Title: Medical electrode for preventing the passage of harmful current to a patient
Abstract: A medical electrode designed to prevent the passage of harmful electric current to a patient, thereby preventing tissue damage and electrocution. In the preferred embodiment, the inventive medical electrode is comprised of a proximal end, a distal end, a conductive lead connecting the proximal and distal ends, and a fuse located upon the medical electrode for preventing the passage of harmful electric current to a patient. For additional protection from induction current, the preferred location of the fuse is aft of the conductive lead element of the electrode. While a fuse is used in the preferred embodiment, the fuse could be replaced with a diode or a circuit breaker.
Patent Number: 6,892,086 Issued on 05/10/2005 to Russell
| Inventors:
|
Russell; Michael J. (715 Falcon, Davis, CA 95616)
|
| Appl. No.:
|
982320 |
| Filed:
|
October 17, 2001 |
| Current U.S. Class: |
600/372; 327/328; 600/382; 600/386 |
| Intern'l Class: |
A61B 005/04 |
| Field of Search: |
128/908
606/32,34,41
607/152
600/372,374,378-379,382,386
|
References Cited [Referenced By]
U.S. Patent Documents
| 3603811 | Sep., 1971 | Day et al.
| |
| 3605728 | Sep., 1971 | Ogle.
| |
| 3761769 | Sep., 1973 | Billin.
| |
| 3986495 | Oct., 1976 | Miller.
| |
| 4301801 | Nov., 1981 | Schneiderman.
| |
| 4303073 | Dec., 1981 | Archibald.
| |
| 4363324 | Dec., 1982 | Kusserow.
| |
| 4418692 | Dec., 1983 | Guay.
| |
| 4494541 | Jan., 1985 | Archibald.
| |
| 4520818 | Jun., 1985 | Mickiewicz.
| |
| 4548207 | Oct., 1985 | Reimels.
| |
| 4741344 | May., 1988 | Danby et al.
| |
| 4744369 | May., 1988 | Kroll.
| |
| 4898169 | Feb., 1990 | Norman et al.
| |
| 5085218 | Feb., 1992 | Heil et al.
| |
| 5265607 | Nov., 1993 | Moberg.
| |
| 5433732 | Jul., 1995 | Hirschberg et al.
| |
| 5498242 | Mar., 1996 | Cooke.
| |
| 5511546 | Apr., 1996 | Hon.
| |
| 5626135 | May., 1997 | Sanfilippo.
| |
| 5761019 | Jun., 1998 | Kroll.
| |
| 5785040 | Jul., 1998 | Axelgaard.
| |
| 5833710 | Nov., 1998 | Jacobson.
| |
| 5968086 | Oct., 1999 | Bonner et al.
| |
Other References
Website printout of Medical Devices; Establishment of a Performance Standard
for Electrode Lead Wires and Patient Cables.
Needle package insert from Nicolet Biomedical.
Pub Med Website printout.
Medtronic XOMED.
International Standard Printout.
Nicolet Biomedical 2000 Supplies Catalog.
5 copies of pictures of electrode male adaptor.
Asto-Med, Inc. Grass Instrument Divisions.
|
Primary Examiner: Gibson; Roy D.
Attorney, Agent or Firm: DLA Piper Rudnick Gray Cary US LLP, Smith; Andrew V.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This is a continuation-in-part of U.S. patent application Ser. No. 09/903,778
filed on Jul. 11, 2001 abandoned.
Claims
1. A medical electrode for preventing the passage of harmful current to a patient,
the electrode comprising:
a distal end for connecting to a medical device;
a proximal end including a portion formed in the shaped shape of a contact lens
for connecting to a patient;
a conductive lead connected between the distal and proximal ends; and
a current stoppage means connected to the electrode at a location for preventing
the passage of harmful current to the proximal end coupled to the proximal end
of the electrode aft of the conductive lead.
2. A medical electrode for preventing the passage of harmful current to a patient,
the electrode comprising:
a distal end for connecting to a medical device;
a proximal end for connecting to a patient;
a conductive lead connected between the distal and proximal ends; and
a current stoppage means connected aft of the conductive lead and immediately
adjacent to the proximal end of the electrode, wherein the current stoppage means
is a circuit breaker.
