Electrosurgical safety circuit

• US 4,200,105 A
• Filed: 05/26/1978
• Issued: 04/29/1980
• Est. Priority Date: 05/26/1978
• Status: Expired due to Term

• Current Assignee: DENTSPLY International Incorporated (Astrazeneca PLC)
• Original Assignee: DENTSPLY International Incorporated (Astrazeneca PLC)
• Inventors: Gonser, Donald I.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US05/909,866
• Time in Patent Office: 704 Days
• Field of Search: 128/303.13, 128/303.14, 128/303.17
• US Class Current: 606/35
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 18/16 Indifferent or passive electrodes for grounding
• CPC Class Codes: H02H 3/05 with means for increasing reliability, e.g. redundancy arrangements for logic circuits H03K19/003
• CPC Class Codes: H02H 3/165 for three-phase systems

Abstract

The invention described herein is a safety circuit for preventing burns to a patient during an electrosurgical operation. In the preferred embodiment, the safety circuit includes a pair of monitors for sensing an imbalance between current flowing to a patient from a radio-frequency generator and current returning to the radio-frequency generator from the patient. When such an imbalance occurs as a result of a stray current path to ground from the patient, an alarm is actuated. In addition, a first alternate current path between chassis ground and the radio-frequency generator and a second alternate current path between system ground and chassis ground are included. A monitor in each alternate current path is designed to actuate an alarm upon detecting a predetermined flow of current. Not only do the monitors provide back-up for each other, but the first alternate path holds near ground potential a dispersive electrode which contacts the patient. Preferably, circuitry is also included for minimizing radio-frequency leakage from the lead carrying current to the patient.

Claims

1. In an electrosurgical device used in an environment having a system ground and having a radio-frequency generator coupled to chassis ground, an active electrode for performing electrosurgery on a patient, an active lead connecting the radio-frequency generator to the active electrode for carrying current from the radio-frequency generator to the active electrode, a dispersive electrode for receiving current which passes from the active lead and through the patient, and a return lead connecting the dispersive electrode to the radio-frequency generator for carrying current from the dispersive electrode back to the radio-frequency generator, an electrosurgical safety circuit, comprising:

a first monitor means for sensing the flow of current in the active lead;

a second monitor means for sensing the flow of current in the return lead;

means responsive to said first monitor means sensing a predetermined greater level of current than said second monitor means for actuating an alarm;

a first low impedance alternate current path coupled between chassis ground and the return lead so as to hold the dispersive electrode near ground potential and to provide a current path from chassis ground to the radio-frequency generator;

a third monitor means for sensing a predetermined current flow in said first alternate current path and for actuating an alarm;

a second alternate current path coupled between system ground and chassis ground so as to establish a return path from system ground to the radio-frequency generator via the first and second alternate current paths; and

a fourth monitor means for sensing a predetermined current flow in said second alternate current path and for actuating an alarm,

whereby radio-frequency current flowing from the patient to a ground results in an alarm generated by said first and second monitor means by virtue of a greater level of current flowing in the active lead than in the return lead irrespective of the operability of said third or fourth monitor means, said first alternate path holds the dispersive electrode near ground potential to prevent the dispersive electrode from floating to a hazardous potential, said third monitor means causes an alarm to be actuated irrespective of the operability of said first, second or fourth monitor means when current flows between chassis ground and the return lead, and said fourth monitor means causes an alarm to be activated irrespective of the operability of said first, second or third monitor means when current flows to system ground.

2. A safety circuit as set forth in claim 1 further including a radio frequency shield around the active lead and a conductor coupling said shield to the return lead, whereby a patient is protected from radio-frequency leakage current from the active lead when the active lead contacts a patient, irrespective of the operability of any or all of said monitor means.