EP1229947A2

EP1229947A2 - Medication delivery apparatus and methods for intravenous infusions

Info

Publication number: EP1229947A2
Application number: EP20000992938
Authority: EP
Inventors: Marc S. Lieberman; David R. Brengle; Michael W. Kleeman
Original assignee: Tandem Medical Inc
Current assignee: Tandem Medical Inc
Priority date: 1999-11-05
Filing date: 2000-11-02
Publication date: 2002-08-14
Also published as: AU2921401A; IL149316A0; CN1402645A; BR0015511A; WO2001032235A2; CA2389981A1; WO2001032235A3; KR20020062937A; JP2003518963A

Abstract

The invention provides a medication delivery system that is preconfigured to administer an infusion therapy by a mechanical pump mechanism upon user activation. The configuration of a multi-chambered flexible bag, each chamber being filled with therapeutic liquid(s), determines the sequence and amount of each liquid to be delivered when the bag is progressively compressed by a constant force spring mechanism in the pump. The spring mechanism is charged by the user manually cocking two covers of the pump housing. A mechanical timer is coupled to the constant force spring to limit the maximum rate at which the spring compresses the flexible bag. In one embodiment of the invention, the medication delivery system further includes a manifold assembly and an administration set. The manifold assembly is configured with internal conduits and valves to direct output from each chamber of the bag to an output port in the manifold, and thence into the administration set. In additional embodiments, there are provided structures in the container to alleviate pressure drop during the application of pressure to the container.

Description

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 admimstration of intermittent medication infusion therapy. The present invention satisfies these and other needs in the art.

BRIEF DESCRIPTION OF THE INVENTION

The present invention overcomes many ofthe 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 chamber(s) to dispense the fluid from the bag.

In accordance with another embodiment ofthe 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 ofthe chambers. In accordance with yet another embodiment ofthe 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 ofthe 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 ofthe plurality of pharmacological agents. The container additionally comprises a manifold assembly having a plurality of valves for controlling the administration ofthe plurality of pharmacological agents to an infusion site. Each chamber ofthe 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 ofthe 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 ofthe 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 ofthe 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 ofthe bag is constrained to a second predetermined volume; and the plurality of chambers are filled through a bulk fill port with the first predetermined 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 ofthe constrained chamber.

In accordance with a further embodiment ofthe 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 further embodiment ofthe 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 ofthe medication delivery container of Figure 1.

Figure 3 is a plan view of a multi-chamber bag ofthe 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. Figure 5 is a plan view of a multi-chamber bag ofthe medication delivery container of Figure 1, showing an alternate embodiment ofthe chamber flex absorbing pattern.

Figure 6 is a plan view of a multi-chamber bag ofthe medication delivery container of Figure 1, showing yet another embodiment ofthe chamber flex absorbing pattern.

Figure 7 is a perspective view of a manifold assembly ofthe medication delivery container of Figure 1.

Figure 8 is a perspective view ofthe manifold assembly of Figure 7 from a reverse direction.

Figure 9 is an exploded perspective view ofthe manifold assembly of Figure 7.

Figure 10 is a schematic diagram showing the internal conduit and valve configuration ofthe 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 ofthe medication delivery pump of Figure 11, with the pump's cover doors in a fully opened position.

Figure 13 is an exploded perspective view ofthe medication delivery pump of Figure 11.

Figure 14 is a perspective view of a spring assembly ofthe medication delivery pump of Figure 11.

Figure 15 is an exploded perspective view ofthe spring assembly of Figure 14.

Figure 16 is a perspective view of a constant force spring, in a stretched position, ofthe spring assembly of Figure 14. Figure 17 is a plan view ofthe constant force spring of Figure 16, in a stretched position.

Figure 18 is an elevation view ofthe constant force spring of Figures 16 and 17.

Figure 19 is an exploded perspective view of a base assembly ofthe medication delivery pump of Figure 11.

Figure 20 is a perspective view of a gear box assembly ofthe medication delivery pump of Figure 11.

