Patent Publication Number: US-2019175416-A1

Title: Multi-Layer Dressings, Systems, And Methods For Applying Reduced Pressure At A Tissue Site

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. Non-Provisional application Ser. No. 13/849,103, filed 22 Mar. 2013, which is a continuation of U.S. Non-Provisional application Ser. No. 12/560,777, filed 16 Sep. 2009, now U.S. Pat. No. 8,425,478, which claims the benefit, under 35 U.S.C § 119(e), of the filing of U.S. Provisional Patent Application Ser. No. 61/098,000, entitled “Multi-Layer Dressing, System, and Method For Applying Reduced Pressure at a Tissue Site,” filed 18 Sep. 2008, and U.S. Provisional Patent Application Ser. No. 61/098,015, entitled “Laminar Dressing, System, and Method For Applying Reduced Pressure at a Tissue Site,” filed 18 Sep. 2008. These applications are incorporated herein by reference for all purposes. 
    
    
     BACKGROUND 
     Clinical studies and practice have shown that providing a reduced pressure in proximity to a tissue site augments and accelerates the growth of new tissue at the tissue site. The applications of this phenomenon are numerous, but application of reduced pressure has been particularly successful in treating wounds. This treatment (frequently referred to in the medical community as “negative pressure wound therapy,” “reduced pressure therapy,” or “vacuum therapy”) provides a number of benefits, including faster healing, and increased formulation of granulation tissue. 
     Reduced-pressure treatment systems are often applied to large, highly exudating wounds present on patients undergoing acute or chronic care, as well as other severe wounds that are not readily susceptible to healing without application of reduced pressure. Low-severity wounds that are smaller in volume and produce less exudate have generally been treated using advanced dressings instead of reduced-pressure treatment. 
     BRIEF SUMMARY 
     Shortcomings with certain aspects of wound care systems and dressings are addressed by the present disclosure as shown and described in a variety of illustrative, non-limiting embodiments herein. According to an illustrative embodiment, a dressing for applying reduced pressure at a tissue site includes a dressing material for transferring the reduced pressure to the tissue site and for receiving liquid from the tissue site. The dressing material includes a tissue-interface layer for contacting the tissue site, the tissue-interface layer being a hydrophobic layer; a manifold for distributing reduced pressure, the manifold being a hydrophobic layer; and a first absorbent layer for absorbing liquid from the tissue site via the tissue-interface layer and the manifold. The manifold may be disposed between the tissue-interface layer and the first absorbent layer. The dressing may further include a drape covering at least a portion of the dressing material. 
     According to another illustrative, non-limiting embodiment, a system for applying a reduced pressure at a tissue site includes a reduced-pressure source for supplying reduced pressure, a reduced-pressure delivery conduit for transferring reduced pressure, a dressing material, and a drape covering at least a portion of the dressing material. The dressing material is in fluid communication with the reduced-pressure source via the reduced-pressure delivery conduit. The dressing material delivers reduced pressure to the tissue site and receives liquid from the tissue site. The dressing material includes a tissue-interface layer adapted to contact the tissue site, which is a hydrophobic layer; a manifold, which is a hydrophobic layer, for distributing reduced pressure; and a first absorbent layer for absorbing liquid from the tissue site via the tissue-interface layer and the manifold. The manifold may be disposed between the tissue-interface layer and the first absorbent layer. 
     According to another illustrative, non-limiting embodiment, a method for applying reduced pressure at a tissue site includes the steps of applying a dressing material to the tissue site, covering at least a portion of the dressing material with a drape, and supplying reduced pressure to the dressing material. The dressing material transfers reduced pressure to the tissue site and receives liquid from the tissue site. The dressing material includes a tissue-interface layer, which is a hydrophobic layer, for contacting the tissue site; a manifold, which is a hydrophobic layer, for distributing reduced pressure; and a first absorbent layer for absorbing liquid from the tissue site via the tissue-interface layer and the manifold. The manifold is disposed between the tissue-interface layer and the first absorbent layer. 
     According to another illustrative, non-limiting embodiment, a method of manufacturing a dressing for applying a reduced pressure at a tissue site includes the steps of providing a tissue-interface layer, which is a hydrophobic layer; providing a manifold having a tissue-facing side; coupling at least a portion of the tissue-facing side of the manifold to the tissue-interface layer; and providing a first absorbent layer having a tissue-facing side and that absorbs liquid. The manifold is a hydrophobic layer that distributes reduced pressure. The method of manufacturing may further include the steps of coupling at least a portion of the tissue-facing side of the first absorbent layer to the manifold. The method may also include providing a second absorbent layer having a tissue-facing side. The second absorbent layer includes a hydrophilic layer for absorbing liquid from the tissue site via the tissue-interface layer, the manifold, and the first absorbent layer. The method may also include coupling at least a portion of the tissue-facing side of the second absorbent layer to the first absorbent layer. 
     According to still another illustrative, non-limiting embodiment, a reduced-pressure wound dressing includes a non-adherent hydrophobic layer having a first side and a second, tissue-facing side; a porous, hydrophobic manifold layer, having a first side and a second, tissue-facing side; a quick-absorbing hydrophilic layer having a first side and a second, tissue-facing side; a fluid-storage layer having a first side and a second, tissue-facing side; and a sealing member having a first side and a second, tissue-facing side. The second, tissue-facing side of the porous, hydrophobic manifold layer is adjacent to the first side of the non-adherent hydrophobic layer. The second, tissue-facing side of the quick-absorbing hydrophilic layer is adjacent to the first side of the porous, hydrophobic manifold layer. The second, tissue-facing side of the fluid-storage layer is adjacent to the first side of the quick-absorbing hydrophilic layer. The second, tissue-facing side of the sealing member is adjacent to the first side of the fluid-storage layer. 
     In yet another embodiment, provided is a dressing for treating a tissue site including a manifold, a first layer, and a second layer. The manifold is adapted to be positioned at the tissue site, the manifold being fluid permeable and substantially hydrophobic. The first layer is adapted to receive fluid communicated from the tissue site through the manifold, the manifold adapted to be disposed between the tissue site and the first layer. The second layer is positioned proximate the first layer, the first layer adapted to be disposed between the manifold and the second layer, wherein the second layer is more hydrophilic than the first layer so that the second layer may pull fluid from the first layer. 
