CA2574864C - Method and system for controlling delivery of energy to divide tissue - Google Patents

Abstract

System and method for controlling delivery of energy to divide tissue are disclosed. The system comprises an electrosurgical instrument having an electrically energizable cutting element which communicates electrical energy to the tissue and a generator to supply the energy to the electrosurgical instrument which supplies the energy to the tissue in a first pulse to react the tissue, in slow pulses to create a desiccation line until impedance at the tissue has reached a threshold, and in rapid pulses to divide tissue across the desiccation line.

Description

METHOD AND SYSTEM FOR CONTROLLING DELIVERY OF
ENERGY TO DIVIDE TISSUE
BACKGROUND
1. Technical Field The present disclosure is directed to electrosurgical generators, and, more particularly, to a control system for electrosurgical generators used for tissue division procedures.

2. Background of Related Art Electrosurgical generators are employed by surgeons in conjunction with electrosurgical instruments to perform a variety of surgical procedures including tissue division. An electrosurgical generator generates and modulates electrosurgical energy which is applied to the tissue by an electrosurgical instrument. Electrosurgical instruments may be either monopolar or bipolar and may be configured for open or endoscopic procedures.
In monopolar electrosurgery, a source or active electrode delivers radio frequency energy from the electrosurgical generator to the tissue and a return electrode carries the current back to the generator. In monopolar electrosurgery, the source electrode is typically part of the surgical instrument held by the surgeon and applied to the tissue to be treated.
Bipolar electrosurgery is conventionally practiced using electrosurgical forceps-type device, where the active and return electrodes are housed within opposing forceps' jaws. The return electrode is placed in close proximity to the active (e.g., current supplying) electrode such that an electrical circuit is formed between the two electrodes (e.g., electrosurgical forceps). In =
this manner, the applied electrical current is limited to the body tissue positioned between the electrodes.
A need exists for a method and system for controlling energy output to divide tissue.
Furthermore, a need exists for controlling energy in response to external input, including user input and/or input from sensors monitoring conditions, such as electrical and/or physical characteristics of the tissue.
SUMMARY
Disclosed are system and method for controlling delivery of energy to divide tissue. The system includes a generator for supplying electrical energy to an electrosurgical instrument. The electrosurgical instrument includes an electrically energizable cutting element which communicates the energy to the tissue to divide it. Energy is applied in several stages, during the first state a first pulse of energy is supplied to react the tissue. In the second stage, energy is supplied in "slow" pulses until an impedance threshold is reached to create a desiccation line in the tissue. In the third stated, energy is supplied in "rapid" pulses to divide the tissue along the desiccation line. The division is terminated upon identifying complete separation of the tissue.
During the division process, impedance and temperature of the tissue as well as voltage and current phase, and power levels are measured. If the obtained measurements exceed a predetermined threshold the division process is complete and the energy supply is terminated.
According to one embodiment of the present disclosure, a system for controlling delivery of energy to divide tissue is disclosed. The system includes an electrosurgical instrument having an electrically energizable cutting element which communicates energy to the tissue and a generator to supply the energy to the electrosurgical instrument which supplies the energy to the tissue in a first pulse to react the tissue, in slow pulses to create a desiccation line until impedance at the tissue has reached a threshold, and in rapid pulses to divide tissue across the desiccation line.
According to another embodiment of the present disclosure, a method for controlling delivery of energy to divide tissue is disclosed. The method includes the step supplying energy to an electrosurgical instrument having an electrically energizable cutting element which communicates the energy to the tissue from a generator. The method also includes the steps of communicating the energy to the tissue in a first pulse to react the tissue, slow pulsing the energy to create a desiccation line until impedance at the tissue has reached a threshold, and rapid pulsing the energy to divide tissue across the desiccation line.
According to a further embodiment of the present disclosure, a method for regulating application of electrosurgical energy for performing tissue division is disclosed. The method includes the steps of applying a first electrosurgical energy waveform to condition the tissue, determining whether the tissue has been conditioned, and applying a second electrosurgical energy waveform to divide the conditioned tissue.
According to a final embodiment of the present disclosure, a system for regulating application of electrosurgical energy for performing tissue division is disclosed. The system includes a generator configured to apply a first electrosurgical energy waveform to condition the tissue, the generator including a control module for determining whether the tissue has been conditioned, the generator further configured to apply a second electrosurgical energy waveform to divide the conditioned tissue.

3 BRIEF DESCRIPTION OF THE DRAWINGS
Various embodiments will be described herein below with reference to the drawings wherein:
Fig. 1 is a perspective view of an exemplary electrosurgical system including an endoscopic forceps configured for electrical division of tissue in accordance with the present disclosure;
Fig. 2 is a block diagram of a control system of the electrosurgical system shown in Fig.
1;
Fig. 3 is a graph of power versus time for energy applied during an electrosurgical procedure in accordance with the present disclosure; and Fig. 4 is a flowchart illustrating a method for regulating application of electrosurgical energy during a procedure in accordance with the present disclosure.
Fig. 5 is a flowchart illustrating a method for regulating application of electrosurgical energy during an electrosurgical procedure in accordance with the present disclosure;
Fig. 6 is a graph of impedance versus time for energy applied during the electrosurgical procedure in accordance with the present disclosure; and Fig. 7 is a perspective view of an open forceps configured for electrical division of tissue in accordance with the present disclosure.
DETAILED DESCRIPTION
Reference should be made to the drawings where like reference numerals refer to similar elements throughout the various figures. Preferred embodiments of the present disclosure will be

