Medical infusion device

A medication infusion device comprises a retainer for holding a medication-containing receptacle of the type which is actuatable to expel the contents of medication therefrom. A sensor is included for sensing a characteristic related to the amount of medication within the receptacle. A timing device allows the selection of the period of time over which the contents of the receptacle are to be expelled. A control mechanism, associated with the sensor and the timing device, actuates the receptacle to expel its contents at a controlled rate over the selected period of time.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a medication infusion deice, and more 
particularly, concerns a syringe infusion pump intended for the 
intravenous administration of medications. 
2. Description of the Prior Art 
Hospitals typically use intravenous (IV) administration sets to deliver 
liquids to patients. When the patient needs a drug, such as an antibiotic, 
it has been standard practice, until recently, to deliver such a drug by a 
"piggy-back" drip into the primary infusion line. Within the last several 
years, however, the procedure for delivering many drugs to patients on IV 
therapy has been changing. Mechanically driven syringes, also known as 
syringe infusion pumps, are now being used to handle the administration of 
drugs and similar medications. 
Presently available syringe pumps for IV use are designed to operate at a 
constant speed or at a number of manually set, constant speeds. Once the 
syringe is positioned on the syringe pump, the syringe drive mechanism 
engages the plunger of the syringe and pushes the plunger at a constant 
speed into the syringe barrel so that the liquid contents are delivered to 
the patient over a fixed period of time. The time in which the medication 
is delivered to the patient is a function of the volume of fluid in the 
syringe. In order to meet the wide variation in syringe barrel dimensions 
for the different size syringes used in hospitals, it is presently 
necessary to have several different syringe pumps. Irrespective of the 
different syringe pumps for different size syringes, the syringe pumps 
remain constant speed devices. 
When a drug is to be delivered to a hospital patient, the physician 
typically prescribes that a certain amount of the drug, by weight, be 
delivered to the patient over a period of time, usually in minutes. The 
hospital pharmacist usually must dilute the prescribed drug so that it may 
be delivered by use of a syringe pump. For presently available syringe 
pumps, however, which operate at constant speed, the pharmacist must 
calculate the volume of the diluted drug in order to be able to deliver 
that drug over the prescribed period of time. In many circumstances, the 
drug dilution calculated and prepared by the pharmacist is not the same 
drug dilution recommended by the drug manufacturer. As a result, drug 
dilutions, different from the recommended amount, may cause difficulties 
for fluid restricted patients or added complications occasioned by 
excessive drug concentrations. Accordingly, there is a present need to 
provide a syringe infusion device, for IV purposes, which may accommodate 
different size syringes and operate at different speeds so that drugs and 
medications may be delivered more conveniently and straightforwardly to 
the patient. 
SUMMARY OF THE INVENTION 
The medication infusion device of the present invention comprises means for 
holding a medication-containing receptacle of the type which is actuatable 
to expel the contents of medication therefrom. Means are provided for 
sensing a characteristic representative of the contents of medication 
within the receptacle. Means allow the establishment of the period of time 
over which the contents of the receptacle are to be expelled. Control 
means, associated with the sensing means and the time establishing means, 
allows the actuation of the receptacle to expel its contents at a 
controlled rate governed by the established period of time. 
In a preferred embodiment of the present invention, a syringe infusion 
device is provided for the administration of liquid medication from a 
syringe having a barrel for holding medication and a plunger for expelling 
medication. The syringe infusion device of the present invention comprises 
a housing and a syringe retainer mounted on the housing. The retainer is 
adapted to hold the syringe and to receive different size syringe barrels 
therein. A movable syringe driver is mounted on the housing and is adapted 
to engage the syringe plunger and push the plunger into the syringe barrel 
to thereby force the liquid contents out of the syringe barrel. Sensor 
means are included for determining the distance the syringe plunger must 
travel to expel the contents of the barrel. The sensor means also provide 
information related to the determined distance. Control means move the 
syringe driver against the plunger to expel the contents of the syringe 
barrel over a pre-selectable period of time at a rate of speed governed by 
information received from the sensor means relating to the distance 
determination. A visual display monitors the period of time over which the 
contents of the syringe barrel are expelled. 
