Controllers, devices, and storage media for controlling high frequency electrical energy provided to living tissue

Abstract

The present invention provides a controller, a device, and a storage medium that control high-frequency electric power supplied to living tissue. A method, a device, and a treatment system for sealing living tissue using high-frequency electric power supplied to the living tissue by a tip end effector of a treatment instrument apply electric power to the living tissue for N (N = a natural number of 1 to 5, inclusive) cycles by increasing the amount of high-frequency electric power supplied to the living tissue in each cycle until the impedance of the living tissue increases to an impedance threshold value of the cycle, and thereafter, decreasing the amount of high-frequency electric power to reduce the impedance of the living tissue by a predetermined value. The cycles are repeated in such a manner that each subsequent cycle has a larger impedance threshold value than the previous cycle, and the cycles are stopped when the impedance reaches an impedance stop value. An initial impedance value can be used to determine the parameters of the cycles.

Description

TECHNICAL FIELD

[0001] The systems, devices, and methods disclosed herein relate to electrosurgery, and in particular to electrothermal tissue sealing. BACKGROUND

[0002] In the following discussion, reference is made to particular structures and / or methods. However, the following references are not to be construed as an admission that these structures and / or methods constitute prior art. Applicants expressly reserve the right to demonstrate that one or more of the structures and / or methods disclosed herein constitute prior art.

[0003] Many medical procedures include sealing biological tissue, such as blood vessels. One technique for sealing blood vessels is known as electrothermal sealing. During an electrothermal sealing procedure, a high frequency current is applied to biological tissue, such as a patient's blood vessel, to be sealed. The current causes localized heating of the biological tissue, which causes the tissue to dehydrate and denature. As the current is applied, the impedance of the biological tissue initially decreases as the tissue begins to dry. However, as the tissue denatures, the impedance of the tissue increases. As a result, the current across the tissue decreases, thereby reducing the rate at which the tissue is heated. This decrease in current results in an increase in the time required to denature the tissue, thereby increasing the time required to seal the tissue.

[0004] While the current can be increased as the impedance of the tissue increases, there is a risk of damaging the tissue due to overheating. In addition, increasing the current as the impedance increases requires increasing the voltage applied across the tissue, thereby making the procedure inefficient and slow. SUMMARY

[0005] To address the above problems in electrothermal sealing, an accurate estimate of the impedance of the biological tissue to be sealed becomes an important factor in improving the time required to seal the tissue. In addition, the present inventors have observed that by allowing the tissue to cool for a short amount of time when the impedance of the tissue reaches a particular threshold, the rate of rise of the tissue impedance can be reduced. Without wishing to be bound by theory, the shorter cooling period can allow fluid, such as blood or saline, to return to the dried portion of the biological tissue, thereby causing the impedance to decrease. This decrease in impedance allows a higher current to be applied. Interestingly, the present inventors have observed that by allowing the tissue to cool for a short amount of time during a heating cycle, the total time required to seal a given biological tissue is reduced. Advantageously, such a procedure provides for more uniform denaturation of the living tissue, and thus provides for a better seal.

[0006] In one aspect, it would be advantageous to have improved techniques to more accurately determine the size of biological tissue to be treated to better regulate the applied output voltage. Accurately determining the size of biological tissue is an important factor in improving sealing time. In a second aspect, it would be advantageous to have an improved sequence for applying the applied output voltage that takes into account the rise in impedance during denaturation and reduces the application time of high frequency current and / or avoids applying higher output voltage values. Thereby reducing the risk of tissue damage during the sealing process.

[0007] Thus, in one aspect of the present invention, a method for sealing living tissue using high frequency electrical energy provided to the living tissue by an end effector of a treatment instrument is disclosed. The method can include applying high frequency electrical energy to the living tissue in at least two cycles. The at least two cycles include an Nth cycle and an N+1th cycle, the N+1th cycle following the Nth cycle, the Nth cycle including: increasing an amount of high frequency electrical energy applied to the living tissue until an impedance of the living tissue reaches an Nth impedance threshold; and reducing the impedance of the living tissue by decreasing the amount of high frequency electrical energy applied to the living tissue when the impedance of the living tissue reaches the Nth impedance threshold. The N+1th cycle includes increasing the amount of high frequency electrical energy applied to the living tissue until an impedance of the living tissue reaches an N+1th impedance threshold. The N+1th impedance threshold is greater than the Nth impedance threshold.

[0008] In some embodiments, the method further includes reducing the impedance of the living tissue by decreasing the amount of high frequency electrical energy applied to the living tissue when the impedance of the living tissue reaches the N+1th impedance threshold.

[0009] In some embodiments, the N+1th impedance threshold is an impedance stop value, and the method further includes stopping the application of high frequency electrical energy to the living tissue when the impedance of the living tissue reaches the impedance stop value.

[0010] In some embodiments, N is a natural number, and a value of N is equal to or greater than 1 to equal to or less than 5.

[0011] In some embodiments, N = 1, and the Nth cycle of the method further includes determining an initial impedance value by applying a constant power to the end effector while the end effector is in contact with the living tissue for a predetermined period of time. The initial impedance value is determined prior to increasing the amount of high frequency electrical energy applied to the living tissue in the Nth cycle.

[0012] In some embodiments, an increase rate of high frequency electrical energy applied to the living tissue in the Nth cycle is determined based on the initial impedance value.

[0013] In some embodiments, the method further comprises determining a value of N based on a value of the initial impedance value.

[0014] In some embodiments, the method further comprises determining a size parameter associated with the living tissue based on the initial impedance value.

[0015] In some embodiments, the method further comprises determining a value of N based on the size parameter.

[0016] In some embodiments, the method further comprises estimating the Nth impedance threshold based on the size parameter.

[0017] In some embodiments, the rate of increase of high frequency electrical energy applied to the living tissue in the N+1st cycle is different than the rate of increase of high frequency electrical energy provided to the living tissue in the Nth cycle.

[0018] In some embodiments, the N+1st cycle of the method further comprises determining an N+1st initial impedance value by applying a constant power to the end effector while the end effector is in contact with the living tissue for a predetermined period of time. The N+1st initial impedance value is determined prior to increasing the amount of high frequency electrical energy applied to the living tissue in the N+1st cycle.

[0019] In some embodiments, the rate of increase of high frequency electrical energy applied to the living tissue in the N+1st cycle is determined based on the N+1st initial impedance value.

[0020] In some embodiments, the rate of increase of high frequency electrical energy applied to the living tissue in the N+1st cycle is different than the rate of increase of high frequency electrical energy provided to the living tissue in the Nth cycle.

