Abstract:
An infusion assembly for delivering therapeutic fluid to plural body sites is provided. The assembly includes a positive displacement pump that discharges the therapeutic fluid. The assembly also includes a flow regulator valve including a valve housing that defines a pressure chamber, an inlet bore that opens into the pressure chamber, and first and second outlet passageways. The first and second outlet passageways extend, respectively, from separate first and second outlet openings to a first catheter and a second catheter through which the therapeutic fluid is directed to the body sites. A controller cyclically regulates the operation of the pump so that, in a first phase of each cycle, the pump is actuated so as to cause a fluid pulse to be presented through the inlet bore of the valve housing to the diaphragm and in a second phase of each cycle, the pump is not actuated.

Description:
RELATED APPLICATIONS  
       [0001]     This application is a continuation of application Ser. No. 10/461,939, filed Jun. 13, 2003, hereby incorporated by reference, which claims priority to U.S. Provisional Patent Application Ser. No. 60/451,161, filed Feb. 28, 2003, and is a continuation-in-part application of U.S. patent application Ser. No. 10/083,266, filed Feb. 23, 2002, now U.S. Pat. No. 6,679,862, which claims priority to and all advantages of U.S. Provisional Patent Application No. 60/271,187, filed Feb. 23, 2001. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to an infusion assembly for delivering therapeutic fluid. More particularly, the present invention relates to the infusion assembly being configured for delivering the therapeutic fluid to plural body sites.  
       BACKGROUND OF THE INVENTION  
       [0003]     Medication delivery systems are known in the art. Medication delivery systems are used to deliver pain control medication and other medications intra-operatively, subcutaneously, and percutaneously to a patient after a surgical, or some other medical, procedure.  
         [0004]     It is sometimes desirable to deliver a fluid using a pulsatile fluid flow or series of pulses. For example, some medication delivery systems which utilize a series of pulsatile fluid pulses to deliver medication, are known in the art. Medication delivery systems may be used to deliver pain control medication and other medications intra-operatively or post-operatively, subcutaneously, and percutaneously to a patient after a surgical, or some other medical, procedure.  
         [0005]     For example, U.S. Pat. No. 5,807,075 to Jacobsen et al. discloses a conventional medication delivery system that includes a base housing and a cassette. The base housing of the &#39;075 patent houses electronic components, such as an electric motor, a power source, and an electronic controller, and the cassette of the &#39;075 patent interacts with a supply of the medication to deliver the medication to the patient.  
         [0006]     A further example of a conventional medication delivery system is disclosed in U.S. Pat. No. 4,650,469 to Berg et al. This patent discloses a medication delivery system that includes a control module and a reservoir module removably connected to the control module. The control module includes a pump mechanism, valves, a power source, electronic controls, and the like, and the reservoir module includes a container that supplies the medication to be delivered to the patient.  
         [0007]     It is known to use an electric motor in such medication delivery systems, where a predetermined number at revolutions or cycles of the motor delivers a preset amount of medication. Such systems are known as positive displacement systems. In such systems, pressurization of the medication is a function of the restrictions in the flow path and the time dependent flow of medication through the system.  
         [0008]     Generally, conventional medication delivery systems provide a flow of medication through an output tube which then is delivered to the patient, as required. However in some procedures, medication is required at two locations with respect to the patient, for example, breast augmentation or reconstruction. Another such procedure where medication delivery is desirable at two sites is an autologous graft procedure where it is desirable to deliver medication at both the graft and the donor sites. If the medication provided by the delivery system is pumped through a “Y” connection, then there are several reasons that the medication may not be delivered to each site or location in the desired proportion. First, unequal pressure at the two infusion sites due to elevation or intracompartmental pressure sets up a siphon where flow occurs from one side to the other side in the period between pulses. Furthermore, natural or unintended variations in flow restriction between the two sides of the “Y” and/or the previously mentioned unequal infusion site pressures may shift the proportion of the flow split, as more flow will follow the path of decreased resistance. This is undesirable.  
         [0009]     In a mechanical system experiencing laminar flow of a non-compressible fluid, a similar phenomenon occurs whereby the pressure between two points is directly proportional to the mass flow rate through the system and the flow restriction between the two points.  
         [0010]     This can be expressed as ΔP={dot over (M)}R, where  
         [0011]     ΔP=Pressure Differential (psi)  
         [0012]     {dot over (M)}=Mass Flow Rate (cc/sec)  
         [0013]     R=Flow Restriction (psi/[cc/sec])  
         [0014]     Similarly,  
         M   .     =       Δ   ⁢           ⁢   P     R         
 
         [0015]     In other words, the instantaneous flow rate in a single-lumen system is directly related to the instantaneous pressure between two points separated by a known flow restriction, and it is inversely proportional to the value of the restriction between those two points.  
         [0016]     In a scenario where more than one distal site is linked to the fluid path, the overall flow rate to both sites as well as the percent flow reaching each site is also related to pressure and restriction. Though capacitance in the system may cause a phase shift in the instantaneous flow rate from location to location, the overall flow from the lumen upstream of the branching node will equal the sum of the overall flow coming through each outlet lumen (leg). z  
         [0017]     In this scenario, the instantaneous flow rate along each leg will be directly related to the difference in pressure between the branching node and the distal outlet of the leg, and it will be inversely proportional to the flow restriction along that leg. The mass flow rate through any given outlet lumen may be calculated as follows:  
           M   .     i     =         Δ   ⁢           ⁢     P   i         R   i       =         P   0     -     P   i         R   i             
 
 where 
 
ΔPi=P 0 −Pi 
 
         [0018]     P 0 =Pressure at branching node (psi gage)  
         [0019]     Pi=Pressure at outlet of lumen i (psi gage)  
         [0020]     Ri=Flow Restriction of outlet lumen i (psi/[cc/sec])  
         [0021]     The total flow through all legs is then  
             M   .     total     =         ∑     i   =   1     n     ⁢       M   .     i       =       ∑     i   =   1     n     ⁢         P   0     -     P   i         R   i             ,       
 
 and the percent flow to any given outlet lumen is  
         %   ⁢           ⁢   F     =       (   100   )     ⁢           M   .     i         M   .     total       .           
 
         [0022]     If a pump with a pulsatile flow delivery system is connected to a fluid delivery path, and it is desired to controllably divide the flow between the multiple outlet sites, the flow restrictions in each outlet lumen may be designed so as to facilitate the desired flow distribution. With each pulse of fluid flow from the pump, the pressure in the inlet lumen and the branching node will rise—with a lower system capacitance before the node leading to a more steep pressure rise. After the pump finishes introducing fluid to the path, a pressure drop will be observed as fluid drains through the outlet lumens, emptying the fluid stored by the capacitance of the system. As stated before, the instantaneous flow rate during this process is related to the pressure differential and the flow restriction; as the pressure drops asymptotically to an equilibrium level, so will the flow decrease proportionally.  
         [0023]     If the pressure at all outlet sites is the same, then ΔP will be the same for each outlet lumen and the flow distribution may be directly controlled by the flow restrictors alone.  
         [0024]     However, if the pressures of the outlets are not equal and not constant, then additional measures are required to equally or accurately distribute the flow as desired to all sites. This can be accomplished by making the pressure at the node high enough that the variation in pressures at each site do not contribute greatly to percent variation in pressure differential. In other words, if P 1 ≠P 2  but P o &gt;&gt;P 1  and P o &gt;&gt;P 2 , then ΔP 1 ≈ΔP 2 . If ΔP 1  and ΔP 2  are then similar, the restriction level of each lumen may once again be relied upon to provide the control necessary to balance the flow percentage to each lumen outlet.  
         [0025]     However, in the case of a pulsatile pump, the time-dependent pressure profile may not provide the necessary conditions to keep P o &gt;&gt;P 1  and P o &gt;&gt;P 2 . A substantial portion of fluid flow occurs as the pressure profile drops during the drain cycle mentioned above, and as the pressure drops, the ΔPi of the various paths will deviate farther and farther from each other, in relation to the difference in Pi at each outlet location.  
         [0026]     One solution would be to provide a check valve in each leg after the “Y” connection. This solution presents several problems, namely, there is a time delay added by the opening and closing of the check valve and differences in manufacturing tolerances contributing to the delay may also lead to uneven delivery of the medication. Furthermore, most check valves restrict flow when open, and unequal or uncontrollable variations in this restriction would lead to unequal flow.  
         [0027]     Another solution would be to provide a large fluid resistor (small orifice) in each leg. Correctly sizing this orifice would cause the pressure to rise substantially higher than the downstream pressure differences. This pressure could be driven up over several pulses. If the pressure remained higher than the highest downstream pressure, no backflow due to siphoning could occur. Furthermore, the difference in the pressure drop in the two downstream legs could be controlled to remain relatively equal. This solution presents several problems. First, if the pump has a user selectable flow rate, the size of the glass orifice must be fixed to work with the lowest possible flow rate. If a higher flow rate were then selected, the level of restriction would cause an increase in pressure beyond acceptable limits for safety or function the system or its components, including features such as an occlusion sensor.  
         [0028]     The present invention is aimed at one or more of the problems set forth above.  
