Electrosurgical generator with output target level adjustment

Abstract

This disclosure describes an electrosurgical system configured to generate and provide a therapeutic signal to tissue in electrical communication with a surgical instrument. The electrosurgical system includes a control circuit in communication with a power source, the power source electrically coupled to the surgical instrument and configured to generate the therapeutic signal. The control circuit is configured for setting an output target level; detecting when the power source is operating at a current limit, a power limit, or a voltage limit; and limiting an increase in the output target level when the current limit, power limit, or voltage limit is reached

Description

ELECTROSURGICAL GENERATOR WITH OUTPUT TARGET LEVEL ADJUSTMENTPRIORITY CLAIM

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 63 / 639,271, filed April 26, 2024, the contents of which are hereby incorporated by reference.FIELD OF THE DISCLOSURE

[0002] This document pertains generally, but not by way of limitation, to the field of medical devices and, more specifically, to electrosurgical systems used during surgical procedures.BACKGROUND

[0003] Electrosurgery is the application of an electrical signal — an electrotherapeutic signal — to produce a change in biological tissue of a surgical patient in some manner. Various electrosurgical techniques are used to cut, coagulate, desiccate, or fulgurate the biological tissue. These electrosurgical techniques and others may be performed during various medical procedures, such as, for example, laparoscopic surgeries. These medical procedures include: appendectomy, cholecystectomy, colectomy, cystectomy, gastric banding, gastric bypass, hernia repair, nephrectomy, Nissen fundoplication, prostatectomy, sleeve gastrectomy, and others. Each of these medical procedures may have one or more electrotherapeutic phases, such as, for example, interrogation phase, heating phase, drying phase, cauterizing phase, etc.

[0004] The electrotherapeutic signals used in such medical procedures may be generated by an electrosurgical generator and then provided to the biological tissue via an electrosurgical instrument, which may be electrically connected to the electrosurgical generator. The electrosurgical instrument may be configured to mechanically and electrically engage the biological tissue to which the electrotherapeutic signal is provided. Various types of such electrosurgical instruments may be employed, including, for example, various types of forceps, conductive spatulas, electrical pads, etc.

[0005] Different medical procedures may implement different electrotherapeutic signals so as to achieve results specific to these different medical procedures. Various electrical metrics of the electrotherapeutic signals provided to the engaged biological tissue may be used to characterize these electrotherapeutic signals. These electrical metrics include: polarity (monopolar, bipolar), AC and / or DC, frequency, signal amplitude, attack and decayprofiles, etc. Electrosurgical generators that generate these various electrotherapeutic signals may control one or more of these electrical metrics so as to provide electrotherapeutic signals that yield efficacious results in the biological tissue engaged by the electrosurgical instrument.SUMMARY OF THE DISCLOSURE

[0006] This disclosure describes techniques to smooth spikes by introducing a feedback loop into the waveform algorithm that stops the algorithm from increasing output when the generator is current limited, voltage limited, or power limited which may occur due to rapid changes in tissue conditions during surgery. By doing so, the algorithm's output demands are kept in check, ensuring they do not exceed the generator's actual delivery capacity.

[0007] In some aspects, this disclosure is directed to an electrosurgical system configured to generate and provide a therapeutic signal to tissue in electrical communication with a surgical instrument, the electrosurgical system comprising: a control circuit in communication with a power source, the power source electrically coupled to the surgical instrument and configured to generate the therapeutic signal, wherein the control circuit is configured for: setting an output target level; detecting when the power source is operating at a current limit, a power limit, or a voltage limit; and limiting an increase in the output target level when the current limit, power limit, or voltage limit is reached.

[0008] In some aspects, this disclosure is directed to a method of operating an electrosurgical system having a power source electrically coupled to a surgical instrument, the power source configured for providing a therapeutic signal to tissue in electrical communication with a surgical instrument, the method comprising: setting an output target level; detecting when the power source is operating at a current limit, a power limit, or a voltage limit; and limiting an increase in the output target level when the current limit, the power limit, or the voltage limit is reached.

[0009] In some aspects, this disclosure is directed to an electrosurgical system configured to generate and provide a therapeutic signal to tissue in electrical communication with a surgical instrument, the electrosurgical system comprising: a control circuit in communication with a power source, the power source electrically coupled to the surgical instrument and configured to generate the therapeutic signal; and a measurement circuit in electrical communication with the control circuit, the measurement circuit configured to measure an impedance of the tissue during an electrosurgical procedure and provide the measured impedance to the control circuit, wherein the control circuit is configured for: setting an output target level; comparing the measured impedance to a threshold value; andswitching, based on the impedance, the power source between a current control mode, a power control mode, and a voltage control mode.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

[0011] FIG. 1 is a perspective view of an electrosurgical system providing electrotherapy to biological tissue of a surgical patient.

[0012] FIG. 2 is a block diagram of an electrosurgical system for sealing biological tissue engaged by an electrosurgical instrument.

[0013] FIG. 3 is a graph depicting a general relationship between output and impedance.

[0014] FIG. 4 is a graph depicting a relationship between output and time.

[0015] FIG. 5 is a graph depicting a relationship between output and time.

[0016] FIG. 6 is a flow diagram of an example of a method of operating an electrosurgical system having a power source electrically coupled to a surgical instrument, where the power source is configured for providing a therapeutic signal to tissue in electrical communication with a surgical instrument.

