Abstract:
A programmable implantable insulin pump is disclosed. The pump includes an implantable pump and a hermetically sealed module. The module provides for varying flow rates of fluid being dispensed from the pump or may provide for a constant flow rate of such fluid. In the case of varying flow rate capabilities, the module preferably includes one or more sensors to determine information relating to the pressure of the fluid, electronics for analyzing the pressure information and determining the flow rate of the fluid, and a mechanism for physically altering the flow rate. First and second resistor capillaries are included in the implantable pump to provide a large range of flow rate capabilities between basal operation and bolus operation. Methods of dispensing a medicament to a patient utilizing such a system are also disclosed, as are variations of the pump system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/779,073 filed Mar. 13, 2013, the disclosure of which is hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to implantable devices, more particularly, programmable implantable pumps allowing for variable flow rates in delivering medication or other fluid to a selected site in the body of a patient. 
         [0003]    Implantable pumps have been well known and widely utilized for many years. Typically, pumps of this type are implanted into patients who require the delivery of active substances or medication fluids to specific areas of their body. For example, patients that are experiencing severe pain may require pain killers daily or multiple times per day. Absent the use of an implantable pump or the like, a patient of this type would be subject to one or more painful injections of such medication fluids. In the case of pain associated with more remote areas of the body, such as the spine, these injections may be extremely difficult to administer and particularly painful for the patient. In certain instances, proper application of such medication may be impossible. Furthermore, attempting to treat conditions such as this through oral or intravascular administration of medication often requires higher doses of medication and may cause severe side effects. Therefore, it is widely recognized that utilizing an implantable pump may be beneficial to both a patient and a treating physician. 
         [0004]    Implantable pumps have also been used for conditions that require frequent drug delivery. For example, patients suffering from diabetes may have an implantable insulin pump to reduce or eliminate the need for daily insulin injections through the skin. Another key advantage on an implantable insulin pump is optimal dispensing of insulin into peritoneal cavity instead of subcutaneous injection, ease of use by the patient and long refill intervals. Implantable insulin pumps may also reduce problems due to patient compliance, and further may track, store, and/or transmit data relating to treatment for purposes of record keeping and analysis. 
         [0005]    Many implantable pump designs have been proposed. For example, commonly invented U.S. Pat. No. 4,969,873 (“the &#39;873 patent”), the disclosure of which is hereby incorporated by reference herein, teaches one such design. The &#39;873 patent is an example of a constant flow pump, which typically includes a housing having two chambers, a first chamber for holding a specific medication fluid to be administered and a second chamber for holding a propellant. A flexible membrane preferably separates the two chambers such that expansion of the propellant in the second chamber pushes the medication fluid out of the first chamber. It is to be understood that the propellant typically expands under normal body temperature. This type of pump also typically includes an outlet opening connected to a catheter for directing the medication fluid to the desired area of the body, a replenishment opening for allowing for refill of the medication fluid into the first chamber and a bolus opening for allowing the direct introduction of a substance through the catheter without introduction into the first chamber. Both the replenishment opening and the bolus opening are typically covered by a septum that allows a needle or similar device to be passed through it, but which properly seals the opening upon removal of the device. As pumps of this type provide a constant flow of medication fluid to the specific area of the body, they must be refilled periodically with the proper concentration of medication fluids suited for extended release. 
         [0006]    Although clearly beneficial to patients and doctors that utilize them, constant flow pumps generally have one major problem, i.e., that only a single flow rate can be achieved from the pump. Thus, implantable pumps have also been developed, which allow for variable flow rates of medication therefrom. These pumps are typically referred to as programmable pumps, and have exhibited many different types of designs. For instance, in a solenoid pump, the flow rate of medication fluid can be controlled by changing the stroke rate of the pump. In a peristaltic pump, the flow rate can be controlled by changing the roller velocity of the pump. Likewise, pumps of the constant flow type have been modified to allow for a variable and programmable flow rate. For instance, commonly owned U.S. Pat. No. 7,637,892 (“the &#39;892 patent”) teaches such a design. The &#39;892 patent, as well as related U.S. patent application Ser. Nos. 11/125,586; 11/126,101; 11/157,437; and 13/338,673 are each incorporated herein by reference. In each case, the benefit of providing variable flow is at the forefront, so that differing levels of medication can be delivered to the patient at different times. 
         [0007]    In the &#39;892 patent, a constant flow-type pump assembly is modified to include a module that converts the constant flow pump into a programmable pump. That control module includes, inter alia, two pressure sensors, a constant flow capillary, and a valve assembly. The pressure centers are utilized to measure pressure directly from a medication chamber, and pressure just prior to entering the valve assembly. These pressure readings are utilized by a computing unit, which in turn causes a motor to operate the valve assembly to allow lesser or greater flow from the pump. The capillary preferably ensures that a maximum flow rate can only be achieved from the pump. The pump taught in the &#39;892 patent is indeed a useful programmable pump, but one which may be improved. 
