U.S. patent application number 14/929125 was filed with the patent office on 2016-05-05 for wireless physiological monitoring device and systems.
The applicant listed for this patent is iRhythm Technologies, Inc.. Invention is credited to Mark Day, Frank Garcia, Hung Ho, Nicholas Hughes, Shena Park, Genaro Sepulveda, Yuriko Tamura.
Application Number | 20160120434 14/929125 |
Document ID | / |
Family ID | 54602012 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160120434 |
Kind Code |
A1 |
Park; Shena ; et
al. |
May 5, 2016 |
WIRELESS PHYSIOLOGICAL MONITORING DEVICE AND SYSTEMS
Abstract
The present disclosure relates to a cardiac monitoring system
and methods for using such a system. Preferred embodiments detect
and record cardiac information via a wearable device, then extract
data features from the recorded cardiac information. The extracted
data features may then be analyzed and used in clinical
diagnosis.
Inventors: |
Park; Shena; (San Francisco,
CA) ; Day; Mark; (San Francisco, CA) ; Garcia;
Frank; (Redwood City, CA) ; Ho; Hung; (San
Francisco, CA) ; Hughes; Nicholas; (Orinda, CA)
; Sepulveda; Genaro; (San Francisco, CA) ; Tamura;
Yuriko; (San Mateo, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
iRhythm Technologies, Inc. |
San Francisco |
CA |
US |
|
|
Family ID: |
54602012 |
Appl. No.: |
14/929125 |
Filed: |
October 30, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62073910 |
Oct 31, 2014 |
|
|
|
Current U.S.
Class: |
600/301 ;
600/391 |
Current CPC
Class: |
A61B 5/02438 20130101;
A61B 5/046 20130101; A61B 5/0472 20130101; A61B 7/04 20130101; A61B
5/04087 20130101; G16H 50/20 20180101; A61B 5/0205 20130101; A61B
5/0468 20130101; A61B 5/6833 20130101; A61B 5/6832 20130101; A61B
5/04015 20130101; A61B 5/04325 20130101; A61B 5/7282 20130101; G16H
40/67 20180101; A61B 5/0022 20130101; A61B 2560/0412 20130101; A61B
5/4839 20130101; A61B 5/04014 20130101; A61B 2562/0219 20130101;
A61B 2560/0209 20130101; G16H 50/30 20180101; A61B 5/6843 20130101;
G16H 40/63 20180101; A61B 5/0404 20130101; A61B 5/02416 20130101;
A61B 5/0456 20130101; A61B 2560/0468 20130101; G16H 80/00 20180101;
A61B 5/04012 20130101; A61B 5/0006 20130101 |
International
Class: |
A61B 5/0408 20060101
A61B005/0408; A61B 5/04 20060101 A61B005/04; A61B 5/00 20060101
A61B005/00; A61B 7/04 20060101 A61B007/04; A61B 5/0456 20060101
A61B005/0456; A61B 5/0205 20060101 A61B005/0205 |
Claims
1-4. (canceled)
5. A wearable physiological monitoring device for monitoring
physiological signals in a mammal, the device comprising: a housing
forming a watertight enclosure, the housing integral with two
flexible wings extending from the housing, the flexible wings
configured to adhere to the skin of the mammal; wherein the
flexible wings comprise electrodes configured to measure a
physiological signal; a processor contained within the housing, the
processor configured to continuously record and extract a plurality
of features from the physiological signal; and a transmitter
contained within the housing, the transmitter configured to
transmit the features and a plurality of references to the
locations of the features to a computing device, the computing
device configured to identify a plurality of positions of
identified signals from the extracted features and references.
6. The device of claim 5, wherein the plurality of features are
extracted during an extraction window.
7. The device of claim 5, wherein the features comprise R peak
information.
8. The device of claim 7, wherein the R peak information comprises
R peak locations.
9. The device of claim 5, wherein the identified signals comprise
heart rhythms requiring a clinical intervention.
10. The device of claim 9, wherein clinical intervention comprises
one of a change in dosage regimen, a surgical procedure, and a
surgical implantation.
11. The device of claim 9, wherein the clinical intervention
comprises continuing a therapy.
12. The device of claim 5, wherein the computing device is a
server.
13. The device of claim 5, wherein the positions of the identified
signals are re-transmitted from the computing device to the
processor.
14. The device of claim 13, wherein the processor is configured to
read the positions of the identified signals and access an area of
memory corresponding to the positions of the identified signals to
infer a rhythm segment.
15. The device of claim 14, wherein the transmitter is further
configured to transmit the rhythm segment.
16. The device of claim 15, wherein the transmitter is configured
to transmit the rhythm segment only if the rhythm segment meets a
confidence determination, the confidence determination comprising
exceeding a defined threshold.
17. The device of claim 5, wherein the computing device is
configured to be in communication with a smartphone.
18. The device of claim 5, wherein the computing device is a
smartphone.
19. The device of claim 5, wherein the processor is configured to
collect a secondary physiological signal and the transmitter is
configured to transmit the secondary physiological signal to the
computing device.
20. The device of claim 19, wherein the secondary physiological
signal comprises a motion signal.
21. The device of claim 19, wherein the secondary physiological
signal comprises acoustic noise
22. The device of claim 19, wherein the processor is further
configured to collect a tertiary physiological signal.
23. A wearable physiological monitoring device for monitoring
physiological signals in a mammal, the device comprising: a housing
enclosing a monitoring circuit and electrodes configured to measure
physiological signals; a processor contained within the circuit,
the processor configured to continuously record and extract a
plurality of descriptive features from the physiological signals;
and a transmitter contained within the circuit, the transmitter
configured to transmit the descriptive features and a plurality of
references to the locations of the descriptive features to a
computing device, the computing device configured to identify a
plurality of positions of identified signals from the extracted
features and references; wherein the computing device is configured
to transmit the positions to the transmitter; and, wherein the
transmitter is configured to transmit a section of physiological
signal after receiving the plurality of positions from the
computing device.
24. The device of claim 23, wherein the processor is configured to
collect a secondary physiological signal and the transmitter is
configured to transmit the secondary physiological signal to the
computing device.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/073,910, filed Oct. 31, 2014, entitled WIRELESS
PHYSIOLOGICAL MONITORING. The content of the aforementioned
application is hereby incorporated by reference in its entirety as
if fully set forth herein. The benefit of priority to the foregoing
application is claimed under the appropriate legal basis,
including, without limitation, under 35 U.S.C. .sctn.119(e).
BACKGROUND
[0002] For purposes of this disclosure, certain aspects,
advantages, and novel features of various embodiments are described
herein. It is to be understood that not necessarily all such
advantages may be achieved in accordance with any particular
embodiment. Thus, various embodiments may be or carried out in a
manner that achieves one advantage or group of advantages as taught
herein without necessarily achieving other advantages as may be
taught or suggested herein.
[0003] 1. Field of the Invention
[0004] System for inferring cardiac rhythm information from heart
beat time series information collected by wearable sensors, and
system for selective transmission of electrocardiographic signal
data from a wearable sensor
[0005] 2. Description of the Related Art
[0006] Abnormal heart rhythms, or arrhythmias, may cause various
types of symptoms, such as loss of-consciousness, palpitations,
dizziness, or even death. An arrhythmia that causes such symptoms
is often an indicator of significant underlying heart disease. It
is important to identify when such symptoms are due to an abnormal
heart rhythm, since treatment with various procedures, such as
pacemaker implantation or percutaneous catheter ablation, can
successfully ameliorate these problems and prevent significant
symptoms and death. For example, monitors such as Holter monitors
and similar devices are currently in use to monitor heart
rhythms.
BRIEF SUMMARY OF EMBODIMENTS
[0007] Embodiments described herein are directed to a physiological
monitoring device that may be worn continuously and comfortably by
a human or animal subject for at least one week or more and more
typically two to three weeks or more. In one embodiment, the device
is specifically designed to sense and record cardiac rhythm (for
example, electrocardiogram, ECG) data, although in various
alternative embodiments one or more additional physiological
parameters may be sensed and recorded. Such physiological
monitoring devices may include a number of features to facilitate
and/or enhance the patient experience and to make diagnosis of
cardiac arrhythmias more accurate and timely.
[0008] In some embodiments, an electronic device for monitoring
physiological signals in a mammal comprises: at least two flexible
wings extending laterally from a rigid housing, wherein the
flexible wings comprise a first set of materials which enable the
wings to conform to a surface of the mammal and the rigid housing
comprises a second set of materials; a printed circuit board
assembly housed within the rigid housing, wherein the rigid housing
is configured to prevent deformation of the printed circuit board
in response to movement of the mammal; at least two electrodes
embedded within the flexible wings, the electrodes configured to
provide conformal contact with the surface of the mammal and to
detect the physiological signals of the mammal; at least two
electrode traces embedded within the wings and mechanically
decoupled from the rigid housing, the electrode traces configured
to provide conformal contact with the surface of the mammal and
transmit electrical signals from the electrodes to the printed
circuit board assembly; and, at least one hinge portion connecting
the wings to the rigid housing, the hinge portions configured to
flex freely at the area where it is joined to the rigid
housing.
[0009] In certain embodiments, each wing may comprise an adhesive.
In embodiments, the electrodes can be in the same plane as the
adhesive. In certain embodiments, each wing comprises at least one
rim, wherein the rim is thinner than an adjacent portion of each
wing. The rigid housing may further comprise dimples configured to
allow for airflow between the rigid housing and the surface of the
mammal. In certain embodiments, the rim is configured to prevent
the release of a portion of the wing from the surface of the
mammal. In some embodiments, an electronic device for monitoring
physiological systems may comprise a measuring instrument
configured to detect motion signals in at least one axis. This
measuring instrument may be an accelerometer that can be configured
to detect motion signals in three axes.
[0010] In embodiments, the motion signals can be collected in time
with the physiological signals. In certain embodiments, a motion
artifact is identified when the physiological signals and the
motion signals match. Further embodiments may call for an event
trigger coupled to the printed circuit board assembly. In some
embodiments, the event trigger input is supported by the rigid
housing so as to prevent mechanical stress on the printed circuit
board when the trigger is activated which, in turn, can reduce a
source of artifact in the recorded signal. The event trigger may be
concave and larger than a human finger such that the event trigger
is easily located. In certain embodiments, the electrode traces are
configured to minimize signal distortion during movement of the
mammal. In particular embodiments, gaskets may be used as a means
for sealable attachment to the rigid housing.
[0011] In certain embodiments, a method for monitoring
physiological signals in a mammal may comprise: attaching an
electronic device to the mammal, wherein the device comprises: at
least two electrodes configured to detect physiological signals
from the mammal, at least one measuring instrument configured to
detect secondary signals, and at least two electrode traces
connected to the electrodes and a rigid housing; and, comparing the
physiological signals to the secondary signals to identify an
artifact.
[0012] In certain embodiments, identification of artifacts
comprises a comparison between the frequency spectrum of the
physiological signals and the frequency spectrum of the secondary
signals. In embodiments, the secondary signals comprise motion
signals that may be used to derive the activity and position of the
mammal. In certain embodiments, the secondary signals are collected
in three axes. In some embodiments, a tertiary signal may also be
collected. In certain embodiments, the secondary signals comprise
information about the connection between the electronic device and
the mammal. In some embodiments, the secondary signals may be used
to detect when the mammal is sleeping.
[0013] In some embodiments, a method of removing and replacing
portions of a modular physiological monitoring device may comprise:
applying the device described above to a mammal for a period of
time greater than 7 days and collecting physiological data; using
the device to detect a first set of physiological signals; removing
the device from the surface of the mammal; removing a first
component from the device; and, incorporating the first component
into a second physiological monitoring device, the second
physiological monitoring device configured to detect a second set
of physiological signals.
[0014] In some embodiments, the first component is electrically
connected to other device components without the use of a permanent
connection. In some embodiments, the device may further comprise
spring connections. In certain embodiments, the first component may
be preserved for a second use by a rigid housing to prevent damage.
In particular embodiments, the first component is secured within a
device by a mechanism that is capable of re-securing a second
component once the first component is removed.
[0015] Certain embodiments may concern a system for inferring
cardiac rhythm information from time-series data of heart beat
intervals, as obtained from either consumer wearable or medical
device products. A further aspect concerns improvements to the
system to enable cardiac rhythm information to be inferred in a
more robust and/or timely manner through the use of additional
sources of data. This additional data may include summary
statistics or specific signal features derived from an ECG, user
activity time series data derived from an accelerometer,
information related to user state, or information related to the
day/time of the recording.
[0016] In certain embodiments, a system for selective transmission
of electrocardiographic signal data from a wearable medical sensor,
where QRS refers to the three fiducial points of an ECG recording
at the time of ventricle depolarization, may comprise:
[0017] a. A wearable medical sensor incorporating a QRS detector
that produces a real-time estimate of each R peak location in the
ECG
[0018] b. Transmission of an R-R interval time series together with
an onset time stamp from the sensor to a smartphone or
internet-connected gateway device, according to a predefined
schedule
[0019] c. Transmission of the R-R interval time series and the
onset time stamp from the smartphone or internet-connected gateway
device to a server
[0020] d. Server-side algorithmic inference of the most probable
rhythms and their onset/offset times from the R-R interval time
series data
[0021] e. Filtering the list of inferred heart rhythms according to
specific filter criteria, such that only inferred rhythms matching
the given criteria are retained after filtering
[0022] f. Transmission of the onset/offset time for each rhythm
remaining after filtering, from the server to the smartphone or
internet-connected gateway device
[0023] g. Transmission of the onset/offset time for each rhythm
remaining after filtering, from the smartphone or
internet-connected gateway device to the wearable sensor
[0024] h. Transmission of the section of recorded ECG corresponding
to each onset-offset time pair from the sensor to the smartphone or
internet-connected gateway device
[0025] i. Transmission of the section of recorded ECG corresponding
to each onset-offset time pair from the smartphone or
internet-connected gateway device to the server
[0026] The rhythm filter criteria may be specified by a physician
or other medical professional prior to the use of the wearable
sensor by a patient. In other embodiments, the rhythm filter
criteria are dynamic and can be updated during the use of the
system according to predefined rules. In some embodiments, these
predefined rules may describe an adjustment to the filter criteria
based on previous findings during use of the system. In some
embodiments, the onset and offset time for each inferred rhythm may
be adjusted such that the resulting duration for each rhythm is
less than a given maximum permissible duration. Computed confidence
measures may be an input to the rhythm filter criteria. In some
embodiments, the system comprises inferring cardiac rhythm
information from R-R interval time series data. In certain
embodiments, the cardiac rhythm inference system is implemented as
a cloud service accessible via an API.
[0027] In certain embodiments, the cardiac rhythm inference system
is provided through a software library that can be incorporated
into a standalone application. The R-R interval values may be are
estimated from a photoplethysmography signal.
