Patent Description:
The invention set forth in the appended claims relates generally to tissue treatment systems and more particularly, but without limitation, to an apparatus for debriding a tissue site with negative pressure.

There is also widespread acceptance that cleansing a tissue site can be highly beneficial for new tissue growth. For example, a wound can be washed out with a stream of liquid solution, or a cavity can be washed out using a liquid solution for therapeutic purposes. These practices are commonly referred to as "irrigation" and "lavage" respectively. "Instillation" is another practice that generally refers to a process of slowly introducing fluid to a tissue site and leaving the fluid for a prescribed period of time before removing the fluid. For example, instillation of topical treatment solutions over a wound bed can be combined with negative-pressure therapy to further promote wound healing by loosening soluble contaminants in a wound bed and removing infectious material. As a result, soluble bacterial burden can be decreased, contaminants removed, and the wound cleansed.

While the clinical benefits of negative-pressure therapy and instillation therapy are widely known, improvements to therapy systems, components, and processes may benefit healthcare providers and patients.

<CIT> and <CIT> disclose systems for treating tissue site. <CIT> discloses a wound dressing for debridement.

New and useful apparatuses for decreasing bio-burden in a negative-pressure therapy environment 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.

An apparatus for debriding a tissue site with negative pressure is provided. The apparatus includes a felted foam having a plurality of perforations, the perforations fluidly coupling a first side of the felted foam to a second side of the felted foam. A film is coupled to the first side of the felted foam. The film has an anti-bioburden agent, wherein the anti-bioburden agent comprises citric acid and/or acetic acid.

The term "tissue site" in this context broadly refers to a wound, defect, or other treatment target located on or within tissue, including but not limited to, a surface wound, bone tissue, adipose tissue, muscle tissue, neural tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, or ligaments. 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 applied to a tissue site to grow additional tissue that may be harvested and transplanted. A surface wound, as used herein, is a wound on the surface of a body that is exposed to the outer surface of the body, such an injury or damage to the epidermis, dermis, and/or subcutaneous layers. Surface wounds may include ulcers or closed incisions, for example. A surface wound, as used herein, does not include wounds within an intra-abdominal cavity. 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.

<FIG> is a simplified functional block diagram of an example embodiment of a therapy system <NUM> that can provide negative-pressure therapy with instillation of topical treatment solutions to a tissue site in accordance with this specification. The therapy system <NUM> may include a source or supply of negative pressure, such as a negative-pressure source <NUM>, a dressing <NUM>, a fluid container, such as a container <NUM>, and a regulator or controller, such as a controller <NUM>, for example. As illustrated in <FIG>, for example, the therapy system <NUM> may include a pressure sensor <NUM>, an electric sensor <NUM>, or both, coupled to the controller <NUM>. As illustrated in the example of <FIG>, the dressing <NUM> may comprise or consist essentially of a tissue interface <NUM>, a cover <NUM>, or both in some embodiments.

The therapy system <NUM> may also include a source of instillation solution. For example, a solution source <NUM> may be fluidly coupled to the dressing <NUM>, as illustrated in the example embodiment of <FIG>. The solution source <NUM> may be fluidly coupled to a positive-pressure source such as the positive-pressure source <NUM>, a negative-pressure source such as the negative-pressure source <NUM>, or both in some embodiments. A regulator, such as an instillation regulator <NUM>, may also be fluidly coupled to the solution source <NUM> and the dressing <NUM> to ensure proper dosage of instillation solution (e.g. saline or sterile water) to a tissue site. For example, the instillation regulator <NUM> may comprise a piston that can be pneumatically actuated by the negative-pressure source <NUM> to draw instillation solution from the solution source during a negative-pressure interval and to instill the solution to a dressing during a venting interval. Additionally or alternatively, the controller <NUM> may be coupled to the negative-pressure source <NUM>, the positive-pressure source <NUM>, or both, to control dosage of instillation solution to a tissue site. In some embodiments, the instillation regulator <NUM> may also be fluidly coupled to the negative-pressure source <NUM> through the dressing <NUM>, as illustrated in the example of <FIG>.

Some components of the therapy system <NUM> 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 therapy. For example, in some embodiments, the negative-pressure source <NUM> may be combined with the solution source <NUM>, the controller <NUM>, and other components into a therapy unit.

For example, the negative-pressure source <NUM> may be directly coupled to the container <NUM>, and may be indirectly coupled to the dressing <NUM> through the container <NUM>. For example, the negative-pressure source <NUM> may be electrically coupled to the controller <NUM>, and may be fluidly coupled to one or more distribution components to provide a fluid path to a tissue site. For example, the tissue interface <NUM> and the cover <NUM> may be discrete layers disposed adjacent to each other, and may be joined together in some embodiments.

A distribution component is preferably detachable, and may be disposable, reusable, or recyclable. The dressing <NUM> and the container <NUM> are illustrative of distribution components.

A negative-pressure supply, such as the negative-pressure source <NUM>, may be a reservoir of air at a negative pressure, or may be a manual or electrically-powered device, such as a vacuum pump, a suction pump, a wall suction port available at many healthcare facilities, or a micro-pump, for example. "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. In many cases, the local ambient pressure may also be the atmospheric pressure at which a tissue site is located. Alternatively, the pressure may be less than a hydrostatic pressure associated with tissue at the tissue site. Unless otherwise indicated, values of pressure stated herein are gauge pressures. 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. 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 -<NUM> Hg (-<NUM> Pa) and -<NUM> Hg (-<NUM> kPa). Common therapeutic ranges are between - <NUM> Hg (-<NUM> kPa) and -<NUM> Hg (-<NUM> kPa).

Sensors, such as the pressure sensor <NUM> or the electric sensor <NUM>, are generally known in the art as any apparatus operable to detect or measure a physical phenomenon or property, and generally provide a signal indicative of the phenomenon or property that is detected or measured. For example, the pressure sensor <NUM> and the electric sensor <NUM> may be configured to measure one or more operating parameters of the therapy system <NUM>. In some embodiments, the pressure sensor <NUM> may be a transducer configured to measure pressure in a pneumatic pathway and convert the measurement to a signal indicative of the pressure measured. In some embodiments, the pressure sensor <NUM> may be a piezoresistive strain gauge. The electric sensor <NUM> may optionally measure operating parameters of the negative-pressure source <NUM>, such as the voltage or current, in some embodiments. Preferably, the signals from the pressure sensor <NUM> and the electric sensor <NUM> are suitable as an input signal to the controller <NUM>, but some signal conditioning may be appropriate.

The tissue interface <NUM> may take many forms, and may have many sizes, shapes, or thicknesses depending on a variety of factors, such as the type of treatment being implemented or the nature and size of a tissue site.

In some embodiments, the cover <NUM> may provide a bacterial barrier and protection from physical trauma. The cover <NUM> 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 cover <NUM> 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. The cover <NUM> may have a high moisture-vapor transmission rate (MVTR) in some applications. For example, the MVTR may be at least about <NUM>/m<NUM> per twenty-four hours in some embodiments. In some example embodiments, the cover <NUM> 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 about <NUM> microns to about <NUM> microns. For permeable materials, the permeability generally should be low enough that a desired negative pressure may be maintained.

The cover <NUM> may comprise, for example, one or more of the following materials: hydrophilic polyurethane; cellulosics; hydrophilic polyamides; polyvinyl alcohol; polyvinyl pyrrolidone; hydrophilic acrylics; hydrophilic silicone elastomers; an INSPIRE <NUM> material from Coveris Advanced Coatings of Wrexham, United Kingdom having, for example, an MVTR (inverted cup technique) of about <NUM>/m<NUM>/<NUM> hours and a thickness of about <NUM> microns; a thin, uncoated polymer drape; natural rubbers; polyisoprene; styrene butadiene rubber; chloroprene rubber; polybutadiene; nitrile rubber; butyl rubber; ethylene propylene rubber; ethylene propylene diene monomer; chlorosulfonated polyethylene; polysulfide rubber; polyurethane (PU); EVA film; copolyester; silicones; a silicone drape; a <NUM> Tegaderm® drape; a polyurethane (PU) drape such as one available from Avery Dennison Corporation of Glendale, California; polyether block polyamide copolymer (PEBAX), for example, from Arkema, France; INSPIRE <NUM>; or other appropriate material.

An attachment device may be used to attach the cover <NUM> to an attachment surface, such as undamaged epidermis, a gasket, or another cover. The attachment device may take many forms. For example, an attachment device may be a medically-acceptable, pressure-sensitive adhesive configured to bond the cover <NUM> to epidermis around a tissue site. In some embodiments, for example, some or all of the cover <NUM> may be coated with an adhesive, such as an acrylic adhesive, which may have a coating weight between about <NUM> grams per square meter (g. ) to about <NUM>. 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 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, and the process of reducing pressure may be described illustratively herein as "delivering," "distributing," or "generating" negative pressure, for example.

In general, exudates and other fluids flow toward lower pressure along a fluid path. Thus, the term "downstream" typically implies a position 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 a position 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. This orientation is generally presumed for purposes of describing various features and components herein. However, the fluid path may also be reversed in some applications (such as by substituting a positive-pressure source for a negative-pressure source) and this descriptive convention should not be construed as a limiting convention.

During treatment of a tissue site, a biofilm may develop on or in the tissue site. Biofilms can comprise a microbial infection that can cover a tissue site and impair healing of the tissue site. Biofilms can also lower the effectiveness of topical antibacterial treatments by preventing the topical treatments from reaching the tissue site. The presence of biofilms can increase healing times, reduce the efficacy and efficiency of various treatments, and increase the risk of a more serious infection. Often, the application of an antibacterial or antimicrobial treatment may require removal of the overlying dressing. Repeated removal of the overlying dressing may cause pain or other trauma to a patient that may prolong a normal treatment period.

Even in the absence of biofilms, some tissue sites may not heal according to the normal medical protocol and may develop areas of necrotic tissue. Necrotic tissue may be dead tissue resulting from infection, toxins, or trauma that caused the tissue to die faster than the tissue can be removed by the normal body processes that regulate the removal of dead tissue. Sometimes, necrotic tissue may be in the form of slough, which may include a viscous liquid mass of tissue. Generally, slough is produced by bacterial and fungal infections that stimulate an inflammatory response in the tissue. Slough may be a creamy yellow color and may also be referred to as pus. Necrotic tissue may also include eschar. Eschar may be a portion of necrotic tissue that has become dehydrated and hardened. Eschar may be the result of a burn injury, gangrene, ulcers, fungal infections, spider bites, or anthrax. Eschar may be difficult to move without the use of surgical cutting instruments.

