Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical energy applicator
Reexamination Certificate
2001-06-28
2003-07-29
Layno, Carl (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical energy applicator
C607S152000
Reexamination Certificate
active
06600957
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to medical electrodes and, more particularly, to disposable medical electrodes intended for high-energy stimulation (i.e., defibrillation, pacing, and the like) with energy dispersion characteristics.
BACKGROUND OF THE INVENTION
Medical electrodes provide an electrical interface between a patient and monitoring equipment (e.g., an electrocardiograph device) or between a patient and stimulating equipment (e.g., interferential and iontophoresis devices). A specific type of stimulating electrode, used to provide an electrical interface between a patient and defibrillation equipment, must be capable of conducting the high-energy level required for defibrillation. The present invention focuses on high-energy defibrillation and pacing electrodes. The general characteristics of, and distinctions among, monitoring electrodes, general stimulating electrodes, and defibrillation electrodes are outlined below.
A. Monitoring Electrodes
Medical monitoring electrode systems help to obtain desired physiologic responses for the assessment or treatment of diseases and injuries in humans. Monitoring electrodes are used to sense electrical signals, which are then transmitted to electrocardiograph (EKG), electroencephalograph (EEG), and electromyograph (EMG) devices. In general, monitoring electrodes for EKG, EEG, and EMG devices are small, for example on the order of a few square centimeters, because a relatively small contact area with a skin surface is sufficient for reception of electrical signals. Monitoring electrodes need only carry very low electrical signals: on the order of milliamps. In general, monitoring electrodes are not capable of conducting and distributing the high levels of energy required in transcutaneous stimulation and defibrillation electrodes.
Various x-ray transmissive monitoring electrodes have been made to facilitate x-ray examination of a patient without requiring removal of the electrodes or significantly impairing the x-ray image. For example, U.S. Pat. No. 5,265,579 issued to Ferrari discloses an x-ray transparent monitoring electrode and method for making that electrode. The electrode is used for continuous EKG monitoring. See column 1, line 55; column 2, line 8. A thin coating (a few microns in thickness; note that 1 mil=0.001 inches=0.0254 mm=25.4 microns) of silver—silver chloride 17
a,
18
a
is applied, by silk screening, to a sheet of conductive carbon or graphite-filled polymer film that forms the x-ray translucent electrodes 17, 18. See column 3, line 67 to column 4, line 22. The x-ray translucent leads 24 have a tow of carbon fibers whose stripped ends are attached to the electrode using pressure-sensitive tape. See column 5, lines 51-54. The stripped ends are sandwiched between two portions of the tape. See column 7, lines 20-22. FIG. 2 of the patent illustrates that the stripped ends are fanned for attachment. A metallic coating such as nickel is applied to the carbon fibers. See column 6, lines 1-2.
B. Stimulating Electrodes
Stimulating electrodes emit electrical pulses for transcutaneous electrical devices, such as transcutaneous electrical nerve stimulation (TENS), electrical muscle stimulation (EMS), neuromuscular stimulation (NMS), functional electrical stimulation (FES), as well as interferential and iontophoresis therapy. Like monitoring electrodes, medical stimulating electrodes are also used to treat diseases and injuries in humans. Unlike and in contrast to monitoring electrodes, however, stimulation electrodes generally require a larger skin surface contact in order to provide sufficient transcutaneous electrical current to effect a desired physiologic response.
Many devices are designed for lower-energy level stimulation applications alone, such as TENS, EMS, NMS, FES, and interferential and iontophoresis therapy. At least some stimulation electrodes are touted as combination electrodes, which can also function as high-energy level defibrillation electrodes. U.S. Pat. No. 5,824,033 issued to Ferrari and was assigned to Ludlow Corporation. The patent discloses a disposable, multifunction (stimulating or defibrillating), x-ray transmissive electrode capable of conducting energy sufficient for defibrillation and which has improved current density distribution between the electrode and the skin of the patient. See column 2, lines 7-13, of the '033 patent. Ferrari notes that monitoring electrodes are incapable of conducting and distributing the high levels of energy required in transcutaneous stimulation and defibrillation electrodes; thus, an important distinction exists between high-energy stimulating or defibrillating electrodes and lower-energy stimulating or monitoring electrodes. See column 1, lines 29-32.
The disclosed electrode 10 includes an electrically conductive metal—metal chloride (e.g., silver—silver chloride) coating 23 applied to one side of a sheet electrode member 21. See column 3, lines 31-41. Ferrari teaches that the sheet electrode as coated with the electrically conductive metal—metal chloride is not alone capable of transmitting and distributing the high levels of energy encountered in defibrillation over the entire surface of the electrode member. See column 4, line 66 to column 5, line 4. Thus, a current distributing mat 27 is required and is adhered to the opposite side of the sheet electrode member.
The electrode member is a thin, flexible sheet of electrically conductive polymer film having a thickness of two to four mils (0.05 to 0.10 mm). The metal—metal chloride ink is applied in a layer or layers, by silk screening, and is preferably less than ten microns in thickness. See column 4, lines 17-30. The ink may be up to 1 mil (0.0254 mm) thick. The silk screen technique of applying the ink coating facilitates the application of multiple layers having different shapes and edge configurations to achieve a tiered effect. See column 10, lines 10-23.
The outer perimeter of the metal—metal chloride coating is spaced inward from the perimeter of the electrode member and outward from the perimeter of the mat. The metal—metal chloride coating is preferable formed in two layers 23′, 23″, each a few microns in thickness. In addition, the layers are serrated or undulated at their outer perimeter. See column 6, lines 12-45.
The electrical conductors 35 are multi-strand metal wires in which the unsheathed end portions 35
a
are strands that are spread out and fanned as shown in FIGS. 1 and 3 of the patent. The fanned ends are bonded to the surface of the mat by pressing them against the mat and folding the mat over the ends. Specifically, the wires are metallized carbon fiber tows with a metal (e.g., nickel or copper) coating. See column 6, line 46 to column 7, line 40.
C. Defibrillation Electrodes
In a malady called “fibrillation,” the normal contractions of a muscle are replaced by rapid, irregular twitchings of muscular fibers (or fibrils). Fibrillation commonly occurs in the atria or ventricles of the heart muscle; the normal, rhythmical contractions of the heart are replaced by rapid, irregular twitchings of the muscular heart wall. A remedy for fibrillation is called “defibrillation,” a procedure which applies an electric shock to arrest the fibrillation of the cardiac muscle (atrial or ventricular) and restore the normal heart rhythm.
Defibrillation electrodes must be capable of conducting the high-energy level required for defibrillation, up to 360 Joules or more. Defibrillation electrodes must also distribute the energy over a relatively large area of the epidermis of the patient to achieve adequate current density distribution within the atria or ventricles. These characteristics are sufficiently important that governmental regulatory agencies and medical industry groups have established standards for defibrillation electrodes. In particular, the American National Standards Institute (ANSI) standards for defibrillation electrodes have been published by the Association for the Advancement of Medical Instrumentation (AAMI). The ANS
Layno Carl
The Ludlow Company LP
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