[0028] In certain embodiments of a method for inferring cardiac
rhythm information, the cardiac rhythm inference system computes a
confidence score for each type of cardiac rhythm, the method
comprising:
[0029] a. Computing the frequency and duration of each cardiac
rhythm type inferred from the collection of R-R interval time
series data for the given user
[0030] b. Estimating a confidence statistic for each rhythm type
based on the inferred frequency and duration of the rhythm across
the collection of R-R interval time series for the given user
[0031] c. Evaluating if the confidence statistic for each inferred
rhythm exceeds a pre-determined threshold value
[0032] d. Providing rhythm information back to the calling software
only for those inferred rhythms for which the confidence statistic
exceeds the threshold value
[0033] In certain embodiments, the cardiac rhythm inference system
accepts additional sources of data, comprising one or more of:
[0034] e. User activity time series data measured by an
accelerometer
[0035] f. Information on the specific day and time of each R-R
interval time series recording
[0036] g. Information on user age, gender, clinical indication for
monitoring, pre-existing medical conditions, medication
information, and medical history
[0037] h. ECG signal features and summary statistics, such as the
mean, median, standard deviation or sum of the ECG signal sample
values within a given time period
[0038] i. A confidence rating provided by the measurement device to
indicate the quality of heart beat estimation, for example, for
each beat or for sequential time periods.
[0039] j. Intra-beat interval measurements
[0040] In embodiments, a system for monitoring cardiac signal data,
comprises:
[0041] a wearable medical sensor, the wearable medical sensor
configured to detect cardiac signals from a mammal and estimate the
R-peak location within the cardiac signal;
[0042] wherein the wearable medical sensor is configured to
transmit an R-R interval time series and a time stamp to an
intermediary device, the intermediary device configured to further
transmit the R-R interval time series and time stamp to a
server;
[0043] wherein the server is configured to infer the most probable
rhythms and their onset/offset times from the R-R interval time
series and time stamp, the server configured to filter the most
probable rhythms according to a first criteria into a filtered data
set;
[0044] wherein the server is configured to transmit the filtered
data set back to the wearable sensor via the intermediary device;
and
[0045] wherein the sensor transmits the full resolution cardiac
signal to the server for a time period surrounding each of the
filtered events.
[0046] In certain embodiments, a system for monitoring cardiac
signal data comprises:
[0047] a server configured to communicate with a wearable sensor,
the wearable sensor configured to detect cardiac signals from a
mammal and estimate the R peak location within the cardiac
signal;
[0048] wherein the wearable sensor is configured to transmit an R-R
interval time series and a time stamp to the server;
[0049] wherein the server is configured to infer the most probable
rhythms and their onset/offset times from the R-R interval time
series and time stamp, the server configured to filter the most
probable rhythms according to a first criteria into a filtered data
set; and
[0050] wherein the server is configured to transmit a summary of
the filtered data.
[0051] In particular embodiments, a server for monitoring cardiac
signal data, comprises:
[0052] a portal configured to communicate with a wearable sensor,
the wearable sensor configured to detect cardiac signals from a
mammal and estimate the R peak location within the cardiac signal,
wherein the wearable sensor is configured to transmit an R-R
interval time series and a time stamp to an intermediary device,
the intermediary device configured to further transmit the R-R
interval time series and time stamp to a server;
[0053] a processor configured to infer the most probable rhythms
and their onset/offset times from the R-R interval time series and
time stamp, the processor configured to filter the most probable
rhythms according to a first criteria into a filtered data set;
and
[0054] wherein the server is configured to transmit a summary of
the filtered data set.
[0055] In embodiments, a non-transitory storage medium having
computer-executable instructions stored thereon, the
computer-executable instructions readable by a computing system
comprising one or more computing devices, wherein the
computer-executable instructions are executable on the computing
system in order to cause the computing system to perform operations
comprises: receiving, by a computing system through a communication
link, physiological sensor data generated by a patient monitoring
device, the physiological sensor data associated with a first
patient; analyzing, by the computing system, the physiological
sensor data to determine whether one or more points in the
physiological data that are likely indicative of one or more
predetermined set of conditions; and after determining that at
least one of the one or more points in the physiological data is
likely indicative of at least one of the one or more predetermined
set of conditions, generating, by the computing system, an
electronic data package for transmission to the patient monitoring
device, the electronic data package including location data
regarding the at least one of the one or more points in the
physiological sensor data that are likely indicative of the at
least one of the one or more predetermined set of conditions.
[0056] In certain embodiments, the physiological sensor data may
comprise a sampling of interval data measured from the recorded
signal data, the sampling of interval data of a data size less than
the recorded signal data.
[0057] In particular embodiments, a system for monitoring
physiological signals in a mammal may comprise: a wearable adhesive
monitor configured to detect and record cardiac rhythm data from a
mammal, the wearable adhesive monitor configured to extract a
feature from the cardiac rhythm data; and wherein the wearable
adhesive monitor is configured to transmit the feature to a
processing device, the processing device configured to analyze the
feature, identify locations of interest, and transmit the locations
of interest back to the wearable adhesive monitor.
[0058] In certain embodiments, a system for assessing physiological
sensor data from a patient monitoring device comprises: a computer
processor and non-transitory computer-readable media combined with
the computer processor configured to provide a program that
includes a set of instructions stored on a first server, the set of
instructions being executable by the computer processor, and
further configured to execute a sensor data inference module of the
program; the sensor data inference module of the program storing
instructions to: receive physiological sensor data generated by a
patient monitoring device, the physiological sensor data associated
with a first patient; analyze the physiological sensor data to
determine whether one or more points in the physiological data that
are likely indicative of one or more predetermined set of
conditions; and after determining that at least one of the one or
more points in the physiological data is likely indicative of at
least one of the one or more predetermined set of conditions,
generating an electronic data package for transmission to the
patient monitoring device, the electronic data package including
location data regarding the at least one of the one or more points
in the physiological sensor data that are likely indicative of the
at least one of the one or more predetermined set of
conditions.
[0059] In certain embodiments, a computerized method may comprise:
accessing computer-executable instructions from at least one
computer-readable storage medium; and executing the
computer-executable instructions, thereby causing computer hardware
comprising at least one computer processor to perform operations
comprising: receiving, by a server computer through a communication
link, physiological sensor data generated by a patient monitoring
device, the physiological sensor data associated with a first
patient; analyzing, by the server computer, the physiological
sensor data to determine whether one or more points in the
physiological data that are likely indicative of one or more
predetermined set of conditions; and after determining that at
least one of the one or more points in the physiological data is
likely indicative of at least one of the one or more predetermined
set of conditions, generating, by the server computer, an
electronic data package for transmission to the patient monitoring
device, the electronic data package including location data
regarding the at least one of the one or more points in the
physiological sensor data that are likely indicative of the at
least one of the one or more predetermined set of conditions.
[0060] These and other aspects and embodiments of the invention are
described in greater detail below, with reference to the drawing
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0061] FIGS. 1A and 1B are perspective and exploded profile views,
respectively, of a physiological monitoring device, according to
one embodiment.
[0062] FIGS. 2A and 2B are top perspective and bottom perspective
views, respectively, of a printed circuit board assembly of the
physiological monitoring device, according to one embodiment.
[0063] FIGS. 3A, 3B, 3C, 3D, and 3E are perspective and exploded
views of a flexible body and gasket of the physiological monitoring
device, according to one embodiment.
[0064] FIG. 4 is an exploded view of a rigid housing of the
physiological monitoring device; according to one embodiment.
[0065] FIGS. 5A and 5B provide a perspective view of a battery
holder of the physiological monitoring device, according to one
embodiment.
[0066] FIGS. 6A and 6B are cross sectional views of the
physiological monitoring device; according to one embodiment.
[0067] FIG. 7 is an exploded view of the physiological monitoring
device including a number of optional items, according to one
embodiment.
[0068] FIGS. 8A and 8B are perspective views of two people wearing
the physiological monitoring device, illustrating how the device
bends to conform to body movement and position, according to one
embodiment.
[0069] FIGS. 9A, 9B, 9C, 9D, 9E, and 9F illustrate various steps
for applying the physiological monitor to a patient's body,
according to one embodiment.
[0070] FIG. 10 illustrates a schematic diagram of an embodiment of
a cardiac rhythm inference service.
[0071] FIG. 11 is a schematic diagram of an embodiment of a system
for extracting and transmitting data features from a physiological
monitor.
[0072] FIG. 12 is a schematic diagram of an embodiment of a system
for extracting and transmitting data features from a physiological
monitor using a transmitting device.
[0073] FIG. 13 is a schematic diagram of an embodiment of a
physiological monitoring system utilizing additional data
channels.
[0074] FIG. 14 is a schematic diagram of an embodiment of a
physiological monitoring system incorporating data filters.
[0075] FIG. 15 is a schematic diagram of an embodiment of a
wearable device system.
[0076] FIG. 16 is a schematic diagram of an embodiment of a
symptomatic transmission system.
[0077] FIG. 17 is a schematic diagram of an embodiment of an
asymptomatic transmission system.
[0078] FIG. 18 is a schematic diagram of an embodiment of a
computer network system.
[0079] FIG. 19 is a schematic diagram of an embodiment of a
programming and distribution module.
DETAILED DESCRIPTION OF EMBODIMENTS
[0080] The following description is directed to a number of various
embodiments. The described embodiments, however, may be implemented
and/or varied in many different ways. For example, the described
embodiments may be implemented in any suitable device, apparatus,
or system to monitor any of a number of physiological parameters.
For example, the following discussion focuses primarily on
long-term, patch-based cardiac rhythm monitoring devices. In one
alternative embodiment, a physiological monitoring device may be
used, for example, for pulse oximetry and diagnosis of obstructive
sleep apnea. The method of using a physiological monitoring device
may also vary. In some cases, a device may be worn for one week or
less, while in other cases, a device may be worn for at least seven
days and/or for more than seven days, for example between fourteen
days and twenty-one days or even longer. Many other alternative
embodiments and applications of the described technology are
possible. Thus, the following description is provided for exemplary
purposes only. Throughout the specification, reference may be made
to the term "conformal." It will be understood by one of skill in
the art that the term "conformal" as used herein refers to a
relationship between surfaces or structures where a first surface
or structure adapts to the contours of a second surface or
structure.
[0081] Since abnormal heart rhythms or arrhythmias can often be due
to other, less serious causes, a key challenge is to determine when
any of these symptoms are due to an arrhythmia. Oftentimes,
arrhythmias occur infrequently and/or episodically, making rapid
and reliable diagnosis difficult. As mentioned above, currently,
cardiac rhythm monitoring is primarily accomplished through the use
of devices, such as Holter monitors, that use short-duration (less
than 1 day) electrodes affixed to the chest. Wires connect the
electrodes to a recording device, usually worn on a belt. The
electrodes need daily changing and the wires are cumbersome. The
devices also have limited memory and recording time. Wearing the
device interferes with patient movement and often precludes
performing certain activities while being monitored, such as
bathing. Further, Holter monitors are capital equipment with
limited availability, a situation that often leads to supply
constraints and corresponding testing delays. These limitations
severely hinder the diagnostic usefulness of the device, the
compliance of patients using the device, and the likelihood of
capturing all important information. Lack of compliance and the
shortcomings of the devices often lead to the need for additional
devices, follow-on monitoring, or other tests to make a correct
diagnosis.
[0082] Current methods to correlate symptoms with the occurrence of
arrhythmias, including the use of cardiac rhythm monitoring
devices, such as Holter monitors and cardiac event recorders, are
often not sufficient to allow an accurate diagnosis to be made. In
fact, Holter monitors have been shown to not lead to a diagnosis up
to 90% of the time ("Assessment of the Diagnostic Value of 24-Hour
Ambulatory Electrocardiographic Monitoring", by DE Ward et al.
Biotelemetry Patient Monitoring, vol. 7, published in 1980).
[0083] Additionally, the medical treatment process to actually
obtain a cardiac rhythm monitoring device and initiate monitoring
is typically very complicated. There are usually numerous steps
involved in ordering, tracking, monitoring, retrieving, and
analyzing the data from such a monitoring device. In most cases,
cardiac monitoring devices used today are ordered by a cardiologist
or a cardiac electrophysiologist (EP), rather than the patient's
primary care physician (PCP). This is of significance since the PCP
is often the first physician to see the patient and determine that
the patient's symptoms could be due to an arrhythmia. After the
patient sees the PCP, the PCP will make an appointment for the
patient to see a cardiologist or an EP. This appointment is usually
several weeks from the initial visit with the PCP, which in itself
leads to a delay in making a potential diagnosis as well as
increases the likelihood that an arrhythmia episode will occur and
go undiagnosed. When the patient finally sees the cardiologist or
EP, a cardiac rhythm monitoring device will usually be ordered. The
monitoring period can last 24 to 48 hours (Holter monitor) or up to
a month (cardiac event monitor or mobile telemetry device). Once
the monitoring has been completed, the patient typically must
return the device to the clinic, which itself can be an
inconvenience. After the data has been processed by the monitoring
company or by a technician on-site at a hospital or office, a
report will finally be sent to the cardiologist or EP for analysis.
This complex process results in fewer patients receiving cardiac
rhythm monitoring than would ideally receive it.
[0084] To address some of these issues with cardiac monitoring, the
assignee of the present application developed various embodiments
of a small, long-term, wearable, physiological monitoring device.
One embodiment of the device is the Zio.RTM. Patch. Various
embodiments are also described, for example, in U.S. Pat. Nos.
8,150,502, 8,160,682 8,244,335, 8,560,046, and 8,538,503, the full
disclosures of which are hereby incorporated herein by reference.
Generally, the physiological patch-based monitors described in the
above references fit comfortably on a patient's chest and are
designed to be worn for at least one week and typically two to
three weeks. The monitors detect and record cardiac rhythm signal
data continuously while the device is worn, and this cardiac rhythm
data is then available for processing and analysis.
[0085] These smaller, long-term, patch-based physiological
monitoring devices provide many advantages over prior art devices.
At the same time, further improvements are desired. One of the most
meaningful areas for improvement is to offer more timely notice of
critical arrhythmias to managing clinicians. The hallmark of these
initial embodiments was that--for reasons of performance,
compliance and cost--the device only recorded information during
the extended wear period, with analysis and reporting occurring
after the recording completed. Thus, a desirable improvement would
be to add the capability of either real-time or timely analysis of
the collected rhythm information. While diagnostic monitors with
such timely reporting capabilities currently exist, they require
one or more electrical components of the system to be either
regularly recharged or replaced. These actions are associated with
reduced patient compliance and, in turn, reduced diagnostic yield.
As such, a key area of improvement is to develop a physiologic
monitor that can combine long-term recording with timely reporting
without requiring battery recharging or replacement.
[0086] Patient compliance and device adhesion performance are two
factors that govern the duration of the ECG record and consequently
the diagnostic yield. Compliance can be increased by improving the
patient's wear experience, which is affected by wear comfort,
device appearance, and the extent to which the device impedes the
normal activities of daily living. Given that longer ECG records
provide greater diagnostic yield and hence value, improvements to
device adhesion and patient compliance are desirable.
