Abstract:
A wound dressing apparatus includes a wound dressing member dimensioned for positioning relative to a wound bed. The wound dressing member including an internal vacuum reservoir and has a port in communication with the vacuum reservoir for applying subatmospheric pressure to the vacuum reservoir to facilitate removal of fluid from the wound bed. The wound dressing member includes a visual pressure indicator associated therewith for indicating a level of pressure within the vacuum reservoir. The visual pressure indicator includes color indicia having a plurality of colors corresponding to a condition of the pressure within the vacuum reservoir. The wound dressing member includes a lower absorbent member positionable adjacent the wound bed and an upper member which at least partially defines the vacuum reservoir. At least one of the top member and the lower absorbent member has the visual pressure indicator mounted thereto.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a continuation application of U.S. patent application Ser. No. 13/775964, filed on Feb. 25, 2013, which is a continuation application of U.S. patent application Ser. No. 12/686813, filed on Jan. 13, 2010, which is a divisional application of U.S. patent application Ser. No. 11/516,925, filed on Sep. 6, 2006, which claims the benefit of U.S. Provisional Patent Application No. 60/714,805, filed on Sep. 7, 2005, now abandoned, the entire contents of each are incorporated herein by this reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an apparatus for treating an open wound, and, more specifically, relates to a wound dressing that draws wound fluids into a vacuum reservoir to facilitate the wound healing process. 
     2. Description of Related Art 
     Wound closure involves the migration of epithelial and subcutaneous tissue adjacent the wound towards the center of the wound until the wound closes. Unfortunately, closure is difficult with large wounds or wounds that have become infected. In such wounds, a zone of stasis (i.e. an area in which localized swelling of tissue restricts the flow of blood to the tissues) forms near the surface of the wound. Without sufficient blood flow, the epithelial and subcutaneous tissues surrounding the wound not only receive diminished oxygen and nutrients, but, are also less able to successfully fight microbial infection and, thus, are less able to close the wound naturally. Such wounds have presented difficulties to medical personnel for many years. 
     Wound dressings have been used in the medical industry to protect and/or facilitate healing of open wounds. One popular technique has been to use negative pressure therapy, which is also known as suction or vacuum therapy. A variety of negative pressure devices have been developed to allow excess wound fluids, i.e., exudates to be removed while at the same time isolating the wound to protect the wound and, consequently, reduce recovery time. Various wound dressings have been modified to promote the healing of open wounds. 
     Issues that continually need to be addressed when using a wound dressing include ease of use, efficiency of healing a wound, and the source of constant or varying negative pressure. Thus, there remains a need to constantly improve negative pressure wound dressings for open wounds. 
     SUMMARY 
     In one preferred embodiment, a wound dressing apparatus includes a wound dressing member dimensioned for positioning relative to a wound bed. The wound dressing member includes an internal vacuum reservoir and having a port in communication with the vacuum reservoir for applying subatmospheric pressure to the vacuum reservoir to facilitate removal of fluid from the wound bed. The wound dressing member includes an access door associated therewith and being selectively movable between a closed position substantially enclosing the vacuum reservoir and an open position permitting access to the vacuum reservoir. 
     The wound dressing member preferably includes a lower absorbent member which is positionable adjacent the wound bed and an upper member. The upper member at least partially defines the vacuum reservoir. The access door is mounted to the upper member. The lower member may comprise a material selected from the group consisting of foams, nonwoven composite fabrics, cellulosic fabrics, super absorbent polymers, hydrogels and combinations thereof. The lower member also may include at least one of a medicament, an anti-infective agent, an antimicrobial, such as polyhexamethylene biguanide (hereinafter, “PHMB”), antibiotics, analgesics, healing factors, vitamins, growth factors, debridement agents and nutrients. The wound dressing member may include an adhesive member which is adapted to be secured about the wound bed to provide a seal between the wound dressing member and tissue surrounding the wound bed. 
     The wound dressing apparatus may further include a vacuum source in fluid communication with the port. The vacuum source is adapted to supply subatmospheric pressure in a range between about 20 mmHg and about 500 mmHg to the vacuum reservoir. The port may include valve means. 