4 described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.
Tissue cutting or tissue division occurs when heating of the tissue leads to expansion of intracellular and/or extra-cellular fluid, which may be accompanied by cellular vaporization, desiccation, fragmentation, collapse and/or shrinkage along a desiccation line in the tissue. By focusing the electrosurgical energy and heating along the desiccation line, the cellular reactions are localized creating a fissure. Localization and maximization of the cutting effect is achieved by utilizing one or more of various geometrical electrode and insulator configurations and regulating the electrosurgical energy delivered to the tissue. Further, the tissue condition may be regulated and energy delivery controlled by utilizing a generator and feedback algorithm.
For the purposes herein, the term "cut effect" or "cutting effect" refers to the actual division of tissue by one or more of the electrical or electro-mechanical methods or mechanisms described below. The term "cutting zone" or "cut zone" refers to the region of tissue where tissue cutting will take place. The term "cutting process" refers to steps that are implemented before, during and/or after tissue division that tend to influence the tissue as part of achieving the cut effect.
Fig. 1 shows a schematic diagram of one embodiment of the presently-disclosed electrosurgical system 10 having an endoscopic electrosurgical instrument 12 for delivering electrosurgical energy to a patient at a surgical site for cutting or dividing tissue. An electrosurgical generator 16 is also provided having a generator module 20 for generating electrosurgical energy and a control system 18 for controlling the generator module 20, which

5 modulates the electrosurgical energy output. The modulated electrosurgical energy is thereafter provided by the generator 16 to the electrosurgical instrument 12.
The electrosurgical instrument 12 is an endoscopic forceps instrument which includes an end-effector assembly 22 having appropriate structures for affecting tissue, such as grasping, dissecting and/or clamping tissue. Those skilled in the art will appreciate that the cutting process discussed herein below may also be applied to an open electrosurgical instrument. The end-effector assembly 22 includes jaw members 30, 32 and at least one delivery device for communicating electrosurgical energy to the tissue, such as an electrode assembly 34 having at least one electrode for delivering the electrosurgical energy to the patient.
It is envisioned that mechanical action, such as clamping, may also be used by the electrosurgical instrument 12 in addition to the application of electrosurgical energy to obtain a surgical effect. As can be appreciated, the electrode assembly 34 may be configured as monopolar, bipolar or macro-bipolar. Further, the electrosurgical instrument may be configured as suitable for performing endoscopic or open surgery.
The jaw members 30 and 32 each include a tissue contacting surface 36 and 38, respectively, which cooperate together to engage the tissue during cutting. At least one of the jaw members, e.g., jaw member 32, includes at least one electrically energizable cutting element 40 disposed therein, wherein the cutting element 40 is part of the electrode assembly 34. The cutting element(s) 40 may further include additional electrodes for other surgical procedures, such as a combination of sealing electrodes, which may be provided as electrically conductive surfaces at the tissue contacting surfaces 36 and 38. Insulators may be provided for providing insulation between conductive elements. The cutting element(s) 40 may be electrically conductive, non-conductive, made from an insulative material with a conductive coating

6 disposed thereon or a combination thereof. An electrosurgical instrument for cutting and sealing tissue is described in U.S. Patent No. 5,702,390. Electrical cutting of tissue is described in U.S.
Patent Publication US2005/0113826, entitled "VESSEL SEALING INSTRUMENT WITH
ELECTRICAL CUTTING MECHANISM", by Johnson.
The electrode assembly 34 may utilize various geometrical configurations of electrodes, cutting element(s) 40, insulators, partially conductive materials and semiconductors to produce or enhance the cutting effect. For example, the geometrical configuration of the electrodes and insulators may be configured to produce a so-called "cut effect" which may be directly related to the amount of vaporization or fragmentation at a point in the tissue or the power density, temperature density and/or mechanical stress applied to a point in the tissue.
Moreover, it is envisioned that the geometrical configurations of the electrodes and insulators may be designed such that they act like electrical sinks or insulators to influence the heat effect within and around the tissue during the sealing or cutting processes.
The particular geometrical configuration of the cutting element(s) 40, tissue contacting surface 1,6, and 3g and insulators is designed to focus current into high areas of power density to produce a cutting effect and/or reduce the likelihood of current straying to adjacent tissue which may ultimately damage the adjacent tissue structures. A variety of polarity configurations of the cutting element(s) 40 and tissue contacting surface 36 and 38 can be utilized to enhance or facilitate cutting. Additionally, surface areas of electrodes having different poles may be configured for establishing selected surface area ratios between the electrical poles for focusing electrical energy at the tissue. The power density and/or current concentration is further affected by proximity of the cutting element(s) 40 to the return electrode(s), e.g., tissue contacting

7 surfaces 36 and/or 38. Furthermore, opposite jaw members may be configured as mirror images or may include a different geometrical configuration or be made of different materials.
The electrosurgical instrument 12 may be configured for performing a variety of electrosurgical procedures in addition to cutting, such as tissue sealing or coagulating.
Accordingly, the cutting element(s) 40 may be substantially dull so that the surgeon is free to manipulate, grasp and clamp the tissue for performing other surgical or electrosurgical procedures with the electrosurgical instrument 12 without the cutting element(s) 40 mechanically cutting into the tissue. The dull cutting element(s) 40 may provide a uniform gap between sealing surfaces 36, 38 during a procedure other than cutting, such as during a sealing phase, and prevent the electrode assembly 34 from shorting during an electrosurgical procedure, such as during sealing and cutting phases. In this fashion, the tissue is initially sealed and thereafter cut without the need to re-grasp the tissue.
The electrosurgical generator 16 generates electrosurgical energy, which may be RF
(radio frequency), microwave, ultrasound, infrared, ultraviolet, laser, thermal energy or other electrosurgical energy. The exemplary electrosurgical module 20 shown in Fig.
1 generates RE
energy and includes a power supply 50 for generating energy and an output stage 52 which modulates the energy which is provided to the delivery device(s), such as the electrode assembly 34, for delivery of the modulated energy to a patient. In one embodiment, the power supply 50 is a high voltage DC or AC power supply for producing electrosurgical current, where control signals generated by the control system 18 adjust parameters of the voltage and current output, such as magnitude and frequency. The output stage 52 modulates the output energy, such as via a waveform generator based on signals generated by the control system 18 to adjust waveform parameters, e.g., waveform shape, pulse width, duty cycle, crest factor, and/or repetition rate.

