RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional
Application Serial No. 61/839,693, titled "THERAPY ELECTRODE INCLUDING
ACOUSTIC SENSOR," filed on June 26, 2013, which is herein incorporated by
reference in its entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] Aspects and embodiments of the present disclosure are directed to medical
therapy systems, and more particularly, to electrode systems such as medical
electrodes including one or more acoustic sensors and systems for analyzing heart
sounds detected by the one or more acoustic sensors.
[0004] 2. Discussion of Related Art
[0005] 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.
[0006] To protect against cardiac arrest and other cardiac health ailments, some at-risk
subjects may use a non-invasive bodily- attached ambulatory medical monitoring and
treatment device, such as the LifeVest® wearable cardioverter defibrillator available
from ZOLL LifedCor Corporation, a subsidiary of ZOLL Medical Corporation. To
remain protected, the subject wears the device nearly continuously while going about
their normal daily activities, while awake, and while asleep.
SUMMARY
[0007] In accordance with an aspect of the present disclosure, there is provided a
therapeutic device comprising a layer configured to deliver a therapy to a subject and
an acoustic sensor on the device and coupled to the layer. The acoustic sensor may
comprise a three axis multiple-channel MEMS accelerometer. The acoustic sensor
and associated electronics may be configured to provide an indication of whether the
therapeutic device has been correctly oriented on a subject. The acoustic sensor may
comprise a three-channel accelerometer.
[0008] In some embodiments, the therapeutic device comprises a therapy electrode
comprising a conductive layer configured to deliver the therapy to the subject. The
therapy electrode may be configured to selectively apply a defibrillation shock to the
subject andor to provide electrical pacing of a heart of the subject. The therapy
electrode may be configured to monitor an ECG of the subject. In other
embodiments, the therapy comprises a defibrillation pulse. In some embodiments, the
therapy electrode further comprises an electrically conductive gel reservoir configured
to release an electrically conductive gel onto a surface of the conductive layer. The
acoustic sensor may be mechanically coupled to the layer, and it may be electrically
coupled to the layer. The acoustic sensor may be acoustically coupled to the surface
of the conductive layer through a cap housing the conductive gel reservoir. The
acoustic sensor may be adhered to an internal surface of the cap. The acoustic sensor
may be adhered to an upper wall of the cap. The acoustic sensor may be coupled to a
system configured to record signals indicative of sounds produced by a heart of a
patient. The therapeutic device may further comprise a connector or signal conductor
electrically coupling the acoustic sensor to a circuit board coupled to the therapeutic
device, the connector or signal conductor coupled to the therapeutic device with
sufficient slack to provide for the therapy electrode to flex. In other embodiments, the
slack may be provided by the extending connector along a multi-dimensional path.
[0009] In some embodiments, the therapeutic device includes an adhesive layer
configured to adhere the device to the subject.
[0010] In some embodiments, the therapeutic device further comprises a controller
configured to prompt the subject to provide a verbal response prior to delivery of a
therapy, in some embodiments a defibrillation pulse, and to halt delivery of the
therapy responsive to the voice of the subject being detected by the acoustic sensor.
The controller may be configured to differentiate between the voice of the subject and
a voice of a person other than the subject detected by the acoustic sensor. The
controller may be configured to perform different actions responsive to detection of
the voice of the subject by the acoustic sensor and detection of the voice of the person
other than the subject by the acoustic sensor.
[001 1] In accordance with another aspect of the present disclosure, there is provided
an electrode assembly comprising a substrate, and an electrically conductive layer
disposed on the substrate. The electrically conductive layer forms an electrode
portion of the electrode assembly. The electrically conductive layer has a first surface
configured to be placed adjacent a patient's skin. The electrode assembly further
comprises an impedance reduction system configured to dispense an electrically
conductive gel onto the first surface of the electrically conductive layer in response to
an activation signal, and an acoustic sensor disposed on the electrode portion of the
electrode assembly and acoustically coupled to the electrically conductive layer. The
electrode assembly may further comprise at least one ECG sensing electrode
configured to monitor an ECG of the patient.
[0012] The acoustic sensor may comprise a three axis multiple-channel MEMS
accelerometer. The acoustic sensor may comprise a three-channel accelerometer. In
some embodiments, a first channel of the three-channel accelerometer is configured to
monitor sounds produced by a heart of the patient, a second channel of the threechannel
accelerometer is configured to monitor a respiration of the patient, and a third
channel of the three-channel accelerometer is configured to monitor movement of the
patient.
[0013] In some embodiments, the acoustic sensor is configured to be electrically
coupled to a system configured to record signals indicative of sounds produced by a
heart of the patient. The system may be further configured to analyze the signals
indicative of the sounds produced by the heart of the patient. The system may be
further configured to warn the patient responsive to the sounds produced by the heart
of the patient being indicative of an abnormal cardiac condition of the patient.
[0014] In some embodiments, the impedance reduction system includes a conductive
gel reservoir configured to releasably store an amount of the electrically conductive
gel to be dispensed onto the first surface of the electrically conductive layer in
response to the activation signal. The acoustic sensor may be acoustically coupled to
the electrically conductive layer through a cap enclosing the conductive gel reservoir.
The acoustic sensor may be mechanically coupled to an internal wall of the cap. The
acoustic sensor may be disposed on an upper internal wall of the cap.