[0021] In another aspect of the application, a device for sealing living tissue can include an energy source configured to generate high frequency electrical energy, and an end effector operably connected to the energy source and configured to provide the high frequency electrical energy to the living tissue. A controller is operably connected to the energy source and the end effector and configured to, in operation, apply high frequency electrical energy to the living tissue in at least two cycles. The at least two cycles include an Nth cycle and an N+1th cycle, the N+1th cycle following the Nth cycle, the controller further configured to, in operation, in the Nth cycle: increase an amount of high frequency electrical energy applied to the living tissue until an impedance of the living tissue reaches an Nth impedance threshold; and decrease the impedance of the living tissue by decreasing the amount of high frequency electrical energy applied to the living tissue when the impedance of the living tissue reaches the Nth impedance threshold. In the N+1th cycle, the controller is further configured to, in operation: increase the amount of high frequency electrical energy applied to the living tissue until the impedance of the living tissue reaches an N+1th impedance threshold. The N+1th impedance threshold is greater than the Nth impedance threshold.

[0022] In some embodiments, in the N+1th cycle, the controller is further configured to, in operation, decrease the impedance of the living tissue by decreasing the amount of high frequency electrical energy applied to the living tissue when the impedance of the living tissue reaches the N+1th impedance threshold.

[0023] In some embodiments, the N+1th impedance threshold is an impedance stop value. In the N+1th cycle, the controller is further configured to, in operation, stop applying high frequency electrical energy to the living tissue when the impedance of the living tissue reaches the impedance stop value.

[0024] In some embodiments, N is a natural number, and a value of N is equal to or greater than 1 to equal to or less than 5.

[0025] In some embodiments, N = 1, and in the Nth cycle, the controller is further configured to, in operation, determine an initial impedance value by applying a constant power to the end effector while the end effector is in contact with the living tissue for a predetermined period of time. The initial impedance value is determined prior to increasing the amount of high frequency electrical energy applied to the living tissue in the Nth cycle.

[0026] In some embodiments, an increase rate of the high frequency electrical energy applied to the living tissue in the Nth cycle is determined based on the initial impedance value.

[0027] In some embodiments, the controller is further configured to, in operation, determine a value of N based on a value of the initial impedance value.

[0028] In some embodiments, the controller is further configured to determine, in operation, a size parameter associated with the living tissue based on the initial impedance value.

[0029] In some embodiments, the controller is further configured to determine, in operation, a value of N based on the size parameter.

[0030] In some embodiments, the controller is further configured to estimate, in operation, the Nth impedance threshold based on the size parameter.

[0031] In some embodiments, the rate of increase of the high frequency electrical energy applied to the living tissue in the Nth+1 cycle is different than the rate of increase of the high frequency electrical energy provided to the living tissue in the Nth cycle.

[0032] In some embodiments, in the Nth+1 cycle, the controller is further configured to determine, in operation, an Nth+1 initial impedance value by applying a constant power to the end effector while the end effector is in contact with the living tissue for a predetermined period of time. The Nth+1 initial impedance value is determined prior to the amount of high frequency electrical energy applied to the living tissue being increased in the Nth cycle.

[0033] In some embodiments, the rate of increase of the high frequency electrical energy applied to the living tissue in the Nth+1 cycle is determined based on the Nth+1 initial impedance value.

[0034] In some embodiments, the rate of increase of the high frequency electrical energy applied to the living tissue in the Nth+1 cycle is different than the rate of increase of the high frequency electrical energy provided to the living tissue in the Nth cycle.

[0035] In yet another aspect of the application, a treatment system can include any of the devices disclosed herein.

[0036] In another aspect of the application, a controller for controlling high frequency electrical energy provided to living tissue, the high frequency electrical energy used by an end effector of a treatment instrument to seal the living tissue, the controller configured to apply high frequency electrical energy to the living tissue in at least two cycles, wherein the at least two cycles include an Nth cycle and an N+1th cycle, the N+1th cycle following the Nth cycle, wherein in the Nth cycle the controller is further configured to: increase an amount of high frequency electrical energy applied to the living tissue until an impedance of the living tissue reaches an Nth impedance threshold, and reduce the impedance of the living tissue by decreasing the amount of high frequency electrical energy applied to the living tissue when the impedance of the living tissue reaches the Nth impedance threshold, and wherein in the N+1th cycle the controller is further configured to: increase the amount of high frequency electrical energy applied to the living tissue until the impedance of the living tissue reaches an N+1th impedance threshold, and wherein the N+1th impedance threshold is greater than the Nth impedance threshold.

[0037] In another aspect of the application, a computer readable storage medium storing a program for causing a processor to execute a method for sealing living tissue using high frequency electrical energy provided to the living tissue by an end effector of a treatment instrument, the method comprising: applying high frequency electrical energy to the living tissue in at least two cycles, wherein the at least two cycles include an Nth cycle and an N+1th cycle, the N+1th cycle following the Nth cycle, wherein the Nth cycle comprises: increasing an amount of high frequency electrical energy applied to the living tissue until an impedance of the living tissue reaches an Nth impedance threshold, and reducing the impedance of the living tissue by decreasing the amount of high frequency electrical energy applied to the living tissue when the impedance of the living tissue reaches the Nth impedance threshold, and wherein the N+1th cycle comprises: increasing the amount of high frequency electrical energy applied to the living tissue until the impedance of the living tissue reaches an N+1th impedance threshold, and wherein the N+1th impedance threshold is greater than the Nth impedance threshold.

[0038] Additional features and advantages will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The disclosed input device aims to and other advantages will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0039] The disclosed aspects will be described in connection with the drawings appended hereto, provided for the purpose of illustration only, and not in limitation of the disclosed aspects, in which like reference numerals designate similar elements.

[0040] Figure 1 A schematic diagram of a medical device for heating tissue according to some embodiments is shown.

[0041] Figure 2 A schematic diagram of a controller according to embodiments is shown.

[0042] Figure 3 An example of impedance changes in tissue caused by cycling the electrical energy provided to the tissue through four cycles according to some embodiments is shown.

[0043] Figure 4 A flowchart of a method of sealing living tissue according to some embodiments is shown.

[0044] Figure 5A And 5B An example of the number of cycles to be used during sealing of a blood vessel and the peak power input to the blood vessel according to some embodiments is shown.

[0045] Figure 6 A flowchart of an alternative method of sealing living tissue according to some embodiments is shown.

