Patent Publication Number: US-2021187174-A1

Title: Dressing Interface With Integrated Fluid Conduit

Description:
RELATED APPLICATION 
     This application claims the benefit, under 35 U.S.C. § 119(e), of the filing of U.S. Provisional Patent Application No. 62/576,137, entitled “DRESSING INTERFACE WITH INTEGRATED FLUID CONDUIT,” filed Oct. 24, 2017, which is incorporated herein by reference for all purposes. 
    
    
     TECHNICAL FIELD 
     The invention set forth in the appended claims relates generally to tissue treatment systems and more particularly, but without limitation, to supplemental drainage with negative-pressure and/or instillation therapy. 
     BACKGROUND 
     Clinical studies and practice have shown that reducing pressure in proximity to a tissue site can augment and accelerate growth of new tissue at the tissue site. The applications of this phenomenon are numerous, but it has proven particularly advantageous for treating wounds. Regardless of the etiology of a wound, whether trauma, surgery, or another cause, proper care of the wound is important to the outcome. Treatment of wounds or other tissue with reduced pressure may be commonly referred to as “negative-pressure therapy,” but is also known by other names, including “negative-pressure wound therapy,” “reduced-pressure therapy,” “vacuum therapy,” “vacuum-assisted closure,” and “topical negative-pressure,” for example. Negative-pressure therapy may provide a number of benefits, including migration of epithelial and subcutaneous tissues, improved blood flow, and micro-deformation of tissue at a wound site. Together, these benefits can increase development of granulation tissue and reduce healing times. 
     There is also widespread acceptance that cleansing a tissue site can be highly beneficial for new tissue growth. For example, a wound can be washed out with a stream of liquid solution, or a cavity can be washed out using a liquid solution for therapeutic purposes. These practices are commonly referred to as “irrigation” and “lavage” respectively. “Instillation” is another practice that generally refers to a process of slowly introducing fluid to a tissue site and leaving the fluid for a prescribed period of time before removing the fluid. For example, instillation of topical treatment solutions over a wound bed can be combined with negative-pressure therapy to further promote wound healing by loosening soluble contaminants in a wound bed and removing infectious material. As a result, soluble bacterial burden can be decreased, contaminants removed, and the wound cleansed. 
     While the clinical benefits of negative-pressure therapy and/or instillation therapy are widely known, improvements to therapy systems, components, and processes may benefit healthcare providers and patients. 
     BRIEF SUMMARY 
     New and useful systems, apparatuses, and methods for providing drainage in a negative-pressure therapy environment are set forth in the appended claims. Illustrative embodiments are also provided to enable a person skilled in the art to make and use the claimed subject matter. 
     For example, in some embodiments, an apparatus for connecting a therapy device to a tissue site is described. The apparatus can include a housing having a flange and a conduit interface. A sheath may be coupled to the conduit interface. A conduit can be inserted through the sheath and the conduit interface. The sheath may form a fluid seal around the conduit, and a fluid conductor may be coupled to the conduit. 
     Additionally or alternatively, example methods may comprise connecting a therapy device to a tissue site having an undermined space. For example, in some embodiments a manifold can be applied to the tissue site, and a passage can be created through the manifold adjacent to the undermined space. A cover can be applied over the manifold, and a hole can be cut in the cover over the passage. A drain may be inserted through the hole and the passage into the undermined space. The drain can be fluidly coupled to a conduit inserted through a conduit interface of a housing. The housing can be moved down the conduit, extending a sheath coupled to the conduit interface and forming a fluid seal around the conduit. A flange of the housing can be attached to the cover, and the conduit can be coupled to the therapy device. 
     A system for connecting a therapy device to a tissue site is also described herein. The system can include a tissue interface configured to be disposed adjacent a tissue site, and a cover configured to be disposed over the tissue site to form a sealed therapeutic environment. A dressing interface can be configured to couple the therapy device to the sealed therapeutic environment. The dressing interface can include a body having a base and a drain port and a flexible coupling coupled to the drain port. A tube may have a first end configured to be coupled to the therapy device and a second end that may be inserted through the flexible coupling and the drain port. The flexible coupling may form a fluid seal around the tube. A drain can be coupled to the second end of the tube. 
     Objectives, advantages, and a preferred mode of making and using the claimed subject matter may be understood best by reference to the accompanying drawings in conjunction with the following detailed description of illustrative embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a functional block diagram of an example embodiment of a therapy system that can provide negative-pressure therapy and/or instillation therapy with drainage in accordance with this specification; 
         FIG. 2  is a perspective view illustrating additional details that may be associated with an example embodiment of the therapy system of  FIG. 1 ; 
         FIG. 3  is a sectional view taken along line  3 - 3  of  FIG. 2 , illustrating additional details of a dressing of the therapy system of  FIG. 2 ; 
         FIGS. 4A and 4B  are detail views of  FIG. 3 , illustrating additional details of the dressing during negative pressure therapy; 
         FIGS. 5A-5F  are sectional views illustrating additional details that may be associated with the application and use of the dressing of  FIG. 2 ; 
         FIG. 6  is a sectional view illustrating additional details that may be associated with another example embodiment of a dressing interface that can be used with the therapy system of  FIG. 2 ; 
         FIGS. 7A and 7B  are detail views illustrating additional details that may be associated with the dressing interface of  FIG. 6  during negative-pressure therapy; 
         FIG. 8  is a perspective view illustrating additional details that may be associated with an example embodiment of a drain that may be used with the therapy system of  FIG. 2 ; 
         FIG. 9  is a perspective view illustrating additional details that may be associated with an example embodiment of another drain that may be used with the therapy system of  FIG. 2 ; and 
         FIG. 10  is a perspective view illustrating additional details that may be associated with an example embodiment of another drain that may be used with the therapy system of  FIG. 2 . 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     The following description of example embodiments provides information that enables a person skilled in the art to make and use the subject matter set forth in the appended claims, but may omit certain details already well-known in the art. The following detailed description is, therefore, to be taken as illustrative and not limiting. 
     The example embodiments may also be described herein with reference to spatial relationships between various elements or to the spatial orientation of various elements depicted in the attached drawings. In general, such relationships or orientation assume a frame of reference consistent with or relative to a patient in a position to receive treatment. However, as should be recognized by those skilled in the art, this frame of reference is merely a descriptive expedient rather than a strict prescription. 
       FIG. 1  is a simplified functional block diagram of an example embodiment of a therapy system  100  that can provide negative-pressure therapy with instillation of topical treatment solutions to a tissue site in accordance with this specification. 
     The term “tissue site” in this context broadly refers to a wound, defect, or other treatment target located on or within tissue, including but not limited to, bone tissue, adipose tissue, muscle tissue, neural tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, or ligaments. A wound may include chronic, acute, traumatic, subacute, and dehisced wounds, partial-thickness burns, ulcers (such as diabetic, pressure, or venous insufficiency ulcers), flaps, and grafts, for example. The term “tissue site” may also refer to areas of any tissue that are not necessarily wounded or defective, but are instead areas in which it may be desirable to add or promote the growth of additional tissue. For example, negative pressure may be applied to a tissue site to grow additional tissue that may be harvested and transplanted. 
