WO2021084443A1

WO2021084443A1 - Manifolding non-adherent layer for use in negative-pressure treatment

Info

Publication number: WO2021084443A1
Application number: PCT/IB2020/060107
Authority: WO
Inventors: Christopher Brian Locke; Timothy Mark Robinson
Original assignee: Kci Licensing, Inc.
Priority date: 2019-10-30
Filing date: 2020-10-28
Publication date: 2021-05-06

Abstract

A dressing may include first layer and a second layer coupled to the first layer. The first layer may comprise a polymer film having a plurality of perforations through the polymer film that are configured to expand in response to a pressure gradient across the polymer film. The second layer may comprise open-cell foam having a density in a range of about 2.6 to about 16.0 lb/ft³ and a free volume in a range of about 9% to about 45%. A cover comprising a polymer film may be disposed adjacent to the second layer.

Description

MANIFOLDING NON-ADHERENT LAYER FOR USE IN NEGATIVE-PRESSURE

TREATMENT CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 62/928,046, filed on October 30, 2019, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The invention set forth in the appended claims relates generally to tissue treatment systems and more particularly, but without limitation, to dressings for tissue treatment and methods of using the dressings for tissue treatment.

BACKGROUND

[0003] Clinical studies and practice have shown that reducing pressure in proximity to a tissue site can augment and accelerate growth of new tissue at the tissue site. The applications of this phenomenon are numerous, but it has proven particularly advantageous for treating wounds. Regardless of the etiology of a wound, whether trauma, surgery, or another cause, proper care of the wound is important to the outcome. Treatment of wounds or other tissue with reduced pressure may be commonly referred to as "negative- pressure therapy," but is also known by other names, including "negative-pressure wound therapy," "reduced-pressure therapy," "vacuum therapy," "vacuum-assisted closure," and "topical negative-pressure," for example. Negative-pressure therapy may provide a number of benefits, including migration of epithelial and subcutaneous tissues, improved blood flow, and micro-deformation of tissue at a wound site. Together, these benefits can increase development of granulation tissue and reduce healing times.

[0004] There is also widespread acceptance that cleansing a tissue site can be highly beneficial for new tissue growth. For example, a wound or a cavity can be washed out with a liquid solution for therapeutic purposes. These practices are commonly referred to as "irrigation" and "lavage" respectively. "Instillation" is another practice that generally refers to a process of slowly introducing fluid to a tissue site and leaving the fluid for a prescribed period of time before removing the fluid. For example, instillation of topical treatment solutions over a wound bed can be combined with negative-pressure therapy to further promote wound healing by loosening soluble contaminants in a wound bed and removing infectious material. As a result, soluble bacterial burden can be decreased, contaminants removed, and the wound cleansed.

[0005] While the clinical benefits of negative -pressure therapy and/or instillation therapy are widely known, improvements to therapy systems, components, and processes may benefit healthcare providers and patients. BRIEF SUMMARY

[0006] New and useful systems, apparatuses, and methods for treating tissue in a negative-pressure therapy environment are set forth in the appended claims. Illustrative embodiments are also provided to enable a person skilled in the art to make and use the claimed subject matter. [0007] For example, in some embodiments, a dressing for treating tissue may be a composite of dressing layers, including a perforated polymer fdm, a manifold, and an adhesive drape. The polymer fdm may be polyethylene, polyurethane, or ethyl methyl acrylate (EMA) in some embodiments. The manifold may include felted open-cell foam in some examples. The thickness of the manifold may vary for different types of tissue or fluid. For example, a manifold layer of felted foam may be relatively thin and hydrophobic to reduce the fluid hold capacity of the dressing. The felted foam may also be thin to reduce the dressing profde and increase flexibility, which can enable it to conform to wound beds and other tissue sites under negative pressure. In other examples, a greater thickness may be advantageous for more viscous fluid or larger areas. The manifold may be adhered to the polymer fdm in some embodiments. Suitable bonds between the manifold and the polymer fdm may include pressure-sensitive adhesive (reactive and non- reactive types); hot melt adhesive (spray applied or deployed as a fdm, woven, or non-woven); hot press lamination; or flame lamination. The polymer fdm may also be co-extruded with a bonding layer in-situ, which may be formed from a hot melt adhesive, for example. In some examples, the polymer fdm may encapsulate the manifold. In other examples, the manifold may have at least one exposed edge, and the dressing may be cut to a desired size before applying the dressing to a tissue. In some embodiments, drape strips or other adhesive strips may be used to seal edges of the dressing and fix the dressing to a patient’s skin.

[0008] Some embodiments of a dressing may include a first layer and a second layer coupled to the first layer. The first layer may be a polymer fdm having a plurality of perforations through the polymer fdm that are configured to expand in response to a pressure gradient across the polymer fdm. The second layer may be open-cell foam having a density in a range of about 2.6 to about 16.0 lb/ft³.

[0009] Other example embodiments of a dressing may include a manifold and a contact layer coupled to the manifold. The manifold may comprise open-cell foam having about 80 to about 500 pores per inch.

[0010] In more particular embodiments, the contact layer may be a polymer fdm having a plurality of perforations through the polymer fdm that are configured to expand in response to a pressure gradient across the polymer fdm. In some particular embodiments, the contact layer may include a plurality of polymer fdm sections. In other particular embodiments, the contact layer may be an open-cell foam having a thickness in a range of about 1 to about 20 microns. In other particular embodiments, the contact layer may be an open-cell foam having a density in a range of about 13 to about 80 lb/ft³. In other particular embodiments, the contact layer may be an open-cell foam having a pore size in a range of about 12 to about 60 microns. In other particular embodiments, the contact layer may be an open-cell foam having a free volume in a range of about 2% to about 9%. In other particular embodiments, the contact layer may be an open-cell foam having about 400 to about 2500 pores per inch.

[0011] A method of applying negative pressure to a tissue site may include providing a tissue interface comprising a first layer and a second layer, disposing the second layer of the tissue interface in proximity to the tissue site, providing a cover over the tissue interface to form a sealed space containing the tissue interface, fluidly coupling a negative-pressure source to the tissue interface, and applying negative pressure to the tissue interface. The first layer may be a felted open-cell foam. The second layer may be a contact layer.

[0012] Other objectives, advantages, and a preferred mode of making and using the claimed subject matter may be understood best by reference to the accompanying drawings in conjunction with the following detailed description of illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a functional block diagram of an example embodiment of a therapy system that can provide negative-pressure treatment and instillation treatment in accordance with this specification; [0014] Figure 2 is an assembly view of an example of a tissue interface that can be associated with some embodiments of the therapy system of Figure 1 ;

[0015] Figure 3 is a schematic view of an example layer that can be associated with some embodiments of the tissue interface of Figure 2;

[0016] Figure 4 is a side view of an example of a tissue interface of Figure 2; [0017] Figure 5 is an assembly view of another example of a tissue interface that can be associated with some embodiments of the therapy system of Figure 1 ;

[0018] Figure 6 is a bottom view of the tissue interface of Figure 5;

[0019] Figure 7 is an assembly view of another example of a tissue interface that can be associated with some embodiments of the therapy system of Figure 1 ; [0020] Figure 8 is a schematic view of an example layer that can be associated with some embodiments of the tissue interface of Figure 7;

[0021] Figure 9 is a schematic view of another example layer that can be associated with some embodiments of a tissue interface;

[0022] Figure 10 is a schematic side view of another example of the layer of Figure 9; [0023] Figure 11 is a schematic side view of another example of the layer of Figure 9;

[0024] Figure 12 is an assembly view of another example of a tissue interface that can be associated with some embodiments of the therapy system of Figure 1;

[0025] Figure 13 is an assembly view of another example of a tissue interface that can be associated with some embodiments of the therapy system of Figure 1; [0026] Figure 14 is a schematic view of another example layer that can be associated with some embodiments of a tissue interface; [0027] Figure 15 is a schematic diagram of an example of the therapy system of Figure 1 applied to a tissue site; and

[0028] Figure 16 is a schematic diagram of another example of the therapy system of Figure 1 applied to a tissue site. DESCRIPTION OF EXAMPLE EMBODIMENTS

[0029] The following description of example embodiments provides information that enables a person skilled in the art to make and use the subject matter set forth in the appended claims, but it may omit certain details already well-known in the art. The following detailed description is, therefore, to be taken as illustrative and not limiting. [0030] The example embodiments may also be described herein with reference to spatial relationships between various elements or to the spatial orientation of various elements depicted in the attached drawings. In general, such relationships or orientation assume a frame of reference consistent with or relative to a patient in a position to receive treatment. However, as should be recognized by those skilled in the art, this frame of reference is merely a descriptive expedient rather than a strict prescription. [0031] Figure 1 is a simplified functional block diagram of an example embodiment of a therapy system 100 that can provide negative-pressure therapy with instillation of topical treatment solutions to a tissue site in accordance with this specification.

[0032] The term “tissue site” in this context broadly refers to a wound, defect, or other treatment target located on or within tissue, including but not limited to, a surface wound, bone tissue, adipose tissue, muscle tissue, neural tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, or ligaments. The term “tissue site” may also refer to areas of any tissue that are not necessarily wounded or defective, but are instead areas in which it may be desirable to add or promote the growth of additional tissue. For example, negative pressure may be applied to a tissue site to grow additional tissue that may be harvested and transplanted. A surface wound, as used herein, is a wound on a body that is exposed to the external environment, such as an injury or damage to the epidermis, dermis, and/or subcutaneous layers. Surface wounds may include ulcers or closed incisions, for example. A surface wound, as used herein, does not include wounds within an intra-abdominal cavity. A wound may include chronic, acute, traumatic, subacute, and dehisced wounds, partial-thickness bums, ulcers (such as diabetic, pressure, or venous insufficiency ulcers), flaps, and grafts, for example. [0033] The therapy system 100 may include a source or supply of negative pressure, such as a negative-pressure source 105, and one or more distribution components. A distribution component is preferably detachable and may be disposable, reusable, or recyclable. A dressing, such as a dressing 110, and a fluid container, such as a container 115, are examples of distribution components that may be associated with some examples of the therapy system 100. As illustrated in the example of Figure 1, the dressing 110 may comprise or consist essentially of a tissue interface 120, a cover 125, or both in some embodiments.

