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 a dressing with a protruding layer allowing for cleansing of wound bed macro deformations that includes a contact layer having walls defining a plurality of holes and a retainer layer comprising portions protruding into holes of the contact layer. <CIT> concerns a negative pressure wound therapy apparatus including a wound dressing with a spacer layer separated from the absorbent layer by intermediate layers or drapes. <CIT> concerns a peel and place dressing having a closed-cell contact layer.

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 present invention provides a dressing for treating a tissue site according to claim <NUM>. Further optional features are defined in the dependent claims.

Illustrative example embodiments are also provided to enable a person skilled in the art to make and use the claimed subject matter.

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 example embodiments.

<FIG> is a 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 include 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 include or may be a manifold. A manifold in this context may include a means for collecting or distributing fluid across or through 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 be, for example, an elastomeric film or membrane that can provide a seal adequate to maintain a negative pressure at a tissue site for a given negative-pressure source. The cover <NUM> may have a high moisture-vapor transmission rate (MVTR) in some applications. For example, the MVTR may be at least <NUM> 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 be, 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.

In general, exudate and other fluid flow toward lower pressure along a fluid path. Thus, the term "downstream" may refer to 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" may refer to a location 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.

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.

Some dressings can be worn for a time period extending beyond seven days, which can be referred to as an extended wear time. Dressings for extended wear time can provide cost-savings, time-efficiencies, and less trauma to a patient during dressing changes. Some highly felted foam materials may be worn for an extended period of time without suffering tissue in-growth. However, some felted foam materials may be quite stiff. Stiffer foam materials may be hard to conform, difficult to resize, and unable to collapse under negative pressure to provide macro-strain to the tissue site. Additionally the stiff foam material may not efficiently deliver fluid and pressure to the tissue site because the manifold is unable to contract radially.

These limitations and others may be addressed by the therapy system <NUM>, which can provide negative-pressure therapy and instillation therapy. In some embodiments, the therapy system <NUM> may include a tissue interface or manifold layer that can prevent tissue-ingrowth but is also flexible, collapsible, and resizable. The tissue interface or manifold layer may include a pattern enabling the manifold to contract radially in all directions, thereby increasing the effectiveness of the therapy system <NUM>.

<FIG> is a perspective view of an example of the tissue interface <NUM> of <FIG>, illustrating additional details that may be associated with some embodiments. Herein, various examples of the tissue interface <NUM> are described that may be suitable for use with the dressing <NUM> and the therapy system <NUM>. Further, features or elements of the tissue interface <NUM> described herein may be referred to as part of the therapy system <NUM> or the dressing <NUM> without reference to the tissue interface <NUM>.

In the example of <FIG>, the tissue interface <NUM> may include or may be a manifold, such as a manifold layer <NUM>. The manifold layer <NUM> may also provide a means for collecting or distributing fluid across the tissue interface <NUM> under pressure. For example, the manifold 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 manifold layer <NUM> may be interconnected to improve distribution or collection of fluids. In some illustrative embodiments, the manifold layer <NUM> may be 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 manifold layer <NUM> may additionally or alternatively include projections that form interconnected fluid pathways. For example, the manifold layer <NUM> may be molded to provide surface projections that define interconnected fluid pathways.

In some embodiments, the manifold layer <NUM> may be a foam having pore sizes that may vary according to needs of a prescribed therapy. For example, 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 manifold layer <NUM> may also vary according to needs of a prescribed therapy. For example, the tensile strength of a foam may be increased for instillation of topical treatment solutions. In some embodiments, the manifold layer <NUM> may have a <NUM>% compression load deflection of about <NUM> to about <NUM> pounds per square inch, and a <NUM>% compression load deflection of about <NUM> to about <NUM> pounds per square inch. In some embodiments, the manifold 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 manifold 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.

In some embodiments, the manifold layer <NUM> may be formed by a felting process. Any porous foam suitable for felting may be used, including the example foams mentioned herein, such as GRANUFOAM™ Dressing. Felting comprises a thermoforming process that permanently compresses a foam to increase the density of the foam while maintaining interconnected pathways. Felting may be performed by any known methods, which may include applying heat and pressure to a porous material or foam material. Some methods may include compressing a foam blank between one or more heated platens or dies (not shown) for a specified period of time and at a specified temperature. The direction of compression may be along the thickness of the foam blank.

The period of time of compression may range from <NUM> minutes up to <NUM> hours, though the time period may be more or less depending on the specific type of porous material used. Further, in some examples, the temperature may range between <NUM> to <NUM>. Generally, the lower the temperature of the platen, the longer a porous material must be held in compression. After the specified time period has elapsed, the pressure and heat will form a felted structure or surface on or through the porous material or a portion of the porous material.

The felting process may alter certain properties of the original material, including pore shape and/or size, elasticity, density, and density distribution. For example, struts that define pores in the foam may be deformed during the felting process, resulting in flattened pore shapes. The deformed struts can also decrease the elasticity of the foam. The density of the foam is generally increased by felting. In some embodiments, contact with hot-press platens in the felting process can also result in a density gradient in which the density is greater at the surface and the pores size is smaller at the surface. In some embodiments, the felted structure may be comparatively smoother than any unfinished or non-felted surface or portion of the porous material. Further, the pores in the felted structure may be smaller than the pores throughout any unfinished or non-felted surface or portion of the porous material. In some examples, the felted structure may be applied to all surfaces or portions of the porous material. Further, in some examples, the felted structure may extend into or through an entire thickness of the porous material such that all of the porous material is felted.