[0017] FIG. 7 is a flow diagram of another example of a method of operating an electrosurgical system having a power source electrically coupled to a surgical instrument, where the power source is configured for providing a therapeutic signal to tissue in electrical communication with a surgical instrument.DETAILED DESCRIPTION

[0018] Measured impedance is an important parameter to monitor on bipolar sealing devices. Though device impedance does not typically vary over the course of a “seal cycle”, the tissue impedance may vary greatly as the tissue properties change over the course of a seal. This is largely due to the loss of conductive fluids from the tissue, known as desiccation. The impedance measurements made during a seal cycle act as a surrogate for the degree of tissue desiccation and generally increase dramatically the more a tissue is desiccated. Power is the time rate of energy use and may be calculated, at least by one method, by multiplying an electrical current by its corresponding voltage (P = I x V). Therefore, current and voltage are other important factors in the determination of power.

[0019] When it comes to tissue desiccation, the application of power is the other consideration with respect to desiccation. Bipolar electrosurgical generators are responsible for power generation and their bipolar sealing devices act as a conduit for directing power application to tissue. Bipolar electrosurgical generators have limits to the power they may provide (including its constituent components current and voltage) and these limitations, in combination with the dynamic impedance characteristics of tissue, lead to a general relationship between power and impedance.

[0020] Aside from physical factors, the power output of a generator is also controlled by a waveform algorithm. The waveform algorithm may dictate target current, voltage, or power for the generator based on the achievement of certain milestones, which are typically associated with a measured impedance that correlates with a tissue desiccation condition.

[0021] Waveform algorithms may be broadly described as power, current, or voltage- controlled, and as their names imply, their algorithms control that component of the generator power while the other components are allowed to float freely. Waveforms may also be a combination of the above-mentioned classifications.

[0022] The present inventors have recognized that an issue arises when the control algorithm, whether power, current, or voltage controlled, becomes divorced from the reality of the output that the generator may provide based on both internal generator limits and the tissue condition. In cases where the algorithm requests more output voltage, current, or power than may be provided by the generator, the generator limits-out until the tissue condition is such that the output may increase. In the cases where the deviation between requested output and actual output is great, and the tissue condition changes rapidly, spikes may occur leading to negative consequences in the tissue.

[0023] This disclosure describes techniques to smooth spikes by introducing a feedback loop into the waveform algorithm that stops the algorithm from increasing output when the generator is either current limited, voltage limited, or power limited, which may occur due to rapid changes in tissue conditions during surgery. By doing so, the algorithm's output demands are kept in check, ensuring they do not exceed the generator's actual delivery capacity.

[0024] In some examples, the control circuit of the electrosurgical system maintains a waveform control approach (e.g., voltage or current or power), and limits ramping the voltage / current / power based on the particular limiting condition (e.g., voltage limit, current limit, or power limit). In other examples, the control circuit switches between control algorithms (e.g., from voltage to current to power) depending on an impedance threshold.

[0025] The feedback loop serves as a dynamic regulatory mechanism, providing real-time adjustments to the output, e.g., power, current, or voltage, depending on a measured tissue impedance. This is important in maintaining a smooth output delivery, especially in scenarios where tissue impedance fluctuates, such as when transitioning from tissue with high conductive fluid content to tissue with minimal conductive fluids. By preventing the algorithm from requesting more output voltage, current, or power than the generator may supply, the system avoids the occurrence of spikes that may potentially cause harm to the tissue or disrupt the surgical process.

[0026] FIG. 1 is a perspective view of an electrosurgical system providing electrotherapy to biological tissue of a surgical patient. In FIG. 1, electrosurgical system 10 includes electrosurgical generator 12 and forceps 14, which is shown engaging biological tissue 16. The electrosurgical generator 12 generates an electrotherapeutic signal, which is provided to engaged biological tissue 16 via forceps 14. Although FIG. 1 depicts forceps 14 engaging and delivering the electrotherapeutic signal to biological tissue 16, various types of electrosurgical instruments, such as those disclosed above, may be used for such purposes.

[0027] Various types of forceps as well may be used for delivering the electrotherapeutic signal to biological tissue 16. For example, forceps 14 may be medical forceps, cutting forceps, or an electrosurgical forceps (e.g., monopolar or bipolar forceps). Forceps 14, in some examples, may be used for medically related procedures, such as open and / or laparoscopic medical procedures to manipulate, engage, grasp, cut, cauterize, seal, or otherwise affect a vessel, biological tissue, vein, artery, or other anatomical feature or object.

[0028] As illustrated in FIG. 1, forceps 14 includes hand piece 18, shaft assembly 20, knife blade assembly 22, and gripping assembly 24. In some examples, such as the illustrated example of FIG. 1, forceps 14 is electrically connected to electrosurgical generator 12, which generates the electrotherapeutic signal and provides the generated electrotherapeutic signal to forceps 14. Forceps 14 then electrically communicates the electrotherapeutic signal to gripping assembly 24 and / or to a remote pad, which may be employed for various electrosurgical techniques, such as cauterizing, sealing, or other such electrosurgical techniques.

[0029] Hand piece 18 includes handle 26, gripping lever 28, knife trigger 30, electrical therapy actuation button 32, and rotation wheel 34. Gripping assembly 24 includes first jaw member 36 and second jaw member 38. Shaft assembly 20 is connected at a proximal end tohand piece 18, and at a distal end to gripping assembly 24. Shaft assembly 20 extends distally from hand piece 18 in longitudinal direction 40 to gripping assembly 24.

[0030] Shaft assembly 20 functions to permit a portion of forceps 14 (e.g., gripping assembly 24 and a distal portion of shaft assembly 20) to be inserted into a patient or other anatomy while a remaining portion of forceps 14 (e.g., hand piece 18 and a remaining proximal portion of shaft assembly 20) are outside of the patient or other anatomy. Though illustrated in FIG. 1 as substantially straight, in other examples, shaft assembly 20 may include one or more angles, bends, and / or arcs. Shaft assembly 20 may be a cylinder with a circular, elliptical, or other cross-sectional profile, or other elongated member that extends from hand piece 18 to gripping assembly 24. In some examples, the shaft may be bendable, steerable or otherwise deflectable.