     In yet another embodiment, provided is a system for treating a tissue site with reduced pressure including a dressing adapted to deliver reduced pressure to the tissue site and to receive fluid from the tissue site. The dressing includes a first layer, a second layer, a third layer, and a fourth layer. The first layer is adapted to be positioned in contact with the tissue site, the first layer being a hydrophobic layer. The second layer is adapted to be positioned proximate the first layer and to distribute reduced pressure to the tissue site, the first layer adapted to be positioned between the tissue site and the second layer. The third layer is adapted to receive fluid communicated from the tissue site through the first layer and the second layer, the second layer disposed between the first layer and the third layer. The fourth layer is positioned proximate to the third layer, the fourth layer being more hydrophilic than the third layer so that the fourth layer may pull fluid from the third layer. 
     In yet another embodiment, provided is a dressing for treating a tissue site including a tissue-interface layer, a first layer, and a second layer. The tissue-interface layer is adapted to be positioned in contact with the tissue site. The first layer is positioned proximate the tissue-interface layer. The second layer is positioned proximate the first layer, the first layer disposed between the tissue-interface layer and the second layer, wherein the second layer is more hydrophilic than the first layer so that the second layer may pull fluid from the first layer and the tissue site. 
     In yet another embodiment, provided is a dressing adapted to receive fluid from a tissue site, the dressing material having a thickness, wherein the dressing is increasingly hydrophilic with increasing distance through the thickness of the dressing. 
     Other features and advantages of the illustrative embodiments will become apparent with reference to the drawings and detailed description that follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram, with a portion in cross section, of an illustrative, non-limiting embodiment of a system for applying reduced pressure at a tissue site; 
         FIG. 2  is an exploded, perspective view of an illustrative, non-limiting embodiment of a dressing for applying reduced pressure at a tissue site; and 
         FIG. 3  is a schematic, cross-sectional view of the dressing of  FIG. 2  deployed for use in applying reduced pressure at a tissue site. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings, forming a part hereof, that depict illustrative embodiments of practicing the subject matter of the present disclosure. These embodiments are sufficiently described to enable those skilled in the art to practice the disclosed subject matter. Other embodiments may be utilized and logical, structural, mechanical, electrical, and chemical changes may be made without departing from the scope of this disclosure. To avoid detail not necessary to enable those skilled in the art to practice the disclosed subject matter, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense, the scope of the present disclosure being defined only by the appended claims. 
     Referring now primarily to  FIG. 1 , an illustrative reduced-pressure treatment system  100 , which includes a dressing  102  and which applies reduced pressure to a tissue site  104 , is presented. The dressing  102  includes a dressing material  106 . The dressing material  106  may include any number of layers or components and a number of illustrative, non-limiting examples will be provided herein. Unless otherwise indicated, as used herein, “or” does not require mutual exclusivity. The dressing material  106  may include one or more laminar layers. The dressing  102  may further include a sealing member  108  and a reduced-pressure connector  110 , reduced-pressure interface, or connection member. 
     The dressing material  106  serves as a manifold for distributing reduced pressure. The term “manifold” as used herein generally refers to a substance or structure that is provided to assist in applying reduced pressure to, delivering fluids to, or removing fluids from a tissue site. The manifold typically includes a plurality of flow channels or pathways to improve distribution of fluids provided to and removed from the tissue site. The dressing material  106  that serves as a manifold may include a number of layers as will be described further below. 
     The tissue site  104  may be the bodily tissue of any human, animal, or other organism, including bone tissue, adipose tissue, muscle tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, ligaments, or any other tissue. While the tissue site  104  may include a wound, diseased tissue, or defective tissue, the tissue site  104  may also be healthy tissue that is not wounded, diseased, or defective. 
     The application of reduced pressure to the tissue site  104  may be used to promote the drainage of exudate and other liquids from the tissue site  104 , as well as to stimulate the growth of additional tissue. In the case in which the tissue site  104  is a wound site, the growth of granulation tissue and removal of exudates and bacteria promotes healing of the wound. The application of reduced pressure to non-wounded or non-defective tissue, including healthy tissue, may be used to promote the growth of tissue that may be harvested and transplanted to another tissue location. 
     As used herein, “reduced pressure” generally refers to a pressure less than the ambient pressure at a tissue site  104  that is being subjected to treatment. In most cases, this reduced pressure will be less than the atmospheric pressure at which the patient is located. Alternatively, the reduced pressure may be less than a hydrostatic pressure at the tissue site  104 . Unless otherwise indicated, values of pressure stated herein are gauge pressures. The reduced pressure delivered may be static or varied (patterned or random) and may be delivered continuously or intermittently. Although the terms “vacuum” and “negative pressure” may be used to describe the pressure applied to the tissue site, the actual pressure applied to the tissue site may be more than the pressure normally associated with a complete vacuum. Consistent with the use herein, an increase in reduced pressure or vacuum pressure typically refers to a relative reduction in absolute pressure. 
     The reduced pressure is provided to the reduced-pressure connector  110  by a reduced-pressure delivery conduit  112 . The reduced-pressure delivery conduit  112  receives reduced pressure from a reduced-pressure source  114 . The reduced-pressure source  114  may be any device or subsystem for supplying a reduced pressure, including but not limited to a manually operated pump, a powered vacuum pump, a wall vacuum source, etc. While the amount and nature of reduced pressure applied to a tissue site will typically vary according to the application, the reduced pressure will typically be between −5 mm Hg and −500 mm Hg and more typically between −100 mm Hg and −200 mm Hg. In one illustrative embodiment, the reduced-pressure source  114  may be a battery-driven vacuum pump. In one illustrative example, the pump uses low amounts of power and is capable of operating for an extended period of time on a single charge of the battery. 
     One or more devices may be fluidly coupled between the reduced-pressure connector  110  and the reduced-pressure source  114 . For example, representative device  116  is shown fluidly coupled on a portion of the reduced-pressure delivery conduit  112 . The representative device  116  may be a fluid reservoir, or collection member, to hold exudates and other fluids removed. Other illustrative, non-limiting examples of devices  116  that may be included on the reduced-pressure delivery conduit  112  or otherwise fluidly coupled to the reduced-pressure delivery conduit  112  include the following non-limiting examples: a pressure-feedback device, a volume detection system, a blood detection system, an infection detection system, a flow monitoring system, a temperature monitoring system, etc. Some of these devices may be formed integrally to the reduced-pressure source  114  or other aspects of the system  100 . 