[0034] A fluid conductor is another illustrative example of a distribution component. A “fluid conductor,” in this context, broadly includes a tube, pipe, hose, conduit, or other structure with one or more lumina or open pathways adapted to convey a fluid between two ends. Typically, a tube is an elongated, cylindrical structure with some flexibility, but the geometry and rigidity may vary. Moreover, some fluid conductors may be molded into or otherwise integrally combined with other components. Distribution components may also include or comprise interfaces or fluid ports to facilitate coupling and de-coupling other components. In some embodiments, for example, a dressing interface may facilitate coupling a fluid conductor to the dressing 110. For example, such a dressing interface may be a SENSAT.R.A.C.™ Pad available from Kinetic Concepts, Inc. of San Antonio, Texas.

[0035] The therapy system 100 may also include a regulator or controller, such as a controller 130. Additionally, the therapy system 100 may include sensors to measure operating parameters and provide feedback signals to the controller 130 indicative of the operating parameters. As illustrated in Figure 1, for example, the therapy system 100 may include a first sensor 135 and a second sensor 140 coupled to the controller 130.

[0036] The therapy system 100 may also include a source of instillation solution. For example, a solution source 145 may be fluidly coupled to the dressing 110, as illustrated in the example embodiment of Figure 1. The solution source 145 may be fluidly coupled to a positive-pressure source, such as a positive- pressure source 150, a negative-pressure source such as the negative-pressure source 105, or both in some embodiments. A regulator, such as an instillation regulator 155, may also be fluidly coupled to the solution source 145 and the dressing 110 to ensure proper dosage of instillation solution (e.g. saline) to a tissue site. For example, the instillation regulator 155 may comprise a piston that can be pneumatically actuated by the negative-pressure source 105 to draw instillation solution from the solution source during a negative-pressure interval and to instill the solution to a dressing during a venting interval. Additionally or alternatively, the controller 130 may be coupled to the negative-pressure source 105, the positive-pressure source 150, or both, to control dosage of instillation solution to a tissue site. In some embodiments, the instillation regulator 155 may also be fluidly coupled to the negative-pressure source 105 through the dressing 110, as illustrated in the example of Figure 1.

[0037] Some components of the therapy system 100 may be housed within or used in conjunction with other components, such as sensors, processing units, alarm indicators, memory, databases, software, display devices, or user interfaces that further facilitate therapy. For example, in some embodiments, the negative-pressure source 105 may be combined with the controller 130, the solution source 145, and other components into a therapy unit.

[0038] In general, components of the therapy system 100 may be coupled directly or indirectly. For example, the negative-pressure source 105 may be directly coupled to the container 115 and may be indirectly coupled to the dressing 110 through the container 115. Coupling may include fluid, mechanical, thermal, electrical, or chemical coupling (such as a chemical bond), or some combination of coupling in some contexts. For example, the negative-pressure source 105 may be electrically coupled to the controller 130 and may be fluidly coupled to one or more distribution components to provide a fluid path to a tissue site. In some embodiments, components may also be coupled by virtue of physical proximity, being integral to a single structure, or being formed from the same piece of material.

[0039] A negative-pressure supply, such as the negative-pressure source 105, may be a reservoir of air at a negative pressure or may be a manual or electrically-powered device, such as a vacuum pump, a suction pump, a wall suction port available at many healthcare facilities, or a micro-pump, for example. “Negative pressure” generally refers to a pressure less than a local ambient pressure, such as the ambient pressure in a local environment external to a sealed therapeutic environment. In many cases, the local ambient pressure may also be the atmospheric pressure at which a tissue site is located. Alternatively, the pressure may be less than a hydrostatic pressure associated with tissue at the tissue site. Unless otherwise indicated, values of pressure stated herein are gauge pressures. References to increases in negative pressure typically refer to a decrease in absolute pressure, while decreases in negative pressure typically refer to an increase in absolute pressure. While the amount and nature of negative pressure provided by the negative- pressure source 105 may vary according to therapeutic requirements, the pressure is generally a low vacuum, also commonly referred to as a rough vacuum, between -5 mm Hg (-667 Pa) and -500 mm Hg (-66.7 kPa). Common therapeutic ranges are between -50 mm Hg (-6.7 kPa) and -300 mm Hg (-39.9 kPa).

[0040] The container 115 is representative of a container, canister, pouch, or other storage component, which can be used to manage exudates and other fluids withdrawn from a tissue site. In many environments, a rigid container may be preferred or required for collecting, storing, and disposing of fluids. In other environments, fluids may be properly disposed of without rigid container storage, and a re-usable container could reduce waste and costs associated with negative-pressure therapy.

[0041] A controller, such as the controller 130, may be a microprocessor or computer programmed to operate one or more components of the therapy system 100, such as the negative-pressure source 105. In some embodiments, for example, the controller 130 may be a microcontroller, which generally comprises an integrated circuit containing a processor core and a memory programmed to directly or indirectly control one or more operating parameters of the therapy system 100. Operating parameters may include the power applied to the negative-pressure source 105, the pressure generated by the negative-pressure source 105, or the pressure distributed to the tissue interface 120, for example. The controller 130 is also preferably configured to receive one or more input signals, such as a feedback signal, and programmed to modify one or more operating parameters based on the input signals. [0042] Sensors, such as the first sensor 135 and the second sensor 140, are generally known in the art as any apparatus operable to detect or measure a physical phenomenon or property, and generally provide a signal indicative of the phenomenon or property that is detected or measured. For example, the first sensor 135 and the second sensor 140 may be configured to measure one or more operating parameters of the therapy system 100. In some embodiments, the first sensor 135 may be a transducer configured to measure pressure in a pneumatic pathway and convert the measurement to a signal indicative of the pressure measured. In some embodiments, for example, the first sensor 135 may be a piezo-resistive strain gauge. The second sensor 140 may optionally measure operating parameters of the negative-pressure source 105, such as a voltage or current, in some embodiments. Preferably, the signals from the first sensor 135 and the second sensor 140 are suitable as an input signal to the controller 130, but some signal conditioning may be appropriate in some embodiments. For example, the signal may need to be filtered or amplified before it can be processed by the controller 130. Typically, the signal is an electrical signal, but may be represented in other forms, such as an optical signal.

[0043] The tissue interface 120 can be generally adapted to partially or fully contact a tissue site. The tissue interface 120 may take many forms, and may have many sizes, shapes, or thicknesses, depending on a variety of factors, such as the type of treatment being implemented or the nature and size of a tissue site. For example, the size and shape of the tissue interface 120 may be adapted to the contours of deep and irregular shaped tissue sites. Any or all of the surfaces of the tissue interface 120 may have an uneven, coarse, or jagged profile.

[0044] In some embodiments, the tissue interface 120 may comprise or consist essentially of a manifold. A manifold in this context may comprise or consist essentially of a means for collecting or distributing fluid across the tissue interface 120 under pressure. For example, a manifold may be adapted to receive negative pressure from a source and distribute negative pressure through multiple apertures across the tissue interface 120, which may have the effect of collecting fluid from across a tissue site and drawing the fluid toward the source. In some embodiments, the fluid path may be reversed or a secondary fluid path may be provided to facilitate delivering fluid, such as fluid from a source of instillation solution, across a tissue site. [0045] In some embodiments, the cover 125 may provide a bacterial barrier and protection from physical trauma. The cover 125 may also be constructed from a material that can reduce evaporative losses and provide a fluid seal between two components or two environments, such as between a therapeutic environment and a local external environment. The cover 125 may comprise or consist of, for example, an elastomeric film or membrane that can provide a seal adequate to maintain a negative pressure at a tissue site for a given negative-pressure source. The cover 125 may have a high moisture-vapor transmission rate (MVTR) in some applications. For example, the MVTR may be at least 250 grams per square meter per twenty-four hours in some embodiments, measured using an upright cup technique according to ASTM E96/E96M Upright Cup Method at 38°C and 10% relative humidity (RH). In some embodiments, an MVTR up to 5,000 grams per square meter per twenty-four hours may provide effective breathability and mechanical properties.

[0046] In some example embodiments, the cover 125 may be a polymer drape, such as a polyurethane film, that is permeable to water vapor but impermeable to liquid. Such drapes typically have a thickness in the range of 25-50 microns. For permeable materials, the permeability generally should be low enough that a desired negative pressure may be maintained. The cover 125 may comprise, for example, one or more of the following materials: polyurethane (PU), such as hydrophilic polyurethane; cellulosics; hydrophilic polyamides; polyvinyl alcohol; polyvinyl pyrrolidone; hydrophilic acrylics; silicones, such as hydrophilic silicone elastomers; natural rubbers; polyisoprene; styrene butadiene rubber; chloroprene rubber; polybutadiene; nitrile rubber; butyl rubber; ethylene propylene rubber; ethylene propylene diene monomer; chlorosulfonated polyethylene; polysulfide rubber; ethylene vinyl acetate (EVA); co-polyester; and polyether block polyamide copolymers. Such materials are commercially available as, for example, Tegaderm® drape, commercially available from 3M Company, Minneapolis Minnesota; polyurethane (PU) drape; polyether block polyamide copolymer (PEBAX), for example; and INSPIRE 2301 and INSPIRE 2327 polyurethane films, commercially available from Expopack Advanced Coatings, Wrexham, United Kingdom. In some embodiments, the cover 125 may comprise INSPIRE 2301 having an MVTR (upright cup technique) of 2600 g/m²/24 hours and a thickness of about 30 microns.

[0047] An attachment device may be used to attach the cover 125 to an attachment surface, such as undamaged epidermis, a gasket, or another cover. The attachment device may take many forms. For example, an attachment device may be a medically-acceptable, pressure-sensitive adhesive configured to bond the cover 125 to epidermis around a tissue site. In some embodiments, for example, some or all of the cover 125 may be coated with an adhesive, such as an acrylic adhesive, which may have a coating weight of about 25-65 grams per square meter (g.s.m.). Thicker adhesives, or combinations of adhesives, may be applied in some embodiments to improve the seal and reduce leaks. Other example embodiments of an attachment device may include a double-sided tape, paste, hydrocolloid, hydrogel, silicone gel, or organogel.

[0048] The solution source 145 may also be representative of a container, canister, pouch, bag, or other storage component, which can provide a solution for instillation therapy. Compositions of solutions may vary according to a prescribed therapy, but examples of solutions that may be suitable for some prescriptions include hypochlorite-based solutions, silver nitrate (0.5%), sulfur-based solutions, biguanides, cationic solutions, and isotonic solutions.

[0049] In operation, the tissue interface 120 may be placed within, over, on, or otherwise proximate to a tissue site. If the tissue site is a wound, for example, the tissue interface 120 may partially or completely fill the wound, or it may be placed over the wound. The cover 125 may be placed over the tissue interface 120 and sealed to an attachment surface near a tissue site. For example, the cover 125 may be sealed to undamaged epidermis peripheral to a tissue site. Thus, the dressing 110 can provide a sealed therapeutic environment proximate to a tissue site, substantially isolated from the external environment, and the negative-pressure source 105 can reduce pressure in the sealed therapeutic environment.

