Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
Many catheters, particularly intravenous and arterial
cathe~ers, carry a separate hub on one end thereof for attach-
ment of the catheter to a source of paren~eral solution, blood
or the like. A serious occasional problem which has been en-
countered with intravenous and arteria:L catheters is that, upon
withdrawing of the catheter from an artery or vein, the hub
separates from the catheter. On occasion the catheter has ac-
tually been lost in the cardiovascular sys~em of the patient.
Obviously, it is important to avoid even a very occasional oc-
curence of this incident.
There are many ways of iEitting a catheter into a hub.
Adhesives or solvent bonding of the catheter tube to the hub
may be used, and various Eriction Eit attachments may also be
used. However, these techniques have proven to be less success-
ful for use in flexible catheters than the technique of this
invention. Speciically, with the other bonding techniques the
catheter and hub still can separate, especially with catheter
materials which have low friction surfaces such as Eluorocarbon
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 cath-
eter materials are used which are stronger than silicone rubber.
DESCRTPTION OF THE INVENTION
The catheter assembly of this invention is provided hav-
ing an improved catheter hub, which comprises: a tubular cath-
- 2 - ~
~ ~ 3 3~
eter defining an end which in turn defines a relatively en-
larged transverse dimension or -the catheter wall and a thick-
ened 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 with-
in the relatively constricted portion of the bore.
Preferably, a rigid, tubular funnel member may be po-
sitioned within the bore of the catheter. The unnel member
may define an enlarged funnel section positioned within the
relatively enlarged portion o~ the hub. The funnel member
may be advantageously made o s~ainless steel, rigid plastics,
such as polypropylene, polyethylene, or various nylons which
are of lower cost than stainless steel, or high friction plas-
tics in order to assure even lower probability that the cathe-
ter may pull out before the ultimate strength of the catheter
2Q ~ is approached. The commercially available C~lTRASIL~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, there-
by having the advantage of the ultimate breaking resistance of
3~7~3
the ma-terial being available for removing the catheter from
the patient.
Preferably, the funnel member may be made of stain-
less steel or the like, and is essentially entireL~ 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. Such materials can have relatively high ten-
sile strength.
~ lternatively, other makerials can be used as a substi
tute for the material described above, i.e.~ Eluorlnated poly-
(ethylene-propylene), polytetrafloroethylene, polyethylene,
polyvinylchloride, (for example, Deseret semi-flexible PVC),
polyurethane, EV~, styrene-rubber block copolymers, block copo-
lyesters, and similar materials. The polyurethane and other
materials may be externally lubricated with silicone oil, gly-
cerine, or the like. The advantages of external lubricantscan be utilized in this invention without significantly weak-
ening the adhesion of the catheter to the hub, since the adhe-
sion in this in~ention depends upon bulk deformation rather
than friction.
In general, the term "flexible" as used in this appli-
cation is intended to include the term "semi-flexible" and
"simi-rigid", including relatively stiff plastics which never-
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nam/ ~4~
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theless 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 ar-
terial catheters~ or any other desired type of catheter.
Figure 1 is a perspective exploded view of -the parts
of -the catheter of this invention prior to assembly.
Figure 2 is an enlarged longitudinal sectional view
of the hub end o the catheter of this invention after assem-
bly.
Figure 3 is an elevational view showing a porkion of
the catheter to be assembled with a hub in accvrdance with
this invention in the process of Eormation of i-ts relatively
enlarged transverse end.
Figure 4 is an elevational view, taken partly in sec
tion, of the enlarged end o~ the ca-theter of Figure 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, alterna-
tively, polyethylene, or a similar material. Silicone rubber
can also be used.
Catheter hub 14 may be of ~enerally conventional de-
sign, containiny 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
t ~
~ E~ bore of catheter 12 as shown in FigureJ~.
~ 4~
The end 28 of catheter 1~ defines a relatively en-
larged transverse dimension for the catheter wall (as shown
in Figures 2 and 4), and also a thickened annular lip 30 at
the catheter end.
5B As shown in ~igure-~ as the respective parts are
assembled, at least a substantial portion of the enlarged
transverse end 28 with the thickened lip 30 occupies the en-
larged bore portion 22 o the hub 14, while the adjacent por-
tion 32 o~ catheter 12 passes through the relatively constrict-
ed 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 cathe~
ter 12 into the relatively constricted bore portion 20 of hub
14, while the funnel section 24 itself resides in the relative-
ly enlarged bore portion 22 to define an annular space and to
press relatively anlarged catheter end 28 into the approximate
: shape of that annular space, It is preferable for the ~idth 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 remain-
ing 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 ~8 of catheter 12 serves as a re-
sistant member, which for all practical pu.rposes prevents the
removal of the catheter from -the hub. Instead, the catheter
can be expected to break ~irst. 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 con-
stricted bore portion 20.
The particular shape of end 28 of -the cathe-ter may
be formed in the manner illustrated in Figures 3 ancl 4 in the
case where a stxessed thermoplastic material is used for
catheter 12. The extruded catheter tube 12 i9 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 Figure 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 150C.,
or another temperature above the softening temperature of the
catheter material,to define the thickened annular lip 30 at the
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extreme end of catheter 12.
Alternatively, end 28 of catheter 1~ 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 Figure 1, and brought together as
described above and as shown in Figure 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 dia-
meter of 0.040 inch may be mounted in accordance with this
invention in hubs as shown herein, ~o withs-tand a 5 to 7
pound pull without separation of the hub from the catheter.
On the other hand, similar catheters not using the inven~
tion 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 or connect-
ina tubing for blood dialyzer or oxygenator circuits, or
for connecting peristaltic pump tubing.
The above has been ofered for illustrative purposes
only and is not intended to limit the invention of this appli-
cation, which is as defined in the claims below.
