Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates generally to selectively aspirating stylet
assemblies; and particularly relates to such stylet assemblies having
selectively
controllable flow paths such as may be used, for example, to optimally
facilitate the
introduction of a catheter, shunt or cannula into a parenchymatous organ or
structure.
The present invention also has application in connection with other
procedures, such
as the placement of a cannula within the body for locating a wire lead or
electrode, or
otherwise establishing a fluid flow path or placing an elongated tubular
member
between first and second locations outside and within the body, respectively.
The stylet assembly of the present invention defines a fluid flow path,
allowing
pressure at the inserted distal end of the stylet to be controlled to permit
regulation of
aspiration of tissue or fluid into the catheter or shunt during withdrawal of
the stylet.
As an example, one primary application of this inventioninvolves intracerebral
ventricular (ICV) catheter placement. Establishing a fluid flow path through
the stylet
and avoiding aspiration of tissue into the catheter requires a mechanism to
prevent the
creation of a vacuum while withdrawing the stylet from the catheter. However,
the
present invention also may be used under circumstances in which some
aspiration is
desired, as in the case of a biopsy from a localized area.
. Insertion of a catheter, shunt or cannula into the body is often
accomplished
with the use of a solid stylet or guidewire which extends into the catheter to
provide
su~cient rigidity to facilitate passage along a desired path through body
tissue. Once
the catheter or shunt is properly positioned, and possibly during the
positioning
procedure itself, the stylet must be withdrawn. Pulling a solid stylet from a
positioned catheter or shunt device creates a vacuum at the inserted open end
of the
device. Fluid or tissue or both is drawn into the catheter to fill the vacuum,
and the
displacement of the tissue may cause undesirable physiologic side effects. In
the case
of an ICV catheter placement, such a vacuum could result in aspiration of
choroid
plexus into the catheter, resulting in extreme ti5aue damage proximate the
catheter.
Hollow stylets have been lrnown previously. For example, U.S. Patent No.
5,098,411 issued to Watson, discloses a hollow stylet. Such hollow stylets
offer an
advantage over solid ones in that they allow fluid to exit. Hollow stylets may
thus be
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utilized to determine, through fluid return, when a desired location in the
brain or
other organ is reached. A specific problem during catheter placement, however,
is
that tissue can be "cored" in the distal opening if an open-ended hollow
catheter/stylet
or cannula/stylet assembly is used, and tissue can intrude through apertures
in the ,
catheter even if the assembly is not open-ended. Additionally, hollow
catheter/stylet
and cannula/stylet assemblies, although solid, may not have optimal rigidity,
making
placement within the body difficult.
Accordingly, the present invention provides new methods and apparatus for
overcoming one or more of these deficiencies by providing a stylet defining a
flow
20 path which may be selectively opened or closed to optimize the rigidity of
the stylet
while minimizing tissue damage proximate an outer tubular member placed
through
use of the stylet.
As explained in more detail below, the present invention overcomes the above-
noted and other shortcomings of prior stylet devices used during placement of
catheters, shunts or cannula. For simplicity of expression, the invention will
be
described in terms of placing a catheter, and the Figures will be referred to
in terms
of defining a catheter. It should be clearly understood that the description
is equally
applicable to placing a shunt or cannula for guiding an electric lead; and
that FIG. 1 is
generic to such other structures. The invention is operable to provide a
closed fluid
column to facilitate placement of the stylet/catheter assembly into a specific
selected
location within the body. The closed fluid column is generally non-
compressible.
Such fluid column may be analogized to the fluid column obtained by crimping
the
top end of a fluid-filled soda straw.
An appropriate valve is used to close off the fluid column near the top end of
the stylet. Although the valve need not be placed immediately on top of the
stylet, it
is preferable that the valve be placed in material which is generally rigid,
and that the
valve be placed as close as possible to the actual top of the stylet to avoid
excess fluid
4
volumes and to avoid use of any members which might change in volume, thereby
forcing fluid out and destroying the fluid column.
