BACKGROUND In modem surgical practice there are many times when electrosurgery is more preferable than the use of the traditional scalpel. In electrosurgery, it is not a sharp blade that does the cutting, but an intense electrical current. The surgeon directs this current to exactly where it is required by wielding a cutting electrode, which because of its cylindrical shape and the way it is held in the hand is commonly called a "pencil".

By activating controls which change the characteristics of the electrical current being sent to the pencil by an electrosurgical generator, the surgeon can use the pencil either to cut or to coagulate areas of bleeding. This makes electrosurgery particularly convenient when surgery requiring extra control of blood loss is being performed.

As in all situations where electrical current is flowing, in electrosurgery a complete circuit must be provided to and from the current source. In this case, the current that enters the body at the pencil must leave it in another place and return to the generator. It will readily be appreciated that when current enough to deliberately cut is brought to the body in one place, great care must be taken that unintentional damage is not also done at the location where that current is leaving the body. The task of collecting the return current safely is performed by a dispersive electrode.

A dispersive electrode performs this task by providing a large surface area through which the current can pass; the same current which was at cutting intensity when focused at the small surface area at the tip of the pencil is harmless when spread out over the large surface area of the dispersive electrode. The dispersive electrode then returns the current to the electrosurgical generator via a cable connecting the two. There

are two major known types of cable systems used for this purpose. Each of the two types has competing advantages and disadvantages.

The first type uses a cable connected permanently to the dispersive electrode when the latter is being manufactured. Such a cable has a specialized connector at the opposite end to make connection with the generator. This has that advantage that the cable-electrode junction is secure and has a low profile, an important consideration since dispersive electrodes are often positioned so as to be lain upon by the surgical patient. Another advantage is that the cable is sterilized with the dispersive electrode so there is no problem with placing a non-sterilized object near the surgical patient. The disadvantage is that dispersive electrodes are typically one-use-only devices, and the expensive cable and connector must be thrown away with the electrode, adding to the hospital's waste stream.

The second type uses a reusable cable with a clamp at the end opposite the generator connector. The clamp makes releasable contact with the dispersive electrode so that the expensive cable need not be discarded. However, this means the clamp is immediately adjacent to the patient and may cause irritate the skin if lain upon.

Further, the cable must either be sterilized, with the associated extra expense and effort of matching up the proper cable to the respective electrosurgical generator, or the cable must be left unsterilized, with the associated risk of having an unsterilized object adjacent the patient.

Because different practitioners weigh these competing advantages and disadvantages differently, it is not uncommon for a hospital to inventory both type of electrodes adding to the hospital's costs and using valuable storage space. From the foregoing, it is clear that the art requires a connection system for a dispersive electrode which is at the same time convenient, sanitary, and inexpensive.

SUMMARY The present invention solves the problem discussed above by providing a connection system for bioelectrodes having a cable in two sections: a reusable section adapted to be connected to the generator, and a disposable section permanently attached to the bioelectrode. The disposable section is provided in a sanitary

condition so that the objects near the patient's body are clean, but the reusable section does not need to be sanitary; the connection between the two sections is removed from the patient and outside the sterile field.

In preferred embodiments, the disposable section of the cable includes a simple length of insulated wire with no special adapter at the end opposite from the end connected to the bioelectrode. This reduces the cost of the bioelectrode and the attached disposable section to the minimum. In these embodiments, the reusable section of the cable has a sophisticated adapter at the end opposite from the end connected to the electrosurgical generator. The expense of this portion is less important; it is reusable and does not need to be out of service to be resterilized between uses.

There are several additional advantages to the invention. First, it provides for additional manufacturing flexibility in that if a certain length of the disposable section is an issue for a given facility, an electrode can be readily fabricated to a different length by simply adjusting the length cutter. Second, since the bioelectrodes of the invention offer a way to have all the advantages of the two types of bioelectrodes previously used, a hospital can inventory only a single model, reducing its costs and storage requirements. And third, because a bulky connector is not disposed of with the bioelectrode at the end of the surgical procedure, the volume of the hospital's waste stream is reduced.

BRIEF DESCRIPTION OF THE DRAWING The present invention will be further described with reference to the accompanying drawing wherein like reference numerals refer to like parts in the several views, and wherein: Figure 1 is a bottom plan view of a biomedical electrode attached to the disposable section of a cable according to the present invention; Figure 2 is a top view of a reusable section of the cable; and Figure 3 is a side cross-section view of a preferred insulation displacement type connector as taken along section lines 3-3 in Figure 2.

DETAILED DESCRIPTION Referring now to Figure 1, a bottom plan view of a biomedical electrode 10 is illustrated attached to a disposable section 12a of a cable 12. In the depicted embodiment, the bioelectrode 10 has two conductors 14 and 16 to disperse the current during electrosurgery of a wide area. However, it should be noted that bioelectrode and electrosurgical generator designs using only a single conductor are known in the art, and so the presence of two conductors should not be taken as a limitation. Two side-by-side layers of conductive adhesive 18 and 20 cover the conductors 14 and 16 and serve to transduce electrical signals between the body of the patient and the conductors. The two conductors 14 and 16 are adhered to a backing 22 by a layer of skin compatible adhesive 24.

