Patent ID: 8864756
Filing Date: 2014-10-21
Classification: A61B

Abstract:
1. An HF-surgery device configured for at least one of cutting and coagulating of biological tissue, the device is configured to monitor a skin contact to a patient, of a connected neutral electrode having at least two separate contact surfaces, the device including at least one parallel resonant circuit arranged in a patient circuit, wherein at least one measurement energy source is arranged, in a measurement circuit galvanically separated from the patient circuit, and configured for producing at least one of a measurement voltage or current acting between the contact surfaces of the neutral electrode, and the device including at least one measuring and computing unit which is configured to determine, by means of the at least one of measurement voltage or current, as applicable, a tissue impedance, which is representative of the patient skin contact, between the contact surfaces, wherein an HF-current flows in an electrically closed patient circuit, during the cutting or coagulation operation, and whereby the measurement voltage, which is independent of the HF-current, can be produced in the measurement circuit, wherein the frequency of the measurement voltage source is substantially equal to a resonance frequency of the parallel resonant circuit and, wherein the HF-surgery device includes a phase angle measurement unit which measures a phase shift angle between the measurement current and the measurement voltage or between values proportional to the measurement current and the measurement voltage, and the measuring and calculating unit is adapted to determine the effective resistance representative of the patient skin contact between the contact surfaces by means of the phase shift angle.