RF energy console including method for vessel sealing

A RF energy console controls RF energy output from a RF generator for sealing blood vessels. The energy console includes a processor that executes routines and a controller feedback circuit that, in combination, control the RF generator. Operation includes a heating stage outputting a RF ramping voltage and determining a decrease in measured current to less than a predetermined % percentage of a maximum measured and stored current value to advance to a sealing stage. Then, the voltage is controlled to maintain an increasing change in impedance until a change in current value approaches a flat curve indicating seal completion, which stops the RF generator output. To reseal or enhance a blood vessel seal, the energy console executes the same routines as in the initial sealing operation.

FIELD OF THE INVENTION

This invention is related to a RF energy console for outputting RF energy to a handpiece and a method for sealing a blood vessel. The RF energy also can be applied to enhance a seal of a blood vessel that was previously desiccated.

BACKGROUND OF THE INVENTION

The use of an RF generator device in combination with a surgical tool to seal blood vessels is known as disclosed, for example, in U.S. Pat. No. 7,090,673. Further, a bi-polar electrosurgical instrument including a cutting knife in combination with jaw members for sealing and subsequently cutting a blood vessel was known. Various approaches for sealing vessels include RF generator devices that apply RF energy pulses to tissue.

In instances when sealing of a blood vessel is complete, resealing to enhance the seal can be difficult. For heating of fluid in a blood vessel to a boiling condition during a resealing operation, a maximum measured current typically has a much smaller value before boiling begins than a maximum current for a first original sealing operation. Therefore, sealing arrangements that merely compare measured values with a maximum or minimum value for one or more of: current, voltage and impedance, typically are modified by providing different algorithms or calculations for resealing a blood vessel as compared to an initial sealing process.

SUMMARY OF THE INVENTION

In order to obviate or at least minimize the disadvantages of complicated energy applying features of known arrangements, the invention utilizes measured voltage, measured current, changes in current and changes in impedance to control the RF generator to seal a blood vessel. At start-up, a predetermined stored ramping RF voltage is applied to the jaws of a handpiece during a heating stage to obtain boiling of liquid in tissue and in a blood vessel. During heating, current is measured and when a current drop or decrease of a certain predetermined percent value occurs, the sealing operation advances from the heating stage to a sealing stage. During the sealing stage the invention relies on a flattening of a change in current curve to accurately determine completion of a seal.

By utilizing a percent decrease in current value to determine boiling of liquid, resealing a blood vessel can occur without requiring different routines, algorithms or comparison values as compared to an initial sealing.

DETAILED DESCRIPTION OF THE INVENTION

A RF energy console10and a method for sealing blood vessels and resealing blood vessels during a medical procedure is described. Note that in this description, references to “one embodiment” or “an embodiment” mean that the feature being referred to is included in at least one embodiment of the present invention. Further, separate references to “one embodiment” or “an embodiment” in this description do not necessarily refer to the same embodiment; however, such embodiments are also not mutually exclusive unless so stated, and except as will be readily apparent to those skilled in the art from the description. For example, a feature, step, etc. described in one embodiment may also be included in other embodiments. Thus, the present invention can include a variety of combinations and/or integrations of the embodiments described herein.

FIG. 1shows a RF energy console10according to certain embodiments of the invention. The RF energy console10has a housing12including a front face panel14. The front face panel14includes a display screen16, an on/off control18to power on the RF energy console10, an RF energy output connector port20and a powered shaver output connector port22. A foot switch connector port24is also provided on the front face panel14. Adjacent the display screen16, the directed energy console10includes an output device selector28and device adjustment controls30that are disposed vertically above and below the output device selector. An RF vessel seal error indicator32is disposed on the front face panel14. A specific error indication can be provided on the display screen16. Further, a progress bar provided on the display screen16indicates progress and completion of a seal.

FIG. 2shows an electrosurgical handpiece40for receiving energy from the RF energy console10. The handpiece40includes a handpiece body42having a fixed handle44. In theFIG. 2embodiment, the handpiece40supports a movable handle46and a pivotable cutting device trigger48. A shaft apparatus50has a proximal end secured to a front end of the handpiece body42. The shaft apparatus50includes a fixed jaw52and a movable jaw54each disposed at a distal end thereof. Force applied to the movable handle46clamps a blood vessel between the jaws52,54. Actuating the cutting device trigger48moves a cutting blade (not shown) outwardly along the longitudinal axis of the shaft apparatus50to cut tissue of a sealed blood vessel disposed between the jaws52,54.

