U.S. patent application number 10/025360 was filed with the patent office on 2002-07-18 for dynamically compliant catheter.
Invention is credited to Duchon, Douglas J., Wilson, Robert F..
Application Number | 20020095117 10/025360 |
Document ID | / |
Family ID | 23097271 |
Filed Date | 2002-07-18 |
United States Patent
Application |
20020095117 |
Kind Code |
A1 |
Wilson, Robert F. ; et
al. |
July 18, 2002 |
Dynamically compliant catheter
Abstract
A catheter enabling a reduced puncture hole size into the skin
and blood vessel is disclosed. In one embodiment, the catheter has
an elongate body having an expandable sheath extending at least a
portion of its length. A pressure constraining sheath is positioned
to surround the expandable sheath, at a selected region to prevent
expansion of the inner sheath at the region of the constraining
sheath. In one preferred use, the constraining sheath is positioned
at the puncture hole. During use, the catheter increases in
cross-section by an expandable sheath expanding from a first
diameter to a second diameter. However, the outer sheath does not
expand, maintaining a small diameter at the puncture site.
Inventors: |
Wilson, Robert F.;
(Roseville, MN) ; Duchon, Douglas J.; (Chanhassen,
MN) |
Correspondence
Address: |
OPPENHEIMER WOLFF & DONNELLY LLP
Ste. 700
840 Newport Center Drive
Newport Beach
CA
92660
US
|
Family ID: |
23097271 |
Appl. No.: |
10/025360 |
Filed: |
December 19, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10025360 |
Dec 19, 2001 |
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09286142 |
Apr 5, 1999 |
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6361528 |
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Current U.S.
Class: |
604/158 ;
600/435; 604/163 |
Current CPC
Class: |
A61M 25/0023
20130101 |
Class at
Publication: |
604/158 ;
604/163; 600/435 |
International
Class: |
A61M 005/178; A61M
025/00 |
Claims
I claim:
1. A catheter for passing a fluid into a patient's body, the
catheter comprising: an elongate body, a portion of which is
radially expandable by the force of a fluid passed therethrough;
and an outer sheath positioned around at least a portion of the
elongate body, the outer sheath capable of constraining the
expansion of the expandable sheath.
2. The catheter according to claim 1, wherein the outer sheath is
at least 5 cm in length.
3. The catheter according to claim 1, wherein the outer sheath has
an outer diameter of at least 1 mm in size.
4. The catheter according to claim 1, wherein a wall thickness of
the outer sheath is at least 0.004 mm.
5. The catheter according to claim 1, wherein the outer sheath is
capable of withstanding a pressure of at least about 500 p.s.i.
without expanding or distorting in the radial direction.
6. The catheter according to claim 1, wherein the outer sheath is
capable of withstanding a pressure of at least about 750 p.s.i.
without expanding or distorting in the radial direction.
7. The catheter according to claim 1, wherein the outer sheath is
capable of withstanding a pressure of at least about 1000 p.s.i.
without expanding or distorting in the radial direction.
8. The catheter according to claim 1, wherein the outer sheath is
capable of withstanding a pressure of at least about 1200 p.s.i.
without expanding or distorting in the radial direction.
9. The catheter according to claim 1, further comprising a backbone
which can be located transmurally or intralumenally.
10. The catheter according to claim 9, wherein the backbone is
removable and replaceable in or out of the body.
11. The catheter according to claim 9, wherein the backbone is at
least 60 cm in length.
12. The catheter according to claim 9, wherein the backbone
comprises Ni-Ti shape-memory alloy.
13. The catheter according to claim 1, wherein a portion of the
elongate body is radially expandable by a twist and lock
mechanism.
14. The catheter according to claim 1, wherein a portion of the
elongate body is radially expandable by direct control of a
user.
15. The catheter according to claim 1, wherein the outer sheath is
made from a material selected from the group consisting of metals,
plastics and composites.
16. The catheter according to claim 9, further comprising an inner
expandable sheath that extends the length of the catheter.
