U.S. patent application number 09/416151 was filed with the patent office on 2001-10-18 for method and apparatus for drug infusion.
This patent application is currently assigned to Eric R. Waldkoetter. Invention is credited to HERUTH, KENNETH T..
Application Number | 20010031947 09/416151 |
Document ID | / |
Family ID | 24572037 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010031947 |
Kind Code |
A1 |
HERUTH, KENNETH T. |
October 18, 2001 |
METHOD AND APPARATUS FOR DRUG INFUSION
Abstract
The present disclosure describes a system wherein a drug or
other fluid to be delivered to a specific desired location within
the body is stored in a reservoir that is directly displaced by a
force to infuse the drug from the device into the patient. Several
specific methods are used to displace the reservoir, including,
generally, hydraulic displacement, mechanical screw-type
displacement, and spring force displacement of the fluid
reservoir.
Inventors: |
HERUTH, KENNETH T.; (MAPLE
GROVE, MN) |
Correspondence
Address: |
Eric R. Waldkoetter
Medtronic, Inc.,
710 Medtronic Parkway
MS: LC340
Minneapolis
MN
55432-5604
US
|
Assignee: |
Eric R. Waldkoetter
|
Family ID: |
24572037 |
Appl. No.: |
09/416151 |
Filed: |
October 11, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09416151 |
Oct 11, 1999 |
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08641362 |
Apr 30, 1996 |
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5976109 |
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Current U.S.
Class: |
604/142 ;
604/151 |
Current CPC
Class: |
A61M 2005/14513
20130101; A61M 5/14276 20130101; A61M 2005/14506 20130101 |
Class at
Publication: |
604/142 ;
604/151 |
International
Class: |
A61M 037/00 |
Claims
What is claimed is:
1. A drug infusion device, comprising: a fluid reservoir; and fluid
reservoir displacement means for directly forcing drug fluid within
said fluid reservoir from said device.
2. The apparatus of claim 1, wherein said fluid reservoir
displacement means comprises hydraulic displacement means.
3. The apparatus of claim 2, wherein said hydraulic displacement
means comprises a pump which circulates a working fluid between a
first reservoir and an expandable second reservoir disposed
proximate said fluid reservoir, so that as said second reservoir
expands, said fluid reservoir is displaced.
4. The apparatus of claim 2, wherein said hydraulic displacement
means comprises a piston assembly which acts to directly displace
said fluid reservoir.
5. The apparatus of claim 1, wherein said fluid reservoir
displacement means comprises mechanical screw-type displacement
means.
6. The apparatus of claim 5, wherein said mechanical screw-type
displacement means comprises a motor operatively coupled to a lead
screw, so that as the motor turns the lead screw about a central
axis, a nut coupled to said fluid reservoir and disposed on said
lead screw is displaced along said central axis, displacing said
fluid reservoir.
7. The apparatus of claim 5, wherein said mechanical screw-type
displacement means comprises a motor that rotates a worm gear to
displace a rack coupled to the fluid reservoir, displacing said
fluid reservoir.
8. The apparatus of claim 1, wherein said fluid reservoir
displacement means comprises spring force displacement means.
9. The apparatus of claim 8, wherein the spring force displacement
means comprises a bellows-like expandable chamber annealed so that
the chamber in its natural state assumes a collapsed position, and
in an expanded state the chamber tends toward its natural collapsed
position under its own action.
10. The apparatus of claim 9, wherein said spring force
displacement means further comprises a motor assembly, including a
motor operatively coupled to a flywheel about which a first end of
a cable having first and second ends is wrapped, said second end of
said cable being attached to said bellows-like expandable chamber
and wherein said motor assembly adjusts the position of the
bellows-like expandable chamber as it relaxes from a first expanded
state to a second more collapsed state to control the displacement
of the fluid reservoir.
11. A drug infusion device, comprising: a fluid reservoir; and
fluid reservoir displacement means for directly drawing drug fluid
into said fluid reservoir.
