U.S. patent application number 13/225387 was filed with the patent office on 2012-03-15 for devices for prevention of pressure ulcers.
This patent application is currently assigned to PERSIMMON SCIENTIFIC, INC.. Invention is credited to Elly Hann.
Application Number | 20120065547 13/225387 |
Document ID | / |
Family ID | 40452929 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120065547 |
Kind Code |
A1 |
Hann; Elly |
March 15, 2012 |
DEVICES FOR PREVENTION OF PRESSURE ULCERS
Abstract
A support surface, such as an underpad, for preventing pressure
sores in a patient is a multi-layer textile assembly having a skin
contact layer formed from a fabric of synthetic filament yarns
woven to provide air permeability and moisture vapor permeability
and having a thickness of less than 1 mm. An absorbent middle layer
is formed from a breathable microfiber fabric woven to provide for
moisture transition from an upper surface of the middle layer to a
bottom surface of the middle layer. The skin contact layer and the
middle layer are stitched together using a stitching pattern
optimized to produce an open pattern with minimal puckering. A
bottom layer is formed from a breathable, waterproof fabric woven
from synthetic yarn to produce a moisture vapor transfer rate
within the range of 5,000 to 20,000 grams per meter squared per 24
hours. The three layers are attached together around their outer
edges.
Inventors: |
Hann; Elly; (La Jolla,
CA) |
Assignee: |
PERSIMMON SCIENTIFIC, INC.
La Jolla
CA
|
Family ID: |
40452929 |
Appl. No.: |
13/225387 |
Filed: |
September 2, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12203040 |
Sep 2, 2008 |
8011041 |
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13225387 |
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60973643 |
Sep 19, 2007 |
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Current U.S.
Class: |
600/587 |
Current CPC
Class: |
A61B 5/11 20130101; A61G
2203/34 20130101; A61G 7/05784 20161101; A61B 5/447 20130101; A61B
5/6892 20130101; A61G 7/057 20130101; A61B 2562/046 20130101; A61B
2562/0247 20130101 |
Class at
Publication: |
600/587 |
International
Class: |
A61B 5/103 20060101
A61B005/103 |
Claims
1.-19. (canceled)
20. In a system for reducing the occurrence of pressure ulcers in
an at-risk patient, a computer monitoring system for receiving
electronic signals generated by an array of pressure sensors
positioned underneath the patient, the computer monitoring system
comprising: a computer processor programmed to execute an algorithm
that identifies a patient-specific pattern using a weighted Braden
score in combination with one or more weighted risk factor selected
from the group consisting of medical diagnosis, clinical
assessment, laboratory data, mattress type and the electronic
signals generated by the array of pressure sensors; and a display
device for displaying the patient-specific pattern.
21. The computer monitoring system of claim 20, wherein the
patient-specific pattern is plotted as a curve of time versus
interface pressure.
22. The computer monitoring system of claim 21, further comprising
an alarm when a pre-determined combination of risk factors
according to the patient-specific pattern is present.
23. The computer monitoring system of claim 22, wherein the
pre-determined combination comprises a pre-selected point on the
curve of time versus interface pressure.
24. The computer monitoring system of claim 20, wherein a weight of
the weighted Braden score is 50% or higher.
25. The computer monitoring system of claim 20, wherein raw data
from each of the one or more weighted risk factors is mined using a
supervised learning algorithm to determine the patient-specific
pattern.
26. A computer-program product embodied on a non-transitory
computer readable medium comprising instructions for executing an
algorithm that identifies a patient-specific pattern for reducing
the occurrence of pressure ulcers in an at-risk patient, the
instructions further comprising: receiving an input comprising
electronic signals generated by an array of pressure sensors
positioned beneath the patient; receiving data comprising a Braden
score and one or more risk factors selected from the group
consisting of medical diagnosis, clinical assessment, laboratory
data, and mattress type, identifying a patient-specific pattern by
applying a first weight to the Braden score and one or more second
weights to the one or more risk factors; generating a curve of
interface pressure versus time using the electronic signals and the
first and second weights; and using the curve to identify a point
at which an alarm is activated to indicate that the patient
requires attention.
27. The computer-program product of claim 26, wherein first weight
is 50% or higher.
28. The computer-program product of claim 26, wherein raw data from
the Braden score and each of the one or more risk factors is mined
using a supervised learning algorithm to determine the
patient-specific pattern.
29. A non-transitory machine readable medium comprising
instructions for executing an algorithm that identifies a
patient-specific pattern for reducing the occurrence of pressure
ulcers in an at-risk patient, which in response to being executed
results in a computing system: receiving an input comprising
electronic signals generated by an array of pressure sensors
positioned beneath the patient; receiving data comprising a Braden
score and one or more risk factors selected from the group
consisting of medical diagnosis, clinical assessment, laboratory
data, and mattress type, identifying a patient-specific pattern by
applying a first weight to the Braden score and one or more second
weights to the one or more risk factors; generating a curve of
interface pressure versus time using the electronic signals and the
first and second weights; and using the curve to identify a point
at which an alarm is activated to indicate that the patient
requires attention.
30. The non-transitory machine-readable medium of claim 29, wherein
first weight is 50% or higher.
31. The non-transitory machine-readable medium of claim 29, wherein
raw data from the Braden score and each of the one or more risk
factors is mined using a supervised learning algorithm to determine
the patient-specific pattern.
Description
RELATED APPLICATIONS
[0001] This application claims the priority of U.S. Provisional
Application No. 60/973,643, filed Sep. 19, 2007, which is
incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] Pressure ulcers can develop in a person who is bedridden,
confined to a wheelchair, or otherwise subject to extended periods
of immobility. An estimated 1.3 to 3 million patients in the United
States have pressure ulcers; incidence is highest in older
patients, especially when hospitalized or in long-term care
facilities. Both intrinsic and extrinsic factors may be involved in
the development of such pressure ulcers. Aging increases risk, in
part because of reduced subcutaneous fat and decreased capillary
blood flow. Some additional intrinsic factors include impaired
mobility, incontinence, skin condition, nutrition, and altered
mental status.
