POWER CONTROL FOR AN ELECTROSURGICAL VESSEL SEALER

Abstract

A power delivery approach for delivering power to an electrosurgical vessel sealer when the jaws of the sealer surround tissue to be desiccated. Power delivery commences at a starting point that is at least 40 Joules and then decreases over a first predetermined period of time to a predetermined minimum power level to provide approximately 15 Joules in total. When the predetermined minimum power level is reached, power is then continuously increased over a second predetermined period of time to fully desiccate the tissue. Power delivery is terminated prior to over-desiccation of the tissue.

Claims

1. An electrosurgical system, comprising: a vessel sealer having a pair of jaws; and an electrosurgical generator coupled to the pair of jaws of the vessel sealer and configured to output radiofrequency energy to the vessel sealer according to a predetermined continuous power curve; wherein the predetermined continuous power curve comprises a first power delivery segment that commences at a first power level and continuously decreases to a second, non-zero power level and a second power delivery segment that commences with the second, non-zero power level and increases to a final power level.

2. The electrosurgical system of claim 1, wherein the first power delivery segment occurs during a time period of between 0.250 and 9.75 seconds.

3. The electrosurgical system of claim 1, wherein the second power delivery segment occurs during a time period of between 0.250 and 9.75 seconds.

4. The electrosurgical system of claim 1, wherein the first power delivery segment delivers an amount of power that will not cause any tissue trapped in the pair of jaws to reach a temperature that results in boiling of any moisture in the tissue.

5. The electrosurgical system of claim 1, wherein the first power delivery segment delivers an amount of power that causes any tissue trapped in the pair of jaws to desiccate.

6. The electrosurgical system of claim 1, wherein the final power level will not cause over-desiccation of any tissue trapped in the pair of jaws.

7. The electrosurgical system of claim 1, wherein the second power delivery segment ends when any tissue in the pair of jaws has an impedance that exceeds a predetermined value.

8. The electrosurgical system of claim 1, wherein the first power delivery segment has a shape selected from the group consisting of linear, concave, convex, and combinations thereof.

9. The electrosurgical system of claim 1, wherein the second power delivery segment has a shape selected from the group consisting of linear, concave, convex, and combinations thereof.

10. The electrosurgical system of claim 1, wherein the first power delivery segment comprises an exponential decay curve and the second power delivery segment is linear.

11. A method of controlling the power output from an electrosurgical generator to a vessel sealer having a pair of jaws, comprising: providing the vessel sealer having the pair of jaws; coupling the electrosurgical generator to the pair of jaws of the vessel sealer; powering the electrosurgical generator to output radiofrequency energy to the vessel sealer according to a predetermined continuous power curve, wherein the predetermined continuous power curve comprises a first power delivery segment that commences at a first power level and continuously decreases to a second power level and a second power delivery segment that commences with the second power level and increases to a final power level.

12. The electrosurgical system of claim 11, wherein the first power delivery segment occurs during a time period of between 0.250 and 9.75 seconds.

13. The electrosurgical system of claim 11, wherein the second power delivery segment occurs during a time period of between 0.250 and 9.75 seconds.

14. The electrosurgical system of claim 1, wherein the first power delivery segment delivers an amount of power that will not cause any tissue trapped in the pair of jaws to reach a temperature that results in boiling of any moisture in the tissue.

15. The electrosurgical system of claim 11, wherein the second power delivery segment ends when any tissue in the pair of jaws has an impedance that exceeds a predetermined value.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0007] The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings, in which:

[0008] FIG. 1 is a perspective view of an electrosurgical system according to the present invention

[0009] FIG. 2 is a schematic of an electrosurgical generator for an electrosurgical system that may be configured to deliver power according to the present invention;

[0010] FIG. 3 is a power delivery curve according to an embodiment the present invention;

[0011] FIG. 4 is a power delivery curve according to another embodiment of a power control algorithm of the present invention;

