U.S. patent application number 11/025319 was filed with the patent office on 2007-01-04 for reinforced multi-lumen catheter.
Invention is credited to Ryan C. Patterson, Walter Shang.
Application Number | 20070005003 11/025319 |
Document ID | / |
Family ID | 34748938 |
Filed Date | 2007-01-04 |
United States Patent
Application |
20070005003 |
Kind Code |
A1 |
Patterson; Ryan C. ; et
al. |
January 4, 2007 |
Reinforced multi-lumen catheter
Abstract
A reinforced multi-lumen catheter and method of manufacturing
the same. An assembly for manufacturing the multi-lumen catheter
includes a catheter body substrate including a septum, one or more
mandrels, a reinforcing element and one or more sleeves. The septum
may have a distal region with a cross-sectional thickness greater
than that of a proximal region. The septum can be separately
formed. The septum can be split along a length of the distal
region. The reinforcing element can be positioned over at least a
proximal region of the catheter body substrate.
Inventors: |
Patterson; Ryan C.;
(Kaysville, UT) ; Shang; Walter; (Irvine,
CA) |
Correspondence
Address: |
MORRISON & FOERSTER, LLP
555 WEST FIFTH STREET
SUITE 3500
LOS ANGELES
CA
90013-1024
US
|
Family ID: |
34748938 |
Appl. No.: |
11/025319 |
Filed: |
December 29, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60533683 |
Dec 31, 2003 |
|
|
|
Current U.S.
Class: |
604/43 ;
264/632 |
Current CPC
Class: |
A61M 25/0052 20130101;
Y10T 156/1052 20150115; A61M 2025/0031 20130101; A61M 2025/0034
20130101; A61M 25/0012 20130101; A61M 25/0029 20130101; Y10T
29/49865 20150115; A61M 25/005 20130101; A61M 2025/0037 20130101;
A61M 25/0032 20130101; A61M 1/3661 20140204; Y10T 156/1082
20150115; Y10T 156/1142 20150115 |
Class at
Publication: |
604/043 ;
264/632 |
International
Class: |
A61M 3/00 20060101
A61M003/00; C04B 35/64 20060101 C04B035/64 |
Claims
1. A reinforced multi-lumen catheter, comprising: an elongate body
including an outer wall and a septum, the outer wall and the septum
defining first and second lumens, the septum comprising a proximal
region and a distal region, the septum distal region including a
cross-sectional thickness greater than a cross-sectional thickness
of the septum proximal region; a reinforcing region comprising a
reinforcing element positioned over a length of the elongate body,
the reinforcing region extending over the septum proximal region
and at least a proximal portion of the septum distal region; and a
sleeve positioned over the reinforcing element and the elongate
body, the septum distal region being split from a distal end
thereof to a dividing point to form a first tip section and a
second tip section, the dividing point being located distal the
reinforcing region.
2. The reinforced multi-lumen catheter according to claim 1,
wherein the elongate body, septum and sleeve are comprised of the
same material.
3. The reinforced multi-lumen catheter according to claim 2,
wherein the material includes medical grade polyurethane, silicone,
polyvinylchloride or polytetrafluoroethylene.
4. The reinforced multi-lumen catheter according to claim 2,
wherein the material includes Carbothane.RTM..
5. The reinforced multi-lumen catheter according to claim 1,
wherein the reinforcing element comprises a wire, and wherein the
reinforcing region comprises the wire wrapped around the elongate
body.
6. A method of making a multi-lumen catheter, comprising: providing
an assembly comprising: a catheter body substrate comprising an
outer wall and a septum, the outer wall and the septum defining
first and second lumens, the septum comprising a proximal region
and a distal region; a first mandrel and a second mandrel inserted
respectively into the first lumen and the second lumen; a
reinforcing element positioned over at least a proximal region of
the catheter body substrate; a sleeve positioned over the
reinforcing element and catheter body substrate; shrink tubing
positioned over the sleeve; heating the assembly; and splitting the
septum distal region from the distal end to a predetermined
dividing point, the dividing point being distal of the septum
proximal region.
7. The method according to claim 6, wherein at least one of the
mandrels include a stepped or tapered distal end, such that a
cross-sectional area of the distal end of the mandrel is less than
a cross-sectional area of a proximal end thereof, and wherein said
assembly further comprises additional material positioned at a
distal end of the catheter body substrate such that upon completion
of the heating step, a cross-sectional thickness of the septum
distal region is greater than a cross-sectional thickness of the
septum proximal region.
8. The method according to claim 6, wherein the catheter body
substrate comprises a proximal catheter body substrate and a distal
catheter body substrate, wherein the septum of the distal catheter
body substrate includes a cross-sectional thickness that is greater
that the septum of the proximal catheter body substrate.
9. The method according to claim 8, wherein the reinforcing element
is positioned substantially over the proximal catheter body
substrate and at least a portion of the distal catheter body
substrate.
10. The method according to claim 6, wherein the catheter body
substrate comprises a proximal catheter body substrate and a first
and second distal catheter body substrate, wherein the first distal
catheter body substrate comprises a lumen that is shaped
substantially similar to the first lumen and the second distal
catheter body substrate is shaped substantially similar to the
second lumen.
11. The method according to claim 10, wherein the reinforcing
element is positioned substantially over the proximal catheter body
substrate and at least a portion of the first and second distal
catheter body substrates.
12. A method of making a multi-lumen catheter, comprising:
providing a cylindrical tube including a reinforcing region;
inserting an independently-formed septum into the tube to define
two or more lumens therein; and bonding the septum to the tube.
13. The method according to claim 12, wherein the inserting step
comprises applying a longitudinal strain to the septum such that
the septum is stretched for placement within the tube.
14. The method according to claim 12, wherein the inserting step
comprises inserting two or more mandrels into the tube along with
the septum, the mandrels and septum together forming a
substantially circular cross-sectional shape, and wherein the
reinforcing region is provided by positioning a reinforcing element
around the cylindrical tube, positioning a second tube over the
reinforcing element to form an assembly and heating the assembly,
wherein the bonding step is accomplished thereby.
