Patent Publication Number: US-2019192751-A1

Title: Sealing Systems And Methods Employing A Switchable Drape

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 14/919,055, entitled “Sealing Systems And Methods Employing A Switchable Drape,” filed on Oct. 21, 2015, which is a continuation of U.S. patent application Ser. No. 13/715,982, entitled “Sealing Systems And Methods Employing A Switchable Drape,” filed Dec. 14, 2012, now U.S. Pat. No. 9,192,444, which claims priority to U.S. Provisional Patent Application No. 61/576,786, entitled “Sealing Systems And Methods Employing A Switchable Drape,” filed on Dec.  16 ,  2011 . All of these applications are incorporated herein by reference for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates generally to medical systems, devices, and methods for treating a patient with reduced pressure, and more particularly, but not by way of limitation, to sealing systems and methods employing a switchable drape. 
     2. Description of Related Art 
     Clinical studies and practice have shown that providing 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, which may include faster healing and increased formulation of granulation tissue. In carrying out the treatment, a portion of the patient is sealed with a medical drape. Traditional drapes involve a balancing between strength of an adhesive on the drape and the degree of pain and disruption that will be caused when removing the drape from the patient. 
     SUMMARY 
     According to an illustrative embodiment, a sealing system for use in treating a tissue site on a patient with reduced pressure includes an outer layer formed from a drape material and has a first side and a second, patient-facing side. The outer layer is formed with a plurality of perforations extending through the outer layer. The sealing system also includes a high-strength adhesive coupled to the second, patient-facing side of the outer layer. The high-strength adhesive has a first side and a second, patient-facing side. The system further includes a switching solution. When applied to the high-strength adhesive, the switching solution changes the bond of the high-strength adhesive to lower the adhesion of the adhesive. 
     According to another illustrative embodiment, a method of manufacturing a switchable drape includes supplying an outer layer formed from a drape material having a first side and a second, patient-facing side. The method perforates the outer layer. The method further includes applying a high-strength adhesive to the second, patient-facing side of the outer layer. The high-strength adhesive has a first side and a second, patient-facing side. The high-strength adhesive covers the plurality of perforations. The method may also include applying a first release member to the first side of the outer layer and applying a second release member to the second, patient-facing side of the high-strength adhesive. 
     According to another illustrative embodiment, a kit for forming a seal over a portion of a patient&#39;s body includes a switchable drape and a switching solution. The switchable drape includes an outer layer and a high-strength adhesive. The outer layer is formed from a drape material and has a first side and a second, patient-facing side. The outer layer is formed with a plurality of perforations extending through the outer layer. The high-strength adhesive is coupled to the second, patient-facing side of the outer layer. The high-strength adhesive has a first side and a second, patient-facing side. When applied to the high-strength adhesive, the switching solution lessens the adhesive strength of the high-strength adhesive. 
     According to another illustrative embodiment, a method of treating a patient with reduced pressure includes deploying a manifold adjacent to the tissue site and deploying a switchable drape over the manifold and at least a portion of the epidermis adjacent to the tissue site to create a sealed space. The method also includes supplying reduced pressure to the sealed space; disposing a switching solution on the first side of the outer layer of the switchable drape; and removing the switchable drape from the patient. 
     According to another illustrative embodiment, a method of treating a tissue site on a patient with reduced pressure includes deploying a manifold approximate to the tissue site; deploying a medical drape over the manifold and a portion of the patient&#39;s intact skin to create a sealed space; and supplying reduced pressure to the sealed space. The method further includes terminating the reduced pressure supplied to the sealed space; creating perforations through the medical drape; and applying a switching solution onto the first side of the drape. The method also includes removing the drape. 
     According to another illustrative embodiment, a sealing system for use in treating a tissue site on a patient with reduced pressure includes an outer layer formed from a drape material that has a first side and a second, patient-facing side. The outer layer is formed with a plurality of perforations extending through the outer layer. The system also includes a high-strength adhesive having a first side and a second, patient-facing side. A soluble layer is coupled to the second, patient-facing side of the outer layer and the first side of the high-strength adhesive. The system further includes a switching solution. The soluble layer is operable to substantially dissolve when wetted with the switching solution. 