[0046] In all drawings, the size of the respective constituent elements is suitably adjusted for the sake of clarity. For ease of viewing, in some cases, only some of the features in the drawings are labeled with reference numerals. DETAILED DESCRIPTION

[0047] Embodiments of an electrothermal sealing method (and devices and treatment systems operably configured to include the electrothermal sealing method) for sealing biological tissue of a patient using high frequency electrical energy apply N (N = a natural number from 1 to 5, inclusive) cycles of electrical energy to the living tissue by increasing the amount of high frequency electrical energy provided to the living tissue in each cycle until the impedance of the living tissue increases to an impedance threshold value for that cycle, after which the amount of high frequency electrical energy is decreased to decrease the impedance of the living tissue by a predetermined value. The cycles are repeated with each subsequent cycle having a greater impedance threshold value than in the previous cycle, and the cycles stop when the impedance reaches an impedance stop value. The initial value of the impedance can be used to determine parameters of the tissue, which in turn are used to adjust parameters of the cycles, such as one or more of the number of cycles, the time of each cycle, the initial power setting for each cycle, the power increase rate with each cycle, the impedance threshold value for each cycle, and the impedance stop value.

[0048] In one aspect of the application, a method for sealing living tissue of a patient using high frequency electrical energy provided to the living tissue by an end effector of a treatment instrument is disclosed. The method can include cycling electrical energy supplied to the living tissue by increasing an amount of high frequency electrical energy provided to the living tissue in an Nth cycle until an impedance of the living tissue increases to an Nth impedance threshold value. When the impedance of the living tissue reaches the Nth impedance threshold value, the amount of high frequency electrical energy provided to the living tissue is decreased to enable the impedance of the living tissue to decrease by a predetermined value. When an impedance stop value is reached in an N+1th cycle, the high frequency electrical energy provided to the living tissue is stopped. The N+1th impedance threshold value is greater than the Nth impedance threshold value. N is a natural number and has a value equal to or greater than 1 to equal to or less than 5 in exemplary embodiments.

[0049] In another aspect of the application, a method for sealing living tissue of a patient using high frequency electrical energy provided to the living tissue by an end effector of a treatment instrument is disclosed. The method can include cycling electrical energy supplied to the living tissue by increasing an amount of high frequency electrical energy provided to the living tissue in an Nth cycle until an impedance of the living tissue increases to an Nth impedance threshold value. When the impedance of the living tissue reaches the Nth impedance threshold value and for a predetermined period of time, the amount of high frequency electrical energy provided to the living tissue is decreased. When an N+1th impedance threshold value reaches an impedance stop value, the high frequency electrical energy provided to the living tissue is stopped. N is a natural number and the N+1th impedance threshold value is greater than the Nth impedance threshold value.

[0050] As used herein, high frequency refers to frequencies in the range of about 100 kHz to about 5 MHz. Thus, depending on the particular application, the device can supply electrical energy to the living tissue by applying a voltage at a frequency of, for example, 100 kHz, 150 kHz, 200 kHz, 250 kHz, 300 kHz, 350 kHz, 400 kHz, 450 kHz, 500 kHz, 600 kHz, 700 kHz, 800 kHz, 900 kHz, 1000 kHz, 1500 kHz, 2000 kHz, 2500 kHz, 3000 kHz, 3500 kHz, 4000 kHz, 4500 kHz, 5000 kHz, or any frequency between any two of these frequencies.

[0051] As used herein, the term "patient" includes any and all organisms and includes the term "subject." The patient can be a human or an animal.

[0052] Medical device for heating tissue

[0053] Figure 1 A schematic view of a medical device for heating tissue according to an embodiment of the application is shown. As Figure 1As shown, the medical device 1 for sealing tissue is provided with an instrument 2, a controller 3 having a processor, and an actuation switch 4. The instrument 2 can be, for example, a clamp for grasping biological tissue during electrosurgical procedures.

[0054] The treatment instrument 2 has a handle 2A1, a shaft 2A2, and a treatment portion consisting of an end effector 10, such as a pair of openable or pivotable gripping portions (including a first gripping portion 11A and a second gripping portion 11B) for grasping living tissue (LT) for treatment. The gripping portions as a whole are also referred to herein as a "treatment section" or "treatment portion" of the medical instrument. Note that hereinafter, when referring to components having the same function and having reference numerals to which A and B are attached to the ends of the reference numerals, respectively, the symbols A or B can be omitted. For example, each of the first gripping portion 11A and the second gripping portion 11B can be referred to as a gripping portion. In some embodiments, the actuation switch can be provided at the handle 2A1.

[0055] The handle 2A1 is connected to the controller 3 via a cable 2L. The handle 2A1 has an opening / closing actuator 2A3 such as a trigger or the like for the surgeon to operate opening and closing of the treatment portion, the shape of which enables the surgeon to easily grip the tissue. The opening / closing actuator 2A3 is arranged at one end of the handle 2A1, and is integrated with the treatment portion to transmit operation of the opening / closing actuator 2A3 to the treatment portion. On the other side of the handle 2A1, a gripping portion 2A4 is provided for the clinician to grip when operating the instrument 2.

[0056] Figure 2 A schematic view of the controller according to an embodiment of the present application is shown. The controller 3 can include a processor 32, a display 36, an input unit 42, and a power supply 44.

[0057] The processor 32 can include a memory 34, a computing unit 46, and a control unit 40. The computing unit 46 and the control unit 40 are formed of an integrated circuit including a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field Programmable Gate Array). The computing unit 46 and the control unit 40 can be formed of a single integrated circuit, or can be formed of a plurality of integrated circuits.

[0058] In some embodiments, various parameters for determining impedance of living tissue, such as size of tissue, type of tissue, or any other factor for determining impedance of tissue, can be stored in the memory 34, for example, in a lookup table within the memory 34. The lookup table can include values for respective parameters for different treatment portions. For example, the lookup table can include parameters for muscle tissue, fat tissue, blood vessels, intestinal wall, or other tissue types. The computing unit 46 is configured to compute impedance at the beginning of a given heating cycle or during a given heating cycle and other parameters required for computing impedance. The control unit 40 is configured to control the power supply 44 and the display 36 based on commands provided by the processor 32 using the parameters computed by the computing unit 46.

[0059] The display 36 that displays treatment conditions and the like and the setting operation section 35 that permits a surgeon to set treatment conditions and the like are located on the front panel of the controller 3. In some embodiments, the controller 3 can be connected to the switch 4 via the cable 4L. The switch 4 can be used by a clinician, for example, between sealing two different blood vessels, for controlling the process for controlling power applied to the instrument.

[0060] In some embodiments, the power supply 44 is operatively coupled to the processor 32 that controls application of power to the instrument 2 via the power supply 44 to appropriately cycle power applied to living tissue during a sealing process.

[0061] To control power input to the instrument 2, the processor 32 can determine impedance of living tissue during a process and determine whether the impedance has reached a particular threshold for a given cycle. In addition, the processor 32 can determine a number of cycles to increase power input to the instrument to appropriately seal living tissue.

[0062] In some embodiments, the number of cycles to increase power input to the instrument 2 to seal living tissue is determined based on an initial impedance Z0 of the tissue determined before the beginning of a first cycle. For example, when a clinician starts a process for sealing living tissue, the processor 32 can control the power supply 44 to apply a constant power to determine the initial impedance Z0.

