Patent Publication Number: US-2023147519-A1

Title: Wound debridement by irrigation with ultrasonically activated microbubbles

Description:
RELATED APPLICATIONS 
     The present invention is a continuation of U.S. patent application Ser. No. 16/595,763, filed Oct. 8, 2019, which is a continuation of U.S. patent application Ser. No. 15/147,666, filed May 5, 2016, now U.S. Pat. No. 10,471,190, which claims the benefit under 35 U.S.C. § 119(e), of the filing of U.S. Provisional Patent Application Ser. No. 62/158,630, filed May 8, 2015, all of which are incorporated herein by reference for all purposes. 
    
    
     TECHNICAL FIELD 
     The invention set forth in the appended claims relates generally to tissue treatment systems and more particularly, but without limitation, to debridement devices, systems, and methods suitable for debriding a tissue site. 
     BACKGROUND 
     Clinical studies and practice have shown that reducing pressure in proximity to a tissue site can augment and accelerate growth of new tissue at the tissue site. The applications of this phenomenon are numerous, but it has proven particularly advantageous for treating wounds. Regardless of the etiology of a wound, whether trauma, surgery, or another cause, proper care of a wound is important to the outcome. Treatment of wounds or other tissue with reduced pressure may be commonly referred to as “negative-pressure therapy,” but is also known by other names, including “negative-pressure wound therapy,” “reduced-pressure therapy,” “vacuum therapy,” “vacuum-assisted closure,” and “topical negative-pressure,” for example. Negative-pressure therapy may provide a number of benefits, including migration of epithelial and subcutaneous tissues, improved blood flow, and micro-deformation of tissue at a wound site. Together, these benefits can increase development of granulation tissue and reduce healing times. 
     There is also widespread acceptance that debridement of a tissue site can be highly beneficial for new tissue growth. Debridement may refer to a process for removing dead, damaged, or infected tissue from a tissue site for improving the healing potential of healthy tissue remaining at the tissue site. Several factors may make proper debridement difficult, such as challenging wound locations, immobile patients, and environmental constraints. Further, debridement may often be painful for the patient, and in some circumstances may also require a high level of skill from the caregiver, thereby presenting additional challenges. Additionally, debridement methods that are less painful to patients may be relatively slow processes. Therefore, improvements to debridement devices, systems, and methods that may reduce the amount of time to debride a tissue site as well as reduce the risks of pain for the patient or damage to healthy tissue associated with conventional methodologies may be desirable. 
     BRIEF SUMMARY 
     New and useful systems, apparatuses, and methods for debriding a tissue site are set forth in the appended claims. Illustrative embodiments are also provided to enable a person skilled in the art to make and use the claimed subject matter. 
     In some embodiments, a system for treating a tissue site may include a dressing, a negative-pressure source fluidly coupled to the dressing, a fluid source, and an ultrasonic bubble generator. The ultrasonic bubble generator may be fluidly coupled to the fluid source and to the dressing and may be configured to generate micro-bubbles and ultrasonic waves in a fluid from the fluid source. 
     In other embodiments, a method for debriding necrotic tissue from a tissue site may include coupling a fluid source to the tissue site, supplying a fluid from the fluid source to an ultrasonic bubble generator, generating micro-bubbles and ultrasonic waves in the fluid with the ultrasonic bubble generator, and delivering the micro-bubbles and ultrasonic waves to the necrotic tissue. The ultrasonic bubble generator may further include an ultra-violet light source. In some embodiments, the method may further include coupling a negative-pressure source to a dressing. 
     Other aspects, features, and advantages of the illustrative embodiments will become apparent with reference to the drawings and detailed description that follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an example embodiment of negative-pressure therapy system that can deliver ultrasonically-activated micro-bubbles in accordance with this specification; and 
         FIG.  2    is a perspective view illustrating additional details that may be associated with some example embodiments of the negative-pressure therapy system of  FIG.  1   . 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     The following description of example embodiments provides information that enables a person skilled in the art to make and use the subject matter set forth in the appended claims, but may omit certain details already well-known in the art. The following detailed description is, therefore, to be taken as illustrative and not limiting. 
