Patent Description:
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/or instillation therapy are widely known, improvements to therapy systems, components, and processes may benefit healthcare providers and patients. <CIT> discloses an instillation assembly for treating a tissue site, the assembly having a fluid distribution lumen and fluid hub which define a fluid instillation pathway together with layers with fenestrations to provide fluid communication.

A selection of optional features of the invention is set out in the dependent claims.

Insofar as the term invention or embodiment is used in the following, or features are presented as being optional, this should be interpreted in such a way that the only protection sought is that of the invention claimed.

Reference(s) to "embodiment(s)" throughout the description which are not under the scope of the appended claims merely represent possible exemplary executions and are not part of the present invention.

The following description of example embodiments provides information that enables a person skilled in the art to make and use the subject matter set forth in the appended claims, and may omit certain details already well-known in the art.

<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 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.

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 one or more dressing layers, such as a tissue interface <NUM>, a cover <NUM>, or both in some embodiments.

The therapy system <NUM> may also include a source of instillation solution, such as saline, for example. 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 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>. The negative-pressure source maybe fluidly coupled to one or more distribution components, which 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. Distribution components may also include or comprise interfaces or fluid ports to facilitate coupling and de-coupling other components, including sensors and data communication devices. ™ Pad available from KCI of San Antonio, Texas.

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, for example, the pressure sensor <NUM> may be a piezo-resistive 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 in some embodiments.

The tissue interface <NUM> can be generally adapted to contact a tissue site. The tissue interface <NUM> may be partially or fully in contact with the tissue site. If the tissue site is a wound, for example, the tissue interface <NUM> may partially or completely fill the wound, or may be placed over the wound. The tissue interface <NUM> may take many forms and have more than one layer in some embodiments. The tissue interface <NUM> may also 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 <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 <NUM>-<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 <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; co-polyester; 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, such as a surface wound. 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 <NUM>-<NUM> grams per square meter (g. 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 something in a fluid path relatively closer to a source of negative pressure or further away from a source of positive pressure. Conversely, the term "upstream" implies something relatively further away from a source of negative pressure or closer to a source of positive pressure. Similarly, it may be convenient to describe certain features in terms of fluid "inlet" or "outlet" in such a frame of reference. 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.

<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 more than one layer. In the example of <FIG>, the tissue interface <NUM> comprises a first layer <NUM> and a second layer <NUM>. In some embodiments, the first layer <NUM> may be disposed adjacent to the second layer <NUM>. For example, the first layer <NUM> and the second layer <NUM> may be stacked so that the first layer <NUM> is in contact with the second layer <NUM>. The first layer <NUM> may also be bonded to the second layer <NUM> in some embodiments.

The first layer <NUM> generally comprises or consists essentially of a manifold or a manifold layer, which provides a means for collecting or distributing fluid across the tissue interface <NUM> under pressure. For example, the first layer <NUM> may be adapted to receive negative pressure from a source and distribute negative pressure through multiple apertures across the tissue interface <NUM>, which may have the effect of collecting fluid from across a tissue site and drawing the fluid toward the source. In some embodiments, the fluid path may be reversed or a secondary fluid path may be provided to facilitate delivering fluid, such as from a source of instillation solution, across the tissue interface <NUM>.

In some illustrative embodiments, the pathways of the first layer <NUM> may be interconnected to improve distribution or collection of fluids. In some illustrative embodiments, the first layer <NUM> may comprise or consist essentially of a porous material having interconnected fluid pathways. For example, open-cell foam, reticulated foam, porous tissue collections, and other porous material such as gauze or felted mat generally include pores, edges, and/or walls adapted to form interconnected fluid channels. Other suitable materials may include a 3D textile (Baltex, Muller, Heathcoates), non-woven (Libeltex, Freudenberg), a 3D polymeric structure (molded polymers, embossed and formed films, and fusion bonded films [Supracore]), and mesh, for example. Liquids, gels, and other foams may also include or be cured to include apertures and fluid pathways. In some embodiments, the first layer <NUM> may additionally or alternatively comprise projections that form interconnected fluid pathways. For example, the first layer <NUM> may be molded to provide surface projections that define interconnected fluid pathways. Any or all of the surfaces of the first layer <NUM> may have an uneven, coarse, or jagged profile.

In some embodiments, the first layer <NUM> may comprise or consist essentially of a reticulated foam having pore sizes and free volume that may vary according to needs of a prescribed therapy. For example, a reticulated foam having a free volume of at least <NUM>% may be suitable for many therapy applications, and a foam having an average pore size in a range of <NUM>-<NUM> microns may be particularly suitable for some types of therapy. The tensile strength of the first 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. The <NUM>% compression load deflection of the first layer <NUM> may be at least <NUM> pounds per square inch, and the <NUM>% compression load deflection may be at least <NUM> pounds per square inch. In some embodiments, the tensile strength of the first layer <NUM> may be at least <NUM> pounds per square inch. The first layer <NUM> may have a tear strength of at least <NUM> pounds per inch. In some embodiments, the first layer <NUM> may be a foam comprised of polyols such as polyester or polyether, isocyanate such as toluene diisocyanate, and polymerization modifiers such as amines and tin compounds. In one non-limiting example, the first layer <NUM> may be a reticulated polyurethane foam such as used in GRANUFOAM™ dressing or V. VERAFLO™ dressing, both available from KCI of San Antonio, Texas.

The first layer <NUM> generally has a first planar surface and a second planar surface opposite the first planar surface. The thickness of the first layer <NUM> between the first planar surface and the second planar surface may also vary according to needs of a prescribed therapy. For example, the thickness of the first layer <NUM> may be decreased to relieve stress on other layers and to reduce tension on peripheral tissue. The thickness of the first layer <NUM> can also affect the conformability of the first layer <NUM>. In some embodiments, a thickness in a range of about <NUM> millimeters to <NUM> millimeters may be suitable.

The second layer <NUM> may comprise or consist essentially of a means for controlling or managing fluid flow. In some embodiments, the second layer <NUM> may comprise or consist essentially of a liquid-impermeable, elastomeric material. For example, the second layer <NUM> may comprise or consist essentially of a polymer film. The second layer <NUM> may also have a smooth or matte surface texture in some embodiments. A glossy or shiny finish better or equal to a grade B3 according to the SPI (Society of the Plastics Industry) standards may be particularly advantageous for some applications. In some embodiments, variations in surface height may be limited to acceptable tolerances. For example, the surface of the second layer may have a substantially flat surface, with height variations limited to <NUM> millimeters over a centimeter.

