Abstract:
An improved propellant pillow and method for filling a propellant chamber of an implantable pump with propellant through the use of such an improved propellant pillow are disclosed. The propellant pillow includes an improved design that prevents the damage of such during evacuating and filling procedures.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an improved apparatus and method for filling the propellant chamber of an implantable pump. In particular, the present invention relates to an improved propellant bag or pillow for use in introducing propellant into the propellant chamber of an implantable pump, as well as methods of utilizing same. 
     Implantable pumps have been well known and widely utilized for many years. Typically, such devices are implanted into patients who require the delivery of active substances or medicaments to specific areas of their body. For instance, patients who 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 subjected to one or more painful injections of medication multiple times during the course of the day. 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. Moreover, attempting to treat conditions like these through oral or intravascular administration of medication often requires higher doses of medication that may cause severe side effects. Thus, it is widely recognized that utilizing an implantable pump may be beneficial to both the patient and the treating physician. 
     Many implantable pump designs have been proposed, including pumps employing mechanical means for and gas pressure driven propellant means for expelling fluids from the pump. The present invention is directly related to the latter. More particularly, the apparatus and methods taught in the present application are capable of being utilized with many different types of gas driven pumps, such as those shown in 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, as well as U.S. Patent Application Publication Nos. 2006/0259015, 2006/0259016, 2006/0271021, 2006/0271022, 2007/0005044, and 2007/0112328. The disclosures of each of the above-noted patents and patent applications are hereby incorporated by reference herein, and certain of these references may be referred to throughout the present application. 
     In general, gas driven implantable pumps, like each of the above-noted patents and patent applications, utilize an expandable propellant (e.g., an isobarically expanding gas) that acts upon a membrane to push medicament or other fluid from the pump. A common problem with such pumps, which have existed for some time, revolves around the filling of the propellant chamber with propellant. Above-noted U.S. Pat. No. 5,766,150 (“the &#39;150 patent”) discloses an apparatus and method for use in such a filling process. As is shown in FIG. 1 of the &#39;150 patent (reprinted as  FIG. 1  of the present case), that patent teaches the use of a propellant pillow  13 , which is filled with a gas propellant and placed into a propellant chamber  7  of an implantable pump. The chamber is thereafter sealed.  FIG. 2  shows pillow  13  in greater detail, in particular the fact that the pillow includes a propellant bag  15  and septum  17  affixed to the bag, which are not labeled as such in the &#39;150 patent. Because bag  15  consists of a material through which the propellant may diffuse (i.e., a permeable material), the gas slowly diffuses through the wall of the pillow and into chamber  7 . Thus, the use of pillow  13  allows time for the propellant chamber and the remainder of the pump to be assembled before the gas escapes therefrom. 
     During assembly of a pump utilizing the device and methods taught in the &#39;150 patent, the assembly steps first include punching bag  15  from an air padded foil or the like, evacuating it of all gases, and subsequently refilling it with a propellant. These steps generally involve the use of at least one cannula, needle, or syringe  19  that pierces self-sealing silicone septum  17  to both evacuate all gases and introduce propellant. After being filled, pillow  13  is then introduced into a pump that has been divided into propellant chamber  7  and a fluid/medicament storage chamber  6 . Subsequent to inserting pillow  13  into propellant chamber  7  of the pump, that chamber is sealed and evacuated of all gases. This allows the propellant to slowly permeate through the walls of bag  15  and into propellant chamber  7 . This method is generally applicable to any gas pressurized implantable pump, including the ones described in the various prior art references listed above. It has also been found that when a heat procedure is utilized to seal a propellant chamber like chamber  7 , bags like bag  15  are caused to erupt (with one or more holes), thereby causing the propellant to more quickly fill the chamber. 
     While the device and methods taught in the &#39;150 patent has been utilized for some time in filling implantable pumps such as those disclosed above, it is not without its drawbacks. For instance, the initial evacuation of and subsequent filling of propellant within pillow  15  sometimes results in the structure of the bag being damaged by the syringe(s)  19 . More particularly, evacuation of gas from bag  15  (i.e., creating a vacuum) causes the walls of the bag to collapse upon themselves and sometimes into contact with the point of the syringe(s). This may result in the walls being pierced, which thereby leads to a faster escape of the propellant from bag  15  than is desired. Thus, while the &#39;150 patent suggests placing the pillow within a sealed propellant chamber in approximately two minutes, this time period is significantly reduced when the bag walls are damaged. More often than not, this damage to pillow  13  results in less propellant ultimately being contained within the propellant chamber. 
