Composite dressing that promotes granulation formation and reduces maceration in negative pressure therapy

Abstract

To provide dressings for tissue treatment with negative pressure and methods for using the dressings for the tissue treatment with the negative pressure.SOLUTION: Dressings 104 for tissue treatment with negative pressure and methods of using thereof, may comprise a dressing having at least three layers assembled in a stacked relationship. A first layer 205 may comprise or consist essentially of a polymer film having a plurality of fluid restrictions that are unstrained or closed. A second layer 210 may comprise a manifold, and a third layer 215 may comprise or consist essentially of a polymer drape. A fourth layer, which may be coupled to the first layer opposite the second layer, may comprise or consist essentially of a silicone gel having a plurality of apertures 235. In some examples, the plurality of apertures in the fourth layer may be registered with the fluid restrictions 220 of the first layer.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of the filing of U.S. Provisional Patent Application No. 62 / 516,540, entitled "TISSUE CONTACT INTERFACE", filed on 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 on 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 on June 7, 2017, each of which is hereby incorporated by reference in its entirety for all purposes.

[0002] The invention as claimed in the appended claims generally relates 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 Art

[0003] Clinical trials and medical treatment have shown that by applying reduced pressure in the vicinity of a tissue site, the growth of new tissue at the tissue site can be enhanced and accelerated. Although there are numerous applications of this phenomenon, it has been found that this phenomenon is particularly advantageous for the treatment of wounds. Appropriate care of a wound, whether it is a trauma, a surgical wound, or due to another cause, is important for the outcome. Treatment by applying reduced pressure to a wound or other tissue 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 "local negative pressure". Negative pressure therapy can provide a number of advantages, including the movement of epithelial and subcutaneous tissue, improvement in blood flow, and micro-deformation of tissue at the wound site. These advantages, combined, can increase the development of granulation tissue and shorten the healing time.

[0004] The clinical benefits of negative pressure therapy are widely known, but improvements to treatment systems, components, and processes can provide benefits to healthcare providers and patients. SUMMARY OF THE INVENTION

[0005] The appended claims set forth a new and useful system, apparatus, and method for treating tissue in a negative pressure therapy environment. Exemplary embodiments are also provided so that those skilled in the art can make and use the claimed subject matter.

[0006] For example, in some embodiments, a dressing for treating tissue can 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 of the polyethylene film can be aligned with the perforation pattern of at least a central region of the silicone gel. In some embodiments, each of the perforations in the central region can have a width or diameter of about 2 millimeters, and each of the fenestrations in the polyethylene film can be a slot having a length of about 3 millimeters and a width of about 0.5 millimeter to about 1 millimeter. The foam can be an open-cell foam, such as a reticulated foam. The foam can also be made relatively thin and hydrophobic so as to reduce the fluid holding capacity of the dressing, thereby facilitating the rapid progression of exudate and other fluids to an external storage location. The foam layer can also be made thin so as to reduce the thickness of the dressing and increase its flexibility, thereby enabling the dressing to conform to the wound bed and other tissue sites under negative pressure. The composite dressing can minimize the potential for maceration, promote granulation, and provide excellent manifolding.

[0007] More generally, some embodiments can comprise a dressing having at least three layers assembled in a stacked relationship. The first layer can comprise or consist essentially of a polymeric film having a plurality of fluid restriction portions. The fluid restriction portions can be described as incomplete elastomeric valves, which cannot fully close and can deform or increase in width when a negative pressure is applied to reduce the restriction imposed on the fluid. When the negative pressure ceases or is reduced, the fluid restriction portions generally return to or approach their original state and provide a higher restriction to fluid flow. The second layer can comprise a manifold, and the third layer can comprise or consist essentially of a polymeric drape. A fourth layer, which can be coupled to the first layer on the side opposite 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 can be configured to be inserted between the first layer and the tissue site.

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

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

[0010] In some embodiments, the fluid restriction portion can comprise a plurality of linear slits or slots. For example, the fluid restriction portion 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 may be suitable. In some embodiments, the fluid restriction portion 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 restriction portion can be dispersed across the polymer film in parallel rows, and the rows can be spaced apart from each other by about 3 millimeters. In some examples, the fluid restriction portions within each row can also be spaced apart from each other by about 3 millimeters.

[0011] Furthermore, some embodiments of the third layer can comprise or be coupled to a fluid port, and the fluid port can be configured to be coupled or coupled to a fluid conductor. In some examples, a negative pressure source can be fluidly coupled to the dressing to provide negative pressure therapy.

[0012] Some embodiments of the dressing or device can comprise 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 can include a first layer, a second layer coupled to the first layer, a third layer coupled to the second layer on a side opposite the first layer, and a fourth layer coupled to the first layer on a side opposite the second layer. The first layer can include a film formed from a hydrophobic material and a plurality of fluid passages extending through the film. The fluid passages can be configured to expand in response to a pressure gradient across the film. The second layer can include or consist essentially of a manifold formed from a hydrophobic material. The third layer can include a polymer drape, and the fourth layer can be formed from a hydrophobic gel having a surface density of less than 300 grams per square meter. A plurality of apertures extending through the fourth layer can be in fluid communication with 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 including a film having a flat surface profile and a plurality of fluid restrictions extending through the film. The fluid restrictions 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 include or consist essentially of a manifold. A third layer can be coupled to the second layer on a side opposite the first layer, and the third layer can include a polymer drape. A fourth layer can be coupled to the first layer on a side opposite the second layer, and the fourth layer can include a gel having a surface density of less than 300 grams per square meter and a hardness of from about 5 Shore OO to about 80 Shore OO. A plurality of apertures extending through the fourth layer can be aligned with the plurality of fluid restrictions extending through the film.

[0015] In some embodiments, an apparatus 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 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, and the second layer can include 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 on a side opposite the first layer, and the third layer can comprise a polymeric drape. A fourth layer can be coupled to the first layer on a side opposite the second layer, and the fourth layer can comprise a silicone gel having a surface density of less than 300 grams per square meter and a hardness of from about 5 Shore OO to about 80 Shore OO. A plurality of apertures 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 polymer film having a substantially flat surface, and a perforated silicone gel having a substantially flat surface. The cover, the manifold, the perforated polymer film, and the perforated silicone gel can be assembled in a stacked relationship with the cover and the perforated silicone gel enclosing the manifold and the perforated polymer film, and the perforated silicone gel can be configured to contact the tissue site. The substantially flat surface of the perforated polymer film can, in some embodiments, have a height variation of not more than 0.2 millimeters per centimeter, and the substantially flat surface of the perforated silicone gel can, in some embodiments, have a height variation of not more than 0.2 millimeters per centimeter. In some embodiments, at least one of the perforated polymer 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 having a manifold, a second layer having a hydrophobic film, the second layer 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 on a side opposite the first layer, and a cover coupled to the first layer on a side 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 using a negative pressure source can include applying a dressing as described to the surface wound, sealing the dressing to the epidermis adjacent to the surface wound, fluidly coupling the dressing to the negative pressure source, and applying a negative pressure from the negative pressure source to the dressing. In some examples, the dressing can be applied across the edge of the surface wound without cutting or trimming.

