U.S. patent application number 10/869978 was filed with the patent office on 2004-12-09 for implantable, refillable infusion device and septum replacement kit.
This patent application is currently assigned to Bard Access Systems, Inc.. Invention is credited to Burke, Paul F., Fine, Kenneth A..
Application Number | 20040249363 10/869978 |
Document ID | / |
Family ID | 23911409 |
Filed Date | 2004-12-09 |
United States Patent
Application |
20040249363 |
Kind Code |
A1 |
Burke, Paul F. ; et
al. |
December 9, 2004 |
Implantable, refillable infusion device and septum replacement
kit
Abstract
An implantable infusion device includes a lightweight, inert
housing which contains an infusate for administration to a patient,
and an enclosed, gas-impermeable variable volume chamber which
contains a pressure source, such as propellant, mechanical spring,
or the like. The variable volume chamber may be in the form of a
rigid-walled expandable bellows structure or a nonstretchable
flexible bag and is attached to the housing so as not to obstruct
the entry port for introduction of infusate. The infusate is
delivered from the device via a catheter in response to expansion
of the variable volume chamber against the volume of infusate in
the housing. A separate bolus injection port is provided which
allows infusate to be safely introduced directly into the catheter
and overrides the controlled pressure-driven delivery. The
lightweight housing may include integrally formed needle stops and
suture fastening loops.
Inventors: |
Burke, Paul F.; (Bellingam,
MA) ; Fine, Kenneth A.; (Sharon, MA) |
Correspondence
Address: |
James M. Hanifin, Jr.
600 Atlantic Avenue
Boston
MA
02210
US
|
Assignee: |
Bard Access Systems, Inc.
Salt Lake City
UT
|
Family ID: |
23911409 |
Appl. No.: |
10/869978 |
Filed: |
June 17, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10869978 |
Jun 17, 2004 |
|
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|
09481298 |
Jan 11, 2000 |
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6764472 |
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Current U.S.
Class: |
604/890.1 |
Current CPC
Class: |
A61M 5/14593 20130101;
A61M 5/14276 20130101; A61M 5/14586 20130101; A61M 2209/045
20130101 |
Class at
Publication: |
604/890.1 |
International
Class: |
A61K 009/22 |
Claims
1. An implantable infusion device, comprising: A. a housing having
(a) an annular portion with an inner wall defining an interior
region having a width dimension D and extending along a central
axis, (b) a bottom portion extending from said annular portion and
spanning a first end of said interior region, and (c) a top portion
extending from said annular portion and spanning a second end of
said interior region, said top portion being opposite said bottom
portion, wherein said interior region is substantially closed; and
B. a closed fluid-impermeable hollow bellows extending from one of
the top and bottom portions of the housing and defining a variable
volume region therein and having a plurality of serially coupled
annular members extending between top and bottom portions of the
bellows, wherein junctions of said coupled annular members are
coupled with flexures, said bellows having a maximum outer width
dimension D' where D' is less than D, wherein the portion of the
housing from which the bellows extends includes a substantially
planar annular peripheral portion disposed about a central portion,
wherein a pressure source is contained within said variable volume
region of said bellows, and wherein said bellows is disposed within
said interior region of said housing and rigidly coupled to said
portion of the housing from which the bellows extends, whereby said
annular members of said bellows are spaced apart from said annular
portion of said housing, wherein said housing includes a recharging
fluid flow path from points external to said housing to a region
adjacent to said central portion of said portion of said housing
from which the bellows extends, and wherein said housing further
defines a fluid exit flow path extending from the region between
said bellows and said annular portion of said housing to points
external to said housing.
2. An implantable infusion device according to claim 1, further
comprising a pierceable, self-sealing septum disposed in said
recharging fluid flow path.
3. An implantable infusion device according to claim 2, wherein the
septum is removable from the housing.
4. An implantable infusion device according to claim 1, further
comprising a recharging fluid reservoir disposed along said
recharging fluid flow path.
5. An implantable infusion device according to claim 1, further
comprising at least one of a flow restrictor and a filter disposed
along said fluid exit flow path.
6. An implantable infusion device according to claim 1, wherein
said housing is made of a gas-impermeable material.
7. An implantable infusion device according to claim 1, wherein the
pressure source comprises one or more of the group consisting of
multiple-phase fluids, springs, shape memory metal alloys, Belville
washers, and compressible materials.
8. An implantable infusion device according to claim 1, wherein a
multiple-phase fluid propellant is present in at least one of a
liquid phase and a gas phase within said variable volume region of
said bellows as a function of ambient temperature, wherein
conversion of the propellant from a liquid phase to a gas phase
increases the volume displaced by the bellows in the interior
region of the housing, thereby exerting a force on a fluid external
to said bellows in said housing so as to provide a substantially
constant flow rate of said fluid through said fluid exit flow
path.
9. An implantable infusion device according to claim 8, wherein
said propellant is disposed in said variable volume region of said
bellows at a pressure which is not less than atmospheric pressure
at ambient temperature.
10. An implantable infusion device according to claim 1, wherein
said bellows is made of a substantially rigid, gas-impermeable
material.
11. An implantable infusion device according to claim 1, wherein
said bellows is hermetically sealed.
12. An implantable infusion device according to claim 1, wherein
said central portion of said bellows is offset from the plane of
said annular peripheral portion of said bellows.
13. An implantable infusion device according to claim 12, wherein a
central region of said portion of said housing from which the
bellows extends is correspondingly offset from the plane of the
annular portion of the housing, wherein the offset central region
of the housing substantially nests within said offset central
portion of said bellows.
