Note: Descriptions are shown in the official language in which they were submitted.
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MEDICATION DELIVERY APPARATUS AND METHODS FOR
INTRAVENOUS INFUSIONS
FIELD OF THE INVENTION
The present invention relates to apparatus and methodology for the
intravenous infusion of medication in accordance with a predetermined medical
therapy. More particularly, the present invention relates to medication
delivery
apparatus and methodology with improved ease of administration of a variety of
therapeutic agents by intravenous infusion.
BACKGROUND OF THE INVENTION
Intravenous medications including antibiotics and the like may be administered
intermittently over an extended period of time. Each administration of an
intravenous
therapy generally follows a predefined procedure that often includes a series
of manual
steps. Such manual steps may include saline flushes and generally terminate
with the
application of anti-clotting medication. The manual steps in the therapy
procedures are a
principle source of error, infection, and other complications that may arise
during
intermittent infusion therapy.
Accordingly, there is still a need in the art for apparatus and methodology
which
improve the administration of intermittent medication infiasion therapy. The
present
invention satisfies these and other needs in the art.
BRIEF DESCRIPTION OF THE INVENTION
The present invention overcomes many of the problems in the art by providing a
medication delivery system comprising a bag having at least one chamber
containing a
medication fluid and a manifold, and a pump having an activating mechanism
configured to activate the chambers) to dispense the fluid from the bag.
In accordance with another embodiment of the present invention, there is
provided a medication delivery container comprising a bag having a plurality
of
chambers, and a manifold assembly coupled to the plurality of chambers for
delivering
medications out of the chambers.
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In accordance with yet another embodiment of the present invention, there is
provided a fluid delivery container comprising a bag having at least one fluid
chamber
and structure for minimizing pressure drop between the chamber and an
associated
conduit upon the application of pressure to the chamber.
In accordance with still another embodiment of the present invention, there is
provided a fluid delivery container for the automated infusion of a plurality
of
pharmacological agents wherein the container comprises a plurality of chambers
each
configured with a respective geometry for controlling the administration of
the
plurality of pharmacological agents. The container additionally comprises a
manifold
assembly having a plurality of valves for controlling the administration of
the
plurality of pharmacological agents to an infusion site. Each chamber of the
fluid
delivery container has a configuration that controls the volume of each
pharmacological agent administered and the regimen with which said
pharmacological agent is administered.
In accordance with another embodiment of the present invention, there is
provided a fluid delivery pump comprising a structure for sequentially
applying constant
force to compress a flexible fluid container from a first end towards a second
end of said
container; and an energy absorption device coupled to the structure for
sequentially
applying constant force for limiting the maximum rate at which said structure
compresses the fluid container.
In accordance with yet another embodiment of the present invention, there is
provided a charging disk comprising first and second spring-loaded pawls, the
first
pawl having a shaft that engages a slot in the second pawl, the shaft and slot
being
configured such that the second pawl is depressed when the first pawl is
depressed,
but the first pawl is not depressed when the second pawl is depressed.
In accordance with still another embodiment of the present invention, there
are
provided methods for filling an invention fluid delivery bag having a
plurality of
chambers. In the invention methods, a first predetermined fluid volume is
measured; at
least one chamber of the bag is constrained to a second predetermined volume;
and the
plurality of chambers are filled through a bulk fill port with the first
predetermined
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volume of fluid such that a constrained chamber is filled with the second
predetermined
volume of fluid. A remaining chamber is then filled with the first
predetermined volume
of fluid minus the fluid of the constrained chamber.
In accordance with a further embodiment of the present invention, there are
provided methods for delivering medication fluids. Invention fluid delivery
methods
comprise compressing a bag having at least one chamber containing a medication
fluid
using a constant force spring to generate a predetermined pressure in the
chamber based
on the chamber's configuration and delivering the medication fluid from the
bag at the
predetermined pressure to an infusion site using a micro-bore tubing having a
length and
an inner diameter that establishes a predetermined flow rate.
In accordance with a still fiwther embodiment of the present invention, there
are
provided methods for charging an infusion pump having a constant force spring
coupled to first and second cover doors by a charging assembly. The invention
charging method comprises opening the first cover door to partially charge the
constant force spring; and opening the second cover door to fully charge the
constant
force spring.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 is a perspective view of a medication delivery container according to
the invention.
Figure 2 is a plan view of the medication delivery container of Figure 1.
Figure 3 is a plan view of a multi-chamber bag of the medication delivery
container of Figure 1, showing the bag's chambers and conduits and one
embodiment
of a chamber flex absorbing pattern.
Figure 4 is a cross-sectional view along line A-A of a multi-chamber bag of
Figure 3.
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Figure 5 is a plan view of a multi-chamber bag of the medication delivery
container of Figure 1, showing an alternate embodiment of the chamber flex
absorbing pattern.
Figure 6 is a plan view of a mufti-chamber bag of the medication delivery
S container of Figure 1, showing yet another embodiment of the chamber flex
absorbing
pattern.
Figure 7 is a perspective view of a manifold assembly of the medication
delivery container of Figure 1.
Figure 8 is a perspective view of the manifold assembly of Figure 7 from a
reverse direction.
Figure 9 is an exploded perspective view of the manifold assembly of
Figure 7.
Figure 10 is a schematic diagram showing the internal conduit and valve
configuration of the manifold assembly of Figures 7-9.
Figure 11 is a perspective view of a medication delivery pump according to
the present invention.
Figure 12 is a perspective view of the medication delivery pump of Figure 11,
with the pump's cover doors in a fully opened position.
Figure 13 is an exploded perspective view of the medication delivery pump of
Figure 11.
Figure 14 is a perspective view of a spring assembly of the medication
delivery pump of Figure 11.
Figure 15 is an exploded perspective view of the spring assembly of Figure 14.
Figure 16 is a perspective view of a constant force spring, in a stretched
position, of the spring assembly of Figure 14.
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Figure 17 is a plan view of the constant force spring of Figure 16, in a
stretched position.
Figure 18 is an elevation view of the constant force spring of Figures 16 and
17.
Figure 19 is an exploded perspective view of a base assembly of the
medication delivery pump of Figure 11.
Figure 20 is a perspective view of a gear box assembly of the medication
delivery pump of Figure 11.
Figure 21 is an exploded perspective view of the gear box assembly of
Figure 20.
Figure 22 is an exploded perspective view of the energy absorption device
shown in the gear box assembly of Figure 20.
Figure 23 is an elevation view of an energy absorption device shown in the
gear box assembly of Figure 20.
Figure 24 is a cross-sectional side elevation view of the medication delivery
pump of Figure 11 taken through the middle of the pump.
Figure 25 is an elevation view of the medication delivery pump of Figure 11
with a side cover removed, showing the position of a charging disk, the spring
assembly and the pump's cover doors with the spring in a fully coiled or
uncharged
position.
Figure 26 is an elevation view of the medication delivery pump of Figure 11
with a side cover removed, showing the position of the charging disk, the
spring
assembly and the pump's cover doors with the spring in a half coiled or half
charged
position.
Figure 27 is an elevation view of the medication delivery pump of Figure 11
with a side cover removed, showing the position of the charging disk, the
spring
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assembly and the pump's cover doors with the spring in a three-fourths
uncoiled or
three-fourths charged position.
Figure 28 is an elevation view of the medication delivery pump of Figure 11
with a side cover removed, showing the position of the charging disk, the
spring
assembly and the pump's cover doors with the spring in a fizlly uncoiled or
charged
position.
Figure 29 is a partially exploded perspective view of the charging disk of the
medication delivery pump of Figure 11, having spring loaded pawls.
Figure 30 is a partial cross-sectional view of the medication delivery pump of
Figure 11 showing forces (as arrows) of a constant force spring upon the
medication-
containing bag.
Figure 31 is a plan view of a spring guard of the medication delivery pump of
Figure 11.
Figure 32 is an elevation view of the spring guard of Figure 31.
Figure 33 is a schematic view of an administration set for use in the
medication delivery system of the invention.
Figure 34 is a perspective view of the medication delivery bag placed in a
receptacle area of the housing of the medication delivery pump.
Figure 35 is a graph showing fluid flow rate, versus time, from chambers 1-4
of a medication delivery bag in accordance with the medication delivery system
of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the present invention, there is provided a medication
delivery
container that is configured to administer an infusion therapy upon activation
by a pump
mechanism. The container is preferably further configured to interface with a
pump
apparatus in a manner that securely maintains the container in position during
pumping.