[0019] A method of 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 to the wound perimeter adjacent to the surface wound, and the cover can be attached to the epidermis surrounding the perforated silicone gel. A negative pressure source can be fluidly coupled to the dressing, and a negative pressure from the negative pressure source can be applied to the dressing. In some embodiments, the dressing can remain over the surface wound for at least 5 days, and in some embodiments at least 7 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 perimeter.

[0020] Advantages of the subject matter of the claims compared to the prior art include: (1) promotion of granulation tissue formation (i.e., faster healing), (2) reduction of the impact force required to remove the dressing (i.e., ease of use, reduction of pain during dressing change), (3) shortening of the time required to apply the dressing (i.e., ease of use) and / or (4) reduction of the risk of maceration of the area surrounding the wound during treatment. Any or all of these enable a 7-day dressing (compared to a 48-hour dressing change), improve treatment compliance, and reduce the cost of care. Other objects, advantages, and preferred forms of the subject matter of the claims can be best understood by reference to the accompanying drawings in conjunction with the following detailed description of the exemplary embodiments.

Brief Description of the Drawings

[0021]

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DETAILED DESCRIPTION OF THE INVENTION

[0022] The following description of the example embodiments provides information that enables those skilled in the art to make and use the subject matter shown in the appended claims, but some details that are already well known in the art may be omitted. Therefore, the following detailed description should be construed as illustrative rather than limiting.

[0023] In this specification, example embodiments may be described in relation to the spatial relationships between various elements shown in the accompanying drawings or the spatial orientations of various elements. Generally, such relationships or orientations correspond to a patient in place for treatment or assume a reference system for such a patient. However, as should be recognized by those skilled in the art, this reference system is not a strict definition but merely a convenient means for explanation.

[0024] FIG. 1 is a simplified functional block diagram of an example embodiment of a treatment system 100 that can provide negative pressure therapy along with the dropping of a topical treatment solution to a tissue site according to this specification.

[0025] In this context, the term "tissue site" broadly refers to a wound, defect, or other treatment target located on or within a 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 wounded or defective, but rather, an area where it may be desirable to add additional tissue or promote its growth. For example, negative pressure can be applied to a 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 outside of the body, such as an injury or damage to the epidermis, dermis, and / or subcutaneous layer. Examples of surface wounds can include, for example, ulcers or closed incisions. As used herein, surface wounds do not include intraperitoneal wounds. Examples of wounds can include, for example, chronic, acute, traumatic, subacute, and dehisced wounds, partial thickness burns, ulcers (such as diabetic ulcers, pressure ulcers, or venous insufficiency ulcers), flaps, and grafts.

[0026] Treatment system 100 can 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. Further, treatment system 100 can include a sensor that measures an operating parameter and provides a feedback signal indicative of the operating parameter to controller 108. For example, as shown in FIG. 1, treatment system 100 can 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 can comprise or consist essentially of one or more dressing layers, such as tissue interface 114, cover 116, or both, in some embodiments.

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

[0028] Some components of treatment system 100 can be housed within or used with other components, such as a sensor, a processing device, an alarm indicator, a memory, a database, software, a display device, or a user interface that further facilitates treatment. For example, in some embodiments, negative pressure source 102 can be coupled with solution source 118, controller 108, and other components to form a treatment unit.

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

[0030] The distribution components are preferably detachable and can be disposable, reusable or recyclable. The dressing 104 and the container 106 are examples of distribution components. A fluid conductor is another exemplary example of a distribution component. A "fluid conductor" in this context includes a tube, pipe, hose, conduit, or other structure having one or more lumens or open paths adapted to convey fluid between two ends. Typically, a tube is an elongate cylindrical structure with some flexibility, but the geometry and rigidity can be varied. Further, some fluid conductors can be fitted within other components or integrally coupled to other components in other ways. The distribution components can also include or comprise an interface or fluid port that facilitates the coupling and separation of other components including sensors and data communication devices. In some embodiments, for example, a dressing interface can facilitate the coupling of a fluid conductor to the dressing 104. For example, such a dressing interface can be the SENSAT.R.A.C. (trademark) pad available from KCI of San Antonio, Texas.

[0031] The negative pressure supply unit such as the negative pressure source 102 can be a storage unit for air at negative pressure, or can be a manual or electric device such as, for example, 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 that is lower than a local ambient pressure such as the ambient pressure in the local environment outside the sealed treatment environment. In many cases, the local ambient pressure can also be the atmospheric pressure at the location 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, the pressure values described in this specification 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 the negative pressure applied to the tissue site can be varied according to treatment requirements, but the pressure is generally a low vacuum, also commonly referred to as a rough vacuum, in the range of -5 mmHg (-667 Pa) to -500 mmHg (-66.7 kPa). A typical treatment range is -50 mmHg (-9.9 kPa) to -300 mmHg (-39.9 kPa).

[0032] The container 106 represents a container, canister, pouch, or other storage component that can be used to manage exudates and other fluids withdrawn from the 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 appropriately disposed of without rigid container storage, and reusable containers can reduce the waste associated with negative pressure therapy and reduce costs.

[0033] A controller, such as controller 108, can be a microprocessor or computer programmed to operate one or more components of the treatment system 100, such as negative pressure source 102. In some embodiments, for example, controller 108 can 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. Operating parameters can include, for example, the power applied to negative pressure source 102, the pressure generated by negative pressure source 102, or the pressure distributed to tissue interface 114. Controller 108 is also preferably configured to receive one or more input signals, such as a feedback signal, and is programmed to modify one or more operating parameters based on the input signals.

[0034] Sensors, such as pressure sensor 110 or electrical sensor 112, are 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 detected or measured phenomenon or property. 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 the pressure in the 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. Electrical sensor 112 can optionally, in some embodiments, measure operating parameters of negative pressure source 102, such as voltage or current. Preferably, the signals from pressure sensor 110 and electrical sensor 112 are suitable as input signals to controller 108, although some signal conditioning can be appropriate in some embodiments. For example, the signal may need to be filtered or amplified before it can be processed by controller 108. Typically, the signal is an electrical signal, although it can 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 contact the tissue site partially or completely. For example, if the tissue site is a wound, the tissue interface 114 can partially or completely fill the wound or be placed over 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 be adapted to the contour of a deep and irregularly shaped tissue site.