     The wound dressing member may include a visual pressure indicator for indicating a level of pressure within the vacuum reservoir. The preferred visual pressure indicator includes color indicia which correspond to a condition of the subatmospheric pressure within the vacuum reservoir. The preferred visual pressure indicator includes a position sensor. The visual pressure indicator may include circuit means and visible alarm means. The circuit means is adapted to actuate the visible alarm means when the position sensor detects a relative positioning of the top member of the wound dressing member to provide a visual indication of the condition of the subatmospheric pressure within the vacuum reservoir. 
     In another embodiment, a wound dressing apparatus includes a wound dressing member dimensioned for positioning relative to a wound bed. The wound dressing member including an internal vacuum reservoir and has a port in communication with the vacuum reservoir for applying subatmospheric pressure to the vacuum reservoir to facilitate removal of fluid from the wound bed and stimulate wound healing. The wound dressing member includes a visual pressure indicator associated therewith for indicating a level of pressure within the vacuum reservoir. The visual pressure indicator may include color indicia having a plurality of colors corresponding to a condition of the pressure within the vacuum reservoir. The wound dressing member includes a lower absorbent member positionable adjacent the wound bed and an upper member which at least partially defines the vacuum reservoir. At least one of the top member and the lower absorbent member has the visual pressure indicator mounted thereto. The visual pressure indicator may include an electronic position sensor. The visual pressure indicator may further include circuit means and visible alarm means. The circuit means is adapted to actuate the visible alarm means when the position sensor detects a relative positioning of the top member of the wound dressing member to provide a visual indication of the condition of the subatmospheric pressure within the vacuum reservoir. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the subject wound dressing are described herein with reference to the drawings wherein: 
         FIG. 1  is a side cross-sectional view of the wound dressing apparatus in accordance with the principles of the present disclosure on a wound bed; 
         FIG. 2  is a view similar to the view of  FIG. 1  illustrating the wound dressing subjected to subatmospheric pressure; 
         FIG. 3  is a top view of the wound dressing; 
         FIG. 4  is a view similar to the view of  FIG. 2  illustrating the access door in an open condition to permit access to the internal vacuum reservoir; 
         FIG. 5  is a cross-sectional view taken along the lines  5 - 5  of  FIG. 3  illustrating the visual pressure indicator; 
         FIG. 6  is a block diagram illustrating the components of the electronic visual indicator device; 
         FIG. 7  is a view similar to the view of  FIG. 1  illustrating an alternate embodiment of the present disclosure; 
         FIG. 8  is a view illustrating an alternate visual indicia arrangement of the visual indicator device; 
         FIG. 9  is a side cross-sectional view of an alternate wound dressing on a wound bed and in the absence of a vacuum; 
         FIG. 10  is a view similar to the view of  FIG. 9  illustrating the wound dressing in a contracted condition when subjected to subatmospheric pressure; and 
         FIG. 11  is a top view of the wound dressing of  FIG. 9 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The composite wound dressing of the present disclosure promotes healing of a wound via the use of a vacuum reservoir. The vacuum reservoir subjects the wound to vacuum or subatmospheric pressure to effectively draw wound fluid including liquid exudates from the wound bed without the continuous use of a vacuum source or pump. Hence, vacuum pressure can be applied once or in varying intervals depending on the nature and severity of the wound until the composite wound dressing is saturated with exudate or the wound is healed. If the wound dressing is saturated with exudate and the wound is not healed, certain and/or all layers of the composite wound dressing can be replaced and the process of applying subatmospheric pressure can be repeated. 
     Referring now to  FIGS. 1-3 , the composite wound dressing  100  in accordance with a preferred embodiment of the present disclosure is illustrated in the form of an article with multiple layers arranged in juxtaposed or superposed relation. The multiple layers include, but, are not limited to a lower or base layer  102 , an absorbent/packing layer  104 , an adherent layer  106 , and a top layer  108  which includes and/or defines the internal vacuum reservoir  110 . 