[0015] In accordance with another aspect of the present disclosure, there is provided a
method of monitoring physiological parameters of a subject. The method comprises
monitoring heart sounds of the subject using an acoustic sensor physically coupled to
a therapeutic device such as a therapy electrode or a defibrillation electrode and
monitoring at least one additional parameter associated with a state of the subject
using the acoustic sensor, the at least one additional parameter including one or more
of a parameter associated with respiration of the subject, gastrointestinal sounds of the
subject, snoring of the subject, and body movement of the subject.
[0016] In some embodiments, the at least one additional parameter further includes
body position of the subject. The parameter associated with respiration of the subject
may include one of sounds of respiration of the subject and movement of a chest of
the subject. Monitoring at least one additional parameter associated with a state of the
subject may comprise monitoring two or more additional parameters associated with a
state of the subject.
[0017] In accordance with another aspect of the present disclosure, there is provided a
method of monitoring physiological parameters of a subject. The method comprises
providing a therapeutic device such as a therapy electrode or a defibrillation electrode
having at least one acoustic sensor acoustically coupled to the therapeutic device, the
at least one acoustic sensor being configured to monitor heart sounds of the subject,
and to further monitor at least one additional physiological parameter of the subject,
the at least one additional physiological parameter including one or more of a
parameter associated with respiration of the subject, gastrointestinal sounds of the
subject, snoring of the subject, and body movement of the subject.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] 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:
[0019] FIG. 1 illustrates a wearable medical device, such as a wearable defibrillator;
[0020] FIG. 2A is a plan view of an electrode portion of a therapy electrode assembly
that may be used with the wearable medical device illustrated in FIG. 1;
[0021] FIG. 2B is a functional block diagram of an impedance reduction system that
may be included in the electrode portion of FIG. 2A;
[0022] FIG. 2C is an isometric view of another embodiment of an electrode portion of
a therapy electrode assembly that may be used with the wearable medical device
illustrated in FIG. 1;
[0023] FIG. 2D is an exploded view of the electrode portion of FIG. 2C;
[0024] FIG. 3A 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;
[0025] FIG. 3B 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
[0026] FIG. 4 illustrates the manner in which the electrode assembly of FIG. 3A may
be worn on the body of a subject.
DETAILED DESCRIPTION
[0027] Aspects and embodiments of the present invention are not limited in
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.
[0028] FIG. 1 illustrates a non-invasive bodily- attached ambulatory medical
monitoring and treatment device 100 (also referred to herein as a wearable medical
device), such as a LifeVest® wearable cardioverter defibrillator available from ZOLL
Medical Corporation. As shown, the wearable medical device 100 includes a harness
110 having a pair of shoulder straps and a belt that is worn about the torso of a
subject. The harness 110 is typically made from a material, such as cotton, which is
breathable, and unlikely to cause skin irritation, even when worn for prolonged
periods of time. In some embodiments, the wearable medical device 100 may include
a plurality of ECG sensing electrodes 112 that are attached to the harness 110 at
various positions about the subject'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 subject 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
112 may be disposed at varying locations about the subject's body.
[0029] The wearable medical device 100 also includes a plurality of therapy
electrodes 114a, 114b that are electrically coupled to the control unit 120 via the
connection pod 130 and which are capable of delivering one or more therapeutic
defibrillating shocks to the body of the subject, if it is determined that such treatment
is warranted. In other embodiments, the therapy electrodes may provide other forms
of therapy, such as electrical pacing of a subject's heart as needed or electric current
to stimulate nerves as a part of Transcutaneous Electrical Nerve Stimulation (TENS)
therapy. As shown, the plurality of therapy electrodes includes a first therapy
electrode 114a that is disposed on the front of the subject's torso and a second therapy
electrode 114b that is disposed on the back of the subject's torso. The second therapy
electrode 114b 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, 114b permits a biphasic shock to be delivered to the body of the
subject, such that a first of the two therapy electrodes may deliver a first phase of the
biphasic shock with the other therapy electrode acting as a return, and the other
therapy electrode may deliver the second phase of the biphasic shock with the first
therapy electrode acting as the return. In some embodiments, the belt of the harness
110 is positioned higher on the torso of a subject than is illustrated in FIG. 1 so that
the plurality of ECG sensing electrodes 112 and the plurality of therapy electrodes
114a, 114b are generally disposed in a plane intersecting the subject's heart. In some
embodiments, any one or more of the ECG sensing electrodes 112 and therapy
electrodes 114a, 114b may include an adhesive layer, for example, an electrically
conductive adhesive, to facilitate holding the electrodes in a proper position on the
subject.
[0030] The connection pod 130 electrically couples the plurality of ECG sensing
electrodes 112 and the plurality of therapy electrodes 114a, 114b 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
subject activity may be monitored.
[0031] In some embodiments, the therapy electrodes 114a, 114b may be multi
purpose electrodes. For example, under control of the control unit 120, the therapy
electrodes 114a, 114b may deliver a defibrillation shock to a subject and may provide
electrical pacing of a subject's heart or electrical current as a part of TENS therapy as
needed.
