Patent Description:
<CIT> concerns a peel and place dressing for thick exudate and instillation.

While the clinical benefits of negative-pressure therapy are widely known, improvements to therapy systems, components, and processes may benefit healthcare providers and patients.

New and useful systems and apparatuses for treating tissue in a negative-pressure therapy environment are set forth in the appended claims. Illustrative embodiments are also provided to enable a person skilled in the art to make and use the claimed subject matter.

For example, in some embodiments, negative pressure applied through a dressing including a manifold layer may provide negative-pressure therapy to a tissue site. The negative pressure may be effective to cause the manifold layer to exhibit radial collapse such that the area of one of more surfaces of the manifold layer, when subjected to negative pressure, decrease. For example, the radial collapse may be substantially due to collapse of one or more of the collapsible apertures present within the manifold layer. In some embodiments, the radial collapse exhibited by the manifold layer <NUM> may have the effect of drawing the edges of the tissue site (e.g., a wound) together, for example, toward the center, which may help to reduce edema and/or to apply load to the edges of the wound, thereby improving the effectiveness of the therapy.

Negative pressure applied through a dressing including a manifold layer is formed from a closed-cell foam, such as an expanded foam. For example, the particular process by which the expanded foam is made may allow additives and modifiers, for example, an antimicrobial materials and/or a superabsorbent polymer, to be incorporated into and made integral to the polymeric material that forms the expanded foam. The incorporation of an antimicrobial materials and/or a superabsorbent polymer into an expanded foam may provide unique and beneficial properties not associated with conventional foams. Additionally, the use of an expanded foam as the manifold layer may also decrease the opportunity for any in-growth of tissue into the foam during healing of a wound or other tissue site.

In some embodiments is a dressing for treating a tissue site with negative pressure. The dressing may comprise a fluid management layer comprising a polymer film having a plurality of fluid restrictions extending through the polymer film and configured to deform. The dressing may also comprise a manifold layer coupled to the fluid management layer. The manifold layer may have a first surface facing the fluid management layer, a second surface opposite the first surface, and a thickness extending between the first surface and the second surface. The manifold layer may also comprise a plurality of collapsible apertures extending at least partially through the thickness of the manifold layer from the first surface. The collapsible apertures may be configured to deform in response to a negative pressure applied to the manifold layer. In some embodiments, the manifold layer may comprise an expanded foam material. The expanded foam material may be formed by a process comprising impregnating a polymeric material with an inert gas at high heat and pressure to form an impregnated polymeric material and expanding the impregnated polymeric material to form the expanded foam material.

Also, in some embodiments is a dressing for treating a tissue site with negative pressure. The dressing may comprise a fluid management layer comprising a polymer film having a plurality of fluid restrictions extending through the polymer film and configured to deform. The dressing may also comprise a manifold layer coupled to the fluid management layer. The manifold layer may have a first surface facing the fluid management layer, a second surface opposite the first surface, and a thickness extending between the first surface and the second surface. The manifold may comprise an expanded foam material. The expanded foam material may be formed by a process comprising impregnating a polymeric material with an inert gas at high heat and pressure to form an impregnated polymeric material and expanding the impregnated polymeric material to form the expanded foam material.

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

<FIG> is a 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 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 <NUM> during a negative-pressure interval and to instill the solution to the dressing <NUM> 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 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 be formed from, 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 Inspire <NUM> polyurethane films, commercially available from Exopack Advanced Coatings, Wrexham, United Kingdom. In some embodiments, the cover <NUM> may comprise an 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 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.

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

<FIG> is an exploded view of an example of the dressing <NUM> of <FIG>, illustrating additional details that may be associated with some embodiments in which the tissue interface <NUM> comprises more than one layer. In the embodiment of <FIG>, the tissue interface <NUM> includes a plurality of layers, for example, a first layer, a second layer, and a third layer. More particularly, in the example of <FIG>, the tissue interface <NUM> comprises a manifold layer <NUM>, a fluid management layer <NUM>, and a contact layer <NUM>. In some embodiments, the manifold layer <NUM> may be disposed adjacent to the fluid management layer <NUM>, and the contact layer <NUM> may be disposed adjacent to the fluid management layer <NUM> opposite the manifold layer <NUM>. For example, the manifold layer <NUM>, the fluid management layer <NUM>, and the contact layer <NUM> may be stacked so that the manifold layer <NUM> is in contact with the fluid management layer <NUM>, and the fluid management layer <NUM> is in contact with the manifold layer <NUM> and the contact layer <NUM>. One or more of the manifold layer <NUM>, the fluid management layer <NUM>, and the contact layer <NUM> may also be bonded to an adjacent layer in some embodiments.

The manifold layer <NUM> may comprise or provide a means for collecting or distributing fluid across the tissue interface <NUM> under negative 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 manifold layer <NUM> may comprise a plurality of pathways, for example, which can be interconnected to improve distribution or collection of fluids. For example, in some embodiments, the manifold layer <NUM> may comprise or be formed from a porous material having interconnected fluid pathways.

In the embodiment of <FIG>, the manifold layer <NUM> comprises a first surface <NUM>, a second surface <NUM>, and a thickness TM extending between the first surface <NUM> and the second surface <NUM>. In various embodiments, the thickness of the manifold layer <NUM> may also vary according to needs of a prescribed therapy. The thickness TM of the manifold layer <NUM> can vary according to the needs of a particular therapy. For example, in some embodiments the manifold layer <NUM> may have a thickness TM in a range of about <NUM> millimeters to <NUM> millimeters, or in a range of about <NUM> millimeters to about <NUM> millimeters, or in a range of about <NUM> to about <NUM> millimeters. In the embodiment of <FIG>, the second surface <NUM> may face the fluid management layer <NUM> and the first surface <NUM> may be opposite the second surface <NUM>.

