U.S. patent number RE29,343 [Application Number 05/659,646] was granted by the patent office on 1977-08-09 for method for forming and sterilizing catheters.
Invention is credited to Kurt Amplatz.
United States Patent |
RE29,343 |
Amplatz |
August 9, 1977 |
Method for forming and sterilizing catheters
Abstract
A catheter for insertion into the human body and made of a
thermoplastic tubing, is preformed to a desired shape by heating it
above its free form temperature and allowing it to cool while held
in that shape. To hold the catheter in position for such forming
.Iadd.and/or for storage before use.Iaddend., a forming board
having a catheter receiving groove of the desired shape is used.
.[.The.]. .Iadd.In the form of the invention shown, the
cross-sectional shape of this groove is wider at the bottom and
narrower at the open top where it becomes a part of the board so as
to hold the catheter in place during the forming and storage and to
allow the catheter to be easily removed thereafter. This
.Iadd.particular form of .Iaddend.forming board is made by vacuum
forming a sheet of thermosetting plastic .Iadd.or thermoplastic
material .Iaddend.over a solid, non-heat responsive, master
representation of the exact longitudinal shape of the final
preformed catheter. The cross-sectional shape of the master is the
negative of the desired cross-section of the final forming board
groove. When the catheter has been .[.so.]. preformed .Iadd.and
lies in one of the forming board grooves, .Iaddend.it and its
forming board are packaged in a sealed plastic bag which is, like
the catheter and the forming board, permeable to sterilizing gas.
The resulting package is gas claved and stored in this sealed
condition until ready for use. The catheter is removed from the
sealed package and .Iadd.from .Iaddend.the forming board
immediately before insertion into the body. When it has served its
purpose, it .[.is.]. .Iadd.can be .Iaddend.removed from the body,
cleaned, positioned back into .[.the.]. .Iadd.a .Iaddend.forming
board, preformed with heat when necessary, placed in another sealed
film container, and resterilized for storage until it is again
needed.
Inventors: |
Amplatz; Kurt (St. Paul,
MN) |
Family
ID: |
26955010 |
Appl.
No.: |
05/659,646 |
Filed: |
February 20, 1976 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
271586 |
Jul 13, 1972 |
03839841 |
Oct 8, 1974 |
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Current U.S.
Class: |
53/425; 53/428;
53/449; 53/472; 264/320; 53/440; 53/474; 53/453 |
Current CPC
Class: |
A61M
25/0009 (20130101); A61M 25/002 (20130101); A61M
25/0041 (20130101) |
Current International
Class: |
A61M
25/00 (20060101); B65B 055/18 () |
Field of
Search: |
;53/21FC,25,21FW,29
;128/348,2M,2.5R ;425/383,392 ;264/320,322,339 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: McGehee; Travis S.
Attorney, Agent or Firm: Burd, Braddock & Bartz
Claims
I claim: .[.1. A method of forming into a predetermined shape an
elongated strip of thermoplastic material having a temperature
above which it is free forming and below which it tends to retain
its shape, the method including the steps of:
1. preparing a forming board having a groove of shape to support a
catheter in a predetermined desired configuration;
2. supporting the catheter in said groove to constitute a forming
board-catheter unit;
3. heating this unit at least to the free form temperature of the
catheter material; and
4. reducing the temperature of the unit to substantially below the
free
form temperature..]. 2. A method of making and preserving in
readiness for use a catheter for use within the human body,
.Iadd.said catheter comprising an elongated strip of thermoplastic
material having a temperature above which it is free forming and
below which it tends to retain its shape, the method
.Iaddend.including the steps .[.enumerated in claim 1, followed by
the following steps.]. .Iadd.of.Iaddend. : .Iadd.
1. preparing a forming board having a groove of shape to support a
catheter in a predetermined desired configuration;
2. supporting the catheter in said groove to constitute a forming
board-catheter unit;
3. heating this unit at least to the free form temperature of the
catheter material;
4. reducing the temperature of the unit to substantially below the
free form temperature; .Iaddend.
