Patent Description:
Treatment of wounds or other tissue with reduced pressure may be commonly referred to as "negative-pressure therapy," but is also known by other names, including "negative- pressure wound therapy," "reduced-pressure therapy," "vacuum therapy," "vacuum-assisted closure," and "topical negative-pressure," for example. Negative-pressure therapy may provide a number of benefits, including migration of epithelial and subcutaneous tissues, improved blood flow, and micro- deformation of tissue at a wound site.

While the clinical benefits of negative-pressure therapy are widely known, improvements to therapy systems, components, and processes may benefit healthcare providers and patients. <CIT> discloses a negative pressure treatment system for treating a plurality of tissue sites including a valve to prevent flow of fluid to one of the tissue sites. <CIT> discloses a negative pressure wound dressing including a barrier layer to separate the dressing into an exudate receptable and a contact layer receptacle. <CIT> discloses a negative pressure drainage assembly with an anti-backflow drainage device.

The invention is defined by the independent claim. A selection of optional features is set out in the dependent claims.

<FIG> is a block diagram of an example embodiment of a therapy system <NUM> that can provide negative-pressure therapy 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, bone tissue, adipose tissue, muscle tissue, neural tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, or ligaments. A wound may include chronic, acute, traumatic, subacute, and dehisced wounds, partial-thickness burns, ulcers (such as diabetic, pressure, or venous insufficiency ulcers), flaps, and grafts, for example. The term "tissue site" may also refer to areas of any tissue that are not necessarily wounded or defective, but are instead areas in which it may be desirable to add or promote the growth of additional tissue. For example, negative pressure may be applied to a tissue site to grow additional tissue that may be harvested and transplanted.

The therapy system <NUM> may include a source or supply of negative pressure, such as a negative-pressure source <NUM>, and one or more distribution components. A distribution component is preferably detachable and may be disposable, reusable, or recyclable. A dressing, such as a dressing <NUM>, and a fluid container, such as a container <NUM>, are examples of distribution components that may be associated with some examples of the therapy system <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.

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 controller <NUM> and other components into a therapy unit <NUM>.

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 provided by the negative-pressure source <NUM> 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).

The container <NUM> is representative of a container, a canister, a pouch, or other storage component, which can be used to manage exudates and other fluids withdrawn from a tissue site.

Sensors, such as the first sensor <NUM> and the second sensor <NUM>, can be 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.

In some embodiments, the tissue interface <NUM> may comprise or consist essentially of a manifold. A manifold in this context may comprise or consist essentially of a means for collecting or distributing fluid across the tissue interface <NUM> under pressure. For example, a manifold 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 across a tissue site.

In some illustrative embodiments, a manifold may comprise a plurality of pathways, which can be interconnected to improve distribution or collection of fluids. In some illustrative embodiments, a manifold may comprise or consist essentially of a porous material having interconnected fluid pathways. Examples of suitable porous material that can be adapted to form interconnected fluid pathways (e.g., channels) may include cellular foam, including open-cell foam such as reticulated foam; porous tissue collections; and other porous material such as gauze or felted mat that generally include pores, edges, and/or walls. Liquids, gels, and other foams may also include or be cured to include apertures and fluid pathways. In some embodiments, a manifold may additionally or alternatively comprise projections that form interconnected fluid pathways. For example, a manifold may be molded to provide surface projections that define interconnected fluid pathways.

In some embodiments, the tissue interface <NUM> may comprise or consist essentially of reticulated foam having pore sizes and free volume that may vary according to needs of a prescribed therapy. For example, reticulated foam having a free volume of at least <NUM>% may be suitable for many therapy applications, and foam having an average pore size in a range of <NUM>-<NUM> microns (<NUM>-<NUM> pores per inch) may be particularly suitable for some types of therapy. The tensile strength of the tissue interface <NUM> may also vary according to needs of a prescribed therapy. The <NUM>% compression load deflection of the tissue interface <NUM> may be at least <NUM> pounds per square inch (<NUM> MPa) and the <NUM>% compression load deflection may be at least <NUM> pounds per square inch (<NUM> MPa). In some embodiments, the tensile strength of the tissue interface <NUM> may be at least <NUM> pounds per square inch (<NUM> MPa). The tissue interface <NUM> may have a tear strength of at least <NUM> pounds per inch (<NUM> MPa). In some embodiments, the tissue interface may be foam comprised of polyols such as polyester or polyether, isocyanate such as toluene diisocyanate, and polymerization modifiers such as amines and tin compounds. In some examples, the tissue interface <NUM> may be reticulated polyurethane foam such as found in GRANUFOAM™ dressing or V. VERAFLO™ dressing, both available from Kinetic Concepts, Inc.

The thickness of the tissue interface <NUM> may also vary according to needs of a prescribed therapy. For example, the thickness of the tissue interface may be decreased to reduce tension on peripheral tissue. The thickness of the tissue interface <NUM> can also affect the conformability of the tissue interface <NUM>. In some embodiments, a thickness in a range of about <NUM> millimeters to <NUM> millimeters may be suitable.

The tissue interface <NUM> may be either hydrophobic or hydrophilic. In an example in which the tissue interface <NUM> may be hydrophilic, the tissue interface <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 tissue interface <NUM> may draw fluid away from a tissue site by capillary flow or other wicking mechanisms. An example of a hydrophilic material that may be suitable is a polyvinyl alcohol, open-cell foam such as V. WHITEFOAM™ dressing available from Kinetic Concepts, Inc. Other hydrophilic foams may include those made from polyether. Other foams that may exhibit hydrophilic characteristics include hydrophobic foams that have been treated or coated to provide hydrophilicity.

In some embodiments, the tissue interface <NUM> may be constructed from bioresorbable materials. Suitable bioresorbable materials may include, without limitation, a polymeric blend of polylactic acid (PLA) and polyglycolic acid (PGA). The polymeric blend may also include, without limitation, polycarbonates, polyfumarates, and capralactones. The tissue interface <NUM> may further serve as a scaffold for new cell-growth, or a scaffold material may be used in conjunction with the tissue interface <NUM> to promote cell-growth. A scaffold is generally a substance or structure used to enhance or promote the growth of cells or formation of tissue, such as a three-dimensional porous structure that provides a template for cell growth. Illustrative examples of scaffold materials include calcium phosphate, collagen, PLA/PGA, coral hydroxy apatites, carbonates, or processed allograft materials.