The tissue site may include biofilms, necrotic tissue, lacerated tissue, devitalized tissue, contaminated tissue, damaged tissue, infected tissue, exudate, highly viscous exudate, fibrinous slough and/or other material that can generally be referred to as debris. The debris may inhibit the efficacy of tissue treatment and slow the healing of the tissue site. If the debris is in the tissue site, the tissue site may be treated with different processes to disrupt the debris. Examples of disruption can include softening of the debris, separation of the debris from desired tissue, such as the subcutaneous tissue, preparation of the debris for removal from the tissue site, and removal of the debris from the tissue site.

The debris can require debridement performed in an operating room. In some cases, tissue sites requiring debridement may not be life-threatening, and debridement may be considered low-priority. Low-priority cases can experience delays prior to treatment as other, more life-threatening, cases may be given priority for an operating room. As a result, low priority cases may need temporization. Temporization can include stasis of a tissue site that limits deterioration of the tissue site prior to other treatments, such as debridement, negative-pressure therapy or instillation.

When debriding, clinicians may find it difficult to define separation between healthy, vital tissue and necrotic tissue. As a result, normal debridement techniques may remove too much healthy tissue or not enough necrotic tissue. If non-viable tissue demarcation does not extend deeper than the deep dermal layer, or if the tissue site is covered by the debris, such as slough or fibrin, gentle methods to remove the debris should be considered to avoid excess damage to the tissue site.

Debridement may include the removal of the debris. In some debridement processes, a mechanical process is used to remove the debris. Mechanical processes may include using scalpels or other cutting tools having a sharp edge to cut away the debris from the tissue site. Other mechanical processes may use devices that can provide a stream of particles to impact the debris to remove the debris in an abrasion process, or jets of high pressure fluid to impact the debris to remove the debris using water-jet cutting or lavage. Typically, mechanical processes of debriding a tissue site may be painful and may require the application of local anesthetics. Mechanical processes also risk over removal of healthy tissue that can cause further damage to the tissue site and delay the healing process.

Debridement may also be performed with an autolytic process. For example, an autolytic process may involve using enzymes and moisture produced by a tissue site to soften and liquefy the necrotic tissue and debris. Typically, a dressing may be placed over a tissue site having debris so that fluid produced by the tissue site may remain in place, hydrating the debris. Autolytic processes can be pain-free, but autolytic processes are a slow and can take many days. Because autolytic processes are slow, autolytic processes may also involve many dressing changes. Some autolytic processes may be paired with negative-pressure therapy so that, as debris hydrates, negative pressure supplied to a tissue site may draw off the debris. In some cases, a manifold positioned at a tissue site to distribute negative-pressure across the tissue site may become blocked or clogged with debris broken down by an autolytic process. If a manifold becomes clogged, negative-pressure may not be able to remove debris, which can slow or stop the autolytic process.

Debridement may also be performed by adding enzymes or other agents to the tissue site that digest tissue. Often, strict control of the placement of the enzymes and the length of time the enzymes are in contact with a tissue site must be maintained. If enzymes are left on a tissue site for longer than needed, the enzymes may remove too much healthy tissue, contaminate the tissue site, or be carried to other areas of a patient. Once carried to other areas of a patient, the enzymes may break down undamaged tissue and cause other complications.

These limitations and others may be addressed by the therapy system <NUM>, which can provide negative-pressure therapy, instillation therapy, disruption of debris, and application of an antibacterial or antimicrobial agent. In some embodiments, the therapy system <NUM> can provide mechanical movement at a surface of the tissue site in combination with cyclic delivery and dwell of topical solutions to help solubilize debris. For example, a negative-pressure source may be fluidly coupled to a tissue site to provide negative pressure to the tissue site for negative-pressure therapy. In some embodiments, a fluid source may be fluidly coupled to a tissue site to provide therapeutic fluid to the tissue site for instillation therapy. In some embodiments, the therapy system <NUM> may include a contact layer positioned adjacent to a tissue site that may be used with negative-pressure therapy, instillation therapy, or both to disrupt areas of a tissue site having debris. Following the disruption of the debris, negative-pressure therapy, instillation therapy, and other processes may be used to remove the debris from a tissue site. The dressing may also include a coating having an antibacterial or antimicrobial agent. In some embodiments, the therapy system <NUM> may be used in conjunction with other tissue removal and debridement techniques. For example, the therapy system <NUM> may be used prior to enzymatic debridement to soften the debris. In another example, mechanical debridement may be used to remove a portion of the debris at the tissue site, and the therapy system <NUM> may then be used to remove the remaining debris while reducing the risk of trauma to the tissue site.

<FIG> is an assembly view of an example of the dressing <NUM> of <FIG>, illustrating additional details that may be associated with some embodiments in which the tissue interface <NUM> comprises multiple layers. In some embodiments, the tissue interface <NUM> includes a debridement tool or contact layer <NUM> and a film layer <NUM>. The contact layer <NUM> has a first surface <NUM>, a second surface <NUM>, and a plurality of through-holes <NUM> extending through the contact layer <NUM> from the first surface <NUM> to the second surface <NUM>. The film layer <NUM> is disposed adjacent to the second surface <NUM> of the contact layer <NUM>. In some embodiments, the film layer <NUM> can be coupled to the second surface <NUM> of the contact layer <NUM>.

The contact layer <NUM> may have a substantially uniform thickness <NUM>. In some embodiments, the thickness <NUM> may be between about <NUM> and about <NUM>. In other embodiments, the thickness <NUM> may be thinner or thicker than the stated range as needed for the tissue site. In a preferred embodiment, the thickness <NUM> may be about <NUM>. In some embodiments, individual portions of the contact layer <NUM> may have a minimal tolerance from the thickness <NUM>. In some embodiments, the thickness <NUM> may have a tolerance of about <NUM>. In some embodiments, the thickness <NUM> may be between about <NUM> and about <NUM>. The contact layer <NUM> may be flexible so that the contact layer <NUM> can be contoured to a surface of the tissue site.

In some embodiments not according to the invention the contact layer <NUM> may be formed from thermoplastic elastomers (TPE), such as styrene ethylene butylene styrene (SEBS) copolymers, or thermoplastic polyurethane (TPU). The contact layer <NUM> may be formed by combining sheets of TPE or TPU. In some embodiments, the sheets of TPE or TPU may be bonded, welded, adhered, or otherwise coupled to one another. For example, in some embodiments, the sheets of TPE or TPU may be welded using radiant heat, radio-frequency welding, or laser welding. Supracor, Inc. , Hexacor, Ltd. , Hexcel Corp. , and Econocorp, Inc. may produce suitable TPE or TPU sheets for the formation of the contact layer <NUM>. In some embodiments, sheets of TPE or TPU having a thickness between about <NUM> and about <NUM> may be used to form a structure having the thickness <NUM>. In some embodiments, the contact layer <NUM> may be formed from a 3D textile, also referred to as a spacer fabric. Suitable 3D textiles may be produced by Heathcoat Fabrics, Ltd. , Baltex, and Mueller Textil Group. The contact layer <NUM> can also be formed from polyurethane, silicone, polyvinyl alcohol, and metals, such as copper, tin, silver or other beneficial metals.

In some embodiments not according to the invention the contact layer <NUM> may be formed from a foam. For example, cellular foam, open-cell foam, reticulated foam, or porous tissue collections, may be used to form the contact layer <NUM>. In some embodiments, the contact layer <NUM> may be formed of V. ® GRANUFOAM™ Dressing, grey foam, or Zotefoam. Grey foam may be a polyester polyurethane foam having about <NUM> pores per inch (ppi). Zotefoam may be a closed-cell crosslinked polyolefin foam. In one non-limiting example, the contact layer <NUM> may be an open-cell, reticulated polyurethane foam such as V. ® GRANUFOAM™ Dressing available from Kinetic Concepts, Inc. of San Antonio, Texas; in other embodiments, the contact layer <NUM> may be an open-cell, reticulated polyurethane foam such as a V. VERAFLO™ dressing, also available from Kinetic Concepts, Inc. , of San Antonio, Texas.

The contact layer <NUM> is formed from a foam that is mechanically or chemically compressed to increase the density of the foam at ambient pressure. A foam that is mechanically or chemically compressed may be referred to as a compressed foam. A compressed foam may be characterized by a firmness factor (FF) that is defined as a ratio of the density of a foam in a compressed state to the density of the same foam in an uncompressed state. For example, a firmness factor (FF) of <NUM> may refer to a compressed foam having a density at ambient pressure that is five times greater than a density of the same foam in an uncompressed state at ambient pressure. Mechanically or chemically compressing a foam may reduce a thickness of the foam at ambient pressure when compared to the same foam that has not been compressed. Reducing a thickness of a foam by mechanical or chemical compression may increase a density of the foam, which may increase the firmness factor (FF) of the foam. Increasing the firmness factor (FF) of a foam may increase a stiffness of the foam in a direction that is parallel to a thickness of the foam. For example, increasing a firmness factor (FF) of the contact layer <NUM> may increase a stiffness of the contact layer <NUM> in a direction that is parallel to the thickness <NUM> of the contact layer <NUM>. In some embodiments, a compressed foam may be a compressed V. ® GRANUFOAM™ Dressing. ® GRANUFOAM™ Dressing may have a density of about <NUM> grams per centimeter<NUM> (g/cm<NUM>) in its uncompressed state. ® GRANUFOAM™ Dressing is compressed to have a firmness factor (FF) of <NUM>, the V. ® GRANUFOAM™ Dressing may be compressed until the density of the V. ® GRANUFOAM™ Dressing is about <NUM>/cm<NUM>. VERAFLO™ dressing may also be compressed to form a compressed foam having a firmness factor (FF) up to <NUM>. In some embodiments, the contact layer <NUM> may have a thickness between about <NUM> to about <NUM>, and more specifically, about <NUM> at ambient pressure. In an exemplary embodiment, if the thickness <NUM> of the contact layer is about <NUM>, and the contact layer <NUM> is positioned within the sealed environment and subjected to negative pressure of about -<NUM> mmHg to about -<NUM> Hg, the thickness <NUM> of the contact layer <NUM> may be between about <NUM> and about <NUM> and, generally, greater than about <NUM>.