Figure 21 is an exploded perspective view ofthe gear box assembly of Figure 20.

Figure 22 is an exploded perspective view ofthe 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 ofthe medication delivery pump of Figure 11 taken through the middle ofthe pump.

Figure 25 is an elevation view ofthe 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 ofthe medication delivery pump of Figure 11 with a side cover removed, showing the position ofthe 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 ofthe medication delivery pump of Figure 11 with a side cover removed, showing the position ofthe charging disk, the spring 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 ofthe medication delivery pump of Figure 11 with a side cover removed, showing the position ofthe charging disk, the spring assembly and the pump's cover doors with the spring in a fully uncoiled or charged position.

Figure 29 is a partially exploded perspective view ofthe charging disk ofthe medication delivery pump of Figure 11, having spring loaded pawls.

Figure 30 is a partial cross-sectional view ofthe 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 ofthe medication delivery pump of Figure 11.

Figure 32 is an elevation view ofthe spring guard of Figure 31.

Figure 33 is a schematic view of an administration set for use in the medication delivery system ofthe invention.

Figure 34 is a perspective view ofthe medication delivery bag placed in a receptacle area ofthe housing ofthe 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 ofthe 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. 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 ofthe bag to the other, and each chamber is activated sequentially from one end ofthe bag to the other, then fluid will be driven out ofthe 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 fused 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 ofthe 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 ofthe conduit depends on the strength ofthe materials used to construct the bag and the pressure ofthe 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 surface of at least one side ofthe container provides flow channels that allow liquid pressure to act along the length ofthe conduit to assist in opening the conduit upon the application of pressure to the respective chamber. Otherwise, if both inner sides ofthe 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 ofthe 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 ofthe bag to the opposite end, individual chambers are sequentially activated. It is presently prefened 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 ofthe 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 ofthe 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 conesponding conduit when pressure is applied to the contents ofthe bag. This is largely due to the formation of kinks in the bag when pressure is applied to the contents ofthe bag. The region of primary concern is the interface between the chamber and its corresponding conduit. Thus in one embodiment ofthe 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 ofthe chamber, incorporation into the chamber of internal structures (e.g., a stent, 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 ofthe pump apparatus, or the like), and the like.

As used herein, "quilting" means forming a structure in the interior ofthe chamber wherein the bottom and top sides ofthe bag are connected, preferably by fusing them together. It is presently preferred that quilting be employed to manage pressure drop. The desired connection between first and second sides ofthe bag can be accomplished by the same methods used to form the perimeter seal ofthe 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 prefened that the quilting be in the region ofthe chamber that is proximal to the conduit. In this region ofthe 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 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 ofthe 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 ofthe 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 ofthe 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 ofthe 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 ofthe seam between the two sheets. In this manner, even when the two sheets are pressed together, a channel will exist along the skewer 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 ofthe bag in the region ofthe exit to provide additional flow pathways not subject to greatly restricted flow by kinks.

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 chamber(s) 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 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 ofthe individual chambers ofthe 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 ofthe 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 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 ofthe 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 ofthe medication from the bag port ofthe conduits to an administration tube set ("administration set"), and also optionally provides a structure for filling the container. As used herein, "bag port ofthe 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 ofthe manifold, where the manifold attaches to and is in fluid communication with the bag ports. Accordingly, the chamber ports are on the bag side ofthe mamfold. Additional reference will be made to an output port ofthe mamfold, 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 ofthe present invention will have mamfold 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 can comprise internally molded chambers connecting the desired portions ofthe manifold, or they may comprise internally mounted tubing connecting the appropriate portions ofthe 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 ofthe present invention. In one embodiment ofthe 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 ofthe 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 ofthe optional bulk fill port ofthe manifold. In an embodiment ofthe present invention, when a bulk fill port is to be used, fluid flow in the manifold is further regulated so that fluid introduced through the bulk fill port can access one or more ofthe 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 port(s) 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 mamfold 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 ofthe present invention, including ball check valves, umbrella check valves, and the like. In a presently preferred embodiment ofthe 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 friction, it is presently preferred that the interior ofthe manifold be configured so that, upon assembly ofthe mamfold, the umbrella valves are held securely in place by the internal structure ofthe manifold. This can be accomplished simply by having a structure that contacts the center ofthe umbrella portion (i.e., the dome ofthe 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 mamfold 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 ofthe 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 flow. Thus, the check valves associated with the chamber ports and the output port can have one cracking pressure while the check valve(s) 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 ofthe 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 ofthe 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 ofthe bag. The chambers comprise a relatively large area ofthe bag in a central portion ofthe bag and are configured to be filled with medication fluids or pharmacological agents. The central chamber portion ofthe 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 he outside ofthe 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 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 prefened that at least one side ofthe bag be transparent to facilitate viewing ofthe contents.

