U.S. patent application number 10/841372 was filed with the patent office on 2004-10-21 for devices, systems, and methods for subcutaneously placing an article.
This patent application is currently assigned to Vasca, Inc.. Invention is credited to Ross, John R., Tobul, James R..
Application Number | 20040210237 10/841372 |
Document ID | / |
Family ID | 21723298 |
Filed Date | 2004-10-21 |
United States Patent
Application |
20040210237 |
Kind Code |
A1 |
Ross, John R. ; et
al. |
October 21, 2004 |
Devices, systems, and methods for subcutaneously placing an
article
Abstract
The present invention provides devices, systems, and methods for
positioning an article, such as a graft or catheter, in a
subcutaneous tunnel between skin and muscle tissue of a patient to
establish improved access to the patient's vascular system for
hemodialysis, hemofiltration, or other extracorporeal blood
treatments. In particular, the present invention provides devices,
systems, and methods which minimize longitudinal forces or friction
acting against the vascular graft as it is being subcutaneously
positioned while still providing a tight seal between the graft and
the subcutaneous tissue, which in turn minimizes hematomas,
bleeding, and infections and enhances needle accessibility of the
graft for extracorporeal treatment. A system for subcutaneously
positioning an article comprises a tunneling tool, a pair of nested
tubes coupleable to a trailing end of the tunneling tool, and a
flexible article which can be slidably received within the pair of
nested tubes. The nested tubes each have a leading end, a trailing
end, and a longitudinal opening.
Inventors: |
Ross, John R.; (Bamberg,
SC) ; Tobul, James R.; (Bamberg, SC) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
Vasca, Inc.
Tewksbury
MA
|
Family ID: |
21723298 |
Appl. No.: |
10/841372 |
Filed: |
May 6, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10841372 |
May 6, 2004 |
|
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10006925 |
Dec 4, 2001 |
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6752827 |
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Current U.S.
Class: |
606/108 |
Current CPC
Class: |
A61F 2/011 20200501;
A61F 2/95 20130101 |
Class at
Publication: |
606/108 |
International
Class: |
A61M 031/00 |
Claims
What is claimed is:
1. A sheath for use with a tunneling tool, the sheath comprising: a
pair of nested tubes, each tube having a leading end, a trailing
end, and a longitudinal opening; and a coupling element attached to
the leading ends of the nested tubes, the coupling element being
removably attachable to a tunneling tool.
2. A sheath as in claim 1, wherein each longitudinal opening
subtends a circumferential arc of the tubes in a range from about
20.degree. to about 190.degree..
3. A sheath as in claim 1, wherein at least one tube is made from a
memory alloy material.
4. A sheath as in claim 1, wherein each tube has an external
diameter in the range from about 1 mm to about 45 mm.
5. A sheath as in claim 1, wherein the pair of nested tubes are
serrated.
6. A sheath as in claim 1, where the tubes are counter rotatable so
that the openings can be selectively aligned to open a passage
therein or staggered apart to close a passage therein.
7. A method for subcutaneously positioning an article, the method
comprising: providing a trailing sheath; inserting an article into
the trailing sheath; coupling the trailing sheath to a tunneling
tool; subcutaneously passing the tunneling tool through patient
tissue to position the article at a desired location; and removing
the sheath from over the article while the article remains at the
desired location.
8. A method as in claim 7, wherein the trailing sheath comprises a
pair of nested tubes, each tube having a longitudinal opening.
9. A method as in claim 8, wherein the removing comprises
withdrawing the tubes sequentially.
10. A method as in claim 8, wherein removing comprises withdrawing
an outer tube from an entrance or exit site.
11. A method as in claim 10, wherein removing further comprises at
least partially expanding an inner tube to allow release of the
article at the desired location.
12. A method as in claim 11, wherein removing further comprises
withdrawing an inner tube from an entrance or exit site.
13. A method as in claim 8, wherein removing comprises withdrawing
the tubes simultaneously in opposite directions.
14. A method as in claim 8, further comprising counter rotating the
tubes so that the openings can be aligned prior to removing the
sheath.
