Patent Description:
Negative-pressure therapy may provide a number of benefits, including migration of epithelial and subcutaneous tissues, improved blood flow, and micro deformation of tissue at a wound site.

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.

While the clinical benefits of negative-pressure therapy and/or instillation therapy are widely known, improvements to therapy systems, components, and processes may benefit healthcare providers and patients. <CIT> discloses a method and apparatus for disrupting tissue using a modulating layer and a macro-column layer, forming nodules under negative pressure. <CIT> discloses a wound treatment system with a foam structure wound insert, having pores of varying cross-sectional areas, and methods for its use. <CIT> discloses devices, systems, and methods for providing negative-pressure therapy to multiple tissue sites simultaneously using a single pressure source.

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

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

The therapy system <NUM> may include a source or supply of negative pressure, such as a negative-pressure source <NUM>, and one or more distribution components. A distribution component is preferably detachable and may be disposable, reusable, or recyclable. A dressing, such as a dressing <NUM>, and a fluid container, such as a container <NUM>, are examples of distribution components that may be associated with some examples of the therapy system <NUM>. As illustrated in the example of <FIG>, the dressing <NUM> may comprise or consist essentially of a tissue interface <NUM>, a cover <NUM>, or both in some embodiments.

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 container <NUM> may comprise a canister having a collection chamber, a first inlet fluidly coupled to the collection chamber and a first outlet fluidly coupled to the collection chamber and adapted to receive negative pressure from a source of negative pressure.

The tissue interface <NUM> may further promote granulation at a tissue site when pressure within the sealed therapeutic environment is reduced. Any or all of the surfaces of the tissue interface <NUM> may have an uneven, coarse, or jagged profile that can induce microstrains and stresses at a tissue site if negative pressure is applied through the tissue interface <NUM>.

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.

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

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

In some embodiments, the cover <NUM> may provide a bacterial barrier and protection from physical trauma. The cover <NUM> may also be constructed from a material that can reduce evaporative losses and provide a fluid seal between two components or two environments, such as between a therapeutic environment and a local external environment. The cover <NUM> may comprise or consist of, for example, an elastomeric film or membrane that can provide a seal adequate to maintain a negative pressure at a tissue site for a given negative-pressure source. The cover <NUM> may have a high moisture-vapor transmission rate (MVTR) in some applications. For example, the MVTR may be at least <NUM> grams per square meter per twenty-four hours in some embodiments, measured using an upright cup technique according to ASTM E96/E96M Upright Cup Method at <NUM> and <NUM>% relative humidity (RH). In some embodiments, an MVTR up to <NUM>,<NUM> grams per square meter per twenty-four hours may provide effective breathability and mechanical properties.

In some example embodiments, the cover <NUM> may be a polymer drape, such as a polyurethane film, that is permeable to water vapor but impermeable to liquid. Such drapes typically have a thickness in the range of <NUM>-<NUM> microns. For permeable materials, the permeability generally should be low enough that a desired negative pressure may be maintained. The cover <NUM> may comprise, for example, one or more of the following materials: polyurethane (PU), such as hydrophilic polyurethane; cellulosics; hydrophilic polyamides; polyvinyl alcohol; polyvinyl pyrrolidone; hydrophilic acrylics; silicones, such as hydrophilic silicone elastomers; natural rubbers; polyisoprene; styrene butadiene rubber; chloroprene rubber; polybutadiene; nitrile rubber; butyl rubber; ethylene propylene rubber; ethylene propylene diene monomer; chlorosulfonated polyethylene; polysulfide rubber; ethylene vinyl acetate (EVA); co-polyester; and polyether block polymide copolymers. Such materials are commercially available as, for example, Tegaderm® drape, commercially available from <NUM> Company, Minneapolis Minnesota; polyurethane (PU) drape, commercially available from Avery Dennison Corporation, Pasadena, California; polyether block polyamide copolymer (PEBAX), for example, from Arkema S. , Colombes, France; and Inspire <NUM> and Inpsire <NUM> polyurethane films, commercially available from Expopack Advanced Coatings, Wrexham, United Kingdom. In some embodiments, the cover <NUM> may comprise INSPIRE <NUM> having an MVTR (upright cup technique) of <NUM>/m<NUM>/<NUM> hours and a thickness of about <NUM> microns.

An attachment device may be used to attach the cover <NUM> to an attachment surface, such as undamaged epidermis, a gasket, or another cover. The attachment device may take many forms. For example, an attachment device may be a medically-acceptable, pressure-sensitive adhesive configured to bond the cover <NUM> to epidermis around a tissue site. In some embodiments, for example, some or all of the cover <NUM> may be coated with an adhesive, such as an acrylic adhesive, which may have a coating weight of about <NUM>-<NUM> grams per square meter (g. Thicker adhesives, or combinations of adhesives, may be applied in some embodiments to improve the seal and reduce leaks. Other example embodiments of an attachment device may include a double-sided tape, paste, hydrocolloid, hydrogel, silicone gel, or organogel.