[0031] In some examples, such as the example of FIG. 1, shaft assembly 20 may include an elongated hollow member (e.g., a tubular outer shaft) that encloses knife blade assembly 22 and mechanical linkage to couple knife blade assembly 22 with knife trigger 30. In general, shaft assembly may be any elongated member having stiffness sufficient to transfer forces along longitudinal direction 40. Shaft assembly 20 also may include conductive elements (e.g., wires, a conductive outer shaft and / or a conductive inner shaft, etc.) to provide electrical communication between hand piece 18 and gripping assembly 24, so as to communicate an electrotherapeutic signal thereby.

[0032] Gripping lever 28, knife trigger 30, electrical therapy actuation button 32, and rotation wheel 34 of hand piece 18, each are configured to cause various actuations, usually at the distal end, of shaft assembly 20. For example, actuation of gripping lever 28 is configured to control operation of gripping assembly 24 at the distal end of shaft assembly 20. Gripping lever 28 is a gripping actuator that is movable between an open configuration position (illustrated in FIG. 1) and a closed configuration position in which gripping lever 28 is moved proximally toward handle 26. Movement of gripping lever 28 proximally toward handle 26 to the closed configuration position causes gripping assembly 24 to transition from the open configuration to the closed configuration. Movement of gripping lever 28 distally (e.g., release of gripping lever 28 to the open configuration position) causes gripping assembly 24 to transition from the closed configuration to the open configuration.

[0033] Such transitions between the open and closed configurations of gripping assembly 24 are realized by one or more of first and second jaw members 36 and 38 moving between an open configuration (illustrated in FIG. 1), in which first and second jaw members 36 and 38 are spaced apart, and a closed configuration, in which the gap between first and secondjaw members 36 and 38 is reduced or eliminated. Various electrosurgical instruments engage biological tissue 16 in various manners. In some electrosurgical instruments, such as the one illustrated in FIG. 1, first and second jaw members 36 and 38 are opposable to one another. In the depicted example first and second jaw members 36 and 38 are configured to clamp biological tissue 16 therebetween in a manner that provides electrical communication between opposable jaw members 36 and 38 via clamped biological tissue 16. Other electrosurgical instruments may engage biological tissue in other manners.

[0034] Mechanical linkage within shaft assembly 20 may be configured to cause one or more of first and second jaw members 36 and 38 to move between the open configuration and the closed configuration in response to actuation of gripping lever 28. One example mechanism for causing movement of a gripping assembly between the open and closed configurations may be found in U. S. Patent Publication No. 2017 / 0196579, entitled “FORCEPS JAW MECHANISM” and filed on Jan. 10, 2017 to Batchelor et al., the contents of which are hereby incorporated by reference in their entirety.

[0035] Actuation of knife trigger 30 is configured to control operation of knife blade assembly 22 located at the distal end of shaft assembly 20. Knife blade assembly 22 is configured to cut, excise, or otherwise affect biological tissue or other object(s) clamped between first and second jaw members 36 and 38. Knife trigger 30 is a knife blade actuator that is movable between a retracted configuration position (illustrated in FIG. 1) and a deployed or extended configuration position in which knife trigger 30 is moved proximally toward handle 26 to cause knife blade assembly 22 to cut biological tissue 16, which is clamped between first and second jaw members 36 and 38. Movement of knife trigger 30 proximally toward handle 26 to the deployed configuration position causes a cutting blade of knife blade assembly 22 to engage biological tissue 16, thereby cutting biological tissue 16. Movement of knife trigger 30 distally (e.g., release of knife trigger 30) causes the knife blade to retract from clamped biological tissue 16. Mechanical linkage, for example, within shaft assembly 20 may be configured to cause the knife blade to engage and retract from engaged biological tissue 16.

[0036] Rotation wheel 34 is configured to control rotational configuration of one or more of knife blade assembly 22, and gripping assembly 24 at the distal end of shaft assembly 20 and / or control rotational configuration of shaft assembly 20. Movement (e.g., rotation) of rotation wheel 34 causes rotation of one or more of shaft assembly 20, knife blade assembly 22, and gripping assembly 24 about an axis extending in longitudinal direction 40. Such rotational control may facilitate alignment of gripping assembly and / or knife blade assembly with clamped biological tissue 16.

[0037] Therapy actuation button 32 is configured to control generation and / or delivery of the electrotherapeutic signal to engaged biological tissue 16. Actuation of therapy actuation button 32 causes an electrotherapeutic signal, drawn from e.g., electrosurgical generator 12, to be applied to one or more of first and second jaw member 36 and 38, a remote pad (not illustrated), or other portions of forceps 14 to cauterize, seal, or otherwise electrically affect a patient or other anatomy. One example of a hand piece utilizing a gripping lever, knife trigger, rotation wheel, and therapy actuation button may be found in U. S. Pat. No. 9,681,883, entitled “FORCEPS WITH A ROTATION ASSEMBLY” and issued on Jun. 20, 2017 to Windgassen et al., the contents of which are hereby incorporated by reference in their entirety.

[0038] FIG. 2 is a block diagram of an electrosurgical system for sealing biological tissue engaged by an electrosurgical instrument. In FIG. 2, the electrosurgical system 10 includes an electrosurgical generator 12 and an electrosurgical instrument 14'. The electrosurgical instrument 14' may be any electrosurgical instrument configured to engage and deliver an electrotherapeutic signal to biological tissue. The electrosurgical generator 12 is configured to generate the electrotherapeutic signal, such as a high frequency (AC) electrical signal, that the electrosurgical instrument 14' delivers to engaged biological tissue 16.

