Abstract:
A system for subatmospheric pressure therapy in connection with healing a wound is provided. The system includes a wound dressing cover dimensioned for positioning relative to a wound bed of a subject to establish a reservoir over the wound bed in which subatmospheric pressure may be maintained, a subatmospheric pressure mechanism including, a housing, a vacuum source disposed in the housing, and a collection canister in fluid communication with the vacuum source. The system further includes an exudate conduit in fluid communication with the wound dressing and the collection canister for collecting exudate removed from the reservoir and deposited in the collection canister under influence of the vacuum source and a vent conduit in fluid communication with the collection canister and the wound dressing for introducing air into the reservoir to facilitate flow of exudate through the exudate conduit.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates generally to treating a wound with negative or reduced pressure. In particular, the disclosure relates to a system for providing continual drainage of fluids from a wound site to a collection canister. 
         [0003]    2. Background of Related Art 
         [0004]    Various techniques to promote healing of a wound involve providing suction to the wound. For example, a vacuum source may serve to carry wound exudates away from the wound, which may otherwise harbor bacteria that inhibit the body&#39;s natural healing process. One particular technique for promoting the body&#39;s natural healing process may be described as negative pressure wound therapy (NPWT). This technique involves the application of a reduced pressure, e.g. sub-atmospheric, to a localized reservoir over a wound. Sub-atmospheric pressure has been found to assist in closing the wound by promoting blood flow to the area, thereby stimulating the formation of granulation tissue and the migration of healthy tissue over the wound. This technique has proven effective for chronic or non-healing wounds, but has also been used for other purposes such as post-operative wound care. 
         [0005]    The general NPWT protocol provides for covering the wound with a flexible cover layer such as a polymeric film, for example, to establish a vacuum reservoir over the wound where a reduced pressure may be applied by individual or cyclic evacuation procedures. To allow the reduced pressure to be maintained over time, the cover layer may include an adhesive periphery that forms a substantially fluid tight seal with the healthy skin surrounding the wound. 
         [0006]    Although some procedures may employ a micro-pump contained within the vacuum reservoir, most NPWT treatments apply a reduced pressure using an external vacuum source. Fluid communication must therefore be established between the reservoir and the vacuum source. To this end, a fluid port is coupled to the cover layer to provide an interface for an exudate conduit extending from the external vacuum source. Fluid being drained from the reservoir through the exudate conduit tends to stagnate with slow fluid buildup. This stagnation results in interrupted and/or incomplete fluid drainage. Accordingly, it would be beneficial to have a negative pressure wound therapy system that included a controlled or fixed “leak” to provide for continuous and/or complete fluid drainage. 
       SUMMARY 
       [0007]    A system for subatmospheric pressure therapy in connection with healing a wound is provided. The system includes a wound dressing cover dimensioned for positioning relative to a wound bed of a subject to establish a reservoir over the wound bed in which subatmospheric pressure may be maintained, a subatmospheric pressure mechanism including, a housing, a vacuum source disposed in the housing, and a collection canister in fluid communication with the vacuum source. The system further includes an exudate conduit in fluid communication with the wound dressing and the collection canister for collecting exudate removed from the reservoir and deposited in the collection canister under influence of the vacuum source and a vent conduit in fluid communication with the collection canister and the wound dressing for introducing air into the reservoir to facilitate flow of exudate through the exudate conduit. 
         [0008]    The vent conduit may define an internal dimension less than a corresponding internal dimension of the exudate conduit. The exudate conduit and the vent conduit may include independent tube segments, or instead may include integral tube segments. A filter may be in fluid communication with the vent conduit. The filter includes a hydrophobic material. The filter may instead or additionally include a bacterial filter. 
         [0009]    Also provided is a system for subatmospheric pressure therapy in connection with healing a wound including a wound dressing cover dimensioned for positioning relative to a wound bed of a subject to establish a reservoir over the wound bed in which subatmospheric pressure may be maintained, a subatmospheric pressure mechanism including, a housing, a vacuum source disposed in the housing, and a collection canister in fluid communication with the vacuum source. The system further includes an exudate conduit in fluid communication with the wound dressing and the collection canister for collecting exudate removed from the reservoir and deposited in the collection canister under influence of the vacuum source and a vent mounted to the wound dressing, the vent being selectively movable between a closed position and an open position, the vent permitting ingress of air within the reservoir when in the open position. 