15. A method as in claim 8, further comprising counter rotating the
tubes so that the article is completely encompassed within the
sheath prior to passing the tunneling tool through patient
tissue.
16. A method as in claim 7, further comprising uncoupling the
tunneling tool from the trailing sheath prior to removing the
sheath.
17. A method as in claim 7, further comprising rotating the sheath
so that the article can be alignable with an artery or vein prior
to removing the sheath.
18. A method as in claim 7, further comprising expanding the sheath
while still encompassing the article completely prior to removing
the sheath.
19. A method for positioning an article in a subcutaneous tunnel,
the method comprising: providing a trailing sheath having a pair of
nested tubes, each tube having a longitudinal opening; inserting
the article into the trailing sheath; coupling the trailing sheath
to a tunneling tool; subcutaneously passing the tunneling tool
through patient tissue to position the article at a desired
location; and removing the sheath from over the article while the
article remains at the desired location by separating the nested
tubes within the tunnel.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of and claims the benefit
of priority from U.S. patent application Ser. No. 10/006,925, filed
Dec. 4, 2001, the full disclosure of which is incorporated herein
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] The present invention relates generally to medical devices,
systems, and methods. More particularly, the present invention
provides devices, systems, and methods for positioning an article,
such as a graft or catheter, in a subcutaneous tunnel between skin
and muscle tissue of a patient to establish improved access to the
patient's vascular system for hemodialysis, hemofiltration, or
other extracorporeal blood treatments.
[0004] Significant attention has been focused on the specific needs
of vascular access for hemodialysis. Hemodialysis is generally the
only treatment alternative for patients unable to receive a kidney
transplant due to medical conditions, age, or absence of a donor.
Hemodialysis, in part, takes up the excretory role of the kidney by
drawing blood from the arterial system into a membrane separation
device outside of the body, which transfers noxious substances from
the blood into dialysate for disposal and returns the cleansed
blood into the venous system of the patient. Hemodialysis and other
extracorporeal treatment regimens that are repeated periodically,
often for the lifetime of the patient, regularly utilize vascular
grafts or catheters to improve blood flow characteristics. Vascular
grafts, such as the Perma-Seal.TM. graft available from Possis
Medical, Inc. and the VAG.TM. (venous arterial graft) available
from Thoratec Laboratories Corporation, are permanently implanted
in a subcutaneous tunnel, where one end of the graft is typically
placed in an artery and the other end of the graft is typically
placed in a vein so as to create an anastomosis between the two
blood vessels. Access to the graft for hemodialysis is then
achieved by percutaneous introduction of a needle or an access
tube.
[0005] Recently, several graft designs have been proposed where the
grafts are made of certain materials, such as
polytetrafluoroethylene (PTFE), silicone, DACRON, polyurethane,
bovine, and the like. These grafts are designed to offer immediate
access to the patient's vasculature with reduced complications of
hematomas between the subcutaneous tissue and the graft, kinking,
thrombosis, pseudoaneurysm formation, or infection. While vascular
grafts offer great promise, one issue to be resolved for the
success and practical utility of vascular grafts is effective
subcutaneous placement of such articles.
[0006] Subcutaneous placement of vascular grafts can be problematic
since the grafts can easily be destroyed if they are stretched
longitudinally as such forces change the graft's material
properties. Previously proposed devices and methods for
subcutaneously positioning a graft include attaching a graft
directly onto a trailing end of a conventional tunneling tool which
creates a subcutaneous path between two blood vessels. Such methods
often result in significant longitudinal forces on the graft (as
the graft is constantly being pulled behind the tunneler) which may
potentially destroy the graft. Moreover, such protocols may result
in twisting or kinking of the graft and a loose seal between the
graft and the subcutaneous tissue as the tunnel created by the
tunneler is typically of equal or larger diameter than the diameter
of the vascular graft. A loose seal is undesirable as it makes it
difficult to properly access the graft with a needle and increases
the chances of hematomas, bleeding, and infection. Other proposed
methods employ feeding a graft into a hollow tunneler or tube that
is already positioned within the subcutaneous tunnel. Similarly,
passing the graft into a hollow tube as well as removing the tube
after the graft is positioned often results in significant
longitudinal forces on the graft which compromise its structural
integrity. In such instances, a loose seal is also created between
the graft and the subcutaneous tissue as the diameter of the hollow
tube will generally be greater than the diameter of the vascular
graft to allow for release of the graft.
