Abstract:
The present disclosure describes a dressing for use in a vacuum wound therapy procedure to promote healing of a wound. The dressing includes a cover layer for positioning over a wound to define a reservoir in which a reduced pressure may be maintained over the wound. A portal member is mounted relative to the cover layer and defines a fluid passage for fluid coupling with a reduced pressure supply conduit for creating the reduced pressure within the reservoir. A filter screen is mounted relative to the fluid passage and is dimensioned to minimize passage of tissue particles of predetermined dimension through the fluid passage of the portal member

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to, and the benefit of, U.S. Provisional Application Ser. No. 61/036,275, filed on Mar. 13, 2008 by Vitaris, the entire contents of which are being hereby incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates generally to a wound dressing for treating an open wound with a vacuum wound therapy procedure. In particular, the disclosure relates to a wound dressing employing a portal member to establish fluid communication between a fluid conduit and a reservoir over a wound in which a negative pressure may be maintained. 
         [0004]    2. Background of Related Art 
         [0005]    The body&#39;s natural wound healing process is a complex series of events beginning at the moment of injury. Initially the body reacts by delivering proteins and other factors to the wound through the blood stream to minimize the damage. Blood clots to prevent blood loss while cells engulf bacteria and debris to carry it away from the wound site. Next, the body begins to repair itself in a stage of healing often referred to as the proliferate phase. This phase is characterized by the deposition granulation tissue in the wound bed. Granulation tissue provides a base structure over which cells may migrate inwardly from the periphery to close the wound. Finally the process ends as collagen gives strength to new tissue over time often forming a scar. 
         [0006]    One technique for promoting the natural healing process, particularly, but not exclusively during the proliferate phase, is known as vacuum wound therapy (VWT). Application of a reduced pressure, e.g. sub-atmospheric, to a localized reservoir over a wound has been found to assist in closing the wound. The reduced pressure may be effective to promote blood flow to the area, to stimulate the formation of granulation tissue and the migration of healthy tissue over the wound by the natural process. Also a reduced pressure may assist in removing fluids exuding from the wound, which may inhibit bacterial growth. This technique has proven effective for chronic or non-healing wounds, but has also been used in for other purposes such as post-operative wound care. 
         [0007]    The general VWT protocol provides for the introduction of a filler material into the wound to absorb exudates and promote fluid transport away from the wound bed. The wound filler may comprise such materials as non-reticulated foams, non-woven reinforcements or gauze. The wound and the absorbent wound filler material may then be covered by a flexible cover layer having an adhesive periphery that forms a substantially fluid tight seal with the healthy skin surrounding the wound. The cover layer thus defines a vacuum reservoir over the wound where a reduced pressure may be maintained over time by individual or cyclic evacuation procedures. 
         [0008]    An aspect of concern in a VWT treatment is the management of wound fluids drawn from the wound. For example, wound fluids may include large particles, which may tend to clog fluid conduits available for exudate transport and may also inhibit penetration of the reduced pressure to the wound. Also bacteria in the wound fluid may generate an unpleasant odor or may present health risks to patients and clinicians. Accordingly, a need exists for a dressing including a vacuum port suitable for managing wound fluids in a VWT procedure. 
       SUMMARY 
       [0009]    The present disclosure describes a dressing for use in a vacuum wound therapy procedure to promote healing of a wound. The dressing includes a cover layer for positioning over a wound to define a reservoir in which a reduced pressure may be maintained over the wound. A portal member is mounted relative to the cover layer and defines a fluid passage for fluid coupling with a reduced pressure supply conduit for creating the reduced pressure within the reservoir. A filter screen is mounted relative to the fluid passage and is dimensioned to minimize passage of tissue particles of predetermined dimension through the fluid passage of the portal member. 
         [0010]    The filter screen may be integral to the portal member. Alternatively, the filter screen may be a distinct component from the portal member, and the portal member may include a cavity therein to receive the filter screen. The filter screen may be dimensioned to be received within the cavity such that the filter screen is substantially flush with a patient facing underside of the portal member. Alternatively, the filter screen may be dimensioned to be received within the cavity such that the filter screen extends beyond the patient facing underside of the portal member. 
         [0011]    The filter screen may include a therapeutic material adapted to control a characteristic of exudate drawn through the fluid passage of the portal member. The therapeutic material may include activated charcoal to control an odor of the exudate, or an antimicrobial to control a bio-burden of the exudate. 
