U.S. patent application number 10/680531 was filed with the patent office on 2004-04-08 for implantable infusion pump.
This patent application is currently assigned to Advanced Neuromodulation Systems, Inc.. Invention is credited to Blischak, Brian Russell, Hooper, Sandra Marie, Wigness, Bruce David.
Application Number | 20040065615 10/680531 |
Document ID | / |
Family ID | 25041122 |
Filed Date | 2004-04-08 |
United States Patent
Application |
20040065615 |
Kind Code |
A1 |
Hooper, Sandra Marie ; et
al. |
April 8, 2004 |
Implantable infusion pump
Abstract
An implantable infusion pump to deliver stored infusate to a
desired fluid delivery site. The pump includes a collapsible fluid
chamber. The pump can include a multi-stage filtration system to
filter micro-emboli as well as larger particles that are
inadvertently introduced into the pump system. An external member
can receive the pump and provide a medium to include additional,
interactive components, e.g., a bolus port, as well as provide a
versatile suture structure to enable the pump to be properly
secured within an implantation site. To improve volumetric
efficiency, the pump can further incorporate an outlet flow passage
within a movable wall of the fluid chamber.
Inventors: |
Hooper, Sandra Marie;
(Allen, TX) ; Wigness, Bruce David; (Minneapolis,
MN) ; Blischak, Brian Russell; (Plano, TX) |
Correspondence
Address: |
FULBRIGHT & JAWORSKI, L.L.P. (ANS)
2200 ROSS AVENUE
SUITE 2800
DALLAS
TX
75201
US
|
Assignee: |
Advanced Neuromodulation Systems,
Inc.
Plano
TX
|
Family ID: |
25041122 |
Appl. No.: |
10/680531 |
Filed: |
October 7, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10680531 |
Oct 7, 2003 |
|
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09755894 |
Jan 4, 2001 |
|
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6666845 |
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Current U.S.
Class: |
210/650 ;
604/6.09; 604/890.1 |
Current CPC
Class: |
A61M 2005/14506
20130101; A61M 5/14276 20130101; A61M 2039/0226 20130101; A61M
5/141 20130101; A61M 2039/0081 20130101; A61M 2005/1652 20130101;
A61M 2205/7545 20130101; A61M 5/16877 20130101 |
Class at
Publication: |
210/650 ;
604/006.09; 604/890.1 |
International
Class: |
A61M 005/00; B01D
061/00 |
Claims
What is claimed is:
1. A filter system for an infusion pump implantable in a living
body to filter emboli from an infusate, the filter system
comprising: a micro-filter stage to filter sub-micron emboli from
an infusate; and a particulate filter stage to filter particles
greater than 1 micron from the infusate, wherein the particulate
filter stage is arranged relative to the micro-filter stage so as
to operatively receive infusate filtered by the micro-filter.
2. A filter system in accordance with claim 1, wherein the
particulate filter stage is adapted to filter particles having a
size of 5 microns and greater.
3. A filter system for an infusion pump for delivering an infusate
to a living body, the filter system comprising: a first filter
stage to filter the infusate; and a second filter stage to filter
the infusate, wherein the first filter stage is disposed in an
infusate flow path of said infusion pump upstream from said second
filter stage, and wherein said first filter stage provides a
smaller filter pore size than that provided by said second filter
stage.
4. The filter system of claim 3, wherein said first filter stage
comprises a micro-filter stage and said second filter stage
comprises a particulate filter stage.
5. The filter system of claim 4, wherein said first filter stage
comprises an organic polymer filter element and said second filter
stage comprises a metal filter element.
6. The filter system of claim 3, wherein said first filter stage
provides filtering of particles less than 1 micron.
7. The filter system of claim 6, wherein said first filter stage
provides filtering of particles approximately 0.2 micron and
greater.
8. The filter system of claim 3, wherein said first filter stage
comprises a microbial filter.
9. The filter system of claim 3, wherein said first filter stage
comprises an emboli filter.
10. The filter system of claim 3, wherein said first filter stage
comprises a tubular filter element configuration.
11. The filter system of claim 3, wherein said second filter stage
provides filtering of particles approximately 5 microns and
greater.
12. The filter system of claim 3, wherein said second filter stage
comprises a particulate filter adapted to filter particles shed by
said first filter stage.
13. An elastomer member for implantation within a living body, the
member comprising: a first portion to receive an implantable
infusion device; a second portion to receive a bolus port; and an
enlarged skirt, extending substantially around a perimeter of the
member, adapted to receive and retain a suture to secure the member
at an implantation site.
14. A member in accordance with claim 13, wherein at least the
skirt includes a reinforcement material to assist in retaining a
received suture.
15. A member in accordance with claim 14, wherein the reinforcement
material extends substantially around the perimeter of the
member.
16. A member in accordance with claim 13, wherein the second
portion includes a fluid inlet and a fluid outlet.
17. A member in accordance with claim 16, wherein the fluid inlet
is connectable to an output of the implantable infusion device
received within the first portion.
18. A member in accordance with claim 16, wherein the second
portion includes a path connecting the fluid inlet and the fluid
outlet, and the path enables fluid communication between the fluid
inlet and the fluid outlet when the second portion receives a bolus
port.
19. A member to receive an implantable infusion device, which
includes a fluid output, for implantation in a living body, the
member comprising: a first mating surface to receive a housing of
an implantable infusion device; and a second mating surface to
receive a bolus port.
20. A member in accordance with claim 19, further comprising a
suture-receiving member, which extends substantially about a
perimeter of the member, wherein the suture-receiving member is
fabricated from a reinforced elastomer.
21. A member in accordance with claim 19, further comprising an
inlet passage, which intersects the second mating surface, and an
outlet passage, which also intersects the second mating
surface.
22. A member in accordance with claim 21, wherein the second mating
surface includes a path connecting the inlet passage and the outlet
passage, and the path enables fluid communication between the inlet
passage and the outlet passage when the second mating surface
supports a bolus port.