In some embodiments, the 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 comprise or consist of, 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> grams per square meter per twenty-four hours in some embodiments, measured using an upright cup technique according to ASTM E96/E96M Upright Cup Method at <NUM> and <NUM>% relative humidity (RH). In some embodiments, an MVTR up to <NUM>,<NUM> grams per square meter per twenty-four hours may provide effective breathability and mechanical properties.

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: polyurethane (PU), such as hydrophilic polyurethane; cellulosics; hydrophilic polyamides; polyvinyl alcohol; polyvinyl pyrrolidone; hydrophilic acrylics; silicones, such as hydrophilic silicone elastomers; natural rubbers; polyisoprene; styrene butadiene rubber; chloroprene rubber; polybutadiene; nitrile rubber; butyl rubber; ethylene propylene rubber; ethylene propylene diene monomer; chlorosulfonated polyethylene; polysulfide rubber; ethylene vinyl acetate (EVA); co-polyester; and polyether block polymide copolymers. Such materials are commercially available as, for example, Tegaderm® drape, commercially available from <NUM> Company, Minneapolis Minnesota; polyurethane (PU) drape, commercially available from Avery Dennison Corporation, Pasadena, California; polyether block polyamide copolymer (PEBAX), for example, from Arkema S. , Colombes, France; and Inspire <NUM> and Inpsire <NUM> polyurethane films, commercially available from Expopack Advanced Coatings, Wrexham, United Kingdom. In some embodiments, the cover <NUM> may comprise INSPIRE <NUM> having an MVTR (upright cup technique) of <NUM>/m<NUM>/<NUM> hours and a thickness of about <NUM> microns.

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 of about <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 process of reducing pressure may be described illustratively herein as "delivering," "distributing," or "generating" negative pressure, for example. In general, exudate and other fluid flow toward lower pressure along a fluid path. Thus, the term "downstream" typically implies a location 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 location relatively further away from a source of negative pressure or closer to a source of positive pressure. 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 therefore, these descriptive terms should not be construed as limiting.

Negative pressure applied to the tissue site through the tissue interface <NUM> in the sealed therapeutic environment can induce macro-strain and micro-strain in the tissue site. Negative pressure can also remove exudate and other fluid from a tissue site, which can be collected in container <NUM>.

In some embodiments, the controller <NUM> may receive and process data from one or more sensors, such as the first sensor <NUM>. The controller <NUM> may also control the operation of one or more components of the therapy system <NUM> to manage the pressure delivered to the tissue interface <NUM>. In some embodiments, controller <NUM> may include an input for receiving a desired target pressure and may be programmed for processing data relating to the setting and inputting of the target pressure to be applied to the tissue interface <NUM>. In some example embodiments, the target pressure may be a fixed pressure value set by an operator as the target negative pressure desired for therapy at a tissue site and then provided as input to the controller <NUM>. The target pressure may vary from tissue site to tissue site based on the type of tissue forming a tissue site, the type of injury or wound (if any), the medical condition of the patient, and the preference of the attending physician. After selecting a desired target pressure, the controller <NUM> can operate the negative-pressure source <NUM> in one or more control modes based on the target pressure and may receive feedback from one or more sensors to maintain the target pressure at the tissue interface <NUM>.

<FIG> depicts an example embodiment of the therapy system <NUM> for treating a tissue site <NUM> of a patient. The tissue site <NUM> may extend through or otherwise involve an epidermis <NUM>, a dermis <NUM>, and a subcutaneous tissue <NUM>. The tissue site <NUM> may be a sub-surface tissue site as depicted in <FIG> that extends below the surface of the epidermis <NUM>. Further, the tissue site <NUM> may be a surface tissue site (not shown) that predominantly resides on the surface of the epidermis <NUM>, such as, for example, an incision. The therapy system <NUM> may provide therapy to, for example, the epidermis <NUM>, the dermis <NUM>, and the subcutaneous tissue <NUM>, regardless of the positioning of the therapy system <NUM> or the type of tissue site. The therapy system <NUM> may also be utilized without limitation at other tissue sites.

Further, the tissue site <NUM> may be the bodily tissue of any human, animal, or other organism, including bone tissue, adipose tissue, muscle tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, ligaments, or any other tissue. Treatment of the tissue site <NUM> may include removal of fluids, e.g., exudate or ascites.

Continuing with <FIG>, the therapy system <NUM> may include the dressing <NUM>, the container <NUM>, and the therapy unit <NUM> that may include the negative-pressure source <NUM>. Further, the therapy system <NUM> may include a filler material <NUM> as an optional component of the therapy system <NUM> that may be omitted for different types of tissue sites or different types of therapy using negative pressure, such as, for example, epithelialization. If equipped, the filler material <NUM> may be adapted to be positioned proximate to or adjacent to the tissue site <NUM>, such as, for example, by cutting or otherwise shaping the filler material <NUM> in any suitable manner to fit the tissue site <NUM> and to fill a space between the tissue site <NUM> and the dressing <NUM>. Similar to the tissue interface <NUM>, the filler material <NUM> may be constructed of the manifold materials described herein and may be adapted to be positioned in fluid communication with the tissue site <NUM> to distribute negative pressure to the tissue site <NUM>. In some embodiments, the filler material <NUM> may be positioned in direct contact with the tissue site <NUM> and between the tissue site <NUM> and the dressing <NUM>. If the filler material <NUM> is omitted, the tissue interface <NUM> of the dressing <NUM> may be positioned in direct contact with the tissue site <NUM>.

