Patent Publication Number: US-11376356-B2

Title: Reduced pressure treatment system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 14/854,717, filed Sep. 15, 2015, which is a continuation of U.S. patent application Ser. No. 14/142,635, filed on Dec. 27, 2013, which is a continuation of U.S. patent application Ser. No. 13/302,175, filed on Nov. 22, 2011, now U.S. Pat. No. 8,628,505, which is a continuation of U.S. patent application Ser. No. 12/938,291, filed on Nov. 2, 2010, now U.S. Pat. No. 8,118,794, which is a continuation application of U.S. patent application Ser. No. 10/652,100, filed on Aug. 28, 2003, now U.S. Pat. No. 7,846,141, which claims the benefit of U.S. Provisional Patent Application No. 60/407,783, filed on Sep. 3, 2002, and U.S. Provisional Patent Application No. 60/430,827, filed on Dec. 4, 2002, the entirety of all five of which are hereby incorporated by reference and made a part of the present disclosure as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an apparatus and a method for treating a wound by applying reduced pressure to the wound. In this context, the term “wound” is to be interpreted broadly, to include any body part of a patient that may be treated using reduced pressure. 
     Description of the Related Art 
     The treatment of open or chronic wounds that are too large to spontaneously close or otherwise fail to heal has long been a troublesome area of medical practice. Closure of an open wound requires inward migration of surrounding epithelial and subcutaneous tissue. Some wounds, however, are sufficiently large or infected that they are unable to heal spontaneously. In such instances, a zone of stasis in which localized edema restricts the flow of blood to the epithelial and subcutaneous tissue forms near the surface of the wound. Without sufficient blood flow, the wound is unable to successfully fight bacterial infection and is accordingly unable to close spontaneously. 
     An initial stage of wound healing is characterized by the formation of granulation tissue which is a matrix of collagen, fibronectin, and hyaluronic acid carrying macrophages, fibroblasts, and neovasculature that forms the basis for subsequent epithelialization of the wound. Infection and poor vascularization hinder the formation of granulation tissue within wounded tissue, thereby inhibiting wound healing. It therefore becomes desirable to provide a technique for increasing blood circulation within wounded tissue to promote spontaneous healing and to reduce infection. 
     Another problem encountered during the treatment of wounds is the selection of an appropriate technique for wound closure during the healing process. Sutures are often used to apply force to adjacent viable tissue in order to induce the edges of a wound to migrate together and heal. However, sutures apply a closure force to only a very small percentage of the area surrounding a wound. When there is scarring, edema, or insufficient tissue, the tension produced by the sutures can become great causing excessive pressure to be exerted by the sutures upon the tissue adjacent to each suture. As a result, the adjacent tissue often becomes ischemic thereby rendering suturing of large wounds counterproductive. If the quantity or size of the sutures is increased to reduce the tension required of any single suture, the quantity of foreign material within the wound is concomitantly increased and the wound is more apt to become infected. Additionally, the size or type of a particular wound may prevent the use of sutures to promote wound closure. It therefore becomes desirable to provide an apparatus and method for closing a large wound that distributes a closure force evenly about the periphery of the wound. 
     Wounds resulting from ischemia, or lack of blood flow, are also often difficult to heal since decreased blood flow to a wound may inhibit normal immune reaction to fight infection. Patients that are bedridden or otherwise non-ambulatory are susceptible to such ischemic wounds as decubitus ulcers or pressure sores. Decubitus ulcers form as a result of constant compression of the skin surface and underlying tissue thus restricting circulation. Since the patient is often unable to feel the wound or to move sufficiently to relieve the pressure, such wounds can become self-perpetuating. Although it is common to treat such wounds with flaps, the conditions that initially caused the wound may also work against successful flap attachment. Wheelchair-bound paraplegics, for example, must still remain seated after treatment of pelvic pressure sores. It therefore becomes desirable to provide a treatment procedure for ischemic wounds that can be conducted in situ upon an immobile or partially mobile patient. 
     Other types of wounds in which ischemia leads to progressive deterioration include partial thickness burns. A partial thickness burn is a burn in which the cell death due to thermal trauma does not extend below the deepest epidermal structures such as hair follicles, sweat glands, or sebaceous glands. The progression of partial thickness burns to deeper burns is a major problem in burn therapy. The ability to control or diminish the depth of burns greatly enhances the prognosis for burn patients and decreases morbidity resulting from burns. Partial thickness burns are formed of a zone of coagulation, which encompasses tissue killed by thermal injury, and a zone of stasis. The zone of stasis is a layer of tissue immediately beneath the zone of coagulation. Cells within the zone of stasis are viable, but the blood flow is static because of collapse of vascular structures due to localized edema. Unless blood flow is re-established within the zone of stasis soon after injury, the tissue within the zone of stasis also dies. The death of tissue within the zone of stasis is caused by lack of oxygen and nutrients, reperfusion injury (re-establishment of blood flow after prolonged ischemia), and decreased migration of white blood cells to the zone resulting in bacterial proliferation. Again, it becomes desirable to provide a technique for treating burn wounds by enhancing blood circulation to the wounded tissue to inhibit burn penetration. 
     There exist various apparatus utilizing reduced pressure for treatment of these types of wounds. See, for example, U.S. Pat. No. 5,636,643. The apparatus existing in the art is generally comprised of a fluid impermeable cover that covers the wound, which is directly or indirectly connected to a source of suction so that an area of reduced pressure is created beneath the cover in the area of the wound. Some type of packing material, such as gauze, is also often placed in the area of the wound beneath the cover to prevent overgrowth of the wound. Apparatus existing in the relevant art, however, suffer from several disadvantages. 
     One such disadvantage is the necessity to change the packing material placed in the wound during the period of treatment. This requirement is expensive because multiple dressings are necessary and medical staff must expend time to change the dressings. In addition, there is an increased risk of infection and intrusion of other harmful foreign material into the wound area. It is therefore desirable to have a reduced pressure wound treatment system having a dressing that does not need to be changed, or needs to be changed fewer times, during the period of treatment. 
     In addition, the existing apparatus do not have adequate means to monitor the pressure in the area of the wound beneath the cover. If the cover is not adequately sealed to the tissue surrounding the wound, reduced pressure cannot be maintained beneath the cover so that the benefits of the treatment are lost or diminished. In addition, pressure leaks through the seal cause the source of suction to operate more frequently, which consumes more energy and causes the suction equipment to wear faster than it would otherwise, reducing its useful life. Further, the flow of air into the wound area as a result of such leaks can result in increased risk of infection and intrusion of other harmful foreign material into the wound area. It is therefore desirable to have a relatively inexpensive means of monitoring the pressure level beneath the cover at the site of the wound. 
     In addition, the existing apparatus do not have a means to determine the amount of blood flow to the tissue at the site of the wound. As discussed above, adequate blood circulation in the area of the wound is essential for the healing process to proceed as desired. Areas of tissue having an increased level of blood circulation generally have a higher temperature than areas that have a comparatively lower level of blood circulation. It is therefore desirable to have a means of monitoring the relative temperature within the area of the wound. 
     Finally, it is sometimes necessary to transport patients in need of reduced pressure wound care. It is also sometimes necessary to provide reduced pressure treatment in the field. It is therefore also desirable to have a wound treatment apparatus that is portable and self-contained, which can accompany the patient during such transport or be used to provide reduced pressure treatment in the field. 
     SUMMARY 
     The present invention is directed to a reduced pressure wound treatment apparatus and method that satisfy the needs described above. As described in greater detail below, it has many advantages over existing apparatus when used for its intended purpose, as well as novel features that result in a new reduced pressure wound treatment apparatus and method that are not anticipated, rendered obvious, suggested, or even implied by any of the prior art apparatuses, either alone or in any combination thereof. 
     In accordance with the present invention a wound treatment apparatus is provided for treating a wound by applying reduced pressure (i.e. pressure that is below ambient atmospheric pressure) to the wound in a controlled manner for a selected time period in a manner that overcomes the disadvantages of currently existing apparatus. The application of reduced pressure to a wound provides such benefits as faster healing, increased formation of granulation tissue, closure of chronic open wounds, reduction of bacterial density within wounds, inhibition of burn penetration, and enhancement of flap and graft attachment. Wounds that have exhibited positive response to treatment by the application of negative pressure include infected open wounds, decubitus ulcers, dehisced incisions, partial thickness burns, and various lesions to which flaps or grafts have been attached. 
     The wound treatment apparatus in accordance with the present invention includes a reduced pressure application appliance that is applied to a treatment site at which there is a wound and normal tissue surrounding the wound. The reduced pressure application appliance includes a fluid impermeable wound cover for covering and enclosing the wound. In a particular embodiment of the present invention, the wound cover also includes means for visually monitoring the pressure in the area of the site of the wound beneath the wound cover. These means include a plurality of protrusions on the surface of the cover that are recessed when a predetermined pressure is present beneath the cover, but are increasingly displaced above the remaining surface of the cover as the pressure beneath the cover increases above a predetermined pressure. In a similar manner, the cover may contain areas that are displaced as protrusions away from the remaining surface of the cover toward the wound when reduced pressure is applied beneath the cover, and the displacement of the protrusions decreases as the pressure beneath the cover increases. The protrusions may also be a different color (or a different shade of the same color) from that on the remaining surface of the cover. In addition, the protrusions may produce a noise as they are displaced away from the remaining surface of the cover, providing an audible indication that the pressure beneath the cover is increasing. 
