Patent Description:
There is also widespread acceptance that cleansing a tissue site can be highly beneficial for new tissue growth. For example, a wound or a cavity can be washed out with 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. <CIT> concerns systems, apparatus and methods for negative-pressure treatment with reduced tissue in-growth. <CIT> concerns a peel and place dressing for negative-pressure therapy.

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.

The invention provides a dressing for treating a tissue site with negative pressure, as set forth in the appended claims. Illustrative embodiments are also provided to enable a person skilled in the art to make and use the claimed subject matter.

The dressing is a composite of dressing layers, including a perforated polymer film, a manifold, and an adhesive drape. The polymer film may be a polyethylene, polyurethane, or ethyl methyl acrylate (EMA) in some embodiments. The manifold may comprise or consist essentially of open-cell foam in some examples. The thickness of the manifold may vary for different types of tissue or fluid. For example, a foam manifold layer may be relatively thin and hydrophobic to reduce the fluid hold capacity of the dressing. The foam may also be thin to reduce the dressing profile and increase flexibility, which can enable it to conform to wound beds and other tissue sites under negative pressure. In other examples, a greater thickness may be advantageous for more viscous fluid or larger areas. The manifold may be adhered to the polymer film in some embodiments. Suitable bonds between the manifold and the polymer film may include pressure-sensitive adhesive (reactive and non-reactive types); hot melt adhesive (spray applied or deployed as a film, woven, or non-woven); hot press lamination; or flame lamination. The polymer film may also be co-extruded with a bonding layer in-situ, which may be formed from a hot melt adhesive, for example. The dressing may have an exposed perimeter, and the dressing may be cut to a desired size before applying the dressing to a tissue. Drape strips or other adhesive strips may be used to seal edges of the dressing and fix the dressing to a patient's skin.

Some dressings may also include a layer of low-tack adhesive, silicone, or other soft polymer layer having perforations. The perforation pattern of the polymer film can be aligned with the perforation pattern of at least a central area of the silicone. In some embodiments, the silicone may additionally include a pattern-coated acrylic, which can further facilitate fixation. For example, an acrylic adhesive can be applied about a peripheral area of the structure to increase bond strength in regions which are likely to be skin rather than a wound area.

In some embodiments, the second layer may have a perimeter that is exposed between the first layer and the cover, which can allow the dressing to be customized for size and shape. The manifold may be configured to maintain at least <NUM>% of an applied negative pressure through the length.

In more particular examples, the perforations of the polymer film may comprise a plurality of slots or slits. The perforations may be elastic and configured to respond to a pressure gradient across the perforations. Some embodiments may further comprise a dressing interface configured to be fluidly coupled to the manifold through the cover. The dressing interface may be disposed at least <NUM> centimeters from an edge of the manifold.

The cover may comprise a non-porous film, and the second layer (manifold) may be adhered to the non-porous film. The first layer (fluid-control layer) may be adhered to the manifold opposite the non-porous film, so that the cover, the manifold, and the fluid-control layer are arranged in a stack with the manifold between the cover and the fluid-control layer. The manifold may have a perimeter that is exposed between the cover and the fluid-control layer. The manifold can be configured to maintain at least <NUM>% of a negative pressure through a distance of at least <NUM> centimeters. In some examples, the dressing may further comprise a fluid port coupled to the cover and fluidly coupled to the manifold through the cover. An attachment device may be configured to seal the perimeter.

A method for treating a tissue site with negative pressure is also described herein, wherein some example embodiments include applying a dressing to the tissue site, wherein the dressing comprises a manifold. A fluid conductor may be fluidly coupled to the manifold and to a negative-pressure source. Negative pressure from the negative-pressure source may be applied to the manifold through the fluid conductor, and at least <NUM>% of the negative pressure in the manifold can be maintained for a distance of at least <NUM> centimeters from the fluid conductor. In some examples, the manifold may have a thickness in a range of about <NUM> millimeters to about <NUM> millimeters. A thickness of about <NUM> millimeters may be particularly advantageous for some applications.

