Patent Publication Number: US-2012046602-A1

Title: Plasma Applicator and Corresponding Method

Description:
FIELD OF THE INVENTION 
     The invention relates to a plasma applicator for applying a non-thermal plasma to a surface, particularly for the plasma treatment of living tissue and especially for the treatment of wounds. 
     Further, the invention relates to a corresponding method for applying a non-thermal plasma to a locally bounded surface, particularly for the treatment of wounds. 
     BACKGROUND OF THE INVENTION 
     The use of non-thermal plasmas for the treatment of wounds and especially for the in-vivo sterilisation, decontamination or disinfection of wounds is disclosed, for example, in WO 2007/031250 A1 and PCT/EP2008/003568. 
     However, it is desirable to improve the healing effect of the wound treatment with the non-thermal plasma. 
     SUMMARY OF THE INVENTION 
     Therefore, it is a general object of the invention to improve the sterilizing effect of the plasma and the wound healing in a plasma therapy. 
     This object is achieved by a novel plasma applicator and a corresponding method according to the independent claims. 
     The plasma applicator according to the invention comprises a sealing cover (e.g. an adhesive plaster) for covering a portion of the surface thereby enclosing a cavity between the sealing cover and the surface, wherein a non-thermal plasma is provided in the cavity so that the non-thermal plasma in the cavity contacts the surface thereby sterilizing the surface and improving the wound healing. 
     The non-thermal plasma is preferably generated within the cavity by an electrode arrangement and/or an antenna arrangement which produces the non-thermal plasma. 
     However, it is alternatively possible that the plasma is generated outside the cavity and then introduced into the cavity through a conduit. 
     In one embodiment of the invention, the electrode or antenna arrangement of the plasma applicator comprises a single electrode only, so that the treated surface forms a counter electrode. In this embodiment, the treated object (e.g. a patient) is preferably electrically grounded and high-voltage is applied to the single electrode thereby producing the plasma in the cavity. 
     In another embodiment of the invention, the electrode or antenna arrangement of the plasma applicator comprises at least two separate electrodes for a bipolar generation of the electrode or antenna arrangement. In this embodiment, the generation of the plasma takes place between the separate electrodes so that it is not necessary to electrically ground the patient. 
     In a preferred embodiment of the invention, the electrode or antenna arrangement is spiral-shaped, particularly in the form of an Archimedien spiral having a constant separation distance between successive turnings of a spiral. However, the electrode or antenna arrangement may be in the form of any other type of spiral, e.g. a logarithmic spiral. Further, it is alternatively possible that the electrode or antenna arrangement is mesh-shaped. However, it should be noted that the invention is not restricted to the afore-mentioned exemplary forms of electrode or antenna arrangements. 
     The electrode arrangement is preferably flexible and can be adapted to the wound geometry. For example, the size of the electrode geometry can be adapted to the size of the wound so that the entire wound is covered by the plasma applicator. Therefore, the afore-mentioned electrode arrangement can be cut or tailored to the wound geometry. Further, the shape of the plasma applicator can be adapted to the shape of the wound so that the plasma applicator follows the contour of the wound. 
     In the preferred embodiment, the plasma applicator according to the invention further comprises a gas-permeable padding which is arranged within the cavity. The padding is preferably porous, e.g. in the form of a sponge, an aerogel or spheres of a polymer. Alternatively, the padding may consist of sacks filled with sand, quartz or the like. 
     Further, the padding is preferably substantially non-compressible and/or permeable to gas, preferably in the pressure range down to approximately 10 hPa. 
     Moreover, the padding can be functionalised by coating or impregnating the padding with a substance which is improving the plasma generation and/or which has a medical effect, particularly a sterilizing effect. For example, the padding can be coated or impregnated with a bactericide, a fungicide and/or an antiviral substance. 
     It should further be noted that the padding is preferably flexible so that it is adaptable to the contour of the treated surface. 
     Further, the electrode or antenna arrangement is preferably permeable to gas so that the electrode or antenna arrangement does not form a barrier for the carrier gas/plasma within the cavity. 
     In one alternative embodiment of the invention, the electrode or antenna arrangement is integrated or embedded into the padding so that the padding defines the relative position of the electrode or antenna arrangement. 
     In another embodiment of the invention, the electrode or antenna arrangement is located above the padding between the padding and the sealing cover and/or attached to the inner surface of the sealing cover. 
     It is also possible to functionalise the electrode or antenna arrangement by coating or impregnating with a substance which is improving the plasma generation and/or which has a medical effect, particularly a sterilizing effect. Therefore, the electrode or antenna arrangement can be coated or impregnated with a bactericide, a fungicide and/or an antiviral substance. 
