Patent Publication Number: US-2021186549-A1

Title: Method and system for providing active tissue site debridement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to U.S. Provisional Application No. 62/676,574, filed on May 25, 2018, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The present disclosure relates generally to tissue treatment systems, and more particularly, but without limitation, to a wound debridement system for active disruption and/or debridement of non-viable tissue at a tissue site without continual user intervention. 
     During treatment of a tissue site, such as, e.g. a wound site, debris may develop on or in the tissue site. In various embodiments, the debris may include biofilms, necrotic tissue, foreign bodies, eschar, lacerated tissue, devitalized tissue, contaminated tissue, damaged tissue, infected tissue, exudate, highly viscous exudate, fibrinous slough and/or other material. The debris may cover all or a portion of the tissue site. 
     The presence of debris in, on, or surrounding a tissue site may cause numerous problems. For example, debris that covers the tissue site may impair healing of the tissue site. Debris can also lower the effectiveness of beneficial tissue site treatments by preventing the treatments from reaching the tissue site. The presence of debris may also increase healing times and the risk of a more serious infection. Accordingly, in various embodiments, it may be desirable to disrupt the debris at a tissue site. 
     SUMMARY 
     One implementation of the present disclosure is an active debridement wound dressing including a wound interface layer and an active layer. The wound interface layer includes an abrasive surface configured to contact a wound and mechanically debride the wound when the wound interface layer moves relative to the wound. The active layer is coupled to the wound interface layer and includes a pneumatic structure configured to expand and collapse responsive to a pneumatic pressure applied to the active layer. The expansion and collapse of the pneumatic structure causes the wound interface layer to move relative to the wound and mechanically debride the wound. 
     In some embodiments, the active layer includes a fenestrated film fixed to the wound interface layer. The pneumatic structure includes a plurality of pneumatic segments fixed to the fenestrated film. In some embodiments, the pneumatic structure includes a central pneumatic hub and a plurality of radial segments extending radially outward from the central hub. In some embodiments, the pneumatic structure includes a pneumatic perimeter forming a closed shape around the central pneumatic hub and the plurality of radial segments. The plurality of radial segments connect the central pneumatic hub to the pneumatic perimeter. 
     In some embodiments, the pneumatic structure includes a plurality of pneumatic pathways that interconnect to form a honeycomb structure. 
     In some embodiments, a drape layer is sealable to a patient&#39;s skin surrounding the wound. The drape layer is configured to maintain the wound at negative pressure. 
     In some embodiments, the active layer is pneumatically coupled to the wound such that the pneumatic pressure applied to the active layer is substantially equivalent to a pressure at the wound. In some embodiments, the active layer is pneumatically isolated from the wound such that the pneumatic pressure applied to the active layer is different from a pressure at the wound. 
     In some embodiments, a first encapsulation layer and a second encapsulation layer encapsulate the active layer and pneumatically isolate the active layer from the wound. The first encapsulation layer is located on a first side of the active layer between the active layer and the wound interface layer. The second encapsulation layer is located on a second side of the active layer opposite the wound interface layer. A foam layer is coupled to the active layer opposite the wound interface layer such that the active layer is encapsulated between the foam layer and the wound interface layer. 
     In some embodiments, a control unit is coupled to the active layer and is configured to apply a positive or negative pneumatic pressure to the active layer. The control unit is configured to communicate with a driver unit outside the wound dressing and to apply the pneumatic pressure to the active layer upon receiving a control signal from the driver unit. 
     In some embodiments, the pneumatic structure is configured to collapse upon application of negative pressure to the active layer and return to a non-collapsed size or shape when the negative pressure is removed. In some embodiments, the pneumatic structure is configured to expand upon application of positive pressure to the active layer and return to a non-expanded size or shape when the positive pressure is removed. In some embodiments, the pneumatic structure is configured to oscillate between an expanded size or shape and a collapsed size or shape to impart oscillating movement to the wound interface layer. 
     One implementation of the present disclosure is an active debridement wound therapy system including a wound dressing and a therapy unit. The wound dressing includes a wound interface layer and an active layer. The wound interface layer includes an abrasive surface configured to contact a wound and mechanically debride the wound when the wound interface layer moves relative to the wound. The active layer is coupled to the wound interface layer and includes a pneumatic structure configured to expand and collapse responsive to a pneumatic pressure applied to the active layer, thereby causing the wound interface layer to move relative to the wound and mechanically debride the wound. The therapy unit is separate from the wound dressing and is configured to cause the pneumatic pressure to be applied to the active layer. 
     In some embodiments, the therapy unit includes a driver unit pneumatically coupled to the active layer via tubing and configured to apply the pneumatic pressure to the active layer via the tubing. In some embodiments, the wound dressing includes a control unit coupled to the active layer and configured to communicate with the therapy unit. The control unit is configured to apply the pneumatic pressure to the active layer upon receiving a control signal from the therapy unit. 
     In some embodiments, the active layer includes a fenestrated film fixed to the wound interface layer. The pneumatic structure includes a plurality of pneumatic segments fixed to the fenestrated film. 
     In some embodiments, the pneumatic structure includes a central pneumatic hub and a plurality of radial segments extending radially outward from the central hub. 
     In some embodiments, the pneumatic structure includes a pneumatic perimeter forming a closed shape around the central pneumatic hub and the plurality of radial segments. The plurality of radial segments connect the central pneumatic hub to the pneumatic perimeter. 
     In some embodiments, the pneumatic structure includes a plurality of pneumatic pathways that interconnect to form a honeycomb structure. 
     In some embodiments, the wound dressing further includes a drape layer sealable to a patient&#39;s skin surrounding the wound and configured to maintain the wound at negative pressure. 
     In some embodiments, the active layer is pneumatically coupled to the wound such that the pneumatic pressure applied to the active layer is substantially equivalent to a pressure at the wound. In some embodiments, the active layer is pneumatically isolated from the wound such that the pneumatic pressure applied to the active layer is different from a pressure at the wound. 
     In some embodiments, the wound dressing further includes a first encapsulation layer and a second encapsulation layer encapsulating the active layer and pneumatically isolating the active layer from the wound. The first encapsulation layer is located on a first side of the active layer between the active layer and the wound interface layer. The second encapsulation layer is located on a second side of the active layer opposite the wound interface layer. The wound dressing further includes a foam layer coupled to the active layer opposite the wound interface layer such that the active layer is encapsulated between the foam layer and the wound interface layer. 
     In some embodiments, the pneumatic structure is configured to collapse upon application of negative pressure to the active layer and return to a non-collapsed size or shape when the negative pressure is removed. In some embodiments, the pneumatic structure is configured to expand upon application of positive pressure to the active layer and return to a non-expanded size or shape when the positive pressure is removed. In some embodiments, the pneumatic structure is configured to oscillate between an expanded size or shape and a collapsed size or shape to impart oscillating movement to the wound interface layer. 
