U.S. patent application number 11/325896 was filed with the patent office on 2006-05-25 for methods and apparatus for aspiration and priming of inflatable structures in catheters.
This patent application is currently assigned to MERCATOR MEDSYSTEMS, INC.. Invention is credited to Kirk Patrick Seward.
Application Number | 20060111672 11/325896 |
Document ID | / |
Family ID | 29584619 |
Filed Date | 2006-05-25 |
United States Patent
Application |
20060111672 |
Kind Code |
A1 |
Seward; Kirk Patrick |
May 25, 2006 |
Methods and apparatus for aspiration and priming of inflatable
structures in catheters
Abstract
An aspiration baffle comprises an outer tube and an inner core
wire. Microholes are provided in the outer tubular member to permit
passage of gas but inhibit the passage of liquids. The aspiration
baffle is used in a catheter having a balloon or other inflatable
structure to assist in priming of the structure. After evacuating
the inflatable structure by applying a vacuum, the aspiration
baffle can collect and trap residual gas which remains during the
priming of the inflatable structure.
Inventors: |
Seward; Kirk Patrick;
(Dublin, CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
MERCATOR MEDSYSTEMS, INC.
San Leandro
CA
|
Family ID: |
29584619 |
Appl. No.: |
11/325896 |
Filed: |
January 4, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10447676 |
May 28, 2003 |
|
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|
11325896 |
Jan 4, 2006 |
|
|
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60384894 |
May 28, 2002 |
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Current U.S.
Class: |
604/122 |
Current CPC
Class: |
A61M 25/007
20130101 |
Class at
Publication: |
604/122 |
International
Class: |
A61M 1/00 20060101
A61M001/00 |
Claims
1. A method for priming an inflatable chamber on a catheter with
liquid, said method comprising: drawing a vacuum in the chamber
through the inflation lumen to remove gas, wherein a residual
amount of gas is left; and filling the chamber with liquid; wherein
an aspiration baffle is disposed in the catheter body said baffle
defining a sealed interior volume open to an interior of the
inflatable chamber through a plurality of microholes only; wherein
the interior volume of the aspiration baffle is evacuated through
the microholes as the vacuum is drawn in the interior of the
inflatable chamber through the inflation lumen so that the residual
amount of gas may pass from the inflatable chamber into the
interior volume of said aspiration tube.
2. A method as in claim 1, wherein the vacuum is drawn to a
pressure of 15 mmHg or lower.
3. A method as in claim 2, wherein the chamber is filled with
liquid at a pressure of at least one atmosphere.
4. A method as in claim 3 wherein the chamber is filled with liquid
at a pressure of at least two atmospheres.
5. A method as in claim 1 wherein the aspiration baffle further
comprises a core wire disposed coaxially within the interior volume
of the tubular member, wherein an annular gas flow path is formed
between an interior wall of the tubular member and an exterior
surface of the core wire.
6. A method as in claim 5, wherein the tubular member has a length
in the range from 10 cm to 200 cm and an outer diameter in the
range from 0.1 mm to 1 mm, and wherein the microholes have a
maximum width in the range from 0.001 mm to 0.1 mm.
7. A method as in claim 6, wherein the microholes are disposed over
only a distal length of the tubular member in the range from 1 cm
to 20 cm.
8. A method as in claim 7, wherein the core wire extends from the
distal end of the tubular member over a distance in the range from
1 cm to 100 cm.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/447,676 (Attorney Docket No. 021621-0011US), filed on
May 28, 2003, which claimed the benefit of Provisional Application
No. 60/384,894 (Attorney/Docket No. 21621-001100US), filed on May
28, 2002, the full disclosures of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to medical devices
and methods. More particularly, the present invention relates to
apparatus and methods for removing air from vascular and other
medical catheters having chambers which are filled with liquid.
