US 3389703 A
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J 1968 B. R. CRISWELL ETAL 3,339,703
DEFIBRILLATOR ELECTRODE OR THE LIKE Filed Feb. 5, 1966 my M O Y TH n NC. r W .P m d M I r n0 m w I ,0 BH ,4 .M I y B United States Patent 3,389,703 EFIBRILLATOR ELECTRODE OR THE LIKE Byron R. Crisweil, Arlington Heights, and Howard Primaclr, Cicero, 111., assignors to Zenith Radio Corporation, Chicago, Ill., a corporation of Delaware Filed Feb. 3, 1966, Ser. No. 524,895 4 Claims. (Cl. 128-404) The present invention relates to a new and improved structure for a defibrillator electrode or the like and, more particularly, is directed to an improved device of the aforesaid type wherein an electrically insulative coating material is applied to all but a contact surface of a substantially rigid metallic base.
A defibrillator electrode is a device which is useful with a second electrode of similar construction for applying a controlled electrical shock of a predetermined waveform, amplitude and duration, developed by an associated energy source, across a human patients heart to terminate fibrillation thereof, that is, a state of arhythmia in the heart muscles which results in irregular and inefiicient operation of the heart, and even death. Conventionally defibrillator electrodes adapted for open chest use are of a paddle-like construction having a conductive face generally contoured to conform to the walls of the heart and a handle extending radially from the face to permit guiding of the paddles into firm contact with opposed walls of the heart, preparatory to delivering the defibrillation impulse. For the safety of those handling the electrodes and to insure that the electrical discharge therebetween only follows a preselected path through the heart, an electrically insulative coating is formed over all but a contact face of the electrode structure. The coating, which may be applied in a variety of ways, must withstand high voltage levels, often exceeding 4000 volts and further must be capable of undergoing repeated sterilization, typically by autoclaving, without separation from the base.
A satisfactory solution of this latter problem has totally eluded the prior art. The severe thermal and hydrolytic stresses of autoclaving have consistently rendered conventional electrodes useless after only a very few sterilization cycles, the coating material lifting and separating from the base with the separation invariably initiating at the edge of the coating adjacent the electrode few and spreading therefrom Numerous and diverse approaches have been proposed in an attempt to solve this difficulty.
For instance, a wide variety of coating materials, numerous application techniques therefor and bonding agents have been employed without success. The surface to be coated has been treated in different manners to improve adherence such as by sandblasting and careful cleaning, but this likewise has not prevented lifting and peeling of the coating particularly at its edge portion. The art has even suggested constructing an electrode by first forming a contoured insulative base and then depositing successive layers of different conductive materials thereon until a contact surface of desired thickness is established. This porcedure is obviously quite expensive and results in an electrode structure which is relatively fragile and prone to breakage.
It is therefore an object of the present invention to provide a new and improved defibrillator electrode or the like having an electrically insulative coating over a major portion thereof which is capable of withstanding repeated autoclaving without separation from a rigid metallic base.
It is a further object of the present invention to provide a structure of the aforementioned type which is economical to manufacture and which is physically sturdy.
Accordingly, the present invention is directed to a defibrillator electrode or the like which is capable of with- "ice standing repeated :autoclaving and which comprises a rigid electrically conductive base having a back portion and a front face portion divided into an inner segment and an outer segment separated one from the other by a groove of a predetermined width and depth. A handle extends from the base and is provided with a hand-grip portion. A continuous adherent electrically insulative coating is provided to cover the back portion, the outer segment of the face portion, and the hand-grip portion of the handle, the coating terminating in the groove between the inner and outer segments. The coating is formed to have a thickness approximating the width of the groove and is captivated by the groove to prevent separation of the insulative coating from the base on autoclaving.
The features of the present invention which are be liev-ed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing, in the several figures of which like reference numerals identify like elements, and in which:
FIGURE 1 is a plan view of a defibrillator electrode constructed in accordance with the present invention;
FIGURE 2 is a side view thereof; and
FIGURE 3 is a fragmentary sectional view illustrating an essential detail of the structure of the invention.
Referring now to FIGURES 1 and 2, there is illustrated in completed form a defibrillator electrode structure having a substantially conventional, paddle-like configuration and bearing an electrically insulative coating over its major portion, as indicated schematically by the stippled portions 10 of the drawing. Specifically, the electrode comprises a shallow circular dish 11 consisting of a rigid metallic base such as stainless steel beneath coating 10. Dish 11 is formed to have a back portion 13 and a front portion divided into an inner segment 14 and an outer segment 16 separated from one another by a circular groove 18, to be considered in detail later herein. Dish 11 is also flared along one sector 12 of its periphery for mating with a preformed slot in a generally cylindrical electrode handle 20. Handle 20 and the electrode dish are securely brazed and the joint carefully finished to eliminate excess material and avoid gaps or pits. As shown, handle 20 which extends radially from dish 11, is provided with a central hand-grip portion and a terminal electrical plug-type connector 21 of reduced crosssection adapted to mate with a conventional type of electrical jack or receptacle, not shown.