In accordance with the principles of the present invention, many of the 
aforementioned problems and deficiencies associated with presently 
available syringe pumps are overcome. Most notably, the present invention 
permits the administration of a drug or the like as a direct 
implementation of the physician's prescription. Further, the present 
invention permits the utilization of any size syringe, but preferably 
those syringes ranging from 3 cc to 60 cc. Furthermore, the medication 
infusion device of the present invention may be set, by the user, to 
deliver the medication over a variable period of time, which is preferably 
from 10 to 60 minutes. As a result of the features of the present 
invention, the hospital pharmacist may mix the prescribed drug directly to 
the manufacturer's recommended dilution, and may use any appropriate size 
syringe to hold the resulting liquid volume. To complete the 
administration of the prescription drug to the patient, the hospital 
attendant merely selects the prescribed time for the drug delivery, or 
relies on the time automatically set by the device, when the infusion 
procedure is ready to begin. 
There are a number of features of the present invention which facilitate 
the advantages as noted above. Because there are large variations in the 
height of the plunger of an empty syringe, there is a sensor incorporated 
into the syringe retainer of the present invention. This sensor makes a 
determination which specific size syringe is mounted in the syringe 
infusion device. Preferably, this sensor makes a determination which one 
of 3,5,10,20,30 or 60 cc syringes is in the syringe pump. Also, since 
there are variations in the height of the plunger in the filled syringe, 
there is another sensor which determines this height with reference to the 
finger flanges at the proximal end of the syringe. In addition, and in 
order to provide better prescription control, the present medication 
infusion device is equipped with a special display. This display allows 
the attending medical team to monitor not only the time remaining for 
infusion, but also the original infusion time setting. Other advantages 
and features of the present invention will be perceived upon a reading of 
the detailed description which follows.

DETAILED DESCRIPTION 
While this invention is satisfied by embodiments in many different forms, 
there is shown in the drawings and will herein be described in detail a 
preferred embodiment of the invention, with the understanding that the 
present disclosure is to be considered as exemplary of the principles of 
the invention and is not intended to limit the invention to the embodiment 
illustrated. The scope of the invention will be measured by the appended 
claims and their equivalents. 
Adverting now to the drawings, and FIG. 1 in particular, there is 
illustrated the preferred medication infusion device of the present 
invention in the form of a syringe infusion pump 10. The primary, 
externally visible components of infusion pump 10 include a top or cover 
section 12, a bottom or back section 14, a driver mechanism 15 and a 
syringe retainer device 16. As seen in FIG. 1, a medication-containing 
receptacle, preferably in the form of a syringe 18, is mounted in the 
infusion pump as it would appear prior to its use for delivering drugs or 
medications, particularly during IV therapy. It can be seen that syringe 
18 includes two main components, a syringe barrel 19 and a plunger 20. A 
finger flange 21 facilitates the mounting of the syringe into retainer 16 
of the infusion pump. At the distal end of the syringe barrel is an 
opening 22 through which liquid contents of the syringe barrel are 
expelled when plunger 20 moves inwardly into syringe barrel 19. 
Top section 12 and bottom section 14 of the present infusion device form a 
housing into which the control mechanisms for operation of the device are 
incorporated. A number of user controls, indicators and displays 
associated with such control mechanisms, are included on the outside panel 
of top section 12. The user controls include a POWER ON button 25 and a 
POWER OFF button 26. An INFUSE button 28 is provided to start the 
operation of syringe driver 15, whereas the STOP INFUSION button 29 is 
included for terminating the operation of the infusion device. An ALARM 
TONE OFF button 30 permits the user to stop an audible alarm which 
activates in the event of a malfunction or other problem related to 
delivering the contents of the syringe. Two TIME SET buttons 32 and 34 are 
associated with a visual timing mechanism 35 displayed on the front panel 
of cover section 12. As will be described more fully hereinafter, TIME SET 
button 32 permits the user to incrementally increase the time of operation 
from the automatically pre-set time, whereas TIME SET button 34 allows the 
user to incrementally decrease the time of operation. An ATTENTION 
indicator light 40 is provided to visually inform the user that a 
malfunction or problem is occurring. A LOW BATTERY indicator light 41 
indicates that the batteries are low on energy and should be changed. The 
final indicator light 42 is an INFUSION COMPLETE indicator to visually 
indicate when the movement of syringe plunger 20 by driver 15 has been 
completed. 