12. The apparatus of claim 11, wherein said fluid reservoir
displacement means comprises hydraulic displacement means.
13. The apparatus of claim 12, wherein said hydraulic displacement
means comprises a pump which circulates a working fluid between a
first reservoir and a contractible second reservoir disposed
proximate said fluid reservoir, so that as said second reservoir
contracts, said fluid reservoir is displaced.
14. The apparatus of claim 12, wherein said hydraulic displacement
means comprises a piston assembly which acts to directly displace
said fluid reservoir.
15. The apparatus of claim 11, wherein said fluid reservoir
displacement means comprises mechanical screw-type displacement
means.
16. The apparatus of claim 15, wherein said mechanical screw-type
displacement means comprises a motor operatively coupled to a lead
screw, so that as the motor turns the lead screw about a central
axis, a nut coupled to said fluid reservoir and disposed on said
lead screw is displaced along said central axis, displacing said
fluid reservoir.
17. The apparatus of claim 15, wherein said mechanical screw-type
displacement means comprises a motor that rotates a worm gear to
displace a rack coupled to the fluid reservoir, displacing said
fluid reservoir.
18. The apparatus of claim 11, wherein said fluid reservoir
displacement means comprises spring force displacement means.
19. The apparatus of claim 18, wherein, the spring force
displacement means comprises a bellows-like expandable chamber
annealed so that the chamber in its natural state assumes a
collapsed position, and in an expanded state the chamber tends
toward its natural collapsed position under its own action.
20. The apparatus of claim 19, wherein said spring force
displacement means further comprises a motor assembly, including a
motor operatively coupled to a flywheel about which a first end of
a cable having first and second ends is wrapped, said second end of
said cable being attached to said bellows-like expandable chamber;
and wherein said motor assembly adjusts the position of the
bellows-like expandable chamber from a first contracted state to a
second more expanded state to displace the fluid reservoir.
21. A method of infusing a drug to a specific desired location
within a patient's body, comprising: placing a measure of the drug
within a fluid reservoir and forcing at least a portion of the drug
from the fluid reservoir and through an established fluid
passageway extending between the fluid reservoir and the specific
desired location within the patient's body by directly displacing
said fluid reservoir.
22. A method of filling a drug reservoir in an implantable drug
infusion device, comprising: providing a supply of fluid; and
directly displacing said fluid reservoir to draw at least a portion
of the provided supply of fluid into said fluid reservoir.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to a method and
apparatus for the delivery of fluids to a desired location within
the body; and more particularly, relates to an implantable drug
infusion device for delivery of pharmaceutical agents or other
fluids directly from a reservoir within the device to a specific
desired location within a patient's body.
BACKGROUND OF THE INVENTION
[0002] Implantable drug infusion devices usually are implanted for
several years, during which time there is no opportunity to service
or repair these devices. Accordingly, both the implanted device and
the drug to be infused must remain operative and be stable for a
long period.
[0003] The current trend is toward extending significantly the
intended life of implanted drug infusion devices. Further, new
drugs having different physical and chemical properties are
continually being developed, the use of which may not be
sufficiently compatible or properly interactive with current
devices.
[0004] Conventional implantable fluid delivery systems for drug
infusion typically include a reservoir to store the fluid, and a
separate pump or other flow control device to deliver the fluid.
This type of implantable drug infusion system is shown generally in
FIG. 1. Reservoirs in conventional implanted drug infusion devices
undergo little motion, so that the materials which form the
reservoir can be selected primarily for compatibility with the drug
that is to be delivered. Pumps, on the other hand, typically have
many moving parts. The materials from which the pumps are made thus
must be selected for specific mechanical properties, such as
flexibility, durability, and strength. The materials used may not
exhibit all desirable mechanical properties, or may not be
compatible with some drugs to be infused. An example is a silicone
tube in a peristaltic pump. Silicone is very flexible and durable,
but is permeable to many fluids and is not as strong as other
elastomers.