A foot switch or foot pedal (not shown) can be plugged into the foot switch connector port24to provide an actuation signal to the RF energy console10to apply energy to the handpiece40for sealing a blood vessel. In some embodiments, an actuation switch (not shown) disposed on the handpiece body42is provided to trigger operation of the RF energy console10for sealing a blood vessel.

Cable56illustrated inFIG. 2protrudes from the surgical handpiece40for connection to RF energy output connector port20of the RF energy console10.

FIG. 3is a block diagram of the RF energy console10, the handpiece40and the cable56providing a connection therebetween. The embodiment shown inFIG. 3includes a RF generator100and an analog voltage/current (V/I) sensor apparatus102disposed in the housing12of the RF energy console10. The analog sensor apparatus102is connected to an analog to digital (A/D) converter104and to an analog controller feedback circuit106. The A/D converter connects to a digital processor110also disposed within the RF energy console10that is provided with a processor memory112.FIG. 3shows the digital processor110including a feedback circuit representation114, a change in impedance calculator representation116, and a change in current calculator representation118. The representations are of calculations or actions that are performed by the digital processor110.

Further, in some embodiments, one or more of a predetermined stored start-up increasing voltage ramping value for a heating stage, a predetermined stored ramp voltage limit value, a predetermined stored ramp current limit value, a predetermined stored current decrease percentage threshold value (defined by the constant “%th” and having a possible value between 1 and 99), a predetermined stored change in impedance value (ΔZseal) for use during a sealing stage, and a predetermined stored change in current shut-off value (ΔIshutoff) for use during a sealing stage can be stored in a handpiece memory130illustrated inFIG. 3and read by the digital processor110.

The block diagram of the handpiece40shown inFIG. 3includes a drive electrode/jaw representation132corresponding to movable jaw54and a ground electrode/jaw representation134corresponding to jaw52that encompass a tissue/blood vessel representation136disposed therebetween.

Cable56as shown inFIG. 3connects the handpiece40to the RF energy console10via the RF output connector port20. The cable56includes a RF output connector140that provides RF energy from the RF generator100to the drive electrode/jaw representation132. Likewise, the cable56includes an RF return/ground connector142that connects the ground electrode/jaw representation134through the RF output connector port20to the analog sensor apparatus102. A 1-wire connector144connects the surgical handpiece memory130, typically a non-volatile random access memory (NVRAM), through the connector port20to the digital processor110disposed within the RF energy console10. The connectors140,142typically extend essentially the length of the shaft apparatus50and through the handpiece body42to the cable56. The handpiece memory130can be located within the handpiece body42adjacent the cable56. The 1-wire connector144for the handpiece memory130typically is located within the body or shell of the cable56at the end that connects to the RF energy output connector port20.

The predetermined start-up increasing voltage ramping value, the predetermined ramp voltage limit value, the predetermined ramp current limit value, the current decrease %ththreshold value, the ΔIshutoffvalue, the ΔZsealvalue and other values, along with a handpiece identifier unique to the particular handpiece40can be obtained from the surgical handpiece memory130and stored in the digital processor memory112.

In another embodiment, only a surgical handpiece identifier is stored in the surgical handpiece memory130. In this embodiment, the digital processor110reads the handpiece identifier from the handpiece memory130and locates the specific predetermined stored values for the identified surgical handpiece40in a remote memory device accessible over a network or similar arrangement. In another embodiment the specific values are pre-stored in the processor memory112, instead of the handpiece memory.

The predetermined stored values typically also include one or more predetermined error time limit values that, for example, discontinue RF output from the RF generator100when a change in the first heating stage1or the second sealing stage2does not occur within a predetermined time limit. The predetermined stored time limit values can be obtained by the processor110in the various ways that the predetermined stored values are obtained as discussed above.

In another embodiment, the predetermined stored values additionally include a predetermined stored and instantaneous short circuit current value that is stored in the handpiece memory130or elsewhere as in the embodiments discussed above. The processor110obtains the short circuit current value and discontinues the output of energy from the RF generator100when an instantaneous measured current value exceeds the instantaneous short circuit current value.