Continuing with <FIG>, the dressing <NUM> may be adapted to provide or distribute negative pressure from the negative-pressure source <NUM> of the therapy unit <NUM> to the tissue site <NUM> directly or through the filler material <NUM>, if equipped. Further, <FIG> illustrates additional features that may be associated with some example embodiments of the tissue interface <NUM> of the dressing <NUM>. For example, the tissue interface <NUM> of the dressing <NUM> may include an optional base layer <NUM>, a manifold <NUM>, an isolation layer <NUM>, and an absorbent material <NUM>. An adhesive layer such as an adhesive <NUM> may be configured to be positioned between the cover <NUM> and a periphery of the tissue site <NUM> to secure the dressing <NUM> relative to the tissue site <NUM>. Components of the dressing <NUM> may be added or removed to suit a particular application.

Referring to <FIG>, the base layer <NUM> may have a periphery <NUM> surrounding a central portion <NUM>, and a plurality of apertures <NUM> disposed through the periphery <NUM> and the central portion <NUM>. The base layer <NUM> may also have corners <NUM> and edges <NUM>. The corners <NUM> and the edges <NUM> may be part of the periphery <NUM>. One of the edges <NUM> may meet another of the edges <NUM> to define one of the corners <NUM>. Further, the base layer <NUM> may have a border <NUM> substantially surrounding the central portion <NUM> and positioned between the central portion <NUM> and the periphery <NUM>. The border <NUM> may be free of the apertures <NUM>. The base layer <NUM> may cover the tissue site <NUM> and tissue surrounding the tissue site <NUM> such that the central portion <NUM> of the base layer <NUM> is positioned adjacent to or proximate to the tissue site <NUM>, and the periphery <NUM> of the base layer <NUM> is positioned adjacent to or proximate to tissue surrounding the tissue site <NUM>. In this manner, the periphery <NUM> of the base layer <NUM> may surround the tissue site <NUM>. Further, the apertures <NUM> in the base layer <NUM> may be in fluid communication with the tissue site <NUM> and tissue surrounding the tissue site <NUM>.

The apertures <NUM> in the base layer <NUM> may have any shape, such as, for example, circles, squares, stars, ovals, polygons, slits, complex curves, rectilinear shapes, triangles, or other shapes. The apertures <NUM> may be formed by cutting, by application of local RF energy, or other suitable techniques for forming an opening. As shown in <FIG>, each of the apertures <NUM> of the plurality of apertures <NUM> may be substantially circular in shape, having a diameter and an area. The area of each of the apertures <NUM> may refer to an open space or open area defining each of the apertures <NUM>. The diameter of each of the apertures <NUM> may define the area of each of the apertures <NUM>. For example, the area of one of the apertures <NUM> may be defined by multiplying the square of half the diameter of the aperture <NUM> by the value <NUM>. Thus, the following equation may define the area of one of the apertures <NUM>: Area = <NUM>*(diameter/<NUM>)^<NUM>. The area of the apertures <NUM> described in the illustrative embodiments herein may be substantially similar to the area in other embodiments (not shown) for the apertures <NUM> that may have non-circular shapes. The diameter of each of the apertures <NUM> may be substantially the same, or each of the diameters may vary depending, for example, on the position of the aperture <NUM> in the base layer <NUM>. For example, the diameter of the apertures <NUM> in the periphery <NUM> of the base layer <NUM> may be larger than the diameter of the apertures <NUM> in the central portion <NUM> of the base layer <NUM>. Further, the diameter of each of the apertures <NUM> may be between about <NUM> millimeter to about <NUM> millimeters. In some embodiments, the diameter of each of the apertures <NUM> may be between about <NUM> millimeter to about <NUM> millimeters. The apertures <NUM> may have a uniform pattern or may be randomly distributed on the base layer <NUM>. The size and configuration of the apertures <NUM> may be designed to control the adherence of the dressing <NUM> to the epidermis <NUM> as described below.

Referring to <FIG> and <FIG>, in some embodiments, the apertures <NUM> positioned in the periphery <NUM> may be apertures 234a, the apertures <NUM> positioned at the corners <NUM> of the periphery <NUM> may be apertures 234b, and the apertures <NUM> positioned in the central portion <NUM> may be apertures 234c. The apertures 234a may have a diameter between about <NUM> millimeters to about <NUM> millimeters. The apertures 234b may have a diameter between about <NUM> millimeters to about <NUM> millimeters. The apertures 234c may have a diameter between about <NUM> millimeters to about <NUM> millimeters. The diameter of each of the apertures 234a may be separated from one another by a distance A between about <NUM> millimeters to about <NUM> millimeters. Further, the diameter of at least one of the apertures 234a may be separated from the diameter of at least one of the apertures 234b by the distance A. The diameter of each of the apertures 234b may also be separated from one another by the distance A. A center of one of the apertures 234c may be separated from a center of another of the apertures 234c in a first direction by a distance B between about <NUM> millimeters to about <NUM> millimeters. In a second direction transverse to the first direction, the center of one of the apertures 234c may be separated from the center of another of the apertures 234c by a distance C between about <NUM> millimeters to about <NUM> millimeters. As shown in <FIG>, the distance B and the distance C may be increased for the apertures 234c in the central portion <NUM> being positioned proximate to or at the border <NUM> compared to the apertures 234c positioned away from the border <NUM>.

As shown in <FIG>, the central portion <NUM> of the base layer <NUM> may be substantially square with each side of the central portion <NUM> having a length D between about <NUM> millimeters to about <NUM> millimeters. In some embodiments, the length D may be between about <NUM> millimeters to about <NUM> millimeters. The border <NUM> of the base layer <NUM> may have a width E between about <NUM> millimeters to about <NUM> millimeters and may substantially surround the central portion <NUM> and the apertures 234c in the central portion <NUM>. In some embodiments, the width E may be between about <NUM> millimeters to about <NUM> millimeters. The periphery <NUM> of the base layer <NUM> may have a width F between about <NUM> millimeters to about <NUM> millimeters and may substantially surround the border <NUM> and the central portion <NUM>. In some embodiments, the width F may be between about <NUM> millimeters to about <NUM> millimeters. Further, the periphery <NUM> may have a substantially square exterior with each side of the exterior having a length G between about <NUM> millimeters to about <NUM> millimeters. In some embodiments, the length G may be between about <NUM> millimeters to about <NUM> millimeters. Although <FIG> depict the central portion <NUM>, the border <NUM>, and the periphery <NUM> of the base layer <NUM> as having a substantially square shape, these and other components of the base layer <NUM> may have any shape to suit a particular application. Further, the dimensions of the base layer <NUM> as described herein may be increased or decreased, for example, substantially in proportion to one another to suit a particular application. The use of the dimensions in the proportions described above may enhance the cosmetic appearance of a tissue site. For example, these proportions may provide a surface area for the base layer <NUM>, regardless of shape, that is sufficiently smooth to enhance the movement and proliferation of epithelial cells at the tissue site <NUM>, and reduce the likelihood of granulation tissue in-growth into the dressing <NUM>.