       SUMMARY OF THE INVENTION  
       [0029]     In one aspect of the present invention, an infusion assembly for delivering therapeutic fluid to plural body sites is provided. The assembly includes a positive displacement pump that discharges the therapeutic fluid. The assembly also includes a flow regulator valve. The valve has a valve housing that defines a pressure chamber, an inlet bore that opens into the pressure chamber, and first and second outlet passageways that extend respectively from separate first and second outlet openings. The outlet passageways extend from the pressure chamber to a first catheter and a second catheter through which the therapeutic fluid is directed to the body sites. The valve also includes a flexible diaphragm disposed in the pressure chamber over the inlet opening and the outlet openings that moves between a closed position and an open position. The diaphragm is positioned to, when in the closed position, simultaneously seat over so as to seal both the first outlet opening and the second outlet opening. Finally, the valve includes a biasing member disposed against the diaphragm so as to normally hold the diaphragm in the closed position absent a fluid pulse from the inlet bore. A conduit supplies discharged fluid from the pump through the inlet bore into the pressure chamber.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]     Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
         [0031]      FIG. 1A  is a perspective view of an integrated medication delivery system according to the subject invention with an infusion tube set;  
         [0032]      FIG. 1B  is a perspective view of an underside of the system illustrating a system mounting clip for securing the system to a patient;  
         [0033]      FIG. 2A  is an exploded perspective view of the system illustrating a medication reservoir, a base housing, reservoir casings, a pump assembly, and a carrying strap of the system;  
         [0034]      FIG. 2B  is an exploded perspective view of the system illustrating a removable overlay label, a patient label, and a top housing of the base housing for assembly to the system;  
         [0035]      FIG. 3  is an exploded perspective view of the system illustrating a port, a plunger, the pump assembly including a motor and first and second pinch levers, an actuator, and the base housing including an integral storage cavity for the carrying strap;  
         [0036]      FIG. 4  is an exploded perspective view of the system illustrating an underside of the top housing, at least one control button, an electronic controller and display, and a detection film having a cantilever portion;  
         [0037]      FIG. 5  is an exploded perspective view of the pump assembly;  
         [0038]      FIG. 6A  is a partially cross-sectional side view of a cam shaft, the pump assembly, and the first and second pinch levers illustrating the pinch levers in a closed position to pinch medication inlet and outlet tubes;  
         [0039]      FIG. 6B  is a partially cross-sectional side view of the system, as disclosed in  FIG. 6A , illustrating the first pinch lever in an open position and the second pinch lever in a closed position to draw medication into the pump assembly;  
         [0040]      FIG. 6C  is a partially cross-sectional side view of the system, as disclosed in  FIG. 6A , illustrating the first pinch lever in a closed position and the second pinch lever in an open position to displace medication from the pump assembly;  
         [0041]      FIG. 6D  is a partially cross-sectional side view of the system, as disclosed in  FIG. 6A , in combination with the plunger and the actuator, with the actuator retaining the pinch levers in the open position;  
         [0042]      FIG. 7  is a partially cross-sectional side view of the pump assembly;  
         [0043]      FIG. 8  is an exploded perspective view of the port and the plunger;  
         [0044]      FIG. 9  is an enlarged partially cross-sectional top view of the plunger disposed in the port illustrating a first, second, and third fluid connector;  
         [0045]      FIG. 10  is a partially cross-sectional side view taken along line  10 - 10  in  FIG. 9  illustrating a seal disposed about the plunger being depressed by leak ribs extending from the port;  
         [0046]      FIG. 11A  is a partially cross-sectional top view of the system with the plunger in an off-position;  
         [0047]      FIG. 11B  is a partially cross-sectional view of the port and the plunger disposed in the port in the off-position from  FIG. 11A ;  
         [0048]      FIG. 12A  is a partially cross-sectional top view of the system with the plunger in a fill-position such that the system can be sterilized and filled with medication;  
         [0049]      FIG. 12B  is a partially cross-sectional view of the port and the plunger disposed in the port in the fill-position from  FIG. 12A  additionally illustrating a syringe for moving the plunger into the fill-position and a fluid cap for sterilization;  
         [0050]      FIG. 13A  is a partially cross-sectional top view of the system with the plunger in a fluid delivery-position such that the medication can be delivered to the patient;  
         [0051]      FIG. 13B  is a partially cross-sectional view of the port and the plunger disposed in the port in the fluid delivery-position from  FIG. 13A  additionally illustrating a connector from the infusion tubing set;  
         [0052]      FIG. 14A  is an enlarged perspective view of the actuator;  
         [0053]      FIG. 14B  is a perspective view of an alternative embodiment for the actuator including a control contact disposed at a distal end of an actuation arm;  
         [0054]      FIG. 15A  is a partially cross-sectional side view of a blockage detection system according to the subject invention when the medication outlet tube is in a normal condition;  
         [0055]      FIG. 15B  is a partially cross-sectional side view of the blockage detection system of  FIG. 15A  when the medication outlet tube is in an expanded condition due to a blockage;  
         [0056]      FIG. 16A  is a partially cross-sectional side view of an empty detection system according to the subject invention when the medication inlet tube is in a normal condition;  
         [0057]      FIG. 16B  is a partially cross-sectional side view of the empty detection system of  FIG. 16A  when the medication inlet tube is in a collapsed condition due to a depletion in the supply of the medication;  
         [0058]      FIG. 17  is a perspective view of a support platform with the medication inlet and outlet tubes which also illustrates alternative embodiments for the blockage detection system and the empty detection system where a coating is applied to the medication inlet and outlet tubes;  
         [0059]      FIG. 18A  is a top perspective view of the system engaged with a testing instrument for confirming proper operation of the system after assembly and prior to use;  
         [0060]      FIG. 18B  is a bottom perspective view of the system engaged with a second testing instrument for confirming proper operation of the system after assembly and prior to use;  
         [0061]      FIG. 19  is a perspective view of the patient using the carrying strap as a shoulder strap to carry the system;  
         [0062]      FIG. 20  is an enlarged top perspective view of the integral storage cavity defined within the base housing of the system;  
         [0063]      FIG. 21  is a perspective view of a surgeon or patient removing the removable overlay label to reveal the patient label;  
         [0064]      FIG. 22  is a plan view of one embodiment of the removable overlay label having a one version of a first set of explanatory indicia;  
         [0065]      FIG. 23  is a plan view of a further embodiment of the removable overlay label having another version of a first set of explanatory indicia;  
         [0066]      FIG. 24  is a plan view of the patient label having a second set of explanatory indicia;  
         [0067]      FIG. 25  is a block diagram schematically illustrating a control system for the integrated medication delivery system of the subject invention;  
         [0068]      FIG. 26  is an electrical diagram illustrating portions of a watchdog circuit of the control system;  
         [0069]      FIG. 27  is an electrical diagram illustrating further portions of the watchdog circuit of the control system.  
         [0070]      FIG. 28  is graphical illustration of a tube set divided into a plurality of legs, according to an embodiment of the present invention;  
         [0071]      FIG. 29A  is a graph illustrating a series of pulses divided into first and second groups, according to an embodiment of the present invention;  
         [0072]      FIG. 29B  is a graph of an exemplary pressure profile during a group of pulses in which the system pressure is allowed to drop to the outlet pressure after the group;  
         [0073]      FIG. 29C  is a graph of an exemplary pressure profile during 2 groups of pulses in which a mechanism is in place to hold system pressure at or above a predetermined level after the first group;  
         [0074]      FIG. 29D  is a diagrammatical illustration of a tube set having a Y-divider, at least one check valve and a flow restrictor in each leg, according to an embodiment of the present invention;  
         [0075]      FIG. 30  is a first isometric view of a two site infusion apparatus, according to an embodiment of the present invention;  
         [0076]      FIG. 31  is second isometric view of the two site infusion apparatus of  FIG. 1 ;  
         [0077]      FIG. 32  is a top down view of the two site infusion apparatus of  FIG. 1 ;  
         [0078]      FIG. 33  is a side view of the two site infusion apparatus of  FIG. 1 ;  
         [0079]      FIG. 34  is a bottom view of the two site infusion apparatus of  FIG. 1 ;  
         [0080]      FIG. 35  is a first cut-away view of the two site infusion apparatus of  FIG. 1 ; and  
         [0081]      FIG. 36  is a second cut-away view of the two site infusion apparatus of  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0082]     Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, an integrated medication delivery system, also referred to as an infusion assembly, is generally disclosed at  10 . The integrated medication delivery system  10 , hereinafter described as the system  10 , delivers medication to a patient  12  (refer to  FIG. 19 ). More specifically, the system  10  is primarily used throughout the medical profession to deliver pain control medication and other medications to the patient  12  after a surgical, or some other medical, procedure. As disclosed in  FIG. 1B , the system  10  is used in combination with an infusion tube set  14  to deliver the medication to the patient  12 . The infusion tube set  14  is described below.  
         [0083]     The system  10  of the subject invention is also suitable for complete sterilization by a sterilization fluid including, but not limited to, ethylene oxide (EtO) gas. Although not ideal, certain liquids may even be used to sterilize the system  10 . For descriptive purposes only, the terminology of “medication” and of “sterilization” fluid may also be described throughout simply as a fluid.  
         [0084]     Referring primarily to  FIGS. 2A-3 , the system  10  includes a base housing  16 . The base housing  16  is further defined as a bottom housing  18 , a middle housing  20  mounted to the bottom housing  18  and a top housing  22 , i.e., a cover. The housings  18 ,  20 ,  22  are preferably mounted together via screws  23 . The system  10  also includes a medication reservoir  24  disposed about the base housing  16 . More specifically, the reservoir  24  is disposed about the middle housing  20 . The reservoir  24  stores the supply of medication that is to be delivered to the patient  12 . Preferably, the reservoir  24  is formed of a flexible, yet durable plastic material. The system  10  further includes a reservoir casing  26  disposed between the bottom and top housings  18 ,  22 . The reservoir casing  26  at least partially surrounds the reservoir  24  to protect the medication that is to be delivered to the patient  12 . The preferred embodiment of the subject invention includes two reservoir casings  26  that surround the reservoir  24  to protect the medication. Of course, it is to be understood that the reservoir casing  26  may be a unitary component and still adequately surround the reservoir  24  to protect the medication. The reservoir casing  26  is particularly useful when the patient  12  is carrying the system  10 . Carrying of the system  10  is described below.  
         [0085]     Referring primarily to  FIGS. 2A, 3 , and  5 - 6 D, a pump assembly  28  is supported by the base housing  16 . Specifically, the pump assembly  28  is mounted to the bottom housing  18 . As understood by those skilled in the art, the pump assembly  28  is responsible for delivering the medication to the patient  12  and is further known as a positive displacement pump. As described below, the pump assembly  28  also serves to prevent inadvertent delivery of the medication to the patient  12 .  
         [0086]     As disclosed best in  FIG. 5 , the pump assembly  28  includes a pump housing  30  having a pump inlet  32  and a pump outlet  34 . The pump housing  30  also has at least one detent  36 . The at least one detent  36  is described below. The pump inlet  32  and the pump outlet  34  alternate between an open and a closed state to deliver the medication to the patient  12 . Referring now to  FIGS. 3 , and  6 A- 6 D, a first pinch lever  38 , also referred to as a pinch valve, is disposed at the pump inlet  32  and a second pinch lever  40  or valve is disposed at the pump outlet  34 . The first pinch lever  38  functions to alternate the pump inlet  32  between the open and the closed state, and the second pinch lever  40  functions to alternate the pump outlet  34  between the open and the closed state.  
         [0087]     As  FIGS. 6B and 6C  disclose, the first pinch lever  38  is moveable between an open position ( FIG. 6B ) and a closed position ( FIG. 6C ) to control a flow of the medication into the pump housing  30  through the pump inlet  32 , and the second pinch lever  40  is moveable between an open position ( FIG. 6C ) and a closed position ( FIG. 6B ) to control a flow of the medication from the pump housing  30  through the pump outlet  34 . The pump assembly  28  further includes a motor  42  that is operatively engaged to the first and second pinch levers  38 ,  40  for moving these levers  38 ,  40  into the open position such that the medication can be delivered to the patient  12 . The motor  42  includes a driving output shaft, not shown in the Figures, for driving the pump assembly  28 . A power source  43  is integrated into the system  10  to provide power to the system  10 , including the motor  42 . Preferably, the power source includes batteries  45  and battery contacts  47 .  
         [0088]     As shown in  FIG. 6A , the first pinch lever  38  is normally-biased to maintain the pump inlet  32  in the closed state and the second pinch lever  40  is normally-biased to maintain the pump outlet  34  in the closed state. To accomplish this, at least one biasing device  44  is included in the pump assembly  28 . Preferably, the at least one biasing device  44  is a compression spring as shown, but not numbered, throughout the Figures. However, it is to be understood that the at least one biasing device  44  may be any device that is suitable for normally-biasing at least one, if not both, of the first and second pinch levers  38 ,  40  into the closed position. The at least one biasing  44  device engages at least one of the first and second pinch levers  38 ,  40  and works in conjunction with the motor  42  to normally bias at least one of the first and second pinch levers  38 ,  40  into the closed position. As such, if the motor  42  fails during delivery of the medication, then the first and second pinch levers  38 ,  40  are biased into and thereafter maintained in the closed position to prevent the inadvertent delivery of the medication to the patient  12 . The motor  42  is able to move the first and second pinch levers  38 ,  40  into the open position despite the bias of the at least one biasing device  44 .  
         [0089]     In the preferred embodiment of the subject invention, the at least one biasing device  44  comprises a first  46  and a second  48  biasing device. The first biasing device  46 , preferably a compression spring, engages the first pinch lever  38 , and the second biasing device  48 , also preferably a compression spring, engages the second pinch lever  40 . As disclosed in  FIG. 6A , the first and second biasing devices  46 ,  48  maintain the first and second pinch levers  38 ,  40  in the closed position during failure of the motor  42  thereby preventing the inadvertent delivery of the medication to the patient  12 . More specifically, the closed first pinch lever  38  prevents the medication from being drawn into the pump assembly  28  through the pump inlet  32 , and the closed second pinch lever  40  prevents the medication from being displaced from the pump assembly  28  through the pump outlet  34 .  
         [0090]     Referring primarily to  FIGS. 5-6D , to effectively operate the system  10  and move the first and second pinch levers  38 ,  40  for delivery of the medication to the patient  12 , the pump assembly  28  of the subject invention further includes a cam shaft  50  supported on the pump housing  30 . The cam shaft  50  is geared to the motor  42 , via a number of gears  52 , to operatively engage the motor  42  to the first and second pinch levers  38 ,  40 . The cam shaft  50  is described in greater detail below.  