A felted foam may be characterized by a firmness factor, which is indicative of the compression of the foam. The firmness factor of a felted foam can be specified as the ratio of original thickness to final thickness. A compressed or felted foam may have a firmness factor greater than <NUM>. The degree of compression may affect the physical properties of the felted foam. For example, felted foam has an increased effective density compared to a foam of the same material that is not felted. The felting process can also affect fluid-to-foam interactions. For example, as the density increases, compressibility or collapse may decrease. Therefore, foams which have different compressibility or collapse may have different firmness factors. In some example embodiments, a firmness factor can range from about <NUM> to about <NUM>. For example, the firmness factor of the manifold layer <NUM> felted foam may be about <NUM> to <NUM> in some embodiments. There is a general linear relationship between firmness level, density, pore size (or pores per inch) and compressibility. For example, foam that is felted to a firmness factor of <NUM> will show a five-fold density increase and compress to about a fifth of its original thickness.

In some embodiments, the manifold layer <NUM> may be a closed-cell foam such as, for example, those manufactured by Zotefoams, Inc. of Walton, Kentucky, U. , including the Azote, Plastazote, Evazote, Supazote, and Zotek grades. Such closed-cell foams may be manufactured by extruding polymer sheets or blocks and crosslinking through high energy radiation. Suitable polymers may include low and high density polyolefins and copolymers with vinyl acetate, fluoropolymers, polyamides, and PEBAX. The polymer sheets may then be softened under heat and exposed to high pressure nitrogen gas which dissolves in the polymer. After cooling, the polymer sheets may be heated again and exposed to subatmospheric pressure, resulting in expansion and formation of the closed-cell foam. In some embodiments, the closed-cell foam may be thermoformed. Thermoforming the foam involves embossing patterns and structures, such as channels, into the surfaces of the foam in order to translate what would otherwise be non-manifolding material into a structure that will manifold pressure and fluid along the channels.

In some embodiments, one or more suitable foam blanks may be used for forming the manifold layer <NUM>. The foam blanks may be open cell foam, felted foam, closed cell foam, or another foam as described herein. However, the properties of any of these foam blanks may have about <NUM> to about <NUM> pores per inch on average, a density of about <NUM> to about <NUM> lb/ft<NUM>, a free volume of about <NUM>% or more, an average pore size in a range of about <NUM> to about <NUM> microns, and/or a <NUM>% compression load deflection of at least <NUM> pounds per square inch. In some embodiments, the foam blank(s) may have a thickness greater than <NUM> millimeters, for example <NUM>-<NUM> millimeters.

As further shown in <FIG>, the manifold layer <NUM> may comprise one or more holes <NUM> extending through a first side <NUM>, a second side <NUM> opposite the first side <NUM>, and a thickness of the manifold layer <NUM>. The thickness of the manifold layer <NUM> may be between about <NUM>-<NUM> millimeters. The plurality of holes <NUM> may be distributed uniformly or randomly across the manifold layer <NUM>. In some embodiments, the plurality of holes <NUM> may be positioned in at least a first row <NUM> and a second row <NUM> that is offset or staggered from the first row <NUM>. The plurality of holes <NUM> extending through the manifold layer <NUM> may form a plurality of walls <NUM> extending through the manifold layer <NUM>. The holes <NUM> may be configured to contract radially in all directions in response to the application of negative pressure to the tissue interface <NUM> such that there is radial mechanical deformation at the tissue site.

In some embodiments, the holes <NUM> may be formed during molding of the manifold layer <NUM>. In other embodiments, the holes <NUM> may be formed by cutting, melting, or vaporizing the manifold layer <NUM>. For example, the holes <NUM> may be formed in the manifold layer <NUM> by laser cutting the felted foam of the manifold layer <NUM>.

<FIG> is an exploded view of another example of the tissue interface <NUM> of <FIG>, illustrating additional details that may be associated with some embodiments. In some embodiments, the tissue interface <NUM> may comprise the manifold layer <NUM> and an optional contact layer <NUM>. In some embodiments, the contact layer <NUM> may optionally be disposed adjacent to the manifold layer <NUM>. For example, the contact layer <NUM> and the manifold layer <NUM> may be stacked so that the contact layer <NUM> is in contact with the manifold layer <NUM>. The contact layer <NUM> may also be heat-bonded or adhered to the manifold layer <NUM> in some embodiments, for example, using hot melt adhesive. In some embodiments, the contact layer <NUM> may optionally include 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 contact layer <NUM> or applied in a pattern. In some embodiments, the contact layer <NUM> may be configured to be positioned between the manifold layer <NUM> and a tissue site. In some embodiments, the contact layer <NUM> may be configured to be positioned in direct contact with the tissue site. The contact layer <NUM> can provide additional protection to the epidermis from irritation that could be caused by expansion, contraction, or other movement of the manifold layer <NUM>. The contact layer <NUM> can also reduce tissue in-growth into the manifold layer <NUM>.

