Abstract:
A method for treating a sinus cavity is provided. The method includes the steps of inserting a plasma applicator into a sinus cavity defined in a bone mass, positioning the plasma applicator adjacent a tissue formation, generating a selectively reactive plasma effluent at the plasma applicator and directing the selectively reactive plasma effluent at the tissue formation. The selective nature of the reactive plasma enables treatment of specific targets inside the sinus while minimizing the effect on other tissues. Such treatment includes, but not limited to, sterilization of bacterial colonies, vaporization of unwanted tissues or foreign masses, stimulation of tissues by enriching the content of reactive oxygen and nitrous oxide pathways, and combinations thereof.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit of and priority to U.S. Provisional Application Ser. No. 61/773,609, filed on Mar. 6, 2013, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to plasma devices and processes for surface processing and tissue removal. More particularly, the disclosure relates to a system and method for generating and directing chemically reactive, plasma-generated species in a plasma device along with excited-state species (e.g., energetic photons) that are specific to the supplied feedstocks for treating tissue. 
         [0004]    2. Background of Related Art 
         [0005]    Electrical discharges in dense media, such as liquids and gases at or near atmospheric pressure, can, under appropriate conditions, result in plasma formation. Plasmas have the unique ability to create large amounts of chemical species, such as ions, radicals, electrons, excited-state (e.g., metastable) species, molecular fragments, photons, and the like. The plasma species may be generated in a variety of internal energy states or external kinetic energy distributions by tailoring plasma electron temperature and electron density. In addition, adjusting spatial, temporal and temperature properties of the plasma creates specific changes to the material being irradiated by the plasma species and associated photon fluxes. Plasmas are also capable of generating photons including energetic ultraviolet photons that have sufficient energy to initiate photochemical and photocatalytic reaction paths in biological and other materials that are irradiated by the plasma photons. 
         [0006]    Chronic sinusitis originates from several sources including, but not limited to, infection by bacteria that may form biofilms, fungus that can form large fungal masses within the sinus, allergic reactions to infecting agents, chronic viral conditions such as HPV, and combinations thereof. These sources create inflammation in the sinus cavity that result in eosinophils, which in turn concentrate in the sinuses creating even greater inflammation and the degeneration of the mucosa into polyp formation and weakening of the underlying bone mass. Over time the sinuses cavities fill with foreign material or polyps that originate from the mucosa that lines the sinus cavity. Conventional treatments strip the sinus cavity of all mucosa, which results in the sinus lining reforming from scar tissue rather than epithelial mucosa. More conservative conventional treatments focus on removing the bulk of the material while attempting to preserve as much mucosa as possible. The preferred surgical tool for sinus surgery is a microdebrider available from many manufacturers and well known in the industry. These devises have no tissue selective properties and cut the softened bone equally as well as the overlying tissue using mechanical cutting. 
       SUMMARY 
       [0007]    Plasmas have broad applicability to provide alternative solutions to industrial, scientific and medical needs, especially workpiece surface processing at low temperature. Plasmas may be delivered to a workpiece, thereby affecting multiple changes in the properties of materials upon which the plasmas impinge. Plasmas have the unique ability to create large fluxes of radiation (e.g., ultraviolet), ions, photons, electrons and other excited-state (e.g., metastable) species which are suitable for performing material property changes with high spatial, material selectivity, and temporal control. Plasmas may also remove a distinct upper layer of a workpiece but have little or no effect on a separate underlayer of the workpiece or it may be used to selectively remove a particular tissue from a mixed tissue region or selectively remove a tissue with minimal effect to adjacent organs of different tissue type. 
         [0008]    One suitable application of the unique chemical species is to drive non-equilibrium or selective chemical reactions at or within the workpiece to provide for selective removal of only certain types of materials. Such selective processes are especially sought in biological tissue processing (e.g., mixed or multi-layered tissue), which allows for cutting and removal of tissue at low temperatures with differential selectivity to underlayers and adjacent tissues. This is particularly useful for removal of biofilms, mixtures of fatty and muscle tissue, debridement of surface layers and removing of epoxy and other non-organic materials during implantation procedures. 