23. A member in accordance with claim 19, further comprising an
outlet passage which intersects the second mating surface.
24. A member in accordance with claim 23, wherein said second
mating surface is configured so as to prevent infusate from a fluid
chamber of the implantable infusion device from flowing through the
bolus port.
25. A member in accordance with claim 19, further comprising a
portion for interfacing with a delivery catheter.
26. A member in accordance with claim 25, wherein said interface
portion encapsulates a portion of said delivery catheter.
27. An elastomer member for implantation within a living body, the
member comprising: a first portion to engage an implantable
infusion device for attachment thereto; a second portion to receive
a suture to secure the implantable infusion device at an
implantation site, said second portion comprising said elastomer to
prevent the in-growth of tissue at an area of said suture.
28. The member of claim 27, wherein said elastomer comprises
silicon rubber.
29. The member of claim 27, wherein said member comprises a
reinforcing material.
30. The member of claim 29, wherein said reinforcing material is
encapsulated therein.
31. The member of claim 27, wherein said member is integral with a
bolus port receptacle.
32. The member of claim 31, wherein said bolus port receptacle is
formed at least in part of said elastomer.
33. The member of claim 31, wherein said bolus port receptacle is
disposed in an output path of said implantable infusion device.
34. The member of claim 31, wherein said bolus port receptacle is
configured so as to prevent infusate from a fluid chamber of the
implantable infusion device from flowing through a bolus port.
35. The member of claim 27, further comprising: a third portion to
engage a delivery catheter.
36. The member of claim 35, wherein said third portion encapsulates
at least a portion of said delivery catheter.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional of co-pending and
commonly IMPLANTABLE INFUSION PUMP assigned U.S. patent application
Ser. No. 09/755,894 entitled "IMPLANTABLE INFUSION PUMP," filed
Jan. 4, 2001, the disclosure of which is hereby incorporated herein
by reference.
TECHNICAL FIELD
[0002] The present invention concerns an implantable infusion pump,
and in particular, an implantable infusion pump as well as
independent components therefor that enable securing the pump
within a living body, multi-stage filtration, and protection of a
fluid-delivery catheter in and about the pump housing while
improving volumetric efficiency of the pump configuration.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to an implantable infusion
pump for infusing drugs or other chemicals or solutions into a body
wherein the infusion pump is implanted, Further, in at least one
embodiment, the present invention relates to an implantable
infusion pump that compensates for changes in both ambient pressure
and ambient temperature so as to accurately control the flow rate
of infusates from the implantable infusion pump into the body.
[0004] Infusion pump designs were rarely seen in medical literature
until the 1950s. Most of these early infusion pumps were
extracorporeal devices of various designs. One such device included
a reciprocating air pump driven by an electric motor. Yet another
design considered comprised a metal housing for a glass syringe and
a compression chamber fed by a tank of nitrogen gas. Yet another
such infusion pump included a motorized syringe pump which included
an electric motor connected to the worm drive that moved a syringe
plunger by a gear box. The gears were interchangeable such that
replacement of the gears permitted different delivery rates. Yet
another infusion pump included a syringe plunger driven by a rider
on a threaded shaft. While this is but a sampling of such devices,
it should be appreciated that numerous other designs were
considered and used for extracorporeal infusion devices.
[0005] Modem constant-flow implantable infusion devices, or
implantable pumps, for delivering an infusate (e.g., medicaments,
insulin, etc.) commonly have a rigid housing that maintains a
collapsible infusate reservoir. The housing includes a
needle-penetrable septum that covers a reservoir inlet. A flow
passage is provided between the reservoir and an exterior surface
of the device, such flow passage includes, or defines, a restrictor
to establish a maximum output infusate flow rate. At the flow
passage outlet, a flexible delivery catheter is provided.
[0006] Practically, such a device is implanted at a selected
location in a body so that (i) the inlet septum is proximate to the
patient's skin and (ii) a distal end of the catheter is positioned
at a selected delivery site. Infusate can then be delivered to the
infusion site by forcing such fluid from the device reservoir. When
the infusate reservoir becomes empty, the reservoir is refillable
through the septum inlet by injecting a new supply of infusate
through the apparatus' inlet septum. Due to the location of the
device in relation to the skin of the patient, injection can be
readily accomplished using a hypodermic needle (or cannula).
[0007] Infusate is expelled from the reservoir to an infusion site
by collapsing the reservoir. While some infusion pumps use an
electrically powered mechanism to force infusate from the
reservoir, other such devices commonly use a two-phase fluid, or
propellant, that is contained within the rigid housing and is
further confined within a fluid-tight space adjacent to the
infusate reservoir.
[0008] The propellant is both a liquid and a vapor at patient
physiological temperatures, e.g., 98.6.degree. F., and
theoretically exerts a positive, constant pressure over a full
volume change of the reservoir, thus effecting the delivery of a
constant flow of infusate. More particularly, when the infusate
reservoir is expanded upon being refilled, the propellant is
compressed, where a portion of such vapor reverts to its liquid
phase and thereby recharges the vapor pressure power source of the
pump. The construction and operation of implantable infusion pumps
of this type are described in detail, for example, in U.S. Pat.
Nos. 3,731,681 and 3,951,147.
[0009] Gas-driven infusion pumps typically provide a cost-effective
means to deliver a consistent flow of infusate throughout a
delivery cycle. Notwithstanding, the rigid housing of the
gas-driven infusion pump allows both environmental temperature and
atmospheric pressure to affect an output fluid flow. With some
drugs, particularly those having small therapeutic indices, such
changes in drug infusion rates are undesirable and, in certain
situations, unacceptable.
[0010] Circumstances readily exist where either environmental
temperature or pressure can rapidly change a significant amount.