15. The method according to claim 12, wherein the cylindrical tube
includes an inner surface with a recessed portion configured to
receive a matching protrusion on an end of the septum, the
inserting step further comprising aligning the septum protrusion
with the tube recessed portion.
16. A method of making a multi-lumen catheter, comprising:
combining an independently-formed septum with two or more mandrels,
the mandrels and septum together forming a substantially circular
cross-sectional shape; wrapping an elongate member around the
mandrels and septum to form an assembly, the elongate member
comprising a coated reinforcing element; heating the assembly.
17. The method according to claim 16, further comprising the step
of positioning a sleeve over the elongate member.
18. The method according to claim 16, wherein the wrapping step
comprises helically wrapping the elongate member such that adjacent
windings of the elongate member are in contact with one another
along the length of the assembly.
19. A method of making a multi-lumen catheter, comprising: creating
an assembly, comprising: providing a first catheter body substrate
comprising a first lumen and a second catheter body comprising a
second lumen, each substrate having a substantially semi-circular
cross-sectional shape; inserting a first mandrel into the first
lumen and a second mandrel into the second lumen, wherein the first
and second mandrels extend beyond both proximal and distal ends of
the substrates; arranging the first and second substrates to form a
substantially circular cross-sectional shape; positioning a
reinforcing element over at least a proximal region of the first
and second substrates; positioning a sleeve over the reinforcing
element and first and second substrates; inserting a shim between
the first and second substrates at a distal end thereof; heating
the assembly; and cutting the sleeve along the position of the shim
and removing the shim.
20. The method according to claim 19, wherein the creating step
further comprises the step of fixing the first and second mandrels
to a fixture apparatus such that the first and second substrates
are held in a fixed position.
21. The method according to claim 20, wherein the heating step
comprises rotating the assembly while heat is applied.
22. The method according to claim 19, wherein the shim comprises
sharp opposing edges, wherein the cutting step comprises utilizing
only the shim.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/533,683, filed Dec. 31, 2003, which is expressly
incorporated by reference as if fully set forth herein.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO A COMPACT DISK APPENDIX
[0003] Not applicable.
BACKGROUND OF THE INVENTION
[0004] Multi-lumen catheters are used for the purpose of creating
two or more separate fluid pathways, such as in hemodialysis
applications. A primary goal of hemodialysis access is to provide a
reliable and effective means of dialysis, which means that a
sufficient volume of blood over a period of time must be removed
from and returned to the patient. Because the contaminated and
cleansed blood must be kept separate for an effective dialysis
procedure, a dual lumen catheter is generally used. Typically, a
dual lumen catheter for hemodialysis is configured so that there is
a shorter lumen that aspirates blood from a blood vessel of a
patient to a dialysis machine where it is processed for the removal
of toxins, and a longer lumen that infuses the purified blood to
the patient. The shorter lumen utilized for aspiration is generally
referred to as the "arterial lumen," while the longer lumen
utilized for infusion is generally referred to as the "venous
lumen." The reason for the different lengths is to minimize
co-mingling of aspirated and infused blood.
[0005] The primary problems occurring in dual lumen dialysis
catheters include thrombosis and fibrin sheath formation, which can
act to occlude distal tips of the dialysis catheter lumens,
resulting in loss of catheter function when such an occlusion
prevents blood flow. This typically occurs initially in the
arterial lumen used for aspiration of blood from a patient. A
secondary problem relates to the arterial lumen "sucking" against
the vessel wall, in which the arterial lumen openings become fully
occluded by the patient's vasculature. To specifically address
these problems, a unique type of dialysis access catheter has been
designed that utilizes independent "free floating" distal tip
sections that separate at a distal end of the catheter in order to
reduce the likelihood of potential occlusion and "sucking" during
dialysis treatment, hereinafter referred to as a "split-tip
catheter." Examples of patents and patent applications describing
split-tip catheters include U.S. Pat. No. 6,001,079 to Pourchez,
U.S. Pat. No. 6,758,836 to Zawacki, and co-pending U.S. patent
application Ser. Nos. 10/371,774, filed Feb. 21, 2003, and Ser. No.
10/842,586, filed May 10, 2004, all of which are incorporated by
reference herein.
[0006] While the split-tip catheter design has led to improved
functioning of dialysis catheters, it has been difficult to
manufacture a split-tip catheter having reinforcement along a
length thereof due to the change in configuration at the distal
end. As one of skill in the art readily appreciates, a reinforcing
region is desirable in an implanted catheter to prevent kinking of
the catheter and/or a reduction in the catheter lumen(s) due to
external pressures. Accordingly, provided herein are improvements
to the design and manufacture of a multi-lumen catheter, and in
particular a split-tip catheter, with respect to reinforcement
along a length thereof.
BRIEF SUMMARY OF THE INVENTION
[0007] In accordance with the invention described herein, several
embodiments are disclosed, which may be improvements to prior art
split-tip catheters or may be novel catheter embodiments heretofore
undisclosed. As used herein, the following terms have the following
meanings:
[0008] "Reinforcing region" refers to the region or section of the
catheter body which has been reinforced with a reinforcing
element.
[0009] "Reinforcing element" refers to a material or materials that
provide kink-resistance, columnar strength, etc. to the reinforcing
region and includes, but is not limited to, a wire or wires, a coil
or coils, braiding, or other reinforcement means. This term is not
intended as limiting and should not be construed as such, for
example, with respect to particular material(s), shapes, sizes,
thicknesses, lengths and/or disposition thereof with respect to the
catheter body.
[0010] "Septum" refers to a dividing element within a catheter body
that defines separate lumens therein. The septum may be integrally
formed with the catheter body or may be formed separately to be
inserted within a lumen of the catheter body.
[0011] "Split-tip catheter" refers to a catheter having a body
enclosing at least two lumens and a dividing point that separates
at least two tip sections from one another distal thereto, each of
the tip sections enclosing at least one lumen and being separated
or separable from one another along their length.