8 The control system 18 is coupled to the generator module 20 by connections that may include wired and/or wireless connections for providing the control signals to the generator module 20.
The control system 18 may be a closed loop or open loop control system.
It is also contemplated that the generator 16 may be connected remotely, e.g., via a network, such as the internet, to an off-site server and/or database providing information, such as instrument operating information, mappings, algorithms and/or programs.
Updated information may be provided on a regular basis and downloaded to the generator as needed and/or prior to surgery. As can be appreciated, this enables the user to obtain updated information regarding operation of the instrument, electrical parameters, and ideal curves for optimizing an electrosurgical cutting procedure. In addition, this also enables the generator manufacturer to provide updated information on a regular basis. It is also contemplated that the user may be able to receive diagnostics remotely in this fashion relating to the instruments and/or generators being utilized, either on demand by the user, prior to an operation or automatically during a scheduled download.
Preferably, the generator 16 delivers energy to the tissue in a variety of waveforms, including continual, pulsed, spiked and/or a ramped. Pulsing refers to a variation of output for a specified duration. Several pairs of pulses having a "high" and a "low" pulse could be provided in a series. The duration of the "high" and "low" pulses may vary within a pair or from pair to pair. The "high" pulse typically refers to a state of higher power delivery and the "low" pulse typically refers to a state of lower power delivery. Spiking refers to a high level of energy applied over a brief period of time. An energy ramp refers to increasing or decreasing levels of energy.