The contact layer <NUM> may include a means for controlling or managing fluid flow. In some embodiments, the contact layer <NUM> may be a fluid control layer comprising a liquid-impermeable, elastomeric material. For example, the contact layer <NUM> may be a polymer film, such as a polyurethane film. In some embodiments, the contact layer <NUM> may be the same material as the cover <NUM>. The contact 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 contact layer <NUM> may have a substantially flat surface, with height variations limited to <NUM> millimeters over a centimeter.

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

The area density of the contact 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 contact layer <NUM> may be 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 contact layer <NUM> may have one or more passages, which can be distributed uniformly or randomly across the contact layer <NUM>. In some embodiments, the passages may be bidirectional and pressure-responsive. For example, each of the passages generally may be an elastic passage that is normally unstrained to substantially reduce liquid flow, and can expand or open in response to a pressure gradient and/or in response to the contraction of the manifold layer <NUM>. As illustrated in the example of <FIG>, the passages may be a plurality of perforations <NUM> disposed through opposing surfaces of the contact layer <NUM>. The plurality of perforations <NUM> may be formed by removing material from the contact layer <NUM>. For example, the plurality of perforations <NUM> may be formed by cutting through the contact layer <NUM>. In the absence of a pressure gradient across the plurality of perforations <NUM>, the plurality of 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 and/or in response to the contraction of the manifold layer <NUM>. In some examples, the passages may be fenestrations in the contact layer <NUM>. Generally, fenestrations are a species of perforation, and may also be formed by removing material from the contact 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 plurality of perforations <NUM> may be formed as slots (or fenestrations formed as slits) in the contact layer <NUM>. In some examples, the plurality of perforations <NUM> may be 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 and/or in response to the contraction of the manifold layer <NUM> to allow increased liquid flow.

<FIG> is a top view of the tissue interface of <FIG>, illustrating additional details that may be associated with some embodiments. As shown in <FIG>, in some embodiments, the tissue interface <NUM> may have a first orientation line <NUM> and a second orientation line <NUM> that is perpendicular to the first orientation line <NUM>. In some embodiments, the first orientation line <NUM> may be parallel to a length LM of the tissue interface <NUM> and the manifold layer <NUM>, and the second orientation line <NUM> may be parallel to a width WM of the tissue interface <NUM> and the manifold layer <NUM>. Generally, the first orientation line <NUM> and the second orientation line <NUM> aid in the description of the tissue interface <NUM>.

In some embodiments, the manifold layer <NUM> may be configured to contract radially in all directions in a plane under the application of negative pressure. For example, the length LM of the manifold layer <NUM> and the width WM of the manifold layer <NUM> may lie in a contraction plane where the manifold layer <NUM> is configured to radially contract in all directions in the contraction plane or a planar area defined by the first side <NUM> and/or the second side <NUM> of the manifold layer. For example, if the tissue interface <NUM> is not subjected to negative pressure, the length LM may be a nominal or relaxed length, and the width WM may be a nominal or relaxed width. In some embodiments, the length LM may be greater than the width WM, such that the width WM, may be less than the length LM. For example, the tissue interface <NUM> may have an elongate shape. In some embodiments, for example, the tissue interface <NUM> may have a length LM to width WM ratio of at least <NUM>:<NUM>. In some embodiments, the length LM may be equal to the width WM. In some embodiments, the length LM may be less than the width WM.

Although the manifold layer <NUM> is shown as having an elongate rectangular shape, the manifold layer <NUM> may have other shapes. For example, the manifold layer <NUM> may have a stadium, diamond, square, oval or circular shape. In some embodiments, the shape of the manifold layer <NUM> may be selected to accommodate the type of tissue site being treated. For example, the manifold layer <NUM> may have an oval or circular shape to accommodate an oval or circular tissue site. In other example embodiments, the manifold layer <NUM> may be resized and formed into any desirable shape by a clinician prior to placement at the tissue site.

As further illustrated in <FIG>, the holes <NUM> may include a first plurality of holes <NUM> in the first row <NUM> and a second plurality of holes <NUM> in the second row <NUM>. Additional rows of holes may be provided, as shown in the non-limiting embodiment of <FIG>. Each of the first plurality of holes <NUM> and the second plurality of holes <NUM> may be configured to have an elongate shape that extends through the first side <NUM>, the second side <NUM>, and the thickness of the manifold layer <NUM>.

In some embodiments, each of the first plurality of holes <NUM> and the second plurality of holes <NUM> may have a length that is longer than and perpendicular to a hole width. In some embodiments, each of the first plurality of holes <NUM> and the second plurality of holes <NUM> may have a shape configured to be a parallelogram. In some embodiments where the holes <NUM> are parallelogram-shaped, each of the first plurality of holes <NUM> may have a length L<NUM> and a width W<NUM> perpendicular to the length L<NUM>, and each of the second plurality of holes <NUM> may have a length L<NUM> and a width W<NUM> perpendicular to the length L<NUM>. In the example of <FIG>, L<NUM> and L<NUM> may be about <NUM>-<NUM> millimeters, and W<NUM> and W<NUM> may be about <NUM>-<NUM> millimeters. In some embodiments, the length L<NUM> may be equal to the length L<NUM>. In some embodiments, the width W<NUM> may be equal to the width W<NUM>. In other embodiments, L<NUM> and L<NUM> may be substantially equal, and W<NUM> and W<NUM> may be substantially equal, within acceptable manufacturing tolerances.

The first plurality of holes <NUM> and the second plurality of holes <NUM> may be distributed across the manifold layer <NUM> in one or more rows in one direction or in different directions. In some embodiments, the rows of the first plurality of holes <NUM> and the second plurality of holes <NUM> may be offset or staggered. In some embodiments, the length L<NUM> of one or more of the first plurality of holes <NUM> in the first row <NUM> may point toward the length L<NUM> of one or more of the second plurality of holes <NUM> in the second row <NUM>. In some embodiments, the length L<NUM> of one or more of the second plurality of holes <NUM> in the second row <NUM> may point toward the length L<NUM> of one or more of the first plurality of holes <NUM> in the first row <NUM>.

In some embodiments, the first plurality of holes <NUM> in the first row <NUM> may overlap with the second plurality of holes <NUM> in the second row <NUM>. For example, at least a portion of the first plurality of holes <NUM> in the first row <NUM> would also be positioned or extend into the second row <NUM> and at least a portion of the second plurality of holes <NUM> in the second row <NUM> would also be positioned or extend into the first row <NUM>. In other embodiments, the first plurality of holes <NUM> in the first row <NUM> may not overlap with the second plurality of holes <NUM> in the second row <NUM>. For example, the first plurality of holes <NUM> may be positioned entirely in the first row <NUM> separate from the second plurality of holes <NUM> positioned entirely in the second row <NUM>.

In some embodiments, the length L<NUM> of one or more of the first plurality of holes <NUM> in the first row <NUM> may be positioned at an angle relative to the length L<NUM> of one or more of the second plurality of holes <NUM> in the second row <NUM>. In some embodiments, the length L<NUM> of one or more of the first plurality of holes <NUM> in the first row <NUM> may be angled toward the hole length L<NUM> of one or more of the second plurality of holes <NUM> in the second row <NUM>. In some embodiments, the length L<NUM> of one or more of the first plurality of holes <NUM> in the first row <NUM> may form an angle of about <NUM> degrees relative to the length L<NUM> of one or more of the second plurality of holes <NUM> in the second row <NUM>. In some embodiments, the length L<NUM> of one or more of the first plurality of holes <NUM> in the first row <NUM> may form an angle of about <NUM> degrees relative to the width W<NUM> of one or more of the second plurality of holes <NUM> in the second row <NUM>.

In some embodiments, the first plurality of holes <NUM> in the first row <NUM> and the second plurality of holes <NUM> in the second row <NUM> may extend along the length LM of the manifold layer <NUM>. In some embodiments, the length L<NUM> of the first plurality of holes <NUM> and the length L<NUM> of the second plurality of holes <NUM> may be positioned at an angle relative to the length LM of the manifold layer <NUM>. For example, each of the first plurality of holes <NUM> may have a first long axis, such as a first reference line <NUM>, which may be parallel to the length L<NUM> of the first plurality of holes <NUM>. Each of the second plurality of holes <NUM> may have a second long axis, such as a second reference line <NUM>, which may be parallel to the length L<NUM> of the second plurality of holes <NUM>. In some embodiments, one or both of the first reference line <NUM> and the second reference line <NUM> may be defined relative to the length LM. For example, the first reference line <NUM> may form a first angle <NUM> relative to the length LM and the second reference line <NUM> may form a second angle <NUM> relative to the length LM. In some embodiments, the first angle <NUM> may be about <NUM>° relative to the length LM and the second angle <NUM> may be about <NUM>° relative to the length LM. In some embodiments, the first angle may about <NUM>° relative to the length LM and the second angle may be about <NUM>° relative to the length LM.

The pattern of holes <NUM> may be characterized by a pitch, which indicates the spacing between corresponding points on holes <NUM> within a pattern. In example embodiments, pitch may indicate the spacing between the centroids of holes <NUM> within the pattern. Some patterns may be characterized by a single pitch value, while others may be characterized by at least two pitch values. For example, if the spacing between centroids of the holes <NUM> is the same in all orientations, the pitch may be characterized by a single value indicating the spacing between centroids in adjacent rows. In some embodiments, a pattern comprising the first plurality of holes <NUM> and the second plurality of holes <NUM> may be characterized by two pitch values, P<NUM> and P<NUM>. P<NUM> may be the spacing between the centroid of one or more of the first plurality of holes <NUM> and another of the first plurality of holes <NUM> in the first row <NUM> along the first orientation line <NUM>. P<NUM> may be the spacing between the centroid of one or more of the first plurality of holes <NUM> in the first row <NUM> and one or more of the second plurality of holes <NUM> in the second row <NUM> perpendicular to the first orientation line <NUM>. In some embodiments, P<NUM> may be about <NUM>-<NUM> millimeters and P<NUM> may be about <NUM>-<NUM> millimeters.

<FIG> is a detail view of the manifold layer <NUM> taken at reference <FIG> in <FIG>. In some embodiments, the rows may be offset or staggered. The stagger may be characterized by an orientation of corresponding points in successive rows relative to an edge or other reference line associated with the manifold layer <NUM>. In some embodiments, the rows of the first plurality of holes <NUM> may be staggered with the rows of the second plurality of holes <NUM>. In some embodiments, the stagger may be characterized by a distance or a stagger value S<NUM>, where S<NUM> may be the spacing between the centroid of one or more of the first plurality of holes <NUM> in the first row <NUM> and one or more of the second plurality of holes <NUM> in the second row <NUM> in a direction parallel to the to the first orientation line <NUM>.

In some embodiments, the plurality of walls <NUM> may form a web including a plurality of alternating first wall portions <NUM> and second wall portions <NUM>. The first wall portions <NUM> may be oriented at an angle Φ with respect to the first orientation line <NUM>. In the example of <FIG>, the first wall portions <NUM> may be about <NUM>° with respect to the first orientation line <NUM>. The second wall portions <NUM> may be oriented at an angle Ψ with respect to the first orientation line <NUM>. In the example of <FIG>, the second wall portions <NUM> may be about <NUM>° with respect to the first orientation line <NUM>. In some embodiments, the first wall portions <NUM> may be parallel to the length L<NUM> of the first plurality of holes <NUM>, and the second wall portions <NUM> may be parallel to the length L<NUM> of the second plurality of holes <NUM>. The first wall portions <NUM> and the second wall portions <NUM> may have an angle β of about <NUM>° between each wall portion.

<FIG> is a top view of an example of the manifold layer <NUM> of <FIG> in a contracted position, illustrating additional details that may be associated with some embodiments. As shown in <FIG>, if negative pressure is applied to the tissue interface <NUM>, the plurality of holes <NUM> of the manifold layer <NUM> may collapse or contract from a relaxed position to a contracted position. In some embodiments, the manifold layer <NUM> may be configured to contract to the contracted position when exposed to a reduced pressure of about -<NUM> Hg. Contraction may occur in all directions as the holes <NUM> become smaller under the compressive force of negative pressure and apposition forces may be generated. The holes <NUM> aid in the delivery of negative pressure and the removal of fluids even when the holes <NUM> are collapsed. When instillation therapy is used, the holes <NUM> may also aid in the delivery of fluids even when contracted. Additionally, if negative pressure is applied to the tissue interface <NUM>, the manifold layer <NUM> may collapse or contract to a contracted length and a contracted width, wherein the contracted length and the contracted width is less than a relaxed length and a relaxed width in the absence of negative pressure. Under an applied negative pressure, the tissue interface <NUM> may collapse or contract to a contracted length LC and a contracted width WCthat is less than the nominal or relaxed length LM and the nominal or relaxed width WM of the tissue interface <NUM>. As the tissue interface <NUM> contracts, the contraction may be applied to the tissue site.

In some embodiments, the manifold layer <NUM> may comprise a first surface area when in the relaxed position and a second surface area when in the contracted position. In a contracted position, such as shown in <FIG>, the second surface area may be between about <NUM>-<NUM> percent less than the first surface area. In some embodiments, the second surface area may be at least <NUM> percent less than the first surface area.

<FIG> is a top view of another example of a manifold layer <NUM> that can be associated with some embodiments of the tissue interface <NUM> of <FIG> and <FIG>. In some embodiments, the manifold layer <NUM> may comprise at least one surface channel <NUM> having a channel length extending along at least one manifold surface or side of the manifold layer <NUM>. For example, the channel length of the at least one surface channel <NUM> may extend along one or both of the first side <NUM> or the second side <NUM> of the manifold layer <NUM>. In some embodiments, the at least one surface channel <NUM> may be a plurality of surface channels <NUM>. In some embodiments, the plurality of surface channels <NUM> may also intersect the plurality of holes <NUM>. The plurality of surface channels <NUM> may also intersect one another at an intersection angle <NUM> to form one or more grid patterns as described herein.

For example, the plurality of surface channels <NUM> may intersect to form a first grid <NUM> and a second grid <NUM>. A first plurality of surface channels <NUM> and a second plurality of surface channels <NUM> of the plurality of surface channels <NUM> may intersect to form the first grid <NUM>. In some embodiments, the first plurality of surface channels <NUM> and the second plurality of surface channels <NUM> of the first grid <NUM> may intersect to form the intersection angle <NUM>. The intersection angle <NUM> may be about <NUM> degrees and form a square grid pattern. In some embodiments, the plurality of surface channels <NUM> may further comprise a third plurality of surface channels <NUM>. The third plurality of surface channels <NUM> may intersect the first plurality of surface channels <NUM> and the second plurality of surface channels <NUM> to form the second grid <NUM>. In some embodiments, the third plurality of surface channels <NUM> may intersect the first plurality of surface channels <NUM> and the second plurality of surface channels <NUM> at the same point where the first plurality of surface channels <NUM> and the second plurality of surface channels <NUM> intersect. In some embodiments, the third plurality of surface channels <NUM> may intersect the first grid <NUM> to form the second grid <NUM>. The third plurality of surface channels <NUM> may intersect the first grid <NUM> at a grid angle <NUM>. In some embodiments, the grid angle <NUM> may be about <NUM> degrees.

In some embodiments, the plurality of surface channels <NUM> may be spaced apart by a separation distance. For example, each of the first plurality of surface channels <NUM> may extend from a first end <NUM> of the manifold layer <NUM> to a second end <NUM> opposite the first end <NUM>. In some embodiments, each of the first plurality of surface channels <NUM> may be spaced apart along the width WM of the manifold layer <NUM> by a distance D<NUM>. The second plurality of surface channels <NUM> may be perpendicular to the first plurality of surface channels <NUM>. In some embodiments, each of the second plurality of surface channels <NUM> may be spaced apart along the length LM of the manifold layer <NUM> by a distance D<NUM>. In the example of <FIG>, D<NUM> and D<NUM> may be between about <NUM> millimeters to about <NUM> millimeters.

<FIG> is a perspective view of the manifold layer <NUM> of <FIG>, illustrating additional details that may be associated with some embodiments. In some embodiments, the plurality of surface channels <NUM> may comprise a channel depth CD and a channel width CW perpendicular to the channel depth CD. The channel depth CD may extend into the thickness of the manifold layer <NUM> from a manifold surface, such as one or both of a first manifold surface <NUM> or a second manifold surface <NUM> opposite the first manifold surface <NUM>. Although not shown in <FIG>, the plurality of surface channels <NUM> may be positioned on the second manifold surface <NUM> in addition to or in lieu of the plurality of surface channels <NUM> shown on the first manifold surface <NUM>. In some embodiments, the channel depth CD may be between about <NUM> millimeter to about <NUM> millimeters and the channel width CW may be between about <NUM> millimeters to about <NUM> millimeters.

In some embodiments, the first plurality of surface channels <NUM> and the second plurality of surface channels <NUM> of the plurality of surface channels <NUM> may each have a first channel depth CD<NUM> and a second channel depth CD<NUM>, respectively. In some embodiments, the second channel depth CD<NUM> is greater than the first channel depth CD<NUM> (CD<NUM> > CD<NUM>). In some embodiments, the third plurality of surface channels <NUM> forming the second grid <NUM> may have a third channel depth CD<NUM> (not shown). In some embodiments, the first channel depth CD<NUM> and the second channel depth CD<NUM> may be equal so that the first plurality of surface channels <NUM> and the second plurality of surface channels <NUM> that form the first grid <NUM> have the same depth (CD<NUM> = CD<NUM>). In some embodiments, the third channel depth CD<NUM> is greater than both first channel depth CD<NUM> and the second channel depth CD<NUM> so that the depth of the second grid <NUM> is greater than the depth of the first grid <NUM> (CD<NUM> > [CD<NUM> = CD<NUM>]).

<FIG> is a perspective view of another example of a manifold layer <NUM> that can be associated with some embodiments of the tissue interface <NUM> of <FIG> and <FIG>. In some embodiments, the plurality of surface channels <NUM> may extend along the first manifold surface <NUM> of the manifold layer <NUM>. In some embodiments, the plurality of surface channels <NUM> may extend along both the first manifold surface <NUM> and the second manifold surface <NUM>. For example, the second plurality of surface channels <NUM> may extend along the first manifold surface <NUM> and the first plurality of surface channels <NUM> may extend along the second manifold surface <NUM>.

<FIG> is a perspective view of the second side <NUM> of the tissue interface <NUM> of <FIG>, illustrating additional features that may be associated with some embodiments. In some embodiments, the first plurality of surface channels <NUM> may extend along the second manifold surface <NUM> at a <NUM> degree angle relative to the second plurality of surface channels <NUM> extending along the first manifold surface <NUM>. Referring to <FIG> and <FIG>, the second channel depth CD<NUM> of the second plurality of surface channels <NUM> may extend from the first manifold surface <NUM> toward the second manifold surface <NUM>, and the first channel depth CD<NUM> of the first plurality of surface channels <NUM> may extend from the second manifold surface <NUM> toward the first manifold surface <NUM>. In some embodiments, the first channel depth CD<NUM> may intersect with the second channel depth CD<NUM> to form a channel aperture <NUM> that extends through the first manifold surface <NUM>, the second manifold surface <NUM>, and the thickness of the manifold layer <NUM>.