[0012] "Dividing point" refers to a point along the length of the
split-tip catheter distal to which at least two tip sections are
separated or are separable from one another.
[0013] "Tip section" refers to a portion of the split-tip catheter,
enclosing at least one lumen, which is separable or is separated
from another tip section along its length distal to a dividing
point.
[0014] In one embodiment, a multi-lumen catheter is provided with a
septum having a cross-sectional thickness in a distal region that
is greater than a cross-sectional thickness in a proximal region.
The difference in septum thickness is provided to enhance
functionability particular to the proximal and distal end of the
catheter. Thus, the proximal region of the catheter will generally
be constructed with a relatively thin septum to allow for better
overall flow performance, while the distal region of the catheter
will generally be constructed with a relatively thick septum to
allow the catheter to be split and tipped in a secondary production
procedure, which provides numerous manufacturing advantages. In
particular, the septum distal region may be cut using a razor or
other tool once the catheter has been constructed. In order to
impart additional kink resistance and support to the septum
proximal region, a reinforcing region may be provided over the
outer wall of the catheter along at least a portion of the length
of the septum proximal region. One noted advantage to such a design
is that a catheter can be provided with different lumen
cross-sectional areas along the length of the catheter without
altering the catheter outer diameter, thereby minimizing the risk
of air embolism during placement of the catheter through an
introducer sheath when compared with a catheter in which the outer
diameter varies along with the variation of lumen cross-sectional
area.
[0015] A shrink down method can be utilized to produce the
above-described embodiment. In one manufacturing variation, two
D-shaped mandrels are placed within D-shaped lumens of a dual lumen
catheter substrate (e.g., a tube having an outer wall enclosing a
centrally positioned septum that defines two lumens having
approximately the same size and shape). The cross-sectional shapes
of the mandrels may be different at a proximal end and a distal
end. For example, the distal end of at least one of the mandrels
may be stepped or tapered such that the cross-sectional area of the
distal end is less than that of the proximal end, thereby allowing
for the formation of a thicker septum at the distal end of the
catheter for reasons discussed above. A reinforcing element is then
positioned over at least a proximal portion of the substrate and a
sleeve is placed over the entire assembly. Shrink tubing is placed
over the sleeve and heat is applied, causing the shrink tubing to
compress the reinforcing element onto the underlying substrate,
which in turn causes the inner lumens to conform to the mandrel
shapes. Because the lumens tend to conform to the shape of the
mandrels during this process, extra material may be added to a
distal portion of the substrate over the stepped or tapered portion
of the mandrels to ensure that the final outer diameter of the
catheter remains constant. The extra material can be provided, for
example, by an additional sleeve over the distal section of the
substrate and/or by thin strips of polyurethane inserted into voids
between the mandrels and septum wall in the lumens of the distal
section where the mandrels extend. After heating, the shrink tubing
is removed and a tipping process is performed. In one variation,
the lumens are separated at the distal end of the catheter, for
example, by cutting through the septum.
[0016] In another manufacturing variation of the present invention,
the reinforced multi-lumen catheter is constructed utilizing two
dual lumen substrates, including a proximal substrate having a
relatively thin septum and a distal substrate having a relatively
thick septum. Two D-shaped mandrels are placed through the lumens
of the proximal substrate and into the proximal end of the distal
substrate. The proximal and distal substrates are brought into
contact with one another and a reinforcing element is disposed over
the proximal substrate (and may overlap onto the distal substrate
to fortify the bond between the proximal and distal substrates). A
sleeve is then placed over the entire assembly and shrink tubing is
placed over the sleeve. Heat is applied, causing the sleeve to melt
onto the substrates and causing the inner lumens to conform to the
mandrel shapes. The shrink tubing is then removed and the distal
end of the catheter undergoes a tipping procedure.
[0017] In yet another manufacturing variation of the present
invention, a reinforced split-tip catheter can be constructed
utilizing a proximal dual lumen substrate and two separate D-shaped
lumen substrates. Two D-shaped mandrels are placed through the
lumens of the proximal substrate and into the proximal end of the
distal substrates. The proximal and distal substrates are brought
into contact with one another and a reinforcing element is disposed
over the proximal substrate (and may overlap onto the distal
substrate to fortify the bond between the proximal and distal
substrates). A sleeve is then placed over the assembly, extending
to a point proximal the distal end of the D-shaped lumen substrates
and shrink tubing is placed over the sleeve. Heat is applied,
causing the sleeve to melt onto the substrates and causing the
inner lumens to conform to the mandrel shapes. The shrink tubing is
then removed. The separate D-shaped lumen substrates should already
be separated over their length distal to where the sleeve and
shrink tubing extended and thus, further separation tipping
procedures are not necessary. However, refinement of the tips
and/or other finishing processing is possible.
[0018] It should be noted that the tensile strength of the bond
between thick and thin septum sections may be improved by moving
the bond to a location beneath the reinforcing element, meaning
that the transition from thin to thick septum portion occurs within
the reinforcing region in the above-described variations. This
improved bond strength may be particularly useful in the case where
two D-shaped lumen substrates are bonded onto a proximal dual lumen
substrate.
[0019] In another embodiment of the present invention, a
multi-lumen catheter is created by inserting an independently
formed septum into a catheter body. The independently formed septum
may exhibit varying longitudinal geometric and material properties
to affect local properties along the length of the catheter
assembly (i.e., bending stiffness, kink resistance, varying lumen
area, etc.). For example, the septum could have a thicker distal
end to facilitate tipping, as discussed above, or could be
pre-split at a distal end thereof for the manufacture of a
split-tip catheter. Other variations include altering the
cross-sectional geometry of the septum to optimize flow.
[0020] In one manufacturing variation of the present invention, an
independently formed septum is inserted into a lumen of a
cylindrical tube that has been provided with a reinforcing element.
