U.S. patent application number 15/887886 was filed with the patent office on 2018-08-09 for measurement of susceptibility to diabetic foot ulcers.
This patent application is currently assigned to BRUIN BIOMETRICS, LLC. The applicant listed for this patent is BRUIN BIOMETRICS, LLC. Invention is credited to Sara BARRINGTON, Martin F. BURNS, Graham O. ROSS.
Application Number | 20180220954 15/887886 |
Document ID | / |
Family ID | 63038420 |
Filed Date | 2018-08-09 |
United States Patent
Application |
20180220954 |
Kind Code |
A1 |
BURNS; Martin F. ; et
al. |
August 9, 2018 |
MEASUREMENT OF SUSCEPTIBILITY TO DIABETIC FOOT ULCERS
Abstract
The present disclosure provides apparatuses and methods for
measuring capacitance as an indication of susceptibility to the
formation of a diabetic foot ulcer.
Inventors: |
BURNS; Martin F.; (Los
Angeles, CA) ; BARRINGTON; Sara; (Thousand Oaks,
CA) ; ROSS; Graham O.; (Glen Mills, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BRUIN BIOMETRICS, LLC |
Los Angeles |
CA |
US |
|
|
Assignee: |
BRUIN BIOMETRICS, LLC
Los Angeles
CA
|
Family ID: |
63038420 |
Appl. No.: |
15/887886 |
Filed: |
February 2, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62454482 |
Feb 3, 2017 |
|
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62521917 |
Jun 19, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 27/2605 20130101;
A61B 5/447 20130101; A61F 13/064 20130101; A61B 5/6829 20130101;
A61B 5/0531 20130101; A61B 5/0537 20130101; A61B 5/4878 20130101;
A61B 5/01 20130101; A61B 5/445 20130101 |
International
Class: |
A61B 5/00 20060101
A61B005/00; A61F 13/06 20060101 A61F013/06; A61B 5/053 20060101
A61B005/053 |
Claims
1. An apparatus for assessing susceptibility of tissue to formation
of a diabetic foot ulcer, said apparatus comprising: a plurality of
electrodes embedded on a substrate, wherein a pair of said
electrodes is capable of forming a capacitive sensor configured to
measure a first capacitance of a first region of tissue proximate
to said capacitive sensor, a drive circuit electronically coupled
to said electrodes, a processor electronically coupled to said
drive circuit, and a non-transitory computer-readable medium
electronically coupled to said processor and comprising
instructions stored thereon that, when executed on said processor,
perform the steps of: receiving information regarding said measured
first capacitance from said drive circuit, comparing said measured
first capacitance to a first reference value, and providing a
signal if said measured first capacitance differs from said first
reference value by an amount greater than a first predetermined
threshold.
2. The apparatus of claim 1, wherein said first reference value is
predetermined.
3. The apparatus of claim 1, wherein said first reference value is
determined by measurement of said first capacitance at a time when
said first region of tissue is healthy.
4. The apparatus of claim 1, wherein said first reference value is
determined from measurements of said first capacitance at said
first region of tissue at one or more times prior to the most
recent measurement of said first capacitance.
5. The apparatus of claim 1, wherein said first reference value is
determined by a measurement from a bisymmetric location. Page 3
6. The apparatus of claim 1, wherein said first reference value is
a measurement of a second capacitance of a second region of tissue
that is separated from said first region of tissue.
7. The apparatus of claim 6, wherein said second region of tissue
is known to be healthy.
8. The apparatus of claim 6, wherein said second capacitance is
measured at approximately the same time as said first
capacitance.
9. The apparatus of claim 1, the apparatus further comprising one
or more temperature sensors that are configured to measure a
temperature of said first region of tissue and are coupled to said
processor, wherein: said instructions further comprise: a step of
receiving information regarding said measured temperature from said
one or more temperature sensors, and a step of comparing said
measured temperature to a second reference value, and a step of
providing a signal comprising providing said signal if said
measured first capacitance differs from said first reference value
by an amount greater than said predetermined first threshold and
said measured temperature differs from said second reference value
by an amount greater than a predetermined second threshold.
10. The apparatus of claim 1, the apparatus further comprising one
or more optical sensors configured to image an underside of a foot
of a patient while said patient is standing on said substrate.
11. A method for assessing susceptibility of tissue to formation of
a diabetic foot ulcer, said method comprising: obtaining a first
capacitance value at a first location of a patient's skin;
obtaining a temperature measurement at said first location of a
patient's skin; and determining that said first location of a
patient's skin is susceptible to formation of a diabetic foot ulcer
when said first capacitance value differs from a first reference
value by an amount greater than a first predetermined threshold and
said temperature measurement differs from a second reference value
by an amount greater than a second predetermined threshold.
12. The method of claim 11, wherein said first reference value is
predetermined.
13. The method of claim 11, wherein said first reference value is
determined by measurement of said first capacitance at a time when
said first location of a patient's skin is healthy.
14. The method of claim 11, wherein said first reference value is
determined from measurements of said first capacitance at said
first location of a patient's skin at one or more times prior to
the most recent measurement of said first capacitance.
15. The method of claim 11, wherein said first reference value is a
measurement of a second capacitance of a second location of a
patient's skin that is separated from said first location of a
patient's skin.
16. The method of claim 15, wherein said second region of a
patient's skin is known to be healthy.
17. The method of claim 15, wherein said second capacitance is
measured at approximately the same time as said first
capacitance.
18.-30. (canceled)
31. The apparatus of claim 1, the apparatus further comprising: at
least two stimulus electrodes disposed on the substrate such that a
portion of a current passing between a pair of the stimulus
electrodes will pass through a portion of the first region of
tissue; and an external controller electrically connected to the at
least two stimulus electrodes and configured to provide a
therapeutic stimulus to the first region of tissue.
32. The integrated apparatus of claim 31, wherein the external
controller is further configured to control the two electrodes to
detect conductive contact with the patient's skin during a sensing
phase and to apply the therapeutic stimulus to the patient during a
therapeutic phase.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority of U.S.
Provisional Application 62/454,482 filed Feb. 3, 2017, and U.S.
Provisional Application 62/521,917 filed Jun. 19, 2017, each of
which is herein incorporated by reference in its entirety.
FIELD
[0002] The present disclosure provides apparatus and methods for
assessment of a foot of a patient at risk for development of
diabetic foot ulcers.
DESCRIPTION OF THE RELATED ART
[0003] Diabetic foot ulcers are responsible for more
hospitalizations than any other complication of diabetes.
Nonenzymatic glycation induced by an elevated level of blood sugar
causes ligaments to stiffen and increases cross-linking in
collagen. These conditions can lead to damage to cellular walls and
blood vessels that result in an initial increase the amount of
extracellular fluid (ECF). Peripheral neuropathy causes loss of
protective sensation and loss of coordination of muscle groups in
the foot and leg. The neuropathy can cause an increase in the
mechanical stresses within the foot during ambulation and standing
that, combined with the weakened tissue induced by the diabetes,
will progress to tissue death if the stress is not reduced. The
neuropathy also reduces the patient's ability to perceive pain that
is normally associated with the stress and tissue damage, thereby
allowing the condition to progress.
[0004] Every year, approximately 5% of diabetics develop a foot
ulcer and 1% will require amputation of a digit or some portion of
the foot. Long term, 15% of patients with diabetes will develop a
foot ulcer and 12-24% will require amputation. Diabetes is the
leading cause of nontraumatic lower extremity amputations in the
United States. 20-30% of the overall cost of treating diabetes is
related to the treatment and healing of foot ulcers after they
occur.
[0005] The current approach to the prevention of diabetic foot
ulcers is patient education, foot skin and toenail care,
appropriate footwear selection, and proactive surgical
intervention. A means of detecting a pre-ulcer condition would
enable implementation of preventive techniques such as offloading
and improved hygiene.
SUMMARY
[0006] In an aspect, the present disclosure provides for, and
includes, an apparatus for assessing susceptibility of tissue to
formation of a diabetic foot ulcer, the apparatus comprising: a
plurality of electrodes embedded on a substrate, where a pair of
the electrodes is capable of forming a capacitive sensor configured
to measure a first capacitance of a first region of tissue
proximate to the capacitive sensor, a circuit electronically
coupled to the electrodes, a processor electronically coupled to
the circuit, and a non-transitory computer-readable medium
electronically coupled to the processor and comprising instructions
stored thereon that, when executed on the processor, perform the
steps of: receiving information from the circuit regarding the
measured first capacitance from the capacitive sensor, comparing
the measured first capacitance to a first reference value, and
providing a signal if the measured first capacitance differs from
the first reference value by an amount greater than a first
predetermined threshold.
