Abstract:
An external infusion device system for infusing a fluid into a patient, the system including a reusable infusion device housing, a gas power source and disposable reservoir. The disposable reservoir is insertable into the reusable infusion device housing to infuse the fluid into the patient. The gas power source is for generating a gas to expel the fluid from the fluid reservoir. The disposable reservoir includes a reservoir housing, a fluid reservoir, an outlet, a gas power source, an expansion chamber and a regulating valve assembly. The fluid reservoir is within the reservoir housing for containing the fluid to be infused into the patient. The outlet is in the reservoir housing and provides a path through which the fluid is expelled to be infused into the patient. The expansion chamber is disposed between the gas power source and the fluid reservoir to receive the gas from the gas power source. The expansion member expands into the fluid reservoir to expel the fluid from the fluid reservoir. The regulating valve assembly is disposed between the fluid reservoir and the outlet to set a predetermined threshold pressure that must be exceeded to permit fluid to be expelled from the fluid reservoir through the outlet. In preferred embodiments, the fluid to be infused is a medication. Also, the regulating valve assembly sets the predetermined threshold pressure at greater than 1.05 atmospheres.

Description:
This application claims benefit of Provisional Applications 60/136,733 filed May 28, 1999 and 60/138,183 filed Jun. 8, 1999. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to external, gas powered programmable infusion devices, and in particular embodiments, to an external gas powered programmable infusion device that utilizes a disposable medication cartridge with gas power source. 
     BACKGROUND OF THE INVENTION 
     Insulin must be provided to people with Type I, and many with Type II diabetes. Traditionally, since it cannot be taken orally, insulin has been injected with a syringe. More recently, use of external infusion pump therapy has been increasing, especially for delivering insulin for diabetics using devices worn on a belt, in a pocket, or the like, with the insulin delivered via a catheter with a percutaneous needle or cannula placed in the subcutaneous tissue. For example, as of 1995, less than 5% of Type I diabetics in the United States were using pump therapy. Currently, of the over 900,000 Type I diabetics in the U.S., about 7% use insulin pump therapy, and the percentage is now growing at an absolute rate of over 2% each year. Moreover, the number of Type I diabetics is growing at 3% or more per year. In addition, growing numbers of insulin using Type II diabetics are also using external insulin infusion pumps. Physicians have recognized that continuous infusion provides greater control of a diabetic&#39;s condition, and are also increasingly prescribing it for patients. In addition, medication pump therapy is becoming more important for the treatment and control of other medical conditions, such as pulmonary hypertension, HIV and cancer. Although offering control, pump therapy can suffer from several complications that make use of traditional external infusion pumps less desirable for the user. 
     For instance, one drawback is that traditional external pumps for profiled delivery of insulin and other drugs that require accurate titration are generally complex and expensive. Regarding costs, traditional external insulin pumps for treating Type 1 diabetes typically cost about $5,000 and the disposables cost about $800 to $1,200 per year. Generally, Type 2 diabetics often spend $3-$8 per day just for an oral medication rather than insulin. Thus, managed care providers are generally resistant to spending $5,000 for a pump, especially for a Type 2 diabetic, but seem less concerned about reimbursing for disposables or for the costly drugs. 
     Traditional external pumps are very sophisticated, with many safety features and checks. However, for some applications, such as for a Type 2 diabetic, a simpler and less expensive non-programmable pump system would often suffice. Conversely, programmability may still be desired or necessary to provide tighter control and flexibility. In addition, a programmable pump provides greater flexibility to use the external pump over a wider range of treatments and for a greater variety of medications. 
     SUMMARY OF THE DISCLOSURE 
     It is an object of an embodiment of the present invention to provide an integrated diabetes management system, which obviates for practical purposes, the above-mentioned limitations. 
     According to an embodiment of the invention, an external infusion device system for infusing a fluid into a patient, the system includes a reusable infusion device housing, a gas power source and disposable reservoir. The gas power source is for generating a gas to expel the fluid from the fluid reservoir. The disposable reservoir is insertable into the reusable infusion device housing to infuse the fluid into the patient. The disposable reservoir includes a reservoir housing, a fluid reservoir, an outlet, an expansion chamber and a regulating valve assembly. The fluid reservoir is within the reservoir housing for containing the fluid to be infused into the patient. The outlet is in the reservoir housing and provides a path through which the fluid is expelled to be infused into the patient. The expansion chamber is disposed between the gas power source and the fluid reservoir to receive the gas from the gas power source. The expansion member expands into the fluid reservoir to expel the fluid from the fluid reservoir. The regulating valve assembly is disposed between the fluid reservoir and the outlet to set a predetermined threshold pressure that must be exceeded to permit fluid to be expelled from the fluid reservoir through the outlet. In preferred embodiments, the fluid to be infused is a medication. Also, the regulating valve assembly sets the predetermined threshold pressure at a pressure somewhat above standard atmospheric pressure, such as greater than 1.05 atmospheres. 
