 |
Description  |
|
|
BACKGROUND OF THE INVENTION
Many catheters, particularly intravenous and arterial catheters, carry a
separate hub on one end thereof for attachment of the catheter to a source
of parenteral solution, blood or the like. A serious occasional problem
which has been encountered with intravenous and arterial catheters is
that, upon withdrawing of the catheter from an artery or vein, the hub
separates from the catheter. On occasion the catheter has actually been
lost in the cardiovascular system of the patient. Obviously, it is
important to avoid even a very occasional occurence of this incident.
There are many ways of fitting a catheter into a hub. Adhesives or solvent
bonding of the catheter tube to the hub may be used, and various friction
fit attachments may also be used. However, these techniques have proven to
be less successful for use in flexible catheters than the technique of
this invention. Specifically, with the other bonding techniques the
catheter and hub still can separate, especially with catheter materials
which have low friction surfaces such as fluorocarbon plastics and
silicone-lubricated elastomers, and hydrogel-coated catheters.
In accordance with this invention the bond between the catheter hub and the
catheter itself is stronger than the tensile strength of the catheter, so
the catheter can actually break before losing its bond with the hub. This
can be even when catheter materials are used which are stronger than
silicone rubber.
DESCRIPTION OF THE INVENTION
The catheter assembly of this invention is provided having an improved
catheter hub, which comprises: a tubular catheter defining an end which in
turn defines a relatively enlarged transverse dimension for the catheter
wall and a thickened annular lip, when compared with an adjacent portion
of said catheter.
A catheter hub defines a bore portion, and the bore portion in turn defines
a relatively constricted portion and a relatively enlarged portion. The
enlarged catheter end is positioned within the relatively enlarged portion
of the bore while the adjacent portion of the catheter is positioned
within the relatively constricted portion of the bore.
Preferably, a rigid, tubular funnel member may be positioned within the
bore of the catheter. The funnel member may define an enlarged funnel
section positioned within the relatively enlarged portion of the hub. The
funnel member may be advantageously made of stainless steel, rigid
plastics, such as polypropylene, polyethylene, or various nylons which are
of lower cost than stainless steel, or high friction plastics in order to
assure even lower probability that the catheter may pull out before the
ultimate strength of the catheter is approached. The commercially
available CENTRASIL catheter sold by Travenol Laboratories, Inc. also uses
a funnel member, but in a manner apart from the structure of this
invention.
The result of the structure of this invention is that the collapse and
subsequent passage of the enlarged catheter end through the relatively
constricted portion of the bore is prevented upon attempted pulling of the
catheter out of the hub. Instead, as stated above, a properly designed
catheter in accordance with this invention can actually be broken apart by
pulling, without the end being pulled out of the hub, thereby having the
advantage of the ultimate breaking resistance of the material being
available for removing the catheter from the patient.
Preferably, the funnel member may be made of stainless steel or the like,
and is essentially entirely positioned within the catheter bore, serving
to enclose the enlarged end of the catheter between the hub and funnel.
The catheter may be made out of any desired material. However, preferably,
it is contemplated to make the catheter out of a mixture of thermoplastic
olefin-type polymers which may contain a chemically reactive
cross-linkable or graftable silicone gum, for example as taught in the
patent application of Dean G. Laurin, et al., Ser. No. 888,253, filed Mar.
17, 1978 now U.S. Pat. No. 4,196,731 issued Apr. 8, 1980, entitled
"Silicone-Containing Thermoplastic Polymers for Medical Uses". Such
materials can have relatively high tensile strength.
Alternatively, other materials can be used as a substitute for the material
described above, i.e., fluorinated poly(ethylene-propylene),
polytetrafluoroethylene, polyethylene, polyvinylchloride, polyurethane,
EVA, styrene-rubber block copolymers, block copolyesters, and similar
materials. The polyurethane and other materials may be externally
lubricated with silicone oil, glycerine, or the like. The advantages of
external lubricants can be utilized in this invention without
significantly weakening the adhesion of the catheter to the hub, since the
adhesion in this invention depends upon bulk deformation rather than
friction.
In general, the term "flexible" as used in this application is intended to
include the term "semi-flexible" and "semi-rigid", including relatively
stiff plastics which nevertheless are still flexible in the broad sense.
While the catheter of this invention is specifically contemplated to be an
IV catheter, it may also be used in arterial catheters, or any other
desired type of catheter.
FIG. 1 is a perspective exploded view of the parts of the catheter of this
invention prior to assembly.
FIG. 2 is an enlarged longitudinal sectional view of the hub of the
catheter of this invention after assembly.
FIG. 3 is an elevational view showing a portion of the catheter to be
assembled with a hub in accordance with this invention in the process of
formation of its relatively enlarged transverse end.
