Surgical dressing

A surgical dressing comprising, a relatively nonadherent sheet comprising a nonwoven fabric having an outer surface defining a layer of substantially hydrophobic fibers. The dressing has a second relatively absorbent sheet comprising a multi-layered bulked open-mesh fabric. The first and second sheets are laminated together to form the dressing with the outer surface of the first sheet facing outwardly from the dressing.

BACKGROUND OF THE INVENTION 
The present invention relates to absorbent articles, and more particularly 
to surgical dressings. 
A number of surgical dressings have been proposed in the past for use on 
patients. Although such dressings may be suitable for a particular 
application, the dressings have failed to account for the varying 
conditions of the patient's wound. The initial stage of wound healing is 
characterized by passage of relatively large amounts of body fluids, and 
it is thus necessary to provide a relatively absorbent dressing to capture 
the fluids during this stage of the healing process. Further, it is 
desirable that the dressing utilized during this stage be very porous, 
such that granulating tissue is permitted to grow into the dressing, and 
debris from the wound is removed with the dressing when withdrawn from the 
wound. 
However, once the wound reaches the maturation stage and the effusion of 
body fluids diminishes, the dressing utilized during the initial state 
becomes inadequate for the wound and may disrupt the healing process. At 
this stage, the dressing should have absorbent characteristics, but should 
be relatively nonadherent to the wound. 
SUMMARY OF THE INVENTION 
A principal feature of the present invention is the provision of an 
improved surgical dressing of simplified construction. 
The dressing of the present invention comprises, a first relatively 
nonadherent sheet comprising a nonwoven fabric having an inner layer of 
substantially hydrophilic fibers, a first surface layer of substantially 
hydrophobic fibers, and a second surface layer of substantially 
hydrophobic fibers on an opposed side of the inner layer relative to the 
first surface layer. The inner and surface layers are bonded together in 
substantially isolated highly compacted areas defining adjacent regions of 
substantially less compaction. The fabric is formed in a repeating series 
of wave-like undulations substantially throughout the dimensions of the 
fabric, with the interfiber spaces in the areas being substantially 
closed, and with the interfiber spaces in the regions being substantially 
open. The dressing has a second relatively absorbent sheet comprising an 
open-mesh, bulked, multi-layered woven fabric, with threads of the fabric 
being distorted into sinuous and tortuous configurations. The first and 
second sheets are laminated together to form the dressing with the first 
surface layer of the first sheet facing outwardly from the dressing. 
A feature of the present invention is that the second sheet is relatively 
porous and has excellent absorbent characteristics. 
Thus, a feature of the present invention is that the second sheet may be 
applied against a patient's wound during the initial stage of the healing 
process. 
Still another feature of the invention is that the first sheet is absorbent 
and is relatively nonadherent to the patient's wound. 
Thus, another feature of the invention is that the first sheet may be 
utilized to contact the patient's wound during a later stage of the 
healing process. 
Another feature of the invention is that the dressing may be utilized 
during various stages of the healing process, and eliminates the necessity 
for inventories of multiple dressings. 
A further feature of the invention is that the laminated dressing reduces 
the number of layers required for the fabric in the second sheet. 
Yet another feature of the invention is that the first sheet provides a 
protective layer over the second sheet when the second sheet is applied 
against the patient's wound. 
Yet another feature of the invention is that the first sheet reduces the 
number of loose threads which may be otherwise found in an edge of the 
second sheet when cut. 
A further feature of the invention is that the second sheet reinforces the 
first sheet when the first sheet is utilized on the patient's wound in 
order to prevent tearing of the first sheet during use. 
Further features will become more fully apparent in the following 
description of the embodiments of this invention and from the appended 
claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIGS. 1 and 1a, there is shown in diagrammatic form an 
apparatus generally designated 10 for constructing a nonwoven fabric and a 
surgical dressing of the present invention. The apparatus 10 may have 
suitable sources S.sub.1 and S.sub.2 which supply first and second outer 
or surface layers 12 and 14 of a heat-sensitive fibrous hydrophobic 
material to an endless belt 15 which is supported and driven by a pair of 
opposed rolls 17 in a direction as indicated by the arrows in the drawing. 
