CA1262325A - Pressure regulated implantable infusion pump - Google Patents
Pressure regulated implantable infusion pumpInfo
- Publication number
- CA1262325A CA1262325A CA000528684A CA528684A CA1262325A CA 1262325 A CA1262325 A CA 1262325A CA 000528684 A CA000528684 A CA 000528684A CA 528684 A CA528684 A CA 528684A CA 1262325 A CA1262325 A CA 1262325A
- Authority
- CA
- Canada
- Prior art keywords
- chamber
- pressure
- drug
- fluid
- drug solution
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
- A61M5/14—Infusion devices, e.g. infusing by gravity; Blood infusion; Accessories therefor
- A61M5/142—Pressure infusion, e.g. using pumps
- A61M5/14244—Pressure infusion, e.g. using pumps adapted to be carried by the patient, e.g. portable on the body
- A61M5/14276—Pressure infusion, e.g. using pumps adapted to be carried by the patient, e.g. portable on the body specially adapted for implantation
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
- A61M5/14—Infusion devices, e.g. infusing by gravity; Blood infusion; Accessories therefor
- A61M5/142—Pressure infusion, e.g. using pumps
- A61M5/14244—Pressure infusion, e.g. using pumps adapted to be carried by the patient, e.g. portable on the body
- A61M2005/14264—Pressure infusion, e.g. using pumps adapted to be carried by the patient, e.g. portable on the body with means for compensating influence from the environment
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M2205/00—General characteristics of the apparatus
- A61M2205/35—Communication
- A61M2205/3507—Communication with implanted devices, e.g. external control
- A61M2205/3523—Communication with implanted devices, e.g. external control using telemetric means
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S128/00—Surgery
- Y10S128/12—Pressure infusion
Landscapes
- Health & Medical Sciences (AREA)
- Vascular Medicine (AREA)
- Engineering & Computer Science (AREA)
- Anesthesiology (AREA)
- Biomedical Technology (AREA)
- Heart & Thoracic Surgery (AREA)
- Hematology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Infusion, Injection, And Reservoir Apparatuses (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An implantable infusion pump (20) for infusing drugs or other chemical or solutions into the body. A
movable diaphragm (26) forming a variable volume drug chamber (22). A fluid piston (32) opposing the force exerted by the diaphragm (26) on the drug solution in the drug chamber (22). The pressure of the fluid piston (32) being controlled by a regulator (33) providing a reference pressure and in fluid communication with the fluid piston (32). The regulator (33) reducing the fluid pressure of the piston fluid (32) as drug solution is expelled from the drug chamber (22) so as to maintain a constant pressure differential between the drug chamber (22) and an infusion site in the body. The implantable infusion pump (20) being readily adaptable to variable or electronic flow control.
An implantable infusion pump (20) for infusing drugs or other chemical or solutions into the body. A
movable diaphragm (26) forming a variable volume drug chamber (22). A fluid piston (32) opposing the force exerted by the diaphragm (26) on the drug solution in the drug chamber (22). The pressure of the fluid piston (32) being controlled by a regulator (33) providing a reference pressure and in fluid communication with the fluid piston (32). The regulator (33) reducing the fluid pressure of the piston fluid (32) as drug solution is expelled from the drug chamber (22) so as to maintain a constant pressure differential between the drug chamber (22) and an infusion site in the body. The implantable infusion pump (20) being readily adaptable to variable or electronic flow control.
Description
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PRESSURE REGULATED IMPLA~TABLE INFUSION PUM~
BACKGROU~D OF THE INVE~TION
The present invention relates to an implan-table infusion pump. More particularly, the present invention relates to an implantable infusion pump which includes a pressure regulator apparatus for producing a constant drive pressure from a more variable driving force exerted on a drug solution contained in a variable volume drug chamber of the implantable infusion pump.
Infusion pump designs rarely appeared in the medical literature until the 1950s. Most of these early infusion pumps were extracorporeal. One such device included a reciprocating air pump driven by an electric motor. Yet another design considered comprised a metal housing for a glass syringe and a compression chamber fed by a tank of nitrogen gas. Yet another such infu-sion pump included a motorized syringe pump which included an electric motor connected to the worm drive that moved a syringe plunger by a gear box. The gears were interchangeable such that replacement of the gears permitted different delivery rates. Yet another infu-sion pump included a syringe plunger driven by a rider on a threaded shaft. ~umerous other designs were con-sidered for these extracorporeal infusion pumps~ P.D.~'.
Soden in his thesis entitled, "A Methodical Design Study of Miniature Profusion Devices For Chemotherapy of Cancer of the Head and Neck", studied possible designs for producing a miniature profusion device to be carried by ambulating patients receiving chemotherapeutic treat-ment for cancer of the head and neck. Quoting from histhesis, ~Approximately two million alternative design solutions were synthesized and recorded in compact matrix form on a 'morphological chart"'. One of the numerous design concepts mentioned by Soden for possible use with an extracorporeal infusion pump was the use of a small tubular arrangement containing an elastic metal ~ellows possibly constructed from preloaded disks so as to form a relatively small diaphragm in the tubular arrangement for exerting a fairly constant force on the drug solution being infused. Due to the size of the diaphragm, this design provided for very little, if any, compensation for changes in atmospheric pressure.
One of the earliest implantable infusion pumps intended for use in laboratory animals comprised a micro-injector comprising a compressed spring held a~ay from a rubber-capped glass tube by a metal alloy disk with a low melting point. Administration of the injec-tion was accomplished by placing the animal near the coils of a high-frequency induction heater. Ac~ivation of the coils melted the alloy disk and the spring ejected infusate into the desired site in the animal. A
second implantable infusion pump for the continuous infusion of drugs utilized the osmotic pressure deve-loped by a saturated aqueous solution of Congo red dye against water as its power source. The infusion pump comprised a partially collapsed rubber compartment filled with Congo red dye separated from a second water compartment by a semi-permeable cellophane member.
Expansion of the rubber compartment as the water moved
PRESSURE REGULATED IMPLA~TABLE INFUSION PUM~
BACKGROU~D OF THE INVE~TION
The present invention relates to an implan-table infusion pump. More particularly, the present invention relates to an implantable infusion pump which includes a pressure regulator apparatus for producing a constant drive pressure from a more variable driving force exerted on a drug solution contained in a variable volume drug chamber of the implantable infusion pump.
Infusion pump designs rarely appeared in the medical literature until the 1950s. Most of these early infusion pumps were extracorporeal. One such device included a reciprocating air pump driven by an electric motor. Yet another design considered comprised a metal housing for a glass syringe and a compression chamber fed by a tank of nitrogen gas. Yet another such infu-sion pump included a motorized syringe pump which included an electric motor connected to the worm drive that moved a syringe plunger by a gear box. The gears were interchangeable such that replacement of the gears permitted different delivery rates. Yet another infu-sion pump included a syringe plunger driven by a rider on a threaded shaft. ~umerous other designs were con-sidered for these extracorporeal infusion pumps~ P.D.~'.
Soden in his thesis entitled, "A Methodical Design Study of Miniature Profusion Devices For Chemotherapy of Cancer of the Head and Neck", studied possible designs for producing a miniature profusion device to be carried by ambulating patients receiving chemotherapeutic treat-ment for cancer of the head and neck. Quoting from histhesis, ~Approximately two million alternative design solutions were synthesized and recorded in compact matrix form on a 'morphological chart"'. One of the numerous design concepts mentioned by Soden for possible use with an extracorporeal infusion pump was the use of a small tubular arrangement containing an elastic metal ~ellows possibly constructed from preloaded disks so as to form a relatively small diaphragm in the tubular arrangement for exerting a fairly constant force on the drug solution being infused. Due to the size of the diaphragm, this design provided for very little, if any, compensation for changes in atmospheric pressure.
