Note: Descriptions are shown in the official language in which they were submitted.
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WOUND PACKING AND PACKAGE THEREFOR ~ . ;
Background of the Invention
The present invention relates to a sterile wound packing -~
and a package therefor, and, more particularly to a wound
packing in the form of a gauze or other similar absorbent
material having a hydrogel material impregnated therein for
absorbing wound exudate and to a package for dispensing the
wound packing.
Secreting skin wounds, such as decubitus ulcers and ope~
surgical wounds, have long presented a medical challenge in
keeping such wounds sterile and relatively dry. Deep wounds
provide an even greater challenge. The accumulation of wound
exudate, such as blood, pustulation, and other wound fluids,
in wound crevices, promotes growth of bacteria and other - i~
organisms which cause infection and delay the healing
process. Such wound exudate may also cause maceration of --
tissue adjacent the wound and support infection thereof.
However, since it is often desirable to allow a wound to
heal in a slightly "moist" or occlusive state, which is
believed to accelerate healing, excess wound exudate must be ~
removed. If excess wound exudate remains in or on a wound, a ~-
"blister" of exudate can form under the wound dressing which
is not only unsightly, but also may cause the dressin~ to
leak, thereby defeating the aim of sterility. However, -
existing methods of aspiration can lead to wound infection or --
can destroy sterility. Additionally, it is not desirable to
remove all the exudate as that would result in a "dry" wound
re~ulting in a slower healing process.
There is a substantial body of prior art relating to
wound and/or surgical dressings or packings for treating skin
lesions, such as decubitus ulcers and open wounds. In some
instances, the wound dressing or packing may be designed to
be only temporary, such as the use of gauze to absorb blood
and/or other wound exudate. In others, the wound dressing is
designed to be more permanent in nature, remaining in place
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for several hours or days durin~ the healing process. In yet ~ -
other instances, the wound dressing material is designed to
be biodegradable and to break down over an extended period of
time as a wound heals.
Aqueous moisture absorbing materials, such as a hydrogel ~
material with a polyethylene glycol liquid curing agent, as ~ ~-
disclosed in Spence, U.S. Patent No. 4,226,232, have been
used as dressings on a wound site, but cannot be sterilized
by irradiation due to the formation of free radicals within
the aqueous material. Another aqueous absorbing material ;-~
used to absorb wound exudate is a hydrophilic polymer as -~
disclosed in Rawlings et al, U.S. Patent No. 4,657,006.
Rawlings et al disclose a wound dressing which comprises a
hydrophilic polymer having moisture and vapor permeability
characteristics. However, a problem with the Rawlings et al
wound dressing is that the wound exudate absorbed by the
hydrophilic polymer hardens or solidifies the polymer,
allowing pockets to develop between the polymer and the
wound, thereby providing an excellent environment for
bacteria proliferation. -
In addition, wound dressings used in the past have not -~
been conducive for healing extremely deep wounds and wounds
having irregular shapes. To that end, wound dressings and
surgical sponges formed from gauze and foam materials have -
been used for many years in surgical practice. These sponges
and wound dressings have attempted to retain both the
advantages of thin, soft and flexible single layer dressings
and the absorptive cushioning and insulating properties of ;-
thicker pad-like structures. As a result, the sponges and
wound dressings have traditionally been formed of multiple
layers of thin, soft, low-count gauze material which are --
unified along fairly widely separated lines usually extending ~ -
lonsitudinally or transversely.
Although such wound dressings and surgical sponges have ;~
been found useful in the past, none have provided the
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capability of absorbing large amounts of wound exudate
without inhibiting the healing of the wound to which they are
contacted. Most all of these dressings, including gauze and
sponges, adhere to the wound upon removal, thereby damaging
the wounds to which they are attached. This in turn prolongs
the healing of such wounds. It would therefore be desirable
to have a wound dressing or packing having a structure which
is thin, flexible and soft yet absorbs wound exudate in the
same manner as the more thick pad-like wound dressings.