     According to another illustrative embodiment, a method of treating a tissue site on a patient with reduced pressure includes deploying a manifold proximate to the tissue site; and deploying a sealing system over the manifold and a portion of the patient&#39;s intact skin to create a sealed space containing the manifold. The sealing system includes an outer layer formed from a drape material that has a first side and a second, patient-facing side. The outer layer is formed with a plurality of perforations extending through the outer layer. The system also includes a high-strength adhesive having a first side and a second, patient-facing side and a soluble layer coupled to the second, patient-facing side of the outer layer and the first side of the high-strength adhesive. The system further includes a switching solution. The soluble layer is operable to substantially dissolve when wetted with the switching solution. The method further includes supplying reduced pressure to the sealed space, applying the switching solution onto the first side of the outer layer until the soluble layer is substantially dissolved, and removing the sealing system. 
     According to another illustrative embodiment, a sealing system for use in treating a tissue site on a patient with reduced pressure includes an outer layer formed from a drape material and having a first side and a second, patient-facing side, and a high-strength adhesive having a first side and a second, patient-facing side. The sealing system also includes a wicking layer disposed adjacent to at least a portion of the high-strength adhesive. The wicking layer has a plurality of wicking-layer ends extending to a periphery of the high-strength adhesive. The system also includes a switching solution. The switching solution is operable to lessen the adhesive strength of the high-strength adhesive. The wicking layer is operable to transport the switching solution from the wicking-layer ends to at least a peripheral portion of the adhesive. 
     According to another illustrative embodiment, a method of treating a tissue site on a patient includes deploying a manifold proximate to the tissue site. The method deploys a sealing system over the manifold and a portion of the patient&#39;s intact skin to create a sealed space containing the manifold. The sealing system includes an outer layer formed from a drape material having a first side and a second, patient-facing side and a high-strength adhesive having a first side and a second, patient-facing side. The sealing system also includes a wicking layer disposed adjacent to at least a portion of the high-strength adhesive. The wicking layer has a plurality of wicking-layer ends extending to a periphery of the high-strength adhesive. The sealing system further includes a switching solution that is operable to lessen the adhesive strength of the high-strength adhesive. The wicking layer is operable to transport the switching solution from the wicking-layer ends to at least a peripheral portion of the high-strength adhesive. The method further includes supplying reduced pressure to the sealed space; applying the switching solution onto the wicking-layer ends until the adhesive strength of the high-strength adhesive is decreased at least at a peripheral portion; and removing the sealing system. 
     Other aspects, 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 perspective view (with a portion shown in cross section) of an illustrative embodiment of a system for treating a tissue site on a patient that employs an illustrative sealing subsystem; 
         FIG. 2  is a perspective view (with a portion shown in cross section) of a portion of the illustrative sealing subsystem of  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of a portion of an illustrative embodiment of a switchable drape; 
         FIG. 4  is a plan view of a portion of an illustrative embodiment of a system for treating a tissue site on a patient that employs an illustrative sealing subsystem; 
         FIG. 5  is a cross-sectional view of an illustrative embodiment of a switchable drape; 
         FIG. 6  is a cross-sectional view of an illustrative embodiment of a switchable drape; 
         FIG. 7  is a perspective view (with a portion shown in cross section) of an illustrative embodiment of a switchable drape; and 
         FIG. 8  is a plan view of an illustrative embodiment of a kit for forming a seal over the portion of a patient&#39;s body. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     In the following detailed description of illustrative, non-limiting embodiments, reference is made to the accompanying drawings that form a part hereof. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be utilized and that logical, structural, mechanical, electrical, and chemical changes may be made without departing from the spirit or scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the embodiments described herein, the description may omit certain information known to those skilled in the art. The following detailed description is not to be taken in a limiting sense, and the scope of the illustrative embodiments is defined only by the appended claims. 
