Abstract:
A device for producing medical foam, for example, a sclerosing agent, a diagnostic agent, a therapeutic agent, etc. The device comprises an active ingredient chamber and a gas chamber. Both chambers are respectively closed by a piston and connected to a foam generator. Both pistons are interconnected, especially by a connecting element, and can be displaced together, in order to supply the active ingredient and the gas to the foam producer.

Description:
1. FIELD OF THE INVENTION 
     The invention refers to a device for producing in particular reproducible medicinal foam or bubble suspension of a gaseous and a liquid medium. In particular, the invention refers to a mixing device for a reproducible preparation and administration of injectables such as sclerosing agents, diagnostic agents, therapeutic agents, homeopathic agents and autologous blood, for example. 
     2. DISCUSSION OF THE BACKGRUOND ART 
     Sclerotherapy means the planned elimination of intracutaneous, subcutaneous and/or transfascial varices and the sclerotization of subfascial vessels in case of venous anomalies by injecting a sclerosing agent. The various sclerosing agents cause damage to the endothelium of the vessels. Thereafter, a secondary vascular occlusion occurs and, in the long term, the veins are transformed into a strand of fibrous tissue, i.e. sclerosis occurs. It is the purpose of the sclerotization treatment to definitely transform the veins into a fibrous strand. This can not recanalize and, in its functional result, corresponds to the surgical procedure for removing a varice. Besides a sclerotization with liquid sclerosing agents, the sclerotization with foamed sclerosing agents becomes ever more important. The foam remains in vein for a longer period. Here, surfactant sclerosing agents, such as Polidocanol, are most often made to achieve a foamy state by pumping the agent back and forth between two pumps or by shaking, whereafter it is injected in a conventional manner. At present, there is no approved technique that would allow a reproducible preparation of a standardized foam. 
     Further, a plurality of preparations suited for use as ultrasonic contrast media are known, some of which contain surfactants that support the formation of micro-bubbles and stabilize these. The micro-bubbles or a foam reflecting ultrasound are the true contrast medium and are produced only immediately before being administered. 
     A mixing device for producing medicinal foam or for producing bubbles is known from EP 0 564 505. Here, a mixer with a helically shaped mixing element is described. The mixer is an accessory element that may be permanently connected to a syringe. When a liquid and/or gaseous medium is expelled from a second syringe, the medium reaches the mixer that contains the gas in a defined volume and nature. Here, the gaseous phase and the liquid phase are mixed along the helical mixing element. Thereby, a therapeutic and/or diagnostic foam may be produced. 
     The mixing device described in EP 0 564 505 is disadvantageous in that the mixer fixedly secured to the syringe can easily break off or be canted because of the long lever, in particular while moving the solution back and forth. Further, the mixer is a component that, due to the helical mixing elements arranged in the mixer, can be made as an injection molded part only with complicated injection molds. 
     It is the object of the present invention to provide a device with which medicinal foam can be produced from a gaseous and a liquid medium in a simple manner. 
     SUMMARY OF THE INVENTION 
     The device of the present invention comprises an active agent chamber and a gas chamber. Both chambers are closed by a respective piston. Further, the device comprises a foam producing means, in particular having one or a plurality of sieves. Both the active agent chamber and the gas chamber are indirectly or directly connected to the foam producing means. According to the invention, both pistons are arranged for displacement in the respective chamber. In particular, both pistons are connected with each other or may be connected while operating the device, so that the two pistons are displaced in common within one of the two chambers, respectively. This increases the pressure in the chambers and thus supplies or conveys the active agent and the gas towards the foam producing means or through the foam producing means. Therefore, the device of the present invention is very simple to handle since one movement moves both pistons and thus both media are pressed or transported toward the foam producing means. The medicinal foam escaping from the foam producing means only has to be collected, yet it may also be applied directly. 