         [0009]    The plasma species are capable of modifying the chemical nature of tissue surfaces by breaking chemical bonds, substituting or replacing surface-terminating species (e.g., surface functionalization) through volatilization, gasification or dissolution of surface materials (e.g., etching). With proper techniques, material choices and conditions, one can remove one type of tissue entirely without affecting a nearby different type of tissue. Controlling plasma conditions and parameters (including S-parameters, V, I, Θ, and the like) allows for the selection of a set of specific particles, which, in turn, allows for selection of chemical pathways for material removal or modification as well as selectivity of removal of desired tissue type. The present disclosure provides for a system and method for creating plasma under a broad range of conditions including tailored geometries, various plasma feedstock media, number and location of electrodes and electrical excitation parameters (e.g., voltage, current, phase, frequency, pulse condition, etc.). 
         [0010]    The supply of electrical energy that ignites and sustains the plasma discharge is delivered through substantially conductive electrodes that are in contact with the ionizable media and other plasma feedstocks. The present disclosure also provides for methods and apparatus that utilize specific electrode structures that improve and enhance desirable aspects of plasma operation such as higher electron temperature and higher secondary emission. In particular, the present disclosure provides for porous media for controlled release of chemical reactants. 
         [0011]    Controlling plasma conditions and parameters allows for selection of a set of specific particles, which, in turn, allows for selection of chemical pathways for material removal or modification as well as selectivity of removal of desired tissue type. The present disclosure also provides for a system and method for generating plasmas that operate at or near atmospheric pressure. The plasmas include electrons that drive reactions at material surfaces in concert with other plasma species. Electrons delivered to the material surface can initiate a variety of processes including bond scission, which enables volatilization in subsequent reactions. The electron-driven reactions act synergistically with associated fluxes to achieve removal rates of material greater than either of the reactions acting alone. 
         [0012]    A method for treating a sinus cavity is provided by the present disclosure. The method includes the steps of inserting a plasma applicator into a sinus cavity defined in a bone mass, positioning the plasma applicator adjacent a tissue formation, generating a selectively reactive plasma effluent at the plasma applicator and directing the selectively reactive plasma effluent at the tissue formation. The selective nature of the reactive plasma enables treatment of specific targets inside the sinus while minimizing the effect on other tissues. Such treatment includes, but not limited to, sterilization of bacterial colonies, vaporization of unwanted tissues or foreign masses, stimulation of tissues by enriching the content of reactive oxygen and nitrous oxide pathways, and combinations thereof. 
         [0013]    A method for treating a tissue cavity is also contemplated by the present disclosure. The method includes the steps of inserting a plasma applicator into a tissue cavity and positioning a plasma applicator adjacent the tissue formation. The plasma applicator includes a shaft having a proximal portion and a deflectable distal portion and a lumen defined therein terminating in an opening at a distal end of the distal portion. The lumen is in fluid communication with an ionizable media source and one or more electrodes disposed at the distal portion and coupled to a power source. The method also includes the steps of generating a selectively reactive plasma effluent at the plasma applicator and directing the selectively reactive plasma effluent at the tissue formation. 
         [0014]    The present disclosure also provides for a method for treating a sinus cavity. The method includes the steps of inserting a plasma applicator into a sinus cavity defined in a bone mass and positioning the plasma applicator adjacent a tissue formation. The method also includes the steps of selecting one or more precursor feedstocks having higher chemical reactivity with the tissue formation than with the bone mass of the sinus cavity, supplying ionizable media and the precursor feedstocks to the plasma applicator and igniting the ionizable media and the precursor feedstocks at the plasma applicator to form a selectively reactive plasma effluent. The method further includes the step of directing the selectively reactive plasma effluent at the tissue formation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the disclosure and, together with a general description of the disclosure given above, and the detailed description of the embodiments given below, serve to explain the principles of the disclosure, wherein: 
           [0016]      FIG. 1  is a schematic diagram of a plasma system according to the present disclosure; 
           [0017]      FIG. 2  is a schematic view of a plasma device according to the present disclosure; 
           [0018]      FIG. 3  is a cross-sectional view of the plasma device of  FIG. 2  along lines  3 - 3 ; 
           [0019]      FIG. 4  is an internal perspective view of a surgical site; and 
           [0020]      FIG. 5  is a flow chart of a method according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Plasmas are generated using electrical energy that is delivered as either direct current (DC) electricity or alternating current (AC) electricity at frequencies from about 0.1 hertz (Hz) to about 100 gigahertz (GHz), including radio frequency (“RF”, from about 0.1 MHz to about 100 MHz) and microwave (“MW”, from about 0.1 GHz to about 100 GHz) bands, using appropriate generators, electrodes, and antennas. Choice of excitation frequency, the workpiece, as well as the electrical circuit that is used to deliver electrical energy to the circuit affects many properties and requirements of the plasma. The performance of the plasma chemical generation, the delivery system and the design of the electrical excitation circuitry are interrelated—as the choices of operating voltage, frequency and current levels (as well as phase) effect the electron temperature and electron density. Further, choices of electrical excitation and plasma device hardware also determine how a given plasma system responds dynamically to the introduction of new ingredients to the host plasma gas or liquid media. The corresponding dynamic adjustment of the electrical drive, such as via dynamic match networks or adjustments to voltage, current, or excitation frequency may be used to maintain controlled power transfer from the electrical circuit to the plasma. 