There are various ways to assure that the septum and the tube fit
tightly together prior to bonding. In one variation, a longitudinal
strain can be applied to the septum during insertion in order to
temporarily reduce the cross sectional area of the septum. Once the
septum is in position within a lumen of the outer tube, the tension
is released, allowing the septum to expand. The reinforcing element
prevents the cylindrical tube from being deformed into an oval
cross-sectional shape when the septum is allowed to expand. In
another variation, the inner surface of the outer tube is modified
(e.g., a notch or recessed area is provided) to accommodate the
septum so that insertion thereof is facilitated without affecting
the cross-sectional shape of the cylindrical tube. The septum is
bonded to the cylindrical tube by chemical (e.g., solvent bonding),
ultrasonic, heat-shrink, or other methods known to one of skill in
the art.
[0021] In another manufacturing variation of the present invention,
a first cylindrical tube is extruded and an independently formed
septum is placed in the lumen of the first tube along with
accompanying mandrels (e.g., a pair of D-shaped mandrels are placed
on either side of a septum having a rectangular cross-sectional
shape such that the cross-section of the septum and mandrels form a
circle filling the lumen of the tube). A reinforcing element is
then positioned over the assembly, followed by a second cylindrical
tube. Shrink tubing is placed over the second cylindrical tube and
heat is applied, melting the component parts together,
encapsulating the reinforcing element between the first and second
tubes and bonding the septum to the first tube. Thereafter, the
mandrels are removed and further tipping procedures are performed
as necessary.
[0022] In yet another manufacturing variation of the present
invention, an independently formed septum and shaped mandrels are
combined to form a core assembly (e.g., a pair of D-shaped mandrels
are placed on either side of a septum having a rectangular
cross-sectional shape such that the cross-section of the septum and
mandrels form a circle filling the lumen of the tube). A coated
reinforcing element is then wrapped around the core assembly and
shrink tubing is placed thereover. Heat is then applied,
compressing and heating the coated reinforcing element to melt the
component parts together, after which the mandrels are removed and
further tipping procedures are performed as necessary. Certainly,
as is the case with all described embodiments herein, numerous
variations are possible with respect to the physical properties
(e.g., shape, size, material, etc.) of both the septum and
mandrel(s).
[0023] In another embodiment of the present invention, a
multi-lumen catheter is created using two thin-walled D-shaped
lumen substrates and two D-shaped mandrels that are placed within
each substrate such that the mandrels fit snugly therein. The
substrates are then assembled together to form a circle in
cross-section (i.e., the flat sides of each are adjoining) and a
reinforcing element is positioned over the assembled substrates
over a proximal portion thereof (i.e., a distal portion is left
uncovered by the reinforcing element). A sleeve is placed over the
entire assembly and a shim is inserted between the lumens at the
distal end thereof (e.g., extending approximately 7-8 cm).
Utilizing shrink tubing and heat, the assembly is then melted
together, after which the mandrels and shrink tubing are removed.
The result is a final product having an proximal outer diameter
greater than a distal outer diameter. In one variation, instead of
a single sleeve being placed over the assembly, two sleeves are
employed, wherein a distal sleeve has a greater wall thickness than
a proximal sleeve in order to produce a final product with
substantially the same outer diameter. The sleeve portion that
surrounds the channel formed by the shim is then slit, resulting in
a split-tip distal section. The shim itself may have sharp edges to
accomplish the slitting process. The shim can be made of metal
(e.g., stainless steel), PTFE or other material with sufficient
tensile strength and smoothness to enable the removal thereof
following the heating process.
[0024] In one variation, the D-shaped lumen substrates are formed
to have a thicker septum than wall (i.e., the flat side of the
D-shaped substrate is thicker than the round side thereof). In
another variation, a single D-shaped substrate is formed and is cut
along its length to provide two D-shaped substrates. The lengths of
the two substrates could be approximately the same or one could be
longer than the other. In another variation, the mandrels placed
within the lumens of the substrates could be shaped with a slight
bow on the side that contacts the flat portion of the substrates to
produce a septum that is slightly thicker at the top and bottom
thereof, which results in a catheter better adapted for high
negative pressure in that the arterial lumen is more resistant to
deformation and collapse. During the assembling process, a fixture
apparatus may be used to both hold the mandrels in place to avoid
relative movement and to rotate the mandrels for disposition of the
reinforcing element. Moreover, the manufacturing process may
include a "pre-shrink" process in which hot air is blown over the
assembly while the assembly is rotated. Further, the heating step
herein may include the use of a convection oven, in which the
temperature is set at the melt temperature of the sleeve or sleeves
and the assembly is heated for a time sufficient to permit the
material to flow.
[0025] These and other embodiments, features and advantages of the
present invention will become more apparent to those skilled in the
art when taken with reference to the following more detailed
description of the invention in conjunction with the accompanying
drawings that are first briefly described.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1A is a perspective view of a split-tip catheter made
according to the present invention.
[0027] FIG. 1B is a cross-sectional view of the split-tip catheter
of FIG. 1A taken along line "B-B."
[0028] FIG. 1C is a cross-sectional view of the split-tip catheter
of FIG. 1A taken along line "C-C."
[0029] FIG. 2 is a cut-away view of an assembly for the manufacture
of a multi-lumen catheter according to the present invention,
showing the component parts through the outer wall of the
sleeve.
[0030] FIG. 3 is a cross-sectional exploded view of the assembly of
FIG. 2.
[0031] FIG. 4 is a cross-sectional view of another embodiment of an
assembly for the manufacture of a multi-lumen catheter according to
the present invention.
[0032] FIG. 5 is a perspective view of one variation of an assembly
for the manufacture of a multi-lumen catheter according to the
present invention.
[0033] FIG. 6 is a view of component parts of another embodiment of
an assembly for the manufacture of a multi-lumen catheter according
to the present invention, showing several possibilities for the
independent septum portion.
[0034] FIG. 7A is a cross-sectional view of a portion of a catheter
substrate and a septum in one variation of the embodiment of FIG.
6.
[0035] FIG. 7B is a cross-sectional view of a portion of a catheter
substrate and a septum in another variation of the embodiment of
FIG. 6.