[0007] For these reasons, it would be desirable to provide devices,
systems, and methods for positioning an article, such as a graft or
catheter, in a subcutaneous tunnel between skin and muscle tissue
of a patient to establish improved access to the patient's vascular
system for hemodialysis, hemofiltration, or other extracorporeal
blood treatments. In particular, it would be desirable if such
devices, systems, and methods would minimize the friction or
longitudinal forces acting against the vascular graft as it is
being subcutaneously positioned. It would be further desirable if
such devices, systems, and methods could provide a tighter seal
between the graft and the subcutaneous tissue, minimize hematomas
and infections, and enhance needle accessibility of the graft for
extracorporeal treatment. The placement devices, systems, and
methods should also allow for rotation of the graft without kinking
or twisting complications. At least some of these objectives will
be met by the devices, systems, and methods of the present
invention described hereinafter.
[0008] 2. Description of the Background Art
[0009] U.S. Pat. No. 4,453,928 describes a catheter tunneling
apparatus where a catheter is passed into a hollow tube which is
already positioned within a subcutaneous tunnel by a conventional
tunneler. U.S. Pat. No. 5,300,106 describes insertion and use of a
tunneling tool. Vascular grafts are described in U.S. Pat. Nos.
4,409,172; 4,604,762; 4,675,361; 4,731,073; 4,861,830; 5,840,240;
and 5,886,217. The full disclosures of each of the above references
are incorporated herein by reference.
BRIEF SUMMARY OF THE INVENTION
[0010] The present invention provides devices, systems, and methods
for positioning an article, such as a graft or catheter, in a
subcutaneous tunnel between skin and muscle tissue of a patient to
establish improved access to the patient's vascular system,
particularly peripheral blood vessels, for performing
extracorporeal treatment on circulating blood. Exemplary
extracorporeal treatment procedures include hemodialysis,
hemofiltration, hemodiafiltration, plasmapheresis, apheresis, and
the like. In particular, the present invention provides devices,
systems, and methods which minimize longitudinal forces or friction
acting against the vascular graft as it is being subcutaneously
positioned while still providing a tight seal between the graft and
the subcutaneous tissue, which in turn minimizes hematomas,
bleeding, and infections and enhances needle accessibility of the
graft for extracorporeal treatment. Moreover, the devices, systems,
and methods of the present invention allow for rotation of the
graft without kinking or twisting complications.
[0011] According to a first aspect of the present invention, a
sheath for use with a tunneling tool comprises a pair of nested
tubes and a coupling element. Each nested tube has a leading end, a
trailing end, and a longitudinal opening or split. The coupling
element is attached to the leading ends of the nested tubes and is
removably attachable to a conventional tunneling tool. The nested
tubes engage the catheter, graft, or other structure to be
implanted. For example, by providing an inner tube with a diameter
the same as or slightly smaller than the diameter or width of the
article to be implanted, the article will be gripped by the inner
tube. An outer tube may then be slid over the inner tube to apply a
radially inward "clamping" force that enhances the inner tube grip.
The longitudinal splits, however, allow the tubes to be easily
opened to facilitate insertion of the articles being implanted.
Once the article is inserted into the sheath, the article is passed
into the subcutaneous tunnel with minimal distraction. Frictionless
release of the article being implanted may then be effected by
removing the sheath from over the article by separating the split
nested tubes within the tunnel.