<FIG> is a perspective, side view of another example of a manifold layer <NUM> that can be associated with some embodiments of the tissue interface <NUM> of <FIG>. In some embodiments, the manifold layer <NUM> may be formed by two or more layers. For example, the manifold layer <NUM> may comprise a first manifold layer <NUM> and a second manifold layer <NUM>. Similar to embodiments of the manifold layer <NUM>, the first manifold layer <NUM> may comprise the first manifold surface <NUM> and the second manifold surface <NUM>. The second manifold layer <NUM> may comprise a third manifold surface <NUM> and a fourth manifold surface <NUM>. In some embodiments, the first manifold surface <NUM>, the second manifold surface <NUM>, the third manifold surface <NUM>, and the fourth manifold surface <NUM> may each comprise the plurality of surface channels <NUM> In some embodiments, the first manifold surface <NUM>, the second manifold surface <NUM>, the third manifold surface <NUM>, and the fourth manifold surface <NUM> may each comprise the first plurality of surface channels <NUM> and the second plurality of surface channels <NUM>.

In some embodiments, the first manifold layer <NUM> and the second manifold layer <NUM> may be bonded together to form the manifold layer <NUM>. In some embodiments, the second manifold surface <NUM> of the first manifold layer <NUM> may be bonded to the third manifold surface <NUM> of the second manifold layer <NUM>. In some embodiments, the first plurality of surface channels <NUM> on the second manifold surface <NUM> may be aligned with the first plurality of surface channels <NUM> on the third manifold surface <NUM>, and the second plurality of surface channels <NUM> on the second manifold surface <NUM> may be aligned with the second plurality of surface channels <NUM> on the third manifold surface <NUM> to form at least one section channel <NUM> extending into the thickness of the manifold layer <NUM> substantially parallel to the first manifold surface <NUM>, the second manifold surface <NUM>, the third manifold surface <NUM>, and the fourth manifold surface <NUM>. In some embodiments, the at least one section channel may be a plurality of section channels <NUM>. In other embodiments, the manifold layer <NUM> may be formed using a single layer, such as the manifold layer <NUM>, and perforating the manifold layer <NUM> along the length and width of the manifold layer <NUM> to form the plurality of section channels <NUM>.

In other embodiments, the manifold layer <NUM> may be a laminate of different densities of closed-cell foam. In such an embodiments, the manifold layer <NUM> may feel more flexible. In other embodiments, the laminate forming the manifold layer <NUM> may comprise three layers, such as two outer layers and an inner layer. The inner layer may be sandwiched between the outer layers. The outer layers may be stiffer than the inner layer, and the inner layer may be softer and more likely to conform. In still other embodiments, the manifold layer <NUM> may be perforated along its length and width through the closed-cell foam to provide lateral manifolding channels, such as the plurality of section channels <NUM>. The plurality of section channels <NUM> may be formed by bonding at least two laminated layers where channels are thermoformed onto the surfaces of the laminated layers. The bonding process does not seal the channels closed. As a result, each thinner layer of closed-cell foam would be embossed on each side and then bonded to form a multi-orientation manifolding structure. Suitable adhesives for bonding include hot melts. The hot melts may be pattern coated onto the surfaces so as not to block the channels. In some embodiments, an adhesive may be sprayed onto the surfaces of the manifold layer <NUM>. A fine mist of adhesive is unlikely to block the channels if the channels are about <NUM>-<NUM> millimeters deep. Additionally or alternatively, solvent borne adhesives may be used, such as acrylic or reactive polyurethanes. A form of heat lamination may also be used, where surface localized heat is applied to the foam layers to soften or tackify the bonding surfaces before pressing the foam layers together. Two-part reactive adhesives may also be used where one surface is coated with a first adhesive and another surface is coated with a second adhesive. The surfaces comprising the first adhesive and the second adhesive are then brought together to form the bond.

In other embodiments, one or both of the outer surfaces of the manifold layer <NUM> may include a texture. For example, one or both of the first manifold surface <NUM> and the fourth manifold surface <NUM> may include a texture. The texture may allow areas of the manifold layer <NUM> not containing channels to form manifolding areas. In some embodiments, the texture may comprise a random pattern of peaks, such as a tough Standex finish; a leather-effect patterns; a patterns of pyramids; a patterns of triangles; or a pattern of other shapes. Additionally or alternatively, one or both of the outer surfaces of the manifold layer <NUM> may be coated with hydrophilic or hydrophobic materials, for example by a plasma coating, to modify the fluid distribution properties of the manifold layer <NUM>. In some embodiments, the channels of the manifold layer <NUM> may be specifically coated with hydrophilic or hydrophobic materials.

In still other embodiments, all or some of the layers forming the manifold layer <NUM> may be different colors. The differing colors may improve visualization of fluids, such as bleeding. A full range of colors may be used to form the manifold layer <NUM>.

Referring primarily to <FIG> and <FIG>, presented is an illustrative embodiment of a portion of the therapy system <NUM>. <FIG> and <FIG> depict the therapy system <NUM> assembled in stages at a tissue site <NUM>, which may be a wound. In some embodiments, the tissue site <NUM> may be a deep wound. In some embodiments, the tissue site <NUM> may include a portion through an epidermis <NUM>, dermis <NUM>, and subcutaneous tissue <NUM>. Referring now to <FIG>, the dressing <NUM> may be disposed within the tissue site <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. The dressing <NUM> may be cut without losing pieces of the tissue interface <NUM> and without separation of the tissue interface <NUM>. In other embodiments, the dressing <NUM> may be placed proximate to the tissue site <NUM>.