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The invention container comprises a multi-chamber bag wherein the chambers,
each configured to deliver predetermined amounts of liquid medication at a
predetermined rate and pressure, and each placed in relation to the others in
a manner
that determines the order in which the fluids contained therein, are
administered.
Each chamber has an associated exit conduit whereby fluid can exit each
chamber for administration to a patient. Thus, for example, a container might
have four
separate chambers, each sized to hold a different amount of fluid. The
container can be
filled so that each chamber has a different medication therein. If the four
chambers are
arranged sequentially in the bag from one end of the bag to the other, and
each chamber
is activated sequentially from one end of the bag to the other, then fluid
will be driven
out of the first chamber, and then the second, and so on until each chamber
has been
emptied.
Each chamber has one or more associated conduits. The conduits provide a
pathway for fluid to enter and/or exit each chamber. The conduits can be
integrally
formed during construction of the container, for example, by leaving channels
unbonded
when two flexible sheets are fizsed together to form the container.
Optionally, additional
internal structure (e.g., rigid or semi-rigid tubing, or the like) may be
provided to
facilitate fluid flow to and from each chamber. It is presently preferred that
the conduits
through which medication exits the chambers lie outside of the compression
region (i.e.,
the region to which pressure is directly applied by contact with a pressure
applying
structure in the pump apparatus). In this manner, mixing of residual
medications in the
conduits with subsequently administered medications from other chambers is
minimized.
Alternatively, the conduits may lie within the compression region,
particularly if mixing
is not a concern.
If the conduits are constructed by leaving unbonded channels in the container,
the conduit will have a generally flat shape but enlarges to have a more
tubular shape
upon the application of pressure to the corresponding chamber. The shape of
the conduit
depends on the strength of the materials used to construct the bag and the
pressure of the
fluid therein. Specifically, more rigid or thicker materials are more
difficult to flex thus
requiring greater pressure for enlarging the conduit. Advantageously, the
textured inner
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g
surface of at least one side of the container provides flow channels that
allow liquid
pressure to act along the length of the conduit to assist in opening the
conduit upon the
application of pressure to the respective chamber. Otherwise, if both inner
sides of the
container are smooth, surface tension may hold them together and a greater
amount of
pressure may be required to open the conduits and initiate flow.
In one embodiment of the present invention, the chambers and corresponding
conduits from each chamber are arranged in the bag so that when pressure is
applied
sequentially from one end of the bag to the opposite end, individual chambers
are
sequentially activated. It is presently preferred that the pressure be applied
evenly.
Even, sequential application of pressure can be accomplished by employing a
constant
force spring, a roller attached to a constant force spring, a motor-driven
roller, or the like.
It may be desirable to mix the contents of two or more chambers immediately
prior to administration. Accordingly, in another embodiment of the present
invention,
frangible seals between two or more adjacent chambers may be formed. In this
manner,
upon application of pressure sufficient to rupture the seal, the contents of
selected
adjacent chambers will be mixed. The chambers may be side by side (i.e.,
configured so
that pressure is applied to each substantially simultaneously), or in
sequence.
Chambers may also be configured to have a "blow down" period between
activation of one chamber and activation of the next chamber during an
infusion
sequence to prevent mixing of medications during the infusion. As described in
greater
detail below, this can be accomplished, for example, by providing a space
between
adjacent chambers, or the like.
It has been observed that there can be a pressure drop between a chamber and
its
corresponding conduit when pressure is applied to the contents of the bag.
This is
largely due to the formation of kinks in the bag when pressure is applied to
the contents
of the bag. The region of primary concern is the interface between the chamber
and its
corresponding conduit. Thus in one embodiment of the present invention,
structure is
provided to alleviate pressure drop between each chamber and its corresponding
conduit.
This can be achieved by one or more of several methods, including quilting of
the
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chamber, incorporation into the chamber of internal structures (e.g., a stmt,
tubing,
conduit bead(s), solid filament, or the like), or employing external
structures (e.g., a
source of pressure on the container, such as a protruding member of the pump
apparatus,
or the like), and the like.
As used herein, "quilting" means forming a structure in the interior of the
chamber wherein the bottom and top sides of the bag are connected, preferably
by fixsing
them together. It is presently preferred that quilting be employed to manage
pressure
drop. The desired connection between first and second sides of the bag can be
accomplished by the same methods used to form the perimeter seal of the
container.
Quilting may be at any region of the chamber that provides a substantially
reduced or
eliminated pressure drop between the chamber and its corresponding conduit. It
is
presently preferred that the quilting be in the region of the chamber that is
proximal to
the conduit. In this region of the chamber, any one of a number of quilt
shapes may be
employed, including a T dot configuration, 55a and 56a, as shown in Figure 2,
a dash
1 S dot configuration, 55b and 56b, as shown in Figure 5, bond blocks 55c and
56c, as
shown in Figure 6, or the like. These types of quilting are discussed in
greater detail
below in reference to specific embodiments.
Other features suitable for minimizing flow resistance (i.e., pressure drop)
caused
by kinks include thermoforming of the conduit, introduction of an internal
conduit bead
in the region where the conduit joins the chamber, coining, or the like.
Thermoforming
involves heating the bag materials in the region of the exit and associated
conduit until
the materials are softened slightly. Air pressure is applied to the chamber to
open (or
inflate) the exit and the conduit. The material is allowed to cool such that
the exit and
conduit retain a slightly circular opening or cross-section after the pressure
is removed.
For employing internal conduit bead(s), a portion of the bag adjacent the exit
to the
conduit is stamped with an offset bonding pattern or shim to provide a three-
dimensional
structure in the region of the exit. (See, e.g., structure 59, Fig. 6). This
can be analogized
to gluing two sheets of paper together at their perimeter and affixing a solid
piece, like a
bamboo skewer along the length of the seam between the two sheets. In this
manner,
even when the two sheets are pressed together, a channel will exist along the
skewer
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where the sheets are prevented from meeting one another. Additionally, coining
(i.e.,
forming a structured pattern in the bag material) may be applied to the sides
of the bag in
the region of the exit to provide additional flow pathways not subject to
greatly restricted
flow by kinks.
5 It is contemplated that each conduit will have an associated port where, at
a
minimum, fluids exit the container. These conduits may serve the dual purpose
of
providing a channel for both the introduction of fluids into the chambers) and
exit of
fluids from the chambers. Containers may be filled in a variety of ways by
suitable
personnel, e.g., by a pharmacist. Similarly, the container may be provided to
a
10 pharmacist in a variety of states. For example, the bag may be provided
filled, or empty
for subsequent sterilization and filling at the pharmacy. It is presently
preferred that the
multi-chambered bag is provided sterile and is then filled at the pharmacy.
The bag may
be appropriately filled using standard pharmaceutical admixture procedures and
equipment. Each chamber may be manually filled using injection ports or the
like.
Alternatively each chamber can be filled by introduction of fluids into a
common filling
conduit that branches off to the respective fill or dual purpose fill/exit
conduit associated
with each chamber. Once the bag is prepared, it is labeled and sent from the
pharmacy to
the end user.
The container may have one or more ports for introduction of fluids into one
or
more of the individual chambers of the container. In one embodiment, these
ports have
associated conduits, separate from the exit conduits. The ports are configured
to allow
regulated, sterile introduction of fluids. This can be accomplished by fitting
the ports
with injection ports, or the like.
Because the container is to be subject to the sequential application of
pressure, it
is desirable for the container to be anchored inside the pump apparatus in a
manner that
prevents the pressure application device from merely moving the container
ahead of it as
the pressure is applied from one end of the bag to the other. Accordingly, it
is presently
preferred that the container be anchorable to the pump apparatus. This can be
accomplished in a variety of ways, including the use of fasteners secured to
the bag that
will mate with counterpart fasteners in the pump apparatus. Such fasteners
include hook
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and loop fasteners, snaps, buttons, zippers, and the like. In a presently
preferred
embodiment, the container is anchored by forming holes in a non-fluid
containing
portion of the bag, and mating these holes with corresponding protrusions such
as pins,
or the like, in the pump housing. These anchoring structures can serve the
dual purpose
of securing the bag and positioning it properly in the pump apparatus. This
latter
purpose can be accomplished by orienting the attachment structures so that
there is only
one orientation with which the bag can be positioned in the pump apparatus.
