Electrosurgical control for a trocar

Claim 1

An electrosurgical control for a trocar comprising: a trocar having a stylet and a cannula coaxially fit to one another and the stylet is movable reciprocally relative to the cannula along an axis common to both, the trocar shaped for insertion in a direction generally along the axis through tissue of a human or animal body in a combined puncture procedure with its stylet; a distal end and a proximal end on the cannula, the cannula elongate between the ends thereof, the distal end for entering the tissue and the proximal end for remaining outside the tissue; a tip on the stylet end which enters the tissue, the tip associated with the distal end of the cannula and normally extending therebeyond in position for puncture through the tissue of a human or animal, the stylet having an end opposite the tip, the stylet arranged to be moveable relative to the cannula for positioning the tip in the extended position to a location with the tip fully within the cannula; an energy supply associated with the stylet for permitting passage of energy between the tip and the end opposite the tip; an electrosurgical generator connected to the energy supply for providing energy to the energy supply, the electrosurgical generator for connecting to the end opposite the tip of the stylet; an electrosurgically active device as part of the tip for connecting to the energy supply along the stylet; a sampling circuit associated with the electrosurgically active device responsive to changes in energy through the energy supply as a function of tissue acted upon by the electrosurgically active device at the tip of the stylet and as energized by the energy supply, the sampling circuit in a circuit with the energy supply and the electrosurgically active device for providing a signal relative to the energy supplied to the electrosurgically active device; a measuring circuit means connected to the sampling circuit to respond to and for analyzing the signal from the sampling circuit, the measuring circuit means for instantly isolating a specific signal therefrom indicative of a significant change in the energy passing through the electrosurgically active device when the tip thereof is in a body cavity and no longer in the tissue, and a comparator connected to the measuring circuit means, the comparator including a settable predetermined threshold amount of energy at which the electrosurgical generator no longer supplies energy to the electrosurgically active device when comparator relates the specific signal indicative of a significant change in the energy passing through the electrosurgically active device to the settable predetermined threshold amount of energy.