In some embodiments, the second layer <NUM> may be hydrophobic. The hydrophobicity of the second layer <NUM> may vary, but may have a contact angle with water of at least ninety degrees in some embodiments. In some embodiments the second layer <NUM> may have a contact angle with water of no more than <NUM> degrees. For example, in some embodiments, the contact angle of the second layer <NUM> may be in a range of at least <NUM> degrees to about <NUM> degrees, or in a range of at least <NUM> degrees to <NUM> degrees. Water contact angles can be measured using any standard apparatus. Although manual goniometers can be used to visually approximate contact angles, contact angle measuring instruments can often include an integrated system involving a level stage, liquid dropper such as a syringe, camera, and software designed to calculate contact angles more accurately and precisely, among other things. Non-limiting examples of such integrated systems may include the FTÅ125, FTÅ200, FTÅ2000, and FTÅ4000 systems, all commercially available from First Ten Angstroms, Inc. , of Portsmouth, VA, and the DTA25, DTA30, and DTA100 systems, all commercially available from Kruss GmbH of Hamburg, Germany. Unless otherwise specified, water contact angles herein are measured using deionized and distilled water on a level sample surface for a sessile drop added from a height of no more than <NUM> in air at <NUM>-<NUM> and <NUM>-<NUM>% relative humidity. Contact angles reported herein represent averages of <NUM>-<NUM> measured values, discarding both the highest and lowest measured values. The hydrophobicity of the second layer <NUM> may be further enhanced with a hydrophobic coating of other materials, such as silicones and fluorocarbons, either as coated from a liquid, or plasma coated.

The second layer <NUM> may also be suitable for welding to other layers, including the first layer <NUM>. For example, the second layer <NUM> may be adapted for welding to polyurethane foams using heat, radio frequency (RF) welding, or other methods to generate heat such as ultrasonic welding. RF welding may be particularly suitable for more polar materials, such as polyurethane, polyamides, polyesters and acrylates. Sacrificial polar interfaces may be used to facilitate RF welding of less polar film materials, such as polyethylene.

The area density of the second layer <NUM> may vary according to a prescribed therapy or application. In some embodiments, an area density of less than <NUM> grams per square meter may be suitable, and an area density of about <NUM>-<NUM> grams per square meter may be particularly advantageous for some applications.

In some embodiments, for example, the second layer <NUM> may comprise or consist essentially of a hydrophobic polymer, such as a polyethylene film. The simple and inert structure of polyethylene can provide a surface that interacts little, if any, with biological tissues and fluids, providing a surface that may encourage the free flow of liquids and low adherence, which can be particularly advantageous for many applications. Other suitable polymeric films include polyurethanes, acrylics, polyolefin (such as cyclic olefin copolymers), polyacetates, polyamides, polyesters, copolyesters, PEBAX block copolymers, thermoplastic elastomers, thermoplastic vulcanizates, polyethers, polyvinyl alcohols, polypropylene, polymethylpentene, polycarbonate, styreneics, silicones, fluoropolymers, and acetates. A thickness between <NUM> microns and <NUM> microns may be suitable for many applications. Films may be clear, colored, or printed. More polar films suitable for laminating to a polyethylene film include polyamide, co-polyesters, ionomers, and acrylics. To aid in the bond between a polyethylene and polar film, tie layers may be used, such as ethylene vinyl acetate, or modified polyurethanes. An ethyl methyl acrylate (EMA) film may also have suitable hydrophobic and welding properties for some configurations.

As illustrated in the example of <FIG>, the second layer <NUM> may have one or more fluid restrictions <NUM>, which can be distributed uniformly or randomly across the second layer <NUM>. The fluid restrictions <NUM> may be bi-directional and pressure-responsive. For example, each of the fluid restrictions <NUM> generally may comprise or consist essentially of an elastic passage that is normally unstrained to substantially reduce liquid flow, and can expand or open in response to a pressure gradient. The fluid restrictions <NUM> are elastomeric valves wthat are normally closed when unstrained to substantially prevent liquid flow, and can open in response to a pressure gradient. A fenestration in the second layer <NUM> may be a suitable valve for some applications. Fenestrations may also be formed by removing material from the second layer <NUM>, but the amount of material removed and the resulting dimensions of the fenestrations may be an order of magnitude less than perforations, and may not deform the edges.

For example, some embodiments of the fluid restrictions <NUM> may comprise or consist essentially of one or more slits, slots or combinations of slits and slots in the second layer <NUM>. In some examples, the fluid restrictions <NUM> may comprise or consist of linear slots having a length less than <NUM> millimeters and a width less than <NUM> millimeter. The length may be at least <NUM> millimeters, and the width may be at least <NUM> millimeters in some embodiments. A length of about <NUM> millimeters and a width of about <NUM> millimeters may be particularly suitable for many applications, and a tolerance of about <NUM> millimeter may also be acceptable. Such dimensions and tolerances may be achieved with a laser cutter, for example. Slots of such configurations may function as imperfect valves that substantially reduce liquid flow in a normally closed or resting state. For example, such slots may form a flow restriction without being completely closed or sealed. The slots can expand or open wider in response to a pressure gradient to allow increased liquid flow.

In the example of <FIG>, the dressing <NUM> may further include an attachment device, such as an adhesive <NUM>. The adhesive <NUM> may be, for example, a medically-acceptable, pressure-sensitive adhesive that extends about a periphery, a portion, or the entire cover <NUM>. In some embodiments, for example, the adhesive <NUM> may be an acrylic adhesive having a coating weight between <NUM>-<NUM> grams per square meter (g. Thicker adhesives, or combinations of adhesives, may be applied in some embodiments to improve the seal and reduce leaks. In some embodiments, such a layer of the adhesive <NUM> may be continuous or discontinuous. Discontinuities in the adhesive <NUM> may be provided by apertures or holes (not shown) in the adhesive <NUM>. The apertures or holes in the adhesive <NUM> may be formed after application of the adhesive <NUM> or by coating the adhesive <NUM> in patterns on a carrier layer, such as, for example, a side of the cover <NUM>. Apertures or holes in the adhesive <NUM> may also be sized to enhance the MVTR of the dressing <NUM> in some example embodiments.

As illustrated in the example of <FIG>, in some embodiments, the dressing <NUM> may include a release liner <NUM> to protect the adhesive <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 second layer <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 schematic view of an example of the second layer <NUM>, illustrating additional details that may be associated with some embodiments. As illustrated in the example of <FIG>, the fluid restrictions <NUM> may each consist essentially of one or more linear slots having a length of about <NUM> millimeters. <FIG> additionally illustrates an example of a uniform distribution pattern of the fluid restrictions <NUM>. In <FIG>, the fluid restrictions <NUM> are substantially coextensive with the second layer <NUM>, and are distributed across the second layer <NUM> in a grid of parallel rows and columns, in which the slots are also mutually parallel to each other. In some embodiments, the rows may be spaced about <NUM> millimeters on center, and the fluid restrictions <NUM> within each of the rows may be spaced about <NUM> millimeters on center as illustrated in the example of <FIG>. The fluid restrictions <NUM> in adjacent rows may be aligned or offset. For example, adjacent rows may be offset, as illustrated in <FIG>, so that the fluid restrictions <NUM> are aligned in alternating rows and separated by about <NUM> millimeters. The spacing of the fluid restrictions <NUM> may vary in some embodiments to increase the density of the fluid restrictions <NUM> according to therapeutic requirements.

