Wound treatment employing reduced pressure

IS 2 151 925 T5

DESCRIPTION

Wound treatment using reduced pressure.

Field of the invention

The present invention relates to an implement for administering a reduced pressure treatment to a wound. Background of the invention

Treating open wounds that are too large to spontaneously close has long been a problem area of ​​medical practice. Closure of an open wound requires inward migration of surrounding epithelial and subcutaneous tissue. Some wounds, however, are large enough or infected enough that they are unable to heal spontaneously. In such cases, a zone of stasis forms near the wound surface in which localized edema restricts blood flow to the epithelial and subcutaneous tissue. Without sufficient blood flow the wound is unable to fight bacterial infection and accordingly is unable to spontaneously close.

An initial phase of wound healing is characterized by the formation of granulation tissue that is a matrix of collagen, fibronectin, and hyaluronic acid that has macrophages, fibroblasts, and neovasculature that form the basis for subsequent epithelialization of the wound. Infection and poor vascularization prevent the formation of granulation tissue within the injured tissue, thereby inhibiting wound healing. Therefore, it is desirable to provide a technique for increasing blood circulation within injured tissue to spontaneously promote healing and to reduce infection.

Poor circulation and infection in the wound can also prevent the attachment of skin grafts or flaps on injured tissue. Skin grafts and flaps will not attach to tissue that is poorly vascularized, infected, or necrotic. However, grafts and flaps can be used with much more success on tissue that, although injured, is capable of forming granulation tissue. Accordingly, a technique to promote blood circulation would also promote the attachment, or "take", of grafts or flaps to the injured tissue as a consequence of increased blood circulation within the grafts or flaps.

Another problem encountered during the treatment of wounds is the selection of an appropriate technique for wound closure during the healing procedure. Sutures are often used to apply force to adjacent viable tissue to induce wound edges to migrate to each other and heal. However, sutures apply a closing force to only a small percentage of the area surrounding a wound. When there is scar, edema, or insufficient tissue, the tension produced by the sutures can be increased by causing excessive pressure to be exerted by the sutures on the tissue adjacent to each suture. As a result, the adjacent tissue often becomes ischemic, thereby making suturing of large wounds counterproductive. If the number or size of the sutures is increased to reduce the required tension of any single suture, the amount of foreign material within the wound is concomitantly increased and the wound is more prone to infection. Additionally, the size or type of a particular wound may preclude the use of sutures to promote wound closure. Therefore, it is desirable to provide an apparatus and method for closing a large wound, which distributes a closing force evenly around the periphery of the wound.

Wounds that result from ischemia, or lack of blood flow, are also often difficult to heal as decreased blood flow to a wound can suppress the normal immune response to fight infection. Patients who are bedridden or otherwise non-ambulatory are susceptible to ischemic injuries such as pressure sores or pressure sores. Pressure ulcers form as a result of constant compression of the skin's surface and underlying tissue, thus restricting circulation. Since the patient is often unable to feel the wound or move sufficiently to relieve pressure, such wounds can become self-perpetuating. Although it is common to treat such wounds with flaps, the conditions that initially caused the injury may also work against successful flap attachment. Wheelchair paraplegics, for example, must remain seated after treatment for pelvic pressure sores. Therefore, it is desirable to provide an ischemic wound treatment procedure that can be performed in situ on an immobile or partially immobile 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 cell death due to thermal trauma does not extend beyond the deeper epidermal structures such as hair follicles, sweat glands, or sebaceous glands. The progression from partial thickness burns to deeper burns is a major problem in burn therapy. The ability to control or decrease the depth of burns greatly improves the prognosis for burn patients and decreases morbidity resulting from burns. Partial-thickness burns consist of a coagulation zone, which includes tissue dead from thermal injury, and a stasis zone. The zone of stasis is a layer of tissue immediately below the clotting zone. Cells within the stasis zone are viable, but blood flow is static due to collapse of vascular structures due to localized edema. Unless blood flow is restored within the stasis zone shortly after injury, the tissue within the stasis zone also dies. The death of the tissue within

ES 2 151 925 T5 of the stasis zone is caused by lack of oxygen and nutrients, reperfusion injury (restoration of blood flow after prolonged ischemia), and decreased migration of white blood cells to the zone resulting in proliferation bacterial. Again, it is desirable to provide a technique for treating burn wounds by improving blood circulation to injured tissue to inhibit penetration of the burn.

WO-A-9309727 is part of the prior art according to Article 54 (3) EPC and describes an implement for administering pressure treatment to a wound. However, it does not disclose a utensil having rigid support means associated with and separated from a sheet-like covering.

US-A-3874387 discloses a valved hemostatic pressure cap in the form of an implement that delivers reduced pressure treatment to a wound. However, a similar covering does not describe a sheet or rigid support means that are associated with and separated from the covering.

US-A-2 280 915 describes a wound treatment utensil using suction according to the preamble of claim 1.