[0003] Exposure to pressure is one extrinsic factor. When a bony
prominence is pressed against a support surface of a bed or a chair
under the person's weight, pressure tends to be focused on that
prominence. Depending on the type of mattress or cushion,
continuous pressure due to immobility can be at least one
contributing factor in causing a break in the person's skin,
reduced blood flow to that tissue and/or the loss of surface tissue
and disintegration and necrosis of epithelial tissue, i.e., an
ulcer.
[0004] The scope and cost of such pressure ulcers in the United
States are significant. Furthermore, no dollar amount can be placed
on the cost of human suffering from this debilitating
condition.
[0005] Implementation of guidelines set forth by the Agency for
Health Care Policy and Research (AHCPR) has produced improvements
in carefully monitored institutions. These studies demonstrated
that with diligent nursing care, many pressure ulcers are
preventable. However, with staff/patient ratios typically found in
many health care facilities, it may be impractical to expect all
aspects of the AHCPR guidelines to be followed for all but
high-risk patients. The extent of this problem can only be expected
to grow as medical advances prolong the life expectancy of
seriously ill patients and as the population over the age of 65
expands.
[0006] Medical conditions that do not necessarily involve
immobility can also increase the risk of the formation of pressure
ulcers or similar types of sores. These sores typically occur in
the lower extremities, such as neuropathic ulcers that are
frequently associated with diabetes, where sores may form as a
result of the patient's reduced sensation and/or circulation in
their feet, sometimes leading to amputation of the foot or leg, or
even death from infection at the site when a sore goes untreated.
Venous ulcers and arterial ulcers can also result from prolonged
pressure and ischemia.
[0007] Approaches for prevention of pressure sores tend to fall
within two broad, but not necessarily mutually exclusive,
categories--underpads, pressure redistribution surfaces and
electronic sensors and monitoring systems. Among pressure
redistribution or support surfaces, proposed solutions include
overlays, replacement mattresses, and specialty beds that attempt
to reduce the amount of pressure to which tissues are subjected.
These approaches tend to vary in effectiveness, practicality of
use, economy and maintenance requirements. Most address a few of
the problems, but none considers all of the conditions that can be
encountered in patient care including shear forces, moisture
management, bunching, surface texture, breathability, odor control,
durability and launderability.
[0008] Current products tend to focus on single-problem solutions,
such as absorbent incontinence pads for handling moisture, or
pressure re-distribution surfaces to reduce pressure. In order to
avoid ruining a mattress or seat cushion, incontinence pads are
often backed with non-breathable waterproof material, so that
moisture is trapped within the pad. These pads frequently have
cotton or synthetic covers and generally do not have
moisture-wicking capability, increasing the risk of ulcer formation
in an at-risk patient if the pad is not changed promptly when wet.
The current industry approach for dealing with the shearing problem
is to coat the top layer of the pad with silicone.
[0009] A number have support surface improvements have been
suggested for reducing the risk of formation of pressure ulcers.
U.S. Patent Publication No. 2007/0277282 of Sheppell, entitled
"Support for Prevention of Decubitus Ulcers", describes a two-layer
pad that is attached at selected portions of the fabric to allow
parallel movement between the layers to absorb shearing forces.
Examples of the layers are spandex for the top layer and nylon for
the second layer. The second layer may also be cotton, wool, felt
or any of a number of synthetic or blended fabrics. While shearing
forces may be reduced, relative movement among the layers raises
the opportunity for bunching, which can create lumps that increase
pressure against the skin. Furthermore, there is no provision for
drawing and keeping moisture away from the skin. The lack of
breathability causes skin warming, which contributes to maceration
of the skin.
[0010] U.S. Patent Publication No. 2007/0261548 Of Vrzalik,
assigned to Kinetic Concepts, Inc., describes a multi-layered
support system for prevention of decubitus ulcers which has three
layers: a vapor permeable layer, a spacer layer having small air
pockets through which air can be pumped, and a third outer layer
that is vapor and air impermeable. An aperture is formed through
one of the outer layers for connection to an air source. The spacer
layer can be open cell foam, polymer particles or similar
materials. Layers are bonded together using RF welding, heat
sealing, or sonic welding. While the contact layer is vapor
permeable, there is nothing to keep the moisture away from the
skin, and the outer layer prevents evaporation, so that moisture
can be retained within the pad.
[0011] U.S. Pat. No. 4,962,769 of Garcia, assigned to Prevent
Products, describes a three-layer structure that can be used in
diapers for bedridden patients. The inner, skin contact layer is
water absorbent. The middle layer provides cushioning in the form
of patterns of bubbles, similar to bubble wrap and is mostly water
impervious except for bores that allow water to pass through. The
outer layer is water impervious. The lack of breathability
increases the risk of skin warming.
[0012] Other proposed approaches include U.S. Pat. No. 7,211,709 of
Shimoe, which describes a multi-layered disposable diaper, and U.S.
Patent Publication No. 2007/0056096 of Assink, which describes a
multi-layer bed pad which includes an upper layer made from very
fine, non-woven polyethylene fibers to provide a smooth, low
friction surface. This approach also suffers from non-breathable
outer layer.
[0013] The second approach to reducing the risk of pressure ulcers
is to provide a series of electronic sensors that detect pressure
and/or moisture on the patient's body, providing input to a
computer monitor which may be used to predict risk conditions or
generate alarms based on a patient's history of ulcer development,
warning a caregiver that the patient needs to be turned or
otherwise attended to. U.S. Pat. No. 6,287,253 of Ortega, assigned
to Sabolich Research and Development, describes a
computer-implemented pressure ulcer management method that applies
electronic pressure sensors directly to locations of a patient's
body that are at risk for sores, providing read-outs from the
sensors to a computer monitoring system, and generating a signal to
indicate when attention is required. U.S. Patent Publication No.
2006/0065060 of Ito, assigned to Pentax Corporation describes a
multi-layer mat with an embedded array of electronic pressure
sensors for detection of pressure and generation of an alarm to
indicate when abnormal pressure is present, notifying the caregiver
that a patient needs to be turned to prevent formation of pressure
sores. Such systems can be quite costly and generally will be
purchased for institutional usage more so that for in home use.
[0014] In view of the foregoing, and as an increased number of
patients are given home care, there is the need for effective and
affordable materials and devices for pressure ulcer management and
prevention.