Referring now to FIGS. 2 and 3 which illustrate the interior components of 
the present infusion device in more detail, driver assembly 45 is shown 
mounted in bottom section 14 of the infusion device. Syringe driver 15 and 
clamp 16 are oriented so that they protrude outwardly from the side of 
bottom section 14. Driver assembly 45 is mounted within bottom section 14 
by virtue of a pair of mounting plates 46 and 48 on opposite sides of the 
driver assembly. Syringe retainer 16, preferably in the form of a clamp, 
is hingedly connected to a mounting block 49. Both clamp 16 and block 49 
are retained within guide rails 52 and are free to move against spring 50. 
Attached to block 49 and contacting potentiometer strip 66 is electrical 
contactor 53. Components 16,49,66, and 53 form the mechanical elements of 
the occlusion detector, as will be described in more detail hereinafter. 
On the other hand, driver 15 is intended to impart linear motion to syringe 
plunger 20. To that end, driver 15 is connected to a mounting block 51 
which slides on one or more guide rails 52 extending between mounting 
plates 46 and 48. Mounting block 51 is also provided with a mechanism for 
mating with the threads of a jack screw 54, also extending between 
mounting plates 46 and 48. A variable speed motor 55 is mounted on plate 
46, and has a drive shaft (not shown) extending through the mounting plate 
and connected to a rotatable gear 56. This gear meshes with another gear 
58 connected to jack screw 54 so that the motor can turn the jack screw 
and therefore move driver 15 in a rectilinear direction substantially 
along the length of the jack screw. 
Driver 15 is further equipped with a release button mechanism 60 which 
permits driver 15 to become temporarily disconnected from jack screw 54. 
In this regard, activation of release button 60 serves as a mechanism 
which normally maintains the driver in actuating engagement with jack 
screw 54. Mechanism 60 is manually releasable to disengage the driver from 
jack screw 54 so that driver 15 is freely movable on guide rail 52. This 
free movement permits the user to position the syringe in place and to 
accommodate the height of syringe plunger 20 against which driver 15 is 
intended to make engagement. 
FIGS. 2 and 3 further illustrate the inclusion of the electrical components 
61 which cooperate with driver assembly 45, as well as the panel-mounted 
controls, indicators and display, to render the present infusion device 
operable. It is expected that state of the art electrical components may 
be selected and utilized to achieve the features consistent with the 
description of the present invention. Operation of the present infusion 
device, however, is preferably regulated by a microprocessor included 
within the electrical components, in conjunction with a closed loop 
servomechanism for controlling the speed of motor 55 and thereby the 
linear speed that syringe driver 15 moves along jack screw 54. This 
microprocessor-based control mechanism for the present device is capable 
of being programmed to accept information with respect to size of the 
syringe barrel and height of the syringe plunger, as will be pointed out 
hereinafter. To render the present infusion device portable, electrical 
energy is preferably provided by one or more batteries 62, shown 
schematically in FIG. 2. 
