Note: Descriptions are shown in the official language in which they were submitted.
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SURC-ICAL ADHESIVE DRESSING
The present invention relates to adhesive dressings
for use on the human body. More particularly this
invention relates to adhesive surgical dressin~s suitable
for use on bo-th exuding wounds and non-exuding wounds.
Moisture vapour permeable thin :Eilms coated with
adhesive were disclosed in British Pa-tent No. 1,280,631
and ~.S. Patent No. 3,645,835 as being suitable for use
as surgical dressings. In recent years one such film
has come to prominence under the trade mark "Qp-Site" and
has found use as a surgical dressin~, for example for
covering burns, donor sites, surgical incisions, intra-
venous catheter sites and the like. The known dressings
have proved usetul because tney keep out bacteria owing
to the microscopically continuous nature of -the film and
adhesive layer but do not cause maceration of -the skin to
which it is applied because both the film and the adhesive
layer have high moisture vapour permeability (~5VP). One
problem with presently available high ~VP dressings is that
~ 7~7~
the ~I~7P is not high enough ior some uses such as covering
exuding wounds when an unsightly blister can occur.
However it has not been thought prac-ticable simply to
increase the MVP of the product overall since this wou]d
lead to drying out of some wounds with a consequent
reduction in the rate Or healing. It has now been
discovered that it is possible to alleviate the known
disadvantages of conventional surgical dressings by
providing dressings which transmit substantially more
moisture vapour when in contact with a wetter wound than
they do when in contact with a dryer wound.
Accordingly the present invention provicles a surgical
dressing which consists essentially of a film which
carries an adhesive layer for securing the dressing to
the body characterised in that (a) the film is continuous
and comprises a polymer which in contact with water has
a higher MVP than when in contact with moisture vapour
but not water (b) the adhesive layer is adapted to allow
access of water to the film when water is in contact with
the adhesivelayer so that (c) said surgical dressing has
a MVP of not less than 2500g/m2 when the adhesive layer
is in contact with water and has an ~P of no-t more than
2000g/m2 when the adhesive is in contact with moisture
vapour but not water; whereby the dressing is suitable
for use on exuding wounds and on non-exuding wounds.
3~
~ hen used herein with reference to "contact" the
term "water" means liquid water (as opposed to moisture
vapour) unless otherwise specified When used herein
MVP units are g/m2/24hrs/37C/]00-10~, rela-tive humidity
and are generally abbreviated -to g/m .
Suitable test methods for determining -the MVP of
a dressing or its components are set forth in the
Description hereinafter. U~hen MVP values quoted therein-
after are referred to as "wet-~P" they refer to values
obtained with the adhesive face in contac-t wi-th water and
when referred to as "dry-~VP" they refer to values
ob-tained with -the adhesive -face not in con-tac-t wl-th wa-ter.
More suitably the dressing of this invention will
have a wet-MVP of not less than 3000g/m2, most suitably
will have a wet-~'P of not less than 3200g/m2 and preferably
will have a wet-MVP of not less than 5000g/m2.
More suitably the dressing of this invention will
have a dry-MVP of not more than ~500g/m2, most suitably
will have a dry-MVP o not more than l~OOg/m2 and preferably
will have a dry-MVP of not more than 1200g~m2.
- The film used in this invention may comprise any
synthetic or modified natural polymer which has a
sufficiently higher wet-~lVP than dry-MVP to produce the
desired ~IVP parameters in the dressing. The method set out
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in the Descriptions may be employed to determine whether
the film materlal exibits the desired ~.~P when in contact
with water. Most aptly the film comprises a synthetic
polymer although modified natural polymers such as
regenerated cellulose or cellulose acetate may be employed
if sufficiently plasticised to conform to the movements
of the body when adhered thereto. Preferably the
synthetic polymer employed is an elastomer so that it
readily conforms to the movement of the skin when the
dressing is in use.
