U.S. patent application number 14/244760 was filed with the patent office on 2015-03-12 for integrated wireless patch for physiological monitoring.
This patent application is currently assigned to HMICRO, INC.. The applicant listed for this patent is James Beck, Lois M. Fisher, Randall Lee, Surendar Magar, Ali Niknejad, Venkateswara R. Sattiraju, Louis C. Yun. Invention is credited to James Beck, Lois M. Fisher, Randall Lee, Surendar Magar, Ali Niknejad, Venkateswara R. Sattiraju, Louis C. Yun.
Application Number | 20150073231 14/244760 |
Document ID | / |
Family ID | 40075752 |
Filed Date | 2015-03-12 |
United States Patent
Application |
20150073231 |
Kind Code |
A1 |
Beck; James ; et
al. |
March 12, 2015 |
INTEGRATED WIRELESS PATCH FOR PHYSIOLOGICAL MONITORING
Abstract
A sensor system in accordance with the present invention
comprises a plane member a plurality of electrodes within the plane
member adapted to contact a human body to detect and monitor human
generated voltages. The sensor can be applied to monitor a variety
of applications relating to health disease progression fitness and
wellness. Some of the specific applications include the monitoring
of ECG EEG EMG glucose electrolytes body hydration dehydration
tissue state and wounds. Various aspects of the invent aspects of
the invention are shown by illustrating certain embodiments. Many
other embodiments can be used to implement the invented
schemes.
Inventors: |
Beck; James; (Berkeley,
CA) ; Sattiraju; Venkateswara R.; (Union City,
CA) ; Niknejad; Ali; (Berkely, CA) ; Yun;
Louis C.; (Los Altos, CA) ; Lee; Randall;
(Hillsborough, CA) ; Magar; Surendar; (Dublin,
CA) ; Fisher; Lois M.; (San Francisco, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Beck; James
Sattiraju; Venkateswara R.
Niknejad; Ali
Yun; Louis C.
Lee; Randall
Magar; Surendar
Fisher; Lois M. |
Berkeley
Union City
Berkely
Los Altos
Hillsborough
Dublin
San Francisco |
CA
CA
CA
CA
CA
CA
CA |
US
US
US
US
US
US
US |
|
|
Assignee: |
HMICRO, INC.
Los Altos
CA
|
Family ID: |
40075752 |
Appl. No.: |
14/244760 |
Filed: |
April 3, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12601373 |
Aug 27, 2010 |
8718742 |
|
|
PCT/US2008/064800 |
May 23, 2008 |
|
|
|
14244760 |
|
|
|
|
60940072 |
May 24, 2007 |
|
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|
Current U.S.
Class: |
600/301 ;
600/391; 600/393 |
Current CPC
Class: |
A61B 5/0422 20130101;
A61B 5/0488 20130101; A61B 5/0476 20130101; A61B 5/04012 20130101;
A61B 5/0478 20130101; A61B 5/1486 20130101; A61B 5/0428 20130101;
A61B 5/0031 20130101; A61B 5/0205 20130101; A61B 5/14532 20130101;
A61B 5/0006 20130101; A61B 5/0492 20130101; A61B 5/04085
20130101 |
Class at
Publication: |
600/301 ;
600/393; 600/391 |
International
Class: |
A61B 5/0408 20060101
A61B005/0408; A61B 5/04 20060101 A61B005/04; A61B 5/0488 20060101
A61B005/0488; A61B 5/145 20060101 A61B005/145; A61B 5/0476 20060101
A61B005/0476; A61B 5/0205 20060101 A61B005/0205; A61B 5/00 20060101
A61B005/00 |
Claims
1. A sensor comprising: a plane member; and a plurality of
electrodes within the plane member and adapted to contact a human
body to detect and monitor human generated voltages.
2. The sensor of claim 1 wherein the plurality of electrodes
comprises a contact electrode for a common connection and plurality
electrodes for detecting and monitoring the human generated
voltages.
3. The sensor of claim 1 wherein the electrodes are arranged in an
array.
4. The sensor of claim 3 wherein the array is any of a circular
array, a linear array, a hex pattern, a radial array, and a
rectangular array.
5. The sensor of claim 1 wherein the sensor includes adhesive areas
and non-adhesive areas.
6. The sensor of claim 1 wherein adhesive areas surround the
plurality of electrodes and the non-adhesive areas separate at
least a portion of the electrodes.
7. The sensor of claim 1 wherein the sensor comprises an
application specific integrated circuit.
