Abstract:
A medical electrode includes a backing layer having a top face and a bottom face, and a shrinkable layer covering at least a portion of the top face of the backing layer. Shrinkage of the shrinkable layer results in flexing of a portion of the backing layer to aid placement and attachment of the electrode to the patient.

Description:
CLAIM OF PRIORITY 
     This application is a Continuation Application which claims the benefit of and priority to U.S. patent application Ser. No. 11/444,926, filed Jun. 1, 2006 (now U.S. Pat. No. 7,860,546), which is expressly incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention is in the field of medical electrodes, and more particularly to disposable medical electrodes. 
     BACKGROUND OF THE INVENTION 
     Biomedical electrodes useful for patient diagnostic and monitoring applications are well known in the art. In the use of medical electrodes, such as those used to obtain an electrocardiogram trace (ECG), a practitioner attaches one or more electrodes to the patient&#39;s body and connects the electrodes to an electrical, diagnostic, therapeutic, or electrosurgical equipment. Biomedical electrodes comprise a conductive medium contacting the patient&#39;s skin and a means for electrical communication between the conductive medium and the electrical equipment. Biomedical tab electrodes generally comprise an electrically conductive tab, extension, or other protrusion extending from the periphery of the electrode that is attached to the equipment by means of alligator clips or other conductive attachment device. Connecting multiple electrodes to a patient for diagnostic and monitoring applications is a time consuming and repetitive task for the practitioner, requiring a certain degree of dexterity and care in order to make proper use of the electrode and prevent damage is or contamination. 
     SUMMARY OF THE INVENTION 
     These actions can be made easier for the practitioner if the electrode has a tab or other protrusion which, in an unstressed configuration, automatically flexes toward the practitioner and away from the patient&#39;s skin. Such a design is desirable to aid the practitioner in quick and efficient placement of the electrodes. Further, such a design is desirable to aid the practitioner in attaching clips to the electrode. 
     A shrinkable layer is attached to a portion of a backing layer on one side of a medical electrode. Shrinkage of the shrinkable layer causes a portion of the backing layer to flex, or bend, in a direction toward the shrinkable layer. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIGS. 1A ,  1 B, and  1 C show cross sections of one embodiment of an electrode with a self-lifting tab and a composite backing layer. 
         FIGS. 2A and 2B  show plan views of two sides of an embodiment of an electrode with a self-lifting tab. 
         FIGS. 3A and 3B  show a card containing multiple electrodes all having lifted tabs. 
         FIGS. 4A ,  4 B, and  4 C show cross-sections of another embodiment of an electrode with a self-lifting tab. 
         FIG. 5  shows a stack of electrode cards with the tabs lifted on the uppermost cards. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1-5  illustrate embodiments of a medical electrode with a self-lifting tab. The embodiments and  FIGS. 1-5  are to be interpreted as exemplary, not limiting. In accordance with common practice, the figures are not drawn to scale, and corresponding features in  FIGS. 1-5  are indicated by the same guide numbers. 
       FIGS. 4A , B, and C show a cross section of a first embodiment of an electrode with self-lifting tab. Electrically conductive layer  15  and flexible backing layer  5  form a basic electrode structure. Backing layer  5  may be an electrically non-conductive film. It may also be opaque to visible, infra-red and ultra-violet light, which will reduce light-induced electrical noise. A shrinkable layer  35  is applied to a portion of the backing layer  5  that is not in contact with the conductive layer  15 . Shrinkable layer  35  is applied to the top of top face of backing layer  5  during fabrication of the electrode. Shrinkable layer  35  may be in the form of a single contiguous region, as shown in  FIGS. 4A-C , or in the form of a plurality of non-contiguous regions, such as a pattern of disconnected circles. To allow the obtaining of x-ray images of the patient with the electrodes in place, the layers  5 ,  15 , and  35  may be made translucent to x-rays. 
     Once applied, layer  35  may also begin to decrease in volume, or shrink, with or without additional treatment. With layer  35  strongly adhered to flexible backing layer  5 , shrinkage of layer  35  causes backing layer  5  to flex, or bend, in a direction toward shrinkable layer  35  and away from conductive layer  15 . The flexing is shown in  FIG. 4B . The flexing is driven by stress on backing layer  5  arising from the shrinking of shrinkable layer  35 . The flexing makes it easier for a medical practitioner to remove the electrode from a package, attach it to a patient, and electrically attach it to a monitoring device (not shown). 
