Syringe pump abstract
An electrochemically driven syringe pump for infusion of medicament
wherein the pump has a detachable barrel in which medicament can
be stored and subsequently infused. The pump is further adapted
for storage as the charge transfer medium is sealed in a reservoir
prior to activation.
Syringe pump claims
In accordance with our invention, we claim:
1. An electrochemical syringe pump comprising:
a syringe for delivering a supply of fluid;
a plunger disposed within said syringe;
a pump housing having an inner and outer surface, said inner surface
is attached to said syringe, said pump housing comprises:
an electrochemical cell;
a power supply selectively connected to said electrochemical cell;
a current control apparatus providing a limited current to said
electrochemical cell from said power supply;
a perforating member defined on said inner surface of said pump
a sealed charge transfer medium reservoir housed between said syringe
and said pump housing wherein upon engagement of said perforating
member with said sealed charge transfer medium reservoir, said perforating
member perforates said sealed charge transfer medium reservoir and
releases a charge transfer medium contained in said reservoir to
contact said electrochemical cell to assist in a chemical reaction
in said cell wherein said reaction causes an increase in pressure
on said plunger to deliver a predetermined amount of said fluid.
2. The invention according to claim 1 wherein said syringe further
comprising a barrel wherein said barrel has a draft angle defined
thereon of substantially zero.
3. The invention according to claim 2 wherein a plunger adapted
to slidingly fit within said barrel and a cruciform seal retained
by said plunger.
4. The invention according to claim 3 wherein said cruciform seal
in combination with said draft angle provides a substantially constant
force of sliding friction therebetween.
5. The invention according to claim 1 wherein said current control
controls a rate of infusion of medicament from said pump.
6. The invention according to claim 1 wherein said syringe further
comprises a cam having a first position and a second position wherein
said first position affixes said syringe to said pump while preventing
activation of said cell.
7. The invention according to claim 6 wherein said second position
activates said cell.
8. The invention according to claim 1 wherein said current control
is a fixed resistive element which determines a rate of infusion
by controlling a current available to said cell.
9. An electrochemically driven syringe pump for delivery of medicament
to a patient; comprising a syringe for delivering a supply of medicament;
a plunger disposed within said syringe;
a pump head having an inner and outer surface wherein said inner
surface is connected to said syringe;
an electrochemical cell located within said pump head;
a power supply and current control apparatus located within said
pump head and selectively connected to said electrochemical cell;
said pump further comprising a reservoir, in movable attachment
to said pump head, which releasably retains a charge transfer medium,
wherein said reservoir is covered by a perforatable membrane and
said membrane is surmounted by a perforating member, extending from
said inner surface of said pump head, which perforates said membrane
when said pump is activated by attachment of said syringe to said
pump head thereby releasing said charge transfer medium to come
into contact with said electrochemical cell so as to assist said
cell in executing an electrochemical reaction which increases pressure
in said syringe to move said plunger and deliver a metered amount
of medicament from said syringe.
10. The invention according to claim 9 wherein said reservoir further
comprises a fluid retaining area and a blotter.
11. The invention according to claim 10 wherein said blotter contacts
said electrochemical cell upon activation of said pump.
12. The invention according to claim 9 wherein said perforating
member is a toothed annulus.
13. A gas driven syringe pump comprising a syringe and a plunger
pump module housing an electrochemical cell;
said pump module having a toothed perforating member extending
a cup-like fluid reservoir, slideably retained about said perforating
a sealing member placed within said reservoir wherein said sealing
member is emplaced between said perforating member and a charge
transfer medium retained in said reservoir; wherein said perforating
member perforates said sealing member upon activation of said pump
by attachment of said pump module to said syringe wherein such attachment
causes said syringe to slide said perforating member into said reservoir,
thereby releasing said charge transfer medium from said reservoir
to come into contact with said electrochemical cell retained within
said pump module thereby assisting in an electrochemical reaction
causing an increase in pressure in said syringe so as to move said
plunger and deliver medicament from said syringe.