9 It has also been determined that RF pulsing may be used to more effectively cut tissue during particular phases of the cutting process. For example, if the energy is not pulsed during an early phase of the procedure, the tissue may not initially cut, but may desiccate, since tissue impedance remains high during the initial stages of cutting. By providing the energy in short, high energy pulses, it has been found that the tissue is more likely to cut.
Moreover, a feedback loop of signals generated by sensors sensing tissue properties (e.g., tissue temperature, tissue impedance, current through the tissue) can be provided for automatically adjusting parameters of the energy, such as intensity and number of pulses, for maximizing the cutting effect and reducing unwanted tissue effects, such as charring and thermal spread. An exampled of an electrosurgical system having a generator controlled by an impedance sensor is shown and described in commonly-owned U.S. Patent No. 6,203,541 entitled "Automatic Activation of Electrosurgical Generator Bipolar Output".
With reference to Fig. 2, the control system 18 is shown, including a processor 202 having a control module 204 executable on the processor 202, and one or more input/output (I/0) ports 206 for communicating with one or more peripheral devices 208 (wherein "peripheral" is used in this case as peripheral to the at least one processor 202 and/or the electrosurgical instrument 12). The peripheral device 208 is in wired or wireless communication with the processor 202 and includes a user interface device 210, a peripheral processor 212, a sensor module 214, and a storage medium 216. It is envisioned that the components of the peripheral device 208 and functions performed therein may be incorporated within the generator 16.
The control module 204 processes information and/or signals input to the processor 202 by the peripheral device(s) 208 and generates control signals for modulating the electrosurgical energy in accordance with the input information and/or signals. Information input via the peripheral device 208 may include pre-surgical data entered prior to the electrosurgical =
procedure or information entered and/or obtained during the electrosurgical procedure through the sensor module 214. The information may include requests, instructions, ideal mapping(s) (e.g., look-up-tables, continuous mappings, etc.), sensed information and/or mode selection.
The control module 204 regulates the generator 16, e.g., the power supply 50 and/or the output stage 52, which adjust various parameters of the electrosurgical energy delivered to the patient during the electrosurgical procedure. Parameters of the delivered electrosurgical energy which may be regulated include, for example, voltage, current, resistance, intensity, power, frequency, amplitude, and/or waveform parameters, e.g., waveform shape, pulse width, duty cycle, crest factor, and/or repetition rate of the output and/or effective energy.
The control module 204 preferably includes software instructions executable by the processor 202 for processing algorithms and/or data received by the peripheral device(s) 208, and for outputting control signals to the generator module 20. The software instructions may be stored in a storage medium such as a memory internal to the processor 202 and/or a memory accessible by the processor 202, such as an external memory, e.g., an external hard drive, floppy diskette, CD-ROM, etc.
Control signals from the control module 204 for controlling the generator 16 may be converted to analog signals by a digital-to-analog converter (DAC) which may be included in the processor 202 or be external thereto. It is contemplated that the processor 202 may include circuitry, e.g., analog devices, for processing information input by the peripheral device(s) 208 and determining the control signals to be provided to the generator 16.
Further, an audio or visual feedback monitor or indicator (not shown) may be employed to convey information to the surgeon regarding the status of a component of the electrosurgical system or the electrosurgical procedure.
Control signals provided to the generator module 20 are determined by processing (e.g., performing algorithms), which may include using information and/or signals entered by the peripheral device(s) 208. Furthermore, the control signals may be determined by accessing further information and/or desired values, such as by accessing a data base and/or consulting a mapping (e.g., an ideal curve, look-up-table, etc.) stored by or accessible by the control module 204.
The control module 204 preferably automatically recognizes various phases of a cutting procedure, where the cutting procedure may include a number of phases, such as (a) at least one phase preceding the cutting process (e.g., before cutting begins, which may include a sealing and/or cauterizing phase); (b) at least one phase during the cutting process, such as a fragmenting phase, a melting phase and/or a tissue rehydration phase; and/or (c) at least one phase following the cutting process, such as division recognition and fragmentation clean-up.
Recognition of the completion of a phase or commencement of a new phase may be in accordance with sensed information, such as from sensors of the sensor module 214 sensing tissue responses, and/or timing information. Phase status information may also be input by an operator.
The control module 204 controls the output of the generator 16 so that the energy is suitable for dividing tissue, including localizing or focusing electrosurgical energy in the cut zone during the cutting process while minimizing energy effects to surrounding tissue; focusing the power density in the cut zone during the cutting process; creating an area of increased temperature in the cut zone during the cutting process (e.g., heating that occurs within the tissue or heating the tissue directly with a heat source); minimizing tissue volume in or around the cut zone to create more favorable conditions for tissue cutting; controlling energy and power delivery to allow vaporization to enhance and or contribute to the cutting process, e.g., controlling the energy delivery to vaporize both intracellular and/or extracellular fluids and/or other cellular materials and foreign fluids within the cut zone; fragmenting the tissue or cellular material during the cutting process to enhance tissue division in the cut zone; melting or collapsing the tissue or cellular material during the cutting process to enhance tissue division in the cut zone, e.g., melting the tissue to create internal stress within the tissue to induce tissue tearing; and controlling tissue temperature, arcing, power density and/or current density during the cutting process to enhance tissue division in the cut zone.
Methods for achieving the control described above include pulsing the energy delivery to influence the tissue in or around the cut zone; spiking the energy delivery (e.g., creating a momentary condition of high energy application for a brief period of time) with an intent to influence the tissue in or around the cut zone during the cut process;
applying increasing or decreasing energy (e.g., an energy ramp) by varying the energy output level to control a tissue response; conditioning the tissue before, during and/or after the cutting process to create more favorable tissue conditions for cutting; making decisions regarding when and how to proceed with an algorithm for controlling energy delivery based on tissue condition feedback; making decisions regarding when and how to proceed with an algorithm for controlling energy delivery based on a predetermined time constant; and/or applying a constant amount of energy over a given time interval or until a tissue condition is achieved.
Conditioning the tissue may include, for example, a tissue pre-heating phase before the cutting process and a tissue rehydration phase during the cutting process.
Determining the current phase of the cutting procedure may include determining from tissue response feedback if a desired state has been achieved.
In addition, the control module 204 may further control application of various mechanical elements to the tissue, such as pressure, tension and/or stress (either internally or externally) to enhance the cutting process; and delivering and controlling various other tissue treatments before or during the cutting process to enhance tissue cutting, e.g., tissue sealing, cauterization and/or coagulation. For example, the electrode assembly 34 may be controlled for independently activating cutting element(s) 40 and/or conductive sealing surfaces 36, 38, or independently controlling parameters of energy output therefrom, respectively, in response to user requests or automatically, such as in accordance with an algorithm or sensed feedback (e.g., upon sensing that a sealing or cutting phase is complete). In an exemplary cutting procedure, the cutting element(s) 40 is energized with a first electrical potential "+" and the opposing sealing surfaces 36 and 38, or selected portions thereof are energized with a second electrical potential "-".
The control module 204 regulates the electrosurgical energy in response to feedback information, e.g., information related to tissue condition at or proximate the surgical site.
Processing of the feedback information may include determining: changes in the feedback information; rate of change of the feedback information; and/or relativity of the feedback information to corresponding values sensed prior to starting the procedure (pre-surgical values) in accordance with the mode, control variable(s) and ideal curve(s) selected.
The control module 204 then sends control signals to the generator module 20 such as for regulating the power supply 50 and/or the output stage 52. It is contemplated that the operator may enter requests via the user interface 210 that override the control information provided by the control module 204.

Regulation of certain parameters of the electrosurgical energy or a tissue response may include recognition of an event, such as a lapse of a period of time or recognition of a rise, fall, leveling, achievement of a target value, achievement of a target change, achievement of a target rate of change and/or achievement of a target change of rate of change of a sensed property (e.g., impedance at the cutting site). Recognition of the event is used for determining what phase of a procedure or stage of a selected ideal mapping has been reached for driving the property along the ideal mapping. It is envisioned that other methods that are known in the art may be used by the control module 204 to control the generator 16 and regulate the electrosurgical energy.
The user interface device 210 may include a switch to allow the surgeon to selectively activate one or more tissue contacting surfaces 36, 38 or the cutting element 40 independently of one another. As can be appreciated, this may allow the surgeon to initially seal tissue and then activate the cutting element by simply turning the switch. It is also envisioned that the sensor module 214 includes a smart sensor assembly (e.g., a smart sensor, smart circuit, computer, and/or feedback loop, etc.) which may cooperate with the switch for automatically triggering the switch to change between a "sealing" mode and a "cutting" mode upon the satisfaction of a particular condition. For example, the smart sensor may include a feedback loop which indicates when a tissue seal is complete based upon one or more of the following parameters:
tissue temperature, tissue impedance at the seal, change in impedance of the tissue over time and/or changes in the power or current applied to the tissue over time. An audible or visual feedback monitor may be employed to convey information to the surgeon regarding the overall seal quality or the completion of an effective tissue seal. Advantageously, the surgeon does not necessarily need to re-grasp the tissue to cut, since the cutting element is already positioned proximate the ideal, center cutting line of the seal.