[0050] The fluid mechanics of using a negative-pressure source to reduce pressure in another component or location, such as within a sealed therapeutic environment, can be mathematically complex. However, the basic principles of fluid mechanics applicable to negative-pressure therapy and instillation are generally well-known to those skilled in the art, and the process of reducing pressure may be described illustratively herein as “delivering,” “distributing,” or “generating” negative pressure, for example.

[0051] In general, exudate and other fluid flow toward lower pressure along a fluid path. Thus, the term “downstream” typically implies something in a fluid path relatively closer to a source of negative pressure or further away from a source of positive pressure. Conversely, the term “upstream” implies something relatively further away from a source of negative pressure or closer to a source of positive pressure. Similarly, it may be convenient to describe certain features in terms of fluid “inlet” or “outlet” in such a frame of reference. This orientation is generally presumed for purposes of describing various features and components herein. However, the fluid path may also be reversed in some applications, such as by substituting a positive-pressure source for a negative-pressure source, and this descriptive convention should not be construed as a limiting convention.

[0052] Negative pressure applied across the tissue site through the tissue interface 120 in the sealed therapeutic environment can induce macro-strain and micro-strain in the tissue site. Negative pressure can also remove exudate and other fluid from a tissue site, which can be collected in container 115.

[0053] In some embodiments, the controller 130 may receive and process data from one or more sensors, such as the first sensor 135. The controller 130 may also control the operation of one or more components of the therapy system 100 to manage the pressure delivered to the tissue interface 120. In some embodiments, controller 130 may include an input for receiving a desired target pressure and may be programmed for processing data relating to the setting and inputting of the target pressure to be applied to the tissue interface 120. In some example embodiments, the target pressure may be a fixed pressure value set by an operator as the target negative pressure desired for therapy at a tissue site and then provided as input to the controller 130. The target pressure may vary from tissue site to tissue site based on the type of tissue forming a tissue site, the type of injury or wound (if any), the medical condition of the patient, and the preference of the attending physician. After selecting a desired target pressure, the controller 130 can operate the negative-pressure source 105 in one or more control modes based on the target pressure and may receive feedback from one or more sensors to maintain the target pressure at the tissue interface 120.

[0054] In some embodiments, the controller 130 may have a continuous pressure mode, in which the negative-pressure source 105 is operated to provide a constant target negative pressure for the duration of treatment or until manually deactivated. Additionally or alternatively, the controller may have an intermittent pressure mode. For example, the controller 130 can operate the negative-pressure source 105 to cycle between a target pressure and atmospheric pressure. For example, the target pressure may be set at a value of 135 mmHg for a specified period of time (e.g., 5 min), followed by a specified period of time (e.g., 2 min) of deactivation. The cycle can be repeated by activating the negative -pressure source 105, which can form a square wave pattern between the target pressure and atmospheric pressure.

[0055] In some example embodiments, the increase in negative-pressure from ambient pressure to the target pressure may not be instantaneous. For example, the negative-pressure source 105 and the dressing 110 may have an initial rise time. The initial rise time may vary depending on the type of dressing and therapy equipment being used. For example, some therapy systems may increase negative pressure at a rate of about 20-30 mmHg/second, and other therapy systems may increase negative pressure at a rate of about 5-10 mmHg/second. If the therapy system 100 is operating in an intermittent mode, the repeating rise time may be a value substantially equal to the initial rise time.

[0056] In some example dynamic pressure control modes, the target pressure can vary with time. For example, the target pressure may vary in the form of a triangular waveform, varying between a negative pressure of 50 and 135 mmHg with a rise rate of negative pressure set at a rate of 25 mmHg/min. and a descent rate set at 25 mmHg/min. In other embodiments of the therapy system 100, the triangular waveform may vary between negative pressure of 25 and 135 mmHg with a rise rate of about 30 mmHg/min and a descent rate set at about 30 mmHg/min. [0057] In some embodiments, the controller 130 may control or determine a variable target pressure in a dynamic pressure mode, and the variable target pressure may vary between a maximum and minimum pressure value that may be set as an input prescribed by an operator as the range of desired negative pressure. The variable target pressure may also be processed and controlled by the controller 130, which can vary the target pressure according to a predetermined waveform, such as a triangular waveform, a sine waveform, or a saw-tooth waveform. In some embodiments, the waveform may be set by an operator as the predetermined or time-varying negative pressure desired for therapy.

[0058] In some embodiments, the controller 130 may receive and process data, such as data related to instillation solution provided to the tissue interface 120. Such data may include the type of instillation solution prescribed by a clinician, the volume of fluid or solution to be instilled to a tissue site (“fill volume”), and the amount of time prescribed for leaving solution at a tissue site (“dwell time”) before applying a negative pressure to the tissue site. The fill volume may be, for example, between 10 and 500 mL, and the dwell time may be between one second to 30 minutes. The controller 130 may also control the operation of one or more components of the therapy system 100 to instill solution. For example, the controller 130 may manage fluid distributed from the solution source 145 to the tissue interface 120. In some embodiments, fluid may be instilled to a tissue site by applying a negative pressure from the negative-pressure source 105 to reduce the pressure at the tissue site, drawing solution into the tissue interface 120. In some embodiments, solution may be instilled to a tissue site by applying a positive pressure from the positive-pressure source 150 to move solution from the solution source 145 to the tissue interface 120. Additionally or alternatively, the solution source 145 may be elevated to a height sufficient to allow gravity to move solution into the tissue interface 120.

[0059] The controller 130 may also control the fluid dynamics of instillation by providing a continuous flow of solution or an intermittent flow of solution. Negative pressure may be applied to provide either continuous flow or intermittent flow of solution. The application of negative pressure may be implemented to provide a continuous pressure mode of operation to achieve a continuous flow rate of instillation solution through the tissue interface 120, or it may be implemented to provide a dynamic pressure mode of operation to vary the flow rate of instillation solution through the tissue interface 120. Alternatively, the application of negative pressure may be implemented to provide an intermittent mode of operation to allow instillation solution to dwell at the tissue interface 120. In an intermittent mode, a specific fill volume and dwell time may be provided depending, for example, on the type of tissue site being treated and the type of dressing being utilized. After or during instillation of solution, negative-pressure treatment may be applied. The controller 130 may be utilized to select a mode of operation and the duration of the negative pressure treatment before commencing another instillation cycle. [0060] Figure 2 is an assembly view of an example of the tissue interface 120 of Figure 1, illustrating additional details that may be associated with some embodiments in which the tissue interface 120 comprises more than one layer. In the example of Figure 2, the tissue interface 120 comprises a first layer 205 and a second layer 210. In some embodiments, the first layer 205 may be disposed adjacent to the second layer 210. For example, the first layer 205 and the second layer 210 may be stacked so that the first layer 205 is in contact with the second layer 210. The first layer 205 may also be heat-bonded or adhered to the second layer 210 in some embodiments. In some embodiments, the first layer 205 optionally includes a low-tack adhesive, which can be configured to hold the tissue interface 120 in place while the cover 125 is applied. The low-tack adhesive may be continuously coated on the first layer 205 or applied in a pattern. [0061] The first layer 205 may comprise or consist essentially of a contact layer configured to contact a tissue site . In some embodiments, the first layer 205 may comprise or consist essentially of a liquid- impermeable, elastomeric material. For example, the first layer 205 may comprise or consist essentially of a polymer film, such as a polyurethane film. In some embodiments, the first layer 205 may comprise or consist essentially of the same material as the cover 125. The first layer 205 may also have a smooth or matte surface texture in some embodiments. A glossy or shiny finish finer or equal to a grade B3 according to the SPI (Society of the Plastics Industry) standards may be particularly advantageous for some applications. In some embodiments, variations in surface height may be limited to acceptable tolerances. For example, the surface of the first layer 205 may have a substantially flat surface, with height variations limited to 0.2 millimeters over a centimeter. [0062] In some embodiments, the first layer 205 may be hydrophobic. The hydrophobicity of the first layer 205 may vary, but may have a contact angle with water of at least ninety degrees in some embodiments. In some embodiments the first layer 205 may have a contact angle with water of no more than 150 degrees. For example, in some embodiments, the contact angle of the first layer 205 may be in a range of at least 90 degrees to about 120 degrees, or in a range of at least 120 degrees to 150 degrees. Water contact angles can be measured using any standard apparatus. Although manual goniometers can be used to visually approximate contact angles, contact angle measuring instruments can often include an integrated system involving a level stage, liquid dropper such as a syringe, camera, and software designed to calculate contact angles more accurately and precisely, among other things. Non-limiting examples of such integrated systems may include the FTAl25, FTA200, FTA2000, and FTA4000 systems, all commercially available from First Ten Angstroms, Inc., of Portsmouth, VA, and the DTA25, DTA30, and DTA100 systems, all commercially available from Kruss GmbH of Hamburg, Germany. Unless otherwise specified, water contact angles herein are measured using deionized and distilled water on a level sample surface for a sessile drop added from a height of no more than 5 cm in air at 20-25°C and 20-50% relative humidity. Contact angles herein represent averages of 5-9 measured values, discarding both the highest and lowest measured values. The hydrophobicity of the first layer 205 may be further enhanced with a hydrophobic coating of other materials, such as silicones and fluorocarbons, either as coated from a liquid, or plasma coated. [0063] The first layer 205 may also be suitable for welding to other layers, including the second layer 210. For example, the first layer 205 may be adapted for welding to polyurethane foams using heat, radio frequency (RF) welding, or other methods to generate heat such as ultrasonic welding. RF welding may be particularly suitable for more polar materials, such as polyurethane, polyamides, polyesters and acrylates. Sacrificial polar interfaces may be used to facilitate RF welding of less polar film materials, such as polyethylene.

[0064] The area density of the first layer 205 may vary according to a prescribed therapy or application. In some embodiments, an area density of less than 40 grams per square meter may be suitable, and an area density of about 20-30 grams per square meter may be particularly advantageous for some applications.