[0087] Signal quality is important throughout the duration of wear,
but may be more important where the patient marks the record,
indicating an area of symptomatic clinical significance. Marking
the record is most easily enabled through a trigger located on the
external surface of the device. However, since the trigger may be
part of a skin-contacting platform with integrated electrodes, the
patient can introduce significant motion artifacts when feeling for
the trigger. A desirable device improvement would be a symptom
trigger that can be activated with minimal addition of motion
artifact.
[0088] Further, it is desirable for the device to be simple and
cost effective to manufacture, enabling scalability at
manufacturing as well as higher quality due to repeatability in
process. Simplicity of manufacture can also lead to ease of
disassembly, which enables the efficient recovery of the printed
circuit board for quality-controlled reuse in another device.
Efficient reuse of this expensive component can be important for
decreasing the cost of the diagnostic monitor.
[0089] There remain clinical scenarios where still longer-duration
and lower-cost solutions may be a valuable addition to a portfolio
of cardiac ambulatory monitoring options. Inspiration for a
potential solution to these needs can be found in the continuous
heart rate sensing functionality that is increasingly being
incorporated in a variety of consumer health and fitness products,
including smart watches and wearable fitness bands. Although
continuous heart rate data can be used to provide the user with
information about their general fitness levels, it is more both
more challenging and valuable to use this data to provide
meaningful information related to their health and wellness. For
example, the ability to detect potential arrhythmias from
continuous heart rate data would enable consumer devices
incorporating heart rate sensing functionality to serve as
potential screening tools for the early detection of cardiac
abnormalities. Such an approach could be clinically valuable in
providing a long-term, cost-effective screening method for at-risk
populations, for example, heart failure patients at risk for Atrial
Fibrillation. Alternatively, this monitoring approach could be
helpful in the long-term titration of therapeutic drug dosages to
ensure efficaciousness while reducing side effects, for example, in
the management of Paroxysmal Atrial Fibrillation. Beyond cardiac
arrhythmia detection, the appropriate analysis of heart rate
information could also yield insight into sleep and stress
applications.
[0090] Long-term ambulatory monitoring with a physiologic device,
such as an adhesive patch, has a number of clinical applications,
particularly when timely information about the occurrence and
duration of observed arrhythmias can be provided during the
monitoring period. In terms of prevalence, particularly as driven
by an aging population, efficiently detecting Atrial Fibrillation
(AF) remains the most significant monitoring need. This need is not
just evident for patients presenting with symptoms, but also--given
the increased risk of stroke associated with this arrhythmia--for
broader, population-based monitoring of asymptomatic AF in
individuals at risk due to one or more factors of advanced age, the
presence of chronic illnesses like Heart Disease, or even the
occurrence of surgical procedures. For the latter group, both
perioperative and post-procedure monitoring can be clinically
valuable, and not just for procedures targeted at arrhythmia
prevention (for example, the MAZE ablation procedure, or hybrid
endo and epicardial procedures, both for treatment of AF), but also
for general surgeries involving anesthesia. For some applications,
the goal of ambulatory monitoring for Atrial Fibrillation will
sometimes be focused on the simple binary question of yes or
no--did AF occur in a given time period. For example, monitoring a
patient following an ablation procedure will typically seek to
confirm success, typically defined as the complete lack of AF
occurrence. Likewise, monitoring a patient post-stroke will be
primarily concerned with evaluating the presence of Atrial
Fibrillation.
[0091] However, even in those scenarios, if AF occurs, it may be
clinically meaningful to evaluate additional aspects to better
characterize the occurrence, such as daily burden (% of time in AF
each day), and duration of episodes (expressed, for example, as a
histogram of episode duration, or as the percentage of episodes
that extend beyond a specified limit, say six minutes), both either
in absolute terms or in comparison to prior benchmarks (for
example, from a baseline, pre-procedure monitoring result). Indeed,
measuring daily AF burden, evaluating AF episode duration, and
reviewing AF occurrence during sleep and waking periods, and
evaluating the presence of AF in response to the degree of a
patient's physical movement can be important in a variety of
clinical scenarios, including evaluating the effectiveness of
drug-based treatment for this arrhythmia.
[0092] Making this information available in a timely manner during
the monitoring period could allow the managing physician to
iteratively titrate treatment, for example, by adjusting the dosage
and frequency of a novel oral anticoagulant drug (NOAC) until
management was optimized. A further example of this management
paradigm is for the patient to be notified of asymptomatic
AF--either directly by the device through audible or
vibration-based alert, through notification from an application
connected to the device, or via phone, email or text-message
communication from the managing clinician--for the timely
application of a "pill in the pocket" for AF management.
[0093] The theme of timely management and/or intervention is
certainly evident in situations where clinically significant
arrhythmias are observed, for example, asymptomatic second-degree
and complete Heart Block, extended pauses, high-rate
supraventricular tachycardias, prolonged ventricular tachycaridas,
and ventricular fibrillation. For example, the clinical scenario
where an extended pause or complete heart block causes Syncope is a
particularly significant case where the availability of a timely
and dependable monitoring method could reduce or even eliminate the
need for in-hospital monitoring of at-risk patients. The theme can
also extend to more subtle changes in morphology, for example, QT
prolongation in response to medications, which has been shown to
have significant cardiac safety implications. Timely awareness of
such prolongation could lead, for example, to early termination of
clinical studies evaluating drug safety and effectiveness or,
alternatively, to adjusting the dosage or frequency as a means to
eliminate observed prolongation.
Physiological Monitoring Devices
[0094] Referring to FIGS. 1A and 1B, perspective and exploded
profile views of one embodiment of a physiological monitoring
device 100 are provided. As seen in FIG. 1A, physiological
monitoring device 100 may include a flexible body 110 coupled with
a watertight, rigid housing 115. Flexible body 110 (which may be
referred to as "flexible substrate" or "flexible construct")
typically includes two wings 130, 131, which extend laterally from
rigid housing 115, and two flexible electrode traces 311, 312, each
of which is embedded in one of wings 130, 131. Each electrode trace
311, 312 is coupled, on the bottom surface of flexible body 110,
with a flexible electrode (not visible in FIG. 1A). The electrodes
are configured to sense heart rhythm signals from a patient to
which monitoring device 100 is attached. Electrode traces 311, 312
then transmit those signals to electronics (not visible in FIG. 1A)
housed in rigid housing 115. Rigid housing 115 also typically
contains a power source, such as one or more batteries.
[0095] The combination of a highly flexible body 110, including
flexible electrodes and electrode traces 311, 312, with a very
rigid housing 115 may provide a number of advantages. A key
advantage is high fidelity signal capture. The highly conformal and
flexible wings 130, 131, electrodes and traces 311, 312 limit the
transmission of external energy to the electrode-skin interface. If
motion is imparted to the rigid housing 115, for example, the
system of conformal adhesion to the skin limits the extent to which
that motion affects the monitored signal. Flexible electrode traces
311, 312 generally may help provide conformal contact with the
subject's skin and may help prevent electrodes 350 (electrodes 350
are not visible in FIG. 1, but are visible in FIG. 6A described
below) from peeling or lifting off of the skin, thereby providing
strong motion artifact rejection and better signal quality by
minimizing transfer of stress to electrodes 350. Furthermore,
flexible body 110 includes a configuration and various features
that facilitate comfortable wearing of device 100 by a patient for
fourteen (14) days or more without removal. Rigid housing 115,
which typically does not adhere to the patient in the embodiments
described herein, includes features that lend to the comfort of
device 100. Hinge portions 132 are relatively thin, even more
flexible portions of flexible body 110. They allow flexible body
110 to flex freely at the area where it is joined to rigid housing
115. This flexibility enhances comfort, since when the patient
moves, housing 115 can freely lift off of the patient's skin.
Electrode traces 311, 312 are also very thin and flexible, to allow
for patient movement without signal distortion.
[0096] Referring now to FIG. 1B, a partially exploded view of
physiological monitoring device 100 illustrates component parts
that make up, and that are contained within, rigid housing 115 in
greater detail. In this embodiment, rigid housing 115 includes an
upper housing member 140, which detachably couples with a lower
housing member 145. Sandwiched between upper housing member 140 and
lower housing member 145 are an upper gasket 370, and a lower
gasket 360 (not visible on FIG. 1B but just below upper gasket
370). Gaskets 370, 360 help make rigid housing member 115
watertight when assembled. A number of components of monitoring
device 100 may be housed between upper housing member 140 and lower
housing member 145. For example, in one embodiment, housing 115 may
contain a portion of flexible body 110, a printed circuit board
assembly (PCBA) 120, a battery holder 150, and two batteries 160.
Printed circuit board assembly 120 is positioned within housing 115
to contact electrode traces 311, 312 and batteries 160. In various
embodiments, one or more additional components may be contained
within or attached to rigid housing 115. Some of these optional
components are described further below, in reference to additional
drawing figures.
[0097] Battery holder 150, according to various alternative
embodiments, may hold two batteries (as in the illustrated
embodiment), one battery, or more than two batteries. In other
alternative embodiments, other power sources may be used. In the
embodiment shown, battery holder 150 includes multiple retain tabs
153 for holding batteries 160 in holder 150. Additionally, battery
holder 150 includes multiple feet 152 to establish correct spacing
of batteries 160 from the surface of PCBA 120 and ensure proper
contact with spring fingers 235 and 236. Spring fingers 235 and 236
are used in this embodiment rather than soldering batteries 160 to
PCBA 120. Although soldering may be used in alternative
embodiments, one advantage of spring fingers 235 and 236 is that
they allow batteries 160 to be removed from PCBA 120 and holder 150
without damaging either of those components, thus allowing for
multiple reuses of both. Eliminating solder connections also
simplifies and speeds up assembly and disassembly of monitoring
device 100.
[0098] In some embodiments, upper housing member 140 may act as a
patient event trigger. When a patient is wearing physiological
monitoring device 100 for cardiac rhythm monitoring, it is
typically advantageous for the patient to be able to register with
device 100 (for example, log into the device's memory) any cardiac
events perceived by the patient. If the patient feels what he/she
believes to be an episode of heart arrhythmia, for example, the
patient may somehow trigger device 100 and thus provide a record of
the perceived event. In some embodiments, trigger of perceived
events by the patient may initiate transmission of data associated
with the triggered event. In some embodiments, trigger of perceived
events may simply mark a continuous record with the location of the
triggered event. In some embodiments, both transmission of
associated data as well as marking of the continuous record may
occur. At some later time, the patient's recorded symptom during
the perceived event could be compared with the patient's actual
heart rhythm, recorded by device 100, and this may help determine
whether the patient's perceived events correlate with actual
cardiac events. One problem with patient event triggers in
currently available wearable cardiac rhythm monitoring devices,
however, is that a small trigger may be hard to find and/or
activate, especially since the monitoring device is typically worn
under clothing. Additionally, pressing a trigger button may affect
the electronics and/or the electrodes on the device in such a way
that the recorded heart rhythm signal at that moment is altered
simply by the motion caused to the device by the patient
triggering. For example, pressing a trigger may jar one or both of
the electrodes in such a way that the recorded heart rhythm signal
at that moment appears like an arrhythmia, even if no actual
arrhythmia event occurred. Additionally, there is a chance that the
trigger may be inadvertently activated, for instance while sleeping
or laying on the monitoring device.
[0099] In the embodiment shown in FIGS. 1A and 1B, however, rigid
housing 115 is sufficiently rigid, and flexible body 110 is
sufficiently flexible, that motion applied to housing 115 by a
patient may rarely or ever cause an aberrant signal to be sensed by
the electrodes. In this embodiment, the central portion of upper
housing member 140 is slightly concave and, when pressed by a
patient who is wearing device 100, this central portion depresses
slightly to trigger a trigger input on PCBA 120. Because the entire
upper surface of rigid housing 115 acts as the patient event
trigger, combined with the fact that it is slightly concave, it
will generally be quite easy for a patient to find and push down
the trigger, even under clothing. Additionally, the concave nature
of the button allows it to be recessed which protects it from
inadvertent activations. Thus, the present embodiment may alleviate
some of the problems encountered with patient event triggers on
currently available heart rhythm monitors. These and other aspects
of the features shown in FIGS. 1A and 1B will be described in
further detail below.
[0100] Referring now to the embodiments in FIGS. 2A and 2B, printed
circuit board assembly 120 (or PCBA) may include a top surface 220,
a bottom surface 230, a patient trigger input 210 and spring
contacts 235, 236, and 237. Printed circuit board assembly 120 may
be used to mechanically support and electrically connect electronic
components using conductive pathways, tracks or electrode traces
311, 312. Furthermore, because of the sensitive nature of PCBA 120
and the requirement to mechanically interface with rigid body 115,
it is beneficial to have PCBA 120 be substantially rigid enough to
prevent unwanted deflections which may introduce noise or artifact
into the ECG signal. This is especially possible during patient
trigger activations when a force is transmitted through rigid body
115 and into PCBA 120. One way to ensure rigidity of the PCBA is in
some embodiments, to ensure that the thickness of the PCBA is
relatively above a certain value. For example, a thickness of at
least about 0.08 cm is desirable and, more preferably, a thickness
of at least about 0.17 cm is desirable. In this application, PCBA
120 may also be referred to as, or substituted with, a printed
circuit board (PCB), printed wiring board (PWB), etched wiring
board, or printed circuit assembly (PCA). In some embodiments, a
wire wrap or point-to-point construction may be used in addition
to, or in place of, PCBA 120. PCBA 120 may include analog circuits
and digital circuits.
[0101] Patient trigger input 210 may be configured to relay a
signal from a patient trigger, such as upper housing member 140
described above, to PCBA 120. For example, patient trigger input
210 may be a PCB switch or button that is responsive to pressure
from the patient trigger (for example, the upper surface of upper
housing portion 140). In various embodiments, patient trigger input
210 may be a surface mounted switch, a tactile switch, an LED
illuminated tactile switch, or the like. In some embodiments,
patient trigger input 210 may also activate an indicator, such as
an LED. Certain embodiments may involve a remotely located trigger
such as on a separate device or as a smart phone app.
[0102] One important challenge in collecting heart rhythm signals
from a human or animal subject with a small, two-electrode
physiological monitoring device such as device 100 described
herein, is that having only two electrodes can sometimes provide a
limited perspective when trying to discriminate between artifact
and clinically significant signals. For example, when a left-handed
patient brushes her teeth while wearing a small, two-electrode
physiological monitoring device on her left chest, the tooth
brushing may often introduce motion artifact that causes a recorded
signal to appear very similar to Ventricular Tachycardia, a serious
heart arrhythmia. Adding additional leads (and, hence, vectors) is
the traditional approach toward mitigating this concern, but this
is typically done by adding extra wires adhered to the patient's
chest in various locations, such as with a Holter monitor. This
approach is not consistent with a small, wearable, long term
monitor such as physiological monitoring device 100.