         [0010]    The vent may include a flap mounted to the wound dressing cover, the flap being movable between the closed position and the open position. The flap may be releasably securable in the closed position with an adhesive. A filter membrane may be mounted adjacent the flap. The filter membrane may include a hydrophobic material. The filter membrane may instead or additionally include a bacterial filter. 
         [0011]    Additionally, provided is a system for subatmospheric pressure therapy in connection with healing a wound including a wound dressing cover dimensioned for positioning relative to a wound bed of a subject to establish a reservoir over the wound bed in which subatmospheric pressure may be maintained, a subatmospheric pressure mechanism including, a housing, a vacuum source disposed in the housing, and a collection canister in fluid communication with the vacuum source. The system further includes an exudate conduit in fluid communication with the wound dressing and the collection canister for collecting exudate removed from the reservoir and deposited in the collection canister under influence of the vacuum source and a filtered air vent mounted to the wound dressing cover, the filtered air vent adapted to permit ingress of air within the reservoir to facilitate flow of exudate through the exudate conduit. 
         [0012]    Additionally, provided is a system for subatmospheric pressure therapy in connection with healing a wound including a wound dressing cover dimensioned for positioning relative to a wound bed of a subject to establish a reservoir over the wound bed in which subatmospheric pressure may be maintained, a subatmospheric pressure mechanism including, a housing, a vacuum source disposed in the housing, and a collection canister in fluid communication with the vacuum source. The system also includes a wound port operatively connected to the wound dressing in fluid communication with the reservoir. The wound port includes a vacuum port and at least one tube piercing through the wound port into the reservoir, the tube being operable to allow ambient air into the reservoir. The system further includes an exudate conduit in fluid communication with the wound port and the collection canister for collecting exudate removed from the reservoir and deposited in the collection canister under influence of the vacuum. 
         [0013]    Additionally, provided is a system for subatmospheric pressure therapy in connection with healing a wound including a wound dressing cover dimensioned for positioning relative to a wound bed of a subject to establish a reservoir over the wound bed in which subatmospheric pressure may be maintained, a subatmospheric pressure mechanism including, a housing, a vacuum source disposed in the housing, and a collection canister in fluid communication with the vacuum source. The system also includes a wound port operatively connected to the wound dressing in fluid communication with the reservoir. The wound port includes a vacuum port and a plurality of holes arranged circumferentially around the wound port, the plurality of holes being operable to allow ambient air into the reservoir. The system further includes an exudate conduit in fluid communication with the wound port and the collection canister for collecting exudate removed from the reservoir and deposited in the collection canister under influence of the vacuum. 
         [0014]    Additionally, provided is a system for subatmospheric pressure therapy in connection with healing a wound including a wound dressing cover dimensioned for positioning relative to a wound bed of a subject to establish a reservoir over the wound bed in which subatmospheric pressure may be maintained, a subatmospheric pressure mechanism including, a housing, a vacuum source disposed in the housing, and a collection canister in fluid communication with the vacuum source. The system also includes a wound port operatively connected to the wound dressing in fluid communication with the reservoir. The wound port includes a vacuum port and an orifice being operable to allow ambient air into the reservoir. The system further includes an exudate conduit in fluid communication with the wound port and the collection canister for collecting exudate removed from the reservoir and deposited in the collection canister under influence of the vacuum. 
         [0015]    Additionally, provided is a system for subatmospheric pressure therapy in connection with healing a wound including a wound dressing cover dimensioned for positioning relative to a wound bed of a subject to establish a reservoir over the wound bed in which subatmospheric pressure may be maintained, a subatmospheric pressure mechanism including, a housing, a vacuum source disposed in the housing, and a collection canister in fluid communication with the vacuum source. The system also includes a wound port operatively connected to the wound dressing in fluid communication with the reservoir. The system further includes an exudate conduit in fluid communication with the wound port and the collection canister for collecting exudate removed from the reservoir and deposited in the collection canister under influence of the vacuum. The exudate conduit has a first conduit for providing a pathway for the exudate between the reservoir and the collection canister and a second conduit in fluid communication with ambient atmosphere and the wound dressing for introducing air into the reservoir to facilitate flow of exudate through the exudate conduit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    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. 
