width field (or the last actual pulse width). When the Desired Voltage has been reduced to the Mini mum Voltage field, then the RF energy pulsing is terminated and the electroSurgical generator 2 enters a cool-down period having a duration that is set by the Maximum Cool SF field and the actual pulse width of the first pulse. Several of the foregoing and other terms are defined with greater specificity as follows (see also FIGS. 7A and 7B). The Actual Pulse width is the time from pulse start to pulse low. The Pulse Peak is the point where the current reaches a maximum value, and does not exceed this value for some
predetermined period of time (measured in milliseconds). The peak value of the Pulse Peak can be reached until the Pulse Peak-X% value is reached, which is the point where the current has decreased to some predetermined determined per centage, X, of the value of Pulse Peak. Pulse Low is the point where the current reaches a low point, and does not go lower for another predetermined period of time. The value of the
obtained with the duration set by the Maximum RF On Time field of the seal parameter LUT 80. Referring to FIG. 6B, the seal parameter LUT 80 is employed by the feedback microcontroller 70B in determin ing how to set the various outputs that impact the RF output of the electrosurgical generator 2. The seal parameter LUT 80 is partitioned into a plurality of storage regions, each being associated with a particular measured initial impedance. More particularly, the Impedance Range defines a plurality of impedance breakpoints (in ohms) which are employed to determine which set of variables are to be used for a particular sealing cycle. The particular Impedance Range that is selected is based on the above described Impedance Sense State (FIGS. 7A and 7B) that is executed at the start of the seal cycle. The individual data fields of the seal parameter LUT 80
The actual values for the Impedance Ranges of Low, Med Low, Med High, or High, are preferably contained in one of a plurality of tables stored in the generator 2, or otherwise accessible to the generator 2. A specific table may be selected automatically, for example, based on signals received from the electroSurgical tool 4 being used, or by the operator indi cating what electroSurgical tool is in use. Power is the RF power setting to be used (in Watts). Max Voltage is the greatest value that the output Voltage can achieve (e.g., range 0-about 190V). Start Voltage is the great est value that the first pulse Voltage can achieve (e.g., range 0-about 190V). Subsequent pulse voltage values are typically modified downwards from this value. The Minimum Voltage is the Voltage endpoint, and the seal cycle can be assumed to be complete when the RF pulse voltage has been reduced to this value. The Voltage Decay scale factor is the rate (in volts) at which the desired voltage is lowered if the current Actual Pulse Width is less than the Desired Pulse Width. The Voltage Ramp scale factor is the rate at which the desired voltage will be increased if the Actual Pulse Width is greater than the Desired Pulse Width. The Maximum RF On Time is the
maximum amount of time (e.g., about 5-20 seconds) that the RF power can be delivered, as described above. The Maxi mum Cool Down Time determines the generator cool down 45
time, also as described above. Pulse Minimum establishes the minimum Desired Pulse Width value. It can be noted that for
each RF pulse, the Desired Pulse Width is equal to the Actual Pulse Width from the previous pulse, or the Desired Pulse field if the first pulse. The Dwell Time scale factor was also discussed previously, and is the time (in milliseconds) that the RF pulse is continued after the current drops to the Pulse Low and Stable point (see FIGS. 7A and 7B). Pulse Off is the off time (in milliseconds) between RF pulses. Desired Pulse Width is a targeted pulse width and determines when the Desired Voltage (Vset) is raised, lowered or kept constant. If the Actual Pulse Width is less than the Desired Pulse Width, then Vset is decreased, while if the Actual Pulse Width is
greater than the Desired Pulse Width, then Vset is increased. If the Actual Pulse Width is equal to the Desired Pulse Width, then Vset is kept constant. The Desired Pulse Width is used as the Desired Pulse Width for each sequential pulse. In general, a new Desired Pulse Width cannot be greater than a previous Desired Pulse Width, and cannot be less than Pulse Minimum.