     Some tissue sites may include an undermined area or a tunnel. An undermined area can be a portion of a tissue site that extends under intact epidermal tissue peripheral to an opening at a surface of a tissue site. For example, the tissue site may be a wound having an opening through the epidermis. An undermined area may be a portion of the tissue site that extends laterally underneath intact epidermis. A tunnel may be a portion of the tissue site that extends further into the tissue. For example, a tissue site may extend through epidermal, dermal and subcutaneous tissue and having a concave shape. A tunnel can be a smaller opening formed in the concavity and extending an additional depth into the subcutaneous tissue. 
     The therapy system  100  may include a source or supply of negative pressure, such as a negative-pressure source  102 , a dressing  104 , a fluid container, such as a container  106 , and a regulator or controller, such as a controller  108 , for example. Additionally, the therapy system  100  may include sensors to measure operating parameters and provide feedback signals to the controller  108  indicative of the operating parameters. As illustrated in  FIG. 1 , for example, the therapy system  100  may include a pressure sensor  110 , an electric sensor  112 , or both, coupled to the controller  108 . As illustrated in the example of  FIG. 1 , the dressing  104  may comprise or consist of a tissue interface  114 , a cover  116 , a drain  124 , a dressing interface  128  or a combination of each in some embodiments. 
     The therapy system  100  may also include a source of instillation solution (e.g. saline). As illustrated in the example embodiment in  FIG. 1 , a solution source  118  may be fluidly coupled to the dressing  104 . The solution source  118  may be fluidly coupled to a positive-pressure source such as a positive-pressure source  120 , a negative-pressure source such as the negative-pressure source  102 , or both in some embodiments. A regulator, such as an instillation regulator  122 , may also be fluidly coupled to the solution source  118  and the dressing  104  to ensure proper dosage of instillation solution (e.g. saline) to a tissue site. For example, the instillation regulator  122  may comprise a piston that can be pneumatically actuated by the negative-pressure source  102  to draw instillation solution from the solution source during a negative-pressure interval and to instill the solution to a dressing during a venting interval. Additionally or alternatively, the controller  108  may be coupled to the negative-pressure source  102 , the positive-pressure source  120 , or both, to control dosage of instillation solution to a tissue site. In some embodiments, the instillation regulator  122  may also be fluidly coupled to the negative-pressure source  102  through the dressing  104 , as illustrated in the example of  FIG. 1 . 
     Some components of the therapy system  100  may be housed within or used in conjunction with other components, such as sensors, processing units, alarm indicators, memory, databases, software, display devices, or user interfaces that further facilitate therapy. For example, in some embodiments, the negative-pressure source  102  may be combined with the solution source  118 , the controller  108  and other components into a therapy unit. 
     In general, components of the therapy system  100  may be coupled directly or indirectly. For example, the negative-pressure source  102  may be directly coupled to the container  106 , and may be indirectly coupled to the dressing  104  through the container  106 . Coupling may include fluid, mechanical, thermal, electrical, or chemical coupling (such as a chemical bond), or a combination of couplings in some contexts. For example, the negative-pressure source  102  may be electrically coupled to the controller  108 , and may be fluidly coupled to one or more distribution components to provide a fluid path to a tissue site. In some embodiments, components may also be coupled by virtue of physical proximity, being integral to a single structure, or being formed from the same piece of material. 
     A distribution component is preferably detachable, and may be disposable, reusable, or recyclable. The dressing  104  and the container  106  are illustrative of distribution components. A fluid conductor is another illustrative example of a distribution component. A “fluid conductor,” in this context, broadly includes a tube, pipe, hose, conduit, or other structure with one or more lumina or open pathways adapted to convey a fluid between two ends. Typically, a fluid conductor, such as a tube, is an elongated, cylindrical structure with some flexibility, but the geometry and rigidity may vary. Moreover, some fluid conductors may be molded into or otherwise integrally combined with other components. Distribution components may also include or comprise interfaces or fluid ports to facilitate coupling and de-coupling other components. In some embodiments, a dressing interface, such as the dressing interface  128 , may facilitate coupling a fluid conductor to the dressing  104 . For example, such a dressing interface may be a SENSAT.R.A.C.™ Pad available from KCI of San Antonio, Tex. 
     A negative-pressure supply, such as the negative-pressure source  102 , may be a reservoir of air at a negative pressure, or may be a manual or electrically-powered device, such as a vacuum pump, a suction pump, a wall suction port available at many healthcare facilities, or a micro-pump, for example. “Negative pressure” generally refers to a pressure less than a local ambient pressure, such as the ambient pressure in a local environment external to a sealed therapeutic environment. In many cases, the local ambient pressure may also be the atmospheric pressure at which a tissue site is located. Alternatively, the pressure may be less than a hydrostatic pressure associated with tissue at the tissue site. Unless otherwise indicated, values of pressure stated herein are gauge pressures. References to increases in negative pressure typically refer to a decrease in absolute pressure, while decreases in negative pressure typically refer to an increase in absolute pressure. While the amount and nature of negative pressure applied to a tissue site may vary according to therapeutic requirements, the pressure is generally a low vacuum, also commonly referred to as a rough vacuum, between −5 mm Hg (−667 Pa) and −500 mm Hg (−66.7 kPa). Common therapeutic ranges are between −50 mm Hg (−6.7 kPa) and −300 mm Hg (−39.9 kPa). 
     The container  106  is representative of a container, canister, pouch, or other storage component, which can be used to manage exudates and other fluids withdrawn from a tissue site. In many environments, a rigid container may be preferred or required for collecting, storing, and disposing of fluids. In other environments, fluids may be properly disposed of without rigid container storage, and a re-usable container could reduce waste and costs associated with negative-pressure therapy. 
     A controller, such as the controller  108 , may be a microprocessor or computer programmed to operate one or more components of the therapy system  100 , such as the negative-pressure source  102 . In some embodiments, for example, the controller  108  may be a microcontroller, which generally comprises an integrated circuit containing a processor core and a memory programmed to directly or indirectly control one or more operating parameters of the therapy system  100 . Operating parameters may include the power applied to the negative-pressure source  102 , the pressure generated by the negative-pressure source  102 , or the pressure distributed to the tissue interface  114 , for example. The controller  108  is also preferably configured to receive one or more input signals, such as a feedback signal, and is programmed to modify one or more operating parameters based on the input signals. 