     Those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices and/or processes described herein, as defined solely by the claims, will become apparent in the detailed description set forth herein and taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional side view of an active wound debridement system applied to a tissue site, according to an exemplary embodiment; 
         FIG. 2A  is an exploded top perspective view of a wound dressing, according to an exemplary embodiment; 
         FIG. 2B  is a cross-sectional side view of an active wound debridement system incorporating the wound dressing of  FIG. 2A  applied to a tissue site, the wound dressing being shown in an initial, expanded configuration, according to an exemplary embodiment; 
         FIG. 2C  is a cross-sectional side view of the active wound debridement system of  FIG. 2B  after the application of negative pressure to the active layer of the wound dressing, according to an exemplary embodiment; 
         FIG. 3  is an exploded top perspective view of a wound dressing according to an exemplary embodiment; 
         FIG. 4  is an exploded top perspective view of a wound dressing according to an exemplary embodiment; 
         FIG. 5  is an exploded top perspective view of a wound dressing according to an exemplary embodiment; and 
         FIG. 6  is a cross-sectional side view of an active wound debridement system applied to a tissue site being used in conjunction with a negative pressure wound therapy system, according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-6 , various embodiments of an active wound debridement system  1  configured to disrupt areas of debris  7  at a tissue site  5 , such as, e.g. a wound site, are shown. The active wound debridement system  1  is configured to provide continued, active mechanical debridement of debris  7  at the tissue site  5  without requiring any additional user skill or effort to operate the wound debridement system  1  other than what would be required to apply and activate an existing negative pressure wound therapy (“NPWT”) system, such as e.g. a V.A.C.® therapy unit as available from Kinetic Concepts, Inc. (KCI) of San Antonio, Tex. 
     As shown in  FIG. 1 , the wound debridement system  1  generally comprises an active debridement wound dressing  100 , a drape layer  20  configured to position the wound dressing  100  at a desired tissue site  5 , a drive unit  70  adapted to activate the active layer  40  and thereby drive the wound interface layer  10  relative to the tissue site  5 , and a control unit  80  adapted to control the delivery of pressure by the drive unit  70  to the active layer  40 . 
     During operation of the wound debridement system  1 , the wound dressing  100  is positioned on or within a desired tissue site  5 . Once positioned, the wound dressing  100  is secured to the patient&#39;s skin  3  using the drape layer  20 . Depending on whether the active layer  40  is intended to be driven by non-localized or isolated changes in pressure, the drape layer  20  may be applied to the patient&#39;s skin  3  so as to form a sealed, substantially fluid-tight treatment space  25  surrounding the tissue site  5  and the wound dressing  100 . 
     The control unit  80  may then be operated to control the application of pressure by the drive unit  70  to the active layer  40  of the wound dressing  100 . The pressure applied by the drive unit  70  is configured to cause the cyclical, alternating or intermittent collapse and expansion of the one or more pneumatic members  45  forming the active layer  40 . The oscillation of the pneumatic members  45  between a collapsed and an expanded state drives the wound interface layer  10 , such that the wound interface layer  10  is translated relative to the tissue site  5 . This movement of the wound interface layer  10  relative to the tissue site  5  acts to mechanically disrupt and debride debris  7  located at the tissue site  5 . 
     In some embodiments, the wound debridement system  1  may be used in conjunction with, or form a part of, an additional therapeutic treatment system configured to provide additional therapeutic treatment to the tissue site  5  to which the wound debridement system  1  is applied. For example, as illustrated in  FIG. 6 , in some embodiments, the wound debridement system  1  may be incorporated into and be used in conjunction with a NPWT system  200 . 
     Wound Dressing 
     In general, the wound dressing  100  includes a wound interface layer  10  configured to provide mechanical movement which disrupts debris  7  at a tissue site  5  and an active layer  40  configured to drive the movement of the wound interface layer  10 . An absorbent layer  30  may optionally also be incorporated into the wound dressing  100 . 
     The wound dressing  100  may be substantially planar or may be contoured for application to body surfaces having high curvature. The size of wound dressing  100  can vary depending on the size of the tissue site  5  to be treated. For example, it is contemplated that the size of wound dressing  100  can be within a range of approximately 50 cm 2  to approximately 3000 cm 2 , and more preferably within a range of approximately 300 cm 2  to approximately 800 cm 2 . However, other shapes and sizes of wound dressing  100  are also possible depending on intended use. 
     i. Wound Interface Layer 
     The wound interface layer  10  is adapted to contact a tissue site  5  along a lower, wound-facing surface  11  of the wound interface layer  10  to mechanically debride debris  7  at the tissue site  5  upon movement of the wound interface layer  10  relative to the tissue site  5 . Although the wound interface layer  10  is shown as having a generally rounded rectangular shape, the wound interface layer  10  may be formed having any number of, and combination of, sizes, shapes, and/or thicknesses depending on a variety of factors, such as, e.g. the type of treatment being implemented or the nature and size of the tissue site  5  being treated, etc. 
     Additionally, the size and shape of the wound interface layer  10  may be selected to accommodate the type of tissue site  5  being treated and the degree of contact (e.g. full or partial contact) desired between the tissue site  5  and the wound interface layer  10 . For example, if the tissue site  5  is a wound, the shape, size and thickness of the wound interface layer  10  may vary depending on whether the wound interface layer  10  is intended to partially or completely fill the wound, or if the wound interface layer  10  is intended to only be placed over the wound. If the wound interface layer  10  is intended to partially or completely fill the wound, the size and shape of the wound interface layer  10  may be adapted to the contours of the wound. 
     Any number of bio-compatible materials may be used to construct the wound interface layer  10 . A non-limiting, non-exhaustive list of the various materials that may be used to form the wound interface layer  10  may include: bioresorbable materials; materials configured to serve as a scaffold for new cell-growth, such as, e.g. calcium phosphate, collagen, PLA/PGA, coral hydroxy apatites, carbonates, or processed allograft materials; thermoplastic elastomers; 3D textiles, also referred to as a spacer fabric, such as the 3D textiles produced by Heathcoat Fabrics, Ltd., Baltex, and Mueller Textil Group; foam, such as e.g. GranuFoam®, V.A.C. VeraFlo® foam, or V.A.C. WhiteFoam®, each available from Kinetic Concepts, Inc. of San Antonio, Texas; etc. 
     The materials used to form the wound interface layer  10 , the properties of the wound-facing surface  11  and/or the configuration and structure of the wound-facing surface  11  may be selected to enhance the ability of the wound interface layer  10  to disrupt debris  7  at the tissue site  5 . For example, in some embodiments, the wound-facing surface  11  may be formed of an abrasive material. In other embodiments, the wound-facing surface  11  may be defined by a textured surface having an uneven, coarse, or jagged profile that can induce strains and stresses at the tissue site  5 . In such embodiments, the wound-facing layer may be formed of an abrasive or non-abrasive material. In yet other embodiments, the wound interface layer  10  may be formed of an abrasive or non-abrasive compressible material, with the compression of the compressible material being adapted to increase the amount by which the wound-facing surface  11  is translated or oscillated in a lateral and/or longitudinal direction relative to the tissue site  5  during treatment. 
     As illustrated in  FIG. 4 , in various embodiments the wound-facing surface  11  of wound interface layer  10  may be formed having a generally solid, continuous, uninterrupted surface. In other embodiments, the ability of the wound interface layer  10  to disrupt debris  7  at the tissue site  5  may be enhanced via the selective removal of areas or portions of the wound-facing surface  11 . For example, as illustrated in  FIG. 3 , in one embodiment, the wound interface layer  10  may be constructed with a plurality of perforations or through-holes  13  extending entirely or partially through the wound interface layer  10  from the wound-facing surface  11  to an upper surface  12  of the wound interface layer  10 . 
     The dimensions of the through-holes  13  may be varied as desired. While in some embodiments each of the through-holes  13  may have identical dimensions, in other embodiments the through-holes  13  may be formed having varied dimensions. Regardless of the dimensions selected for the through-holes  13 , in embodiments in which the wound interface layer  10  is formed from a foam-like or other porous material, it is to be understood that the through-holes  13  do not include the pores of the material forming the wound interface layer  10 , but rather are discrete perforations formed through the material forming the wound interface layer  10 . 