[0007] In one aspect, the present disclosure provides for, and
includes, a method for assessing susceptibility of tissue to
formation of a diabetic foot ulcer, the method comprising:
[0008] obtaining a first capacitance value at a first location of a
patient's skin; obtaining a temperature measurement at the first
location of a patient's skin; and determining that the first
location of a patient's skin is susceptible to formation of a
diabetic foot ulcer when the first capacitance value differs from
the first reference value by an amount greater than a first
predetermined threshold and the temperature measurement differs
from the second reference value by an amount greater than a second
predetermined threshold.
[0009] In an aspect, the present disclosure provides for, and
includes, a method for assessing susceptibility of tissue to
formation of a diabetic foot ulcer, the method comprising:
obtaining a first sub-epidermal moisture (SEM) value at a first
location of a patient's skin; obtaining a temperature measurement
at the first location of a patient's skin; and determining that the
first location of a patient's skin is susceptible to formation of a
diabetic foot ulcer when the first SEM value differs from the first
reference value by an amount greater than a first predetermined
threshold and the temperature measurement differs from the second
reference value by an amount greater than a second predetermined
threshold.
[0010] In one aspect, the present disclosure provides for, and
includes, an integrated apparatus for treating a diabetic foot
ulcer in a patient in need thereof, said apparatus comprising: a
plurality of sensors disposed on a flexible substrate, wherein the
plurality of sensors are configured to measure sub-epidermal
moisture (SEM) values at respective locations of the patient's
skin; two electrodes disposed on the flexible substrate; and an
external controller electrically connected to the two electrodes,
where the external controller controls the two electrodes to detect
conductive contact with the patient's skin during a SEM measurement
period, and the external controller controls the two electrodes to
apply a therapeutic stimulus to the patient during a therapeutic
phase.
[0011] In an aspect, the present disclosure provides for, and
includes, an integrated apparatus for treating a diabetic foot
ulcer in a patient in need thereof, the apparatus comprising: a
sensor comprising two electrodes disposed on a flexible substrate
such that a current passing between the electrodes will pass
through tissue proximate to a location of the patient's skin; and
an external controller electrically connected to the two
electrodes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Aspects of the disclosure are herein described, by way of
example only, with reference to the accompanying drawings. With
specific reference now to the drawings in detail, it is stressed
that the particulars shown are by way of example and are for
purposes of illustrative discussion of aspects of the disclosure.
In this regard, the description and the drawings, considered alone
and together, make apparent to those skilled in the art how aspects
of the disclosure may be practiced.
[0013] FIG. 1A depicts the anatomy of a foot.
[0014] FIG. 1B is an enlarged view of area A of FIG. 1A.
[0015] FIG. 2A depicts an initial open ulcer at time_0.
[0016] FIG. 2B depicts the pressure profile created in the
condition of FIG. 2A.
[0017] FIG. 2C depicts the same region of tissue of FIG. 2A at
time_1.
[0018] FIG. 2D depicts the same region of tissue of FIGS. 2A and 2C
at time_2.
[0019] FIG. 3A discloses a toroidal bioimpedance sensor.
[0020] FIG. 3B discloses an idealized field map created by the
toroidal sensor of FIG. 3A when activated.
[0021] FIG. 3C discloses a SEM scanner that comprises the sensor of
FIG. 3A.
[0022] FIG. 4 is a first exemplary array of electrodes.
[0023] FIG. 5 is an exemplary array of electrodes according to the
present disclosure.
[0024] FIG. 6A illustrates a first example of how the array of
electrodes disclosed in FIG. 5 is configured to form a bioimpedance
sensor according to the present disclosure.
[0025] FIG. 6B illustrates a first example of how the array of
electrodes disclosed in FIG. 5 is configured to form a bioimpedance
sensor according to the present disclosure.
[0026] FIG. 6C illustrates an example of a first sensor formed in
an array of electrodes according to the present disclosure.
[0027] FIG. 6D illustrates an example of how a second sensor is
formed to overlap with the first sensor of FIG. 6C according to the
present disclosure.
[0028] FIG. 6E shows an example of how sensors as shown in FIG. 6A
are formed from an array of electrodes that is larger than the
portion of the patient's skin that is being positioned against the
array, according to the present disclosure.
[0029] FIG. 6F illustrates locations on the left and right feet for
SEM measurements according to the present disclosure.
[0030] FIG. 6G is a plot of SEM values associated with known
relative locations for identifying bisymmetric locations according
to the present disclosure.
[0031] FIG. 7A depicts a first example of a mat assembly that
incorporates a plurality of bioimpedance sensors according to the
present disclosure.
[0032] FIG. 7B depicts a second example of a mat assembly that
comprises arrays of electrical sensors, according to the present
disclosure, disposed so as to underlie the left and right feet,
respectively, of a patient while standing on the mat assembly.
[0033] FIG. 7C depicts a third example of a mat assembly that
comprises one or more sensors disposed within each of the outlines
according to the present disclosure.
[0034] FIG. 8A discloses a foot cover that incorporates
bioimpedance sensors according to the present disclosure.
[0035] FIG. 8B is a cutaway view of the foot cover of FIG. 8A,
showing the location of the bioimpedance sensors according to the
present disclosure.
[0036] FIG. 9 disclose a sandal that incorporates bioimpedance
sensors according to the present disclosure.
[0037] FIG. 10A depicts a first example configuration of the
addressable electrodes of FIG. 5 that vary the performance
capabilities of the sensor according to the present disclosure.
[0038] FIG. 10B depicts a second example configuration of the
addressable electrodes of FIG. 5 that vary the performance
capabilities of the sensor according to the present disclosure.
[0039] FIG. 10C depicts a third example configuration of the
addressable electrodes of FIG. 5 that vary the performance
capabilities of the sensor according to the present disclosure.
[0040] FIG. 11A shows an exemplary configuration of a substrate
shaped to be positioned in a known position on a patient's skin
according to the present disclosure.
[0041] FIG. 11B shows a front view of the exemplary configuration
of FIG. 11A according to the present disclosure.
[0042] FIG. 12 depicts a schematic depiction of an integrated
system for measurement, evaluation, storage, and transfer of SEM
values according to the present disclosure.
[0043] FIG. 13 depicts a sensing band according to the present
disclosure.
[0044] FIGS. 14A, 14B, and 14C depict an integrated sensor and
stimulator assembly suitable for treatment of a pressure ulcer,
according to the present disclosure.
[0045] FIG. 14D depicts a bandage assembly suitable for treatment
of a pressure ulcer, according to the present disclosure.
[0046] FIG. 15A illustrates an exemplary method for taking SEM
measurements starting at the posterior heel in accordance with the
present disclosure.
[0047] FIG. 15B illustrates an exemplary method for taking SEM
measurements starting at the lateral heel in accordance with the
present disclosure.
[0048] FIG. 15C illustrates an exemplary method for taking SEM
measurements starting at the medial heel in accordance with the
present disclosure.
DETAILED DESCRIPTION
[0049] The present disclosure describes measurement of various
electrical characteristics and derivation of SEM values indicative
of an increase in the amount of ECF and the application of this
information to the assessment of susceptibility to diabetic foot
ulcers as well as treatment of ulcers.
[0050] Diabetic foot ulcers are known to occur in areas subject to
repetitive moderate loads, particularly in areas where bony
portions of the foot apply transfer body weight to the adjacent
tissue while standing. Damage may initially occur in tissue below
the skin and is, therefore, not detectable by visual inspection.
The initial damage will release fluid into the extracellular
spaces, which can be detected through the measurement of electrical
properties of the sub-epidermal tissue, for example the capacitance
of the tissue. Monitoring the ECF in at-risk areas will detect
deterioration of the tissue that, if left unchecked, will progress
to an open ulcer.
[0051] This description is not intended to be a detailed catalog of
all the different ways in which the disclosure may be implemented,
or all the features that may be added to the instant disclosure.
For example, features illustrated with respect to one embodiment
may be incorporated into other embodiments, and features
illustrated with respect to a particular embodiment may be deleted
from that embodiment. Thus, the disclosure contemplates that in
some embodiments of the disclosure, any feature or combination of
features set forth herein can be excluded or omitted. In addition,
numerous variations and additions to the various embodiments
suggested herein will be apparent to those skilled in the art in
light of the instant disclosure, which do not depart from the
instant disclosure. In other instances, well-known structures,
interfaces, and processes have not been shown in detail in order
not to unnecessarily obscure the invention. It is intended that no
part of this specification be construed to effect a disavowal of
any part of the full scope of the invention. Hence, the following
descriptions are intended to illustrate some particular embodiments
of the disclosure, and not to exhaustively specify all
permutations, combinations and variations thereof
[0052] Unless otherwise defined, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this disclosure belongs. The
terminology used in the description of the disclosure herein is for
the purpose of describing particular aspects or embodiments only
and is not intended to be limiting of the disclosure.