The 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 a position in a fluid path relatively closer to a source of negative pressure or further away from a source of positive pressure. Conversely, the term "upstream" implies a position relatively further away from a source of negative pressure or closer to a source of positive pressure. Similarly, it may be convenient to describe certain features in terms of fluid "inlet" or "outlet" in such a frame of reference. This orientation is generally presumed for purposes of describing various features and components herein. However, the fluid path may also be reversed in some applications, such as by substituting a positive-pressure source for a negative-pressure source, and this descriptive convention should not be construed as a limiting convention.

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>.

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

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

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

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

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

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

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

Furthermore, some dressings for treating a tissue site may comprise a tissue interface configured to mechanically debride slough and loosen tissue. The tissue interface may rely primarily on mechanical action in a single direction or along one primary axis. For example, the tissue interface may collapse vertically into the wound and provide only some lateral movement to debride the tissue site under negative pressure. While a tissue interface having mechanical action along a primary axis can provide beneficial debridement treatment, there is a desire to further increase the effectiveness of the tissue interface for debridement treatment.

These limitations and others may be addressed by the therapy system <NUM>, which can provide negative-pressure therapy, instillation therapy, and disruption of debris. In some embodiments, the therapy system <NUM> can provide mechanical movement at a surface of the tissue site in combination with cyclic delivery and dwell of topical solutions to help solubilize debris. For example, a negative-pressure source may be fluidly coupled to a tissue site to provide negative pressure to the tissue site for negative-pressure therapy. In some embodiments, a fluid source may be fluidly coupled to a tissue site to provide therapeutic fluid to the tissue site for instillation therapy. In some embodiments, the therapy system may include a tissue interface comprised of a felted foam and having a plurality of ovular-shaped pores. The ovular-shaped pores may be preferentially aligned within the tissue interface. For example, the ovular-shaped pores may be aligned within the tissue interface so that when the tissue interface is positioned at a tissue site, the ovular-shaped pores resist vertical compression under negative pressure and are susceptible to horizontal compression. The ovular-shaped pores may enable the tissue interface to collapse in the horizontal direction to provide a second axis of mechanical action to disrupt debris at the tissue site. Following the disruption of the debris, negative-pressure therapy, instillation therapy, and other processes may be used to remove the debris from the tissue site. In some embodiments, the therapy system <NUM> may be used in conjunction with other tissue removal and debridement techniques. For example, the therapy system <NUM> may be used prior to enzymatic debridement to soften the debris. In another example, other mechanical debridement may be used to remove a portion of the debris at the tissue site, and the therapy system <NUM> may then be used to remove the remaining debris while reducing the risk of trauma to the tissue site.

<FIG> is an assembly view of an example of the dressing <NUM> of <FIG>, illustrating additional details that may be associated with some embodiments. In some embodiments, the dressing <NUM> may comprise the tissue interface <NUM>. The tissue interface <NUM> may have a first surface <NUM> and a second surface <NUM>. The first surface <NUM> may configured to face a tissue site. The second surface <NUM> may be opposite the first surface <NUM>. The tissue interface <NUM> may have a substantially uniform thickness <NUM> extending from the first surface <NUM> to the second surface <NUM>. In some embodiments, the thickness <NUM> may be between about <NUM> and about <NUM>. In other embodiments, the thickness <NUM> may be thinner or thicker than the stated range as needed for the particular application of the dressing <NUM>. In some embodiments, the tissue interface <NUM> may have a plurality of apertures or holes, such as a plurality of holes <NUM>, extending into the tissue interface <NUM> from the first surface <NUM> toward the second surface <NUM>.

In some embodiments, the dressing <NUM> may include a fluid conductor <NUM> and a fluid port, such as a dressing interface <NUM>. In some embodiments, the fluid conductor <NUM> may be a flexible tube. In some embodiments, the fluid conductor may comprise a first end <NUM> and a second end <NUM>. The first end <NUM> of the fluid conductor <NUM> may be configured to be fluidly coupled to the dressing interface <NUM> and the second end <NUM> of the fluid conductor <NUM> may be configured to be fluidly coupled to the negative-pressure source <NUM> (not shown).

In some embodiments, the dressing interface <NUM> may be an elbow connector, as shown in the example of <FIG>, which can be coupled to the cover <NUM> and fluidly coupled to the tissue interface <NUM>. In some embodiments, the dressing interface <NUM> may be placed over an aperture <NUM> in the cover <NUM> to provide a fluid path between the fluid conductor <NUM> and the tissue interface <NUM>. In other embodiments, the first end <NUM> of the fluid conductor <NUM> may be inserted directly through the cover <NUM> into the tissue interface <NUM>. The cover <NUM> may be configured to be disposed over the tissue interface <NUM> to create a sealed space. In some embodiments, the cover <NUM> may be configured to be disposed over the second surface <NUM> of the tissue interface <NUM>. In some embodiments, the cover <NUM> may include the aperture <NUM>. In other embodiments, the aperture <NUM> may be cut into the cover <NUM> before or after positioning the cover <NUM> over the tissue interface <NUM>. In some embodiments, the aperture <NUM> may be centrally disposed in the cover <NUM>. In other embodiments, the position of the aperture <NUM> may be off-center or adjacent to an end or edge of the cover <NUM>.