[0063] In some embodiments, the processor 32 is configured to determine various parameters associated with living tissue based on a measured impedance of the living tissue. For example, the processor 32 can determine a size of the living tissue based on the initial impedance Z0. For example, in the case of a blood vessel, there is a direct correlation between the size (e.g., diameter) of the blood vessel and the impedance of the blood vessel. Thus, the processor 32 determines the size of the blood vessel based on the initial impedance Z0.

[0064] Thus, the initial impedance of the tissue can be indicative of the size of the tissue, as well as parameters such as the number of cycles required to seal the size of tissue, and the threshold impedance at various points in time at which the electrical energy provided to the tissue is to be increased or decreased. However, depending on the particular situation, the initial impedance of the tissue can not be an accurate indication of the size. For example, if there is an excess of external fluid surrounding the tissue, the initial impedance can be lower than a typical tissue of that size. Thus, estimating the state of the tissue during the procedure can help improve the efficiency of the procedure as well as improve patient safety by avoiding damage to the tissue during the procedure.

[0065] Thus, in some embodiments, the processor 32 can also be configured to determine the state of the living tissue based on the impedance of the tissue at various points in time during the procedure, to, for example, determine the end point of the procedure. Additionally or alternatively, the state of the living tissue determined during the procedure can be used to determine when the electrical energy supplied to the tissue should be increased or decreased and / or by how much the electrical energy supplied to the tissue should be increased or decreased. As used herein, the state of the living tissue can refer to the amount of water in the tissue (i.e., the dryness of the tissue) or the denaturation state of the tissue. In embodiments in which the impedance is determined at various points in time during the procedure, such impedance can be the initial impedance of the tissue Z0before the start of each cycle, or can be impedance values determined at various predetermined times during each cycle (e.g., at one or more fractions of the estimated cycle time, such as at intervals of 0.1, 0.2, 0.25, 0.3, 0.33, 0.4, 0.5, 0.6, 0.67, 0.7, 0.75, 0.8, and 0.9 of the cycle time T c,N For example, in embodiments, a low constant power is applied to the tissue at the start of the phase for a predetermined time (such as about 250 ms), and the average of the tissue impedance over the end period of the predetermined time (which is typically during the low constant power output period of the predetermined time) (such as from about 230 ms to about 250 ms over a 250 ms predetermined time) is considered to be the initial impedance.

[0066] As discussed herein, water in the tissue can decrease the impedance, while denaturation of the tissue can increase the impedance. Thus, the measured impedance of the tissue can be indicative of the state of the living tissue depending on the point in time during the procedure at which the impedance is measured. Thus, the processor 32 can determine whether the end point of the procedure has been reached or whether the cycles of electrical energy supplied to the tissue should continue. For example, if the impedance of the tissue reaches a particular impedance stop value Z stop stop value Z

[0067] During the cycling of electrical energy into the living tissue, the processor 32 can initially increase the electrical energy input to the living tissue until the impedance of the tissue increases to a given threshold value determined based on the number of completed cycles. For example, during the Nth cycle, the amount of electrical energy input to the tissue is increased until the impedance of the tissue increases to the Nth impedance threshold value.

[0068] Once the processor 32 determines that the impedance of the tissue has reached a given threshold value (e.g., the Nth impedance threshold value Z N ), the amount of electrical energy supplied to the tissue is decreased for a certain amount of time. Without wishing to be bound by theory, this temporary decrease in the electrical energy supplied to the tissue allows water to return to the tissue, thereby decreasing the impedance of the tissue. Once the impedance of the tissue decreases by a certain value, the processor 32 begins the next cycle (i.e., the N+1th cycle) and increases the electrical energy supplied to the tissue to increase the impedance of the tissue to the N+1th impedance threshold value Z N that is greater than Z N+1 . When Z N+1 reaches an impedance stop value Z Stop indicating that the sealing process is complete, the cycling stops.

[0069] Figure 3 An example of the change in impedance of the tissue caused by cycling the electrical energy provided to the tissue for four cycles according to an embodiment of the present application is shown. As shown in Figure 3 , after determining the initial impedance of the tissue Z0 by applying a constant power (e.g., a low power) across the tissue, the voltage is increased at a constant rate in subsequent phases of the cycle, and the tissue impedance initially decreases to R min1 , and then increases to a first impedance threshold value Z1 at the end of cycle 1. A low constant power is then applied to the tissue at the beginning of cycle 2 and for a predetermined period of time during which the impedance of the tissue decreases to R min2 . The voltage is then again increased at a constant rate such that the impedance of the tissue increases to a second impedance threshold value Z2 at the end of the second cycle. During the third cycle, a low constant power is again applied to the tissue for a predetermined period of time during which the impedance of the tissue decreases to R min3 . When the impedance reaches R min3 , the voltage is again increased, thereby increasing the impedance of the tissue to a third impedance threshold value Z3 at the end of the third cycle. During the fourth cycle, a low constant power is again applied to the tissue for a predetermined period of time during which the impedance of the tissue decreases to R min4 , and the voltage is again increased, thereby increasing the impedance of the tissue to a fourth impedance threshold value at the end of the fourth cycle, which in this example is the impedance stop value Z stop . Upon determining that the impedance of the tissue has reached Z stop , the electrical energy supplied to the tissue is stopped to complete the process.

[0070] In Figure 3 In the illustrated embodiment, the cycle begins with a higher impedance, and during the cycle, the impedance first decreases and then increases to a particular threshold. In some embodiments, the processor 32 can define the beginning of the cycle with a lower impedance, and during the cycle, the impedance first increases and then decreases. Thus, those skilled in the art will appreciate that the beginning and end of the cycle can be defined arbitrarily, so long as the cycle can be defined reproducibly. However, it is a more logical choice to define the beginning of the cycle at the point of transition between increasing or decreasing impedance (i.e., increasing or decreasing the voltage applied across the tissue). In the illustrated embodiment, the cycle begins with a higher impedance, and during the cycle, the impedance first decreases and then increases to a particular threshold. In some embodiments, the processor 32 can define the beginning of the cycle with a lower impedance, and during the cycle, the impedance first increases and then decreases. Thus, those skilled in the art will appreciate that the beginning and end of the cycle can be defined arbitrarily, so long as the cycle can be defined reproducibly. However, it is a more logical choice to define the beginning of the cycle at the point of transition between increasing or decreasing impedance (i.e., increasing or decreasing the voltage applied across the tissue).