         [0091]     As disclosed best in  FIGS. 5 and 7 , the pump assembly  28  also includes a piston  54  disposed in the pump housing  30 . The motor  42  moves the piston  54  within the pump housing  30  to draw the medication into the pump housing  30  when the first pinch lever  38  is in the open position and the second pinch lever  40  is in the closed position (see  FIG. 6B ). The motor  42  also moves the piston  54  within the pump housing  30  to displace the medication from the pump housing  30  when the first pinch lever  38  is in the closed position and the second pinch lever  40  is in the open position (see  FIG. 6C ). The piston  54  includes an actuation end  56  and a pumping end  58 . A diaphragm seal  60  is disposed at the pumping end  58  of the piston  54 . The diaphragm seal  60  is secured at the pumping end  58  of the piston  54  by a piston cap  62 . The piston  54  also includes at least one slot  62  at the actuation end  56 . The at least one detent  36  of the pump housing  30 , originally introduced above, engages the at least one slot  62  at the actuation end  56  of the piston  54  to prevent unwanted rotation of the piston  54  as the piston  54  is moved within the pump housing  30  by the motor  42  and the cam shaft  50 .  
         [0092]     The cam shaft  50  supports first and second outside cams  64 ,  66  and an inside cam  68 . The inside cam  68  of the cam shaft  50  is disposed between the first and second outside cams  64 ,  66 . The first outside cam  64  engages the first pinch lever  38  to move the first pinch lever  38  between the open and closed position, and the second outside cam  66  engages the second pinch lever  40  to move the second pinch lever  40  between the open and closed positions. The inside cam  68  engages the actuation end  56  of the piston  54  to move the piston  54  within the pump housing  30 .  
         [0093]     Referring to  FIG. 5 , the first and second outside cams  64 ,  66  include a plurality of slits  70  along an outer circumference  72  of the cams  64 ,  66 . These slits  70  are used during assembly and testing of the system  10  to confirm dimensional tuning of the cams  64 ,  66 . Also, at least one of the first and second outside cams  64 ,  66 , preferably the first outside cam  64 , includes an assembly slot  74  defined within the outer circumference  72  of the cams  64 ,  66 . This assembly slot  74  facilitates assembly of the pump assembly  28 . In particular, this assembly slot  74  facilitates mounting of the cam shaft  50 , including the cams  64 ,  66 , after the first and second pinch levers  38 ,  40  have already been incorporated into the system  10 .  
         [0094]     Each of the first and second pinch levers  38 ,  40  comprise a cam follower  76  and lever guides  78 . The lever guides  78  are described below. The cam followers  76  of the pinch levers  38 ,  40  are engaged by the cam shaft  50  for alternating movement of the first and second pinch levers  38 ,  40  between the open and closed positions such that the medication can be delivered to the patient  12 . More specifically, the cam follower  76  of the first pinch lever  38  is engaged by the first outside cam  64  for alternating movement of the first pinch lever  38  between the open and closed positions, and the cam follower  76  of the second pinch lever  40  is engaged by the second outside cam  66  for alternating movement of the second pinch lever  40  between the open and closed positions. Even more specifically, each of the first and second outside cams  64 ,  66  include internal cam surfaces  80 . As disclosed in  FIGS. 6A-6D , the cam follower  76  of the first pinch lever  38  rides within the internal cam surface  80  of the first outside cam  64  for alternating movement of the first pinch lever  38 , and the cam follower  76  of the second pinch lever  40  rides within the internal cam surface  80  of the second outside cam  66  for alternating movement of the second pinch lever  40 .  
         [0095]     Referring primarily to  FIGS. 3 , and  8 - 10 , the system  10  further includes a port assembly  82  that enables various fluids, such as the medication or the sterilization fluid, to flow into, from, and within the system  10 . The port assembly  82 , hereinafter described as the port  82 , extends from the base housing  16 . More specifically, the port  82  extends from the middle housing  20 . The port  82  is in fluid communication with the reservoir  24  and the pump assembly  28 . During sterilization, the port  82  provides access for the sterilization fluid to flow into the reservoir  24  and the pump assembly  28 . During filling, the port  82  provides access for the medication to flow into the reservoir  24  and the pump assembly  28 . During delivery of the medication to the patient  12 , the port  82  provides access for the medication to be delivered to the patient  12 .  
         [0096]     Referring particularly to  FIGS. 9 , and  11 A- 13 B, the port  82  includes an elongated housing  84 . The elongated housing  84  includes a proximate end  86 , a distal end  88 , and an interior wall  90  defining a fluid chamber  92  between the proximate and distal ends  86 ,  88 . It is the proximate end  86  of the elongated housing  84  that extends from the system  10  to provide access for the fluid to flow both into and from the system  10 . The port  82  further includes a first fluid connector  94 , a second fluid connector  96 , and a third fluid connector  98 . The first fluid connector  94 , alternatively referred to as an outlet of the port  82 , extends from the elongated housing  84  to allow the fluid to flow from the fluid chamber  92  into the pump assembly  28 . The second fluid connector  96 , alternatively referred to as an inlet to the port  82 , extends from the elongated housing  84  to allow the fluid to flow from the pump assembly  28  into the fluid chamber  92 . The third fluid connector  98 , alternatively referred to as an access to the reservoir  24 , extends from the elongated housing  84  to allow the fluid to flow between the fluid chamber  92  and the reservoir  24 . In the preferred embodiment of the subject invention, there are two third fluid connectors  98 , one third fluid connector  98  extending from opposite sides of the elongated housing  84 .  
         [0097]     Referring primarily to  FIGS. 3, 6D ,  8 - 10 , and  11 A- 13 B, the port  82  further includes a plunger  100 . The plunger  100  is disposed in the fluid chamber  92  of the port  82  and is moveable between an off-position ( FIGS. 11A-11B ), a fill-position ( FIGS. 12A-12B ), and a fluid delivery-position ( FIGS. 13A-13B ). As disclosed in  FIGS. 11A-11B , in the off-position, the first, second, and third fluid connectors  94 ,  96 ,  98  are isolated from the proximate end  86  of the elongated housing  84  by the plunger  100 . As a result, the flow of fluid through the port  82  is prevented. As disclosed in  FIGS. 12A-12B , in the fill-position, the first and third fluid connectors  94 ,  98  are in fluid communication with the proximate end  86  of the elongated housing  84 . As a result, a fluid flow path, shown but not numbered in  FIGS. 12A-12B , is provided between the proximate end  86  of the elongated housing  84 , the medication reservoir  24 , and the pump assembly  28  such that the fluid can be filled through the proximate end  86  of the housing and into the medication reservoir  24  and the pump assembly  28 . This fluid flow path is defined between the port  82 , the reservoir  24 , and the pump assembly  28  such that the flow of sterilization fluid through the fluid flow path is continuous during sterilization of the system  10 . The fill-position of the plunger  100  is utilized when the system  10  is being sterilized with the sterilization fluid and also when the system  10  is being filled with medication. As disclosed in  FIGS. 13A-13B , in the fluid delivery position, the first, second, and third fluid connectors  94 ,  96 ,  98  are in fluid communication with the proximate end  86  of the elongated housing  84  and with each other for supplying the pump assembly  28  and for delivering the fluid to the patient  12 .  
         [0098]     Referring primarily to  FIGS. 3, 6D ,  11 A,  12 A,  13 A, and  14 A- 14 B, the system  10  further includes an actuator  102  disposed in the base housing  16 . The actuator  102  is moveable between a disengaged position and an engaged position. The disengaged position of the actuator  102  is described below. As disclosed in  FIG. 6D , in the engaged position, the actuator  102  operatively engages the pump inlet  32  and the pump outlet  34  to retain, i.e., lock, both the pump inlet  32  and the pump outlet  34  in the open state during sterilization. With the pump inlet  32  and the pump outlet  34  in the open state, the sterilization fluid can penetrate throughout the entire system  10  to completely sterilize the system  10 . That is, the sterilization fluid can penetrate into the reservoir  24 , the pump inlet  32 , the pump housing  30 , and the pump outlet  34  to completely sterilize the system  10 .  
         [0099]     More specifically, the actuator  102  interacts with the first and second pinch levers  38 ,  40  to retain both the pump inlet  32  and the pump outlet  34  in the open state during sterilization. In the engaged position, the actuator  102  moves the first pinch lever  38  away from the pump inlet  32  into the open position to retain the pump inlet  32  in the open state, and the actuator  102  moves the second pinch lever  40  away from the pump outlet  34  into the open position to retain the pump outlet  34  in the open state. The actuator  102  retains both the first and second pinch levers  38 ,  40  in the open position for sterilization despite the bias of the at least one biasing device  44 .  
         [0100]     On the other hand, when the actuator  102  is in the disengaged position, as indicated by the absence of the actuator  102  from  FIGS. 6B-6C , the actuator  102  is operatively disengaged from the pump inlet  32  and the pump outlet  34 . The actuator  102  is in the disengaged position when it is necessary to deliver the medication to the patient  12  such that the pump inlet  32  and the pump outlet  34  can alternate between the open and closed states to deliver the medication the patient  12 . Disengagement of the actuator  102  permits the pump inlet  32  and the pump outlet  34  to alternate between the open and closed states.  
         [0101]     Referring particularly to  FIGS. 14A-14B , the actuator  102  is disclosed in greater detail. The actuator  102  includes a base portion  104  and at least one engagement arm  106  extending from the base portion  104 . The at least one engagement arm  106  of the actuator  102  operatively engages the pump assembly  28  to retain the pump inlet  32  and the pump outlet  34  in the open state during sterilization. In the preferred embodiment of the subject invention, the actuator  102  more specifically includes first and second engagement arms  108 ,  110 , respectively, extending from the base portion  104 . In the preferred embodiment, the actuator  102  also includes an actuation arm  112 . The actuation arm  112  extends from the base portion  104  between the first and second engagement arms  108 ,  110 . As shown in the Figures, the actuation arm  112  extends upwardly from the base portion  104  between the first and second engagement arms  108 ,  110 .  
         [0102]     During sterilization, the first engagement arm  108  of the actuator  102  engages the first pinch lever  38  to move the first pinch lever  38  away from the pump inlet  32  to retain the pump inlet  32  in the open state. Similarly, during sterilization, the second engagement arm  110  of the actuator  102  engages the second pinch lever  40  to move the second pinch lever  40  away from the pump outlet  34  to retain the pump outlet  34  in the open state.  
         [0103]     After sterilization it is desirable to move the actuator  102  into the disengaged position such that the pump assembly  28  can operate and the medication can be delivered to the patient  12 . As indicated by the arrow (A) in  FIG. 6D , the plunger  100  moves to displace the actuator  102  from the engaged position thereby moving the actuator  102  into the disengaged position. To displace the actuator  102 , the plunger  100  engages the actuation arm  112 . The plunger  100  displaces the actuator  102  from the operative engagement with the pump assembly  28  after sterilization such that the pump inlet  32  and the pump outlet  34  can alternate between the open and the closed state to deliver the medication to the patient  12 . More specifically, the plunger  100  displaces the actuator  102  from the engagement with the first and second pinch levers  38 ,  40  after sterilization such that medication can be delivered to the patient  12 . As such, the motor  42 , which is operatively engaged to the first and second pinch levers  38 ,  40 , can move these levers  38 ,  40  for drawing the medication into the pump housing  30  through the pump inlet  32  and for displacing the medication from the pump housing  30  through the pump outlet  34 .  
