U.S. patent application number 10/067475 was filed with the patent office on 2003-08-07 for medical electrodes.
Invention is credited to Dupelle, Michael R., White, Sheldon S..
Application Number | 20030149462 10/067475 |
Document ID | / |
Family ID | 22076236 |
Filed Date | 2003-08-07 |
United States Patent
Application |
20030149462 |
Kind Code |
A1 |
White, Sheldon S. ; et
al. |
August 7, 2003 |
Medical electrodes
Abstract
Medical electrodes are provided for use in applications that
require long shelf life and/or shelf life at high temperatures.
Some electrodes include high temperature adhesives and/or foams and
an encapsulated electrolyte.
Inventors: |
White, Sheldon S.;
(Brookline, MA) ; Dupelle, Michael R.; (N.
Attleboro, MA) |
Correspondence
Address: |
FISH & RICHARDSON PC
225 FRANKLIN ST
BOSTON
MA
02110
US
|
Family ID: |
22076236 |
Appl. No.: |
10/067475 |
Filed: |
February 4, 2002 |
Current U.S.
Class: |
607/142 |
Current CPC
Class: |
A61N 1/0472 20130101;
A61N 1/0492 20130101; A61N 1/0496 20130101; A61N 1/046
20130101 |
Class at
Publication: |
607/142 |
International
Class: |
A61N 001/04 |
Claims
What is claimed is:
1. A medical electrode comprising: a housing; a conductor and an
electrolyte disposed within the housing; and a high temperature
adhesive that remains capable of adhering the electrode to a
patient's skin after the adhesive has been exposed to temperatures
of up to 200.degree. F. for 4 hours, positioned to adhere a surface
of the electrode to a patient's skin.
2. The electrode of claim 1 wherein said housing comprises a molded
elastomeric member.
3. The electrode of claim 1 further comprising a high temperature
adhesive positioned to secure components of the electrode to each
other.
4. The electrode of claim 1 wherein said electrolyte is
encapsulated.
5. The electrode of claim 1 wherein said high temperature adhesive
is selected from the group consisting of high performance silicone
or acrylic adhesives.
6. The electrode of claim 1 wherein said high temperature adhesive
comprises a high performance silicone transfer adhesive.
7. The electrode of claim 4 wherein said electrolyte is disposed in
breakable capsules.
8. The electrode of claim 7 wherein said conductor comprises a
metal screen positioned between the capsules and the surface that
is adhered to the patient.
9. The electrode of claim 3 wherein the electrode includes a foam
backing joined to the conductor by the high temperature
adhesive.
10. A medical electrode constructed to be applied to a patient's
skin, the electrode comprising: a housing; a conductor within the
housing; and an electrolyte disposed within a chamber that is
constructed to separate the electrolyte from the conductor until
the electrode is to be used; wherein the electrode is constructed
so that said electrolyte, when released from said chamber, flows
freely from the chamber towards the patient's skin without
application of pressure to the chamber.
11. A medical electrode constructed to be applied to a patient's
skin, the electrode comprising: a housing; a conductor within the
housing; an electrolyte disposed within a chamber that is
constructed to separate the electrolyte from the conductor until
the electrode is to be used; and an absorbent pad, positioned
adjacent the conductor, on the side of the conductor that is closer
to the patient's skin when the electrode is in use, and configured
to absorb the electrolyte when it is released from the chamber and
provide a wet layer between the conductor and the patient's
skin.
12. A medical electrode constructed to be applied to a patient's
skin, the electrode comprising: a housing; a conductor within the
housing; and an electrolyte disposed within a chamber that is
constructed to separate the electrolyte from the conductor until
the electrode is to be used, the chamber being formed of a brittle
material that is breakable by the application of a force to the
chamber.
13. The electrode of claim 12 wherein the brittle material is
selected from the group consisting of glass, ceramic, and bakelite
plastics.
14. The electrode of claim 12 wherein the chamber material is
brittle at room temperature.
15. The electrode of claim 10, 11, or 12 wherein the chamber
comprises a glass ampule.
16. The electrode of claim 10, 11 or 12 wherein the electrolyte is
a saline solution.
17. The electrode of claim 10 or 12 further comprising an absorbent
pad, positioned adjacent the conductor on the side of the conductor
that is closer to the patient's skin when the electrode is in
use.
18. The electrode of claim 17 wherein said absorbent pad comprises
an absorbent material selected from the group consisting of
sponges, gauze, carbon fiber mat, cellulose, and natural and
synthetic fibrous batts.
19. The electrode of claim 10, 11 or 12 wherein the conductor
comprises a screen or mesh material.
20. The electrode of claim 10, 11 or 12 wherein the housing
comprises an elastomeric member.