[0036] FIG. 8 is a perspective view of another embodiment of an
assembly for the manufacture of a multi-lumen catheter according to
the present invention.
[0037] FIG. 9A is a perspective view of another embodiment of an
assembly for the manufacture of a multi-lumen catheter according to
the present invention.
[0038] FIG. 9B is an end view of the embodiment of FIG. 9A, showing
an additional component in the manufacture of the multi-lumen
catheter.
DETAILED DESCRIPTION OF THE INVENTION
[0039] The following detailed description should be read with
reference to the drawings, in which like elements in different
drawings are identically numbered. The drawings, which are not
necessarily to scale, depict selected preferred embodiments and are
not intended to limit the scope of the invention. The detailed
description illustrates by way of example, not by way of
limitation, the principles of the invention. This description will
clearly enable one skilled in the art to make and use the
invention, and describes several embodiments, adaptations,
variations, alternatives and uses of the invention, including what
is presently believed to be the best mode of carrying out the
invention.
[0040] It should be appreciated that while many of the designs and
methods for making a multi-lumen catheter discussed herein are
particular to a split-tip catheter, they would be equally
applicable to other types of catheters. Therefore, the examples and
embodiments provided herein should not act to limit the scope of
the present invention to split-tip catheters. Further, while
examples are provided herein with respect to materials for
component parts of the described multi-lumen catheter, the
invention should not be limited to these materials as numerous
other materials not specifically mentioned herein, which are
well-known to one of skill in the art, are equally contemplated for
use in construction of the inventive catheter.
[0041] In addition, the description of the manufacture of a
multi-lumen catheter herein focusses on the catheter body which
comprises that region of a multi-lumen catheter distal to an
extracorporeal connector (e.g., Y-connector, etc.) utilized to
fluidly connect the catheter lumens to one or more devices outside
of the body. Although not specifically described herein, the
present invention is intended to encompass all types of connectors
utilized in conjunction with multi-lumen catheters and therefore
should not be limited to specific connectors or connector systems
for use therewith. For example, while not specifically discussed
herein, the multi-lumen catheter of the present invention could be
formed with an integral connector at the proximal end thereof or
could be constructed to accommodate an attachable/detachable
connector, as described, for example, in commonly assigned
co-pending U.S. patent application Ser. Nos. 10/803,207 and
10/803,512, filed Mar. 18, 2004, each of which are incorporated by
reference herein.
[0042] FIG. 1A is a perspective view of an example of a multi-lumen
catheter made according to the present invention. Split-tip
catheter 10 has catheter body 11 enclosing two lumens 12, 13 (FIGS.
1B and 1C) that are defined by an outer wall and a bisecting planar
septum 22 of the catheter body 11. The two lumens 12, 13 extend
from the proximal end of the catheter to the distal end thereof and
have a D-shape configuration due to the planar septum 22. The
proximal end of the catheter is attached to a Y-connector 18, which
in turn is connected to extension tubing 20, as is standard in
dialysis catheters. The Y-connector 18 and extension tubing 20
fluidly connect the lumens to a blood treatment unit or dialysis
machine (not shown). The distal end of the split-tip catheter 10 is
bifurcated into a pair of distal tip sections 14, 16, which are
distal to a dividing point 15. Each of the tip sections 14, 16
enclose a lumen that is respectively continued from the pair of
distinct lumens 12, 13 enclosed in the catheter body 11. The
catheter body also includes a reinforcing element 19 along a length
thereof, extending from a proximal portion to a distal portion, but
terminating proximal the dividing point 15. The septum 22 of
split-tip catheter 10 has a cross-sectional thickness that is
greater along a distal region than along a proximal region as shown
in FIGS. 1B and 1C. In particular, septum cross-sectional thickness
26 along a distal region is greater than septum cross-sectional
thickness 24 along a proximal region.
[0043] In one variation for manufacturing a multi-lumen catheter of
the present invention, a shrink down method is utilized, wherein
the component parts of the catheter are assembled, shrink tubing is
positioned over the component parts and the entire assembly is
heated to melt the component parts together. The primary component
parts utilized for the manufacture of a multi-lumen catheter of the
present invention include, but are not limited to: one or more
mandrels, one or more catheter body substrates, a septum within the
one or more catheter body substrates that is either integrally
formed with the substrate(s) or is a separately formed component to
be inserted therein, a reinforcing element and one or more sleeves.
Of course, depending on the particular embodiment, there are
numerous other possible component parts, some of which will be
discussed in detail below. Also, while not specifically discussed
herein, one or more adhesive layers can be utilized to assist in
the bonding of the component parts.
[0044] Examples of materials used for the catheter body substrates,
septum and sleeves of the present invention include, but are not
limited to, medical grade polyurethane including Carbothane.RTM.
(e.g., Barium filled 85 Shore A), silicone, polyvinylchloride (PVC)
and polytetrafluoroethylene (PTFE). Examples of materials used for
the shrink tubing include fluorinated ethylene propylene (FEP),
PTFE and ethylenetetrafluoroethylene (ETFE). In one example, the
mandrels are made of stainless steel and have a Teflon.RTM. coating
disposed thereon to facilitate insertion and withdrawal into and
out of the lumens of the catheter body substrate(s). The
reinforcing element can comprise a wire, ribbon, etc. that is
either braided or helically wrapped directly onto the catheter body
substrate or that is first encased or surrounded by a polymer or
other type of material along its length. Examples of possible
materials for the reinforcing element include, but are not limited
to, stainless steel, Nitinol, polytetrafluoroethylene (PTFE), high
density polyethylene (HDPE) and high durometer polyurethanes.
[0045] A cut-away view of an assembly of one variation of the
present invention is illustrated in FIG. 2. Assembly 30 includes
two D-shaped mandrels 31, a catheter body substrate 32, a
reinforcing element 34 disposed over a proximal region of the
catheter body substrate 32, a first sleeve 36 positioned over the
catheter body substrate 32 and reinforcing element 34, a second
sleeve 38 positioned over a distal portion of the catheter body
substrate 32, and shrink tubing 39 positioned over the sleeve 38.