[0036] In some embodiments, the cover 116 can provide protection from bacterial barriers and physical trauma. The cover 116 can also be composed of a material that can reduce evaporative losses and provide a fluid seal between two environments, such as between two components or between the treatment environment and the local external environment. The cover 116 can be, for example, an elastomeric film or membrane that can provide a seal suitable for maintaining negative pressure at the tissue site relative to a given negative pressure source. The cover 116 can, in some applications, have a high water vapor transmission rate (MVTR). For example, the MVTR can be at least 300 g / m per 24 hours in some embodiments. 2It can be. In some example embodiments, the cover 116 can 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 to 50 microns. In the case of a permeable material, the permeability rate generally must be low enough to be able to maintain the desired negative pressure. The cover 116 can include, for example, one or more of the following materials. That is, hydrophilic polyurethane, cellulose derivative, hydrophilic polyamide, polyvinyl alcohol, polyvinyl pyrrolidone, hydrophilic acrylic resin, hydrophilic silicone elastomer, for example, INSPIRE 2301 material from Coveris Advanced Coatings, Wrexham, United Kingdom, which has an MVTR (inverted cup technique) of 14400 g / m 2 / 24 hours and a thickness of about 30 microns, 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 drape, 3M Tegaderm® drape, polyurethane (PU) drapes available from Avery Dennison Corporation, Glendale, California, etc., for example, polyether block polyamide copolymer (PEBAX) of Arkema, France, INSPIRE 2327, or other suitable materials.

[0037] The attachment device can be used to attach the cover 116 to an attachment surface such as an intact epidermis, 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 around a tissue site such as a surface wound. In some embodiments, for example, a part or all of the cover 116 can be coated with an adhesive such as an acrylic adhesive that can have an adhesion amount of 25 to 65 grams per square meter (g.s.m.). In some embodiments, a thicker adhesive, or a combination of adhesives, can be provided to improve sealing and reduce leakage. Other examples of embodiments of the attachment device can include double-sided tape, glue, hydrocolloid, hydrogel, silicone gel, or organogel.

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

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

[0040] Generally, exudates and other fluids flow along a fluid path towards the lower pressure. Thus, the term "downstream" usually means closer to a negative pressure source or farther from a positive pressure source in a fluid path. Conversely, the term "upstream" means farther from a negative pressure source or closer to a positive pressure source. Similarly, it may be convenient to describe some features regarding a fluid "inlet" or "outlet" in such a reference system. This orientation is generally assumed for the purpose of explaining various features and components in this specification. However, the fluid path can also be reversed in some applications (such as by using a positive pressure source instead of a negative pressure source), and this explanatory convention should not be construed as a limiting convention.

[0041] Figure 2 is an assembled view of an example of the dressing 104 of FIG. 1 and shows further details that can be associated with some embodiments in which the tissue interface 114 comprises more than one layer. 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 disposed adjacent to the second layer 210, and the third layer 215 can be disposed adjacent to the second layer 210 on the side opposite the first layer 205. For example, the first layer 205, the second layer 210, and the third layer 215 can be laminated 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 joined to an adjacent layer.

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

[0043] In some exemplary embodiments, the first layer 205 can comprise a plurality of paths 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 paths. For example, open cell foams, reticulated foams, aggregates of porous tissue, and other porous materials such as gauze or felt mats can generally include pores, edges, and / or walls that are adapted to form interconnected fluid flow paths. Liquids, gels, and other foams can also include or be hardened to include apertures and fluid paths. In some embodiments, the first layer 205 can further or alternatively comprise protrusions that form interconnected fluid paths. For example, the first layer 205 can be shaped to provide surface protrusions that define interconnected fluid paths. Any or all of the surfaces of the first layer 205 can have a non-uniform, rough, or jagged profile.

[0044] In some embodiments, the first layer 205 can include or consist essentially of a reticulated foam having pore sizes 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 may 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) may be particularly suitable for some types of therapy. The tensile strength of the 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 the dropping of a topical treatment solution. The 25% compression load deflection of the first layer 205 can be at least 0.35 pounds per square inch, and the 65% compression load deflection can be at least 0.43 pounds per square inch. In some embodiments, the tensile strength of the first layer 205 can be at least 10 pounds per square inch. The first layer 205 can have a tear strength of at least 2.5 pounds per inch. In some embodiments, the first layer 205 can be a foam composed of a polyol such as polyester or polyether, an isocyanate such as toluene diisocyanate, and a polymerization regulator such as an amine and a tin compound. In one non-limiting example, the first layer 205 can be a reticulated polyurethane ether foam such as the GRANUFOAM™ dressing or the V.A.C. VERAFLO™ dressing, both available from KCI of San Antonio, Texas.

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

[0046] The second layer 210 can comprise or consist essentially of means for controlling or managing fluid flow. In some embodiments, the second layer can include or consist essentially of a liquid-impermeable, elastomeric material. For example, the second layer 210 can include or consist essentially of a polymeric film. In some embodiments, the second layer 210 can also have a smooth or matte surface finish. For some applications, a gloss or luster finish that is better than or equal to grade B3 according to the SPI (Society of the Plastics Industry, USA) standard specifications can be particularly advantageous. In some embodiments, the surface height variation can be limited to an acceptable tolerance. For example, the surface of the second layer can have a substantially flat surface, with the height variation limited to 0.2 millimeters per 1 centimeter.

[0047] In some embodiments, the second layer 210 can be hydrophobic. The hydrophobicity of the second layer 210 can be modified and can have a water contact angle of at least 90 degrees in some embodiments. 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. The water contact angle can be measured using any standard device. A manual goniometer can be used to visually approximate the contact angle, but contact angle measuring instruments often require an integrated system that includes, among other things, a horizontal stage, a liquid dropper such as a syringe, a camera, and software designed to calculate the contact angle more accurately and precisely. Non-limiting examples of such integrated systems include the FTÅ125, FTÅ200, FTÅ2000, and FTÅ4000 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, the water contact angle herein is measured using deionized distilled water on a horizontal sample surface for a sessile drop added from a height of 5 cm or less in air at 20 - 25 °C and 20 - 50% relative humidity. The contact angles reported herein represent the average of 5 - 9 measurements, discarding both the highest and lowest measured values. The hydrophobicity of the second layer 210 can be further enhanced by a hydrophobic coating of other materials such as silicone and fluorocarbon, either coated from a liquid 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 can be adapted to be welded to a 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 acrylate. A sacrificial polar interface can be used to facilitate RF welding of less polar film materials such as polyethylene.