21. The electrode of claim 10, 11 or 12 wherein an edge of the
conductor is molded into a portion of the housing.
22. A medical electrode product comprising: (a) an electrode
comprising: a housing; a conductor within the housing; and an
electrolyte disposed within a chamber that is constructed to
separate the electrolyte from the conductor until the electrode is
to be used; and (b) a package, in which said electrode is disposed
prior to use, including an actuator device constructed to release
said electrolyte from said chamber when the electrode is removed
from the package.
23. The product of claim 22 wherein said chamber comprises a
breakable capsule.
24. The product of claim 23 wherein said breakable capsule
comprises a glass ampule.
25. The product of claim 22 wherein said actuator comprises rolls
through which the electrode is pulled during removal from the
package.
26. The product of claim 25 wherein said rolls are positioned to
rupture said chamber during removal.
27. The product of claim 22 wherein said electrode further
comprises an absorbent pad, positioned adjacent the conductor on
the side of the conductor that is closer to the patient's skin when
the electrode is in use.
28. The product of claim 22 wherein said conductor comprises a
screen or mesh material.
29. A medical electrode constructed to be applied to a patient's
skin, the electrode comprising: a housing; a conductor within the
housing; an electrolyte disposed within a chamber that is
constructed to separate the electrolyte from the conductor until
the electrode is to be used; and an indicator constructed to
provide an indication to the user of whether the electrolyte has
been released from the chamber.
30. The electrode of claim 29 wherein said indication is a visual
and/or audible indication.
31. The electrode of claim 29 wherein said indication comprises a
color change.
32. The electrode of claim 29 said indicator includes a
semiconductor chip configured to store information concerning the
status of the electrolyte and provide this information to a
defibrillator control box upon demand.
33. The electrode of claim 29 or 32 wherein said indicator is
configured to detect the presence of moisture.
34. The electrode of claim 29 wherein the indicator is configured
to detect moisture, and, upon detecting moisture, to send
information via the chip to the defibrillator control box upon
demand.
35. A medical electrode product constructed to be applied to a
patient's skin, the product comprising: (a) an electrode comprising
a housing and a conductor and an electrolyte disposed within the
housing; and (b) a package, within which the electrode is stored
until use, that is pressurized sufficiently to minimize electrolyte
loss through evaporation.
36. A medical electrode product constructed to be applied to a
patient's skin, the product comprising: (a) an electrode comprising
a housing and a conductor and an electrolyte disposed within the
housing; and (b) a cover disposed over the electrolyte in sealing
engagement, the cover defining a region adjacent the electrolyte
that is pressurized sufficiently to minimize electrolyte loss
through evaporation.
37. The medical electrode product of claim 35 or 36 wherein the
package or region is pressurized to a pressure that is at least 25%
above the ambient pressure at the time of sealing.
38. A coupling device for use with a defibrillator paddle, the
coupling device comprising: a housing; a conductor within the
housing; an electrolyte disposed within a chamber that is
constructed to separate the electrolyte from the conductor until
the electrode is to be used; and a mounting device constructed to
allow the coupling device to be removably mounted on the
defibrillator paddle.
39. The coupling device of claim 38 wherein the mounting device
comprises a clip.
40. The coupling device of claim 38 wherein the mounting device
comprises an adhesive.
41. The coupling device of claim 38 wherein the coupling device is
configured to provide a conductive path from the defibrillator
paddle to a patient's skin.
42. The coupling device of claim 38 wherein the chamber comprises a
breakable capsule.
43. The coupling device of claim 42 wherein the chamber comprises a
glass ampule.
44. The coupling device of claim 42 wherein the capsule is
configured to be broken by applying pressure to the coupling
device.
45. The coupling device of claim 38 further comprising an absorbent
pad, positioned adjacent the conductor on the side of the conductor
that is opposite the defibrillator paddle when the coupling device
is in use.
46. The coupling device of claim 38 wherein the conductor comprises
a screen or mesh material.
47. The coupling device of claim 42 wherein the coupling device
further comprises a screen configured to prevent fragments of the
capsules from contacting a patient's skin when the capsules are
broken.
48. A medical electrode constructed to be applied to a patient's
skin, the electrode comprising: an elastomeric housing, configured
to conform to the body contours of the patient; a conductor within
the housing; and, within the housing, an electrolyte disposed
within a chamber that is constructed to separate the electrolyte
from the conductor until the electrode is to be used.
49. The medical electrode of claim 10, 11, 12 or 48, further
comprising a high temperature adhesive that remains capable of
adhering the electrode to a patient's skin after the adhesive has
been exposed to temperatures of up to 200.degree. F. for 4 hours,
positioned to adhere a surface of the electrode to a patient's
skin.
