Abstract:
A pump for pumping drugs, medicaments or other liquids is disclosed having suture loops co-extensive with the outside wall of the pump. At least one depression is formed in the outside wall of the pump to strengthen the wall.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to apparatus for delivering fluid drugs, medicaments or other medicinal liquids to a desired location within a human body and more particularly relates to means for reinforcing the surface structure of such devices. 
     2. Description of Related Art 
     A number of approaches have been followed in the prior art for the dispensing of medical substances in the body. One particularly effective method has been to implant a reservoir of fluid medical substances and a pump in a patient&#39;s body. The reservoir and pump are connected to a catheter that delivers the fluid medical substance to a desired location in the body. 
     A number of reservoirs, pumps and combinations of reservoirs and pumps have been developed. For example, U.S. Pat. No. 3,527,220 shows an implantable drug administrator that operates with a refillable bladder reservoir and a roller pump that is driven by a magnet located outside the body. U.S. Pat. No. 3,951,147 shows a reservoir formed from a bellows enclosed within a housing. The contents of the reservoir are pressurized by a fluorocarbon fluid located in the space between the housing and bellows. The unit continuously dispenses the liquid to the body site through a capillary tube. 
     U.S. Pat. No. 4,146,029 shows a dispenser that dispenses drugs in a predetermined manner which may be modified somewhat by means external to the body. A piston and bellows pumping device is used to dispense the drug. 
     Additional pumps and reservoirs are shown in U.S. Pat. No. 4,931,050, issued Jun. 5, 1990 to Samir F. Idriss entitled “Constant Pressure Variable Flow Pump”; U.S. Pat. No. 4,838,887, issued Jun. 5, 1990 to Samir F. Idriss entitled “Programmable Valve Pump”; U.S. Pat. No. 4,714,462, issued Jun. 5, 1990 to Robert A. DiDomenico entitled “Positive Pressure Programmable Infusion Pump”; U.S. Pat. No. 4,714,462, issued Jun. 5, 1990 to Samir F. Idriss entitled “Passive Shuttle Metering Device For Implantable Drug Delivery System”; and U.S. Pat. No. 5,176,641 issued Jan. 5, 1993 to Samir F. Idriss entitled “Implantable Drug Infusion Reservoir Having Fluid Impelling Resilient Foam Member”. 
     Further pumps and reservoirs are shown in U.S. Pat. No. 5,575,770 issued Nov. 19, 1996 to Gerald S. Melsky and Bradley J. Enegren entitled “Implantable Drug Infusion System With Safe Bolus Capability”; U.S. Pat. No. 4,978,338 issued Dec. 18, 1990 to Gerald S. Melsky and Frank R. Prosl entitled “Implantable Infusion Apparatus”; U.S. Pat. No. 5,908,414 issued Jun. 1, 1999 to Karl-Heinz Otto, Manfred Wieland, Hans Baumann and Jorg-Roger Peters entitled “Implantable Infusion Pump”; and U.S. Pat. No. 5,769,823 issued Jun. 23, 1998 to Karl-Heinz Otto entitled “Implantable Infusion Pump”. The collective teachings of the patents listed above are incorporated herein in their entireties by reference. 
     A number of approaches have been followed in the prior art for the dispensing of medical substances in the body. One particularly effective method has been to implant an implantable infusion pump  10  (FIG. 1) in a patient&#39;s body. The pump  10  has a reservoir  12  for storing the medical substances in the pump  10 . Pump  10  is connected to a catheter  14  that delivers the fluid medical substance from the reservoir  12  to a desired location in the body. Such a pump  10  and catheter  14  combination is able to deliver the medical substance to a specific site in the body in tightly controlled, yet minute dosages. Both the pump  10  and catheter  14  are implanted within the body. 
     A typical pump  10  for storing and delivering fluid medicaments to a desired location in a body according to the present invention is shown in cross-section in FIGS. 2 and 3. As mentioned above, pump  10  stores and dispenses medical substances from a reservoir  12 . Reservoir  12  is formed by a reservoir structure  16  having a reservoir structure upper end  18  and a reservoir structure terminal end  20 . Reservoir structure  16  is typically a bellows  22  having pleated sides  24  and a substantially planar bottom  26  sealingly connected to the sides  24 . Pleated sides  24  are made up of a series of inwardly directed annular rings  28  and outwardly directed annular rings  30  sealingly connected at inner connection points  32  and outer connection points  34 . In the typical pump  10 , bellows  22  terminates at its upper end  18  with an ultimate inwardly direct annular ring  36 . Ultimate inwardly direct annular ring  36  terminates in a bellows terminal end  38  so that the bellows terminal end  38  is the reservoir structure terminal end  20  for a bellows type reservoir structure  16 . Bottom  26  is usually circular so that bellows  22  is cylindrical. Because bellows  22  is cylindrical, bellows terminal end  38  is annular. 
