Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~23~
This invention relates to a programmable infusion
system for providing medication to a living body and is a
division of copending application Serial No.417,979 filed
December 17, 1982, now allowed.
The present invention relates to the field of
dispensing medication to a living being. Although mainly
intended for use by human patients requiring infusions of a
drug, e.g. insulin, glucose, heparin, or any of various other
chemotherapeutic agents, the invention extends to use in any
living body te.g. domestic animals) and to the infusion of any
liquid (e.g. blood) or colloidal suspension, or gas or
granulated solid, which may provide a curative or healing
effect. Although a principal use envisioned is for
implantable devices, it i6 also envisioned that it could be
used external to a living being for the infusion of medication.
Various techniques and devices have been suggested and
are currently under study which address the problem of
dispensing a drug or other medicative liquid into a living
body. Of these techniques and devices, however, sufficient
, 20 safety features in the environment of the flexibility achieved
by programming dosage ineuts are rarely contemplated.
One liquid infusion device discussed in U.S. Patent
No. 4,077,405 issued March 7, 1978 to Haerton et al discloses a
controllable dosing arrangement which provides for human
operator interaction. syringe forces liquid through a
~Z31Z~
pressure valve into a supply reservoir and a bellows pump
forces drug from the reservoir through a flow limiter into the
body. This device fails to address various safety problems,
e.g. leakage, excessive pumping, and excessive requests for
drug. No provision for detecting leaks in the device, for
signalling malfunctions, for restricting the number of or
quantity of drug doses, or for monitoring proper operation of
the device is suggested.
~123~
ike Haeeton et al, U.S. Patent No. 3,692,027 issued
September 10, 1972 to Ellinwood teaches an implanted,
self-powered drug dispenser having a bellows pump which employs
one-way valves. The Ellinwood device i6 not progeammable and
varies dosage by opening and closing portals or selecting a
dose of medication from one of a plucality of pumps having
different dosage volumes and/or different medications stored
therein. Safety redundancy pertaining to filling, leakage
;:::; ..
problems, patient and doctoc interaction with the dispenser,
and dosage input programming are not considered.
An invention of Blackshear et al (U.S. Patent No.
3,731,681 i6sued May 8. 1973) show6 another infusion pump
without appreciable safety features. Blackshear et al do not
look for pressure integrity before filling the device with
drug, nor teach any means for monitoring pump operation.
Richter (U.S. Patent No. 3,894,538 issued July 15,
,, . :
1975) considers, in a medicine supplying device, one safety
feature: an exit plug for preventing, contaminants from
entering the device and for limiting drug outflow. The flow
from the Richter device does not provide a smooth pulsatile
flow of drug which is infused over a relatively long period.
It furthec fails to disclose any means for reliably controlling
or varying the flow rate oc for monitoring the rate of
operation.
Several eecent publications have also underscored the
need for an implantable medication infusion device. Two
articles by Rhode et al ("One Year of Heparin Anticoagulation":
Minnesota Medicine: October, 1977 and "Pco~racted Parenteral
- --2--
~Z3~8~L
Dcug Infusion in Ambulatory Subjects Using an Implantable
Infusion Pump"; American Society for Artificial Internal Organs
Transaction, Volume XXIII, 1977) described an implantable
infusion pump. No check for pcessuce integrity before filling
or during operation, no progcamming means, and no patient or
doctor interaction with the device are contemplated.
An article by Spencer ("For Diabetics: an electronic
-- pancrea6" IEE-Spectrum; June, 1978) discusses current trends
in the implantable drug pump field. Programming the rate of
drug flow over time depending on food intake is mentioned.
Efforts in the development of an implantable bellows pump are
also discussed. Spencer further mentions the use of an alarm
which 60unds if a pump fails to pcovide drug in accordance with
the preprogrammed rate. The Spencer article generally
discussed drug dispenser technology but fails to address many
specific problems. As in the othee cited works, safety
featuces such as an antechamber: leak detection; distinctive
subcutaneous stimulation to indicate various device
malfunctions: safe methods of programming the device regardless
of wock, food-intake, or time schedules and telemetering of
information pertaining to the actual operation of the pump are
not considered.
Finally, German Patent Application DE 31-12916-Al,
published February 15, 1982, in the name of Medtronic Inc.,
teaches an implantable medicine dispensec which is externally
programmable. Receipt ox progcamming commands can be verified
by an acoustic signal. No means are shown or suggested or
~L~3~
sensing, stocing, and telemetecing information pertaining to
aetual pump opecation. As a result, only the instruetions
given to this aparatus ean be vecified and ehanges in the
physiologieal cesponse of the patient, often detrimental, are
the only way to monitoc pump opecation.
Aeeocdingly, an objeet of a broad aspeet o. this
invention is to pcovide an impcoved infusion system foc
providing medieation to a living body of a patient.
, .,..,. ,.,
- -
......
-3a-
1~3~
By a broad aseect of this invention, a programmable
infusion system is provided for providing medication to a
living body including an infusion apparatus having infusion
means for infusing a selected medication stored in a medication
reservoir into a living body, the inusion means having a
commandable infusion rate which is variable upon command, the
infusion apparatus comprising: inhibiting means for inhibiting
the infusion means from infusing the selected medication if a
preselected medication infusion rate is exceeded.
-
The preselected medication infusion rate may be
remotely selectable, or may comprise a remotely selectable rate
and a fixed rate, the remotely selectable rate being limited to
the fixed rate.