5. encompassing the forming board-elongated strip unit in a
hermetically sealed envelope;
6. sterilizing the interior of the envelope and the contents
thereof; and
7. retaining the catheter in the forming board and in the envelope
until it
is ready to be used. 3. The method of claim 2 wherein the steps of
supporting the catheter in the groove consists of constituting the
groove as of pear-shaped configuration in cross section, the groove
opening to the surface of the forming board, and having a top
surface dimension less than that of the normal diameter of the
catheter, and having a larger,
lower, dimension sufficient to encompass the catheter. 4. The
method of claim 2 wherein the forming board has been prepared to
have a groove of shape to support a catheter by preparing a master
having such predetermined desired configuration, setting this
master on an air permeable base, heating a sheet of thermosetting
plastic, and drawing it down on the master and the base by vacuum
forming methods, allowing it to cool and removing it from the base
and the master from it. .Iadd. 5. A method of preparing and
preserving in readiness for use a catheter for use within the human
body, said catheter comprising an elongated strip of thermoplastic
material having a temperature above which it is free forming and
below which it tends to retain its shape, the method including the
steps of:
1. preparing a forming board having a groove of shape to support a
catheter in a predetermined desired configuration;
2. supporting a catheter in said predetermined desired
configuration;
3. heating the catheter at least to the free form temperature of
the catheter materials;
4. reducing the temperature of the catheter to substantially below
the free form temperature;
5. supporting the catheter in said groove of said forming board to
constitute a forming board catheter unit;
6. encompassing the forming board-elongated catheter unit in a
hermetically sealed envelope;
7. sterilizing the interior of the envelope and the contents
thereof; and
8. retaining the catheter in the forming board and in the envelope
until it is ready to be used. .Iaddend. .Iadd. 6. The method of
claim 5 wherein the forming board has been prepared to have a
groove of shape to support a catheter by preparing a master having
such predetermined desired configuration, setting this master on an
air permeable base, heating a sheet of thermosetting plastic, and
drawing it down on the master and the base by vacuum forming
methods, allowing it to cool and removing it from the base and the
master from it. .Iaddend..Iadd. 7. The method of claim 5 wherein
the steps of supporting the catheter in the groove of the forming
board consists of constituting at least part of the groove as of
pear-shaped configuration in cross-section, the groove opening to
the surface of the forming board, and having a top surface
dimension less than that of the normal diameter of the catheter,
and having a larger, lower, dimension sufficient to encompass the
catheter. .Iaddend.
Description
BACKGROUND OF THE INVENTION
This invention relates to catheters of preformed shape for
insertion into the human body for a variety of purposes, and to the
manufacture of such catheters, the sterilization and storage of
them until ready for use, and the reclamation, reworking and
restorage of them for additional use.
Reuse of catheters of preformed shape before the present invention
was difficult, and in many cases impossible, making it necessary to
discard such a catheter after a single use. This was occasioned by
the fact that the Freon or other gases used to sterilize the
catheters tended to soften them and tended to cause them to lose
their preformed shape. Also, many of the best materials for
manufacture of these catheters become free form at around
100.degree. C.; and in cleaning and sterilizing the catheters for
reuse, any time this temperature was reached or approached, the
preformed shape of the catheter tended to be lost.
Before the present invention, in order to preform the catheter to
the desired preformed shape so that it could be reused, it was
necessary to insert a bendable, non-resilient wire through the
center of the catheter, and to bend the wire and the catheter into
what the technician or doctor considered the best preformed shape
before sterilization thereof. This wire-catheter combination was
then put inside of a gas permeable plastic bag which was sealed,
and then put into a gas sterilizer or gas clave unit. In the
sterilizer, the pressure was increased at least slightly above
atmospheric, and the temperature raised to about the free form
temperature of .[.100.degree. C..]. .Iadd.115.degree. F.
.Iaddend.The ethylene oxide or Freon, or other suitable sterilizing
gas, was introduced into the sterilizer and allowed to permeate
throughout the plastic bag, and through the side walls of the
catheter. See U.S. Pat. No. 3,612,038, granted Oct. 12, 1971 to J.
C. Halligan.
Unfortunately, there was no effective way to determine the action
of the sterilizing gas medium on bacteria which would be lodged
between the side wall of the catheter and the stiffening wire. Thus
no positive assurances could be given that the sterilization was
complete. Further, even though sterile, it was objectionable to
introduce a wire into the catheter and then take it out just before
the catheter was introduced into the body, because of the
possibility that some deleterious material had adhered to the
stiffening wire and would be scraped from it and thus would remain
inside of the catheter.