The layers 12 and 14 may be constructed from any suitable heat-sensitive 
hydrophobic fiber such as polypropylene or nylon, and, in a preferred 
form, the layers 12 and 14 comprise textile-length polyester fibers. Also, 
if desired, the surface of the fibers in layers 12 and 14 may be treated 
with a wetting agent to render them more hydrophilic, thus improving the 
fluid transfer rate and adsorbent capacity of the nonwoven fabric in the 
dressing without impairing the nonadherency of the dressing for a 
patient's wound. A suitable polyester fiber for use in the layers 12 and 
14 having a solid hydrophilic finish is sold by Eastman Kodak Company, 
Rochester, New York, under the fiber product No. 432. The apparatus 10 
also has a source S.sub.3 of substantially hydrophilic fibers, such as a 
blend of hydrophobic fibers and predominant hydrophilic fibers, which is 
supplied to the belt 15 in the form of an inner or central layer 20 
intermediate the outer layers 12 and 14. In a preferred form, the inner 
layer 20 comprises a blend or mixture of textile-length rayon fibers and 
textile-length polyester binder fibers, and the polyester fibers may be 
provided with a hydrophilic finish, as previously discussed in connection 
with the outer layers 12 and 14, if desired. In a suitable form, the inner 
layer 20 may comprise rayon fibers in a range of 20 to 99% by weight and 
polyester fibers in a corresponding range of 80 to 1% by weight, and a 
preferred range of 75 to 85% rayon fibers and 25% to 15% polyester fibers 
by weight. In a preferred form, the polyester binder fibers in the central 
layer 20 soften at a temperature lower than the fibers in the layers 12 
and 14, and may comprise a 3.0 denier, 11/2 inch polyester fiber, Type 
450, sold by Celanese Fibers Marketing Company, New York, New York. Each 
of the outer layers 12 and 14 may have a weight approximating 20% of the 
total fabric weight, while the inner layer may have a weight approximating 
the remaining 60% of the fabric. Typically, for a fabric having a weight 
of 30 g./sq. yd. each of the outer layers 12 and 14 has a weight of 6 
g./sq. yd. while the inner layer has a weight of 18 g./sq. yd. 
As shown, the belt 15 passes the overlying layers 12, 20, and 14 to the nip 
24 of a pair of opposed heated rolls 26 and 28 which are rotatably driven 
by suitable means in a direction as indicated by the arrows in the 
drawing. With reference to FIG. 1a, the layers are fused or bonded 
together in areas by heat and pressure as the layers pass between the 
rolls 26 and 28, which are both engraved with a pattern of helical lands 
30 and grooves 32, in order to form a series or pattern of pressure areas 
of various extent in a nonwoven fabric 33. An apparatus disclosed in U.S. 
Pat. No. 3,507,943, incorporated herein by reference, may be utilized to 
accomplish this result. 
The characteristics of the fiber displacement pattern in the fabric 33 
resulting from fusion of the fibers by the rolls 26 and 28 will be 
discussed in connection with FIGS. 3 and 3a. As shown, the bonded fabric 
33 has highly compacted and fused areas 34 at locations where a land on 
the roll 26 has traversed a land on the roll 28. The nonwoven fabric 33 
also has intermediately compressed areas 36 where a land on one roll has 
traversed a groove on the other roll. The fabric 33 also has substantially 
noncompacted areas 38 where a groove on one roll has traversed a groove on 
the other roll. The areas 34, 36, and 38 are in the form of quadrilaterals 
with parallel sides, although adjacent sides may not have equal lengths, 
and hence the areas may be termed rhomboidal. As shown, the combined areas 
36 and 38 define relatively noncompacted and unbonded regions 40 which 
surround and isolate each of the bonded areas 34, with the spaced areas 34 
having interfiber spaces substantially closed during fusion by the rolls. 
While the fabric shown in the drawings has an inner layer located between 
a pair of outer hydrophobic layers, it will be understood that a single 
outer layer of hydrophobic fibers may be utilized to define an outer 
surface of the fabric, if desired. 