Other objectives, advantages, and a preferred mode of making and using the claimed subject matter may be understood best by reference to the accompanying drawings in conjunction with the following detailed description of illustrative embodiments.

<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 a body that is exposed to the external environment, such as 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>, 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.

The therapy system <NUM> may also include a source of instillation solution. For example, a solution source <NUM> may be fluidly coupled to the dressing <NUM>, as illustrated in the example embodiment of <FIG>. The solution source <NUM> may be fluidly coupled to a positive-pressure source, such as a positive-pressure source <NUM>, a negative-pressure source such as the negative-pressure source <NUM>, or both in some embodiments. A regulator, such as an instillation regulator <NUM>, may also be fluidly coupled to the solution source <NUM> and the dressing <NUM> to ensure proper dosage of instillation solution (e.g. saline) 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 controller <NUM>, the solution source <NUM>, and other components into a therapy unit.

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).

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, such as fluid from a source of instillation solution, across 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 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 polyamide copolymers. Such materials are commercially available as, for example, Tegaderm® drape, commercially available from <NUM> Company, Minneapolis Minnesota; polyurethane (PU) drape; polyether block polyamide copolymer (PEBAX), for example; and INSPIRE <NUM> and INSPIRE <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 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, exudate and other fluid 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.

Negative pressure applied across 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>.

In some embodiments, the controller <NUM> may have a continuous pressure mode, in which the negative-pressure source <NUM> is operated to provide a constant target negative pressure for the duration of treatment or until manually deactivated. Additionally or alternatively, the controller may have an intermittent pressure mode. For example, the controller <NUM> can operate the negative-pressure source <NUM> to cycle between a target pressure and atmospheric pressure. For example, the target pressure may be set at a value of <NUM> mmHg for a specified period of time (e.g., <NUM>), followed by a specified period of time (e.g., <NUM>) of deactivation. The cycle can be repeated by activating the negative-pressure source <NUM>, which can form a square wave pattern between the target pressure and atmospheric pressure.

In some example embodiments, the increase in negative-pressure from ambient pressure to the target pressure may not be instantaneous. For example, the negative-pressure source <NUM> and the dressing <NUM> may have an initial rise time. The initial rise time may vary depending on the type of dressing and therapy equipment being used. For example, some therapy systems may increase negative pressure at a rate of about <NUM>-<NUM> mmHg/second, and other therapy systems may increase negative pressure at a rate of about <NUM>-<NUM> mmHg/second. If the therapy system <NUM> is operating in an intermittent mode, the repeating rise time may be a value substantially equal to the initial rise time.

In some example dynamic pressure control modes, the target pressure can vary with time. For example, the target pressure may vary in the form of a triangular waveform, varying between a negative pressure of <NUM> and <NUM> mmHg with a rise rate of negative pressure set at a rate of <NUM> mmHg/min. and a descent rate set at <NUM> mmHg/min. In other embodiments of the therapy system <NUM>, the triangular waveform may vary between negative pressure of <NUM> and <NUM> mmHg with a rise rate of about <NUM> mmHg/min and a descent rate set at about <NUM> mmHg/min.

In some embodiments, the controller <NUM> may control or determine a variable target pressure in a dynamic pressure mode, and the variable target pressure may vary between a maximum and minimum pressure value that may be set as an input prescribed by an operator as the range of desired negative pressure. The variable target pressure may also be processed and controlled by the controller <NUM>, which can vary the target pressure according to a predetermined waveform, such as a triangular waveform, a sine waveform, or a saw-tooth waveform. In some embodiments, the waveform may be set by an operator as the predetermined or time-varying negative pressure desired for therapy.