     The base layer  102  is in direct contact with the wound bed “w”. The base layer  102  is typically porous allowing passage of subatmospheric pressure to the wound bed. In one preferred embodiment, the base layer includes a “non-adherent” material. “Non-adherent” as used herein refers to a material that does not adhere to tissues in and around the wound bed. “Porous” as used herein refers to a material which contains numerous small perforations or pores which allow wound fluids of all kinds to pass through the material to the dressing layers above. The passage of wound fluid through the porous material may be unidirectional such that wound exudate does not flow back to the wound bed. This direction flow feature could be in the form of directional apertures imparted into the material layer, a lamination of materials of different absorption to the base layer  102  or specific material selection that encourages directional flow. Exemplary materials used as the base layer  102  include a contact layer sold under the trademark XEROFLOW® by Kendall Corp., a division of TycoHealthcare. In the alternative, the base layer  102  may include an adherent material. 
     In addition, agents such as hydrogels and medicaments could be bonded or coated to the base layer  102  to reduce bioburden in the wound, promote healing and reduce pain associated with dressing changes or removal. Medicaments include, for example, antimicrobial agents, growth factors, antibiotics, analgesics, debridement agents and the like. Furthermore, when an analgesic is used, the analgesic could include a mechanism that would allow the release of that agent prior to dressing removal or change. Exemplary triggers of a release mechanism could be temperature change. 
     The layer proximal to the base layer  102  or composite structures making the base layer  102  is the absorbent/packing layer  104 . The absorbent/packing layer  104  of the wound dressing  100  is intended to absorb and capture wound fluid and exudates. Exemplary absorbent materials include foams, nonwoven composite fabrics, hydrogels, cellulosic fabrics, super absorbent polymers, and combinations thereof. Typically, the absorbent/packing layer  104  can absorb up to about 100 cubic centimeters (cc) or more of wound fluid. Preferably, the absorbent material includes the antimicrobial dressing sold under the trademark KERLIX® by Kendall Corp., a division of TycoHealthcare. In one preferred embodiment, the absorbent/packing layer  104  could be preformed or shaped to conform to varying shapes of the wound bed. Those skilled in the art will recognize that the absorbent/packing layer  104  can be formed in any suitable shape. Absorbent/packing layer  104  may include multiple layers. The only requirement as to shape is that the absorbent/packing layer  104  is suitable to treat a particular shape of the wound. 
     Additionally, the absorbent/packing layer  104  could be treated with medicaments. Medicaments include, for example, an anti-infective agent such as an antiseptic or other suitable antimicrobial or combination of antimicrobials, polyhexamethylene biguanide (hereinafter, “PHMB”), antibiotics, analgesics, healing factors such as vitamins, growth factors, nutrients and the like, as well as a flushing agent such as isotonic saline solution. 
     With continued reference to  FIGS. 1-3 , the adherent layer  106  at least encompasses the perimeter of the wound dressing  100  to surround the wound bed to provide a seal around the perimeter of the wound bed “w”. For instance, the sealing mechanism may be any adhesive bonded to a layer that surrounds the wound bed “w” or an adhesive applied directly to the skin. The adhesive must provide acceptable adhesion to the tissue “t” surrounding the wound bed “w” skin, e.g., the periwound area, and be acceptable for use on skin without contact deterioration (for example, the adhesive should preferably be non-irritating and non-sensitizing.) The adhesive may be semi-permeable to permit the contacted skin to transmit moisture or may be impermeable. Additionally, the adhesive could be activated or de-activated by an external stimulus such as heat or a given fluid solution or chemical reaction. Adhesives include, for example, the dressing sold under the trademark ULTEC® Hydrocolloid dressing by Kendall Corp., a division of TycoHealthcare. 
     The adherent layer  106  may also be in the form of an entire layer proximal to the absorbent/packing layer  104  or preferably is annular or “donut shaped” as shown. Preferably, the adherent layer  106  is not bonded to the absorbent/packing layer  104  to allow for easy replacement of the absorbent/packing layer  104 . In a preferred embodiment, the adherent layer  106  is at least bonded to the periphery of the base layer  102 . In turn, the peripheral portion  108   a  of the top layer  108  may be bonded to the adherent layer  106  to provide a seal around the perimeter of the wound. Alternatively, the adherent layer  106  may be positioned on the peripheral portion  108   a  of the top layer  108  and secured to the tissue “t” about the wound bed “w”, and not bonded to the base layer  102 . As a further alternative, the peripheral portion  108   a  of the top layer  108  may include an adhesive surface. It is anticipated that removable contact liners may also be used to protect the adhesive surface of the adherent layer  106  prior to use. 