     Sensors, such as the pressure sensor  110  or the electric sensor  112 , are generally known in the art as an apparatus operable to detect or measure a physical phenomenon or property, and generally provide a signal indicative of the phenomenon or property that is detected or measured. For example, the pressure sensor  110  and the electric sensor  112  may be configured to measure one or more operating parameters of the therapy system  100 . In some embodiments, the pressure sensor  110  may be a transducer configured to measure pressure in a pneumatic pathway and convert the measurement to a signal indicative of the pressure measured. For example, the pressure sensor  110  may be a piezoresistive strain gauge. The electric sensor  112  may optionally measure operating parameters of the negative-pressure source  102 , such as the voltage or current, in some embodiments. Preferably, the signals from the pressure sensor  110  and the electric sensor  112  are suitable as an input signal to the controller  108 , but some signal conditioning may be appropriate in some embodiments. For example, the signal may need to be filtered or amplified before it can be processed by the controller  108 . Typically, the signal is an electrical signal, but may be represented in other forms, such as an optical signal. 
     The tissue interface  114  can generally be adapted to partially or fully contact a tissue site. The tissue interface  114  may take many forms, and may have many sizes, shapes, or thicknesses depending on a variety of factors, such as the type of treatment being implemented or the nature and size of a tissue site. For example, the size and shape of the tissue interface  114  may be adapted to the contours of deep and irregular shaped tissue sites. Moreover, any or all of the surfaces of the tissue interface  114  may have projections or an uneven, course, or jagged profile that can induce strains and stresses on a tissue site, which can promote granulation at the tissue site. 
     In some embodiments, the tissue interface  114  may be a manifold. A “manifold” in this context generally includes any substance or structure providing a plurality of pathways adapted to collect or distribute fluid across a tissue site under pressure. For example, a manifold may be adapted to receive negative pressure from a source and distribute negative pressure through multiple apertures across a tissue site, which may have the effect of collecting fluid from across a tissue site and drawing the fluid toward the source. In some embodiments, the fluid path may be reversed or a secondary fluid path may be provided to facilitate delivering fluid such as from a source of instillation solution across a tissue site. 
     In some illustrative embodiments, the pathways of a manifold may be interconnected to improve distribution or collection of fluids across a tissue site. In some illustrative embodiments, a manifold may be a porous foam material having interconnected cells or pores. For example, cellular foam, open-cell foam, reticulated foam, porous tissue collections, and other porous material such as gauze or felted mat generally include pores, edges, and/or walls adapted to form interconnected fluid channels. Liquids, gels, and other foams may also include or be cured to include apertures and fluid pathways. In some embodiments, a manifold may additionally or alternatively comprise projections that form interconnected fluid pathways. For example, a manifold may be molded to provide surface projections that define interconnected fluid pathways. 
     The average pore size of foam may vary according to needs of a prescribed therapy. For example, the tissue interface  114  may be foam having pore sizes in a range of about 400-600 microns. The tensile strength of the tissue interface  114  may also vary according to needs of a prescribed therapy. For example, the tensile strength of foam may be increased for instillation of topical treatment solutions. In some examples, the tissue interface  114  may be reticulated polyurethane foam such as found in GRANUFOAM™ dressing or V.A.C. VERAFLO™ dressing, both available from KCI of San Antonio, Tex. 
     The tissue interface  114  may be either hydrophobic or hydrophilic. In an example in which the tissue interface  114  may be hydrophilic, the tissue interface  114  may also wick fluid away from a tissue site, while continuing to distribute negative pressure to the tissue site. The wicking properties of the tissue interface  114  may draw fluid away from a tissue site by capillary flow or other wicking mechanisms. An example of a hydrophilic foam is a polyvinyl alcohol, open-cell foam such as V.A.C. WHITEFOAM™ dressing available from KCI of San Antonio, Tex. Other hydrophilic foams may include those made from polyether. Other foams that may exhibit hydrophilic characteristics include hydrophobic foams that have been treated or coated to provide hydrophilicity. 
     The tissue interface  114  may further promote granulation at a tissue site when pressure within the sealed therapeutic environment is reduced. For example, any or all of the surfaces of the tissue interface  114  may have an uneven, coarse, or jagged profile that can induce microstrains and stresses at a tissue site if negative pressure is applied through the tissue interface  114 . 
     In some embodiments, the tissue interface  114  may be constructed from bioresorbable materials. 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 tissue interface  114  may further serve as a scaffold for new cell-growth, or a scaffold material may be used in conjunction with the tissue interface  114  to promote cell-growth. A scaffold is generally 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. Illustrative examples of scaffold materials include calcium phosphate, collagen, PLA/PGA, coral hydroxy apatites, carbonates, or processed allograft materials. 
     In some embodiments, the cover  116  may provide a bacterial barrier and protection from physical trauma. The cover  116  may also be constructed from a material that can reduce evaporative losses and provide a fluid seal between two components or two environments, such as between a therapeutic environment and a local external environment. The cover  116  may be, for example, an elastomeric film or membrane that can provide a seal adequate to maintain a negative pressure at a tissue site for a given negative-pressure source. The cover  116  may have a high moisture-vapor transmission rate (MVTR) in some applications. For example, the MVTR may be at least about 300 g/m 2  per twenty-four hours in some embodiments. In some example embodiments, the cover  116  may be a polymer drape, such as a polyurethane film, that is permeable to water vapor but impermeable to liquid. Such drapes typically have a thickness in the range of about 25-50 microns, inclusive of an attachment device. For permeable materials, the permeability generally should be low enough that a desired negative pressure may be maintained. 
     An attachment device may be used to attach the cover  116  to an attachment surface, such as undamaged epidermis, a gasket, or another cover. The attachment device may take many forms. For example, an attachment device may be a medically-acceptable, pressure-sensitive adhesive configured to bond the cover  116  to epidermis around a tissue site. In some embodiments, some or all of the cover  116  may be coated with an adhesive, such as an acrylic adhesive, which may have a coating weight between about 25-65 grams per square meter (g.s.m.). Thicker adhesives, or combinations of adhesives, may be applied in some embodiments to improve the seal and reduce leaks. Other example embodiments of an attachment device may include a double-sided tape, paste, hydrocolloid, hydrogel, silicone gel, or organogel. 
     The solution source  118  may also be representative of a container, canister, pouch, bag, or other storage component, which can provide a solution for instillation therapy. Compositions of solutions may vary according to a prescribed therapy, but examples of solutions that may be suitable for some prescriptions include hypochlorite-based solutions, silver nitrate (0.5%), sulfur-based solutions, biguanides, cationic solutions, and isotonic solutions. 
     The fluid mechanics of using a negative-pressure source to reduce pressure in another component or location, such as within a sealed therapeutic environment, can be mathematically complex. However, the basic principles of fluid mechanics applicable to negative-pressure therapy and instillation are generally well-known to those skilled in the art, and the process of reducing pressure may be described illustratively herein as “delivering,” “distributing,” or “generating” negative pressure, for example. 
     In general, exudates and other fluids flow toward lower pressure along a fluid path. Thus, the term “downstream” typically implies a position in a fluid path relatively closer to a source of negative pressure or further away from a source of positive pressure. Conversely, the term “upstream” implies a position relatively further away from a source of negative pressure or closer to a source of positive pressure. Similarly, it may be convenient to describe certain features in terms of fluid “inlet” or “outlet” in such a frame of reference. This orientation is generally presumed for purposes of describing various features and components herein. However, the fluid path may also be reversed in some applications (such as by substituting a positive-pressure source for a negative-pressure source) and this descriptive convention should not be construed as a limiting convention. 
