IV catheter abstract
A surgical dressing consisting of a film which carries an adhesive
layer wherein the film has a hydration rate of at least 0.1 g/in.sup.2
/min.; becomes saturated when in contact with water in 3 minutes
or less and absorbs at least its own weight of water. The film comprises
a polyethylene oxide and a polymer or polymers selected from an
ether based polyurethane and a polyether block amide. The dressing
finds special use as a IV catheter site cover.
IV catheter claims
What is claimed is:
1. A surgical dressing which consists essentially of a continuous
film in direct contact with an adhesive layer for securing the dressing
to the human body wherein
a) said film has a hydration rate of at least 0.1 g/in.sup.2 /min
becomes saturated when in contact with liquid water, has a higher
MVTR than when in contact with water vapor in the absence of liquid
water, said film being coextruded and comprising a hydrophobic top
layer and a hydrophilic bottom layer, wherein said adhesive layer
is in direct contact with said hydrophilic layer,
b) said adhesive layer is porous and allows access of water to
the film when water is in contact with said adhesive layer
and wherein said dressing has a MVTR of not less than 3000 g/m.sup.2
/day when in contact with liquid water and a MVTR greater than 2000
g/m.sup.2 /day when in contact with water vapor but not in contact
with liquid water.
2. The dressing of claim 1 wherein said film when fully hydrated
contains at least its own weight of water.
3. The dressing of claim 1 wherein said film when fully hydrated
contains 1 to 11/2 times its own weight of water.
4. The dressing of claim 1 wherein said film when fully hydrated
contains 11/2 to 21/2 times its own weight of water.
5. The dressing of claim 1 wherein said film has a thickness of
1 mil (0.001 inch) to 5 mil.
6. The dressing of claim 1 wherein said adhesive is an acrylic
pressure sensitive adhesive.
IV catheter description
FIELD OF THE INVENTION
This invention relates to an adhesive dressing for use where high
moisture vapor transmission is desirable. This invention particularly
relates to an adhesive composite for use as a medical dressing on
exuding wounds. The invention relates even more particularly to
an IV Catheter adhesive dressing.
BACKGROUND OF THE INVENTION
Moisture vapor permeable thin films coated with adhesive are known
to be suitable for use as surgical dressings. They have found use
as a covering for burns, donor sites, surgical incisions, intravenous
IV catheter sites and the like. The known dressings have proved
useful because they keep out bacteria owing to the microscopically
continuous nature of the film and the adhesive layer, but do not
cause maceration of the skin to which they are applied because both
the film and the adhesive layer have high moisture vapor transmission
rates (MVTR). One problem with presently available high MVTR dressings
is that the MVTR is not high enough for some uses. It would be desirable
to have a higher MVTR for a dressing covering an IV catheter site.
Condensed moisture is occasionally found under film dressings over
IV catheter hubs and such moisture is associated with an increased
risk of bacterial colonization of the catheter site.
In extreme cases, diaphoretic patients or fluid leakage from the
IV line will collect at the site and form a blister. The MVTR of
dressings used to cover exuding wounds is purposefully limited so
that the wound is not allowed to become dry due to the excessive
transfer of moisture. This is not a problem with catheter sites.
Since there is no exuding wound to dry out, it is desirable to have
an extremely high MVTR so as to remove leaking liquid which may
cause a blister under the dressing and also to maintain the catheter
site as dry as possible so as to reduce the risk of infection. The
presence of a liquid blister can cause adhesion to the skin failure
which in turn can allow bacteria entry.
A second problem which can occur with presently available dressings
is that the adhesive layer must be applied in an open pattern so
as to allow sufficient moisture/film contact area to effect the
necessary moisture vapor transmission. Currently available film
dressings have up to 30% or even greater open area to effect the
necessary moisture vapor transfer. The pattern adhesive application
is a costly process and the resultant product may provide channels
for liquid leakage and/or bacterial invasion.
It has now been found that if the rate of hydration of the film
is sufficiently great the adhesive layer may have as little as 3%
open area and still allow the dressing to be fully functional. With
hydrophilic films which have a hydration rate of at least 0.1 g/sq.
in./min., which absorb liquid in amount at least equal to their
own weight, and which when in contact with liquid become saturated
in 3 minutes or less, the MVTR of the dressing is independent of
the adhesive layer surface coverage between 3% and 40% open area.
This means that the adhesive may be applied in essentially a continuous
coating via a less expensive process. It also means the dressing
product has more adhesive contact area with the skin of the user
and is less likely to leak and to fail, permitting bacterial intrusion.
It is, therefore, an object of the present invention to provide
a surgical dressing for use with a catheter.