         [0012]    The wound dressing may include a treatment element mounted adjacent the filter screen, wherein the treatment element includes a material adapted to control a characteristic of exudate drawn through the fluid passage of the portal member. The material of the treatment element may be adapted to control one of odor and microbials. The wound dressing may include a second filter screen and the treatment element may be secured between first and second filter screens to define an insert for reception into the cavity. 
         [0013]    The portal member may include a flange defining an outer surface and a patient surface generally facing the wound, and the fluid passage may extend through the outer surface and the patient surface. The portal member may also include a connector segment for connection to the reduced pressure supply conduit. The flange of the portal member may be secured to the cover layer of the dressing. A negative pressure source may be in fluid communication with the reduced pressure supply conduit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the detailed description of the embodiments given below, serve to explain the principles of the disclosure. 
           [0015]      FIG. 1  is an exploded perspective view of a vacuum wound therapy system in accordance with the present disclosure; 
           [0016]      FIG. 2  is an orthographic view of a wound facing side of the cover layer of  FIG. 1 ; 
           [0017]      FIG. 3  is an exploded cross sectional view taken along the line  3 - 3  of  FIG. 2 ; 
           [0018]      FIG. 4A  is a cross sectional view of the vacuum wound therapy system of  FIG. 1  installed over wound on a patient prior to application of a reduced pressure; 
           [0019]      FIG. 4B  is a cross sectional view of the vacuum wound therapy system of  FIG. 1  installed over wound on a patient following an application of a reduced pressure; 
           [0020]      FIG. 5  is a top plan view of a vacuum port of  FIG. 1 ; 
           [0021]      FIG. 6  is a perspective view of the vacuum port of  FIG. 5 ; 
           [0022]      FIG. 7  is a perspective view of an alternative embodiment of a vacuum port; 
           [0023]      FIG. 8  is an exploded perspective view of an alternative embodiment of a vacuum port assembly including a portal member and an independent filter screen; 
           [0024]      FIG. 8A  is a perspective view of the filter screen of  FIG. 8  in an alternate orientation; 
           [0025]      FIG. 8B  is a perspective view of an alternate embodiment of an independent filter screen; 
           [0026]      FIG. 9  is a bottom plan view of the portal member of  FIG. 8 ; 
           [0027]      FIG. 10  is a partial cross sectional view of the vacuum port assembly assembled in a wound dressing; and 
           [0028]      FIG. 11  is an exploded perspective view of an alternative embodiment of a vacuum port assembly including a treatment element. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0029]    The wound dressing of the present disclosure promotes healing of a wound by providing a reservoir over the wound where a reduced pressure may be maintained. The reservoir subjects the wound to a sub-atmospheric pressure to effectively draw wound fluid, including liquid exudates, from the wound without the continuous use of a vacuum pump. Hence, vacuum pressure may be applied once, or in varying intervals depending on the nature and severity of the wound. To facilitate fluid transport from the wound, a filler material may be included within the reservoir to promote the wicking of wound fluids subject to a reduced pressure. The use of a wound dressing in this manner has been found to promote healing by reducing the probability of infection, stimulating the deposition of granulation tissue and other beneficial processes. The wound dressing of the present disclosure includes a cover layer having a reinforcement structure to enhance the effect of a vacuum wound therapy treatment. 
         [0030]    The attached figures illustrate exemplary embodiments of the present disclosure and are referenced to describe the embodiments depicted therein. Hereinafter, the disclosure will be described in detail by explaining the figures wherein like reference numerals represent like parts throughout the several views. 
         [0031]    Referring initially to  FIG. 1 , a vacuum wound therapy system according to the present disclosure is depicted generally as  10  for use on a wound “w” surrounded by healthy skin “s.” The vacuum wound therapy system  10  includes a vacuum system  12  in fluid communication with a vacuum reservoir  14  ( FIG. 4A ) defined by or within wound dressing  16 . The vacuum system  12  includes a vacuum source  18  coupled to the dressing  16  through a one-way valve  20  and a vacuum tube  24 . A collection canister  28  may be provided for wound drainage and debris. The vacuum system  12  is adapted to provide a reduced pressure to the vacuum reservoir  14  appropriate to stimulate healing of the wound “w.” A more detailed description of an appropriate vacuum system  12  is found in commonly assigned U.S. Patent Application Publication 2007/0066946, the entire contents of which are incorporated herein by reference. 