     The example embodiments may also be described herein with reference to spatial relationships between various elements or to the spatial orientation of various elements depicted in the attached drawings. In general, such relationships or orientation assume a frame of reference consistent with or relative to a patient in a position to receive treatment. However, as should be recognized by those skilled in the art, this frame of reference is merely a descriptive expedient rather than a strict prescription. 
     Referring now primarily to  FIG.  1   , a therapy system  100  that can provide negative-pressure therapy with instillation of topical treatment solutions for treating a tissue site  102  is presented. The tissue site  102  may include, without limitation, any irregularity with a tissue, such as an open wound, surgical incision, or diseased tissue. The therapy system  100  is presented in the context of a tissue site  102  that includes a wound  104 , which is through the epidermis  106 , or generally skin, and the dermis  108  and reaching into a hypodermis, or subcutaneous tissue  110 . The therapy system  100  may be used to treat a wound of any depth, as well as many different types of wounds including open wounds or other tissue sites. The tissue site  102  may be the bodily tissue of any human, animal, or other organism, including bone tissue, adipose tissue, muscle tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, ligaments, or any other tissue. Treatment of the tissue site  102  may include removal of fluids, for example, exudate or ascites. 
     The term “tissue site” in this context broadly refers to a wound or defect located on or within tissue, including but not limited to, bone tissue, adipose tissue, muscle tissue, neural tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, or ligaments. A wound may include chronic, acute, traumatic, subacute, and dehisced wounds, partial-thickness burns, ulcers (such as diabetic, pressure, or venous insufficiency ulcers), flaps, and grafts, for example. The term “tissue site” may also refer to areas of any tissue that are not necessarily wounded or defective, but are instead areas in which it may be desirable to add or promote the growth of additional tissue. For example, negative pressure may be used in certain tissue areas to grow additional tissue that may be harvested and transplanted to another tissue location. 
     As used herein, the terms “debride,” “debriding,” and “debridement,” relate to the act of removing or the removal of undesirable tissue, such as, eschar, necrotic, damaged, infected, contaminated, or adherent tissue, or foreign material from a tissue site. Several methods of debridement may be employed to treat a wound  104  having necrotic tissue  112 , including surgical debridement, mechanical debridement, chemical or enzymatic debridement, and autolytic debridement. 
     However, each of these methods has both advantages and disadvantages. For example, while mechanical debridement is perhaps the fastest method of debridement, it is almost invariably painful or at least submits the patient to a significant level of discomfort. Additionally, mechanical debridement typically requires a high level of skill from the caregiver. 
     Chemical, or enzymatic, debridement entails the use of chemical enzymes to convert the necrotic tissue to slough. Chemical debridement may be fast-acting and cause minimal damage to healthy tissue if the chemicals are applied properly. However, chemical debridement has disadvantages as well. The process may be expensive and traditional chemical debridement methods and systems, such as low pH systems, may be painful to a patient. Other debriding agents, such as papain, may have other health implications and only have limited usage that is restricted by law. Other agents may be used, such as medical grade honey, but can become quickly mobile in the presence of fluid, such as wound exudate, and an applied negative pressure. 
     Autolytic debridement, or autolysis, entails the use of the body&#39;s own enzymes and white blood cells, along with moisture, to hydrate and liquefy the necrotic tissue  112  and slough. Since autolytic debridement is a naturally occurring process, it is relatively painless and does not risk damage to healthy tissue. Further, autolytic debridement does not require wound fluid to remain in contact with the necrotic tissue  112 , and can be facilitated by the use of films, hydrocolloids, and hydrogels. A disadvantage of autolytic debridement is that autolytic debridement is slower than other types of debridement, rendering the wound susceptible to infection. 
     Thus, there is a need for a debriding process that accelerates, and thereby enhances, the naturally-occurring debridement process without the disadvantages associated with mechanical debridement, while also not using enzymes or other chemicals or drugs. Moreover, it is desirable to have a system and method that allow negative-pressure treatment to occur. As disclosed herein, the therapy system  100  may address these outstanding needs and others. For example, the therapy system  100  may provide a low-pain alternative for enhanced debridement and healing of wounds that can be used in conjunction with negative-pressure treatment. 