         [0104]     Referring now to  FIG. 14B , a control contact  114 , preferably a spring-like control contact  114 , may be disposed at a distal end  116  of the actuation arm  112  away from the base portion  104  to indicate to the system  10  whether the actuator  102  is in the engaged or the disengaged position. The control contact  114  interacts with the actuation arm  112  of the actuator  102  upon the movement of the actuator  102  between the engaged or the disengaged position. If the control contact  114  is included, it is preferred that when the actuator  102  is disengaged from the first and second pinch levers  38 ,  40 , i.e., when the actuator  102  is in the disengaged position, it contacts the control contact  114  to active an electronic controller  118 . The electronic controller  118  is activated to permit the pump assembly  28  to operate for delivering the medication to the patient  12 . As indicated above, it is preferred that the actuation arm  112  of the actuator  102  is in contact with the control contact  114  when the actuator  102  is in the disengaged position. Of course, it is to be understood that the opposite could be true. That is, the system  10  can be designed such that the actuation arm  112  of the actuator  102  is in contact with the control contact  114  when the actuator  102  is in the engaged position.  
         [0105]     The system  10  further includes a medication inlet tube  120  and a medication outlet tube  122 . The medication inlet tube  120  is connected between the port  82  and the pump inlet  32  to provide access for the sterilization fluid to flow from the port  82  into the pump assembly  28 , specifically into the pump inlet  32 . The medication outlet tube  122  is connected between the pump outlet  34  and the port  82  to provide access for the sterilization fluid to flow from the pump assembly  28 , specifically from the pump outlet  34 , into the port  82 . The medication inlet tube  120  and the first pinch lever  38  together establish the pump inlet  32 , and the medication outlet tube  122  and the second pinch lever  40  together establish the pump outlet  34 .  
         [0106]     When the at least one biasing device  44  engages the first pinch lever  38  to normally-bias the first pinch lever  38  into the closed position, the medication inlet tube  120  is pinched. As such, the pump inlet  32  is maintained in the closed state. Similarly, when the at least one biasing device  44  engages the second pinch lever  40  to normally-bias the second pinch lever  40  into the closed position, the medication outlet tube  122  is pinched. As such, the pump outlet  34  is maintained in the closed state. However, as disclosed in  FIG. 6D , when the actuator  102  is in the engaged position during sterilization, the actuator  42  overcomes the bias of the at least one biasing device  44  to move the first pinch lever  38  away from the medication inlet tube  120  such that the pump inlet  32  remains in the open state, and the actuator  102  overcomes the bias of the at least one biasing device  44  to move the second pinch lever  40  away from the medication outlet tube  122  such that the pump outlet  34  remains in the open state.  
         [0107]     Referring particularly to  FIGS. 3 , and  8 - 10 , the port  82  and the plunger  100  are described in greater detail. The plunger  100  includes a length L, a circumference C, and a plurality of seats  124  disposed along the length L and about the circumference C of the plunger  100 . The seats  124  extend outwardly from the circumference C of the plunger  100  to the interior wall  90  of the elongated housing  84  of the port  82  to segregate the fluid chamber  92  of the elongated housing  84 . A fluid passage, not numbered, is defined between each of the seats  124  and the interior wall  90  of the housing. These fluid passages control the flow of fluid within the port  82 . Although the seats  124  may suitably segregate the fluid chamber  92 , it is preferred that seals  126  are disposed about each of the seats  126  to assist with sealing the fluid passages from one another. In the most preferred embodiment, which is shown in the Figures, these seals are O-rings. At least one leak rib  128  extends at least partially along the interior wall  90  of the elongated housing  84 . The at least one leak rib  128  selectively causes at least one of the seals  126  to leak when the plunger  100  is in the fill-position. As disclosed in the Figures, preferably there are two leak ribs  128  that extend along the interior wall  90  of the elongated housing  84 .  
         [0108]     As shown in  FIGS. 11A-13B , the plunger  100  is at least partially hollow. As such, the plunger  100  defines an internal fluid bore  130  that extends within the plunger  100  between the seats  124 . The plunger  100  further includes an access end  132  and a plunger actuation end  134 . A plunger biasing device  136 , preferably a compression spring, is disposed about the plunger actuation end  134  of the plunger  100  to bias the plunger  100  into the off-position. The internal fluid bore  130  extends from the access end  132 , where the fluid flows into and from the internal fluid bore  130 , toward the plunger actuation end  134 . The internal fluid bore  130  includes a fluid duct  138  in fluid communication with one of the fluid passages such that the flow can flow into and from the internal fluid bore  130 .  
         [0109]     In the most preferred embodiment of the subject invention, the plurality of seats  124  are further defined as a first, second, third, and fourth seat  140 ,  142 ,  144 ,  146 , respectively. The first seat  140  is disposed toward the access end  132  of the plunger  100 , the fourth seat  146  is disposed toward the plunger actuation end  134  of the plunger  100 , and the second and third seats  142 ,  144  are disposed successively between the first and fourth seats  140 ,  146 . In this embodiment, the fluid passages are further defined as a first, second, and third fluid passage  148 ,  150 ,  152 , respectively. The first fluid passage  148  is defined between the first and second seats  140 ,  142  and the interior wall  90 , the second fluid passage  150  is defined between the second and third seats  142 ,  144  and the interior wall  90 , and the third fluid passage  152  is defined between the third and fourth seats  144 ,  146  and the interior wall  90 .  
         [0110]     A first seal  154  is disposed about the first seat  140  for sealing the first fluid passage  148  from the access end  132  of the plunger  100 , a second seal  156  is disposed about the second seat  142  for sealing the first and second fluid passages  148 ,  150  from one another, a third seal  158  is disposed about the third seat  144  for sealing the second and third fluid passages  150 ,  152  from one another, and a fourth seal  160  is disposed about the fourth seat  146  for sealing the third fluid passage  152  from the plunger actuation end  134  of the plunger  100 . In this embodiment, the at least one leak rib  128  extends along the interior wall  90  of the elongated housing  84  from the proximate end  86  toward the distal end  88  just beyond the first seal  154  such that only the first seal  154  selectively leaks when the plunger  100  is in the fill-position.  
         [0111]     In this most preferred embodiment, the internal fluid bore  130  extends within the plunger  100  from the access end  132  to the third seat  144 . As such, the fluid duct  138  is in fluid communication with the second fluid passage  150  defined between the second and third seats  142 ,  144  and the interior wall  90  such that the fluid can flow into and from the internal fluid bore  130  at the second fluid passage  150 .  
         [0112]     The off-, fill-, and fluid delivery-positions of the plunger  100  are now described in the context of this most preferred embodiment having four seats  140 ,  142 ,  144 ,  146 , three fluid passages  148 ,  150 ,  152 , and four seals  154 ,  156 ,  158 ,  160 . Referring to  FIGS. 11A-11B , when the plunger  100  is in the off-position, the first, second, and third fluid connectors  94 ,  96 ,  98  are isolated from the proximate end  86  of the elongated housing  84  and from the access end  132  of the plunger  100  by the first, second, and third seats  140 ,  142 ,  144 . In this off-position, the first and third fluid connectors  94 ,  98  are aligned with the third fluid passage  152 .  
         [0113]     Referring to  FIGS. 12A-12B , when the plunger  100  is in the fill-position, the first and third fluid connectors  94 ,  98  are in fluid communication with the proximate end  86  of the elongated housing  84  and with the access end  132  of the plunger  100  through the second fluid passage  150  and the fluid duct  138  of the internal fluid bore  130 . In this fill-position, the first and third fluid connectors  94 ,  98  are aligned with the second fluid passage  150 . As such, the fluid can be filled through the access end  132  of the plunger  100 , through the internal fluid bore  130  and the fluid duct  138 , and into the reservoir  24  and the pump assembly  28 . In the fill-position, the second fluid connector  96  is isolated from the proximate end  86  of the elongated housing  84 , from the access end  132  of the plunger  100 , and from the first and third fluid connectors  94 ,  98  by the third and fourth seats  144 ,  146 .  
         [0114]     Referring to  FIGS. 13A-13B , when the plunger  100  is in the fluid delivery-position, the second fluid connector  96  is in fluid communication with the proximate end  86  of the housing and with the access end  132  of the plunger  100  through said second fluid passage  150  and the fluid duct  138  of the internal fluid bore  130 . In the fluid delivery-position, the medication is delivered from the pump assembly  28  to the patient  12 . In the fluid delivery-position, the first and third fluid connectors  94 ,  98  are isolated from the proximate end  86  of the housing and from the access end  132  of the plunger  100  by the first and second seats  140 ,  142 . However, the first and third fluid connectors  94 ,  98  are in fluid communication with the reservoir  24  through the first fluid passage  148  to supply the pump assembly  28  with the fluid, i.e., with the medication. That is, in the fluid delivery-position, the first and third fluid connectors  94 ,  98  are aligned with the first fluid passage  148 .  
         [0115]     A fluid filling device, shown generally in  FIG. 12B  at  162 , engages the proximate end  86  of the housing to automatically move the plunger  100  into the fill-position for filling the reservoir  24  and the pump assembly  28 . If the system  10  is being sterilized, then the fluid filling device  162  is preferably a fluid, or sterilization, cap  164  (shown detached from the system  10  in  FIG. 12B ) that moves the plunger  100  into the fill-position to enable a sterilization fluid to penetrate into the reservoir  24  and the pump assembly  28 . The fluid cap  164 , by design, automatically moves the plunger  100  into the fill-position. Therefore, when the system  10  is introduced into a chamber filled with the sterilization fluid, preferably EtO gas, then the sterilization fluid flows, or seeps, through the fluid cap  164 , through the proximate end  86  of the elongated housing  84  and the access end  132  of the plunger  100 , through the internal fluid bore  130  and the fluid duct  138 , into the second fluid passage  150 , through the third fluid connector  98  into the reservoir  24 , and through the first fluid connector  94  into the pump assembly  28 .  
         [0116]     If the system  10  is being filled with medication, then the fluid filling device  162  is preferably a syringe  166  that moves the plunger  100  into the fill-position for filling the reservoir  24  and the pump assembly  28 . The syringe  166  (shown attached to the system  10  in  FIG. 12B ) engages the access end  132  of the plunger  100  and, by design, automatically moves the plunger  100  into the fill-position for filling the reservoir  24  and the pump assembly  28  through the internal fluid bore  130 . Therefore, when the system  10  is being filled, the syringe  166  interacts with the proximate end  86  of the elongated housing  84  and the access end  132  of the plunger  100  and, as the syringe plunger is depressed, the medication flows through the internal fluid bore  130  and the fluid duct  138 , into the second fluid passage  150 , through the third fluid connector  98  into the reservoir  24 , and through the first fluid connector  94  into the pump assembly  28 .  
         [0117]     To deliver the medication to the patient  12 , the system  10  is utilized in combination with the infusion tube set  14 . Referring back to  FIG. 1A , the infusion tube set  14  includes a fluid end  168  and a patient end  170 . The fluid end  168  of the tube set  14 , through a delivery connector  172 , engages the proximate end  86  of the elongated housing  84  and the access end  132  of the plunger  100  to automatically move the plunger  100  into the fluid delivery-position for delivering the medication to the patient  12 . Therefore, as shown in  FIGS. 13A-13B , when the pump assembly  28  is operating, the medication is drawn from the reservoir  24  through the third fluid connector  98  into the port  82  at the first fluid passage  148 , and through the first fluid connector  94  into the pump inlet  32 . The medication is then displaced out of the pump assembly  28  through the pump outlet  34 , through the second fluid connector  96  into the port  82  at the second fluid passage  150 , through the fluid duct  138  and the internal fluid bore  130  of the plunger  100 , and out the access end  132  of the plunger  100  at the fluid end  168  of the infusion tube set  14 . From there, the medication flows through the infusion tube set  14 , out the patient end  170 , and to the patient  12 .  
         [0118]     Referring back to  FIG. 4 , the system  10  further includes the electronic controller  118 . The electronic controller  118  controls an amount of the medication that is to be delivered to the patient  12 . The electronic controller  118  is mounted to the base housing  16 , specifically to the top housing  22  of the base housing  16 . Furthermore, the electronic controller  118  remains mounted to the base housing  16  during sterilization such that the entire system  10 , including all mechanical components, the reservoir  24 , and the electronic controller  118 , is simultaneously sterilized. An electronic display  174  and at least one control button  176  are mounted to the base housing  16 . The electronic display  174  and the control button  176  interact with the electronic controller  118  to control the amount of the medication to be delivered to the patient  12 . As with the electronic controller  118 , the electronic display  174  and the control button  176  also remain mounted to the base housing  16  during sterilization.  