SUMMARY OF THE INVENTION
[0015] The present invention addresses one aspect of the
aforementioned needs by providing a multi-layered textile assembly
that possesses all of the qualities that are important for reducing
the risk of pressure sore formation through improved comfort,
moisture wicking, breathability, shear reducing, rapid drying and
anti-microbial, while being durable, launderable and
lightweight.
[0016] The multi-layered textile assembly of the present invention
may be used as a bed pad, also known as an underpad, for placement
on top of a mattress for direct contact with a patient's skin, a
mattress cover or seat cushion cover for use in combination with
foam or other cushioning layer, or even as a shoe insole liner.
[0017] In one aspect of the invention, a support surface is
provided for preventing pressure sores in a patient, the support
surface comprising a multi-layer composite textile having a skin
contact layer formed from a woven fabric of synthetic filament
yarns woven to provide air and moisture vapor permeability and a
non-shearing surface, with a thickness of less than 1 mm, the skin
contact layer having an upper, skin contact surface and a bottom
surface; an absorbent middle layer abutting the bottom surface of
the skin contact layer, the middle layer formed from a breathable
microfiber fabric woven from synthetic fibers having a
cross-sectional shape that includes a plurality of voids for
generating a capillary effect for moisture transition from an upper
surface of the middle layer to a bottom surface of the middle
layer, wherein the skin contact layer and the middle layer are
stitched together using a stitching pattern that is optimized to
produce an open pattern with minimal puckering; and
a bottom layer attached to the skin contact layer and the middle
layer at a peripheral edge of each layer, the bottom layer formed
from a breathable, waterproof fabric having a thickness of less
that 1 mm that is woven from synthetic yarn to produce a moisture
vapor transfer rate within the range of 5,000 to 20,000 grams per
meter squared per 24 hours. In one embodiment, the stitching
pattern by which the upper two layers are assembled comprises a
plurality of straight and curved lines, wherein no lines cross over
other lines.
[0018] In an exemplary embodiment, a three-layer textile assembly
includes an upper layer, typically for direct skin contact or
contact with the patient's gown or pajamas, which is a thin (<1
mm), lightweight (.about.2.5 ounce) polyester that is breathable,
non-shearing, anti-microbial, moisture wicking and quick drying.
Examples of appropriate fabrics for this upper layer include the
fabric described in U.S. Pat. No. 6,277,770 of Smith, (incorporated
herein by reference) which is assigned to Precision Fabrics, Inc.
(Greensboro, N.C.), or similar fabrics made by Precision Fabrics or
by Teijin Fibers Ltd. (Tokyo, Japan), such as Teijin's
NANOFRONT.TM. polyester fiber. The middle layer of the assembly is
an absorbent, breathable microfiber layer that is flexible and
conforms to the body, with a thickness on the order of 1.5 to 3.5
mm, more preferably less than 3 mm and most preferably less than 2
mm. A preferred microfiber material has a density of 180-340
gm/m.sup.2, such as the microfiber materials used in the AQUIS.RTM.
products available from Britanne Corporation or SILVERSTAR2000
microfiber fabric available from Silverstar Corporation Ltd.
(Welcron Company Ltd.) (South Korea). Such microfiber fabrics
absorb liquid faster than cotton by the capillary effect created
within tiny spaces between the threads and are able to dry rapidly
by communicating the liquid away from the source. The outer layer
of the assembly is a thin, lightweight, waterproof, breathable
fabric such as the polyester or nylon fabrics coated with
polyurethane. Such fabrics are available from Young Poong Filltex
Co. Ltd. (South Korea), Formosa Taffeta Company, Ltd. (Taiwan), or
PORELLE.RTM. membranes available from PILMembranes Ltd. (formerly
Porvair International)(U.K.)
[0019] A factor that affects the smoothness and comfort of the
surface is the assembly method used for combining the multiple
layers and finishing the edges of a pad or cushion. The assembly
method also effects launderability and drying time. In the
preferred embodiment, the multi-layer fabric is stitched using a
smooth polyester thread to form a quilted pattern with features and
dimensions that are optimized to minimize puckering or bunching,
minimize washing and drying time, while maximizing comfort,
durability and breathability. Seams, if any, should be free of
puckering and are preferably limited to those used for finishing
the outer edges of the pad, or the sides of a cushion or mattress
cover, so that the skin contact surface is substantially seamless.
In one embodiment, a friction-enhancing strip, such as silicone or
other rubber-like synthetic material, may be formed or attached to
selected areas on the outer edges of the bottom side of a pad to
facilitate gripping by a care giver when the patient is moved or
bedding is changed. The stitching or other attachment method used
to apply the grip strip should have minimal impact on the
smoothness of the upper skin contact surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIGS. 1a and 1b are diagrammatical top and cross-sectional
views, respectively, of a first embodiment of a multi-layer support
surface for prevention of pressure sores. FIG. 1b is magnified to
show detail. FIG. 1c is a second embodiment of the support surface
showing a different stitching pattern.
[0021] FIGS. 2a-2d are diagrammatical views of alternative
stitching patterns for a multi-layer support surface.
[0022] FIG. 3 is a perspective, partially exploded view of an
embodiment of the invention with a pressure sensing array.
[0023] FIG. 4 is a block diagram of the electronic components for
generating, receiving and processing signals.
[0024] FIGS. 5a and 5b are top and bottom views of a second
embodiment of the support surface
[0025] FIGS. 6a-c are curves illustrating different algorithms for
use in monitoring of a patient.
[0026] FIG. 6d is a diagram showing the data sources that may be
used for creating and executing an algorithm for monitoring a
patient.
[0027] FIG. 7 is a graph comparing the absorbency of microfiber
versus cotton.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0028] According to the present invention, a support surface for
prevention of pressure ulcers is a multi-layer composite fabric
which is assembled to overcome most of the important factors that
are involved in formation of such ulcers. Each layer addresses at
least one specific risk factor for pressure ulcer formation while
the assembly as a whole enhances these features, at the same time
taking into consideration the qualities that make such a product
easy to manufacture and affordable such that it can be made widely
available for both institutional and home use.
[0029] In the preferred embodiment, a three-layer assembly includes
an upper layer, typically for direct skin contact, which is a thin
(<1 mm, preferably less than 0.5 mm), lightweight (.about.2.5
ounce) polyester that is breathable, non-shearing, anti-microbial,
moisture wicking and quick drying. Examples of appropriate fabrics
for this upper layer include the fabric described in U.S. Pat. No.