     Referring now to the figures and primarily to  FIGS. 1-2 , an illustrative embodiment of a system  100  for treating a tissue site  101  with reduced pressure is presented. The system  100  includes a sealing subsystem  104 . The sealing subsystem  104  includes a switchable drape  106  that strongly adheres to an epidermis  112  adjacent the tissue site  101  during use, but is then changed or switched to a less adhering mode for removal. In this way, a strong connection may be made between the switchable drape  106  and the tissue site  101  to avoid leaks, and yet, after use, the switchable drape  106  may be removed from the tissue site  101  with minimal or at least tolerable pain. 
     The tissue site  101  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. Unless otherwise indicated, as used throughout this document, “or” does not require mutual exclusivity. Treatment of the tissue site  101  may include removal of fluids, for example, exudate or ascites. The tissue site  101  in this example is shown as a wound that is through the epidermis  112 , a dermis  114 , and into a subcutaneous tissue  116 , but any wound size, depth, or tissue may be involved. 
     In treating the tissue site  101 , a manifold  118  can be deployed proximate to the tissue site  101 . The manifold  118  is a substance or structure that is provided to assist in applying reduced pressure to, delivering fluids to, or removing fluids from the tissue site  101 . The manifold  118  includes a plurality of flow channels or pathways that distribute fluids provided to and removed from the tissue site  101 . In one illustrative embodiment, the flow channels or pathways are interconnected to improve distribution of fluids provided to or removed from the tissue site  101 . The manifold  118  may comprise one or more of the following: a biocompatible material that is capable of being placed in contact with the tissue site  101  and distributing reduced pressure to the tissue site  101 ; devices that have structural elements arranged to form flow channels, such as, for example, cellular foam, open-cell foam, porous tissue collections, liquids, gels, and foams that include, or cure to include, flow channels; porous material, such as foam, gauze, felted mat, or any other material suited to a particular biological application; or porous foam that includes a plurality of interconnected cells or pores that act as flow channels, for example, a polyurethane, open-cell, reticulated foam such as GranuFoam® material manufactured by Kinetic Concepts, Incorporated of San Antonio, Tex.; a bioresorbable material; or a scaffold material. In some situations, the manifold  118  may also be used to distribute fluids such as medications, antibacterials, growth factors, and various solutions to the tissue site  101 . Other layers may be included in or on the manifold  118 , such as absorptive materials, wicking materials, hydrophobic materials, and hydrophilic materials. 
     In one illustrative, non-limiting embodiment, the manifold  118  may be constructed from a bioresorbable material that may remain in a patient&#39;s body following use. Suitable bioresorbable materials may include, without limitation, a polymeric blend of polylactic acid (PLA) and polyglycolic acid (PGA). The polymeric blend may also include, without limitation, polycarbonates, polyfumarates, and capralactones. The manifold  118  may further serve as a scaffold for new cell-growth, or a scaffold material may be used in conjunction with the manifold  118  to promote cell-growth. A scaffold is a substance or structure used to enhance or promote the growth of cells or the formation of tissue, such as a three-dimensional porous structure that provides a template for cell growth. Illustrative examples of scaffold materials include calcium phosphate, collagen, PLA/PGA, coral hydroxy apatites, carbonates, or processed allograft materials. 
     The switchable drape  106  of the sealing subsystem  104  covers the manifold  118  and a portion of the epidermis  112  adjacent the tissue site  101  to form a sealed space  120 . The sealed space  120  contains the manifold  118 . Reduced pressure is supplied to the sealed space  120  to treat the tissue site  101  with reduced pressure. 
     Reduced pressure is typically a pressure less than the ambient pressure at a tissue site 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. Unless otherwise indicated, quantitative values of pressure stated herein are gauge pressures. The reduced pressure delivered may be constant 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, unless otherwise indicated, an increase in reduced pressure or vacuum pressure typically refers to a reduction in absolute pressure. 
     The reduced pressure may be delivered from a reduced-pressure source  122  to a reduced-pressure interface  124  by a reduced-pressure delivery conduit  126 . The reduced-pressure interface  124  is in fluid communication with the sealed space  120 . 
