Electrosurgical instrument and method of frequency monitoring for sealing tissue

A method for performing an electrosurgical procedure using a surgical system, wherein the surgical system includes an electrosurgical instrument having an electrode configured to operate on a tissue of a patient, the method comprising:

• (a) engaging the tissue with the electrode;
• (b) applying a therapeutic signal to the tissue;
• (c) applying a non-therapeutic signal to the tissue via the electrode;
• (d) varying a frequency of the non-therapeutic signal between a plurality of predetermined frequencies;
• (e) receiving a return signal generated from the tissue in response to the non-therapeutic signal, the non-therapeutic signal comprising a voltage and a current;
• (f) detecting a phase angle between the voltage and the current of the non-therapeutic signal at each of the plurality of predetermined frequencies during the varying of the frequency of the non-therapeutic signal;
• (g) after determining each phase angle, identifying, as a center frequency, the frequency when a magnitude of the phase angle of the non-therapeutic signal is at a minimum;
• (h) establishing a signal parameter for the therapeutic signal based upon the center frequency;
• (i) analyzing an operational characteristic of the system to determine whether the operational characteristic has degraded beyond a predefined threshold;
• and
• (j) when the operational characteristic has degraded beyond the predefined threshold, updating and applying the therapeutic signal with the signal parameter.

A surgical system for performing an electrosurgical procedure, the surgical system comprising:

• an end effector comprising jaws configured to transition between an opened condition and a closed condition;
• a plurality of electrodes a positioned within the jaws of the end effector and configured to operate on a tissue of a patient;
• one or more waveform generators configured to apply a therapeutic signal and non-therapeutic signal to the tissue via the plurality of electrodes;
• and
• a control unit configured to store an algorithm configured to cause the control unit to:
• (a) apply a first non-therapeutic signal to the tissue via the one or more waveform generators;
• (b) vary a frequency of the first non-therapeutic signal to include a first frequency, a second frequency, and a third frequency, the second frequency being between the first frequency and the third frequency on a frequency range;
• (c) receive a first return signal generated from the tissue in response to the first non-therapeutic signal, the first non-therapeutic signal comprising a voltage and a current;
• (d) detect a phase angle of each of the first, second, and third frequencies between the voltage and the current of the first non-therapeutic signal during the varying of the frequency of the first non-therapeutic signal;
• (e) identify, as a first center frequency, the frequency when a magnitude of the phase angle of the first return signal is at a minimum, the first center frequency being the second frequency;
• and
• (f) apply a therapeutic signal to the tissue at the first center frequency via at least one electrode of the plurality of electrodes.