Summary of the invention

The present invention seeks to provide a wound treatment implement for treating a wound by applying reduced pressure (ie, a pressure that is below ambient atmospheric pressure) to the wound in a controlled manner for a selected period of time. Applying reduced pressure to a wound provides benefits such as faster healing, increased granulation tissue formation, closure of chronic open wounds, reduction of bacterial density within wounds, inhibition of burn penetration , and the improvement of the union of flaps and grafts. Wounds that have exhibited a positive response to treatment by applying negative pressure include infected open wounds, pressure ulcers, dehiscences, partial thickness burns, and various injuries to which flaps or grafts have been attached.

In accordance with the present invention there is provided an implement in accordance with subsequent claim 1 for administering a reduced pressure treatment to a wound. The sealing means may be in the form of an adhesive applied to the underside of the wound cover to seal 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 sealing ring in the form of a tubular patch or an inflatable sleeve secured to the wound covering to be positioned around the periphery of the wound. At selected times, the reduced pressure within the sealed shell under the wound cover can serve to seal the wound cover in place at the wound site. The reduced pressure implement also includes a suction port to deliver reduced pressure within the sealed volume enclosed under the wound covering. The suction hole can also be in the form of a nozzle on the wound covering. Alternatively, the suction port may also be in the form of a tube attached to the wound cover or provided as a through feed under the wound cover. The implement may also include a porous wound screen for placement in the wound or in a position superimposed on the wound to prevent overgrowth of wound tissue during treatment. The wound screen is sufficiently porous to allow gas flow into the wound. The porous wound screen may be in the form of a sponge or open cell foam material for staining into the wound. The porous screen can also include a rigid or semi-rigid screen to overlap the wound.

A vacuum system connects to the reduced pressure utensil to provide suction or reduced pressure to the utensil. For this purpose, the vacuum system includes a suction pump or a suction device for connection to the suction port of the implement to produce the reduced pressure on the wound site. The vacuum system may include a hose or tube section, such as a vacuum hose, that interconnects the suction device with the suction port of the device to provide the reduced pressure at the wound site. A collection device in the form of a fluid separator may be provided intermediate the vacuum hose of the suction device and the suction port to separate any exudate that may be drawn from the wound by the negative pressure implement. A stop mechanism may also be provided for the vacuum system to interrupt the production of the reduced pressure at the wound site in the event that an excessive amount of exudate has been collected. The apparatus may also include a control device to control the pump and to provide intermittent or cyclical production of reduced pressure.

In a particular embodiment of the invention, the wound cover for the reduced pressure implement may be in the form of a gas-tight cover sheet of flexible polymer material, such as polyethylene, which has an adhesive backing that provides the gasket to secure the sheet over the wound site to provide a gas tight or fluid tight sealed envelope over the wound site. The vacuum system of the wound treatment apparatus may include a suction pump having a vacuum hose that is connected to a suction tube that serves as a suction port for the implement. The suction tube for the utensil passes under the cover sheet which is sealed in position over the wound site and into the fluid tight envelope provided under the cover sheet. An adhesive backing is used on the cover sheet to provide a fluid tight seal around the feed-through for the suction tube at the wound site. Inside the envelope,

ES 2 151 925 T5 the suction tube is connected to a piece of open-celled foam to place in the wound. The open cell foam functions to more evenly apply reduced pressure or suction over the wound site while keeping the cover sheet substantially out of the wound during the application of reduced pressure at the wrapped wound site.

An implement according to the invention can be used to treat tissue damage by applying negative or reduced pressure to a wound over an area sufficient to promote migration of epithelial and subcutaneous tissue into the wound and for a period of time sufficient to facilitate wound closure. This is useful for treating pressure sores.

An implement according to the invention can also be used to treat a burn wound by applying negative or reduced pressure to the burn over an area and for a time sufficient to inhibit progression in the depth of the burn. This use is useful on a partial thickness burn shortly after it occurs.

An implement according to the invention can be used to treat tissue damage by applying negative or reduced pressure to a wound for a time sufficient to reduce the bacterial density in the wound. The implement can be applied to a wound for a selected period of time, such as at least three days, to reduce the bacterial density of an infected wound to the point where surgical closure can be attempted.

An implement according to the invention can be used to improve the attachment of adjacent tissue to a wound by applying negative or reduced pressure to a bound complex of the adjacent living tissue and the wound at a sufficient amount of reduced pressure and in a sufficient duration of time to promote the migration of epithelial and subcutaneous tissue into the complex. This improves the attachment of adjacent tissue to tissues at the edges of the wound. Another use of the tool is to improve the attachment of an open skin graft to the wound tissue.