Invention containers further comprise a manifold to regulate delivery of the
medication from the bag port of the conduits to an administration tube set
("administration set"), and also optionally provides a structure for filling
the container.
As used herein, "bag port of the conduit" and "bag port" refer to the terminal
portion of
each conduit leading to/from a chamber in the bag. The bag ports may have an
adapter
affixed thereto for mating the bag ports with the manifold, or the manifold
may be
attached directly to the bag ports. The manifold can be any structure that is
attachable to
the bag ports (or adapters) in a fluid-tight manner while providing a common
outlet for
all bag ports to the administration set.
In describing the manifold, reference will be made to the bag side, where the
manifold attaches to the bag ports, and the infusion side, where the manifold
attaches to
the administration set. Further reference will be made to chamber ports of the
manifold,
where the manifold attaches to and is in fluid communication with the bag
ports.
Accordingly, the chamber ports are on the bag side of the manifold. Additional
reference will be made to an output port of the manifold, where the manifold
attaches to
and is in fluid communication with the administration set. Although optional,
it is
presently preferred that the manifold also have a bulk fill port, where the
manifold can
be attached to, and be in fluid communication with, a source of fluid
medications for
introduction into the bag.
Manifolds contemplated for use in the practice of the present invention will
have
manifold conduits for directing fluid from chamber ports to the output port
for exit to the
administration set, and from the bulk fill port, when employed, to the chamber
ports.
These manifold conduits can be isolated from one another in a fluid-tight
manner and
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can comprise internally molded chambers connecting the desired portions of the
manifold, or they may comprise internally mounted tubing connecting the
appropriate
portions of the manifold, combinations thereof, or the like.
In order to regulate the flow of fluid through the manifold and to prevent
backflow from the output port to the chamber ports, it is presently preferred
that the
manifold have check valves therein. Check valves can be configured in a
variety of
manners to regulate fluid flow as desired; all such configurations are
contemplated as
being within the scope of the present invention. In one embodiment of the
present
invention, fluid flow is regulated so that fluid exiting the container and
entering the
manifold through the chamber ports can only exit the manifold through the
output port
without returning to the bag by way of any other chamber port. This is
accomplished by
interposing a first check valve in a first conduit between each chamber port
and the
output port. The check valve only allows fluid to flow from the bag side of
the manifold
towards the infusion side where the output port is located.
It is important to note that some or all of the bag chambers may be
individually
filled by way of optional separate fill ports on the bag rather than by way of
the optional
bulk fill port of the manifold. In an embodiment of the present invention,
when a bulk
fill port is to be used, fluid flow in the manifold is fiu ther regulated so
that fluid
introduced through the bulk fill port can access one or more of the chamber
ports for
filling of chambers in the bag. Accordingly, chamber ports to be used for both
filling
and dispensing fluids will have two manifold conduits associated therewith: a
first
manifold conduit, as described above, for directing fluids from the chamber
ports) to the
output port; and a second manifold conduit branching off of the first at a
point between
each chamber port and the first check valve. In this embodiment, a second
check valve is
located on each second manifold conduit between the chamber port and the bulk
fill port.
The second check valve only allows fluid to flow from the bulk fill port
towards the
chamber port. A schematic of one example of this embodiment is provided in
Figure 10,
as further described below.
Any type of check valve can be employed in the practice of the present
invention, including ball check valves, umbrella check valves, and the like.
In a
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presently preferred embodiment of the present invention, an umbrella check
valve is
employed. Umbrella valves are inexpensive, simple in their operation and easy
to
install. Because umbrella valves are held in place by fi-iction, it is
presently preferred
that the interior of the manifold be configured so that, upon assembly of the
manifold,
the umbrella valves are held securely in place by the internal structure of
the manifold.
This can be accomplished simply by having a structure that contacts the center
of the
umbrella portion (i.e., the dome of the umbrella) to bias the valve towards
its associated
passageway. In this manner, the force of liquid flowing past the valve will
open but not
unseat the valve.
The ports, valves and conduits of the manifold may be configured in any manner
that permits the desired flow of fluid through the manifold. It is presently
preferred that
the conduits and output port be configured so that fluid exiting each
sequentially
activated bag chamber flows through its associated first check valve and then
past all
conduits leading from previously emptied bag chambers, before the output port
is
encountered. In this manner, residual fluid output from each bag chamber is
pushed
through the manifold and out through the output port by fluid from
subsequently emptied
bag chambers.
In order for the fluid flow to be further regulated (e.g., to prevent
unintentional
fluid flow from the bag through to the output port), it is desirable that the
check valves
be controllable as to when flow is permitted therethrough. This can be
accomplished in
a number of ways, depending on the type of check valve employed. For example,
a
valve can be employed having a threshold operating pressure (i.e., a cracking
pressure)
that opens the valve. The cracking pressure of the valve may be any pressure
suitable for
the intended application. Suitable cracking pressures should be no higher,
obviously,
than the pressure generated by the pump apparatus, yet high enough to prevent
unintentional flow through the manifold. Cracking pressures can be in the
range of about
0.25 lbs per square inch up to about 2 lbs per square inch. It is presently
preferred that
the cracking pressures be in the range of about 0.50 lbs per square inch up to
about 1 lbs
per square inch. In a most preferred embodiment, the cracking pressure is
about 0.75 lbs
per square inch. The cracking pressures should be consistent in a given
direction of fluid
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flow. Thus, the check valves associated with the chamber ports and the output
port can
have one cracking pressure while the check valves) associated with the bulk
fill port has
a different cracking pressure. Due to economies of scale, it is presently
preferred that the
valve types and cracking pressures be consistent throughout the manifold.
With reference to Figures 1 and 2, the medication delivery container 10 of the
invention includes a multi-chamber bag 12, a manifold assembly 14 and a tube
assembly 16. The container provides improved infusion therapy administration
which is
particularly advantageous for reducing errors, infections and other
complications
associated with manual infusion techniques.
The multi-chamber bag, as shown in Figures 3 and 4, may include four
chambers 18, 20, 22 and 24, six ports 26, 28, 30, 32, 34 and 35, and six
conduits 36, 38,
40, 42, 44 and 46 for coupling each of the respective ports to a chamber. The
multi-
chamber bag may have other chamber, port and conduit configurations of varying
number, sizes, and shapes in accordance with the invention. The ports may lie
at the end
48 or along one or more edges of the bag. The chambers comprise a relatively
large area
of the bag in a central portion of the bag and are configured to be filled
with medication
fluids or pharmacological agents. The central chamber portion of the bag may
be
referred to as a compression region which is sequentially compressed by
application of
an external pressure (e.g. a pump having a constant force spring as described
herein) to
drive liquid from the chambers through the respective conduits and out the
ports in
accordance with the infusion therapy. The conduits generally lie outside of
the
compression region to avoid residual medications in the conduits from mixing
with
subsequently administered medications from other chambers. The conduits may
lie
within the compression region particularly if mixing is not a concern.
The multi-chamber bag 12 is preferably formed of two flexible sheets 50 and
52,
of material and has a generally rectangular flat shape. The flexible sheets
may be ethyl
vinyl acetate (EVA), polyvinyl chloride (PVC), polyolefin or other suitable
material.
One sheet may have a relatively smooth inner surface and the other sheet may
have a
taffeta texture (or similar pattern that is not smooth, such as ribs) embossed
on its inner
surface. Alternatively, both sheets may have an inner surface that is not
smooth. The
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sheets are bonded together to create the patterns for the chambers, conduits,
and ports.
The materials may be bonded by suitable means, e.g., by a radio frequency (rf)
seal,
sonication, by heat seal, adhesive, or the like, to form an air and fluid
tight seal between
the chambers and the conduits. When filled with medication fluids, the
chambers bulge
creating a "pillow-like" shape (Figure 4). It is also presently preferred that
at least one
side of the bag be transparent to facilitate viewing of the contents.
The first chamber 18 is fiwthest from the port side 48 of the bag and may
contain
a first medication fluid of an infusion therapy sequence. The first chamber is
coupled to
a first bag port 26 by a first conduit 36. The first chamber is filled with
fluid through the
10 first bag port.
