FLEXIBLE THERAPY ELECTRODE
BACKGROUND OF THE INVENTION
I . Field of the Invention
The present invention is directed to medical electrodes, and more particularly,
to flexible medical electrodes that may be used with a wearable medical device, such
as a defibrillator.
2. Discussion of Related Art
Cardiac arrest and other cardiac health ailments are a major cause of death
worldwide. Various resuscitation efforts aim to maintain the body's circulatory and
respiratory systems during cardiac arrest in an attempt to save the life of the victim.
The sooner these resuscitation efforts begin, the better the victim's chances of
survival. These efforts are expensive and have a limited success rate, and cardiac
arrest, among other conditions, continues to claim the lives of victims.
To protect against cardiac arrest and other cardiac health ailments, some atrisk
patients may use a wearable defibrillator, such as the LifeVest® wearable
cardioverter defibrillator available from ZOLL Medical Corporation of Chelmsford,
Massachusetts. To remain protected, the patient wears the device nearly continuously
while going about their normal daily activities, while awake, and while asleep.
SUMMARY
In accordance with an aspect of the present invention, there is provided an
electrode system. The electrode system comprises a substrate including a plurality of
conductive gel reservoirs disposed on a first side thereof, a first of the plurality of
conductive gel reservoirs disposed in a first segment of the substrate and a second of
the plurality of the conductive gel reservoirs disposed in a second segment of the
substrate, a fluid channel in fluid communication with a fluid source, the first of the
plurality of conductive gel reservoirs, and the second of the plurality of the conductive
gel reservoirs, and one of a slot or a gap defined in the substrate and extending from a
region proximate the fluid channel and between the first of the plurality of conductive
gel reservoirs and the second of the plurality of the conductive gel reservoirs to an
edge of the substrate distal from the fluid channel. The one of the slot or the gap
physically separates at least a portion of the first segment of the substrate from the
second segment of the substrate.
In accordance with some embodiments, the electrode system further comprises
an electrically conductive layer having a first surface disposed on a second side of the
substrate and having a second surface configured to be disposed adjacent to a patient's
skin.
In accordance with some embodiments, the plurality of conductive gel
reservoirs and the fluid channel are included in a first impedance reduction system
configured to dispense a first amount of a first electrically conductive gel onto the
second surface of the electrically conductive layer in response to a first activation
signal, and wherein the electrode system further includes a second impedance
reduction system configured to dispense a second amount of a second electrically
conductive gel onto the second surface of the electrically conductive layer in response
to a second activation signal.
In accordance with some embodiments, the first impedance reduction system
is similar in construction to the second impedance reduction system.
In accordance with some embodiments, the electrode system further comprises
a garment wearable on a torso of a patient, the garment including a pocket formed
from a layer of fabric and configured to receive the electrode system, wherein the
electrode system is configured to dispense an amount of a conductive gel through the
layer of fabric and into contact with the patient's skin.
In accordance with some embodiments, the electrode system further comprises
an electrically conductive layer disposed on a second side of the substrate, the
electrically conductive layer including a plurality of apertures configured to dispense
the amount of the conductive gel.
In accordance with some embodiments, the electrode system further comprises
an electrically conductive pathway included in the layer of fabric, the electrically
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conductive pathway configured to deliver electrical energy to the patient's skin
through the amount of conductive gel dispensed from the electrode system.
In accordance with some embodiments, the layer of fabric is formed from an
electrically conductive material.
In accordance with some embodiments, each of the substrate and the pocket
are tapered to permit the electrode system to be received in the pocket in only a single
orientation.
In accordance with some embodiments, the electrode system further comprises
at least one ECG sensing electrode configured to monitor an ECG signal of a patient,
the at least one ECG sensing electrode being disposed on a second side of the
substrate and electrically insulated from portions of the electrode system configured to
receive conductive gel.
In accordance with some embodiments, the electrode system further includes
at least one additional sensor configured to monitor a physiological parameter of the
patient other than an ECG signal of the patient.
In accordance with some embodiments, the at least one additional sensor is
disposed on a third segment of the substrate, the third segment of the substrate at least
partially physically separated by one of a slot or a gap defined in the substrate from
portions of the substrate on which the plurality of conductive gel reservoirs are
disposed.
In accordance with some embodiments, the substrate further comprises a
plurality of additional segments positioned adjacent to one another and at least
partially physically separated from one or another by slots or gaps defined in the
substrate, each of the plurality of additional segments including a conductive gel
reservoir disposed on first side thereof.
In accordance with some embodiments, the fluid pressure source is disposed
on a third segment of the substrate, the third segment of the substrate being at least
partially physically separated by one of a slot or a gap defined in the substrate from
portions of the substrate on which the plurality of conductive gel reservoirs are
disposed.
In accordance with some embodiments, the substrate is tapered from a first
end to a second end, the taper of the substrate preventing insertion of the electrode
system into a tapered pocket of a wearable medical device in an undesired direction.
In accordance with some embodiments, the electrode system further comprises
a magnet disposed on a portion of the substrate and configured to apply a force to a
magnet disposed on a pocket of a garment in w iich the electrode system can be
inserted, the applied force providing an indication of proper orientation of the
electrode system in the pocket.
In accordance with some embodiments, the electrode system further comprises
a snap disposed on a portion of the substrate and configured to engage a
corresponding snap disposed on a pocket of a garment in which the electrode system
can be inserted, the engagement of the snap with the corresponding snap providing an
indication of proper orientation of the electrode system in the pocket.