         [0008]    Certain prior art pumps are used primarily for the delivery of pain medicine. These pumps may be conceptually similar and even structurally similar to pumps to deliver insulin, but improvements may be made to prior art pumps to make them more suitable for the delivery of insulin. For example, a pump for delivering pain medicine may deliver, at a minimum basal rate of approximately 100 μL of medicine per day. A diabetes patient, on the other hand, may require a basal rate of approximately 15 μL of medicine (e.g. insulin) a day. Similarly, pumps for delivery of pain medicine may deliver a maximum flow rate of medicine up to approximately 2 mL per day. Insulin pumps, on the other hand, may be expected to deliver a instantaneous bolus rate of medicine (e.g. insulin) up to approximately 18 mL per day. The ratio between a low basal delivery rate and the maximum bolus delivery rate for pain pumps may thus be about 1:20 (100 μL:2000 μL). The ratio between a low basal delivery rate and the maximum bolus delivery rate for insulin pumps, on the other hand, may be about 1:12,00 (15 μL:18,000 μL). As can be seen, the range of normal and bolus rates for pain pumps and insulin pumps may be quite different. Existing technologies are generally not capable of delivering (a) such low basal rate without severely affecting the flow accuracy and (b) a wide delivery range as foreseeably required for an insulin pump. As such, prior art pumps directed to delivering pain medicine may benefit from modification and/or improvement to better suit the needs of a diabetic patient, particularly in terms of rates of medicine delivery from implantable pumps. 
         [0009]    Therefore, there exists a need for an improved programmable implantable pump design. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    A first aspect of the invention is a programmable pump for dispensing a fluid at varying flow rates to a patient. The pump includes a constant flow module including a first chamber housing the fluid, first and second resistor capillaries in fluid communication with the first chamber and a first opening in fluid communication with a catheter. The pump also includes a hermetically sealed control module attached to the constant flow module and including a first motor assembly and valve block, the valve block being in fluid communication with the first and second resistor capillaries and the first opening, the first motor assembly having a first motor and a first valve connected with the motor. The flow rate of the fluid dispelled from the first chamber is affected by varying positioning of the valve. The fluid may be one adapted to treat a diabetic patient, such as insulin. 
         [0011]    The first resistor capillary may have a maximum flow rate and the second resistor capillary may also have a maximum flow rate, the maximum flow rate of the first resistor capillary being less than the maximum flow rate of the second resistor capillary. The maximum flow rate of the second resistor capillary may be, for example, at least 200 or 10,000 times greater than the maximum flow rate of the first resistor capillary. On the other hand, the maximum flow rate of the first resistor capillary is designed to be in the vicinity of the minimum flow rate desired of the second resistor capillary. 
         [0012]    The pump may include a second valve configured to limit flow of fluid from the second resistor capillary to the valve block. The second resistor capillary may have a first end in fluid communication with the first chamber and a second end in fluid communication with the valve block. The second valve may be positioned after the second end of the second resistor capillary. Alternately, the second valve may be positioned between the first and second end of the resistor capillary. 
         [0013]    During operation of the pump, fluid dispelled from the first chamber passes through the first resistor capillary, into the valve block, into contact with the first valve, out of the valve block, into the first opening and through the catheter. The second valve may have an “on” position and an “off” position. When in the “open” position, fluid dispelled from the first chamber passes through the second resistor capillary, into the valve block, into contact with the first valve, out of the valve block, into the first opening and through the catheter. When in the “closed” position, fluid dispelled from the first chamber passes through the second resistor capillary, but does not pass into the valve block. Another embodiment may include one or more intermediate positions of the secondary valve, such as partially open, that allows for additional values of flow as desired. 
         [0014]    The constant flow module may further include a second chamber separated from the first chamber by a first flexible membrane. The second chamber may be filled with a propellant that acts upon the flexible membrane to push the fluid from the first chamber through the first and second resistor capillaries. The control module may further include a first pressure sensor for monitoring a pressure of the fluid in the first chamber and a second pressure sensor for monitoring the pressure of the fluid in the valve block. 
         [0015]    The pump may further include an enclosure top attached to the constant flow module and covering the control module. The pump may also include a second motor configured to drive the second valve. The pump may also include a motor drive configured to drive the first motor and the second motor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    For more complete appreciation of the subject matter of the present invention and the various advantages thereof can be realized by reference to the following detailed description in which reference is made to the accompanying drawings in which: 
           [0017]      FIG. 1  is a perspective view of a programmable implantable pump in accordance with one embodiment of the present invention. 
           [0018]      FIG. 2  is a top view of the programmable implantable pump shown in  FIG. 1 . 
           [0019]      FIG. 3  is a bottom view of the implantable programmable pump shown in  FIG. 1 . 
           [0020]      FIG. 4  is a right side view of the programmable implantable pump shown in  FIG. 1 . 
           [0021]      FIG. 5  is a left side view of the programmable implantable pump shown in  FIG. 1 . 
           [0022]      FIG. 6  is a rear view of the programmable implantable pump shown in  FIG. 1 . 
           [0023]      FIG. 7  is a front view of the programmable implantable pump shown in  FIG. 1 . 
           [0024]      FIG. 8  is a perspective view of the implantable programmable pump shown in  FIG. 1  with an enclosure top removed therefrom. 
           [0025]      FIG. 9  is a perspective view of a constant flow module assembly of the programmable implantable pump shown in  FIG. 1 . 
           [0026]      FIG. 10  is a top view of the constant flow module assembly shown in  FIG. 9 . 
           [0027]      FIG. 11  is cross-sectional view of the constant flow module assembly taken along line AA of  FIG. 10 . 
           [0028]      FIG. 12  is a perspective view of a control module assembly of the programmable implantable pump shown in  FIG. 1 . 
           [0029]      FIG. 13  is a top view of the control module assembly shown in  FIG. 12 . 
           [0030]      FIG. 14  is a bottom view of the control module assembly shown in  FIG. 12 . 
           [0031]      FIG. 15  is a perspective view of the control module assembly shown in  FIG. 12 , with a titanium enclosure top removed therefrom. 