     Referring again to  FIG.  1   , the wound  104  may include necrotic tissue  112 , and in many instances, it may be desirable to remove the necrotic tissue  112  in order to promote healing of the wound  104 . The illustrative, non-limiting embodiment shows the therapy system  100  in the context of the wound  104  having a localized, or discrete area, of necrotic tissue  112  within the wound. The therapy system  100  may be used in broader contexts, including with any tissue site having undesirable tissue. Such undesirable tissue may include, necrotic, damaged, infected, contaminated, or adherent tissue, foreign material within the wound  104 , and may include a layer of necrotic tissue  112  that covers the entire surface of the wound  104 . 
     The therapy system  100  may include a dressing, a negative-pressure source, a fluid source, and a micro-bubble source. For example, a dressing  114  may be fluidly coupled to a negative-pressure source  116 , a fluid source  117 , and a micro-bubble subsystem  118 , as illustrated in  FIG.  1   . The therapy system  100  may also include a container for supplying fluid as well as collecting exudates, such as a container  120 , coupled to the dressing  114  and to the negative-pressure source  116 . 
     In general, components of the therapy system  100  may be coupled directly or indirectly. For example, the negative-pressure source  116  may be directly coupled to components of the micro-bubble subsystem  118  and the container  120 , and indirectly coupled to the dressing  114  through the micro-bubble subsystem  118  and the container  120 . In some embodiments, components may be coupled by virtue of physical proximity, being integral to a single structure, or being formed from the same piece of material. Coupling may also include mechanical, thermal, electrical, or chemical coupling (such as a chemical bond) in some contexts. 
     Components may also be fluidly coupled to each other to provide a path for transferring fluids (i.e., liquid and/or gas) between the components. In some embodiments, for example, components may be fluidly coupled through a tube. A “tube,” as used herein, broadly refers to a tube, pipe, hose, conduit, or other fluid conductor with one or more lumina adapted to convey fluid between two ends. Typically, a tube is an elongated, cylindrical structure with some flexibility, but the geometry and rigidity may vary. A fluid conductor may also be integrally molded into a component in some embodiments. 
     The dressing  114  may be placed within, over, on, or otherwise proximate to the tissue site  102 . The dressing  114  may be sealed to tissue near the tissue site  102 . For example, the dressing  114  may be sealed to undamaged epidermis peripheral to the tissue site  102 . Thus, the dressing  114  can provide a sealed therapeutic environment proximate to the tissue site  102 , substantially isolated from the external environment, and the negative-pressure source  116  can reduce the pressure in the sealed therapeutic environment. Negative pressure applied across the tissue site  102  through the dressing  114  in the sealed therapeutic environment can induce macro-strain and micro-strain in the tissue site, as well as remove exudate and other fluid from the tissue site  102 , which can be collected in the container  120 . 
     The fluid mechanics of using a negative-pressure source to reduce pressure in another component or location, such as within a sealed therapeutic environment, can be mathematically complex. However, the basic principles of fluid mechanics applicable to negative-pressure therapy and instillation are generally well-known to those skilled in the art. 
     In general, fluid flows toward lower pressure along a fluid path. Thus, the term “downstream” typically implies something in a fluid path relatively closer to a source of negative pressure or further away from a source of positive pressure; conversely, the term “upstream” implies something relatively further away from a source of negative pressure or closer to a source of positive pressure. Similarly, it may be convenient to describe certain features in terms of fluid “inlet” or “outlet” in such a frame of reference, and the process of reducing pressure may be described illustratively herein as “delivering,” “distributing,” or “generating” reduced pressure, for example. This orientation is generally presumed for purposes of describing various features and components herein. 
     “Negative pressure” generally refers to a pressure less than a local ambient pressure, such as the ambient pressure in a local environment external to a sealed therapeutic environment provided by the dressing  114 . In many cases, the local ambient pressure may also be the atmospheric pressure at which a tissue site is located. Alternatively, negative pressure may be a pressure less than a hydrostatic pressure associated with tissue at the tissue site. Unless otherwise indicated, values of pressure stated herein are gauge pressures. Similarly, references to increases in negative pressure typically refer to a decrease in absolute pressure, while decreases in negative pressure typically refer to an increase in absolute pressure. 