[0053] All publications, patent applications, patents and other
references cited herein are incorporated by reference in their
entireties for the teachings relevant to the sentence and/or
paragraph in which the reference is presented. References to
techniques employed herein are intended to refer to the techniques
as commonly understood in the art, including variations on those
techniques or substitutions of equivalent techniques that would be
apparent to one of skill in the art.
[0054] U.S. patent application Ser. No. 14/827,375 discloses an
apparatus that uses radio frequency (RF) energy to measure the
sub-epidermal capacitance using a bipolar sensor similar to the
sensor 90 shown in FIG. 3A, where the sub-epidermal capacitance
corresponds to the moisture content of the target region of skin of
a patient. The '375 application also discloses an array of these
bipolar sensors of various sizes.
[0055] U.S. patent application Ser. No. 15/134,110 discloses an
apparatus for measuring sub-epidermal moisture (SEM) similar to the
device shown in FIG. 3C, where the device emits and receives an RF
signal at a frequency of 32 kHz through a single coaxial sensor and
generates a bioimpedance signal, then converts this signal to a SEM
value.
[0056] Both U.S. patent application Ser. Nos. 14/827,375 and
15/134,110 are incorporated herein by reference in their
entireties.
[0057] Unless the context indicates otherwise, it is specifically
intended that the various features of the disclosure described
herein can be used in any combination. Moreover, the present
disclosure also contemplates that in some embodiments of the
disclosure, any feature or combination of features set forth herein
can be excluded or omitted.
[0058] The methods disclosed herein include and comprise one or
more steps or actions for achieving the described method. The
method steps and/or actions may be interchanged with one another
without departing from the scope of the present invention. In other
words, unless a specific order of steps or actions is required for
proper operation of the embodiment, the order and/or use of
specific steps and/or actions may be modified without departing
from the scope of the present invention.
[0059] As used in the description of the disclosure and the
appended claims, the singular forms "a," "an" and "the" are
intended to include the plural forms as well, unless the context
clearly indicates otherwise.
[0060] As used herein, "and/or" refers to and encompasses any and
all possible combinations of one or more of the associated listed
items, as well as the lack of combinations when interpreted in the
alternative ("or").
[0061] The terms "about" and "approximately" as used herein when
referring to a measurable value such as a length, a frequency, or a
SEM value and the like, is meant to encompass variations of
.+-.20%, .+-.10%, .+-.5%, .+-.1%, .+-.0.5%, or even .+-.0.1% of the
specified amount.
[0062] As used herein, phrases such as "between X and Y" and
"between about X and Y" should be interpreted to include X and Y.
As used herein, phrases such as "between about X and Y" mean
"between about X and about Y" and phrases such as "from about X to
Y" mean "from about X to about Y."
[0063] As used herein, the term "sub-epidermal moisture" or "SEM"
refers to the increase in tissue fluid and local edema caused by
vascular leakiness and other changes that modify the underlying
structure of the damaged tissue in the presence of continued
pressure on tissue, apoptosis, necrosis, and the inflammatory
process.
[0064] As used herein, a "system" may be a collection of devices in
wired or wireless communication with each other.
[0065] As used herein, "interrogate" refers to the use of
radiofrequency energy to penetrate into a patient's skin.
[0066] As used herein, a "patient" may be a human or animal
subject.
[0067] As used herein, "healthy" may describes tissue that does not
exhibit symptoms of damage to cellular walls or blood vessels,
where the presence of an increased amount of ECF is an indication
of such damage.
[0068] As used herein, "extracellular fluid" or "ECF" refers to
bodily fluid contained outside of cells, including plasma,
interstitial fluid, and transcellular fluid.
[0069] As used herein, "susceptible to formation of a diabetic foot
ulcer" may describe tissue that exhibit symptoms of damage to
cellular walls or blood vessels, such as edema or an increased
amount of ECF, yet no open ulcer is present.
[0070] As used herein, "time_0" refers to an initial time point,
for example, when an open ulcer is first detected.
[0071] As used herein, "time_1" refers to a time point later than
time_0.
[0072] As used herein, "time 2" refers to a time point later than
time_1.
[0073] FIG. 1A is a side view of a portion of the anatomy of a foot
20. The areas of the foot that are most likely to develop a
diabetic foot ulcer are the heel, located below the calcaneus bone
21, and the pad of the foot, located under the metatarsal bone
22.
[0074] FIG. 1B is an enlarged view of the area "A" of FIG. 1A. The
ends of the metatarsal bone 22 and the adjoining phalange bone 23
are shown in proximity to the skin 24 of the sole of the foot 20. A
portion of the body weight of the patient creates a compressive
force 30 applied by the metatarsal bone 22 to the tissue in region
40. Force 30 is opposed by resistive force 36 applied by the floor
to the skin 24 under region 40 to support the patient. Muscular
activity by the patient, for example walking or simply balancing on
their feet while standing, creates shear force 32 between the
metatarsal bone 22 and tissue 40 as well as the resisting shear
force 38 between the floor and the skin 24. Thus, the tissue in
region 40 is simultaneously subject to both compression and shear
forces.
[0075] It has been observed that a healthy patient will shift their
weight from foot to foot as well as shift their center of mass
relative to their feet while standing stationary. This limits the
duration of time during which forces are applied to any particular
region of tissue. Peripheral neuropathy, however, reduces the
sensation in the tissue that is created by the patient's weight
and, therefore, reduces the unconscious shifting of their weight
and patients suffering from peripheral neuropathy are observed to
lack the normal motion while standing. This leads to extended
period of time of continuous compressive force being applied to
local areas of tissue, such as region 40. This extended exposure to
moderate levels of force is thought to contribute to the formation
of ulcers in these areas.
[0076] FIGS. 2A, 2B, 2C, and 2D depict the conditions and
progression of an open ulcer. FIG. 2A depicts an initial open ulcer
50A at time_0. The ulcer 50A is surrounded by a ring of increased
pressure 52A.
[0077] FIG. 2B shows the pressure profile created in the condition
of FIG. 2A. The force applied by the floor, or by a shoe worn by
the patient, is applied as a locally uniform pressure 56 to the
skin 24 of the foot 20. The applied pressure 56 is opposed
internally by forces 53. No pressure can be applied over the ulcer
50, as the tissue has sloughed away. Thus, the internal forces in
the toroidal region 52A increase to a peak 54 to pick up the force
that would have been applied to the ulcer 50. This peak force 54 is
high enough to cause further tissue damage in the ring 52A. A
callus will commonly form over the region 52A as the body attempts
to protect itself from the increased pressure. The tissue below the
callus, however, is still being damaged and will exhibit an
increase in ECF.
[0078] FIG. 2C depicts the same region of tissue at time_1 that is
subsequent to time_0. The increased level of pressure in region 52A
led to tissue death in region 52A and the tissue in region 52 has
sloughed away so that the ulcer 50B is larger than the prior ulcer
50A. The applied pressure 56 has not changed, however, so now the
tissue in the region 52B around the larger ulcer 50B must pick up
even more force. This accelerates the expansion of the ulcer 50 as
the tissue in are region 52B dies quicker under the higher applied
load.
[0079] FIG. 2D depicts the same region of tissue as FIGS. 2A and
2C, now at time_2 that is subsequent to time_1. The ulcer 50 has
grown to size 50C and the region 52C of increased pressure is large
than the prior regions 52A, 52B.
[0080] In the situation shown in FIG. 2A, where an ulcer has
formed, interventional therapies will be introduced to prevent the
growth of the ulcer 50 and allow the body to heal the open ulcer
50. Therapies may involve placing pressure-relieving pads around
the ulcer to spread the pressure 56 over a larger region of healthy
tissue and eliminate the peak 54 that leads to further damage.
Determining whether the therapy is working, however, is only
possible by observation over time that the ulcer is not
progressing.
[0081] FIG. 3A discloses a toroidal bioimpedance sensor 90. In this
exemplary configuration, a center electrode 110 is surrounded by a
ring electrode 120. Without being limited to a particular theory,
the gap between the two electrodes affects the depth of field
penetration into the substrate below sensor 90. In one aspect, a
ground plane (not visible in FIG. 3A), is parallel to and separate
from the plane of the electrodes and, in an aspect, extends beyond
the outer diameter of ring electrode 120. Without being limited to
a particular theory, a ground plane may limit the field between
electrodes 110 and 120 to a single side of the plane of electrodes
110 and 120 that is on the opposite side of the plane of electrodes
110 and 120 from the ground plane.
[0082] FIG. 3B discloses an idealized field map created by a
toroidal sensor of FIG. 3A when activated by a drive circuit (not
shown in FIG. 3B). When an electric voltage is applied across
electrodes 110 and 120, an electric field 140 is generated between
electrodes 110 and 120 that extends outward from the plane of
electrodes 110 and 120 to a depth of field 150. The diameter of
center electrode 110, the inner and outer diameters of ring
electrode 120, and the gap between electrodes 110 and 120 may be
varied to change characteristics of the field 140, for example the
depth of field 150.