         [0032]    A vacuum port  30 , depicted in greater detail in  FIG. 5  and  FIG. 6 , may also be included to facilitate connection of the vacuum system  12  to the dressing  16 . The vacuum port  30  may be configured as a rigid or semi-rigid, low-profile component adapted to receive the vacuum tube  24  in a releasable and fluid-tight manner. The vacuum port  30  may be configured to include a wide and flexible flange  32  about its perimeter. The flange  32  permits an adhesive to be attached to either an underside of flange  32  for securement to an outer surface of cover layer  44 , or to a top side of flange  32  to provide for mounting to the underside of the reinforcement layer  46 . Either configuration provides a mechanism for connecting to the dressing  16 . A hollow interior of the vacuum port  30  provides fluid communication between the vacuum tube  24  and the reservoir  14  defined by or within dressing  16 . A connector segment  33  extends above the flange  32  for facilitating connection with the vacuum tube  24 . It is envisioned that because of the possible intimate proximity of the vacuum port  30  to either reservoir  14  or wound filler  38 , the performance of vacuum port  30  may be enhanced by the incorporation of a filter screen  58  as depicted in  FIG. 6  and  FIG. 7 . Filter screen  58  may inhibit the migration of large particles that may otherwise be drawn into the vacuum port  30  and consequently create a restriction or blockage of the vacuum tube  24 . The filter screen  58  may be integral to the configuration of the vacuum port  30  as part of the port flange  32 . The filter screen  58  may include a number of openings, each smaller than a cross-sectional area of the vacuum tube  24  or the opening in the vacuum port  30  adapted to receive the vacuum tube  24 , and collectively greater than the cross-sectional area of vacuum tube  24  or the opening in the vacuum port  30  adapted to receive the vacuum tube  24 . For example, the filter screen  58  of vacuum port  30  may include four relatively large openings, while the filter screen  58 A of vacuum port  30 A depicted in  FIG. 7  may include six relatively small openings. The openings in the filter screens  58 ,  58 A are dimensioned to minimize the passage of tissue particles of a predetermined dimension through the respective vacuum port  30 ,  30 A. 
         [0033]    Another alternate embodiment of a vacuum port is depicted generally as  30 B in  FIGS. 8 ,  9 ,  10  and  11 . Vacuum port  30 B may be configured to accept a filter screen  59  or  60  as a distinct or independently manufactured component as depicted in  FIGS. 8 ,  10  and  11 . An opening or cavity  31  depicted in the plan view of  FIG. 9  and shown in phantom in  FIG. 8  on an underside of vacuum port  30 B may be adapted to permit filter screen  59  to be permanently bonded therein such that filter screen  59  is substantially flush with the underside of vacuum port  30 B. Alternatively, filter screen  60  may be bonded to the opening on the underside of vacuum port  30 B. Filter screen may  60  includes a generally flat base  62  through which the openings  65  extend, and a pair lips  64  projecting from the base  62  along opposite edges of the filter screen  60 . The lips  64  may be dimensioned to be flush with a patient facing under surface of the flange when received within the cavity  31 . Alternatively the lips  64  may extend beyond the under surface of the flange to extend beyond the cavity  31  in the portal member  30 B as depicted in  FIG. 10 . Filter screen  60  may exhibit an increased surface area available for bonding within cavity  31  of vacuum port  30 B. Filter screen  60  may be secured within cavity  31  by bonding, cements, adhesives or the like. In one embodiment, filter screen  62  is positioned within cavity  31  with lips  64  facing toward the wound ( FIGS. 8 and 10 ). In another embodiment, filter screen  62  is positioned within lips  64  facing toward vacuum port  30 B and away from the wound (FIG.  8 A). In another embodiment, base  62  is devoid of lips  64  as shown in  FIG. 8B , and is substantially planar. 
         [0034]    It is also envisioned that filter screens  59  and  60  may be provided in combination with a treatment element  61  comprising a therapeutic material as depicted in  FIG. 11 . Treatment element  61  may be inserted between filter screens  59 ,  60  and may secured to vacuum port  30 B by an appropriate adhesive bond. The treatment element  61  and filter screens  59 ,  60  may define an insert for reception into cavity or opening  31  on the underside of portal member  30 B. This arrangement may provide a convenient method of treating the wound exudate as it is drawn from the wound “w.” Treatment element  61  may comprise fibrous or granulated materials contained in a porous container or wrap to facilitate placement between filter screens  59  and  60 . Treatment element  61  may include materials such as activated charcoal or other odor control or neutralizing substances. Treatment element  61  may include anti-bacterials such as polyhexamethylene biguanide (PHMB). Also, antimicrobials such as ionic metals or biguinides may be included to reduce the bio-burden of the exudate or microbials within the exudate as the exudate is drawn in to a collection canister  28 . In the alternative, filter screens  59 ,  60  may comprise charcoal, antimicrobials, anti-odor substances. 