     In the device of the present invention, it is not necessary to move a gas and a liquid or a gas and a detergent back and forth between two syringes. Therefore, it is much simpler to produce a standardized sterile foam. Further, no pressurized gas container need be provided in the device of the invention. 
     Preferably, both pistons are interconnected through a connecting element. Here, the connecting element is preferably designed such that one of the two chambers is opened when the connecting element is displaced. Further, the displacement of the connecting element may effect a connection of both pistons. Preferably, both pistons are connected only through the operation of the device. This is advantageous in that both chambers are completely separated from each other and may be sealed. It is particularly preferred herein to form the connecting element as a feed channel, e.g. as a hollow needle. By moving the connecting element together with one of the pistons, the connecting channel is introduced into one of both chambers. If the connecting element is designed as a hollow needle, both chambers are pierced, for example, by the hollow needle penetrating the second piston. 
     It is particularly preferred to provide an entrainment element on the connecting element, which may in particular be designed as a bead or a plate. This allows, when moving the connecting element towards one of both pistons closing the chambers after having, for example, pierced or opened this piston, to push the same into the corresponding chamber and to increase the pressure in the chamber, so that the medium in the chamber preferably flows into the hollow needle and through the same to the foam producing means. 
     Instead of displacing both pistons in common that are preferably interconnected through the connecting element, it is also possible to displace both chambers. All that is relevant is the relative movement between the chambers and the pistons. 
     Preferably, one of the two pistons is, in particular, rigidly connected with the foam producing means. Further, one of the two pistons may also be loosely connected with the foam producing means. Preferably, the medium flows through the piston into the foam producing means. It is further preferred that also the medium from the second chamber flows through this piston. In this preferred embodiment, both media preferably mix in the foam producing means and/or immediately before the foam producing means. It is particularly preferred to press the medium from the chamber farther away from the foam producing means through a feed channel provided in the connecting element and to supply it at least partly directly to the foam producing means. In this embodiment, the media are mixed immediately in the foam producing means. If desired, a mixing element may be provided in or before the foam mixing means in which a pre-mixing of both media is effected before these are pressed through the foam producing means. This mixing element may be a kind of sponge or sintered material, for example, serving at the same time to slow down the active agent. This improves the production of foam. 
     Further, it is possible to provide the foam producing means within the syringe, e.g. in the hub that also forms the Luer lock. 
     Preferably, a foam exit opening of the foam producing means may be connected to a foam collecting receptacle. The foam collecting receptacle may be, for example, a conventional syringe which may then be connected to the foam exit opening through a Luer lock, for example. 
     The device of the present invention is particularly suitable for one-way use due to its simple and economic structure made of simple parts that are preferably individually producible. Particularly because of the one-way use, the required sterility can be guaranteed. It is another advantage of the present device that the drug and the gas come into contact only immediately before being applied. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following is a detailed description of a preferred embodiment of the invention with reference to the accompanying drawings. 
       In the Figures: 
         FIGS. 1-3  schematic, partly sectional side elevational views of the device in three different mixing states, and 
         FIG. 4  a schematic exploded view of the present device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The device of the present invention for producing medicinal foam comprises an active agent chamber  10  and a gas chamber  12 . The active agent chamber  10  is designed as a carpule  14  ( FIG. 4 ) and sealed with a first piston  16  that may be a rubber stopper or the like. The carpule  14  is held in a holder  18 , the carpule  14  being pushed into the holder  18  in the direction of the arrow  20  assuming the position illustrated in  FIGS. 1 to 3 . Here, the carpule  14  is fixed in position by catch elements  22  and stops  24  ( FIG. 4 ) opposite the catch elements  22 . The holder  18 , which accommodates the preferably also circular cylindrical carpule  14  in the cylindrical opening  26 , is connected with a cylindrical hub  28 . The gas chamber  12  is formed within the cylindrical hub  28 . 
