U.S. patent application number 12/640643 was filed with the patent office on 2010-07-15 for patient support.
Invention is credited to Paul Canatella, Jean-Francois Girard, Sylvain Lacasse, Patrick Lafleche, Christopher Weyl, Patrick Gaudreau Wong.
Application Number | 20100175196 12/640643 |
Document ID | / |
Family ID | 42238845 |
Filed Date | 2010-07-15 |
United States Patent
Application |
20100175196 |
Kind Code |
A1 |
Lafleche; Patrick ; et
al. |
July 15, 2010 |
PATIENT SUPPORT
Abstract
A patient support includes a cover and a compressible layer that
includes air flow passages extending laterally, longitudinally, and
transversely through the layer. The cover envelopes the
compressible layer and forms a patient support surface thereon and
further is adapted to be liquid impermeable, yet allow moisture
vapor flow through the cover into the compressible layer and also
allow moisture vapor flow out of the cover at a location other than
the interface between a patient's body and patient support surface
so that together the cover and the compressible layer will
transport away moisture from the patient's body at the interface at
the patient support surface and direct the moisture vapor to the
location other than the interface at the patient support
surface.
Inventors: |
Lafleche; Patrick;
(Kalamazoo, MI) ; Girard; Jean-Francois; (Quebec
City, CA) ; Weyl; Christopher; (Newark, DE) ;
Canatella; Paul; (Bel Air, MD) ; Wong; Patrick
Gaudreau; (Quebec, CA) ; Lacasse; Sylvain;
(St-Romuald, CA) |
Correspondence
Address: |
VAN DYKE, GARDNER, LINN & BURKHART, LLP
SUITE 207, 2851 CHARLEVOIX DRIVE, S.E.
GRAND RAPIDS
MI
49546
US
|
Family ID: |
42238845 |
Appl. No.: |
12/640643 |
Filed: |
December 17, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61138354 |
Dec 17, 2008 |
|
|
|
Current U.S.
Class: |
5/707 ; 5/724;
5/726 |
Current CPC
Class: |
A61G 7/05769 20130101;
Y10T 29/481 20150115; A61G 7/05784 20161101; A61G 7/05715
20130101 |
Class at
Publication: |
5/707 ; 5/724;
5/726 |
International
Class: |
A47C 27/14 20060101
A47C027/14; A47C 27/00 20060101 A47C027/00; A47C 27/08 20060101
A47C027/08 |
Claims
1. A patient support comprising: a cover; and a compressible layer,
the compressible layer including air flow passages extending
laterally, longitudinally, and transversely through the layer, the
cover enveloping the compressible layer and providing a patient
support surface thereon for a patient, the cover being adapted to
allow moisture vapor flow through the cover into the compressible
layer at an interface between a patient and the patient support
surface and also allow moisture vapor flow out of the cover at a
location other than the interface so that together the cover and
the compressible layer will transport away moisture from the
patient's body at the patient support surface and direct the
moisture to the location other than the patient support
surface.
2. The patient support according to claim 1, wherein the
compressible layer comprises a 3D fabric layer or a gel layer.
3. The patient support according to claim 1, wherein the cover
comprises a liquid impermeable, moisture vapor permeable
material.
4. The patient support according to claim 1, wherein said cover
comprises a fabric laminate or a coated fabric.
5. The patient support according to claim 1, further comprising one
or more conduits for directing air flow into the compressible layer
to thereby enhance the air circulation through the compressible
layer.
6. The patient support according to claim 1, further comprising a
resilient layer, the compressible layer being supported on the
resilient layer.
7. The patient support according to claim 6, wherein said resilient
layer comprises a foam layer.
8. The patient support according to claim 1, wherein said cover is
adapted to allow air and moisture vapor flow through the cover into
the compressible layer.
9. A patient support for a patient comprising: a layer of bladders,
the bladders each having an upwardly facing surface for facing and
supporting the patient, the bladders being configured such that if
one or more bladders are compressed by a part of the patient's
body, the bladders surrounding the compressed bladder or bladders
envelope that part of the patient's body to thereby distribute the
weight of that part of the patients body over a greater contact
area than just the facing surface of the bladder or bladders that
are compressed by that part of the body; a permeable layer
supported by the bladders; and a cover, the permeable layer, and
the bladders enclosed in the cover, and the cover comprising a
moisture vapor permeable, but generally liquid impermeable cover
wherein moisture vapor may pass through the cover and into the
permeable layer, and the permeable layer forming a reservoir for
the moisture vapor passing through the cover.
10. The patient support according to claim 9, wherein each of the
bladders is in fluid communication with its surrounding bladders
and also with one or more pressure relief valves to allow air to
escape the bladders when the pressure in at least some of the
bladders exceeds a predetermined pressure.
11. The patient support according to claim 9, wherein the permeable
layer comprises a compressible permeable layer.
12. The patient support according to claim 11, wherein the
compressible permeable layer comprises a 3D fabric layer and/or a
gel layer.
13. A patient support comprising: a layer of fluid filled chambers;
a permeable layer overlying the layer of fluid filled chambers; a
gel layer supported on the permeable layer, the gel layer forming a
substantially smooth upper surface for supporting a patient, and
the gel layer configured to allow moisture vapor flow at least
laterally or longitudinally through the gel layer; and a cover
enveloping the layer of fluid filled chambers, the permeable layer,
and the gel layer and comprising a moisture vapor permeable, but
generally liquid impermeable cover, wherein moisture vapor may pass
through the cover and into the gel layer for circulation in the gel
layer.
14. The patient support according to claim 13, wherein the gel
layer includes a plurality of hollow gel bodies.
15. The patient support according to claim 14, wherein the hollow
gel bodies are interconnected by a plurality of gel webs, the gel
webs connecting the gel bodies at the upper surface wherein the gel
bodies and the gel webs form the substantially smooth upper
surface.
16. The patient support according to claim 13, wherein each of the
fluid filled chambers has a compressible body therein for reforming
the shape of the chamber after a load is removed from the
chamber.
17. The patient support according to claim 13, wherein the
permeable layer comprises a compressible permeable layer.
18. The patient support according to claim 13, wherein the
permeable layer comprises a spacer fabric, the spacer fabric
forming a reservoir allowing moisture vapor to flow into the spacer
fabric from the gel layer
19. The patient support according to claim 18, wherein the spacer
fabric comprises a 3D fabric layer.
20. The patient support according to claim 13, wherein the cover
comprises a GORE.RTM. Medical Fabric.
21. The patient support according to claim 13, wherein the cover is
adapted to allow air and moisture vapor to pass through the
cover.
22. A patient support comprising: a resilient layer, the resilient
layer having a patient facing side; a moisture vapor permeable and
liquid impermeable layer overlying the patient facing side; and a
space below the moisture vapor permeable and liquid impermeable
layer, the space adapted in the absence of a powered air supply to
allow moisture vapor to flow across or through the resilient layer
to thereby enhance the removal of moisture from a patient's body
supported on the moisture vapor permeable and liquid impermeable
layer.
23. The patient support according to claim 22, wherein the space is
formed by a spacer fabric.
24. The patient support according to claim 22, wherein the
resilient layer comprises a plurality of fluid filled bladders.
25. The patient support according to claim 22, wherein the moisture
vapor permeable and liquid impermeable layer comprises an air and
moisture vapor permeable and liquid impermeable layer.
