U.S. patent number 3,825,007 [Application Number 05/216,077] was granted by the patent office on 1974-07-23 for pledgets.
Invention is credited to Robert W. Rand.
United States Patent |
3,825,007 |
Rand |
July 23, 1974 |
PLEDGETS
Abstract
A "pledget" is disclosed which comprises a piece of an
absorbent, fiberous material having a surface covered by a covering
of a flexible, resilient polymer material which extends over and
around and into the interstices of the fibers at the surface of the
piece of material. Such a structure can be created by contacting
the surface with a layer of a latex of the polymer material for a
sufficient period so that the liquid vehicle within the latex will
be absorbed into the fiberous material, resulting in the formation
of the covering on the fibers at the surface of the material, and
then removing the liquid vehicle from the material and from the
covering.
Inventors: |
Rand; Robert W. (Los Angeles,
CA) |
Family
ID: |
22805587 |
Appl.
No.: |
05/216,077 |
Filed: |
January 7, 1972 |
Current U.S.
Class: |
604/365;
428/309.9; 428/532; 604/373; 604/377; 442/321; 428/496 |
Current CPC
Class: |
A61F
13/00008 (20130101); A61F 13/2051 (20130101); Y10T
428/31971 (20150401); Y10T 442/51 (20150401); Y10T
428/31841 (20150401); Y10T 428/24996 (20150401) |
Current International
Class: |
A61F
13/00 (20060101); A61F 13/15 (20060101); A61F
13/20 (20060101); A61f 013/00 () |
Field of
Search: |
;161/39,43,151,159,160,170,244,410,265 ;117/140,163
;128/29W,296 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lesmes; George F.
Assistant Examiner: Bell; James J.
Attorney, Agent or Firm: O'Brian; Edward D.
Claims
I claim:
1. A pledget which comprises:
a piece of an absorbant, fibrous material in which the fibers are
prebonded together having surfaces, one of said surfaces being
covered by a covering of a continuous, porous, flexible, resilient,
elastomeric polymer material which is inert with respect to living
tissue, said polymer material in said covering extending over,
around and into the interstices of the fibers of said piece
adjacent to said surface so as to physically block off the exposed
surfaces of said fibers at said surface so that said piece is
isolated from anything contacting said surface.
2. A pledget as claimed in claim 1 wherein:
said absorbent, fiberous material is cotton felt, said polymer
material is natural rubber and said covering is porous so as to
permit the absorption of fluids by said piece through said
covering.
Description
BACKGROUND OF THE INVENTION
The term "pledget" is primarily a medical term utilized to
designate small, generally felt masses of absorbent fibers such as
cotton fibers which are utilized in connection with various
operations on living bodies and in various types of medical
treatment procedures. A complete understanding of the use of these
pledgets is unnecessary to an understanding of the present
invention. Their use and their advantages and disadvantages are
well established in the medical field. However, a brief review of
their utilization is important in understanding the reasons for the
present invention and how the present invention provides pledgets
which are more desirable than various different known pledgets.
One utilization of pledgets is in various different brain and
spinal cord operations. They are utilized in such operations to
protect neural tissue as operations are continued, and so as to
absorb fluids which might interfere with the operating procedures
and treatments. As such operations are being finished the pledgets
used are, of course, removed from the body where they are employed.
Such removal of known pledgets has been acknowledged to cause
problems and complications detrimentally affecting treatment.
This is best further explained by referring to known pledgets. Most
generally, these structures have been pieces of pure, absorbent
cotton felt. In many pledgets the fibers within a material of this
type are chemically bonded to one another so as to give the felt a
relatively high wet strength. In such structures the surface of the
felt applied to living tissue contains various absorbent fibers. As
a pledget is left in place such fibers will tend to be permeated by
the fluid present and will tend to adhere to a degree to the body
tissue contacted by the pledget.
As a consequence of this when a pledget is removed there is a
significant degree of danger of the tissue adhering to the pledget.
Such adherence can be extremely detrimental. As an example of this,
a pledget utilized in brain surgery may be utilized against the
arachnoid in the brain. After such a known pledget has been left in
place during an operation, it tends to adhere to a sufficient
extent so that there is a danger of it producing a subarachnoid
hemorrhage as it is lifted off the brain surface. In general, the
longer a pledget is left in the place the more pronounced the
adherence between it and the living tissue and the greater the
potential of damage when the pledget is removed.
