U.S. patent application number 17/326501 was filed with the patent office on 2021-09-02 for monitoring cpr by a wearable medical device.
The applicant listed for this patent is ZOLL Medical Corporation. Invention is credited to Rachel H. Carlson, Gregory R. Frank, Gary A. Freeman, Thomas E. Kaib.
Application Number | 20210267843 17/326501 |
Document ID | / |
Family ID | 1000005598873 |
Filed Date | 2021-09-02 |
United States Patent
Application |
20210267843 |
Kind Code |
A1 |
Freeman; Gary A. ; et
al. |
September 2, 2021 |
MONITORING CPR BY A WEARABLE MEDICAL DEVICE
Abstract
A wearable medical device comprises a garment configured to be
worn about a torso of a patient. The wearable medical device
further comprises a CPR sensor for detecting a characteristic of a
CPR therapy provided to the patient. The CPR sensor is coupled to
the garment to provide movement between a stowed position and a
deployed position. The CPR sensor is positioned at a center of a
chest of the patient when the CPR sensor is in the deployed
position. The wearable medical device further comprises an output
device. The wearable medical device further comprises a processor
configured for processing information from the CPR sensor and
providing, to the output device, information about the CPR therapy
provided to the patient.
Inventors: |
Freeman; Gary A.; (Waltham,
MA) ; Kaib; Thomas E.; (Irwin, PA) ; Frank;
Gregory R.; (Mt. Lebanon, PA) ; Carlson; Rachel
H.; (Falls Creek, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZOLL Medical Corporation |
Chelmsford |
MA |
US |
|
|
Family ID: |
1000005598873 |
Appl. No.: |
17/326501 |
Filed: |
May 21, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16730360 |
Dec 30, 2019 |
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17326501 |
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15463117 |
Mar 20, 2017 |
10561575 |
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16730360 |
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62315803 |
Mar 31, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61H 2201/1614 20130101;
G09B 5/02 20130101; A61H 31/005 20130101; A61H 2201/165 20130101;
G09B 23/288 20130101; A61H 2201/1623 20130101; G09B 5/06 20130101;
A61H 2201/1619 20130101; A61N 1/0484 20130101; A61H 2201/5061
20130101; A61B 5/00 20130101; A61H 2201/5097 20130101; A61N 1/39044
20170801; A61H 2201/5046 20130101; G09B 5/04 20130101; A61H
2201/5084 20130101 |
International
Class: |
A61H 31/00 20060101
A61H031/00; G09B 23/28 20060101 G09B023/28; G09B 5/02 20060101
G09B005/02; G09B 5/04 20060101 G09B005/04; G09B 5/06 20060101
G09B005/06; A61N 1/04 20060101 A61N001/04; A61B 5/00 20060101
A61B005/00; A61N 1/39 20060101 A61N001/39 |
Claims
1-90. (canceled)
91. A wearable medical device, comprising: a garment configured to
be worn about a torso of a patient; a CPR sensor for detecting a
characteristic of a CPR therapy provided to the patient, the CPR
sensor being coupled to the garment to provide movement between a
stowed position and a deployed position, wherein the CPR sensor is
positioned at a center of a chest of the patient when the CPR
sensor is in the deployed position; an output device; and a
processor configured for processing information from the CPR sensor
and providing, to the output device, information about the CPR
therapy provided to the patient.
92. The wearable medical device of claim 91, wherein: the garment
comprises a flap; and the flap and the CPR sensor are configured to
allow for the movement between the stowed position and the deployed
position.
93. The wearable medical device of claim 92, wherein: the garment
further comprises a belt; the flap is attached to the belt; and the
movement causes the flap to fold away from the belt and be
positioned at a location above a xiphoid process of the
patient.
94. The wearable medical device of claim 92, wherein the
characteristic of the CPR therapy comprises one or more of a chest
compression depth or a chest compression rate.
95. The wearable medical device of claim 92, wherein the CPR sensor
is attached to the flap using a hook-and-loop fastener.
96. The wearable medical device of claim 92, wherein the processor
is further configured to provide, via the output device,
instructions for a rescuer to move the CPR sensor from the stowed
position to the deployed position before initiating the CPR
therapy.
97. The wearable medical device of claim 92, wherein: the garment
comprises a belt and a shoulder strap; and the flap is attached to
the belt.
98. The wearable medical device of claim 97, wherein the flap and
the CPR sensor are positioned in front of the belt when the CPR
sensor is in the stowed position.
99. The wearable medical device of claim 92, wherein the flap is
pivotable between the stowed position and the deployed
position.
100. The wearable medical device of claim 91, wherein the garment
comprises a pocket configured to receive the CPR sensor when the
CPR sensor is in the stowed position.
101. The wearable medical device of claim 100, wherein the CPR
sensor is configured to wirelessly communicate with the
processor.
102. The wearable medical device of claim 100, wherein the garment
further comprises a pivoting flap having the CPR sensor attached
thereto.
103. The wearable medical device of claim 102, wherein the CPR
sensor is attached to the pivoting flap using a snap fastener.
104. The wearable medical device of claim 100, wherein: the garment
comprises a waistband and a shoulder strap; and the pocket is
provided on the waistband.
105. The wearable medical device of claim 104, wherein the CPR
sensor is positioned at a central portion of the waistband when the
CPR sensor is in the stowed position.
106. The wearable medical device of claim 104, wherein the
waistband is positioned over a rib of the patient when the patient
wears the garment.
107. The wearable medical device of claim 100, wherein the
characteristic of the CPR therapy comprises one or more of a chest
compression depth or a chest compression rate.
108. The wearable medical device of claim 100, wherein the
processor is further configured to provide, via the output device,
instructions for a rescuer to remove the CPR sensor from the pocket
and position the CPR sensor in the deployed position before
initiating the CPR therapy.
109. The wearable medical device of claim 91, wherein the processor
is further configured to provide, via the output device,
instructions for a rescuer to move the CPR sensor from the stowed
position to the deployed position before initiating the CPR
therapy.
110. The wearable medical device of claim 91, wherein the CPR
sensor is configured to wirelessly communicate with the processor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/730,360 (filed 30 Dec. 2019), which is a
continuation of U.S. patent application Ser. No. 15/463,117 (filed
20 Mar. 2017), which claims the benefit of U.S. Provisional Patent
Application 62/315,803 (filed 31 Mar. 2016). All subject matter set
forth in the above referenced applications is hereby incorporated
by reference in its entirety into the present application as if
fully set forth herein.
BACKGROUND
[0002] This disclosure relates to systems and techniques for
monitoring cardiopulmonary resuscitation (CPR) by a wearable
medical device.
[0003] There are a wide variety of electronic and mechanical
devices for monitoring and treating patients' medical conditions.
In some examples, depending on the underlying medical condition
being monitored or treated, medical devices such as defibrillators
may be surgically implanted or connected externally to the patient.
In some cases, physicians may use medical devices alone or in
combination with drug therapies to treat patient medical
conditions.
[0004] One of the most deadly cardiac arrhythmias is ventricular
fibrillation, which occurs when normal, regular electrical impulses
are replaced by irregular and rapid impulses, causing the heart
muscle to stop normal contractions and to begin to quiver. Normal
blood flow ceases, and organ damage or death can result in minutes
if normal heart contractions are not restored. Because the victim
has no perceptible warning of the impending fibrillation, death
often occurs before the necessary medical assistance can arrive.
Other cardiac arrhythmias can include excessively slow heart rates
known as bradycardia. "Cardiac Arrest" refers generically to the
medical condition of a patient in which various arrhythmias of the
heart, such as ventricular fibrillation, ventricular tachycardia,
pulseless electrical activity (PEA), and asystole (heart stops all
electrical activity), result in the heart providing insufficient
levels of blood flow to the brain and other vital organs for the
support of life.
[0005] Implantable cardioverter/defibrillators (ICDs) or external
defibrillators (such as manual defibrillators or automated external
defibrillators (AEDs), termed "conventional external
defibrillators") have significantly improved the ability to treat
these otherwise life-threatening conditions. Such devices operate
by applying corrective electrical pulses directly to the patient's
heart. Ventricular fibrillation or ventricular tachycardia can be
treated by an implanted or external defibrillator.
SUMMARY
[0006] In an aspect, a wearable medical device includes a garment
configured to be worn about a torso of a patient. The wearable
medical device also includes at least one ventilation sensor for
detecting a characteristic of ventilations of a cardiopulmonary
resuscitation (CPR) therapy. The wearable medical device also
includes an output device. The wearable medical device also
includes a processor configured for processing information from the
at least one ventilation sensor and providing, to the output
device, information about the CPR therapy.
[0007] Implementations can include one or more of the following
features.
[0008] In some implementations, the wearable medical device
includes at least one chest compression sensor for detecting a
characteristic of chest compressions of the CPR therapy.
[0009] In some implementations, the at least one ventilation sensor
and the at least one chest compression sensor is the same
sensor.
[0010] In some implementations, the same sensor comprises an
accelerometer.
[0011] In another aspect, a wearable medical device includes a
garment configured to be worn about a torso of a patient. The
wearable medical device also includes at least one chest
compression sensor for measuring a characteristic of chest
compressions of a CPR therapy. The at least one chest compression
sensor is attached to the garment and configured on the garment
such that it is positioned parasternally on the patient. The
wearable medical device also includes an output device that
provides feedback to a rescuer. The wearable medical device also
includes a processor configured for processing information from the
at least one chest compression sensor and providing, to the output
device, information about the CPR therapy. The wearable medical
device also includes memory connected to the processor. The
wearable medical device also includes a representation of a
geometry of the patient's chest used by the wearable medical device
to determine one or more adjustment to be applied to motion data
from the at least one chest compression sensor to enhance an
accuracy of the measured characteristic of the chest
compressions.
[0012] Implementations can include one or more of the following
features.
[0013] In some implementations, the representation of the geometry
of the patient's chest is based on generic anthropometric data from
a patient population.
[0014] In some implementations, the representation of the geometry
of the patient's chest is based on measurements of the patient.
[0015] In some implementations, the one or more adjustment is based
on one or more of a table lookup, a linear adjustment function, and
a non-linear adjustment function.
[0016] In another aspect, a wearable medical device includes a
garment configured to be worn about a torso of a patient. The
wearable medical device also includes one or more CPR sensors for
detecting a characteristic of a CPR therapy. The wearable medical
device also includes an output device. The wearable medical device
also includes a processor configured for processing information
from the one or more CPR sensors and providing, to the output
device, information about the CPR therapy. At least one of the one
or more CPR sensors is movably attached to the garment. The at
least one CPR sensor is configured to be positioned to the center
of the patient's chest prior to initiation of the CPR therapy.
[0017] Implementations can include one or more of the following
features.
[0018] In some implementations, the at least one CPR sensor is
configured to be repositioned from a location at the garment to the
center of the patient's chest prior to initiation of the CPR
therapy.
[0019] In some implementations, the CPR therapy includes chest
compressions.
[0020] In some implementations, the CPR therapy includes
ventilations.
[0021] In some implementations, the at least one CPR sensor is a
chest compression sensor.
[0022] In some implementations, the chest compression sensor
includes a motion sensor.
[0023] In some implementations, the motion sensor includes an
accelerometer.
[0024] In some implementations, the at least one CPR sensor is
stored in a compartment of the garment.
[0025] In some implementations, the at least one CPR sensor is
removed from the compartment and placed at the center of the
patient's chest prior to initiation of the CPR therapy.
[0026] In some implementations, the compartment includes a flap
that is configured to fold away from the garment such that the at
least one CPR sensor is repositioned to the center of the patient's
chest when the flap is folded away from the garment.
[0027] In some implementations, the at least one CPR sensor is
attached to the garment in a manner chosen to increase patient
compliance with respect to wearing the garment.
[0028] In some implementations, the characteristic of the CPR
therapy includes a depth of chest compressions.
[0029] In some implementations, the characteristic of the CPR
therapy includes a rate of chest compressions.
[0030] In some implementations, at least one of the one or more CPR
sensors includes an accelerometer.
[0031] In some implementations, at least one of the one or more CPR
sensors is positioned at the side of the patient's abdomen when the
garment is worn by the patient.
[0032] In some implementations, at least one of the one or more CPR
sensors is positioned behind the patient when the garment is worn
by the patient.
[0033] In some implementations, motion information from the CPR
sensor positioned behind the patient is subtracted from motion
information from the CPR sensor positioned to the center of the
patient's chest.
[0034] In some implementations, the at least one CPR sensor is
configured to be repositioned to a location above the patient's
xiphoid process prior to initiation of the CPR therapy.
[0035] In some implementations, at least one of the one or more CPR
sensors is configured to communicate wirelessly with the
processor.
[0036] In some implementations, the wearable medical device
includes at least one sensing electrode for sensing a cardiac
arrhythmia condition of the patient, and at least one therapy
electrode for delivering at least one therapeutic pulse to the
patient in response to the sensed cardiac arrhythmia condition.
[0037] In some implementations, at least one of the one or more CPR
sensors is integrated with the at least one therapy electrode.
[0038] In some implementations, at least one of the one or more CPR
sensors is discrete from the at least one sensing electrode and the
at least one therapy electrode.
[0039] In some implementations, the processor is configured to
process information related to a location of a rescuer's hand
during the CPR treatment.
[0040] In some implementations, the output device includes an audio
output device.
[0041] In some implementations, the audio output device is
configured to provide rhythmic audio indicative of a target rate of
chest compressions for the CPR therapy.
[0042] In some implementations, the audio output device is
configured to provide one or more verbal commands to a user
administering the CPR therapy to the patient.
[0043] In some implementations, the one or more verbal commands are
related to one or both of a rate of chest compressions and a depth
of chest compressions of the CPR therapy being administered to the
patient.
[0044] In some implementations, the output device includes a
wireless transceiver for communicating with an external device
having a display.
[0045] In some implementations, the display is configured to
present information related to one or both of a rate of chest
compressions and a depth of chest compressions of the CPR therapy
being administered to the patient.
[0046] In some implementations, the display is configured to
present one or more instructions to a user administering the CPR
therapy to the patient.
[0047] In some implementations, the one or more instructions are
related to one or both of a rate of chest compressions and a depth
of chest compressions of the CPR therapy being administered to the
patient.
[0048] In some implementations, the garment includes a
pressure-sensitive fabric.
[0049] In another aspect, a wearable medical device includes a
garment configured to be worn about a torso of a patient. The
wearable medical device also includes at least two sensors for
detecting a characteristic of a CPR therapy. The at least two
sensors are positioned at locations at the anterior surface of the
patient's chest chosen to identify a characteristic of the center
of the patient's chest. The wearable medical device also includes
an output device. The wearable medical device also includes a
processor configured for processing information from the sensors
and providing, to the output device, information about the CPR
therapy. The processing includes determining information about a
geometry defined by the sensors.
[0050] Implementations can include one or more of the following
features.
[0051] In some implementations, the CPR therapy includes chest
compressions.
[0052] In some implementations, the CPR therapy includes
ventilations.
[0053] In some implementations, the characteristic of the center of
the patient's chest includes a distance between the patient's
sternum and the posterior of the patient.
[0054] In some implementations, the characteristic of the center of
the patient's chest includes a location above the patient's xiphoid
process relative to the posterior of the patient.