     In particular embodiments, the gas power source utilizes electrolysis to generate the gas. In other embodiments, the gas power source includes a housing, and the gas power source uses the housing of the gas power source as an electrode. Also, the disposable reservoir can include a pressure sensor coupled to the gas power source to determine a pressure in the expansion chamber to detect an occlusion. In preferred embodiments, the disposable reservoir has a circular cross-section, while in other embodiments, the disposable reservoir has an oval cross-section. Preferably, the expansion chamber is formed as a sack, and in some embodiments the sack has a circular cross-section. In still further embodiments, the regulating valve assembly is compressed prior to use to set the predetermined threshold pressure. In particular embodiments, the gas power source is contained in the disposable reservoir. In other embodiments, the gas power source is contained in the device housing and engages with the disposable reservoir. 
     Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, various features of embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A detailed description of embodiments of the invention will be made with reference to the accompanying drawings, wherein like numerals designate corresponding parts in the several figures. 
     FIG. 1 a  is a cross-sectional view of a disposable reservoir containing a gas power source in accordance with a first embodiment of the present invention. 
     FIG. 1 b  is an enlarged cross-sectional diagram of the regulating valve shown in FIG. 1 a.    
     FIG. 2 is an end isometric view of the disposable showing the contacts that connect to a current generator in an infusion device shown in FIG.  4 . 
     FIG. 3 is an end view of the electrical contacts on the inside of the infusion pump that is utilized to connect with the electrical contacts on the disposable reservoir. 
     FIG. 4 a  is a front plan view of an infusion device in accordance with an embodiment of the present invention that utilizes the disposable reservoir shown in FIG. 1 a.    
     FIG. 4 b  is an end plan view of the infusion device shown in FIG. 4 a.    
     FIG. 5 a  is and isometric view of a disposable reservoir in accordance with a second embodiment of the present invention. 
     FIG. 5 b  is a partial cross-sectional view of the electrical contacts in the infusion device for contacting with the electrical contacts of the disposable reservoir shown in FIG. 5 a.    
     FIG. 6 is a front plan view of an infusion device in accordance with an embodiment of the present invention for use with the disposable reservoir shown in FIG. 5 a.    
     FIG. 7 a  shows an end view of the electrodes in the disposable reservoir shown in FIG. 5 a  that are used to generate the gas. 
     FIG. 7 b  shows a fluid cell for use with the electrodes of the disposable reservoir shown in FIG. 5 a.    
     FIG. 8 a  shows a top cross-sectional view of a disposable reservoir in accordance with a third embodiment of the present invention. 
     FIG. 8 b  shows a side cross-sectional view of the disposable reservoir shown in FIG. 8 a.    
     FIG. 9 is a cross-sectional view of a regulating valve assembly in accordance with another embodiment. 
     FIG. 10 is a cross-sectional view of a regulating valve assembly in accordance with a further embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in the drawings for purposes of illustration, the invention is embodied in an infusion device for infusion of a liquid, such as medication, chemicals, enzymes, antigens, hormones, vitamins or the like, into a body of a user. In preferred embodiments of the present invention, the infusion device uses a disposable reservoir containing a gas power source. However, it will be recognized that further embodiments of the invention may be used with a gas power source that is resident in the infusion device rather than the disposable reservoir. Particular embodiments are directed towards the use in humans; however, in alternative embodiments, the infusion devices may be used in animals. Preferred embodiments may utilize features that are similar to those found on other external programmable infusion devices, such as can be found in U.S. patent application Ser. No. 60/096,994 filed Aug. 18, 1998 (published as PCT application WO 00/10628) and is entitled “INFUSION DEVICE WITH REMOTE PROGRAMMING, CARBOHYDRATE CALCULATOR AND/OR VIBRATION ALARM CAPABILITIES,” which is herein incorporated by reference. 