The inhibiting means may include at least one means
; for defining a fixed infusion rate limit. Furthermore, the
inhibiting means may comprise at least one programmable rate
--` memory unit, each of the at least one programmable rate memory
units for receiving and storing an infusion rate input command
corresponding to the remotely selectable rate; at least one
limit control unit, each of the at least one limit control
units providing a fixed rate limit; and means for comparing
each of the infusion rate input commands to a corresponding
fixed rate limit, infusion of the medication at a rate
exceeding the fixed rate limit being inhibited.
Alternatively, the inhibiting means may include time dependent
means for precluding infusion of the medication by the infusion
means when the selected commandable infusion rate
~3~
exceeds the preselected medication infusion rate during a
window of time of a predetermined length which shifts
continuously.
The infusion means preferably includes a pump means
which executes in pulses, and the inhibiting means preferably
comprises a programmable memory rate unit for storing initially
a dose limit number corresponding to a first maximum number of
infusion pulses preselected as allowable during a first
shifting time window of a predetermined length, pulse
quantitie6 being subtracted from the number 6tored in the
programmable memory rate unit as infusion pulses are executed
by the infusion means, pulse quantities being added to the
stored number as time elapses such that the number does not
exceed the first maximum number, the subtraction and addition
being accomplished in running integral fashion, and the
inhibitlng means not permitting pulsing of the pump means at a
rate in excess of the rate represented by the dose limit number
stored in the programmable memory rate unit. Preferably, such
memory rate unit also records the number of pulses which have
, 20 been inhibited and causes the pump means of the infusion means
to execute the pulses when the pulses can be subtracted as a
result of the elapse of time from the dose limit number stored
in the programmable memory rate unit. Furthermore, such
programmable memory rate unit may also store initially another
dose limit number corresponding to a second maximum number of
infusion pulses preselected as allowable during a second
shifting time window of a predetermined length,
.,
-4a-
~IZ3~
the second shifting time window being longer in length than the
first shifting time window, pulse quantities being subtracted
from the other dose limit number stored in the programmable
memory rate unit as infusion pulses are executed by the
infusion means, pulse quantities being added to the other dose
limit number as time elapses 6uch that said another dose limit
number does not exceed the first maximum number, the
subtraction and addition being accomplished in running integral
fashion, and the inhibiting means not permitting pulsing of the
eump means at a rate in excess of the rate represented by the
other dose limit number stored in the programmable memory rate
unit. Still further, the programmable memory unit may also
record the number of pulses which have been inhibited and
causes the pump means of the infusion means to execute the
pulses when the pulses can be subtracted from both the dose
limit numbers stored in the programmable memory rate unit.
It is preferred that such inhibiting means further
include at least one fixed infusion rate limit which limits the
total maximum infusion rate of the infusion mean6.
, 20 The programmable infusion system may include means for
recording when the inhibiting means inhibits the infusion means
or may include means for generating an alarm signal when any
commanded infusion rate results in the inhibiting of pulsing of
the pump means by the inhibiting means.
The infusion apparatus is preferably adapted to
implantation into a living body.
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.,
:IZ3~
In the accompanying drawings:
FIG. 1 illustrates a general block diagram of the
entire medication infusion system embracing the present
invention;
FIGS. 2 and 3 show a front cross-sectional and toe
view, respectively, of the implantable portion of a medication
infusion system embcacing the pcesent invention;
FIG 4 shows, in detail the mechanical construction of
:. a pulsatable pup element of a medication infusion system
embracing the present invention;
FIG. 5 is a block diagcam showing the electronics of
a medication infusion system embracing the present invention;
FIG. 6 shows a method of programming the rate of
medication infusion into a patient by the use of the maximum
running integral dosage limiting technique; and
FIGS. 7 and 8 are illustrative of a patient
programming unit in which FIG. 7 shows a front view
illustrating a sample apearatus foc select'ing dosage depending
on meal size and recognized body condition factors, and FIG. 8
shows a rear portion which provides infocmation celative to the
last programming of the patient programming unit.
Generally, the medication infusion system embracing
the present invention pcovides an antechamber which is nocmally
filled with saline solution to act as a buffec between the
medication intake point and the majoc medication ceservoic in
the device. The Leservoir may contain a fatal amount of dcug
lZ31Z~l
or other medication. It is thus isolated from the body by a
filter, one-way inlet valve, the saline-containing antechamber
and a septum providing a self-sealing opening to the
antechambec. Fuether, the reservoir is at a pressure below
the ambient body preS6ure. Thus, even if the inlet valve and
seetum leak, body fluids would enter the antechamber and slowly
ooze into the reservoic through the flow-impeding filter. Any
othec leak of medication from the reservoir or leakage of body
fluid thcough the outer shell of the implanting device would be
sensed by a fluid detector outside the reservoir. Similar
safety back-ups are peovided at the outlet output of the
reservoir which is provided with two one-way valves and a
filter.
The outlet, however, also is provided with a
deformable wall which combines with the outlet filter to yield
an exponentially decaying flow of medication. This smooth
flow over a long, predertermined period provides enhanced
safety and flow control. The deformabie wall serves the
function of an accumulator and the output filter provides the
function of a flow resistor or restrictor; thus the deformable
wall provides the `'C" and the filter "R" of an "RC" time
constant or the decrease of flow after a pulse of medication
has been delivered into an outlet chamber prior to infusion
into the body via the O network. Also at the outlet is an
element foe cocrelating medication requests with medication
dispensing, thus providing an opecational indicator and safety
feature.
