Composite dressing that promotes granulation and reduces maceration in negative pressure treatment

Abstract

To provide a dressing for tissue treatment using negative pressure, and a method of using a dressing for tissue treatment using negative pressure.SOLUTION: A dressing 104 includes: a cover 116; a manifold 205 including a foam; a polymer film 210 having a plurality of openings 220; and a gel 215 having at least one aperture 235. The gel is configured such that the plurality of openings of the polymer film and a part of the polymer film are exposed through the at least one aperture. The cover, the manifold, the polymer film, and the gel are assembled in a stacking relation in which the manifold and the polymer film are arranged between the cover and the gel.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 516,540, entitled "TISSUE CONTACT INTERFACE," filed June 7, 2017; U.S. Provisional Patent Application No. 62 / 516,550, entitled "COMPOSITE DRESSINGS FOR IMPROVED GRANULATION AND REDUCED MACERATION WITH NEGATIVE-PRESSURE TREATMENT," filed June 7, 2017; and U.S. Provisional Patent Application No. 62 / 516,566, entitled "COMPOSITE DRESSINGS FOR IMPROVED GRANULATION AND REDUCED MACERATION WITH NEGATIVE-PRESSURE TREATMENT," filed June 7, 2017, each of which is incorporated herein by reference for all purposes.

[0002] The present invention, as set forth in the accompanying claims, relates generally to tissue treatment systems and, more particularly, but without limitation, to dressings for tissue treatment using negative pressure and methods of using dressings for tissue treatment using negative pressure. [Background technology]

[0003] Clinical trials and clinical practice have shown that applying reduced pressure proximate to a tissue site can enhance and accelerate the growth of new tissue at the tissue site. While the applications of this phenomenon are numerous, it has proven particularly advantageous in the treatment of wounds. Regardless of the etiology of the wound, whether traumatic, surgical, or otherwise, proper care of the wound is critical to the outcome. Treatment of wounds or other tissues with reduced pressure can generally be referred to as "negative pressure therapy," but is also known by other names, including, for example, "negative pressure wound therapy," "reduced pressure therapy," "vacuum therapy," "vacuum-assisted closure," and "topical negative pressure." Negative pressure therapy can provide many benefits, including mobilization of epithelial and subcutaneous tissue, improved blood flow, and microdeformation of tissue at the wound site. These benefits, combined, can increase the development of granulation tissue and shorten healing time.

[0004] While the clinical benefits of negative pressure therapy are widely known, improvements in treatment systems, components, and processes can benefit healthcare providers and patients. Summary of the Invention

[0005] The accompanying claims set forth new and useful systems, devices, and methods for treating tissue in a negative pressure therapy environment. Exemplary embodiments are also provided to enable those skilled in the art to make and use the claimed subject matter.

[0006] For example, in some embodiments, a dressing for treating tissue may be a composite of dressing layers including a polyethylene release film, a perforated silicone gel, a fenestrated polyethylene film, a foam, and an adhesive drape. The fenestration pattern in the polyethylene film may be aligned with the perforation pattern in at least a central region of the silicone gel. In some embodiments, each of the perforations in the central region may have a width or diameter of about 2 millimeters, and each of the fenestrations in the polyethylene film may be a slot having a length of about 3 millimeters and a width of about 0.5 millimeters to about 1 millimeter. The foam may be an open-cell foam, such as a reticulated foam. The foam may also be relatively thin and hydrophobic to reduce the fluid retention capacity of the dressing, thereby promoting the rapid transfer of exudates and other fluids to an external reservoir. The foam layer may also be thin to reduce the thickness and increase the flexibility of the dressing, thereby allowing the dressing to conform to a wound bed and other tissue sites under negative pressure. Composite dressings can minimize the potential for maceration, promote granulation, and provide excellent manifolding.

[0007] More generally, some embodiments can include a dressing having at least three layers assembled in a laminated relationship. The first layer can comprise or consist essentially of a polymer film having a plurality of fluid restriction portions. The fluid restriction portions can be described as imperfect elastomeric valves that cannot close completely and can deform or increase in width when negative pressure is applied, providing less restriction to fluid flow. When the negative pressure is stopped or reduced, the fluid restriction portions generally return to or approach their original state, providing greater restriction to fluid flow. The second layer can comprise a manifold, and the third layer can comprise or consist essentially of a polymer drape. A fourth layer, which can be bonded to the first layer on the opposite side from the second layer, can comprise or consist essentially of a silicone gel having a plurality of apertures. In some examples, the plurality of apertures in the fourth layer can be aligned with the fluid restriction portions of the first layer, and in some embodiments, can be aligned one-to-one with the fluid restriction portions. At least one of the first layer and the third layer may be configured to be interposed between the first layer and the tissue site.

[0008] In some embodiments, the manifold may comprise a foam, more particularly a reticulated polymer foam. A hydrophobic manifold having a thickness of less than 7 millimeters and at least 90% free volume may be suitable for many therapeutic applications.

[0009] In some instances, polyethylene may be a suitable material for the third layer polymer film. In a more specific example, the polymer film may be polyethylene having an areal density of less than 40 grams per square meter. It may also be advantageous for the third layer polymer film to be hydrophobic. In some instances, the polymer film may have a water contact angle of greater than 90 degrees.

[0010] In some embodiments, the fluid restricting portions can comprise a plurality of linear slits or slots. For example, the fluid restricting portions can comprise a plurality of linear slots having a length of about 4 millimeters or less and a width of about 2 millimeters or less. For many therapeutic applications, a length of about 3 millimeters and a width of about 1 millimeter can be suitable. In some embodiments, the fluid restricting portions can be dispersed across the polymer film in a uniform pattern, such as a grid of parallel rows and columns. In some embodiments, the fluid restricting portions can be dispersed across the polymer film in parallel rows and columns, with the rows spaced about 3 millimeters apart from one another. The fluid restricting portions in each of the rows can also be spaced about 3 millimeters apart from one another, in some instances.

[0011] Additionally, some embodiments of the third layer may include or be coupled to a fluid port, which may be coupled or configured to be coupled to a fluid conductor. In some examples, a negative pressure source may be fluidly coupled to the dressing to provide negative pressure therapy.

[0012] Some embodiments of the dressing or device can include a sealing layer, a fluid control layer adjacent to the sealing layer, a manifold layer adjacent to the fluid control layer, and a cover adjacent to the manifold. The fluid layer can have a plurality of imperfect valves configured to respond to a pressure gradient. The sealing layer can have a plurality of apertures positioned to expose the plurality of imperfect valves to the underside of the dressing.

[0013] Some embodiments may include a first layer, a second layer coupled to the first layer, a third layer coupled to the second layer on an opposite side of the first layer, and a fourth layer coupled to the first layer on an opposite side of the second layer. The first layer may include a film formed from a hydrophobic material and a plurality of fluid passages extending through the film. The fluid passages may be configured to expand in response to a pressure gradient across the film. The second layer may include or consist essentially of a manifold formed from a hydrophobic material. The third layer may include a polymeric drape, and the fourth layer may be formed from a hydrophobic gel having an areal density of less than 300 grams per square meter. A plurality of apertures extending through the fourth layer may be fluidly coupled to at least some of the plurality of fluid passages extending through the film.

[0014] In some embodiments, a dressing for treating a tissue site using negative pressure can include a first layer comprising a film having a flat surface texture and a plurality of fluid-restricting portions extending through the film. The fluid-restricting portions can be configured to respond to a pressure gradient across the film. A second layer can be coupled to the first layer, and the second layer can comprise or consist essentially of a manifold. A third layer can be coupled to the second layer on an opposite side from the first layer, and the third layer comprises a polymeric drape. A fourth layer can be coupled to the first layer on an opposite side from the second layer, and the fourth layer comprises a gel having an areal density of less than 300 grams per square meter and a hardness of about 5 Shore 00 to about 80 Shore 00. A plurality of apertures extending through the fourth layer can be aligned with the plurality of fluid-restricting portions extending through the film.

[0015] In some embodiments, a device for treating a tissue site using negative pressure can include a first layer comprising a polyethylene film having a surface with a height variation of less than 0.2 millimeters per centimeter and a water contact angle greater than 90 degrees. A plurality of fluid passageways extending through the first layer can be configured to be normally restricted and expand in response to a pressure gradient across the first layer. A second layer can be coupled to the first layer, the second layer comprising a reticulated polyurethane ether foam having at least 90% free volume and a thickness of less than 7 millimeters. A third layer can be coupled to the second layer opposite the first layer, the third layer comprising a polymeric drape. A fourth layer can be coupled to the first layer opposite the second layer, the fourth layer comprising a silicone gel having an areal density of less than 300 grams per square meter and a hardness of about 5 Shore 00 to about 80 Shore 00. A plurality of apertures extending through the fourth layer can be aligned with the plurality of fluid passageways in the first layer.

[0016] In some embodiments, a dressing for treating a tissue site can include a cover, a manifold, a perforated polymeric film having a substantially planar surface, and a perforated silicone gel having a substantially planar surface. The cover, manifold, perforated polymeric film, and perforated silicone gel can be assembled in a laminated relationship with the cover and perforated silicone gel encapsulating the manifold and perforated polymeric film, and the perforated silicone gel can be configured to contact the tissue site. The substantially planar surface of the perforated polymeric film can, in some embodiments, have a height variation of no more than 0.2 millimeters per centimeter, and the substantially planar surface of the perforated silicone gel can, in some embodiments, have a height variation of no more than 0.2 millimeters per centimeter. In some embodiments, at least one of the perforated polymeric film and the perforated silicone gel can be configured to be inserted between the manifold and the tissue site.

[0017] In some embodiments, the dressing can include a first layer comprising a manifold, a second layer comprising a hydrophobic film having a plurality of elastomeric valves configured to open in response to a pressure gradient across the hydrophobic film, a third layer coupled to the second layer opposite the first layer, and a cover coupled to the first layer opposite the second layer. The third layer can comprise or consist essentially of a hydrophobic gel having a plurality of apertures.

[0018] A method of treating a surface wound with a negative pressure source can include applying a dressing as described to the surface wound, sealing the dressing to the epidermis adjacent the surface wound, fluidly coupling the dressing to a negative pressure source, and applying negative pressure from the negative pressure source to the dressing. In some examples, the dressing can be applied across the edges of the surface wound without cutting or trimming.

[0019] A method for promoting granulation in a surface wound can include applying a dressing to the surface wound, the dressing comprising a cover, a manifold, a perforated polymer film having a substantially flat surface, and a perforated silicone gel having a substantially flat surface. The perforated silicone gel can be sealed around the wound periphery adjacent the surface wound, and the cover can be attached to the epidermis around the perforated silicone gel. A negative pressure source can be fluidly coupled to the dressing, and negative pressure from the negative pressure source can be applied to the dressing. In some embodiments, the dressing can remain on the surface wound for at least five days, and in some embodiments, at least seven days. In some embodiments, a wound filler can be disposed between the perforated silicone gel and the surface wound. For example, a foam wound filler can be applied to the surface wound inside the wound periphery.