For example, in regard to temperature, an internalized pump
pressure can change as much as 0.5 psi for each 1.degree. F. change
in body temperature. Thus, for example, assuming a pump driving
force of 8 psi at 98.6.degree. F., a twenty-five percent (25%)
increase in pressure and drug flow rate can result from a fever of
only 102.6.degree. F.
[0011] An even more serious situation results from changes in
atmospheric pressure. Although minor variations in atmospheric
pressure at any given location on earth does not significantly
affect delivery flow rates, with modem modes of transportation, a
patient can rapidly change altitude during travel, such as when
traveling in the mountains or when traveling by plane.
[0012] Again, the rigid housing of the conventional, gas-driven
infusion pump is intended to produce a constant internal pressure
(at constant temperature) independent of the external pressure.
Largely due to compliance by the lungs and venous circulatory
system, hydrostatic pressure within the human body closely follows
atmospheric pressure. The net effect is a pressure differential
across the fluid flow restrictor of infusion pump (typically a
capillary tube or the like) which changes linearly with external
pressure. Consequently, a delivered infusate flow rate can increase
as much as forty percent (40%) when a patient takes a common
commercial airline flight.
[0013] A viable solution to address changes in atmospheric
conditions for constant-flow infusion pumps is disclosed in U.S.
Pat. No. 4,772,263, herein incorporated by reference in its
entirety. Specifically, in place of the conventional rigid
enclosure that maintains a two-phase fluid, the disclosure teaches
forming the fluid reservoir between a rigid portion (which
maintains at least the inlet septum and the restrictor) and a
flexible drive-spring diaphragm. The diaphragm is exposed to the
body of the patient and "senses" internal body pressure so as to
compensate for changes in the internal body pressure caused by
changes in atmospheric pressure and temperature.
[0014] While the disclosure of U.S. Pat. No. 4,772,263 provides a
foundational description for a pump having a drive-spring diaphragm
capable of constant-flow delivery, such patent does not fully
consider alternatives for restrictor and/or flow passage outlet
placement that may provide for a safer practical configuration as
well as capitalize on the unique structure of the drive-spring
diaphragm.
[0015] Moreover, U.S. Pat. No. 4,772,263 is silent to a means to
incorporate a conventional bolus port with its unique drive-spring
diaphragm design. A bolus port enables direct infusion of a fluid
through the delivery catheter. A bolus port is typically a separate
septum that is in fluid communication with an outlet of an
associated infusion pump and a delivery catheter therefor.
Typically, certain one-way valving structures can prevent fluid
that is injected through the bolus port from flowing upstream to
the infusate reservoir of the infusion pump.
BRIEF SUMMARY OF THE INVENTION
[0016] The present invention relates to an infusion pump for
implantation in a living body. The infusion pump includes a housing
having a fluid chamber, wherein the housing includes a
spring-energy source for driving an infusate (e.g., medicaments,
insulin, etc.) out of the fluid chamber and compensating for
changes in internal body pressure and/or internal body temperature.
The housing further includes an inlet conduit in communication with
the fluid chamber and an outlet conduit in communication with the
fluid chamber that leads to an infusion site in the body. A
self-sealing, penetrable member is provided in the inlet conduit to
facilitate periodic refilling of the drug chamber when the infusion
pump is implanted. The spring-energy source allows a pressure
differential between the fluid chamber and the internal body
pressure to remain constant and unaffected by changes in body
temperature or atmospheric pressure.
[0017] In accordance with one aspect of the present invention, the
spring-energy source is a spring diaphragm that forms a flexible,
exterior rear wall of the fluid chamber that operatively applies
pressure on a fluid solution stored in the fluid chamber equivalent
to a predetermined constant force collectively exerted by the
spring diaphragm and an internal body pressure of the patient.
[0018] In accordance with another aspect of the present invention,
an infusion pump for implantation in a living body has a
variable-volume fluid chamber, a housing, and a driving spring. An
inlet conduit of the pump includes a self-sealing penetrable member
and extends between a surface of the housing and the fluid chamber.
An outlet conduit of the pump communicates with the fluid chamber
and is connectable to a delivery catheter. In addition to the
driving spring being adapted to supply a principle force to drive a
fluid stored in the fluid chamber into the body, the driving spring
also includes the outlet conduit, which enters, passes through, and
exits the driving spring.
[0019] Another aspect of the present invention is directed to an
implantable pump having a housing, an outlet conduit, and a
multi-stage filter system. The housing defines a variable-volume
fluid chamber to store infusate. The outlet conduit is in
communication with the fluid chamber and connectable to a delivery
catheter. The multi-stage filter system, positioned within the
outlet conduit, filters infusate prior to delivery via the delivery
catheter.
[0020] Another aspect of the present invention is directed to an
implantable pump that includes a housing having both a collapsible
fluid chamber to store infusate and an energy source to collapse
the fluid chamber. The pump further includes an inlet conduit and
an outlet conduit. The inlet conduit, having a self-sealing
penetrable member positioned therein, is located at a first
position relative to the housing and in communication with the
fluid chamber. The outlet conduit is in communication with the
fluid chamber and connectable to a delivery catheter. The pump
further includes a member having (i) a first mating surface to
receive the housing and (ii) a reinforced-elastomer suture
structure, extending substantially about a perimeter of the member,
to receive and maintain applied sutures to secure the pump within a
living body.
[0021] Another aspect of the present invention is directed to an
implantable pump that includes a bolus port and a housing having a
collapsible fluid chamber to store infusate and an energy source to
collapse the fluid chamber. The pump further includes an inlet
conduit and an outlet conduit. The inlet conduit, having a
self-sealing penetrable member positioned therein, is located at a
first position relative to the housing and in communication with
the fluid chamber. The outlet conduit is in communication with the
fluid chamber. The pump further includes a member having (i) a
first mating surface to receive the housing and (ii) a bolus port
receptacle, having an inlet and an outlet, to receive the bolus
port, wherein the outlet is connectable to a delivery catheter. A
connection conduit operatively couples the inlet of the bolus port
receptacle and the outlet conduit.