Brief description of the drawings

The preceding summary, as well as the following detailed description of the preferred embodiments of the invention, will be better understood when read in conjunction with the accompanying drawings, in which:

Figures 1-3 and 10-11 are not within the definition of claim 1, but are used to clarify the invention;

Figure 1 is an elevational view of an exemplary implement for administering a reduced pressure treatment to a wound, including the implement, shown in partial section, a flexible, fluid impervious wound cover, sealed over the wound, and a foam wound screen positioned in the wound, and wherein a vacuum system provides reduced pressure within the wound covering of the utensil;

Figure 2 is a schematic sectional elevation view of a second exemplary reduced pressure implement having a rigid, fluid impervious wound cover sealed over a wound and a rigid or semi-rigid screen that overlaps to the wound;

Figure 3 is a schematic sectional elevation view of a third reduced pressure implement having a rigid fluid impervious wound cover sealed over a wound;

Figure 4 is a schematic sectional elevation view of a reduced pressure implement in accordance with the present invention, having a semi-rigid fluid impervious covering that surrounds a wound and a rigid or semi-rigid screen that overlaps the wound, with a superimposed, flexible, fluid impervious cover sheet, which seals the wrap over the wound.

Figure 5 is a schematic elevational view of a reduced pressure implement, shown in partial section, in accordance with another embodiment of the present invention, having a flexible, fluid-impermeable wound covering over a glass cup. support, porous, rigid, internal;

Figure 6 is a schematic elevational view of a reduced pressure implement, shown in partial section, having a rigid outer frame with support legs to support a flexible, fluid impervious sealing cover over a wound;

Figure 7 is a partial sectional schematic elevation view of an alternative fluid collection implement having a float valve for use in the vacuum system of Figure 1;

Figure 8 is a schematic view of an alternative vacuum system;

Figure 9 is a schematic view of an alternative vacuum system incorporating a fluid collection implement having an actuator to deactivate the vacuum system by collecting a predetermined amount of fluid;

Figure 10 is a schematic cross-sectional view of a reduced or negative pressure utensil comprising an open cell polymer foam screen, a flexible hose for connecting the screen of

ES 2 151 925 T5 foam with a vacuum system and a flexible polymer backing sheet that overlaps the foam-hose assembly to provide a seal over a wound; and Figure 11 is a schematic cross-sectional view of a reduced or negative pressure implement comprising a rigid porous screen for a wound, a rigid or semi-rigid cup for covering the wound, having an inflatable sleeve attached around the cup, and a flexible hose extending from the cup for connection to a vacuum system.

Detailed description of the preferred modalities

A wound treatment apparatus is provided for treating a wound by applying reduced pressure (i.e., below atmospheric) so that suction can be applied to a wound site in a controlled manner over a period of time. selected. As shown schematically in Figure 10, a wound treatment apparatus includes a reduced pressure implement, generally referred to as 600, which is applied to a wound site to treat the wound through the application of reduced pressure. The implement 600 is sealed in position over the wound site to create a generally fluid tight or gas tight envelope over the wound site.

The implement 600 includes a substantially flat section 610 section of open cell polyester foam (Fisher Scientific, Pittsburg, PA 15219) large enough to cover the wound and thus prevent wound overgrowth, a flexible hollow 610 tube (Fisher Scientific) inserted into the 610 section of open cell foam and bonded thereto with an adhesive and extended to be attached at its opposite end with a Gast Vacuum pump (Fisher Scientific) and a 612 sheet of Ioban adhesive (Minnesota Mining and Manufacturing, St. Paul, MN 55144) that overlaps the foam section 610 and tube 611 and adheres to the skin surrounding the wound, thus forming a gasket that allows a vacuum to be created when the suction pump operates. Such utensil 600 will most preferably be packaged in a sterile condition to mitigate the need for sterilization of the apparatus prior to use. The adhesive sheet 612 can be packaged separately from the foam-tube assembly 610 and 611. A particular advantage of this configuration is its use with pressure sores because the device can be placed deep within the wound and the patient can lie on the device without affecting the usefulness of the device or further damaging the wound. This becomes critical if the patient is unable to move from his posture for medical or other reasons.

As shown in Figure 11, a reduced pressure implement, generally designated 615, is schematically depicted. The reduced pressure implement 615 includes an adult CPR 620 shield (Doug Brown and Associates, Huntington Beach, CA 92648) comprising a rigid or semi-rigid fluid impervious cup 621 having an inflatable sleeve 622 mounted around the periphery of the base of the cup 622 to come into contact with the skin, an open-cell polyester sieve 624 that is superimposed on the wound, and a 6.35 cm (1/4-inch) diameter flexible 623 hose (Fisher Scientific) connected by a Nalgene tubing connector that extends through a sealed hole in the cup for connection to a vacuum pump (Fisher Scientific). Hose 623 is connected to pump 40 of a vacuum system 30 of the type shown in Figure 1 to provide reduced pressure within cup 621. The vacuum created within the cup 621 by the vacuum system may be sufficient to seal the cup in position over the wound site. Alternatively, fluid impervious adhesive strips or coverings may also be used to seal utensil 615 in proper position.