In order to manufacture and to initially preform catheters before
the present invention, solid metal plates were laboriously grooved
out to form exact representations of both sides of the negative
image of the catheters, and the catheters were confined in these
aligned, facing, hemispherical grooves while they were heated to be
preformed. This procedure was, of course, costly and unwieldy, and
basically only usable at the point of manufacture of the catheter.
Even so, these devices were somewhat effective. They were
completely ineffective, however, in the manufacture of shapes which
did not lie in a single plane. For example, production of a
"pigtail" catheter, where the leading edge is shaped like a portion
of a corkscrew, were impossible using the aforesaid method. Here
only the stiffened insert wire method could be used, with its
questionable sterilization practice and with its inaccuracy in
forming and holding the desired shapes.
After catheters were properly formed by the old methods, it was
extremely difficult to safely maintain them in a sterilized
condition, to store them indefinitely and effectively until needed,
and to transport them from the place of manufacture to the place of
use. If, in storage or transportation, the catheters were bent out
of the desired final preformed shape, any time they were
accidentally subjected to heat .[.over 100.degree. C..].
.Iadd.about 115.degree. F., .Iaddend.they would become free form,
and when cooled again, would have the preset form of the shape in
which they were stored rather than the shape in which they were
formed. Even when catheters were cushioned between gauze layers and
the like, and stored in boxes each large enough to completely
encompass the catheter in its desired final form, three dimensional
forms like the corkscrew form discussed above could not be
protected and would tend to fall from their own weight when they
were accidentally stored or purposely sterilized at a temperature
approaching the free form temperature of the material of which they
were made. Similar loss of shape tended to occur when the action of
the sterilizing gas on them caused them to tend to lose their
preformed stiffness.
BRIEF SUMMARY OF THE INVENTION
The above mentioned difficulties in the manufacture, storage,
sterilization, use and reuse of catheters are all overcome by the
method and structure and apparatus of the present invention.
Catheters are put inside of the body into various organs for
various purposes. In the case of a catheter into the heart, for
example, the leading 3 or 4 inches of the catheter are preformed to
have a particular shape so that the catheter will go into the right
place in the heart once it reaches the heart through a blood
vessel. Such catheters must be flexible to follow a tortuous route
into position, but should take on .[.the free form.]. .Iadd.a
predetermined .Iaddend.shape when they reach a point where they are
not closely confined by the sides of the passageway through which
they enter.
A forming board having a groove therein of the exact longitudinal
configuration desired in the catheter is used. A length of suitable
thermoplastic tubing is positioned in this groove, and the combined
forming board and catheter unit are heated to a temperature at or
above the free form temperature of the particular plastic making up
the catheter tube. When the catheter cools down, it will be in, and
will retain or come back to the preformed shape unless, before
used, it is again heated to or above, or close to its free form
temperature, or chemically softened by sterilization gases.
.[.The.]. .Iadd.When the same forming board is to be used to
sterilize and store the catheter, the .Iaddend. forming board
groove, in addition to being the exact longitudinal shape of the
desired final product, has a cross-sectional .[.shape.].
.Iadd.configuration .Iaddend.which is generally pear-shaped. That
is, a wider groove portion for confining the catheter tubing is
situated on one side of the plane of the forming board, and a
narrower .[.groove.]. portion suitable for preventing the tubing
from accidentally falling out of the groove forms the top of the
groove and ends integral with the board in the plane of the
board.
In order to make a forming board of the exactly correct shape, a
master representation of the exact longitudinal shape of the final
catheter and of the cross-sectional shape of the desired forming
board groove is mounted over a vacuum forming press bed, and the
forming board is drawn down by the usual vacuum methods over the
master. The plastic of the forming board being flexible, the master
can be removed after the forming board has cooled in final shape
and is ready for use in manufacture of catheters as explained
above.
After the forming board and catheter have been raised to above the
free form temperature of the plastic in the catheter and cooled to
preform or preset the shape of the catheter, the resulting
board-catheter unit can be sterilized and stored in a sealed
plastic bag or otherwise until just before the catheter is to be
used for its intended purpose of insertion into the body. The
catheter and the forming board can be of a plastic which is
permeable to sterilization gases, as can a plastic envelope into
which the board-catheter unit is sealed. Where such a sealing
envelope is impervious to air, the interior of the package
including the board-catheter unit, will remain in sterile condition
for an indefinite period.