     The dressing  102  is adapted to contact or cover the tissue site  104  that is to be treated. As used herein, the term “cover” includes partially or fully covering. Also, a first object that covers a second object may directly or indirectly touch the second object, or may not touch the second object at all. 
     The dressing material  106  is covered fully or partially by the sealing member  108 , or drape. The sealing member  108  may be any material that provides a fluid seal over the dressing material  106  and a portion of a patient&#39;s epidermis  118 . The sealing member  108  may, for example, be an impermeable or semi-permeable, elastomeric material. “Elastomeric” means having the properties of an elastomer, such as a polymeric material that has rubber-like properties. More specifically, most elastomers have elongation rates greater than 100% and a significant amount of resilience. The resilience of a material refers to the material&#39;s ability to recover from an elastic deformation. Examples of elastomers may include, but are not limited to, natural rubbers, polyisoprene, styrene butadiene rubber, chloroprene rubber, polybutadiene, nitrile rubber, butyl rubber, ethylene propylene rubber, ethylene propylene diene monomer, chlorosulfonated polyethylene, polysulfide rubber, polyurethane, EVA film, co-polyester, and silicones. Specific examples of sealing member materials include a silicone drape, 3M Tegaderm® drape, acrylic drape such as one available from Avery Dennison, or an incise drape. 
     The sealing member  108  may be provided in “sheet” form, or in a pourable or sprayable form that is applied over the dressing material  106  after placement of the dressing material  106  in contact with the tissue site  104 . Ins some embodiments, sealing member  108  may include a device that is placed over the dressing material  106  and the tissue site  104  to provide sealing functionality, including but not limited to, a suction cup, a molded cast, and a bell jar. The sealing member  108  has a first side  120  and a second, tissue-facing side  122 . 
     An attachment device  124  may be used to hold the sealing member  108  against the patient&#39;s epidermis  118  or another layer, such as a gasket or additional sealing member. The attachment device  124  may take numerous forms. For example, the attachment device  124  may be a medically acceptable, pressure-sensitive adhesive  126  that extends about a periphery, or perimeter  128 , of the sealing member  108 . 
     In one embodiment, the sealing member  108  is configured to provide a sealed connection with the patient&#39;s epidermis  118  (or other tissue surrounding the dressing material  106 ) and the tissue site  104 . The sealed connection may be provided by the adhesive  126  positioned along the perimeter  128  of the sealing member  108 , or on any portion of the sealing member  108 , to secure the sealing member  108  to the dressing material  106  or the tissue surrounding the tissue site  104 . The adhesive  126  may be pre-positioned on the sealing member  108  or may be sprayed or otherwise applied to the sealing member  108  immediately prior to installing the sealing member  108 . Prior to the application of the sealing member  108  to the tissue site  104 , the adhesive  126  may also be covered by an adhesive support layer or removable backing. The adhesive support layer may provide rigidity to the sealing member  108  prior to application and may also aid in the actual application of the sealing member  108  onto the tissue site  104  or tissue near the tissue site  104 . The adhesive support layer may be peeled off or otherwise removed before applying the sealing member  108 . 
     The reduced-pressure connector  110  is coupled to the sealing member  108  and provides reduced pressure to an interior space  130  formed between the second, tissue-facing side  122  of the sealing member  108  and the tissue site  104 . In another embodiment, the reduced-pressure delivery conduit  112  may directly couple the reduced-pressure source  114  to the dressing  102 . 
     The reduced-pressure delivery conduit  112  may be any tube or flow path through which a gas, liquid, gel, or other fluid may flow. The possible embodiments of the reduced-pressure delivery conduit  112  are numerous, and non-limiting examples follow. The reduced-pressure delivery conduit  112  may have any cross-sectional shape, such as a circle, oval, or polygon. In addition, the reduced-pressure delivery conduit  112  may be made from any material, and may be either flexible or inflexible. In  FIG. 1 , the reduced-pressure delivery conduit  112  couples the reduced-pressure connector  110  to the representative device  116 , and couples the representative device  116  to the reduced-pressure source  114 . However, reduced-pressure delivery conduit  112  may directly couple reduced-pressure source  114  to the dressing  102 . Also, the reduced-pressure delivery conduit  112  may include one or more paths or lumens through which fluid may flow. For example, the reduced-pressure delivery conduit  112  may include two lumens with one lumen used to administer pressure measurements to determine the amount of reduced pressure being applied at the tissue site  104 . The other lumen may be used to deliver fluids, such as air, antibacterial agents, antiviral agents, cell-growth promotion agents, irrigation fluids, or other chemically active agents, to the tissue site  104 . The fluid source from which these fluids originate is not shown in  FIG. 1 . 
     The reduced-pressure connector  110  permits the passage of a fluid (such as exudates, air, etc.) from the dressing material  106  to reduced-pressure delivery conduit  112 , and vice versa. In another illustrative embodiment (not shown), the reduced-pressure treatment system  100  does not include the reduced-pressure connector  110 . In this illustrative embodiment, the reduced-pressure delivery conduit  112  may be inserted directly into the sealing member  108  or the dressing material  106  such that an end of the reduced-pressure delivery conduit  112  is adjacent to or in contact with the sealing member  108  or any of the dressing material  106  in a manner that allows for the delivery of reduced pressure. In the non-limiting example shown in  FIG. 1 , the sealing member  108  includes an aperture  111  through which the reduced-pressure connector  110  is disposed. 
     The reduced-pressure connector  110  may be located anywhere relative to the dressing material  106 . For example, although  FIG. 1  shows the reduced-pressure connector  110  and the opening or aperture  111  in the sealing member  108  through which the reduced-pressure connector  110  extends as centrally located relative to the dressing material  106 , the reduced-pressure connector  110  and the opening or aperture  111  may be located adjacent to the edges of the dressing material  106  or at other locations. 
