Impedance feedback monitor for electrosurgical instrument

A method of operating a device for electrosurgically treating tissue during a surgical procedure, said method comprising the steps of:

• applying RF energy to tissue to be electrosurgically treated by means of an electrosurgical instrument;
• measuring the impedance of the tissue treated by said electrosurgical instrument;
• generating an impedance signal representative of the measured impedance value of said tissue;
• determining a representative minimum impedance value;
• determining a representative target impedance value as a function of said minimum impedance value;
• comparing measured impedance values to said target impedance value;
• and
• generating a control signal to control the RF energy to said electrosurgical instrument in response to said measured impedance value exceeding said target impedance value.

An electrosurgical impedance feedback control device, said device comprising:

• impedance measurement circuitry adapted to be coupled to tissue contacting electrodes connected to a tissue treating portion of a surgical instrument and to an energy source arranged to supply therapeutic electrosurgical energy to said electrodes, wherein said impedance measurement circuitry is adapted to measure the impedance of tissue engaged by the tissue treating portion of the surgical instrument;
• said impedance measuring circuitry comprising:
• a first device for determining a minimum impedance value;
• a target determining device coupled to said first device, for determining the target impedance value as a function of said minimum impedance value;
• and
• a first comparison device for comparing measured impedance values to said target impedance value and generating a signal indicating whether said measured impedance value exceeds said target impedance value.