8. The sensor of claim 1 wherein the total area of the sensor is
less than 200 cm.sup.2.
9. The sensor of claim 1 wherein each electrode has an area that is
less than 10 cm.sup.2.
10. The sensor of claim 1 wherein the electrodes are measuring ECG
signal.
11. The sensor of claim 1 wherein the electrodes are measuring one
physiological signal.
12. The sensor of claim 1 wherein the electrodes are measuring
multiple physiological signals.
13. The sensor of claim 1 wherein the sensor wirelessly
communicates with a stationary patient monitoring device.
14. The sensor of claim 1 wherein the sensor communicates with a
mobile device.
15. The sensor of claim 1 wherein the sensor processes on board
clinical analysis algorithms.
16. The sensor of claim 1 wherein the sensor has a warning/output
device.
17. The sensor of claim 1 wherein the sensor is integrated into a
catheter, fluid bag, or container for a biological sample.
18. A patch comprising: a plane member; an electrode adapted to
contact a human body for providing a common connection; and at
least one pair of electrodes arranged in an array which are adapted
to contact a human body to detect and monitor human generated
voltages.
19. The sensor of claim 17 wherein the at least one pair of
electrodes are located on non-adhesive areas and are separated by
adhesive areas.
20. The sensor of claim 17 wherein the at least one pair electrodes
are located in adhesive areas and are separated by non-adhesive
areas.
21. The sensor of claim 18 wherein the array is any of a circular
array, a linear array, a hex pattern, a radial array, and a
rectangular array.
22. A sensor system comprising: a plane member; a plurality of
electrodes within the plane member and adapted to contact a human
body to detect and monitor human generated voltages; and a circuit
for providing signals over a wireless link, wherein the circuit
comprises: an amplifier for amplifying signals received from the
electrodes; a filter for the signals; an analog to digital
converter (ADC) for converting the signals to digital signals; a
digital signal processor for processing the digital signals; and a
radio for wirelessly transmitting the digital signals.
23. The system of claim 22 wherein the amplifier detects
differential signals from opposite pairs of electrodes.
24. The system of claim 22 wherein the amplifier comprises a
plurality of amplifiers and the filter wherein comprises a
plurality of filters, wherein each of plurality of amplifiers
detects differential signals from opposite pairs of electrodes.
25. The system of claim 22 which includes a multiplexer for
receiving the signals from the plurality of filters and providing
the signals to the analog to digital converter.
26. The system of claim 22 wherein a portion of the sensor system
is disposable.
27. The system of claim 22 wherein a multiplexer is inserted
between the plurality of electrodes and plurality of amplifiers
Description
CROSS REFERENCE
[0001] This application is a continuation of the U.S. application
Ser. No. 12/601,373, filed on Aug. 27, 2010, which is a U.S.
National Stage Application of the PCT Application No.
PCT/US2008/064800, filed on May 23, 2008, which claims priority to
U.S. Provisional Patent Application Ser. No. 60/940,072, filed on
May 24, 2007, which is incorporated herein by reference in their
entirety.
FIELD OF THE INVENTION
[0002] The present Invention relates generally to a wireless
healthcare system and more particularly to sensors utilized with
such a system.
BACKGROUND OF THE INVENTION
[0003] Wireless healthcare systems, referred to as WHc systems are
being used increasingly to help reduce healthcare costs, increase
patient independence and provide better outcomes. FIG. 1 is a
simple block diagram of a WHc system 10. The WHc system includes
three main elements: wireless sensors 12a-12n, a host monitor 14,
and a remote server 16. Wireless Sensors 12a-12n measure elements
and the physiological signals from the body and wirelessly transmit
them to a nearby device, as a host monitor 14 in FIG. 1. A host
monitor 14 receives the signals and can relay them to a remote
server 16 via a cellular or other type of network. The host monitor
14 could be a cell phone, portable monitor, catheter, or tissue
sampling system, or the device could also be a laboratory
instrument, such as a portable analyzer, point of care test kit, or
any other laboratory Instrument system. A host monitor 14 could be
a stationary device such as a hospital bedside patient monitor, a
point of care test kit or a lab instrument. The host monitor 14
could also be a portable device such as holter monitor, a glucose
meter or a compact patient monitor. In emerging WHc systems 10, the
host monitor 14 could be a mobile device such as a cell phone or a
personal digital assistant. In all these cases the host monitor 14
can have the capability to collect data from wireless sensors
12a-12n and to perform clinical analysis on the data. The host
monitor 14 could also be simply a wireless gateway or access point
that collects physiological data from wireless sensors 12a-12n and
simply transmit it to remote server 16 for clinical analysis. In
some cases, the wireless sensors 12a-12n can have on-board
processors to perform clinical analysis and occasionally
communicate with the host monitor 14 and/or remote server 16.