[0055] In some implementations, the wearable medical device
includes two sensors.
[0056] Determining information about the geometry defined by the
sensors includes determining motion of a line defined by the two
sensors.
[0057] In some implementations, the garment includes a waistband
and two shoulder straps. A first sensor is positioned on the
waistband and a second sensor is positioned on one of the shoulder
straps.
[0058] In some implementations, the wearable medical device
includes three sensors.
[0059] Determining information about the geometry defined by the
sensors includes determining motion of a triangular plane defined
by the three sensors.
[0060] In some implementations, the garment includes a waistband
and two shoulder straps. A first sensor is positioned on the
waistband and a second and third sensor are positioned on the
shoulder straps.
[0061] In another aspect, a wearable medical device includes a
garment configured to be worn about a torso of a patient. The
wearable medical device also includes one or more sensors for
measuring a characteristic of a CPR therapy. The wearable medical
device also includes an output device. The wearable medical device
also includes a processor configured for receiving input from a
measuring device that is configured for measuring information
related to a geometry of the patient's chest prior to initiation of
CPR. The measuring device is also configured for providing, to the
output device, information about the CPR therapy based on the
characteristic of the CPR therapy and the information related to
the geometry of the patient's chest.
[0062] Implementations can include one or more of the following
features.
[0063] In some implementations, the measuring device includes one
or more accelerometers.
[0064] In some implementations, at least one of the accelerometers
is configured to measure information related to acceleration in
three axes.
[0065] In some implementations, at least one of the accelerometers
is configured to measure information related to tilt.
[0066] In some implementations, the processor is configured to use
the information related to the geometry of the patient's chest to
generate a 3D representation of the patient's chest prior to
initiation of CPR.
[0067] In some implementations, the measuring device is configured
to measure information indicative of a location of the one or more
sensors.
[0068] In some implementations, the geometry of the patient's chest
includes transverse diameter of the chest.
[0069] In some implementations, the geometry of the patient's chest
includes anterior-posterior diameter of the chest.
[0070] In some implementations, the geometry of the patient's chest
includes contours of the chest.
[0071] In some implementations, the measuring device includes one
or more cameras.
[0072] In some implementations, the one or more cameras are
configured to scan a surface of the patient's chest.
[0073] In another aspect, a wearable medical device includes a
garment configured to be worn about a torso of a patient. The
wearable medical device also includes one or more sensing
electrodes for receiving one or more cardiac signals from the
patient. The wearable medical device also includes one or more CPR
sensors for detecting a characteristic of a CPR therapy. The
wearable medical device also includes a processor configured for
determining that the patient is experiencing pulseless electrical
activity (PEA) based on the received one or more cardiac signals,
and providing feedback related to the CPR therapy based on the
detected characteristic. The feedback is for assisting a rescuer in
performing the CPR therapy.
[0074] Implementations can include one or more of the following
features.
[0075] In some implementations, the CPR therapy includes chest
compressions.
[0076] In some implementations, the CPR therapy includes
ventilations.
[0077] In some implementations, the CPR therapy stimulates coronary
circulation in the patient such that the patient's heart regains
sufficient cardiac output to generate a pulse.
[0078] In some implementations, the feedback related to the CPR
therapy assists the rescuer in causing a buildup of aortic pressure
in the patient's heart to be optimized.
[0079] In another aspect, a wearable medical device includes a
garment configured to be worn about a torso of a patient. The
wearable medical device also includes one or more sensing
electrodes for receiving one or more cardiac signals from the
patient. The wearable medical device also includes one or more CPR
sensors for detecting a characteristic of a CPR therapy. The
wearable medical device also includes a processor configured for
determining that the patient is experiencing fine ventricular
fibrillation (VF) based on the received one or more cardiac
signals, and providing feedback related to the CPR therapy based on
the detected characteristic. The feedback is for assisting a
rescuer in performing the CPR therapy.
[0080] Implementations can include one or more of the following
features.
[0081] In some implementations, the CPR therapy includes chest
compressions.
[0082] In some implementations, the CPR therapy includes
ventilations.
[0083] In some implementations, the CPR therapy causes the fine VF
to change to a coarse VF.
[0084] In some implementations, the feedback related to the CPR
therapy assists the rescuer in causing an amplitude of the VF to be
maximized.
[0085] In another aspect, a method includes receiving, by a sensing
electrode of a wearable medical device, one or more cardiac signals
from a patient. The method also includes detecting, by a CPR sensor
of the wearable medical device, a characteristic of a CPR therapy.
The method also includes determining, by a processor of the
wearable medical device, that the patient is experiencing PEA based
on the received one or more cardiac signals. The method also
includes providing, by the processor, feedback related to the CPR
therapy based on the detected characteristic. The feedback is for
assisting a rescuer in performing the CPR therapy.
[0086] Implementations can include one or more of the following
features.
[0087] In some implementations, the CPR therapy includes chest
compressions.
[0088] In some implementations, the CPR therapy includes
ventilations.
[0089] In some implementations, the CPR therapy stimulates coronary
circulation in the patient such that the patient's heart regains
sufficient cardiac output to generate a pulse.
[0090] In some implementations, the feedback related to the CPR
therapy assists the rescuer in causing a buildup of aortic pressure
in the patient's heart to be optimized.
[0091] In another aspect, a method includes receiving, by a sensing
electrode of a wearable medical device, one or more cardiac signals
from a patient. The method also includes detecting, by a CPR sensor
of the wearable medical device, a characteristic of a CPR therapy.
The method also includes determining, by a processor of the
wearable medical device, that the patient is experiencing fine VF
based on the received one or more cardiac signals. The method also
includes providing, by the processor, feedback related to the CPR
therapy based on the detected characteristic. The feedback is for
assisting a rescuer in performing the CPR therapy.
[0092] Implementations can include one or more of the following
features.
[0093] In some implementations, the CPR therapy includes chest
compressions.
[0094] In some implementations, the CPR therapy includes
ventilations.
[0095] In some implementations, the CPR therapy causes the fine VF
to change to a coarse VF.
[0096] In some implementations, the feedback related to the CPR
therapy assists the rescuer in causing an amplitude of the VF to be
maximized.
[0097] In another aspect, a wearable medical device includes a
garment configured to be worn about a torso of a patient. The
wearable medical device also includes one or more CPR sensors for
detecting a characteristic of a CPR therapy delivered by a rescuer.
The wearable medical device also includes an output device. The
wearable medical device also includes a network interface
configured to communicate with a remote server. The wearable
medical device also includes a processor configured for processing
information from the one or more CPR sensors and providing, to the
output device and the remote server, information about the CPR
therapy. The output device is configured to provide, to the
rescuer, an indication of a quality of the CPR therapy.
[0098] Implementations can include one or more of the following
features.
[0099] In some implementations, the remote server is configured to
interact with the wearable medical device to provide one or more
CPR instructions to the rescuer during CPR administration.
[0100] In some implementations, the remote server is configured to
interact with the wearable medical device to provide one or more
CPR instructions to the rescuer based on the indication of the
quality of the CPR therapy.
[0101] In some implementations, the one or more CPR instructions
include applying deeper chest compressions.
[0102] In some implementations, the one or more CPR instructions
include applying shallower chest compressions.
[0103] In some implementations, the one or more CPR instructions
include increasing a rate of chest compressions.
[0104] In some implementations, the one or more CPR instructions
include decreasing a rate of chest compressions.
[0105] In some implementations, the remote server is configured to
interact with the wearable medical device to provide one or more
CPR instructions to the rescuer. The one or more CPR instructions
include applying ventilations.
[0106] In some implementations, the remote server is configured to
interact with the wearable medical device to provide one or more
CPR instructions to the rescuer. The one or more CPR instructions
include ceasing the administration of the CPR therapy.
[0107] In some implementations, the remote server is configured to
interact with the wearable medical device to provide one or more
CPR instructions to the rescuer in real-time.
[0108] Implementations can include one or more of the following
advantages.
[0109] In some implementations, the wearable medical device can be
used to detect characteristics of the CPR therapy, including the
rate and depths of the chest compressions, and provide appropriate
feedback to the rescuer. For example, if the compressions are not
deep enough, the wearable medical device can instruct the rescuer
to push deeper; if the compressions are being applied too quickly,
the wearable medical device can instruct the rescuer to slow
down.
[0110] In some implementations, the wearable medical device is
configured with CPR detection capability without sacrificing
patient compliance with respect to wearing the garment. For
example, patients may elect to refrain from wearing the wearable
medical device if the garment is excessively burdensome and/or
uncomfortable. The wearable medical device can be configured such
that the sensor for detecting a CPR characteristic can be
repositioned prior to initiation of CPR. That is, the sensor may be
primary stored in a portion of the garment that does not affect the
comfort level of the garment; prior to initiation of CPR, the
sensor may be repositioned to the center of the patient's chest. In
this way, the efficacy of the wearable medical device can be
maximized without sacrificing patient compliance.
[0111] In some implementations, the wearable medical device may be
configured to detect characteristics of the CPR without requiring a
sensor to be placed at the center of the patient's chest. For
example, one or more sensors positioned elsewhere on the wearable
medical device may be configured to measure motion information
during administration of chest compressions. The processor is
configured to process the motion information from the one or more
sensors to determine (e.g., infer) the motion that is occurring at
the center of the patient's chest, which is typically the target
location for determining depths of chest compressions. For example,
a correction factor that is based on expected relative motions of
various portions of the chest may be applied to the motion
information to determine the depths of the chest compressions.
[0112] In some implementations, the wearable medical device may be
calibrated or otherwise configured such that the correction factor
can be refined for a particular patient or a particular type of
patient. For example, in some implementations, the wearable medical
device may consider one or more dimensions of the patient's chest
to determine which correction factor should be applied and/or how a
correction factors should be modified to better suit the patient.
In some implementations, before administration of CPR, a measuring
device can be used to measure dimensions and/or contours of the
patient's chest. The measurements can be used to tailor the
correction factors to the particular patient wearing the wearable
medical device.
[0113] Other features and advantages of the invention will be
apparent from the drawings, detailed description, and claims.
DESCRIPTION OF DRAWINGS
[0114] The accompanying drawings are not intended to be drawn to
scale. In the drawings, components that are identical or nearly
identical may be represented by a like numeral. For purposes of
clarity, not ever component is labeled in every drawing. In the
drawings:
[0115] FIGS. 1A-1B show a front and back view, respectively, of an
example wearable medical device that includes a garment, a medical
device controller, and a sensor for detecting characteristics of a
CPR therapy.
[0116] FIGS. 2A-2B shows an example of the medical device
controller of FIGS. 1A-1B.
[0117] FIG. 3 shows a schematic of an example of the medical device
controller.
[0118] FIGS. 4 and 5 depicts CPR feedback information provided by
the medical device controller.
[0119] FIG. 6 shows an example of the wearable medical device that
includes a wireless sensor stored in a waistband of the
garment.
[0120] FIG. 7 shows an example of the wearable medical device that
includes a sensor incorporated into a therapy electrode.
[0121] FIG. 8 shows an example representation of a chest of a
patient.
[0122] FIG. 9 shows an example of the wearable medical device that
includes three sensors for detecting characteristics of a CPR
therapy.
[0123] FIG. 10 shows an example of the wearable medical device that
includes two sensors for detecting characteristics of a CPR
therapy.
[0124] FIG. 11 shows an example of a device that can be used to
measure information related to a geometry of a patient's chest.
[0125] FIG. 12 shows an example of a system in which the medical
device controller is configured to communicate with a remote
server.
[0126] FIG. 13 shows an example of CPR performance information.
DETAILED DESCRIPTION
[0127] A wearable cardiac monitoring and/or treatment device can
include a garment configured to be worn about a torso of a patient
and one or more sensors (e.g., including one or more
accelerometers) for detecting characteristics of a cardiopulmonary
resuscitation (CPR) therapy administered to the patient. For
example, while a user is administering CPR to the patient, an
accelerometer performing the function of a chest compression sensor
positioned on the patient's chest can collect motion data that is
used to determine a rate and/or depth of the chest compressions
being applied to the patient. Based on the determined rate and/or
depth of the chest compressions, the wearable medical device can
provide feedback (e.g., coaching) to assist the user in providing
appropriate CPR therapy. For example, the wearable medical device
may include a speaker that is configured to emit a rhythmic tone
(e.g., a metronome) at a rate that matches a desired rate of chest
compressions to be applied to the patient. In some implementations,
the speaker may provide verbal commands to the user (e.g., "push
more quickly to match tone," "push slower to match tone," "push
harder," "push softer," "push deeper," "push less deep," etc.) for
assisting the user in providing chest compressions at an
appropriate rate and/or depth. In some implementations, instead of
or in addition to the speaker, the wearable medical device may
include a display for providing visual feedback to the user or can
communicate with an external device, such as a tablet or
smartphone, having a display that can be used for this purpose.
[0128] In some embodiments, the CPR therapy that is being measured
and for which feedback is being provided is ventilator therapy
(i.e. the "pulmonary" in "cardiopulmonary resuscitation"). This
might be accomplished via a sound sensor, i.e. a "ventilation
sensor," for measuring lung sounds. The proper rate of ventilations
for victims of cardiac arrest may be 6-10 ventilations per minute.
In addition, each ventilation may be delivered, ideally, in between
pauses in compressions so as to minimize potentially excessive
intrathoracic pressures that may lead to lung damage. For example,
the chest compression sensor can detect when a pause occurs during
delivery of chest compressions, and then prompt the rescuer to
deliver a ventilation. The ventilation sensor can then acquire lung
sounds to verify that the rescuer has delivered the ventilation,
and provide feedback if the ventilation is delayed or takes too
long. In some embodiments, the same accelerometer that is used for
performing the function of a chest compression sensor may also be
able to perform the function of a ventilation sensor. When speaking
of a sensor with the generic function of measuring one or both of
chest compressions and ventilation, we term the sensor a "CPR
sensor." Therefore, a CPR sensor may perform either one or both of
the functions of measuring chest compressions and ventilations.
[0129] In some implementations, the sensor may be configured to be
repositioned from a first location on the garment to a second
location at the patient's chest prior to initiation of CPR. For
example, the sensor may be stored in a compartment of the garment,
such as a pocket, when CPR treatment is not needed. Prior to
administration of CPR, the CPR sensor may be removed from the
compartment and repositioned to the center of the patient's chest
(e.g., above the patient's xiphoid process). In some
implementations, the sensor may be stored in a flap of the garment
that is attached to a belt of the garment. The flap may be
configured to assume a first position in which the flap and sensor
are positioned in front of the belt, and a second position in which
the flap and sensor are positioned at the center of the patient's
chest. That is, the flap may be configured to fold away from the
belt such that the sensor is repositioned to the center of the
patient's chest. In some implementations, the sensor may be movably
attached (e.g., by a hook-and-loop fastener, a snap fastener, a
pivoting flap, etc.) to a location on the garment where the sensor
may reside when CPR treatment is not needed.
[0130] The wearable medical device for use with the systems and
techniques as disclosed herein can be configured to monitor and/or
treat a patient. For example, the medical device can be configured
to monitor physiological signals from the patient, and on detecting
a medical event based on the monitored signals, treat the patient
as needed. As described herein, a treatment sequence can include
detecting a treatable medical condition, preparing the device for
the treatment of the condition, providing a notification to the
patient and/or others about an impending treatment, and/or
delivering the treatment when certain conditions are met.