[0005] With respect to another incongruity of design objectives,
because implantable infusion devices preferably are small in size,
the devices typically have only limited internal space, so that any
materials used in the manufacture of the device must be of the type
that can be used to manufacture very small parts. One example of
such a material is silicon formed by micromachining. Silicon,
however, is difficult to join to other materials.
[0006] Along the same lines, although it is desirable to have
implantable fluid delivery systems that are small in size, the
reduced size of certain conventional devices can be problematic in
some applications. For example, pumps or valves with very small
passages are not able to effectively deliver certain fluids. Some
drugs, such as insulin, often are damaged by shear forces when
flowing through such small passages.
[0007] Finally, another design incongruity arises with conventional
drug infusion devices in which the drug is routed from the
reservoir to the pump, and then to the device outlet where it is
delivered to a desired location within the body. A certain amount
of the drug thus is contained in the pump and fluid passages. This
fluid, held in what commonly is referred to as the "dead space,"
must be displaced whenever the drug in the reservoir is changed.
Delivery systems with relatively more dead space require more
unused, unwanted drug to be infused before the drug can be
changed.
SUMMARY OF THE INVENTION
[0008] The fluid delivery assembly and method of the present
invention overcomes the above-noted and other shortcomings of prior
drug infusion systems. In accordance with the present invention, a
drug or other fluid to be delivered to a specific desired location
within the body is stored in a reservoir that is directly displaced
by a force to infuse the drug from the device into the patient.
Several methods can be used to displace the reservoir, which are
described in more detail below. For simplicity the present
invention is described herein in terms of three presently preferred
embodiments which include, generally, hydraulic displacement,
mechanical screw-type displacement, and spring force displacement
of the fluid reservoir. However, one of ordinary skill in the art
having the benefit of this disclosure will recognize that the
invention is not limited strictly to the embodiments described
herein. The Figures and other description contained herein is
merely illustrative of the present invention. Actual implementation
of the present invention in an implantable drug infusion device
will undoubtedly vary depending upon the particular circumstances
involved with its intended use, particularly with respect to the
exact shape, size, specifications, etc. of the device. In any event
each embodiment herein described incorporates the teachings of the
present invention, and achieves the advantages of (a) eliminating
contact and interaction between the drug and, other materials,
including those comprising the pump; (b) eliminating small drug
passages, for example, through the pump; and (c) of allowing
controlled filling and emptying of the drug reservoir.
[0009] The first preferred method of displacing the reservoir,
given as an example, is hydraulic. See FIGS. 2 and 3. In this
configuration, three separate reservoir compartments are used along
with a separate pump. The pump does not contact the drug, but
recirculates a working fluid inside the device. The working fluid
can be selected to be non-corrosive, or even to enhance the
operation of the pump. Again, the choice of working fluid depends
upon the circumstances involved in a particular application.
However, examples of working fluids include sterile water, sterile
saline, silicone oil, or a lubricant.
[0010] In operation, the pump withdraws the working fluid from the
bottom reservoir and pumps it into an intermediate reservoir under
the drug reservoir. The drug and intermediate reservoirs are
separated by, for example, a diaphragm (See FIG. 2) or a piston
(See FIG. 3). Of particular importance is that the drug and
intermediate reservoirs be sealed, so that no fluid may pass from
one into the other.
[0011] As the intermediate reservoir fills, and the drug reservoir
is displaced, the drug is forced out of the device. The pump is
programmable to any pattern or rate utilized in an implantable
device. The drug infusion will follow the rate or pattern
programmed. Examples of program rates and patterns include those
commonly used with the SynchroMed.TM. Programmable Pump, available
commercially from Medtronic, Inc., Minneapolis, Minn.
[0012] A means of maintaining constant pressure in the device, such
as a volatile fluid, is required under the internal drug reservoir.
To refill the drug reservoir, a syringe is introduced into the
reservoir via a hypodermic needle. The drug exit path is closed and
the pump is then reversed to draw the drug from the syringe into
the reservoir. This method also eliminates the possibility of
forcing the drug into the reservoir with the syringe and damaging
the device or over-infusing the drug.