     The through-holes  13  may be arranged about the wound interface layer  10  in any number of desired arrangements or patterns, including a random arrangement of the through-holes  13  about the wound interface layer  10 . As illustrated in  FIG. 3 , in some embodiments, the through-holes  13  may be arranged linearly, with adjacent rows of through-holes  13  optionally being offset from one another. 
     As shown in  FIG. 3 , in some embodiments, the through-holes  13  may have a circular shape. In other embodiments, the through-holes  13  may be formed having any number of other shapes, or any combination of different shapes, including, e.g. hexagonal, ovoid, or triangular shapes. When contracted, through-holes  13  having different cross-sectional shapes may generate and distribute concentrated stresses in different dimensions, and may accordingly influence disruption of debris  7  in different ways. As such, in various embodiments the cross-sectional shape of the through-holes  13  may be based on the tissue site  5  being treated and/or the degree of abrasion that may be desired at the tissue site  5 . 
     Regardless of the shape, size, arrangement, or degree to which the through-holes  13  extend through the wound interface layer  10 , the through-holes  13  formed in the wound interface layer  10  define void spaces in the wound-facing surface  11 . In response to the wound interface layer  10  being subjected to negative pressure and/or being compressed, the voids provide spaces into which the wound-facing surface  11  is laterally and/or longitudinally collapsed. As the wound-facing surface  11  is compressed from its initial, relaxed configuration into the spaces defined by the voids, the lateral and/or longitudinal translation of the wound-facing surface  11  relative to the tissue site  5  concentrates a shear force on the tissue site  5  that allows for the disruption of the debris  7  at the tissue site  5 . 
     The disruption of the debris  7  at the tissue site  5  may also be augmented by the localization of forces along the edges  14  of the through-holes  13  during the application of negative pressure to and/or the compression of the wound interface layer  10 , which may result in the edges  14  acting as cutting surfaces that disrupt debris  7  at the tissue site  5 . Additionally, in some embodiments, during the application of negative pressure and/or as a result of the compression of the wound interface layer  10 , debris  7  may become trapped within the voids as the through-holes  13  collapse. Forces concentrated by the inner vertical surfaces  15  of the walls of the through-holes  13  on this trapped debris  7  may act to provide additional disruption of the debris  7  at the tissue site  5 . 
     As illustrated in  FIGS. 2A and 5 , in some embodiments, the selective removal of areas or portions of the wound interface layer  10  may be provided in the form of the wound interface layer  10  being formed of a plurality of discrete or connected segments  17 . In an initial configuration—prior to the application of negative pressure and/or the compression of the wound interface layer  10 —the segments may be arranged and spaced relative to one another with voids separating adjacent segments  17 , such that the wound-facing surface  11  of the wound interface layer  10  is defined by a non-solid, interrupted surface. The segments  17  may be arranged relative to one another such that, upon negative pressure being applied to and/or compression of the wound interface layer  10 , the segments  17  collapse inwards to form a substantially solid, compact surface defined by the inter-fitted arrangement of adjacent segments  17  with one another. 
     The effect of the contraction of the segments  17  of wound interface layer  10  embodiments such as those illustrated in, e.g.  FIGS. 2A and 5 , is similar to the effect of the contraction and collapse of through-holes  13  of wound interface layer  10  embodiments such as that illustrated in, e.g.  FIG. 3 . In particular, the translation of the segments  17  relative to the tissue site  5  in a lateral and/or longitudinal direction concentrates a shear force on the tissue site  5  as the segments  17  are collapsed and translated into the inter-fitted, compressed segment  17  configuration illustrated in, e.g.  FIG. 2C . Also, concentrated forces imparted by the edges  18  of segments  17  on the debris as well as forces imparted by the vertical surfaces  19  of segments  17  on debris  7  that becomes trapped between adjacent segments  17  as the wound interface layer  10  collapses assist in the debridement of debris  7  at the tissue site  5 . 
     Although embodiments of the wound interface layer  10  formed with through-holes  13  or segments  17  each assist in tissue site  5  debridement, in various embodiments, the larger wound-facing surface  11  surface area, the greater amount of defined edges  18 , and the greater total surface area defined by vertical surfaces  15  characterizing embodiments of the wound interface layer  10  having segments  17  (such as e.g. illustrated in  FIGS. 2A and 5 ) may allow for a greater degree of debris  7  disruption as compared to embodiments of the wound interface layer  10  formed with through-holes  13  (such as e.g. illustrated in  FIG. 3 ). 
     In the wound interface layer  10  embodiments formed with through-hole  13  or segment  17  illustrated in  FIGS. 3 and 5 , respectively, the through-holes  13  and segments  17  are illustrated as defining voids in the wound-facing surface  11  when the wound interface layer  10  is in an initial configuration, and as being adapted to collapse into a compressed configuration upon the application of negative pressure. However, it is to be understood that, in other embodiments, the wound surface layer  10  may be configured such that, in an initial configuration the wound-interface surface  11  defines a substantially continuous, solid surface, with the wound surface layer  10  being adapted to transition into an expanded configuration having voids defined by through-holes  13  and/or segments  17  upon the application of positive pressure to the wound interface layer  10 . 
     ii. Active Layer 
     Active layer  40  is configured to intentionally oscillate, translate, collapse, or otherwise move the wound interface layer  10  such that unhealthily tissue or other debris  7  may be debrided from the tissue site  5 . The active layer  40  generally comprises one or more pneumatic members  45  that may be operably coupled to the wound interface layer  10  via an interconnection, such as, e.g. film layer  60 . The one or more pneumatic members  45  are configured to expand and collapse responsive to a pneumatic pressure applied to the active layer  40  by a drive unit  70 . 
     a. Pneumatic Members 
     The transition of the pneumatic members  45  of the active layer  40  between an expanded and collapsed configuration is adapted to impart a translational and/or oscillating movement to the wound interface layer  10 . The design of and the materials used to the form pneumatic members  45  are adapted to allow the pneumatic members  45  to collapse and expand in response to changes in pressure applied by the drive unit  70 . 
     In some embodiments, the pneumatic members  45  may be configured to collapse upon application of negative pressure and return to a non-collapsed configuration when the negative pressure is removed. In other embodiments, the pneumatic members  45  may be configured to expand upon application of positive pressure and return to a non-expanded configuration when the positive pressure is removed. In some embodiments, the pneumatic members  45  may include a combination of pneumatic members  45  configured to collapse from an initial expanded configuration upon application of negative pressure and pneumatic members  45  configured to expand from an initial compressed configuration upon application of positive pressure. 
     In embodiments in which the drive unit  70  is adapted to apply both negative and positive pressure to drive the active layer  40 , the pneumatic members  45  may be formed without being biased to either an expanded or collapsed position, with the cyclical application of positive and negative pressure causing the pneumatic members  45  to transition from an expanded to a collapsed state. 
     Generally, the pneumatic members  45  are adapted to be highly compressible, allowing the active layer  40  to easily collapse and expand. The rigidity of the materials selected to form the pneumatic members  45  may be used as one way to control the rate of oscillation and/or the degree of translation that will be imparted onto the wound interface layer  10  by the active layer  40 . 
     The pneumatic members  45  may be configured to collapse in one, all, or a combination of the lateral, longitudinal, and/or vertical directions. For example, in various embodiments, the pneumatic members  45  may be configured to collapse in only the lateral and longitudinal directions in response to changes in pressure. In other embodiments, the pneumatic members  45  may be adapted to allow for collapse along only a single direction. 
