Automatic bipolar control for an electrosurgical generator

• US 5,514,129 A
• Filed: 12/03/1993
• Issued: 05/07/1996
• Est. Priority Date: 12/03/1993
• Status: Expired due to Term

• Current Assignee: Covidien AG (Medtronic Plc)
• Original Assignee: Valleylab Inc. (Medtronic Plc)
• Inventors: Smith, Gregory C.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US08/161,737
• Time in Patent Office: 886 Days
• Field of Search: 606/38, 606/40, 606/51
• US Class Current: 606/40
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/1402 Probes for open surgery
• CPC Class Codes: A61B 2018/00666 using a threshold value
• CPC Class Codes: A61B 2018/00672 lower
• CPC Class Codes: A61B 2018/00678 upper
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00708 switching the power on or off
• CPC Class Codes: A61B 2018/00827 Current
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/00892 Voltage
• CPC Class Codes: A61B 2018/1273 including multiple generators in one device

Abstract

An automatic circuit measures electrosurgical generator output and controls in accord with impedance between activated movable bipolar electrodes able to contact tissue. Voltage monitor in parallel and current monitor in series with the electrodes measure instantaneous variations and generate proportional signals. First and second calculators receive the signals and find respectively, by dividing the voltage by current, short circuit impedances and impedances other than short circuit impedances between the electrodes. First and second comparators receive the respective outputs from the first and second calculators and assess them against respective first and second references providing signs of short conditions and assessments of changes in impedance between the electrodes. A logic analyzer receives the signs and assessments and evaluates them to permit the instantaneous starting, operating or stopping of the electrosurgical generator. The electrodes include an instrument and a set of cables with a preselected combined impedance so the maximum instantaneous impedance between the electrodes is less than the preselected combined impedance. The second reference is user adjustable. Switches, associated with each of the voltage monitor and the current monitor, choose the gain applied to the proportional signals respectively therefrom. First and second calculator gain changers receive the signals for setting the range across which those respective signals are used. Methods have steps of monitoring voltage and current, generating signals, dividing the voltage signal by current signal to find short circuit impedance between the electrodes and the instantaneous changes in impedance for other than the short circuit impedance, assessing those findings against references and permitting the starting, operating, or stopping of the electrosurgical generator.

Claims

1. An automatic circuit that measures electrosurgical generator output and controls it in accord with impedance between activated bipolar electrodes attached thereto, comprising:

an electrosurgical generator;

a pair of spaced apart bipolar electrodes able to move together and apart for contacting tissue therebetween connected to the electrosurgical generator;

a voltage monitor connected in parallel with the pair of bipolar electrodes for measuring an instantaneous voltage variation therebetween and generating proportional signals relative to each measured instantaneous variation of voltage;

a current monitor connected in series with the pair of bipolar electrodes for measuring an instantaneous current variation therebetween and generating proportional signals relative to each measured instantaneous variation of current;

a first calculator attached to the voltage monitor and the current monitor for receiving the proportional signals to find by in effect dividing the voltage by current for generating proportional signals relative to the instantaneous indications of short circuit impedances between the pair of bipolar electrodes;

a second calculator attached to the voltage monitor and the current monitor for receiving the proportional signals to find by in effect dividing the voltage by current for generating proportional signals relative to the instantaneous changes in impedances between the pair of bipolar electrodes for other than short circuit impedance;

a first comparator connected to receive the proportional signals from the first calculator, assess these proportional signals against a first reference and provide instantaneous signs identifying short conditions between the pair of bipolar electrodes;

a second comparator connected to receive the proportional signals from the second calculator, assess these proportional signals against a second reference and provide assessments of the instantaneous signs identifying changes in impedance between the pair of bipolar electrodes; and

a logic analyzer connected to receive the signs and assessments of the first and second comparators and to control the electrosurgical generator for evaluating the signs and assessments to permit the starting, operating or stopping of the electrosurgical generator based on the evaluation.

