Surgery – Instruments – Electrical application
Reexamination Certificate
1999-11-06
2001-04-10
Cohen, Lee (Department: 3739)
Surgery
Instruments
Electrical application
C607S152000
Reexamination Certificate
active
06214000
ABSTRACT:
INTRODUCTION
This invention relates to electrosurgery and more particularly to reusable return electrodes that are adapted for providing effective and safe electrosurgical energy return without conducting or dielectric gels or polymers.
BACKGROUND OF THE INVENTION
As is known to those skilled in the art, modern surgical techniques typically employ radio frequency (RF) cautery to cut tissue and coagulate bleeding encountered in performing surgical procedures. For historical perspective and details of such techniques, reference is made to U.S. Pat. No. 4,936,842.
As is known to those skilled in the medical arts, electro-surgery is widely used and offers many advantages including that of the use of a single surgical tool for both cutting and coagulation. Every electrosurgical generator system, to be fully used, must have an active electrode which is applied by the surgeon to the patient at the surgical site to perform surgery and a return path from the patient back to the generator. The active electrode at the point of contact with the patient must be small in size to produce a high current density in order to produce a surgical effect of cutting or coagulating tissue. The return electrode, which carries the same current as the active electrode, must be large enough in effective surface area at the point of communication with the patient such that a low density current flows from the patient to the return electrode. If a relative high current density is produced at the return electrode, the temperature of the patient's skin and tissue will rise in this area and can result in an undesirable patient burn.
In 1985, the Emergency Care Research Institute, a well known medical testing agency published the results of testing they had conducted on electrosurgical return electrode site burns, stating that the heating of body tissue to the threshold of necrosis occurs when the current density exceeds 100 milliamperes per square centimeter.
The Association for the Advancement of Medical Instrumentation has published standards that require that the maximum patient surface tissue temperature adjacent an electrosurgical return electrode shall not rise more than 6 degrees Celsius under stated test conditions.
Over the past twenty years, industry has developed products in response to the medical need for a safer return electrode in two major ways. First, they went from a small, about 12×7 inches, flat stainless steel plate coated with a conductive gel, that was placed under the patient's buttocks, thigh, shoulders, or any location where gravity can ensure adequate contact area to a flexible foam-backed electrode. These flexible electrodes which are about the same size as the stainless steel plates, are coated with a conductive or dielectric polymer and have an adhesive border on them so they will remain attached to the patient without the aide of gravity and are disposed of after use. By the early 1980's, most hospitals in the United States had switched over to using this type of return electrode. These return electrodes are an improvement over the old-steel plates and resulted in fewer patient return electrode burns but have resulted in additional surgical costs in the United States of several tens of million dollars each year. Even with this improvement, hospitals were still experiencing some patient burns caused by electrodes that would accidentally fall off the patient during surgery.
Subsequently, there was proposed a further improvement, an Electrode Contact Quality Monitoring System that would monitor the contact area of the electrode that is in contact with the patient and turn off the electrosurgical generator whenever there was insufficient contact area. Such circuits are shown, for example, in U.S. Pat. No. 4,231,372. This system has resulted in a much greater reduction in patient return electrode burns but requires a special disposable electrode and an added circuit in the generator which drove the cost per procedure even higher. Today, fifteen years after this system was first introduced, fewer than 40 percent of all the surgical operations performed in the United States use this standard of safety because of its high costs.
BRIEF SUMMARY OF THE INVENTION
The present invention overcomes the problems of the prior art and provides a reusable return electrode that eliminates patient burns without the need for expensive disposable electrodes and monitoring circuits in specialized RF generators.
Briefly, the improved return electrode according to the invention hereof includes an effective surface that is very much larger than any other return electrode that has been disclosed or used in surgery previously. It is so large and so adapted for positioning relative to the body of a patient that it eliminates any need for use of conductive or dielectric jells or polymers. Moreover, the exposed surface is of a material that is readily washable and/or sterilizable so as to facilitate easy and rapid conditioning for repeated reuse. It employs geometries and materials whose resistive and capacitive reactance (impedance) characteristics at typically used electrosurgical frequencies are such that it is self-limiting to limit current densities (and corresponding temperature rises) to safe thresholds should the effective area of the working surface of the electrode be reduced below otherwise desirable levels. Accordingly, the need for the foregoing expensive monitoring circuits in specialized RF generators is eliminated.
OBJECTS AND FEATURES OF THE INVENTION
It is one general object of the invention to improve electrosurgical electrodes.
It is another object of the invention to improve safety of electrosurgical return electrodes.
It is another object of the invention to reduce cost per use for electrosurgical return electrodes.
It is yet a further object of the invention to simplify deployment of electrosurgical return electrodes.
It is still a further object of the invention to facilitate reusability of electrosurgical return electrodes.
Accordingly, in accordance with a feature of the invention, an electrosurgical return electrode is made sufficiently large to present sufficiently low electrical impedance and current densities at typical electrosurgery frequencies used in medical procedures so as to avoid excessive temperature elevation in adjacent patient tissue (i.e., above 6 degrees Celsius) thus avoiding tissue necrosis or other undesired patient trauma.
In accordance with another feature of the invention, the working surface of the electrode (the electrode surface that is in contact with or in close proximity to the patient) is made sufficiently large in area that current flow will not be reduced to a point where it impedes the surgeon's ability to perform surgery at the surgical site.
In accordance with another feature of the invention, in one embodiment, the electrosurgical return electrode is a simple two-layer construction, thus minimizing cost.
In accordance with yet another feature of the invention, in one embodiment controlled electrical conductivity is imparted to one of the layers of material by the inclusion therein of electrically conductive materials such as conductive threads or carbon black, thus limiting conductivity as a function of surface area to levels which, together with capacitive reactance, limit passage of current therethrough to safe values.
In accordance with still another feature of the invention, in another embodiment, a moisture impervious working surface is provided for positioning adjacent an adjoining surface of the body of a patient, thus facilitating cleansing and reuse of the electrosurgical electrode.
In accordance with yet another feature of the invention, the aforementioned moisture impervious working surface is made resistant to normally encountered sterilizing agents, thus further facilitating cleansing and reuse.
In accordance with still one further feature of the invention, in another embodiment, a sleeve is provided for cooperative use with the electrosurgical electrode, thus protecting the electrode from inadvertent damage w
Fleenor Richard P.
Isaacson James D.
Kieda David B.
LandOfFree
Capacitive reusable electrosurgical return electrode does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Capacitive reusable electrosurgical return electrode, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Capacitive reusable electrosurgical return electrode will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2461673