[0004] Balloon angioplasty, stent treatment, and numerous other
intravascular procedures employ catheters which are introduced to
the vasculature and advanced intravascularly to a target location,
often in the coronary vasculature. Many such intravascular
catheters have inflatable balloons and other structures intended to
effect or assist in performing a therapeutic procedure, e.g.
balloon angioplasty, stent placement, and/or drug delivery. Such
expandable structures can take a variety of forms, including
non-distensible balloons of the type typically used for performing
angioplasty, elastomeric balloons of the type often used for vessel
occlusion, and driving structures of the type used for advancing
needles and manipulating other tools.
[0005] Because of the dangers of the release of air into the
bloodstream, such expandable structures are typically inflated with
a liquid, such as saline, in order to achieve inflation within the
vasculature. In order to purge the inflatable structures prior to
use, the catheters are typically primed with liquid immediately
prior to use. A common method of priming relies on vacuum
aspiration of air from the inflatable structure through a lumen in
the catheter, typically the inflation lumen which is subsequently
used to introduce the liquid inflation medium. Thus, a vacuum is
typically applied through the inflation lumen to lower the air
pressure within the inflatable structure to a fraction of
atmospheric pressure, typically 15 mm Hg or below. A liquid
inflation medium is then introduced into the inflatable structure
while preventing the reintroduction of air and other gasses.
[0006] While this procedure significantly limits the presence of
air and other gasses within the inflatable structure, it will be
appreciated that there will usually be a small residual amount of
gas within the inflatable structure since the vacuum drawn is not
complete. In order to even further enhance the safety, it is
desirable to reduce or eliminate such residual gas amount within
the inflatable structure.
[0007] The most common method for eliminating such residual gas in
the balloon or other inflatable structure is to provide a vent tube
or hole from the interior of the inflatable structure to the
atmosphere. In this way, as the balloon or other inflatable
structure is primed with liquid inflation medium, the residual air
or gas will migrate toward the vent and be released into the
atmosphere. The release of liquid medium is reduced or eliminated
by providing vent tubes or holes having small or capillary
dimensions. Thus, the vent tubes or holes will allow gas to pass
but will inhibit the passage of the liquid inflation medium at the
priming pressures and subsequent therapeutic pressures used in the
procedures.
[0008] While the use of vent tubes and holes has been generally
successful, the need to provide a passage from the interior of the
inflatable structure to the atmosphere can compromise the integrity
and design of the inflatable structure. Thus, it would be desirable
to provide alternative and improved structures for removing or
sequestering residual gas inside an inflatable structure on a
vascular or other catheter prior to use. In particular, it would be
desirable if the apparatus and methods did not require significant
alteration in the structure of the balloon or other inflatable
structure on the catheter. Some of these objectives will be met by
the invention described herein below.
[0009] 2. Description of the Background Art
[0010] Vascular catheters having balloons with vent structures are
described in U.S. Pat. Nos. 4,638,805; 4,692,200; 4,715,378;
4,810,455; 4,821,722; 5,035,705; 5,049,130; 5,100,385; 5,176,698;
and 5,256,143.
BRIEF SUMMARY OF THE INVENTION
[0011] The present invention provides apparatus and methods for
purging gas from inflatable structures on intravascular and other
medical catheters while said structures are being primed with a
liquid inflation medium. While the inflatable structures will
typically be angioplasty balloons, stent delivery balloons,
elastomeric isolation balloons, embolectomy balloons, occlusion
balloons, and like, there may also be other inflatable structures
intended for distinct purposes. In particular, the purging
apparatus and methods of the present invention may find particular
use with inflatable structures intended for driving needles,
cutting blades, and other tools and implements intended for
intravascular and other therapeutic procedures.
[0012] In a first aspect of the present invention, an aspiration
baffle for purging gas from a liquid-filled chamber in a catheter
comprises a tubular member having a distal end, a proximal end, and
an interior volume extending between said ends. The tubular member
will be sealed over its entire surface except for a plurality of
"microholes." The microholes have dimensions selected to permit the
passage of gas under the differential pressures expected during the
priming process. Such selected dimensions, however, will also
inhibit or prevent the flow of liquid inflation medium through the
microholes under the both the priming pressures as well as the
inflation pressures expected during use of the catheter and
vasculature. In angioplasty procedures, such inflation pressures
can be as high as 10 atmospheres, 20 atmospheres, or even higher in
some circumstances. Particular dimensions for the microholes are
set forth below.