[0103] An alternate approach to the problem described above is to
provide one or more additional data channels to aid signal
discrimination. In some embodiments, for example, device 100 may
include a data channel for detecting patch motion. In certain
embodiments, an accelerometer or other suitable device may provide
patch motion by simply analyzing the change in magnitude of a
single axis measurement, or alternatively of the combination of all
three axes. The accelerometer may record device motion at a
sufficient sampling rate to allow algorithmic comparison of its
frequency spectrum with that of the recorded ECG signal. If there
is a match between the motion and recorded signal, it is clear that
the device recording in that time period is not from a clinical
(for example, cardiac) source, and thus that portion of the signal
can be confidently marked as artifact. This technique may be
particularly useful in the tooth brushing motion example
aforementioned, where the rapid frequency of motion as well as the
high amplitude artifact is similar to the heart rate and
morphology, respectively, of a potentially life-threatening
arrhythmia like Ventricular Tachycardia. Other suitable devices
described herein this section and elsewhere in the specification
may also be utilized to provide motion information.
[0104] In some embodiments, using the magnitude of all three axes
for such an analysis would smooth out any sudden changes in values
due to a shift in position rather than a change in activity. In
other embodiments, there may be some advantage in using a specific
axis of measurement such as along the longitudinal axis of the body
to focus on a specific type of artifact introduced by upward and
downward movements associated with walking or running. In a similar
vein, the use of a gyroscope in conjunction with the accelerometer
may provide further resolution as to the nature of the motion
experienced. While whole body movements may be sufficiently
analyzed with an accelerometer on its own, specific motion of
interest such as rotational motion due to arm movement is
sufficiently complex that an accelerometer alone might not be able
to distinguish.
[0105] In addition to detecting motion artifact, an accelerometer
tuned to the dynamic range of human physical activities may provide
activity levels of the patient during the recording, which can also
enhance accuracy of algorithmic true arrhythmia detection. Given
the single-lead limitation of device 100, arrhythmias that require
observation of less prominent waves (for example P-wave) in
addition to rate changes such as Supraventricular Tachycardia pose
challenges to both computerized algorithms as well as the trained
human eye. This particular arrhythmia is also characterized by the
sudden nature of its onset, which may be more confidently
discriminated from a non-pathological Sinus Tachycardia if a sudden
surge in the patient's activity level is detected at the same time
as the increase in heart rate. Broadly speaking, the provision of
activity information to clinical professionals may help them
discriminate between exercise-induced arrhythmia versus not. As
with motion artifact detection, a single-axis accelerometer
measurement optimized to a particular orientation may aid in more
specifically determining the activity type such as walking or
running. This additional information may help explain symptoms more
specifically and thereby affect the subsequent course of
therapeutic action.
[0106] In certain embodiments, an accelerometer with 3 axes may
confer advantages beyond what magnitude of motions can provide.
When the subject is not rapidly moving, 3-dimensional accelerometer
readings may approximate the tilt of PCBA 120, and therefore body
orientation relative to its original orientation. The original body
orientation can be assumed to be in either an upright or supine
position which is required for appropriate positioning and
application of the device to the body. This information may aid in
ruling out certain cardiac conditions that manifest as beat-to-beat
morphology changes, such as cardiac alternans where periodic
amplitude changes are observed, often in heart failure cases.
Similar beat-to-beat morphology changes are observable in healthy
subjects upon shift in body position due to the shift in heart
position relative to the electrode vector, for example from an
upright to a slouching position. By design, the single-channel
device 100 does not have an alternate ECG channel to easily rule
out potential pathological shifts in morphology, however,
correlation with shifts in body orientation will help explain these
normal changes and avoid unnecessary treatment due to false
diagnosis.
[0107] In other embodiments, the accelerometer may also be used as
a sleep indicator, based on body orientation and movement. When
presenting clinical events (for example, pauses), it is
diagnostically helpful to be able to present information in a
manner that clearly separates events that occurred during sleep
from those during waking hours. In fact, certain algorithms such as
for ECG-derived respiratory rate only make sense to run when the
patient is in a relatively motionless state and therefore subtle
signal modulation introduced by chest movement due to breathing is
observable. Respiratory rate information is useful as one channel
of information necessary to detect sleep apnea in certain patient
populations.
[0108] In certain embodiments, the accelerometer may also be used
to detect free-falls, such as fainting. With an accelerometer,
device 100 may be able to mark fainting (syncope) and other
free-fall events without relying on patient trigger. In some
embodiments, such free-fall event triggers may initiate
transmission of associated data. In order to allow timely detection
of such critical events, yet considering the battery and memory
limitations of a small, wearable device such as device 100,
acquisition of accelerometer readings may be done in bursts, where
only interesting information such as a potential free fall is
written to memory at a high sampling rate. An expansion of this
event-trigger concept is to use specific tapping motions on device
100 as a patient trigger instead of or in conjunction with the
button previously described. The use and detection of multiple
types of tapping sequences may provide better resolution and
accuracy into what exactly the patient was feeling, instead of
relying on the patient to manually record their symptom and
duration in a trigger log after the fact. An example of such added
resolution is to indicate the severity of the symptom by the number
of sequential taps.
[0109] Alternatively, in other embodiments, optical sensors may be
used to distinguish between device motion and patient body motion.
Further, in additional embodiments, the device may not require a
button or trigger. In still more embodiments, suitable devices
described herein this section or elsewhere in the specification may
also be used.
[0110] Another optional data channel that may be added to
physiological monitoring device 100 is a channel for detecting flex
and/or bend of device 100. In various embodiments, for example,
device 100 may include a strain gauge, piezoelectric sensor or
optical sensor to detect motion artifact in device 100 itself and
thus help to distinguish between motion artifact and cardiac rhythm
data. Yet another optional data channel for device 100 may be a
channel for detecting heart rate. For example, a pulse oximeter,
microphone or stethoscope may provide heart rate information.
Redundant heart rate data may facilitate discrimination of ECG
signals from artifact. This is particularly useful in cases where
arrhythmia such as Supraventricular Tachycardia is interrupted by
artifact, and decisions must be made whether the episode was
actually multiple shorter episodes or one sustained episode.
Another data channel may be included for detecting ambient
electrical noise. For example, device 100 may include an antenna
for picking up electromagnetic interference. Detection of
electromagnetic interference may facilitate discrimination of
electrical noise from real ECG signals. Any of the above-described
data channels may be stored to support future noise discrimination
or applied for immediate determination of clinical validity in
real-time.
[0111] With reference now to the embodiments of FIGS. 3A and 3B,
flexible body 110 is shown in greater detail. As illustrated in
FIG. 3A, flexible body 110 may include wings 130, 131, a thin
border 133 (or "rim" or "edge") around at least part of each wing
130, 131, electrode traces 311, 312, and a hinge portion 132 (or
"shoulder") at or near a junction of each wing 130, 131 with rigid
housing 115. Also shown in FIG. 3A is upper gasket 370, which is
not considered part of flexible body 110 for this description, but
which facilitates attachment of flexible body 110 to rigid housing
115.
[0112] Hinge portions 132 are relatively thin, even more flexible
portions of flexible body 110. They allow flexible body 110 to flex
freely at the area where it is joined to rigid housing 115. This
flexibility enhances comfort, since when the patient moves, housing
115 can freely lift off of the patient's skin. Electrode traces
311, 312 are also very thin and flexible, to allow for patient
movement without signal distortion. Borders 133 are portions of
flexible body 110 that is thinner than immediately adjacent
portions and that provide for a smooth transition from flexible
body 110 to a patient's skin, thus preventing edge-lift and
penetration of dirt or debris below flexible body 110.
[0113] As shown in greater detail in FIG. 3B, flexible body 110 may
include multiple layers. As mentioned previously, in some
embodiments, upper gasket 370 and lower gasket 360 are not
considered part of flexible body 110 for the purposes of this
description but are shown for completeness of description. This
distinction is for ease of description only, however, and should
not be interpreted to limit the scope of the described embodiments.
Flexible body 110 may include a top substrate layer 300, a bottom
substrate layer 330, an adhesive layer 340, and flexible electrodes
350. Top and bottom substrate layers 300, 330 may be made of any
suitable, flexible material, such as one or more flexible polymers.
Suitable flexible polymers can include, but are not limited to,
polyurethane, polyethylene, polyester, polypropylene, nylon, teflon
and carbon impregnated vinyl. The material of substrate layers 300,
330 may be selected based on desired characteristics. For example,
the material of substrate layers 300, 330 may be selected for
flexibility, resilience, durability, breathability, moisture
transpiration, adhesion and/or the like. In one embodiment, for
example, top substrate layer 300 may be made of polyurethane, and
bottom substrate layer 330 may be made of polyethylene or
alternatively polyester. In other embodiments, substrate layers
300, 330 may be made of the same material. In yet another
embodiment, substrate layer 330 may contain a plurality of
perforations in the area over adhesive layer 340 to provide for
even more breathability and moisture transpiration. In various
embodiments, physiological monitoring device 100 may be worn
continuously by a patient for as many as 14-21 days or more,
without removal during the time of wear and with device 100 being
worn during showering, exercising and the like. Thus, the
material(s) used and the thickness and configuration of substrate
layers 300, 330 affect the function of physiological monitoring
device 100. In some embodiments, the material of substrate layers
300, 330 acts as an electric static discharge (ESD) barrier to
prevent arcing.
[0114] Typically, top and bottom substrate layers 300, 330 are
attached to one another via adhesive placed on one or both layers
300, 330. For example, the adhesive or bonding substance between
substrate layers 300, 330 may be an acrylic-based, rubber-based, or
silicone-based adhesive. In other alternative embodiments, flexible
body 110 may include more than two layers of flexible material.
[0115] In addition to the choice of material(s), the
dimensions--thickness, length and width--of substrate layers 300,
330 may be selected based on desired characteristics of flexible
body 110. For example, in various embodiments, the thickness of
substrate layers 300, 330 may be selected to give flexible body 110
an overall thickness of between about 0.1 mm to about 1.0 mm.
According to various embodiments, flexible body 110 may also have a
length of between about 7 cm and 15 cm and a width of about 3 cm
and about 6 cm. Generally, flexible body 110 will have a length
sufficient to provide a necessary amount of separation between
electrodes 350. For example, in one embodiment a distance from the
center of one electrode 350 to the center of the other electrode
350 should be at least about 6.0 cm and more preferably at least
about 8.5 cm. This separation distance may vary, depending on the
application. In some embodiments, substrate layers 300, 330 may all
have the same thickness. Alternatively, the two substrate layers
300, 330 may have different thicknesses.
[0116] As mentioned above, hinge portions 132 allow the rigid body
115 to lift away from the patient while flexible body 110 remains
adhered to the skin. The functionality of hinge portions 132 is
critical in allowing the device to remain adhered to the patient
throughout various activities that may stretch and compress the
skin. Furthermore, hinge portions 132 allow for significantly
improved comfort while wearing the device. Generally, hinge
portions 132 will be sufficiently wide enough to provide adequate
lift of rigid body 115 without creating too large of a peel force
on flexible body 110. For example, in various embodiments, the
width of hinge portion 132 should be at least about 0.25 cm and
more preferably at least about 0.75 cm.
[0117] Additionally, the shape or footprint of flexible body 110
may be selected based on desired characteristics. As seen in FIG.
3A, wings 130, 131 and borders 133 may have rounded edges that give
flexible body 110 an overall "peanut" shape. However, wings 130,
131 can be formed in any number of different shapes such as
rectangles, ovals, loops, or strips. In the embodiment shown in
FIGS. 3A and 3B, the footprint top substrate layer 300 is larger
than the footprint of bottom substrate layer 330, with the
extension of top substrate layer 300 forming borders 133. Thus,
borders 133 are made of the same polyurethane material that top
layer 300 is made of. Borders 133 are thinner than an adjacent
portion of each wing 130, 131, since they includes only top layer
300. The thinner, highly compliant rim 133 will likely enhance
adherence of physiologic monitoring device 100 to a patient, as it
provides a transition from an adjacent, slightly thicker portion of
wings 130, 131 to the patient's skin and thus helps prevent the
edge of device 110 from peeling up off the skin. Border 133 may
also help prevent the collection of dirt and other debris under
flexible body 110, which may help promote adherence to the skin and
also enhance the aesthetics of device 110. In alternative
embodiments, the footprint of substrate layers 300, 330 may be the
same, thus eliminating borders 133.
[0118] While the illustrated embodiments of FIGS. 1A-3B include
only two wings 130, 131, which extend from rigid housing 115 in
approximately opposite directions (for example, at a 180-degree
angle relative to each other), other configurations are possible in
alternative embodiments. For example, in some embodiments, wings
130, 131 may be arranged in an asymmetrical orientation relative to
one another and/or one or more additional wings may be included. As
long as sufficient electrode spacing is provided to permit
physiological signal monitoring, and as long as wings 130, 131 are
configured to provide extended attachment to the skin, any suitable
configuration and number of wings 130, 131 and electrode traces
311, 312 may be used. The embodiments described above have proven
to be advantageous for adherence, patient comfort and accuracy of
collected heart rhythm data, but in alternative embodiments it may
be possible to implement alternative configurations.
[0119] Adhesive layer 340 is an adhesive that is applied to two
portions of the bottom surface of bottom substrate layer 330, each
portion corresponding to one of wings 130, 131. Adhesive layer 340
thus does not extend along the portion of bottom substrate layer
330 upon which rigid housing 115 is mounted. Adhesive layer 340 may
be made of any suitable adhesive, although certain adhesives have
been found to be advantageous for providing long term adhesion to
patient skin with relative comfort and lack of skin irritation. For
example, in one embodiment, adhesive layer 340 is a hydrocolloid
adhesive. In another embodiment, the adhesive layer 340 is
comprised of a hydrocolloid adhesive that contains
naturally-derived or synthetic absorbent materials which take up
moisture from the skin during perspiration.
[0120] With reference now to FIG. 3B, each of the two portions of
adhesive layer 340 includes a hole, into which one of electrodes
350 fits. Electrodes 350 are made of flexible material to further
provide for overall conformability of flexible body 110. In one
embodiment, for example, flexible electrodes 350 may be made of a
hydrogel 350. Electrodes 350 generally provide conformal,
non-irritating contact with the skin to provide enhanced electrical
connection with the skin and reduce motion artifact. In some
embodiments, hydrogel electrodes 350 may be punched into adhesive
layer 340, thus forming the holes and filling them with hydrogel
electrodes 350. In one alternative embodiment, electrodes 350 and
adhesive 340 may be replaced with an adhesive layer made of a
conductive material, such that the entire adhesive layer on the
underside of each wing 130, 131 acts as an electrode. Such an
adhesive layer may include a hybrid adhesive/conductive substance
or adhesive substance mixed with conductive elements or particles.
For example, in one embodiment, such an adhesive layer may be a
hybrid of a hydrogel and a hydrocolloid adhesive. Rigid housing 115
of FIG. 1A also protects the electronics and power source contained
in housing 120, enhances the ability of a patient to provide an
input related to a perceived cardiac event, and allows for simple
manufacturing and reusability of at least some of the contents of
housing 115. These and other features of physiological monitoring
device 100 are described in greater detail below.