     In operation, the dressing  102  is deployed on the tissue site  104  and reduced pressure is delivered to the tissue site  104 . More specifically, the dressing material  106  is deployed proximate the tissue site  104  where treatment is desired. The sealing member  108  is deployed over the dressing material  106  and at least a portion of the patient&#39;s epidermis  118  to form the interior space  130 , or sealed space. If not already accomplished, the aperture  111  may be formed in the sealing member  108  and the reduced-pressure connector  110  applied. If not already accomplished, the reduced-pressure delivery conduit  112  is fluidly coupled to the reduced-pressure connector  110  and to the reduced-pressure source  114 . The reduced-pressure source  114  is activated and reduced pressure is delivered to the tissue site  104 . 
     Referring now primarily to  FIG. 2 , an exploded view of an illustrative dressing  200 , which is suitable for use as dressing  102  in  FIG. 1 , is presented. The dressing  200  includes a dressing material  202 , a sealing member  204  covering the dressing material  202 , and a reduced-pressure connector  206 . The reduced-pressure connector  206  may be disposed in part between the dressing material  202  and the sealing member  204 . The dressing material  202  may be used to manifold, or distribute, pressure to a tissue site  207 , e.g., a wound. The sealing member  204  provides a seal over the dressing material  202  and a portion of a patient&#39;s epidermis  209 . The sealing member  204  has a first side  208  and a second, tissue-facing side  210 . The sealing member  204  may also be formed with an aperture  212 . 
     The dressing material  202  includes a number of components, e.g., layers or portions of material. First, a tissue-interface layer  214  has a first side  216  and a second, tissue-facing side  218 . The tissue-interface layer  214  is adapted to contact the tissue site  207 . In an example in which the dressing  200  is used to treat a wound, the tissue-interface layer  214  may be partially or fully in contact with the tissue site  207 . The tissue site  207  may directly contact any portion of the second, tissue-facing side  218  of the tissue-interface layer  214 , including the center or peripheral portions of the tissue-interface layer  214 . The second, tissue-facing side  218  of the tissue-interface layer  214  may also directly contact a periwound area of the tissue site  207 , which may include healthy tissue that surrounds the tissue site  207 . In the illustrative embodiments, the tissue-interface layer  214 , either alone or when used in conjunction with other layers, may reduce or eliminate maceration at or near the tissue site  207 , including the periwound area and healthy epidermis  209  that surrounds the tissue site  207 . 
     In an illustrative embodiment, the tissue-interface layer  214  is a hydrophobic layer. The hydrophobic characteristics of the tissue-interface layer  214  prevent the tissue-interface layer  214  from directly absorbing liquid, such as exudate, from the tissue site  207 , but allow the liquid to pass through. Thus, the liquid may be drawn away from the tissue site  207  via the tissue-interface layer  214  using a reduced-pressure source, such as the reduced-pressure source  114  in  FIG. 1 , or may be absorbed by one or more other layers in the dressing material  202 . Thus, the tissue-interface layer  214  permits the passage of liquid away from the tissue site  104 , while maintaining contact with the tissue site  207 . 
     Because the tissue-interface layer  214  does not absorb (or hold) liquid, the tissue site  207  is not exposed, or otherwise in contact, with any hydrophilic material that is substantially saturated with liquid and that could promote maceration. Also, no capillary action takes place in a direction along the surface of the tissue site  207 . Thus, the hydrophobic characteristics of the tissue-interface layer  214  may also restrain or prevent the spread of liquid along an interface between the tissue site  207  and the second, tissue-facing side  218  of the tissue-interface layer  214 . 
     The tissue-interface layer  214  may be composed of any of a variety of materials, and have a variety of structures, including materials and structures that allow fluid, e.g., liquid or gas, to pass through the tissue-interface layer  214 . In one example, the tissue-interface layer  214  may be composed of or include nylon. In another example, the tissue-interface layer  214  may be composed of or include a polymer-based mesh fabric. In another example, the tissue-interface layer  214  may be composed of or include Teflon®-impregnated polyethylene. The tissue-interface layer  214  may also be composed of or include spandex or Elastane® material. The tissue-interface layer  214  may be a thin, non-adherent, hydrophobic, non-stitch layer. The tissue-interface layer  214  may function, typically under reduced-pressure, to quickly transport moisture from the tissue site  207 . The tissue-interface layer  214  may be non-absorbent in nature. 
     The tissue-interface layer  214  may also exhibit non-adherent properties such that the tissue-interface layer  214  does not stick to or adhere to the tissue site  207 . The tissue-interface layer  214  may also be stretchable, or elastic, in nature. The stretchable properties of the tissue-interface layer  214  may facilitate placement of the tissue-interface layer  214  adjacent to tissue sites and wounds having a variety of shapes, topologies, or flexibility requirements. 
     The tissue-interface layer  214  may be used to promote granulation at the tissue site  207  when reduced pressure is applied through the dressing  200 . For example, any or all of the surfaces of the tissue-interface layer  214  may have an uneven, coarse, or jagged profile that causes microstrains and stresses at the tissue site  207  when a pressure is applied. Thus, the reduced pressure supplied may cause the tissue-interface layer  214  to create microstrain and thereby encourage granulation. The tissue-interface layer  214  may further serve as a scaffold for new cell-growth, or a scaffold material may be used in conjunction with the tissue-interface layer  214  to promote cell-growth. A scaffold is a substance or structure used to enhance or promote the growth of cells or formation of tissue, such as a three-dimensional porous structure that provides a template for cell growth. 
     The tissue-interface layer  214  may have any size, shape, or thickness depending on a variety of factors, such as the type of treatment being implemented or the nature of the tissue site  207 . The size and shape of the tissue-interface layer  214  may be customized by a user to cover a particular portion of the tissue site  207  or nearby tissue. The tissue-interface layer  214  may also have a laminar size or thickness that is the same or different from any one of the other layers in the dressing material  202 . In another example, the tissue-interface layer  214  may be thinner than any of the other layers in the dressing material  202 . 
     The dressing material  202  also includes a manifold  220 , or manifold layer or manifold member, for distributing reduced pressure from a reduced-pressure source, such as reduced-pressure source  110  in  FIG. 1 . The manifold  220  may also distribute liquid, such as exudate, from the tissue-interface layer  214  to other layers in the dressing material  202 . The manifold  220  has a first side  222  and a second, tissue-facing side  224 . The second, tissue-facing side  224  of the manifold  220  is disposed proximate the first side  216  of the tissue-interface layer  214 . 