17. The catheter according to claim 16, wherein the inner sheath
surrounds the backbone.
18. The catheter according to claim 16, wherein the inner sheath is
radially expandable by the force of a fluid passed
therethrough.
19. The catheter according to claim 18, wherein the inner sheath is
radially expandable in a controlled and repeatable manner.
20. The catheter according to claim 16, wherein the inner sheath is
radially expandable from one diameter to at least a second
diameter, the second diameter being greater in size than the first
diameter.
21. The catheter according to claim 20, wherein the inner sheath
has sufficient non-elastic material to provide a circumference
related to the second diameter.
22. The catheter according to claim 21, wherein the inner sheath is
folded upon itself inside the outer sheath.
23. The catheter according to claim 16, wherein the inner sheath is
made from a material selected from the group consisting of metals,
plastics and composites.
24. The catheter according to claim 23, wherein the inner sheath
comprises polymeric materials
25. The catheter according to claim 24, where in the inner sheath
comprises elastic.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to angiography and/or
particularly to an improved catheter for injecting medical fluids
such as radiographic contrast fluid into living organisms.
BACKGROUND OF THE INVENTION
[0002] Angiography is a procedure used in the treatment of
cardiovascular conditions including abnormalities or restrictions
in blood vessels of a human or animal body. During angiography, a
radiographic contrast material is injected through a catheter into
a vein or artery, which then passes to vascular structures in fluid
communication with the vein or artery. When X-rays are passed
through the region of the body into which the contrast material is
injected, they are absorbed by the contrast material, providing
radiographic images of the desired vascular structure(s). The
images can be recorded on film or video tape and/or displayed on a
fluoroscope monitor. The images can be used for many purposes, as
for example diagnostics, and for operative procedures such as
angioplasty, wherein a balloon is inserted into a vascular system
and inflated to open a stenosis.
[0003] The contrast material can be injected into the catheter by
either manual or automated injection systems. Although the
apparatus for injecting the contrast material can vary, many
current systems include a syringe operatively connected with the
catheter. The syringe has a chamber for holding the contrast
material and a plunger reciprocally moveable within the chamber. An
example of one such apparatus is U.S. Pat. No. 5,573,515, the
entire disclosure of which is incorporated herein by reference. In
this apparatus, the contrast material is suctioned into the chamber
when the plunger is moved to create a partial vacuum within the
chamber. A reversal of the plunger direction first forces air out
of the chamber and then delivers the contrast material to the
catheter at a rate and volume determined by the speed of movement
of the plunger.
[0004] In a manual system the user or operator loads the syringe
and ejects air from the chamber before connecting the syringe to
the catheter. The user of a manual system adjusts the rate and
volume of injection by altering the manual force applied to the
plunger. The maximum injection pressure for manual systems is
typically limited to 200 p.s.i. (i.e. the maximum pressure that can
be applied by the human hand), and the maximum quantity of fluid is
about 12 cc.
[0005] Angiography can include the injection of fluids other than
the contrast material. For example, a saline flush and/or the
injection of fluid medications may be desired.
[0006] The catheter through which the contrast agent or other fluid
is supplied is typically inserted percutaneously and into the
desired artery or vein. When inserted percutaneously, a puncture
hole is created in both the skin and blood vessel wall at the
insertion point in order to correctly position the catheter. It is
preferable to use a puncture hole that is as small as possible, to
avoid leakage around the catheter and to minimize the subsequent
wound size. Additionally, the larger the puncture hole, the greater
the opportunity for complications and the more time needed to stop
the bleeding after the catheter is removed.
[0007] Many presently available catheters have a fixed size
(diameter) that extends the entire length of the catheter.
Resistance to fluid flow in the catheter is determined by the
inside diameter. Therefore, the size of catheter chosen for a
specific procedure is based upon the inside diameter needed to
achieve the particular flow rates associated with the procedure.