[0083] In use, a drive circuit can measure an electrical property
or parameter that comprises one or more electrical characteristics
selected from the group consisting of a resistance, a capacitance,
an inductance, an impedance, a reluctance, and other electrical
characteristics as sensed by electric field 140. Depending on the
type of drive circuit being employed in an apparatus, a sensor of
an apparatus may be a bipolar radiofrequency sensor, a bioimpedance
sensor, a capacitive sensor, or an SEM sensor. In an aspect, a
measured electrical parameter is related to the moisture content of
the epidermis of a patient at a depth that is determined by the
geometry of electrodes 110 and 120, the frequency and strength of
electrical field 140, and other operating characteristics of the
apparatus drive circuit. In one aspect, a measured moisture content
is equivalent to the SEM content with a value on a predetermined
scale. In an aspect, a predetermined scale may range from 0 to 20,
such as from 0 to 1, from 0 to 2, from 0 to 3, from 0 to 4, from 0
to 5, from 0 to 6, from 0 to 7, from 0 to 8, from 0 to 9, from 0 to
10, from 0 to 11, from 0 to 12, from 0 to 13, from 0 to 14, from 0
to 15, from 0 to 16, from 0 to 17, from 0 to 18, from 0 to 19. In
one aspect, a predetermined scaled can be scaled by a factor or a
multiple based on the values provided herein. In an aspect,
multiple measurements are taken while varying one or more of these
operating characteristics between readings, thereby providing
information related to the moisture content at various depths of
the skin.
[0084] One or more regions may be defined on a body. In an aspect,
measurements made within a region are considered comparable to each
other. A region may be defined as an area on the skin of the body
wherein measurements may be taken at any point within the area. In
an aspect, a region corresponds to an anatomical region (e.g.,
heel, ankle, lower back). In an aspect, a region may be defined as
a set of two or more specific points relative to anatomical
features wherein measurements are taken only at the specific
points. In an aspect, a region may comprise a plurality of
non-contiguous areas on the body. In an aspect, the set of specific
locations may include points in multiple non-contiguous areas.
[0085] In an aspect, a region is defined by surface area. In an
aspect, a region may be, for example, between 5 and 200 cm.sup.2,
between 5 and 100 cm.sup.2, between 5 and 50 cm.sup.2, or between
10 and 50 cm.sup.2, between 10 and 25 cm.sup.2, or between 5 and 25
cm.sup.2.
[0086] In an aspect, measurements may be made in a specific pattern
or portion thereof. In an aspect, the pattern of readings is made
in a pattern with the target area of concern in the center. In an
aspect, measurements are made in one or more circular patterns of
increasing or decreasing size, T-shaped patterns, a set of specific
locations, or randomly across a tissue or region. In an aspect, a
pattern may be located on the body by defining a first measurement
location of the pattern with respect to an anatomical feature with
the remaining measurement locations of the pattern defined as
offsets from the first measurement position.
[0087] In an aspect, a plurality of measurements are taken across a
tissue or region and the difference between the lowest measurement
value and the highest measurement value of the plurality of
measurements is recorded as a delta value of that plurality of
measurements. In an aspect, 3 or more, 4 or more, 5 or more, 6 or
more, 7 or more, 8 or more, 9 or more, or 10 or more measurements
are taken across a tissue or region.
[0088] In an aspect, a threshold may be established for at least
one region. In an aspect, a threshold of 0.2, 0.3, 0.4, 0.5, 0.6,
0.7, 0.8, 0.9, or other value may be established for the at least
one region. In an aspect, a delta value is identified as
significant when the delta value of a plurality of measurements
taken within a region meets or exceeds a threshold associated with
that region. In an aspect, each of a plurality of regions has a
different threshold. In an aspect, two or more regions may have a
common threshold.
[0089] In an aspect, a threshold has both a delta value component
and a chronological component, wherein a delta value is identified
as significant when the delta value is greater than a predetermined
numerical value for a predetermined portion of a time interval. In
an aspect, the predetermined portion of a time interval is defined
as a minimum of X days wherein a plurality of measurements taken
that day produces a delta value greater than or equal to the
predetermined numerical value within a total of Y contiguous days
of measurement. In an aspect, the predetermined portion of a time
interval may be defined as 1, 2, 3, 4, or 5 consecutive days on
which a plurality of measurements taken that day produces a delta
value that is greater than or equal to the predetermined numerical
value. In an aspect, the predetermined portion of a time interval
may be defined as some portion of a different specific time period
(weeks, month, hours etc.).
[0090] In an aspect, a threshold has a trending aspect wherein
changes in the delta values of consecutive pluralities of
measurements are compared to each other. In an aspect, a trending
threshold is defined as a predetermined change in delta value over
a predetermined length of time, wherein a determination that the
threshold has been met or exceeded is significant. In an aspect, a
determination of significance will cause an alert to be issued. In
an aspect, a trend line may be computed from a portion of the
individual measurements of the consecutive pluralities of
measurements. In an aspect, a trend line may be computed from a
portion of the delta values of the consecutive pluralities of
measurements.
[0091] In an aspect, the number of measurements taken within a
single region may be less than the number of measurement locations
defined in a pattern. In an aspect, a delta value will be
calculated after a predetermined initial number of readings, which
is less than the number of measurement locations defined in a
pattern, have been taken in a region and after each additional
reading in the same region, wherein additional readings are not
taken once the delta value meets or exceeds the threshold
associated with that region.
[0092] In an aspect, the number of measurements taken within a
single region may exceed the number of measurement locations
defined in a pattern. In an aspect, a delta value will be
calculated after each additional reading.
[0093] In an aspect, a quality metric may be generated for each
plurality of measurements. In an aspect, this quality metric is
chosen to assess the repeatability of the measurements. In an
aspect, this quality metric is chosen to assess the skill of the
clinician that took the measurements. In an aspect, the quality
metric may include one or more statistical parameters, for example
an average, a mean, or a standard deviation. In an aspect, the
quality metric may include one or more of a comparison of
individual measurements to a predefined range. In an aspect, the
quality metric may include comparison of the individual
measurements to a pattern of values, for example comparison of the
measurement values at predefined locations to ranges associated
with each predefined location. In an aspect, the quality metric may
include determination of which measurements are made over healthy
tissue and one or more evaluations of consistency within this
subset of "healthy" measurements, for example a range, a standard
deviation, or other parameter.
[0094] In one aspect, a measurement, for example, a threshold
value, is determined by SEM Scanner Model 200 (Bruin Biometrics,
LLC, Los Angeles, Calif.). In another aspect, a measurement is
determined by another SEM scanner.
[0095] In an aspect, a measurement value is based on a capacitance
measurement by reference to a reference device. In an aspect, a
capacitance measurement can depend on the location and other
aspects of any electrode in a device. Such variations can be
compared to a reference SEM device such as an SEM Scanner Model 200
(Bruin Biometrics, LLC, Los Angeles, Calif.). A person of ordinary
skill in the art understands that the measurements set forth herein
can be adjusted to accommodate a difference capacitance range by
reference to a reference device.
[0096] FIG. 3C provides top and bottom views of a SEM scanner 170
that contains electronics that drive sensor 174, which is similar
to sensor 90 of FIG. 3A, and measure a capacitance between
electrodes 110 and 120. This capacitance may be converted to a SEM
value that is displayed on display 176.
[0097] Aspects of sensor 90 and SEM scanner 170 are disclosed in WO
2016/172263, from which the U.S. patent application Ser. No.
15/134,110 was filed as a national phase entry, all of which are
incorporated by reference herein in their entireties.
[0098] FIG. 4 depicts an exemplary electrode array 290, according
to the present disclosure. Array 290 is composed of individual
electrodes 300 disposed, in this example, in a regular pattern over
a substrate 292. In an aspect, each electrode 300 is separately
coupled (through conductive elements not shown in FIG. 4) to a
circuit (not shown in FIG. 4) that is configured to measure an
electrical parameter. In one aspect, a "virtual sensor" is created
by selective connection of predetermined subsets of electrodes 300
to a common element of a circuit. In this example, a particular
electrode 310 is connected as a center electrode, similar to
electrode 110 of FIG. 3A, and six electrodes 320A-320F are
connected together as a "virtual ring" electrode, similar to
electrode 120 of FIG. 3A. In an aspect, two individual electrodes
are individually connected to the circuit to form a virtual sensor,
for example electrodes 310 and 320A are respectively connected as
the two electrodes of a sensor. In one aspect, one or more
electrodes 300 are connected together to form one or the other of
the electrodes of a two-electrode sensor.