The first chamber 18 is furthest from the port side 48 ofthe 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 first bag port.

The spacings 60, 62 and 64 between the chambers advantageously provides a "blow-down" period during an infusion 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 down", or flow until the residual pressure is below the cracking pressure ofthe associated check valves in the manifold. The area ofthe spacing 62 may be sealed only around the perimeter with no bond between completion ofthe 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 infusion ofthe medication in the second chamber and the beginning ofthe infusion of medication in the third chamber so as to minimize or prevent mixing ofthe medication in the second chamber with the medication in the third chamber. This time period is sufficient to allow the material spring strength ofthe 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 ofthe chamber, the rate of infusion, 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 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 ofthe 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 ofthe relatively large pillow-like shape ofthe second chamber (and the flexible nature ofthe 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 ofthe 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 ofthe T causes the chamber to kink laterally and preferentially above the outlet 54. The leg ofthe T further causes a longitudinal kink away from the outlet 54. After the chamber has been compressed to the first opening 57, the "pillow" ofthe compressed chamber is of a size that is less susceptible to exit kinks. The second "dot" bond further discourages kinking ofthe second opening 58. The quilt pattern may be provided to other ports ofthe 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 ofthe medication from the second chamber into the respective conduit 38.

In an alternative embodiment ofthe 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. In another embodiment ofthe invention, the quilt pattern may consist ofthe 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 Vi 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 ofthe 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 ofthe infusion therapy. A short plastic tube 66 couples each respective port to the respective mamfold 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 ofthe 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, conesponding 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 ofthe tube (EVA) would be heat sealed to the bag (EVA) and the inside ofthe tube (PVC) would be solvent bonded to the outside of a corresponding port ofthe manifold (ABS).

In one application ofthe 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 ofthe infusion therapy to a patient.

The multi-chamber bag 12 also may include a plurality of alignment holes, e.g., 68 and 70. The ahgnment 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 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 ofthe first, second and third chambers, 18, 20 and 22, through the bulk fill port and delivery ofthe 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 mamfold, 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 multi-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 ofthe umbrella valves 97 and conduits 19 for directing fluid flow between the ports in 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 ofthe umbrella valves and conduits (not shown) for directing fluid flow within the manifold assembly, as well as protrusions designed to contact the middle ofthe dome ofthe 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 ofthe container and manifold configuration shown in Figures 1-10 has demonstrated effective delivery of fluids.

In accordance with another embodiment ofthe 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 ofthe invention container from the bag and delivering the medications to an infusion site. The pump provides improved admimstration 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 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 one or more conduits associated with each chamber, and into an intravenous (i.v.) drug delivery system (e.g., an admimstration set comprising microbore tubing that is attachable to a standard i.v. needle).