     FIGS. 1 a - 4   b  illustrate an infusion device  100  that utilizes a disposable reservoir  102  inserted into a reservoir chamber  40 . FIG. 4 a  shows the infusion device  100  and in dotted lines how the disposable reservoir  102  (or cartridge) fits into the reservoir chamber  40 . When the disposable reservoir  102  is inserted into the reservoir chamber  40 , it can be locked in place by a variety of methods, such as friction, tabs, threads, snap fits, or the like. One version, shown in FIG. 4 b , utilizes a slide lock  69  that includes a slot  106  formed by fingers  69 ′ that surround a neck  20  of the disposable cartridge  102  to secure the disposable reservoir in the reservoir chamber  40  of the infusion device  100 . In operation, the slide lock  69  is pushed across the end of the infusion device  100  to slide the fingers  69 ′ around the neck  20  of the disposable reservoir  102 . Also shown in FIG. 4 a  are a display  43  and control switches  44 ,  45 ,  46  and  47  to program the infusion device  100 . For instance, the keys  44 - 47  and display  43  may be used to program the electrical current to be applied across the gas power source  3 , such as an electrolysis cell or the like, to generate the gas that expands a reservoir sack  11  in the disposable cartridge  102  to push the medication, or the like, in a medication reservoir  4  out through an outlet  16  and through the regulating valve assembly  15  at the end of the disposable reservoir  102 . 
     FIGS. 1 a - 2  illustrate a disposable reservoir  102  in accordance with the first embodiment of the present invention. The disposable reservoir  102  includes a housing  2 , a gas power source assembly  104 , an elastomeric sack  11 , a regulating valve assembly  15  and an outlet  16 . Preferably, the housing  2  is in the form of a cylindrical tube. In alternative embodiments, different cross-sectional shapes may be used, such as square, oval, elliptical, triangular, polygonal, or the like. Preferably, the disposable reservoir  102  is formed from glass, although other materials, such as plastic, metal, composites, laminates, or the like, may be used. Preferably, the gas power source assembly  104  and the regulating valve assembly  15  are inserted into the ends of the housing  102  to close and seal the disposable reservoir  102 . Particular embodiments may secure and seal the gas power source  3  and the regulating valve assembly  15  using pressure fits, friction, snaps, detentes, “O” rings, adhesives, combinations of the preceding, or the like. Generally, all parts of the medication infusion device  100  or the disposable reservoir  102  that are in contact with medication should be made of materials that are protein compatible (such as bromobutyl rubber, glass, metal or the like) and should preferably be coated with a protein compatible coating, such as that disclosed in U.S. patent application Ser. No. 09/042,138 filed Mar. 13, 1998 (published as PCT application WO 98/19627) and entitled “Implantable Medication Infusion system with Protein Stabilized Coating”, and U.S. patent application Ser. No. 09/324,783 filed Jun. 3, 1999 and entitled “Medication Device with Polymer Protein Stabilized Surface Coating”, both of which are herein specifically incorporated by reference. 
     As discussed, the back end of the disposable reservoir  102  includes a gas power source assembly  104 , such as an electrolysis cell assembly, that is inserted as a plug  3 . In the illustrated embodiment, the gas power source assembly  104  includes an interior cavity portion, which contains a conducting fluid such as dilute saline, or the like, in pure water. In alternative embodiments, other fluids such as acids, bases, or the like, may be used, or solids (such as potassium hydroxide, sodium hydroxide, or the like) or gels (such as gelatin mixed with electrolytes, polyhydroxy ethyl methacrylate, or the like) may be used for the conducting fluid. When current is applied across the two electrodes  5  and  6 , which protrude through the plug  3  from the interior cavity of the gas power assembly  104  to the exterior of the disposable reservoir  102 , electrolysis occurs in the solution contained in the interior cavity, creating a mixture of hydrogen and oxygen. For a single use disposable reservoir having 2 or 3 ml fluid capacity, the amount of saline solution required is small, on the order of less than 1/1000 of the drug capacity, but some excess fluid should be available to assure conduction throughout use. Because it is important to keep the electrodes  5  and  6  wet and conducting, some moistened sponge material or wicking material  8  can be used to maintain electrical contact between the electrolysis fluid and the electrodes  5  and  6 . In alternative embodiments, the electrodes  5  and  6  may be large and close together so that the conducting path is small, and the hollow area of the plug can also be very small. In alternative embodiments, a flexible and/or gas permeable membrane  10  may provide sufficient pressure to compress and maintain the electrolysis fluid against the electrodes  5  and  6  as the liquid is slowly electrolyzed, and the sponge or wicking material may be omitted. When the gas is generated in the interior cavity, it diffuses through the membrane  10 . Preferably, the membrane  10  is retained by a ring  9 , or another part, of the gas power source assembly  104 . 