[0065] In some embodiments, for example, the first layer 205 may comprise or consist essentially of a hydrophobic polymer, such as a polyethylene film. The simple and inert structure of polyethylene can provide a surface that interacts little, if any, with biological tissues and fluids, providing a surface that may encourage the free flow of liquids and low adherence, which can be particularly advantageous for many applications. Other suitable polymeric films include polyurethanes, acrylics, polyolefin (such as cyclic olefin copolymers), polyacetates, polyamides, polyesters, copolyesters, PEBAX block copolymers, thermoplastic elastomers, thermoplastic vulcanizates, polyethers, polyvinyl alcohols, polypropylene, polymethylpentene, polycarbonate, styreneics, silicones, fluoropolymers, and acetates. A thickness between 20 microns and 100 microns may be suitable for many applications. Films may be clear, colored, or printed. More polar films suitable for laminating to a polyethylene film include polyamide, co-polyesters, ionomers, and acrylics. To aid in the bond between a polyethylene and polar film, tie layers may be used, such as ethylene vinyl acetate, or modified polyurethanes. An ethyl methyl acrylate (EMA) film may also have suitable hydrophobic and welding properties for some configurations.

[0066] The first layer 205 may be configured to control fluid movement across or through the first layer 205. For example, the first layer 205 may have one or more passages, which can be distributed uniformly or randomly across the first layer 205. The passages may be bi-directional and pressure- responsive. For example, each of the passages generally may comprise or consist essentially of an elastic passage that is normally unstrained to substantially reduce liquid flow, and can expand or open in response to a pressure gradient. As illustrated in the example of Figure 2, the passages may comprise or consist essentially of perforations 215 in the first layer 205. Perforations 215 may be formed by removing material from the first layer 205. For example, perforations 215 may be formed by cutting through the first layer 205. In the absence of a pressure gradient across the perforations 215, the perforations 215 may be sufficiently small to form a seal or fluid restriction, which can substantially reduce or prevent liquid flow. Additionally, or alternatively, one or more of the passages may be or may function as an elastomeric valve that is normally closed when unstrained to substantially prevent liquid flow, and can open in response to a pressure gradient. In some examples, the passages may comprise or consist essentially of fenestrations in the first layer 205. Generally, fenestrations are a species of perforation, and may also be formed by removing material from the first layer 205. The amount of material removed and the resulting dimensions of the fenestrations may be up to an order of magnitude less than perforations.

[0067] In some embodiments, the perforations 215 may be formed as slots (or fenestrations formed as slits) in the first layer 205. In some examples, the perforations 215 may comprise or consist of linear slots having a length less than 4 millimeters and a width less than 1 millimeter. The length may be at least 2 millimeters, and the width may be at least 0.4 millimeters in some embodiments. 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. Such dimensions and tolerances may be achieved with a laser cutter, for example. Slots of such configurations may function as imperfect elastomeric valves that can substantially reduce liquid flow in a normally closed or resting state. For example, such slots may form a flow restriction without being completely closed or sealed. The slots can expand or open wider in response to a pressure gradient to allow increased liquid flow.

[0068] The second layer 210 generally comprises or consists essentially of a manifold or a manifold layer, which can provide a means for collecting or distributing fluid across the tissue interface 120 under pressure. For example, the second layer 210 may be adapted to receive negative pressure from a source and distribute negative pressure through multiple apertures across the tissue interface 120, which may have the effect of collecting fluid from across a tissue site and drawing the fluid toward the source. In some embodiments, the fluid path may be reversed or a secondary fluid path may be provided to facilitate delivering fluid, such as from a source of instillation solution, across the tissue interface 120. [0069] In some illustrative embodiments, the pathways of the second layer 210 may be interconnected to improve distribution or collection of fluids. In some illustrative embodiments, the second layer 210 may comprise or consist essentially of a porous material having interconnected fluid pathways. Examples of suitable porous material that comprise or can be adapted to form interconnected fluid pathways (e.g., channels) may include cellular foam, including open-cell foam such as reticulated foam; porous tissue collections; and other porous material such as gauze or felted mat that generally include pores, edges, and/or walls. Liquids, gels, and other foams may also include or be cured to include apertures and fluid pathways. In some embodiments, the second layer 210 may additionally or alternatively comprise projections that form interconnected fluid pathways. For example, the second layer 210 may be molded to provide surface projections that define interconnected fluid pathways. [0070] In some embodiments, the second layer 210 may be formed by a felting process. Any porous foam suitable for felting may be used, including the example foams mentioned herein, such as GRANUFOAM™. Felting comprises a thermoforming process that permanently compresses a foam to increase the density of the foam while maintaining interconnected pathways. Felting may be performed by any known methods, which may include applying heat and pressure to a porous material or foam material. Some methods may include compressing a foam blank between one or more heated platens or dies (not shown) for a specified period of time and at a specified temperature. The direction of compression may be along the thickness of the foam blank. [0071] The period of time of compression may range from 10 minutes up to 24 hours, though the time period may be more or less depending on the specific type of porous material used. Further, in some examples, the temperature may range between 120°C to 260°C. Generally, the lower the temperature of the platen, the longer a porous material must be held in compression. After the specified time period has elapsed, the pressure and heat will form a felted structure or surface on or through the porous material or a portion of the porous material.

[0072] The felting process may alter certain properties of the original material, including pore shape and/or size, elasticity, density, and density distribution. For example, struts that define pores in the foam may be deformed during the felting process, resulting in flattened pore shapes. The deformed struts can also decrease the elasticity of the foam. The density of the foam is generally increased by felting. In some embodiments, contact with hot-press platens in the felting process can also result in a density gradient in which the density is greater at the surface and the pores size is smaller at the surface. In some embodiments, the felted structure may be comparatively smoother than any unfinished or non-felted surface or portion of the porous material. Further, the pores in the felted structure may be smaller than the pores throughout any unfinished or non-felted surface or portion of the porous material. In some examples, the felted structure may be applied to all surfaces or portions of the porous material. Further, in some examples, the felted structure may extend into or through an entire thickness of the porous material such that the all of the porous material is felted.

[0073] A felted foam may be characterized by a firmness factor, which is indicative of the compression of the foam. The firmness factor of a felted foam can be specified as the ratio of original thickness to final thickness. A compressed or felted foam may have a firmness factor greater than 1. The degree of compression may affect the physical properties of the felted foam. For example, felted foam has an increased effective density compared to a foam of the same material that is not felted. The felting process can also affect fluid-to-foam interactions. For example, as the density increases, compressibility or collapse may decrease. Therefore, foams which have different compressibility or collapse may have different firmness factors. In some example embodiments, a firmness factor can range from about 2 to about 10, preferably about 3 to about 5. For example, the firmness factor of the second layer 210 felted foam may be about 5 in some embodiments. There is a general linear relationship between firmness level, density, pore size (or pores per inch) and compressibility. For example, foam that is felted to a firmness factor of 3 will show a three-fold density increase and compress to about a third of its original thickness.

[0074] In some embodiments, a suitable foam blank (e.g. of pre-felted foam) for formation of the second layer 210 may have about 40 to about 50 pores per inch on average, a density of about 1.3 to about 1.6 lb/ft³, a free volume of about 90% or more, an average pore size in a range of about 400 to about 600 microns, a 25% compression load deflection of at least 0.35 pounds per square inch, and/or a 65% compression load deflection of at least 0.43 pounds per square inch. In some embodiments, the foam blank may have a thickness greater than 10 millimeters, for example 10-35 millimeters, 10-25 millimeters, 10-20 millimeters, or 15-20 millimeters. In some embodiments, the foam blank may be felted to provide denser foam for the second layer 210. For example, the foam blank may be felted to a firmness factor of 2-10. In some embodiments, the foam blank may be felted to a firmness factor of 3-10. Some embodiments may felt the foam blank to a firmness factor of 5.

[0075] In some embodiments, the second layer 210 may comprise an open-cell foam having a free volume in a range of about 9% to about 45%, a density of about 2.6 to about 16.0 lb/ft³, about 80 to about 500 pores per inch on average (e.g., as measured in the direction of compression), and/or average pore size of about 40 to about 300 microns (e.g., as measured in the direction of compression), which may be particularly advantageous under negative pressure. For example, the denser foam may better resist the compressive effects when used under a compression garment and/or may better maintain fluid flow when under negative pressure. In some embodiments, the density of the foam of the second layer 210 may be about 6.5 to about 8.0 lb/ft³. In some embodiments, the free volume of the foam maybe about 18%. In some embodiments, the average pore size of the second layer 210 may be about 80 to about 120 micron. In some embodiments, the second layer 210 may have about 200 to about 250 pores per inch on average. In some embodiments, the second layer 210 may have a 25% compression load deflection of at least 1.05 pounds per square inch and a 65% compression load deflection of at least 1.29 pounds per square inch. In some embodiments, the foam of the second layer 210 may have a 25% compression load deflection of at least 1.75 pounds per square inch and a 65% compression load deflection of at least 2.15 pounds per square inch. In some embodiments, the foam of the second layer 210 may have a 25% compression load deflection of about 1.05 to about 3.5 pounds per square inch and a 65% compression load deflection of about 1.29 to about 4.30 pounds per square inch.

[0076] Other suitable materials for the second layer 210 may include non-woven fabrics; three- dimensional (3D) polymeric structures, such as molded polymers, embossed and formed films, and fusion- bonded films, and mesh, for example.

[0077] In some examples, the second layer 210 may include a 3D textile. A 3D textile of polyester fibers may be particularly advantageous for some embodiments. For example, the second layer 210 may comprise or consist essentially of a three-dimensional weave of polyester fibers. In some embodiments, the fibers may be elastic in at least two dimensions. A puncture-resistant fabric of polyester and cotton fibers having a weight of about 650 grams per square meter and a thickness of about 1-2 millimeters may be particularly advantageous for some embodiments. Such a puncture-resistant fabric may have a warp tensile strength of about 330-340 kilograms per square centimeter (kg/cm²) and a weft tensile strength of about 270- 280 kilograms per square centimeter (kg/cm²) in some embodiments. Another particularly suitable material may be a polyester spacer fabric having a weight of about 470 grams per square meter, which may have a thickness of about 4-5 millimeters in some embodiments. Such a spacer fabric may have a compression strength of about 20-25 kilopascals (at 40% compression). Additionally or alternatively, the second layer 210 may comprise or consist of a material having substantial linear stretch properties, such as a polyester spacer fabric having 2-way stretch and a weight of about 380 grams per square meter. A suitable spacer fabric may have a thickness of about 3-4 millimeters, and may have a warp and weft tensile strength of about 30-40 kilograms in some embodiments. The fabric may have a close-woven layer of polyester on one or more opposing faces in some examples.

