Electrosurgical system and method for checking the electrical connection between a neutral electrode and a patient
An electrosurgical system includes a supply apparatus and a neutral electrode. A measurement signal is applied or impressed to the neutral electrode and the resulting impedance actual value (Z ist ) of the neutral electrode current circuit can be determined. The measurement signal (US, IS) is applied at different measurement frequencies (ω) and one impedance actual value (Z ist ) for each measurement frequency (ω) is determined. The impedance actual values characterize a frequency-dependent progress of the impedance and can be checked by a predefined frequency-dependent check criterion. It can thereby be recognized whether the conductive connection between the neutral electrode and the patient complies with the specifications defined by the check criterion. Particularly it is checked whether a sufficiently large area portion of the neutral electrode is conductively connected to the patient, so that excessive current densities in the region of the neutral electrode inside the tissue of the patient can be avoided.
1 . An electrosurgical system ( 15 ), comprising:
a supply apparatus ( 16 ) having a neutral connection ( 18 ); and
a neutral electrode ( 23 ) connected to the neutral connection ( 18 ) that is configured to be electrically conductively connected to a patient via at least one contact surface ( 34 ) thereof;
wherein the supply apparatus ( 16 ) is configured to provide a measurement signal (US, IS) solely to the neutral connection ( 18 ) at multiple different measurement frequencies (ω) at different times and to determine an impedance actual value (Z ist (ω)) of the neutral electrode ( 23 ) for individual ones of the multiple different measurement frequencies and to check the determined impedance actual values (Z ist (ω)) based on a predefined frequency-dependent check criterion;
wherein the predefined frequency-dependent check criterion is based on a frequency-dependent model impedance ( 39 );
wherein the frequency-dependent model impedance ( 39 ) provides multiple parameters to characterize the neutral electrode ( 23 ) including a spatial dependency of surface portions of the at least one contact surface ( 34 ) of the neutral electrode ( 23 ) that are electrically connected to the patient with sufficiently low resistance or that do not have an electrical connection to the patient with sufficiently low resistance.
2 . The electrosurgical system according to claim 1 , wherein the neutral electrode ( 23 ) comprises an electrically conductive first electrode section ( 30 ) and an electrically conductive second electrode section ( 31 ), wherein electrical potentials of the electrically conductive first and second electrode sections ( 30 , 31 ) are separated from one another.
3 . The electrosurgical system according to claim 2 , wherein the first electrode section ( 30 ) is electrically connected with the neutral connection ( 18 ) via a first conductor ( 25 ) and the second electrode section ( 31 ) is electrically connected with the neutral connection ( 18 ) via a second conductor ( 26 ).
4 . The electrosurgical system according to claim 2 , wherein the first electrode section ( 30 ) and the second electrode section ( 31 ) comprise at least one of areas of equal size and identical geometries.
5 . The electrosurgical system according to claim 2 , wherein the first electrode section ( 30 ) and the second electrode section ( 31 ) are arranged at a distance with respect to one another and symmetrically with respect to a reference plane (B) that extends through the neutral electrode ( 23 ).
6 . The electrosurgical system according to claim 2 , wherein the neutral electrode ( 23 ) comprises an electrically conductive third electrode section ( 32 ), wherein an electrical potential of the third electrode section ( 32 ) is separated from the electrical potentials of the first electrode section ( 30 ) and the second electrode section ( 31 ).
7 . The electrosurgical system according to claim 6 , wherein the third electrode section ( 32 ) surrounds the first electrode section ( 30 ) and the second electrode section ( 31 ).
8 . The electrosurgical system according to claim 1 , wherein the predefined frequency-dependent check criterion is based on at least one predefined frequency-dependent impedance comparison value Z max (ω), Z min (ω)).
9 . The electrosurgical system according to claim 1 , wherein the frequency-dependent model impedance ( 39 ) comprises a Warburg impedance ( 40 ).
10 . The electrosurgical system according to claim 9 , wherein the frequency-dependent model impedance ( 39 ) comprises a parallel connection ( 42 ) in which the Warburg impedance ( 40 ) and a constant phase element ( 41 ) are connected in parallel to one another.
11 . The electrosurgical system according to claim 1 , wherein the supply apparatus ( 16 ) comprises a supply connection ( 17 ) and an instrument ( 19 ) having an operating electrode ( 22 ), wherein the instrument ( 19 ) is electrically connected to the supply connection ( 17 ), wherein at least one of the supply apparatus ( 16 ) and the instrument ( 19 ) are configured to supply at least one of an operating voltage (UA) and an operating current (IA) to the operating electrode ( 22 ).
12 . The electrosurgical system according to claim 11 , wherein the supply apparatus ( 16 ) is configured to apply the measurement signal (US, IS) to the neutral connection ( 18 ) only if no operating voltage (UA) and no operating current (IA) are supplied to the operating electrode ( 22 ).
13 . The electrosurgical system according to claim 11 , wherein the supply apparatus ( 16 ) is configured to set a measurement frequency (ω) of the multiple different measurement frequencies of the measurement signal (US, IS) differently compared to at least one of an operating frequency of the operating voltage (UA) and the operating current (IA), if the measurement signal (US, IS) is provided to the neutral connection ( 18 ) while the operating electrode ( 22 ) is supplied with at least one of an operating voltage (UA) and an operating current (IA).
14 . A method for checking an electrical connection between a neutral electrode ( 23 ) and a patient, wherein the method comprises the following steps:
attaching the neutral electrode ( 23 ) via at least one contact surface ( 34 ) thereof to the patient so that an electrically conductive connection exists between the neutral electrode ( 23 ) and the patient;
applying a measurement signal (US, IS) respectively at multiple different measurement frequencies (ω) solely to the neutral electrode ( 23 ) at different times;
determining an impedance actual value (Z ist (ω)) for individual measurement frequencies (ω) of the multiple different measurement frequencies (ω) of the measurement signal (US, IS);
checking the determined impedance actual values (Z ist (ω)) based on a predefined check criterion, and
initiating a measure depending on a result of the checking of the determined impedance actual values (Z ist (ω));
wherein the predefined check criterion is based on a frequency-dependent model impedance ( 39 );
wherein the frequency-dependent model impedance ( 39 ) provides multiple parameters to characterize the neutral electrode ( 23 ) including a spatial dependency of surface portions of the at least one contact surface ( 34 ) of the neutral electrode ( 23 ) that are electrically connected to the patient with sufficiently low resistance or that do not have an electrical connection to the patient with sufficiently low resistance.
15 . The electrosurgical system according to claim 2 , wherein the supply apparatus ( 16 ) is configured to determine the impedance actual value (Z ist (ω)) of the neutral electrode ( 23 ) between the electrically conductive first electrode section ( 30 ) and the electrically conductive second electrode section ( 31 ) for individual ones of the multiple different measurement frequencies at different times and to determine a frequency-dependent impedance value progression from the impedance actual values for the individual ones of the multiple different measurement frequencies.
16 . The method of claim 14 , wherein applying a measurement signal (US, IS) respectively at multiple different measurement frequencies (ω) to the neutral electrode ( 23 ) comprises varying the measurement frequency of the measurement signal over a period of time, wherein one impedance actual value is determined for each of the measurement frequencies at different times.
17 . The method of claim 16 , further comprising determining a frequency-dependent impedance progression based on the impedance actual values determined for each of the measurement frequencies at the different times.