     Attached to the interior side of the gas power source assembly  104  is an elastomeric sack  11  made of a drug compatible material such as bromobutyl rubber. In alternative embodiments, other flexible materials could be utilized. At the closed end of the sack  11  is a stiffening disk  12 , to cause the elastomeric sack  11  to expand more uniformly. Alternatively, the elastomeric sack  11  may be a flexible elongated tube, which when empty is compressed when the disposable reservoir  102  is full. The elastomeric sack  11  expands as gas is generated by the gas power source to press against the sides of the housing  2  to expel medication (contained in the medication reservoir  4 ) through the outlet  16 . In an alternative embodiment, the elastomeric sack  11  and stiffening disk  12  can be replaced with a syringe type plunger (without handle), with “O” rings or other seals to block leakage around the plunger, medication cartridge with a piston or the like. However, the use of these versions would be dependent on sufficiently low stiction between the plunger (or piston) and the syringe body (or medication cartridge) to avoid irregular and inconsistent infusion of the medication through the outlet  16 . 
     A potential problem with conventional gas powered devices can occur due to changes in the ambient air pressure, since this can affect the flow rate of medication from the disposable reservoir. For instance, if the ambient pressure changes, the gas volume generated by a given electrolysis current will be inversely proportional to the absolute pressure, such that the rate of drug flow for a given current would be changed and result in the delivery of the medication at different rates. In another example of conventional systems, when the elastomeric sack  11  already contains a considerable gas volume (i.e., when the disposable reservoir is not fill), a sudden change in pressure, such as going up or down in an airplane, vehicle, or the like, can interrupt delivery or, even worse, can create a sudden bolus, which for some drugs could be dangerous. With a sudden decrease in ambient pressure, the gas volume will expand and cause an unprogrammed amount of drug to be delivered. With a sudden increase in ambient pressure, the gas volume in the gas power source  3  would be compressed, stopping delivery and causing body fluids to enter through an infusion set  50  (see FIG. 4 a ). However, these problems can be largely eliminated or substantially reduced by using the pressure regulating valve assembly  15  at the outlet  16 . 
     The regulating valve assembly  15  illustrated in FIGS. 1 a  and  1   b  includes a chamber filled with a pressurized gas at a “reference” pressure slightly higher than standard atmospheric pressure. For instance, the “reference” pressure inside the reference pressure chamber  108  is preferably set slightly above atmospheric pressure, such as at 1.1 atmospheres. However, in alternative embodiments, higher (up to 2, 3, or more atmospheres) or slightly lower pressures (to 1.05 atmospheres) may be used. The reference pressure is an absolute pressure that adjusts due to changes in temperature and is a reference relative to the gas pressure generated by the gas power source  14 . Thus, when the temperature of the gas in the gas power source  14  and the reference pressure chamber  108  are the same, the device will deliver fluid at the proper rate. 
     The reference pressure chamber  108  consists of a back plate  19 , a chamber tube  18  (such as a bellows that can expand and contract longitudinally) and a valve sealing surface  22 . The reference pressure chamber  108  is contained within the valve plate  17  and the valve body  21 . Near the joint between the chamber tube  18  and the back plate  19  are gaps  110  around the chamber tube  18  for the medication to flow out through the regulating valve assembly  15 , through the outlet  16  to the infusion set  50  (see FIG. 4 a ), which connects to the Luer fitting or other connection means  23  to the infusion set  50 . The gas power source assembly  104  will generate sufficient gas in the gas chamber  105  to reach an internal pressure that is just above the reference pressure, which then compresses the chamber tube  18  toward the back plate  19 , opening the valve sealing surface  22  and permitting flow around the chamber tube  18  to the outlet  16 . No ambient pressure below the reference pressure will affect delivery, since the chamber tube  18  and the valve sealing surface  22  will not be displaced. The regulating valve assembly  15  will not protect against higher ambient pressures, so the reference pressure should be set at the highest level likely to be experienced under normal operating conditions. For unusual exposures, such as for swimming, the infusion device  100  could simply be removed so that any higher pressure is unlikely to be encountered. A one-way valve could also be incorporated to prevent back flow at high pressures. However, since the infusion device can be removed before these unusual exposures, a one-way valve may be omitted. Not incorporating a one-way valve is an advantage since a slightly higher filling pressure than the reference pressure will enable filling the disposable reservoir  102  through the outlet. 