~ lost suitably the film used in this invention will
be hydrophilic, that is will absorb water when immersed
therein. Aptly the film material when hydrated will
contain 5~v to 50% water (w/w at 20C), more aptly from
10~3 to 40~c~ of water and favourably from 20~ to 30~3 of
water.
Suitable hydrophilic film material will include
polyurethanes, polyether polyamide block copolymers,
polyether polyester block copolymers, cross-linked polyvinyl
alcohols, acrylic copolymers, polyamides, regenerated
cellulose, cellulose acetate and the like, provided said
film material are highly conformable ( whether per se or by
plasticisation) and that the material used most suitably has
the preceeding water contents when hydrated.
7;'~7 ~
The -film employed will be a continuous fllm,
-that is it will be free of holes (whether microporolls
or macroporous) which allow the passage of bacteria.
The desirable properties of this invention may be
best obtained by employing a film of hydrophilic
polyurethane in combination with an adhesive layer
adapted to allow access of water to the film when water
is presented to the adhesive face of the dressing.
~'ost suitably the film will be from 15 to 80
I n microns -thic~i, will more usually be from 20 to 60
microns thick and will pre-Lerably be :from 25 to 50 microns
thick, for example 30, 35 or 40 microns thick.
Aptly the film will be formed from a hydrophilic
polyurethane which when hydrated contains from 5C~ to
50C1c of water, more aptly from lOC,~', to 40C7/ of water and
favourably from 20C7~c~ to 30C,'~ water.
In order to enable visual observation of the wound
it is desirable :For the film used in this invention to be
transparent. This in turn requires tha-t the film should
20 be capable of being self supporting, that is sufficiently
coherent when we-t or dry to be used without recourse to
additional support such as a fabric, for example a gau~e,
net or the like. It has been -found that polyether
polyurethanes are particularly sui-table for use in the
formation of such films. Favoured polyether polyurethanes
are essentially free of reactive substituents such as
hydroxyl or carboxyl groups. It has been found that
certain apt polyurethanes for use in this invention are
random polymers containing units derived from diolic
compounds and di-isocyanates.
Suita~le polyurethanes may be ~rocluced by the
methods described in British Patent Specification No.
20~3190~ at ~a~Je 6 line 35 to na~e 8, line 41.
The adhesive layer present on the body contacting
surface of the film is favourably an interrupted layer so
that areas of the film are free of adhesive, aptly 20 to
75% of the film is free of adhesive, more aptly 30 to 70ch
of the film face is free of adhesive and preferably 40 to
60~ of the film face is free of adhesive. The use of an
interrupted layer in such a manner has been found to be
highly beneficial in allowing the desirable variabilit~v of
~P to be achieved.
The adhesive is generally emnloyed at a mass per
unit area of lO to 80g/m2, m~re a~tly 20 to 45g/m2 and
favourably from 25 to 35g/m2.
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The adhesive may be applied around the periphery of
-the dressings, in lines over the face oI -the dressing
(parallel, at right angles, forming diamond pa-ttern or
the like) or in combina-tions of such sys-tems.
The adhesive is preferably one which itself transmits
water vapour, for example one which if present as a film
25 microns thick would have a ~qV~ of at least 300g/m2,
more suitably at least 500g/m2 and preferably a-t least
700g/m2. Such permeabilities may be achieved by using
a non-porous or porous (including microporous)pattern spread
adhesive but generally it is preferred to employ a non-
rorous pattern spread adhesive, Suitable adhesives include
nol yvinyl ethyl ether adhesive and acrylate surgical
adhesives. Preferred adhesives include those described
in European Patent Application No. 31300~47 (Publication
No. 0035399)-
The dressings of the invention may be made by any
convenient process, for example a film of, for example
hydrophilic polyurethane may be roller printed or hand
printed with a pattern of adhesive. Alternatively any
o-ther convenient method o~ providing a non-continuous
adhesive may be employed. The coated films may then be
cut, packaged and sterilised in conventional manner, for
example by irradiation, heat or ethylene oxide.
~ L&~5~
In a favoured aspect this inventi.on provides a
dressing as hereinbefore described in sterile form.