[0032] 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 may be attached to the subject's clothing or to the harness 110, 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 140
typically includes a number a number of buttons by which the subject, or a bystander
may communicate with the control unit 120, and a speaker by which the control unit
120 may communicate with the subject or the bystander. For example, where the
control unit 120 determines that the subject is experiencing cardiac arrhythmia, the
control unit 120 may issue an audible alarm via a speaker (not shown) on the control
unit 120 and/or the user interface pod 140 alerting the subject and any bystanders to
the subject's medical condition. The control unit 120 may also instruct the subject to
press and hold one or more buttons on the control unit 120 or on the user interface
pod 140 to indicate that the subject is conscious, thereby instructing the control unit
120 to withhold the delivery of one or more therapeutic defibrillating shocks. If the
subject does not respond, the device may presume that the subject is unconscious, and
proceed with the treatment sequence, culminating in the delivery of one or more
defibrillating shocks to the body of the subject. In some embodiments, the
functionality of the user interface pod 140 may be integrated into the control unit 120.
[0033] 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™ DSP56311
Digital Signal Processor. Such a power conserving processor arrangement is
described in co-pending Application Serial No. 12/833,096, titled SYSTEM AND
METHOD FOR CONSERVING POWER IN A MEDICAL DEVICE, filed July 9,
2010 (hereinafter the "'096 application") which is incorporated by reference herein in
its entirety. The at least one processor of the control unit 120 is configured to monitor
the subject's medical condition, to perform medical data logging and storage, and to
provide medical treatment to the subject in response to a detected medical condition,
such as cardiac arrhythmia. The control unit 120 also includes a display (not shown),
for example, a touch screen display (not shown), through which the subject may
receive messages and interact with the wearable medical device. The wearable
medical device 100 may include additional sensors 117, other than the ECG sensing
electrodes 112, capable of monitoring the physiological condition or activity of the
subject. 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 subject may also be provided.
[0034] It has been discovered that the analysis of the sounds 101 made by a subject's
heart due to electro-mechanical activity of the heart may provide valuable information
regarding the state of health of the subject's heart. This information may be used in
conjunction with or in place of ECG data to provide, for example, an indication of
possible problems with a subject's heart or of a potential impending cardiac event
such as cardiac arrest. The analysis of the sounds of a subject's heart may also be
monitored over longer periods of time, for example, days, weeks, or months, to
identify whether the subject's cardiac condition is improving or worsening. Examples
of systems and methods for analyzing the sounds from a subject's heart and the
information such analysis may provide are described in U.S. Patent Nos. 7,302,290,
7,668,589, and 8,409,108, each of which are incorporated herein by reference in their
entireties.
[0035] Thus, in some embodiments, in addition to or in place of ECG sensing
electrodes 112, the wearable medical device 100 may include one or more acoustic
sensors or audio transducers 260 (shown in FIG. 3A) configured to detect sounds
made by the subject's heart. The acoustic sensor(s) or audio transducer(s) 260 may be
provided on or within one or more portions of the wearable medical device 100. The
acoustic sensor(s) or audio transducer(s) 260 may be disposed within portions of the
harness 110 or within or coupled to one of the ECG electrodes 112 or therapy
electrodes 114a, 114b. The acoustic sensor(s) or audio transducer(s) 260 may be
disposed on or within electrodes which are disposed on any of the front, rear, or side
of a subject. The acoustic sensor(s) or audio transducer(s) 260 may be disposed
within electrodes which are attached to the harness 110 and held against the skin of a
subject wearing the wearable medical device 100 and/or disposed within adhesive
electrodes which are adhered to the skin of the subject (see FIG. 4). The acoustic
sensor(s) or audio transducer(s) 260 may be disposed within electrodes including
multiple integrated components including, for example, ECG electrodes, therapy
electrodes, and impedance reduction systems or may be included in an otherwise
single function electrode.
[0036] In some embodiments it may be desirable to locate the acoustic sensor(s) or
audio transducer(s) 260 proximate to or in contact with the skin of a subject so that
heart sounds may be more easily detected than if the acoustic sensor(s) or audio
transducer(s) 260 were spaced from the subject's body. It may be desirable that the
acoustic sensor(s) or audio transducer(s) 260 are acoustically coupled to the subject's
heart even if the acoustic sensor(s) or audio transducer(s) 260 are not in direct
physical contact with the subject's skin. In some embodiments it may be desirable to
locate the acoustic sensor(s) or audio transducer(s) 260 proximate to or in contact with
the skin of a subject proximate the subject's heart, for example, proximate the left
ventricle of the heart, so that the heart sounds are not attenuated by travel through a
significant portion of the subject's body. In some embodiments, an electrode portion
of a therapy electrode assembly in a wearable medical device 100 may be located
above a subject's heart in contact with the subject's skin when the wearable medical
device 100 is worn. Thus, in some embodiments, the acoustic sensor(s) or audio
transducer(s) 260 may be disposed on or in the electrode portion of a therapy
electrode assembly which is arranged to be located proximate the subject's heart, for
example, proximate the left ventricle of the subject's heart.
[0037] The control unit 120 may include a memory unit to record data regarding the
heart sounds. In some embodiments, recorded heart sound data may be stored on a
removable memory card, for example, an SD card. A processor within the control
unit may analyze the heart sounds for indications of potential problems with the
subject's heart. Alternatively or additionally, the data regarding the heart sounds may
be transmitted to an external system for processing and analysis. This transmission
may occur through a wired connection to an external system or wirelessly, through,
for example, Bluetooth™, Wi-Fi, or through a cellular network.
