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Description  |
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This invention relates to a catheter. It relates more particularly to
improved means for connecting a flexible infusion catheter to a source of
infusate.
BACKGROUND OF THE INVENTION
The treatment of certain diseases of the human body often requires the
short-term or long-term infusion of drugs, blood products or nutritional
or other fluids into the patient's venous or arterial system. While such
fluids can be administered extracorporeally by transcutaneous injection,
in some cases, as when a particular patient's regime requires repeated
access for drug infusion, or where infection is of acute concern, it is
desirable to provide the patient with a totally implanted infusion system.
Such a system includes an injection portal which is an infusate chamber
implanted subcutaneously and placed on the chest wall or other convenient
body location. The portal is fitted with a needle-penetrable septum which
is located directly under the skin by which drugs or other fluids may be
introduced into the portal by transcutaneous injection through the septum.
The portal has a fluid outlet tube or stem which is connected to one end
of a flexible catheter which leads to the infusion site which is usually a
blood vessel or particular body cavity, e.g., the peritoneum. Since the
system is completely implanted, it reduces the risk of infectious
complications and allows drug infusion which is targeted to the specific
patient malady. Even though the delivery system may be implanted for a
long period, the patient remains ambulatory and can be treated on an
out-patient basis and the system does not interfere with the normal daily
activities of the patient.
A similar prosthesis can be used to draw blood from an artery or vein for
blood sampling purposes.
Since an implantable device of this type may remain in the patient's body
for many months, it is essential that the connection of the catheter to
the portal remain secure and fluid-tight during the entire period of
implantation. If the connection should fail or if there should be an
infusate leak at that location, the infusate dose required to treat the
patient which is injected into the portal will not be conducted to the
targeted infusion site in the patient's body. Rather, some or all of the
infusate will be dispensed at the site of the portal and could cause
complications at that body location. In this connection, it should be
appreciated that after a drug delivery system is implanted, the catheter
is subjected to various stresses and strains due to movements of the
patient's body, weight changes, etc. These are reflected in tensile and
twisting forces at the connection of the catheter to the portal outlet
which tend to upset the integrity of that union.
In an attempt to avoid this leakage problem and the attendant
complications, various steps have been taken to strengthen the connection
between the catheter and the portal. These include the providing of raised
circular rings or ribs on the portal outlet stem over which the catheter
wall is stretched. These lines of localized resilient engagement resist
sliding movements of the catheter from the portal stem. In some systems,
the connection is made somewhat more secure by providing a locking ring or
bushing which encircles the catheter and is releasably captured on the
catheter segment engaged on the portal stem by the raised ribs thereon.
We have found, however, that these prior catheter connections are not
entirely satisfactory. Sometimes the tensile forces exerted on the
catheter due to movements of the patient still suffice to separate the
catheter from the portal or to tear the catheter at that point of
connection because of a poor distribution of stresses on the catheter
wall. Certain prior systems are disadvantaged in that it is quite
difficult to connect the catheter to the portal outlet stem. This is
because that stem is often very small (e.g. 1 mm OD), and to make the
connection, the stem must be threaded into the end of the catheter lumen
which is itself equally small. Furthermore, when inserting the portal stem
into the catheter, if one is not quite careful, the catheter will be
punctured by the end of stem which, being so small, constitutes a sharp
point.
In addition, it should be kept in mind that it may be necessary to
disconnect the catheter from an already implanted injection portal in the
event that the catheter has to be replaced for one reason or another. For
example, it sometimes happens that the catheter lumen becomes clogged by
clots or other debris. Therefore, it is desirable that any connection
between the catheter and the portal be separable from the portal with a
minimum amount of effort and finger manipulation by the surgeon who must
make that repair subcutaneously. The prior catheter connection systems of
which applicant is aware, do not facilitate such ready connection and
disconnection of the catheter to and from the portal.
SUMMARY OF THE INVENTION
Accordingly, the present invention aims to provide an improved catheter
connection system.
Another object of the invention is to provide a catheter connection system
which is very strong, yet which can be released quite easily if the need
should arise.
Another object of the invention is to provide a catheter connection which
is specially adapted for use in an implantable infusion system for joining
the catheter to an injection portal.
Yet another object of the invention is to provide a connection system of
this type which minimizes localized stresses on the catheter in the region
of the connection.
Other objects will, in part, be obvious and will, in part, appear
hereinafter.
The invention accordingly comprises the features of construction,
combination of elements and arrangement of parts which will be exemplified
in the following detailed description, the scope of the invention will be
indicated in the claims.
