U.S. patent application number 12/917964 was filed with the patent office on 2011-03-03 for reinforced venous access catheter.
Invention is credited to Barbara Bell, George Bourne, Kristian Dimatteo, Raymond Lareau.
Application Number | 20110054312 12/917964 |
Document ID | / |
Family ID | 34967271 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110054312 |
Kind Code |
A1 |
Bell; Barbara ; et
al. |
March 3, 2011 |
Reinforced Venous Access Catheter
Abstract
A catheter for medical procedures comprises a shaft portion
having a distal end insertable into a body lumen, the shaft portion
having a wall defining a working lumen extending therewithin and a
first strengthening element coupled to the wall to increase a burst
pressure of the shaft portion, wherein the first strengthening
element cooperates with a base material of the wall to define a
flexible region of the shaft portion allowing the shaft portion to
be atraumatically inserted into the body lumen.
Inventors: |
Bell; Barbara; (Sudbury,
MA) ; Bourne; George; (Southborough, MA) ;
Lareau; Raymond; (Westford, MA) ; Dimatteo;
Kristian; (Waltham, MA) |
Family ID: |
34967271 |
Appl. No.: |
12/917964 |
Filed: |
November 2, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10894992 |
Jul 20, 2004 |
7850675 |
|
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12917964 |
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Current U.S.
Class: |
600/435 |
Current CPC
Class: |
A61M 2025/0059 20130101;
A61M 2025/0063 20130101; A61M 2025/0031 20130101; A61M 2025/0037
20130101; A61M 25/0052 20130101; A61M 25/0045 20130101; A61M
25/0069 20130101 |
Class at
Publication: |
600/435 |
International
Class: |
A61M 25/00 20060101
A61M025/00; A61B 6/00 20060101 A61B006/00 |
Claims
1.-54. (canceled)
55. A catheter, comprising: an elongated shaft extending from a
proximal end to a distal end and having a first channel extending
longitudinally therethrough, the elongated shaft comprising a
reinforced portion extending along a first predetermined length
thereof and a non-reinforced portion separated from the reinforced
portion along a longitudinal axis of the catheter, the
non-reinforced portion extending along a second predetermined
length of the shaft, reinforced portion comprising a first inner
layer defining an outer wall of the first channel and having a
first material with a first durometer and a second outer layer
forming an outer wall of the elongated shaft and having a second
material with a second durometer, the first durometer being greater
than the second durometer and the non-reinforced portion comprising
the second material.
56. The catheter of claim 55, wherein the elongated shaft further
comprises a partition wall separating the first channel from a
second channel extending longitudinally through the catheter.
57. The catheter of claim 56, wherein the partition wall is formed
of the second material.
58. The catheter of claim 56, wherein the partition wall is formed
of the first material.
59. The catheter of claim 55, further comprising a strengthening
material embedded within the second outer later.
60. The catheter of claim 59, wherein the strengthening material is
one of a braid, a mesh, a layered multi-material composite
structure and a plurality of reinforcing particles.
61. The catheter of claim 59, wherein the strengthening material is
formed of one of metal, stainless steel, a shape-memory material, a
polymer, a polyolefin, kevlar, vectran and silk.
62. The catheter of claim 55, further comprising a strengthening
material disposed around an outer surface of the second outer
layer.
63. The catheter of claim 62, wherein the strengthening material is
bonded to the outer surface of the second outer layer.
64. The catheter of claim 62, wherein the strengthening material is
longitudinally slidable relative to the outer surface.
65. The catheter of claim 55, further comprising a designated
failure point of the elongated shaft configured to withstand a
pressure reduced with respect to the reinforced portion.
66. The catheter of claim 65, wherein the designated failure point
is a reduced thickness portion of the elongated shaft.
67. The catheter of claim 65, wherein the designated failure point
is an extension tube having one or both of an irregular inner
cross-section and an irregular outer cross-section.
68. The catheter of claim 67, wherein the inner cross-sectional
shape is substantially rectangular and the outer cross-sectional
shape is substantially circular.
69. A catheter for introducing a contrast media into a patient,
comprising: an elongated shaft extending from a proximal end to a
distal end and having a first channel extending longitudinally
therethrough, the shaft further comprising: a substantially
flexible outer layer defining an outer wall of the elongated shaft
and configured for atraumatic insertion into a body; a
substantially rigid inner layer defining an outer wall of the
channel, the inner layer having a durometer greater than a
durometer of the outer layer, the rigid inner layer configured to
raise a burst pressure of the elongated shaft to permit an
increased flow rate through the channel
70. The catheter of claim 69, further comprising a strengthening
material embedded within the inner layer.