A compressed foam is referred to as a felted foam. As with a compressed foam, a felted foam undergoes a thermoforming process to permanently compress the foam to increase the density of the foam. A felted foam may also be compared to other felted foams or compressed foams by comparing the firmness factor of the felted foam to the firmness factor of other compressed or uncompressed foams. Generally a compressed or felted foam may have a firmness factor greater than <NUM>.

The firmness factor (FF) may also be used to compare compressed foam materials with non-foam materials. For example, a Supracor® material may have a firmness factor (FF) that allows Supracor® to be compared to compressed foams. In some embodiments, the firmness factor (FF) for a non-foam material may represent that the non-foam material has a stiffness that is equivalent to a stiffness of a compressed foam having the same firmness factor. For example, if a contact layer is formed from Supracor®, as illustrated in Table <NUM> below, the contact layer may have a stiffness that is about the same as the stiffness of a compressed V. ® GRANUFOAM™ Dressing material having a firmness factor (FF) of <NUM>.

Generally, if a compressed foam is subjected to negative pressure, the compressed foam exhibits less deformation than a similar uncompressed foam. If the contact layer <NUM> is formed of a compressed foam, the thickness <NUM> of the contact layer <NUM> may deform less than if the contact layer <NUM> is formed of a comparable uncompressed foam. The decrease in deformation may be caused by the increased stiffness as reflected by the firmness factor (FF). If subjected to the stress of negative pressure, the contact layer <NUM> that is formed of compressed foam may flatten less than the contact layer <NUM> that is formed from uncompressed foam. Consequently, if negative pressure is applied to the contact layer <NUM>, the stiffness of the contact layer <NUM> in the direction parallel to the thickness <NUM> of the contact layer <NUM> allows the contact layer <NUM> to be more compliant or compressible in other directions, e.g., a direction perpendicular to the thickness <NUM>. The foam material used to form a compressed foam may be either hydrophobic or hydrophilic. The foam material used to form a compressed foam may also be either reticulated or un-reticulated. The pore size of a foam material may vary according to needs of the contact layer <NUM> and the amount of compression of the foam. For example, in some embodiments, an uncompressed foam may have pore sizes in a range of about <NUM> microns to about <NUM> microns. If the same foam is compressed, the pore sizes may be smaller than when the foam is in its uncompressed state.

The film layer <NUM> is a film of a material having antimicrobial and/or antibacterial properties. For example, the film layer <NUM> can be formed from a mixture containing silver, citric acid, acetic acid, or a combination thereof. In some embodiments, the film layer <NUM> can be a coating of silver, a film of citric acid, or a film of acetic acid. For example, the contact layer <NUM> may be an open-cell reticulated foam having a thin layer of silver coated onto the foam to form the film layer <NUM>. The reticulated, open-cell structure of the foam may be maintained after the coating process. For example, following the application of a silver coating, the foam may have pore sizes in the range of about <NUM> microns to about <NUM> microns. In some embodiments, the silver coating of the film layer <NUM> may have a thickness of about <NUM> micron to about <NUM> microns and, in particular, about <NUM> microns. In some embodiments, the coating of silver may extend through the open-cell reticulated foam of the contact layer <NUM> so that substantially all surfaces of the contact layer <NUM> may be coated. In other embodiments, the silver coating of the film layer <NUM> may only be applied to a portion of the contact layer <NUM> or to the second surface <NUM> of the contact layer <NUM>. The silver coating may be <NUM>% pure metallic silver that is bonded to the contact layer <NUM>. In some embodiments, the contact layer <NUM> may be felted or un-felted V. ® GRANUFOAM SILVER™ Dressing available from KCI, Inc.

In other embodiments, the film layer <NUM> can be formed from acetic acid. For example, the film layer <NUM> can be a <NUM> millimolar ("mM") acetic acid. In an exemplary formulation, <NUM> grams of collagen and oxidized regenerated cellulose ("ORC") can be placed in <NUM> milliliters ("mL") of <NUM> molarity ("M") acetic acid. The collagen/ORC can absorb or swell with the acetic acid for about <NUM> minutes. Mixing of the collagen/ORC and the acetic acid can be followed by the addition of glycerol. The glycerol can be added by drop and mixed until a concentration of the solution ("v/v") is approximately <NUM> microliters ("µL") of glycerol per <NUM> of acetic acid or <NUM>% v/v. In the example embodiment, about <NUM>µL of glycerol were added to the <NUM> of acetic acid. The resulting solution can be mixed and placed in a vacuum chamber to draw out gas bubbles from the solution.

In some embodiments, the solution can be placed into trays in about <NUM> quantities and incubated at <NUM> to produce a film having a thickness between about <NUM> microns and about <NUM> microns. The film layer <NUM> can be coated onto the second surface <NUM> of the contact layer <NUM>. For example, the second surface <NUM> of the contact layer <NUM> can be placed into a tray having the solution while the solution cures into the film layer <NUM>. In other embodiments, the acetic acid can be produced in the ratios described to produce sheets of film. The sheets can be positioned over the contact layer <NUM> and placed in contact with the contact layer <NUM>. The natural tackiness of the acetic acid sheet can couple the sheet to the contact layer <NUM>. For example, the tackiness of the acetic acid sheet of the film layer <NUM> can bond the sheet to the contact layer <NUM>. In some embodiments, the film layer <NUM> can cover the through-holes <NUM> of the contact layer <NUM>. In other embodiments, the film layer <NUM> can be removed from the contact layer <NUM> at the plurality of through-holes <NUM>, leaving the film layer <NUM> coating the walls <NUM> of the second surface <NUM>. In still other embodiments, the through-holes <NUM> of the contact layer <NUM> can be formed after the film layer <NUM> is coupled to the contact layer <NUM>.

In other embodiments, the film layer <NUM> can be formed from citric acid. For example, the film layer <NUM> can be a <NUM> millimolar ("mM") citric acid. For example, citric acid powder can be dissolved into water or other similar solution. Glycerol can be titrated into the citric acid as described above to produce sheets of the citric acid film. The process produced an exemplary <NUM> citric acid solution and an exemplary <NUM> citric acid solution. The <NUM> citric acid solution had a formula weight of about <NUM> Daltons, a volume of <NUM>, and a mass of about <NUM> grams. The film layer <NUM> can be coated onto the second surface <NUM> of the contact layer <NUM>. In some embodiments, the film layer <NUM> can cover the through-holes <NUM> of the contact layer <NUM>. In other embodiments, the film layer <NUM> can be removed from the contact layer <NUM> at the plurality of through-holes <NUM>.

As illustrated in the example of <FIG>, in some embodiments, the dressing <NUM> may include a release liner <NUM> to protect an optional adhesive on a portion of the cover <NUM> prior to use. The release liner <NUM> may also provide stiffness to assist with, for example, deployment of the dressing <NUM>. The release liner <NUM> may be, for example, a casting paper, a film, or polyethylene. Further, in some embodiments, the release liner <NUM> may be a polyester material such as polyethylene terephthalate (PET), or similar polar semi-crystalline polymer. The use of a polar semi-crystalline polymer for the release liner <NUM> may substantially preclude wrinkling or other deformation of the dressing <NUM>. For example, the polar semi-crystalline polymer may be highly orientated and resistant to softening, swelling, or other deformation that may occur when brought into contact with components of the dressing <NUM>, or when subjected to temperature or environmental variations, or sterilization. Further, a release agent may be disposed on a side of the release liner <NUM> that is configured to contact the tissue interface <NUM>. For example, the release agent may be a silicone coating and may have a release factor suitable to facilitate removal of the release liner <NUM> by hand and without damaging or deforming the dressing <NUM>. In some embodiments, the release agent may be a fluorocarbon or a fluorosilicone, for example. In other embodiments, the release liner <NUM> may be uncoated or otherwise used without a release agent.

<FIG> also illustrates one example of a fluid conductor <NUM> and a dressing interface <NUM>. As shown in the example of <FIG>, the fluid conductor <NUM> may be a flexible tube, which can be fluidly coupled on one end to the dressing interface <NUM>. The dressing interface <NUM> may be an elbow connector, as shown in the example of <FIG>, which can be placed over an aperture <NUM> in the cover <NUM> to provide a fluid path between the fluid conductor <NUM> and the tissue interface <NUM>.

<FIG> is a plan view, illustrating additional details that may be associated with some embodiments of the contact layer <NUM>. The contact layer <NUM> includes a plurality of through-holes <NUM> or other perforations extending through the contact layer <NUM> to form walls <NUM>. In some embodiments, an exterior surface of the walls <NUM> may be parallel to sides of the contact layer <NUM>. In other embodiments, an interior surface of the walls <NUM> may be generally perpendicular to the second surface <NUM> and the first surface <NUM> of the contact layer <NUM>. Generally, the exterior surface or surfaces of the walls <NUM> may be coincident with the second surface <NUM> and the first surface <NUM>. The interior surface or surfaces of the walls <NUM> may form a perimeter <NUM> of each through-hole <NUM> and may connect the second surface <NUM> to the first surface <NUM>. In some embodiments, the through-holes <NUM> may have a circular shape as shown. In some embodiments, the through-holes <NUM> may have diameters between about <NUM> and about <NUM>, and in some embodiments, the diameters of the through-holes <NUM> may be about <NUM>. The through-holes <NUM> may have a depth that is about equal to the thickness <NUM> of the contact layer <NUM>. For example, the through-holes <NUM> may have a depth between about <NUM> to about <NUM>, and more specifically, about <NUM> at ambient pressure.

In some embodiments, the contact layer <NUM> may have a first orientation line <NUM> and a second orientation line <NUM> that is perpendicular to the first orientation line <NUM>. The first orientation line <NUM> and the second orientation line <NUM> may be lines of symmetry of the contact layer <NUM>. A line of symmetry may be, for example, an imaginary line across the second surface <NUM> or the first surface <NUM> of the contact layer <NUM> defining a fold line such that if the contact layer <NUM> is folded on the line of symmetry, the through-holes <NUM> and walls <NUM> would be coincidentally aligned. Generally, the first orientation line <NUM> and the second orientation line <NUM> aid in the description of the contact layer <NUM>. In some embodiments, the first orientation line <NUM> and the second orientation line <NUM> may be used to refer to the desired directions of contraction of the contact layer <NUM>. For example, the desired direction of contraction may be parallel to the second orientation line <NUM> and perpendicular to the first orientation line <NUM>. In other embodiments, the desired direction of contraction may be parallel to the first orientation line <NUM> and perpendicular to the second orientation line <NUM>. In still other embodiments, the desired direction of contraction may be at a non-perpendicular angle to both the first orientation line <NUM> and the second orientation line <NUM>. In other embodiments, the contact layer <NUM> may not have a desired direction of contraction. Generally, the contact layer <NUM> may be placed at the tissue site so that the second orientation line <NUM> extends across debris located at the tissue site. Although the contact layer <NUM> is shown as having a generally rectangular shape including longitudinal edges <NUM> and circular edges <NUM>, the contact layer <NUM> may have other shapes. For example, the contact layer <NUM> may have a diamond, square, or circular shape. In some embodiments, the shape of the contact layer <NUM> may be selected to accommodate the type of tissue site being treated. For example, the contact layer <NUM> may have an oval or circular shape to accommodate an oval or circular tissue site. In some embodiments, the first orientation line <NUM> may be parallel to the longitudinal edges <NUM>.