[0020] Advantages of the claimed subject matter over the state of the art include (1) promotion of granulation tissue formation (i.e., more rapid healing), (2) reduction in the force required to remove the dressing (i.e., ease of use, reduced pain during dressing changes), (3) reduction in the time to apply the dressing (i.e., ease of use), and / or (4) reduction in the risk of maceration of the peri-wound area during treatment, any or all of which may allow for a 7-day dressing (vs. a 48-hour dressing change), improving treatment compliance and reducing the cost of care. Other objects, advantages, and preferred modes of making and using the claimed subject matter can best be understood by reference to the accompanying drawings in conjunction with the following detailed description of exemplary embodiments. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a functional block diagram of an example embodiment of a treatment system capable of providing tissue treatment in accordance with the present disclosure. [Figure 2] FIG. 2 is an assembled view of an example dressing showing further details that may be associated with some embodiments of the treatment system of FIG. [Figure 3] FIG. 3 is a schematic diagram of an example configuration of a fluid restriction portion in one layer that may be associated with some embodiments of the dressing of FIG. [Figure 4] FIG. 4 is a schematic diagram of an example configuration of apertures in another layer showing further details that may be associated with some embodiments of the dressing of FIG. [Figure 5] FIG. 5 is a schematic diagram of the example layers of FIG. 4 superimposed on the example layers of FIG. [Figure 6] FIG. 6 is a schematic diagram of another example of another dressing layer showing further details that may be associated with some embodiments. [Figure 7] FIG. 7 illustrates another example configuration of a fluid restriction that may be associated with some embodiments of the layers of the dressing of FIG. [Figure 8]FIG. 8 illustrates another example configuration of a fluid restriction that may be associated with some embodiments of the layers of the dressing of FIG. [Figure 9] FIG. 9 is a graphical representation of the maximum peel force measurements (N) at 7 days following dressing application and removal for each test dressing and the control dressing. [Figure 10] Figure 10 is a graphical representation of tissue ingrowth measurements. Thickness (mm) is measured for each test dressing and control dressing. [Figure 11] FIG. 11 is a light micrograph demonstrating granulation tissue thickness for each test dressing and the control dressing. [Figure 12] FIG. 12 is a graphical representation of FIG. 11 demonstrating the quantitative morphometric granulation tissue thickness for each test dressing and the control dressing. DETAILED DESCRIPTION OF THE INVENTION

[0022] The following description of example embodiments provides information to enable one skilled in the art to make and use the claimed subject matter, but may omit some details already known in the art. Thus, the following detailed description should be construed as illustrative rather than limiting.

[0023] Example embodiments may be described herein with reference to spatial relationships between or spatial orientations of various elements as shown in the accompanying figures. Generally, such relationships or orientations assume a frame of reference that corresponds to or is relative to a patient in position to receive treatment. However, as those skilled in the art will recognize, this frame of reference is merely a convenient means of explanation, rather than a strict specification.

[0024] FIG. 1 is a simplified functional block diagram of an example embodiment of a treatment system 100 capable of providing negative pressure therapy in conjunction with the instillation of a topical treatment solution to a tissue site in accordance with the present disclosure.

[0025] In this context, the term "tissue site" broadly refers to a wound, defect, or other treatment target located on or within tissue, including, but not limited to, a surface wound, bone tissue, adipose tissue, muscle tissue, nerve tissue, skin tissue, vascular tissue, connective tissue, cartilage, tendon, or ligament. The term "tissue site" may also refer to any area of ​​tissue that is not necessarily a wound or defect, but instead is an area where it may be desirable to add or promote the growth of additional tissue. For example, negative pressure may be applied to the tissue site to grow additional tissue that can be harvested and transplanted. As used herein, a surface wound is a wound on the surface of the body that is exposed to the exterior of the body, such as an injury or damage to the epidermis, dermis, and / or subcutaneous layer. Surface wounds can include, for example, an ulcer or a closed incision. As used herein, a surface wound does not include wounds within the abdominal cavity. Wounds can include, for example, chronic, acute, traumatic, subacute and dehiscence wounds, partial thickness burns, ulcers (such as diabetic ulcers, pressure ulcers or venous insufficiency ulcers), flap and grafts.

[0026] Treatment system 100 may include, for example, a source or supply of negative pressure, such as negative pressure source 102, a dressing 104, a fluid container, such as container 106, and a regulator or controller, such as controller 108. Additionally, treatment system 100 may include sensors that measure operating parameters and provide feedback signals indicative of the operating parameters to controller 108. For example, as shown in FIG. 1 , treatment system 100 may include a pressure sensor 110, an electrical sensor 112, or both, coupled to controller 108. As shown in the example of FIG. 1 , dressing 104 may, in some embodiments, comprise or consist essentially of one or more dressing layers, such as tissue interface 114, cover 116, or both.

[0027] The treatment system 100 may also include a source of dripping solution, such as saline. For example, the solution source 118 may be fluidly coupled to the dressing 104, as shown in the example embodiment of FIG. 1 . In some embodiments, the solution source 118 may be fluidly coupled to a positive pressure source, such as a positive pressure source 120, a negative pressure source, such as the negative pressure source 102, or both. To ensure proper administration of the dripping solution (e.g., saline) to the tissue site, a regulator, such as a drip regulator 122, may also be fluidly coupled to the solution source 118 and the dressing 104. For example, the drip regulator 122 may comprise a piston that may be pneumatically actuated by the negative pressure source 102 to draw dripping solution from the solution source during negative pressure intervals and drip the solution onto the dressing during drain intervals. Additionally or alternatively, the controller 108 may be coupled to the negative pressure source 102, the positive pressure source 120, or both, to control the administration of the dripping solution to the tissue site. In some embodiments, the drip regulator 122 may also be fluidly coupled to the negative pressure source 102 through the dressing 104, as shown in the example of FIG.

[0028] Some components of the treatment system 100 may be housed within or used with other components, such as sensors, processing units, alarm indicators, memory, databases, software, displays, or user interfaces that further facilitate treatment. For example, in some embodiments, the negative pressure source 102 may be combined with the solution source 118, the controller 108, and other components into a treatment unit.

[0029] Generally, the components of the treatment system 100 may be directly or indirectly coupled. For example, the negative pressure source 102 may be directly coupled to the container 106 or indirectly coupled to the dressing 104 through the container 106. A coupling may include a fluidic, mechanical, thermal, electrical, or chemical coupling (such as a chemical bond), or any combination of couplings, depending on the context. For example, the negative pressure source 102 may be electrically coupled to the controller 108. The negative pressure source may be fluidically coupled to one or more distribution components that provide a fluid path to the tissue site. In some embodiments, components may also be coupled by being physically close, integrated into a single structure, or formed from the same piece of material.

[0030] The distribution components are preferably detachable and may be disposable, reusable, or recyclable. The dressing 104 and the container 106 are examples of distribution components. A fluid conductor is another illustrative example of a distribution component. A "fluid conductor" in this context includes a tube, pipe, hose, conduit, or other structure with one or more lumens or open pathways adapted to transport fluid between two ends. Typically, a tube is an elongated, cylindrical structure with some flexibility, although the geometry and stiffness can vary. Furthermore, some fluid conductors can be telescoped within or otherwise integrally coupled to other components. The distribution components can also include or comprise interfaces or fluid ports that facilitate the coupling and detachment of other components, including sensors and data communication devices. In some embodiments, for example, a dressing interface can facilitate coupling of a fluid conductor to the dressing 104. For example, such a dressing interface can be a SENSAT.RAC™ pad available from KCI of San Antonio, Texas.

[0031] A negative pressure source, such as negative pressure source 102, can be a reservoir of air at negative pressure or can be a manual or powered device, such as a vacuum pump, a suction pump, a wall suction port available in many medical facilities, or a micropump. "Negative pressure" generally refers to a pressure below local ambient pressure, such as the ambient pressure in the local environment outside the enclosed treatment environment. In many cases, the local ambient pressure can also be atmospheric pressure where the tissue site is located. Alternatively, the pressure can be less than the hydrostatic pressure associated with the tissue at the tissue site. Unless otherwise indicated, pressure values ​​mentioned herein are gauge pressures. When referring to an increase in negative pressure, it generally refers to a decrease in absolute pressure, while a decrease in negative pressure generally refers to an increase in absolute pressure. The amount and nature of negative pressure applied to the tissue site can be varied according to treatment requirements, but the pressure is generally a low vacuum, commonly referred to as a rough vacuum, between -5 mmHg (-667 Pa) and -500 mmHg (-66.7 kPa). A typical treatment range is between -50 mmHg (-9.9 kPa) and -300 mmHg (-39.9 kPa).

[0032] Container 106 represents a container, canister, pouch, or other storage component that can be used to manage exudates and other fluids drawn from a tissue site. In many environments, a rigid container may be preferred or desired for fluid collection, storage, and disposal. In other environments, fluids can be properly disposed of without rigid container storage, and a reusable container can reduce waste and costs associated with negative pressure therapy.

[0033] A controller, such as controller 108, may be a microprocessor or computer programmed to operate one or more components of treatment system 100, such as negative pressure source 102. In some embodiments, for example, controller 108 may be a microcontroller, which generally comprises an integrated circuit including a processor core and memory, programmed to directly or indirectly control one or more operating parameters of treatment system 100. The operating parameters may include, for example, the power applied to negative pressure source 102, the pressure generated by negative pressure source 102, or the pressure delivered to tissue interface 114. Controller 108 is also preferably configured to receive one or more input signals, such as feedback signals, and is programmed to modify one or more operating parameters based on the input signals.

[0034] A sensor, such as pressure sensor 110 or electrical sensor 112, is generally known in the art as any device operable to detect or measure a physical phenomenon or property and generally provide a signal indicative of the phenomenon or property being detected or measured. For example, pressure sensor 110 and electrical sensor 112 can be configured to measure one or more operating parameters of treatment system 100. In some embodiments, pressure sensor 110 can be a transducer configured to measure pressure in a pneumatic path and convert the measurement into a signal indicative of the measured pressure. In some embodiments, for example, pressure sensor 110 can be a piezoresistive strain gauge. Optionally, electrical sensor 112 can measure an operating parameter of negative pressure source 102, such as voltage or current, in some embodiments. Preferably, signals from pressure sensor 110 and electrical sensor 112 are suitable as input signals to controller 108, although some signal conditioning may be appropriate in some embodiments. For example, the signals may need to be filtered or amplified before they can be processed by controller 108. Typically, the signal is an electrical signal, but may be represented in other forms, such as an optical signal.

[0035] The tissue interface 114 can generally be adapted to contact the tissue site. The tissue interface 114 can be in partial or complete contact with the tissue site. For example, if the tissue site is a wound, the tissue interface 114 can partially or completely fill the wound or be placed on top of the wound. The tissue interface 114 can take many forms and, in some embodiments, can have two or more layers. The tissue interface 114 can also have many sizes, shapes, or thicknesses, depending on various factors, such as the type of treatment being performed or the nature and size of the tissue site. For example, the size and shape of the tissue interface 114 can conform to the contours of a deep and irregularly shaped tissue site.