However, such fixed diameter catheters have the same outside
diameter at the puncture site as at other points on the catheter.
As a result of this design, the wound at the puncture site may be
unduly large for the particular procedure to be performed.
[0008] Although the presently available catheters are well accepted
by the medical profession and function as required, it is desirable
to have a catheter that minimizes the vascular puncture site
diameter, but allows minimal resistance to fluid flow. In other
words, it is desirable to provide a catheter that minimizes the
trauma to a patient but provides versatility to the user for many
varied applications and uses of the catheter.
OBJECTS AND SUMMARY OF THE INVENTION
[0009] In view of the foregoing, it is an object of the present
invention to overcome the deficiencies of existing catheters.
[0010] It is a further object of the present invention to provide a
catheter that minimizes the wound size for use of the catheter and
yet still provides a wide variety of potential uses.
[0011] It is a further object of the present invention to provide a
catheter that is economical to produce.
[0012] It is a further object of the present invention to provide a
method of ensuring adequate fluid flow through a catheter with the
smallest diameter patient incision as possible.
[0013] The present invention attempts to address these objects and
other objects not specifically enumerated herein through the use of
a catheter that has an outer surface, a portion of which is
compliant and has an adjustable diameter and another portion which
is not adjustable, or non-compliant. It further may include a
backbone, a compliant and expandable sheath surrounding the
backbone, and an outer non-compliant sheath which covers a portion
of the expandable sheath. At least a portion of the outer
non-compliant sheath is not expandable.
[0014] The backbone allows the catheter to retain a predetermined
shape for ease of manipulation and placement of the catheter. The
outer non-compliant, nonexpandable sheath limits the expansion of
the catheter and is positioned at the insertion point into the
patient. The adjustable sheath, however, expands. Thus, the
catheter retains the narrow insertion point but expands at either
side of the insertion point.
[0015] The catheter sheath selectively expands to provide an
expanded area and a non-expanded area, which expansion may occur
either during, or prior to, the injection of a fluid. This
selective expansion is advantageous because the puncture hole at
the entry site into the patient is minimized.
[0016] In a preferred method of inserting the catheter, the
flexible catheter tip and body are compressed, folded or otherwise
manipulated to be smaller in diameter than the diameter of outer
non-compliant sheath. The outer sheath can be inserted through the
skin and vascular wall after which the body of the catheter is
inserted through the constraining outer sheath. The body is then
expanded to the desired size.
[0017] In a second embodiment, there may be no discrete inner
expandable sheath at the position where the outer non-compliant
sheath is located. Instead, the nonexpandable sheath may be
integral with the expandable sheath.
[0018] In a further embodiment, the backbone can be removable and
replaceable with a different backbone in order to provide a
different shape to the catheter.
[0019] In yet a further embodiment, the outer non-compliant sheath
may be expandable on demand, for example by mechanical structures.
This option may be desired when a large device, such as an
atherectomy catheter, needs to be inserted through the catheter.
Alternately, the outer sheath may be replaceable with an outer
sheath having a larger diameter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a cross-sectional view of a catheter of the
invention inserted into a blood vessel of a patient;
[0021] FIG. 2 is a perspective side view of a catheter of the
invention in an unexpanded, first position;
[0022] FIG. 3 is a perspective side view of the catheter of FIG. 2
in an expanded, second position;
[0023] FIG. 4 is a cross-sectional view of a catheter of the
invention taken along line 4-4 of FIG. 2;
[0024] FIG. 5 is a cross-section view of another embodiment of the
invention taken along line 4-4 of FIG. 2;
[0025] FIG. 6 is a perspective side view of a spring in expanded
and unexpanded forms; and
[0026] FIG. 7 is a perspective side view of a coil in expanded and
unexpended forms.
DETAILED DESCRIPITON
[0027] Referring to FIG. 1, a catheter 10 in one embodiment of the
present invention is shown inserted into a patient to supply
fluids, for example a contrast agent, to the blood stream. The
catheter 10 is inserted into the patient through a puncture hole in
the patient's skin 20 and in a blood vessel wall 22.