<FIG> is a plan view illustrating additional details that may be associated with some embodiments of the through-hole <NUM> of the contact layer <NUM> of <FIG>. In <FIG>, a single through-hole <NUM> having a circular shape is shown. The through-hole <NUM> may include a center <NUM> and the perimeter <NUM>. The through-hole <NUM> may have a perforation shape factor (PSF). The perforation shape factor (PSF) may represent an orientation of the through-hole <NUM> relative to the first orientation line <NUM> and the second orientation line <NUM>. Generally, the perforation shape factor (PSF) is a ratio of ½ a maximum length of the through-hole <NUM> that is parallel to the desired direction of contraction to ½ a maximum length of the through-hole <NUM> that is perpendicular to the desired direction of contraction. For descriptive purposes, the desired direction of contraction is parallel to the second orientation line <NUM>. The desired direction of contraction may be indicated by a lateral force <NUM>. For reference, the through-hole <NUM> may have an X-axis <NUM> extending through the center <NUM> parallel to the first orientation line <NUM>, and a Y-axis <NUM> extending through the center <NUM> parallel to the second orientation line <NUM>. The perforation shape factor (PSF) of the through-hole <NUM> may be defined as a ratio of a line segment <NUM> on the Y-axis <NUM> extending from the center <NUM> to the perimeter <NUM> of the through-hole <NUM>, to a line segment <NUM> on the X-axis <NUM> extending from the center <NUM> to the perimeter <NUM> of the through-hole <NUM>. If a length of the line segment <NUM> is <NUM> and the length of the line segment <NUM> is <NUM>, the perforation shape factor (PSF) would be <NUM>. In other embodiments, the through-holes <NUM> may have other shapes and orientations, for example, oval, hexagonal, square, triangular, or amorphous or irregular and be oriented relative to the first orientation line <NUM> and the second orientation line <NUM> so that the perforation shape factor (PSF) may range from about <NUM> to about <NUM>.

<FIG> is a plan view illustrating additional details of a portion of the contact layer <NUM> of <FIG>. The contact layer <NUM> may include the plurality of through-holes <NUM> aligned in parallel rows to form an array. The array of through-holes <NUM> may include a first row <NUM> of the through-holes <NUM>, a second row <NUM> of the through-holes <NUM>, and a third row <NUM> of the through-holes <NUM>. In some embodiments, a width of the wall <NUM> between the perimeters <NUM> of adjacent the through-holes <NUM> in a row, such as the first row <NUM>, may be about <NUM>. The centers <NUM> of the through-holes <NUM> in adjacent rows, for example, the first row <NUM> and the second row <NUM>, may be characterized by being offset from the second orientation line <NUM> along the first orientation line <NUM>. In some embodiments, a line connecting the centers of adjacent rows may form a strut angle (SA) with the first orientation line <NUM>. For example, a first through-hole 210A in the first row <NUM> may have a center 402A, and a second through-hole 210B in the second row <NUM> may have a center 402B. A strut line <NUM> may connect the center 402A with the center 402B. The strut line <NUM> may form an angle <NUM> with the first orientation line <NUM>. The angle <NUM> may be the strut angle (SA) of the contact layer <NUM>. In some embodiments, the strut angle (SA) may be less than about <NUM>°. In other embodiments, the strut angle (SA) may be between about <NUM>° and about <NUM>° relative to the first orientation line <NUM>. In other embodiments, the strut angle (SA) may be about <NUM>° from the first orientation line <NUM>. Generally, as the strut angle (SA) decreases, a stiffness of the contact layer <NUM> in a direction parallel to the first orientation line <NUM> may increase. Increasing the stiffness of the contact layer <NUM> parallel to the first orientation line <NUM> may increase the compressibility of the contact layer <NUM> perpendicular to the first orientation line <NUM>. Consequently, if negative pressure is applied to the contact layer <NUM>, the contact layer <NUM> may be more compliant or compressible in a direction perpendicular to the first orientation line <NUM>. By increasing the compressibility of the contact layer <NUM> in a direction perpendicular to the first orientation line <NUM>, the contact layer <NUM> may collapse to apply the lateral force <NUM> to the tissue site described in more detail below.

In some embodiments, the centers <NUM> of the through-holes <NUM> in alternating rows, for example, the center 402A of the first through-hole 210A in the first row <NUM> and a center 402C of a through-hole 210C in the third row <NUM>, may be spaced from each other parallel to the second orientation line <NUM> by a length <NUM>. In some embodiments, the length <NUM> may be greater than an effective diameter of the through-hole <NUM>. If the centers <NUM> of through-holes <NUM> in alternating rows are separated by the length <NUM>, the exterior surface of the walls <NUM> parallel to the first orientation line <NUM> may be considered continuous. Generally, the exterior surface of the walls <NUM> may be continuous if the exterior surface of the walls <NUM> do not have any discontinuities or breaks between through-holes <NUM>. In some embodiments, the length <NUM> may be between about <NUM> and about <NUM>.

Regardless of the shape of the through-holes <NUM>, the through-holes <NUM> in the contact layer <NUM> may leave void spaces in the contact layer <NUM> and on the second surface <NUM> and the first surface <NUM> of the contact layer <NUM> so that only the exterior surface of the walls <NUM> of the contact layer <NUM> remain with a surface available to contact the tissue site. It may be desirable to minimize the exterior surface of the walls <NUM> so that the through-holes <NUM> may collapse, causing the contact layer <NUM> to collapse and generate the lateral force <NUM> in a direction perpendicular to the first orientation line <NUM>. However, it may also be desirable not to minimize the exterior surface of the walls <NUM> so much that the contact layer <NUM> becomes too fragile for sustaining the application of a negative pressure. The void space percentage (VS) of the through-holes <NUM> may be equal to the percentage of the volume or surface area of the void spaces of the second surface <NUM> created by the through-holes <NUM> to the total volume or surface area of the second surface <NUM> of the contact layer <NUM>. In some embodiments, the void space percentage (VS) may be between about <NUM>% and about <NUM>%. In other embodiments, the void space percentage (VS) may be about <NUM>%. The organization of the through-holes <NUM> can also impact the void space percentage (VS), influencing the total surface area of the contact layer <NUM> that may contact the tissue site. In some embodiments, the longitudinal edge <NUM> and the circular edge <NUM> of the contact layer <NUM> may be discontinuous. An edge may be discontinuous where the through-holes <NUM> overlap an edge causing the edge to have a non-linear profile. A discontinuous edge may reduce the disruption of keratinocyte migration and enhance re-epithelialization while negative pressure is applied to the dressing <NUM>.

In other embodiments, the through-holes <NUM> of the contact layer <NUM> may have a depth that is less than the thickness <NUM> of the contact layer <NUM>. For example, the through-holes <NUM> may be blind holes formed in the second surface <NUM> of the contact layer <NUM>. The through-holes <NUM> may leave void spaces in the contact layer <NUM> on the second surface <NUM> so that only the exterior surface of the walls <NUM> of the contact layer <NUM> on the second surface <NUM> remain with a surface available to contact the tissue site at ambient pressure. If a depth of the through-holes <NUM> extending from the second surface <NUM> toward the first surface <NUM> is less than the thickness <NUM>, the void space percentage (VS) of the first surface <NUM> may be zero, while the void space percentage (VS) of the second surface <NUM> is greater than zero, for example <NUM>%.

In some embodiments, the through-holes <NUM> may be formed during molding of the contact layer <NUM>. In other embodiments, the through-holes <NUM> may be formed by cutting, melting, drilling, or vaporizing the contact layer <NUM> after the contact layer <NUM> is formed. For example, the through-holes <NUM> may be formed in the contact layer <NUM> by laser cutting the compressed foam of the contact layer <NUM>. In some embodiments, the through-holes <NUM> may be formed so that the interior surfaces of the walls <NUM> of the through-holes <NUM> are parallel to the thickness <NUM>. In other embodiments, the through-holes <NUM> may be formed so that the interior surfaces of the walls <NUM> of the through-holes <NUM> form a non-perpendicular angle with the second surface <NUM>. In still other embodiments, the interior surfaces of the walls <NUM> of the through-holes <NUM> may taper toward the center <NUM> of the through-holes <NUM> to form conical, pyramidal, or other irregular through-hole shapes. If the interior surfaces of the walls <NUM> of the through-holes <NUM> taper, the through-holes <NUM> may have a height less than the thickness <NUM> of the contact layer <NUM>.

In some embodiments, formation of the through-holes <NUM> may thermoform the material of the contact layer <NUM>, for example a compressed foam or a felted foam, causing the interior surface of the walls <NUM> extending between the second surface <NUM> and the first surface <NUM> to be smooth. As used herein, smoothness may refer to the formation of the through-holes <NUM> that causes the interior surface of the walls <NUM> that extends between the second surface <NUM> and the first surface <NUM> to be substantially free of pores if compared to an uncut portion of the contact layer <NUM>. For example, laser-cutting the through-holes <NUM> into the contact layer <NUM>, may plastically deform the material of the contact layer <NUM>, closing any pores on the interior surfaces of the walls <NUM> that extend between the second surface <NUM> and the first surface <NUM>. In some embodiments, a smooth interior surface of the walls <NUM> may limit or otherwise inhibit ingrowth of tissue into the contact layer <NUM> through the through-holes <NUM>. In other embodiments, the smooth interior surfaces of the walls <NUM> may be formed by a smooth material or a smooth coating.