     The appliance also includes sealing means for sealing the wound cover to the surrounding tissue of the wound in order to maintain reduced pressure in the vicinity of the wound during wound treatment. When the wound cover is sealed in position over the wound site, a generally fluid-tight or gas-tight sealed enclosure is formed over the wound site. The sealing means may be in the form of an adhesive applied to the underside of the wound cover for sealing the wound cover around the periphery of the wound. The sealing means may also include a separate sealing member such as an adhesive strip or a sealing ring in the form of a tubular pad or inflatable cuff secured to the wound cover for positioning around the periphery of the wound. In selected embodiments, the reduced pressure within the sealed enclosure under the wound cover may serve to seal the wound cover in position at the wound site. The reduced pressure appliance also includes a suction port for supplying reduced pressure within the sealed volume enclosed beneath the wound cover. The suction port may be in the form of a nipple on the wound cover. Alternatively, the suction port may be in the form of a tube attached to the wound cover or provided as a feedthrough beneath the wound cover. 
     The appliance may also include an absorbable matrix for placement in the wound in order to encourage tissue in the area of the wound to grow into the matrix during treatment. The absorbable matrix is constructed of an absorbable material that is absorbed into the epithelial and subcutaneous tissue in the wound as the wound heals. The matrix may vary in thickness and rigidity, and it may be desirable to use a spongy absorbable material for the patient&#39;s comfort if the patient must lie upon the appliance during treatment. The matrix may also be perforated and constructed in a sponge-type or foam-type structure to enhance gas flow and to reduce the weight of the matrix. Because of the absorbable nature of the absorbable matrix, the matrix should require less frequent changing than other dressing types during the treatment process. In other circumstances, the matrix may not need to be changed at all during the treatment process. 
     A vacuum system is connected with the reduced pressure appliance in order to provide suction or reduced pressure to the appliance. For this purpose, the vacuum system includes a suction pump or suction device for connection with the suction port of the appliance for producing the reduced pressure over the wound site. The vacuum system may include a section of hose or tube, such as a vacuum hose, that interconnects the suction device with the suction port of the appliance to provide the reduced pressure at the wound site. A fluid collection system may be provided intermediate the vacuum hose of the suction device and the suction port of the appliance to trap any exudate that may be aspirated from the wound by the negative pressure appliance. A stop mechanism may also be provided for the vacuum system to halt production of the reduced pressure at the wound site in the event that an excessive quantity of exudate has been collected. The apparatus may also include a control device for controlling the pump. 
     In a particular embodiment of the invention, the wound cover for the reduced pressure appliance may be in the form of a gas impermeable covering sheet of flexible polymer material, such as polyethylene, having an adhesive backing that provides the seal for securing the sheet over the wound site to provide a gas-tight or fluid-tight sealed enclosure over the wound site. The vacuum system of the wound treatment apparatus may include a suction pump having a vacuum hose that is connected with a suction tube serving as a suction port for the appliance. The suction tube for the appliance runs beneath the cover sheet that is sealed in position over the wound site and into the fluid-tight enclosure provided under the cover sheet. An adhesive backing on the cover sheet is used to provide a fluid-tight seal around the feedthrough for the suction tube at the wound site. Within the enclosure, the suction tube is connected with the absorbable matrix for placement in the wound. The absorbable matrix functions to more uniformly apply reduced pressure or suction over the wound site while holding the cover sheet substantially out of the wound during the application of reduced pressure at the enclosed wound site. 
     In another particular version of the invention, the wound treatment apparatus also includes means to monitor the temperature of the tissue in the area of the wound. In a particular embodiment of this version of the invention, a temperature sensitive layer composed of a temperature sensitive material is placed adjacent to the lower surface of the wound cover. The temperature sensitive layer changes color, or changes from one shade of a color to another shade of the same color, as the temperature of the material changes. In this embodiment of the invention, the wound cover is composed of a transparent or semi-transparent material allowing the temperature sensitive material to be observed from above the wound cover. Alternatively, the wound cover is composed of a temperature sensitive material that changes color, or changes from one shade of a color to another shade of the same color, as the temperature of the material changes. In another embodiment of this version of the invention, one or more temperature measuring devices are placed in the area of the wound. The temperature measuring devices are preferably placed adjacent to the wound tissue, but may also be placed in other locations under or above the wound cover, to monitor the temperature of said tissue. Temperature measuring devices located under the wound cover have leads that feedthrough beneath the wound cover. The leads are connected to an alarm system that produces one or more alarm signals when the temperature measured by one or more of the temperature measuring devices exceeds or is lower than a predetermined value. In another embodiment of this version of the invention, the temperature measuring devices are also connected through their respective leads and the alarm system to a temperature display or recording device that produces a display or record of the temperature in the area of the wound. 
     In another particular version of the invention, the wound treatment apparatus is portable and self-contained. In this version of the invention, a miniature vacuum source is used to provide suction to the reduced pressure appliance. Similarly, the fluid collection system is of the minimum size desired to collect and maintain the amount of exudate expected to be aspirated from the wound during the time of anticipated use of the portable wound treatment apparatus. A filter may also be placed in the connection between the vacuum source and the fluid collection system to avoid contamination of the source by the fluid aspirated from the wound. As a result, reduced pressure treatment of a wound can continue even if it becomes necessary to transport the patient because the apparatus can accompany a patient during the transport. The portable apparatus is not, however, limited to this use alone. It can be used in any application where a portable treatment apparatus is advantageous, such as treatment of wounds in the field. 
     There has thus been outlined, rather broadly, the more primary features of the present invention. There are additional features that are also included in the various embodiments of the invention that are described hereinafter and that form the subject matter of the claims appended hereto. In this respect, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the following drawings. This invention may be embodied in the form illustrated in the accompanying drawings, but the drawings are illustrative only and changes may be made in the specific construction illustrated and described within the scope of the appended claims. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description of the preferred embodiments of the present invention, will be better understood when read in conjunction with the appended drawings, in which: 
         FIG. 1  is a schematic elevational view of a wound treatment apparatus in accordance with a particular embodiment of the present invention in which a reduced pressure appliance, shown in partial section, includes a flexible, fluid impermeable wound cover sealed over the wound and an absorbable matrix positioned in the wound, and in which a vacuum system provides reduced pressure within the wound cover of the appliance; 
         FIG. 2 a    is a schematic sectional elevational view of the reduced pressure appliance of  FIG. 1 , illustrating an absorbable matrix having three layers of absorbable material, such layers being of different absorbable materials; 
         FIG. 2 b    is a schematic sectional elevational view of the reduced pressure appliance of  FIG. 1 , illustrating an absorbable matrix having generally concentric layers of absorbable material, such layers being of different absorbable materials; 
         FIG. 3  is a schematic sectional elevational view of a reduced pressure appliance in accordance with another embodiment of the present invention, shown in partial section, in which the reduced pressure appliance includes a rigid, fluid impermeable, cone-shaped wound cover overlying the wound site; 
         FIG. 4 a    is a schematic elevational view of a wound treatment apparatus in accordance with a particular embodiment of the present invention in which a reduced pressure appliance, shown in partial section, includes a flexible, fluid impermeable wound cover sealed over the wound and an absorbable matrix positioned in the wound, and in which a vacuum system provides reduced pressure within the wound cover of the appliance; 
         FIG. 4 b    is a sectional elevational detailed view of the shutoff mechanism portion of the collection system of  FIG. 4   a;    
         FIG. 5 a    is a schematic sectional elevational view of a reduced pressure appliance in accordance with another embodiment of the present invention, shown in partial section, in which the reduced pressure appliance includes a flexible, fluid impermeable wound cover sealed over the wound, said cover having embedded within it protrusions that are displaced above the remaining surface of the cover; 
         FIG. 5 b    is a detailed perspective view of a protrusion from the reduced pressure appliance of  FIG. 5 a   , in the fully displaced configuration; 
         FIG. 5 c    is a schematic sectional elevational view of the reduced pressure appliance of  FIG. 5 a   , illustrating the cover having the protrusions in the depressed configuration when sufficient vacuum is present beneath the cover; 
         FIG. 5 d    is a detailed perspective view of a protrusion from the reduced pressure appliance of  FIG. 5 a   , in the fully depressed configuration; 
         FIG. 5 e    is a schematic sectional elevational view of the reduced pressure appliance of  FIG. 5 a   , illustrating alternative protrusions having a bellows-type of configuration; 
         FIG. 5 f    is a perspective view of the reduced pressure appliance of  FIG. 5 a   , illustrating a pattern of protrusions on the wound cover; 
         FIG. 6  is a schematic sectional elevational view of a reduced pressure appliance in accordance with another embodiment of the present invention, shown in partial section, in which the reduced pressure appliance includes a packing material or an absorbable matrix positioned in the wound, and a flexible, fluid impermeable wound cover sealed over the wound, and a layer of temperature sensitive material located between the cover and the wound; 
         FIG. 7  is a schematic sectional elevational view of a reduced pressure appliance in accordance with another embodiment of the present invention, shown in partial section, in which the reduced pressure appliance includes a packing material positioned in the wound, and a flexible, fluid impermeable wound cover sealed over the wound, and a plurality of temperature sensors located at and surrounding the site of the wound, and in which an alarm system and a temperature display and recording device are connected to the temperature sensors; 
         FIG. 8 a    is a perspective view of a wound treatment apparatus in accordance with another embodiment of the present invention, shown from above, in which a reduced pressure appliance, a vacuum source, a filter, and a fluid collection system are connected together as a compact and portable apparatus; and 
         FIG. 8 b    is a sectional elevational detailed view of the shutoff mechanism portion of the collection system of  FIG. 8   a.    