Cartmell et al, U.S. Patent No. 5,115,801, disclose a
thin-film burn dressing containing an aqueous hydrogel
material partially impregnated in a foam or nonwoven material
which contacts the wound directly, thus preventing damage to
the new tissue when the dressing is removed. However, such
an aqueous hydrogel wound dressing contains a high percentage
of water, and thus is not as readily absorbent as other wound
dressings. In addition, due to the large water content of
the aqueous hydrogel material, the burn dressing requires
additional backing and adhesive layers to properly support
the hydrogel material which leads to increased production
costs.
Accordingly, there is a need in the art for a wound
packing which is capable of absorbing large amounts of wound
exudate without inhibiting the healing of the wound to which
it is contacted and without the need for additional support
layers. There is also a need for a wound dressing which has
a pliable, soft structure so as to permit the wound dressing
to be readily applied to wounds having irregular shapes and
depths. Finally, there is a need for such a wound dressing
which can be conveniently packaged and dispensed while -
maintaining its sterility.
Summary of the Invention
The present invention meets those needs by providing a
sterile wound packing material and package therefor. The
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wound packing is in the form of a gauze or similar absorbent -
material and may have a partially or substantially dehydrated
hydrogel material impregnated therein for absorbing wound
exudate. The wound packi~g is capable of readily absorbing
large amounts of wound exudate without requiri~lg additional `
supporting layers or structure. The wound pac}~ing does not
adhere to the wound and is readily removed without inhibiting
the healing of the wound to which it i~ contacted. In ` -
addition, the present wound packing is soft and pliable,
which permits the wound packing to be readily applied to
wounds having irregular shapes and depths. Further, in
embodiments where the hydrogel still contains some amount of -
water, the wound dressing provides a cooling effect on the
wound and surrounding areas of a patient's skin due to the
evaporation oE moisture from the hydrogel in use.
According to one aspect of the present invention, a
sterile wound packing is provided and includes a sterile,
wound packing and a package therefor. The wound packing
includes an absorbent layer capable of absorbing wound
exudate. In a preferred embodiment, the wound packing is in
the form of a substantially flat, coiled, spirally-cut layer.
The absorbent layer of the wound packing is preferably
sel~cted fro~ the group consisting of woven gauze, fabric,
nonwoven natural or synthetic fibers, polymeric sheets and
films/ and the like.
In certain embodiments of the invention where it is
desired that the wound packing remain in place for an ~ -
extended period, the absorbent layer is impregnated with a
hydrogel, which may be a partially dehydrated hydrogel ~ -
containing from about 5 to 55~ by weight water, and more
preferably, from about 40~ to about 45~ by weight water. By
partially dehydrated, it is meant that at least a portion,
but not all of the water has been removed from the hydrogel
material. Preferably, the absorbent layer includes
interstices, and the partially dehydrated hydrogel material
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,
is completely impregnated in the interstices such that the
hydrogel material is substantially exposed at the outer
surface of the absorbent layer.
In this way, the partially dehydrated hydrogel material
is substantially in contact with the wound while contact of ~-
the absorbent layer thereto is minimized so as to preclude
the absorbent layer from adhering to the wound. This is
desirable since healing of the wound is inhibited when the
absorbent layer sticks or otherwise adheres to the new cell
tissua forming in the wound. This arrangement is also
desirable in that the partially dehydrated hydrogel material
provides a desirable cooling effect when the wound packing i9.
applied to a patient's skin due to the evaporation of water
from the hydrogel in use. It has also been found that the
partially dehydrated hydrogel material adheres sufficiently
to the absorbent layer and has sufficient structural
integrity so as to eliminate the need for backing or adhesive
layers to provide additional support for the hydrogel
material. -
In an alternative embodiment of the invèntion, the
absorbent layer of the wound packing is impregnated with a
substantially dehydrated hydrogel containing less than 5~ by 5
weight water. The substantially dehydrated hydrogel is
preferably impregnated in the interstices of the absorbent
layer as described above such that the hydrogel material is
substantially exposed at the outer surface of the absorbent
layer. Because the wound packing contains little or no
water, it can also be used without the use of any additional
support layers.
