Electrosurgical instrument and method of use
An electrosurgical medical device and method for creating thermal welds in engaged tissue. In one embodiment, at least one jaw of the instrument defines a tissue engagement plane carrying a conductive-resistive matrix of a conductively-doped non-conductive elastomer. The engagement surface portions thus can be described as a positive temperature coefficient material that has a unique selected decreased electrical conductance at each selected increased temperature thereof over a targeted treatment range. The conductive-resistive matrix can be engineered to bracket a targeted thermal treatment range, for example about 60° C. to 80° C., at which tissue welding can be accomplished. In one mode of operation, the engagement plane will automatically modulate and spatially localize ohmic heating within the engaged tissue from Rf energy application—across micron-scale portions of the engagement surface. In another mode of operation, a conductive-resistive matrix can induce a “wave” of Rf energy density to sweep across the tissue to thereby weld tissue.
1. A method of bi-polar Rf electrosurgical energy delivery for creating high strength tissue welds, the method comprising:
providing an instrument with first and second openable-closcable jaws having respective first and second Rf energy delivery surfaces with a positive temperature coefficient of resistance material carried in an Rf energy delivery surface;
engaging tissue between the first and second energy delivery surfaces;
delivering bipolar Rf current flows to the engaged tissue to cause ohmic heating of the tissue wherein said Rf current flows are limited by changes in temperature in at least portions of the positive temperature coefficient of resistance material to denature proteins within the engaged tissue while substantially preventing desiccation of the tissue so that the denatured proteins can cross-link upon thermal relaxation to form a weld.
2. The method of claim 1 , wherein the positive temperature coefficient of resistance material prevents arcs between an energy delivery surface and the tissue.
3. The method of claim 1 , wherein the positive temperature coefficient of resistance material causes substantially uniform denaturation of proteins in the tissue.
4. The method of claim 1 , wherein the positive temperature coefficient of resistance material spatially modulates paths of said Rf current flows within tissue regions in correspondence with the temperature of adjacent positive temperature coefficient of resistance regions.
5. The method of claim 4 , wherein the positive temperature coefficient of resistance material modulates the current level in said paths in correspondence with the temperature of adjacent positive temperature coefficient of resistance regions.
6. The method of claim 4 , wherein the positive temperature coefficient of resistance material creates a substantially uniform temperature in the tissue for a selected time interval.
7. A bi-polar Rf electrosurgical method for welding tissue, the method comprising:
engaging tissue between first and second opposing jaws having bi-polar Rf energy delivery surfaces, said surfaces including at least one positive temperature coefficient of resistance positive temperature coefficient of resistance body having a switching temperature; and
delivering bi-polar Rf current between the energy delivery surfaces to ohmicly heat tissue; wherein the positive temperature coefficient of resistance body is utilized to i) limit Rf current flow to tissue adjacent regions of the positive temperature coefficient of resistance body that reach the switching temperature and ii) allow Rf current flow within tissue adjacent regions of the positive temperature coefficient of resistance body that thermally relax from said switching temperature.
8. The method of claim 7 , wherein the bi-polar current is delivered with substantially no arcs between an energy delivery surface and the tissue.
9. The method of claim 7 , wherein the tissue is heated without substantial desiccation.
10. The method of claim 7 , further comprising:
causing substantially uniform denaturation of proteins in the tissue.