System and method for controlling electrode gap during tissue sealing

An electrosurgical system for sealing tissue is disclosed that includes an electrosurgical forceps. The forceps includes a drive rod and an end effector assembly coupled to the drive rod at a distal end thereof. The end effector assembly includes jaw members wherein longitudinal reciprocation of the drive rod moves the jaw members from a first position in spaced relation relative to one another to a subsequent position wherein the jaw members cooperate to grasp tissue therebetween. Each of the jaw members includes a sealing plate that communicates electrosurgical energy through tissue held therebetween. The jaw members are adapted to connect to an electrosurgical generator. The system also includes one or more sensors that determine a gap distance between the sealing plates of the jaw members and a pressure applicator coupled to the drive rod. The pressure applicator is configured to move the drive rod in a longitudinal direction. The system further includes a controller adapted to communicate with the sensors and to control the pressure applicator in response to the determined gap distance during the sealing process.

BACKGROUND

1. Technical Field

The present disclosure relates to an electrosurgical instrument and method for performing electrosurgical procedures. More particularly, the present disclosure relates to an open or endoscopic bipolar electrosurgical forceps that includes opposing jaw members each having a sealing plate for grasping tissue and supplying electrosurgical energy thereto. The pressure exerted by the sealing plates on the tissue is adjusted using a feedback control loop that utilizes gap distance between the sealing plates as a control variable.

2. Background of Related Art

Electrosurgery involves application of high radio frequency electrical current to a surgical site to cut, ablate, coagulate, cauterize, desiccate or seal tissue. Tissue or vessel sealing is a process of liquefying the collagen, elastin and ground substances in the tissue so that they reform into a fused mass with significantly-reduced demarcation between the opposing tissue structures. Cauterization involves the use of heat to destroy tissue and coagulation is a process of desiccating tissue wherein the tissue cells are ruptured and dried.

In bipolar electrosurgery, one of the electrodes of the hand-held instrument functions as the active electrode and the other as the return electrode. The return electrode is placed in close proximity to the active 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. When the electrodes are sufficiently separated from one another, the electrical circuit is open and thus inadvertent contact with body tissue with either of the separated electrodes does not cause current to flow.

A forceps is a pliers-like instrument that relies on mechanical action between its jaws to grasp, clamp and constrict vessels or tissue. So-called “open forceps” are commonly used in open surgical procedures whereas “endoscopic forceps” or “laparoscopic forceps” are, as the name implies, are used for less invasive endoscopic surgical procedures. Electrosurgical forceps (open or endoscopic) utilize mechanical clamping action and electrical energy to effect hemostasis on the clamped tissue. The forceps includes electrosurgical sealing plates that apply the electrosurgical energy to the clamped tissue. By controlling the intensity, frequency and duration of the electrosurgical energy applied through the sealing plates to the tissue, the surgeon can coagulate, cauterize and/or seal tissue.

Tissue sealing procedures involve more than simply cauterizing tissue. In order to affect a proper seal in vessels or tissue, it has been determined that a variety of mechanical and electrical parameters must be accurately controlled: the pressure applied to the tissue; the gap distance between the electrodes (i.e., distance between opposing jaw members when closed about tissue); and amount of energy applied to tissue.

Numerous electrosurgical instruments have been proposed in the past for various open and endoscopic surgical procedures. However, most of these instruments cauterize or coagulate tissue and are not designed to create an effective or a uniform seal. Other instruments generally rely on clamping pressure alone to procure proper sealing thickness and are often not designed to take into account gap tolerances and/or parallelism and flatness requirements, which are parameters that, if properly controlled, can assure a consistent and effective tissue seal.

