Patent ID: 6174308
Filing Date: 2001-01-16
Classification: A61B

Abstract:
A method of operating an electrosurgical apparatus having at least a tissue desiccation mode and a tissue vaporisation mode, the apparatus comprising an electrosurgical instrument and a radio frequency generator, the electrosurgical instrument comprising an instrument shaft and an electrode assembly at the distal end of the shaft, the radio frequency generator being coupled to the electrode assembly for the treatment of tissue in the presence of an electrically-conductive fluid medium, the electrode assembly comprising a tissue treatment electrode and a return electrode which is electrically insulated from the tissue treatment electrode by means of an insulation member, the tissue treatment electrode being exposed at the extreme distal end of the assembly, the return electrode having a fluid contact surface spaced from the exposed end of the tissue treatment electrode by the insulation member, the method comprising the steps of:feeding cool electrically-conductive fluid to the region of the exposed end of the tissue treatment electrode;removing heated electrically-conductive fluid, via a fluid return channel formed within the instrument shaft, from the region of the exposed end of the tissue treatment electrode; andcontrolling the output power of the radio frequency generator to lie within a first output range for the tissue desiccation mode and to lie within a second range for the tissue vaporisation mode, the first output range being such that the power supplied to the electrode assembly maintains the conductive fluid adjacent to the tissue treatment electrode substantially at boiling point for tissue desiccation without creating a vapour pocket surrounding the tissue treatment electrode, and the second output range being such that the output power supplied to the electrode assembly for vaporisation of tissue is such as to maintain a vapour pocket surrounding the tissue treatment electrode.