     The top or upper layer  108  typically seals the top of the wound dressing  100  and helps maintain the appropriate vacuum level within the wound dressing  100 . In one preferred embodiment, the top layer  108  includes the flexible transparent dressing manufactured under the trademark POLYSKIN® II by Kendall Corp., a division of TycoHealthcare. POLYSKIN® II is a transparent, semi-permeable material which permits moisture and oxygen exchange with the wound site, and provides a barrier to microbes and fluid containment. In the alternative, the top layer  110  may be impermeable. As a further alternative, the top layer  108  may include a resilient, e.g., elastomeric, material in the shape, e.g., of a dome. 
     The top layer  108  defines a sealed or enclosed vacuum reservoir  110 . The vacuum reservoir  110  is preferably maintained at an appropriate vacuum level for a predetermined period of time sufficient to initiate or complete healing of the wound bed “w”, i.e., to draw wound fluid and exudate away from the wound bed “w” while subjecting the wound to subatmospheric pressure. The vacuum may be re-applied as needed to maintain a therapeutic effect. The vacuum may be continuous or intermittent as desired. 
     As best seen in  FIG. 1 , the vacuum reservoir  110  is defined within the dome of the top layer  108 . As shown in  FIG. 2 , once vacuum is applied, the dome of the top layer  108  is drawn downwardly toward the absorbent/packing layer  104  with the vacuum or subatmospheric reservoir  110  created beneath the top layer  108 . Typically, the top layer  108  includes a vacuum port or connector  114  in fluid communication with the vacuum reservoir  110 . Preferably, the vacuum port  114  includes a one-way valve (shown schematically as reference numeral  116 ) which provides unidirectional flow of suction and may provide a means for allowing connection of the composite wound dressing  100  to the vacuum source  112 . The one way valve  116  may be incorporated within the vacuum port  114  or, alternatively, be “in line” with the vacuum source  112 . A flexible tubing  118  is connected to the vacuum port  114  and the vacuum source  112 . The tubing  118  provides suction to the wound from the vacuum source  112  and enables the wound fluid to be transferred from the wound dressing  100 . The tubing  118  may be fabricated from PVC, silicone based material or other flexible materials (polymers). The tubing  118  may optionally include a connection to a collection canister  120  for wound drainage and debris. Hence, the vacuum source  112  can draw wound fluid through the composite wound dressing  100  and tubing  118  into the canister  120 . In a preferred embodiment of the present disclosure, the canister  120  is portable so that the patient will have the freedom to move about rather than being confined to a fixed location. The canister  120  may also house an absorbent material to absorb wound fluid and exudate. 
     The vacuum source  112  may apply vacuum to the wound by means such as a manual pump as disclosed in commonly assigned U.S. Pat. No. 5,549,584 to Gross, the entire contents of which are hereby incorporated herein by reference. In the alternative, the vacuum source  112  may include an automated pump. Typically, the vacuum level is in a range between about 20 mmHg to about 500 mmHg, more preferably, about 40 mmHg and about 125 mmHg. The automated pump may be a wall suction apparatus such as those available in an acute or sub-acute care facility. The automated pump may be in the form of a portable pump. The portable pump may include a small or miniature pump that maintains or draws adequate and therapeutic vacuum levels. In a preferred embodiment, the pump is a portable, lightweight, battery operated, suction pump which attaches to the distal end of the tubing. Typically, the vacuum source  112  has regulation means to apply the optimal vacuum pressure for healing the wound. Furthermore, the vacuum source  112  would preferably contain a mechanism to detect a leak in the system if the optimal vacuum pressure is not achieved. Preferably, the vacuum source  112  would also contain an indicator (not shown) to indicate when the optimal vacuum pressure is achieved. In the alternative, a hand pump in the form of a squeeze bulb or a foot pump may serve as the vacuum source  112 . 