6,277,770 of Smith, (incorporated herein by reference) which is
assigned to Precision Fabrics, Inc. (Greensboro, N.C.), or similar
fabrics made by Precision Fabrics, such as those sold under the
trademark DERMATHERAPY.RTM., or by Teijin Fibers Ltd. (Tokyo,
Japan), such as Teijin's NANOFRONT.TM. polyester fiber.
[0030] The thin, lightweight upper layer conforms well to the
user's body and dries quickly. The fabric used for the upper layer
has a combination of air porosity (to allow venting through the
fabric's planar surface), moisture vapor transport (to enhance
comfort), fabric flexibility (also a comfort-enhancing property),
extremely small pore size, a non-shearing surface (for reduced
friction), and durability to laundering. The fabric thickness is
less than 1 mm, with a typical thickness of 0.2 mm. This
combination of properties is provided by weaving fine-denier
synthetic filament yarns (polyester or nylon-polyester blend) into
a tight plain-weave construction with post finishing processes that
maximize fiber coverage and filtration efficiency. Because the
fabric is woven from continuous synthetic filament and/or spun
yarns, there are no short fibers to irritate skin or become
embedded in a wound or sore. The fabric is finished to provide a
fabric with a mean pore size of 4 to 10 microns, an air
permeability of 0.5-30 cubic feet per minute per square foot of
fabric at 0.5 inches of water ("cfm," measured by Federal Test
Method Standard (FTM) 5450, also known as ASTM D-737), a mean
fabric flexibility of 0.5 to 6.5 grams (bending resistance), and a
moisture vapor permeability in excess of 800 g/m.sup.2 per 24
hours. The coefficient of friction for the fabric is on the order
of 0.5, which is approximately one-half of the coefficient of
friction for a cotton or polyester/cotton blend with roughly the
same fiber and weave. Any suitable antimicrobial or fluorochemical
finish can be used; such finishes are known in the art (e.g., U.S.
Pat. No. 4,822,667). An example of a suitable antimicrobial finish
that can be applied is a compound of
3-(trimethoxysilyl)-propyidimethyloctadecyl ammonium chloride (DOW
CORNING 5700). This finish protects the fabric against bacteria and
fungi, and inhibits the growth of odor-causing bacteria.
[0031] As shown in Table 1, compared with currently
commercially-available products, the preferred skin contact layer
provides all of the desired qualities for prevention of pressure
ulcers.
TABLE-US-00001 TABLE 1 Fabric Disposable 100% Cotton 100% Polyester
(e.g., (e.g., (e.g., Present MEDLINE MEDLINE DURO-MED invention -
ULTRA- flannel 3-ply Feature top layer SORBS .TM.) soaker) quilted)
Moisture yes yes no no wicking Breathable yes yes yes no Quick
Drying yes NA no no (<5 min.) Anti-microbial yes NA no no Body
yes no no no conforming Non-shearing yes yes no no Weight light
light heavy heavy Thickness <1 mm <1 mm 2 mm 3-4 mm Washable
yes no yes yes Recyclable yes no NA NA potential
[0032] The light, thin top layer is particularly advantageous for
purposes of quilting, since the thicker the fabric, the greater the
chance of puckering and bunching when quilted, which can form
pressure points against the patient's skin.
[0033] The middle layer of the assembly is an absorbent, breathable
polyester microfiber that is flexible and conforms to the body,
with a thickness on the order of 1.5 to 3.5 mm, more preferably
less than 3 mm and most preferably less than 2 mm. A preferred
microfiber has a density of 180-340 gm/m.sup.2, such as the
microfiber materials used in the AQUIS.RTM. products available from
Britanne Corporation, or SILVERSTAR2000.TM. microfiber fabric
available from SilverStar Corporation Ltd. (Welcron Company Ltd.)
(Seoul, South Korea) (see U.S. Pat. No. 6,381,994 of Lee, which is
incorporated herein by reference). Such microfiber fabrics are
formed by weaving synthetic filaments or fibers that have many
channels extending along the fiber length, thus creating fine voids
within their cross-sections. The microfiber fabrics are able to
absorb liquid faster and in greater volume than cotton due to the
capillary effect produced by the voids and channels within the
fibers and, thus, are able to dry rapidly by communicating the
liquid away from the source. FIG. 7 is a graph of the relative
absorbency of microfiber and cotton with time, showing that the
microfiber has a moisture absorbing capacity more than two times
that of cotton.
[0034] Table 2 provides a comparison of relevant characteristics of
the absorbent middle layer of the multi-layer fabric of the
preferred embodiment of the present invention to currently
commercially-available products.
TABLE-US-00002 TABLE 2 Fabric Present Disposable invention - (e.g.,
MEDLINE MEDLINE 100% middle ULTRA- polyester Polyester Feature
layer SORBS .TM.) soaker DURO-MED Absorbs yes yes no no fluids
Washable yes no yes yes Body- yes no no no conforming Breathable
yes no no no Discourages yes NA NA NA microbes Thickness 2 mm
irregular 3-4 mm 3-4 mm (absorbent gel forms clumps) Recyclable yes
no NA NA potential
[0035] The outer layer of the assembly is a thin, lightweight,
waterproof, breathable fabric such as the polyester or nylon, i.e.,
synthetic, fabrics coated with polyurethane available from Young
Poong Filltex Co. Ltd. (South Korea), Formosa Taffeta Company, Ltd.
(Taiwan), or PORELLE.RTM. membranes available from PILMembranes
Ltd. (formerly Porvair International)(U.K.).