3. A medical side-snap electrode for preventing the passage of harmful current
to a patient, the electrode comprising:
a distal end for connecting to a medical device;
a proximal end for connecting to a patient;
a conductive lead connected between the distal and proximal ends; and
a current stoppage means selected from the group consisting of a fuse or a circuit
breaker,
the current stoppage means coupled to the proximal end of the side-snap electrode
aft of the conductive lead.
4. A medical electrode having separable members for preventing the passage of
harmful current to a patient, the electrode comprising:
a distal end for connecting to a medical device;
a separable structure including top and bottom separable members, the separable
structure being located at a proximal end of said electrode, the separable structure
for connecting to a patient, the top member being positioned atop the bottom member,
the bottom member comprising a pad for contacting a patient's skin, the pad located
adjacent a connector portion, and a current stoppage means located between the
pad and the connector portion.
5. The bottom member as recited in claim 4, wherein the current stoppage means
is selected from the group consisting of a fuse, a diode or a circuit breaker.
6. The bottom member as recited in claim 4, wherein the current stoppage means
is an indicator fuse.
7. The bottom member as recited in claim 4, wherein the connector portion further
comprises a male connector.
Description
TECHNICAL FIELD
This invention relates to medical electrodes, and more particularly, to preventing
the passage of harmful electric current through a medical electrode attached to
a patient.
BACKGROUND
Medical electrodes have been used for years to accomplish various clinical
functions, including nerve stimulation, bio-feedback monitoring, electromyographs,
and electroencephalograph (EEG) tests, to name a few. Medical electrodes are designed
to either send electric current, from an electrical medical device to a living
being, or else receive electric current generated by a living being. Medical electrodes
can be used in both a human patient environment and in a veterinary environment.
Medical electrodes are generally comprised of a proximal end for coupling
to a patient, a distal end for connecting to a medical appliance, such as an EEG
machine, and an elongate wire lead located between the proximal and distal ends,
for receiving or sending electrical current. Of these elements, the proximal end
varies in structure according to the function necessary for a particular medical
procedure. The different structural configurations of the proximal end of exemplary
electrodes, include needle, plate, snap, and corkscrew electrodes, to name a few.
The passage of electrical current through a medical electrode is usually accomplished
according to safe protocols, and generally does not result in any injury to a patient.
However, it has been documented in a number of cases that the passage of current
through a medical electrode connected to a patient has resulted in tissue burns,
and even death by electrocution. The inventor has traced these unfortunate incidents
back to five basic causes: 1) Equipment Failure; 2) Induction Current Phenomena;
3) Defective Machine and/or Defective Grounding of a Machine; 4) Constant DC current;
and 5) Plugging an electrode having a male adaptor distal end directly into an
AC power source.
The following actual case incidents, which are exemplary of each of the causes
listed above, are being submitted here to further inform the reader of the problems
with electrodes presently existing in the medical arts:
Case 1—Equipment Failure
An external stimulator hooked to a patient's ankle with medical electrodes was
used with a computer averager to record somatosensory evoked potentials. The computer
was wired so that it would drive the stimulator and record the averages of the
potentials. During this case, an electro-cautery device was moved near a cord coupled
to the external stimulator. The electro-cautery put out an inductive current that
was strong enough to trigger the stimulator at a rate that was tied to the oscillating
rate of the electro-cautery. This case lasted for eleven hours, at the end of which
time, the stimulating platinum-iridium needle electrode tips were examined. It
was found that enough heat had been generated such that the needles had vaporized
and left a hole in the patient's ankle.
Case 2—Inductive Current Phenomena
A technician had encountered a minor problem with an electrode burn on a patient,
which had occurred during feedback to an electro-cautery machine being used in
an operating room, while performing a neuromonitoring procedure. The technician,
being concerned about the possibility of this happening again, decided to disconnect
the neuromonitoring equipment from the distal end of the electrodes, when she was
not taking actual readings. However, the proximal ends of the electrodes remained
connected to the patient. The technician coiled the disconnected electrode leads
up, and taped them to a bed frame holding the patient, so that they would be out
of the way, and available when she needed them again. A surgeon then used the electro-cautery
equipment again, and this surgeon had a habit of pressing the "on" button of the
electro-cautery probe when it was away from the patient. This particular electro-cautery
probe used a very high voltage current and when the probe was turned on, away from
the patient, the current took the path of least resistance into the coiled wires.