[0078] Figure 3 is a schematic view of another example of the first layer 205, illustrating additional details that may be associated with some embodiments. For example, as illustrated in Figure 3, the perforations 215 may comprise a first plurality of perforations 305 and a second plurality of perforations 310. Each of the first plurality of perforations 305 and the second plurality of perforations 310 may be linear or curved perforations, such as slots or slits. In some embodiments where the perforations 215 are linear slots or slits, each of the first plurality of perforations 305 may have a length Li and each of the second plurality of perforations 310 may have a length L2. In some embodiments, where the perforations 215 are curved slots or slits, each of the first plurality of perforations 305 may have a length Li measured from an end of the curved slot or slit to the other end of the curved slot or slit, and each of the second plurality of perforations 310 may have a length L2 measured from an end of the curved slot or slit to the other end of the curved slot or slit. In some embodiments, the length Li may be equal to the length L2. The first plurality of perforations 305 and the second plurality of perforations 310 may be distributed across the first layer 205 in one or more rows in one direction or in different directions.

[0079] In example embodiments, each of the first plurality of perforations 305 may have a first long axis. In some embodiments, the first long axis may be parallel to a first reference line 315 running in a first direction. In illustrative examples, each of the second plurality of perforations 310 may have a second long axis. In example embodiments, the second long axis may be parallel to a second reference line 320 running in a second direction. In some embodiments, one or both of the first reference line 315 and the second reference line 320 may be defined relative to an edge 325 or line of symmetry of the first layer 205. For example, one or both of the first reference line 315 and the second reference line 320 may be parallel or coincident with an edge 325 or line of symmetry of the first layer 205. In some illustrative embodiments, one or both of the first reference line 315 and the second reference line 320 may be rotated an angle relative to an edge 325 of the first layer 205. In example embodiments, an angle a may define the angle between the first reference line 315 and the second reference line 320.

[0080] In some example embodiments, the centroid of each of the first plurality of perforations 305 within a row may intersect athird reference line 330 running in athird direction. In illustrative embodiments, the centroid of each of the second plurality of perforations 310 within a row may intersect a fourth reference line 335 running in a fourth direction. In general, a centroid refers to the center of mass of a geometric object. In the case of a substantially two dimensional object such as a linear slit, the centroid of the linear slit will be the midpoint.

[0081] The pattern of perforations 215 may also be characterized by a pitch, which indicates the spacing between corresponding points on perforations 215 within a pattern. In example embodiments, the pitch may indicate the spacing between the centroids of perforations 215 within the pattern. Some patterns may be characterized by a single pitch value, while others may be characterized by at least two pitch values. For example, if the spacing between centroids of the perforations 215 is the same in all orientations, the pitch may be characterized by a single value indicating the spacing between centroids in adjacent rows. In example embodiments, a pattern comprising a first plurality of perforations 305 and a second plurality of perforations 310 may be characterized by two pitch values, Pi and Pi, where Pi is the spacing between the centroids of each of the first plurality of perforations 305 in adjacent rows, and Pi is the spacing between the centroids of each of the second plurality of perforations 310 in adjacent rows.

[0082] In example embodiments, within each row of the first plurality of perforations 305, each perforation may be separated from an adjacent perforation by a distance /)_/. In some embodiments, within each row of the second plurality of perforations 310, each perforation may be separated from an adjacent perforation by a distance Di. In some patterns, the rows may be staggered. The stagger may be characterized by an orientation of corresponding points in successive rows relative to an edge or other reference line associated with the first layer 205. In some embodiments, the rows of the first plurality of perforations 305 may be staggered. For example, a fifth reference line 340 in a fifth direction runs through the centroids of corresponding perforations 215 of adjacent rows of the first plurality of perforations 305. In some example embodiments, the stagger of the rows of the first plurality of perforations 305 may be characterized by the angle b formed between the first reference line 315 and the fifth reference line 340. In additional illustrative embodiments, the rows of the second plurality of perforations 310 may also be staggered. For example, a sixth reference line 345 in a sixth direction runs through the centroids of corresponding perforations 215 of adjacent rows of the second plurality of perforations 310. In some embodiments, the stagger of the rows of the second plurality of perforations 310 may be characterized by the angle y formed between the first reference line 315 and the sixth reference line 345.

[0083] In the example of Figure 3, each of the first plurality of perforations 305 and the second plurality of perforations 310 may be linear slots or slits. The first reference line 315 may be parallel with an edge 325, and the second reference line 320 may be orthogonal to the edge 325. In example embodiments, the third reference line 330 is orthogonal to the first reference line 315, and the fourth reference line 335 is orthogonal to the second reference line 320. For example, the third reference line 330 may be incident with the centroids of corresponding perforations in alternating rows of the second plurality of perforations 310, and the fourth reference line 335 may intersect the centroids of corresponding perforations in alternating rows of the first plurality of perforations 305. In the example of Figure 3 , the perforations 215 are arranged in a cross-pitch pattern in which each of the first plurality of perforations 305 is orthogonal along its first long axis to each of the second plurality of perforations 310 along its second long axis. For example, in Figure 3, Pi is equal to Pi (within acceptable manufacturing tolerances), and the cross-pitch pattern may be characterized by a single pitch value. Additionally, Li and Li may be substantially equal, and / ⁾ _/ and Di may be also be substantially equal, all within acceptable manufacturing tolerances. The rows of the first plurality of perforations 305 and the rows of the second plurality of perforations 310 may be characterized as staggered. For example, in some example embodiments of Figure 3, a may be about 90°, b may be about 135°, y may be about 45°. /'_/ may be about 4 millimeters, Pi may be about 4 millimeters, Li may be about 3 millimeters, L2 may be about 3 millimeters, /⁾ _/ may be about 5 millimeters, and D2 may be about 5 millimeters.

[0084] Figure 4 is a side view of an example of the tissue interface 120 of Figure 2 that may be associated with some embodiments of the therapy system of Figure 1. As shown in Figure 4, the tissue interface 120 has an exposed perimeter 400. More particularly, in the example of Figure 4, the first layer 205, and the second layer 210 each have an exposed perimeter, and there is no seam, weld, or seal along the exposed perimeter 400.

[0085] The second layer 210 generally has a first planar surface and a second planar surface opposite the first planar surface. The thickness Ti of the second layer 210 between the first planar surface and the second planar surface may also vary according to needs of a prescribed therapy. For example, the thickness Ti of the second layer 210 may be decreased to relieve stress on other layers and to reduce tension on peripheral tissue. The thickness of the second layer 210 can also affect the conformability and manifolding performance of the second layer 210. In some embodiments, a suitable foam may have a thickness 7^' _/ in a range of about 1 millimeter to about 5 millimeters. In other examples, a suitable foam having a thickness 77 in a range of about 1 millimeters to about 3 millimeters may be suitable. In some embodiments, the second layer 210 may be compressed during the felting process to have the thickness 77. In some embodiments, after the felting process, the second layer 210 may be skived to the thickness 77. For example, the second layer 210 may be felted to have a firmness factor of 5 and then may be skived down to have a thickness in a range of about 1 millimeter to about 3 millimeters. Fabrics, including suitable 3D textiles and spacer fabrics, may have a thickness 77 in a range of about 1 millimeter to about 8 millimeters. The second layer 210 also has a length L₃, which can vary according needs of a particular tissue site or prescribed therapy. For example, a length L3 in a range of about 3 centimeters to about 30 centimeters may be suitable for some applications.

[0086] Figure 5 is an assembly view of another example of the tissue interface 120 of Figure 1, illustrating additional details that may be associated with some embodiments of the tissue interface 120. In the example of Figure 5, the first layer 205 may comprise a plurality of polymer film sections 505. In some embodiments, the sections 505 may be discontinuous. In some embodiments, the sections 505 may comprise dots. The sections 505 may have many shapes, including circles, squares, stars, ovals, polygons, rectilinear shapes, triangles, for example, or may have some combination of such shapes. Fluid and/or negative pressure may be manifolded through the gaps between the sections 505 of the first layer 205.

[0087] Figure 6 is a bottom view of the tissue interface 120 of Figure 5, illustrating additional details that may be associated with some embodiments of the first layer 205. In the example of Figure 6, the sections 505 are generally circular and have a width Wi, which may be about 5 millimeters in some examples. Figure 6 also illustrates an example of a uniform distribution pattern of the sections 505. In Figure 6, the sections 505 are distributed across the second layer 210 in a grid of parallel rows and columns. Within each row and column, the sections 505 may be equidistant from each other, as illustrated in the example of Figure 6. The rows may be spaced a distance /T. and the sections 505 within each of the rows may be spaced a distance D4. For example, a distance l) of about 5 millimeters on center and a distance D4 of about 10 millimeters on center may be suitable for some embodiments. The sections 505 in adjacent rows may be aligned or offset. For example, adjacent rows may be offset, as illustrated in Figure 6, so that the sections 505 are aligned in alternating rows separated by a distance l)s. A distance l)s of about 10 millimeters may be suitable for some examples. The size and/or spacing of the sections 505 may vary in some embodiments to increase the density of the sections 505 according to therapeutic requirements.

[0088] Figure 7 is an assembly view of another example of the tissue interface 120 of Figure 1, illustrating additional details that may be associated with some embodiments. In the example of Figure 7, first layer 205 may comprise or consist essentially of a sealing layer formed from a soft, pliable material, such as a tacky gel, suitable for providing a fluid seal with a tissue site, and may have a substantially flat surface. For example, the first layer 205 may comprise, without limitation, a silicone gel, a soft silicone, hydrocolloid, hydrogel, polyurethane gel, polyolefin gel, hydrogenated styrenic copolymer gel, a foamed gel, a petrolatum gel, a soft closed cell foam such as polyurethanes and polyolefins coated with an adhesive, polyurethane, polyolefin, or hydrogenated styrenic copolymers. The first layer 205 may include an adhesive surface on an underside and a patterned coating of acrylic on a top side. The patterned coating of acrylic may be applied about a peripheral area to allow higher bonding in regions that are likely to be in contact with skin rather than the wound area. In other embodiments, the first layer 205 may comprise a low-tack adhesive layer instead of silicone. In some embodiments, the first layer 205 may have a thickness between about 200 microns (pm) and about 1000 microns (pm). In some embodiments, the first layer 205 may have a hardness between about 5 Shore OO and about 80 Shore OO. Further, the first layer 205 may be comprised of hydrophobic or hydrophilic materials.

[0089] In some embodiments, the first layer 205 may be a hydrophobic -coated material. For example, the first layer 205 may be formed by coating a porous material, such as, for example, woven, nonwoven, molded, or extruded mesh with a hydrophobic material. The hydrophobic material for the coating may be a soft silicone, for example.