TABLE-US-00003 TABLE 3 Fabric Present Disposable invention - (e.g.,
MEDLINE MEDLINE 100% middle ULTRA- polyester Polyester Feature
layer SORBS .TM.) soaker DURO-MED Waterproof yes yes yes yes
Breathable yes yes no no Body- yes no no no conforming Washable yes
no yes yes Weight light light heavy heavy Thickness <1 mm <1
mm 2-3 mm 2-3 mm Recyclable yes no NA NA potential
[0036] Exemplary characteristics of a preferred fabric for the
outer (bottom) layer of the inventive multi-layer support surface
include a fabric weight on the order of 80-100 gm/m.sup.2 that is
waterproof and breathable. The breathability of the outer layer is
measured according to moisture vapor transfer rate (MVTR),
expressed in units of grams/meter.sup.2/day. For purposes of the
present invention, a MVTR range of 5,000 to 20,000 g/m.sup.2/day is
preferred. Table 4 below provides a comparison of the breathability
of three different fabrics from Young Poong and Formosa after
applying 2 ml of water to the fabric. The degree of dryness was
tested on the underside of the fabric, which would correspond to
the moisture to which a mattress beneath the fabric would be
exposed. The MVTR values were provided by the manufacture and were
not independently confirmed.
TABLE-US-00004 TABLE 4 Product (MVTR) FORMOSA FORMOSA Hr:Min after
FILLTEX .TM. BLUE YELLOW applying water (7,000 g/m.sup.2/day)
(7,000 g/m.sup.2/day) (10,000 g/m.sup.2/day) 0:00 80% dry 80% dry
80% dry 0:05 85% dry 85% dry 85% dry 0:10 90% dry 90% dry 90% dry
0:15 95% dry 95% dry 95% dry 0:45 98% dry 98% dry 98% dry 2:30
Completely Dry Completely Dry Completely Dry
The tests indicated that MVTR ratings of 7,000 and 10,000
g/m.sup.2/day were equally effective in drawing away the moisture
at a desired rate. The corresponding information for the
PORELLE.RTM. fabric was not available because it was determined to
be relatively non-breathable, suitable only as a waterproof
layer.
[0037] A factor that affects the smoothness and comfort of the
surface is the assembly method used for combining the multiple
layers and finishing the edges of a pad or cushion. The assembly
method and materials also affect launderability and drying time.
For example, a cotton thread tends to have a heavier weight, less
give (stretchability) and a longer drying time. In the preferred
embodiment, the multi-layer fabric is stitched using a smooth
polyester thread. The polyester thread is stronger, lighter, and
faster drying with better give. The top two layers of the
multi-layer assembly were stitched to form a quilted pattern shown
in FIG. 1a, with features and dimensions that are optimized to
minimize puckering or bunching, minimize washing and drying time,
while maximizing comfort, durability and breathability.
[0038] In a comparison of stitch length, a 1.5 mm stitch using
polyester thread produced significant puckering with taut stitches,
while a 2.5 mm stitch eliminated all puckering, with all of the
stitches lying flat. The longer stitch produced a quilted assembly
that was smoother to the touch with faster wash and dry times. The
stitch tension was also optimized for producing the smoothest
possible finish. Using a Towa Bobbin Case Tension Gauge
(manufactured by Towa Industrial Company, Ltd. of Japan), a tool
that is well known among quilters, the tension was optimized to
minimize puckering and improve smoothness of the quilted surface. A
tension of 20 gf (gram-force), or 200 milliNewtons, was found to
produce more puckering, while 18 gf (180 mN) provided a smooth
surface with no puckering.
[0039] The quilting patterns used to combine the upper two layers
of the multi-layer assembly were evaluated for a number of
qualities including aesthetic appeal, comfort, bunching,
washability and drying rate, fabric longevity and commercial
manufacturability. The different patterns considered are shown in
FIGS. 2a-2d: FIG. 2a shows a series of attached rings; FIG. 2b, a
continuous scroll pattern, FIG. 2c, detached rings with parallel
lines, and FIG. 2d shows parallel wavy lines. Table 5 below
provides the results of this comparison.
TABLE-US-00005 TABLE 5 Pattern Attached Detached Parallel, rings
with Continuous rings & par- continuous free spaces scroll
allel lines wavy lines Qualities (FIG. 2a) (FIG. 2b) (FIG. 2c)
(FIG. 2d) Uniqueness yes no yes no Sense appeal poor yes yes yes
Washability good poor good good Ease of drying good poor good good
Bunching significant no no no Fabric Longevity good poor good good
Manufacturability no no no yes
[0040] The size of the quilted features, i.e., the distance to the
closest stitching, was found to impact bunching, moisture trapping
and drying time. For the ring patterns, ring diameters of 25 mm
(.about.1 inch) were found to produce more puckering, more moisture
trapping and longer drying time compared to rings of 50 mm (2 inch)
diameter. However, if much larger diameter rings were used, there
was an increased risk of movement between the upper and middle
layers that could cause bunching when the patient moves. Generally,
a ring diameter of 25-50 mm can be used. The separation between
adjacent rings is determined in part by the desired pattern, but as
indicated in Table 5, abutting circles resulted in significant
bunching of the fabric. In the preferred embodiment, ring diameters
of about 45 mm are used. A separation on the order of 10 mm between
the closest neighboring circles was used. Similarly, the distance
between parallel lines, both the straight lines of FIG. 2c and the
wavy lines of FIG. 2d, should generally be within the range of
25-50 mm and in the exemplary embodiment was selected as about 45
mm.
[0041] FIG. 1a illustrates the first pattern with circles and
parallel after optimization of the quilting pattern and stitching
parameters. The combination of parallel lines 110 and circles
(rings) 102 provides an interesting, aesthetically pleasing pattern
that provides a combination of horizontal and vertical connectivity
(viewing as oriented in the figure) between the upper two layers.
The circles are arranged in short, angled lines, with two adjacent
circles at approximate 45 degree angles to each other. The parallel
lines do not pass through the circles, but end on one side and
resume on the opposite side of the circle, so that one stitch line
does not cross another. In general, while stitch lines may come
together to define an intersection point 104, they preferably will
not be allowed to cross, thus avoiding locations of high stitch
density that could negatively impact drying time as well as
increasing the chance of puckering. The pattern is repeated to
produce a two-layer assembly that eliminates the possibility of
movement between the layers while remaining sufficiently open to
minimize drying time. This quilting pattern had all of the
desirable performance features, however, the complicated design is
difficult to commercialize on a large scale, i.e., in an automated
assembly line, because it requires a single-needle assembly
process. As a result, the wavy line pattern of FIG. 2d and FIG. 8a
was selected for commercialization. This pattern should follow the
general rules discussed above relative to the design of FIG.
2c--the separation between adjacent lines 200 should be within the
range of 25-50 mm, the stitch tension and length should be a
previously specified, and no two lines should cross because of the
possibility of puckering around that point.