     The reduced-pressure source  122  may be any device for supplying a reduced pressure, such as a vacuum pump, wall suction, micro-pump, or other source. 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 (−667 Pa) and −500 mm Hg (−66.7 kPa) and more typically between −75 mm Hg (−9.9 kPa) and −300 mm Hg (−39.9 kPa). 
     The reduced pressure developed by the reduced-pressure source  122  is delivered through the reduced-pressure delivery conduit  126  to the reduced-pressure interface  124 . In one illustrative embodiment, the reduced-pressure interface  124  is a T.R.A.C.® Pad or Sensa T.R.A.C.® Pad available from KCI of San Antonio, Tex. The reduced-pressure interface  124  allows the reduced pressure to be delivered to the sealed space  120 . In some embodiments, the reduced-pressure interface  124  may be a portion of the reduced-pressure delivery conduit  126  extending into the sealed space  120  or may simply be a vacuum port on a micro-pump that extends into the sealed space  120 . 
     The sealing subsystem  104  includes the switchable drape  106  and a switching solution. Referring now primarily to  FIGS. 2 and 3 , the switchable drape  106  includes an outer layer  128  formed from a drape material and having a first side  130  and a second, patient-facing side  132 . The outer layer  128  is formed with a plurality of perforations  134  extending through the outer layer  128 . 
     The plurality of perforations  134  may be apertures of any shape in which the drape material has been removed or may be slits of any shape with no drape material removed. In one illustrative embodiment, the removed drape material creates openings that have an average effective diameter in the range of about 0.05 mm to about 0.40 mm. In another illustrative embodiment, the plurality of perforations  134  may comprise a plurality of apertures, wherein the surface area of the removed material averages between about 0.2% to about 13% of the surface area of the outer layer  128 . The plurality of perforations  134  may cover all of the outer layer  128  or a portion of the outer layer  128 . As shown in  FIG. 4 , a portion of the outer layer  128  includes the plurality of perforations  134 . The pitch of the perforations  134  is typically about two to about six times the thickness of a high-strength adhesive  136 . For example, a switchable drape  106  having a high-strength adhesive  136  having a thickness 0.5 mm would typically have a pitch in the range of about 1.0 to about 3.0 mm in both directions. The pitch, the measurement of the distance between adjacent perforations, can vary in each direction, can be non-uniform in each direction, and may have gaps in the pattern. The size and distribution of perforations  134  are used to control the rate of solution attack on the high-strength adhesive  136 . The size and distribution of perforations  134  are also used to control the tear strength of the outer layer  128 . 
     The drape material from which the switchable drape  106  is formed may be drape materials that provide a fluid seal. The drape material may be, for example, an impermeable or semi-permeable elastomeric material. For semi-permeable materials, the permeability must be low enough that for a given reduced-pressure source, the desired reduced pressure may be maintained. Elastomeric material generally refers to a polymeric material that has rubber-like properties. More specifically, most elastomers have ultimate elongations greater than 100% and a significant amount of resilience. The resilience of a material refers to the ability of the material to recover from an elastic deformation. Examples of elastomers 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 (PU), EVA film, co-polyester, and silicones. Additional, examples of drape materials include a silicone drape, a 3M Tegaderm® drape, or a polyurethane (PU) drape such as one available from Avery Dennison Corporation of Pasadena, Calif. 
     The drape material may be a high-moisture-vapor-transfer-rate drape material. “Moisture vapor transmission rate” or “MVTR” represents the amount of moisture that can pass through a material in a given period of time. For example, the high-moisture-vapor-transfer-rate drape may have an MVTR greater than about 300 g/m 2 /24 hours or, more typically, greater than about 1000 g/m 2 /24 hours or more. Additional examples of suitable drape materials include one or more of the following: hydrophilic polyurethanes, cellulosics, hydrophilic polyamides, polyvinyl alcohol, polyvinyl pyrrolidone, hydrophilic silicone polymers, hydrophilic acrylics, hydrophilic silicone elastomers and copolymers of these. As one specific, illustrative, non-limiting embodiment, the drape material may be a breathable cast mat polyurethane film sold under the name INSPIRE 2301 from Exopack Advanced Coatings of Wrexham, United Kingdom, having an MVTR (inverted cup technique) of 14500-14600 g/m 2 /24 hours. The outer layer  128  may have various thicknesses, such as about 10 to about 100 microns (μm), e.g., 15, 20, 30, 40, 50, 60, 70, 80, 90, 100 microns or any number in the stated range. 