The package for the wound packing includes sealed first
and second sheets with the wound packing therebetween. The
first and second sheets are made of any suitable material
capable of maintaining the sterility of the contents of the
package such as metal foil, metal-coated polymer, polymer, - -
paper, or coated paper. ~-
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The package is preferably opened by peeling apart the
first and second sealed sheets. Preferably, a portion of the - .
package is sealed such that a free-lifting edge or corner is
provided to facilitate peeling apart the sheets.
In embodiments where the wound packing is in the form of -~
a substantially flat, spirally-cut layer, the package may be
designed to be opened by puncturing one of the sheets to form ~ ~;
an opening in the package. The spirally-cut packing may then
be removed by pulling on one end thereof out through the
opening. The wound packing may be cut to length as needed or
may be designed to be packaged in different widths and
lengths.
To aid in opening the package, the package may include
means for stiffening the package to promote easy puncture.
The stiffening means comprises card stock or a stiff ;~
polymeric sheet disposed in the package. Alternatively, the
stiffening means comprise a release liner on the flexible
material. In another embodiment, one or both of the sheets
forming the package may include a weakened area, again to aid
-20 in opening the packing. The weakened area may comprise, for -~
example, a pattern of score lines or perforations which can
be readily broken to facilitate access to an end of ~he
spirally-cut wound packing in the package. However, in order
to maintain sterility of the package, the score lines or
perforations should not penetrate the package.
In another embodiment, the package includes an opening
in one of the first and second sheets located adiacent one
end of the packing material for providing access to the ;~ -~
packing material, and removable means for sealing the -~ ~-
opening. Again, to aid in the opening of the package, there `
may be means for stiffening the area around the opening such
as card stock laminated to an inner surface of the package
around the opening. The opening may be located substantially
at the center of the package adjacent one end of the
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spirally-cut wound packing or, alternatively, near an edge ~f
the package adjacent the opposite end of the wound packing.
In embodiments where the wound packing is spirally cut, `-
the package also preferably includes a backing layer adhered
to a portion of the inner surface of one of the first and
second sheets, with the wound packing positioned on the
backing layer. Preferably, the backing layer comprises a
polymer such as polyester which includes a release coating on ~ -
its surface. The wound packing is positioned on the backing
layer such that it contacts the release coating. The backing
layer prevents the wound packing from shifting inside the
unopened package, and, once the package has been opened,
supports the packing while it is being dispensed. --
The package also preferably includes means for
protecting the wound packing from contamination prior to
dispensing it from the opened package comprising a release ~
liner or card stock which overlies the wound packing inside -~ -
the package.
Accordingly, it is a feature of the present invention to
provide a wound packing which is capable of readily absorbing ~-
large amounts of wound exudate without inhibiting the healing
of the wound to which it is contacted and without the need -
for ~dditional support layers. It is also a f~ature of the
invention to provide a wound packing which possesses a
pliable, soft structure for application to wounds having
irregular shapes and depths. Finally, it is a feature of the
present invention to provide a package which allows the wound
packing to be easily dispensed and stored indefinitely in a
compact, sterile condition. These, and other features and
advantages of the present invention will become apparent from
the following detailed description, the accompanying
drawings, and the appended claims.
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Brief Description of the Drawinqs ~ -
Fig. 1 is a top view of a wound packing in accordance
with the present invention;
Fig. lA is a top view of a wound packing illustrating
the spiral-cut configuration;
Fig. 2 is a perspective view of a sealed package
containing the wound packing with a free-lifting edge for
peeling;
Fig. 2A is an alternative embodiment of the package
shown in Fig. 2;
Fig. 3 is an exploded perspective view of the wound
packing and package of Fig. 2A;
Fig. 3A is a variation of the embodiment shown in Fig.
