U.S. patent number 3,731,681 [Application Number 05/217,879] was granted by the patent office on 1973-05-08 for implantable indusion pump.
This patent grant is currently assigned to The Regents of the University of Minnesota. Invention is credited to Perry L. Blackshear, Jr., Perry J. Blackshear, Henry Buchwald, Frank D. Dorman, Richard L. Varco.
United States Patent |
3,731,681 |
Blackshear , et al. |
May 8, 1973 |
IMPLANTABLE INDUSION PUMP
Abstract
An implantable pump for infusing drugs or other chemicals or
solutions into the body at a uniform slow flow rate. The pump
comprises a housing divided into two chambers separated by a
bellows, diaphragm or other pressure-communicating interphase. A
volatile liquid partially filling one chamber provides 9 constant
pressure energy source to act upon the interphase to force liquid
infusate from the other chamber through a capillary tube or other
flow-regulating resistance element to the infusion site. The
infusate chamber is closed as by means of a self puncture sealing
refill stopper. The pump is implanted with the refill stopper
disposed under the skin and the pump is refilled periodically by
injection through the skin.
Inventors: |
Blackshear; Perry J.
(Mahtomedi, MN), Dorman; Frank D. (St. Paul, MN),
Blackshear, Jr.; Perry L. (Mahtomedi, MN), Buchwald;
Henry (Edina, MN), Varco; Richard L. (St. Paul, MN) |
Assignee: |
The Regents of the University of
Minnesota (Minneapolis, MN)
|
Family
ID: |
34138116 |
Appl.
No.: |
05/217,879 |
Filed: |
January 14, 1972 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
38356 |
May 18, 1970 |
|
|
|
|
Current U.S.
Class: |
604/141;
222/386.5 |
Current CPC
Class: |
A61M
5/141 (20130101); A61M 5/14276 (20130101); A61M
5/16877 (20130101) |
Current International
Class: |
A61M
5/142 (20060101); A61M 5/14 (20060101); A61m
005/00 () |
Field of
Search: |
;128/214R,214F,214.2,216,1R,260 ;222/386.5 ;3/1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
196,550 |
|
Mar 1958 |
|
OE |
|
664,419 |
|
Aug 1938 |
|
DD |
|
960,535 |
|
Jun 1964 |
|
GB |
|
Primary Examiner: Medbery; Aldrich F.
Parent Case Text
This application is a continuation of application, Ser. No. 38,356,
filed May 18, 1970, and now abandoned.
Claims
We claim:
1. An infusion pump for implantation in a living body
comprising:
A. a housing,
B. means for dividing the housing into first and second fluid-tight
chambers, the dividing means being movable relative to the housing
so as to vary the volumes of the chambers in a reciprocal
manner,
C. an inlet conduit located at a first position on the housing
leading to the second chamber,
D. at least one outlet conduit located at a second position on the
housing adjacent to but spaced from said inlet conduit
communicating with the second chamber and for leading to an
infusion site in the body,
E. means in the first chamber for moving the dividing means to
reduce the volume of the second chamber so that a fluid in the
second chamber may be forced through the outlet conduit, and
F. a self-sealing, penetrable member in said inlet conduit, said
member being unobstructed so that the pump can be implanted in the
body with the unobstructed penetrable member situated adjacent a
surface area of the body whereby the second chamber can be refilled
with fluid periodically by injection through the skin.
2. The pump defined in claim 1 wherein the moving means is
comprised of a volatile fluid in the first chamber which exerts a
sufficient vapor pressure at physiological temperatures to more the
dividing means and force the contents of the second chamber through
the outlet conduit.
3. The pump defined in claim 2 and further including:
A. an entry port to the chamber from the outside of the housing,
and
B. a fluid-tight closure for the entry port.
4. The pump defined in claim 1 and further including fluid flow
regulating means in the outlet conduit.
5. An infusion pump for implantation in a living body
comprising:
A. a housing including an inlet means,
B. a metal bellows within the housing, the bellows
1. having a closed end wall,
2. being sealed with respect to the interior of the housing,
and
3. being compressible in response to pressure exerted on the ouside
of the end wall,
C. an inlet conduit leading to the interior of the bellows from the
outside of the housing,
C. an outlet conduit communicating with the interior of the bellows
for conducting fluid from the interior of the bellows to an
infusion site in the body, and
E. a self-sealing, penetrable member in the inlet conduit, said
penetrable member being unobstructed so that the pump can be
implanted in the body with the unobstructed member situated
adjacent a surface area of the body whereby the bellows can be
refilled with fluid periodically by injection through the skin.
6. The pump defined in claim 5 and further including a volatile
liquid in the housing outside the bellows which exerts a sufficient
vapor pressure at physiological temperatures to compress the
bellows and force the bellows contents through the outlet
conduit.