     A negative-pressure source, such as the negative-pressure source  116 , may be a reservoir of air at a negative pressure, or may be a manual or electrically-powered device that can reduce the pressure in a sealed volume, such as a vacuum pump, a suction pump, a wall suction port available at many healthcare facilities, or a micro-pump, for example. A negative-pressure source may be housed within or used in conjunction with other components, such as sensors, processing units, alarm indicators, memory, databases, software, display devices, or user interfaces that further facilitate negative-pressure therapy. While the amount and nature of negative pressure applied to a tissue site may vary according to therapeutic requirements, the pressure is generally a low vacuum, also commonly referred to as a rough vacuum, between −5 mm Hg (−667 Pa) and −500 mm Hg (−66.7 kPa). Common therapeutic ranges are between −75 mm Hg (−9.9 kPa) and −300 mm Hg (−39.9 kPa). 
     The fluid source  117  may be housed within or used in conjunction with other components to facilitate movement of a fluid. The fluid source  117  may be a fluid pump, for example a peristaltic pump. Alternatively, in some embodiments, the fluid source  117  may be a fluid reservoir, which may store and deliver fluid. In any embodiment, the fluid source  117 , such as a fluid pump or a fluid reservoir, may include a container, such as a canister, pouch, or other storage component. In some embodiments the fluid source  117  may be a fluid pump that helps supply the micro-bubble subsystem  118  with the fluid that may ultimately be delivered to a tissue site. 
     The dressing  114  may include a manifold  122  and a drape  124 . The dressing  114  may also include an attachment device  126  that affixes the drape  124  to the epidermis  106  of the patient. The drape  124  may also include an adhesive surface that seals directly against the epidermis  106  of the patient without the need for an attachment device. The manifold  122  may be positioned between a tissue-facing surface of the drape  124  and the tissue site  102 . 
     The manifold  122  may generally include any substance or structure providing a plurality of pathways adapted to collect or distribute fluid across a tissue site. For example, a manifold may be adapted to receive negative pressure from a source and distribute negative pressure through multiple apertures across a tissue site, which may have the effect of collecting fluid from across a tissue site and drawing the fluid toward the source. In some embodiments, the fluid path may be reversed or a secondary fluid path may be provided to facilitate distributing fluid across a tissue site. 
     In some illustrative embodiments, the pathways of a manifold may be interconnected to improve distribution or collection of fluids across a tissue site. For example, cellular foam, open-cell foam, reticulated foam, porous tissue collections, and other porous material such as gauze or felted mat generally include pores, edges, and/or walls adapted to form interconnected fluid pathways. Liquids, gels, and other foams may also include or be cured to include apertures and fluid pathways. In some illustrative embodiments, a manifold may be a porous foam material having interconnected cells or pores adapted to distribute negative pressure across a tissue site. The foam material may be either hydrophobic or hydrophilic. The pore size of a foam material may vary according to needs of a prescribed therapy. For example, in some embodiments, the manifold  122  may include a wound filler, which may be a foam having a large pore size or may be a perforated felted foam. The pores or perforations of the wound filler may be in the range of 3-7 millimeters (mm) in diameter, and preferably about 5 mm in diameter. The tensile strength of the manifold  122  may also vary according to needs of a prescribed therapy. For example, the tensile strength of a foam may be increased for instillation of topical treatment solutions. In one non-limiting example, the manifold  122  may be an open-cell, reticulated polyurethane foam such as GranuFoam® dressing available from Kinetic Concepts, Inc. of San Antonio, Tex.; in other embodiments the manifold  122  may be an open-cell, reticulated polyurethane foam such as a VeraFlo® foam, also available from Kinetic Concepts, Inc., of San Antonio, Tex. 
     In an example in which the manifold  122  may be made from a hydrophilic material, the manifold  122  may also wick fluid away from a tissue site, while continuing to distribute negative pressure to the tissue site. The wicking properties of the manifold  122  may draw fluid away from a tissue site by capillary flow or other wicking mechanisms. An example of a hydrophilic foam is a polyvinyl alcohol, open-cell foam such as V.A.C. WhiteFoam® dressing available from Kinetic Concepts, Inc. of San Antonio, Tex. Other hydrophilic foams may include those made from polyether. Other foams that may exhibit hydrophilic characteristics include hydrophobic foams that have been treated or coated to provide hydrophilicity. 