     Bellows terminal end  38  is connected to an annular bracket  40 . Viewed in cross-section, bracket  40  has a horizontal leg  42 . Horizontal leg  42  has an inner terminal end  43  and an outer terminal end  44 . Bellows terminal end  38  is connected to bracket  40  at  45  near the inner terminal end  43  by means well understood in the art such as welding. Annular bracket  40  also includes a vertical leg  46 . Vertical leg  46  has an upper terminal end  47  and a lower terminal end  48 . Horizontal leg  42  and vertical leg  46  are joined at outer terminal end  44  and upper terminal end  47 , preferably by bending annular bracket  40  at outer terminal end  44  and upper terminal end  47  or by forming annular bracket to bend at outer terminal end  44  and upper terminal end  47 . Bracket  40  greatly eases the manufacturing process of pump  10  as will be described hereafter. 
     Pump  10  also includes a bulkhead  50  having a top surface  52 , a bottom surface  54  and an outer periphery  56 . Pump  10  includes a metering system  58  usually attached to the top surface  52  of bulkhead  50 . Metering system  58  may take the form of a peristaltic pump, a piston pump, a tubular or micro-machined capillary flow restrictor, a piezoelectric micropump or other metering means as will clear to those skilled in the art. Metering system  58  is connected to reservoir  12  through an output conduit  60 . 
     The bottom surface  54  of bulkhead  50  includes an annular recess  62  extending into bulkhead  50  toward top surface  52 . Recess  62  has an inner vertical wall  64  and a horizontal wall  65  connected together at  66 . Recess  62  also has an outer vertical wall  67  connected to the horizontal wall  65  at  68 . Horizontal leg  42  is about the same length as horizontal wall  66  while vertical leg  46  is about the same length as outer vertical wall  67 . Bellows  22  is attached to bulkhead  50  at recess  62  by bracket  40  as described below. 
     Pump  10  also typically has a primary seal-sealing septum  70  through which a drug, fluid or other medicament is placed in the reservoir  12 . A hypodermic needle can be inserted through the skin and through the primary seal-sealing septum  70  into a chamber  72  that is connected to reservoir  12  through an inlet conduit  74 . Through the hypodermic needle, a quantity of a liquid agent, such as a medication, a growth factor, an antisense agent, an ionic solution, one or more antibodies, a hormone, proteins or peptides, viruses, cell suspension, a chemotherapeutic agent or toxin or some drug is inserted into the reservoir  12 . The liquid agent is then delivered from reservoir  12  through the metering system  58  and through catheter  14  that is attached to pump  10  through a catheter conector  76  that is attached to the metering system  58 . The catheter  14  is positioned to deliver the agent to infusion sites in the patient&#39;s body. 
     Pump  10  may also have a catheter access port septum  78  through which a bolus injection of drug, fluid or other medicament may be administered directly to the patient through the catheter  14 , bypassing the metering system  58 . Catheter access port septum  78  may also be used to take a sample of cerebrospinal fluid (CSF) from catheter  14  or for checking the patency of catheter  14  in the event of a loss of therapeutic benefit. 
     Pump  10  also includes an upper case  80  and a lower case  82  that substantially defines the outer dimensions of pump  10  and protects the inner parts, bellows  22 , bulkhead  50  and metering system  58 , of pump  10 . Upper and lower cases  80 ,  82  are typically attached to the bulkhead  50  at the outer periphery  56  of the bulkhead  50  by means such as welding. Lower case  82  has a bottom surface  86  and a side wall  88 . 
     A propellant chamber  90  is placed between lower case  82  and the reservoir structure  16 . A propellant gas is place in propellant chamber  90 . The propellant gas acts as a pressure-providing means to the reservoir structure  16  that compresses the reservoir structure  16  to discharge the drug or other agent stored in the reservoir  12 . The propellant gas used to drive such a “gas driven” pump  10  is a fluid that is in phase change between a liquid state and a gas state when, i.e., in equilibrium between phases at around 35-37 degrees (Celsius), which is the usual temperature range of the human body. 