7. The pump defined in claim 5 and further including means for
controlling the rate of flow of fluid through the outlet
conduit.
8. The pump defined in claim 5 wherein the penetrable member is
comprised of a penetrable self-sealing stopper.
9. The pump defined in claim 5 and further including means for
limiting the extent to which the bellows can be compressed in
response to the pressure exerted on its end wall.
10. An infusion pump for implantation in a living body
comprising:
A. a housing,
B. first and second chambers within the housing,
C. a liquid-tight, vapor-tight, pressure-communicating metal
bellows separating the chambers, said bellows having an open mouth
at one end and closed wall at the other end, the mouth of the
bellows being secured in liquid-tight, vapor-tight relation, the
first chamber being provided with an inlet means and lying between
the inside walls of the housing and the bellows and the second
chamber lying within the bellows,
D. an entry port into the second chamber and liquid-tight closure
means therefor, the closure means being penetrable from the outside
of a living body after implantation therein by injection through
the skin, and
E. at least one discharge port from the second chamber spaced from
but adjacent to said entry port.
11. A pump according to claim 10 further characterized in that:
A. a recessed, cup-like member is disposed in one end of the
housing extending within the mouth of the bellows,
B. an aperture is provided in the cup-like member with a fitting
therein having a channel in communication with the second chamber,
and
C. the bellows is collapsible into an annular space between the
cup-like member and the housing wall.
12. The pump according to claim 10 and further characterized in
that:
A. the penetrable closure means is an elastic member, and
B. an annular retainer having a central aperture is secured to the
external end of the fitting in engagement with the elastic
member.
13. The pump according to claim 12 and further characterized in
that:
A. the housing and the fitting having contours conforming generally
to the contours of the implantation site in the body, and
B. a conduit is connected to the discharge port for conducting
infusate from the bellows to an infusion site in the body.
14. The pump according to claim 13 wherein the conduit is a length
of capillary tubing.
15. The pump according to claim 10 and further characterized in
that the first chamber is partially filled with a stable, volatile
liquid that exerts a vapor pressure of greater than 1 atmosphere at
physiological temperatures, whereby the pump is self-powered
through body warmth.
16. The method of infusing liquids into a living boby, said method
comprising:
A. implanting a self-powered pump according to claim 15 in a living
body, with the closure means to the entry port of the second
chamber of the pump underlying and facing the skin,
B. connecting the discharge port to at least one infusion site in
the body,
C. injecting infusate through the skin of the body and through the
closure means to fill the second chamber thereby condensing the
vapor within the first chamber to charge the power source, and
D. expanding the vapor in the first chamber through body warmth to
gradually collapse the second chamber to expel the infusate in the
second chamber through the discharge port to the infusion site.
17. The method of infusing fluids into a living body, said method
comprising the steps of:
A. charging the power cell of a vapor pressure pump with a stable,
volatile liquid that exerts an appreciable vapor pressure at
physiological temperatures,
B. forming a self-sealing, penetrable member in the discharge port
of the pump,
C. implanting the pump in the body so that the penetrable member
underlies the skin,
D. expanding the pressure-exerting vapor in the power cell through
body warmth to pump infusate through the discharge port to an
infusion site in the body, and
E. injecting additional fluid through the skin and through the
penetrable member periodically to refill the pump with infusate
and, at the same time, condense the pressure-exerting vapor so as
to recharge the power cell.
Description
The invention described herein was made in the course of work under
a grant or award from the Department of Health, Education and
Welfare.
This invention is directed to a permanently implantable
self-recycling low-flow constant rate multi-purpose infusion pump
of simple design. The pump is percutaneously refillable. It
operates without any kind of intrinsic or extrinsic electrical
power source. It can function independently of Vascular pressure to
provide continuous uniform rate infusion. Drugs or other chemical
substances or fluids can be infused intravenously, intra-arterially
or into a body cavity or tissue at a constant volume slow flow
delivery rate. It may be used for such purposes as continuous
heparinization, artificial pancreas insulin injection,
chemotherapeutic organ infusion, anti-hyperlipidemic agent
infusion, regional vasodilator infusion, and the like.
Previous methods of infusion have required external connections and
tubing. No completely permanently implantable infusion pump with
percutaneous refilling access has been known. The pump of the
present invention utilizes a recycling chemical vapor-liquid
constant pressure energy source, avoiding the disadvantages of any
electrically powered pump, whether operated from an external or
internal power pack, atomic powered pump, magnetic powered pump, or
the like. The present pump utilizes the pressure used to fill the
inner chamber as the kinetic energy source for restoring the
potential energy to the chemical pump. Operation of the pump
depends upon the physical concept that a vapor in equilibrium with
its liquid phase exerts a constant vapor pressure at a given
temperature, regardless of volume.