[0036] In some embodiments, the cover 116 can provide a microbial barrier and protection from physical trauma. The cover 116 can also be constructed from a material that can reduce evaporative loss and provide a fluid seal between two components or two environments, such as between a treatment environment and a local external environment. The cover 116 can be, for example, an elastomeric film or membrane that can provide an adequate seal to maintain negative pressure at the tissue site for a given negative pressure source. The cover 116 can have a high moisture vapor transmission rate (MVTR) in some applications. For example, the MVTR can be at least 300 g / m² per 24 hours in some embodiments. 2In some example embodiments, the cover 116 may be a polymer drape, such as a polyurethane film, that is permeable to water vapor but impermeable to liquids. Such drapes typically have a thickness in the range of 25-50 microns. For permeable materials, the permeability must generally be low enough to maintain the desired negative pressure. The cover 116 may, for example, comprise one or more of the following materials: hydrophilic polyurethane, cellulose derivatives, hydrophilic polyamide, polyvinyl alcohol, polyvinylpyrrolidone, hydrophilic acrylic resin, hydrophilic silicone elastomer, e.g., 14400 g / m 2 INSPIRE 2301 material from Coveris Advanced Coatings of Wrexham, United Kingdom, having a MVTR (inverted cup technique) of 1 / 24 hours and a thickness of about 30 microns, thin uncoated polymer drapes, natural rubber, polyisoprene, styrene butadiene rubber, chloroprene rubber, polybutadiene, nitrile rubber, butyl rubber, ethylene propylene rubber, ethylene propylene diene monomer, chlorosulfonated polyethylene, polysulfide rubber, polyurethane (PU), EVA film, copolyester, silicone, silicone drapes, 3M Tegaderm® drapes, polyurethane (PU) drapes such as those available from Avery Dennison Corporation of Glendale, California, polyether block polyamide copolymer (PEBAX), INSPIRE 2327 from Arkema, France, or other suitable materials.

[0037] An attachment device can be used to attach the cover 116 to a mounting surface, such as an intact epidermis, a gasket, or another cover. The attachment device can take many forms. For example, the attachment device can be a medically acceptable pressure-sensitive adhesive configured to adhere the cover 116 to the epidermis surrounding a tissue site, such as a superficial wound. In some embodiments, some or all of the cover 116 can be coated with an adhesive, such as an acrylic adhesive, which can have a coverage of 25 to 65 grams per square meter (gsm). In some embodiments, a thicker adhesive or combination of adhesives can be applied to improve the seal and reduce leakage. Other example embodiments of attachment devices can include double-sided tape, glue, hydrocolloid, hydrogel, silicone gel, or organogel.

[0038] Solution source 118 may also represent a container, canister, pouch, bag, or other storage component that can provide solution for instillation therapy. While the composition of the solution can vary according to the indicated therapy, examples of solutions that may be suitable for some indications include hypochlorite-based solutions, silver nitrate (0.5%), sulfur-based solutions, biguanides, cationic solutions, and isotonic solutions.

[0039] The fluid dynamics of using a negative pressure source to reduce pressure in another component or location, such as within an enclosed treatment environment, can be mathematically complex. However, the basic principles of fluid dynamics applicable to negative pressure therapy and instillation are generally well known to those skilled in the art, and the process of reducing pressure will be illustratively described herein as, for example, "delivering," "distributing," or "generating" negative pressure.

[0040] Generally, exudates and other fluids flow along a fluid path toward lower pressure. Thus, the term "downstream" typically means relatively closer to a negative pressure source or farther from a positive pressure source in a fluid path. Conversely, the term "upstream" means relatively farther from a negative pressure source or nearer to a positive pressure source. Similarly, it may be convenient to describe some features in terms of a fluid "inlet" or "outlet" in this frame of reference. This orientation is generally assumed for purposes of describing various features and components herein. However, the fluid path may be reversed in some applications (e.g., by using a positive pressure source instead of a negative pressure source), and this descriptive convention should not be construed as a limiting convention.

[0041] 2 is an assembled view of the example dressing 104 of FIG. 1 , illustrating further details that may be relevant to some embodiments in which the tissue interface 114 comprises two or more layers. In the example of FIG. 2 , the tissue interface 114 comprises a first layer 205, a second layer 210, and a third layer 215. In some embodiments, the first layer 205 can be positioned adjacent to the second layer 210, and the third layer 215 can be positioned adjacent to the second layer 210 on an opposite side from the first layer 205. For example, the first layer 205, the second layer 210, and the third layer 215 can be stacked such that the first layer 205 contacts the second layer 210 and the second layer 210 contacts the first layer 205 and the third layer 215. In some embodiments, one or more of the first layer 205, the second layer 210, and the third layer 215 can also be bonded to an adjacent layer.

[0042] The first layer 205 may comprise or consist essentially of a manifold or manifold layer that provides a means for collecting or distributing fluid under pressure across the tissue interface 114. For example, the first layer 205 may be adapted to receive negative pressure from a negative pressure source and distribute the negative pressure through a plurality of apertures across the tissue interface 114, which may have the effect of collecting fluid from the tissue site and drawing the fluid toward the negative pressure source. In some embodiments, the fluid path may be reversed or a second fluid path may be provided to facilitate delivery of fluid, such as from a dripping solution source, across the tissue interface 114.

[0043] In some exemplary embodiments, the first layer 205 can include multiple channels that can be interconnected to facilitate fluid distribution or collection. In some embodiments, the first layer 205 can include or consist essentially of a porous material having interconnected fluid pathways. For example, open-cell foam, reticulated foam, porous tissue aggregates, and other porous materials such as gauze or felt mats can generally include pores, edges, and / or walls adapted to form interconnected fluid flow paths. Liquids, gels, and other foams can also include or be hardened to include apertures and fluid pathways. In some embodiments, the first layer 205 can additionally or alternatively include protrusions that form the interconnected fluid pathways. For example, the first layer 205 can be molded to provide surface protrusions that define the interconnected fluid pathways. Any or all of the surfaces of the first layer 205 can have uneven, rough, or jagged contours.

[0044] In some embodiments, first layer 205 can include or consist essentially of a reticulated foam having a pore size and free volume that can be varied according to the needs of the indicated therapy. For example, a reticulated foam having at least 90% free volume can be suitable for many therapeutic applications, and a foam having an average pore size in the range of 400-600 microns (40-50 pores per inch) can be particularly suitable for some types of therapy. The tensile strength of first layer 205 can also be varied according to the needs of the indicated therapy. For example, the tensile strength of the foam can be increased for instillation of a topical therapeutic solution. The 25% compressive load deflection of first layer 205 can be at least 0.35 pounds per square inch, and the 65% compressive load deflection can be at least 0.43 pounds per square inch. In some embodiments, the tensile strength of first layer 205 can be at least 10 pounds per square inch. First layer 205 can have a tear strength of at least 2.5 pounds per square inch. In some embodiments, first layer 205 can be a foam composed of a polyol, such as a polyester or polyether, an isocyanate, such as toluene diisocyanate, and a polymerization modifier, such as an amine or a tin compound. In one non-limiting example, first layer 205 can be a reticulated polyurethane ether foam, such as GRANUFOAM™ Dressing or VACVERAFLO™ Dressing, both available from KCI of San Antonio, Texas.

[0045] The thickness of first layer 205 can also be varied according to the needs of the indicated therapy. For example, the thickness of first layer 205 can be reduced to relieve stress on other layers and reduce tension on surrounding tissue. The thickness of first layer 205 can also affect the comfort of first layer 205. In some embodiments, a thickness in the range of approximately 5 millimeters to 10 millimeters may be suitable.

[0046] The second layer 210 may comprise or consist essentially of a means for controlling or managing fluid flow. In some embodiments, the second layer may include or consist essentially of a liquid-impermeable, elastomeric material. For example, the second layer 210 may include or consist essentially of a polymer film. In some embodiments, the second layer 210 may also have a smooth or matte surface texture. For some applications, a polished or glossy finish of better than or equal to grade B3 according to the SPI (American Society of Plastics Industry) standard may be particularly advantageous. In some embodiments, the surface height variation may be limited to an acceptable tolerance. For example, the surface of the second layer may have a substantially flat surface, with a height variation limited to 0.2 millimeters per centimeter.

[0047] In some embodiments, the second layer 210 can be hydrophobic. The hydrophobicity of the second layer 210 can be varied, and in some embodiments, the second layer 210 can have a water contact angle of at least 90 degrees. In some embodiments, the second layer 210 can have a water contact angle of 150 degrees or less. For example, in some embodiments, the contact angle of the second layer 210 can be in the range of at least 90 degrees to about 120 degrees, or in the range of at least 120 degrees to 150 degrees. Water contact angles can be measured using any standard device. While a manual goniometer can be used to visually approximate the contact angle, contact angle measurement instruments often include integrated systems requiring, among other things, a horizontal stage, a liquid dropper such as a syringe, a camera, and software designed to more accurately and precisely calculate the contact angle. Non-limiting examples of such integrated systems include the FTA125, FTA200, FTA2000, and FTA4000 systems, all commercially available from First Ten Angstroms, Inc., Portsmouth, VA, and the DTA25, DTA30, and DTA100 systems, all commercially available from Kruss GmbH, Hamburg, Germany. Unless otherwise specified, water contact angles herein are measured using deionized and distilled water on a horizontal sample surface against a sessile drop added from a height of 5 cm or less in air at 20-25°C and 20-50% relative humidity. Contact angles reported herein represent the average of 5-9 measurements, discarding both the highest and lowest readings. The hydrophobicity of the second layer 210 can be further enhanced by hydrophobic coatings of other materials, such as silicones and fluorocarbons, either liquid-coated or plasma-coated.

[0048] The second layer 210 may also be suitable for welding to other layers, including the first layer 205. For example, the second layer 210 may be adapted to be welded to polyurethane foam using other methods that generate heat, such as heat, radio frequency (RF) welding, or ultrasonic welding. RF welding may be particularly suitable for more polar materials, such as polyurethane, polyamide, polyester, and acrylates. A sacrificial polarity interface may be used to facilitate RF welding of less polar film materials, such as polyethylene.

[0049] The areal density of second layer 210 can vary according to the indicated therapy or application. In some embodiments, an areal density of less than 40 grams per square meter may be suitable, and for some applications, an areal density of about 20-30 grams per square meter may be particularly advantageous.

[0050] In some embodiments, for example, the second layer 210 can include or be composed of a hydrophobic polymer, such as a polyethylene film. The simple and inert structure of polyethylene can provide a surface that interacts little, if at all, with biological tissue and fluids, promoting free flow of liquids and low adhesion, which can be particularly advantageous for many applications. More polar films suitable for laminating to polyethylene film include polyamides, copolyesters, ionomers, and acrylics. Layers such as ethylene vinyl acetate or modified polyurethanes can be used to aid in bonding the polyethylene to the polar film. Ethyl methyl acrylate (EMA) film can also have suitable hydrophobic and welding properties for some configurations.