[0090] The first layer 205 may have comers 705 and edges 710. The first layer 205 may include apertures 715. The apertures 715 may be formed by cutting or by application of local RF or ultrasonic energy, for example, or by other suitable techniques for forming an opening. The apertures 715 may have a uniform distribution pattern, or may be randomly distributed on the first layer 205. The apertures 715 in the first layer 205 may have many shapes, including circles, squares, stars, ovals, polygons, slits, complex curves, rectilinear shapes, triangles, for example, or may have some combination of such shapes.

[0091] Each of the apertures 715 may have uniform or similar geometric properties. For example, in some embodiments, each of the apertures 715 may be circular apertures, having substantially the same diameter. In some embodiments, the diameter of each of the apertures 715 may be between about 1 millimeter and about 50 millimeters. In other embodiments, the diameter of each of the apertures 715 may be between about 1 millimeter and about 20 millimeters. [0092] In other embodiments, geometric properties of the apertures 715 may vary. For example, the diameter of the apertures 715 may vary depending on the position of the apertures 715 in the first layer 205. The apertures 715 may be spaced substantially equidistant over the first layer 205. Alternatively, the spacing of the apertures 715 may be irregular. [0093] As illustrated in the example of Figure 7, some embodiments of the tissue interface 120 may include a release liner 720 to protect the first layer 205 prior to use. The release liner 720 may also provide stiffness to facilitate handling and applying the tissue interface 120. The release liner 720 may be, for example, a casting paper, a film, or polyethylene. Further, in some embodiments, the release liner 720 may be a polyester material such as polyethylene terephthalate (PET), or similar polar semi-crystalline polymer. The use of a polar semi-crystalline polymer for the release liner 720 may substantially preclude wrinkling or other deformation of the tissue interface 120. For example, the polar semi-crystalline polymer may be highly orientated and resistant to softening, swelling, or other deformation that may occur when brought into contact with components of the tissue interface 120, or when subjected to temperature or environmental variations, or sterilization. Further, a release agent may be disposed on a side of the release liner 720 that is configured to contact the first layer 205. For example, the release agent may be a silicone coating and may have a release factor suitable to facilitate removal of the release liner 720 by hand and without damaging or deforming the tissue interface 120. In some embodiments, the release agent may be a fluorocarbon or a fluorosilicone, for example. In other embodiments, the release liner 720 may be uncoated or otherwise used without a release agent. [0094] Figure 8 is a schematic view of an example configuration of the apertures 715, illustrating additional details that may be associated with some embodiments of the first layer 205. In some embodiments, the apertures 715 illustrated in Figure 8 may be associated only with an interior portion of the first layer 205. In the example of Figure 8, the apertures 715 are generally circular and have a width W₂. which may be about 2 millimeters in some examples. Figure 8 also illustrates an example of a uniform distribution pattern of the apertures 715. In Figure 8, the apertures 715 are distributed across the first layer 205 in a grid of parallel rows and columns. Within each row and column, the apertures 715 may be equidistant from each other, as illustrated in the example of Figure 8. The rows may be spaced a distance De, and the apertures 715 within each of the rows may be spaced a distance D7. For example, a distance Dr, of about 3 millimeters on center and a distance D7 of about 6 millimeters on center may be suitable for some embodiments. The apertures 715 in adjacent rows may be aligned or offset. For example, adjacent rows may be offset, as illustrated in Figure 8, so that the apertures 715 are aligned in alternating rows separated by a distance Z¾. A distance Z¾ of about 6 millimeters may be suitable for some examples. The size and/or spacing of the apertures 715 may vary in some embodiments to increase the density of the apertures 715 according to therapeutic requirements. [0095] Figure 9 is a schematic view of another example of the first layer 205, illustrating additional details that may be associated with some embodiments. As illustrated in the example of Figure 9, in some embodiments, the first layer 205 may include standoffs 905, which can be distributed uniformly or randomly across the first layer 205. The standoffs 905 may include any raised feature. For example, the standoffs 905 may comprise or consist essentially of embossments, projections, ribs, and ridges. A standoff 905 may include any feature on the first layer 205 that may be configured to enhance pressure manifolding, fluid manifolding, and/or direct instillation fluid. The standoffs 905 may be formed, for example, by heat, embossing, micro embossing, stamping, casting, or by other suitable techniques for forming a standoff. The standoffs 905 may have a uniform distribution pattern, or may be randomly distributed on the first layer 205. The standoffs 905 in the first layer 205 may have many shapes, including circles, squares, stars, ovals, polygons, complex curves, rectilinear shapes, triangles, for example, or may have some combination of such shapes. [0096] Each of the standoffs 905 may have uniform or similar geometric properties. For example, in some embodiments, each of the standoffs 905 may be circular, having substantially the same diameter. In some embodiments, the diameter of each of the standoffs 905 may be in a range of about 0.5 millimeters to about 5 millimeters. In other embodiments, the diameter of each of the standoffs 905 may be about 0.8 millimeters. In some embodiments, the diameter of the standoffs 905 may be less than 0.8 millimeters. In some embodiments, the standoffs 905 may have an area in a range of about 0.2 mm² to about 20 mm². In some embodiments, the standoffs 905 may have an area of about 0.5 mm². In some embodiments, the standoffs 905 may have an area less than 0.5 mm².

[0097] In other embodiments, geometric properties of the standoffs 905 may vary. For example, the diameter of the standoffs 905 may vary depending on the position of the standoffs 905 in the first layer 205. The standoffs 905 may be spaced substantially equidistant over the first layer 205. Alternatively, the spacing of the standoffs 905 may be irregular.

[0098] In the example of Figure 9, the standoffs 905 are generally circular and have a width W . which may be about 0.8 millimeters in some examples. Figure 9 also illustrates an example of a uniform distribution pattern of the standoffs 905. In Figure 9, the standoffs 905 are distributed across the first layer 205 in a grid of parallel rows and columns. Within each row and column, the standoffs 905 may be equidistant from each other, as illustrated in the example of Figure 9. The rows may be spaced a distance Dg, and the standoffs 905 within each of the rows may be spaced a distance Dm. For example, a distance Dg of about 2 millimeters on center and a distance Dm of about 4 millimeters on center may be suitable for some embodiments. The standoffs 905 in adjacent rows may be aligned or offset. For example, adjacent rows may be offset, as illustrated in Figure 9, so that the standoffs 905 are aligned in alternating rows separated by a distance Du. A distance Dn of about 4 millimeters may be suitable for some examples. The size and/or spacing of the standoffs 905 may vary in some embodiments to increase the density of the standoffs 905 according to therapeutic requirements.

[0099] Figure 10 and Figure 11 are schematic side views other examples of the first layer 205, illustrating additional details that may be associated with some embodiments. As illustrated in the example of Figure 10, the standoffs 905 may be hemispherical projections extending from a base portion 1005 of the first layer 205. The base portion 1005 is the portion of the first layer 205 that does not have a standoff 905. As illustrated in the example of Figure 11, the standoffs 905 may be projections having a flat top. In each of Figure 10 and Figure 11, the base portion 1005 of the first layer 205 may have a first thickness ^'A and the standoffs 905 may have a second thickness A. In some embodiments, the second thickness A may be about 50% of the first thickness A. In some embodiments, the second thickness A may range from about 10% to about 70% of the first thickness A. In some embodiments, the standoffs 905 may all extend the same direction. In other embodiments, some of the standoffs 905 may extend in first direction and some of the standoffs 905 may extend in a second direction opposite the first direction. In some embodiments, the first layer 205 may include standoffs 905 and perforations 215 distributed across the first layer 205.

[00100] Figure 12 is an assembly view of an example of the tissue interface 120 of Figure 1, illustrating additional details that may be associated with some embodiments in which the first layer 205 is integrally formed with the second layer 210. The second layer 210 may comprise a felted foam on which the first layer 205 is formed. The first layer 205 may be formed on the second layer 210 by any known method, which may include applying heat to the second layer 210, exposing the second layer 210 to flames, or by applying a chemical to the second layer 210. For example, in some embodiments, the first layer 205 may be integrally formed with the second layer 210 by a flame-forming process. An apparatus for use in flame forming may include one or more rows of nozzles configured to form a flat flame. The nozzles may be placed above a conveyor system on which the felted foam of the second layer 210 may pass. The one or more rows of nozzles may extend across the width of the conveyor system such that the full width of the second layer 210 may be exposed to the flat flames of the nozzles. In some embodiments, the one or more rows of nozzles may extend a width of about 2 meters. The second layer 210 may be placed on the conveyer system and passed under the one or more rows of nozzles so that the top side of the second layer 210 may be exposed to the flames from the one or more rows of nozzles for a desired period of times (e.g., about 1 to about 5 seconds) to soften the top side of the second layer 210. In some embodiments, the second layer 210 may be passed under a roller or a platen press to consolidate the softened top side of the second layer 210. In some embodiments, the top side of the second layer 210 may be heated in a range of about 150 to about 350 degrees Celsius. The top side of the second layer 210 may then be cooled using air jets. In another example, the first layer 205 may be formed by a heat forming process, wherein hot rollers or press platens may be used in place of the flames. The rollers or press platens may be heated in a range of about 150 to about 350 degrees Celsius. The top side of the second layer 210 may then be heated by the hot rollers or the press platens. The consolidation and cooling steps may then take place.

[00101] The heat or flame forming process integrally forms the first layer 205 on the second layer 210. The first layer 205 may be a porous film . The porosity of the first layer 205 may decrease as the heating temperature, the heating time, the consolidation time, and the applied pressure increase. In some embodiments, the first layer 205 may have a thickness % in a range of about 1 to about 20 microns. In some embodiments, the first layer may comprise an open-cell foam having a free volume in a range of about 2% to about 9%, a density of about 13.0 to about 80.0 lb/ft³, about 400 to about 2500 pores per inch on average (e.g., as measured in the direction of compression), and/or average pore size of about 8 to about 60 microns (e.g., as measured in the direction of compression). In some embodiments, the density of the foam of the first layer 205 may be about 26.0 to about 80.0 lb/ft³. In some embodiments, the free volume of the foam may be in a range of about 2% to about 5%. In some embodiments, the average pore size of the first layer 205 may be about 8 to about 20 microns. In some embodiments, the first layer 205 may have about 800 to about 2500 pores per inch on average. In some embodiments, a third layer identical or substantially similar to the first layer 205 may be heat or flame formed on the top side the second layer 210.