         [0119]     The subject invention also provides a blockage detection system which is generally disclosed at  178  in  FIGS. 15A-15B . The blockage detection system  178  detects a blockage in the flow of the medication to the patient  12 . The blockage detection system  178  comprises the base housing  16 , the reservoir  24 , the port  82 , the pump assembly  28 , the medication outlet tube  122 , and the electronic controller  118 . The blockage detection system  178  also includes a detection film  180  which is described below.  
         [0120]     In the blockage detection system  178 , the electronic controller  118  is mounted to the base housing  16  adjacent the outlet tube  122 . The outlet tube  122  is mounted to the base housing  16  and, as described above, is connected between the pump assembly  28  and the port  82  to provide access for the medication to flow from the pump assembly  28  into the port  82  and to the patient  12 . The outlet tube  122  has a diameter that is contractible and expandable between a normal condition (see  FIG. 15A ) and an expanded condition (see  FIG. 15B ). The diameter of the outlet tube  122  contracts and expands in response to variations in pressure that result from the flow of the medication from the reservoir  24  through the pump assembly  28  into the port  82  and to the patient  12 .  
         [0121]     As disclosed in the Figures, the outlet tube  122  is mounted to the base housing  16  via a support platform  182 . That is, the support platform  182  is mounted on the base housing  16  to support the outlet tube  122  on the base housing  16 . The support platform  182  includes at least one tube slot  184 . The at least one tube slot  184  houses the diameter of the outlet tube  122 . The outlet tube  122  is mounted in the tube slot  184  such that at least a portion, not numbered, of the diameter of the outlet tube  122  is exposed to the detection film  180 .  
         [0122]     The detection film  180  is disposed between the electronic controller  118  and the outlet tube  122 . The detection film  180  is in contact with the outlet tube  122  and remains spaced from the electronic controller  118  when the diameter of the outlet tube  122  is in the normal condition, as in  FIG. 15A . On the other hand, the detection film  180  is in contact with the outlet tube  122  and contacts the electronic controller  118  to activate the electronic controller  118  when the diameter of the outlet tube  122  is in the expanded condition, as in  FIG. 15B , in response to increased pressure resulting from the blockage in the flow of the medication to the patient  12 . More specifically, it is preferred that an electronic switch  186  is embedded in the electronic controller  118  between the electronic controller  118  and the detection film  180 . The detection film  180  interacts with the electronic controller  118  by contacting the electronic switch  186  to activate the electronic controller  118  when the diameter of the outlet tube  122  is in the expanded condition.  
         [0123]     For activating the electronic controller  118  when the diameter of the outlet tube  122  is in the expanded condition, it is also preferred that the detection film  180  is conductive. Once activated by the detection film  180 , the electronic controller  118  deactivates the pump assembly  28  to prevent delivery of the medication to the patient  12  when the diameter of the outlet tube  122  is in the expanded condition. Deactivation of the pump assembly  28  prevents further blockage and further increases in pressure. To properly ensure that the there is a blockage in the outlet tube  122 , it is most preferred that the electronic controller  118 , and therefore the pump assembly  28 , are deactivated only if the diameter of the outlet tube  122  is in the expanded condition for more than at least one cycle of the pump assembly  28 . This additional measure avoids false readings and the deactivation of the pump assembly  28  when the outlet tube  122  is truly not blocked.  
         [0124]     Additionally, once activated by the detection film  180 , the electronic controller  118  may also activate an alarm  188 , shown schematically in the Figures. The alarm  188 , which can be audible and/or visually displayed on the electronic display  174 , would indicate the blockage that is due to the blockage in the flow of the medication to the patient  12 .  
         [0125]     It is preferred that the detection film  180  is mounted to the electronic controller  118 . Although the detection film  180  is mounted to the electronic controller  118 , a portion, not numbered, of the detection film  180  remains at least partially-spaced from the electronic controller  118  when the diameter of the outlet tube  122  is in the normal condition. The detection film  180  is mounted to the electronic controller  118  with an adhesive layer  190 . The adhesive layer  190  also establishes a thickness that is necessary to space the detection film  180 , specifically the portion of the detection film  180 , from the electronic controller  118  when the diameter of the outlet tube  122  is in the normal condition. The portion of the detection film  180  contacts the electronic controller  118  to activate the electronic controller  118  when the diameter of the outlet tube  122  is in the expanded condition in response to increased pressure in the outlet tube  122 .  
         [0126]     An alternative embodiment for the blockage detection system  178  is disclosed in  FIG. 17 . In this alternative embodiment, the detection film  180  is eliminated, and a coating  192  is included. The coating  192  is applied to the outlet tube  122 . The coating  192  activates the electronic controller  118  when the diameter of the outlet tube  122  is in the expanded condition in response to increased pressure resulting from the blockage in the flow of the medication to the patient  12 . As with the detection film  180 , the coating  192  is preferably conductive. If the coating  192  is present, it is most preferred that the coating  192  is formed of conductive carbon. However, other coatings may be used that impart conductive properties to the coating  192 .  
         [0127]     For the most part, the other characteristics of this alternative embodiment for the blockage detection system  178  are identical to the characteristics that were described above in the preferred embodiment for the blockage detection system  178 . Notably, the outlet tube  122  is mounted in the tube slot  184  in this alternative embodiment such that at least a portion of the coating  192  is exposed beyond the tube slot  184 .  
         [0128]     The subject invention also provides an empty detection system which is generally disclosed at  194  in  FIGS. 16A-16B . The empty detection system  194  determines when a supply of the medication has been depleted. The empty detection system  194  comprises the base housing  16 , the reservoir  24  for storing the supply of the medication to be delivered to the patient  12 , the port  82 , the pump assembly  28 , the medication inlet tube  120 , and the electronic controller  118 . As with the blockage detection system  178 , the preferred embodiment of the empty detection system  194  also includes a detection film, also numbered  180 , which is described below.  
         [0129]     In the empty detection system  194 , the electronic controller  118  is mounted to the base housing  16  adjacent the inlet tube  120 . The inlet tube  120  is mounted to the base housing  16  and, as described above, is connected between the reservoir  24  and the pump assembly  28  to provide access for the medication to flow from the reservoir  24  into the pump assembly  28  and to the patient  12 . The inlet tube  120  has a diameter that is contractible and expandable between a normal condition (see  FIG. 16A ) and a collapsed condition (see  FIG. 16B ). The inlet tube  120  contracts into the collapsed condition and expands from the collapsed condition into the normal condition. The diameter of the inlet tube  120  contracts and expands in response to variations in pressure that result from a lack of the flow of the medication from the reservoir  24  through the pump assembly  28  and to the patient  12 .  
         [0130]     As disclosed in the Figures, the inlet tube  120  is mounted to the base housing  16  via the support platform  182 . That is, the support platform  182  is mounted on the base housing  16  to support the inlet tube  120  on the base housing  16 . The support platform  182  includes the at least one tube slot  184 . The at least one tube slot  184  houses the diameter of the inlet tube  120 . The inlet tube  120  is mounted in the tube slot  184  such that at least a portion of the diameter of the inlet tube  120  is exposed to the detection film  180 .  
         [0131]     The detection film  180  is disposed between the electronic controller  118  and the inlet tube  120 . As shown in  FIG. 16A , the detection film  180  is in contact with the inlet tube  120  and contacts the electronic controller  118  to activate the electronic controller  118  when the diameter of the inlet tube  120  is in the normal condition. On the other hand, as shown in  FIG. 16B , the detection film  180  becomes spaced from the electronic controller  118  to deactivate the electronic controller  118  when the diameter of the inlet tube  120  is in the collapsed condition in response to the lack of flow of the medication that results from the supply of the medication being depleted.  
         [0132]     It is preferred that an electronic switch  186  is embedded in the electronic controller  118  between the electronic controller  118  and the detection film  180 . The detection film  180  contacts the electronic switch  186  to activate the electronic controller  118  when the diameter of the inlet tube  120  is in the normal condition, and the detection film  180  becomes spaced from the electronic switch  186  to deactivate the electronic controller  118  when the diameter of the inlet tube  120  is in the collapsed condition.  
         [0133]     As best disclosed in  FIG. 4 , the detection film  180  more specifically includes a film base portion  196  and a cantilever portion  198 . The film base portion  196  of the detection film  180  is mounted to the electronic controller  118  away from the electronic switch  186 , and the cantilever portion  198  of the detection film  180  is adjacent the electronic switch  186 . More specifically, the cantilever portion  198  extends from the film base portion  104  to contact the electronic switch  186  when the diameter of the inlet tube  120  is in the normal condition. It is the cantilever portion  198  of the detection film  180  that becomes spaced from the electronic controller  118  to deactivate the electronic controller  118  when the diameter of the inlet tube  120  is in the collapsed condition. For activating the electronic controller  118  when the diameter of the inlet tube  120  is in the normal condition, it is also preferred that the detection film  180 , specifically the cantilever portion  198  of the detection film  180 , is conductive. Preferably, the detection film  180  is mounted to the electronic controller  118  with an adhesive layer  190 . Of course, it is the film base portion  196  of the detection film  180  that is directly mounted to the electronic controller  118 . The cantilever portion  198  of the detection film  180  is not directly mounted, or otherwise adhered, to the electronic controller  118  such that this portion of the detection film  180  can become spaced from the electronic controller  118  when the diameter of the inlet tube  120  is in the collapsed condition.  
         [0134]     Once the detection film  180  becomes spaced from the electronic controller  118 , i.e., when the diameter of the inlet tube  120  is in the collapsed condition, the portion of the electronic controller  118  that interacts with the pump assembly  28  is deactivated such that the pump assembly  28  is deactivated. Deactivation of the pump assembly  28  after it has been determined that the supply of the medication has been depleted prevents a build up of air in the system. To properly ensure that the supply of the medication has been depleted, it is most preferred that the electronic controller  118 , and therefore the pump assembly  28 , are deactivated only if the diameter of the inlet tube  120  is in the collapsed condition for more than at least one cycle of the pump assembly  28 . This additional measure avoids false readings and the deactivation of the pump assembly  28  when the supply of the medication is truly not depleted.  
         [0135]     Additionally, deactivation of the portion of the electronic controller  118  that interacts with the pump assembly  28  may also cause the electronic controller  118  to activate the alarm  188 . The alarm  188 , which can be audible and/or visually displayed on the electronic display  174 , would indicate the lack of flow of the medication when the diameter of the inlet tube  120  is in the collapsed condition due to the lack of flow of the medication to the patient  12 .  
         [0136]     An alternative embodiment for the empty detection system  194  is disclosed in  FIG. 17 . In this alternative embodiment, the detection film  180  is eliminated, and the coating  192  is included. The coating  192  is applied to the inlet tube  120 . The coating  192  contacts the electronic controller  118  to activate the electronic controller  118  when the diameter of the inlet tube  120  is in the normal condition. On the other hand, the coating  192  becomes spaced from the electronic controller  118  to deactivate the electronic controller  118  when the diameter of the inlet tube  120  is in the collapsed condition in response to the lack of flow of the medication resulting from the supply of the medication being depleted. As with the detection film  180 , the coating  192  is preferably conductive. If the coating  192  is present, it is most preferred that the coating  192  is formed of conductive carbon. However, other coatings may be used that impart conductive properties to the coating  192 .  
         [0137]     For the most part, the other characteristics of this alternative embodiment for the empty detection system  194  are identical to the characteristics that were described above in the preferred embodiment for the empty detection system  194 . Notably, the inlet tube  120  is mounted in the tube slot  184  in this alternative embodiment such that at least a portion of the coating  192  is exposed beyond the tube slot  184 .  