14. An implantable infusion device according to claim 1, wherein
the housing and bellows are cylindrical.
15. An implantable infusion device according to claim 1, further
comprising a separate bolus port in fluid communication with said
fluid exit flow path.
16. An implantable infusion device according to claim 15, further
comprising a pair of septa disposed in said bolus port, wherein the
septa are spaced apart to define a bolus reservoir therebetween,
wherein a delivery needle having an opening near the center of its
length is required to deliver infusate to the bolus reservoir.
17. An implantable infusion device according to claim 1, wherein
the bellows extends from the top portion of the housing.
18. An implantable infusion device according to claim 1, wherein
the bellows extends from the bottom portion of the housing.
19. An implantable infusion device, comprising: A. a housing having
(a) an annular portion with an inner wall defining an interior
region having a width dimension D and extending along a central
axis, (b) a bottom portion extending from said annular portion and
spanning a first end of said interior region, and (c) a top portion
extending from said annular portion and spanning a second end of
said interior region, said top portion being opposite said bottom
portion, wherein said interior region is substantially closed; and
B. a closed fluid-impermeable hollow bellows disposed about a
variable volume region and having a top member, a bottom member,
and a plurality of serially coupled annular members extending
therebetween, wherein junctions of said coupled annular members are
coupled with flexures, said bellows having a maximum outer width
dimension D' where D' is less than D, wherein at least one of said
top and bottom members includes a substantially planar annular
peripheral portion disposed about a central portion, wherein a
pressure source is contained within said variable volume region of
said bellows, and wherein said bellows is disposed within said
interior region of said housing with one of said top and bottom
members facing and rigidly coupled to a corresponding portion of
said housing, whereby said annular members of said bellows are
spaced apart from said annular portion of said housing, wherein
said housing includes a recharging fluid flow path from points
external to said housing to a region adjacent to said central
portion of one of said top and bottom members of said bellows, and
wherein the region of coupling between said housing and said
bellows defines a fluid dispersal flow path from said region
adjacent to said central portion of said coupled member of said
bellows to a region between said annular members of said bellows
and said annular portion of said housing, and wherein said housing
further defines a fluid exit flow path extending from the region
between said bellows and said annular portion of said housing to
points external to said housing.
20. An implantable infusion device according to claim 19, further
comprising a pierceable, self-sealing septum disposed in said
recharging fluid flow path.
21. An implantable infusion device according to claim 20, wherein
the septum is removable from the housing.
22. An implantable infusion device according to claim 19, further
comprising a recharging fluid reservoir disposed along said
recharging fluid flow path.
23. An implantable infusion device according to claim 19, further
including at least one of a flow restrictor and a filter disposed
along said fluid exit flow path.
24. An implantable infusion device according to claim 19, wherein
said housing is made of a gas-impermeable material.
25. An implantable infusion device according to claim 19, wherein
the pressure source comprises one or more of the group consisting
of multiple-phase fluids, springs, shape memory metal alloys,
Belville washers, and compressible materials.
26. An implantable infusion device according to claim 19, wherein a
multiple-phase fluid propellant is present in at least one of a
liquid phase and a gas phase within said variable volume region of
said bellows as a function of ambient temperature, wherein
conversion of the propellant from a liquid phase to a gas phase
increases the volume displaced by the bellows in the interior
region of the housing, thereby exerting a force on a fluid external
to said bellows in said housing so as to provide a substantially
constant flow rate of said fluid through said fluid exit flow
path.
27. An implantable infusion device according to claim 26, wherein
said propellant is disposed in said variable volume region of said
bellows at a pressure which is not less than atmospheric pressure
at ambient temperature.
28. An implantable infusion device according to claim 19, wherein
said bellows is made of a substantially rigid, gas-impermeable
material.
29. An implantable infusion device according to claim 19, wherein
said bellows is hermetically sealed.
30. An implantable infusion device according to claim 19, wherein
said central portion of at least one of the top and bottom members
of said bellows is offset from the plane of said annular peripheral
portion of said top and bottom members of said bellows.
31. An implantable infusion device according to claim 30, wherein a
central region of said portion of said housing coupled to the
bellows is correspondingly offset from the plane of the annular
portion of the housing, wherein the offset central region of said
portion of the housing coupled to the bellows substantially nests
within said central portion of the coupled portion of said
bellows.
32. An implantable infusion device according to claim 19, wherein
the bellows is coupled to the top portion of the housing.
33. An implantable infusion device according to claim 19, wherein
the bellows is coupled to the bottom portion of the housing.
34. An implantable infusion device according to claim 19, wherein
the fluid dispersal flow path includes regions of increased surface
contact area in the coupled region between the housing and the
bellows.
35. An implantable infusion device according to claim 19, wherein
the housing and bellows are cylindrical.
36. An implantable infusion device according to claim 19, further
comprising a separate bolus port in fluid communication with said
fluid exit flow path.
37. An implantable infusion device according to claim 36, further
comprising a pair of septa disposed in said bolus port, wherein the
septa ape spaced apart to define a bolus reservoir therebetween,
wherein a delivery needle having an opening near the center of its
length is required to deliver infusate to the bolus reservoir.