[0099] Any pair of electrodes, whether composed of single
electrodes or a set of electrodes coupled together to form virtual
electrodes, is coupled to electronics (not shown in FIG. 4) that
are configured to measures an electrical property or parameter that
comprises one or more of a resistance, a capacitance, an
inductance, an impedance, a reluctance, or other electrical
characteristic with one or more of sensors 90, 174, 290, 430, 440,
or other two-electrode sensor. Electronics of the present
disclosure may be further configured to compare the measured first
capacitance to a reference value and providing a signal if the
measured capacitance differs from the reference value by an amount
greater than a threshold. In an aspect, one or both of the
reference value and the threshold are predetermined.
[0100] FIG. 5 depicts another exemplary array 400 of electrodes
410, according to the present disclosure. In this non-limiting
example, each of the electrodes 410 is an approximate hexagon that
is separated from each of the surrounding electrodes 410 by a gap
420. In one aspect, electrodes 410 are one of circles, squares,
pentagons, or other regular or irregular shapes. In an aspect, gap
420 is uniform between all electrodes 410. In one aspect, gap 420
varies between various electrodes. In one aspect, gap 420 has a
width that is narrower than the cross-section of each of the
electrodes 410. Electrodes 410 may be interconnected to form
virtual sensors as described below with respect to FIGS. 6A-6B and
10A-10C.
[0101] FIG. 6A depicts an array 400 of electrodes 410 that are
configured, e.g. connected to a measurement circuit, to form an
exemplary sensor 430, according to the present disclosure. A single
hexagonal electrode 410 that is labeled with a "1" forms a center
electrode and a ring of electrodes 410 that are marked with a "2"
are interconnected to form a ring electrode. In an aspect,
electrodes 410 between the center and ring electrode are
electrically "floating." In one aspect, electrodes 410 between the
center and ring electrode are grounded or connected to a floating
ground. In an aspect, electrodes 410 that are outside the ring
electrode are electrically "floating." In one aspect, electrodes
410 that are outside a virtual ring electrode are grounded or
connected to a floating ground.
[0102] FIG. 6B depicts an alternate aspect where an array 400 of
electrodes 410 has been configured to form a virtual sensor 440,
according to the present disclosure. In an aspect, multiple
electrodes 410, indicated by a "1," are interconnected to form a
center electrode while a double-wide ring of electrodes, indicated
by a "2," are interconnected to form a ring electrode. In one
aspect, various numbers and positions of electrodes 410 are
interconnected to form virtual electrodes of a variety of sizes and
shapes.
[0103] FIGS. 6A and 6B depict an exemplary configuration of an
electrode array 400 that is capable of forming sensors 430 in
multiple overlapping locations, according to the present
disclosure. In FIG. 6A, a virtual sensor 430A has been formed with
center electrode 432 formed by a single electrode 410, indicated by
a "1," and a ring electrode 434 formed by a plurality of electrodes
410, indicated by a "2." This same array 400 is shown in FIG. 6B,
where a new virtual sensor 430B has been formed with a center
electrode 436, indicated by a "3," and ring electrode 438,
indicated by a "4." The position of virtual sensor 430A is shown by
the dark outline. It can be seen that virtual sensor 430B overlaps
the position of virtual sensor 430A, this allowing measurements to
be made at a finer resolution than the diameter of sensors 430.
[0104] FIG. 6E shows how sensors 430 may be formed from an array of
electrodes 400 that is larger than the portion of a patient's skin
that is being positioned against the array, according to the
present disclosure. In this example, the outline of contact area
450 of sole 22R of a right foot of a patient, as seen from
underneath the foot, is shown overlaid on array 400. In this
example, sensor 430C has been formed in a location where a portion
of sensor 430C extends beyond the edge of contact area 450. In such
a position, the capacitance or other electrical parameter measured
by sensor 430C is lower than the capacitance measured by sensor
430D, which is positioned completely within contact area 450. It
can be seen that a sensor 430 may be formed at any point within
array 400 and, depending on the position of sensor 430, may
partially overlap the contact area at any level within the range of
0-100%.
[0105] In an aspect, two sensors may overlap 0-50%, such as 0-10%,
5-15%, 10-20%, 15-25%, 20-30%, 25-35%, 30-40%, 35%-45%, 40-50%,
0-25%, 15-35%, or 25-50%. In one aspect, two sensors may overlap
25-75%, such as 25-35%, 30-40%, 35%-45%, 40-50%, 45-55%, 50-60%,
55-65%, 60-70%, 65-75%, 25-50%, 40-55%, or 50-75%. In one aspect,
two sensors may overlap 50-100%, such as 50-60%, 55-65%, 60-70%,
65-75%, 70-80%, 75%-85%, 80-90%, 85-95%, 90-100%, 50-75%, 65-85%,
or 75-100%.
[0106] In one aspect, an array of sensors 400 may further comprise
a plurality of contact sensors (not shown on FIG. 6E) on the same
planar surface as, and surrounding, each of the electrodes to
ensure complete contact of the one or more virtual sensors to the
skin surface. The plurality of contact sensors may be a plurality
of pressure sensors, a plurality of light sensors, a plurality of
temperature sensors, a plurality of pH sensors, a plurality of
perspiration sensors, a plurality of ultrasonic sensors, a
plurality of bone growth stimulator sensors, or a plurality of a
combination of these sensors. In some embodiments, the plurality of
contact sensors may comprise four, five, six, seven, eight, nine,
or ten or more contact sensors surrounding each electrode.
[0107] FIGS. 6F and 6G depict an example of how comparison of SEM
values associated with sensors in known relative locations can
identify bisymmetric locations, according to the present
disclosure. In this example, sensors 430 are formed at
non-overlapping locations, marked "A" to "H" in FIG. 6F, across a
contact area 450R of a right foot 20R. The SEM values measured at
each location are plotted in the graph of FIG. 6G. In this example,
the SEM value of locations "A" and "H" are low or zero, reflecting
the non-overlap of sensor 430 with contact area 450 in those
locations. The SEM values associated with locations "B" and "G" are
higher, as sensor 430 overlaps a portion of contact area 450 in
those positions. The SEM values for locations C-D-E-F are higher
and, in this example, approximately the same, indicating that
sensor 430 was completely within contact area 450 at those
locations. In an aspect, an SEM measurement apparatus such as
apparatus 180 may determine that certain locations, for example
locations "C" and "F," are bisymmetric with respect to a centerline
452R of right foot 20R. In one aspect, where a similar set of
measurements is made at locations A'-H' on a left foot 20L, a
location on each foot 20L and 20R, for example locations E and E',
may be determined to be approximately bisymmetric.
[0108] FIG. 7A depicts an exemplary mat assembly 500 that
incorporates a plurality of bioimpedance sensors 520, according to
the present disclosure. Although sensors 520 are shown as toroidal
sensors similar to sensors 90 depicted in FIG. 3A, sensors 520 may
be any configuration of electrical measurement sensor, including
the configurations shown in FIGS. 4, 5, and 6A-6B. Sensors 520 are
distributed across substrate 510. In an aspect, a portion of
substrate 510 is flexible. In one aspect, a portion of substrate
510 is rigid. In an aspect, electrodes of sensor 520 are
electrically bare, thereby allowing conductive electrical contact
with a patient's foot when a patient stands on mat assembly 500. In
one aspect, electrodes of sensor 520 are electrically insulated,
for example by an insulating cover layer (not shown in FIG. 7A),
thereby allowing only capacitive electrical contact with a
patient's foot when a patient stands on mat assembly 500.
[0109] In an aspect, mat assembly 500 comprises one of more
temperature sensors (not shown in FIG. 7A), that detect the
temperature of one or more locations on a foot. In one aspect, a
temperature sensor is co-located with SEM sensor 520 so as to
provide temperature and SEM measurements of a common location.
[0110] In one aspect of mat assembly 500, a signal is provided when
the measured capacitance differs from a reference capacitance value
by an amount greater than a first threshold and the measured
temperature differs from a temperature reference value by an amount
greater than a second threshold. In an aspect, one or both of the
thresholds are predetermined. In one aspect, a first threshold is
set at the corresponding reference capacitance value plus at least
5%, such as at least 10%, at least 15%, at least 20%, at least 25%,
at least 30%, at least 35%, at least 40%, at least 45%, at least
50%, at least 55%, at least 60%, at least 65%, at least 70%, at
least 75%, at least 80%, at least 85%, at least 90%, at least 95%,
at least 100%, at least 150%, at least 200%, at least 250%, at
least 300%, at least 400%, or at least 500%. In one aspect, a
second threshold is set at the corresponding reference temperature
value plus at least 5%, such as at least 10%, at least 15%, at
least 20%, at least 25%, at least 30%, at least 35%, at least 40%,
at least 45%, at least 50%, at least 55%, at least 60%, at least
65%, at least 70%, at least 75%, at least 80%, at least 85%, at
least 90%, at least 95%, at least 100%, at least 150%, at least
200%, at least 250%, at least 300%, at least 400%, or at least
500%. In one aspect, one or both of the capacitance and temperature
reference values are determined from prior measurements, for
example a rolling average of the past 5 sequential measurements or
by an average of multiple measurements made in an earlier time
period, e.g. a month earlier.