SUMMARY

The present disclosure relates to a vessel or tissue sealing instrument that is designed to manipulate, grasp and seal tissue utilizing jaw members. According to one aspect of the present disclosure, an electrosurgical system for sealing tissue is disclosed that includes an electrosurgical forceps. The forceps includes a drive rod and an end effector assembly coupled to the drive rod at a distal end thereof. The end effector assembly includes jaw members wherein longitudinal reciprocation of the drive rod moves the jaw members from a first position in spaced relation relative to one another to a subsequent position wherein the jaw members cooperate to grasp tissue therebetween. Each of the jaw members includes a sealing plate that communicates electrosurgical energy through tissue held therebetween. The jaw members are adapted to connect to an electrosurgical generator. The system also includes one or more sensors that determine a gap distance between the sealing plates of the jaw members and a pressure applicator coupled to the drive rod. The pressure applicator is configured to move the drive rod in a longitudinal direction. The system further includes a controller adapted to communicate with the sensors and to control the pressure applicator in response to the determined gap distance during the sealing process.

The present disclosure also relates to a method for sealing tissue including the step of providing an electrosurgical forceps for sealing tissue. The forceps having at least one shaft member having a drive rod and an end effector assembly mechanically coupled to the drive rod at a distal end thereof. The end effector assembly includes jaw members wherein longitudinal reciprocation of the drive rod moves the jaw members from a first position in spaced relation relative to one another to a subsequent position wherein the jaw members cooperate to grasp tissue therebetween. Each of the jaw members includes a sealing plate that communicates electrosurgical energy through tissue held therebetween. The jaw members are adapted to connect to an electrosurgical generator. The method also includes the steps of providing a controller having a pressure applicator mechanically coupled to the drive rod and configured to move the drive rod in a longitudinal direction as well as grasping tissue between the sealing plates and measuring a gap distance between the sealing plates. The method further includes the step of controlling a pressure applicator as a function of the measured gap distance.

DETAILED DESCRIPTION

Particular embodiments of the present disclosure are described hereinbelow 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. Those skilled in the art will understand that the invention according to the present disclosure may be adapted for use with either monopolar or bipolar electrosurgical system.

The present disclosure provides for an apparatus, system and method of controlling pressure exerted by opposing jaw members on tissue grasped therebetween during sealing. Since tissue thickness corresponds to the gap distance “G” between opposing jaw members, it is envisioned that adjusting the pressure exerted on the tissue based on the desired rate of change of the gap distance “G” controls the decrease in the tissue thickness during the sealing process resulting in a confident, more reliable tissue seal. In other words, controlling the rate at which the thickness of the tissue decreases is beneficial in creating a strong seal since the optimum amount of tissue remains enclosed between the opposing jaw members.

FIG. 1Ashows an electrosurgical system having an endoscopic vessel sealing bipolar forceps10electrically coupled to an electrosurgical generator20that is adapted to supply electrosurgical high radio frequency (RF) energy thereto. The forceps10is shown by way of example and other suitable electrosurgical forceps are also envisioned that allow control of RF output to provide a reliable seal. Those skilled in the art will understand that the invention according to the present disclosure may be adapted for use with either an endoscopic instrument or an open instrument.

It should also be appreciated that different electrical and mechanical connections and other considerations apply to each particular type of instrument. However, the novel aspects with respect to controlling pressure as a function of the gap distance “G” and the operating characteristics of the instruments remain generally consistent with respect to both the open or endoscopic designs.

FIGS. 1A-1Bshow the forceps10that is configured to support an end effector assembly100at a distal end thereof. More particularly, forceps10generally includes a housing21, a handle assembly30, a rotating assembly80, and a trigger assembly70that mutually cooperate with the end effector assembly100to grasp, seal and, if desired, divide tissue.

The forceps10also includes a shaft12that has a distal end14that mechanically engages the end effector assembly100and a proximal end16that mechanically engages the housing21proximate the rotating assembly80. In the drawings and in the description that follows, the term “proximal”, refers to the end of the forceps10that is closer to the user, while the term “distal” refers to the end of the forceps that is further from the user.

The forceps10also includes a plug300that connects the forceps10to a source of electrosurgical energy, e.g., the electrosurgical generator20, via an electrical cable23. Handle assembly30includes a fixed handle50and a movable handle40. Handle40moves relative to the fixed handle50to actuate the end effector assembly100and enables a user to grasp and manipulate tissue “T” as shown inFIG. 2.