14. The invention according to claim 13 wherein said charge transfer
medium being water.
15. The invention according to claim 14 wherein there is a said
medium comprising a medium storage area and a medium delivery apparatus;
said apparatus comprising a blotter to deliver said medium from
said storage area to said electrochemical cell.
16. The invention according to claim 15 wherein said medium storage
area further comprising a rupturable cover wherein said cover is
adapted to be ruptured upon engagement with said pump module.
Syringe pump description
FIELD OF THE INVENTION
The present invention relates to medical infusion devices for parenteral
delivery of fluids and more specifically to medical infusion pumps.
BACKGROUND OF THE INVENTION
The medical infusion pump art is one of great breadth and diversity.
Even within the art of syringe pumps a great deal of work has been
Syringe pumps generally are used to infuse a relatively small quantity
of concentrated medicament as opposed to large volume pumps which
are designed to infuse accurately a medicament which is formed in
admixture with a large quantity of diluent.
Syringe pumps run the gamut from highly accurate and correspondingly
expensive electro mechanical pumps such as the Baxter AS40 and other
devices from various manufacturers to very inexpensive and correspondingly
less accurate disposables; an example thereof being the Disetronic
Infusor, which is a galvanic cell, generating Hydrogen, attached
to a syringe. Another example of a disposable infusion device is
the SmartDoseII.TM. by River Medical Inc. This device uses an acid-base
reaction to produce gas operative to collapse a bag of medicament.
As can be seen by a review of the disposable syringe pump art,
of which the above are exemplary, disposable syringe pumps, particularly
gas driven syringe pumps, lack the requisite accuracy to deliver
many of the latest and most efficacious drugs, particularly drugs
for oncology treatments and antibiotics and the like.
The instant invention provides for a level of accuracy similar
to that of an electromechanical syringe pump whilst maintaining
the simplicity and low cost associated with disposable devices.
This accuracy is achieved by use of an accurately current-controlled
electrochemical cell which preferentially transfers oxygen out of
the air into a specially designed syringe having an essentially
constant coefficient of friction throughout the length thereof against
the syringe plunger.
An additional shortcoming of gas driven infusion devices is that
as the drive gas is being generated there is a delay in infusion
at the desired flow rate as the gas pressure rises. In the instant
device, the syringe is prepressurized so as to minimize this lead
The electrochemistry of electrically driven cells is well characterized.
The instant device preferentially uses a cell made of Nafion.RTM.
from E.I. DuPont de Nemours & Co. Nafion is an acidic material
which provides for the reaction:
which serves to fill the syringe with oxygen gas. As can be seen
from the above reaction, the water is not consumed but rather is
recycled as the reaction continues. The water necessary for proton
transport when the cell becomes excessively dehydrated is contained
in the pump in a novel blotter arrangement which shall be subsequently
The combination of the novel electrochemical cell, blotter and
prepressurized syringe as well as other aspects of the invention,
which shall be subsequently described, provides for an accurate
and cost effective pump.
SUMMARY AND OBJECTS OF THE INVENTION
It is a primary object of the invention to provide for a syringe
pump having greatly improved accuracy in the delivery of medicaments.
It is another object of the invention to reduce the lead time inherent
in gas driven pumps.
It is a third object of the invention to provide a compact and
self-contained syringe driving apparatus.
It is a fourth object of the invention to provide for a syringe
having an essentially constant coefficient of sliding friction along
the throw thereof.
It is a fifth object of the invention to provide for simultaneous
assembly and activation of the pump.
It is a sixth object of the invention to provide for an electrochemical
cell having a minimized current density gradient across the surface
It is a seventh object of the invention to provide for an escape
valve for excess gas within the syringe.
It is an eighth object of the invention to provide an accurate
current controller to an electrochemical cell in an infusion pump.
It is a ninth object of the invention to provide for a sealing
ring associated with the plunger of the syringe adapted to provide
an essentially constant sliding coefficient of friction.
It is a tenth object of the invention to provide for a syringe
that can be prefilled, attached to a pump and subsequently activated.
