Note: Descriptions are shown in the official language in which they were submitted.
CA 02387774 2002-04-17
WO 01/32141 PCT/US00/28673
VALVE PORT AND METHOD FOR VASCULAR ACCESS
CROSS-REFERENCES TO RELATED APPLICATIONS
The present application is a continuation-in-part of non-provisional
Application Serial No. 08/942,990, filed on October 2, 1997, which claimed the
benefit of
provisional Application Serial No. 60/036,124, filed on January 21, 1997, the
full
disclosures of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the design and use of medical
devices, and more particularly to the design and use of an implantable port
for
establishing temporary access to a patient's vascular system for hemodialysis
and other
extracorporeal blood treatments.
Access to a patient's vascular system can be established by a variety of
temporary and permanently implanted devices. Most simply, temporary access can
be
provided by the direct percutaneous introduction of a needle through the
patient's skin and
into a blood vessel. While such a direct approach is relatively simple and
suitable for
applications, such as intravenous feeding, intravenous drug delivery, and
other
applications which are limited in time, they are not suitable for hemodialysis
and other
extracorporeal procedures that must be repeated periodically; often for the
lifetime of the
patient.
For hemodialysis and other extracorporeal treatment regimens, a variety of
implantable ports have been proposed over the years. Typically, the port
includes a
chamber and an access region, such as a septum, where the chamber is attached
to an
implanted catheter which in turn is secured to a blood vessel. In the case of
veins, the
catheter is typically indwelling and in the case of arteries, the catheter may
be attached by
conventional anastomosis.
Of particular interest to the present invention, implantable ports typically
include a needle-penetrable septum which permits the percutaneous penetration
of a
needle into the internal chamber. The chamber, in turn, is connected to one
end of the
catheter, and the other end of the catheter is indwelling in the blood vessel.
While
workable, such designs suffer from a number of problems. Repeated penetration
of the
CA 02387774 2002-04-17
WO 01/32141 PCT/US00/28673
septum often leads to degradation over time, presenting a substantial risk of
small
particulates entering the blood stream and/or need to periodically replace the
port.
Second, the passage of blood through the chamber or plenum will often
encounter regions
of turbulence or low flow, either of which can degrade the quality of blood
over time.
S To overcome these problems, some implantable ports have an internal
valve structure which isolates the interior of the port from the lumen of the
implanted
catheter when the port is not in use. Such valued ports, however, have their
own
shortcomings. For example, self penetrating needles often cannot be used since
they will
be damaged by and/or cause damage to the port. In such instances, it is
frequently
necessary to use a catheter combined with a removable stylet, which is both
more costly
and more inconvenient than use of a simple needle. Moreover, many valued ports
have
no means or mechanism to assure that the valve is fully opened, particularly
when
insertion of the access needle opens the valve. In such instances, partial
insertion of the
needle can result in partial opening of the valve.
1 S Needle-actuated valued ports are described in a number of the patents
listed below. For example, the ports described in U.S. Patent Nos. 5,741,228
and
5,702,363, show a port having a duckbill valve which is opened by an
elastomeric plug
which is elongated by insertion of a needle. So long as the needle is fully
inserted, the
valve will be fully opened. It would be possible, however, to only partially
insert the
needle, resulting in only partial opening of the duckbill valve. Such partial
opening could
significantly degrade and alter the valve performance.
For these reasons, it would be desirable to provide improved valued
implantable access ports for percutaneously accessing a patient's blood
vessels, including
both arteries and veins. The access ports will comprise a valve structure for
isolating the
port from an associated implanted catheter when the port is not in use. The
valve will
preferably provide little or no structure within the blood flow lumen of the
access port
and will even more preferably not require passage of a needle or other access
tube
through the seating portion of a valve in order to open the valve.