The catheter connection system of interest here may be used in any
application where it is necessary to releasably connect the end of a
flexible resilient catheter or other tube to a stem, tube or rod by
inserting the stem, tube or rod into the end of the catheter. Since the
invention has particular application to the connection of a catheter to
the outlet stem of an implantable injection portal, we will describe the
invention in this context. It should be understood, however, that the
invention may be applied to other applications where similar flexible
tube-to-rigid-tube connections are required.
Briefly, the present connection system involves the coaction and
cooperation of a flexible resilient catheter, a relatively rigid stem or
tube onto which the catheter is slid to effect the connection and a
specially designed, clam shell-type locking retainer which encircles the
stem and catheter segment thereon to retain the catheter on the stem. The
system provides strain relief to the catheter and minimizes localized
stresses on the catheter due to tensile and other forces exerted on the
catheter in use.
The stem component of the system is formed with an axially symmetric radial
enlargement. In one arrangement, this projection takes the form of a
three-dimensional barb or bulb whose pointed end corresponds to the distal
end of the stem. This barb, rather than being pointed with sharp edges, is
generally pear-shaped with a blunted distal end whose diameter is less
than the diameter of the lumen in the catheter being connected to the stem
and a larger proximal end that is appreciably larger than that lumen.
When sliding the catheter onto the end of the stem, the barb end functions
as a guide to center the stem in the catheter lumen to facilitate sliding
the catheter onto the stem, the elastic wall of the catheter stretching
outward as required to accommodate the larger diameter proximal end of the
barb. Thus, when the end segment of the catheter has received the full
extent of the stem, the catheter resiliently engages the outer surface of
the stem and conforms closely to the barbed segment thereof.
In another embodiement of my system, the stem enlargement is located at the
proximal end of the stem and is not encircled by the catheter segment slid
onto the stem.
The third component of my connection system, namely the retainer, includes
a sleeve which is engaged on and encircles the catheter prior to sliding
the end of the catheter onto the portal stem. The sleeve has a distal end
segment which is tubular and faces the distal end of the catheter, i.e.,
the end thereof not being connected to the portal. The opposite or
proximal end segment of the sleeve is split lengthwise into two
mirror-image, hinged together sections that form a clamshell arrangement.
That is, one half of this split sleeve segment is a collinear extension of
the tubular sleeve segment and the other half is hinged to the first half
so that it can be swung open and closed; when closed, those split segments
form a tubular extension of the tubular sleeve segment.
The passage through the tubular segment of the sleeve is sized to snugly
receive the catheter so that when the split segment of the sleeve is open,
the sleeve can be slid along the catheter so that it encircles the length
thereof that surrounds the outlet stem of the injection portal. The
passage through the split segment of the sleeve includes a radial
enlargement extending around both halves of that segment and which
corresponds in size and location to the radial enlargement or barb on the
portal stem. When the sleeve is slid onto the catheter segment surrounding
the portal stem and the movable or swingable half of the split sleeve
segment swung to its closed position, that sleeve segment encircles and
captures the stem enlargement and any catheter wall segment stretched
around that enlargement.
The retainer also includes a locking ring which reposes on the tubular
segment of the sleeve when the split segment thereof is open. After the
hinged half of the split sleeve segment is swung closed to clamp the stem
enlargement, that ring may be slid along the sleeve so that it tightly
encircles the split sleeve segment to maintain that segment in its closed,
clamping condition.
As will be described shortly in greater detail, when the retainer component
of my connection system is seated on the portal stem and catheter thereon
and locked in place, there results a very secure connection of the
catheter to the stem. Even very strong pulling, twisting and bending
forces exerted on the catheter are unable to disconnect the catheter from
the outlet tube or to break the fluid-tight integrity of that connection.
Actually, as will be seen, such forces enhance that connection. Moreover,
those forces are distributed over a relatively wide area of the catheter
wall to minimize the build-up of localized strains in the catheter wall
which could result in a puncture or tear in that wall. As a result, even
when very large tensile forces are applied to the catheter, the catheter
will usually break somewhere along its length before its connection to the
portal outlet stem will fail.
The catheter connection system described here is also quite easy and
inexpensive to make, being composed of simple, molded plastic and metal
parts which can be manufactured in quantity at minimum cost. Also, the
connection is easy to make and to release, even if that needs to be done
in the case of an injection portal already implanted in the body. In other
words, the present apparatus facilitates sliding a catheter onto the end
of a portal outlet stem and simple finger movements suffice to manipulate
the connector's retaining sleeve and locking ring to secure the catheter
to the stem or to release the catheter from the stem. Consequently, the
present connection system should find wide application wherever it is
necessary to releasably connect a flexible catheter or other tube to a
relatively rigid rod or stem.