     1. Single Direction Collapsible Structures 
     As illustrated in  FIGS. 2-4 , in various embodiments, the one or more pneumatic members  45  of the active layer  40  may comprise one or more single-direction collapsible structures  43  designed to collapse in a single direction, such as, e.g. along a longitudinal axis of the pneumatic member  45 . The single-direction collapsible structures  43  may be centered about and extend generally uniformly (i.e. in a linear manner) or may extend non-linearly (e.g. along a curve) with respect to the axis the single-direction collapsible structures  43  are configured to collapse along (e.g. the longitudinal axis). 
     As will be discussed in more detail below, when arranged with other single-direction collapsible structures  43  to form the active layer  40 , the arrangement of the single-direction collapsible structure  43  may allow for movement of the active layer  40  in more than one direction, even though each individual single-direction collapsible structure  43  forming the active layer  40  is configured to only collapse and expand along a single direction. 
     The single-direction collapsible structures  43  may be designed to expand from an initial, collapsed state upon the application of positive pressure, and automatically retract to their initial configuration when the positive pressure is removed. Alternatively, the single-direction collapsible structures  43  may be designed to collapse from an initial, expanded state upon the application of negative pressure, returning to their initial configuration once the negative pressure is removed. 
     Referring to  FIGS. 2-4 , the single-direction collapsible structures  43  may be formed having any number of configurations, and may be formed of any number of materials that allow the single-direction collapsible structures  43  to collapse and expand in a single direction in response to changes in pressure. In some embodiments, such as e.g. illustrated in  FIGS. 2A and 3 , the single-direction collapsible structures  43  may be formed having a hollow interior  41 , with one or more apertures  42  optionally being provided about an exterior of the single-direction collapsible structure  43  to provide for fluid communication between the hollow interior  41  and the ambient environment. In other embodiments, such as, e.g. shown in  FIG. 4 , the single-direction collapsible structures  43  may define a substantially solid structure, formed without a hollow interior  41 . 
     As shown in  FIGS. 2A-2C , in some embodiments the single-direction collapsible structures  43  may be formed as bellows  46  made, e.g., from molded plastic. The folded arrangement of the bellows  46  may advantageously allow for significant extension/contraction of the single-direction collapsible structures  43 , thereby allowing the active layer  40  to induce a significant amount of lateral and/or longitudinal translation and/or oscillation of the wound interface layer  10  relative to the tissue site  5 . In such embodiments, the configuration of and/or dimensions of the bellows  46  may be varied depending on the degree of movement of the wound interface layer  10  that is desired. 
     In some embodiments, such as illustrated e.g. in  FIG. 3 , the single-direction collapsible structures  43  may be formed of thin-walled collapsible tubes  47 . As shown in  FIG. 3 , in some embodiments, the thin-walled collapsible tubes  47  forming the single-direction collapsible structures  43  may be arranged in a hub and spoke arrangement. In other embodiments, the thin-walled collapsible tubes  47  forming the single-direction collapsible structures  43  may be arranged in any other number of configurations that would allow for radial contraction and expansion of the active layer and/or contraction and expansion of the active layer  40  in any other desired direction. 
     In other embodiments, such as, e.g. shown in  FIG. 4 , the single-direction collapsible structures  43  may be formed from a compressible material, such as, e.g. an open-cell foam, with the materials and hole patterns defining the compressible material being adapted to allow for only unidirectional collapse and expansion. In yet another embodiment (not shown), the single-direction collapsible structures  43  may be formed of a network of hollow or solid, articulated, non-compressible segments that are configured to collapse and expand in an accordion-like manner. 
     The one or more single-direction collapsible structures  43  may be spaced and positioned about the active layer  40  in any desired pattern, design or arrangement. Although the single-direction collapsible structures  43  are themselves individually adapted to collapse and expand along a single direction, the arrangement of the single-direction collapsible structures  43  about the active layer  40  may allow for either uni- or multi-directional movement of the active layer  40 . Accordingly, in various embodiments, the configuration, arrangement and/or positioning of the single-direction collapsible structures  43  about the active layer  40  may be based on the direction and/or degree of movement of the wound interface layer  10  that is desired. In some embodiments, such as, e.g. illustrated in  FIGS. 2-4 , the single-direction collapsible structures  43  may be arranged such the single-direction collapsible structures  43  collapse inwards towards a center of the wound dressing  100  upon the application of negative pressure. 
     The pattern, design and arrangement of the single-direction collapsible structures  43  about the active layer  40  may define a pneumatic member  45  formed of a plurality of discretely positioned single-direction collapsible structures  43 , or may define a pneumatic member  45  formed of a plurality of single-direction collapsible structures  43  forming a single, unitary structure having a desired pattern and design. While in some embodiments the one or more single-direction collapsible structures  43  may be arranged uniformly and/or symmetrically about the active layer  40 , in other embodiments the single-direction collapsible structures  43  may be positioned randomly about the active layer  40 . 
     As illustrated by  FIGS. 2-4 , in some embodiments, a plurality of radially outwardly extending single-direction collapsible structures  43  may be arranged to form a unitary, spoke-like pneumatic member  45 , with the inwardly located ends of the single-direction collapsible structures  43  optionally being attached to and extending outwards from a centrally located anchor point or hub  48 . In some embodiments, a single-direction collapsible structure extending continuously or interruptedly about a perimeter of the active layer  40  may optionally be attached to and be in fluid, pneumatic communication with the outwardly located ends of the single-direction collapsible structures  43  defining the spoke-like pneumatic member  45 . In addition to assisting in the expansion and contraction of the active layer  40 , the inclusion of one or more single-direction collapsible structures  43  forming an outer ring surrounding the periphery of the hub and spoke assembly may also facilitate the manufacture and assembly of the active layer  40 . 
     In embodiments in which the pneumatic member  45  is formed of a plurality of single-direction collapsible structures  43  having hollow interiors  41 , such as, e.g. illustrated by  FIGS. 2A-2C , the hollow interiors  41  of some or all of the single-direction collapsible structures  43  may be fluidly (i.e. pneumatically) connected. In other embodiments, the hollow interiors  41  of some or all of the single-direction collapsible structures  43  may be fluidly (i.e. pneumatically) isolated from adjacent hollow interior  41  single-direction collapsible structures  43 . 
     In embodiments in which discrete, non-interconnected single-direction collapsible structures  43  having hollow interiors  41  form the active layer  40 , each of the discrete, non-interconnected single-direction collapsible structures  43  may be formed with one or more apertures  42  configured to allow for fluid communication between the hollow interior  41  of the single-direction collapsible structure  43  and the external environment. The apertures  42  are adapted to allow for changes in pressure external to the single-direction collapsible structure  43  to be transferred to the hollow interior  41  of the single-direction collapsible structure  43 , with the resultant change in pressure in the hollow interior  41  of the single-direction collapsible structure  43  adapted to cause the collapse or expansion of the single-direction collapsible structure  43 . 
     In embodiments in which one or more hollow interior  41  single-direction collapsible structures  43  are attached to form an interconnected structure, such as, e.g. illustrated in  FIGS. 2 and 3 , it may be sufficient that one or more apertures  42  be provided on only one of the single-direction collapsible structures  43  forming the interconnected structure, with the fluid communication between the hollow interiors  41  of the fluidly interconnected single-direction collapsible structures  43  allowing for the collapse or expansion of each of the interconnected single-direction collapsible structures  43  in response to a change in external pressure. 