In some embodiments, the tissue interface <NUM> may be provided as a portion of an assembly or kit for forming the dressing <NUM>. In other embodiments, the tissue interface <NUM> may be provided separately from the cover <NUM>, the fluid conductor <NUM>, and the dressing interface <NUM> for assembly of the dressing <NUM> at the point of use.

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

<FIG> is a plan view of the tissue interface <NUM> of <FIG>, illustrating additional details that may be associated with some embodiments. In some embodiments, the plurality of holes <NUM> may be distributed about the first surface <NUM> of the tissue interface <NUM>. The plurality of holes <NUM> can be evenly distributed. In other embodiments, the plurality of holes <NUM> may be preferentially disposed in a portion of the tissue interface <NUM>.

In some embodiments, the plurality of holes <NUM> extending into the tissue interface <NUM> may form walls <NUM>. In some embodiments, an exterior surface of the walls <NUM> may be parallel to sides of the tissue interface <NUM>. In other embodiments, an interior surface of the walls <NUM> may be generally perpendicular to the first surface <NUM> and the second surface <NUM> of the tissue interface <NUM>. The interior surface or surfaces of the walls <NUM> may form a perimeter <NUM> of each hole. In some embodiments, the holes <NUM> may have a circular shape. In other embodiments, each hole <NUM> of the plurality of holes <NUM> may be polygonal, ovular, or amorphous in shape. In some embodiments, the holes <NUM> may have average effective diameters between about <NUM> and about <NUM>. Preferably, each hole <NUM> of the plurality of holes <NUM> may have an average effective diameter of about <NUM>.

In some embodiments, the tissue interface <NUM> may comprise a length <NUM> and a width <NUM>. The length <NUM> of the tissue interface <NUM> may be between about <NUM> and about <NUM>. The width <NUM> of the tissue interface <NUM> may be between about <NUM> and about <NUM>. In some embodiments, the tissue interface <NUM> may have a contraction axis <NUM> positioned parallel to the length <NUM>. The contraction axis <NUM> may also be positioned parallel to the first surface <NUM> and the second surface <NUM>. In some embodiments, the contraction axis <NUM> may be used to refer to a desired direction of contraction of the tissue interface <NUM>. For example, the desired direction of contraction of the tissue interface <NUM> may be perpendicular to the contraction axis <NUM>. In other embodiments, the desired direction of contraction may be parallel to the contraction axis <NUM>. In other embodiments, the desired direction of contraction may be at a non-perpendicular angle to the contraction axis <NUM>. In still other embodiments, the tissue interface <NUM> may not have a desired direction of contraction.

<FIG> is a sectional view taken along line <NUM>-<NUM> of <FIG>, illustrating additional details that may be associated with some embodiments. In some embodiments, the plurality of holes <NUM> may extend through the thickness <NUM> of the tissue interface <NUM> from the first surface <NUM> to the second surface <NUM>. The plurality of holes <NUM> may have a depth that is substantially equal to the thickness <NUM> of the tissue interface <NUM>. In other embodiments, the plurality of holes <NUM> may comprise a plurality of blind holes or apertures. For example, the plurality of holes <NUM> may extend from the first surface <NUM> toward the second surface <NUM> at a depth less than the thickness <NUM> of the tissue interface <NUM>. The depth of the plurality of blind holes or apertures may be between about <NUM> and about <NUM>.

<FIG> is a detail view of the tissue interface <NUM> of <FIG>, illustrating additional details that may be associated with some embodiments. The tissue interface <NUM> may be formed from a dressing material such as a foam. For example, cellular foam, open-cell foam, reticulated foam, or porous tissue collections, may be used to form the tissue interface <NUM>. The tissue interface <NUM> may comprise a plurality of pores <NUM>. In some embodiments, each of the pores <NUM> of the tissue interface <NUM> may have pore sizes or average effective diameters in a range of about <NUM> microns to about <NUM> microns. In other embodiments, the pores <NUM> may have pore sizes or average effective diameters in a range of about <NUM> microns to about <NUM> microns. The tensile strength of the tissue interface <NUM> may 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 tissue interface <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 tissue interface <NUM> may be at least <NUM> pounds per square inch. The tissue interface <NUM> may have a tear strength of at least <NUM> pounds per inch. In one non-limiting example, the tissue interface <NUM> may be an open-cell, reticulated polyurethane foam such as V. ® GRANUFOAM™ Dressing available from Kinetic Concepts, Inc. of San Antonio, Texas; in other embodiments the tissue interface <NUM> may be an open-cell, reticulated polyurethane foam such as a V. VERAFLO™ dressing, also available from Kinetic Concepts, Inc. , of San Antonio, Texas. In other embodiments, the tissue interface <NUM> may be formed of an un-reticulated open-cell foam.

