Multi-element electrode

#This invention is generally directed to a multi-element body electrode for therapeutic and diagnostic applications in medical and veterinary use. The subject invention is related to the copending and commonly assigned applications Ser. No. 711,044, filed Mar. 12, 1985, Ser. No. 783,093 filed Oct. 2, 1985 and Ser. No. 788,216 filed Oct. 16, 1985, the entire disclosures of which are hereby incorporated by reference.

#Numerous types of electrodes have been used in the medical field, for both diagnostic applications such as EKG, EMG and EEG and therapeutic applications such as electrical muscle stimulators, transcutaneous electrical nerve stimulators and iontophoresis drug delivery stimulators. The need to place electrodes at the correct locations has long been recognized as important as well as the need to use electrodes of a correct size. The requirements for correct placement and correct size become even more important for electrical signals that are monophasic or asymmetrical in shape. Two or more electrodes of the same or varying sizes are individually placed on the patient undergoing some form of electrotherapy or diagnostic procedure. In many cases, optimum results are not obtained because the electrodes are not placed on the subject in the correct fashion.

#It is often necessary to establish a localized electrical contact with the external body surface of a living subject. Such contact is typically achieved by the use of electrically conductive electrodes having extended surface areas placed in electrical contact with a desired portion of an external body surface through an intermediate electrode gel, liquid or other preparation designed to ensure good and continuous electrical contact between the living body surface and the conductive electrode surface. Such electrical connections to living subjects are now commonly required for therapeutic and diagnostic applications in both medical and veterinary usage. For example, electro-therapeutic stimulation has now been recognized to promote the healing of bones and other body tissues and/or to have other advantageous physiological effects. Many diagnostic techniques (e.g., electrocardiograms) also require electrical connections to body surfaces so as to monitor electrical body surface potentials.

#FIG. 1 is an exploded perspective view of the various components used in an exemplary embodiment of the adhesively applied multi-element electrode of this invention;

#FIG. 2 is a cross-sectional view of the assembled electrode of FIG. 1;

#FIGS. 3 and 4 are perspective and cross-sectional views of the FIGS. 1 and 2 embodiment in place with the external body surface of a living subject;

#This invention relates to multiple element electrodes that have predetermined relative sizes and locations relative to an aperture in a common substrate which is applied as a single unit, with the aperture conveniently being used to (1) properly locate the electrodes vis-a-vis the desired treatment site and (2) provide access to the treatment site after affixation of the electrode structure. The electrode elements are constructed of a metal foil or film such as aluminum or a conductive film such as silver paint or carbon compound paint. These elements are affixed to an adhesive coated, thin, clear film such as pvc or mylar or are screened on a thin, clear film with adhesive selectively screened on at the same time. The multi-element electrode is produced with an opening or treatment site window to identify correct placement of the multi-electrode unit over the wound or injury. A release liner is provided on the back of the electrode. A two element example of this multi-element electrode that is useful for treating small skin wounds or burns is shown in FIG. 1. A monophasic or asymmetrical wave may be conventionally applied across the two elements correctly by use of different size electrical connectors or snaps that mate with the corresponding wires from a stimulator.

#An important feature of this invention is that one element, identified as the treatment electrode, is maintained at a fixed and optimum distance from the other remote electrode element(s) and at the same time is maintained at a close, but fixed optimum distance from the injury by means of properly locating the treatment site window over the treatment site. Also typically important in such situations is the fact that the surface area of the treatment electrode may be smaller than the surface area of the remote electrode(s) and that a fixed size ratio and relative location is maintained between electrode elements by use of this multi-element electrode. The current density at the injury or treatment site is maintained at a correct higher therapeutic level while the current density under the remote electrode(s) is lower due to the larger surface area of the remote electrode(s). As those in the art will appreciate, when a given current level I passes through a tissue/skin electrode of a given size or area A, the resulting current density (e.g., amperes per square centimeter) is a function of I/A. Thus, for a given current level, the current density can be increased by making the electrode of smaller size or, vice versa, it can be decreased by making the electrode of larger size. And, as will also be appreciated, the distance of a given tissue mass from an electrode (and its relative location with respect to the anode-cathode current path) will also affect the actual current density through the tissue mass (e.g., a wound). In this fashion, the relative sizes and placements of anode and cathode electrodes can be used to determine the effective current density through a wound.

#Typically, for repair of bone fractures, an electrode 103 of relatively large area as shown in FIG. 1, is utilized as an anode while a relatively smaller electrode 102 is applied relatively closer to a desired treatment site marker hole 116 (so as to provide an increased physiologically significant electrical current density thereabout) as a cathode electrode, and connected to the signal source (not shown) by lead wire 50. Electrical signals are then conventionally applied to the electrodes so as to achieve desired treatment effects.