     The switchable drape  106  also includes the high-strength adhesive  136 , which has a first side  138  and a second, patient-facing side  140 . It should be noted that the switchable drape  106  does not leak through the plurality of perforations  134  because the high-strength adhesive  136  covers the plurality of perforations  134 . For this reason, the high-strength adhesive  136  is typically applied to the second, patient-facing side  132  of the outer layer  128  after the plurality of perforations  134  have been formed. 
     The high-strength adhesive  136  typically has an adhesive strength one to two times stronger than adhesives used on most medical drapes. For example, without limitation, one medical drape, for example, MED1827A by Avery, has a bond strength to polythene, 90 degree, of 144 N/m. Whereas, according to one illustrative embodiment, a switchable drape produced according to the embodiments described herein may have a bond strength in the range of greater than about 144 N/m to about 288 N/m under similar testing conditions. The high-strength adhesive  136  typically has a thickness in the range of about 0.3 mm to about 1.5 mm. The high-strength adhesive  136  may be formed from an acrylic adhesive or other adhesive. The high-strength adhesive  136  is typically soft enough and thick enough that the high-strength adhesive  136  fills any cracks or crevices in the epidermis  112  adjacent the tissue site  101  to form a strong fluid seal and maintains that seal when negative pressure is applied to the sealed space  120 . 
     As shown best in  FIG. 3 , the first side  130  of the outer layer  128  may be covered by a first release member  142 . The first release member  142  may be a material that seals the surface of or provides additional handling rigidity to the outer layer  128 . The first release member  142  may also be a material that is removable. The first release member  142  may comprise one or more of the following: a polyurethane film, high density polyethylene, a high-MVTR film, polymers such as acrylic copolymers, polyvinyl acetate, polyether block amide copolymers (PEBAX), polyvinyl alcohol and copolymers, polyamide, polyvinylchloride, or polyvinylidene chloride. As shown in  FIG. 3 , the first release member  142  may be a two-part member having two gripping portions  144 ,  146  to facilitate removal. The first release member  142  may be retained only during deployment of the outer layer  128  and then removed. Alternatively, the first release member  142  may remain in place covering the plurality of perforations  134  until removal of the outer layer  128  from the tissue site  101  is desired. In this latter situation, the first release member  142  prevents accidental exposure of the high-strength adhesive  136  to a switching solution through the plurality of perforations  134 . 
     As shown in  FIG. 3 , a second release member  148 , which is analogous to the first release member  142 , may be used to cover the second, patient-facing side  140  of the high-strength adhesive  136  prior to use. The second release member  148  is removed before the high-strength adhesive  136  is deployed against the epidermis  112  adjacent the tissue site  101 . The second release member  148  may include a first gripping member  150  and a second gripping member  152  to facilitate removal of the second release member  148  from the high-strength adhesive  136 . 
     As previously noted, the plurality of perforations  134  may be formed with or without removing portions of the drape material. If no material is removed, the perforations may be formed, for example, without limitation, as slits such as half-moon slits, which are then covered on the second, patient facing side  132  by the high-strength adhesive  136 . In this way, the plurality of perforations  134  act as small valves and minimize exposure of the high-strength adhesive  136  to the first side  130  of the outer layer  128 . If the drape material is removed in forming the plurality of perforations  134 , the high-strength adhesive  136  may extend through the perforations  134  and causes a tackiness to be experienced on the first side  130  of the outer layer  128 . In this case, the first release member  142  may be left in place to cover the perforations  134  on the first side  130  of the outer layer  128  until removal of the switchable drape  106  is desired. Alternatively, a powder or sealing agent may be applied on the first side  130  of the outer layer  128 . 