By applying the series of RF pulses to the tissue, the sur gical generator 2 effectively raises the tissue temperature to a certain level, and then maintains the temperature relatively constant. If the RF pulse width is too long, then the tissue may
US 9,375,271 B2 15 be excessively heated and may stick to the electrodes 21A, 21B of the Surgical instrument 4, and/or an explosive vapor ization of tissue fluid may damage the tissue. Such as the vessel 3. If the RF pulse width is too narrow, then the tissue will not reach a temperature that is high enough to properly seal. As such, it can be appreciated that a proper balance of duty cycle to tissue type is important. During the pulse off cycle that is made possible in accor dance with the teachings herein, the tissue relaxes, thereby allowing the steam to exit without tissue destruction. The tissue responds by rehydrating, which in turn lowers the tis sue impedance. The lower impedance allows the delivery of more current in the next pulse. This type of pulsed operation thus tends to regulate the tissue temperature so that the tem perature does not rise to an undesirable level, while still performing the desired electroSurgical procedure, and may also allow more energy to be delivered, and thus achieving
16 The method can terminate the generation of subsequent RF energy pulses upon a determination that the current transient is absent or that the voltage has been reduced to a predefined level. In another embodiment of the present invention, the initial pulse may be combined with at least the first subse quent pulse. Reference is now made to FIGS. 10 and 11 for a description of a novel overvoltage limit and transient energy Suppression aspect of the system disclosed herein. A bi-directional transorb TS1 normally is non-operational. As long as the operating RF output levels stay below the turn-on threshold of TS1, electro surgical energy is provided at a controlled rate of tissue desiccation. However, in the
event that rapid tissue desiccation occurs, or that arcing is present in the surgical tissue field, the RF output may exhibit operating voltage levels in excess of the normal RF levels
used to achieve the controlled rate of tissue desiccation. If the
As each RF pulse is delivered to the tissue, the tissue desiccates and shrinks due to pressure being applied by the jaws of the Surgical instrument 4. The inventors have realized that if the Voltage applied to the tissue is not reduced, then as the spacing between the jaws of the Surgical instrument 4 is gradually reduced due to shrinking of the tissue, an undesir able arcing can develop which may vaporize the tissue, result ing in bleeding. As is made evident in the Vs trace of FIG. 8, and as was described above, the voltage of each successive RF pulse can be controllably decreased, thereby compensating for the des iccation-induced narrowing of the gap between the Surgical
excess Voltage present is left unrestrained, the tissue 3 may begin to exhibit undesirable clinical effects contrary to the desired clinical outcome. The TS1 is a strategic threshold that is set to turn on above normal operating levels, but below and just prior to the RF output reaching an excess Voltage level where undesirable tissue effects begin to occur. The voltage applied across TS1 is proportionately scaled to follow the RF output voltage delivered to the tissue 3. The transorb TS1 is selected Such that its turn on response is faster than the gen erator source RF signal. This allows the transorb TS1 to automatically track and respond quickly in the first cycle of an excess RF output overvoltage condition. Note should be made in FIG. 10 of the capacitor compo nents or network C2, C3, and C4 that parallel the magnetic drive network (MDN1) which has an inductive characteristic and is contained within the electroSurgical generator 2. The combination of the inductive MDN1 and the capacitive net works forms a resonant tuned network which yields the wave shape configuration of the RF source signal shown in FIG.11.
instrument electrodes 21A and 21B. That is, the difference in
electric potential between the electrodes is decreased as the gap between the electrodes decreases, thereby avoiding arc 1ng.
As was noted previously, the Seal Intensity front panel adjustment is not a simple RF power control. The adjustment of the seal intensity is accomplished by adjusting the power of the electroSurgical generator 2, as well as the generator Volt age, the duty cycle of the RF pulses, the length of time of the seal cycle (e.g., number of RF pulses), and the rate of Voltage reduction for successive RF pulses. FIGS. 9B and 9C illus trate an exemplary set of parameters (Power, Start Voltage, Voltage Decay and Dwell Time), and how they modify the contents of the seal parameter LUT 80 depending on the setting of the Seal Intensity control 82 shown in FIG. 9A. Generally, higher settings of the Seal Intensity control 82 increase the seal time and the energy delivered while lower settings decrease the seal time and the energy delivered.
A turn on of transorb device TS1, which functions as a 40
In the FIG.9B embodiment, it is instinctive to note that for
the Medium, High and Very High Seal Intensity settings the RF Power remains unchanged, while variations are made instead in the Start Voltage, Voltage Decay and Dwell Time
As the peak Voltage decreases, the excess overVoltage is automatically limited and is restricted to operating levels below that which cause negative clinical effects. Once the excess RF output voltage level falls below the transorb thresh old, the TS1 device turns off and the electrosurgical generator 2 returns to a controlled rate of tissue desiccation.
dance with the measured electrical characteristic, determin
ing an initial set of pulse parameters for use during a first RF energy pulse that is applied to the tissue; and (D) varying the pulse parameters of individual ones of Subsequent RF energy pulses in accordance with at least one characteristic of an electric current transient that occurs at the beginning of each individual one (pulses) of the Subsequent RF energy pulses.
known to those skilled in the art, and is not further discussed herein.