[0013] In the second preferred embodiment, the internal drug
reservoir is directly displaced mechanically, either by a motor and
lead screw (See FIG. 4) or a motor and worm gear (See FIG. 5).
[0014] In the first configuration of the second preferred
embodiment, the motor rotates and displaces a nut on the lead
screw. The nut is attached directly to the reservoir base and
directly displaces it as it moves. This system is less susceptible
to changes in pressure inside the device during operation. However,
a volatile fluid still may be used to ensure that a relatively
constant internal pressure is maintained. Again, the motor may be
programmed to any pattern or rate, such as those used in
commercially available implantable devices like the SynchroMed.TM.,
and the motor is reversed to refill the drug reservoir. This first
configuration is most suited for a donut-type bellows to ensure
that no contaminant reaches the interior of the drug reservoir.
[0015] In the second configuration of the second preferred
embodiment of the present invention, a motor rotates a worm gear
that displaces a rack coupled to the bottom portion of the drug
reservoir. A flexible side bellows allows the drug reservoir base
to be displaced upwards as the worm gear turns, forcing drug from
the reservoir to the desired delivery site. Again, the motor may be
programmed so that drug is delivered at a desired rate or pattern,
and may be reversed to facilitate the refilling of the drug
reservoir. The side bellows are hermetically sealed to keep the
drug free of possible contamination from unwanted sources, and to
protect any adverse impact which might result from their contacting
the drugs.
[0016] The third embodiment of the present invention utilizes the
spring force of the reservoir bellows to displace the drug
reservoir. The bellows is annealed, so that in its relaxed, natural
state it is completely collapsed. In this configuration (See FIG.
6), the bellows is expanded by a device such as a motor which turns
a flywheel or pulley to wind one end of a cable about the pulley or
flywheel, the other end of the cable being connected to the bottom
of the drug reservoir. Once the reservoir is filled, the
pulley/cable is relaxed to allow the bellows to return to its
natural, collapsed state. Again, the motor may be programmed to any
pattern or rate to ensure that the displaced drug is delivered
according to the desired schedule, and the motor may be programmed
to allow for controlled refilling.
[0017] As stated above, and although the present invention
described herein in terms of three separate embodiments, there are
certain advantages which all three embodiments share over prior
devices. For example, again, in each embodiment the drug contacts
only one material. Preferably, the material used is titanium or
some other inert material suitable for use in a wide variety of
medical applications. Moreover, the active mechanism in each
embodiment, a pump or motor, is completely sealed off from the drug
to be delivered. Further, there are no small passages for the drug
to travel through, and the amount of dead space is minimized.
Finally, the active mechanism is able to empty and refill the
reservoir, eliminating the need for medical personnel to do so.
This minimizes the possibility of overfilling.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a schematic illustration of a conventional
implantable drug infusion device.
[0019] FIG. 2 is a schematic illustration of an embodiment of an
implantable drug infusion device according to the present invention
and including a diaphragm and a hydraulic displacement
mechanism.
[0020] FIG. 3 is a schematic illustration of an embodiment of an
implantable drug infusion device according to the present invention
and including a piston and a hydraulic displacement method.
[0021] FIG. 4 is a schematic illustration of an embodiment of an
implantable drug infusion device according to the present invention
and incorporating direct mechanical displacement by a motor and
lead screw.
[0022] FIG. 5 is a schematic illustration of an embodiment of an
implantable drug infusion device according to the present invention
and incorporating direct mechanical displacement by a worm
gear.
[0023] FIG. 6 is a schematic illustration of an embodiment of an
implantable drug infusion device according to the present invention
and incorporating a spring forced bellows urgeable from a relaxed
collapsed position by a pulley mechanism.