[0012] The nested tubes will usually have a uniform diameter along
their entire length, typically being in the range from about 1 mm
to 45 mm, preferably being in the range from 3 mm to 10 mm. The
lengths of the nested tubes will usually be in the range from 10 mm
to 200 cm, preferably being in the range from 20 mm to 24 cm. Each
longitudinal opening or split subtends a circumferential arc of the
tubes in the range from about 20.degree. to about 190.degree.,
preferably in the range from 60.degree. to about 180.degree.. The
tubes may be formed from the same or different material. For
example, the outer tube may be formed from a stiffer material while
the inner tube is formed from a more expansible material. Suitable
tube material includes polymer materials, such as polyethylene,
polypropylene, and the like. The tubes may further be counter
rotatable so that the openings can be aligned to open a passage
therein or the openings can be staggered apart to close a passage
therein. The coupling element may comprise a male connection and a
female sleeve, wherein the male connection is received within the
female sleeve. In some instances the male connection may be
threaded and/or knurled to provide a secure coupling between the
nested tubes and the tunneling tool. The male connection and female
sleeve may be formed from stainless steel, plastic, or like
materials.
[0013] In another aspect of the present invention, a system for
positioning an article in a subcutaneous tunnel between skin and
muscle tissue of a patient comprises a tunneling tool, a pair of
nested tubes coupleable to a trailing end of the tunneling tool,
and a flexible article which can be slidably received within the
pair of nested tubes. The nested tubes, as described above, each
have a leading end, a trailing end, and a longitudinal opening. The
tunneling tool may be any conventional tunneler that comprises a
shaft like structure suitable for creating a subcutaneous tunnel
between skin and muscle tissue of a patient. Generally, the tunnel
therein lies a short distance beneath the surface of the patient's
skin, typically being within 0.5 mm to 4.0 mm from the skin's
surface. The article may comprise a catheter or preferably an
arteriovenous graft, such as the Perma-Seal.TM. graft available
from Possis Medical, Inc. and the VAG.TM. graft available from
Thoratec Laboratories Corporation. One end of the graft, which may
optionally have a cuff or hood on an end thereof, may be placeable
in a vein and the other end of the graft may be placeable in an
artery so as to create an anastomosis between the two blood
vessels.
[0014] The present system advantageously minimizes longitudinal
forces or friction acting against the vascular graft as it is being
subcutaneously positioned. In particular, the split tubes structure
inhibits graft distraction as the graft is passed and released in
the subcutaneous tunnel, which in turn reduces trauma to the graft
and discomfort to the patient. In some instances, at least one tube
may be made from a memory alloy material or have a spring mechanism
attached thereto to allow for expansion of the split tubes which in
turn facilitates frictionless release of the graft. Additionally,
the pair of nested tubes may be serrated along longitudinal lines
to accommodate gripping of serrated articles. Moreover, the sheath
structure allows the graft to be rotated within the subcutaneous
tunnel without kinking or twisting complications, which is of
particular benefit when utilizing hooded type grafts that need to
be properly aligned with a blood vessel.
[0015] The external diameter of each nested tube will generally be
equal to or slightly smaller than an expanded diameter of the
flexible graft. The graft will generally have a uniform expanded
diameter along its entire length, typically being in the range from
about 2 mm to about 50 mm, preferably from about 4 mm to 11 mm,
when the graft is made operational from vessel pressure which
expands the graft. Placement of the graft in a subcutaneous tunnel
that is slightly smaller than the expanded diameter of the flexible
graft provides a tight and secure fit between the subcutaneous
tissue and the graft. This in turn minimizes occurrences of
hematomas, bleeding, and infections and enhances needle
accessibility of the graft for extracorporeal treatment. The length
of the graft will usually be in the range from 20 mm to 210 cm,
preferably being in the range from 30 mm to 25 cm. The graft may
also be trimmed to length after placement so that it is
sufficiently long for the intended use. The grafts will be formed
from polytetrafluoroethylene (PTFE), silicone, DACRON,
polyurethane, bovine, and like materials.
[0016] In yet another aspect of the present invention, methods for
subcutaneously positioning an article generally comprise providing
a trailing sheath, inserting the article into the trailing sheath,
and coupling the trailing sheath to a trailing end of a tunneling
tool. The tunneling tool is then subcutaneously passed through the
patient tissue to position the article at a desired location. The
trailing sheath is then removed from over the article while the
article remains at the desired location. The trailing sheath, as
described above, comprises a pair of nested tubes wherein each tube
has a longitudinal opening or split.