,
--6--
~L23~
Also, for safety, a filling proceduee i6 taught which
insures that medication is not injected into the device until
pressure integrity at the input is determined. In the
mechanical pump itself, the amount of medication pulsing it can
provide is restricted in the preferred embodiment by a pressure
limit intrinsic in the pump design.
In programming the system embraced by the present
invention, convenience and safety are again major concerns. A
flexible, maximum running integral program for limiting
medication dosage inputs communicated by a patient satisfies
not only a patient's need for proper amounts of medication but
also satisfies a variable work and eating schedule requirement
of the patient and can provide a safe, peoper medication
schedule even though the patient experiences time zone or work
schedule changes. In addition to a progcammable rate of
medication input, a haedwired limit is also included. If
requests exceed the limits set by the program, the hardwired
limits will inhibit the pulsing of excessive medication into
the patient. Finally, the system provides a history of
medication infusion which a physician can read out theough
telemetry means. This telemetry means is also used to program
and check the system.
Referring to FIG. 1, the varous portions of the
implantable programmable medication infusion system embracing
the present invention are shown. An implantable portion 2 in
a patient's body can be programmed either by the medication
progcamming system 1 or by the patients programming unit
-7-
3~;~83~
400. Commands from the medication prog{amming system
emitted from the communication head 300 are transmitted to
electronics in the implantable portion 2 in order to program
and effectuate the infusion of medication into the body in a
safe, controlled fashion. The medication programming system 1
is also caeable ox reading information out of the implantable
portion 2 concecning the amount of medication dispensed over a
specified time period and furthermore the medication
programming system 1 is capable of calibrating the per pulse of
- 10 medication of the implantable portion 2. medication
injection unit 7 is connected to a double hypodermic syringe 4
which is used to provide medication to an-- implantable
medication reservoir 18 (shown in FIGS. 2 and 3) included
within the implantable portion 2. Fill commands to the
medication injection unit 7 emanate from a medication
programming unit 3. A patient's programming unit 400 is
controlled by the user to request doses of medication. The
... .....
dosage eequests are contcolled by safey units embodied in fixed
hardware elements and programmable elements found in the
implantable portion 2. To recharge a rechargeable cell
contained within the implantable portion 2, and extecnal
charging head 9 connected to a battery charging unit 11 is
included. The need for the charging head 9 and battery
chacging unit 11 can be obviated by the inclusion in the
implantable portion 2 of a power supply (such as a lithium
cell which is of sufficient lifetime to negate the need for
recharging. The medication programming unit 3 outputs to a
paper printer 13 which provides hard, readable output that can
be readily interpreted by a physician.
~L23~Z13~
Referring now to FIGS, 2 and 3, the implantable poction 2 of an
implantable programmable medication infusion system embracing
the present invention is shown. Medication is provided to the
implantable portion 2 by means of a double hypodermic syringe 4
which penetrates the skin 5 and a self-sealing rubber septum 6
which covers an antechamber 8 in leak-proof fashion.
medication is introduced into the antechamber 8 through syringe
4 under pressure the level of which is controllable externally.
A reservoir chambe{ lO, in which the medication is stored under
, .
relatively constant pressure, is fed from the antechamber 8 via
a ceramic filter 12 and an inlet pressure valve 14 which
permits flow only from the antechamber 8 into the reservoir
chamber lO when the pressure differential between them exceeds
a predetermined threshold.
The inlet ceramic filter 12 performs various
functions. Besides filtering contaminants from medication
being fed into the reservoir chamber 10, the ceramic filter 12
serves to limit the rate of medication flow from the
antechambeL 8 into the reservoic chamber 10 or, conversely from
the reservoir chamber 10 into antechamber 8 should the inlet
pressure valve 14 leak or malfunction. Further, should the
self-sealing rubber septum 6 leak, the ceramic filter 12
together with the inlet pressure valve 14 prevents the inflow
of body fluids into the ceservoir chamber 10. Further, should
the inlet pressure valve 14 and the septum 6 both leak or
otherwise malfunction, the inlet ceramic filter 12 would permit
only a slow flow of body fluids to enter the rese{voir chamber
1~;3121~
- 10 -
10, until Cody ambient pressure is a~hievçd, at. which time some
meditation could diffusç through the ceramic filter 12 but at a
rate that would not bQ hazardou,s to a typical pat,ient in which
the system would bç implanted.
The rçservoir chamfer 10 comprises a 'liquid-vapour
portion 16 which rests atop a reservoir of medication 18, the
liquid vapor portion 16 and the reservQir 18 being separated by
a flexible diaphragm 20. The flexible diaphragm 20 could
comprise an elastomer, a Moveable bellows, or othçr
substitutive lexible diaphragm means Nhich wol~ld ,separate the
meditation reservoir 1~3 from the liquid portion 16. The liquid
vapor volume in the vapor portion 16 prefsrably ~ompri~e.s a
saturated vapor in equilibrium with a small amount of FREON 113
(registered trade mark of a fluorocarbon refrigerant) liquid.