In some embodiments, the tissue interface <NUM> may be formed from a foam that is mechanically or chemically compressed, often as part of a thermoforming process, to increase the density of the foam at ambient pressure. A foam that is mechanically or chemically compressed may be referred to as a compressed foam or a felted foam. A felted foam may be characterized by a firmness factor (FF), 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. For example, a firmness factor (FF) of <NUM> may refer to a compressed foam having a density at ambient pressure that is five times greater than a density of the same foam in an uncompressed state at ambient pressure. Generally, 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> and preferably about <NUM> to about <NUM>. For example, the firmness factor of the tissue interface <NUM> felted foam may be about <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 three-fold density increase and compress to about a third of its original thickness.

In some embodiments, a compressed foam may be a compressed V. ® GRANUFOAM™ Dressing. ® GRANUFOAMTM Dressing may have a density of about <NUM> grams per centimeter<NUM> (g/cm3) in its uncompressed state. ® GRANUFOAM™ Dressing is compressed to have a firmness factor (FF) of <NUM>, the V. ® GRANUFOAM™ Dressing may be compressed until the density of the V. ® GRANUFOAM™ Dressing is about <NUM>/cm<NUM>. ® VERAFLO™ dressings may also be compressed to form a compressed foam having a firmness factor (FF) up to <NUM>. For example, V. ® VERAFLO™ Dressing, may have a density between about <NUM> pounds per foot<NUM> (lb/ft<NUM>) or <NUM> grams per centimeter<NUM> (g/cm3) and about <NUM> lb/ft<NUM> or <NUM>/cm<NUM>. ® VERAFLO™ Dressing is compressed to have a firmness factor (FF) of <NUM>, the V. ® VERAFLO™ Dressing may be compressed until the density of the V. ® VERAFLO™ Dressing is between about <NUM>/cm<NUM>and about <NUM>/cm<NUM>.

Felting comprises a thermoforming process that permanently compresses a foam to increase the density of the foam while maintaining interconnected pathways. For example, felting may be performed by applying heat and pressure to a dressing material that is porous such as a 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. In some embodiments, the direction of compression may be parallel to the thickness of the foam block. For example, the direction of the force applied to a blank of the dressing material may be parallel to the thickness and perpendicular to the surface the force is acting on. In other embodiments, the direction of compression may be perpendicular to the thickness of the blank of the dressing material. For example, the direction of the force applied to a foam blank of the dressing material may act on the thickness and be parallel to a surface perpendicular to the thickness.

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 dressing 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 dressing 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 dressing material or a portion of the dressing material.

Generally, if a compressed foam is subjected to negative pressure, the compressed foam exhibits less deformation than a similar uncompressed foam. If the tissue interface <NUM> is formed of a compressed foam, the thickness <NUM> of the tissue interface <NUM> may deform less than if the tissue interface <NUM> is formed of a comparable uncompressed foam. The decrease in deformation may be caused by the increased stiffness as reflected by the firmness factor (FF). If subjected to the stress of negative pressure, the tissue interface <NUM> that is formed of compressed foam may flatten less than the tissue interface <NUM> that is formed from uncompressed foam. Consequently, if negative pressure is applied to the tissue interface <NUM>, the stiffness of the tissue interface <NUM> in the direction parallel to the thickness <NUM> of the tissue interface <NUM> allows the tissue interface <NUM> to be more compliant or compressible in other directions, e.g., a direction perpendicular to the thickness <NUM>. The foam material used to form a compressed foam may be either hydrophobic or hydrophilic. The foam material used to form a compressed foam may also be either reticulated or un-reticulated.

The 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 pore 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 dressing material. Further, the pores <NUM> in the felted structure may be smaller than the pores throughout any unfinished or non-felted surface or portion of the dressing material. In some examples, the felted structure may be applied to all surfaces or portions of the dressing material. Further, in some examples, the felted structure may extend into or through an entire thickness of the dressing material such that the all of the dressing material is felted.

The pore size of a foam material may vary according to needs of the tissue interface <NUM> and the amount of compression of the foam. For example, in some embodiments, the pores of an uncompressed foam may have pore sizes in a range of about <NUM> microns to about <NUM> microns. If the same foam is compressed, the pores of the compressed foam may have pore sizes that are smaller than when the foam is in its uncompressed state.

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 the plurality of pores <NUM> in the foam may be deformed during the felting process. The deformed struts can decrease the elasticity of the foam. The deformed struts can also cause a flattening in pore shapes. For example, an un-felted foam may have a plurality of pores having a substantially circular or spherical shape. By felting the foam, the pores <NUM> of the tissue interface <NUM> may have a non-circular shape. In some embodiments, each of the plurality of pores <NUM> may have a generally elliptical or ovoid shape.

The deformation of the struts and pore shape can be applied preferentially. For example, the pores <NUM> can be deformed so that a shape of each of the pores <NUM> is oriented in a particular direction within the tissue interface <NUM>. In some embodiments, the orientation of the pores <NUM> can be controlled by felting the dressing material. For example, the pores <NUM> can be deformed so that the deformation of the pores <NUM> is oriented with respect to a surface of the tissue interface <NUM> that is intended to contact the tissue site. In some embodiments, the pores <NUM> can be preferentially deformed with respect to the first surface <NUM>. For example, a blank of the dressing material forming the tissue interface <NUM> can be felted by applying heat and compression to the thickness <NUM>. The direction of the force applied to the dressing material is parallel to the first surface <NUM> of the tissue interface <NUM>.