[0004] In general, progress has been made by Industry to make the
host monitors 14 smaller, more capable and providing flexible
networking connectivity (e.g. wireless) with remote servers 16.
However, wireless sensors 12a-12n still remains a major problem.
Therefore, in most cases, the patients remain tethered to host
monitors, wearing traditional physiological sensors that are
sending data to host monitors through wires. It is Important to
create effective wireless sensors 12a-12n to enable wide deployment
of wireless healthcare.
Physical Monitoring
[0005] Many variables of physiological significance are measured as
voltage signals (e.g. ECG, EEG, EMG, continuous glucose monitoring,
electrolytes). The signals may be measured via electrodes placed
variously on, within, or near a biological sample or,
alternatively, integrated into a testing device. Electrodes may be
placed on the skin, mounted on catheters, placed within the
vascular or urinary system, inserted into biological tissue, or
integrated into other devices such as invasive micromechanical
devices or external analytical instrumentation used to evaluate
samples of biological tissue or fluids. An electrode is a
conducting connector between a biological sample and an electronic
circuit, where the biological sample may be skin, tissue, blood or
blood components, interstitial fluid, or urine. The material used
for surface electrodes is typically silver or a silver compound
which may be covered with an electrolyte for enhanced conductivity.
Materials used in other sensors may vary to support sensors linked
to highly specific reagents such as ion-specific resins or gels,
various immunoassay formats mounted on a substrate, electrochemical
or crystalline systems, or other types of diagnostic testing
schemes.
[0006] Analysis of the physiological signals may be performed by
any of the three devices in the system to extract the information
about a person's health state--sensor 12a-12n, host monitor 14 or
remote server 16. Data may alternatively be stored and later
displayed for analysis by a human or computer. Analysis can also be
performed in a distributed fashion, jointly by any combination of
these three devices.
Wireless Sensors
[0007] Wireless sensors 12a-12n typically include one or more
electrodes. What is meant by a sensor is a device containing one or
more electrodes which may be placed on the skin, mounted on
catheters, placed within the vascular or urinary system, inserted
into biological tissue, or integrated into other devices such as
invasive micromechanical devices or external analytical
instrumentation used to evaluate samples of biological tissue or
fluids. Furthermore, the sensor could be a patch for the surface of
the skin or an implantable sensor embedded in the body.
[0008] Wireless sensors 12a-12n need to have very small form
factors to accommodate patient convenience and comfort, ease-of-use
and ease-of-integration into small systems. Wireless sensors
12a-12n should also be low cost, particularly if used as a
disposable. These requirements call for a design that is highly
integrated in every respect, including the electrode structure. To
date, wireless sensors 12a-12n have been bulky, power-hungry,
expensive and difficult to use.
[0009] Also, the lead placement scheme of many previous
physiological measurement procedures (e.g. 12-lead ECG) is not well
suited to compact integrated wireless systems. Many such systems
were developed decades ago based on the electronic components
available at that time and the wired connectivity. Today's
electronic components are far more precise which can resolve much
smaller signals from the body. The wireless connectivity also
alleviates the noise picked up by long wires in wired sensor
systems. Therefore, migration to wireless systems avails a fresh
opportunity to create a new class of compact wireless sensors that
can displace traditional bulky electrode systems used in
applications such as 12-lead ECG. The present invention addresses
such a need.
SUMMARY OF THE INVENTION
[0010] A sensor patch in accordance with the present invention
comprises a plane member, a plurality of electrodes within the
plane member, adapted to contact a human body to detect and monitor
human generated voltages. The sensor can be applied to monitor a
variety of applications relating to health, disease progression,
fitness and wellness. Some of the specific applications include the
monitoring of ECG, EEG, EMG, glucose, electrolytes, body hydration,
dehydration, tissue state and wounds. Various aspects of the
invention are shown by illustrating certain embodiments. Many other
embodiments can be used to implement the invented schemes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is an illustration of a wireless healthcare
monitoring system.
[0012] FIG. 2a is a first embodiment of a patch sensor with
multiple electrodes in accordance with the present invention.
[0013] FIG. 2b is a second embodiment of a patch sensor with
multiple electrodes in accordance with the present invention.
[0014] FIG. 3a is an embodiment of a sensor with one electrode and
showing a schematic of the electronics processing.