The base layer <NUM> may be a soft, pliable material suitable for providing a fluid seal with the tissue site <NUM> as described herein. For example, the base layer <NUM> may comprise a silicone gel, a soft silicone, hydrocolloid, hydrogel, polyurethane gel, polyolefin gel, hydrogenated styrenic copolymer gels, a foamed gel, a soft closed cell foam such as polyurethanes and polyolefins coated with an adhesive described below, polyurethane, polyolefin, or hydrogenated styrenic copolymers. The base layer <NUM> may have a thickness between about <NUM> microns (µm) and about <NUM> microns (µm). In some embodiments, the base layer <NUM> has a stiffness between about <NUM> Shore OO and about <NUM> Shore OO. The base layer <NUM> may be comprised of hydrophobic or hydrophilic materials.

In some embodiments (not shown), the base layer <NUM> may be a hydrophobic-coated material. For example, the base 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. In this manner, the adhesive <NUM> may extend through openings in the spaced material analogous to the apertures <NUM> described below.

The adhesive <NUM> may be in fluid communication with the apertures <NUM> in at least the periphery <NUM> of the base layer <NUM>. In this manner, the adhesive <NUM> may be in fluid communication with the tissue surrounding the tissue site <NUM> through the apertures <NUM> in the base layer <NUM>. As described below and shown in <FIG>, the adhesive <NUM> may extend or be pressed through the plurality of apertures <NUM> to contact the epidermis <NUM> for securing the dressing <NUM> to, for example, the tissue surrounding the tissue site <NUM>. The apertures <NUM> may provide sufficient contact of the adhesive <NUM> to the epidermis <NUM> to secure the dressing <NUM> about the tissue site <NUM>. However, the configuration of the apertures <NUM> and the adhesive <NUM>, described below, may permit release and repositioning of the dressing <NUM> about the tissue site <NUM>.

At least one of the apertures 234a in the periphery <NUM> of the base 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 base layer <NUM>. As shown in <FIG>, a plurality of the apertures 234a 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 234a positioned proximate to or at the edges <NUM> may be spaced substantially equidistant around the periphery <NUM> as shown in <FIG>. However, in some embodiments, the spacing of the apertures 234a proximate to or at the edges <NUM> may be irregular. The adhesive <NUM> may be in fluid communication with the edges <NUM> through the apertures 234a being exposed at the edges <NUM>. In this manner, the apertures 234a at the edges <NUM> may permit the adhesive <NUM> to flow around the edges <NUM> for enhancing the adhesion of the edges <NUM> around the tissue site <NUM>, for example.

Continuing with <FIG>, the apertures 234b at the corners <NUM> of the periphery <NUM> may be smaller than the apertures 234a in other portions of the periphery <NUM> as described above. For a given geometry of the corners <NUM>, the smaller size of the apertures 234b compared to the apertures 234a may maximize the surface area of the adhesive <NUM> exposed and in fluid communication through the apertures 234b 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>. Also as shown, the corners <NUM> may have a radius of about <NUM> millimeters. Three of the apertures 234b 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>. The size and number of the apertures 234b 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> as described above. Further, the apertures 234b at the corners <NUM> may be fully housed within the base layer <NUM>, substantially precluding fluid communication in a lateral direction exterior to the corners <NUM>. The apertures 234b at the corners <NUM> being fully housed within the base 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 the tissue site <NUM>. 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.

Similar to the apertures 234b in the corners <NUM>, any of the apertures <NUM> may be adjusted in size and number to maximize the surface area of the adhesive <NUM> in fluid communication through the apertures <NUM> for a particular application or geometry of the base layer <NUM>. For example, in some embodiments (not shown) the apertures 234b, or apertures of another size, may be positioned in the periphery <NUM> and at the border <NUM>. Similarly, the apertures 234b, or apertures of another size, may be positioned as described above in other locations of the base layer <NUM> that may have a complex geometry or shape.

The adhesive <NUM> may be a medically-acceptable adhesive. The adhesive <NUM> may also be flowable. For example, the adhesive <NUM> may comprise an acrylic adhesive, rubber adhesive, high-tack silicone adhesive, polyurethane, or other adhesive substance. In some embodiments, the adhesive <NUM> may be a pressure-sensitive adhesive comprising an acrylic adhesive with coating weight of <NUM> grams/m<NUM> (gsm) to <NUM> grams/m<NUM> (gsm). The adhesive <NUM> may be a layer having substantially the same shape as the periphery <NUM> of the base layer <NUM> as shown in <FIG>. In some embodiments, the layer of the adhesive <NUM> may be continuous or discontinuous. Discontinuities in the adhesive <NUM> may be provided by apertures (not shown) in the adhesive <NUM>. The apertures 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> adapted to face the epidermis <NUM>. Further, the apertures in the adhesive <NUM> may be sized to control the amount of the adhesive <NUM> extending through the apertures <NUM> in the base layer <NUM> to reach the epidermis <NUM>. The apertures in the adhesive <NUM> may also be sized to enhance the Moisture Vapor Transfer Rate (MVTR) of the dressing <NUM>.