FIG. 3 illustrates the assembly 30 of FIG. 2 in a lengthwise
cross-sectional view. From this view, strips of material 37 can be
seen, which in this example are utilized to produce a thicker
distal septum. In assembly 30, two D-shaped mandrels 31 are
inserted within a dual lumen substrate 32 such that each mandrel
extends beyond both proximal and distal ends thereof as shown in
FIGS. 2-3. The mandrels 31 are sized to conform to the desired
lumen geometry of the substrate 32 and, in one variation, are sized
slightly smaller in cross-section than the lumens of the substrate
so that they can easily be inserted therethrough. The substrate 32
may be formed through extrusion, injection molding or other
processes known to one of skill in the art with an integral septum
33 dividing the substrate into substantially equivalent portions.
The substrate 32 may have many cross-sectional shapes, but in this
example is circular. Likewise, although a septum could be placed in
various different locations within the substrate 32 and itself may
have numerous different cross-sectional shapes and sizes to create
two or more lumens of varying configurations, the septum 33 in this
example has a rectangular cross-section and is positioned within
the substrate 32 to create similarly-sized D-shaped lumens.
[0046] As mentioned, a thicker septum at the distal end of a
multi-lumen catheter according to the present invention provides
certain advantages in facilitating tipping procedures following
initial formation of the catheter body. For example, if a split-tip
catheter is being produced, having a thicker distal septum eases
the step of cutting the septum to create distal tip sections. Thus,
as shown in FIG. 3, the mandrels 31 have a step at the distal end
thereof, which when placed within the lumens of the substrate 32
create a void between the mandrels 31 and the septum 33. Of course,
the same effect can be achieved through a distal taper of the
mandrels as well. The thicker septum is created at the distal end
upon heating whereby material flows into the voids. However, in
order to ensure that the outer diameter of the catheter body
remains substantially the same before and after heating, additional
material may be positioned at the distal end of the assembly 30,
including, for example, strips of material 37, a distal sleeve 38
or both. Of course, it may also be possible to create the catheter
body substrate with a septum that increases in thickness from a
proximal to distal end, in which case it may not be necessary to
utilize the distal sleeve 38 and/or the strips of material 37.
[0047] Following the insertion of the mandrels 31 into the lumens
of the catheter body substrate 32, the reinforcing element 34 is
positioned around the outer wall of the substrate 32, creating a
reinforcing region 35. The reinforcing region 35 may extend from a
proximal region of the catheter to a distal region thereof (making
certain that the reinforcing region 35 does not extend past the
desired location of the dividing point). In the variation shown in
FIGS. 2-3, the reinforcing element 34 extends at least to the point
along the length of the catheter body substrate where the septum 33
increases in thickness so that the catheter body region with a
thinner relative septum is provided with additional support. A
sleeve 36 is positioned over the reinforcing element 34 and the
remainder of the catheter body substrate 32 and a distal sleeve 38
is then optionally positioned over a distal region of the sleeve
36. In one variation, the sleeve 36 is sized slightly larger than
the outside diameter of the substrate 32 to facilitate positioning
(e.g., 0.020 in. larger diameter) and similarly, the distal sleeve
38 is sized slightly larger than the sleeve 36. Optionally, as
mentioned above, strips of material 37 may also be positioned
within the lumens of the catheter substrate 32 at the distal end
thereof between the septum 33 and the mandrels 31.
[0048] Shrink tubing 39, which in one variation is sized to easily
slide over sleeves 36, 38, is positioned over sleeve 36 and sleeve
38. The assembly 30 is then heated to a temperature suitable to
compress the shrink tubing 39 onto the sleeves 36, 38, such that
the reinforcing element is encapsulated between the outer wall of
the catheter body substrate 32 and the sleeve 36, the lumens of the
catheter body substrate 32 conform to the shapes of the mandrels,
and the component parts of the assembly 30, including the strips
37, melt together to form a final catheter body. In one variation,
FEP is utilized for the shrink tubing 39 and the assembly 30 is
heated, for example in a convection oven, to a temperature of
between approximately 300.degree. C. and 360.degree. C. for a time
of between approximately 1 and 5 minutes. Following formation of
the catheter body, the assembly 30 is permitted to cool at room
temperature and the shrink tubing 39 is removed. Tipping procedures
are then implemented, which include, but are not limited to:
cutting the distal septum in a proximal direction to a
pre-determined point, resulting in the formation of a dividing
point and two distal tip sections, using tipping procedures known
in the art to configure the tips to a desired geometry (e.g., using
radio-frequency energy to round the tips) and forming side holes in
the distal tip sections. Also, as discussed above, the catheter
body can undergo additional manufacturing steps with respect to
configuring the proximal end of the catheter to accommodate an
attachable connector or connector system.
[0049] In one variation of the present invention, instead of a
single catheter body substrate, two catheter body substrates are
utilized to form the multi-lumen catheter as shown in FIG. 4.
Assembly 40 includes a proximal catheter body substrate 42 having a
septum with a first thickness and a distal catheter body substrate
43 having a septum with a second thickness, wherein the second
thickness is greater than the first thickness. Although in this
example, the catheter body substrates 42, 43 have lumens that are
approximately equivalent in size and shape, it should be
appreciated that the shapes and sizes of the respective lumens of
catheter body substrates 42, 43 can be manipulated through the use
of mandrels along with elevated temperatures as the lumens will
conform to the shape of the mandrels. In this example, the mandrels
41 have D-shaped cross-sections to match the D-shaped lumens of the
catheter body substrates 42, 43; however, any shape and size of
mandrel may be utilized to impart a desired geometry to the
catheter lumens. Although certainly contemplated as one
possibility, the mandrels 41 in this example do not extend through
the entire length of the catheter body substrates 42, 43 and
instead extend through the proximal body substrate 42 and into only
a proximal region of the distal catheter substrate 43.