Referring to Figure 1, there is depicted a wound treatment apparatus, designated 25, having a reduced pressure implement 29 for wrapping a wound site to provide a fluid tight or gas tight envelope over the wound. site of a wound to effect treatment of a wound 24 with reduced or negative pressure. Wound treatment apparatus 25 includes a reduced pressure implement, generally designated 29, which is applied to and sealed over a wound site to wrap the wound site for treatment with suction or reduced pressure within a wrap. sealed generally fluid-tight or gas-tight. For the purpose of creating suction within implement 29, device 29 is connected to a vacuum system, generally referred to as 30, to provide a source of suction or reduced pressure for sealed implement 29 at the wound site. Device 29 includes a fluid impermeable wound covering 18 in the form of a flexible, adhesive, fluid impermeable polymer sheet to cover and envelop wound 24 and surrounding normal skin 22 at the wound site. The wound cover 18 includes an adhesive backing which functions to seal the wound cover to normal skin 22 around the periphery of the wound 24 to provide a generally fluid tight or gas tight wrap over the wound 24 . The adhesive cover sheet 18 must have sufficient adhesion to form a fluid-tight or gas-tight seal 19 around the periphery of the wound and to keep the sheet 18 in sealed contact with the skin during the application of suction or pressure. reduced or negative.

The implement 29 also includes a porous wound screen 10 that is positioned within the wound 24. The wound screen 10 is positioned substantially over the extension of the wound to prevent overgrowth. The size and configuration of the wound screen 10 can be adjusted to suit the individual wound. It can be formed from a variety of porous materials. The material must be porous enough to allow oxygen to reach the wound. The wound screen 610 may be in the form of an open cell polymer foam, such as a polyurethane foam, that is sufficiently porous to allow gas flow to and / or from the wound 24. Foams that vary in thickness and stiffness, although it may be desirable to use a sponge material

ES 2 151 925 T5 for the comfort of the patient if the patient must be lying on the utensil during the treatment. The foam can also be perforated to improve gas flow and to reduce the weight of the utensil. As shown in Figure 1, the screen 10 is cut to an appropriate shape and size to fit within the wound 24. Alternatively, the screen may be large enough to overlap the skin 22 surrounding the wound.

The implement 29 also includes a suction port in the form of a hollow suction tube 12 that is connected to the vacuum system 30 to provide suction within the sealed shell. Suction tube 12 serves as a suction port for implement 29. An end segment 12a of tube 12 is embedded within foam screen 10 to provide suction or reduced pressure within the envelope provided under wound covering 10. Embedding the open end of the tube 12 segment 12a within the foam screen 10 allows the foam screen 10 to function as a protector to help prevent the wound cover 18 from being accidentally sucked into a sealing engagement with the open end of the tube thus sealing tube 12 and restricting gas flow. Tube segment 12a embedded within foam screen 10 preferably has at least one side hole 14 for placement within foam screen 10 to promote substantially uniform application of reduced pressure throughout the shell. Placing the side hole 14 of tube segment 12a within the foam screen 10 allows the foam screen 10 to function as a protector for the side hole to thereby prevent the wound covering 18 from being sucked into the hole. 14 laterally and thereby restrict the gas flow. The open cells of the foam screen 10 facilitate gas flow throughout the shell. In addition, the foam screen 10 functions to prevent wound overgrowth and to keep the wound cover 18 away from contact with the wound 24 during the application of suction within the envelope.

Tube 12 and tube segment 12a are flexible enough to allow tube movement but rigid enough to resist constriction when reduced pressure is supplied to implement 29 or when the position of the wound is such that the patient must sit or lie down. on tube 12 or on reduced pressure utensil 29. The screen-tube assembly comprising foam screen 10 and tube 12 can be manufactured by sliding the end of tube segment 12a through an internal passageway of foam screen 10 such as by dragging the end of tube segment 12a through of the passage using tweezers. Alternatively, the fabrication of the screen-tube assembly may be accomplished by suspending the end of tube segment 12a in a suitable mold or die and then causing the foam to expand in the mold or die to embed tube end segment 12a within the expansion molded foam screen. The sieve-tube assembly 12 and 10 is preferably prepared prior to use under sterile conditions and then stored in an aseptic package.

To use the reduced pressure implement 29 at the wound site 24, the flexible, adhesive, gas-impermeable wound cover sheet 18 is secured in place at the wound site by overlapping the foam screen 10. disposed within the wound 24. The wound cover sheet 18 is secured and sealed to the surrounding normal skin 22 by an adhesive layer 20 on the lower surface of the wound cover 18 to form a gas-tight seal 19 around the periphery of the wound cover. wound 24. Wound cover 18 also provides a gas tight seal around tube 12 at position 22a of the feed-through where tube 12 emerges from below wound cover 18. The wound cover 18 is preferably formed of a flexible fluid impermeable or gas impermeable adhesive sheet such as Ioban, a product of the 3M corporation of Minneapolis, Minn.