     FIG. 9 shows a cross-section of a regulating valve assembly  200  in accordance with another embodiment of the present invention. The regulating valve assembly  200  is included in a reservoir housing  202  that holds a gas power source  204  and has an outlet  206  for fluid to be provided to a patient. The regulating valve assembly  200  includes a reference gas cell  208  with a top protrusion  210  and a bottom diaphragm  212 . The bottom diaphragm  212  is connected to a needle valve  214  to control the flow of fluid through an opening  216  leading to the outlet  206 . The top protrusion  210  is capable of being depressed (such as to the position A shown in dotted lines in FIG. 9) to set the reference gas pressure, as described above. Generally, the top protrusion  210  is depressed just prior to use, such as upon insertion of the reservoir housing  202  into an infusion device. This allows the reference gas cell  208  to be made from polymeric materials, such as rubber, plastic or the like. Thus, the reference gas cell does not require a metallic surface to prevent gas escaping during storage, since polymeric materials often allow gas to diffuse out of the gas cell over time. This would tend to reduce the cost of manufacturing the gas reference cell, since less expensive materials and manufacturing techniques could be used. The selected reference gas pressure is set by selecting a volume of the reference gas cell  208  and determining how much the volume will be decreased by compression of the top protrusion portion  210 . Any suitable pressure can be selected by the choice of the relative volume sizes. 
     FIG. 10 shows a cross-section of a regulating valve assembly  300  in accordance with another embodiment of the present invention. The regulating valve assembly  300  is included in a reservoir housing  302  that holds a gas power source  304  and has a fluid compartment  306  for fluid to be provided to a patient. The regulating valve assembly  300  includes a reference gas cell  308  with a compression wall  310  and a diaphragm  312 . The diaphragm  312  contacts valve members  314  to control the flow of fluid through an opening to an outlet  316 . The regulating valve assembly  300  is secured to the reservoir housing  302  by a slidable cap  318  that includes the valve members  314  and the outlet  316 . The reservoir housing  302  also includes a compression member  320  for compressing the compression wall  310  to reduce the volume of the reference gas cell  308  when the slidable cap  318  is slid back against the reservoir housing  302 . Preferably, the slidable cap  318  locks in position with a snap fit. However, alternative embodiments may utilize adhesives, threaded parts, or the like. The compression wall  310  is capable of being compressed to set the reference gas pressure, as described above. Generally, as in the embodiments shown in FIG. 9, the compression wall  310  is compressed just prior to use. This allows the reference gas cell  308  to be made from polymeric materials, such as rubber, plastic or the like. The selected reference gas pressure is set by selecting a volume of the reference gas cell  308  and determining how much the volume will be decreased by compression of the compression wall  310 . Any suitable pressure can be selected by the choice of the relative volume sizes. This embodiment also provides an ability to fill the fluid compartment  306  through the outlet  316  prior to use, since the reference gas cell  308  is not engaged in a flow restricting configuration with the valve members  314  prior to sliding the slidable cap  318  against the reservoir housing  302 . This permits filling through the outlet at the site of use, rather than prefilling at the site of manufacture. 
     FIG. 2 shows the rear of the disposable reservoir  102  illustrating the electrical contacts  31  and  32 . In preferred embodiments, the electrical contacts  31  and  32  have “spring” contacts that upon insertion of the disposable reservoir  102  into the infusion device  100  make contact with the contact electrodes  41  and  42  on the inside rear of the reservoir chamber  40  of the infusion device  100  housing as shown in FIG.  3 . The spring contacts  31  and  32 , which are more fragile, are applied at the rear of the disposable reservoir  102 , since they are replaced with each use and unlikely to wear out. Alternatively, if the spring contacts can be made sufficiently robust, the spring contacts may be placed on the infusion device  100  instead of and/or in addition to the spring contacts  31  and  32  on the disposable reservoir  102 . Since the disposable reservoir  102  in this embodiment is round, the electrical contacts on the infusion device  100  should formed as rings  42  and  107  to assure proper electrical contact with the contacts  31  and  32  on the disposable reservoir. 