The spacings 60, 62 and 64 between the chambers advantageously provides a
"blow-down" period during an infizsion sequence to prevent mixing of
medications
during the infusion. The spacing 62 between the second chamber 20 and the
third
chamber 22 is sized based on the time needed for the chamber and conduit to
"blow
15 down", or flow until the residual pressure is below the cracking pressure
of the
associated check valves in the manifold. The area of the spacing 62 may be
sealed only
around the perimeter with no bond between completion of the sheets in the
central
spacing area to provide additional kink and flex absorbing characteristics to
the bag.
This spacing 62 is configured to allow a sufficient time period between
completion of
the infixsion of the medication in the second chamber and the beginning of the
infusion
of medication in the third chamber so as to minimize or prevent mixing of the
medication in the second chamber with the medication in the third chamber.
This time
period is sufficient to allow the material spring strength of the flexible
sheets, 50 and 52,
that form the conduits to pull the respective conduit 38 flat to expel
residual fluid from
the conduit. The time required will, of course, vary with the size of the
chamber, the rate
of infi.~sion, and the like. Note that the spacing 60 between the first
chamber 18 and the
second chamber is effectively as large as the spacing 62 because a significant
portion of
the second chamber must be compressed before the pressure is sufficient to
expel
residual fluid from the second chamber. Thus, the spacing between chambers
provides a
delay between chambers to allow expulsion of residual conduit fluid before the
start of
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16
the infusion of medication from the next chamber. This is especially
advantageous for
preventing mixing of agents from non-adjacent chambers.
The second chamber 20 typically has the largest fluid volume of the four
chambers. As discussed in more detail below, the second chamber is coupled to
the
second port 28 and the sixth port 35 by respective conduits. When filled with
medication, the second chamber has a pillow-like shape. As a result of the
relatively
large pillow-like shape of the second chamber (and the flexible nature of the
materials
used to construct the bag), when pressure is applied to the second chamber,
there may be
a resistance to flow because the chamber has a tendency to kink near the
chamber exit 54
to the conduit, often cutting off fluid flow to the conduit. To prevent a
pressure drop due
to kinks from forming at the exit port, a "quilt" pattern of bonds may be
placed near the
exit. The quilt pattern may consist of two spot bonds, 55a and 56a, having a
"T dot"
configuration. The quilt pattern moves the chamber's kinking tendencies to
other areas
of the bag where kinking is not of concern, away from the exit 54. The first
bond 55a
has a "T" shape providing first and second openings, 57 and 58. From
observation, it
appears that the cross bar of the T causes the chamber to kink laterally and
preferentially
above the outlet 54. The leg of the T fiu-ther causes a longitudinal kink away
from the
outlet 54. After the chamber has been compressed to the first opening 57, the
"pillow"
of the compressed chamber is of a size that is less susceptible to exit kinks.
The second
"dot" bond further discourages kinking of the second opening 58. The quilt
pattern may
be provided to other ports of the chamber to prevent kinking while removing
air, etc.
Empirical tests have determined that the quilt pattern configuration
discourages kinks at
the exit and allows reliable delivery of the medication from the second
chamber into the
respective conduit 38.
In an alternative embodiment of the invention, the quilt pattern may consist
of
the two spot bonds, 55b and 56b, shown in Figure 5. The first spot bond 55b
may have
a generally elongated oval shape and may be preferably placed at a 45 degree
angle with
respect to the chamber sides. The second spot bond 56b may have a shorter oval
shape
and is preferably placed between the first spot bond and the exit or entrance
to
conduit 38.
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In another embodiment of the invention, the quilt pattern may consist of the
bond
blocks, 55c and 56c, shown in Figure 6. The first bond block may have a
generally
elongated angle shape with a protrusion and may be preferably placed about %Z
inch from
the exit 54 to conduit 38. The second bond block may have a corner shape and
is
preferably placed nearly between the first bond block and the exit 54 (or
entrance) to
conduit 38.
Referring to Figure 2, the third chamber 22 is coupled to the third port 30 by
a
respective conduit 40. The fourth chamber 24 is coupled to the fourth and
fifth ports, 32
and 34, by respective conduits 42 and 44.
The six ports are used to fill and/or empty the fluid in the chambers. Two of
the
ports, the fifth and sixth ports, 34 and 35 (see Figure 2, for example), are
directly
coupled to the fourth chamber 24 and second chamber 20, respectively. The four
remaining ports, 26, 28, 30 and 32, are coupled to a manifold assembly 14 for
filling the
chambers and for delivering the medications of the infizsion therapy. A short
plastic tube
66 couples each respective port to the respective manifold port or injection
fill site 67.
The tubes extend into the ports between the plastic sheets, 50 and 52, and are
sealed to
the sheets to form closed, sealed fluid connections.
The bag may be constructed of an EVA (ethylene vinyl acetate) or like film
material which is often used in the construction of intravenous solution
containers. This
material is generally rugged, durable and biocompatible. The bag is configured
to
withstand pressures greater than those achieved during an infusion. The
interior of the
pump housing where the bag resides is configured such that a filled bag will
be
positioned correctly and securely. In the depicted embodiment, this is
accomplished by
the use of registration pins 151 (or similar features) in the pump receptacle
(Figure 12) to
engage, for example, corresponding holes 68 and 70 in the bag (See Figure 2).
The tubes may be formed of co-extruded plastic for providing a compatible
bonding surface. For example, if the bag 12 is formed of EVA and the manifold
is
formed of acrylonitrile butadiene styrene (ABS), the co-extruded tube 66 would
have an
exterior of EVA and an interior of PVC. The outside of the tube (EVA) would be
heat
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18
sealed to the bag (EVA) and the inside of the tube (PVC) would be solvent
bonded to the
outside of a corresponding port of the manifold (ABS).
In one application of the invention, the first, second and third chambers,18,
20
and 22, may be filled with a diluent such as a saline solution, a dextrose
solution or
sterile water, and the fourth chamber 24 is filled with heparinized saline
(e.g., through
the fifth port 34). A medication, such as an antibiotic, may be injected into
the second
chamber through the sixth port 35 before commencing delivery of the infusion
therapy to
a patient.
The mufti-chamber bag 12 also may include a plurality of alignment holes,
e.g.,
68 and 70. The alignment holes may be offset and aligned with corresponding
features
such as pins in a pump. The alignment holes ensure that the bag is installed
into the
pump in the correct position, and maintained in that position during pumping.
With reference to Figures 7-8, the manifold assembly 14 has a tube or output
port
72, a bulk fill port 74 and four chamber ports 76, 78, 80 and 82. The four
chamber ports
1 S are connected, respectively, to the first, second, third and fourth bag
ports 26, 28, 30 and
32 (see Figure 6). The manifold assembly allows filling of the first, second
and third
chambers,18, 20 and 22, through the bulk fill port and delivery of the fluids
in the first,
second, third and fourth chambers through an output port. Seven check valves,
84, 86,
88, 90, 92, 94 and 96 (Figure 9), control the fluid flow direction within the
manifold, in
concert with manifold conduits formed by bonding manifold pieces together. The
manifold assembly may have additional or fewer check valves and ports based on
the
number and configuration of chambers implemented by the mufti-chamber bag.
In a particular embodiment, as shown in Figure 9, for example, the manifold
assembly may be constructed of three molded pieces and seven check valves. The
three
molded pieces may be formed of any suitable biologically compatible rigid or
semi-rigid
material, e.g., ABS plastic, or the like. The three molded pieces are a bag
side piece 98,
a middle piece 25, and an infusion side piece 27. The bag side piece has the
four
chamber ports 76, 78, 80 and 82. The bag side piece also has recesses 23 for
three of the
umbrella valves 97 and conduits 19 for directing fluid flow between the ports
in
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19
conjunction with the other manifold pieces. The middle piece 25 has valve
through
holes 21 for receiving the umbrella valves and for providing fluid
communication
through the middle piece. The middle piece also has conduits on both sides
that
correspond to the conduits on the respective side pieces. The infusion side
piece 27
includes the output port 72 and the bulk fill port 74. The infusion side piece
also has
internal recesses (not shown) for four of the umbrella valves and conduits
(not shown)
for directing fluid flow within the manifold assembly, as well as protrusions
designed to
contact the middle of the dome of the umbrella for biasing the check valve in
the proper
position. The three manifold pieces are attached together by suitable
adhesive, clips or
the like to form the manifold assembly. The manifold assembly can be further
shaped so
that it can only be correctly placed in a corresponding receptacle in the pump
apparatus.