Furthermore, the port
structure including the valve elements therein will have a substantially
uniform cross-
sectional area and will present no significant constrictions or enlargements
to disturb fluid
flow therethrough. Preferably, the port designs will permit percutaneous
access using a
conventional needle, such as a fistula needle, without damage to either the
port or the
needle. Still more preferably, the ports will include means for locking the
valve
2
CA 02387774 2002-04-17
WO 01/32141 PCT/US00/28673
structures open in response to insertion of the needle or other access device.
Ports and
valves according to the present invention will meet at least some of these
objectives.
2. Description of the Background Art
U.S. Patent No. 5,562,617 and WO 95/19200, assigned to the assignee of
the present application, describe implantable vascular access systems
comprising an
access port having an internal slit or duckbill valve for preventing back flow
into the port.
Vascular access ports having various valves for isolating the port from the
vascular
system in the absence of external percutaneous connection to the port are
described in the
following U.S. Patents: 5,954,691; 5,741,228; 5,702,363; 5,527,278; 5,527,277;
5,520,643; 5,503,630; 5,476,451; 5,417,656; 5,350,360; 5,281,199; 5,263,930;
5,226,879;
5,180,365; 5,057,084; and 5,053,013. Other patents and published applications
which
show implantable ports having valve structures opened by insertion of a needle
include
U.S. Patent Nos. 4,569,675; 4,534,759; 4,181,132; 3,998,222; and WO 96/31246.
U.S.
Patent No. 5,637,088 describes a septum-type implantable port which employs a
dual
needle to help prevent dislodgment.
SUMMARY OF THE INVENTION
The present invention provides devices and methods for percutaneously
accessing a body lumen through an implanted access port. More particularly,
the present
invention provides methods and devices for locking open a valve assembly
within an
access port by the act of inserting the access tube. Insertion may involve
simply
advancing the access tube in the forward direction, or it may involve
additional or
alternative movements such as rotation. Reversal of the needle movement and/or
removal
of the access tube will in turn release the lock and close the valve assembly.
The present
invention provides a "positive" locking action and reduces any variability in
access, such
as a "half opened" valve, and reduces the risk of blood loss due to valve
closure during
fluid transfers.
The implantable access ports for use with the present invention are
preferably capable of high volume withdrawal and/or return of blood or other
fluids,
particularly for patients undergoing an extracorporeal blood therapy, such as
hemodialysis, hemofiltration, hemodiafiltration, apheresis, or the like. The
vascular
access ports allow for high volumetric rates of blood or other fluid flow
therethrough,
typically allowing for rates above 250 ml/min, usually above 300 ml/min,
preferably at
WO 01/32141 CA 02387774 2002-04-17 pCT~S00/28673
least 400 ml/min, and often 500 mL'min or higher, using a single needle or
other access
device. Such high volumetric flow rates are quite advantageous in reducing the
time
required for performing the extracorporeal blood treatment, particularly for
otherwise
lengthy treatments which require large total volumes of treated blood, such as
S hemofiltration. To ensure high flow rates and minimum time requirements, it
is useful to
know that the valve is completely open, allowing full access to the body lumen
through
the conduit while the access tube is in place. Likewise, it is beneficial to
know that the
valve is completely closed when the access tube is removed, either by careful
disengagement or by accidental pull-out, since such high flow rates will cause
a
significant amount of fluid to be lost if the valve is unknowingly left open.
According to a first aspect of the method of the present invention, a body
lumen in the patient may be accessed by percutaneously inserting an access
tube into an
implanted access port. The access tube may be percutaneously inserted into the
access
port so that the access tube engages a valve lock having a latch which opens a
valve
structure within the port or the conduit. Alternatively, the latch may open
the valve
structure as a result of rotational or other movement of the access tube
during or
subsequent to insertion. The valve structure is located remotely from that
portion of the
access port into which the access tube has been inserted and may be present in
the conduit
itself or in a separate assembly within the port. The latch may be mechanical
or
hydraulic, usually being mechanically coupled to a spring-loaded valve
assembly or a
spring-loaded plunger assembly which mechanically opens a valve.