With reference to the lower right-hand portion of FIG. 1, the bonded 
nonwoven fabric 33 is then passed to a compacting device 42 which 
microcrepes and bulks the fabric 33 into a micrexed nonwoven fabric 43. 
The device 42 may be of any suitable type, such as an apparatus disclosed 
in U.S. Pat. No. 3,260,778, incorporated herein by reference. In a 
alternative form, the device 42 may be any suitable apparatus which 
softens the fabric 33. 
With reference to FIG. 7a, the micrexing or compacting procedure causes the 
interfiber spaces in the unbonded regions 40 of the fabric 43 to become 
substantially open without destroying the structural integrity of the 
fused areas 34. Thus, the regions 40 have relatively open interfiber 
spaces for enhanced absorbency in the fabric 43, since the absorbency is 
largely dependent upon the spacing between the fibers. In this regard, the 
fabric 33 typically has an absorbent capacity approximating six times its 
own weight, while the absorbent capacity of the fabric 43 typically has an 
increased absorbent capacity approximately eleven times its own weight 
after the micrexing operation. In addition, the interfiber spaces in the 
fused areas 34 remain substantially closed, and the closed areas 34 in 
combination with the outer layers of hydrophobic fibers provides a 
nonadherent surface for contacting a patient's wound. In addition, the 
micrexing operation results in formation of the fabric into a repeating 
series of wave-like undulations substantially throughout the length of the 
fabric, with the undulations extending across the width of the fabric. 
Thus, the fabric assumes a very bulky configuration in order to provide a 
soft and conformable sheet in the dressing with cushioning characteristics 
for added comfort to the patient. 
The following example is illustrative of a nonwoven fabric which may be 
utilized as a surgical dressing according to the present invention: 
EXAMPLE: 
An array of fiber layers comprising a pair of outer or surface layers of 
100% 1.5 denier, 11/2" polyester fibers, each being approximately 20% of 
the total fabric weight (gms/sq. yd.), are placed around an inner core 
layer comprising 85% 1.5 denier 1 9/16" rayon fibers and 15% 3.0 denier, 
11/2" polyester binder fibers, with the inner layer being approximately 
60% of the total fabric weight, and the layers bonded with heat and 
pressure as previously described in connection with FIGS. 1 and 1a. The 
layered fabric is then treated with a mechanical compactor, such as 
disclosed in U.S. Pat. No. 3,260,778, in order to impart a repeating 
series of wave-like undulations substantially throughout the fabric length 
and width and to open the interfiber spaces of the nonbonded regions. The 
resulting fabric weighs approximately 37.6 gms/sq. yd., and has a 
thickness of 26.0 mils (as measured by the Ames-Mercer gauge), a bulk of 
14.7 cm..sup.3 /gm., and an absorbent capacity of approximately 1100%. The 
comparative figures of the fabric prior to micrexing are as follows: 34 
gm/sq. yd., a thickness of 12.5 mils, a bulk of 7.85, and an absorbent 
capacity of 640%. 
With reference again to the lower right-hand portion of FIG. 1, a second 
sheet or web 44 of an absorbent material is unwound from a roll 46, and is 
placed against a surface of a first sheet 41 comprising the micrexed 
nonwoven fabric 43. As shown, the first and second sheets 41 and 44 are 
supplied to a suitable device 48 which laminates the sheets 41 and 44 
together. In a suitable form, the device 48 may supply heat in order to 
melt the heat-sensitive fibers adjacent the second sheet 44, and fuse the 
sheets 41 and 44 together. In an alternative form, the device 48 may 
supply adhesive as the second sheet 44 is placed against the first sheet 
41 in order to bond the sheets together. As shown, the laminated sheets 41 
and 44 pass from the device 48, and are wound into a suitable roll 50 for 
subsequent handling. 
The second sheet 44 comprises a gauze fabric or an openmesh, bulked 
multi-layered, woven fabric with threads 51 of the fabric being distorted 
into sinuous and tortuous configurations, as shown in FIG. 4, defining 
relatively large open spaces 53 between the threads 51, and the sheet 44 
may comprise a washed gauze sponge, as disclosed in U.S. Pat. Nos. 
2,081,370 and 3,190,289, incorporated herein by reference. As disclosed 
therein, the fabric may be constructed from especially treated tobacco or 
cheese cloth, rayon or mixtures of the two to give it a pronounced 
three-dimensional structure as contrasted to the substantially planar 
structure of ordinary gauze. The preferred open-mesh cloth for the 
dressing of this invention may be made of 20s to 60s yarn size with range 
of 30s to 40s being preferred. The twist multiple (turns per inch over 
square root of yarn number) of the yarn may range from 3 to 7 with the 
warp yarns preferably having a slightly higher twist multiple than the 
filler yarns. It is preferred that the warp yarns have a twist multiple in 
the range of 4.25 to 5.0 with the filler yarns having a twist multiple of 
about 4. The thread count may vary from about 8.times.8 mesh to about 
18.times.12 mesh with the optimum about 14.times.8 mesh before treatment. 
The material may be subjected to standard bleaching procedures and the 
cotton may additionally be subjected to standard boiling procedures. 
The bleached tobacco cloth or cheese cloth as above described may be 
immersed in a water bath, preferably a hot bath in the presence of 
detergent, and while it is immersed or saturated it is strongly agitated 
causing at least the warp threads to assume sinuous or tortuous formations 
while the fabric shrinks and becomes thick and bulky. The bulkiness, and 
the configurations which the warp and weft threads assume, is set in the 
drying process. These configurations of the threads of the fabric are 
retained in the dried fabric and persist to a substantial extent even when 
the fabric is wetted again with exudate from a wound. It is possible to 
obtain a fabric in which the number of e bends is very great and such a 
fabric is satisfactory for the dressings of this invention, although it is 
preferred to stop the processing just short of the formation of e bends. 
Preferably, the fabric threads of the second sheet comprise a hydrophilic 
material, such as cotton, rayon, or a cotton-rayon blend. Alternatively, 
the threads of the second sheet may comprise a thermoplastic material, 
such as polypropylene fibers or polyester fibers treated with a 
hydrophilic finish. 
In alternative form, as illustrated in the upper right-hand portion of FIG. 
1, the second sheet 44 may be unwound from the roll 46 and placed against 
the first sheet 41 comprising the nonwoven fabric 33. The first and second 
sheets 41 and 44 are passed to a device 52 which laminates the sheets 41 
and 44 together, such as by the application of adhesive as the second 
sheet 44 is placed against the first sheet 41, and microcrepes or micrexes 
the first sheet 41 after placement of the second sheet 44 against the 
first sheet 41. The compacting device 42 previously discussed may be 
utilized in the device 52 to perform the micrexing operation in the device 
52. As shown, the laminated and microcreped sheets 41 and 44 are wound 
into a suitable roll 50'. 
An alternative apparatus 10' for constructing the surgical dressing is 
illustrated in FIG. 2, in which like reference numerals designate like 
parts. In this device, the second sheet 44 of absorbent fabric is unwound 
from the roll 46, and the sources S.sub.1, S.sub.2, and S.sub.3 of fibers 
place the fibrous layers on the second sheet 44 after which the second 
sheet and overlying fibrous layers are passed to the nip 24 of the rolls 
26 and 28, as previously discussed in connection with FIGS. 1 and 1a. 
Thus, the rolls 26 and 28 form bonded and unbonded regions in the fibrous 
layers, as previously discussed in connection with FIGS. 3 and 3a, while 
simultaneously fusing the fibrous layers to the second sheet through the 
medium of the fused heat-sensitive fibers in the fused areas 34. The 
laminated first nonwoven sheet 41 and second absorbent sheet 44 are then 
passed to a device 42 which microcrepes the nonwoven fabric 33 in a manner 
as previously described in connection with FIG. 1, after which the first 
and second sheets 41 and 44 are wound into a suitable roll 50". Thus, the 
surgical dressing may be constructed in alternative manners as discussed 
in connection with FIGS. 1 and 2, and, for convenience, the resulting 
rolls 50, 50' and 50" will be designated by the common reference numeral 
50. 
With reference to FIGS. 7 and 7a, the rolls 50 may be cut to suitable 
length in order to form surgical dressings generally designated 54 of the 
present invention. As shown, the dressing 54 has the first sheet 41 
comprising the micrexed nonwoven material 43 formed into a repeating 
series of wave-like undulations substantially throughout the dimensions of 
the fabric. The dressing 54 also has the second sheet 44 of open-mesh 
woven fabric, with the first and second sheets 41 and 44 being laminated 
together by suitable means 56 at their joining surface, such as adhesive 
or fusion of the fibers in the first sheet 41, as previously discussed. In 
suitable form, the second sheet 44 may comprise one to three plies of the 
open-mesh woven fabric, with the first sheet decreasing the number of 
plies in the second sheet normally required for a surgical sponge. 
In use, the second sheet 44 of the dressing 54 is placed against a 
patient's wound during the initial stage of the healing process. The 
second sheet 44 is highly absorbent and permits the body fluids to readily 
pass into the dressing 54. At the same time, the first sheet 41 provides a 
protective layer for the second sheet 44 when placed against the wound. 
Further, the first sheet 41 provides an aesthetically pleasing appearance 
for the dressing 54 when utilized in this manner, and also minimizes loose 
threads which may otherwise appear in cut edges of the second sheet 44. 
During the initial stage of the healing process, the porous second sheet 
44 permits desired ingrowth of granulating tissue in order to permit 
removal of debris from the wound when the dressing is removed from the 
patient. Further, the second sheet 44 provides a relatively high rate of 
fluid transfer into the dressing, and the second sheet 44 is relatively 
bulky and conformable in order to provide softness for the dressing and 
apply pressure to the wound during use. 
During a later stage in the healing process when the rate of fluid passage 
from the wound has diminished, the first sheet 41 of the dressing 54 may 
be placed against the patient's wound. The first sheet 41 provides 
sufficient absorbency for this stage of the healing process, and the first 
sheet 41 is relatively nonadherent to the wound and minimizes the growth 
of tissue into the dressing which is desired at this stage of the healing 
process. During use of the dressing in this manner, the second sheet 44 
reinforces the first sheet 41, and prevents tearing of the relatively weak 
first sheet 41. 
Thus, in accordance with the present invention, the first and second sheets 
41 and 44 cooperate with each other to define an improved surgical 
dressing for use in various stages of a healing process. Further, the 
dressing 54 of the present invention eliminates the necessity for 
maintaining inventories of separate dressings which must otherwise be 
selected for use during different stages of the healing process. 
With reference to FIG. 8, the dressing 54 may be supplied to the physician 
in the form of a roll 58 in which separate sheets 60 of the dressing 54 
may be severed along suitable perforation lines 62 extending at spaced 
intervals across the length of the dressing. In an alternative form, as 
shown in FIG. 9, the dressings 54 may be supplied in the form of stacked 
sheets 64 of suitable size. 
Although in a preferred form the dressing 54 utilizes the microcreped 
nonwoven fabric 43 previously discussed in connection with FIGS. 1-3a, 7, 
and 7a, the surgical dressing may utilize the nonmicrexed nonwoven fabric 
33. Thus, with reference to FIG. 5, in which like reference numerals 
designate like parts, the dressing 54' has a first sheet 41 comprising the 
nonwoven fabric 33 prior to micrexing, with the sheet 41 being laminated 
to the second sheet 44 in a suitable manner, such as by the application of 
adhesive or heating, as previously discussed. In an alternative form, as 
shown in FIG. 6, in which like reference numerals designate like parts, 
the dressing 54" has the first sheet 41 comprising a plurality of layers 
of the nonwoven fabric 33 prior to micrexing, with the layers of the first 
sheet 41 and second sheet 44 being laminated together, as previously 
described. Of course, it will be understood that multiple layers of the 
micrexed nonwoven fabric 43 may be utilized to form the first sheet 41 
which is laminated to the second sheet 44 in a manner as previously 
discussed in connection with FIGS. 7 and 7a. 
The foregoing detailed description is given for clearness of understanding 
only, and no unnecessary limitations should be understood therefrom, as 
modifications will be obvious to those skilled in the art.