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In accordance with the present invention, a wound treatment apparatus is provided for treating a wound by application of reduced pressure (i.e., below atmospheric pressure) so that suction may be applied to a wound site  25  in a controlled manner for a selected period of time.  FIG. 1  schematically shows one version of the wound treatment apparatus, generally designated  20 , which includes a reduced pressure appliance, generally designated  30 , for enclosing a wound site  25  to provide a fluid-tight or gas-tight enclosure over the wound site  25  to effect treatment of a wound  25  with reduced or negative pressure. For the purpose of creating suction within the appliance  30 , the appliance  30  is connected with a vacuum system, generally designated  50 , to provide a source of suction or reduced pressure for the sealed appliance  30  at the wound site  25 . Intermediate the appliance  30  and the vacuum system  50  is a fluid collection system, generally designated  70 , for intercepting and retaining exudate that is aspirated from the wound site  25 . 
       FIG. 1  also illustrates one embodiment of the reduced pressure appliance  30 , which includes an absorbable matrix  32  that is placed within the wound  25 , a fluid impermeable wound cover  40 , and a suction port in the form of hollow tubing  45  that connects the appliance  30  to the vacuum system  50  (through the collection system  70 ) to provide reduced pressure in the area beneath the cover  40  in the area of the wound  25 .  FIG. 1  also illustrates one embodiment of an absorbable matrix  32 , which is placed within the wound  25 . 
     The absorbable matrix  32  is placed over substantially the expanse of the wound  25  to encourage growth of tissue in the area of the wound  25  into the matrix  32  as the wound heals. The size and configuration of the absorbable matrix  32  can be adjusted to fit the individual wound  25 . It can be formed from a variety of absorbable materials, preferably a material that is also porous. The matrix  32  should be constructed in a manner so that it is sufficiently porous to allow oxygen to reach the wound  25 . The absorbable matrix  32  is preferably constructed of a non-toxic material that is absorbable by the epithelial and subcutaneous tissue within the area of the wound  25 , such as collogens derived from healthy mammals, absorbable synthetic polymers, or other materials similar to those used for absorbable dressings. An example is a dehydrating material derived from seaweed for treatment of exudating wounds. The matrix  32  may vary in thickness and rigidity, although it may be desirable to use a spongy or layered, non-woven absorbable material for the patient&#39;s comfort if the patient must lie upon the appliance  30  during treatment. The matrix  32  may also be perforated and constructed in a foam-type, sponge-type, or non-woven layered structure to enhance gas flow and to reduce the weight of the appliance  30 . As shown in  FIG. 1 , the matrix  32  is cut to an appropriate shape and size to fit within the wound  25 . Alternatively, the matrix  32  may be sufficiently large to overlap the surrounding skin  24 . Further, the matrix  32  may be of uniform thickness over its entire area, as is the case where monitoring the temperature of tissue in the area of the wound is desired as a part of the treatment process. 
     In another embodiment of the invention, the absorbable matrix  32  has the same features as described above and as illustrated in  FIG. 1 , but may also be constructed of more than one absorbable material, such material having different rates of absorption into body tissue. By preselecting the materials of the matrix  32 , and placing them in areas of the wound  25  in which different rates of absorption are desired, it may be possible to enhance wound healing. An example of this embodiment of the absorbable matrix  32  is illustrated in  FIG. 2 a   , where the matrix  32  is composed of three layers, each layer being composed of an absorbable material different from the material in the adjacent layer. Thus, in a matrix  32  of three layers having the lowest layer  33  being constructed of an absorbable material, and the middle layer  34  of the matrix  32  being constructed of a material having a lower rate of absorption than the lowest layer  33 , and the layer of the matrix  32  closest to the cover  40  (i.e., the highest layer  35 ) being constructed of a material having a rate of absorption lower than the other two layers, the area of the wound  25  adjacent to the lowest layer  26  would be allowed to close at a faster rate than the area of the wound  25  adjacent to the middle layer  27 , and the area of the wound  25  adjacent to the highest layer  28  would be allowed to close at a faster rate than the area of the wound  25  adjacent to the middle layer  27  and the lowest layer  26 . This embodiment of the invention is not limited to three layers or this gradation of absorption rates. Any combination of number of layers and absorbent materials desirable for wound treatment is possible and may be preferred. For example, the matrix  32  may have a highest layer  35  of absorbent material having a rate of absorption higher than the rate of absorption of the middle layer  34 , which middle layer  34  has a higher rate of absorption than the rate of absorption of the lowest layer  33 . Similarly, the highest layer  35  and the lowest layer  33  may have rates of absorption that are approximately equal to one another, such rate of absorption being greater or lesser than the rate of absorption of the middle layer  33 . 
     In addition, this embodiment of the matrix  32  is not limited to layers. The matrix  32  may be constructed in any configuration having materials of different absorption rates in any portion of the matrix  32  that is desired to promote wound healing. For example, as illustrated in  FIG. 2 b   , the material on the periphery  36  of the matrix  32  may be constructed of material having one rate of absorption, while the inner portions  37  of the matrix  32  may be constructed of one of more materials having different rates of absorption. This would allow for the wound  25  to close at one rate during the initial portion of the treatment period, and for the wound  25  to close at different rates during later portions of the treatment period. Other configurations that are possible include having approximately opposite sides or ends of the matrix  32  being constructed of a different material from the intermediate portions of the matrix  32 . 
     The fluid-impermeable wound cover  40  in the embodiment of the reduced pressure appliance  30  illustrated in  FIG. 1  is in the form of a flexible, adhesive, fluid impermeable polymer sheet for covering and enclosing the wound  25 , including the absorbable matrix  32  within it, and the surrounding normal skin  24  at the wound site  25 . The wound cover  40  includes an adhesive backing  41  which functions to seal the wound cover  40  to the normal skin  24  around the periphery of the wound  25  to provide a generally gas-tight or fluid-tight enclosure over the wound  25 . The adhesive cover sheet  40  must have sufficient adhesion to form a fluid-tight or gas-tight seal  42  around the periphery of the wound  25  and to hold the sheet  40  in sealed contact with the skin  24  during the application of suction or reduced or negative pressure. The wound cover  40  also provides a gas-tight seal around the tubing  45  at the feedthrough location  46  where the tubing  45  emerges from beneath the wound cover  40 . The wound cover  40  is preferably formed of a fluid impermeable or gas impermeable flexible adhesive sheet such as Ioban, a product of the 3M Corporation of Minneapolis, Minn. 
     The reduced pressure appliance  30  is not, however, limited to the configuration illustrated in  FIG. 1 . The appliance  30  may also have a wound cover of almost any size, shape, and configuration adapted to treat the wound. An example of this type of cover  40  is illustrated in the embodiment of the appliance  30  shown in  FIG. 3 , which has a wound cover  140  comprised of a rigid, fluid impermeable, generally cone-shaped wound cover  140  overlying the wound site  25 . Alternatively, the cover overlying the wound site may be comprised of a rigid, fluid impermeable, flat, bowl-shaped, or cup-shaped wound cover to protect the site of a wound  25  from impact or abrasion during treatment. The wound cover may also be comprised of a fluid impermeable, flexible cover supported by rigid support members overlying the wound site  25 . All of these cover types may be sealed to the normal skin  24  surrounding the wound  25  by using the suction created under the cover and a soft and flexible padding material  143  around the periphery of the cover  140 , which is in contact with the skin  24 . More preferably, the cover  140  is sealed to the skin  24  using a fluid-impermeable adhesive material  141  such as an adhesive tape or an adhesive sheet that has been cut to surround and at least partially overlie the periphery of the cover  140 . As an additional example, the cover may be comprised of a CPR mask, which may be sealed to the skin surrounding the wound with an inflatable air cuff that is a part of the mask, with a fluid-impermeable adhesive material, or by some other fluid-impermeable means. Where the cover  140  is not in contact with the absorbable matrix  32 , and is therefore not exerting force adequate to keep the matrix  32  in place within the wound  25 , a rigid or semi-rigid porous screen  147  may be placed over the matrix  32  and under the cover  140  in a position so that the periphery of such screen  147  is held in place by a portion of the cover  140  or the seal  142  that holds the cover  140  in place against the skin  24 . In such case, the screen  147  is of a thickness and rigidity necessary to hold the matrix  32  in place within the wound  25 , but having a porous structure so that fluids (including gases) are able to pass through the screen  147 . 