38. An implantable infusion device, comprising: A. a housing having
(a) an annular portion with an inner wall defining an interior
region having a width dimension D and extending along a central
axis, (b) a bottom portion extending from said annular portion and
spanning a first end of said interior region, and (c) a top portion
extending from said annular portion and spanning a second end of
said interior region, said top portion being opposite said bottom
portion, wherein said interior region is substantially closed; B. a
closed fluid-impermeable hollow bellows extending from one of the
top and bottom portions of the housing and defining a variable
volume- region therein and having a plurality of serially coupled
annular members extending between top and bottom portions of the
bellows, wherein junctions of said coupled annular members are
coupled with flexures, said bellows having a maximum outer width
dimension D' where D' is less than D, wherein the portion of the
housing from which the bellows extends includes a substantially
planar annular peripheral portion disposed about a central portion,
wherein a pressure source is contained within said variable volume
region of said bellows, and wherein said bellows is disposed within
said interior region of said housing and rigidly coupled to said
portion of the housing from which the bellows extends, whereby said
annular members of said bellows are spaced apart from said annular
portion of said housing, wherein said housing includes a recharging
fluid flow path from points external to said housing to a region
adjacent to said central portion of said portion of said housing
from which the bellows extends, and wherein said housing further
defines a fluid exit flow path extending from the region between
said bellows and said annular portion of said housing to points
external to said housing; and C. a separate bolus port in fluid
communication with said fluid exit flow path, wherein said bolus
port includes a pair of septa disposed therein and spaced apart to
define a bolus reservoir therebetween, wherein a delivery needle
having an opening near the center of its length is required to
deliver infusate to the bolus reservoir.
39. An implantable infusion device, comprising: A. a housing having
(a) an annular portion with an inner wall defining an interior
region having a width dimension D and extending along a central
axis, (b) a bottom portion extending from said annular portion and
spanning a first end of said interior region, and (c) a top portion
extending from said annular portion and spanning a second end of
said interior region, said top portion being opposite said bottom
portion, wherein said interior region is substantially closed; B. a
closed fluid-impermeable hollow bellows disposed about a variable
volume region and having a top member, a bottom member, and a
plurality of serially coupled annular members extending
therebetween, wherein junctions of said coupled annular members are
coupled with flexures, said bellows having a maximum outer width
dimension D' where D' is less than D, wherein at least one of said
top and bottom members includes a substantially planar annular
peripheral portion disposed about a central portion, wherein a
pressure source is contained within said variable volume region of
said bellows, and wherein said bellows is disposed within said
interior region of said housing with one of said top and bottom
members facing and rigidly coupled to a corresponding portion of
said housing, whereby said annular members of said bellows are
spaced apart from said annular portion of said housing, wherein
said housing includes a recharging fluid flow path from points
external to said housing to a region adjacent to said central
portion of one of said top and bottom members of said bellows, and
wherein the region of coupling between said housing and said
bellows defines a fluid dispersal flow path from said region
adjacent to said central portion of said coupled member of said
bellows to a region between said annular members of said bellows
and said annular portion of said housing, and wherein said housing
further defines a fluid exit flow path extending from the region
between said bellows and said annular portion of said housing to
points external to said housing; and C. a separate bolus port in
fluid communication with said fluid exit flow path, wherein said
bolus port includes a pair of septa disposed therein and spaced
apart to define a bolus reservoir therebetween, wherein a delivery
needle having an opening near the center of its length is required
to deliver infusate to the bolus reservoir.
40. A septum replacement kit for an enclosed device which is sealed
with a septum, wherein the enclosed device defines a fluid
reservoir, a fluid flow inlet and a fluid flow outlet, the kit
comprising: a compressible septum adapted to sealingly engage in
the fluid flow inlet of the reservoir; and a septum installation
tool adapted to compress the septum to a nominal insertion size,
maintain said nominal insertion size of said septum prior to
installation of the septum, and install the septum in the fluid
flow inlet of the reservoir.
41. A septum replacement kit according to claim 40, wherein the
septum installation tool comprises a tubular member adapted for
insertion into the fluid flow inlet of the reservoir, an opening in
the tubular member for insertion and retention of said septum
therein, and a plunger member disposable in said tubular member for
expulsion of said septum from the tubular member, wherein insertion
of the septum into the tubular member compresses the septum, and
wherein expulsion of the septum from the tubular member into the
fluid inlet reservoir permits the septum to expand to fill in and
seal the fluid inlet reservoir.
42. A septum replacement kit according to claim 40, wherein the
septum is made of a self-sealing elastomeric material.
Description
[0001] This application is a continuation of U.S. application Ser.
No. 09/481,298, filed Jan. 11, 2000, now pending.
TECHNICAL FIELD
[0002] The invention relates to implantable infusion devices for
controllable in vivo delivery of drugs to a patient.
BACKGROUND OF THE INVENTION
[0003] Implantable infusion devices provide a patient with an in
vivo source of a drug to be administered, in a device which permits
controlled delivery of the drug over a predetermined time period.
Certain drugs, such as, for example, chemotherapy drugs and
opioids, may be most effective if administered at a constant dose
rate, instead of at discrete intervals.
[0004] A typical infusion device or pump includes a hermetically
sealed outer housing which holds a vapor pressure fluid or other
means for exerting a compressive force on a compressible or
flexible inner drug reservoir which communicates with a drug
delivery port. Alternatively, the drug may be disposed in the outer
housing, with a propellant disposed in the inner housing. When the
outer housing is filled with the drug, the propellant in the inner
housing is compressed and changes state from a vapor to a liquid,
thereby recharging the driving mechanism of the device. In still
other embodiments, the outer housing may be divided into two
chambers separated by a liquid-impermeable diaphragm. One chamber
contains the drug and includes a drug delivery port, and the other
chamber contains a propellant or spring member for exerting a force
against the diaphragm so as to expel the drug through the delivery
port.