Over normal body temperatures, FREON 1 13 has a linear pressure
characteristic ranging from -4 psig Nat 98) to approximately
-2.5 psig at 104F. Using FREON 113, the medication reservoir
18 will be maintained at a pressure below that of the human
body pressure up to altitudes of 8500 feet. For patients who
may live ahove that altitude, ot,her fluorocarbon.s at lower
pressure may ke employed. In this way, should both the septum
6 and the inlet pressure valve 14 leak, the effect would be to
cause body fluids to diffuse slowly, via the inlçt cçramic
filter 12, into the medication reservoir l rathçr than to have
a rapid flow of medication enter the body where it could cause
harm to the patient. Because of the pres,sure differential
~LZ3~Z~l
- 11 -
between the body and the medication re.servoir l medication
will not. flow from the re.servoir l into the body. A.s the
amount of medication in the medicat,ion reservoir l varle.s, t,he
flexible diaphragm 20 move up or down, with the FREON 113
being converted zither from livid to vapor, or from vapor to
liquid to provide an essentially constant pressure which will
always be below one atmosphere and bQIow normal body pressure.
A reservoir chamber having a volume of approximately 10 cc
would ye sufficient for most application.s. This amount of
concçntrated medication, insulin for example, could be fatal if
injected over a short time. The volume of the antechamber is
le,ss than 1Q% the size of the reservoir chamber 10. In the
wor.st ca.se of leakage if medication leaked from the reservoir
chamber 10 into the antechamber and even if the antechamher
leaked as well, only diluted medication would ent,er the body
gradually passing from an area of low pressure to one of higher
pre.ssure. There is thus little likelihood of the dose being
fatal. As readily seen in FIG. 2, decreasing or expanding the
size of the reservoir chamber 10 would be a simple modification
of the arrangement of elements in the system. Included in the
reservoir chamber 10 is a dual pressure .switch which can
comprise a reservoir fill switch 23 for indicating when the
pre.ssure in the reservoir chamber 10 reaches a predetermined
level, e.g. -2 psig, and a second switch 25 for indicating when
the pressure reaches -1 p.sig. Fill switch 2~ is used during
~Z3~
the fllling pr~edure to indicate (hy telemetry system to be
decried later) when the level of medication in the reservoir
chamfer 1 n has reached a
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specific value. Should body fluids leak into the medication
resecvoir 18 for any reason, an increase in pressure would
result that would activate the second pees6ure switch 25. For
examele, when body f luids entering reservoir 18 reach
eressure of -1 psig, this would set off a subcutaneous
electrical stimulation alarm system. By having the fill
switch 23 set at a lower pres6ure than the body fluid leak
detection pres6ure switch 25, the filling of the reservoir 18
can be accomplished without setting off an alarm signal.
10In order to fill the reservoir chamber 10 with
medication, a sequence ox steps is hollowed. The antechamber
8 i5 normally filled with a saline or other innocuous solution
which provides a buffer between the body and the reservoir
; chamber 10 and which if the septum failed would cause no harm
to the patient. At the time of filling, a double hypodermic
syringe is directed into the antechamber 8 and saline is
introduced into the antechamber 8 through one needle and exits
through the other in order to flush the antechamber 8 with more
saline. Once flushed, the antechamber 8 is checked for
pressure integrity with saline introduced under a pressure
which is less than that required to open the inlet pressure
valve 14. When pressure integrity is determined, the
antechamber 8 is flushed with the desired medication (e.g.
insulin). Medication is then forced into the antechamber 8 at
a pressure greater than what required to open inlet pressure
valve l The insulin fills the medication reservoir 18 of
the reservoir chamber 10 until the flexible membrane 20
--12-
~23~'~8~
- 13 -
contacts the dual prey re witch 22, forcing t,he re~ervoi.r
fill witch 23 to generate a signal, (e.g. at -2 prig), which
indicates that the fill.ing has been completed. The amo-lnt of
medication required to fill the medication reservoir l is
noted and then t,he anteGhamber B I 1u~hed once agQin ilk
innocuous saline solution. The entire reservoir chamber 10 is
surrounded my a wall 24 and is isolated Erom the ot,her foment
of the ~y~tem by mean of the inlet pressure valve 14 and an
interface pre~ure valve 2~ which connects the reservoir t,o a
pulsatile pump 2~ which it shown in FIG. 4. The remaining
element of the implant,ed portion 2 are alto shown in FIG. 2:
an electronic section 30 with a battery ~ub~ection 32. As is
already seen in Fig. 2, a hermeti.cally sealed enclosure 34
surrounds the re~erVQir Ghamber 10 a well as the pulsQtile
pump 2~ (see FIG. 4) and the electronic section 30 with the
battery subjection 32. To provide an enhanced safety feature,
a fluid detector 35 it provided between the wall 24 and the
hermetically sealed enclosure 34. Should either the outer
hermetic enclosure 34, or the reservoir chamber 10 leak, the
fluid detector 35 it placed at a 1OcQtion where the leaking
hody fluids or medication would be detected. The fluid
detector 35 cQuld be a very high re~i~tQnce resistor, (e.g. 10
megohms), whose reliance drops significantly in the preæence
of fluid. A malfunction signal to warn the patient if such
leak is detected, it provided. similarly, a medication leakQge
~;233~
- 1~a -
det~tor 37 in the liquid-va~or voll~lm~ 16 wollld indi~atQ ~h~n
m~di~atiQn way leaking into that ~h~m~or
~3~
16. Thi6 detector may also be a ce6istor whose value will be
significantly altered by the presence of the medication. The
medication leakage detectoc 37 when actuated would set off a
distinct subcutaneous electeical stimulation alarm signal that
can be detected hy the patient.