The generator20includes input controls (e.g., buttons, activators, switches, touch screen, etc.) for controlling the generator20. In addition, the generator20may include one or more display screens for providing the surgeon with a variety of output information (e.g., intensity settings, treatment complete indicators, etc.). The controls allow the surgeon to adjust the RF energy, waveform, and other parameters to achieve the desired waveform suitable for a particular task (e.g., coagulating, tissue sealing, intensity setting, etc.). The forceps10may also include a plurality of input controls that may be redundant with certain input controls of the generator20. Placing the input controls at the forceps10allows for easier and faster modification of RF energy parameters during the surgical procedure without requiring interaction with the generator20.

FIG. 3shows a schematic block diagram of the generator20having a controller24, a high voltage DC power supply27(“HVPS”) and an RF output stage28. The HVPS27provides high voltage DC power to RF output stage28, which then converts high voltage DC power into RF energy and delivers the RF energy to an active electrode. In particular, the RF output stage28generates sinusoidal waveforms of high frequency RF energy. The RF output stage28is configured to generate a plurality of suitable waveforms having various duty cycles, peak voltages, crest factors, and other parameters. Certain types of waveforms are suitable for specific electrosurgical modes. For instance, the RF output stage28generates a 100% duty cycle sinusoidal waveform in a so called “cut mode,” which is best suited for dissecting tissue and a 25% duty cycle waveform in a so called “coagulation mode,” which is best used for cauterizing tissue to stop bleeding.

The controller24includes a microprocessor25connected to a memory26, which may be volatile type memory (e.g., RAM) and/or non-volatile type memory (e.g., flash media, disk media, etc.). The microprocessor25includes an output port that is connected to the HVPS27and/or RF output stage28allowing the microprocessor25to control the output of the generator20according to either open and/or closed control loop schemes.

The sensor circuitry22may include a plurality of sensors for measuring a variety of tissue and/or energy properties (e.g., tissue impedance, tissue temperature, output current and/or voltage, gap distance, etc.). The sensor circuitry22is also connected to sensors170aand170b, which measure the gap distance “G” between the opposing jaw members110and120(FIG. 1B). Such sensors are within the purview of those skilled in the art. A closed loop control scheme is a feedback control loop wherein sensor circuitry22provides feedback to the controller24. The controller24signals the HVPS27and/or RF output stage28, which then adjusts the output of DC and/or RF energy, respectively. The sensor circuitry22also transmits measured gap distance “G” information to the controller24, which then adjusts the pressure exerted by the opposing jaw members110and120exerted on the tissue grasped therein. The controller24also receives input signals from the input controls of the generator20or the forceps10. The controller24utilizes the input signals to adjust power outputted by the generator20and/or performs other suitable control functions thereon.

With references toFIGS. 1A-1B, the end effector assembly100includes a pair of opposing jaw members110and120each having an electrically conductive sealing plate112and122, respectively, attached thereto for conducting electrosurgical energy through tissue “T” held therebetween. More particularly, the jaw members110and120move in response to movement of the handle40from an open position to a closed position. In open position the sealing plates112and122are disposed in spaced relation relative to one another. In a clamping or closed position the sealing plates112and122cooperate to grasp tissue and apply electrosurgical energy thereto.

The jaw members110and120are activated using a drive assembly (not explicitly shown) enclosed within the housing21. The drive assembly cooperates with the movable handle40to impart movement of the jaw members110and120from the open position to the clamping or closed position. Examples of handle assemblies are shown and described in commonly-owned U.S. application Ser. No. 10/369,894 entitled “VESSEL SEALER AND DIVIDER AND METHOD MANUFACTURING SAME” and commonly owned U.S. application Ser. No. 10/460,926 entitled “VESSEL SEALER AND DIVIDER FOR USE WITH SMALL TROCARS AND CANNULAS”.

In addition, the handle assembly30of this particular disclosure may include a four-bar mechanical linkage, which provides a unique mechanical advantage when sealing tissue between the jaw members110and120. For example, once the desired position for the sealing site is determined and the jaw members110and120are properly positioned, handle40may be compressed fully to lock the electrically conductive sealing plates112and122in a closed position against the tissue. Movable handle40of handle assembly30is ultimately connected to a drive rod32that, together, mechanically cooperate to impart movement of the jaw members110and120from an open position wherein the jaw members110and120are disposed in spaced relation relative to one another, to a clamping or closed position wherein the jaw members110and120cooperate to grasp tissue therebetween.