Turning more particularly to FIG. 3, it can be seen that driver assembly 45 
includes a linear potentiometer 65 extending substantially parallel to 
jack screw 54 and extending substantially between mounting plates 46 and 
48. This linear potentiometer includes an electrically conductive strip 
66. Mounting block 51, associated with syringe driver 15, includes a pair 
of electrical contacts 68 which contact linear potentiometer 65 and 
cooperate with conductive strip 66 to develop a position-sensitive 
electrical resistance. Thus, an analog voltage may be developed which 
changes according to the position of syringe driver 15 with respect to 
syringe retainer clamp 16. The position-sensitive analog voltage is thus 
representative of the height that the plunger extends out of the syringe 
barrel when mounted on the infusion device. By sensing this analog 
voltage, the microprocessor knows the distance that syringe driver 15 must 
travel in order to bottom-out against syringe clamp 16. With syringe 18 
properly mounted on the infusion device, the aforementioned distance of 
travel of driver 15 is analogous to the distance plunger 20 must travel 
within syringe barrel 19 to expel the liquid contents therefrom. 
FIG. 4 illustrates in greater detail the function of syringe clamp 16 so as 
to be able to receive and hold different size syringe barrels. Clamp 16 is 
pivotally mounted, by means of pivot pin 70, to mounting block 49. Clamp 
16 is provided with an arcuate cut-out portion 71 and block 49 has a 
similar arcuate portion 72. These arcuate portions facilitate the receipt 
of the round diameter of syringe barrel 19 therebetween. Clamp 16 further 
includes a thumb lever 74 so that the user may push against this lever to 
manually move clamp 16 to an open position to insert the syringe barrel 
between the arcuate surfaces. A spring 75 is associated with pivot pin 70 
so that arcuate surface 71 of the clamp is normally biased toward arcuate 
surface 72 of the mounting block. In this regard, different size syringe 
barrels may be positioned between the two arcuate surfaces of this 
grasping arrangement to thereby hold the syringe barrel in fixed position 
during the infusion procedure. 
Affixed to mounting block 49 is an insulator board 80 with a plurality of 
electrically-conductive pads 82,84,85 and 86. The number of 
electrically-conductive pads as herein described is merely for exemplary 
purposes, and is not intended to limit the invention to any fixed number. 
Although not shown in FIG. 4, wires are connected to the respective 
electrical pads for connection to the electrical control means as 
hereinbefore described. Protruding from clamp 16 is an electrical 
insulator 90 from which extends a plurality of electrically conductive 
tabs 91,92 and 94. These tabs are also preferably wire-connected (not 
shown) to the electrical controls of the present invention. It can be seen 
that the electrical tabs associated with the clamp are positioned to 
contact the electrical pads associated with the mounting block. The 
electrical tabs contact different pads depending upon the position of 
arcuate surface 71 with respect to arcuate surface 72. Thus, syringe 
barrel 19 (illustrated in phantom in FIG. 4) of one size causes certain 
pads to be contacted by the tabs, whereas a different size syringe barrel 
causes other pads to be contacted by the tabs. This syringe barrel 
diameter sensing arrangement is intended to make a gross diameter scan of 
the syringe barrel and categorize the barrel as belonging to a syringe of 
a certain size. 
Most commonly used syringes for hospital purposes have designations based 
on total volume and have an outside diameter which is a function of the 
volume. In the present sensing arrangement described herein and 
illustrated in FIG. 4, and merely for exemplary purposes, six different 
size syringes may be sensed depending upon which electrical pads are 
contacted by the tabs. For instance, if a 10 cc syringe is positioned 
between arcuate surfaces 71 and 72, pads 82 and 85 may be contacted by the 
electrical tabs associated with the clamp. The microprocessor control 
elements may be programmed to acknowledge that, when pads 82 and 85 are in 
electrical contact, a 10 cc syringe is in place in the infusion device. In 
similar fashion, different standard size syringes may be sensed by the 
mechanism herein described. It is preferred that the present invention 
permit the sensing of at least 3,5,10,20,30 and 60 cc syringes. Once the 
microprocessor acknowledges the size of the syringe positioned in the 
infusion device, the sensed size information is used to govern the rate of 
movement of the syringe driver which actuates the syringe plunger. 