In some embodiments, the controller <NUM> may receive and process data, such as data related to instillation solution provided to the tissue interface <NUM>. Such data may include the type of instillation solution prescribed by a clinician, the volume of fluid or solution to be instilled to a tissue site ("fill volume"), and the amount of time prescribed for leaving solution at a tissue site ("dwell time") before applying a negative pressure to the tissue site. The fill volume may be, for example, between <NUM> and <NUM>, and the dwell time may be between one second to <NUM> minutes. The controller <NUM> may also control the operation of one or more components of the therapy system <NUM> to instill solution. For example, the controller <NUM> may manage fluid distributed from the solution source <NUM> to the tissue interface <NUM>. In some embodiments, fluid may be instilled to a tissue site by applying a negative pressure from the negative-pressure source <NUM> to reduce the pressure at the tissue site, drawing solution into the tissue interface <NUM>. In some embodiments, solution may be instilled to a tissue site by applying a positive pressure from the positive-pressure source <NUM> to move solution from the solution source <NUM> to the tissue interface <NUM>. Additionally or alternatively, the solution source <NUM> may be elevated to a height sufficient to allow gravity to move solution into the tissue interface <NUM>.

The controller <NUM> may also control the fluid dynamics of instillation by providing a continuous flow of solution or an intermittent flow of solution. Negative pressure may be applied to provide either continuous flow or intermittent flow of solution. The application of negative pressure may be implemented to provide a continuous pressure mode of operation to achieve a continuous flow rate of instillation solution through the tissue interface <NUM>, or it may be implemented to provide a dynamic pressure mode of operation to vary the flow rate of instillation solution through the tissue interface <NUM>. Alternatively, the application of negative pressure may be implemented to provide an intermittent mode of operation to allow instillation solution to dwell at the tissue interface <NUM>. In an intermittent mode, a specific fill volume and dwell time may be provided depending, for example, on the type of tissue site being treated and the type of dressing being utilized. After or during instillation of solution, negative-pressure treatment may be applied. The controller <NUM> may be utilized to select a mode of operation and the duration of the negative pressure treatment before commencing another instillation cycle.

<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 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 heat-bonded or adhered to the second layer <NUM> in some embodiments. In some embodiments, the first layer <NUM> optionally includes a low-tack adhesive, which can be configured to hold the tissue interface <NUM> in place while the cover <NUM> is applied. The low-tack adhesive may be continuously coated on the first layer <NUM> or applied in a pattern.

The first layer <NUM> may comprise or consist essentially of a means for controlling or managing fluid flow. In some embodiments, the first layer <NUM> may be a fluid control layer comprising or consisting essentially of a liquid-impermeable, elastomeric material. For example, the first layer <NUM> may comprise or consist essentially of a polymer film, such as a polyurethane film. In some embodiments, the first layer <NUM> may comprise or consist essentially of the same material as the cover <NUM>. The first layer <NUM> may also have a smooth or matte surface texture in some embodiments. A glossy or shiny finish finer 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 first layer <NUM> may have a substantially flat surface, with height variations limited to <NUM> millimeters over a centimeter.

In some embodiments, the first layer <NUM> may be hydrophobic. The hydrophobicity of the first layer <NUM> may vary, but may have a contact angle with water of at least ninety degrees in some embodiments. In some embodiments the first 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 first 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. Nonlimiting 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 herein represent averages of <NUM>-<NUM> measured values, discarding both the highest and lowest measured values. The hydrophobicity of the first 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 first layer <NUM> may also be suitable for welding to other layers, including the second layer <NUM>. For example, the first 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 first 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 first 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.

The first layer <NUM> may have one or more passages, which can be distributed uniformly or randomly across the first layer <NUM>. The passages may be bi-directional and pressure-responsive. For example, each of the passages 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. As illustrated in the example of <FIG>, the passages may comprise or consist essentially of perforations <NUM> in the first layer <NUM>. Perforations <NUM> may be formed by removing material from the first layer <NUM>. For example, perforations <NUM> may be formed by cutting through the first layer <NUM>. In the absence of a pressure gradient across the perforations <NUM>, the perforations <NUM> may be sufficiently small to form a seal or fluid restriction, which can substantially reduce or prevent liquid flow. Additionally, or alternatively, one or more of the passages may be or may function as an elastomeric valve that is normally closed when unstrained to substantially prevent liquid flow, and can open in response to a pressure gradient. In some examples, the passages may comprise or consist essentially of fenestrations in the first layer <NUM>. Generally, fenestrations are a species of perforation, and may also be formed by removing material from the first layer <NUM>. The amount of material removed and the resulting dimensions of the fenestrations may be up to an order of magnitude less than perforations.

In some embodiments, the perforations <NUM> may be formed as slots (or fenestrations formed as slits) in the first layer <NUM>. In some examples, the perforations <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 elastomeric valves that can 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.

The second layer <NUM> generally comprises or consists essentially of a manifold or a manifold layer, which can provide a means for collecting or distributing fluid across the tissue interface <NUM> under pressure. For example, the second 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 second layer <NUM> may be interconnected to improve distribution or collection of fluids. In some illustrative embodiments, the second layer <NUM> may comprise or consist essentially of a porous material having interconnected fluid pathways. Examples of suitable porous material that comprise or 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 second layer <NUM> may additionally or alternatively comprise projections that form interconnected fluid pathways. For example, the second layer <NUM> may be molded to provide surface projections that define interconnected fluid pathways.

In some embodiments, the second 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 second 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 second 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 second layer <NUM> may be at least <NUM> pounds per square inch. The second layer <NUM> may have a tear strength of at least <NUM> pounds per inch. In some embodiments, the second 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 some examples, the second 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.

Other suitable materials for the second layer <NUM> may include non-woven fabrics; three-dimensional (3D) polymeric structures, such as molded polymers, embossed and formed films, and fusion-bonded films, and mesh, for example.

In some examples, the second layer <NUM> may include a 3D textile. A 3D textile of polyester fibers may be particularly advantageous for some embodiments. For example, the second layer <NUM> may comprise or consist essentially of a three-dimensional weave of polyester fibers. In some embodiments, the fibers may be elastic in at least two dimensions. A puncture-resistant fabric of polyester and cotton fibers having a weight of about <NUM> grams per square meter and a thickness of about <NUM>-<NUM> millimeters may be particularly advantageous for some embodiments. Such a puncture-resistant fabric may have a warp tensile strength of about <NUM>-<NUM> kilograms and a weft tensile strength of about <NUM>-<NUM> kilograms in some embodiments. Another particularly suitable material may be a polyester spacer fabric having a weight of about <NUM> grams per square meter, which may have a thickness of about <NUM>-<NUM> millimeters in some embodiments. Such a spacer fabric may have a compression strength of about <NUM>-<NUM> kilopascals (at <NUM>% compression). Additionally or alternatively, the second layer <NUM> may comprise or consist of a material having substantial linear stretch properties, such as a polyester spacer fabric having <NUM>-way stretch and a weight of about <NUM> grams per square meter. A suitable spacer fabric may have a thickness of about <NUM>-<NUM> millimeters, and may have a warp and weft tensile strength of about <NUM>-<NUM> kilograms in some embodiments. The fabric may have a close-woven layer of polyester on one or more opposing faces in some examples.

