An apparatus for the patient-controlled delivery of a beneficial agent comprising a dose reservoir for receiving and storing a beneficial agent, inlet means to and outlet means from the dose reservoir and pump means operative in response to an external force supplied to the pump means for drawing beneficial agent into the dose reservoir at a relatively constant rate and for discharging the beneficial agent out of the dose reservoir through the outlet means.

TECHNICAL FIELD OF THE INVENTION 
The present invention is directed to the controlled delivery of a 
pre-selected quantity of beneficial agent to a patient, and is more 
particularly directed to an apparatus and method for such delivery wherein 
the amount of beneficial agent administered can be controlled, up to a 
maximum preselected amount. 
BACKGROUND OF THE INVENTION 
Analgesics are often prescribed to relieve post-operative pain. The great 
difficulty in properly administering analgesics stems from a variety of 
factors. Age, hypatic function, renal function and other medication all 
affect the pharmacokinetics of analgesics and greatly affect the patient's 
need for analgesics. Thus while some patients never request (and thus do 
not need) analgesics for pain relief, some patients continue to suffer 
even after conventional doses of analgesics have been administered. 
Further, doctors tend to underprescribe the use of analgesics and nurses 
tend to underadminister them because of the fear that the patient will 
become addicted to the analgesic. 
In the last several years, there has been considerable activity directed to 
devices and systems which permit the patient to control how much analgesic 
he or she receives up to a maximum predetermined limit. It has been found 
that as a group, patients controlling the quantity of analgesic they 
receive use less analgesic than patients who request the administration of 
an analgesic. Apparently, one factor is the psychological relief present 
when a patient knows he or she is in control of the amount of drug to be 
received, up to a maximum limit. 
Devices that are on the market, or that are in the process of obtaining 
government regulatory approval, that are directed to the 
patient-controlled delivery of analgesics, include the Cardiff Palliator 
by Pye Dynamics Ltd. or Graseby Dynamics of the United Kingdom; the 
On-Demand Analgesic Computer (ODAC) Model JSI 0299 made by Janssen 
Scientific Instruments; a PCA infuser by Abbott Laboratories, Inc.; the 
Harvard PCA Pump by C. R. Bard Inc.; and a pump by Deltec Systems Inc. All 
of these pumps are large and bulky, the smallest pump being the Deltec 
pump, which is approximately as large as a telephone. All of the 
above-mentioned devices are electromechanical in nature, requiring a 
separate power source. Although the Deltec unit may conceivably be worn by 
patients, it is believed that the remainder of the pumps mentioned above 
confine the patient to a bed, or some other fixed location. 
Another problem associated with these devices is that after the drug is 
loaded into the pump, certain control factors must be set by the nurse or 
other person who actually sets up the pump with the patient. Yet another 
problem with existing devices is that they are relatively expensive and 
may include some rather complex electronic components. 
Another apparatus and system for patient-controlled analgesic is described 
in PCT International Publication Number 87/00758. The apparatus includes a 
dose reservoir for receiving and storing a dose of the analgesic, an inlet 
and an outlet to the dose reservoir, and control means operative by the 
patient for selectively expressing beneficial agent out of the dose 
reservoir through the outlet means. The inlet to the dose reservoir 
receives the analgesic under pressure from a pump means separate from the 
patient-controlled analgesic device itself which pumps the analgesic to 
the apparatus from an external supply source. 
Known patient-controlled analgesic systems have several drawbacks. They are 
generally very complex and difficult to use. Often times they must be 
calibrated prior to use and this typically requires the user to be 
extensively trained in the use of the device. Also an auxiliary pumping 
source is typically needed to feed beneficial agent to the 
patient-controlled analgesic apparatus. In addition, such systems are 
comparatively expensive. Further, because of their size, many of the known 
patient-controlled analgesic systems are not suitable for ambulatory use. 
Thus there remains a need for an accurate, self-driven, low cost, 
patient-controlled analgesic apparatus, and in particular, such an 
apparatus that is adaptable for ambulatory use. 