         [0022]    Referring initially to  FIG. 1 , a plasma system  10  is disclosed. The system  10  includes a plasma device  12  that is coupled to a power source  14 , an ionizable media source  16  and a precursor source  18 . Power source  14  includes any suitable components for delivering power or matching impedance to plasma device  12 . More particularly, the power source  14  may be any radio frequency generator or other suitable power source capable of producing power to ignite the ionizable media to generate plasma. The plasma device  12  may be utilized as an electrosurgical pencil for application of plasma to tissue and the power source  14  may be an electrosurgical generator that is adapted to supply the device  12  with electrical power at a frequency from about 0.1 MHz to about 2.450 MHz and in another embodiment from about 1 MHz to about 13.56 MHz. The plasma may also be ignited by using continuous or pulsed direct current (DC) electrical energy. 
         [0023]    The precursor source  18  may be a bubbler or a nebulizer configured to aerosolize precursor feedstocks prior to introduction thereof into the device  12 . The precursor source  18  may also be a micro droplet or injector system capable of generating predetermined refined droplet volume of the precursor feedstock from about 1 femtoliter to about 1 nanoliter in volume. The precursor source  18  may also include a microfluidic device, a piezoelectric pump, or an ultrasonic vaporizer. 
         [0024]    The system  10  provides a flow of plasma through the device  12  to a workpiece “W” (e.g., tissue). Plasma feedstocks, which include ionizable media and precursor feedstocks, are supplied by the ionizable media source  16  and the precursor source  18 , respectively, to the plasma device  12 . During operation, the precursor feedstock and the ionizable media are provided to the plasma device  12  where the plasma feedstocks are ignited to form plasma effluent containing ions, radicals, photons from the specific excited species and metastables that carry internal energy to drive desired chemical reactions in the workpiece “W” (e.g., tissue) or at the surface thereof. The feedstocks may be mixed upstream from the ignition point or midstream thereof (e.g., at the ignition point) of the plasma effluent, as shown in  FIG. 1  and described in more detail below. 
         [0025]    The ionizable media source  16  provides ionizable feedstock to the plasma device  12 . The ionizable media source  16  is coupled to the plasma device  12  and may include a storage tank, a pump, and a cooling source (not explicitly shown). The ionizable media may be a liquid or a gas such as argon, helium, neon, krypton, xenon, radon, carbon dioxide, nitrogen, hydrogen, oxygen, etc. and their mixtures, and the like, or a liquid. These and other gases may be initially in a liquid form that is gasified during application. The gases maybe cooled prior to ionization such as energy is added the ionization process the effluent remains below the targeted maximum temperature associated with cold plasma reactions. 
         [0026]    The precursor source  18  provides precursor feedstock to the plasma device  12 . The precursor feedstock may be either in solid, gaseous or liquid form and may be mixed with the ionizable media in any state, such as solid, liquid (e.g., particulates or droplets), gas, and the combination thereof. The precursor source  18  may include a heater, such that if the precursor feedstock is liquid, it may be heated into gaseous state prior to mixing with the ionizable media. 