           [0032]      FIG. 16  is another perspective view similar to that shown in  FIG. 15 . 
           [0033]      FIG. 17  is a top view of the control module assembly shown in  FIGS. 15 and 16 . 
           [0034]      FIG. 18  is another view of the control module assembly shown in  FIGS. 15-17 , with an additional portion removed therefrom. 
           [0035]      FIG. 19  is a top view of the control module assembly shown in  FIG. 18 , with a further additional portion removed therefrom. 
           [0036]      FIG. 20  is a top view of the control module assembly shown in  FIG. 19 , with an even further additional portion removed therefrom. 
           [0037]      FIG. 21  is a top view of a motor and valve block assembly included in the control module assembly shown in  FIG. 12 . 
           [0038]      FIG. 22  is a top view of a motor, bushing, and valve assembly included in the construct shown in  FIG. 21 . 
           [0039]      FIG. 23  is a top view of the assembly shown in  FIG. 22  with the bellows removed therefrom. 
           [0040]      FIG. 24  is a view similar to that of  FIG. 23 , with a stem bushing construct removed therefrom. 
           [0041]      FIG. 25  is a top view of the valve block depicted in  FIG. 21 . 
           [0042]      FIG. 26  is a left side view of the valve block shown in  FIG. 25 . 
           [0043]      FIG. 27  is a bottom view of the valve block shown in  FIG. 25 . 
           [0044]      FIG. 28  is a view similar to that shown in  FIG. 21 , with the valve block shown in phantom. 
           [0045]      FIG. 29  is a cross-sectional view taken along line BB of  FIG. 26 . 
           [0046]      FIG. 30  is a perspective view of union nut included in the pump shown in  FIG. 1 . 
           [0047]      FIG. 31  is a top view of an alternate embodiment constant flow module. 
           [0048]      FIG. 32  is a top perspective view of the constant flow module shown in  FIG. 31 . 
           [0049]      FIG. 33  is a side cross-sectional view of the constant flow module shown in  FIG. 31 . 
           [0050]      FIG. 34  is a top perspective view of an alternate embodiment control module assembly, with a titanium enclosure top removed therefrom. 
           [0051]      FIG. 35  is another top perspective view of the control module assembly shown in  FIG. 34 , with a titanium enclosure and circuit board removed therefrom. 
           [0052]      FIG. 36  is an exploded view of an alternate embodiment motor and valve block assembly included in the control module assembly shown in  FIG. 34 . 
           [0053]      FIG. 37  is another exploded view of the motor and valve block assembly shown in  FIG. 34 , with certain portions removed therefrom. 
           [0054]      FIG. 38  is a schematic view of a medication pump with two resistor capillaries. 
           [0055]      FIG. 39  is a sectional view of a dual-resistor capillary pump. 
           [0056]      FIG. 40  is a perspective view of the internal components of another embodiment of a dual-resistor capillary pump. 
           [0057]      FIG. 41  is a sectional view of a portion of the pump illustrated in  FIG. 40 . 
           [0058]      FIG. 42  illustrates a perspective view of a valve block for a dual-resistor capillary pump. 
           [0059]      FIG. 43  illustrates the valve block of  FIG. 42  in partial phantom view. 
       
    
    
     DETAILED DESCRIPTION 
       [0060]    In describing the preferred embodiments of the subject matter illustrated and to be described with respect to the drawings, specific terminology will be used for the sake of clarity. However, the invention is not intended to be limited to any specific terms used herein, and it is to be understood that each specific term includes all technical equivalents which operate in a similar matter to accomplish a similar purpose. 
         [0061]    Referring to the drawings, wherein like reference numerals refer to like elements, there is shown in  FIGS. 1-7  a programmable implantable pump designated generally by reference numeral  10 . As shown in those figures, pump  10  includes a constant flow module assembly  12  (shown alone in  FIGS. 9-11 ), an enclosure top  14 , and a union nut  16  (shown alone in  FIG. 30 ). Moreover, as best shown in  FIG. 8 , where enclosure top  14  has been removed, pump  10  includes a control module assembly  18  engaged with the top portion of constant flow module  12 . 
         [0062]    In constructing pump  10 , control module assembly  18  is placed on top of constant flow module assembly  12 , and union nut  16  is threaded onto a threaded portion  20  of the constant flow module (best shown in  FIGS. 9-11 ). A flange  22  formed on control module assembly  18  (best shown in  FIGS. 12 and 13 ) allows for the control module assembly to be captured by the union nut  16  and thusly fixably attached to constant flow module assembly  12 . A gasket or the like (shown as element  50  in  FIGS. 9 and 10 ) may be placed between constant flow module  12  and control module assembly  18  so as to ensure a sealed fluid connection between the various corresponding ports of those two components (discussed more fully below). Finally, enclosure top  14  is preferably snapped over the construct to form pump  10  as shown in  FIGS. 1-7 . 
         [0063]    As is also shown in  FIGS. 1-7  (as well as other figures), pump  10  also includes suture apertures  24  and a catheter connector  26 , both on the constant flow module assembly  12 . The former are useful in fixing pump  10  within a patient&#39;s body, while the latter is preferably connectable with a longer, and in some cases more flexible, catheter that extends further within the patient&#39;s body. Catheter connector  26  preferably includes a strain relief  28  for reducing stresses and strains at or near the connection between catheter  26  and constant flow module assembly  12 . Such strain relief can be of any design as are known in the art, and in the embodiment shown, strain relief  28  is designed to slide over catheter  26  and connect with a portion of constant flow module  12 . 