26. The patient support according to claim 22, wherein the moisture
vapor permeable and liquid impermeable layer is formed by a cover,
the cover enclosing the resilient layer.
27. The patient support according to claim 26, wherein the cover
comprises a GORE.RTM. Medical Fabric.
Description
[0001] This application claims the benefit of U.S. provisional
application, entitled PATIENT SUPPORT, Ser. No. 61/138,354, and
filed Dec. 17, 2008, which is incorporated in its entirety by
reference herein.
TECHNICAL FIELD AND BACKGROUND OF THE INVENTION
[0002] The present invention relates to a support and, more
particularly, a patient support, such as a mattress that is adapted
for use on a patient bed used in a hospital or other patient care
facilities, including long term care facilities or the like.
[0003] When patients are hospitalized or bedridden for any
significant amount of time, patients can develop pressure sores or
ulcers. These pressure sores or ulcers can be exacerbated by the
patient's own poor circulation, such as in the case of diabetic
patients, but typically form as a result of prolonged immobility,
which allows the pressure exerted on the patient's skin from the
mattress to decrease circulation in the patient's tissue. Many
attempts have been made to reduce the occurrence of pressure sores,
ranging from simply repositioning the patient on the mattress to
alternating the pressure so that the high pressure points on the
patient's body are redistributed to other areas on the patient's
body. Despite these efforts, pressure sores still remain a health
issue.
[0004] In addition to reducing circulation in the patients' tissue,
lack of mobility can also cause moisture build-up at the point of
contact with the mattress. Moisture build-up can cause maceration
in the skin--which makes the skin more permeable and vulnerable to
irritants and stresses, such as stresses caused by pressure or by
shear, for example when a patient is moved across a mattress.
[0005] Accordingly there is a need for a mattress that can reduce
the pressure on a patient's skin and further that can improve air
circulation to the patient's skin, all in an attempt to improve the
care of a patient.
SUMMARY OF THE INVENTION
[0006] The present invention provides a patient support that
provides improves immersion and envelopment of the patient into the
surface of the patient support to thereby increase the contact
surface area between the patient support and the patient, which
reduces the pressure on the patient's body. Further, the patient
support may incorporate a microclimate management system that
improves air circulation at the interface between the patient and
the patient support.
[0007] In one form of the invention, a patient support includes a
cover and a compressible layer that includes air flow passages
extending laterally and transversely through the layer. The cover
envelopes the compressible layer and forms a patient support. The
cover is adapted to allow moisture vapor, and optionally air, to
pass through the cover and into the compressible layer at an
interface between a patient and the patient support surface and
also allow moisture vapor to flow out of the cover at a location
other than the interface so that together the cover and
compressible layer will provide enhanced air circulation and
further wick away moisture from the patient's body at the interface
at the patient support surface and optionally direct the moisture,
and optionally air, to a location other than the interface at the
patient support surface.
[0008] In one aspect, for example, the compressible layer may
comprise a 3D fabric layer. Alternately or in addition, the
compressible layer may comprise a gel layer. The cover may comprise
a moisture vapor permeable, but liquid impermeable material, such
as GORE.RTM. Medical Fabric, for example. The cover optionally may
also be air permeable.
[0009] In another aspect, the patient support further includes one
or more conduits for directing air flow into the compressible layer
to thereby enhance the air circulation through the compressible
layer.
[0010] In a further aspect, the compressible layer is supported on
a foam layer. The foam layer is also compressible, but may have a
lower permeability than the compressible layer. Additionally, the
foam layer may then be supported on a bladder layer, with all the
layers enclosed in the cover.
[0011] To further facilitate air circulation, the cover may include
one or more vents that allow moisture to exhaust from the
support.
[0012] In another form of the invention, a patient support includes
a layer of bladders. The bladders each have an upwardly facing
surface for facing and supporting the patient. The bladders may be
arranged in a matrix and configured such that if a bladder is
compressed by a part of the patient's body, the bladders
surrounding that compressed bladder may remain at least partially
uncompressed by that part of the patient's body and instead
envelope that part of the patient's body to thereby distribute the
weight of that part of the patient's body over a greater contact
area than just the facing surface of the bladder that is compressed
by that part of the patient's body. Further, each of the bladders
may be in fluid communication with its surrounding bladders to
allow redistribution of the pressure from the compressed bladder to
its surrounding bladders.
[0013] Optionally, the compressed bladder is in fluid communication
either directly or indirectly with enough of the surrounding
bladders so that the surrounding bladders do not exhibit a
significant increase in pressure so that they retain their unloaded
stiffness or compressibility.
[0014] In yet a further aspect, the bladders may be in fluid
communication either directly or indirectly with one or more
pressure relief valves to allow air to escape from the bladders
when the pressure in at least some of the bladders exceeds a
predetermined pressure.
[0015] According to yet other aspects, a compressible, permeable
layer may be supported by the bladders, which is enclosed with the
bladders in a cover. The cover may comprise a moisture vapor
permeable, but a generally liquid impermeable cover so that
moisture vapor may pass through the cover and into the compressible
permeable layer, with the compressible, permeable layer forming a
reservoir for the moisture vapor passing through the cover. For
example, the compressible layer may comprise a 3D fabric layer
and/or a gel layer.
[0016] In another form of the invention, a patient support includes
a gel layer formed from a plurality of substantially spherical gel
bodies, which are arranged in an array to define an upper surface
of the gel layer and a lower surface of the gel layer. Each gel
body is compressible along its central vertical axis from an
uncompressed state to a compressed state when a load is applied to
the gel body. When the load is removed, the bodies reform to their
uncompressed state. Each gel body has a gel sidewall that is
interconnected with the gel sidewall of at least one adjacent gel
body by a gel web, which limits lateral deflection of the gel
bodies when a lateral force is applied across the gel layer.
[0017] In other aspects, the gel webs and the gel bodies define
there between chambers bounded between a lower plane extending
through the lower surface if the gel layer and an upper plane
extending through the upper surface of the gel layer, which form
low pressure areas. For example, the gel webs and gel bodies may
together form the upper surface of the gel layer. Further, at least
a group of the gel bodies may each have an opening at its upper
surface. Additionally, at least a group of the gel bodies may each
have an opening at its lower surface.
[0018] In further aspects, at least one of the gel webs between two
adjacent chambers forms a fluid flow passageway at or above the
lower plane to provide fluid communication between the adjacent
chambers. For example, the passageway may extend through the gel
web. Optionally, a group of the gel webs each form a passageway at
or above the lower plane to provide fluid communication between
their respective adjacent chambers.
[0019] In another form of the invention, a patient support includes
a gel layer formed from a plurality of gel bodies that are arranged
in an array to define an upper surface of the gel layer and a lower
surface of the gel layer. The gel bodies are compressible along
their respective central vertical axes from an uncompressed state
to a compressed state when a load is applied to the bodies, which
reform to their uncompressed state when the load is removed. Each
gel body has a gel sidewall, which is interconnected with the gel
sidewall of at least one adjacent gel body by a gel web, which
together define there between chambers bounded between a lower
plane extending through the lower surface of the gel layer and an
upper plane extending through the upper surface of the gel layer.
At least some of the gel webs form transverse passages there
through to allow fluid to flow between their respective adjacent
chambers.