[0050] Once the mandrels 41 have been inserted, the proximal and
distal catheter body substrates 42, 43 are brought into abutting
relationship with one another and the reinforcing element 44 is
positioned around the outer wall of at least a portion of the
proximal catheter body substrate in order to provide rigidity due
to the relative thinness of the septum thereof. In addition, the
reinforcing element 44 may be positioned over at least the proximal
end of the distal catheter body substrate 43 to improve the tensile
strength of the bond between substrates 42, 43. In one variation,
the reinforcing element 44 is positioned around a majority of the
length of the proximal catheter body substrate 42 as well as a
proximal region of the distal catheter body substrate 43. A sleeve
46 is then placed over the substrates 42, 43 and the reinforcing
element 44, followed by shrink tubing, which is positioned over the
sleeve 46. Heat is then applied to the assembly as discussed above
and the shrink tubing is removed for further tipping procedures, if
necessary.
[0051] In another variation, of the present invention, three
catheter body substrates are utilized, as illustrated in FIG. 5.
Assembly 50 comprises a proximal catheter body substrate 51 and two
distal catheter body substrates 52 and 53. In this example, the
proximal catheter body substrate 51 has a dual lumen configuration
with two D-shaped lumens separated by a septum, while each distal
catheter body substrate 52, 53 has a single D-shaped lumen and has
a semi-circular cross-sectional shape. In one variation, the distal
catheter body substrates 52 and 53 have different lengths. For
example, in a hemodialysis application, distal catheter body
substrate 52 can be longer than distal catheter body substrate 53,
such that when implanted in a patient, substrate 53 is utilized for
aspiration of blood, while substrate 52 is utilized for infusion of
blood, in order to minimize co-mingling of aspirated and infused
blood. Providing substrates 52, 53 having final desired lengths
with respect to one another simplifies the tipping procedures
necessary following assembly of the catheter. As with the previous
examples, mandrels are inserted through the proximal catheter body
substrate 51 and into either just a proximal end of the distal
catheter body substrates 52, 53 or completely therethrough. The
substrates 51, 52, 53 are then brought into abutting relationship
with one another and a reinforcing element 54 is disposed about the
proximal catheter body substrate 51 and optionally over a proximal
region of the distal catheter body substrates 52, 53 in order to
fortify the bond between the substrates. A sleeve 56 is then
positioned over the proximal catheter body substrate 51 and at
least a proximal region of the distal catheter body substrates 52,
53 and shrink tubing is positioned over the sleeve. The entire
assembly 50 is heated and the shrink tubing is removed for further
tipping procedures, if necessary.
[0052] In another embodiment of the present invention, a
multi-lumen catheter is created using an independently formed
septum, which is inserted into a reinforced substrate. The
reinforced substrate is produced by first providing a tubular
substrate, which in one variation has a thin wall (e.g., a
thickness of between approximately 0.003 in. and 0.020 in.), and
positioning the substrate over a mandrel, such as a high density
polyethylene (HDPE) mandrel. A reinforcing element is then disposed
about the tubular substrate and adhered thereto by either embedding
the reinforcing element in the wall of the substrate, utilizing an
adhesive, positioning a sleeve over the reinforcing element and
heating (as described above), or by other methods known to one of
skill in the art. Next, as illustrated in FIG. 6, the mandrel is
removed and a preformed septum 64 is inserted into the lumen of the
reinforced substrate 62. After insertion, the septum 64 is bonded
to the substrate 62 by known methods, such as solvent bonding,
ultrasonic bonding, heat shrink bonding, etc.
[0053] While the septum 64 has a uniform rectangular shape, there
are numerous other possibilities for the septum shape, some of
which are also illustrated in FIG. 6, including pre-split septum
65, triple lumen septum 66, varying thickness septum 67, single
arched septum 68 and double arched septum 69. Some of the
advantages to the varying thickness septum 67 are described above,
whereas one advantage of the arched septum 68 and double arched
septum 69 is that it imparts optimal flow to a catheter in that the
arched shape defining a catheter lumen is more resistant to lumen
closure when withdrawing blood or fluid therethrough. Depending on
the type of catheter to be formed, the septum can take on any
desired shape and size. Because the septum is inserted following
manufacture of a reinforced substrate, a multi-lumen catheter may
be produced with thinner walls and thus a smaller outside diameter
due to the elimination of the necessity of providing wide
tolerances. With particular respect to providing pre-split septum
65, manufacture of a split-tip catheter is facilitated in that
tipping procedures involving the slicing or cutting of the septum
(as described above) are unnecessary. With respect to the triple
lumen septum 66, the varying thickness septum 67, the arched septum
68, the double arched septum 69 and other preformed septum designs,
including pre-split septum 65, manufacture of a catheter
incorporating the preformed septum is facilitated due to ease of
forming a thin-walled tube as opposed to a catheter with a complex
lumen configuration, as well as, in some variations, the
elimination of the use of D-shaped mandrels in the bonding process.
Further, the outside diameter of a multi-lumen catheter formed by
this method can be more tightly controlled.
[0054] In one manufacturing variation, insertion of the preformed
septum 64, which is sized to fit snugly within the lumen of the
reinforced substrate 62, is assisted by applying longitudinal
pulling tension to the septum in order to stretch the septum 64 and
slightly reduce its height. After insertion of the septum 64 into
the lumen of the reinforced substrate 62, the tension is released,
causing the septum 64 to resume to its natural height and fit
tightly therein. The reinforcing element permits this action
without resulting in deformation of the cross-sectional shape of
the substrate by acting as a stabilizing force. In another
variation, the top and bottom sides of the septum are curved or
otherwise contoured to match the lumen inside diameter. In yet
another variation, the tubular substrate is formed with septum
accommodating features, such as notches or cut-away portions on the
inner wall. Examples of potential embodiments of such features are
illustrated in FIGS. 7A and 7B. FIG. 7A shows an assembly 70 with a
substrate 72 having notched or recessed portion 74 on an inner
surface thereof, which is configured for receiving a septum 76
having a cooperating protrusion 78. The same notched or recessed
portion 74 can also be fashioned on an opposite side of substrate
72 to receive a like protrusion 78 on the opposite end of the
septum 76, although certainly other types of cooperating shapes,
rounded portions, etc. are possible and are within the scope of
this invention. FIG. 7B shows a different type of cooperating shape
for an assembly 80, where substrate 82 has a jagged cut-away
portion 84 to mesh with jagged protrusion 88 on septum 86. As with
FIG. 7A, the opposite side of the substrate 82 and septum 86 can be
similarly shaped, although not required.