The tissue interface <NUM> can be placed in, over, on, or otherwise proximate to the tissue site <NUM>. The manifold layer <NUM> may be cut to size, folded, and rolled into the tissue site <NUM>. In some embodiments, the cover <NUM> may be placed over the manifold layer <NUM>. The cover <NUM> may be configured to create a sealed space containing the manifold layer <NUM> at the tissue site. The negative-pressure source <NUM> may be configured to be positioned in fluid communication with the sealed space and the manifold layer <NUM> through the cover <NUM>.

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

The adhesive <NUM> can be disposed on a bottom side of the cover <NUM>, and the adhesive <NUM> may pressed onto the cover <NUM> and epidermis <NUM> (or other attachment surface) to fix the dressing <NUM> in position and to seal the tissue interface <NUM> over the patient. In some embodiments, the adhesive <NUM> can be disposed only around edges of the cover <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. In some examples, the tissue interface <NUM> can be applied to the tissue site 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 position of the aperture <NUM> may be off-center or adjacent to an end or edge of the cover <NUM>. In other examples, the aperture <NUM> may be centrally disposed. 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>. The dressing <NUM> may be a bolster to aid in closing the tissue site <NUM>. The tissue interface <NUM> may contract in response to the application of negative pressure. In some embodiments, the manifold layer <NUM> of the tissue interface <NUM> is configured to contract. For example, under an applied negative pressure, the manifold layer <NUM> may contract radially in all directions.

<FIG> is a table illustrating an improved percentage of collapse of the tissue interface <NUM> according to this disclosure. Testing was performed on manifolds comprising a plurality of holes shaped like an oval, a star, a parallelogram, and a parallelogram with overlapping perforations. The testing measured the percent collapse of each of the manifolds under negative pressure (about -<NUM> Hg). The percentage of collapse is generally between about <NUM>% and <NUM>% of the initial area of the manifold. However, the percentage of collapse of a manifold with holes shaped like a parallelogram and a manifold with holes shaped like a parallelogram with overlapping perforations in accordance with this disclosure resulted in a collapse of <NUM>% and <NUM>%, respectively, higher than any other tested shapes or patterns.

<FIG> is a graph of negative pressure measured at four locations in a sealed environment formed by the dressing <NUM> of <FIG> plotted versus time, illustrating a range of reduced-pressure being maintained at all four locations. In the testing apparatus associated with the graph of <FIG>, the tissue interface <NUM> was fluidly coupled to a system capable of providing both negative-pressure therapy and instillation therapy. The tissue interface <NUM> was monitored during negative-pressure and instillation cycles by pressure sensors in fluid communication with the sealed environment at four locations: an instillation port; a dressing interface, such as the dressing interface <NUM>; a middle port disposed at the center of the tissue interface <NUM>; and an upper port disposed on the tissue interface <NUM> at an opposite side from the dressing interface <NUM>. During testing, fluid was infused at a rate of about <NUM> cc/hour and continuous negative pressure at about -<NUM> Hg was suppled at the dressing interface.

A method of manufacturing the manifold layer <NUM> is also disclosed. The method may comprise cutting a plurality of patterns into a foam layer and felting a foam. The method may further comprise perforating the foam layer along the plurality of patterns. In some embodiments, a cutting tool may be used to perforate the foam layer. The method may further include extracting the perforated material from the foam layer. In some embodiments, a high flow vacuum system may be used to extract the perforated material from the foam layer.

The systems, apparatuses, and methods described herein may provide significant advantages. The manifold layer <NUM> is able to collapse radially in all directions, is easily conformable, and can be worn for an extended period of time without experiencing tissue in-growth. Specifically, the plurality of holes <NUM> shaped like parallelograms in the manifold layer <NUM> enable the manifold layer <NUM> to collapse radially in all directions. This improves fluid and pressure manifolding through the manifold layer <NUM> to the tissue interface <NUM>. The radial collapse also draws the edges of the wound together and reduces the overall wound size.

The plurality of holes <NUM> in the manifold layer <NUM> make the manifold layer <NUM> easier to size, with or without tools. The manifold layer <NUM> is also flexible and conformable to enable a user to push the manifold layer <NUM> into deep and undermined spaces.

Additionally, the manifold layer <NUM> prevents tissue ingrowth. The manifold layer <NUM> also has a higher tensile strength than standard foam fillers to prevent materials from being left in the wound after the manifold layer <NUM> is removed.

Claim 1:
A dressing for treating a tissue site, comprising;
a manifold layer including a first side configured to face the tissue site, a second side opposite the first side, and a thickness between the first side and the second side, the manifold layer comprising foam including a <NUM>% compression load deflection between about <NUM> kPa to about <NUM> kPa (about <NUM> to about <NUM> pounds per square inch) and pores having an average pore size between about <NUM> microns to about <NUM> microns; and
a plurality of holes extending through the first side, the second side, and the thickness of the manifold layer and being positioned at least in a first row and a second row that is offset from the first row, each of the plurality of holes including a hole length that is longer than and perpendicular to a hole width, the hole length of at least one of the holes in the first row being positioned at an angle relative to the hole length of another of the holes in the second row.