71. The catheter of claim 70, wherein the strengthening material is
longitudinally aligned with a longitudinal axis of the elongated
shaft.
72. The catheter of claim 71, wherein the strengthening material is
one of a braid, a mesh and a layered multi-material composite
structure.
Description
BACKGROUND OF THE INVENTION
[0001] The treatment of chronic disease often requires repeated and
prolonged access to a patient's vascular system to, e.g., to
administer medications, blood products, nutrients and other fluids
and/or to withdraw blood. When such procedures must be frequently
repeated, it may be impractical and/or dangerous to insert and
remove the catheter and the needle for each session. In this case,
a semi-permanent catheter, (e.g., a peripherally inserted central
catheter (PICC)), may be used. As would be understood by those
skilled in the art, a PICC is a catheter that is inserted in a vein
at a peripheral location, such as the arm or leg and threaded
through the vein to the chest, in proximity to the heart.
[0002] To simplify the insertion process and reduce patient
discomfort, PICCs and other semi-permanent catheters are generally
made small and thin. Accordingly, their structural strength is
limited by the thickness and type of material forming the
catheter's walls. The amount of pressure and flow rate that the
catheter can support without damage is also limited. If the maximum
pressure the catheter can withstand (the burst pressure) or the
maximum flow rate is exceeded, the catheter may be damaged or may
completely fail possibly spilling fluids from the catheter into the
body. During high pressure injections, escaping fluid may also
damage the surrounding tissues.
[0003] Modern medical procedures rely considerably on visualization
techniques to diagnose and treat diverse conditions. Some of these
techniques include the injection of a contrast media to the
vascular system to improve visualization of blood vessels and other
biological structures during fluoroscopy, radiology, or other
imaging. The contrast media is generally a liquid that is opaque to
the visualization method used, so that body lumens containing the
media appear distinct from other tissues. Typically, contrast media
is introduced using a separate catheter designed to withstand the
high injection pressures and flow rates necessary to disperse the
media throughout the organs of interest. For example in the case of
fluoroscopy, the contrast media may be a substance opaque to X-ray
radiation. More modern visualization methods such as, for example,
enhanced computed tomography (CT) may require the introduction of
different contrast media, as would be understood by those skilled
in the art.
[0004] Conventional PICC catheters are unable to withstand the high
pressures and flow rates associated with the introduction of
visualization media which are often substantially above what is
used for the infusion of medications. Thus, it is often necessary
to insert one or more additional catheters dedicated to the
contrast media increasing patient discomfort and the time and costs
associated with the procedure. If the patient exhibits poor
peripheral venous access, the insertion of an additional contrast
media catheter may be difficult.
SUMMARY OF THE INVENTION
[0005] In one aspect, the present invention is directed to a
catheter for medical procedures comprising a shaft portion having a
distal end insertable into a body lumen, the shaft portion
including a wall defining a working lumen extending therewithin and
a first strengthening element coupled to the wall to increase a
burst pressure of the shaft portion, wherein the first
strengthening element cooperates with a base material of the wall
to define a flexible region of the shaft portion allowing the shaft
portion to be atraumatically inserted into the body lumen.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a cross sectional view showing a first embodiment
of a venous access catheter with layered materials, according to
the present invention;
[0007] FIG. 2 is a cross sectional view showing a second embodiment
of a venous catheter with layered materials, according to the
present invention;
[0008] FIG. 3 is a cross sectional view showing a third embodiment
of a venous catheter with a braid, according to the present
invention;
[0009] FIG. 4 is a cross sectional view showing a further
embodiment of a venous catheter having a braid and layered
materials, according to the present invention;
[0010] FIG. 5 is a cross sectional view showing another embodiment
of a venous catheter having an externally placed braid;
[0011] FIG. 6 is a cross sectional view showing a different
embodiment of a venous catheter having a micro-particle
reinforcement;
[0012] FIG. 7 is a perspective view showing a venous catheter
partially reinforced according to the invention; and
[0013] FIG. 8 is a perspective view showing a venous catheter with
exemplary designed failure points.
DETAILED DESCRIPTION
[0014] The present invention may be further understood with
reference to the following description and the appended drawings,
wherein like elements are referred to with the same reference
numerals. The invention is related to medical devices used to
introduce a contrast media fluid into a patient, preferably at high
pressure and with a large flow rate. Specifically, the devices
according to the invention may be used to inject the contrast media
using a PICC.
[0015] As described above, where repeated access to the vascular
system is required, a semi-permanent central venous catheter may be
inserted in a vein kept in place for up to two years. A PICC
typically comprises a flexible elongated portion tunneled from a
remote peripheral location (an arm or leg) to a location near the
heart. The proximal end of the PICC may be accessed via a port
placed, for example, subcutaneously in the arm or chest of the
patient or which may remain outside of the body.