In some embodiments, the manifold layer <NUM> also comprises a plurality of apertures extending into the thickness TM from, the first surface <NUM>, the second surface <NUM>, or between the first surface <NUM> and the second surface <NUM>. One or more of the apertures may be characterized with respect to one or more of its length, its width, and/or its depth. The length of an aperture may refer to a major dimension in a plane generally parallel to the first surface <NUM> and/or the second surface <NUM>. The width may refer to a dimension in the plane generally parallel to the first surface <NUM> and/or the second surface <NUM> and perpendicular to the length. The depth may refer to a dimension perpendicular to the plane generally parallel to the first surface <NUM>, as measured from the first surface <NUM>, the second surface <NUM>, or both.

For example, referring to <FIG>, in some embodiments the manifold layer <NUM> comprises a plurality of collapsible apertures <NUM> extending into the thickness TM from either the first surface <NUM> or the second surface <NUM>. The collapsible apertures <NUM> may be characterized with respect to a length LCA, a width WCA, and a depth DCA (shown in <FIG>). The collapsible aperture <NUM> may be an aperture generally configured to exhibit a relatively high degree of deformation in response to a negative pressure applied to the manifold layer <NUM>. For example, the collapsible apertures <NUM> may be configured to exhibit a relatively high percentage change in the area of a cross-section in a plane parallel to either the first surface <NUM> or the second surface <NUM>. For example, in response to negative pressure applied to the manifold layer <NUM>, the collapsible apertures <NUM> may be configured to deform so as to exhibit a decrease in the cross-section in the plane parallel to either the first surface <NUM> or the second surface <NUM>, for example, as a function of a decrease to the length LCA and/or the width WCA thereof. For example, the cross-sectional area of one of the collapsible apertures <NUM> may decrease to about <NUM>% of the cross-sectional area of that collapsible aperture <NUM> in the absence of the negative pressure, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>% of the cross-sectional area of the collapsible aperture <NUM> in the absence of the negative pressure.

In various embodiments, the collapsible apertures <NUM> may comprise any suitable shape configured to deform upon application of the negative pressure to the manifold layer <NUM>. For example, in various embodiments, one or more of the collapsible apertures <NUM> may be characterized as having a shape in a plane perpendicular to the depth DCA of the collapsible aperture <NUM> that is rectangular, elongate, diamond-shaped, square, oval, ovoid, irregular, polygonal (for example, hexagonal), or amorphous.

In some embodiments, one or more of the plurality of the collapsible apertures <NUM> may have a length LCA from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>. Additionally or alternatively, in some embodiments, one or more of the plurality of the collapsible apertures <NUM> may have a width WCA from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or about <NUM>. For example, one or more of the plurality of the collapsible apertures <NUM> may have a length LCA that is at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA, or at least about <NUM>% of the width WCA.

One or more of the collapsible apertures <NUM> may be characterized with respect to the orientation of the collapsible aperture <NUM>, for example, with respect to a line parallel to the length LCA of the collapsible aperture <NUM>. In some embodiments, the manifold layer <NUM> may include collapsible apertures <NUM> having a first orientation and collapsible apertures <NUM> having a second orientation, which may be different from the first orientation. For example, as shown in the embodiment of <FIG>, the manifold layer <NUM> may comprise a first portion <NUM> of the collapsible apertures <NUM> and a second portion <NUM> of the collapsible apertures <NUM>. The first portion <NUM> of the collapsible apertures <NUM> may be disposed in the manifold layer <NUM> in a first angle or orientation α, as shown by reference to a first orientation line <NUM> parallel to the length LCA of the first portion <NUM> of the collapsible apertures <NUM> and a reference line <NUM> generally parallel to the length of the manifold layer <NUM>. Also, the second portion <NUM> of the plurality of the collapsible apertures <NUM> may be disposed in the manifold layer <NUM> in a second angle or orientation β, as shown by reference to a second orientation line <NUM> parallel to the length LCA of the second portion <NUM> of the collapsible apertures <NUM> and the reference line <NUM> generally parallel to the length of the manifold layer <NUM>. In various embodiments, the first orientation α, may range from about <NUM> degrees to about <NUM> degrees and the second orientation β may range from about <NUM> degrees to about <NUM> degrees.

In some embodiments, the first orientation α and the second orientation β may be such that an angle of deviation θ between the first orientation α and the second orientation β is from about <NUM> degrees to about <NUM> degrees, or from about <NUM> degrees to <NUM> degrees, or from about <NUM> degrees to about <NUM> degrees, or from about <NUM> degrees to about <NUM> degrees, or from about <NUM> degrees to about <NUM> degrees, or from about <NUM> degrees to about <NUM> degrees. In some embodiments, the angle of deviation θ may be about <NUM> degrees, for example, such that the first orientation α may be perpendicular or substantially perpendicular to the second orientation β.

Additionally or alternatively, in various embodiments, the first portion <NUM> of the collapsible apertures <NUM> may be disposed in the manifold layer <NUM> in one or more first rows <NUM> and/or first columns <NUM>. Also, the second portion <NUM> of the collapsible apertures <NUM> may be disposed in the manifold layer <NUM> in one or more second rows <NUM> and/or second columns <NUM>.

In some embodiments, two or more of the collapsible apertures <NUM> may also be characterized by a pitch, which may refer to a spacing between corresponding points of the two respective collapsible apertures as disposed within the manifold layer <NUM>. For example, in some embodiments the pitch may indicate the spacing between the respective centroids of two or more collapsible apertures <NUM>. Some patterns of the collapsible apertures <NUM> may be characterized by a single pitch value, while other patterns of the collapsible apertures <NUM> may be characterized by at least two pitch values. For example, if the spacing between centroids of the collapsible apertures <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, the pattern comprising the first portion <NUM> of the collapsible apertures <NUM> and the second portion <NUM> of the collapsible apertures <NUM> may be characterized by five pitch values, P<NUM>, P<NUM>, P<NUM>, P<NUM>, and P<NUM>. P<NUM> may be the spacing between the centroids of two of the first portion <NUM> of the collapsible apertures <NUM> in adjacent first rows <NUM> in a direction perpendicular to the first rows <NUM>. P<NUM> may be the spacing between the centroids of each of the second portion <NUM> of the collapsible apertures <NUM> in adjacent second rows <NUM> in a direction perpendicular to the second rows <NUM>. P<NUM> may be the spacing between adjacent centroids of two collapsible apertures <NUM> of the first portion <NUM> of the collapsible apertures <NUM> within each the first rows <NUM> and parallel to the first rows <NUM>. P<NUM> may be the spacing between adjacent centroids of two of the collapsible apertures <NUM> of the second portion <NUM> of the collapsible apertures <NUM> within each of the second rows <NUM> and parallel to the second rows <NUM>. P<NUM> may be the spacing between the centroid of one of the first portion <NUM> of the collapsible apertures <NUM> and the centroid of one of the second portion <NUM> of the collapsible apertures <NUM> in adjacent rows. In some embodiments, P<NUM> and P<NUM> may be substantially equal and P<NUM> and P<NUM> may be substantially equal, within acceptable manufacturing tolerances. In some embodiments, for example, where P<NUM> is substantially equal to P<NUM> (e.g., P<NUM> = P<NUM>), then P<NUM> may be equal to about half of P<NUM> each of and P<NUM> (e.g., P<NUM>=<NUM> × P<NUM>=<NUM> × P<NUM>). For example, in some embodiments, P<NUM> and P<NUM> may be about <NUM> millimeters to about <NUM> millimeters, P<NUM> and P<NUM> may be about <NUM> millimeters, and P5 may be about <NUM> millimeters to about <NUM> millimeters.