         [0138]     Referring now to FIGS.  1 B,  6 A- 6 D, and  18 A- 18 B, the system  10  of the subject invention can be tested using a testing instrument  200  after assembly of the system  10 . The system  10  is tested after assembly and prior to shipment and use by the surgeons, patients, and the like to confirm various operations of the system  10 . In the preferred embodiment, to test the system  10 , the system  10  is mounted onto the testing instrument  200 . One operation of the system  10  that is confirmed after assembly of the system  10  is the operation of the pump assembly  28 .  
         [0139]     To confirm these operations, the system  10  includes at least one testing access port  202 . The at least one testing access port  202  is defined within the base housing  16  and is aligned with at least one of the pump inlet  32 , the pump outlet  34 , and the actuator  102 . Preferably, the at least one testing access port  202  is aligned with all three of the pump inlet  32 , the pump outlet  34 , and the actuator  102 . The at least one testing access port  202  provides access for the testing instrument  200  to move the actuator  102  between the disengaged position and the engaged position. If the at least one testing access port  202  is aligned with the pump inlet  32  and the pump outlet  34  then it is aligned with the first and second pinch levers  38 ,  40 , respectively. Also, as for the alignment with the actuator  102 , the at least one testing access port  202  is more specifically aligned with the at least one engagement arm  106  of the actuator  102 . This provides access for the testing instrument  200  to move the actuator  102  between the disengaged position and the engaged position.  
         [0140]     The system  10  is preferably assembled with the actuator  102  in the engaged position such that the first and second pinch levers  38 ,  40  are in the open position and the resiliency and life of the medication inlet and outlet tubes  120 ,  122  is not compromised. Because the at least one testing access port  202  provides access for the testing instrument  200  to move the actuator  102  between the disengaged position and the engaged position, the testing instrument  200  can be inserted into the at least one testing access port  202  to disengage the actuator  102 , i.e., to move the actuator  102  into the disengaged position. As such, the pump inlet  32  and the pump outlet  34  can alternate between the open and closed states after assembly and during testing of the system  10 .  
         [0141]     The at least one testing access port also provides access for the testing instrument  200  such that the pump inlet  32  and the pump outlet  34  can be retained in the open state after the system  10  has been tested to prepare the system  10  for sterilization. That is, after the system  10  has been tested, the actuator  102  is moved from the disengaged position back into the engaged position to prepare the system  10  for sterilization. In the engaged position, the first and second pinch levers  38 ,  40  are retained in the open state.  
         [0142]     In the preferred embodiment, the at least one testing access port  202  is further defined as first, second, and third testing access ports  204 ,  206 ,  208 , respectively. The first testing access port  204  is aligned with the pump inlet  32 , the second testing access port  206  is aligned with the pump outlet  34 , and the third testing access port  208  is aligned with the actuator  102  for providing access to the testing instrument  200  to move the actuator  102  into the engaged position. More specifically, the first testing access port  204  is aligned with the first pinch lever  38  such that the first pinch lever  38  is engaged by the testing instrument  200 . Once inside the first testing access port  204 , the testing instrument  200  forces the first pinch lever  38  away from the pump inlet  32  and forces the pump inlet  32  into the open state. Similarly, the second testing access port  206  is aligned with the second pinch lever  40  such that the second pinch lever  40  is engaged by the testing instrument  200 . Once inside the second testing access port  206 , the testing instrument  200  forces the second pinch lever  40  away from the pump outlet  34  and forces the pump outlet  34  into the open state. The first and second pinch levers  38 ,  40  include the lever guides  78  opposite the cam follower  76  of each pinch lever  38 ,  40 . To move the first and second pinch levers  38 ,  40 , the testing instrument  200  engages the lever guides  78  upon insertion into the first and second testing access ports  204 ,  206 . After the testing instrument  200  forces the first and second pinch levers  38 ,  40  away from the pump inlet  32  and the pump outlet  34 , respectively, the testing instrument  200  is introduced into the third testing access port  208  and the actuator  102  is moved into the engaged position to engage and retain the pinch levers  38 ,  40  in the open position such that the system  10  is now prepared for sterilization. It is to be understood by those skilled in the art that the testing instrument  200  includes male prongs, generally indicated at  210 , that are introduced into the testing access ports  204 ,  206 ,  208 .  
         [0143]     The system  10  further includes at least one controller access port  212  defined within the base housing  16 . In the preferred embodiment, the at least one controller access port  212  is defined within the top housing  22  or cover. The at least one controller access port  212  is aligned with the electronic controller  118  to provide access for a second testing instrument  214 . It is to be understood that the second testing instrument  214  and the testing instrument  200  may be a unitary component, as disclosed in the Figures. The second testing instrument  214  causes the electronic controller  118  to activate the motor  42  such that the motor  42  is powered to alternate the pump inlet  32  and the pump outlet  34  between the open and closed states after assembly and during testing of the system  10 . The second testing instrument  214  also preferably includes male prongs  210  that are introduced into the controller access ports  212 .  
         [0144]     Referring primarily to  FIGS. 2A-3 , and  19 - 20 , the system  10  of the subject invention is also suitable to be carried by the patient  12 . To facilitate carrying of the system  10  so the patient  12  can remain ambulatory, a carrying strap  216  is mounted within the base housing  16  for the carrying of the system  10  by the patient  12 . An integral storage cavity  218  is defined within the base housing  16 . The carrying strap  216  is at least partially disposed in the integral storage cavity  218 . The carrying strap  216  at least partially extends from the integral storage cavity  218  to interact with the patient  12  for carrying the system  10 .  
         [0145]     The system  10  further includes a plurality of cavity walls. The cavity walls extend from the bottom housing  18  to define the integral storage cavity  218  between the bottom  18  and top  22  housings. Referring particularly to  FIG. 20 , the cavity walls are further defined as a front wall  220 , a rear wall  222 , and first and second side walls  224  extending between the front and rear walls  220 ,  222  to support the front and rear walls  220 ,  222  and to define the integral storage cavity  218 . At least one strap slot  226  is defined within the front wall  220  such that at least a portion, not numbered, of the carrying strap  216  extends from the integral storage cavity  218  and through the strap slot  226 . The patient  12  can then access the portion of the carrying strap  216  when desired.  
         [0146]     In interacting with the carrying strap  216 , the patient  12  simply manipulates, or grabs, the portion of the carrying strap  216  to pull a length of the carrying strap  216  from the integral storage cavity  218 . This length is then looped about the head of the patient  12  as specifically disclosed in  FIG. 19 . In the preferred embodiment, the carrying strap  216  is retractable into the integral storage cavity  218  after the length has been pulled from the integral storage cavity  218  by the patient  12 . The system  10  further includes a clip  228  that connects opposing ends of the carrying strap  216  such that the carrying strap  216  is adjustable to fit patients  12  of all sizes. In the most preferred embodiment of the subject invention, which is disclosed in  FIG. 19 , the carrying strap  216  is further defined as a shoulder strap. The shoulder strap suspends from a shoulder of the patient  12  for carrying the system  10 .  
         [0147]     Also, as particularly disclosed in  FIG. 1B , the system  10  may also further include a system mounting clip  230  that extends from an exterior facing  232  of the base housing  16 . The system mounting clip  230  can be mounted to a belt  234  of the patient  12 . Of course, it is to be understood that the system mounting clip  230  is not to be limited to a clip for a belt  234 . Instead, the system mounting clip  230  may be mounted to a shirt, a pocket, and the like.  
         [0148]     Referring to  FIGS. 2B , and  21 - 24 , the subject invention further provides a method of controlling the system  10 . This method is designed to be convenient for both the surgeon, or other medical professional, and the patient  12 . A patient label  236 , having a second set of explanatory indicia, i.e., instructions, is mounted, preferably adhered, to the system  10 . A removable overlay label  238 , having a first set of explanatory indicia, i.e., instructions, is mounted, preferably adhered, to the patient label  236  to at least partially cover the patient label  236 .  
         [0149]     The method includes the steps of selecting the amount of the medication in accordance with the first set of explanatory indicia on the removable overlay label  238 . The medical professional selects the amount of the medication. As such, the first set of explanatory indicia is intended to be readily understood by the medical professional. Typically, the amount of the medication is selected by selecting the flow rate for the medication. Other parameters including, but not limited to, the bolus amount, the drug or medication concentration, and like, can also be selected.  
         [0150]     Throughout the step of selecting, the medical professional and/or patient  12  interfaces with the electronic display  174  to view his or her selections. More specifically, the electronic display  174  presents a readable output for the medical professional and the patient  12 . The readable output displayed on the electronic display  174  is correlated with the removable overlay label  238  and the patient label  236 . That is, the readable output is correlated to the first and second sets of instructions. A first readable output is presented on the electronic display  174 . The first readable output is linked with the first set of explanatory indicia when the removable overlay label  238  is displayed. Similarly, a second readable output is presented on the electronic display  174 . The second readable output is linked with the second set of explanatory indicia after the system  10  has been locked. Locking the system  10  is described immediately below.  
         [0151]     After the amount of the medication has been selected, the system  10  is locked such that selected amount of the medication to be delivered to the patient  12  is unable to be modified. After the medical professional is satisfied with his or her selection, the medical professional depresses the “LOCK” portion of the first set of explanatory indicia on the removable overlay label  238  to lock the system  10 .  
         [0152]     Once the system  10  is locked, either the medical professional or the patient  12  can remove the removable overlay label  238  to reveal the patient label  236  (as shown in  FIG. 21 ). To accomplish this, the user, either the medical professional or the patient  12 , simply pulls the removable overlay label  238  off the patient label  236 . This reveals the control button  176  that was originally masked under the removable overlay label  238 . The system  10  is then operated in accordance with a second set of explanatory indicia on the patient label  236 . The second set of explanatory indicia is intended to be readily understood by the patient  12 . Once the system  10  is locked, the system  10  is designed to be convenient for use by the patient  12 .  
         [0153]     Upon locking the system  10 , a functionality of the control button  176  is modified. As such, the functionality of the control button  176  is different when the removable overlay label  238  is displayed on the system  10  as compared to when the patient label  236  is displayed on the system  10 . In other words, the functionality of the control button  176  is different when the medical professional interacts with the system  10  via the removable overlay label  238  as compared to when the patient  12  interacts with the system  10  via the patient label  236 . When the removable overlay label  238  is displayed on the system  10 , the control button  176  is at least tri-functional. On the other hand, after the system  10  has been locked and the patient label  236  is displayed on the system  10 , the functionality of the control button  176  is converted from being at least tri-functional to being bi-functional.  
         [0154]     In operating the system  10 , the system  10  may be deactivated, if necessary, to stop delivery of the medication to the patient  12 . To deactivate the system  10 , the patient  12  depresses the “ON/OFF” portion of the, now bi-functional, control button  176  in response to the second set of explanatory indicia on the patient label  236 . If the system  10  is deactivated, then the patient  12  may also use the control button  176  to activate the system  10  to re-start delivery of the medication to the patient  12 . To accomplish this, the patient  12  depresses the “ON/OFF” portion of the control button  176  again.  
         [0155]     Alternatively, in operating the system  10 , the patient  12  may request an additional amount of the medication relative to the selected amount of the medication, and provided the Bolus amount will not be violated, the patient  12  will receive an additional amount of the medication. To request an additional amount of the medication relative to the selected amount, the patient  12  actuates the control button  176 .  
         [0156]     With specific reference to  FIG. 25 , a control system  240  for the system  10 , according to an embodiment of the present invention is shown. The control system  240  includes the electronic controller  118  and a motor control circuit  242 . The electronic controller  118  controls operation of the system  10  as described above.  
         [0157]     In one embodiment, the electronic controller  118  includes a microprocessor  244 . One suitable microprocessor  244  is available from Philips Semiconductor of Sunnyvale, Calif. as model no. 87LPC764. The electronic controller  118  is programmed to control operation of the motor control circuit  242  with a computer software program. In general, the electronic controller  118  generates control signals in accordance with the computer software program and delivers the control signals to the motor control circuit  242 .  