In accordance with some embodiments, the substrate comprises a fabric
permeable to conductive gel which the electrode assembly is configured to dispense.
In accordance with some embodiments, the substrate is perforated.
In accordance with some embodiments, the electrode system includes an
indicator disposed on an externally visible surface of the electrode system and
configured to visually indicate whether the fluid source has been actuated.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings are not intended to be drawn to scale. In the
drawings, each identical or nearly identical component that is illustrated in various
figures is represented by a like numeral. For purposes of clarity, not every component
may be labeled in every drawing. In the drawings:
FIG. 1 illustrates a wearable medical device, such as a wearable defibrillator;
FIG. 2A is a top plan view of a therapy electrode assembly that may be used
with the wearable medical device illustrated in FIG. 1;
FIG. 2B is a functional block diagram of an impedance reduction system that
may be included in the therapy electrode assembly of FIG. 2A;
FIG. 2C is a bottom plan view of an electrode portion of the therapy electrode
assembly of FIG. 2A;
FIG. 3A is a top plan view of a therapy electrode assembly that may be used
with the wearable medical device illustrated in FIG. 1;
FIG. 3B is a bottom plan view of an electrode portion of a therapy electrode
assembly that may be used with the wearable medical device illustrated in FIG. ;
FIG. 3C is a top plan view of another therapy electrode assembly that may be
used with the wearable medical device illustrated in FIG. ;
FIG. 3D is a top plan view of another therapy electrode assembly that may be
used with the wearable medical device illustrated in FIG. ;
FIG. 3E is a top plan view of another therapy electrode assembly that may be
used with the wearable medical device illustrated in FIG. 1;
FIG. 4 is a cross sectional view of a therapy electrode assembly that may be
used with the wearable medical device illustrated in FIG. 1 applied to fabric against
the skin of a patient;
FIG. 5 is an elevational view of a therapy electrode assembly that may be used
with the wearable medical device illustrated in FIG. 1;
FIG. 6A illustrates placement of therapy electrode assemblies in a rear portion
of a wearable medical device;
FIG. 6B illustrates placement of a therapy electrode assembly in a front
portion of a wearable medical device;
FIG. 6C is a plan view of the rear of a wearable medical device including
tapered pockets for therapy electrode assemblies;
FIG. 7 is an exploded view of a pocket of a wearable medical device and
therapy electrode assembly intended to reside within the pocket;
FIG. 8 is a functional block diagram of a redundant impedance reduction
system in accordance with an aspect of the present invention;
FIG. 9 is a schematic diagram of an electrode assembly that includes ECG
sensing electrodes, a therapy electrode, and redundant impedance reduction systems
in accordance with another aspect of the present invention; and
FIG. 10 illustrates a manner in which the electrode assembly of FIG. 9 may be
worn on the body of a patient.
DETAILED DESCRIPTION
This invention is not limited in its application to the details of construction and
the arrangement of components set forth in the following description or illustrated in
the drawings. The invention is capable of other embodiments and of being practiced
or of being carried out in various ways. Also, the phraseology and terminology used
herein is for the purpose of description and should not be regarded as limiting. The
use of "including," "comprising," "having," "containing," "involving," and variations
thereof herein is meant to encompass the items listed thereafter and equivalents
thereof as well as additional items.
FIG. I illustrates a wearable medical device, such as a LifeVest® wearable
cardioverter defibrillator available from ZOLL Medical Corporation of Chelmsford,
Massachusetts. As shown, the wearable medical device 100 includes a harness 0
having a pair of shoulder straps and a belt that is worn about the torso of a patient.
The harness 110 is typically made from a material, such as cotton, that is breathable,
and unlikely to cause skin irritation, even when worn for prolonged periods of time.
The wearable medical device 100 includes a plurality of ECG sensing electrodes 112
that are attached to the harness 1 at various positions about the patient's body and
electrically coupled to a control unit 120 via a connection pod 130. The plurality of
ECG sensing electrodes 112, which may be dry-sensing capacitance electrodes, are
used by the control unit 120 to monitor the cardiac function of the patient and
generally include a front/back pair of ECG sensing electrodes and a side/side pair of
ECG sensing electrodes. Additional ECG sensing electrodes may be provided, and
the plurality of ECG sensing electrodes 2 may be disposed at varying locations
about the patient's body.
The wearable medical device 00 also includes a plurality of therapy
electrodes 14a, 114b that are electrically coupled to the control unit 120 via the
connection pod 0 and which are capable of delivering one or more therapeutic
defibrillating shocks to the body of the patient, if it is determined that such treatment
is warranted. As shown, the plurality of therapy electrodes 114a, 14b includes a first
therapy electrode 114a that is disposed on the front of the patient's torso and a second
therapy electrode 14b that is disposed on the back of the patient's torso. The second
therapy electrode 14b includes a pair of therapy electrodes that are electrically
coupled together and act as the second therapy electrode 114b. The use of two
therapy electrodes 114a, 4b permits a biphasic shock to be delivered to the body of
the patient, such that a first of the two therapy electrodes can deliver a first phase of
the biphasic shock with the other therapy electrode acting as a return, and the other
therapy electrode can deliver the second phase of the biphasic shock with the first
therapy electrode acting as the return. The connection pod 130 electrically couples
the plurality of ECG sensing electrodes 2 and the plurality of therapy electrodes
114a, 14b to the control unit 120, and may include electronic circuitry. For example,
in one implementation, the connection pod 130 includes signal acquisition circuitry,
such as a plurality of differential amplifiers to receive ECG signals from different
ones of the plurality of ECG sensing electrodes 112 and to provide a differential ECG
signal to the control unit 120 based on the difference therebetween. The connection
pod 130 may also include other electronic circuitry, such as a motion sensor or
accelerometer by which patient activity may be monitored.
As shown in FIG. 1, the wearable medical device 100 also includes a user
interface pod 140 that is electrically coupled to the control unit 120. The user
interface pod 140 can be attached to the patient's clothing or to the harness 0, for
example, via a clip (not shown) that is attached to a portion of the interface pod 140.
Alternatively, the user interface pod 140 may simply be held in a person's hand. In
some embodiments, the user interface pod 140 may communicate wirelessly with the
control unit 120, for example, using a Bluetooth®, Wireless USB, ZigBee, Wireless
Ethernet, GSM, or other type of communication interface. The user interface pod 40
typically includes a number a number of buttons by which the patient, or a bystander
can communicate with the control unit 120, and a speaker by which the control unit
120 may communicate with the patient or the bystander. For example, where the
control unit 20 determines that the patient is experiencing cardiac a hmia, the
control unit 120 may issue an audible alarm via a loudspeaker (not shown) on the
control unit 20 and/or the user interface pod 40 alerting the patient and any
bystanders to the patient's medical condition. The control unit 120 may also instruct
the patient to press and hold one or more buttons on the control unit 120 or on the user
interface pod 40 to indicate that the patient is conscious, thereby instructing the
control unit 120 to withhold the delivery of one or more therapeutic defibriilating
shocks. If the patient does not respond, the device may presume that the patient is
unconscious, and proceed with the treatment sequence, culminating in the delivery of
one or more defibriilating shocks to the body of the patient. In some embodiments,
the functionality of the user interface pod 40 may be integrated into the control unit
120.
The control unit 120 generally includes at least one processor, microprocessor,
or controller, such as a processor commercially available from companies such as
Texas Instruments, Intel, AMD, Sun, IBM, Motorola, Freescale and ARM Holdings.
In one implementation, the at least one processor includes a power conserving
processor arrangement that comprises a general purpose processor, such as an Intel®
PXA270 processor and a special purpose processor, such as a Freescale™ DSP563
Digital Signal Processor. Such a power conserving processor arrangement is
described in co-pending U.S. Patent Application Serial No. 12/833,096, titled
SYSTEM AND METHOD FOR CONSERVING POWER IN A MEDICAL
DEVICE, filed July 9, 20 0 which is incorporated by reference herein in its entirety.
The at least one processor of the control unit 20 is configured to monitor the
patient's medical condition, to perform medical data logging and storage, and to
provide medical treatment to the patient in response to a detected medical condition,
such as cardiac arrhythmia. Although not shown, the wearable medical device 00
may include additional sensors, other than the ECG sensing electrodes 1 2 , capable of
monitoring the physiological condition or activity of the patient. For example,
sensors capable of measuring blood pressure, heart rate, thoracic impedance, pulse
oxygen level, respiration rate, heart sounds, and the activity level of the patient may
also be provided.
As discussed above, to provide protection against cardiac arrest, patients that
use a wearable medical device, such as a wearable defibrillator, generally wear the
device nearly continuously while they are awake and while they are asleep. Because
the wearable medical device is worn nearly continuously, dry electrodes are typically
used for both the plurality of ECG sensing electrodes 112 and the plurality of therapy
electrodes 14a, 114b for comfort and to prevent irritation of the patient's skin.
Where it is determined that one or more defibrillating shocks are to be delivered to the
body of the patient and the patient is non-responsive, the control unit 120 sends a
signal to the plurality of therapy electrodes 14a, 14b causing them to release an
impedance reducing gel prior to delivery of one or more defibrillating shocks. The
impedance reducing gel reduces the impedance between the conductive surface of the
therapy electrodes and the patient's skin, thereby improving the efficiency of the
energy delivered to the patient and reducing the chance of damage (e.g., in the form of
burning, reddening, or other types of irritation) to the patient's skin.
FIG. 2A is a plan view of a therapy electrode assembly 200 that includes an
impedance reduction system and which may be used with a wearable medical device,
such as the wearable defibrillator described above with respect to FIG. . FIG. 2B is a
functional block diagram of impedance reduction system 2 that is included in the
therapy electrode assembly 200 shown in FIG. 2A. The impedance reduction system
201, when activated, dispenses an impedance reducing (i.e., electrically conductive)
gel onto the exposed surface of the therapy electrode assembly that, in use, is placed
most proximate to the patient's body. The therapy electrode assembly 200 is a
multiple layer laminated structure that includes an electrically conductive layer
disposed adjacent the bottom surface of the therapy electrode assembly 200 and an
impedance reduction system 201. The electrically conductive layer forms the
electrode portion 202 of the therapy electrode assembly 200 as shown in FIG. 2C. In
use, the electrically conductive layer is disposed adjacent the patient's skin, although
the conductive layer need not make direct contact with the patient. For example,
portions of the harness 0 (FIG. 1) may be present between the electrically
conductive layer and the patient's skin. As shown in FIG. 2A, the impedance
reduction system 201 is disposed on a side of the therapy electrode assembly 200 (i.e.,
the top-side shown in FIG. 2A) that is opposite the side on which the conductive layer
is formed.
T e impedance reduction system 201 includes a plurality of conductive gel
reservoirs 210, each of which has a respective gel delivery outlet 220, that are fSuidly
coupled to a fluid channel 230, and a fluid pressure source 240. The fluid pressure
source 240 is fiuidly coupled to the fluid channel 230, and when activated by an
activation signal, forces a fluid, such as nitrogen gas, into the channel 230. The
hydraulic pressure of the fluid from the activated fluid pressure source 240 in the fluid
channel 230 forces the conductive gel stored in each of the plurality of gel reservoirs
out of the plurality of gel delivery outlets 220 through apertures formed in the bottom
surface of the electrode portion 202 and onto the exposed bottom surface of the
electrode portion 202. The apertures are generally aligned with the plurality of gel
delivery outlets 220 so that when activated, the electrically conductive gel is
dispensed onto the exposed surface of the electrode portion that is disposed most
proximate to the patient's body. Further details regarding the construction of the
therapy electrode assembly 200 are described in U.S. Patent No. 5,078,134
(hereinafter "the ' 134 patent") which is incorporated herein by reference in its
entirety.
To perform effectively, it is desirable that the therapy electrode portion 202 be
configured to conform to a variety of body contours and shapes so that, in use, a
significant, or in some embodiments, substantially an entire area of the bottom surface
(the surface to be in contact with or positioned proximate a patient's body) of the
electrode portion 202 is in intimate contact with a patient's body or with the fabric of
a garment worn by the patient, for example, the wearable medical device 0 of FIG.
1. As a patient goes through daily routines including walking, sitting, sleeping, or
performing other tasks, the patient's body shape and contours where a therapy
electrode is positioned may be subject to various degrees of deformation. A therapy
electrode may thus desirably be flexible and shape conforming to facilitate
maintaining contact between a surface of the therapy electrode and a patient's body or
garment.
Conventional therapy electrodes have traditionally been formed on a single
non-segmented substrate which in some instances includes a flexible metal material or
a polymeric material with a layer of metallic material deposited thereon.
FIGS. 3A-3E illustrate embodiments of a therapy electrode assembly 300
which may be more flexible and facilitate maintaining a greater amount of contact
between a surface of the therapy electrode and a patient's body or garment than a
conventional therapy electrode assembly. The substrate 305 of the electrode portion
302 of a therapy electrode assembly illustrated in FIGS. 3A-3E is divided into
multiple connected segments 305a. The multiple segments 305a may move at least
partially independently from one another. Each of the segments 305a may include at
least one conductive gel reservoir 310 and at least one gel delivery outlet 320, which
may be similar in construction and function as the gel reservoirs 210 and gel delivery
outlets 220 described above. The various segments 305a may be at least partially
physically separated from one another by, for example, one or more of a slot 315a, a
gap 315b, or other open area between adjacent segments 305a. The various segments
305a may be physically coupled together by a central spine including one or more
fluid conduits 330 configured to deliver fluid to the conductive gel reservoirs 3 0 to
cause the release of conductive gel therefrom.
As illustrated, the slots 315a and/or gaps 315b may extend from a central
portion of the substrate 305 of the therapy electrode assembly 300 proximate a central
fluid conduit 330 and between adjacent segments 305a to an edge of the substrate 305.
Providing for the various segments 305a of the electrode portion to move at least
partially independently of one another may facilitate conformance of the electrode
portion 302 to curves or contours of a patient's body. A segmented electrode portion
302 as illustrated in FIG. 3B may provide for a greater area, or a greater percentage of
the total area, of the electrode portion to be in contact with the patient's body than if
the electrode portion 302 were formed of a single, non-segmented substrate, such as
illustrated in, for example, FIG. 2C.
In some embodiments, a segment 305b of a therapy electrode including a fluid
pressure source 340 or other features, for example, an ECG electrode or a sensor for
some other parameter indicative of a patient's medical condition may be at least
partially physically separated from one or more of the segments 305a. This partial
physical separation may be provided by including a slot 3 5a, a gap 315b, or other
open area betw een a portion of the therapy electrode assembly 300 including the gel
reservoirs 310 and the segment 305b of the therapy electrode assembly including the
fluid pressure source 340 or other feature(s). In some embodiments, the segment
305b may be connected to the segments 305a by a fitting, for example, a tube 330a of
a first diameter coupled to one of the segments 305a and 305b inserted into the bore
of a tube 330b of a second diameter coupled to the other of the segments 305a and
305b, such as shown in FIG. 3C. Such a construction provides for the segment 305b
to rotate relative to the segments 305a and may provide for a reduced tendency for the
segment 305 b of the electrode to constrain movement of the one or more segments
305a including the gel reservoirs 0.
As one of ordinary skill in the art would recognize, the shapes and positions of
the segments 305a and 305b and of the slots 315a and/or gaps 315b may be provided
in different configurations from those illustrated in FIG. 3A. For example, the various
segments 305a may include rounded or squared ends or have different aspect ratios
than illustrated. The slots 315a and/or gaps 3 15b may be curved as illustrated in FIG.
3A, squared as illustrated in FIG. 3D, or may include re-entrant portions 315c
extending between one of the gel reservoirs 3 0 and gel delivery outlets 320 and a
portion of the fluid conduit 330 as illustrated in FIG. 3E.
In some embodiments, the electrode portion 302 may include a metalized or
otherwise conductive film on a portion of, or an entirety of, the bottom side of the
electrode portion which is to be positioned against or face the skin of a patient. Prior
to a defibrillating shock being delivered to the patient, conductive gel may be released
from the gel reservoirs 3 0 to form a low impedance conductive path between the
metalized side of the electrode portion 302 and the skin of the patient. Current may
be applied through the metalized side of the electrode portion, the conductive gel, and
the skin of the patient.
In other embodiments, the therapy electrode assembly 300 does not include a
conductive film forming an electrode portion 302 on the bottom side of the electrode
assembly 300 to be positioned against or face the skin of a patient. The majority of,
or the entirety of the bottom surface of the electrode assembly 300 facing the skin of
the patient may be substantially or completely non-conductive. Current may be
applied to the patient to deliver a defibrillating shock by a method which does not
involve passing current through or along any surface of the electrode assembly.
For example, as illustrated in FIG. 4, a therapy electrode assembly 300 having
no conductive material present on the surface 350 facing the skin 360 of a patient may
be disposed in a pocket in a garment worn by the patient or otherwise secured to an
external surface of the garment. As used herein, the term "garment" includes
clothing, for example, a shirt or jacket, as well as wearable medical devices, for
example, a LifeVest® wearable cardioverter defibrillator.
The substrate 305 of the therapy electrode assembly 300 may be formed of a
natural or synthetic fabric, for example, cotton, wool, or polyester. In instances where
the substrate is not waterproof, the gel reservoirs 210, 310 may be formed with a
membrane, for example, a plastic film, where the gel reservoirs contact the fabric to
facilitate retaining conductive gel within the gel reservoirs and prevent it from
escaping through the substrate. In other embodiments, the fabric may include a
waterproof coating where the gel reservoirs 2 , 310 contact the fabric. Forming the
substrate 305 out of a fabric material may provide for the substrate to easily conform
to the contours of the body of a patient. The substrate 305 may include perforations.
Forming the substrate 305 out of a fabric material and/or with perforations may
facilitate passage of conductive gel through the substrate upon release of the
conductive gel from the gel reservoirs 210, 310.
Fabric 370 of the garment between the surface 350 of the therapy electrode
assembly 300 and the skin 360 of the patient may be conductive and/or may include
conductive stitching 380. Upon release of conductive gel from the gel reservoirs 310
through the gel delivery outlets 320, the conductive gel may pass through the weave
of the fabric 370 and may contact the conductive stitching 380 and the skin 360 of the
patient on the opposite side of the garment fabric 370 from the surface 350. The
released conductive gel may form a low impedance conductive path between the
conductive stitching 380 or conductive fabric of the garment and the skin 360 of the
patient. A defibrillating shock may be delivered to the patient through the conductive
stitching 380 or conductive fabric of the garment and through the released conductive
gel into the skin of the patient.
T e therapy electrode assembly 300 may be provided with a relatively large,
easy-to-grip pull tab 495 (illustrated in FIG. 5) to facilitate insertion or removal of the
therapy electrode assembly 300 from a pocket of a garment or wearable medical
device. In accordance with one embodiment, the pull tab 495, or another visible
surface of the therapy electrode assembly may include an indicator that identifies
whether the impedance resistance system has been activated or not. Such indicators
may include, for example, an additional gel reservoir coupled to the fluid channel
which may release a dye or other colored substance upon activation of the impedance
reduction system. The indicator may also include, for example, a section of wiring, or
a fuse or other device which may change color responsive to the application of
electrical energy to the electrode. Other indicator devices known to those in the art
are also contemplated and embodiments of the present invention are not limited to any
particular indicator device.
Therapy electrode assemblies in accordance with various embodiments may
include one or more features which facilitate proper insertion of the therapy electrode
assembly into a garment to be worn by a patient. For example, as illustrated in FIG.
5, a therapy electrode assembly 400 may be formed with a tapered shape. A first end
485 of the therapy electrode assembly 400, for example, an end proximate the fluid
pressure source (not visible in FIG. 5), when present, may be wider than a second end
490 of the therapy electrode assembly 400, for example, an end distal from the fluid
pressure source. The provision of corresponding tapered pockets 5 0 on a wearable
medical device 0 as illustrated in FIGS. 6A and 6B (where the fabric overlying the
therapy electrode assemblies is removed for clarity) allows therapy electrode
assemblies 400 to be inserted only tapered end first. FIG. 6C illustrates a rear side of
a wearable medical device 100 including tapered pockets 510 in which tapered
therapy electrode assemblies may be placed and which may limit the direction in
which the tapered therapy electrode assemblies are inserted.
The shape of tapered therapy electrode assemblies 400 are not limited to that
illustrated in the figures. In some embodiments, both edges of a therapy electrode
assembly 400 may be tapered and in other embodiments only a single edge is tapered.
The degree of taper on each edge of a therapy electrode assembly 400 may differ. In
some embodiments, a portion of one or both edges of a therapy electrode assembly
400 may include a cut out portion, which may be, for example, rectangular, instead of
a gradually tapering profile as illustrated. A therapy electrode assembly 400 in
accordance with embodiments of the present invention may be shaped in any manner
which may facilitate insertion of the therapy electrode into the pocket in a correct
orientation.
An additional feature which may facilitate proper insertion of the therapy
electrode assembly into a garment to be worn by a patient is illustrated in FIG. 7,
which is an exploded view of portions of a pocket of a garment and a therapy
electrode assembly 500 intended to be placed within the pocket. The therapy
electrode assembly 500 of FIG. 7 includes two magnets 520 located on the substrate
515. Corresponding magnets 530 may be located on material forming inner and/or
outer portions 540, 550, respectively, or both, of a pocket of a wearable medical
device 100 into which the therapy electrode assembly 500 is to be inserted. The
magnets 520, 530 may be arranged such that the magnets 530 in the material of the
pocket will be repelled from the magnets 520 in the substrate unless the therapy
electrode assembly 500 is inserted properly, for example, with the side onto which the
conductive gel is to be released facing the side of the pocket against the skin of a
patient. For example, each of the magnets 520 could be arranged with North poles
facing in a direction away from an electrode side of the therapy electrode assembly
500 and South poles facing in an intended direction of the body of a patient wearing
the wearable medical device 100. The fabric of the outer portion of the pocket could
then include magnets with South poles facing inward toward the side of the garment
intended to lie against the skin of the patient. The fabric of the inner portion of the
pocket could include magnets with North poles facing away from the side of the
garment intended to lie against the skin of the patient. Unless the magnets were
attracted to each other and "clicked' together, a patient would know that the therapy
electrode assembly 500 was not properly inserted into the pocket. Fewer or greater
than two magnets may be included in any of the therapy electrode assembly 500 and
either one or both of the inner and outer portions 540, 550, respectively, of the pocket
of the wearable medical device 100. The orientation of the poles of the magnets could
be altered as desired.
In alternate embodiments, one or more of the magnets 520, 530 may be
replaced or supplemented by snaps having male sides and female sides. For example,
a female side of a snap may be placed on the surface of the upper side (the side
intended to face away from a patient) of the substrate. A corresponding male half of
the snap may be provided on the internal surface of fabric of an outer layer of a pocket
of a wearable medical device 100 into which the therapy electrode assembly 500 is
intended to be inserted. The male and female portions of the snap would only be able
to engage if the therapy electrode assembly 500 was inserted into the pocket in the
correct orientation. Other directional snaps or fasteners having male and female sides,
for example, hook and loop fasteners, may also or alternatively be used.
Applicants have appreciated that there may be instances where it would be
desirable to have redundancy in the impedance reduction system described above. An
electrode that incorporates redundant impedance reduction systems is now described
with respect to FIGS. 8-10 below.
FIG. 8 is a functional block diagram of a redundant impedance reduction
system that may be incorporated into a therapy electrode assembly in accordance with
an aspect of the present invention. As shown, the redundant impedance reduction
system 600 includes at least two independent impedance reduction systems 6 , 602
similar in construction and operation to that described previously with respect to
FIGS. 3A-3E. Although only two impedance reduction systems 601, 602 are shown
in FIG. 8, it should be appreciated that additional impedance reduction systems may
be provided.
As shown, a first impedance reduction system 6 of the at least two
impedance reduction systems 601, 602 includes a first plurality of gel reservoirs 610a,
each containing an electrically conductive gel, with each respective gel reservoir
including a gel delivery outlet 620a. Each of the first plurality of gel reservoirs 610a
is fluidly coupled to a first fluid channel 630a that is, in turn, fluidly coupled to a first
fluid pressure source 640a. The first fluid pressure source 640a has an input 641a to
receive a first electrical activation signal and a fluid outlet 642a that is fluidly coupled
to the first fluid channel 630a. A rupturable membrane and/or a filter (not shown)
may be positioned between the fluid outlet 642a and the first fluid channel 630a as
described in the 134 patent. As described in the ' 34 patent, the first fluid pressure
source 640a may include a gas generating cartridge that ignites a chemical pellet (such
as a lead styphnate igniter and a gas generating mixture of ammonium dichromate and
nitroguanidine) that rapidly decomposes and generates quantities of a gas, such as
nitrogen. It should be appreciated that other types of fluid pressure sources may be
used, as the present invention is not limited to any particular type of fluid pressure
source.
In response to the first activation signal received at the input 641a of the first
fluid pressure source 640a, a fluid, such as nitrogen gas, is forced into the first fluid
channel 630a and then into each of the first plurality of gel reservoirs 610a. The
hydraulic pressure of the fluid flowing into each of the first plurality of gel reservoirs
610a forces the electrically conductive gel contained in each gel reservoir toward its
respective gel delivery outlet 620a, thereby fracturing a membrane separating the gel
delivery outlet from a respective aperture formed in the electrically conductive layer
of the electrode portion.
The second impedance reduction system 602 of the at least two impedance
reduction systems 601, 602 is similar to the first impedance reduction system 6 and
includes a second plurality of gel reservoirs 610b, each containing an electrically
conductive gel, with each respective gel reservoir including a gel delivery outlet 620b.
The electrically conductive gel contained in the second plurality of gel reservoirs
610b may, but need not, be the same type of gel as that contained in the first plurality
of ge reservoirs 610a. For example, the electrically conductive gel contained in the
second plurality of gel reservoirs 610b may have a different color, or have a longer
drying time than the gel contained in the first plurality of gel reservoirs 610a. Each of
the plurality of gel reservoirs 610b is fluidly coupled to a second fluid channel 630b
that is, in turn, fluidly coupled to a second fluid pressure source 640b. The second
fluid pressure source 640b has an input 641b to receive a second electrical activation
signal and a fluid outlet 642b that is fluidly coupled to the second fluid channel 630b.
The second fluid pressure source 640b may similar in construction to the first fluid
source 640a described above.
As shown in FIG. 8, the input 641a of the first fluid pressure source 640a may
be electrically connected to the input 641b of the second fluid pressur e sour ce, such
that a single activation signal activates each of the at least two impedance reduction
systems 601, 602 substantially simultaneously. Should one of the redundant
impedance reduction systems 601 , 602 fail to operate (either partially or completely),
the other can still operate to dispense conductive gel onto the exposed surface of the
electrode. The activation signal provided to the input 64 a of the first fluid pressure
source 640a may be provided by the control unit 120 (FIG. 1) to the first fluid
pressure source 640a using an electrical conductor that is physically distinct from that
which provides the activation signal to the input 641b of the second fluid pressure
source 640b to permit further redundancy, for example, should one of the electrical
conductors be damaged. Alternatively, a single electrical conductor may be provided
between the control unit 120 and the electrode assembly, with the single electrical
conductor being connected to both the input 641a of the first fluid pressure source
640a and the input 641b of the second fluid pressure source 640b.
It should be appreciated that each of the first and second pressure sour ces
640a, 640b may alternatively receive separate activation signals, as the present
invention is not limited to receiving a single activation signal. The separate activation
signals may be sent, for example by the control unit 120, to each of the first fluid
pressure source 640a and the second fluid pressure source 640b at substantially the
same time, or at different times. For example, a first activation signal may be
provided to the input 641a of the first fluid pressure source 640a at a first time, and a
second activation signal may be provided to the input 641b of the second fluid
pressure source 640b at a second time that is subsequent to the first time. In
accordance with one embodiment, the control unit 120 (FIG. 1) may send the first
activation signal to the first fluid pressure source 640a at a first time, and send the
second activation signal to the second fluid pressure source 640b at a second and
subsequent time where it is determined that the first impedance reduction system 601
failed to operate. Alternatively, the second activation signal may be sent to the
second fluid pressure source 640b at a second and subsequent time even where
activation of the first fluid pressure source 640a is successful Such a subsequent
activation of the second fluid pressure source 640b would permit a second
deployment of conductive gel onto the exposed surface of the electrode and permit the
electrode to maintain a high conductivity with the patient for a longer period of time
than if both impedance reduction systems 601, 602 were activated at substantially the
same time.
FIG. 9 illustrates a therapy electrode assembly that combines one or more
ECG sensing electrodes, a therapy electrode, and redundant impedance reduction
systems in a single integrated electrode assembly in accordance with a further aspect
of the present invention. As shown, the electrode assembly 600 includes a pair of
ECG sensing electrodes 612a, 612b for monitoring the cardiac function of a patient.
The electrode assembly 600 further includes a therapy electrode 614, and at least two
impedance reduction systems 601, 602, similar to those described previously with
respect to FIG. 8. It should be appreciated that in an alternative embodiment, only a
single impedance reduction system may be provided. The pair of ECG sensing
electrodes 612a, 612b may be electrically separated from the therapy electrode 614,
for example, by an insulator. It should be appreciated that in other embodiments, the
electrode assembly 600 may include only a single ECG sensing electrode, while in
other embodiments, more than two ECG sensing electrodes may be provided. In such
alternative embodiments, the number and placement of ECG sensing electrodes and
may vary from that shown in FIG. 9. The electrode assembly 600 may include one or
more sections 605a which may include one or more gel reservoirs and/or fluid
channels, and which may be at least partially separated from one or more other
sections 605a and/or sections 605b which may include the sensing electrodes 612a,
612b and/or pressure sources 640a, 640b. The one or more sections 605a, 605b may
be at least partially physically separated from one another by slots and/or gaps as
described above with reference to FIGS. 3A-3E.
In yet a further embodiment, the integrated electrode assembly can include
additional sensors 616, other than the one or more ECG sensing electrodes and the
therapy electrode, that are capable of monitoring other physiological parameters of a
patient, such as blood pressure, heart rate, thoracic impedance, pulse oxygen level,
respiration rate, heart sounds, etc.
The electrode assembly 600 may be worn on the patient's body such that one
of the pair of ECG sensing electrodes 612a, 612b is disposed approximately in the
center of the patient's torso, and the other of the pair of ECG sensing electrodes 612a,
612b is disposed on the side of the patient's torso. For example, as shown in FIG. 10,
the electrode assembly 600 may be worn on the front of the patient's torso, so that the
ECG sensing electrode 612a is disposed approximately in the center of the patient's
chest, and the other ECG sensing electrode 612b is disposed on the patient's side. A
second electrode assembly 600' may be worn on the back of the patient's torso to
provide a second pair of ECG sensing electrodes 612a', 612b', so that one of the ECG
sensing electrodes (e.g., ECG sensing electrode 612a') of the second pair of ECG
sensing electrodes 600' is disposed approximately in the center of the patient's back,
and the other ECG sensing electrode (e.g., ECG sensing electrode 612b') of the
second pair of ECG sensing electrodes 600' is disposed on the patient's side opposite
the other ECG sensing electrode (e.g., ECG sensing electrode 612b) of the first pair of
ECG sensing electrodes 612a, 612b, as shown in FIG. 10. Such an arrangement
provides a front-to-back pairing of ECG sensing electrodes (e.g., 612a, 612a') and a
side-to-side pairing of ECG sensing electrodes (e.g., 612b, 612b'). It should be
appreciated that other placements for the first electrode assembly 600 and the second
electrode assembly 600' may alternatively be used. For example, the first electrode
assembly 600 may be placed on one side of the patient's torso, and the second
electrode assembly 600' placed on the other side of the patient's torso to provide sideto-
side pairings of ECG sensing electrodes.
Having thus described several aspects of at least one embodiment of this
invention, it is to be appreciated various alterations, modifications, and improvements
will readily occur to those skilled in the art. Such alterations, modifications, and
improvements are intended to be part of this disclosure, and are intended to be within
the scope of the invention. Accordingly, the foregoing description and drawings are
by way of example only.

What is claimed is:
CLAIMS
1. An electrode system comprising:
a substrate including a plurality of conductive gel reservoirs disposed on a first
side thereof, a first of the plurality of conductive gel reservoirs disposed in a first
segment of the substrate and a second of the plurality of the conductive gel reservoirs
disposed in a second segment of the substrate;
a fluid channel in fluid communication with a fluid source, the first of the
plurality of conductive gel reservoirs, and the second of the plurality of the conductive
gel reservoirs;
one of a slot or a gap defined in the substrate and extending from a region
proximate the fluid channel and between the first of the plurality of conductive gel
reservoirs and the second of the plurality of the conductive gel reservoirs to an edge of
the substrate distal from the fluid channel, the one of the slot or the gap physically
separating at least a portion of the first segment of the substrate from the second
segment of the substrate.
2. The electrode system of claim 1, further comprising an electrically conductive
layer having a first surface disposed on a second side of the substrate and having a
second surface configured to be disposed adjacent to a patient's skin.
3. The electrode system of claim 2, wherein the plurality of conductive gel
reservoirs and the fluid channel are included in a first impedance reduction system
configured to dispense a first amount of a first electrically conductive gel onto the
second surface of the electrically conductive layer in response to a first activation
signal, and wherein the electrode system further includes a second impedance
reduction system configured to dispense a second amount of a second electrically
conductive gel onto the second surface of the electrically conductive layer in response
to a second activation signal.
4. The electrode system of claim 3, wherein the first impedance reduction system
is similar in construction to the second impedance reduction system.
5. The electrode system of any of claims 1-4, further comprising a garment
wearable on a torso of a patient, the garment including a pocket formed from a layer
of fabric and configured to receive the electrode system, wherein the electrode system
is configured to dispense an amount of a conductive gel through the layer of fabric
and into contact with the patient's skin.
6. The electrode system of claim 5, further comprising an electrically conductive
layer disposed on a second side of the substrate, the electrically conductive layer
including a plurality of apertures configured to dispense the amount of the conductive
gel.
7. The electrode system of claim 5, further comprising an electrically conductive
pathway included in the layer of fabric, the electrically conductive pathway
configured to deliver electrical energy to the patient's skin through the amount of
conductive gel dispensed from the electrode system.
8 . The electrode system of claim 5, wherein the layer of fabric is formed from an
electrically conductive material.
9. The electrode system of claim 5, wherein each of the substrate and the pocket
are tapered to permit the electrode system to be received in the pocket in only a single
orientation.
1 . The electrode system of claim any of claims 1-4, further comprising at least
one ECG sensing electrode configured to monitor an ECG signal of a patient, the at
least one ECG sensing electrode being disposed on a second side of the substrate and
electrically insulated from portions of the electrode system configured to receive
conductive gel.
11. The electrode system of claim 10, further comprising at least one additional
sensor configured to monitor a physiological parameter of the patient other than an
ECG signal of the patient.
2. The electrode system of claim , wherein the at least one additional sensor is
disposed on a third segment of the substrate, the third segment of the substrate at least
partially physically separated by one of a slot or a gap defined in the substrate from
portions of the substrate on which the plurality of conductive gel reservoirs are
disposed.
13. The electrode system of any of claims 1-4, wherein the substrate further
comprises a plurality of additional segments positioned adjacent to one another and at
least partially physically separated from one or another by slots or gaps defined in the
substrate, each of the plurality of additional segments including a conductive gel
reservoir disposed on first side thereof.
14. The electrode system of any of claims 1-4, wherein the fluid pressure source is
disposed on a third segment of the substrate, the third segment of the substrate being
at least partially physically separated by one of a slot or a gap defined in the substrate
from portions of the substrate on which the plurality of conductive gel reservoirs are
disposed.
15. The electrode system of any of claims 1-4, wherein the substrate is tapered
from a first end to a second end, the taper of the substrate preventing insertion of the
electrode system into a tapered pocket of a wearable medical device in an undesired
direction.
16 . The electrode system of any of claims 1-4, further comprising a magnet
disposed on a portion of the substrate and configured to apply a force to a magnet
disposed on a pocket of a garment in which the electrode system can be inserted, the
applied force providing an indication of proper orientation of the electrode system in
the pocket.
17. The electrode system of any of claims 1-4, further comprising a snap disposed
on a portion of the substrate and configured to engage a corresponding snap disposed
on a pocket of a garment in which the electrode system can be inserted, the
engagement of the snap with the corresponding snap providing an indication of proper
orientation of the electrode system in the pocket.
. The electrode system of any of claims 1-4, wherein the substrate comprises a
fabric permeable to conductive gel which the electrode system is configured to
dispense.
19. The electrode system of any of claims 1-4, wherein the substrate is perforated.
20. The electrode system of any of claims 1-4, wherein the electrode system
includes an indicator disposed on an externally visible surface of the electrode system
and configured to visually indicate whether the fluid source has been actuated.