The coiled wires acted as an induction coil receiver and further amplified the
signal causing a significant bum on the patient.
Case 3—Defective Machine and/or Defective Grounding of a Machine
A neuromonitoring technician placed skin surface electrodes on a patient, but
did
not insure that the grounding impedances were low. The technician then recorded
somatosensory evoked potentials for a back surgery. The electro-cautery being used
in the surgery was faulty, and the neuromonitoring equipment allowed current to
pass from the patient to the ground leads and caused bums upon the patient.
Case 4—Constant D.C. Current
An experienced engineer was testing equipment and placed a 1.5 volt D.C. battery
in line with some equipment that he was testing on himself, while he had a pair
of needle electrodes connected to his hand. The engineer became so focused on his
work that he did not bother to remove the electrodes for over two hours. He did
not notice that he was developing an electrolytic bum on this hand from the constant
D.C. current, and now has a permanent scar.
Case 5—Plugging an Electrode Directly into an AC Power Source
In 1985, the first reported incidents of electrocution deaths from the exposed
male connector pins of electrode lead wires being plugged into either AC power
cords or wall outlets were recorded. Between 1985 and 1994, 24 infants or children
received "macro-shock" (large externally applied currents) from medical electrodes,
including five children who died by electrocution. These incidents were documented
in the background section of the Apr. 28, 1997 final rule making for 21 CFR Part
898 entitled: "Medical Devices; Establishment of a Performance Standard for Electrode
Lead Wires and Patient Cables" authored by the United States Food and Drug Administration (FDA).
The previous case examples demonstrate that medical electrode injuries and death
can occur under a variety of real-world conditions. However, to date, the major
focus with regard to medical electrode safety measures has been to deal with the
electrocution problem, because this is the problem that can have the gravest consequences.
As noted in case 5, above, electrocution has resulted from the distal ends of
medical electrodes, which have traditionally had male connector pins, being plugged
into an AC power wall outlets. The solution, thus far, has been to change the distal
end of medical electrodes to female connectors, thereby eliminating the male connector
pins. Due to the fact that medical devices which couple to the electrodes still,
by in large, require a male input, this problem has been solved by providing adaptors
which couple a male pin back onto the female connector, which, in turn, is plugged
into the medical device. These adaptors typically bear warning indicia such as
"Warning: Do Not Use With AC Power Source or Apnea Monitors." However, these adaptors
still convert the female connector end back to a male end, which despite such warnings,
still present a real possibility of causing electrocution from plugging into a
wall outlet.
Moreover, while the addition of adaptors present a better solution to the
problem of electrocution from wall sockets, adaptors do not solve the problem of
tissue bums and electrocution due to induction current phenomena. Induction current
phenomena can be caused by RF leakage from defective medical devices such as an
electro-cautery, or else can be cause from perfectly good devices, such as an MRI,
which, by their nature produce significant amounts of electromagnetic energy. As
noted in case 2, above, this induction current phenomena can occur when the electrode
leads are uncoupled from a medical device, or an AC power source. So far, the answer
to this inductance problem has been to post warnings on electrode packaging of
the type shown on the packaging produced by Astro-Med, Inc., Grass Instrument Division
of West Warwick, R.I. While package warnings certainly help keep medical personnel
alert to the inductance problem, mere warnings are insufficient to stop tissue
all tissue burns and electrocutions from occurring.
Various means have been devised for electrical medical appliances, in general,
to prevent the passage of harmful current causing injuries or death. U.S. Pat.
No. 5,433,732 (Hirschberg et al.) discloses an implantable heart defibrillator
comprising a charging circuit located inside a housing with exterior electrodes
for providing defibrillating current to a patient's heart. A complex current limiter
is provided, exterior to the charging circuit, and in-line with the electrode wires.