It is a further object of the invention to provide a catheter dressing
which has a sufficiently fast rate of hydration so that the dressing
may have an adhesive coating with as little as 3-10% open area.
It is yet a further object of this invention to provide a catheter
dressing which has a hydration rate of at least 0.1 g./sq.in./min.
and which when in contact with liquid becomes saturated within 3
minutes and which when saturated holds at least its own weight in
It is yet a further object of this invention to provide a catheter
dressing which has a MVTR of at least 2000 g./m.sup.2 /day when
in contact with moisture vapor and a MVTR of greater than 3000
g/m.sup.2 /day when in contact with water.
Moisture vapor permeable adhesive coated thin films are disclosed
in U.S. Pat. No. 4595001 U.S. Pat. No.4798201; U.S. Pat. No.
3645835 and European Patent Application 0437944.
European patent application 0437944 requires at least three layers
comprising a backing layer, a high moisture vapor transmission layer,
and a skin contacting adhesive layer.
A pressure sensitive adhesive material comprising a backing material
and a pressure sensitive adhesive is disclosed in U.S. Pat. No.
3645835. The material has a moisture vapor permeability of at
least 300 g/m.sup.2 /24 hrs.
U.S. Pat. No. 4595001 is to a surgical dressing which consists
essentially of a film which carries an adhesive layer. The film
is continuous and comprises a polymer which in contact with water
has a higher moisture vapor permeability (MVP) than when in contact
with moisture vapor. The dressing has a MVP of not less than 2500
g/m.sup.2 when the adhesive layer is in contact with water and has
a MVP of not more than 2000 g/m.sup.2 when the adhesive is in contact
with moisture vapor.
U.S. Pat. 4798201 also discloses a surgical dressing which consists
essentially of a film which carries an adhesive layer. In this instance
the dressing has a MVP of not less than 2500 g/m.sup.2 when the
adhesive layer is in contact with water and a MVP of not more than
2000 g/im.sup.2 when the adhesive is in contact with moisture vapor.
The dressings of the prior art have upper limits on the MVP so
that the dressing does not dry out the exuding wound site. The prior
art dressings require significant open area in the adhesive layer
so as to achieve the required MVP for wound management.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more clearly understood by reference to the
following detailed description and the accompanying drawings in
FIG. 1 is a perspective of the adhesive dressing of the invention,
with one corner of the dressing being turned so as to show the lower
FIG. 2 is a cross-section taken along line 2--2 of FIG. 1;
FIG. 3 is a perspective of another dressing of the invention; and
FIG. 4 is a cross-section taken along line 4--4 of FIG. 3.
FIG. 5 is a typical response curve obtained in the MVTR determination.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, FIG. 1 shows in perspective a dressing
10 comprising a film layer 12 coated with an adhesive layer 14.
FIG. 2 is a cross sectional view of the dressing 10 taken along
line 2--2 of FIG. 1.
FIG. 3 shows another embodiment of this invention comprising a
three layer dressing 16 wherein a coextruded film comprising a top
protective layer 18 and a bottom absorbing film layer 20 is coated
with an adhesive 22. FIG. 4 is a cross sectional view of the dressing
16 taken along the line 4--4 of FIG. 3.
The surgical dressing 1016 of this invention consists essentially
of a film 1220 which carries an adhesive layer 1422 wherein the
film has a hydration rate of at least 0.1 g/in.sup.2 /min., becomes
saturated when in contact with water in 3 minutes or less, absorbs
at least its own weight of water, and which when in contact with
water has a higher moisture vapor transmission rate (MVTR) than
when in contact with moisture vapor. The adhesive layer 1422 is
porous in that it has an essentially uniformly spaced patternless
open area. The surgical dressing of this invention has an MVTR of
not less than 3000 g/m.sup.2 /day when in contact with water, and
an MVTR of at least 2000 g/m.sup.2 /day when in contact with moisture
The hydrophilic film 1220 when fully hydrated will contain at
least its own weight, i.e., 100% of water. More preferably the film
will contain 100-150% water and even more preferred, the film will
contain 150-250% water.
The hydrophilic film may comprise any synthetic polymer, copolymer,
graft or block copolymer, or polymer blend which provides the required
hydration rate, absorbency and MVTR. Ideally, the polymers should
be melt processable to allow manufacture by melt extrusion, but
such films may also be produced by casting the film from solvent.
The preferred films are made from polymer melt blends which have
balanced hydrophilic and hydrophobic properties. A preferred melt
blend is an alloy of an ether based polyurethane (PU) and a high
molecular weight polyethylene oxide (PEO) wherein the PEO has a
molecular weight of greater than 100000. The concentration of PEO
can vary from 5 to 50% of the alloy by weight. The preferred concentration
of PEO is from 10 to 30%. The preferred molecular weight of the
PEO is 100000 to 1000000. In order to obtain a uniform blend
or alloy, the polyurethane must have a polyether linkage on the
polymer backbone. The polyurethane controls the alloy film strength.