[0013] The tubular member of the aspiration baffle, will be adapted
to be disposed axially in the catheter so that the microholes are
present in the interior of the chamber which is first purged of gas
and later filled with liquid inflation medium. Thus, the microholes
will initially allow residual gas present in the inflatable chamber
after initial vacuum aspiration to pass into the interior of the
tubular member as a priming liquid is introduced, typically at
atmospheric pressure or higher. While the inflatable chamber is
being primed with the liquid inflation medium, the residual gas
will thus be able to pass into the interior of the tubular member
which remains at or close to the vacuum which had been achieved
during the initial vacuum step. Thus, the aspiration baffle acts as
a low-pressure reservoir or "sponge" for drawing and trapping the
residual gas volume present in the inflatable chamber after the
initial vacuum aspiration. The near-vacuum pressure is maintained
since the gas volume is very low and the entrance of liquid into
the interior of the tubular member (which liquid would quickly
relieve the vacuum) is prevented by the small size of the
microhole.
[0014] In a preferred construction, the aspiration baffle further
comprises a core wire or other interior structure to provide
mechanical strength. For example, the core wire may be coaxially
disposed within the interior volume of the tubular member, running
axially over at least a portion of the length of the tubular
member, usually over the entire length. The exterior surface of the
core wire and interior surface of the tubular member thus define an
annular flow path or volume for receiving the residual gas through
the microholes.
[0015] Typically, the tubular member will have a length in the
range 12 cm to 200 cm, often from 20 cm to 150 cm. The tubular
member will have an outside diameter usually in the range from 0.1
mm to 1 mm, and the microholes will have a maximum width, usually a
diameter in the case of circular microholes, in the range of 0.001
mm to 0.1 mm. The microholes may extend over the entire length of
the exterior of the tubular member, or may optionally extend over
only a portion of the length, e.g. in the range from 1 cm to 20 cm.
The microholes may be arranged axially in one or more rows, may be
arranged spirally, or may be arrange in any other random or regular
pattern. The number of microholes may range from 2 to 1,000,
typically being from 5 to 500. The core wire may extend the entire
length of the tubular member or, alternatively, may only extend
through a portion thereof, typically from 1 cm to 100 cm.
[0016] In a second aspect of the present invention, a catheter
comprises a catheter body having a proximal end, a distal end, and
an inflation lumen therethrough. An inflatable chamber is disposed
on the catheter body to receive inflation medium from the inflation
lumen, and an aspiration baffle is disposed in the catheter body.
The aspiration baffle defines a sealed interior volume open to an
interior of the inflatable chamber through a plurality of
microholes. Thus, by applying a vacuum to the interior of the
inflatable chamber, typically through the inflation lumen, the
interior volume of the aspiration baffle is initially evacuated to
a sub atmospheric pressure. After such initial evacuation, the
inflatable chamber is primed with a liquid inflation medium,
typically at atmospheric pressure or higher, such that residual gas
remaining after the initial evacuation passes from the inflatable
chamber into the interior volume of the aspiration tube.
[0017] Depending on the desired use, the inflatable chamber may be
an angioplasty balloon, may be adapted to carry an expandable
tubular prosthesis, such as a stent, graft, or the like, or may
carry a needle in order to effect extraluminal drug delivery.
Optionally, the catheter body may also include a guide wire lumen.
The aspiration lumen may optionally be held within yet another
lumen within the catheter body. In some embodiments, the additional
catheter body lumen may actually form part of the aspiration
baffle, e.g. an end of the tubular member may be opened into a
volume defined by the additional lumen in the catheter body. So
long as said additional lumen were otherwise sealed, the luminal
volume would then form part of the interior volume of the
aspiration baffle. Other aspects of the aspiration baffle forming
part of the catheter of the present invention have been described
above with respect to the aspiration baffle embodiments.