[0042] FIG. 1b shows the three layer structure of the inventive
support pad. The first layer 70 is the contact layer, second layer
80 is the absorbent layer, and third layer 90 provides the
waterproof, breathable backing layer. Only layers 70 and 80 are
quilted together. Bottom layer 90 is attached only around its edges
so as not to destroy the benefits of the waterproof layer. The
stitching at the periphery of the support surface that is to be
used as a bed pad or other flat pad is as flat and smooth as
possible. In the preferred embodiment, an overlock stitch 95, which
may be single thread or, preferably, multi-thread overlock, is used
to simultaneously attach the layers and finish the edges.
Alternatively, the upper layer may be cut slightly larger than the
middle and bottom layers so that it extends beyond the edges of the
lower layers. This excess fabric is then folded over and sewn,
either with a straight stitch, similar to that used for the
quilting, or an overlock stitch may be used. This assembly method
is generally not commercializable due to the difficulty in
repeatably aligning the different sizes of fabric. If the support
surface is being assembled into a cushion cover or pillowcase,
inside seams finished to prevent bunching should be used.
[0043] Referring again to the embodiment shown in FIG. 1a, at the
bottom of the assembly is a rectangular box 96 formed by stitching
four straight lines within which is located the product trademark
or logo. The stitching used for the box and the logo is the same as
that used to form the quilted pattern. As described above, so that
the lines of stitching do not cross, the parallel lines 110
terminate on one side of the box 96 and resume at the other side of
the box. Even in everyday clothing, tags can be a source of
discomfort. By embroidering the trademark as part of the overall
design, the need for tags to identifying the source of the goods is
eliminated.
[0044] In one embodiment, a friction-enhancing strip, such as
silicone, rubber or suede, may be formed or attached to areas on
the outer edges of the bottom side of a pad to facilitate gripping
by a care giver when the patient is moved or bedding is changed.
FIG. 1a shows a pair of grips 98 (dashed lines) sewn onto one edge
of the pad, while FIG. 5b shows a continuous strip of silicone or
rubber running along two sides of the pad. The grips can be placed
on all four edges, on two, opposing edges, or along one edge only.
The stitching or other attachment method used to apply the grip
strips should have minimal impact on the smoothness of the upper
skin contact surface and preferably will be located well away from
where the patient will be positioned. In an alternate embodiment,
grips can be formed by deposition of an epoxy, rubber, or synthetic
polymer directly onto the fabric, preferably on the bottom of the
third layer, to form a flexible strip that can produce sufficient
strength and surface friction to facilitate gripping.
[0045] The total combined thickness of the multi-layer assembly of
the present invention is on the order of 2-5 mm, preferably at the
lower end of the range. The minimal thickness enhances the
assembly's ability to conform comfortably to the patient's body. It
also provides a pad that is easy to launder and dries quickly.
Table 6 below provides a comparison of the moisture wicking
capability of a multi-layer pad made according to the present
invention, which is sold under the trademark EPIBI.TM., relative to
several commercially-available bed pads and underpads. The amount
of water used in the test was 200 mL. "Time" refers to the amount
of time that had passed after the water was poured on the top layer
of the pad.
TABLE-US-00006 TABLE 6 Product EPIBI Disposable Time/ (Present
(MEDLINE MEDLINE 100% Polyester Quality invention) ULTRASORBS .TM.)
cotton soaker DUROMED 1 min. Moisture wicking Wet Wet Wet; fluid
Wet; fluid (fluid puddles before puddles puddles wicking into
porous channels) Surface texture Smooth Smooth Rough Rough
Breathable Yes Yes No No Waterproof Yes Yes Yes Yes 10 min.
Moisture wicking Damp Dry Wet; fluid Wet; fluid puddles puddles
Surface texture Smooth Smooth Rough Rough Breathable Yes Yes No No
Waterproof Yes Yes Yes Yes 22 min. Moisture wicking Damp/Dry
Damp/Dry Wet Wet 30 min. Moisture wicking Damp/Dry Damp/Dry Wet Wet
Washable Yes No Yes Yes Recyclable Yes No NA NA potential Dry cycle
after 20 90% dry with N/A Damp Very damp min. in home dryer small
patches of dampness in tightly stitched areas
[0046] It was also noted that the disposable product had large
porous channels in the top surface, which allowed moisture to
escape towards the skin for at least four hours.
[0047] The multi-layer textile assembly of the present invention is
optimized to provide the features appropriate for minimizing the
risk of development of pressure ulcers by a patient using a pad
made from the assembly. In addition to being moisture wicking,
breathable, flexible and non-shearing, an important feature of the
assembly is its extremely light weight compared to other
commercially-available products. A bed pad having the commonly-used
dimensions of 81 cm (32 in.) by 69 cm (27'') constructed according
to the present invention weighs only 9 ounces, compared to the 20
ounce weight of a conventional cotton or polyester bed pad of the
same dimensions. In addition to being more conformable to the
patient's body, and therefore, more comfortable, the inventive pad
can significantly reduce laundry costs. In an institutional
setting, the cost of laundering linens is calculated in terms of
weight per average patient day. Because the inventive pad weighs
less than half the weight of the most widely used bed pads, the
linen costs incurred by hospitals, nursing homes and hospices will
be dramatically reduced. In addition, the amount of energy and
water consumed during laundering will be significantly reduced.
[0048] Bed pads made from the multi-layer composite fabric of the
present invention have been evaluated by patients and medical
professionals, including nurses and surgeons, and praised as a
major advancement in patient care. By addressing each of the many
problems that are encountered with patient bedding, a novel pad has
been developed that can improve the health and comfort of patients
undergoing treatment in a wide range of medical fields. In addition
to providing an important tool for pressure ulcer treatment and
prevention in at-risk patients, other medical areas that can
benefit from the improved comfort, breathability, moisture wicking
capability and many other features of the composite fabric include
wound care, burn treatment, and labor and delivery.
[0049] In another aspect of the invention, devices are disclosed
for sensing and monitoring one or more conditions related to the
health of a patient and especially related to the development,
prevention and treatment of pressure ulcers and similar sores. The
present invention particularly provides a novel and improved
medical sensor and system and method of monitoring one or more
pressure sensitive areas of a human body.
