Patent Application
20080082153
The invention is best understood from the following detailed description when read in connection with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawing are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following figures:
Referring now to the drawing, wherein like reference numbers refer to like elements throughout, the various embodiments of the present invention will be explained in detail.
As illustrated in
In one embodiment, the patient contacting layer 30 comprises a pad of electrically conductive gel in contact with the release cover sheet 40 prior to the use of the electrode. The gel pad may be approximately 65 mm wide and 122 mm long. The gel pad may comprise a skin compatible conductive hydrogel or adhesive having good ability to retain moisture content and adhesive tack. Examples of suitable hydrogels include conductive hydrogels commercially available from the Kendall-LTP division of Tyco Healthcare Group LP, Mansfield, Mass., such as RG-63B conductive hydrogel.
Patient contacting layer 30 is in electrical contact with electrode member 10. In a second embodiment, shown in
An impedance gradient may also be formed with a two-layer conductive coating. A conductive coating, such as silver/silver chloride, may be applied to a bottom face of electrode member 10, with the outer perimeter of the coating spaced inwardly from the perimeter of the electrode member 10. The coating may be formed in two layers each of a few microns in thickness with a first layer having an outer perimeter spaced inwardly of the perimeter of the electrode member 10 and a second layer having an outer perimeter spaced inwardly from the perimeter of the first layer. The two layers may be applied successively on electrode member 10 to allow the first layer to dry before applying the second. The second layer may be applied first with the first layer underlying the second layer. The dual layers provide higher electrical conductivity in the area where the layers overlap, with the conductivity stepping down in the single layer and decreasing to the conductivity of a carbon filled polymer of the electrode member 10 in the area outwardly of the coating. The area where the layers overlap, which corresponds to the area of the first layer, may be made substantially equal to the minimum active electrode area prescribed by ANSI/AAMI. For example, the two layers can each have a thickness of about 3 to 5 microns, with a combined thickness in the area of overlap of about six to ten microns. In addition, the outer perimeter of the two layers are advantageously serrated or undulated. This arrangement further decreases the current density by increasing the effective perimeter of the electrode member and, in combination with the use of disconnected conductive regions 50, minimizes the likelihood of skin burns or irritation.
The electrode member 10 may be formed of a thin, flexible sheet of electrically conductive polymer film such as graphite-filled polyvinyl chloride film. The film may also contain carbon black, acetylene black, or other forms of carbon. An example of carbon filled polymer which can be used is commercially available thin carbon filled polyvinyl chloride (PVC).
A pattern of disconnected regions of electrically conductive material 50 is in contact with the top face of the electrode member 10. The pattern may comprise separated, disconnected regions of an electrically conductive material 50, such as a conductive ink. The regions 50 may have the shape of stripes, filled polygons, unfilled polygons, filled closed curves, concentric closed curves, unfilled closed curves, letters, logos, and any combination thereof. Examples of such patterns of disconnected regions 50 are shown in
The disconnected regions of electrically conductive material may be formed by printing the electrically conducting material in a discontinuous pattern. Alternatively, the regions may be formed by forming a sheet comprising an electrically conductive material and printing a pattern of electrically non-conducting material on the sheet. The regions not covered by the non-conducting material form the disconnected regions of electrically conductive material. The sheet may then be laminated to the top face of the electrode member 10 to complete the formation of regions 50. As a specific example, forming the sheet of electrically conductive material may comprise flood-coating the top face of electrode member 10 with an electrically conductive fluid, such as a silver/silver chloride ink, and allowing the fluid to dry or otherwise solidify.
An electrical connector 88 is situated in direct contact with the disconnected pattern of electrically conducting material 50. The electrical connector 88 is connected to a conductor which together function to convey electrical signals between the electrode and an apparatus (not shown) such as a defibrillator or electrocardiograph. In the embodiment shown in
The connector 88 is kept in physical and electrical contact with the disconnected conductive regions 50, and hence with the electrode member 10, by sandwiching it with a cover sheet 70 which is adhered to the top face of the electrode member 10 with an adhesive layer 34. The adhesive layer 34 may be a pressure sensitive adhesive. The cover sheet 70 may be a continuous foam backing sheet without any openings and having a thickness of about 1 mm. In the embodiment shown in
In the embodiment shown in
Within the pattern of disconnected regions 50, the shapes and sizes of regions and spaces between the regions may be chosen so as to achieve a distribution of electrical current in the electrode which optimizes the electrode impedance for a given application, while also minimizing the effects of high current concentration in some regions of the electrode which could result in patient skin irritation and burning. By way of example, if the sizes of each of the disconnected regions 50 are too small, or their density (number of regions per unit area) is too small, the electrical impedance of the electrode may be unacceptably high due to insufficient metal-to-metal contact between the connector 88 and the disconnected conductive regions 50. Conversely, if the regions 50 are too large or too dense, the electrical impedance of the electrode may result in burning or irritation of the patient's skin. It follows that there is a desired range of patterns (region sizes and densities) that minimize patient skin irritation and burning, while achieving optimal values of overall impedance.
In some applications it is desirable that connector 88 be X-ray transmissive. X-ray transmissive conductors may be formed of metallized carbon fiber tows with an insulating sheath formed of an X-ray transparent material. The carbon fiber tows may be of a size having between 3,000 to 12,000 fibers and metal plated with a metal coating that is about 20% to 50% by weight of the metal plated carbon fiber tow. The higher weight plating on the larger size tows provides improved current carrying capacity for repeated defibrillation pulses. Fiber tows may be made from a polyacrylonitrile precursor and are referred to as pan base carbon fiber and are commercially available from Amoco Performance Products, Inc., Atlanta, Ga. Since the density of the carbon fiber tows is very low as compared to the density of the metal coating, a metal coating of 30% to 40% by weight of the metal plated carbon fiber tow is very thin and is X-ray transparent. The metal coating may be nickel which provides good electrical conductivity and corrosion resistance at moderate cost, but other metals such as copper or silver or gold could be used alone or in combination with the nickel coating.
In electrode applications where X-ray translucency of the connector 88 is not required, the connector 88 can be formed of metal such as copper, tin, silver, or gold. For example, a fanned wire, such as that shown in
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.
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.