     Preferably, a pump is used as the vacuum source  112 . Typical pumps include diaphragm or voice coil activated styles that can deliver variable vacuum up to 50 cc/minute. 
     With reference now to  FIGS. 1-4 , the top layer  108  may include an access door  122  to provide access to the interior of the wound dressing  100  and/or the wound bed “w”. The door  122  could be a flap integrally formed with the top layer  108  or a separate component connected to the top layer  108  via a hinge or the like. The door  122  is preferably resealable to maintain the integrity of the vacuum reservoir  110  and provide a seal relative to the top layer  108 . One suitable means for releasably sealing the door  122  includes a snap fit arrangement, tongue and groove arrangement, “zip Lock®” arrangement, adhesives, VELCRO®, etc. The door  122  preferably provides access to the wound bed “w” to enable the clinician to monitor the status of the wound, change the absorbent/packing layer  104 , or apply additional medical treatment to the wound such as antimicrobial agents, growth factors, debriders, or other wound healing agents as needed. Once the desired procedure is completed, the door  122  would be resealed relative to the top layer  108  to maintain the integrity of the vacuum reservoir  110 .  FIG. 4  illustrates the removal of the absorbent/packing layer  104  through the door  122  when the door  122  is in an open position. As discussed, a new absorbent/packing layer  104  subsequently may be introduced through the door  122  to absorb the exudates from the wound bed “w”. 
     With reference now to  FIGS. 3 and 5 , in conjunction with  FIGS. 1-2 , the wound dressing  100  may include a visual indicator device  124  mounted to the top layer  108  to provide a visual indication of vacuum pressure within the wound dressing  100 . The visual indicator device  124  may include at least one electronic position indicator for detecting the relative position of the top layer  108  and the wound bed, and, thus the state of the vacuum within the wound dressing  100 . In accordance with this embodiment, the top layer  108  may have a resilient characteristic either through the material of construction of the top layer  108  or through reinforcement (e.g., elastomeric) members incorporated in the top layer  108 . 
     In one embodiment depicted in  FIG. 6 , the visual indicator device  124  includes at least one, preferably, three position-sensitive switches  126   a - 126   c , and a self-powered electronic signaling module  128 . The module  128  may include an electronic signaling module circuit board  130 , a battery power source  132 , at least one transducer including three light emitting diodes (LED)  134   a - c  and/or a loudspeaker  136  electrically connected  138  to the circuit board  130 . The LEDs  134   a - c  are color coded red, yellow and green respectively. The position-sensitive switches  126   a - 126   c  each may be a pressure sensor which electrically bridges contacts  140   a ,  140   b  of the visual indicator device  124 . 
     In the embodiment shown, three position switches  126   a - c  are mounted to top layer  108 . The switches  126   a - c  include switch plates or contact arms arranged as a series of decreasing diameter annular coaxial elements. Alternatively, the switches may be linear in configuration depending downwardly from the top layer  108 . The switch plate or contact arm of switches  126   a - c  are of predetermined length extending downwardly from the top layer  108  within the vacuum reservoir  110 . ( FIGS. 4 and 5 ) The contact arm of outer switch  126   a  of the pressure indicator  124  has the greatest length. The contact arm of the middle switch  126   b  has a length less than the length of the contact arm of the outer ring  126   a . The contact arm of the inner switch  126   c  has the smallest length. The contacts  140   a  of switches  126   a - c  are integrated within the contact arms. Contacts  140   b  of the switches  126   a - c  may be disposed on the top surface of the absorbent/packing layer  104  or integrated within the absorbent/packing layer  104  in general longitudinal alignment with their respective contact arms. Alternatively, the position sensor may be a magnetic proximity sensor. The self-powered electronic signaling module  130  may be any conventional modules adapted to emit light and/or audible sound etc. upon closing of the switch. 
     When the top layer  108  is drawn down by vacuum pressure within the vacuum reservoir  110  toward its vacuum state of  FIG. 2 , inner switch  126   c  is in contact with a respective coupler or contact  140   b  disposed within the absorbent/packing layer  104  thereby energizing the visual indicator device  124  to illuminate the green LED  134   c  within the pressure indicator device mounted to the top layer  108 . The green light of the LEDs  134   c  indicates a full vacuum condition of the vacuum reservoir  110 . As appreciated, switches  126   a ,  126   b  may also be in contact with their respective couplers in this vacuum condition of top layer  108 . However, it is envisioned that circuit board  130  will incorporate circuitry to override the electrical contact of these two switches when switch  126   c  is in contact with its respective coupler. 