[0016] As would be understood by those skilled in the art, the
pressure exerted by the fluid is a function of the flow rate, the
viscosity and the cross sectional flow area of the catheter, among
other variables. Accordingly, limitations on the fluid pressure
and/or flow rate are often specified for various types of catheters
to ensure that the catheter will not be damaged during use by
excessive strains. However as mentioned above, modern imaging
methods often rely on the introduction of contrast fluids at high
flow rates.
[0017] The catheter according to the present invention, may be used
for both central venous access and the injection of contrast media
decreasing patient discomfort and the time and expense of
procedures. The catheter according to this invention, e.g., a PICC
venous catheter, is at least partially reinforced to enhance its
burst pressure and maximum flow rate to levels suitable for the
introduction of contrast media without compromising kink resistance
or increasing the cross sectional profile of the catheter, as
compared to conventional PICC devices.
[0018] For example, a catheter according to the present invention
will withstand a flow rate of about 4 to about 6 cc/sec and a
pressure of more than about 300PSi typical of power injection
devices. A reinforcement is included in the exemplary catheter
according to the invention to increase the burst pressure. In one
embodiment, both the shaft of the catheter and an extension tube
thereof are reinforced, to give a substantially uniform resistance
to the increased pressure. Alternatively, only the shaft may be
reinforced.
[0019] FIG. 1 shows an exemplary embodiment of a catheter
comprising a reinforced portion in accord with the present
invention. The exemplary catheter 100 is a dual lumen catheter in
which the lumens 110 are separated by a partition 108 extending
along a longitudinal axis of the catheter 100. In the exemplary
embodiment, the catheter 100 has a layered construction, in which
layers of stronger material are formed near layers of more flexible
material to obtain desired mechanical characteristics of an outer
wall 102. For example, an outer layer 104 of a material having a
lower durometer value may be used, to retain the flexibility of a
conventional catheter. Materials such as members of the
polyurethane family that are alcohol compatible may be used
advantageously in this function. An inner portion 106 of the
catheter shaft wall 102 may be made of a material with a higher
durometer value, to give strength to the composite assembly. For
example, high strength thermoplastic polyurethanes, polyether
block-amides and polyolefines may be used.
[0020] It is often necessary, in the course of a catheterization
procedure, to adjust the length of the portion of the catheter
inserted into the patient. Generally, the surgeon cuts a distal
portion of the catheter to a desired length. Thus, in the case of a
catheter 100 reinforced according to the present invention, the
reinforcing material is preferably selected so that it can be
easily cut with a blade. The exemplary materials described above
fall within this category, so that the reinforced catheter 100 may
be cut to a desired length using conventional methods.
Alternatively, a material that is more difficult to cut may be used
and/or a portion of the catheter 100 may be left unreinforced so
that it may be cut. For example, the weakest portions of the
catheter, such as the portion immediately distal to the suture
wing, may be reinforced, leaving a 20-40 cm section of the tip of
the catheter unreinforced. Because the portion immediately distal
to the suture wing is one of the weakest and most likely to fail,
reinforcement around the weak areas will prevent most failures from
occurring. The unreinforced section of the catheter will continue
to permit surgeons to easily cut the catheter in conventional
manners, such as with a blade.
[0021] According to the present embodiment, the catheter 100 may be
composed of various layers with each layer being formed of a
material of different hardness, thereby allowing the catheter 100
to be atraumaticly inserted while exhibiting an improved resistance
to the pressures associated with high flow rate power injection. As
would be understood by those skilled in the art, the manufacture of
the catheter 100 may be accomplished using a co-extrusion or a
lamination process. For example, the softer, more flexible outer
layer 104 of the shaft wall 102 may be co-extruded with the
stiffer, higher durometer inner layer 106. This configuration
provides both the flexible outer portion and the pressure resistant
inner portion of the catheter 100.
[0022] The co-extrusion process may be carried out with polymers
that are either compatible or non-compatible with one another. If
non compatible polymers are used, it may be necessary to provide an
intermediate tie layer along an interface 112 between the outer
layer 104 and the inner layer 106. In this exemplary embodiment, a
soft thermoplastic polyurethane (TPU) may be used for the outer
layer 104 while a stiff polyester block-amide (PEBA), a stiff
polyether block-amide, polyolefin or polytetrafluoroethylene (PTFE)
may be used for the inner layer 106. The outer TPU exhibits
softening while within the body, giving the desired flexibility,
etc., and allowing atraumatic insertion. However the PEBA of the
inner layer 106 retains its inherent strength and resistance to
pressure.