For example, the manifold may include one or more beveled edges 109 (Figure 7)
for
correctly aligning the container 10 in a pump mechanism.
The medication delivery container 10 may have a wide variety of configurations
and dimensions based on the prescribed infusion therapy. For example, when
infusion
therapies permit (e.g., when small volumes of concentrated solution are to be
infused),
bags may be sufficiently small to incorporate into an easily portable pump
apparatus.
Chambers may be configured for the simultaneous infusion of medicaments from
separate chambers. Empirical evaluation of the container and manifold
configuration
shown in Figures 1-10 has demonstrated effective delivery of fluids.
In accordance with another embodiment of the present invention, there is
provided a pump that is configured to administer an infusion therapy using an
invention
medication delivery container by expelling medications in the flexible bag of
the
invention container from the bag and delivering the medications to an infusion
site. The
pump provides improved administration of infusion therapy which is
particularly
advantageous for reducing errors, infections and other complications
associated with
manual infusion techniques.
The pump can be configured to administer an infusion therapy using an
invention
medication delivery container. The pump can be further configured to
specifically
interface with an invention medication delivery container (hereinafter, "bag")
that is
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compartmentalized to contain multiple, separate medication solutions, and to
deliver the
solutions in a sequential, rate-controlled manner. Accordingly, invention
pumps
comprise a structure for applying constant force to a bag in a manner that
sequentially
activates chambers within the bag so that fluid contained therein is driven
out through
S one or more conduits associated with each chamber, and into an intravenous
(i.v.) drug
delivery system (e.g., an administration set comprising microbore tubing that
is
attachable to a standard i.v. needle).
In accordance with yet another embodiment of the present invention, there is
provided a housing for receiving and retaining an invention medication
delivery
10 container (bag), as described herein, during the pumping operation. The
housing further
contains the structure for applying constant force to the bag.
The housing (e.g., a pump housing as described herein) can be configured to
specifically receive a particular type of bag. This configuration can comprise
any
structures) that will serve to hold a specific bag in operative relationship
with the
15 mechanism for constant force. As used herein, "operative relationship with
the
mechanism for applying force" means that the bag is retained in a manner that
allows the
mechanism for applying force to activate bag chambers in the intended
sequence,
without displacing the bag so as to prevent correct operation. For example,
the housing
can include positioning pins that match holes in a medication container bag,
fasteners
20 (e.g., hook and loop, snaps, buttons, zippers, or the like) that mate with
counterparts on
the bag, or the like. In a particular embodiment, the housing is fixrther
configured to
receive a manifold attached to the bag. By employing sufficient structure to
retain the
manifold, the bag is further secured.
In a preferred embodiment, the mechanism for applying force to expel liquid
from the container contemplated for use in the practice of the present
invention is a
pump with a constant force spring. However it should be understood that other
structures for applying force may be substituted therefor, including a roller
attached to a
constant force spring, a motor-driven roller, or the like. Each such mechanism
will
require a different housing configuration to retain the structure and to
maintain it in
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21
operative relationship with the bag during the pumping or activation process.
All such
housing configurations are contemplated as within the scope of the present
invention.
Because it is often desirable to further control the rate at which force is
applied
by the constant force spring, in one embodiment, invention pumps comprise an
energy
absorption device. Any suitable energy absorption device may be employed.
Energy
absorption devices contemplated for use in the practice of the present
invention include
both mechanical and electrically operated devices. Mechanical devices include
watch-
type gear assemblies (as further described herein), watch escapements, an air
resistance
device, a resistance rack, an eddy current gear, a viscous damper, and the
like. As used
herein 'watch-type gear assembly" means an assembly comprising a plurality of
interconnected toothed cogs or gears that operate, in a manner known to those
of skill in
the art, to absorb energy by rotating and also to modulate the rate of
rotation in a
predictable manner. The energy absorption device can be secured to the
constant force
spring at its hub. Thus, the constant force spring has a maximum rate it can
travel as
determined by the strength of the spring, the configuration of the bag, and
the amount
and nature of the fluid contained in the bag. The energy absorbing device then
further
limits the rate at which the constant force spring can travel (i.e., work).
The invention pump can fiuther comprise an activating mechanism for charging
or cocking the mechanism for applying force to the container. This can be
accomplished
in a variety of ways depending on the exact type of activating mechanism
employed. In
an embodiment where a constant force spring is used, the charging mechanism
will act
to translate energy input by the user into stored energy in the constant force
spring. This
can be accomplished in a variety of ways, depending on the exact type of
constant force
spring employed. In one embodiment, wherein the constant force spring
comprises a
coiled leaf of metal or other suitable material attached to a hub at the
center of the coil,
the charging mechanism is attached to the hub. The other end of the spring is
fixed to
the pump housing proximal to one end of the housing. In this manner, force can
be
applied to the center of the hub and directed away from the fixed end of the
spring,
thereby causing the spring to unroll. It is presently preferred that the hub
of the spring
protrude from either side of the spring so that the hub can be captured in a
track or like
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22
structure for retaining and guiding the travel of the constant force spring.
In this manner,
the travel of the spring can be controlled during charging and in performing
its work. It
is even more preferred that the hub have additional structure for facilitating
even
retraction of the spring (i.e., so that one side is not unrolled faster than
the other). This
can be accomplished in a variety of ways, including employing a toothed gear
and track
assembly, as fixrther described herein, or the like. The hub, gear and track
assembly
serves an additional fiznction of providing an attachment point for the energy
absorption
device described herein, as well as a means to control the forward (i.e., work
producing)
travel of the spring.
Charging mechanisms contemplated for use in the practice of the present
invention can include a force transmission structure suitable for pushing or
pulling the
hub of the spring in the intended direction (i.e., away form the fixed end of
the
spring). Suitable force transmission structures include chains, belts, rods or
the like, if
the hub is to be pulled; and rods, or the like if the hub is to be pushed.
More
specifically, charging can be accomplished by employing a crank, a
pneumatically
operated mechanism, a plunger, a slide, or the like. It is presently preferred
that the force
transmission structure be connected to a mechanism for providing a mechanical
advantage to the user, as the energy required to charge the constant force
spring can be
substantial. A mechanical advantage can be provided in the form of a lever
mechanism,
a multi-stage cocking mechanism, or the like. A multi-stage cocking mechanism
allows
partial cocking or charging of the constant force spring during each stage of
the cocking.
In this manner, the often substantial force required to charge the constant
force spring
can be parceled out over several operation stages, thereby making cocking
easier than if
a single stage mechanism where employed.
Advantageously, the pump will also comprise an indicator such as a wheel, or
the like to indicate the progress of infusion of the medication to the
patient. The
indicator can interface with the activating mechanism and any associated
gearing to
provide a true indication of the progress made by the activating mechanism. In
a
preferred embodiment, the indicator is geared in a manner to amplify the
progress of
infizsion.
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In one embodiment, described with reference to Figures 11, 12, and 13, the
medication delivery pump 110 of the invention includes a receptacle 112 for
receiving a
bag of the medication delivery container. A spring assembly 114 in the
receptacle rolls
up and compresses the bag at a maximum rate controlled by an energy absorbing
device
116 in the form of a timer assembly. Medications in the chambers) of the bag
are
expelled from the bag through a suitable exit structure, e.g., a manifold
assembly, and
into an administration set attached to the manifold assembly. The
administration set
delivers the medications to an infusion site. The pump, in combination with
the
container, provides improved administration of infusion therapy which is
particularly
advantageous for reducing errors, infections and other complications
associated with
manual infusion techniques.
Figure 13 illustrates a pump housing that includes a base 118 and a pair of
cover
doors,120 and 122, respectively. The cover doors are opened to provide access
to the
container receptacle and to charge the spring assembly. In embodiments where a
two-
stage, door-operated charging mechanism is not employed, a single door can be
used.
The pump housing, illustrated in Figures 11, 12 and 13, preferably includes a
handle 124
for carrying the pump and to assist in holding the pump as the first and
second cover
doors are opened to charge the spring. The cover doors also optimally include
a window
or opening,126 and 128, in each cover to allow viewing of the spring assembly
and the
bag in the receptacle. The base includes a container receptacle, a mechanism
for
applying constant force, such as a spring assembly 114, optional access points
such as a
bottom cover 112, a charging assembly 134 and an energy absorption device 116.