     The one or more apertures  42  may be formed at any desired locations about the exterior surfaces of the single-direction collapsible structures  43 , and the apertures  42  may be arranged, spaced, dimensioned, and shaped in any number of desired configurations. As will be understood, in some embodiments, the arrangement and placement of apertures  42  about the exterior of the single-direction collapsible structures  43  may depend on the arrangement of and/or the other layers incorporated into the wound dressing  100 . For example, in embodiments in which the active layer  40  is arranged between an upper absorbent layer  30  and a lower wound interface layer  10  and/or embodiments in which the materials forming the various layers of the wound dressing  100  have no or limited porosity, the one or more apertures  42  may be formed about the outwardly facing ends of the single-direction collapsible structures  43 , so as to minimize the risk that the apertures  42  become occluded during use. 
     As an alternative to providing apertures  42  about the exterior surfaces of hollow interior  41  single-direction collapsible structures  43 , in some embodiments, one or more ports  49  may be formed about the exteriors of the surfaces of hollow interior  41  single-direction collapsible structures  43 . The ports  49  may be configured to fluidly connect to the drive unit  70  (via, e.g. tubing  75 ). This direct connection between the hollow interior  41  of the single-direction collapsible structure  43  and the drive unit  70  may provide for a greater degree of control over the collapse and expansion of the single-direction collapsible structure  43 . 
     As with the apertured single-direction collapsible structure  43  embodiments described above, each discrete, non-interconnected single-direction collapsible structure  43  may be provided with a port  49 , whereas in embodiments in which one or more hollow interior  41  single-direction collapsible structures  43  are attached to form an interconnected structure it may be sufficient to provide only a single port  49  on one of the single-direction collapsible structures  43  forming the interconnected structure. 
     2. Multi-Direction Collapsible Structure 
     As illustrated in  FIG. 5 , in various embodiments, the one or more pneumatic members  45  of the active layer  40  may comprise one or more multi-direction collapsible structures  53  designed to collapse and expand in more than one direction in response to changes in pressure. In some embodiments, the multi-direction collapsible structure(s)  53  may be configured to collapse in both the longitudinal and lateral directions. In various embodiments, the multi-direction collapsible structure  53  may be made from a compressible material, such as an open-cell foam, and may define a plurality of pneumatic pathways  55  extending through the multi-direction collapsible structure  53  that interconnect to form a honeycomb-like structure. 
     The multi-direction collapsible structure  53  forming the active layer  40  may operate on principles similar to and in a manner like the operation of the wound interface layer  10  embodiments formed with through-holes  13  as described above. However, given the different purpose and role in the functioning of the wound dressing  100  that the multi-direction collapsible structure  53  plays as compared to embodiments of the wound interface layer  10  formed with through-holes  13 , there are notable differences between the configuration and design of the multi-direction collapsible structure  53  of the active layer  40  and that of embodiments of the wound interface layer  10  formed with through-holes  13 . 
     In configuring, sizing and arranging the through-holes  13  in the wound interface layer  10  embodiments described above, considerations must be made to balance the ability of the through-holes  13  to provide the desired degree of collapse of the wound-facing surface  11  of the wound interface layer  10  and the amount of surface area of the wound-facing surface  11  that is available to contact the tissue site  5  in order to achieve the desired degree of debris  7  disruption. In particular, incorporating larger dimensioned through-holes  13  in the wound interface layer  10  may come at the cost of decreasing the surface area of the wound-facing surface  11 . Accordingly, even though the larger dimensioned through-holes  13  may allow for greater collapse of—and resultant lateral and/or longitudinal translation of—the wound-facing surface  11  relative to the tissue site  5 , the limited surface area of the wound-facing surface  11  may restrict the amount of contact that the wound interface layer  10  may have with debris  7  at the tissue site  5 . With more limited debris  7  contact, the degree to which the wound interface layer  10  may achieve desired tissue site  5  debridement may be limited. 
     On the other hand, attempting to maximize the surface area of the wound-facing surface  11  may come at the cost of decreasing the dimensions of the through-holes  13 . Accordingly, even though the wound-facing surface  11  may have a surface area that provides a desired degree of contact with the tissue site  5 , the limited ability of the though-holes  13  to collapse may result in the wound interface layer  10  not being translated laterally and/or longitudinally relative to the tissue site  5  by an amount sufficient to result in the desired debris  7  debridement. 
     In contrast, because the multi-direction collapsible structure  53  of the active layer  40  is not intended to be in contact with the tissue site  5 , the configuration, sizing and arrangement of the pneumatic pathways  55  of the honeycomb-like multi-direction collapsible structure  53  need not be limited based on surface area considerations. Accordingly, the pneumatic pathways  55  of the multi-direction collapsible structure  53  may be configured, sized and arranged based on the degree and amount of wound interface layer  10  movement that is desired. In some embodiments, the only constraint on the size of the pneumatic pathways  55  may be ensuring that the walls separating adjacent pneumatic pathways  55  are not so small so as to be too fragile to sustain the application of pressure to the active layer  40 . 
     Turning to  FIG. 5 , the multi-direction collapsible structure  53  may be constructed with a plurality of perforations or pneumatic pathways  55  extending entirely or partially through the multi-direction collapsible structure  53  from a lower surface  51  to an upper surface  52  of the multi-direction collapsible structure  53 . The dimensions of the pneumatic pathways  55  may be varied as desired. While in some embodiments each of the pneumatic pathways  55  will have identical dimensions, in various embodiments, the pneumatic pathways  55  may be formed having varied dimensions. 
     Regardless of the dimensions selected for the pneumatic pathways  55 , in embodiments in which the multi-direction collapsible structure  53  is formed from a foam-like or other porous material, it is to be understood that the pneumatic pathways  55  do not include the pores of the material forming the multi-direction collapsible structure  53 , but rather are discrete perforations formed through the material forming the multi-direction collapsible structure  53 . 
     The pneumatic pathways  55  may be arranged about the active layer  40  in any number of desired arrangements or patterns, including a random arrangement of the pneumatic pathways  55  about the multi-direction collapsible structure  53 . As illustrated in  FIG. 5 , in some embodiments, the pneumatic pathways  55  may be arranged linearly, with adjacent rows of pneumatic pathways  55  optionally being offset from one another. 
     As shown in  FIG. 5 , in some embodiments, the pneumatic pathways  55  may have a hexagonal shape. In other embodiments, the pneumatic pathways  55  may define any number of, or any combination of, other shapes, including, e.g. circular, ovoid, or triangular shapes. When contracted, pneumatic pathways  55  having different cross-sectional shapes may collapse in different directions and by different distances. Given that the movement of the multi-direction collapsible structure  53  as the pneumatic pathways  55  collapse is adapted to translate and/or oscillate the wound interface layer  10 , in various embodiments the cross-sectional shape of the pneumatic pathways  55  may be based on the degree, direction, and/or type of lateral and/or longitudinal movement of the wound interface layer  10  relative to the tissue site  5  that is desired. 