DETAILED DESCRIPTION OF THE INVENTION
[0024] As shown in FIG. 1, prior implantable drug infusion devices
generally comprise an infusion assembly 10 including an internal
drug reservoir 12 and a pump 14. A drug that is to be delivered to
a specific desired location within a patient's body is supplied
manually via a hypodermic needle 16 inserted into the reservoir 12.
Access to the reservoir 12 is achieved through an access port 18 by
inserting the needle 16 through the septum 20 which otherwise acts
to prevent fluids or other substances from gaining entry to or
leaving the reservoir 12. The pump 14 pulls the drug to be infused
to the patient from reservoir 12 via exitway 22. After passing
through pump 14, the drug is delivered via outlet line 24 to the
desired location within the patient's body.
[0025] The use of prior implantable drug infusion devices such as
the one shown generally in FIG. 1 has significant drawbacks.
However, as noted above, the present invention overcomes these
shortcomings. In particular, it should be noted that the drug in
pump 10 contacts multiple different materials, that the pump 14 is
in contact with the drug, that the drug must traverse any small
passageway in pump 14, and that the rate of introduction of drug
into reservoir 12 is controlled solely by the clinician filling the
device and is not metered by pump 10.
[0026] As shown in FIG. 2, the first configuration of what for
convenience is termed herein as the "hydraulic" embodiment of the
present invention includes three separate reservoirs: a drug
reservoir 30, an intermediate reservoir 32, and a lower reservoir
34. The drug to be infused to a desired location within a patient's
body is introduced into reservoir 30 via needle 36 inserted through
septum 38 disposed within access port 40.
[0027] In accordance with the present invention, intermediate
chamber 32 initially contains a working fluid such as sterile
water, sterile saline, silicone oil, or a lubricant. A membrane or
diaphragm 48 separates drug reservoir 30 from intermediate
reservoir 32. Once the delivery needle 36 is inserted in place so
that its tip is within reservoir 30, the pump 42 draws working
fluid from intermediate chamber 32 and delivers the withdrawn fluid
into lower chamber 34. As the volume of fluid in intermediate
chamber 32 decreases, the size of chamber 32 will decrease too, and
drug fluid will be drawn into reservoir 30 from the supply needle
36. The change in volumes of reservoirs 30 and 32 is possible in
view of the use of the bellows-like sidewall 44. The amount of
working fluid transferred from intermediate chamber 32 to lower
chamber 34 varies according to the desired amount of drug to be
drawn into drug reservoir 30.
[0028] Once drug reservoir 30 holds a desired amount of drug fluid,
and the needle 36 has been withdrawn, delivery of the drug to a
specific desired location within a patient's body via outlet line
46 is accomplished by reversing pump 42. That is, pump 42 draws
working fluid from lower chamber 34 and injects it into
intermediate chamber 32. When this occurs, the volume of
intermediate chamber 32 increases, and membrane 48 is displaced, so
that the size of drug reservoir 30 decreases and drug is forced out
through exitway 46.
[0029] Thus, by controlling the operation of pump 42, the delivery
of drug to the patient is also controlled. Preferably, the pump 42
is programmable, allowing the physician or other clinician to set
the rate and/or pattern of the transfer of the working fluid, and
hence the rate and/or pattern for the infusion of drug fluid.
[0030] A second configuration of the "hydraulic" embodiment of the
present invention is shown in FIG. 3. The structure of this second
configuration generally resembles that of the first configuration.
Drug is introduced into reservoir 50 via a needle 52 inserted
through septum 54 disposed within access port 56. A pump 58 acts to
transfer a working fluid between intermediate chamber 60 and a
lower chamber 62. The drug is infused to the patient's body through
exitway 64 by the action of pump 58, the transfer of the working
fluid, and the displacement of the reservoir 50, much like the
infusion takes place within the first configuration. However, the
second hydraulic configuration includes, instead of a membrane, a
sliding piston 66 adapted with a seal 68 to separate intermediate
chamber 60 from drug reservoir 50. The seal 68 helps to ensure that
no fluid or drug is transferred between chambers 50 and 60.