[0015] FIG. 3b is a first embodiment of a sensor coupled to
multiple electrodes.
[0016] FIG. 3c is a second embodiment of a sensor coupled to
multiple electrodes.
[0017] FIG. 4 is an illustration of a fully disposable
multi-electrode patch.
[0018] FIG. 5 shows the essential components required of both
variants of the partially reusable patch for a specific design.
[0019] FIG. 6a is an illustration of ECG views using opposite
electrode pairs.
[0020] FIG. 6b is an illustration of ECG views using alternate
electrode pairs.
[0021] FIG. 7 is an illustration of the graphic aid to attach the
patch to the body.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] The present invention relates generally to a wireless
healthcare system and more particularly to sensors utilized with
such a system. The following description Is presented to enable one
of ordinary skill in the art to make and use the invention and is
provided in the context of a patent application and its
requirements. Various modifications to the preferred embodiment and
the generic principles and features described herein will be
readily apparent to those skilled in the art. Thus, the present
invention is not intended to be limited to the embodiment shown but
is to be accorded the widest scope consistent with the principles
and features described herein.
[0023] A system and method in accordance with the present invention
relates to a method and system in accordance with the present
invention for providing integrated wireless sensors. The wireless
sensor for use in a wireless healthcare system (Whc) needs the
following elements: [0024] Electrodes to sense signals [0025]
Electronic circuits to amplify and condition signals [0026]
Optional analog to digital (A/D) converter [0027] Processor to
manage the signals prior to transmission [0028] Radio for
transmission to a nearby mobile device or any other device [0029]
Energy source (battery) to power the electronics (add the bullet
dot?) [0030] Means to attach the patch to body [0031] Protective
covering to withstand environmental hazards
[0032] In a system and method in accordance with one embodiment of
the present Invention, a patch with multiple conductive electrodes
to make contact with the body to detect and monitor human-generated
body voltages is provided. The electrodes are connected to multiple
electronic amplifiers and associated filters, etc., which in turn
connect to a radio. A patch may include one or more electrodes
depending upon the application. In some cases, the various
electrodes may be used to measure different variables in the same
biological sample or at the same biological interface. In other
cases, differential voltages are measured across a pair or pairs of
electrodes, where spatial information is important for a single
variable, such as ECG and EEG measurements. To describe the
features of the present invention in more detail, refer now to the
following description in conjunction with the accompanying
figures.
[0033] As before mentioned, although the embodiments of the present
invention described herein refer to patches placed on the skin
surface, one of ordinary skill in the art readily recognizes that
the present invention can be utilized in a variety of environments
where sensors are used. For example, electrodes may be placed on
the skin, mounted on catheters, placed within the vascular or
urinary system, inserted into biological tissue, or integrated into
other devices such as invasive micromechanical devices or external
analytical Instrumentation used to evaluate samples of biological
tissue or fluids.
[0034] In one embodiment electrodes are fabricated on the bottom
plane of a patch which contacts the body or biological sample.
Multiple electrodes can be arranged in a variety of ways--a
circular array, a rectangular array or a linear array, for example,
depending on the desired application. The size and shape of the
electrodes and the total number of electrodes may also vary.
Trade-offs are made in a given application to achieve the desired
specifications for that application.
[0035] FIG. 2a represents a first embodiment of a multi-electrode
patch 100. FIG. 2b represents a second embodiment of a
multi-electrode patch 150. In both embodiments, a plurality of
electrodes are arranged in a circular array with an additional
electrode placed in the middle of the array. One possible
arrangement of the electrodes would be similar to the drawing shown
in FIG. 2a. In this particular case, multiple pairs of electrodes
102a-102n in the circular array can be simultaneously sampled to
optimally detect differential voltages traveling in any
direction.
[0036] In this embodiment each of the electrodes 102a-102f are
surrounded by non-adhesive areas 106a-106f. There is also an
adhesive and electrode contact separator 108 between the
non-adhesive areas 106 of the patch 100. In this embodiment, the
six skin contact electrodes 102a-102f are used in pairs to provide
a differential measurement for the patch. For example, electrode
pair 102a-102d would provide one measurement, electrode pair 102b
and 102e would provide a second measurement, and electrode pair
102c and 102f would provide a third measurement.
[0037] Each of the pairs 102a-102d, 102b-102e, and 102c-102f could
be utilized to measure different conditions within the body or they
could be utilized to measure one condition or any number in
between. Furthermore, there can be as little as two electrodes on
the patch or as many as can be placed thereon to provide the
differential measurement of signals.