     Therefore, there exists a need for an improved pillow for use in an improved method of filling the propellant chamber of an implantable pump. 
     SUMMARY OF THE INVENTION 
     A first aspect of the present invention is a pillow for use in filling a gas pressure driven implantable pump. In a preferred embodiment, the pillow preferably includes a propellant bag for containing a propellant, the bag being formed of permeable material facilitating release of the propellant therefrom. The pillow also preferably includes a self-sealing septum structure having a top surface, a bottom surface, and a septum opening extending from the bottom surface partially through the septum structure. The bottom surface of the septum structure is preferably affixed to the bag. 
     In other embodiments according to the above-described first aspect, the septum structure includes two separate septa. In such a case, a first septum may include the bottom surface and the septum opening and a second septum is solid and includes the top surface. Other embodiments may include a bag that is unitary. The bag may also include a bag opening aligned with the septum opening. With regard to this latter embodiment, the bag opening may be formed subsequent to affixation of the septum structure to the bag. Still further embodiments employ a bag constructed of polyolefins, such as polypropylene or polyethylene, and a septum structure constructed of silicone rubber. 
     A second aspect of the present invention is a process for filling of a propellant chamber of a gas pressure driven implantable pump with a propellant. One preferred embodiment of this second aspect includes the steps of providing a pump having a medicament chamber and a propellant chamber, providing a propellant pillow including a permeable propellant bag and a self-sealing septum structure having a top surface, a bottom surface, and a septum opening extending from the bottom surface partially through the septum structure, the bottom surface being affixed to the bag, filling the pillow with the propellant, wherein the filling step includes laterally inserting a syringe into the septum structure, inserting the pillow filled with the propellant in the propellant chamber, and closing the propellant chamber. 
     Other embodiments of this second aspect may further include the step of evacuating the propellant chamber of substantially all gases. The evacuating step may be performed after the inserting step. The method may also include the step of evacuating the pillow of substantially all gases. The evacuating step may be performed through the use of the syringe inserted into said septum opening. Still further, the septum structure may include a first septum including the bottom surface and the septum opening and a second septum including the top surface. In such a case, the method may also include the steps of affixing the first septum to the bag and affixing the second septum to the first septum, through the use of an adhesive or the like. 
     A third aspect of the present invention is another pillow for use in filling a gas pressure driven implantable pump. In accordance with one preferred embodiment of this third aspect, the pillow includes a propellant bag for containing a propellant, the bag being formed of permeable material facilitating release of the propellant therefrom. The pillow may also include a first septum including a septum opening and a second septum being of a solid construction. The first septum is preferably affixed to the bag and the second septum is preferably affixed to the first septum. 
     In other embodiments of this third aspect, the bag is unitary. Likewise, the bag may include a bag opening aligned with the septum opening. Such an opening may be formed subsequent to affixation of the septum structure to the bag. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A 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 references made to the accompanying drawings in which: 
         FIG. 1  is a cross-sectional side view of a prior art propellant pillow disposed within a propellant chamber of an implantable pump. 
         FIG. 2  is an enlarged cross-sectional illustration of the propellant pillow shown in  FIG. 1  with a needle inserted therein. 
         FIG. 3  is a perspective view of a propellant pillow in accordance with one embodiment of the present invention. 
         FIG. 4  is a cross-sectional side view of the propellant pillow shown in  FIG. 3 . 
         FIG. 5  is a cross-sectional side view of a propellant bag portion of the propellant pillow shown in  FIG. 3  prior to assembly with other portions of the pillow. 
         FIG. 6  is a cross-sectional side view of the propellant pillow of  FIG. 3  with a first septum attached thereto. 
         FIG. 7  is a cross-sectional side view of the propellant pillow of  FIG. 3  illustrating the introduction of propellant into the propellant bag. 
         FIG. 8  is a cross-sectional side view illustrating the placement of the propellant pillow shown in  FIG. 3  between two flexible membranes of an implantable pump. 
         FIG. 9  is a cross-sectional side view of a fully assembled implantable pump with the propellant pillow of  FIG. 3  placed within its propellant chamber. 
     
    
    
     DETAILED DESCRIPTION 
     In describing the preferred embodiments of the subject 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 manner to accomplish a similar purpose. 
     Referring to  FIGS. 3 and 4 , there is shown an improved propellant pillow  20  in accordance with the present invention. As shown in that figure, as well as those figures that follow, pillow  20  includes a propellant bag  22 , a first septum  24  including an opening  26 , and a second septum  28  overlying the first septum. Although shown in the figures as being of a circular shape, propellant pillow  20 , as well as its components, may take on any shape suitable for use in placement in an implantable pump or the like. 