         [0027]    In one embodiment, the precursors may be any chemical species capable of forming reactive species such as ions, electrons, excited-state (e.g., metastable) species, molecular fragments (e.g., radicals) and the like, when ignited by electrical energy from the power source  14  or when undergoing collisions with particles (electrons, photons, or other energy-bearing species of limited and selective chemical reactivity) formed from ionizable media  16 . More specifically, the precursors may include various reactive functional groups, such as acyl halide, alcohol, aldehyde, alkane, alkene, amide, amine, butyl, carboxlic, cyanate, isocyanate, ester, ether, ethyl, halide, haloalkane, hydroxyl, ketone, methyl, nitrate, nitro, nitrile, nitrite, nitroso, peroxide, hydroperoxide, oxygen, hydrogen, nitrogen, and combination thereof. In embodiments, the chemical precursors may be water, halogenoalkanes, such as dichloromethane, tricholoromethane, carbon tetrachloride, difluoromethane, trifluoromethane, carbon tetrafluoride, and the like; peroxides, such as hydrogen peroxide, acetone peroxide, benzoyl peroxide, and the like; alcohols, such as methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, alkalises such as NaOH, KOH, amines, alkyls, alkenes, and the like. Such chemical precursors may be applied in substantially pure, mixed, or soluble form. 
         [0028]    The precursors and their functional groups may be delivered to a surface to react with the surface species (e.g., molecules) of the workpiece “W.” In other words, the functional groups may be used to modify or replace existing surface terminations of the workpiece “W.” The functional groups react readily with the surface species due to their high reactivity and the reactivity imparted thereto by the plasma. In addition, the functional groups are also reacted within the plasma volume prior to delivering the plasma volume to the workpiece. 
         [0029]    Some functional groups generated in the plasma can be reacted in situ to synthesize materials that subsequently form a deposition upon the surface. This deposition may be used for stimulating healing, killing bacteria, and increasing hydrophilic or hydroscopic properties. In addition, deposition of certain function groups may also allow for encapsulation of the surface to achieve predetermined gas/liquid diffusion, e.g., allowing gas permeation but preventing liquid exchange, to bond or stimulate bonding of surfaces, or as a physically protective layer. 
         [0030]    With reference to  FIGS. 1 and 2 , the precursor source  18  and the ionizable media source  16  may be coupled to the plasma device  12  via tubing  114  and  113 , respectively. The tubing  114  and  113  may be combined into unified tubing to deliver a mixture of the ionizable media and the precursor feedstock to the device  12  at a proximal end thereof. This allows for the plasma feedstocks, e.g., the precursor feedstock and the ionizable gas, to be delivered to the plasma device  12  simultaneously prior to ignition of the mixture therein. 
         [0031]    In another embodiment, the ionizable media source  16  and the precursors source  18  may be coupled to the plasma device  12  via the tubing  114  and  113  at separate connections, such that the mixing of the feedstocks occurs within the plasma device  12  upstream from the ignition point. In other words, the plasma feedstocks are mixed proximally of the ignition point, which may be any point between the respective sources  16  and  18  and the plasma device  12 , prior to ignition of the plasma feedstocks to create the desired mix of the plasma effluent species for each specific surface treatment on the workpiece “W.” 
         [0032]    In a further embodiment, the plasma feedstocks may be mixed midstream, e.g., at the ignition point or downstream of the plasma effluent, directly into the plasma. It is also envisioned that the ionizable media may be supplied to the device  12  proximally of the ignition point, while the precursor feedstocks are mixed therewith at the ignition point. In a further illustrative embodiment, the ionizable media may be ignited in an unmixed state and the precursors may be mixed directly into the ignited plasma. Prior to mixing, the plasma feedstocks may be ignited individually. The plasma feedstock is supplied at a predetermined pressure to create a flow of the medium through the device  12 , which aids in the reaction of the plasma feedstocks and produces a plasma effluent. The plasma according to the present disclosure is generated at or near atmospheric pressure under normal atmospheric conditions. 
         [0033]    The system  10  also includes a coolant system  15  for cooling the device  12  and particularly the plasma plume  32 . The coolant system  15  includes a supply pump  17  and a supply tank  18 . The supply pump  17  may be a peristaltic pump or any other suitable type of pump known in the art. The supply tank  17  stores the coolant fluid (e.g., saline, propylene glycol) and, in one embodiment, may maintain the fluid at a predetermined temperature. In another embodiment, the coolant fluid may be a gas and/or a mixture of fluid and gas. The system  10  further includes a negative pressure source  19  to siphon tissue and unreacted components from the treatment site. The negative-pressure source  17  may be a vacuum pump, fan, circulator, and the like and is coupled to the device  12 . 