Alternatively, a
hydraulic latch could be provided where a pushing force on a plunger assembly
is
hydraulically actuated or a valve opened by insertion of the access tube.
In a more particular aspect of the present invention, an implantable port
comprises a base having a passage for receiving an access tube. A valve
assembly is
disposed in the base and includes a bore which is aligned with the passage in
the base and
which also receives the access tube. The valve assembly is locked by action of
a latch
which shifts position to lock the valve assembly open in response to movement
of the
access tube. The latch is disposed between the passage in the base and the
bore in the
valve. The latch typically comprises at least one space-filling element. One
or a number
of these elements are displaced into one or more receptacles adjacent to the
passage by
movement of the access tube in the passage, wherein the presence of the space-
filling
elements, typically opposed balls, in the receptacle locks the valve open.
When the valve
is opened by action of a plunger, such as a plunger protruding through a
duckbill or miter
4
WO 01/32141 CA 02387774 2002-04-17 pCT~S00/28673
valve, the balls or other space-filling elements move downward and outward to
depress
the plunger and lock the plunger open.
The space-filling elements of the latch typically comprise a pair of balls,
usually opposed stainless steel balls similar to small ball bearings, disposed
between the
passage in the base and the bore in the valve. In valve assemblies that open
and close
with the action of a spring-loaded plunger, the balls are spring-biased to
close against one
another between the passage and the bore in the valve assembly. In one
embodiment, the
insertion of the access tube through the passage forces the balls apart and
the access tube
passes into the bore of the valve assembly. As the balls move apart (outward),
they also
move downward into receptacles. This movement is directed by interior walls
sloping
outward between the passage and the bore. Such action depresses the plunger,
which
opens the valve. While the access tube is inserted, the balls are held against
the tube and
in the receptacles by the spring-loaded plunger and the angled interior walls.
Not only
does this lock the valve open, but the static friction of the balls against
the tube may help
to hold the access tube in the passage. Interior walls with an angle of 50
degrees or
greater (relative to a lateral plane through the port) have been found to
provide higher
frictional forces for needle retention. Removal of the tube allows the balls
to move out of
the receptacles in an upward direction, by action of the spring-loaded
plunger, and an
inward motion directed by the angled interior walls so that they are again in
contact in the
passage. In alternative embodiments, insertion of the access tube may be
coupled with a
rotational movement of the access tube. Such rotational motion would force the
balls
apart and facilitate the movement of the balls into the receptacles, thus
opening the valve.
Reversal of such movement by the access tube and/or removal of the access tube
subsequently closes the valve.
In a second aspect of the method of the present invention, percutaneous
access to a patient's blood vessel is provided by maintaining a conduit
between an
implanted access port and the blood vessel. An access tube is percutaneously
inserted
into a tube seat within the access port to establish a generally fluid tight
seal therein.
When inserted, the access tube actuates a valve lock to open a valve structure
to permit
flow through the conduit. The valve structure will usually be internal to the
port but, in
some cases, could be located outside of the port itself. Preferably, the tube
seat comprises
a tapered bore within the access port which frictionally engages the outside
access tube as
the tube is inserted into the bore. More preferably, insertion of the access
tube into the
tube seat depresses the tube seat relative to a base of the access port in
order to actuate the
5
CA 02387774 2002-04-17
WO 01/32141 PCT/US00/28673
valve lock which opens the conduit. The valve lock may take a variety of
forms,
including latch motions as described above.
The tube seat will remain locked in its depressed condition until the access
tube is removed from the base. By forming the tube seat from (or lining the
tube seat
with) a hard material, preferably a material harder than the needle or other
access device
which is to be used, the likelihood of damage to the valve can be greatly
reduced.
Moreover, the tapered tube seat design is not prone to damaging needles when
they are
inserted into the port. Thus, the port of the present invention is
particularly suited for use
with self penetrating, sharpened needles, such as fistula needles, unlike many
ports of the
prior art.