The sensor module 214 senses various electrical and/or physical parameters or properties at the operating site and communicates with the control module 204 to regulate the output electrosurgical energy. It is envisioned that the sensor module 214 may be configured to measure, i.e., "sense", various electrical, physical and/or electromechanical conditions, such as at or proximate the operating site, including: tissue impedance, tissue temperature, leakage current, applied voltage, applied current, tissue thickness, volume of tissue between jaws of electrosurgical instrument, tissue light transmission, reflectivity and/or absorption properties, tissue moisture content, tissue elastomeric properties, tissue viability, indications of imminent or actual damage to tissue surrounding the surgical site, and/or tissue reactive pressure. For example, sensors of the sensor module 214 may include optical sensor(s), proximity sensor(s), pressure sensor(s), tissue moisture sensor(s), temperature sensor(s), and/or real-time and RMS
current and voltage sensing systems. Preferably, the sensor module 214 measures one or more of these conditions continuously or in real-time such that the control module 204 can continually modulate the electrosurgical output in real-time. In the case where analog signals corresponding to the sensing are provided by the sensor module 214, the analog signals are converted to digital signals via an analog-to-digital converter, which in turn are provided to the control module 204.
It is further envisioned that more than one sensor of the sensor module for sensing a particular property may be provided at different positions, such as along a jaw member of the electrosurgical instrument. For example, proximity sensors positioned at several different positions along the jaw member may sense varying tissue thickness along the jaw member.
Sampling may be employed by the sensor module 214 for sensing properties.
Signals corresponding to sensing by the sensor module 214 may be sampled, such as during the process of converting the signals to digital, and/or by the control module for regulating the generator 16 in accordance with the sampled signals.
The at least one storage medium 216 may store instrument operating information, diagnostic information, ideal mappings for optimizing parameters at particular phases of a procedure, algorithms or programs which can be updated and provided (e.g., accessible by or downloaded to) to the generator and/or control module 204 as needed and/or prior to surgery.
A method for controlling an electrosurgical generator in accordance with the present disclosure will be described in relation to FIGS. 3 and 4. At step 402, the control module 204 processes any pre-surgical data entered. At step 404, the electrosurgical instrument 12 interfaces with tissue by grasping the tissue between The jaw members 30 and 32 and the control module 204 controls the generator 16 and regulates energy output for phase I of the electrosurgical procedure, where phase I is indicated by reference numeral 302 in FIG. 3.
Phase I is initiated with the onset of RF energy as the electrosurgical instrument 12 interfaces with the tissue.
Purpose of phase I is to supply energy to heat the tissue held between the jaw members 30 and 32 to a point where the impedance of the tissue rises to a specified level, ranging from about 1 Ohm to about 200 Ohms above the minimum value reached, and/or the point of vaporization of tissue fluids. After that point is reached (e.g., end of phase I), energy supply is halted. It is also envisioned that at the end of phase I that the supply of energy is decreased sufficiently to minimize energy delivery and heating without completely shutting off the energy supply, so that some electrical energy supplied is sufficient to accurately measure the tissue state through feedback sensors.

It is further envisioned that in certain situations phase I may be shortened or omitted.
More specifically, in situations where tissue has been pre-treated through another process that places tissue into state of fusion and/or sealing or where tissue has been heated, etc.
At step 406, a determination is made if a predetermined condition has been achieved, such as a desired reaction, e.g., when a first predetermined tissue condition has been sensed. If the first predetermined condition has not been achieved, the control module 204 continues to control the generator for phase I application of the electrosurgical energy.
The control module 204 may regulate, for example, the voltage, current and/or power of the output electrosurgical energy. The tissue conditioning prepares the tissue for optimal effect during the next phase(s) of the electrosurgical procedure. At the end of phase I, intra- and inter-cellular fluids have begun to vaporize in the cut region. However, by halting or significantly decreasing the energy as to no longer affect the tissue after the point of reaction, adjacent tissue to the cut region has maintained hydration and vaporization has been kept to a minimum.
At the end of phase I, if division has occurred and/or the tissue has been sufficiently broken down as to allow for division with minimal physical force, the electrosurgical energy supply is shut down and the division process is completed. If division has not occurred during phase I, the energy delivery process enters phase II, the purpose of which is to focus energy delivery into a local region, breaking down the tissue in the cut zone, which initiates and/or finalizes division.
90 After it is determined that the first predetermined condition has been achieved, step 408 is executed, in which the control module 204 proceeds to control the generator 16 to regulate the electrosurgical energy output for phase II of the electrosurgical procedure, where phase II is indicated by reference numeral 304 in FIG. 3. The preferred energy delivery modality during phase II is a pulsed series, consisting of an on-pulse and off-pulse periods, since through pulsing, sufficient energy can be supplied to the tissue to promote degradation thereof and fluid vaporization. The degradation and other associated changes of the tissue can be kept isolated to a small localized region, defining the cut zone. Therefore, through pulsing, the state of the tissue adjacent to the cut zone is kept hydrated. Hydration maintains low impedance at the tissue which permits transfer of maximum energy through the tissue during the energy pulses and focusing of the energy into the affected cut zone. Additionally, during the energy pulsing, the tissue in the cut zone is broken down to a point of fragmentation.
It is also envisioned that energy delivery during phase II can be of non-pulsing or other modalities which allow energy delivery to be focused within the cut zone of the tissue. One example of a non-pulsing modality may include delivery directed based upon real-time or predetermined interval values, such as tissue property values (e.g., impedance, current, temperature, etc.) Therefore, a derivative or integral calculation of the values occurring in real-time or following a predetermined path may be used to direct the energy levels over time in a non-pulsing modality during phase II to focus energy into the cut zone.
At step 410, a determination is made if a second predetermined condition has been achieved from available feedback, which is based on impedance. It is envisioned that other feedback can be utilized to identify a second predetermined condition such as current, voltage, temperature, etc. Feedback is collected while energy is supplied to the tissue through continuous monitoring of tissue impedance for a specific rise thereof and/or absolute value and/or relative value and/or minimum impedance value before the off-pulse period. For the on and off pulses during phase II, values and ranges have nearly infinite possibilities ranging from constant levels to non-linear combinations of previous information, specific to tissue types and directly related to the power levels. It is envisioned that on-pulse stage can be controlled in a plurality of ways, such as, allowing the period to continue for a set period of time, monitoring current, voltage, power, temperature, etc. until a predetermined threshold is reached. The duration of the off-pulse period is determined in a plurality of ways, such as, allowing the period to continue for a set period of time, monitoring current, voltage, power, temperature, etc.
until a predetermined threshold is reached. The purpose of both of the on-pulse and off-pulse monitoring is to verify that the tissue is at an appropriate level to allow for repeated energy delivery to the cut zone.
Phase II continues until the second predetermined condition is satisfied, which may be a time related event and/or an event related to feedback information, e.g., sensed impedance across tissue, and/or current, voltage and/or power measured at the surgical site.
The second predetermined condition and/or the parameters of the applied electrosurgical energy may be determined in accordance with information gathered during phase I and/or phase II of the electrosurgical procedure.
At the end of the phase II, if division has occurred and/or the tissue has been sufficiently broken down as to allow for division with minimal physical force, the electrosurgical energy supply is shut down and the division process is completed. If division has not occurred during phase II, the energy delivery process enters phase III.
If the second predetermined condition has not been achieved, the control module 204 continues to control the generator for phase II application of the electrosurgical energy. The control module 204 continues to regulate, for example, the voltage, current and/or power of the output electrosurgical energy.