[0131] The wearable medical device may be an ambulatory device
(e.g., a device that is capable of and designed for moving with the
patient as the patient goes about his or her daily routine). In
some examples, the wearable medical device can be configured as a
wearable defibrillator, such as the LifeVest.RTM. wearable
defibrillator available from ZOLL.RTM. Medical Corporation of
Chelmsford, Mass. The physiological signals monitored by the device
can include cardiac signals (e.g., ECG signals, heart sound
signals, and other cardiac-related physiological signals) and/or
one or more other signals. The wearable defibrillator may include a
garment worn by the patient to which sensing and therapy electrodes
are affixed for determining whether the patient may be experiencing
a condition, such as a cardiac condition, and causing an
appropriate treatment to be applied to the patient.
[0132] In some implementations, the wearable medical device can be
configured as a cardiac monitor that is configured to transmit
cardiac information in a manner similar to those employed in mobile
cardiac telemetry (MCT) and/or continuous event monitoring (CEM)
applications.
[0133] One of the most deadly cardiac arrhythmias is ventricular
fibrillation (VF), which occurs when normal, regular electrical
impulses are replaced by irregular and rapid impulses, causing the
heart muscle to stop normal contractions and to begin to quiver.
Normal blood flow ceases, and organ damage or death can result in
minutes if normal heart contractions are not restored. Because the
victim has no perceptible warning of the impending fibrillation,
death often occurs before the necessary medical assistance can
arrive. Other cardiac arrhythmias can include excessively slow
heart rates known as bradycardia. "Cardiac Arrest" refers
generically to the medical condition of a patient where various
arrhythmias of the heart such as VR, ventricular tachycardia (VT),
pulseless electrical activity (PEA), and asystole (heart stops all
electrical activity), result in the heart providing insufficient
levels of blood flow to the brain and other vital organs for the
support of life.
[0134] Implantable cardioverter/defibrillators (ICDs) or external
defibrillators (e.g., such as manual defibrillators and/or
automated external defibrillators (AEDs), sometimes referred to as
"conventional external defibrillators") have significantly improved
the ability to treat these otherwise life-threatening conditions.
Such devices operate by applying corrective electrical pulses
directly to the patient's heart. VF and VT can be treated by an
implanted or external defibrillator.
[0135] In distinction to conventional external defibrillators, some
external defibrillators, termed "wearable defibrillators" (e.g.,
the wearable medical device), can be worn by the patient in a
continuous (e.g., substantially continuous) fashion, and the
patient's physiologic state can be continuously monitored, e.g.,
monitoring the patient's heart through one or more sensing
electrodes for treatable arrhythmias and, when such is detected,
the device can apply corrective electrical pulses directly to the
heart through one or more therapy electrodes.
[0136] In the case of conventional external defibrillators, it is
well known to those skilled in the art that adjunctive therapies in
addition to defibrillation and electrical therapy are essential in
many cases in order to resuscitate the cardiac arrest victim. The
most typical--and sometimes the most important--adjunctive therapy
is Cardiopulmonary Resuscitation (CPR) of a patient in cardiac
arrest. CPR includes a collection of activities revolving around
chest compressions to provide some level of blood flow to the
victim's brain, heart and other vital organs both before and after
defibrillation as well as some form of ventilation to the victim's
lungs. The more important of these two activities is typically
chest compressions. Defibrillation is a very time-sensitive
therapy, and delays of even 2 minutes from onset of cardiac arrest
can have a significantly deleterious effect on the patient's chance
of survival. Typically, conventional external defibrillators arrive
4-15 minutes after the onset of cardiac arrest; without adequate
CPR, these patients will sometimes have survival rates of less than
1-2%. Even with adequate CPR, survival rates may only reach
15-20%.
[0137] In contradistinction to conventional external
defibrillators, it is known to those skilled in the art that for
the case of ICDs such as implanted pacemakers and defibrillators,
CPR is typically not needed for resuscitation of the cardiac arrest
victim. In fact, survival rates after treatment from an ICD and
without CPR will typically be in the range of 80-100%. Similar
rates or survival are achieved for wearable defibrillators without
the need for CPR. Thus, wearable defibrillators do not have an
immediately-apparent need for CPR sensors.
[0138] It is only newly discovered by the inventors, and one of the
objects of the systems and techniques described herein, that there
are certain medical conditions--such as PEA or fine VF--that could
be especially aided by treatment from a wearable defibrillator with
one or more CPR sensors. For example, such medical conditions may
benefit from the administration of CPR activities such as chest
compressions. Thus, the incorporation of CPR monitoring and
feedback features in a wearable defibrillator could benefit a
subclass of patients who experience such medical conditions.
Therefore, including one or more CPR sensors in the wearable
defibrillator may have a more positive effect with respect to
survival rate than previously realized, and in some cases for
reasons unrelated to or in addition to the typical goals of
CPR.
[0139] Pulseless electrical activity (PEA), also known as
electromechanical dissociation, is a type of cardiac arrest in
which a heart rhythm is observed in cardiac signals that should be
producing a pulse, but it is not (e.g., an impaired pulse). When
PEA is occurring, there is electrical activity in the heart, but
there is insufficient cardiac output to generate a pulse and supply
blood to the organs. Defibrillation is typically not an effective
treatment for PEA. Rather, CPR can be performed to improve the
circulation of blood in the blood vessels of the heart muscle. For
example, performing chest compressions can cause aortic pressure to
build up in the heart, thereby stimulating additional coronary
circulation and strengthening the heart to the point that it can
sufficiently beat on its own. Providing CPR feedback during such
activities can ensure maximum efficacy and/or optimization.
[0140] Fine ventricular fibrillation (VF) is a type of VF in which
the amplitude of the electrical activity of the heart is relatively
small. Fine VF can be compared to coarse VF, in which the amplitude
of the electrical activity is relatively larger. For example,
prolonged VF typically results in decreasing cardiac waveform
amplitude, from initial coarse VF to fine VR, and in some cases, to
asystole. Such a regression occurs due to depletion of myocardial
energy stores.
[0141] Coarse VF typically has a relatively high probability of
successful defibrillation. On the other hand, fine VF has a
significantly lower probability of defibrillation. The wearable
defibrillator may determine an appropriate defibrillation treatment
based on whether the patient is experiencing coarse VF or fine VF.
For example, a defibrillation treatment having default
characteristics may be used to treat coarse VF, whereas a
defibrillation treatment having specialized characteristics may be
required to treat fine VF. For situations in which the patient is
experiencing fine VF, a rescuer may attempt to "coarsen up" the VF
(e.g., cause the amplitude of the electrical activity to increase)
by performing CPR activities such as chest compressions. Survival
rates can be significantly improved by causing fine VF to revert
back to coarse VF before defibrillation is administered. For
example, administering chest compressions over a period of time may
cause the amplitude of the VF to increase beyond a threshold (e.g.,
300 mV) that classifies the VF as coarse VF. Once coarse VF is
present, a default defibrillation pulse or shock may be
administered. Again, providing CPR feedback to the rescuer during
the administration of CPR activities can ensure maximum efficacy
and/or optimization of the chest compressions, thereby increasing
the amplitude of the heart's electrical activity to the fullest
possible extent to reassume coarse VF.
[0142] The wearable medical device can be configured to monitor the
patient for an arrhythmia condition such as bradycardia, VT, VF
(both fine and coarse), PEA, and/or asystole, among others.
Bradycardia, also known as bradyarrythmia, is a slow heart rate
(e.g., in some implementations, a slow resting heart rate of under
60 beats per minute in adults), which can result in fatigue,
weakness, dizziness, and potentially fainting. While the detection
methods and systems described hereinafter are disclosed as
detecting certain medical conditions, this is not to be construed
as limiting the invention. Other arrhythmias, such as, but not
limited to, atrial arrhythmias such as premature atrial
contractions (PACs), multifocal atrial tachycardia, atrial flutter,
and atrial fibrillation, supraventricular tachycardia (SVT),
junctional arrhythmias, tachycardia, junctional rhythm, junctional
tachycardia, premature junctional contraction, and ventricular
arrhythmias such as premature ventricular contractions (PVCs) and
accelerated idioventricular rhythm, may also be detected. In some
implementations (e.g., implementations in which the wearable
medical device is a treatment device, such as a pacing and/or a
defibrillating device), if an arrhythmia condition is detected, the
wearable medical device can automatically provide a pacing or
defibrillation pulse or shock to treat the condition.
[0143] After it is determined that a monitored patient may be
experiencing a cardiac condition, the wearable medical device can
be configured to select a treatment sequence for treating the
particular condition. For example, the medical device may be
configured to determine that a series of defibrillation shocks at
particular intensities is appropriate for treating the particular
cardiac condition. In some implementations, the device can issue up
to five bi-phasic shocks if the device determines that the cardiac
condition is present after each preceding shock. The device can
issue more or fewer shocks to the patient as the situation may
require. In some implementations, the wearable medical device may
provide one or more indications (e.g., warnings or alerts) to the
monitored patient or other device operator that a treatment shock
is about to be delivered before it is actually delivered to the
patient. On perceiving the alert, the patient or device operator
may be able to instruct the wearable medical device to refrain from
delivering the treatment shock. For example, the patient or the
device operator may instruct the medical device to refrain from
applying a treatment shock if the monitored patient is well and the
wearable medical device falsely identified a cardiac event.
[0144] The wearable medical device is capable of continuous (e.g.,
substantially continuous) use by the patient. In some
implementations, the continuous use may be substantially continuous
in nature. That is, the wearable medical device may be continuously
used, except for sporadic periods during which the use temporarily
ceases (e.g., while the patient bathes, while the patient is refit
with a new and/or a different garment, while the battery is
charged/changed, while the garment is laundered, etc.). For
example, such substantially continuous use as described herein may
nonetheless qualify as continuous use.
[0145] The wearable medical device is also capable of extended use,
and in some implementations, extended long-term use. For example,
the wearable medical device can be configured to be used by the
patient for hours, days, weeks, months, or even years. In some
implementations, the extended use may be continuous in nature.
[0146] The use (e.g., the continuous and/or extended use) of the
wearable medical device can include continuous wear by the patient,
continuous attachment to the patient, and/or continuous monitoring
of the patient.
[0147] The wearable medical device is configured to continuously
monitor the patient for cardiac-related information (e.g., ECG
information, including arrhythmia information, heart sounds, etc.)
and/or non-cardiac information (e.g., blood oxygen, the patient's
temperature, glucose levels, tissue fluid levels, and/or lung
sounds).
[0148] The wearable medical device may carry out its monitoring in
periodic or aperiodic time intervals or times. For example, the
monitoring during intervals or times can be triggered by a user
action or another event. For example, one or more durations between
the periodic or aperiodic intervals or times can be
user-configurable.
[0149] In some implementations, the patient may require another
type of therapy in addition to or instead of the therapy provided
by the therapy electrodes. For example, the patient may require CPR
while he or she is experiencing a cardiac event, or the patient may
require CPR irrespective of a cardiac event. The wearable medical
device may be configured to detect characteristics of the CPR being
administered to the patient by a rescuer and provide information
about the CPR to the rescuer. For example, the wearable medical
device may include one or more sensors (e.g., including one or more
accelerometers) that are configured to detect motion that occurs
during the administration of CPR. The wearable medical device can
use the motion data from the sensors to determine characteristics
of the CPR, such as the depth and rate of chest compressions being
administered to the patient. Based on the determined CPR
characteristics, the wearable medical device can provide feedback
to assist the rescuer (e.g., to help the rescuer refine the
treatment to achieve maximum efficacy). For example, the wearable
medical device may instruct the rescuer to adjust the depth and/or
rate of the chest compressions. In some implementations, the
feedback may be audio, visual, and/or tactile, although other
feedback methods may also be used.
Example Wearable Medical Device
[0150] FIGS. 1A-1B show a front and back view, respectively, of an
example wearable medical device 100 that is configured to provide
information about a CPR therapy being administered to a patient
wearing the medical device 100. The wearable medical device 100
includes a plurality of sensing electrodes 112 that can be disposed
at various positions about the patient's body. In this example, one
sensing electrode 112 is positioned at the front of the patient,
one sensing electrode 112 is positioned at the back of the patient,
and two sensing electrodes 112 are positioned at opposite sides of
the back of the patient. The sensing electrodes 112 are configured
to monitor the cardiac function of the patient (e.g., by monitoring
one or more cardiac signals of the patient). The sensing electrodes
112 are electrically coupled to a distribution node 130 that is
positioned at the back of the patient. The distribution node 130 is
electrically coupled to a medical device controller 120 that can be
mounted on or attached to the patient or the patient's clothing
(e.g., a belt).
[0151] The wearable medical device 100 can also optionally include
a plurality of therapy electrodes 114 that are electrically coupled
to the medical device controller 120 through the distribution node
130. In this example, one therapy electrode 114 is positioned at
the front of the patient, and two therapy electrodes 114 are
positioned at the middle of the back of the patient. The therapy
electrodes 114 are configured to deliver one or more therapeutic
defibrillating shocks to the body of the patient if it is
determined that such treatment is warranted. In some
implementations, the wearable medical device 100 may be a
monitoring only device that omits the therapy delivery capabilities
and associated components (e.g., the therapy electrodes 114). In
some implementations, various treatment components may be packaged
into various modules that can be attached to or removed from the
wearable medical device 100 as needed.
[0152] Components of the wearable medical device 100 are affixed to
a garment 110 that can be worn by the patient (e.g., on the
patient's torso). For example, the sensing electrodes 112, therapy
electrodes 114, and distribution node 130 can be assembled into,
integrated into, or attached to the garment 110. The garment 110
includes a waistband 104 and shoulder straps 106. In some
implementations, the sensing electrodes 112 and/or the therapy
electrodes 114 may be removably attached to the garment 110 (e.g.,
by a hook-and-loop fastener, a snap fastener, etc.). In some
implementations, the garment 110 includes one or more compartments
that the sensing electrodes 112 and/or the therapy electrodes 114
may be stored in. For example, the therapy electrodes 114 may be
placed inside associated compartments of the garment 110 such that
the therapy electrodes 114 are appropriately placed on the
patient's body when the garment 110 is being worn. The compartments
may include conductive fabric that is able to conduct the
electrical therapy delivered to the patient.
[0153] In some cases, the medical condition experienced by the
patient may be unable to be treated by one or more therapy shocks,
or it may be appropriate to supplement the therapy shocks with
another kind of medical treatment. For example, if the patient is
experiencing an abnormal non-viable non-shockable heart rhythm or
asystole (e.g., no cardiac activity), applying therapy shocks to
the patient will be ineffective. In such cases, CPR may be employed
to keep the patient alive (e.g., until an advanced life support
team arrives). Due to the emergency nature of such situations, CPR
is often delivered by laypersons who may be unfamiliar with proper
CPR procedures. Thus, the wearable medical device 100 is configured
to provide feedback to the rescuer to assist the rescuer in
performing CPR.