One of the earliest implantable infusion pumps intended for use in laboratory animals comprised a micro-injector comprising a compressed spring held a~ay from a rubber-capped glass tube by a metal alloy disk with a low melting point. Administration of the injec-tion was accomplished by placing the animal near the coils of a high-frequency induction heater. Ac~ivation of the coils melted the alloy disk and the spring ejected infusate into the desired site in the animal. A
second implantable infusion pump for the continuous infusion of drugs utilized the osmotic pressure deve-loped by a saturated aqueous solution of Congo red dye against water as its power source. The infusion pump comprised a partially collapsed rubber compartment filled with Congo red dye separated from a second water compartment by a semi-permeable cellophane member.
Expansion of the rubber compartment as the water moved
2~ by osmosis into the Congo red solution ejected the drug fro~. the infusion pump.
Implantable infusion pumps were clinically introduced in 1975. Implantable infusion pumps currently in clinical use or in animal trials antici-patin~ clinical studies in the near future, include~apor pressure powered pumps, peristaltic pumps, and pulsatile solenoid pumps. The vapor pressure powered pump was developed at the University of Minnesota and is described hereafLer. The peristaltic pump generally
Implantable infusion pumps were clinically introduced in 1975. Implantable infusion pumps currently in clinical use or in animal trials antici-patin~ clinical studies in the near future, include~apor pressure powered pumps, peristaltic pumps, and pulsatile solenoid pumps. The vapor pressure powered pump was developed at the University of Minnesota and is described hereafLer. The peristaltic pump generally
3~ comprises a flexible tube placed in 2 u-shaped chamber "~
-in contact with rollers that press against the tube with sufficient force to occlude the tube's lumen. The rollers are rotated by a motor. As the rotor turns and the rollers compress the lumen of the tube, fluid is moved toward an exit. The rollers and housing are arxanged so that a second roller begins to squeeze the tube before the first disengaged, preventing backflow of the infusate. Sandia Laboratories, Siemens AG, and Medtronic, Inc. have developed implantable pumps with peristaltic pumping mechanjsm5~ A pulsatile solenoid pump includes a solenoid driven reciprocating chamber with two check valves to move infusate from the reservoir out through the delivery catheter. Infusate is stored in a flexible metal diaphragm reservoir. Such a pump has been developed by Fischell and colleagues at Johns ~opkins University Applied Physics Laboratory and by the Pacesetter Corporation.
Much- effort has been expended in developing external infusion devices which provide a steady pressure on the drug solution so as to provide a steady flow of drug solution to the patient. For example, U.S.
Patent Nos. 2,815,152 and 3,023,750 as well as French Patent 1,314,002 are examples of such devices.
Currently available lmplantable infusion pumps also have difficulty in maintaining constant pressure as the volume of the drug solution in their drug chambers changes. Typically, the output flow of drug solution is regulated by external means, an example of which is il7ustrated in U.S. Patent No. 4,299,2~0, or if passive flow restrictors are used to control the drug solution output, flow variation must be tolerated. The two ambient conditions that commonly cause flow variation are temperature and atmospheric pressure. In the vapor-pressure powered infusion pl~mp disclosed in U.S. ~atent 3~ No. 3,731,~81, both of these conditions cause the . "
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pressure differential between the drug chamber and the internal Dody pressure to change thereby causing a corresponding change in drug solution flow rate from the infusion pump into an infusion site in the body. In addition, the spring action of the metal bellows typi-cally used to separate the drug solution from the two-phase fluid adds a variable force to the otherwise volume independent force exerted by the vapor pressure, thereby causing a steady, although predictable decline in flow rates as the drug chamber empties.
In many applications it is necessary to change the flow rate of the drug solution freguently, more fre-guently than can be done by changing the concentration by an empty-refill cycle on a constant flow rate infu-sion pump. Examples of such a~plications are: (1) thedelivery of insulin to a brittle diabetic with no resi-dual insulin production, (2) the delivery of a che-motherapeutic agent that has a strons dependence on biological timing, or (3) the delivery of a hormone that is timed to the natural rhythm of the body~
Infusion pumps; for example, U.S. Patent Nos.
-in contact with rollers that press against the tube with sufficient force to occlude the tube's lumen. The rollers are rotated by a motor. As the rotor turns and the rollers compress the lumen of the tube, fluid is moved toward an exit. The rollers and housing are arxanged so that a second roller begins to squeeze the tube before the first disengaged, preventing backflow of the infusate. Sandia Laboratories, Siemens AG, and Medtronic, Inc. have developed implantable pumps with peristaltic pumping mechanjsm5~ A pulsatile solenoid pump includes a solenoid driven reciprocating chamber with two check valves to move infusate from the reservoir out through the delivery catheter. Infusate is stored in a flexible metal diaphragm reservoir. Such a pump has been developed by Fischell and colleagues at Johns ~opkins University Applied Physics Laboratory and by the Pacesetter Corporation.
Much- effort has been expended in developing external infusion devices which provide a steady pressure on the drug solution so as to provide a steady flow of drug solution to the patient. For example, U.S.
Patent Nos. 2,815,152 and 3,023,750 as well as French Patent 1,314,002 are examples of such devices.
Currently available lmplantable infusion pumps also have difficulty in maintaining constant pressure as the volume of the drug solution in their drug chambers changes. Typically, the output flow of drug solution is regulated by external means, an example of which is il7ustrated in U.S. Patent No. 4,299,2~0, or if passive flow restrictors are used to control the drug solution output, flow variation must be tolerated. The two ambient conditions that commonly cause flow variation are temperature and atmospheric pressure. In the vapor-pressure powered infusion pl~mp disclosed in U.S. ~atent 3~ No. 3,731,~81, both of these conditions cause the . "
'1~
pressure differential between the drug chamber and the internal Dody pressure to change thereby causing a corresponding change in drug solution flow rate from the infusion pump into an infusion site in the body. In addition, the spring action of the metal bellows typi-cally used to separate the drug solution from the two-phase fluid adds a variable force to the otherwise volume independent force exerted by the vapor pressure, thereby causing a steady, although predictable decline in flow rates as the drug chamber empties.
In many applications it is necessary to change the flow rate of the drug solution freguently, more fre-guently than can be done by changing the concentration by an empty-refill cycle on a constant flow rate infu-sion pump. Examples of such a~plications are: (1) thedelivery of insulin to a brittle diabetic with no resi-dual insulin production, (2) the delivery of a che-motherapeutic agent that has a strons dependence on biological timing, or (3) the delivery of a hormone that is timed to the natural rhythm of the body~
Infusion pumps; for example, U.S. Patent Nos.
4,373,527 and 4,146,02~, have been developed which uti-lize electronic controls that respond to transmitted electromagnetic signals and thus can be programmed by a non-invasive procedure. The electronics in these infu-sion pumps work relatively well due to the availability of very complex, low powered integrated circuits.
90wever, such infusion pumps have complex flow control components that must respond to the electronic signals.
An approach commonly used is to have the flow control i device provide an impulse of drug solution flow for every impulse of electrical signal from the electronic ¦ control circuit. By having very small (microliter) individual impulses and repeating them within the normal clearanc time of an infused drug solution in the ~lood ' '.
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,~
stream (e.g. one to ten minutes), an approximation of steady flow is obtained. This method is very flexible in that both steady flow and variable flow up to bolus doses can be delivered by a single flow control mecha-nislD~ ~owever, the high cycle rate of the flow control mecha~ism in~eases the wear rate of the components, increases power losses in start and stop events, and increases probability of failure of some component. If a particular component has a finite failure rate per cycle, the mean time to failure decreases as the rate of cycling goes up. When a repeatedly cycled valve is used to produce a constant flow rate for an extended time period (several hours) there is an unnecessary hazard involved that would not be present if the same fixed flow rate ~ere achieved by other means. If the fixed flow rate were known, a simple capillary tube could deliver that rate with only one cycle of valve open and fixed dose, rather than a hundred or so open dose cycles which might be required in an electronic impulse controlled sys~em.