[0121] As discussed above, in some embodiments, adhesive layer 340
may cover a portion of the underside of lower substrate layer 330,
such that at least a portion of the bottom side of flexible body
110 does not include adhesive layer 340. As seen in FIG. 3A, hinges
132 may be formed in the flexible body 110 as portions of each wing
130, 131 on which adhesive layer 340 is not applied. Hinge portions
132 are generally located at or near the junction of flexible body
110 with rigid housing 115, and thus provide for flexing of device
100 to accommodate patient movement. In some embodiments, hinge
portions 132 may have a width that is less than that of adjacent
portions of wings 130, 131, thus giving device 100 its "peanut"
shape mentioned above. As shown in FIG. 8, as a subject moves,
device 100 flexes along with patient movement. Device flexion may
be severe and is likely to occur many times during long term
monitoring. Hinge portions 132 may allow for dynamic conformability
to the subject, while the rigidity of rigid housing 115 may allow
housing 115 to pop up off the patient's skin during device flexion,
thus preventing peeling of the device 100 off of the skin at its
edge.
[0122] Flexible body 110 further includes two electrode traces 311,
312 sandwiched between upper substrate layer 300 and lower
substrate layer 330. Each electrode trace 311, 312 may include an
electrode interface portion 310 and an electrocardiogram circuit
interface portion 313. As illustrated in the embodiments of FIGS.
3C and 3D, ECG circuit interface portions 313 are in physical
contact with spring fingers 237 and provide electrical
communication with PCBA 120 when device 100 or zoomed-in device
portion 101 is assembled. Electrode interface portions 310 contact
hydrogel electrodes 350. Thus, electrode traces 311, 312 transmit
cardiac rhythm signals (and/or other physiological data in various
embodiments) from electrodes 350 to PCBA 120.
[0123] The material and thickness of electrode traces 311, 312 are
important for providing a desired combination of flexibility,
durability and signal transmission. For example, in one embodiment,
electrode traces 311, 312 may include a combination of silver (Ag)
and silver chloride (AgCl). The silver and silver chloride may be
disposed in layers. For example, one embodiment of electrode traces
311, 312 may include a top layer of silver, a middle layer of
carbon impregnated vinyl, and a bottom (patient-facing) layer of
silver chloride. In another embodiment, both top and bottom layers
of electrode traces 311, 312 may be made of silver chloride. In one
embodiment, the top and bottom layers may be applied to the middle
layer in the form of silver ink and silver chloride ink,
respectively. In an alternative embodiment, each electrode trace
may include only two layers, such as a top layer of silver and a
bottom layer of silver chloride. In various embodiments, the
material of a bottom layer of each electrode trace 311, 312, such
as AgCl, may be selected to match the chemistry of the hydrogel
electrodes 350 and create a half-cell with the body of the
subject.
[0124] The thickness of the electrode traces 311, 312 may be
selected to optimize any of a number of desirable properties. For
example, in some embodiments, at least one of the layers of
electrode traces 311, 312 can be of a sufficient thickness to
minimize or slow depletion of the material from an anode/cathode
effect over time. Additionally, the thickness may be selected for a
desired flexibility, durability and/or signal transmission
quality.
[0125] As mentioned above, in some embodiments, top gasket 370 and
bottom gasket 360 may be attached upper substrate 300 and lower
substrate 330 of flexible body 110. Gaskets 360, 370 may be made of
any suitable material, such as urethane, which provides a water
tight seal between the upper housing member 140 and lower housing
member 145 of rigid housing 115. In one embodiment, top gasket 370
and/or bottom gasket 360 may include an adhesive surface. FIG. 3E
depicts yet another embodiment where top gasket 370 includes tabs
371 that protrude away from the profile of top housing 140 while
still being adhered to upper substrate 300. The tabs 371 cover a
portion of electrode traces 311, 312 and provide a strain relief
for the traces at the point of highest stress where the flexible
body meets the rigid housing.
[0126] With reference now to the embodiment of FIG. 4, upper
housing member 140 and lower housing member 145 of rigid housing
115 are shown in greater detail. Upper and lower housing members
140, 145 may be configured, when coupled together with gaskets 360,
370 in between, to form a watertight enclosure for containing PCBA
120, battery holder 150, batteries 160 and any other components
contained within rigid housing 115. Housing members 140, 145 may be
made of any suitable material to protect internal components, such
as water resistant plastic. In one embodiment, upper housing member
140 may include a rigid sidewall 440, a light pipe 410 to transmit
visual information from the LEDs on the PCBA through the housing
member, a slightly flexible top surface 420, and an inner trigger
member 430 extending inward from top surface 420. Top surface 420
is configured to be depressed by a patient when the patient
perceives what he or she believes to be an arrhythmia or other
cardiac event. When depressed, top surface 420 depresses inner
trigger member 430, which contacts and activates trigger input 210
of PCBA 120. Additionally, as discussed previously, top surface 420
may have a concave shape (concavity facing the inside of housing
115) to accommodate the shape of a finger. It is believed that the
design of upper housing member 140 isolates activation of the
trigger input 210 from electrodes 350, thereby minimizing artifact
in the data recording.
[0127] With continued reference to FIG. 4, lower housing member 145
may be configured to detachably connect with upper housing member
140 in such a way that housing members 140, 145 may be easily
attached and detached for reusability of at least some of the
component parts of monitoring device 100. In some embodiments, a
bottom surface 445 (patient facing surface) of lower housing member
145 may include multiple dimples 450 (or "bumps," "protrusions" or
the like), which will contact the patient's skin during use.
Dimples 450 may allow for air flow between bottom surface 445 and
the patient's skin, thus preventing a seal from forming between
bottom surface 445 and the skin. It is believed that dimples 450
improve comfort and help prevent a perception in currently
available devices in which the patient feels as if monitoring
device 100 is falling off when it housing 115 lifts off the skin
and breaks a seal with the skin. In yet another embodiment the
bottom surface 445 of lower housing member 450 may include multiple
divots (recesses instead of protrusions) to prevent a seal from
forming.
[0128] Referring now to the embodiment of FIG. 5A, battery holder
150 is shown in greater detail. Battery holder 150 may be made of
plastic or other suitable material, is configured to be mounted to
PCBA 120 and subsequently attached to rigid housing 115, and is
capable of holding two batteries 160 (FIG. 1B). In alternative
embodiments, battery holder 150 may be configured to hold one
battery or more than two batteries. A plurality of protrusions 152
provide a stable platform for batteries 160 to be positioned a
fixed distance above the surface of PCBA 120, avoiding unwanted
contact with sensitive electronic components yet providing for
adequate compression of spring contacts 235 (FIG. 5B). Protrusions
153 lock batteries 160 into position and resist the upward force on
the batteries from spring contacts 235. Battery holder 150 also
positions batteries appropriately 160 to provide for adequate
compression of spring contacts 236. Use of battery holder 150 in
conjunction with spring contacts 235 and 236 allows for batteries
160 to be electrically connected to PCBA 120 while still having
additional electronic components between batteries 160 and PCBA 120
and maintain a very compact assembly. Battery holder 150 may
include a flexible hook 510 which engages a corresponding rigid
hook 440 of upper housing member 140. Under normal assembly
conditions the flexible hook 510 remains securely mated with rigid
hook 440. For disassembly, flexible hook 510 can be pushed and bent
using an appropriate tool passed through top housing 140 causing it
to disengage from rigid hook 440 and subsequently allow top housing
140 to be removed.
[0129] With reference now to the embodiments of FIGS. 6A and 6B,
physiological monitoring device 100 is shown in side view
cross-section. As shown in 6A, physiological monitoring device 100
may include flexible body 110 coupled with rigid housing 115.
Flexible body 110 may include top substrate layer 300, bottom
substrate layer 330, adhesive layer 340 and electrodes 350.
Electrode traces 311, 312 are also typically part of flexible body
110 and are embedded between top substrate layer 300 and bottom
substrate layer 330, but they are not shown in FIG. 6. Flexible
body 110 forms two wings 130, 131, extending to either side of
housing 115, and a border 133 surrounding at least part of each
wing 130, 131. Rigid housing 115 may include an upper housing
member 140 coupled with a lower housing member 145 such that it
sandwiches a portion of flexible body 110 in between and provides a
watertight, sealed compartment for PCBA 120. Upper housing member
140 may include inner trigger member 430, and PCBA may include
patient trigger member 210. As discussed previously, lower housing
member 145 may include multiple dimples 450 or divots to enhance
the comfort of the monitoring device 100.
[0130] It is desirable that PCBA 120 is sufficiently rigid to
prevent bending and introducing unwanted artifact into the signal.
In certain embodiments, an additional mechanism to reduce and
prevent unwanted bending of PCBA 120 may be used. This mechanism is
shown in FIG. 6B. Support post 460 is integral to lower housing 145
and is positioned directly under patient trigger input 210. During
patient symptom triggering, upper housing member 140 is depressed,
engaging inner trigger mechanism 430 and transmitting a force
through patient trigger input 210 into PCBA 120. The force is
further transmitted through PCBA 120 and into support post 460
without creating a bending moment, thus avoiding unwanted
artifact.
[0131] Referring to FIG. 7, in some embodiments, physiological
monitoring device 100 may include one or more additional, optional
features. For example, in one embodiment, monitoring device 100 may
include a removable liner 810, a top label 820, a device identifier
830 and a bottom label 840. Liner 810 may be applied over a top
surface of flexible member 110 to aid in the application of device
100 to the subject. As is described in further detail below, liner
810 may help support borders 133 of flexible body 110, as well as
wings 130, 131, during removal of one or more adhesive covers (not
shown) that cover adhesive surface 340 before use. Liner 810 may be
relative rigid and/or firm, to help support flexible body 110
during removal of adhesive covers. In various embodiments, for
example, liner 810 may be made of cardboard, thick paper, plastic
or the like. Liner 810 typically includes an adhesive on one side
for adhering to the top surface of wings 130, 131 of flexible body
110.
[0132] Labels 820, 840 may be any suitable labels and may include
produce name(s), manufacturer name(s), logo(s), design(s) and/or
the like. They may be removable or permanently attached upper
housing member 140 and/or lower housing member 145, although
typically they will be permanently attached, to avoid unregulated
reuse and/or resale of the device by an unregistered user. Device
identifier 830 may be a barcode sticker, computer readable chip,
RFID, or the like. Device identifier 830 may be permanently or
removably attached to PCBA 120, flexible body 110 or the like. In
some embodiments, it may be beneficial to have device identifier
830 stay with PCBA 120.
[0133] Referring now to the embodiments of FIGS. 8A and 8B,
physiological monitoring device 100 generally includes hinge
portions 132 at or near the juncture of each wing 130, 131 with
rigid housing 115. Additionally, each wing 130, 131 is typically
adhered to the patient via adhesive layers 340, while rigid body
115 is not adhered to the patient and is thus free to "float" (for
example, move up and down) over the patient's skin during movement
and change of patient position. In other words, when the patient's
chest contracts, rigid housing pops up or floats over the skin,
thus minimizing stress on device 100, enhancing comfort, and
reducing the tendency of wings 130, 131 to peel off of the skin.
The advantage provided by the combination of the floating rigid
body 115 and the adhered wings 130, 131 is illustrated in FIGS. 8A
and 8B. In FIG. 8A, a patient is sleeping, and in FIG. 8B, a
patient is playing golf. In both examples, monitoring device 100 is
squeezed together by the patient's body, causing rigid housing 115
to float above the skin as wings 130, 131 move closer together.
This advantage of a floating, non-attached portion of a
physiological monitoring device is described in further detail in
U.S. Pat. No. 8,560,046, which was previously incorporated by
reference.
[0134] Referring now to FIGS. 9A-9F, one embodiment of a method for
applying physiological monitoring device 100 to the skin of a human
subject is described. In this embodiment, before the first step
shown in FIG. 9A, the patient's skin may be prepared, typically by
shaving a small portion of the skin on the left chest where device
100 will be placed and then abrading and/or cleaning the shaved
portion. As shown in FIG. 9A, once the patient's skin is prepared,
a first step of applying device 100 may include removing one or
both of two adhesive covers 600 from adhesive layers 340 on the
bottom surface of device 100, thus exposing adhesive layers 340. As
illustrated in FIG. 9B, the next step may be to apply device 100 to
the skin, such that adhesive layer 340 adheres to the skin in a
desired location. In some embodiments, one adhesive cover 600 may
be removed, the uncovered adhesive layer 340 may be applied to the
skin, and then the second adhesive cover 600 may be removed, and
the second adhesive layer 340 may be applied to the skin.
Alternatively, both adhesive covers 600 may be removed before
applying device 100 to the skin. While adhesive covers 600 are
being removed, liner 810 acts as a support for flexible body 110,
provides the physician or other user with something to hold onto,
and prevents flexible body 110 and borders 133 of flexible body 110
from folding in on themselves, forming wrinkles, and so forth. As
described above, liner 810 may be made of a relatively stiff, firm
material to provide support for flexible body 110 during
application of device 100 to the skin. Referring to FIG. 9C, after
device 100 has been applied to the skin, pressure may be applied to
flexible body 110 to press it down onto the chest to help ensure
adherence of device 100 to the skin.
[0135] In a next step, referring to FIG. 9D, liner 810 is removed
from (for example, peeled off of) the top surface of flexible body
110. As shown in FIG. 9E, once liner 810 is removed, pressure may
again be applied to flexible body 110 to help ensure it is adhered
to the skin. Finally, as shown in FIG. 9F, upper housing member 140
may be pressed to turn on physiological monitoring device 140. This
described method is only one embodiment. In alternative
embodiments, one or more steps may be skipped and/or one or more
additional steps may be added.
[0136] In certain embodiments, when a desired monitoring period has
ended, such as about 14 to 21 days in some cases, a patient (or
physician, nurse or the like) may remove physiological monitoring
device 100 from the patient's skin, place device 100 in a prepaid
mailing pouch, and mail device 100 to a data processing facility.
At this facility, device 100 may be partially or completely
disassembled, PCBA 120 may be removed, and stored physiological
data, such as continuous heart rhythm information, may be
downloaded from device 100. The data may then be analyzed by any
suitable method and then provided to a physician in the form of a
report. The physician may then discuss the report with the patient.
PCBA 120 and/or other portions of device 100, such as rigid housing
115, may be reused in the manufacture of subsequent devices for the
same or other patients. Because device 100 is built up as a
combination of several removably coupled parts, various parts may
be reused for the same embodiment or different embodiments of
device 100. For example, PCBA 120 may be used first in an adult
cardiac rhythm monitor and then may be used a second time to
construct a monitor for sleep apnea. The same PCBA 120 may
additionally or alternatively be used with a differently sized
flexible body 110 to construct a pediatric cardiac monitor. Thus,
at least some of the component parts of device 100 may be
interchangeable and reusable.
[0137] In further embodiments described in greater detail below,
the monitoring data may be transmitted wirelessly or through other
communication mediums to be analyzed, rather than requiring
physical shipment of the device for analysis and reporting.
[0138] Advantageously, physiological monitoring device 100 may
provide long term adhesion to the skin. The combination of the
configuration of flexible and conformal body 110, the watertight,
low profile configuration of rigid housing 115, and the interface
between the two allows device 100 to compensate for stress caused
as the skin of the subject stretches and bends. As a result, device
100 may be worn continuously, without removal, on a patient for as
many as 14 to 21 days or more. In some cases, device 100 may be
worn for greater or less time, but 14 to 21 days may often be a
desirable amount of time for collecting heart rhythm data and/or
other physiological signal data from a patient.