The current limiter prevents heart-damaging current from passing through to the
electrode terminus. U.S. Pat. No. 4,418,692 (Guay) discloses an electro-cautery
tip, which has a circuit breaker inside of the tip, for reducing the possibility
of accidental activation of the device, which could damage tissue. Finally, the
following patents disclose various electrical medical devices that have a fused
component located in the circuitry of the device: U.S. Pat. No. 4,520,818 (Mickiewicz),
U.S. Pat. No. 4,548,207 (Reimels), U.S. Pat. No. 4,363,324 (Kusserow), U.S. Pat.
No. 4,494,541 (Archibald), U.S. Pat. No. 4,303,073 (Archibald), U.S. Pat. No. 4,301,801
(Schneiderman), U.S. Pat. No. 4,898,169 (Norman et al.).
While current stoppage means such as circuit breakers, current limiters, and
fuses have been applied in the medical arts with regard to electrical medical devices,
solutions for medical electrodes remain wanting. Many of the case histories noted
previously involved electrical devices that had some type of built-in current stoppage
means, yet harmful current was still passed to the electrodes to injure patients.
Therefore, past solutions, have been inadequate to prevent the problem of bums
and electrocution from harmful current passage through electrodes. Also, to this
day, the international standards for medical electrical equipment (International
Electrical Commission publication 60601-2-401) issue clear warnings regarding the
danger of bums existing at the site of medical electrode input. These standards
clearly show that as of yet, medical electrode design has not provided any closure
to this burning problem.
Therefore, a need exists for a medical electrode that can both prevent
injuries and death due to electrocution, from AC power sources and also injuries
due to the inductance current phenomena.
The foregoing reflects the state of the art of which the inventor is aware, and
is tendered with a view toward discharging the inventors' acknowledged duty of
candor, which may be pertinent to the patentability of the present invention. It
is respectfully stipulated, however, that the foregoing discussion does not teach
or render obvious, singly or when considered in combination, the inventor's claimed invention.
SUMMARY OF THE INVENTION
The present invention is a medical electrode having a current stoppage means
for preventing harmful electric current from passing to a patient. This stoppage
means may be located at any point upon the electrode for purposes of preventing
harmful levels of current passing from an AC power source to a patient. However,
for additionally preventing induction current from passing to a patient, the preferred
location of the current stoppage means is on the proximal end of the electrode,
aft of the wire lead element of the electrode.
In the preferred embodiment, the current stoppage means is a fuse located upon
the medical electrode, the fuse burning through when a certain harmful current
passes into the fuse. However, the fuse could be replaced with a diode, a circuit
breaker, or some other current stoppage means.
Accordingly, the following objects and advantages of the invention apply:
It is an object of this invention to provide a medical electrode that is safer
than medical electrodes currently in existence.
It is an object of this invention to provide a medical electrode that can prevent
the passage of harmful current to a patient.
It is another object of this invention to provide a medical electrode that is
inexpensive to manufacture.
It is another object of this invention to provide a medical electrode that can
prevent the passage of harmful current to a patient, wherein the harmful current
originates from either an AC power source or an inductance current source.
Further objects and advantages of the invention will be brought out in the
following portions of the specification, wherein the detailed description is for
the purpose of fully disclosing preferred embodiments of the invention, without
placing limitations thereon.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood by reference to the following drawings
that are for illustrative purposes only:
FIG. 1 is a graph of variables affecting current density for an EEG needle electrode.
FIG. 2. is a graph of variables affecting current density for a felt
pad bar electrode.
FIG. 3 is a perspective view of the inventive medical electrode, this embodiment
being a needle electrode
FIG. 4 is a perspective view of the inventive medical electrode, again showing
a needle electrode style embodiment, this embodiment clearly showing the current
stoppage means positioned aft of the wire lead.
FIG. 5 is a close-up view of the proximal end of the inventive medical electrode,
again showing a needle electrode style embodiment, this view also showing an indicator
fuse serving as a current stoppage means.