In some embodiments, an effective diameter of the through-holes <NUM> may be selected to permit flow of particulates through the through-holes <NUM>. In some embodiments, the diameter of the through-holes <NUM> may be selected based on the size of the solubilized debris to be lifted from the tissue site. Larger through-holes <NUM> may allow larger debris to pass through the contact layer <NUM>, and smaller through-holes <NUM> may allow smaller debris to pass through the contact layer <NUM> while blocking debris larger than the through-holes. In some embodiments, successive applications of the dressing <NUM> can use contact layers <NUM> having successively smaller diameters of the through-holes <NUM> as the size of the solubilized debris in the tissue site decreases. Sequentially decreasing diameters of the through-holes <NUM> may also aid in fine tuning a level of tissue disruption to the debris during the treatment of the tissue site. The diameter of the through-holes <NUM> can also influence fluid movement in the contact layer <NUM> and the dressing <NUM>. For example, the contact layer <NUM> can channel fluid in the dressing <NUM> toward the through-holes <NUM> to aid in the disruption of the debris on the tissue site. Variation of the diameters of the through-holes <NUM> can vary how fluid is moved through the dressing <NUM> with respect to both the removal of fluid and the application of negative pressure. In some embodiments, the effective diameter of the through-holes <NUM> is between about <NUM> and about <NUM> and, more specifically, about <NUM>.

An effective diameter of a non-circular area is defined as a diameter of a circular area having the same surface area as the non-circular area. In some embodiments, each through-hole <NUM> may have an effective diameter of about <NUM>. In other embodiments, each through-hole <NUM> may have an effective diameter between about <NUM> and about <NUM>. The effective diameter of the through-holes <NUM> should be distinguished from the porosity of the material forming the walls <NUM> of the contact layer <NUM>. Generally, an effective diameter of the through-holes <NUM> is an order of magnitude larger than the effective diameter of the pores of a material forming the contact layer <NUM>. For example, the effective diameter of the through-holes <NUM> may be larger than about <NUM>, while the walls <NUM> may be formed from V. ® GRANUFOAM™ Dressing having a pore size less than about <NUM> microns. In some embodiments, the pores of the walls <NUM> may not create openings that extend all the way through the material. Generally, the through-holes <NUM> do not include pores formed by the foam formation process, and the through-holes <NUM> may have an average effective diameter that is greater than ten times an average effective diameter of pores of a material.

Referring now to both <FIG> and <FIG>, the through-holes <NUM> may form a pattern depending on the geometry of the through-holes <NUM> and the alignment of the through-holes <NUM> between adjacent and alternating rows in the contact layer <NUM> with respect to the first orientation line <NUM>. If the contact layer <NUM> is subjected to negative pressure, the through-holes <NUM> of the contact layer <NUM> may contract. As used herein, contraction can refer to both vertical compression of a body parallel to a thickness of the body, such as the contact layer <NUM>, and lateral compression of a body perpendicular to a thickness of the body, such as the contact layer <NUM>. In some embodiments the void space percentage (VS), the perforation shape factor (PSF), and the strut angle (SA) may cause the contact layer <NUM> to contract along the second orientation line <NUM> perpendicular to the first orientation line <NUM> as shown in more detail in <FIG>.

<FIG> is a plan view illustrating additional details of the contact layer <NUM> of <FIG> in a contracted state. If the contact layer <NUM> is positioned on the tissue site, the contact layer <NUM> may generate the lateral force <NUM> along the second orientation line <NUM>, contracting the contact layer <NUM>, as shown in more detail in <FIG>. The lateral force <NUM> may be optimized by adjusting the factors described above as set forth in Table <NUM> below. In some embodiments, the through-holes <NUM> may be circular, have a strut angle (SA) of approximately <NUM>°, a void space percentage (VS) of about <NUM>%, a firmness factor (FF) of about <NUM>, a perforation shape factor (PSF) of about <NUM>, and a diameter of about <NUM>. If the contact layer <NUM> is subjected to a negative pressure of about -<NUM> mmHg, the contact layer <NUM> asserts the lateral force <NUM> of approximately <NUM> N. If the diameter of the through-holes <NUM> of the contact layer <NUM> is increased to about <NUM>, the void space percentage (VS) changed to about <NUM>%, the strut angle (SA) changed to about <NUM>°, and the perforation shape factor (PSF) and the firmness factor (FF) remain the same, the lateral force <NUM> is decreased to about <NUM> N. In other embodiments, the through-holes <NUM> may be hexagonal, have a strut angle (SA) of approximately <NUM>°, a void space percentage (VS) of about <NUM>%, a firmness factor (FF) of about <NUM>, a perforation shape factor (PSF) of about <NUM>, and an effective diameter of about <NUM>. If the contact layer <NUM> is subjected to a negative pressure of about -<NUM> mmHg, the lateral force <NUM> asserted by the contact layer <NUM> is about <NUM> N. If the effective diameter of the through-holes <NUM> of the contact layer <NUM> is increased to <NUM>, the lateral force <NUM> is decreased to about <NUM> N.

Referring to <FIG>, the contact layer <NUM> is in the second position, or contracted position, as indicated by the lateral force <NUM>. In operation, negative pressure is supplied to the sealed environment with the negative-pressure source <NUM>. In response to the supply of negative pressure, the contact layer <NUM> contracts from the relaxed position illustrated in <FIG> to the contracted position illustrated in <FIG>. In some embodiments, the thickness <NUM> of the contact layer <NUM> remains substantially the same. When the negative pressure is removed, for example, by venting the negative pressure, the contact layer <NUM> expands back to the relaxed position. If the contact layer <NUM> is cycled between the contracted and relaxed positions of <FIG> and <FIG>, respectively, the second surface <NUM> of the contact layer <NUM> may disrupt the debris on the tissue site by rubbing the debris from the tissue site. The edges of the through-holes <NUM> formed by the second surface <NUM> and the interior surfaces or transverse surfaces of the walls <NUM> can form cutting edges that can disrupt the debris in the tissue site, allowing the debris to exit through the through-holes <NUM>. In some embodiments, the cutting edges are defined by the perimeter <NUM> where each through-hole <NUM> intersects the second surface <NUM>.

In some embodiments, the material, the void space percentage (VS), the firmness factor, the strut angle, the hole shape, the perforation shape factor (PSF), and the hole diameter may be selected to increase compression or collapse of the contact layer <NUM> in a lateral direction, as shown by the lateral force <NUM>, by forming weaker walls <NUM>. Conversely, the factors may be selected to decrease compression or collapse of the contact layer <NUM> in a lateral direction, as shown by the lateral force <NUM>, by forming stronger walls <NUM>. Similarly, the factors described herein can be selected to decrease or increase the compression or collapse of the contact layer <NUM> perpendicular to the lateral force <NUM>.

In some embodiments, the therapy system <NUM> may provide cyclic therapy. Cyclic therapy may alternately apply negative pressure to and vent negative pressure from a sealed space or sealed environment containing the tissue interface <NUM>. In some embodiments, negative pressure may be supplied to the tissue site until the pressure in the sealed environment reaches a predetermined therapy pressure. If negative pressure is supplied to the sealed environment, the debris and the subcutaneous tissue underlying the debris may be drawn into the through-holes <NUM>. In some embodiments, the sealed environment may remain at the therapy pressure for a predetermined therapy period such as, for example, about <NUM> minutes. In other embodiments, the therapy period may be longer or shorter as needed to supply appropriate negative-pressure therapy to the tissue site.

Following the therapy period, the sealed environment may be vented. For example, the negative-pressure source <NUM> may fluidly couple the sealed environment to the atmosphere (not shown), allowing the sealed environment to return to ambient pressure. In some embodiments, the negative-pressure source <NUM> may vent the sealed environment for about <NUM> minute. In other embodiments, the negative-pressure source <NUM> may vent the sealed environment for longer or shorter periods. After venting of the sealed environment, the negative-pressure source <NUM> may be operated to begin another negative-pressure therapy cycle.

In some embodiments, instillation therapy may be combined with negative-pressure therapy. For example, following the therapy period of negative-pressure therapy, the solution source <NUM> may operate to provide fluid to the sealed environment. In some embodiments, the solution source <NUM> may provide fluid while the negative-pressure source <NUM> vents the sealed environment. For example, the positive-pressure source <NUM> may be configured to move instillation fluid from the solution source <NUM> to the sealed environment. In some embodiments, the solution source <NUM> may not have a pump and may operate using a gravity feed system. In other embodiments, the negative-pressure source <NUM> may not vent the sealed environment. Instead, the negative pressure in the sealed environment is used to draw instillation fluid from the solution source <NUM> into the sealed environment.

In some embodiments, the solution source <NUM> may provide a volume of fluid to the sealed environment. In some embodiments, the volume of fluid may be the same as a volume of the sealed environment. In other embodiments, the volume of fluid may be smaller or larger than the sealed environment as needed to appropriately apply instillation therapy. Instilling of the tissue site may raise a pressure in the sealed environment to a pressure greater than the ambient pressure, for example to between about <NUM> mmHg and about <NUM> mmHg and, more specifically, about <NUM> mmHg. In some embodiments, the fluid provided by the solution source <NUM> may remain in the sealed environment for a dwell time. In some embodiments, the dwell time is about <NUM> minutes. In other embodiments, the dwell time may be longer or shorter as needed to appropriately administer instillation therapy to the tissue site. For example, the dwell time may be zero.

At the conclusion of the dwell time, the negative-pressure source <NUM> may be operated to draw the instillation fluid into the container, completing a cycle of therapy. As the instillation fluid is removed from the sealed environment with negative pressure, negative pressure may also be supplied to the sealed environment, starting another cycle of therapy.

<FIG> is a sectional view of a portion of the contact layer <NUM>, illustrating additional details that may be associated with some embodiments. The contact layer <NUM> and the film layer <NUM> may be placed at a tissue site <NUM> having debris <NUM> covering subcutaneous tissue <NUM>. The film layer <NUM> may be adjacent to the debris <NUM> and the contact layer <NUM> adjacent to the film layer <NUM>. In embodiments having the film layer <NUM> coupled to or coating the second surface <NUM> of the contact layer <NUM>, the second surface <NUM> of the contact layer <NUM> may be positioned adjacent to the debris <NUM>. The cover <NUM> may be placed over the contact layer <NUM> and the film layer <NUM> to provide a sealed environment for the application of negative-pressure therapy or instillation therapy.