[0071] The amount by which the impedance is allowed to decrease during a given cycle (i.e., Z N – R minN+1 ) can be predetermined based on, for example, the cycle number, the size of the tissue, the initial impedance of the tissue, or some combination thereof. Additionally or alternatively, the value to which the impedance is allowed to decrease during a given cycle (i.e., R minN+1 ) can be predetermined based on the same or different combination of parameters. Furthermore, the value to which the impedance is allowed to decrease during a given cycle (e.g., the N+1 cycle) can be greater than the value to which the impedance is allowed to decrease during the immediately preceding cycle (e.g., the N cycle).

[0072] In other words, in each subsequent cycle, the processor 32 cycles the electrical energy supplied to the tissue such that the maximum impedance during the cycle is greater than the maximum impedance during the immediately preceding cycle, and the minimum impedance during the cycle is greater than the minimum impedance during the immediately preceding cycle, e.g., Z N+1 > Z N , and R minN+1 > R minN .

[0073] In example embodiments, the impedance threshold for each cycle is determined by adding a predetermined value to the minimum value from the previous cycle. For each subsequent cycle, this predetermined value can be increased by a constant value. Example constant values for the increment are in the range of 20 Ω to 100 Ω, such as 20 Ω, 30 Ω, 40 Ω, 50 Ω, 60 Ω, 70 Ω, 80 Ω, or any value between these values. In one specific example, the constant value for the increment is 50 Ω. Thus, as an example, if the N cycle has a minimum impedance (R minN ), then the impedance threshold for the N+1 cycle would be (R minN + 50 Ω). Continuing to the next cycle, if the N+1 cycle has a minimum impedance (R minN+1 ), then the impedance threshold for the next cycle (the N+2 cycle) would be (R minN+1 + 100 Ω). Additional cycles would have impedance thresholds that are increased by an additional +50 Ω increment (e.g., +150 Ω, +200 Ω, etc.), until the last cycle and the process stops.

[0074] In some embodiments, the processor 32 can determine one or more of the following when determining the initial impedance Z0: (a) the number of cycles, (b) the value to which the impedance of the tissue is allowed to increase during each cycle, (c) the amount of electrical energy supplied to the tissue (overall or on a per-cycle basis or both) while the impedance of the tissue is allowed to increase, (d) the amount of time (overall, or on a per-cycle basis, or both) for which the impedance of the tissue is allowed to increase, (e) the value to which or by which the impedance of the tissue is allowed to decrease during each cycle, (f) the amount of time during which the electrical energy supplied to the tissue is decreased during each cycle, (g) the value by which the electrical energy supplied to the tissue is decreased during each cycle, (h) the impedance threshold for cycles in which the electrical energy supplied to the tissue is decreased, and (i) the impedance stop value at which the process of electrical energy supplied to the tissue is stopped.

[0075] In some embodiments, the processor 32 can determine one or more of the parameters (a) through (i) at the beginning of each cycle. Those skilled in the art will appreciate that the determination of some of these parameters can be based on the determination of some of the other parameters. For example, the determination of (d) can depend on the determination of (b) and (c).

[0076] Thus, when the clinician begins the sealing process, the processor 32 first determines the initial impedance by applying a predetermined constant power and measuring the current through the living tissue. The processor 32 then provides cycles of electrical energy to the tissue until the measured impedance of the tissue reaches the impedance stop value. The iterative increases are made based on one or more of the parameters (a) through (i).

[0077] In another aspect, the present application is directed to a method for sealing living tissue using high frequency electrical energy that reduces the total amount of time required to seal the living tissue. For example, in some embodiments, the method includes applying an amount of electrical energy provided to the living tissue in cycles to first increase and then decrease the impedance of the tissue in each cycle. During each subsequent cycle, the impedance of the tissue is allowed to increase to a greater value than in the immediately preceding cycle when the electrical energy supply to the tissue is stopped and the sealing process is complete until the impedance reaches an impedance stop value.

[0078] Figure 4 A flowchart of a method of sealing living tissue according to some embodiments is shown. Reference is made to Figure 4 In some embodiments, the method of sealing living tissue can optionally include determining an initial impedance of the tissue at S401. To determine the initial impedance, in some embodiments, a constant power is applied across the tissue and for an amount of time. The current flowing through the tissue during that time can then be measured to determine the initial impedance of the tissue.

[0079] Those skilled in the art recognize that the application of power across a tissue can cause the impedance of the tissue to increase as the tissue dehydrates, depending on the power being applied and the time for which the power is applied. Thus, the value of the power and the amount of time for which the power is applied are appropriately selected to minimize dehydration of the tissue. For example, in some embodiments, a constant power can be applied for about 10 ms, about 20 ms, about 30 ms, about 40 ms, about 50 ms, about 60 ms, about 70 ms, about 80 ms, about 90 ms, about 100 ms, about 120 ms, about 140 ms, about 160 ms, about 180 ms, about 200 ms, about 250 ms, about 300 ms, about 350 ms, about 400 ms, about 450 ms, about 500 ms, or any time period between any two of these values. Similarly, the power applied can be about 5 W, about 10 W, about 15 W, about 20 W, about 25 W, about 30 W, about 35 W, about 40 W, about 45 W, about 50 W, about 55 W, about 60 W, about 65 W, about 70 W, about 75 W, about 80 W, about 85 W, about 90 W, about 95 W, about 100 W, about 110 W, about 120 W, about 130 W, about 140 W, about 150 W, about 175 W, about 200 W, or any value between any two of these values.

[0080] One or more parameters related to the tissue, such as the size of the tissue, are determined based on the initial impedance of the tissue. In addition, other parameters, such as, for example, the number of cycles to be used for sealing and the peak power that can be used during the sealing process, are determined based on the size of the tissue.

[0081] Figure 5A An example of the determination of the number of cycles to be used during sealing of a blood vessel and the peak power to be input to the blood vessel is shown, according to some embodiments. For example, if the size of the blood vessel is "Size 1", the sealing process is performed for at least two cycles and a peak power less than PI is used. If the size of the blood vessel is "Size 2" (greater than "Size 1"), the sealing process is performed for at least three cycles and a peak power in the range of PI to P2 is used. If the size of the blood vessel is "Size 3" (greater than "Size 2"), the sealing process is performed for at least four cycles and a peak power greater than P2 is used.

[0082] Figure 5B Another example of the number of cycles to be used during sealing of a blood vessel and the peak power to be input to the blood vessel is shown, according to some embodiments. In this example, the size (diameter, in mm) of the blood vessel is given and the associated minimum number of cycles and peak power range (in Watts) are given and these are based on empirical studies.

[0083] Returning to Figure 4The method of sealing living tissue graphically illustrated in FIG. 1 continues with setting a cycle counter N to 1 at S402.