A further understanding of the nature and advantages of the invention will
become apparent by reference to the remaining portions of the specifications
and
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of an access port having a flexible conduit
extending therefrom constructed in accordance with the principles of the
present
tnventton.
Fig. 2 is a side, cross-sectional view of the access port of Fig. 1 shown
with a closed internal clamp structure.
Fig. 2A is a partial cross-sectional view taken along line 2A-2A of Fig. 2.
Fig. 3 is a side, cross-sectional view of the access port of Fig. 1 as shown
with the internal clamp structure opened in response to the insertion of an
access needle.
Fig. 3A is a partial cross-sectional view taken along line 3A-3A of Fig. 3.
Figs. 4A and 4B illustrate an alternative pinch tube connection design.
Figs. 5A and SB illustrate a slide valve embodiment of the implantable
port of the present invention.
Figs. 6A and 6B illustrate an access port having a valve lock mechanism
which functions with a duckbill valve.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
The present invention provides methods and apparatus for facilitating
percutaneous access to a body lumen of a patient. Exemplary body lumens,
include blood
vessels, the peritoneal cavity, and the like. The methods are particularly
useful for
6
WO 01/32141 CA 02387774 2002-04-17 pCT~S00/28673
accessing blood vessels, including both arterial blood vessels and venous
blood vessels.
While the remaining description is directed particularly at blood vessels, it
will be
appreciated that the invention applies to all body lumens and cavities where
selective
percutaneous access might be desired. For example, the ports can be used for
introduction and removal of dialysate in peritoneal dialysis procedures.
Access ports
according to the present invention are implanted subcutaneously so that a
passage therein
lies a short distance beneath the surface of the patient's skin, typically
being within 3 mm
to 20 mm of the skin's surface. An access tube may then be percutaneously
inserted into
the passage in the access port in order to provide communication with the
blood vessel or
other body lumen via the access port. Such access can be provided for a
variety of
purposes, usually involving withdrawal of blood, the extracorporeal treatment
of the
withdrawn blood, andlor the return of the treated blood to the patient. Such
extracorporeal blood treatment will most often be for hemodialysis, but can
also be for
hemofiltration, hemodiafiltration, apheresis, and the like. In addition to
extracorporeal
treatment, the access port of the present invention can be used for perfusing
drugs, fluids,
and other materials directly into a patient's circulation for a variety of
purposes.
The present invention relies on implantation of the access port and
connection of the port to the target blood vessel or other body lumen via a
conduit, which
is regulated by a valve. The valve is opened by movement of an access tube in
the port,
and closed by reversal of the movement, such movement may involve simply
inserting
the access tube or it may involve rotational motion or the like. When motion
is applied,
the access tube will engage a valve lock having a latch which shifts position
to lock the
valve assembly open. Locking the valve open ensures both that the valve is
completely
open and that the valve remains open to prevent accidental closure. When the
tube is
removed, the latch will shift back to its previous position and unlock and the
valve, both
ensuring that the valve is completely closed and avoiding the possibility of
accidental
leakage.
The access tube will usually be a needle which can be directly pierced
(percutaneously introduced) through the patient's skin and into the implanted
port. Thus,
the needle will usually have a sharpened tip in order to permit it to be self
introduced
through the skin. Of course, access tubes having blunt distal ends could be
used by first
piercing the skin with a separate blade, stylet, needle, or the like, and
thereafter
introducing the access tube into the resulting incision or hole. The access
tube could also
be introduced using an internal stylet which is subsequently withdrawn,
leaving the tube
7
WO 01/32141 CA 02387774 2002-04-17 pCT~S00/28673
in place in the port. While the port of the present invention can accept a
wide variety of
different access tubes, it is significant that it can be used with standard
hypodermic
needles, standard fistula needles, large fistula needles, e.g. 16 gauge, 14
gauge, or larger,
and the like. Prior port designs which employ a septum require the use of
relatively small
non-coring Huber needles or the use of a combination tube/stylet in order to
avoid
significant damage to the septum. The same is true of ports which employ slit
valves
through which a tube must pass, such as many of the Ensminger designs
described above.