     In operation, the tissue interface  114  may be placed within, over, on, or otherwise proximate to a tissue site. If the tissue site is a wound, for example, the tissue interface  114  may partially or completely fill the wound, or may be placed over the wound. The cover  116  may be placed over the tissue interface  114  and sealed to an attachment surface near the tissue site. For example, the cover  116  may be sealed to undamaged epidermis peripheral to a tissue site. Thus, the dressing  104  can provide a sealed therapeutic environment proximate to a tissue site, substantially isolated from the external environment, and the negative-pressure source  102  can reduce the pressure in the sealed therapeutic environment. Negative pressure applied across the tissue site through the tissue interface  114  in the sealed therapeutic environment can induce macrostrain and micro-strain in the tissue site, as well as remove exudates and other fluids from the tissue site, which can be collected in container  106 . 
     Negative-pressure therapy can provide evacuation of fluids and exudates from a tissue site, including a tissue site having an undermined area or a tunnel, and instillation therapy can provide therapeutic fluids to a tissue site, including an undermined area or a tunnel. In addition to negative-pressure therapy and/or instillation therapy, supplemental fluid conductors can be used to drain or to supply additional fluids to an undermined area or a tunnel of a tissue site. A separate exit for a supplemental fluid conductor may pass between the cover and the periwound epidermis. An exit between the periwound epidermis and the cover may be difficult to fluidly seal or require supplemental devices to ensure a fluid seal between the periwound epidermis and the cover. Ultimately, a separate exit from the sealed therapeutic environment can create an avenue for leakage across a cover. Leakage can decrease the efficiency of a negative-pressure source or an instillation source, decreasing the effectiveness of therapy. 
     Use of a supplemental fluid conductor for drainage or supplemental fluids can lead to other undesirable outcomes. For example, a supplemental fluid conductor used for drainage, such as a Jackson-Pratt drain, having a separate exit from the sealed therapeutic environment does not use negative pressure to draw fluids and exudates from the sealed therapeutic environment, which can decrease drainage efficiency. If the supplemental fluid conductor is inserted into the undermined area or tunnel, a user may have difficulty appropriately sizing the fluid conductor. For example, the volume of the sealed therapeutic environment can change during a cycle of negative-pressure therapy. If the supplemental fluid conductor is too long, the fluid conductor can impinge an end of the undermined area or tunnel when the sealed therapeutic environment is at a minimum volume, causing additional tissue trauma. Alternatively, if the supplemental fluid conductor is too short, the fluid conductor can be completely removed from the undermined area or tunnel when the sealed therapeutic environment is at a maximum volume, preventing the fluid conductor from providing drainage or supply of fluids to the undermined area or the tunnel. 
     A fluid conductor affixed to a dressing interface may manifold negative pressure only to an undermined area or tunnel and not to a tissue interface, which can decrease the effectiveness of the negative-pressure therapy. Devices having a fluid conductor affixed to a dressing interface may also require specialized training to place and use the fluid conductor and the dressing interface. 
     The therapy system  100  can overcome these and other problems by providing a fluid conductor coupled to a dressing interface. The fluid conductor can provide drainage or fluids to an undermined area or a tunnel while also providing distribution of fluids to a tissue interface. The fluid conductor can also move relative to the dressing interface. For example, in some embodiments of the therapy system  100 , the therapy system  100  includes the drain  124 , fluidly coupled to the dressing interface  128 . The drain  124  provides drainage through the dressing interface  128 , while accommodating the application of therapies, such as negative-pressure therapy and instillation therapy. 
       FIG. 2  is a perspective view of an example of a therapy system  200 , illustrating additional details that may be associated with some embodiments. The therapy system  200  may be similar to and include elements of the therapy system  100  of  FIG. 1 . Similar components have similar numbers indexed to  200 . The therapy system  200  can include a negative-pressure source  202  and a dressing  204  forming a sealed therapeutic environment over a tissue site  201 . The negative-pressure source  202  may be fluidly coupled to the dressing  204  with a fluid conductor such as a conduit  203 . 
     The negative-pressure source  202  may be similar to and operate as described above with respect to the negative-pressure source  102 . The negative-pressure source  202  can include a container, similar to the container  106 , a controller, similar to the controller  108 , and one or more sensors, similar to the pressure sensor  110  and the electric sensor  112 . The conduit  203  may have a first end  205  coupled to the negative-pressure source  202  and a second end  207 . The conduit  203  may have one or more lumens configured to provide a fluid path between the dressing  204  and the negative-pressure source  202 . For example, the conduit  203  may have a central lumen extending between the first end  205  and the second end  207 . In other embodiments, the conduit  203  may have a central lumen or primary lumen and one or more peripheral lumens or ancillary lumens surrounding the central lumen. 
     The dressing  204  may be similar to and operate as described above with respect to the dressing  104 . The dressing  204  can include a tissue interface  214 , a cover  216 , a drain  224 , and a dressing interface  228 . The tissue interface  214 , the cover  216 , the drain  224 , and the dressing interface  228  may be similar to and operate as described above with respect to the tissue interface  114 , the cover  116 , the drain  124 , and the dressing interface  128 . 
       FIG. 3  is a sectional view taken along line  3 - 3  of  FIG. 2 , illustrating additional details of the dressing  204  of the therapy system  200  of  FIG. 2 . The dressing interface  228  may include a base, such as a flange  230  and a housing, such as a connector body  232 . The connector body  232  may be a dome-shaped body forming a cavity  234  having a cavity aperture  236 . In some embodiments, the cavity aperture  236  may have a circular shape. In other embodiments, the cavity aperture  236  may be ovoid or other shapes. The flange  230  may be an annular body having an inner diameter  238  and an outer diameter  240 . The inner diameter  238  of the flange  230  may be coupled to the connector body  232  at the cavity aperture  236  and extend radially outward to the outer diameter  240 . In some embodiments, the flange  230  and the cavity aperture  236  may be occupy a same horizontal plane, and the cavity aperture  236  and the inner diameter  238  of the flange  230  may be coincident. 
     A conduit interface, such as a drain port  242 , may be coupled to the connector body  232 . For example, the drain port  242  can be an elbow connector extending from the connector body  232 . In the illustrated embodiment, the drain port  242  may be tubular body coupled to the connector body  232  proximate an apex of the connector body  232 . The drain port may extend a distance radially outward and parallel to the flange  230 . An end of the drain port  242  is spaced from an exterior surface of the connector body  232 . In other embodiments, the drain port  242  may be coupled to an apex of the connector body  232  and extend away from the connector body perpendicular to the flange  230  so that an end of the drain port  242  is spaced from an exterior surface of the connector body  232 . The drain port  242  may include a drain port lumen  244  fluidly coupled to the cavity  234  and configured to receive a fluid conductor, such as the drain  224  or the conduit  203 . The drain port lumen  244  may have a radius between about 2.5 mm and about 3.5 mm. In some embodiments, the flange  230 , the connector body  232 , and the drain port  242  may be integrally formed into the dressing interface  228 . For example, the dressing interface  228  may be mold, cast, or machined to include the flange  230 , the connector body  232 , and the drain port  242 . 