[0049] The areal density of the second layer 210 can be varied 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 may comprise or be composed of a hydrophobic polymer such as a polyethylene film. The simple and inert structure of polyethylene provides a surface that interacts very little, if at all, with biological tissues and fluids and can promote free flow of liquids and low adhesion, which can be particularly advantageous for many applications. More polar films suitable for laminating to a polyethylene film include polyamide, copolyester, ionomer, and acrylic resin. Layers such as ethylene vinyl acetate or modified polyurethane can be used to aid in joining polyethylene to a polar film. Ethyl methyl acrylate (EMA) films 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, and the fluid restriction portions 220 can be uniformly or randomly dispersed across 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 not distorted so as 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 into the second layer 210, and in some embodiments, the edges of the perforations can also be deformed by such cuts. 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. Further or alternatively, one or more of the fluid restriction portions 220 can be an elastomeric valve, which is normally closed to substantially prevent liquid flow when not distorted and can open in response to a pressure gradient. For some applications, an opening in the second layer 210 can be a suitable valve. The opening can also be formed by removing material from the second layer 210, but the amount of material removed and the resulting dimensions of the opening can be orders of magnitude smaller than those of the perforations and there is no possibility of deforming 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 can be at least 2 millimeters and the width can be at least 0.4 millimeters. A length of about 3 millimeters and a width of about 0.8 millimeters may be particularly suitable for many applications, and a tolerance of about 0.1 millimeter may also be acceptable. A tolerance of about 0.1 millimeter may also be acceptable. Such dimensions and tolerances can be achieved, for example, using a laser cutter. Slots of such a configuration can typically function as an incomplete valve that substantially reduces liquid flow in a closed or resting state. For example, such slots can form a fluid restriction without being completely closed or sealed. The slot can expand or open wider in response to a pressure gradient to allow an increase in liquid flow.

[0053] The third layer 215 can be a sealing layer that includes or is composed of a soft and flexible 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, hydrophilic colloid, hydrogel, polyurethane gel, polyolefin gel, hydrogenated styrene copolymer gel, foamed gel, adhesive, polyurethane, polyolefin, or a soft closed-cell foam such as polyurethane and polyolefin coated with a hydrogenated styrene copolymer. In some embodiments, the third layer 215 can have a thickness of about 200 micrometers (μm) to about 1000 micrometers (μm). In some embodiments, the third layer 215 can have a hardness of about 5 Shore OO to about 80 Shore OO. Further, the third layer 215 can be composed of a hydrophobic or hydrophilic material. For example, the third layer 215 can be composed of a hydrophobic material or a 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, for example, a woven fabric, non-woven fabric, molded or extruded mesh, etc. with a hydrophobic material. The hydrophobic material for the coating can be, for example, a soft silicone.

[0055] The third layer 215 can have an inner portion 230 that surrounds or a peripheral edge 225 around it, and an aperture 235 disposed through the peripheral edge 225 and the inner portion 230. The inner portion 230 can, in some examples, correspond to the surface area of the first layer 205. The third layer 215 can also have corners 240 and edges 245. The corners 240 and edges 245 can be part of the peripheral edge 225. The third layer 215 can have an inner boundary 250 around the inner portion 230 disposed between the inner portion 230 and the peripheral edge 225. As shown in the example of FIG. 2, the inner boundary 250 can be substantially free of apertures 235. In some examples, as shown in FIG. 2, the inner portion 230 is symmetric and can be centered in the third layer 215.

[0056] The aperture 235 can be formed, for example, by cutting, or by applying local RF or ultrasonic energy, or by other suitable techniques for forming an opening. The aperture 235 can have a uniform distribution pattern or can be randomly dispersed over the third layer 215. The apertures 235 in the third layer 215 can have many shapes, including, for example, circular, square, star-shaped, oval, polygonal, slit, complex curve, linear shape, triangular, 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 from about 1 millimeter to about 50 millimeters. In other embodiments, the diameter of each of the apertures 235 can be from about 1 millimeter to about 20 millimeters.

[0058] In other embodiments, the geometric characteristics of the apertures 235 can be changed. For example, as shown in FIG. 2, the diameter of the apertures 235 can be changed according to the position of the apertures 235 in the third layer 215. In some embodiments, the diameter of the apertures 235 at the peripheral portion 225 of the third layer 215 can be made larger than the diameter of the apertures 235 at the inner portion 230 of the third layer 215. For example, in some embodiments, the apertures 235 disposed at the peripheral portion 225 can have a diameter from about 9.8 millimeters to about 10.2 millimeters. In some embodiments, the apertures 235 disposed at the corner portion 240 can have a diameter from about 7.75 millimeters to about 8.75 millimeters. In some embodiments, the apertures 235 disposed at the inner portion 230 can have a diameter from about 1.8 millimeters to about 2.2 millimeters.

[0059] At least one of the apertures 235 in the peripheral portion 225 of the third layer 215 can be positioned at the edge 245 of the peripheral portion 225 and can have an internal cutout that is open or exposed at the edge 245 and is in lateral fluid communication with the edge 245. The lateral direction shall refer to the direction in the same plane as the third layer 215 towards the edge 245. As shown in the example of FIG. 2, the aperture 235 in the peripheral portion 225 can be positioned in proximity to or at the edge 245 and in lateral fluid communication with the edge 245. The apertures 235 positioned in proximity to or at the edge 245 can be arranged substantially equidistantly around the peripheral portion 225, as shown in the example of FIG. 2. Alternatively, the spacing of the apertures 235 in proximity to or at the edge 245 can be irregular.

[0060] In the example of FIG. 2, the dressing 104 can further include a mounting device such as an adhesive 255. The adhesive 255 can be, for example, a medically acceptable pressure-sensitive adhesive that extends to the peripheral portion, a part, or the whole of the cover 116. In some embodiments, for example, the adhesive 255 can be an acrylic adhesive having an adhesion amount of 25 to 65 grams per square meter (g.s.m.). In some embodiments, a thicker adhesive or a combination of adhesives can be provided to improve the sealing performance and reduce leakage. The adhesive 255 can be a layer having substantially the same shape as the peripheral portion 225. In some embodiments, such a layer of the adhesive 255 can be continuous or discontinuous. The discontinuity in the adhesive 255 can be provided by an aperture or a hole (not shown) in the adhesive 136. The aperture or hole in the adhesive 255 can be formed after the application of the adhesive 255 or by coating the adhesive 255 in some patterns on a carrier layer, such as on one side of the cover 116. The aperture or hole in the adhesive 255 can, in some exemplary embodiments, be sized to improve the MVTR of the dressing 104.