BRIEF DESCRIPTION OF THE DRAWING
For a fuller understanding of the nature and objects of the invention,
reference should be had to the following detailed description taken in
connection with the accompanying drawing, in which:
FIG. 1 is a fragmentary isometric view of an implantable infusion portal
incorporating a catheter connection system of this invention;
FIG. 2 is a fragmentary, exploded, isometric view on a much larger scale
showing the catheter connection system in greater detail;
FIG. 3 is a side elevational view with parts in section of the connection
system; and
FIG. 4 is a similar view of another embodiment of the catheter connection
system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1 of the drawing, my catheter connection system indicated
generally at 10 is shown connecting the proximal end of a catheter 12 to
the tubular outlet stem 14 of an implantable injection portal 16. The
portal is made of a material, such as stainless steel, and in use it is
implanted at a convenient location in the body, such as on the chest wall.
This portal might be used, for example, to conduct infusate to a vein
leading from the heart. Usually, small eyes 16a are provided around the
base of the portal through which sutures may be passed to anchor the
portal to the chest wall. The portal also includes a septum 16b composed
of a suitable resilient, needle-penetrable material, such as silicone
rubber. When the portal is implanted, the septum is situated directly
under the patient's skin so that infusate can be introduced into the
portal by transcutaneous injection through septum. The infusate thereupon
flows through the portal outlet stem 14 to the catheter 12 whose distal
end is placed at a selected infusion site in the body, such as a blood
vessel or a body cavity such as the peritoneum. Catheter 12 is made of a
flexible, resilient biocompatible material, such as silicone rubber. The
inside diameter of the catheter, which corresponds more or less to the
outside diameter of portal stem 14, may vary depending upon the particular
application, from, say, 0.5 to 3.0 mm. Likewise, the volume of the portal
16 may vary from, say, 0.4 ml to 1.0 ml.
Referring now to FIG. 2 of the drawing, connection system 10 is composed of
three distinct parts or components. These include the proximal end segment
12a of the catheter, the portal outlet stem 14 and a special locking
retainer shown generally at 17. The tubular stem 14 is formed with a
radial enlargement 15 along its length. In the system embodiment depicted
in FIG. 2, the enlargement 15 is located at the outer or distal end of the
stem and it takes the form a pear-shaped bulb or barb. In other words, the
enlargement has a relatively large, rounded shoulder 15' whose diameter is
appreciably larger than the inside diameter of catheter 12. The
enlargement tapers from that shoulder to a relatively small diameter blunt
end 15b whose diameter is appreciably smaller than the inside diameter of
the catheter. Accordingly, it is relatively easy to align the proximal end
of the catheter with the enlargement end 15b to engage the catheter on the
stem 14.
The shape of the enlargement is such that a relatively long frustoconical
segment 15c of the enlargement can be introduced into the catheter lumen
for a distance corresponding to about half its length without extending or
stretching the catheter wall. Further penetration of the outlet tube into
the catheter segment 12a results in the catheter wall deforming to
accommodate enlargement 15, particularly shoulder 15a. That is, the
silicone plastic catheter 12 is a very visco-elastic material that flows
when put under compression. This property is used to apply ever-increasing
force on the catheter to effect its sliding connection to stem 14. Thus,
as shown in FIG. 3, due to the resiliency of the catheter material, the
catheter segment 12a assumes the shape of outlet stem 14, including
enlargement 15.
Referring now to FIGS. 2 and 3, the locking retainer 17 comprises two
distinct parts, namely a tubular retainer sleeve indicated generally at 18
and a locking ring 22 slidably engaged around sleeve 18. Desirably, sleeve
18 is a molded part made of a suitable biocompatible plastic material,
such as polypropylene. Ring 22 is likewise an easily fabricated,
relatively inexpensive stamped metal (e.g., stainless steel) or molded
plastic (e.g., polypropylene) part.
Retainer sleeve 18 is a unitary piece that has three sections. It has a
tubular section 18a at the distal end of the sleeve which encirles the
catheter. Projecting forwardly from section 18a, i.e., toward the portal
16, is a semi-cylindrical section 18b which is collinear with section 18a.