FIG. illustrates the pulsatile pump 28 shown in the
top view of the implanted eoction 2 shown in FIG. 3. The
interface pressure valve 26 shows where medication entecs the
pulsatile pump 28 when the diffecential in peessuee between the
reservoir chamber 10 and a medication storing means 200 (inside
the pulsatile pump 28) reaches a level sufficient to open the
inlet pressuee valve 26. In the preferred embodiment shown in
FIG. 4, this diffeeential in pressure is caused by the
expansion of a spring bellows 202 in response to an electrical
pulse intcoduced to a pulsing coil 204 which surrounds a plate
206 which is attached to the spring bellows ~02. When a pulse
passes through the pulsing coil 204, plate 206 is dciven to a
forward stop 208. This action of expanding the storing means
200 causes the interface pressure valve 26 to open, thereby
allowing medication from the reservoir chamber 10 to fill the
medication stocing means 200. The plate 206 is a permanent
magnet (oe, possibly, a magnetizable material) which moves in
eesponse to a current induced magnetic focce. When current in
the pulsing coil 204 ceases, the spring force of the bellows
202 returns the plate 206 to a position against a backstop
member 210. The amount of travel of plate 206 is thus fixed,
rendering the stroke volume of the pulsatile pump 28 constant
-lq-
:~L;Z3~Z~
and independent of the electrical pulse current or pulse width
into the pulsing coil Z04 as long as certain minimum currents
and pulse width is provided. The maximum pressure that can be
exerted by the pulsatile pump 28 is dependent on the spring
force that can be exerted by the bellows 202 as well as the
cross section area of plate 206 which is in contact with the
medication in the storing means 200. More simply, PmaX=F/A
:: where PmaX is the maximum pre5sure that can be created by the
speing foece of the bellows within the medication storing means
200, F is the spring focce of bellows 202, and A is the portion
o surface of plate 206 which is in contact with the medication
in the medication storing means 200 which extends into the
bellows 202. Should a malfunction occur in the electronics
and a continuous sequence of rapid pulses be introduced to the
pulsing coil 204, causing the plate 206 to reciprocate, the
... return of the plate 206 to its original position against the
backstop member 210 would be inhibited once the pressure in the
storing means 200 exceeded PmaX. The pressure builds up
rapidly because of the output flow resistance caused by the
ceramic filter 218. The possibility of introducing drugs or
other medication at an unsafe high pressure or high rate is
thus essentially eliminated.
An outlet pressure valve 21Z connects the storing
means 200 in the pulsatile pump 208 with an outlet chamber
214. In operation, when the plate 206 returns toward its
- original position against backstop 210 after being reciprocated
by the action of the pulsing coil 204 and the bellows 202, an
;iL23~2~
increasç in pressure in the storing means 200 re~:ults. When
the pressure differential betwçen the pressllre in the storing
means 20~ and thç pressure outlet chamber 214 exceeds that
required to open outlet pres~;ure valve 212, medication flowæ
into outlet chamber 214 from the medication storing means 200.
To prevent large spurt,s or pul~;es of medication from entering
the hody over a short period of time, an ela~:tic wall 216 and
an output ceramic filter 21~ are provided at the entrance to
the outlet 220 of outlet chamber 214. The output ceramic
filter 218 serve.s to resi,st the flow of medication from the
outlet chamber 214 into the living body. The elastic wall 216
acts as a type of capacitance to flow, deforming when a pulse
of medication it; fed into the outlet chamber 214, the elastic
wal] 216 thus serving as a fluid accumulator. The combination
of thQ ela,stic wall 216 and the output ceramic filter 21
comprises; a fluid or mechanical RC network that providers
medication into the body within an initial rise followçd by a
decaying flow. The time constant which i.s fairly long, is
determined hy the elasticity of the elastic wall 216 and the
resirstance of th~3 output ceramic filtçr 218. In addition, thç
output ceramic filter 21~ disallows medication from being
diffu~;ed into the body at a high rate, should both the
interface pressure valve 26 and the outlet pressure valve 212
fail to seal.
lZ3~Z~
- 16 a
hollld valve 212 leak, there would ye a slow diffll,sior
of medicatiQn through the ceramic filter 218 until the pre~sur~
in the stor.ing mean 2 no i.5 essentially equal to
~3~Z~
ambient body pressure. However, since the volume mean 200 i6
very 6mall and since the medication fluid is essentially
incompressible, vec~v little medication can difuse out and that
amount only at a slow rate. Should both valve 26 and 212
leak, body fluids would then diffuse into the eeservoir 18
because it is at a pressure below body ambient pressure. A
rise in pressure in the medication reservoir 18 relative to
that of the ambient body pressure would cause the -1 psig
switch to be activated setting off an alarm. Further, the
medication then could not difuse through the outlet ceramic
filter 218 at an unsafe rate because there is no pressure
differential across the flow resistance of the ceramic filter
218.
Safety of the output is best understood by considering
the various pressure levels in the pulsatile pump 28. With a
bellows speing force which gives a maximum pressure, Pmax, f
--I 15 psig and with an outlet pressure valve drop of 5 psi, it is
possible for the pulsatile pump 28 to provide a pressure as
high as 10 psig in the outlet chamber 214. The pressure in
the outlet chamber 214 is significantly greater than the body
ambient pressure of approximately 0 psig or the diastolic blood
pressure- which is approximately 2 psig. The resistance of the
outeut ceramic filter 21B is selected to limit the drug flow to
a given safe level, for example less than 50% the maximum
pumping flow at which the pulsatile pump 28 is designed to
operate. As with the inlet ceramic filter 12 (of FIG.2) the
outlet ceramic filter 218 also filters out contaminants moving
-17-
~3~;281
in either direction, from thy outlet chamber 214 into the body
or fcom the body into the outlet chamber 214. Also included
in the pulsatile pump 28 i8 a pee6sure transducer 2Z2 which is
shown located in the outlet chamber 214 but could be located
wherever it could detect and respond to a pressure change
corresponding to medication being pumped from the pump 28.