With reference to Figures 14-15, the spring assembly 114 includes a constant
force pump spring mechanism 136, such as a torsion spring 138, for keeping the
constant force spring wound to provide appropriate radial force, and a pump
spring shaft
140. The constant force spring, shown in Figures 16-18, is formed of any
suitable
material having resilient properties, e.g., a sheet of steel. The pump spring
preferably
has a structure such as holes 142 at one end for convenient attachment to the
base 118.
Those of skill in the art recognize that other structures for attachment can
be employed
such as a clamp or adhesive. A drum 144 is suitably attached, e.g., welded, to
the other
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end of the pump spring. At rest, the pump spring is completely coiled. The
torsion
spring has one end connected by suitable means, e.g., a first bushing 146 to
the drum
inside of the pump spring. The other end of the torsion spring is connected to
the shaft
by a suitable device, e.g., a second bushing 148. In order to prevent the
second bushing
from rotating on the shaft, the bushing is attached to the shaft by a pin 150,
or other
suitable structure. The first and second bushings are held in place on the
shaft by
respective retention devices such as nuts, or, as depicted in Figure 15, first
and second B-
rings 152 that engage slots on the sha$. As discussed in more detail below the
torsion
spring is one device that can be employed to provide radial tension on the
pump spring
as it compresses and rolls up the bag.
As shown in Figure 19, the base 118 includes a frame 156 and structure (e.g.,
slots 172 and pair of racks 158) for retaining the pump spring hub and guiding
the travel
of the pump spring. The frame has at least four sides that form the sides of
the container
receptacle 112. At a convenient location, e.g., at a front side of the frame,
is a handle
124 and a side opening to a tube exit 160. Adjacent the tube exit is a recess
configured
to receive a manifold assembly if one is present on the container. In the
depicted
embodiment, the pump spring assembly 114 has one end (opposite the drum end)
attached using a plate 163 to the frame adjacent to the front side. Any manner
suitable
for attaching the pump spring to the housing base can be employed in the
practice of the
present invention.
It can be advantageous to access the components of the pump for purposes such
as maintenance or adjustment; accordingly, in one embodiment of the present
invention,
the housing can have one or more removable portions to provide the needed
access. For
example, a bottom cover 132 can be removably secured to the bottom of the
frame. The
housing is sized to accommodate the pump spring in any state of charging. In
one
embodiment, the bottom (or bottom cover, when employed) has an inclined plate
164
(FIG. 3) that is tapered to accommodate an increasing spring diameter as the
spring rolls
up the bag. Accommodations are also included for the energy absorption device
and the
charging assembly. In the depicted embodiment, at the rear side of the frame
is a
compartment 166 for attaching the charging assembly and the timing assembly.
As with
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other key components of the pump, it is advantageous to provide access to
these
components for maintenance. A window 168 is preferably provided into the
compartment for viewing an indicator device, such as a wheel 170, that
indicates the rate
of movement of the pump spring. On two long sides of the frame are structures
to
receive the hub of the spring (or roller); contemplated structures are
exemplified by slots
172 and adjacent ledges 174. The racks 158 are mounted on the respective
ledges, or are
otherwise accommodated within the housing in alternative embodiments. Side
covers
252 may be employed to cover the spring gear and rack.
The constant force pump spring assembly can be retained in the housing in a
10 variety of ways. Refernng to the embodiment shown in Figure 19, the spring
assembly
114 fits in the bottom of the container receptacle with the shaft extending
through the
slots 172 in the long sides of the frame 156. Located at each end of the
spring shaft 140
are suitable drive structures, e.g., first and second gears 176, respectively.
Other drive
structures such as a bearing and race assembly, or the like, can be employed
in the
15 alternative. Structures for further retaining the spring include two
horizontal slides or
guide blocks 178 which are on the shaft between each gear and the pump spring
and are
configured to slide along the respective slots while allowing the shaft to
rotate. Each
gear is held on the shaft by suitable attachment devices, e.g., a pin 180 and
an e-ring 182.
Each gear engages the corresponding rack 158 to rotate the shaft as the spring
assembly
20 slides in the slots.
A mechanism for charging the constant force spring can be attached to the
spring
hub for pulling or pushing the hub away from the fixed end of the spring. In
one
embodiment, the charging mechanism is coupled to the spring hub by a belt
assembly.
In this embodiment, the hub will have sufficient structure, either as part of
the hub, or
25 attached to the hub, to facilitate secure attachment of the charging
mechanism to the hub.
For example, at each end of the shaft, adjacent to the respective gear (if
employed), can
be a belt hub 184 (Figure 13). Each belt hub is attached to one end of a belt
186 (Figure
25) formed of suitable material, e.g., a spring of steel. The other end of
each belt is
attached to the charging mechanism assembly 134. In this embodiment, the belt
performs a dual purpose, i.e., both charging and rate control. The belt is
also attached to
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26
the energy absorption device which controls the maximum rate at which the
constant
force spring can work. Thus, the energy absorption device serves to hold back,
via the
belt, forward progress of the constant force spring.
A constant force spring 136 has a tendency to roll up the bag 188 (Figure 30)
faster than the fluid may be expelled from the chambers because the hub of the
spring is
of fixed diameter, while the diameter of the spring changes as it rolls up. As
a result, the
tension on the spring can vary (i.e., lesser in the early portion of the
pumping process
and greater during the later portion of the spring travel), thereby allowing
the spring to
roll over fluid-containing chambers in the bag in the early portion of the
spring travel,
while possibly stalling due to increased tension in the later portion of the
spring travel.
Accordingly, a tension force may be applied to the end of the constant force
spring that
is distal to the hub in order to maintain the spring in a tightly coiled
configuration in the
early stages of the spring travel while lessening the tension in the later
stages of the
spring travel. It is presently preferred to have the distal end of the
constant force spring
fixed. Thus, in the presently preferred embodiment, a structure is provided to
allow for
relative motion between the hub and the constant force spring so that the
constant force
spring is tightened during the early stages of its travel and slackened during
the later
stages of its travel. The force provided by the energy absorption device can
be translated
to the constant force spring, while still allowing the relative motion between
the hub and
the spring by employing a tensioner mechanism as exemplified in Figure 15.
This figure
depicts a torsion spring 138 that is internal to the drum 144. As force is
applied to the
hub, it is transferred to the tension spring which discourages or prevents the
constant
force spring from rolling over chambers of the bag that still contain fluid.
In the embodiment depicted in the Figures 11-13, the position of an uncharged
constant force spring assembly 114 is at a front or handle end of the
container receptacle
112. Mechanical energy is stored in the pump spring 136 using a charging
assembly
134. As discussed in more detail below, the charging assembly uses a ratchet
mechanism coupled to the two cover doors, 120 and 122. Although other charging
mechanisms may be employed in the practice of the present invention, a two-
door
ratchet mechanism is presently preferred because it reduces the force required
to be
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27
'applied to open a cover door during charging of the pump spring. The pump
spring is
pulled back a substantial portion of the distance across the receptacle, e.g.,
25-75%, by
opening the outer cover to an open position. The pump spring is pulled back
the
remaining distance by opening the inner door. Of course, other charging
mechanisms
S can be employed, such as a wind up mechanism comprising a reduction gear, an
external
handle attached to a reduction gear or ratchet mechanism, or the like.
The charging assembly 134 includes the belts 186, two belt drums 144 (Figure
13), charging disks 194, and hub rings,198 and 100, on the cover doors,
respectively. It
is presently preferred, for even application of force to the spring, that the
charging
assembly is substantially symmetric with similar components along both sides
of the
pump. The components on each side of the charging assembly are coupled by a
gear
box assembly 202. For cosmetic and protective purposes, the charging assembly
can be
covered on both sides by end caps 204.
The gear box assembly 202, shown in Figures 20-21, includes a gear box 206,
and associated gearing to transmit force from a charging interface such as a
handle, or
the like, to the constant force spring. In one embodiment, the associated
gearing
includes a link shaft 208, first and second spur gears 210, and first and
second charging
gears 212 on first and second charging shafts 214, respectively. The spur
gears and the
charging gears will have an appropriate gear ratio for ease of operation. The
ratio will,
of course vary with the size of the pump apparatus and the nature of the pump
spring.