     FIGS. 1 and 2 also show a hole  112  with a pressure sensor  33 . The pressure sensor  33  detects when the pressure in the disposable cartridge  102  rises materially above the “reference” pressure in the reference pressure chamber  108 , indicating an occlusion of the outlet or catheter. There are a variety of ways such a pressure sensor can function. In this case a rubber or other elastomeric membrane  33  is stretched across the hole  112  in the plug  3 . In this arrangement this membrane  33  is made conductive and contacts with electrode  31 , one of the two electrical contacts on the disposable reservoir  102 . When the pressure increases sufficiently to cause an occlusion alarm, the membrane  33  protrudes and makes contact with a ring electrode  107 , which closes an alarm circuit in the infusion device  100 , the other pole being the center electrode  31  of the gas power source assembly  104 . As a safety feature, the pressure sensor can also turn off the electrolysis current to stop gas generation and avoid the possibility of high pressures. Other pressure sensor devices may be used. Also, other pressure sensors on the infusion device  100  may be used to measure ambient pressure and to adjust the gas generation rate to alter the internal pressure of the disposable reservoir  102  so that medication delivery is more precisely controlled. 
     The first embodiment utilizes a round disposable reservoir  102 . However, there is no need for the disposable reservoir to be round. FIG. 5 a  shows a disposable reservoir  114  with an oval cross-section. Although such a reservoir would not use standard round tubing and would call for a different sealing system at the opening into the infusion device  116  to inhibit water penetration, the thickness of the infusion device  116  would be reduced and the electrical contacts  56  formed on the disposable reservoir  114  to the infusion device  116  would be simpler, since the electrodes  56  would always be in a suitable orientation (i.e. one way or reversed 180° (the reversal would make no difference since polarity is not important)). A pressure sensor  57  would generally be located in the center. FIG. 5 b  illustrates the corresponding electrical contacts inside the infusion device  116 . Here the+and−contacts  58  are located symmetrically to the sides and the pressure sensor contact  59  is in the center. 
     FIG. 6 illustrates an infusion device  116  incorporating the oval disposable reservoir  114  shown in FIG. 5 a . The primary difference between the embodiments of FIGS. 4 and 6, other than details described above, is in the method of retaining the cartridge in the infusion device. In the embodiment of FIG. 6, a lip  53  of the valve regulating assembly is larger than the oval tube forming the disposable reservoir  114  so that it protrudes outside the tube. The surface of this lip  53  can retain a flat sealing gasket (or an “O” ring)  54  to seal against the housing of the infusion device  116 . In use, the disposable reservoir would simply be inserted into the infusion device  116 , compressing the gasket  54  and making electrical contact between electrodes  56  to their respective counterparts  58  on the infusion device  116 . The slide retainer  69  or other retaining device on the pump is then pushed to lock the disposable reservoir  114  in the infusion device  116 , forming a seal to maintain a moisture barrier to the inside of the disposable reservoir chamber of the infusion device  116 . Since the moisture protection in the disposable reservoir chamber is not likely to be truly waterproof, the disposable reservoir chamber in the infusion device  116  that holds the disposable reservoir  114  should be separate from the section containing the display, control circuits, battery and the programming keys. 
     FIGS. 7 a  and  7   b  show a method of promoting electrolysis using electrodes that are formed as long wires  71  on the inside of a gas power source  118 . The wires  71  protrude to the rear at the contacts and are staked at the far end. These electrodes are then buried in a wicking foam moisture cell  72 . The long wires are more likely to be in contact with the electrically conducting fluid absorbed into the sponge. In alternative embodiments, the casing of the electrolysis cell (or gas power source) may be used as a ground terminal; obviating the need for two electrodes. 
     FIGS. 8 a  and  8   b  illustrates a sack  80  made of thin film so that when essentially empty the sides roll up or down as shown at  80  and  80 ′. When full of gas, the sack  80  will fill up, from the empty state of  80 ′, and will fill virtually the entire inside of the cartridge  55 , forcing essentially all the medication from the reservoir through the outlet  16 , as shown in the dotted lines  80 . This would replace the design shown in FIG. 1 a.    
     Additional alternative embodiments may separate the gas power source and the medication reservoir into separate components. This would be beneficial when the gas power source is capable of being used for longer periods of time than the amount time needed to deliver the medication in the medication reservoir. For instance, the gas power source may be loaded into the device for two or more uses, and a replacement medication reservoir is engaged with the gas power source each time a new medication supply is required. When the gas power source is depleted a new gas power source is inserted into the device. In alternative embodiments, the gas power source is permanently mounted into the device and refilled with electrolytes and other necessary materials as required. 
     While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention. 
     The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.