Typical systems employed in such electroni-cally controlled infusion pumps include: (a) cyclic filling and emptying of a small drug accumulator with ~ upstream and downstream valves; (b) an active piston i 25 pump with passive valves, and (c) miniature roller (peristaltlc) pumps. In all three of these mechanisms, the drug solution storage chamber is passive and is held I at a fixed pressure usually a little above atmospheric i pressure in order to suppress bubble formation from 1 30 dissolved air. The low pressure serves to reduce the potential hz2ard of an infusator leak. ~ccumulator systems use a higher drug chamber pressure to set posi-tive filling cycles.
The above described electronically controlled infusion pumps have an unnecessarily wide dynamic range .~
..
and response time for many applications. Moreover, they are complex, expensive and subject to failure. On the other hand, the fixed flow rate infusion pump has been shown to provide adequate therapy for a range of disease states with no flow control for a given cycle. An infu-sion pump is required which provides a degree of drug solution flow control which is better than currently available infusion pumps of the constant flow design but which is less complex than that of the presently available electronically controlled infusion pumps.
The present invention solves these and many other problems associated with currently existing infu-sion pumps.
SUMMARY OF THE INVENTION
The present invention relates to an apparatus and method for controlling the pressure applied to a drug solution in the drug chamber of an implantable infusion pump.
The preferred embodiment of the present inven-tion utilizes a pressurized support piston and-pressure regulator arrangement to produce a constant force (drive pressure) on a drug solution in the drug chamber from a more variable driving force that might be a spring mechanism or any other force producing device.
, Moreover, the pressure can be maintained without sub-! jecting the drug solution to the high shear force at the exit port of the pressure regulator.
, A preferred embodiment of the present inven-j 30 tion readily lends itself to electronic control wh2re~y ~ the flow rate of the drug solution can be changed by ! transmitted electromagnetic signals. Moreover, the electronic control can be preprogrammed to vary the àrug '5~ solution flow rate as re~uiredO
3~
The present invention provides an electroni-cally controlled infusion pump which is less complex than existing, electronically controlled infusion pumps.
In an electronically controlled embodiment of the pre-sent invention, telemetry can be used either to directlyset the re~erence pressure of the infusion pump's regu-lator by supplying telemetered power to an otherwise passive motor control circuit or provide commands to an electronic timing circuit that can execute the command at a later time using internal battery power. Many applications of the infusion pu~p of the present inven-tion will require only a non-invasi~e method of resetting the drug Solution flow rate and maintaining the flow rate until the next cycle time. An example of this might include most insulin delivery systems where the increase in flow rate to adjust for mealtime demand is done by the patient on his/her own schedule (e.g. at night the insulin flow rate is typically reduced to adjust for the lower demand during sleep). In applica-tions where drug solution is delivered on a fixedvariable rate schedule, such as in the case of hormone or chemotherapeutic agents, the infusion pump of the present invention can be preprogrammed and not reguire any intervention by the patient.
~5 The preferred embodiment of the present inven-tion has a variable volume drug chamber formed partially by a movable, relatively rigid diaphragm which moves under the influence of a force producing device to expel the drug solution from the drug chamber.
,3~ ~ovement of the diaphragm is opposed by a column of ;pressllrized fluid, herein referred to as a support piston, whose pressure is controlled by the reference pressure of a pressure regulator apparatus so as to allow only a constant force to be applied by the diaphragm on the dru3 sclution in the drug cham~er. Any 3~
excess force exerted by the diaphragm is absorbed by t~e support piston~ The re~erence pressure of the regulator is interconnected to the support piston by a one-way flow valve which regulates ~luid flow from the support piston to a reference pressure chamber of the regulator.
In the preferred embc,diment, the regulator need only release fluid from the support piston at a controlled rate in order to maintain constant drug solution pressure.
In some embodiments of the present invention, the reference pressure of the regulator will be preselected by appropriate configuration of a force producing device such as a spring device which acts on a diaphragm of the regulator so as to produce the reg~lator reference pressure.
In various embodiments of the present inven-tion, the pressure regulator can maintain either an absolute internal drug chamber pressure or a relative internal drug chamber pressure wherein the regulator compensates for atmospheric pressure so as to maintain a constant pressure differential between the drug chamber and the internal body pressure.
In various embodiments of the present inven-tion, the support piston will utilize a closed system 2~ wherein its operating fluid is kept separate from the drug solution or an open system wherein the drug solu-tion itself is used as the operating fluid of the sup-! port piston.
1An advantage of the regulator of the present j30 invention is that power is required only to change the jreference pressure of the regulator in order to change the drug solution flow rate. The actual work needed to ideliver the drug solution at the selected flow rate is <accomplished by the pressure of the drug chamber. The 35 pressure of the drug chamber can be readily varied by changing the reference pressure of the regulator since the dr~g chamber pressure is the difference between the total force being exerted by the drug chamber diaphraqm and the countering force of the support piston whose pressure is controlled by the re~erence pressure of the regulator. In the preferred embodiment, to reduce drug chamber pressure, the regulator decreases the outflow of fluid from the support piston. In order to increase the drug cha~ber pressure, the fluid in the support piston is released more rapidly by the regulator. Accordingly, the regulator need only vary the flow of fluid out of the support piston in order to vary drug chamber pressure.
An advantage of the present invention is that by using a variable drug chamber pressure design, much of the safety and ease of use of the steady flow infu-sion pump designs is retained.
An eléctronically controlled embodiment of the present invention might use an electromechanical arrangement to compress or expand the regulator diaphragm in order to vary the reference pressure of the regulator.
These and various other advantages and features of novelty which characterize the present 2~ invention are pointed out with particularity in the claims and next hereto and forming a part hereof.
However, for a better understanding of the invention, its advantages and objects obtained by its use, reference shou~d be had to the drawings which form a further part hereof and to the acco~,panying descriptive matter in which there is illustrated and described a preferred embodiment of the present invention.
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,, BRIEF DESCRIPTIO~ OF THE DRAWINGS
_ In the drawings, in which like reference numerals and letters indicate corresponding part throughout the several views;
5Figure 1 is a diagrammatic/cross-sectional view of an embodiment of the present invention wherein the regulator compensates for atmospheric pressure;
Figure 2 is a diagrammatic/cross-sectional view of an embodiment of the present invention wherein the drug solution is used as the support fluid of the support piston;
Figure 3 is a diagrammatic/cross-sectional view wherein the regulator does not compensate for atmospheric pressure;
1~Figure 4 is a diagrammatic/cross-sectional view of an embodiment of the present invention wherein the regulator does not compensate for atmospheric pressure and the drus solution serves as the support fluid for the support piston;
20Figure 5 is a diagrammatic/cross-sectional view illustrating an electronically controlled embodi-ment of the present invention;
Figure 6 is a diagrammatic/cross-sectional view illustrating a possible packaging arrangement of 2~ components of an embodiment of an infusion pump in accordance with the princip.les ~f the present invention;
Figure 7 is a diagrammatic/cross-sectional view of an e~bodiment of the present invention which utilizes an adjustable force applicator device for varying the reference pressure of the regulator, Figure 8 is an enlarged partial sectional view of the regulator valve in an increased flow setting, and Figure 9 is a view similar to Figure 8 wherein the regulator valve is in a reduced flow setting.