Also, in some embodiments, the first portion <NUM> of the collapsible apertures <NUM> may be characterized with respect to their alignment to one or more of the second portion <NUM> of the collapsible apertures <NUM>; likewise, the second portion <NUM> of the collapsible apertures <NUM> may be characterized with respect to their alignment to one or more of the first portion <NUM> of the collapsible apertures <NUM>. In some embodiments, the alignment of the first portion <NUM> of the collapsible apertures <NUM> with respect to the second portion <NUM> of the collapsible apertures <NUM> and/or the alignment of the second portion <NUM> of the collapsible apertures <NUM> with respect to the first portion <NUM> of the collapsible apertures <NUM> may be configured to cause the one or more of the plurality of the collapsible apertures <NUM> to be deformed upon the application of negative pressure to the manifold layer <NUM>.

For example, referring to <FIG>, a detailed view of a portion of the manifold layer <NUM> is illustrated. In the embodiment of <FIG>, a first perpendicular bisector <NUM> of the length LCA (e.g., a line extending through the midpoint of the length LCA, perpendicular to the length LCA) of one of the first portion <NUM> of the collapsible apertures <NUM> may be bounded by or intersect a portion of the width WCA of one or more of the second portion <NUM> of the collapsible apertures <NUM>. For example, the first perpendicular bisector <NUM> may pass through a midpoint <NUM> of the width WCA of one or more of the second portion <NUM> of the collapsible apertures <NUM>.

Additionally or alternatively, and as also shown in the embodiment of <FIG>, a second perpendicular bisector <NUM> of the length LCA of one of the second portion <NUM> of the collapsible apertures <NUM> may be bounded by or intersection of portion of the width WCA of one or more of the first portion <NUM> of the collapsible apertures <NUM>. For example, the second perpendicular bisector <NUM> may pass through a midpoint <NUM> of the width WCA of one or more of the first portion <NUM> of the collapsible apertures <NUM>.

One or more of the plurality of the collapsible apertures <NUM> may be characterized with respect to its response to a negative pressure. For example, in response to the application of a negative pressure to the manifold layer <NUM>, one or more of the collapsible apertures <NUM> may be characterized as exhibiting a decrease in the area of the cross-sectional plane perpendicular to the depth DCA (shown in <FIG>) of the collapsible aperture <NUM>, for example, as a function of a decrease to the length LCA and/or the width WCA thereof. More particularly, in some embodiments, the decrease in the area of the cross-sectional plane perpendicular to the depth DCA of the collapsible aperture <NUM> may be predominantly due to a decrease in the width WCA of the collapsible aperture <NUM>. For example, referring to <FIG>, an example of a portion of the manifold layer <NUM> is shown exhibiting a response to negative pressure In the example of <FIG>, the collapsible apertures <NUM> exhibit a decrease in the area of the cross-sectional plane perpendicular to the depth DCA of the collapsible aperture <NUM>, in particular, substantially due to a decrease in the width WCA of the collapsible apertures <NUM>.

Additionally, in some embodiments the manifold layer <NUM> may be characterized as exhibiting radial collapse. Radial collapse may refer to a deformation of the manifold layer <NUM> or a portion thereof such that the manifold layer <NUM> exhibits a decrease in at least one dimension of the first surface <NUM> and/or the second surface <NUM> relative to a nominal or relaxed length and/or width, when the manifold layer <NUM> is not subjected to negative pressure. The radial collapse exhibited by the manifold layer <NUM> may be determined by various factors related to the collapsible apertures <NUM>, for example, the dimension of the collapsible apertures (e.g., the length LCA, the width WCA, and the size relationship between the length LCA and width WCA), the relationship between two of the collapsible apertures <NUM> (e.g., the pitch, orientation, and/or alignment between two or more collapsible apertures <NUM>), and combinations thereof. In various embodiments, manipulation of one or more of these parameters may be effective to vary the radial collapse exhibited by the manifold layer <NUM> to meet the needs of a particular therapy. For example, in various embodiments the manifold layer <NUM> may be characterized as exhibiting radial collapse such that the area of the first surface <NUM> and/or the second surface <NUM> when subjected to negative pressure is not more than about <NUM>% of the area of the respective surface when the manifold layer <NUM> is not subjected to negative pressure, or not more than about <NUM>%, or not more than about <NUM>%, or not more than about <NUM>%, or not more than about <NUM>% of the area of the respective surface when the manifold layer <NUM> is not subjected to negative pressure.

For example, in some embodiments where the width WCA of the collapsible apertures <NUM> may substantially define a proportion of collapse exhibited by the plurality of the collapsible apertures <NUM>, the width WCA of the collapsible apertures <NUM> may also, at least in part, determine the overall radial collapse demonstrated by the manifold layer <NUM>.