[0139] In various alternative embodiments, the shape of a
particular physiological monitoring device may vary. The shape,
footprint, perimeter or boundary of the device may be circular, an
oval, triangular, a compound curve or the like, for example. In
some embodiments, the compound curve may include one or more
concave curves and one or more convex curves. The convex shapes may
be separated by a concave portion. The concave portion may be
between the convex portion on the rigid housing and the convex
portion on the electrodes. In some embodiments, the concave portion
may correspond at least partially with a hinge, hinge region or
area of reduced thickness between the body and a wing.
[0140] While described in the context of a heart monitor, the
device improvements described herein are not so limited. The
improvements described in this application may be applied to any of
a wide variety of physiological data monitoring, recording and/or
transmitting devices. The improved adhesion design features may
also be applied to devices useful in the electronically controlled
and/or time released delivery of pharmacological agents or blood
testing, such as glucose monitors or other blood testing devices.
As such, the description, characteristics and functionality of the
components described herein may be modified as needed to include
the specific components of a particular application such as
electronics, antenna, power supplies or charging connections, data
ports or connections for down loading or off-loading information
from the device, adding or offloading fluids from the device,
monitoring or sensing elements such as electrodes, probes or
sensors or any other component or components needed in the device
specific function. In addition or alternatively, devices described
herein may be used to detect, record, or transmit signals or
information related to signals generated by a body including but
not limited to one or more of ECG, EEG and/or EMG. In certain
embodiments, additional data channels can be include to collect
additional data, for example, device motion, device flex or bed,
heart rate and/or ambient electrical or acoustic noise.
[0141] The physiological monitors described above and elsewhere in
the specification may further be combined with methods and systems
of data processing and transmission that improve the collection of
data from the monitor. Further, the methods and systems described
below may improve the performance of the monitors by enabling
timely transmission of clinical information while maintaining the
high patient compliance and ease-of-use of the monitor described
above. For example, the methods and systems of data processing and
transmission described herein this section of elsewhere in the
specification may serve to extend the battery life of the monitor,
improve the accuracy of the monitor, and/or provide other
improvements and advantages as described herein this section or
elsewhere in the specification.
Device Monitoring and Clinical Analysis Platform
[0142] The systems and methods described in detail below, in
reference to the embodiments of FIGS. 10 to 17, may selectively
extract, transmit, and analyze electrocardiographic signal data and
other physiological data from a wearable physiological monitor,
such as is described above in relation to FIGS. 1 through 9. The
systems and methods described below can improve the performance of
a wearable physiological monitor that simultaneously records and
transmits data through multiple means. For example, selective
transmission of extracted data allows for decreased power
consumption because the wearable patch is not required to transmit
all recorded data. By sending extracted data, much of the analysis
may be performed away from the wearable device without requiring
full on-board rhythm analysis, which can also be highly power
consumptive, reducing battery life. Further, remote analysis
without the power constraints inherent to a wearable device may
allow for greater sensitivity and accuracy in analysis of the data.
Decreased power consumption serves to improve patient compliance
because it prolongs the time period between or even eliminates the
need for device replacement, battery changes or battery recharging
during the monitoring cycle. By decreasing battery consumption,
longer monitoring times may be enabled without device replacement,
for example, at least one week, at least two weeks, at least three
weeks, or more than three weeks.
[0143] FIG. 10 depicts a general overview of an embodiment of a
system 900 for inferring cardiac rhythm information from an R-R
interval time series 902, as may be generated by a continuous heart
rate monitoring device 904. Such systems will be described in much
greater detail below in relation to FIGS. 11 to 17. The R-R
interval time series 902 inputted to the system may include a
series of measurements of the timing interval between successive
heartbeats. Typically each interval represents the time period
between two successive R peaks as identified from an ECG signal. R
peaks are part of the QRS complex, a combination of three graphical
deflections typically seen on an ECG, representing the
depolarization of the left and right ventricles of a mammal's
heart. The R peak is generally the tallest and most visible upward
deflection on an ECG, and thus makes for an appropriate reference
point. However, in further embodiments, any characteristic ECG
fiducial point (such as the QRS complex onset or offset) may be
used in place of the R peak to provide an estimate of the R-R
interval time series. As described above in relation to FIGS. 1
through 9, the physical characteristics of the monitoring device
are constructed in such a way as to improve signal fidelity,
therefore the high signal fidelity allows for a high level of
confidence in accurately extracting R-R peak data.
[0144] The R-R interval time series 902 data may be extracted from
or received from a dedicated heart rate monitor such as a heart
rate chest strap or heart rate watch, or a wearable health or
fitness device 906, 908 that incorporates heart rate sensing
functionality. Alternatively, the R-R interval time series 902 may
be derived from a wearable patch designed to measure an ECG signal
904 (for instance, by locating the R peaks in the ECG using a QRS
detection algorithm). Furthermore, the R-R interval time series 902
may be estimated from an alternative physiological signal such as
that obtained from photoplethysmography (PPG). In this scenario,
the peak-to-peak interval time series determined from the PPG
signal may be used as an accurate estimate of the R-R interval time
series.
[0145] In one aspect, a cardiac rhythm inference system 910 is
implemented as a cloud service or server-based system that exposes
an application programming interface (API) enabling R-R interval
time series data or other signal data to be transmitted to the
system (for instance, via HTTP) and the resulting cardiac rhythm
information to be returned to the calling software. The R-R
interval time series data 902 or other signal data may be
transmitted to the cloud service directly from the heart-rate
monitoring device itself, or indirectly via a smartphone 912,
tablet or other internet-enabled communication device 914 that can
receive data from the heart rate monitoring device in either a
wireless or wired manner. In addition, the R-R interval time series
data 902 or other signals may be transmitted from a server 916 that
stores the data for a number of users.
[0146] In some embodiments, a cardiac rhythm inference system 910
is provided through a software library that can be incorporated
into a standalone application for installation and use on a
smartphone, tablet or personal computer. The library may provide
identical functionality to that of the inference service, but with
R-R interval time series data 902 or other signal data transmitted
directly through a functional call, as opposed to through a web
service API.
[0147] In certain embodiments, a cardiac rhythm inference system
may accept a plurality of R-R interval time series measured from
devices of a given user 918, in addition to an individual R-R
interval time series 902. In this scenario, the system computes the
frequency and duration of each of the cardiac rhythm types inferred
from the collection of time series data. These results may then be
used to estimate confidence statistics for each type of cardiac
rhythm based on the frequency and duration of occurrence of that
rhythm across the various time series. In addition, the rhythm
confidence statistics may be updated in a sequential manner for
each separate call of the inference service. Furthermore, in some
embodiments, the cardiac rhythm information inferred by the system
may be provided back to the calling software only in the event that
the confidence score for a given rhythm type exceeds a
pre-determined threshold value.
[0148] In particular embodiments, a cardiac rhythm inference system
910 may accept additional sources of data, generally described as
alternate sensor channels, in addition to R-R interval time series
data, to enhance the accuracy and/or value of the inferred results.
One additional source of data includes user activity time series
data, such as that measured by a 3-axis accelerometer concurrently
with the R-R interval time series measurements. In addition, the
system may accept other relevant metadata that may help to improve
the accuracy of the rhythm analysis, such as user age, gender,
indication for monitoring, pre-existing medical conditions,
medication information, medical history and the like, and also
information on the specific day and time range for each time series
submitted to the system. Furthermore, the measurement device might
also provide some measure of beat detection confidence, for
example, for each R-Peak or for sequential time periods. This
confidence measure would be based on analysis the recorded signal
that, in typical embodiments, would not be recorded due to storage
space and battery energy requirements. Finally, in the particular
case that the R-R interval time series data are derived from an ECG
signal, the system may accept additional signal features computed
from the ECG. These features may include a time series of
intra-beat interval measurements (such as the QT or PR interval, or
QRS duration), or a time series of signal statistics such as the
mean, median, standard deviation or sum of the ECG signal sample
values within a given time period.
[0149] The various aspects described above could be used either
individually or in combination to provide an application providing
insights into an individual's health, stress, sleep, fitness and/or
other qualities.
[0150] Some embodiments concern a system for selective transmission
of electrocardiographic signal data from a wearable medical sensor.
Current wearable sensors, such as the iRhythm ZioPatch.TM. 904, and
further described above in relation to FIGS. 1-9, are capable of
recording a single-lead electrocardiogram (ECG) signal for up to
two weeks on a single battery charge. In many situations however,
it is desirable for the sensor to be able to transmit, in real-time
or near real-time, specific sections of the recorded ECG signal
with clinical relevance to a computer device, such as either a
smartphone 912 or an internet-connected gateway device 914 for
subsequent processing and analysis. In this way, the patient or
their physician can be provided with potentially valuable
diagnostic ECG information during the period that the patient wears
the sensor.
[0151] As described above, a significant challenge with this
approach is to manage the battery life of the wearable sensor
without requiring replacement or recharging, both of which reduce
user compliance. Each transmission of an ECG from the sensor to a
smartphone or local gateway device (using, for example, Bluetooth
Low Energy) results in a subsequent reduction in the total charge
stored in the sensor battery. Some embodiments of the present
disclosure, particularly those of FIGS. 10 to 17 address this issue
through the use of a novel hardware and software combination to
enable the selective transmission of clinically relevant sections
of ECG from a wearable sensor.
[0152] In certain embodiments, the wearable sensor incorporates
either a software, hardware or hybrid QRS detector that produces a
real-time estimate of each R-peak location in the ECG. The R-peak
location data is then used to compute an R-R interval time series
that is subsequently transmitted to a smartphone or gateway device
according to a predefined schedule (for example, once per hour). In
addition, a time stamp is also transmitted which stores the onset
time for the R-R interval time series relative to the start of the
ECG recording. Since the R-R interval time series for a given
section of ECG is significantly smaller (in terms of bytes
occupied) than the ECG signal itself, it can be transmitted with
considerably less impact on battery life.
[0153] In some embodiments of a second stage of the system, the R-R
interval time series together with the onset time stamp is
subsequently transmitted by the smartphone or gateway device to a
server. On the server, the R-R interval time series is used to
infer a list of the most probable heart rhythms, together with
their onset and offset times, during the period represented by the
time series data. The list of inferred heart rhythms is then
filtered according to specific criteria, such that only rhythms
matching the given criteria are retained after filtering. A measure
of confidence may also be used to assist in filtering the events in
a manner that might improve the Positive Predictivity of
detection.
[0154] In certain embodiments of a third stage of the system, for
each rhythm in the filtered rhythm set, the server transmits to the
smartphone or gateway device the onset and offset time for that
specific rhythm. In the event that the inferred rhythm duration
exceeds a pre-defined maximum duration, the onset and offset times
may be adjusted such that the resulting duration is less than the
maximum permissible duration. The onset and offset times received
by the gateway are then subsequently transmitted to the wearable
sensor, which in turn transmits the section of the recorded ECG
signal between the onset and offset times back to the gateway. This
section of ECG is then transmitted to the server where it can be
analyzed and used to provide diagnostic information to the patient
or their physician.
[0155] In some embodiments, the system fundamentally allows a
device worn for up to about: 14, 21, or 30 days or beyond without
battery recharging or replacement (both activities that reduce
patient compliance and, therefore, diagnostic value) to provide
timely communication of asymptomatic arrhythmia events. This
development is motivated by technology constraints: in order to
enable a small, wearable device that does not require battery
change or recharging while providing continuous arrhythmia analysis
with high accuracy, it is desirable to limit the complexity of
analysis performed on-board. Similarly, streaming of all of the
recorded ECG data to an off-board analysis algorithm may not be
practical without imposing greater power requirements. This
motivates a more creative "triage" approach where selected features
of the recorded ECG signal, including but not limited to R-R
intervals, are sent for every beat, allowing a customized algorithm
to locate a number (for example, 10) of 90-second events to request
from the device in full resolution to support comprehensive
analysis, for example, a resolution capable of supporting clinical
diagnosis.
[0156] In other embodiments, the system would provide the ability
to detect asymptomatic arrhythmias in a timely manner on a
wearable, adhesively affixed device that does not require frequent
recharging or replacement. This would be used to enhance the value
of some current clinical offerings, which only provide clinical
insight after the recording is completed and returned for
analysis.
[0157] In certain embodiments, the system would allow actionable
clinical insight to be derived from data collected on low-cost,
easy-to-use consumer wearable devices that are otherwise only
focused on fitness and wellness. For example, the technology could
be used to create a very effective, low-cost screening tool capable
of detecting the presence of Atrial Fibrillation in the at-large
population. By using such a tool, not only would patients in need
of care be found more easily, but it may be done earlier and more
cost effectively, which lead to better outcomes--namely, through
reducing stroke risk by identifying AF more quickly.
[0158] In particular embodiments, the system may provide the
service through a downloadable application that, after receiving
customer consent for data access and payment approval, would
initiate access and analysis of heart beat data stored from
wearable devices, either stored locally in a mobile device or in an
online repository. This data pull and analysis would happen through
an Algorithm API, and would result in a clinical finding being sent
back to the application to be provided to the user. If the data was
sufficient to support a "screening oriented" finding, for example,
"Likely presence of an irregular rhythm was detected", the
application would direct them to a cardiologist where a more
diagnostically focused offering, for example, the ZIO.RTM. Service,
could be provided to support clinical diagnosis and treatment. In
further embodiments, as also described elsewhere in the
specification, the system may trigger an alarm if a particular
measurement and/or analysis indicates that an alarm is needed.
[0159] Further examples of additional scenarios of clinical value
may include coupling ambulatory arrhythmia monitoring with a
blood-alcohol monitor to study the interaction of AF and lifestyle
factors. For example, ambulatory arrhythmia monitoring could be
coupled with a blood-glucose monitor to study the impact of
Hypoglycemia on arrhythmias. Alternatively, ambulatory arrhythmia
monitoring could be coupled with a respiratory rate and/or volume
monitor to study the interaction of sleep apnea and breathing
disorders. Further, there could be evaluation of the high rates of
supraventricular ectopic beats as a potential precursor for AF (for
example, 720 SVEs in 24-hour period).