50. The medical electrode of claim 48 wherein the housing is a
unitary, integrally molded part.
51. The medical electrode of claim 48 wherein the housing comprises
a thermoplastic elastomer.
Description
TECHNICAL FIELD
[0001] This invention relates to medical electrodes, e.g.,
electrodes for use with external defibrillators.
BACKGROUND
[0002] Medical electrodes for use in procedures such as
defibrillation typically include a conductor formed of metal, or
formed of a conductive ink printed on a substrate, and a liquid or
solid electrically conductive gel covering the conductor. The
electrolyte is used to provide coupling between the conductor and
the patient's skin. These electrodes often also include a foam
backing layer, to which the conductor is adhered. An adhesive layer
is used to adhere the electrodes to a patient. Such electrodes can
be rendered unusable during storage by corrosion of the conductor
and/or evaporation or degradation of the electrolyte. If the
electrode is unusable at the time that the a caregiver needs to
defibrillate a patient, the patient's life can be jeopardized or
lost due to delay in locating a usable electrode.
SUMMARY
[0003] Public access defibrillators (PADs) and other types of
automated external defibrillators (AEDs) are designed to be used by
lay caregivers and/or emergency workers such as EMTs and
firefighters to resuscitate victims of cardiac distress. PADs and
AEDs are thus often stored in public buildings and emergency
vehicles. As AEDs gain widespread acceptance for use by the general
public, they will most likely also be stored in areas where they
will be accessible to individuals who are in danger of cardiac
distress, e.g., in the trunk of a car. Other types of external
defibrillators may also be stored in adverse environments.
[0004] Electrodes that are used with such defibrillators may be
stored for long periods of time at elevated temperatures. For
example, a defibrillator stored in a vehicle, e.g., the trunk of a
police car or the storage area of a fire truck, in a hot climate
may be subjected to temperatures of 100-120.degree. F. for weeks or
even months at a time. Temperatures in a vehicle trunk can even
reach 200.degree. F. or more under some conditions.
[0005] We have found that these temperatures typically damage the
electrode, often rendering it inoperable. Damage occurs in several
ways. First, heat tends to accelerate corrosion of the conductor.
Heat also tends to cause deterioration of the adhesives that are
used in conventional electrodes. Finally, conventional electrolyte
gels generally include materials that decompose or dissociate at
temperature above about 140.degree. F., causing deterioration of
the electrolyte during high temperature storage. (Such gels may
also lose their flexibility or even solidify at low temperatures,
limiting the usefulness of the electrode in cold climates.)
[0006] Thus, when the electrode is needed in an emergency, it may
not be functional, endangering the life of the person needing
resuscitation if an extra electrode is not readily available. While
it is often recommended that electrodes be inspected and replaced
at predetermined intervals, e.g., yearly, it is generally difficult
for consumers to remember to do this. Moreover, if the electrodes
are exposed to very high temperature between replacement intervals,
the electrodes may be rendered useless before the next replacement
is due. In institutional settings, such as airports, it is more
likely that electrodes will be regularly replaced, but doing so is
costly and represents a significant cost in locations that require
a number of defibrillators.
[0007] The present invention features electrodes that exhibit
excellent shelf life at both high and low storage temperatures,
i.e., the electrodes can be stored for extended periods at elevated
or reduced temperatures without significant deterioration or loss
of functionality. Thus, for example, the electrodes can be used
after storage in vehicles kept outdoors at extreme temperatures
without risk that the electrodes will be inoperative when
needed.
[0008] In one aspect, the invention features a medical electrode
including a housing; a conductor and an electrolyte disposed within
the housing; and a high temperature adhesive that remains capable
of adhering the electrode to a patient's skin after the adhesive
has been exposed to temperatures of up to 200.degree. F. for 4
hours, positioned to adhere a surface of the electrode to a
patient's skin.
[0009] Some implementations of this aspect of the invention include
one or more of the following features. The housing comprises a
molded elastomeric member. The electrode further includes a high
temperature adhesive positioned to secure components of the
electrode to each other. The electrolyte is encapsulated. The high
temperature adhesive is selected from the group consisting of high
performance silicone or acrylic adhesives. The high temperature
adhesive includes a high performance silicone transfer adhesive.
The electrolyte is disposed in breakable capsules. The conductor
includes a metal screen positioned between the capsules and the
surface that is adhered to the patient. The electrode includes a
foam backing that is joined to the conductor by a high temperature
adhesive.
[0010] In another aspect, the invention features a medical
electrode constructed to be applied to a patient's skin, the
electrode including: (a) a housing; (b) a conductor within the
housing; and (c) an electrolyte disposed within a chamber that is
constructed to separate the electrolyte from the conductor until
the electrode is to be used; the electrode being constructed so
that the electrolyte, when released from the chamber, flows freely
from the chamber towards the patient's skin without application of
pressure to the chamber.