         [0064]    The constant flow module operates in much of the same fashion as in previous pumps, including those taught in the aforementioned &#39;892 patent, as well as in other commonly owned patents such as U.S. Pat. Nos. 4,969,873, 5,085,656, 5,336,194, 5,836,915, 5,722,957, 5,814,019, 5,766,150 and 6,730,060, the disclosures of which are hereby incorporated by reference herein. Essentially, and as is shown more particularly in the cross-sectional view of  FIG. 11 , constant flow module assembly  12  includes a medication chamber  30  defined by an upper portion  32  of the constant flow module and a flexible membrane  34 , and a propellant chamber  36  defined by membrane  34  and a lower portion  38  of the constant flow module. Like in other pump designs, propellant chamber  36  may in actuality be defined as a propellant pillow consisting of membrane  34  and a lower membrane  34 A (not shown). As shown in  FIG. 11 , propellant chamber  36  is preferably filled utilizing a propellant pillow  37 , such as that taught U.S. Pat. No. 5,766,150 or U.S. patent application Ser. No. 12/947,187, the disclosures of which are hereby incorporated by reference herein. As is also shown in  FIG. 11 , upper portion  32  and lower portion  38  of the constant flow module assembly  12  are preferably screwed together, thereby capturing membrane  34  (and membrane  34 A) therebetween. Of course, in other embodiments, other connection means may be employed. 
         [0065]    As best shown in  FIGS. 9 and 10 , constant flow module assembly  12  further includes a catheter access opening  40  through which a portion (e.g., a shoulder shown as a portion of below-discussed gasket  50 )  42  of catheter  26  extends, a structure  44 , an exit  46 , and an entrance/exit  48 . More particularly, opening  40  acts to both allow direct injection of fluid through catheter access port and to accept fluid dispelled from control module assembly  18  (as will be discussed more fully below). Structure  44  preferably aids in creating a sealable connection between constant flow module assembly  12  and control module assembly  18  by creating a symmetrical upper surface of assembly  12 , thereby evenly spreading compression of a gasket (discussed below) between the two assemblies. Second exit  46  provides fluid to control module assembly  18  to be routed through a valve assembly (also discussed more fully below). Entrance/exit  48  allows for both medication to be injected into chamber  30  and a pressure reading to be taken by a pressure sensor (also discussed more fully below). Assembly  12  also includes a notch  49 . 
         [0066]      FIGS. 9 and 10  also depict component gasket  50  and circumferential antenna  52 . With regard to the former, the gasket is shown as a thin circular portion of silicone or the like which acts to seal around the various openings in flow module assembly  12 . Likewise, circumferential antenna  52  is shown as a circular component that fits over threaded portion  20  of the constant flow module and on top of a shoulder formed in the module. This shoulder is better shown in  FIG. 11 . The antenna is particularly useful in receiving signals emitted from a secondary device during operation or reprogramming of the pump. Circumferential antenna  52  includes a tab  53  which extends into notch  49  so as to be capable of cooperating with control module assembly  18 , as will be discussed more fully below. Finally, constant flow module  12  also includes union pins  54   a  and  54   b  for engagement with control module  18 . 
         [0067]    Turning now to  FIGS. 12-14 , a fully constructed control module assembly  18  is depicted. The module includes two titanium outer portions, namely, upper portion  56  and lower portion  58 . Above-discussed flange  22  is formed on lower portion  58 . A refill aperture  60  is formed through the center of upper portion  56 . A catheter access aperture  62  is formed offset from refill aperture  60 . As best shown in  FIG. 13 , refill aperture  60  allows for a needle to pierce a central septum  64 , while catheter access aperture  62  allows for a needle to engage screen member  66 . It is to be understood that screen member  66  is designed with a plurality of apertures that are sized so as to prevent needles having a certain size from extending therethrough. This allows for larger needles to be designated for a refill procedure (through central septum  64 ), while smaller needles are provided for catheter direct access. This is an added safety measure, that is discussed in application Ser. No. 13/276,469 entitled “Mesh Protection System,” and screen member  66  is similar to the like structure formed in that application. 
         [0068]      FIG. 14  depicts a view of lower portion  58  of module  18 . As shown, lower portion  58  includes several openings, including refill opening  70 , reception opening  72 , exit opening  74  and electronic access opening  76 . An alternate embodiment antenna assembly  77  is shown removed from within electronic access opening  76 , but with wires that attach the antenna to the module depicted. It is to be understood that pump  10  can utilize either antenna assembly depicted in the present application, both antenna assemblies, or an alternate assembly not shown herein. Moreover, union pin reception openings  78   a  and  78   b  are provided for receiving union pins,  54   a  and  54   b , respectively. Refill opening  70  serves two purposes, namely, allowing for fluid injected through refill aperture  60  to pass into chamber  30  through entrance/exit opening  48 , and allowing for access (as will be discussed below) to a pressure sensor disposed within module  18 . Reception opening  72  allows for fluid dispelled from exit  46  of constant flow module  12  to be introduced into a valve assembly disposed within module  18 . Exit opening  74  overlies opening  40  and shoulder  42  of constant flow module  12  in a fully assembled state. This allows for fluid ultimately dispelled from the valve assembly included within module  18  to flow through catheter  26 , and thusly to the patient. Finally, electronic access opening  76  provides a corridor for certain internal electronic structures discussed below to communicate with tab  53  of antenna  52 . 