One or more of the components of the dressing <NUM> may additionally be treated with an antimicrobial agent in some embodiments. For example, the first layer <NUM> may be a foam, mesh, or non-woven coated with an antimicrobial agent. In some embodiments, the first layer may comprise antimicrobial elements, such as fibers coated with an antimicrobial agent. Additionally or alternatively, some embodiments of the second layer <NUM> may be a polymer coated or mixed with an antimicrobial agent. In other examples, the fluid conductor <NUM> may additionally or alternatively be treated with one or more antimicrobial agents. Suitable antimicrobial agents may include, for example, metallic silver, PHMB, iodine or its complexes and mixes such as povidone iodine, copper metal compounds, chlorhexidine, or some combination of these materials.

Additionally or alternatively, one or more of the components may be coated with a mixture that may include citric acid and collagen, which can reduce bio-films and infections. For example, the first layer <NUM> may be a foam coated with such a mixture.

Individual components of the dressing <NUM> may be bonded or otherwise secured to one another with a solvent or non-solvent adhesive, or with thermal welding, for example, without adversely affecting fluid management.

The cover <NUM>, the first layer <NUM>, and the second layer <NUM>, or various combinations may be assembled before application or in situ. For example, the cover <NUM> may be laminated to the first layer <NUM>, and the second layer <NUM> may be laminated to the first layer <NUM> opposite the cover <NUM> in some embodiments. The second layer <NUM> may provide a smooth surface opposite the first layer <NUM>. In some embodiments, one or more layers of the tissue interface <NUM> may coextensive. For example, the second layer <NUM> may be cut flush with the edge of the first layer <NUM>, exposing the edge of the first layer <NUM>, as illustrated in the embodiment of <FIG>. In other embodiments, the second layer <NUM> may overlap the edge of the first layer <NUM>. In some embodiments, the dressing <NUM> may be provided as a single, composite dressing. For example, the second layer <NUM> may be coupled to the cover <NUM> to enclose the first layer <NUM>, wherein the second layer <NUM> is configured to face a tissue site.

In use, the release liner <NUM> (if included) may be removed to expose the second layer <NUM>, which may be placed within, over, on, or otherwise proximate to a tissue site, particularly a surface tissue site and adjacent epidermis. The second layer <NUM> may be interposed between the first layer <NUM> and the tissue site and adjacent epidermis, which can substantially reduce or eliminate adverse interaction with the first layer <NUM>. For example, the second layer <NUM> may be placed over a surface wound (including edges of the wound) and undamaged epidermis to prevent direct contact with the first layer <NUM>. Treatment of a surface wound or placement of the dressing <NUM> on a surface wound includes placing the dressing <NUM> immediately adjacent to the surface of the body or extending over at least a portion of the surface of the body. Treatment of a surface wound does not include placing the dressing <NUM> wholly within the body or wholly under the surface of the body, such as placing a dressing within an abdominal cavity. The cover <NUM> may be sealed to an attachment surface, such as epidermis peripheral to a tissue site, around the first layer <NUM> and the second layer <NUM>.

The geometry and dimensions of the tissue interface <NUM>, the cover <NUM>, or both may vary to suit a particular application or anatomy. For example, the geometry or dimensions of the tissue interface <NUM> and the cover <NUM> may be adapted to provide an effective and reliable seal against challenging anatomical surfaces, such as an elbow or heel, at and around a tissue site. Additionally or alternatively, the dimensions may be modified to increase the surface area for the second layer <NUM> to enhance the movement and proliferation of epithelial cells at a tissue site and reduce the likelihood of granulation tissue in-growth.

Thus, the dressing <NUM> in the example of <FIG> can provide a sealed therapeutic environment proximate to a tissue site, substantially isolated from the external environment, and the negative-pressure source <NUM> can reduce the pressure in the sealed therapeutic environment. Negative pressure in the sealed environment may compress the first layer <NUM> into the second layer <NUM>, which can deform the surface of the second layer <NUM> to provide an uneven, coarse, or jagged profile that can induce macrostrain and micro-strain in the tissue site in some embodiments. Negative pressure applied through the tissue interface <NUM> can also create a negative pressure differential across the fluid restrictions <NUM> in the second layer <NUM>, which can open the fluid restrictions <NUM> to allow exudate and other liquid movement through the fluid restrictions <NUM> into the first layer <NUM> and the container <NUM>. For example, in some embodiments in which the fluid restrictions <NUM> may comprise perforations through the second layer <NUM>, a pressure gradient across the perforations can strain the adjacent material of the second layer <NUM> and increase the dimensions of the perforations to allow liquid movement through them, similar to the operation of a duckbill valve.

In some embodiments, the first layer <NUM> may be hydrophobic to minimize retention or storage of liquid in the dressing <NUM>. In other embodiments, the first layer <NUM> may be hydrophilic. In an example in which the first layer <NUM> may be hydrophilic, the first layer <NUM> may also wick fluid away from a tissue site, while continuing to distribute negative pressure to the tissue site. The wicking properties of the first layer <NUM> may draw fluid away from a tissue site by capillary flow or other wicking mechanisms, for example. An example of a hydrophilic first layer <NUM> is a polyvinyl alcohol, open-cell foam such as V. WHITEFOAM™ dressing available from KCI of San Antonio, Texas. Other hydrophilic foams may include those made from polyether. Other foams that may exhibit hydrophilic characteristics include hydrophobic foams that have been treated or coated to provide hydrophilicity.

If the negative-pressure source <NUM> is removed or turned-off, the pressure differential across the fluid restrictions <NUM> can dissipate, allowing the fluid restrictions <NUM> to return to an unstrained or resting state and prevent or reduce the return rate of exudate or other liquid moving to the tissue site through the second layer <NUM>.

In some applications, a filler may also be disposed between a tissue site and the second layer <NUM>. For example, if the tissue site is a surface wound, a wound filler may be applied interior to the periwound, and the second layer <NUM> may be disposed over the periwound and the wound filler. In some embodiments, the filler may be a manifold, such as an open-cell foam. The filler may comprise or consist essentially of the same material as the first layer <NUM> in some embodiments.

Additionally or alternatively, the tissue interface <NUM> may be formed into strips suitable for use as bridges or to fill tunnel wounds, for example. Strips having a width of about <NUM> millimeters to <NUM> millimeters may be suitable for some embodiments.

Additionally or alternatively, the second layer <NUM> may comprise reinforcing fibers to increase its tensile strength, which may be advantageous for use in tunnel wounds.

Additionally or alternatively, instillation solution or other fluid may be distributed to the dressing <NUM>, which can increase the pressure in the tissue interface <NUM>. The increased pressure in the tissue interface <NUM> can create a positive pressure differential across the fluid restrictions <NUM> in the second layer <NUM>, which can open or expand the fluid restrictions <NUM> from their resting state to allow the instillation solution or other fluid to be distributed to the tissue site.