[0039] In some examples, the electrosurgical instrument 14' is a forceps having a handpiece coupled to opposable jaw members via a shaft assembly, such as the forceps 14 depicted in FIG. 1. In other examples, the electrosurgical instrument 14' is a conductive spatula, a conductive pad, or other electrosurgical devices. These various types of electrosurgical instruments have various ways of engaging biological tissues (e.g., clamping, touching, surrounding, penetrating, radiating, etc.)

[0040] The electrosurgical generator 12 includes an instrument interface 42, an electricalenergy source 44, a measurement circuit 46, a control circuit 48, and a user interface 50.The instrument interface 42 may include signal drivers, buffers, amplifiers, ESD protection devices, and an electrical connector 52, for example. The electrical connector 52 is configured to electrically couple electrosurgical instrument 14' to electrosurgical generator 12 so as to provide electrical communication between the electrosurgical generator 12 and the electrosurgical instrument 14'. Such electrical communication may be used to transmit operating power and / or electrical signals therebetween. The electrosurgical instrument 14', in turn, may provide electrical communication between the electrical connector 52 and biological tissue engaged thereby.

[0041] The electrical-energy source 44 is configured to generate an electrotherapeutic signal to be delivered to the engaged biological tissue via an electrically connected electrosurgical instrument 14'. The generated electrotherapeutic signal may be controlled so as to obtain the desired result for a specific electrosurgical procedure. In one example, for example, the electrotherapeutic signal is configured to resistively heat the engaged biological tissue so as to surgically affect, such as seal, the engaged biological tissue. Such controlling of the electrotherapeutic signal will be further disclosed below.

[0042] The measurement circuit 46 is configured to measure, using one or more sensors, one or more electrical parameters of biological tissue engaged by connected electrosurgical instrument 14'. The measurement circuit 46 is configured to measure an impedance of the tissue during an electrosurgical procedure and provide the measured impedance to the control circuit 48. In some examples, the control circuit 48 is configured for switching the power source 44 between a current control mode (graphically depicted as a current control region 302 in FIG. 3), a power control mode (graphically depicted as a power control region 304 in FIG. 3), and a voltage control mode (graphically depicted as a voltage control region 306 in FIG. 3) based on the impedance of the tissue.

[0043] The measurement circuit 46 is in electrical communication with connected electrosurgical instrument 14' when the electrosurgical generator 12 is electrically connected to the electrosurgical instrument 14' via the electrical connector 52. Various examples of the measurement circuit 46 are configured to measure various electrical parameters. For example, the measurement circuit 46 may be configured to measure voltage difference delivered across and / or electrical current conducted by the engaged biological tissue. In some examples, the measurement circuit 46 may be configured to measure the phase angle between voltage difference delivered across and electrical current conducted by the engaged biological tissue. In some examples, the measurement circuit 46 is configured to measure DC and or AC electrical parameters of the engaged biological tissue.

[0044] Measured parameters, such as voltage difference delivered across and / or electrical current conducted by the engaged biological tissue may be used to determine other electrical metrics. For example, measurements of voltage difference delivered across and / or electrical current conducted by the engaged biological tissue may be used to determine the electrical resistance of the engaged biological tissue. Measurements of voltage difference delivered across and electrical current conducted by the engaged biological tissue, as well as the phase angle therebetween, may be used to determine the complex impedance of the engaged biological tissue. Measurements of voltage difference delivered across an electrical current conducted by the engaged biological tissue, as well as the phase angle between, may also beused to determine apparent power (VA) and / or real power (W) provided to the engaged biological tissue.

[0045] Such measurements of electrical parameters may be used for controlling an electrotherapeutic signal during delivery to an engaged biological tissue. For example, measurements of the voltage difference delivered across and measurements of the electrical current conducted by the engaged biological tissue may be used to determine and / or control the real power provided to the engaged tissue. This determined real power may then be compared with an electrotherapeutic schedule. Such a comparison could be used to generate an error signal. Measurements of electrical parameters may also be used to determine phasecontrol criteria for controlling phases of electrotherapy. Phase-control criteria may include criteria for commencement and termination of a phase, as well as criteria for intra-phase control.

[0046] A control circuit 48 is configured to control operation of the electrical -energy source 44 (or power source 44) and / or the measurement circuit 46. The control circuit 48 is electrically connected to the electrical-energy source 44 and the measurement circuit 46. The control circuit 48 causes an electrical-energy source to provide an electrotherapeutic signal to biological tissue engaged by an electrically connected electrosurgical instrument 14'. The electrical-energy source 44 includes a current limit mode, a voltage limit mode, and a power limit mode. When in current limit mode, the electrical-energy source 44 has reached its maximum current output capability and cannot provide more current without potentially causing damage to itself or the connected load. When in voltage limit mode, the electrical-energy source 44 has reached its maximum voltage output capability and is unable to increase the voltage further. When in power limit mode, the electrical-energy source 44 has reached its maximum power output capability and is unable to increase the power further.

[0047] The control circuit 48 causes the electrical-energy source 44 to generate the electrotherapeutic signal using a waveform algorithm (or control algorithm), such as stored in the memory 56, and according to an electrotherapeutic schedule such that the generated electrotherapeutic signal is controlled for a specific electrosurgical procedure. The control circuit 48 uses the waveform algorithm to generate an electrotherapeutic signal (or waveform) that is based on various electrotherapy information, such as including one or more of pulse width, duty cycle, on duration, off duration, repetition rate, amplitude, phase, ramp and descent rates, or the like.

[0048] Various electrotherapeutic schedules may be used to effectuate various types of electrotherapy. For example, in some examples, real power (W) of the electrotherapeutic signal provided to the engaged biological tissue is controlled according to an electricalpower schedule. In other examples, voltage difference (V) of the electrotherapeutic signal delivered across the engaged biological tissue is controlled according to a voltage schedule. In other examples, electrical current (A) of the electrotherapeutic signal conducted by the engaged biological tissue is controlled according to an electrical-current schedule. In still other examples, apparent power (VA) of the electrotherapeutic signal provided to the engaged biological tissue may be controlled according to a voltage-amperage schedule. The control circuit may switch between schedules.