[0028] Referring to FIGS. 1, 2 and 3, the catheter 10 has a hollow
elongate body 12 that extends from the patient's exterior and
terminates inside the blood vessel. The distal end 21 of the
catheter 10 is the end inserted into the patient whereas the
proximal end of the catheter 10 is the end closest to the user
(usually a physician or clinician).
[0029] Located internally in the catheter 10 is a backbone 14,
which serves to shape the catheter 10. The backbone 14 is shown as
an interior structure of the catheter 10 and is encompassed by the
conduit 15 of the catheter 10, which conduit is the outermost
portion of the catheter 10. The backbone 14 further provides
strength, structure and integrity to the catheter 10 to allow
insertion of the catheter 10 into the patient. The backbone 14 is
generally sufficiently rigid to penetrate the patient's skin and
vessel wall into the lumen of the vessel. However, the backbone 14
is also fairly thin so that unnecessary bulk and thickness are not
added to the catheter 10.
[0030] The conduit 15 of the catheter 10 includes an outer sheath
16 and an inner sheath 18 wherein the outer sheath 16 is a
noncompliant, non-expandable sheath and wherein the inner sheath 18
is a compliant, expandable sheath that can readily stretch or
expand or both, for example by the pressure of fluid flowing
therethrough.
[0031] The interior of the conduit 15 is a hollow passage and is
designed to provide a passage for fluid or a medical device, for
example contrast agent or angioplasty catheter, respectively, or
any other applicable liquid or device. In the case of fluid, the
fluid enters the catheter 10 at an inlet 17 located at the proximal
end of the catheter 10, passes through the interior of the conduit
15, and exits the catheter 10 at an outlet 19 at the distal end 21
of the catheter 10. The inlet 17 can include typical connector
systems such as Luer.RTM. locks, threads, and other known systems.
The pressure of the fluid passing through the catheter 10 may be
sufficient to expand expandable sheath 18, but is insufficient to
expand outer sheath 16.
[0032] The outer sheath 16 is located at the point on the catheter
10 where the catheter 10 passes through the skin and vascular wall.
The outer sheath 16 is rigid, non-compliant and non-expandable, and
should be able to withstand pressures of at least about 500 p.s.i.,
preferably at least about 750 p.s.i., and more preferably at least
about 1200 p.s.i. without radially expanding or deforming. The
diameter of the outer sheath 16 is directly related to the diameter
of the puncture hole needed for insertion of the catheter 10 into
the patient. It is preferable to have the outer sheath 16 as small
as possible so as to minimize the puncture hole. Preferably, the
outer diameter of the outer sheath 16 is about 0.8 to 5 mm.
[0033] An inner expandable sheath 18 extends the length of the
catheter's elongate body 12 and surrounds and covers the backbone
14. If the backbone 14 is in the interior of catheter 10, the inner
sheath 18 is preferably connected to the backbone 14 in several
spots, for example, at the tip 19. Alternatively, the backbone 14
may be integral with the inner sheath 18, that is, the backbone 14
may be located within the wall of the inner sheath 18.
[0034] FIG. 2 shows catheter 10 of the present invention in a
first, or nonexpanded position prior to insertion in a patient. The
inner sheath 18 has a diameter less than or equal to the outer
sheath 16. Preferably, the tip 19 of the catheter (at distal end
21) and the inner sheath 18 have a diameter less than the outer
sheath 16.
[0035] FIG. 3 shows the catheter 10 in a second, or expanded
position. In this position, the inner sheath 18 has expanded to a
diameter greater than that of the outer sheath 16. The inner sheath
18 has expanded from its first position in FIG. 2 to a second
position in FIG. 3. The outer sheath 16 has not expanded or
distorted, but has retained the same diameter and shape as before
the inner sheath 18 was expanded.