<FIG> is an assembly view of another example of the dressing <NUM> of <FIG>, illustrating additional details that may be associated with some embodiments in which the tissue interface <NUM> may comprise additional layers. In the example of <FIG>, the tissue interface <NUM> comprises a third layer <NUM> in addition to the first layer <NUM> and the second layer <NUM>. In some embodiments, the third layer <NUM> may be adjacent to the second layer <NUM> opposite the first layer <NUM>. The third layer <NUM> may also be bonded to the second layer <NUM> in some embodiments.

The third layer <NUM> may comprise or consist essentially of a sealing layer formed from a soft, pliable material suitable for providing a fluid seal with a tissue site, and may have a substantially flat surface. For example, the third layer <NUM> may comprise, without limitation, a silicone gel, a soft silicone, hydrocolloid, hydrogel, polyurethane gel, polyolefin gel, hydrogenated styrenic copolymer gel, a foamed gel, a soft closed cell foam such as polyurethanes and polyolefins coated with an adhesive, polyurethane, polyolefin, or hydrogenated styrenic copolymers. In some embodiments, the third layer <NUM> may have a thickness between about <NUM> microns (µm) and about <NUM> microns (µm). In some embodiments, the third layer <NUM> may have a hardness between about <NUM> Shore OO and about <NUM> Shore OO. Further, the third layer <NUM> may be comprised of hydrophobic or hydrophilic materials.

In some embodiments, the third layer <NUM> may be a hydrophobic-coated material. For example, the third layer <NUM> may be formed by coating a spaced material, such as, for example, woven, nonwoven, molded, or extruded mesh with a hydrophobic material. The hydrophobic material for the coating may be a soft silicone, for example.

The third layer <NUM> may have a periphery <NUM> surrounding or around an interior portion <NUM>, and apertures <NUM> disposed through the periphery <NUM> and the interior portion <NUM>. The interior portion <NUM> may correspond to a surface area of the first layer <NUM> in some examples. The third layer <NUM> may also have corners <NUM> and edges <NUM>. The corners <NUM> and the edges <NUM> may be part of the periphery <NUM>. The third layer <NUM> may have an interior border <NUM> around the interior portion <NUM>, disposed between the interior portion <NUM> and the periphery <NUM>. The interior border <NUM> may be substantially free of the apertures <NUM>, as illustrated in the example of <FIG>. In some examples, as illustrated in <FIG>, the interior portion <NUM> may be symmetrical and centrally disposed in the third layer <NUM>.

The apertures <NUM> may be formed by cutting or by application of local RF or ultrasonic energy, for example, or by other suitable techniques for forming an opening. The apertures <NUM> may have a uniform distribution pattern, or may be randomly distributed on the third layer <NUM>. The apertures <NUM> in the third layer <NUM> may have many shapes, including circles, squares, stars, ovals, polygons, slits, complex curves, rectilinear shapes, triangles, for example, or may have some combination of such shapes.

Each of the apertures <NUM> may have uniform or similar geometric properties. For example, in some embodiments, each of the apertures <NUM> may be circular apertures, having substantially the same diameter. In some embodiments, the diameter of each of the apertures <NUM> may be between about <NUM> millimeter to about <NUM> millimeters. In other embodiments, the diameter of each of the apertures <NUM> may be between about <NUM> millimeter to about <NUM> millimeters.

In other embodiments, geometric properties of the apertures <NUM> may vary. For example, the diameter of the apertures <NUM> may vary depending on the position of the apertures <NUM> in the third layer <NUM>, as illustrated in <FIG>. In some embodiments, the diameter of the apertures <NUM> in the periphery <NUM> of the third layer <NUM> may be larger than the diameter of the apertures <NUM> in the interior portion <NUM> of the third layer <NUM>. For example, in some embodiments, the apertures <NUM> disposed in the periphery <NUM> may have a diameter between about <NUM> millimeters to about <NUM> millimeters. In some embodiments, the apertures <NUM> disposed in the corners <NUM> may have a diameter between about <NUM> millimeters to about <NUM> millimeters. In some embodiments, the apertures <NUM> disposed in the interior portion <NUM> may have a diameter between about <NUM> millimeters to about <NUM> millimeters.

At least one of the apertures <NUM> in the periphery <NUM> of the third layer <NUM> may be positioned at the edges <NUM> of the periphery <NUM>, and may have an interior cut open or exposed at the edges <NUM> that is in fluid communication in a lateral direction with the edges <NUM>. The lateral direction may refer to a direction toward the edges <NUM> and in the same plane as the third layer <NUM>. As shown in the example of <FIG>, the apertures <NUM> in the periphery <NUM> may be positioned proximate to or at the edges <NUM> and in fluid communication in a lateral direction with the edges <NUM>. The apertures <NUM> positioned proximate to or at the edges <NUM> may be spaced substantially equidistant around the periphery <NUM> as shown in the example of <FIG>. Alternatively, the spacing of the apertures <NUM> proximate to or at the edges <NUM> may be irregular.

As illustrated in the example of <FIG>, in some embodiments, the release liner <NUM> may be attached to or positioned adjacent to the third layer <NUM> to protect the adhesive <NUM> prior to use. In some embodiments, the release liner <NUM> may have a surface texture that may be imprinted on an adjacent layer, such as the third layer <NUM>. Further, a release agent may be disposed on a side of the release liner <NUM> that is configured to contact the third layer <NUM>.

<FIG> is a schematic view of an example configuration of the apertures <NUM>, illustrating additional details that may be associated with some embodiments of the third layer <NUM>. In some embodiments, the apertures <NUM> illustrated in <FIG> may be associated only with the interior portion <NUM>. In the example of <FIG>, the apertures <NUM> are generally circular and have a diameter of about <NUM> millimeters. <FIG> also illustrates an example of a uniform distribution pattern of the apertures <NUM> in the interior portion <NUM>. In <FIG>, the apertures <NUM> are distributed across the interior portion <NUM> in a grid of parallel rows and columns. Within each row and column, the apertures <NUM> may be equidistant from each other, as illustrated in the example of <FIG> illustrates one example configuration that may be particularly suitable for many applications, in which the apertures <NUM> are spaced about <NUM> millimeters apart along each row and column, with a <NUM> millimeter offset.

<FIG> is a schematic view of the example third layer <NUM> of <FIG> overlaid on the second layer <NUM> of <FIG>, illustrating additional details that may be associated with some example embodiments of the tissue interface <NUM>. For example, as illustrated in <FIG>, the fluid restrictions <NUM> may be aligned, overlapping, in registration with, or otherwise fluidly coupled to the apertures <NUM> in some embodiments. In some embodiments, one or more of the fluid restrictions <NUM> may be registered with the apertures <NUM> only in the interior portion <NUM>, or only partially registered with the apertures <NUM>. The fluid restrictions <NUM> in the example of <FIG> are generally configured so that each of the fluid restrictions <NUM> is registered with only one of the apertures <NUM>. In other examples, one or more of the fluid restrictions <NUM> may be registered with more than one of the apertures <NUM>. For example, any one or more of the fluid restrictions <NUM> may be a perforation or a fenestration that extends across two or more of the apertures <NUM>. Additionally or alternatively, one or more of the fluid restrictions <NUM> may not be registered with any of the apertures <NUM>.