The invention is illustrated in the accompanying drawings in which
the corresponding parts are identified by the same numerals and in
which:
FIG. 1 is a perspective view of the implantable infusion pump,
partly broken away and partly in section, and showing the
components in exploded relation;
FIG. 2 is a top plan fiew of the pump;
FIG. 3 is a bottom plan view; and
FIG. 4 is a transverse sectional view, on a slightly enlarged
scale, of the assembled pump.
Referring now to the drawings, the infusion pump according to the
present invention comprises an outer cylindrical housing, indicated
generally at 10, and having a cylindrical side wall 11, circular
bottom wall 12 and annular top wall 13. A shallow cup-like member,
indicated generally at 14, of lesser diameter than housing 10,is
fitted into the space within annular housing top wall 13. Cup-like
member 14 is open at the top and includes a cylindrical side wall
15, generally circular bottom wall 16 and outwardly extending
annular flange 17. The elements of housing 10 and cup-like member
14 are formed and secured together in liquid-tight vapor-tight
junctions.
A bellows, indicated generally at 18, and comprised of a stack of
plurality of concentric flat annular rings 19, a circular bottom
wall 20, an annular top wall 21 and a cylindrical mouth or lip 22
is positioned within housing 10. Lip 22 is secured to the inner
periphery of top wall 21 and to flange 17 of cup-like member 14 in
liquid-tight vapor-tight relation. Adjacent rings 19 are secured
together alternately at their inner and outer peripheries, the
bottom-most ring is secured to the outer periphery of bottom wall
20 and the topmost ring is secured to the outer periphery of top
wall 21, all in liquid-tight vapor-tight relation, in the usual
manner to form an expandable-contractible bellows structure. The
annular space between the housing wall and the cup-like member
provides a recess into which the bellows may be collapsed.
Bellows 18 divides the interior of housing 10 into an outer chamber
23 and inner chamber 24 of varying volume. As chamber 23 becomes
larger through contraction of the bellows, chamber 24 becomes
smaller, and vice versa. Housing bottom wall 12 is provided with a
screw-threaded fitting 25 defining a central inlet port or aperture
to chamber 23 to receive a threaded plug 26. The head 27 of screw
plug 26 is provided with a transverse slot 28 on its outer surface
to facilitate closing of the opening, and an annular channel on its
inner surface to receive a resilient O-ring 29 to form a
liquid-tight vapor-tight seal.
The bottom wall 16 of cup-like member 14 is provided with a central
aperture and annular fitting 30 internally threaded to receive one
end 32 of nipple 31. The central portion of nipple 31 is of greater
diameter than threaded portion 32, and is desirably hexagonal or
other polygonal shape. Its bottom surface is provided with an
annular groove or channel to receive an O-ring 33 adapted to be
compressed against the upper surface of fitting 30 to form a
liquid-tight seal.
The upper portion 34 of nipple 31 is of somewhat greater diameter
than the lower portion 32 and is externally threaded to receive an
internally threaded knurled cap 35 having a central top opening 36.
A longitudinal passage 37 extends through nipple 31. The upper end
of passage 37 receives a plug or stopper 38 formed of elastic self
puncture-sealing material, which serves as an entry port to chamber
24. Stopper 38 has an outwardly flanged top 39 which engages the
upper end of nipple 31, the stopper being secured by knurled ring
35 in liquid-tight relation.
The fitting enclosing passage 37 may also be elongated, or bent, as
in the case where the pump itself would lie some distance under the
skin, i.e. in a body cavity, between two muscle planes, etc. The
liquid-tight closure apparatus, 35-39, would necessarily lie at the
end of this extension directly underneath the skin for percutaneous
refilling ease. This closure apparatus is not limited to a
puncture-sealing rubber stopper as shown, but may be replaced by
any displaceable self-sealing mechanism, such as a ball valve.
The expressions "upper," "lower," "top," "bottom," etc. are
relative and refer only to positions as shown in the drawings.
These relationships may vary in use when the pump is implanted in
the body with the opening 36 of cap 35 and stopper 38 accessible
under the skin for injection of refills of the drug or other
chemical to be infused.
One end of a thin small-diameter flexible capillary tube 40
(preferably within a larger protective tube) is secured in a radial
discharge passage in the body of nipple 31 so as to be in direct
fluid communication with the longitudinal passage through the
nipple and with chamber 24 to serve as a discharge therefrom. Tube
40 serves primarily as the pressure-drop flow regulator (e.g. may
be replaced by a porous plug or other flow regulating device) and
is of variable length and diameter. It is coiled around nipple 31
and fits within cup-like member 14. Tubing 40 extends to the
infusion site where the infused material is dispensed from its
opposite end. This capillary is preferably enclosed in a larger
polyethylene or Silastic cannula to facilitate placement.