In accordance with yet another embodiment ofthe present invention, there is provided a housing for receiving and retaining an invention medication delivery 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 structure(s) that will serve to hold a specific bag in operative relationship with the 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 conect operation. For example, the housing can include positioning pins that match holes in a medication container bag, fasteners (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 further 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 ofthe 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 operative relationship with the bag during the pumping or activation process. All such housing configurations are contemplated as within the scope ofthe 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 ofthe 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 ofthe spring, the configuration ofthe bag, and the amount and nature ofthe 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 further 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 ofthe coil, the charging mechanism is attached to the hub. The other end ofthe spring is fixed to the pump housing proximal to one end ofthe housing. In this manner, force can be applied to the center ofthe hub and directed away from the fixed end ofthe spring, thereby causing the spring to unroll. It is presently preferred that the hub ofthe spring protrude from either side ofthe spring so that the hub can be captured in a track or like structure for retaining and guiding the travel ofthe constant force spring. In this manner, the travel ofthe 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 ofthe 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 further described herein, or the like. The hub, gear and track assembly serves an additional function 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 ofthe spring.

Charging mechanisms contemplated for use in the practice ofthe present invention can include a force transmission structure suitable for pushing or pulling the hub ofthe spring in the intended direction (i.e., away form the fixed end ofthe 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 ofthe constant force spring during each stage ofthe 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 ofthe medication to the patient. The indicator can interface with the activating mechanism and any associated gearing to provide a true indication ofthe progress made by the activating mechanism. In a prefened embodiment, the indicator is geared in a manner to amplify the progress of infusion. 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 ofthe 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 chamber(s) 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 admimstration set delivers the medications to an infusion site. The pump, in combination with the container, provides improved admimstration of infusion therapy which is particularly advantageous for reducing ercors, 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 mechamsm 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 end ofthe 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 ofthe pump spring. The other end ofthe 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 e- rings 152 that engage slots on the shaft. 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 ofthe pump spring. The frame has at least four sides that form the sides ofthe container receptacle 112. At a convenient location, e.g., at a front side ofthe 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 ofthe present invention.

It can be advantageous to access the components ofthe pump for purposes such as maintenance or adjustment; accordingly, in one embodiment ofthe 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 ofthe 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 ofthe frame is a compartment 166 for attaching the charging assembly and the timing assembly. As with other key components ofthe 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 ofthe pump spring. On two long sides ofthe frame are structures to receive the hub ofthe 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 variety of ways. Referring to the embodiment shown in Figure 19, the spring assembly 114 fits in the bottom ofthe container receptacle with the shaft extending through the slots 172 in the long sides ofthe frame 156. Located at each end ofthe 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 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 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 ofthe 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 ofthe hub, or attached to the hub, to facilitate secure attachment ofthe charging mechanism to the hub. For example, at each end ofthe 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 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 ofthe 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 ofthe spring is of fixed diameter, while the diameter ofthe spring changes as it rolls up. As a result, the tension on the spring can vary (i.e., lesser in the early portion ofthe pumping process and greater during the later portion ofthe spring travel), thereby allowing the spring to roll over fluid-containing chambers in the bag in the early portion ofthe spring travel, while possibly stalling due to increased tension in the later portion ofthe spring travel. Accordingly, a tension force may be applied to the end ofthe constant force spring that is distal to the hub in order to maintain the spring in a tightly coiled configuration in the early stages ofthe spring travel while lessening the tension in the later stages ofthe spring travel. It is presently prefeπed to have the distal end ofthe 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 transfened to the tension spring which discourages or prevents the constant force spring from rolling over chambers ofthe 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 ofthe 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 ofthe present invention, a two-door ratchet mechanism is presently preferred because it reduces the force required to be applied to open a cover door during charging ofthe pump spring. The pump spring is pulled back a substantial portion ofthe 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 can be employed, such as a wind up mechanism comprising a reduction gear, an external handle attached to a reduction gear or ratchet mechamsm, 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 prefened, for even application of force to the spring, that the charging assembly is substantially symmetric with similar components along both sides ofthe pump. The components on each side ofthe 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 ofthe pump apparatus and the nature ofthe pump spring. Presently, a ratio of approximately 3:1 is prefened. The belt drums (Figure 13) are attached to the respective ends ofthe 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 ofthe 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 ofthe start/stop mechanism 226 (Figure 21) to permit and halt rotation ofthe 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 ofthe charging operation and the second catch engages during the second stage ofthe charging operation. When pawls are employed, at least the inner pawl has a tip beveled on one side so that a conesponding 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 ofthe 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 ofthe receptacle. The hub ring 200 ofthe 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 ofthe outer hub ring for engaging the outer pawl 228 ofthe charging disk during the first stage ofthe charging operation (i.e., by opening the outer door). Thus by opening the outer door, the outer tooth engages the 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 in further pulling ofthe spring shaft as follows. The hub ring 198 ofthe 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 ofthe 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 ofthe inner tooth rides over the beveled side ofthe 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 ofthe 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 coπect administration ofthe desired infusion therapy. The receptacle may have two spring guards 246, shown in Figures 31-32, that prevent ready access to the edges ofthe constant force spring 136 which tend to curl up when the spring is in the charged position. Another optional, yet presently prefened feature is an internal structure, such as a set of pins 248 on the spring guard, that mate with the bag for conect positioning of the bag in the receptacle. The pins are designed so that the bag 188 will lift off the 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 fully opened. The pump may also have a start button interlock 250 (Figure 13) that detects if either ofthe covers are opened during the infusion. The start button engages the start/stop pawl when the door is closed, allowing the pump to operate. As a prefened 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 infusion is aborted. Further, the start button interlock also disables the start/stop button so that the spring motion cannot be reinitiated without recharging the pump. Aborting the infusion and disabling the start/stop button prevent improper administration caused by user interference with the bag configuration in the receptacle.