[0018] In a third aspect of the present invention, a method for
priming an inflatable chamber on a catheter with liquid comprises
drawing a vacuum in the chamber through an inflation lumen in the
catheter to remove gas from the chamber. Depending on the level of
vacuum which is drawn, a residual amount of gas will be left in the
inflatable chamber. The chamber is then filled or "primed" with a
liquid, typically the same liquid which will be used for inflating
the chamber during use. An aspiration baffle is disposed in the
catheter body such that microholes are in communication with the
interior of the inflatable chamber. The aspiration baffle is able
to draw and sequester at least a major portion of the residual air
or gas volume which remains in the inflatable chamber after the
initial vacuum aspiration step. Typically, the initial vacuum will
be drawn down to a pressure of about 15 mm Hg or lower, and the
inflatable chamber will then be filled with liquid at a pressure of
at least one atmosphere, and often two atmospheres or greater.
Particular aspects of the aspiration baffle used in these methods
are generally as described above in connection with the aspiration
baffle itself.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a perspective view of an aspiration baffle
constructed in accordance with the principles of the present
invention.
[0020] FIG. 2 is an enlarged distal end view of the aspiration
baffle of FIG. 1, shown in partial section.
[0021] FIGS. 3 and 4 are schematic illustrations showing the
difference in gas flow and liquid flow through a microhole of the
dimensions utilized in the aspiration baffles of the present
invention.
[0022] FIG. 5 is a schematic illustration of a balloon catheter
comprising an aspiration baffle in accordance with the principles
of the present invention.
[0023] FIGS. 6 and 7 are a cross-sectional and end views of a
needle injection catheter including an aspiration baffle in
accordance with the principles of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] An aspiration baffle 10 constructed in accordance with the
principles of the present invention comprises an outer tubular
member 12 and, optionally, an inner core wire 14 (FIGS. 1 and 2). A
plurality of microholes 16 are formed in the wall of the outer
tubular member 12, thus defining passages from a region exterior to
the aspiration baffle to an annular region 17 defined between an
exterior surface of the core wire 14 and an interior surface of the
outer tubular member 12 (FIG. 2). Core wire 14 is attached to the
outer tubular member, for example by a polymeric plug 21 formed in
a distal end 18 of the tubular member. A similar or alternative
plug 23 is also provided at the proximal end 19 of the tubular
member 12. Thus, the outer tubular member defines a completely
sealed environment in its interior which is open to the exterior
only through the microholes 16.
[0025] Note that while the tubular member 12 is shown in FIGS. 1
and 2 as being an integrated or self-contained unit, it is possible
to form portions of the aspiration tube from other portions of the
catheter into which it is to be placed. For example, the proximal
end 20 may be left opened and attached to an interior lumen,
receptacle, or other cavity or volume formed within the catheter
body itself. In the latter case, however, it is still necessary
that the cavity or volume provided in the catheter body be sealed
so that the only passages between the interior of the aspiration
baffle and the exterior (which is within the inflatable chamber on
the catheters described herein below) be the microholes.
[0026] Referring now to FIGS. 3 and 4 the microholes 16 will have
dimensions, generally as set forth above, which permit the flow of
a gas G (FIG. 3) from a high pressure region (P.sup.+) on one side
of the tubular member 12 to a low pressure region (P.sup.-) on the
other side of the member. Thus, the gas will flow in the direction
of the arrows shown in FIG. 3. In the case of a liquid L, however,
the dimensions of microholes 16 are selected so that flow is
inhibited at the differential pressure between regions P.sup.+and
P.sup.-, as shown in FIG. 4.
[0027] Referring now to FIG. 5, a catheter 20 having an inflatable
chamber in the form of a balloon 22 is schematically illustrated.