         [0158]     The motor control circuit  242  includes a first switch  246 . The first switch  246  has an open state and a closed state.  
         [0159]     The control system  240  also includes a watchdog circuit  248  coupled to the electronic controller  118 . The watchdog circuit  248  includes a monitor circuit  250  and a second switch  252 . The second switch  252  has an open state and a closed state and is coupled to the first switch  246 . The monitor circuit  250  is adapted to detect an abnormal condition of the control system  240  and to turn the second switch  252  off if the abnormal condition is detected. Examples of an abnormal condition include, but are not limited to, too many revolutions of the motor  42 , failure of the electronic controller  118 , failure of the first switch  246 , or failure of a motor sensor  254  (see below).  
         [0160]     The motor control circuit  242  is adapted to receive control signals from the electronic controller  118  and to responsively supply power to the motor  42  by placing the first switch  246  in the closed state. Power is supplied to the motor  42  if the first and second switches  246 ,  252  are in the closed state.  
         [0161]     With reference to  FIGS. 26 and 27 , in one embodiment the first and second switches  246 ,  252  are field effect transistors (FETs)  256 ,  258 . In one embodiment, the control system  240  includes the control buttons  176 . A user such as the surgeon or the patient  12  is able to program the control system  240  to deliver medication at the desired flow rate. Based on the desired flow rate, the electronic controller  118  controls energization of the motor  42  to deliver the medication.  
         [0162]     In one embodiment, each revolution of the motor  42  delivers a set amount of the medication during a known period of time. A predetermined number of revolutions of the motor  42  delivers a “pulse” of medication. In order to meet the desired flow rate, the electronic controller  118  calculates a period of time between revolutions of the motor  42 .  
         [0163]     In one embodiment of the present invention, the period of time calculated by the controller  118  (between pulses) is constant fixed for the desired flow rate.  
         [0164]     In one aspect of the present invention, the controller  118  controls the pump assembly  28  to provide a series of pulses of medication to provide the desired flow of medication. With reference to  FIGS. 28, 29A ,  29 B, and  29 C, the fluid flow output of the system  10  may be subdivided. As shown, the fluid flow from the tube set  14  may be divided by a flow divider  288  to provide fluid flow to a plurality of legs  290 . In the illustrated embodiment, there are n legs each having a respective fluid flowrate of {dot over (M)}.  
         [0165]     In one embodiment, the series of pulses are determined to provide an outlet pressure at the pump outlet adapted to reduce the effect of any differential pressure between the legs. In other words, a differential pressure across two legs, e.g., Leg  1  and Leg  2 , may result in a differential flow rate through each leg. The controller  118  manipulates the pulses to maintain the total pressure through the tube set  14  high enough for a long enough period of time to reduce the effect of the differential pressure at the legs. For example, the pulses may be spaced together closely enough so that each pulse begins before a significant drop in fluid pressure level occurs following the previous pulse.  
         [0166]     With reference to  FIG. 29A  in another aspect of the present invention, the controller  118  controls the pump assembly  28  to provide groups  292  of pulses. In one embodiment, the number of pulses in a group  292  is predetermined. For exemplary purposes only, first and second groups  292 A,  292 B are shown with eight pulses each. A first time period, t 1 , separates the start of each pulse within a group  292  and a second time period, t 2 , separates the start of each group. The first and second time periods may be determined by the controller  118  to provide the desired flow rate while maintaining the desired flow through each leg  290  and reducing the effect of any pressure differential. For example, the number of pulses in each group  290  may be 10, the first time period may be equal to 1.8 seconds and the second time period may be 100 to 1300 seconds. Of course, the numbers are for explanation purposes only. The present invention is not limited to any such examples.  
         [0167]     In another embodiment, the first time period is fixed and the controller  118  determines the second period as a function of the desired fluid flow.  
         [0168]     In another aspect of the present invention, a method for delivering medication using a medication delivery system  10  including the steps of storing a supply of medication, receiving a desired flow of medication, and providing a flow of medication from the supply of medication in the form of a series of pulses. The flow is provided through an outlet and is subdivided into a plurality of legs  290 . The series of pulses are determined to provide an outlet pressure at the pump outlet adapted to reduce an effect of any differential pressure between the legs.  
         [0169]     Since a higher pulse frequency may lead to an average flow rate during pulsing that is higher than the desired flow rate, the pulses may be delivered in groups of a given number of pulses (see above); the time elapsing between each group may be set as a function of the overall time-averaged flow rate desired from the pump (see above). This grouping of pulses can negatively affect the flow distribution to the various sites because the final pulse in a group will conclude with an asymptotic pressure drain during which the flow balance degrades as the pressure drops. To compensate for this, a group size may be selected so that the amount of flow occurring during the steady-state period of intermittent pulsing will sufficiently reduce the effect of the imbalanced flow that happens subsequent to the final pulse. With reference to  FIGS. 29B and 29C , a representative sketch of a pressure profile during a group of pulses is shown. Pcritical represents a pressure level above which acceptable flow distribution may be assured. This value is dependent upon the desired level of accuracy and the level of variation in the outlet pressures.  
         [0170]     The pump pulse method described above controls pressure and provides good flow splitting characteristics. In one embodiment of the present invention, the flow divider  288  may be designed to, in conjunction with the pump pulse method described above, to provide back pressure assistance, anti-siphon characteristics, and controlled restriction.  
         [0171]     With reference to  FIG. 29D , in one aspect of the present invention, the flow divider  288  includes a valve system  294  which provides flow restriction and anti-siphoning components to control flow split. In the illustrated embodiment, the valve system  294  includes two legs each leading to an extended fenestration catheter  296 .  
         [0172]     As shown, in the illustrated embodiment, the infusion tube set  14  includes a priming adapter  294 A, an on/off clamp  294 B, and a filter  294 C. A divider, shown as a Y-connector,  294 D is coupled to the filter  294 C.  
         [0173]     Each leg of the infusion set  14  after the Y-connector may include one or more low resistance, low cracking check valves  294 E. The check valves  294 E alleviates the siphoning problems during inactivity of the pump assembly  28  (see above).  
         [0174]     Although the pressure deteriorates nearly to zero after the last pulse in a group, the number of pulses and the spacing of the pulses in a group may be determined so that the average pressure is great enough to provide adequate distribution of flow to each leg (see  FIG. 29B  and discussion above).  
         [0175]     Each leg may also include a flow restrictor  294 F. In the illustrated embodiment, the flow restrictors  294 F are coupled to one of the check valves  294 E. The flow restrictors  294 F have an orifice (not shown) with a predetermined flow restriction value. The predetermined flow restriction value may be coordinated with the average flow rate during a group of pulses to keep the average pressure differential at a desired level for flow balance.  
         [0176]     With reference to  FIGS. 30-36 , in another aspect of the present invention, the infusion tube set  14  may include a multiple site infusion apparatus  310  such as a flow regulator valve. The multiple site infusion apparatus  310  may be coupled to an output tube  312  of the system  10  to split the medication delivered from the delivery system  10  and deliver the medicine through first and second outlet passageways  314 A,  314 B. In the illustrated embodiment, the apparatus  310  is shown as a two site infusion apparatus  310 , however, it should be noted that the present invention may provide medicine to a plurality of sites.  
         [0177]     The apparatus  310  includes a valve housing  316 . The valve housing  316  includes a first end  318  and a second end  320 . The first end  318  includes the first and second outlet passageways  314 A,  314 B.  
         [0178]     An end cap  330  has a closed end  332  and an open end  334 . The end cap  330  is coupled to the valve housing  316  at the open end  334 . A flexible diaphragm  336  is coupled between the end cap  330  and the valve housing  316  and is movable from a closed position to and an open position by the fluid energy of the pulse. The second end  320  of the valve housing  316  and the flexible diaphragm  336  form a pressure chamber  322 . The valve housing  316  further includes an inlet passageway  324 . The inlet passageway  324  is coupled to the pressure chamber  322 . The first and second outlet passageways  314 A,  314 B are coupled to the pressure chamber  322  by first and second outlet conduits  328 A,  328 B, respectively. The flexible diaphragm  336  seals the pressure chamber  322  from the first and second outlet conduits  328 A,  328 B when the flexible diaphragm  336  is in the closed position and opens the first and second outlet conduits  328 A,  328 B to the pressure chamber  322  when the flexible diaphragm  336  is in the open position.  
         [0179]     The valve housing  316  also includes a routing passageway  326  adjacent the inlet passage  324 . The routing passageway  326  allows the medication delivery system inlet tube  312  to be secured within the valve housing  316 . In one embodiment of the present invention, the end of the inlet tube  312  coated with a solvent and inserted through the inlet of passageway  324 . The inlet passageway  324  and the output tube  312  have an interference fit. The solvent bonds the inlet tube  312  and the inlet passageway  324 .  
         [0180]     As shown, in one embodiment of the present invention, the open end  334  of the cap  330  has an outer perimeter  338 . The outer perimeter  338  includes a ridge  340 . The second end  320  of the valve housing  316  includes a detent  342  along its outer perimeter  344 . The detent  342  receives the ridge  340  which allows the valve housing  316  and the end cap  330  to be snapped together.  
         [0181]     In another aspect of the present invention, the apparatus  310  includes a biasing mechanism  344  coupled between the cap  330  and the flexible diaphragm  336  for biasing the flexible diaphragm  336  towards the closed position. In one embodiment of the present invention, the biasing mechanism  344  includes a biasing spring  346 . The biasing spring  346  may be either tubular or conical.  
         [0182]     In another aspect of the present invention, a piston  348  may be juxtaposed between the biasing spring  346  and the flexible diaphragm  336 . In one embodiment, the flexible diaphragm  336  includes a piston receiving aperture  350  for receiving a first end  352  of the piston  348 .  
         [0183]     As shown, in one embodiment, the piston  348  is hollow and includes a spring receiving chamber  354 . The end cap  330  includes a spring positioning pin  356 . One end of the spring  346  is seated within the spring receiving chamber  354  and the other end is centered on the spring position pin  356 .  
         [0184]     In another aspect of the present invention, the apparatus  310  includes first and second bushings  358 A,  358 B which are located within and have an interference fit with the first and second outlet passageway  314 A, 314 B. First and second restriction orifices  360 A,  360 B are positioned within and have an interference fit with the first and second bushings  358 A,  358 B, respectively. Flexible outlet tubes (not shown) are coupled to the passageways  314 A,  314 B to deliver medication to the sites, as needed.  
         [0185]     In one aspect of the present invention, the inner diameter of the orifice  360 A,  360 B are relatively small, e.g., 0.001 to 0.005 inches with a small manufacturing tolerance. The orifices  360 A,  360 B are dimensioned to provide a large resistance to the flow of medication relative to resistance provided by the flexible outlet tubes and the sites where the medication is delivered. This assists in controlling the back pressure and thus minimizing the risk of an unequal amount of medication to be delivered to the two sites.  
         [0186]     In another aspect of the present invention, the flexible diaphragm  336  includes an integrally molded O-ring  362  around its outer perimeter  364 . The O-ring  362  is press fit within a circular groove  366  in the valve housing  316 . The valve housing  316  includes one or more air release apertures  368  which allow air to escape the groove  366  as the O-ring  362  is pressed into the groove  366 . The O-ring  362  and the groove  366  ensures that the outer perimeter  364  is coupled to the valve housing, thereby forming the pressure chamber  322 .  
         [0187]     In operation, the medication delivery system delivers medication through the inlet tube  312  in pulses. With reference to  FIG. 35 , when the flexible diaphragm  336  is in the closed position, the flexible diaphragm  336  creates a seal on the outlet valve seats. As fluid is pumped in, a pressure is created (Pinlet) within the pressure chamber  322 . With the flexible diaphragm  336  in the closed position, no flow of medication is allowed from the pressure chamber  322  to the output passageways  314 A,  314 B. Thus, while the flexible diaphragm  336  is in the closed position, the pressure at the outlet conduits  328 A,  328 B (Poutlet) is substantially zero.  
