Patent ID: 8216223

Claim:
An electrosurgical generator for tissue fusion, comprising: an RF output stage adapted to supply electrosurgical energy to tissue to an electrosurgical instrument, wherein the electrosurgical instrument includes at least one active electrode adapted to apply electrosurgical energy to tissue; impedance sensing circuitry configured to measure impedance of tissue; and a processor configured to: determine whether tissue reaction has occurred as a function of a minimum impedance value and a predetermined rise in impedance, wherein tissue reaction corresponds to a boiling point of tissue fluid; generate a target impedance trajectory as a function of measured impedance and desired rate of change based on the tissue reaction determination, wherein the target impedance trajectory includes a plurality of target impedance values; detect a negative deviation between the measured tissue impedance and a corresponding target impedance value associated with an unexpected drop in tissue impedance, wherein if the negative deviation is detected for more than a predetermined time period the processor recalculates and generates a subsequent reset impedance trajectory to compensate for the negative deviation, the reset impedance trajectory configured to mirror the target impedance trajectory; interrupt the supply of electrosurgical energy to tissue to effectuate a cooling period; and indicate expiration of the cooling period.