[0049] The control circuit 48, for example, may cause the electrical-energy source 44 to provide energy to engaged biological tissue, such that a product of a voltage difference across and an electrical current conducted by the engaged biological tissue is controlled according to the electrotherapeutic schedule. The control circuit 48 may use the comparison of the determined real power with an electrotherapeutic schedule to generate an error signal. Such an error signal may be used in a closed-loop feedback system that includes the electrical-energy source 44, so as to generate the electrotherapeutic signal according to the electrotherapeutic schedule.

[0050] As illustrated in FIG. 2, the control circuit 48 includes a processor 54 and a memory 56. The control circuit 48 may include a timer and / or a clock. In some examples, the timer and / or the clock are part of the processor 54. In other examples, the timer and / or clock are separate from the processor 54. The processor 54, in one example, is configured to implement functionality and / or process instructions for execution within electrosurgical the system 10. For instance, the processor 54 may be capable of receiving from and / or processing instructions stored in program memory 56P. The processor 54 may then execute program instructions so as to cause the electrical-energy source 44 to generate the electrotherapeutic signal according to a predetermined electrotherapeutic schedule. The predetermined electrotherapeutic schedule may be retrieved from data memory 56D, for example. The processor 54 may compare electrical parameters measured by the measurement circuit 46 with the retrieved predetermined electrotherapeutic schedule. The processor 54 may send commands to the electrical-energy source 44 and / or the measurement circuit 46. The processor 54 also may also send or receive information from the user interface 50.

[0051] In various examples, the electrosurgical generator 12 may be realized using the elements illustrated in FIG. 2 or various other elements. For example, the processor 54 mayinclude any one or more of a microprocessor, a control circuit, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other equivalent discrete or integrated logic circuitry.

[0052] The memory 56 may be configured to store information within electrosurgical system 10 during operation. The memory 56, in some examples, is described as computer- readable storage media. In some examples, a computer-readable storage media may include a non-transitory medium. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in RAM or cache). In some examples, the memory 56 is a temporary memory, meaning that a primary purpose of memory 56 is not long-term storage. The memory 56, in some examples, is described as volatile memory, meaning that memory 56 does not maintain stored contents when power to the electrosurgical system 10 is turned off. Examples of volatile memories may include random access memories (RAM), dynamic random access memories (DRAM), static random access memories (SRAM), and other forms of volatile memories. In some examples, the memory 56 is used to store program instructions for execution by the processor 54. The memory 56, in one example, is used by software or applications running on the electrosurgical system 10 (e.g., a software program implementing electrical control of an electrotherapeutic signal provide to biological tissue engaged by an electrosurgical instrument) to temporarily store information during program execution, such as, for example, in the data memory 56D.

[0053] In some examples, the memory 56 may also include one or more computer-readable storage media. The memory 56 may be in the device or in the electrosurgical generator. The memory 56 may be configured to store larger amounts of information than volatile memory. The memory 56 may further be configured for long-term storage of information. In some examples, the memory 56 includes non-volatile storage elements. Examples of such non-volatile storage elements may include magnetic hard discs, optical discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories.

[0054] A user interface 50 may be used to communicate information between the electrosurgical system 10 and a user (e.g., a surgeon or technician). The user interface 50 may include a communications module. The user interface 50 may include various user input and output devices. For example, the user interface may include various displays, audible signal generators, as well switches, buttons, touch screens, mice, keyboards, etc.

[0055] The user interface 50, in one example, utilizes the communications module to communicate with external devices via one or more networks, such as one or more wireless or wired networks or both. The communications module may include a network interface card, such as an Ethernet card, an optical transceiver, a radio frequency transceiver, or any other type of device that may send and receive information. Other examples of such network interfaces may include Bluetooth, 3G, 4G, and Wi-Fi radio computing devices as well as Universal Serial Bus (USB) devices.

[0056] FIG. 3 is a graph 300 depicting a general relationship between output and impedance. The x-axis represents tissue impedance in ohms and the y-axis represents the available output, such as voltage, current, or power, an electrosurgical system. The graph includes a current control region 302, a power control region 304, and a voltage control region 306.

[0057] The current control region 302 extends from 0 ohms to X ohms. Between 0 ohms and X ohms, the available output in the current control region 302 ramps upward, such as in a substantially linear manner, from 0 to W. A control circuit, such as the control circuit 48 of FIG. 2, is configured for operating the power source 44 in a current control mode when the measured impedance is at or below a first impedance threshold, e.g., X ohms, which is indicative of high conductivity. The control circuit may stop ramping of current, voltage, or power based on an impedance threshold.

[0058] The power control region 304 extends from X ohms to Y ohms, where Y is greater than X. Between X ohms and Y ohms, the available output in the power control region 304 is substantially constant at W. The control circuit is configured for transitioning the power source to a power control mode when the measured impedance is at or above the first impedance threshold, e.g., X ohms, and at or below a second impedance threshold, e.g., Y ohms, which is indicative of tissue desiccation.

[0059] The voltage control region 306 extends from Y ohms to Z ohms, where Z is greater than Y. Between Y ohms and X ohms, the available output in the power control region 304 ramps downward, such as in a substantially linear manner, from W to 0. The control circuit is configured for transitioning the power source to a voltage control mode when the measured impedance exceeds the second impedance threshold, e.g., Y ohms, which is indicative of the power source output approaching the voltage limit.

[0060] Generally speaking, the graph 300 illustrates that when tissue impedance is low and there are many conductive fluids in the tissue, the generator is limited in its ability to provide output due to current limitations. At intermediate tissue impedance, output is onlylimited by the generator’s power limits. At higher tissue impedance when there are minimal conductive fluids in the tissue, the generator is limited in its ability to provide output due to voltage limitations.

