Impedance mediated control of power delivery for electrosurgery

摘要

A method of controlling electrosurgical power delivery based on a comparison of sensed tissue impedance to various impedance threshold values is provided. Energy is delivered to tissue in a sealing cycle as a series of pulses. An initial pulse has a profile with a preset energy starting value that increases at a ramping rate to a preset end value. Sensed impedance data are monitored throughout each pulse and compared to each of an impedance threshold value for RF setpoint, an impedance threshold value for cumulative time, and an impedance threshold value for energy cutback. Based on sensed impedance during a pulse, the profile of a subsequent pulse can be modified. In the event of a high impedance event that reflects low tissue presence, energy may be cutback. A sealing cycle is stopped when a cumulative amount of time with an impedance value over the impedance cumulative time threshold value reaches a sealing cycle duration limit.

主权项

1. An electrosurgical system comprising:
an RF generator configured to deliver energy through an electrosurgical device to a target tissue in a sealing cycle comprising a series of pulses, the series beginning with an initial pulse having a profile comprising a preset RF level start value that increases at a preset ramping rate to a preset RF end value; and a comparator configured to compare sensed impedance values of the target tissue to each of three preset impedance threshold values, these three preset impedance threshold values comprising: a first impedance threshold value for RF setpoint, a second impedance threshold value for cumulative time, and a third impedance threshold value for energy cutback; wherein the RF generator is further configured to control the delivery of energy during the sealing cycle by responding to the comparison of the sensed impedance values to the first, second and third impedance threshold values, wherein the first impedance threshold value for RF setpoint is the lowest threshold value, the second impedance threshold value for cumulative sealing cycle duration is an intermediate threshold value higher than the first impedance threshold value, and the third impedance threshold value for energy cutback is higher than the second impedance threshold value, and wherein the system is configured to cease the sealing cycle when a cumulative time of tissue showing an impedance value over the second impedance threshold value reaches a preset sealing cycle duration limit.