     Regardless of the shape, size, arrangement, or degree to which the pneumatic pathways  55  extend through the multi-direction collapsible structure  53 , the pneumatic pathways  55  define voids in the multi-direction collapsible structure  53 . In response to the multi-direction collapsible structure  53  being subjected to negative pressure, the voids provide spaces into which the multi-direction collapsible structure  53  is laterally and/or longitudinally collapsed. As the multi-direction collapsible structure  53  is compressed from its initial, relaxed configuration, the translation of the multi-direction collapsible structure  53  into the voids is transferred to the wound interface layer  10  to which the active layer  40  is attached, thereby driving the wound interface layer  10  in a desired manner. 
     b. Film Layer 
     In various embodiments, the active layer  40  may optionally include a film layer  60  to which the pneumatic members  45  may be mounted, laminated or otherwise attached or interconnected to. Additionally, in various embodiments, the film layer  60  may be used as the basis by which the pneumatic members  45  are affixed to the wound interface layer  10 . Alternatively, in some embodiments, the film layer  60  may be omitted from active layer  40 , with the pneumatic members  45  of the active layer  40  being attached directly to the wound interface layer  10 . 
     The size and shape of the film layer  60  may be varied as desired. In various embodiments, the outer periphery of the film layer  60  may be shaped and sized to generally correspond to, or optionally be smaller than, the outer periphery of the wound interface layer  10 . 
     The film layer  60  may be adapted to elastically deform upon application of a stretching force to the wound dressing  100 . For example, in some embodiments, the film layer  60  may be designed to elastically stretch when a stretching force is applied and elastically recover when the stretching force is removed, such as, e.g. may occur as a result of the collapse and expansion of the pneumatic members  45  that are supported by film layer  60 . In other words, film layer  60  may be configured to exhibit substantially elastic deformation and recovery. 
     Film layer  60  may be a thin layer made of any number of elastic materials. For example, film layer  60  may be a polyurethane film, a polyethylene film, or other thin elastic. In some embodiments, film layer  60  may be substantially impermeable to liquid and substantially permeable to moisture vapor. 
     As illustrated e.g. in  FIGS. 2, 3 and 5 , film layer  60  may optionally include one or more fenestrations  63  adapted to allow for the transfer of fluids and pressure to/from the wound interface layer  10 . The fenestrations  63  may also be adapted to reduce the amount of force required to stretch film layer  60 . In some embodiments, such as illustrated, e.g. in  FIGS. 3 and 4 , film layer  60  may comprise an upper film  61  and a lower film  62  that encapsulate the pneumatic members  45 . In some such embodiments, such as illustrated in  FIG. 3 , one or both of the upper film  61  and the lower film  62  may include fenestrations  63 , such that the interior  66  of the film layer  60  and the pneumatic members  45  encapsulated therein are in fluid communication with (and thereby subject to changes in the pressure of) the external environment. 
     Referring to  FIG. 4 , in other dual-film film layer  60  embodiments, both the upper film  61  and the lower film  62  may be formed without fenestrations  63 , with the edges of the upper film  61  and lower film  62  being attached together to form a fluid-tight seal that isolates the interior  66  of the film layer  60  from the external environment. In such embodiments, the film layer  60  may comprise one or more outlets, such as e.g. a port  67 , by which fluid communication may be established between the film layer  60  interior  66  and the external environment, and by which the pressure in the film layer  60  interior  66  may be controlled as desired. 
     In film layer  60  embodiments having a pneumatically isolated interior, such as, e.g. illustrated in  FIG. 4 , the film layer  60  may be dimensioned smaller than the wound interface layer  10 , such that fluid and negative pressure may pass through to the wound interface layer  10 . In other embodiments, one or more fenestrations  63  may extend through the portions of the upper film  61  and lower film  62  extending outwards from an outer periphery of the film layer  60  interior  66 . 
     iii. Absorbent Layer 
     An absorbent layer  30  may optionally be coupled to the active layer  40  opposite the wound interface layer  10 , such that the active layer  40  is encapsulated between the absorbent layer  30  and the wound interface layer  10 . The absorbent layer  30  may act as a manifold that is adapted to collect and/or distribute fluid and/or pressure across a tissue site  5 . For example, the absorbent layer  30  may be adapted to receive and distribute negative pressure across a tissue site  5  to which the wound dressing  100  is applied, allowing for the wicking of fluid (e.g. exudate) from the tissue site  5  and providing a distributed compressive force along the tissue site  5 . As another example, the absorbent layer  30  may be used to facilitate the delivery of fluid across a tissue site  5 . 
     In embodiments incorporating an absorbent layer  30 , the size and shape of the absorbent layer  30  may be varied as desired. In various embodiments, the outer periphery of the absorbent layer  30  may be shaped and sized to generally correspond to, or optionally be smaller than, the outer periphery of the wound interface layer  10 . 
     Any material or combination of materials might be used for the absorbent layer  30 . In some embodiments, the absorbent layer  30  may comprise a porous and permeable foam layer, with the absorbent layer  30  being formed from a reticulated, open-cell polyurethane or polyether foam that allows good permeability of wound fluids while under a reduced pressure. In one non-limiting example, the absorbent layer  30  may be an open-cell, reticulated polyurethane foam such as GranuFoam® dressing available from Kinetic Concepts, Inc. of San Antonio, Tex. In other embodiments the absorbent layer  30  may be an open-cell, reticulated polyurethane foam such as a V.A.C. VeraFlo® foam, also available from Kinetic Concepts, Inc., of San Antonio, Tex. In yet other embodiments, the absorbent layer  30  may be formed of un-reticulated open-cell foam. 
     Drape Layer 
     A drape layer  20  adapted to seal to a patient&#39;s skin  3  may advantageously be provided to position and maintain the active debridement wound dressing  100  about the desired treatment tissue site  5 . An attachment device, such as e.g. an adhesively coated margin  23  as illustrated in  FIGS. 1 and 6 , may be used to attach the drape layer  20  to a desired location along the patient&#39;s skin  3 . In various embodiments, the drape layer  20  may provide a bacterial barrier and protection from physical trauma, and may be permeable to water vapor but impermeable to liquid. 
     Drape layer  20  may be formed from any number of materials, such as, e.g. polyurethane film. In some embodiments, the drape  20  may be adapted to provide a fluid-tight seal with the patient&#39;s skin  3  surrounding the tissue site  5  that is to be treated. In such embodiments, the drape layer  20  may be constructed from a material adapted to reduce evaporative losses and provide and maintain a fluid seal. As non-limiting examples, the drape layer  20  may be formed from materials that include a silicone, 3M Tegaderm® drape material, acrylic drape material such as one available from Avery, or an incise drape material. 
     Drive Unit 
     As explained above, the active layer  40  is designed to intentionally oscillate or translate the wound interface layer  10  in response to the collapse and expansion of the pneumatic members  45  forming the active layer  40 . To that effect, wound debridement system  1  may include a drive unit  70  adapted to generate the required changes in pressure to achieve the desired movement of the wound interface layer  10 . The drive unit  70  may comprise any number of or any combination of known devices adapted to generate and deliver negative and/or positive pressure. 
     The drive unit  70  may be directly or indirectly pneumatically coupled to the active layer  40  and is adapted to intermittently apply pressure to the active layer  40 . In general, the drive unit  70  is adapted to apply pressure to collapse or expand the pneumatic members  45  from an initial configuration, following which the drive unit  70  is adapted to interrupt the application of pressure (or, in some embodiments, apply a second, opposite pressure is applied to counter the first applied pressure), thereby allowing the pneumatic members  45  to expand or collapse to their initial configuration. 
