Electrosurgical return electrode monitor

• US 6,258,085 B1
• Filed: 05/11/1999
• Issued: 07/10/2001
• Est. Priority Date: 05/11/1999
• Status: Expired due to Term

• Current Assignee: Covidien AG (Medtronic Plc)
• Original Assignee: Sherwood Services AG
• Inventors: Eggleston, Jeffrey L.
• Primary Examiner(s): Dvorak, Linda C. M.
• Assistant Examiner(s): Kearney, R.
• Application Number:
  US09/310,059
• Time in Patent Office: 791 Days
• Field of Search: 606/32, 606/34, 606/35, 606/37, 606/38-42, 606/46-50, 607/115, 607/116
• US Class Current: 606/35
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 18/16 Indifferent or passive electrodes for grounding

Abstract

The present disclosure provides a method for determining the probability of a patient burn under a return electrode in a momopolar electrosurgical system comprising calculating a heating factor adjacent the return electrode utilizing a first algorithm, calculating a cooling factor adjacent the return electrode utilizing a second algorithm, subtracting the calculated cooling factor from the calculated heating factor to obtain a difference value, comparing the difference value to a threshold value, and adjusting the power dependent on the relationship of the difference value to the threshold value.

Claims

1. An electrosurgical system comprising:

an electrosurgical generator having an electrosurgical tool for treating tissue,

a return electrode, and

an impedance sensor in electrical communication with the return electrode to measure impedance of the return electrode,

wherein said electrosurgical generator further comprises;

a current sensor for measuring an output current delivered by the electrosurgical generator;

a microprocessor electrically connected to the current sensor and the impedance sensor for calculating a heating factor and a cooling factor of the tissue under the return electrode, the calculation of the heating factor being based at least in part on the measured output current; and

a controller electrically connected to the microprocessor for adjusting a power supply of the generator in response to a relationship of the calculated heating and cooling factors.

2. The generator of claim 1, wherein the microprocessor includes a first algorithm for calculating the heating factor and a second algorithm for calculating the cooling factor.

3. The generator of claim 2, wherein the second algorithm is defined as

4. The generator of claim 2, wherein the first algorithm is defined as

5. The generator of claim 4, wherein the measured impedance is indicative of the degree of adherence to the tissue of the return electrode.

6. The electrosurgical generator of claim 1, wherein the microprocessor includes an algorithm for subtracting the cooling factor from the heating factor to calculate a difference value, and the generator further comprises a comparator electrically connected to the microprocessor for comparing the difference value to a threshold value, the comparator being electrically connected to the controller to generate a first signal indicative of the relationship of the difference value and the threshold value.

7. The electrosurgical generator of claim 6, further comprising an alarm electrically connected to the comparator for generating a warning signal if the difference value exceeds the threshold value by a predetermined amount.

8. The electrosurgical generator of claim 6, wherein the controller generates a shut off signal to terminate power if the difference value exceeds a predetermined value, the predetermined value being greater than the threshold value.

9. The electrosurgical generator of claim 8, wherein the controller generates a second signal to reduce the power if the difference value exceeds the threshold value but does not exceed the predetermined value.