     The switching solution is a solution that when applied to the high-strength adhesive  136  lessens the adhesive strength of the high-strength adhesive  136 . In other words, if the high-strength adhesive  136  has an initial adhesive strength of A 1 , after application of the switching solution, the high-strength adhesive  136  has a lesser adhesive strength, A 2 , for example, A 2 &lt;A 1 . The adhesive strength A 2  after application of the switching solution may be less than about 70% of the original adhesive strength, 70% A 1 , or even less, for example, 60% A 1 , 50% A 1 , 40 A 1 , 30% A 1 , 20% A 1 , 10% A 1 , or 0% A 1 . Many permutations are possible, but in one embodiment, the switchable drape  106  has twice the adhesive strength of a traditional drape, but at removal has only half or less than half of the adhesive strength of a traditional drape. 
     The switching solution may be one or more of the following: alcohols, such as methanol, propyl alcohols, and other alcohols such as butanols, esters such as butyl ethanoate (acetate), ketones, such as propanone (acetone), natural oils such as linseed, soyer, and blends of all these materials with each other, and may also be blended with water. The switching solution may contain additional components such as a local pain killer or analgesic, for example, Lidocaine, prilocaine, bupivacaine, or mixtures of these, or another suitable substance. The switching solution may be kept in a bottle, vial, pouch, sealed wipe, or other convenient storage or delivery means. 
     The switchable drape  106  may be formed in numerous ways. According to one illustrative embodiment, the outer layer  128  is formed from a drape material. The plurality of perforations  134  are then formed through the outer layer  128  by punching, cutting, or drilling, for example. The high-strength adhesive  136  is applied to the second, patient-facing side  132  of the outer layer  128 . The first release member  142  is applied to the first side  130  of the outer layer  128 . The second release member  148  is applied to the second, patient-facing side of the high-strength adhesive  136 . 
     In operation, according to one illustrative embodiment, the manifold  118  is deployed adjacent to the tissue site  101 . The switchable drape  106  is deployed over the manifold  118  and a portion of the epidermis  112  adjacent to the tissue site  101  to create the sealed space  120 . If not already applied, the reduced-pressure interface  124  is applied to provide fluid communication from a point exterior of the switchable drape  106  to the sealed space  120 . A reduced-pressure delivery conduit  126  is fluidly coupled between the reduced-pressure interface  124  and the reduced-pressure source  122 . The reduced-pressure source  122  is activated and reduced pressure is supplied to the sealed space  120  and distributed by the manifold  118 . After a desired treatment time has passed, the switchable drape  106  is removed. 
     The switchable drape  106  is removed by removing the first release member  142 , if applicable, and applying the switching solution on the first side  138  of the switchable drape  106 . The switching solution travels through the plurality of perforations  134  and wets the high-strength adhesive  136 . Wetting the high-strength adhesive  136  causes the adhesive strength of the high-strength adhesive  136  to decrease. The outer layer  128  of the switchable drape  106  is then removed from the patient  102 . 
     In another illustrative embodiment, a micro-pump is used as the reduced-pressure source  122 . In this embodiment, the micro-pump is coupled to the switchable drape  106 . In another illustrative embodiment, the switchable drape  106  may be used as a dressing without reduced pressure. 
     Referring now primarily to  FIG. 4 , a portion of another illustrative embodiment of a sealing subsystem  104  is presented. The sealing subsystem  104  is analogous in most respects to the sealing subsystem  104  of  FIGS. 1-3 , and accordingly, some parts are labeled but not further described here. This embodiment differs primarily in that the plurality of perforations  134  are formed only on a peripheral portion  154  of the outer layer  128 . The peripheral portion  154  is an outer band on the outer layer  128  that is sized to be exclusively or nearly exclusively over the epidermis  112  adjacent the tissue site  101 . In contrast, a central portion  156  of the outer layer  128  is over the tissue site  101  and does not have perforations  134 . The high-strength adhesive (analogous to  136  in  FIG. 3 ) is applied to the second, patient-facing side  132  of the outer layer  128  only on the peripheral portion  154 . A lower adhesive strength adhesive is used on the central portion  156  of the second, patient-facing side  132  of the outer layer  128 . This approach may allow for an even stronger adhesive to be used as the high-strength adhesive  136  without causing undue pain to the patient. 