     It should further be noted that the electrode or antenna arrangement is preferably substantially two-dimensional so that the electrode or antenna arrangement forms a mat. For example, the electrode or antenna arrangement can be a perforated foil. Further, the electrode or antenna arrangement is preferably flexible so that the electrode or antenna arrangement can be adapted to the wound geometry. 
     Moreover, the electrode or antenna arrangement is preferably flexible so that it is adaptable to the contour of the treated surface. 
     Further, the sealing cover is preferably substantially impermeable to gas. This is preferred since it allows to create a plasma environment surrounding the treated surface. 
     Moreover, the sealing cover is preferably at least partially adhesive for adhering the plasma applicator to the surface. Particularly, the plasma applicator according to the invention preferably comprises an adhesive boarder strip which can be adhered to the skin of a patient surrounding a wound. 
     Further, it is also possible to functionalise the sealing cover by coating or impregnating the sealing cover with a substance which is improving the plasma generation and/or which has a medical effect, particularly a sterilizing effect. Therefore, the sealing cover can be coated or impregnated with a bactericide, a fungicide and/or an antiviral substance. 
     It should further be noted that the sealing cover is preferably flexible so that it is adaptable to the contour of the treated surface. This is important when the plasma applicator is attached to a curved surface of the skin of a patient. Therefore, the entire plasma applicator is preferably flexible. 
     It should further be noted that the plasma applicator according to the invention preferably comprises a gas inlet for introducing a carrier gas into the cavity between the sealing cover and the treated surface, wherein the gas inlet can be connected to a gas source. The gas source can provide a carrier gas (e.g. argon, ambient air). Alternatively, the gas source can provide a mixture of the carrier source and any additive which is improving the wound healing and/or which is improving the plasma characteristics and/or the sterilizing effect. Alternatively, the plasma applicator according to the invention may comprise several gas inlets for introducing the carrier gas (e.g. ambient air, argon) and the additive (e.g. silver compounds) separately. 
     Further, the plasma applicator according to the invention preferably comprises a gas outlet for exhausting gas out of the cavity, wherein the gas outlet can be connected to a suction pump. The gas outlet allows a reduction of the pressure in the cavity before the carrier gas (e.g. argon) is introduced into the cavity through the gas inlet. Thus, it is easy to replace the ambient air in the cavity by the carrier gas. Further, a reduction of the pressure in the cavity facilitates the plasma generation in the cavity. 
     However, the reduction of the pressure in the cavity can result in a compression of the flexible padding due to the atmospheric pressure on the outside of the plasma applicator. Therefore, a rigid strut (e.g. a box frame or a box base) can be arranged in the cavity thereby holding up the flexible padding even in case of a low pressure in the cavity. 
     Moreover, the plasma applicator according to the invention preferably comprises an electrical contact being connected with the electrode or antenna arrangement for generating the plasma, wherein the electrical contact can be connected to an external high-voltage source for exciting the electrode or antenna arrangement thereby producing the plasma in the cavity. 
     It is already apparent from the above description that the plasma applicator according to the invention is preferably designed as an adhesive plaster which can be adhered to the skin in order to apply the non-thermal plasma to the skin. 
     The invention further encompasses a plasma application device comprising the afore-mentioned plasma applicator according to the invention, preferably in the form of an adhesive plaster. 
     Further, the plasma application device according to the invention preferably comprises a high-voltage source, which is connected to the electrical contact of the plasma applicator for energizing the electrode or antenna arrangement of the plasma applicator. 
     Further, the plasma application device according to the invention preferably comprises a suction pump being connected to the gas outlet of the plasma applicator for drawing gas out of the cavity of the plasma applicator thereby reducing the pressure in the cavity. 
     Moreover, the plasma application device according to the invention preferably comprises a gas source being connected to the gas inlet of the plasma applicator for introducing a carrier gas into the cavity, wherein the carrier gas can be the ambient air, argon, or a mixture of several gases with additives, which are improving the wound healing and/or the plasma generation. 
     The gas flow into the cavity of the plasma applicator is preferably controlled by a flow controller and/or an inlet valve which is arranged between the gas source and the gas inlet of the plasma applicator. 
     Further, the gas flow out of the cavity is preferably controlled by an outlet valve which is arranged between the gas outlet of the plasma applicator and the suction pump. 
     Moreover, the plasma application device according to the invention preferably comprises a control unit for controlling the inlet valve, the outlet valve and/or the high-voltage generator. 
     Further, the invention encompasses an operating method for the afore-mentioned plasma applicator. 
     For example, the plasma applicator can operate continuously for a specific treatment time so that the plasma applicator is switched on at the beginning of the treatment and switched off at the end of the treatment. The treatment time can be adjusted according to medical requirements. 