In another embodiment, P-I-D values are stored in the handpiece memory130and are read by the processor110. The processor110applies the P-I-D values to operate in part as a software based P-I-D controller.

During use of the RF energy console10shown inFIGS. 1-3, the RF generator100outputs RF energy to the handpiece40. Energy output from the movable jaw54passes through tissue that includes a blood vessel136and is received at the fixed jaw52. Connector142provides an electrical return path from the fixed jaw52through the cable56to the RF energy console10.

In another embodiment, the fixed jaw52receives RF energy and the energy received by the fixed jaw52passes through tissue to the movable jaw54. In this embodiment, the movable jaw54is connected to the RF energy console10via connector142, and the fixed jaw52connects to the RF generator100via the connector140and the cable56.

As shown inFIG. 3, after passing through tissue136, energy is received at ground electrode/jaw representation134and provided to the analog V, I sensor apparatus102via connector142. The analog sensor apparatus102determines RMS voltage and current values for the RF energy output by the RF generator100and returned to jaw52. The measured RMS voltage and current values are provided to the analog controller feedback circuit106, as well as to an A/D converter104. The A/D converter104converts the analog measured current and voltage values to digital values that are provided to the digital processor110.

The digital processor110functions to control RF energy output from the RF generator100by providing a control signal to the analog controller feedback circuit106. The controller feedback circuit106operates orders of magnitude faster than the P-I-D software routine and other processing executed by the processor110. Thus, the analog controller feedback circuit106, in response to the digital processor control signal, along with measured voltage (Vmeas) and/or measured current (Imeas) values received from the analog sensor apparatus102, controls the RF generator100to output RF energy for sealing a blood vessel.

More specifically, the feedback circuit representation114of the digital processor110represents software that functions as a P-I-D controller and other circuitry that adjust the output to the RF generator100to prevent or minimize drastic erroneous changes in the RF energy output to the handpiece40. Further, the digital processor110receives the Vmeasand Imeasvalues through the A/D converter and executes algorithms or routines that act as a comparator to output the proper values from the RF generator100and as a feedback circuit to stabilize the processor control signal provided from the digital processor110to the analog controller feedback circuit106to assist in controlling and stabilizing the output of the RF generator100.

OPERATION

In one embodiment, upon powering up of the RF energy console10, the digital processor110operates as follows. Initially, the digital processor110receives a handpiece identifier via connector144from a memory130of a handpiece40when a handpiece cable56is secured to the RF energy output port20. From the handpiece memory130, the digital processor110receives information to determine the specific type and model of the handpiece40and that the handpiece is intended for sealing blood vessels. Moreover, the digital processor110obtains the predetermined stored start-up increasing voltage ramping value, the predetermined stored ramp voltage limit value, the predetermined stored ramp current limit value, the %thvalue, the ΔIshutoffvalue, the ΔZsealvalue and one or more of the additional values discussed above, as necessary. The predetermined stored values correspond to the specific handpiece40and enable a RF energy output that efficiently seals a blood vessel.

In one embodiment, the RF energy device console10operates as shown in the flow charts ofFIGS. 4 and 5. The RF energy console applies the routines200,212to a specific handpiece40which results in the measured values shown in the graphs ofFIGS. 6-9.

Upon manual actuation of the RF energy console10by a user using a foot pedal or handpiece mounted trigger, during a first heating stage at step214shown inFIG. 4, the digital processor110outputs a control signal to the controller feedback circuit106that begins operation of the RF generator100at the start-up increasing voltage ramping value. Thereafter, the processor110recalculates the output signal that controls the controller feedback circuit106to control the RF generator100to ramp the voltage value applied to the blood vessel including tissue136via the jaws52,54at an essentially constant increasing rate in accordance with the specific predetermined stored voltage ramping value. The voltage graph ofFIG. 6shows the ramping voltage value beginning at 0 volts at start-up and advancing to 20 volts in slightly more than one second. The ramping voltage is intended to increase at a constant rate, and in some embodiments increases at a value in a range from about 10 volts/second to about 100 volts/second. Start-up of the RF generator100occurs after about 0.3 seconds in the embodiment shown inFIGS. 6-9, as no voltage or current is output by the RF generator100during the first about 0.3 seconds.