         [0035]    Vacuum tube  30  may be configured to accept a variety of tubing geometries such as round, oblong or elliptical. Vacuum port  30  may be provided as a pre-affixed component of dressing  16 , as part of vacuum system  12  or entirely independently. Also vacuum port  30  may not be necessary depending on the configuration of dressing  16 . 
         [0036]    Wound dressing  16  generally includes a contact layer  34 , filler  38  and a reinforced cover layer  40 . Reinforced cover layer  40  may be formed from a composite including a backing layer  44 , a reinforcement layer  46  and an adhesive layer  48 . Each layer of wound dressing  16  is described in greater detail below. 
         [0037]    Contact layer  34  may be sufficiently conformable to be positioned in direct contact with an irregularly shaped surface of a wound bed “w.” A thin film of polyethylene or other suitable non-adherent material may form the contact layer  34  to limit the adherence of filler  38  and other substances to the wound “w.” Apertures or perforations in the film permit fluids to pass through the contact layer  34 , allowing for the sub-atmospheric pressure to penetrate into the wound “w” and for exudates to flow freely out of the wound “w.” By selecting an appropriate film material, the passage of wound exudate through contact layer  34  may be controlled so as to be substantially unidirectional to prevent wound exudate from flowing back into the wound. To promote a unidirectional flow, a conical apertured film, such as those provided by Tredegar Film Products of Richmond, Va., may be selected for forming contact layer  34 . This type of film is arranged with apertures positioned at the peaks of cone shaped formations in the film material such that exudate encounters the film as an array of micro-funnels in one direction and an array of collecting basins in the other. Though it is depicted in a square configuration, the shape of the contact layer  34  can be customized to better suit the wound geometry. Unidirectional flow of exudates may also be promoted by the selection of other materials including a lamination of layers having varying absorptive characteristics. One exemplary material, which may be used as a contact layer is sold under the trademark XEROFLO® by Kendall Corp., a division of Covidien. 
         [0038]    Filler  38  may be arranged over contact layer  34  to fill wound “w” to the level of the surrounding healthy skin “s” or may over-fill the wound “w” as depicted in  FIG. 4A . An absorbent material such as non-woven gauze or reticulated foam may be used for filler  38  to trap or transport any exudate that migrates through contact layer  34 . An antimicrobial dressing sold under the trademark KERLIX® by Kendall Corp., a division of Covidien, may be suitable for use as filler  38 . To prevent adhesion to the wound “w,” the filler  38  may also comprise a material configured such that any stray fibers do not tend to protrude through apertures of contact layer  34  where they may become engulfed by newly forming granulation tissue. One particular type of material exhibiting this characteristic is often referred to as “tow.” The manufacturing process for synthetic fibers often includes an extrusion of an indeterminate length of continuous filaments, which are spun together to form fibers. It is the continuous lengths of un-spun filaments which are referred to as tow. A single length of tow formed from a hydrophobic material such as polyolefin may be laid in the wound bed “w” to form filler  38 . This arrangement allows for a complete removal of filler  38  when the dressing  16  is changed without re-injuring the wound “w.” 
         [0039]    Cover layer  40  may be placed over the wound “w” enclosing the contact layer  34  and filler  38  therein. The periphery of cover layer  40  extends laterally beyond the perimeter of the wound bed “w” so as to contact the healthy skin “s” to form a seal over the wound “w.” As depicted in  FIG. 2 , adhesive layer  48  may extend to the periphery of cover layer  40  to provide the seal with the use of a medical-grade, pressure-sensitive adhesive. The adhesive layer  48  may be adapted to provide a fluid-tight and bacteria-tight seal around a peripheral region of dressing  16  such that exudate cannot escape through the edges of the dressing  16  and external air and contaminants may not enter the wound area. To provide such a barrier, the adhesive layer  48  may, for example, be on the order of 1.0 to 10 mils thick depending on the adhesive used. In general, a high peal-strength adhesive may be used to resist inadvertent lift-off, roll or “flagging,” i.e., a failure of the dressing to adhere to itself or the patient, at the edges of the cover layer  40 . The adhesive defining the adhesive layer  48  may include, but is not limited to, medical grade acrylics, rubber base or silicone adhesives. Preferably, those adhesives included with the dressing sold under the trademark Polyskin II Transparent Dressings by Kendall Corp., a division of Covidien, may be used. Adhesive layer  48  forms a continuous band around the peripheral region of cover layer  40 , but contains an opening such that the adhesive layer does not extend inwardly to the central areas of cover layer  40 . 