     The manifold  220  may be a hydrophobic, porous material that is capable of distributing reduced pressure to the tissue site  207 . The manifold  220  may be made from foam, gauze, felted mat, or any other material suited to a particular biological application. The manifold  220  may include a plurality of flow channels or pathways to facilitate distribution of reduced pressure or fluids to or from the tissue site  207 . In one embodiment, the manifold  220  is a porous foam and includes a plurality of interconnected cells or pores that act as flow channels. The porous foam may be a polyurethane, open-cell, reticulated foam, such as the GranuFoam® dressing available from Kinetic Concepts, Inc. of San Antonio, Tex. If an open-cell foam is used, the porosity may vary. The flow channels allow fluid communication throughout a portion of the manifold  220  having open cells. The cells and flow channels may be uniform in shape and size, or may include patterned or random variations in shape and size. Variations in the shape and size of the cells of the manifold  220  result in variations in the flow channels, and such characteristics may be used to alter the flow characteristics of fluid through the manifold  220 . In one non-limiting example, the manifold  220  may be made from the same material as the tissue-interface layer  214 . 
     A number of additional layers may be added to absorb fluid from the manifold  220  or tissue-interface layer  214 . The additional layers may be absorbers. The additional layers are selected so that the farther the additional layers are located in situ from the tissue site  207 , the more the layers can absorb. The additional layers thus may be increasingly hydrophilic. In the illustrative embodiment of  FIG. 2 , a first absorbent layer  226 , which has a first side  228  and a second, tissue-facing side  230 , may be included with the dressing material  202 . The second, tissue-facing side  230  may be disposed proximate to the first side  222  of the manifold  220 . The first absorbent layer  226  is for receiving and absorbing the liquids distributed by the manifold  220 . 
     A second absorbent layer  232 , or reservoir layer, which has a first side  234  and a second, tissue-facing side  236 , may also be included with the dressing material  202 . Additional absorbent layers analogous to the first absorbent layer  226  or second absorbent layer  232  may also be included in other embodiments. The second, tissue-facing side  236  of the second absorbent layer  232  may be disposed proximate the first side  228  of the first absorbent layer  226 . As with other layers, the first absorbent layer  226  and second absorbent layer  232  may be coextensive or may be different sizes. 
     The absorbent layers  226 ,  232  receive and absorb liquids from the manifold  220 . The manifold  220  may facilitate the migration of liquid from the tissue site  207  radially outward toward the edges of the manifold  220  so that the liquid is distributed more uniformly across either or both of the absorbent layers  226  and  232  as indicated generally by the multi-directional arrows  238  shown for reference on the first absorbent layer  226 . The absorbent layers  226  and  232  will retain more liquid if the liquid is more uniformly distributed across the surface of the absorbent layers  226  and  232 . Also, such distribution of the liquid from the tissue site  207  in the directions indicated by the multi-directional arrows  238  may occur with or without the presence of reduced pressure. Thus, a fuller utilization of either or both of the absorbent layers  226  and  232  may be achieved using the manifold  220  even when reduced pressure is not being applied to the dressing  200 . 
     The manifold  220  may also act as a separator between the tissue-interface layer  214  and either or both of the absorbent layers  226  and  232 . In this example, the manifold  220 , reduces, restrains, or prevents liquid, such as exudate, that has been absorbed by either or both of the absorbent layers  226  and  232  from contacting either or both of the tissue-interface layer  214  or the tissue site  207 . Thus, the manifold  220  may further help to prevent maceration at or near the tissue site  207 . 
     The manifold  220  may have any size, shape, or thickness depending on a variety of factors, such as the type of treatment being implemented or the nature of the tissue site  207 . For example, the thickness of the manifold  220  may be increased or decreased to optimize the effectiveness of the manifold&#39;s  220  role as a separator between the tissue-interface layer  214  and either or both of the absorbent layers  226  and  232 . In applications in which the tissue site  207  releases a large amount of liquid that is absorbed by either or both of the absorbent layers  226  and  232 , a relatively thicker manifold  220  may be desirable to restrain or prevent the liquid that is absorbed by either or both of the absorbent layers  226  and  232  from contacting either or both of the tissue-interface layer  214  or the tissue site  207 . A relatively thinner manifold  220  may be desirable in applications in which a lower amount of liquid is present. In illustrative, non-limiting embodiments, the manifold  220  may be about 4 millimeters, 2 millimeters, or 1 millimeter thick. The manifold  220  may also have a laminar size or thickness that is the same or different from any one of the other layers in the dressing material  202 . 
     The first absorbent layer  226  may be disposed adjacent to the manifold  220  and absorb liquid, such as exudate, from the tissue site  207  via the tissue-interface layer  214  and the manifold  220 . In one example, the first absorbent layer  226  is disposed between the manifold  220  and the second absorbent layer  232 . 
     The first absorbent layer  226  may be formed from a hydrophilic material to facilitate absorption of the liquid from the tissue site  207 . In one embodiment, the first absorbent layer  226  is formed of a material that absorbs liquid from the tissue site  207  at a faster rate than the second absorbent layer  232 . For example, the first absorbent layer  226  may include a fast-wicking material, such as cotton, terrycloth, paper towel material, etc. To quicken the rate at which the first absorbent layer  226  absorbs liquid from the tissue site  207 , the surface area of the first absorbent layer  226  may be increased. The first absorbent layer  226  may also be made from a woven or mesh material. 
     In one embodiment, the fast-wicking characteristics of the first absorbent layer  226 , including the first absorbent layer&#39;s  226  ability to absorb liquid at a faster rate than the second absorbent layer  232 , helps to quickly draw liquid away from the tissue site  207  and toward the second absorbent layer  232 , which may have a higher absorptive capacity than the first absorbent layer  226 . The first absorbent layer&#39;s  226  ability to quickly draw liquid away from the tissue site  207  may prevent the accumulation of liquid at or near the tissue site  207 , and therefore may help to prevent maceration at or near the tissue site  207 . 
     The first absorbent layer  226  may have any size, shape, or thickness depending on a variety of factors, such as the type of treatment being implemented or the nature of the tissue site  207 . The first absorbent layer  226  may also have a size or thickness that is the same or different from any one of the other layers in the dressing material  202 . 