Factors that may be utilized to control the adhesion strength of the dressing <NUM> may include the diameter and number of the apertures <NUM> in the base layer <NUM>, the thickness of the base layer <NUM>, the thickness and amount of the adhesive <NUM>, and the tackiness of the adhesive <NUM>. An increase in the amount of the adhesive <NUM> extending through the apertures <NUM> generally corresponds to an increase in the adhesion strength of the dressing <NUM>. A decrease in the thickness of the base layer <NUM> generally corresponds to an increase in the amount of adhesive <NUM> extending through the apertures <NUM>. Thus, the diameter and configuration of the apertures <NUM>, the thickness of the base layer <NUM>, and the amount and tackiness of the adhesive utilized may be varied to provide a desired adhesion strength for the dressing <NUM>. For example, the thickness of the base layer <NUM> may be about <NUM> microns, the layer of adhesive <NUM> may have a thickness of about <NUM> microns and a tackiness of <NUM> grams per <NUM> centimeter wide strip, and the diameter of the apertures 234a in the base layer <NUM> may be about <NUM> millimeters.

In some embodiments, the tackiness of the adhesive <NUM> may vary in different locations of the base layer <NUM>. For example, in locations of the base layer <NUM> where the apertures <NUM> are comparatively large, such as the apertures 234a, the adhesive <NUM> may have a lower tackiness than other locations of the base layer <NUM> where the apertures <NUM> are smaller, such as the apertures 234b and 234c. In this manner, locations of the base layer <NUM> having larger apertures <NUM> and adhesive <NUM> with lower tackiness may have an adhesion strength comparable to locations having smaller apertures <NUM> and adhesive <NUM> with higher tackiness.

Clinical studies have shown that the configuration described herein for the base layer <NUM> and the adhesive <NUM> may reduce the occurrence of blistering, erythema, and leakage when in use. Such a configuration may provide, for example, increased patient comfort and increased durability of the dressing <NUM>.

Referring to the embodiment of <FIG>, a release liner <NUM> may be attached to or positioned adjacent to the base layer <NUM> to protect the adhesive <NUM> prior to application of the dressing <NUM> to the tissue site <NUM>. Prior to application of the dressing <NUM> to the tissue site <NUM>, the base layer <NUM> may be positioned between the cover <NUM> and the release liner <NUM>. Removal of the release liner <NUM> may expose the base layer <NUM> and the adhesive <NUM> for application of the dressing <NUM> to the tissue site <NUM>. 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, 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 base 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 flourosilicone. In other embodiments, the release liner <NUM> may be uncoated or otherwise used without a release agent.

Continuing with <FIG>, the cover <NUM> may be substantially as described above with reference to <FIG>. The cover <NUM> may have a margin or a periphery <NUM> and a central portion <NUM>. The cover <NUM> may also have a first surface <NUM> and a second surface <NUM> opposite the first surface <NUM>. The cover <NUM> may additionally include an aperture <NUM>. The aperture <NUM> may be an opening or a hole through the cover <NUM>. In some embodiments, the aperture <NUM> may be located substantially centered on the cover <NUM>. The aperture <NUM> may be configured to allow fluid communication from the first surface <NUM> of the cover <NUM> through the dressing <NUM>. The periphery <NUM> of the cover <NUM> may be positioned proximate to the periphery <NUM> of the base layer <NUM> such that the central portion <NUM> of the cover <NUM> and the central portion <NUM> of the base layer <NUM> define an enclosure <NUM>.

The adhesive <NUM> may be positioned at least between the periphery <NUM> of the cover <NUM> and the periphery <NUM> of the base layer <NUM>. The cover <NUM> may cover the tissue site <NUM> and the tissue interface <NUM> to provide a fluid seal and a sealed space <NUM> between the tissue site <NUM> and the cover <NUM> of the dressing <NUM>. Further, the cover <NUM> may cover other tissue, such as a portion of the epidermis <NUM>, surrounding the tissue site <NUM> to provide the fluid seal between the cover <NUM> and the tissue site <NUM>. In some embodiments, a portion of the periphery <NUM> of the cover <NUM> may extend beyond the periphery <NUM> of the base layer <NUM> and into direct contact with tissue surrounding the tissue site <NUM>. In other embodiments, the periphery <NUM> of the cover <NUM>, for example, may be positioned in contact with tissue surrounding the tissue site <NUM> to provide the sealed space <NUM> without the base layer <NUM>. Thus, the adhesive <NUM> may also be positioned at least between the periphery <NUM> of the cover <NUM> and tissue, such as the epidermis <NUM>, surrounding the tissue site <NUM>. The adhesive <NUM> may be disposed on a surface of the cover <NUM> adapted to face the tissue site <NUM> and the base layer <NUM>.

The absorbent material <NUM>, the isolation layer <NUM> and the manifold <NUM> may be disposed within the enclosure <NUM>, the sealed space <NUM>, or both. The isolation layer <NUM> may be positioned between the absorbent material <NUM> and the manifold <NUM>, the absorbent material <NUM> may be encapsulated between the cover <NUM> and the isolation layer <NUM>, and the manifold <NUM> may be positioned between the isolation layer <NUM> and the tissue site <NUM> and the base layer <NUM>, if equipped.

The absorbent material <NUM> may be a super absorbent and may have a first surface <NUM> and a second surface <NUM> opposite the first surface <NUM>. The absorbent material <NUM> may further include an opening <NUM> configured to align with the aperture <NUM> of the cover <NUM>. The first surface <NUM> of the absorbent material <NUM> may be adjacent to the second surface <NUM> of the cover <NUM>. According to the invention, the absorbent material <NUM> is isolated from the manifold <NUM> and the tissue site <NUM> when negative pressure is being applied to the tissue site <NUM>. When negative pressure is not being applied to the tissue site <NUM>, the absorbent material <NUM> is in fluid communication with the manifold <NUM> and the tissue site <NUM> through the isolation layer <NUM>. The absorbent material <NUM> may be configured to absorb fluid from the tissue site <NUM> when the absorbent material <NUM> is in fluid communication with the manifold <NUM> and the tissue site <NUM> through the isolation layer <NUM>. Materials suitable for the absorbent material may include Luquafleece® material, Texsus FP2326, BASF 402C, Technical Absorbents <NUM> available from Technical Absorbents (www. techabsorbents. com), sodium polyacrylate super absorbers, cellulosics (carboxy methyl cellulose and salts such as sodium CMC), or alginates.