     The appliance  30  also includes a suction port in the form of a hollow suction tube  45  that connects with the vacuum system  50  to provide suction within the sealed enclosure. The suction tubing  45  serves as a suction port for the appliance  30 . In the embodiment of the invention illustrated in  FIG. 1 , an end segment  45   a  of the tubing  45  is embedded within the absorbable matrix  32  for providing suction or reduced pressure within the enclosure provided under the wound cover  40 . Embedding the open end of segment  45   a  of tubing  45  within the interior of the absorbable matrix  32  permits the absorbable matrix  32  to function as a shield to help prevent the wound cover  40  from being inadvertently sucked into sealing engagement with the open end of the tube thereby plugging the tube  45  and restricting gas flow. The tube segment  45   a  embedded within the absorbable matrix  32  preferably has at least one side port  47  for positioning within the interior of the absorbable matrix  32  to promote substantially uniform application of reduced pressure throughout the enclosure. Positioning the side port  47  of tube segment  45   a  within the interior of the absorbable matrix  32  permits the absorbable matrix  32  to function as a shield for the side port to thereby prevent the wound cover  40  from being sucked into the side port  47  and thereby restricting gas flow. The open cells of the absorbable matrix  32  facilitate gas flow throughout the enclosure. In addition, the absorbable matrix  32  functions to encourage the growth of tissue in the area of the wound  25  into the matrix  32  and to hold the wound cover  40  generally out of contact with the wound  25  during the application of suction within the enclosure. 
     Tubing  45  and tube segment  45   a  are sufficiently flexible to permit movement of the tubing but are sufficiently rigid to resist constriction when reduced pressure is supplied to the appliance  30  or when the location of the wound  25  is such that the patient must sit or lie upon the tubing  45  or upon the reduced pressure appliance  30 . The matrix-tube assembly comprising the absorbable matrix  32  and the tube  45  may be fabricated by snaking the end of the tube segment  45   a  through an internal passageway in the absorbable matrix  32  such as by pulling the end of the tube segment  45   a  through the passageway using forceps. The matrix-tube assembly  32  and  45  is preferably prepared prior to use under sterile conditions and then stored in an aseptic package. 
     As shown in  FIG. 4 a   , the vacuum system  50 , which produces a source of reduced pressure or suction that is supplied to the reduced pressure appliance  30 , includes a vacuum pump  51 , a control device  52 , a filter  53 , and tubing  54  that connects the vacuum pump  51  to the collection system  70 . Predetermined amounts of suction or reduced pressure are produced by the vacuum pump  51 . The vacuum pump  51  is preferably controlled by a control device  52  such as a switch or a timer that may be set to provide cyclic on/off operation of the vacuum pump  51  according to user-selected intervals. Alternatively, the vacuum pump  51  may be operated continuously without the use of a cyclical timer. A filter  53  such as micropore filter is preferably attached to the exhaust of the pump  51  to prevent potentially pathogenic microbes or aerosols from being vented to atmosphere by the vacuum pump  51 . 
     As shown in  FIG. 4 a   , a fluid collection system, generally designated  70 , is interconnected between the suction pump  51  and the appliance  30  to remove and collect any exudate which may be aspirated from the wound  25  by the reduced pressure appliance  30 . The appliance  30  functions to actively draw fluid or exudate from the wound  25 . Collection of exudate in a fluid collection system  70  intermediate the pump  51  and the appliance  30  is desirable to prevent clogging of the pump  51 . The fluid collection system  70  is comprised of a fluid-impermeable collection container  71  and a shutoff mechanism  75 . The container  71  may be of any size and shape capable of intercepting and retaining a predetermined amount of exudate. Many examples of such containers are available in the relevant art. The preferred container in this embodiment of the invention is illustrated in side elevation view in  FIG. 4 a   , said container having two openings in the top of the container  71 . The container  71  includes a first port  72  at the top opening of the container for sealed connection to suction tubing  45 . The first port  72  enables suction to be applied to the reduced pressure appliance  30  through the tubing  45  and also enables exudate from the wound  25  covered by reduced pressure appliance  30  to be drained into the container  71 . The container  71  provides a means for containing and temporarily storing the collected exudate. A second port  73  is also provided on the top of the container to enable the application of suction from the vacuum pump  51 . The second port  73  of the collection system  70  is connected to the vacuum pump  51  by a vacuum line  54 . The collection system  70  is sealed generally gas-tight to enable the suction pump  51  to supply suction to the appliance  30  through the collection system  70 . 
     The container  71  may also include a fluid impenetrable flexible liner within its volume that is used to collect the exudate in a manner that avoids contaminating the container  71  with pathogenic microbes and other harmful matter present in the exudate. In such case, the flexible liner may be directly connected to the first port  72  and second port  73  in a manner so that no exudate comes into direct contact with the container  71 . In this embodiment, the preferred liner is a flexible bag constructed of a polymer material, which is connected to the first port  72 . 
     The vacuum system  50  and collection system  70  preferably include a shutoff mechanism for halting or inhibiting the supply of the reduced pressure to the appliance  30  in the event that the exudate aspirated from the wound  25  exceeds a predetermined quantity. Interrupting the application of suction to the appliance  30  is desirable to prevent exsanguination in the unlikely event a blood vessel ruptures under the wound cover  40  during treatment. If, for example, a blood vessel ruptures in the vicinity of the wound  25 , a shut-off mechanism would be useful to prevent the vacuum system  50  from aspirating any significant quantity of blood from the patient. 
     The shutoff mechanism  75  may be comprised of any means that enables the vacuum system  50  to halt the supply of reduced pressure to the wound cover  40  at any time that the volume of exudate from the wound  25  exceeds a predetermined amount. Such means may include mechanical switches, electrical switches operably connected to the vacuum system controller  52 , optical, thermal or weight sensors operably connected to the vacuum system controller  52 , and any other means that are currently known in the relevant art or which may hereafter be discovered. The shutoff mechanism  75 , as illustrated in  FIG. 4 b   , is preferably a float valve assembly in the form of a ball  76  which is held and suspended within a cage  77  positioned below a valve seat  78  disposed within the opening at the top of the container below the second port that will float upon the exudate and will be lifted against the valve seat  78  as the container fills with exudate. When the ball  76  is firmly seated against the valve seat  78 , the float valve blocks the second port  73  and thereby shuts off the source of suction from the vacuum system  50 . Other types of mechanisms may also be employed to detect the liquid level within the container  71  in order to arrest operation of the vacuum system  50 . 
     In another version of the invention, the wound treatment apparatus includes means to monitor the pressure beneath the wound cover  40  at the site of the wound  25 . In one embodiment of this version of the invention, as illustrated in  FIG. 5 a   , the wound cover  40  has a plurality of protrusions  60  in the form of hills or bumps embedded in the cover  40 . As illustrated in  FIG. 5 a   , the protrusions  60  protrude above the remaining surface  43  of the cover  40  when the cover  40  is not in use for wound treatment. A detailed view of a protrusion  60   a  in this configuration is shown in perspective view in  FIG. 5 b   . Generally, as illustrated in  FIG. 5 c   , in some embodiments, when the cover  40  is in use (i.e., sealed over the wound site  25  with reduced pressure applied beneath the cover  40 ), the protrusions  60  are displaced inwardly (or downward when the cover  40  is in the orientation depicted in  FIG. 5 c   ) so that they are depressed to a level almost the same as that of the remaining surface  43  of the cover  40 . A detailed view of a protrusion  60   b  in the depressed configuration is shown in perspective view in  FIG. 5 d   . In another embodiment, the protrusions  60   c  are configured in the form of bellows, as shown in  FIG. 5 e   . In this version of the invention, as the pressure beneath the cover  40  decreases (i.e., the level of reduced pressure increases), the top of the protrusion  60   c  is displaced downward toward the level of the remaining surface  43  of the cover  40 . The protrusions  60  may be placed in any location, as well as in any pattern or lack of pattern, on the surface of the cover  40 . An example of one possible pattern is illustrated in  FIG. 5   f.    
     The protrusions  60  may be constructed of the same material as the remainder of the cover  40 , or may be constructed of a material different from the remainder of the cover  40 , depending upon the sensitivity of pressure monitoring desired. Similarly, the protrusions  60  may be constructed of material having the same thickness as the remainder of the cover  40 , or material of a different thickness, depending upon the sensitivity of pressure monitoring desired. For example, if the reduced pressure beneath the cover  40  is of a relatively low level, so that the difference between the ambient atmospheric pressure above the cover  40  is relatively small when compared to the reduced pressure beneath the cover  40 , it may be desirable to have the protrusions  60  be able to change shape with relatively small changes in pressure beneath the cover  40  during the treatment period. In such case, it may be preferable to have the protrusions  60  of a thickness less than the thickness of the remaining cover material. It may also be preferable to have the protrusions  60  constructed of a material more pliable than the material of which the remainder of the cover  40  is constructed. Similarly, if the reduced pressure beneath the cover  40  is of a relatively high level, so that the difference between the ambient atmospheric pressure above the cover  40  is relatively large when compared to the reduced pressure beneath the cover  40 , it may be desirable to have the protrusions  60  be able to change shape with relatively large changes in pressure beneath the cover  40  during the treatment period. In such case, it may be preferable to have the protrusions  60  of a thickness more similar to the thickness of the remaining cover material. It may also be preferable to have the protrusions  60  constructed of a material that is more similar to the material of which the remainder of the cover  40  is constructed in terms of pliability. 
     By preselecting the thickness and pliability of the material used to construct the protrusions  60 , it may also be possible to monitor the pressure by partial deflections of the protrusions  60 . For example, the protrusions  60  may be displaced in an increasing amount above the remaining surface  43  of the cover  40  as the pressure beneath the cover  40  increases (i.e., the level of reduced pressure decreases). This relationship of displacement of the protrusions  60  to the increase in pressure beneath the cover  40  may be linear or based upon some other function. Similarly, the protrusions  60  may be constructed so that they only begin to be displaced when a predetermined pressure differential occurs between the area under the cover  40  and the area above the cover  40 . It should be noted, however, that this version of the invention is intended as a means to provide an inexpensive and approximate visual indication of the occurrence of loss of reduced pressure beneath the cover and may not be a means to accurately measure the actual pressure beneath the cover or the actual difference between the pressure above the cover and the reduced pressure beneath the cover. 