Accordingly it is a principal object of the present invention to provide a 
patient-controlled analgesic device which is self-driven. A related object 
is to provide such a device in which the device itself includes a single 
power source for both filling the device with beneficial agent and for 
discharging up to a maximum predetermined dose of the beneficial agent to 
the patient upon demand of the patient. It is a further related object to 
provide such a device wherein the power source has a linear fill rate over 
its entire fill range in order to prevent overdosing. 
It is yet another object of the present invention to provide a 
patient-controlled analgesic device that can be used with prefilled 
containers of the beneficial agent to be administered to the patient. It 
is also an object of the invention to provide a patient-controlled 
analgesic device that is suitable for ambulatory use. 
These and other objects and advantages of the present invention will become 
apparent from the following detailed description of the invention and from 
the accompanying drawings. 
SUMMARY OF THE INVENTION 
A patient-controlled analgesic device capable of delivering a full dose or 
intermittently a fractional dose of a beneficial agent such as, for 
example, an analgesic, an antibiotic, heparin, insulin, or the like is 
provided. The device includes a single power source comprising pump means 
which draws beneficial agent into the device at a relatively constant rate 
of flow and also serves as the means for delivering beneficial agent to 
the patient. To further control the rate at which beneficial agent is fed 
to the device, a restriction means (administration set) is used in 
combination with the patient-controlled analgesic device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIGS. 1-3 the patient-controlled analgesic device 10 of 
the present invention includes a housing 11. Housing 11 forms mounting 
pins 12, 13 to which wrist band portions 14, 15 may be secured. The wrist 
band portions may be Velcro.RTM. or other bands that are capable of mating 
and securing the device to a wrist. The device 10 may thus be worn in the 
same manner as a watch. 
The housing 11 of the device 10 includes a casing 16 and a back plate 17 
secured to the casing, as for example with a plurality of screws (not 
shown). A portion of the back plate 17 forms a raised plateau 18 that 
forms one wall of a dose reservoir 30. Back plate 17 further includes a 
dose reservoir inlet 19 in communication with the dose reservoir and a 
dose reservoir outlet 20 also in communication with the dose reservoir. 
Referring to FIG. 3, in the illustrated embodiment, the outlet 20 includes 
a disc valve 21, and valve seal 21a to sealingly engage disc valve 21 in 
communication with dose reservoir 30. Disc valve 21 is normally closed so 
that beneficial agent drawn into dose reservoir 30 is retained therein 
until expressed out of the device 10 by the patient, as will be more fully 
described below. It will be appreciated that the dose reservoir inlet 19 
may include a valve means (not shown) or flow restrictive means (not 
shown) to limit backflow of beneficial agent through the inlet during 
operation of the device. 
In the illustrated embodiment, pump means 23 has an annular cross section. 
Pump means 23 comprises a foot portion 24, an arcuate leg portion 25 and a 
head 26. The foot portion 24 of pump means 23 lies adjacent the plateau 
portion 18 of the back plate 17 and is in sealing engagement therewith. 
Arcuate-shaped leg portion 25 curves upwardly from foot portion 24 to head 
26 of pump means 23. Head 26 of pump means 23 extends upwardly through 
annular opening 22 in casing 16 to facilitate access of the pump means to 
an external force, such as, for example, the patient. The interior portion 
25a of arcuate-shaped leg portion 25 and the interior portion 26a of head 
26 of pump means 23 together with the plateau 18 of back plate 17 define 
dose reservoir 30. 
In accordance with one aspect of the present invention pump means 23 is 
designed so that it will draw beneficial liquid from a supply source 35, 
through conduit means 40 into dose reservoir 30 at a constant rate. It has 
been found that to accomplish that end, the arcuate-shaped portion 25 of 
pump means 23 should have a constant curvature over its entire length from 
foot portion 24 to head 26 and head 26 should be sufficiently rigid so 
that when pump means 23 is acted upon by an external force the 
arcuate-shaped leg portion 25 of pump means 23 will collapse under that 
force. The pump means so designed provides a substantially linear recovery 
rate throughout its entire range of motion relative to the dose reservoir. 