     The drive unit  70  may be incorporated into the wound debridement system  1  in any number of different forms. For example, in some embodiments, such as, e.g. illustrated in  FIGS. 2B and 2C , the drive unit  70  may be formed within or on the wound dressing  100 , while in other embodiments, such as, e.g. illustrated in  FIG. 1 , the drive unit  70  may be provided as a standalone device that is separate from the wound dressing  100 . 
     i. Non-Localized Pressure Application 
     In various embodiments, such as e.g. illustrated in  FIG. 6 , the drive unit  70  may be used to control changes in the ambient environment in which the wound dressing  100  (including the active layer  40 ) is enclosed to indirectly activate the pneumatic members  45  of the active layer  40  and thereby drive the wound interface layer  10  in a lateral and/or longitudinal direction relative to the tissue site  5 . In such embodiments, drape layer  20  may be adapted to define a sealed, substantially fluid-tight treatment space  25  between a lower surface of the drape layer  20  and the patient&#39;s skin  3 . A fluid connection between the drive unit  70  and the treatment space  25  (via, e.g. tubing  75  attached to a port  28  attached to the drape layer  20 ) may allow for the pressure within the treatment space  25  to be varied by the drive unit  70 . 
     In such embodiments, a desired activation (i.e. collapse and/or expansion) of the pneumatic members  45  and resultant lateral and/or longitudinal movement of the wound interface layer  10  relative to the tissue site  5  may be achieved by varying the type or amount of pressure that is delivered by the drive unit  70  to the treatment space  25 . Because the delivery of pressure to drive the pneumatic members  45  is not localized to the active layer  40 , in such embodiments the pressure applied by the drive unit  70  to drive the active layer  40  may also result in pressure being applied to the tissue site  5  that is located within the treatment space  25 , with the pressure at the tissue site  5  being substantially equivalent to the pressure at the active layer  40 . Accordingly, operation of such wound debridement system  1  embodiments may result not only in debridement of debris  7  at the tissue site  5 , but may also advantageously provide benefits similar to or the same as those of NPWT treatments to the tissue site  5  in doing so. 
     ii. Isolated Pressure Application 
     In various embodiments, it may be desirable that the other components of the wound dressing  100  and/or the tissue site  5  to which the wound dressing  100  is applied not be subject to the same changes in pressure that the active layer  40  is subjected to during operation of the wound debridement system  1 . Accordingly, in some embodiments, the active layer  40  may be pneumatically isolated from the rest of the wound dressing  100  such that the pressures that the pneumatic members  45  are subjected to by the drive unit  70  are not necessarily transmitted to the remaining portions of the wound dressing  100  and/or tissue site  5 . 
     As illustrated in  FIG. 1 , in one embodiment, this isolation of the active layer  40 , and in particular the pneumatic members  45  of the active layer  40 , may be achieved by encapsulation of the pneumatic members  45  of the active layer  40  within the film layer  60 . At least the portions of the upper film  61  and lower film  62  defining the hollow interior  66  of the film layer  60  within which the pneumatic members  45  are encapsulated are provided free of any fenestrations  63 . Accordingly, pressure delivered by the drive unit  70  is applied directly to the pneumatic members  45  encapsulated by the film layer  60  and is localized to the interior  66  of the film layer  60 . As such, in such embodiments, the pressure to which the active layer  40  is subjected to is not necessarily the same pressure as the pressure at the tissue site  5 . As illustrated in  FIG. 1 , the pneumatic connection between the drive unit  70  and the interior  66  of the film layer  60  may be provided via a connection between tubing  75  and a port  67  extending through the film layer  60 . 
     Although the embodiment described above (i.e. in which each of the pneumatic members  45  of the active layer  40  is encapsulated by the film layer  60 ) may allow for the isolated application of pressure to the active layer  40 , each of the one or more pneumatic members  45  forming the active layer  40  are subjected to the same pressure. In particular, the pressure to which each pneumatic member  45  is subject is equal to the pressure that is applied to the interior  66  of the film layer  60  by the drive unit  70 . However, in some embodiments, it may be desirable to use the drive unit  70  to apply different amounts and/or types of pressure to achieve individualized and independent activation and control of the one or more pneumatic members  45  forming the active layer  40 . 
     Accordingly, in some embodiments, the one or more of the pneumatic members  45  forming the active layer  40  may be individually encapsulated (e.g. by the film layer  60 ) such that each encapsulated pneumatic member  45  is pneumatically isolated from the other pneumatic members  45  forming the active layer  40 . A fluid connection between the drive unit  70  and the individually pneumatic members  45  may allow the drive unit  70  to selectively collapse and expand each of the pneumatic members  45  independently from the activation (i.e. collapse and expansion) of the remaining pneumatic members  45  forming the active layer  40 . 
     As illustrated in  FIGS. 2B and 2C , in embodiments in which the pneumatic members  45  comprise one or more non-apertured single-direction collapsible structures  43  having hollow interiors  41 , the pneumatic isolation of the pneumatic members  45  may be achieved by establishing a fluid connection between the hollow interiors  41  of the non-apertured single-direction collapsible structures  43  and the drive unit  70 . As shown in  FIGS. 2B and 2C , in some embodiments, this fluid connection may be provided via a connection of the drive unit  70  to a port  49  formed on the single-direction collapsible structure  43 . This fluid, pneumatic connection between the drive unit  70  and the port  49  of the single-direction collapsible structure  43  may allow for the isolated control of the single-direction collapsible structure  43  to which the drive unit  70  is coupled. 
     As will be understood, in embodiments in which the drive unit  70  is pneumatically connected to the hollow interior(s)  41  of one or more non-apertured single-direction collapsible structures  43 , the interconnectedness of the hollow interiors  41  of a non-apertured single-direction collapsible structures  43  forming the active layer  40  may allow for the independent control of one or more single-direction collapsible structures  43 . For example, where the hollow interiors  41  of the one or more non-apertured, single-direction collapsible structures  43  are fluidly connected, a connection between the drive unit  70  and a port  49  on a single one of the interconnected single-direction collapsible structures  43  may allow the drive unit  70  to activate each of the interconnected single-direction collapsible structures  43 . Accordingly, in the embodiment of  FIGS. 2A-2C , where the hollow interiors  41  each of the bellowed limbs  43  and the hub  48  of the spoke-like pneumatic member  45  are fluidly connected, pressure applied to the hub  48  by the drive unit  70  may be transferred amongst the bellowed limbs, resulting in the desired collapse and expansion of the active layer  40 . 
     In contrast, in embodiments in which the hollow interiors  41  of non-apertured singled-direction collapsible structures  43  are pneumatically isolated from one another, each of the single-direction collapsible structures  43  may be controlled independent from one another. In such embodiments, the selective pneumatic attachment of the drive unit  70  to particular pneumatic members  45  and the selective delivery of pressure by the drive unit  70  to these particular pneumatic members  45  may allow the drive unit  70  to provide multiphasic, multi-directional oscillation and/or translation of the active layer  40 . 
     For example, in one embodiment (not shown), the active layer  40  may comprise a pneumatic member  45  formed of a plurality of laterally extending pneumatic members  45  and a plurality of longitudinally extending pneumatic members  45  that form a grid-like pattern. The drive unit  70  may be operably connected to at least one of the laterally extending pneumatic members  45  and at least one of the longitudinally extending pneumatic members  45 . By selectively varying the delivery or negative or positive pressure to the laterally and/or longitudinally extending pneumatic members  45 , the drive unit  70  may be adapted to allow for activation of the active layer  40  is such a manner that allows for both lateral and/or longitudinal translation of the wound interface layer  10  relative to the tissue site  5 . 
     Control Unit 
     In various embodiments, the delivery of pressure by the drive unit  70  to the active layer  40  to collapse or expand the pneumatic members  45  of the active layer  40  may be based upon signals received from an optionally included control unit  80 . In some embodiments, the control unit  80  may communicate with the drive unit  70  using any number of known communication methods, including wireless communication. 