<FIG> is a schematic view of another example of the first layer <NUM>, illustrating additional details that may be associated with some embodiments. As illustrated in the example of <FIG>, the perforations <NUM> may each consist essentially of one or more linear slots having a length L. A length L of about <NUM> millimeters may be suitable for some examples. <FIG> additionally illustrates an example of a uniform distribution pattern of the perforations <NUM>. In <FIG>, the perforations <NUM> are substantially coextensive with the first layer <NUM>, and are distributed across the first layer <NUM> in a grid of parallel rows and columns, in which the slots are also mutually parallel to each other. The rows may be spaced a distance D1, and the perforations <NUM> within each of the rows may be spaced a distance D2. For example, a distance D1 of about <NUM> millimeters on center and a distance D2 of about <NUM> millimeters on center may be suitable for some embodiments. The perforations <NUM> in adjacent rows may be aligned or offset. For example, adjacent rows may be offset, as illustrated in <FIG>, so that the perforations <NUM> are aligned in alternating rows separated by a distance D3. A distance D3 of about <NUM> millimeters may be suitable for some examples. The spacing of the perforations <NUM> may vary in some embodiments to increase the density of the perforations <NUM> according to therapeutic requirements.

<FIG> is a side view of an example of the dressing <NUM> of <FIG> that may be associated with some embodiments of the therapy system of <FIG>. As shown in <FIG>, the tissue interface <NUM> has an exposed perimeter <NUM>. More particularly, in the example of <FIG>, the cover <NUM>, the first layer <NUM>, and the second layer <NUM> each have an exposed perimeter, and there is no seam, weld, or seal along the exposed perimeter <NUM>.

The second layer <NUM> generally has a first planar surface and a second planar surface opposite the first planar surface. The thickness T of the second 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 T of the second layer <NUM> may be decreased to relieve stress on other layers and to reduce tension on peripheral tissue. The thickness of the second layer <NUM> can also affect the conformability and manifolding performance of the second layer <NUM>. In some embodiments, a suitable foam may have a thickness T in a range of about <NUM> millimeters to <NUM> millimeters. In other examples, a suitable foam having a thickness T in a range of about <NUM> millimeters to about <NUM> millimeters may be suitable, and a thickness T of at least <NUM> millimeters may be advantageous. Fabrics, including suitable 3D textiles and spacer fabrics, may have a thickness T in a range of about <NUM> millimeters to about <NUM> millimeters. The second layer <NUM> also has a length L, which can vary according needs of a particular tissue site or prescribed therapy. A length L in a range of about <NUM> millimeters to about <NUM> millimeters may be suitable for some applications.

<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 first layer <NUM> opposite the second layer <NUM>. The third layer <NUM> may also be bonded to the first layer <NUM> in some embodiments.

The third layer <NUM> may comprise or consist essentially of a sealing layer formed from a soft, pliable material, such as a tacky gel, 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. The third layer <NUM> may include an adhesive surface on an underside and a patterned coating of acrylic on a top side. The patterned coating of acrylic may be applied about a peripheral area to allow higher bonding in regions that are likely to be in contact with skin rather than the wound area. In other embodiments, the third layer <NUM> may comprise a low-tack adhesive layer instead of silicone. 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 porous 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 corners <NUM> and edges <NUM>. The third layer <NUM> may include apertures <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 and about <NUM> millimeters. In other embodiments, the diameter of each of the apertures <NUM> may be between about <NUM> millimeter and 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>. The apertures <NUM> may be spaced substantially equidistant over the third layer <NUM>. Alternatively, the spacing of the apertures <NUM> may be irregular.

As illustrated in the example of <FIG>, some embodiments of the dressing <NUM> may include a release liner <NUM> to protect the third layer <NUM> prior to use. The release liner <NUM> may also provide stiffness to facilitate handling and applying 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 third 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> 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 an interior portion of the third layer <NUM>. In the example of <FIG>, the apertures <NUM> are generally circular and have a width W, which may be about <NUM> millimeters in some examples. <FIG> also illustrates an example of a uniform distribution pattern of the apertures <NUM>. In <FIG>, the apertures <NUM> are distributed across the third layer <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>. The rows may be spaced a distance D4, and the apertures <NUM> within each of the rows may be spaced a distance D5. For example, a distance D4 of about <NUM> millimeters on center and a distance D5 of about <NUM> millimeters on center may be suitable for some embodiments. The apertures <NUM> in adjacent rows may be aligned or offset. For example, adjacent rows may be offset, as illustrated in <FIG>, so that the apertures are aligned in alternating rows separated by a distance D6. A distance D6 of about <NUM> millimeters may be suitable for some examples. The spacing of the apertures <NUM> may vary in some embodiments to increase the density of the apertures <NUM> according to therapeutic requirements.