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DETAILED DESCRIPTI~N OF A
PREFERRED EMBODIME~T OF THE PRESE~T INVE~TIO~
Referring now to the drawings, there is illustrated in Figures 1 through 7 various embodiments of an implantable infusion pump in accordance with the principles of the present invention, the infusion pump being generally referenced by the reference numeral 20.
The embodiment of the infusion pump 20 illustrated in Figure 1 includes a variable volume drug chamber 22 formed by a wall structure 24 of the infusion pump 20 and a diaphragm 26 interconnected to the wall structure 24 by a spring arrangement 28. The spring arrangement 28 functions as a force producing (Fp) device causing the diaphragm 26 to exert a variable force on the drug solution in the drug chamber 22. It will be appre-ciated, that any other number of force producing devices might be used to exert a force on the drug solution.
Interconnecting the wall structure 24 to the diaphragm 26 is a cylindrical column of under pressure fluid (Ps) enclosed by a flexible bellows arrangement 30 so as to form a support piston 32 which counters the force being exerted by the diaphragm 26 on the drug solution in the drug chamber 22. The support piston 32 is interconnected to a regulator appara-2~ tus 33 including a chamber 34 defined by adiaphragm 36 and force producing spring arrangement 38 which produces a predetermined force (FR) on the diaphragm 36. The support fluid of the support piston is interconnected to the regulator chamber 34 by a one-way valve arrangement 40 which controls the fluid flow into the regulator chamber 34. It will be appreciated that the spring 38 can exert a variable force over a ranae of movemen' and still be used to provide a predetermined force, since in opera-tion, the diaphragm 36 will move very little. The valve -arrangement 40 will provide a steady, regulated flow.
In the embodiment shown in Figure 1, the support fluid of the support piston 32 is contained in the regulator chamber 34 and a chamber 42 interconnected to the chamber 34 by a pathway 45 and including a diaphragm 41 and bellows 43 arrangement, so as to be kept separate from the drug solution in the drug chamber 22.
Additionally, the diaphragm 36 is exposed to the inter-nal body pressure which reflects the atmospheric pressure. In this manner, the regulator 33 comprising diaphragm 36 and spring bellows 38 is referenced to atmospheric pressure and produces a constant flow rate regardless of atmospheric changes.
The embodiment illustrated in Figure 2 utili-zes the drug solution as the support fluid for the piston 32 and thus does not include the fluid chamber 42. Since the drug solution itself is used as the sup-port ~luid in`the support piston, it must pass through the regulator v21ve 40. This embodiment achieves a larger volumetric efficiency and a lower cost due to fewer parts compared to electronic or vapor pressure driven pumps. Moreover, the regulator diaphragm 36 is exposed to the external pressure as illustrated in Figure 1.
Figure 3 illustrates an embodiment of the pre-sent invention wherein the regulator diaphragm 36 is internally referenced to a chamber 50 enclosed by an immovable shell structure 52, the chamber 50 being filled with gas at atmospheric pressure (or lowe-).
This embodiment dGes not provide any reference to the atmospheric pressure and as a result, has to operate at a higher pressure ln order to avoid variation in a.mospheric pressure. This embodiment, as well ~s that shown in Figure 4 which has the same closed chamber 50 but no support piston fluid reservoir 42, are designs ~ ,.....
3~,~
s that allow more freedom in construction since the small regulator mechanism can be placed in the pump interior with no connection to the exterior. It also provides a sealed place for electronic controls that can mechani-cally change the regulator pressure (PR) or set point.
In the embodiments illustrated in Figure 1 and~igure 3, at the end of a cycle when the drug chamber 22 is empty, most of the operating fluid of the piston 32 will be transferred to the chamber 42. When drug solu-tion is injected into the infusion pump through therefill septum, the pressure (PD) in the drug chamber 22 will rise and the diaphragm 26 will retract producing negative pressure across the regulator 33. This excess negative drug pressure will cause the regulator 33 to close to allow the internal pressure to fall to the control point. In order to reset the infusion pump for another cycle, a bypass check valve 41 responds to the negative pressure and allows operating fluid to flow back into the Support piston 32. When the infusion pump drug chamber is full, the regulator 33 takes over control of the drug chamber pressure as soon as a small amount of drug solution has left the drug chamber.
In the embodiment illustrated in Figures 2 and 4, the drug solution itself refills the support piston chamber, through the check valve. The embodiment illustrated in Figure 5 illustrates an electronically controlled version of an infusion pump in accordance with the principles of the present invention. In the air space in the chamb0r 50 behind the regulator diaphragm 36 there are placed conventional telemeter receiver controlling circuits ~4 for receiving commands from a telemetry transmitter 56 and for controlling small electromechanical components or servomechanisms 55 ~ `3 that can vary the force exerted on the diaphragm 36 and thus vary ~he regulator reference pressure. It wiil be appreciated that any number of well known devices might be utilized. For example, this might be in the form of a small electric motor and gear train that would compress or expand the spring arrangement 38 supplying the force on the diaphragm 36. Battery power would be required only when the settings were changed. The tele-metry transmitter and receiver could be of the type pre-sently used for transcutaneous signal transmission andare availa~le commercially. Examples of such control circuitry are disclosed in U.S. Patent ~os. ~,373,~27 and 4,146,029. Signal coding could be used to decrease the possibility of accidental operation. The receiver controls might be passive circuits that obtain their power from the transmitter since they would be activated only to change the pressure.
The regulator of the present invention is par-ticularly suited to changing the reference pressure set point slowly due to the slow flow rate out of the infu-sion pump, and rapid changes in drug solution flow rate are not particularly suited for this design. The pressure control circuit would preferably be in the form of an adjustable basal rate rather than the flexible control used in other pumps that can be used to deliver fast bolus flows. This slow control greatly increases the safety of its operation.
The most con~pact design of an infusion pump of the present invention uses the outer shell structure of the infusion pump as a spring element that stores energy in the form of tension and compression of the metal or plastic material comprising the shell structure. The reference pressure for the regulator can be o~tained from either the top or bottom of the pump in the form of 3~ a thin, large diameter diaphragm that separates the pressure transmitting fluid from ~he body tissue.
Figure 6 illustrates a possible packaging of the com-- ponents of the embodiment illustrated in Figure 3.
As with other infusion pumps, such as U.S.
~ 5 Patent ~o. 3,731,681, the present invention will include an inlet port 60 and an outlet port 62. Suitably positioned in the inlet port 60 is a self-sealing, penetrable septum member 64, a filter 65 being posi~ioned in the outlet port. A
capillary flow restrictor 66 is interconnected to the outlet port by a suitable connecter 68. The capillary flow restrictor might then be interconnected to a catheter for delivery of the drugs to an infusion site in the body although any number of other well known devices might be used. A convoluted diaphragm 67 is utilized to allow nesting of the drug chamber diaphragm 26 therewith. (In this illustration, the regulator 34 is generally iilustrated without any of its individual , components.) i 20 The total force on the diaphragm 26 is opposed by the sum of the drug solution pressure in the drug cham~er 22 and the support piston 32 fluid pressure:
Fp ~ (PAAp) = (PsAs) + (PDAD) wherein;
Fp =spring force of diaphragm PA =pressure of atmosphere Ap =area of diaphragm 26 Ps =pressure of fluid in support piston ~5 =2rea of support piston diaphragm PD =pressure in drug chamber AD =2rea of drug chamber di2phragm Regulation of the drug solution pressure (P3) occurs due to mechanical negative feedback action of the valve 40 so 25 to maintain a balanced force on the diaphragm 36. If the pressure (PD) of the drug solu~ion dro~s s^ does the reaulator ~ressure (PR~ which causes the valve 40 to open to allow entry of more of the fluid from the support piston chamber which is at a high pressure (Ps)~ This is illustrated in Figure 8 wherein the valve 40 provides a larger opening 39 so as to allo~
more of the support solution in the support piston 32 to flow into the regulator reservoir 34. Figure g illustrates the valve 40 in a reduced flow setting wherein a smaller opening 37 is provide for drug solu~
tion flow~ As illustrated in Figures 8 and 9, the valve 40 will preferably include a seal 35, such as an O-ring or the like. This restores the balance forces on the regulation diaphragm 36 by increasing regulator pressure (PR). The control equations are:
PRAR ~ PAAR = FR
15 wherein;
PR =pressure in regulation chamber AR -area of r~gulator diaphragm PA =pressure of atmosphere FR =spring force on regulator diaphragm The fluid storage chamber 42 has a soft bellows so the pressure (PD) is about equal to (PR).