FIG. 6 is a close-up view of the proximal end of the inventive medical electrode
showing a micro-circuit breaker as a current stoppage means.
FIG. 7 is a close-up view of the proximal end of the inventive medical electrode
showing a diode as a current stoppage means.
FIG. 8 is a close-up plan view of the inventive medical electrode, this embodiment
being a plate electrode.
FIG. 9 is a close-up perspective view of the inventive medical electrode, this
embodiment being a corkscrew electrode.
FIG. 10 is a close-up perspective view of the inventive medical electrode, this
embodiment being a strap electrode that is shown here wrapped around a patient's finger.
FIG. 11 is a close-up perspective view of the inventive medical electrode, this
embodiment being an earplug electrode, shown inserted into a patient's ear canal.
FIG. 12 is a close-up perspective view of the inventive medical electrode, this
embodiment being a clip electrode.
FIG. 13 is a close-up perspective view of the inventive medical electrode, this
embodiment being a contact lens electrode.
FIG. 14 is a close-up perspective view of the inventive medical electrode, this
embodiment comprising two separable members.
FIG. 15 is a side view of the embodiment shown in FIG. 14, here shown with the
top and bottom members being separated.
FIG. 16 is a close-up perspective view of the inventive medical electrode, this
embodiment comprising two separable members.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The inventive medical electrode described herein stops the passage of harmful
current to a patient. "Harmful current" as it is used here translates to current
densities that are capable of causing tissue burns or even death by electrocution.
Current density corresponds to the amount of current being applied to a square
centimeter of tissue surface area. The International Electrotechnical Commission
(IEC standard 60601-2-40) has established a current density of 2 mA r.m.s./cm
2
as a safety limit. Current densities beyond this safety limit tend to cause
burns or electrocution.
FIGS. 1 and 2 illustrate graphs showing the relationship of the variables of
electrode surface area, time of applied current, and current frequency (in Hertz)
on current density(mA r.m.s./cm
2). FIG. 1, is illustrative of a needle
electrode, which has a small surface area, and FIG. 2 is for a felt-pad bar electrode
having a large surface area. Each curve on the graphs is representative of current
densities present at different times of applied current at different frequencies.
Lengthier applications of current remain closer to the current density safety limit
of 2 mA r.m.s./cm
2 for similar current frequency, than when compared
to shorter applications. Also comparing the two graphs shows that the needle electrode,
with its smaller surface area operates more closely to the safety limit at similar
current frequencies than the felt pad bar electrode. These graphs also illustrate
that while short applications of current at low frequencies are more likely to
exceed the safety limit and cause burns, that even long applications of low frequencies
can exceed the safety limit and cause bums. The variables of electrode surface
area, time of applied current, and current frequency can be manipulated intentionally,
or unintentionally such that a current density beyond 2 mA r.m.s./cm
2 can
be reached rather easily in a hospital environment and cause bums.
Current sources of particular focus in a hospital environment include direct
current (DC), alternating current (AC), and inductive current. Of these, AC and
inductive current are most commonly present in a patient environment. AC results
from power sources such as medical machinery, and from AC wall outlets. Inductive
current results from stray RF leakage from electromagnetic machinery in perfectly
good condition, such as nuclear magnetic resonance imaging (MRI) machines, but
can come from other electrical sources, such as from a faulty electro-cautery device.
When AC is passed through a medical electrode, it is usually intended for the
AC to pass from say, an electrical medical device. However, AC passage can also
be unintended, such as when a technician accidentally plugs the distal ends of
an electrode into a wall outlet. For the most part, the passage of inductive current
through a medical electrode is unintended, and often results from the wire leads
of the electrode acting as a "pick up" for the inductive current. Both AC and inductive
current can reach harmful levels which, when passed through a medical electrode,
cause current densities which exceed the safety limit and result in tissue burns.
The inventive medical electrode works to prevent harmful current, whether intended,
or unintended, from passing to a patient, and causing tissue bums or electrocution.
This can be accomplished by stopping the flow of current altogether, or through
limiting the current to non-harmful levels. In FIG. 3, the inventive medical electrode
10 is shown, in the form of a needle electrode. Electrode
10 has
a distal end
12, a proximal end
14, and a wire lead
16 extending
between the proximal and distal ends, here shown in a partially coiled configuration.