To have a desired strength the polyurethane must have a maximum
melt index of 20 g/min. at 190.degree. C.
Another polymer alloy usable in this invention comprises polyurethane,
PEO and a polyether block amide (PEBA). The urethane and PEO are
as described above. The PEO may be varied between 5 and 50% by weight
with the remainder of the alloy being divided between the PU and
the PEBA factions.
The polymer alloys are extruded by standard procedures well known
in the art into single layer films having a thickness of 1 mil (0.001
inch) to 5 mil.
Coextruded, i.e., two layer films as shown in FIG. 3 and 4 may
also be employed in this invention. In this case a relatively hydrophobic
layer is used as a top layer 18. The top layer is the layer which
does not contact the adhesive and is the layer which in use is the
furthest removed from the skin. The hydrophobic layer is used to
protect the bottom hydrophilic layer 20. By varying the relative
thickness of the two layers, the MVTR can be controlled and the
desired level achieved. Polyurethane, PEBA, polyether based polyester
or blends of hydrophobic and hydrophilic resins can be used as the
top layer. The bottom layer must be more hydrophilic and is as described
Due to the rapid rate of hydration of the films of this invention
and due to the absorbent capacity of the films, the porous adhesive
coating applied to the film may have as little as 3% open area.
It is preferred that the adhesive layer have an open area of 3-10%.
By open area is meant that portion of the film surface in which
there is no adhesive covering. It has been found that by using the
films of this invention in an IV Catheter dressing that the MVTR
of the dressing is not influenced by the adhesive coverage when
the open area is between 3 and 40%.
The adhesive may be any of the pressure sensitive adhesives well
known in the art that are useful for skin contact. The preferred
material is an acrylic pressure sensitive adhesive. The adhesive
is generally employed at a mass per unit area of 10 to 100 g/m.sup.2
and it is preferred to apply 15 to 40 g/m.sup.2.
Since an adhesive coating with low open area is preferred, the
adhesive can be applied by a conventional reverse roll coating process.
By adding a small amount of an evaporatible nonsolvent to the adhesive
system, the open area of the coated material can be controlled.
For example, adding a small amount of hydrocarbon solvent to a water
based adhesive system or by adding a small amount of water to a
solvent based adhesive system will, on drying, provide pores or
open area in the adhesive layer due to the different evaporation
The following examples illustrate the practice of the invention.
An ether based polyurethane (PU) resin identified as Estane 58630
and supplied by B. F. Goodrich is mixed with a polyethylene oxide
(PEO) resin, Polyox N-750 as supplied by Union Carbide. The mixture
contains 80% by weight PU and 20% by weight of PEO. The polymers
are melt blended by extruding using a twin screw extruder at a melt
temperature of 180.degree. C. A string die is used which discharges
into a cold water quenching tank. The string is chopped into pellets.
The blended pellets are fed to a film extruder which has an L/D
of 24/1 and operates at a melt temperature of 180.degree. C. using
a standard film die. A 2 mil (0.002 inch) film is prepared, air
cooled and rolled up. The extruders for melt blending and for film
production are operated in a standard manner well known to those
skilled in the art.
A commercially available solvent based acrylic adhesive, Monsanto
2674 is coated on release paper by reverse roll coating. The adhesive
is coated at a weight of 20 g/m.sup.2. The coated adhesive has an
open area of 30%. The release paper containing the adhesive coating
is combined with the film to provide a layered structure with the
adhesive between the release paper and the film. The coating and
the laminating process are both well known to those skilled in the
The film adhesive laminate with release paper is then die cut to
appropriate size for dressing use. The dressing is tested for MVTR
by the Gravimetric Absorvency Tester (GAT). Method hereinafter described
and found to have an MVTR of 1650 g/m.sup.2 /day. The film has a
hydration rate of 0.37 g/in.sup.2 /min and saturates within 0.2
The procedure of Example 1 is followed except the film polymer
blend is 100% Estane 58630. The same adhesive is used and the coating
is applied so as to provide essentially a continuous coating with
no open area. This commercially available product when tested showed
no liquid absorption and did not hydrate.
The procedure of Example 1 is followed except the film polymer
blend is 100% Estane 58630. The same adhesive coating at the same
level and open area is used. The dressing when tested has an MVTR
of 275 g/m.sup.2 /day. It did not absorb liquid and did not hydrate.