         [0069]      FIGS. 15-17  depict module  18  with upper portion  56  removed therefrom. As shown, within its interior, module  18  includes a circuit board  80 , a first pressure sensor  82 , a second pressure sensor  84 , a valve block  86 , a motor assembly  88 , a buzzer  90 , and a flexible conductive element  92 .  FIGS. 16 and 17  depict similar views to  FIG. 15 , albeit from different perspectives. Circuit board  80  is held to a circuit board support  94 , which is better shown in  FIG. 18  where circuit board  80  is removed. Screws  96   a - 96   d  hold circuit board  80  to circuit board support  94 . Flexible conductive element  92  preferably provides electrical interconnection among circuit board  80 , first pressure sensor  82 , second pressure sensor  84 , motor assembly  88  and buzzer  90 . Module further includes a feed through  98 , which is also preferably connected with flexible conductive element  92 , and which extends through electronic access opening  76  on the bottom of module  18 . This element preferably provides the interconnection of the internals of module  18  with antenna  52 , specifically tab  53 . 
         [0070]    As noted above,  FIG. 18  depicts the internals of module  18  with circuit board  80  removed therefrom. In this view, it is shown that module  18  also includes batteries  100   a  and  100   b  for powering the pump. Also shown, is the interconnection among flexible conductive element and flexible conductive element  92  and both batteries.  FIG. 19  shows the internal structure of module  18 , this time with circuit board support  94  removed therefrom. In this figure, the configuration and interconnection among the elements and flexible conductive element  92  are further depicted. In the embodiments shown, flexible conductive element is constructed of a polymide material, but can be any other conductive element, including wires or the like. Also more clearly shown in  FIGS. 18 and 19  is the connection between motor assembly  88  and lower portion  58 . Specifically, a set screw  102  is provided at one end of the motor assembly and threaded into a portion of lower portion  58 . Moreover,  FIG. 19  shows apertures  104   a - d , which are designed to accept screws  96   a - 96   d , respectively. Thus, circuit board is held tightly not only to circuit board support  94 , but also lower portion  58 . 
         [0071]      FIG. 20  depicts module  18  in a similar view to that of  FIG. 19 , but with flexible conductive element  92  and batteries  100   a  and  100   b  being removed therefrom. In this view, a capacitor  106  is shown. This component allows for the generation of higher voltage than batteries  100   a  and  100   b  themselves. In general, capacitor  106  operates like a standard capacitor, storing charge for use in powering the pump. It is to be understood that capacitor  106  could be removed depending upon the particular batteries that are utilized. For instance, batteries that generate higher voltages and less current typically will negate the need for a capacitor. However, batteries suitable for inclusion in module  18  tend to be produced in the lower voltage range (3.2V-3.8V). Moreover, smaller capacitors could be included on circuit board  80  to achieve the same goal as capacitor  106 . 
         [0072]    FIGS.  21  and  25 - 29  focus on valve block  86 , its internal components, and its cooperation with motor assembly  88 . As shown, valve block  86  includes a pressure sensor receiving aperture  106 , as well as catheter access aperture  62 . Pressure sensor receiving aperture  106  is designed to receive second pressure sensor  84 , as well as allow for fluid to come into contact with that pressure sensor. Valve block  86  also includes a first body portion  108  and a second body portion  110 . First body portion  108  includes apertures  62  and  106 , as well as several fluid passageways and a valve receiving channel (best shown in  FIG. 28 ) for allowing fluid flow within the valve block and ultimately to the patient. Second body portion  110  is essentially a hollow cylindrical body, the interior of which is designed to receive a portion of the valve. This again is best shown in  FIG. 28 , with  FIG. 26  depicting a front view of same. It is noted that valve block  86  is depicted by itself in  FIGS. 25-27 , with  FIG. 27  depicting a bottom surface thereof. As shown in that drawing, apertures  62   a  and  106   a  cooperate with the above discussed apertures  62  and  106 , respectively. 
         [0073]    As also shown in  FIG. 21 , motor assembly  88  is connected with valve block  86  by two screws  112   a  and  112   b , which extend through apertures in a flange portion  114  of the motor assembly, and into apertures  116   a  and  116   b , respectively, of the valve block (best shown in  FIG. 26 ). This cooperation fixably connects motor assembly  88  with valve body  86 . As noted above, motor assembly  88  is also connected to module  18  via set screw  102 . Likewise, valve block  86  is connected to other portions of module  18  via pin  118 , as best shown in  FIG. 26 . That pin preferably includes a bulbous head portion that, once inserted within a hole in module  18 , acts to prevent removal of the valve block. 
         [0074]      FIG. 22  depicts motor assembly  88  without valve body  86 , and highlights the portions of the assembly that extend into the valve body. Specifically, motor assembly  88  includes a bellows  120 , valve  122 , and an o-ring  124 . Bellows  120  is preferably welded to weld ring  126 , which in turn is welded to flange  114 . Likewise, bellows  120  is preferably welded to valve at surface  128 . Referring now to  FIG. 23 , in which bellows  120  is removed, it is shown that valve  122  consists of a valve stem  130  which extends through a valve bushing  132 . It is around this valve bushing that o-ring  124  is disposed. Valve stem  130  includes at a distal end a tapered portion.  FIG. 24  on the other hand depicts the assembly with a motor housing  134  removed therefrom. In this view, weld ring  126  is clearly shown. Also shown is a motor mount plug  136  which screwably connects with motor housing  134 . 