[0051] As shown in the example of FIG. 2 , the second layer 210 can have one or more fluid restriction portions 220, which can be uniformly or randomly distributed throughout the second layer 210. The fluid restriction portions 220 can be bidirectional and pressure-sensitive. For example, the fluid restriction portions 220 can generally comprise or consist essentially of elastic passages that are normally unstrained to substantially reduce liquid flow and can expand in response to a pressure gradient. In some embodiments, the fluid restriction portions 220 can comprise or consist essentially of perforations in the second layer 210. The perforations can be formed by removing material from the second layer 210. For example, the perforations can be formed by cutting the second layer 210, which, in some embodiments, can also deform the edges of the perforations. When there is no pressure gradient across the perforations, the passages can be small enough to form a seal or fluid restriction, thereby substantially reducing or preventing liquid flow. Additionally or alternatively, one or more of the fluid restrictions 220 can be elastomeric valves, which are normally closed to substantially prevent liquid flow when unstrained and can open in response to a pressure gradient. For some applications, fenestrations in the second layer 210 can be suitable valves. Fenestrations can also be formed by removing material from the second layer 210, although the amount of material removed and the resulting dimensions of the fenestrations can be orders of magnitude smaller than perforations and are not likely to deform the edges.

[0052] For example, some embodiments of the fluid restriction portion 220 may comprise or consist essentially of one or more slots or combinations of slots in the second layer 210. In some examples, the fluid restriction portion 220 may comprise or consist of a linear slot having a length of less than 4 millimeters and a width of less than 1 millimeter. In some embodiments, the length may be at least 2 millimeters and the width may be at least 0.4 millimeters. A length of approximately 3 millimeters and a width of approximately 0.8 millimeters may be particularly suitable for many applications, and a tolerance of approximately 0.1 millimeters may also be acceptable. Such dimensions and tolerances may be achieved, for example, using a laser cutter. Slots of such a configuration may function as imperfect valves that substantially reduce liquid flow in a normally closed or quiescent state. For example, such slots may form a fluid restriction portion without being completely closed or sealed. The slots may expand or open wider in response to a pressure gradient to allow increased liquid flow.

[0053] The third layer 215 can be a sealing layer including or constructed of a soft, pliable material suitable for providing a fluid seal with the tissue site and can have a substantially flat surface. For example, the third layer 215 can include, without limitation, silicone gel, soft silicone, hydrocolloid, hydrogel, polyurethane gel, polyolefin gel, hydrogenated styrene copolymer gel, foam gel, adhesive, polyurethane, polyolefin, or hydrogenated styrene copolymer coated soft closed-cell foam such as polyurethane and polyolefin. In some embodiments, the third layer 215 can have a thickness of about 200 microns (μm) to about 1000 microns (μm). In some embodiments, the third layer 215 can have a hardness of about 5 Shore 00 to about 80 Shore 00. Furthermore, the third layer 215 can be constructed of a hydrophobic or hydrophilic material. For example, the third layer 215 can be constructed of a hydrophobic or hydrophilic material.

[0054] In some embodiments, the third layer 215 can be a hydrophobic coated material. For example, the third layer 215 can be formed by coating a spaced apart material, such as a woven fabric, a nonwoven fabric, a molded or extruded mesh, or the like, with a hydrophobic material. The hydrophobic material for the coating can be, for example, soft silicone.

[0055] The third layer 215 can have a perimeter 225 surrounding or around the inner portion 230 and apertures 235 disposed through the perimeter 225 and the inner portion 230. The inner portion 230 can correspond to a surface region of the first layer 205 in some examples. The third layer 215 can also have corners 240 and edges 245. The corners 240 and edges 245 can be part of the perimeter 225. The third layer 215 can have an inner boundary 250 around the inner portion 230 disposed between the inner portion 230 and the perimeter 225. As shown in the example of FIG. 2, the inner boundary 250 can be substantially free of apertures 235. In some examples, the inner portion 230 can be symmetrical and centrally disposed in the third layer 215, as shown in FIG. 2.

[0056] The apertures 235 can be formed, for example, by cutting, or by application of localized RF or ultrasonic energy, or by other suitable techniques for forming openings. The apertures 235 can have a uniform distribution pattern or can be randomly dispersed on the third layer 215. The apertures 235 in the third layer 215 can have many shapes, including, for example, circles, squares, stars, ovals, polygons, slits, complex curves, linear shapes, triangles, or any combination of such shapes.

[0057] Each of the apertures 235 can have uniform or similar geometric characteristics. For example, in some embodiments, each of the apertures 235 can be a circular aperture having substantially the same diameter. In some embodiments, the diameter of each of the apertures 235 can be between about 1 millimeter and about 50 millimeters. In other embodiments, the diameter of each of the apertures 235 can be between about 1 millimeter and about 20 millimeters.

[0058] In other embodiments, the geometric characteristics of the apertures 235 may vary. For example, as shown in FIG. 2 , the diameter of the apertures 235 may vary depending on the location of the apertures 235 in the third layer 215. In some embodiments, the diameter of the apertures 235 at the periphery 225 of the third layer 215 may be larger than the diameter of the apertures 235 at the interior portion 230 of the third layer 215. For example, in some embodiments, the apertures 235 located at the periphery 225 may have a diameter between about 9.8 millimeters and about 10.2 millimeters. In some embodiments, the apertures 235 located at the corners 240 may have a diameter between about 7.75 millimeters and about 8.75 millimeters. In some embodiments, the apertures 235 located at the interior portion 230 may have a diameter between about 1.8 millimeters and about 2.2 millimeters.

[0059] At least one of the apertures 235 in the periphery 225 of the third layer 215 can be positioned at an edge 245 of the periphery 225 and can have an open or exposed internal cutout at the edge 245 that is in lateral fluid communication with the edge 245. Lateral refers to a direction toward the edge 245 and in the same plane as the third layer 215. As shown in the example of FIG. 2 , the apertures 235 in the periphery 225 can be positioned proximate to or at the edge 245 in lateral fluid communication with the edge 245. The apertures 235 positioned proximate to or at the edge 245 can be spaced substantially equidistantly around the periphery 225, as shown in the example of FIG. 2 . Alternatively, the spacing of the apertures 235 proximate to or at the edge 245 can be irregular.

[0060] In the example of FIG. 2 , dressing 104 can further include an attachment device such as adhesive 255. Adhesive 255 can be, for example, a medically acceptable pressure-sensitive adhesive that extends around the periphery, a portion, or the entirety of cover 116. In some embodiments, adhesive 255 can be, for example, an acrylic adhesive having a coverage of 25 to 65 grams per square meter (gsm). In some embodiments, a thicker adhesive or combination of adhesives can be applied to improve the seal and reduce leakage. Adhesive 255 can be a layer having substantially the same shape as periphery 225. In some embodiments, such a layer of adhesive 255 can be continuous or discontinuous. Discontinuities in adhesive 255 can be provided by apertures or holes (not shown) in adhesive 136. The apertures or holes in adhesive 255 can be formed after application of adhesive 255 or by coating adhesive 255 in a pattern on a carrier layer, such as on one side of cover 116. The apertures or holes in the adhesive 255 may also be sized to improve the MVTR of the dressing 104 in some example embodiments.

[0061] As shown in the example of FIG. 2 , in some embodiments, a release liner 260 can be attached to or positioned adjacent to the third layer 215 to protect the adhesive 255 prior to use. The release liner 260 can also provide stiffness, for example, to aid in deployment of the dressing 104. The release liner 260 can be, for example, process paper, film, or polyethylene. Further, in some embodiments, the release liner 260 can 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 260 can substantially eliminate wrinkling or other deformation of the dressing 104. For example, polar semi-crystalline polymers can be highly oriented and resistant to softening, swelling, or other deformation that may occur when in contact with components of the dressing 104 or when subjected to temperature or environmental fluctuations or sterilization. In some embodiments, the release liner 260 can have a surface texture that can be imprinted onto an adjacent layer, such as the third layer 215. Additionally, a release agent can be disposed on the side of the release liner 260 that is configured to contact the third layer 215. For example, the release agent can be a silicone coating and can have suitable release factors to facilitate removal of the release liner 260 by hand without damaging or deforming the dressing 104. In some embodiments, the release agent can be, for example, a fluorocarbon or fluorosilicone. In other embodiments, the release liner 260 can be uncoated or otherwise used without a release agent.

[0062] Figure 2 also shows an example of a fluid conductor 265 and a dressing interface 270. As shown in the example of Figure 2, the fluid conductor 265 can be a flexible tube that can be fluidly coupled at one end to the dressing interface 270. The dressing interface 270 can be an elbow connector that can be positioned over an aperture 275 in the cover 116 to provide a fluid path between the fluid conductor 265 and the tissue interface 114, as shown in the example of Figure 2.

[0063] FIG. 3 is a schematic diagram of an example second layer 210, illustrating additional details that may be relevant to some embodiments. As shown in the example of FIG. 3, the fluid-restricting portions 220 can consist essentially of one or more linear slots, each having a length of approximately 3 millimeters. FIG. 3 also illustrates an example of a uniform distribution pattern of the fluid-restricting portions 220. In FIG. 3, the fluid-restricting portions 220 are substantially coextensive with the second layer 210 and are distributed across the second layer 210 in a grid of parallel rows and columns, where the slots are also mutually parallel to one another. In some embodiments, as shown in the example of FIG. 3, the rows can be spaced approximately 3 millimeters apart on center, and the fluid-restricting portions 220 in each of the rows can be spaced approximately 3 millimeters apart on center. The fluid-restricting portions 220 in adjacent rows can be aligned or offset. For example, adjacent rows can be offset as shown in FIG. 3, such that the fluid-restricting portions 220 are aligned in every other row and spaced approximately 6 millimeters apart. The spacing of the fluid restriction portions 220 can be varied in some embodiments to increase the density of the fluid restriction portions 220 according to treatment requirements.

[0064] FIG. 4 is a schematic diagram of an example configuration of apertures 235, showing further details that may be associated with some embodiments of the third layer 215. In some embodiments, the apertures 235 shown in FIG. 4 may be associated only with the inner portion 230. In the example of FIG. 4, the apertures 235 are generally circular and have a diameter of approximately 2 millimeters. FIG. 4 also shows an example of a uniform distribution pattern of apertures 235 in the inner portion 230. In FIG. 4, the apertures 235 are distributed across the inner portion 230 in a grid of parallel rows and columns. As shown in the example of FIG. 4, within each row and column, the apertures 235 may be equidistant from one another. FIG. 4 shows one example configuration that may be particularly suitable for many applications, in which the apertures 235 are spaced approximately 6 millimeters apart and offset by 3 millimeters along each row and column.

[0065] FIG. 5 is a schematic diagram of the example third layer 215 of FIG. 4 superimposed on the second layer 210 of FIG. 3 , illustrating further details that may be relevant to some example embodiments of the tissue interface 114. For example, as shown in FIG. 5 , in some embodiments, the fluid restriction portions 220 may be aligned with, overlap with, aligned with, or otherwise fluidly coupled to the apertures 235. In some embodiments, one or more of the fluid restriction portions 220 may be aligned with the apertures 235 only at the inner portion 230, or may be only partially aligned with the apertures 235. The fluid restriction portions 220 in the example of FIG. 5 are generally configured such that each of the fluid restriction portions 220 is aligned with only one of the apertures 235. In other examples, one or more of the fluid restriction portions 220 may be aligned with two or more of the apertures 235. For example, any one or more of the fluid restriction portions 220 may be perforations or fenestrations that extend across two or more of the apertures 235. Additionally or alternatively, one or more of the fluid restriction portions 220 may not be aligned with any of the apertures 235.