[0022] An object of the present invention is to provide an
implantable infusion pump having an outlet flow passage that is
protected by the upper housing and is removed from potential damage
during a refill operation.
[0023] Another object of the present invention is to provide an
implantable infusion pump having a drive-spring diaphragm with an
outlet flow passage that passes through the drive-spring
diaphragm.
[0024] Another object of the present invention is to provide a
suture structure that receives and is attachable to an infusion
pump, wherein this structure enables a received infusion pump to be
conveniently secured at an implantation site.
[0025] Another object of the present invention is to provide a
structure that receives and is attachable to an infusion pump and
that facilitates a fluid connection between the infusion pump and a
bolus port.
[0026] Another object of the present invention is to provide a
two-stage filtration system for an implantable infusion pump,
wherein a first stage functions to filter micro-emboli and a second
stage functions to filter greater particulate matter.
[0027] Other objects and advantages of the present invention will
be apparent to those of ordinary skill in the art having reference
to the following specification together with the drawings.
[0028] The foregoing has outlined rather broadly the features and
technical advantages of the present invention in order that the
detailed description of the invention that follows may be better
understood. Additional features and advantages of the invention
will be described hereinafter which form the subject of the claims
of the invention. It should be appreciated that the conception and
specific embodiment disclosed may be readily utilized as a basis
for modifying or designing other structures for carrying out the
same purposes of the present invention. It should also be realized
that such equivalent constructions do not depart from the invention
as set forth in the appended claims. The novel features which are
believed to be characteristic of the invention, both as to its
organization and method of operation, together with further objects
and advantages will be better understood from the following
description when considered in connection with the accompanying
figures. It is to be expressly understood, however, that each of
the figures is provided for the purpose of illustration and
description only and is not intended as a definition of the limits
of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] For a more complete understanding of the present invention,
reference is now made to the following descriptions taken in
conjunction with the accompanying drawing, in which:
[0030] FIG. 1 is a perspective view of a conventional embodiment of
a spring-driven infusion pump;
[0031] FIG. 2 is a sectional view of the infusion pump shown in
FIG. 1, wherein certain portions are being shown
diagrammatically;.
[0032] FIG. 3 is a force/deflection curve for the spring-energy
source of the present invention, wherein this curve illustrates a
constant force over a predetermined range of spring deflection;
[0033] FIG. 4 is a sectional view of one embodiment of a
conventional single conical spring-energy source in accordance with
the present invention;
[0034] FIG. 5 is a sectional view of an infusion pump in accordance
with the present invention;
[0035] FIG. 6A illustrates a side view of the spring diaphragm for
the infusion pump of FIG. 5, FIG. 6B illustrates a plan view of
such spring diaphragm, and FIG. 6C provides a partial sectional
view of an inlet to the outlet passage of the spring diaphragm of
FIG. 6B taken along line 6C-6C thereof;
[0036] FIG. 7 illustrates a bottom view of the spring diaphragm for
the infusion pump of FIG. 5 connected to a delivery catheter;
[0037] FIGS. 8a and 8b illustrate a second stage of a filter system
in accordance with the present invention;
[0038] FIG. 9 is a perspective, exploded assembly view of the
infusion pump of FIG. 5 and a boot incorporating a suture structure
and a bolus port receptacle;
[0039] FIG. 10 is a sectional view of the boot of FIG. 9 taken
along line 10-10 thereof;
[0040] FIG. 11 is a partial sectional view of a bolus port
positioned within the bolus port receptacle of the boot of FIGS. 9
and 10; and
[0041] FIG. 12 is a partial sectional view of a pump assembly in
accordance with one aspect of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0042] As a foundation for a detailed description of the present
inventions set forth in this disclosure, reference will first be
made to that known in the art, and in particular, that generally
disclosed in U.S. Pat. No. 4,772,263.
[0043] Referring now to the drawings, there is illustrated in FIGS.
1 and 2 an embodiment of an implantable infusion pump in accordance
with at least one aspect of the present invention, the pump being
generally designated by the reference numeral 20. The pump 20 has a
housing 22 with top and bottom wall portions 24, 26 interconnected
by a side wall portion 28 forming a hardened outer shell structure.
The expressions "top" and "bottom" are relative and refer only to
positions that are generally shown in the drawings.
[0044] The top wall portion 24 is constructed of a hardened,
non-reactive material, e.g., stainless steel, titanium, etc. In
contrast, the bottom wall portion 26 includes a flexible spring
diaphragm 25 which cooperates with the remainder of the housing to
define a variable-volume, fluid-tight drug chamber 30 for holding
insulin, a drug solution or other chemicals or solutions to be
infused into an infusion site of a patient's body where the
delivery catheter is implanted. The outside surface of the spring
diaphragm 25 is exposed to the body and "senses" an internal body
pressure so as to compensate for changes in such internal body
pressure caused by changes in atmospheric pressure and temperature.
The flexible spring diaphragm 25 communicates the internal body
pressure to the drug chamber 30.
[0045] Notwithstanding the spring diaphragm 25, the infusion pump
20 further includes those features required of an implantable and
refillable infusion pump. An inlet conduit 32 extends from the
exterior of the housing 22 to the variable-volume, collapsible drug
chamber 30 so as to provide for fluid communication from outside
the housing 22 to the drug chamber 30. An upper end of the inlet
conduit 32 includes a self-sealing, penetrable member or septum 34,
suitably positioned therein to provide a fluid-tight seal and yet
enable the refilling of the drug chamber 30 by injection. An outlet
passage 36 leads from the drug chamber 30 to the exterior of the
housing 22 to provide for outflow of drug solution from the drug
chamber 30 to the exterior of the housing 22. The outlet passage 36
is illustrated as including a suitable filter 38 for filtering out
bacteria and trapped gas, which might be inadvertently introduced
into the infusion pump 20 during the manufacturing or the refilling
process.