Also, in some embodiments where the width WCA of the collapsible apertures <NUM> may substantially define a proportion of collapse exhibited by the plurality of the collapsible apertures <NUM>, the compressibility of the manifold layer <NUM> may increase in a direction as the orientation (e.g., the length) of the collapsible aperture <NUM> approaches perpendicular to that direction. For example, as the first orientation α of the first portion <NUM> of the collapsible apertures <NUM>, shown by reference to the first orientation line <NUM>, approaches the orientation of the reference line <NUM> generally parallel to the length of the manifold layer <NUM> and/or as the second orientation β of the second portion <NUM> of the collapsible apertures <NUM>, as shown by reference to a second orientation line <NUM>, approaches the orientation of the reference line <NUM> generally parallel to the length of the manifold layer <NUM>, the compressibility of the manifold layer <NUM> perpendicular to the reference line <NUM> may increase. Consequently, if negative pressure is applied to the manifold layer <NUM>, the manifold layer <NUM> may contract more in one direction than another.

Additionally or alternatively, referring again to the embodiment of <FIG>, in some embodiments the manifold layer <NUM> may comprise a plurality of fluid apertures <NUM> extending through the thickness TM between the first surface <NUM> and the second surface <NUM>. One or more of the fluid apertures <NUM> may include or be an aperture generally configured to exhibit a relatively low degree of deformation in response to a negative pressure applied to the manifold layer <NUM>, for example, to exhibit a relatively low percentage change in a cross-section in a plane parallel to either the first surface <NUM> or the second surface <NUM>. For example, in response to negative pressure applied to the manifold layer <NUM>, the fluid apertures <NUM> may be configured to exhibit limited deformation such that the cross-section in the plane parallel to either the first surface <NUM> or the second surface <NUM> retains at least to about <NUM>% of the cross-sectional area in the absence of the negative pressure, or at least about <NUM>%, or at least about <NUM>%, or at least about <NUM>%, or at least about <NUM>% of the cross-sectional area in the absence of the negative pressure. Generally, the fluid apertures <NUM> may be configured to remain open to allow for the communication of a fluid between the first surface <NUM> and the second surface <NUM>.

In various embodiments, the fluid apertures <NUM> may comprise any suitable shape or combination of shapes configured to withstand deformation upon application of the negative pressure to the manifold layer <NUM>. For example, in various embodiments, one of more of the fluid apertures <NUM> may be characterized as having a shape that is circular, rectangular, diamond-shaped, square, oval, ovoid, irregular, polygonal (for example, hexagonal), or amorphous. In some embodiments, in comparison to the collapsible apertures <NUM>, the fluid apertures <NUM> may be characterized as having a cross-sectional shape that does not deviate by more than about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>% when subjected to negative pressure.

In some embodiments, the fluid apertures <NUM> may be disposed in the manifold layer <NUM> in a suitable pattern, for example, in a plurality of rows and/or columns. For example, in the embodiment of <FIG>, the fluid apertures <NUM> may be interposed between the collapsible apertures <NUM> of the first portion <NUM> of the collapsible apertures <NUM>, for example, within the first rows <NUM> and the first columns <NUM>. Also, in the embodiment of <FIG>, the fluid apertures <NUM> may be interposed between the collapsible apertures <NUM> of the second portion <NUM> of the collapsible apertures <NUM>, for example, within the second rows <NUM> and the second columns <NUM>. In some embodiments, one of the fluid apertures <NUM> may be disposed substantially equidistant between two collapsible apertures <NUM> of a given row or column.

The plurality of the collapsible apertures <NUM> and the plurality of the fluid apertures <NUM> may collectively form a percent open area the manifold layer <NUM>. The percent open area of the manifold layer <NUM> may be equal to the percentage of sum of the area of the plurality of the plurality of the collapsible apertures <NUM> and fluid apertures <NUM> relative to the area of the manifold layer <NUM>. In some embodiments, the percent open area may be between about <NUM>% and about <NUM>%. In other embodiments, the percent open area may be about <NUM>%.

In some embodiments, the first surface <NUM> and/or the second surface <NUM> may be generally characterized as planar surfaces, for example, although not necessarily perfectly flat, being generally recognizable as flat or capable of being laid flat. For example, a planar surface may include minor undulations and/or deviations from a single geometric plane.

Additionally or alternatively, in some embodiments the first surface <NUM> and/or the second surface <NUM> may comprise a sculpted surface; for example, comprising one or more surface features. For example, in some embodiments the first surface <NUM> and the second surface <NUM> may comprise one or more features characterized as grooves, furrows, hollows, passageways, or channels. For example, referring to the embodiment of <FIG>, the manifold layer <NUM> may comprise a plurality of channels <NUM> disposed within the first surface <NUM>. The channels <NUM> may have any suitable size and configuration. For example, in various embodiments the channels <NUM> may be characterized as having straight side-walls and a square or rectangular cross-section or curved side-walls. In various embodiments, the channels <NUM> may have any suitable spacing and may intersect at a suitable angle. For example, in the embodiment of <FIG> the channels <NUM> may generally form a grid pattern. For example, a first portion of the channels <NUM> may deviate from a second portion of the channels <NUM> such that the first and second portion of the channels <NUM> may intersect, for example, at an angle between about <NUM> degrees and about <NUM> degrees, or for example, at about <NUM> degrees.

In some embodiments, the plurality of the channels <NUM> may cooperatively define one or more additional surface features, for example, a plurality of pillars <NUM> substantially bounded by the channels <NUM>.

In some embodiments, one or more of the channels <NUM> may be disposed within the first surface <NUM> and/or the second surface <NUM> such that the channels <NUM> may provide a route of fluid communication to or from the collapsible apertures <NUM> and/or the fluid apertures <NUM>. For example, one or more of the channels <NUM> may be aligned with one or more of the collapsible apertures <NUM>, one or more of the fluid apertures <NUM>, or one or more of both the collapsible apertures <NUM> and the fluid apertures <NUM>. In the embodiment of <FIG>, one of the first portion of the channels <NUM> may intersect one of the second portion of channels <NUM> at a location aligned with each of the collapsible apertures <NUM> and the fluid apertures <NUM>. In such embodiments, the channels <NUM> may further contribute to the distribution of fluids via the manifold layer <NUM>, for example, both through the manifold layer <NUM> and across the first surface <NUM> and/or the second surface <NUM> of the manifold layer <NUM>.