The pres6ure transducer 222 eroduces an electrical output when
a pressure pulse of medication enters the outlet chamber 214.
he peessure transducer 222, in other words, detects the
pressure pulses which are peovided each time the spring bellows
202 returns the plate 206 to its ociginal posi-tion against
backstop 210. By comparing the pulsing from pulsing coil 204
with the pulsing generated by pressure transducer 222, an
indication is given as to whether an absence or insufficient
number of pulses or medication have been provided to the
body. An indication of extra pulses of medication compared to
I: the number of electrical pulses may also be provided.
The pulsing signal to pulsing coil 204 as well as the
eulse output from the pressure transducer 222 are better
understood with reference to FIG. 5 a block diagram of the
electronics section 30 shown in FIGS. 2 and 3. As seen in
FIG. 5, the electronics section 30 communicates with a
communication head 300 which is external to the body,
communicating through skin S by means of radio signals which
includes an alternating magnetic field. The communications
head 300 provides both power inputs and commands, including
programmable inputs, to the electronics section 30. Power is
--18-
23~
provided by means of an alternat,ing field, e.g., a magnetic
Eield, which I comml.lnicated I:o a pickup coil 304 s7hich it;
implant,ed together wit,h the ret of the electronic ection 30
in the body. The pickup coil 304 regive an AC power ~3ignal
from communication; hçad 300 and pees it on to a ull wave
rectifier 306. One rectified output from the full wave
rectifier 306 enter; a batter charge cont,rol ~08 which provides;
a fixed DC charging signal to a power cell 310. The power cell
310 can be a nickel-cadmium cell which is readily rechargeahle
off a rectified ~;ignal at a typiGal frequency of 20 kHz.
Alternat,ively, a lithium-type .~olid state l~attery can be u:~;ed
in~3tead of the nickel-cadmium cell, in which case the charging
circuitry would be eliminated, the lithium-type battery
providing :~ufficient power over a long te3rm, therehy obviating
the need for recharging. The power cell 310 provide.s a bia~;ing
voltage to a tran~ tor switch 312, the output of which enter:
the pulsing coil 204 previously described in the context of the
pul~;atile pump 28. In addition to providing power to the powçr
cell 310, rectified power it al.~o introduced to a DC to AC
converter 314 the purpose of which it; to provide power at the
proper level to the various load in the :~ys~;tem. In addition
to the A. power signal, pickup coil 304 alto receive a train
of ~:erial digital lit from the communication head 3Qn. The
digital bit comprise command for programmak-le input: which
are conveyed, via the pickuE~ coil 304 to a command receiver
316. The ~:ignal~ from the command receiver 316 enter
~L~3~LZ~3~
- 20
a command decoder l whlch dçtçrmines if the digital bit arQ
in a proper sç~uen~e and, if Jo, what action in the systçm thç
command.s dictate. It should bç noted that the full wave
rectifier 30~, the buttery chargç controller 308, the command
receiver 316, and the command decoder 31t3 are powçred only when
an A signal is pickçd up hy the pickup coil 304. This, of
course, prevents the possibility of detecting stray signals a
commands and provides power savings. To be sure, the pnwer
.saving.s achieved could make possible the use of thç
aforementioned lithium cell which would not require recharging.
From the command decoder 31~, programmable inputs and othçr
commands can bç prQvided to a number of elements. A
programmable base rate iæ entçred into a basç rate memory unit
320 which storçs a value indicating thç number of pulses of
medication which are requested to be provided to a patient
during a normal preselectçd pçriod of time. A second
programmable input is provided, namçly a patient-controlled
ratç mçmory unit 322 which stores a value indicating a number
of pulses of medication that are requested to be introduced
into the body over a given period of time during which the
patient çatrs a meal or otherwise alters the chemical balance of
the body (as by e.~ercising). Associated with the base rate
memory unit 320 is a hardwired base ratç limit control 324
which jets a maximum rate that can override requests of the
base rate memory unit 320 which are exce~ive. similarly, a
hardwired patient controlled rate limit control 326 provides a
~L~3~'~8~
- 21 -
fixed maximum number of pul.ses which Jan by provided at, a time
after a meal or at other times and unrler other conditions. As
lQng AS the base rat,e and the patient,-controlled rate values
stored in memory unit 320 and 322 respectively, do not exceed
the hardwirQd values fixQd within limi-t controls 324 and 326,
re~spectivQly, an out,put pulse is provided to the input of
transistor switch 312 to stimulAte Q pulsQ output from pul.sing
coil 204. Should the rate of either memory unit 320 or 322
exceed the hardwired limits in the limit cont,rol elQmQnts 324
or 32~ respectivQly, a "rate request exeeds limit" signal is
fed from the limit, control elemQnt 324 or 32h into a
programmable alarm generator 32~ which providçs an electricil
signal to the stimulation electrode 330 implanted
rsubcutaneQIlsly. my means of the stimulation electrQde 330, the
patiQnt is inormed, by meanrs of subcutaneous .stimulation, that
one of the memory unit-s 32Q or 322 is re~uersting more -than the
maximum all ow able number of pulse.s.