It is also envisioned that phase II may include application of electrosurgical energy in the form of a continual waveform or a waveform having pulses, spikes and/or a ramp. Amplitude of the waveform may vary or remain constant.
When it is determined that the second predetermined condition has been achieved, step 412 is executed, in which the control module 204 proceeds to control the generator 16 to regulate the electrosurgical energy output for phase III of the electrosurgical procedure, where phase III is indicated by reference numeral 306 in FIG. 3.
Phase III includes a series of rapid pulses defined by "quick" on and off pulses. The rapid pulse train serves to "fatigue" the tissue, promoting fragmentation and continually vaporizes any remaining tissue fluid. Control of the phase III pulsing is based on predetermined duration of on and off period, monitoring of the current, voltage, power, impedance, etc. for predetermined levels. In addition to predetermined durations, it is envisioned that these rapid pulses be based on real-time feedback from the tissue through either the impedance, current, voltage, temperature, etc.
An additional modality for energy delivery during phase III includes constant energy delivery at levels determined through feedback. Energy delivery ceases after division has completed or the tissue is effectively broken down so that division can be accomplished with minimal force.
At step 414, a determination is made if a third predetermined condition has been achieved. If the third predetermined condition has not been achieved, the control module 204 continues to control the generator for phase III application of the electrosurgical energy. The control module 204 may regulate, for example, the voltage, current and/or power of the output electrosurgical energy. Phase III may include application of electrosurgical energy in the form of a continual waveform or a waveform having pulses, spikes and/or a ramp.
Amplitude of the waveform may vary or remain constant. During phase III the energy application is configured for creating a final or a complete tissue division. At the end of phase III, the tissue is completely divided or broken down to such an extent that division is achieved with minimal application of force.
The third predetermined condition may be a time related event and/or an event related to feedback information, e.g., sensed impedance across tissue, and/or current, voltage and/or power measured at the surgical site. The third predetermined condition and/or the parameters of the applied electrosurgical energy may be determined in accordance with information gathered during phase I, II and/or III of the electrosurgical procedure.
When it is determined that the third predetermined condition has been achieved, the electrosurgical procedure is terminated. It is contemplated that the electrosurgical procedure may have one or two phases or more than three phases. It is also contemplated that any of the phases may include sub-phases.
The goal of controlled energy delivery feedback pulsing is to focus power and heat into a localized region and breakdown tissue for division. Methods for achieving the controlled energy delivery include applying energy in three different phases. Phases I, II, III
may include various techniques for applying energy to properly divide, according to another embodiment of the present disclosure a related method of energy application is disclosed.
During the first phase, activation occurs which involves the tissue contacting surfaces 36, 38 to come in contact with tissue. The tissue reacts with the tissue contacting surface 36, 38 as energy is applied thereto. During the second phase, after the tissue reacts, the energy is pulsed until a predetermined threshold from about 50.0 to about 2500S2 above the minimum value is reached to create a fine line of desiccation. The pulses may be defined by external variables (e.g., impedance, current, power, voltage, temperature, etc.) which may be monitored by the sensor module 214 during the cutting process or extracted from pre-surgical data. During phase three, a final burst of energy is supplied to the tissue in rapid cycles to divide the tissue.
The cutting process according to the present disclosure will now be discussed with reference to Figs. 3 and 4. Fig. 5 shows a flowchart illustrating a method for regulating application of electrosurgical energy and Fig. 6 is a graph of impedance versus time. In step 300 the electrosurgical instrument 12 is placed at a surgical site to divide tissue. Tissue is grasped by the jaw members 30, 32 and the energizable cutting element 40 is brought in contact with the tissue. In addition, energy is supplied to the tissue through the energizable cutting element 40 so that the tissue reacts, which involves preheating the cutting zone.
Fig. 6 shows a graph of impedance over time as tissue is divided according to the method of the present disclosure. Impedance measurement at the tissue may be accomplished by using a sensing current. As the impedance of the tissue changes, the sensing current changes inversely proportionally if the voltage remains constant. This is defined by Ohm's law:
V=RI, wherein V is the voltage across the electrodes in volts, I is the current through the electrodes (and tissue) in milliamps and R is the resistance or impedance of the tissue measured in Ohms.
By this equation, it can be readily appreciated that when the tissue impedance increases the current will decrease and conversely, if the tissue impedance decreases, the current will increase.
Therefore, by measuring the changes in the sensing current the impedance can be measured by the sensor module 214.