     As a result, the preferable thicknesses and materials to be used in constructing the cover  40  and protrusions  60  in this version of the invention are dependent upon a multitude of factors, including the desired pressure beneath the cover  40 . Preferably, the wound cover  40  is constructed of polyurethane, having a thickness of only a few mils to ⅛th inch, and having protrusions  60  constructed of the same material as the remaining portion of the cover  40 , said protrusions  60  having a thickness only slightly less than the thickness of the cover  40  to a relatively small fraction of the thickness of the cover  40 . 
     Further, the protrusions  60  may be constructed of material that is of a different color than the color of the remaining surface  43  of the cover  40 . Similarly, the protrusions  60  may be of a different shade of the same color as the remaining surface  43  of the cover  40 . As the protrusions  60  are displaced away from the remaining surface  43  of the cover  40 , the protrusions  60  may change color as a result of the expansion of the material comprising the protrusions  60 . 
     In another embodiment of this version of the invention, the protrusions work in the manner opposite to that described above. In this embodiment, the cover has within it a plurality of areas that are displaced away (i.e., pulled down) from the remaining surface of the cover toward the wound when reduced pressure is applied beneath the cover. This downward displacement is the result of the reduced pressure suction, which causes tension that pulls the protrusions away from the remaining surface of the cover. As the pressure beneath the cover increases, the tension on the protrusions weakens allowing the protrusions to recede back into the cover. The principles discussed above with respect to thickness, materials, color, and partial deflection monitoring of pressure apply to this embodiment of the invention as well. It should be noted that bellows-type protrusions are not used in this embodiment. 
     The protrusions  60  may also have a means whereby they produce an audible sound as the protrusions  60  are being displaced away from the remaining surface  43  of the cover  40 . This sound may be produced by the “crinkling” or vibration of the material as it is displaced away from the remaining surface  43  of the cover  40 . 
     It should be noted that the means to monitor the pressure beneath the cover described in this embodiment of the invention may be used independently of any other feature of this invention. In addition, the means to monitor pressure beneath the cover is not limited to use in treatment of open wounds, decubitus ulcers, dehisced incisions, partial thickness burns, and various lesions to which flaps or grafts have been attached. Instead, said pressure monitoring means may be used in any application involving reduced pressure in the treatment of any portion of the body of a patient, such as cosmetic surgery, cosmetic healing, and prophylactic suctioning for cosmetic and psychological reasons. In addition, the cover may be of any configuration, including the cover configurations specifically discussed above. Further, it is not necessary that any packing material or matrix be present in the area of the wound beneath the cover in this version of the invention. Nor is it necessary that the features included in this version of the invention be included as a part of any other version or embodiment of this invention. 
     In another version of the invention, the wound treatment apparatus includes means to monitor the temperature in the area of the wound  25 . In one embodiment of this second version of the invention, as illustrated in  FIG. 6 , a layer of temperature sensitive material  80  is placed adjacent to the lower surface  44  of the wound cover  40 . Alternatively, the cover  40  and the layer  80  may be joined together to form a single integrated unit. In such case, the cover  40  and the layer  80  may be joined in any manner that is fluid-impermeable and allows the color (or other property exhibiting the change of temperature) of the temperature sensitive layer  80  to be observed from above the wound cover  40 . The preferred means to join the cover  40  and the layer  80  is a transparent or semi-transparent adhesive material. Alternatively, the wound cover  40  may itself be composed of a temperature sensitive material, so that a separate temperature sensitive layer is not required. 
     The temperature sensitive layer  80  (or the cover  40 , if it is composed of a temperature sensitive material) may be composed of any material that changes properties in a manner that does not adversely affect the operation of the reduced pressure appliance  30 . Preferably, the temperature sensitive layer  80  is composed of a material that changes color, or changes from one shade of a color to another shade of the same color, as the temperature of the material changes. The change in color or shade preferably occurs within the temperature range that may be expected in the area of the wound  25 . In other words, the change in color or shade of the material should be significant enough to adequately indicate changes in temperature within the range of temperatures expected in the area of the wound  25 . More preferably, the temperature sensitive material is a material that changes color in the range from approximately 95 degrees Fahrenheit to approximately 105 degrees Fahrenheit. 
     In the embodiment of the invention shown in  FIG. 6 , the temperature sensitive layer  80  is placed over a packing material or matrix  32   a , which packing material or matrix  32   a  is placed within the area of the wound  25 . The matrix  32   a  may be an absorbable matrix  32   a , as described above. The packing material may be constructed of any material that is suitable for placement within a wound  25 , which may be to prevent its overgrowth, but still allows for fluid and gas flow to and from the wound  25 , such as a porous polymer material or gauze. In order to provide for uniform temperature monitoring, the packing material or matrix  32   a  is preferably of relatively uniform thickness when placed within the area of the wound  25 . In addition, the packing material or matrix  32   a  should be thin enough to allow for the temperature of the tissue to affect the temperature of the temperature sensitive layer  80 . More preferably, the thickness of the packing material or matrix  32   a  should not exceed slightly greater than zero to one half inches. The packing material or matrix  32   a  may, however, be of non-uniform thickness where the temperature sensitive layer  80  is comprised of temperature sensitive material in a manner that compensates for the differences in thickness of the packing material or matrix  32   a.    
     The wound cover  40  is placed over the temperature sensitive layer  80  and sealed to the normal skin  24  surrounding the wound  25 . If the cover  40  and the temperature sensitive layer  80  are an integrated unit, however, the unit is placed over the packing material or matrix  32   a  without a separate temperature sensitive layer  80 . If the cover  40  is composed of a temperature sensitive material, it is placed over the packing material or matrix without an additional temperature sensitive layer  80 . It should be noted, however, that the temperature sensitive material used in this embodiment of the invention is intended as a means to provide an approximate visual indication of the temperature in the area of the wound  25  beneath the cover  4 , and may not accurately measure the actual temperature beneath the cover  40 . 
     In another embodiment of this second version of the invention, one or more temperature measuring devices  81  are placed within the area of the wound  25  and connected to an alarm system, generally designated as  82 . The temperature measuring devices  81  may also be connected to a temperature display and recording device  83 . An example of this embodiment is illustrated in  FIG. 7 , which shows temperature measuring devices  81  placed in the area of the wound  25 . The temperature measuring devices  81  may be placed in any area of the wound  25  and the reduced pressure appliance  30 . For example, the temperature measuring devices  81  may be placed adjacent to and in direct contact with the tissue in the area of the wound  25 . Alternatively, the temperature measuring devices  81  may be embedded in any packing material or matrix  32  placed in the area of the wound  25 , or in the area between such packing material or matrix  32  and the cover  40 , or embedded within the cover  40 , or adjacent to either surface of the cover  40 . 
     The temperature measuring devices  81  are preferably capable of measuring temperatures in the range of temperatures expected in the area of the wound  25 . More preferably, the temperature measuring devices  81  are capable of measuring temperatures in the range of 95 degrees Fahrenheit to 105 degrees Fahrenheit. The temperature measuring devices  81  may be any device that measures temperature in the desired range and produces a corresponding signal that may be interpreted by the alarm system  82  and temperature display and recording device  83 . The temperature measuring devices  81  must, however, not be harmful to body tissue. The temperature measuring devices  81  are preferably thermocouples or optical sensors or detectors. The temperature measuring devices  81  are more preferably thermocouples that generate an electronic signal representing the temperature measured by the thermocouple. 
     The temperature measuring devices  81  are connected by leads  84  to an alarm system  82 . The leads  84  may be in any form compatible with the temperature measuring devices  81  and the alarm system  82  and recording device  83 . Preferably, the leads  84  are cables or wires constructed of an electrically conductive material, optical fiber, or other medium enabling data transmission that transfers the signals from the temperature measuring devices  81  to the alarm system  82  and the display and recording device  83 . Leads  84  placed under the wound cover  40  feedthrough the seal  42  beneath the cover  40  in a manner similar to that for the tubing (as illustrated and discussed above in connection with  FIG. 1 ) that maintains the fluid impermeable nature of the seal  42 . 
     The alarm system  82  is comprised of a computer or other data processor  85  and an alarm device  86 . The computer or data processor  85  receives the signals from the temperature measuring devices  81  and converts them to electronic or other signals that are recognized by the alarm device  86 . The computer or data processor  85  is of a type that is commonly available in the relevant art. The alarm device  86  may produce any type of audible sound as an alarm, such as a ringing sound, buzzing, chirping or other common alarm noise. Alternatively, the alarm device  86  may include a digitally produced audible voice that presents predetermined messages corresponding to different temperature conditions in the area of the wound  25 . The alarm device  86  preferably produces different levels of alarm depending upon the temperature measurements received from the temperature measuring devices  81 . For example, as the temperature drops below or rises above successive preselected values of temperature, as measured by any temperature measuring device  81 , the alarm device  86  may sound successive predetermined alarm pitches, sounds, messages or series of sounds. Similarly, as the temperature measured by multiple temperature measuring devices  81  successively falls below or rises above a preselected temperature, the alarm device  86  may sound successive predetermined alarm pitches, sounds, messages or series of sounds. The alarm system  82  may also be connected to the vacuum supply  50 , so that upon production of a predetermined alarm by the alarm device  86 , the vacuum pump controller  52  causes the pump  51  to cease operation. 