When one of a ramp current limit value or a ramp voltage limit value is obtained by the RF generator output, the processor110prevents the Vmeasvoltage or Imeascurrent from increasing beyond the respective current or voltage limit value during the heating stage. The ramp voltage limit value is approximately 60 volts for the particular handpiece40of the embodiment shown inFIGS. 6-9. The ramp current limit value is about 2,500 milliamps (mA). InFIG. 7, the Imeascurrent is then maintained at about 2,500 mA during the heating stage. Heating stage1continues for about 2.7 seconds to about 2.9 seconds in the embodiment shown inFIGS. 6-9.

In some embodiments, the ramp voltage limit value is a single value within a range from about 30 volts to about 100 volts, and preferably within a range from about 60 volts to about 70 volts. The ramp voltage limit value depends on the size of a blood vessel, type of tissue, properties of the handpiece40and other factors. These types of factors affect which of the ramp voltage limit value or the ramp current limit value is first obtained for controlling the voltage output during the heating stage of the sealing operation. In some embodiments, the ramp current limit value is a single value within a range of about 1000 mA to about 5000 mA. The measurements of Vmeasvoltage and Imeascurrent occur during step202as shown inFIG. 4until the ramp current limit value or the ramp voltage limit value is obtained and thereafter occur while the limit value is maintained.

As shown inFIG. 4at step204, the analog voltage/current sensor apparatus102measures the Vmeasvoltage value and the Imeascurrent value. Besides the digital processor110maintaining or attempting to maintain the Vmeasvoltage value at a value that is less than the predetermined ramp voltage limit value, the digital processor also maintains the Imeascurrent value below the predetermined ramp current limit value, such as 2,500 mA. The Vmeasvoltage value and the Imeascurrent value are provided to the feedback circuit106. The feedback circuit106and the digital processor110account for changes in current, voltage and other factors to maintain the Vmeasvoltage value at or below the predetermined ramp voltage limit value and the Imeascurrent value at or below the ramp current limit value.

Initially increasing the Vmeasvoltage value over the first heating stage as shown inFIG. 6, and thereafter while maintaining the ramp current limit value of 2,500 mA, the digital processor110also compares the Imeascurrent value to a maximum (Imax) RMS current value for heating stage1as shown at step206inFIG. 4. Typically, the Imaxcurrent value at start-up is a relatively low current value and the Imeascurrent value output by the RF generator100increases as shown inFIG. 7as the voltage ramping value increases. If the ramp voltage limit value is obtained first, the Imeascurrent value is at a value less than the ramp current limit value. InFIG. 7, the Imeascurrent value is essentially 0 mA at start-up and is about 2500 mA when the ramp current limit voltage value is obtained. Regardless of whether the Imeascurrent value attains the current limit value in less than a second, when the Imeascurrent value is greater than the stored Imaxcurrent value, the routine or algorithm200shown inFIG. 4advances to step208. At step208, the Imaxcurrent value stored in the digital processor memory112is updated to the greater Imeascurrent value and the routine200returns to step204and repeats determining a Vmeasvoltage value and an Imeascurrent value. Thus, the Imaxcurrent value stored by the processor110is eventually updated to a value of about 2500 mA for the embodiment ofFIGS. 6-9. As discussed above, the digital processor110and the analog controller feedback circuit106operate to ensure that the Imeascurrent value does not exceed the ramp current limit value and that the Vmeasvoltage value output by the RF generator100does not exceed the predetermined ramp voltage limit value.

At step206, when the Imeascurrent value is less than or equal to the Imaxcurrent value, the routine200advances to step210. At step210, the digital processor110compares the Imeascurrent value to the predetermined stored current decrease threshold %thof the Imaxcurrent value. The %thvalue is dependent on the type of handpiece40being utilized. For example, the %thvalue can be a single value in a range between about 20% and about 95%, in a range between about 60% and about 90% or in a specific range between about 70% and about 85%. Before fluid in tissue of a blood vessel begins to boil, the Imeascurrent value typically increases during the start up heating stage for less than one second of operation and does not decrease significantly as shown in the graph ofFIG. 7for more than the next two seconds of operation. Thus, for the embodiment shown inFIGS. 6-9, the routine200continues to return to step204and repeats for more than two seconds of operation.