[0005] The infusion device must meet numerous requirements for
safety and efficacy. For example, the housing material must not
react with body fluids or with the drugs and propellants inside the
housing. Further, the membrane or flexible barrier between the
chambers must not leak and must be impermeable to gas-phase fluids
so as to prevent contamination of the drug with the propellant.
Since the device is designed for implantation into a patient, great
care must be taken to prevent any leakage of either the drug or the
propellant into the patient's body. In addition, the device is
desirably as small and lightweight as possible so as to cause
minimum invasive trauma, discomfort and disfigurement to the
patient, yet sufficiently large to provide a useful therapeutic
dosage of the drug being administered and minimize the frequency
with which the device must be recharged. It is desirable to make
the pump refillable so that it need not be surgically removed and
replaced when the drug is depleted. However, refillability of the
pump requires a port which is either outside of the skin or
transcutaneously accessible without introducing infection or
risking the release of an excessive and potentially harmful amount
of the drug into the patient. Also, in those devices in which a
propellant is contained within a flexible bag which expands and
contracts in response to changes in the propellant pressure, it is
necessary to ensure that introduction of the drug to the drug
reservoir surrounding the propellant bag is not impeded by the
presence and location of the bag in the reservoir and/or does not
puncture or pinch the bag. Thus, it may be necessary to affix the
propellant chamber or bag to the housing so as to avoid such
problems. There is the additional problem of ensuring that the drug
reservoir can be fully depleted and refilled, for optimum
efficiency of the device.
[0006] Administration of a desired dosage of a drug over a period
of time may require a controllable, constant flow of the drug from
the device. However, as the drug is depleted from the reservoir, or
if the force exerted on the drug reservoir cannot be controlled, a
constant dose rate may be difficult to sustain.
[0007] U.S. Pat. No. 3,840,009 to Michaels et al. discloses a vapor
pressure drug delivery device which has two chambers separated by a
flexible wall or bladder. The outer chamber contains a drug to be
administered to a patient, and the inner chamber contains a
pressure fluid which expands to conform to the shape of the outer
chamber, thereby enabling expulsion of substantially all of the
drug within the outer chamber. The pressure fluid is maintained at
a positive pressure at the temperature at which the device is used,
so that no external power source is required.
[0008] U.S. Pat. No. 5,167,633 to Mann et al. discloses a
medication infusion pump in which a constant pressure is exerted on
a liquid medication to be administered. The pump includes a
pressure reservoir in the form of a hollow enclosure with at least
one flexible wall for containing a pressure fluid. The medication
to be administered is outside of the pressure reservoir. The
pressure fluid undergoes a phase change from a liquid to a vapor so
as to expel the drug from the pump. The Mann et al. device is
maintained at a negative pressure at the temperature of use to
avoid leakage of medication from the pump into the patient.
[0009] U.S. Pat. No. 5,514,103 to Srisathapat et al. discloses a
medication infusion pump including a drug reservoir and a pressure
fluid reservoir which are separated by a movable wall or flexible
bag. The pressure fluid reservoir includes a spacer therein to
prevent contraction of the pressure fluid reservoir below a minimum
volume which is slightly greater than the liquid phase volume of
the pressure fluid, so that a portion of the pressure fluid always
remains in a vapor phase. As a result, even when the drug reservoir
is completely filled, the pressure fluid is not entirely in the
liquid phase. Thus, additional energy to reinstate a vapor phase is
not required.
[0010] U.S. Pat. No. 3,951,147 to Tucker et al. discloses a
refillable implantable infusate pump in which a bellows containing
a drug is contained within a housing which is filled with a
pressure fluid or propellant. The Tucker et al. pump includes a
filtering chamber to ensure removal of debris from the infusate
drug prior to its delivery to the patient.
[0011] U.S. Pat. No. 5,045,064 to Idriss discloses a constant
pressure implantable pump which employs shape-memory metal bands
around a reservoir containing a fluid to be infused. The bands
compress the reservoir containing the fluid to be infused, thereby
eliminating the need for a propellant.
[0012] U.S. Pat. No. 5,395,324 to Hinrichs et al. discloses an
infusion pump having a primary entry port leading to a drug
reservoir, a separate bolus port leading to a bolus chamber, and
means for ensuring that the bolus chamber is not inadvertently
filled with the drug intended for the primary drug reservoir.
[0013] U.S. Pat. No. 5,769,823 to Otto discloses an implantable
infusion pump which comprises a plastic housing, a bellows chamber
enclosing a propellant, and two separate resilient plastic bags
enclosing an infusate. The bags are surrounded by glycerin or the
like which binds with any propellant passing through the bellows
wall into the housing, thereby preventing passage of the propellant
through the housing into the patient.
[0014] U.S. Pat. No. 5,575,770 to Melsky et al. discloses an
implantable infusion pump having a valve-actuated bolus delivery
chamber. Inadvertent administration of an overdose to the patient
through the bolus delivery chamber is prevented by a design which
requires the use of a side-access delivery needle, which is
inserted through a pair of septa which are spaced apart to define a
bolus chamber. The tip of the needle extends beyond the lower
septum and depresses a lever to actuate the normally-closed valve.
The side opening of the needle is disposed between the septa in the
bolus chamber for delivery of the bolus dose to the bolus chamber.