[0038] Feedback 102 may be provided to the subject through a display or speaker on,
for example, the control unit 120 if the analysis of the subject's heart sounds 101
provides an indication of a problem with the subject's heart or of a potential for an
impending cardiac event, for example, cardiac arrest. The results of the analysis of
the subject's heart sounds may also be accessed through an external device, for
example, a home computer through a web site or through a display of an external
system to which the heart sound data may have been transmitted for analysis.
[0039] In healthy adults, there are two normal heart sounds, commonly referred to as
SI and S2. A third heart sound, commonly referred to as S3 (also called a
protodiastolic gallop or ventricular gallop), may be indicative of a problem with a
subject's heart when present. For example, in subjects over 40 years old, S3 has been
associated with an abnormal diastolic filling pattern. The presence of S3 may signal
cardiac problems like a failing left ventricle as in dilated congestive heart failure. A
fourth heart sound, commonly referred to as S4 (also called a presystolic gallop or
atrial gallop), is indicative of a problem with a subject's heart when present. For
example, S4 is often associated with an increased left ventricular stiffness. Heart
murmurs may also be present in some subjects and may indicate cardiac problems.
[0040] The acoustic sensor(s) or audio transducer(s) 260 and associated recording and
analysis systems may be configured to detect and record any one or all of SI, S2, S3,
and S4. Other heart sound parameters which may be monitored and recorded by the
heart sound recording and monitoring system may include any one or more of
electromechanical activation time (EMAT), percentage of EMAT (%EMAT), systolic
dysfunction index (SDI), and left ventricular systolic time (LVST). EMAT is
generally measured from the onset of the Qwave on the ECG to the closure of the
mitral valve within the S1 heart sound. Prolonged EMAT has been associated with
reduced left ventricular ejection fraction (LV EF, being a measure of how much blood
is being pumped out of the left ventricle of the heart with each contraction). %
EMAT is EMAT divided by the dominant RR interval. EMAT is related to the
efficiency of the pump function of the heart. SDI is a multiplicative combination of
ECG and sound parameters (EMA, S3, QRS duration and QR interval). SDI predicts
left ventricular systolic dysfunction with high specificity. LVST is defined as the
time interval between the SI and the S2 heart sounds. It is the systolic portion of the
cardiac cycle. LVST has some heart rate dependence, and tends to be approximately
40% (range 30-50%) of the cardiac cycle but is affected by disease that produces poor
contractility and/or a low ejection fraction.
[0041] Data regarding any one or more of the above referenced heart sound
parameters may be recorded and displayed in, for example, trend charts that may be
accessed by a subject or care provider through the control unit 120 or an external
device. Additionally, control limits regarding any one or more of these heart sound
parameters may be set. The control unit 120 or an external system to which the heart
sound data is transmitted may compare the observed (or calculated) heart sound
parameters with the control limits and if any one or more of the control limits are
violated a warning may be provided to the subject, for example, through a speaker or
display of the control unit 120 or user interface pod 140.
[0042] In some embodiments, the acoustic sensor(s) or audio transducer(s) 260 and
associated recording and analysis systems may be configured to detect and identify
the voice of a subject wearing the wearable medical device so that a patient voice
signature may be used as a response mechanism. The processor within the control
unit 120 may be trained to recognize the voice of the subject during an initial learning
period, using speech recognition and voice analysis methods known in the art. The
control unit 120 may then prompt the subject, for example, through a speaker or a
display, to indicate whether the subject is conscious by saying a predetermined word
or phrase. For example, where the control unit 120 determines that the subject is
experiencing cardiac arrhythmia, the control unit 120 may issue an audible alarm via a
speaker (not shown) on the control unit 120 and/or the user interface pod 140 alerting
the subject and any bystanders to the subject's medical condition. The control unit
120 may also instruct the subject to speak a word or a phrase, which is detected by the
acoustic sensor(s) or audio transducer(s) 260 and transmitted to the control unit 120,
to indicate that the subject is conscious, thereby instructing the control unit 120 to
withhold the delivery of one or more therapeutic defibrillating shocks. If the subject
does not respond, the device may presume that the subject is unconscious, and
proceed with the treatment sequence, culminating in the delivery of one or more
defibrillating shocks to the body of the subject.
[0043] The control unit 120 may be configured to differentiate between the voice of
the subject and the voice of a person other than the subject, for example, a bystander,
first responder, or professional EMT. If, in response to a prompt, a person speaks, the
control unit 120 may analyze the voice to determine whether the voice is that of the
subject or another. If it is the voice of another, the control unit 120 may repeat its
instructions to the subject to speak a word or a phrase. The control unit may modify
the instructions to request silence from other persons around the subject so that the
subject may comply with the instructions. In addition, if, in response to a prompt, the
subject does not respond by speaking, the control unit 120 may monitor a signal from
the acoustic sensor(s) or audio transducer(s) 260 to determine if other persons are
present proximate the subject. If the control unit 120 detects a voice of a person
indicative of the presence of the person proximate the subject, the control unit 120
may issue instructions, for example, through a speaker or a display, requesting the
person to take some action, for example, to provide the control unit 120 with
information regarding the state of the subject through an interface of the control unit
120, to call for assistance, to indicate when professional assistance has arrived, or
perform one or more other actions. The control unit 120 may alter a course of
treatment, for example, postpone or abort the delivery of one or more defibrillating
shocks to the body of the subject, provide data about the subject and his condition, if,
for example, the presence of a bystander is detected by detection of the voice of the
bystander, and the bystander responds to a prompt by the control unit 120 indicating
that professional assistance has arrived to assist the subject. The control unit 120,
upon identification of the presence of professional assistance, may also move into an
alternate mode of operation in which the ambulatory medical monitoring and
treatment device 100 operates as support for the medical assistance being provided.