After the catheter has served its intended purpose inside of the
body and is withdrawn, it can be cleaned, reinserted in the same
forming board or one having a similar or new desired groove shape,
reheated to its free form temperature, and cooled, sterilized and
packaged to be stored until it is again to be used.
Where preforming in three dimensions is necessary or desirable, two
such boards can be made. The first board is drawn down over the
master representation which has been set in a horizontal shape to
appear above the floor. The second board is made by drawing down
over a second remaining portion of the preformed shape which
extends out of a similar horizontal floor.
IN THE DRAWINGS
FIG. 1 is a top plan view of a forming board with a catheter
positioned in the forming groove;
FIG. 2 is an enlarged sectional view taken on the line 2--2 in FIG.
1;
FIG. 3 is a plan view of the catheter and forming board unit of
FIG. 1 on reduced scale and pictured inside of a transparent
plastic envelope for sterile storage;
FIG. 4 is a fragmentary vertical sectional view of the forming
board of FIGS. 1 through 3 in the process of being manufactured and
showing its positioning on a fragment of a vacuum form press bed
and encompassing a master representation of the desired catheter
shape;
FIG. 5 is a further enlarged sectional view of a fragment of the
forming board and catheter illustrating how the catheter is held in
the forming board groove;
FIG. 6 is an elevational view of a portion of a three dimensional
preformed catheter;
FIG. 7 is an elevational view of the three dimensional end portion
of the catheter of FIG. 6, a portion of a first forming board and
the second forming board used in initially preforming the catheter,
holding it during sterilization and storage, and reforming it when
this should be necessary or desirable; and
FIG. 8 is an enlarged vertical sectional view taken on the line
8--8 in FIG. 7.
DESCRIPTION OF PREFERRED EMBODIMENTS
Typically, a catheter 10 consists of an attachment fitting 12 and a
length of flexible tubing 14. A leading end portion 16 of this
tubing is provided with suitable openings to allow ingress and/or
egress to the catheter from the body once the catheter is properly
positioned therein.
In some instances, there is no particular advantage to be gained by
preforming the outer end portion 16 of the catheter, but the method
and apparatus of the invention are still effective in the making,
storing, sterilizing, and reforming of the catheter for reuse.
A particular problem presents itself, however, when it is necessary
or desirable to preform the leading end portion 16 to a specific
shape so that the catheter will naturally assume its proper
position within the body once it is free of the confinement of the
passageway through which it was introduced into the body. The
present invention is particularly useful in overcoming this
problem.
Assuming that it is desired to preform the end portion 16 of the
catheter 10 as seen in FIGS. 1 through 3 into the shape as seen in
FIG. 1, a non-heat responsive master representation 18 of the
desired final longitudinal catheter shape is made up. The
cross-sectional shape of this master 18 will be as seen in FIG. 4,
where the master 18 is shown to be positioned on a screen 20 of a
vacuum forming press bed 22. By any usual or preferred method, a
thermosetting plastic sheet 24 is drawn down over the master 18,
allowed to cool, and trimmed to the shape shown in FIG. 1 to
constitute the forming board 26. Once the sheet 24 has cooled, it
has sufficient flexibility so that it can be removed from the
master 18, thus leaving an open pearshaped groove 28 as an integral
part of the forming board 26, as clearly seen in FIGS. 2, 4 and 5.
The forming board is made of plastic which, once set in the desired
shape, is non-heat responsive at temperatures encountered in the
preforming, sterilization and storage of the catheter. Sheets of
polystyrene have been found excellent for the purpose.
Catheters are typically made from plastics which will become free
form at around .[.100.degree. C..]. .Iadd.115.degree. F.
.Iaddend.Polyurethane, polyvinyl, and polyethylene, among other
materials, have been successfully used.
To manufacture a catheter in accordance with the method of the
invention, a forming board such as the board 26 is prepared
.Iadd.as .Iaddend.described above, the attachment fitting 12 is
fastened to an appropriate length of flexible tubing 14, and the
tubing forced into the groove 28 of the forming board 26 to have
position as seen in FIG. 1.