Extraction, Transmission, and Processing Systems
[0160] FIG. 11 is a schematic illustration of an embodiment of a
system and method 1000 for a wearable medical sensor 1002 with
transmission capabilities, similar to the system and/or method
described above in relation to FIG. 10. In some embodiments, sensor
1002, which may be any type of sensor or monitor described herein
this section or elsewhere in the specification, continuously senses
an ECG or comparable biological signal 1004 and continuously
records an ECG or comparable biological signal 1004. In certain
embodiments, the sensing and/or recording steps may be performed
intermittently. The collected signal 1004 may then be continuously
extracted into one or more features 1006, representing example
features A, B, and C. The features are not intended to be samplings
of different temporal sections of the signal, instead (as will be
described in greater detail below) the different features may
correspond to different types or pieces of data such as R-peak
locations or R-peak amplitudes. The features of the ECG or
comparable biological signal are extracted to facilitate analysis
of the signal 1004 remotely. In certain embodiments, features are
extracted on a windowed basis, with the window size varying for
example between 1 hour or multiple hours to a few seconds. In
certain embodiments, the window may be at most: about 0.1 second,
about 1 second, about 2 seconds, about 3 seconds, about 5 seconds,
about 10 seconds, about 30 seconds, about 1 minute, about 5
minutes, about 30 minutes, about 1 hour, about 2 hours, about 4
hours, or more than 4 hours. The extraction windows may be
separated by various amounts of time if they are repeated. For
example, the extraction windows may be separated by at least: about
30 seconds, about 1 minute, about 5 minutes, about 30 minutes,
about 1 hour, about 3 hours, about 6 hours, about 12 hours, about
24 hours, about 48 hours, or more than three days. In certain
embodiments, the windowing sizes may vary depending on the feature
extracted. Feature extraction may be limited to one type or various
types of features, and features chosen for extraction may vary
depending on the nature of the signal observed.
[0161] A wide variety of different types of ECG or comparable
biological signal features may be extracted. For example, R-peak
locations may be extracted. In certain embodiments, the R-peak
locations are extracted via various methods such as: a Pan-Tompkins
algorithm (Pan and Tompkins, 1985), providing a real-time QRS
complex detection algorithm employing a series of digital filtering
steps and adaptive thresholding, or an analog R-peak detection
circuit comprising an R-peak detector consisting of a bandpass
filter, a comparator circuit, and dynamic gain adjustment to locate
R-peaks. The RR-intervals may be calculated from peak locations and
used as the primary feature for rhythm discrimination. In
embodiments, an R-peak overflow flag may be extracted. If more than
a certain number of R-peaks were detected during a given time
window such that not all data can be transmitted, a flag may be
raised by the firmware. Such an extraction may be used to eliminate
noisy segments from analysis, on the basis that extremely short
intervals of R-R are not physiologically possible. With similar
motivation, an R-peak underflow flag may be extracted to indicate
an unrealistically long interval between successive R peaks,
provided appropriate considerations for asystole are made in this
evaluation. In an alternative implementation with the same goal,
the lack of presence of R peaks in a prolonged interval could be
associated with a confidence measure, which would describe the
likelihood that the interval was clinical or artifact.
[0162] Another example of a feature that may be extracted 1006
includes a saturation flag, a firmware or hardware-determined
indication that the signal saturated during a given time window
(for example 1 second). Such an extraction may be used to eliminate
noisy segments from analysis. In certain embodiments, P/T-wave
locations may be extracted. This is similar to R-peak detection,
but tuned to lower frequency waves. R-peak locations may be used to
determine the areas of possible wave components. Still another
example of a feature that may be extracted includes the breathing
rate. ECG-derived respiration (EDR) may be derived from studying
the amplitude modulation of ECG signal amplitude. EDR may be
associated with other clinical indicators of arrhythmia. In
embodiments, R-peak amplitude may be extracted, by measuring the
ECG signal amplitude at R-peak locations. This pattern may be
studied to discriminate between true and false peak detection,
and/or to detect changes in beat morphology.
[0163] In particular embodiments, the ECG signal amplitude proxy
may be extracted. This feature may include: the range of the raw
signal data during a given time period, the maximum value of the
signal during a given time period, or the minimum value of the
signal during a given time period. This feature may be used as a
data point for noise detection or possible changes in morphology of
the ECG (for example ventricular ectopy). In some embodiments,
additional ECG signal samples may be extracted. Sampling a few data
points at regular intervals or consecutively from a region
in-between selected R-peaks will allow for determination of the
confidence of rhythm and/or noise classification. Such a selection
may be based on R-R interval length. For instance, if the interval
is longer than 3 seconds, it may be an indicator of a pause. Local
ECG signal energy may also be extracted, for example by taking the
sum square of signal values within a window centered on a point of
interest, for example an R-peak, thereby providing an integral of
ECG sample values in a given time window. This information may be
used to characterize the morphology of beats (supraventricular
tachycardia (SVT) vs. ventricular tachycardia (VT)).
[0164] In certain embodiments, spectral information may be
extracted via extracting statistics from the output from one or
more filters, either realized on hardware (during signal
acquisition) or firmware. Filters may be implemented as a filter
bank, such as a short-time Fourier transform (STFT) or wavelet
transform. Such information may be used to characterize the
morphology of heart beats. Output from simple machine-learned
models may be extracted. For example, the likelihood of a selected
ECG signal segment under a probability model, for example Gaussian,
given raw collected data values or any combination of features
derived from available channels of data may be extracted. The use
of a simple machine-learned model may allow transmission of less
data. In embodiments, the output can directly or indirectly give
insight into: the type of underlying rhythm, the presence of ECG
features such as a P-wave, the confidence level of R-peak
detection, and the presence of noise.
[0165] Once the feature extraction as described above is completed,
various features 1008 may then be transmitted 1010 to a processing
device/server 1012. The features 1008 (and alternate sensor channel
data and/or features as described below) are transmitted 1010 at
regular intervals to a processor 1012 that is not a physical part
of the sensor 1002. The interval definition may be pre-set or,
configurable with each use, or dynamically configurable.
Transmission 1010 of features 1008 may also be bundled and sent
when another reason for communication exists, such as transmission
of symptomatic data (described in greater detail below in relation
to FIG. 16). In certain embodiments, the processing device 1012 may
be: a cloud-based server, a physical server at a company location,
a physical server at patient or clinic location, a smartphone,
tablet, personal computer, smartwatch, automobile console, audio
device and/or an alternate device on or off-site. In particular
embodiments, the transmission 1010 may utilize short-range RF
communication protocols, such as: Bluetooth, ZigBee, WiFi (802.11),
Wireless USB, ANT or ANT+, Ultrawideband (UWB), and/or custom
protocols. The transmission 1010 may be via infrared communication,
such as IrDA and/or inductive coupling communication, such as NFC.
In certain embodiments, transmission may be accomplished via
cellular data networks and/or wired communication protocols, such
as: USB, Serial, TDMA, or other suitable custom means.
[0166] In some embodiments, the transmitted features 1014 are
processed by the remote processor utilizing the data features 1014
to perform analysis via a rhythm inference system 1016 that
analyzes and identifies segments/locations 1018 likely to include
arrhythmia. For example, arrhythmia and ectopy types that may be
identified could include: Pause, 2.sup.nd or 3.sup.rd degree AVB,
Complete Heart Block, SVT, AF, VT, VF, Bigeminy, Trigeminy, and/or
Ectopy. Confidence of determination may be included in the
identification of rhythms. Further, the rhythm inference system
1016 may also utilize patient demographic data, such as age,
gender, or indication to improve accuracy and/or refine confidence
in determinations.
[0167] The identified arrhythmia locations 1018 are then
transmitted 1020 back to the sensor 1002. The transmission 1020
back to the sensor may be accomplished by any communication
protocols/technology described herein this section or elsewhere in
the specification, for example via Bluetooth. The sensor then reads
the transmitted identified locations 1022 and accesses 1024 the
areas of memory corresponding to the transmitted identified
locations 1022 of the ECG. In some embodiments, the sensor applies
additional analysis of the identified segments to further build
confidence in the arrhythmia identification. This further rhythm
confidence determination step 1026 allows for increasing positive
predictivity prior to the power-hungry transmission step. In
embodiments, if the confidence exceeds a defined threshold the data
segment is transmitted. For example, the defined threshold may be a
preset value or it may be set per user and monitoring session. In
embodiments, the defined threshold may be changed dynamically
depending on the nature of the rhythm, the history of accurate
detection within the monitoring period, and/or the confidence of
the rhythm inference system. Additional analysis may also be
performed. Examples of possible analysis techniques include any
methods disclosed herein this section or elsewhere in the
specification, for example: R-peak amplitude, ECG signal amplitude
proxy, ECG signal samples, local ECG signal energy, spectral
information, and/or output from a simple machine-learned model.
[0168] If the confidence exceeds a threshold as described above,
the sensor 1002 may transmit the requested ECG segments 1028 to the
processing device via any transmission means described herein this
section or elsewhere in the specification. The processing device
may complete further analysis on the segments to confirm accuracy
of predicted arrhythmia before using data to report to a user
and/or physician, as needed.
[0169] FIG. 12 is a schematic illustration of an embodiment of a
system and method 2000 for a wearable ECG and/or medical sensor
2002 with transmission capabilities very similar to the system
and/or method 1000 described above in relation to FIG. 11. The
system of FIG. 12 differs from the system of FIG. 11 in that it
includes secondary transmitting devices 2004. For example, possible
secondary transmitting devices include: smartphones, tablets,
personal computers, dedicated custom gateways, audio devices,
wearable activity monitors, automobile consoles, other devices
described herein this section or elsewhere in the specification,
and other available devices for passing data.
[0170] FIG. 13 is a schematic illustration of an embodiment of a
system and method 3000 for a wearable ECG and/or medical sensor
3002 with transmission capabilities, very similar to the system
and/or methods described above in relation to FIGS. 11 and 12. FIG.
13 differs from FIGS. 11 and 12 in that FIG. 13 illustrates
alternate sensor channels 3004, 3006 producing alternate outputs
and/or extraction 3008 of features 3010. Collection of other
channels of data may serve to further augment ECG-extracted
features. Data from the alternate sensor channels may be sent whole
or specific features 3010 of the data channel may be extracted
3008. In certain embodiments, an alternate data channel may record
galvanic skin response/impedance. This data may indicate whether
the sensor 3002 leads are on or off, for example, via a Boolean
algorithm indicating whether the leads are in an on/off state
during a given time period, based on a preset threshold and
built-in hysteresis. This information could be further used to
remove periods of non-contact of the device with the body from
analysis. In certain embodiments, in addition to the on/off
indication Boolean, the collection of more granular impedance data
points may provide insight into the change in patient activity
levels, due to changes in sweat levels. In embodiments, an
alternative sensor data channel may be from an accelerometer. Such
a device may provide free-fall detection via an on-board algorithm
to detect free-fall, an indication that the patient may have
suddenly fallen due to arrhythmia-induced syncope. Further, the
magnitude of acceleration detected by the accelerometer may be used
to detect periods of sleep, activity levels, types of activity,
and/or possibility of motion artifact, all of which may correlate
with the prevalence of certain rhythm types. In particular
embodiments, raw accelerometer values may be used to determine body
orientation given a reference point (for example, whether the
patient was upright when they were first patched). Additionally,
change in orientation of the accelerometer may be used to
distinguish clinically relevant morphology changes vs. not
clinically relevant changes, in addition to providing more insight
into activity type.
[0171] In some embodiments, an alternative data channel may be
provided by a pulse oximeter. For example, a photoplethysmogram
(PPG) may be generated by the pulse oximeter. The PPG may provide
an alternative source for R-peak locations or as a cross-check on
R-peak detection by the ECG circuitry. Further, the PPG data
channel may be combined with multiple PPG/BioZ channels to output
confidence of R-peak detection confidence levels. In further
embodiments, SpO2/perfusion via the pulse oximeter may provide
further clinical indications of a severe arrhythmia. In certain
embodiments, an alternative sensor channel may involve
bioimpedance, which may be used to determine heart beat location
and/or act as an alternative source for R-peak data. In some
embodiments, temperature data may be provided via an alternative
sensor channel. This data can be used in conjunction with other
metrics of activity to discern activity type, level, and/or sleep.
In some embodiments, the alternative data channel may provide
information from a clock, for example the time of day or an
indication of daytime or nighttime. In certain embodiments, the
alternative data channel may be provided by a
microphone/stethoscope, providing an audible recording of heart
beat. Lastly, an alternative data channel may be provided by a flex
or bend sensor which may allow for identification of motion
artifacts.
[0172] FIG. 14 is a schematic illustration of an embodiment of a
system and method 4000 for a wearable ECG and/or medical sensor
4002 with transmission capabilities, very similar to the system
and/or methods described above in relation to FIGS. 11 to 13. FIG.
14 differs from FIGS. 11 to 13 because the embodiment of FIG. 14
incorporates additional data filters. In some embodiments, the
Processing Device 4004 may also filter rhythms 4006 identified by
the rhythm inference system 4008 by applying filter criteria that
may derive from multiple sources. For example, filter criteria may
be drawn from: physician interest in timely reporting of particular
rhythm types, physician interest in viewing a rhythm similar to one
that was viewed previously (for example if multiple 3-second pauses
were already reported to the physician, changing the threshold of
interest to 4- or 5-seconds). In certain embodiments, filtering may
include automated filtering to limit repeated retrieval of similar
rhythm types and durations. Automated filtering can limit repeated
retrieval of low positive-predictivity events, for example, a
record with high levels of motion artifact where positive
predictivity of the rhythm inference engine was low, and may allow
automating filtering on subsequent requests. Such an approach may
utilize confidence intervals assigned by the Rhythm inference
system as well as the tracked history of rhythm inference system
positive predictivity for a given monitoring session.
[0173] FIG. 15 is a schematic illustration of an embodiment of a
system 5000 for a consumer wearable device without full ECG
detection, with some similarities to the medical sensors of FIGS.
10 to 14. The sensors 5002 need not be medical-grade ECG sensors,
but merely allow detection of beats. In embodiments, the sensor
5002 may continuously sense a data channel from which heart beat
locations can be derived. Possible data sources include: PPG
(optionally with multiple channels to increase accuracy),
bio-impedance, and ECG without full implementation due to
insufficient signal quality as compared to the sensors of FIGS. 10
to 14. Similar to the devices of FIGS. 10 to 14, features may be
extracted from this signal, for example: R-peak locations, R-peak
overflow flag, saturation flag, breathing rate, P/T wave locations,
R-peak amplitude (or proxy), or ECG signal amplitude proxy. The
data extraction may be performed via any method described herein
this section or elsewhere in the specification. In certain
embodiments, other channels of data are collected to improve
confidence in rhythm assessments. The consumer device system 5000
further transmits and processes data via any method described
herein this section or elsewhere in the specification. Based on
these determinations, the results of the rhythm analysis may be
sent to a user.
[0174] The consumer device system 5000 without full ECG sensing
advantageously enables arrhythmia analysis using consumer-available
heart-rate sensors, thereby reducing the cost and increasing the
availability of the device. Consequently, this may enable
arrhythmia screening on a larger population, including via
over-the-counter screening.
[0175] FIG. 16 is a schematic diagram of an embodiment of an ECG
monitor system 6000 with symptomatic transmission. Such a system
would involve a wearable ECG sensor, similar to the sensors
described in relation to FIGS. 1 to 14. As described above, such a
sensor senses and records ECG continuously. Each symptom trigger by
a patient may initiate transfer of an ECG data strip. The data
strip may vary in temporal location as well as duration, and may be
centered around a triggered event. In certain embodiments, the data
strip may be biased towards a time period prior to symptom trigger
or it may be biased towards time period after symptom trigger. The
data strip may be of a duration as short as a few heartbeats
(.about.5-10 seconds), or of 60-90 second duration, or longer still
(.about.5-20 minutes). In embodiments, the data strip duration may
be dynamically changed, either programmatically based on clinical
need or auto-adjusting based on patient trigger frequency. The ECG
data strip may be transmitted via any of the means disclosed herein
this section or elsewhere in the specification. If transmission is
enabled without need for patient intervention (for example not NFC
or wired transmission), data transfer may initiate automatically
and opportunistically without requiring further patient interaction
beyond symptom trigger.