<FIG> is a sectional view of a portion of the dressing <NUM> during negative-pressure therapy, illustrating additional details that may be associated with some embodiments. For example, <FIG> may illustrate a moment in time where a pressure in the sealed environment may be about <NUM> mmHg of negative pressure. In some embodiments, the contact layer <NUM> may be a precompressed or felted foam. In response to the application of negative pressure, the contact layer <NUM> may not compress. In some embodiments, negative pressure in the sealed environment can generate concentrated stresses in the debris <NUM> adjacent to the through-holes <NUM> in the contact layer <NUM>. The concentrated stresses can cause macro-deformations of the debris <NUM> and the subcutaneous tissue <NUM> that draws portions of the debris <NUM> and the subcutaneous tissue <NUM> into the through-holes <NUM>. Similarly, the film layer <NUM> can be drawn into the through-holes <NUM>, remaining in contact with the debris <NUM>.

<FIG> is a detail view of the contact layer <NUM>, illustrating additional details of the operation of the contact layer <NUM> during negative-pressure therapy. The through-holes <NUM> of the contact layer <NUM> may create macro-pressure points in portions of the film layer <NUM>, the debris <NUM>, and the subcutaneous tissue <NUM> that are in contact with the second surface <NUM> of the contact layer <NUM>, causing tissue puckering and nodules <NUM> in the film layer <NUM>, the debris <NUM>, and the subcutaneous tissue <NUM>.

A height of the nodules <NUM> over the surrounding tissue may be selected to maximize disruption of debris <NUM> and minimize damage to subcutaneous tissue <NUM> or other desired tissue. Generally, the pressure in the sealed environment can exert a force that is proportional to the area over which the pressure is applied. At the through-holes <NUM> of the contact layer <NUM>, the force may be concentrated as the resistance to the application of the pressure is less than in the walls <NUM> of the contact layer <NUM>. In response to the force generated by the pressure at the through-holes <NUM>, the debris and the subcutaneous tissue <NUM> that forms the nodules <NUM> may be drawn into and through the through-holes <NUM> until the force applied by the pressure is equalized by the reactive force of the film layer <NUM>, the debris <NUM>, and the subcutaneous tissue <NUM>. In some embodiments where the negative pressure in the sealed environment may cause tearing, the thickness <NUM> of the contact layer <NUM> may be selected to limit the height of the nodules <NUM> over the surrounding tissue. In some embodiments, the height of the nodules <NUM> may be limited to a height that is less than the thickness <NUM> of the contact layer <NUM>. In an exemplary embodiment, the thickness <NUM> of the contact layer <NUM> may be about <NUM>. During the application of negative pressure, the height of the nodules <NUM> may be limited to about <NUM> to about <NUM>. By controlling the height of the nodules <NUM> by controlling the thickness <NUM> of the contact layer <NUM>, the aggressiveness of disruption to the debris <NUM> and tearing can be controlled.

In some embodiments, the height of the nodules <NUM> can also be controlled by controlling an expected compression of the contact layer <NUM> during negative-pressure therapy. For example, the contact layer <NUM> may have a thickness <NUM> of about <NUM>. If the contact layer <NUM> is formed from a compressed foam, the firmness factor of the contact layer <NUM> may be higher; however, the contact layer <NUM> may still reduce in thickness in response to negative pressure in the sealed environment. In one embodiment, application of negative pressure of between about -<NUM> mmHg and about -<NUM> mmHg, between about -<NUM> Hg and about -<NUM> mmHg and, more specifically, about - <NUM> mmHg in the sealed environment may reduce the thickness <NUM> of the contact layer <NUM> from about <NUM> to about <NUM>. The height of the nodules <NUM> may be limited to be no greater than the thickness <NUM> of the contact layer <NUM> during negative-pressure therapy, for example, about <NUM>. By controlling the height of the nodules <NUM>, the forces applied to the debris <NUM> by the contact layer <NUM> can be adjusted and the degree that the debris <NUM> is stretched can be varied.

In some embodiments, the formation of the nodules <NUM> can cause the debris <NUM> to remain in contact with a tissue interface <NUM> during negative pressure therapy. For example, the nodules <NUM> may contact the sidewalls of the through-holes <NUM> of the contact layer <NUM>, while the surrounding tissue may contact the film layer <NUM> coating the second surface <NUM> of the contact layer <NUM>. Similarly, the film layer <NUM> may be in contact with the debris <NUM> throughout therapy. The film layer <NUM> can provide a continuous application of antimicrobial/antibacterial agents to the debris <NUM>, allowing the antimicrobial/antibacterial properties of the film layer <NUM> to remain effective throughout therapy. In some embodiments, formation of the nodules <NUM> may lift debris <NUM> and particulates off of the surrounding tissue, operating in a piston-like manner to move debris <NUM> toward the retainer layer <NUM> and out of the sealed environment.

In response to the return of the sealed environment to ambient pressure by venting the sealed environment, the debris <NUM> and the subcutaneous tissue <NUM> may leave the through-holes <NUM>, returning to the position shown in <FIG>.

In some embodiments, repeated application of negative-pressure therapy and instillation therapy while the contact layer <NUM> is disposed over the debris <NUM> may disrupt the debris <NUM>, allowing the debris <NUM> to be removed during dressing changes. In other embodiments, the contact layer <NUM> may disrupt the debris <NUM> so that the debris <NUM> can be removed by negative pressure. In still other embodiments, the contact layer <NUM> may disrupt the debris <NUM>, aiding removal of the debris <NUM> during debridement processes. With each cycle of therapy, the contact layer <NUM> may form nodules <NUM> in the debris <NUM>. The formation of the nodules <NUM> and release of the nodules <NUM> by the contact layer <NUM> during therapy may disrupt the debris. With each subsequent cycle of therapy, disruption of the debris <NUM> can be increased.

Disruption of the debris <NUM> can be caused, at least in part, by the concentrated forces applied to the debris <NUM> by the through-holes <NUM> and the walls <NUM> of the contact layer <NUM>. The forces applied to the debris <NUM> can be a function of the negative pressure supplied to the sealed environment and the area of each through-hole <NUM>. For example, if the negative pressure supplied to the sealed environment is about <NUM> mmHg and the diameter of each through-hole <NUM> is about <NUM>, the force applied at each through-hole <NUM> is about <NUM> lbs. If the diameter of each through-hole <NUM> is increased to about <NUM>, the force applied at each through-hole <NUM> can increase up to <NUM> times. Generally, the relationship between the diameter of each through-hole <NUM> and the applied force at each through-hole <NUM> is not linear and can increase exponentially with an increase in diameter.

In some embodiments, the negative pressure applied by the negative-pressure source <NUM> may be cycled rapidly. For example, negative pressure may be supplied for a few seconds, then vented for a few seconds, causing a pulsation of negative pressure in the sealed environment. The pulsation of the negative pressure can pulsate the nodules <NUM>, causing further disruption of the debris <NUM>.

In some embodiments, the cyclical application of instillation therapy and negative pressure therapy may cause micro-floating. For example, negative pressure may be applied to the sealed environment during a negative-pressure therapy cycle. Following the conclusion of the negative-pressure therapy cycle, instillation fluid may be supplied during the instillation therapy cycle. The instillation fluid may cause the contact layer <NUM> to float relative to the debris. As the contact layer <NUM> floats, it may change position relative to the position the contact layer <NUM> occupied during the negative-pressure therapy cycle. The position change may cause the contact layer <NUM> to engage a slightly different portion of the debris <NUM> during the next negative-pressure therapy cycle, aiding disruption of the debris <NUM> and the application of antimicrobial/antibacterial agents by the film layer <NUM>.

In some embodiments, the contact layer <NUM> may be provided as a component of a dressing kit. The kit may include a punch, and the contact layer <NUM> may be provided without any through-holes <NUM>. When using the contact layer <NUM>, the user may use the punch to place the through-holes <NUM> through portions of the contact layer <NUM> that may be placed over the debris. The kit provides a user, such as a clinician, the ability to customize the contact layer <NUM> to the particular tissue site, so that the through-holes <NUM> are only disrupting the debris and not healthy tissue that may be near or surround the debris.

The through-holes <NUM> of the contact layer <NUM> may generate concentrated stresses that influence disruption of the debris in different ways. For example, different shapes of the through-holes <NUM> may also focus the stresses generated by the contact layer <NUM> in advantageous areas. A lateral force, such as the lateral force <NUM>, generated by a contact layer, such as the contact layer <NUM>, may be related to a compressive force generated by applying negative pressure at a therapy pressure to a sealed therapeutic environment. For example, the lateral force <NUM> may be proportional to a product of a therapy pressure (TP) in the sealed environment, the compressibility factor (CF) of the contact layer <NUM>, and a surface area (A) the second surface <NUM> of the contact layer <NUM>. The relationship is expressed as follows: <MAT>.

In some embodiments, the therapy pressure TP is measured in N/m<NUM>, the compressibility factor (CF) is dimensionless, the area (A) is measured in m<NUM>, and the lateral force is measured in Newtons (N). The compressibility factor (CF) resulting from the application of negative pressure to a contact layer may be, for example, a dimensionless number that is proportional to the product of the void space percentage (VS) of a contact layer, the firmness factor (FF) of the contact layer, the strut angle (SA) of the through-holes in the contact layer, and the perforation shape factor (PSF) of the through-holes in the contact layer. The relationship is expressed as follows: <MAT>.

Based on the above formulas, contact layers formed from different materials with through-holes of different shapes were manufactured and tested to determine the lateral force of the contact layers. For each contact layer, the therapy pressure TP was about -<NUM> mmHg and the dimensions of the contact layer were about <NUM> by about <NUM> so that the surface area (A) of the tissue-facing surface of the contact layer was about <NUM><NUM> or <NUM><NUM>. Based on the two equations described above, the lateral force for a Supracor® contact layer <NUM> having a firmness factor (FF) of <NUM> was about <NUM> where the Supracor® contact layer <NUM> had hexagonal through-holes <NUM> with a distance between opposite vertices of <NUM>, a perforation shape factor (PSF) of <NUM>, a strut angle (SA) of approximately <NUM>°, and a void space percentage (VS) of about <NUM>%. A similarly dimensioned V. ® GRANUFOAM™ Dressing contact layer <NUM> generated the lateral force <NUM> of about <NUM> Newtons (N).

In some embodiments, the formulas described above may not precisely describe the lateral forces due to losses in force due to the transfer of the force from the contact layer to the wound. For example, the modulus and stretching of the cover <NUM>, the modulus of the tissue site, slippage of the cover <NUM> over the tissue site, and friction between the contact layer <NUM> and the tissue site may cause the actual value of the lateral force <NUM> to be less than the calculated value of the lateral force <NUM>.