[0044] As discussed above, to provide protection against cardiac arrest, subjects 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 114a, 114b for comfort and to prevent irritation of the subject's skin.
Where it is determined that one or more defibrillating shocks are to be delivered to the
body of the subject and the subject is non-responsive, the control unit 120 sends a
signal to the plurality of therapy electrodes 114a, 114b 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 subject's skin, thereby improving the efficiency of the
energy delivered to the subject and reducing the chance of damage (for example, in
the form of burning, reddening, or other types of irritation) to the subject's skin.
[0045] FIG. 2A is a plan view of an electrode portion of a therapy electrode assembly
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. 1. FIG. 2B is a functional block diagram of the impedance reduction system that
is included in the electrode portion of the therapy electrode assembly shown in FIG.
2A. The impedance reduction system, when activated, dispenses an impedance
reducing (i.e., electrically conductive) gel onto the exposed surface of the electrode
portion of the therapy electrode assembly that, in use, is placed most proximate to the
subject's body. The electrode portion 200 is a multiple layer laminated structure that
includes an electrically conductive layer 202 (not visible in FIG. 2A, but disposed on
the bottom surface of the embodiment of the electrode portion 250 shown in FIG. 2D)
that forms the electrode and an impedance reduction system 201. In use, the
electrically conductive layer is disposed adjacent the subject's skin, although the
conductive layer need not make direct contact with the subject, as portions of the
harness 110 (FIG. 1) and/or portions of the subject's clothing may be present between
the electrically conductive layer and the subject's skin. As shown in FIG. 2A, the
impedance reduction system 201 is disposed on a side of the electrode portion 200
(i.e., the top-side shown in FIG. 2A) that is opposite the side on which the conductive
layer is formed.
[0046] The impedance reduction system 201 includes a plurality of conductive gel
reservoirs 210, each of which has a respective gel delivery outlet 220, that are fluidly
coupled to a fluid channel 230, and a fluid pressure source 240. The fluid pressure
source 240 is fluidly 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
electrically conductive layer and onto the exposed surface of the electrically
conductive layer that, in use, is placed most proximate to the subject's body. The
apertures in the electrically conductive layer 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 subject's body. Further details regarding the construction of the
electrode portion 200 are described in U.S. Patent No. 5,078,134 (hereinafter "the
' 134 patent") which is incorporated herein by reference.
[0047] FIG. 2C illustrates an electrode portion 250 of a therapy electrode assembly
including an acoustic sensor 260. FIG. 2D is an exploded view of the electrode
portion of FIG. 2C. The exposed conductive surface of the electrode portion is
dimensioned to be capable of delivering large amounts of energy to a subject, for
example, about 200 Joules, such as to perform defibrillation. The acoustic sensor 260
is illustrated in FIG. 2C as disposed within a cap 215' enclosing one of the conductive
gel reservoirs 210 of the electrode portion 250. The cap 215' is formed of a sound
conducting material, for example, a hard plastic. The cap 215' is illustrated as
transparent in FIG. 2C to better illustrate the position of the acoustic sensor 260. The
acoustic sensor 260 is mechanically and acoustically coupled to an upper internal wall
of the cap 215' with an adhesive, for example, epoxy or another form of glue, or by
one or more mechanical fasteners, for example, one or more snaps, tabs, or other
fasteners known in the art. A space is provided between the conductive gel reservoir
210 within the shell 215' and the acoustic sensor 260. The acoustic sensor 260 is
positioned and arranged to be acoustically coupled to the body of a subject to which
the electrode portion 250 is applied. The acoustic coupling of the acoustic sensor 260
to the body of a subject to which the electrode portion 250 is applied may be through
the shell 215' and the substrate 280. The acoustic coupling may be facilitated by the
minimization or elimination of any gaps between the acoustic sensor 260 and shell
215' and between the shell 215' and the substrate 280 of the electrode portion 250. A
protective cover 290 which may be formed from, for example, foam rubber, may be
provided to cover the upper face of the electrode portion 250.
[0048] The cap 215' housing the acoustic sensor 260 may in some embodiments be
shaped differently than caps 215 enclosing the conductive gel reservoirs 210 of the
electrode portion 250 which do not include the acoustic sensor 260. For example, the
cap 215' including the acoustic sensor may have an upper wall which is flattened to
facilitate attachment of the acoustic sensor 260. The caps 215 which do not include
acoustic sensors may, in contrast, have substantially rounded upper walls.
[0049] A connector or signal conductor 270 which may include, for example, a
plurality of wires, a ribbon cable, a coaxial cable, or other forms of electrical signal
conductors known in the art provides electrical connection between the acoustic
sensor 260 and a circuit board 275 coupled to the electrode portion 250. In some
embodiments, the signal conductor is coupled, for example, by an adhesive or one or
more mechanical fasteners to one or more portions of the electrode portion 250. As
illustrated in FIG. 2C, the signal conductor 270 may be provided with some slack by,
for example, being routed along a multi-dimensional path such that it allows for
flexure of the electrode portion 250 without becoming detached from the acoustic
sensor 260 or circuit board 275. The provision of slack in the signal conductor may
be especially desirable in electrode portions 250 which have been designed for
enhanced flexibility, for example, one or more of the electrode portions disclosed in
co-pending Application Serial No. 13/784,074, titled FLEXIBLE THERAPY
ELECTRODE, filed March 4, 2013, which is incorporated by reference herein in its
entirety.