         [0075]    Motor  89  of motor assembly  88  is preferably a piezoelectric motor, as such a motor does not include a permanent magnet, which makes the motor MRI compatible. In addition, piezoelectric motors are generally of a smaller size and require less energy for operation. Still further, piezoelectric motors operate in a straight line, which is ideal in the present instance, as will be discussed below. However, it is to be understood that motor  89  could be other types of motors, including stepper motors or the like. Of course, certain of the above-mentioned benefits of the piezoelectric motor may not be met by such alternate motor designs. Operation of motor  89  imparts a force upon valve stem  130 , which moves within second body portion  110  of valve block  86 . The combination of bellows  120  and o-ring  124  insures that any fluid flowing within valve block  186  cannot seep outside of that component. In other words, bellows  120  and o-ring  124  insure a sealable connection between motor assembly  88  and valve block  86 . As is shown in  FIGS. 28 and 29 , the most distal portion of valve stem  130  extends within the fluid flow path, and the conical nature of that distal portion provides that movement of the valve stem results in greater or lesser fluid flow threw valve block  86 . The inclusion of a stepper motor such as the one discussed above insures that fine adjustments of flow rate through the valve block can be realized. In fact, movement of the valve relates in a linear or near linear fashion to the flow rate. The above-discussed sealable nature of bellows  120  and o-ring  124  insures hermetic sealing within the valve block, and thusly prevents fluid from flowing anywhere other than the valve block. This is particularly important given the other components of module  18 . 
         [0076]    In the embodiment shown, valve stem  130  and valve portion  132  are shown as constructed of titanium material. It is to be understood that any suitable material may be employed. Moreover, it is to be understand that valve stem  130 , at its most distal end, could include a silicon covering or the like in order to insure a full closure of the valve if desired. Likewise, while o-ring  124  as shown as being constructed of a silicon material, any other suitable material may be employed. For instance, Teflon may be employed, as can a material known as PORON®. 
         [0077]    In operation, fluid dispelled from chamber  30  (under pressure provided by chamber  36 ) travels through both exits  46  and  48 . The fluid dispelled through exit  48  is preferably directed into contact with first pressure sensor  82 , so a pressure reading of the fluid within chamber  30  can be taken. The fluid dispelled through exit  46  preferably first travels through a filter and capillary construction, as are known in the art. In one example of such a structure, a filter and capillary are coiled around an underside of upper portion  32 . Fluid flows through the filter, which is designed to prevent particulates and other undesirable matter of flowing into the capillary, and thereafter flows through the capillary, which is essentially a very small tube with a small diameter that allows a maximum flow rate of fluid therethrough. That fluid then flows through aperture  106   a  and into the passages provided in valve block  86 . Second pressure sensor  84  takes a pressure reading of the fluid within the valve block. 
         [0078]    Once within valve block  86 , the fluid flows into contact with the distal end of valve stem  130 . Depending upon the positioning of the valve stem, the flow of the fluid will either be reduced or remain the same as the maximum flow rate dictated by the aforementioned capillary. Second pressure sensor  84  is positioned to take a reading of the pressure before the valve portion, and thusly the comparison of the readings taken by first pressure sensor  82  and second pressure sensor  84  can be utilized to determine the actual flow rate of the fluid after passing through the resistor and the valve. This is preferably determined by circuit board  80 , as sensors  82  and  84  are electrically connected thereto by flexible conductive element  92 . If the flow rate is not desired, motor  89  can be operated to vary the position of valve stem  130 . Subsequent to contacting the valve, fluid flows through other passages formed in valve block  86 , through aperture  62   a  and ultimately through catheter  26 . Depending upon the placement of the catheter within the patient, the fluid is delivered to the desired portion of the patient in which the catheter is directed. 
         [0079]    It is to be understood that pump  10  preferably operates with little outside interaction required. Aside from refilling chamber  30  with an active substance, a doctor or other medical professional likely only needs to interact with the pump in order to set a desired flow rate. This may be accomplished through the use of a wand or other transmitter/receiver (not shown) that interfaces with antenna  92 . Once the flow rate is set, pump  10  preferably operates on its own to maintain the flow rate. Pump  10  may also be programmed to provide different flow rates at different times of the day. For instance, patients may require lesser doses of pain medication while sleeping, and heavier doses of pain medication upon waking up. Similarly, diabetic patients may need higher doses of insulin prior to eating a meal or lower doses of insulin during heavy exercise. Circuit board  80  can be designed to allow for such programming. Above-noted buzzer is designed to emit an audible warning upon certain conditions, including low battery, low fluid level within chamber  30 , low or high temperature conditions, and high pressure, which may indicate overfilling of chamber  30 , low pressure differential across the resistor capillary or blockage within catheter  26 . Upon recognizing the audible sound, the patient can contact his or her medical professional. 
         [0080]    Valve  122  may also include a positioning sensor (not shown) or the like associated therewith. Such a sensor may be capable of providing information relating to the positioning of the valve to circuit board  80 . Such positioning sensors can include many different designs. For example, light reflective technology can be employed to determine at any given moment the position of the valve. Likewise, valve  122  may be provided with one or more conductive elements that interact with conductive elements provided on or near valve block  86 . The completion of an electrical circuit in such a case can indicate the positioning of valve  122 . Still further, the positioning sensor can take the form of an induction coil capable of determining the positioning of the valve therein. A slide potentiometer may also be employed, as can a stack switch. 
         [0081]    During a refill procedure, pump  10  can be monitored through the use of the wand or other transmitter/receiver. A computer program associated with such device and pump  10  can indicate to the doctor whether the refill needle is correctly placed within the pump. Known problems with refilling implantable pumps are misapplications of a refill needle to the tissue of the patient (so called pocket fills) and to a bolus opening such as catheter access aperture  62 . Directly injecting a patient with a dose of medication meant for prolonged release from chamber  30  can have dire consequences. During the monitoring of the refill procedure, a quick change in pressure within chamber  30  can be recognized by the medical professional, thereby ensuring placement of the needle within refill aperture  60 . This is a significant safety feature in pump  10 . 