[0020] In any of the above forms, at least one of the gel bodies
comprises a hollow gel body. Further, each of the gel bodies may
comprise a hollow gel body. In addition, each of the gel bodies may
have an opening at the upper surface, and further may have an
opening at the lower surface.
[0021] In any of the above forms, the gel webs and the gel bodies
may be joined at their upper surfaces to thereby form a generally
smooth upper surface. Alternately, the gel webs may be recessed
below the upper surface.
[0022] Again in any of the above forms of the gel layer, the gel
bodies may be arranged in rows, with each row of gel bodies being
offset from an adjacent row of gel bodies.
[0023] Optionally, the above-described supports may also include a
layer of foam for supporting the gel layer. Further, the gel layer
may be coupled to the foam layer, such as by an adhesive. For
example, the gel bodies and/or the gel webs may be coupled to the
foam layer by the adhesive.
[0024] Alternately or in addition, the supports may incorporate a
compressible layer formed from a plurality of air chambers, with
the gel layer supported either directly by the air chambers or
indirectly through a foam layer interposed between the gel layer
and the chambers.
[0025] In another form of the invention, a patient support includes
a plurality of foam blocks, with each respective block being
encapsulated in fluid impermeable layers to form a chamber about
the respective block. Each of the chambers is in fluid
communication with an adjacent chamber and a shared inlet and a
shared outlet. The shared inlet includes a check valve, which is in
fluid communication with the atmosphere outside the chambers and
allows fluid to flow into the chambers through the shared inlet
when the pressure in the chambers is below the atmosphere outside
the chambers. The shared outlet includes a pressure relief valve,
which allows fluid to exit the chambers when the pressure in the
chambers exceeds a predetermined pressure.
[0026] In further aspects, the impermeable layers encapsulating the
foam blocks comprise one or more impervious sheets. For example,
the impermeable layer encapsulating the foam blocks may comprise
upper and lower impervious sheets, such as nylon sheets.
[0027] In yet further aspects, each of the chambers is in fluid
communication with an adjacent chamber through channels formed by
the sheets.
[0028] In other aspects, the foam blocks are arranged in rows
extending laterally across the mattress and in rows extending
longitudinally across the mattress wherein the foam blocks form a
matrix of foam blocks. Further, each of the chambers may have a
substantially planar upper surface when unloaded wherein the
chambers provide a substantially continuous support surface.
[0029] According to yet another form of the invention, a patient
support includes a plurality of foam blocks. Each respective block
is encapsulated in upper and lower impermeable layers to form a
chamber about the respective block. The chambers are in fluid
communication with their respective adjacent chamber or chambers
through a conduit and are in fluid communication with a shared
inlet and a shared outlet. The shared inlet has a check valve,
which is in fluid communication with the atmosphere outside the
chambers and allows fluid to flow into the chambers through the
shared inlet when the pressure in the chambers is at a
predetermined minimum pressure below the atmosphere outside the
chambers. The shared outlet has a pressure relief valve associated
therewith and allows fluid to exit the chambers when the pressure
in the chambers exceeds a predetermined maximum pressure.
[0030] In one aspect, the conduit is formed at the impermeable
layers. For example, the impermeable layers may be formed by at
least two sheets of impermeable material, such as a nylon, which
are heat sealed together about the foam blocks. Further, the
conduits may be formed between the sheets, for example, by portions
of the sheets that are not heat sealed together.
[0031] In yet other aspects, the foam blocks are separate, detached
foam blocks.
[0032] In yet another form of the invention, a patient support
includes a plurality of separate, detached foam blocks, and at
least two sheets of impermeable material encapsulating the blocks
to form chambers about the blocks and form a base layer on which
the blocks are supported. The chambers include a first group of
chambers, with each of the chambers in the first group of chambers
being in fluid communication with their respective adjacent
chambers in the first group of chambers and, further, being in
fluid communication with a first shared inlet and a first shared
outlet. The chambers also include a second group of chambers, with
each of the chambers of the second group of chambers being in fluid
communication with their respective adjacent chambers in the second
group of chambers and being in fluid communication with a second
shared inlet and a second shared outlet. Each of the shared inlets
includes a check valve associated therewith, which are in fluid
communication with the atmosphere. The check valve of the first
inlet allows fluid to flow into the first group of chambers from
the atmosphere through the first shared inlet when the pressure in
the chambers is at a predetermined minimum pressure below the
atmosphere outside the first group of chambers. The check valve of
the second shared inlet allows fluid to flow into the second group
of chambers through the second shared inlet when the pressure in
the second group of chambers is at a predetermined minimum pressure
below the atmosphere outside the second group of chambers. Each of
the shared outlets has a pressure relief valve associated
therewith. The relief valve of the first shared outlet allows fluid
to exit the first group of chambers when the pressure in the first
group of chambers exceeds a predetermined maximum pressure. The
relief valve of the second shared outlet allows fluid to exit the
second group of chambers when the pressure in the second group of
chambers exceeds a predetermined maximum pressure.
[0033] In one aspect, the patient support also includes a plurality
of conduits to provide communication between the respective
chambers. For example, the conduits may be provided at the base
layer. Further, they may be formed between the sheets.
[0034] According to yet another form, a patient support includes a
layer of fluid filled chambers, a compressible layer overlying the
layer of fluid filled chambers, and a gel layer supported on the
compressible layer, which forms a substantially smooth upper
surface for supporting a patient and which is configured to allow
air flow at least laterally or longitudinally through the gel
layer.
[0035] In further aspects, the gel layer includes a plurality of
hollow gel bodies. Further, the hollow gel bodies may be
interconnected by a plurality of gel webs, which connect the gel
bodies at the upper surface wherein the gel bodies and the gel webs
form the substantially smooth upper surface.
[0036] In other aspects, each of the fluid filled chambers has a
compressible body therein for reforming the shape of the chamber
after a load is removed from the chamber.
[0037] In addition, the support may include a structural fabric
layer, such as a 3D fabric layer, beneath the gel layer which forms
a reservoir for allowing moisture vapor or moisture vapor and air
to flow into the fabric layer from the gel layer.
[0038] In other aspects, each of the fluid filled chambers has a
compressible body therein for reforming the shape of the chamber
after a load is removed from the chamber.
[0039] According to yet other forms of the invention, a patient
support includes a resilient layer, which has a patient facing
side, a moisture vapor permeable and liquid impermeable layer
overlying the patient facing side of the resilient layer, and a
space below the moisture vapor permeable and liquid impermeable
layer, which is adapted in the absence of a powered air supply to
allow moisture vapor to flow across or through the resilient layer
to thereby enhance the removal of moisture from a patient's body
supported on the moisture vapor permeable and liquid impermeable
layer.
[0040] In one aspect, when a source of liquid and/or moisture is
present on the moisture vapor permeable and liquid impermeable
layer, the moisture vapor transfer (MVT) into the support through
the moisture vapor permeable and liquid impermeable layer is, after
a first period of time, at a first MVT, with the first MVT decaying
after a second prior time to a second MVT that is less than the
first MVT, and then decaying to a third MVT after a third period of
time which is less than the first and second MVTs, with the third
MVT being greater than 20 g/(m.sup.2hr),
[0041] In a further aspect, the third MVT is at least 30
g/(m.sup.2hr) and further optionally in a range of approximately 30
to 48 g/(m.sup.2hr).