[0011] The invention also features a medical electrode constructed
to be applied to a patient's skin, including: (a) a housing; (b) a
conductor within the housing; (c) an electrolyte disposed within a
chamber that is constructed to separate the electrolyte from the
conductor until the electrode is to be used; and (d) an absorbent
pad, positioned adjacent the conductor, on the side of the
conductor that is closer to the patient's skin when the electrode
is in use, and configured to absorb the electrolyte when it is
released from the chamber and provide a wet layer between the
conductor and the patient's skin.
[0012] The invention further features a medical electrode
constructed to be applied to a patient's skin, including: (a) a
housing; (b) a conductor within the housing; and (c) an electrolyte
disposed within a chamber that is constructed to separate the
electrolyte from the conductor until the electrode is to be used,
the chamber being formed of a brittle material that is breakable by
the application of a force to the chamber.
[0013] Some implementations of these aspects of the invention may
include one or more of the following features. The chamber material
is selected from the group consisting of glass, ceramic, and
bakelite plastics. The chamber material is brittle at room
temperature. The chamber includes a glass ampule. The electrolyte
is a saline solution. The absorbent pad includes an absorbent
material selected from the group consisting of sponges, gauze,
carbon fiber mat, cellulose, and natural and synthetic fibrous
batts. The conductor includes a screen or mesh material. The
housing includes an elastomeric member. An edge of the conductor is
molded into a portion of the housing.
[0014] In a further aspect, the invention features a medical
electrode product including (a) an electrode comprising: (i) a
housing; (ii) a conductor within the housing; and (iii) an
electrolyte disposed within a chamber that is constructed to
separate the electrolyte from the conductor until the electrode is
to be used; and (b) a package, in which said electrode is disposed
prior to use, including an actuator device constructed to release
said electrolyte from said chamber when the electrode is removed
from the package.
[0015] Some implementations include one or more of the following
features. The chamber includes a breakable capsule, e.g., a glass
ampule. The actuator includes rolls through which the electrode is
pulled during removal from the package. The rolls are positioned to
rupture the chamber during removal. The electrode further includes
an absorbent pad, positioned adjacent the conductor on the side of
the conductor that is closer to the patient's skin when the
electrode is in use. The conductor includes a screen or mesh
material.
[0016] In another aspect, the invention features a medical
electrode constructed to be applied to a patient's skin, the
electrode including: (a) a housing; (b) a conductor within the
housing; (c) an electrolyte disposed within a chamber that is
constructed to separate the electrolyte from the conductor until
the electrode is to be used; and (d) an indicator constructed to
provide an indication to the user of whether the electrolyte has
been released from the chamber.
[0017] Some implementations include one or more of the following
features. The indication is a visual and/or audible indication. The
indication includes a color change. The indicator includes a
semiconductor chip configured to store information concerning the
status of the electrolyte and provide this information to a
defibrillator control box upon demand. The indicator is configured
to detect the presence of moisture. The indicator is configured,
upon detecting moisture, to send information via the chip to the
defibrillator control box upon demand.
[0018] In yet another aspect, the invention features a medical
electrode product constructed to be applied to a patient's skin,
the product including: (a) an electrode comprising a housing and a
conductor and an electrolyte disposed within the housing; and (b) a
package, within which the electrode is stored until use, that is
pressurized sufficiently to minimize electrolyte loss through
evaporation. By "minimize", we mean that evaporation is
sufficiently slow so that the electrode will contain sufficient
electrolyte to perform its intended function throughout the storage
life of the electrode, i.e., until the next replacement of the
electrode is due. Preferably, the package is pressurized
sufficiently so that evaporation is prevented.
[0019] The invention also features a medical electrode product
including (a) an electrode comprising a housing and a conductor and
an electrolyte disposed within the housing; and (b) a cover
disposed over the electrolyte in sealing engagement, the cover
defining a region adjacent the electrolyte that is pressurized
sufficiently to minimize electrolyte loss through evaporation.
[0020] Preferably, the package or region is pressurized to a
pressure that is at least 25% above the ambient pressure at the
time of sealing.
[0021] In a further aspect, the invention features a coupling
device for use with a defibrillator paddle. The coupling device
includes: (a) a housing; (b) a conductor within the housing; (c) an
electrolyte disposed within a chamber that is constructed to
separate the electrolyte from the conductor until the electrode is
to be used; and (d) a mounting device constructed to allow the
coupling device to be removably mounted on the defibrillator
paddle.