FIG. 4 is an elevational view, taken partly in section, of the enlarged end
of the catheter of FIG. 1 in a further processing step for forming the
thickened annular lip.
Referring to the drawings, catheter assembly 10 is shown which comprises a
catheter 12, which may be made of a thermoplastic material such as
described above, or, alternatively, polyethylene, or a similar material.
Silicone rubber can also be used.
Catheter hub 14 may be of generally conventional design, containing
attachment wings 16 and a bore 18 which, in turn, is subdivided into a
relatively constricted portion 20 and a relatively enlarged portion 22. A
rigid tubular funnel member 23 which has an enlarged funnel section 24,
and which carried a tubular section 26, may be positioned within the bore
of catheter 12 as shown in FIG. 2.
The end 28 of catheter 12 defines a relatively enlarged transverse
dimension for the catheter wall (as shown in FIGS. 2 and 4), and also a
thickened annular lip 30 at the catheter end.
As shown in FIG. 2, as the respective parts are assembled, at least a
substantial portion of the enlarged transverse end 28 with the thickened
lip 30 occupies the enlarged bore portion 22 of the hub 14, while the
adjacent portion 32 of catheter 12 passes through the relatively
constricted bore portion 20, with the catheter 12 projecting out of the
bottom of hub 14 in a normal manner.
Funnel member 23 is then forcefully inserted through outer end 34 of the
hub into the bore 36 of catheter 12, with the tubular portion 26 of the
funnel extending through catheter 12 into the relatively constricted bore
portion 20 of hub 14, while the funnel section 24 itself resides in the
relatively enlarged bore portion 22 to define an annular space and to
press relatively enlarged catheter end 28 into the approximate shape of
that annular space. It is preferable for the width of the widest portion
of funnel section 24 to essentially equal the width of relatively enlarged
bore portion 22, being just sufficiently smaller if necessary to permit
insertion into enlarged bore portion 22.
As can be seen, a still further enlarged bore portion 37 may also be
provided to provide a fitting for a connector or the like of a fluid
conduit.
As a result of the above, the thickened, stressed end 28 generally assumes
a harder characteristic than the remaining portions of the catheter
because it is thicker. Accordingly, when catheter 12 is pulled in an
attempt to yank it out of the hub 14, the enlarged portion 28 of catheter
12 serves as a resistant member, which for all practical purposes prevents
the removal of the catheter from the hub. Instead, the catheter can be
expected to break first. The presence of funnel 24 serves to enhance the
strength of the connection between the hub and the catheter, since it
prevents collapse of thickened end 28, which would facilitate its removal
through the constricted bore portion 20.
The particular shape of end 28 of the catheter may be formed in the manner
illustrated in FIGS. 3 and 4 in the case where a stressed thermoplastic
material is used for catheter 12. The extruded catheter tube 12 is placed
through an aperture 38 in a plate member 40, which generally serves to
protect the majority of the length of the catheter from the heat of
heating coil 42, or other heating means.
The exposed end 28 of the catheter is heated by the heating coil 42, which
may be a standard ring-shaped heating member, causing end 28 to shorten in
length and to thicken in width as stresses are relieved in the heated
portion of the catheter.
Alternatively, hot water, oil or the like may be used as a substitute heat
source for the air heating step specifically illustrated in FIG. 3.
Thereafter, plate 40 may be taken away from the heating coil and catheter
12 removed from aperture 38. Then, catheter 12 is preferably pressed
against the surface of cool plate 44 while the plastic is of a temperature
of about 150.degree. C., or another temperature above the softening
temperature of the catheter material, to define the thickened annular lip
30 at the extreme end of catheter 12.
Alternatively, end 28 of catheter 12 may be heat formed in a mold or die to
the proper shape, if desired.
The resulting catheter is then assembled in the manner illustrated in FIG.
1, and brought together as described above and as shown in FIG. 2, to
provide a catheter having an extra strong hub.
Specifically, a catheter having an outer diameter along its unthickened
wall of 0.069 inch and an inner diameter of 0.040 inch may be mounted in
accordance with this invention in hubs as shown herein, to withstand a 5
to 7 pound pull without separation of the hub from the catheter. On the
other hand, similar catheters not using the invention of this application
tend to separate from their hubs with as little as a two pound pull.
This invention can also be used for connecting other tubing besides
catheters, for example for connecting tubing for blood dialyzer or
oxygenator circuits, or for connecting peristaltic pump tubing.
The above has been offered for illustrative purposes only and is not
intended to limit the invention of this application, which is as defined
in the claims below.
* * * * *
|
|
 |
|
 |
Description |
|