[0084] Based on these parameters, at S403, in the Nth cycle, the electrical energy supplied to the tissue is increased to increase the impedance of the tissue. During S403, the voltage applied across the tissue is increased for an amount of time or until the impedance of the tissue reaches an Nth impedance threshold. In some embodiments, the rate at which the voltage applied across the tissue is increased can be determined based on one or more parameters, such as the size and / or type of tissue, etc. For example, depending on the size and / or type of tissue, a peak voltage to be applied across the tissue can be determined, and then a rate of increase of the voltage can be determined. In some embodiments, the voltage can be increased over a period of time ranging from about 600 ms to about 3000 ms. For example, the voltage can be increased for about 600 ms, about 610 ms, about 620 ms, about 630 ms, about 640 ms, about 650 ms, about 660 ms, about 670 ms, about 680 ms, about 690 ms, about 700 ms, about 720 ms, about 740 ms, about 760 ms, about 780 ms, about 800 ms, about 825 ms, about 850 ms, about 875 ms, about 900 ms, about 950 ms, about 1000 ms, about 1100 ms, about 1200 ms, about 1300 ms, about 1400 ms, about 1500 ms, about 1600 ms, about 1700 ms, about 1800 ms, about 1900 ms, about 2000 ms, about 2200 ms, about 2400 ms, about 2600 ms, about 2800 ms, about 3000 ms, or any amount of time between any two of these values. While those skilled in the art will recognize certain advantages and disadvantages of increasing the voltage over a period of less than 600 ms or greater than 3000 ms, processes of increasing the voltage over a period of less than 600 ms or greater than 3000 ms are also contemplated within the scope of the present disclosure.

[0085] The rate of increase of the high frequency electrical energy applied to the living tissue in the Nth cycle and the N+1th cycle can be the same, or the rate of increase of the high frequency electrical energy applied to the living tissue in each cycle can be different. For example, in some embodiments, the rate of increase of the high frequency electrical energy applied to the living tissue in the Nth cycle is determined based on the initial impedance value, and the rate of increase of the high frequency electrical energy applied to the living tissue in the N+1th cycle is different from the rate of increase of the high frequency electrical energy provided to the living tissue in the Nth cycle. For another example, the rate of increase of the high frequency electrical energy applied to the living tissue in the N+1th cycle is determined based on the N+1th initial impedance value, and the rate of increase of the high frequency electrical energy applied to the living tissue in the N+1th cycle is different from the rate of increase of the high frequency electrical energy provided to the living tissue in the Nth cycle. Example differences in the rate of increase between the Nth cycle and the N+1th cycle include, but are not limited to, 20 V / s, 22 V / s, 24 V / s, 26 V / s, 28 V / s, 30 V / s, 32 V / s, 34 V / s, 36 V / s, 38 V / s, 40 V / s, 42 V / s, 44 V / s, 46 V / s, 48 V / s, 50 V / s, 52 V / s, 54 V / s, 56 V / s, 58 V / s, 60 V / s, 62 V / s, 64 V / s, 66 V / s, 68 V / s, 70 V / s, or any value between any two of these values, depending on the size of the tissue, such as a blood vessel. For example, in some embodiments, the rate of voltage increase is about 36 V / s for a small blood vessel, and about 52 V / s for a large blood vessel.

[0086] At S404, the impedance of the tissue is compared to the Nth impedance threshold. In some embodiments, if it is determined that the impedance has not reached the Nth impedance threshold, additional electrical energy can be supplied to the tissue. If it is determined that the impedance of the tissue is greater than or equal to the Nth impedance threshold, the process proceeds to S405.

[0087] At S405, the impedance of the tissue is compared to an impedance stop value at which the sealing process is considered complete. If the impedance of the tissue is greater than or equal to the impedance stop value, the sealing process jumps to S410, where the power input to the tissue is stopped to stop the sealing process.

[0088] If the impedance of the tissue at S405 is determined to be less than the impedance stop value, the process proceeds to S406, where the electrical energy supplied to the tissue is reduced to allow the impedance of the tissue to decrease.

[0089] As discussed elsewhere herein, once the electrical energy supplied to the tissue is reduced, for example, by reducing the power input to the tissue (by reducing the voltage across the tissue), the impedance of the tissue can decrease, for example, by allowing the tissue to replenish moisture or by allowing electrolytes to diffuse into the tissue.

[0090] At S406, the electrical energy supplied to the tissue is reduced until the tissue's impedance decreases by a predetermined value. In some embodiments, the predetermined value may depend on the size and / or type of the tissue. In some embodiments, the predetermined value in a given cycle is based on a cycle counter N.

[0091] At S407, it is determined whether the tissue impedance has decreased by a predetermined value after the electrical energy supplied to the tissue has been reduced. If it is determined that the impedance has not decreased by a predetermined value, the electrical energy is further reduced, or if it is not possible to reduce it further, the electrical energy is maintained at the reduced level for a longer period of time to allow the impedance to decrease by the predetermined value.

[0092] If it is determined that the impedance has decreased by a predetermined value, then at S408, the threshold impedance of the subsequent cycle (i.e., the N+1th impedance threshold) is set to be higher than the threshold impedance of the current cycle (i.e., the Nth cycle). In some embodiments, the N+1th impedance threshold may be set to be larger than a specific predetermined value. In some embodiments, this predetermined value (wherein the N+1th impedance threshold is larger than the Nth impedance threshold by the predetermined value) may be based on the size and / or type of tissue.

[0093] Then, at S409, the loop counter is set to N+1 (i.e., N = N+1), and the processing continues at S403.

[0094] Figure 6 A flowchart illustrating an alternative method for sealing living tissue according to some embodiments is shown. Figure 6 The processing shown is the same as Figure 4 The difference shown in the processing is that, Figure 6 The energy supplied to the tissue is reduced and continues for a predetermined amount of time, instead of as Figure 4 This continues until the impedance decreases to a predetermined value. Therefore, this paper only describes the differences between the two processes in detail to avoid repetition.

[0095] For example, up to S605, Figure 6 The processing shown is the same as Figure 4 The processing shown is the same. However, in Figure 6 In the illustrated process, at S606, the electrical energy supplied to the tissue is reduced by a certain value and / or for a certain amount of time. For example, the electrical energy supplied to the tissue can be reduced to zero and / or reduced to a low value that cannot affect the tissue being treated, for example, by reducing the voltage across the tissue to zero and maintaining it for a certain amount of time (such as 10ms, 15ms, 20ms, 30ms, 35ms, 40ms, 50ms, 60ms, 70ms, 80ms, 90ms, 100ms, 125ms, 150ms, 200ms, or any amount of time between any two of these values).

[0096] Once the electrical energy supplied to the tissue is reduced and for a predetermined amount of time, at S607, the threshold impedance of the subsequent cycle (i.e., the N+1 impedance threshold) is set to be higher than the threshold impedance of the current cycle (i.e., the N cycle). In some embodiments, the N+1 impedance threshold can be set to be a particular predetermined value greater than the N impedance threshold. In some embodiments, the predetermined value (where the N+1 impedance threshold is greater than the N impedance threshold by the predetermined value) can be based on the size of the tissue and / or the type of tissue.

