GB2374532A

GB2374532A - Electrosurgery apparatus monitoring impedance of split-plate return electrode

Info

Publication number: GB2374532A
Application number: GB0104614A
Authority: GB
Inventors: David Armstrong
Original assignee: DOTTEREL Ltd; Smiths Group PLC; Eschmann Holdings Ltd
Current assignee: DOTTEREL Ltd; Smiths Group PLC; Eschmann Holdings Ltd
Priority date: 2001-02-23
Filing date: 2001-02-23
Publication date: 2002-10-23
Anticipated expiration: 2021-02-23
Also published as: GB0104614D0; GB2374532B

Abstract

An electrosurgery apparatus including an electrosurgery generator 10, a connection 12 for an active surgical electrode 2 and a connection 36 for a return plate electrode 3 of the kind having at least two conductive areas 31, 32 isolated from one another at the plate, the apparatus including means for measuring impedance 20 between said areas and between each of said areas and ground and for providing an output if impedance should fall below a predetermined low value. The apparatus may also provide an output if the impedance between the two active areas 31 32 of the return plate electrode 3 is higher than a predetermined value. Preferably the low or high impedance output signals raise an alarm condition and can cause the generator 10 to be disabled or the active electrode 2 to be disconnected. The two alarm condition may trigger individual warning lights 41 42.

Description

ELECTROSURGERY APPARATUS This invention relates to electrosurgery apparatus.

Electrosurgery or diathermy apparatus is used to cut or coagulate tissue during surgery. A hand-held electrode is used to apply high-frequency current to the surgical site and a large area return electrode adhered to the patient's skin at a different location is used to return the current to the electrosurgery generator. In order to prevent bums where the current flows from the patient to the return electrode, it is important to ensure that this remains in good contact with the skin over a large area to reduce current density to a minimum.

Electrosurgery apparatus often have some provision to detect separation of the return electrode from the skin. Most usually this is achieved by using a return electrode that is divided into at least two separate plates so that the impedance between the plates rises if the plates should separate from the skin. The apparatus monitors this impedance and sounds an alarm if the impedance should fall. This arrangement also reduces the risk that surgery will be started without the return electrode having been applied to the patient.

This arrangement works satisfactorily in most circumstances. However, some surgeons reuse the return electrodes and may stick them to the metal frame of the surgical table between patients. This can electrically bridge the plates of the electrode producing a low impedance and will prevent the electrosurgery unit producing an alarm. Thus, an electrosurgery procedure could be started without a return electrode being connected to the patient. Current applied to the patient may then find an alternative return path with the consequent risk of burns.

It is an object of the present invention to provide alternative electrosurgery apparatus.

According to one aspect of the present invention there is provided electrosurgery apparatus including an electrosurgery generator, a connection for an active surgical electrode and a connection for a return plate electrode of the kind having at least two conductive areas isolated from one another at the plate, the apparatus including means for measuring impedance between said areas and between each of said areas and ground and for providing an output if impedance should fall below a predetermined low value.

The apparatus is preferably arranged to provide an alarm output when the impedance between said areas falls below about 5 ohm. The apparatus is preferably also arranged to produce an output if the impedance between the areas rises above a predetermined high value. The output is preferably supplied to an alarm and to prevent application of power to the active electrode.

Apparatus according to the present invention will now be described, by way of example, with reference to the accompanying drawing, which shows the apparatus schematically.

The apparatus comprises an electrosurgery unit 1, an active, hand-held electrode 2 and a large area return electrode 3.

The unit 1 includes a conventional electrosurgery generator 10, which provides an rf electrosurgery output current to the active electrode 2 via a connection 12 and receives the return current from the return electrode 3 via a connection 13. The return current flows to the generator 10 via an impedance measuring circuit 20, within the unit 1, which will be described in detail later.

The return electrode 3 is in the form of a flexible plate with two conductive areas 31 and 32 on one surface 33. The surface 33 is adhesive so that it can be stuck onto the skin of the patient. The conductive areas 31 and 32 are electrically isolated from one another at the electrode and are connected to the unit 1 via separate wires 34 and 35 within a cable 36.

The impedance measuring circuit 20 measures three different impedances, namely: the impedance between the two areas 31 and 32, the impedance between one area 31 and ground, and the impedance between the other area 32 and ground. The circuit 20 operates in the conventional manner to detect if the impedance between the two areas 31 and 32 exceeds a predetermined high value, which indicates that the two areas are not in good contact with the skin surface. When such a high impedance is detected, the circuit provides an output on line 40 to disable the generator 10 and to an alarm 41. The circuit 20 also detects if the impedance between the two areas 31 and 32, or if the impedance between either of the areas and ground falls below a predetermined low value, typically about 5 ohm. When such a low impedance is detected, the circuit 20 also disables the generator 10 via a signal on line 40 and activates a different alarm 42.

In normal operation, the return electrode 3 is applied to the skin of the patient so that the impedance between the conductive areas 31 and 32 via the skin surface is relatively low but is above the predetermined low value. The unit 1 provides an rf electrosurgery signal to the electrode 2 to enable cutting or coagulation, and the return current flows via the two conductive areas 31 and 32 on the return electrode 3 back to the generator 10.

If the return electrode 3 should lift slightly off the skin, or not be applied correctly to the skin, the impedance between the conductive areas 31 and 32 will rise above the predetermined high value. The circuit 20 will then stop the application of power to the active electrode 2 and will activate the alarm 41 to indicate separation of the electrode from the skin.

If, between patients, the return electrode 3 is stuck to a conductive surface, such as the metal frame of an operating table, and the electrosurgery unit 1 is started without removing the electrode, the impedance between the conductive areas 31 and 32 will be below the predetermined lower value so the circuit 20 will again disable power supply to the active electrode 2 and will activate the alarm 42. Similarly, if the electrode 3 is placed in contact with an object at ground potential so that there is a low impedance between either one of the areas 31 or 32 and ground, this will also be detected by the circuit 20 and prevent supply of power to the active electrode 2.

It can be seen that the present invention provides increased safety to the patient and user compared with previous arrangements.

Claims

CLAIMS:

1. An electrosurgery apparatus including an electrosurgery generator, a connection for an active surgical electrode and a connection for a return plate electrode of the kind having at least two conductive areas isolated from one another at the plate, the apparatus including means for measuring impedance between said areas and between each of said areas and ground and for providing an output if impedance should fall below a predetermined low value.

2. An electrosurgery apparatus according to claim 1 wherein the apparatus is arranged to provide an alarm output when the impedance between said areas falls below about 5 ohm.

3. An electrosurgery apparatus according to claim 1 or claim 2 wherein if the impedance is below the predetermined low value, the means for measuring impedance disables the generator.

4. An electrosurgery apparatus according to any of claims 1 to 3 wherein the apparatus is also arranged to produce an output if the impedance between the areas rises above a predetermined high value.

5. An electrosurgery apparatus according to claim 4 wherein if the impedance between the areas rises above a predetermined high value, the output is supplied to an alarm and to prevent application of power to the active electrode.

6. An electrosurgery apparatus substantially as hereinbefore described with reference to the accompanying drawing.