           [0017]      FIG. 1  depicts an embodiment of a NPWT system in accordance with the present disclosure; 
           [0018]      FIG. 2  depicts an embodiment of an NPWT treatment apparatus including a vent conduit; 
           [0019]      FIG. 3A  is a partial cross sectional view of the conduits of the NPWT treatment apparatus of  FIGS. 1 and 2  connected in an alternate configuration; 
           [0020]      FIG. 3B  is a partial cross sectional view of an alternative embodiment of the fluid port of  FIGS. 1 and 2 ; 
           [0021]      FIG. 4  is a cross sectional view of an alternative embodiment of the wound dressing in accordance with the present disclosure; 
           [0022]      FIGS. 5A and 5B  depict alternative embodiments of the wound dressing in accordance with the present disclosure; 
           [0023]      FIGS. 6A and 6B  depict alternative embodiments of the wound dressing in accordance with the present disclosure; 
           [0024]      FIGS. 7A and 7B  depict alternative embodiments of the wound dressing in accordance with the present disclosure; 
           [0025]      FIGS. 8A and 8B  depict alternative embodiments of the wound dressing in accordance with the present disclosure; 
           [0026]      FIG. 9  depicts an alternative embodiment of the wound port in accordance with the present disclosure; 
           [0027]      FIGS. 10A and 10B  depict alternative embodiments of the wound port in accordance with the present disclosure; and 
           [0028]      FIGS. 11A-11D  depict alternative embodiments of the wound port in accordance with the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0029]    Various embodiments of the present disclosure provide negative pressure wound therapy systems (or apparatus) including a collection canister having a chamber to collect wound fluids. Embodiments of the presently disclosed negative pressure wound therapy systems are generally suitable for use in applying negative pressure to a wound to facilitate healing of the wound in accordance with various treatment modalities. Embodiments of the presently disclosed negative pressure wound therapy systems are entirely portable and may be worn or carried by the user such that the user may be completely ambulatory during the therapy period. Embodiments of the presently disclosed negative pressure wound therapy apparatus and components thereof may be entirely reusable or may be entirely disposable after a predetermined period of use or may be individually disposable whereby some of the components are reused for a subsequent therapy application. 
         [0030]    Hereinafter, embodiments of the presently disclosed negative pressure wound therapy systems and embodiments of the presently disclosed sensors for use in negative pressure wound therapy systems will be described with reference to the accompanying drawings. Like reference numerals may refer to similar or identical elements throughout the description of the figures. As used herein, “wound exudate”, or, simply, “exudate”, generally refers to any fluid output from a wound, e.g., blood, serum, and/or pus, etc. As used herein, “fluid” generally refers to a liquid, a gas or both. 
         [0031]    Referring to  FIG. 1 , a NPWT apparatus according to an embodiment of the present disclosure is depicted generally as  10  for use on a wound bed “w” surrounded by healthy skin “s”. Negative pressure wound therapy apparatus  10  includes a wound dressing  12  positioned relative to the wound bed “w” to define a vacuum chamber  14  about the wound bed “w” to maintain negative pressure at the wound area. Wound dressing  12  includes a contact layer  18 , a wound filler  20  and a wound cover  24 . 
         [0032]    Contact layer  18  is intended for placement within the wound bed “w” and may be relatively non-supportive or flexible to substantially conform to the topography of the wound bed “w”. A variety of materials may be used for the contact layer  18 . Contact layer  18  selection may depend on various factors such as the patient&#39;s condition, the condition of the periwound skin, the amount of exudate and/or the condition of the wound bed “w”. Contact layer  18  may be formed from perforated film material. The porous characteristic of the contact layer  18  permits exudate to pass from the wound bed “w” through the contact layer  18 . Passage of wound exudate through the contact layer  18  may be substantially unidirectional such that exudate does not tend to flow back into the wound bed “w”. Unidirectional flow may be encouraged by directional apertures, e.g., apertures positioned at peaks of undulations or cone-shaped formations protruding from the contact layer  18 . Unidirectional flow may also be encouraged by laminating the contact layer  18  with materials having absorption properties differing from those of the contact layer  18 , or by selection of materials that promote directional flow. A non-adherent material may be selected for forming the contact layer  18  such that the contact layer  18  does not tend to cling to the wound bed “w” or surrounding tissue when it is removed. One example of a material that may be suitable for use as a contact layer  18  is commercially available under the trademark XEROFLOW® offered by Tyco Healthcare Group LP (d/b/a Covidien). Another example of a material that may be suitable for use as the contact layer  18  is the commercially available CURITY® non-adherent dressing offered by Tyco Healthcare Group LP (d/b/a Covidien). 