[0023] FIG. 2 shows a second embodiment of the catheter 120
according to the invention. In this exemplary embodiment, the shaft
wall 122 is reinforced by an inner layer 126 of a material with
greater durometer values. Here, instead of an entire inner portion
of the shaft 120 formed of a higher durometer material as in the
example of FIG. 1, both the inner layer 126 and the outer layer 124
are formed of lower durometer, more flexible material.
Specifically, the outer layer 124 of the wall 122 as well as the
inner core 132 of a lumen divider 128 are formed from one piece of
the lower durometer material. To this basic catheter shaft is then
added a coating of higher durometer material on the inner sides of
the two lumens 110, forming the inner layer 126 of the wall 122 as
well as outer portions 130 of the divider 128. This embodiment
provides for a flexible outer surface of the catheter 120, together
with increased mechanical reinforcement of the stiffer lining of
the dual lumens 110. Alternatively, the inner layers 126, 130 may
be part of a separate tube of smaller diameter which is inserted
into, but not bonded to the shaft of the catheter 120.
[0024] A further exemplary embodiment of a catheter shaft according
to the invention is shown in FIG. 3. In this case, the increased
resistance to fluid pressure within the lumens 110 is provided by a
braid included therewithin. As shown, the catheter 140 includes an
outer wall 142 comprising a braid 144, shown here in cross section.
The braid 144 may be formed of any of a variety of materials,
depending on the amount of additional pressure resistance desired.
The braid 144 may be formed, for example, of a metal or alloy such
as Nitinol or stainless steel. A material having shape memory
properties may be especially well suited for reinforcement braids
used in extension tubes of the catheter. In use, the proximal ends
of these catheters are clamped shut between uses. Thus, the
reinforcing braid will preferably be selected so that it will not
retain the clamped shape, but will return to the original tubular
shape when the clamping force is released. As would be understood
by those skilled in the art, for catheters which are to be used in
conjunction with MRI, the braid 144 is preferably formed of a
non-ferro-magnetic material, for example, kevlar, vectran, silk,
members of the polyolefin family and other types of polymer or
other suitable material.
[0025] A variation of the braid reinforcement is shown in cross
section in FIG. 4. The exemplary embodiment shown there comprises a
braid 154 together with a dual material layered construction of the
wall 152. The catheter shaft 150 includes two lumens with an inner
portion 156 of the wall 152 formed of a material having an
increased durometer with respect to a material comprising an outer
portion 158 thereof. All of the variations in design described
above with respect to the embodiments of FIGS. 1-3 may also be
applied to the construction of the exemplary catheter shaft 150. It
will be apparent to those of skill in the art that the radial
location of the braid 154 within the wall 152 of the catheter shaft
150 may also be varied. It will also be apparent that the same
reinforced construction methods described herein may be used for
other components of a catheter, such as extension tubes, or for
other medical tubes.
[0026] In a different embodiment, the reinforcement braid may be
disposed on the outside of the catheter body. For example, FIG. 5
shows a dual lumen catheter 160 having an outer wall 162 and a
braid 164 disposed outside the surface of the wall 162. This
configuration may provide manufacturing benefits compared to a
configuration in which the braid 164 is embedded within the
material of the catheter wall. For example, the braid 164 may be
added to the assembly after the catheter has been formed by
extrusion. The braid 164 may then be bonded to the catheter wall
162, or may be left free to slide longitudinally relative to the
catheter. In this latter embodiment, the user may be allowed to
longitudinally move the external braid to a desired position.
[0027] To further improve the pressure resistance and ultimate hoop
strength of the base catheter material, micro particles may be
added to the compound forming the catheter wall. The micro
particles (sometimes referred to as nano-particles, depending on
their size) may include clay and fumed silica. FIG. 6 shows an
exemplary embodiment, in which a catheter shaft 170 is formed with
a wall 172 comprising strengthening particles 174. The presence of
the micro particles 174 increases the radial stiffness of the
catheter wall 172, resulting in a more durable and more pressure
resistant base material for the catheter. The distribution of the
micro particles 174 both radially and longitudinally along the
catheter 170 may be selected to obtain desired mechanical
properties of the device. For example, a more pliable section of
the catheter may be formed by locally reducing the amount of micro
particles 174 added to the material of wall 172 while areas of
increased stiffness may be created by increasing the amount of
micro particles 174 in a region.
[0028] As an alternative to introducing strengthening particles
into the catheter material, cross linking agents may be
incorporated into the base material of the catheter shaft. For
example, agents such as silanes, dicumyl peroxide, maleic anhydride
and functionalized polymers may be added. These agents are
effective in partially cross-linking thermoplastic polymers.