[0111] In one aspect, one or both of the capacitance and
temperature reference values are determined from measurements made
when the tissue was in a known healthy state, for example while in
a doctor's office when a clinician has made an examination of the
tissue and determined that the tissue is healthy, i.e. not
susceptible to the formation of a diabetic foot ulcer.
[0112] FIG. 7B depicts another exemplary mat assembly 502 that
comprises arrays 530L and 530R of electrical sensors 520, where
arrays 530L and 530R are disposed so as to underlie the left and
right feet, respectively, of a patient while standing on mat
assembly 502. In an aspect, outlines 540L and 540R of the left and
right feet are drawn over arrays 530L and 530R so as to guide the
patient to stand in the proper location.
[0113] FIG. 7C depicts an aspect of a mat assembly 504 that has one
or more sensors 520 disposed within each of the outlines 540L and
540R. In an aspect, a sensors 520A is located in a position
corresponding to portions of the foot that are most likely to
develop an ulcer, for example the ball of a foot. In one aspect,
sensors 520B may be located under the heel or other locations of a
foot.
[0114] In one aspect, substrate 510 is partially transparent and
mat 504 comprises a second substrate 512 on which are mounted one
or more optical sensors 550. In an aspect, optical sensor 550 is a
camera capable of imaging the underside of a foot of a patient
standing on mat 504. In one aspect, optical sensor 550 is sensitive
to visible light. In an aspect, optical sensor 550 is sensitive to
infrared light.
[0115] The use of mat assemblies 500, 502, 504 and the like on a
regular basis by patients can serve to detect changes in the health
of their feet. For example, a baseline will be established by
measurement of electrical characteristics, such as capacitance, of
each foot at the time of examination by a clinician who verifies
that there is no ulcer or indication of damage that would lead to
formation of an ulcer in a patient. The patient then places the mat
500, 502, 504 in a readily accessible location in their home, for
example in front of the bathroom sink. On a regular basis, such as
daily while brushing their teeth, the patient triggers a
measurement of their feet by the sensors 520. If the patient is
standing on the same location, for example being guided by outlines
540L and 540R, then each sensor 520 and 550 is measuring the same
position for each repeated measurement. In an aspect, a temperature
measurement is made by an infrared sensor 550 or one of more
temperature sensors (not shown in FIG. 7C) in mat assembly 500,
502, 504. In one aspect, an image is captured by an optical sensor
550 in mat assembly 504. This information is stored in a local
memory or transmitted to a remote storage location, such as the
doctor's office. Each daily measurement is compared to reference
derived from previous measurements, for example a measurement made
in a clinician's office or an average of last week's measurements.
If the most recent measurement deviates from the reference, the
patient is informed of the deviation. The patient can then consult
a clinician for further evaluation and possible intervention. In an
aspect, a change in the measured SEM value larger than the
threshold triggers a notification. In one aspect, a change in the
measured SEM value larger than a first threshold and a change in
the measured temperature larger than a second threshold together
trigger a notification. In an aspect, either a change in the
measured SEM value larger than a first threshold or a change in the
measured temperature larger than a second threshold triggers a
notification. In one aspect, a first threshold is set at the
corresponding reference SEM value plus at least 5%, such as at
least 10%, at least 15%, at least 20%, at least 25%, at least 30%,
at least 35%, at least 40%, at least 45%, at least 50%, at least
55%, at least 60%, at least 65%, at least 70%, at least 75%, at
least 80%, at least 85%, at least 90%, at least 95%, at least 100%,
at least 150%, at least 200%, at least 250%, at least 300%, at
least 400%, or at least 500%. In one aspect, a second threshold is
set at the corresponding reference temperature value plus at least
5%, such as at least 10%, at least 15%, at least 20%, at least 25%,
at least 30%, at least 35%, at least 40%, at least 45%, at least
50%, at least 55%, at least 60%, at least 65%, at least 70%, at
least 75%, at least 80%, at least 85%, at least 90%, at least 95%,
at least 100%, at least 150%, at least 200%, at least 250%, at
least 300%, at least 400%, or at least 500%. In an aspect,
information such as an image of the underside of a patient's foot
is always sent to a clinician for review.
[0116] In an aspect, measurements of the left and right foot are
compared to each other. For example, with reference to FIGS. 6F and
6G, locations E and E' are compared to each other. In one aspect, a
difference between the left and right measurements is compared to a
reference and the patient notified if the difference exceeds a
threshold.
[0117] FIG. 8A discloses a foot cover 600 that incorporates
bioimpedance sensors 520 as shown in the cut-away view of FIG. 8B,
according to the present disclosure. In an aspect, foot cover 600
comprises a sock or other flexible, conforming garment 610 into
which a foot can be inserted. In one aspect, a flexible, conforming
garment 610 may be a flexible shoe, similar to a "water shoe," made
from a flexible, elastic material such as rubber. In an aspect, a
flexible, conforming garment 610 may be a conventional shoe, for
example a leather dress shoe or a sneaker. Sensors 520 are located
in one or more locations that correspond to areas of concern for
development of ulcers. In one aspect, sensors 520 are located under
or around the heel of a flexible, conforming garment 610. In an
aspect, sensors 520 are located on the sole of a flexible,
conforming garment 610. In one aspect, sensors 520 are located in
the area around the toes (not visible in FIG. 8B) of a flexible,
conforming garment 610.
[0118] FIG. 9 discloses a sandal 650 that incorporates bioimpedance
sensors 520, according to the present disclosure. One or more
sensors 520 are disposed on a sandal in locations that correspond
to areas of potential ulcer development.
[0119] FIGS. 10A, 10B, and 10C depict configurations of addressable
electrodes of FIG. 5 that vary the performance capabilities of a
sensor, according to the present disclosure. FIG. 10A depicts an
exemplary first configuration 700, where electrodes 710 are
connected so as to form a center electrode 720 and a ring electrode
730, similar to electrodes of FIGS. 6A and 6B. Sensor configuration
700 has a gap 740 of a single row of electrodes 710, which results
in a first field depth 150, with reference to FIG. 3B.
[0120] FIG. 10B depicts a second exemplary configuration 702 of the
same array of sensors 710, where one electrode is connected to form
a center electrode 722 while a plurality of electrodes 710 are
connected to form a ring electrode 732 that is larger in diameter
than ring electrode 730 and having a gap 742 that is larger than
gap 740. Sensor configuration 702 will have a second field depth
150 that is larger than that of sensor configuration 700.
[0121] FIG. 10C depicts a third exemplary configuration 704 of the
same array of sensors 710, where one electrode is connected to form
a center electrode 724 while a plurality of electrodes 710 are
connected to form a ring electrode 734 that is larger in diameter
than ring electrodes 730 and 732 and having a gap 744 that is
larger than gaps 740 and 742. Sensor configuration 704 will have a
third field depth 150 that is larger than either of sensor
configurations 700 or 702.
[0122] In an aspect, a mat assembly 500 comprises an array of
electrodes 710 distributed across a portion of substrate 510. At a
location of an array that corresponds to an area of concern on a
patient's foot, mat assembly 500 is configured to form a sensor
configuration 700 and make a first measurement, then reconfigure
electrodes 710 to form a sensor configuration 702 and make a second
measurement. The first and second measurements provide information
about the difference in ECF at different depths below the skin of a
foot, thereby providing improved knowledge of the tissue condition
within the foot. In one aspect, mat assembly 500 is configured to
then form a sensor configuration 704 and take a third measurement.
Comparison of the three measurements provides even greater
resolution of the internal tissue condition.
[0123] FIGS. 11A and 11B depict an exemplary aspect of a sensor
assembly 500 configured to be placed in a known position on a
patient's skin, according to the present disclosure. In this
example, sensor assembly 500 has a shaped substrate 510 that is
configured to conform to posterior and bottom surfaces of the heel
of a foot 20. In one aspect, shaped substrate 510 is suitable for
use with both a left foot 20L and a right foot 20R. Sensor assembly
500 comprises one or more sensors 520 disposed on the inner surface
of shaped substrate 510. In this example, sensors 520 are
configured as toroidal sensors as shown in FIG. 1A. In an aspect,
the inner surface of shaped substrate 510 is lined with an array
400 of electrodes 410, with reference to FIG. 5, such that virtual
sensors may be formed at any location. In one aspect, sensors of
other shapes and configurations are provided on the inner surface
of shaped substrate 510. In an aspect, shaped substrate 510 is a
flexible panel (not shown in FIG. 11A) that can be conformed to a
patient's skin, for example wrapped around the back of an ankle. In
one aspect, sensor assembly 500 comprises a cable 530 to connect
sensors 520 to one or more of a power source, a circuit configured
to measure one or more of capacitance or other electrical property,
a processor, a communication subsystem, or other type of electronic
assembly (not shown in FIG. 11A).