         [0033]    Wound filler  20  is positioned in the wound bed “w” over the contact layer  18  and is intended to transfer wound exudate. Wound filler  20  is conformable to assume the shape of any wound bed “w” and may be packed up to any level, e.g., up to the level of healthy skin “s” or to overfill the wound such that wound filler  20  protrudes over healthy skin “s”. Wound filler  20  may be treated with agents such as polyhexamethylene biguanide (PHMB) to decrease the incidence of infection and/or other medicaments to promote wound healing. A variety of materials may be used for the wound filler  20 . An example of a material that may be suitable for use as the wound filler  20  is the antimicrobial dressing commercially available under the trademark KERLIX™ AMD™ offered by Tyco Healthcare Group LP (d/b/a Covidien). 
         [0034]    Cover layer  24  may be formed of a flexible membrane, e.g., a polymeric or elastomeric film, which may include a biocompatible adhesive on at least a portion of the cover layer  24 , e.g., at the periphery  26  of the cover layer  24 . Alternately, the cover layer  24  may be a substantially rigid member. Cover layer  24  may be positioned over the wound bed “w” such that a substantially continuous band of a biocompatible adhesive at the periphery  26  of the cover layer  24  forms a substantially fluid-tight seal with the surrounding skin “s”. An example of a material that may be suitable for use as the cover layer  24  is commercially available under the trademark CURAFORM ISLAND® offered by Tyco Healthcare Group LP (d/b/a Covidien). 
         [0035]    Cover layer  24  may act as both a microbial barrier and a fluid barrier to prevent contaminants from entering the wound bed “w” and to help maintain the integrity thereof. 
         [0036]    In one embodiment, the cover layer  24  is formed from a moisture vapor permeable membrane, e.g., to promote the exchange of oxygen and moisture between the wound bed “w” and the atmosphere. An example of a membrane that may provide a suitable moisture vapor transmission rate (MVTR) is a transparent membrane commercially available under the trade name POLYSKIN® II offered by Tyco Healthcare Group LP (d/b/a Covidien). A transparent membrane may help to permit a visual assessment of wound conditions to be made without requiring removal of the cover layer  24 . 
         [0037]    Wound dressing  12  may include a vacuum port  30  having a flange  34  to facilitate connection of the vacuum chamber  14  to a vacuum system. Vacuum port  30  may be configured as a rigid or flexible, low-profile component and may be adapted to receive a conduit  36  in a releasable and fluid-tight manner. An adhesive on at least a portion of the underside of the flange  34  may be used to provide a mechanism for affixing the vacuum port  30  to the cover layer  24 . The relative positions, size and/or shape of the vacuum port  30  and the flange  34  may be varied from an embodiment depicted in  FIG. 1 . For example, the flange  34  may be positioned within the vacuum chamber  14  such that an adhesive on at least a portion of an upper side surface of the flange  34  affixes the vacuum port  30  to the cover layer  24 . A hollow interior portion of the vacuum port  30  provides fluid communication between the conduit  36  and the vacuum chamber  14 . Conduit  36  extends from the vacuum port  30  to provide fluid communication between the vacuum chamber  14  and the vacuum source  40 . Alternately, the vacuum port  30  may not be included in the dressing  12  if other provisions are made for providing fluid communication with the conduit  36 . 
         [0038]    Any suitable conduit may be used for the conduit  36 , including conduit fabricated from flexible elastomeric or polymeric materials. In the negative pressure wound therapy apparatus  10  illustrated in  FIG. 1 , the conduit  36  includes a first conduit section  36 A, a second conduit section  36 B, a third conduit section  36 C and a fourth conduit section  36 D. The first conduit section  36 A extends from the vacuum port  30  and is coupled via a fluid line coupling  100  to the second conduit section  36 B, which extends to the collection canister  38 . The third conduit section  36 C extends from the collection canister  38  and is coupled via another fluid line coupling  100  to the fourth conduit section  36 D, which extends to the vacuum source  40 . The shape, size and/or number of conduit sections of the conduit  36  may be varied from the first, second, third and fourth conduit sections  36 A,  36 B,  36 C and  36 D depicted in  FIG. 1 . 
