Surgery – Instruments – Electrical application
Reexamination Certificate
2001-01-31
2003-04-08
Cohen, Lee (Department: 3739)
Surgery
Instruments
Electrical application
C606S035000, C607S152000, C128S908000
Reexamination Certificate
active
06544258
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
This invention relates to both electrosurgery and pressure sore pads. More particularly, this invention relates to pressure sore pads that conform to a patient's body to minimize the incidence of decubitus ulcers or pressure sores, while being capable of acting as an effective and safe electrosurgical energy return without the need for conducting or dielectric gels.
2. The Relevant Technology
It is well known in the medical field that patients may develop decubitus ulcers, also known as pressure sores during a prolonged period of immobility. Typically, pressure sores develop in elderly patients who are confined to their beds or otherwise have limited movement. The pressure sores arise in those areas of the patient's body where a prolonged pressure is applied to the patient's tissue, usually over an underlying bony prominence. The prolonged pressure causes ischemic damage and tissue necrosis due to the maintenance of blood pressure above the normal capillary blood pressure of 32 mmHg. Although pressure sores typically occur in those patients who remain in one position for an extended period of time, pressure sores may arise from application of an intense pressure applied over a short period of time, approximately two hours, to a localized area, such as during various surgical procedures.
Generally, to prevent pressure sores the position of the patient is frequently changed to provide relief to the patient's tissue. Additionally, the patient may rest upon one of a variety of mattresses or pads, such as foam pads, sheepskin layers, air filled mattresses, water mattresses, and the like, that reduce the pressure applied to the sensitive areas of the patient's body, such as tissue over an underlying bony prominence. Although it is desirable to reposition the patient every 2 hours, whether or not the patient is lying on a pressure reducing mattress or pad, this is often difficult to perform during various surgical procedures, such as during electrosurgical procedures.
During an electrosurgical procedure, radio frequency (RF) power is employed 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, issued to D'Amelio et al., and entitled “Electrosurgical Probe Apparatus,” the disclosure of which is incorporated by this reference.
As is known to those skilled in the medical arts, electrosurgery is widely used and offers many advantages including the use of a single surgical tool for both cutting and coagulation. Every monopolar electrosurgical generator system, however, must have an active electrode that 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 relatively 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. According to the Emergency Care Research Institute, a well-known medical testing agency, the heating of body tissue to the threshold of necrosis occurs when the current density exceeds 100 milliamperes per square centimeter. Furthermore, the Association for the Advancement of Medical Instrumentation (“AAMI”) has published standards that require that the maximum patient surface tissue temperature adjacent an electrosurgical return electrode shall not rise more than six degrees (6°) 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 placed under the patient's buttocks, thigh, shoulders, or any location where gravity can ensure adequate contact area to a flexible electrode. These flexible electrodes, which are generally 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 aid of gravity. Upon completion of the electrosurgical procedure, these flat flexible electrodes are disposed of. 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 millions of dollars each year. Even with this improvement, hospitals were still experiencing some patient burns caused by electrodes that would accidentally fall off or partially separate from 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, issued to Newton, and entitled “Safety Monitoring Circuit for Electrosurgical Unit,” the disclosure of which is incorporated by this reference. This system has resulted in additional reduction in patient return electrode burns, but requires a special disposable electrode and an added circuit in the generator that drives the cost per procedure even higher. Fifteen years after this system was first introduced, fewer than 40 percent of all the surgical operations performed in the United States use this system because of its high costs.
Although various advances have been made in the electrosurgical arts, as discussed previously, there remains problems associated with preventing the creation of pressure sores during electrosurgical and other surgical procedures.
As briefly mentioned above, typically, a patient is placed upon a pressure reducing mattress or pad during a surgical procedure to reduce or substantially eliminate the forces applied to the sensitive areas of the body where tissue covers underlying bony prominences. One device that may be used to prevent pressure sores in an operational scenario is a foam pad, approximately 3-4 inches in height, which is placed between the operating table and the patient. Although foam pads have many advantages, such as being inexpensive and lightweight, they provide minimal relief to the patient while trapping body heat that may aid in generating pressure sores. Furthermore, by trapping heat the foam pad may aid in increasing the patient's tissue temperature so that during an electrosurgical procedure the tissue temperatures may rise above the six degrees (6°) Celsius temperature rise required by the AAMI. Additionally, foam pads are typically discarded proceeding a surgical procedure since they are difficult to sterilize and clean. Furthermore, the material forming the foam pad may release lethal fumes if ignited during a fire.
An alternate pressure reducing mattress or pad is a layer of sheepskin placed on the operating table. Unfortunately, sheepskin provides poor protection to the patient and does not effectively distribute the patient's pressure throughout the entire surface upon which they are laying. As with the foam pad discussed above, sheepskin is difficult to sterilize and clean following a surgical procedure.
Yet another type of pressure reducing device is the air inflated mattress that includes a vinyl sleeve
Borgmeier Paul R.
Fleenor Richard P.
Isaacson James D.
Kieda David B.
Cohen Lee
Mega-Dyne Medical Products, Inc.
Workman & Nydegger & Seeley
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