[0066] As shown in the example of FIG. 5 , the apertures 235 can be sized to expose portions of the second layer 210, the fluid limiting portions 220, or both through the third layer 215. In some embodiments, each of the apertures 235 can be sized to expose fewer than two of the fluid limiting portions 220. In some examples, the length of each of the fluid limiting portions 220 can be substantially equal to or less than the diameter of each of the apertures 235. In some embodiments, the average dimension of the fluid limiting portions 220 is substantially similar to the average dimension of the apertures 235. For example, the apertures 235 can be elliptical in some embodiments, and the length of each of the fluid limiting portions 220 can be substantially equal to the major axis or minor axis. However, in some embodiments, the dimensions of the fluid limiting portions 220 can exceed the dimensions of the apertures 235, and the size of the apertures 235 can limit the effective size of the fluid limiting portions 220 exposed at the underside of the dressing 104.

[0067] In some embodiments, one or more of the components of the dressing 104 can be further treated with an antimicrobial agent. For example, the first layer 205 can be a foam, mesh, or nonwoven fabric coated with an antimicrobial agent. In some embodiments, the first layer can include an antimicrobial element, such as a fiber coated with an antimicrobial agent. Additionally or alternatively, some embodiments of the second layer 210 can be a polymer coated with or mixed with an antimicrobial agent. In other examples, the fluid conductor 265 can also or alternatively be treated with one or more antimicrobial agents. Suitable antimicrobial agents can include, for example, metallic silver, PHMB, iodine or its complexes, and mixtures such as povidone-iodine, copper metal compounds, chlorhexidine, or any combination of these substances.

[0068] The individual components of the dressing 104 can be bonded or otherwise secured to one another without adversely affecting fluid management, for example, with solvent or non-solvent adhesives, or by heat welding. Additionally, the second layer 210 or first layer 205 can be joined to the interface 250 of the third layer 215 in any suitable manner, such as, for example, by welding or adhesive.

[0069] The cover 116, first layer 205, second layer 210, third layer 215, or various combinations can be assembled prior to application or in situ. For example, in some embodiments, the cover 116 can be bonded to the first layer 205, and the second layer 210 can be bonded to the first layer 205 on an opposite side of the cover 116. In some embodiments, the third layer 215 can also be bonded to the second layer 210 on an opposite side of the first layer 205. In some embodiments, one or more layers of the tissue interface 114 can be coextensive. For example, as shown in the embodiment of FIG. 2, the first layer 205 can be coextensive with the second layer 210. In some embodiments, the dressing 104 can be provided as a single composite dressing. For example, the third layer 215 can be bonded to the cover 116 to encapsulate the first layer 205 and the second layer 210, with the third layer 215 configured to face the tissue site.

[0070] In use, the release liner 260 (if included) can be removed to expose the third layer 215, which can be placed within, across, on, or otherwise adjacent to a tissue site, particularly a superficial tissue site and adjacent epidermis. The third layer 215 and the second layer 210 can be interposed between the first layer 205 and the tissue site, thereby substantially reducing or eliminating adverse interactions with the first layer 205. For example, the third layer 215 can be placed over a superficial wound (including wound edges) and intact epidermis to prevent direct contact with the first layer 205. Treating a superficial wound or placing the dressing 104 on a superficial wound includes placing the dressing 104 immediately adjacent to the surface of the body or spreading it over at least a portion of the surface of the body. Treating a superficial wound does not include placing the dressing 104 completely within the body or completely below the surface of the body, such as placing the dressing in the abdominal cavity. In some applications, inner portion 230 of third layer 215 can be positioned adjacent to, proximate to, or over the tissue site. In some applications, at least a portion of second layer 210, fluid restricting portion 220, or both can be exposed to the tissue site through third layer 215. Peripheral edge 225 of third layer 215 can be positioned adjacent to or proximate to tissue surrounding or surrounding the tissue site. Third layer 215 can be sufficiently adhesive to hold dressing 104 in place while also allowing dressing 104 to be removed or repositioned without trauma to the tissue site.

[0071] Removal of release liner 260 can also expose adhesive 255, allowing cover 116 to be attached to the attachment surface. For example, the cover can be attached to the epidermis around first layer 205 and second layer 210 and around the periphery of the tissue site. In some embodiments, adhesive 255 can be in fluid communication with the attachment surface through apertures 235 at least at peripheral edge 225 of third layer 215. Adhesive 255 can also be in fluid communication with edge 245 through apertures 235 exposed in edge 245.

[0072] Once the dressing 104 is in the desired position, adhesive 255 can be forced through apertures 235 to adhere the dressing 104 to the mounting surface. The apertures 235 in the edge 245 allow the adhesive 255 to flow around the edge 245 to facilitate adhesion of the edge 159 to the mounting surface.

[0073] In some embodiments, the apertures or holes in the third layer 215 can be sized to control the amount of adhesive 255 in fluid communication with the apertures 235. For a given geometric shape of the corner 240, the relative sizes of the apertures 235 can be configured to maximize the surface area of ​​the adhesive 255 exposed and in communication through the apertures 235 at the corner 240. For example, as shown in FIG. 2 , edges 245 can intersect at a substantially right angle, i.e., approximately 90 degrees, to define the corner 240. In some embodiments, the corner 240 can have a radius of approximately 10 millimeters. Furthermore, in some embodiments, three of the apertures 235, having diameters of approximately 7.75 millimeters to approximately 8.75 millimeters, can be positioned in a triangular configuration at the corner 240 to maximize the exposed surface area for the adhesive 255. In other embodiments, depending on the selected geometry of the corner 240, the size and number of apertures 235 at the corner 240 can be adjusted as needed to maximize the exposed surface area of ​​the adhesive 255. Furthermore, the apertures 235 at the corner 240 can be completely contained within the third layer 215, substantially preventing lateral fluid communication outside the corner 240. Having the apertures 235 at the corner 240 completely contained within the third layer 215 can substantially prevent fluid communication of the adhesive 255 outside the corner 240, improving handling of the dressing 104 during deployment at the tissue site. Furthermore, the substantial absence of adhesive 136 outside the corner 240 can increase the flexibility of the corner 240 for improved comfort.

[0074] In some embodiments, the adhesive strength of the adhesive 255 can vary in different locations of the dressing 104. For example, the adhesive 255 can have a relatively low adhesive strength in locations adjacent the third layer 215 where the apertures 235 are relatively large, and a relatively high adhesive strength in locations where the apertures 235 are relatively small. An adhesive 255 having a relatively low adhesive strength in combination with a relatively large aperture 235 can provide comparable adhesion to an adhesive 255 having a relatively high adhesive strength in locations with a relatively small aperture 235.

[0075] The geometry and dimensions of the tissue interface 114, the cover 116, or both, can be modified to suit a particular application or anatomical structure. For example, the geometry or dimensions of the tissue interface 114 and the cover 116 can be adapted to provide an effective and reliable seal for difficult-to-seal anatomical structures at and around the tissue site, such as the elbow or heel. Additionally or alternatively, the dimensions can be modified to increase the surface area for the third layer 215 to promote epithelial cell migration and proliferation at the tissue site and reduce the likelihood of granulation tissue ingrowth.

[0076] Additionally, the dressing 104 may be reapplied or repositioned to reduce or eliminate leaks that may be caused by folds or other discontinuities in the dressing 104 and tissue site. The ability to correct leaks may, in some embodiments, improve treatment reliability and reduce power consumption.

[0077] 2 can provide a sealed treatment environment proximate to the tissue site that is substantially isolated from the external environment, and the negative pressure source 102 can apply reduced pressure in the sealed treatment environment. The third layer 215 can provide an effective and reliable seal at or around the tissue site against difficult-to-seal anatomical surfaces, such as the elbow or heel. Additionally, the dressing 104 can allow for the correction of air leaks caused by folds and other discontinuities in the dressing 104, for example, by reapplication or repositioning. The ability to correct leaks can, in some embodiments, increase the efficacy of treatment and reduce power consumption.

[0078] If not already configured, the dressing interface 270 is placed over the aperture 275 and attached to the cover 116. The fluid conductor 265 may be fluidly coupled to the dressing interface 270 and to the negative pressure source 102.

[0079] Negative pressure applied through the tissue interface 114 can create a negative pressure differential across the fluid restriction 220 in the second layer 210, causing the fluid restriction 220 to open or expand from their resting state. For example, in some embodiments in which the fluid restriction 220 can comprise a substantially closed fenestration through the second layer 210, a pressure gradient across the fenestration can strain the adjacent material of the second layer 210, increasing the size of the fenestration and allowing fluid movement therethrough, similar to the action of a duckbill valve. Opening the fluid restriction 220 can allow movement of exudates and other fluids through the fluid restriction 220 and into the first layer 205 and reservoir 106. Pressure changes can also cause the first layer 205 to expand and contract, and the inner boundary 250 can protect the epidermis from irritation. The second layer 210 and the third layer 215 can also substantially reduce or prevent tissue exposure to the first layer 205, thereby inhibiting tissue growth into the first layer 205.

[0080] In some embodiments, the first layer 205 can be hydrophobic to minimize liquid retention or storage in the dressing 104. In other embodiments, the first layer 205 can be hydrophilic. In instances where the first layer 205 can be hydrophilic, the first layer 205 can also wick fluid away from the tissue site while continuing to distribute negative pressure to the tissue site. The wicking properties of the first layer 205 can draw fluid away from the tissue site, for example, by capillary flow or other wicking mechanisms. An example of a hydrophilic first layer 205 is a polyvinyl alcohol, open-cell foam, such as VACWHITEFOAM™ dressing available from KCI of San Antonio, Texas. Other hydrophilic foams can include those made from polyethers. Other foams that can exhibit hydrophilic characteristics include hydrophobic foams that have been treated or coated to provide hydrophilic properties.

[0081] When the negative pressure source 102 is removed or turned off, the pressure differential across the fluid restriction portions 220 can disappear, causing the fluid restriction portions 220 to move to their resting state and preventing or reducing the rate at which exudates or other liquids return through the second layer 210 to the tissue site.

[0082] In some applications, a filler material may also be disposed between the tissue site and the third layer 215. For example, if the tissue site is a superficial wound, a wound packing material may be applied inside the wound perimeter, and the third layer 215 may be disposed around the wound perimeter and over the wound packing material. In some embodiments, the packing material may be a manifold, such as an open-cell foam. In some embodiments, the packing material may include or consist essentially of the same material as the first layer 205.

[0083] Additionally or alternatively, an instillation solution or other fluid can be dispensed into the dressing 104, thereby increasing the pressure within the tissue interface 114. The increase in pressure within the tissue interface 114 can create a positive pressure differential across the fluid restriction portions 220 in the second layer 210, thereby causing the fluid restriction portions 220 to open or expand from their resting state and allowing the instillation solution or other fluid to be dispensed to the tissue site.