     The computer or data processor  85  may also be connected to a temperature display and recording device  83  that records the temperatures measured by one or more of the temperature measuring devices  81 . The temperature recording device  83  may be any device designed to record or display data that is compatible with the signals produced by the computer or data processor  85 . Such devices are preferably devices that record data on compact disks, floppy disks, magnetic tape, integrated circuits, or other similar media in digital form or “manual” devices that record or display data in a visually depicted form, such as a chart recorder or visual electronic display, such as an LCD or CRT monitor. The more preferred temperature display and recording device  83  is a device recording data on a compact disk used in conjunction with an LCD monitor. 
     It should be noted that in this embodiment of this version of the invention the cover  40  may be of any configuration, including the cover configuration illustrated in  FIG. 3  and the other cover configurations specifically discussed above in connection with  FIG. 3 . In addition, it is not necessary that any packing material or matrix  32  be present in the area of the wound  25  beneath the cover  40  in this version of the invention. It is also not necessary that the temperature display and recording device  83  be included in every embodiment of this version of the invention. Nor is it necessary that the features included in this version of the invention be included as a part of any other version or embodiment of this invention. 
     In another version of the invention, the wound treatment apparatus  220  is portable and may be self-contained. In a first embodiment of this version of the invention, as illustrated in  FIG. 8 a   , a miniature and portable vacuum source  250  is connected to a wound cover. The vacuum source  250  is preferably a miniature and portable vacuum pump. The vacuum source  250  may also be connected to a filter  253 , which is connected to a collection system  270 . The vacuum source  250  is used to provide suction to the reduced pressure appliance, generally designated as  230 . It is portable in the sense that it is of a size small enough to be positioned directly on the surface of the wound cover  240 . The vacuum source  250  is also lightweight to avoid placing too much pressure on any body part being treated by the apparatus  220  and to allow the apparatus  220  to be easily transported. The vacuum source  250  may be powered by electricity received through a cord plugged into a standard wall socket, or the vacuum source  250  may be powered by a battery, fuel cell, or other alternative means, such as solar or photo electric sells or a windmill or watermill operated generator. The vacuum source  250  may also be operated by other means, such as pneumatics or hydraulics, if such means are available. 
     The wound cover  240  may be of almost any size, shape, and configuration adapted to treat the wound. Thus, the wound cover  240  is not limited to the embodiment illustrated in  FIG. 8 a   . As illustrated and discussed above in relation to  FIG. 3 , the cover may be comprised of a rigid, fluid impermeable, cone-shaped, bowl-shaped, or cup-shaped wound cover to protect the site of a wound  25  from impact or abrasion during treatment. Alternatively, the cover may be comprised of a flexible or rigid flat wound cover. 
     The vacuum source  250  may be attached to the cover  240  using any means that is compatible with the structure of the cover  240  and the vacuum source  250 . For example, if the cover  240  is constructed of a flexible, fluid impermeable material, the vacuum source  250  may be attached to the cover  240  using an adhesive material, such as a glue or other liquid or sprayed adhesive, adhesive tape, and similar means that are currently known in the relevant art or which may hereafter be discovered. As another example, if the wound cover  240  is constructed of a rigid material, the vacuum source  250  may be attached to the cover  240  using a variety of fasteners and similar means, such as anchors, bolts, rivets, screws, nuts, latch and clasp, hook and loop fasteners (such as that commonly sold under the trade name VELCRO), ultrasonic welding, and similar structures that are currently known in the relevant art or which may hereafter be discovered. The vacuum source  250  may therefore be permanently attached to the cover  240 , or the vacuum source  250  may be removably attached to the cover  240  allowing the vacuum source  250  to be reused after being used for a treatment even if the cover  240  is no longer usable after such treatment. The means of fastening the vacuum source  250  to the cover  240  must, however, be accomplished in a manner that allows the cover  240  to maintain the desired reduced pressure beneath the cover  240  while it is in use. Thus, gasket or sealant material may be used to seal any areas of perforation of the cover  240  where the fastener penetrates the surface of the cover  240 . 
     The fluid collection system  270  in the embodiment illustrated in  FIG. 8 a    includes a container  271  to collect the exudate and a shutoff mechanism  275 , one embodiment of which is illustrated in  FIG. 8 b   , to halt operation of the vacuum source  250  if the level of exudate in the container  271  exceeds a predetermined level. The container  271  is of the minimum size desired to collect and maintain the amount of exudate expected to be aspirated from the wound during the time of anticipated use of the portable wound treatment apparatus  220 . Alternatively, a small container  271  may be used, in which the fluid is changed intermittently as necessary during the treatment period. The container  271  has two ports, a first port  272  for connecting the container  271  to the reduced pressure appliance  230  and a second port  273  for connecting the container  271  to the vacuum source  250 . A filter  253  may also be connected intermediate the vacuum source  250  and the container  271 . The shutoff mechanism may be comprised of any means that enables the vacuum system  250  to halt the supply of reduced pressure to the wound cover  240  at any time the volume of exudate from the wound exceeds a predetermined amount to prevent, thereby preventing such exudate from contaminating the vacuum source  250 . Such means may include mechanical switches, electrical switches operably connected to the vacuum source  250 , optical, thermal or weight sensors operably connected to the vacuum source  250 , and any other means that are currently known in the relevant art or which may hereafter be discovered. Where the shutoff mechanism transfers electrical or other data signals to the vacuum source  250 , the vacuum source  250  may contain a control mechanism to convert said signals to the form necessary to halt the production of reduced pressure by the vacuum source  250 . Such means is preferably the float valve shutoff mechanism  275  illustrated in  FIG. 8 b   , connected to the second port  273  of the container  271 , which has the same features as the float valve illustrated in and discussed above in connection with  FIG. 4   a.    
     As illustrated in  FIG. 8 a   , this embodiment of the invention may also include a filter  253  to prevent potentially pathogenic microbes or aerosols from contaminating the vacuum source  250 . The filter  253  is generally comprised of a filter element encased in a fluid impermeable housing that has an inlet port  256  and an outlet port  257 . The filter element is preferably a hydrophobic and micropore filter capable of filtering out pathogenic microbes or aerosols. The housing of the filter  253  may be constructed in a manner that enables the filter element to be changed if desired. The filter  253  need not, however, be used in every embodiment of this version of the invention. 
     In the embodiment illustrated in  FIG. 8 a   , tubing  245  is used to connect the reduced pressure appliance  230  covering a wound  225  to the collection system  270  by means of the first port  272  located on the container  271 . The features of this tubing  245  and reduced pressure appliance  230  are substantially the same as illustrated and discussed above in connection with  FIG. 1  and  FIG. 4 a   . In addition, in the embodiment of the invention illustrated in  FIG. 8 a   , the second port  273  of the container  271  is connected to the inlet port  256  of the filter  253  by flexible vacuum tubing  254 , such as that used to connect the collection system  270  to the reduced pressure appliance  230 . This is not, however, the only means of connecting the collection system  270  to the filter  253 . For example, the connection may be made by using a rigid, fluid impermeable structure, such as a short length of rigid polymer tube, permanently connecting the filter  253  and the collection system  270 . The filter  253  may also be directly attached to the container  271  without the use of any tubing or other means, causing the container  271  and the filter  253  to be integrated as a single unit. In the embodiment of the invention illustrated in  FIG. 8 a   , the outlet port  257  of the filter  253  is connected to the vacuum source  250  by flexible vacuum tubing  254   a , such as that used to connect the collection system  270  to the reduced pressure appliance  230 . This is not, however, the only means of connecting the collection system  270  to the filter  253 . For example, the connection may be made by using a rigid, fluid impermeable structure, such as a short length of rigid polymer tube permanently connecting the filter  253  and the vacuum source  250 . The filter  253  may also be directly attached to the vacuum source  250  without the use of any tubing or other means, causing the container  271  and the filter  253  to be integrated as a single unit. As illustrated in  FIG. 8 a   , the vacuum source  250 , the filter  253 , and the container  271  may also be directly attached to one another to form a single integrated unit. Such attachment may be made by any of the means described above that may be used to attach the vacuum source  250  to the cover  240 . 
     Use of the wound treatment apparatus can be illustrated by a prospective example involving a reduced pressure appliance  30  of the type discussed in connection with  FIG. 1 . After preparing the bed of the wound  25 , one end of a length of vacuum tubing  45  is embedded in an absorbable matrix  32  that is trimmed to be the size and shape of the wound  25 . The matrix  32  is saturated with saline and placed in the wound  25 . As illustrated in  FIG. 7 , if temperature monitoring is desired, temperature measuring devices  81  are placed in the desired locations and connected to an alarm system  82 , and if desired, a display and recording device  83 . Alternatively, a temperature sensitive layer  80  is placed over the matrix, as illustrated in  FIG. 6 . A fluid impermeable or gas impermeable flexible adhesive sheet  40 , such as IOBAN, is placed over the matrix  32  (and temperature measuring means, if utilized) and the wound  25  and sealed to the normal skin  24  surrounding the wound  25 . The site of feedthrough of the vacuum tube  45  and any leads  84  from under the cover  40  is then sealed with a liquid or paste adhesive. Negative pressure is then applied to the reduced pressure appliance  30  by the vacuum system  50 , through the intermediate fluid collection system  70 . 