3;
Fig. 3B is an exploded perspective view of a wound
package including a backing layer and a release layer;
Fig. 4 is a perspective view of a package containing a
spiral cut wound packing being removed through a centrally
located access hole after removal of the sealing tab;
Fig. 4A is a perspective view of a package containing a
spiral cut wound packing being peeled away from a backing ,
layer of the packaging;
Figs. 5 and 5A are enlarged, partially cut away~ ;r
perspectives of various applications of the wound packing of -
the present invention;
Figs. 6 and 6A are schematic views illustrating a
process by which the wound packing and package can be made;
Fig. 7 illustrates one embodiment of the wound packing
after it has been applied to a draining wound; and
Fig. 8 is a cross-sectional view of the wound packing of
Fig. 7,
Detailed Description of the Preferred Embodiments
The present invention provides a wound packing in the
form of an absorbent material which may have a partially or ; - -
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substantially dehydrated hydrogel material impregnated
therein for absorbing wound exudate. The use of a partially
or substantially dehydrated hydrogel material E)rovides
sevexal advantages over previously used wound dressings.
Because at least a portion of the water has been removed from
the hydrogel material, the wound packing more readily absorbs
fluids from the wound than aqueous hydrogel wo~md dressings.
For the embodiment using a partially dehydrated hydrogel
material, the hydrogel still contains enough water such that
a desired cooling effect results when the wound dressing
contacts a patient's skin. The use of a partially or
substantially dehydrated hydrogel also provides the advantage
that the hydrogel is sufficiently supported by the gauze or
other absorbent material without the need for additional
support layers, structure, or packing materials.
As shown in Fig. 1, the present in~ention provides a
wound packing 10 in the form of a thin, pliable, absorbent
structure suitable for use in the treatment of wounds on a
patient. The wound packing 10 comprises a flexible absorbent
layer 12 which may optionally have a partially or ~;
substantially dehydrated hydrogel material 14 impregnated - -
therein for absorbing wound exudate. While those skilled in -~
the art will appreciate the difficulty in illustrating the
presence of a hydrogel material 14 in absorbent layer 12, it -
should be understood that the partially or substantially -
dehydrated hydrogel material when used is preferably
completely impregnated in the interstices between fibers of ;~
the absorbent layer 12.
It is preferred that the absorbent layer 12 be formed of - -~
material which is capable of absorbing wound exudate and or
blood cells, as well as being capable of supporting the
optional hydrogel material 14. Those skilled in the art will
appreciate that materials having interstices within which
materials may be absorbed or impregnated are particularly
suitable for such purposes.
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The partially or substantially dehydrated hydrogel ;
material 14 must be able to adhere to the absorbent layer 12
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90 as to form a pliable, thin structure which, when contacted
with a draining wound on a patient, absorbs large amounts of
wound exudate without inhibiting the healing of such wound.
Examples of suitable matexials for absorbent layer 12
include woven gauze, natural or synthetic fabrics, nonwoven
natural or synthetic fibers (e.g., felts), or polymeric
sheets and films to the extent that they can be fabricated to
include interstices and be absorbent. Absorbent layer 12 can
comprise a single fibrous layer, a plurality of layers
stacked one atop the other, or a felt-like nonwoven material.
Typically, the material of absorbent layer 12 will have a
thickness of from several mils to a few hundred mils (about
.076 mm to 7.6 mm).
As shown in Fig. lA, wound packing 10 may also be in the
form of a substantially flat, coiled spiral-cut layer of
material. The material may be manufactured in the form of a -- ~
continuous web which can then optionally be impregnated with -~-
a hydrogel and cut into desired sizes. For èxample, an
approximately 13 cm diameter disk of absorbent material may
be spiral cut into a continuous 0.6 cm width strip to provide
about 2 meters of wound packing. Similarly,~ ar approximately
20 cm diameter disk of absorbent material may be spiral cut -
into a continuous 2.5 cm width strip to provide about 1 meterof wound packing. Those skilled in this art will recognize
that there are many combinations of widths and lengths of the
wound packing material which can be manufactured. Because of
the spiral cut design, the wound packing may be easily
packaged compactly and in a variety of widths and lengths.
Referring now to Fig. 2, a package 20 is provided for
the wound packing. Package 20 includes peripherally sealed
first and second sheets 22, 24 which contain wound packing 10 ~ -
(not shown) therebetween. First and second sheets 22, 24 may -~
be made from any suitable material capable of maintaining the
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sterility of the wound packing 10 within the package.