Therefore, the drus chamber pressure can be expressed as:
DAR ~ PAAR = FR
Solving for PD:
PD ~ FR + PA
AR
The flow through the capillary tube 66 is expressed in terms of the pressure difference across it divided by the fluid resistance:
Q = PD ~ PA
_ wherein, ^ Q =Clow in volume per unit time R =fluid resistance of capillary 3~23 Solving for Q putting in terms for the pressure PD:
RQ = PD - PA = FR + PA ~ PA
AR
The two terms for atmospheric pressure cancel to give:
Q = FR
ARR
The regulator force `(FR), the regulator diaphragm area (~) and the capillary resistance R are fixed quantities, therefore, the flow Q will be fixed independent of the atmospheric pressure and the force on the drug chamber diaphragm 26. In a non-electronically controlled version of the infusion pump, the regulator force (FR) might be preset by selecting a spring member 38 which creates the required force (FR). In Figure 7, another embodiment is illustrated wherein an adjustable force applicator 25 is utilized to apply a predetermined force (FR) on the diaphragm 36.
It is to be understood that even though the above numerous characteristics and advantages of the invention have been set forth in the foregoing descrip-tion, together with details of the structure and function of the invention, the disclosure is illustra-tive only, and changes may be in detail, especially in matter of shape, size and arrangement of parts with the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
90wever, such infusion pumps have complex flow control components that must respond to the electronic signals.
An approach commonly used is to have the flow control i device provide an impulse of drug solution flow for every impulse of electrical signal from the electronic ¦ control circuit. By having very small (microliter) individual impulses and repeating them within the normal clearanc time of an infused drug solution in the ~lood ' '.
J
,~
stream (e.g. one to ten minutes), an approximation of steady flow is obtained. This method is very flexible in that both steady flow and variable flow up to bolus doses can be delivered by a single flow control mecha-nislD~ ~owever, the high cycle rate of the flow control mecha~ism in~eases the wear rate of the components, increases power losses in start and stop events, and increases probability of failure of some component. If a particular component has a finite failure rate per cycle, the mean time to failure decreases as the rate of cycling goes up. When a repeatedly cycled valve is used to produce a constant flow rate for an extended time period (several hours) there is an unnecessary hazard involved that would not be present if the same fixed flow rate ~ere achieved by other means. If the fixed flow rate were known, a simple capillary tube could deliver that rate with only one cycle of valve open and fixed dose, rather than a hundred or so open dose cycles which might be required in an electronic impulse controlled sys~em.
Typical systems employed in such electroni-cally controlled infusion pumps include: (a) cyclic filling and emptying of a small drug accumulator with ~ upstream and downstream valves; (b) an active piston i 25 pump with passive valves, and (c) miniature roller (peristaltlc) pumps. In all three of these mechanisms, the drug solution storage chamber is passive and is held I at a fixed pressure usually a little above atmospheric i pressure in order to suppress bubble formation from 1 30 dissolved air. The low pressure serves to reduce the potential hz2ard of an infusator leak. ~ccumulator systems use a higher drug chamber pressure to set posi-tive filling cycles.
The above described electronically controlled infusion pumps have an unnecessarily wide dynamic range .~
..
and response time for many applications. Moreover, they are complex, expensive and subject to failure. On the other hand, the fixed flow rate infusion pump has been shown to provide adequate therapy for a range of disease states with no flow control for a given cycle. An infu-sion pump is required which provides a degree of drug solution flow control which is better than currently available infusion pumps of the constant flow design but which is less complex than that of the presently available electronically controlled infusion pumps.
The present invention solves these and many other problems associated with currently existing infu-sion pumps.
SUMMARY OF THE INVENTION
The present invention relates to an apparatus and method for controlling the pressure applied to a drug solution in the drug chamber of an implantable infusion pump.
The preferred embodiment of the present inven-tion utilizes a pressurized support piston and-pressure regulator arrangement to produce a constant force (drive pressure) on a drug solution in the drug chamber from a more variable driving force that might be a spring mechanism or any other force producing device.
, Moreover, the pressure can be maintained without sub-! jecting the drug solution to the high shear force at the exit port of the pressure regulator.
, A preferred embodiment of the present inven-j 30 tion readily lends itself to electronic control wh2re~y ~ the flow rate of the drug solution can be changed by ! transmitted electromagnetic signals. Moreover, the electronic control can be preprogrammed to vary the àrug '5~ solution flow rate as re~uiredO
3~
The present invention provides an electroni-cally controlled infusion pump which is less complex than existing, electronically controlled infusion pumps.
In an electronically controlled embodiment of the pre-sent invention, telemetry can be used either to directlyset the re~erence pressure of the infusion pump's regu-lator by supplying telemetered power to an otherwise passive motor control circuit or provide commands to an electronic timing circuit that can execute the command at a later time using internal battery power. Many applications of the infusion pu~p of the present inven-tion will require only a non-invasi~e method of resetting the drug Solution flow rate and maintaining the flow rate until the next cycle time. An example of this might include most insulin delivery systems where the increase in flow rate to adjust for mealtime demand is done by the patient on his/her own schedule (e.g. at night the insulin flow rate is typically reduced to adjust for the lower demand during sleep). In applica-tions where drug solution is delivered on a fixedvariable rate schedule, such as in the case of hormone or chemotherapeutic agents, the infusion pump of the present invention can be preprogrammed and not reguire any intervention by the patient.
~5 The preferred embodiment of the present inven-tion has a variable volume drug chamber formed partially by a movable, relatively rigid diaphragm which moves under the influence of a force producing device to expel the drug solution from the drug chamber.
,3~ ~ovement of the diaphragm is opposed by a column of ;pressllrized fluid, herein referred to as a support piston, whose pressure is controlled by the reference pressure of a pressure regulator apparatus so as to allow only a constant force to be applied by the diaphragm on the dru3 sclution in the drug cham~er. Any 3~
excess force exerted by the diaphragm is absorbed by t~e support piston~ The re~erence pressure of the regulator is interconnected to the support piston by a one-way flow valve which regulates ~luid flow from the support piston to a reference pressure chamber of the regulator.
In the preferred embc,diment, the regulator need only release fluid from the support piston at a controlled rate in order to maintain constant drug solution pressure.
In some embodiments of the present invention, the reference pressure of the regulator will be preselected by appropriate configuration of a force producing device such as a spring device which acts on a diaphragm of the regulator so as to produce the reg~lator reference pressure.
In various embodiments of the present inven-tion, the pressure regulator can maintain either an absolute internal drug chamber pressure or a relative internal drug chamber pressure wherein the regulator compensates for atmospheric pressure so as to maintain a constant pressure differential between the drug chamber and the internal body pressure.
In various embodiments of the present inven-tion, the support piston will utilize a closed system 2~ wherein its operating fluid is kept separate from the drug solution or an open system wherein the drug solu-tion itself is used as the operating fluid of the sup-! port piston.