     The control unit  80  may be adapted to vary the type and amount of pressure that is to be delivered by the drive unit  70  based on any number of factors including, but not limited to: the tissue site  5  being treated (such as, but not limited to bone tissue, adipose tissue, muscle tissue, neural tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, or ligaments, chronic, acute, traumatic, subacute, and dehisced wounds, partial-thickness burns, ulcers, flaps, grafts, etc.); the type of debris  7  being debrided (such as, but not limited to necrotic tissue, eschar, impaired tissue, other sources of infection, exudate, slough including hyperkeratosis, pus, foreign bodies, biofilm, or other types of bioburden, etc.); the thickness, consistency, color and/or moisture levels of the debris  7 ; the desired relative amount of lateral and/or longitudinal movement of the wound interface layer  10  relative to the tissue site  5 ; etc. In some embodiments the control unit  80  and drive unit  70  may be formed as a single unit, while in other embodiments the drive unit  70  and control unit  80  may be provided separately. 
     Use with Other Treatment Systems 
     As illustrated by the embodiment of  FIG. 1 , in various embodiments, wound debridement system  1  may be used as a standalone therapy device, with drive unit  70  and optional control unit  80  being provided solely for the operation of the wound debridement system  1 . However, as noted previously, in other embodiments it may be possible to utilize the wound debridement system  1  in conjunction with one or more additional therapeutic treatment systems configured to provide a desired therapeutic treatment to the tissue site  5  in addition to the debris  7  debridement provided by the wound debridement system  1 . 
     In embodiments in which the wound debridement system  1  is used in conjunction with one or more additional therapeutic treatment systems, one or more of the components of the wound debridement system  1  may optionally comprise one or more elements of the additional therapeutic treatment system. For example, the drape layer  20  may optionally be omitted from the wound dressing  100  in embodiments in which the wound debridement system  1  is used in conjunction with an additional therapeutic treatment system incorporating a backing layer to position and maintain an element of the additional therapeutic treatment system against a patient&#39;s skin  3  during therapy. Accordingly, as illustrated e.g. by  FIG. 6 , in embodiments in which the additional therapeutic treatment system is a NPWT system  200 , the backing layer  220  of the NPWT system  200  that is sealed to a patient&#39;s skin  3  may optionally also serve as the drape layer  20  of the wound debridement system  1 . 
     Similarly, in some embodiments the drive unit  70  may comprise a pressure source included as a part of an additional therapeutic treatment system that the wound debridement system  1  is used in conjunction with. In some such embodiments, the pressure source of the additional therapeutic treatment system may be adapted to independently regulate and deliver pressure to a plurality of devices, such that the pressure source may allow the drive unit  70  to deliver pressure to the wound dressing  100  independently from the pressure that is delivered by the pressure source to the additional therapeutic treatment system. For example, as illustrated in  FIG. 6 , the pump  270  of the NPWT system  200  may also serve as the drive unit  70 . 
     In other embodiments, the pressure source of the additional therapeutic treatment system may not be adapted to allow for independent regulation and delivery of pressure to a plurality of devices, with the operation of the drive unit  70  being dependent on the pressure that is delivered by the pressure source to the additional therapeutic treatment system. 
     In some embodiments, the wound debridement system  1  may be used in conjunction with (either before, during or after) existing tissue removal and debridement systems and methods. For example, the wound debridement system  1  may be used prior to enzymatic debridement to soften the debris  7 . In another example, an existing mechanical debridement technique or method may be used to remove a portion of the debris  7  at the tissue site  5 , and the wound debridement system  1  may then be used to remove the remaining debris  7  while reducing the risk of trauma to the tissue site  5 . 
     As illustrated in  FIG. 6 , in various embodiments, the additional therapeutic treatment system that the wound debridement system  1  is used in conjunction with may be a NPWT system  200 . The use of the wound debridement system  1  with the NPWT system  200  may improve the functioning of both the systems, as the debridement of the debris  7  at the tissue site  5  may improve the efficacy of the NPWT treatment of the tissue site  5 , while the negative pressure applied by the NPWT system  200  may advantageously assist in removing the debris  7  that has been loosened and removed from the tissue site  5  by the wound debridement system  1 . 
     In some embodiments in which the wound debridement system  1  is used in conjunction with a NPWT system, the rigidity of the materials used in the active layer  40  of the wound dressing  100  and the rate of the intermittent application of negative pressure used to drive the active layer  40  may be selected to ensure that the intermittent release of negative pressure utilized to drive the active layer  40  does not interfere with the continuous, uninterrupted application of negative pressure by the NPWT system. 
     In particular, the pneumatic members  45  of the active layer  40  may be constructed such that the activation (i.e. collapse) of the pneumatic members  45  will not occur until a predetermined threshold pressure is reached, with the predetermined threshold pressure being a negative pressure that is greater than the negative pressure applied as part of the NPWT treatment. The activation of the pneumatic members  45  can then be controlled by intermittently ramping up the negative pressure within the treatment space  25  from an initial negative pressured applied as part of the NPWT treatment to the predetermined threshold level, and subsequently decreasing the negative pressure to the initial, negative pressure level. 
     By configuring the active layer  40  such that the threshold pressure required to collapse the active layer  40  is greater than the negative pressure applied as part of the NPWT treatment, the wound debridement system  1  allows for the continuous driving of the wound interface layer  10  by the active layer  40 , even when the NPWT system is sustaining a negative pressure within the treatment space  25 . Also, because the activation of the pneumatic members  45  is based on the cyclical variation of pressure from a first negative pressure (i.e. the NPWT treatment pressure) to a second, greater pressure (threshold pressure), operating the pump  270  of the NPWT system on an intermittent cycle in which the pressure applied by the pump  270  is cycled between the first and second pressure will allow the pump  270  of the NPWT system to control both the NPWT treatment and the wound debridement. 
     Alternatively, in some embodiments in which the wound debridement system  1  is used in conjunction with a NPWT system  1 , such as e.g. illustrated in  FIG. 6 , the risk of interfering with the continuous negative pressure that is applied during NPWT treatment may be entirely avoided by pneumatically isolating the pneumatic members  45 . In such embodiments, the pneumatic members  45  can be driven independently from the pressure at the tissue site  5  that is imparted by the NPWT system  200 . 
     In some embodiments, the wound debridement system  1  may be used in conjunction with an instillation therapy system. In such embodiments, a NPWT system may also optionally be included. The instillation therapy system may assist in the hydration and flushing of the tissue site  5 , which may facilitate the debridement of the debris  7  by the wound debridement system  1 . In turn, the wound debridement system  1  may allow for greater control of the instillation therapy system. 
     More specifically, in some embodiments, the active layer  40  may be actuated by the drive unit  70  during the instillation fill, soak and removal phases of instillation therapy. During the fill phase, the actuation of the active layer  40  may encourage a thorough and uniform distribution of the instillation fluid at the tissue site  5  by the wound interface layer  10 . During the soak phase, the hydrating effect of the instillation fluid at the tissue site  5  may increase the debridement efficiency of wound interface layer  10 . Additionally, in some embodiments, the instillation fluid may optionally contain a topical solution that may assist in reducing patient discomfort during the debridement process. Finally, the flushing and fluid removal phase of the instillation therapy may encourage and assist in the removal of debrided debris  7  from the tissue site  5 . 
     Configuration of Exemplary Embodiments 
     The construction and arrangement of the systems and methods as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements can be reversed or otherwise varied and the nature or number of discrete elements or positions can be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps can be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure.