Method and apparatus for impedance measurement in a multi-channel electro-surgical generator

• US 6,293,941 B1
• Filed: 10/06/1998
• Issued: 09/25/2001
• Est. Priority Date: 10/06/1997
• Status: Expired due to Fees

• Current Assignee: Somnus Medical Technologies, Inc. (Olympus Corporation)
• Original Assignee: Somnus Medical Technologies, Inc. (Olympus Corporation)
• Inventors: Strul, Bruno, Koenig, Franklin R.
• Primary Examiner(s): Peffley, Michael
• Assistant Examiner(s): RUDDY, DAVID M
• Application Number:
  US09/167,215
• Time in Patent Office: 1,085 Days
• Field of Search: 606/32, 606/34, 606/35, 606/38, 606/41-50, 607/96-101, 607/122, 607/156
• US Class Current: 606/34
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/14 Probes or electrodes therefor
• CPC Class Codes: A61B 18/1402 Probes for open surgery
• CPC Class Codes: A61B 2017/00482 with a code
• CPC Class Codes: A61B 2018/00178 Electrical connectors
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/0075 Phase
• CPC Class Codes: A61B 2018/00779 Power or energy
• CPC Class Codes: A61B 2018/00791 Temperature
• 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 2018/00988 Means for storing information, e.g. calibration constants, or for preventing excessive use, e.g. usage, service life counter
• CPC Class Codes: A61B 2018/1273 including multiple generators in one device
• CPC Class Codes: Y10S 128/923 by comparison of patient data to other data

Abstract

This invention is an improved method and apparatus for tissue electrical impedance determination and electrical power control in a surgical device.

In an embodiment of the invention an apparatus for controlling power delivery in an electro-surgical instrument is disclosed. The electro-surgical instrument includes a first channel and a second channel for delivery of energy to a surgical site. The apparatus includes: a switch, a measuring unit, a processor and a drive unit. The switch electrically isolates the second channel during a first measurement interval and the first channel during a second measurement interval. The measuring unit is coupled to the first and the second channel. The measurement unit measures a first power level of the first channel during a first measurement interval and a second power level of the second channel during a second measurement interval. The processor is coupled to the measuring unit and to the switch. The processor adjusts the first power level and the second power level to minimize a difference between a measured value of a control parameter and a target value of the control parameter. The drive unit is controlled by the processor. The drive unit delivers the adjusted first and second power levels to the surgical site via respectively the first channel and the second channel during a heating interval.

In an alternate embodiment of the invention a method for controlling power delivery in an electro-surgical instrument is disclosed.

Claims

1. A method for controlling power delivery in an electro-surgical instrument including a first channel and a second channel for delivery of an energy to a surgical site, and the method for controlling power comprising the acts of:

determining a target value for a control parameter for the first channel and the second channel, the target value determined by matching an elapsed operating time with a corresponding control parameter profile of a control parameter schedule listing values for the control parameter as a function of time;

measuring a first power level of the first channel during a first measurement interval in which the first channel is electrically isolated from the second channel;

measuring a second power level of the second channel during a second measurement interval in which the second channel is electrically isolated from the first channel; and

adjusting the first power level and the second power level to minimize a difference between a measured value of the control parameter and the target value of the control parameter, to deliver the energy to the surgical site during a heating interval.

2. The method of claim 1, wherein the measured value and the target values of the control parameter in said determining and adjusting acts correspond to a one respectively of:

an actual temperature at the surgical site together with a desired temperature of the surgical site; and

an actual power delivered to the surgical site together with a desired power delivered to the surgical site.

3. The method of claim 1, wherein the act of measuring the first power level further comprises the act of:

terminating delivery of energy to the second channel to electrically isolate the first channel.

4. The method of claim 3, wherein the act of measuring the second power level further comprises the act of:

terminating delivery of energy to the first channel to electrically isolate the second channel.

5. The method of claim 1,

wherein the acts of measuring the first power level and the second power level further comprises the acts of:

a) applying a fixed voltage to the first channel and the second channel; and

b) measuring a corresponding impedance for each of the first channel and the second channel;

and wherein the act of adjusting the first power level and the second power level further comprises the act of;

calculating voltages to be applied to the first channel and the second channel on the basis of the corresponding impedances of the first channel and the second channel.

6. The method of claim 5, wherein said act of measuring a corresponding impedance further comprises the act of:

measuring a current and a voltage delivered on each of the first and the second channel.

7. The method of claim 5, wherein the fixed voltage applied during said applying act exceeds the heating voltages applied during said act of adjusting the first power level and the second power level.

8. The method of claim 1, wherein the acts of measuring the first power level and the second power level further includes the act of:

time interval multiplexing an application of a fixed voltage to the first channel and the second channel.

9. The method of claim 8, wherein the fixed voltage applied during said act of time division multiplexing exceeds voltages applied to said first channel and said second channel during said adjusting act.

10. The method of claim 1, wherein the first interval and the second interval are together less in duration than the heating interval.

11. The method of claim 10, wherein the first interval and the second interval are chosen to minimize the effect of energy delivered to the surgical site during said intervals.

12. The method of claim 1, wherein a total power applied to the surgical site during said first and said second measuring acts is fractionally related to the power applied during the heating interval to minimize an effect on the surgical site of the power delivered to the surgical site during said first and said second measuring acts.

13. An apparatus for controlling power delivery in an electro-surgical instrument including a first channel and a second channel for delivery of energy to a surgical site, and the apparatus for controlling power comprising:

a switch for electrically isolating the second channel during a first measurement interval and electrically isolating the first channel during a second measurement interval; and

a power measuring unit coupled to the first and the second channel for measuring a first power level of the first channel during a first measurement interval and a second power level of the second channel during a second measurement interval;

a processor coupled to the measuring unit and to the switch for adjusting the first power level and the second power level to minimize a difference between a measured value of a control parameter and a target value of the control parameter;

a storage unit with a control parameter profile listing values for the control parameter as a function of time wherein the processor couples to the storage unit to obtain the target value by matching an elapsed operating time with the corresponding control parameter profile; and

a power drive unit controlled by the processor to deliver the adjusted first and second power levels to the surgical site via respectively the first channel and the second channel during a heating interval.

14. The apparatus of claim 13, wherein the measured value and the target values of the control parameter correspond to a one of respectively:

an actual temperature at the surgical site together with a desired temperature of the surgical site; and

an actual power delivered to the surgical site together with a desired power delivered to the surgical site.

15. The apparatus of claim 13, wherein the switch decouples the drive unit from the second channel during the first measurement interval and decouples the drive unit from the first channel during the second measurement interval.

16. The apparatus of claim 13, further comprising:

a first sensor and a second sensor for measuring respectively a voltage together with a current on the first channel and the voltage together with a current on the second channel, and each of the sensors coupled to the measuring unit.

17. A method for controlling power delivery in an electro-surgical instrument including a plurality of channels for delivery of an energy to a surgical site, and the method for controlling power comprising the acts of:

measuring in a first time interval, the impedance of each of said channels measured by sequentially isolating each channel from others of the channels; and

adjusting in a second time interval, power levels of said channels to minimize a difference between a measured value of a control parameter and a target value of the control parameter, the target value determined by matching an elapsed operating time with a corresponding control parameter profile of a control parameter schedule listing values for the control parameter as a function of time, to deliver the energy to the surgical site during a heating interval.