[0017] Near frictionless placement of the article at the desired
location may be carried out in several fashions. For example,
removing may comprise withdrawing the sheath tubes sequentially
from the tunnel. Preferably, an outer tube is completely removed
first from either an entrance or exit site of the tunnel followed
by removal of an inner tube from the entrance or exit site. In some
instances, the inner tube may be formed from a memory alloy
material so that it at least partially expands after the outer tube
is removed to further facilitate frictionless release of the
article at the desired location. Optionally, removing may comprise
withdrawing the tubes simultaneously from the tunnel in opposite
directions. Still further, the tubes may be counter rotated so that
the article is completely encompassed within the sheath prior to
passing the tunneling tool through the patient tissue. The openings
are then aligned prior to removing the sheath so that the graft
remains in tact at the desired location while the sheath is
removed. Any of the above protocols allow the split tubes sheath to
protect the graft against longitudinal forces as the graft is
subcutaneously passed and released within the tunnel. Typically,
the tunneling tool will be uncoupled from the trailing sheath prior
to removing the sheath. The sheath may further be rotated so that
the article can be alignable with an artery or vein prior to
removing the sheath. The trailing sheath may also have expansion
capabilities while still encompassing the article completely prior
to removing the sheath.
[0018] In still another aspect of the present invention, methods
for positioning an article in a subcutaneous tunnel may comprise
providing a trailing sheath having a pair of nested tubes wherein
each tube has a longitudinal opening. The article is inserted into
the trailing sheath and the trailing sheath is coupled to a
trailing end of a tunneling tool. The tunneling tool is then
subcutaneously passed through the patient tissue to position the
article at a desired location. The trailing sheath is then removed
from over the article while the article remains at the desired
location by separating the nested tubes within the tunnel.
[0019] A further understanding of the nature and advantages of the
present invention will become apparent by reference to the
remaining portions of the specification and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a cross-sectional view of an exemplary device for
positioning an article in a subcutaneous tunnel constructed in
accordance with the principles of the present invention.
[0021] FIG. 2 is another cross-sectional view taken along line 2-2
of the sheath of FIG. 1.
[0022] FIG. 3 is a cross-sectional view of a system for
subcutaneously positioning a graft comprising a tunneling tool, a
pair of nested tubes, and a flexible article.
[0023] FIG. 4 is another cross-sectional view taken along line 4-4
of the sheath of FIG. 3.
[0024] FIG. 5 is a cross-sectional view illustrating alignment of
the sheath openings.
[0025] FIG. 6 is a cross-sectional view of a serrated sheath.
[0026] FIG. 7 is a perspective view of a hooded graft which may be
used in conjunction with the present invention.
[0027] FIG. 8 is a cross-sectional view of the graft of FIG. 7.
[0028] FIG. 9A-9H illustrate a method according to the present
invention employing the device of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0029] The present invention provides devices, systems, and methods
for positioning an article, such as a graft or catheter, in a
subcutaneous tunnel between skin and muscle tissue of a patient to
establish improved access to the patient's vascular system,
particularly peripheral blood vessels, for performing hemodialysis,
hemofiltration, or other extracorporeal blood treatments. In
particular, the present invention provides devices, systems, and
methods which minimize longitudinal forces or friction acting
against the vascular graft as it is being subcutaneously positioned
while still providing a tight seal between the graft and the
subcutaneous tissue, which in turn minimizes hematomas, bleeding,
and infections and enhances needle accessibility of the graft for
extracorporeal treatment.
[0030] Referring now to FIG. 1, an exemplary sheath 10 for use with
a tunneling tool comprises a pair of nested tubes 12 and 14 and a
coupling element 16. Each nested tube 12, 14 has a leading end 18,
a trailing end 20, and a longitudinal opening 22 or split. The
coupling element 16 is attached to the leading ends 18 of the
nested tubes 12, 14 and is removably attachable to a conventional
tunneling tool. It will be appreciated that the following
depictions are for illustration purposes only and does not
necessarily reflect the actual shape, size, or dimensions of the
trailing sheath 10. This applies to all depictions hereinafter.