The same procedure as Example 1 is followed except the resin composition
comprises by weight 40% Pebax 4011 a polyether block amide supplied
by Atochem, 30% Pellethane 2103-70A, a polyether based polyurethane
supplied by Dow Chemical, and 30% Polyox N-750 a polyethylene oxide
supplied by Union Carbide. Using the same adhesive and coating as
Example 1 the dressing is tested by the GAT method has a MVTR of
4500 g/m.sup.2 /day. When fully hydrated it absorbed 190% its own
weight of water.
Using the same film and adhesive as Example 4 except the adhesive
used here was a water based acrylic with a small amount of hexane
present which on drying yielded an open area of 3.8%. The MVTR of
this dressing was found to be 4750 g/m.sup.2 /day. When fully hydrated
the dressing absorbed 190% its own weight of water.
Following the same procedure as Example 1 except that the film
resin formulation is by weight 60% Pebax 4011 30% Pellethane 2103-70A,
and 10% Polyox N-750 the resultant dressing has an MVTR of 4650
g/m.sup.2 /day. This dressing when fully hydrated absorbed 115%
its own weight of water.
The same film and procedure of Example 6 is used except the applied
adhesive has an open area of 5%. This dressing has a MVTR of 4340
g/m.sup.2 /day. When fully hydrated this dressing absorbed 115%
its own weight of water.
A dressing is prepared using the procedure of Example 1 except
the film comprises by weight 50% Pebax 4011 30% Pellethane 2103-70A
and 20% Polyox N-80 (M.W. 200000). This dressing has a MVTR of
5890 g/m.sup.2 /day. When fully hydrated the dressing absorbed 168%
its own weight of liquid.
A coextruded two layered film was prepared using a standard extruder
process. The top protective layer was 100% Pebax 5533 supplied by
Atochem and the bottom and adhesive contacting layer was the same
composition as the film of Example 5. The extruded film was 0.0018
inches thick. The top layer comprised 20% of the film thickness
and the bottom layer comprised the remaining 80% of the film thickness.
The film was adhesive coated as in Example 5. The resultant dressing
had an MVTR of 2600 g/m.sup.2 /day. When fully hydrated the dressing
absorbed 116% of its own weight of liquid.
TABLE 1 ______________________________________ Time for Film Rate
of Adhesive to Reach Film Open Area MVTR Saturation Hydration Film
(%) g/m.sup.2 /day (min) g/in.sup.2 /min ______________________________________
Example 1 30 1650 0.3 0.37 Example 2 0 125 Did not No Absorb Hydration
Example 3 30 275 Did not No Absorb Hydration Example 4 30 4500 2
0.13 Example 5 3.8 4750 2 0.13 Example 6 30 4650 0.7 0.28 Example
7 5 4340 0.7 0.28 Example 8 30 5890 0.5 0.37 Example 9 6 2600 0.3
The Moisture Vapor Transmission Rate (MVTR is determined using
the "Gravimetric Absorbency Tester" of U.S. Pat. No. 4357827
which is incorporated herein by reference. MVTR is determined using
the apparatus and test cell shown in FIGS. 1 and 4 of the '827 patent.
A chart recorder is connected to the weighing device (16 of FIG.
1 of the '827 patent) to automatically record the weight gain of
the test specimen. All tests are done at a room temperature of 25.degree.
C. using a 1% saline solution as the liquid. The test cell (FIG.
4 of the '827 patent) employs a porous plate with a diameter of
9 cm. and pore size of 25-40 microns. The porous plate is maintained
at 0.5 cm. higher than the liquid level so as to provide a negative
pressure during the sample absorption process.
The test specimen, either dressing or fiber, is placed on the porous
plate and the liquid is introduced to the plate. The weight change
with time is recorded. The resultant chart is shown in FIG. 5 wherein:
A is taken as the time for film saturation as determined by reading
the inflection point.
B is the rate of film hydration.
C is MVTR.
As can be seen the dressing (film) first goes through a rapid absorption
as the film is hydrated. This hydration is the initial steep curve
shown in the figure above. After the film is saturated with liquid,
a constant evaporation takes place.
The slope of this part of the curve is defined as the MVTR as calculated
from the test specimen area, and the weight change with time.
For the test of the rate of film hydration, the test specimen is
held in contact with the porous plate by placing a 100 g. glass
plate on top of the specimen.
Degree of Hydration
To determine the degree of hydration of the film a preweighed dressing
is immersed in water at room temperature for 1/2 hour. The test
specimen is then removed from the water, blotted to remove free
water using a paper towel and is immediately weighted. The weight
gain is determined by the following equation: ##EQU1## where wet
weight=weight of specimen after immersion. dry weight=weight of
specimen before immersion.