In step 302, the control system 18 determines whether the tissue has reacted, as shown in Fig. 6 this occurs from about 50 msec to about 7 sec. Reaction encompasses the vaporization of either or both intra-cellular or extra-cellular fluids and/or the onset of the tissue desiccation process and/or a state change in the tissue that is identifiable by molecular denaturization. The sensor module 214 measures the impedance and transmits the measurement to the control module 204, which compares the measurement to a predetermined threshold (e.g., 1000 Ohms).
If the measurement value exceeds the threshold then the control system 18 terminates the energy supply as represented by a flat line in Fig. 6, wherein the line denotes that there was no rise in impedance.
In step 304, a desiccation line is created without completely dividing tissue by "slow"
pulsing the energy supplied to the cutting element 40. Pulsing is accomplished by supplying energy in cycles instead of a constant flow. The control system 18 briefly supplies power to the tissue (e.g., 0.5 sec) then terminates the supply for the same period (e.g., 0.5 sec) thereby pulsing the energy. The "slow" pulses are illustrated in Fig. 6 beginning at about 7 seconds and ending at about 10 seconds, where the rise in impedance corresponds to time periods during which energy is supplied and the drop in impedance with energy cut-off. "Slow"
pulsing of the energy results in heating and rehydration of the tissue, this gradually breaks down the tissue and produces a fine line of desiccation.
"Slow" pulsing or phase II is accomplished via feedback based pulsing used at this stage in the algorithm. The feedback pulsing is using real-time impedance measurements to determine when to shut the energy off during each pulse. Therefore, each on-pulse duration might be different throughout the stage and is defined by the rate of tissue reaction during the energy delivery and a coded relationship. The on-pulse impedance values that are used to identify the stop point of the on pulse are calculated from the off impedance of the Phase I and an equation built into the logic. The equation can take the form of either a linear or non-linear relationship.
Furthermore, the off-times related to these pulses are fixed at 300 ms but it is recognized an operational range exists from 10 ms to 5 seconds. In addition, it is also envisioned that the off-pulses be based on a real-time impedance value as the on pulses with some relationship which is not currently known.
"Slow" pulsing continues until a second threshold is reached. Each pulse raises the impedance of the tissue by a specific amount and, in step 306, after each pulse, the control system 18 determines whether the second impedance threshold has been reached.
As illustrated in Fig. 6 that threshold is approximately 1500 Ohms, the threshold for the "slow" pulsing stage can exist from about 501-2 to about 2500n above the minimum value. If the threshold is not reached, the "slow" pulsing continues, when the threshold has been reached then in step 308, a single energy pulse is applied to the tissue. The single energy pulse is represented in Fig. 6 by an upward sloping line immediately following the "slow" pulsing. In step 310, "rapid" pulsing is commenced to divide the tissue along the desiccation line previously creating during "slow"
pulsing. Whereas "slow" pulses apply energy for about 0.5 sec, "rapid" pulses apply energy for about 0.05 sec. The on-times of the rapid pulsing range from about 1 ms to about 1 second and the off-times range from about 1 ms to about 2 second. The "rapid" pulsing continues for approximately 2 seconds until the tissue is divided.
In step 312, the control system 18 determines whether division is complete.
This may be accomplished by measuring one or any combination of impedance, phase of the voltage and current, power, and temperature. These measurements are performed by the sensor module 214.
Impedance measurement is performed by transmitting a sensing current through the tissue and measuring the impedance thereof. The impedance is then compared by the processor 202, and more specifically by the control module 204, to open circuit impedance of the electrosurgical system 10. If the measured impedance is equal to the open circuit impedance, then division is complete and energy supply is shut off.
Phase detection is accomplished by measuring the phase change between the voltage and current to determine when the separation has occurred. During the division process the voltage and the current are in phase, once the process is complete the voltage and the current are out-of-phase. Thus, detecting when the phase change occurs allows for determining when the division process is complete. The phase measurements are performed by the sensor module 214 and the analysis of the phases of the voltage and current are carried out by the processor 202, and more specifically by the control module 204. Phase encompasses impedance phase as well as the phase angle between current and voltage.
Monitoring power delivery is another way to for determining when the division process has completed. As the division process progresses tissue contact between the cutting element 40 decreases. As a result, power requirements decrease and impedance increases.
Once the power level reaches a certain threshold from about 0 W to about 40 W as measured by the sensor module 214, the division process is complete. Comparison and analysis of the power level is carried out by the processor 202, and more specifically by the control module 204.
Monitoring temperature is another method for determining when the division process is complete. The sensor module 214 measures temperature either at the cutting element 40 or the tissue. The temperature is then compared by the processor 202, and more specifically by the control module 204, to determine if it is at or above a predetermined threshold, such as, for example from about 100 C to about 120 C. If the temperature at the cutting element 40 or the tissue is at or above the threshold then the division process is complete and the energy supply is terminated.
If the division process is not complete (e.g., one of the above measurement are not at or above a predetermined threshold) then the process returns to step 310 where the "rapid" pulsing continues until measurements are taken again to determine if the process is complete.
Those skilled in the art will understand that the impedance values and pulse cycles discussed above are illustrative and that the actual values may vary depending on a plurality of factors (e.g., type of tissue, moisture content, etc.).
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. It is envisioned that forceps and/or the electrode assembly of the end effector may be designed such that they are fully or partially disposable or "reposable", i.e., a new or different electrode assembly (or electrode assembly and shaft) selectively replaces the old electrode assembly as needed. Moreover, it is envisioned that a reusable forceps could be sold as a kit haying different electrodes assemblies for different tissue types. The surgeon simply selects the appropriate electrode assembly for a particular tissue type.
Furthermore, it is contemplated that any pulsing techniques, methods and mechanisms disclosed herein may be employed on a monopolar electrosurgical instrument or open forceps such as the open forceps 400 disclosed in Fig. 7.
The forceps 400 includes an end effector assembly 600 which attaches to the distal ends 516a and 516b of shafts 512a and 512b, respectively. The end effector assembly 600 includes pair of opposing jaw members 610 and 620 which are pivotally connected about a pivot pin 665 and which are movable relative to one another to grasp vessels and/or tissue.
An electrically energizable cutting element such as the cutting element 40 described with respect to Figs. 1-4 may be disposed within the end effector 600. In addition, the generator (not shown) which supplies power to the forceps 400 may be configured to pulse energy to divide tissue in the same manner as discussed above.
Each shaft 512a and 512b includes a handle 515 and 517, respectively, disposed at the proximal end 514a and 514b thereof which each define a finger hole 515a and 517a, respectively, therethrough for receiving a finger of the user. Finger holes 515a and 517a facilitate movement of the shafts 512a and 512b relative to one another which, in turn, pivot the jaw members 610 and 620 from an open position wherein the jaw members 610 and 620 are disposed in spaced relation relative to one another to a clamping or closed position wherein the jaw members 610 and 620 cooperate to grasp tissue or vessels therebetween.
Further details relating to one particular open forceps are disclosed in commonly-owned U.S.
Patent Publication US2005/0154387 entitled "OPEN VESSEL SEALING INSTRUMENT WITH CUTTING
MECHANISM AND DISTAL LOCKOUT".
Although the subject electrosurgical generator has been described with respect to preferred embodiments, it will be readily apparent to those having ordinary skill in the art to = which it appertains that changes and modifications may be made thereto.
It is also envisioned that the electro surgical generator may be controlled to perform any known bipolar or monopolar function such as electrocautery, hemostasis, and/or desiccation utilizing one or both jaw members to treat the tissue.