[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 before use. The release liner 260 can also provide stiffness, for example, to assist in the deployment of the dressing 104. The release liner 260 can be, for example, a 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 wrinkles or other deformations of the dressing 104. For example, the polar semi-crystalline polymer is highly oriented and can be resistant to softening, swelling, or other deformations that may occur when in contact with the components of the dressing 104, or when subjected to temperature or environmental variations or sterilization. In some embodiments, the release liner 260 can have surface properties that can be engraved onto an adjacent layer such as the third layer 215. Further, a release agent can be disposed on the side of the release liner 260 configured to contact the third layer 215. For example, the release agent can be a silicone coating and can have a release factor suitable for facilitating the removal of the release liner 260 without damaging the dressing 104 by hand 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 used without a release agent in other ways.

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

[0063] FIG. 3 is a schematic diagram of an example of the second layer 210 and shows further details that can be associated with some embodiments. As shown in the example of FIG. 3, the fluid restriction 220 can be substantially composed of one or more linear slots each having a length of about 3 millimeters. FIG. 3 further shows an example of a uniform dispersion pattern of the fluid restriction 220. In FIG. 3, the fluid restriction 220 has substantially the same spread as the second layer 210 and is dispersed across the second layer 210 in a grid of parallel rows and columns, where the slots are also parallel to each other. In some embodiments, as shown in the example of FIG. 3, the rows can be spaced apart by about 3 millimeters at the center, and the fluid restrictions 220 in each of the rows can be spaced apart by about 3 millimeters at the center. The fluid restrictions 220 in adjacent rows may or may not be aligned. For example, as shown in FIG. 3, adjacent rows can be offset, such that the fluid restrictions 220 are aligned in every other row and spaced apart by about 6 millimeters. The spacing of the fluid restrictions 220 can be changed in some embodiments to increase the density of the fluid restrictions 220 according to treatment requirements.

[0064] FIG. 4 is a schematic diagram of a configuration example of the aperture 235 and shows further details that can be associated with some embodiments of the third layer 215. In some embodiments, the aperture 235 shown in FIG. 4 can be associated only with the inner portion 230. In the example of FIG. 4, the aperture 235 is generally circular and has a diameter of about 2 millimeters. FIG. 4 also shows an example of a uniform dispersion pattern of the apertures 235 in the inner portion 230. In FIG. 4, the apertures 235 are dispersed 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 can be equidistant from each other. FIG. 4 shows one configuration example that can be particularly suitable for many applications, where 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 third layer 215 as an example of FIG. 4 superimposed on the second layer 210 of FIG. 3 and shows further details that can be associated with some example embodiments of the tissue interface 114. For example, as shown in FIG. 5, in some embodiments, the fluid restriction portion 220 can be aligned with, overlap, be positioned with, or otherwise be fluidly coupled to the aperture 235. In some embodiments, one or more of the fluid restriction portions 220 can be aligned with or only partially aligned with the aperture 235 only in the inner portion 230. 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 can be aligned with two or more of the apertures 235. For example, any one or more of the fluid restriction portions 220 can be a perforation or opening that extends 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 aperture 235 can be sized to expose a portion of the second layer 210, the fluid restriction 220, or both, through the third layer 215. In some embodiments, each of the apertures 235 can be sized to expose less than two of the fluid restrictions 220. In some examples, the length of each of the fluid restrictions 220 can be substantially less than or equal to the diameter of each of the apertures 235. In some embodiments, the average dimension of the fluid restrictions 220 is substantially the same as the average dimension of the apertures 235. For example, the aperture 235 can be elliptical in some embodiments, and the length of each of the fluid restrictions 220 can be substantially equal to the major axis or the minor axis. However, in some embodiments, the dimensions of the fluid restrictions 220 can exceed the dimensions of the apertures 235, and the size of the apertures 235 can limit the effective size of the fluid restrictions 220 exposed on the lower surface of the dressing 104.

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

[0068] The individual components of the dressing 104 can be joined to each other or otherwise secured, for example, with a solvent or non-solvent adhesive or by heat welding, without adversely affecting fluid management. Further, the second layer 210 or the first layer 205 can be coupled to the boundary 250 of the third layer 215 by any suitable method, such as by welding or with an adhesive.

[0069] The cover 116, the first layer 205, the second layer 210, the third layer 215, or various combinations thereof can be assembled before application or in situ. For example, in some embodiments, the cover 116 can be affixed to the first layer 205, and the second layer 210 can be affixed to the first layer 205 on the opposite side of the cover 116. In some embodiments, the third layer 215 can also be coupled to the second layer 210 on the opposite side of the first layer 205. In some embodiments, one or more layers of the tissue interface 114 can have the same extent. For example, as shown in the embodiment of FIG. 2, the first layer 205 can have the same extent as 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 coupled to the cover 116 so as to enclose the first layer 205 and the second layer 210, and the third layer 215 is 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 across, over, or otherwise in proximity to a tissue site, particularly a surface tissue site and adjacent epidermis. The third layer 215 and the second layer 210 can be inserted 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 surface wounds (including wound edges) and intact epidermis to prevent direct contact with the first layer 205. Treatment of a surface wound or placement of the dressing 104 over a surface wound includes placing the dressing 104 immediately adjacent to the body surface or spreading it over at least a portion of the body surface. Treatment of a surface wound does not include placing the dressing entirely within the abdominal cavity or entirely under the body surface. In some applications, the inner portion 230 of the third layer 215 can be positioned adjacent to, in proximity to, or covering the tissue site. In some applications, at least a portion of the second layer 210, the fluid restriction portion 220, or both can be exposed to the tissue site through the third layer 215. The peripheral edge 225 of the third layer 215 can be positioned adjacent to or in proximity to tissue surrounding or enclosing the tissue site. The third layer 215 can be sufficiently adhesive to hold the dressing 104 in place while also allowing the dressing 104 to be removed or repositioned without trauma to the tissue site.

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

[0072] When the dressing 104 reaches the desired position, the adhesive 255 can be pushed through the aperture 235 to adhere the dressing 104 to the mounting surface. Due to the aperture 235 at the edge 245, the adhesive 255 can flow around the edge 245 to facilitate the attachment 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 the adhesive 255 that is in fluid communication with the aperture 235. For a given geometric shape of the corner 240, the relative size of the aperture 235 can be configured to maximize the exposed surface area of the adhesive 255 that communicates through the aperture 235 at the corner 240. For example, as shown in FIG. 2, the edges 245 can intersect at a substantially right angle, i.e., about 90 degrees, to define the corner 240. In some embodiments, the corner 240 can have a radius of about 10 millimeters. Further, in some embodiments, three of the apertures 235 having a diameter of about 7.75 millimeters to about 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, the size and number of the apertures 235 at the corner 240 can be adjusted as needed to maximize the exposed surface area of the adhesive 255 according to the selected geometric shape of the corner 240. Further, 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. By completely containing the apertures 235 within the third layer 215 at the corner 240, the fluid communication of the adhesive 255 outside the corner 240 can be substantially prevented, and the handling of the dressing 104 during deployment at the tissue site can be improved. Further, the absence of substantially the adhesive 136 outside the corner 240 can increase the flexibility of the corner 240 to improve comfort.