[0084] FIG. 6 is a schematic diagram of another example of the third layer 215, illustrating further details that may be relevant to some embodiments. As shown in the example of FIG. 6, the third layer 215 can have one or more fluid restriction portions, such as a valve 605, instead of or in addition to the aperture 235 in the inner portion 230. Furthermore, the valve 605 can be included in the third layer 215 in addition to or instead of the fluid restriction portion 220 in the second layer 210. In some embodiments in which the third layer 215 includes one or more of the valves 605, the second layer 210 can be omitted. For example, in some embodiments, the tissue interface 114 can consist essentially of the first layer 205 and the third layer 215 of FIG. 6, with the valve 605 disposed in the inner portion 230.

[0085] 7 and 8 show other configurations of valve 605, where valve 605 each includes a cross slit or a combination of cross slits.

[0086] A method for treating a surface wound to promote healing and tissue granulation includes applying a dressing 104 to the surface wound and sealing the dressing 104 to the epidermis adjacent the surface wound. For example, a third layer 215 can be placed over the surface wound, covering at least a portion of the edge of the surface wound and the perimeter of the wound adjacent the surface wound. A cover can also be attached to the epidermis around the third layer 215. The dressing 104 can be fluidly coupled to a negative pressure source, such as negative pressure source 102. Negative pressure from the negative pressure source can be applied to the dressing 104 to open the fluid restriction 220. The fluid restriction 220 can be closed by blocking, terminating, or reducing the negative pressure. The second layer 210 and the third layer 215 can substantially prevent exposure of tissue in the surface wound to the first layer 205 and inhibit tissue in-growth into the first layer 205. The dressing 104 may also substantially prevent peri-wound maceration.

[0087] The systems, devices, and methods described herein can offer significant advantages over conventional dressings. For example, some negative pressure therapy dressings can require time and skill to properly size and apply to achieve a good fit and seal. In contrast, some embodiments of the dressing 104 provide a negative pressure dressing that is easy to apply, reducing application and removal time. In some embodiments, for example, the dressing 104 can be a fully integrated negative pressure therapy dressing that can be applied to a tissue site (including around a wound) in a single step without cutting to size, while still providing or improving upon many of the benefits of other negative pressure therapy dressings that require sizing. These advantages can include superior manifolding, favorable granulation, protection of surrounding tissue from maceration, and low trauma and high sealing integrity. These features can be particularly advantageous for superficial wounds with moderate depth and medium-to-high levels of exudate. Some embodiments of the dressing 104 can remain on the tissue site for at least five days, and some embodiments can remain for at least seven days. The antimicrobial agent in the dressing 104 can extend the usable life of the dressing 104 by reducing or eliminating the risk of infection that may be associated with long-term use, particularly use on infected or heavily exuding wounds. [Example]

[0088] Some of the advantages associated with the systems, devices and methods described herein can be further demonstrated by the following non-limiting examples.

[0089] Example 1 - Evaluation of dressings in a Swine model of a full-thickness defect wound the purpose The primary objective of this study was to evaluate an embodiment of a dressing having the characteristics described above (designated "GM" for purposes of the study) in association with VAC® Therapy and VACVERAFLO™ Therapy compared to conventional VAC® Therapy with GRANUFOAM™ dressings and other Advanced Wound Care dressings without VAC® Therapy. Wounds were evaluated for granulation tissue formation, the presence of maceration in the peri-wound skin, and ease of dressing removal, as determined by: i. Histological evaluation of granulation tissue thickness ii. Peel strength test iii. Visual assessment of bleeding iv. Visual assessment of dressing particles remaining on the wound bed after dressing removal v. Histological evaluation of dressing particles, necrosis, hemorrhage, edema, and inflammation vi. Maceration of intact skin (tissue moisture content) vii. Histological evaluation of intact skin for bacteria, edema, and inflammation

[0090] Test and control items TIFF2025157228000002.tif137170

[0091] Animal models This investigation was carried out using the animal model outlined below. TIFF2025157228000003.tif57170

[0092] Study design TIFF2025157228000004.tif69170

[0093] TIFF2025157228000005.tif78170

[0094] Surgical procedure Defect wound creation - Day 0 Initial pilot animals (Group 1) underwent all wound creation and treatment before scheduling treatment for additional Group 2 and 3 animals. A sterile template was used to create up to 10 full-thickness skin defect wounds (approximately 3 × 7.5 cm) on each animal (maximum of five wounds on each side of the spine). Each wound was spaced apart (approximately 6 cm or more from wound edge to wound edge between adjacent wounds, with sufficient spacing between all wounds to allow adequate space for proper placement of dressings and drapes). If the length of the animal's back did not provide sufficient space for 10 wounds and dressings (as determined on Day 0), eight wounds (four on each side of the spine) were created. A scalpel blade was used to surgically create wounds down to, but without disrupting, the subcutaneous fascial layer (just above the muscle). Any disruption of the subcutaneous fascial layer was noted in the study log. Care was taken not to scrape around the wound during wound creation. Two paravertebral wounds were created, striving to maintain the spine between the apex of the shoulder and the coccygeal eminence. Hemostasis was achieved using direct pressure with sterile gauze. In cases of excessive bleeding that did not subside with direct pressure, hemostatic forceps were used to clamp the bleeding source. Moisture was maintained during the creation of the other wounds using sterile 0.9% saline-soaked gauze. The wounds were photographed.

[0095] Dressings and negative pressure therapy applications Following wound creation (Day 0), all wounds received either the test or control article. On Day 4 (Group 3 only), wounds with the dressing removed received either the test or control article.

[0096] On the designated dressing change day (after peel testing, TEWL, visual observation, and photography), the periwound area was wiped clean with sterile 0.9% saline-soaked gauze and allowed to dry. Dressings were applied to individual wound sites in a randomized fashion.

[0097] Regardless of the type of dressing for a particular wound, an adhesive such as benzene was placed on the skin, surrounding the outermost perimeter of the test article edge, and the periwound area was surrounded by adhesive, leaving approximately a 1 cm perimeter around the wound free of benzene. This meant that benzene adhesive could not be applied to the intermediate periwound skin, as this could affect EpiD readings. Adhesive was placed on the skin in any area where a VAC® drape was applied. Alternatively (or in addition), Hollister (medical-grade silicone adhesive) was applied as an additional adhesive to help maintain a seal.

[0098] To the test article wound pair (test article receiving VAC® Therapy) and / or VACVERAFLO™ Therapy (test article using VACVERAFLO™ Therapy with saline) wound, a pair of electrodes (e.g., aluminum sheet or wire) was applied so that they were located in the peri-wound area (under the test article but above the peri-wound skin).

[0099] Where applicable, the skin directly beneath the foam bridge strip was covered with a VAC® drape for protection. Each bridged wound group was covered with a VAC® drape included in the dressing kit, a single hole was punched in the drape, and a SENSAT.RAC™ pad or VACVERAT.RAC™ pad (if applicable) was placed directly over the hole as per the instructions for use (IFU). Each pad was surrounded by a VAC® drape along each side to keep it in place and ensure a seal.

[0100] A VACULTA™ unit was present in the surgical set on the day of wound creation and was appropriately connected to each pad to ensure each wound group was properly sealed following application.

[0101] To test the seal around the wound, negative pressure wound therapy (NPWT) was initiated at a continuous vacuum of -125 mmHg using the SEAL CHECK™ feature on the VACULTA™ unit. Once an adequate seal was confirmed, the VACULTA™ unit was turned off, and the procedure was repeated, if applicable. Following all seal checks, an additional layer of VAC® drape was placed around the edges to reinforce the seal and prevent leaks.

[0102] For wounds receiving VACVERAFLO™ therapy, the Fill Assist function was used to determine the amount of fluid (i.e., saline) needed to saturate the dressing in paired wounds. These determinations were performed on paired wounds at each dressing change, as appropriate. Using the SEAL CHECK™ function on the VACULTA™ unit, VACVERAFLO™ therapy NPWT was initiated at a continuous vacuum pressure of -125 mmHg. Once an adequate seal was confirmed, the VACULTA™ unit was turned off, and this procedure was repeated, if applicable. Following all seal checks, an additional layer of VAC® drape was placed around the edges to reinforce the seal and prevent leaks. The soak / rest time per cycle was 10 minutes, and the NPWT time per cycle was 3.5 hours at a target pressure of -125 mmHg.

[0103] To prevent dressing migration, the entire area covered by the VAC® drape was covered with a tear-resistant mesh (e.g., organza material) secured to the VAC® drape, Elastikon®, or equivalent.

[0104] Provisional dressing change - Day 4 Group 3 only Resistance readings were taken from underneath the dressing. One wound from each treatment pair was subjected to a wound peel force test. The other half of each wound pair had the dressing removed by hand unless the dressing was intended to stay in place (i.e., TANTI and TANPTI (n=2 animals)). Wound assessments were performed (if applicable) and photographed.

[0105] Peel test and observation Peel force testing was performed on one wound from each treatment pair (the same wound as the dressing change, if applicable). TEWL was performed on the wound from which the dressing was removed, and wound assessments were performed and photographs were taken.

[0106] For Groups 1 and 2 (day 4), five wounds underwent peel force testing, TEWL, and evaluation. The remaining five wounds were collected with the dressing in situ for histopathology processing and evaluation.

[0107] For Group 3 (day 7), five wounds underwent peel force testing, TEWL and evaluation, and the remaining five wounds were collected with the dressing in situ for histopathology processing and evaluation.

[0108] Peel force tests were performed on an inclined operating table. Peel force tests were performed using a device that flipped the edge of the test material while measuring the force required to peel the dressing from the wound at an angle of approximately 180° to the peel tester. A digital protractor was used to verify the angle. The peel strength value indicates the ease with which the test material could be removed from the wound bed. Removal of the test material was performed using a 20N Shimpo Digital Force Gauge attached to a Shimpo Motorized Test Stand and controlled via a computer with LabView.

[0109] A scalpel was used to gently delineate the drape over the test article for the peel test, taking care not to disturb tissue ingrowth into the sides of the dressing. During treatment with the test article for the peel test, a scalpel was used to remove excess dressing not in contact with the wound. This was done by cutting the dressing along the sides, bottom, and top where the outer edge of the wound would be visible after negative pressure therapy. Clips were used to attach the inner end of the dressing or dressing tab to a force meter (no delineation of the dressing). The dressing was then pulled from the wound (inside to outside) at a constant speed in a medial-to-lateral direction. The peel force was measured and then evaluated. Continuous peel force readings were recorded and saved for each wound in LabView via the force meter. Following the peel test, the dressing was saved for analysis of tissue remaining within the dressing.

[0110] 9 demonstrates the results of maximum peel force measurements (N) on day 7 following dressing application and removal for the test articles (designated "TANPT" and "TANPTI") and control dressings. As shown, the test articles required less peel force with or without VACVERAFLO™ therapy.

[0111] After peel force testing and TEWL measurements, two biopsy punches (5 mm, or not exceeding 8 mm each) were collected from the center of each wound, if applicable.