The design prevents erroneous dose delivery by requiring the
simultaneous opening of the valve with delivery of the drug into
the bolus using a side-access delivery needle.
[0015] It would be advantageous to provide an implantable infusion
pump which is of simple construction and operation, made of
lightweight materials, inexpensive to manufacture, efficient in the
delivery of medicine, and easy to refill.
SUMMARY OF THE INVENTION
[0016] According to one aspect of the invention, there is provided
an implantable infusion device, comprising a housing having an
annular portion with an inner wall defining an interior region
having a width dimension ID and extending along a central axis, a
bottom portion extending from the annular portion and spanning a
first end of the interior region, and a top portion extending from
the annular portion and spanning a second end of the interior
region and being opposite the bottom portion, the interior region
being substantially closed. The device further includes a closed
fluid-impermeable hollow bellows extending from one of the top and
bottom portions of the housing and defining a variable volume
region therein and having a plurality of serially coupled annular
members extending between top and bottom portions of the bellows.
Junctions of the coupled annular members are coupled with flexures.
The bellows has a maximum outer width dimension D' where D' is less
than D. The portion of the housing from which the bellows extends
includes a substantially planar annular peripheral portion disposed
about a central portion. A pressure source is contained within the
variable volume region of the bellows. The bellows is disposed
within the interior region of the housing and rigidly coupled to
the portion of the housing from which it extends. The annular
members, of the bellows are spaced apart from the annular portion
of the housing. The housing includes a recharging fluid flow path
from points external to the housing to a region adjacent to the
central portion of the portion of the housing from which the
bellows extends. The housing further defines a fluid exit flow path
extending from the region between the bellows and the annular
portion of the housing to points external to the housing.
[0017] The device further includes a pierceable, self-sealing
septum disposed in the recharging fluid flow path and may further
include a recharging fluid reservoir disposed along the recharging
fluid flow path. The septum may be removable from the housing.
[0018] The device further includes at least one of a flow
restrictor and a filter disposed along the fluid exit flow
path.
[0019] In one embodiment, the housing is made of a gas-impermeable
material, and the bellows which encloses the pressure source is
made of a substantially rigid, gas-impermeable material. In a
preferred embodiment, the bellows is hermetically sealed.
[0020] The pressure source comprises one or more of the group
consisting of multiple-phase fluids, springs, shape memory metal
alloys, Belville washers, and compressible materials. In one
embodiment, a multiple-phase fluid propellant is present in at
least one of a liquid phase and a gas phase within the variable
volume region of the bellows as a function of ambient temperature.
Conversion of the propellant fluid from a liquid phase to a gas
phase increases the volume displaced by the bellows in the interior
region of the housing, thereby exerting a force on a fluid external
to the bellows in the housing so as to provide a substantially
constant flow rate of the fluid through the fluid exit flow
path.
[0021] In a preferred embodiment, the propellant is disposed in the
variable volume region of the bellows at a pressure which is not
less than atmospheric pressure at ambient temperature.
[0022] In one embodiment, the central portion of the bellows is
offset from the plane of the annular peripheral portion of said
bellows. A central region of the portion of the housing from which
the bellows extends is correspondingly offset from the plane of the
annular portion of the housing. The offset central region of the
housing substantially nests within the offset central portion of
the bellows.
[0023] In one embodiment, the housing and bellows are
cylindrical.
[0024] The device can further include a separate bolus port in
fluid communication with the fluid exit flow path. The bolus port
can include a pair of septa which are spaced apart to define a
bolus reservoir therebetween. A side-access delivery needle having
an opening near the center of its length is required to delivery a
bolus dose of the infusate to the bolus reservoir.
[0025] In one preferred embodiment, the bellows extends from the
top portion of the housing. In another preferred embodiment, the
bellows extends from the bottom portion of the housing.
[0026] According to another aspect of the invention, there is
provided an implantable infusion device, comprising a housing
having an annular portion with an inner wall defining an interior
region having a width dimension D and extending along a central
axis, a bottom portion extending from the annular portion and
spanning a first end of the interior region, and a top portion
extending from the annular portion and spanning a second end of the
interior region, the top portion being opposite the bottom portion,
the interior region being substantially closed. The device further
includes a closed fluid-impermeable hollow bellows disposed about a
variable volume region and having a top member, a bottom member,
and a plurality of serially coupled annular members extending
therebetween. Junctions of the coupled annular members are coupled
with flexures. The bellows has a maximum outer width dimension D'
where D' is less than D. At least one of the top and bottom members
includes a substantially planar annular peripheral portion disposed
about a central portion. A pressure source is contained within the
variable volume region of the bellows, and the bellows is disposed
within the interior region of the housing with one of the top and
bottom members facing and rigidly coupled to a corresponding
portion of the housing. The annular members of the bellows are
spaced apart from the annular portion of the housing. The housing
includes a recharging fluid flow path from points external to the
housing to a region adjacent to the central portion of one of the
top and bottom members of the bellows. The region of coupling
between the housing and the bellows defines a fluid dispersal flow
path from the region adjacent to the central portion of the coupled
member of the bellows to a region between the annular members of
the bellows and the annular portion of the housing. The housing
further defines a fluid exit flow path extending from the region
between the bellows and the annular portion of the housing to
points external to the housing.
[0027] In one embodiment, a central portion of at least one of the
top and bottom members of the bellows is offset from the plane of
the annular peripheral portion of the top and bottom members of the
bellows. A central region of the portion of the housing which is
coupled to the bellows is correspondingly offset from the plane of
the annular portion of the housing, so that the offset central
region of the portion of the housing which is coupled to the
bellows nests within the central portion of the coupled portion of
the bellows.