     Alternatively, a pulsed operation of the plasma applicator is possible, wherein the plasma applicator is operating with a specific pulse rate so that the plasma applicator is continuously switched on and off during the treatment. The pulse rate and the treatment time can be adjusted according to medical requirements. 
     Further, the invention also encompasses the novel use of the afore-mentioned plasma applicator for the treatment of wounds, living tissue or skin diseases or skin disorders. 
     The invention further encompasses a novel method for applying a non-thermal plasma to a locally bounded surface, particularly for the treatment of wounds. 
     The method according to the invention comprises the step of attaching a sealing cover to the locally bounded surface thereby providing a cavity between the sealing cover and the locally bounded surface. 
     Further, the method according to the invention comprises the step of providing a non-thermal plasma within the cavity in contact with the locally bounded surface, so that the non-thermal plasma improves the wound healing. 
     Moreover, the method according to the invention preferably comprises the step of sealing the cavity substantially gas-tight so that the pressure in the cavity can be reduced by exhausting gas out of the cavity. Therefore, the method according to the invention preferably comprises the step of reducing the pressure within the cavity by exhausting gas out of the cavity. 
     Further, the method according to the invention preferably comprises the step of introducing a carrier gas into the cavity and finally the step of exciting an electrode or antenna arrangement in the cavity thereby generating the non-thermal plasma in the cavity. 
     Therefore, the plasma is preferably generated in situ, i.e. within the cavity. However, it is alternatively possible that the plasma is generated in a separate plasma generator and then introduced into the cavity through a conduit. 
     In case of a single electrode or antenna arrangement, the method according to the invention preferably comprises the steps of electrically grounding the treated surface and exciting the electrode after the grounding of the treated surface. 
     It should further be noted that the non-thermal plasma according to the invention preferably comprises a gas temperature (i.e. the temperature of the atoms and molecules) below +40° C., when measured on the treated surface. 
     Further, the pressure of the plasma within the plasma applicator is preferably in the range of 1 hPa-1.200 hPa and more preferably in the range of 10 hPa-500 hPa, wherein a pressure of approximately 100 hPa is preferred. 
     Moreover, the degree of ionization (i.e. the percentage of the ionized atoms or molecules) of the carrier gas is preferably above 1·10 −9 , 2·10 −9 , 5·10 −9 , 10 −8 , 2·10 −8  or 5·10 −8 . 
     The invention and its particular features and advantages will become apparent from the following detailed description considered with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a cross-sectional view of a plasma applicator according to the invention along line A-A in  FIG. 1B , 
         FIG. 1B  is a top view of the plasma applicator according to  FIG. 1A  on the skin of a patient, 
         FIG. 2  is a cross-sectional view of a plasma applicator according to another embodiment of the invention. 
         FIG. 3  is a flowchart illustrating the method according to the invention for applying a non-thermal plasma to a surface. 
         FIG. 4A  is a schematic view of an electrode arrangement in the form of an Archimedian spiral. 
         FIG. 4B  is another embodiment of an electrode arrangement which can be used in the afore-mentioned plasma applicator according to the invention, 
         FIG. 5  is a cross-sectional view of a plasma applicator according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A and 1B  illustrate a preferred embodiment of a plasma applicator  1  for generating and applying a non-thermal plasma to a locally bounded wound  2  of a patient  3 . 
     The plasma applicator comprises a flexible and gas tight sealing cover  4  which can be adhered to the skin surrounding the wound  2 . Therefore, the sealing cover  4  comprises an adhesive boarder strip  5  which is coated with an adhesive  6  for adhering the boarder strip  5  of the sealing cover  4  to the skin of the patient  3  surrounding the wound  2 . 
     The sealing cover  4  encloses a cavity between the wound  2  and the sealing cover  4 , wherein the cavity is filled with a gas-permeable and porous padding  7  which is functionalised by impregnating the padding  7  with a substance which is improving the wound healing. 
     Further, the plasma applicator  1  comprises a single electrode  8  for producing the non-thermal plasma in the cavity between the sealing cover  4  and the wound  2 . The electrode  8  is connected to an external electrical contact  9  through a gastight feedthrough. 
     Further, the plasma applicator  1  comprises a gas inlet  10  for introducing a carrier gas into the cavity between the sealing cover  4  and the wound  2 . 
     Moreover, the plasma applicator  1  comprises a gas outlet  11  for exhausting gas out of the cavity between the sealing cover  4  and the wound  2 . 
     The gas inlet  10  of the plasma applicator  1  is connected to a gas source  12  via a conduit  13  and an inlet valve  14 . 
     Further, the gas outlet  11  is connected to a suction pump  15  via an outlet valve  16  and a conduit  17 . 