The fit and form ofthe pump with the doors closed is shown in the embodiment exemplified by cross-sectional diagram of Figure 24. Conosion resistant material may be used for those parts that may come in contact with fluids. The frame ofthe housing may be constructed of suitable conosion 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.

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 prefened embodiment, the pump is a mechanical device which does not require electrical energy nor software to conectly implement an infusion therapy.

An administration set is optionally provided in one embodiment ofthe 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 ofthe mamfold and at the opposite (distal) end for connection to a standard intravenous-type needle. Standard luer connectors, or the like may be used in the practice ofthe 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 ofthe administration 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:

_Λ Ap - π - D⁴ „ . ,

Q - — Equation 1

^ 1 19288.- #/ .- E

Where Q is the flow rate, Δp is the pressure drop across a flow controlling orifice, D is the inside diameter ofthe orifice, //is the dynamic viscosity ofthe fluid and L is the length ofthe 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 admimstration set may further comprise a clamp, or the like, for stopping fluid flow, as desired.

The embodiment ofthe admimstration 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 ofthe 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 admimstration 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 ofthe administration set. The use of standard luer connectors provides assurance that the connection will be achieved easily and conectly. The air eliminating filter removes particulates larger than about 0.2 micron in diameter, and expels air in the fluid stream out ofthe air vent. In another embodiment ofthe present invention there is provided a restrictor set for attachment to the distal end ofthe 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 determined by the configuration ofthe 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 ofthe various components described below need not necessarily be used in conjunction with the other specific embodiments shown.

In accordance with a specific embodiment ofthe invention methods, the user attaches the administration set (Figure 33) to the bag, opens the two doors ofthe pump, thereby charging the activation mechamsm, and places the bag inside a receptacle area within the pump housing (Figure 34). The user then closes the doors ofthe pump, 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 ofthe housing. A mechanical spring (e.g., a constant force spring) within the pump sequentially compresses each ofthe bag's four chambers. The fluid within each chamber is sequentially expressed out ofthe bag, through the administration set, and into the patient. In a prefened 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 solutions in the conect 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 ofthe 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 ofthe spring. When the rate of travel ofthe constant force spring exceeds the maximum rate allowed by the governor, the governor absorbs some ofthe spring energy to limit the speed ofthe spring's travel. The governor allows the spring to move over the entire distance ofthe 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 ofthe 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 ofthe 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 ofthe "start" button. The cut out windows in the inner and outer door allow the user to observe the position ofthe spring as it moves in relation to the bag. Accordingly, the user is able to visually monitor the progress ofthe infusion.