[0028] In one preferred embodiment, the bellows is coupled to the
top portion of the housing. In another preferred embodiment, the
bellows is coupled to the bottom portion of the housing.
[0029] According to still another aspect of the invention, there is
provided a septum replacement kit for an enclosed device which is
sealed with a septum, wherein the enclosed device defines a fluid
reservoir, a fluid flow inlet and a fluid flow outlet. The kit
comprises a compressible septum adapted to sealingly engage in the
fluid flow inlet of the reservoir, and a septum installation tool
adapted to compress the septum to a nominal insertion size,
maintain the nominal insertion size of the septum prior to
installation of the septum, and install the septum in the fluid
flow inlet of the reservoir.
[0030] The septum installation tool preferably comprises a tubular
member adapted for insertion into the fluid flow inlet of the
reservoir, an opening in the tubular member for insertion and
retention of the septum therein, and a plunger member disposable in
the tubular member for expulsion of the septum from the tubular
member. Insertion of the septum into the tubular member compresses
the septum. Expulsion of the septum from the tubular member into
the fluid inlet reservoir permits the septum to expand to fill in
and seal the fluid inlet reservoir.
[0031] The septum is preferably made of a pierceable, self-sealing
elastomeric or rubber-like material.
[0032] These and other objects and advantages of the invention will
in part be obvious and will in part appear hereinafter. The
invention accordingly comprises the apparatus possessing the
construction, combination of elements and arrangement of parts
which are exemplified in the following detailed disclosure, the
scope of which will be indicated in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] For a fuller understanding of the nature and objects of the
present invention, reference should be made to the following
detailed description taken in connection with the accompanying
drawings, in which:
[0034] FIG. 1 is a perspective view of an infusion device according
to the invention;
[0035] FIG. 2 is a schematic diagram of the device which
illustrates its structure and principles of operation;
[0036] FIG. 3 is a sagittal view of the device of FIG. 1;
[0037] FIG. 4 is a sagittal view of an alternate design of the
device, in which the sideport bolus port is located at an angle on
a peripheral edge of the device;
[0038] FIG. 5 is a sagittal view of a replaceable septum in a
device according to the present invention;
[0039] FIGS. 6A-6C illustrate a septum replacement kit and the
steps for installing a replacement septum with a septum replacement
tool; and
[0040] FIGS. 7A-7B illustrate a bolus port safety feature which
prevents inadvertent administration of an overdose of drug to the
patient through the bolus injection port.
[0041] Like features in the drawings are indicated with like
numerals.
DETAILED DESCRIPTION OF THE DRAWINGS
[0042] The infusion device of the present invention combines
several features known in the art in a novel and unobvious way. The
device has a relatively low profile, as shown in FIGS. 1, 3 and 4,
and is remarkable in several aspects. First, the device can be
housed in a lightweight, biologically inert material which need not
be hermetically sealed. This is because, unlike most prior art
infusion devices, the pressure source in the claimed device, which
can be a propellant fluid, a mechanical spring or the like, or a
combination of such elements, is contained in a separate enclosed
container within the housing of the device, and the infusate, or
drug to be administered, is outside the container containing the
pressure source.
[0043] The container for the pressure source ideally is in the form
of a variable volume container, such as a metal bellows or a
flexible bag or envelope. However, unlike an expandable balloon
bag, the variable volume container has a defined maximum and
minimum volume. The infusate is administered to the patient from
the device upon expansion of the variable volume container within
the interior region of the housing until the variable volume
container effectively fills the interior volume of the housing, at
which point the infusate is substantially depleted.
[0044] The device can also be transcutaneously recharged with
infusate without requiring that the device be removed from the
patient. Recharging the infusate effectively recharges the pressure
source by compressing the variable volume container to its minimum
volume and creating pressure which is used to expel the infusate
from the device.
[0045] The device also includes a separate bolus injection port for
introduction of a bolus dose to the patient which bypasses the
pressure source-driven delivery of the infusate from the principal
reservoir of the device. Pierceable, self-sealing septa through
which infusate can be injected into the device are located in the
primary and bolus ports of the device for convenient introduction
and containment of infusate and bolus injections.
[0046] In addition, because the housing can be made of a
lightweight material, such as plastic, many features, such as fluid
flow channels, compartments, needle stops and suture loops, can be
integrated into the housing during its manufacture, which can be
accomplished by molding or other low-cost, high-volume
manufacturing processes.
[0047] FIG. 1 shows a perspective view of the infusion device 10
according to the invention. FIG. 2 illustrates in schematic form
the basic structure and principle of operation of the device. FIG.
3 is a detailed sectional view of the device of FIG. 1 along a
sagittal (vertical longitudinal) axis. FIG. 4 is a sagittal view of
an alternate design of the device, in which the side bolus port is
located at an angle from a top edge of the device. FIG. 5 is a
sagittal view of a replaceable septum for the device. FIGS. 6A-6C
illustrate a septum replacement kit and a method of using it to
remove a worn septum and replace it with a fresh septum. FIGS.
7A-7B illustrate a bolus safety feature which prevents the
inadvertent administration of a principal dose of the drug to be
infused through the bolus injection port.