     The gas chamber  12  is also sealed with a second piston  30 . Optionally, the gas chamber may also be designed as a carpule. The also cylindrically shaped gas chamber  12  has a larger diameter than the active agent chamber  10 . Of course, the arrangement of active agent and gas in the two chambers may also be inverted. This is particularly suitable with active agents that require only a little volume of gas for foaming, i.e. with active agent which are inherently easily foamed. The height of the gas chamber  12  and the active agent chamber  10  is substantially the same, the gas chamber  12  preferably being slightly higher to be able, if desired, to deplete both chambers  10 ,  12  entirely when the pistons  16 ,  30  are pushed in completely. 
     Connected to the second piston  30  is a connecting element  32  designed as a hollow needle. For this purpose, the piston  30  comprises a suitable, for example cylindrical hub  34  ( FIG. 4 ) into which the hollow needle  32  may be inserted and retained, e.g., by gluing. 
     Further, a foam producing means  38  is rigidly or loosely and, if desired, removably connected to the piston  30  which sealingly abuts the inner wall  36  of the gas chamber  12 . In particular, the foam producing means  38  comprises two sieves  40  that cause the whirling and mixing of the two media and thus the production of foam. The foam producing means  38  is connected to the piston  30  through a holder  42 . 
     In addition to or instead of two or more sieves, the foam producing means  38  may also comprise, for example, one or more sinter filters, impellers, coils and/or spirals. 
     A loose or removable connection between the foam producing means  38  and the piston  30  is advantageous in that the foam producing means  38  can be pulled from the cylindrical hub  38  of the present device together with the syringe  46 . When expelling the foam from the syringe  46 , the foam is again pushed through the foam producing means  38  so that the quality of the foam produced can further be improved. Moreover, it is possible to provide the inner side of the cylindrical hub  29  with catch elements that prevent the piston  30  from being pulled from the cylindrical hub  28 . Similarly, the piston  30  may comprise catch elements that, when the piston  30  is pulled too far out from the hub  28 , engage in recesses, for example, provided in the hub  28 . 
     The holder  42  has a foam exit opening  44  ( FIG. 4 ) through which the foam produced in the foam producing means  38  escapes. In the particularly preferred embodiment of the invention illustrated, the foam exit opening is a Luer to which a conventional syringe  46  may be connected. The syringe  46  serves as a foam collecting receptacle, as is evident from  FIGS. 2 and 3 . 
     To produce foam, the holder  42  is placed on a substrate so that the device is orientated vertically, as illustrated in  FIGS. 1-3 . Thereafter, the syringe barrel is pushed downward in the direction of the arrow  50 , for example using the hubs  48  illustrated in the Figures. The position of the syringe piston or syringe plunger  52  is not changed in the process. Shifting the syringe barrel downward into the holder  28 , particularly shifts the foam producing means  38  as well as the second piston  30  downward. Together with the piston  30 , the hollow needle  32  rigidly connected to the piston  30  is pushed downward. In doing so, the tip  54  of the hollow needle  32  pierces the first piston  16  and thus opens the active agent chamber  10 . 
     Since an entrainment element  56 , such as a plate, is rigidly connected to the connecting element or the hollow needle  32 , the plate  56  presses the first piston  16  into the active agent chamber  10 . The shifting of both pistons  30 ,  16  causes a pressure increase both in the active agent chamber ( 10 ) and in the gas chamber  12 . Thereby, active agent is pressed through the hollow needle  32  into the foam producing means  38 . Further, gas is pressed from the gas chamber  12  into the foam producing means  38  through openings  58  present in the piston  30  and/or through transverse bores in the hollow needle  32 . Through the foam exit opening  44  of the foam producing means  38 , the foam produced reaches the space  60  within the syringe barrel cleared by the movement of the syringe barrel. 
     It is an essential advantage of the present device that foam is produced in the syringe  46  by a single piston stroke, i.e. by pushing the two pistons  16 ,  30  down as illustrated in  FIGS. 1-3 . After the foam has been produced, the syringe may be removed from the Luer adapter so that the foam may then be applied directly.