As illustrated in the example of <FIG>, the apertures <NUM> may be sized to expose a portion of the second layer <NUM>, the fluid restrictions <NUM>, or both through the third layer <NUM>. In some embodiments, one or more of the apertures <NUM> may be sized to expose more than one of the fluid restrictions <NUM>. For example, some or all of the apertures <NUM> may be sized to expose two or three of the fluid restrictions <NUM>. In some examples, the length of each of the fluid restrictions <NUM> may be substantially equal to the diameter of each of the apertures <NUM>. More generally, the average dimensions of the fluid restrictions <NUM> are substantially similar to the average dimensions of the apertures <NUM>. For example, the apertures <NUM> may be elliptical in some embodiments, and the length of each of the fluid restrictions <NUM> may be substantially equal to the major axis or the minor axis. In some embodiments, though, the dimensions of the fluid restrictions <NUM> may exceed the dimensions of the apertures <NUM>, and the size of the apertures <NUM> may limit the effective size of the fluid restrictions <NUM> exposed to the lower surface of the dressing <NUM>.

Individual components of the dressing <NUM> in the example of <FIG> may be bonded or otherwise secured to one another with a solvent or non-solvent adhesive, or with thermal welding, for example, without adversely affecting fluid management. Further, the second layer <NUM> or the first layer <NUM> may be coupled to the border <NUM> of the third layer <NUM> in any suitable manner, such as with a weld or an adhesive, for example.

The cover <NUM>, the first layer <NUM>, the second layer <NUM>, the third layer <NUM>, or various combinations may be assembled before application or in situ. For example, the cover <NUM> may be laminated to the first layer <NUM>, and the second layer <NUM> may be laminated to the first layer <NUM> opposite the cover <NUM> in some embodiments. The third layer <NUM> may also be coupled to the second layer <NUM> opposite the first layer <NUM> in some embodiments. In some embodiments, one or more layers of the tissue interface <NUM> may coextensive. For example, the second layer <NUM>, the third layer <NUM>, or both may be cut flush with the edge of the first layer <NUM>, exposing the edge of the first layer <NUM>, as illustrated in the embodiment of <FIG>. In other embodiments, the second layer <NUM>, the third layer <NUM>, or both may overlap the edge of the first layer <NUM>. In some embodiments, the dressing <NUM> may be provided as a single, composite dressing. For example, the third layer <NUM> may be coupled to the cover <NUM> to enclose the first layer <NUM> and the second layer <NUM>, wherein the third layer <NUM> is configured to face a tissue site. Additionally or alternatively, the second layer <NUM>, the third layer <NUM>, or both may be disposed on both sides of the first layer <NUM> and bonded together to enclose the first layer <NUM>.

In use, the release liner <NUM> (if included) may be removed to expose the third layer <NUM> of the example of <FIG>, which may be placed within, over, on, or otherwise proximate to a tissue site, particularly a surface tissue site and adjacent epidermis. The third layer <NUM> and the second layer <NUM> may be interposed between the first layer <NUM> and the tissue site, which can substantially reduce or eliminate adverse interaction with the first layer <NUM>. For example, the third layer <NUM> may be placed over a surface wound (including edges of the wound) and undamaged epidermis to prevent direct contact with the first layer <NUM>. In some applications, the interior portion <NUM> of the third layer <NUM> may be positioned adjacent to, proximate to, or covering a tissue site. In some applications, at least some portion of the second layer <NUM>, the fluid restrictions <NUM>, or both may be exposed to a tissue site through the third layer <NUM>. The periphery <NUM> of the third layer <NUM> may be positioned adjacent to or proximate to tissue around or surrounding the tissue site. The third layer <NUM> may be sufficiently tacky to hold the dressing <NUM> in position, while also allowing the dressing <NUM> to be removed or re-positioned without trauma to the tissue site.

Removing the release liner <NUM> in the example of <FIG> can also expose the adhesive <NUM> and the cover <NUM> may be attached to an attachment surface, such as epidermis peripheral to a tissue site, around the first layer <NUM> and the second layer <NUM>. For example, the adhesive <NUM> may be in fluid communication with an attachment surface through the apertures <NUM> in at least the periphery <NUM> of the third layer <NUM>. The adhesive <NUM> may also be in fluid communication with the edges <NUM> through the apertures <NUM> exposed at the edges <NUM>.

Once the dressing <NUM> is in the desired position, the adhesive <NUM> may be pressed through the apertures <NUM> to bond the dressing <NUM> to the attachment surface. The apertures <NUM> at the edges <NUM> may permit the adhesive <NUM> to flow around the edges <NUM> for enhancing the adhesion of the edges <NUM> to an attachment surface.

In some embodiments, apertures or holes in the third layer <NUM> may be sized to control the amount of the adhesive <NUM> in fluid communication with the apertures <NUM>. For a given geometry of the corners <NUM>, the relative sizes of the apertures <NUM> may be configured to maximize the surface area of the adhesive <NUM> exposed and in fluid communication through the apertures <NUM> at the corners <NUM>. For example, as shown in <FIG>, the edges <NUM> may intersect at substantially a right angle, or about <NUM> degrees, to define the corners <NUM>. In some embodiments, the corners <NUM> may have a radius of about <NUM> millimeters. Further, in some embodiments, three of the apertures <NUM> having a diameter between about <NUM> millimeters to about <NUM> millimeters may be positioned in a triangular configuration at the corners <NUM> to maximize the exposed surface area for the adhesive <NUM>. In other embodiments, the size and number of the apertures <NUM> in the corners <NUM> may be adjusted as necessary, depending on the chosen geometry of the corners <NUM>, to maximize the exposed surface area of the adhesive <NUM>. Further, the apertures <NUM> at the corners <NUM> may be fully housed within the third layer <NUM>, substantially precluding fluid communication in a lateral direction exterior to the corners <NUM>. The apertures <NUM> at the corners <NUM> being fully housed within the third layer <NUM> may substantially preclude fluid communication of the adhesive <NUM> exterior to the corners <NUM>, and may provide improved handling of the dressing <NUM> during deployment at a tissue site. Further, the exterior of the corners <NUM> being substantially free of the adhesive <NUM> may increase the flexibility of the corners <NUM> to enhance comfort.

In some embodiments, the bond strength of the adhesive <NUM> may vary in different locations of the dressing <NUM>. For example, the adhesive <NUM> may have a lower bond strength in locations adjacent to the third layer <NUM> where the apertures <NUM> are relatively larger, and may have a higher bond strength where the apertures <NUM> are smaller. Adhesive <NUM> with lower bond strength in combination with larger apertures <NUM> may provide a bond comparable to adhesive <NUM> with higher bond strength in locations having smaller apertures <NUM>.