As best illustrated inFIG. 1C, drive rod32includes a pin slot39disposed at the distal tip of the drive rod32and dimensioned to house the cam pin170such that longitudinal reciprocation of the drive rod32translates the cam pin170, which, in turn, rotates the jaw members110and120about pivot pin160. The cam pin170rides within slots172and174of the jaw members110and120, respectively, which causes the jaw members110and120to rotate from the open to closed positions about the tissue. In particular, as the drive rod32is pulled proximally the cam pin170is moved proximally within cam slots172and174and closes the jaw members110and120relative to one another. The drive rod32is configured to be actuated via the handle40and/or other suitable pressure application mechanisms.

FIG. 1Dshows a motor-controlled pressure applicator200that includes an electric motor202powered by a power source204. The power source204may either be a stand-alone low voltage DC source (e.g., battery) or an integrated low-voltage power source as part of the HVPS27. The drive rod32includes a threaded portion208that is in mechanical communication with the motor202. In particular, the motor202includes a gear box206that is mechanically coupled to the threaded portion208so that when the motor202is activated, the gears of the gear box206rotate and thereby longitudinally move the drive rod32. Pulling the drive rod32proximally and moving the jaw members110and120apart or pushing the drive rod32distally and moving the jaw members110and120together is accomplished by varying the direction of rotation of the motor202. The rate of closure of the jaw members110and120is controlled by varying the gears within the gear box208and/or the power supplied to the motor202, which, in turn, adjusts the rate of rotation and torque exerted on the drive rod32. Control of the motor202is achieved via the controller24, which automatically adjusts the operating parameters thereof based on user input or sensed feedback from the sensor circuitry22and/or the sensors170aand170b.

FIG. 1Eshows another embodiment of a pressure applicator300that includes a linear actuator302powered by the power source204. The linear actuator302includes a housing cylinder310and a shaft308. The shaft208is mechanically coupled to the to the drive rod32at an interface304and the housing cylinder310is mechanically coupled to the interior wall of the housing21at an interface306. The linear actuator302moves the drive rod32in a longitudinal direction proximally or distally by expanding or contracting, respectively, between the interfaces304and306. The linear actuator302includes either an electric motor or a pneumatic or hydraulic cylinders that extend or retract the shaft308. Those skilled in the art will readily appreciate that if the linear actuator302is pneumatic, the shaft308may be part of the pneumatic cylinder. The power source204is connected to the linear actuator302and provides electrical power thereto. The controller24controls the operating parameters of the linear actuator302either directly or by controlling the power source202based on user input or sensed feedback from the sensor circuitry22and/or the sensors170aand170b.

The pressure applicators200and300may be housed within the housing21or outside thereof along the shaft12to enable the pressure applicators200and300to interface with drive rod32.

The details relating to the inter-cooperative relationships of the inner-working components of forceps10are disclosed in the above-cited commonly-owned U.S. patent application Ser. No. 10/369,894. Another example of an endoscopic handle assembly that discloses an off-axis, lever-like handle assembly, is disclosed in the above-cited U.S. patent application Ser. No. 10/460,926.

Referring back toFIGS. 1A-1B, the forceps10also includes a trigger70that advances a knife190disposed within the end effector assembly100. Once a tissue seal is formed, the user optionally activates the trigger70to separate the tissue “T” along the tissue seal. Knife190preferably includes a sharpened edge195for severing the tissue “T” held between the jaw members110and120at the tissue sealing site. The knife190longitudinally reciprocates in a longitudinally-oriented channel (not explicitly shown) defined in the conductive sealing plates112and122extending from the proximal end to the distal end thereof. The channel facilitates longitudinal reciprocation of the knife190along a preferred cutting plane to effectively and accurately separate the tissue “T” along a formed tissue seal.