[0061] FIG. 4 is a graph 400 depicting a relationship between output and time. The x-axis depicts time in milliseconds and the y-axis depicts output. The graph 400 depicts an algorithm output 402 and an actual output 404. The algorithm output 402 is the output, e.g., power, voltage, or current, that the control circuit 48 commands, based on the waveform algorithm, the power source 44 to deliver, via the electrosurgical instrument 14', to the tissue. The actual output 404 is the output, e.g., power, voltage, or current, that the power source 44 delivers to the tissue.

[0062] In some instances, an issue arises when the waveform algorithm, whether power, current, or voltage controlled, becomes divorced from the reality of the output that the electrosurgical generator 12 may provide based on both internal generator limits and the tissue condition. In cases where the algorithm requests more output than may be provided by the generator, the generator limits-out until the tissue condition is such that the output may increase. In the cases where the deviation between requested output (algorithm output 402) and actual output (actual output 404) is large, such as shown by the gap 406 in FIG. 4, and the tissue condition changes rapidly, a spike 408 may occur.

[0063] For example, the power source 44 is in current limit and delivers a constant actual output 404, which results in the gap 406 shown in FIG. 4. If tissue conditions suddenly change, rather than increasing the actual output 404, the power source 44 will try to reach the algorithm output 402 as quickly as possible, resulting in the spike 408. That sudden increase may cause rapid boiling of fluid in the tissue, which may be undesirable.

[0064] This disclosure describes techniques to smooth spikes by including a feedback loop into the waveform algorithm that stops the algorithm from increasing the output, e.g., power, voltage, or current, when the electrosurgical generator 12 is current limited, power limited, or voltage limited. By doing so, the algorithm's demands are kept in check, ensuring they do not exceed the generator's actual delivery capacity.

[0065] In some examples, the control circuit of the electrosurgical system maintains the waveform control approach (e.g., voltage or current or power), and limits ramping the voltage / current / power based on the particular limiting condition (e.g., voltage limit, current limit, or power limit). In other examples, the control circuit switches between control algorithms (e.g., from voltage to current to power) depending on an impedance threshold.

[0066] The feedback loop serves as a dynamic regulatory mechanism, providing real-time adjustments to the output. This is important in maintaining a smooth output delivery, especially in scenarios where tissue impedance fluctuates, such as when transitioning from tissue with high conductive fluid content to tissue with minimal conductive fluids. By preventing the algorithm from requesting more output than the generator may supply, the system avoids the occurrence of spikes that may potentially cause harm to the tissue or disrupt the surgical process.

[0067] To smooth spikes, a control circuit, such as the control circuit 48 of FIG. 2, sets a output target level, such as a power output target level, voltage output target level, or current output target level. As an example, the output target level is a desired level of output that an electrosurgical generator, such as the electrosurgical generator 12 of FIG. 2, is set to deliver during a surgical procedure. The output target level is set point within the safe operating range of the electrosurgical generator is not the actual output delivered by the power source.

[0068] The control circuit detects when the power source, such as the power source 44 of FIG. 2, is operating at a current limit or a voltage limit. For example, the measurement circuit 46 monitors various electrical parameters and communicates those electrical parameters to the control circuit 48. Using the electrical parameters, the control circuit 48 detects when the conditions exist for the power source 44 to be in current limit or voltage limit. Then, the control circuit limits an increase in the output target level when the current limit or voltage limit is reached, such as shown in FIG. 5.

[0069] FIG. 5 is a graph 500 depicting a relationship between output and time. The x-axis depicts time in milliseconds and the y-axis depicts output. The graph 500 depicts the algorithm output 402 and the actual output 502. The power source 44 is in current limit or voltage limit and the power gap 406 is present.

[0070] As mentioned above, and in accordance with this disclosure, in some examples, the control circuit maintains the waveform control approach (e.g., voltage or current or power), and limits ramping the voltage / current / power based on the particular limiting condition (e.g., voltage limit, current limit, or power limit). The control circuit has set a first output target level 504a, e.g., power output target level, voltage output target level, or current output target level, and limits an increase in the first output target level 504a because the power source 44 is in current limit, power limit, or voltage limit. That is, the control circuit limits the first output target level 504a from increasing to a second output target level 504b, and from the second output target level 504b to a third output target level 504c. In thismanner, the control circuit prevents a spike, such as the spike 408 of FIG. 4, and allows the actual output 502 to more gradually approach the algorithm output 402.

[0071] In some examples, the control circuit limits the increase in the output target level when the current limit, power limit, or voltage limit such that the increase is substantially linear, such as resulting in the actual output 502 linearly increasing until it reaches the algorithm output 402. In other examples, the control circuit limits the increase in the output target level when the current limit, power limit, or voltage limit such that the increase is nonlinear, such as resulting in the actual output 502 increasing in a nonlinear manner until it reaches the algorithm output 402.

[0072] In some examples, the control circuit limits the increase in the output target level when the current limit, power limit, or voltage limit by limiting a rate of increase in the output target level. That is, the control circuit limits how quickly the first output target level 504a may increase to the second output target level 504b, and so forth.

[0073] In other examples, the control circuit limits the increase in the output target level when the current limit, power limit, or voltage limit by delaying the increase in the output target level when the current limit or voltage limit is reached.

[0074] As mentioned above, the measurement circuit, such as the measurement circuit 46 of FIG. 2, is configured to measure an impedance of the tissue during an electrosurgical procedure and provide the measured impedance to the control circuit, such as the control circuit 48 of FIG. 2. As the measurement circuit continuously monitors the impedance of the tissue, the control circuit receives this data in real-time. Tissue impedance may change during surgery due to various factors such as the type of tissue being targeted, the presence of fluids, or the degree of desiccation. The control circuit uses the impedance information to dynamically adjust the power output to match the changing conditions. In this manner, the control circuit is configured for providing real-time adjustments to the power source to maintain power delivery to the tissue.

