System And Method For Measuring Initial Tissue Impedance

Abstract

An electrosurgical system and method are disclosed. The system includes an electrosurgical generator adapted to supply electrosurgical energy to tissue. The generator is further adapted to supply an electrical signal having at least one substantially constant value to tissue to determine initial tissue impedance response. The generator includes sensor circuitry adapted to continuously monitor initial tissue impedance response, wherein the initial tissue impedance response includes one of an initial impedance, an impedance drop, an impedance minimum and a first impedance rise. The generator also includes a microprocessor adapted to generate at least one tissue parameter based as a function of the initial impedance, the impedance drop, the impedance minimum and the first impedance rise. The system also includes an electrosurgical instrument including at least one active electrode adapted to apply electrosurgical energy to tissue for treatment.

1 . An electrosurgical system comprising:
 an electrosurgical generator configured to supply electrosurgical energy and an electrical signal having at least one substantially constant value to tissue to determine an initial tissue impedance response;   wherein, in response to application of the electrosurgical energy, the generator controls the tissue impedance response such that the tissue exhibits a non-linear impedance profile having a first phase wherein the initial tissue impedance response drops to reach a minimum impedance, a second phase wherein the tissue impedance rises at a first rate, and a third phase wherein the tissue impedance rises at a second rate, the second rate being less than the first rate and the second rate stabilizing over a period of time.   
     
     
         2 . The electrosurgical system as in  claim 1 , wherein the initial tissue impedance response is used to determine an amount of the electrosurgical energy to the tissue prior to tissue treatment. 
     
     
         3 . The electrosurgical system as in  claim 1 , wherein the electrosurgical generator further includes sensor circuitry adapted to continuously monitor the initial tissue impedance response. 
     
     
         4 . The electrosurgical system as in  claim 1 , wherein the electrosurgical generator further includes a controller adapted to generate at least one tissue treatment parameter as a function of the initial tissue impedance response. 
     
     
         5 . The electrosurgical system as in  claim 4 , wherein the controller is in electrical communication with a memory to store collected impedance and tissue information, the memory including at least a look up table for storing collected impedance values from a plurality of uses of the electrosurgical system. 
     
     
         6 . The electrosurgical system as in  claim 4 , wherein the controller is further adapted to adjust an output of the electrosurgical generator based on the at least one tissue treatment parameter. 
     
     
         7 . The electrosurgical system as in  claim 4 , wherein the at least one tissue treatment parameter is selected from a group consisting of pressure to be applied to tissue, duration of energy application, amount of energy to be supplied, and target impedance trajectory. 
     
     
         8 . The electrosurgical system as in  claim 1 , wherein an electrosurgical instrument is configured to be connected to the electrosurgical generator for transmitting electrosurgical energy to be supplied to the tissue. 
     
     
         9 . The electrosurgical system as in  claim 8 , wherein the electrosurgical instrument is an electrosurgical forceps including at least one shaft member having an end effector assembly disposed at a distal end thereof, the end effector assembly including jaw members movable from a first position in spaced relation relative to one another to at least one subsequent position wherein the jaw members cooperate to grasp the tissue therebetween. 
     
     
         10 . The electrosurgical system as in  claim 9 , wherein the electrosurgical forceps includes a sealing plate attached to each of the jaw members in opposing relation thereto, the sealing plates adapted to connect to the electrosurgical generator such that the sealing plates communicate electrosurgical energy through the tissue held therebetween. 
     
     
         11 . An electrosurgical generator adapted to supply electrosurgical energy to tissue, the electrosurgical generator comprising:
 an RF output stage configured to supply an electrical signal having at least one substantially constant value to tissue to determine an initial tissue impedance response;   sensor circuitry adapted to continuously monitor the initial tissue impedance response; and   a controller adapted to generate at least one tissue treatment parameter as a function of the initial tissue impedance response;   wherein, in response to application of the electrosurgical energy, the generator controls the tissue impedance response such that the tissue exhibits a non-linear impedance profile having a first phase wherein the initial tissue impedance response drops to reach a minimum impedance, a second phase wherein the tissue impedance rises at a first rate, and a third phase wherein the tissue impedance rises at a second rate, the second rate being less than the first rate and the second rate stabilizing over a period of time.   
     
     
         12 . The electrosurgical generator as in  claim 11 , wherein the initial tissue impedance response is used to determine an amount of the electrosurgical energy to the tissue prior to tissue treatment. 
     
     
         13 . The electrosurgical generator as in  claim 11 , wherein the electrosurgical generator is connected to an electrosurgical instrument including at least one active electrode adapted to apply electro surgical energy to the tissue. 
     
     
         14 . The electrosurgical generator as in  claim 11 , wherein the controller is further adapted to adjust an output of the electrosurgical generator based on the at least one tissue treatment parameter. 
     
     
         15 . The electrosurgical generator as in  claim 11 , wherein the at least one tissue treatment parameter is selected from a group consisting of pressure to be applied to tissue, duration of energy application, amount of energy to be supplied, and target impedance trajectory. 
     
     
         16 . The electrosurgical generator as in  claim 11 , wherein the controller is in electrical communication with a memory to continuously store collected impedance and tissue information, the memory including at least a look up table for storing collected impedance values from a plurality of uses of an electrosurgical instrument. 
     
     
         17 . The electrosurgical generator as in  claim 16 , wherein the electrosurgical instrument is an electrosurgical forceps for sealing the tissue. 
     
     
         18 . The electrosurgical generator as in  claim 17 , wherein the electrosurgical forceps includes at least one shaft member having an end effector assembly disposed at a distal end thereof, the end effector assembly including jaw members movable from a first position in spaced relation relative to one another to at least one subsequent position wherein the jaw members cooperate to grasp the tissue therebetween. 
     
     
         19 . The electrosurgical generator as in  claim 18 , wherein the electrosurgical forceps includes a sealing plate attached to each of the jaw members in opposing relation thereto, the sealing plates adapted to connect to the electrosurgical generator such that the sealing plates communicate electrosurgical energy through the tissue held therebetween. 
     
     
         20 . The electrosurgical generator as in  claim 11 , wherein the constant value of the electrical signal is selected from a group consisting of constant voltage, constant current, constant power, and constant energy.