The depicted disposable section 12a has two wires 26a and 28a, each permanently attached to and in electrical contact with one of the conductors 14 and 16 respectively. Each wire 26a and 28a is substantially surrounded by an insulating sheath 30a and 32a respectively, preferably joined together along most of their length.

It will be seen that end 34 of disposable portion 12a opposite from the end connected to the bioelectrode 10 terminates at a simple butt ending without any special adapter being present.

Referring now to Fig. 2, a top view of the reusable section 12b of the cable 12 is depicted. Wires 26b and 28b (seen in Fig. 3) are substantially surrounded by insulating sheaths 30b and 32b. At one end, reusable section 12b terminates in a generator connector 36 adapted to be connected to a medical electronic device such as an electrosurgical generator. At the other end, the reusable section 1 2b has a cable connector 38 adapted to be connected to the disposable section 12a at end 34, end 34 being at a point removed from the bioelectrode 10. Although in the depicted embodiment the generator connector 36 and the cable connector 38 are shown as being separated by a substantial length of wires 26b and 28b, it will be appreciated that no particular length is a requirement. Indeed, the generator connector and the cable connector could be combined in a single housing with no flexible aspect between them and still be within the scope of the invention. As will be discussed in connection with Fig. 3, the cable connector 38 is preferably of the insulation

displacement type and is adapted to place wire 26a in electrical contact with wire 26b and wire 28a in electrical contact with wire 28b by piercing or cutting insulating sheaths 30a and 32a.

Referring now to Fig. 3, a side cross-section view of cable connector 38 is illustrated. Wire 28b enters the rear end 40 of the body 42 of the cable connector 38 and is gripped by a clasp 44 against and in electrical connection with a contact 46.

Contact 46 has a piercing point 48. Cable connector 38 has a cover 50 pivotally mounted to body 42 with a pivot 52. Cover 50 has a passageway 56 sized to allow the insertion of end 34 of disposable portion 12a. Once the end 34 has been inserted into passageway 56, the cover 50 can be pivoted towards the body 42; then the piercing point 48 enters passageway 56 through opening 58 piercing insulating sheath 32a and making contact with wire 28a. The cover 50 is provided with a projection 60 which makes an interference press fit with undercut 62 on the body to latch the cover in the closed position until the surgical procedure is completed and the user releases the latch to free the disposable portion 12a. Once released the biomedical electrode 10 and the disposable portion 1 2a are disposed of together.

Backing Backing 22 can be electrically insulative, and preferably is very conformable to the human body. Many material may be used for this purpose, as will be apparent to those skilled in the art. In one presently preferred embodiment, a closed-cell foam is considered particularly suitable; one such material is commercially available as Volara foam from Voltek, Inc. of Massachusetts. The backing has a thickness ranging from about 0.75 mm (0.03 inch) to about 1.5 mm (0.06 inch), and preferably 1.0 mm (0.04 inch).

Conductors For the depicted application as a dispersive electrode for electrosurgery, the conductors 14 and 16 ofthe bioelectrode 10 is conveniently made from thin aluminum laminated to polyethylene terephthalate (PET) film. The PET film is conveniently approximately 0.05 mm (0.002 inch) thick, and the aluminum

layer conveniently ranges in thickness between about 0.0075 mm (0.0003 inch) to about 0.025 mm (0.001 inch) and preferably 0. 012 mm (0.0005 inch). For diagnostic applications, where non-polarizability is a consideration, the conductive layer is conveniently formed from an electrically non-conductive sheet of plastic coated with silver/silver chloride on the surface adjacent the conductive adhesive.

Such a coating is conveniently accomplished by use of a silver/silver chloride ink; one suitable ink is commercially available as R-301 from Ercon of Waltham, MA.

Alternatively, the conductive layer can be constructed from materials disclosed in PCT publications WO 94/26950 and WO 95/20350. As a further alternative, the conductive layer can be constructed from graphite materials as disclosed in U.S.

Patent 5,215,087.

Conductive adhesive Nonlimiting examples of conductive adhesives useful in connection with the present invention include those compositions disclosed in U.S. Patent Nos.

4,524,087 (Engel); 4,539,996 (Engel); 4,848,353 (Engel); 5,225,473 (Duan); 5,276,079 (Duan et al); 5,338,490 (Dietz et al); 5,362,420 (Itoh et al); 5,385,679 (Uy et al); 5,133,356 (Bryan et al); PCT Publication Nos. WO 95/20634 and WO 94/12585; and PCT Patent Application Serial Nos. US95/17079 (Docket No.

51537PCT6A); US95/16993 (Docket No. 51290PCT8A); and US95/16996 (Docket No. 48381PCT1A).

Skin adhesive Nonlimiting examples of skin adhesives 24 useful in connection with the present invention include acrylate ester adhesives, and more particularly acrylate ester copolymer adhesives. Such adhesives are generally described in U.S. Patent Nos. 2,973,826; Re 24,906; Re 33,353; 3,389,827; 4,112,213; 4,310,509; 4,323,557; 4,732,808; 4,917,928; 4,917,929; and European Patent Publication 0 051 935.

Various modifications and alterations of the present invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not limited to the illustrative embodiments set forth herein.