[0075] In some examples, the control circuit is configured for comparing the measured impedance to a threshold value. Then, the control circuit limits the increase in the output target level when the current limit, power limit, or voltage limit by preventing, based on the comparison, the increase in the output target level. For example, if the power source is in current limit, the measured impedance may be so low (at or below the threshold value) that any increase in the output target level would be undesirable.

[0076] In other examples, the threshold value may change based on the surgical instrument. For example, the threshold value is associated with the surgical instrument,such as the electrosurgical instrument 14' of FIG. 2. For example, the control circuit determines the type of surgical instrument that is connected to the electrosurgical generator 12, such as a forceps or conductive spatula, or a user inputs the type of surgical instrument and, in response, the control circuit retrieves a threshold value from the memory device, such as the memory 56 of FIG. 2, associated with that surgical instrument. In some examples, a first surgical instrument, e.g., a forceps, has a first threshold value, and a second surgical instrument, e.g., a conductive spatula, has a second threshold value different from the first threshold value.

[0077] As mentioned above, and in accordance with this disclosure, in some examples, the control circuit switches between control algorithms (e.g., from voltage to current to power) depending on an impedance threshold. In FIG. 5, the control circuit has set a first output target level 504a, e.g., power output target level, voltage output target level, or current output target level. Then, the control circuit compares the measured impedance to a threshold value, and the control circuit switches, based on a measured impedance, the power source between a current control mode, a power control mode, and a voltage control mode. For example, and referring to FIG. 3, based on the measured impedance, the control circuit selects a current control mode, a power control mode, and a voltage control mode to operate in a corresponding one of the current control region 302, the power control region 304, or the voltage control region 306.

[0078] In some examples, the impedance threshold is a percentage increase above a minimum impedance value, e.g., 10% above a minimum measured impedance value. In other examples, the impedance threshold is a fixed increase above a minimum impedance value, e.g., 10 ohms above a minimum measured impedance value. In yet other examples, the impedance threshold is a percentage increase above a minimum impedance value plus a fixed increase above a minimum impedance value, e.g., 10% above a minimum measured impedance value plus 3 ohms.

[0079] FIG. 6 is a flow diagram of an example of a method 600 of operating an electrosurgical system having a power source electrically coupled to a surgical instrument, where the power source is configured for providing a therapeutic signal to tissue in electrical communication with a surgical instrument. In some examples, the control circuit 48 of the electrosurgical generator 12 of FIG. 2 is configured for performing the functions described with respect to the method 600.

[0080] At block 602, the method 600 sets an output target level. At block 604, the method 600 detects when the power source is operating at a current limit, a power limit, or a voltagelimit. At block 606, the method 600 limits an increase in the output target level when the current limit, power limit, or voltage limit is reached. In some examples, the method 600 limits the increase in the output target level based on a measured impedance.

[0081] In some examples, the method 600 includes measuring an impedance of the tissue and switching the power source between a current control mode, power control mode, and a voltage control mode based on the impedance of the tissue.

[0082] In some examples, the method 600 includes measuring an impedance of the tissue, comparing the measured impedance to a threshold value, and limiting, based on the measured impedance of the tissue, the increase in the output target level. In some examples, the method includes switching the power source between a current control mode, power control mode, and a voltage control mode based on the impedance of the tissue.

[0083] In some examples, the method 600 includes operating the power source in the current control mode when the measured impedance is below a first impedance threshold.

[0084] In some examples, the method 600 includes transitioning the power source to a power control mode when the measured impedance is above the first impedance threshold and below a second impedance threshold indicative of tissue desiccation.

[0085] In some examples, the method 600 includes transitioning the power source to a voltage control mode when the measured impedance exceeds the second impedance threshold, indicative of the power source approaching the voltage limit.

[0086] In some examples, the method 600 includes providing real-time adjustments to the power source to maintain power delivery.

[0087] In some examples, the method 600 includes comparing a measured impedance to a threshold value, where limiting the increase in the output target level when the current limit, power limit, or voltage limit is reached includes preventing, based on the comparison, an increase in the output target level when the current limit or voltage limit is reached. The threshold value may be associated with the surgical instrument. In some examples, a first surgical instrument has a first threshold value, and a second surgical instrument has a second threshold value different from the first threshold value.

[0088] FIG. 7 is a flow diagram of another example of a method 700 of operating an electrosurgical system having a power source electrically coupled to a surgical instrument, where the power source is configured for providing a therapeutic signal to tissue in electrical communication with a surgical instrument. In some examples, the control circuit 48 of the electrosurgical generator 12 of FIG. 2 is configured for performing the functions described with respect to the method 700.

[0089] At block 702, the method 700 includes setting an output target level. At block 704, method 700 includes comparing a measured impedance to a threshold value. At block 706, the method 700 includes switching, based on the impedance, the power source between a current control mode, a power control mode, and a voltage control mode.

[0090] In some examples, the method 700 includes providing real-time adjustments to the power source to maintain power delivery.

[0091] In some examples, the method 700 includes operating the power source in the current control mode when the measured impedance is below a first impedance threshold.

[0092] In some examples, the method 700 includes transitioning the power source to a power control mode when the measured impedance is above the first impedance threshold and below a second impedance threshold indicative of tissue desiccation.

[0093] In some examples, the method 700 includes transitioning the power source to a voltage control mode when the measured impedance exceeds the second impedance threshold, indicative of the power source approaching the voltage limit.