In other words those two sections have a common longitudinal axis of
curvature. The third sleeve section 18c is likewise a semi-cylinder and it
is connected edgewise by means of a living hinge 24 to an edge of section
18b so that section 18c can be swung between an open position shown in
FIG. 2 and a closed position illustrated in FIG. 3. In other words, sleeve
sections 18b and 18c constitute a clamshell arrangement which projects
from the proximal end of sleeve section 18a so that when section 18c is in
its closed position, the sleeve 18 as a whole constitutes a continuous
tube whose outer diameter is more or less the same along the length of the
sleeve.
As best seen in FIG. 2, the sleeve section 18a has an axial passage 26
whose diameter is more or less the same as the outer diameter of catheter
12 so that the catheter is snugly received in that passage. As noted
previously, the inner diameter of the unstressed catheter 12 corresponds
to the diameter of enlargement 15 partway along the length of that
enlargement. Thus, when the catheter segment 12a is engaged on portal stem
14, sleeve 18 can be slid toward the proximal end of the stem until
enlargement 15 projects partway into the end of passage 26 of sleeve
section 18a, as shown in dotted lines in FIG. 3. Preferably, the proximal
end of that passage is tapered at 26a to more or less match the taper of
stem enlargement 15 as shown in FIG. 2. As seen there, this locates the
enlargement shoulder 15a positioned opposite sleeve section 18b. The
opposite or distal end 26b of passage 26 is flared as shown in FIG. 3.,
for reasons to be described later.
Still referring to FIG. 2, the inside wall of section 18b has a
semicylindrical recess 28a at the distal end of that section which is
sized to receive enlargement shoulder 15a, including the catheter segment
stretched thereon. The remaining length 28b of that interior wall has more
or less the same diameter as passage 26 in sleeve section 18a. Accordingly
when sleeve section 18c is in its open position shown in FIG. 2, and the
sleeve is slid along the stem 14 until it is stopped by the engagement of
enlargement 15 with the wall of passage 26, the catheter segment 12a and
stem 14 will lie coaxially in sleeve section 28a, with the enlargement
shoulder 15a being seated in recess 28a in that section.
Sleeve section 18c is a mirror image of section 18b so that it has a
semicylindrical recess 28a and wall segment 28b that match those in
section 18b. Thus, when section 18c is swung to its closed position shown
in FIG. 3, catheter segment 12a and portal stem 14, including its
enlargement 15, are captured between the two sleeve sections 18b and 18c
as clearly seen in that drawing figure.
With these two sections closed together as shown, the locking ring 22 can
be slid from sleeve section 18a along the sleeve so as to encircle and
capture sleeve sections 18b and 18c, thereby maintaining sections 18c in
its closed position. The inside diameter of the ring is held in close
tolerance to the outside diameter of the sleeve to maintain position and
closing pressure on sleeve section 18c and, thus, clamping force on
catheter 12. Desirably, that ring has a flange 22a to strengthen the ring
and to provide a gripping location for the surgeon. Also, as shown in FIG.
3, it may have a lead angle or bevel 22b on its inside wall to facilitate
its sliding onto sleeve sections 18b and 18c. Radial flanges 32a and 32b
are formed at the opposite ends of sleeve 18 in order to limit the sliding
motion of ring 22. Preferably also, sleeve 18 has an interference diameter
bump, rib, or other enlargement 32c on its outer wall adjacent to the
distal ends of sections 18b and 18c thereof to inhibit ring 22 from
sliding from its locking position shown in FIG. 3 to its unlocking
position illustrated in FIG. 2. In other words, an appreciable axial force
should be required to slide the ring 22 from sections 18b to its unlocking
position on section 18a.
It will be appreciated from the foregoing that the connection of catheter
12 to outlet stem 14 can be made quite easily with one hand, even when the
surgeon has no clear view of the connection site. To do this, the surgeon
grasps the end of the catheter and, feeling with his fingers, slides the
catheter onto the pointed end 15b of portal stem 14. He then pushes the
end of the catheter over enlargement 15 until the catheter engages portal
16. Next, the surgeon slides retainer sleeve 18 along the catheter until
that sliding motion is stopped by the engagement of the sleeve passage 26
wall by the portion of catheter 12 that is stretched by stem enlargement
15 to a diameter greater than the diameter of passage 26. Then the surgeon
swings sleeve section 18c to its closed position and slides the locking
ring 22 to its stop at sleeve flange 32b. Removal of the catheter 12 from
stem 14 simply involves reversing the above procedure.