In some embodiments, one or more of the collapsible apertures <NUM>, the fluid apertures <NUM>, or various surface features of the manifold layer <NUM> such as the channels <NUM> or pillars <NUM>, may be disposed in the manifold layer <NUM> by any suitable process, an example of which includes thermoforming. Thermoforming of a foam may involve embossing patterns and structures, such as apertures or channels, into the surfaces of the foam under heat and/or pressure.

In some embodiments, the manifold layer <NUM> may comprise or be formed from a reticulated foam having pore sizes and free volume that may vary according to needs of a prescribed therapy. In some embodiments, the reticulated foam may comprise one or more of a polyol, such as polyester or polyether, an isocyanate, such as toluene and diisocyanate, and polymerization modifiers such as amines and tin compounds. In one non-limiting example, the manifold layer <NUM> may be a reticulated polyurethane ether foam such as used in a V. ® GRANUFOAM™ Dressing or a V. ® VERAFLO™ Dressing, both available from Kinetic Concepts, Inc.

In some embodiments, the manifold layer <NUM> may comprise a felted foam, for example, a foam formed by a felting process. Any porous foam suitable for felting may be used, including the example foams mentioned herein, such as GRANUFOAM™ Dressing. In some embodiments, the felting process comprises a thermoforming process that permanently compresses a foam to increase the density of that 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 felting methods may include compressing a foam blank, for example, a reticulated foam blank, between one or more heated platens or dies 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. In some embodiments, multiple iterations of compressing and heating may be performed. For example, the felting process may comprise two, three, four, five, six, seven, eight, or more iterations of heating and compression.

Not intending to be bound by theory, 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 an 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 imparted 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 the all of the porous material is felted.

A felted foam may be characterized with respect to 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. In some embodiments, the felted foam of the manifold layer <NUM> 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>, preferably about <NUM> to about <NUM>. For example, the firmness factor of the manifold layer <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 cm / pores per inch) and compressibility. For example, a 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, one or more suitable foam blanks may be used for forming the manifold layer <NUM>. The foam blank(s) may have about <NUM> to about <NUM> pores per cm (about <NUM> to about <NUM> pores per inch) on average, a density of about <NUM> to about <NUM>/m<NUM> (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, a <NUM>% compression load deflection of at least <NUM> N/m<NUM> (at least <NUM> pounds per square inch), and/or a <NUM>% compression load deflection of at least <NUM> N/m<NUM> (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, <NUM>-<NUM> millimeters, <NUM>-<NUM> millimeters, or <NUM>-<NUM> millimeters. In some embodiments, the foam blank(s) may be felted to provide denser foam for the manifold layer <NUM>. For example, one or more foam blanks may be felted to a firmness factor of <NUM>-<NUM> to form the manifold layer <NUM>. In some embodiments, the foam blank may be felted to a firmness factor of from about <NUM> to about <NUM>, for example, a firmness factor of about <NUM>.

The manifold layer <NUM> comprises a closed-cell foam. For example, in some embodiments, the manifold layer <NUM> may comprise an expanded foam, for example, a foam formed from a process by which comprises expansion of a foam precursor material. For example, in some embodiments an expanded foam may be formed from a process comprising extrusion of a polymeric material, impregnation of the polymeric material with an inert gas at high heat and pressure to form an impregnated polymeric material, and expansion of the impregnated polymeric material to form the expanded foam material.

During the extrusion step, raw polymeric material is melted and forced through a die to form a generally continuous stock material, for example, the extruded polymeric material. The polymeric material may comprise any suitable polymer, copolymer, or combination thereof, dependent upon the needs of a prescribed therapy. For example, in various embodiments, the polymeric material comprises cross-linked ethylene-vinyl acetate copolymer, a cross-linked polyolefin, for example, cross-linked polyethylene, or a cross-linked ethyl-methyl-acrylate copolymer.

In some embodiments, the polymeric material may have one or more additives or modifiers incorporated in an amount effective to impart a desired effect during the extrusion step. For example, in some embodiments, an antimicrobial material may be incorporated within the polymeric material during extrusion. Suitable examples of an antimicrobial material include a metal, such as silver, which may be present in metallic form, in ionic form (e.g., a silver salt), or both. In some embodiments, silver may be present in combination with one or more additional metals, for example, gold, platinum, ferro-manganese, copper, zinc, or combinations thereof. In some examples, silver may be incorporated into the polymeric material in an amount from about <NUM>% to about <NUM>% by weight of the polymeric material.

Additionally or alternatively, in some embodiments a superabsorbent polymer (SAP) may be incorporated within the polymeric material during extrusion. Generally, relative to their mass, SAPs can absorb and retain large quantities of liquid, and in particular water. Many medical disposables, such as canisters and dressings, use SAPs to hold and stabilize or solidify wound fluids. The SAPs may be of the type often referred to as "hydrogels," "super-absorbents," or "hydrocolloids. " For example, SAPs may absorb liquids by bonding with water molecules through hydrogen bonding. In some examples, a SAP may be incorporated into the polymeric material in an amount from about <NUM>% to about <NUM>% by weight of the polymeric material.

During the impregnation step, the polymeric material is exposed to an inert gas under elevated heat and pressure, causing the inert gas to permeate the polymeric material. The inert gas may comprise nitrogen gas, for example, at least <NUM>% nitrogen gas, or at least <NUM>% nitrogen gas, or at least <NUM>% nitrogen gas, by weight. The parameters associated with the impregnation step, for example, the temperature, partial pressure of the inert gas and the duration of the impregnation, may be manipulated to alter the properties of the impregnated polymeric material and, accordingly, the properties of the resultant expanded foam.

During the expansion step, the impregnated polymeric material is subjected to heat in the presence of a reduced pressure, for example, a pressure that is less than the pressure employed during the impregnation step. In some embodiments, the impregnated polymeric material may be expanded in a low-pressure autoclave. Not intending to be bound by theory, during the expansion step, the reduction in pressure may allow the inert gas to expand, causing the formation of pores or cells within the expanded polymeric material. The parameters associated with the expansion step, for example, the temperature, pressure, and the duration of the expansion, may be manipulated to alter the properties of the expanded polymeric material, the expanded foam.