The capillary tubing 40 serves a two-fold function, as a
flow-regulating resistance element and a discharge port into the
site of infusion. This may be replaced by a combination of any two
devices accomplishing the same end; for example, the resistance
element may be a porous metal plug or other filter, or any other
type of flow regulator, in direct fluid communication with the
infusion site by means of a conduit, such as a catheter or cannula.
Also, these resistance elements may number more than one, as in the
case of more than one site of infusion.
Bellows 18 is one form of liquid-tight, vapor-tight,
pressure-communicating interphase means which can be used to
separate the two chambers of the pump. Alternatively the chambers
may be separated by a resilient diaphragm which is compatible with
the substances within the chambers; or the second chamber may be
formed, in part at least, from a flexible bladder which is
compatible with the materials and capable of expanding and
contracting under influence of the infusate and vapor-producing
material in the first chamber, and the like.
A vapor in equilibrium with its liquid phase exerts a constant
vapor pressure at a given temperature regardless of volume. The
outer pump chamber 23 at its minimum volume is partially filled
with a stable volatile liquid that exerts a vapor pressure of
greater than one atmosphere at physiological temperatures
(approximately 37.degree. C) to form the vapor-liquid mixture of
the chemical power source. Volatile liquids among the members of
this very large group of compounds include: Perfluoro pentane,
Tetramethyl silane, Ethyl ether, Methyl formate, Ethanethiol,
Dimethyl sulfide, Ethylamine, 2-Methyl butane, Hydrocyanic acid,
Trichlorofluro methane, and Nitrogen tetroxide. These compounds, of
course, should be compatible with the substance serving as the
enclosure for chamber 23. The inner chamber 24 contains the
displaceable infusate. The flow rate of the infusate is varied
through the use of the capillary tubing 40 for the pressure drop,
which is governed by the equation: Q = (.pi.D.sup.4
.DELTA.P)/128.mu.L, where Q = flow in m1/sec., D = diameter in cm.,
.mu. = viscosity in poise, .DELTA. P = pressure in dynes/cm.sup.2,
and L = length in cm. The most readily adjustable parameters are
the length and diameter of the capillary and the viscosity of the
infusate. Refills of infusate are injected into the inner chamber
through the self-sealing stopper 38. The pressure generated by this
injection is sufficient to recycle the pump by condensing the
volatile vapor phase within outer chamber 23.
One or more spacer members 41 are desirably provided on the inside
of bellows bottom wall 20 (or cup bottom wall 16) to prevent wall
members 20 and 16 from becoming adhered through surface tension of
the infusate. Desirably a filter is installed on both the inlet and
outflow sides of the pump to reduce the possibility of particulate
contamination. The pump is constructed of materials non-toxic to
the host animal and compatible with both the infusate and the
chemical power source. Stainless steel is a desirable material for
forming the housing, bellows, fittings, etc. All exposed parts of
the pump are covered with Silastic, Teflon, or similar material,
compatible with body fluids and well-known for the coating of
devices to be implanted within the body.
In-vitro tests in an incubator at 37.degree. C have shown a high
degree of constancy in infusion rates at adjusted levels of
extremely low flow over various time increments. Representative
mean adjusted flow rates .+-. standard error for different time
periods include: 0.078 .+-. 0.0017 m1/hr for a 39 hour period;
0.101 .+-. 0.00035 m1/hr for an 82 hour trail; 0.183 .+-. 0.0073
m1/hr for a 68 hour trial; 0.363 .+-. 0.0046 m1/hr for a 43 hour
trial; 0.373 .+-. 0.013 m1/hr for a 44 hour trial; and 0.613 .+-.
0.020 m1/hr for a 13 hour trial. The capacity of a unit in which
the housing 10 measures about 21/2 by 7 cm. is approximately 20 m1.
This means that low flow may be maintained over 10 days before
refilling is necessary.
In-vivo trials in dogs, utilizing chronic heparinization as the
measureable parameter, have confirmed in-vitro pump specifications.
The pump is placed beneath the external oblique muscle with the
delivery catheter threaded into the inferior vena cava through the
femoral vein and the refill nipple or stopper is placed
subcutaneously to be readily accessible to percutaneous needle
injection. Constant infusion flows have been maintained so that the
daily Lee White clotting times and activated partial thromboplastin
times have remained at twice control values.
It is apparent that many modifications and variations of this
invention is hereinbefore set forth may be made without departing
from the spirit and scope thereof. The specific embodiments
described are given by way of example only and the invention is
limited only by the terms of the appended claims.
* * * * *