[0031] Referring now to FIG. 2, the nested tubes will comprise an
inner tube 14 and an outer tube 12. Each tube will usually have a
uniform diameter 24 along its entire length, typically being in the
range from about 1 mm to 45 mm, preferably being in the range from
3 mm to 10 mm. The lengths of the nested tubes 12, 14 will usually
be in the range from 10 mm to 200 cm, preferably being in the range
from 20 mm to 24 cm. Each longitudinal opening 22 or split subtends
a circumferential arc of the tubes in the range from about
20.degree. to about 190.degree., preferably in the range from
60.degree. to about 180.degree., more preferably about 90.degree.
with the opening being separated by about 90.degree.. The coupling
element 16 may comprise a male connection 26 and a female sleeve
28, wherein the male connection 26 is received within the female
sleeve 28. In some instances, the male connection 26 may be
threaded and/or knurled to provide a secure coupling between the
nested tubes 12, 14 and the tunneling tool. The male connection 26
and female sleeve 28 may be formed from stainless steel, plastic,
or like materials.
[0032] Referring now to FIG. 3, a system for positioning an article
30 in a subcutaneous tunnel between skin and muscle tissue of a
patient comprises a tunneling tool 32, a pair of nested tubes 12,
14 coupleable to a trailing end of the tunneling tool 32, and a
flexible article 30 which can be slidably received within the pair
of nested tubes 12, 14. The tunneling tool 32 may be any
conventional tunneler that comprises a solid or hollow shaft
suitable for creating a subcutaneous tunnel between skin and muscle
tissue of a patient.
[0033] The nested tubes 12, 14 will have lengths, lumen diameters,
and other dimensions as generally set forth above. Referring now to
FIGS. 4 and 5, the tubes 12, 14 may be counter rotatable so that
the openings 22 can be staggered apart, preferably by about
90.degree., to completely encompass the article 30 within the
sheath (FIG. 4). The tubes may also be counter rotated so the that
openings 22 can be aligned to open a passage for the article 30, as
shown in FIG. 5. With reference to FIG. 6, the pair of nested tubes
12', 14' may also be serrated to accommodate placement of serrated
articles.
[0034] Referring now to FIGS. 7 and 8, the article 30 may comprise
a catheter or preferably an arteriovenous graft, such as the
Perma-Seal.TM. graft available from Possis Medical, Inc. and the
VAG.TM. graft available from Thoratec Laboratories Corporation. One
end of the graft 30 may be placeable in a vein and the other end of
the graft may be placeable in an artery so as to create an
anastomosis between the two blood vessels. As illustrated in FIG.
7, the graft 30 may have a hood 34 or cuff on an end thereof which
becomes ingrown in the vessel tissue. With reference to FIG. 8, an
expanded diameter 36 of the flexible graft 30 will generally be
equal to or slightly larger than the external diameter of each
nested tube 12, 14. The graft 30 will have a uniform expanded
diameter 36 along its entire length, typically being in the range
from about 2 mm to about 50 mm, preferably from about 4 mm to 11
mm, when the graft is made operational from vessel pressure which
expands the graft. Placement of the graft in a subcutaneous tunnel
that is slightly smaller than the expanded diameter of the flexible
graft provides a tight and secure fit between the subcutaneous
tissue and the graft. This in turn minimizes occurrences of
hematomas, bleeding, and infections and enhances needle
accessibility of the graft for extracorporeal treatment. The length
of the graft 30 will usually be in the range from 20 mm to 210 cm,
preferably being in the range from 30 mm to 25 cm. The grafts will
be formed from polytetrafluoroethylene (PTFE), silicone, DACRON,
polyurethane, and like materials.