[0022] Some implementations include one or more of the following
features. The mounting device includes a clip. The mounting device
includes an adhesive. The coupling device is configured to provide
a conductive path from the defibrillator paddle to a patient's
skin. The chamber includes a breakable capsule, e.g., a glass
ampule. The capsule is configured to be broken by applying pressure
to the coupling device. The device further includes an absorbent
pad, positioned adjacent to the conductor on the side of the
conductor that is opposite the defibrillator paddle when the
coupling device is in use. The conductor includes a screen or mesh
material. The coupling device further includes a screen configured
to prevent fragments of the capsules from contacting a patient's
skin when the capsules are broken.
[0023] The invention also features a medical electrode constructed
to be applied to a patient's skin, the electrode including: (a) an
elastomeric housing, configured to conform to the body contours of
the patient; (b) a conductor within the housing; and, (c) within
the housing, an electrolyte disposed within a chamber that is
constructed to separate the electrolyte from the conductor until
the electrode is to be used.
[0024] Some implementations include one or more of the following
features. The electrode further includes a high temperature
adhesive that remains capable of adhering the electrode to a
patient's skin after the adhesive has been exposed to temperatures
of up to 200.degree. F. for 4 hours, positioned to adhere a surface
of the electrode to a patient's skin. The housing is a unitary,
integrally molded part. The housing includes a thermoplastic
elastomer.
[0025] Other features and advantages of the invention will be
apparent from the detailed description and drawings, and from the
claims.
DESCRIPTION OF DRAWINGS
[0026] FIG. 1 is a schematic view of an external defibrillator.
[0027] FIG. 2 is a cross-sectional view of an electrode according
to one embodiment of the invention.
[0028] FIG. 3 is a cross-sectional view of an electrode according
to an alternate embodiment of the invention.
[0029] FIG. 4 is a schematic side view of a package containing an
electrode, with the end of the packaged removed to expose the
internal structure of the package.
[0030] FIG. 5 is a cross-sectional view of a coupling device
according to one embodiment of the invention. FIG. 5A is a
schematic view showing the coupling device in use on a
defibrillator paddle.
[0031] FIG. 6 is a cross-sectional view of an electrode according
to another alternate embodiment on the invention.
[0032] FIG. 7 is a cross-sectional view of an electrode according
to another alternate embodiment of the invention.
DETAILED DESCRIPTION
[0033] Electrode Structure
[0034] Preferred electrodes are suitable for use with external
defibrillators, including Automated External Defibrillators. As
shown in FIG. 1, an external defibrillator 10 includes a
defibrillator control box 12, a pair of electrodes 20, and a cable
14 connecting the electrodes to the control box. The electrodes are
generally stored with the control box. When a patient is in need of
resuscitation, a caregiver removes the electrodes and prepares them
for use as will be discussed below. When the electrodes are ready
for use, the caregiver adheres each electrode to the skin of the
patient's chest. The caregiver may then be instructed by the
control box to stand back and apply a defibrillating shock to the
patient.
[0035] Referring to FIG. 2, electrode 20 includes a molded
elastomeric housing 22 that defines a well 24 and a
patient-contacting surface 26. A layer of pressure sensitive
adhesive 28 is provided on surface 26, to enable the electrode 20
to be adhered to a patient's skin. The molded, one-piece
construction of the housing is durable and is capable of
withstanding extended storage at high temperatures. While the
elastomeric housing 22 is shown as being relatively thick, it may
be thinner if desired.
[0036] A conductive screen 30 is attached to the side wall 32 of
well 24, e.g. by insert molding the screen into the housing. The
conductive screen 30 functions as the conductor for the electrode.
If desired, the screen 30 may be formed of a non-conductive
material, e.g., plastic, and a separate conductor (not shown) may
be included. If a separate conductor is used, the conductor
generally should include holes, to allow passage of electrolyte
through the conductor when the electrolyte is released, as will be
discussed below.
[0037] An elastomeric block 34, containing four glass ampules 36,
is positioned between the screen 30 and the upper wall 38 of well
24. (The number of ampules will vary, and is selected based on the
size of the ampules and size of the electrode.) The glass ampules
36 contain an electrolyte 44. Until the electrode is to be used,
the electrolyte remains sealed in the ampules, preventing the
electrolyte from evaporating and eliminating corrosion of the
conductor by the electrolyte during storage. Because the
electrolyte is separated from the conductor in this manner, it is
also not necessary to store the electrode in a hermetically sealed
package. As long as the electrode is protected from impact during
storage, as discussed below, release will not occur until the
caregiver is ready to apply the electrode to a patient.