         [0039]    The first, second, third and fourth conduit sections  36 A,  36 B,  36 C and  36 D of the conduit  36  may be connected to components of the apparatus  10  by conventional air-tight means, such as, for example, friction fit, bayonet coupling, or barbed connectors. The connections may be made permanent. Alternately, a quick-disconnect or other releasable connection means may be used to provide some adjustment flexibility to the apparatus  10 . 
         [0040]    Collection canister  38  may be formed of any type of container that is suitable for containing wound fluids. For example, a semi-rigid plastic bottle may be used for the collection canister  38 . A flexible polymeric pouch or other hollow container body may be used for the collection canister  38 . Collection canister  38  may contain an absorbent material to consolidate or contain the wound fluids or debris. For example, super absorbent polymers (SAP), silica gel, sodium polyacrylate, potassium polyacrylamide or related compounds may be provided within collection canister  38 . At least a portion of canister  38  may be transparent or semi-transparent, e.g., to permit a visual assessment of the wound exudate to assist in evaluating the color, quality and/or quantity of exudate. A transparent or semi-transparent portion of the collection canister  38  may permit a visual assessment to assist in determining the remaining capacity or open volume of the canister and/or may assist in determining whether to replace the collection canister  38 . 
         [0041]    The collection canister  38  is in fluid communication with the wound dressing  12  via the first and second conduit sections  36 A,  36 B. The third and fourth conduit sections  36 C,  36 D connect the collection canister  38  to the vacuum source  40  that generates or otherwise provides a negative pressure to the collection canister  38 . Vacuum source  40  may include a peristaltic pump, a diaphragmatic pump or other suitable mechanism. Vacuum source  40  may be a miniature pump or micropump that may be biocompatible and adapted to maintain or draw adequate and therapeutic vacuum levels. The vacuum level of subatmospheric pressure achieved may be in the range of about 20 mmHg to about 500 mmHg. In embodiments, the vacuum level may be about 75 mmHg to about 125 mmHg, or about 40 mmHg to about 80 mmHg. One example of a peristaltic pump that may be used as the vacuum source  40  is the commercially available Kangaroo PET Eternal Feeding Pump offered by Tyco Healthcare Group LP (d/b/a Covidien). Vacuum source  40  may be actuated by an actuator (not shown) which may be any means known by those skilled in the art, including, for example, alternating current (AC) motors, direct current (DC) motors, voice coil actuators, solenoids, and the like. The actuator may be incorporated within the vacuum source  40 . 
         [0042]    In embodiments, the negative pressure wound therapy apparatus  10  includes one or more fluid line couplings  100  that allow for selectable coupling and decoupling of conduit sections. For example, a fluid line coupling  100  may be used to maintain fluid communication between the first and second conduit sections  36 A,  36 B when engaged, and may interrupt fluid flow between the first and second conduit sections  36 A,  36 B when disengaged. Thus, fluid line coupling  100  may facilitate the connection, disconnection or maintenance of components of the negative pressure wound therapy apparatus  10 , including the replacement of the collection canister  38 . Additional or alternate placement of one or more fluid line couplings  100  at any location in line with the conduit  36  may facilitate other procedures. For example, the placement of a fluid line coupling  100  between the third and fourth conduit sections  36 C,  36 D, as depicted in  FIG. 1 , may facilitate servicing of the vacuum source  40 . 
         [0043]    Referring to  FIG. 2 , an NPWT apparatus similar to the NPWT apparatus of  FIG. 1  is depicted generally as  10  for use on a wound “w” surrounded by healthy skin “s.” The NPWT apparatus  10  of  FIG. 2  includes a vent conduit  37  that extends from between contact layer  18  and cover layer  22  of wound dressing  12  to collection canister  38 . Vent conduit  37  may be integral formed with wound dressing  12 . Alternatively, vent conduit  37  may be inserted between contact layer  18  and cover layer  22  by a clinician during application of the wound dressing  12 , or may have been previously inserted therebetween prior to application. Vent conduit  37  may be releasably connected to the collection canister  38  by conventional air-tight means such as friction fit, bayonet coupling, or barbed connectors. 