[0046] Interconnected to an outer end of the outlet passage 36 by a
suitable connector 40 is a flow restrictor 42, or in this instance,
capillary tubing, which serves as a flow regulating element. The
capillary tubing 42 might be interconnected at an opposite end to a
rubber catheter or the like that leads to the site of infusion in
the body.
[0047] For controlling a rate of delivered flow, the most readily
adjustable parameters are (i) the restrictor (i.e., the length and
diameter of the capillary) and (ii) the viscosity of the infusate.
Addressing the former, the flow rate through the flow restrictor 42
is governed by the Poisseuille equation:
Q=(.pi..multidot.r.sup.4.multidot..DELTA.P)/(8.multidot..mu..multidot.L)
[0048] where,
[0049] Q=flow (ml/sec),
[0050] r=radius of restrictor passage (cm),
[0051] .mu.=viscosity (poise),
[0052] .DELTA.P=pressure (dynes/cm.sup.2), and
[0053] L=restrictor length (cm).
[0054] Several feet of capillary tubing 42 is typically required,
for example, 0.5-100 feet, and preferably, 20-100 feet, and more
preferably, 50-100 feet.
[0055] As illustrated, the capillary tubing 42 might be wrapped
about the housing 22 in a groove 44 and suitably secured by a
material compatible with body fluids. It will be appreciated that
other types of structures or devices might be used to provide for
drug output or outflow resistance; for example, spiral groove
plate, etched glass, steel capillary tubing, silica chip, etc.
Moreover, the resistance elements may number more than one, as in
the case of more than one site of infusion.
[0056] The outer surface of the top wall portion 24 of the housing
22 is preferably shaped to allow easy identification of the inlet
conduit 32 (see also FIG. 5) and suitably protected with a layer of
metal or the like to be protected from needle damage during the
process of refilling the drug chamber 30. The bottom wall portion
26 and side wall portion 28 might also be similarly protected by a
metal layer. As another alternative, the spring diaphragm 25 may
include an integrated material (e.g., Kevlar.TM. [DuPont Corp.,
Wilmington, Del.]) to assist in preventing aberrational
needle-penetrations during refill operations.
[0057] It will be appreciated that the overall design of the
infusion pump 20 of the present invention can be more compact and
have higher volumetric efficiency than gas-driven pumps since there
is no second chamber and the outer shell structure of the infusion
pump serves a dual purpose as the infusate-driving energy source
and the protective shell.
[0058] In the embodiment of the infusion pump shown in FIGS. 1 and
2, the spring diaphragm 25 is formed of a series of nested conical
sections 48 interconnected by stiff cylindrical ring sections 50 so
as to form a substantially flat spring diaphragm. The conical
sections 48 are constructed of an elastomer with a low elastic
constant, and the ring sections 50 are preferably constructed of
metal with a high elastic constant. The preferred construction
technique is to mold the metal ring sections 50 into an elastomer
structure forming the conical sections 48. If necessary, the inner
surface of the spring diaphragm 25 can be coated with a plastic
liner or provided with a thin metal liner to resist drug action on
the elastomer and reduce gas diffusion from the body into the drug
chamber 30.
[0059] This arrangement of conical sections 48 and ring sections 50
provide a spring diaphragm 25 with a useful range of movement or
stroke. Moreover, by separating the single conical spring into a
nested series of conical sections interconnected by relatively
stiff cylindrical ring sections, a substantially flat spring
diaphragm having an effective stroke or range of movement in the
substantially flat portion of the force/deflection curve shown in
FIG. 3 is achievable. The flat portion of the curve of FIG. 3 is a
constant force region that can be used to produce a constant
pressure over a range of displacement volume and is desirable
region of operation.
[0060] The spring diaphragm 25 can be extended beyond its nested
position when assembled such that the spring diaphragm 25 is
therefore under stress. The initial displacement is selected to
bring the pressure or force exerted by the spring diaphragm 25 to
the flat portion of the force/displacement curve illustrated of
FIG. 3. Appreciably, the functional volume of the infusion pump 20
is that displacement which takes place over this substantially flat
region of the force/deflection curve.
[0061] To limit the filling of the infusion pump to a desired
displacement of the spring diaphragm 25, a telescoping section 54
can be interconnected to the spring diaphragm 25 and extend into
the inlet conduit 32. When the telescoping section 54 is fully
extended, collar portion 56 cooperates with a collar portion 58 of
the inlet conduit 32 to prevent the spring diaphragm 25 from
traveling more than the desired distance. As illustrated, the
telescoping section 54 is interconnected to a substantially flat
portion 60 of the spring diaphragm. The telescoping section 54,
thus limits the stroke of the spring diaphragm 25 as indicated
generally by the arrows 62 and causes the filling back pressure to
increase rapidly, thereby reducing the risk of damaging the spring
diaphragm 25 or causing errors in a drug flow rate due to excess
pressure in the drug chamber.
[0062] An alternative design of the spring diaphragm 25 can take
the form of a single Belleville washer, as generally shown in FIG.
4. Not unlike the first spring diaphragm 25 discussed above, a
Belleville washer with the proper selection of cone angle and
thickness can yield a desired force displacement curve in
accordance with FIG. 3. If a strong material like titanium is used,
cone height must be very small, i.e., 10 to 20 thousandths of an
inch, so as to provide force in the range suitable for infusion
pumps, e.g., 4 to 15 psi. This range of heights, which constitutes
the effective stroke of a spring diaphragm 35 that includes a
single conical spring, is too small to be practical for use in
infusion pumps. In order to retain a flat pressure curve and
achieve a longer stroke or range of movement of the spring
diaphragm 25, a spring material with a lower elastic constant
should be used, for example, plastics and elastomers. When low
elastic materials are used, the thickness of the conical section
can be increased and the cone angle made larger. Accordingly, it is
preferred that the spring material used should also have a much
greater percent elongation in the elastic region of its stress
strain curve. This allows the spring diaphragm 25 to have a much
longer range of travel in the substantially flat portion of the
curve shown in FIG. 3.
