Electrosurgical instrument and method of use

Abstract

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 variable resistive body of a positive temperature coefficient material that has a selected decreased electrical conductance at each selected increased temperature thereof over a targeted treatment range. The variable resistive body 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 variable resistive body will focus conductive heating in a selected portion of the engagement surface.

1 . An electrosurgical system, comprising: 
 an instrument body having a proximal end and a working end that has an engagement surface for engaging tissue;    a voltage source that defines a selected power output-impedance curve; and    a variable resistive body carried in the working end that is positioned intermediate said engagement surface and an interior electrode coupled to the voltage source, the variable resistive body having a positive temperature coefficient of resistance that defines a selected temperature-impedance curve;    wherein the temperature-impedance curve and power output-impedance curve are selected to define a selected equilibrium temperature at which the variable resistive body dissipates power output from the voltage source to thereby maintain said equilibrium temperature in the matrix.    
   
   
       2 . The electrosurgical system of  claim 1 , wherein the selected equilibrium temperature is between about 60° C. and 100° C.  
   
   
       3 . The electrosurgical system of  claim 1 , wherein the selected equilibrium temperature is between about 65° C. and 85° C.  
   
   
       4 . An electrosurgical system for controlled application of energy to tissue, comprising: 
 an instrument with a working end that has an engagement surface for engaging tissue;    a voltage source that defines a selected power output-impedance curve; and    a variable resistive body carried in the working end that is positioned intermediate said engagement surface and an interior electrode coupled to the voltage source, the variable resistive body having a positive temperature coefficient of resistance that defines a selected temperature-impedance curve;    wherein the temperature-impedance curve and power output-impedance curve are selected to define a breakdown voltage across a gap of a selected dimension.    
   
   
       5 . An electrosurgical system for controlled application of energy to tissue, comprising: 
 an instrument with a working end that has an engagement surface for engaging tissue;    a voltage source and controller for operatively coupled to the engagement surface;    a variable resistive body carried in the working end that is positioned intermediate said engagement surface and an interior working end electrode coupled to the voltage source, the variable resistive body having a positive temperature coefficient of resistance that defines a selected temperature-impedance curve;    wherein the controller defines means for modulating energy delivery between continuous modes and pulsed modes in response to the impedance of the variable resistive body.    
   
   
       6 . The electrosurgical system of  claim 5 , wherein the controller defines means for modulating energy delivery between continuous modes and pulsed modes in response to the impedance of the combination of variable resistive body and the engaged tissue.  
   
   
       7 . An electrosurgical method, comprising the steps of: 
 providing an instrument with a working end that has an engagement surface for engaging tissue;    providing a voltage source that defines a power output-impedance curve;    providing a variable resistive body that is intermediate the engagement surface and the voltage source, the variable resistive body having a positive temperature coefficient of resistance and thereby defining a selected temperature-impedance curve; and    engaging tissue with the engagement surface and applying electrosurgical energy to the tissue through the variable resistive body;    wherein the selected temperature-impedance curve and power output-impedance curve will define a point at which the variable resistive body dissipates power to maintain a selected temperature in the engaged tissue.    
   
   
       8 . The electrosurgical method of  claim 7 , wherein the selected temperature is between about 60° C. and 100° C.  
   
   
       9 . The electrosurgical method of  claim 7 , wherein the selected temperature is between about 65° C. and 85° C.  
   
   
       10 . An electrosurgical method, comprising the steps of: 
 providing an instrument with a working end that has an engagement surface for engaging tissue;    providing a voltage source operatively coupled to the working end;    providing a variable resistive body within the working end that is intermediate the engagement surface and an interior electrode coupled to the voltage source, the variable resistive body defining a positive temperature coefficient of resistance;    engaging tissue with the engagement surface and applying electrosurgical energy to the tissue through the variable resistive body;    wherein the combined impedance of the tissue and the variable resistive body is such that voltage developed across any gap between the engagement surface and the tissue is less than the breakdown voltage required to cross a selected gap dimension.