Preferably, the valve will be a rotary valve such as a stop-cock valve as used
in intravenous delivery systems. However, a poppet or other longitudinally
shifting
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type of valve may also be satisfactory. The important
consideration is that the valve used not displace fluid
during an operation; accordingly, a stop-cock valve having a
rotary motion, or a poppet valve having a transverse motion
relative to the fluid passageway, is currently believed to
be most appropriate.
The fluid column may be established by pumping a
selected fluid through a catheter/stylet assembly against
some resistance (e.g. the use of a hypodermic syringe into a
small vial of similar fluid), so as to provide an air-free
column of fluid within the catheter/stylet assembly. The
valve may then be closed to isolate the column. Tissue in
the path of the stylet/catheter assembly is parted during
insertion of the assembly into the brain or other organ.
Fluid may be obtained through the hollow stylet and may be
monitored to determine when a desired location is reached.
Additionally, the valve may be opened, and pressures
equalized, after insertion of the catheter/stylet assembly
to place the end of the catheter at the desired location.
Fluid can be infused down the lumen of the stylet, filling
the space created by any withdrawal of the stylet. Using
replacement fluid rather than drawing fluid from the distal
locale may prevent harmful side effects caused by either
displacing the fluid, and/or tissue damage near the tip of
the device caused by a vacuum. Once the desired location is
reached, the hollow stylet is to be completely removed,
leaving only the flexible catheter in the brain or other
organ.
The invention may be summarized according to one
broad aspect as a selectively aspirating stylet for use in
placing a generally tubular member in a patient's body, said
generally tubular member having an inside diameter surface
and an upper end, said stylet comprising: a stylet body
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having a lower hollow portion configured to be placed within
said generally tubular member and an upper hollow portion
configured to extend outside said generally tubular member,
said lower hollow portion having a first end and a second
end and an outside diameter surface; a valve assembly
coupled to said upper and lower portions of said stylet body
to provide selective fluid communication from said upper
portion through said valve to said lower portion, said valve
assembly coupled to said lower portion of said stylet body
at said first end of said stylet body; and sealing means
placed between said inside diameter surface of said
generally tubular member and said stylet body to prevent
unwanted escape of fluid between said stylet body and said
generally tubular member when said stylet body is placed
within said generally tubular member.
According to another broad aspect the invention
provides a selectively aspirating stylet for use in placing
a catheter in a patient's body, said catheter having an
inside diameter surface and an upper end, said stylet
comprising: a stylet body having a lower hollow portion
configured to be placed within said catheter and an upper
hollow portion configured to extend outside said catheter,
said lower hollow portion having a first end and a second
end and an outside diameter surface; a valve assembly
coupled to said upper and lower portions of said stylet body
to provide selective fluid communication from said upper
portion through said valve to said lower portion, said valve
assembly coupled to said lower portion of said stylet body
at said first end of said stylet body; and sealing means
placed between said inside diameter surface of said catheter
and said stylet body to prevent unwanted escape of fluid
between said stylet body and said catheter when said stylet
body is placed within said catheter.
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According to another broad aspect the invention
provides a system for placing a generally tubular member in
a patient's body, said system comprising: a generally
tubular member having an inside diameter surface and an
upper end, a stylet body having a lower hollow portion
placed within said generally tubular member and an upper
hollow portion configured to extend outside said generally
tubular member, said lower hollow portion having a first end
and a second end and an outside diameter surface; a valve
assembly coupled to said upper and lower portions of said
stylet body to provide selective fluid communication from
said upper portion through said valve to said lower portion,
said valve assembly coupled to said lower portion of said
stylet body at said first end of said stylet body; and a
fluid column between said lower hollow portion of said
stylet body and said inside diameter of said generally
tubular member; whereby, said fluid column adds rigidity to
said system while moving said generally tubular member into
a patient's body.
According to another broad aspect the invention
provides a system for placing a catheter in a patient's
body, said system comprising: a catheter having an inside
diameter surface and an upper end, a stylet body having a
lower hollow portion placed within said catheter and an
upper hollow portion configured to extend outside said
catheter, said lower hollow portion having a first end and a
second end and an outside diameter surface; and a valve
assembly coupled to said upper and lower portions of said
stylet body to provide selective fluid communication from
said upper portion through said valve to said lower portion,
said valve assembly coupled to said lower portion of said
stylet body at said first end of said stylet body; and a
fluid column between said lower hollow portion of said
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stylet body and said inside diameter of said catheter;
whereby, said fluid column adds rigidity to said system
while moving said catheter into a patient's body.