Examples of suitable sheet material include metal foils, ~ -
metal coated polymer sheets, polymers (including but not
limited to those which provide moisture and/or gas barrier
properties), paper, or coated paper. Where an optional
partially dehydrated hydrogel is impregnated into the wound
packing, it is preferred that packaging with moisture barrier
properties be used to insure a long shelf life for the
package.
As shown in Fig. 2, one side portion of the perimeter of
the package is sealed so that the edges of the two sheets are
free-lifting and may be peeled apart. It will be appreciated
that other variations of this embodiment may also be
employed. For example, the package can be configured so that
the sheets include a free-lifting corner section of the
package. If desired, a tab may be included between the two
sheets along an edge or in a corner to facilitate grasping
and peeling apart of the sheets. The package may also
include a cut or notch along an edge which will facilitate ;--
tearing for opening of the package. ~- -
The sheets may be heat sealed together or adhesively
sealed, such as by a bead of peripheral adhesive 26 (shown in
Fig. 3) on one or both sheets. Alternatively, any sealing -
process which results in an air-tight seal to maintain the
sterility of the wound packing within the package is ~-
suitable.
In an alternative embodiment shown in Figs. 2A and 4,
package 20 may be designed to be opened by puncturing one or ~
both of sheets 22, 24 to form an opening through which one ~ - -
end of absorbent layer 12 may be pulled.
In the embodiment shown in Figs 2A and 3, package 20 -
includes a precut opening 27 in sheet 22 which is located
adjacent one end of the spirally-cut wound packing. In Figs.
2A and 3, this opening is shown as being central~y located on -` -`;
the package over the end of the wound packing nearest the ~ ~
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center of absorbent layer 12. Alternatively, the opening may
be located over the opposite end of the wound packing. While
being shown for illustration purposes as being circular, the -~
size and shape of the opening is not critical so long as
ready access to one end of the wound packing 10 i9 provided.
Package 20 includes removable means for sealing the
opening such as a tab 30 which may be adhered or otherwise
sealed over opening 27. If a pressure sensitive adhesive is
used to seal the tab over opening 27, then the tab may also
be used to reseal the opening if desired after a desired
length of wound packing 10 has been removed and cut. Tab 30
may include a free or clean-lifting edge 32 which may be
grasped to facilitate its removal. Once tab 30 has been
removed, an end of absorbent material 12 may be pulled from
the opening 27 as shown in Fig. 4 to a desired length or
amount. The flexible material may then be cut.
Alternatively, the entire contents of package 20 may be
removed and used at the same time. --
As shown in Fig. 3, package 20 may also include a ~`
stiffening means therein to promote easy puncture or opening
of the package. Such stiffening means may comprise card
stock 34 or a stiff polymeric sheet disposed in the package. --- -
Card stock 34 may itself include a corresponding opening 35
and be positioned or secured to the underside of sheet 22
beneath opening 23.
In an alternative embodiment of the invention shown in
Fig. 3A, where like reference numerals represent like
elements, sheet 22 includes a weakened area 36 to aid in the
opening of package 20. Weakened area 36, as shown, comprises
a series of score lines or perforations which can be readily
broken to facilitate to access to an end of absorbent layer -~
12. Again, the pattern and size of the weakened area is not ~ -
critical as long as ready access to an end of wound packing
10 is provided. However, care should be taken so that the
score lines or perforations do not penetrate completely into
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the package and cause the packing to lose its sterility~ In
this embodiment shown in Fig. 3A, a release liner 38
underlies flexible absorbent layer 12. Release liner 38 may
also act as the stiffening means to promote easy opening of
package 20.
In yet another alternative embodiment sho~m in Fig. 3B,
the package includes a backing layer 28 which i.s adhered to
the inner surface of sheet 24. The backing layer preferably
comprises a polymer such as polyester or polyethylene
although other suitable materials such as paper may be used.