1An advantage of the regulator of the present j30 invention is that power is required only to change the jreference pressure of the regulator in order to change the drug solution flow rate. The actual work needed to ideliver the drug solution at the selected flow rate is <accomplished by the pressure of the drug chamber. The 35 pressure of the drug chamber can be readily varied by changing the reference pressure of the regulator since the dr~g chamber pressure is the difference between the total force being exerted by the drug chamber diaphraqm and the countering force of the support piston whose pressure is controlled by the re~erence pressure of the regulator. In the preferred embodiment, to reduce drug chamber pressure, the regulator decreases the outflow of fluid from the support piston. In order to increase the drug cha~ber pressure, the fluid in the support piston is released more rapidly by the regulator. Accordingly, the regulator need only vary the flow of fluid out of the support piston in order to vary drug chamber pressure.
An advantage of the present invention is that by using a variable drug chamber pressure design, much of the safety and ease of use of the steady flow infu-sion pump designs is retained.
An eléctronically controlled embodiment of the present invention might use an electromechanical arrangement to compress or expand the regulator diaphragm in order to vary the reference pressure of the regulator.
These and various other advantages and features of novelty which characterize the present 2~ invention are pointed out with particularity in the claims and next hereto and forming a part hereof.
However, for a better understanding of the invention, its advantages and objects obtained by its use, reference shou~d be had to the drawings which form a further part hereof and to the acco~,panying descriptive matter in which there is illustrated and described a preferred embodiment of the present invention.
,~
3~
,, BRIEF DESCRIPTIO~ OF THE DRAWINGS
_ In the drawings, in which like reference numerals and letters indicate corresponding part throughout the several views;
5Figure 1 is a diagrammatic/cross-sectional view of an embodiment of the present invention wherein the regulator compensates for atmospheric pressure;
Figure 2 is a diagrammatic/cross-sectional view of an embodiment of the present invention wherein the drug solution is used as the support fluid of the support piston;
Figure 3 is a diagrammatic/cross-sectional view wherein the regulator does not compensate for atmospheric pressure;
1~Figure 4 is a diagrammatic/cross-sectional view of an embodiment of the present invention wherein the regulator does not compensate for atmospheric pressure and the drus solution serves as the support fluid for the support piston;
20Figure 5 is a diagrammatic/cross-sectional view illustrating an electronically controlled embodi-ment of the present invention;
Figure 6 is a diagrammatic/cross-sectional view illustrating a possible packaging arrangement of 2~ components of an embodiment of an infusion pump in accordance with the princip.les ~f the present invention;
Figure 7 is a diagrammatic/cross-sectional view of an e~bodiment of the present invention which utilizes an adjustable force applicator device for varying the reference pressure of the regulator, Figure 8 is an enlarged partial sectional view of the regulator valve in an increased flow setting, and Figure 9 is a view similar to Figure 8 wherein the regulator valve is in a reduced flow setting.
~ `:
. .
DETAILED DESCRIPTI~N OF A
PREFERRED EMBODIME~T OF THE PRESE~T INVE~TIO~
Referring now to the drawings, there is illustrated in Figures 1 through 7 various embodiments of an implantable infusion pump in accordance with the principles of the present invention, the infusion pump being generally referenced by the reference numeral 20.
The embodiment of the infusion pump 20 illustrated in Figure 1 includes a variable volume drug chamber 22 formed by a wall structure 24 of the infusion pump 20 and a diaphragm 26 interconnected to the wall structure 24 by a spring arrangement 28. The spring arrangement 28 functions as a force producing (Fp) device causing the diaphragm 26 to exert a variable force on the drug solution in the drug chamber 22. It will be appre-ciated, that any other number of force producing devices might be used to exert a force on the drug solution.
Interconnecting the wall structure 24 to the diaphragm 26 is a cylindrical column of under pressure fluid (Ps) enclosed by a flexible bellows arrangement 30 so as to form a support piston 32 which counters the force being exerted by the diaphragm 26 on the drug solution in the drug chamber 22. The support piston 32 is interconnected to a regulator appara-2~ tus 33 including a chamber 34 defined by adiaphragm 36 and force producing spring arrangement 38 which produces a predetermined force (FR) on the diaphragm 36. The support fluid of the support piston is interconnected to the regulator chamber 34 by a one-way valve arrangement 40 which controls the fluid flow into the regulator chamber 34. It will be appreciated that the spring 38 can exert a variable force over a ranae of movemen' and still be used to provide a predetermined force, since in opera-tion, the diaphragm 36 will move very little. The valve -arrangement 40 will provide a steady, regulated flow.
In the embodiment shown in Figure 1, the support fluid of the support piston 32 is contained in the regulator chamber 34 and a chamber 42 interconnected to the chamber 34 by a pathway 45 and including a diaphragm 41 and bellows 43 arrangement, so as to be kept separate from the drug solution in the drug chamber 22.
Additionally, the diaphragm 36 is exposed to the inter-nal body pressure which reflects the atmospheric pressure. In this manner, the regulator 33 comprising diaphragm 36 and spring bellows 38 is referenced to atmospheric pressure and produces a constant flow rate regardless of atmospheric changes.
The embodiment illustrated in Figure 2 utili-zes the drug solution as the support fluid for the piston 32 and thus does not include the fluid chamber 42. Since the drug solution itself is used as the sup-port ~luid in`the support piston, it must pass through the regulator v21ve 40. This embodiment achieves a larger volumetric efficiency and a lower cost due to fewer parts compared to electronic or vapor pressure driven pumps. Moreover, the regulator diaphragm 36 is exposed to the external pressure as illustrated in Figure 1.
Figure 3 illustrates an embodiment of the pre-sent invention wherein the regulator diaphragm 36 is internally referenced to a chamber 50 enclosed by an immovable shell structure 52, the chamber 50 being filled with gas at atmospheric pressure (or lowe-).
This embodiment dGes not provide any reference to the atmospheric pressure and as a result, has to operate at a higher pressure ln order to avoid variation in a.mospheric pressure. This embodiment, as well ~s that shown in Figure 4 which has the same closed chamber 50 but no support piston fluid reservoir 42, are designs ~ ,.....
3~,~
s that allow more freedom in construction since the small regulator mechanism can be placed in the pump interior with no connection to the exterior. It also provides a sealed place for electronic controls that can mechani-cally change the regulator pressure (PR) or set point.
In the embodiments illustrated in Figure 1 and~igure 3, at the end of a cycle when the drug chamber 22 is empty, most of the operating fluid of the piston 32 will be transferred to the chamber 42. When drug solu-tion is injected into the infusion pump through therefill septum, the pressure (PD) in the drug chamber 22 will rise and the diaphragm 26 will retract producing negative pressure across the regulator 33. This excess negative drug pressure will cause the regulator 33 to close to allow the internal pressure to fall to the control point. In order to reset the infusion pump for another cycle, a bypass check valve 41 responds to the negative pressure and allows operating fluid to flow back into the Support piston 32. When the infusion pump drug chamber is full, the regulator 33 takes over control of the drug chamber pressure as soon as a small amount of drug solution has left the drug chamber.