[00102] Figure 13 is an assembly view of another example of the tissue interface 120 of Figure 1, illustrating additional details that may be associated with some embodiments in which the tissue interface 120 may comprise additional layers. In the example of Figure 5, the tissue interface 120 comprises a third layer 1305, in addition to the first layer 205 and the second layer 210. In some embodiments, the third layer 1305 may be adjacent to the second layer 210 opposite the first layer 205. The third layer 1305 may also be bonded to the second layer 210 in some embodiments. In some embodiments the third layer 1305 may be the same as or substantially similar to the first layer 205.

[00103] Figure 14 is a schematic view of another example of the second layer 210, illustrating additional details that may be associated with some embodiments. As illustrated in the example of Figure 14, the second layer 210 may include apertures 1405. The apertures 1405 may be formed by cutting or by application of local RF or ultrasonic energy, for example, or by other suitable techniques for forming an opening. The apertures 1405 may have a uniform distribution pattern, or may be randomly distributed on the second layer 210. The apertures 1405 in the second layer 210 may have many shapes, including circles, squares, stars, ovals, polygons, slits, complex curves, rectilinear shapes, triangles, for example, or may have some combination of such shapes.

[00104] Each of the apertures 1405 may have uniform or similar geometric properties. For example, in some embodiments, each of the apertures 1405 may be circular apertures, having substantially the same diameter. In some embodiments, the diameter of each of the apertures 1405 may be between about 1 millimeter and about 50 millimeters. In other embodiments, the diameter of each of the apertures 1405 may be between about 1 millimeter and about 20 millimeters.

[00105] In other embodiments, geometric properties of the apertures 1405 may vary. For example, the diameter of the apertures 1405 may vary depending on the position of the apertures 1405 in the second layer 210. The apertures 1405 may be spaced substantially equidistant over the second layer 210. Alternatively, the spacing of the apertures 1405 may be irregular.

[00106] In some embodiments, the apertures 1405 illustrated in Figure 14 may be associated only with an interior portion of the second layer 210. In the example of Figure 14, the apertures 1405 are generally circular and have a widthW4, which may be about 5 millimeters in some examples. Figure 14 also illustrates an example of a uniform distribution pattern of the apertures 1405. In Figure 14, the apertures 1405 are distributed across the second layer 210 in a grid of parallel rows and columns. Within each row and column, the apertures 1405 may be equidistant from each other, as illustrated in the example of Figure 14. The rows may be spaced a distance Dn, and the apertures 1405 within each of the rows may be spaced a distance Du. For example, a distance Dn of about 5 millimeters on center and a distance Du of about 10 millimeters on center may be suitable for some embodiments. The apertures 1405 in adjacent rows may be aligned or offset. For example, adjacent rows may be offset, as illustrated in Figure 14, so that the apertures 1405 are aligned in alternating rows separated by a distance Du. A distance Du of about 10 millimeters may be suitable for some examples. The size and/or spacing of the apertures 1405 may vary in some embodiments to increase the density of the apertures 1405 according to therapeutic requirements. In some embodiments, the apertures 1405 may be distributed in a straight pattern. For example, the distance Dn may be zero. The apertures 1405 in the second layer 210 may provide increased flexibility and/or conformability to the second layer 210. Additionally, the apertures 1405 may assist with manifolding of negative pressure and the application and/or removal of fluid.

[00107] In some embodiments, one or more of the components of the dressing 110 may additionally be treated with an antimicrobial agent. For example, the second layer 210 may be a foam, mesh, or non- woven coated with an antimicrobial agent. In some embodiments, the second layer 210 may comprise antimicrobial elements, such as fibers coated with an antimicrobial agent. Additionally or alternatively, some embodiments of the first layer 205 may be a polymer coated or mixed with an antimicrobial agent. In other examples, a fluid conductor or other distribution components may additionally or alternatively be treated with one or more antimicrobial agents. Suitable antimicrobial agents may include, for example, metallic silver, PHMB, iodine or its complexes and mixes such as povidone iodine, copper metal compounds, chlorhexidine, or some combination of these materials. [00108] Additionally or alternatively, one or more of the components may be coated with a mixture that may include citric acid and collagen, which can reduce bio-films and infections. For example, the second layer 210 may be foam coated with such a mixture.

[00109] The first layer 205, the second layer 210, the third layer 1305, or various combinations may be assembled before application or in situ. For example, the first layer 205 may be laminated to the second layer 210. In some embodiments, one or more layers of the tissue interface 120 may coextensive. For example, the first layer 205 may be cut flush with the edge of the second layer 210, exposing the edge of the second layer 210. In other embodiments, the first layer 205 may overlap the edge of the second layer 210. In some embodiments, the cover 125 may be applied over the first layer 205 and the second layer 210 and may have a larger surface area than the first layer 205 and/or the second layer 210. [00110] Figure 15 is a schematic diagram of an example of the therapy system 100 applied to a tissue site. In the example of Figure 15, the tissue site comprises or consists essentially of a wound 1505, which may extend through or otherwise involve an epidermis 1510, a dermis 1515, and a subcutaneous tissue 1520. In some embodiments, the wound 1505 may extend below the surface of the epidermis 1510. A portion of the epidermis 1510 surrounding the wound 1505 may be considered a periwound 1525. The wound 1505 may also include an edge 1530 between the wound 1505 and the periwound 1525. In use, a release liner (if included) may be removed to expose the tissue interface 120. The geometry and dimensions of the tissue interface 120, the cover 125, or both may vary to suit a particular application or anatomy. For example, the dressing 110 may be cut to size for a specific region or anatomical area, such as for amputations. The dressing 110 may be cut without losing pieces of the tissue interface 120 and without separation of the tissue interface 120.

[00111] The tissue interface 120 can be placed within, over, on, or otherwise proximate to the tissue site. In the example of Figure 15, the first layer 205 forms an outer surface of the dressing 110, and can be placed over the tissue site, including the edge 1530 and epidermis 1510. The first layer 205 may be interposed between the second layer 210 and the tissue site, which can prevent direct contact between the second layer 210 and epidermis 1510.

[00112] As illustrated in the example of Figure 15, in some applications a filler 1535 may also be disposed between the tissue site and the first layer 205. For example, the filler 1535 may be applied in the wound 1505, interior to the edge 1530, and the first layer 205 may be disposed over the filler 1535. In some embodiments, the filler 1535 may be a manifold, such as open-cell foam. The filler 1535 may comprise or consist essentially of the same material as the second layer 210 in some embodiments.

[00113] In some examples, the dressing 110 may include one or more attachment devices. In some embodiments, one or more of the attachment devices may comprise or consist essentially of an adhesive 1540. In some examples the adhesive 1540 may be, for example, a medically-acceptable, pressure-sensitive adhesive that extends about a periphery, a portion, or an entire surface of the cover 125. In some embodiments, for example, the adhesive 1540 may be an acrylic adhesive having a coating weight between 25-65 grams per square meter (g.s.m.). Thicker adhesives, or combinations of adhesives, may be applied in some embodiments to improve the seal and reduce leaks. In some embodiments, such a layer of the adhesive 1540 may be continuous or discontinuous. Discontinuities in the adhesive 1540 may be provided by apertures or holes (not shown) in the adhesive 1540. The apertures or holes in the adhesive 1540 may be formed after application of the adhesive 1540 or by coating the adhesive 1540 in patterns on a carrier layer, such as, for example, the cover 125. Apertures or holes in the adhesive 1540 may also be sized to enhance the MVTR of the attachment devices in some example embodiments.

[00114] The adhesive 1540 can be disposed around edges of the cover 125, and the adhesive 1540 may be pressed onto the cover 125 and the epidermis 1510 (or other attachment surface) to fix the dressing 110 in position and to seal the exposed perimeter 400 of the second layer 210.

[00115] Figure 15 also illustrates one example of a fluid conductor 1545 and a dressing interface 1550. As shown in the example of Figure 15, the fluid conductor 1545 may be a flexible tube, which can be fluidly coupled on one end to the dressing interface 1550. The dressing interface 1550 may be an elbow connector, as shown in the example of Figure 15. In some examples, the tissue interface 120 can be applied to the tissue site before the cover 125 is applied over the tissue interface 120. The cover 125 may include an aperture 1555, or the aperture 1555 may be cut into the cover 125 before or after positioning the cover 125 over the tissue interface 120. The aperture 1555 of Figure 15 is centrally disposed. In other examples, the position of the aperture 1555 may be off-center or adjacent to an end or edge of the cover 125. The dressing interface 1550 can be placed over the aperture 1555 to provide a fluid path between the fluid conductor 1545 and the tissue interface 120. In other examples, the fluid conductor 1545 may be inserted directly through the cover 125 into the tissue interface 120.

[00116] If not already configured, the dressing interface 1550 may be disposed over the aperture 1555 and attached to the cover 125. The fluid conductor 1545 may be fluidly coupled to the dressing interface 1550 and to the negative-pressure source 105.

[00117] Negative pressure from the negative-pressure source 105 can be distributed through the fluid conductor 1545 and the dressing interface 1550 to the tissue interface 120. Negative pressure applied through the tissue interface 120 can also create a negative pressure differential across the perforations 215 in the first layer 205, which can open or expand the perforations 215. For example, in some embodiments in which the perforations 215 may comprise substantially closed fenestrations through the first layer 205, a pressure gradient across the fenestrations can strain the adjacent material of the first layer 205 and increase the dimensions of the fenestrations to allow liquid movement through them, similar to the operation of a duckbill valve. Opening the perforations can allow exudate and other liquid movement through the perforations into the second layer 210. The second layer 210 can provide passage of negative pressure and exudate, which can be collected in the container 115.

[00118] Changes in pressure can also cause the second layer 210 to expand and contract. The first layer 205 can protect the epidermis 1510 from irritation that could be caused by expansion, contraction, or other movement of the second layer 210. The first layer 205 can also substantially reduce or prevent exposure of a tissue site to the second layer 210, which can inhibit growth of tissue into the second layer 210. [00119] If the negative-pressure source 105 is removed or turned off, the pressure differential across the perforations 215 can dissipate, allowing the perforations 215 to close and prevent exudate or other liquid from returning to the tissue site through the first layer 205.

[00120] Additionally, or alternatively, instillation solution or other fluid may be distributed to the dressing 110, which can increase the pressure in the tissue interface 120. The increased pressure in the tissue interface 120 can create a positive pressure differential across the perforations 215 in the first layer 205, which can open the perforations 215 to allow the instillation solution or other fluid to be distributed to the tissue site.