Operation of the infusion device, and features of the device associated 
with its operation, will now be described. Syringe 18, preferably being 
one of the six sizes mentioned above, is typically prefilled by the 
pharmacist and contains a diluted quantity of a drug to be administered to 
the patient. Plunger 20 typically extends outwardly from syringe barrel 19 
when the syringe barrel has liquid contents therein, as represented by the 
appearance of the syringe in FIG. 1. The syringe is positioned in the 
infusion device by a few simple manipulative steps. The user depresses 
release button 60 and lifts syringe driver 15 upwardly; thumb lever 74 of 
clamp 16 is then depressed so that syringe barrel 19 is positioned between 
arcuate surfaces 71 and 72. In positioning the syringe, it is preferred 
that flange 21 at the proximal end of the syringe barrel rest against the 
top of mounting block 49, as seen in FIG. 1. Then, the user once again 
depresses release button 60 of driver 15, and lowers the driver until it 
engages the upper end of plunger 20. No matter what the size of the 
syringe, its volumetric contents or the height that the plunger extends 
from the syringe barrel, the procedure for loading the syringe onto the 
infusion device is the same as described above. Prior to operation, an 
appropriate tubing connection is made between opening 22, at the distal 
end of the syringe barrel, and the patient. 
To commence operation, POWER ON button 25 is depressed. With the 
microprocessor and electrical components turned on, the device is 
programmed to run through diagnostic procedures in which all of the alarm 
indicators are energized and time display 35 set for the operating mode. 
As seen in FIG. 1, time display 35 includes a series of lights, LED's or 
LCD segments 36 each representative of 2.5 minute increments. Thus, in the 
embodiment being described, the operating time range for a single 
procedure extends from 10 to 60 minutes. When the infusion device is 
turned on, the time setting of the timing mechanism of display 35 is 
automatically set at 30 minutes, which corresponds to the most common 
delivery time for administering medications to patients. This 
automatically set time is merely for convenience purposes, and may be 
pre-set to a different time, if desired. In the event that the delivery 
time is prescribed for a time other than 30 minutes, the user may make an 
alteration by depressing TIME SET button 32 to increase the delivery time 
or by depressing TIME SET button 34 or to decrease the delivery time. Such 
alteration is accomplished in 2.5 minute segments, and the LCD 36 
corresponding to the selected time to complete the infusion remains 
lighted. 
To initiate the infusion procedure, INFUSE button 28 is manually depressed. 
This activates the microprocessor and servo system, as described above, so 
that movement of syringe driver can be started. However, before syringe 
driver 15 is put into motion, the depression of the INFUSE button causes 
the microprocessor to scan syringe barrel 19 by virtue of the sensor 
mechanism incorporated within clamp 16, and as described in detail in 
conjunction with FIG. 4. The size of syringe barrel 19 is determined by 
the clamp sensor so that the microprocessor can relate that size with one 
of the pre-determined syringe sizes. Information about syringe size is 
used by the microprocessor to call up information with respect to the 
height of the plunger in an empty syringe of the same size. Plunger 
heights of empty syringes, i.e., the plunger all the way into the syringe 
barrel, of the six pre-selected sizes may be pre-fed into the memory of 
the microprocessor. 
In conjunction with the sensing mechanism associated with linear 
potentiometer 65, the microprocessor receives position-sensitive 
information related to the height of the plunger rod of the filled 
syringe. The microprocessor is pre-programmed to subtract the pre-known 
height of the plunger of the empty syringe from the height of the plunger 
of the filled syringe. As a result, a determination is made for the 
distance that plunger 20 must travel in order to expel the contents of the 
syringe barrel. With the time of delivery previously entered and displayed 
on time display 35, the microprocessor calculates the appropriate motor 
speed of motor 55 (shown in FIG. 2) which controls the rate of speed of 
syringe driver 15. Linear motion of syringe driver 15 is imparted to 
plunger 20 to thereby push the plunger into the syringe barrel for 
expelling the liquid contents at a controlled rate. For purposes of the 
present invention, but without limiting the invention thereto, syringe 
driver 15 may travel within a speed range of 1 inch per hour (2.5 cm per 
hour) to 25 inches per hour (62.5 cm per hour). During the delivery of 
liquid medication, the microprocessor continually scans for the plunger 
position, in conjunction with the linear potentiometer, to determine its 
position and to alter the motor speed if necessary. 