<FIG> is a schematic view of the third layer <NUM> of <FIG> overlaid on the first 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 perforations <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 perforations <NUM> may be registered with the apertures <NUM> only in an interior portion, or only partially registered with the apertures <NUM>. The perforations <NUM> in the example of <FIG> are generally configured so that each of the perforations <NUM> is registered with only one of the apertures <NUM>. In other examples, one or more of the perforations <NUM> may be registered with more than one of the apertures <NUM>. For example, any one or more of the perforations <NUM> may extend across two or more of the apertures <NUM>. Additionally or alternatively, one or more of the perforations <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 first layer <NUM>, the perforations <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 perforations <NUM>. For example, some or all of the apertures <NUM> may be sized to expose two or three of the perforations <NUM>. In some examples, the length of each of the perforations <NUM> may be substantially equal to the diameter of each of the apertures <NUM>. More generally, the average dimensions of the perforations are substantially similar to the average dimensions of the apertures <NUM>. For example, the apertures <NUM> may be elliptical in some embodiments, and each of the perforations <NUM> may have a length L that is substantially equal to the major axis or the minor axis of the ellipse. In some embodiments, the dimensions of the perforations <NUM> may exceed the dimensions of the apertures <NUM>, and the size of the apertures <NUM> may limit the effective size of the perforations <NUM> exposed through the third layer <NUM>.

<FIG> is an assembly view of another example of the dressing <NUM>, illustrating additional details that may be associated with some example embodiments of the therapy system of <FIG>. In the example of <FIG>, the tissue interface <NUM> comprises a tie layer <NUM> in addition to the first layer <NUM> and the second layer <NUM>. The tie layer <NUM> may have perforations <NUM> and may have a thickness between <NUM> microns and <NUM> microns in some embodiments. The tie layer <NUM> may be clear, colored, or printed. As illustrated in <FIG>, the tie layer <NUM> may be disposed between the first layer <NUM> and the second layer <NUM>. The tie layer <NUM> may also be bonded to at least one of the first layer <NUM> and the second layer <NUM> in some embodiments.

The tie layer <NUM> may comprise polyurethane film, for example, which can be bonded to the first layer <NUM> and the second layer <NUM>. For example, if the first layer <NUM> is formed of a polyethylene film and the second layer <NUM> is polyurethane foam, the first layer <NUM> may be more readily bonded to the tie layer <NUM> than directly to the second layer <NUM>.

In some embodiments, one or more of the components of the dressing <NUM> may additionally be treated with an antimicrobial agent. For example, the second layer <NUM> may be a foam, mesh, or non-woven coated with an antimicrobial agent. In some embodiments, the second layer <NUM> may comprise antimicrobial elements, such as fibers coated with an antimicrobial agent. Additionally or alternatively, some embodiments of the first 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 second layer <NUM> may be foam coated with such a mixture.

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 first layer <NUM> may be laminated to the second layer <NUM>, and the cover <NUM> may be laminated to the second layer <NUM> opposite the first layer <NUM> in some embodiments. The third layer <NUM> may also be coupled to the first layer <NUM> opposite the second layer <NUM> in some embodiments. In some embodiments, one or more layers of the tissue interface <NUM> may coextensive. For example, the first layer <NUM> and the second layer <NUM> may be cut flush with the edge of the cover <NUM>, exposing the edge of the second layer <NUM>. In other embodiments, the first layer <NUM> may overlap the edge of the second layer <NUM>.