[0124] FIG. 11B depicts an exemplary configuration of sensor
assembly 500 where multiple sensors 520 disposed on shaped
substrate 510 such that, for example when sensor assembly 500 is
placed against the skin of a patient around the back, sides, and
bottom of the right heel center. This enables multiple SEM
measurements to be taken in repeatable location on the heel with
sensor assembly 500 in a single position. In one aspect (not shown
in FIGS. 11A and 11B), sensor assembly 500 is configured to be
placed on a portion of the back of a patient thus providing the
capability to make measurements at bisymmetric locations on the
back. In an aspect, shaped substrate 510 is configured to match
anatomical features of the target area of a patient. In one aspect,
shaped substrate 510 comprises markings or other indicators that
can be aligned with features of a patient's body, so as to enable
measurements to be taken at the same location at time intervals
over a period of time in the general range of hours to weeks. In
one aspect, sensor assembly 500 is integrated into a lining of a
garment or shoe or other article of clothing. In an aspect, sensor
assembly 500 is integrated into a sheet, blanket, liner, or other
type of bed clothing. In one aspect, sensor assembly 500 comprises
a wireless communication capability, for example a passive radio
frequency identification (RFID) or an inductive coupling, to allow
actuation of sensors 520 without physically connecting to sensor
assembly 500.
[0125] In an aspect, sensors 520 are coupled to electronics (not
shown in FIG. 11B) that are configured to compare a current set of
measurements to each other and to past measurements made in the
same location. In an aspect, electronics of the present disclosure
may provide a signal if one or more of certain conditions are met.
Such conditions may include, but are not limited to, a change in
the difference between measurements made at two locations when
compared to the difference in measurements made at the same two
locations at a previous time, and a change in the measured value at
a particular location from prior measurements at the same location
that is greater than a threshold amount.
[0126] FIG. 12 depicts a schematic depiction of an integrated
system 800 for measurement, evaluation, storage, and transfer of
SEM values, according to the present disclosure. In this example,
system 800 comprises a SEM measurement apparatus 810, for example a
SEM scanner 170, that comprises the capability to wirelessly
communicate with a WiFi access point 820. Apparatus 810
communicates with one or more of a SEM application running on a
server 850, an application running on a laptop computer 840, a
"smart phone" 830, or other digital device. In an aspect, laptop
computer 840 and smart phone 830 are carried by the user of
apparatus 810, for example a nurse, and the application provides
feedback and information to the user. In an aspect, information
received from apparatus 180 for a patient is stored in a database
850. In one aspect, information received from apparatus 810 for a
patient is stored in a database 860. In an aspect, information
received from apparatus 810 is transferred over a network 855 to
another server 880 that stores a portion of the information in an
electronic medical record (EMR) 870 of the patient. In one aspect,
information from apparatus 810 or retrieved from database 860 or
EMR 870 is transferred to an external server 890 and then to a
computer 895, for example a computer at the office of a doctor who
is proving care for the patient.
[0127] In an aspect, apparatus 810 is one of a mat assembly 500, a
foot cover 600, or other measurement device and one or both of
smart phone 830 and laptop 840 are used by the patient to receive
information and notifications related to measurements made by mat
assembly 500.
[0128] FIG. 13 depicts a sensing band 550, according to the present
disclosure. In one aspect, a SEM sensor as described herein, for
example sensor 90 or sensor 400, is embedded in a band 554 that can
be wrapped around a calf 60 as shown in FIG. 13. In an aspect, band
554 comprises sensors configured to measure one or more of
oxygenation of the tissue, which may comprise measurement of one or
both of oxyhemoglobin and deoxyhemoglobin, temperature of one or
more points on the skin, pulse rate, blood volume and blood
pressure. In one aspect, the combination of measurements made by
band 554 provides information regarding the flow of blood to the
foot, where reduced blood flow is a possible indication of
susceptibility to formation of DFUs. In an aspect, this information
comprises measurement of blood volume and refill times on the
portion of the calf 60 that is proximate to band 554.
[0129] FIG. 14A depicts an integrated sensor and stimulator
assembly 201 suitable for treatment of a pressure ulcer, according
to the present disclosure. In an aspect, an integrated sensor and
stimulator assembly 201 is provided to a patient in need thereof.
Assembly 201 has a substrate 210 with a plurality of sensors 90
disposed on a first surface. Sensors 90 are configured to measure
sub-epidermal moisture (SEM) as an indication of tissue health at
the location of the respective sensor 90. In an aspect, there are
two electrodes 212A and 212B that are in conductive contact with
the skin of a patient (not shown in FIG. 14A) when the assembly 201
is placed on the skin. These electrodes 212A, 212B are connected to
an external controller (not shown in FIG. 14A) that is configured
to apply a therapeutic electrical stimulus to the tissue between
the electrodes 212A, 212B, with the stimulus applied for periods
having a time duration and a time interval between the periods. In
an aspect, low level voltage and/or currents may enhance the
healing of a pressure ulcer. Sensors 90 are individually connected
to an external controller (not shown in FIG. 14A) that is
configured to measure the capacitance of the respective sensors 90.
In an aspect, the capacitance is measured in a time interval
between the stimulus periods. In one aspect, a time interval can be
in the general range of hours to weeks. In an aspect, assembly 201
comprises an absorbent pad and a non-stick layer (not shown in FIG.
14A) overlaid upon sensors 90 and electrodes 212A, 212B. In an
aspect, assembly 201 comprises a layer of adhesive (not shown in
FIG. 14A) overlaid upon a portion of substrate 210 so as to allow
assembly 201 to be adhesively attached to the skin of a patient. In
an aspect, substrate 201 may be permeable to gas while impervious
to fluid.
[0130] The combination of a standard bandage (the absorbent pad,
non-stick layer, and covering substrate) with a therapeutic
instrument, such as electrodes 212A, 212B and the associated
external controller, with one or more sensors 90 provides a means
of protecting the wound, improving the healing process, and
monitoring the healing without disturbing the assembly 201.
[0131] FIG. 14B depicts the sole of a foot 20 of a patient having a
pressure ulcer 205.
[0132] FIG. 14C depicts an assembly 201 adhered to the sole of foot
20 over the pressure ulcer 205. In an aspect, assembly 201 is
placed over ulcer 205 and left in place for several days. In an
aspect, assembly 201 comprises a toroidal pad that relieves the
pressure on the pressure ulcer 205. The external controller of
electrodes 212A, 212B is periodically attached to electrodes 212A,
212B to apply a therapeutic stimulus. During the interval between
these stimuli, the external controller of the sensors 90 is
attached to one or more of the sensors 90 to make a SEM
measurement.
[0133] In an aspect, assembly 201 comprises a battery and wireless
communication capability that enables the external controller to
cause the stimulus to be applied through electrodes 212A, 212B
without a wired connection to the assembly. Similarly, the assembly
may be configured to allow the external controller to communicate
with the sensors 90 to make and receive SEM measurements without a
wired connection. In an aspect, the assembly 201 comprises a
microcontroller configured to apply the therapeutic stimulus and
make SEM measurements and wirelessly transmit information, such as
the SEM values.
[0134] It will be apparent to those of ordinary skill in the art
that the concept of combining therapeutic instruments and SEM
sensors can be applied to other types of wounds and to other
locations on the body besides the sole of the foot, such as an
ankle, or a bony prominence.
[0135] FIG. 14D depicts a bandage assembly 202 adapted for
placement over a pressure ulcer on the sacrum of a patient in need
thereof. The assembly 202 comprises substrate 220 that is porous to
gas while impervious to fluid. The assembly 202 comprises a pad 222
(seen from the external side in FIG. 14D) that provides both
protective padding and absorption. In this example, a single sensor
90 is positioned on the underside of the pad 222 such that the
sensor is directly over the pressure ulcer when the assembly is
applied over an early-stage pressure ulcer with unbroken skin. The
electrodes 214A, 214B are location adjacent to the sensor 90 and on
the same underside so that they will be in contact with the skin of
the patient. In this configuration, the assembly 202 can be placed
over an early-stage ulcer and protect, improve the healing process,
and monitor the progress of the healing with removal of the
assembly 202 or disturbance of the wound.
[0136] Having now generally described the invention, the same will
be more readily understood through reference to the following
examples that are provided by way of illustration, and are not
intended to be limiting of the present disclosure, unless
specified.