Should the plunger position relative to clamp block 49 not change, as might 
result in the case of a clogged infusion, the microprocessor is programmed 
to stop power to the motor and to energize the alarms, including the 
ATTENTION indicator 40. In addition, an audible alarm is sounded when 
ATTENTION indicator 40 is activated. In the alarm condition, movement of 
syringe driver 15 is stopped. The alarm condition of the present invention 
is preferably related to a maximum force which syringe driver 15 may 
deliver to plunger 20. This force is developed by the movement of clamp 
block 49 against spring 50. The movement of clamp block 49 is sensed by 
measuring the voltage change of wiper 53 as it moves down potentiometer 
strip 66. When that force reaches a threshold, the microprocessor 
considers such force level as an occlusion or clogged infusion, so that 
movement of the syringe clamp is terminated and the alarm is activated. 
For each of the different size syringes, a maximum force to be delivered 
by the driver is pre-programmed into the microprocessor thereby 
establishing thresholds for initiating the alarm condition. Thus, if a 
clogged infusion occurs while there is time remaining for delivery of the 
medication, movement of the syringe driver will be automatically stopped. 
The alarm condition is permitted to continue until the user depresses STOP 
INFUSION button 29. Once the impediment causing the alarm condition has 
been removed, infusion may continue by once again depressing INFUSE button 
28. 
When syringe driver 15 is operating to push plunger into syringe barrel 19 
to expel the liquid contents, INFUSE button 28 is designed so that it 
blinks to indicate correct operation; at the same time, the LCD indicative 
of time remaining on time display 35 also flashes. The flashing time 
segment continues to move down display 35 to indicate the time to complete 
the infusion. Driver 15 continues to expel fluid until the plunger bottoms 
in the syringe. At this point, the unit would appear to have an occlusion 
as all further movement of the plunger moves the syringe clamp block 49. 
In order to allow for all tolerances present in syringe components, an 
occlusion sensed in the last 2.5 minutes of delivery is considered as a 
completed infusion. When the infusion has been completed, the blinking of 
the INFUSE button ceases, and the INFUSION COMPLETE indicator light 42 is 
energized. The LED of time display 35 corresponding to 0 time is lighted 
when the infusion has been completed. Furthermore, when infusion has been 
completed, movement of syringe driver 15 is automatically terminated since 
the contents of the syringe barrel have been expelled. Another feature of 
the present invention relates to the display of the original time which 
had been selected for the complete infusion procedure. Thus, when the 
flashing LED's move downwardly along display 35 to indicate the time 
remaining to complete the infusion, the LED corresponding to the 
originally pre-selected time continues to remain lighted throughout the 
complete infusion period. 
It should also be pointed out that STOP INFUSION button 29 may be activated 
by the user at any time during the infusion procedure to terminate 
movement of syringe driver 15 against plunger 20, irrespective of whether 
an alarm condition exists. In the STOP INFUSION mode, the LED 
corresponding to the original pre-set time and the LED corresponding to 
time remaining for infusion continue to be displayed. 
Thus, it can be seen that the medication infusion device of the present 
invention is not only portable but may be used with syringes or like 
receptacles of many different sizes. Syringe size is automatically 
assessed by the present device, as is the distance that the plunger must 
travel to expel the contents from the syringe. This syringe size and 
plunger distance information is utilized by the microprocessor-regulated 
servomechanism to control the speed of the motor, drive mechanism and 
syringe driver. Most advantageously, the medication infusion device of the 
present invention permits the hospital attendant to directly implement the 
physician's prescription. The pharmacist may mix the prescribed drug or 
medication directly in accordance with the manufacturer's recommended 
dilution, and use any appropriate size syringe to hold the resulting 
liquid volume. To deliver the prescription, the attendant simply loads the 
filled syringe into the infusion device, selects the prescribed time for 
delivery, and pushes a button whereupon infusion automatically occurs at 
the prescribed rate.