The geometry and dimensions of the tissue interface <NUM>, the cover <NUM>, or both may vary to suit a particular application or anatomy. For example, the geometry or dimensions of the tissue interface <NUM> and the cover <NUM> may be adapted to provide an effective and reliable seal against challenging anatomical surfaces, such as an elbow or heel, at and around a tissue site. Additionally or alternatively, the dimensions may be modified to increase the surface area for the third layer <NUM> to enhance the movement and proliferation of epithelial cells at a tissue site and reduce the likelihood of granulation tissue in-growth.

Further, the dressing <NUM> may permit re-application or re-positioning to reduce or eliminate leaks, which can be caused by creases and other discontinuities in the dressing <NUM> or a tissue site. The ability to rectify leaks may increase the reliability of the therapy and reduce power consumption in some embodiments.

Thus, the dressing <NUM> in the example of <FIG> can provide a sealed therapeutic environment proximate to a tissue site, substantially isolated from the external environment, and the negative-pressure source <NUM> can reduce the pressure in the sealed therapeutic environment. The third layer <NUM> may provide an effective and reliable seal against challenging anatomical surfaces, such as an elbow or heel, at and around a tissue site. Further, the dressing <NUM> may permit re-application or re-positioning, to correct air leaks caused by creases and other discontinuities in the dressing <NUM>, for example. The ability to rectify leaks may increase the efficacy of the therapy and reduce power consumption in some embodiments.

If not already configured, the dressing interface <NUM> may be disposed over the aperture <NUM> and attached to the cover <NUM>. The fluid conductor <NUM> may be fluidly coupled to the dressing interface <NUM> and to the negative-pressure source <NUM>.

Negative pressure applied through the tissue interface <NUM> can create a negative pressure differential across the fluid restrictions <NUM> in the second layer <NUM>, which can open or expand the fluid restrictions <NUM>. For example, in some embodiments in which the fluid restrictions <NUM> may comprise substantially closed fenestrations through the second layer <NUM>, a pressure gradient across the fenestrations can strain the adjacent material of the second layer <NUM> and increase the dimensions of the fenestrations to allow liquid movement through them, similar to the operation of a duckbill valve. Opening the fluid restrictions <NUM> can allow exudate and other liquid movement through the fluid restrictions <NUM> into the first layer <NUM> and the container <NUM>. Changes in pressure can also cause the first layer <NUM> to expand and contract, and the interior border <NUM> may protect the epidermis from irritation. The second layer <NUM> and the third layer <NUM> can also substantially reduce or prevent exposure of tissue to the first layer <NUM>, which can inhibit growth of tissue into the first layer <NUM>.

If the negative-pressure source <NUM> is removed or turned off, the pressure differential across the fluid restrictions <NUM> can dissipate, allowing the fluid restrictions <NUM> to close and prevent exudate or other liquid from returning to the tissue site through the second layer <NUM>.

In some applications, a filler may also be disposed between a tissue site and the third layer <NUM>. For example, if the tissue site is a surface wound, a wound filler may be applied interior to the periwound, and the third layer <NUM> may be disposed over the periwound and the wound filler. In some embodiments, the filler may be a manifold, such as an open-cell foam. The filler may comprise or consist essentially of the same material as the first layer <NUM> in some embodiments.

Additionally or alternatively, instillation solution or other fluid may be distributed to the dressing <NUM>, which can increase the pressure in the tissue interface <NUM>. The increased pressure in the tissue interface <NUM> can create a positive pressure differential across the fluid restrictions <NUM> in the second layer <NUM>, which can open the fluid restrictions <NUM> to allow the instillation solution or other fluid to be distributed to the tissue site.

<FIG> is a top view of another example the third layer <NUM>, illustrating additional details that may be associated with some embodiments. As shown in the example of <FIG>, the third layer <NUM> may have one or more elastomeric valves <NUM> instead of or in addition to the apertures <NUM> in the interior portion <NUM>. The valves <NUM> may be included in the third layer <NUM> in addition to or instead of the second layer <NUM>. In some embodiments in which the third layer <NUM> includes one or more of the valves <NUM>, the second layer <NUM> may be omitted. For example, in some embodiments, the tissue interface <NUM> may consist essentially of the first layer <NUM> and the third layer <NUM> of <FIG> with the valves <NUM> disposed in the interior portion <NUM>.

<FIG> and <FIG> illustrate other example configurations of the valves <NUM>, in which the valves <NUM> each generally comprise a combination of intersecting slits or cross-slits.

<FIG> is an assembly view of another example of the tissue interface <NUM> of <FIG>. In the example of <FIG>, the second layer <NUM> is disposed adjacent to two sides of the first layer <NUM>. In some embodiments, for example, the second layer <NUM> may be laminated or otherwise mechanically bonded to two sides of the first layer <NUM>. Additionally or alternatively, the third layer <NUM> may be disposed adjacent to one or more sides of the first layer <NUM>, or may be disposed adjacent to the second layer <NUM> as shown in the example of <FIG>. In some embodiments, the third layer <NUM> may form a sleeve or envelope around the first layer <NUM>, the second layer <NUM>, or both.

<FIG> is a perspective view of another example configuration of the first layer <NUM> and the second layer <NUM>. In the example of <FIG>, the second layer <NUM> may form a sleeve around the first layer <NUM>. For example, the second layer <NUM> may be folded or rolled around the first layer <NUM>, and edges of the second layer <NUM> may be attached to each other. In other examples, the edges may be attached to form a sleeve before inserting the first layer <NUM>, or the edges may be attached to the first layer <NUM>. The second layer <NUM> may leave one or more edges of the first layer <NUM> exposed, as illustrated in the example of <FIG>. The example configuration of <FIG> may be used in combination with or instead of other configurations of the first layer <NUM> and the second layer <NUM> described above.

<FIG> is a partial cutaway view of another example configuration of the first layer and the second layer <NUM>. In the example of <FIG>, the second layer <NUM> may form an envelope around the first layer <NUM>. For example, the second layer <NUM> may be disposed on two sides of the first layer <NUM>, and the edges may be mechanically coupled to each other around the first layer <NUM> to form an envelope. The example configuration of <FIG> may be used in combination with or instead of other configurations of the first layer <NUM> and the second layer <NUM> described above.

The apparatuses, described herein may provide significant advantages over prior dressings. For example, some dressings for negative-pressure therapy can require time and skill to be properly sized and applied to achieve a good fit and seal. In contrast, some embodiments of the dressing <NUM> provide a negative-pressure dressing that is simple to apply, reducing the time to apply and remove. In some embodiments, for example, the dressing <NUM> may be a fully-integrated negative-pressure therapy dressing that can be applied to a tissue site (including on the periwound) in one step, without being cut to size, while still providing or improving many benefits of other negative-pressure therapy dressings that require sizing. Such benefits may include good manifolding, beneficial granulation, protection of the peripheral tissue from maceration, protection of the tissue site from shedding materials, and a low-trauma and high-seal bond. These characteristics may be particularly advantageous for surface wounds having moderate depth and medium-to-high levels of exudate. Some embodiments of the dressing <NUM> may remain on the tissue site for at least <NUM> days, and some embodiments may remain for at least <NUM> days. Antimicrobial agents in the dressing <NUM> may extend the usable life of the dressing <NUM> by reducing or eliminating infection risks that may be associated with extended use, particularly use with infected or highly exuding wounds.