The isolation layer <NUM> may be disposed between the absorbent material <NUM> and the manifold <NUM>. The isolation layer <NUM> may have a first surface <NUM> and a second surface <NUM> opposite the first surface <NUM>. The first surface <NUM> of the isolation layer <NUM> may be adjacent to the second surface <NUM> of the absorbent material <NUM>. The isolation layer <NUM> may further include an opening <NUM>. The opening <NUM> may be aligned with the opening <NUM> of the absorbent material <NUM> but may be smaller than the opening <NUM> of the absorbent material <NUM>. The isolation layer <NUM> may be configured to restrict fluid flow from the tissue site <NUM> to the absorbent material <NUM> when negative pressure is applied to the dressing <NUM>.

Continuing with <FIG>, <FIG>, <FIG>, and <FIG>, the isolation layer <NUM> may include a first layer <NUM> and a second layer <NUM>. The first layer <NUM> may include a plurality of valve flaps <NUM> and the second layer may include a plurality of holes <NUM>. The plurality of holes <NUM> of the second layer <NUM> may be aligned with the plurality of valve flaps <NUM> of the first layer <NUM>. Referring to <FIG>, the plurality of valve flaps <NUM> may be configured to be closed when negative pressure is applied to the dressing <NUM>. When closed, the plurality of valve flaps <NUM> may fluidly seal the plurality of holes <NUM> of the second layer <NUM>. Referring to <FIG>, the plurality of valve flaps <NUM> may be configured to move away from the plurality of holes <NUM> when negative pressure is not being applied to the dressing <NUM> to provide a passage <NUM> through the isolation layer <NUM>. The plurality of valve flaps <NUM> may be configured to permit fluid flow in a first direction from the second surface <NUM> of the isolation layer <NUM> towards the first surface <NUM> of the isolation layer <NUM> when negative pressure is not being applied to the dressing <NUM>. The plurality of valve flaps <NUM> may prevent fluid flow in a second direction from the first surface <NUM> of the isolation layer <NUM> towards the second surface <NUM> of the isolation layer <NUM>. When negative pressure is being applied to the dressing <NUM>, the plurality of valve flaps <NUM> may prevent fluid flow in all directions, for example, both the first direction and the second direction. In other embodiments, the isolation layer <NUM> may be only one layer that may include the plurality of valve flaps <NUM> that are configured to close when negative pressure is applied to the dressing <NUM> and are configured to open when negative pressure is not being applied to the dressing to provide a passage through the isolation layer <NUM>.

The first layer <NUM> of the isolation layer <NUM> may have a first surface that may be the first surface <NUM> of the isolation layer <NUM>. The first layer <NUM> of the isolation layer <NUM> may have a second surface <NUM> opposite the first surface <NUM>. The plurality of valve flaps <NUM> may be configured to open from the second surface <NUM> of the first layer <NUM> towards the first surface <NUM> of the isolation layer <NUM>. The first layer <NUM> of the isolation layer <NUM> may be thick enough to enable the plurality of valve flaps <NUM> to open and expose the plurality of holes <NUM> of the second layer <NUM> without any portion of the plurality of valve flaps <NUM> coming into contact with the absorbent material <NUM>.

The plurality of valve flaps <NUM> of the isolation layer <NUM> may be check valves in some embodiments. Exemplary check valves may include ball check valves, diaphragm check valves, flap-style check valves, swing check valves, stop-check valves, duckbill valves, pneumatic non-return valves, or other one-way valves configured to automatically permit fluid flow in a single direction and to prevent fluid flow in any other direction.

In some embodiments, there may be at least one spacer or projection positioned between the isolation layer <NUM> and the absorbent material <NUM>. The at least one spacer or projection may be positioned around or adjacent to one or more of the valve flaps <NUM> and configured in any suitable manner to provide a pathway or additional space between the isolation layer <NUM> and the absorbent material <NUM>. The pathway may ensure that the plurality of valve flaps <NUM> have enough space to open to expose the plurality of holes <NUM> of the second layer <NUM> of the isolation layer <NUM> when the negative-pressure source <NUM> is stopped.

Both the first layer <NUM> and the second layer <NUM> of the isolation layer <NUM> may be comprised of a liquid impermeable film. In some embodiments, the first layer <NUM> and the second layer <NUM> of the isolation layer <NUM> may comprise 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 Expopack 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 Pasadena, California; polyether block polyamide copolymer (PEBAX), for example, from Arkema, France; Expopack <NUM>; or other appropriate material.

In some embodiments, the first layer <NUM> and the second layer <NUM> of the isolation layer <NUM> may be a flexible, breathable film, membrane, or sheet having a high MVTR of, for example, at least about <NUM>/m<NUM> per <NUM> hours. In other embodiments, a low or no vapor transfer drape might be used. The first layer <NUM> and the second layer <NUM> of the isolation layer <NUM> may comprise a range of medically suitable films having a thickness between about <NUM> microns (µm) to about <NUM> microns (µm). In other embodiments, the first layer <NUM> and the second layer <NUM> of the isolation layer <NUM> may be a non-breathable film, membrane, or sheet that may be substantially vapor and liquid impermeable.

Continuing with <FIG>, <FIG>, and <FIG>, the manifold <NUM> may have a first surface <NUM> and a second surface <NUM> opposite the first surface <NUM>. The manifold <NUM> may comprise or consist essentially of a means for distributing fluid relative to the tissue site <NUM>. For example, the manifold <NUM> may be adapted to receive negative pressure from the negative-pressure source <NUM> and distribute negative pressure through multiple apertures across or through the manifold <NUM>, which may have the effect of collecting fluid from the tissue site <NUM> and drawing the fluid toward the negative-pressure source <NUM>.