         [0188]     When the “pulse” of medication from the medication delivery system begins, Pinlet quickly ramps up from a non-zero value. When the force exerted by the pressurized medication within the pressure chamber  322  on the flexible diaphragm  336  is great enough to overcome the force exerted by the biasing mechanism  344 , the flexible diaphragm  336  is moved from the closed position towards the open position. After the flexible diaphragm  336  is moved away from the closed position, fluid flows out of the valve and pressure decays down towards a non-zero value until the force exerted by the biasing mechanism  344  overcomes the force exerted on the flexible diaphragm by the medication within the pressure chamber  322  such that the diaphragm closes over the passageways  314 A,  314 B. The rate of fluid flow and therefore pressure decrease is controlled by the restrictors  360 A,  360 B. This control is important since too low of a restriction would not force a complete opening of the valve. In that case the restriction of flow across the valve seats would be significant and minor variations in manufacturing tolerances and/or finishes would control the flow resistance and resultant distribution. With proper flow restrictor selection, the apparatus  310  fully opens and this does not occur.  
         [0189]     Likewise, when the flexible diaphragm  36  is moved away from the closed position, Poutlet (in conduits  328 A,  328 B) quickly ramps up to a pressure substantially equal to or slightly less than Pinlet. While the flexible diaphragm  336  is open, Pinlet tracks Poutlet. Since the resistance seen within the first and second passageways  314 A,  314 B is a result of the resistance of the first and second orifices  360 A,  360 B, Poutlet at the first and second outlet passageways  314 A,  314 B are substantially equal. Once the flexible diaphragm  336  closes, Poutlet quickly drops back down to substantially zero.  
         [0190]     The pulsing method discussed above may be used in applications in which the medication delivery system  10  delivers medicine to more than one site. The pulsing method may be used to control pressure and to facilitate the desired flow splitting characteristics. Additionally, the infusion tube set  14  may include enhanced features to provide controlled restriction and anti-siphoning characteristics. As described above, in one embodiment the infusion tube set  14  includes check valves and flow restrictors to provide the desired characteristics. In another embodiment, the infusion tub set includes the multiple site infusion apparatus  310 .  
         [0191]     Returning to  FIGS. 4 and 5 , in one embodiment, the motor control circuit  242  includes the motor sensor  254  (see  FIG. 4 ). The motor sensor  254  is coupled to the motor  42  and is adapted to detect a revolution of the motor  42  and to responsively generate a motor revolution signal in response to completion of the motor  42  revolution. In one embodiment, the motor sensor  254  is a opto-coupler sensor which is adapted to detect the presence of an indicating flag  260  (see  FIG. 5 ) connected to the motor  42 . The indicating flag  260  extends from one of the first and second outside cams  64 ,  66  to assist in monitoring the amount of the medication that has been delivered to the patient  12 . The sensor  254  is optically-coupled with the indicating flag  260  to count revolutions of the indicating flag  260 . One suitable sensor  254  is available from Omron of Schaumburg, Ill., as model no. EE-SX1109.  
         [0192]     In one embodiment, the electronic controller  118  is adapted to reset the watchdog circuit  248  prior to sending control signals to the motor  42  control circuit to energize the motor  42 . The watchdog circuit  248  is adapted to place the second switch  252  in the opened state if two motor revolution signals are received without the watchdog circuit  248  being reset.  
         [0193]     In other words, the electronic controller  118  must reset the watchdog circuit  248  prior to or between each revolution of the motor  42 . Thus, if a failure of the electronic controller  118  or the microprocessor  244  erroneously causes a control signal to be delivered to the motor control circuit  242  to continuously place the first switch  246  in the closed state, and thus, to erroneously energize the motor  42 , the second switch  252  will be placed in the opened state. With the second switch  252  in the opened state, power will not be delivered to the motor  42 .  
         [0194]     Additionally, if a failure of the first switch  246  leaves the first switch  246  in the closed state, successive motor revolution signals will be received by the watchdog circuit  248  without the watchdog circuit  248  being reset and the watchdog circuit  248  will place the second switch  252  in the opened state, thus preventing power from being supplied to the motor  42 .  
         [0195]     In one embodiment, the electronic controller  118  is adapted to track the time after a motor control signal has been sent and to enter a disabled state if the time between the sent control signal and received motor revolution signal exceeds a predetermined threshold.  
         [0196]     With specific reference to  FIG. 26 , in one embodiment the monitor circuit  248  includes first and second flip-flops  262 ,  264 . The first flip-flop  262  is coupled to the electronic controller  118  and the second flip-flop  264 . The second flip-flop  264  is coupled to the second FET  258 .  
         [0197]     In the illustrated embodiment, the first and second flip-flops  262 ,  264  are JK flip-flops. The inverse output ({overscore (Q)}) of the second flip-flop  264  is connected to the gate of the second FET  258 . The clock input (CLK) of the second flip-flop  264  is coupled to the output (O) of the first flip-flop  262 . Power is supplied by the microprocessor  244  to the first and second flip-flops  262 ,  264  to the J and K inputs of the first flop  262  and to the J input of the second flip-flop  264 . The drain of the second FET  258  is coupled to the first FET  256  and the source of the second FET  258  is connected to electrical ground.  
         [0198]     The watchdog circuit  248  is reset by shutting off and restoring power to the first and second flip-flops  262 ,  264 , to the J and K inputs of the first flop  262 , and to the J input of the second flip-flop  264 . In one embodiment, the electronic controller  118  shuts off power to the first and second flip-flops  262 ,  264  after each revolution of the motor  42  and supplies power prior to turning on the first switch  246  to begin the next cycle. This has two effects: conserving power and resetting the first and second flip-flops  262 ,  264 .  
         [0199]     The clock input (CLK) of the first flip-flop  262  is connected to the output of the motor sensor  254 . The clock input (CLK) of the first flip-flop  262  is also connected to the microprocessor  244  via a third FET  266 . The third FET  266  provides isolation between the microprocessor  244  and the motor sensor  254  and the monitor circuit  248 . This isolation prevents a shorted pin on the electronic controller  118  from preventing revolution pulses from reaching the flip-flops  262 ,  264 .  
         [0200]     The inverse clear input ({overscore (CLP)}) of the first and second flip-flops  262 ,  264  are coupled to the microprocessor  244  via a buffer circuit  268 . In the illustrated embodiment, the buffer circuit  268  includes a first buffer  270 , a first resistor  272  and a capacitor  274 . The electronic controller  118  may continuous supply power to the motor  42  by turning on the first switch  246  and continuously resetting the first and second flip-flops  262 ,  264  through the inverse clear inputs without turning off power to the flip-flops  262 ,  264 .  
         [0201]     In one embodiment, the flip-flops  262 ,  264  are triggered by logic level high (“HIGH”) to logic level low (“LOW”) transitions. The buffer circuit  268  prevents erroneous signal transitions when the input to the buffer circuit  268  is held HIGH by the microprocessor  244 .  
         [0202]     With specific reference to  FIG. 27 , the motor control circuit  242  includes the first FET  256  and the opto-coupler sensor  276 . A flashback diode  278  is coupled across first and second motor junctions  280 A,  280 B. The opto-coupler sensor  276  is coupled to the second motor junction  280 B. The transmitting diode of the opto coupler sensor  276  is coupled to power (V+) and ground through switch  256 . In this arrangement the sensor  276  is only powered during the time the motor  42  is running thus conserving battery life. An output of the opto-coupler sensor  276  is coupled to the third transistor  266  via a second buffer  282 .  
         [0203]     The gate of the first FET  256  is coupled to the microprocessor  244 . The drain of the first FET  256  is coupled to the motor  42  and the source of the first FET  256  is connected to the drain of the second FET  258 .  
         [0204]     As described above, the electronic controller  118  is adapted to supply medication by energizing the motor  42 . A desired flow rate is achieved by energizing the motor  42  and waiting between revolutions of the motor  42  for a calculated period of time. The motor  42  is energized by turning on the first FET  256 . In the illustrated embodiment, the first FET  256  is turned on by the microprocessor  244  by changing the state of the gate of the first FET  256  from LOW to HIGH. If the second FET  258  is also on, then power flows through the motor  42  and the first and second FETs  256 ,  258 . When the motor  42  has made one (1) complete revolution, then the output of the motor sensor  254  transitions from HIGH to LOW. In the illustrated embodiment, this transition is the motor revolution signal. The motor revolution signal is also transmitted to the microprocessor  244  via the third FET  266 . After receiving the motor revolution signal the microprocessor  244  turns off the first FET  256  by changing the state of the gate of the first FET  256  from HIGH to LOW.  
         [0205]     During normal operation, the microprocessor  244  then turns off power to the first and second flip-flops  262 ,  264 . As described above, based on the desired flow rate and the known quantity of medication delivered per revolution of the motor  42 , the microprocessor  244  calculates a wait period between motor revolutions. After the wait period (or right before the wait period ends), the microprocessor  244  restores power to the first and second flip-flops  262 ,  264 . As discussed above, this resets the first and second flip-flops  262 ,  264 . Then the microprocessor  244  may again turn on the first FET  256  to energize the motor  42 .  
         [0206]     If a failure condition of the control system  240  exists, such as a microprocessor  244  failure or other failure, and the watchdog circuit  248  is not reset, then watchdog circuit  248  turns off the second FET  258 , thereby preventing power from being supplied to the motor  42 .  
         [0207]     For example, if the microprocessor  244  fails while the first FET  256  is on, then the motor  42  will continue to be energized. The motor sensor  254  will generate motor revolution signals each time a motor revolution is completed. However, the microprocessor  244  does not or is unable to reset the watchdog circuit  248 . Two successive motor revolution signals received on the CLK input of the first flip-flop  262  without the watchdog circuit  248  being reset will flip the inverse output of the second flip-flop  264  (from HIGH to LOW) and thus turn off the second FET  258 .  
         [0208]     Likewise, a failure of the first transistor  256  in the closed state will continuously energize the motor  42 . If the microprocessor  244  does not reset the watchdog circuit  248 , then successive motor revolution signals received on the CLK input of the first flip-flop  262  will flip the inverse output of the second flip-flop  264  and thus turn off the second FET  258 .  
         [0209]     With the second FET  258  in the off state, power will not be delivered to the motor  42 .  
         [0210]     Returning to  FIG. 25 , the control system  240  further includes a key  284  which is connected to the electronic controller  118  only during initialization. In one embodiment, the key  284  is part of the testing instrument  200  which is also used to test the control system  240  after it has been assembled and the batteries  45  are installed. Upon initial power-up, the control system  240  will only initialize if the key  284  is present. If the key  284  is not present, then the control system  240  enters a disabled mode and medication cannot be delivered.  
         [0211]     In one embodiment, upon initial power-up the control system  240  sends a signal to the key  284 . If present, the key  284  delivers a return signal to the control system  240  indicating its presence. The use of the key  284  ensures that the system  10  cannot be improperly reset by removing and then re-inserting the batteries  45  or other power supply  43 . If this occurs and the key  284  is not present, the system  10  will not work.  
         [0212]     The control system  240  includes a crystal  285  coupled to the microprocessor  244 . The crystal  285  controls the frequency at which the microprocessor  244  operates in a conventional manner. However, if the crystal  285  is operating improperly, the microprocessor  244  could begin to operate at either a higher frequency or a lower frequency than intended. The microprocessor  244  also includes an internal oscillator  286 . In one embodiment, the control system  240  is adapted to compare a frequency of the crystal  285  with a frequency associated with the internal oscillator  286 . The electronic controller  118  adapted to compare a difference between the first and second frequencies and enter a disabled state if the difference is greater than a predetermined threshold. Thus, if the crystal  285  experiences a failure, the control system  10  will be disabled.  
         [0213]     The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.  
         [0214]     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described.