     Shrinking of shrinkable layer  35  may be brought about by exposure of the layer to light, heat, charged particles, or other forms of energy in any combination. Shrinkage may occur due to the evaporation of a solvent from shrinkable layer  35 . 
     Shrinkable layer  35  may be applied as a liquid, such as a varnish or a polymer solution. A specific example is the ultraviolet-curable varnish designated RC1188 available from Sun Chemical (Parsippany, N.J.) and EICEC027 available from Environmental Inks &amp; Coatings (Morganton, N.C.). Also usable as shrinkable layers are varnishes or other materials which are cured by exposure to an electron beam. Still another category of suitable materials for shrinkable layer  35  is room-temperature vulcanizing (RTV) materials. The amount of bending of base layer  5  may be controlled by varying the thickness (coat weight) of the shrinkable layer  35  and varying the degree of crosslinking in shrinkable layer  35 . Another way to control the amount of bending for a given shrinkable material may be to vary the amount of material dissolved in a solvent—a more dilute varnish or polymer solution may result in a lesser degree of bending. 
     Other examples of shrinkable layer materials useful for shrinkable layer  35  are solid films which may be bonded to backing layer  5  and then treated to induce shrinkage, by heating, for example. The solid film could be a polymer film, containing, for example, polyolefins such as linear, low density polyethylene or polypropylene. For heat shrinking, many polyolefin films have this property. 
     Shrinkable layer  35  could also be deposited from the gas phase using, for example, chemical vapor deposition (CVD). If the deposition is done at elevated temperature, for example, the deposited film may shrink upon returning to room temperature. Metal films may be deposited in this manner. Suitable metals include aluminum, silver, and gold. 
     The upward flexing of a portion of the backing layer shown in  FIG. 4B  facilitates the preparation of the electrode, attachment of the electrode to the patient&#39;s skin, and attachment of electrical conductors to the electrode.  FIG. 4C  shows how an electrical conductor  45 , such as a wire, might be electrically connected to the electrode by means of clip  40  once backing layer  5  has flexed. Conductor  45  may be connected at its other end to a medical instrument, such as an electrocardiograph or a defibrillator (not shown). Clip  40  may be of the “alligator” type, with a spring to hold the clip in good physical and electrical contact with the electrode. In the embodiment of  FIG. 4C , the backing layer  5  is electrically conductive. Clip  40  makes electrical contact with backing layer  5 . An electrically conducting path is thereby established from conductor  45  through, in succession, clip  40 , backing layer  5 , electrically conductive layer  15 , and the patient (not shown). Electrical energy may flow in either direction along this path. 
     Electrically conductive layer  15  may be a conductive gel, such as a skin-compatible hydrogel. One such hydrogel is marketed by Tyco Healthcare Kendall-LTP division, Chicopee, Mass., under the trademark QTrace 5400. When the electrode is attached to a patient, the gel is in contact with the patient&#39;s skin and acts to establish a conducting path for conveying electrical energy between the patient&#39;s body and an apparatus, in either direction. A gel layer also serves to adhere the electrode to the patient&#39;s skin. 
       FIGS. 1A ,  1 B, and  1 C show a cross-section of a second embodiment of an electrode with a self lifting tab. In this embodiment backing layer  5  contains two sublayers,  25  and  30 , bonded together. Alternatively, additional sublayers may also be used. In particular, sublayer  25  may be electrically conductive while sublayer  30  may be electrically insulating. Either or both sublayers may be made opaque to visible, infra-red, and ultraviolet light. Suitable materials for an insulating sublayer  30  include non-conducting plastics. Suitable materials for conductive sublayer  25  include conductive polymers, such as carbon filled or metal filled polymers. 
     As in the first embodiment, a shrinkable layer  35  is applied to the top of backing layer  5 , in contact with the topmost sublayer  30 . As before, shrinking of shrinkable layer  35  causes the multilayer backing layer  5  to flex, as shown in  FIGS. 1B and 1C . 