In some illustrative embodiments, the manifold <NUM> may comprise a plurality of pathways, which can be interconnected to improve distribution or collection of fluids. In some illustrative embodiments, the manifold <NUM> may comprise or consist essentially of a porous material having interconnected fluid pathways. Examples of suitable porous material that can be adapted to form interconnected fluid pathways (e.g., channels) may include cellular foam, including open-cell foam such as reticulated foam; porous tissue collections; and other porous material such as gauze or felted mat that generally include pores, edges, and/or walls. Liquids, gels, and other foams may also include or be cured to include apertures and fluid pathways. In some embodiments, the manifold <NUM> may additionally or alternatively comprise projections that form interconnected fluid pathways. For example, the manifold <NUM> may be molded to provide surface projections that define interconnected fluid pathways.

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

The thickness of the manifold <NUM> may also vary according to needs of a prescribed therapy. For example, the thickness of the manifold <NUM> may be decreased to reduce tension on peripheral tissue of the tissue site <NUM>. The thickness of the manifold <NUM> can also affect the conformability of the manifold <NUM>. In some embodiments, a thickness in a range of about <NUM> millimeters to <NUM> millimeters may be suitable.

In some exemplary embodiments, the manifold <NUM> may be hydrophilic. In an example in which the manifold <NUM> may be hydrophilic, the manifold <NUM> may also wick fluid away from a tissue site, while continuing to distribute negative pressure to the tissue site <NUM>. The wicking properties of the manifold <NUM> may draw fluid away from the tissue site <NUM> by capillary flow or other wicking mechanisms. An example of a hydrophilic material that may be suitable is a polyvinyl alcohol, open-cell foam such as V. WHITEFOAM™ dressing available from Kinetic Concepts, Inc. 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.

Continuing with <FIG>, with reference to <FIG>, a conduit interface <NUM> may be configured to fluidly couple the dressing <NUM> to the container <NUM> and the therapy unit <NUM>. The conduit interface <NUM> may include a fluid connection <NUM> and a negative pressure port <NUM>. The negative pressure port <NUM> may be disposed through the fluid connection <NUM> and the fluid connection <NUM> may fluidly isolate the negative pressure port <NUM> from the absorbent material <NUM>. The fluid connection <NUM> may extend into or be received by a negative pressure passage <NUM> defined by an alignment of the aperture <NUM> of the cover <NUM>, the opening <NUM> of the absorbent material <NUM>, and the opening <NUM> in the isolation layer <NUM>. The fluid connection <NUM> may have a first surface <NUM> that may be configured to couple to the first surface <NUM> of the isolation layer <NUM>. The fluid connection <NUM> may have a second surface <NUM> opposite the first surface <NUM>. In other embodiments, the fluid connection <NUM> may extend through the cover <NUM>, the absorbent material <NUM>, and the isolation layer <NUM> to couple to the first surface <NUM> of the manifold <NUM>.

The negative pressure port <NUM> may extend through the fluid connection <NUM> from the second surface <NUM> to the first surface <NUM>. The negative pressure port <NUM> may have an end <NUM> that may be configured to deliver negative pressure from the negative-pressure source <NUM> to the manifold <NUM>. The end <NUM> of the negative pressure port <NUM> may be proximate to the opening <NUM> of the isolation layer <NUM> and below or between the second surface <NUM> of the absorbent material <NUM> and the manifold <NUM> to deliver negative pressure through the opening <NUM> to the manifold <NUM>. In some examples, the end <NUM> of the negative pressure port <NUM> may be fluidly sealed about the opening <NUM> of the isolation layer <NUM>. In other examples, the negative pressure port <NUM> may bypass or extend through the absorbent material <NUM> such that the end <NUM> is positioned at or between the second surface <NUM> of the absorbent material <NUM> and the manifold <NUM>. The negative pressure port <NUM> may couple to a conduit <NUM> that may couple to the container <NUM> and the negative-pressure source <NUM> of the therapy unit <NUM>.

<FIG> depicts the therapy system <NUM> of <FIG> in an operational state with the negative-pressure source <NUM> of the therapy unit <NUM> delivering negative pressure to the tissue site <NUM>. In operation, the negative-pressure source <NUM> may draw fluid or exudate <NUM> from the tissue site <NUM> and the exudate <NUM> may flow through the optional filler material <NUM>, the optional base layer <NUM>, and the manifold <NUM> to reach the negative pressure passage <NUM>. The exudate <NUM> may then flow through the negative pressure passage <NUM> to the negative pressure port <NUM> and through the conduit <NUM> to the container <NUM>. The container <NUM> may have filters or other mechanisms to retain the exudate <NUM> within the container <NUM> and prevent aspiration of the exudate <NUM> into the therapy unit <NUM>.

The plurality of valve flaps <NUM> of the first layer <NUM> of the isolation layer <NUM> may be closed when the negative-pressure source <NUM> is actuated. The plurality of valve flaps <NUM> may fluidly seal the plurality of holes <NUM> of the second layer <NUM> of the isolation layer <NUM>. While the negative-pressure source <NUM> is actuated, the negative pressure passage <NUM> may be in direct fluid communication with the manifold <NUM> and fluidly isolated from the absorbent material <NUM> such that the exudate <NUM> may not reach the absorbent material <NUM>.

<FIG> depicts the therapy system <NUM> of <FIG> and <FIG> after the negative-pressure source <NUM> has stopped delivering negative pressure to the tissue site <NUM>. Once the negative-pressure source <NUM> has stopped delivering negative pressure to the tissue site <NUM>, the plurality of valve flaps <NUM> of the first layer <NUM> of the isolation layer <NUM> may open. When open, the plurality of valve flaps <NUM> may expose the plurality of holes <NUM> of the second layer <NUM> of the isolation layer <NUM>. The exudate <NUM> may flow from the tissue site <NUM> and the manifold <NUM> through the plurality of holes <NUM> and the plurality of valve flaps <NUM> of the isolation layer <NUM> and may be absorbed by the absorbent material <NUM>. If the negative-pressure source <NUM> were actuated, the plurality of valve flaps <NUM> would close and the exudate <NUM> would no longer be able to reach the absorbent material <NUM>. The exudate <NUM> would then flow through the negative pressure passage <NUM> to the container <NUM> of the therapy system <NUM>.