[0154] According to the International Liaison Committee on
Resuscitation guidelines, CPR on adults should be administered with
chest compressions between 5 cm (2.0 in) and 6 cm (2.4 in) deep and
at a rate of 100 to 120 compressions per minute. In addition to
providing chest compressions, the rescuer may also provide breaths
by exhaling into the patient's mouth or nose to push air into the
patient's lungs. Current recommendations place emphasis on
high-quality chest compressions. The wearable medical device 100
can provide feedback to the rescuer to ensure that the chest
compressions are performed at the appropriate depth and rate.
[0155] The wearable medical device 100 includes a sensor 140 (e.g.,
sometimes referred to generically as a CPR sensor) that is
configured to detect characteristics of a CPR therapy (e.g., chest
compressions, ventilation, or both). Thus, the sensor 140 is
sometimes referred to as a CPR sensor, a chest compression sensor,
and/or a ventilation sensor depending on the context of use. The
CPR sensor 140 may be connected to the controller 120 via one or
more wires (e.g., via the distribution node 130). In some
implementations, the CPR sensor 140 is configured to wirelessly
communicate with the controller 120. The CPR sensor 140 may include
one or more accelerometers that are configured to detect motion
that occurs during the administration of CPR. The accelerometers of
the CPR sensor 140 may be single or dual axis. In some
implementations, the accelerometer is a solid-state ADXL202
accelerometer. The controller 120 is configured to process
information (e.g., motion information) received from the CPR sensor
140 and provide information about a CPR therapy to an output device
(e.g., 324 of FIG. 3) or a user interface (e.g., 308 of FIG. 3).
For example, the controller 120 is configured to determine
information related to the motion of the CPR sensor 140 as CPR is
being administered.
[0156] The chest compression sensor 140 is configured to detect
characteristics of the compressions, such as the depth and rate of
chest compressions administered to the patient. For example,
accelerometers incorporated into the chest compression sensor 140
may provide acceleration, velocity, and/or displacement information
to the controller 120, and the controller 120 can process the
information to determine the depths of the chest compressions and
the rate at which the chest compressions are administered. In some
implementations, acceleration readings are provided by the
accelerometer at fixed time intervals (e.g., one-millisecond
intervals). The depths of chest compressions are typically measured
at the center of the patient's chest (e.g., at a location above the
patient's xiphoid process). That is, the depth of a chest
compression may be a measure of the displacement of the center of
the patient's chest from an initial position (e.g., with no
pressure applied to the chest) to a compressed position (e.g., when
peak pressure is applied to the chest). Thus, positioning the chest
compression sensor 140 above the patient's xiphoid process may
provide accurate information related to the characteristics of the
chest compressions, as described in more detail below.
[0157] Patient compliance is an important consideration in the
design of many medical procedures and devices. Medical
professionals are always trying to maximize the efficacy of a
medical device without placing undue burdens on the patient. For
example, if a medical device is designed for maximum efficacy but
the design is very cumbersome to use, some patients may elect to
not use the device due to the burden, thereby reducing the efficacy
down to zero. Thus, the burden to the patient must be balanced with
the medical effectiveness of the device.
[0158] In the context of the wearable medical device 100 configured
to provide CPR feedback, it may be useful to position a sensor
(e.g., the chest compression sensor 140) at the center of the
patient's chest, such as above the patient's xiphoid process, to
provide motion information that is especially relevant for
determining chest compression characteristics. However, doing so
may require a portion of the garment 110 to be constantly
positioned at this location. That is, the garment 110 may require a
strap that wraps around the center of the patient's chest.
Considering that the wearable medical device 100 is configured for
moving with the patient as the patient goes about his or her daily
routine, and in some cases may be continuously (e.g., substantially
continuously) worn for hours, days, weeks, months, or even years,
such a burden may result in decreased compliance. In other words,
the patient may elect to simply not wear the medical device 100
because it is uncomfortable. While such an implementation is within
the scope of this disclosure, other configurations may provide
sufficient function without creating an undue burden on the
patient.
[0159] In some implementations, the chest compression sensor 140 is
movably attached to the garment 110. The chest compression sensor
140 is configured to be repositioned to the center of the patient's
chest prior to initiation of the CPR therapy. Thus, when CPR is not
being delivered (e.g., a significant majority of the time that the
patient is wearing the medical device 100), the patient does not
experience the potentially cumbersome and/or uncomfortable
placement of the chest compression sensor 140 at the center of his
or her chest. In this way, neither efficacy nor compliance is
sacrificed.
[0160] In the example shown in FIGS. 1A-1B, the chest compression
sensor 140 is stored in a compartment of the garment 110. The
compartment may be a flap 142 that is attached to the waistband 104
of the garment 110 (e.g., at a central portion of the waistband
104) and configured to fold away from the garment 104. When the
wearable medical device 100 is properly worn by the patient, the
waistband 104 may be positioned over the bottom few ribs and just
below the xiphoid process of the patient. When the flap 142 is
folded away from the garment 110 (e.g., prior to initiation of
CPR), the flap 142 and the chest compression sensor 140 are
positioned at a location above the patient's xiphoid process. In
this way, the chest compression sensor 140 may be in proper
position for providing accurate CPR feedback information during
administration of the CPR therapy. In some implementations, the
chest compression sensor 140 may be attached to the garment 110 in
a manner chosen to increase patient compliance with respect to
wearing the garment 110.
[0161] While FIGS. 1A-1B show four sensing electrodes 112 and three
therapy electrodes 114, any number of sensing electrodes 112 and/or
therapy electrodes 114 may be provided and disposed at various
locations about the patient's body. Similarly, while only one chest
compression sensor 140 is shown, the wearable medical device 100
may include additional chest compression sensors, as described in
more detail below.
[0162] FIGS. 2A-2B show an example of the medical device controller
120 of FIGS. 1A-1B. The controller 120 may be powered by a battery
212 (e.g., a rechargeable battery) that can be removable from a
housing 206 of the controller 120 to allow for recharging. The
controller 120 includes a user interface such as a touch screen 220
that can provide information (e.g., information related to a CPR
treatment) to the patient and/or a rescuer, as described in more
detail below. The patient can interact with the touch screen 220 in
order to communicate with and control the wearable medical device
100. The controller 120 also includes a speaker 230 that can
provide information to the patient and/or a rescuer. The controller
120 also includes a port 202 to which the distribution node 130 can
be attached and response buttons 210 that the patient can interact
with in order to cause the wearable medical device 100 to withhold
delivery of a treatment (e.g., if the patient is well and the
wearable medical device 100 falsely identified a cardiac
event).
[0163] FIG. 3 shows a schematic of an example of the medical device
controller 120 of FIGS. 1A-1B and 2A-2B. The controller 120
includes a processor 318, a cardiac event detector 320, an output
device 324, a patient sensor interface 312, an optional therapy
delivery interface 302, data storage 304 (which may include patient
data storage 316), an optional network interface 306, and a user
interface 308 (e.g., including the touch screen 220 shown in FIG.
2A). In some implementations, the user interface 308 may include
the output device 324. That is, the user interface 308 and the
output device 324 may be the same component of the controller 120.
The patient sensor interface 312 is coupled to the patient sensing
electrodes 112 via the distribution node 130, and the therapy
delivery interface 302 (if included) is coupled to the patient
therapy or therapy electrodes 114 via the distribution node 130.
The patient sensor interface 312 and the therapy delivery interface
302 implement a variety of coupling and communication techniques
for facilitating the exchange of data between the patient
electrodes 112, 114 and the controller 120.
[0164] In some implementations, the processor 318 can perform a
series of instructions that control the operation of the other
components of the controller 120. The cardiac event detector 320 is
configured to monitor the cardiac activity of the patient and
identify cardiac events experienced by the patient based on
received cardiac signals. In some examples, the cardiac event
detector 320 can access patient baseline information in the form of
templates (e.g., which may be stored in the data storage 304 as
patient data 316) that can assist the cardiac event detector 320 in
identifying cardiac events experienced by the patient, as described
above. The baseline ECG recordings may be obtained during initial
setup of the device.
[0165] In some examples, the network interface 306 can facilitate
the communication of information between the controller 120 and one
or more other devices or entities over a communications network via
either a wired or wireless connection. In some examples, the
network interface 306 is configured to communicate with a server
(e.g., a remote server 322). In some implementations, the remote
server 322 is a remote medical server that can be accessed by a
medical service provider, such as a doctor, to obtain information
related to the patient being monitored and/or treated by the
wearable medical device 100. In this way, the medical service
provider can remotely monitor the patient's medical condition and
take appropriate action. After a treatment is delivered, a status
and results of such treatment may be transmitted to the remote
server 322. The transmissions may occur continuously, at fixed
intervals, or upon occurrences of particular events, among others.
In some implementations, the communication may occur via a
telephone network or a cellular network (e.g., 2G, 3G, 4G), among
others.
[0166] As mentioned above, in some implementations, the wearable
medical device 100 is capable of and designed for being worn by a
patient who is at risk of developing cardiac problems, but who does
not yet meet criteria to be outfitted with a medical device that
includes a treatment component (e.g., a defibrillator). In such
implementations, the controller 120 may omit the treatment
components, including the therapy delivery interface 302 and the
therapy electrodes 114. A wearable medical device 100 that does not
include treatment components is sometimes referred to as a monitor
(e.g., a cardiac monitor). The cardiac monitor may be prescribed so
that continuous and/or event-based data can be sent from the
cardiac monitor to a server (e.g., the remote server 322). A
caregiver can access the data from the remote server 322 and
determine whether the patient is experiencing or has experienced a
cardiac problem. In some implementations, after determining that
the patient is experiencing a cardiac problem, the caregiver may
instruct the patient to begin wearing a medical device with
treatment capabilities.
[0167] In addition to controlling the cardiac monitoring and the
delivery of therapeutic shocks by the wearable medical device 100,
processor 318 is also configured to process information from the
chest compression sensor 140 to determine one or more
characteristics of a CPR therapy administered to the patient. For
example, accelerometers incorporated into the chest compression
sensor 140 may provide acceleration, velocity, and/or displacement
information to the processor 318, and the processor 318 can process
such motion information to determine the depths and rate of the
chest compressions being administered. The processor 318 can
determine whether the depths and/or the rates of the chest
compressions satisfy predetermined criteria, including determining
whether the depths and/or rates are within predetermined ranges,
and cause the wearable medical device 100 to respond
accordingly.
[0168] FIG. 4 shows a visual depiction of audio CPR feedback
information 400 that can be provided by the medical device
controller 120 in response to a CPR therapy administered to the
patient. In some implementations, the wearable medical device 100
may provide an initial indication that CPR should be administered
to the patient using the output device (324 of FIG. 3). The output
device 324 may include the touch screen 220 and/or the speaker 204
of FIGS. 2A-2B. For example, the wearable medical device 100 may
provide an initial indication that CPR should be administered by
providing a message via the touch screen 220 or by emitting a
verbal command via the speaker 204. The wearable medical device 100
may instruct the rescuer to position the chest compression sensor
140 to the center of the patient's chest. For example, the rescuer
may be instructed to fold the flap 142 in which the chest
compression sensor 140 is stored away from the garment such that
the flap 142 is repositioned to the center of the patient's chest,
or the rescuer may be instructed to remove the chest compression
sensor 140 from the compartment and reposition the chest
compression sensor 140 to the center of the patient's chest.
[0169] Once the chest compression sensor 140 is properly
positioned, the rescuer may be instructed to begin chest
compressions. In some implementations, the wearable medical device
100 may provide additional information related to how the chest
compressions should be performed. For example, the wearable medical
device 100 may instruct the rescuer to place his or her hands at
the center of the patient's chest and push at a rate of
approximately 120 compressions per minute. In some implementations,
the wearable medical device 100 may also instruct the rescuer to
strive for applying compressions having depths of approximately 2.0
to 2.5 inches; however, specific initial instructions related to
the depths of chest compressions may be of limited help to a
layperson, and are sometimes initially omitted.
[0170] As CPR is administered, the chest compression sensor 140
determines characteristics related to the CPR therapy and provides
motion information to the processor 318. The motion information may
include data related to the acceleration, velocity, and/or
displacement of the chest compression sensor 140. The processor 318
processes the data to determine the rate and depths of the
compressions that are being delivered to the patient. A visual
depiction of the motion data 406 shows the motion of the chest
compression sensor 140 as a function of time. The motion data may
comprise acceleration data, velocity data, and/or displacement
data. The visual depiction of the motion data 406 includes a first
portion 408 during which the rate and depths of the chest
compressions are initially determined. The first portion 408 of the
motion data indicates that the actual rate of the compressions
being administered is approximately 150 compressions per minute.
According to medical guidelines, such a compression rate is too
fast.
[0171] The processor 318 is configured to instruct the speaker 204
of the controller 120 to emit a verbal command 402 instructing the
rescuer to "slow down." The verbal command 402 may also include an
instruction to "match the compression rate to the emitted tone."
The speaker 204 may then emit a periodic tone 404 (e.g., a
metronome) that is emitted at a rate that corresponds to the
desired rate of the chest compressions. In this way, the rescuer
has an audible cue indicating the proper chest compression rate.
Utilizing such audio feedback allows the rescuer to focus his or
her attention to providing treatment to the patient without
requiring the rescuer to look away.
[0172] The visual depiction of the motion data 406 includes a
second portion 410 that indicates the detected rate of the chest
compressions after the "slow down" instruction was given. The
second portion 410 indicates that the rescuer has successfully
slowed the compression down to a rate of approximately 120
compressions per minute, which falls within acceptable medical
guidelines. However, if the rate of compressions is still too fast,
the speaker 204 may emit another verbal command 402 to "slow down"
along with a reminder to "match the compression rate to the emitted
tone." In some implementations, the second message may be provided
with increased volume to capture the rescuer's attention and/or to
indicate that the rescuer has not satisfied the initial verbal
command.
[0173] If after emitting the verbal command 402 the compressions
have slowed down below an acceptable threshold (e.g., below 100
compressions per minute), the speaker 204 may instruct the rescuer
to "speed up" and remind the rescuer to "match the compression rate
to the emitted tone."
[0174] While the CPR feedback is shown as a visual depiction of
audio CPR feedback information 400, compression rate feedback can
be provided in other ways. For example, information similar to the
visual depiction may be provided on the touch screen 220 of the
controller 120 in addition to or instead of the audio CPR
feedback.
[0175] The motion data may also include information used by the
processor 318 to determine the depths of the chest compressions
being administered. For example, the processor 318 may use
displacement data provided by the chest compression sensor 140 to
determine the compression depths. Based on the determined depths of
the compressions, the processor 318 is configured to instruct the
speaker 204 to emit another verbal command instructing the rescuer
to "push harder" or "push deeper," or "push softer" or "push less
deep." The degree by which the rescuer should push softer/less deep
or harder/deeper may be indicated by the language of the verbal
command. For example, the verbal commands may include "push much
softer" or "push much less deep," or "push much harder" or "push
much deeper," among others. In some implementations, the degree by
which the rescuer should push softer/less deep or harder/deeper may
be indicated in other ways. For example, the volume of the verbal
command may be proportional to the depths of the compressions that
the rescuer should strive for (e.g., a very loud "push deeper"
command may indicate that the rescuer should push much deeper).