[0038] FIG. 2b is similar to FIG. 2a except that each of the
electrodes 152a-152f is surrounded by adhesive areas 154 while the
separator areas 156 around the electrodes 152a-152f are
non-adhesive. The larger adhesive area 154 supports the patch 150
while allowing for a clear channel to expose more skin to air. A
central electrode 104 and 158 of FIGS. 2a and 2b, respectively, is
used by an electronic circuit (not shown) as the "ground"
connection which serves as a reference to help reject unwanted
electric signals (noise). The patch 100 could include in an
embodiment output devices such as LEDs, displays or an audible tone
that may function as warning signals or may signify other
conditions to the patient.
[0039] Although these embodiments contemplate the measurement of
differential voltages across multiple pairs of electrodes, the same
structure could be used to support a sensor system using different
electrode materials such as gels, resins, or substrates supporting
various diagnostic testing methodologies described previously. It
should be understood that the electrodes can be in any array and
they would be in the scope of the present invention. The number,
shape, physical size and arrangement of the electrodes as well as
the overall size of its pairs may also vary. The overall size of
the patch will vary accordingly. In one embodiment, the contact
area of the sensor patch is less than 200 cm.sup.2. In one
embodiment the area of an electrode is less than 10 cm.sup.2.
Patch or Sensor Electronics
[0040] The electronic circuits for a wireless patch will vary by
application but will support certain common signal acquisition and
conditioning functions. One embodiment of the electronic circuits
that need to be connected for a single electrode pair wireless
patch is shown in FIG. 3a. As shown, the electronics perform the
function of picking up signals from the electrodes, then
amplifying, filtering, digitizing and transmitting the signals over
a wireless link. The functions shown in the figures may be
instantiated with discrete circuits, one or more ASICs (Application
Specific Integrated Circuits) or any combination of them.
[0041] The electronics can be modified to connect to multiple
electrode structures as well. An electronic circuit that can be
used with the specific multi-electrode structure shown in FIGS. 2a
and 2b is illustrated in FIG. 3b. In this scheme, three
instrumentation amplifiers 202a-202c and analog filters 204a-204c
detect the differential signals collected from opposite pairs of
electrodes. A multiplexer brings all three signals to a shared A/D
converter 206 and radio 210 for wireless transmittal 214.
[0042] Collecting signals from opposite pairs of differential
electrodes, as shown in FIG. 3b, yields the best results (highest
voltages) for physiological signal vectors that are naturally
aligned with one of the three major axes defined by the pairs of
opposite electrodes. Although the example shows six electrodes, a
patch using just four electrodes (two pairs) would produce signals
that could theoretically be processed to resolve the same vectors
seen with more electrodes.
[0043] Two alternatives to the signal processing approach using
four electrodes are to increase the number of electrodes--for
example to six, as shown here--and to measure voltages across
non-opposite pairs of electrodes. A patch with six electrodes, for
example, can provide a total of six axes of measurement, spaced 30
degrees apart, if non-opposite electrode pairs can be used for the
measurement.
[0044] FIG. 3c is another embodiment of a multi-electrode patch
system. The system adds a multiplexer circuit 216 between the
electrodes of the patch 100 and the amplifiers 202a-202c. In this
embodiment, all six axes can be measured, using various pairs of
electrodes selected by the multiplexer. An additional benefit of
including the multiplexer circuit is that it provides a reliability
advantage; in the event one electrode loses contact with the skin
and becomes unusable, signals from a different pair aligned along
the same axis could be selected Instead.
[0045] The instrumentation amplifiers shown in all three diagrams
represent one embodiment for providing the gain required in the
first stage of processing, but other schemes using other types of
amplifiers are possible. Specifically, multiple single-ended
amplifiers could be used in place of the instrumentation
amplifiers, reducing cost.
[0046] The electronic circuits need to be integrated with the
electrodes and battery, etc. to form the complete patch. Additional
electronics (not shown in the figures) may be added to enhance the
user interface, such as switches, LEDs, displays and mechanical
transducers. Other circuitry not shown may be included to improve
operation of the patch, such as clocks, timers, power supplies,
battery chargers and test Interfaces.
[0047] Although the description of the electronics above is based
on the measurement of differential voltages across a pair or pairs
of electrodes, the same electronics could be used to support a
sensor system featuring multiple electrode sensors employed in
various diagnostic testing methodologies described previously.