[0112] Transepidermal water loss Determination of moisture levels at the dressing-skin (intact) interface was performed using a Delfin Technologies (Kuopio, Finland) Moisture Meter EpiD Compact. Measurements were taken immediately after wound creation on Day 0, on the day of dressing change (if applicable), and at termination before euthanasia. An EpiD Compact instrument was used to measure the specific conductivity of the skin. On the day of wound creation (Day 0), four consecutive moisture measurements were collected from the intact skin of each animal near the midpoint between the wound and the edge of the wound pad where the test article and advanced wound dressing were located. On the day of dressing change and at termination (if applicable), four consecutive moisture measurements were collected. These measurements were repeated for each available wound site on each animal. All measurements / data were recorded.

[0113] Wound assessment Overall Observation At the time of dressing change and / or termination procedure, wound observations were made and recorded as follows: Wound bleeding - none, slight, moderate or severe General observation - dryness (dull / non-shiny), moistness (shiny appearance), infiltration (presence of fluid), eschar (thin, firm-looking tissue), decay (removable yellowish layer) and its location at the wound site Discharge - none, serous (thin, watery, clear), serosanguineous (thin, pale red to pink), sanguineous (thin, bright red), purulent (opaque tan to yellow, thin or thick)

[0114] Dressing and tissue residue Following dressing removal or peel testing, dressing residue (small particles and large debris) was assessed. After removal of the dressing from the wound, dressing residue on the wound was visually assessed and recorded. All removed dressings were visually assessed for tissue residue and digitally photographed.

[0115] FIG. 10 demonstrates that TAMPT and TANPTI significantly reduced tissue ingrowth.

[0116] histopathology If the wound site was in 70% ethanol, it was processed immediately; if placed in NBF, the wound was transferred to 70% ethanol for a period of time before being further processed according to the histopathology testing site's standard procedures. The wound site plus dressing (if intact) was embedded in an oversized paraffin block, and the entire site en bloc was sectioned transversely once at approximately 5 μm thickness, and the resulting slides were stained with hematoxylin and eosin (H&E). Images of the specimen's cut surface were taken overall before processing and embedding in paraffin. Oversized slides were used to accommodate the entire tissue cross-section, including the unaffected skin border, on all sides.

[0117] A board-certified veterinary pathologist semiquantitatively graded the histopathological response on a scale of 1 to 5 (1 = very mild, 2 = mild, 3 = moderate, 4 = severe, 5 = very severe) unless otherwise specified. All stained sections were microscopically evaluated for histomorphological changes to the wound, including, but not limited to, granulation tissue thickness and characteristics, amount of granulation tissue embedded in the dressing (if present), tissue inflammation, edema, vascularity (if present), presence of bacteria, necrosis, and other related factors, as determined by the pathologist. The periwound area was evaluated for features consistent with maceration, as determined by the pathologist.

[0118] 2D photographs of individual wound sites Two-dimensional (2D) photographs of individual wound sites were taken at the following time points: Day 0 (newly formed wounds) - all wounds Day 4 after dressing removal and before application of a new dressing (day of dressing change or termination, if applicable) - all wounds 2D photographs were taken of the freshly removed dressing adjacent to the wound Day 7 after dressing removal and before euthanasia 2D photographs were taken of the freshly removed dressing adjacent to the wound

[0119] Histopathological evaluation of individual wound sites The light micrographs in Figure 11 demonstrate that TANTI had significantly more overlying granulation than NPT and NPTI.

[0120] Additionally, Figure 12 is a graphical representation comparing granulation tissue thickness between the test and control treatments on day 7. TANPT and TANPTI showed significantly higher granulation tissue thickness in comparison.

[0121] Research Conclusions The data demonstrate that the test article had surprisingly positive results and improved when combined with VACVERAFLO™ Therapy. The test article with VACVERAFLO™ Therapy performed relatively better by demonstrating increased granulation tissue thickness, reduced tissue ingrowth, epithelialization rate, and mean angiogenesis score.

[0122] Furthermore, by day 7, all treatments with the test article demonstrated significantly greater granulation tissue than NPT and NPTI. The increase in granulation depth using the test article (measured after the 7-day treatment period) was at least 75% for NPT and 200% for NPTI. No evidence of adverse events or safety issues was found. Peri-wound tissue moisture decreased over time (all treatment groups), reducing the risk of maceration.

[0123] All test article treatments also demonstrated a surprising reduction in tissue ingrowth, as evidenced by a significant reduction in peel force. After 7 days of either continuous VAC® therapy or VACVERAFLO™ therapy without dressing changes, less than 2 N of peel force was required to remove the test article. Specifically, a peel force of 1.8 N was used to remove the TANPTI test article, and a peel force of 1.5 N was used to remove the TANPT test article. Compared to CA1 with VAC® therapy, peel force was reduced by 87% and 89%, respectively.

[0124] While shown in several exemplary embodiments, those skilled in the art will recognize that the systems, apparatus, and methods described herein are susceptible to various modifications and variations that are within the scope of the appended claims. Furthermore, the description of various alternatives using terms such as "or" does not require mutual exclusivity unless the context clearly requires otherwise, and the articles "a" or "an" do not limit subject matter to a single example unless the context clearly requires otherwise.

[0125] Features, elements, and aspects described in connection with some embodiments may also be omitted, combined, or replaced with alternative features serving the same, equivalent, or similar purpose without departing from the scope of the invention as defined by the appended claims. For example, one or more features of some layers may be combined with features of other layers to provide equivalent functionality. Alternatively, or in addition, one or more of the fluid restriction portions 220 may have a shape similar to the shapes described as exemplary for the valve 605.

[0126] Components may be combined or removed in various configurations for purposes of sale, manufacture, assembly, or use. For example, in some configurations, the dressing 104, the container 106, or both may be omitted or separated from the other components for manufacture or sale. In other configurations, the controller 108 may also be manufactured, configured, assembled, or sold independently of the other components.

[0127] The appended claims set forth novel and inventive aspects of the subject matter described above, but may also encompass additional subject matter not specifically described in detail. Certain features, elements, or aspects may be omitted from the claims if they are known to those skilled in the art and therefore not necessary to identify novel and inventive features.

Claims

1. 1. A dressing for treating a tissue site using negative pressure, comprising: a first layer comprising a polymer film having a plurality of fluid restriction portions therethrough configured to expand in response to a pressure gradient across the polymer film; a second layer coupled to the first layer, the second layer comprising a manifold; a third layer bonded to the second layer opposite the first layer, the third layer comprising a polymeric drape; A dressing comprising:

2. 10. The dressing of claim 1, wherein the first layer is configured to be interposed between the manifold and the tissue site and to be at least partially exposed to the tissue site.

3. 3. The dressing of claim 1 or 2, further comprising a fourth layer bonded to the first layer opposite the second layer, the fourth layer comprising a hydrophobic gel having a plurality of apertures.

4. 4. The dressing of claim 3, wherein said third and fourth layers encapsulate said first and second layers.

5. 4. The dressing of claim 3, wherein the third and fourth layers encapsulate the first and second layers, and the fourth layer is adapted to contact the tissue site.

6. 3. The dressing of claim 1, further comprising a fourth layer bonded to the first layer on the side opposite the second layer, the fourth layer comprising a hydrophobic gel having a plurality of apertures aligned with at least some of the plurality of fluid restricting portions in the first layer.

7. 6. A dressing according to any one of claims 3 to 5, wherein the plurality of apertures are aligned with the fluid restriction portion.

8. 6. A dressing according to claim 3, wherein each of the plurality of apertures exposes at least a portion of one of the fluid restriction portions.

9. 3. The dressing of claim 1, further comprising a fourth layer bonded to the first layer on the opposite side of the second layer, the fourth layer comprising a hydrophobic gel having a plurality of apertures coextensive with the second layer, and substantially all of the plurality of apertures being aligned with the fluid restricting portion in the first layer.

10. 10. The dressing of any one of claims 1 to 9, wherein the fourth layer is configured to be interposed between the manifold and the tissue site.

11. 11. A dressing according to any one of claims 3 to 10, wherein the fluid restriction portion has an average length that does not substantially exceed the average dimension of the apertures.

12. 11. A dressing according to any one of claims 3 to 10, wherein the aperture limits the effective size of the fluid restriction portion.

13. 11. A dressing according to any one of claims 3 to 10, wherein each of the apertures is sized to expose no more than two of the fluid restriction portions.

14. 3. The dressing of claim 1 or 2, further comprising a fourth layer bonded to the first layer on the side opposite the second layer, the fourth layer comprising a hydrophobic gel having a plurality of apertures and an areal density of less than 300 grams per square meter.

15. 11. A dressing according to any one of claims 3 to 10, wherein the hydrophobic gel is a silicone gel.

16. 16. The dressing of claim 1, wherein the polymer drape comprises an outer edge extending beyond the first and second layers and an adhesive layer disposed on the outer edge.

17. 17. A dressing according to any preceding claim, wherein the manifold comprises foam.

18. 18. The dressing of claim 17, wherein the foam is a polymer foam.

19. 18. A dressing according to claim 17, wherein the foam is a polyurethane ether foam.

20. 18. The dressing of claim 17, wherein the foam is reticulated.

21. 18. The dressing of claim 17, wherein the foam is a reticulated polymer foam.

22. 18. The dressing of claim 17, wherein the foam is a reticulated polyurethane ether foam.

23. 23. A dressing according to any one of claims 17 to 22, wherein the foam is reticulated and has a free volume of at least 90%.

24. A dressing according to any one of claims 17 to 23, wherein the foam is porous and has an average pore size in the range 400 to 600 microns.

25. 25. A dressing according to any one of the preceding claims, wherein the manifold has a thickness of less than 7 millimeters.

26. 26. A dressing according to any preceding claim, wherein the manifold is hydrophobic.

27. 27. A dressing according to any preceding claim, wherein the polymer film is hydrophobic.

28. 28. The dressing of claim 27, wherein the polymer film has a water contact angle greater than 90 degrees.

29. 28. The dressing of claim 27, wherein the polymer film is a polyethylene film.

30. 28. The dressing of claim 27, wherein the polymeric film is a polyethylene film having an areal density of less than 30 grams per square meter.

31. 31. A dressing according to any one of claims 1 to 30, wherein the fluid restriction portion comprises a plurality of slots, each of the slots having a length of less than 4 millimeters.

32. 31. A dressing according to any preceding claim, wherein the fluid restriction portion comprises a plurality of slots, each of said slots having a width of less than 2 millimeters.

33. 31. A dressing according to any one of claims 1 to 30, wherein the fluid restriction portion comprises a plurality of slots, each of the slots having a length of less than 4 millimeters and a width of less than 2 millimeters.

34. 34. The dressing of claim 33, wherein said width is less than 1 millimeter.

35. 34. The dressing of claim 33, wherein the length is less than 3 millimeters and the width is less than 1 millimeter.

36. 34. The dressing of claim 33, wherein the width is at least 0.5 millimeters.

37. 34. The dressing of claim 33, wherein the length is at least 2 millimeters.

38. 38. A dressing according to any preceding claim, wherein the fluid restriction portion is coextensive with the polymeric film.

39. 38. A dressing according to any preceding claim, wherein the fluid restriction portion is coextensive with the manifold.

40. 40. A dressing according to any one of claims 1 to 39, wherein the tissue-facing surface of the dressing is smooth.

41. 40. A dressing according to any one of claims 1 to 39, wherein the tissue-facing surface of the dressing is matte.