     In one embodiment, the second absorbent layer  232  absorbs liquid from the tissue site  207  via the tissue-interface layer  214 , the manifold  220 , and the first absorbent layer  226 . In another illustrative embodiment (not shown), the dressing material  202  does not include the first absorbent layer  226 , in which case the second absorbent layer  232  is the only absorbent layer present in the dressing material  202 . In this embodiment, the second absorbent layer  232  absorbs liquid from the tissue site  207  via the tissue-interface layer  214  and the manifold  220 . In other embodiments, more than two absorbent layers may be included. 
     The second absorbent layer  232  may be composed of any material capable of absorbing liquid, such as exudate, from the tissue site  207 . The material from which the second absorbent layer  232  is composed is also capable of transferring reduced pressure. In one embodiment, the second absorbent layer  232  has a higher fluid storage capacity than the first absorbent layer  226 . The difference in fluid storage capacity may be due to the respective materials from which absorbent layers  226  and  232  are composed. In one example, the second absorbent layer  232  may be capable of storing liquid that is  20  or more times heavier or voluminous than the dry weight or volume, respectively, of the second absorbent layer  232 . 
     In the illustrative example of  FIG. 2 , the second absorbent layer  232  wicks liquid away from the first absorbent layer  226 , and stores that liquid. To facilitate the second absorbent layer&#39;s  232  function of wicking liquid away from the first absorbent layer  226 , the second absorbent layer  232  may be composed of a material that is more hydrophilic than the material from which the first absorbent layer  226  is composed. 
     In one embodiment, the second absorbent layer  232  may be composed of a hydrocolloid or hydrogel, which may be, for example, a First Water® Net2O hydrogel from First Water, Ltd. of Wiltshire, U.K. The hydrogel from which the second absorbent layer  232  is composed may also include polyethylene glycol. Further, although hydrogel infers the inclusion of water, the hydrogel from which the second absorbent layer  232  may be composed may be a dried back hydrogel polymer base, which substantially or completely lacks water. 
     In another illustrative example, the second absorbent layer  232  may be made from a super absorbent fiber material. The super absorbent fibers may hold onto or bond to the liquid in conjunction with a physical or chemical change to the fibers. In one non-limiting example, the super absorbent fiber may include the Super Absorbent Fiber (SAF) material from Technical Absorbents, Ltd. of Lincolnshire, UK. The fibers may thus form a fibrous material in which the fibers absorb liquid from the tissue site  207 . Also, the fibers in the second absorbent layer  232  that contact the liquid may gel upon contact with the liquid, thereby trapping the liquid. Spaces or voids between the fibers may allow a reduced pressure that is applied to the dressing  200  to be transferred within and through the second absorbent layer  232 . The structure of the second absorbent layer  232  that contains the fibers may be either woven or non-woven. 
     The second absorbent layer  232  may have any size, shape, or thickness depending on a variety of factors, such as the type of treatment being implemented or the nature of the tissue site  207 . For example, the width or thickness of the second absorbent layer  232  may be increased to cause a corresponding increase in the fluid storage capacity of the second absorbent layer  232 . The second absorbent layer  232  may also have a size or thickness that is the same or different from any one of the other layers in the dressing material  202 . 
     The dressing material  202  also includes a distribution manifold  242  that is adjacent to the second absorbent layer  232 . The distribution manifold  242  has a first side  244  and a second, patient-facing side  246 . The second, patient-facing side  246  of the distribution manifold  242  is disposed adjacent to the first side  234  of the second absorbent layer  232 . The distribution manifold  242  distributes reduced pressure to one or more layers in the dressing material  202  that are nearer the tissue site  207  and may do so more uniformly across an entire surface of the one or more layers in the dressing material  202 . Because the distribution manifold  242  is disposed further away from the tissue site  207  than the absorbent layers  226  and  232 , liquid, such as exudate, from the tissue site  207  does not typically reach the distribution manifold  242 . In one illustrative embodiment, however, liquid may be allowed to reach the distribution manifold  242 . 
     The distribution manifold  242  may be made from any material capable of distributing gas or liquid. In one example, the distribution manifold  242  is formed from a reticulated polyurethane foam layer or other porous manifolding material. In another example, the distribution manifold  242  may be formed from the same or similar material as the manifold  220 . The distribution manifold  242  may also distribute liquid, such as exudate, from the tissue site  207  that is not absorbed by either or both of the absorbent layers  226  and  232 . The distribution manifold  242  may also have any size, shape, or thickness. 
     Although not explicitly shown in the embodiment of  FIG. 2 , the dressing  200  may also include a hydrophobic filter that is capable of restraining or preventing the flow of liquid, such as exudate from the tissue site  207 , from reaching the reduced-pressure connector  206  or a reduced-pressure conduit that may be connected to the dressing  200 . By preventing liquid from reaching the reduced-pressure conduit, the hydrophobic filter also prevents the liquid from reaching a reduced-pressure source, such as reduced-pressure source  114  in  FIG. 1 , which may be connected to the reduced-pressure delivery conduit. 
     In one illustrative embodiment, the hydrophobic filter is disposed adjacent to the distribution manifold  242 . The second, tissue-facing side of the hydrophobic filter may abut the first side  244  of the distribution manifold  242  and the first side of the hydrophobic filter may abut the second, tissue-facing side  210  of the sealing member  204  or the reduced-pressure connector  206 . As used herein, the term “abut” includes both fully and partially abutting. 
     The hydrophobic filter may also restrict or prevent the passage of reduced pressure to the tissue site  207  when the hydrophobic filter becomes substantially saturated, clogged, blocked, or wetted with liquid from the tissue site  207 . The hydrophobic filter may also prevent the passage of reduced pressure to the tissue site  207  when a layer that abuts the hydrophobic filter becomes substantially saturated with liquid. For example, if the second absorbent layer  232  abutted the hydrophobic filter in a particular embodiment, the substantial saturation of the second absorbent layer  232  with liquid may cause the hydrophobic filter to prevent the passage of reduced pressure. 
     The hydrophobic filter may have any size, shape, or thickness. In one example, the hydrophobic filter may be smaller than other layers in the dressing material  202  or may be larger than other layers. The hydrophobic filter may also be wider than the reduced-pressure connector  206  and an aperture  212  in the sealing member  204  so that liquid from the tissue site  207  cannot reach the reduced-pressure connector  206  or the aperture  212 . 