It should be noted that thç signal to the stimulation
electrode 330 can serve the dual function not only of providing
the patient with a subcutaneous eleGtrical rstimulation, but
also may be the .source of a signal detected by the
communication head 300 communicated either to the patient or to
his physician or hoth, that, a failure has occurred. As shown
in FIG. 5, the electrode 330 will ke isolated and should be
insulated from the outside o-E the hermetically-sealQd enclosure
34 of the implanted portion 2.
~23~
- 22 -
A particularly significant featllre of the inl1~ion
system emkracing aspectæ of the present invention re,sides in
the programmabilit.y of t.he alarm generator 32~ based on inpl1t
command from the Gommand decoder 31~. The alarm generator 328
can bQ swit.ched on or off and the voltage produced by thç
generator, and henGe to the elçGtrode 330, can be varied in
response to signal emanating from the communication hçad 300
and channeled through the command reGsiver 31Ç to the Gommand
decoder 31~. In addition, to Gheck the proper operation of the
system, the command decoder 31~ can receive test .signals whish
can simulate actual occurrences to detçrmine whether the
Gir~uitry in the eleGtroniG section 30 is operating properly.
For example, extra pul.~es from the command decoder 31~3 Gan bç
enterçd into the hardwired limit control elements 324 and 32Ç.
These extra pulses can ye added to the pulse pro~idçd by the
bate rate and the patient-controlled rate memory units in order
to ex~eçd the hardwirçd base rate and the hardwired patient-
controlled rate, respectivçly. When the rates are e~ceQded,
the alarm generator 323 will providç a signal. In this way,
the alarm generator 32~3 can be used to check the operation of
thç limit Gontrol elements 324 and 32Ç and also to familiarize
the patient with the corresponding subcutaneolls signals emittçd
by the tickle elect.rode 330. The programmable alarm gçnerator
328 also receiYes inputs from the pressure switch 22 and the
fluid detector 35, both shown in FIX. 2. If body fluids leak
~Z3~
- ~2~ -
into the reservoir l the prQ~sl~re with 2.5 wi]l be
activated, indicating this fault condition to the patient by
means of the activati,on of -the a].arm generator 32~ and t,he
electrode 3~0. If thy patient was llncon~ciol.ls, voltage levels
of the p~tlent'~ skin at the site of the implanted portion 2
1231'~
could be used by the phsyician to indicate if a malfunction has
occurred and which malfunction it was. Further, as previously
described, should fluid leak out of the reservoir chamber 10
and onto the lining of the enclosure 34 or, alternatively, if
body fluid should leak in through the enclosure 34, the fluid
detector 35 would sense such leakage and, as shown in FIG. 5,
would provide input to the alarm generator 328. Still another
input to the alarm genecator 320 comes from the power cell 310
associated with transistor switch 312. The voltage level of
the vower cell 310 is communicated to the alarm generator 328,.
a tickle or subcutaneous stimulation being generated when the
voltage is below a predetermined level. Finally, referring
back to the pulsatile pump 28 of FIG. 4, the electrical
pressure transducer 222 provides a signal which is compared to
a programmed "insufficient rate" value emanating from the
command decode 318. If the number of pulses sensed by the
pressure transducer 222 over a specified period of time are
less than the number of eulses associated with the
"insufficient rate" command input, a pulse rate detector 332
will provide an output indicating that an insufficient amount
of medication is being provided to the patient over the
specified time. The output of pulse rate detector 332 (FIG.
5) also enters the tickle generator 328 to provide a
subcutaneous tickle detectable by the patient. It should be
noted that the various mentioned failures in the system result
in subcutaneous stimulations each of which may be different in
stimulation magnitude, duration, or periodicity. For example,
~23~2~
- 24 -
the stimulation may range between one to four vo]ts and may
very in frequency abovç and below 20 pulses per second and mo.~t
importantly, a. variety oE pulse patterns may be used each
uni.que to a particular malfunct.iQn or warning. Additional
warnings that m.ight be used are: (1) meditation has leaked
into the liquid-vapQr volume; (2) only 1Q% of the medication
remain.c in the reservoir; and (.3) onl.y 5 days medisation
remains.
In addition to pulsing the pump toil 204, the outputs
of the ].imit çontrol elements 324 and 326 al.so provide input to
a pulse recorder 334. Pulse recorder 334 maintains a running
history of how many ele~tri~al pulsss have been prov.ided to the
pulsatile pump 28 singe the last refill of thç reservoir 18 (in
FIX. 1). An "interrogate" signal from the command decoder 318
instructs the pulse reorder 334 to provide the history to a
telemetry transmitter 336 which communicates the pulse history
to a telemçtry coil 33~3. The pulse recorder 334 would record
both t.he number of pulsçs delivered to the pumping coil 204 and
the number of puts detected by the pressure transducer 222
and/or the difference between these two numbers. The telemetry
coil 33~3, in turn, providçs its output thrQugh radio frequency
signals to a telemetry-receiving antenna in the communication
head 300. In addition to the pulse history, the telçmetry
transmitter 336 also rç~eives, during programming, inputs from
the base rate memory unit 320 and patient-~ontrolled rate
memory unit 322 which are transmitted hack to the communication
head 30Q indicating that the desired base rate and patient
contro].led rate, respectively, have been programmed
~L~3~
in the corresponding memory unit 32 or 322. Similarly, other
key parameterc 337 of the system are alGo conveyed by means of
the telemetry tcansmitter 336 back to the communication head
300. For example, the exact pcessure transducer output
wavefoLm would be telemetered. Of course, the pressure
wavefoem signal would be transmitted when the telemetry system
is powered. Similarly, the reservoir fill switch 23 placed in
the reservoir chamber 10 to indicate when it has reached a
predetermined fill level is also connected via the telemetry
transmitter 336 and telemetry coil 338 to the communication
head 300 to indicate when the reservoir 18 has been filled with
medication. Finally, a simulated low battery voltage signal
can be conveyed feom the command decoder 318 to the telemetry
transmitter 336 to check that portion of the status
.....
circuitry. As with the full wave rectifier 306, battery
charge control 308, command receiver 316, and command decoder
- 318, the telemetry transmitter 336 is powered only during
programming, interrogation, testing with simulation signals,
and power cell charging.