Polyester is the preferred backing layer for the present
invention as it is a strong film which is easy to kiss-cut ~ ;
for manufacturing purposes as will be explained in greater
detail below. The backing layer is coated on its surface -~ ~
with a release coating such as silicone, and is coated on its ~;
opposite surface with a pressure sensitive adhesive which
adheres to the inner surface of sheet 24. The wound packing
10 i8 positioned on the backing layer 28 such that it
contacts the release coating. Once adhered to the inside of
the package, the backing layer supports the wound packing in ~ - -
position until it is dispensed.
The package also preferably includes means for
protecting the wound packing from contamination prior to `-
dispensing which comprises a release liner 38. The release -
liner preferably comprises polyethylene and may include a
release coating on the side of the liner which contacts wound
packing 10. Card stock, preferably coated, may also be used
as an alternative means of protection.
Referring now to Fig. 4A, once the first and second - -
sheets 22 and 24 have been peeled apart, and release liner 38
has been peeled away from the wound packing, an end of
absorbent material 12 may be peeled away from the backing
layer 28 to a desired length or amount. The absorbent
material 12 may then be cut. Alternatively, the entire
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contents of package 20 may be removed and used at the same
time.
For purposes of providing a more intuitive understanding
of the wound packing 10 and package 20, one process by which
the wound packing 10 and package can be made iS schematically
illustrated in Figs. 6 and 6A. As seen in Fig. 6, a backing -~
sheet 28, preferably with a release coating on its surface, ~ ;
is advanced on a feed line. The sheet 28 has a pressure
sensitive adhesive on its opposite surface which is covered
with a release liner 46.
An absorbent layer 12 is also fed in continuous web form
onto the feed line so that the web is in contact with the
release coated surface of the backing sheet 28, such as, for
example, a silicone coated polyester. The absorbent layer 12
is fed under an applicator 40 capable of receiving and
applying a liquid or uncured hydrogel material 45 from a - ;~
source (not shown) without permitting it to cure within its
components. Applicator 40 applies uncured hydrogel material
45 onto absorbent layer 12 in an amount sufficient to
impregnate the interstices therein and provide exposure of ~-
the hydrogel at the outer surfaces of layer 12. As those
skilled in the art will appreciate, the amount of uncured
hydrogel material 45 applied will vary with the particular
material used as absorbent layer 12 and the width and
thickness of the web to be coated.
Uncured hydrogel material 45 is then allowed to cure
downstream on the feed line to form a hydrated hydrogel `~
material 52 surrounding and impregnating absorbent layer 12
(Fig. 8). Thereafter, the wound packing 10 is partially `
dried, oven-baked or otherwise partially dehydrated so as to
evaporate a portion of the water contained in the hydrogel
material 52. Typically, 50~ by weight or more of the water
initially in the hydrogel will be removed.
However, it should also be appreciated that the wound
packing may be dried or oven-baked so that all of almost all
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of the water contained in the hydrogel material 52 is
evaporated. The resulting substantially dehydrated hydrogel ~ -
material should contain less than 5~ by weight water. While
such a hydrogel material is capable of absorbing large
amounts of wound exudate, the resulting wound packing becomes
somewhat stiffer due to the dryness of the hydrogel. For
this reason, it is preferred that the hydrogel material is
only partially dehydrated as described above so that it
contains from about 5~ to about 55~ by weight water, and more ;-
preferably, from about 40% to about 45~ by weight water.
Once the absorbent layer has been impregnated with
hydrogel, a release coated polymer film 31 is laminated to
the top of the hydrogel-impregnated absorbent layer 12 such :
that the absorbent layer is sandwiched between sheets 31 and
28 as shown in Fig. 6A.
Thereafter, the continuous web of wound packing 10 may
be cut into individual sheets. If desired, the wound packing - -
may then be spiral cut to the form shown in Fig. 1. Spiral
cutting is accomplished using a kiss-cut die, where the die
cuts through the release-coated film 31 and the hydrogel ~ -
impregnated absorbent layer 12, but not the backing sheet 28.
After cutting, film 31 is then removed, and a fresh sheet of - j
a release-coated matsrial such as silicone coated ~--
polyethylene is laminated to the spiral-cut wound packing. - ~
This sheet of polyethylene remains on the wound packing as ~ ;;
release liner 38.