[0176] The location for data strip analysis may vary. For example,
analysis may occur local to the patient on a smartphone, tablet or
PC. Alternatively, analysis may occur local to the clinic on a
server or other processing device, or analysis may occur local to
the ECG analysis service provider on a server or other processing
device. Lastly, in embodiments, the analysis may occur using
cloud-based distributed processing resources. In certain
embodiments, a report may be provided for each symptomatic ECG data
strip, however, a report may not be provided if the symptomatic ECG
data strip is not determined to be clinically interesting. In some
cases, the report may be made available, but notification to the
user may be limited to those cases of particular clinical
relevance. Offering this option can limit the demands on a user's
time.
[0177] In certain embodiments, the report may be delivered in a
variety of ways. For example, the report may be delivered: through
a website, through a smartphone, tablet or PC application, through
an Electronic Health Record (EMR/EHR) system with interoperability
and integration into multiple providers' systems, or through
automatic messaging such as email, SMS, app-based messaging. The
recipient of the report may vary, in some applications the report
recipient may be the patient-user while in other applications, the
report recipient may be a clinician.
[0178] In particular embodiments, when monitoring is complete, the
patient removes the device and sends the complete continuous ECG
record to a data processing location. The method of sending may
vary, for example, it may be sent via physical transfer of the
entire device, such as mail or bringing the device to the
prescribing clinic or it may be sent send via local download of
data and subsequent download to a data processing location. In some
cases, the patient may not wait to remove the device before sending
a partial segment of the continuous ECG record, this would be
enabled by transfer methods that do not require removal of the
device, for example NFC or ultra-low-power wireless data transfer.
As with symptomatic ECG analysis described above, the data
processing location may vary.
[0179] FIG. 17 is a schematic diagram of an embodiment of an ECG
monitor system 7000 with both symptomatic and asymptomatic
transmission. The wearable sensor is similar to the sensors
described herein this section or elsewhere in the specification.
However, in embodiments, each asymptomatic trigger initiates
transfer of an ECG data strip such as described above. Further
physical features of the physiological monitoring device described
herein this section or elsewhere in the specification facilitate
implementation as described. As with the other embodiments
described above, high-fidelity ECG recording, as enabled by the
designs detailed herein this section or elsewhere in the
specification, allows increased confidence in the accuracy of the
feature extraction.
Computing Systems and Methods
[0180] In some embodiments, the systems, tools and methods of using
same described above enable interactivity and data collection
performed by a computing system 13000. FIG. 18 is a block diagram
showing an embodiment in which the computing system 13000 is in
communication with a network 13002 and various external computing
systems 13004, such as a wearable system 13005, a gateway device
13006, which are also in communication with the network 13002. The
computing system 13000 may be used to implement systems and methods
described herein. While the external system 13004 are shown as
grouped it is recognized that each of the systems may be external
from each other and/or remotely located.
[0181] In some embodiments, the computing system 13000 includes one
or more computing devices, for example, a server, a laptop
computer, a mobile device (for example, smart phone, smart watch,
tablet, personal digital assistant), a kiosk, automobile console,
or a media player, for example. In one embodiment, the computing
device 13000 includes one or more central processing units (CPUs)
13105, which may each include a conventional or proprietary
microprocessor. The computing device 13000 further includes one or
more memory 13130, such as random access memory (RAM) for temporary
storage of information, one or more read only memory (ROM) for
permanent storage of information, and one or more mass storage
device 13120, such as a hard drive, diskette, solid state drive, or
optical media storage device. In certain embodiments, the
processing device, cloud server, server or gateway device, may be
implemented as a computing system 1300. In one embodiment, the
modules of the computing system 13000 are connected to the computer
using a standard based bus system. In different embodiments, the
standard based bus system could be implemented in Peripheral
Component Interconnect (PCI), Microchannel, Small Computer
computing system Interface (SCSI), Industrial Standard Architecture
(ISA) and Extended ISA (EISA) architectures, for example. In
addition, the functionality provided for in the components and
modules of computing device 13000 may be combined into fewer
components and modules or further separated into additional
components and modules.
[0182] The computing device 13000 may be controlled and coordinated
by operating system software, for example, iOS, Windows XP, Windows
Vista, Windows 7, Windows 8, Windows 10, Windows Server, Embedded
Windows, Unix, Linux, Ubuntu Linux, SunOS, Solaris, Blackberry OS,
Android, or other operating systems. In Macintosh systems, the
operating system may be any available operating system, such as MAC
OS X. In other embodiments, the computing device 13000 may be
controlled by a proprietary operating system. Conventional
operating systems control and schedule computer processes for
execution, perform memory management, provide file system,
networking, I/O services, and provide a user interface, such as a
graphical user interface (GUI), among other things.
[0183] The exemplary computing device 13000 may include one or more
I/O interfaces and devices 13110, for example, a touchpad or
touchscreen, but could also include a keyboard, mouse, and printer.
In one embodiment, the I/O interfaces and devices 13110 include one
or more display devices (such as a touchscreen or monitor) that
allow visual presentation of data to a user. More particularly, a
display device may provide for the presentation of GUIs,
application software data, and multimedia presentations, for
example. The computing system 13000 may also include one or more
multimedia devices 13140, such as cameras, speakers, video cards,
graphics accelerators, and microphones, for example.
[0184] The I/O interfaces and devices 13110, in one embodiment of
the computing system and application tools, may provide a
communication interface to various external devices. In one
embodiment, the computing device 13000 is electronically coupled to
a network 13002, which comprises one or more of a local area
network, a wide area network, and/or the Internet, for example, via
a wired, wireless, or combination of wired and wireless,
communication link 13115. The network 13002 can communicate with
various sensors, computing devices, and/or other electronic devices
via wired or wireless communication links.
[0185] In some embodiments, the filter criteria, signals and data
are processed by rhythm inference module an application tool
according to the methods and systems described herein, may be
provided to the computing system 13000 over the network 13002 from
one or more data sources 13010. The data sources may include one or
more internal and/or external databases, data sources, and physical
data stores. The data sources 13010, external computing systems
13004 and the rhythm interface module 13190 may include databases
for storing data (for example, feature data, raw signal data,
patient data) according to the systems and methods described above,
databases for storing data that has been processed (for example,
data to be transmitted to the sensor, data to be sent to the
clinician) according to the systems and methods described above. In
one embodiment of FIG. 19, the sensor data 14050 may, in some
embodiments, store data received from the sensor, received from the
clinician, and so forth. The Rules Database 14060 may, in some
embodiments, store data (for example, instructions, preferences,
profile) that establish parameters for the thresholds for analyzing
the feature data. In some embodiments, one or more of the databases
or data sources may be implemented using a relational database,
such as Sybase, Oracle, CodeBase, MySQL, SQLite, and Microsoft.RTM.
SQL Server, and other types of databases such as, for example, a
flat file database, an entity-relationship database, and
object-oriented database, NoSQL database, and/or a record-based
database.
[0186] The computing system, in one embodiment, includes a rhythm
interface module 13190 that may be stored in the mass storage
device 13120 as executable software codes that are executed by the
CPU 13105. The rhythm interface module 13190 may have a Feature
Module 14010, an Alternate Data Module 14020, an Inference Module
14030, a Feedback Module 14040, a Sensor Data Database 14050, and a
Rules Database 14060. These modules may include by way of example,
components, such as software components, object-oriented software
components, subroutines, segments of program code, drivers,
firmware, microcode, circuitry, data, databases, data structures,
tables, arrays, and variables. These modules are also configured to
perform the processes disclosed herein including, in some
embodiments, the processes described with respect to FIGS. 10 to
17.
[0187] In general, the word "module," as used herein, refers to
logic embodied in hardware or firmware, or to a collection of
software instructions, possibly having entry and exit points,
written in a programming language, such as, for example, Python,
Java, Lua, C and/or C++. A software module may be compiled and
linked into an executable program, installed in a dynamic link
library, or may be written in an interpreted programming language
such as, for example, BASIC, Perl, or Python. It will be
appreciated that software modules may be callable from other
modules or from themselves, and/or may be invoked in response to
detected events or interrupts. Software modules configured for
execution on computing devices may be provided on a computer
readable medium, such as a compact disc, digital video disc, flash
drive, or any other tangible medium. Such software code may be
stored, partially or fully, on a memory device of the executing
computing device, such as the computing system 13000, for execution
by the computing device. Software instructions may be embedded in
firmware, such as an EPROM. It will be further appreciated that
hardware modules may be comprised of connected logic units, such as
gates and flip-flops, and/or may be comprised of programmable
units, such as programmable gate arrays or processors. The block
diagrams disclosed herein may be implemented as modules. The
modules described herein may be implemented as software modules,
but may be represented in hardware or firmware. Generally, the
modules described herein refer to logical modules that may be
combined with other modules or divided into sub-modules despite
their physical organization or storage.
[0188] Each of the processes, methods, and algorithms described in
the preceding sections may be embodied in, and fully or partially
automated by, code modules executed by one or more computer systems
or computer processors comprising computer hardware. The code
modules may be stored on any type of non-transitory
computer-readable medium or computer storage device, such as hard
drives, solid state memory, optical disc, and/or the like. The
systems and modules may also be transmitted as generated data
signals (for example, as part of a carrier wave or other analog or
digital propagated signal) on a variety of computer-readable
transmission mediums, including wireless-based and
wired/cable-based mediums, and may take a variety of forms (for
example, as part of a single or multiplexed analog signal, or as
multiple discrete digital packets or frames). The processes and
algorithms may be implemented partially or wholly in
application-specific circuitry. The results of the disclosed
processes and process steps may be stored, persistently or
otherwise, in any type of non-transitory computer storage such as,
for example, volatile or non-volatile storage.
[0189] The various features and processes described above may be
used independently of one another, or may be combined in various
ways. All possible combinations and subcombinations are intended to
fall within the scope of this disclosure. In addition, certain
method or process blocks may be omitted in some implementations.
The methods and processes described herein are also not limited to
any particular sequence, and the blocks or states relating thereto
can be performed in other sequences that are appropriate. For
example, described blocks or states may be performed in an order
other than that specifically disclosed, or multiple blocks or
states may be combined in a single block or state. The example
blocks or states may be performed in serial, in parallel, or in
some other manner. Blocks or states may be added to or removed from
the disclosed example embodiments. The example systems and
components described herein may be configured differently than
described. For example, elements may be added to, removed from, or
rearranged compared to the disclosed example embodiments.
[0190] Conditional language, such as, among others, "can," "could,"
"might," or "may," unless specifically stated otherwise, or
otherwise understood within the context as used, is generally
intended to convey that certain embodiments include, while other
embodiments do not include, certain features, elements and/or
steps. Thus, such conditional language is not generally intended to
imply that features, elements and/or steps are in any way required
for one or more embodiments or that one or more embodiments
necessarily include logic for deciding, with or without user input
or prompting, whether these features, elements and/or steps are
included or are to be performed in any particular embodiment. The
term "including" means "included but not limited to." The term "or"
means "and/or."
[0191] Any process descriptions, elements, or blocks in the flow or
block diagrams described herein and/or depicted in the attached
figures should be understood as potentially representing modules,
segments, or portions of code which include one or more executable
instructions for implementing specific logical functions or steps
in the process. Alternate implementations are included within the
scope of the embodiments described herein in which elements or
functions may be deleted, executed out of order from that shown or
discussed, including substantially concurrently or in reverse
order, depending on the functionality involved, as would be
understood by those skilled in the art.
[0192] All of the methods and processes described above may be at
least partially embodied in, and partially or fully automated via,
software code modules executed by one or more computers. For
example, the methods described herein may be performed by the
computing system and/or any other suitable computing device. The
methods may be executed on the computing devices in response to
execution of software instructions or other executable code read
from a tangible computer readable medium. A tangible computer
readable medium is a data storage device that can store data that
is readable by a computer system. Examples of computer readable
mediums include read-only memory, random-access memory, other
volatile or non-volatile memory devices, CD-ROMs, magnetic tape,
flash drives, and optical data storage devices.
[0193] It should be emphasized that many variations and
modifications may be made to the above-described embodiments, the
elements of which are to be understood as being among other
acceptable examples. All such modifications and variations are
intended to be included herein within the scope of this disclosure.
The foregoing description details certain embodiments. It will be
appreciated, however, that no matter how detailed the foregoing
appears in text, the systems and methods can be practiced in many
ways. For example, a feature of one embodiment may be used with a
feature in a different embodiment. As is also stated above, it
should be noted that the use of particular terminology when
describing certain features or aspects of the systems and methods
should not be taken to imply that the terminology is being
re-defined herein to be restricted to including any specific
characteristics of the features or aspects of the systems and
methods with which that terminology is associated.
[0194] Various embodiments of a physiological monitoring device,
methods, and systems are disclosed herein. These various
embodiments may be used alone or in combination, and various
changes to individual features of the embodiments may be altered,
without departing from the scope of the invention. For example, the
order of various method steps may in some instances be changed,
and/or one or more optional features may be added to or eliminated
from a described device. Therefore, the description of the
embodiments provided above should not be interpreted as unduly
limiting the scope of the invention as it is set forth in the
claims.
[0195] Various modifications to the implementations described in
this disclosure may be made, and the generic principles defined
herein may be applied to other implementations without departing
from the spirit or scope of this disclosure. Thus, the scope of the
disclosure is not intended to be limited to the implementations
shown herein, but are to be accorded the widest scope consistent
with this disclosure, the principles and the novel features
disclosed herein.
[0196] Certain features that are described in this specification in
the context of separate embodiments also can be implemented in
combination in a single embodiment. Conversely, various features
that are described in the context of a single embodiment also can
be implemented in multiple embodiments separately or in any
suitable subcombination. Moreover, although features may be
described above as acting in certain combinations and even
initially claimed as such, one or more features from a claimed
combination can in some cases be excised from the combination, and
the claimed combination may be directed to a subcombination or
variation of a subcombination.
[0197] Similarly, while operations are depicted in the drawings in
a particular order, such operations need not be performed in the
particular order shown or in sequential order, or that all
illustrated operations be performed, to achieve desirable results.
Further, the drawings may schematically depict one more example
processes in the form of a flow diagram. However, other operations
that are not depicted can be incorporated in the example processes
that are schematically illustrated. For example, one or more
additional operations can be performed before, after,
simultaneously, or between any of the illustrated operations.
Moreover, the separation of various system components in the
embodiments described above should not be interpreted as requiring
such separation in all embodiments. Additionally, other embodiments
are within the scope of the following claims. In some cases, the
actions recited in the claims can be performed in a different order
and still achieve desirable results.
* * * * *