The forceps10also includes a rotating assembly80mechanically associated with the shaft12and the drive assembly (not explicitly shown). Movement of the rotating assembly80imparts similar rotational movement to the shaft12, which, in turn, rotates the end effector assembly100. Various features along with various electrical configurations for the transference of electrosurgical energy through the handle assembly20and the rotating assembly80are described in more detail in the above-mentioned commonly-owned U.S. patent application Ser. Nos. 10/369,894 and 10/460,926.

As best seen with respect toFIGS. 1A-1B, the end effector assembly100attaches to the distal end14of shaft12. The jaw members110and120are preferably pivotable about a pivot160from the open to closed positions upon relative reciprocation, i.e., longitudinal movement, of the drive assembly (not explicitly shown). Again, mechanical and cooperative relationships with respect to the various moving elements of the end effector assembly100are further described by example with respect to the above-mentioned commonly-owned U.S. patent application Ser. Nos. 10/369,894 and 10/460,926.

The forceps10may be designed such that it is fully or partially disposable depending upon a particular purpose or to achieve a particular result. For example, end effector assembly100may be selectively and releasably engageable with the distal end14of the shaft12and/or the proximal end16of the shaft12may be selectively and releasably engageable with the housing21and handle assembly30. In either of these two instances, the forceps10may be either partially disposable or reposable, such as where a new or different end effector assembly100or end effector assembly100and shaft12are used to selectively replace the old end effector assembly100as needed.

Since the forceps10applies energy through electrodes, each of the jaw members110and120includes an electrically conductive sealing plate112and122, respectively, disposed on an inner-facing surface thereof. Thus, once the jaw members110and120are fully compressed about the tissue T, the forceps10is now ready for selective application of electrosurgical energy as shown inFIG. 2. At that point, the electrically conductive plates112and122cooperate to seal tissue “T” held therebetween upon the application of electrosurgical energy. Jaw members110and120also include insulators116and126, which together with the outer, non-conductive plates of the jaw members110and120are configured to limit and/or reduce many of the known undesirable effects related to tissue sealing, e.g., flashover, thermal spread and stray current dissipation as shown inFIG. 1B.

The gap distance “G” is used as a sensed feedback to control the thickness of the tissue being grasped. More particularly, a pair of opposing sensors170aand170bare configured to provide real-time feedback relating to the gap distance between the sealing plates112and122of the jaw members110and120during the sealing process via electrical connection171aand171b, respectively. The sensors170aand170bprovide sensed feedback to the sensor circuitry22, which then signals the controller24. The controller24then signals the pressure applicator to adjust the pressure applied to the tissue based on the measured gap distance “G.” Consequently, this controls the rate at which tissue grasped between the sealing plates112and122is being compressed.

The sensors170aand170bmay be any suitable sensors, such as laser distancers, LED distancers, optical encoders, and the like. The laser and LED distancers operate by bouncing light beams from an opposing surface and measuring the duration of the beam of light to travel back to the sensors170aand170b. The sensors170aand170bbounce light beams from the opposing surfaces (e.g., sealing plates112and122). Each of the sensors170aand170bprovides an individual measurement of the distance between the jaw members110and120. An optical encoder (e.g., a linear encoder) is a sensor paired with a scale (not explicitly shown) that corresponds to a particular position of the jaw members110and120. The sensor170areads the scale and converts the encoded position into an analog or digital signal, which can then be decoded into position by a digital readout (e.g., sensor circuitry22). Motion of the jaw members110and120is determined by change in position over time. Linear encoder technologies include capacitive, inductive, eddy current, magnetic, and optical. Optical technologies include shadow, self imaging and interferometric. The sensor circuitry22and/or the controller24then average the result to arrive at the gap distance “G” separating the jaw members110and120. The sensor circuitry22and/or the controller24may perform various other types of calculations based on the gap distance “G” measurements to obtain desired empirical values for sensed feedback control.

The sensors170aand170bmay also be configured to measure suitable tissue properties, such as tissue impedance and temperature. Such sensors are within purview of those skilled in the art.