2. The automatic circuit for an electrosurgical generator of claim 1 wherein the pair of bipolar electrodes further includes a bipolar instrument and a set of cables, the set of cables connect between the electrosurgical generator and the bipolar instrument, the bipolar instrument and the set of cables having a preselected combined impedance and wherein a maximum instantaneous impedance between the pair of bipolar electrodes as found by the second calculator is significantly less than the preselected combined impedance of the set of cables and the instrument so that the preselected combined impedance does not mask changes in the measured impedance between the pair of bipolar electrodes.

3. The automatic circuit for an electrosurgical generator of claim 2 wherein the maximum instantaneous impedance between the pair of bipolar electrodes as found by the second calculator and the preselected combined impedance differ by at least about one hundred and fifty percent so that the maximum instantaneous impedance between the pair of bipolar electrodes is significantly less than the preselected combined impedance to prevent masking changes in the measured impedance between the pair of bipolar electrodes.

4. The automatic circuit for an electrosurgical generator of claim 2 wherein the preselected combined impedance is greater than about one hundred and fifty percent of the maximum instantaneous impedance between the pair of bipolar electrodes.

5. The automatic circuit for an electrosurgical generator of claim 4 wherein the preselected combined impedance is a result of selecting the impedance of either the set of cables or the bipolar instrument or the pair of bipolar electrodes.

6. The automatic circuit for an electrosurgical generator of claim 5 wherein the set of cables includes a connector for conjugating with the electrosurgical generator output and allowing only the set of cables to operate the electrosurgical generator.

7. The automatic circuit for an electrosurgical generator of claim 1 wherein the second reference is connected to an adjuster for setting a variable threshold device in the second reference.

8. The automatic circuit for an electrosurgical generator of claim 7 wherein the adjuster consists of a potentiometer connected to an adjustable diode which establishes a variable threshold above which current is permitted to flow through the adjustable diode.

9. The automatic circuit for an electrosurgical generator of claim 1 wherein the voltage monitor and the current monitor each include a gain switch connected to receive and influence the proportional signals therefrom.

10. The automatic circuit for an electrosurgical generator of claim 1 wherein the first and second calculators each include a gain changer connected to receive the proportional signals therefrom for setting a range across which those respective signals are useful for acceptable automatic operation of the electrosurgical generator.

11. The automatic circuit for an electrosurgical generator of claim 1 wherein a control in circuit with the electrosurgical generator output delays activation thereof from zero to several seconds.

12. A method for automatically measuring and controlling an output from an electrosurgical generator in accord with impedance between a pair of activated bipolar electrodes attached thereto, including the following steps:

holding a pair of bipolar electrodes able to move together and apart to contact tissue therebetween;

monitoring voltage levels in a circuit connected in parallel with the pair of bipolar electrodes by measuring each instantaneous voltage variation therebetween;

generating proportional voltage signals relative to each instantaneous voltage variation thereof;

monitoring current levels in a circuit connected in series with the pair of bipolar electrodes by measuring each instantaneous current variation therebetween;

generating proportional signals relative to each instantaneous current variation thereof;

dividing the instantaneous proportional voltage signal by the instantaneous proportional current signal to obtain instantaneous indications of short circuit impedance between the pair of bipolar electrodes;

dividing the proportional instantaneous voltage signal by the instantaneous proportional current signal to obtain instantaneous indications of impedance for other than the short circuit impedance;

assessing the instantaneous indications of short circuit impedance against a first reference for providing instantaneous signals identifying short circuit conditions between the pair of bipolar electrodes;

assessing the instantaneous indications of impedance for other than short circuit impedance against a second reference for providing instantaneous indications of other than short circuit conditions between the pair of bipolar electrodes; and

permitting the starting, operating, or stopping of the electrosurgical generator based on evaluating the indications of short circuit conditions and of impedance for other than short circuit conditions by a logic analyzer.

13. The method of claim 12 further including a step of maintaining a maximum instantaneous impedance between the pair of bipolar electrodes at a value significantly less than a preselected combined impedance of a pair of bipolar electrodes further consisting of a bipolar instrument and a set of cables.