Eventually, the fluid in the tissue and in the blood vessel between the jaws52,54begins boiling causing tissue impedance to increase and current to decrease, and thus the Imeascurrent value suddenly decreases a large amount.FIG. 7shows the measured current decreasing from about 2500 mA to almost about 500 mA in a small number of milliseconds, which is about a 80% decrease in the Imeascurrent value. Thus, the Imeascurrent value suddenly becomes less than or equal to %thof the Imaxcurrent value which signifies boiling, so long as the %thvalue is greater than about 20%. Then, the routine200advances from step210to the sealing stage2illustrated by the sealing routine212shown inFIG. 5. In the embodiment shown inFIGS. 6-9, the sealing stage2begins about 2.7 seconds to about 2.9 seconds after the RF generator100starts outputting RF energy and continues for about 2.6 to about 2.8 additional seconds before stopping, which results in a total operating time of about 5.5 seconds to complete a seal.

In the sealing routine212shown inFIG. 5, the start-up voltage ramping value, and other values used during the heating stage1are no longer utilized.

The sealing routine212begins at step216, whereat the Vmeasvoltage value and the Imeascurrent value are obtained. The routine212advances from step216to step218wherein the processor110uses the Imeascurrent value and one or more previously stored Imeascurrent values to calculate a change in current (ΔIcalc) value for the energy output by the RF generator100and provided through the jaws52,54to apply to tissue at a blood vessel. More specifically, the ΔIcalcvalue is calculated from changes in Imeascurrent values over a certain time resulting in a ΔIcalcvalue that is measured in mA/second. The Vmeasvoltage value is compared with one or more previously stored Vmeasvoltage values to calculate a change in voltage (ΔVcalc) that is measured in volts/second. In one embodiment, at each measurement of Vmeasand Imeas, an impedance value is calculated. An impedance value is compared with or more previously stored impedance values to calculate a change in impedance (ΔZcalc) value that is measured in ohms/second. In another embodiment, ΔZcalcis determined by dividing an essentially real-time ΔVcalcvalue by an essentially real-time ΔIcalcvalue. After performing the calculations at step218, the routine212advances to step220.

At step220shown inFIG. 5, the digital processor110compares the ΔZcalcvalue with the predetermined stored positive change in impedance ΔZsealvalue for the specific handpiece40. In some embodiments, the ΔZsealvalue is a value with a range of about 25 ohms/second to about 200 ohms/second. In view of the comparison results, the processor110in combination with the controller feedback circuit106, adjusts the voltage value output by the RF generator100to maintain the increasing ΔZsealvalue for the current path between the jaws52,54and through the tissue including a blood vessel. The increasing linear impedance as measured is shown inFIG. 8, wherein impedance begins to increase after about 2.7 to 2.8 seconds from the start of the sealing operation and continues until the seal is complete. The ΔZsealvalue is selected for a handpiece40in order to maximize the sealing quality for the blood vessel receiving RF energy from the handpiece. Thus, the purpose of the ΔZsealvalue used during the sealing stage is to gradually dessicate the tissue and vessel at a controlled rate slow enough to ensure a quality seal by minimizing charring, but fast enough so the procedure time length is minimized. After the voltage adjustment at step220, the routine212advances to step222.

During the sealing operation routine212shown inFIG. 5, the repeatedly calculated ΔIcalcvalues are negative values as the current is decreasing during the sealing stage2which starts at about 3.1 seconds, which is about 2.8 seconds after the RF generator100is energized and continues for about 2.5 to 2.6 seconds more as shown inFIG. 7. At step222, the value is compared to the predetermined stored change in current ΔIshutoffvalue for the sealing stage. As shown inFIG. 7, after blood vessel sealing nears completion, the Imeascurrent value begins to plateau at a Imeascurrent value of about 250 mA and the change in current begins to flatten toward a change in current of 0 mA/sec. So long as the ΔIcalcvalue is decreasing at a large enough rate, in one embodiment the ΔIshutoffvalue is −50 mA/second, the routine212returns to step216and continues to perform steps216,218,220,222. In some embodiments, the ΔIshutoffvalue has a value within a range of about −20 mA/second to about −80 mA/second.