     In some embodiments, the dressing interface  228  may include a drape ring or a drape pad. A drape ring may be a ring of adhesive material. A drape ring can be affixed to a surface of the flange  230  of the dressing interface  228  that is on an opposite side of the flange  230  from the drain port  242 . A drape pad may be a ring of material similar to the cover  216 . A drape pad can be affixed to a surface of the flange  230  of the dressing interface  228  that is on an opposite side of the flange  230  from the drain port  242 . Both a drape ring and a drape pad may have an opening coincident with the cavity aperture  236 . In some embodiments, the drape ring and a drape pad can couple the dressing interface  228  to the cover  216 . In other embodiments, the dressing interface  228  can be affixed to the cover  216  using drape tape or other similar devices. 
     The drain  224  may have a distal end, such as a first end  249 , and a proximal end, such as a second end  251 . The drain  224  can also include at least one lumen  250 , and a plurality of perforations  252 . For example, the drain  224  may be a conduit having the at least one lumen  250  suitable for conveying fluid from the first end  249  of the drain  224  to the second end  251  of the drain  224 . A length between the first end  249  and the second end  251  may be between about 50 mm and about 150 mm. The plurality of perforations  252  may penetrate a sidewall of the drain  224 , providing fluid communication between the lumen  250  and a surrounding environment across the sidewall. In some embodiments, the plurality of perforations  252  may extend the length of the drain  224  from the first end  249  to the second end  251 . In other embodiments, the plurality of perforations may extend a portion of the length of the drain  224  between the first end  249  and the second end  251 . The plurality of perforations  252  may have a regularly repeating pitch both around a circumference of the drain  224  and the length of the drain  224 . In other embodiments, the pitch of the plurality of perforations  252  may not be regularly repeating. The plurality of perforations  252  may each have a diameter sized to provide fluid flow to the lumen  250 . For example, each perforation of the plurality of perforations  252  may have a diameter between about 1 mm and about 2 mm. 
     The first end  249  of the drain  224  may protrude from the cavity  234 . For example, the first end  249  of the drain  224  extends from the cavity  234  through a plane occupied by the flange  230  and the cavity aperture  236 . The second end  251  of the drain  224  may pass through the drain port  242 . For example, the second end  251  of the drain  224  may pass through the drain port lumen  244  of the drain port  242 . Preferably, the drain port lumen  244  of the drain port  242  may have a radius about 0.2 mm to about 0.5 mm larger than a radius of the exterior of the drain  224 . For example, if the drain  224  has a radius of about 2 mm to about 3.5 mm, a diameter between about 4 mm and about 7 mm, the drain port lumen  244  may have a radius between about 2.5 mm and about 3.5 mm, a diameter between about 5 mm and about 7 mm. In some embodiments, the drain  224  may move through the drain port lumen  244  relative to the drain port  242 . For example, the drain  224  and the drain port  242  may have a low relative coefficient of friction, permitting the drain  224  to slide through the drain port lumen  244  relative to the drain port  242 . 
     The second end  251  of the drain  224  may be coupled to the second end  207  of the conduit  203 , forming a solid bond between the drain  224  and the conduit  203 . For example, the second end  251  of the drain  224  may be bonded, adhered, fused, welded, or otherwise joined to the second end  207  of the conduit  203 . In an exemplary embodiment, the conduit  203  and the drain  224  may be formed of a polyurethane material, and the conduit  203  and the drain  224  may be coupled using an adhesive or joining component suitable for adhering polyurethane materials. In other embodiments, the drain  224  may be a portion of the conduit  203  having the plurality of perforations  252  formed therein. For example, the conduit  203  may have a portion that is perforated to form the plurality of perforations  252 . 
     A flexible coupling, such as a sheath  246 , can be coupled to the drain port  242 . The sheath  246  can be a tube having an inner diameter  254  configured to receive an end of the drain port  242 . In some embodiments, the sheath  246  may be formed from a polythene film, polyurethane film, or other soft flexible polymer film. The sheath  246  may have a wall thickness or film thickness between about 40 microns and about 70 microns. In other embodiments, the sheath  246  may have a wall thickness between about 70 microns and about 100 microns. A first end  256  of the sheath  246  may be coupled to the drain port  242 . In some embodiments, the sheath  246  may be bonded to the drain port  242  using an adhesive or joining component. For example, the drain port  242  and the sheath  246  may be formed from a polyurethane material. The first end  256  of the sheath  246  may be placed around the drain port  242  and sealed to the drain port  242  using a suitable adhesive, such as an acrylic pressure sensitive adhesive. In other embodiments, a polyurethane, acrylic, silicone, or hydrogel adhesive having a thickness between about 20 gsm and about 50 gsm may be used. Preferably, the coupling process establishes a solid bond. A solid bond may be a coupling having a bond strength greater than the elastic limit of the materials being joined so that the material would fail prior to the bond between the materials failing. 
     The sheath  246  may have a second end  258  opposite the first end  256 . The second end  258  of the sheath  246  may receive the conduit  203 . For example, the conduit  203  having the drain  224  coupled to the second end  207  may be inserted into the second end  258  of the sheath  246  and through the drain port  242 . The first end  249  of the drain  224  can protrude from the dressing interface  228  as described above. The second end  258  of the sheath  246  can be coupled to the conduit  203  so that the second end  258  of the sheath  246  moves with the conduit  203  in response to relative motion between the conduit  203  and the dressing interface  228 . Preferably, the sheath  246  and the conduit  203  may be joined using a coupling method suitable for the materials of the respective components. For example, if the sheath  246  is formed from polyurethane and the conduit  203  is formed from polyurethane, an adhesive suitable for joining polyurethane materials may be used to adhere the sheath  246  to the conduit  203 . In some embodiments, the second end  258  of the sheath  246  may be adhered to the conduit  203  using an acrylic pressure sensitive adhesive. In other embodiments, a polyurethane, acrylic, silicone, or hydrogel adhesive having a thickness between about 20 gsm and about 50 gsm may be used. Other coupling methods can be used to couple the sheath  246  and the conduit  203 , including bonding, welding, friction coupling, or other suitable joining methods. In some embodiments, a portion of the conduit  203  may extend into the sheath  246 , so that the second end  258  of the sheath  246  is spaced apart from the second end  207  of the conduit  203 . In other embodiments, the sheath  246  can be coupled to the conduit  203  where the conduit  203  joins the drain  224 . Preferably, the sheath  246  may be coupled to the drain port  242  and the conduit  203  so that the sheath  246  forms a fluid seal to both the drain port  242  and the conduit  203 . 
