| abstract |
Tissue impedance or tissue impedance in combination with tissue temperature is used to control electrosurgical tissue treatment. Tissue impedance alone provides better control of electrosurgical treatment by determining an initial maximum tissue impedance, a minimum tissue impedance selecting a point between the maximum and minimum impedances, preferably the average, as an impedance threshold, and turning off rf power to the electrosurgical instrument when the impedance reaches the threshold as it rises from the minimum. Control may also be by the combination of tissue impedance and temperature. Temperature is controlled to maintain a selected preferred temperature and a maximum temperature is also selected so that if the tissue reaches the maximum temperature, power is turned off. Impedance control is combined with temperature control so that the temperature of the instrument is maintained at a selected preferred temperature unless a maximum temperature is exceeded, which normally will not happen. The impedance is also monitored with maximum and minimum values being determined as well as a threshold impedance between the max and the min. When the threshold, preferably the average impedance, is reached, power is removed from the instrument. |