         [0044]    Vent conduit  37  is configured to provide a low flow of air from the reservoir  14  to the collection canister  38 . Vent conduit  37  includes a smaller diameter than exudate conduit  36  and may be formed of any suitable conduit including those fabricated from flexible elastomeric or polymeric materials. An air filter  39  positioned along the air flow path filters the air flowing from collection canister  38  to remove any impurities, including bacteria and other infectious material. Filter  39  may include a hydrophobic material to prevent wetting. 
         [0045]    In operation, wound dressing  12  is placed adjacent a wound “w” with the vent conduit  37  extending from between the contact layer  18  and the cover layer  22 . If the vent conduit  37  is not integral formed with the wound dressing  12 , the clinician may be required to position the vent conduit  37  between the layers during application of the wound dressing  12 . Vacuum source  50  is then activated to produce a sub-atmospheric pressure in the reservoir  14  of the wound dressing  12 . Fluid from the reservoir  14  is drawn through aperture  24  in cover layer  22 , into fluid port  30  and along exudate conduit  36  to be deposited in collection canister  40 . As fluid and other exudates are drawn through exudate conduit  36 , filtered air is received within the reservoir  14  of the wound dressing  12  through the vent conduit  37 . The low flow filtered air flowing from the collection canister  38  through the vent conduit  37 , in combination with the high flow drainage occurring through exudate conduit  36 , creates a sump action between the reservoir  14  and the collection canister  40 . This sump action ensures continuous flow through exudate conduit  36 , thereby preventing fluid stagnation and its complications. Because of capillary action, fluid from reservoir  14  only flows through the larger diameter exudate conduit  36 . 
         [0046]    With reference now to  FIG. 3A , in an alternative embodiment of the present disclosure, a wound dressing  112  is substantially similar to wound dressing  12  described hereinabove, and will only be described as relates to the differences therebetween. Wound dressing  112  includes a cover layer  122  having a first or fluid aperture  124  and a second or vent aperture  125 . A fluid port  130  is in fluid communication with fluid aperture  124  and is configured for operable engagement with exudate conduit  136 . A vent port  131  is in fluid communication with vent aperture  125  and is configured for operable engagement with vent conduit  137 . Fluid and vent ports  130 ,  131  may be affixed to cover layer  122  in any suitable manner. Each of fluid and vent port  130 ,  131  are in fluid communication with collection canister  38  ( FIGS. 1 and 2 ). 
         [0047]    Wound dressing  112  operates in substantially the same manner as wound dressing  12 . When connected to collection canister  40  and the vacuum source  50  is activated, the sub-atmospheric pressure produced by the vacuum source  50  creates a suction that draws fluid from the reservoir  114 . Vent conduit  137  provides the reservoir  114  with a low flow of filtered air to ensure continuous fluid flow through the exudate conduit  136 . 
         [0048]    Turning now to  FIG. 3B , in another embodiment, wound dressing  212  is substantially similar to the wound dressings  12 ,  112  described hereinabove. Wound dressing  212  includes a cover layer  222  having a first and second aperture  224 ,  225 . Positioned adjacent first and second apertures  224 ,  225  is a fluid/vent port  230 . Port  230  is configured to fluidly communicate first aperture  224  of wound dressing  212  with collection canister  38  ( FIGS. 1 and 2 ) via exudate conduit  236 . Port  230  is further configured to fluidly communicate second aperture  225  of wound dressing  212  with collection canister  40  via vent conduit  237 . As discussed above, the difference in size between exudate conduit  236  and vent conduit  237  results in capillary action that causes fluid to flow only through the larger exudate conduit  36 . 
         [0049]    With reference now to  FIG. 4 , in yet another embodiment, a wound dressing  312  similar to those described above including a vent assembly  340  formed in a cover layer  322 . Vent assembly  340  includes a filter member  342  and a flap or cover member  344 . Filter member  342  may be integrally formed with, or otherwise affixed to, the cover layer  322 . In one embodiment, filter member  342  is secured to the cover layer  322  with an adhesive. Filter member  342  is configured to provide reservoir  314  of wound dressing  312  with filtered air. To prevent wetting, the filter member  342  may be hydrophobic. Filter member  342  may be sized depending on the desired flow therethrough. A larger filter member  342  would provide a greater amount of airflow; however, if the filter member  342  is too large, it may reduce the effectiveness of the NWPT. 