       FIG. 4A  and  FIG. 4B  are detail views of a portion of the dressing interface  228  of  FIG. 3 , illustrating additional details during negative-pressure therapy. In some embodiments, the sheath  246  may move between a first position and a second position. As shown in  FIG. 4A , the sheath  246  may have a first length  247 . The first length  247  of the sheath  246  may be between about 5 mm and about 10 mm. The sheath  246  and the drain  224  may form an annulus  253  between an exterior of the drain  224  and the inner diameter  254  of the sheath  246 . As shown in  FIG. 4B , the sheath  246  may have a second length  248 . The second length  248  may be between about 50 mm and about 150 mm. The sheath  246  may have an elasticity permitting the sheath  246  to transition between the first length  247  and the second length  248 . In some embodiments, the sheath  246  may transition between the first length  247  and the second length  248  by stretching. For example, the sheath  246  may be formed from a polyurethane material having an elasticity permitting an elongation to about three times the un-extended length of the sheath  246  without an elastic force urging retraction. 
       FIGS. 5A-5F  are sectional views illustrating additional details that may be associated with application and use of the dressing  204  of  FIG. 2 . As shown in  FIG. 5A , a tissue site  201  may have a tunnel  260 . In some embodiments, a tissue site  201  may be evaluated to determine if the tissue site  201  includes the tunnel  260 . The depth of the tunnel  260  can be evaluated to determine an approximate depth of the tunnel  260 . In view of the depth of the tunnel  260 , the drain  224  can be evaluated to determine if the drain  224  can be shortened, such as by cutting. The drain  224  may need to be shortened if the tunnel  260  is relatively shallow relative to the tissue site  201 . Cutting may not be needed as the drain  224  and the dressing interface  228  may accommodate relative movement. As shown in  FIG. 5B , the tissue interface  214  can be shaped and placed into the tissue site  201 . Shaping the tissue interface  214  can include forming an opening  262  through the tissue interface  214 . For example, a portion of the tissue interface  214  may be removed from a region of the tissue interface  214  above or adjacent to the tunnel  260 . 
     As shown in  FIG. 5C , a cover, such as the cover  216 , can be placed over the tissue interface  214  and secured to epidermis surrounding the tissue site  201 . An opening  264  can be cut in the cover  216 . The opening  264  can be adjacent to the opening  262  formed in the tissue interface  214  over the tunnel  260 . In some embodiments, the opening  264  may be larger than the opening  262  so that a portion of the surface of the tissue interface  214  is exposed through the cover  216 . Preferably, the opening  264  may have a diameter approximately equal to a diameter of the cavity aperture  236 . As shown in  FIG. 5D , the drain  224  can be inserted through the opening  264  and the opening  262  and into the tunnel  260 . In some embodiments, the second end  251  of the drain  224  may be flush with a surface of the tissue interface  214  exposed through the opening  264 . Preferably, the second end  251  of the drain  224  may protrude from the opening  262  through the opening  264 . 
     As shown in  FIG. 5E , the dressing interface  228  can be secured to the cover  216 . The dressing interface  228  may be coupled to the conduit  203  through the sheath  246 . While the drain  224  is being inserted into the opening  262 , the sheath  246  may have the first length  247 . The flange  230  of the dressing interface  228  can be brought adjacent to the cover  216 . In some embodiments, the cavity aperture  236  may be positioned coincident with the opening  264  in the cover  216 . As the dressing interface  228  is brought adjacent to the cover  216 , the sheath  246  may stretch from the first length  247 . In some embodiments, the sheath  246  may stretch from the first length  247  to the second length  248 . Preferably, the sheath  246  may stretch from the first length  247  to a length less than the second length  248 . 
     Referring to  FIG. 5F , the conduit  203  can be connected to the negative-pressure source  202 , and the negative-pressure source  202  can be operated to draw fluid from the sealed therapeutic environment formed by the cover  216  and the dressing interface  228 . As the negative-pressure source  202  draws fluid from the sealed therapeutic environment, atmospheric pressure can compress the tissue interface  214  and the cover  216  into the tissue site  201 , decreasing a volume of the sealed therapeutic environment. As the dressing  204  compresses, the tissue interface  214  and the cover  216  may move toward the tunnel  260  of the tissue site  201 ; the flange  230  of the dressing interface  228  may move with the cover  216  through the coupling between the flange  230  and the cover  216 . Movement of the flange  230  will similarly draw the connector body  232  and the drain port  242  toward the tunnel  260 . The first end  249  of the drain  224  contacts a surface of the tunnel  260 , preventing the drain  224  from moving further into the tunnel  260 . In response, the conduit  203  will similarly not be drawn toward the tunnel  260 . The sheath  246 , coupling the conduit  203  to the drain port  242 , can stretch, so that the optimal length of the drain  224  remains in the tunnel  260 . In some embodiments, the sheath  246  stretches from the first length  247  to the second length  248  to accommodate the relative movement between the drain  224  and the dressing interface  228 . 
     Fluid may be distributed through the tissue site  201  and the tunnel  260 . For example, during negative-pressure therapy, the conduit  203  may draw fluid from the drain  224 . In turn, the drain  224  may draw fluid from the tunnel  260  through the lumen  250 . The drain  224  may also draw fluid form the cavity  234  through the plurality of perforations  252  exposed to the cavity  234  proximate the second end  251  of the drain  224 . The fluid drawn from the cavity  234  can cause fluid to be drawn from the tissue interface  214  through the cavity aperture  236  and the opening  264  in the cover  216 . Fluid may also be drawn from the tissue interface  214  through the plurality of perforations  252  of the drain  224  in portions of the drain  224  between the first end  249  and the second end  251  exposed to the tissue interface  214  through the opening  262 . Similar fluid pathways may be formed during an instillation cycle; however, fluid may flow in the opposite direction. 
     In some embodiments, the annulus  253  may be formed between the exterior surface of the conduit  203 , the exterior surface of the drain  224 , and the inner diameter  254  of the sheath  246 . As fluid is drawn from the sealed therapeutic environment, atmospheric pressure may urge the inner diameter  254  of the sheath  246  into contact with the drain  224 , collapsing the annulus  253 . The sheath  246  may collapse onto the exterior surface of the drain  224 ; however, the thickness of the film forming the sheath  246  can prevent the sheath  246  from being drawn into the plurality of perforations  252 . The sheath  246  may cover the plurality of perforations  252 , blocking fluid flow across the sidewall of the drain  224 . Fluid flow can continue through the lumen  250  of the drain  224 . If a therapeutic target pressure is reached in the sealed therapeutic environment, the sheath  246  may be fully collapsed around the drain  224 , inhibiting further movement of the drain  224  relative to the dressing interface  228 . 