         [0034]    With reference to  FIGS. 2 and 3 , the device  12  is shown as a plasma applicator  100 . The applicator  100  includes a handle  101  and a longitudinal shaft  102  coupled thereto. The shaft  102  includes a proximal portion  104  coupled to the handle  101  and a distal portion  106 . The catheter shaft  102  includes a plasma lumen  103  defined therein and extending the entire length thereof and terminating in an opening  105  at distal end of the distal portion  106 . The shaft  102  may have a diameter from about 5 mm to about 10 mm allowing the applicator  100  to be inserted through operating ports for application of the plasma effluent  32  at the operating site during laparscopic procedures or through natural body orifices. In another embodiment, the applicator  100  may be configured for use within or accompanied by a flexible endoscope. 
         [0035]    In one embodiment, the distal portion  106  is configured for controlled deflection. A pull-wire  107  ( FIG. 3 ) or another suitable actuation mechanism extends from the handle  101  at the proximal end of the catheter  100  through a lumen in the catheter shaft  102  and is fastened to the distal portion  106 . The pull-wire  107  is movable from a first generally relaxed position wherein the distal portion  106  is disposed in a generally longitudinally-aligned position relative to the proximal portion  104  to a second retracted or tensed position wherein the distal portion  106  flexes (e.g., deflects) from the proximal portion  104  at a desired angle as shown in  FIG. 2 . 
         [0036]    The distal portion  106  is constructed to be more flexible than the proximal portion  104 , such that when the handle  101  is pulled back or otherwise actuated, the pull-wire bends the distal portion  106  from an undeflected position to a deflected position. In particular, the proximal portion  104  may include a wire or other support materials (not shown) therein to provide tensile strength to the catheter shaft  102  while still maintaining flexibility for maneuvering through a vascular system. The distal portion  106  is formed from a flexible biocompatible material such as polytetrafluoroethylene, polyurethane, polyimide, and the like to allow for maneuverability thereof. 
         [0037]    The applicator  100  includes two or more electrodes  108  and  110  disposed at the distal portion  106 . The electrodes  108  and  110  may be formed from a conductive material and have a ring-like shape. The electrodes  108  and  110  may be disposed over the distal portion  106  to provide for capacitive coupling with the ionizable media. In another embodiment, the electrodes  108  and  110  may be formed as needle electrodes (e.g., pointed tip) and may be disposed within the distal portion  106 . 
         [0038]    The electrodes  108  and  110  are coupled to conductors (not shown) that extend through the catheter shaft  102  and are connected to the power source  14  via electrical connectors  112 . The catheter shaft  102  is also coupled to the ionizable media source  16  via gas tubing  114  and to the precursors source  16  via tubing  113 . The ionizable media source  16  and the precursors source  16  may include various flow sensors and controllers (e.g., valves, mass flow controllers, etc.) to control the flow of ionizable media to the applicator  100 . In particular, the lumen  103  is in gaseous and/or liquid communication with the ionizable media source  16  and the precursors source  18  allowing for the flow of ionizable media and precursor feedstocks to flow through the catheter shaft  102  to the distal portion  106 . The ionizable media in conjunction with the precursor feedstocks is ignited by application of energy through the electrodes  108  and  110  to form plasma plume  32  exiting through the opening  105 . 
         [0039]    The applicator  100  also includes a suction lumen  150  coupled to the negative pressure source  19 . This allows for the removal of unreacted feedstocks, debris and tissue particles to be removed from the tissue site. The lumen  150  may be incorporated into the shaft  102  ( FIG. 3 ) or may be a separate tube coupled in parallel to the shaft  102 . 
         [0040]    The applicator  100  is suitable for treatment of various sinus cavities, such as paranasal sinuses. Sinuses are commonly accessed through nasal passages using open or endoscopic instruments. Treatment of sinus cavities may involve debulking of the soft tissue located within the sinuses to prevent infections thereof. In particular, the goal of the procedure may be to remove polyps, tumors, fungal masses and other tissue structures while preserving as much of the mucosal lining as possible. 
         [0041]    With reference to  FIGS. 4 and 5 , a functional sinus procedure using the applicator  100  is discussed.  FIG. 4  illustrates the paranasal sinuses and  FIG. 5  illustrates a flow chart of a method for treating the sinuses. The surgical site includes multiple sinus cavities  200  formed within the bone mass  202 . The sinus cavity  200  includes a formation  204  (e.g., tumors, polyps, fungal masses, etc.) that affects the health of the sinus cavities  200 . 