Presently, a ratio of approximately 3:1 is preferred. The belt drums (Figure
13) are
attached to the respective ends of the link shaft. The energy absorption
assembly also
resides in the gear box.
The energy absorption device/assembly 116, shown in Figures 22-23, controls
the maximum rate at which the spring 136 may travel and compress the bag 188.
Because the energy absorption assembly and the charging mechanism are both
attached
to the constant force spring, it is desirable to be able to disengage the
energy absorption
assembly during charging. Accordingly, in one embodiment, the link shaft 208
between
the energy absorption assembly and the gear box assembly 202 includes a clutch
assembly 216 that disengages the energy absorption assembly during charging of
the
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28
pump spring. An idler gear couples the energy absorption assembly to the
clutch
assembly. On energy absorption assembly shaft 220 is a ratchet gear 222 that
may be
engaged by a start pawl 224 of the start/stop mechanism 226 (Figure 21) to
permit and
halt rotation of the energy absorption assembly shaft and thus start and stop
movement
of the pump spring 136. Once a chamber of the bag is under compression, the
fluid
therein generates back pressure on the spring as it winds up on the shaft. The
back
pressure may limit the speed at which the spring travels. Thus, the energy
absorption
assembly's principle function is to limit the spring's maximum rate of travel,
however,
there likely will be times when the rate of spring travel is effectively
limited by the fluid
back pressure rather than the energy absorption device.
A charging disk 194, shown in Figure 17, can be attached to the outside end of
each charging shaft 214. When a two stage charging mechanism is employed, the
charging disk has two catch mechanisms such as spring loaded pawls, 228 and
230, or
the like. The first catch is engaged during the initial stage of the charging
operation and
the second catch engages during the second stage of the charging operation.
When
pawls are employed, at least the inner pawl has a tip beveled on one side so
that a
corresponding structure (e.g., the ramped tooth described below) on the hub
ring (or its
equivalent) can smoothly engage the pawl, while still providing a positive
lock (when
the non-beveled side of the pawl engages the ramped tooth). It is desirable
that the shaft
and slot are configured such that the inner pawl is depressed when the outer
pawl is
depressed; however, the outer pawl is not depressed when the inner pawl is
depressed.
Thus, in one embodiment, the outer pawl 228 includes a shaft 232 that engages
a slot
234 on the inner pawl 230, thereby facilitating the desired operation.
The pump spring charging operation will now be described with reference to
Figures 24-28. The uncharged pump is shown in Figures 24-25. In this
embodiment,
the pump spring 136 is at the handle end of the receptacle. The hub ring 200
of the outer
cover 120 has a ramped tooth 236 and a bypass ramp 238. The ramped tooth has
one
side that is perpendicular to the circumference of the outer hub ring for
engaging the
outer pawl 228 of the charging disk during the first stage of the charging
operation (i.e.,
by opening the outer door). Thus by opening the outer door, the outer tooth
engages the
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outer pawl and partially rotates the charging disk, thereby partially charging
the spring as
shown in Figure 26. The charging disk rotation is transferred to the belt drum
84 which
winds up the belt 186 thus pulling back the spring shaft 140.
As shown in Figure 27, the inner door further rotates the charging disk
resulting
S in further pulling of the spring shaft as follows. The hub ring 198 of the
inner cover 122
also has a ramped tooth 240 having a perpendicular side for engaging the inner
pawl
when the inner door is opened, thereby continuing the rotation of the charging
disk to
complete the charging operation. The inner tooth engages the inner pawl
because, as the
outer door is fully opened, the beveled side of the inner tooth rides over the
beveled side
of the inner pawl, depressing the inner pawl 230 (not shown) to clear the
inner tooth. A
start/stop pawl 224 (Figure 13) in the receptacle is automatically engaged by
a ratchet
wheel 122 causing the gearbox assembly 202 to be locked into place. The bag
188 may
now be placed in the pump 110 and both doors closed. A start button 244
(Figure 13)
can be activated after closing the doors. During discharge of the spring
(i.e., during
pumping operation), the bypass ramp 238 operates to depress the outer pawl
(and,
consequently, the inner pawl), thereby allowing the inner pawl to clear the
inner tooth as
the charging disk rotates back around in the opposite direction it rotated
during charging.
The pump may include a number of features for ensuring the correct
administration of the desired infusion therapy. The receptacle may have two
spring
guards 246, shown in Figures 31-32, that prevent ready access to the edges of
the
constant force spring 136 which tend to curl up when the spring is in the
charged
position. Another optional, yet presently preferred feature is an internal
structure, such
as a set of pins 248 on the spring guard, that mate with the bag for correct
positioning of
the bag in the receptacle. The pins are designed so that the bag 188 will lift
offthe pins
as it rolls up into the spring. The pins are offset from one another within
the receptacle
so that the bag can be easily placed in the receptacle in only one direction.
Interlocks can also be included so that the pump can only operate as intended.
For example, a door interlock can be employed to prevent the inner door from
being
opened until the outer door is fizlly opened. The pump may also have a start
button
interlock 250 (Figure 13) that detects if either of the covers are opened
during the
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infusion. The start button engages the start/stop pawl when the door is
closed, allowing
the pump to operate. As a preferred safety feature, when the outer door is
opened, the
start button disengages from the start/stop pawl, and the pump is stopped. If
the inner
door is opened, the infixsion is aborted. Further, the start button interlock
also disables
S the start/stop button so that the spring motion cannot be reinitiated
without recharging
the pump. Aborting the infizsion and disabling the start/stop button prevent
improper
administration caused by user interference with the bag configuration in the
receptacle.
The fit and form of the pump with the doors closed is shown in the embodiment
exemplified by cross-sectional diagram of Figure 24. Corrosion resistant
material may
10 be used for those parts that may come in contact with fluids. The frame of
the housing
may be constructed of suitable corrosion resistant materials of sufficient
rigidity, etc.,
e.g., polybutylene terephthalate (PBT) or similar polymer material. The rack
and gears
may be constructed of a metal such as brass, or the like, or a plastic
material of suitable
strength.
15 The medication delivery pump automates a number of labor steps typically
used
to administer multiple intravenous solutions in the proper volumes and in the
proper
sequence with minimal user interaction. Further, in a preferred embodiment,
the pump is
a mechanical device which does not require electrical energy nor software to
correctly
implement an infusion therapy.
20 An administration set is optionally provided in one embodiment of the
present
invention and can optionally be included in the invention medication delivery
system.
The administration set comprises a length of medical grade tubing, such as a
micro-bore
tube, or the like, with structures at each end: at one end (proximal end) for
connecting
the tubing to the output port of the manifold and at the opposite (distal) end
for
25 connection to a standard intravenous-type needle. Standard luer connectors,
or the like
may be used in the practice of the present invention.
The administration set may be further configured to regulate the rate of fluid
administration to the patient. It is necessary to know the pressure generated
by the
pump/manifold combination in order to calibrate the delivery rate of the
administration
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set. The pump apparatus generates predictable fluid pressures based on the
volume of
solution in each chamber. Using the predictable fluid pressures, the flow rate
from the
bag may be selectable using administration sets having predetermined tubing
lengths and
inner diameters. The flow rate through the administration set is selected by
varying the
microbore tubing's inner diameter and length. The relationship is approximated
by
Poiseulle's equation:
Q = ~ ~ ~ ~ D 4 Equation 1
128~,u~L
Where Q is the flow rate, Op is the pressure drop across a flow controlling
orifice, D is the inside diameter of the orifice, ~C is the dynamic viscosity
of the fluid and
L is the length of the orifice. Thus, any structures included in the
administration set will
effect the flow rate in a predictable and calculable manner. Structures
contemplated for
optional incorporation into the administration set include particulate
filters, air
elimination filters, fluid flow restrictors, and the like. The administration
set may further
comprise a clamp, or the like, for stopping fluid flow, as desired.
The embodiment of the administration set shown in Figure 34 includes male and
female luer connectors (338 and 346, respectively), or other equivalent
attachment
structures, a tubing clamp 340, an air-eliminating filter 342, a particulate
filter (not
shown), micro-bore tubing 346, and a flow restrictor (not shown). The tubing
of the
administration set may be composed of any biocompatible material such as a non-
phthalate containing polyvinyl chloride (PVC) (i.e. non-DOP, dioctyl phthalate
and non-
DEHP, di-2-ethyl-hexyl-phthalate), or like tubing material which is commonly
used in
commercially available devices. The administration set may be connected to the
bag by
means of a standard male luer connector 348 on the bag that couples to the
female luer
connector of the administration set. The use of standard luer connectors
provides
assurance that the connection will be achieved easily and correctly. The air
eliminating
filter removes particulates larger than about 0.2 micron in diameter, and
expels air in the
fluid stream out of the air vent.