Activation of the cross linking agents may be accomplished in a
conventional manner, for example through secondary exposure to high
energy sources such as electron beams to increase the strength of
the base material. As indicated above, both the radial and
tangential distribution of cross linking agents through the
material of the catheter shaft may be selected to obtain desired
mechanical properties, as would be understood by those skilled in
the art.
[0029] It will be apparent to those of skill in the art that the
various methods described herein to increase the strength of a
catheter shaft wall may be applied selectively to certain portions
of the catheter in question. For example, FIG. 7 shows a catheter
shaft 200 having a reinforced portion 204 and an unreinforced
portion 202. The reinforced portion 204 may comprise any of the
reinforcement elements or treatments described above, such as a
mesh 206 embedded within wall 208 of the catheter shaft 200. It
will be apparent to those of skill in the art that different types
or combinations of reinforcements may be used, such as an external
mesh, a layered multi-material composite structure, or the addition
of reinforcing particles in the wall material. In the example
depicted in FIG. 7, the shaft wall 208 is altered along its length,
in the longitudinal direction. However, for different applications,
the variation in structural reinforcement may be carried out in the
angular direction or in the radial direction, as was described
above. The non-uniform reinforcement construction may be applied to
both catheter shaft and to the extension tubes, as needed.
[0030] In one exemplary application, the longitudinal variation in
the strength of catheter wall 208 may be used to allow the user to
trim the distal end of the catheter shaft 200, to provide a better
fit in the patient. Leaving the unreinforced portion 202 without
the reinforcement elements 206 included elsewhere (i.e., in
reinforced portion 204) to increase pressure resistance allows the
user to cut the wall 208 more easily, The reinforcement elements
206 may thus be selected to have greater strength, since it is not
necessary that the user be able to cut therethrough to trim the
catheter shaft 200 to the desired length. In one example, between
about 15 cm and 20 cm of the distal end of catheter shaft 200 may
form the unreinforced portion 202.
[0031] In another exemplary application, the wall of shaft 200 may
be composed of varying materials, or may be otherwise reinforced by
different amounts along its length to allow for increased strength
and durability at specified stress points. These points of
increased stress may occur during power injection of a fluid only
at certain locations, such as near the injection point or near
bends in the catheter. In this manner, the additional material used
to strengthen the catheter may be targeted where it is most
effective, without having to reinforce the entire catheter. This
construction may be simpler and less costly than forming a catheter
with reinforcements along its entire length.
[0032] According to another exemplary embodiment of the invention,
the catheter shaft or the extension tube may be constructed with an
inherent weak point designed to fail before the rest of the device
does. When the catheter experiences excessive pressure, the
extension tube will fail and release the pressure, leaving the
catheter shaft intact. The extension tube may be formed with a
tapered region of lesser strength, or by profiling the wall
thickness of the tube to create the designated failure point. As
shown in FIG. 8, a catheter extension tube 250 comprises a reduced
thickness portion 252 in which the wall 254 is much thinner and is,
at this point, able to withstand a pressure reduced with respect to
the rest of the catheter. It will be apparent to those skilled in
the art that the wall thickness reduction may be achieved by
removing material from the outside of the wall (as shown), the
inside of the wall or both.
[0033] In another embodiment, the inherent weak point may be formed
by making either or both of the inside and outside diameters of the
tube irregular in cross section. The non uniform wall thickness
thus created, for example in the extension tube, defines specific
sites for failure of the tube. As shown in the example of FIG. 8, a
rectangular inner profile 256 of the extension tube 250 may be
placed within a generally circular extension tube 250. This
configuration may be used to define four thin walls 258 at the
corners of the profile 256, which will tend to fail before thicker
portions of the wall. In addition, the corners 260 act as stress
concentrators, further ensuring that the extension tube 250 will
fail at the location of the rectangular profile 256 when subject to
excessive pressure. It will be apparent to those skilled in the art
that the rectangular profile 256 may be used separately or in
conjunction with the reduced thickness portion 252, as desired in
specific applications.
[0034] The present invention has been described with reference to
specific embodiments, and more specifically to a MC catheter used
for power injection of contrast media used in CT imaging. However,
other embodiments may be devised that are applicable to other
medical devices and procedures, without departing from the scope of
the invention. Accordingly, various modifications and changes may
be made to the embodiments, particularly with regard to dimensions
and materials, without departing from the broadest spirit and scope
of the present invention as set forth in the claims that follow.
The specification and drawings are accordingly to be regarded in an
illustrative rather than restrictive illustrative rather than
restrictive sense.
* * * * *