         [0050]    Flap  344  may be integrally formed with cover layer  322 . Alternatively, flap  344  may be releasably secured over filter member  342 . Flap  344  may be attached to or separable from cover member  322 . Flap  344  may be configured to selectively partially or completely uncover filter member  342 . In this manner, a clinician may affect the flow of air into the reservoir  314 . Although shown including flap  344 , it is envisioned that wound dressing  312  may be provided with filter member  342  exposed. 
         [0051]    In use, wound dressing  312  is applied to a wound “w” in a conventional manner. Activation of the vacuum source  40  ( FIGS. 1 and 2 ) initiates drainage from reservoir  314  of wound dressing  312 . At any time prior to or during the drainage process, flap  344  may be partially or complete pulled back to expose filter member  342 . As described above, the more of filter member  342  that is exposed, the greater the possible airflow into reservoir  14 . The airflow provided to reservoir  14  through filter member  342  acts in a manner similar to the sump action described above. In this manner, vent assembly  340  permits continuous fluid flow through exudate conduit  336 , thereby preventing fluid stagnation and its complications. 
         [0052]    With reference to  FIGS. 5A and 5B , in yet another embodiment, a wound port  500  is shown. Wound port  500  is suitable for use with the above described wound dressings. Wound port  500  has a plastic cover  510  which includes a vacuum port  512 . In addition to the vacuum port  512 , the plastic cover  510  has tube  520 . Tube  520  may be made of a small-bore stainless steel or rigid plastic. Tube  520  is used to provide a controlled or fixed leak by admitting air into the wound dressing. Tube  520  can be arranged to allow the insertion of tube  520  into the wound port  500  so that depth adjustment and placement within the wound packing material is possible as indicated by the arrows in  FIGS. 5A and 5B . As such, air can be injected into the wound packing material to direct movement of excess exudate toward the vacuum port and out of the wound. Tube  520  may have a valve (not shown) to adjust the flow rate of air into the wound bed. The valve may be a small needle valve that can be attached to the tube  520  to allow for infinite adjustment of air flow into the wound dressing. 
         [0053]    The end of tube  520  that may be exposed to ambient atmosphere or to a source of air may include a filter  522 . Filter  522  may be a q-tip like air filter to prevent clogging of the tube and also prevent dirt and other contaminants from entering the wound site. Alternatively, filter  522  may include a charcoal filter to prevent odor, a hydrophobic filter, or any sintered or porous material. The tip of tube  520  that is inserted into the wound packing material may be equipped with a puncturing tip  524  to allow for easier insertion into the wound packing material. 
         [0054]    With reference to  FIGS. 6A and 6B , in yet another embodiment, a wound port  600  is shown. As shown in  FIG. 6A , wound port  600  has tube  610  in separate locations around a circumference of the wound port  600 . Each tube may include a punctured tip or a filter as described above. As shown in  FIG. 6B , the distance “a” between tube  610  and tube  612  may be one distance and the distance “b” between tube  610  and  614  may be a distance different the distance “a”. On the other hand, the difference between each tube may be similar as in the distance “c” between tube  620  and  622  and tube  620  and  624 . Although  FIGS. 6A and 6B  show a specific number of tubes, any number of tubes may be arranged outside a circumference of the wound port  600 . 
         [0055]    With reference to  FIGS. 7A and 7B , in yet another embodiment, a wound port  700  is shown having a tube  710  which is similar to the tubes described above. Tube  710  may be slightly larger in diameter to allow for fluids to enter the wound site. The fluids may include a solution to flush the wound such as saline or it may be an anesthetic to anesthetize the wound area. Tube  710  may be fitted with valve  712  to open and close the pathway into the wound site. Additionally, the end of tube  710  may be fitted with a luer connector  714  to create a fluid tight connection with additional tubing, syringes, or any other conduits. Alternatively, instead of a valve, a plug (not shown) could be used to close the luer connector. With reference to  FIG. 7B , a hypodermic needle  716  may be inserted into tube  710 . Hypodermic needle  716  could be used to deliver a solution to a specific area of the wound or it could be used to obtain a sample of blood, exudate or tissue from the wound site. 