     In some embodiments, the manifold  122  may be constructed from bioresorbable materials. Suitable bioresorbable materials may include, without limitation, a polymeric blend of polylactic acid (PLA) and polyglycolic acid (PGA). The polymeric blend may also include without limitation polycarbonates, polyfumarates, and capralactones. The manifold  122  may further serve as a scaffold for new cell-growth, or a scaffold material may be used in conjunction with the manifold  122  to promote cell-growth. A scaffold is generally a substance or structure used to enhance or promote the growth of cells or formation of tissue, such as a three-dimensional porous structure that provides a template for cell growth. Illustrative examples of scaffold materials include calcium phosphate, collagen, PLA/PGA, coral hydroxy apatites, carbonates, or processed allograft materials. 
     In some embodiments, the drape  124  may provide a bacterial barrier and protection from physical trauma. The drape  124  may also be constructed from a material that can reduce evaporative losses and provide a fluid seal between two components or two environments, such as between a therapeutic environment and a local external environment. The drape  124  may be, for example, an elastomeric film or membrane that can provide a seal adequate to maintain a negative pressure at a tissue site for a given negative-pressure source. In some example embodiments, the drape  124  may be a polymer drape, such as a polyurethane film, that is permeable to water vapor but impermeable to liquid. Such drapes typically have a thickness in the range of 25-50 microns. For permeable materials, the permeability generally should be low enough that a desired negative pressure may be maintained. 
     In some embodiments, an attachment device  126  may be used to attach the drape  124  to an attachment surface, such as undamaged epidermis, a gasket, or another cover. The attachment device  126  may take many forms. For example, an attachment device may be a medically-acceptable, pressure-sensitive adhesive that extends about a periphery, a portion, or the entire drape  124 . In some embodiments, for example, some or all of the drape  124  may be coated with an acrylic adhesive having a coating weight between 25-65 grams per square meter (g.s.m.). Thicker adhesives, or combinations of adhesives, may be applied in some embodiments to improve the seal and reduce leaks. Other example embodiments of an attachment device may include a double-sided tape, paste, hydrocolloid, hydrogel, silicone gel, or organogel. 
     The negative pressure provided by the negative-pressure source  116  may be delivered through a conduit  128  to a negative-pressure interface  130 , which may be an elbow port  132 . In one illustrative embodiment, the negative-pressure interface  130  is a T.R.A.C.® Pad or Sensa T.R.A.C.® Pad available from KCI of San Antonio, Tex. The negative-pressure interface  130  allows the negative pressure to be delivered to the drape  124  and realized within an interior portion of the drape  124  and the manifold  122 . In this illustrative, non-limiting embodiment, the elbow port  132  extends through the drape  124  to the manifold  122 , but numerous arrangements are possible. 
     The container  120  is representative of a container, canister, pouch, or other storage component, which can be used to manage exudate and other fluid withdrawn from a tissue site. In many environments, a rigid container may be preferred or required for collecting, storing, and disposing of fluid. In some preferred embodiments, the container  120  may be positioned in fluid communication between the negative-pressure source  116  and the dressing  114  to collect fluid drawn from a tissue site. The container  120  may also include features that enable filtering of the effluent that is withdrawn from the dressing  114  and tissue site  102 . In some embodiments, the container  120  may attach to the negative-pressure source  116 , as illustrated in  FIG.  1   . 
     The container  120  may include multiple ports and connection interfaces for integration with the negative-pressure source  116 , the fluid source  117 , and the other components of the therapy system  100 . For example, the container  120  may have two outlets, one of which may be for fluidly connecting the container  120  to the fluid source  117 , and the second of which may be for fluidly connecting the container  120  to the negative-pressure source  116 . 
     The micro-bubble subsystem  118  may include a UV light sterilizer  136  and an ultrasonic bubble generator  138 . The UV light sterilizer  136  may be positioned in fluid connection between the negative-pressure source  116  and the ultrasonic bubble generator  138 . In some embodiments, the micro-bubble subsystem  118  may be fluidly connected to the negative-pressure source  116  and the dressing  114  by the supply conduit  140 . In some embodiments, the micro-bubble subsystem  118  may be in close physical proximity to the dressing  114 , or optionally incorporated as part of the dressing  114 . In other embodiments, some or all of the components of the micro-bubble subsystem  118  may be incorporated within the negative-pressure source  116 . 