The vacuum system 30 includes a suction pump 40 that produces a source of reduced pressure or suction that is supplied to the reduced pressure implement 29 through the suction tube 12. As shown in Figure 1, a fluid separator, generally designated 28, is interconnected between the suction pump 40 and the implement 29 to remove and collect any exudate that may be drawn from the wound 24 by the reduced pressure implement. The implement 29 functions to actively draw fluid or exudate from the wound 24. Collection of the exudate in an intermediate fluid separator 28 between the pump 40 and the implement 29 is desirable to prevent plugging of the pump 40. A fluid separator 28 A suitable one may be mounted from a 31 Erlenmeyer or side arm flask having a top opening and a side arm opening. Fluid separator 18 includes a first hole 32 in the top opening of the flask for sealed connection to suction tube 12. The first hole 32 allows suction to be applied to the reduced pressure implement 29 through the tube 12 and also allows wound exudate covered by the reduced pressure implement to be drawn into the flask 31. The flask 31 provides a collection container 33 for the fluid separator to temporarily contain and store the collected exudate. A suction port 34 is provided in the side arm opening of the flask to allow application of suction from the vacuum pump. Suction port 34 of fluid separator 28 is connected to vacuum pump 40 via vacuum conduit 36. Fluid separator 28 is sealed generally gastight to allow suction pump 40 to supply suction to utensil 29 through fluid separator 28. A filter 38, such as a microporous filter, is preferably attached to the outlet of the pump 40 to prevent potentially pathogenic microbes or aerosols from being brought into communication with the atmosphere by the vacuum pump 40.

Predetermined amounts of suction or reduced pressure are produced by the vacuum pump 40. The vacuum pump 40 is preferably controlled by a control device 44 such as a switch or timer that can be set to provide cyclical on / off operation of the vacuum pump in accordance with user-selected intervals. Alternatively, the vacuum pump 40 can be operated continuously without the use of a cyclic timer.

IS 2 151 925 T5

Vacuum system 30 preferably includes a shutoff mechanism to interrupt or inhibit the supply of reduced pressure to implement 29 in the event that exudate aspirated from wound 24 exceeds a predetermined amount. It is desirable to discontinue the application of suction to implement 29 to avoid exsanguination in the unlikely event that a blood vessel ruptures under wound covering 18 during treatment. If, for example, a blood vessel is ruptured in the vicinity of the wound 24, a disconnect mechanism would be useful to prevent the vacuum system 30 from sucking up any significant amount of blood from the patient. As a safety feature, various mechanisms may be employed. mechanical or electrical detection devices to detect the level of exudate in fluid separator 28.

As shown in Figure 7, a fluid separator 28 is provided employing a collection bottle or flask 35 for the intermediate connection between pump 40 and implement 29 to collect exudate from the wound site. The flask 35 has a side arm hole 43 connected to the suction tube 12 that leads to the reduced pressure utensil 29 and to a suction hole 34 located at the top 44 of the flask 35 connected to the vacuum hose 36 that leads to the vacuum pump 40. For the purpose of sensing the level of liquid within flask 35, a float valve assembly, generally referred to as 39, is provided. The float valve assembly 39 functions to close and seal the suction port 34 of the fluid separator 28 when the amount of exudate in the collection container 33 exceeds a certain amount. The float valve assembly 39 is provided in the form of a ball 46 that is held and suspended within a cage 47 located below a valve seat 48 disposed within the opening in the top 44 of the flask 35. Ball 46 has a specific gravity below that of exudate so ball 46 will float on exudate and rise against valve seat 48 as container 33 fills with exudate. When the ball 46 is firmly seated against the valve seat 48, the float valve 39 blocks the suction port 34 and thereby disconnects the suction source from the vacuum conduit 36. The suction within the implement 29 at the wound site is cut off thereby interrupting the aspiration of exudate from the wound.

Other types of mechanisms may be employed to sense the level of liquid within the fluid separator 28 to shut down the operation of the vacuum source. An alternative vacuum system 30a is shown in Figure 8 in which a filter 38a is employed in the vacuum conduit 36 ​​to filter the flow of fluid or gas through the vacuum conduit 36 ​​and to detect the level of liquid in the fluid separator 28. The exudate from the wound is collected in container 33. When the container 33 fills, the aspiration of more exudate from the wound causes the vacuum line 36 to begin to collect exudate that finally reaches the in-line filter 38a located in the intermediate vacuum conduit 36 ​​between the fluid separator 28 and the pump 40 a having control 44 a of the operation. Filter 38a contains a filter element that is selected to plug when exposed to sufficient amounts of moisture to thereby interrupt the supply of suction through fluid separator 28 to utensil 29. Filter 38a is preferably a submicron filter with in-line, disk-shaping having a PTFE filter element to filter particles greater than about 0.1 µm from the vacuum conduit 36. In addition to preventing suction of excess fluid, filter 38a in vacuum conduit 36 ​​prevents contamination of vacuum pump 40 by filtering potentially pathogenic microbes and aerosols.

Other types of detection devices may also be employed to detect a predetermined level of liquid collected in the collection container 33. For example, collecting exudate above a predetermined amount may allow actuation of an electronic switch that turns off the vacuum pump or otherwise interrupts the supply of suction to the reduced pressure implement 29. Referring to Figure 9, the suction tube 12 from the reduced pressure implement 29 is connected to a three-port coupling device 160 that interconnects the suction tube 12, the vacuum conduit 36b and the collection apparatus 131. fluid. Coupling device 160 allows transmission of suction from vacuum conduit 36b of pump 40b to the suction tube. Coupling device 160 also allows exudate aspirated from tube 12 to be collected in an expandable reservoir, such as a bag 162 for intravenous fluid, housed below coupling device 160 in a rigid housing container 33b. As exudate is collected, bag 162 expands to conform to the shape of the interior surface of surrounding rigid housing container 33b. An actuator 166, such as a spring actuator switch, is located within the side wall of rigid container 33b and operates to disconnect pump 40b when switch 166 is actuated. When bag 162 expands sufficiently to contact and actuate switch 166, as shown by dotted lines at 162a in Figure 9, switch 166 opens and power supply to pump 40b is interrupted along from conduit 164 and the supply of suction to implement 29 is stopped. Actuator switch 166 may also cooperate with control 44b for pump 40b to stop operation of pump 40b. Other types of device may also be employed to detect fluid levels in fluid separator 28. For example, weight detectors can be used to detect a predetermined weight limit as the fluid separator fills with exudate or other liquid. Alternatively, optical sensors or detectors can also be used.

For the purpose of protecting the wound site from impact or abrasion during treatment, a reduced pressure implement employing a rigid or semi-rigid wound cover may be used over the wound site. As shown in FIG. 2, a reduced pressure implement 29a includes a CPR shield 58 that provides a rigid wound cover for enveloping an appropriately sized wound 74. Shield 59 is fluid or gas impermeable so that a fluid tight or gas tight wrap is effected over the wound site. Shield 59 is rigid enough to support itself away from the wound during application of suction or reduced pressure so that shield 59 does not collapse in wound 74. CPR shield 58 is of the type that has an inflatable air sleeve 59 around it. from the base of the shield. Sleeve 59 can be inflated

ES 2 151 925 T5 through an external valve to seal the shield 59 against normal skin 72 around the periphery of the wound 74. The air sleeve 59 also prevents the base of the shield from entering the skin 72 during application reduced pressure. An optional screen 50 to prevent wound overgrowth 72 can be positioned to overlap wound 74. Screen 50 may be formed of a rigid or semi-rigid perforated polymer surgical mesh such as Prolene mesh. Alternatively, a section of honeycomb polyethylene sheet may be cut to a size and shape suitable to overlap wound 74. Screen 50 is held against surrounding normal skin 72 in position by overlapping wound 74 by sleeve 59 which overlaps at least a portion of the periphery of the screen 50. The CPR shield 58 also includes a suction port in the form of a hose connector 54 to which one end of a suction tube 52 is attached. The other end of tube 52 is connected to a vacuum system 30 of the type previously described to provide a source of suction or reduced pressure for implement 29a. The suction produced within implement 29a may be sufficient to seal hose 59 to the skin and thereby seal implement 29a in position over the wound site. However, to ensure a gas tight seal between the reduced pressure implement 29a and the surrounding skin 72, the shield 58 may also be secured to the treatment site with a fluid impermeable adhesive seal 68. Adhesive gasket 68 may be formed of a flexible adhesive material such as adhesive tape or adhesive sheet that has been cut to surround and at least partially overlap sleeve 59. As shown in Figure 2, the adhesive gasket is secured to the base portion of the rigid shield 58 and to normal skin 72 around the periphery of the air sleeve 59 to seal the shield in position over the wound site.

As shown in FIG. 3, a reduced pressure implement 29b is depicted having a rigid, fluid impervious, cup-shaped cover 88 that overlaps a wound site. The implement 29b is used to treat a wound 114 without any screen on the wound or superimposed on the wound. Cover cup 88 may be formed of a polymer such as polystyrene, HDPE, or other suitably rigid material. Cup 88 must be rigid enough to bear out of contact with wound 114 during application of suction or negative pressure so that cup 88 does not collapse within the wound. Reduced pressure is supplied to the interior of cup 88 through suction tube 82 connected to suction port 84 in the form of a nozzle sealed in position on cup 88. Tube 82 is also connected to a suitable vacuum system 30 of the type previously described to provide a source of suction or negative pressure within implement 29b. The base of the cup 88 supports an inflatable air sleeve 89 to seal the cup 88 to the skin and to prevent the cup 88 from penetrating the skin 92 and causing discomfort when reduced pressure is applied. Sleeve 89 is located on normal skin 92 surrounding wound 94. Although the suction created within the cup 88 may be sufficient to hold the utensil in position by causing the air sleeve to seal to the skin, a more effective attachment of the device to the surrounding skin 92 can be obtained through the use of a strip of fluid impervious adhesive material secured to skin 102 and cup base 88 on air sleeve 89 around the periphery of cup base 88. The layer of adhesive material 98 helps to ensure that a fluid-tight or gas-tight seal is maintained between the cup 88 and the surrounding skin 92 so that a fluid-tight envelope is formed over the wound site.