In some embodiments, a closed-cell foam such as an expanded foam may comprise a plurality of pores or cells that can be generally characterized as not being interconnected. In some embodiments, an expanded foam may be characterized as resilient such that in the presence of a negative pressure, the expanded foam exhibits a resistance to compression, for example, a resistance to compression that is relatively high in comparison to an open-cell foam. Not intending to be bound by theory, were the expanded foam too soft, it might collapse in the presence of negative pressure such that the expanded foam would not manifold the negative pressure.

The resistance to compression exhibited by the expanded foam may be dependent upon, among other parameters, the density of the expanded foam and the hardness of the material forming the expanded foam, as well as the closed-cell nature of the expanded foam. For example, the expanded foam may be characterized as having a density of from about <NUM>/cm^<NUM> to about <NUM>/cm^<NUM> according to ISO <NUM>:<NUM>, or from about <NUM>/cm^<NUM> to about <NUM>/cm^<NUM>, about <NUM>/cm^<NUM>. Additionally, the expanded foam may be characterized as having a Shore Hardness on the OO Scale of from about <NUM> to <NUM> according to ISO <NUM>:<NUM>, or from about <NUM> to about <NUM>, or about <NUM>. In some embodiments, the expanded foam may be characterized as exhibiting a compression stress-strain at <NUM>% compression of about <NUM> for a <NUM> cell-cell according to ISO <NUM>:<NUM> and/or a compression stress-strain at <NUM>% compression of about <NUM> for a <NUM> cell-cell according to ISO <NUM>:<NUM>.

In some embodiments, the manifold layer <NUM> may comprise a closed-cell cross-linked polyolefin foam such as one of the AZOTE® range of foams available from Zotefoams Plc, of London, England. In various non-limiting examples, the manifold layer <NUM> may comprise a closed-cell cross-linked polyethylene foam such as one of the Plastazote® line of foams, a closed-cell cross-linked ethylene copolymer foam such as one of the Evazote® line of foams, or a closed-cell, cross-linked ethylene copolymer foam such as one of the Supazote® line of foams, all available from Zotefoams Plc, of London, England. In a particular example embodiment, the manifold layer <NUM> may comprise a closed-cell cross-linked ethylene copolymer foam as Evazote® EV50.

In some embodiments, an expanded foam may be advantageously employed as the manifold layer <NUM>. For example, the particular process by which the expanded foam is made allows additives and modifiers, for example, antimicrobial materials and/or SAPs, to be incorporated into and made integral to the polymeric material that forms the expanded foam. Efforts to likewise incorporate such additional materials into conventional foams, such as those created by chemical reaction, have proven unsuccessful, for example, due to the nature of the processes by which such conventional foams are made. As such, antimicrobials and SAPs, for example, have not successfully been likewise incorporated into such conventional foams and, instead, have been applied or coated onto the surfaces of such conventional foams. As such, the incorporation of antimicrobial materials or SAPs into an expanded foam may provide unique and beneficial properties not associated with conventional foams. Additionally, the use of an expanded foam as the manifold layer <NUM> may also decrease the opportunity for any in-growth of tissue into the foam during healing of a wound or other tissue site.

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

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

The area density of the fluid management 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 fluid management layer <NUM> may comprise or be formed from 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. More polar films suitable for laminating to a polyethylene film include polyamide, co-polyesters, ionomers, and acrylics. To aid in the bond between a polyethylene and polar film, tie layers may be used, such as ethylene vinyl acetate, or modified polyurethanes. An ethyl methyl acrylate (EMA) film may also have suitable hydrophobic and welding properties for some configurations.

As illustrated in the example of <FIG>, the fluid management layer <NUM> may have one or more fluid restrictions <NUM>, which can be distributed uniformly or randomly across the fluid management layer <NUM>. The fluid restrictions <NUM> may be characterized bi-directional and pressure-responsive. For example, the fluid restrictions <NUM> can generally comprise an elastic passage that is normally unstrained to substantially reduce liquid flow, and can expand in response to a pressure gradient or deformation of the fluid management layer <NUM>. In some embodiments, the fluid restrictions <NUM> may comprise perforations in the fluid management layer <NUM>. Perforations may be formed by removing material from the fluid management layer <NUM>. For example, perforations may be formed by cutting through the fluid management layer <NUM>, which may also deform the edges of the perforations in some embodiments. In the absence of a pressure gradient across the perforations or deformation of the fluid management layer <NUM>, the passages may be sufficiently small to form a seal or flow restriction, which can substantially reduce or prevent liquid flow. Additionally or alternatively, one or more of the fluid restrictions <NUM> may be an elastomeric valve that is normally closed when unstrained to substantially prevent liquid flow, and can open in response to a pressure gradient or deformation of the fluid management layer <NUM>. A fenestration in the fluid management layer <NUM> may be a suitable valve for some applications. Fenestrations may also be formed by removing material from the fluid management layer <NUM>, but the amount of material removed and the resulting dimensions of the fenestrations may be an order of magnitude less than perforations, and may not deform the edges.

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

In some embodiments, the fluid restrictions <NUM> may be distributed across the fluid management layer <NUM> such that, when the fluid management layer <NUM> is positioned with respect to the manifold layer <NUM>, the fluid restrictions <NUM> will be aligned with, overlap, in registration with, or otherwise fluidly coupled to the collapsible apertures <NUM>, the fluid apertures <NUM>, the channels <NUM>, or combinations thereof.