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

[0075] The geometric shape and dimensions of the tissue interface 114, the cover 116, or both can be varied to conform to a particular application or anatomical structure. For example, the geometric shape or dimensions of the tissue interface 114 and the cover 116 can be adapted to provide an effective and secure seal against anatomical structures that are difficult to seal, such as the elbow or heel, at and around the tissue site. Additionally or alternatively, the dimensions can be varied to increase the surface area relative to the third layer 215 so as to promote the movement and proliferation of epithelial cells at the tissue site and reduce the likelihood of ingrowth of granulation tissue.

[0076] Furthermore, the dressing 104 can be enabled, by reapplication or repositioning, to reduce or eliminate leaks that may be caused by creases or other discontinuities in the dressing 104 and at the tissue site. By being able to correct leaks, in some embodiments, the reliability of treatment can be improved and the power consumption can be reduced.

[0077] Thus, the dressing 104 in the example of FIG. 2 can provide a sealed treatment environment that is substantially isolated from the external environment and is proximate to the tissue site, and the negative pressure source 102 can reduce pressure in the sealed treatment environment. The third layer 215 can provide an effective and secure seal against anatomical surfaces that are difficult to seal, such as the elbow or heel, at or around the tissue site. Further, the dressing 104 can be configured to enable, for example, by reapplication or repositioning, correction of air leakage caused by folds and other discontinuities in the dressing 104. By being able to correct the leakage, in some embodiments, the efficacy of the treatment can be increased and the power consumption can be reduced.

[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 can be fluidly coupled to the dressing interface 270 and to the negative pressure source 102.

[0079] The negative pressure applied through the tissue interface 114 can create a negative differential pressure across the fluid restriction 220 in the second layer 210, thereby opening or expanding the fluid restriction 220 from their rest state. For example, in some embodiments where the fluid restriction 220 can comprise a substantially closed aperture through the second layer 210, the pressure gradient across the aperture can distort the adjacent material of the second layer 210 and increase the size of the aperture, similar to the operation of a duckbill valve, to allow movement of liquid therethrough. By opening the fluid restriction 220, movement of exudates and other liquids through the first layer 205 and into the container 106 through the fluid restriction 220 can be enabled. The change in pressure 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 exposure of tissue to the first layer 205, thereby preventing growth of tissue into the first layer 205.

[0080] In some embodiments, the first layer 205 can be hydrophobic to minimize the retention or storage of liquid in the dressing 104. In other embodiments, the first layer 205 can be hydrophilic. In examples where the first layer 205 can be hydrophilic, the first layer 205 can also be capable of absorbing fluid from the tissue site while the negative pressure is being continuously distributed to the tissue site. The wicking properties of the first layer 205 can pull fluid away from the tissue site, for example, by capillary flow or other wicking mechanisms. Examples of hydrophilic first layers 205 are polyvinyl alcohol, open-cell foams such as the V.A.C. WHITEFOAM™ dressing available from KCI of San Antonio, Texas. Other hydrophilic foams can include those made from polyethers. Other foams that can exhibit hydrophilic characteristics can include hydrophobic foams that have been treated or coated to provide hydrophilicity.

[0081] When the negative pressure source 102 is removed or turned off, the differential pressure across the fluid restriction 220 can disappear, whereby the fluid restriction 220 can move to their rest state and prevent or reduce the rate at which exudate or other liquid returns through the second layer 210 to the tissue site.

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

[0083] Additionally or alternatively, a dripping solution or other fluid can be dispensed into the dressing 104, thereby increasing the pressure within the tissue interface 114. An increase in the pressure within the tissue interface 114 can result in a positive differential pressure across the fluid restriction portions 220 in the second layer 210, thereby releasing or expanding the fluid restriction portions 220 from their quiescent state and enabling the dripping 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, showing further details that can be associated with 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 apertures 235 in the inner portion 230. Further, the valve 605 can be included in the third layer 215 in addition to or instead of the fluid restriction portions 220 in the second layer 210. In some embodiments where 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, and the valve 605 is disposed in the inner portion 230.

[0085] FIGS. 7 and 8 show other configuration examples of the valve 605, where the valve 605 comprises a combination of intersecting slits or cross slits, respectively.

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

[0087] The systems, devices, and methods described herein can provide significant advantages compared to conventional dressings. For example, some dressings for negative pressure therapy may require time and skill to be properly sized and applied to achieve a good fit and seal. In contrast, some embodiments of dressing 104 provide a negative pressure dressing that can be easily applied and that reduces the time for application and removal. In some embodiments, for example, dressing 104 can be applied to a tissue site (including over the wound perimeter) in one step without cutting to a certain size, while still providing or improving many of the advantages of other negative pressure therapy dressings that require sizing. Such advantages can include excellent manifolding, favorable granulation, protection of surrounding tissue from maceration, and low trauma and high seal bonding. These features can be particularly advantageous for superficial wounds having a moderate depth and medium to high levels of exudate. Some embodiments of dressing 104 can remain over the tissue site for at least five days, and some embodiments can remain for at least seven days. The antimicrobial agent in dressing 104 can extend the useful life of dressing 104 by reducing or eliminating the risk of infection associated with long-term use, particularly in infected or highly 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 Full-Thickness Defect Wounds Objective The primary objective of this investigation was to evaluate embodiments of dressings having the characteristics described above (designated as "GM" for purposes of the investigation) in relation to V.A.C. Therapy and V.A.C. VERAFLO Therapy, compared to conventional V.A.C. Therapy using GRANUFOAM (trademark) dressings and other Advanced Wound Care dressings without V.A.C. Therapy. Wounds were evaluated for granulation tissue formation, the presence of maceration in the skin surrounding the wound, and ease of dressing removal, as determined below. i. Histological evaluation of granulation tissue thickness ii. Peel strength test iii. Visual evaluation of bleeding iv. Visual evaluation of dressing particles remaining on the wound bed after dressing removal v. Histological evaluation of dressing particles, necrosis, bleeding, edema, and inflammation vi. Maceration of intact skin (tissue water content) vii. Histological evaluation of intact skin for bacteria, edema, and inflammation

[0090] Test articles and controls TIFF0007700172000001.tif137170

[0091] Animal model This investigation was conducted using the animal model outlined below. TIFF0007700172000002.tif57170