     Referring now primarily to  FIG. 5 , a portion of another illustrative embodiment of a switchable drape  106  is presented. The switchable drape  106  is analogous in most respects to the switchable drape  106  of  FIGS. 1-3 , and accordingly, some parts are labeled but not further described here. This embodiment differs primarily in that the high-strength adhesive  136  further comprises a plurality of expansion members  158 . The expansion members  158  are configured to expand primarily perpendicularly to the second, patient-facing side  132  of the outer layer  128  when activated by the switching solution. The expansion members  158  may be, for example, compressed foam, where the foam is compressed and cooled below a transition temperature to temporarily fix the “set.” The “set” is released when the foam is contacted by a plasticizer contained within the switching solution. For example, a polyvinyl acetate foam could be set in this way and contacted with ethanol to plasticize the foam, thereby releasing the “set” and allowing the foam to expand. The expansion members  158  may also contain a foaming agent, such as a bicarbonate salt. When using the bicarbonate salt, the switching solution may include water and a weak acid (such as citric acid). When the water and the weak acid come into contact with the bicarbonate salt, carbon dioxide gas is released, providing an expanding force. The expansion members  158  expand perpendicularly to the epidermis  112  adjacent the tissue site  101  when activated by the switching solution, thereby lifting the outer layer  128  and weakening the high-strength adhesive  136 . This action facilitates removal of the switchable drape  106  from the patient. 
     Referring now primarily to  FIG. 6 , a portion of another illustrative embodiment of a switchable drape  106  is presented. The switchable drape  106  is analogous in most respects to the switchable drape  106  of  FIGS. 1-3 , and accordingly, some parts are labeled but not further described here. This embodiment differs primarily in that the switchable drape  106  includes a soluble layer  160  between the outer layer  128  and the high-strength adhesive  136 . The soluble layer  160  has a first side  162  and a second, patient-facing side  164 . The first side  162  is adjacent to the second, patient facing side  132  of the outer layer  128 . The second, patient-facing side  164  is adjacent to the first side  138  of the high-strength adhesive  136 . 
     The soluble layer  160  is such that when the switching solution or another solution (for example, water or aqueous solutions) is applied, the soluble layer  160  dissolves, or substantially dissolves, thereby loosening the soluble layer&#39;s grip on the first side  138  of the high-strength adhesive  136 . In this way, the outer layer  128  may be quickly removed. The soluble layer  160  may also keep the high-strength adhesive  136  from entering the perforations  134  during manufacture. 
     Referring now primarily to  FIG. 7 , a portion of another illustrative embodiment of a switchable drape  106  is presented. The switchable drape  106  is analogous in most respects to the switchable drape  106  of  FIGS. 1-3 , and accordingly, some parts are labeled but not further described here. This embodiment differs primarily in that a wicking layer  166  is disposed between the outer layer  128  and the high-strength adhesive  136 . The wicking layer  166  may be separate as shown or embedded in the high-strength adhesive  136 . The wicking layer  166  may be a lightweight, open material of woven or non-woven material. In some embodiments, the wicking layer  166  uses single threads. The threads of the woven or non-woven material of the wicking layer  166  may be continuous, may be scatter coated, or randomly distributed in the wicking layer  166 . The random fiber distribution may disrupt leak paths that may occur from the perimeter to the center. 
     The wicking layer  166  has a plurality of wicking-layer ends  168  at an edge  170  of the switchable drape  106 . The wicking layer  166  is operable to transport the switching solution from the wicking-layer ends  168  to at least a peripheral portion  172  of the high-strength adhesive  136 . The peripheral portion  172  may be similar to the peripheral portion  154  and may be an outer band of the adhesive layer  136  that is sized to be exclusively or nearly exclusively over the epidermis  112  adjacent the tissue site  101 . Because the wicking layer  166  moves the switching solution from the edge  170  inboard and exposes the switching solution to the high-strength adhesive  136  in the process, the outer layer  128  does not require perforations. If the wicking layer  166  causes a leak, the leak will not be to the tissue site  101  but to the reduced-pressure interface  124  as the adhesive layer  136  is interposed between the wicking layer  166  and the tissue site  101 . The wicking layer  166  may be laminated with a solvent soluble coating to decrease instances of leaks. 
