Variable output crest factor electrosurgical generator

• US 7,255,694 B2
• Filed: 12/04/2003
• Issued: 08/14/2007
• Est. Priority Date: 12/10/2002
• Status: Active Grant

• Current Assignee: Covidien AG (Medtronic Plc)
• Original Assignee: Sherwood Services AG
• Inventors: Keppel, David S.
• Primary Examiner(s): PEFFLEY, MICHAEL F
• Application Number:
  US10/728,259
• Publication Number:
  US 20040147918A1
• Time in Patent Office: 1,349 Days
• Field of Search: 606 32- 42
• US Class Current: 606/34
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00726 Duty cycle
• CPC Class Codes: A61B 2018/00857 harmonic
• CPC Class Codes: A61B 2018/00875 Resistance or impedance

Abstract

An electrosurgical generator is disclosed capable of controlling the output crest factor, as well as the output power of the electrosurgical generator across a range of tissue impedances during electrosurgery. The control occurs automatically, in real time and continuously during the duration of electrosurgical activation of the electrosurgical generator by varying both the output crest factor and output power based on the changing impedance of the tissue. The electrosurgical generator also includes controls for allowing a surgeon to manually select the appropriate crest factor value and power output value for a particular surgical procedure. By automatically adjusting the output crest factor and by giving the surgeon the ability to manually “tailor” the output crest factor across a range of tissue impedance, the electrosurgical generator enhances the ultimate surgical effect and desirable surgical results.

Claims

1. An electrosurgical generator capable of varying both the output crest factor and output power of at least one waveform based on the changing impedance of tissue during electrosurgery, said electrosurgical generator comprising:

a processing unit for receiving at least one signal indicative of an output voltage and an output current of the at least one waveform, said processing unit executing a set of programmable instructions for determining the tissue impedance using the output voltage and output current of the at least one waveform and transmitting at least one waveform adjustment signal; and

a waveform generator for receiving the at least one waveform adjustment signal which alters the duty cycle of the at least one waveform to adjust the output crest factor and output power of the at least one waveform based on the determined tissue impedance, wherein said at least one waveform adjustment signal includes data to alter the duty cycle of the at least one waveform generated by the waveform generator in accordance with the following formula;

CF=[(1−

D)/D]^1/2, wherein D is the duty cycle and CF is the crest factor of the generated waveform.

2. An electrosurgical generator as in claim 1, wherein said processing unit further determines a corresponding output crest factor value and output power value of the at least one waveform for the determined tissue impedance by accessing at least one data structure.

3. An electrosurgical generator as in claim 2, wherein said at least one waveform adjustment signal includes data for setting the output crest factor and output power of the at least one waveform to the values provided by the at least one data structure.

4. An electrosurgical generator as in claim 2, wherein said at least one data structure includes at least one look-up table.

5. An electrosurgical generator as in claim 1, wherein said at least one waveform adjustment signal includes data to alter at least one of the positive peak and the RMS value of the at least one waveform generated by the waveform generator in accordance with the following formula:

CF=V_PEAK/V_RMS, where V_PEAK is the positive peak of the at least one waveform and V_RMS is the RMS value of the at least one waveform.

6. An electrosurgical generator as in claim 1, wherein said at least one waveform adjustment signal includes data to alter at least one of the duty cycle, the positive peak value, and the RMS value of the at least one waveform generated by the waveform generator.

7. An electrosurgical generator as in claim 1, wherein said processing unit executes the set of programmable instructions automatically, in real time and continuously during electrosurgical activation.

8. An electrosurgical generator as in claim 1, further comprising at least one control for manually selecting a value for the output crest factor of the at least one waveform.

9. A method for varying both the output crest factor and output power of at least one waveform generated by an electrosurgical generator based on the changing impedance of tissue during electrosurgery, said method comprising the steps of:

determining tissue impedance using an output voltage and an output current of the at least one waveform of the electro surgical generator; and

altering the duty cycle of the at least one waveform to adjust the output crest factor and output power of the at least one waveform generated by said electrosurgical generator based on the determined tissue impedance, wherein said at least one waveform adjustment signal includes data to alter the duty cycle of the at least one waveform generated by the waveform generator in accordance with the following formula;

CF=[(1−

D)/D]^1/2, wherein D is the duty cycle and CF is the crest factor of the generated waveform.

10. A method as in claim 9, wherein said adjusting step comprises the step of determining a corresponding output crest factor value and output power value of the at least one waveform for the determined tissue impedance by accessing at least one data structure.

11. A method as in claim 10, wherein said adjusting step comprises the step of setting the output crest factor and output power of the at least one waveform to the values provided by the at least one data structure.

12. A method as in claim 10, wherein said at least one data structure includes at least one look-up table.

13. A method as in claim 9, wherein said adjusting step comprises the step of sending a signal to a waveform generator of said electrosurgical generator to alter at least one of the positive peak and the RMS value of the at least one waveform generated by the waveform generator in accordance with the following formula:

CF=V_PEAK/V_RMS, where V_PEAK is the positive peak of the generated waveform and V_RMS is the RMS value of the at least one waveform.

14. A method as in claim 9, wherein said adjusting step comprises the step of sending at least one signal to a waveform generator of said electrosurgical generator to alter at least one of the duty cycle, the positive peak value, and the RMS value of the at least one waveform generated by the waveform generator.

15. A method as in claim 9, further comprising the step of manually selecting a value for the output crest factor and a value for the output power of the at least one waveform.

16. A method as in claim 9, wherein said method is performed automatically, in real time and continuously for the duration of the electro surgery.

17. An electrosurgical generator capable of varying both the output crest factor and output power of at least one waveform based on the changing impedance of tissue during electrosurgery, said electrosurgical generator comprising:

means for determining tissue impedance using an output voltage and output current of the at least one waveform generated by the electrosurgical generator; and

means for altering the duty cycle of the at least one waveform to adjust the output crest factor and output power of the at least one waveform generated by said electrosurgical generator based on the determined tissue impedance, wherein said at least one waveform adjustment signal includes data to alter the duty cycle of the at least one waveform generated by the waveform generator in accordance with the following formula;

CF=[(1−

D)/D]^1/2,wherein D is the duty cycle and CF is the crest factor of the generated waveform.

18. A power source for generating an output voltage and an output current for an electrosurgical generator system, said electrosurgical system is capable of varying both the output crest factor and output power of at least one waveform based on the changing impedance of tissue during electrosurgery, and said electrosurgical system including a processing unit for receiving at least one signal indicative of the output voltage and the output current of the at least one waveform, said processing unit executing a set of programmable instructions for determining the tissue impedance using the output voltage and output current of the at least one waveform and transmitting at least one waveform adjustment signal;

said electrosurgical system further including a waveform generator for receiving the at least one waveform adjustment signal for altering the duty cycle of the at least one waveform to adjust the output crest factor and output power of the at least one waveform based on the determined tissue impedance, wherein said at least one waveform adjustment signal includes data to alter the duty cycle of the at least one waveform generated by the waveform generator in accordance with the following formula;

CF=[(1−

D)/D]^1/2, wherein D is the duty cycle and CF is the crest factor of the generated waveform.