42. 40. A dressing according to any one of claims 1 to 39, wherein the tissue-facing surface of the dressing is not rough.

43. 43. The dressing of any one of claims 1 to 42, wherein the second layer has a rough tissue-facing surface and is configured to not be exposed to tissue when the dressing is placed over the tissue site.

44. 44. A dressing according to any one of the preceding claims, wherein the fourth layer has a smooth underside.

45. 45. A dressing according to any preceding claim, wherein the fluid restriction portions are distributed across the polymer film in a uniform pattern.

46. 46. ​​A dressing according to claim 45, wherein the uniform pattern comprises a grid of parallel rows and columns.

47. 47. A dressing according to any one of claims 1 to 46, the fluid restriction portions are distributed across the polymer film in parallel rows and columns; the rows are spaced approximately 3 millimeters apart on center; The fluid restriction portions in each of the rows are spaced approximately 3 millimeters apart on center.

48. 48. A dressing according to claim 47, wherein the fluid restriction features in adjacent rows are staggered.

49. 49. A dressing according to any one of the preceding claims, wherein the polymeric film has a substantially flat surface.

50. 50. A dressing according to any one of claims 3 to 49, wherein the fourth layer has a hardness of from about 5 Shore 00 to about 80 Shore 00.

51. 51. A dressing according to any one of claims 1 to 50, wherein the fluid restricting portion comprises or consists essentially of a normally closed elastomeric valve in the polymer film.

52. 52. The dressing of claim 51, wherein the elastomeric valve is a fenestration.

53. 53. A dressing according to any preceding claim, wherein the first layer is coextensive with the second layer.

54. 54. A dressing according to any one of claims 1 to 53, wherein the second layer is adjacent to the first layer and the third layer is adjacent to the second layer on the opposite side from the first layer.

55. 55. The dressing of any one of claims 1 to 54, further comprising a fluid port coupled to the third layer, the fluid port adapted to be coupled to a fluid conductor.

56. 56. A dressing according to any one of the preceding claims, wherein the third and fourth layers are adapted to provide a fluid-tight seal.

57. 1. A system for treating a tissue site, comprising: A dressing according to any one of claims 1 to 56; a negative pressure source fluidly coupled to the dressing; A system comprising:

58. 58. The system of claim 57, further comprising a fluid reservoir fluidly coupled between the dressing and the negative pressure source.

59. 1. A method of treating a superficial wound using a negative pressure source, comprising: applying a dressing according to any one of claims 1 to 56 to the surface wound; sealing the dressing to the epidermis adjacent the superficial wound; fluidly coupling the dressing to a source of negative pressure; applying negative pressure from the negative pressure source to the dressing to promote healing and tissue granulation; A method comprising:

60. 60. The method of claim 59, wherein the second layer is not substantially exposed to the tissue site during the step of applying negative pressure.

61. 61. The method of claim 59 or 60, wherein the first layer and the fourth layer are configured to be exposed to the tissue site during the applying negative pressure step.

62. 62. The method of any one of claims 59 to 61, wherein the step of applying the dressing comprises placing at least a portion of the dressing over the edges of the superficial wound.

63. 63. The method of any one of claims 59 to 62, wherein the step of applying negative pressure opens the fluid restriction in the first layer.

64. 64. The method of claim 63, further comprising reducing the negative pressure from the negative pressure source, wherein reducing the negative pressure source closes the fluid restriction portion of the first layer.

65. 64. The method of any one of claims 59 to 63, further comprising the steps of fluidly coupling a fluid container between the dressing and the negative pressure source, and transferring exudate from the dressing to the fluid container.

66. 66. The method of any one of claims 59 to 65, further comprising the step of applying a manifold between the dressing and the surface wound.

67. 1. A method for promoting granulation in a superficial wound, comprising: applying a dressing to the superficial wound, the dressing comprising a cover, a manifold, a perforated polymeric film having a substantially flat surface, and a perforated silicone gel having a substantially flat surface; sealing the perforated silicone gel to the surface wound and covering at least a portion of the wound periphery adjacent the surface wound; attaching the dressing to the epidermis around the perforated silicone gel; fluidly coupling the dressing to a source of negative pressure; applying negative pressure from the negative pressure source to the dressing; A method comprising:

68. 68. The method of claim 67, wherein the dressing remains on the superficial wound for at least 5 days.

69. 68. The method of claim 67, wherein the dressing remains on the superficial wound for at least 7 days.

70. 70. The method of any one of claims 67 to 69, wherein the perforated silicone gel and the perforated polymer film substantially prevent exposure of tissue in the superficial wound to the manifold and inhibit tissue growth into the manifold.

71. 71. The method of any one of claims 67 to 70, further comprising applying a wound packing material between the perforated silicone gel and the superficial wound.

72. 72. The method of claim 71, wherein the wound packing is applied inside the wound perimeter.

73. 73. The method of claim 71 or 72, wherein the wound packing material is a foam.

74. 71. The method of any one of claims 67 to 70, wherein the dressing substantially prevents maceration around the wound.

75. 75. The method of any one of claims 67 to 74, wherein the perforated polymeric film is a perforated polyethylene film.

76. 1. A dressing for treating a tissue site using negative pressure, comprising: a fluid control layer comprising a plurality of imperfect valves, the plurality of imperfect valves configured to respond to a pressure gradient; a manifold layer adjacent to the fluid control layer; a cover adjacent the manifold layer opposite the fluid control layer; a sealing layer adjacent the fluid control layer opposite the manifold layer, the sealing layer including a plurality of apertures aligned with the plurality of imperfect valves; A dressing comprising:

77. 1. A dressing for treating a tissue site using negative pressure, comprising: a first layer comprising a film formed from a hydrophobic material; a plurality of fluid passages through the film, the plurality of fluid passages configured to expand in response to a pressure gradient across the film; a second layer bonded to the first layer, the second layer comprising a manifold formed from a hydrophobic material; a third layer bonded to the second layer opposite the first layer, the third layer comprising a polymeric drape; a fourth layer bonded to the first layer opposite the second layer, the fourth layer comprising a hydrophobic gel having an areal density of less than 300 grams per square meter; a plurality of apertures through the fourth layer fluidly coupled to at least some of the plurality of fluid passages through the film; A dressing comprising:

78. 1. A dressing for treating a tissue site using negative pressure, comprising: a first layer comprising a film having a flat surface texture; a plurality of fluid restriction sections extending through the film, the plurality of fluid restriction sections being configured to respond to a pressure gradient across the film; a second layer coupled to the first layer, the second layer comprising a manifold; a third layer bonded to the second layer opposite the first layer, the third layer comprising a polymeric drape; a fourth layer bonded to the first layer opposite the second layer, the fourth layer comprising a gel having an areal density of less than 300 grams per square meter and a hardness of about 5 Shore 00 to about 80 Shore 00; a plurality of apertures through the fourth layer aligned with the plurality of fluid restriction portions through the film; A dressing comprising:

79. 1. An apparatus for treating a tissue site using negative pressure, comprising: a first layer comprising a polyethylene film having a surface with a height variation of less than 0.2 millimeters per centimeter and a water contact angle of greater than 90 degrees; a plurality of fluid passages through the first layer that are normally restricted and configured to expand in response to a pressure gradient across the first layer; a second layer bonded to the first layer, the second layer comprising a reticulated polyurethane ether foam having a free volume of at least 90% and a thickness of less than 7 millimeters; a third layer bonded to the second layer opposite the first layer, the third layer comprising a polymeric drape; a fourth layer bonded to the first layer opposite the second layer, the fourth layer comprising a silicone gel having an areal density of less than 300 grams per square meter and a hardness of about 5 Shore 00 to about 80 Shore 00; a plurality of apertures through the fourth layer aligned with the plurality of fluid passages in the first layer; An apparatus comprising:

80. 1. An apparatus for treating a tissue site using negative pressure, comprising: a first layer comprising a polyethylene film; a plurality of slots in the first layer, each of the slots having a length in a range of 2 to 4 millimeters and a width in a range of 0.5 to 2 millimeters, and configured to expand in response to a pressure gradient across the first layer; a second layer coupled to the first layer, the second layer comprising a manifold; a third layer bonded to the second layer opposite the first layer, the third layer comprising a polymeric drape; a fourth layer coupled to the first layer opposite the second layer, the fourth layer comprising a silicone gel; a plurality of apertures through the fourth layer aligned with at least some of the plurality of slots in the first layer; An apparatus comprising:

81. 1. A dressing for treating a tissue site using negative pressure, comprising: Cover and A manifold; a perforated polymeric film having a substantially flat surface; a perforated silicone gel having a substantially flat surface; Equipped with the cover, the manifold, the perforated polymeric film, and the perforated silicone gel are assembled in a laminated relationship, with the cover and the perforated silicone gel encapsulating the manifold and the perforated polymeric film, and the perforated silicone gel configured to contact the tissue site.

82. 82. The dressing of claim 81, wherein at least one of the perforated polymeric film and the perforated silicone gel is configured to be interposed between the manifold and the tissue site.

83. 83. The dressing of claim 81 or 82, the substantially flat surface of the perforated polymeric film has a height variation of no more than 0.2 millimeters per centimeter; A dressing wherein the substantially flat surface of the perforated silicone gel has a height variation of no more than 0.2 millimeters per centimeter.

84. 1. A dressing for treating a tissue site using negative pressure, comprising: a first layer comprising a manifold; a second layer comprising a hydrophobic film having a plurality of elastomeric valves configured to open in response to a pressure gradient across the hydrophobic film; a third layer coupled to the second layer opposite the first layer, the third layer comprising a hydrophobic gel having a plurality of apertures; a cover coupled to the first layer opposite the second layer; A dressing comprising:

85. 85. The dressing of claim 84, wherein at least one of the second layer and the third layer is configured to be interposed between the manifold and the tissue site.

86. 86. A dressing according to claim 84 or 85, wherein the cover and the third layer encapsulate the first and second layers.

87. 87. The dressing of any one of claims 84 to 86, wherein the third layer is adapted to contact the tissue site and the cover is the top surface of the dressing.

88. 88. The dressing of any one of claims 84 to 87, wherein the plurality of apertures are fluidly coupled to at least some of the plurality of elastomeric valves.

89. 89. The dressing of any one of claims 84 to 88, wherein at least some of the apertures are configured to expose at least some of the second layer to the tissue site.

90. 89. The dressing of any one of claims 84-88, wherein at least some of the apertures are configured to expose at least some of the elastomeric valves to the tissue site.

91. 90. A dressing according to any one of claims 84 to 89, wherein at least some portion of the second layer is exposed through the aperture in the third layer.

92. 92. A dressing according to any one of claims 84 to 91, wherein at least some portion of the elastomeric valve is exposed through the aperture in the third layer.

93. 93. Use of any of the dressings, devices, systems or methods of any one of claims 1 to 92 for at least 5 days to promote granulation using a negative pressure source.

94. 93. Use of any of the dressings, devices, systems or methods of any one of claims 1 to 92 for at least 5 days to minimize tissue ingrowth using a negative pressure source.

95. 10. A system, apparatus and method substantially as herein described.

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