[0055] Another embodiment of the present invention is illustrated
in FIG. 8. Assembly 90 is shown with a septum 94 sandwiched between
two mandrels 92. In this example, the septum 94 has a rectangular
cross-sectional shape and the mandrels have a D-shaped
cross-sectional shape; however, it should be appreciated that many
shapes and sizes are possible for the septum and mandrels to form
any number of catheter lumens of different sizes and
configurations, some of which are discussed herein. Wrapped around
the combination of mandrels 92 and septum 94 is an elongate member
96, which comprises a reinforcing element 97 with a coating 98, the
coating being a polymer, such as polyurethane. The member 96 as
shown is cylindrical, having a circular cross-sectional shape,
although numerous cross-sectional shapes are possible, depending
on, for example, the shape and size of the reinforcing element 97.
The member 96 can be wrapped around the mandrels 92 and septum 94
in many different patterns. In the example shown in FIG. 8, the
member 96 is wrapped in a helical fashion so that adjacent windings
of the member 96 are in contact with one another. The length that
the member 96 extends over the mandrels 92 and septum 94 defines
the length of the catheter being formed as the member 96, in this
example, forms the catheter body. However, in another example, a
catheter body substrate is positioned around the mandrels 92 and
septum 94 prior to the member 96 being wrapped therearound and
thus, the catheter body length in that case is defined by the
catheter body substrate. The assembly is then heated (e.g., using
shrink tubing) to melt the component parts together, after which
the mandrels are removed from the now formed catheter for tipping
procedures as necessary.
[0056] In another embodiment of the present invention, illustrated
in FIGS. 9A and 9B as assembly 100, two D-shaped mandrels 104 are
inserted through two D-shaped lumen substrates 102, which may have
relatively thin walls, and the substrates are brought together to
form a circle in cross-section. The D-shaped mandrels 104, in one
variation, are slightly bowed on the side that contacts the flat
portion of the D-shaped substrates 102 to provide a final catheter
with a septum that is slightly thicker at the top and bottom
thereof. Such a catheter is adapted for high negative pressures
without leading to lumen deformation and collapse. The flat portion
of the D-shaped substrates 102 may have a thicker wall than that of
the round portion to also provide resistance to lumen deformation
and collapse. While the substrates 102 are held together, for
example, by a fixture apparatus that holds the mandrels 104 at a
fixed distance from one another to avoid relative movement and to
rotate the mandrels, a reinforcing element 106 is positioned over a
predetermined length of the substrates 102 to form a reinforcing
region. The reinforcing element 106 in this example terminates at a
point proximal the distal ends of the substrates 102 (e.g., between
approximately 8-10 cm from the distal ends of the substrates
102).
[0057] The assembly to this point, in one variation, is heated to
slightly embed or otherwise fix the reinforcing element 106 in
place to prevent movement thereof during further processing steps.
A sleeve 108 is then positioned over the entire assembly and, as
shown in FIG. 9B, a shim 110 is positioned between the substrates
102 a short distance (e.g., 7-8 cm) equal to that desired for the
length of the separate distal tips of a split-tip catheter to be
formed in order to prevent bonding of the adjacent walls of the
substrates 102 along that length (of course, in the case of the
formation of a different type of multi-lumen catheter, the shim may
not be necessary at this stage). In one variation, in addition to
sleeve 108, a distal sleeve is placed over the region distal the
reinforcing region prior to heating in order to provide a
substantially uniform outer diameter over the entire length of the
catheter. In another variation, a proximal sleeve is placed over
the reinforcing region, while a distal sleeve of greater thickness
is placed over the region distal the reinforcing region to provide
a catheter with a substantially uniform outer diameter. Such use of
two separate sleeves of different thicknesses is also contemplated
with respect to each embodiment and variation described herein.
[0058] After the sleeve or sleeves have been disposed around the
reinforcing element 106 and substrates 102, shrink tubing is
positioned thereover and the entire assembly 100 is heated to melt
the component parts together. The heating step may comprise the use
of a "pre-shrink" process in which hot air is blown over the
assembly from one end to the other while the assembly is rotated,
for example, through the use of the fixture apparatus described
above. This process will eliminate any air that may exist in the
space between the substrates 102. Following heating, the shrink
tubing is removed from the assembly 100 and the sleeve portion that
surrounds the shim 110, which is kept in place, is slit along the
shim 110 to produce two distal tip sections. The shim 110 is then
removed from the assembly 100. In one variation, the shim 110 has
sharp edges to slit the sleeve or sleeves. The shim 110 is made of
a material with sufficient tensile strength to maintain its profile
during the heating process and with sufficient smoothness to enable
the removal thereof following the heating process. Examples of
potential materials for the shim 110 include stainless steel and
PTFE.
[0059] This invention has been described and specific examples of
the invention have been portrayed. While the invention has been
described in terms of particular variations and illustrative
figures, those of ordinary skill in the art will recognize that the
invention is not limited to the variations or figures described. In
addition, where methods and steps described above indicate certain
events occurring in certain order, those of ordinary skill in the
art will recognize that the ordering of certain steps may be
modified and that such modifications are in accordance with the
variations of the invention. Additionally, certain of the steps may
be performed concurrently in a parallel process when possible, as
well as performed sequentially as described above. Therefore, to
the extent there are variations of the invention, which are within
the spirit of the disclosure or equivalent to the inventions found
in the claims, it is the intent that this patent will cover those
variations as well. Finally, all publications and patent
applications cited in this specification are herein incorporated by
reference in their entirety as if each individual publication or
patent application were specifically and individually put forth
herein.
* * * * *