Stated another way, the rate at which the collapsed pump means recovers 
from a collapsed condition to its fully uncompressed starting position is 
linear over its entire stroke, from a fully compressed condition, as for 
example when the dose reservoir is completely emptied, to its original 
uncompressed condition, as for example when the dose reservoir is 
completely filled, and at all points between those two conditions. 
The linear recovery rate of the pump means provides a constant suction to 
draw beneficial liquid from external supply source 35 into dose reservoir 
30. Thus, after the pump means is depressed by an external force, such as 
the patient pushing on head 26 to discharge beneficial agent, upon release 
of the external force, head 26 returns to its original position at a 
controlled and linear rate. Accordingly, regardless of the position of the 
head relative to the dose reservoir after expressing beneficial agent from 
the dose reservoir by depressing the head, the incremental amount of 
beneficial agent drawn into the dose reservoir as the head rebounds to its 
original uncompressed position is directly proportional to the time the 
head was depressed by the external force. By way of example, if the 
recovery time to completely refill an emptied dose reservoir is T, then 
the recovery time will be one-half T for a dose reservoir that is only 
one-half emptied and one-fourth T for a dose reservoir that is only 
one-fourth emptied, et cetera. 
The pump means is preferably constructed of a resilient material which is 
biocompatible with the human body and is likewise compatible with the 
beneficial agent to be administered to the patient. For example, silicone 
rubber is an acceptable resilient material. However, other elastomers can 
be used to construct the pump means. 
In the illustrated embodiment of the invention shown in FIGS. 1-3, pump 
means 23 comprises a silicone rubber having a durometer of 30 to 50 (Shore 
A). A 30 to 50 durometer for the silicone elastomer pump means provides 
sufficient elasticity to perform the functions of both drawing beneficial 
agent from a supply source into the dose reservoir and expressing 
beneficial agent from the dose reservoir to the patient. It will be 
appreciated that a change in the durometer of the elastomer used for the 
pump means will affect the drawing power of the pump means and may thus 
affect the rate at which the dose reservoir is filled. For example, the 
greater the elastomer durometer, the greater the drawing power of the pump 
means will be. 
As previously indicated, the head 26 of pump means 23 is more rigid than 
the arcuate-shaped leg portion 25. In the preferred embodiment, the pump 
means is a unitary structure so that head 26 must be thicker than the 
arcuate-shaped leg portion to impart the necessary rigidity to the head. 
Thus, head 26 must be sufficiently thick so that when external pressure is 
applied to it, pump means 23 is compressed by collapse of the 
arcuate-shaped leg portion 25. That is, the head 26 is sufficiently thick 
that it does not compress significantly under the externally-applied 
force. Further, as described, the arcuate-shaped leg portion 25 has a 
constant curvature over its entire length, and will collapse under the 
application of an external force in order to express beneficial agent out 
of the outlet means and to the patient. 
In a preferred embodiment of the present invention, pump means 23 is formed 
from a silicone rubber elastomer with a durometer of 30 to 50 (Shore A), 
and the arcuate-shaped leg portion 25 has a thickness (in cross-section) 
of about two-thirds the thickness of head 26. It is especially preferred 
for such pump means that the head have a thickness of about 0.12 inch and 
the arcuate-shaped leg portion 25 have a width of about 0.08 inch. The 
arcuate-shaped leg portion 25 has a uniform radius of curvature over its 
entire length, and together with head 26 define a pump means 23 having an 
annular area of constant cross-section. 
As depicted in FIGS. 1-3, the resilient compressible pump means 23 assumes 
a first uncompressed condition. In this condition the patient-controlled 
apparatus may be primed for subsequent use by the patient by filling the 
dose reservoir with liquid and removing air from the apparatus. 
As previously indicated, pump means 23 is operable in response to the 
application of an external force applied to head 26 of pump means 23. The 
external force may be, for example, the finger or thumb of the patient 
pushing downwardly on head 26. In response to the external force applied 
to head 26 of pump means 23, the arcuate-shaped leg portion 25 collapses. 
As the arcuate-shaped leg portion 25 of pump means 23 collapses, the 
normally closed valve means 21 in outlet means 20 opens and beneficial 
agent is expressed from the dose reservoir, through the outlet means to 
the patient. The valve means 21 remains open as long as the external force 
is applied to the pump means. However, during that time the maximum amount 
of beneficial agent that will be expressed to the patient is a full dose. 