[0038] An absorbent pad 40 is positioned below the screen 30, with
its exposed surface 42 generally aligned with the
patient-contacting surface 26 of the housing. The absorbent pad is
generally held in the electrode by adhering it to the screen 30 or
by insert molding it in place in the housing. Because the absorbent
pad is positioned in well 24, there is a ring of elastomeric
material around the absorbent to restrict flow of electrolyte away
from the area defined by well 24. If the volume of electrolyte is
balanced with the size and absorption properties of the absorbent
pad, flow of electrolyte can be minimized, in which case the ring
of elastomeric material may be eliminated.
[0039] When the electrode is to be used, the caregiver breaks the
ampules, e.g., by removing the electrode from a package that is
designed to break the ampules (as will be discussed below) or by
the caregiver applying pressure to the electrode. The electrolyte
is released as a result of an action performed by the caregiver and
quickly saturates the absorbent pad, readying the electrode for
use. The screen 30 catches the fragments of the broken ampules,
preventing any contact of the fragments with the patient's
skin.
[0040] Preferably, as shown, the ampules are molded into the
elastomeric block 34 so that only a small radial portion 46 of each
ampule extends beyond surface 47 of the elastomeric block. Portion
46 is sufficiently large so that, when the ampule is broken, the
electrolyte can easily flow out of the ampule, but sufficiently
small so that most of the glass remains embedded in the elastomeric
block.
[0041] FIG. 3 shows an electrode 50 according to an alternative
embodiment, in which the molded elastomeric housing 22 is replaced
by a foam backing 52. In this case, the elastomeric block 34 is
adhered to a first surface 54 of the foam backing by an adhesive
layer 56. Foam backing 54 includes open areas (not shown) through
which liquid can flow from the ampules 36 to the absorbent pad 40.
A conductor 58 is adhered to a second, opposite surface 60 of the
foam backing. The conductor 58 is a screen or mesh, or includes
apertures through which the liquid electrolyte can pass. As
discussed above, an absorbent pad 40 is positioned below the
conductor and is adhered thereto or otherwise secured to the
electrode. A second layer 62 of foam is adhered to the foam backing
52 to define a well in which the absorbent 40 sits and to provide a
patient-contacting surface 26' that carries pressure sensitive
adhesive 28.
[0042] Suitable Materials
[0043] The ampules may be commercially available pre-filled saline
ampules. The glass of the ampules is preferably 0.005 to 0.010 inch
thick, more preferably 0.006 to 0.007 inch thick. The ampules may
have any desired dimensions that will fit in the available space,
but are typically cylindrical, measuring about 2.5 to 3 inches in
length and about 0.25 to 0.35 inch in diameter. The ampules should
be breakable with relatively light pressure, and should be of a
glass that will break into relatively large fragments. The glass of
the ampules may be scored, to facilitate breakage at low applied
pressures. Preferably, the ampules are not completely filled with
electrolyte, so that there is sufficient headspace to allow for
expansion of the electrolyte if it freezes and increased gas
pressure of the electrolyte at elevated temperatures, preventing
rupture of the ampule under these conditions. Other suitable
brittle materials for the ampules include ceramics and brittle,
high temperature resistant plastics such as high glass transition
temperature or highly cross-linked plastics.
[0044] It is generally preferred that the electrolyte be a low
viscosity conductive liquid, such as a saline solution. A low
viscosity electrolyte will flow freely into the absorbent pad when
the ampules are broken, without requiring excessive pressure to be
applied to the electrode. Preferably, the electrolyte is selected
to flow into the absorbent pad by gravity and/or capillary action,
without the need for application of any pressure (pressure may be
applied to the electrode if desired for other reasons, e.g., to
adhere the electrode to a patient, but pressure is not necessary to
achieve flow of the electrolyte to the patient's skin). Saline
solutions are advantageous for use in electrodes that will be
stored at high and/or low temperatures. Water may be used in the
ampules instead of a saline solution, if the electrode will be
stored and used above 0.degree. C. If water is used, the absorbent
pad may be impregnated with a salt if additional conductivity is
desired.
[0045] The absorbent pad 40 has sufficiently high absorbency to
prevent the electrolyte from flowing out of the electrode and being
lost, but sufficiently low absorbency to allow the electrolyte to
contact and wet the patient's skin. If desired, the absorbent
material may be impregnated with a thickening agent, e.g.,
2-acrylamido-2-methylpropane sulfonic acid (AMPS), to thicken or
gel the low viscosity electrolyte and thereby control its flow
properties. Suitable absorbent materials include sponges, gauze,
carbon fiber mat, and absorbents suitable for use in diapers such
as cellulose and natural and synthetic fibrous batts. The thickness
of the absorbent pad will depend on the absorbency of the material
used. Preferably the absorbent pad is configured (a) to provide a
wet surface at the interface between the pad and the patient's
skin, and a wet layer between the conductor and the interface
between the pad and the patient's skin, while (b) minimizing flow
of liquid from the electrode out over the patient's skin beyond the
periphery of the electrode.