It is an eleventh object of the invention to provide for an integral
assembly operative to supply a source of water to an electrochemical
It is a twelfth object of the invention to provide for an electrochemical
pump which is storable for an extended period without loss of efficacy.
It is a thirteenth object of the invention to provide for an improved
structure of an electrochemical cell.
These and other objects of the instant invention will become apparent
upon review of the claims, specification and drawings appended hereto.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the instant invention with the
pump head assembled to the syringe.
FIG. 2 is a cross-sectional view substantially along line A--A
of FIG. 1.
FIG. 3 is a plan view of the electrochemical cell assembly.
FIG. 4 is a cross-sectional view substantially along line C--C
of FIG. 3.
FIG. 5 is a cross-sectional view of the syringe and plunger substantially
along the line A--A of FIG. 1.
FIG. 6 is an exploded view of the instant invention.
FIG. 7 is a perspective view of the blotter assembly.
FIG. 8 is a perspective view of the bottom of the pump assembly
detailing the sub-assembly associated with the blotter assembly
of FIG. 7.
FIG. 9 is a perspective view of the cruciform sealing ring
FIG. 10 is a cross-sectional view along the line D--D of the blotter
sub-assembly shown in FIG. 7.
FIG. 11 is a perspective view of the blotter assembly as assembled
on the sub-assembly shown in FIG. 8.
FIGS. 12a and 12b are perspective views of the syringeward side
of the pump head and the distal end of the syringe.
FIG. 13 is a cross-sectional view of the gas relief valve.
FIG. 14 is a detailed cross-sectional view substantially along
the line A--A showing the prepressunrzation means.
FIG. 15 is a schematic diagram of the control circuitry of the
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in FIGS. 1 and 6 the preferred embodiment of the instant
invention consists of a pump assembly 10 which can be subdivided
into a pump module 12 and a syringe body 14. The pump module 12
further consists of a pump housing 16 which is operative to contain
the various sub-assemblies of the pump module 12. As shown in FIGS.
12a and 12b, housing 16 defines a peripheral lip 18 which is operative
to engage a radially extensive cam 20 associated with the syringe
body 14. Peripheral cam 20 defines a first stop position corresponding
to a first cam flat 22 which serves to allow the syringe body 14
to be connected to the pump module 12 without activating the pump
assembly 10. In the docked but unactivated position, cam flat 22
is engaged with indent 25 so as to allow for the syringe 14 to be
engaged with housing 16 without activating the pump. The peripheral
cam 20 also defines a second ramp 24 at which point the syringe
body 14 is fully engaged with the pump module 12 at which time second
ramp 24 has lifted syringe 12 into place so as to allow cam flat
22 to be engaged with lip 18.
As best seen in FIG. 2 syringe barrel 14 has associated therewith
an aft aperture 96 which is adapted to receive a plunger assembly
99. Immediately forward of the aft aperture is a first radial angle
98 shown in FIGS. 12a and 12b, having a height and radial angle
defined thereon. Moving forward is annular wall 100 and an annular
ramp 90 which is operative to reduce the interior dimension of the
syringe barrel 14 to its nominal dimension.
Forward of annular ramp 90 is stop 97 which is operative with plunger
assembly 99 to define the syringe volume as well as to retain plunger
assembly 99 in syringe barrel 14. The remainder of the syringe barrel
being essentially cylindrical and defining an essentially zero draft
angle wherein the draft angle is defined as the angle between an
axis parallel to the longitudinal axis of the syringe barrel and
the wall of the syringe barrel. This minimization of draft angle
being operative to provide, in combination with the cruciform sealing
ring 200 shown in FIG. 9 which shall subsequently be described,
an essentially constant co-efficient of sliding friction between
the plunger 210 and the syringe barrel interior 102. Foremost in
the syringe is a centrally located output aperture 104 which is
adapted to be attached in the preferred embodiment to a luer-type
fitting 106 wherein the attachment is operative to connect the syringe
to an output tube set so as to deliver medicament to the patient.