     In a particular type of pump  10 , metering system  58  takes the form of a tubular or micro-machined capillary flow restrictor. In such a pump, the medical substance is dispensed from the reservoir  12  at a constant rate that depends primarily on the geometry of the tubular or micro-machined flow restrictor. In such a pump  10 , it is relatively important that the pressure in propellant chamber  90  be maintained at a higher pressure than is necessary in a pump  10  having a metering system  58  comprising a peristaltic pump, a piston pump or a piezoelectric micropump. For example, the propellant pressure in a peristaltic pump such as the Synchromed® pump manufactured and sold by Medtronic, Inc. of Minneapolis, Minn. is about 0.276 bar (4.00 Psi). On the other hand, the propellant pressure in a constant rate pump having a tubular flow restrictor such as the Isomed® pump also manufactured and sold by Medtronic, Inc. of Minneapolis, Minn. is about 2.10 bar (30.46 Psi). The reason for a higher pressure in the propellant chamber  90  in a constant rate pump  10  with a capillary tube flow restrictor is that this higher pressure reduces the variability in flow rates of the drug or other agent due to atmospheric conditions such as barometric pressure. 
     In manufacturing pump  10 , the bellows terminal end  38  of bellows  22  is attached to the horizontal leg  42  of bracket  40  near the inner terminal end  43  by means such as welding. Since both bellows terminal end  38  and bracket  40  are annular, bellows terminal end  38  is connected to bracket  40  around an annular path as connection point  45  is moved around horizontal leg  42 . At this stage of the manufacturing process, access to connection point  45  is relatively free since bellows  22  has not yet been joined to bulkhead  50 . 
     Once bellows terminal end  38  has been joined to horizontal leg  42  of bracket  40 , bracket  40  is moved onto horizontal wall  66  of recess  62 . As described above, horizontal leg  42  is about the same length as horizontal wall  66 . This allows bracket  40  to be moved into recess  62  so that the inner terminal end  43  of horizontal leg  42  comes into contact with horizontal wall  66 . In this position, vertical leg  46  also comes into contact with outer vertical wall  67 . Bracket  40  is then connected to the recess  62  at lower terminal end  48  by means such as welding around the entire annular lower terminal end  48 . In this way, bellows  22  is sealingly attached to bulkhead  50  at lower terminal end  48  of bracket  40 . 
     After a pump  10  is manufactured and before the pump  10  can be used as a medical device, the pump  10  must be thoroughly sterilized. One part of the sterilization process involves heating the pump  10  to a relatively high temperature for a relatively long period of time with the propellant in the propellant chamber  90 . For example, in the Isomed® pump mentioned above, the pump  10  is heated to about 124 Celsius (255.2° F.) for about 30 minutes. This heating results in an increase in the pressure in the propellant chamber from about to about 7 bar (101.5 Psi). This pressure is exerted, among other parts of the pump  10 , on the lower case  82 . 
     If the walls of the lower case  82  have the same thickness everywhere, as the pressure increases in the propellant chamber  90 , the walls of the lower case  82  often deforms or bulges out under the pressure. This is clearly not a desirable condition. 
     To remedy this deformation problem, a reinforcing plate  92  has been added to the bottom surface  86  of lower case  82 . Reinforcing plate  92  is typically a disk shaped or annular plate that is either attached to the bottom surface  86  or formed in the bottom surface  86 . Reinforcing plate  92  substantially covers the entire bottom surface  86  and has a thickness such that reinforcing plate  92  prevents deformation of the lower case  82 . Reinforcing plate  92  is typically welded to the bottom surface  86 . Reinforcing plate  92  has the effect of creating a thicker portion of the bottom surface  86  where the reinforcing plate is present than would be present were not the reinforcing plate  92  used. Because the bottom surface  86  is thicker with reinforcing plate  92 , bottom surface  86  is able to more easily withstand the high pressures caused by the heating process without the undesirable deformation. 
     Unfortunately, the function of strengthening the bottom surface  86  by the reinforcing plate  92  is needed only during the heating process. After the heating process is complete, the reinforcing plate  92  merely adds size and weight to the pump  10 . Further, the addition of a reinforcing plate  92  adds a part and requires the additional manufacturing step of welding the reinforcing plate  92  to the bottom surface  86 . It is desirable to make the pump  10  as small and light as possible and as cheap and easy to manufacture as possible. Therefore, it is highly desirable to make a pump  10  that may be autoclaved without buckling the lower case  82  and that does not require a reinforcing plate  92 . 
     SUMMARY OF THE INVENTION 
     A pump for pumping drugs, medicaments or other liquids is disclosed having surface recesses placed in the outer surface of the lower case. The recesses reinforce the lower case sufficiently to remove a reinforcing plate. 
     It is therefore an object of the present invention to provide a pump that does not require a reinforcing plate to allow the lower case to withstand the pressure of heating the pump as part of the sterilization process. 
     These and other objects of the invention will be clear from the description of the invention contained herein and more particularly from the description in conjunction with the drawings attached hereto. Throughout this description, wherever referred to, like elements are referred to by like reference numbers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages of the present invention will become more apparent by referring to the following detailed description and accompanying drawings, in which: 
     FIG. 1 is a schematic view of a typical pump and catheter. 