     The dressing  200  may include the sealing member  204 . The sealing member  204  may cover at least a portion of the dressing material  202 . In this embodiment, the sealing member  204  may fully cover the dressing material  202  and may secure the dressing material  202  to the tissue site  207 . The sealing member  204  may also assist in maintaining a fluid seal around a portion of the tissue site  207 . The sealing member  204  may also provide a protective covering for the dressing  200 . As used herein, “fluid seal,” or “seal” means a seal adequate to maintain reduced pressure at a desired site given the particular reduced-pressure source involved. 
     In one illustrative embodiment, the sealing member  204  may be an adhesive drape. In this embodiment, the adhesion of the sealing member  204  may be due to the nature of the material with which the sealing member  204  is made, or may be due to an adhesive layer, e.g., like adhesive  126  in  FIG. 1 , on a surface of the sealing member  204 . Any portion of the sealing member  204  may be adhesive. For example, the entire second, tissue-facing side  210  of the sealing member  204  may be adhesive. In this example, the second, tissue-facing side  210  of the sealing member  204  may adhere to at least a portion of the reduced-pressure connector  206 , a portion of the tissue site  207  (or epidermis  209  around and that may be regarded as part of the tissue site  207 ), or any layer or component of the dressing material  202 . 
     In another embodiment, only the peripheral portions of the second, tissue-facing side  210  of the sealing member  204  may be adhesive. In this embodiment, the peripheral portions are adjacent to the edges of the sealing member  204 . The adhesive peripheral portions on the tissue-facing side of the sealing member  204  may be adapted to adhere to the tissue site  207  to secure the dressing material  202  to the tissue site  207 . 
     In another illustrative example, the sealing member  204  may be a drape and may be designed such that the drape will not adhere to wet surfaces, but will adhere to dry surfaces. Thus, when applying such a drape, the drape will not stick to moistened gloves or hands, thereby will permit easier handling of the drape until the drape is placed on a dry tissue site, such as a dry periwound region. The sealing member  204  may have any size, shape, or thickness. In one example, the sealing member  204  may be wider or larger than any layer or components of the dressing material  202 . 
     Reduced pressure may be applied to the dressing material  202  via the reduced-pressure connector  206  extending through the aperture  212  in the sealing member  204 . In the illustrative example of  FIG. 2 , the aperture  212  is shown centrally located on the sealing member  204 . However, the aperture  212  may be located anywhere on the sealing member  204 , including a peripheral portion of the sealing member  204  that is adjacent to an edge of the sealing member  204 . Although the aperture  212  is shown to be circular, it should be understood that the aperture  212  may have any shape, e.g., square, elliptical, irregular, etc. In one example, the shape of the aperture  212  is adapted to contour, or substantially coordinate, with one or more portions of the reduced-pressure connector  206 . 
     The reduced-pressure connector  206  may provide an interface between a reduced-pressure conduit and the dressing material  202 . In particular, the reduced-pressure connector  206  may be adapted to be in fluid communication, or fluidly coupled, to a reduced-pressure conduit, such as reduced-pressure delivery conduit  112  in  FIG. 1 . The reduced-pressure conduit transfers reduced pressure to the dressing  200  or the tissue site  207  via the reduced-pressure connector  206 . 
     The reduced-pressure connector  206  may be a connector pad that is adapted to abut the aperture  212 . In particular, the reduced-pressure connector  206  may be adapted to be partially disposed within the aperture  212 . Although the reduced-pressure connector  206  is shown to have a low profile dome shape, the reduced-pressure connector  206  may have any shape. The low profile of the reduced-pressure connector  206  may help to keep the dressing  200  compact and convenient for use by a user. The reduced-pressure connector  206  may includes a flanging portion  248 , which is disposed around the periphery of the reduced-pressure connector  206 . In the example of  FIG. 2 , the tissue-facing side of the edge defining the aperture  212  may be adapted to adhere to the flanging portion  248  such that the reduced-pressure connector  206  is secured to at least one layer or component of the dressing material  202 . 
     Although not shown in  FIG. 2 , in one embodiment the dressing material  202  may include an odor filter. The odor filter may retrain or prevent odor from exiting the dressing  200 . The odor filter may be a carbon odor filter, which may include charcoal. For example, the odor filter may be a charcoal cloth. The odor filter may be positioned anywhere in the dressing material  202 . For example, in the embodiment in which the dressing  200  includes a hydrophobic filter, the odor filter may be disposed adjacent to a first, drape-facing side of the hydrophobic filter. When in use, the odor filter may also abut the first, drape-facing side of the hydrophobic filter. 
     Although the sealing member  204 , the distribution manifold  242 , the absorbent layers  226  and  232 , the manifold  220 , and the tissue-interface layer  214  are each shown to have a square shape, each of these components, as well as other layers disclosed herein with respect to other embodiments, may have any shape as desired or required to provide adequate reduced-pressure therapy to the tissue site  207 . For example, these components and layers may have any polygonal shape, a rectangular shape, a circular shape, an oval shape, an irregular shape, a customized shape, etc. The shape of these components and layers may also be customized to contour the tissue site  207 . 
     The layers forming the dressing material  202  may be manufactured in the order shown in  FIG. 2  or any other order. As previously noted, one or more layers may be omitted. The layers forming the dressing material may be bonded to form an integrated member or remain as separate stacked members. As used herein, “bonding” may include coupling items using any known technique, including without limitation welding (e.g., ultrasonic or RF welding), bonding, adhesives, cements, material attraction, etc. The layers may be bonded and then cut. 
     Referring now primarily to  FIG. 3 , the illustrative dressing  200  of  FIG. 2  is shown assembled and deployed to treat the tissue site  207 . The second, tissue-facing side  218  of the tissue-interface layer  214  is shown abutting the tissue site  207 , which includes a wound and a portion of the epidermis  209  in this illustration. The first side  244  (or at least a portion) of the distribution manifold  242  may abut the sealing member  204 . 
     The second, tissue-facing side  250  of the reduced-pressure connector  206  abuts the distribution manifold  242 . Also, a portion of the reduced-pressure connector  206  is shown to protrude from the aperture  212  in the sealing member  204 . The flanging portion  248  of the reduced-pressure connector  206  is sandwiched between the sealing member  204  and the distribution manifold  242 . The sealing member  204  helps secure the reduced-pressure connector  206  relative to at least one component or layer in the dressing material  202 , such as the distribution manifold  242 . 