In all cases, the needle or other access tube will be rigid and possess
sufficient column
strength in order to actuate a linkage for relieving clamping of the conduit,
as described in
more detail below.
The port of the present invention is also advantageous since it will not
generally be damaged by use of an inappropriately sized needle or other access
tube.
While most prior art ports can be damaged through use of the wrong type or
size of
needle, the port of the present invention will not be damaged by larger
needles (which
simply engage the access aperture and do not pass into the port) or by smaller
needles
(which enter the access aperture but pass harmlessly into the interior of the
base). In
particular, the passage in the access port which receives the needle or other
access tube
may have at least one bend, usually a 90° elbow, which presents a
surface which is
engaged by a smaller needle. By forming or backing the passage from a material
which is
harder than the needle, e.g. a stainless steel, the port will be protected
from any damage
from improper insertion of a small needle.
An exemplary access port 10 comprising a base 12 and flexible conduit 14
is illustrated in Figs. 1, 2, 2A, 3, and 3A. As shown in Fig. l, the flexible
conduit 14
extends from the base 12 and terminates at a distal end 16 which is suitable
for direct
anastomosis (suturing) to a blood vessel. Suitable conduit structures are
described in U.S.
Patent No. 5,562,617, the full disclosure of which is incorporated herein by
reference.
Exemplary conduit structures may be composed of silicone rubber.
The base 12 of access port 10 comprises an upper shell 18, a base plate 20,
an internal cylinder 22, and a vertically reciprocating plunger 23 disposed
within an
actuator block 24, where the assembly of the plunger and actuator block are
together
disposed within the cylinder 22. As shown in Figs. 2 and 2A, a spring 26 urges
the
plunger 23 and actuator block 24 upwardly relative to the base 20. When the
plunger 23
and actuator block 24 are in their upward position, the conduit 14 is pinched
closed
between an upper lip 28 which is a portion of the wall of cylinder 22 and a
lower lip 30
CA 02387774 2002-04-17
WO 01/32141 PCT/LTS00/28673
which is portion of the actuator block 24. A proximal end of the conduit 14 is
connected
to the lower end of a tube 32 which depends into an interior volume of the
actuator block
24. The depending tube 32 provides an axial bore 34 for receiving a needle N,
as
illustrated in Figs. 3 and 3A. A tapered region 33 is formed near the upper
end of axial
bore 34 and is sized to engage and seal against the outer side wall of a
needle or other
access tube which is introduced into the bore, as best seen in Fig. 3.
The needle N is introduced through an opening 36 at the upper end of the
axial bore 34. Typically, though not necessarily, the opening 36 has a slight
chamfer
(conical shape) which allows the needle N to be introduced into the bore 34. A
pair of
balls 40 are disposed in an upper portion of the tube 32 and contained within
a circular
aperture 42 in the shell 18 on the actuator block 24 as in its raised
configuration, as shown
in Fig. 2. When needle N is introduced through the opening 36, it will
encounter the balls
40 and depress the plunger 23 and the actuator block 24 downward until the
block reaches
its lower configuration, as shown in Fig. 3. At that time, the balls 40 will
move radially
outward into an expanded portion or ramp 44 of the aperture 42. The balls 40
will thus
become locked within the expanded portion or ramp 44, holding the actuator
block 24 in
its lowered position, so long as the needle N remains in place.
When the actuator block 24 has been lowered, as shown Figs. 3 and 3A,
the opposed lips 28 and 30 are opened in order to relieve external clamping on
the conduit
14. Thus, as the needle N is inserted into the access port 10, the clamping
mechanism
which has previously closed the flexible conduit 14 will be opened. When the
needle N is
removed, the spring 26 will urge the actuator block 24 upwardly, and the
access port will
return to the configuration shown in Figs. 2 and 2A.