[0042] In another aspect, when a source of liquid and/or moisture
is present on the moisture vapor permeable and liquid impermeable
layer, the moisture vapor transfer (MVT) into the support through
the moisture vapor permeable and liquid impermeable layer is, after
about thirty minutes, at a first MVT, with the first MVT decaying
after time to a second MVT that is less than the first MVT, with
the second MVT being greater than 20 g/(m.sup.2hr),
[0043] In a further aspect, the second MVT is at least 30
g/(m.sup.2hr) and further optionally in a range of approximately 30
to 48 g/(m.sup.2hr).
[0044] In yet another aspect, when a source of liquid and/or
moisture is present on the moisture vapor permeable and liquid
impermeable layer, the moisture vapor transfer (MVT) into the
support through the moisture vapor permeable and liquid impermeable
layer is initially at a first MVT, with the first MVT decaying
after time to a second MVT that is less than the first MVT, with
the first MVT being at least 60 g/(m.sup.2hr), and optionally in a
range of 70 to 105 g/(m.sup.2hr),
[0045] Accordingly, the present invention provides a patient
support that reduces the pressure points on a patient lying on the
support. Further, the support may be configured to increase fluid
(e.g. moisture vapor or moisture vapor and air) circulation through
the support to wick moisture away from the patient's skin.
[0046] These and other objects, advantages, purposes, and features
of the invention will become more apparent from the study of the
following description taken in conjunction with the drawings.
DESCRIPTION OF THE FIGURES
[0047] FIG. 1 is a perspective view of a patient surface of the
present invention;
[0048] FIG. 2 is an exploded perspective view of a patient surface
of FIG. 1 with the cover removed;
[0049] FIG. 3 is a plan view of the bladder layer of the
surface;
[0050] FIG. 4 is an end elevation view of the bladder layer of the
surface;
[0051] FIG. 5 is an enlarged cross-section through line V-V of FIG.
4;
[0052] FIG. 6 is a cross-section taken through line VI-VI of FIG.
4;
[0053] FIG. 7 is a bottom perspective of the gel layer;
[0054] FIG. 8 is a top plan view of the gel layer;
[0055] FIG. 9 is a top perspective view of the gel layer;
[0056] FIG. 10 is a cross-section view taken along line X-X of FIG.
7;
[0057] FIG. 11 is a perspective view of another embodiment of the
gel layer of the present invention;
[0058] FIG. 12 is a plan view of the gel layer of FIG. 11;
[0059] FIG. 13 is a cross-section view of the gel layer of FIG.
13;
[0060] FIG. 14 is a cross-section taken through one embodiment of
the patient support of the present invention; and
[0061] FIG. 15 is a graph representing test data for the moisture
vapor transfer through several embodiments of the patient support
of the present invention and of several prior art patient supports
incorporating a coated nylon cover.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0062] Referring to FIG. 1, the numeral 10 generally designates a
patient support of the present invention. As will be more fully
described below, support 10 may be configured as a mattress for a
bed, such as a hospital bed, and comprises a system of layers that
together provide increased comfort for the patient. For example,
support 10 may be configured to reduce high pressure points on the
patient's body when lying on the support by increasing the
immersion and envelopment of the patient's body into the support's
upper surface. Further, support 10 may be configured to provide
increased air circulation in the support itself to thereby reduce
the moisture build up at the interface between the patient and the
support. As noted above, with reduced moisture build up, the
patient's skin properties are less likely compromised due to
maceration. Although support 10 is described as a non-powered
support, the support of the present invention may also be
configured as a powered support, as described in more detail
below.
[0063] As best seen in FIGS. 1 and 2, in the illustrated
embodiment, support 10 includes a first compressible, resilient
layer in the form of a bladder layer 12 and a fluid (gas and
liquid) permeable layer 14, which is supported on the bladder layer
12. As will be more fully described, below, layer 14 may also be
compressible. The permeable layer is optionally supported on
bladder layer 12 by a second compressible, resilient layer in the
form of a foam crib 16, which may be formed from a viscoelastic
foam, for example. Crib 16 includes downwardly extending sidewalls
16a and end walls 16b, and a top wall or layer 16c, which extends
over the side walls and end walls and over the bladder layer to
support the permeable layer 14. Top layer 16c and walls 16a and 16b
enclose bladder layer 12 in the cavity formed between the sidewalls
and end walls and beneath the top layer. The cavity may extend over
the full length of the top wall or may extend for only a portion of
the top wall, for example at the torso end of the patient
support.
[0064] Top layer 16c may, for example, comprise a foam layer having
a thickness, for example in a range of about 1/4 inch to 3 inches.
In addition to contribution to the overall resiliency of support,
crib 16 also can provide stability to the bladder layer and,
further, may be used for line management, e.g. to contain conduits,
such as tubing, which may be used to direct fluid, namely air, to
and from the bladders in the case of a powered version of the
support. Further, the foam crib 16, which has a substantially
rectangular perimeter, may provide a surface that better holds a
sheet in place and further eases handling of the support as a unit.
Though as described more fully below in reference to another
embodiment, the upper perimeter edges or corners of the foam crib
may be softened or rounded. In addition, top layer 16c may provide
an anchor layer for layer 14. Once assembled, the crib and the
permeable layer supported by the crib are then enclosed in a fire
sock (not shown) and then a cover 19, which may be formed from a
moisture vapor permeable, but liquid impermeable material, such as
GORE.RTM. Medical Fabric, available from W. L. Gore &
Associates, Inc., of Elkton, Md. Further, the cover may also be gas
or air permeable.
[0065] As noted, cover 19 optionally comprises a moisture vapor
permeable, but liquid impermeable cover, which may be formed from
one or more sheets of moisture vapor permeable, but liquid
impermeable fabric that are joined together to form a pocket in
which the other layers (or layer) are enclosed. The cover may
include a zipper or other attachment devices, such as hook and loop
fasters to close the cover about the layers. Cover 19 may be
selected from a material or materials that allow moisture, and
optionally as noted air, to permeate through cover but is adapted
to prevent liquids, for example bodily fluids, from permeating the
cover. However, as noted moisture in the form of vapor, for example
caused from perspiration, may permeate the cover.
[0066] The moisture vapor transmission rate (MVTR) of both layer 14
and cover 19 may vary considerably. For example, it may be
desirable to have a higher permeability in layer 14 than in cover
19 to assure that the moisture vapor that permeates cover 19 can be
quickly distributed throughout layer 14. In one embodiment of the
invention, cover 19 may have a MVTR in a range of 100 g/m.sup.2/24
hours or greater, while layer 14, for example, may have a higher
permeability. For example, depending on the application, suitable
materials for the cover may include coated fabrics such as, for
example, DARTEX fabric (Dartex Coatings, Inc., Slatersville, R.I.),
having a MVTR of about 150-200 g/m.sup.2/24 hours. Materials, such
as Dartex, may be suitable where moisture management is less
critical and pressure reduction is a primary concern.
