Electrosurgical instrument
A working end of a surgical instrument that carries first and second jaws for delivering energy to tissue. In a preferred embodiment, at least one jaw of the working end defines a tissue-engagement plane that contacts the targeted tissue. The cross-section of the engagement plane reveals that it defines (i) a first surface conductive portion or a variably resistive matrix of a temperature-sensitive resistive material or a pressure-sensitive resistive material, and (ii) a second surface portion coupled to a fixed resistive material that coupled in series or parallel to a voltage source together with the first portion. In use, the engagement plane will apply active Rf energy to ohmically heat the captured tissue until the point in time that a controller senses an electrical parameter of the tissue such as impedance. Thereafter, the controller switches energy delivery to the second surface portion that is resistively heated to thereby apply energy to tissue by conductive heat transfer.
1. A working end of a surgical thermotherapy instrument, comprising: first and second jaw members moveable between an open position and a closed position, each jaw defining a jaw body and a jaw surface for engaging tissue; a first body portion of said at least one jaw comprising a conductive electrode exposed in the jaw surface coupled to a voltage source, the first body portion for providing ohmic heating in engaged tissue; a second body portion of at least one jaw comprising a material exposed in the jaw surface having a fixed resistance to electrical flow therethrough, the second body portion for conducting heat from the jaw surface to engaged tissue and a third body portion of at least one jaw surface that comprises a material that defines a pressure-sensitive variable resistance to electrical flow therethrough.
2. The working end of claim 1 further comprising a controller for selectively delivering energy from the voltage source to either the first body portion or the second body portion.
3. The working end of claim 1 wherein said first and second body portions are coupled in serial to said voltage source.
4. The working end of claim 1 wherein said first and second body portions are coupled in parallel to said voltage source.
5. The working end of claim 1 wherein said first, second and third body portions of said at least one jaw are coupled in serial to said voltage source.
6. The working end of claim 1 wherein a pair of said first, second and third body portions of said at least one jaw are coupled in serial to said voltage source.