[0012] FIG. 5 is a power delivery curve according to a further embodiment of a power control algorithm of the present invention;

[0013] FIG. 6 is a power delivery curve according to an additional embodiment of a power control algorithm of the present invention;

[0014] FIG. 7 is a power delivery curve according to yet another embodiment of a power control algorithm of the present invention; and

[0015] FIG. 8 is a graph of the energy plot superimposed over a power delivery curve according to an embodiment of a power control algorithm of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0016] Referring to the figures, wherein like numeral refer to like parts throughout, there is seen in FIG. 1 an electrosurgical system 10 comprising a vessel sealer 12 having a pair of conductive opposing jaws 14 that are interconnected to an electrosurgical generator 16 that can supply RF energy to electrodes of jaws 14 for the desiccation of a blood vessel trapped between jaw 14. The dimensions of jaws 14 and the type of RF energy supplied will produce desiccation of the blood vessel in a region of a particular width as determined by the thermal spread of the energy being supplied to the blood vessel. As is known in the art, jaws 14 are pivotally mounted to vessel sealer 12 for movement between an open position and a closed position in response to a user operating a lever 18 extending from the main body 20 of sealer 12.

[0017] Referring to FIG. 2, electrosurgical generator 16 comprises the electronics and circuitry response for precisely delivering RF energy to jaws 14 according to the present invention. The components, connections, sensing elements, electrical circuits, power source, user controls, and programmable control elements of electrosurgical generator 16 are known in the art and only discussed herein with respect to the specific aspects of electrosurgical generator 16 that are configured for implementation of the present invention. More specifically, electrosurgical generator 16 comprises a controller 22 that is programmed to execute substantially all of the feedback and regulation functionality of electrosurgical generator 16 and, more specifically, output radiofrequency energy from an RF output 24 according to one or more predefined power delivery curves according to the present invention that are stored in a power curve module 26. RF output 24 is coupled to an active path 28 and a return 30 of electrosurgical generator 16 that may be coupled to an electrosurgical instrument, such as vessel sealer 12, to deliver radiofrequency according to one or more of the power delivery curves to jaws 14 and thus desiccation of any tissue trapped within jaws 14. Electrosurgical generator 16 includes feedback circuit 32 so that controller 22 can monitor the output of radiofrequency energy from RF output 24. As is known in the art, feedback information provided by feedback circuit 32 can be used by controller 22 to control, regulate, and adjust the delivery of radiofrequency according to one or more of the power delivery curves, and to monitor the amount of power delivered to vessel sealer 12 over time.

[0018] Referring to FIG. 3, electrosurgical generator 16 is programmed to output power to jaw 14 according to a power delivery curve 50 of the present invention to accomplish a sealing cycle where tissue held between the jaws is fully desiccated. More specifically, power delivery curve 50 for the sealing cycle involves the delivery of power over time according to a first power delivery segment 52 and then a second power delivery segment 54. First power delivery segment 52 commences at a power level of at least 40 Watts and then the power level is continuously decreased to a predetermined non-zero minimum power M.sub.p over a time period of between 0.250 and 9.75 seconds, and optimally about 0.750 seconds. First power delivery segment 52 is configured to generate a quantity of energy sufficient to raise the temperature of the inherent thermal mass of the electrodes and jaw components without raising the temperature of the tissue to its boiling point. First power delivery segment 52 may be configured so that the energy quantity of first power delivery segment 52 is optimized for the smallest vessel and thinnest tissues expected to be sealed in a surgical procedure. The nominal value of the energy quantity for first power delivery segment 52 is fifteen (15) Joules, but can range between 1 and 50 Joules depending on the circumstances.