[0063] No matter which diaphragm design is employed, it will be
appreciated that the shape and thickness of the spring diaphragm 25
may vary in order to exhibit the required force/deflection
characteristics.
[0064] FIG. 5 illustrates another embodiment of the pump 20 that
includes a single conical spring diaphragm 25. The pump 20 of this
embodiment is shown in an expended or collapsed state (i.e.,
substantially no infusate within the fluid chamber 30). In
reference to the drawings, the same numerical designations are used
to represent like structure between the disclosed embodiments.
Accordingly, when this embodiment includes structure substantially
identical to that of the embodiment of FIGS. I and 2, description
of such structure will not be repeated.
[0065] The top wall portion 24 offers a simplified configuration
over that used for the embodiment shown in FIGS. 1 and 2.
Specifically, the top wall portion 24 does not function as a
manifold for the outlet passage 36 and related structure, rather
the outlet passage 36 is formed in and passes through the spring
diaphragm 25. This allows the pump restrictor and delivery catheter
connector 40, which is an extension of the outlet passage 36, to be
positioned away from the upper surface of the pump 20, thus
avoiding the exposure of this sensitive structure from potential
damage during a refilling procedure. As will be discussed in
greater detail below, this embodiment incorporates a filter system
38 and a flow restrictor 42 within the internalized outlet passage
36.
[0066] For one structural arrangement, the inlet conduit 32 is
defined by a needle stop 32a that includes at least one aperture
32b. The needle stop 32a is formed from a hardened material, e.g.,
stainless steel, titanium, etc. The needle stop 32a receives and
holds a resilient material 32c, which serves to effectively stop a
needle (not shown) that is inserted through the septum 34 and avoid
damage through its contact with the lowest portion of the needle
stop 32a. The needle stop 32a is held in place by a retaining
structure 32d, which is secured (e.g., welded) to an undersurface
of the top wall portion 24. Although FIG. 5 illustrates (and the
above description discusses) the use of the resilient material 32c,
it should be appreciated that the resilient material 32c is not
critical to the present invention, whereas the needle stop 32a can
be provided without the resilient material 32c (FIG. 12).
[0067] FIGS. 6A and 6B further illustrate the spring diaphragm 25
of this embodiment. FIG. 6A is a side view of the spring diaphragm
25 and is consistent with the sectional view shown in FIG. 5. FIG.
6B is a plan view, which better illustrates the structure of the
spring diaphragm 25, including a central portion 29 that can
closely receive the needle stop 32a (FIG. 5), the outlet passage
36, the outlet passage inlet 27 (FIG. 6C), and the delivery
catheter connector 40.
[0068] Operatively, infusate is injected using a needle (not shown)
into the inlet conduit 32. The injected infusate passes from the
inlet conduit 32 into the fluid chamber 30 via the at least one
aperture 32b. Infusate within the fluid chamber 30 enters the
outlet passage 36 through the outlet passage inlet 27, which can
interface with the aperture 32b in even a collapsed state (see FIG.
6c).
[0069] Embedding the outlet passage 36 within the spring diaphragm
25 creates a more compact overall pump design, allows the outlet
passage 36 to be made using a basic molding process, and eliminates
the need for a separate manifold to house a restrictor and/or
filter, such as shown in FIG. 1. Accordingly, this embodiment
exhibits greater volumetric efficiency, lower weight, ease of
assembly, and requires no substantive change in the overall shape
of the pump 20. Moreover, an embedded outlet passage 36 minimizes
the occurrence of extreme stretching, compressing, flexing, or
kinking of component couplings and joints.
[0070] As but one fabrication example, the spring diaphragm 25 is
fabricated by first supporting tubing (e.g., silicone tubing) on a
flexible mandrel (not shown) within the cavity of a spring mold
(not shown). The tubing is selected based largely on its inner
diameter-the inner diameter should accommodate a bacteriostatic
filter therein but still allow adequate flow thereabout. The
mandrel holds the tubing in accordance with a desired shape
relative to the final spring diaphragm 25. In this particular
example, the mandrel maintains the tubing in a gentle spiral that
extends substantially from a top surface of the spring diaphragm
(i.e., outlet passage inlet 27) to a position slightly beyond
(preferably, 0.1"-1.0") the lower surface thereof (i.e., connector
40). A liquid elastomer (e.g., silicone rubber) is then injected
into the mold cavity in and about the supported tubing.
Consequently, the supported tubing is integrated with the spring
diaphragm 25 during vulcanization. The flexible mandrel is then
removed, thus leaving a hollow tubular channel within the wall of
the spring diaphragm 25. The portion of the tubing that extends
from the lower surface of the formed spring diaphragm 25 is adapted
to be connected to (i) a delivery catheter 70 or (ii) tubing for
connection to additional pump structure (e.g., a bolus port).
[0071] It should be appreciated that the specific technique
utilized to form the internalized outlet passage 36 is not critical
to this invention.
[0072] As may be seen in both the configurations of FIGS. 2 and 5,
it is preferred that an inner surface 52 of the top wall portion 24
be configured to have a somewhat convoluted shape so as to allow
the spring diaphragm 25 to nest into the complimentary shape of the
inner surface 52. This enables the spring diaphragm 25 to expel
substantially all of the drug solution from the fluid chamber 30
during an infusate delivery cycle.
FILTRATION
[0073] As stated before, it is intended that the outlet passage 36
include both a filter 38 and a flow restrictor 42.
[0074] In regard to the filter 38, it is a requirement that drug
infusion pumps include a means of micro-filtering infusates in
order to insure their sterility. While a preferred filter structure
would be sintered metal due to its durability, sintered metal
filters are not currently available with a micro-filtration pore
size. Consequently, filters with sub-micron pore size are
conventionally fabricated from organic polymers such as
polysulfone, Nylon.RTM., polytetrafluoroethlyene, and cellulose
acetate. These organic-based filters are not as durable as metal
filters and are more likely to shed particles large enough to
partially or completely obstruct some part of the pump flow path,
valve seats, and interstices. Modem implantable infusion pumps have
flow paths that range in size from 5 microns to 50 microns.