<FIG> is an assembly view of an example of the dressing <NUM> of <FIG>, illustrating additional details that may be associated with some embodiments in which the tissue interface <NUM> comprises multiple layers. In some embodiments, the tissue interface <NUM> can include the contact layer <NUM>, the film layer <NUM>, and a retainer layer <NUM>. The contact layer <NUM> may have the first surface <NUM>, the second surface <NUM>, the plurality of through-holes <NUM> extending through the contact layer <NUM> from the first surface <NUM> to the second surface <NUM>, and the thickness <NUM>. The retainer layer <NUM> can have a first surface <NUM> and a second surface <NUM> on an opposite side of the retainer layer <NUM> from the first surface <NUM>. The film layer <NUM> may be disposed adjacent to the second surface <NUM> of the retainer layer <NUM>. In some embodiments, the film layer <NUM> can be coupled to the second surface <NUM> of the retainer layer <NUM>. In some embodiments, the retainer layer <NUM> may be positioned over the contact layer <NUM>. In other embodiments, the retainer layer <NUM> may be positioned over the contact layer <NUM>, and if the depth of the tissue site is greater than a thickness of the retainer layer <NUM> and the thickness <NUM> of the contact layer <NUM> combined, another retainer layer <NUM> may be placed over the contact layer <NUM> and the retainer layer <NUM>.

In some embodiments, the retainer layer <NUM> may be a foam having pore sizes in a range of about <NUM> microns to about <NUM> microns. In other embodiments, the retainer layer <NUM> may be a foam having pore sizes in a range of about <NUM> microns to about <NUM> microns. The tensile strength of the retainer layer <NUM> 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 retainer layer <NUM> may be an open-cell, reticulated polyurethane foam such as V. ® GRANUFOAM™ Dressing available from Kinetic Concepts, Inc. of San Antonio, Texas; in other embodiments the retainer layer <NUM> may be an open-cell, reticulated polyurethane foam such as a V. VERAFLO™ dressing, also available from Kinetic Concepts, Inc. , of San Antonio, Texas. In other embodiments, the retainer layer <NUM> may be formed of an un-reticulated open-cell foam.

In some embodiments, the retainer layer <NUM> may be an open-cell reticulated foam having a thin layer of silver coated onto the foam to form the film layer <NUM>. In other embodiments, the film layer <NUM> can be formed from citric acid or acetic acid. For example, the film layer <NUM> can be a <NUM> millimolar ("mM") citric acid or a <NUM> millimolar ("mM") acetic acid. The film layer <NUM> can be coated onto the second surface <NUM> of the retainer layer <NUM>. For example, the second surface <NUM> of the retainer layer <NUM> can be placed into a tray having the solution of the citric acid or the acetic acid while the solution cures into the film layer <NUM>. In other embodiments, the solution of the citric acid or the acetic acid can be produced in sheets. The sheets can be positioned over the second surface <NUM> of the retainer layer <NUM> and placed in contact with the second surface <NUM>. The natural tackiness of the citric acid and the acetic acid can couple the sheet to the retainer layer <NUM> and form the film layer <NUM>. For example, the tackiness of the citric acid or the acetic acid sheet of the film layer <NUM> can bond the film layer <NUM> to the retainer layer <NUM>.

As illustrated in the example of <FIG>, in some embodiments, the dressing <NUM> may include a release liner <NUM> to protect an optional adhesive on a portion of the cover <NUM> prior to use. The release liner <NUM> may also provide stiffness to assist with, for example, deployment of the dressing <NUM>. <FIG> also illustrates one example of a fluid conductor <NUM> and a dressing interface <NUM>. As shown in the example of <FIG>, the fluid conductor <NUM> may be a flexible tube, which can be fluidly coupled on one end to the dressing interface <NUM>. The dressing interface <NUM> may be an elbow connector, as shown in the example of <FIG>, which can be placed over an aperture <NUM> in the cover <NUM> to provide a fluid path between the fluid conductor <NUM> and the tissue interface <NUM>.

<FIG> is a sectional view of a portion of the contact layer <NUM>, illustrating additional details that may be associated with some embodiments. The contact layer <NUM>, the film layer <NUM>, and the retainer layer <NUM> may be placed at the tissue site <NUM> having the debris <NUM> covering the subcutaneous tissue <NUM>. The film layer <NUM> can be coupled to the second surface <NUM> of the retainer layer <NUM>. The cover <NUM> may be placed over the retainer layer <NUM> to provide the sealed environment for the application of negative-pressure therapy or instillation therapy. As shown in <FIG>, the retainer layer <NUM> may have a thickness <NUM> if the pressure in the sealed environment is about an ambient pressure. In some embodiments, the thickness <NUM> may be about <NUM>. In other embodiments, the thickness <NUM> may be about <NUM>.

<FIG> is a sectional view of a portion of the dressing <NUM> during negative-pressure therapy, illustrating additional details that may be associated with some embodiments. For example, <FIG> may illustrate a moment in time where a pressure in the sealed environment may be about <NUM> mmHg of negative pressure. In some embodiments, the retainer layer <NUM> may be a non-felted foam, and the contact layer <NUM> may be a felted foam. In response to the application of negative pressure, the contact layer <NUM> may not compress, and the retainer layer <NUM> may compress so that the manifold has a thickness <NUM>. In some embodiments, the thickness <NUM> of the retainer layer <NUM> during negative-pressure therapy may be less than the thickness <NUM> of the retainer layer <NUM> if the pressure in the sealed environment is about the ambient pressure.

In some embodiments, negative pressure in the sealed environment can generate concentrated stresses in the retainer layer <NUM> and the film layer <NUM> adjacent to the through-holes <NUM> in the contact layer <NUM>. The concentrated stresses can cause macro-deformation of the retainer layer <NUM> and the film layer <NUM> that draws portions of the retainer layer <NUM> and the film layer <NUM> into the through-holes <NUM> of the contact layer <NUM>. Similarly, negative pressure in the sealed environment can generate concentrated stresses in the debris <NUM> adjacent to the through-holes <NUM> in the contact layer <NUM>. The concentrated stresses can cause macro-deformations of the debris <NUM> and the subcutaneous tissue <NUM> that draws portions of the debris <NUM> and the subcutaneous tissue <NUM> into the through-holes <NUM>.

<FIG> is a detail view of the contact layer <NUM>, illustrating additional details of the operation of the contact layer <NUM> during negative-pressure therapy. Portions of the retainer layer <NUM> and the film layer <NUM> in contact with the first surface <NUM> of the contact layer <NUM> may be drawn into the through-holes <NUM> to form bosses <NUM>. The bosses <NUM> may have a shape that corresponds to the through-holes <NUM>. A height of the bosses <NUM> from the retainer layer <NUM> may be dependent on the pressure of the negative pressure in the sealed environment, the area of the through-holes <NUM>, and the firmness factor of the retainer layer <NUM>. Similarly, the through-holes <NUM> of the contact layer <NUM> may create macro-pressure points in portions of the debris <NUM> and the subcutaneous tissue <NUM> that are in contact with the second surface <NUM> of the contact layer <NUM>, causing tissue puckering and formation of the nodules <NUM> in the debris <NUM> and the subcutaneous tissue <NUM>.

In some embodiments, the retainer layer <NUM> may limit the height of the nodules <NUM> to the thickness <NUM> of the contact layer <NUM> under negative pressure if the contact layer <NUM> is compressible. In other embodiments, the bosses <NUM> of the retainer layer <NUM> may limit the height of the nodules <NUM> to a height that is less than the thickness <NUM> of the contact layer <NUM>. By controlling the firmness factor of the retainer layer <NUM>, the height of the bosses <NUM> over the surrounding material of the retainer layer <NUM> can be controlled. The height of the nodules <NUM> can be limited to the difference of the thickness <NUM> of the contact layer <NUM> and the height of the bosses <NUM>. In some embodiments, the height of the bosses <NUM> can vary from zero to several millimeters as the firmness factor of the retainer layer <NUM> decreases. In an exemplary embodiment, the thickness <NUM> of the contact layer <NUM> may be about <NUM>. During the application of negative pressure, the bosses <NUM> may have a height between about <NUM> to about <NUM>, limiting the height of the nodules to about <NUM> to about <NUM>. By controlling the height of the nodules <NUM> by controlling the thickness <NUM> of the contact layer <NUM>, the firmness factor of the retainer layer <NUM>, or both, the aggressiveness of disruption to the debris <NUM> and tearing can be controlled.

The bosses <NUM> and the nodules <NUM> place the debris <NUM> into contact with the film layer <NUM>. In some embodiments, the nodules <NUM> and the bosses <NUM> trap the bacterial material that may reside in the debris <NUM> against the film layer <NUM> drawn into the through-holes <NUM> by the bosses <NUM>. For example, portions of the film layer <NUM> can be drawn into the through-holes <NUM> by the bosses <NUM>, positioning the film layer <NUM> in contact with debris <NUM>. The film layer <NUM> may be spaced from both the tissue site <NUM> and the cover <NUM>, extending the usable life of the film layer <NUM>. The antimicrobial/antibacterial properties of the film layer <NUM> can apply antimicrobial/antibacterial agents to the debris <NUM> that limit and inhibit the growth of bacteria, microbes, and other entities that can slow or inhibit healing. Furthermore, as the debris <NUM> and the tissue are torn or cracked by the application of negative-pressure therapy, the antimicrobial/antibacterial properties of the film layer <NUM> can prevent the development of infection in the newly opened areas of tissue.

In response to the return of the sealed environment to ambient pressure by venting the sealed environment, the nodules <NUM> and the bosses <NUM> may leave the through-holes <NUM>, returning to the position shown in <FIG>.

<FIG> is an assembly view of an example of the dressing <NUM> of <FIG>, illustrating additional details that may be associated with some embodiments in which the tissue interface <NUM> comprises multiple layers. In some embodiments, the tissue interface <NUM> can include the contact layer <NUM> and a cover layer or a retainer layer <NUM>. The contact layer <NUM> may have the first surface <NUM>, the second surface <NUM>, the plurality of through-holes <NUM> extending through the contact layer <NUM> from the first surface <NUM> to the second surface <NUM>, and the thickness <NUM>. The retainer layer <NUM> can have the first surface <NUM> and the second surface <NUM>. In some embodiments, the retainer layer <NUM> may be positioned over the contact layer <NUM>. In other embodiments, the retainer layer <NUM> may be positioned over the contact layer <NUM>, and if the depth of the tissue site is greater than a thickness of the retainer layer <NUM> and the thickness <NUM> of the contact layer <NUM> combined, another retainer layer <NUM> may be placed over the contact layer <NUM> and the retainer layer <NUM>.