     As vacuum pressure decreases and the dome of the top layer  108  begins to assume its normal condition of  FIG. 1 , through, e.g., the resilient characteristic of the top layer  108  discussed hereinabove, the inner switch  126   c  loses contact with the absorbent/packing layer  104  while the middle switch  126   b  maintains/establishes electrical contact with its associated contact  140   b . The electrical connection of the middle switch  126   b  results in illumination of the yellow LED  134   b . The yellow LED  134   b  represents a partial vacuum or marginal vacuum condition of the vacuum reservoir  110 . As the vacuum pressure further decreases and the top layer  108  moves towards its fully expanded or normal condition of  FIG. 1 , the outer switch  126   a  is the remaining switch in contact with its associated contact  140   b  within the absorbent/packing layer  104 . In this condition, the red LED  134   a  is energized and visible to the clinician essentially providing a warning that the vacuum within the vacuum reservoir has dissipated or is nearly dissipated (i.e., subatmospheric pressure is close to or no longer present). Consequently, the vacuum source  112  may be actuated either manually or automatically to reestablish the vacuum state within the vacuum reservoir  110 . Further vacuum loss will result in the remaining switch  126   c  losing its contact where no lights are visible to the patient. 
     It is also envisioned that the circuit board  130  could be devoid of the aforementioned override circuitry. As a result, in the full vacuum condition of dressing  100 , each of the green, yellow and red LEDs  134   a - 134   c  would be illuminated while in the partial vacuum state, the yellow and red LEDs  134   a ,  134   b  would be illuminated and in the warning state, the red LED  134   a  would be illuminated. It is further envisioned that the loudspeaker  136  could emit an audible alarm when any of the aforementioned vacuum states are realized. 
       FIG. 7  illustrates an alternate embodiment of the visual pressure indicator  124 . In accordance with this embodiment, the visual pressure indicator  124  is mounted to the absorbent/packing layer  104  or positioned on the absorbent/packing layer  104  in juxtaposed relation. The top layer  108  is preferably transparent to permit viewing of the pressure indicator  124  through the top layer  108  and into the vacuum reservoir  110 . The positioning of the visual pressure indicator  124  is reversed or arranged on its back in a manner where the respective switches  126   a - c  extend upwardly toward top layer  108 . The respective coupler or contacts  140   b  are incorporated within the top layer  108 . In the full vacuum state or condition of  FIG. 2 , the contact  140   b  of the top layer  108  is in contact with the switch  126   c  thereby energizing the LED  134   c  to display the green color to the clinician. During healing, as the vacuum reservoir begins to lose its vacuum, the top layer  108  moves towards its open condition of  FIG. 1 , the inner switch  126   c  loses its contact with its respective coupler  140   b  of the top layer  108  resulting in electrical contact with the yellow LED  134   b  indicating a partial vacuum condition of the vacuum reservoir  110 . Continued loss of vacuum within the vacuum reservoir  110  causes the electrical contact of the coupler  140   b  with the outer switch  126   c . This contact of the LED  134   c  with the outer switch  126   c  is indicated by the presence of its red color and may correspond to a loss or near loss of vacuum within the vacuum reservoir  110  thus prompting the clinician to activate the vacuum source  112  or pursue other clinical measures. 
       FIG. 8  illustrates another embodiment where the LEDs  134   a - 134   c  are supplemented with additional visual indicia. The visual indicia may include various symbols which correspond to the state of the vacuum within the vacuum reservoir  110 . When a desired level of vacuum is reached, the “smiley” symbol  152  would illuminate indicating an adequate vacuum state. A partial vacuum state would result in the illumination of the “caution triangle” symbol  154 . A loss or near loss of vacuum would result in the illumination of the “octagon” symbol (no vacuum)  156 . One skilled in the art will readily appreciate the design of electronic circuitry to achieve this objective. 