     As fluid is moved from the negative-pressure source  116  through the supply conduit  140  to the ultrasonic bubble generator  138 , the fluid may pass through the UV light sterilizer  136 . The UV light sterilizer  136  may contain a UV light source, which may dose the fluid passing through the UV light sterilizer  136  with UV light to kill any pathogens that may be in the fluid. Once the fluid has passed through the UV light sterilizer  136 , the fluid may be delivered to the ultrasonic bubble generator  138  through supply conduit  140 . 
     The ultrasonic bubble generator  138  may function to generate both micro-bubbles and an ultrasonic waveform in a fluid. For example, the ultrasonic bubble generator  138  may be an apparatus for generating an output flow of liquid, including an acoustic transducer for introducing acoustic energy into the liquid and a gas bubble generator for generating gas bubbles within the liquid, as described in U.S. Patent Application Publication No. US 2012/0227761 A1, which is hereby incorporated by reference in its entirety. As illustrated in  FIG.  1   , fluid may be delivered from the UV light sterilizer  136  through supply conduit  140  to the ultrasonic bubble generator  138 . As the fluid passes through the ultrasonic bubble generator  138 , the ultrasonic bubble generator  138  may generate and inject gas bubbles within the fluid. While the micro-bubbles may be generated in a range of sizes, the micro-bubbles may typically be approximately 15-200 micrometers (μm) in diameter. The ultrasonic bubble generator  138  may then generate an ultrasonic waveform that may be conducted through the fluid as it flows through the ultrasonic bubble generator  138 . In some embodiments, the ultrasonic bubble generator  138  may include a transducer that emits acoustic energy. The acoustic energy may be emitted as intermittent pulses. Referring also to  FIG.  2   , as micro-bubbles  202  are hit by the ultrasonic waves, the micro-bubbles may undergo significant deformation which may manifest itself as a ripple  204  at the gas/liquid interface. As a result of this ripple, the micro-bubble can exert a scrubbing action on surfaces it touches as the micro-bubble  206  is deformed, and the turbulence formed around the micro-bubble may also cause the micro-bubble to be drawn to surfaces and into cracks and crevices, such as deformities at a tissue site. 
     In some embodiments, the manifold  122  may be tailored to cause minimal attenuation of the ultrasonic energy generated by the micro-bubble source  118 . For example, the manifold  122  may be largely constructed from polymers that are hydrophilic, which may contain water or be configured to absorb water. Such hydrophilic polymers may include poly hydroxy ethyl methacrylate, copolymer of N-vinyl pyrrolidone and 2-hydroxy ethyl methacrylate, terpolymer based on glycerol methacrylate, copolymer of N-vinyl pyrrolidone and methyl methacrylate, as well as polymethyl methacrylate (PMMA). Additionally, the manifold  122  may be constructed from hydrophilic polyurethane polymers, such as TECOPHILIC hydrophilic polyurethanes available from The Lubrizol Corp. of Wickliffe, Ohio, which in extrusion grade formulations, may absorb water up to 100% of the weight of dry resin (900% of weight of dry resin for hydrogel grades) while retaining structural integrity. In some embodiments, the manifold  122  may be formed from one of the hydrophilic polymers listed above into a porous or foamed structure with pores measuring approximately 5-10 mm in diameter, which may minimize the number of struts that could interfere with the passage of bubbles. In other embodiments, the manifold  122  may be formed from one of the hydrophilic polymers formed into a perforated sheet having protrusions on one side. In some instances, the protrusions may be spaced about 5-10 mm apart from each other, and may be hemispherical or polygonal in shape. The protrusions may act as spacers between the wound  104  and the drape  124 . 
     The therapy system  100  presented in  FIG.  1    may also include a second interface, such as fluid-delivery interface  142 . The fluid-delivery interface  142  may be fluidly coupled to the dressing  114  and may pass through a hole cut in the drape  124 . The hole cut in the drape for the fluid-delivery interface  142  may be separated as far apart as possible from the location or other hole cut in the drape through which the negative-pressure interface  130  may pass. The fluid-delivery interface  142  may allow for a fluid to be delivered by the therapy system  100  through the drape  124  and to the manifold  122  and the tissue site  102 . 