The gap distance “G” is directly related to the thickness of tissue being grasped between the sealing plates112and122. Therefore, the thickness of tissue being grasped may be controlled based on the gap distance “G.” As shown in a graph ofFIG. 5, thickness of the tissue (and therefore the gap distance “G”) decreases as pressure and energy are applied thereto. Tissue thickness decreases for at least two reasons. First, the pressure applied to the tissue by the sealing plates112and122compresses tissue. Second, RF energy applied to the tissue increases the temperature therein at which point intra-cellular fluids being to boil thereby causing the cells to rupture uncontrollably.

The graph ofFIG. 5shows a plot450of gap distance “G” between electrode plates of a conventional electrosurgical sealing forceps where RF energy is supplied at a constant rate and pressure is unregulated. In the plot450, the gap distance “G” falls to approximately half of the original value very quickly (e.g., approximately 0.5 seconds). This demonstrates as pressure and energy are applied at a constant rate during initial stages of a sealing procedure, thickness of the tissue rapidly decreases as the tissue is being cooked.

Plot452shows a more desirable progression of the gap distance “G.” In particular, if the thickness of the tissue decreases at a more controlled rate the mucosa and submucosa tissues remain in the seal area. Conventionally, the mucosa and submucosa layers are pressed out of the seal area due to uncontrolled delivery of RF energy, resulting in a less secure seal. Therefore, the controlled decrease of the gap distance “G” of the plot452allows for controlled decreases of the tissue thickness. This may be accomplished by controlling pressure as a function of the gap distance “G.” More specifically, an embodiment of the present disclosure controls application of pressure to tissue during sealing based on the gap distance “G” to maintain the desired rate of cell rupture, thereby controlling the thickness of the tissue being grasped.

A sealing method according to one embodiment of the present disclosure is shown inFIG. 4. In step400, the forceps10grasps the tissue “T” using the jaw members110and120. The sealing plates112and122are activated and are in contact with the tissue “T” but are not fully closed. When the sealing plates112and122contact the tissue “T” electrosurgical energy is applied thereto and the collagen contained therein is denatured and becomes more mobile (i.e., liquefies).

In step402, initial gap distance “G” is determined by sensors170a,170b, which measure the distance between jaw members110and120. The initial gap distance “G” measurement is useful in determining the thickness of the tissue being grasped. The thickness is particularly important since various adjustments to the procedure may be made based on relative tissue thickness. For instance, thin tissue types (e.g., small blood vessels) may require a certain amount of energy and pressure to properly seal desiccation whereas thicker tissue types may require more pressure and more energy. Other tissue parameters may be used to determine thickness and/or properties of the tissue. A second sensor or one of the sensors170aand170bmay be adapted to measure boundary conditions, jaw fill, hydration. This may be accomplished by using optical sensors adapted to measure opacity of the tissue. The tissue property measurements are transmitted to the controller24through the sensor circuitry22, wherein adjustments to the generator20and the pressure applicator are made in real-time based on the measurements.

In step404, energy, tissue and other treatment parameters are selected. More specifically, the initial gap distance “G” measurement is transmitted to the controller24where the tissue thickness is determined as a function thereof. The determination may be accomplished by matching the measured initial gap distance “G” with gap distance “G” values stored in a look-up table stored in memory26. The look-up table may include a plurality of gap distance “G” values and corresponding tissue thickness values. Upon finding a match, corresponding tissue thickness is obtained. In addition, the look-up table may also include suitable energy and pressure parameters associated with the corresponding tissue thickness. Energy and pressure parameters may also be loaded based on the initial gap distance “G” determination without determining the tissue thickness.

In step406, the forceps10begins to apply pressure and energy to the tissue “T” using the jaw members110and120based on the energy and pressure parameters loaded in step504. The pressure may be constant or be applied to according to a desired pattern (e.g., a control curve). The desired gap distance “G” may be expressed as a desired gap distance “G” trajectory, namely, plot452. The gap distance trajectory “G” includes a plurality of desired gap distance “G” values. The look-up table may include a plurality of parameters, such as starting and ending gap distances “G,” desired slope(s), etc. The microprocessor25uses these parameters to construct the plot452(i.e., the desired trajectory), which may be linear, quasi-linear, or non-linear. The gap distance “G” may also be controlled according to preset parameters and time increments based on pre-existing empirical data and not in real-time according to real changes in gap distance “G.”