       FIGS. 9-11  illustrate an alternate embodiment of the present disclosure. In accordance with this embodiment, the visual indicator device  124  may include a series of rings  200 , 202 , 204  disposed on the underside of the top layer  108 , e.g., printed on the top layer  108 , and arranged in concentric relation as shown. The rings include outer ring  200 , middle ring  202  and inner ring  204  and are color coded red, yellow and green, respectively. Each colored ring  200 , 202 , 204  is positioned to contact the absorbent/packing layer  104  depending on the state or condition of the vacuum within the vacuum reservoir  110 . Under full vacuum depicted in  FIG. 10 , all the rings  200 , 202 , 204  would contact absorbent/packing layer  104  and thus be activated and visible through the top of the wound dressing. As the vacuum within the reservoir dissipates or is reduced, the top layer  110  pulls away from the absorbent/packing layer  104 . In one embodiment with an elastomeric dome, the inner ring  204  first loses contact followed by the middle and outer rings,  202 ,  200 , respectively, as the vacuum is reduced. As each colored ring  200 , 202 , 204  loses contact with absorbent/packing layer  104 , the respective ring becomes less visible or not visible from above the wound dressing  100  thus indicating to the clinician the condition of the vacuum within the vacuum reservoir. The rings  200 , 202 , 204  may incorporate electronic switches to be activated in the manner discussed hereinabove in connection with the embodiment of  FIGS. 1-6 . Alternatively, each ring  200 , 202 , 204  may incorporate an analytical test strip device which, e.g., may detect the presence of a predetermined analyte in the exudates contained in the absorbent/packing layer  104 . Upon contact with the predetermined analyte, the test strip device of each ring  200 , 202 , 204  assumes a color such as red, yellow or green. When a respective ring  200 , 202 , 204  loses contact with the predetermined analyte, the color of the respective ring may fade or assume a neutral color. One exampled of a color coded test strip device suitable for use with the present disclosure is disclosed in U.S. Pat. No. 7,049,130 to Carroll et al., issued May 23, 2006, the entire contents of which are incorporated herein by reference. One skilled in the art may determine the parameters and characteristics of a test strip device to perform the objectives discussed hereinabove. 
     In addition, the door  122  of the embodiment of  FIGS. 9-11  is adapted to pivot along hinge  208  to provide access to the vacuum reservoir  110 . The opening of the door  122  is disposed adjacent the periphery of the wound dressing  102  and thus provides a relatively large access opening upon pivoting or opening the door  122  along the hinge  208 . This facilitates removal and replacement of absorbent/packing layer  104 . 
     It is further contemplated that the wound dressing apparatus may incorporate external means or applications to stimulate tissue growth and/or healing. For example, an ultrasonic transducer may be incorporated into the wound dressing apparatus to impart mechanical energy for the treatment of the tissue such as, for instance, directing thermal or vibratory energy on the wound area to stimulate healing and/or further encouraging exudates removal by vacuum and/or introducing various drugs into the human body through the skin. Other sensor types are also contemplated for incorporation into the wound dressing apparatus including oxygen, chemical, microbial and/or temperature sensors. The detection of oxygen adjacent the wound area would assist the clinician in determining the status of wound healing. The presence of an elevated temperature may be indicative of an infection. 
     While the disclosure has been illustrated and described, it is not intended to be limited to the details shown, since various modifications and substitutions can be made without departing in any way from the spirit of the present disclosure. For example, it is envisioned the subject matter of the commonly assigned U.S. patent application Ser. No. 11/517,210, filed on Sep. 6, 2006, and which claims priority to U.S. Provisional Application Ser. No. 60/714,812, filed on Sep. 6, 2005, and the subject matter of the commonly assigned U.S. patent application Ser. No. 11/516,216, filed on Sep. 6, 2006, and which claims priority to provisional application No. 60/714,912, filed on Sep. 7, 2005, (the entire contents of each application being incorporated herein) may be incorporated into the present disclosure. As such, further modifications and equivalents of the invention herein disclosed can occur to persons skilled in the art using no more than routine experimentation, and all such modifications and equivalents are believed to be within the spirit and scope of the disclosure as defined by the following claims.