Examples of the more important features of this
invention have been broadly outlined in order that the
detailed description that follows may be better understood
and so that contributions which this invention provides to
the art may be better appreciated. There are, of course,
additional features of the invention which will be described
herein and which will be included within the subject matter
of the claims appended hereto.
BRIEF DESCRIPTION OF THE DRAVdINGS
FIG. 1 is an illustration of an open tip
configuration of an exemplary hollow stylet/tubular member
assembly in accordance with the present invention, depicted
in vertical section, and partially in schematic
representation.
FIG. 2 is an illustration of the hollow
stylet/tubular member assembly shown in FIG. 1, depicted in
a cross-sectional view taken along the line 2-2 in FIG. 1.
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FIG. 3 is an illustration of a closed tip configuration for a hollow
stylet/catheter assembly in accordance with the present invention, depicted in
vertical
section.
FIG. 4 is an illustration of a configuration of an exemplary upper end of a ,
generally tubular member adapted with a sealing means in accordance with 'the
present
invention, depicted in vertical section.
As noted previously, the depicted tubular member/stylet assembly 8 in
accordance with the present invention is shown in FIG. 1, and will be
described in
ZO terms of a catheter/stylet assembly. A stylet 10 generally comprises a
valve assembly
12 operatively coupled between an upper stylet body portion 14 and a lower
stylet
body portion 16. Both the upper and lower stylet body portions 14, 16 are
hollow,
rigid tubular members. The lower stylet body portion 16 is adapted for
placement
within catheter 18. The inner diameter of catheter 18 typically will be on the
order of
.025 inches, so that the outer diameter of the lower stylet body portion 16
generally
will be approximately .020 inches. The inner diameter of the lower stylet body
portion 16 typically will measure about .010 to .016 inches. The dimensions of
the
upper stylet body portion 14 generally may be about the same as the dimensions
of the
lower stylet body portion or larger, but it is desirable to minimize its mass.
Of
course, devices of other sizes are within the scope of the present invention.
The valve assembly 12 is able to provide selective fluid communication from
one side of the valve to the other. Preferably, valve assembly 12 is a rotary
valve
such as a stop cock valve of the type typically used in intervenous delivery
systems.
However, as noted above, a poppet valve or another type of valve may be used,
provided that the valve does not displace fluid, or displaces only a minimal
volume of
fluid, beneath the valve during operation. Suitable stop cock valves for use
in
connection with the present invention are widely available from numerous
commercial
suppliers. One such supplier is Burron Medical, Inc.
The upper stylet body portion 14 has two ends, the first end connected to a
first side of a valve assembly 12 and the second end connected to a fluid
supply. The
lower stylet body portion 16 also has two ends, the first end connected to a
second
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side of valve assembly 12 and the second end distally located away from the
valve
assembly and at or near the tip 20 of the catheter/stylet assembly.
The tip 20 of the catheter/stylet assembly may be of an open tip
configuration,
as shown in Fig. 1, or may be of a closed tip configuration, as shown in Fig.
2.
Selection of either an open tip or closed tip catheter/stylet assembly for a
particular
patient will depend in each case upon the circumstances surrounding the
treatment to
be performed. Generally, however, an open tip catheter/stylet assembly will be
used
when the infusion target is not to be invaded, while a closed tip
configuration is
preferred if the infusion target requires invasion for optimal perfusion.
As shown in Fig. 1, the lower stylet body portion 16 is configured to be
placed within catheter 18. A sealing means 22 preferably is used to prevent
unwanted
escape of fluid from around the stylet at the upper end of the catheter.
Sealing means
22 preferably comprises a silicone rubber material placed so as to fill and
close the
annular space between the inside diameter surface of catheter 18 and the
outside
diameter surface of the first end of lower stylet body portion 16. As shown in
FIG.