In the embodiment illustrated in Figures 2 and 4, the drug solution itself refills the support piston chamber, through the check valve. The embodiment illustrated in Figure 5 illustrates an electronically controlled version of an infusion pump in accordance with the principles of the present invention. In the air space in the chamb0r 50 behind the regulator diaphragm 36 there are placed conventional telemeter receiver controlling circuits ~4 for receiving commands from a telemetry transmitter 56 and for controlling small electromechanical components or servomechanisms 55 ~ `3 that can vary the force exerted on the diaphragm 36 and thus vary ~he regulator reference pressure. It wiil be appreciated that any number of well known devices might be utilized. For example, this might be in the form of a small electric motor and gear train that would compress or expand the spring arrangement 38 supplying the force on the diaphragm 36. Battery power would be required only when the settings were changed. The tele-metry transmitter and receiver could be of the type pre-sently used for transcutaneous signal transmission andare availa~le commercially. Examples of such control circuitry are disclosed in U.S. Patent ~os. ~,373,~27 and 4,146,029. Signal coding could be used to decrease the possibility of accidental operation. The receiver controls might be passive circuits that obtain their power from the transmitter since they would be activated only to change the pressure.
The regulator of the present invention is par-ticularly suited to changing the reference pressure set point slowly due to the slow flow rate out of the infu-sion pump, and rapid changes in drug solution flow rate are not particularly suited for this design. The pressure control circuit would preferably be in the form of an adjustable basal rate rather than the flexible control used in other pumps that can be used to deliver fast bolus flows. This slow control greatly increases the safety of its operation.
The most con~pact design of an infusion pump of the present invention uses the outer shell structure of the infusion pump as a spring element that stores energy in the form of tension and compression of the metal or plastic material comprising the shell structure. The reference pressure for the regulator can be o~tained from either the top or bottom of the pump in the form of 3~ a thin, large diameter diaphragm that separates the pressure transmitting fluid from ~he body tissue.
Figure 6 illustrates a possible packaging of the com-- ponents of the embodiment illustrated in Figure 3.
As with other infusion pumps, such as U.S.
~ 5 Patent ~o. 3,731,681, the present invention will include an inlet port 60 and an outlet port 62. Suitably positioned in the inlet port 60 is a self-sealing, penetrable septum member 64, a filter 65 being posi~ioned in the outlet port. A
capillary flow restrictor 66 is interconnected to the outlet port by a suitable connecter 68. The capillary flow restrictor might then be interconnected to a catheter for delivery of the drugs to an infusion site in the body although any number of other well known devices might be used. A convoluted diaphragm 67 is utilized to allow nesting of the drug chamber diaphragm 26 therewith. (In this illustration, the regulator 34 is generally iilustrated without any of its individual , components.) i 20 The total force on the diaphragm 26 is opposed by the sum of the drug solution pressure in the drug cham~er 22 and the support piston 32 fluid pressure:
Fp ~ (PAAp) = (PsAs) + (PDAD) wherein;
Fp =spring force of diaphragm PA =pressure of atmosphere Ap =area of diaphragm 26 Ps =pressure of fluid in support piston ~5 =2rea of support piston diaphragm PD =pressure in drug chamber AD =2rea of drug chamber di2phragm Regulation of the drug solution pressure (P3) occurs due to mechanical negative feedback action of the valve 40 so 25 to maintain a balanced force on the diaphragm 36. If the pressure (PD) of the drug solu~ion dro~s s^ does the reaulator ~ressure (PR~ which causes the valve 40 to open to allow entry of more of the fluid from the support piston chamber which is at a high pressure (Ps)~ This is illustrated in Figure 8 wherein the valve 40 provides a larger opening 39 so as to allo~
more of the support solution in the support piston 32 to flow into the regulator reservoir 34. Figure g illustrates the valve 40 in a reduced flow setting wherein a smaller opening 37 is provide for drug solu~
tion flow~ As illustrated in Figures 8 and 9, the valve 40 will preferably include a seal 35, such as an O-ring or the like. This restores the balance forces on the regulation diaphragm 36 by increasing regulator pressure (PR). The control equations are:
PRAR ~ PAAR = FR
15 wherein;
PR =pressure in regulation chamber AR -area of r~gulator diaphragm PA =pressure of atmosphere FR =spring force on regulator diaphragm The fluid storage chamber 42 has a soft bellows so the pressure (PD) is about equal to (PR).
Therefore, the drus chamber pressure can be expressed as:
DAR ~ PAAR = FR
Solving for PD:
PD ~ FR + PA
AR
The flow through the capillary tube 66 is expressed in terms of the pressure difference across it divided by the fluid resistance:
Q = PD ~ PA
_ wherein, ^ Q =Clow in volume per unit time R =fluid resistance of capillary 3~23 Solving for Q putting in terms for the pressure PD:
RQ = PD - PA = FR + PA ~ PA
AR
The two terms for atmospheric pressure cancel to give:
Q = FR
ARR
The regulator force `(FR), the regulator diaphragm area (~) and the capillary resistance R are fixed quantities, therefore, the flow Q will be fixed independent of the atmospheric pressure and the force on the drug chamber diaphragm 26. In a non-electronically controlled version of the infusion pump, the regulator force (FR) might be preset by selecting a spring member 38 which creates the required force (FR). In Figure 7, another embodiment is illustrated wherein an adjustable force applicator 25 is utilized to apply a predetermined force (FR) on the diaphragm 36.
It is to be understood that even though the above numerous characteristics and advantages of the invention have been set forth in the foregoing descrip-tion, together with details of the structure and function of the invention, the disclosure is illustra-tive only, and changes may be in detail, especially in matter of shape, size and arrangement of parts with the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Claims (15)
1. An infusion pump for implantation in a living body, comprising:
a) a housing having a variable volume, drug chamber for holding a drug solution;
b) outlet port means for conducting the drug solution from the drug chamber to a first site outside the housing;
c) inlet port means for introducing the drug solution into the drug chamber from a second site outside the housing;
d) force means including a diaphragm for exerting a force on the drug solution in the drug chamber;
e) fluid piston means for opposing the force exerted by the diaphragm of the force means on the drug solution; and f) regulator means for regulating the pressure of the fluid of the piston means such that a constant total force is exerted on the drug solution in the drug chamber.
a) a housing having a variable volume, drug chamber for holding a drug solution;
b) outlet port means for conducting the drug solution from the drug chamber to a first site outside the housing;
c) inlet port means for introducing the drug solution into the drug chamber from a second site outside the housing;
d) force means including a diaphragm for exerting a force on the drug solution in the drug chamber;
e) fluid piston means for opposing the force exerted by the diaphragm of the force means on the drug solution; and f) regulator means for regulating the pressure of the fluid of the piston means such that a constant total force is exerted on the drug solution in the drug chamber.
2. An infusion pump in accordance with claim 1, wherein the housing includes an external wall structure, a first portion of the external wall structure being sub-stantially rigid, the force means including movable spring diaphragm means forming a second portion of the external wall structure.
3. An infusion pump in accordance with claim 1, wherein the diaphragm forms an external wall portion of the housing so as to be subjected to the internal body pressure.
4. An infusion pump in accordance with claim 3, wherein the diaphragm includes a plurality of conical spring sections integral therewith.
5. An infusion pump for implantation in a living body comprising:
a) a housing having a variable volume drug chamber for holding a drug solution;
b) outlet port means for conducting the drug solution from the drug chamber to a first site outside the housing;
c) inlet port means for introducing the drug solution into the drug chamber from a second site outside the housing;
d) first diaphragm means for exerting a force on the drug solution in the drug chamber; and e) regulator means for regulating the pressure of the drug solution, the regulator means including fluid piston means including a column of pressurized fluid for opposing the force of the first diaphragm means and second diaphragm means exerting a predetermined force on a second chamber of the housing so as to provide a reference pressure, the second chamber being in fluid communication and inter-connected to the fluid piston means by one-way valve means for regulating fluid flow from the fluid piston means to the second chamber whereby a constant total force is exerted on the drug solution of the drug chamber, the fluid pressure of the second chamber corresponding to the fluid pressure of the drug chamber.
a) a housing having a variable volume drug chamber for holding a drug solution;
b) outlet port means for conducting the drug solution from the drug chamber to a first site outside the housing;
c) inlet port means for introducing the drug solution into the drug chamber from a second site outside the housing;
d) first diaphragm means for exerting a force on the drug solution in the drug chamber; and e) regulator means for regulating the pressure of the drug solution, the regulator means including fluid piston means including a column of pressurized fluid for opposing the force of the first diaphragm means and second diaphragm means exerting a predetermined force on a second chamber of the housing so as to provide a reference pressure, the second chamber being in fluid communication and inter-connected to the fluid piston means by one-way valve means for regulating fluid flow from the fluid piston means to the second chamber whereby a constant total force is exerted on the drug solution of the drug chamber, the fluid pressure of the second chamber corresponding to the fluid pressure of the drug chamber.