     In some embodiments, the therapy system  200  may be used to provide instillation therapy. For example, the negative-pressure source  202  may be replaced with an instillation source. Fluids can be delivered to the tissue site  201  through the drain  224 . In both an instillation therapy and a negative-pressure therapy environment, the sheath  246  may accommodate movement of the conduit  203  and the drain  224  relative to the dressing interface  228 , while maintaining a fluid seal between the conduit  203  and the drain port  242 . The ability to accommodate relative movement between the conduit  203  and the dressing interface  228  decreases instances of leaks from the sealed therapeutic environment due to patient movement. 
       FIG. 6  is a sectional view, illustrating additional details of another drain  324  and dressing interface  328 . The drain  324  and the dressing interface  328  may be similar to and operate as described above with respect to the drain  224  and the dressing interface  228 . Similar components may have similar reference numbers indexed to  300 . The dressing interface  328  may include a base, such as a flange  330  and a housing, such as a connector body  332 , forming a cavity  334  and a cavity aperture  336 . The flange  330  may be an annular body having an inner diameter  338  and an outer diameter  340 . The inner diameter  338  of the flange  330  may be coupled to the connector body  332  at the cavity aperture  336  and extend radially outward to the outer diameter  340 . 
     A drain port  342  may be coupled to the connector body  332 . For example, the drain port  342  may be coupled to an apex of the connector body  332  and extend vertically and perpendicular to the flange  330  so that an end of the drain port  342  is spaced from an exterior surface of the connector body  332 . The drain port  342  may include a drain port lumen  344  fluidly coupled to the cavity  334  and configured to receive a fluid conductor, such as the drain  324  or the conduit  203 . In some embodiments, the flange  330 , the connector body  332 , and the drain port  342  may be integrally formed into the dressing interface  328 . For example, the dressing interface  328  may be mold, cast, or machined to include the flange  330 , the connector body  332 , and the drain port  342 . In some embodiments, the dressing interface  328  may include a drape ring or a drape pad. In some embodiments, the drape ring and a drape pad can couple the dressing interface  328  to the cover  216 . In other embodiments, the dressing interface  328  can be affixed to the cover  216  using drape tape or other similar devices. 
     The drain  324  may have a distal end, such as a first end  349 , and a proximal end, such as a second end  351 . The drain  324  can also include at least one lumen  350 , and a plurality of perforations  352 . A length between the first end  349  and the second end  351  may be between about 50 mm and about 150 mm. The plurality of perforations  352  may penetrate a sidewall of the drain  324 , providing fluid communication with the lumen  350  across the sidewall. In some embodiments, the plurality of perforations  352  may extend the length of the drain  324  from the first end  349  to the second end  351 . The plurality of perforations  352  may each have a diameter sized to provide fluid flow to the lumen  350 . 
     The first end  349  of the drain  324  may protrude from the cavity  334 . For example, the first end  349  of the drain  324  extends from the cavity  334  through a plane occupied by the flange  330  and the cavity aperture  336 . The second end  351  of the drain  324  may pass through the drain port  342 . For example, the second end  351  of the drain  324  may pass through the drain port lumen  344  of the drain port  342 . The second end  351  of the drain  324  may be coupled to the second end  207  of the conduit  203 , forming a solid bond between the drain  324  and the conduit  203 . For example, the second end  351  of the drain  324  may be bonded, adhered, fused, welded, or otherwise joined to the second end  207  of the conduit  203 . Preferably, the drain port lumen  344  of the drain port  342  may have a diameter between about 5 mm and about 7 mm. Preferably, the radius of the drain port lumen  344  is about 0.2 mm to about 0.5 mm larger than a radius of the exterior of the drain  324 . In some embodiments, the drain port  342  may include ribs or fins  372  extending radially inward from a surface of the drain port lumen  344 . The fins  372  may be coupled to the surface of the drain port lumen  344 . The fins  372  may extend a length of the drain port  342  from the cavity  334  to an end of the drain port  342 . In some embodiments, the fins  372  may extend radially from a surface of the drain port  242  into the drain port lumen  344  between about 0.2 mm and about 0.5 mm. 
       FIG. 7A  is a sectional view taken along line  7 A- 7 A of  FIG. 6 , illustrating additional details of the dressing interface  328 . The fins  372  may be circumferentially spaced around the drain port lumen  344 . In some embodiments, four fins  372  can be circumferentially spaced around the drain port lumen  344 . In other embodiments, there may be more or fewer fins  372 . For example, if the diameter of the drain port lumen  344  is increased, additional fins  372  may be used. Similarly, if the diameter of the drain port lumen  344  is decreased, fewer fins  372  may be used. In some embodiments, the drain  324  may move through the drain port lumen  344  relative to the drain port  342 . For example, the drain  324  and the fins  372  may have a low relative coefficient of friction, permitting the drain  324  to slide through the drain port lumen  344  relative to the drain port  342 . 
       FIG. 7B  is a detail view illustrating additional details of the dressing interface  328  of  FIG. 6 . A flexible coupling, such as a sheath  346  having a bellows  370  can be coupled to the drain port  342  and the conduit  203 . The sheath  346  can be a tube having an inner diameter  354  configured to receive an end of the drain port  342 . In some embodiments, the sheath  346  may be formed from a polythene film, polyurethane film, or other soft flexible polymer film. The sheath  346  may have a wall thickness or film thickness between about 40 microns and about 70 microns. In other embodiments, the sheath  346  may have a wall thickness between about 70 microns and 100 microns. A first end  356  of the sheath  346  may be coupled to the drain port  342 . In some embodiments, the sheath  346  may be bonded to the drain port  342  using an adhesive or joining component. For example, the drain port  342  and the sheath  346  may be formed from a polyurethane material. The first end  356  of the sheath  346  may be placed around the drain port  342  and sealed to the drain port  342  using a suitable adhesive, such as an acrylic pressure sensitive adhesive. In other embodiments, a polyurethane, acrylic, silicone, or hydrogel adhesive having a thickness between about 20 gsm and about 50 gsm may be used. Preferably, the coupling process establishes a solid bond. 
     The sheath  346  may have a second end  358  opposite the first end  356 . The second end  358  of the sheath  346  may receive the conduit  203 . For example, the conduit  203  having the drain  324  coupled to the second end  207  may be inserted into the second end  358  of the sheath  346  and through the drain port  342 . The second end  358  of the sheath  346  can be coupled to the conduit  203  so that the second end  358  of the sheath  346  can move with the conduit  203 . Preferably, the sheath  346  and the conduit  203  may be joined using a coupling method suitable for the materials of the respective components. For example, if the sheath  346  is formed from polyurethane and the conduit  203  is formed from polyurethane, an adhesive suitable for joining polyurethane materials may be used to adhere the sheath  346  to the conduit  203 . In some embodiments, the second end  358  of the sheath  346  may be adhered to the conduit  203  using an acrylic pressure sensitive adhesive. Other coupling methods can be used to couple the sheath  346  and the conduit  203 , including bonding, welding, friction coupling, or other suitable joining methods. In some embodiments, a portion of the conduit  203  may extend into the sheath  346 , so that the second end  358  of the sheath  346  is spaced apart from the second end  207  of the conduit  203 . In other embodiments, the sheath  346  can be coupled to the conduit  203  where the conduit  203  joins the drain  324 . Preferably, the sheath  346  may be coupled to the drain port  342  and the conduit  203  so that the sheath  346  forms a fluid seal to both the drain port  342  and the conduit  203 . In some embodiments, the sheath  346  may move between a first position and a second position facilitated by the bellows  370 . The bellows  370  may be a portion of the sheath  346  having concertinaed sides, permitting the bellows  370  to expand and contract. As shown in  FIG. 7A , the sheath  346  may have a length  347 . The length  347  of the sheath  346  may be between about 5 mm and about 10 mm. 