Alternatively, in an embodiment of the invention where a fabric
laminate is used, for example, in applications where moisture
management is of greater concern, the cover layer 19 may have a
MVTR of 1000 g/m.sup.2/24 hours. For example, suitable materials
for the cover may comprise fabric laminates such as, for example,
GORE.RTM. Medical Fabrics having a MVTR on the order of 1000
g/m.sup.2/24 hours or greater, and even as high a 3000 g/m.sup.2/24
hours or greater, and even as high as 6000 g/m.sup.2/24 hours or
greater, depending on the desire to tailor the properties of the
resulting patient support. In this manner, cover 19 can help wick
away moisture from the interface I between the patient's body B and
the upper surface 10a of the support 10, and layer 14 can disperse
the moisture through layer 14 to facilitate evaporation (see FIG.
14).
[0067] For the purpose of determining Moisture Vapor Transmission
Rate (MVTR), the following test is carried out: The samples
(measuring larger than 6.5 cm in diameter) were conditioned in a
23.degree. C., 50%+/-2% RH test room. Test cups were prepared by
placing 70 grams of a Potassium Acetate salt slurry into a 4.5
ounce polypropylene cup having an inside diameter of 6.5 cm at the
mouth. The slurry was comprised of 53 grams of potassium acetate
crystals and 17 g of water. The slurry was thoroughly mixed with no
undissolved solids present and stored for 16 hours in a sealed
container at 23.degree. C. An expanded PTFE membrane (ePTFE),
available from W. L. Gore and Associates, Inc., Elkton, Md., was
heat sealed to the lip of the cup to create a taut, leakproof
microporous barrier holding the salt solution in the cup. A similar
ePTFE membrane was mounted taut within a 12.7 cm embroidery hoop
and floated upon the surface of a water bath in the test room. Both
the water bath and the test room were temperature controlled at
23.degree. C.
[0068] Samples to be measured were laid upon the floating membrane,
and a salt cup inverted and placed upon each sample. The salt cups
were allowed to pre-condition for 10 minutes. Each salt cup was
then weighed, inverted and placed back upon the sample. After 15
minutes, each salt cup was removed, weighed, and the moisture vapor
transmission rate was calculated from the weight pickup of the cup
as follows:
MVTR g / ( m 2 .times. 24 hours ) = Weight ( g ) water pickup in
cup [ Area ( m 2 ) of cup mouth .times. Time ( days ) of test ] .
##EQU00001##
[0069] The average of five tests was used.
[0070] Further, cover 19 may include one or more vents 19a, which
are formed in, for example, the sides of the support. Vents 19a may
be as simple as openings or may be screened openings. For example,
the perimeters of the top and bottom sheets forming the cover may
be left unjoined to form the opening, with a fabric screen sewn or
otherwise secured over the opening. Additionally, fabric flaps may
be provided to conceal the vents. In this manner the moisture can
be drawn away from the patient support surface at interface I with
the patient and redirected through layer 14 to a location other
than at the interface between the patient and the patient support
surface, for example, to the openings or vents in the cover.
[0071] As noted, layer 14 facilitates the wicking away of moisture
from the interface between the patient and the support. Further,
layer 14 may comprise a compressible, permeable layer, such as a
spacer fabric, such a 3D fabric. For example a 3D fabric with a
thickness in a range of 1/8 inch to 1/2 inch, including 1/4 inch
thick to 3/8 inch thick may be sufficient. 3D fabrics are woven in
three dimensions and, as noted, may be compressible. Because of
their internal structure, 3D fabrics have a plurality of
interstices that allow fluid flow, especially air flow both
transversely, laterally, and longitudinally through the fabric.
Transversely in this context means through the thickness of the
fabric. Laterally generally is used in this context to mean through
the width, and longitudinally is used in this context to mean
through the length of the fabric. Therefore, when layer 14 is
positioned beneath cover 19, layer 14 allows the moisture vapor
that permeates cover 19 to then flow transversely, laterally and/or
longitudinally through layer 14. The direction of flow can vary
depending on the internal structure of the spacer fabric and the
temperature gradient through layer 14. Thus, layer 14 absorbs
humidity and further forms a reservoir wherein the moisture vapor
can be dispersed. Once air flow is established through layer 14,
either by way of passing through cover 19 (if cover 19 is air
permeable) or through one or more vents or openings provided in
cover 19, the moisture vapor and air may be discharged from layer
14 away from the patient/support interface, for example, through
other vents or openings 19a.
[0072] Referring to FIG. 14, when a patient's body B is lying on
support 10, the patient's perspiration and/or bodily fluids will
tend to collect at the interface I between the patient's body and
the upper surface or patient support surface 10a of support 10,
which is defined as the upwardly facing surface 19b of cover 19
beneath the patient's body. As noted, cover 19 may be formed from a
moisture vapor permeable but liquid impermeable fabric so that
moisture at interface I passes through cover 19, as shown by the
arrows A1 in FIG. 14, into layer 14. Given the permeable nature of
layer 14, the moisture vapor can pass or flow transversely,
longitudinally, and/or laterally through layer 14, and may exit
support 10 through the cover (19) at a location other than
interface I, as shown by arrows A2, or may pass into layer 16 as
shown by arrows A3. Further, the moisture vapor may pass or flow
into layer 20, for example, into the spaces between the respective
bladders, as shown by arrows A4. Additionally, moisture vapor may
flow to the edges of layer 14 (as well as layer 16), such as shown
by arrows A5. Consequently, the one or more layers under cover 19
act as a reservoir or reservoirs and a medium to wick the moisture
away from the patient's body at the interface with support surface
10a of support 10.
[0073] Alternately, as more fully described below, the support may
incorporate an air flow system that directs air into layer 14 to
circulate air through layer 14 and further facilitate the wicking
away of moisture from the patient/support interface, which also
facilitates the discharge of the vapor and air from the support
from a location other than the patient support surface formed on
the patient facing side of support 10. This system may be powered
by an external air supply or may be supplied with air from the
bladder layer, more fully described below.
[0074] As noted above, layer 14 may be anchored to top layer 16c.
For example, layer 14 may be fastened to top layer 16c by an
adhesive or other fastening methods, including hook and loop
fasteners or the like. In addition, layer 14 may be extended and
anchored to the side walls and/or end walls of crib 16, also by an
adhesive or other fastening methods. Further, when anchored to the
walls of crib 16, layer 14 may be tensioned over crib 16 so as to
round off the upper perimeter edges of the crib. This may eliminate
or reduce the pinch points when the support is placed on a bed
frame.
[0075] Alternately, layer 14 may be placed directly on the bladder
layer and further, optionally be formed by a plurality of patches
or sections of fabric that are located at the upwardly facing
surfaces of at least a group of the bladders, more fully described
below
[0076] As best seen in FIGS. 3-7, bladder layer 12 includes a
plurality of bladders 20 that are arranged in rows across the
mattress both in the lateral direction or axis and longitudinal
direction or axis. In this manner, bladders 20 are arranged in a
matrix, and with each bladder being relatively compact in size,
which tends to make the control over the pressure in the surface
more precise. Further, the bladders provide better immersion and
envelopment of the patient's body. For example, if a patient's body
is resting on a bladder (or several bladders), that bladder (or
bladders) will compress and the bladders surrounding the compressed
bladder (or bladders) may remain uncompressed and therefore will in
effect cradle that portion of the patient's body. Further, with
each bladder being independently compressible from the surrounding
bladders, the compressed bladders will allow for greater immersion
of the patient into the surface. The combined effect of greater
immersion and increased envelopment is to increase the area of
interface between the patient and the support which will improve
the distribution of stress across the patient's body.