[0075] In addition to the concern of filter break up, it is
necessary to filter potentially damaging particles that may be
introduced during the manufacturing process. First, silicone
rubber, which can be used extensively in the fabrication of the
present invention, has the propensity to attract electrostatically
charged particles. It is more common than not that silicone rubber
parts of the pump 20 will carry and introduce 5-25 micron particles
into the pump system that can individually cause device failure.
Second, particle control is an issue with respect to the sequence
in which the pump 20 is assembled. The microbial filter 38a (e.g.,
0.2 micron polysulfone tubular fiber) can be installed within the
outlet passage 36 at a relatively early stage of the manufacturing
process, but the flow restrictor 42 is fabricated, inspected, and
installed at a relatively later stage. The practical concern is
that system-harmful particles may be introduced into the pump
system, downstream of the microbial filter 38a, despite the
strictest of particle control standards and measures.
[0076] FIG. 7 illustrates a bottom view of the spring diaphragm 25
of this embodiment, which illustrates the position of both the
micro-filter stage 38a and the particle filter stage 38b of the
multi-stage filtration system 38, wherein the particle filter stage
38b is downstream of the micro-filter stage 38a. The micro-filter
stage 38a is a filter with sub-micron pore size and is preferably
fabricated from conventional, organic polymers such as polysulfone,
Nylon.RTM., polytetrafluoroethlyene- , cellulose acetate, or the
like. The particle filter stage 38b is illustrated in FIGS. 8a and
8b.
[0077] In FIG. 8a, the restrictor 42-particle filter stage 38b
assembly is generally shown. In particular, a delivery catheter 70
is positioned through the catheter connector 40 and into the outlet
passage 36. The union between the connector 40 and the delivery
catheter 70 is reinforced with a sleeve 74. The delivery catheter
70 and/or the sleeve 74 are held in place by an adhesive, friction,
mechanical fastener, or the like.
[0078] A tubing section 72 extends from a proximal end of the
delivery catheter 70. A particle filter 38b is fixed to a proximal
end of the tubing section 72 so as to cover the inlet to the lumen
of the tubing section 72. While the particle filter 38b can assume
any structure capable of preventing at least a 20 micron or greater
particle from entering the lumen of the tubing section 72, it is
preferred that the particle filter 38b take the form of a sintered,
stainless steel mesh. In one embodiment, the mesh of the particle
filter 38b is arranged so as to prevent the passage of particles
having a size of approximately 20 microns or greater. More
preferably, the mesh prevents the passage of particles having a
size of approximately 10 microns or greater. Most preferably,
however, the mesh prevents the passage of particles having a size
of approximately 5 microns or greater. The particle filter 38b is
fixed to the tubing section 72 by adhesive, friction, mechanical
fasteners, or the like.
[0079] FIG. 8b illustrates a partial sectional view of the
structure shown in FIG. 8a. Capillary tubing, or the restrictor 42,
shares and extends between the lumens of the delivery catheter 70
and the tubing section 72. Adhesive may be used to fix the relative
positions of the delivery catheter 70, tubing section 72, and the
restrictor 42. The restrictor 42 is preferably formed from a
relatively short length of tubing (e.g., 0.1 cm-3.0 cm) of a
prescribed inner diameter (e.g., 10 microns, 15 microns, 20
microns, 25 microns, 30 microns). The restrictor 42 may be
fabricated from of a variety of medical grade materials, including
silica. Furthermore, it is preferred that a proximal end of the
restrictor 42 be treated with trimethychlorosilane or a
functionally similar substance.
[0080] The concerns of particle control are not limited to the pump
20 of the present invention. Accordingly, the multi-stage
filtration system 38 is suitable and particularly applicable to any
implantable infusion pump or like device.
SUTURE-SECURING STRUCTURE
[0081] At the site of implantation, modern implantable infusion
pumps are sutured to nearby tissue to insure their desired
placement. Conventional implantable infusion pumps include three or
four suture rings (i.e., eyelets), formed of metal or the like,
fixed to a side-surface of the respective housings. The suture
rings are equally spaced about the housings' perimeter. While
suture rings typically offer a suitable means in which to secure an
implantable pump, their circumferential placement often constrains
pump/suture placement. Accordingly, it is perceived that a need
exists for a structure that allows a physician to readily place a
suture at largely any position about the pump.
[0082] FIG. 9 illustrates an elastomer-reinforced boot 80 in
accordance with one aspect of the present invention. The boot 80
has an interior surface 83 that receives the pump 20 and
specifically the upper wall portion 24 of the housing 22. The lip
84 of the boot 80 functions to contact the upper-most part of the
upper wall portion 24 and insure that the boot 80 is properly
positioned relative to the pump 20. Although the boot 80 could
function without the lip 84 or the lip 84 could be arranged as to
alternatively contact the lower wall portion 26, it is preferred
that the lip 84 be configured in accordance with that illustrated
in FIGS. 9 and 12. The boot 80 can be fixed to the pump 20 using an
adhesive, friction, mechanical fasteners, or the like.
[0083] A suture pad 82 extends substantially about the
circumference of the boot 80. While the boot 80 is preferably
fabricated from a medical grade elastomer, e.g., silicone rubber,
silicone rubber cannot alone resist normal forces and stresses
concentrated at the sutures sites. Accordingly, a reinforcing
material 82a is embedded within the boot 80 (FIG. 10).
[0084] In a preferred embodiment, the reinforcing material 82a is a
polyester mesh, but it should be understood that the reinforcing
material 82a could also be a metal mesh, fabric, or the like.