Conveniently, a silicone overmolding 50 is provided around the base of the
access port 10 in order to facilitate implantation of the access port. A
flange 52 extending
radially outwardly from the base plate 20 will include holes (not illustrated)
for suturing
into tissue. The inclusion of the silicone overmolding 50 will prevent tissue
ingrowth into
the holes. Preferably, a silicone seal 54 will be provided between an internal
surface of
the upper shell 18 and an upper portion of the tube 32. The silicone seal 54
prevents the
intrusion of blood or other fluids from surrounding tissue and/or which may
leak from the
needle N into the interior of the access port 10.
In a preferred aspect of the access port 10 of the present invention, the
axial bore 34 will be tapered in the downward direction. The size of the bore
and degree
of the taper will be selected to frictionally engage conventional needles or
other access
9
CA 02387774 2002-04-17
WO 01/32141 PCT/US00/28673
tubes so that a tight seal is formed as the access tubes are inserted into the
axial bore 34.
The taper also provides a stop so that the needle N will not penetrate into
the horizontal
lumen defined by the conduit 14.
It can thus be seen that the combination of needle, access port 10, and
flexible conduit 14 provides a substantially continuous and smooth flow path
for fluids
from and/or to the patient's vascular system. In particular, the use of
external clamping
for closing flow through the conduit 14 eliminates the need for an internal
valve structure
within the conduit or elsewhere within the access port to define a valve seat,
i.e. that
portion of the valve which closes to inhibit flow therethrough. The particular
linkage
shown for relieving clamping from the flexible conduit is simple, reliable,
and relatively
inexpensive to produce. Very few moving parts are needed, yet a positive seal
is reliably
achieved every time the needle N is withdrawn from the access port 10.
Moreover, once
the needle N is introduced into the access port 10, the clamp mechanism is
locked in its
open configuration to assure that full flow through the lumen of the flexible
tube and
other portions of the access port are maintained.
Refernng now to Figs. 4A and 4B, an additional embodiment of an access
port 500 constructed in accordance with the principles of the present
invention includes a
body 512 having a nipple 514 extending laterally outward from the body 512.
The nipple
514 is suitable for connection to a flexible conduit (not shown). The body 512
includes
an upper shell 518, a base plate 520, an internal cylinder 522, a vertically
reciprocating
plunger 523 and an actuator block 524. The plunger 523/actuator block 524 as
shown in
their vertically raised position in Fig. 4A and its vertically depressed or
lowered
configuration in Fig. 4B.
Since the conduit does not extend into the base 512, the port embodiment
500 of Figs. 4A and 4B employs a separate pinch tube 525, where the pinch tube
is
pinched closed between an upper lip 528 which is part of the cylinder 522 and
a lower lip
530 which is part of the reciprocating actuator block 524. When the actuator
block 524 is
lowered, as shown in Fig. 4B, the external clamping of the pinch tube 525 is
relieved.
The actuator block 524 is urged upwardly by spring 526 which is mounted
over a pin 527, and the plunger 523 comprises an axial bore 534 for receiving
a needle N,
as shown in Fig. 4B. The needle N passes through aperture 536 and into the
passage 534
in the plunger 523. As the needle enters the passage 534, it passes through
opposed balls
540 which first cause lowering of the plunger 523 and the actuator block 524
and then are
captured in an expanded portion or ramp 544 of the passage 545, as illustrated
in Fig. 4B.
WO 01/32141 CA 02387774 2002-04-17 pCT/US00/28673
While the entry of needle N into the passage 534 and through opposed
balls 540 may be effected simply by inserting the needle vertically downward,
once the
needle is fully lowered, and engaged by the tapered wall of passage 534 (as
shown in Fig.