     Still referring to the embodiment of  FIGS. 1A , B, C, below conducting sublayer  25 , and in contact with it, is a discontinuous pattern  20  of a second electrically conductive material. This material may be a metal/metal chloride coating or ink, such as silver/silver chloride or tin/tin chloride. A metal/metal chloride coating may be applied by silk-screening or by flexographic printing. 
     An electrically conductive gel layer  15 ′ covers and makes contact with both discontinuous pattern  20  and conducting sublayer layer  25 . Discontinuous pattern  20  and gel layer  15 ′ together form a composite electrically conductive layer which provides a conductive path between conductive layer  25  and the patient. In this embodiment, a release layer  10  covers the entire area of gel layer  15  prior to use of the electrode and protects gel layer  15 ′ from contamination. Release layer  10  extends beyond the gel layer  15 ′ on all sides. Suitable materials for release layer  10  include paper or a siliconized polymer such as silicone-coated polyethylene terephthalate (PET). When backing layer  5  flexes, due to the action of shrinkable layer  35 , the separation between the backing layer  5  and the release layer  10  over the region of flexing is increased, as shown in  FIG. 1B , facilitating the removal of the release layer by a practitioner. 
       FIG. 1C  shows the second embodiment of the electrode after the release layer  10  has been removed.  FIG. 1C  also shows an electrical clip  40  and conductor  45  attached to the electrode. In this embodiment one side of the clip makes electrical contact with conducting sublayer  25 . An electrically conducting path is then established through conductor  45 , clip  40 , conductive sublayer  25 , discontinuous conductive pattern  20  and gel layer  15 ′, to the patient. Electrical energy may also be conducted along the same path in reverse order. 
       FIGS. 2A and 2B  are respectively top and bottom plan views of an embodiment of the electrode similar to that shown in  FIGS. 1A ,  1 B, and  1 C, with corresponding reference numbers. Referring to  FIG. 2A , a label  50  may be printed on the top face of top film  30  showing, for example, the logo of the electrode manufacturer. Shrinkable layer  35  is applied to protruding tab  60  shown here as having an essentially semicircular shape. In this embodiment shrinkable layer  35  is shown applied essentially over the entire area of tab  60 , but complete coverage of the tab area is not necessary to achieve sufficient flexing and lifting of the tab  60 . In this embodiment the discontinuous conductive pattern  20  has the form of diagonal stripes, sometimes called “racing stripes”. 
       FIG. 3A  is an exploded perspective view of a set of ten electrodes, with self lifting tabs, each of the type disclosed. The electrodes are all attached to one release layer  10 , as they might be in an electrode set designed for acquiring an ECG trace.  FIG. 3B  is a side view of the card in  FIG. 3A  from the direction indicated by the arrow. As shown in the magnified portion B, each tab  60  of each electrode is in a lifted position, brought about by the shrinkage of shrinkable layer  35 . 
     Electrode cards similar to that shown in  FIG. 3  are often sold stacked together in a package. An example of such a stack is shown in  FIG. 5 . As shown in the magnified portion A, tabs  60  on a card may be held flat or partially flexed by the presence of the cards surrounding it in the stack. Tabs  60  of each electrode on the card at an end (top) of the stack will, however, be maximally flexed through the action of shrinkage of shrinkable layer  35 , thereby facilitating the medical practitioner&#39;s job of peeling each electrode from release layer  10 , attaching each electrode to the patient&#39;s body, and attaching conductor  45  to each electrode. Likewise, tabs  60  will fully lift on any card removed from anywhere in the stack. 
     In an alternate embodiment release layer  10  could be omitted. In one example of this embodiment, a plurality of electrodes could be attached to one another by linear perforated regions and wound into a roll, resembling a rolled sheet of postage stamps. While the electrodes are attached to one another each tab  60  remains coplanar with the remainder of the electrode, held there by the perforated attachments and the surrounding electrodes. The tab will flex when a practitioner separates an electrode from the roll by tearing at the perforations. 
     Shrinkable layer  35  may be applied to existing medical electrodes to create self-lifting tabs on these electrodes. An example of such electrodes is disclosed in FIGS. 1 and 1A of U.S. Pat. No. 5,337,748. 
     Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.