The pump may be designed to separate the bag compartment or receptacle from most ofthe pump's moving parts. Conosion resistant materials may be used for any parts that may come in contact with liquids. This attention to the physical design facilitates cleaning ofthe 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 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 ofthe 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-ehmination 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 ofthe bag 314. The hydraulic lock may be overcome upon the application of a threshold pressure to the respective chambers or release ofthe 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 ofthe bag.

By restraining chambers 1 and 3 with the interior walls ofthe 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 conect 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 operator bulk fills chambers 1, 2 and 3 ofthe 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 mis in chambers 1 and 3, and 100 mis in chamber 2, by setting the standard pharmacy filling equipment to dispense 120 ml. The fluid will flow into the bag, filling chambers 1 and 3 to 10 mis. The filling fixture will constrain chambers 1 and 3 to this volume and the remainder ofthe fluid (100 mis) 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 filhng fixture. The bag is now ready to have solution added to chambers 2 and 4 via the injection sites, 362 and 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 ofthe solutions.

The invention will now be described in greater detail by reference to the 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:

Chamber 1 5-10 mis.

Chamber 2 100-120 mis.

Chamber 3 5-10 mis.

Chamber 4 5 mis.

A typical flow profile of fluid flow from the four bag chambers over time is shown in Figure 2. The larger chamber 2 has a relatively flat administration profile until the end ofthe administration at which time the flow peaks and then rapidly drops to zero. The smaller chambers similarly exhibit peaked admimstration profiles. The flow rate may be selected by selecting the inner diameter and the length ofthe 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 prefened embodiments thereof, it will be understood that modifications and variations are within the spirit and scope of that which is described and claimed.

Claims

WHAT IS CLAIMED IS:

1. 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 said chamber(s) to dispense said fluid from the bag.

2. A system according to claim 1 , wherein the activating mechanism generates a predetermined pressure in each chamber.

3. A system according to claim 2, wherein a configuration ofthe chamber(s) determines the pressure generated therein by the activating mechamsm.

4. A system according to claim 1 , wherein said activating mechanism comprises a constant force spring.

5. A system according to claim 1, wherein chambers in said bag are activated based on a predetermined configuration of said chambers.

6. A system according to claim 1 , further comprising an administration set that receives the medication fluid from the bag at the predetermined pressure and delivers the medication fluid to an infusion site at a predetermined flow rate.

7. A system according to claim 6, wherein the admimstration set includes a micro-bore tubing having a length and an inner diameter that establishes the predetermined flow rate.

8. A system according to claim 6, wherein the administration set includes an air-eliminating filter for eliminating air bubbles from the medication fluid before delivery ofthe fluid to the infusion site.

9. A system according to claim 8, wherein said mamfold comprises at least one back check valve associated with a respective chamber ofthe bag, wherein a hydrauhc lock is formed between the back check valves and the air-eliminating filter, which lock is overcome upon the application of a threshold pressure on the chamber.

10. 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 ofthe chambers.

11. A medication delivery container according to claim 10, further comprising an administration set coupled to the manifold assembly for delivering medications from the manifold assembly to an infusion site.

12. A medication delivery container according to claim 11 , wherein said administration set comprises one or more of an air elimination filter, a particulate filter, and a restrictor set.

13. A medication delivery container according to claim 10, wherein the bag includes a plurahty of conduits for coupling the chambers to the manifold assembly.

14. A medication delivery container according to claim 13 , wherein the plurality of chambers lie within a compression region ofthe bag and the plurality of conduits generally he outside ofthe compression region ofthe bag.

15. A medication delivery container according to claim 13, wherein the bag is formed of two flexible sheets of plastic bonded together in a pattern that forms the plurahty of chambers and the plurality of conduits.