<FIG> is a schematic diagram of an example of the therapy system <NUM> applied to a tissue site <NUM>. In the example of <FIG>, the tissue site <NUM> is a surface wound. In use, a release liner (if included) may be removed to expose the tissue interface <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 dressing <NUM> may be cut to size for a specific region or anatomical area, such as for amputations. The dressing <NUM> may be cut without losing pieces of the tissue interface <NUM> and without separation of the tissue interface <NUM>.

The tissue interface <NUM> can be placed within, over, on, or otherwise proximate to the tissue site <NUM>. In the example of <FIG>, the first layer <NUM> forms an outer surface of the dressing <NUM>, and can be placed over the tissue site <NUM>, including the edge <NUM> and epidermis <NUM>. The first layer <NUM> may be interposed between the second layer <NUM> and the tissue site <NUM>, which can prevent direct contact between the second layer <NUM> and epidermis <NUM>. In other examples, the third layer <NUM> may form an outer surface of the dressing <NUM> and can provide temporary fixation over the tissue site <NUM>.

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

In some examples, the dressing <NUM> may include one or more attachment devices <NUM>. In some embodiments, one or more of the attachment devices <NUM> may comprise or consist essentially of a polymer strip, such as a polyurethane strip, having an adhesive <NUM> thereon. In some examples the adhesive <NUM> may be, for example, a medically-acceptable, pressure-sensitive adhesive that extends about a periphery, a portion, or an entire surface of each of the attachment devices <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 attachment devices <NUM>. Apertures or holes in the adhesive <NUM> may also be sized to enhance the MVTR of the attachment devices <NUM> in some example embodiments. In some embodiments, one or more of the attachment devices <NUM> may comprise or consist essentially of a composite strip of a perforated gel, substantially similar to the third layer <NUM>, and a backing with an adhesive.

The attachment devices <NUM> can be disposed around edges of the cover <NUM>, and the adhesive may pressed onto the cover <NUM> and epidermis <NUM> (or other attachment surface) to fix the dressing <NUM> in position and to seal the exposed perimeter <NUM> of the second layer <NUM>.

<FIG> also illustrates one example of a fluid conductor <NUM> and a dressing interface <NUM>. As shown in the example of <FIG>, the fluid conductor <NUM> may be a flexible tube, which can be fluidly coupled on one end to the dressing interface <NUM>. The dressing interface <NUM> may be an elbow connector, as shown in the example of <FIG>. In some examples, the tissue interface <NUM> can be applied to the tissue site <NUM> before the cover <NUM> is applied over the tissue interface <NUM>. The cover <NUM> may include an aperture <NUM>, or the aperture <NUM> may be cut into the cover <NUM> before or after positioning the cover <NUM> over the tissue interface <NUM>. The aperture <NUM> of <FIG> is centrally disposed. In other examples, the position of the aperture <NUM> may be off-center or adjacent to an end or edge of the cover <NUM>. The dressing interface <NUM> can be placed over the aperture <NUM> to provide a fluid path between the fluid conductor <NUM> and the tissue interface <NUM>. In other examples, the fluid conductor <NUM> may be inserted directly through the cover <NUM> into the tissue interface <NUM>.

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 from the negative-pressure source <NUM> can be distributed through the fluid conductor <NUM> and the dressing interface <NUM> to the tissue interface <NUM>. Negative pressure applied through the tissue interface <NUM> can also create a negative pressure differential across the perforations <NUM> in the first layer <NUM>, which can open or expand the perforations <NUM>. For example, in some embodiments in which the perforations <NUM> may comprise substantially closed fenestrations through the first layer <NUM>, a pressure gradient across the fenestrations can strain the adjacent material of the first 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 perforations can allow exudate and other liquid movement through the perforations into the second layer <NUM>. The second layer <NUM> can provide passage of negative pressure and exudate, which can be collected in the container <NUM>.