[0077] For example, the bladders are generally cube-shaped with a
width or length dimension, for example, in a range of 1'' to 4''.
Further, the thickness of the side chambers walls of the bladder
may be thinner than the upper or top chamber walls of the bladders.
For example, the thickness of the side walls of the bladders and
the thickness of the upper chamber wall may be in a range of 0.003
to 0.025 inches. As will be more described below, each bladder 20
forms an air spring with a generally smooth and generally flat or
planar upper surface. Further, the bladders are arranged in
generally close proximity to each other. For example, bladders 20
may be arranged so that they have gaps in a range of 1/32 of an
inch to 1/2 inch between them when assembled and in an unloaded
state. It should be understood these dimensions are exemplary only
and that other dimensions may be used. In this manner, bladders 20
provide a substantially continuous smooth upper support surface
with only small regions of no support.
[0078] Referring to FIG. 5, each bladder 20 is formed from a foam
block 22 that is encapsulated by impervious layers 24, which form a
chamber 26 around each block 22. In the illustrated embodiment, the
impervious layers are formed by two impervious sheets 28, 30 that
are molded around the foam blocks, for example, by thermal forming.
In this manner, the lower sheet 30 forms a base layer for bladder
layer 12. Though it should be understood that a single sheet may be
used that is folded over to form the upper and lower impermeable
layers. A suitable material for the sheet or sheets includes a
flexible impermeable material, such as polyurethane or nylon. The
method of forming bladder layer 12 will be described below. The
patches or sections of the permeable material can then be located
on the upper support surface of the bladders (at least the bladders
that would be likely to be under a patient's body). The patches are
optionally secured at the upper support surfaces of the bladders,
for example by an adhesive.
[0079] In the illustrated embodiment, and as best seen in FIG. 3,
each chamber 26 is in fluid communication with its adjacent
chambers by a conduit 32, for example, which may be provided at the
base layer. Conduits 32 may be formed from tubing or, as shown, may
be formed between and by sheets 28 and 30. For example, when heat
sealing the two sheets together around the foam blocks, the mold
that heat seals the two sheets together may have relief areas so
that selected regions of the sheets are not welded together, which
unsealed regions form the passageways. Alternately, tubes may be
placed between the sheets or a release material may be applied to
one or more of the facing sides of the sheets at discrete portions
that extend between the chambers, which prevents the two sheets
from being joined together and from forming seals (29, see e.g.
FIG. 6) where the release material is applied. In this manner,
passageways can be created between the adjacent chambers to allow
air flow between the chambers.
[0080] Consequently, each bladder is independently compressible
from its surrounding bladders and further when compressed does not
significantly impact the pressure in the adjacent chambers since
any redistribution of air is redistributed to all the bladders
surrounding the compressed bladder, which surrounding bladders in
turn redistribute any increase in pressure to their respective
surrounding bladders. Consequently, as noted above, when pressure
is applied to one bladder, the surrounding bladders will remain
substantially in their static or unloaded configuration and hence
will cradle that portion of the patient's body that is immersed
into the compressed bladder. Further, because the pressure in the
surrounding bladders is not significantly increased, they
substantially retain their same compressibility and stiffness and
do not inhibit movement of the patient even though the patient may
be fairly deeply immersed into the surface.
[0081] In this embodiment, flow of air into and out of layer 12 is
controlled by one or more inlet check valves 40 and one or more
outlet pressure relief valves 42, which are mounted for example at
the outer seam formed at the perimeter of layer 12 and are each in
fluid communication with the atmosphere outside the chambers. The
check valve (or valves) allow air to flow into the chambers when
the pressure inside the bladders falls below a predetermined
minimum pressure value below the atmosphere (which selected as the
set pressure of the check valve). The pressure relieve valve (or
valves) open to allow air to flow from the chambers when the
pressure in the chambers exceeds a preselected maximum pressure
value (which is selected as the release pressure for the valve) and
thereby vent to the atmosphere.
[0082] In the illustrated embodiment, layer 12 includes three
groups of chambers. One group of chambers, for example, may be
provided at the foot end of the layer, another group at the torso
region, and the other group may be provided at the head end of the
layer. Each group of chambers is isolated from the other group, but
with each chamber in each group in fluid communication with its
adjacent chambers. Therefore, in order to provide air flow to each
group of chambers, layer 12 may include one or more check valves 40
and one or more pressure relief valves 42 for each group of
chambers. When forming the three groups of bladder from two sheets,
the three groups may be formed in a similar manner to a single
group of chambers except the passageways between the adjacent
chambers in the different groups are not formed. In other words,
only the chambers in the same group will have passageways formed
between their adjacent chambers. Alternately, each group of
bladders may be made separately and then optionally coupled to the
adjacent group of bladders.
[0083] In another embodiment of the bladder layer, one or more
bladders in each group of bladders may be isolated from the other
bladders and, therefore, may include their own inlet and outlet
valves. Alternately, one or more bladders may be sealed.
[0084] In the illustrated embodiment, two inlet check valves and
two pressure relief valves are associated with each group of
chambers. Further, the valves may be mounted at ports 40a and 42a
formed between the two sheets 28 and 30, for example, as noted at
the sides of bladder layer in the seam formed by perimeter flanges
43, which are formed around the perimeter of layer 12 when the two
sheets are thermal formed together. It should be understood that
the valves may be in fluid communication with the ports via a
conduit, such as tubing. However, with the present design, tubing
for inflating the bladders can be entirely eliminated, at least for
a non-powered surface. It should be understood that tubing may
still be needed for other purposes, for example, a low air loss
system. Even then, as more fully described below, the low air loss
system may be supplied by the bladders themselves.
[0085] The foam forming foam blocks 20 may be formed from a single
sheet of foam, for example, a foam sheet having a thickness in a
range of 1 inch to 4 inches. Suitable foams include foams having a
LDI in a range of 15 to 90 or in a range of 30 to 50. The foam
sheet is then cut into the foam blocks by a cutter. The foam blocks
are then positioned between two sheets (or two folded portions of
one sheet) of flexible impermeable material, such as polyurethane
or nylon. Then using a mold and heat (thermoforming), the upper
sheet conforms to the foam blocks and is welded to the lower sheet
between each block to thereby encapsulate the foam blocks between
the two sheets. Further, as noted above, the mold may have reliefs
formed in the molding surface where a seal or weld is not desired,
such as to form the passageways (to allow the chambers to have
fluid communication) or at the ports.
[0086] Bladder layer 12 may also be formed by dipping foam blocks
in molten rubber or the rubber may be sprayed onto the foam blocks.
Alternately, the bladder layer may be formed from an injection
molding process. For example, the material forming the impermeable
outer layer may be injected into a mold cavity to form the side of
the bladder layer with the chambers. After cooling, the foam blocks
may then be placed into the respective cavities and thereafter
enclosed by the second sheet of the impermeable outer layer placed
over the blocks to thereafter welded or glued to the first layer.
Alternately, the material forming the impermeable outer layer may
be injected into a mold cavity around the foam blocks.