In some embodiments, the film layer <NUM> can comprise a coating <NUM> disposed on the interior surfaces of the walls <NUM>. The interior surfaces of the walls <NUM> can also be referred to as the sidewalls of the through-holes <NUM>. The coating <NUM> can comprise a thin layer of silver coated onto the through-holes <NUM>. In other embodiments, the coating <NUM> can be formed from citric acid or acetic acid. For example, the coating <NUM> can be a <NUM> millimolar ("mM") citric acid or a <NUM> millimolar ("mM") acetic acid.

As illustrated in the example of <FIG>, in some embodiments, the dressing <NUM> may include the release liner <NUM>, the fluid conductor <NUM>, and the dressing interface <NUM>, which can be placed over the aperture <NUM> in the cover <NUM> to provide a fluid path between the fluid conductor <NUM> and the tissue interface <NUM>.

<FIG> is a plan view illustrating additional details of a portion of the contact layer <NUM> of <FIG>. In <FIG>, a portion of the contact layer <NUM> of <FIG> is shown. The contact layer <NUM> may include the plurality of through-holes <NUM> aligned in parallel rows to form an array. The coating <NUM> can be coupled to the interior surfaces of the walls <NUM>. In some embodiments, the coating <NUM> can substantially coat the interior surfaces of the walls <NUM> between the first surface <NUM> and the second surface <NUM>. The coating <NUM> can be a thin layer of silver coated onto the interior surfaces of the walls <NUM>. The silver coating of the coating <NUM> may have a thickness of about <NUM> micron to about <NUM> microns and, in particular, about <NUM> microns. The silver of the coating <NUM> may be <NUM>% pure metallic silver that is bonded to the interior surfaces of the walls <NUM>.

The coating <NUM> is a citric acid and/or an acetic acid. The contact layer <NUM> can be submerged into a tray having the solution of the citric acid or the acetic acid previously described. The solution can cure into the coating <NUM> covering the submerged surfaces of the contact layer <NUM>. The first surface <NUM> and the second surface <NUM> can be shaved or otherwise planed to remove the coating <NUM> from the first surface <NUM> and the second surface <NUM>. If necessary, the through holes <NUM> can be re-cut or drilled to form the coating <NUM> having a thickness between <NUM> microns and about <NUM> microns. In other embodiments, the thickness of the coating can be reduced, for example, the coating <NUM> could have a thickness between about <NUM> micron and about <NUM> microns and preferably about <NUM> microns. In other embodiments, the solution of the citric acid or the acetic acid can be produced in sheets. The sheets can be positioned over the contact layer <NUM> and placed in contact with the interior surfaces of the walls <NUM>. Material not in contact with the interior surfaces of the walls <NUM> can be removed to leave the first surface <NUM> and the second surface <NUM> free from the coating <NUM>. The natural tackiness of the sheet formed from the citric acid and the acetic acid can couple the sheet to the interior surfaces of the walls <NUM> of the contact layer <NUM>. In some embodiments, the average effective diameter of the through-holes <NUM> is between about <NUM> and about <NUM> and, more specifically, about <NUM> following the addition of the coating <NUM>.

<FIG> is a sectional view of a portion of the contact layer <NUM>, illustrating additional details that may be associated with some embodiments. The contact layer <NUM> having the coating <NUM> and the retainer layer <NUM> may be placed at the tissue site <NUM> having the debris <NUM> covering the subcutaneous tissue <NUM>. The cover <NUM> may be placed over the retainer layer <NUM> to provide the sealed environment for the application of negative-pressure therapy or instillation therapy. As shown in <FIG>, the retainer layer <NUM> may have the thickness <NUM> if the pressure in the sealed environment is about an ambient pressure.

In some embodiments, negative pressure in the sealed environment can generate concentrated stresses in the retainer layer <NUM> and the film layer <NUM> adjacent to the through-holes <NUM> in the contact layer <NUM>. The concentrated stresses can cause macro-deformation of the retainer layer <NUM> that draws portions of the retainer layer <NUM> into the through-holes <NUM> of the contact layer <NUM>. Similarly, negative pressure in the sealed environment can generate concentrated stresses in the debris <NUM> adjacent to the through-holes <NUM> in the contact layer <NUM>. The concentrated stresses can cause macro-deformations of the debris <NUM> and the subcutaneous tissue <NUM> that draws portions of the debris <NUM> and the subcutaneous tissue <NUM> into the through-holes <NUM>.

<FIG> is a detail view of the contact layer <NUM>, illustrating additional details of the operation of the contact layer <NUM> during negative-pressure therapy. Portions of the retainer layer <NUM> in contact with the first surface <NUM> of the contact layer <NUM> may be drawn into the through-holes <NUM> to form the bosses <NUM>. Similarly, the through-holes <NUM> of the contact layer <NUM> may create macro-pressure points in portions of the debris <NUM> and the subcutaneous tissue <NUM> that are in contact with the second surface <NUM> of the contact layer <NUM>, causing tissue puckering and the formation of the nodules <NUM> in the debris <NUM> and the subcutaneous tissue <NUM>. The bosses <NUM> and the nodules <NUM> place the debris <NUM> into contact with the coating <NUM> on the interior surfaces of the walls <NUM>. In some embodiments, formation of the nodules <NUM> and the bosses <NUM> may press the bacterial material that may reside in the debris <NUM> against the coating <NUM>. As the debris <NUM> and the associated bacterial material is forced into contact with the coating <NUM> and the debridement process occurs, the coating <NUM> can have increased exposure to portions of the debris <NUM> that may be cracked or torn by the debridement process. The antimicrobial/antibacterial properties of the coating <NUM> can apply antimicrobial/antibacterial agents to the debris <NUM> that limit and inhibit the growth of bacteria, microbes, and other entities that can slow or inhibit healing to the cracked and torn portions of the debris <NUM>. The antimicrobial/antibacterial properties of the film layer <NUM> can prevent the re-development of infection in the newly exposed areas of tissue. In response to the return of the sealed environment to ambient pressure by venting the sealed environment, the debris <NUM> and the subcutaneous tissue <NUM> may leave the through-holes <NUM>, returning to the position shown in <FIG>.

In some embodiments, the tissue interface <NUM> can include both the film layer <NUM> and the coating <NUM>. For example, the film layer <NUM> can be coated to the second surface <NUM> of the contact layer <NUM> or the second surface <NUM> of the retainer layer <NUM>, and the coating <NUM> can be coupled to the interior surface of the walls <NUM> of the contact layer <NUM>. In some embodiments, the tissue interface <NUM> can include a first film layer <NUM> coated to the second surface <NUM> of the contact layer <NUM>, a second film layer <NUM> coated to the second surface <NUM> of the retainer layer <NUM>, and the coating <NUM> can be coupled to the interior surface of the walls <NUM> of the contact layer <NUM>. In still other embodiments, additional retainer layers <NUM> having additional film layers <NUM> can be added to the tissue interface <NUM> as needed to substantially fill the tissue site. In embodiments having one or more film layers <NUM> and the coating <NUM>, the film layers <NUM> and the coating <NUM> can be formed from the same material, for example, silver, citric acid, or acetic acid. The one or more film layers <NUM> and the coating <NUM> can also be formed from different materials for example, the first film layer <NUM> can be formed from silver, the coating <NUM> can be formed from citric acid, and if included, the second of other additional film layers <NUM> can be formed from acetic acid or any combination thereof.

The apparatuses described herein may provide significant advantages. For example, combining the mechanical rubbing action of a contact layer with the hydrating and flushing action of instillation and negative-pressure therapy may enable low or no pain debridement of a tissue site. A contact layer as described herein may also require less monitoring from a clinician or other attendant as compared to other mechanical debridement processes and enzymatic debridement processes. In addition, contact layers as described herein may not become blocked by removed necrotic tissue as may occur during autolytic debridement of a tissue site. Furthermore, the contact layers described herein can aid in removal of necrosis, eschar, impaired tissue, sources of infection, exudate, slough including hyperkeratosis, pus, foreign bodies, debris, and other types of bioburden or barriers to healing. The contact layers can also decrease odor, excess wound moisture, and the risk of infection while stimulating edges of a tissue site and epithelialization. The contact layers described herein can also provide improved removal of thick exudate, allow for earlier placement of instillation and negative-pressure therapy devices, may limit or prevent the use of other debridement processes, and can be used on tissue sites that are difficult to debride.

The film layer and the coating described herein can provide continuous delivery of antibacterial/antimicrobial agents direct to the area in contact with the tissue site. The dressings are easy to use, provide effective protection to reduce bacteria (aerobic, anaerobic, gram positive and negative), yeast, and fungi and can reduce infection. The dressing can also provide an effective barrier to bacterial penetration. The dressing can remove thick wound exudate and provide a wound cleansing option and decreasing bioburden.

In some embodiments, the therapy system may be used in conjunction with other tissue removal and debridement techniques. For example, the therapy system may be used prior to enzymatic debridement to soften the debris. In another example, mechanical debridement may be used to remove a portion of the debris at the tissue site, and the therapy system may then be used to remove the remaining debris while reducing the risk of trauma to the tissue site.

While shown in a few illustrative embodiments, a person having ordinary skill in the art will recognize that the apparatuses described herein are susceptible to various changes and modifications that fall within the scope of the appended claims. 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. Components may be also be combined or eliminated in various configurations for purposes of sale, manufacture, assembly, or use. For example, in some configurations the dressing, the container, or both may be eliminated or separated from other components for manufacture or sale. In other example configurations, the controller may also be manufactured, configured, assembled, or sold independently of other components.

Claim 1:
An apparatus for debriding a tissue site with negative pressure, the apparatus comprising:
a felted foam (<NUM>) having a plurality of perforations (<NUM>), the perforations (<NUM>) fluidly coupling a first side of the felted foam (<NUM>) to a second side of the felted foam (<NUM>); and
a film (<NUM>) coupled to the first side of the felted foam (<NUM>), the film (<NUM>) having an anti-bioburden agent, wherein the anti-bioburden agent comprises citric acid and/or acetic acid.