         [0040]    As depicted in  FIG. 3 , reinforcement layer  46  may overlap adhesive layer  48  at an outer edge such that an outer periphery of reinforcement layer  46  is firmly affixed to backing layer  44 . Reinforcement layer  46  extends to a peripheral region of cover layer  40 , but not necessarily to an outer perimeter of the cover layer  40 . Reinforcement layer  46 , particularly any portion not overlapping the adhesive layer  48 , may be affixed to backing layer  44  with a light coat of an adhesive  57  applied to the appropriate side of the reinforcement layer  46  or the backing layer  44 . A portion of a wound facing side  52  of the reinforcement layer  46  carries no adhesive to prevent adhesion of the cover layer  40  to the filler  38 . An aperture  54  extends through the reinforcement layer  46  to permit fluid communication between the reservoir  14  and vacuum system  12 . 
         [0041]    The reinforcement layer  46  may comprise a mesh of polyethylene terephtalate (PET) fibers, which offer good liquid resistance making it suitable for use in a moist wound environment. PET fibers may be used to form woven or non-woven reinforcements having large pore sizes. Some PET reinforcement manufacturing methods provide for interlinking the fiber junctions to yield a mesh that is flexible in multiple directions and also does not unravel when cut. One such method is known as hydro-entanglement. PET reinforcements thus manufactured tend to have a high shear stiffness that may be useful in reinforcing cover layer  40 . One exemplary material, which may be suitable for incorporation into reinforcement layer  46 , is sold under the trademark Sontara® by DuPont. Alternatively, reinforcement layer  46  may be formed from another reinforcement or mesh structure having suitable shear stiffness. Examples of suitable structures include extruded netting and apertured films. Suitable materials for use in such alternate structures include PET, polyethylene, nylon and polypropylene. Additionally, woven structures may be used for reinforcement layer  46 . Acceptable woven materials may include cotton gauze, woven acetate and nylon. 
         [0042]    Extending to the periphery of the cover layer  40  is backing layer  44 . Backing layer  44  provides a substrate to which reinforcement layer  46  and adhesive layer  48  may be affixed. An aperture  56  extends through the backing layer  44  to permit fluid communication between the reservoir  14  and vacuum system  12 . Backing layer  44  may be formed from a flexible polymeric membrane to serve as a fluid barrier to allow for a sub-atmospheric pressure to be established in vacuum reservoir  14 , and also as a microbial barrier preventing contaminants from entering the wound area. For example, backing layer  44  may comprise a polyurethane film having a thickness from about 0.8 mils to about 1.0 mil. Preferably, the backing layer  44  is formed from a moisture vapor permeable membrane to promote the exchange of oxygen and moisture vapor between the wound site and the atmosphere. One exemplary material is a transparent membrane sold under the trade name POLYSKIN® II by Kendall Corp., a division of Covidien. Other materials which may be suitable for use in a backing layer include the thin films marketed under the names TEGADERM™ by 3M of St. Paul, Minn. and OPSITE™ by Smith and Nephew PLC of London, UK. Reinforcement layer  46  may be configured so as not to impede the transmission of moisture vapor by including, for example, a large pore size. 
         [0043]    As seen in  FIG. 4A , reservoir  14  is defined by or within wound dressing  16  when applied to the skin. Filler  38  may be included to fill the reservoir  14 . Evacuating atmospheric gasses from the reservoir  14  may impart a tendency for cover layer  40  to flatten against the wound “w” as depicted in  FIG. 4B . This tendency of cover layer  40  to deform may draw the peri-wound margins into the wound “w” and put the surrounding skin “s” in tension. This tendency may be counteracted or resisted by the shear stiffness in reinforcement layer  46  such that the cover layer  40  may better main its shape. Because reinforcement layer  46  extends to a peripheral region of cover layer  40  and backing layer  44  anchored to healthy skin “s,” the forces associated with evacuating reservoir  14  may be transferred beyond the perimeter of the wound “w,” and may be manifested as compression forces. Thus reinforcement layer  46  reinforces cover layer  40  and vacuum reservoir  14 . 
         [0044]    A central region of reinforcement layer  46  may be devoid of an adhesive coating, such that the reinforcement layer  46  may not tend to adhere to or disturb filler  38 , particularly as the reduced pressure is removed from reservoir  14 . Reinforcement layer  46  thus further protects wound “w” to promote healing throughout the evacuation cycles of a VWT procedure. 
         [0045]    Although the foregoing disclosure has been described in some detail by way of illustration and example, for purposes of clarity or understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.