     FIG. 2 is a side cross-sectional view of a typical prior art drug pump with a reinforcing plate. 
     FIG. 3 is a close-up side cross-sectional view of the prior art drug pump of FIG.  2 . 
     FIG. 4 is a top view of the lower case of the drug pump of FIG.  2 . 
     FIG. 5 is a perspective view of the bottom of the drug pump of the present invention. 
     FIG. 6 is a bottom view of the lower case of the drug pump of FIG.  5 . 
     FIG. 7 is a bottom view of an alternate embodiment of the drug pump of FIG.  5 . 
     FIG. 8 is a bottom view of an alternate embodiment of the drug pump of FIG.  5 . 
     FIG. 9 is a side cross-sectional view of the lower case of the drug pump of FIG.  5 . 
     FIG. 10 is a side cross-sectional view of an alternate embodiment of the lower case of the drug pump of FIG.  5 . 
     FIG. 11 is a side cross-sectional view of an alternate embodiment of the lower case of the drug pump of FIG.  5 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 5-9, a drug pump  10  incorporating the present invention is shown. As can be seen, pump  10  has a lower case  82  having an outside wall  94 , an interior  96  and central axis  98 . In the embodiment shown in FIGS. 5-9, pump  10  is substantially disk shaped with bottom surface  86  of lower case  82  transitioning to side wall  88  at  100 . Side wall  88  is roughly equidistant from the central axis  98 . 
     Although pump  10  is shown as being disk shaped to illustrate the present invention, this is not a requirement for the present invention. In fact, any shape for pump  10  may make use of the present invention so long as pump  10  has an outside wall  94 . In pumps that are not disk shaped, central axis  98  merely indicates an approximate center of pump  10 . 
     In the present invention, the outside wall  94  of pump  10  contains at least one depression  102  that extends inwardly from the outside wall  94  toward the interior  96 . In the preferred embodiment, several depressions  102  are located at sites on the outside wall  94 . For example, FIG. 6 shows three depressions  102  equally spaced around the outside wall  94 . More or fewer depressions  102  may be used as desired. For example, FIGS. 7-8 show four and eight depressions  102  to show but a few possible variants. Further, the depressions  102  may also be non-equally spaced. 
     Depressions  102  are preferably shallow depressions in the lower case  82  forming a depression surface  104 . In the embodiment shown in FIGS. 5-9, depressions  102  are formed in the lower case  82  in both the bottom surface  86  and side wall  88  where the side wall  88  transitions to the bottom surface  86  of pump  10 . Also in the embodiment shown in FIGS. 5-9, the depression surface  104  is convex with respect to the interior  96  of pump  10 . Alternately, the depression surface  104  may be concave with respect to the interior  96  of pump  10  or any other shape so long as the depression surface  104  forms a depression  102 . 
     Depressions  102  may have any depth toward the interior  96  from the bottom surface  86  or side wall  88  although a preferable depth of depressions  102  is about 1.5-2.00 mm measured from the outside wall  94  toward the interior  96 . It is recognized that depressions extend into the interior  96  into the propellant chamber  90 . As a result, the only limitation on the depth of depressions  102  is the deformation capability of the material of the lower case  82  and the desire to preserve space in the propellant chamber  90  resulting from the intrusion of depressions  102  into propellant chamber  90 . 
     Where depressions  102  are formed in the bottom surface  86  of lower case  82 , depressions  102  preferably extend a significant distance toward the central axis  98  of the pump  10  as shown in FIGS. 5-9. However, depressions  102  may extend a greater (FIG. 10) or lesser (FIG. 11) distance on the bottom surface  86  from the side wall  88  toward or through the central axis  98  or may extend across the bottom surface oblique to the central axis. Further, although depressions  102  have been described as being formed in the bottom surface  86  and side wall  88 , depressions  102  may be formed exclusively in the bottom surface  86 , side wall  88  or in the upper case  80  or in any combination of these. 
     Although the preferred embodiment of depressions  102  is a groove, depressions  102  may take any form so long as the depression surface  104  is moved toward the interior  96  of pump  10  from the ordinary outside wall  94  of the pump  10 . For example, depressions  102  make take the form in cross-section of semi-spherical depressions or truncated discoid depressions to name but a possible few configurations in addition to the trough-like depressions  102  described above. Whatever the form of depressions  102 , the primary function of depressions  102  is to form a shallow depression from the outside wall  94 . These depressions  102  substantially strengthen lower case  82  without the need for a reinforcing plate  92 . 
     The description contained herein is intended to be illustrative of the invention and not an exhaustive description. Many variations and alternatives to the disclosed embodiments will occur to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claim attached hereto.