[0087] Referring again to FIG. 1, layer 14 may be substituted for
or supplemented with a third compressible, resilient layer, namely
a gel layer 18. Gel layer 18 may be placed on layer 14 and may be
anchored to layer 14 and also enclosed with crib 16, layer 14 and
bladder layer 12 in cover 19. Where gel layer 18 is provided in
lieu of layer 14, then gel layer 18 may be anchored directly to top
layer 16c or may be placed directly on bladder layer 12. Further,
as more fully described below, gel layer 18 may also be adapted to
allow moisture vapor and optionally air to flow transversely,
laterally, and/or longitudinally through gel layer 18. Therefore,
in addition to forming a resilient layer, gel layer 18 may also
form a permeable layer to facilitate the wicking away of moisture
from the interface between a patient's body and the patient support
surface
[0088] Referring to FIGS. 7-10, gel layer 18 includes a plurality
of gel bodies 44. Gel bodies 44 are generally spherical in shape
and further optionally hollow so that they provide a low stiffness
or soft spring for resiliently supporting the patient's body.
However, in order to eliminate the noticeable point contact that is
associated with some prior art surfaces, such as disclosed in PCT
WO 2007/128113, gel bodies 44 are interconnected by a plurality of
gel webs 46, which connect the respective sidewalls 48 of adjacent
gel bodies 44 at the upper surface of layer 18 to thereby form the
upper surface of the gel layer along with the gel bodies. Gel webs
46 have a wall thickness that may be greater than the wall
thickness of the sidewalls of the gel bodies so that they provide
similar spring stiffness to the gel bodies.
[0089] Further, the gel webs each have an upper facing surface 50
that is generally continuous with the upper surface 52 of each gel
body 44 so that together the gel bodies and gel webs form a
substantially smooth upper surface, which reduces, if not
eliminates, the feeling of being supported on discrete points. In
addition, by extending the connection between the gel webs and the
respective gel bodies over substantially the full height of the gel
bodies, the gel webs stiffen the gel body walls. Further, this
construction limits the lateral movement of the individual gel
bodies by tying them together in a grid. By limiting the lateral
movement of the gel bodies, the drag on a cover, which is placed
over the gel layer, is reduced, which may reduce the shear on a
patient's skin.
[0090] Referring again to FIG. 6, gel bodies 44 are generally
equally spaced from each other and together with gel webs 46 form
cavities or chambers between them that are bounded by a generally
horizontal plane that extends through the upper surface of bladder
layer 12 and the generally horizontal plane that extends through
the lower surface of bladder layer 12, which is closed by
compressible layer 18. Similarly, the upper plane is closed by the
cover noted above. Hence, gel layer 14 includes a plurality of
pockets or chambers 54 defined between the cover and layer 18 and
between gel webs 46 and gel bodies 44, which may be used as part of
a fluid circulation system, described below. Further, these
chambers form areas of low pressure, while bodies 44 form areas of
higher pressure.
[0091] As noted above, gel bodies 44 may comprise hollow gel
bodies. In order to allow air to escape from the chambers formed in
the hollow gel bodies, each gel body may include an upper opening
44a so that when a load is applied to the gel bodies, air will flow
out of the gel body. The downwardly facing side of each gel body
also includes an opening 44b, which may be covered by layer 14, as
noted below. The size of the upper opening may be adjusted to
control to some degree how quickly the gel body will compress when
a load is applied.
[0092] As noted, chambers 54 formed between gel bodies 44 and gel
webs 46 may be part of a fluid movement system to increase
circulation through the support similar to the 3D fabric layer
referenced above. Further, as noted, it may replace the 3D fabric
layer or the thickness of the 3D fabric may be reduced. In the
illustrated embodiment, fluid communication between the chambers 54
may be provided by forming passageways through or below gel webs
46, which allow fluid to flow laterally and longitudinally through
the gel layer. As best seen in FIG. 9, each gel web 46 includes a
recessed portion 56 at its lower edge at their juncture with layer
14, which forms fluid passageways between the adjacent chambers.
This recess may be provided by forming an opening in the respective
webs or may be formed when molding the webs, with the latter most
likely providing the most efficient method of forming the fluid
passageways. In this manner, each of the chambers may be in fluid
communication with each other. Consequently, air can flow laterally
and longitudinally through gel layer, and also transversely, which
allows moisture to be wicked away from the patient's skin.
[0093] As noted above, gel layer 18 may be secured to layer 14. For
example, gel layer 18 may be secured to layer 14 by an adhesive.
When joining gel layer 18 to layer 14, the adhesive may be applied
between the gel webs as well as the perimeter of openings 44b so
that both the webs and gel bodies are anchored to layer 14.
[0094] In order to further enhance fluid (moisture vapor and/or
moisture vapor and air) circulation through surface 10, surface 10
may include another permeable layer 60 on top of gel layer 18,
which is moisture vapor permeable, or air and moisture vapor
permeable or which is permeable to all fluids. For example, a
suitable moisture vapor permeable layer may be formed from
GORE.RTM. Medical Fabric. Alternately, a permeable layer may
include a spacer fabric, such as a 3-D fabric. With the 3-D fabric,
as noted, the porosity of the material not only provides
permeability transversely through the thickness of the layer but
also laterally and longitudinally through the layer.
[0095] In addition, support 10 may include a low air loss system or
air circulation system. For example, separate perforated conduits,
such as perforated tubing, may be mounted between the bladders and,
further, may be positioned between selected chambers so that the
conduits run across the width or length (or both) of layer 12 at
discrete locations below top layer 16c. The tubes or tubing may
then direct air into layer 14. For example, top layer 16c may
incorporate one or more openings to allow the ends of one or more
tubes to be positioned to direct air to flow into layer 14.
[0096] These tubes or tubing is then coupled to a supply of air,
for example an air blower or pump, which is then regulated by a
conventional control. Further, the pump and any supporting control
system may be mounted in the support itself, such as described in
U.S. Pat. Nos. 5,325,551, and 5,542,136, both commonly owned by
Stryker Corporation of Kalamazoo, Mich.
[0097] Alternately or in addition, bladder layer 12 may be adapted
to form the low air loss system or air circulation system. In one
form, air flow to bladder layer 12 may be controlled by a powered
system that includes a blower or pump that is in fluid
communication with one or more of groups of chambers, for example
by tubing, to supply air flow to the chambers. Perforations then
may be formed or otherwise provided in the upwardly facing side of
chambers, which allow air to flow upwardly to thereby form a
low-air loss system or air circulation system. In this manner, the
upper surfaces of the bladders are at least permeable to the flow
of air. Alternately, the top sheet forming the bladders may be
formed from a gas permeable material but with a transfer rate that
permits air to inflate the respective bladders and maintain
inflation of the bladders but which permits sufficient air to flow
from the top surface of the bladders to help wick away
moisture.
[0098] In yet another embodiment, the self-adjusting bladders may
be coupled to one or more tubes or tubing, which may be coupled to
the bladders through the pressure relief valves. In this manner,
rather than exhausting the excess air from the bladders at the side
of the bladder layer when the pressure in the bladder layer exceeds
a desired pressure value, the exhaust air may be redirected to
layer 14 for climate control purposes. In this manner, the
patient's movement may power the air circulation or low air loss
system.
[0099] In any of these applications, as noted, layer 14 preferably
comprises a permeable layer so that air flowing from the bladder
layer or tubes will pass through layer 14 so that the flowing air
will facilitate the wicking away of moisture from the patient's
skin.