16. A medication delivery container according to claim 15, wherein one sheet of plastic has a relatively smooth surface and the second sheet of plastic has a textured surface, wherein flexible sheets are bonded such that the smooth surface faces the textured surface to form flow channels between the sheets at locations associated with the chambers and the conduits.

17. A medication delivery container according to claim 16, wherein each sheet of plastic has a textured surface, wherein flexible sheets are bonded such that the textured surfaces are adjacent to form flow channels between the sheets at locations associated with the chambers and the conduits.

18. A medication delivery container according to claim 10, further comprising a plurahty of exit ports between the respective plurality of chambers and plurality of conduits, wherein at least one chamber has a bond adjacent to the exit port to discourage the exit from closing upon the application of pressure to said chamber.

19. A medication delivery container according to claim 10, further comprising a plurality of exit ports between the respective plurality of chambers and plurality of conduits, wherein at least one chamber has a quilt pattern of bonds adjacent to the exit port to discourage the exit from closing upon the application of pressure to said chamber.

20. A medication delivery container according to claim 19, wherein the quilt pattern of bonds has a T-dot configuration.

21. A medication delivery container according to claim 10, further comprising a structure for alleviating pressure drop, said structure being associated with at least one chamber to allow fluid flow from the respective chamber to an associated conduit upon the application of pressure to the respective chamber.

22. A medication delivery container according to claim 21, wherein the structure for alleviating pressure drops comprises a thermoformed conduit having a normally open shape.

23. A medication delivery container according to claim 21, wherein the structure for alleviating pressure drops comprises internal conduit beads adjacent to an intersection between the respective chamber and the associated conduit.

24. A medication delivery container according to claim 21 , wherein the structure for alleviating pressure drops comprises a quilt pattern of bonds adjacent to the exit port to discourage the exit from closing upon the application of pressure to said chamber.

25. A medication delivery container according to claim 10, wherein the bag is formed of two flexible sheets of EVA plastic, the manifold is formed of ABS plastic, and the bag further comprises a plurahty of ports, each port associated with a chamber of the bag, a plurality of co-extruded tubes, each tube having an exterior surface of EVA plastic that is heat seal bonded to the plastic sheets at the respective port and an interior surface of polyvinylchloride (PVC) that is solvent bonded to a conesponding port ofthe manifold.

26. A medication dehvery container according to claim 10, further comprising a spacing between at least two selected adjacent chambers that is configured to allow a time period between the delivery of fluid from the selected adjacent chambers to reduce mixing ofthe respective chamber fluids.

27. A medication delivery container according to claim 10, wherein the manifold assembly includes a bulk fill port for filling a plurality ofthe bag's chambers.

28. A medication delivery container according to claim 11 , wherein the administration set includes a micro-bore tube for controlling the fluid flow rate from the bag.

29. A medication delivery container according to claim 12, wherein the manifold assembly includes a plurality of back check valves, each back check valve associated with a respective chamber ofthe bag, and wherein a hydraulic lock may be formed between the back check valves and the air-eliminating filter to prevent leakage of fluid from the chambers during storage, handling, or transport ofthe container.

30. A fluid dehvery 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.

31. A fluid delivery container according to claim 30, wherein the structure for minimizing pressure drop comprises a bond adjacent to an exit port ofthe chamber to discourage the exit port or associated conduit from closing upon the application of pressure to said chamber.

32. A fluid delivery container according to claim 30, wherein the structure for minimizing pressure drop comprises a quilt pattern of bonds adjacent to an exit port ofthe chamber to discourage the exit port or associated conduit from closing upon the application of pressure to said chamber.

33. A fluid delivery container according to claim 32, wherein the quilt pattern of bonds has a T-dot configuration.

34. A fluid dehvery container according to claim 30, wherein the structure for minimizing pressure drop comprises internal conduit bead(s) between the plastic sheets in a region ofthe container where the chamber and its associated conduit meet.

35. A fluid delivery container according to claim 30, wherein the structure for minimizing pressure drop comprises thermoformed conduit having a normally open shape.