The polyethylene and polyester sheets are then die cut
so that both sheets extend beyond the edges of the wound
packing. The release liner 46 is then removed from the -~
adhesive coated surface of backing layer 28. The backing
layer 28 may then be adhered to the inner surface of one of ~ ~
the sheets of the package, with the spiral cut wound packing ~ ~ -
sandwiched between the backing layer 28 and the release liner
38. The first and second sheets of the package are then
adhered together to form a sealed package 20 as shown in
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Fig. 2.
Referring now to Fig. 7, which has been greatly enlarged
for purposes of illustration, a small piece of wound packing
10, after having been contacted with a draining wound, is
illustrated. Where a partially or substantially dehydrated
hydrogel has been used, Fig. 7 illustrates the expansion or
swelling (as depicted by the arrows in do~ted lines) of the
hydrogel material upon acquisition of bodily fluids, such as
wound exudate, from the wound to which the wound packing 10
is applied. The expanded or hydrated hydrogel material is -
referred to herein by reference numeral 52. Wound packing
10, when it contains ~ptional hydrogel, is therefore
analogous to a sponge in that its initial partially or ;~ -
substantially dehydrated state expands as fluids are
absorbed.
Fig. 8 may also be considered to illustrate a cross~
sectional view of a small piece of wound packing 10 depicted
in Fig. 7 and shows hydrogel material 52 swelled in and
around absorbent layer 12. As those skilled in the art will
appreciate, hydrogel material 52 depicted in Fig. 7 is the
same as the cured hydrogel material 52 discussed with respect
to the process by which wound packing 10 is made and
~llustrat~d in Fig. 6. In essence, cured and hydrated
hydrogel material 52 may be initially partially or - ~ -
substantially dehydrated for packaging and then returned to
its original hydrated state upon wound exudate absorption.
The preferred hydrogel material for use in the present
invention is formed from an aqueous mixture of polyhydric
alcohol, an aliphatic diisocyanate terminated prepolymer,
polyethylene oxide based diamine and sodium chloride. Such
an aqueous hydrogel material is taught in Cartmell et al,
U.S. Patent No. 5,115,801, and contains approximately 61~ -
water by weight when fully hydrated. Preferably, the
polyhydric alcohol is selected from the group consisting of
polypropylene glycol, polyethylene glycol and glycerine.
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After curing the mixture, at least a portion of the water is
removed from the resulting hydrogel as descrlbed above to .
form the partially or substantially dehydrated hydrogel
material.
The hydrogel material 52 in its partially or
substantially dehydrated state, which is referred to herein
as hydrogel material 14, provides a highly absorbent material
capable of retaining large amounts of wound exudate, thereby
rendering it very suitable for use in wound dressings. By
forming the hydrogel material 14 from the aforementioned
aqueous mixture and then--removing water, the wound dressing
10 remains intact as it absorbs wound exudate from the wound. ~ -~
Moreover, the preferred hydrogel material does not
adhere or stick to the wound thereby allowing for easy
removal of wound packing 10 substantially as a single piece.
Additionally, the biocompatibility of the hydrogel material
within the wound is extremely favorable. Thus, the resulting
hydrogel material 52, and therefore the dehydrated hydrogel ~ -
material 14, provides a bio-compatible, non-irritating, fluid
absorbing, bacterial protective, cushioning, skin-like media ~;
over the wound site. An additional advantage of the hydrogel ~-
material 52 is that it may be transparent, rendering it
possible to inspect the wound site through absorbent layer 12
without removing wound packing 10.