Wire lead
16 may be of various lengths capable of spanning the distance
between a medical device to which the distal end
12 is removably attached,
and the patient, upon whom the proximal end
14 is connected. Wire lead
16
can be comprised of insulated metallic wire such as 23-30 gage stainless steel
or platinum wire, or another electrically conductive material. Distal end
12
is shown here as being a female connector, because present international standards
require distal end to be a female connector, to avoid accidental plugging into
AC wall outlets. Proximal end
14 is shown here as a needle which is inserted
into the tissue of a patient. Usually a housing
18 is adjacent to proximal
end
14, the housing
18 being used to manipulate proximal end
14
into a connection with the patient's tissue. While here distal end is a female
connector and proximal end is a needle, the invention is not limited to this configuration
and further non-limiting embodiments are discussed, below.
Continuing with FIG. 3, the inventive medical electrode
10 includes
a current stoppage means
20 located thereon for preventing the passage of
harmful current to the tissue of a patient. In FIG. 3, the preferred current stoppage
means
20 is a fuse located in-line with the wire lead
16, about halfway
down its length. A {fraction (1/16)} A (66 mA) "indicator" fuse manufactured by
Littlefuse, Inc. located in-line upon the inventive medical electrode
10
has been found to adequately prevent the passage of harmful current to the tissue
of a patient. This fuse would "blow" prior to harmful current reaching a patient's
tissue. The configuration shown in FIG. 3 would adequately prevent the passage
of harmful AC current should distal end
12 of electrode somehow be accidentally
inserted into a wall outlet, for example.
For preventing the passage of both harmful AC current and harmful inductive current,
the configuration shown in FIG. 4 is preferred. Here, current stoppage means
20
is placed aft of wire lead
16, and connected to proximal end
14 of
electrode
10. Placement of current stoppage means
20 aft of wire
lead
16 eliminates any portion of wire lead from becoming a conduit for
the pick up and passage of harmful inductive current through to proximal end, and
into a patient's tissue. In the prior embodiment
10 shown in FIG. 3, a portion
of wire lead
16 was located aft of current stoppage means
20, which
portion of wire lead
16 could still conceivably pick up harmful inductive
current from an outside RF source, for example, and relay it to a patient's tissue,
through proximal end
14.
FIG. 5 is a close-up view of an indicator fuse, which can act as a current stoppage
means
20 for purposes of the invention. Indicator fuse
20 is positioned
aft of wire lead
16 in the manner described for the embodiment of FIG.
4.
An indicator fuse has been found to be useful in that upon burning out, a technician
can readily view the burned out fuse and know that an electrode has been exposed
to harmful current, and remedial measures can be taken to find the source of the
harmful current for purposes of rendering the patient environment much safer.
FIG. 6 is a close-up view of a micro-circuit breaker acting as a current stoppage
means
20. This configuration is especially useful because it allows expensive
medical electrodes to be salvaged and used again by merely tripping the micro-circuit
breaker
20, unlike most fuses which are typically destroyed (and the electrode
with it) once they blow.
FIG. 7 is a close-up view of a diode acting as a current stoppage means
20.
This diode
20 would severely restrict the passage of current, such that
the current that was ultimately passed to a patient would not be harmful. This
diode embodiment demonstrates that the inventive medical electrode
10 is
not limited to current stoppage means which "stop" harmful current altogether,
such as with fuses and micro-circuit breakers, but also includes current stoppage
means which restrict or reduce harmful levels of current to levels which are not
harmful. A diode which has been found to meet the needs of the invention by blocking
current that exceeds 2 mA r.m.s/cm
2 is the MINI™ Diode manufactured
by Littlefuse, Inc.