Patch Usability and Patient Experience
[0048] Many features of the integrated multi-electrode wireless
patch are particularly attractive for long-term monitoring
situations. In addition to battery operation, wireless connectivity
and "single patch" application, other features are Included to
maximize monitoring success. If the patch is not comfortable and
the patient removes it--even temporarily--any data collected may be
seriously compromised.
[0049] In order for a patch to perform long-term (multiple days to
weeks) monitoring, it must withstand moisture, including total
immersion in water. The following lists the target design criteria
(from most to least Important) the patch will meet under worst-case
moisture conditions, such as swimming in salt water: [0050] 1.
Cause no harm to the patient [0051] 2. No damage to the patch
electronics or reduction of battery life [0052] 3. Continue to
adhere to the patient's skin [0053] 4. Operate normally once the
patient has dried off [0054] 5. While wet, take data and store
temporarily on patch [0055] 6. While wet, continue to operate
normally, taking data and relaying it via radio to a Mobile
Device
[0056] Because of the electrical characteristics of water, the last
criterion is unlikely to be met, in which case, only items 1-5 will
apply. To meet these criteria will require a combination of
technologies, including but not limited to: [0057] 1. Conformal
coating on circuit board to protect traces and devices [0058] 2.
Sealing layers of plastic to protect battery and circuits [0059] 3.
Advanced adhesives and electrode gels compatible with human skin
for long-term use.
[0060] The usability features detailed above contemplate electrodes
placed on the skin. Additional requirements would be appropriate
for electrode sensors 12a-12n placed in contact with a biological
sample or tissue, immersed in a biological fluid, or placed in the
vascular system or urinary tract. Additional requirements would
include compatibility with blood, blood products, or urine,
including resistance to clotting and durability against corrosion
caused by various salts.
[0061] Additional details related to user experience are presented
in the following sections.
Patch Construction
[0062] A multi-electrode wireless patch can be built in a variety
of ways. Two broad categories of patch design are fully disposable
and partially reusable. In the fully disposable design, the entire
patch is discarded after a single use, while the reusable design
retains the electronics (and optionally, the battery) and only the
electrode component is discarded.
[0063] For the fully disposable wireless patch 400, one embodiment
uses a single flexible substrate 401, as shown in FIG. 4.
[0064] On the left side in the figure, electrodes 402a-402f are
fabricated on the substrate while electronic components 404-410 are
mounted on the right side. The connecting "bridge" 412 between the
two sides includes conductors to connect the electrodes to the
electronics. The patch is folded over and bonded at the perimeter.
A battery 408 (not shown) may be sandwiched between the top and
bottom or attached outside the substrate 401 and connected to the
electronics side 403 of the patch 408. The electrode side 405 now
becomes the bottom of the patch that attaches to the body. The
radio antenna 407 is fabricated as part of the circuitry on the
electronics side 403 of the patch 400.
[0065] For the partially reusable patch, two design variants are
described here. In the first variant, the battery and electrodes
are combined into a single module and the electronics is packaged
as a separate manufactured unit. The two units are connected
together by the patient or medical assistant at the time of the
patch application. When the monitoring is complete or the battery
runs out, the electrode+battery module is discarded and a new one
is attached to the electronics unit for continued operation.
[0066] The second partially reusable design variant combines the
electronics and a rechargeable battery in a reusable unit, with a
separate disposable electrode unit. This design has the advantage
of less waste, since the battery is not discarded after each use. A
disadvantage of this approach is the need to recharge the battery
between applications.
[0067] In both of these reusable designs, two substrates are
required--one for the electrodes and the other for electronic
circuits. The two substrates need to be bonded together with some
type of contact scheme between the electrodes and electronics, with
one such scheme described below.
[0068] FIG. 5 shows the essential components required of both
variants of the partially reusable patch 500 for a specific design.
As is seen, there are disposable components 502 that comprises a
front cover 506, an adhesive 508, a plastic member 510, and a rear
cover 512, while the reusable component is a circuit board 514. The
number of electrodes, size of electrodes and size of overall patch
will vary with different applications.
[0069] A quantity of conductive electrode gel is placed in each of
the holes in the foam and polyester sandwich 508-510 at the time of
manufacture. Additionally, thin sheets of plastic 506 and 512 are
applied to the front and rear of the disposable substrate to cover
and protect the gel from contamination until the patch is applied.
The entire sandwich comprising the disposable component will be
sealed in a package during manufacture to prevent dehydration of
the electrode gel.