[0092] Investigation design TIFF0007700172000003.tif69170

[0093] TIFF0007700172000004.tif78170

[0094] Surgical procedures Defect wound creation - Day 0 The initial pilot animals (Group 1) received all wound generation and treatment prior to scheduling treatment for the additional animals in Groups 2 and 3. Up to 10 full-thickness skin defect wounds (approx. 3 x 7.5 cm) (up to 5 wounds on each side of the spine) were generated on each animal using a sterile template. There was a space between each of the wounds (at least about 6 cm from wound edge to wound edge between adjacent wounds, sufficient space between all wounds to allow proper placement of dressings and drapes). If the length of the animal's back did not provide sufficient space for 10 wounds and dressings (determined on Day 0), 8 wounds (4 on each side of the spine) were generated. The wounds were surgically created using a scalpel blade down to but not disrupting the subcutaneous fascia layer (just above the muscle). If disruption of the subcutaneous fascia layer occurred, it was recorded in the study record. Care was taken not to excise the area around the wound during wound generation. Efforts were made to maintain the spine between the apex of the shoulder and the coccygeal prominence and create wounds on two paravertebral sites. Hemostasis was obtained using direct pressure with sterile gauze. In cases of excessive bleeding not controlled by direct pressure, hemostatic forceps were used to clamp the bleeding source. During the generation of other wounds, the wounds were kept moist using sterile 0.9% saline-soaked gauze. The wounds were photographed.

[0095] Application of Dressings and Negative Pressure Therapy Following wound generation (Day 0), the test article or control article was applied to all wounds. On Day 4 (Group 3 only), the test article or control article was applied to wounds where the dressing had been removed.

[0096] On the indicated dressing change days (after the peel test, TEWL, visual observation, and photography), the area around the wound was gently wiped and dried with sterile 0.9% saline-soaked gauze. Dressings were applied to individual wound sites by a randomization method.

[0097] Regardless of the type of dressing for a particular wound, an adhesive such as benzene was placed on the skin surrounding the outermost periphery of the test article edge, leaving an approximately 1 cm outer periphery around the wound free of benzene, and the wound surrounding area was enclosed with the adhesive. This means that there is no possibility of the benzene adhesive being applied to the intermediate skin surrounding the wound, as the benzene adhesive may affect the EpiD reading value. The adhesive was placed on the skin in any area where the V.A.C. (registered trademark) drape was applied. Alternatively (or additionally), Hollister (medical grade silicone adhesive) was applied as an additional adhesive to help maintain airtightness.

[0098] For the test article wound pair (test article undergoing V.A.C. (registered trademark) therapy) and / or the test article wound undergoing V.A.C. VERAFLO (trademark) therapy (test article using V.A.C. VERAFLO (trademark) therapy with physiological saline), a pair of electrodes (for example, aluminum sheet or wire) was applied to be located in the wound surrounding area (under the test article but above the skin surrounding the wound).

[0099] When applicable, the skin directly under the strip of the foam bridge was covered with a V.A.C. (registered trademark) drape for protection. Each cross-linked wound group was covered with a V.A.C. (registered trademark) drape included in the dressing kit, one hole was made in the drape, and a SENSAT.R.A.C. (trademark) pad or V.A.C.VERAT.R.A.C. (trademark) pad (when applicable) was directly attached over the hole as per the instructions for use (IFU). Each pad was maintained in place and each side of the pad was enclosed with a V.A.C. (registered trademark) drape to ensure airtightness.

[0100] The V.A.C. ULTA (trademark) unit was present in the surgical set on the day of wound creation and was properly connected to each pad to confirm that each wound group was properly sealed following application.

[0101] To check the seal around the wound, negative pressure wound therapy (NPWT) was initiated at a continuous vacuum pressure of -125 mmHg using the SEAL CHECK (trademark) function in the V.A.C. ULTA (trademark) unit. Once appropriate seal was confirmed, the V.A.C. ULTA (trademark) unit was turned off and this procedure was repeated if applicable. Following all seal checks, an additional layer of V.A.C. (registered trademark) drape was placed around the edges to reinforce the seal and prevent leakage.

[0102] For wounds receiving V.A.C. VERAFLO (trademark) therapy, the Fill Assist function was used to determine the amount of fluid (i.e., saline) necessary to saturate the dressing in the paired wound. These determinations were appropriately made for each wound pair at each dressing change. V.A.C. VERAFLO (trademark) therapy NPWT was initiated at a continuous vacuum pressure of -125 mmHg using the SEAL CHECK (trademark) function in the V.A.C. ULTA (trademark) unit. Once appropriate seal was confirmed, the V.A.C. ULTA (trademark) unit was turned off and this procedure was repeated if applicable. Following all seal checks, an additional layer of V.A.C. (registered trademark) drape was placed around the edges to reinforce the seal and prevent leakage. 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 movement, the entire area covered by the V.A.C. (registered trademark) drape was covered with a tear-resistant mesh (e.g., organza material) secured with V.A.C. (registered trademark) drape, Elastikon (registered trademark) or equivalent.

[0104] Provisional dressing change - Day 4, Group 3 only Resistance readings were taken from under the dressing. For one wound from each treatment pair, a peel force test was performed on the wound. Unless the dressing was intended to stay in place, the dressing was removed by hand for the other half of each wound pair (i.e., TANPT and TANPTI (n = 2 animals)). Wound evaluations were performed (when applicable) and photographs were taken.

[0105] Peel Test and Observation A peel force test was performed on one wound from each treatment pair (the same wound as the dressing change, if applicable). For the wounds where the dressing was removed, TEWL was performed, wound evaluations were made, and photographs were taken.

[0106] For groups 1 and 2 (day 4), five wounds were subjected to peel force tests, TEWL, and evaluations. The remaining five wounds were collected with the dressing in situ for histopathological processing and evaluation.

[0107] For group 3 (day 7), five wounds were subjected to peel force tests, TEWL, and evaluations. The remaining five wounds were collected with the dressing in situ for histopathological processing and evaluation.

[0108] The peel force test was performed on an inclined operating table. The peel force test was performed using a device that flips 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 confirm the angle. The peel strength value indicates the ease with which the test material can 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 equipped with LabView.

[0109] Using a surgical scalpel, a boundary line was gently drawn on the drape over the test article for the peel test, taking care not to interfere with the ingrowth of tissue into the side portions of the dressing. During the treatment of the test article for the peel test, using a surgical scalpel, the excess dressing not in contact with the wound was removed. This was done by cutting the dressing along the sides, bottom, and top at locations where the outer edges of the wound were visible after negative pressure therapy. Using a clip, the inner end of the dressing or dressing tab was attached to the force gauge (the boundary line of the dressing was not drawn). Then, the dressing was pulled from the wound (from the inside to the outside) at a constant speed in the inside-to-outside direction. After measuring the peel force, an evaluation was performed. Continuous peel force readings were recorded by LabView via the force gauge and saved for each wound. Following the peel test, the dressing was saved for analysis of the tissue remaining in the dressing.