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

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

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

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

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

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

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

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

As illustrated in the example of <FIG>, in some embodiments, a release liner <NUM> may be attached to or positioned adjacent to the contact layer <NUM>, for example, to protect the adhesive <NUM> prior to use. The release liner <NUM> may also provide stiffness, such as to assist with deployment of the dressing <NUM>. The release liner <NUM> may be, for example, a casting paper, a film, or polyethylene. Further, in some embodiments, the release liner <NUM> may be a polyester material such as polyethylene terephthalate (PET), or a similar polar semi-crystalline polymer. The use of a polar semi-crystalline polymer for the release liner <NUM> may substantially preclude wrinkling or other deformation of the dressing <NUM> For example, the polar semi-crystalline polymer may be highly orientated and resistant to softening, swelling, or other deformation that may occur when brought into contact with components of the dressing <NUM>, or when subjected to temperature or environmental variations, or sterilization. In some embodiments, the release liner <NUM> may have a surface texture that may be imprinted on an adjacent layer, such as the contact layer <NUM>. Further, a release agent may be disposed on a side of the release liner <NUM> that is configured to contact the contact layer <NUM>. For example, the release agent may be a silicone coating and may have a release factor suitable to facilitate removal of the release liner <NUM> by hand and without damaging or deforming the dressing <NUM>. In some embodiments, the release agent may be a fluorocarbon or a fluorosilicone, for example. In other embodiments, the release liner <NUM> may be uncoated or otherwise used without a release agent.

<FIG> also illustrates one example of a fluid conductor <NUM> and a dressing interface <NUM>. As shown in the example of <FIG>, the fluid conductor <NUM> may be a flexible tube, which can be fluidly coupled on one end to the dressing interface <NUM>. The dressing interface <NUM> may be an elbow connector, as shown in the example of <FIG>, which can be placed over an aperture <NUM> in the cover <NUM> to provide a fluid path between the fluid conductor <NUM> and the tissue interface <NUM>.

In some embodiments, for example, in the example of <FIG>, the cover <NUM> and the contact layer <NUM> may be sized such that a peripheral portion of the cover <NUM> and the periphery <NUM> of the contact layer <NUM> each extend beyond the perimeter of the manifold layer <NUM> and the fluid management layer <NUM>. For example, the cover <NUM> and the contact layer <NUM> may have dimensions such that a perimeter of the cover <NUM> is substantially coextensive with the edges <NUM> of the periphery <NUM> of the contact layer <NUM> when the cover <NUM>, the manifold layer <NUM>, the fluid management layer <NUM>, and the contact layer <NUM> are positioned with respect to each other. In some embodiments, the contact layer <NUM> and the cover <NUM> may be coupled, such as via the adhesive <NUM>, to enclose the manifold layer <NUM> and the fluid management layer <NUM>, also allowing a portion of the adhesive <NUM> to be exposed through the apertures <NUM>.

Alternatively, in some embodiments, the cover <NUM>, the manifold layer <NUM>, the fluid management layer <NUM>, and the contact layer <NUM> may have substantially equivalent sizes and shapes, for example, such that each of the cover <NUM>, the manifold layer <NUM>, the fluid management layer <NUM>, and the contact layer <NUM> are coextensive with respect to outline or perimeter when the cover <NUM>, the manifold layer <NUM>, the fluid management layer <NUM>, and the contact layer <NUM> are positioned with respect to each other. Also in some embodiments, each of the cover <NUM>, the manifold layer <NUM>, the fluid management layer <NUM>, and the contact layer <NUM> may be attached, such as via an adhesive or RF welding, to an immediately-adjacent layer.

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

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

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

As illustrated in the example of <FIG>, the apertures <NUM> may be sized to expose a portion of the fluid management layer <NUM>, the fluid restrictions <NUM>, or both through the contact layer <NUM>. In some embodiments, each of the apertures <NUM> may be sized to expose no more than two of the fluid restrictions <NUM>. In some examples, the length of each of the fluid restrictions <NUM> may be substantially equal to or less than the diameter of each of the apertures <NUM>. In some embodiments, the average dimensions of the fluid restrictions <NUM> are substantially similar to the average dimensions of the apertures <NUM>. For example, the apertures <NUM> may be elliptical in some embodiments, and the length of each of the fluid restrictions <NUM> may be substantially equal to the major axis or the minor axis. In some embodiments, though, the dimensions of the fluid restrictions <NUM> may exceed the dimensions of the apertures <NUM>, and the size of the apertures <NUM> may limit the effective size of the fluid restrictions <NUM> exposed to the lower surface of the dressing <NUM>.

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

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

The cover <NUM>, the manifold layer <NUM>, the fluid management layer <NUM>, the contact layer <NUM>, or various combinations may be assembled before application or in situ. For example, the cover <NUM> may be laminated to the manifold layer <NUM>, and the fluid management layer <NUM> may be laminated to the manifold layer <NUM> opposite the cover <NUM> in some embodiments. The contact layer <NUM> may also be coupled to the fluid management layer <NUM> opposite the manifold layer <NUM> in some embodiments. In some embodiments, two or more layers of the tissue interface <NUM> may be coextensive. For example, the manifold layer <NUM> may be coextensive with the fluid management layer <NUM>, as illustrated in the embodiment of <FIG>. In some embodiments, the dressing <NUM> may be provided as a single, composite dressing. For example, the contact layer <NUM> may be coupled to the cover <NUM> to enclose the manifold layer <NUM> and the fluid management layer <NUM>, wherein the contact layer <NUM> is configured to face a tissue site.

In use, the release liner <NUM> (if included) may be removed to expose the contact layer <NUM>, which may be placed within, over, on, or otherwise proximate to a tissue site, particularly a surface tissue site and adjacent epidermis. The contact layer <NUM> and the fluid management layer <NUM> may be interposed between the manifold layer <NUM> and the tissue site, which can substantially reduce or eliminate adverse interaction with the manifold layer <NUM>. For example, the contact layer <NUM> may be placed over a surface wound (including edges of the wound) and undamaged epidermis to prevent direct contact with the manifold layer <NUM>. Treatment of a surface wound or placement of the dressing <NUM> on a surface wound includes placing the dressing <NUM> immediately adjacent to the surface of the body or extending over at least a portion of the surface of the body. Treatment of a surface wound does not include placing the dressing <NUM> wholly within the body or wholly under the surface of the body, such as placing a dressing within an abdominal cavity. In some applications, the interior portion <NUM> of the contact layer <NUM> may be positioned adjacent to, proximate to, or covering a tissue site. In some applications, at least some portion of the fluid management layer <NUM>, the fluid restrictions <NUM>, or both may be exposed to a tissue site through the contact layer <NUM>. The periphery <NUM> of the contact layer <NUM> may be positioned adjacent to or proximate to tissue around or surrounding the tissue site. The contact layer <NUM> may be sufficiently tacky to hold the dressing <NUM> in position, while also allowing the dressing <NUM> to be removed or re-positioned without trauma to the tissue site.