[0019] Second power delivery segment 54 commences when the predetermined non-zero minimum power M.sub.p is reached, and thus first power delivery segment 52 has ended. Second power delivery segment 54 involves a continuous increase in the power level over a predetermined period of time until a predetermined final power level F.sub.p is reached. Second power delivery segment 54 commences at predetermined non-zero minimum power M.sub.p a power and increases to final power level F.sub.p over a time period of between 0.250 and 9.75 seconds, and optimally about 4.25 seconds. Second power delivery segment 54 is intended to deliver sufficient energy to vessels to desiccate tissue but terminate prior to over-desiccation of the tissue. Over-desiccation can be observed as burning, excessive thermal spread, and low vessel burst pressures. Tissues having lower masses will need to terminate sooner than those with greater mass. Final power level F.sub.p is selected to provide desiccation of tissue without any charring. The gradually increasing nature of second power delivery segment 54 precludes over-desiccation of smaller tissue masses, which generally comprise vessels smaller than 3 millimeters in diameters as well as thin connective tissues, while larger tissue masses comprise vessels of 7 millimeters in diameter and greater. Termination of second power delivery segment 54, and thus the entire power control cycle 50, occurs when the detected tissue impedance exceeds a threshold value.

[0020] The power delivered according to the algorithm is continuous, non-constant, non-switching, and non-pulsed. Referring to FIG. 3, the overall shape of each of first power delivery segment 52 and second power delivery segment 54 can be linear, concave, convex, or combinations thereof. For example, as seen in FIG. 3, first power delivery segment 52 can approximate an exponential decay curve while second power delivery segment 54 is generally linear. The rates of change of first power delivery segment 52 and second power delivery segment 54 of power cycle 50 are fixed throughout the sealing cycle in the embodiment of FIG. 3, but may be varied throughout the sealing cycle, as seen in the embodiments of FIGS. 4 through 6, illustrating power control cycle 50 variations having power delivery segment 62 and second power delivery segment 64, power delivery segment 72 and second power delivery segment 74, and power delivery segment 82 and second power delivery segment 84, and power delivery segment 92 and second power delivery segment 94,

[0021] In a further embodiment, tissue impedance may be used to set the rate of change of first power delivery segment 52 and second power delivery segment 54. In another embodiment, the rates of change of first power delivery segment 52 and second power delivery segment 54 may be set according to the rate of change of tissue impedance.

[0022] Referring to FIG. 8, the transfer function for power delivery curve 50 is expressed as P=A×e.sup.−B.Math.t+C+D.Math.t, where P is the power level, t is the time since initiation of the sealing cycle, A is a constant used to influence the maximum power level, B is a constant used to influence the rate of decay of first segment 52, C is a constant used to influence the minimum power level, and D is a constant used to influence the rate of increase of second segment 54. The power transfer function can be integrated with respect to time to yield the energy delivered:

[00001]$E=\frac{-A}{B}.Math.e^{-B.Math.t}+C.Math.t+\frac{D}{2}.Math.t^2+\frac{A}{B}$

[0023] As a first example, electrosurgical generator 16 providing power according to first power delivery segment 52 will deliver approximately 15 Joules of energy within a period of 100 to 1500 milliseconds after sealing cycle initiation. First power delivery segment 52 initiates when between 1 and 50 Joules of energy has been delivered. First power delivery segment 52 and second power delivery segment 54 will typically deliver a total energy of 90 Joules and terminate within 2 to 10 seconds after sealing cycle initiation.

[0024] As described above, the present invention may be a system, a method, and/or a computer program associated therewith and is described herein with reference to flowcharts and block diagrams of methods and systems. The flowchart and block diagrams illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer programs of the present invention. It should be understood that each block of the flowcharts and block diagrams can be implemented by computer readable program instructions in software, firmware, or dedicated analog or digital circuits. These computer readable program instructions may be implemented on the processor of a general purpose computer, a special purpose computer, or other programmable data processing apparatus to produce a machine that implements a part or all of any of the blocks in the flowcharts and block diagrams. Each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical functions. It should also be noted that each block of the block diagrams and flowchart illustrations, or combinations of blocks in the block diagrams and flowcharts, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.