Notwithstanding the "open" structure of these examples, the
reinforcing material 82a is preferably encapsulated within the
elastomer material of the boot 80 to prevent the in-growth of
tissue in the reinforcing material 82a. Otherwise, if the
reinforcing material 82a is exposed, tissue can grow in and about
such a structure, which could make any pump revision (i.e.,
replacement) unnecessarily complicated and more traumatic to the
surrounding tissue.
[0085] While the reinforcing material 82a may certainly be used
throughout the entire structure of the boot 80, it is satisfactory
and more convenient for fabrication to incorporate the reinforcing
material 82a only in the suture pad 82. Moreover, although the
suture pad 82 can assume an inclined form (i.e., forming a
truncated conical form), embedding the reinforcing material 82a can
be more consistently achieved when the suture pad 82 remains
substantially flat. The reinforcing material 82a spans continuously
(or substantially continuously) about the circumference of the boot
80, thus providing the greatest potential for desirable suture
placement.
[0086] The illustrated embodiment of the boot 80 includes a bolus
port receptacle 86 adapted to receive a bolus port 90. As
illustrated in FIG. 11, the bolus port 90 is constructed in a
manner generally consistent with the refill port (i.e., inlet
conduit 32) of the pump 20. The bolus port 90 is defined by a
needle stop 92a that includes at least one aperture 92b. The needle
stop 92a is formed from a hardened material, e.g., stainless steel,
titanium, etc. The needle stop 92a receives and holds a resilient
material 92c, which serves to effectively stop a needle (not shown)
that is inserted through the septum 94 and avoid damage through its
contact with the lowest portion of the needle stop 92a. A retaining
structure 92d holds the septum 94 relative to the needle stop 92a.
The bolus port 90 is secured within the bolus port receptacle 86
using adhesive, friction, mechanical fasteners, or the like.
[0087] While not critical to the invention, the septum 94 and the
resilient material 92c are intended to occupy a significant
majority of the volume defined by the needle stop 92a. If this
configuration is adopted, this arrangement: (i) minimizes a
potential fluid volume within the bolus port 90 and (ii) creates a
"keyed" space 96 that can only be accessed by a special needle that
has a discharge aperture alignable with the space 96.
[0088] The bolus port receptacle 86 of the boot 80 is positioned
between, and is in fluid communication with, an inlet 86a and an
outlet 86b. A groove 86c is formed in and follows at least a
portion of the perimeter of the bolus port receptacle 86. It is
preferred that the groove 86c be aligned with the inlet 86a and the
outlet 86b, thereby creating a continuous flow path. The groove 86c
may be formed about 360.degree. of the interior surface of the
receptacle 86 with one aperture 92b formed in the needle stop 92a.
Alternatively, the groove 86c may be formed about only 180.degree.
of the interior surface of the receptacle 86 with two oppositely
positioned apertures 92b formed in the needle stop 92a (FIGS. 10
and 11). Alternatively, to further minimize the potential volume of
the groove 86c, the groove 86c may be formed about only 90.degree.
of the interior surface of the receptacle 86 with at least two
apertures 92b formed in the needle stop 92a. Notwithstanding, for
each of the above options, it is possible to have only a single
aperture 92b between the bolus port 90 and the groove 86c so as to
prevent the possibility of infusate (from the fluid chamber 30)
flowing through the bolus port 90.
[0089] The bolus port receptacle 86 is connected to the output from
pump 20 via a tubing extension 98. The tubing extension 98 extends
between the connector 40 and the inlet 86a and is held in place by
adhesive, friction, mechanical fasteners, or the like.
[0090] While the boot 80 described and illustrated includes a bolus
port receptacle 86, it is should be understood that inclusion of
the bolus port receptacle 86 is not a requirement of the present
invention but an option. Rather, if a bolus port is believed to not
be needed for a particular application, the boot 80 can be formed
without the receptacle 86. For this configuration, the delivery
catheter 70 would be connected directly to the connector 40. Also,
it should be further understood that the boot 80 may serve as a
medium to collectively arrange a pump and, for example, a bolus
port; however, other means or structure other than the suture pad
82 could be provided to enable the assembly to be secured within an
implantation site.
[0091] While not shown, it should be further appreciated that as an
alternative to the boot 80 receiving the pump 20 within an interior
surface 83 of the boot 80, at least the suture pad 82 of the boot
80 could be integrated between upper and lower halves of the pump
20.
[0092] It will be appreciated that the drug infusion site must be
considered in the design of the infusion pump. For example, if the
catheter must deliver an infusate into the relatively high pressure
of the arterial system, a pump pressure will need to be greater to
maintain the same error limits that can be obtained when delivering
infusate for other operative purposes, e.g., intravenously,
intraperitoneally.
[0093] Moreover, although preferred embodiments of the present
inventions have been described above, it will be appreciated that
other pressure compensating mechanisms in accordance with the
principles of the present invention might be utilized. In
particular, other constant force spring arrangements might be
utilized as an infusate drive source.
[0094] It is to be understood that even though the above numerous
characteristics and advantages of the invention have been set forth
in the foregoing description, together with details of the
structure and function of the invention, the disclosure is
illustrative only, and changes may be made in detail, especially in
matters of shape, size and arrangement of parts within the
principle of the invention to the full extent indicated by the
broad general meaning of the terms in which the appended claims are
expressed.
[0095] Although the present invention and its advantages have been
described in detail, it should be understood that various changes,
substitutions and alterations can be made herein without departing
from the invention as defined by the appended claims. Moreover, the
scope of the present application is not intended to be limited to
the particular embodiments of the process, machine, manufacture,
composition of matter, means, methods and steps described in the
specification. As one will readily appreciate from the disclosure,
processes, machines, manufacture, compositions of matter, means,
methods, or steps, presently existing or later to be developed that
perform substantially the same function or achieve substantially
the same result as the corresponding embodiments described herein
may be utilized. Accordingly, the appended claims are intended to
include within their scope such processes, machines, manufacture,
compositions of matter, means, methods, or steps.
* * * * *