Changes in pressure can also cause the second layer <NUM> to expand and contract. The first layer <NUM> can protect the epidermis <NUM> from irritation that could be caused by expansion, contraction, or other movement of the second layer <NUM>. The first layer <NUM> can also substantially reduce or prevent exposure of a tissue site to the second layer <NUM>, which can inhibit growth of tissue into the second layer <NUM>.

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

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 perforations <NUM> in the first layer <NUM>, which can open the perforations <NUM> to allow the instillation solution or other fluid to be distributed to the tissue site <NUM>.

<FIG> is a line chart that illustrates how the thickness T of a manifold, such as the second layer <NUM>, can affect the manifolding performance in the presence of thick exudate. The data in the chart of <FIG> reflects the change in negative pressure at increasing distances from a point at which a negative-pressure source is coupled to the manifold. More specifically, simulated wound fluid was instilled into various embodiments of the dressing <NUM> at the furthest point from the negative-pressure source. The simulated wound fluid was instilled at a rate of <NUM> cc/<NUM> hours over a period of days, and the pressure in the manifold was monitored at known distances from the negative-pressure source over the instillation period and averaged. Sample <NUM> and Sample <NUM> each comprised a manifold having a thickness of about <NUM> millimeters; Sample <NUM> and Sample <NUM> each comprised a manifold having a thickness of about <NUM> millimeters; and Sample <NUM> and Sample <NUM> each comprised a manifold having a thickness of about <NUM> millimeters. The data illustrated in <FIG> demonstrates that a manifold having a thickness of about <NUM> millimeters performs substantially better than configurations having a thickness of about <NUM> millimeters. More particularly, the negative pressure in Sample <NUM> and Sample <NUM> drops below <NUM>% of the applied negative pressure at a distance of between <NUM> centimeters and <NUM> centimeters, while Sample <NUM> and Sample <NUM> maintain levels above <NUM>% to distances greater than <NUM> centimeters. Significantly, Sample <NUM> and Sample <NUM> maintain an applied negative pressure comparably well to the configurations of Sample <NUM> and Sample <NUM> having a thickness of about <NUM> millimeters.

As <FIG> illustrates, a manifold having a thickness of about <NUM> millimeters to about <NUM> millimeters may be advantageous for maintaining at least <NUM>% of applied negative pressure larger dressings in the presence of viscous exudate. For example, if the dressing interface <NUM> is centrally disposed, as illustrated in <FIG>, a thickness of about <NUM> millimeters may be advantageous for manifolds having a length of at least <NUM> centimeters. In some embodiments, a thickness of about <NUM> millimeters may be particularly advantageous for manifolds having a length of at least <NUM> centimeters, up to a length of about <NUM> centimeters. If the dressing interface <NUM> is disposed toward an edge of the dressing, a thickness of <NUM> millimeters may be advantageous for manifolds having a length of about one-half of the length of a dressing having a centrally-disposed interface.

The systems, apparatuses, and methods 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> can be 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. Some embodiments of the dressing <NUM> may alternatively be cut to size and readily sealed to a tissue site while still providing such benefits. 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.

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. 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 separated from other components for manufacture or sale. In other example configurations, the controller <NUM> may also be manufactured, configured, assembled, or sold independently of other components.

Claim 1:
A dressing (<NUM>) for treating a tissue site (<NUM>) with negative pressure, comprising:
a first layer (<NUM>) comprising a polymer film having a plurality of perforations (<NUM>);
a second layer (<NUM>) comprising a manifold disposed adjacent to the polymer film, the manifold having a length of between <NUM> centimeters and about <NUM> centimeters and thickness of between <NUM> millimeters and about <NUM> millimeters; and
a cover (<NUM>) adjacent to the second layer (<NUM>), the cover (<NUM>) comprising a polymer film,
wherein the first layer (<NUM>), the second layer (<NUM>), and the cover (<NUM>) are stacked so that the second layer (<NUM>) is disposed between the first layer (<NUM>) and the cover (<NUM>).