     Propellant bag  22  (shown by itself in  FIG. 5 ) is preferably constructed of polyolefins, such as polypropylene or polyethylene, and, like in the &#39;150 patent, is punched out from a larger sheet of similar bags. While the material is discussed above as being polypropylene or polyethylene, any material suitable for containing a propellant utilized in an implantable pump and thereafter allowing such to permeate through its walls can be used. In its initial state, propellant bag  22  is a completely sealed enclosure, but as will be discussed more fully below, at least one opening  30  is created in the propellant bag. 
     Septa  24  and  28  are preferably created of silicone material, such as silicone rubber, but may be any material suitable for allowing resealing after the introduction of a needle therethrough. As is mentioned above, first or lower septum  24  is formed with opening  26  that allows for access to a portion of propellant bag  22 . Overlying septum  24  is second or upper septum  28 , which is a solid structure that not only overlies the first septum, but also opening  16 . As shown in  FIG. 6 , first septum  24  is first affixed to propellant bag  22 , with, second septum  28  thereafter being affixed to the first septum. Both of the septa are preferably affixed utilizing glue or other adhesive, such as cyanacrylate. However, other means of attaching these components to the propellant bag and each other may be utilized. 
     After septa  24  and  28  are placed on propellant bag  22 , propellant pillow  20  is capable of being utilized to fill the propellant chamber of an implantable pump. Such a filling operation generally includes several steps. First, a syringe or other like device is inserted through septum  28  and opening  26  in first septum  24 , and into contact with the portion of propellant bag  22  that opening  26  overlies (not shown). The introduction of the syringe creates opening  30  in propellant bag  22  at this location. Once opening  20  in propellant bag  22  is created, the syringe or needle is withdrawn. However, it is also contemplated to provide a propellant bag  22  which initially includes this opening prior to the application of septa  24  and  28  thereto. This is in fact shown in  FIG. 5 , and would negate the need for a separate opening forming step. 
     Second, the same or another needle or syringe  32  is inserted laterally through first septum  24  until the tip of the needle extends into opening  26  (best shown in  FIG. 7 ). In this position, the needle can be utilized to evacuate all air or other gas that is contained within propellant bag  22 , such that the air or other gas exits through opening  30  of propellant bag  22 , into opening  26  of first septum  24 , and through the needle. Like in the prior art propellant pillows, this evacuation step generally results in propellant bag  22  collapsing upon itself. However, because of the design of the present propellant pillow, needle  32  is not permitted to engage any portion of propellant bag  22  during its collapse. 
     Once the air or other gas has been evacuated from propellant bag  22 , thereby creating a vacuum, the same laterally inserted syringe  32 , or a subsequently inserted syringe, can be utilized to infuse propellant bag  22  with propellant. Again, any propellant exiting syringe  32  goes through opening  26  in first septum  24 , through opening  30  of propellant bag  22 , and into the propellant bag. After this filling step is completed, syringe  32  may be removed from first septum  24 , which preferably self-seals because of its material. Propellant pillow  20  is now infused with gas that is only allowed to exit via a slow permeation through the material of propellant bag  22 . The propellant pillow may then be placed in the propellant chamber of an implantable pump, much like is discussed in the &#39;150 patent, and as is shown in  FIGS. 8 and 9  of the present application. In particular,  FIG. 8  shows propellant pillow  20  placed between two flexible membranes of an implantable pump, while  FIG. 9  shows the propellant pillow placed in a fully assembled implantable pump. It is to be understood that like in the context of the &#39;150 patent, the propellant chamber of the pump may be evacuated of all gas in order to create a vacuum. Further, this may be done before or after insertion of pillow  20  in the chamber. It is to be understood that other devices, like cannulas or needles, may be utilized in the foregoing steps. 
     It is contemplated that other designs for propellant pillow  20  may be employed. For instance, propellant bag  22  may, instead of being punched from a sheet of previously formed bags, be formed through the use of two membranes of like permeable material adjoined to one another. Likewise, it is contemplated that first and second septa  24  and  28  may in fact be integrally formed as a single septum. In this case, a lower surface of that single septum would include an opening corresponding to above-discussed opening  26 . Finally, it is to be understood that the various embodiment propellant pillows  20  discussed herein, as well as the methods of utilizing same, can be utilized in conjunction with many different implantable pumps. Certain examples are provided in the present application, but these are by no means meant to limit the use of the propellant pillow to such disclosed pumps. 
     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.