[0036] Having described the general structure of a first embodiment
of the present invention, the various components and variants
thereof are now discussed in greater detail. It will be understood
that a catheter in accordance with the present invention may
incorporate any number of combinations of the specific aspects of
the disclosed components.
[0037] Backbone
[0038] The backbone 14 of the catheter 10 extends longitudinally
alone the body and provides the catheter 10 with much of its
structural properties. Additionally, the backbone 14 will allow the
catheter 10 to be advanced to the preferred location in the blood
vessel or may allow for rotation of the catheter 10 once in
position.
[0039] The backbone 14 of the catheter 10 may be similar to the
backbones used in conventional catheters. Moreover, the backbone 14
is typically about 60 to 100 cm long and generally extends the
length of the catheter 10.
[0040] The backbone 14 is generally located within the conduit 15
of the catheter 10. That is, it is embedded in the catheter 10,
either in the interior of the conduit 15 or within a wall of the
conduit 15; that is, the backbone 14 is positioned transmurally.
Alternatively, the backbone 14 may be centrally located in the
hollow interior of the conduit 15 or it may be displaced to one
side or another of the interior. FIGS. 4 and 5 show the backbone 14
placed to one side of the interior area of conduit 15.
[0041] Another alternative embodiment is to provide the backbone 14
within a lumen of the catheter 10; that is, the backbone 14 is
positioned intralumenally. If positioned in a lumen, the backbone
14 is typically loosely held so that the backbone 14 can be rotated
and advanced as desired. The lumen may be positioned inside or
outside of the inner and outer sheaths 16, 18. Generally, when a
backbone 14 is said to be "removable" and/or "replaceable", the
backbone 14 is positioned in a lumen, however backbones 14 located
in the interior of the catheter 10 may also be removable and
replaceable.
[0042] Examples of typical backbone 14 materials include
thermoplastic and thermoset polymers, such as nylon, polypropylene,
polyethylene, polycarbonate, metals and alloys, such as titanium,
stainless steel, ceramics, and composite materials, which can
include combinations of ceramics, organic polymers, inorganic
materials, and metals. A preferred material is a Ni-Ti shape-memory
alloy commonly known as "nitinol".
[0043] In one embodiment, the backbone 14 is removable from the
catheter 10 after insertion in a patient and replaceable with a
different backbone 14, one that, for example, changes the shape of
the catheter 10. When exchanging the backbone 14, it is not
necessary to replace or move the catheter 10. In particular, it is
not necessary to disturb the puncture hole where the outer sheath
18 is positioned.
[0044] Outer Sheath
[0045] At least a portion of the outer sheath 16 is a rigid,
noncompliant, non-expandable section. This non-compliant outer
sheath 16 maintains a minimal puncture hole in the skin and
vascular wall through which the catheter 10 is passed. Preferably,
the puncture hole is less than about 3 mm.
[0046] The outer sheath 16 constrains the inner sheath 18 such that
the inner sheath 18 is constrained from expanding beyond a
predetermined limit established by the outer sheath 16. The outer
sheath 16 is positioned at least at the site of entry of the
catheter 10 into the body and the vessel. The outer sheath 16
maintains the diameter of the catheter 10 minimally small at the
puncture hole, yet allows expansion of the catheter 10 (in
particular the compliant sheath 18) along its length either on both
the distal and proximal sides of the outer sheath 16 or on one side
of the outer sheath 16. The unexpanded area created by the outer
sheath 16 restricts the flow of the contrast agent through the
catheter 10 yet allows sufficient volume flow of the agent.
[0047] The outer sheath 16 may be permanently affixed to the inner
expandable sheath 18 or it may be movable along the length of the
catheter 10. For example, when a movable outer sheath 16 is used,
the user is capable of positioning the outer sheath 16 in the
desired position on the catheter 10. This may be particularly
useful in patients where it is not possible to get a deep
penetration of the catheter 10 into and along the blood vessel.
Additionally, a movable outer sheath 16 may be completely removed
from the catheter 10 and replaced with a different diameter outer
sheath 16.