[0070] When the patch is to be applied, the disposable component
502 will be removed from its packaging and the rear cover 512
removed. The user will then attach the electronics circuit board
514 to the exposed rear section, after aligning the conductive pads
with the gel areas. The adhesion of the gel alone may be
sufficiently strong to hold the circuit board to the disposable
component, or additional adhesive may be applied. Lastly, the front
protective liner 506 is removed, exposing the other side of the gel
contacts so the patch can then be placed on the patient's skin to
begin monitoring.
[0071] Because the substrate holes allow conduction between the
front (patient side) and rear (electronics side) patches of gel,
essentially an electric "via" is formed, but without requiring the
complicated processing steps needed for making a similar structure
in a conventional circuit board. Note that the use of a single
circular hole per "via" in the foam 508 or polyester 510 is not a
particular requirement of this scheme; different shapes as well as
multiple smaller holes per contact area (rather than a single
larger one) could function in the same manner and may have some
technical or other advantages.
[0072] The electronics substrate in this embodiment uses
conventional flexible or rigid circuit board technology. All of the
components are mounted on the top side of the board, with the
bottom reserved for the pattern of conductive metal that mates with
the pattern of conductive gel on the disposable electrode
substrate. The conductive metal pattern on the bottom is plated
with a metallic preparation (typically silver-based, although other
metals are possible) compatible with the gel used for the
electrodes.
[0073] When the monitoring period is over, the disposable electrode
sandwich 508-510 is peeled off the electronics substrate and
discarded. The reusable electronics substrate 504 can then be
disinfected, recharged and reapplied as required.
[0074] Because the disposable electrode substrate 502 does not
require a plated silver contact area, it can potentially be very
Inexpensive. It also could be fabricated with biodegradable
materials, such as cellulose or other organic polymers, to minimize
waste handling issues.
[0075] In yet another scheme, the patch substrate can have a three
dimensional profile, formed either by molding ridges into a
somewhat rigid substrate, or by selectively adding layers of
thicker material to a more flexible substrate. The third dimension
can be used to build in features for various purposes including
enhanced patient convenience and improved contact reliability.
[0076] For example, to minimize skin irritation over a long
monitoring period, the patch may contact the skin only in those
areas specifically where the either the electrodes or the adhesive
needs to touch. Between the seven sections shown in FIGS. 2a and 2b
for example, the patch could be elevated off the skin to allow air
and perspiration to move freely. With sufficiently flexible
substrates, these elevated "non-contacting" areas could also serve
as moveable joints that improve comfort for the patient.
[0077] Another possible use for a three dimensional profile is to
simplify the manufacturing process. An example is to form "wells"
In the substrate to contain the gel material as it is initially
applied during manufacture. The wells could also, once applied to a
patient's skin, act as barriers to external contaminants.
[0078] The wireless patch presented here can be used for detecting
and monitoring physiological voltage signals for various
applications such as the brainwave activity (EEG), heart health
(ECG), muscle performance (EMG) or a variety of other electric
characteristics of the human body. These methods play important
roles in emergency and acute care, long-term monitoring of chronic
conditions and even normal fitness training. Wireless sensors for
many other health applications can also be built by using this
multiple-electrode scheme for voltage sensing. For example, a body
impedance sensor can be built by injecting constant current into
the body through electrodes and measuring the voltage. Impedance
sensors are used to monitor a variety of human body conditions such
as hydration, dehydration, tissue state, wound state, etc.
Hydration measurements are used to monitor conditions such as CHF
(congestive heart failure). Dehydration measurements are useful to
monitor the conditions of firefighters, athletes, seniors and
military personnel.
[0079] Similar design schemes can also be pursued for electrode
sensors, which also can be made either fully disposable or
partially disposable. For example, in a fully disposable design, a
single substrate can also be used to support the sensor
electrode(s) structure and the electronics in a construction that
features a connecting bridge between the two. The unit may be
folded, bonded, and applied to, or inserted into, a connecting
receptacle integrated into a catheter or other device. In a
partially reusable design, the battery and electronics can be
Incorporated Into a reusable instrument or device. A separate
disposable electrode unit can be mounted on an appropriate
substrate and connected to the battery and electronics.
Multiple Electrode Patches Examples
Convenience of Placement
[0080] The electric signals to be monitored with E*G methods vary
from person to person, with the voltage levels, frequency ranges
and details of the waveforms, examples of some of those
differences. Other measurement-instance differences can add to the
variables, often making analysis considerably more difficult.
Example of instance issues are electrode placement, skin
preparation, electrode composition and conduction-enhancing
electrolytes (such as pastes or gels), if used.