In step408, as RF energy and pressure are applied to tissue, gap distance “G” is continually monitored and compared with the plot452in particular with corresponding desired gap distance “G” values. The gap distance “G” may also be controlled based in response to other tissue properties, such as tissue impedance and temperature. Impedance and temperature are continually monitored along with the gap distance “G” and are transmitted by the sensors170aand170bto the controller24wherein the controller24makes appropriate adjustments to the pressure applicator to control the pressure.

In step410, the controller24adjusts the pressure based on the measured gap distance “G” or other tissue properties by matching measured gap distance “G” with desired gap distance “G.” This is accomplished at specific time increments, which may be predetermined or dynamically defined. Namely, for every time increment, measured gap distance “G” is compared with a corresponding desired gap distance “G.” If the measured gap distance drops off rapidly and is below the desired corresponding gap distance “G” value of the plot452, the controller24adjusts pressure output of the pressure applicator (e.g., lowers the pressure).

An apparatus and method according to the present disclosure allow for tissue sealing procedures that retain the collagen at the sealing site, which is known to enhance the consistency, effectiveness, and strength of tissue seals. This may be accomplished by using a “slow close” activation to initially denature the collagen and then close the sealing plates under pressure at a predetermined rate. Further details relating to “slow close” activation are disclosed in commonly-owned U.S. application Ser. No. 11/095,123 filed Mar. 31, 2005 entitled “ELECTROSURGICAL FORCEPS WITH SLOW CLOSURE SEALING PLATES AND METHOD OF SEALING TISSUE”, which is herein incorporated by reference. This allows for limited extrusion of the cured and mixed collagen mass from the sealing site, which contributes to an effective and uniform seal.

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. For example and as mentioned above, any of the slow closure techniques, methods and mechanisms disclosed herein may be employed on an open forceps such as the open forceps700disclosed inFIG. 6. The forceps700includes an end effector assembly600that attaches to the distal ends516aand516bof shafts512aand512b, respectively. The end effector assembly600includes pair of opposing jaw members610and620that are pivotally connected about a pivot pin665and are movable relative to one another to grasp vessels and/or tissue. Stop member assemblies, such as those described with respect toFIGS. 1A-1B,3and4, and sensors170aand170bmay be disposed within the end effector600to regulate the RF energy according to real-time measurements and changes to the gap distance “G” during sealing.

Each shaft512aand512bincludes a handle515and517, respectively, disposed at the proximal end514aand514bthereof each of the handles515and517define a finger hole515aand517a, respectively, therethrough for receiving a finger of the user. Finger holes515aand517afacilitate movement of the shafts512aand512brelative to one another, which, in turn, pivot the jaw members610and620from an open position wherein the jaw members610and620are disposed in spaced relation relative to one another to a clamping or closed position wherein the jaw members610and620cooperate to grasp tissue or vessels therebetween. Further details relating to one particular open forceps are disclosed in commonly-owned U.S. application Ser. No. 10/962,116 filed Oct. 8, 2004 entitled “OPEN VESSEL SEALING INSTRUMENT WITH CUTTING MECHANISM AND DISTAL LOCKOUT”.

In addition, the presently disclosed forceps may include an electrical cutting configuration to separate the tissue either prior to, during or after cutting. One such electrical configuration is disclosed in commonly-assigned U.S. patent application Ser. No. 10/932,612 entitled “VESSEL SEALING INSTRUMENT WITH ELECTRICAL CUTTING MECHANISM,” which is herein incorporated by reference.

Moreover, only one sensor in one jaw member may be utilized to measure the initial and real-time changes in the gap distance “G.” The sensor may be configured to provide an initial gap distance value to the microprocessor or generator, which enables a predetermined starting gap distance value, trajectory and ending gap distance value.

In addition, the gap distance “G” may be selectively regulated by adjusting one or more stop members that extend from the tissue sealing surfaces. Several configurations of this feature are shown in a commonly-owned U.S. patent application Ser. No. 10/846,262 entitled “TISSUE SEALER WITH NON_CONDUCTIVE VARIABLE STOP MEMBERS AND METHOD OF SEALING TISSUE,” which is herein incorporated by reference.