       FIG. 7C  is a detail view of  FIG. 6 , illustrating additional details of the dressing interface during negative-pressure therapy. Application of negative-pressure therapy to the sealed therapeutic environment formed by the cover  216  and the dressing interface  328  may move the dressing interface  328  toward a surface of the tissue site  201 . In response, the bellows  370  may expand so that the sheath  346  may have a second length  348 . The second length  348  may be between about 50 mm and about 150 mm. 
       FIG. 8  is a perspective view illustrating additional details that may be associated with an example embodiment of a drain  424  that may be used with the therapy system of  FIG. 2 . The drain  424  may have a plurality of lumens  450  extending a length of the drain  424 . In some embodiments, the drain  424  may include four lumens  450  circumferentially spaced around the drain  424 . In other embodiments, the plurality of lumens  450  may be preferentially placed in a particular area of the drain  424 , rather than circumferentially spaced. The drain  424  may also include a plurality of slits  453 . Each slit of the plurality of slits  453  may extend a length of the drain  424 . In some embodiments, the plurality of slits  453  may be circumferentially spaced around the drain  424 . In other embodiments, the plurality of slits  453  may be preferentially placed in a particular area of the drain  424 , rather than circumferentially spaced. 
       FIG. 9  is a perspective view illustrating additional details that may be associated with an example embodiment of a drain  524  that may be used with the therapy system  200  of  FIG. 2 . The drain  524  may have a plurality of lumens  550  extending a length of the drain  524 . In some embodiments, the drain  524  may include four lumens  550  circumferentially spaced around the drain  524 . In other embodiments, the plurality of lumens  550  may be preferentially placed in a particular area of the drain  524 , rather than circumferentially spaced. The drain  524  can also include a central lumen  551 . The central lumen  551  may be disposed along an axis of the drain  524  and extend a length of the drain  524 . In some embodiments, the drain  524  may include a plurality of perforations  552 . The plurality of perforations  552  may be disposed in a sidewall of the central lumen  551  and provide fluid communication between the central lumen  551  and the plurality of lumens  550 . The drain  524  may also include a plurality of slits  553 . Each slit of the plurality of slits  553  may extend a length of the drain  524 . In some embodiments, the plurality of slits  553  may be circumferentially spaced around the drain  524 . In other embodiments, the plurality of slits  553  may be preferentially placed in a particular area of the drain  524 , rather than circumferentially spaced. In some embodiments, the plurality of slits  553  may be aligned with the plurality of perforations  552 . In other embodiments, the plurality of slits  553  may be misaligned with the plurality of perforations  552 . 
     In an embodiment, the plurality of perforations  552  may be removed. The central lumen  551  may be fluidly coupled to an instillation supply, and the plurality of lumens  550  may be fluidly coupled to the negative-pressure source  202 . Fluid may be supplied to the tissue site  201  through the central lumen  551 , and fluid may be drawn off and negative-pressure applied through the plurality of lumens  550 . 
       FIG. 10  is a perspective view illustrating additional details that may be associated with an example embodiment of a drain  624  that may be used with the therapy system  200  of  FIG. 2 . The drain  624  may have at least one lumen  650  extending a length of the drain  624 . In some embodiments, the drain  624  may include a plurality of perforations  652 . The plurality of perforations  652  may be disposed in a sidewall of the at least one lumen  650  and provide fluid communication between the at least one lumen  650  and an area surrounding the drain  624 . In some embodiments, the drain  624  may be disposed between the tissue site  201  and the tissue interface  214 . The conduit  203  can then be coupled to an instillation source. In other embodiments, the drain  624  may be disposed between the tissue interface  214  and the cover  216 . The conduit  203  can then be coupled to an instillation source. In still other embodiments, a portion of the tissue interface  214  can be disposed into the tissue site  201 , the drain  624  can be disposed over the portion of the tissue interface  214 , and another portion of the tissue interface  214  can be positioned over the drain  624 . These arrangements can provide for preferential or maximum distribution of fluids via the perforated, hydrophilic foam media of the tissue interface  214 . If negative pressure is also applied, effective wound washing may occur. 
     The systems, apparatuses, and methods described herein may provide significant advantages. For example, the drain and the dressing interface described herein provide a simplified application process. The dressing interface and the drain can also decrease the number of instances that the drain may have to be cut to appropriately fit an undermined area of a tissue site. The drain and the dressing interface can remove the need to provide separate exits from the sealed therapeutic environment. For example, a negative-pressure therapy connection and a drain connection can be provided through a single penetration of a cover, while providing seamless integration of a drain into the negative-pressure therapy application process. Furthermore, some embodiments described can remove fluids from undermined areas that may close or clog with components of a tissue interface. The drain and the dressing interface also manifold of negative pressure to the tissue interface as negative pressure may be distributed both at the top of the tissue interface and underneath the tissue interface through the drain. The described embodiments can also increase the duration of negative-pressure therapy. With use of some tissue interfaces, the tissue interface may become clogged with material from the tissue site, inhibiting distribution of negative pressure. The drain may also provide fluid removal from the sealed therapeutic environment as the tissue interface may become clogged with exudates and other material from the tissue site. The described embodiments provide an additional fluid path through the tissue interface, if the tissue interface becomes clogged. 
     While shown in a few illustrative embodiments, a person having ordinary skill in the art will recognize that the systems, apparatuses, and methods described herein are susceptible to various changes and modifications that fall within the scope of the appended claims. Moreover, descriptions of various alternatives using terms such as “or” do not require mutual exclusivity unless clearly required by the context, and the indefinite articles “a” or “an” do not limit the subject to a single instance unless clearly required by the context. Components may be also be combined or eliminated in various configurations for purposes of sale, manufacture, assembly, or use. For example, in some configurations the dressing  104 , the container  112 , or both may be eliminated or separated from other components for manufacture or sale. In other example configurations, the controller  108  may also be manufactured, configured, assembled, or sold independently of other components. 
     The appended claims set forth novel and inventive aspects of the subject matter described above, but the claims may also encompass additional subject matter not specifically recited in detail. For example, certain features, elements, or aspects may be omitted from the claims if not necessary to distinguish the novel and inventive features from what is already known to a person having ordinary skill in the art. Features, elements, and aspects described in the context of some embodiments may also be omitted, combined, or replaced by alternative features serving the same, equivalent, or similar purpose without departing from the scope of the invention defined by the appended claims.