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 and/or for storage before use, a forming board having a catheter receiving groove of the desired shape is used. The 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 particular form of forming board is made by vacuum forming a sheet of thermosetting plastic or thermoplastic material 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 and lies in one of the forming board grooves, 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 from the forming board immediately before insertion into the body. When it has served its purpose, it is can be removed from the body, cleaned, positioned back into the a forming board, preformed with heat when necessary, placed in another sealed film container, and resterilized for storage until it is again needed.

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°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°C 115° F. 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 as 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 Such a 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 . and allowed to cool to substantially below that temperature. 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 not 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.

Claims

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, 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 enumerated in claim 1, followed by the following 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;

4. reducing the temperature of the unit to substantially below the free form temperature;

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.

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.

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.

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.