The catheter 20 has an inflation lumen 24, it is shown with an
optional inflation tube 26 which extends into the interior of the
balloon 22. An aspiration baffle 28, which may be identical to
baffle 10 illustrated above, it is disposed within the body of
catheter 20 so that the microholes 16 on the baffle 28 are disposed
within the interior of the balloon 22. The baffle 28 may extend
proximally within the catheter by selected distance, optionally the
entire distance of the catheter body. Optionally, as discussed
above, portions of the interior volume of the aspiration baffle 28
may be formed by lumens or other internal cavities of the body of
catheter 20.
[0028] The catheter 20 may be prepared for use in a patient as
follows. A conventional balloon catheter vacuum and inflation
device, such as those available from Guidant Corporation, Johnson
& Johnson, Boston Scientific, and the like, is used to first
draw a vacuum through the inflation lumen or tube 24/26 to a
desired low pressure, typically about 15 mm of Hg. After the
pressure has been achieved, the balloon 22 is then primed with
saline or other inflation medium to a conventional pressure,
typically one atmosphere, two atmospheres, or higher.
[0029] In the initial vacuum aspiration step, air or other gas from
the interior of the aspiration baffle 28 is withdrawn through the
microhole 16 together with the other air or gasses which are
present in the balloon 22. When the liquid inflation medium is
introduced into the balloon 22, however, the liquid is prevented
from entering the interior of aspiration baffle 28 as the flow
through individual microholes 16 is blocked, generally shown in
FIG. 4 above. Thus, even though the pressure within the balloon
quickly rises from vacuum to one atmosphere, two atmospheres, or
higher, the pressure within the aspiration baffle remains at the
near-vacuum level achieved during the initial vacuum aspiration
step. The presence of the vacuum allows the residual gas remaining
in the balloon 22 to migrate toward the microholes. When the gas
reaches individual microholes, the gas will pass into the interior
of the aspiration baffle, generally shown in FIG. 3 above, where it
will remain since the interior pressure of the baffle remains
significantly sub-atmospheric. Thus, during the priming step, at
least a major portion of the residual air or other gas within the
balloon will be collected and trapped within the interior of the
aspiration baffle. Moreover, so long as the interior of balloon 22
contains the priming medium or subsequent inflation medium, the
vacuum within the aspiration baffle will remain since liquid inflow
is inhibited and the gas is retained because of the differential
pressure, i.e. a vacuum within the interior of the baffle, an
atmospheric or higher pressure within the interior of the balloon
22. Even if the balloon 22 should burst during use, the escape of
gas through microhole 16 is still prevented since the blood which
could enter the burst balloon would still maintain the seal on the
microholes, thus preventing loss of hair or other gas.
[0030] Catheter 20 of FIG. 5 is representative of a variety of
balloon-type catheters, including angioplasty catheters, stent
delivery catheters, balloon isolation catheters, balloon occlusion
catheters, and the like. The aspiration tubes of the present
invention, however, may find use with any type of catheter having
an inflatable chamber which is to be inflated with a liquid
inflation medium. For example, the aspiration baffles will find
particular use with needle injection catheters such as those
described in co-pending application Ser. Nos. 10/421,997 (Attorney
Docket No. 21621-000510US) and 10/393,700 (Attorney Docket No.
21621-001500US), the full disclosures of which are incorporated
herein by reference. An exemplary needle catheter employing the
aspiration baffle of the present invention is illustrated in FIGS.
6 and 7. A catheter 40 comprises a structure 42 carrying a needle
44 within an involuted cavity 46 preformed within the catheter. The
involuted structure is formed from the catheter body itself and
includes a C-shaped inflatable interior 48 which receives an
inflation medium from an inflation lumen (not shown). According to
the present invention, the aspiration tube 16 may be provided
through the catheter body and extending into the inflatable
interior 48, as shown in FIG. 6. Thus, prior to inflation of the
device, as shown in FIG. 7, the aspiration baffle 16 may be used to
remove residual gasses during a priming procedure which may be
performed identically to that described in connection with FIG. 5
above.
* * * * *