[0048] The device 10 is contained within a housing 12 made of a
lightweight, durable, and biologically inert material, such as
plastic. The housing is conveniently formed of an upper housing 12a
and a lower housing 12b, which are joined with an o-ring 14 between
them to create a fluid-impermeable seal. The halves of the housing
can be joined by, for example, ultrasonic or thermal welding,
solvent bonding, or other adhesive-based bonding.
[0049] The housing of the device defines an interior region which
forms a principal reservoir 16 for the infusate 18, which is
typically a drug to be administered over a period of time at a
constant low dose to a patient into which the device has been
surgically implanted. The infusate is introduced into the principal
reservoir via a principal entry port 20, which is sealed with a
pierceable, self-sealing septum 22. The infusate is delivered from
the principal reservoir to a catheter 24 via exit flow path 25,
which may contain at least one of a filter 26 and a flow restrictor
28.
[0050] In one preferred embodiment of the invention, the device can
include a separate restrictor chamber in the upper half 12a. This
separate restrictor chamber permits the use of interchangeable
restrictors for establishing different infusate flow rates.
[0051] Delivery of the infusate from the principal reservoir is
driven by a pressure source P contained within a variable volume
enclosed chamber 30, which may be attached to the housing,
preferably to the upper housing 12a, as detailed more fully below.
The pressure source may be a multiple-phase fluid which expands
from a liquid phase to a gas phase with increasing temperature,
thereby increasing in volume and pushing against the walls of the
variable volume container to enlarge it, thereby decreasing the
volume of the principal reservoir 16 and expelling the infusate
therein from the device. Alternatively, the pressure source can be
a mechanical device, such as a spring or other compressible member,
or a shape-memory metal alloy. A combination of a propellant fluid
and a compressible mechanical member may also be used to obtain a
desired infusate delivery rate from the device. The mechanical
member may, but need not, exert a constant force throughout its
stoke range.
[0052] If a propellant fluid is used as the pressure source within
the variable volume chamber, it is desirable to have the minimum
volume of the chamber be greater than the liquid volume of the
propellant fluid, so that the propellant fluid must always exist in
the chamber in both liquid and gas phases. In addition, it is
desirable to select a propellant fluid which is at a pressure of
not less than one atmosphere at ambient temperature, so that at the
temperature of use (typically nominal body temperature of the
patient) the propellant is at a pressure which is even higher than
one atmosphere of pressure. This allows the surgeon to prime and
operate the device at ambient temperature in order to verify its
performance prior to implantation of the device in the patient,
thereby eliminating the need to warm the device and the infusate to
body temperature. In addition, such a positive pressure device
eliminates the risk that outside air or gases will be drawn into
the device during storage of the device.
[0053] The inert plastic housing containing the infusate 12 may,
but need not, be hermetically sealed. The housing, if made of a
moldable or easily formed material, may include, for example,
integrally formed needle stops 32, 34 for the primary and bolus
injection sites, as well as one or more integrally formed suture
loops 36 for passage of anchoring sutures therethrough.
[0054] The variable volume chamber 30 is desirably a substantially
rigid, gas-impermeable bellows structure, as illustrated in FIGS. 3
and 4, or other similar rigid-walled or spring-driven structure
which occupies a volume which approximates the volume of the
principal reservoir 16. Preferred materials for the bellows chamber
include metals and plastics. An important feature of the variable
volume chamber is its width dimension or diameter D' relative to
the diameter D of the housing. It is necessary to have D' be less
than D, so that the bellows walls are spaced from the housing
walls, but only by so much as will allow the bellows walls to move
freely within the housing. It is desirable to have the bellows
walls as close as possible to the housing walls so that maximum
displacement of infusate can be achieved by movement of the bellows
in the reservoir. However, drag of the bellows walls on the housing
walls must be avoided. Thus, it is desirable to have the variable
volume chamber centered in the principal reservoir for maximum
volume and avoidance of drag and so that the distance D-D' is
sufficient to avoid such drag.
[0055] Although the device and bellows are illustrated as
cylindrical in a preferred embodiment, they may have any convenient
shape.
[0056] Another important consideration is that the variable volume
chamber must not be located so that it obstructs the principal
entry port for infusate when the principal reservoir is empty and
the variable volume chamber is at its maximum volume. In a
preferred embodiment, the variable volume chamber 30 may be
attached to the housing so as to define a fluid flow path between
the variable volume chamber and the housing. Alternatively, the
chamber 30 and housing 12 may be designed to share a common wall
which may be channeled to provide fluid flow paths along the
interface between the housing and the chamber 30. In still another
alternate embodiment, the bellows may be freely located in the
interior region of the housing. In this embodiment, the free
bellows is desirably held away from the infusate entry port by
standoffs extending from the bellows or from the infusate entry
port.
[0057] To ensure as low a profile as possible for the device, it is
desirable to construct the housing so that the central portion of
one or both of its top and bottom portions, along with
corresponding central portions of the top and bottom members of the
bellows, is offset or depressed from the nominal plane of the
central portions as shown in FIGS. 3 and 4 to form a nested
structure. The infusate entry port nests within a recessed central
portion of the bellows. Although only the top portions of the
housing and bellows are shown as nested in FIGS. 3 and 4, the
bottom portions of the housing and bellows could also be nested to
further reduce the height of the device. Reductions in the volume
of the infusate chamber 30 reduce the amount of infusate that can
be administered and increase the frequency with which the chamber
30 must be recharged if drug delivery is to take place over an
extended period. However, the pressure source can be selected so as
to maximize delivery from a given volume.