[0046] Screen 30 preferably has the smallest possible mesh size
that will allow the particular electrolyte that is used to flow
freely through the screen without the need for application of
pressure to the electrode. Generally, for a saline solution, the
mesh size is from about 300 to 500 openings per square inch. A
suitable screen for use with a saline solution is an expanded metal
mesh having diamond shaped openings with a mesh size of about 400
openings per square inch and a screen thickness of about 0.005 to
0.020 inch. Suitable mesh size will depend on the thickness of the
screen, the viscosity of the electrolyte, temperature, and other
factors. For example, if a more viscous electrolyte is used, a
screen having a larger mesh size may be required.
[0047] If a conductive screen is used (rather than a non-conductive
screen and a separate conductor) the screen is generally formed of
a metal. Preferably, the conductive screen is an expanded metal or
etched metal mesh, as a woven metal screen may produce some
undesirable electrical noise due to relative movement of the
strands. If a separate conductor is provided, the screen may be
formed of plastic or any desired non-conductive material that can
be fabricated into a screen or mesh. A porous fabric, e.g.,
cheesecloth, may be used; preferably the fabric is relatively
non-absorbent.
[0048] Suitable elastomers for housing 22 and elastomeric block 34
include thermoplastic elastomers, e.g., block copolymers such as
those available from Shell under the tradename KRATON rubbers.
Suitable elastomers will have sufficient flexibility so that the
molded housing 22 and elastomeric block 34 will flex and conform to
body contours when the electrode is adhered to a patient. This is
particularly important in relatively large defibrillation
electrodes, which extend over a significant area of the patient's
chest and thus generally need to bend to accommodate the curvature
of a patient's chest and/or the patient's breast tissue. If the
electrode does not adequately conform to body contours, sufficient
electrical contact may not be achieved and defibrillation may be
impossible or ineffective, endangering the patient's life.
[0049] If the electrode is expected to encounter high temperatures
during storage the pressure sensitive adhesive 28 that is used to
adhere the electrode to a patient should be high temperature
stable, and should adhere well to the patient at the temperature
that the electrode is likely to be at when it is used (generally
ambient temperature or somewhat higher if the electrode has just
been removed from a hot storage area). Preferably, the adhesive
remains capable of adhering the electrode to a patient's skin after
the adhesive has been exposed to temperatures of up to 200.degree.
F. for 4 hours or longer. Suitable high temperature contact or
pressure sensitive adhesives include high performance silicone or
acrylic adhesives. An example of a suitable high temperature
adhesive is a transfer high performance silicone adhesive
commercially available from Adhesives Research, Inc., Glen Rock,
Pa., under the tradename ARclad.RTM. 7876. If the electrode will
not be stored at high temperatures, a conventional pressure
sensitive adhesive suitable for use in an electrode may be used. If
an adhesive is used to hold layers of the electrode together, for
example in the embodiment shown in FIG. 3, this adhesive should
also be stable at high temperatures, and capable of holding the
layers securely together. The high performance adhesives discussed
above would be suitable for adhering the layers together.
[0050] Electrode Packaging
[0051] In order to protect the ampules from unintentional breakage,
it is generally preferred that the electrode be stored in a
relatively rigid, protective package. Suitable materials for the
packaging include rigid plastics, metals, and other rigid and
semi-rigid materials.
[0052] If desired, the package may include an actuating device that
will rupture the ampules as the electrode is being removed from the
packaging. For example, as shown in FIG. 4 the package 100 may
include a rigid box 102 in which are mounted a series of rolls 104.
The rolls 104 define a tortuous path through which the electrode 20
must pass as it is pulled (arrow A) through the opening 106 of the
box. A leader 108 extends from the electrode 20 to provide a tab
110 which may be pulled by the user to start the removal of the
electrode 20 from the box. Prior to use, box 102 is sealed, e.g.,
by flap 112. As discussed above, it is not necessary to
hermetically seal the box.
[0053] Other types of actuation devices may be used, or the ampules
may be broken by the caregiver after removing the electrode from
the package, e.g., by placing the electrode on the patient or a
relatively firm surface and applying pressure to the top surface of
the electrode.
[0054] Coupling Devices for Defibrillator Paddles
[0055] A structure similar to that described above with reference
to FIG. 2 may be used to form a coupling device for use with a
defibrillator paddle. Coupling devices are used to provide an
electrolyte interface between the surface of the paddle and the
skin of the patient.
