HF-SURGERY DEVICE AND METHOD FOR AN HF-SURGERY DEVICE

• US 20100217259A1
• Filed: 05/14/2008
• Published: 08/26/2010
• Est. Priority Date: 10/24/2007
• Status: Active Grant

• Current Assignee: Celon AG Medical Instruments
• Original Assignee: Celon AG Medical Instruments
• Inventors: Strauss, Timo
• Granted Patent: US 8,864,756 B2
• Time in Patent Office: Days
• US Class Current: 606/38
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 18/1477 Needle-like probes
• CPC Class Codes: A61B 18/16 Indifferent or passive electrodes for grounding
• CPC Class Codes: A61B 2018/00607 Coagulation and cutting with the same instrument
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00875 Resistance or impedance

Abstract

The invention concerns an HF-surgery device for cutting and/or coagulating biological tissue and a method for same, which in operation monitors the patient skin contact of a connected neutral electrode having at least two separate contact surfaces. The HF-surgery device includes at least one parallel resonant circuit arranged in a patient circuit, at least one measurement energy source arranged in a measurement circuit galvanically separated from the patient circuit for producing a measurement voltage/current acting between the contact surfaces of the neutral electrode, and at least one measuring and computing unit which in operation determines by means of the measurement voltage/current a tissue impedance which is representative of the patient skin contact and which acts between the contact surfaces. An HF-current flows in the patient circuit which is closed in the cutting or coagulation operation and the measurement voltage which is independent of the HF-current can be produced in the measurement circuit. To provide an improved HF-surgery device it is provided according to the invention that the frequency of the measurement voltage source is substantially equal to a resonance frequency of the parallel resonant circuit.

Claims

1. An HF-surgery device for cutting and/or coagulating biological tissue, which in operation monitors the patient skin contact of a connected neutral electrode having at least two separate contact surfaces, including at least one parallel resonant circuit arranged in a patient circuit, at least one measurement energy source arranged in a measurement circuit galvanically separated from the patient circuit for producing a measurement voltage/current acting between the contact surfaces of the neutral electrode, and at least one measuring and computing unit which in operation determines by means of the measurement voltage/current a tissue impedance which is representative of the patient skin contact and which acts between the contact surfaces, wherein an HF-current flows in the patient circuit which is closed in the cutting or coagulation operation and 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.

2. An HF-surgery device according to claim 1, wherein the HF-surgery device has a transformer galvanically separating the measurement circuit from the patient circuit and the parallel resonant circuit includes a secondary side of the transformer, that is associated with the patient circuit, and at least one anti-faradisation capacitor.

3. An HF-surgery device according to claim 1, wherein the HF-surgery device has in the measurement circuit at least one measurement resistor connected in series with the transformer.

4. An HF-surgery device according to claim 1, 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.

5. An HF-surgery device according to claim 1, wherein the HF-surgery device has at least one filter unit for filtering the measurement current and/or the measurement voltage.

12. An HF-surgery device according to claim 2, wherein the HF-surgery device has in the measurement circuit at least one measurement resistor connected in series with the transformer.

6. An method for an HF-surgery device for monitoring the skin contact of a neutral electrode which is electrically connected to the HF-surgery device and which has at least two separate contact surfaces, in which a measurement voltage/current is produced in a measurement circuit, the measurement voltage/current is transferred from the measurement circuit into a galvanically separated patient circuit in which an HF-current flows in operation in the closed condition, the measurement voltage/current in the patient circuit is passed by way of a parallel resonant circuit and the tissue between the contact surfaces and the tissue impedance representative of the patient skin contact is determined by means of the measurement voltage/current, wherein the frequency of the measurement voltage/current is set substantially to a resonance frequency of the parallel resonant circuit.

7. A method according to claim 6, wherein a total voltage across a measurement energy source and a partial voltage across a series-connected measurement resistor are measured to determine the tissue impedance in the measurement circuit.

8. A method according to claim 7, wherein the total voltage and/or the partial voltage are filtered prior to the measurement operation.

9. A method according to claim 6, wherein a phase shift angle between the measurement current and the measurement voltage or between proportional values to the measurement current and the measurement voltage is determined.

10. A method according to claim 6, wherein an effective resistance of the tissue between the contact surfaces, representative of the patient skin contact of the neutral electrode, is determined from the impedance and the phase shift angle.

11. A method according to claim 10, wherein, in dependence on the value of the effective resistance, an operational signal or a warning signal is delivered and/or the patient circuit of the HF-surgery device is interrupted.