A recognition of the danger of such damage has lead to various
proposed solutions to minimize such damage. As an example of one
such proposed solution it has been common for surgeons such as
neurosurgeons to attempt to facilitate the release of pledgets from
tissue contacted by the pledgets by liberally applying a
physiological saline solution to the regions where the pledgets are
utilized. This type of procedure is considered to have obvious
disadvantages growing out of the fact that an extra step -- the
irrigation -- is necessary with it and growing out of the obvious
disadvantages of the use of significant amounts of saline
solution.
Another proposed solution to the problem of pledget adherence has
involved the utilization of a release strip or layer on one side of
a conventional pledget. It is considered that in all cases where
this procedure has been attempted, the release strip has been a
sheet of rubber, serving essentially as a dam tending to hold back
the pledget so that it both will not stick to body tissue and also
so as to isolate the pledget so that it cannot do the effective job
of absorbing fluid. Procedures of this type are considered to be
disadvantageous because of problem of pledgets not fitting the
sheets of release material used and/or tending to move to one side
or another off of such sheets. Whenever this occurs there is of
course danger of adherence.
SUMMARY OF THE INVENTION
It is an intention of the present invention to provide pledgets
which eliminate this danger of adherence and yet which still retain
the desired ability to absorb fluids present. From this it will be
seen that in effect a broad objective of the present invention is
to provide new and improved pledgets. To avoid confusion it is to
be understood that such pledgets are sometimes referred to by other
names than the specific term "pledgets." At times they are referred
to as a type of "surgical sponge" and occasionally they are
designated as "neuro sponges" or "patty."
Another broad objective of the present invention is to provide new
and improved procedures for producing pledgets. In connection with
this it is an objective of se'present invention to provide a
procdure as indicated which may be easily and conveniently carried
out at a comparatively nominal cost utilizing inexpensive
equipment. A related objective of the invention is to provide
pledgets as produced by this procedure which not only are
effective, but which are also comparatively nominal in cost. 21
In accordance with this invention these and various other
objectives of the present invention are achieved by the production
of pledgets comprising a piece of absorbent, fiberous material
having a surface covered by a cover of a flexible, resilient
polymer material extending around, over and into the interstices of
the fibers at this surface of the piece of material through the
steps of contacting a surface of a piece of such material with a
latex of a polymer material for a sufficient period so that the
contact results in the liquid vehicle being absorbed into the
fiberous material at the surface so as to form this covering and
then removing the liquid vehicle from both the material and the
covering.
BRIEF DESCRIPTION OF THE DRAWING
A summary of this type is inherently incapable of indicating many
important features and aspects of an invention. Items of this type
will be apparent from a detailed consideration of the remainder of
this specification, the appended claims and the accompanying
drawing in which:
FIG. 1 indicates in a diagrammatic manner an initial step in
creating a pledget in accordance with this invention;
FIG. 2 indicates in a diagrammatic manner a second step in creating
such a pledget; and
FIG. 3 indicates in a diagrammatic manner a final step in creating
this product.
For the purpose of clarifying the nature of the invention it is to
be specifically noted that the accompanying drawing does not
indicate the invention per se' since the invention involves
intangible concepts as are set forth and defined in the appended
claims. The accompanying drawing is primarily intended for
explanatory purposes in indicating the nature of a presently
preferred pledget in accordance with the invention and a manner of
making such a pledget.
DETAILED DESCRIPTION
In accordance with this invention a pledget is formed utilizing a
latex of a flexible, resilient polymer material. Where a pledget is
intended to be utilized within a living body or in contact with
living tissue, to avoid toxic effects it is considered necessary to
utilize a polymer material which is inert or substantially inert
with respect to the body and living tissue. To avoid the danger of
the pledget causing damage the particular polymer material utilized
should be flexible so as to be capable of conforming to particular
tissue against which a pledget is to be utilized. The polymer
materials should also be somewhat resilient or at least to a degree
rubber-like in character so as to minimize the chances of the
polymer material becoming damaged during the handling and use of
the pledget.