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In another embodiment of the present invention there is provided a restrictor
set
for attachment to the distal end of the administration set. In this manner,
the rate of fluid
flow can be altered with the simple addition of a restrictor set, rather than
by re-
engineering the administration set. Of course, the maximum fluid flow rate
will be
S determined by the configuration of the administration set, with fine-tuning
to slower
rates provided by the restrictor set.
The invention methods will now be described in greater detail by reference to
specific, non-limiting embodiments as illustrated in Figures 33-36. Moreover,
each of
the embodiments of the various components described below need not necessarily
be
used in conjunction with the other specific embodiments shown.
In accordance with a specific embodiment of the invention methods, the user
attaches the administration set (Figure 33) to the bag, opens the two doors of
the pump,
thereby charging the activation mechanism, and places the bag inside a
receptacle area
within the pump housing (Figure 34). The user then closes the doors of the
pump,
1 S attaches the administration set to a patient's intravenous (i.v.) catheter
site, and starts the
activation mechanism, for example, by pushing a start button on the exterior
of the
housing. A mechanical spring (e.g., a constant force spring) within the pump
sequentially compresses each of the bag's four chambers. The fluid within each
chamber is sequentially expressed out of the bag, through the administration
set, and into
the patient. In a preferred embodiment, an indicator notifies the user when
the infusion is
complete. The indicator may be visual, audible, (e.g., a bell, or the like),
tactile, or the
like.
The medication delivery system is designed to be simple, safe, intuitive, and
cost
effective. Further, the system is designed to ( 1 ) reduce the need for
supplies,
(2) diminish manual manipulations and labor complexity, (3) decrease entries
into the
patient's IV catheter, and (4) ensure fluids will be administered in the
proper volumes
and in the proper sequence.
The invention medication delivery pump provides the advantage that it is a
mechanical device which does not require electrical energy nor software to
infuse the
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solutions in the correct volume, order, and flow rate. An activating mechanism
such as a
constant force stainless steel spring provides the mechanical energy to
express the fluids
as it compresses each solution chamber of the bag.
The solution pressures and infusion rates are determined by the system's
configuration. A governing mechanism in the pump works to limit the maximum
allowable speed of advance of the spring. When the rate of travel of the
constant force
spring exceeds the maximum rate allowed by the governor, the governor absorbs
some
of the spring energy to limit the speed of the spring's travel. The governor
allows the
spring to move over the entire distance of the pump at a minimum,
predetermined
amount of time. Thus, the pump generates predictable fluid pressures based on
the
volume of solution in each chamber. Using the predictable fluid pressures, the
flow rate
from the bag may be selectable using administration sets having predetermined
tubing
lengths and inner diameters. The continuous force by the spring on the bag, in
combination with check valves in a manifold of the container, prevents the
reverse flow
of fluids from the administration set to the container.
In the embodiment where the pump comprises a two stage charging mechanism
comprising inner and outer doors, the pump's outer door and inner door must be
opened
in order to place a filled bag inside the pump. The opening motion of the
outer door and
inner door is the mechanism by which the mechanical pump spring is pulled back
to the
start position. After the inner and outer doors are closed, the pump is ready
to be started
upon pushing of the "start" button. The cut out windows in the inner and outer
door
allow the user to observe the position of the spring as it moves in relation
to the bag.
Accordingly, the user is able to visually monitor the progress of the
infusion.
The pump may be designed to separate the bag compartment or receptacle from
most of the pump's moving parts. Corrosion resistant materials may be used for
any
parts that may come in contact with liquids. This attention to the physical
design
facilitates cleaning of the pump.
The flow of solution from each chamber is initiated due to a pressure build up
caused by the pump spring compressing the filled chamber. As the pressure
increases, a
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check valve in the manifold opens, allowing the fluid to flow from the
chamber, down a
fluid conduit, past the valve, and out through a single outlet tubing into the
patient.
When the solution is expelled from the chamber, a drop of pressure occurs
which allows
the valve to close. It is the opening and closing of the valves that governs
the starting
and stopping of solution flow from each respective chamber. The controlled
rate at
which the spring compresses the bag maintains the solution pressure below the
typical
maximum safe pressure for i.v. devices (i.e., catheters, luers, needles, and
the like).
Features for filling and using the invention medication delivery system are
described with reference to Figures 33 and 34. Bag 314 is shown with a fill
port 360 for
bulk filling of chambers 1, 2, and 3 (referenced by numbers 328, 330 and 334,
respectively). The system also has two separate injection sites, 362 and 364,
for
chambers 330 and 334 to allow one to add additional solutions. The
administration set
316 may be primed by filling the manifold 336 and the tubing 344 through the
bulk fill
port 360 while the clamp 340 is locked until the air in the tubing is
eliminated through
the air-elimination filter 342. Further, a hydraulic lock feature may be
formed between
the air filter and the check valves by filling the manifold assembly and the
tube to a
positive pressure great enough to prevent the valves from opening and allowing
leakage
from the chambers during storage, handling, or transport of the bag 314. The
hydraulic
lock may be overcome upon the application of a threshold pressure to the
respective
chambers or release of the pressure by opening the clamp.
The bag includes a shipping clamp 368 for preventing leakage of any solutions
subsequent to filling. When the bag is inserted in the filling fixture, the
clamp is released
to allow filling. Conversely, when filling is completed, the shipping clamp is
closed to
prevent leakage of solution from the filled bag prior to use.
A filling fixture is a pharmacy tool used only in filling the chambers of the
bag.
By restraining chambers 1 and 3 with the interior walls of the filling
fixture, the operator
assures that the filling fixture provides a physical constraint to the bag 314
to assure that
each of chambers 1, 2 and 3 is filled to the correct nominal fill volume.
Thus, in use, the
operator places the bag 314 into the filling fixture prior to initiating the
fill. Once the
bag is in the filling fixture, the shipping clamp on the bag, if provided, is
opened and the
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operator bulk fills chambers 1, 2 and 3 of the bag through the bulk fill port
360 in one
step, using standard pharmacy filling equipment and procedures.
For example, the operator may fill the bag with 10 mls in chambers 1 and 3,
and
100 mls in chamber 2, by setting the standard pharmacy filling equipment to
dispense
5 120 ml. The fluid will flow into the bag, filling chambers 1 and 3 to 10
mls. The filling
fixture will constrain chambers 1 and 3 to this volume and the remainder of
the fluid
(100 mls) will flow into chamber 2. When the bag chambers 1, 2 and 3 are
filled, each
to the desired volume, the operator removes the bag from the filling fixture.
The bag is
now ready to have solution added to chambers 2 and 4 via the injection sites,
362 and
10 364, respectively, as required by the operator. The chamber 2 and chamber 4
injection
sites are accessed via standard pharmacy filling equipment and procedures.
Upon
completion of filling, the bag is ready for insertion into the pump 310 for
delivery of the
solutions.
The invention will now be described in greater detail by reference to the
15 following non-limiting example.
EXAMPLE
The following example illustrates flow from the invention medication delivery
system using a four-chambered bag having the following chamber fill volumes:
20 Chamber 1 5-10 mls.
Chamber 2 100-120 mls.
Chamber 3 5-10 mls.
Chamber 4 S mls.
A typical flow profile of fluid flow from the four bag chambers over time is
25 shown in Figure 2. The larger chamber 2 has a relatively flat
administration profile until
the end of the administration at which time the flow peaks and then rapidly
drops to
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zero. The smaller chambers similarly exhibit peaked administration profiles.
The flow
rate may be selected by selecting the inner diameter and the length of the
micro-bore
tubing in the administration set. A smaller inner diameter or a longer length
of tubing
reduces the flow rate and increases the administration time. Conversely, a
larger inner
diameter or a short length of tubing increases the flow rate and decreases the
administration time.
While the invention has been described in detail with reference to certain
preferred embodiments thereof, it will be understood that modifications and
variations
are within the spirit and scope of that which is described and claimed.