<FIG> is a detail view illustrating additional details that may be associated with some embodiments of the plurality of pores <NUM> of <FIG>. In <FIG>, a single pore of the plurality of pores <NUM> of the tissue interface <NUM> is shown. In some embodiments, the tissue interface <NUM> may have a first axis <NUM> and a second axis <NUM>. The first axis <NUM> may be parallel to the thickness <NUM> and perpendicular to the first surface <NUM> and the second surface <NUM> of the tissue interface <NUM>. The second axis <NUM> may be perpendicular to the first axis <NUM> and parallel to the first surface <NUM> and the second surface <NUM> of the tissue interface <NUM>.

In some embodiments, each of the plurality of pores <NUM> may be oriented at an angle to the first surface <NUM> and the second surface <NUM> of the tissue interface <NUM>. For example, each pore <NUM> of the plurality of pores <NUM> may have a major axis <NUM> extending through a center of the pore <NUM>. The major axis <NUM> may be oriented parallel to the first axis <NUM> and perpendicular to the second axis <NUM>. In some embodiments, the major axis <NUM> may be oriented perpendicular to the first surface <NUM> and the second surface <NUM> and parallel to the thickness <NUM>. In some embodiments, the major axis <NUM> may be oriented at an angle to the second axis <NUM>. For example, the angle between the second axis <NUM> and the major axis <NUM> may be about <NUM>°. In some embodiments, each pore <NUM> of the plurality of pores <NUM> may have a pore length <NUM> extending generally parallel to the major axis <NUM> and a pore width <NUM> extending generally perpendicular to the major axis <NUM>. In some embodiments, the pore length <NUM> of the plurality of pores <NUM> may be greater than the pore width <NUM>.

The pores <NUM> may be oriented by the manufacturing process. During felting, a force <NUM> can be applied to a foam blank of the dressing material. The force <NUM> can change the shape of the pore <NUM> by forcing surfaces of the pore <NUM> perpendicular to the force <NUM> toward each other and pushing surfaces parallel to the force <NUM> away from each other. As a result, the pore <NUM> stretches parallel to the first axis <NUM> and compresses parallel to the second axis <NUM>. The heat applied during the felting process can set the pore <NUM> in the shape formed by the force <NUM>. In other embodiments, the force <NUM> can be applied at a non-normal angle to the first axis <NUM>, causing the pore <NUM> to compress at an angle to the first axis <NUM> and stretch at an angle to the first axis <NUM>. Generally, the pore width <NUM> of the pore <NUM> may be parallel to the direction of the force <NUM> and the pore length <NUM> of the pore <NUM> may be perpendicular to the direction of the force <NUM>.

In some embodiments, the orientation of the plurality of pores <NUM> may allow the plurality of pores <NUM> to compress more in a direction parallel to the second axis <NUM> and resist compression in a direction parallel to the first axis <NUM>. For example, each of the plurality of pores <NUM> may be configured to contract in a direction perpendicular to the major axis <NUM>. In some embodiments, each of the plurality of pores <NUM> may be configured to contract in a direction parallel to the first surface <NUM> and the second surface <NUM>. In some embodiments, each of the plurality of pores <NUM> may be configured to contract in all directions toward the major axis <NUM>. In some embodiments, the pores <NUM> may resist collapse more in a direction parallel to the major axis <NUM> than in a direction perpendicular to the major axis <NUM>. As a result, the tissue interface <NUM> formed form the pores <NUM> may collapse laterally under negative pressure. See, for example, the following experimental data.

The following samples were provided: three unfelted Granufoam blocks with a starting size of <NUM> (height) by <NUM> (width) and approximately spherical pores, three 3X felted (e.g., firmness factor of <NUM>) Granufoam blocks with starting size of <NUM> (height) by <NUM> (width) and ovoid pores oriented with the major axis approximately parallel to the thickness (e.g., height), and three 5X felted (e.g., firmness factor of <NUM>) Granufoam blocks with starting size of <NUM> (height) by <NUM> (width) and ovoid pores oriented with the major axis approximately parallel to the thickness (e.g., height). Negative pressure of approximately -<NUM> mmHg was applied to all three samples, and the height and width measurements under applied negative pressure were recorded as follows:.

In some embodiments, the felted foam with ovoid pores oriented with the major axis approximately parallel to the thickness (e.g., height) may draw down in thickness under applied negative pressure approximately ½ or less the amount compared to similar unfelted foam. For example, the felted foam with ovoid pores oriented with the major axis approximately parallel to the thickness may draw down in thickness under applied negative pressure approximately ½ - <NUM>/<NUM> the amount compared to similar unfelted foam. In some embodiments, the felted foam with ovoid pores oriented with the major axis approximately parallel to the thickness may have lateral contraction under applied negative pressure of approximately <NUM> or more times greater than the amount compared to similar unfelted foam. For example, the felted foam with ovoid pores oriented with the major axis approximately parallel to the thickness may have lateral contraction under applied negative pressure which is approximately <NUM> - <NUM> times greater than the amount compared to similar unfelted foam.