[0050] In other embodiments, the acoustic sensor 260 may be located on or in other
areas of the electrode portion 250. For example, as illustrated in FIG. 3B, the acoustic
sensor 260 may be disposed on a portion of the flat substrate 280 of the electrode
portion 250. The acoustic sensor 260 may in alternate embodiments be disposed in
any location where it may acoustically couple to the body of a subject. The electrode
portion 250 may include a single acoustic sensor as illustrated, or may include
multiple acoustic sensors 260.
[0051] The acoustic sensor 260 may comprise any device that may detect sounds
from a subject's heart and provide an output signal responsive to the detected heart
sounds. In some embodiments the acoustic sensor 260 comprises a microphone. In
some embodiments the acoustic sensor 260 comprises an accelerometer. The acoustic
sensor 260 may comprise a microelectromechanical system (MEMS) accelerometer.
In some embodiments the acoustic sensor 260 comprises a multi-channel
accelerometer, for example, a three-channel accelerometer. The acoustic sensor may
comprise a three-channel accelerometer configured to sense movement in each of
three orthogonal axes. An example of an accelerometer which may be utilized in
some embodiments is a LIS344ALH accelerometer, available from
STMicroelectronics. The acoustic sensor 260 and associated electronics may be
configured to monitor any one or more of a subject's respiration, a subject's heart
sounds, a subject's position, and an activity level of a subject. The acoustic sensor
260 and associated electronics may additionally or alternatively be configured to
monitor other sounds which may be indicative of a state of health of a subject, for
example, gastrointestinal sounds or the sounds of snoring or the absence of such
sounds, for example, to provide an indication of the subject experiencing sleep apnea.
The acoustic sensor 260 may provide signals indicative of the subject's respiration on
a first channel, signals indicative of the subject's heart sounds on a second channel,
and signals indicative of the subject's position on a third channel. In other
embodiments, the different channels may be utilized to provide signals indicative of
more than one physiological parameter or other parameter associated with the state of
the subject. For example, in one embodiment, the acoustic sensor 260 may provide
signals indicative of the subject's heart sounds on a first channel, signals indicative of
the subject's respiration on a second channel, and signals indicative of the subject's
body position on any or all of the first, second, and third channel. It should be
appreciated that dependent on the underlying parameter that is being monitored,
multiple signals related to the parameter being monitored may be received over a
single channel or a number of different channels. The acoustic sensor 260 and
associated electronics may also in some embodiments be configured to detect sounds
associated with the release of conductive gel from the conductive gel reservoirs 210 of
an electrode portion 250 of a therapy electrode assembly and provide an indication of
the release of the conductive gel to a controller or alarm system associated with the
therapy electrode assembly.
[0052] Further, when including an accelerometer, the acoustic sensor 260 and
associated electronics may be configured to provide an indication of whether a
therapy electrode assembly including the acoustic sensor has been correctly placed on
a subject. The acoustic sensor 260 and associated electronics may be configured to
detect, for example, by sensing the direction of the pull of the Earth's gravity, the
orientation of the acoustic sensor 260, and of the therapy electrode assembly in which
it is included. The acoustic sensor 260 and associated electronics may thus be utilized
to provide an indication of whether the therapy electrode assembly has been correctly
placed on a subject or whether it has been incorrectly placed, for example, in an
inverted position.
[0053] The acoustic sensor 260 and associated electronics may be configured to
detect whether CPR is being performed on the subject and to output a signal
responsive to the detection of the performance of CPR. Further, electronics
associated with the acoustic sensor 260 may be configured to analyze the motion
associated with the performance of CPR, for example, the rate and depth of chest
compressions. In some embodiments, an acoustic sensor 260 may be provided on a
portion of a therapy electrode assembly, for example, a tab extending from an
electrode portion 250, or on a position of a wearable medical device 100, which
would be proximate the xiphoid 116 of a subject when worn by the subject, as
illustrated in FIG. 1. Such placement of an acoustic sensor would facilitate measuring
the depth of chest compressions during the administration of CPR to the subject in
addition to detecting whether CPR is being performed. The electronics associated
with the acoustic sensor 260 may be configured to provide feedback to a person
administering the CPR through, for example, one or more indicators or through a
speaker to adjust the rate and/or depth of chest compressions to provide for a more
effective administration of CPR.
[0054] Applicants have appreciated that there may be instances where it would be
desirable to have redundancy in the impedance reduction system described above.
Electrodes including redundant impedance reduction systems are disclosed in coowned
U.S. Patent No. 8,406,842 which is incorporated by reference herein in its
entirety.