Upon release of the external force, the resilient pump means tends to 
rebound to its first uncompressed condition, valve means 21 returns to its 
normally closed position and the dose reservoir is sealed. Thus, as pump 
means 23 rebounds to its first uncompressed condition, at least a partial 
vacuum is created in the dose reservoir. The vacuum in the dose reservoir 
is sufficient to draw beneficial liquid from an external supply source 35 
through conduit means 40 and into dose reservoir 30 to replenish 
beneficial agent that was expressed from the device. Because of the design 
of the pump means, it rebounds to its first uncompressed condition at a 
relatively constant rate and, therefore, liquid is likewise drawn from 
external supply source 35 into dose reservoir 30 at a relatively constant 
rate. 
The dose reservoir 30 is filled in a predetermined time period which will 
depend on the volume of dose reservoir, the pump means employed and the 
restriction means, if any, between the beneficial agent supply source 35 
and the device 10. It will be appreciated, however, that a 
patient-controlled analgesic device with a particular pumping rate and 
dose reservoir volume when manufactured may be used for a variety of 
dosage requirements by adjusting the concentration of beneficial agent in 
the supply source to be delivered to the device. 
With the device as described, a patient who has depressed head 26 of pump 
means 23 and has thereby received a dose of beneficial agent may receive 
another full dose of beneficial agent after the expiration of 
predetermined refill time period T. While the patient may wait longer than 
the predetermined time period T if desired, the patient must wait at least 
the predetermined time period T in order to receive a full dose. However, 
if the patient depresses pump means 23 sometime before the predetermined 
time period T required to fill the dose reservoir has expired, the patient 
will receive only a fraction of the full dose. Because the rebound rate of 
the pump means is linear over the entire range of completely empty to 
completely filled, the dose fraction that the patient receives will be 
equal to the fraction of the refill time period T that has elapsed during 
the patient's intermittent demand for beneficial agent. For example, if 
the patient depresses the pump means at a time equal to one-half the 
predetermined fill time T, the patient will receive only one-half of a 
full dose volume. Thus no matter how often the patient depresses the pump 
means, he will never receive more than a single full dose of beneficial 
agent during the predetermined fill period T. 
It will be appreciated that while pump mean 23 of the patient-controlled 
analgesic device 10 of the present invention is capable of drawing 
beneficial liquid into the dose reservoir 30 at a linear rate, the precise 
rate at which liquid is drawn may be controlled by suitably restricting 
the rate at which the beneficial liquid is drawn from the supply source. 
To that end, either the inlet means itself may be designed to limit its 
rate of flow, or some other restrictive means within the supply source or 
between the supply source and the inlet means may be used. In a preferred 
embodiment of the invention, a conventional administration set is used to 
control the rate at which beneficial agent is drawn from the supply 
source. Such administrative sets are available with flow restrictive 
orifices of a fixed or adjustable design and may be used advantageously in 
combination with the patient controlled analgesic device of the present 
invention to control the rate at which beneficial agent is delivered from 
the supply source. 
As depicted in FIG. 4, the device 10 of the present invention may be used 
with automated equipment to deliver a dose of beneficial agent 
continuously or automatically at timed intervals, particularly when the 
patient is asleep. The automated equipment is capable of automatically 
depressing the pump means 23 of the device 10 at preset intervals and may 
be relatively inexpensive compared to a separate automated pump and power 
source. It need not be a sophisticated electronic pump because all 
metering and dosing of beneficial agent will still be done by the device 
10, without an external pump. The automated equipment may carry a patient 
override to permit the patient to override the preset intervals for dose 
administration. Dosing with such an arrangement is still controlled by the 
device 10 itself, as previously described, so that patient overdosing is 
precluded. 
The present invention thus provides an accurate, self-driven, low-cost 
patient controlled analgesic apparatus that is versatile in use. It can be 
used by ambulatory patients during their waking hours and it can be 
readily adapted for use by patients at night with relatively inexpensive 
automated equipment.