[0176] In some implementations, conveying information related to
the desired depths of the chest compressions may be accomplished by
visual indicators. FIG. 5 shows an example of visual CPR feedback
information 500 that can be provided by the medical device
controller 120 in response to a CPR therapy administered to the
patient. In a manner similar to that described above with respect
to FIG. 4, the rescuer may initially be instructed to position the
chest compression sensor 140 to the center of the patient's chest
and begin chest compressions. As CPR is administered, the CPR
sensor 140 determines characteristics related to the CPR therapy
and provides motion information, heart sound information, and/or
lung sound information to the processor 318. The processor 318 is
configured to cause the touch screen 220 to present the depth 502
and rate 504 of chest compressions currently being administered to
the patient. The compression depth 502 and/or rate 504 may be
presented as an instantaneous measurement. In some implementations,
the depth and/or rate 504 is presented as an average of the last
few depth and/or rate measurements as determined by the processor
318.
[0177] In some implementations, the touch screen 220 is also
configured to present a depth graph 506 and a rate graph 508 that
show the depth/rate trends of the administered chest compressions.
Such graphs 506, 508 can provide relative information to the
rescuer to allow the rescuer to put the current compression depth
and/or rate into context. The depth graph 506 may present the
depths of compressions administered over a fixed period of time
(e.g., over the past 10 seconds). In this way, the rescuer can
visualize how adjustments to the compression effort applied to the
patient's chest have manifested in terms of the compression depths
detected by the chest compression sensor 140. The depth graph 506
may include a shaded portion that indicates a target zone within
which the actual depths of the compressions should reside. The
target compression depth may be 2.25 inches, which may be
approximately halfway between the maximum target compression depth
of 2.5 inches and the minimum target compression depth of 2.0
inches. In some implementations, the shaded portion may change
color based on whether the depths of compressions currently being
administered is within the target range. For example, if the
current compression depths are 2.2 inches, as shown in FIG. 5, the
shaded portion may be green; if the compression depths were to rise
above 2.5 inches or fall below 2.0 inches, the shaded portion may
turn red. In some implementations, the intensity of the color of
the shaded portion may correspond to the degree of compliance with
the target compression depth. For example, if the compression
depths are exactly 2.25 inches, the shaded portion may be bright
green; as the compression depths move away from the ideal target
depth, the bright green may change to a faded green; as the
compression depths approach the upper or lower limit, the faded
green may begin to turn to faded red; and when the compression
depths fall outside of the target zone, the faded red may change to
bright red.
[0178] Similarly, the rate graph 508 may present the rate of
compressions administered over a fixed period of time (e.g., over
the past 10 seconds). In this way, the rescuer can visualize how
adjustments to the rate of the compressions applied to the
patient's chest have manifested in terms of the compression rate
detected by the chest compression sensor 140. The rate graph 508
may include a shaded portion that indicates a target zone within
which the actual rate of the compressions should reside. The target
compression rate may be 110 compressions per minute, which may be
approximately halfway between the maximum target compression rate
of 120 compressions per minutes and the minimum target compression
rate of 100 compressions per minute. In some implementations, the
shaded portion may change color based on whether the current
compression rate is within the target range. For example, if the
current compression rate is 116 compressions per minute, as shown
in FIG. 5, the shaded portion may be green; if the compression rate
were to rise above 120 compressions per minute or fall below 100
compressions per minute, the shaded portion may turn red. In some
implementations, the intensity of the color of the shaded portion
may correspond to the degree of compliance with the target
compression rate. For example, if the compression rate is exactly
110 compressions per minute, the shaded portion may be bright
green; as the compression rate move away from the ideal target
rate, the bright green may change to a faded green; as the
compression rate approach the upper or lower limit, the faded green
may begin to turn to faded red; and when the compression rate falls
outside of the target zone, the faded red may change to bright
red.
[0179] In some implementations, the touch screen 220 is also
configured to present an adaptable shape that indicates both the
depths and rate of compressions being administered. The adaptable
shape is sometimes referred to as a perfusion performance indicator
(PPI) 510. The PPI 510 may be presented instead of or in addition
to the depth 502, rate 504, depth graph 506, and/or rate graph 508.
The PPI 510 has an outer border 512 having a shape (e.g., a
diamond) that is shaded 514 (e.g., with color) over time. The
amount of the shading 514 that fills the outer border 512 (e.g.,
the fill amount) provides feedback about both the rate and depth of
the compressions being administered. For example, when CPR is being
performed at or near ideal parameters, the shading 514 may fill the
entire outer border 512; as the rate and/or depth decreases toward
the lowest acceptable limits, the amount of fill lessens; as the
rate and/or depth increases toward the highest acceptable limits,
the amount of fill increases beyond the outer border 512 of the PPI
510. In some implementations, the outer border 512 corresponds to
the ideal target compression rate and depth. The PPI 510 can
provide a concise visual indication of the quality of the CPR such
that the rescuer can aim to keep the PPI 510 completely filled.
[0180] In some implementations, the PPI 510 includes two axes--a
vertical axis and a horizontal axis. The vertical axis may
correspond to the depth of chest compressions, and the horizontal
axis may correspond to the rate of chest compressions. For example,
when the depth of chest compressions decreases toward the lower
acceptable limit, the shading 514 of the PPI 510 in the vertical
direction may be relatively small. Similarly, when the rate of
chest compressions decreases toward the lower acceptable limit, the
shading 514 of the PPI 510 in the horizontal direction may be
relatively small. In the example shown in FIG. 5, the depths of the
compressions are slightly below the ideal target value and the rate
of the compressions is above the ideal target value; accordingly,
the shading 514 of the PPI 510 has a short, wide diamond shape.
Such a shading 514 indicates that the rescuer should slightly
increase the depths of the compressions and reduce the rate of the
compressions.
[0181] In some implementations, the color of the shading 514 may
correspond to the compliance of the compression depths and/or rate.
For example, if one or both of the depths of compressions and the
rate of compressions falls below the corresponding lowest
acceptable limit or the corresponding highest acceptable limit, the
shading 514 may have a red color; when both of the depths of
compressions and the rate of compressions are within the
corresponding target ranges, the shading 514 may have a yellow
color (e.g., indicating that the depths and rates are within the
target range but there exists room for improvement) or a green
color (e.g., indicating that the depths and rates are at or near
the ideal target values).
[0182] In some implementations, the wearable medical device 100 may
include a wireless transceiver configured to communicate with one
or more external devices. For example, output device 324 may
include a wireless transceiver, or the output device 324 may be
configured to interact with the network interface (306 of FIG. 3)
to communicate with an external device having a display. In some
implementations, rather than or in addition to the touch screen 220
of the controller 120 presenting the information described above
with reference to FIGS. 4 and 5, the controller 120 may cause the
external device to present information related to the CPR therapy
and/or feedback information. In some implementations, the
controller 120 is configured to wirelessly communicate with a
mobile computing device such as a tablet, smartphone, or laptop,
among others. In some implementations, the network interface (306
of FIGS. 3 and 12) and/or the remote server (322 of FIGS. 3 and 12)
are configured to interact with an external device in order to
provide CPR information and/or feedback information to one or more
remote entities. In this way, remote medical personnel can observe
information related to the therapy being administered to the
patient.
[0183] In some implementations, the controller 120 is configured to
communicate with the remote server 322, thereby allowing a remote
entity to interact with the controller 120. FIG. 12 shows an
example of a system 1200 in which the controller 120 is configured
to communicate with the remote server 322 via a network 1202 (e.g.,
a wireless network). For example, instead of or in addition to
providing information about the CPR therapy to the output device
324 based on processing and/or computations that take place at the
controller 120, the processor 318 may be configured to provide
information about the CPR therapy to the remote server 322. The
information may then be examined by the remote entity at the remote
server 322 (e.g., via a computing device such as a computer,
laptop, tablet, or smartphone, among others). The remote entity may
be a caregiver such as a doctor, nurse, or other medical
professional.
[0184] The caregiver can access the information about the CPR
therapy at the remote server 322 and provide appropriate feedback
in response. For example, the remote server 322 may receive
information from the one or more CPR sensors related to
ventilations, a rate of chest compressions, and/or a depth of chest
compressions being applied to a patient 1204 by a rescuer 1206.
Based on the information, the caregiver can determine a quality of
the CPR therapy that is being administered by the rescuer 1206. The
caregiver may then provide an indication of the quality of the CPR
therapy to the controller 120 via the network 1202, and the
controller 120 can provide the indication via the output device 324
to be observed by the rescuer 1206. In this way, real-time CPR
feedback can be provided to the rescuer 1206 by an actual caregiver
who may have a relatively greater level of medical expertise.
[0185] FIG. 13 shows an example of information related to the
performance of CPR being administered. The information may be
provided to the caregiver at the remote server 322 to indicate the
overall quality of the CPR being administered to the patient 1204
by the rescuer 1206. In some examples, the information is presented
on a computing device in communication with the remote server 322.
The presentation of information in this example is split into two
portions--a top portion that shows averaged performance over an
entire incident, and a bottom portion that shows the performance
average over each of a number of past CPR intervals, with display
of current compression depth and rate displayed under the second
portion. In addition to the compression depth and rate information
largely described herein, the CPR performance information can
include an indication of a compression fraction, a pre-shock pause,
a post-shock pause, and a perfusion index. The information may be
based on data received at the remote server 322 from the one or
more CPR sensors.
[0186] In this example, the caregiver sees that the rescuer 1206 is
currently administering chest compressions at a depth of 3.2 inches
and at a rate of 110 compressions per minute. Based on this
information, the caregiver may determine that the depths of the
compressions are too deep, but the rate of the compressions is just
right. In response, the caregiver may provide one or more CPR
instructions to the rescuer 1206 at the remote server 322 via the
network 1202. For example, the caregiver may input one or more CPR
instructions into the computing device and cause the CPR
instruction to be transmitted to the controller 120 via the network
1202. In this example, the instruction may instruct the rescuer
1206 to apply shallower chest compressions and maintain the current
rate of the compressions.
[0187] The rescuer 1206 may adjust the administration of the CPR
therapy based on the one or more CPR instructions provided by the
caregiver. The caregiver may again access the information related
to the CPR therapy at the remote server 322 to determine whether
the CPR therapy is now being administered appropriately. If further
adjustment is necessary, the caregiver may provide one or more
additional CPR instructions. In this way, the CPR therapy can be
refined with real-time evaluation from the caregiver until
appropriate CPR characteristics are attained and/or maintained. The
real-time CPR evaluation may be limited only by the processing
and/or transmitting capabilities of the controller 120, the network
1202, and/or the remote server 322.
[0188] In some implementations, the CPR instructions may be
directed to other aspects of the CPR therapy. For example, the CPR
instruction may direct the rescuer to apply deeper chest
compressions or to increase/decrease the compression rate. In some
implementations, the instruction may direct the rescuer 1206 to
apply ventilations to the patient 1204 or adjust characteristics of
ventilations being applied to the patient 1204. In some
implementations, the instruction may direct the rescuer 1206 to
cease the administration of the CPR therapy altogether. The
particular instructions that the caregiver remotely provides to the
rescuer 1206 may be based on the totality of the CPR information at
the remote server 322, including the information related to the
overall performance of the CPR and the information related to past
CPR intervals. In this way, the medically-qualified caregiver has
the freedom to make on-demand judgment calls in real-time as to the
appropriate adjustments to the CPR that should be applied for
maximum efficacy, thereby providing an additional aspect of
personalization over implementations in which the controller 120
determines the adjustments according to predetermined rules.
[0189] The one or more CPR instructions remotely provided by the
caregiver may be provided via the output device 324 (e.g.,
including the touch screen 220 and/or the speaker 204 of the
controller 120). For example, the caregiver's CPR instructions may
be presented as messages on the touch screen 220 and/or as a spoken
instructions emitted from the speaker 204. In some implementations,
the caregiver may provide real-time CPR feedback in a manner
similar to that described above with respect to the perfusion
performance indicator (PPI) 510 of FIG. 5. In some implementations,
CPR instructions provided by the caregiver may automatically
override instructions automatically determined at the controller
120 itself. For example, if the controller 120 determines that a
remote caregiver is actively monitoring the CPR therapy and
providing instructions in real-time, the controller 120 may refrain
from providing its own instructions so long as the caregiver
continues monitoring. In some implementations, the controller 120
may continue to provide its own instructions, and the caregiver's
instructions may serve to supplement those.
[0190] In some implementations, some or all of the processing of
the information from the CPR sensor may be performed at the remote
server 322. For example, the one or more CPR sensors may provide
raw and/or minimally processed data to the remote server 322 via
the network 1202. The remote server 322 may process the data and
provide, to the controller 120, information about the CPR therapy.
For example, the one or more CPR sensors may provide raw
accelerometer data to the remote server 322, and the remote server
322 may determine the rate and depth of chest compressions based on
the data. The remote server 322 may also determine appropriate
feedback for refining the CPR therapy based on the determined
characteristics. Thus, remote computing systems having enhanced
processing capabilities may be utilized without requiring the
controller 120 to support extensive processing locally.
[0191] In some implementations, the indication of the quality of
the CPR may be an indication of the overall quality of the CPR
therapy. For example, the indication of the quality of the CPR may
be based on a combination of information related to chest
compression depth, chest compression rate, ventilations,
compression fraction, pre-shock pause, post-shock pause, and/or
perfusion index. Such a combination of information across multiple
activities being performed on the patient may be used to generate a
score or grade for the care provided to the patient, so as to
indicate manners in which the rescuer can change subsequent care
that is given. For example, measurements from the one or more CPR
sensors may indicate that the rescuer is too excited or too relaxed
in administering the CPR treatment (e.g., because the rescuer is
applying compressions that are too deep or too shallow, or the
rescuer is acting too quickly or too slowly in certain portions of
the CPR interval). In such a situation, an indication may be
provided for the rescuer to be more or less active in their care.
Exemplary techniques for providing CPR performance information,
including CPR quality feedback, are described in U.S. Pat. No.
8,738,129, filed on Nov. 14, 2011, and titled "Real-Time Evaluation
of CPR Performance," and U.S. Pat. Pub. No. 2013/0296719, filed on
Mar. 13, 2013, and titled "Rescue Performance Metric," the entire
contents of both of which are hereby incorporated by reference.
[0192] While the wearable medical device 100 shown in FIGS. 1A-1B
has been described as storing the CPR sensor 140 in a flap 142 of
the garment 110, in some implementations, the wearable medical
device 100 includes one or more sensors that are stored elsewhere
on the garment 110 (e.g., instead of or in addition to the CPR
sensor 140 of FIG. 1). FIG. 6 shows an example of the wearable
medical device 100 in which a wireless sensor 640 (e.g., sometimes
referred to as a CPR sensor, a chest compression sensor, and/or a
ventilation sensor) is stored in the waistband 104 of the garment
110. The wireless CPR sensor 640 may be configured to operate
substantially similarly to the CPR sensor 140 described above with
respect to FIGS. 1A-1B and 2A-2B.
[0193] The garment 110 can include a compartment that is configured
to removably store the wireless CPR sensor 640. For example, the
compartment may be a pocket 642 that is sewn into the garment 110
and configured to store the wireless CPR sensor 640 when CPR is not
being administered. In this way, the patient does not experience
the potentially cumbersome and/or uncomfortable placement of the
wireless CPR sensor 640 when it is not needed.