Referring to FIG. 4, there is depicted a reduced pressure device 29c in accordance with the present invention for wrapping a wound site for wound treatment 114 with suction or reduced pressure. The reduced pressure device 29c includes a fluid impervious wound cover having an external flexible adhesive polymer sheet 117 applied over an internal, generally circular, semi-rigid protector 118, such as a polystyrene protector. to cover and wrap the wound site. The base of the protector 118 is located on a circular plug 109 which may be formed by a flexible tube to prevent the base of the cup from penetrating the skin 102 and causing discomfort when suction is applied to the utensil 29c. The dowel 109 may also facilitate sealing of the cover protector 118 in position over the wound site to form a fluid-tight or gas-tight envelope over the wound site. The plug 109 can be placed directly on the normal skin 102 surrounding the wound 114 or, as shown in Figure 4, the plug 109 can be superimposed on an outer peripheral portion of a rigid screen 100 to maintain the screen 100 in a position that overlaps the wound to prevent wound overgrowth. A suction port 104 is provided in the top of shield 118 to allow gas tight connection with suction tube 112. Suction port 104 may be in the form of a removable connector that screws into place on top of shield 118. Suction tube 112 functions to connect implement 29c to a suitable vacuum system 30 of the type previously described. In order to improve the sealing of the implement 29c in position over the wound site, an oversized, adhesive, fluid-impermeable, fluid-impermeable polymer sheet 117 is adhered and secured to the upper surface of protector 118. The oversized adhesive sheet 117 extends beyond the outer periphery of the shield 118 so that the adhesive sheet 117 provides a material sealing ring 119 around the periphery of the shield. The sealing ring 119 seals and adheres to the normal skin 102 around the outer periphery of the stud 109. When sealed in position to overlap wound 114, implement 29c provides a generally fluid tight or gas tight wrap over the wound site.

Referring to FIG. 5, another reduced pressure implement 29d is shown in accordance with the present invention, for wrapping and treating a wound 124 with suction or reduced pressure. A rigid or semi-rigid porous cup 138 is placed edge down over a porous screen or plug 120 located within a wound 124. Cup 138 has perforations 133 to equalize pressure inside and outside of cup 138. A flexible, fluid-impervious, adhesive, polymeric cover sheet 128 is extended over cup 138 to wrap wound 124. The sheet

IS 2 151 925 T5

128 The adhesive cover sheet adheres and is sealed to the upper portion of the cup 138 and the surrounding normal skin 122 by the adhesive layer 129 on the underside of the cover sheet 128 to provide a fluid-tight envelope under the sheet 128. Cup 138 provides generally central support under cover sheet 128 to keep cover sheet 128 away from contact with wound 124 during application of suction. Cup 138 has a central suction hole 134 sealed in position in the top of cup 128 to allow connection via suction tube 132 to a vacuum system 130 of the type previously described. When reduced pressure is applied to utensil 29d, cover sheet 128 deforms downward and inward to position 128a as shown in transparency in Figure 5. The stress developed within the deformed sheet 128a by virtue of suction is exerted on the surrounding skin by the sheet at position 128a. The outer periphery 124a of wound 124 is drawn inward by virtue of such tension to the position shown in transparency at 124b to promote wound closure. The tension within the sheet at position 128a also exerts a downward force on cup 138 which presses cup 138 more firmly onto wound 124. Such downward force on cup 138 may be desired in applications such as flap or graft attachment. to promote contact between the flap or graft and the underlying tissue. The cleat 124 under the cup 138 helps to alleviate the discomfort caused by the downward force on the cup 138.