         [0056]    With reference to  FIGS. 8A and 8B , in yet another embodiment, a wound port  800  is shown. Instead of using tubes as described above to allow a controlled or fixed leak, a number of small holes arranged in a circumference around the wound port  800  may be provided. The holes may take the form of a simple puncture  810  of a given size as shown in  FIG. 8A . Alternatively, the holes  822  may be formed in a plate  820  that is radio frequency (RF) welded to the wound port  800 . 
         [0057]    With reference to  FIG. 9 , in yet another embodiment, a cross section of wound port  900  is shown. Wound port  900  is operatively connected to wound dressing  910  and includes a flange  912 . Flange  912  may have a circular or any polygonal shape. A body  914  is connected to the flange  912  which is fluidly connected to conduit  916 . Conduit  916  leads directly or indirectly to the collection canister. Body  914  has as small orifice  920  used to provide a controlled leak into the wound site. The diameter of the orifice  920  and the pressure difference between the outside of the wound port  900  and the inside of the wound port  90  create a controllable air leak into the wound port  900  via the orifice. The small orifice  920  can be created in various ways. The orifice  920  can be integral to the port design, such as a molded in feature. It can be created via post molding micro-piercing into the port using a needle or syringe. Alternatively, assembly or insertion of a small tube that allows for communication of air from outside the wound port  900  to inside the wound port  900  can be used to create the orifice  920 . 
         [0058]    With reference to  FIGS. 10A and 10B , in yet another embodiment, a wound port  1000  is shown. Wound port  1000  is operatively connected to wound dressing  1010  and includes a flange  1012 . Flange  1012  may have a circular or any polygonal shape. A body  1014  is connected to the flange  1012  which is fluidly connected to conduit  1016 . Conduit  1016  leads directly or indirectly to the collection canister. Conduit  1016  includes a main lumen  1110  used to provide a pathway for exudate between the wound “w” and the collection canister. A secondary lumen or vent lumen is provided in conduit  1016  to provide a controlled leak to the wound site. Exudate enters lumen  1110  at area  1114  and air exits lumen  1112  at area  1116 . Secondary lumen  1112  is exposed to the ambient environment or to a source of air to provide a controlled leak in the wound port  1000 . Although  FIG. 10B  depicts lumens  1110  and  1112  in a single conduit  1016 , lumens  1110  and  1112  can be provided as separate conduits. 
         [0059]    With reference to  FIG. 11A , in yet another embodiment, a wound dressing  1200  is shown having a wound port  1210 . Wound dressing  1200  and wound port  1210  are similar to wound dressing  12 ,  112 , and  212  and wound port  1210  are similar to wound port  30 ,  130  and  230  described hereinabove. A vent conduit  1220  may be inserted into the top of wound port  1210  to provide a source of filtered air into the wound dressing  1200  through the vent conduit  1220 . Vent conduit  1220  may be a stainless steel needle having a lumen extending through the needle. The end of vent conduit  1220  has filter  1225  to filter the air from the ambient atmosphere. The low flow filtered air flowing from the ambient atmosphere through the vent conduit  1220 , in combination with the high flow drainage occurring through an exudate conduit, creates a sump action between the wound and a collection canister. This sump action ensures continuous flow through exudate conduit  36 , thereby preventing fluid stagnation and its complications. As discussed above, the difference in size between exudate conduit and vent conduit  1220  results in capillary action that causes fluid to flow only through the larger exudate conduit.  FIGS. 11B-11D  depict a wound port  1210  similar to the wound port in  FIG. 11A . In  FIGS. 11B-11D , the vent conduit  1220  is placed on the side of the wound port  1210  rather than the top of the wound port  1210  as shown in  FIG. 11A .  FIG. 11D  depicts the end of vent conduit  1220  being located in the wound port  1210  above an exudate orifice  1230 . 
         [0060]    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. For example, the individual fluid and vent conduits may be substituted for by a conduit having a dual lumen. To ensure the capillary action, one lumen must be larger than the other; however, the lumens may be coaxial or parallel.