         [0082]    The exterior portions of pump  10  are preferably constructed of PEEK, including constant flow module assembly  12 , enclosure top  14  and union nut  16 . On the other hand, the exterior portions of control module assembly are constructed of titanium, which ensures the hermetic nature of that component. However, certain interior portions of the module are also constructed of PEEK, including circuit board support  94 . While these are indeed the materials utilized in the construction of a preferred pump  10 , other materials may be employed in other embodiments. For instance, other polymeric materials may be employed that provide for similar strength, while maintaining the low overall weight provided for by the PEEK material. Likewise, other metallic materials may be substituted for titanium, such as stainless steel or the like. The only limitation is that the materials selected should be bio-compatible to ensure such are not rejected by the patient after implantation. 
         [0083]    Several variations of above-discussed pump  10  will now be discussed. It is to be understood that all or some of these variations may be incorporated into an implantable pump according to the present invention. Where possible, like elements to those discussed above are referred with reference numerals in a different 100-series of numbers. 
         [0084]    For instance,  FIG. 31  depicts a top portion of an alternate embodiment constant flow module  312 , which includes a differently shaped gasket  350 . That gasket has been removed from  FIG. 32 . In this embodiment, a portion  342  stands alone as part of catheter  326 .  FIG. 33  depicts a side cross section of constant flow module  312 . As is seen in this view, module  312  differs from that of module  12  in that a bottom thereof is no longer contoured, but rather, exhibits a flat configuration. Constant flow module  312  has also been provided with two o-rings  313   a  and  313   b . Where ring  313   a  ensures a sealing of the propellant and medication chambers of module  312 , ring  313   b  ensures no material can leak from module  312 . Still further, module  312  includes holes  315   a - c . Hole  315   a  preferably receives a pin or the like (not shown) that acts to prevent the two housing portions included in module  312  from inadvertently disengaging by preventing unscrewing of those portions. On the other hand, holes  315   b  and  315   c  aid in connecting those portions to each other. Specifically, holes  315   b  and  315   c  are capable of interfacing with a tool for use in screwing the module portions together. Of course, other embodiments may include any number of similar holes. 
         [0085]      FIG. 34  depicts an alternate embodiment control module assembly  318  in which an element similar to the above-discussed flexible conductive element  92  has been eliminated. In this embodiment assembly  318 , a circuit board  380  acts to connect all of the electrical elements of the module.  FIG. 35  depicts the module  318  with circuit board  380  removed. 
         [0086]      FIGS. 36 and 37  depict alternate embodiment valve block  386  and motor assembly  388 , as well as the cooperation of those two elements. The major differences between this embodiment and those discussed above lies in several areas. For one, valve  422  includes a valve stem  430 , which includes an overmolded silicone valve tip  432 . This tip ensures full seating within a valve seat (not shown) located in block  386 , as well as allows for fine adjustment of flow rates therethrough. In addition, motor assembly  388  includes a solid housing  434 , and does not include a portion similar to plug  136 . Finally, motor  389  is held in place by clamp elements  389   a  and  389   b . Both elements are fitted into or onto different portions of the motor and thereafter affixed to block  386 , preferably through the use of epoxy. 
         [0087]      FIG. 38  illustrates a schematic view of an alternate embodiment of a pump  510 . Pump  510  is structurally similar to other embodiments described above in many ways, but may include features particularly adapted for use in implantable insulin pumps. For example, the pump  510  may include a first resistor capillary  511  and a second resistor capillary  513 . The first resistor capillary  511  may be, for example, a low flow resistor capillary. This first resistor capillary  511  may be smaller than one used for a pump with pain medicine, as the basal delivery rate for insulin may be significantly less than the basal delivery rate for pain medicine in patients. However, to be able to reach the higher delivery rates of insulin that may be required during bolus delivery, a second resistor capillary  513  may be a high flow resistor capillary, larger than the first resistor capillary  511  and larger than resistor capillaries that may be used in pumps that deliver pain medicine. 
         [0088]    Both the first and second resistor capillaries  511 ,  513  are in fluid communication with a medication chamber  530 , which may include one of various drugs. Preferably, the medication chamber  530  contains a drug useful in the treatment of diabetes, such as insulin or an insulin analog or derivative. As in embodiments described above, a first pressure sensor  582  is located in the pump housing in fluid communication with medication chamber  530  and is configured to take a pressure reading of the fluid in the medication chamber. A first end of the first resistor capillary  511  is in fluid communication with the medication chamber  530 , and a second end of the first resistor capillary is in fluid communication with a second pressure sensor  584 . Similarly, a first end of the second resistor capillary  513  is in fluid communication with the medication chamber  530 , and a second end of the second resistor capillary  513  is in fluid communication with the second pressure sensor  584 . The second pressure sensor  584  is similar to that described in embodiments above, and is configured to take a second pressure reading of the medication fluid upon exiting one or both of the resistor capillaries. 