[0100] Further, while described above as having foam blocks in each
bladder, when the present invention is used as a powered system,
e.g. when used in combination with a pump or blower and a control
system, then the foam in one or more of the bladders may be
eliminated.
[0101] Referring to FIGS. 11-13, the numeral 118 refers of another
embodiment of the gel layer of the present invention. Gel layer 118
similar to gel layer 18 includes a plurality of gel bodies 144. Gel
bodies 144 are generally semi-spherical in shape and also
optionally hollow so that they provide a low stiffness or soft
spring for supporting the patient's body. Gel bodies 144 are also
interconnected by a plurality of gel webs 146, which connect the
respective sidewalls 148 of adjacent gel bodies 144 at the upper
surface of layer 118 to thereby form the upper surface of the gel
layer along with the gel bodies. Gel webs 146 have a wall thickness
that may be greater than or generally equal to the wall thickness
of the sidewalls of the gel bodies so that they provide a similar
spring stiffness to the gel bodies.
[0102] Similar to layer 18, layer 118 includes a plurality of
chambers or cavities between the gel bodies and the gel webs that
are in fluid communication with each other to provide lateral and
longitudinal air flow through layer 118.
[0103] In the illustrated embodiment, layer 118 is formed from two
gel layers, each formed as shown in FIG. 13, but which are then
oriented so that the open ends of the semi-spherical bodies are
facing each other to thereby form spherical gel bodies. The layers
are joined at their respective facing surfaces, for example by an
adhesive. For further details of layer 118, reference is made to
layer 18.
[0104] In either embodiment, the gel bodies have a height that is
less than or equal to the width of the gel body. In this manner,
the gel bodies will not buckle and instead will compress along
their central vertical axes.
[0105] As mentioned, the surface of the present invention may also
be a powered surface. In which case, rather than having the check
and pressure relief valves open to the atmosphere the valves may be
coupled to a system of tubes or tubing that is coupled to an air
pump or blower that is controlled by a control system as simple as
an on-off switch or a control system that includes a controller
that provides more advanced control functions and optional feedback
controls. Further, the valves may be provided in the form of one or
more manifolds, which then are controlled to control the flow of
fluid to and/or away from the surface. Thus in a powered
application, the foam in the bladders may be eliminated.
[0106] Accordingly, as would be understood, the patient support may
be formed from one or more resilient layers (e.g. a gel layer, a
bladder layer, and/or a foam layer (crib)) and one or more
permeable layers (e.g. spacer fabric or 3D layer and or gel layer)
and one or more moisture vapor permeable, but liquid impermeable
layers (such as a layer formed from GORE.RTM. Medical Fabric).
Further, where the resilient layer can provide an adequate space to
form a reservoir or reservoirs, the separate permeable layer may
also be eliminated so that the patient support may include the
resilient layer and the one or more moisture vapor permeable, but
liquid impermeable layers (such as a layer or layers formed from
GORE.RTM. Medical Fabrics). As described, the layers work as a
system to provide resilient support to a patient, optionally with
the improved emersion described herein, and further to wick away
moisture form the interface between a patient's body and the
patient support. This is achieved at least in part by providing a
space under the upper moisture vapor permeable, but liquid
impermeable layer that can act as a reservoir for the moisture
vapor that passes through the upper layer so that the moisture can
be drawn away from the patient's body and redirected to another
location, such as a location outside the support, all while
protecting the resilient layers from liquid intrusion.
[0107] Referring to FIG. 15, moisture vapor transfer tests were
performed using the test procedure described by Reger, Steven I.,
in Validation Test for Climate Control on Air-Loss Supports, Arch
Phys. Med. Rehabil., May 2001, pp. 597-603, vol. 82. The tests were
performed over a 2 hour period on several embodiments of the
present invention, namely, non-powered patient supports with a
bladder layer, a foam crib on top of the bladder layer, a 3D fabric
layer on top of the foam crib, and a cover formed from GORE.RTM.
Medical Fabric with moisture vapor transfer rates (MVTR) in a range
of 3900=7000 g/m.sup.2/24 hours and also on several prior art
mattresses with conventional coated nylon covers. The tests were
performed with a loading gauge, which was used to act as a torso of
an average size male. Water was circulated to the loading gauge,
which was placed on a dry moisture reservoir, and connected to a
water bath to keep the interface at 37.degree.+/-0.5.degree. C. The
loading gauge and support surface were adjusted 23 cm below the
water bath level and the air flow through the interface was then
initiated. After the dry moisture reservoir came to temperature
equilibrium for 30 minutes, it was replaced with a wet one that was
saturated with 36 g of saline. The saturated reservoir simulated
the moisture and humidity from a human body lying on a support
surface. The evaporation rate was recorded over a 120 minute test
period.
[0108] The test results are shown in graphical form, which
illustrate the differences in the performance curves 200, 202 of
the respective patient supports, with curves 200 representing the
test data for patient supports of the several embodiments of the
present invention, and curves 202 representing the test data for
prior art mattresses with coated nylon covers.
[0109] As best seen in FIG. 15, performance curves 200 have an
initial moisture vapor transfer (MVT) (measured 30 minutes after
the start of the test) M1, which is greater than 60 g/(m.sup.2hr),
greater than 70 g/(m.sup.2hr), and falls in a range of
approximately 70 to 105 g/(m.sup.2hr), which decays after
approximately 30 minutes to a lower MVT M2 of greater than 40
g/(m.sup.2hr), greater than 45 g/(m.sup.2hr), and in a range of
approximately 50 to 65 g/(m.sup.2hr) and decays to a second lower
MVT M3 greater than 35 g/(m.sup.2hr) and of at least 40
g/(m.sup.2hr), and in a range of 40 to 55 g/(m.sup.2hr) after
another 30 minutes. After another 30 minute period, the MVT then
decays to a fourth, and in some cases steady state, MVT M4 greater
than 20 g/(m.sup.2hr), at least 30 g/(m.sup.2hr) and in a range of
approximately 30 to 48 g/(m.sup.2hr).
[0110] In contrast, the initial MVT M5 (after 30 minutes) of the
prior art mattresses with nylon covers falls in a range of
approximately 24 g/(m.sup.2hr) to 10 g/(m.sup.2hr), which after 30
minutes decays to a MVTM6 in a range of 11 g/(m.sup.2hr) to 4
g/(m.sup.2hr), and decays to a steady state MVT M7 in a range of 8
g/(m.sup.2hr) to 4 g/(m.sup.2hr), which remain generally constant
so that the MVT M7 values are approximate equal to the MVT M8
values measured after 2 hours after the start of the test.
[0111] Consequently, it can be seen that a patient support of the
present invention exhibits a significantly improved moisture vapor
management system (in the absence of power) over prior art
mattresses by providing a greatly increased initial MVT, which
decays to MVT that also far exceeds not only the steady state MVT
of a conventional mattress with a coated nylon cover but also
exceeds their initial maximum MVT.
[0112] While several forms of the invention have been shown and
described, other changes and modifications will be appreciated by
those skilled in the relevant art. Therefore, it will be understood
that the embodiments shown in the drawings and described above are
merely for illustrative purposes, and are not intended to limit the
scope of the invention which is defined by the claims which follow
as interpreted under the principles of patent law including the
doctrine of equivalents.
* * * * *