System and method for return electrode monitoring

• US 20090036885A1
• Filed: 08/01/2007
• Published: 02/05/2009
• Est. Priority Date: 08/01/2007
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Tyco Healthcare Group LP (Medtronic Plc)
• Inventors: Gregg, William N.
• Granted Patent: US 8,100,898 B2
• Time in Patent Office: Days
• 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
• CPC Class Codes: A61B 2017/00026 Conductivity or impedance, e.g. of tissue
• CPC Class Codes: A61B 2017/00119 alarm; indicating an abnormal situation
• CPC Class Codes: A61B 2018/1467 using more than two electrodes on a single probe

Abstract

A system for determining probability of tissue damage is disclosed. The system includes an electrosurgical generator adapted to generate an electrosurgical current and a plurality of return electrodes adhered to a patient and adapted to couple to the electrosurgical generator. Each of the return electrodes includes an impedance sensor attached thereto. The system also includes a current monitor connected in series with each of the plurality of the return electrodes to measure the electrosurgical current passing therethrough and a processor coupled to each of the current monitors. The processor is configured to calculate a cooling factor and a heating factor for each of the plurality of the return electrodes. The processor further configured to determine probability of tissue damage for each of the plurality of the return electrodes as a function of the cooling factor and the heating factor.

Claims

1. A system for determining probability of tissue damage, the system comprising:

an electrosurgical generator adapted to generate an electrosurgical current;

a plurality of return electrodes adhered to a patient and adapted to couple to the electrosurgical generator, wherein each of the return electrodes includes an impedance sensor operatively associated therewith;

a current monitor connected in series with each of the plurality of the return electrodes which measures the electrosurgical current passing therethrough; and

a processor coupled to each of the current monitors, the processor configured to calculate a cooling factor and a heating factor with respect to each of the plurality of return electrodes, the processor further configured to determine probability of tissue damage for each of the plurality of the return electrodes as a function of at least one of the cooling factor and the heating factor.

2. A system according to claim 1, wherein the processor is further configured to calculate the heating factor as a function of the measured electrosurgical current passing through the corresponding return electrode.

3. A system according to claim 2, wherein the processor is further configured to calculate the heating factor as a function of measured impedance of the corresponding return electrode.

4. A system according to claim 3, wherein the processor is further configured to calculate the heating factor as a function of an adherence constant representative of the adherence of the corresponding return electrode.

5. A system according to claim 4, wherein the processor is further configured to calculate the heating factor as a function of on time of the corresponding return electrode, wherein the on time is a time period during which the corresponding return electrode is in electrical communication with the electrosurgical generator.

6. A system according to claim 1, wherein the processor is further configured to calculate the cooling factor of as a function of off time of the corresponding return electrode, wherein the off time is a time period during which limited or no electrosurgical current flows through the corresponding return electrode.

7. A system according to claim 1, wherein the processor is further configured to calculate the cooling factor as a function of a constant indicative of the body'"'"'s ability to remove heat.

8. A system according to claim 1, wherein the processor is further configured to determine the probability of tissue damage by comparing a difference between the cooling factor and the heating factor with a predetermined threshold.

9. A system according to claim 1, wherein if the difference between the cooling factor and the heating factor exceeds the predetermined threshold the processor is configured to perform an action selected from the group consisting of generating an alarm, signaling the electrosurgical generator to adjust output of the electrosurgical current, and signaling the electrosurgical generator to terminate output of the electrosurgical current.

10. A method for determining probability of tissue damage, the method comprising:

providing a plurality of return electrodes adhered to a patient and adapted to couple to an electrosurgical generator that is configured to generate an electrosurgical current, wherein each of the return electrodes includes an impedance sensor and a current monitor connected in series with each of the plurality of the return electrodes;

measuring the electrosurgical current passing through each of a plurality of the return electrodes;

measuring the impedance of each of the plurality of the return electrodes;

calculating a heating factor adjacent the return electrode for each of the plurality of the return electrodes;

calculating a cooling factor adjacent the return electrode for each of the plurality of the return electrodes; and

determining probability of tissue damage for each of the plurality of the return electrodes as a function of at least one of the cooling factor and the heating factor.

11. A method according to claim 10, wherein the step of calculating the heating factor further comprises the step of calculating the heating factor as a function of the measured electrosurgical current passing through the corresponding return electrode.

12. A method according to claim 11, wherein the step of calculating the heating factor further comprises the step of calculating the heating factor as a function of measured impedance of the corresponding return electrode.

13. A method according to claim 12, wherein the step of calculating the heating factor further comprises the step of calculating the heating factor as a function of an adherence constant representative of adherence of the corresponding return electrode.

14. A method according to claim 13, wherein the step of calculating the heating factor further comprises the step of calculating the heating factor as a function of on time of the corresponding return electrode, wherein the on time is a time period during which the corresponding return electrode is in electrical communication with the electrosurgical generator.

15. A method according to claim 10, wherein the step of calculating the cooling factor further comprises the step of calculating the cooling factor of as a function of off time of the corresponding return electrode, wherein the off time is a time period during which no electrosurgical current flows through the corresponding return electrode.

16. A method according to claim 10, wherein the step of calculating the cooling factor further comprises the step of calculating the cooling factor as a function of a constant indicative of the body'"'"'s ability to remove heat.

17. A method according to claim 10, wherein the step of determining probability of tissue damage further comprises the step of comparing a difference between the cooling factor and the heating factor with a predetermined threshold.

18. A method according to claim 10, further comprising the step of:

performing an action selected from the group consisting of generating an alarm, signaling the electrosurgical generator to adjust output of the electrosurgical current, and signaling the electrosurgical generator to terminate output of the electrosurgical current if the difference between the cooling factor and the heating factor exceeds the predetermined threshold.