         [0042]    In step  300 , the applicator  100  inserted into the sinus cavity  200  through a nasal cavity  203 . Access may be gained through or by enlargement of an existing ostium or creating an opening to the sinus cavity  200  from the nasal cavity  203  or perforation through other organs (e.g., percutaneous). 
         [0043]    The distal portion  106  may be deflected to direct the plasma effluent  32  toward the tissue formation  204 . In one embodiment, the deflection may be from about 0° to about 45° with respect to a longitudinal axis defined by the shaft  102 . In step  302 , the ionizable media along with precursors is supplied to the applicator  100  and is ignited therein to form the plasma effluent  32 . In one embodiment, the ionizable media may be argon, helium or a mixture thereof and the precursors may be hydrogen peroxide, water, oxygen, nitrogen or mixtures thereof. 
         [0044]    In step  304 , the applicator  100  is moved across the tissue formation  204  ensuring that the plasma effluent  32  is directed at the tissue to remove the soft tissue. As tissue is ablated, unreacted tissue particles and other debris is removed from the treatment site through the suction lumen  150  via the negative pressure source  19 . The temperature of the plasma effluent  32  is from about 60°, allowing the plasma to be used within the confines of the sinus cavity  200  without ablating surrounding critical tissue masses. The relatively low temperature of the plasma effluent  32  does not affect its ability to remove tissue, since the primary effect on tissue is due to the chemical reactivity of the plasma constituents (e.g., ionized plasma feedstocks). 
         [0045]    The precursors supplied to the applicator  100  are specifically chosen to generate a selectively reactive plasma effluent  32 . In other words, the precursors, when ignited, produce a plasma effluent  32  that interacts with certain types of tissue, namely tissue formation  204 , and has little to no effect on the underlying bone tissue. The selected precursor feedstocks have higher chemical reactivity with the tissue formation  204  relative to the chemical reactivity with the calcified tissue (e.g., bone). This allows for the plasma effluent  32  to etch and remove the tissue formation  204  without perforating the bone. 
         [0046]    The plasma effluent  32  ablates and coagulates tissue via heat to stop bleeding. The plasma effluent  32  effectively ablates tissue formation  204  while simultaneously cauterizing the tissue preventing bleeding. In one embodiment, bleeding may be also controlled by administration of various drugs (e.g., hemostatic agents) that prevent bleeding within the sinus cavity  200 . The drugs may be administered topically to the tissue or through the plasma effluent  32  as chemical precursor feedstocks. 
         [0047]    Sinus cavities may be very close to the brain or orbit of the eye, making conventional instruments, such as microdebriders very dangerous due to their aggressive cutting action that may remove the surrounding bone tissue and damage nearby organs. In addition, diseased sinuses have already thinned bones further reducing differentiation between targeted soft tissues and bone tissue, thereby further increasing the possibility of perforation into adjacent critical structures. 
         [0048]    The present disclosure prevents such damage without requiring great care and expensive surgical navigational systems (e.g., endoscopes) that are practically required when using conventional microdebriders. The present disclosure provides for a chemically reactive plasma that has higher chemical reactivity with the soft tissue than calcified tissue (e.g., bone) thereby etching the soft tissue while leaving calcified or partially calcified tissue unaffected. This provides for safer removal of tissue masses near critical structures. The reactivity, removal rates and/or selectivity of the plasma effluent may be modified by supplying different chemical precursors to the applicator  100  based on the tissue being treated. 
         [0049]    The applicator  100  also provides another advantage over mechanical microdebriders, namely, a deflectable distal portion  106 . Mechanical debriders and/or cutters have inflexible shafts which are either straight or curved having fixed radial bends in the instrument shaft. Deflection of the distal portion  106  allows for usage of the applicator  100  at virtually any reach within a general target mass or within the sinuses. 
         [0050]    The plasma effluent according to the present disclosure also generates little heat and may be produced at a relatively low temperature (e.g., room temperature). This provides another advantage over conventional methods that utilize electrosurgical instruments. Such instruments generate too much heat that is poorly dissipated within the sinuses, which may damage critical structures. 
         [0051]    Although the illustrative embodiments of the present disclosure have been described herein with reference to the accompanying drawings, it is to be understood that the disclosure is not limited to those precise embodiments, and that various other changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the disclosure. In particular, as discussed above this allows the tailoring of the relative populations of plasma species to meet needs for the specific process desired on the workpiece surface or in the volume of the reactive plasma, such adapting the disclosed system and method for use on other body cavities where selective removal of tissue is desired.