         [0089]    A shut-off valve  515  may be interposed between the first and second ends of the second resistor capillary  513 . The shut-off valve  515  may alternately be positioned after the second end of the second resistor capillary  513 . The shut-off valve  515  may be configured to allow a user to selectively interrupt the fluid communication between the second resistor capillary  513  and the second pressure sensor  584 , as well as the remainder of an outflow portion of the pump  510 . The shut-off valve  515  may be operably connected to electronics within the pump  510 , for example a motor drive  517 , that communicates with the shut-off valve, causing the shut-off valve to alternate from an open position to a closed position, or vice versa. In one embodiment, the motor drive  517  that operates the shut-off valve  515  also operates the valve block  586  in a similar fashion as described above. The motor drive  517  may alternately communicate between the shut-off valve  515  or the valve block  586 , for example, depending on the status of a switch  519 . 
         [0090]    In operation, the pump  510  works much the same as in embodiments described above. Insulin or other fluid dispelled from the medication chamber  530  (under pressure provided by a propellant chamber) travels through a filter capillary, as is known in the art, and into a first resistor capillary  511  and a second resistor capillary  513 . The fluid is also forced into contact with a first pressure sensor  582 , which may be effected in the manner described above in relation to other embodiments of the pump. This allows a pressure reading of the medication chamber  530  to be taken. If the shut-off valve  515  is in the closed position, fluid in the second resistor capillary  513  does not pass the shut-off valve  515 . Fluid in the first resistor capillary  511  flows through an aperture, as described above in other embodiments of the pump, and into passages provided in valve block  586 . The second pressure sensor  584  takes a pressure reading of the fluid within the valve block  586 . The fluid continues traveling through the pump  510  and in to the patient in the same or a similar manner as described above with relation to other embodiments of the pump. 
         [0091]    When the shut-off valve  515  is in the closed position, the maximum flow rate is limited by the maximum flow rate of the smaller first resistor capillary  511 . The flow rate may be further decreased, as described above, using valve block  586 . If the shut-off valve  515  is in the open position, the second resistor capillary  513  is in fluid communication with the remainder of the pump  510  and fluid travels through the second resistor capillary  513 , feeding into the valve block  586  and eventually the patient. Generally, it is contemplated that the shut-off valve  515  would be switched to the closed position during delivery of a medicine at a basal rate, while the shut-off valve would be switched to the open position during delivery of medicine at a bolus rate that is greater than the basal rate. The higher bolus rate may be useful, for example, just prior to a diabetic patient eating a meal. 
         [0092]    In cases in which the shut-off valve  515  is open and in which the second resistor capillary  513  is much larger (in inner diameter) than the first resistor capillary  511 , the maximum flow rate of the fluid into the patient is essentially the maximum flow rate allowed by the second resistor capillary  513 . Even though fluid is flowing through both resistor capillaries  511 ,  513 , the second resistor capillary will often be so much larger than the first resistor capillary that the additional flow rate provided by the first resistor capillary is negligible compared to the maximum flow rate of the second resistor capillary. 
         [0093]    An additional shut-off valve (not illustrated) may be provided between the first and second ends of the first resistor capillary  511 , such that the first resistor capillary could be blocked when the second resistor capillary  513  is opened. This may help ensure very precise maximum flow rates if desired, but may be generally unnecessary when the maximum flow rate of the second resistor capillary  513  is much larger than the maximum flow rate of the first resistor capillary. 
         [0094]    As described in other embodiments of the pump, the pressure readings taken from the first and second pressure sensors  582 ,  584  may provide information about flow rate to decide whether, and to what degree, the flow rate should be slowed by changing the position of the valve block  586 . In the proposed method with two resistor capillaries, no additional pressure sensors are required in addition to the prior art with single resistor capillary. This is achieved through software wherein based on the position of shutoff valve, the equations for computing flow rates are adjusted accordingly using the same two pressure sensors. Also as in other embodiments described herein, a catheter access aperture  562  may be provided to allow direct injection of a fluid into the catheter  526 , bypassing the majority of the pump  510 . 
         [0095]      FIG. 39  illustrates a cross section of one embodiment of the pump  510 . The pump is similar to those described above, with a vertical shut-off valve  515 . The shut-off valve  515  is controlled by an actuator, such as a membrane piezoelectric actuator  516 . As described above, when the actuator  516  is in a first position, the shut-off valve  515  allows the medication fluid through the second resistor capillary  513  and into the valve block  586 . When the actuator  516  is in a second position, the shut-off valve  515  blocks the medication fluid from flowing through the second resistor capillary  513  and into the valve block  586 .  FIGS. 40-41  illustrate another embodiment of the pump  510  with an alternate shut-off valve  515 ′ and actuator  516 ′. In this embodiment, the shut-off valve  515 ′ is driven by a linear piezoelectric actuator  516 ′ to block or allow flow from the second resistor capillary  513 . 
         [0096]    An embodiment of the valve block  586  is illustrated in  FIGS. 42-43 .  FIG. 43  particularly illustrates one embodiment of fluid flow pathways. Fluid flowing through the second resistor capillary  513  flows into the valve block  586  through high-flow inlet  600 . When the shut-off valve  515  is open, the fluid continues through the high-flow outlet  602  into the valve block  586 . Similarly, fluid flowing through the first resistor capillary  511  enters the valve block  586  through low-flow inlet  604 . The fluid entering through the high-flow outlet  602  and the low-flow inlet  602  enters into a chamber where the fluid may mix. From that chamber, the combined fluid continues through the valve block  586  through combined inlet  606 , where the fluid flow may be further restricted in essentially the same fashion as described above with reference to valve block  86 . The fluid continues through the valve block  586  and exits the pump  510  through delivery outlet  608 . This fluid is delivered in essentially the same fashion as described above with relation to the pain medication exiting the pump through a delivery catheter. 
         [0097]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.