14. The method of claim 13 wherein the step of maintaining the maximum instantaneous impedance between the pair of bipolar electrodes requires maintaining the maximum instantaneous impedance at about one hundred and fifty percent of the preselected combined impedance.

15. The method of claim 12 further including a step of adjusting the second reference to establish a variable threshold above which current is permitted to flow therethrough as a second reference.

16. The method of claim 12 further including the step of setting a range for acceptable automatic electrosurgical generator operation by adjusting a gain changer.

17. The method of claim 12 further including a step of conjugating a preselected set of cables with the electrosurgical generator output wherein only the preselected set of cables are allowed to operate with the electrosurgical generator.

18. The method of claim 12 further including a step of delaying the activation of the electrosurgical generator output for about zero to several seconds with a control in circuit with the electrosurgical generator.

19. An automatic circuit that measures electrosurgical generator output and controls it in accord with impedance between activated bipolar electrodes attached thereto, comprising:

an electrosurgical generator;

a pair of spaced apart bipolar electrodes able to move together and apart for contacting tissue therebetween and wherein the pair of bipolar electrodes includes a bipolar instrument and a set of cables, the set of cables connect between the electrosurgical generator and the bipolar instrument, the bipolar instrument and the set of cables having a preselected combined impedance;

a voltage monitor connected in parallel with the pair of bipolar electrodes for measuring each instantaneous voltage variation therebetween and generating proportional signals relative to each instantaneous variation of voltage;

a current monitor connected in series with the pair of bipolar electrodes for measuring instantaneous current variations therebetween and generating proportional signals relative to each instantaneous variation of current;

gain switches connected to the voltage monitor and the current monitor choose the amount of gain applied to the proportional signals respectively therefrom;

a first calculator attached to the voltage monitor and the current monitor for receiving the proportional signals to find by in effect dividing the voltage by current and generate indications of short circuit impedance between the pair of bipolar electrodes;

a second calculator attached to the voltage monitor and the current monitor for receiving the proportional signals to find by in effect dividing the voltage by current and generate indications of other than short circuit impedance between the bipolar electrodes;

gain changers in each of the first and second calculators, the gain changer connected to receive the proportional signals there from for setting a range across which those respective signals are useful for acceptable automatic electrosurgical generator operation;

a first comparator connected to receive the indications of short circuit impedance from the first calculator and an output from a first reference for assessing and generating instantaneous signs identifying short circuit conditions between the pair of bipolar electrodes;

a second comparator connected to receive the indications of other than short circuit impedance from the second calculator and an output from a second reference for assessing and generating instantaneous signs of changes in impedance between the pair of bipolar electrodes and wherein the second reference is set by an adjuster which affects a variable threshold device in the second reference and wherein the adjuster is a potentiometer and the variable threshold device is an adjustable diode;

wherein the maximum instantaneous impedance between the pair of bipolar electrodes as found instantaneously by the second calculator is significantly less than a preselected combined impedance of a set of cables and a bipolar instrument so that the preselected combined impedance does not mask measured changes in impedance between the pair of bipolar electrodes and wherein the maximum instantaneous impedance differs by about one hundred and fifty percent so that impedance measured between the pair of bipolar electrodes is significantly less than the preselected combined impedance to prevent masking changes in the measured impedance between the pair of bipolar electrodes or wherein the preselected combined impedance is greater than one hundred and fifty percent of the maximum instantaneous impedance between the pair of bipolar electrodes relative to measured variations of voltage and wherein the preselected combined characteristic impedance is a result of selecting the impedance of either the set of cables or the bipolar instrument or the pair of bipolar electrodes;

wherein the preselected set of cables includes a connector for conjugating with the electrosurgical generator output and allowing only the preselected set of cables to operate the electrosurgical generator;

wherein a control in circuit with the electrosurgical generator output delays activation thereof from zero to several seconds; and

a logic analyzer connected to receive the signs and assessments of the first and second comparators and to control the electrosurgical generator for evaluating the signs and assessments to permit the starting, operating or stopping of the electrosurgical generator based on the evaluation.