     Negative pressure appliances are useful for treating a variety of wounds. Treatment of a wound can be carried out by securing a negative pressure appliance to the treatment site as previously shown and described, and then maintaining a substantially continuous or cyclical reduced pressure within the appliance until the wound has reached a desired improved condition. A selected state of improved condition may include formation of granulation tissue sufficient for the attachment of a flap or graft, reduction of microbial infection in the wound, arrest or reversal of burn penetration, closure of the wound, integration of a flap or graft with the underlying wounded tissue, complete healing of the wound, or other stages of improvement or healing appropriate to a given type of wound or wound complex. 
     It may be preferable to change the appliance periodically during treatment, particularly when using appliances incorporating a packing material on or in the wound. The time between changing the appliance where an absorbable matrix is placed on or in the wound would ordinarily be a greater time interval that is generally dependent upon the nature of the wound. Where it is necessary to change the absorbable matrix during the treatment period, it may also be necessary to remove a portion of the matrix, but leave in place the portion of the matrix into which there has been significant tissue growth. In such cases, the portion of the matrix without significant tissue growth incorporated therein should be carefully removed by cutting or tearing away such portion from the remaining portion. New absorbable material can be placed in the area from which the prior material has been removed. 
     The wound treatment apparatus is preferably operated using a negative or reduced pressure ranging from 0.01 to 0.99 atmospheres, and more preferably practiced using a negative or reduced pressure ranging between 0.5 to 0.8 atmospheres. The time period for use of the wound treatment apparatus on a wound may preferably be at least 12 hours, but can be, for example, extended for one or more days. There is no upper limit beyond which use of the wound treatment apparatus is no longer beneficial; use of the wound treatment apparatus increases the rate of closure up to the time the wound actually closes. Satisfactory treatment of various types of wounds has been obtained via the use of reduced pressures equivalent to about 2 to 7 in. Hg below atmospheric pressure. 
     Supplying reduced pressure to the appliance in an intermittent or cyclic manner has also been demonstrated to be useful for treating wounds. Intermittent or cyclic supply of reduced pressure to an appliance may be achieved by manual or automatic control of the vacuum system  50 . A cycle ratio, the ratio of “on” time to “off” time, in such an intermittent reduced pressure treatment may be as low as 1:10 or as high as 10:1. The preferred ratio is approximately 1:1 which is usually accomplished in alternating 5 minute intervals of reduced pressure supply and non-supply. 
     A suitable vacuum system  50  includes any suction pump capable of providing at least 0.1 pounds of suction to the wound, and preferably up to three pounds suction, and most preferably up to fourteen (14) pounds suction. The pump can be any ordinary suction pump suitable for medical purposes that is capable of providing the necessary suction. The dimension of the tubing interconnecting the pump and the reduced pressure appliance is controlled by the pump&#39;s ability to provide the suction level needed for operation. A ¼ inch diameter tube may be suitable. 
     In treating damaged tissue, use of the invention usually comprises the steps of applying negative pressure to a wound for a selected time and at a selected magnitude sufficient to reduce bacterial density in the wound. Open wounds are almost always contaminated with harmful bacteria. The application of negative pressure to a wound appears to reduce the bacterial density of the wound. It is believed that this effect is due to either the bacteria&#39;s incompatibility with a negative pressure environment or the increased blood flow to the wound area, as blood brings with it cells and enzymes to destroy the bacteria. 
     Burns may generally be treated using a method that comprises the steps of applying negative pressure to the burn over an area with predetermined reduced pressure and for a time sufficient to inhibit formation of a full thickness burn. A partial thickness burn, one which has a surface layer of dead tissue and an underlying zone of stasis, is often sufficiently infected so that it will transform within 24-48 hours into a full thickness burn, one in which all epidermal structures are destroyed. The application of negative pressure to the wound prevents the infection from becoming sufficiently severe to cause destruction of the underlying epidermal structures. The magnitude, pattern, and duration of pressure application can vary with the individual wound. 
     Further embodiments of this patent application include the embodiments described in U.S. Provisional Application No. 60/430,827, filed on Dec. 4, 2002, and U.S. Provisional Application No. 60/407,783, filed on Sep. 3, 2002. These embodiments are described further below, with reference to the figures from these provisional applications that are incorporated by reference herein. 
     A subject of this patent application is an improved process of applying continuous sub atmospheric pressure to a wound to assist in healing by using a layer of material that is thermal sensitive. This thermal sensitive material has several distinct properties. Feedback from this thermal layer is transmitted to a microprocessor which in turn will control distinct areas, cells or divisions of the wound healing apparatus to adjust the pressure in each area to an optimal amount. 
     This system improves upon other methodologies of healing wounds. A wound can be defined as a change in the integrity of the skin which would allows fluid, gases, and other materials to pass through below topical levels into the body or allow bodily fluids to pass through the skin to the outside atmosphere. The human and other conditions need to have a barrier in place to prevent a variety of trauma, to the tissues and organs. 
     FIG. 7 of U.S. Provisional Application No. 60/430,827 depicts the system in its simplest format. A material that is occlusive or semi-occlusive is applied to the wound. The material of this cover dressing is temperature sensitive and will change colors to reflect the temperature of the wound surface. The purpose of this temperature change is to show the clinician, patient, and others area that may have difficulty with blood flow or low temperature or too high of a temperature. The temperature that the material reflects may need to be adjusted based on distance from the wounds and any insulating materials that may have to lie between the material and the wound. Here, a simple depiction shows the relationship but in actuality there may need to be other materials between these two layers to assist in the wound healing process. 
     FIG. 1 of U.S. Provisional Application No. 60/430,827 depicts the system that includes the system to create a sub-atmospheric pressure on the wound bed or generation of suction or pressure differentials. It also includes an occlusive or semi-occlusive dressing and a system of a sponge, gauze or foam. The system is sealed to the wound with a sealing paste or adhesive on the dressing. The cover dressing that is occlusive or semi-occlusive, this material that changes colors may be the same material that responds to temperature or it may be a secondary layer. There is a tubing system that transmits the pressure differential between the suction device and the wound site where the sponge, gauze, or foam and occlusive dressing is present. There is a seal between the occlusive or semi-occlusive dressing and the wound allowing for a buildup of negative pressure. Finally there is a feedback system that allows for adjustment of the suction device that generates pressure differentials based on the readings of the various sites throughout the wound treatment system. 
     As another embodiment the occlusive or semi-occlusive layer may also change color to show the local pressure on the wound site. The system then has measurement device of suction or pressure differentials through the wound treatment system. This measurement device is again, actually present in the cover dressing and the dressing responds to the amount of pressure applied by changing colors. This layer or the cover dressing would also have the ability to insure that the proper pressures are measured on the wound bed as well as what shows on the suction pump. 
     FIG. 1 of U.S. Provisional Application No. 60/430,827 depicts the system that has been invented. It improves upon previous systems. First, the system allows for application of the pressure differentials in several locations. The locations are shown here as Area  1 , Area  2 , and so on to Area end. The amount of areas can be as small as two or tens of thousands if needed. These measurement systems are connected with the suction pump in a feedback system. This feedback system allows for the pump to generate additional suction or less suction based on the readings. The reading may be of pressure or temperature depending on what application is selected. The feedback system may incorporate a microprocessor that would allow for various analyses of the readings and then generate instructions for the pump to produce more vacuum or reduce the vacuum level. This feedback connection may be of mechanical, electrical, optical or other mechanism. The feedback system encompasses two areas. The first area is the feedback of the system based on the pressure actually in the wound site. The other feedback mechanism is based on the amount of temperature that is present in each area of the wound bed. The amount of temperature or suction actually in the wound bed is feed through a microprocessor that is programmed to optimal change the pressure reading to insure optimal wound healing. The amount of temperature or suction needed would be based on the sensor layer that was present on the dressing. This may also be a separate layer. 
     The invention envisions a complex system that because of the physics involved with the material in the wound site, foam, gauze, or a sponge that a pressure gradient would be established. This pressure gradient because of the complexity of the system would allow for various pressures to be set up in the wound site. Thus a system would be created where there were multiple pressures. For example in  FIG. 1  (of U.S. Provisional Application No. 60/430,827), there would be an initial suction reading outside of the pump, a secondary suction reading at the top of the occlusive or semi-occlusive dressing. There may be a third pressure in at the base of the sponge. Many other suction gradients may be present in the wound. 
     The suction in the invention would be applied in a systematic way through a solenoid. This solenoid would open and close valves or other mechanisms that would allow distinct pressure setting to be present in the wound. This would be done through smaller tubes that would be feed to the wound bed and into the materials. Each area in the wound bed would have a sealed area that would enable the system to generate the pressure that was needed separate and distinct form other areas, cells, or divisions. 
     FIG. 2 of U.S. Provisional Application No. 60/430,827 depicts this system again. Here a clearer view of the separate areas with the separate pressures is seen. Each cell, division, or area can have a separate pressure and separate feedback mechanisms. Here again the canister system that collects fluids along with an overflow device and a bacteriological overflow hydrophobic filter is present. The purpose here again is to create a sub-atmospheric pressure that will assist in healing as well as removal of fluids. 