At step222, when the absolute value of the ΔIcalcvalue is less than absolute value of the ΔIsealvalue, for example a ΔIcalcvalue of −45 mA/second for comparison with a ΔIsealvalue of −50 mA/second, the routine212advances from step222to step224.

At step224, the digital processor110stops the output of energy from the RF generator100. Further, in some embodiments, a progress bar displayed on the display screen16provides a visual indication that the seal is complete. The progress bar shows the advancement of the sealing operation and relies on ΔIcalcto do so during the sealing stage. In some embodiments, an audible indication of seal completion is provided.

FIG. 9is provided to illustrate power output during heating and sealing stages of the embodiment illustrated inFIGS. 6-8.

INCOMPLETE SEAL

WhileFIGS. 4 and 5illustrate a method for completing a sealing operation, the digital processor110is capable of performing additional operations during the routines200,212, such as stopping the output of energy from the RF generator100and providing an indication if the applied RF energy does not result in a proper blood vessel seal.

During the routine200shown inFIG. 4, the digital processor110essentially simultaneously executes a timing routine that essentially continuously or periodically measures in real-time, the exact time of the heating stage1operation and compares the measured time with a predetermined stored heating error time limit value corresponding to the particular handpiece40connected thereto. In an instance wherein the Imeascurrent value does not become less than %thof the Imaxcurrent value (sealing beginning) within the predetermined stored heating error time limit value during the heating stage, the RF output seal error indicator32provides a visual indication of sealing failure and RF energy output from the RF generator100is discontinued. An audible error message or alarm is provided in some embodiments and a detailed error message is provided on the display screen16. In some embodiments, the heating error time limit value for the heating stage is a value with a range from about 2 seconds to about 6 seconds.

During the sealing stage2operation as illustrated by the routine212shown inFIG. 5, the digital processor110also continues to measure the time length since the beginning of the sealing operation. In one embodiment, if the measured time exceeds a predetermined stored sealing error time limit value that is stored in the processor memory112, the seal error indicator32provides a visual seal error indication and the RF energy that is output by the RF generator100is discontinued. In some embodiments, an audible error message or another alarm is provided and a specific error message can be provided on the display screen16. In various embodiments, the sealing error time limit value is from about 5 seconds to about 12 seconds from the beginning of a sealing operation, which includes the heating stage.

In some embodiments, a predetermined instantaneous short circuit current value stored in the handpiece memory130is sent to the digital processor110and then provided to a separate analog circuit (not shown) that determines a sudden rise in instantaneous current beyond the short circuit current value. If the instantaneous measured current value (not a RMS value) is greater than the short circuit current value, the RF energy output from the RF generator is stopped and the seal error indicator32provides a visual indication of sealing failure. Likewise, in some embodiments a specific short circuit error message is provided on the display screen16and/or an audible message.

RESEALING OPERATION

In the event a sealing error occurs, an operator may subsequently attempt to seal or reseal the blood vessel using the same routines200,212shown inFIGS. 4 and 5. Such resealing operation occurs while maintaining the jaws52,54at the sealing area.

For various reasons, during a resealing operation a heating stage measured current value that is stored as the Imaxcurrent value typically does not approach a value remotely close to an Imaxcurrent value measured during a first sealing attempt. By multiplying the stored Imaxcurrent value by the predetermined percentage value %thto determine the boiling of liquid in a blood vessel, the digital processor110determines a boiling condition even when the Imaxcurrent value does not attain a generally expected current value for an initial sealing attempt. Thus, utilizing a predetermined percentage %thof the Imaxcurrent value provides proper boiling detection as compared to utilizing a predetermined required current limit value or a voltage limit value that may never be obtained. In the sealing stage routine212shown inFIG. 5, the processor110determines a completed seal when the decreasing ΔIcalc, value is less than a ΔIshutoffvalue as discussed above. Thus, no specific large or small Imeascurrent value or Vmeasvoltage value is required to determine completion of the resealing of a blood vessel. Therefore, providing a different routine or algorithm to perform calculations is not necessary to reseal the blood vessel.