6. An infusion pump in accordance with claim 5, wherein the fluid of the second chamber and the fluid piston means is maintained separate from that of the drug solution.
7. An infusion pump in accordance with claim 5, wherein the fluid of the fluid piston means is the drug solution itself.
8. An infusion pump in accordance with claim 5, wherein the second diaphragm is enclosed by a rigid outer shell such that the force exerted by the second diaphragm on the second chamber remains constant regardless of atmos-pheric pressure changes.
9. An infusion pump in accordance with claim 5, wherein the second diaphragm is exposed to internal body pressure such that the force exerted by the second diaphragm on the fluid of the second chamber reflects changes in atmos-pheric pressure.
10. An infusion pump in accordance with claim 5, wherein the reference pressure of the regulator means is electronically controlled.
11. An infusion pump in accordance with claim 5, wherein the regulator means is programmable so as to provide for varying the reference pressure and predetermined times.
12. An infusion pump for implantation in a living body, comprising:
a) a housing having a first wall portion and a second wall portion defining a variable volume drug chamber for holding the drug solution;
b) outlet port means for conducting the drug solution from the drug chamber to a first site outside the housing;
c) inlet port means for introducing the drug solution into the drug chamber from a second site outside the housing;
d) force means for forcing the second wall portion toward the first wall portion whereby the drug solution in the drug chamber is placed under pressure;
e) regulator means for regulating the pressure of the drug solution in the drug chamber, and thus the infusion rate of the drug solution into the body, the regulator means including fluid piston means interconnecting the first and second wall portions of the housing and including an enclosed column of fluid under pressure for opposing the force exerted by the second wall portion, the regulator means further including a regulator chamber in fluid communication with, and interconnected to, the fluid piston means by one-way valve means for allowing fluid flow from the fluid piston means into the regulator chamber, the regulator chamber being operatively interconnected to the drug chamber such that the pressure of the fluid in the regulator chamber and the drug solution pressure correspond, the regulator means being operated on by reference force means defining the operational drug solution pressure of the infusion pump.
a) a housing having a first wall portion and a second wall portion defining a variable volume drug chamber for holding the drug solution;
b) outlet port means for conducting the drug solution from the drug chamber to a first site outside the housing;
c) inlet port means for introducing the drug solution into the drug chamber from a second site outside the housing;
d) force means for forcing the second wall portion toward the first wall portion whereby the drug solution in the drug chamber is placed under pressure;
e) regulator means for regulating the pressure of the drug solution in the drug chamber, and thus the infusion rate of the drug solution into the body, the regulator means including fluid piston means interconnecting the first and second wall portions of the housing and including an enclosed column of fluid under pressure for opposing the force exerted by the second wall portion, the regulator means further including a regulator chamber in fluid communication with, and interconnected to, the fluid piston means by one-way valve means for allowing fluid flow from the fluid piston means into the regulator chamber, the regulator chamber being operatively interconnected to the drug chamber such that the pressure of the fluid in the regulator chamber and the drug solution pressure correspond, the regulator means being operated on by reference force means defining the operational drug solution pressure of the infusion pump.
13. An infusion pump in accordance with claim 12, wherein the reference force means is adjustable.
14. An infusion pump in accordance with claim 12, including electronic receiver means for receiving control signals transmitted from a location exterior of the body, the electronic receiver means being operatively inter-connected to means for varying the reference force whereby the infusion rate of the implantable infusion pump can be electronically controlled.
15. An infusion pump in accordance with claim 12, wherein the housing includes an external, flexible wall portion formed in part by the second wall portion.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/825,246 US4718893A (en) | 1986-02-03 | 1986-02-03 | Pressure regulated implantable infusion pump |
| US825,246 | 1986-02-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1262325A true CA1262325A (en) | 1989-10-17 |
Family
ID=25243500
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000528684A Expired CA1262325A (en) | 1986-02-03 | 1987-02-02 | Pressure regulated implantable infusion pump |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4718893A (en) |
| EP (1) | EP0291510A4 (en) |
| JP (1) | JPS63503359A (en) |
| AU (1) | AU594269B2 (en) |
| CA (1) | CA1262325A (en) |
| DK (1) | DK521287A (en) |
| IL (1) | IL81444A (en) |
| WO (1) | WO1987004629A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4886514A (en) * | 1985-05-02 | 1989-12-12 | Ivac Corporation | Electrochemically driven drug dispenser |
| US4772263A (en) * | 1986-02-03 | 1988-09-20 | Regents Of The University Of Minnesota | Spring driven infusion pump |
| US4846806A (en) * | 1987-10-06 | 1989-07-11 | 501 Regents Of University Of Minnesota | Implantable intravascular access system |
| US5006997A (en) * | 1987-12-15 | 1991-04-09 | Shiley Infusaid, Inc. | Pump diagnostic system |
| US4931050A (en) * | 1988-04-13 | 1990-06-05 | Shiley Infusaid Inc. | Constant pressure variable flow pump |
| US5222362A (en) * | 1989-01-10 | 1993-06-29 | Maus Daryl D | Heat-activated drug delivery system and thermal actuators therefor |
| US5716343A (en) * | 1989-06-16 | 1998-02-10 | Science Incorporated | Fluid delivery apparatus |
| US5067943A (en) * | 1989-09-26 | 1991-11-26 | Infusaid, Inc. | Pressure regulator for implantable pump |
| US5120312A (en) * | 1990-04-20 | 1992-06-09 | Regents Of The University Of Minnesota | Method and apparatus for catheterization |
| US5203770A (en) * | 1990-04-20 | 1993-04-20 | Regents Of The University Of Minnesota | Method and apparatus for catheterization |
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-
1986
- 1986-02-03 US US06/825,246 patent/US4718893A/en not_active Expired - Lifetime
-
1987
- 1987-02-02 AU AU70319/87A patent/AU594269B2/en not_active Ceased
- 1987-02-02 CA CA000528684A patent/CA1262325A/en not_active Expired
- 1987-02-02 EP EP19870901802 patent/EP0291510A4/en not_active Withdrawn
- 1987-02-02 WO PCT/US1987/000208 patent/WO1987004629A1/en not_active Application Discontinuation
- 1987-02-02 IL IL81444A patent/IL81444A/en unknown
- 1987-02-02 JP JP62501339A patent/JPS63503359A/en active Pending
- 1987-10-05 DK DK521287A patent/DK521287A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| DK521287A (en) | 1988-08-04 |
| EP0291510A1 (en) | 1988-11-23 |
| IL81444A (en) | 1991-07-18 |
| JPS63503359A (en) | 1988-12-08 |
| EP0291510A4 (en) | 1989-08-16 |
| DK521287D0 (en) | 1987-10-05 |
| WO1987004629A1 (en) | 1987-08-13 |
| US4718893A (en) | 1988-01-12 |
| AU7031987A (en) | 1987-08-25 |
| IL81444A0 (en) | 1987-09-16 |
| AU594269B2 (en) | 1990-03-01 |
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