EXAMPLES
Example 1
Taking SEM Measurements at Multiple Locations of the Foot
[0137] SEM measurements were taken at the foot using one of three
methods below to ensure complete contact of an electrode with the
skin of a human patient.
[0138] FIG. 15A illustrates a method used to take SEM measurements
starting at the posterior heel using an apparatus according to the
present disclosure. First, the forefoot was dorsiflexed such that
the toes were pointing towards the shin. Second, a bioimpedance
sensor 1520 was positioned at the base of the heel 1530. The
electrode was adjusted for full contact with the heel, and multiple
SEM measurements were then taken in a straight line towards the
toes, including the ball of the foot 1540. The ball of the foot is
one of the primary locations of diabetic foot ulcer.
[0139] FIG. 15B illustrates a method used to take SEM measurements
starting at the lateral heel using an apparatus according to the
present disclosure. First, the toes were pointed away from the body
and rotated inward towards the medial side of the body. Second, an
electrode was placed on the lateral side of the heel 1550. A
bioimpedance sensor 1520 was adjusted for full contact with the
heel, and multiple SEM measurements were taken in a straight line
towards the bottom of the foot. The ball of the foot 1540 is also
shown in FIG. 15B.
[0140] FIG. 15C illustrates a method used to take SEM measurements
starting at the medial heel using an apparatus according to the
present disclosure. First, the toes were pointed away from the body
and rotated outwards toward the lateral side of the body. Second,
the electrode was placed on the medial side of the heel 1560. A
bioimpedance sensor 1520 was adjusted for full contact with the
heel, and multiple measurements were taken around the back of the
heel in a curve.
[0141] From the foregoing, it will be appreciated that the present
invention can be embodied in various ways, which include but are
not limited to the following:
[0142] Embodiment 1. An apparatus for assessing susceptibility of
tissue to formation of a diabetic foot ulcer, the apparatus
comprising: a plurality of electrodes embedded on a substrate,
where a pair of the electrodes is capable of forming a capacitive
sensor configured to measure a first capacitance of a first region
of tissue proximate to the capacitive sensor, a drive circuit
electronically coupled to the electrodes, a processor
electronically coupled to the drive circuit, and a non-transitory
computer-readable medium electronically coupled to the processor
and comprising instructions stored thereon that, when executed on
the processor, perform the steps of: receiving information
regarding the measured first capacitance from the drive circuit,
comparing the measured first capacitance to a first reference
value, and providing a signal if the measured first capacitance
differs from the first reference value by an amount greater than a
first predetermined threshold.
[0143] Embodiment 2. The apparatus of embodiment 1, where the first
reference value is predetermined.
[0144] Embodiment 3. The apparatus of embodiment 1, where the first
reference value is determined by measurement of the first
capacitance at a time when the first region of tissue is
healthy.
[0145] Embodiment 4. The apparatus of embodiment 1, where the first
reference value is determined from measurements of the first
capacitance at the first region of tissue one or more times prior
to the most recent measurement of the first capacitance.
[0146] Embodiment 5. The apparatus of embodiment 1, where the first
reference value is determined by a measurement from a bisymmetric
location.
[0147] Embodiment 6. The apparatus of embodiment 1, where the first
reference value is a measurement of a second capacitance of a
second region of tissue that is separated from the first region of
tissue.
[0148] Embodiment 7. The apparatus of embodiment 6, where the
second region of tissue is known to be healthy.
[0149] Embodiment 8. The apparatus of embodiment 6, where the
second capacitance is measured at approximately the same time as
the first capacitance.
[0150] Embodiment 9. The apparatus of embodiment 1, the apparatus
further comprising one or more temperature sensors that are
configured to measure a temperature of the first region of tissue
and are coupled to the processor, where: the instructions further
comprise: a step of receiving information regarding the measured
temperature from the one or more temperature sensors, and a step of
comparing the measured temperature to a second reference value, and
a step of providing a signal comprising providing the signal if the
measured first capacitance differs from the first reference value
by an amount greater than the predetermined first threshold and the
measured temperature differs from the second reference value by an
amount greater than a predetermined second threshold.
[0151] Embodiment 10. The apparatus of embodiment 1, the apparatus
further comprising one or more optical sensors configured to image
an underside of a foot of a patient while the patient is standing
on the substrate.
[0152] Embodiment 11. A method for assessing susceptibility of
tissue to formation of a diabetic foot ulcer, the method
comprising: obtaining a first capacitance value at a first location
of a patient's skin; obtaining a temperature measurement at the
first location of a patient's skin; and determining that the first
location of a patient's skin is susceptible to formation of a
diabetic foot ulcer when the first capacitance value differs from a
first reference value by an amount greater than a first
predetermined threshold and the temperature measurement differs
from a second reference value by an amount greater than a second
predetermined threshold.
[0153] Embodiment 12. The method of embodiment 11, where the first
reference value is predetermined.
[0154] Embodiment 13. The method of embodiment 11, where the first
reference value is determined by measurement of the first
capacitance at a time when the first location of a patient's skin
is healthy.
[0155] Embodiment 14. The method of embodiment 11, where the first
reference value is determined from measurements of the first
capacitance at the first location of a patient's skin at one or
more times prior to the most recent measurement of the first
capacitance.
[0156] Embodiment 15. The method of embodiment 11, where the first
reference value is a measurement of a second capacitance of a
second location of a patient's skin that is separated from the
first location of a patient's skin.
[0157] Embodiment 16. The method of embodiment 15, where the second
region of a patient's skin is known to be healthy.
[0158] Embodiment 17. The method of embodiment 15, where the second
capacitance is measured at approximately the same time as the first
capacitance.
[0159] Embodiment 18. A method for assessing susceptibility of
tissue to formation of a diabetic foot ulcer, the method
comprising: obtaining a first sub-epidermal moisture (SEM) value at
a first location of a patient's skin; obtaining a temperature
measurement at the first location of a patient's skin; and
determining that the first location of a patient's skin is
susceptible to formation of a diabetic foot ulcer when the first
SEM value differs from a first reference value by an amount greater
than a first predetermined threshold and the temperature
measurement differs from a second reference value by an amount
greater than a second predetermined threshold.
[0160] Embodiment 19. The method of embodiment 18, where the first
reference value is predetermined.
[0161] Embodiment 20. The method of embodiment 18, where the first
reference value is determined by measurement of the first SEM value
at a time when the first location of a patient's skin is
healthy.
[0162] Embodiment 21. The method of embodiment 18, where the first
reference value is determined from measurements of the first SEM
value at the first location of a patient's skin at one or more
times prior to the most recent measurement of the first SEM
value.
[0163] Embodiment 22. The method of embodiment 18, where the first
reference value is a measurement of a second SEM value of a second
location of a patient's skin that is separated from the first
location of a patient's skin.
[0164] Embodiment 23. The method of embodiment 22, where the second
location of a patient's skin is known to be healthy.
[0165] Embodiment 24. The method of embodiment 22, where the second
SEM value is measured at approximately the same time as the first
SEM value.
[0166] Embodiment 25. An integrated apparatus for treating a
diabetic foot ulcer in a patient in need thereof, the apparatus
comprising: a plurality of sensors disposed on a flexible
substrate, where the plurality of sensors are configured to measure
sub-epidermal moisture (SEM) values at respective locations of the
patient's skin; two electrodes disposed on the flexible substrate;
and an external controller electrically connected to the two
electrodes, where the external controller controls the two
electrodes to detect conductive contact with the patient's skin
during a SEM measurement period, and the external controller
controls the two electrodes to apply a therapeutic stimulus to the
patient during a therapeutic phase.
[0167] Embodiment 26. The apparatus of embodiment 25, further
comprising an absorbent pad.
[0168] Embodiment 27. The apparatus of embodiment 25, further
comprising a layer of adhesive.
[0169] Embodiment 28. The apparatus of embodiment 25, where the
flexible substrate is permeable to gas while impervious to
fluid.
[0170] Embodiment 29. An integrated apparatus for treating a
diabetic foot ulcer in a patient in need thereof, the apparatus
comprising: a sensor comprising two electrodes disposed on a
flexible substrate such that a current passing between the
electrodes will pass through tissue proximate to a location of the
patient's skin; and an external controller electrically connected
to the two electrodes.
[0171] Embodiment 30. The integrated apparatus of embodiment 29,
where the external controller controls the two electrodes to detect
conductive contact with the patient's skin during a SEM measurement
period, and the external controller controls the two electrodes to
apply a therapeutic stimulus to the patient during a therapeutic
phase.
[0172] While the invention has been described with reference to
particular aspects, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to a
particular situation or material to the teachings of the invention
without departing from the scope of the invention. Therefore, it is
intended that the invention not be limited to the particular
aspects disclosed but that the invention will include all aspects
falling within the scope and spirit of the appended claims.
* * * * *