[0081] The placement of electrodes for standard diagnostic E*G
methods has evolved over 150+ years to minimize the amount of
variability due to placement alone. In the case of ECGs, ten
electrodes are used in twelve wiring combinations to produce a
standard suite of traces for analysis by medical experts trained in
the method.
[0082] There are cardiac monitoring situations that do not require
all ten electrode connections, such as Holter and event monitors
that may use as few as two.
[0083] If the two electrodes needed for the "minimal" case are
physically connected together, such as in a single adhesive patch
with two conductive gel areas, and applied to the skin, the
relative location of the two electrodes would require the patch be
applied at a specific angle with respect to the expected signal to
be measured for best signal quality. The multiple electrode
structure described above simplifies placement on the body while
attaining high signal quality.
Coverage of Multiple Views
[0084] In traditional multiple-lead ECG measurement systems,
several wired electrodes are placed on the body to get different
"views" of the potential electric vectors traveling through the
body at different angles and different locations. In the
multi-electrode patch scheme, in accordance with the present
invention, these views are captured by using the appropriate
electrode pairs within a single patch at one location. For cases
where a single patch is unable to resolve all the views required,
additional patches may be added to different locations on the
body.
[0085] For a six electrode (plus reference ground) patch, three
different views are possible by measuring the signals across
opposite pairs of electrodes, as shown in FIG. 6a. Using adjacent
pairs of electrodes, six more combinations are possible, but the
measurement angles are all duplicates of the original three, so
using adjacent pairs is less useful. However, by connecting between
non-opposite, non-adjacent pairs, three more unique views are
possible, bringing the total to six. As shown in the figure, the
views all correspond to six of the standard measurement angles
obtained from a 12-lead ECG.
[0086] FIG. 6b shows the same combination of views, but with the
patch turned 60 degrees. Although the same six views are covered,
this orientation may be preferable if only three views are deemed
necessary for successful monitoring.
[0087] Even though the multi-electrode patch reduces or even
eliminates the requirement for controlling the angle of placement
on the patient, the complexity of the electronics and the quality
of the signal could still be related factors. In addition, the
patient experience could possibly be improved if there was an
indication that the patch was placed "correctly", especially in a
situation where it is self-applied. To address this issue, FIG. 7
shows an example of a graphic aid--a heart--imprinted on the top of
the patch to help the patient orient the patch on their body.
[0088] These figures show only certain possibilities in the case of
ECG. The multiple electrode schemes can be used in many other ways
in case of ECG, EEG, EMG and other applications, such as an
Impedance sensor.
Obtaining Enhanced Physiological Signals
[0089] Another application of multiple-electrodes is the
enhancement of physiological signal being monitored (e.g. ECG). The
signals from multiple electrodes can be combined, and various
signal processing algorithms, such as averaging and filtering can
be used to enhance the quality of signal.
Electrode Sensors
[0090] Some of the measurements of physiological significance are
also based on electrodes that measure a conductance change in the
presence of a particular analyte. Examples include glucose,
electrolytes, blood gases, and other biosensors where selectivity
is based on the use of various reagents such as enzymes, proteins,
or oligonucleotides. Wireless electrode sensor(s) allow for
enhanced patient mobility in all settings. In acute care
environments, wireless electrode sensor(s) have additional
benefits: reducing the risk of hospital-acquired infections from
contaminated wires; decluttering the workspace, and the reduction
of signal noise introduced by the presence of wires.
[0091] All these are some of the examples of the multiple-electrode
scheme to achieve various objectives of an integrated wireless
physiological monitoring system. There are many other
possibilities.
SUMMARY
[0092] A wireless sensor has been described that uses a fresh
perspective of wireless physiological monitoring, as opposed to
simply migrating the "wired links" of today's wired physiological
monitoring systems to "wireless links". The invention relates to
many different technologies to define a wireless sensor that is
highly integrated, small, and low cost. An integrated
multi-electrode scheme is proposed to attain many of these
advantages. Certain manufacturing methods are proposed, and the
concepts of disposable and reusable options are discussed. A sensor
in accordance with the present invention can be utilized to monitor
a variety of applications relating to health, disease progression,
fitness and wellness. Some of the specific applications include the
monitoring of ECG, EEG, EMG, glucose, electrolytes, body hydration,
dehydration, tissue state and wounds.
[0093] Although the present invention has been described in
accordance with the embodiments shown, one of ordinary skill in the
art will readily recognize that there could be variations to the
embodiments and those variations would be within the spirit and
scope of the present invention. Accordingly, many modifications may
be made by one of ordinary skill in the art without departing from
the spirit and scope of the appended.
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