     FIG. 3 of U.S. Provisional Application No. 60/430,827 again depicts the system in a simpler form. Here present is the thermal sensing layer that shows visually the temperature of the underlying wound. These temperatures of the cells, areas, or divisions, are transmitted to a microprocessor where the temperatures are interpreted and then feedback occurs to the individual cells, divisions, or areas, via the suction source. This suction is transmitted via tubing and with a canister and overflow/bacterial tilter in place to the individual cells. Present is an occlusive layer if needed and a matrix material such as gauze foam or other material that wound distribute the suction across the wound bed. 
     FIG. 4 of U.S. Provisional Application No. 60/430,827 again shows the system in a simpler form. This form shows some of the areas depicted as A1 through A8 where the suction would be distributed. Here in this figure the arterial blood supply is shown with areas that lack sufficient blood now. The thermal layer that is depicted would show visually and also transmit to the microprocessor the temperature parameters so that the suction source can feedback the distinct areas. 
     FIG. 5 of U.S. Provisional Application No. 60/430,827 shows another new area of the invention, Here the thermal sensing layer has areas that expand in the presence of atmospheric pressure. This expansion of the “Mountains” is also an idea that could be applied to other cover dressing that were occlusive or semi-occlusive without a thermal sensing layer. They make distinct “Mountains” when exposed to normal atmospheric pressure. These mountains could vary in shape from pyramidal, cylindrical, square to virtual any shape that has a three dimensional form. The purpose of these mountains is to alert the clinician that there may be a leak in the wound ben or a distinct area. The dressing may have only one of these “mountains” or they may have as many as there area areas. When the dressing is under pressure at a low level say 5 mmHg to 50 mmHg of sub atmospheric pressure these “mountains” contract into the dressing and are not evident. When a leak should occur in the dressing or other event that compromises the negative pressure the “mountains” would climb or expand and this would alert the clinician that the dressing needs to be check for integrity. 
     FIG. 6 of U.S. Provisional Application No. 60/430,827 shows the another embodiment of the suction source for each area. A suction source is present along with a filter, tubing for connections, and a canister for overflow and a solenoid device. The solenoid is operated by the microprocessor that allows the suction source to adjust the pressure in each of the cells. Upon receiving instructions from an area that has a temperature setting the microprocessor would adjust the solenoid and allow for the proper pressure in an individual area such as A1 or A2. This would continue in a random, sequential, or orderly manner. The programming could also be that any emergency such as loss of pressure would override the microprocessor and attempt to bring the pressure to a proper stage. If this does not occur alarms could ring notifying the clinician that the dressing needs to be changed. The system that is depicted also shows the separate and individual tubing that transmits the suction to the distinct area. These area individual tubes that may combine together into larger tubing bundle (each tube still being distinct). The tubing&#39;s in the end portion are redistributed throughout the wound bed. Each area that needs to be controlled with need a separate and distinct suction source. 
     The invention that is shown in the patent is designed to respond to an individual wound on a micro level. Insuring that adequate blood flow occurs into the wound by the use of this invention of a thermal sensing layer, an occlusive layer, a matrix material that distributes the suction and separate and distinct areas, cells or divisions will provide optimal wound healing. This invention is set apart from prior art by its applications in a number of areas. Notably the cells, divisions, or areas are unique and allow a more tailored solution to an individual wound. Additionally, the use of the “mountain” concepts allows us to see if there are any leaks in the system. 
     The system will have built in alarms that show low pressure, any type of malfunction, and the reading may be via LED or analog gauges. Too high a pressure, canister full readings. 
     Another subject of this patent application is an improved process for healing wounds using reduced pressure. The invention using a unique system of a matrix material to form a skeleton that cells in the healing process can adhere to and begin to form new tissue. This tissue then continues to build upon itself and enters into the matrix and finally engulfs and assumes the matrix. The matrix is made of unique elements that allow for it to biodegrade so that it would not have to be removed from the wound. 
     The invention consists first of a suction appliance that is designed to reduce the pressure in the surrounding space. This reduction in pressure is transmitted to the wound site via tubing. The tubing may have several lumens too that other materials such as antibiotics or liquids or gases that promote healing or retard infectious growth can be introduced. The tubing then enters the matrix and can do so by several connection points, as shown in FIG. 3 of U.S. Provisional Application No. 60/407,783. The suction then enters the matrix and is distributed through the matrix to the wound site. The matrix is covered by a semi-occlusive material or occlusive material. This material is sealed to the wound either by an adhesive that is attached to the material or by a separate adhesive substance. Over the materials there can exist measurement devices that can measure the suction pressure in the wound site. There can be several of these devices. They are linked via a feedback mechanism to the pump to allow for variations in the suction appliance based on readings in the wound. A suction canister collects excess wound fluid. 
     This system improves upon other methodologies of healing wounds. A wound can be defined as a change in the integrity of the skin which would allows fluid, gases, and other materials to pass through below topical levels into the body or allow bodily fluids to pass through the skin to the outside atmosphere. The human and other conditions need to have a barrier in place to prevent a variety of trauma to the tissues and organs. 
     The matrix is the key element of this system. It consists of unique materials that are bio-degradable in the wound and the matrix wound not have to be removed. Alternatively the matrix can be made of several types of materials with the layer that has boundaries with the wound being biodegradable and absorbable and the other layers not absorbable. These “top” layers can be removed if needed with the bottom layer staying in the wound. The concept of this patent application and the matrix is to form a skeleton upon which the wound healing process can build. The various cells can adhere to the matrix and then tissue can grow from these initial cells and engulf the matrix. The matrix being absorbed into the body does not need to be removed. FIG. 2 of U.S. Provisional Application No. 60/407,783 shows 3 stages of tissue engulfing matrix. Multiple stages can occur. 
     The matrix material can be of a foam or a gauze or a sponge with the intent of having the various cells of the body enter the matrix and then begin to build tissue. The matrix should be of a material that conforms easily to the body and fills the cavity of the wound. A deeper wound may require a larger matrix than a smaller one. The matrix material needs to have sufficient properties to attract human cells as well the ability overtime to be absorbed back into the body. That is the matrix itself would be destroyed by the tissue or process of building the tissue over time. 
     The matrix may also have sections or zones established with separate systems in operation. Pictured in FIG. 4B of U.S. Provisional Application No. 60/407,783 is a 4 section system, each being controlled by the suction appliance and with a complete separate system. 
     The matrix can be a regular or irregular shape. The matrix could have a uniform appearance such as a system of spheres that are interconnected in multiple locations that appear uniform and at regularly spaced intervals. The matrix can also be irregular with a variety of shapes and patterns. The diameter of the wholes can be irregular or uniform. The thickness of the material in the matrix can be irregular or uniform. 
     This is an improvement over previous designs that required that any type of packing materials be removed from the wound. Another feature of the system is the multilumen tubing. This multilumen tubing would allow for the ingress of a variety of materials that were hostile to infections or invading organisms and complimentary to the healing process or new cellular growth. See FIG. 4 of U.S. Provisional Application No. 60/407,783. Pictured here is a 4 lumen tube that allows suction or a pressure differential to enter the matrix. Also show is ozone (O3) chlorine, and water to enter the matrix. More lumens could be added. The feedback mechanism for the pressure motoring will also allow for the introduction of various hostile/complementary materials into the wound site. This secondary feedback mechanism will monitor the growth of tissue in the matrix and the state of the wound and via microprocessor or other methodology programmed into the pump will release materials accordingly. (FIG. 4A of U.S. Provisional Application No. 60/407,783) 
     One role of reduced pressure is to remove the fluids that accumulate in the healing process and to provide a pressure differential to encourage cells to move into the matrix. The fluids can contain materials that help with the healing process as well as those that have outlived their usefulness. The reduced pressure may have to moved from connection site to connection site as pictured in FIG. 3 of U.S. Provisional Application No. 60/407,783. The proximity of the suction source to the wound is a variable that will change during the wound healing process. During healing the suction source may be needed to move closer or father away from the wound. This process of changing the suction location can be automatic or manual. 
     The system incorporates a variety of sensors that will detect the actual pressure differential in the wound and outside the wound (FIG. 1 of U.S. Provisional Application No. 60/407,783). It will also measure the pressure differential between the suction appliance and the actual readings in the wound. The feedback system will allow the suction appliance to increase or decrease the suction differential based on instruction from the user of the device. The feedback system is attached to all the sensors and then relays information to and from the sensors to the suction appliance which contains microprocessors that interpret the information and then increase or decrease suction accordingly. 
     The suction system can also be designed so that is integrated into the occlusive dressing. (FIG. 5 of U.S. Provisional Application No. 60/407,783) This integration will allow for suction to be created on the wound site by a variety of methods. Some of these methods can include venture suction, use of the body&#39;s movement to generate suction, use of wind, light, photons, or a transmitted energy source to create suction. The system can also be more traditional of a suction pump that creates a pressure differential by diaphragm, rotary vane or piston action. Either traditional or new ways of generating suction can be integrated into the occlusive dressing or the pump can be attached to the dressing but be a separate piece. The pump in either case would not need tubing to connect to the dressing. The suction generated by these devices will be small in terms of liter capacity. The device will have a valve system to capture these small amounts of suction into larger usable amounts. There will be a regulation system that will prevent the accumulation of too high of a suction level. (FIG. 5 of U.S. Provisional Application No. 60/407,783). With this system there would be no need for tubing as the suction device is directly attached to the wound.