Arrangement for contact coagulation of biological tissue
An arrangement having a device for providing high-frequency voltage U App for contact coagulation of the biological tissue. The device is equipped to operate with a high voltage that is normally not suitable for contact coagulation, but otherwise used for spark coagulation, for example, more than 400V at the beginning of the contact coagulation. During the operation of the generator the tissue impedance Z is monitored. This can occur by means of continuously measuring the voltage U App of the flowing current I App and the phasing φ between the voltage and the flowing current. Using both, the measuring unit continuously determines the tissue impedance Z . A minimum detector is provided to determine if an impedance minimum Z min has passed through and if such is found, to induce the generator control to reduce the voltage U App delivered by the device to a value that avoids spark generation as well as desiccation of the tissue.
1. An arrangement for contact coagulation of biological tissue having an initial impedance before a coagulation process, the arrangement comprising:
a generator configured to provide high-frequency voltage and deliver high-frequency current;
a generator control, by means of which the high-frequency voltage provided by the generator can be influenced;
an instrument having at least one electrode and being supplied with high-frequency current by the generator;
a measuring unit configured to monitor the tissue impedance; and
a minimum detector configured to detect a minimum of the tissue impedance, the minimum detector being connected with the generator control in order to induce the generator, upon detecting a minimum of the tissue impedance, to thereupon provide a reduced high-frequency voltage,
wherein the generator control has a stored adjustment value representing the reduced high-frequency voltage that is to be applied, and the generator control is equipped to induce the generator when the biological tissue still has its initial impedance at the beginning of the coagulation process to provide voltage higher than that represented by the stored adjustment value.
2. The arrangement of claim 1 , wherein the voltage that is to be applied at the beginning of the coagulation process is at least twice as high as the stored adjustment value.
3. The arrangement of claim 1 , wherein the generator control is equipped to respond to the detection of a first minimum of the tissue impedance by inducing the generator to provide the voltage that is to be applied at a value that is not higher than the stored adjustment value.
4. The arrangement of claim 1 , wherein the generator control is equipped to respond to the detection of a second minimum of the tissue impedance by inducing the generator to provide the voltage that is to be applied at a value that is lower than the stored adjustment value.
5. The arrangement of claim 4 , wherein the generator control is equipped to respond to the detection of a second minimum of the tissue impedance by inducing the generator to provide the voltage that is to be applied at a value that is 10% lower than the previously supplied voltage.
6. The arrangement of claim 4 , wherein the generator control is equipped to terminate the high-frequency application of the generator when the voltage to be applied has reached a value that does not exceed a specified fraction of the stored adjustment value.
7. The arrangement of claim 1 , wherein the stored adjustment value can be specified variable by means of a setting tool.
8. The arrangement of claim 1 , wherein the actual tissue impedance is captured at chronological intervals that are smaller than 0.2 msec, preferably at most 0.1 msec.
9. The arrangement of claim 8 , wherein the measuring unit is equipped to capture the tissue impedance in scanning windows the duration of which is at least as long as one oscillation period of the voltage.
10. The arrangement of claim 9 , wherein the measuring unit is equipped to capture at least one parameter of the voltage that is being applied during the measurement interval, at least one parameter of the flowing current and at least one parameter of the phasing between the voltage applied and the flowing current, and based on such, form a ratio relative to the electric flux density of the phasing between the voltage applied and flowing current that identifies the tissue impedance.
11. The arrangement of claim 8 , wherein the measuring unit is equipped to form a moving average value consisting of the tissue resistance values captured during several chronological intervals.
12. The arrangement of claim 10 , wherein the minimum detector is equipped upon the determination of an increase in the tissue impedance compared with a previously measured tissue impedance to signal reaching and passing a tissue impedance minimum.
13. The arrangement of claim 10 , wherein the minimum detector is equipped to signal upon determination of an increase of the tissue impedance or a smoothed average value of the tissue impedance compared with the lowest tissue impedance of a group of previously measured tissue resistance values, when a tissue impedance minimum has been reached and passed through.
14. The arrangement of claim 1 , wherein the minimum detector is equipped to determine the trend of the progression of the tissue impedance in order to make a prognosis for the next tissue impedance that is to be measured, whereby reaching and passing a tissue impedance minimum will be signaled when the next measured tissue impedance is above the next tissue impedance that is to be measured by a predetermined value.