[0050] The present invention provides real-time monitoring of
pressure status over time, whereby at-risk patients requiring
immediate intervention can be quickly identified. The preferred
embodiment also offers the advantage of relatively inexpensive
disposable sensors that safely monitor exposure time to
pressure.
[0051] In an exemplary embodiment, a flexible array of pressure
transducers is encased in a protective cover. A bed pad having a
similar multi-layer structure to that described above can be used
in conjunction with the sensors described below.
[0052] The basic components of the bedding system with pressure
monitoring sensors according are illustrated in FIG. 3 and include
an optionally antimicrobial treated, porous cloth 16 attached over
a layer 17 of moisture-absorbing material backed by a waterproof
barrier 12. Underneath the barrier is an array 21 of pressure
transducers laid on top of a cushioning pad 20. The processor 22
used for collecting the signals from the sensors in the array and
for executing the software for analyzing the data may be a standard
personal computer programmed according to techniques known to those
skilled in the data processing arts. The software will preferably
include a subroutine for generating a display map on a graphical
interface showing the various pressure points along with a variety
of warning and alarm indicators when risk conditions for pressure
ulcers are present.
[0053] In an exemplary embodiment, the top surface 16 of the
underpad is a lightweight, breathable, flexible, anti-microbial,
non-cotton material that wicks away moisture, such as that
described previously with reference to FIGS. 1a and 1b.
Alternatively, it may be formed from disposable materials based on
a combination of cellulose and synthetic fibers. The absorptive
layer 17 of the underpad is formed from a thin microfiber fabric
that is highly flexible and wick moisture away from the upper layer
so as to keep the top surface layer dry. This avoids the problem of
typical disposable pads, which become stiff when they get wet. The
waterproof layer 12 on the bottom is a thin, breathable, highly
flexible material coated with polyurethane to prevent moisture from
entering the electronics of the sensors as well as the mattress or
chair cushion below.
[0054] An embodiment for use with chairs, including wheelchairs, a
cushioned seat pad includes extra cushioned overhangs that extend
beyond the front edge of the chair at the points where the legs
would be extending away from the seat surface, so that the cushions
angle down when the chair is in use. This extra cushioning protects
the backs of the patient's thighs from the edge of the chair, which
can interfere with circulation below the contact points. The
thickness of the chair pad increases on both sides of a
front-to-back centerline so that additional cushioning is located
below the ischial tuberosity, aka, the Sitz bone. The bottom
surface of the cushion has a generally rough texture so that
friction is generated between the top of the chair seat and the
bottom of the cushion.
[0055] Preferably, the cushion will include a cover made according
to the inventive support surface. The cover should be removable for
washing. The cushion can formed from a multi-layered material
having alternating layers of a flexible, resilient layer with shock
absorbing qualities (similar to common yoga mats) and a molded pad
of flexible, resilient material. The first layer may be a foam
material that is sufficiently open cell to permit air to be
retained within the material until the material is compressed. The
second layer may be formed from a material that has greater density
than the foam layer, and may include a gel filling for shock
absorption. This second layer consists of a flat sheet with
integrally formed ribs extending from both the top and the bottom
surfaces of the flat sheet. The ribs are angled in such a way that
a cross-section of the layer has the appearance of a herringbone
pattern. Depending on the material used to make the second layer,
each rib will have air or gel trapped within the ribs that is
squeezed out of the rib when a weight is applied. The angled
orientation of the ribs serves to reduce the shear factor that in
conventional pads contributes to pressure ulcers. Multiple
alternating layers of each of the two layers can be used to produce
the cushion. The number of layers can be adjusted according to the
patient's weight.
[0056] For use with bedridden or wheelchair-bound patients, the
sensor array is embedded in a resilient protective cover that is
surrounded by an envelope of impermeable material that can be
releasably attached to the undersurface of a multi-layer pad, as
shown in FIG. 3. The pad comprises a sheet of permeable cloth, a
moisture-absorbing material, a waterproof material and, optionally,
a pressure re-distribution surface such as resilient foam or a
gel-filled pad. Electrical connection to the sensor array is
provided by a cable connected to a processor, or by wireless (RF)
transmission.
[0057] In one embodiment, a sensor array is embedded in a thin
layer of resilient, flexible material formed in the shape of a foot
pad shoe liner. An exemplary liner is disclosed in U.S. Pat. No.
5,033,291, which is incorporated herein by reference. The sensors
detect real-time pressures against the boney prominences on the
foot and generates signals corresponding to the pressure. Signals
from the sensor array can be connected to a microcontroller that
controls a LED readout on the exterior of the shoe to provide
feedback to the wearer to warn of excessive pressure against one or
more locations on the foot, which can be used as an advisory to
remove or change the shoes, or to rest the feet. Alternatively, the
sensor array is connected to a wireless transmitter that transmits
a signal to a receiver and microcontroller that can be carried in
or on the user's clothing to activate a visual or audible alarm to
notify the user that pressure has exceeded a pre-determined
pressure for a pre-determined time period.
[0058] In another embodiment, an array of sensors is embedded in a
sleeve that can be inserted into or incorporated in a stocking that
extends at least part way up the lower leg for monitoring pressure
generated within varicose veins, for treatment and/or prevention of
venous ulcers. The sensor array provides input to a microcontroller
which in one application generates a display or alarm indicating
increased pressure and possible venous congestion that could lead
to ulceration. The patient or caregiver could then activate
electronic muscle stimulators to cause the surrounding muscles to
contract, as if the patient were walking or flexing the ankle, to
alleviate the pressure and restore normal flow. Alternatively,
mechanical compression can be applied by a pneumatic or hydraulic
pump. In another variation, electronic stimulators can be embedded
in the sleeve and connected to the microcontroller, which will
activate the stimulators in response to an increase in the detected
pressure at a location on the leg. The patient could wear the
sleeve/stocking when they are awake and sitting in a chair or wheel
chair, or even when walking.
[0059] Other embodiments of the pressure detecting sensor array can
be embedded in a protective flexible material that has been molded
or otherwise configured in thin cup-like shapes that conform to and
partially encompass a patient's heels or elbows. A textile cover
would be placed against the skin for comfort.