Based on the foregoing it can be appreciated that an aspect of this disclosure is a method for electroSurgically sealing a tissue. Referring to FIG. 12, the method includes steps of: (A) applying an initial pulse of RF energy to the tissue, the pulse having characteristics selected so as not to excessively heat the tissue; (B) measuring at least one electrical characteristic of the tissue in response to the applied pulse; (C) in accor
Voltage controlled Switch, instantaneously connects the serial capacitance C1 across the capacitor network C2, C3, and C4. An immediate change then appears in the tuning of the reso nant network mentioned above, which then instantaneously alters the waveshape of the RF source signal shown in FIG. 11. The time base T1 of the nominally half-sine signal shown increases incrementally in width out to time T2, which auto matically lowers the peak voltage of the RF output signal. The peak voltage decreases because the Voltage-Time product of the signal shown in FIG. 11 is constant for a given operating quiescence. The concept of a Voltage-Time product is well
In the event that arcing is present in the Surgical tissue field, undesirable excess transient RF energy may exist and may be reflected in the RF output of the electrosurgical generator 2. This in turn may generate a corresponding excess RF output Voltage that creates sufficient transient overvoltage to turn on the transorb TS1. In this condition the cycle repeats as described above, where TS1 turns on, alters the resonant
tuned network comprised of the magnetic and capacitive components, and thus also alters the RF source signal wave shape. This automatically reduces the excess overvoltage.
US 9,375,271 B2 17 In accordance with this aspect of the disclosure, the excess RF transient energy is Suppressed and the overVoltage is limited by the dynamic, real-time automatic detuning of the RF energy delivered to the tissue being treated.
18 starting Voltage level, in a similar fashion as described above with reference to FIGS. 9A and 9B.
As shown in FIG. 15, a preferred Seal Intensity control panel of the present inventive embodiment includes six set It should be noted that the embodiment of FIGS. 10 and 11 5 tings, i.e., “Off 150A, “VLOW 150B, “LOW 150C, can be used to improve the operation of conventional electro “MED 150D, “HIGH 150E and “VHIGH 150F. The Seal Surgical generators, as well as with the novel pulsed output Intensity front panel settings 150 adjust the seal parameter values of the Seal Parameter Table as shown by FIGS.9B and electroSurgical generator 2 that was described previously. 9C. The selected Seal Parameter Table, adjusted by the Seal In an additional embodiment the measured electrical char Intensity front panel settings 150 is then utilized by an RF acteristic of the tissue, preferably the impedance (Z), and the 10 generation as described above, and an initial RF RMS current pulse width (P) may be used to determine a sealing pulsesystem, is then started. fixed Voltage reduction factor (V) to be used for Subsequent The Seal Intensity front panel settings, as shown in FIGS. pulses, and to determine a fixed number of pulses (P) to be 9B and 9C, represent approximate parametric values of sev delivered for the sealing procedure. The relationship among 15 eral preferred embodiments, identified as an example to the Voltage reduction factor, the measured impedance and the achieve vessel sealing performance in clinical procedures. RMS current pulse width may be defined as V=F (ZP), The variety of tissue types and Surgical procedures requires and the relationship among the number of pulses, the mea the use of one or more Seal Intensity front panel settings. sured impedance and the RMS current pulse width may be FIG. 16 is a logic flow diagram that illustrates a method in defined as PF" (Z, P). In FIG. 14 a fixed number of accordance with the vessel sealing system. At step A', a RF pulses, P, 100 determined from the measured impedance and pulse is applied to tissue. At step B', the current or tissue the RMS current pulse width are shown. Each subsequent impedance rate of change is continuously monitored. At step pulse may be reduced by the fixed voltage reduction factor C', a determination is made whether the tissue impedance rate (V) 110, also determined from the measured impedance of change has passed a predetermined limit. If yes, at step D", 25 RF pulsing is terminated and any previously changed pulse and the RMS current pulse width. In a further additional embodiment, tissue sealing is parameters are reset back to the original defaults. If no, the accomplished by the electroSurgical system described above process proceeds to step E'. by continuously monitoring or sensing the current or tissue At step E", a determination is made as to whether the RF impedance rate of change. If the rate of change increases pulse has ended. Ifno, the process loops back to step B'. If yes, above a predetermined limit, then RF pulsing is automatically 30 the process proceeds to step F". At step F", the ending current terminated by controlling the electroSurgical generator 2 or tissue impedance is measured. At step G', the measured accordingly and any previously changed pulse parameters ending values are used for determining if the seal cycle should (e.g., power, Voltage and current increments) are reset to the end (based on the current level or ending impedance of the last original default values. In this embodiment, the