[0194] Prior to administration of CPR, the wireless CPR sensor 640
may be removed from the pocket 642 and placed at the center of the
patient's chest (e.g., above the xiphoid process). In some
implementation, the pocket 642 may include a mechanism for closing
the pocket 642, such as a zipper or a hook-and-loop fastener that
prevents the wireless CPR sensor 640 from falling out of the pocket
642 when not in use. In some implementations, the pocket 642 may be
positioned at another location of the garment 110 or at some other
portion of the wearable medical device 100. For example, the
wireless CPR sensor 640 may be stored in or on the controller 120
or the distribution node 130 when the wireless CPR sensor 640 is
not needed.
[0195] While the CPR sensor 640 has been described as being a
wireless sensor, in some implementations, the CPR sensor 640 may be
connected to the controller 120 by one or more wires (e.g., via the
distribution node 130).
[0196] As described above, it may be beneficial to position the
chest compression sensor at the center of the patient's chest
(e.g., above the patient's xiphoid process) to improve the accuracy
of the compression depths as determined by the processor 318 of the
controller 120. However, in some implementations, the wearable
medical device 100 may be configured to primarily provide CPR
feedback related to the rate of the chest compressions being
administered; in such implementations, providing information
related to the depths of the chest compressions may be a secondary
concern, and thus the positioning of the chest compression sensor
may be less critical.
[0197] FIG. 7 shows an example of the wearable medical device 100
in which a sensor 740 (e.g., a CPR sensor, a chest compression
sensor, and/or a ventilation sensor) is incorporated into one of
the therapy electrodes 714. For example, the chest compression
sensor 740 may be incorporated into the therapy electrode 714 that
is positioned at the front/side of the patient's abdomen when the
garment 110 is worn by the patient. The chest compression sensor
740 may be configured to operate substantially similarly to the
chest compression sensors (140 of FIGS. 1A-1B and 2A-2B; 640 of
FIG. 6) described above.
[0198] The therapy electrode 740 may include a sensor (e.g., a
motion sensor) that is configured for measuring heart sounds of the
patient. The sensor may include one or more accelerometers that
detect motion information that is used for measuring the heart
sounds. In some implementations, the sensor utilizes AUDICOR.RTM.
Technology from Inovise Medical of Beaverton, Oreg. Typical
accelerometer sensitivities appropriate for the measurement of
chest compressions may be approximately +/-2 g full scale range,
with data rates of approximately 100-2,000 Hz. Such a sensor may
function as the CPR sensor 740 of FIG. 7.
[0199] In some implementations, the sensor utilizing AUDICOR.RTM.
technology may be used to sense lung sounds in order to determine
whether or not ventilations are being delivered by the rescuer in
order to provide feedback to the rescuer on both the rate and
timing of the delivered ventilations. In this case, when measuring
the performance of ventilations (e.g., rather than chest
compressions) during the course CPR, the sensor may be more
adequately termed a "ventilation sensor" because it is not
measuring chest compressions, but rather ventilator/pulmonary
therapy.
[0200] The AUDICOR.RTM. sound sensor may act as a chest compression
sensor by detecting heart sounds rather than chest wall motion due
to compression of the chest, for example, by verifying adequacy of
chest compressions via detection of heart valve closures that are
the result of chest compressions.
[0201] As compressions are administered to the patient, the one or
more accelerometers of the chest compression sensor 740 experience
a rhythmic motion. A component of the motion signal detected by the
accelerometer (e.g., the z-component of the acceleration signal)
may include a series of peaks and valleys that correspond to the
compressions. The motion signal is provided to the processor 318,
and the processor 318 identifies compressions within the signal
using a peak detection method. For example, each time the
z-component of the acceleration signal crosses a predetermined
threshold (e.g., a zero-crossing), the processor 318 may identify
the occurrence of a compression. In some implementations, one or
more integration, linear detrending, and/or voltage offset
canceling steps may be performed on the data. Once the compressions
are identified, the processor 318 correlates the compressions with
the timings thereof to determine the rate of the chest
compressions. The processor 318 may then instruction the wearable
medical device to provide chest compression rate feedback
information to the rescuer using the techniques described above
with respect to FIGS. 4 and 5.
[0202] In some implementations, the motion data that the chest
compression sensor 740 provides to the processor 318 may also be
used to determine information related to the depths of the chest
compressions, and such information may be used by the processor 318
to provide feedback related to compression depths. However, for the
reasons described above, implementations in which compression depth
feedback is desired may employ a chest compression sensor that can
be repositioned to the center of the patient's chest (e.g., 140 of
FIGS. 1A-1B or 640 of FIG. 6) or multiple chest compression sensors
that are positioned at locations at the anterior of the patient's
chest chosen to identify a characteristic of the center of the
patient's chest, as described in more detail below.
[0203] While the chest compression sensor 740 has been described as
being incorporated into the therapy electrode 714 that is
positioned at the front/side of the patient's abdomen, the chest
compression sensor 740 may be incorporated into any of the therapy
electrodes 114 and/or positioned elsewhere on the wearable medical
device 100. In some implementations, the chest compression sensor
740 may be positioned at the controller 120 or the distribution
node 130. In some implementations, the chest compression sensor 740
may be positioned at one of the sensing electrodes or at any
location on the garment 110.
[0204] Even when a chest compression sensor is not positioned at
the center of the patient's chest, accurate compression depth
information can be obtained by receiving motion data from multiple
chest compression sensors positioned at various locations at the
chest of the subject. The motion data from the multiple chest
compression sensors can be mathematically adjusted to identify a
characteristic of the center of the patient's chest. For example,
the motion data from the multiple chest compression sensors can be
used to infer the displacement of the center of the patient's chest
during compressions.
[0205] FIG. 8 shows an example representation of a patient's chest
800. Chest compressions are applied by the rescuer placing his or
her hands at the center of the patient's chest (e.g., above the
xiphoid process 802) and applying downwards pressure in a rhythmic
fashion. The sternum 804 connects to the patient's sternal
cartilage 806, which connects to the ribs 808, and the entire chest
reacts to chest compressions generally as a single unit.
[0206] While the chest structure reacts in a generally unified
manner to the chest compressions, there can exist some degree of
flex between the various portions of the patient's chest. For
example, the patient's sternum 804 may flex relative to the sternal
cartilage 806 and to a greater extent relative to the ribs 808. In
this way, the sternum 804 may be displaced by a greater amount
relative to the displacement of the sternal cartilage 806, and the
sternal cartilage 806 may be displaced by a greater amount relative
to the displacement of the ribs 808. The representation of the
chest 800 includes shading that indicates such flexibility, where
the portions of the chest that have a darker shades indicate a
greater degree of displacement relative to portions of the chest
that have lighter shades. For example, the representation 800
indicates the sternum 804 moves to a greater degree as compared to
the other portions of the chest in response to chest compressions.
In particular, the shading indicates that some portions of the
sternal cartilage 806 experience a displacement of approximately
88.5% of the displacement of the sternum 804, and some portions of
the ribs 808 experience a displacement of approximately 63.5% of
the displacement of the sternum 804. Other portions of the
patient's body (e.g., the clavicle, the spine, etc.) experience
minimal and/or negligible displacement relative to the displacement
of the sternum 804.
[0207] In knowing the relationships between the typical relative
motions of the various portions of the patient's chest, it is
possible to infer the displacement of the center of the patient's
chest (e.g., the location above the xiphoid process) by measuring
the displacement of one or more other locations of the chest. For
example, suppose it was known that the tenth rib (e.g., the bottom
rib) is always displaced at 50% of the displacement of the center
of the patient's chest. One could position a motion sensor (e.g., a
CPR sensor) at the tenth rib, measure the displacement, multiply
the displacement by a correction factor of two, and determine the
displacement at the center of the chest. In practice, however, such
a conversion may not be so simple because the human body is not
uniform from patient to patient.
[0208] Various different patient characteristics may impact the
relative flexibilities of the different portions of the chest. For
example, a person having a wide chest may exhibit a greater
disparity between the displacement of the sternum 804 and the
displacement of the ribs 808, or older patients may exhibit less
displacement disparity (e.g., due to calcification in body tissue).
Also, due to different chest dimensions across different patients,
the motion sensor may not be positioned on the patient exactly
where expected, thereby introducing error into the displacement
conversion. Further, while the magnitude of displacement may be
known for the various portions of the patient's chest, additional
motion information may be helpful to determine the characteristics
of the chest compressions. For example, rotational displacement
measurements (e.g., tilt measurements) of the chest relative to the
floor, which typically results from chest compression, may provide
useful information that can be considered in determining the depths
of the compressions. In some implementations, such information may
be more accurately obtained by including multiple chest compression
sensors on the wearable medical device 100 and/or by fitting and
calibrating the wearable medical device 100.
[0209] In some implementations, before the wearable medical device
100 is first used by the patient, one or more parameters related to
the patient's chest measurements may be provided. Such parameters
may be provided via the user interface 318 of the controller 120
(e.g., via the touch screen 220 of FIGS. 2A-2B). Examples of
measurements that may be provided include the transverse diameter
(e.g., width) of the chest, the anterior-posterior diameter (e.g.,
length between the sternum and the spine) of the chest, and the
distance between the waistband 104 of the garment 110 and the
patient's xiphoid process, among others.
[0210] Using the provided patient measurements and/or other patient
parameters, the wearable medical device 100 may be configured to
adjust an algorithm for determining the displacement of the center
of the patient's chest to better fit the particular patient. For
example, in an uncalibrated state, the wearable medical device 100
may use a default chest motion model for determining the
displacement of the center of the patient's chest relative to the
displacement of one or more other locations of the chest. Referring
again to FIG. 8, the default chest motion model may cause the
wearable medical device 100 to multiply displacement measurements
by a correction factor that corresponds to the relative shading of
the chest representation 800. In other words, the chest
representation 800 shown in FIG. 8 may represent a default chest
motion model that indicates particular correction factors that are
to be applied to motion measurements from one or more motion
sensors.
[0211] Should the patient's particular chest measurements deviate
from those of the default chest motion model, the model may be
refined accordingly. For example, if the dimensions of the
patient's chest are smaller than the values assumed for the default
model, the correction factors may need to be adjusted accordingly
(e.g., reduced); if the dimensions of the patient's chest are
larger than the values assumed for the default model, the
correction factors may need to be adjusted accordingly (e.g.,
increased). The appropriate adjustments may be based on
experimental data measurements obtained from a number of patients
having various chest dimensions. In this way, the wearable medical
device 100 may be calibrated to provide CPR feedback information
that tends to be more accurate for patients who have
characteristics in line with the particular patient.
[0212] Continuing with the example provided above, suppose the
default chest motion model is based on relative chest motions of a
patient having chest dimensions typically seen in an adult male.
That is, based on experimental data, the default chest motion model
may indicate that displacements measured at the tenth rib (e.g.,
the bottom rib) should be multiplied by a correction factor of two
in order to infer the motion at the center of the patient's chest
(e.g., because the tenth rib is only displaced at 50% of the
displacement of the center of the patient's chest). However,
experimental data may also indicate that in patients having smaller
chest dimensions, the tenth rib typically experiences a
displacement relative to the center of the patient's chest that is
significantly smaller (e.g., 40%). Thus, to more accurately infer
the motion of the center of such a patient's chest based on
displacement measurements taken at the tenth rib, it may be more
appropriate to multiply the displacement measurements by a
correction factor of 2.5. The values provided here are exemplary
and are being used simply to illustrate the idea that the wearable
medical device 100 may consider various patient characteristics,
including chest dimensions, in determining information about the
CPR therapy being administered.
[0213] As mentioned above, in addition to calibrating the wearable
medical device 100 for a particular patient or a particular type of
patient, the motion of the center of the patient's chest may be
inferred more accurately when motion data from multiple sensors
situated at different locations on the chest are obtained. FIG. 9
shows an example of the wearable medical device 100 that includes
three sensors 940a-c (e.g., sometimes referred to as CPR sensors,
chest compression sensors, and/or ventilation sensors) for
detecting characteristics of the CPR therapy. The chest compression
sensors 940a-c may include one or more accelerometers that are
configured to detect motion that occurs during the administration
of CPR. In this example, a first chest compression sensor 940a is
positioned at the side of the waistband 140 of the garment 110, a
second chest compression sensor 940b is positioned on one of the
shoulder straps 106 of the garment 110, and a third chest
compression sensor 940c is positioned on the other shoulder strap
106 of the garment 110. The chest compression sensors 940a-c define
a triangular plane 942 on the chest of the patient. The medical
device controller 120 is configured to process information (e.g.,
motion information) received from the chest compression sensors
940a-c and provide information about the CPR therapy. For example,
the controller 120 is configured to determine information related
to the motion of the triangular plane 942 as chest compressions are
being administered.
[0214] The chest compression sensors 940a-c are configured to
detect characteristics of the chest compressions, such as the depth
and rate of chest compressions administered to the patient. For
example, accelerometers incorporated into the chest compression
sensors 940a-c may provide acceleration, velocity, and/or
displacement information to the controller 120, and the controller
120 can process the information to determine the depths of the
chest compressions and the rate at which the chest compressions are
administered.
[0215] As mentioned above, the depths of chest compressions are
typically measured at the center of the patient's chest (e.g., at a
location above the patient's xiphoid process). In this way, the
depth of a chest compression may be a measure of the displacement
of the center of the patient's chest from an initial position
(e.g., with no pressure applied to the chest) to a compressed
position (e.g., when peak pressure is applied to the chest).
Because none of the chest compression sensors 940a-c are positioned
at the center of the patient's chest, the depths of chest
compressions can be determined by performing additional processing
(e.g., mathematical adjustments) of the motion information received
from the chest compression sensors 940a-c.
[0216] In some implementations, one or more correction factors may
be applied to the motion information to infer the displacement of
the center of the patient's chest during compressions. For example,
the displacement information received from the second and third
chest compression sensors 940b, 940c may be multiplied by a first
correction factor, and the displacement information received from
the first chest compression sensor 940a may be multiplied by a
second correction factor. The corrected displacement information
from the three chest compression sensors 940a-c may then be
averaged in order to infer the displacement that occurs at the
center of the patient's chest (e.g., the depth of the chest
compressions).
[0217] The chest compression sensors 940a-c define a triangular
plane 942 on the chest of the patient. In some implementations, the
motion information from the chest compression sensors 940a-c is
used to determine the motion of the triangular plane 942. For
example, if the displacement over time of the three vertices of the
triangular plane 942 is known, the displacement of any position of
the triangular plane 942 (e.g., including the portion of the
triangular plane 942 that resides at the center of the patient's
chest) can be determined using appropriate mathematical adjustment.
The inclusion of additional chest compression sensors may further
improve the accuracy of such determinations.
[0218] In some implementations, one or more of the chest
compression sensors 940a-c is configured to measure information
related to tilt (e.g., relative to a reference plane). The tilt
information can be used to determine the rotational displacement of
the chest. For example, when compressions are applied to the
patient's chest, the chest experiences a rotational displacement
about an axis near the top of the patient's chest. Chest
compression sensors positioned toward the bottom of the chest
(e.g., the first chest compression sensor 940a) will experience
relatively more displacement due to the rotation than chest
compression sensors positioned toward the top of the chest (e.g.,
the second and third chest compression sensors 940b, 940c). In some
implementations, it may be desired to differentiate between
displacement due to the rotation and substantially vertical
displacement. For example, the substantially vertical displacement
may be the appropriate measure to use for determining the actual
depths of the chest compressions.