[0097] The cycle counter is then set to N+1 (i.e., N = N+1) at S608, after which processing continues at S603.

[0098] The systems and methods disclosed herein reduce the time required to seal living tissue during electrosurgical procedures. The systems and methods disclosed herein also reduce the incidence of overheating of the tissue, thereby improving patient safety. Additionally, by controlling the rate of rise of the impedance of the living tissue, the systems and methods disclosed herein improve the efficiency of the process of sealing the living tissue.

[0099] While the application has been described in connection with the above exemplary embodiments, it will be understood that many modifications, additions, and deletions can be made to the embodiments without departing from the spirit and scope of the application as set forth in the following claims.

[0100] The preceding description is meant to be illustrative only. Various modifications, additions and substitutions are intended in the scope and spirit of the disclosed technology as defined by the following claims.

[0101] There can be many other ways to implement the subject technology. Various functions and elements of the described technology can be partitioned differently from what is shown without departing from the scope and spirit of the subject technology. Various modifications to these configurations will be readily apparent to those skilled in the art, and generic principles defined herein can be applied to other configurations. Thus, many changes and modifications can be made to the subject technology, by one having ordinary skill in the art, without departing from the scope and spirit of the subject technology.

[0102] It should be understood that the particular order in which the steps of the disclosed processes have been presented and / or described is merely exemplary. The steps of the disclosed processes can be rearranged in their specific order or hierarchy without departing from the spirit of the exemplary methods. Some steps can be performed simultaneously. The accompanying method claims set forth elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

[0103] In some embodiments, any clause herein can be dependent on any one independent clause or any one dependent clause. In an aspect, any clause (e.g., dependent or independent) can be combined with any other one or more clauses (e.g., dependent or independent). In an aspect, a claim can include some or all of the words recited in a clause, sentence, phrase, or paragraph (e.g., steps, operations, components, or elements). In an aspect, a claim can include some or all of the words recited in one or more clauses, sentences, phrases, or paragraphs. In an aspect, some words can be deleted from each clause, sentence, phrase, or paragraph. In an aspect, additional words or elements can be added to a clause, sentence, phrase, or paragraph. In an aspect, the subject technology can be implemented without utilizing some components, elements, functions, or operations described herein. In an aspect, the subject technology can be implemented with additional components, elements, functions, or operations.

[0104] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a plunger assembly" includes a reference to one or more plunger assemblies and reference to "a magnet" includes a reference to one or more magnets.

[0105] In one or more aspects, the terms "about," "substantially," and "approximately" can provide an industry-accepted tolerance for the correlation between their respective terms and / or items, such as less than one to five percent.

[0106] As used herein, the term "substantially" refers to a complete or nearly complete range or degree of an action, characteristic, attribute, state, structure, item, or result.

[0107] It should be understood that ranges format is used herein only for convenience and brevity and that the use of such language is merely intended to provide flexibility to the scope and the meaning of each term. Thus, for example, "about 0.5 to 10 cm" is intended to include the explicitly recited values of about 0.5 cm to about 10.0 cm, but also to include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 5, and 7 and sub-ranges such as 2 to 8, 4 to 6, etc. This same principle applies to ranges reciting only one numerical value. Furthermore, this interpretation should apply regardless of the breadth of the range or the characteristic being described.

[0108] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although any methods, devices and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, representative methods, devices and materials are described below.

[0109] The reference to singular shall not mean “one and only one” unless explicitly stated, but rather “one or more.” Male gender pronouns, such as his, include female and neutral gender pronouns, such as her and its, and vice versa. The term “some” refers to one or more. Underlined and / or italicized headings and subheadings are used for convenience and do not limit the subject technology, and are not referred to in connection with the description of the subject technology. All structural and functional equivalents to the elements of the various configurations described throughout this application that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by the subject technology. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether these disclosure are explicitly recited in the above description.

[0110] The technology described herein can be implemented in hardware, software, firmware, or any combination thereof, unless explicitly described as being implemented in a specific technique. Any feature described as a module or component can also be implemented together in an integrated logic device, or separately as discrete but interoperable logic devices. If implemented in software, the technology can be realized at least in part by a non-transitory processor-readable storage medium comprising instructions that, when executed, performs one or more of the methods described above.

[0111] The non-transitory processor-readable storage medium can include random access memory (RAM) such as synchronous dynamic random access memory (SDRAM), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, or other known storage media. Additionally or alternatively, the technology can be realized at least in part by a processor-readable communication medium that carries or communicates code in the form of instructions or data structures and that can be accessed, read, and / or executed by a computer or other processor. For example, a carrier wave can be employed to carry the computer-readable electronic data such as data being sent from and received at a transmitting and receiving electronic mail system or when accessing a network such as the Internet or a local area network (LAN). Many modifications to the configuration are possible in light of the foregoing, without departing from the scope or spirit of the claimed subject matter.

[0112] Although the detailed description contains many specifics, these should not be construed as limiting the scope of the subject technology but merely as illustrating different examples and aspects of the subject technology. It should be appreciated that the scope of the subject technology includes some embodiments that are not discussed in detail above. Various other modifications, changes and variations which will become apparent to one having ordinary skill in the art can be made in the arrangement, operation and details of the methods and apparatus of the subject technology disclosed herein without departing from the scope of the application. References to an element or elements in singular do not mean "one and only one" unless expressly so stated, but rather "one or more." Further, the apparatus or methods should not be construed as limited to including only those elements that are absolutely necessary to make the apparatus or methods according to the different embodiments of the application. "Can" and "could" as used herein are understood to express a possibility of an event occurring in the sense that a statement that something "can" or "could", "can not" or "could not", happen, does not imply that there is a determined possibility of it happening. The application illustratively described herein suitably can be practiced in the absence of any element or elements not specifically disclosed herein.

[0113] Related Applications

[0114] This application is based on and claims priority to U.S. Provisional Application 63 / 151,969, filed February 22, 2021, under 35 U.S.C. § 119, the entire contents of which are incorporated herein by reference.