ENHANCEMENT RESEALING OPERATION

Besides resealing a blood vessel in response to an indication that a sealing operation may be incomplete as disclosed above, many surgical personnel routinely perform a resealing operation to enhance the quality of the seal. Examples of enhancement resealing operations are shown in the graphs ofFIGS. 10 and 11, which specifically illustrate an original sealing followed by an enhancement resealing operation. The current measurement graph ofFIG. 10shows a first sealing operation occurring within the first six seconds of time and a second resealing operation is shown on the same graph for purposes of comparison that starts at a time of about 7.5 seconds and ends about 10 seconds after the first previous sealing operation occurred. The graph of the current for the first sealing operation shown inFIG. 10is the same as the sealing operation for the current as shown inFIG. 7. A gap of more than 1.5 seconds is shown between the first sealing and the second enhancement sealing operation. The time gap is insignificant and simply corresponds to the delay before a user manually begins a second enhancement operation of the RF generator100.

As in the embodiment disclosed inFIGS. 6-9, and specifically in the graph of current shown inFIG. 7, the measured current as shown inFIG. 10increases rapidly during voltage ramping of the heating stage and the current value obtains the ramp current limit value of 2,500 mA. Thus, the stored Imaxcurrent value is 2,500 mA. After about 3 seconds, the Imeascurrent then suddenly decreases to a value of about 600 mA, which is a decrease to about 26% of the Imaxcurrent value. This sudden decrease to an Imeascurrent value of about 600 mA is much less than a %ththreshold of, for example, 85% of the Imaxcurrent value of 2,500 mA. The processor110then advances the sealing operation from heating stage1to sealing stage2as a result of the Imeascurrent value being less than 85% of 2,500 mA.

At the second enhancement sealing operation shown inFIG. 10, and during the voltage ramping shown inFIG. 11, there is a similar quick increase in Imeascurrent until a level of about 1,350 mA is obtained. Thus, for the enhancement resealing, the Imeascurrent value does not approach either the ramp current limit value of 2,500 mA or the ramp voltage limit value as in the first sealing operation. As shown inFIG. 10, a sudden decrease in current to a value of about 350 mA occurs, which is a % decrease to about 27% of the Imaxcurrent value. As the %ththreshold is a single value between about 60% and about 90%, the sealing operation advances to the sealing stage. Thereafter, the sealing stage operates as in the embodiments previously described. Note that the entire enhancement resealing operation shown inFIGS. 10 and 11requires less than 3 seconds. Thus, the amount of voltage and current output required to enhance the seal for the tissue and blood vessels is not as great as compared to completing an original seal. Therefore, the benefit of relying on the %thmeasurement of a decrease in current, rather than Imeascurrent values to control the sealing enhancement operation is clearly observable.

FIG. 12shows another current versus time graph for sealing and enhancement sealing of tissue, and specifically application of RF energy to seal mesentery tissue. Actuation of the RF generator100begins at about 0.5 seconds on theFIG. 12graph. Mesentary tissue is typically much stronger and thicker than other tissue. In this use of a RF energy console10with a handpiece40, during the heating stage with voltage ramping occurring, the Imeascurrent value increases in about one second to a Imeasvalue of less than 2,000 mA as shown inFIG. 12. The Imeascurrent value, when boiling of liquid and tissue begins, suddenly decreases to about 23% of the previously stored Imaxcurrent value of almost 2,000 mA. This value is much less than the single %ththreshold value from 60% to 90% provided to the processor110from the handpiece memory130. As in the earlier embodiments, the processor110advances to the sealing stage and operates until stopping about 2.7 to 3.0 seconds after the starting of the sealing operation when a completed seal is indicated.

As shown inFIG. 12, a second enhancement resealing operation begins wherein during the voltage ramping of the heating stage, the Imeascurrent value attains a value of about 600 mA. Thereafter, a decrease to about 44% of the measured and stored Imaxcurrent value of about 600 mA occurs. Thus, in theFIG. 12example, the percentage decrease in current is much less than in original initial sealing. Therefore, the approach of measuring percentage current decreases provides better results for the RF energy console.

The RF energy output by the RF generator100of the RF energy console10is a continuous RF output, and thus is free from RF energy pulses.

The flow charts shown inFIGS. 4 and 5represent one embodiment of the invention. Other embodiments include additional steps, such as for determining when the sealing operation exceeds an error time limit value. Further, the various steps can be provided in a different order or a single step can be defined as a group of sub-steps.

Although the present invention has been described with respect to specific exemplary embodiments, it will be recognized that the invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense.