MXPA97009425A - Exit spark control of an electroquirurg generator - Google Patents

Abstract

An electrosurgical generator is described that includes a spark control system that suppresses the output sparks, the output sparks occur when the energy passes in the form of an arc to the patient as the active electrode is removed from the patient; the output spark is automatically changing the frequency at which the final amplifier is excited when the conditions for an output spark are detected, the change in frequency acts to reduce the gain and efficiency in the final amplifier and dissipate energy as heat; Output spark control system includes an adjustable frequency waveform generator and a logical capacity to determine the conditions when the spark is likely to occur, preferably an algorithm is required in a microcontroller to detect the above conditions to the appearance of an exit spark, it is also preferred that the algorithm also controls the sequence of events: by first interrupting the electrosurgical output to avoid forming an arc and then changing the excitation frequency appropriately to discard the excess stored energy, the output waveform can be interrupted only for a short time or the surgeon will detect a drag while cutting the tissue

Description

CONTROL OF EXIT SPARS FROM AN ELECTROCHIRURGICAL GENERATOR The related applications incorporated herein and forming part thereof by reference, were filed with the United States Patent and Trademark Office on the same date, namely: "Power control for an electrosurgical generator", U.S.S.N. 08 / 471,116; PC8826; "A control system for neurosurgery", U.S.S.N. 08 / 470,533; PC9162; "Control apparatus for the output power of an electrosurgical generator", U.S.S.N. 08 / 468,950; PC8827; "Generation of digital waveform for electrosurgical generators", U.S.S.N. 08 / 471,344; PC9210.

FIELD OF THE INVENTION The present invention relates to electrosurgical generators and, more particularly, to a design for electrosurgical generators that decreases the severity of exit crackling when the electrode is removed from the tissue.

ANTECEDENTS OF THE DESCRIPTION An electrosurgical generator is used in surgical procedures to deliver electrical power to a patient's tissue. An electro-surgical generator includes a radio frequency generator and its controls. When an electrode is connected to the generator, the electrode can be used to cut or coagulate the tissue of a patient with high frequency electrical energy. During the operation, the current flows from the generator through an active electrode, passes through the tissue and body fluids of the patient and returns to the generator through a return electrode. He ID electrical circuit formed by the electrodes and the patient is called the patient circuit. Electric power has its waveform configured to enhance its ability to cut or coagulate tissue. Different waveforms correspond to i5 to different modes of operation of the generator and, each mode provides the surgeon with various operating advantages. Modes may include cutting, coagulation and mixing thereof for drying or spraying. A problem that can be found in the use of Electrosurgical instruments is that the electrode forms an arc with the patient when the electrode is removed from the tissue. This is due to the power control systems in the electrosurgical generator that are designed to increase the output voltage when the tissue is present higher impedances. This is usually done to maintain the output power. In the event that the electrode is removed, the control system in the electrosurgical generator can function as if the impedance of the tissue has dramatically increased and attempts to maintain the power supply. The control system can rapidly increase the tension, thus causing the active electrode to make the arc jump with the tissue during its withdrawal. This phenomenon is called "exit sizzle" and is undesirable because it causes an unwanted tissue injury. The designers of electro-surgical generators wish to minimize this circumstance. The sputtering output can also occur due to the electrical energy that is stored in the capacitive and inductive elements of the final amplification stage in an electrosurgical generator. Although the generator output can be disconnected once the electrode has been removed from the tissue, the energy that is stored in the final amplification stage must dissipate. If no other dissipation path is available, the stored energy will make an arc jump between the patient. The first designs of electrosurgical generators prevented the problems of exit sputtering in various ways. One way to avoid sputtering output is to avoid high voltages occurring in the active electrode. High voltages can be avoided by actively controlling the output voltage or also by passive means. In many of the first generators, the electrical capacities of the generator were not sufficient to produce high voltages in the active electrode when the impedance of the load was high and, therefore, the exit crackling problem was passively avoided. The closed-loop power control systems of modern electrosurgical generators can enhance the possibility of output crackling. Closed-loop control of the output power could cause the output voltage of the generator to rise with increasing tissue impedance. When the active electrode is removed from the tissue, the measured impedance of the load may increase sharply. The closed-loop control system increases the voltage in response to this perceived increase in impedance. The resulting high output voltage can cause an output spark. U.S. Patent 4,969,885 describes an active control apparatus for controlling the output voltage of an electrosurgical generator. Since the output crackling is, more likely, a problem in generators controlling the output power (instead of the output voltage), the '949 patent does not address the problem of output crackling. U.S. Patent 5,099,840 describes an electrosurgical generator that adjusts the resonant frequency of its output stage according to the impedance of the load. This is done to increase the efficiency of the exit stage. The output crackling problem is not contemplated in the '509 patent. In contrast to the patent 5,099,840, the present invention attempts to decrease the gain and, therefore, decrease the efficiency of the output stage to avoid output sputtering. This is the result contrary to the patent 5,099,840. Other patents of the United States have related technology, although they are not directed to the problem of the control of the sparks of exit. U.S. Patent 4,658,819 has a circuit in which the power supplied to the electrode is a function of the voltage of a DC power source and the load is measured by voltage and current sensors of the load. A controller with a microprocessor digitalizes the detected signals and calculates the impedance of the load and the actual power that is being released. The microprocessor controller therefore repeats the measurement, calculation and correction procedure approximately while the generator is operating. U.S. Patent 4,372,315 discloses a circuit that measures impedances after supplying a given number of radiofrequency pulses from one maximum pulse to another. U.S. Patent 4,321,926 has a feedback system for controlling the delivery of the electrosurgical effect, but the detection of the impedance is not performed in real mode. U.S. Patents 3,964,487, 3,980,085, 4,188,927 and 4,092,986 have circuitry for reducing the output current in accordance with the increase in load impedance. In said patents, the output voltage is kept constant while the intensity decreases with the increase of the impedance of the load. U.S. Patent 4,094,320 has a circuit that responds to changes in impedance measured by detecting the intensity at the active and return electrodes. The detected intensities are subtracted from one another and, if this exceeds a variable threshold value, the generator shuts down. The variable threshold is a function of the power level and the loss current that passes through the parasitic capacitance. One of the objects of the present invention is to overcome the problem of output crackling while maintaining a high power at the active electrode.

BRIEF DESCRIPTION OF THE INVENTION An electrosurgical generator including an output spark control system is described. A basis to control the sparks of exit is to make temporary adjustments in the operation of the electrosurgical generator, provided that the conditions are prone to occur sparks output. Adjustments include disconnecting the output of the electrosurgical generator and then temporarily changing the excitation frequency of the output stage of the electrosurgical generator, in order to reduce the gain of the output stage. The amplified circuits are adjusted to operate effectively at a particular frequency. By exciting the amplification circuit at a different frequency an "unadjusted" state occurs which has a lower gain and efficiency. However, an unbalanced state will produce voltages in the electrical components and therefore should be performed only for brief periods of time. Preferably, detectors and an algorithm are required in a microcontroller to detect the conditions that precede the appearance of the output crackling. It is also preferred that, the algorithm also controls the occurrence of cases: by first interrupting the electro-magnetic output to prevent the formation of an arc and then modifying the excitation frequency in an appropriate manner to dissipate the excess stored energy. The output waveform can be interrupted only for a short period of time or the surgeon will detect a drag while cutting the tissue. Preferably, this time varies from five to two hundred milliseconds. Two cases have been recognized that indicate the state in which sparks of exit appear. A first case is that the electrosurgical generator has been activated to treat tissue from a patient and, in fact, tissue is being treated. This is necessary because the spark to initiate electrosurgery should not be influenced by the control of the output sparks. This first case can be detected by an impedance control function of the electrosurgical generator. Preferably, whenever the impedance is in a typical operating range, for example, below 4069 Ohms, it is believed that the active electrode is in the patient's tissue. A second case is when the comparator generates a high signal that indicates that the output voltage has crossed the voltage threshold. Another way to detect the conditions for controlling the output sparks would be to control the impedance of the load. In a closed-loop power control system, the output voltage will increase with the increase in the impedance. Normally, the voltage threshold will be set at 80% of the maximum voltage expected for normal operating conditions. Since the electrosurgical generator has many operating conditions with different maximum voltages, a microprocessor stores, maintains and sets the appropriate voltage thresholds for each of the operating conditions. Normally, these thresholds will depend mainly on the power setting that the surgeon has selected and the mode of operation, that is, cut, combined or dried. For example, low power settings in the cut mode result in a low voltage threshold. However, the voltage threshold could also be a constant value that is high enough to induce an output spark. In some modes of operation, exit sputtering may not present a problem for surgeons. Normally, these modes would be the modes of coagulation, such as fulguration or pulverization. In each of these modes, sparks are expected to emanate from the active electrode, and therefore, control of the output sparks could be used only to limit the maximum voltage at which sparks occur. The output spark control system usually involves a combination of hardware and software in the electrosurgical generator. The software can be arranged so that it executes the logical stages that determine the conditions for the appearance of exit crackling. In some electrosurgical generators, the waveforms are preferably produced by microprocessors and, therefore, in some type of additional software it may be necessary to modify the frequency of the waveforms in response to a signal that may produce output sizzle. The circuits of the physical support can be used to check the behavior of the output of the voltage detector.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram of the L circuit of a crackling control circuit. Figure 2 is a functional block diagram of an electrosurgical generator with a sizzle control system.

DETAILED DESCRIPTION OF THE INVENTION An electrosurgical generator 10 has an output spark control system that suppresses the sputtering in a patient circuit 11 from the active electrode 12 to the patient 13. The spark control system has detection and logic capability to detect the conditions in the that sputtering output may possibly occur, and a waveform generator 14 that is capable of changing its frequency when said conditions have been detected. The electrosurgical generator 10 has a board 15 of the surgeon to which the surgeon has access to adjust the desired level of output power. The electrosurgical generator 10 also has a microcontroller 16 which is electrically connected for the reception of the desired output power level of the surgeon's board 15. The microcontroller 16 can also adjust the voltage threshold based on the desired level of output power. An adjustable waveform generator 14 is used in the electrosurgical generator 10 to produce radiofrequency waveforms and adjust the frequency of the waveforms. The adjustable waveform generator 14 can be designed to produce a digital or analog output. For the reception of the radiofrequency waveforms, a radio frequency output stage 17 has been electrically connected to the generator of adjustable waveforms. The output stage 17 is designed to generate an output voltage and an output current for transmission to the patient circuit 11. A voltage detector 18 is connected to the radio frequency output stage 17 for the reception of the output voltage, and may produce a first signal that is proportional to the output voltage. A spark control circuit 19 is electrically connected to the microcontroller 16 for receiving the voltage threshold thereof. The spark control circuit 19 is also electrically connected to the voltage detector 18 for the reception of the first signal, and the spark control circuit 19 is electrically connected to the adjustable waveform generator 14 to temporarily interrupt and then adjust the frequency of waveforms. The spark control circuit 19 performs the temporary interruption and adjusts, partly in response when the first signal is greater than the voltage threshold. The set frequency causes a drop in gain and efficiency through the radio frequency output stage 17, thus preventing a high voltage from occurring and dissipating energy in the form of heat.

The preferred embodiment of the spark control system comprises a spark control circuit 19 and a microcontroller 16. With reference to Figure 1, the spark control circuit 19 is provided with a maximum detector, a comparator and a monostable circuit. . The maximum detector is connected to the output of the voltage detector 18. The maximum detector is designed to store each local maximum of the output voltage detector 18. The signal from the output voltage detector 18 is rectified but not filtered when it reaches the maximum detector. The comparator is connected for the reception of the maximum values of the maximum detector and is also connected for the reception of the voltage threshold, which has been called VMAX_CLP in Figure 1. The comparator is designed to generate a signal of great value whenever the value of the peak exceeds the voltage threshold. The monostable circuit is connected for the reception of the high value signal of the comparator. The purpose of the monostable circuit is to produce an impulse for the microcontroller 16 whenever the comparator generates a signal of great value. The pulse is called SPARK_C0N in Figure 1. The microcontroller 16 has an input for the pulse of the monostable circuit. In the preferred embodiment, a spark control circuit 19 is used to test the output of the voltage detector 18. The rectified but not filtered waveform of the output voltage detector 18 is fed to a maximum detector having U170 and CR11. This input signal is called V? EN_SCC in Figure 1. U17B is a high-impedance compensator that maintains the integrity of the maximum detected signal. The output of this compensator is divided and fed to a comparator that has U16A. The other input to the comparator is an adjustment of the threshold level in the microcontroller 16 which depends on the mode and adjustment of the power. When the maximum detected sample of the output voltage exceeds the threshold, a monostable circuit U15A is activated and generates a three millisecond pulse that is sent to the microcontroller board 16. This pulse is unsound if this occurs approximately during the first two 0.2 seconds of activation. Otherwise, the pulse causes the microcontroller 16 to disconnect the output of the waveform generator 14 for a period ranging from 5 milliseconds to 200 milliseconds in the preferred embodiment. The microcontroller 16 detects that a spark has been suppressed. In one embodiment, the microcontroller 16 adjusts the disconnection time depending on the mode. For example, in the desiccation mode, the disconnection time could be 10 milliseconds or 100 milliseconds in the pure cut mode. The microcontroller 16 restarts the waveform generator 14 at a frequency of 470 kHz. The frequency of the waveform generator 14 returns to 394 kHz, either after a second of continuous activation or when the generator 10 is reactivated. In the preferred embodiment, the microcontroller 16 also controls the impedance of the load on the circuit 11 of the patient in order to determine one of the conditions preceding the exit crackling. Thus, in the preferred embodiment, the spark control circuit 19 further comprises a current detector 20 and a device 21 for measuring the impedance. The intensity detector 20 is connected to the radio frequency output stage 17 for receiving the output current, and can produce a second signal that is proportional to the output current. The impedance measurement device 21 may be an analog circuit, or a logic device, or also a microprocessor-based device. The impedance measuring device 21 is electrically connected for the reception of the first signal and the second signal and for calculating the impedance of the load in the circuit 11 of the patient. In the preferred embodiment, the impedance is subsequently used in the microcontroller 16 to determine the occurrence of cases that activate the output spark control. Once the spark control has been activated, the microcontroller 16 has an algorithm to disconnect the output stage 17 for about 5 milliseconds to 2Q0 milliseconds and then send a signal to the adjustable waveform generator 14 to adjust the frequency of the signals. waveforms.

A method for controlling the output sparks in an electrosurgical generator 10 includes the step of changing the frequency of the adjustable waveform generator 14 whenever outgoing crackling conditions occur, so that the gain of the output stage 17 decreases . In the preferred embodiment, the method comprises the steps of controlling the impedance of the output load, controlling the output voltage, adjusting a voltage threshold and activating a spark control system as long as the impedance is less than about 4096 Ohms and the voltage is greater than the voltage threshold. Other steps in a method for controlling sputtering output comprise: setting a desired level of output power on a surgeon board 15; receiving the desired output power level of the surgeon's board 15 with a microcontroller 16; adjusting a voltage threshold based on the desired level of output power with the microcontroller 16; producing radiofrequency waveforms with a generator 14 of adjustable waveforms; adjust the frequency of the waveforms with the generator 14 of adjustable waveforms; receiving the radiofrequency waveforms with a radio frequency output stage 17 electrically connected to the generator of adjustable waveforms; generating an output voltage and an output current for transmission to the patient circuit 11 with the radiofrequency output stage 17; receive the tension of LR output with a voltage detector 18 connected to the radio frequency output stage 17; producing a first signal that is proportional to the output voltage with the voltage detector 18; receiving the output current with a b voltage detector 20 connected to the radio frequency output stage 17; producing a second signal that is proportional to the output current with a current detector 20; receiving the first signal and the second signal with a measuring circuit of the impedance electrically connected to the voltage and intensity detector 20; calculating the impedance of the load in the circuit 11 of the patient with the circuit of measurement of the impedance; receiving the voltage threshold of the microcontroller 16 electrically with a spark control circuit 19; receiving the first voltage detector signal 18 with the spark control circuit 19; and adjusting the frequency of the waveforms in response to a state in which the impedance of the load is, in general, less than about 4096 Ohms and the first signal is greater than the voltage threshold.

Claims (9)

1. 7 NOVELTY OF THE INVENTION CLAIMS

1. - An electrosurgical generator (10) with a spark control system that suppresses the output sparks in a circuit (11) of the patient, the electrosurgical generator (10) comprising: a generator (14) of adjustable waveforms in the generator electrosurgical (10) to produce radiofrequency waveforms, and which can adjust the frequency of the waveforms; a radio frequency output stage (17) electrically connected to the adjustable waveform generator (14) for receiving the radiofrequency waveforms and for generating an output voltage and an output current for the transmission to the circuit (11) ) of the patient; a voltage detector (18) connected to the radio frequency output stage (17) for receiving the output voltage, which can produce a first signal q? e is proportional to the output voltage; a spark control circuit (19) electrically connected to the voltage detector (18) for the reception of the first signal, the spark control circuit (19) being electrically connected to the generator (14) of adjustable waveforms to cause the temporary interruption of the waveform generator 14 and then temporarily adjusting the frequency of the waveforms, partly in response to the first signal, in which the adjusted frequency produces a decrease in the gain through the stage (17) ) of radio frequency output.

2. Apparatus according to claim 1, wherein the spark control circuit (19) further comprises:? N intensity detector (20) connected to the radio frequency output stage (17) for the reception of the intensity of the output, and that can produce a second signal that is proportional to the output current, and an electrically connected impedance measuring device (21) for the reception of the first signal and the second signal and calculate the impedance of the load in the circuit (11) of the patient.

3. Apparatus according to claim 2, further comprising a microcontroller (16) which is provided with an electrically connected input for receiving the impedance of the load of the impedance measuring device (21), and the microcontroller (16). ) is provided with an output electrically connected to the generator (14) of adjustable waveforms to activate the spark control circuit (19).