This resulting forming board-catheter unit is then heated in an
appropriate oven or otherwise to or above the free form temperature
of the tubing, and allowed to cool to substantially below that
temperature.
.[.The.]. .Iadd.Such a .Iaddend.board-catheter combination is
inserted into a plastic envelope 30 of polyvinyl or other
appropriate material, which is then hermetically sealed as at
32.
The catheter, board, and envelope are of materials which are
permeable to the usual sterilizing gases such as ethylene oxiode or
Freon, and the package is put into a gas clave where the
temperature and pressure are elevated to cause the gas to
completely permeate the catheter, forming board and, of course, the
envelope. When removed from this gas clave, this catheter package
can be stored indefinitely and will remain in sterile condition
until such time as it is to be used. The gases used in
sterilization often have a tendency to soften the plastic of the
catheter, and so the fact that the catheter is supported at all
times in the groove 28 of the forming board 26 insures that the
desired preformed shape will not be lost. Also, should the
temperatures to which stored packages are subjected reach or
approach the free form temperature of the catheter, the shape of
the catheter will not change, and when the temperature again drops
into a more normal range, the catheter will still have the desired
preformed shape.
When the catheter is to be used, the sterile envelope package will
be opened, the forming board and catheter removed, the catheter
removed from the forming board and inserted into the body as
needed. When it has served its purpose in the body, it will be
removed, and can be cleaned. To reshape it to insure that it will
have the same preformed shape for reuse or to give it any other
desired preformed shape, it is again inserted in a groove .[.28.].
in an appropriate forming board, and the board-catheter unit again
brought up to the free form temperature of the plastic in the
catheter .[...]. .Iadd.and allowed to cool to substantially below
that temperature. .Iaddend.After being sealed in an envelope as
previously explained, it can be resterilized, and stored until
ready for further use.
Referring now to FIGS. 6 through 8, a three dimensional catheter
110 includes flexible tubing 114 and a three dimensional
"corkscrew" or "pigtail" leading end portion 116 having ingress
and/or egress orifices 117 therein.
In order to prepare a pair of matching forming boards to position
the catheter in the performance of the method described in
connection with FIGS. 1 through 5, a master representation of the
longitudinal shape of the desired finished catheter and of the
appropriate pear-shaped cross-sectional form will be prepared.
While such a master representation is .[.now.]. .Iadd.not
.Iaddend.shown in the drawings, it will very closely approximate
the shape of catheter 110. The master representation will be
associated with a plane, vacuum forming press bed screen surface
similar to the surface of screen 20 in the first form of the
invention in such a manner that the portion of it corresponding to
the portion of catheter 110 shown below the plane A--A in FIG. 8
will be above the screen so that a first forming board 126 can be
made by the method described in connection with the first form of
the invention. After that board is made, the master representation
will be associated with a vacuum forming press bed screen in such a
manner that the portion of leading end portion 116 of the catheter
above plane A-- A in FIG. 8 will be above the screen, so that a
second forming board 127 can be made. Both of these boards have
grooves 128 therein which are shaped to retain a catheter until
such time as the catheter is forcibly removed therefrom.
Once these forming boards 126 and 127 are made, an appropriate
length of flexible catheter tubing 114 will be snapped into place
in the groove 128 of board 126, leaving an appropriate length to
complete the loops of end portion 116 sticking out at the proper
place. This protruding portion is encompassed by the groove 128 in
second forming board 127, and, as shown in FIG. 7, pressure
sensitive adhesive strips 129 are used to temporarily fixedly
position the two boards with respect to each other to support the
catheter in its three dimensional form. The resulting forming
board-catheter unit are then heated to the free form temperature of
the plastic in the catheter and allowed to cool, thus preforming
the desired three dimensional shape in the leading end portion 116,
as clearly seen in FIGS. 6, 7 and 8.
This board-catheter unit will then be encompassed in an envelope,
such as the envelope 32 in connection with the first form of the
invention, the resulting package hermetically sealed, and
sterilized and stored until the catheter is to be used.
After the catheter has served its purpose in the body and is
removed, it may be cleaned up and utilized in the same forming
boards, or it can be utilized in other appropriate forming boards
to preform other desired shapes.
* * * * *