[0219] Tilt information determined by individual ones of the chest
compression sensors 940a-c can be provided to the processor 318,
and the processor 318 can consider the tilt information to properly
account for the rotational displacement. In some implementations,
the tilt information is used to adjust the correction factor to be
applied to motion information from a particular one of the chest
compression sensors 940a-c. In some implementations, instead of or
in addition to individual ones of the chest compression sensors
940a-c being configured to provide tilt information, motion data
from two or more of the chest compression sensors that reside at
different vertical locations of the patient's chest may be used to
infer the tilt of the patient's chest relative to the floor. For
example, the displacement measured by the first chest compression
sensor 940a and the second chest compression sensor 940b, or the
displacement measured by the first chest compression sensor 940a
and the third chest compression sensor 940c, may be used to
determine the angle of the patient's chest relative to the floor
that results from the application of chest compressions.
[0220] In some versions of the wearable medical device 100, there
may not be a convenient location to place the CPR sensor. For
example, conventional state-of-the-art chest measurement sensors
require that the motion sensor be placed directly on the patient's
sternum (e.g., at the location where the rescuer delivers the chest
compressions). With conventional methods of measuring chest
compression characteristics, if the chest compression sensor is
offset by any amount from underneath where the rescuer is
delivering the compressions, then the accuracy measurement can be
significantly degraded. It can be uncomfortable for the patient to
have a portion of the garment continuously covering the sternal
portion during daily use. It may therefore be preferable for the
chest compression sensor to be placed in an already-existing
portion of the garment. Such portions of the garment are
parasternal (i.e. located off of the patient's sternum).
[0221] In order to allow for the chest compression sensor to be
placed parasternally and still achieve satisfactory accuracy in the
measurement of chest compressions, a representation of the geometry
of the patient's chest may be used by the wearable medical device
100 to determine particular adjustments to the motion data that can
be applied to determine chest compression characteristics with
enhanced accuracy. In the simplest embodiment, the geometric
representation of the patient's chest used to determine particular
adjustments to the motion data may be a preprogrammed, generic
representation based on known statistical anthropometric data
collected from a relevant patient population. The adjustments may
be in the form of a table lookup, a linear adjustment function, or
a non-linear adjustment function. There may be separate adjustments
(e.g., tables) for different patient populations, for instance,
separate tables for women, men, and potentially different weight
groups.
[0222] The motion of the center of the patient's chest may also be
estimated using two sensors positioned at different parasternal
locations on the chest. FIG. 10 shows an example of the wearable
medical device 100 that includes two chest compression sensors
1040a, 1040b for detecting characteristics of the CPR therapy. The
chest compression sensors 1040a, 1040b may include one or more
accelerometers that are configured to detect motion that occurs
during the administration of CPR. In this example, a first chest
compression sensor 1040a is positioned at the side of the waistband
104 of the garment 110 and a second chest compression sensor 1040b
is positioned at one of the shoulder straps 106 of the garment 110.
In some implementations, the second chest compression sensor 1040b
is positioned at the other shoulder strap 106 of the garment 110
(e.g., the shoulder strap 104 diagonal from the first chest
compression sensor 1040a). The chest compression sensors 1040a,
1040b define a line 1042 on the chest of the patient. The
controller 120 is configured to process information (e.g., motion
information) received from the chest compression sensors 1040a,
1040b and provide information about the chest compressions. For
example, the controller 120 is configured to determine information
related to the motion of the line 1042 as CPR is being
administered.
[0223] The chest compression sensors 1040a, 1040b are configured to
detect characteristics of the CPR in a manner substantially similar
to that described above with reference to the sensors 940a-c of
FIG. 9. For example, accelerometers incorporated into the chest
compression sensors 1040a, 1040b may provide acceleration,
velocity, and/or displacement information to the controller 120,
and the controller 120 can process the information to determine the
depths of the chest compressions and the rate at which the chest
compressions are administered. The information received from the
chest compression sensors 1040a, 1040b may be mathematically
adjusted (e.g., by a correction factor) to infer the depths of
chest compressions at the center of the patient's chest. In some
implementations, the angle of the chest relative to the floor may
be determined based on a comparison of the displacement information
of the chest compression sensors 1040a, 1040b and/or information
related to tilt as measured by the individual ones of the chest
compression sensors 1040a, 1040b.
[0224] The description related to FIGS. 8-10 explains that the
accuracy of the measurements of the chest compression therapy that
are determined can be improved by providing patient characteristic
information (e.g., chest measurements) and/or by including
additional chest compression sensors; knowing the patient's chest
measurements can help to refine the appropriate correction factor
to be applied to the motion data, and inclusion of additional
sensors can minimize variation between an expected location of a
chest compression sensor and the actual location of the sensor on
the patient. However, the accuracy of the chest compression
characteristics may be even further improved by providing more
extensive patient thoracic geometry information so as to tailor the
wearable medical device 100 to a particular patient. For example,
chest measurement information that provides a representation of the
geometry of the particular patient's chest may be used by the
wearable medical device 100 to determine particular adjustments to
the motion data that can be applied to determine chest compression
characteristics of enhanced accuracy. Alternatively, simple
estimates of patient geometry--e.g., size-related: "small",
"medium", or "large"; or chest conformation-related:
"barrel-chested", "flat-chested", "narrow", "wide", etc.--may be
utilized to enhance the accuracy.
[0225] In some implementations, information related to the geometry
of the particular patient's chest may be determined prior to
initiation of CPR. In this way, the correction factors to be
applied to the motion data from the chest compression sensors may
be tailored to the particular patient, thereby resulting in more
accurate compression depth and/or rate detection, and in turn more
accurate feedback provided to the rescuer.
[0226] FIG. 11 shows an example of a measuring device, such as a
wand 1102, that can be used to measure information related to a
geometry of the patient's chest prior to initiation of CPR. The
wand 1102 may include one or more motion sensors that are
configured to provide information to the controller 120 that
identifies the coordinates of the wand 1102. The motion sensors may
include one or more accelerometers that are configured to measure
acceleration, velocity, displacement, and/or tilt information and
provide such information to the controller 120. In some
implementations, the motion sensors are configured to measure
motion and/or positional information in three axes. The one or more
motion sensors may be positioned at a tip of the wand 1102 and/or
throughout the wand 1102.
[0227] The geometry of the particular patient's chest may be
determined by moving the wand 1102 around the various portions of
the patient's chest. For example, the wand 1102 may be placed at an
initial position (e.g., a known position), the three dimensional
coordinates of which are known to the controller 120. As the wand
1102 navigates the contours of the patient's chest, motion and/or
positional information (e.g., related to acceleration, velocity,
displacement, and/or tilt) is provided to the controller 120. Such
information can be used to continuously (e.g., substantially
continuously) determine the position of the wand 1102 relative to
the starting position, thereby providing a mapping of the geometry
of the patient's chest commensurate with the amount of positional
locations gathered by the wand 1102.
[0228] The completeness of the determined geometry of the chest may
be proportional to the number of positional locations gathered by
the wand 1102. In some implementations, it may be sufficient to map
a discrete number of chest locations of the patient. For example,
the wand 1102 may be used to map coordinates to particular chest
locations of interest, such as the patient's xiphoid process,
sternal notch, inferior margin of the ribs (e.g., bottom of the
ribs), individual ribs, and/or the perimeter of the ribcage, among
others. The mapping information can be used to generate a
representation of the patient's chest.
[0229] In some implementations, the wand 1102 is also used to map
the coordinates of the one or more chest compression sensors
relative to locations on the patient's chest. For example, when the
wand 1102 is positioned at a location of a chest compression
sensor, an indication may be provided to the controller 120 (e.g.,
via the touch screen 220) indicating such. In some implementations,
the wand 1102 and the chest compression sensors are configured to
communicate with each other through a wireless and/or a wired
connection. For example, the wand 1102 and the one or more chest
compression sensors may include electrical contacts. When the wand
1102 is positioned at a location where a chest compression sensor
resides, the electrical contacts may touch each other. The contact
between the wand 1102 and the chest compression sensor may indicate
to the controller 120 that the coordinates of the wand 1102 are to
be mapped to the position of the particular chest compression
sensor. Using this technique, the controller 120 may obtain a
complete representation of the particular patient's chest that can
be used to determine the dimensions and contours of the chest,
including the anterior-posterior diameter and transverse diameter
of the chest, among others. The representation can include the
coordinates of the various portions of the chest and the
coordinates of the one or more chest compression sensors relative
to the various portions of the chest. Using the information
included in the representation, the controller 120 can infer how
the center of the patient's chest responds relative to the motion
of the chest locations where the one or more chest compression
sensors are positioned. In this way, the controller 120 can process
the motion information obtained from the one or more chest
compression sensors in conjunction with the information contained
in the chest representation to determine the motion that occurs at
the at the center of the patient's chest.
[0230] In some implementations, a 3D representation (e.g., a 3D
model) of the patient's chest may be generated based on the
information obtained from the wand 1102. For example, a
representation similar to that shown in FIG. 8 may be generated
based on the coordinate mapping. In some implementations, the 3D
representation may include similar shading that indicates the
expected relative motions of the various portions of the patient's
chest in response to chest compressions. Such information may be
used to determine an appropriate correction factor to be applied to
motion information obtained from particular chest compression
sensors to infer the displacement of the center of the patient's
chest during compressions.
[0231] In some implementations, the information related to the
geometry of the patient's chest and/or the representation of the
patient's chest may be used to determine optimal placement of the
chest compression sensors. In some examples, the garment 110 may
provide multiple possible locations for positioning the one or more
chest compression sensors. For example, multiple hook-and-loop
fasteners and/or multiple compartments may be positioned at various
locations on the garment 110. Based on the determined geometry
information and/or representation of the patient's chest, the
wearable medical device 100 may suggest that the chest compression
sensors be placed at particular locations. For example, briefly
referring to FIG. 9, suppose the patient has a unique chest
geometry that results in the first chest compression sensor 940a
being positioned too far to the middle of the patient's chest
(e.g., such that the first chest compression sensor 940a does not
reside over the patient's ribs). As explained above, because the
entire chest generally moves as a single unit during administration
of chest compressions, a chest compression sensor that is not
positioned over the patient's ribs may provide motion information
that is of limited value. In some implementations, the waistband
104 of the garment 110 may include multiple compartments positioned
along the upper portion of the waistband 104. Based on the
determined geometry of the patient's chest and the determined
relative positions of the chest compression sensors 940a-c, the
wearable medical device 100 may suggest that the patient move the
first chest compression sensor 940a to a different compartment of
the garment 110. For example, the wearable medical device 100 may
instruct the patient to move the first chest compression sensor
940a to a lateral compartment that resides over the patient's lower
ribs. In some implementations, the wearable medical device 100 may
also or instead suggest that the patient swap the garment 110 for
another garment having a size that is more appropriate for the
patient's chest geometry.
[0232] After characteristics of the CPR therapy (e.g., including
the rate and/or depths of chest compressions) are determined with
the help of the information related to the geometry of the
patient's chest, the controller 120 is configured to provide
information related to the CPR therapy to the output device (324 of
FIG. 3). The information that can be provided is substantially
similar to that which is described above with respect to FIGS. 4
and 5. For example, the controller 120 may provide visual and/or
audio information related to compression depths and/or compression
rate via the touch screen 220 and/or the speaker 204. The
information may be provided in the form of feedback for assisting
the rescuer in refining the CPR therapy. For example, the feedback
may include rhythmic audio tones indicative of a target rate of
chest compressions and/or verbal commands that instruct the rescuer
to speed up the compression rate, slow down the compression rate,
increase the depths of compressions, and/or decrease the depths of
compressions, among others.
Alternative Implementations
[0233] While certain implementations have been described, other
implementations are possible.
[0234] While the device for measuring information related to the
geometry of the patient's chest has largely been described as a
wand that includes motion sensors (e.g., the wand 1102 of FIG. 11),
other implementations are possible. For example, in some
implementations, the measuring device may include one or more
cameras that are configured to scan a surface of the patient's
chest. The scan may include capturing multiple images of the
patient's chest from multiple angles and/or by the multiple
cameras. The processor of the medical device controller is
configured to generate a 3D representation of the patient's chest
using the information obtained by the scan, and the representation
can be used to determine dimensions and contours of the chest. In
this way, a 3D model of the patient's chest may be generated. The
3D model may be in the form of a 3D polygon surface mesh. In some
implementations, a 3D surface imaging technology with anatomical
integrity can be used, such as the 3dMDthorax System available from
3dMD LLC of Atlanta, Ga.
[0235] In some implementations, the one or more cameras may be used
to map coordinates to particular chest locations of interest, such
as the patient's xiphoid process, sternal notch, inferior margin of
the ribs, individual ribs, and/or the perimeter of the ribcage,
among others. In some implementations, the one or more cameras may
be used to measure information related to the geometry of the
patient's chest while the patient is wearing the medical device. In
this way, the one or more cameras may be used to map the
coordinates of the one or more chest compression sensors relative
to locations on the patient's chest.
[0236] Each of the one or more chest compression sensors may
include a visual identifiers (ID) that may indicate the particular
chest compression sensor and information related to the particular
chest compression sensor. For example, briefly referring to FIG. 9,
each of the chest compression sensors 940a-c may include a visual
ID that indicates the general position of the corresponding chest
compression sensor 940a-c; the visual ID of the first chest
compression sensor 940a may indicate that it is positioned on the
waistband 104 of the garment 110, the visual ID of the second chest
compression sensor 940b may indicate that it is positioned on the
left shoulder strap 106 of the garment 110, and the visual ID of
the third chest compression sensor 940c may indicate that it is
positioned on the right shoulder strap 106 of the garment 110. The
visual IDs may be in the form of a barcode or a QR code, to name a
few. The one or more cameras are configured to identify the visual
ID by comparing the captured image information to stored data
(e.g., data stored in a database).
[0237] The one or more cameras along with the processor of the
medical device controller may be configured to determine the actual
location of the chest compression sensors 940a-c relative to their
expected locations. For example, with respect to the second chest
compression sensor 940b, the wearable medical device 100 may expect
the second chest compression sensor 940b to be positioned at the
middle of the patient's third rib (e.g., the third rib from the
top). That is, the wearable medical device 100 may be calibrated
such that motion information received from the second chest
compression sensor 940b is mathematically modified based on an
assumption that the second chest compression sensor 940b is
positioned at the middle of the patient's third rib. Referring also
to the representation 800 of FIG. 8, if the second chest
compression sensor 940b is actually positioned elsewhere (e.g., at
the sternal cartilage 806 adjacent to the patient's third rib), the
second chest compression sensor 940b may experience more
displacement as a result of chest compressions than expected. Thus,
it may be appropriate to modify the correction factor applied to
the second chest compression sensor's 940b motion information to
account for the positional disparity.