4. Apparatus according to claim 3, further comprising an algorithm in the microcontroller (16) for disconnecting the output stage (17) for a time in the range of 5 milliseconds to 200 milliseconds.

5. Apparatus according to claim 1, wherein the spark control circuit (19) further comprises: a maximum detector that is connected for the reception of the first signal of the voltage detector (18) and for maintaining the values maximum of the first signal, and a comparator that is connected for the reception of the maximum values of the maximum detector and is also connected for the reception of a voltage threshold, the comparator generating a signal of great value as long as the maximum value exceeds the voltage threshold; a monostable circuit connected for the reception of the high-value signal of the comparator, the monostable circuit of an output electrically connected to the generator (14) of adjustable waveforms being provided, the monostable circuit being adjusted to produce a pulse at the output whenever a signal of great value is received from the comparator.

6. An electrosurgical generator (10) with a spark control system that suppresses the sputtering output through the circuit (11) of the patient and towards the patient (13) when used by a surgeon, comprising the electrosurgical generator ( 10): a board (15) of the surgeon on the electrosurgical generator (10) which the surgeon can access to adjust the desired level of output power; a microcontroller (16) in the electrosurgical generator (10) which is electrically connected for the reception of the desired output power level of the board (15) of the surgeon, and which can adjust a voltage threshold based on the desired level of power of the surgeon. departure; a generator (14) of adjustable waveforms in the electrosurgical generator 10 to produce radiofrequency waveforms, and adjust the frequency of the waveforms; a radio frequency output stage (17) electrically connected to the waveform generator (14) stable for the reception of radio frequency waveforms and for generating an output voltage and an output current for transmission to the radio frequency generator; circuit (11) of the patient; a voltage detector (18) connected to the radio frequency output stage (17) for receiving the output voltage, and which can produce a first signal that is proportional to the output voltage; a spark control circuit (19) electrically connected to the microcontroller (16), the spark control circuit (19) being electrically connected to the voltage detector (18) for the reception of the first signal, and the circuit (19) being ) of spark control electrically connected to the generator (14) of adjustable waveforms to cause temporary interruption and then temporarily adjust the frequency of the waveforms, partly in response, when the first signal is greater than the voltage threshold , producing the adjusted frequency produces a decrease in gain through the radio frequency output stage (17).

7. A method for controlling the output sparks in an electrosurgical generator (10) with a spark control system that suppresses the sputtering output through a circuit (11) of the patient and towards the patient (13), when the steps of: adjusting a desired level of output power on a board (15) of the surgeon, accessible by the surgeon and located in the electrosurgical generator (10), is used by a surgeon, including the suppression procedure; receiving the desired level of power output from the board (15) of the surgeon with a microcontroller (16) electrically connected to the electrosurgical generator (10); adjust a voltage threshold based on the desired level of output power with the microcontroller (16); producing radiofrequency waveforms with a generator (14) of adjustable waveforms in the electrosurgical generator (10); receiving the radiofrequency waveforms with a radio frequency output stage (17) electrically connected to the generator (14) of adjustable waveforms; generating an output voltage and an output current for transmission to the circuit (11) of the patient with the radiofrequency output stage (17); receiving the output voltage with a voltage detector (18) connected to the radio frequency output stage (17); producing a first signal that is proportional to the output voltage with the voltage detector (18); receiving the output current with an intensity detector (20) connected to the radio frequency output stage (17); producing a second signal that is proportional to the output current with the intensity detector (20); receiving the first signal and the second signal with a measurement circuit of the impedance electrically connected to the voltage detector (18) and the intensity detector (20); calculating the impedance of the load in the circuit (11) of the patient with the impedance measuring circuit; receiving the voltage threshold of the microcontroller (16) electrically with a spark control circuit (19); receiving the first signal from the voltage detector (18) with the spark control circuit (19); adjust the frequency of the waveforms with the generator (14) of adjustable waveforms, so that the gain that passes through the output stage (17) is reduced, the adjustment of the response to a condition in which the impedance The load is generally less than about 4096 Ohms and the first signal is greater than the voltage threshold.

8. Method according to claim 7, wherein the method has the step of activating the spark control circuit (19) while the impedance of the load is less than about 4096 Ohms.

9. Method according to claim 7, wherein the method has the steps of disconnecting the output stage (17) for approximately 5 milliseconds to approximately 200 milliseconds with the microcontroller (16) and then adjusting the frequency of the waveforms with the generator (14) of adjustable waveforms.