[0048] In some embodiments it may be desirable to provide an outer
sheath 16 that is expandable at some location or locations along
its length. For example, the outer sheath 16 may be designed to
remain at its unexpanded diameter at the outer sheath 16 mid-point
and then expand gradually each direction along its length. This
configuration may increase the stability of the catheter at the
puncture point.
[0049] Controlled expansion of portions of the outer sheath 16 or
of the entire outer sheath 16 itself may be accomplished by
material selection, or by mechanical means. For example, once the
catheter 10 is correctly positioned, the portion of the outer
sheath 16 immediately on each side of the puncture point may be
expanded, for example by a "twist and lock" or other mechanism. Any
expansion of the outer sheath 16 may be directly controllable by
the user, or may be a function of the fluid pressure flowing
through the catheter 10. The expandable portions may have a single
expanded position or may be incrementally expandable. However, at
least some portion of the outer sheath 16 usually remains
unexpanded from its initial diameter.
[0050] The outer sheath 16 is preferably a cylindrical tube, but
other shapes may be utilized if desired. The length of the outer
sheath 16 is typically about 5 to 30 cm. Generally, the outer
sheath 16 will be positioned so that it is located at the skin 20
and vessel puncture hole and extends minimally in either direction
past this point. Preferably, the non-compliant, non-expanding outer
sheath 16 extends at least 5 mm past the puncture point in the skin
20 and blood vessel wall 22.
[0051] The diameter of the outer sheath 16 should be as small as
feasible to provide as small of a puncture hole as possible insofar
as the diameter of the outer sheath 16 is directly related to the
diameter of the puncture hole needed for insertion of the catheter
10 into the patient. The outer sheath 16 should not, however, be so
small as to prevent insertion of the compliant sheath 18 and
catheter backbone 14 therethrough.
[0052] Typically, the outer sheath 16 will have an outer diameter
between about 1 and 4 mm, preferably 1 to 2 mm. Different sizes of
the outer sheath 16 can be available for different uses. The inner
wall diameter should be minimally less than the outer diameter.
That is, it is preferable to have the wall of the outer sheath 16
as thin as possible without compromising strength and integrity.
Typical wall thickness include 0.004 to 0.010 mm, but other
thickness may be utilized depending on the specific outer sheath 16
material used.
[0053] The outer sheath 16 is preferably manufactured from
medically acceptable materials such as metals (for example
stainless steel or nitinol), plastics (for example nylon, urethane
or Polyethylene Terephthalate (PET)), and composites. The material
of the outer sheath 16 may be reinforced, for example by fibers or
other strengthening agents, so as to further increase the tensile
strength and decrease any distortion possibilities. The outer
sheath 16 should be capable of constraining pressure in excess 500
p.s.i., preferably more than 750 p.s.i., more preferably more than
1200 p.s.i. (approximately 8 atmospheres) in the radial direction
without expanding or distorting in shape or size. In another
preferred embodiment, the outer sheath 16 is capable of resisting
pressures between about 1200-1500 p.s.i. without distorting. Many
materials can have their properties, such as elasticity and
stiffness, etc., altered by various processing methods.
[0054] Inner Expandable Sheath
[0055] Placed within the outer non-compliant sheath 16 is an inner
expandable sheath 18 that generally extends the length of the
catheter 10. In embodiments where the backbone 14 is located in the
interior of the catheter 10, the inner sheath 18 surrounds the
backbone 14. It is through the inner sheath 18 that the fluid being
administered, for example the contrast fluid, passes. The
expandable sheath 18 is radially expandable, preferably by the
pressure of the fluid flowing therethrough, preferably in a
controlled and repeatable manner. The amount of expansion, or
diameter change, can be designed to be responsive to the needs of
the user.