[0060] In one implementation, the sensors in the array are
relatively inexpensive disposable sensors that are embedded in a
disposable sheet, such as those disclosed in U.S. Pat. No.
5,033,291 mentioned above.
[0061] Referring to FIG. 5, the electronic portion 31 of the
invention will be described. The pressure value signals 32
generated by the transducer array 21 are led to a signal
conditioning unit 33a before entering a multiplexer 33b, the output
of the multiplexer is then provided to a video imaging unit 34 and
to a signal analyzer 35. The video imaging unit generates a video
signal which is used by a video monitor to provide a display 36 of
all the pressure points. The signal analyzer is programmed to
detect pressure points that exceed a preset limit as well as
pressure points of a given level that last for more than a preset
limit of time. The results of the analysis may also be fed to the
video imaging system and displayed as a visual alarm as part of the
mat display 36. The analysis results may also be used to trigger an
audio alarm 37 when excessive conditions have been identified by
the signal analyzer.
[0062] The entire electronic portion 31 including the transducer
array 21 data processing components and alarm indicators can be
implemented with a pressure-monitoring system such as the one
available from Tekscan, Inc. of South Boston, Mass., or XSensor
Corporation of Calgary, Canada.
[0063] In one embodiment, the signals generated by the sensors in
the array are converted by the signal analyzer 35 into an LED or
LCD display that is configured in a bar graph arrangement with
scaling corresponding to the interface pressures in increments of
10, depending on the measurement scale used, e.g., mmHg or
kilopascals. Thresholds set in the signal processor determine the
color of the bar graph. For example, where the pressure is below 25
mmHg, the color of the graph will be green. Between 25 and 40 mmHg,
the bar(s) will be yellow, and above 40 mmHg the bar will be red.
Multiple bars correspond to different regions as indicated by
identified sensors or sensor combinations. The signal processor
will store the detected pressure values in a memory and will record
a time associated with each measured pressure value to generate a
record of the patient's condition, when and how frequently elevated
pressures were detected, and when and how the pressure was
relieved, to help generate a patient management program.
[0064] In addition to the display generated by the processor, data
may also be output to a printer at regular intervals, for example,
every 24 hours, to produce a paper record for the patient's file,
or electronically transferred to a computer storage medium or
central network database on a continuous or regular periodic
basis.
[0065] In a preferred embodiment, a set of algorithms is provided
for continuous pressure monitoring based upon the Braden pressure
ulcer risk analysis tool along with one or more clinical parameters
related to the patient. As is known in the art, the Braden scale is
used to generate a numeral score for predicting pressure ulcer risk
based on factors including sensory perception, moisture, activity,
mobility, nutrition and friction. A study done by researchers in
Spain has determined that the Braden scale risk analysis
sensitivity and specificity are 57.1% and 67.5%, respectively.
(Pancoba-Hidalgo, et al., J Adv. Nurs. 2006 April; 54(1):94-110.)
Other methods that can be used include the Norton scale and the
Waterlow scale, however, these were found in the study to be less
reliable than the Braden scale.
[0066] In addition to the Braden factors, other important factors
involved in pressure ulcer risk include Spinal Cord Injury (SCI),
advanced disease state, and prior history of pressure ulcers.
Additional factors may include sedation, hypotension, history of
arterial insufficiency (evidenced by leg pains or reduced pulses),
age of patient, BMI (body mass index), recent hip or knee surgery,
type of mattress (lack of pressure re-distribution surface,
alternating pressure air mattress, or low pressure mattress, for
example), diabetes, advanced cancer, skin lactic acid level, or
loss of tissue turgor, perceived humidity of the sensor.
[0067] The diagram provided in FIG. 6d identifies different
possible data sources that can provide the information needed to
accurately and repeatably calculate and monitor a patient's risk of
developing ulcers. The first category of possible data points comes
from the physician's assessment of the patient, i.e., diagnosis of
a disease or condition. The second category comes from the clinical
assessment process that occurs, for example, during patient intake.
The third category uses the Braden scores--numerical values
assigned during patient assessment according to the Braden scale.
Laboratory data may also be considered, e.g., lactic acid levels,
etc., as is mattress type and the data generated by the pressure
sensors that are placed underneath the patient in a bed pad or
other pad. Raw data from each of these sources is input into a
supervised learning algorithm, such as a neural network, decision
tree or support vector machine, that processes and classifies,
i.e., "mines" the data, to identify patterns that may be used in
supporting human decisions or for establishing custom monitoring
criteria that are individually tailored for each patient. Such a
process would include steps of data selection, pre-processing the
data to clean and reconfigure it for processing, transforming the
data into an optimal form for analysis, and pattern extraction. The
analysis result is reported to the caregiver and/or stored within a
database containing the patient's history.
[0068] To provide a few simple examples of how a monitoring
algorithm can be applied, based upon the patient's Braden score and
the other data, a time-interface pressure curve can be applied to
generate indications that a caregiver's attention is required.
FIGS. 7a-c provide three examples of curves. The sample curves in
FIG. 6a are for a patient older than 65, who is frail, has not had
immediate surgery, and is in a nursing home, homecare or in a
hospital on a regular medical floor. In this case, the curves are
based on 50% Braden weighted score and 50% non-blanchable erythema.
Two different curves are shown, one for Braden score 16+NBE and one
for Braden score 12+NBE. Because the lower score represents greater
risk of developing ulcers, the amount of time that a patient is
allowed to remain at a given interface pressure threshold will be
less than a patient with a higher Braden score. In FIG. 6b, a
second algorithm is used for an acute care setting, for example, in
MICU, CCU, or when there is challenging fluid management issue. In
this algorithm, Braden score is weighted 75% and pitting edema of
the sacrum (PES) is weighted 25%. Again, there are two curves, one
for Braden 16+PES, the other for Braden 12 and PES. Sample curves
for a healthy young person with acute trauma are shown in FIG. 6c
and are generated by a combination of the Braden scale and some
other factor, e.g., nature of the injury, such as spinal cord
injury or head trauma. When the measured pressure exceeds the
threshold pressure as determined by the predictive algorithm, the
system controller will generate an alarm or other indicator that
attention is required.
[0069] While the preferred embodiments of the invention have been
described, modifications can be made and other embodiments may be
devised without departing from the spirit of the invention and the
scope of the appended claims.
* * * * *