Surgery – Diagnostic testing – Structure of body-contacting electrode or electrode inserted...
Reexamination Certificate
1999-08-19
2001-06-26
Cohen, Lee (Department: 3739)
Surgery
Diagnostic testing
Structure of body-contacting electrode or electrode inserted...
C600S395000, C607S115000, C029S825000
Reexamination Certificate
active
06253099
ABSTRACT:
BACKGROUND
This invention relates generally to electrodes, for example electrocardiograph (ECG) electrodes, and more particularly, to an electrode having a domed contact surface and a method of making and using such domed electrode.
ECG electrodes are well known in the art and are typically placed in direct contact with a patient's skin in the vicinity of the patient's heart. These electrodes can be used to sense the patient's heart functions.
Conventionally, capacitive electrode elements are flat disks which have been stamped or punched from flat sheets of metal. An example of a once commonly used capacitive ECG electrode is described in U.S. Pat. No. 3,882,846 to Fletcher, et al. Fletcher describes an ECG electrode assembly having an insulated electrode element, which is square-shaped, and an impedance transformer contained in a small plastic housing. Fletcher discloses that the electrode element consists of a thin layer of dielectric material deposited by radio frequency sputtering onto a conductive substrate. Also, the impedance transformer includes an operational amplifier with an FET input stage that is configured to provide a low cut-off frequency. Conductive epoxy is used for the wire connection to the substrate and the electrode is attached to the skin with double-sided adhesive tape. The oxide coating can be, among other types listed, tantalum pentoxide and the substrate materials used include silicon.
In conventional stamping processes, the edges of the electrode element typically have no oxide coating. Unless the bare edges are covered prior to use, an ionic condition can occur with the resultant motion artifacts inherent to a conductive electrode element. Stamping can also create significant burs along the edges of the electrode element which could irritate the skin if not removed. Fletcher accounts for both problems by using an insulating resin to cover the edges of the electrode element. The insulating material covers the burs and may prevent any contact between the skin and the bare substrate of the electrode element.
However, a disadvantage of such flat electrode elements is that they can lose contact intermittently with the skin. Particularly under conditions of patient movement, such as lying down or rolling over while sleeping, the flat electrode element may tilt with respect to the surface of the skin. Consequently, much or all of the active electrode surface may lose contact with the skin. Moreover, the use of an insulating resin, adhesive disk or other means to seal the edges of the electrode element, to prevent the aforementioned ionic condition from occurring, only compounds the intermittent contact problem. The insulating material used to cover the edges also can greatly reduce the active surface area of the electrode, thus increasing the likelihood of loss of contact with the skin if the electrode is tilted.
U.S. Pat. No. 5,333,616 to Mills discloses a flat, dry, skin-contacting electrode made from stainless steel which is plated with 3 micron zones of titanium nitride, titanium carbide or titanium carbonitride. However, this electrode is conductive rather than capacitive and the plating is primarily for wear resistance and appearance.
Accordingly, there is a need for an electrode having a domed electrode element wherein the edge is fully coated or shielded so as to prevent the occurrence of an ionic condition and also which has no burs or such burs are sealed from contact with the skin. Such electrode should, at the same time, provide improved and continuous contact with the skin even if the electrode is substantially tilted with respect to the skin.
SUMMARY
The invention relates to cardiac function sensing electrodes, such as, for example, an ECG electrode having a domed electrode element. The domed electrode element can be attached to a housing which can contain an interface disk to which the domed electrode connects. An annular groove can be formed in the interface disk in which the outer edge of the domed electrode element can be received. A signal lead wire can have one end attached to the non-skin-contacting side of the dome. Another end of the signal lead wire can be connected to a signal transition printed circuit board and a buffer amplifier circuit, which can also be contained within the housing. The transition board provides a termination point for resistors electrically attached to the lead wire in order to provide protection to the buffer amplifier from the high voltage defibrillation pulse. The buffer amplifier stage presents a very high input impedance to the ECG signals produced by the body, and provides a very low output impedance to the system monitor computer and analog module.
Epoxy resin can be used to affix the domed electrode element to the interface disk and the interface disk to the housing. The epoxy resin can also serve to immobilize the signal lead wire by filling the space between the domed electrode element and the signal transition printed circuit board.
To make a domed electrode element according to the invention, a conductive substrate is formed into a dome-shaped element. Next, an oxide layer is formed on the domed surface of the substrate. The oxide layer is preferably formed over the entire domed surface, including the edges and a small portion of the back, non-skin-contacting, side of the dome.
The convex surface of the domed electrode can be positioned against the skin of a patient and the electrode can be coupled to a cardiac activity monitoring device for sensing arrhythmic cardiac conditions. The electrodes can also be coupled to a defibrillator to provide cardiac sensing capabilities.
Separate energy delivery electrodes can also be positioned adjacent the patient's skin for delivery of therapeutic energy from a defibrillator if desired.
Other details, objects and advantages of the invention will become apparent from the following detailed description and the accompanying drawing figures of certain presently preferred embodiments thereof.
REFERENCES:
patent: 2318207 (1943-05-01), Ellis
patent: 3744482 (1973-07-01), Kaufman et al.
patent: 3883846 (1975-05-01), Fletcher et al.
patent: 4679572 (1987-07-01), Baker, Jr.
patent: 4926879 (1990-05-01), Sevrain et al.
patent: 5333616 (1994-08-01), Mills et al.
patent: 5833714 (1998-11-01), Loeb
patent: 2633439 (1978-01-01), None
patent: 396048 (1990-11-01), None
Kern, Werner, Process for Forming Tantalum Pentoxide Films For Capacitor Applications, Feb., 1996, Pittsburgh, PA.
Hulings Robert J.
Oskin Emil
Quinnell Scott D.
Buchanan Ingersoll P.C.
Cohen Lee
Lifecor, Inc.
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