Coating 10 is of a suitable composition, preferably a plastic such as polyethylene, polytetrafiuoroethylene, methyl methacrylate, or the like, and may be most satisfactorily applied to dish 11 and handle 20 by spraying or dip coating to develop a continuous, adherent electrically insulative layer thereon, the inner face segment 14 of dish 11 and connector plug 21 being appropriately masked during the coating procedure. The mask may take a variety of forms well understood in the art, but the mask for interior segment 14 of the electrode face is carefully located to lie entirely within the innermost sidewall of groove 18. If desired the unmasked portion of the structure may be subjected to sandblasting to roughen the metallic surfaces and then washed and/or cleaned to improve adherence of the coating material thereto, prior to application of the coating material. It has been found that a coating material, of the fluorocarbon type, such as commercially available from Minnesota Mining and Manufacturing Corporation under the trade designation KEL-F 630 is entirely satisfactory for present purposes, and preferably is spray applied in a plurality of layers, with appropriate intervening drying and curing periods between sprayings, to build up a coating of a desired thickness. Care should be taken during each spray application to uniformly coat the electrode surface including the interior of groove 18. In this regard, it is preferred that groove 18 be virtically directed with respect to the plane formed by the circular periphery of dish 11 so that the applied coating material has direct line of sight access to all portions of the groove. It is of course understood that the cited material and the described method of applying this material are illustrative only and not a limitation on the structure of the present invention.
In accordance with the present invention, and as previously mentioned, inner segment 14 of the electrode face portion is separated from outer segment 16 by a groove of a predetermined width and depth. Preferably this groove traces a circular opening for face 14 which is concentric with the outer periphery of dish 11. Referring now to FIGURE 3, there is shown a cross-sectional view of the electrode dish 11 wherein the thickness of coating 10 with respect to dish 11 has been exaggerated for purposes of illustration. As shown, the width of groove 18 is substantially equal to the thickness of coating 10 and preferably coating 10 entirely fills groove 18. Empirical evaluation has shown that use of groove 18 in the manner described entirely captivates the edge of the coating material to the end that peeling or separation of the coating does not occur even with repeated autoclaving. Lifting of the coating also does not occur at the edge of handle 20 adjacent plug 21 as this coating edge terminates in an edge totally encircling handle 20 with a minimum circumferential length. Under these circumstances, the tensile strength of the coating material together with the adherence of the coating to the handle are entirely adequate to resist peeling on repeated autoclaving.
Thus, this relatively simple expedient which requires only minor changes in a conventional electrode configuration, namely the imposition of a narrow and shallow groove in the electrode face, has been found to provide an entirely satisfactory result, sample paddles having sustained several hundred autoclaving cycles without separa-' tion of the coating material from the metallic base portion.
While a particular embodiment of the invention has been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.
1. A defibrillator electrode or the like capable of withstanding repeated autoclaving, comprising:
4 a rigid electrically conductive base having a back portion and having a front face portion divided into an inner segment and an outer segment separated from said inner segment by a groove of predetermined width and depth; a handle extending from said base and provided with a hand-grip portion;
and a continuous adherent electrically insulative coating covering said back portion, said outer segment of said face portion, and said hand-grip portion of said handle and terminating in said groove between said inner and outer segments, said coating having a thickness approximating the width of said groove, and being captivated by said groove to prevent separation of said insulative coating from said base on autoclaving.
2. The combination according to claim 1 in which said electrode base is of a shallow, circular dish-like configuration and said groove is substantially concentric with the periphery of said base and located on the concave surface of said base and further in which said coating substantially fills said groove.
3. The combination according to claim 2 in which said handle portion is of an elongated at least generally cylindrical configuration and in which said coating is of a sprayed plastic material, and further in which said coating terminates in an edge of minimum circumferential length around said handle, the tensile strength of said coating material as well as the adherence of said coating resisting peeling at said edge on autoclaving.
4. The combination according to claim 2 in which said dish-like electrode base has an outer periphery defining a plane and in which said groove is oriented to open in a direction substantially perpendicular to said plane.
References Cited UNITED STATES PATENTS 2,809,399 10/1957 Mead et al 156-293 XR 2,985,172 5/1961 Jones 128-416 3,151,619 10/1964 Sullivan 128417 3,216,424 11/1965 Chardack 128--418 OTHER REFERENCES Stover, Jr.: U.S. Armed Forces Medical Journal, vol. II, No. 1, January 1951, pp. 57-61.
RICHARD A. GAUDET, Primary Examiner.
0 W. E. KAMM, Examiner.