     According to an illustrative embodiment associated  FIG. 7 , a tissue site on a patient is treated by applying a manifold (not shown, but analogous to  118 ) over the tissue and then applying the switchable drape  106  over the manifold and a portion of the epidermis adjacent to the tissue site to form a sealed space. Reduced pressure is applied to the sealed space to provide a reduced-pressure treatment. When a desired treatment time has elapsed, the user applies a switching solution to the wicking-layer ends  168 . The switching solution is wicked into the fibers of the wicking layer  166 . The high-strength adhesive  136  is thereby wetted by the switching solution on at least the peripheral portion  172  of the high-strength adhesive  136 . As a result, the high-strength adhesive  136  loses tackiness. After losing sufficient tackiness in the high-strength adhesive  136 , the outer layer  128  is removed. 
     Referring now primarily to  FIG. 8 , the sealing subsystem  104  may be stored and presented for use in a kit  174 . The kit  174  may have a package or container  176 . The container  176  may have a first compartment  178  for receiving the switchable drape  106 . The container  176  may have a second compartment  180  for receiving a container, vial  182 , wipe, or other item containing the switching solution. Another compartment (not shown) may be added to include skin preparation materials. In one embodiment, sealed skin preparation wipes may be disposed in the second compartment  180 . One skin preparation wipe may be used to prepare the skin and another to rub on the first side  130  of the outer layer  128  to remove the outer layer  128  after use of the sealing subsystem  104 . 
     According to an alternative method for treating a tissue site, a manifold is deployed proximate to the tissue site. The manifold and a portion of the patient&#39;s intact skin are covered with a medical drape (for example, switchable drape  106  but without perforations) to form a sealed space. Reduced pressure is delivered to the sealed space. After a desired treatment time, the reduced pressure is terminated. A hand tool is then used to form a plurality of perforations in the medical drape around the tissue site, and a switching solution is applied over the perforations. The switching solution causes the adhesive strength of the adhesive on the medical drape to decrease. The medical drape is removed. 
     In some illustrative embodiments, the perforations  134  may be located only in certain places or may be located in key places or concentrated in certain places for different effects. For example, as explained in connection with  FIG. 4 , the perforations  134  may only be in a peripheral portion  154 . In addition, the perforations  134  may be concentrated to form tear lines or tear patterns. The tear patterns or tear lines allow the switchable drape  106  to be torn by hand along the tear line or tear pattern. In this way, the switchable drape  106  may be sized by hand with out tools. In some embodiments, the perforations  134  may be located at locations, for example, over a joint, to facilitate stretching of the switchable drape  106 . 
     The systems, sealing subsystems, and switchable drapes herein may offer numerous advantages. Some of the advantages may include that the switchable drape may be “switched”—activated to have less adhesive strength—without requiring external energy; use of the switchable drape does not require special skills from current practices; the system is cost effective; the switchable drape provides an improved seal with the epidermis adjacent the tissue site; and the switchable drape can be used with existing systems. Other benefits and advantages exist. 
     Although the present invention and its advantages have been disclosed in the context of certain illustrative, non-limiting embodiments, it should be understood that various changes, substitutions, permutations, and alterations can be made without departing from the scope of the invention as defined by the appended claims. It will be appreciated that any feature that is described in connection to any one embodiment may also be applicable to any other embodiment. 
     It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. It will further be understood that reference to “an” item refers to one or more of those items. 
     The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate as understood by one skilled in the art. 
     Where appropriate, aspects of any of the embodiments described above may be combined with aspects of any of the other embodiments described to form further examples having comparable or different properties and addressing the same or different problems. 
     It will be understood that the above description of preferred embodiments is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments of the invention. Although various embodiments of the invention have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of the claims.