[0055] FIG. 3A illustrates an 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 400 includes a pair of ECG
sensing electrodes 412a, 412b for monitoring the cardiac function of a subject. The
electrode assembly 400 further includes a therapy electrode 414, and at least two
impedance reduction systems 301, 302. The pair of ECG sensing electrodes 412a,
412b may be electrically separated from the therapy electrode 414, for example, by an
insulator. It should be appreciated that in other embodiments, the electrode assembly
400 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 may vary from
that shown in FIG. 3A. In yet a further embodiment, the integrated electrode
assembly may include additional sensors 416, other than the one or more ECG
sensing electrodes and the therapy electrode, that are capable of monitoring other
physiological parameters of a subject, such as blood pressure, heart rate, thoracic
impedance, pulse oxygen level, respiration rate, heart sounds, etc. The additional
sensors 416 may include, for example, one or more acoustic sensors 260.
[0056] The electrode assembly 400 may be worn on the subject's body such that one
of the pair of ECG sensing electrodes 412a, 412b is disposed approximately in the
center of the subject's torso, and the other of the pair of ECG sensing electrodes 412a,
412b is disposed on the side of the subject's torso. For example, as shown in FIG. 4,
the electrode assembly 400 may be worn on the front of the subject's torso, so that the
ECG sensing electrode 412a is disposed approximately in the center of the subject's
chest, and the other ECG sensing electrode 412b is disposed on the subject's side. A
second electrode assembly 400' may be worn on the back of the subject's torso to
provide a second pair of ECG sensing electrodes 412a', 412b', so that one of the ECG
sensing electrodes (for example, ECG sensing electrode 412a') of the second pair of
ECG sensing electrodes 400' is disposed approximately in the center of the subject's
back, and the other ECG sensing electrode (for example, ECG sensing electrode
412b') of the second pair of ECG sensing electrodes 400' is disposed on the subject's
side opposite the other ECG sensing electrode (for example, ECG sensing electrode
412b) of the first pair of ECG sensing electrodes 412a, 412b, as shown in FIG. 4.
Such an arrangement provides a front-to-back pairing of ECG sensing electrodes (for
example, 412a, 412a') and a side-to-side pairing of ECG sensing electrodes (for
example, 412b, 412b'). It should be appreciated that other placements for the first
electrode assembly 400 and the second electrode assembly 400' may alternatively be
used. For example, the first electrode assembly 400 may be placed on one side of the
subject's torso, and the second electrode assembly 400' placed on the other side of the
subject's torso to provide side-to-side pairings of ECG sensing electrodes.
[0057] The first and second electrode assemblies 400, 400' may include an
electrically conductive adhesive layer so that the electrodes assemblies may be
directly attached to the subject's skin, or alternatively, they may be attached to the
harness as depicted in FIG. 1 and held in position against the torso of the subject.
Where only one of the electrode assemblies includes an acoustic sensor 260, the
electrode assembly may be positioned so that the acoustic sensor is disposed
proximate the subject's heart.
[0058] In further embodiments, acoustic sensors 260 for monitoring any of the
various parameters described herein, for example, sounds associated with a subject's
heart or respiration, orientation of a subject, or motion associated with the
administration of CPR to a subject, etc., may be included in electrodes having shapes
and materials of construction different from those depicted in, for example, FIGS. 2C
and 2D. For example, acoustic sensors may be included in electrodes which consist
essentially of a conductive layer and a conductive adhesive or adhesive film for
retaining the electrode on the skin of a subject. Electrodes which may include
acoustic sensors 260 having the functionality described herein are not limited to any
particular form or type.
[0059] 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.
[0060] What is claimed is:

CLAIMS
1. A therapeutic device comprising:
a layer configured to deliver a therapy to a subject; and
an acoustic sensor on the device and coupled to the layer.
2. The therapeutic device of claim 1, wherein the acoustic sensor
comprises an accelerometer.
3. The therapeutic device of claim 2, wherein the acoustic sensor
comprises a MEMS accelerometer.
4. The therapeutic device of claim 3, wherein the acoustic sensor
comprises a multi-channel accelerometer.
5. The therapeutic device of claim 4, wherein the acoustic sensor
comprises a three-channel accelerometer.
6. The therapeutic device of claim 1, wherein the acoustic sensor is a
three axis multiple-channel accelerometer.
7. The therapeutic device of claim 6, wherein the acoustic sensor and
associated electronics is configured to provide an indication of whether the
therapeutic device has been correctly oriented on a subject.
8. The therapeutic device of claim 6,
wherein the therapeutic device comprises a therapy electrode with a
conductive layer and the therapy comprises an electrical pulse;
wherein the therapy electrode further comprises an electrically conductive gel
reservoir configured to release an electrically conductive gel onto a surface of the
conductive layer; and
wherein the acoustic sensor is acoustically coupled to the surface of the
conductive layer through a cap housing the conductive gel reservoir.
9. The therapeutic device of claim 8, wherein the acoustic sensor is
adhered to an internal surface of the cap.
10. The therapeutic device of claim 9, wherein the acoustic sensor is
adhered to an upper wall of the cap.
11. The therapeutic device of claim 1, wherein the acoustic sensor is
coupled to a system configured to record signals indicative of sounds produced by a
heart of a patient.
12. The therapeutic device of claim 1, including an adhesive layer
configured to adhere the electrode to the subject.
13. The therapeutic device of claim 1, configured to selectively apply at
least one of a defibrillation shock to the subject, electrical current as a part of
Transcutaneous Electrical Nerve Stimulation (TENS) therapy, and electrical pacing of
a heart of the subject.