Some of the advantages associated with the systems, apparatuses, and methods described herein may be further demonstrated by the following non-limiting example.

The primary objective of this study was to evaluate an embodiment of a dressing having features described above (designated as "GM" for purposes of the study), in conjunction with V. ® Therapy and V. VERAFLO™ Therapy as compared to traditional V. ® Therapy with GRANUFOAM™ dressing and to other Advanced Wound Care dressings without V. Wounds were assessed for granulation tissue formation, presence of maceration in periwound skin and ease of dressing removal as determined by:.

This study was conducted using the animal model outlined below:.

The initial pilot animal (Group <NUM>) underwent all wound creation and therapy prior to scheduling procedures on the additional Group <NUM> and <NUM> animals. Up to Ten (<NUM>) full thickness skin excisional wounds (~<NUM> x <NUM>) were created on each animal (up to <NUM> wounds on each side of the spine) with the aid of a sterile template. There was spacing between each of the wounds (approximately <NUM> or more from wound edge to wound edge between adjacent wounds, and sufficient spacing between all wounds to provide enough space to properly place the dressings and the drape. If the length of the back of the animal did not provide enough space for <NUM> wounds and dressings (determined on Day <NUM>) then <NUM> wounds (<NUM> on each side of spine) was created. A scalpel blade was used to surgically create the wound down to the subcutaneous fascial layer (just over the muscle) but without disrupting it. If disruption of the subcutaneous fascial layer occurred, it was documented in the study records. Care was taken during wound creation so as not to undermine the perimeter of the wound. The wounds were prepared in two paraspinal columns with efforts made to keep the columns between the crest of the shoulders and the coccygeal tuberosity. Direct pressure with sterile gauze was utilized to obtain hemostasis. In the event of excessive bleeding that did not subside with direct pressure, a hemostat was used to clamp the source of bleeding. Wound sites were kept moist with sterile <NUM>% saline-soaked gauze during the creation of other wounds. Wounds were photographed.

Following the creation of wounds (Day <NUM>) all wounds received Test or Control Article. On Day <NUM> (Group <NUM> only), those wounds undergoing dressing removal received Test or Control Article.

On the designated dressing change day (after peel testing, TEWL, visual observations and photographs), the periwound area was wiped clean with sterile <NUM>% saline-soaked gauze and allowed to dry. Dressings were applied to the individual wound sites per a randomization scheme.

An adhesive such as benzoin was placed on the skin surrounding the very perimeter of the test article edges, regardless of the type of dressing for a particular wound, so that the periwound area was framed with adhesive leaving a ~<NUM> perimeter of periwound free of benzoin. This means that the immediate periwound skin cannot have benzoin adhesive applied as this may affect the EpiD readings. The adhesive was placed on the skin in any area that V. ® Drape was applied. Alternatively (or in addition to), Hollister (a medical grade silicone adhesive) was applied as an extra adhesive to help maintain a seal.

For the test article wound pair (test article with V. ® Therapy), and/or the test article with V. VERAFLO™ Therapy (test article using V. VERAFLO™ Therapy with saline) wounds, a pair of electrodes (e.g. aluminum sheet or wire) was applied so it rested in the peri-wound area (under test article but on top of periwound skin).

As applicable, the skin underneath the strips of the foam bridge were covered with V. ® Drape to protect it. Each bridged wound group was covered with the V. ® Drape included in the dressing kit, one hole will be made in the drape , and a SENSAT. ™ Pad or a V. ™ Pad (as applicable) was attached directly above the hole as per instructions for use (IFU). Each of the pads was framed with V. ® Drape along each side to keep it in place and to make sure there was a seal.

ULTA™ unit was present in the surgical suite on the day of wound creation and was appropriately connected to each pad to verify that each wound group had been sealed properly following the application.

To check the seal around the wounds, negative-pressure wound therapy (NPWT) began at a continuous vacuum pressure of -<NUM> mmHg using the SEAL CHECK™ function on the V. ULTA™ Unit. Upon verification of a proper seal, the V. ULTA™ unit was turned off and this procedure was repeated as applicable. Following verification of all seals, additional layers of V. ® Drape was placed around the edges to reinforce the seals and prevent leaks.

For wounds receiving V. VERAFLO™ Therapy the Fill Assist feature was used to determine the volume of fluid (i.e. saline) required to saturate the dressings in the paired wounds. These determinations were made for wound pairs at each dressing change, as appropriate. VERAFLO™ Therapy NPWT was begun at a continuous vacuum pressure of -<NUM> mmHg using the SEAL CHECK™ function on the V. ULTA™ Unit. Upon verification of a proper seal, the V. ULTA™ unit was turned off and this procedure was repeated as applicable. Following verification of all seals, additional layers of V. ® Drape were placed around the edges to reinforce the seals and prevent leaks. The soak/dwell time per cycle was <NUM> minutes, NPWT time per cycle was <NUM> hours with a target pressure of -<NUM> mmHg.

The entire V. ® Drape-covered area was draped with a tear-resistant mesh (e.g. organza material) secured with V. ® Drape, Elastikon® or equivalent to prevent dislodgement of the dressings.

Resistance readings from under the dressings were performed. Peel force testing for wounds were performed on one wound from each treatment pair. The dressings were removed by hand for the other half of each wound pair, unless dressings were intended to stay in place (i.e. TANPT and TANPTI (n=<NUM> animals)). Wound assessments were performed (as applicable) and photographs taken.

Peel force testing was performed on one wound from each treatment pair (same wounds as dressing change, if applicable). For wounds where the dressing had been removed, TEWL was performed, wound assessments were performed and photographs taken.

For Groups <NUM> & <NUM>, (Day <NUM>), peel force testing, TEWL and assessments were performed on <NUM> wounds. The remaining <NUM> wounds were collected with dressings in situ for histopathology processing and evaluation.

For Group <NUM> (Day <NUM>), peel force testing, TEWL and assessments were performed on <NUM> wounds. The remaining <NUM> wounds were collected with dressings in situ for histopathology processing and evaluation.

Peel force testing was performed on a tilting operating table. The peel force test was performed using a device that peels back the test material edge while measuring the force that is required to peel the dressing from the wound at an angle of ~<NUM>° relative to the peel tester. A digital protractor was used to confirm the angle. The peel strength values indicate the ease with which the test materials can be removed from the wound bed. Removal of the test materials was performed using a 20N Shimpo Digital Force Gauge that was mounted onto a Shimpo Motorized Test Stand and controlled via a computer equipped with LabView.