     In some embodiments, the fluid-delivery interface  142  may include an inlet pad. The inlet pad may be a non-dampening material or a material that is not sound-absorbing. In some embodiments, the inlet pad may be an elastomer. For example, the inlet pad may be an elastic polymer, such as polyurethane, thermoplastic elastomers, polyether block amide (PEBAX), polyisoprene, polychloroprene, chlorosulphonated polythene, and polyisobutylene, blends and copolymers. 
     The composition of the fluid may vary according to a prescribed therapy, but examples of solutions that may be suitable for some prescriptions include a saline solution with a low level of surfactant, such as &lt;0.1%, and more typically 0.015%. Such surfactants may include Pluronic F68, polyolefin oxides, and polyolefin glycols. By including a surfactant in the fluid, the generated micro-bubbles may be preserved for a longer duration as they travel from the ultrasonic bubble generator  138  to the tissue site  102 . 
     The therapy system  100  may also include a particulate filter  134 , which may be positioned in fluid communication between the container  120  and/or the negative-pressure source  116  and the dressing  114 . The particulate filter  134  may function to remove particulate matter from the effluent that has circulated through the dressing  114 . For example, in the embodiment pictured in  FIG.  1   , fluid delivered to the dressing  114  and to the tissue site  102  may be drawn out of the dressing  114  through the negative-pressure interface  130  and transported through negative-pressure conduit  128  to the particulate filter  134 . The fluid may be filtered to remove particulate matter in the particulate filter  134 , before being recollected in the container  120 . 
     In operation, the negative-pressure source  116  may pump fluid, such as a saline solution through the supply conduit  140  to a UV light sterilization unit, such as UV light sterilizer  136 . Once the fluid has passed through the UV light sterilizer  136 , the fluid may continue through supply conduit  140  to the ultrasonic bubble generator  138 , where micro-bubbles may be generated in the fluid, followed by the fluid and micro-bubbles being activated by ultrasonic energy applied by the ultrasonic bubble generator  138 . The activated fluid may then pass through the fluid-delivery interface  142  and into the dressing  114 . The activated fluid may then pass through the manifold  122  and reach the wound  104 , where the activated fluid may debride necrotic tissue  112 . 
     Following the debridement of the necrotic tissue  112  by the activated fluid, the remaining effluent may be drawn out of the dressing  114  by negative pressure applied to the dressing  114  and tissue site  102  by the negative-pressure source  116 . For example, the effluent may be drawn from the wound  104 , through the manifold  122 , and out of the dressing  114  through the negative-pressure interface  130 . The effluent may then pass through negative-pressure conduit  128  to the particulate filter  134 , where particulate matter may be filtered out of the effluent. The filtered fluid may then be collected by the container  120  before being recirculated by the negative-pressure source  116  through the UV light sterilizer  136  and ultrasonic bubble generator  138  to the wound  104 . 
     The systems, apparatuses, and methods described herein may provide significant advantages. For example, a therapy system described above may provide a low-pain, clean method to achieve an alternative form of mechanical debridement. The therapy system can keep a wound enclosed, thus reducing the possible risk of infection, and can also store any particulate matter in a convenient location that may be easily disposed. The therapy system may also reduce the risk of contaminating the environment external to a wound with potentially infectious matter, and can also keep odors contained. 
     While shown in a few illustrative embodiments, a person having ordinary skill in the art will recognize that the systems, apparatuses, and methods described herein are susceptible to various changes and modifications. Moreover, descriptions of various alternatives using terms such as “or” do not require mutual exclusivity unless clearly required by the context, and the indefinite articles “a” or “an” do not limit the subject to a single instance unless clearly required by the context. 
     The appended claims set forth novel and inventive aspects of the subject matter described above, but the claims may also encompass additional subject matter not specifically recited in detail. For example, certain features, elements, or aspects may be omitted from the claims if not necessary to distinguish the novel and inventive features from what is already known to a person having ordinary skill in the art. Features, elements, and aspects described herein may also be combined or replaced by alternative features serving the same, equivalent, or similar purpose without departing from the scope of the invention defined by the appended claims.