Claims

1. A controller for controlling high-frequency electrical energy provided to living tissue, the high-frequency electrical energy used by an end effector of a treatment instrument to seal the living tissue, the controller configured to apply high-frequency electrical energy to the living tissue in at least two cycles, wherein the at least two cycles including an Nth cycle and an N+1th cycle, the N+1th cycle following the Nth cycle, wherein, in the Nth cycle, the controller is further configured to: increase an amount of high-frequency electrical energy applied to the living tissue until an impedance of the living tissue reaches an Nth impedance threshold, and decrease the impedance of the living tissue by decreasing the amount of high-frequency electrical energy applied to the living tissue when the impedance of the living tissue reaches the Nth impedance threshold, and wherein, in the N+1th cycle, the controller is further configured to: increase the amount of high-frequency electrical energy applied to the living tissue until an impedance of the living tissue reaches an N+1th impedance threshold, and wherein the N+1th impedance threshold is greater than the Nth impedance threshold, wherein, in a 1st cycle, the controller is further configured to determine a size parameter associated with the living tissue by applying a constant power to the end effector while the end effector is in contact with the living tissue for a predetermined period of time, wherein determining the size parameter occurs prior to increasing the amount of high-frequency electrical energy applied to the living tissue in the 1st cycle.

2. The controller of claim 1, further configured to decrease the impedance of the living tissue by decreasing the amount of high-frequency electrical energy applied to the living tissue when the impedance of the living tissue reaches the N+1th impedance threshold.

3. The controller of claim 1, wherein, the N+1th impedance threshold is a stop impedance value, and wherein the controller is further configured to stop applying high-frequency electrical energy to the living tissue when the impedance of the living tissue reaches the stop impedance value.

4. The controller of claim 1, further configured to determine a value of N based on the size parameter.

5. The controller of claim 1, further configured to estimate the Nth impedance threshold based on the size parameter.

6. The controller of claim 1, wherein, a rate of increase of the high-frequency electrical energy applied to the living tissue in the N+1th cycle is different than a rate of increase of the high-frequency electrical energy provided to the living tissue in the Nth cycle.

7. The controller of claim 1, wherein, in the N+1th cycle, the controller is further configured to determine an N+1th size parameter by applying a constant power to the end effector while the end effector is in contact with the living tissue for a predetermined period of time, wherein the N+1th size parameter is determined prior to increasing the amount of high-frequency electrical energy applied to the living tissue in the N+1th cycle.

8. The controller of claim 7, wherein, a rate of increase of the high-frequency electrical energy applied to the living tissue in the N+1th cycle is determined based on the N+1th size parameter.

9. The controller of claim 8, wherein, a rate of increase of the high-frequency electrical energy applied to the living tissue in the N+1th cycle is different than a rate of increase of the high-frequency electrical energy provided to the living tissue in the Nth cycle.

10. An apparatus for sealing living tissue, the apparatus comprising: an energy source configured to generate high-frequency electrical energy; an end effector operably connected to the energy source and configured to provide the high-frequency electrical energy to the living tissue; and a controller operably connected to the energy source and the end effector and configured to, in operation, apply the high-frequency electrical energy to the living tissue in at least two cycles, wherein the at least two cycles include an Nth cycle and an (N+1)th cycle, the (N+1)th cycle following the Nth cycle, wherein, in the Nth cycle, the controller is further configured to, in operation: increase an amount of the high-frequency electrical energy applied to the living tissue until an impedance of the living tissue reaches an Nth impedance threshold, and decrease the impedance of the living tissue by decreasing the amount of the high-frequency electrical energy applied to the living tissue when the impedance of the living tissue reaches the Nth impedance threshold, and wherein, in the (N+1)th cycle, the controller is further configured to, in operation: increase an amount of the high-frequency electrical energy applied to the living tissue until an impedance of the living tissue reaches an (N+1)th impedance threshold, and wherein the (N+1)th impedance threshold is greater than the Nth impedance threshold, wherein, in a 1st cycle, the controller is further configured to, in operation, determine a size parameter associated with the living tissue by applying a constant power to the end effector while the end effector is in contact with the living tissue for a predetermined period of time, wherein the determination of the size parameter occurs before the increase in the amount of the high-frequency electrical energy applied to the living tissue in the 1st cycle.

11. The apparatus of claim 10, wherein, In the (N+1)th cycle, the controller is further configured to, in operation, decrease the impedance of the living tissue by decreasing the amount of the high-frequency electrical energy applied to the living tissue when the impedance of the living tissue reaches the (N+1)th impedance threshold.

12. The apparatus of claim 10, wherein, The (N+1)th impedance threshold is an impedance stop value, and wherein, in the (N+1)th cycle, the controller is further configured to, in operation, stop applying the high-frequency electrical energy to the living tissue when the impedance of the living tissue reaches the impedance stop value.

13. The apparatus of claim 10, wherein, The controller is further configured to, in operation, determine a value of N based on the size parameter.

14. The apparatus of claim 10, wherein, The controller is further configured to, in operation, estimate the Nth impedance threshold based on the size parameter.

15. The apparatus of claim 10, wherein, An increase rate of the high-frequency electrical energy applied to the living tissue in the (N+1)th cycle is different from an increase rate of the high-frequency electrical energy provided to the living tissue in the Nth cycle.

16. The apparatus of claim 10, wherein, In the (N+1)th cycle, the controller is further configured to, in operation, determine an (N+1)th size parameter by applying a constant power to the end effector while the end effector is in contact with the living tissue for a predetermined period of time, and wherein the (N+1)th size parameter is determined before the increase in the amount of the high-frequency electrical energy applied to the living tissue in the (N+1)th cycle.

17. The apparatus of claim 16, wherein, An increase rate of the high-frequency electrical energy applied to the living tissue in the (N+1)th cycle is determined based on the (N+1)th size parameter.

18. The apparatus of claim 17, wherein, An increase rate of the high-frequency electrical energy applied to the living tissue in the (N+1)th cycle is different from an increase rate of the high-frequency electrical energy provided to the living tissue in the Nth cycle.

19. A computer readable storage medium storing a program for causing a processor to execute a method for sealing living tissue using high frequency electrical energy provided to the living tissue by an end effector of a treatment instrument, the method comprising: applying high frequency electrical energy to the living tissue in at least two cycles, wherein the at least two cycles include an Nth cycle and an N+1th cycle, the N+1th cycle following the Nth cycle, wherein the Nth cycle includes: increasing an amount of high frequency electrical energy applied to the living tissue until an impedance of the living tissue reaches an Nth impedance threshold, and reducing the impedance of the living tissue by decreasing the amount of high frequency electrical energy applied to the living tissue when the impedance of the living tissue reaches the Nth impedance threshold, and wherein the N+1th cycle includes: increasing an amount of high frequency electrical energy applied to the living tissue until an impedance of the living tissue reaches an N+1th impedance threshold, and wherein the N+1th impedance threshold is greater than the Nth impedance threshold, wherein a 1st cycle includes determining a size parameter associated with the living tissue by applying a constant power to the end effector while the end effector is in contact with the living tissue and for a predetermined period of time, wherein determining the size parameter occurs prior to increasing the amount of high frequency electrical energy applied to the living tissue in the 1st cycle.

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