[00121] Figure 16 is a schematic diagram of another example of the therapy system 100 applied to the wound 1505. In the example of Figure 16, the wound 1505 may be a deep wound that extends through the epidermis 1510, the dermis 1515, and the subcutaneous tissue 1520. The tissue interface 120 may be pushed into the wound 1505. For example, the tissue interface 120 may be worked into the wound 1505, including any deep recesses in the wound 1505. The tissue interface 120 may be readily deformed into the wound 1505 but may remain flat over the periwound 1525. The tissue interface 120 may also be placed into tunneled wounds. [00122] Following the application of the tissue interface 120 into the wound 1505, the filler 1535 may be placed into the wound 1505 above the tissue interface 120. The filler 1535 may be sized and/or shaped to fit the size and shape of the wound 1505 so that the filler 1535 can fill the wound 1505. In some embodiments, based on the size and shape of the wound 1505, filling the wound 1505 may be accomplished with more than one filler 1535. The first layer 205 may be interposed between the second layer 210 and the epidermis 1510, which can prevent direct contact between the second layer 210 and the periwound 1525, providing a barrier between the periwound 1525 and the second layer 210. [00123] The systems, apparatuses, and methods described herein may provide significant advantages. For example, in some embodiments of the tissue interface 120, the felted foam structure of the second layer 210 and the non-adherent first layer 205 may provide a highly flexible tissue interface layer that is non-adherent to granulation, yet promotes granulation formation through its ability to manifold. Additionally, the dressing 110 can be simple to apply, reducing the time to apply and remove. For example, in some embodiments of the dressing 110, the first layer 205 and the second layer 210 maybe used to overlap a periwound and may provide a barrier between the periwound and the filler 1535 (if used), which can significantly reduce or eliminate the need to size the filler 1535 for a wound. Additionally, the ability of the first layer 205 and the second layer 210 to be deformed to the contours of a deep wound may ensure good contact between the first layer 205 and the wound bed throughout the course of negative-pressure therapy. In some embodiments, the tissue interface 120 may be formed into shapes that can be placed in tunneled areas or around drainage tubes.

[00124] The benefits provided by the dressing 110 may include good manifolding, beneficial granulation, protection of the peripheral tissue from maceration, protection of the tissue site from shedding materials, and a low-trauma and high-seal bond. These characteristics may be particularly advantageous for surface wounds having moderate or high depth and medium -to-high levels of exudate. Some embodiments of the dressing 110 may remain on the tissue site for at least 5 days, and some embodiments may remain for at least 7 to 14 days. Antimicrobial agents in the dressing 110 may extend the usable life of the dressing 110 by reducing or eliminating infection risks that may be associated with extended use, particularly use with infected or highly exuding wounds. Additionally, upon removal of the dressing 110, the entire tissue interface 120 may be removed by pulling on the tissue interface 120, allowing a one-step removal of the dressing 110 without fear of removing or pulling on in-growth.

[00125] While shown in a few illustrative embodiments, a person having ordinary skill in the art will recognize that the systems, apparatuses, and methods described herein are susceptible to various changes and modifications that fall within the scope of the appended claims. Moreover, descriptions of various alternatives using terms such as “or” do not require mutual exclusivity unless clearly required by the context, and the indefinite articles “a” or “an” do not limit the subject to a single instance unless clearly required by the context. Components may be also be combined or eliminated in various configurations for purposes of sale, manufacture, assembly, or use. For example, in some configurations the dressing 110, the container 115, or both may be separated from other components for manufacture or sale. In other example configurations, the controller 130 may also be manufactured, configured, assembled, or sold independently of other components. [00126] The appended claims set forth novel and inventive aspects of the subject matter described above, but the claims may also encompass additional subject matter not specifically recited in detail. For example, certain features, elements, or aspects may be omitted from the claims if not necessary to distinguish the novel and inventive features from what is already known to a person having ordinary skill in the art. Features, elements, and aspects described in the context of some embodiments may also be omitted, combined, or replaced by alternative features serving the same, equivalent, or similar purpose without departing from the scope of the invention defined by the appended claims.

Claims

CLAIMS What is claimed is:

1. A dressing for treating a tissue site with negative pressure, the dressing comprising: a first layer comprising a polymer film having a plurality of perforations through the polymer film that are configured to expand in response to a pressure gradient across the polymer film; and a second layer coupled to the first layer, the second layer comprising open-cell foam having a density in a range of about 2.6 to about 16.0 lb/ft³.

2. The dressing of claim 1, wherein the second layer has a free volume in a range of about 9% to about 45%.

3. The dressing of any of claims 1-2, wherein the open-cell foam has about 80 to about 500 pores per inch.

4. The dressing of any of claims 1-3, wherein the open-cell foam has an average pore size of about 60-300 microns.

5. The dressing of any of claims 1-4, wherein the second layer has a thickness of 1 to 5 mm.

6. The dressing of any of claims 1-5, wherein the second layer has a thickness of 1 to 3 mm.

7. The dressing of any of claims 1-6, wherein the open-cell foam has a density of about 6.5 to about 8.0 lb/ft³.

8. The dressing of any of claims 1-7, wherein the open-cell foam has an average pore size of about 80 to about 120 microns.

9. The dressing of any of claims 1-8, wherein the open-cell foam has about 200 to about 250 pores per inch on average.

10. The dressing of any of claims 1-9, wherein the open-cell foam has a free volume in a range of about 18%.

11. The dressing of any of claims 1-9, wherein the open-cell foam has a 25% compression load deflection of at least 1.05 pounds per square inch and a 65% compression load deflection of at least 1.29 pounds per square inch.

12. The dressing of any of claims 1-9, wherein the open-cell foam has a 25% compression load deflection of at least 1.75 pounds per square inch and a 65% compression load deflection of at least 2.15 pounds per square inch.

13. The dressing of any of claims 1-9, wherein the open-cell foam has a 25% compression load deflection in a range of about 1.05-3.50 pounds per square inch and a 65% compression load deflection in a range of about 1.29-4.30 pounds per square inch.

14. The dressing of any of claims 1-13, wherein the open-cell foam comprises felted foam with a firmness factor of 2-10.

15. The dressing of any of claims 1-13, wherein the open-cell foam comprises felted foam with a firmness factor of 3-10.

16. The dressing of any of claims 1-13, wherein the open-cell foam comprises felted foam with a firmness factor of about 5.

17. The dressing of any of claims 1-15, wherein the open-cell foam has a plurality of perforations through the open-cell foam.

18. The dressing of any of claims 1-17, wherein the polymer film of the first layer comprises polyurethane.

19. The dressing of any of claims 1-18, wherein the first layer has a plurality of standoffs.

20. The dressing of claim 19, wherein the plurality of standoffs are configured to enhance pressure and/or fluid manifolding.

21. The dressing of any of claims 18-20, wherein the plurality of standoffs are configured to direct instillation fluid.

22. The dressing of any of claims 1-15, further comprising: a third layer coupled to the second layer opposite the first layer, the third layer comprising a polymer film having a plurality of perforations through the polymer film that are configured to expand in response to a pressure gradient across the polymer film.

23. The dressing of any of claims 1-22, further comprising a filler manifold configured to be proximate the second layer.

24. The dressing of any of claims 1-23, further comprising a cover configured to be disposed over the second layer.

25. A dressing for treating a tissue site with negative pressure, the dressing comprising: a manifold comprising open-cell foam having about 80 to about 500 pores per inch; and a contact layer coupled to the manifold.

26. The dressing of claim 25, wherein the contact layer comprises a polymer fdm having a plurality of perforations through the polymer fdm that are configured to expand in response to a pressure gradient across the polymer film.

27. The dressing of claim 25, wherein the contact layer comprises a plurality of polymer film sections.

28. The dressing of claim 27, wherein the polymer film sections are discontinuous.

29. The dressing of any of claims 27-28, wherein the polymer film sections comprise dots.

30. The dressing of claim 25, wherein the contact layer comprises an open-cell foam having a thickness in a range of about 1 to about 20 microns.

31. The dressing of claim 30, wherein the open-cell foam of the contact layer has a density in a range of about 13 to about 80 lb/ft³.

32. The dressing of any of claims 30-31, wherein the open-cell foam of the contact layer has a pore size in a range of about 12 to about 60 microns.

33. The dressing of any of claims 30-32, wherein the open-cell foam of the contact layer has a free volume in a range of about 2% to about 9%.

34. The dressing of any of claims 30-33, wherein the open-cell foam of the contact layer has about 400 to about 2500 pores per inch.

35. The dressing of any of claims 25-34, wherein the open-cell foam of the manifold has a pore size in a range of about 80 to about 300 microns.

36. The dressing of any of claims 25-35, wherein the open-cell foam of the manifold has a density in a range of about 2.6 to about 16.0 lb/ft³.

37. The dressing of any of claims 25-36, wherein the open-cell foam of the manifold has a free volume in a range of about 9% to about 45%.

38. A method of applying negative pressure to a tissue site, the method comprising: providing a tissue interface comprising a first layer and a second layer, the first layer comprising a contact layer and the second layer comprising an open-cell foam having a density in a range of about 2.6 to about 16.0 lb/ft³; disposing the first layer of the tissue interface in proximity to the tissue site; providing a cover over the tissue interface to form a sealed space containing the tissue interface; fluidly coupling a negative-pressure source to the tissue interface; and applying negative pressure to the tissue interface.

39. The method of claim 38, wherein the first layer comprises a polymer film having a plurality of perforations through the polymer film that are configured to expand in response to a pressure gradient across the polymer film.

40. The method of any of claims 38-39, wherein the first layer comprises a plurality of polymer film sections.

41. The method of claim 40, wherein the polymer film sections are discontinuous.

42. The method of any of claims 40-41, wherein the polymer film sections comprise dots.

43. The method of claim 38, wherein the first layer comprises an open-cell foam having a thickness in a range of about 1 to about 20 microns.

44. The method of claim 43, wherein the open-cell foam of the first layer has a density in a range of about 13 to about 80 lb/ft³.

45. The method of any of claims 43-44, wherein the open-cell foam of the first layer has a pore size in a range of about 8 to about 60 microns.

46. The method of any of claims 43-45, wherein the open-cell foam of the first layer has a free volume in a range of about 2% to about 9%.

47. The method of any of claims 43-46, wherein the open-cell foam of the first layer has about 400 to about 2500 pores per inch.

48. The method of any of claims 38-47, wherein the open-cell foam of the second layer has a pore size in a range of about 80 to about 300 microns.

49. The method of any of claims 38-48, wherein the open-cell foam of the second layer has about 80 to about 250 pores per inch.

50. The method of any of claims 38-49, wherein the open-cell foam of the second layer has and a free volume in a range of about 9% to about 45%.

51. The systems, apparatuses, and methods substantially as described herein.