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

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

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

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

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

Additionally or alternatively, in some embodiments, such as where all components of the tissue interface <NUM> have a common perimeter or outline (for example, in an embodiment where the cover <NUM>, the manifold layer <NUM>, the fluid management layer <NUM>, and the contact layer <NUM> are coextensive with respect to outline or perimeter), an attachment device can be disposed around edges of the cover <NUM>. An adhesive disposed on the attachment device may pressed onto the cover <NUM> and the epidermis peripheral to a tissue site (or other attachment surface) to fix the dressing <NUM> in position and to seal the exposed perimeter of the tissue interface <NUM>.

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

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

In some embodiments, negative pressure applied through the tissue interface <NUM> may be applied to the tissue interface <NUM>. The negative pressure may be effective to cause the manifold layer <NUM> to exhibit radial collapse such that the area of the first surface <NUM> and/or the second surface <NUM>, when subjected to negative pressure, is decreased relative to the area of the respective surface when the manifold layer <NUM> is not subjected to negative pressure. For example, the radial collapse may be substantially due to collapse of one or more of the collapsible apertures <NUM>. While the collapsible apertures <NUM> may collapse when subjected to negative pressure, the fluid apertures <NUM> may remain substantially un-deformed, for example, such that fluids may be communicated between the first surface <NUM> and the second surface <NUM> via the fluid apertures <NUM>.

In some embodiments, the radial collapse exhibited by the manifold layer <NUM> may have the effect of drawing the edges of the tissue site (e.g., a wound) together, for example, toward the center, which may help to reduce edema and/or to apply load to the edges of the wound. The radial collapse resulting from the collapse of the collapsible apertures <NUM> may be particularly beneficial in the context of a closed-cell foam or, alternatively, a felted foam, for example, because such foams may not have the capacity to collapse radially as a result of the collapse of the internal pores as with conventional, unfelted, open-cell foams. With closed-cell foams, the pores are not evacuated under negative pressure and cannot collapse to cause radial collapse of the manifold layer <NUM>. As such, the collapsible apertures <NUM> may allow a closed-cell foams to exhibit radial collapse while nonetheless imparting additional advantages such as imperviousness to in-growth and/or incorporation of additives such as antimicrobials and SAPs.

If the negative-pressure source <NUM> is removed or turned-off, the pressure differential across the fluid restrictions <NUM> the negative pressure applied through the tissue interface <NUM> may dissipate, allowing the collapsible apertures <NUM> to return to an uncollapsed or resting state and, likewise, allowing the manifold layer <NUM> to return to an uncollapsed or resting state.

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

Also if the negative-pressure source <NUM> is removed or turned-off, the pressure differential across the fluid restrictions <NUM> may dissipate, allowing the fluid restrictions <NUM> to return to their resting state and prevent or reduce the rate at which exudate or other liquid from returning to the tissue site through the fluid management layer <NUM>.

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

<FIG> is a schematic view of another example of the contact layer <NUM>, illustrating additional details that may be associated with some embodiments. As shown in the example of <FIG>, the contact layer <NUM> may have one or more fluid restrictions, such as valves <NUM>, instead of or in addition to the apertures <NUM> in the interior portion <NUM>. Moreover, the valves <NUM> may be included in the contact layer <NUM> in addition to or instead of the fluid restrictions <NUM> in the fluid management layer <NUM>. In some embodiments in which the contact layer <NUM> includes one or more of the valves <NUM>, the fluid management layer <NUM> may be omitted. For example, in some embodiments, the tissue interface <NUM> may consist essentially of the manifold layer <NUM> and the contact layer <NUM> of <FIG> with the valves <NUM> disposed in the interior portion <NUM>.

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

Methods of treating a surface wound to promote healing and tissue granulation may include applying the dressing <NUM> to a surface wound and sealing the dressing <NUM> to epidermis adjacent to the surface wound. For example, the contact layer <NUM> may be placed over the surface wound, covering at least a portion of the edge of the surface wound and a periwound adjacent to the surface wound. The cover <NUM> may also be attached to epidermis around the contact layer <NUM>. The dressing <NUM> may be fluidly coupled to a negative-pressure source, such as the negative-pressure source <NUM>. Negative pressure from the negative-pressure source <NUM> may be applied to the dressing <NUM>, opening the fluid restrictions <NUM>. The fluid restrictions <NUM> can be closed by blocking, stopping, or reducing the negative pressure. The fluid management layer <NUM> and the contact layer <NUM> can substantially prevent exposure of tissue in the surface wound to the manifold layer <NUM>, inhibiting growth of tissue into the manifold layer <NUM>. The dressing <NUM> can also substantially prevent maceration of the periwound.

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

Claim 1:
A dressing (<NUM>) for treating a tissue site with negative pressure, the dressing (<NUM>) comprising:
a fluid management layer (<NUM>) comprising a polymer film having a plurality of fluid restrictions (<NUM>) extending through the polymer film and configured to deform; and
a manifold layer (<NUM>) coupled to the fluid management layer (<NUM>), the manifold layer (<NUM>) having a first surface (<NUM>) facing the fluid management layer (<NUM>), a second surface (<NUM>) opposite the first surface (<NUM>), and a thickness extending between the first surface (<NUM>) and the second surface (<NUM>), the manifold layer (<NUM>) comprising a closed-cell foam, the manifold layer (<NUM>) comprising a plurality of collapsible apertures (<NUM>) extending at least partially through the thickness of the manifold layer (<NUM>) from the first surface (<NUM>), the collapsible apertures (<NUM>) configured to deform in response to a negative pressure applied to the manifold layer (<NUM>) so that the an area of the first surface (<NUM>), the second surface (<NUM>), or both, when subjected to negative pressure, is decreased relative to the area of the first surface (<NUM>) or the second surface (<NUM>) when the manifold layer (<NUM>) is not subjected to negative pressure.