[0035] Referring now to FIGS. 9A through 9H, an exemplary method
for frictionless placement of a graft in a subcutaneous tunnel with
the device of FIG. 1 will be described. As illustrated in FIG. 9A,
the graft 30 is inserted into a trailing sheath having a pair of
nested tubes 12, 14 by first placing the graft in the clear inner
tube 14 via opening 22. The inner tube 14 grips the graft 30 as the
inner tube diameter is the same as or slightly smaller than the
diameter of the graft to be implanted. The red outer tube 12 then
slides over the clear inner tube 14 (with the tube openings being
separated by about 90.degree.) and applies a radially inward
"clamping" force that enhances the inner tube grip. The
longitudinal splits 22, however, allow the tubes to be easily
opened to facilitate insertion of the graft. The graft 30 will
generally be displaced by a distance of about 2 cm from the leading
ends 18 of the tubes 12, 14. FIG. 9B illustrates a patient's arm PA
in which the graft 30 will preferably be positioned to establish
improved access to the patient's vascular system, particularly
peripheral blood vessels in the forearm. It will be appreciated
that graft placement is not limited to the forearm, and that in
some instances the graft may be positioned in the patient's leg,
chest, or torso. A conventional tunneling tool 32 penetrates the
patient's forearm tissue at an entrance site 38 and through an exit
site 40 to create a subcutaneous tunnel 42 therebetween. Generally,
the tunnel 42 therein lies a short distance beneath the surface of
the patient's skin, typically being within 0.5 mm to 40 mm from the
skin's surface. The conventional tunneler 32 may additionally
anesthetize the penetrated tissue via an irrigator or syringe
attachment. As illustrated in FIGS. 9C and 9D, the nested tubes 12,
14 together with the graft 30 are coupled to the tunneling tool 32
by coupling elements 26 and 28.
[0036] Referring now to FIG. 9E, the tunneling tool 32 is then
passed through the subcutaneous tunnel 42 to position the graft 30
at a desired location. The tunneling tool 32 is uncoupled from the
trailing sheath 12, 14 once the graft is positioned. The nested
tubes 12, 14 may further be rotated within the subcutaneous tunnel
42 without kinking or twisting complications, which is of
particular benefit when utilizing hooded type grafts that need to
properly aligned with a blood vessel. The trailing sheath 12, 14
may also expand while still encompassing the graft 30
completely.
[0037] Referring now to FIGS. 9F through 9H, the trailing sheath
12, 14 is then removed from over the graft 30 while the graft
remains at the desired location. Near frictionless placement of the
graft at the desired location may be carried out in several
fashions. Preferably, removing comprises withdrawing the nested
tubes 12, 14 sequentially from the tunnel 42, wherein the outer
tube 12 is completely removed first from either the entrance 38 or
exit site 40 of the tunnel 42 (FIG. 9F) followed by removal of the
inner tube 14 from the entrance 38 or exit site 40 (FIG. 9H). The
graft 30 may then be trimmed to length after placement and
extracorporeal blood flow established by accessing the graft with a
needle. The present invention advantageously minimizes longitudinal
forces or friction acting against the vascular graft as it is being
subcutaneously positioned. In particular, the tubular sheath
inhibits graft distraction as it is being passed into the tunnel
and separating the split nested tubes 12, 14 within the tunnel 42
allows for near frictionless release of the graft at the desired
location. With reference to FIG. 9G, the inner tube 14 may be
formed from a memory alloy material or have a spring mechanism
attached thereto so that the inner tube 14 at least partially
expands after the outer tube 12 is removed to further facilitate
frictionless release of the graft 30 at the desired location.
[0038] Alternatively, removing may comprise withdrawing the tubes
12, 14 simultaneously from the tunnel 42 in opposite directions.
For instance, the outer tube 12 may be withdrawn from the entrance
site 38 while the inner tube 14 is withdrawn from the exit site.
Still further, the tubes may be counter rotated (to close a passage
therein) so that the graft is completely encompassed within the
sheath prior to passing the tunneling tool through the patient
tissue to facilitate insertion of the graft (FIG. 4). The openings
22 are then aligned in the tunnel (to open a passage therein) prior
to removing the sheath so that the graft remains in tact at the
desired location while the sheath is removed (FIG. 5). Any of the
above protocols allow the trailing sheath to protect the graft
against longitudinal forces as it is subcutaneously passed and
positioned within the tunnel.
[0039] Although certain preferred embodiments and methods have been
disclosed herein, it will be apparent from the foregoing disclosure
to those skilled in the art that variations and modification of
such embodiments and methods may be made without departing from the
true spirit and scope of the invention. Therefore, the above
description should not be taken as limiting the scope of the
invention which is defined by the appended claims.
* * * * *