36. A fluid delivery container for the automated infusion of a plurality of pharmacological agents, said container comprising a plurality of chambers each configured with a respective geometry for controlling the administration ofthe plurality of pharmacological agents; and

a manifold assembly having a plurality of valves for controlling the administration ofthe plurality of pharmacological agents to an infusion site, wherein each chamber has a configuration that controls the volume of each pharmacological agent administered and the regimen with which said pharmacological agent is administered.

37. A fluid delivery container according to claim 36, further comprising a tube assembly for coupling the manifold assembly to the infusion site and for controlling the administration rate ofthe pharmacological agents.

38. A fluid delivery container according to claim 36, wherein the chambers are configured to sequentially administer the agents.

39. A fluid delivery container according to claim 36, wherein each chamber's size and shape controls the volume, time, and duration that the agents are administered.

40. A fluid delivery container according to claim 36, wherein each chamber's position controls the relative time the agents are administered.

41. A fluid delivery container according to claim 38, wherein the fluid bag is constructed from medical grade plastic sheets that are bonded together in a manner to define the plurality of separate chambers lying in a plane, each chamber being configured with a respective geometry, position and sequence for controlling the volume, time, and duration of medication administration.

42. A fluid delivery container according to claim 41, wherein the rate of fluid flow from the chambers is controlled by an orifice.

43. A fluid delivery container according to claim 42, further comprising a tube set, wherein the orifice resides in the tube set.

44. 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.

45. A fluid delivery pump according to claim 44, wherein said structure for sequentially applying constant force is a constant force spring.

46. A fluid dehvery pump according to claim 45, wherein the constant force spring is associated with a receptacle for receiving the fluid container.

47. A fluid delivery pump according to claim 45, wherein the receptacle includes a bottom cover having an inclined plate for accommodating an increasing spring diameter as the constant force spring compresses the flexible fluid container.

48. A fluid delivery pump according to claim 46, wherein the receptacle includes a spring guard for covering the edges ofthe constant force spring.

49. A fluid delivery pump according to claim 46, wherein the receptacle includes structure for aligning the flexible fluid container in the receptacle.

50. A fluid delivery pump according to claim 49, wherein said structure comprises pins configured to fit in a mating set of holes in said flexible fluid container.

51. A fluid delivery pump according to claim 50, wherein the alignment pins are offset for insuring proper alignment ofthe flexible fluid container in the receptacle.

52. A fluid delivery pump according to claim 45, wherein the constant force spring is coupled to a tension spring for tightly winding the constant force spring as the constant force spring compresses the flexible fluid container.

53. A fluid delivery pump according to claim 45, wherein the structure is a constant force spring configured to compress a flexible fluid container, and wherein the pump further comprises first and second pump doors for charging the constant force spring, wherein opening the first pump door partially charges the constant force spring and opening the second pump door fully charges the constant force spring.

54. A fluid delivery pump according to claim 53, further comprising a charging assembly having first and second outer ring hubs coupled to the first pump door, first and second inner ring hubs coupled to the second pump door, and first and second charging disks each having first and second pawls, wherein the first pawls of the charging disks engage respective teeth on the outer ring hubs during opening of the first pump door and the second pawls ofthe charging disks engage respective teeth on the inner ring hubs during opening ofthe second pump door.

55. 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 and the first pawl is not depressed when the second pawl is depressed.

56. A method for filling a fluid dehvery bag having a plurality of chambers, said method comprising: measuring a first predetermined fluid volume; constraining at least one chamber to a second predetermined volume; and filling the plurality of chambers through a bulk fill port with the first predetermined volume of fluid such that a constrained chamber is filled with the second predetermined volume of fluid and a remaining chamber is filled with a predetermined volume of fluid determined by the first predetermined volume of fluid minus the fluid of the constrained chamber.

57. A method for delivering medication fluids, said method comprising:

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;

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.

58. A method for charging an infusion pump having a constant force spring coupled to first and second cover doors by a charging assembly, comprising: 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.