ending cur few RF pulses which did not change by more than a prede rent or tissue impedance, i.e., the current or tissue impedance 35 termined amount). If yes, the process terminates at step H'. If at the end of each RF pulse, is also continuously monitored or no, the process continues at Step I', where the ending values sensed. The ending values are then used to determine the are used for determining the pulse parameters, i.e., the power, pulse parameters for the subsequent RF pulse; to determine if pulse width, current and/or Voltage levels, and the duty cycle the seal cycle should end (based on the ending values of the of the subsequent RF pulse from an entry in one of a plurality last few RF pulses which did not change by more than a 40 of lookup tables. The process then loops back to step A'. One predetermined amount); and to determine the duty cycle of of the plurality of lookup tables is selected manually or auto the subsequent RF pulse. matically, based on a choice of an electroSurgical tool or Further, in this embodiment, RF power, pulse width, cur instrument. rent and/or voltage levels of subsequent RF pulses can be kept While the system has been particularly shown and constant or modified on a pulse-by-pulse basis depending on 45 described with respect to preferred embodiments thereof, it whether the tissue has responded to the previously applied RF will be understood by those skilled in the art that changes in energy or pulse (i.e., if the tissue impedance has begun to form and details may be made therein without departing from rise). For example, if the tissue has not responded to a previ its scope and spirit. What is claimed is: ously applied RF pulse, the RF power output, pulse width, current and/or Voltage levels are increased for the Subsequent 50 1. An electroSurgical generator, comprising: an RF energy source configured to provide RF energy; RF pulse. an output configured to couple the RF energy source to Hence, since these RF pulse parameters can Subsequently opposing first and second electrodes of a Surgical instru be modified following the initial RF pulse, the initial set of RF pulse parameters, i.e., a magnitude of a starting RF power ment and provide the RF energy thereto, the opposing level, a magnitude of a starting Voltage level, a magnitude of 55 first and second electrodes when positioned about tissue the starting pulse width, and a magnitude of a starting current forming a gap therebetween; and a controller configured to regulate the RF energy from the level, are selected accordingly such that the first or initial RF RF energy source, the controller configured to decrease pulse does not excessively heat the tissue. One or more of these starting levels are modified during Subsequent RF the output of the RF energy as the gap between the first electrode and second electrode is decreased. pulses to account for varying tissue properties, if the tissue 60 has not responded to the previously applied RF pulse which 2. The generator according to claim 1, wherein the control ler controllably decreases an amplitude of the RF energy to includes the initial RF pulse. The above functions are implemented by a seal intensity compensate for a decrease in the gap due to thermally-in algorithm represented as a set of programmable instructions duced shrinkage of tissue. configured for being executed by at least one processing unit 65 3. The generator according to claim 1, wherein the control of a vessel sealing system. The vessel sealing system includes ler applies a plurality of pulses of RF energy between the first a Seal Intensity control panel for manually adjusting the and second electrodes and controllably decreases an ampli
US 9,375,271 B2 19 tude between each individual RF energy pulse as the gap between the first and second electrodes decreases.
20 and subsequent electrical potential between first and second electrodes being decreased as the gap between the first and second electrodes is decreased. 6. An electrosurgical generator comprising: a controller configured to apply an initial pulse of RF energy to the tissue, the initial pulse forming an electri cal potential between first and second electrodes posi tioned about tissue having a gap defined therebetween, the controller configured to decrease the amplitude of Subsequent pulses of RF energy as the gap between the
4. The generator according to claim 3, wherein the ampli tude is controllably decreased to compensate for a decrease in gap between the first and second electrodes due to thermally 5 induced shrinkage of tissue. 5. An electrosurgical generator comprising: a controller configured to apply an initial pulse of RF energy to opposing first and second electrodes having a 10 gap defined therebetween, the initial pulse of RF energy first and second electrodes is decreased. forming an electrical potential between the first and 7. The generator according to claim 6 wherein the control Second electrodes when positioned about tissue, the con controllably decreases the amplitude of subsequent pulses troller configured to apply at least one subsequent pulse ler of RF energy to compensate for a decrease in the gap between of RF energy to the first and second electrodes forming 15 the first and second electrodes due to thermally-induced a subsequent electrical potential between the first and shrinkage of tissue. second electrodes when positioned about tissue, the dif ference in the at least one subsequent pulse of RF energy