FIGS. 8-13 are various views of other types of the inventive medical electrode
10 intended to be exemplary and non-limiting. FIG. 8 is a plate electrode
having an approximately flat proximal end
14, this end having an undersurface
22 for connecting to a patient. Here, the undersurface
22 is shown
placed against a surface
23 (dotted lines), such as a patient's skin. Plate
electrodes are typically disk shaped as shown, but can be rectangular, oval, oblong
or even heart-shaped, to name a few additional configurations. In use, the undersurface
22 is typically adhered to a patient for monitoring purposes, such as in
an EKG procedure. FIG. 9 is an electrode wherein the proximal end
14 is
configured as a corkscrew
24, which is often used for monitoring during
surgical procedures. The corkscrew
24 is designed for insertion into the
tissue of a patient, and upon insertion, housing
18 has ridges
26
for gripping and turning, thereby turning corkscrew deeper into a patient's tissue,
and insuring that the electrode will not fall out of a patient during a procedure.
FIG. 10 is a strap electrode
10, shown wrapped around a patient's finger
27. FIG. 11 is an earplug electrode
10 which is inserted into a patient's
ear canal
28. FIG. 12 is a clip electrode
10. FIG. 13 is a contact
lens electrode
10 for an eye
29 application.
FIGS. 14-15 show an electrode
10 having separable members. These types
of electrodes generally comprise two separable members
30,
32 connectable
by an electrical conducting means such as a snap
34 or connecting pin. FIG.
14 illustrates this embodiment of the inventive medical electrode as having a top
member
30 and a bottom member
32. Top member
30 has a female
portion
36 of snap
34, which is more visible in FIG.
15. Top
member
30 would typically comprise a reusable portion of this embodiment
of a safety electrode. Bottom member
32 is preferably disposable. Bottom
member
32 is shown in FIG. 14 in its normal position for contacting a surface
23, such as a patient's skin. Current stoppage means
20 is preferably
located beneath the male portion
38 of snap
34. Current stoppage
means
20 is preferably comprised of a {fraction (1/16)} A (66 mA) pico fuse
#251 manufactured by Littlefuse, Inc. Male portion
38 of bottom member
32
snaps into female portion
36 of top member
30, with current stoppage
means
20 creating a fusible link between the two members. In this configuration,
fuse
20 of bottom member
32 will blow prior to harmful current reaching
a patient's tissue.
Referring now to FIG. 16, an embodiment of the invention for a side snap
electrode
10 is shown. Unlike the snap electrode of FIGS. 14-15, the side
snap electrode has a pad
40 for contacting a patient's skin, with a bottom
member
32 of snap
34 that is offset to the side of pad
40.
An indicator fuse
20 forms a bridge
42 between snap portion
34
and pad
40, thereby creating a fusible link for preventing the passage of
current from the snap portion
34 to the pad
40. Here, the indicator
fuse
20 can be partially comprised of a heat sensitive dye contained within
the fuse that turns color when the fusible link heats and blows. This configuration
is preferred over the separable embodiment of FIGS. 14-15, if it is desirable to
be able to see that the fuse has blown.
The inventive medical electrode described herein in various embodiments and equivalents
solves a serious problem that has been overlooked by those skilled in the medical
electrode arts. This problem is burning and electrocution caused by the passage
of harmful current through an electrode to the tissue of a patient. Harmful current
can be passed through an electrode whether it is plugged into an electrical medical
device, or unplugged, as in the case of inductive current phenomena. Present methods,
such as fusing electrical medical devices have proven wholly inadequate, as there
are numerous cases of faulty fused machines still passing harmful current through
to electrodes connected to such machines. The solution, as provided by the inventive
medical electrode described herein has been to locate a current stoppage means
such as a fuse, circuit breaker or diode upon the electrode itself. Also, to most
thoroughly prevent any possibility of harmful current from induction, it is preferred
that the current stoppage means be placed aft of the wire lead at the proximal
end of the electrode. This preferred arrangement has proven to effectively prevent
the passage of both harmful AC current from wall outlets and machine sources, as
well as harmful inductive current picked up from RF sources in the medical environment.
Finally although the description above contains many specificities, these
should not be construed as limiting the scope of the invention but as merely providing
illustrations of some of the presently preferred embodiments of this invention.
This invention may be altered and rearranged in numerous ways by one skilled in
the art without departing from the coverage of any patent claims that are supported
by this specification.
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