[0056] The expandable sheath 18 can be radially adjusted from a
first diameter to a second diameter with the use of fluid pressure,
mechanical means, or other forces. The first diameter of the inner
sheath 18 is generally less than the smallest diameter of the outer
sheath 16, whereas the second diameter of the inner sheath 18 is
greater than the largest diameter of the outer sheath 16. The
expansion of the inner sheath 18 to the second diameter may either
be a permanent or temporary deformation, that is, it may be capable
of returning to the first diameter without any permanent
deformation. Any expansion may be incremental.
[0057] The expandable sheath 18 can be manufactured from medically
acceptable materials such as metals, plastics, and composites,
however polymeric materials are preferred. Insofar as the
expandable sheath 18 must be capable of expanding from one diameter
to at least a second diameter, it is preferable that the material
used for the expandable sheath is elastic. However, expandability
may be achieved by other methods, such as by providing an inner
sheath 18 that has sufficient non-elastic material to provide a
circumference related to the second diameter. The inner sheath 18
is then folded upon itself inside the outer sheath 16.
[0058] FIGS. 4 and 5 show cross-sectional views of two embodiments
of the inner sheath 18 placed within the outer sheath 16. FIGS. 4
and 5 are taken from line 4-4 in FIG. 2. FIG. 4 shows the inner
sheath 18 flatly and continuously disposed within the outer sheath
16. In such an embodiment, the inner sheath 18 is elastic and will
expand radially at the points where the outer sheath 16 is not
present when pressure is applied from the inside.
[0059] The inner sheath 18 of FIG. 5 will likewise expand radially
at the points where the outer sheath 16 is not present, however,
the inner sheath 18 is not elastic or is likely less elastic than
that disclosed in FIG. 4. Rather, extra material of the inner
sheath 18 is folded on itself so that when pressure is applied, the
inner sheath 18 will unfold, thus providing an expanded
diameter.
[0060] Methods of Expanding the Expandable Sheath
[0061] The expandable sheath 18 may be expanded by mechanical
means, fluid pressure, or other feasible methods. In a first
embodiment, the expandable sheath 18 expands simply as a result of
an increase in fluid pressure passing through the catheter 10. The
initial pressure of the fluid causes the inner sheath 18 to expand
at locations where it is not constricted by the outer sheath 16.
The catheter 10 remains in this expanded configuration for the
duration of the procedure after which the catheter 10 collapses or
is simply pulled out through the narrower outer sheath 16.
[0062] In another embodiment, mechanical means, such as a spring 24
or coil 26, shown in FIGS. 6 and 7, can be used to expand the inner
sheath 18. For example, a tightly wound spring 24 may be part of
the catheter 10 between the backbone 14 and the expandable sheath
18. The spring 24 would be capable of expanding and increasing its
diameter, thus increasing the diameter of the expandable sheath 18.
The spring 24 may be actuated by mechanical manipulation, such as
twisting or pulling, in order to increase the diameter of the
catheter 10.
[0063] In yet another embodiment, the backbone 14 of the catheter
10 may also be used as a "key" or other device to alter the
catheter's 10 shape. The backbone 14 may be removed and inserted in
a manner that distorts the expandable sheath 18 so that a second
diameter is obtained. Alternately, a stylet (other than the
backbone 14) can be placed inside the catheter 10 for manipulation
of the catheter's 10 shape and size.
[0064] And in another embodiment, the expandable inner sheath 18
may be made from a material that is expandable when heated, such as
nitinol. Application of heat to the catheter 10 may cause the inner
sheath 18 to expand whereas removal of the heat, or cooling, will
cause the inner sheath 18 to retract to, or close to, its original
diameter. Alternatively, the patient's body temperature (typically
98.6.degree. F.) may be sufficient to cause the inner sheath 18 to
expand.
[0065] The foregoing description addresses embodiments encompassing
the principles of the present invention. The embodiments may be
changed, modified and/or implemented using various types of
arrangements. Those skilled in the art will readily recognize
various modifications and changes which may be made to the
invention without strictly following the exemplary embodiments and
applications illustrated and described herein, and without
departing from the scope of the invention which is set forth in the
following claims.
* * * * *