4B), the valve is "locked" open by the balls 540. The needle is held in place
by friction fit
in the tapered region of the passage 534. In addition, the static friction of
the balls against
the tube may help to hold the access tube in the passage. Such retention
protects the
patient against accidental loss of the needle. It has been found that simple
removal
techniques allow the needle to be pulled from the port without significant
hindrance.
Thus, the combination of opposed balls 540 and the expanded portion 544 for
capturing
the balls not only locks the valve open, it also secures the needle in place
until it is
desired to remove the needle.
Referring now to Figs. 5A and SB, an alternative valve structure for use in
the implantable ports of the present invention is illustrated. Instead of
employing a pinch
valve, as previously described, the ports may employ a sliding valve 600 or a
reciprocating block 602 is formed within the base enclosure 604 (only a
portion of which
is illustrated). The reciprocating block 602 defines an inlet portion 606 of a
passage
through the port. An outlet portion 608 of the passage is also provided in the
port.
Initially, when no needle is present a spring 610 urges the reciprocating
block 602 upward
so that a side portion 612 of the passage is out of alignment with the outlet
portion 608.
Thus, the sliding valve structure 600 is closed. By introducing a needle N or
other access
tube into the valve structure 600, the reciprocating block 602 is lowered so
that the side
branch 612 of the passage comes into alignment with the outlet portion 608, as
illustrated
in Fig. 5B. The valve is thus open. The valve can be held in the open position
by a pair
of opposed balls 620 which are received in an enlarged recess 622, generally
as described
above in connection with the previous embodiments.
Referring now to Figs. 6A and 6B, an alternative valve structure for use in
the implantable ports of the present invention is illustrated. Instead of
employing a pinch
valve or sliding valve, as previously described, a port may employ a duckbill
or miter
valve. An exemplary port 700 having duckbill valve assembly comprises a base
having a
passage 701, balls 702, a receptacle or ramp 703, an axial bore 704, a
vertically
reciprocating plunger 705, and a duckbill valve 707. A spring 706 urges the
plunger 705
upwardly relative to the duckbill valve 707. When the plunger 705 is in its
upward
position, the duckbill valve 707 is closed and the conduit 708 is not
accessible. A tapered
region 709 is formed near the upper end of the axial bore 704 and is sized to
engage and
11
CA 02387774 2002-04-17
WO 01/32141 PCT/US00/28673
seal against the outer side wall of a needle or other access tube which is
introduced into
the bore 704.
A needle N is introduced through an opening 710 at the upper end of the
axial bore 704. Typically, though not necessarily, the opening 710 has a
slight chamfer
(conical shape) which allows the needle N to be introduced into the bore 704.
A pair of
balls 702 is disposed in the passage 701 and held in position by the plunger
705 in its
raised configuration, as shown in Fig. 6A. When needle N is introduced through
the
opening 710, it will encounter the balls 702, urging the balls forwardly to
engage and
depress the plunger 705 downward until the plunger 705 reaches its lower
configuration
where the duckbill valve 707 is opened, as shown in Fig. 6B. At that time, the
balls 702
move radially outward into a receptacle 703. The balls 702 thus become locked
within
the receptacle 703, holding the plunger 705 in its lowered position, so long
as the needle
N remains in place.
In a preferred aspect of the access port 700 of the present invention, the
axial bore 704 will be tapered in the downward direction. The size of the bore
and degree
of the taper will be selected to frictionally engage conventional needles or
other access
tubes so that a tight seal is formed as the access tubes are inserted into the
axial bore 704.
The taper also provides a stop so that the needle N will not penetrate the end
of the
plunger 705. In a further preferred aspect of the access port 700 of the
present invention,
the plunger assembly 705 will comprise an end cap 711 affixed to its end. The
cap 711
will be adapted to withstand repeat contact with the access tube, resisting
passage of the
tube such that the tube will not penetrate or damage the valve 707.
Although the foregoing invention has been described in some detail by
way of illustration and example, for purposes of clarity of understanding, it
will be
obvious that certain changes and modifications may be practiced within the
scope of the
appended claims.
12