[0094] In some examples, aspects of the method 600 and aspects of the method 700 may be combined.Various Notes

[0095] Each of the non-limiting claims or examples described herein may stand on its own, or may be combined in various permutations or combinations with one or more of the other examples.

[0096] The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are also referred to herein as “examples.” Such examples may include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more claims thereof), either with respect to a particular example (or one or more claims thereof), or with respect to other examples (or one or more claims thereof) shown or described herein.

[0097] In the event of inconsistent usages between this document and any documents so incorporated by reference, the usage in this document controls.

[0098] In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

[0099] Method examples described herein may be machine or computer-implemented at least in part. Some examples may include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods may include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code may include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, in an example, the code may be tangibly stored on one or more volatile, non-transitory, or nonvolatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media may include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact discs and digital video discs), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.

[0100] The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more claims thereof) may be used in combination with each other. Other embodiments may be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims arehereby incorporated into the Detailed Description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments may be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

CLAIMSWhat is claimed is:

1. An electrosurgical system configured to generate and provide a therapeutic signal to tissue in electrical communication with a surgical instrument, the electrosurgical system comprising: a control circuit in communication with a power source, the power source electrically coupled to the surgical instrument and configured to generate the therapeutic signal, wherein the control circuit is configured for: setting an output target level; detecting when the power source is operating at a current limit, a power limit, or a voltage limit; and limiting an increase in the output target level when the current limit, power limit, or voltage limit is reached.

2. The electrosurgical system of claim 1, further comprising: a measurement circuit in electrical communication with the control circuit, the measurement circuit configured to measure an impedance of the tissue during an electrosurgical procedure and provide the measured impedance to the control circuit, and wherein the control circuit is configured for switching the power source between a current control mode, a power control mode, and a voltage control mode based on the impedance of the tissue.

3. The electrosurgical system of claim 2, wherein the control circuit is configured for operating the power source in the current control mode when the measured impedance is below a first impedance threshold.

4. The electrosurgical system of claim 3, wherein the control circuit is configured for transitioning the power source to a power control mode when the measured impedance is above the first impedance threshold and below a second impedance threshold.

5. The electrosurgical system of claim 4, wherein the control circuit is configured for transitioning the power source to a voltage control mode when the measured impedance exceeds the second impedance threshold.

6. The electrosurgical system of claim 1, wherein the control circuit is configured for providing real-time adjustments to the power source to maintain power delivery.

7. The electrosurgical system of claim 1, further comprising: a measurement circuit in electrical communication with the control circuit, the measurement circuit configured to measure an impedance of the tissue during an electrosurgical procedure and provide the measured impedance to the control circuit, and wherein the control circuit is configured for: comparing the measured impedance to a threshold value, and limiting, based on the measured impedance of the tissue, the increase in the output target level.

8. The electrosurgical system of claim 7, wherein the control circuit is further configured for: switching, based on the impedance, the power source between a current control mode, a power control mode, and a voltage control mode.

9. The electrosurgical system of claim 7, wherein the threshold value is associated with the surgical instrument.

10. The electrosurgical system of claim 9, wherein the threshold value is a first threshold value, wherein a first surgical instrument has the first threshold value, and wherein a second surgical instrument has a second threshold value different from the first threshold value.

11. The electrosurgical system of claim 1, wherein the control circuit configured for limiting the increase in the output target level when the current limit or voltage limit or power limit is reached is configured for: limiting a rate of increase in the output target level.

12. The electrosurgical system of claim 1, wherein the control circuit configured for limiting the increase in the output target level when the current limit or voltage limit or power limit is reached is configured for: delaying the increase in the output target level when the current limit or voltage limit is reached.

13. A method of operating an electrosurgical system having a power source electrically coupled to a surgical instrument, the power source configured for providing a therapeutic signal to tissue in electrical communication with a surgical instrument, the method comprising:setting an output target level; detecting when the power source is operating at a current limit, a power limit, or a voltage limit; and limiting an increase in the output target level when the current limit, the power limit, or the voltage limit is reached.

14. The method of claim 13, comprising: switching the power source between a current control mode, a power control mode, and a voltage control mode based on an impedance of the tissue.

15. The method of claim 14, comprising: operating the power source in the current control mode when the measured impedance is below a first impedance threshold.

16. The method of claim 13, comprising: comparing a measured impedance to a threshold value, and limiting, based on the measured impedance of the tissue, the increase in the output target level.

17. The method of claim 16, comprising: switching, based on the impedance, the power source between a current control mode, a power control mode, and a voltage control mode.

18. The method of claim 16, wherein the threshold value is associated with the surgical instrument.

19. The method of claim 18, wherein the threshold value is a first threshold value, wherein a first surgical instrument has the first threshold value, and wherein a second surgical instrument has a second threshold value different from the first threshold value.

20. An electrosurgical system configured to generate and provide a therapeutic signal to tissue in electrical communication with a surgical instrument, the electrosurgical system comprising: a control circuit in communication with a power source, the power source electrically coupled to the surgical instrument and configured to generate the therapeutic signal; and a measurement circuit in electrical communication with the control circuit, the measurement circuit configured to measure an impedance of the tissue during anelectrosurgical procedure and provide the measured impedance to the control circuit, wherein the control circuit is configured for: setting an output target level; comparing the measured impedance to a threshold value; and switching, based on the impedance, the power source between a current control mode, a power control mode, and a voltage control mode.

21. The electrosurgical system of claim 20, wherein the control circuit is configured for operating the power source in the current control mode when the measured impedance is below a first impedance threshold.

22. The electrosurgical system of claim 21, wherein the control circuit is configured for transitioning the power source to a power control mode when the measured impedance is above the first impedance threshold and below a second impedance threshold.

23. The electrosurgical system of claim 22, wherein the control circuit is configured for transitioning the power source to a voltage control mode when the measured impedance exceeds the second impedance threshold.

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