In some embodiments, resistance to contraction in thickness due to orientation of the ovoid pores may maintain a surface area that will transmit a higher lateral force under applied negative pressure as compared to the lateral force from similar unfelted foam. For example, 3X felted foam (e.g. foam with a firmness factor of <NUM>) with ovoid pores oriented approximately parallel to the thickness may have a lateral force which is approximately <NUM>-<NUM>% better than similar unfelted foam, under applied negative pressure. Similarly, if a specific lateral force is desired under applied negative pressure, then that amount of lateral force may be generated using less negative pressure when felted foam with ovoid pores oriented approximately parallel to the thickness is used instead of similar unfelted foam.

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

<FIG> is a plan view illustrating additional details of the plurality of holes <NUM> of the tissue interface <NUM> of <FIG>. As illustrated in <FIG>, the tissue interface <NUM> may include the plurality of holes <NUM> aligned in parallel rows to form an array. The array of holes <NUM> may include a first row <NUM> of the holes <NUM>, a second row <NUM> of the holes <NUM>, and a third row <NUM> of the holes <NUM>. In some embodiments, a width of the wall <NUM> between the perimeters <NUM> of adjacent holes <NUM> in a row, such as the first row <NUM>, may be between about <NUM> about <NUM>. In some embodiments, the width of the wall <NUM> between perimeters <NUM> of adjacent holes may preferably be <NUM>.

In some embodiments, a line connecting the centers of adjacent rows may form a strut angle (SA) with the first orientation line <NUM>. For example, a first hole 206A in the first row <NUM> may have a center 704A, and a second hole 206B in the second row <NUM> may have a center 704B. A strut line <NUM> may connect the center 704A with the center 704B. The strut line <NUM> may form an angle <NUM> with the first orientation line <NUM>. The angle <NUM> may be the strut angle (SA) of the tissue interface <NUM>. In some embodiments, the strut angle (SA) may be less than about <NUM>°. In other embodiments, the strut angle (SA) may be between about <NUM>° and about <NUM>° relative to the first orientation line <NUM>. In other embodiments, the strut angle (SA) may be about <NUM>° from the first orientation line <NUM>. Generally, as the strut angle (SA) decreases, a stiffness of the tissue interface <NUM> in a direction parallel to the first orientation line <NUM> may increase. Increasing the stiffness of the tissue interface <NUM> parallel to the first orientation line <NUM> may increase the compressibility of the tissue interface <NUM> perpendicular to the first orientation line <NUM>. Consequently, if negative pressure is applied to the tissue interface <NUM>, the tissue interface <NUM> may be more compliant or compressible in a direction perpendicular to the first orientation line <NUM>. By increasing the compressibility of the tissue interface <NUM> in a direction perpendicular to the first orientation line <NUM>, the tissue interface <NUM> may collapse to apply the lateral force <NUM> to the tissue site as described in more detail below.

In some embodiments, the centers <NUM> of the holes <NUM> in alternating rows, for example, the center 704A of the first hole 206A in the first row <NUM> and a center 704C of a hole 206C in the third row <NUM>, may be spaced from each other parallel to the second orientation line <NUM> by a length <NUM>. In some embodiments, the length <NUM> may be greater than an effective diameter of the hole <NUM>. If the centers <NUM> of holes <NUM> in alternating rows are separated by the length <NUM>, the exterior surface of the walls <NUM> parallel to the first orientation line <NUM> may be considered continuous. Generally, the exterior surface of the walls <NUM> may be continuous if the exterior surface of the walls <NUM> do not have any discontinuities or breaks between holes <NUM>. In some embodiments, the length <NUM> may be between about <NUM> and about <NUM>.

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

<FIG> is a plan view illustrating additional details of the tissue interface <NUM> of <FIG> in a contracted state. If the tissue interface <NUM> is positioned on the tissue site, the tissue interface <NUM> may generate the lateral force <NUM> perpendicular to the contraction axis <NUM>, contracting the tissue interface <NUM> as shown. In operation, negative pressure is supplied to the sealed space with the negative-pressure source <NUM>. In response to the supply of negative pressure, the tissue interface <NUM> contracts from the relaxed position illustrated in <FIG> to the contracted positioned illustrated in <FIG>. When the negative pressure is removed, for example, by venting the negative pressure from the sealed space, the tissue interface <NUM> expands back to the relaxed position. If the tissue interface <NUM> is cycled between the contracted and relaxed positioned of <FIG> and <FIG>, respectively, the first surface <NUM> of the tissue interface <NUM> may disrupt debris on the tissue site by rubbing the debris from the tissue site. The edges of the holes <NUM> formed by the first surface <NUM> and the interior surfaces or transverse surfaces of the walls <NUM> can form cutting edges that can disrupt the debris in the tissue site, allowing the debris to exit though the holes <NUM>. In some embodiments, the cutting edges are defined by the perimeter <NUM> where each hole <NUM> intersects the first surface <NUM>.