[0056] A coupling device 150 is shown in FIG. 5. The structure of
the coupling device is the same as that of the electrode 20 shown
in FIG. 2, except that adhesive 28 is omitted (because the
defibrillator is held in place on a patient rather than adhered to
the patient), clips 152 are provided to secure the coupling device
to the defibrillator paddle, and a lead 30B and conductive plate
30A are provided to establish a conductive path between conductor
30' and the defibrillator paddle 156.
[0057] The coupling device 150 is shown in use in FIG. 5A. Clips
152 securely attach the coupling device 150 to shoulder 154 of
defibrillator paddle 156.
[0058] To release the electrolyte from ampules 36, the caregiver
may clap the defibrillator paddles together, with the coupling
devices 150 in place, or may press the defibrillator paddles
against the patient or a relatively firm surface.
[0059] Safety Features
[0060] If desired, the electrode or coupling device may include an
indicator, to indicate to the caregiver whether the electrolyte has
been accidentally released during storage, rendering the electrode
ineffective. Without such an indicator, the caregiver may not
realize that the electrolyte has been inadvertently released during
storage, if the electrolyte has evaporated and the electrode is dry
to the touch.
[0061] The indicator may include a color change element, e.g., an
integrated circuit chip that changes color if conductivity is
detected. Instead or in addition, the indicator may include an
audio alarm, e.g., an audible signal emitted by the control box of
the defibrillator. The alarm may be continuous from the time the
accidental release occurs, or may be emitted only when the
defibrillator detects that a caregiver may be activating the
defibrillator, e.g., when the defibrillator cover is removed.
[0062] The electrode or coupling device would in either case
include a test circuit that would read infinite resistance as long
as the electrolyte remained encapsulated, and would detect current
in the event of accidental electrolyte release.
[0063] If the electrode is pre-connected to a defibrillator, when
current is detected a warning will be sent directly to the
defibrillator. If the electrode is not pre-connected (or,
optionally, as an additional safeguard if it is pre-connected) the
electrode will include a semiconductor chip configured to send a
signal to the defibrillator control box indicating the status of
the electrode. In either case, the defibrillator will provide a
visual and/or audible indication to the caregiver.
[0064] Other Embodiments
[0065] Other embodiments are within the scope of the following
claims.
[0066] For example, while glass ampules have been shown and
described above, other techniques for encapsulating the electrolyte
may be used. For example, as shown in FIG. 6, in an alternative
electrode 170, the electrolyte can be encapsulated in an
elastomeric reservoir 172. The reservoir 172 can be filled, during
manufacturing, by creating a vacuum in the reservoir, e.g., by
compressing the elastomeric reservoir to largely exclude air, and
allowing the electrolyte to be drawn into the reservoir by the
vacuum, e.g., by releasing the compression with an opening in the
reservoir immersed in a supply of the electrolyte. Subsequent
pressure applied to the reservoir 172 when the caregiver prepares
the electrode for use will cause the electrolyte to be released
from the reservoir and flow through a tube 174 to a sub-reservoir
176. The electrolyte then flows into the absorbent pad 40, as
described above, and the electrode is ready to use.
[0067] Further, while low viscosity electrolytes, e.g., saline
solution, have been described as preferred, a conventional
electrolyte gel may be encapsulated if desired.
[0068] Also, while electrodes including encapsulated electrolyte
have been described above and shown in the figures, the high
temperature adhesives discussed above are also suitable for use in
other types of electrodes including conventional electrodes in
which the electrolyte is not encapsulated.
[0069] Moreover, in an alternate embodiment (electrode 180, shown
in FIG. 7), the electrolyte is not encapsulated, but is instead
prevented from drying out by placing a pressurized cover 182 over
the electrolyte. The package or cover is pressurized, for example,
to a pressure that is approximately 25% higher than the ambient
pressure at the time of assembly. In this embodiment, the
electrolyte is typically an electrolyte gel, provided in a
pre-gelled absorbent pad 40A. The area 184 under the cover 182 can
be pressurized, for example, by including a check valve (not shown)
in the cover 182 and pressurizing area 184 through the check
valve.
[0070] Additionally, while single electrodes are discussed above,
the electrode structures disclosed are suitable for use in
electrode assemblies, in which a pair of electrodes are mounted on
a single, integral backing for ease of application to a
patient.
[0071] While the embodiments discussed above include a screen to
prevent passage of glass fragments to the patient's skin, the
screen can be omitted if desired. For example, if the absorbent pad
is constructed to prevent passage of glass fragments, a screen is
not necessary.
[0072] Further, it is not necessary to encapsulate the electrolyte
to practice aspects of the invention that do not require
encapsulation, e.g., use of a high temperature adhesive, and use of
a pressurized package or cover.
* * * * *