When the connection 10 is made and locked as shown in FIG. 3, it is
practically impossible to pull catheter 12 from the portal stem 14. The
aforementioned flare 26b at the distal end of sleve passage 26 provides
strain relief to the catheter to prevent its being damaged when the
catheter is tensioned at an angle to the sleeve centerline or axis. Any
pulling or twisting forces applied to the catheter only serve to tighten
the connection between the catheter and the outlet stem. That is, when
catheter 12 is tensioned, it stretches so that its wall becomes thinner as
it moves axially. Sleeve 18, being in contact with the catheter is pulled
with the catheter. Resultantly, a circular area of contact C (FIGS. 2 and
3) of the passage 26 wall is moved closer to a short frustoconical surface
15d of barb 15 located proximate to the inner end of the stem 14, thereby
increasing the clamping force on the catheter. Thus, such tensile loads
effectively pull enlargement 15 even more tightly into the sleeve section
passage 28b. Accordingly, a frustoconical catheter segment 12b is
sandwiched or compressed ever more tightly between enlargement 15 and the
end of passage 28b, as clearly seen in FIG. 3. That engaged segment 12b of
the catheter is centered in passage 28b and the areal contact is
sufficiently small to cause considerable compression or "squeeze" on the
catheter, but not so small as to produce localized stresses on the
catheter wall that might tend to cause tears or punctures in that wall.
Consequently, there is very little likelihood of the catheter pulling away
from the portal outlet stem 14 or tearing due to movements of the patient
in which the prosthesis is implanted so that the integrity of the
connection system 10 should be maintained for the entire period of
implantation. Yet, if it should become necessary to replace the catheter
12 for some reason, the present system 10 facilitates that as well.
Indeed, the same locking retainer and portal stem can be assembled and
disassembled many times if need be.
FIG. 4 illustrates another connection system embodiment. This arrangement
is particularly useful for connecting to a portal stem or tube 34 a
catheter 33, made of a material such as polyurethane which is quite strong
and can withstand compression without cutting, tearing or thinning. In
this arrangement, the stem 34 has an enlargement consisting of a single
radial flange 38, located adjacent the proximal end of the stem. In use,
the end segment 33a of the catheter 33 is slid onto stem 34 until the
proximal end of the catheter engages flange 38, there being a snug fit
between the catheter and the stem. In this system, the locking retainer
shown generally at 42 comprises a retainer sleeve 44 and a locking ring 46
which are slightly different from those parts of system 10.
The sleeve 44 includes a tubular section 44a at its distal end having a
longitudinal passage 43, flared at its distal end, for snugly receiving
catheter 33. The sleeve also includes a pair of integral, collinear,
hinged-together, mirror image, semicylindrical sections 44b and 44c,
somewhat similar to those in sleeve 18 described above. The internal walls
of sleeve sections 44b and 44c are provided with lengthwise passage
segments 47 having registering semicylindrical recesses 48 adjacent the
proximal end of the sleeve. These are arranged to receive flange 38 when
the sleeve is slid along the catheter to the position shown in FIG. 4.
Then, when sleeve section 44c is swung to its closed position shown in
that figure, flange 38 is captured in recesses 48.
In the FIG. 4 system, the inner walls of passage segments 47 have opposed
linear series of, e.g. three, semicircular bosses or ribs 52 distributed
along the length of those passage segments. When sleeve section 44c is
swung to its closed position, three circular bands or segments 33b of
catheter 33 are compressed between stem 34 and those ribs 52. These
compressive engagements help to inhibit sliding motion of the catheter on
the stem due to tensile forces on the catheter. If such sliding motion
does occur, the sleeve 44 tends to be pulled along with the catheter.
However, since the sleeve is retained by flange 38, such movement is
prevented and the catheter ultimately fails in tension.
Sleeve section 44c is maintained in its closed position by locking ring 46
which is slidable on the sleeve from its unlocking position on sleeve
section 44a to its locking position shown in FIG. 4 wherein it encircles
and captures sleeve sections 44b and 44c. Preferably, the ring is
externally tapered as shown to facilitate gripping it.
In other respects, the FIG. 4 connection system has all of the advantages
discussed above in connection with system 10.
It will be seen from the foregoing, then, that our catheter connection
system establishes a reliable, releasible, fluid-tight and easily made
joint or connection between the end of a catheter and a rigid tube, stem
or other fluid pathway. The system's sleeve and locking ring are easy to
manipulate when connecting and disconnecting the catheter from the tube,
even if the surgeon's view is obstructed. Yet, the components of the
system are relatively easy and inexpensive to make so that the providing
of this secure connection does not materially increase the overall cost of
the injection portal or other prosthesis incorporating the invention.
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