<FIG> is a detail view illustrating additional details that may be associated with the plurality of pores <NUM> of the tissue interface <NUM> of <FIG> in a contracted state or a contracted position. In response to the supply of negative pressure, the plurality of pores <NUM> may collapse from the relaxed positioned illustrated in <FIG> to the contracted position illustrated in <FIG>. For example, the plurality of pores <NUM> may be configured to collapse in a direction parallel to the first surface <NUM> and the second surface <NUM> of the tissue interface <NUM>, as indicated by the lateral force <NUM>. The ovular shape of the plurality of pores <NUM> combined with the plurality of holes <NUM> allows the tissue interface <NUM> to contract laterally, as indicated by the lateral force <NUM>, debriding tissue. In some embodiments, the lateral force <NUM> may be perpendicular to the contraction axis <NUM>. In still other embodiments, the lateral force <NUM> may be generated at an angle to the contraction axis <NUM>.

<FIG> is a sectional view of a portion of the dressing <NUM> of <FIG>, illustrating additional details that may be associated with some embodiments. The tissue interface <NUM> may be placed at a tissue site <NUM> having debris <NUM> covering subcutaneous tissue <NUM>. For example, a clinician may place the tissue interface <NUM> at the tissue site <NUM>. In some embodiments, the length <NUM> and the width <NUM> of the tissue interface <NUM> may be greater than an opening of the tissue site <NUM>. The tissue interface <NUM> may be sized to permit the tissue interface <NUM> to be passed through the opening of the tissue site <NUM> to be placed adjacent to the debris <NUM>. Sizing can include removing a portion of the tissue interface <NUM> for example, by cutting, tearing, melting, dissolving, vaporizing, or otherwise separating a portion of the tissue interface <NUM> from remaining portions of the tissue interface <NUM>. Following sizing and placement of the tissue interface <NUM> at the tissue site <NUM>, the cover <NUM> may be placed over the tissue interface <NUM> to provide a sealed environment for the application of negative-pressure therapy or instillation therapy.

<FIG> is a sectional view of a portion of the dressing <NUM> of <FIG> during negative-pressure therapy, illustrating additional details that may be associated with some embodiments. For example, <FIG> may illustrate a moment in time where a pressure in the sealed environment may be about -<NUM> Hg of negative pressure. In response to the application of negative pressure, the pores <NUM> of the tissue interface <NUM> oriented so that the pore length <NUM> of the pores <NUM> is parallel to the thickness <NUM> and the pore width <NUM> of the pores <NUM> is parallel to the first surface <NUM> may resist collapse. In response, the tissue interface <NUM> may not compress or may compress minimally. Preferably, the thickness <NUM> remains substantially the same. In other embodiments, the thickness <NUM> of the tissue interface <NUM> during negative-pressure therapy may be slightly less than the thickness <NUM> of the tissue interface <NUM> if the pressure in the sealed environment is about the ambient pressure.

In some embodiments, negative pressure in the sealed environment can generate concentrated stresses in the tissue interface <NUM> and the debris <NUM> adjacent to the holes <NUM> in the tissue interface <NUM>. The concentrated stresses can cause macro-deformations of the debris <NUM> and the subcutaneous tissue <NUM> that draws portions of the debris <NUM> and the subcutaneous tissue <NUM> into the holes <NUM>. For example, as the holes <NUM> collapse in the direction parallel to the first surface <NUM> and the second surface <NUM> under negative pressure, portions of the subcutaneous tissue <NUM> and the debris <NUM> may be drawn into the holes <NUM> by a pinching action. Additionally, as the tissue interface <NUM> resists compression in the direction parallel to the thickness <NUM>, portions of the subcutaneous tissue <NUM> and the debris <NUM> may be drawn into the thickness <NUM> of the tissue interface <NUM> under negative pressure.

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

In some embodiments, the formation of the nodules <NUM> can cause the debris <NUM> to remain in contact with the tissue interface <NUM> during negative pressure therapy. For example, the nodules <NUM> may contact the sidewalls of the holes <NUM> of the tissue interface <NUM>. In some embodiments, formation of the nodules <NUM> may lift debris <NUM> and particulates off the surrounding tissue, operating in a piston-like manner to move debris <NUM> toward the cover <NUM> and out of the sealed environment.

In response to the return of the sealed environment to ambient pressure, the nodules <NUM> may leave the holes <NUM>, returning to the position shown in <FIG>. In some embodiments, repeated application of negative-pressure therapy and instillation therapy while the tissue interface <NUM> is disposed over the debris <NUM> may disrupt the debris <NUM>, allowing the debris <NUM> to be removed during dressing changes. In other embodiments, the tissue interface <NUM> may disrupt the debris <NUM> so that the debris <NUM> can be removed by negative pressure. In still other embodiments, the tissue interface <NUM> may disrupt the debris <NUM>, aiding removal of the debris <NUM> during debridement processes. With each cycle of therapy, the tissue interface <NUM> may form nodules <NUM> in the debris <NUM>. The formation of the nodules <NUM> and release of the nodules <NUM> by the tissue interface <NUM> during therapy may disrupt the debris. With each subsequent cycle of therapy, disruption of the debris <NUM> can be increased.