14. The therapeutic device of claim 1, configured to selectively apply a
plurality of forms of therapy to the subject.
15. The therapeutic device of claim 1, configured to monitor an ECG of
the subject.
16. The therapeutic device of claim 1, further comprising a signal
conductor electrically coupling the acoustic sensor to a circuit board coupled to the
therapy electrode, the signal conductor coupled to the therapy electrode with
sufficient slack to provide for the therapeutic device to flex.
17. The therapeutic device of claim 16, wherein the signal conductor
extends along a multidimensional route to supply the slack to the signal conductor
when the therapeutic device is flexed.
18. The therapeutic device of claim 1, further comprising a controller
configured to prompt the subject to provide a verbal response prior to delivery of a
therapy, and to halt delivery of the therapy responsive to the voice of the subject being
detected by the acoustic sensor.
19. The therapeutic device of claim 18, wherein the controller is
configured to differentiate between the voice of the subject and a voice of a person
other than the subject detected by the acoustic sensor.
20. The therapeutic device of claim 19, wherein the controller is
configured to perform different actions responsive to detection of the voice of the
subject by the acoustic sensor and detection of the voice of the person other than the
subject by the acoustic sensor.
21. A medical device assembly comprising:
a substrate;
a layer disposed on the substrate, the layer forming an therapeutic device
portion of the medical device assembly, the layer having a first surface configured to
be placed adjacent a patient's skin and to selectively apply a therapy to the patient in
response to an activation signal; and
an acoustic sensor acoustically coupled to the layer.
22. The medical device assembly of claim 21, wherein the acoustic sensor
includes an accelerometer.
23. The medical device assembly of claim 22, wherein the acoustic sensor
includes a MEMS accelerometer
24. The medical device assembly of claim 22, wherein the acoustic sensor
includes a three axis multi-channel accelerometer.
25. The medical device assembly of claim 24, wherein the acoustic sensor
includes a three-channel accelerometer.
26. The medical device assembly of claim 25, wherein a first channel of
the three-channel accelerometer is configured to monitor sounds produced by a heart
of the patient, a second channel of the three-channel accelerometer is configured to
monitor a respiration of the patient, and a third channel of the three-channel
accelerometer is configured to monitor movement of the patient.
27. The medical device assembly of claim 21, wherein the acoustic sensor
is configured to be electrically coupled to a system configured to record signals
indicative of sounds produced by a heart of the patient.
28. The medical device assembly of claim 27, wherein the system is
further configured to analyze the signals indicative of the sounds produced by the
heart of the patient.
29. The medical device assembly of claim 28, wherein the system is
further configured to warn the patient responsive to the sounds produced by the heart
of the patient being indicative of an abnormal cardiac condition of the patient.
30. The medical device assembly of claim 28, wherein the impedance
reduction system includes a conductive gel reservoir configured to releasably store an
amount of the electrically conductive gel to be dispensed onto the first surface of the
electrically conductive layer in response to the activation signal, and wherein the
acoustic sensor is acoustically coupled to the electrically conductive layer through a
cap enclosing the conductive gel reservoir.
31. The medical device assembly of claim 28, wherein the acoustic sensor
is mechanically coupled to an internal wall of the cap.
32. The medical device assembly of claim 31, wherein the acoustic sensor
is disposed on an upper internal wall of the cap.
33. The medical device assembly of claim 21, wherein the layer comprises
an electrically conductive layer forming an electrode portion, wherein the therapy
comprises providing an electric current to the patient in response to the activation
signal, and wherein the medical device assembly further comprises an impedance
reduction system configured to dispense an electrically conductive gel onto the first
surface of the electrically conductive layer in response to the activation signal.
34. The medical device assembly of claim 28, wherein the electrode
assembly further comprises at least one ECG sensing electrode configured to monitor
an ECG of the patient.
35. A method of monitoring physiological parameters of a subject, the
method comprising:
monitoring heart sounds of the subject using an acoustic sensor coupled to a
therapeutic device configured to provide a therapy to the subject in response to an
activation signal; and
monitoring at least one additional parameter associated with a state of the
subject using the acoustic sensor, the at least one additional parameter including one
or more of a parameter associated with respiration of the subject, gastrointestinal
sounds of the subject, snoring of the subject, and body movement of the subject.
36. The method of claim 35, wherein the at least one additional parameter
further includes body position of the subject.
37. The method of claim 35, wherein the parameter associated with
respiration of the subject includes one of sounds of respiration of the subject and
movement of a chest of the subject.
38. The method of claim 35, wherein monitoring at least one additional
parameter associated with a state of the subject comprises monitoring two or more
additional parameters associated with a state of the subject.
39. The method of claim 35, wherein monitoring heart sounds of the
subject further comprising using an acoustic sensor physically coupled to a therapy
electrode configured to provide an electric current to the patient in response to the
activation signal.
40. A method of monitoring physiological parameters of a subject, the
method comprising:
providing a therapeutic device having at least one acoustic sensor acoustically
coupled to the therapeutic device, the at least one acoustic sensor being configured to
monitor heart sounds of the subject, and to further monitor at least one additional
physiological parameter of the subject, the at least one additional physiological
parameter including one or more of a parameter associated with respiration of the
subject, gastrointestinal sounds of the subject, snoring of the subject, and body
movement of the subject.
41. The method of claim 40, wherein providing the therapeutic device
comprises providing a defibrillation electrode.