4, the upper end of catheter 18 may be adapted with the sealing means 22.
Alternatively, the lower stylet body portion 16 may be adapted with sealing
means 22
(see FIG. 1), or the sealing means 22 may be separate from both lower stylet
body
portion 16 and catheter 18 and independently placed so as to fill and close
the annular
space between catheter 18 and lower stylet portion 16.
Sealing means 22 can be of a variety of shapes and sizes. As shown in Fig. 1,
sealing means 22 is tapered, with the sealing material nearest valve assembly
12 being
relatively thick as compared to the sealing material located away from valve
assembly
12. However, the present invention is not so limited. The shape of the sealing
means
may vary, for example, with the size and shape of the stylet and catheter
being used.
That is, where either the stylet or catheter is tapered along the area to be
sealed, a
sealing means 22 having uniform thickness may be satisfactory. Again, the
important
consideration is that the sealing means 22 prevent unwanted escape of fluid
from
around the stylet at the upper end of the catheter.
The lower stylet body portion 16 is adapted with a backfill opening 24 located
between the valve assembly 12 and the second or lower end of lower stylet body
portion 16. The backfill opening 24 allows fluid to flow from within the
stylet to fill
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the annular space between the catheter and the stylet. Such flow is necessary
in
creating an air-free fluid column within the catheter/stylet assembly.
As noted above, placement of the stylet within the catheter provides a more
rigid assembly for passage along a desired path through body tissue.
Introducing a
fluid column within both the stylet and catheter makes each more rigid. Thus,
allowing fluid to flow from within the stylet to fill the annular space
between the
catheter and the stylet provides additional rigidity to the catheter/stylet
assembly.
Accordingly, ease of placement is further enhanced.
In a catheter/stylet assembly having a closed tip configuration, the distal,
second end of lower stylet body portion 16 is closed off and generally rounded
to
prevent its damaging the closed tip 26 of catheter 18. However, the sides of
both
catheter 18 and lower stylet body portion 16 will have at their lower ends a
plurality
of holes 28, 30 that permit the passage of fluid. Preferably, both the
catheter and
stylet are configured with four groups of three longitudinally spaced side
holes equally
spaced around its circumference, although the side holes 28 of the catheter
and side
holes 30 of the stylet need not be aligned. The exact number and placement of
the
holes may vary depending on the particular application.
Selective aspiration of organ tissue is achieved as follows: The lower stylet
body portion 16 is placed within catheter 18 so that the space between the
first end of
. lower stylet body portion 16 and the upper end of catheter 18 is sealed, and
the
second end of lower stylet body portion 16 is located within catheter 18 at or
near tip
20. Valve assembly 12 is opened to permit a supply of fluid under pressure to
flow
through upper stylet body portion 14 and through valve assembly 12 to fill
completely
both catheter 18 and lower stylet body portion 16. As noted above,
establishing fluid
columns within the catheter and stylet may be accomplished by pumping a
selected
fluid through the catheter/stylet assembly against some resistance, e.g. using
a
hypodermic syringe in a vial of fluid to provide an air-free column of fluid
within the
catheter/stylet assembly. Once catheter 18 and lower stylet body portion 16
are filled
with fluid, valve assembly 12 is closed to prevent any fluid communication
between
the upper and lower stylet body portion 14, 16. At this point, the
catheter/stylet
assembly may be inserted to a desired location within the patient's body in a
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conventional manner. Then, valve assembly 12 is opened or closed as necessary
so
that the desired selective aspiration is obtained.
Although the preferred embodiment of this invention has been described
hereinabove in some detail, it should be appreciated that a variety of
embodiments
will be readily available to persons utilizing the invention for a specific
end use. The
description of the apparatus and method of this invention is not intended to
be limiting
on this invention, but is merely illustrative of the preferred embodiment of
this
invention. Other apparatus and methods which incorporate modifications or
changes
to that which has been described herein are equally included within this
application.
1O Additional objects, features and advantages of the present invention will
become
apparent by referring to the above description of the invention in connection
with the
accompanying drawings.