[0058] The device includes a separate bolus injection port 38,
which includes a bolus entry port 40 sealed with a pierceable,
self-sealing septum 42, and leading to a bolus reservoir 44, which
is in fluid communication with the fluid exit flow path 25 and
delivery catheter 24, yet downstream of the filter 26 and flow
restrictor 28. Infusate introduced into the bolus port goes
directly into the delivery catheter and bypasses the controlled
release provided by the action of the pressure source and variable
volume chamber on the infusate in the principal reservoir.
[0059] Both the principal infusate entry port and the bolus
injection port may include sensing devices known in the art which
assist the patient and medical staff in locating the devices
transdermally so that additional infusate can be introduced to the
device without the need for external palpation or surgical removal
of the device.
[0060] The life of an implantable infusion device such as those
described herein is determined in large part by the life of the
septum through which the infusate is introduced. Use of a
self-sealing material, such as an elastomer, silicone rubber or
similar material, for the septum allows the septum to reseal after
it has been pierced with a needle. However, even self-sealing
materials lose some elasticity after a certain number of uses and
must be replaced to ensure that no infusate leaks out of the
device.
[0061] Septum life, and thus infusion device life, can be optimized
by careful selection of the septum material and the dimensions of
the septum and the septum chamber in the device. This is shown in
FIG. 5. The ratio of the opening dimension of the septum chamber
(B) to the width of the septum chamber (A) must be such that the
entire septum volume can fit within the chamber opening B when the
septum is compressed, and such that the chamber width A adequately
compresses the septum to provide satisfactory puncture life. The
selection of a material for the septum is also an important
consideration, as its hardness, as measured by a durometer, must
allow for adequate compression of the septum during insertion
without comprising puncture life. The height of the septum chamber
(C) must be sufficient to permit the compressed septum to fill the
chamber and still be sufficiently axially compressed to achieve the
desired puncture life.
[0062] A septum replacement kit allows the surgeon to replace a
worn septum without surgically removing the device from the
patient. Such a kit is illustrated in FIGS. 6A-6C. FIG. 6A shows a
septum 22, which is typically in the form of a cylindrical or
square plug of height H and width W. The septum is preferably made
of a compressible, resilient, penetrable, self-sealing material,
such as a rubber or elastomer. FIG. 6B shows the septum lodged in a
tubular member 46, which is sized to fit into the entry port 20,
having width B, of the infusion device 12. The septum is easily
compressed sufficiently to be lodged into the tubular member 46,
and a plunger 48 is used to dislodge the septum from the tubular
member into the septum chamber 50, which has width A and height C,
after it is inserted into the entry port 20, as shown in FIG. 6C.
The septum is radially compressed in the chamber to form a
penetrable seal. The plunger and tubular member can then be
withdrawn.
[0063] Removal of a worn septum can be accomplished by inserting a
sharp instrument into the septum to cut it into sections that can
then be removed from the septum chamber with tweezers or other
suitable instrument.
[0064] Although the FIGS. illustrate use of the septum replacement
kit for replacing the primary septum 22, the kit can also be used
to replace the bolus septum 42 in the bolus injection port 40.
[0065] In addition, the device may include safety filling devices
known in the art to ensure that the patient and medical staff can
distinguish between the primary entry port and the bolus injection
port so as to avoid inadvertent administration of relatively large
doses intended to be administered over time to the patient. When an
implanted infusion pump is to be refilled, it may be difficult to
determine whether a refill needle is positioned to enter the
principal infusate port or the bolus port. Entry of the refill
needle into the wrong port for the dose being administered can
result in a patient receiving an excessive dose of the drug and
therefore must be prevented.
[0066] A bolus safety feature in accordance with the present
invention is shown and described in connection with FIGS. 7A-7B.
FIG. 7A illustrates the two infusate ports in a typical implantable
infusion pump according to the invention. The device includes a
principal, or center, access port (1) for administration of
infusate into the device, and a bolus access port (2) for
administration of a bolus injection directly to the patient. The
center access port (1) includes a single septum, below which is
disposed an infusate reservoir R. To fill the center access port
(1), a refill needle having a hole in the tip, as shown in (1), is
required.
[0067] In contrast, the side bolus access port (2) includes two
septa which are spaced apart to define an infusate reservoir R
between them. The top septum in the bolus access port (2) secures
the delivery needle in place and provides a seal to prevent leakage
of the bolus dose once the needle is removed from the bolus port.
The bottom septum blocks the opening in the tip of a standard
refill needle, shown in (1), should such a needle be inserted into
the bolus port. Only a special needle with a side-access opening
near the center of its length, as shown in (2), instead of at or
near the tip, as shown in (1), can be used to fill the bolus
port.
[0068] FIG. 7B shows the result of using a standard delivery needle
in the bolus port. The standard delivery needle includes an opening
at its tip and no opening in the side. The opening in the tip will
be blocked by the lower septum when the needle is inserted into the
bolus port, and no infusate will be delivered.
[0069] This design of the center and bolus ports in the device of
the invention ensures that no bolus dose can be administered
inadvertently to a patient, because only a bolus (side-access
opening) needle can be used in the bolus port. If a standard
delivery needle is accidentally inserted into the bolus port, no
infusate can be delivered, and the surgeon can see immediately that
the wrong needle is being toed, without administering any harmful
dose to the patient.
[0070] Because certain changes may be made in the above apparatus
without departing from the scope of the invention herein disclosed,
it is intended that all matter contained in the above description
or shown in the accompanying drawings shall be interpreted in an
illustrative and not a limiting sense.
* * * * *