     Moreover, the electrical contact  9  of the plasma applicator  1  is connected to a high-voltage generator  18  through a cable  19 . 
     Finally, the plasma application device shown in  FIGS. 1A and 1B  comprises a control unit  20  which is controlling the gas source  12 , the suction pump  15 , the high-voltage generator  18 , the inlet valve  14  and the outlet valve  16 . 
     Further, the control unit  20  is connected to a pressure sensor  21  which measures the pressure in the plasma applicator  1 . The control unit  20  controls the inlet valve  14  and the outlet valve  16  in such a way that a target value of about p TARGET =100 hPa is adjusted. 
     In the following, the operation of the afore-mentioned plasma application device is illustrated with reference to the flow chart shown in  FIG. 3 . 
     In a first step S 1 , the plasma applicator  1  is adhered to the skin of the patient  3  surrounding the wound  2 . 
     In a second step S 2 , the gas outlet  11  of the plasma applicator  1  is connected to the suction pump  15 . 
     Then, the gas inlet  10  of the plasma applicator  1  is connected to the gas source  12  in step S 3 . 
     In another step S 4 , the high-voltage generator  18  is connected to the electrical contact  9  of the plasma applicator  1 . 
     Then, in a step S 5 , the control unit  20  closes the inlet valve  14  and opens the outlet valve  16  so that the suction pump  15  draws air out of the plasma applicator  1  thereby reducing the pressure in the cavity between the sealing cover  4  and the skin of the patient  3 . 
     In a next step S 6 , the control unit  20  closes the outlet valve  16  and switches the suction pump  15  off. Further, the control unit  20  opens the inlet valve  14  so that the gas source  12  delivers a carrier gas (e.g. argon) into the plasma applicator  1 . 
     Then, the control unit  20  closes the inlet valve  14  and activates the high-voltage generator  18  in a step S 7 , so that a non-thermal plasma is produced between the single electrode  8  and the electrically grounded patient  3 . 
     Then, in step S 8 , the patient  3  is treated with the non-thermal plasma. 
       FIG. 2  shows a cross-sectional view of another embodiment of a plasma applicator  1  according to the invention which is similar to the embodiment shown in  FIGS. 1A and 1B . Therefore, reference is made to the above description and the same reference numerals are used for corresponding details, parts and components. 
     One characteristic of this embodiment is that the electrode arrangement for producing the plasma in the plasma applicator  1  comprises two separate electrodes  8 . 1 ,  8 . 2  for a bipolar generation of the plasma between the electrodes  8 . 1 ,  8 . 2 . This is advantageous since it is not necessary to electrically ground the patient  3 . 
       FIG. 4   a  shows an exemplary embodiment of the electrode  8  in the form of an Archimedian spiral with a constant distance w between successive turnings  22  of the spiral. 
       FIG. 4B  shows another embodiment of the electrode  8  in the form of a mesh. 
       FIG. 5  shows a cross-sectional view of another embodiment of a plasma applicator  1  according to the invention which is similar to the embodiment shown in  FIGS. 1A and 1B . Therefore, reference is made to the above description and the same reference numerals are used for corresponding details, parts and components. 
     One distinctive feature of this embodiment is that there is a rigid strut  23  arranged in the cavity thereby preventing the compression of the padding  7  in case of a low pressure in the cavity. 
     The strut  23  is gas permeable so that the pressure sensor  21  can measure the gas pressure within the cavity although the pressure sensor  21  is arranged outside the strut  23 . 
     Further, the strut  23  comprises a circumferential base  24  resting on the skin of the patient  3  outside the wound  2  so that the wound  2  is not affected by the pressure exerted by the base  24  and plasma applicator  1  dos not cause any pain to the patient  3 . 
     Although the invention has been described with reference to the particular arrangement of parts, features and the like, these are not intended to exhaust all possible arrangements of features, and indeed many other modifications and variations will be ascertainable to those of skill in the art. 
     LIST OF REFERENCE NUMERALS  
       1  Plasma applicator 
       2  Wound 
       3  Patient 
       4  Sealing cover 
       5  Border strip of the sealing cover 
       6  Adhesive 
       7  Padding 
       8  Electrode 
       8 . 1  Electrode 
       8 . 2  Electrode 
       9  Electrical contact 
       10  Gas inlet 
       11  Gas outlet 
       12  Gas source 
       13  Conduit 
       14  Inlet valve 
       15  Suction pump 
       16  Outlet valve 
       17  Conduit 
       18  High-voltage generator 
       19  Cable 
       20  Control unit 
       21  Pressure sensor 
       22  Turning of spiral 
       23  Strut 
       24  Base of strut