Patent ID: 8221406

Claim:
A high frequency current application apparatus for thermal sclerosing of body tissue, comprising a high frequency generator to which there are connected at least two electrodes of which at least one electrode is to be introduced into body tissue, and a measuring and calculating device which is adapted to ascertain from at least two of the parameters current strength, voltage, phase relationship and active power the impedance or the ohmic resistance between the two electrodes, between which a therapeutic high frequency current respectively flows, or to ascertain same by means of a measuring circuit independent of the therapeutic circuit, and a control device connected to the measuring and calculating device for varying the electrical output power of the high frequency generator, characterised in that the measuring and calculating device is adapted during a high frequency current application to form the first derivative from the characteristic in respect of time of the impedance or the ohmic resistance and to deliver a value dependent on the value of the first derivative, and the control device is adapted to significantly reduce the output power when the signal of the measuring and calculating device indicates that the derivative in respect of time of the impedance or the ohmic resistance exceeds a positive threshold which is characteristic for a threatening tissue desiccation and to restore the output power to the original power again when the signal of the measuring and calculating device indicates that the first derivative of the characteristic in respect of time of the impedance or ohmic resistance exceeds in the direction of positive values a negative threshold which is characteristic of adequate rehydration of the body tissue.