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

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

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

A method of manufacturing a dressing for a tissue site is also described herein, wherein some example embodiments include providing a dressing material having a surface configured to contact the tissue site. The dressing material may have a plurality of pores. In some embodiments, the dressing material may comprise an open-cell reticulated foam. The method may further comprise applying a compressive force to the dressing material at an angle to the surface, causing a permanent deformation of the plurality of pores. In some embodiments, the angle may be about <NUM>°. In some embodiments, applying the compressive force to the dressing material may comprise increasing a density of the dressing material. In some embodiments, the method may further comprise forming a plurality of holes in the dressing material. The plurality of holes may extend into the dressing material from the surface. In some embodiments, the plurality of holes may be formed in the dressing material after applying the compressive force to the dressing material. In some embodiments, the method may further comprise heating the dressing material.

In some embodiments, causing the permanent deformation of the plurality of pores may comprise forming a plurality of compressed pores. Forming a plurality of compressed pores may comprise compressing the pores from a generally circular shape to a generally ovular shape. In some embodiments, the method may further comprise orienting a major axis of the ovular-shaped pores perpendicular to the surface. In some embodiments, the plurality of compressed pores may be configured to collapse from a relaxed position to a contracted position in response to an application of negative pressure. In some embodiments, the plurality of compressed pores may be configured to collapse in a direction parallel to the surface.

Alternatively, other example embodiments may describe a system for providing negative-pressure therapy to a tissue site. The system can include a tissue interface, a sealing member configured to be disposed over the tissue interface to create a sealed space, and a negative pressure source fluidly coupled to the sealed space. In some embodiments, the sealing member may comprise a polymer film. In some embodiments, the sealing member may be configured to be coupled to the second surface of the tissue interface with an adhesive. The tissue interface can include a first surface configured to face the tissue site; a second surface opposite the first surface; a thickness extending from the first surface to the second surface; and a plurality of pores, each of the pores having an ovoid shape oriented at an angle to the first surface. In some embodiments, the angle may be about <NUM>°. In some embodiments, the plurality of pores may be configured to contract in a direction parallel to the first surface and the second surface.

A tissue interface for treating a tissue site, is also described herein, wherein the tissue interface can be formed by a process including providing a dressing material and applying a compressive force to the dressing material. The dressing material can have a surface configured to contact the tissue site and a plurality of pores. The compressive force can be applied to the dressing material at an angle to the surface. The compressive force can also cause permanent deformation of the plurality of pores. In some embodiments, applying a compressive force to the dressing material may include compressing the dressing material from a first thickness to a second thickness. In some embodiments, the first thickness may be greater than the second thickness.

A method of treating a tissue site is also described herein. Some example embodiments include applying a tissue interface to the tissue site. The tissue interface may comprise a first surface configured to face the tissue site, a second surface opposite the first surface, a thickness extending from the first surface to the second surface, and a plurality of pores having an elliptical shape and a major axis oriented perpendicular to the first surface and the second surface. In some embodiments, the plurality of pores are configured to contract in a direction parallel to the first surface and the second surface. The method further comprises covering the tissue interface with a cover to form a sealed space continuing the tissue interface, fluidly coupling a fluid conductor to the tissue interface, fluidly coupling a negative-pressure source to the fluid conductor, applying negative pressure from the negative pressure source to the tissue interface through the fluid conductor, and contracting the tissue interface from a first width to a second width in response to an application of negative pressure to the tissue interface. The second width may be less than the first width.

The systems, apparatuses, and methods described herein may provide significant advantages. For example, the embodiments described herein provide a tissue interface that can contract in a lateral direction, while resisting vertical compression. The lateral contraction and resistance to vertical compression can provide improved wound healing and cleansing. For example, the tissue interface can contract in a direction parallel to the surface of the tissue site, loosening slough and providing tissue debridement.

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 eliminated or 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 system for providing negative-pressure therapy to a tissue site, the system comprising:
a dressing for treating the tissue site, the dressing comprising a tissue interface (<NUM>) having:
a first surface (<NUM>) configured to face the tissue site;
a second surface (<NUM>) opposite the first surface;
a thickness (<NUM>) extending from the first surface (<NUM>) to the second surface (<NUM>) a plurality of holes (<NUM>) extending from the first surface (<NUM>) to the second surface (<NUM>); and
a plurality of pores, the plurality of pores having an elliptical shape and a major axis oriented perpendicular to the first surface and the second surface;
a cover layer (<NUM>) configured to be disposed over the tissue interface to create a sealed space; and
a negative pressure source (<NUM>) fluidly coupled to the sealed space;
wherein the plurality of pores are configured to contract in a direction parallel to the first surface (<NUM>) and the second surface (<NUM>);
wherein the tissue interface (<NUM>) comprises a felted foam.