~.lost aptly the sterile dressing is pac~aged i.n a
bacteria-proof package such as a paper or aluminium foil
pouch.
Suitable polyurethane may be produced by the methods
described in British ~atent .Specification No. 20~3190
at ~age 6, line 35 to page 6, line ~1 thereof.
Normally the dressings are provided for use with a
silicone release paper to protect the adhesive which
protector is removed prior to use of the dressing.
The following Examples illustrate the invention:
_g_
Description
"Dry" MVP Determination
Discs of the material under test are clamped over
Payne Permeability Cups (flanged metal cups) using
sealing rings and screw clamps. The exposed surface
area of the test sample is lOcm2, Each cup contains
approximately lOml, of distilled water.
After weighing the cups are placed in a fan
assisted electric oven which is maintained at 37 - 1C.
The relative humidity within the oven is maintained at
approximately 10~ by placing l~g. O:e anhydrous 3-~ mesh
calcium chloride on the :Eloor O:e :the oven.
The cups are removed after 24 hours, allowed to
cool for 20 minutes and re-weighed. The MVP of the
test material is calculated -erom the weight loss and
expressed in units of grams of weight per square metre
per 24 hours.
"Wet" MVP determination
The method described above is employed except
that the Payne Cups are inverted in the oven so that the
water within the cups is in contact with the test material.
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E_ample 1
Preparation of Eilm
A solution of a hydrophilic polyurethane (of Example
2 of ~K No. 2093190A) :in industrial methylated spiri-ts
(18~? solids) was cast using a doctor blade on-to a silicone
treated release paper to produce a coa-ting weight after
drying of 30 - 3g/m2. The cast film was dried at 80C
to remove solvent.
Pattern Spreading of Film with Adhesive
A solution O-r acrylic adhesive in acetone (solids
con-tent 35,J) was coated directly onto the :ri lm ol`
hydrophilic polyurethane using an en~raved roller so as to
produce ~ reticulated ~cross hatched) coatlng O r adhesive.
After coating the adhesive was all.owed to dy in air before a
silicone treated paper protector was applied. The
average weight of the adhesive coating was 30 - 3g/m2.
The area of film covered by the adhesive was approximately
50% of the total available area. (The adhesive was tha-t
of Example 1 of European Patent Application No. 813008~7.1).
The dry-MVP of the product of this Example was
1250g/m2 and the wet-MVP was 3600g/m'' (compare corresponding
values o-f about llOOg/m2 and about 1250g/m2 for an analogous
material which employed Estate 571~ - a non-hydrophilic
polyurethane in place of the hydrophilic polyurethane).
Example 2
The product of Example 1 was cut into 10 x 10cm
squares and sealed into pouches. The product was
sterilised using ethylene oxide. The resulting sterile
dressing may be emp]oyed to cover wounds.
Example 3
The procedures of Examples 1 and 2 may be carried
out replacing the hydrophilic polyurethane by those of
British Patent Specification No. 2093190A at page 6 line
35 to page 7 line 25. The resulting dressings are
suitable for covering wounds.
:EYamP1e ~
The procedures of Examples 1 and 2 may be repeated
using a vinyl ethyl ether adhesive in place of the acrylic
adhesive. The resulting dressings may be employed to
cover wounds.
Example 5
A 25 micron film of polyether polyamide blocls
copolymer (Pebax ~011 supplied by ATO Chemical Products,
NewL~ury, UK) had applied thereto by roller a cross hatched
pattern of polyvinyl ethyl ether adhesive. The adhesive
covered about 75,~. of area of the film surface and the
diamond shaped interstices accounted for about 25% of
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the area of -the film. The average weight of the adhesive
layer was approximately 60gsm. The resulting material
was cut into 15cm x 15cm squares, placed on silicone
release paper (adhesive side to release layer), placed
in pouches and sterilised using ethylene oxide.
The dressing had a dry-~P of about 1800g/m2 and
a wet-MVP of greater than 5000g/m2.