Returning to the aft or distal end of the syringe annular wall 100
is cooperative with translatable gasket 75 associated with extension
34 so as to provide for a reduction in volume in the gas receiving
chamber 110 which is defined within the volume of the syringe barrel
14 the gas receiving chamber being an area within the syringe barrel
14 which is abaft the syringe plunger 210 and sealing ring 200.
Translatable gasket 75 is operative to move down the annular wall
100 and by such movement provide for a reduction in volume within
the gas receiving chamber 110 so as to cause an increase in pressure
in the atmosphere contained therein and is thereby operative to
prepressurize the syringe 14 and thereby reduce the lead time before
achieving the desired flow rate. This reduction in volume corresponds
to the linear translation of the syringe between a first position
corresponding to locating cam flat 22 within indent 25 and a second
position corresponding to the cam flat 22 engaged with lip 18 shown
in FIGS. 12a and 12b, as aforedescribed and being defined as the
initial volume of the gas receiving chamber as defined previously
and a final volume which is reduced by the difference in position
between the first position and the second position.
In operation the syringe body 14 would be attached to the pump
module 12 and rotated into the position corresponding to the first
cam flat 22 being engaged with indent 25; wherein the filled syringe
would remain in such position until time for actual activation by
a patient. At this time the syringe body 14 would be rotated relative
to the pump module 12 thereby causing the radial extension 18 to
engage the first cam flat 22. At this time the radial stop 97 associated
with the syringe body 14 would engage cup 80 shown in FIG. 10
and effect the linear translation of the cup as aforedescribed.
Simultaneously, translatable gasket or o-ring seal 75 shown in
FIG. 6 would move down annular wall 100 thereby reducing the volume
of the gas receiving chamber 110 and increasing the pressure therein.
Simultaneous thereto, the toothed perforating member 60 best seen
in FIG. 11 would puncture the perforatable seal or cover 86 and
release the charge transfer medium from the reservoir 82 and affect
a transfer of such medium through the charge transfer medium transfer
blotter 88 to the electrochemical cell 54.
As seen in FIGS. 12a and 12b, the aft edge of the syringe body
14 includes an aperture 96 wherein the aperture 96 defined by syringe
body 14 further defines a first radial angle associated therewith,
wherein the first radial angle 98 is operative to provide an initial
seat for translatable gasket or o-ring 75. Afore the fist radial
angle 98 is the annular wall 100 and a second diameter reducing
annular ramp 90 is operative to reduce the syringe body diameter
to a final dimension operative to provide a sliding mate with syringe
plunger assembly 99.
As shown in FIGS. 2 and 6 syringe plunger assembly 99 displays
a two piece construction wherein the aft plunger body 210 is substantially
a stepped cylinder defining an aft extension operative to eliminate
tilt of the plunger body 210 within the syringe barrel 14. Mounted
on plunger body 210 is a forward cylindrical retaining ring 212
wherein the ring 212 has a slightly smaller external radial dimension
than the aft section 210A of the syringe plunger body 210. Best
seen in FIG. 5 located in the interstice between the cylindrical
retaining member 212 and the aft extension of the syringe plunger
210A is a sliding plunger seal 200. Sliding plunger seal 200 displays
a cruciform cross-section as seen in FIGS. 5 and 9 and in cross
section FIG. 14 wherein this cross-section is designed to provide
for an essentially constant sliding coefficient of friction between
plunger assembly 99 and syringe barrel interior 102.
Pump housing 16 further defines a substantially centrally located
longitudinal web 30 which has defined thereon a plurality of battery
supporting indents 32 and further serves to stiffen housing 16.
Additionally associated with housing 16 is a lid 33 and coaxial
extension 34 which serves to support the majority of the components
associated with housing 16. Nested within the coaxial extension
34 is a printed circuit board 36 which supports current control
circuitry 38. The output of this circuitry 38 is transferred via
electrode 52 to the electrochemical cell housing 54 which shall
be subsequently described. Spring contacts 28 serve to connect batteries
56 electrically to circuit board 36.