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 preferred embodiments. The scope of the claims should not be limited by the preferred embodiments set forth herein, but should be given the broadest interpretation consistent with the description as a whole.

Claims (14)

The embodiments of the present invention for which an exclusive property or privilege is claimed are defined as follows:

1. A system for controlling delivery of energy to divide tissue comprising:
an electrosurgical instrument having an electrically energizable electrode which communicates energy to the tissue; and a generator to supply the energy to the electrosurgical instrument which supplies the energy to the tissue in several phases, wherein in a first phase energy is supplied to the tissue in a first pulse to react the tissue during a second phase, energy is supplied to the tissue in a series of on and off pulses to create a desiccation line until impedance at the tissue has reached a predetermined threshold and during a third phase, energy is supplied to the tissue in a series of on and off rapid pulses to divide the tissue across the desiccation line;
wherein the pulses in the second phase are slow pulses and the slow pulses are of longer duration than the rapid pulses.

2. The system as in claim 1, wherein the electrosurgical instrument is a bipolar forceps comprising an end effector assembly disposed at a distal end thereof, the end effector assembly including jaw members movable from a first position in spaced relation relative to one another to at least one subsequent position wherein the jaw members cooperate to grasp tissue therebetween, the end effector assembly further includes the electrically energizable cutting element.

3. The system as in claim 2, wherein the bipolar forceps is configured for endoscopic surgery.

4. The system as in claim 2, wherein the bipolar forceps is configured for open surgery.

5. The system as in claim 1, wherein the electrosurgical instrument is a monopolar instrument.

6. The system as in claim 1, wherein the predetermined threshold is from about 50 Ohms to about 2500 Ohms.

7. The system as in claim 1, further comprising:
a sensor module for measuring at least one of a tissue property and an energy property;
and a processor for determining when the tissue has been divided as a function of the tissue property.

8. The system as in claim 7, wherein the tissue property is selected from the group consisting of impedance and temperature.

9. The system as in claim 7, wherein the energy property is selected from the group consisting of voltage phase, current phase, and power.

10. The system according to any one of claims 1 to 9, wherein the generator is configured to recognize an occurrence of at least one event and to alter the first pulse waveform in accordance with the recognized at least one event.

11. The system according to claim 10, wherein the at least one event is selected from the group consisting of a time related event and a predetermined tissue response.

12. The system according to any one of claims 1 to 11, wherein the generator is further configured to regulate parameters of the electrosurgical energy selected from the group consisting of power, frequency, current, voltage and waveform.

13. The system according to claim 12, wherein the generator is configured to regulate the waveform of the electrosurgical energy to have at least one characteristic selected from the group consisting of pulses, at least one spike, at least one ramp and a continual curve, the control module further configured to regulate parameters of the waveform selected from the group consisting of waveform shape, pulse width, duty cycle, crest factor, and repetition rate.

14. The system according to any one of claims 1 to 13, wherein during the first phase, energy is supplied to the tissue in the first pulse as a continual pulse until the impedance of the tissue rises to a specified level, ranging from about 1 Ohm to about 200 Ohm, above a minimum value reached.