Reference is now made to FIG. 6 which shows a method
of programming the patient controlled memory untit 322. The
significance o the method lies in the fact that it provides
two maximum running integral dose limits in response to
requests for medication. Two maximum integral number of pulses
for two different time periods are provided. Both are
independent of the time of day and thecefore would be effective
regardless of the patients eating or working schedule, which
-25-
3L~23~
schedule change might be a cesult of the patient changing time
zones. In the sample gcaph of FIG. 6, a maximum of eight
pulses for a four hour period and twenty-four pulses for any
twenty-four hour period are imposed as maximum running integral
dose limits. These rate settings can, of course, be altered
depending on eatient needs and medication to be administered
and time periods other than four hours or 24 hours could be
used. In FIG. 6, the number of pulses i6 shown as function of
time.
In Fig. 6, at midnight, the number of pulses that are
allowed in the four hour period is eight. Shortly-after 8
A.M. five pulses are requested diminishing the number of
additional pulses allowed to three pulses. Prior to noon,
within the four hour time peeiod, a five pulse request is
entered. In accordance with the maximum running integral four
hour restraint, only three pulses are permitted but the
remaining two pulses in the request are stored in the memory
unit 322 (FIG. S) to be executed at the end of the four hour
period beginning immediately after four hours past the delivery
time for the after breakfast pulsing. Shortly after noon,
when the four hours are over the two pulses are executed. It
should be noted that shortly after noon the three pulses
provided just before noon were subtracted from the eight pulse
allowance. The dispensing of three pulses prior to noon is
not eradicated until four hours thereafter, OL shortly before 4
P.M. Shortly before 4 P.M. the three pulse allowance is
automatically raised to six pulses, accounting for the three
-26-
~3~
pulses executed just befoce noon. Shortly after 4 P.M., thy
allowance automatically rises to eight pulses theceby
accounting for the two pulses executed shortly after noon. At
approximately 6 P.M. the patient has dinner requiring five
pulses and the allowance diminishes to three pulses. Shortly
before 10 P.M. the patient has a snack which requires two
pulses of medication diminishing the allowance to one pulse.
At approximately 10 P.M. the five pulses provided at dinner are
:: .........
- no longer of import and the allowance is raised by those five
pulses to a six pulse level allowance. The importance of FIG.
5 is readily apparent when one considers the various time zones
or York schedules a patient may go theough from time to time in
the course of his life. The program in FIG. 6 provides
., sufficient safety and flexibility for a wide variety of
patients.
Referring now to FIG. 7, the front view of a patient
. .
programming unit 400 is shown. In the center of the unit is a
dial 402 which can be rotated to indicate,the size of a meal
eaten by the patient or the amount of exercise he had
undergone, in order to provide inputs indicating the amount of
medicàtion needed. Output from the patient programming unit
400 is detected by the pickup coil 304 of FIG. 5 as commands.
Whether or not the request is valid is determined in the
electronic section 30 and is conveyed back to the patient
programming unit 400 by telemetry. signal by the patient
programming unit 400 to the patient indicates whether his
request has been satisfied. The patient programming unit 400
~23~
will be provided both with audio and visual outputs rendering
it particularly useful for those patients having either visual
or hearing handicaps.
In FIG. 8 is the rear view of the patient programming
unit 400. The rear side of the patient programming unit 400
will provide inormation indicating the number of pulses sent
at the last request 403; the time of the last request 404: and
possibly (but is not shown) the number of pulses which can be
sent within the program restraints. By pcogramming ROMS (not
shown) in the patient programming unit 400 in accordance with
the running integral programs shown in FIG. 5 an "OK" or "TOO
MUCH REQUESTED" video and/or audible output can be provided.
The audio output would emanate from the loudspeaker 405. When
the request leads to the dispensing of a pulse or pulses of
medication into the outlet chambert, a "MEDICATION SENT" signal
from the implanted portion 2 is relayed to the patient
programming unit 400 to actuate an audio indication by
loudspeaker 405 or by visual means.
It should be understood that alternative embodiments
' 20 are contemplated for the infusion system embcacing the eresent
invention. For example, the antechamber 8 can comprise a
vitreous carbon insert in the skull, or other suitable,
accessible elace on the body, coueled with a tube directed to
the reservoir chamber lO which may be located in the torso.
The filling procedure and elements o antechamber 8 (e.g., the
septum 6) would remain the same with the vitreous carbon
insert. The inlet pressure valve 14 and filter 12 would 6till
-28-
~231~
separate the insert and tube from the reservoir chamber 10.
Similarly, in addition to the patient programming unit 500, a
physician's unit may be provided`~which indicates: when the
medication reservoir lB (of FIG. 1) has been filled, the pulse
history from the pulse recorder 334, and other signals from the
telemetry transmitter 336 of FIG. 4. Such a physician's unit
would be connected to the telemetry portion of the
communication head 300.
-29-