Turning now to FIG. 8 the bottom of housing 16 is shown. Associated
with the base of coaxial extension 34 is a toothed perforating member
60 which consists of a plurality of longitudinally extensive teeth
62. Located interior to perforating member 60 is a cell housing
supporting indent 64 which has associated therewith support posts
66 which are operative to support the interior surface of the electrochemical
cell housing 54. Also associated with indent 64 is feed through
port 68 which is adapted to allow spring contact 52 to come into
contact with housing 54.
Exterior to indent 64 and parallel therewith housing 16 has defined
therein a gas relief valve port 70 which serves to support and contain
the overpressure relief valve 300 as shall be subsequently described.
Relief valve port 70 is axially extensive to the top of extension
Returning to FIGS. 12a and 12b, extension 34 further defines a
radial step 72 which is cooperative with the reservoir cap 80 to
retain the cap 80 in a plurality of specific positions which shall
be subsequently described. Additionally associated with extension
34 is coaxial groove 76 which is adapted to receive a corresponding
coaxial rim 78.
Located uppermost on extension 34 is a sealing ring engaging surface
79 which is adapted to receive sealing ring 75.
Cap 80 which can best be seen in FIGS. 7 and 10 defines a plurality
of features. As seen in FIG. 10 cap 80 has a charge transfer medium
reservoir 82 resident therein which also defines an aperture 84
across the top thereof, which is perforatably sealed with a rupturable
seal or cover 86 placed across the aperture 84 aforementioned. Surmounting
medium storage area 82 and perforatable seal 86 is a medium delivery
apparatus 88 which in the preferred embodiment consists of a capillary
active blotter assembly 88 which, upon perforation of the rupturable
seal or cover 86 is operative to effect delivery of the charge
transfer media from the reservoir or storage area 82 to the electrochemical
cell housing 54 as shown in FIG. 11.
As aforementioned, extension 34 is adapted to allow cap 80 to assume
a plurality of positions. In the first of these positions cap 80
is located outwardmost from extension 34. In this configuration
the charge transfer medium is retained by rupturable seal 86 within
Upon assembly of pump module 12 with syringe 14 and rotation to
a first position corresponding to a first cam flat 22 engaged with
indent 25 as aforementioned, the cup is placed into this initial
position. Upon further rotation of syringe body 14 corresponding
to a rotation of radial cam 20 the syringe advances up ramp 24 to
engage flat 22 with lip 18 causing annular ramp 90 to impinge upon
the exteriorally extensive cup ridge 92 thereby executing a linear
motion of the cup 80 and driving the reservoir 82 and perforatable
seal 86 into the toothed perforating member 60 and thereby releasing
the charge transfer medium into the medium delivery apparatus 88
thereby transferring the medium to the electrochemical cell 54 coincident
with electrical activation of the cell 54.
Situated in the pump module 12 and in fluid communication with
the gas receiving chamber 110 a overpressure relief valve assembly
300 is operative to release gas generated by the electrochemical
cell 54 and introduced into the gas receiving chamber 110.
Should an occlusion or other interruption of the flow of medicament
be experienced by the pump, an overpressure relief valve assembly,
as shown in FIG. 13 is provided to allow reaction products to escape
the syringe. The overpressure relief valve assembly 300 consists
of a substantially cylindrical port 70 which is occluded by a elastomeric
valving member 314 which is cooperative with valve seat 316 to provide
for a fixed overpressure release. In operation the overpressure
release valve 300 is acted upon by the presence of a pressurized
atmosphere within the gas receiving chamber 110 wherein this atmosphere
acts to provide a force againist the elastomeric member 314 tending
to displace the elastomeric valving member 314 from the valve seat
316. This displacement is counteracted by the elastic properties
of the elastomeric valving member 314 to such an extent as to keep
the elastomeric valving member 314 in contact with the valve seat
316 up to a specific predetermined pressure wherein the force supplied
by the atmosphere resident in the gas chamber 110 is sufficient
to move the elastomeric valving member 314 off of the valve seat
316 thereby allowing gas to escape through gas release ports 318
to the exterior of the pump module 12 at which time the elastic
properties of the elastomeric valve member 314 will provide sufficient
force to reset same against the valve seat 316 thereby closing off
port 318 and allowing the gas receiving chamber to repressurize
up to the final pressure prior to actuation of the overpressure
relief valve 300.