The preferred aliphatic diisocyanate terminated
prepolymer is an isophorone diisocyanate terminated
prepolymer based on polyols containing more than about 40
polyethylene oxide and having an isocyanate content of about ;~
3~ by weight. The molecular weight of the isophorone
diisocyanate terminated prepolymer is preferably in a range - ~ -~
from about 1500 to about 8000 and most preferably, from about
4000 to about 5000. The polyethylene oxide based polyamine
is preferably a polyethylene oxide based diamine having a
molecular weight in a range from about 200 to about 6000 and -~
most preferably, about 2000. It is also preferable that the
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aliphatic diisocyanate terminated prepolymer and the
polyethylene oxide based polyamine have a stoichiometric
ratio of about 1 1. Those skilled in the art will appreciate
that all of the constituents with the preferrecl hydrogel
material may be readily synthesized or purchased commercially
neither of which is more preferred.
It has been found that a more preferred hydrogel -
material 52, and therefore the dehydrated hydrogel material
14, is formed from an aqueous mixture including from about 0%
to about 90% by weight polyhydric alcohol; from about 6% to
about 60% by weight aliphatic diisocyanate terminated
prepolymer; from about 4~ to about 40% by weight polyethylene
oxide based polyamine; up to about 2% by weight sodium
chloride; and the balance water. A more preferred hydrogel
composition for forming the hydrogel material 52 is formed
from a mixture comprising from about 15% to about 30% by
weight polypropylene glycol; from about 8~ to about 14% by
- weight isophorone diisocyanate ~erminated prepolymer; from
about 5% to about 10~ by weight polyethylene oxide based
diamine; and up to about 1% by weight sodium chloride; and
the balance water. Most preferably, the hydrogel material 52
is formed from a mixture comprising: (a) from about 16~ to --
17~ by weight polypropylene glysol; (b) from about 10% to 12%
by weight isophoxone diisocyanate terminated prepolymer; (c)
from about 7% to 9~ by weight polyethylene oxide based
diamine; (d) about 0.5% to 1~ by weight sodium chloride; and
(e) the balance water.
The aforementioned preferred hydrogel compositions
provide a wound packing 10 having the desired properties of
excellent biocompatibility and absorption of exudate
properties without adhering to the wound. However, other
materials having such characteristics, including but not
limited to the aforementioned hydrogel compositions, may be
used to form the hydrogel material 52 in accordance with the
present invention. -
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While the wound packing 10 of the present invention may
serve as an extremely viable wound packing by itself, the
wound packing 10 may also be incorporated into other wound ~ -
packings in order to improve their performance. By way of
example only, a few of such wound packing embodiments are
illustrated in Figs 5 and 6. Fig. 5 illustrates the use of
the wound packing in a bandage 41 of the self-adhesive type. ;~ ~-
The self-adhesive bandage 41 comprises a substrate 42 having
first and second sides 44 and 43, respectively, wherein the
-side 44 contacts a patient and includes a pressure sensitive
adhesive ~oated onto at least one portion of side 44. -- ~-
As seen in Fig. 5, the bandage 41 has pressure sensitive
adhesive coated over all portions which ultimately contact
the patient. The bandage 41 also includes the wound packing
10 secured to the side 44 for contacting a wound on the
patient. Preferably, the wound packing 10 performs and is
formed as described above. In this way, the wound dressing ~ -
10 in the bandage 41 swells as it absorbs wound exudate from -~
the wound to which it is attached. It-should be understood
that the bandage 41 may include additional materials other
than that of which is described herein without departing from
the scope of the invention. ~ ~
Turning now to Fig. 6, the wound packing 10 is ~ -
illustrate din the form of a roll dispenser 50. The wound -
packing 10 is formed as described above and then wrapped
around a spool 54 or similar device such that the wound
packing }0 can be easily accessed. As a result, the roll
dispenser 50 facilitates quick and easy access to the wound
packing 10 in that a user can cut a sufficient amount of the
wound packing 10 to treat a wound on a patient. It should
now be apparent to those skilled in the art that the wound
packing 10 can be used in a wide variety of existing wound
dressings as well as on its own.
While certain representative embodiments and details ~ :
have been shown for purposes of illustrating the invention,
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it will be apparent to those skilled in the art that various -~
changes in the methods and apparatus disclosed herein may be
made without departing from the scope of the in~ention, ~hich
is defined in the appended claims. -~
The embodiments of the invention in whi.ch an exclusive
property or privilege is claimed are defined as follows~
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