A latex of any such polymer material is utilized in order to
facilitate the application to a piece of fiberous, absorbent
material as hereinafter indicated of the polymer material so that
ultimately the polymer material will form a cover extending over
and around fibers in the piece and will extend into the interstices
of such fibers. To avoid question the term "latex" is used here to
designate a collodial dispersion or a nearly collodial dispersion
of a polymer material as indicated in a liquid vehicle. Normally
such a vehicle is water, but on occasion other liquid carriers can
be utilized for comparatively or fine particles of polymer
material.
For best results in avoiding stratification or settling the latex
it is considered that the particles within such a latex should be
of no greater size than about 10 microns in diameter. If desired, a
latex to be used with this invention can include secondary agents
such as known dispersing agents, emulsifying agents, stablizers,
thickeners and wetting agents in amounts as are conventional in the
latex industry. Such agents and the amounts of them which are
commonly used are well established in the latex industry.
Further information relative to latices is found in a number of
different texts. In this connection reference is made to the text,
"Rubber Technology" by Morton, published by the Reinhold Publishing
Corp., N.Y., 1959, pages 441 to 454, inclusive. The disclosures of
these pages of this text are incorporated herein by reference for
the purpose of supplementing this disclosure.
One of the most common polymer materials easily obtained in the
form of a latex and possessing the physical properties indicated in
the preceding is natural rubber. As supplied for use a latex of
this material contains particles referred to as "gel" and "sol"
rubber particles varying in size from between about 0.1 to about
2microns. A normal rubber latex as sold for use will contain from
about 60 to about 70 percent by weight solids in a water vehicle,
and will contain minor amounts of ammonia serving as a stablizer. A
natural rubber latex of this type is preferably employed with the
invention because of its availability, its cost and the physical
properties of the rubber material itself.
Within the broad scope of the present invention it is possible to
utilize latices of other materials such as butadiene-styrene
latices, nitrile latices, polychloroprene latices and the like. The
applicability of any such polymer material for use in a pledget of
this invention will, of course, depend upon the inertness of the
specific polymer material under the intended use of the specific
pledget. Thus, for example, pledgets using a polymer material of a
specific character or type may not be suitable for one use, and yet
may be suitable for another ultimate application. So far as is now
known, pledgets made utilizing natural rubber may be satisfactorily
employed in any pledget application.
In general, a latex of any material as indicated should contain as
high a solids concentration as reasonably practical to obtain in
order to facilitate the application of the polymer material to a
piece of absorbent fiberous material in an amount necessary to
accomplish a desired physical structure in an ultimate pledget of
this invention. If the solids concentration is too high, the
application of the latex will tend to be relatively difficult while
if the solids concentration is too low the latex used may not
completely cover fiber surfaces as hereinafter indicated.
Broadly it is considered that this objective can be achieved using
a latex containing from about 20 to 80 percent by weight solids,
but that the application of desired amounts of the polymer material
is facilitated using a latex of from about 50 to about 75 percent
by weight of the polymer material. It is to be realized that these
percentage ranges of latex concentrations are rough approximations
inasmuch as because of inherent physical properties it is
impossible to use exactly the same latex concentrations with all
polymer materials. It is considered that the amounts given are
rough approximations which will be sufficient to enable others to
practice the invention with a minimum of difficulty.
In the presently preferred manner of practicing the invention a
latex as indicated in the preceding discussion is sprayed so as to
form a layer 10 of this latex on a surface 12 of a sheet 14 of an
imporous material such as glass in much the way in which a coat of
paint is sprayed upon a surface to receive such a coating. The
thickness of the layer created in this manner is important to the
physical properties of the ultimate pledget created, but is not
critical in the sense that a certain temperature or a certain pH
may be critical in connection with various chemical reactions.
The layer formed should be a continuous layer with no obvious
spaces containing only carrier between the particles so as to make
sure that there will be solid polymer material opposite a piece of
absorbent fiberous material 16 used in the second step in
practicing the invention. It is considered that this layer 10
should, however, be sufficiently thin so that it will not run off
of the sheet 14 when this sheet 14 is tilted at an angle to the
horizontal. In other words, the layer 10 should be sufficiently
thin so that it will not run like paint will run when applied in
too great a quantity for all of it to adhere to a surface.
If more than this amount of latex material is utilized it is
considered that in general the surface of a pledget produced will
tend to unnecessarily imporous. While for some applications this
may not be critical, for others it is considered to be relatively
important. Because of the variations in polymer materials and
latices of such materials these limitations are not to be
considered absolute in a physical sense. They are indicated herein
primarily to facilitate a clear understanding as to how to practice
the present invention. In general, the thickness referred to
corresponds to thicknesses corresponding to these of from about one
sheet to about four sheets of common bond paper.
Once a layer such as the layer 10 has been created the next step is
to apply a piece of material such as the piece 16 to this layer.
This piece 16 may conveniently be formed of any known fiberous
material such as is commonly utilized in forming pledgets. Because
of absorbency and physical strength it is, however, considered
preferable that this piece 16 be of a cotton felt of a high wet
strength character having individual fibers within the felt bonded
together by a known resinous material in accordance with
established techniques.
As the piece 16 is applied, the surface 18 of this piece is
preferably layed upon the layer 10 so as to not to physically
disrupt or "mop" this layer in order to disturb its uniform
character. As this occurs the liquid vehicle in the latex will tend
to be absorbed into the fibers exposed at this surface 18 so as to
form a covering extending over and around these fibers into the
interstices of them. This is essentially a physical process and the
time that it will require will depend upon a number of factors such
as the nature of the liquid vehicle, the amount of the vehicle
present in the latex used, the absorption characteristics of the
fibers for this vehicle and the like. When as preferred a natural
rubber latex is used, in general satisfactory results can be
achieved in a period of from about 10 minutes to about 1 hour, and
this period can be shortened to within the lower end of this range
by coupling the period allowed for this absorption with the removal
of the liquid vehicle used.
Thus, for example, a piece 16 located against a layer 10 of a
commercial latex as described containing about 62 percent by weight
natural rubber solids may, immediately after the application of the
piece 16 be inserted into a drying oven such as an oven at
200.degree. F. for a period of from about 25 to 30 minutes or until
it is determined that a change is taking place within the polymer
material. This will remove the liquid vehicle from within the piece
16 and a covering 20 of the character previously indicated is
created from within the material of the layer 10 by the absorption
of this vehicle. In most cases this vehicle may also be removed by
simple air drying or the like techniques which will result in
vehicle evaporation.
After removal of the vehicle in the latex a final ultimate pledget
22 in accordance with this invention may be obtained by the simple
steps as indicated in FIG. 3 of the drawing of pulling up the edge
of the piece 16 and blowing the pledget 22 off of this sheet
through the use of a compressed air gun. The pledget 22 obtained in
this manner can be cut to any desired size or shape using a
conventional cutting instrument so as to be ready to use.
In the event a pledget such as the pledget 22 is created using a
polymer system such as an elastomer system, which because of its
physical characteristics and/or its ultimate utilization should be
physically stronger than is normally considered necessary, the
latex used in forming this pledget may contain one or more
vulcanizing agents, cure activators and/or accelerators in
accordance with conventional practice. When such materials are used
it is considered preferable that a pledget produced as described be
treated under conventional vulcanizing conditions so as to develop
the final physical properties desired in a polymer composition
used. At times this can be accomplished concurrently with the
removal of the liquid vehicle.
In a pledget of the invention such as the pledget 22 the necessary
physical properties desired are essentially related to a physical
blocking off of the exposed surfaces of the fibers at the surface
18 of the piece 16 so that they cannot contact tissue or
tissue-like materials so as to tend to adhere to the same. When a
pledget 22 is created as described the polymer material forms a
covering which extends over and around the fibers of the piece 16
and into the interstices of such fibers which are exposed to or
adjacent to the surface 18 so as to penetrate such a surface to a
sufficient extent to isolate the piece 16 from whatever is
contacted by the pledget 22 as it is used.
This action is accomplished in a pledget such as the pledget 22
without forming a film which will destroy the porosity of the
pledget 22 when it is created as described in the preceding
discussion. Normally such porosity is important in obtaining a
desired absorbent action during the use of a pledget such as the
pledget 22. If for any reason a completely imporous covering 20 is
desired, such a covering may be obtained by continuously repeating
the process steps indicated in the preceding discussion.
These same process steps can be carried out in various different
ways which will be apparent to those in the coating art on the
basis of the disclosure embodied within this specification. Thus,
for example, the sheet 14 utilized is essentially employed as a
means of applying the layer 10 to the piece 16. Other known
substantially equivalent or related application procedures can be
used instead of the precise procedure herein indicated to apply a
layer as described to a surface of a piece of material such as the
piece 16.
* * * * *