The electrochemical cell assembly 54 as shown in FIGS. 3 and 4
consists of an anode body 256 which further includes the exterior
of the assembly. Interior to the anode body 256 is an annular seal
258 wherein this annular electrochemical cell seal 258 resides conterminous
with the interior dimension of the anode body 256. Interior to the
seal 258 is a cathode body 260 which also structurally comprises
the interior body of the assembly 54. Located conterminous with
the cathode body 260 is the electrochemically active medium or membrane
262 which in the preferred embodiment is composed of Nafion as aforedescribed.
The electrochemical membrane 262 is placed in contact with the cathode
body and upon assembly the cathode body and electrochemical membrane
are pressed past seal 258 so as to place the electrochemical membrane
under tension due to frictional forces between the electrochemical
membrane 262 and the seal 258 as the cathode body 260 and electrochemical
membrane 262 are emplaced thereagainst. At this time seal 258 is
already resident within the anode body 256 so as to provide a positive
seat during assembly. Returnng now to the cathode body, as can be
seen on the FIGS. 3 and 4 the central surface 260S of the cathode
body 260 is uniaxially undulate. These undulations are placed as
aforementioned along a first electrochemical cell axis 260A defined
as being parallel to the longitudinal dimension of these undulations
260U. Placed therebelow, wherein the membrane is interstitial between
the anode body 256 and cathode body 260 the anode body 256 further
defines a second electrochemical cell axis which is defined as being
parallel with the longitudinal extension of the undulations 260U
impressed upon the anode body.
In the preferred embodiment the first electrochemical cell axis
and the second electrochemical cell axis are at an angle to each
other so as to provide a plurality of distributed electrical contact
areas across the surface of the membrane 262. To allow feedstock
to enter and reaction products to leave the surface of the membrane
262 a first plurality of holes 270 is defined upon the cathode body
and a second plurality of holes 272 is defined upon the anode body
wherein the first plurality of holes which are defined upon the
cathode body 256 also known as cathode ports 270 and the second
plurality of holes 272 defined on the anode body 256 which are also
referred to as anode ports 272 are mutually disjoint so as to provide
an even and uniform means for spiration of feedstock and reaction
products to and from the membrane 262. An additional effect of the
first and second undulate suffaces and the intersection therebetween
across the membrane 262 is a marked reduction in the current gradient
across the membrane surface wherein in the instant invention current
is supplied across the membrane, and the undulate sufaces 260U,
by providing a plurality of contact points, serves to minimize any
variation in current supply through the membrane 262.
The electronic configuration of governing current control to the
electrochemical cell 54 is depicted schematically in FIG. 15. A
battery 56 supplies electrical power to the circuitry which is controlled
by a current controlling chip which in the preferred embodiment
is a Micronics Incorporated precision current controller type MX963
40 or a TPS 7101 manufactured by Texas Instruments Corp. Controller
chip 40 is connected to a load resistor via the sense leads 42.
These leads provide feedback for the controlling chip 40 to sense
the amount of current passing through the electrochemical cell 54.
The purpose of the resistor 46 is to provide a base current limiting
to the sense portion of the integrated circuit 40 thereby determining
the rate at which gas is generated by the electrochemical cell which
is proportional to the rate of infusion. The output of current controlling
chip 40 is thereafter connected to the electrochemical cell and
returns to the battery via ground lead 50 thereby completing the
circuit. Returning to switch 28 this switch corresponds to the
reed switch aforedescribed.
This description of the presently preferred embodiment is indicative
of the presently preferred configuration of the invention and is
not to be construed to limit the scope of the invention to any extent
greater than recited in the claims hereto appended.