[0031] The second preferred embodiment of the present invention
generally is directed to an assembly that uses mechanical,
screw-type displacement of a drug reservoir to deliver
pharmaceutical agents or other fluids to a specific desired
locations within a patient's body. Again, there are two general
configurations of this preferred embodiment.
[0032] In the first configuration, shown in FIG. 4, a motor 70 is
operatively coupled to a lead screw 72, so that as the motor 70
rotates the screw 72, a nut 74 is displaced along the longitudinal
axis of the screw 72. The nut 74 is operatively coupled to both
lead screw 72 and the base of drug reservoir 76, so that
displacement of the nut 74 in either direction along the axis of
screw 72 results in a corresponding displacement of the base of the
drug reservoir 76.
[0033] As the base of the drug reservoir 76 moves, the volume of
the drug chamber 76 changes. Preferably, sidewall 78 and inner wall
80 comprise a donut-shaped bellows-like assembly that permits the
volume change to occur.
[0034] The introduction and expulsion of the drug to and from the
drug reservoir 76 is accomplished much like in the first preferred
embodiment of the present invention, i.e., by displacement of the
drug reservoir itself. Again, access to the reservoir 76 may be had
by way of a needle 82 inserted through a septum 84 disposed within
access port 86, and the drug exits the reservoir 76 via exitway
88.
[0035] The second configuration of the second preferred embodiment
is shown in FIG. 5. A motor 90 drives a worm gear 92 that meshes
with a toothed bar or rack 94. The rack 94 is fixedly attached or
otherwise operatively coupled on one end to the bottom of the drug
reservoir 96. The drug reservoir 96 is shown as having flexible,
i.e., collapsible sides 98, rather than bellows-like sides as in
the other Figures. The exact shape of the sides is not necessarily
critical; of primary importance is that the sides allow the
reservoir 96 to be displaced, so that drug introduced by needle 100
through septum 102 disposed in port 104 may be delivered via
exitway 106 to a specific desired location in the patient's
body.
[0036] The third preferred embodiment of the present invention is
shown in FIG. 6. The drug infusion assembly comprises a reservoir
108 including a base 110 and bellows 112. The bellows 112
preferably is annealed in a bellows-like shape so that in its
natural state the wall is collapsed, i.e., in a condition
corresponding to the state of lowest volume of the reservoir 108. A
motor 114 is operatively coupled to a pulley or flywheel 116. A
wire, rope, cord, chain or similar such connecting means 118 is
coupled on one end to the base 110, and on its other end to the
flywheel 116. As the motor 114 turns in one direction, the flywheel
116 turns and wraps the connecting means 118 about the flywheel
116, so that the base 110 is displaced, increasing the volume of
the reservoir 108. As the volume of the reservoir 108 is increased,
drug or other fluids to be infused to the patient may be introduced
into the reservoir 108 from the needle 120 extending through septum
122 disposed in port 124 in the manner described above. The
annealing of the bellows 112 ensures that the reservoir acts like a
spring; that is, in tending toward a natural state, the reservoir
places in tension the connecting means 118.
[0037] To deliver drug to the patient, then, the direction of the
motor 114 is reversed, so that the reservoir is displaced back
toward its natural state. As the volume of the reservoir decreases,
the drug is forced to exit through opening 126. The motor 114, like
the motors and pumps of the other embodiments, may be programmed so
that delivery of the drug takes place at a desired rate or
pattern.
[0038] Although the preferred embodiment of this invention has been
described hereinabove in some detail, it should be appreciated that
a variety of embodiments will be readily available to persons
utilizing the invention for a specific end use. The description of
the apparatus and method of this invention is not intended to be
limiting on this invention, but is merely illustrative of the
preferred embodiment of this invention. Other apparatus and methods
which incorporate modifications or changes to that which has been
described herein are equally included within this application.
Additional objects, features and advantages of the present
invention will become apparent by referring to the above
description of the invention in connection with the accompanying
drawings.
* * * * *