     Although empty space is shown between the peripheral portions of the sealing member  204  and the tissue site  207 , in one example when under reduced pressure, little or no space is present between the peripheral portions of the sealing member  204  and the tissue site  207 . Also, although the tissue-interface layer  214 , the manifold  220 , the absorbent layers  226  and  232 , and the distribution manifold  242  are shown to have a uniform width, the width of any combination of these layers may vary from one another. Similarly, the thickness of any combination of these layers may be uniform or may vary from one another. In one example, the second absorbent layer  232  is thicker than the first absorbent layer  226 . 
     When reduced pressure from a reduced-pressure delivery conduit, such as reduced-pressure delivery conduit  112  in  FIG. 1 , passes to the dressing  200 , the reduced pressure is applied to the tissue site  207  via the dressing material  202  and the reduced-pressure connector  206 . The reduced-pressure delivery conduit may be connected to the reduced-pressure connector  206  using a recess  252  in the reduced-pressure connector  206 , an attachment base, or other device. Under reduced pressure, the second absorbent layer  232  (or reservoir layer) may absorb liquid from the tissue site  207  via the tissue-interface layer  214 , the manifold  220 , and the first absorbent layer  226 . 
     In one embodiment, a method of using the dressing  200  includes deploying the dressing material  202  adjacent the tissue site  207 . The method may also include covering at least a portion of the dressing material  202  with the sealing member  204 , and applying reduced pressure. 
     In one illustrative example of the operation of the dressing  200  as part of a reduced-pressure system, reduced pressure is delivered to the dressing  200  and causes liquid, such as exudate, to be drawn away from the tissue site  207 . The liquid passes through the tissue-interface layer  214  while the tissue-interface layer  214  maintains substantial contact with the tissue site  207 . The hydrophobic nature of the tissue-interface layer  214  prevents liquid from being directly absorbed (or held) by the tissue-interface layer  214  and remaining near the surface of the tissue site  207 . In addition, the fast-wicking characteristics of the first absorbent layer  226  allows the first absorbent layer  226  to absorb liquid via the manifold  220  such that the liquid is drawn quickly away from the tissue site  207 . Upon being wicked by the first absorbent layer  226 , the second absorbent layer  232  may receive and store the liquid. The manifold  220  provides an intervening layer that prevents liquid that is absorbed by either or both of the absorbent layers  226  and  232  from returning to the tissue site  207 . In this example of the operation of the dressing  200 , maceration of the epidermis  209  near the tissue site  207 , is reduced or prevented due to the liquid being quickly drawn away from the tissue site  207  and stored at a location that has little or no effect on the tissue site  207 . 
     One aspect upon which the operation of the dressing  200  may be implemented is that one or more faster-absorbing, lower-storage-capacity absorbing layers, such as the first absorbent layer  226 , may be positioned closer to the tissue site  207  than slower-absorbing, higher-storage-capacity absorbing layers, such as the second absorbent layer  232 . Using this approach, liquid may be drawn away from the tissue site  207  before the liquid is able to damage the surface at or near the tissue site  207 , while also providing a storage layer for this liquid that has a large storage capacity. The tissue-interface layer  214  or hydrophobic layers may be disposed between the absorbent layers  226  and  232  and the tissue site  207 . Such a hydrophobic layer help keep liquids away from the tissue site  207 . Due, at least in part, to the uptake of liquid by the absorbent layers  226  and  232 , these hydrophobic layers also reduce or prevent the lateral spread of the liquid along the interface between the tissue-interface layer  214  and the surface of the tissue site  207 , and thereby further prevents or reduces maceration of the tissue at or near the tissue site  207 . 
     The illustrative dressings and systems herein include a dressing material adapted to transfer reduced pressure to a tissue site and that may store liquids and help avoid maceration. The illustrative embodiments provide numerous non-limiting examples of materials and non-limiting examples of layer configurations that may be included in the dressing material. Moreover, each of the layers described herein may be used in any combination with one another. For example, in each of the figures and examples showing or describing a non-limiting configuration of the dressing material, any one or more of the shown or described layers or components may be excluded, any one or more layers or components from the same or different example or figures may be added, or any one or more layers or components from the same or different example or figure may substitute another layer or component shown in the example or figure. In addition, the order, size, thickness, position, and other characteristics of the layers or components in each of the described layer configurations in the examples and figures may be altered. 
     According to one illustrative embodiment, a dressing material has a plurality of channel walls that form a plurality of channels. The plurality of channels may be parallel to one another. In another illustrative embodiment, the channels may be slanted relative to a skin surface at the tissue site. The plurality of channels may form an acute angle with the skin surface at the tissue site. 
     According to one illustrative embodiment, a wound dressing for use with a reduced-pressure treatment system includes at least one laminar layer having a first side and a second, tissue-facing side. The laminar layer includes a plurality of channel walls forming a plurality of channels; wherein the channel walls are gas permeable and liquid impermeable; wherein the channels are angled with an angle alpha (a) to a surface on the second, tissue-facing side of the laminar layer; and wherein the angle alpha (a) is an acute angle. The walls may be gas permeable and liquid impermeable. 
     According to one illustrative embodiment, a reduced-pressure wound dressing includes a non-adherent hydrophobic layer having a first side and a second, tissue-facing side; a porous, hydrophobic manifold layer, having a first side and a second, tissue-facing side; a quick-absorbing hydrophilic layer having a first side and a second, tissue-facing side; a fluid-storage layer having a first side and a second, tissue-facing side; and a sealing member having a first side and a second, tissue-facing side. The second, tissue-facing side of the porous, hydrophobic manifold layer is adjacent to the first side of the non-adherent hydrophobic layer. The second, tissue-facing side of the quick-absorbing hydrophilic layer is adjacent to the first side of the porous, hydrophobic manifold layer. The second, tissue-facing side of the fluid-storage layer is adjacent to the first side of the quick-absorbing hydrophilic layer. The second, tissue-facing side of the sealing member is adjacent to the first side of the fluid-storage layer. 
     Various changes, substitutions, permutations, and alterations can be made to the illustrative embodiments described herein without departing from the scope of this disclosure as defined by the appended claims. Any feature that is described in a connection to any one embodiment may also be applicable to any other embodiment.