<FIG> depict another embodiment of an isolation layer <NUM> that can be used with the therapy system <NUM>. The isolation layer <NUM> may include a first layer <NUM> and a second layer <NUM>. There may be an opening <NUM> that extends through both the first layer <NUM> and the second layer <NUM>. The first layer <NUM> may include a plurality of holes <NUM> and the second layer may include a plurality of holes <NUM>. The first layer <NUM> may be corrugated or textured in a resting state as shown in <FIG> and <FIG>. When in a resting state, the plurality of holes <NUM> of the first layer <NUM> and the plurality of holes <NUM> of the second layer <NUM> may allow fluid flow through the isolation layer <NUM>.

Referring to <FIG> and <FIG>, when negative pressure is applied to the dressing <NUM>, the first layer <NUM> may flatten such that a second surface <NUM> of the first layer <NUM> is pressed against a first surface <NUM> of the second layer <NUM>. When the first layer <NUM> is flat, the plurality of holes <NUM> of the first layer <NUM> may be misaligned with the plurality of holes <NUM> of the second layer <NUM> such that the plurality of holes <NUM> of the second layer are fluidly sealed by the first layer <NUM> and the plurality of holes <NUM> of the first layer <NUM> are fluidly sealed by the second layer <NUM>. Thus, when the negative-pressure source <NUM> is actuated, the absorbent material <NUM> may be fluidly isolated from the manifold <NUM> and the tissue site <NUM>. When the negative-pressure source <NUM> is stopped, the first layer <NUM> may move back to its resting state and fluid may flow through the plurality of holes <NUM> of the first layer <NUM> and the plurality of holes <NUM> of the second layer <NUM> to reach the absorbent material <NUM>.

As described above, some embodiments of the dressing <NUM> may include the at least one spacer or projection to provide a pathway or space between the isolation layer <NUM> and the absorbent material <NUM>. The pathway or space may allow the first layer <NUM> of the isolation layer <NUM> to move between its resting state and its flattened state when the negative-pressure source <NUM> is applying negative pressure to the dressing <NUM>.

<FIG> depict another embodiment of an isolation layer <NUM> that can be used with the therapy system <NUM>. The isolation layer <NUM> may include an opening <NUM>, a valve flap <NUM>, and a plurality of holes <NUM> surrounding the valve flap <NUM>. The opening <NUM> may be coupled to the negative pressure passage <NUM> as previously described, and the valve flap <NUM> may be configured to open and expose the opening <NUM> when the negative-pressure source <NUM> is actuated. When the negative-pressure source <NUM> is stopped, the valve flap <NUM> may close to stop fluid communication between the dressing <NUM> and the negative pressure passage.

The plurality of holes <NUM> may enable fluid communication between the absorbent material <NUM> and the manifold <NUM>. However, when the negative-pressure source <NUM> is actuated, the exudate <NUM> may flow preferentially from the tissue site <NUM> through the manifold <NUM>, the opening <NUM>, and through the negative pressure passage <NUM> to the container <NUM>. Some of the exudate <NUM> may flow through the plurality of holes <NUM> and be absorbed by the absorbent material <NUM> but most of the exudate <NUM> will be pulled into the container <NUM> by the negative-pressure source <NUM>. When the negative-pressure source <NUM> is stopped, the valve flap <NUM> may close the opening <NUM> and the exudate <NUM> may flow through the plurality of holes <NUM> of the isolation layer <NUM> and be absorbed by the absorbent material <NUM>.

In some embodiments, the plurality of holes <NUM> may each have a corresponding valve flap to restrict fluid flow through the isolation layer <NUM> when the negative-pressure source <NUM> is actuated. In any of the above described embodiments, the valve flap <NUM> may be any kind of check valve that permits fluid flow in a first direction from the tissue site towards the cover <NUM> of the dressing <NUM> and restricts fluid flow in a second direction from the absorbent material <NUM> towards the tissue site <NUM>.

Also described herein is a method of treating a tissue site. The method may include applying the dressing <NUM> to the tissue site <NUM>, fluidly coupling the negative-pressure source <NUM> to a treatment space, for example, the sealed space <NUM> shown in <FIG>, between the isolation layer <NUM> and the tissue site <NUM> such that the absorbent material <NUM> is bypassed, and actuating the negative-pressure source <NUM> to apply negative pressure to the treatment space. The isolation layer <NUM> may have one or more valves, such as the plurality of valve flaps <NUM>, which may be moved from an open state without negative pressure to a closed state by operation of the negative pressure being applied.

The method may further include stopping the negative-pressure source <NUM> and collecting fluids from the tissue site <NUM> with the absorbent material <NUM>. The fluids may be configured to flow through the isolation layer <NUM> to the absorbent material <NUM> when the negative-pressure source <NUM> is stopped and the one or more valves return to the open state.

Claim 1:
A dressing for treating a tissue site with negative pressure, the dressing comprising:
a cover (<NUM>) comprising a first surface and a second surface opposite the first surface;
an absorbent material (<NUM>) comprising a first surface and a second surface opposite the first surface, the first surface of the absorbent material (<NUM>) adjacent to the second surface of the cover (<NUM>);
an isolation layer (<NUM>, <NUM>) configured to restrict fluid flow from the tissue site to the absorbent material (<NUM>) when a negative pressure is applied to the dressing, the isolation layer (<NUM>, <NUM>) comprising a first surface and a second surface opposite the first surface, the first surface of the isolation layer (<NUM>, <NUM>) adjacent to the second surface of the absorbent material (<NUM>); and
a manifold (<NUM>) comprising a first surface and a second surface opposite the first surface, the first surface of the manifold (<NUM>) adjacent to the second surface of the isolation layer (<NUM>, <NUM>);
wherein each of the cover (<NUM>), the absorbent material (<NUM>), and the isolation layer (<NUM>, <NUM>) further comprise a negative pressure passage aligned (<NUM>) with each other and configured to enable fluid communication between the manifold (<NUM>) and a negative-pressure source (<NUM>); and
wherein the negative pressure passage (<NUM>) is in direct fluid communication with the manifold (<NUM>) and fluidly isolated from the absorbent material (<NUM>).