The drape over the control articles for peel testing was gently circumscribed with a scalpel, taking care to not disrupt the tissue ingrowth into the sides of the dressing. On treatments with the test article for peel testing, a scalpel was used to remove the excess dressing that was not in contact with the wound. This was done by cutting the dressing along the sides, bottom and top where the margins of the wound are visible after negative pressure therapy. The medial end of the dressing or dressing tab was attached to the force gauge with the clip (no circumscribing of the dressing will be performed). The dressing was then pulled from the wound (medial to lateral) at a constant rate from a medial to lateral direction. After the peel force measurements were taken, assessments were performed. Continuous peel force readings were recorded through LabView via the Force Gauge and saved for each wound. Following peel testing, the dressings were saved for analysis of the tissue that remains within the dressing.

<FIG> demonstrates the results of maximum peel force measurements (N) on day <NUM> following dressing application and removal of test articles (designated as "TANPT" and TANPTI) and control dressings. As can be seen, the test article with and without V. VERAFLO™ Therapy required significantly less peel force.

After peel force testing and TEWL measurements, two biopsy punches (<NUM>, or not to exceed <NUM> each) were collected from the center of each wound as applicable.

Determination of the level of moisture at the dressing-skin (intact) interface was performed using a Moisture Meter the EpiD Compact from Delfin Technologies (Kuopio, Finland). This measurement was done immediately after wound creation on Day <NUM>, at the dressing change day (as applicable), and at termination prior to euthanasia. To measure the dielectric constant of the skin, the EpiD Compact instrument was turned used. On the day of wound creation (Day <NUM>), four consecutive measurements of moisture was collected from intact skin on each animal approximating midway between the wound and edge of the wound pad of where the test article and the advanced wound dressings were. On dressing change day and at termination (as applicable), four consecutive measurements of moisture were collected. These measurements were repeated on each of the available wound sites for each animal. All of the measurements/data was recorded.

Wound observations were performed and documented at the dressing change and/or at the termination procedure as follows:.

Dressing retention (small particles and large pieces) was assessed following dressing removal or peel testing. After removal of the dressings from the wound, dressing retention in the wound was visually assessed and documented. All removed dressings was visually assessed for tissue retention and digitally photographed.

<FIG> demonstrates that there was a significant reduction in tissue ingrowth with TANPT and TANPTI.

If wound sites were in <NUM>% ethanol they were immediately processed and if received in NBF wounds were transferred to <NUM>% ethanol for a period of time before further processing per Histopathology Test Site standard procedures. The wound site + dressings (if intact), were embedded in oversized paraffin blocks, entire en bloc site was cross sectioned once at ~<NUM> thickness and resulting slides stained with Hematoxylin and Eosin (H&E). Gross images were taken of the cut surface of the specimens prior to processing and embedding in paraffin. In order to accommodate the entire tissue section with border of non-affected skin on all sides, oversized slides were used.

The histopathological response was scored semi-quantitatively by a board-certified veterinary pathologist, on a scale of <NUM>-<NUM> where <NUM>=minimal, <NUM>=mild, <NUM>=moderate, <NUM>= marked and <NUM>=severe, except where otherwise specified. Microscopic evaluation of all stained sections for morphological changes for the wound including, but not limited to, granulation tissue thickness and character, amount of granulation tissue embedded in dressing (if possible), tissue inflammation, edema, vascularity (if possible), presence of bacteria, necrosis and other relevant factors as determined by the pathologist. The peri-wound area was evaluated for characteristics consistent with maceration as determined by the pathologist.

Two dimensional (<NUM>-D) photographs of the individual wound sites were taken at the following time points:.

The optical micrographs pictures in <FIG> demonstrate that TANPT had significantly more granulation than NPT and NPTI.

Further <FIG> is a graphical representation comparing the Day <NUM> granulation tissue thickness between the test and control treatments. TANPT and TANPTI showed significantly higher granulation tissue thickness.

The data demonstrate that the test article had surprisingly positive results, with improvement when combined with V. VERAFLO™ Therapy. The test article with V. VERAFLO™ Therapy performed superiorly by showing an increase in granulation tissue thickness, a reduction in tissue ingrowth, percent epithelialization and average vascularization score.

Additionally, by Day <NUM>, all treatments with the test article showed significantly greater granulation tissue than NPT and NPTI. The percent increase in granulation depth using the test article (measured after a <NUM> day treatment period) was at least <NUM>% for NPT, and <NUM>% for NPTI. No evidence of adverse events or safety concerns were found. Periwound tissue moisture decreased over time (all treatment groups) reducing risk of maceration.

All treatments with the test article also showed surprising reductions in tissue in-growth, as evidenced by the significant reductions in peel force. After <NUM> days of either continuous V. ® Therapy or V. VERAFLO™ Therapy with no dressing change, a peel force of less than 2N was needed to remove the test article. Specifically, a peel force of <NUM>. 8N was used to remove the TANPTI test article, and a peel force of <NUM>. 5N was used to remove the TANPT test article. Compared to CA1 with V. ® Therapy, the peel force was reduced by <NUM>% and <NUM>%, respectively.

While shown in a few illustrative embodiments, a person having ordinary skill in the art will recognize that the systems, apparatuses, and methods described herein are susceptible to various changes and modifications 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.

Features, elements, and aspects described in the context of some embodiments may also be omitted, combined, or replaced by alternative features serving the same, equivalent, or similar purpose without departing from the scope of the invention defined by the appended claims. For example, one or more of the features of some layers may be combined with features of other layers to provide an equivalent function. Alternatively or additionally, one or more of the fluid restrictions <NUM> may have shapes similar to shapes described as exemplary for the valves <NUM>. In other examples, the second layer <NUM>, the third layer <NUM>, or some combination of the second layer <NUM> and the third layer <NUM> may be coupled to both sides of the first layer <NUM>.

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 <NUM>, the container <NUM>, or both may be eliminated or separated from other components for manufacture or sale. In other example configurations, components of the dressing <NUM> may also be manufactured, configured, assembled, or sold independently or as a kit.

Claim 1:
An apparatus for treating a tissue site with negative pressure, the apparatus comprising:
a tissue interface comprising a manifold (<NUM>) and a film (<NUM>) covering at least two sides of the manifold (<NUM>), the manifold (<NUM>) and the film (<NUM>) formed from a hydrophobic material;
a plurality of elastomeric valves (<NUM>) through the film (<NUM>), the plurality of elastomeric valves (<NUM>) configured to expand in response to a pressure gradient across the film (<NUM>); and
a cover (<NUM>) configured to be attached to the tissue site;
wherein the cover (<NUM>) and the tissue interface are assembled in a stacked relationship with the cover (<NUM>) configured to be attached to an attachment surface adjacent to the tissue site;
wherein each of the elastomeric valves (<NUM>) is normally closed when unstrained to substantially prevent liquid flow, and opens in response to the pressure gradient.