[0110] Figure 9 demonstrates the results (N) of the maximum peel force measurements on day 7 following dressing application and removal for the test articles (designated "TANPT" and "TANPTI") and the control dressing. As shown, the test articles did not require much peel force, with or without V.A.C. VERAFLO (trademark) therapy.

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

[0112] Trans-epidermal water loss Using the Moisture Meter EpiD Compact from Delfin Technologies (Kuopio, Finland), the level of moisture at the dressing - skin (uninjured) interface was determined. These measurements were taken immediately after wound generation on day 0, on dressing change days (if applicable), and at the end prior to euthanasia. The EpiD Compact instrument was used to measure the relative permittivity of the skin. Four consecutive moisture measurements were collected from the uninjured skin of each animal, near the middle between the wound and the edge of the wound pad where the test article and advanced wound dressing were located, on the day of wound generation (day 0). On dressing change days and at the end (if applicable), four consecutive moisture measurements were collected. These measurements were repeated for each available wound site for each animal. All measurements / data were recorded.

[0113] Wound evaluation Overall observation At the time of dressing change and / or during the termination procedure, wound observations were made and recorded as follows. · Wound bleeding - none, mild, moderate or severe · Overall observation - dry (dull / matte), moist (shiny appearance), wet (presence of fluid), eschar (thin black and hard - looking tissue), slough (removable yellowish layer) and its location at the wound site · Exudate - none, serous (thin, watery, clear), serosanguinous (thin, pale red to pink), sanguineous (thin, bright red), purulent (opaque yellow - brown to yellow, thin or thick)

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

[0115] Figure 10 demonstrates that tissue internal growth was significantly reduced by TANPT and TANPTI.

[0116] Histopathology When the wound site was in 70% ethanol, it was immediately processed. When placed in NBF, before being further processed according to the standard procedure for histopathology test sites, the wound was transferred to 70% ethanol for a period of time. The wound site + dressing (if intact) was embedded in an extra-large paraffin block, and the entire site was cut transversely once at a thickness of approximately 5 μm, and the resulting slides were stained with hematoxylin and eosin (H&E). Before processing and embedding in paraffin, an overall image of the cut surface of the specimen was taken. Extra-large slides were used to accommodate the entire tissue section including the border of the unaffected skin on all four sides.

[0117] A board-certified veterinary pathologist semi-quantitatively evaluated the histopathological response on a scale of 1 - 5 (1 = very mild, 2 = mild, 3 = moderate, 4 = severe, 5 = very severe), unless otherwise specified. Microscopic evaluation of all stained sections for morphological changes in the wound, including but not limited to granulation tissue thickness and characteristics, amount of granulation tissue embedded in the dressing (if any), tissue inflammation, edema, vascularity (if any), presence of bacteria, necrosis, and other relevant factors, as judged by the pathologist. The area around the wound was evaluated for features consistent with maceration as judged by the pathologist.

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

[0119] Histopathological evaluation of individual wound sites The photomicrograph in Figure 11 demonstrates that TANPT had significantly more covering granulation than NPT and NPTI.

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

[0121] Investigation conclusion The data demonstrate that the test article has unexpectedly positive results and improves when combined with the V.A.C. VERAFLO™ therapy. The test article with the V.A.C. VERAFLO™ therapy demonstrated relatively excellent performance by showing an increase in granulation tissue thickness, a reduction in tissue ingrowth, an epithelialization rate, and an average angiogenesis score.

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

[0123] All treatments with the test article also showed an unexpectedly significant reduction in tissue ingrowth, as demonstrated by a significant reduction in the peel force. For both continuous V.A.C.® therapy or V.A.C. VERAFLO™ therapy without dressing change, the peel force required to remove the test article after 7 days was less than 2 N. 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 V.A.C.® therapy, the peel force was reduced by 87% and 89% respectively.

[0124] Although shown in several exemplary embodiments, those skilled in the art will understand that the systems, devices, and methods described herein are capable of various modifications and changes within the scope of the appended claims. Further, the description of various alternative examples using terms such as "or" does not require mutual exclusivity unless clearly necessary from the context, and the articles "a" or "an" do not limit the subject to a single instance unless clearly necessary from the context.

[0125] The features, elements, and aspects described in connection with some embodiments can also be omitted, combined, or replaced with alternative features that serve the same, equivalent, or similar purposes without departing from the scope of the invention as defined by the appended patent claims. For example, one or more of the features of some layers can be combined with the features of other layers to provide equivalent functionality. Alternatively or additionally, one or more of the fluid restrictors 220 can have a shape similar to the shape described by way of example for the valve 605.

[0126] It is also possible to combine or remove the components in various configurations for the purposes of sale, manufacture, assembly, or use. For example, in some configurations, the dressing 104, the container 106, or both can be eliminated or separated from other components for manufacture or sale. In other configurations, the controller 108 can also be manufactured, configured, assembled, or sold independently of other components.

[0127] The appended patent claims set forth novel and inventive aspects of the above-described subject matter, but can also include additional subject matter that is not specifically described in detail. Some features, elements, or aspects may be omitted from the claims when not necessary to identify novel and inventive features known to those skilled in the art.

Claims

**Claim 1** In a dressing for treating a tissue site using negative pressure, a fluid control layer having a plurality of openings, wherein the plurality of openings are configured to respond to a pressure gradient; a manifold layer adjacent to the fluid control layer; a cover adjacent to the manifold layer on a side opposite to the fluid control layer; a sealing layer adjacent to the fluid control layer on a side opposite to the manifold layer, the sealing layer comprising at least one aperture including an edge disposed to contact the fluid control layer, with a portion of the fluid control layer extending beyond the edge, whereby the at least one aperture is configured to expose at least a portion of the fluid control layer and the plurality of openings to the tissue site; A dressing, characterized by comprising the above. **Claim 2** The dressing according to claim 1, characterized in that at least one of the fluid control layer and the sealing layer is configured to be inserted between the manifold and the tissue site. **Claim 3** The dressing according to claim 1, characterized in that a peripheral edge of the cover is disposed in proximity to a peripheral edge of the sealing layer to enclose the manifold layer. **Claim 4** The dressing according to claim 1, characterized in that the sealing layer is adapted to contact the tissue site and the cover is the uppermost surface of the dressing. **Claim 5** The dressing according to claim 1, characterized in that the at least one aperture of the sealing layer is configured to expose at least a portion of the fluid control layer around the plurality of openings to the tissue site, and the plurality of openings comprise a plurality of imperfect valves.

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