[0238] In some implementations, the controller may suggest that an
alternative garment be used by the patient such that the chest
compression sensors are positioned more closely to their expected
positions. In some examples, the garment may be available in
multiple sizes that each position the chest compression sensors
slightly differently relative to each other. If the image
information indicates that the chest compression sensors are
generally positioned too centric on the patient's chest, the
controller may suggest that the patient switch to a larger sized
garment. The patient may then undergo a new scan to determine
whether the larger garment serves to position the chest compression
sensors more appropriately. In some implementations, slight
deviations between the expected and actual positions of the chest
compression sensors may be alleviated by mathematically adjusting
the received motion information in the manner described above.
[0239] In some implementations, once the information related to the
geometry of the patient's chest is obtained by the one or more
cameras and/or the representation of the patient's chest is
generated, the medical device controller may use such information
in substantially the same ways as described above with respect to
FIG. 11. For example, the information and/or the representation can
be used to determine the dimensions and contours of the chest,
including the anterior-posterior diameter and transverse diameter
of the chest, among others. The representation can include the
coordinates of the various portions of the chest and the
coordinates of the one or more chest compression sensors relative
to the various portions of the chest. Using the information
included in the representation, the controller can infer how the
center of the patient's chest responds relative to the motion of
the chest locations where the one or more chest compression sensors
are positioned. In this way, the controller can process the motion
information obtained from the one or more chest compression sensors
in conjunction with the information contained in the chest
representation to determine the motion that occurs at the at the
center of the patient's chest during CPR.
[0240] In some implementations, the wearable medical device may be
configured to determine a location of a rescuer's hand during
administration of the CPR treatment, including chest compressions.
That is, the processor of the medical device controller may be
configured to process information related to the location of the
rescuer's hand and present information to the rescuer based on the
determined location and/or positioning. In some implementations,
the location of the rescuer's hand may be inferred based on
information received from the one or more chest compression
sensors.
[0241] In some implementations, the wearable medical device may
include one or more components for determining the amount and/or
location of pressure applied to the patient's chest during
administration of chest compressions. For example, the garment may
include a pressure sensitive fabric that is configured to convey to
the processor information related to the location and/or magnitude
of pressure being applied.
[0242] In some implementations, the pressure sensitive fabric
resides at or near the center of the patient chest. The pressure
sensitive fabric may be in the form of a strain sensor. For
example, the pressure sensitive fabric may include one or more
conductive elements (e.g., including inductive elements and/or
capacitive elements) that are incorporated into the fabric of the
garment. The conductive elements are configured to stretch, expand,
and/or otherwise deform with the fabric of the garment. Thus, when
pressure is applied to the fabric during the administration of
chest compressions, the fabric and the conductive elements deform
with the fabric.
[0243] The inductive element may include a conductive wire or
thread that is configured in a coiled pattern (e.g., spring shaped)
that includes a plurality of windings (or turns). In some
implementations, a magnetic core may be disposed within the
windings. In some implementations, the inductive element may be
configured in a serpentine patter that includes a plurality of
serpentine turns. The capacitive element may include conductive
wires of threads configured in parallel with each other in a coiled
or serpentine pattern. In some implementations, the capacitive
element includes two wires with a space therebetween. The space can
be occupied by an insulator, a dielectric material, or air such
that the two wires act as a capacitor when supplied with power. The
inductive element and/or the capacitive element can be shielded,
jacketed, or insulated, and may be configured to connect to the
controller to receive power.
[0244] When the pressure sensitive fabric and the conductive
elements are deformed, the radii of the windings or turns of the
coiled or serpentine pattern change. When these radii change, the
inductance of the inductive element and/or the capacitance of the
capacitive element changes. One or both of the inductive element
and the capacitive element can provide a measured value (e.g., an
inductance value or a capacitance value) to the controller that is
indicative of a magnitude of deformation experienced by the
pressure sensitive fabric. Further, the controller can determine
precisely where pressure is being applied based on which of the
capacitive elements and/or inductive elements are deformed and
supplying signals to the controller.
[0245] While the processor of the medical device controller has
been described as being configured to provide information about the
CPR therapy to the output device that includes rate of chest
compressions and depths of chest compressions, the processor may
provide other information as well. In some implementations, the
processor is configured to cause the output device to provide
feedback to the rescuer related to the positioning of the rescuer's
hands. For example, based on the readings received from the
pressure sensitive fabric, the processor may determine that the
rescuer is not applying chest compressions at the appropriate
location. The processor may cause the output device (e.g., the
touch screen and/or the speaker of the controller) to instruct the
rescuer to adjust his or her hand positioning accordingly. For
example, the speaker may provide a verbal command to "move your
hands higher on the chest" or "move your hands lower on the chest,"
among others. In some implementations, the touch screen may provide
a schematic of a patient chest that includes a target location
where chest compressions should be applied and an actual location
where the compressions are being applied; the touch screen may
instruct the rescuer to move his or her hands to the target
location indicated in the schematic.
[0246] In some implementations, the information received from the
pressure sensitive fabric may be used to determine or assist in
determining the depths of the compressions being applied to the
patient. However, in some implementations, it may be more important
to directly measure how deeply the rescuer is compressing the chest
than to measure how hard the rescuer is pressing; thus, a pressure
reading alone may be insufficient for providing complete feedback
related to the depths of the chest compressions.
[0247] In some implementations, one or more chest compression
sensor may be positioned behind the patient (e.g., on the back of
the patient) when the garment is worn by the patient. Motion
information received from the chest compression sensor positioned
on the patient's back may be considered by the medical device
controller to more accurately determine characteristics of the CPR
therapy. In some implementations, CPR may be performed on a patient
lying on a soft surface. When chest compressions are applied to the
patient, the patient's entire body may move in response. That is,
while a portion of the rescuer's compressions applied to the center
of the patient's chest may result in desired compressions to the
chest, some of the compression effort may result in movement of the
patient's entire body. The movement of the entirety of the
patient's body may result in motion artifacts that skew the motion
data received from the chest compression sensors.
[0248] For example, a first chest compression sensor positioned on
the front surface of the patient's chest (e.g., at the center of
the patient's chest) may indicate a displacement of three inches in
response to chest compressions applied to a patient who is lying on
a soft bed. While the first chest compression sensor may be
displaced by a total amount of three inches, the entirety of the
patient's body may be displaced by two inches due to the softness
of the bed. Thus, the net compressions of the front surface of the
patient's chest relative to the patient's back is only one inch.
Unless the wearable medical device is provided with some frame of
reference, it may erroneously determine that compressions are being
applied with a depth of three inches and instruct the rescuer to
apply compressions having less depth.
[0249] In some implementations, a second chest compression sensor
is positioned on the back of the patient (e.g., in a back portion
of the garment 110) substantially behind the first CPR sensor. The
second chest compression sensor experiences motion due to the
entirety of the patient's body depressing into the soft bed, but
may not experience motion that corresponds to the front surface of
the patient's chest moving relative to the patient's back. In some
implementations, the motion information received from the second
chest compression sensor may be subtracted from the motion
information received from the first chest compression sensor to
offset the effects of the universal motion. Using the motion
information from both sensors, the wearable medical device can
correctly determine that the chest compressions are resulting in
compressions depths of only one inch, and thereby instruct the
rescuer to apply compressions having more depth.
[0250] In some implementations, the motion information received
from the second chest compression sensor may be used to
mathematically adjust the motion information from the first chest
compression sensor in some other fashion. In some implementations,
each chest compression sensor positioned on the front surface of
the patient's chest has a corresponding chest compression sensor
positioned on the patient's back substantially behind the chest
compression sensor on the front surface.
[0251] In some implementations, as chest compressions are
administered, the patient's sternal cartilage may soften, resulting
in increased motion of the sternum relative to the other portions
of the patient's chest. To account for the softening, the
controller may be configured to adjust the correction factor
commensurate with the length of time that the compressions have
been administered. In some implementations, the correction factor
applied to motion data received from one or more sensors may
increase over time accordingly.
[0252] While the wearable medical device has been largely described
as providing information (e.g., feedback information) related to
the CPR therapy during administration of the CPR, in some
implementations, such information is provided after or in between
portions of CPR therapy. For example, feedback information may be
provided to the rescuer after a series of chest compressions have
been applied. In this way, the feedback does not overwhelm the
rescuer during administration of a portion of treatment. In some
implementations, the wearable medical device may determine that CPR
therapy is no longer needed, and the feedback may include an
instruction to cease administration of CPR. In some
implementations, the wearable medical device may instruct the
rescuer to temporarily cease administration of CPR. For example,
the wearable medical device may determine that a therapeutic shock
should be applied to the patient (e.g., by the therapy electrodes);
the wearable medical device may instruct the rescuer to not touch
the patient and/or step away from the patient prior to the shock
being delivered.
[0253] In some implementations, the wearable medical device may
instruct the patient to temporarily cease administration of CPR
before performing an ECG analysis of the patient (e.g., to
determine how the patient is responding to the therapy). In some
implementations, if the analysis were to be performed during the
chest compressions, the chest compressions may affect the sensed
electrical rhythm. In some implementations, an ECG analysis can be
performed during pauses between sets of compressions (for example,
during a pause after every fifth chest compression). In one
example, the wearable medical device may initially determine that
the patient is experiencing a non-shockable rhythm such as
bradycardia, in which case CPR should be administered in order to
keep the patient alive; during a subsequent ECG analysis, the
wearable medical device may determine that the patient's heart
rhythm has changed to ventricular fibrillation, in which case CPR
should be ceased to allow the wearable medical device to perform
more analysis and possibly apply one or more shocks to the patient.
The wearable medical device may instruct the rescuer accordingly.
In this way, the rescuer is integrated into a scheme that allows
complex combinations of therapy.
[0254] In some implementations, one or more of the CPR sensors may
be incorporated into a OneStep.TM. electrode that is configured to
provide defibrillation, pacing, and/or CPR assistance to the user.
The OneStep.TM. electrode may include one or more accelerometers
and/or gyroscopes for measuring motion data.
Example Infrastructure
[0255] Software running on the medical device controller can be
realized by instructions that upon execution cause one or more
processing devices to carry out the processes and functions
described above. The instructions can include, for example,
interpreted instructions such as script instructions, or executable
code, or other instructions stored in a computer readable
medium.
[0256] A server (e.g., the remote server 322 of FIGS. 3 and 12) can
be distributively implemented over a network, such as a server
farm, or a set of widely distributed servers or can be implemented
in a single virtual device that includes multiple distributed
devices that operate in coordination with one another. For example,
one of the devices can control the other devices, or the devices
may operate under a set of coordinated rules or protocols, or the
devices may be coordinated in another fashion. The coordinated
operation of the multiple distributed devices presents the
appearance of operating as a single device.
[0257] In some examples, the components of the controller may be
contained within a single integrated circuit package. A system of
this kind, in which both a processor (e.g., the processor 318 of
FIG. 3) and one or more other components (e.g., the cardiac event
detector 320) are contained within a single integrated circuit
package and/or fabricated as a single integrated circuit, is
sometimes called a microcontroller. In some implementations, the
integrated circuit package includes pins that correspond to
input/output ports (e.g., that can be used to communicate signals
to and from one or more of the input/output interface devices).
[0258] Although an example processing system has been described
above, implementations of the subject matter and the functional
operations described above can be implemented in other types of
digital electronic circuitry, or in computer software, firmware, or
hardware, including the structures disclosed in this specification
and their structural equivalents, or in combinations of one or more
of them. Implementations of the subject matter described in this
specification, such as storing, maintaining, and displaying
artifacts can be implemented as one or more computer program
products, i.e., one or more modules of computer program
instructions encoded on a tangible program carrier, for example a
computer-readable medium (e.g., the data storage 304 of FIG. 3),
for execution by, or to control the operation of, a processing
system. The computer readable medium can be a machine readable
storage device, a machine readable storage substrate, a memory
device, or a combination of one or more of them.
[0259] The term "system" may encompass all apparatus, devices, and
machines for processing data, including by way of example a
programmable processor, a computer, or multiple processors or
computers. A processing system can include, in addition to
hardware, code that creates an execution environment for the
computer program in question, e.g., code that constitutes processor
firmware, a protocol stack, a database management system, an
operating system, or a combination of one or more of them. In some
implementations, operating systems can include a Windows based
operating system, OSX, or other operating systems.
[0260] A computer program (also known as a program, software,
software application, script, executable logic, or code) can be
written in any form of programming language, including compiled or
interpreted languages, or declarative or procedural languages, and
can be deployed in any form, including as a standalone program or
as a module, component, subroutine, or other unit suitable for use
in a computing environment. A computer program does not necessarily
correspond to a file in a file system. A program can be stored in a
portion of a file that holds other programs or data (e.g., one or
more scripts stored in a markup language document), in a single
file dedicated to the program in question, or in multiple
coordinated files (e.g., files that store one or more modules, sub
programs, or portions of code). A computer program can be deployed
to be executed on one computer or on multiple computers that are
located at one site or distributed across multiple sites and
interconnected by a communication network.
[0261] Computer readable media suitable for storing computer
program instructions and data include all forms of non-volatile or
volatile memory, media and memory devices, including by way of
example semiconductor memory devices, e.g., EPROM, EEPROM, and
flash memory devices; magnetic disks, e.g., internal hard disks or
removable disks or magnetic tapes; magneto optical disks; and
CD-ROM, DVD-ROM, and Blu-Ray disks. The processor and the memory
can be supplemented by, or incorporated in, special purpose logic
circuitry. Sometimes a server (e.g., the remote server 322) is a
general purpose computer, and sometimes it is a custom-tailored
special purpose electronic device, and sometimes it is a
combination of these things. Implementations can include a back end
component, e.g., a data server, or a middleware component, e.g., an
application server, or a front end component, e.g., a client
computer having a graphical user interface or a Web browser through
which a user can interact with an implementation of the subject
matter described is this specification, or any combination of one
or more such back end, middleware, or front end components. The
components of the system can be interconnected by any form or
medium of digital data communication, e.g., a communication network
such as the connection between the remote server 322 and the
network interface 306, as shown in FIG. 3. Examples of
communication networks include a local area network ("LAN") and a
wide area network ("WAN"), e.g., the Internet.
[0262] Having described several aspects of at least one example of
this disclosure, the examples of the methods and apparatuses
discussed herein are not limited in application to the details of
construction and the arrangement of components set forth in this
description or illustrated in the accompanying drawings. The
methods and apparatuses are capable of implementation in other
examples and of being practiced or of being carried out in various
ways. Examples of specific implementations are provided herein for
illustrative purposes only and are not intended to be limiting. In
particular, acts, elements and features discussed in connection
with any one or more examples are not intended to be excluded from
a similar role in any other examples. Accordingly, the foregoing
description and drawings are by way of example only.
[0263] Also, the phraseology and terminology used herein is for the
purpose of description and should not be regarded as limiting. Any
references to examples or elements or acts of the systems and
methods herein referred to in the singular may also embrace
examples including a plurality of these elements, and any
references in plural to any example or element or act herein may
also embrace examples including only a single element. References
in the singular or plural form are not intended to limit the
presently disclosed systems or methods, their components, acts, or
elements. The use herein of "including," "comprising," "having,"
"containing," "involving," and variations thereof is meant to
encompass the items listed thereafter and equivalents thereof as
well as additional items. References to "or" may be construed as
inclusive so that any terms described using "or" may indicate any
of a single, more than one, and all of the described terms.
* * * * *