For applications where downward pressure of the utensil within a wound is not desired, a reduced pressure utensil 29e, as shown in Figure 6, may be used having a support structure, generally designated 151, that is located externally. to a flexible sealing sheet 148 to cover a wound 144. The flexible covering sheet 148 is in the form of a flexible, fluid-impermeable, adhesive polymer sheet. The reduced pressure implement 29e shown in Figure 6 includes an external support frame 151 in the form of a series of spider-like legs 158 extending outwardly from a central support hub 155. Legs 158 hold central hub 155 directly over wound 144. A connector 153 is removably mounted to hub 155 to allow a suction tube 152 to connect to flexible cover sheet 148. Connector 153 can be screwed and unscrewed to allow the connector to be removably mounted relative to hub 155. Flexible adhesive sheet 148 adheres to connector 153 on hub 155 and the surrounding normal skin 142 so that the sheet is suspended onto wound 144 from the bucket in a tent-like fashion. The adhesive sheet is adhesively sealed to connector 153 on hub 155 and is also adhesively sealed to skin 142 around the periphery of wound 144 to form a fluid-tight and gas-tight envelope over the wound site. Legs 158 of weft 153 extend radially outward from hub 155 and are supported on foot members 159 that can rest on the outer periphery of sheet 148 to help hold cover sheet 148 in position to be sucked. during the application of suction. Alternatively, foot members 159 may extend beyond cover sheet 148. Connector 153 supported on hub 155 provides a suction port 154 through which suction is supplied to implement 29e through suction tube 152. Tube 152 is connected to a vacuum system 30 of the type previously described to supply reduced pressure within cover sheet 148. When suction or reduced pressure is introduced through orifice 154, sheet 148 deforms inwardly and downwardly to the position shown in transparency at 148a thereby developing stress that is exerted on surrounding skin 142. The deformed sheet at position 148a drags the edges of wound 144 inward to the position indicated in transparency at 144b thereby promoting closure of wound 144.

Negative pressure utensils are useful for treating a variety of wounds. Treatment of a wound can be accomplished by securing a negative pressure implement to the treatment site as shown and described previously, and then maintaining a reduced and substantially continuous or cyclical pressure within the implement until the wound has reached a desired improved condition. . A selected state of improved condition may include formation of sufficient granulation tissue for attachment of a flap or graft, reduction of microbial infection in the wound, detection or reversal of penetration of a burn, closure of the wound, the integration of a flap or graft into the underlying injured tissue, the 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 utensil periodically, such as at 48 hour intervals, during treatment, particularly when using utensils incorporating a sieve on or in the wound. The method is preferably practiced using a negative or reduced pressure ranging from 1.01 to 100.31 kPa (0.01 to 0.99 atmospheres) and more preferably is practiced using a negative or reduced pressure that varies between 50.66 and 81.06 kPa (0.5 to 0.8 atmospheres). The period of time for the use of the method on a wound may preferably be at least 12 hours, but, for example, it may extend for one or more days. There is no upper limit beyond which the use of the method is no longer beneficial; the method increases the speed of closure until the time when the wound actually closes. Successful treatment of various types of wounds has been obtained through the use of reduced pressures equivalent to about 6.77 to 23.70 kPa (2 to 7 inches Hg) below atmospheric pressure.

It has also been shown to be useful in treating wounds to supply reduced pressure to the implement in an intermittent or cyclical manner. Intermittent or cyclical delivery of reduced pressure to a utensil can be achieved by manual or automatic control of the vacuum system. A cyclic ratio, the ratio of "on" time to "off" time, in such intermittent reduced pressure treatment can be as low as 1:10 or as high as 10: 1. The preferred ratio is about 1: 1, which is usually done at alternating 5 minute intervals of reduced pressure delivery and no delivery.

A suitable vacuum system includes any suction pump capable of delivering at least 45.3 g (0.1

ES 2 151 925 T5 pounds) of suction to the wound, and preferably up to three pounds of suction, and most preferably up to fourteen (14) pounds of suction. The pump can be any normal suction pump suitable for medical purposes that is capable of providing the necessary suction. The size of the tube that interconnects the pump and the reduced pressure implement is controlled by the ability of the pump to provide the level of suction necessary for operation. A 6.35 cm (1/4 inch) diameter tube may be suitable.

A method of treating damaged tissue comprises the steps of applying negative pressure to a wound for a selected time and to a selected amount sufficient to reduce the bacterial density in the wound. Open wounds are almost always contaminated with harmful bacteria. Generally, a bacterial density of 10⁵ Bacterial organisms per gram of tissue is considered infected. It is generally accepted that at this level of infection, the grafted tissue will not adhere to a wound. These bacteria must be destroyed, through the wound sufferer's natural immune response or through some external method, before a wound is closed. Applying negative pressure to a wound appears to reduce the bacterial density of the wound. This effect is believed to be due to bacterial incompatibility with a negative pressure environment or increased blood flow to the wound area, as the blood carries cells and enzymes with it to destroy bacteria. The method can be used to reduce the bacterial density in a wound by at least half. More preferably, it can be used to reduce bacterial density by at least 1,000 times. Most preferably, the method can be used to reduce bacterial density by at least 1,000,000 times.

One method of treating a burn comprises the steps of applying a negative pressure to the burn over an area with a predetermined reduced pressure and for a time sufficient to inhibit the formation of a full thickness burn. A partial-thickness burn, one that has a superficial layer of dead tissue and a zone of stasis, is often sufficiently infected to transform within 24-48 hours into a full-thickness burn, one in which all epidermal structures they are destroyed. The application of negative pressure to the wound prevents the infection from becoming severe enough to cause destruction of the underlying epidermal structures. The magnitude, pattern, and duration of pressure application may vary with the individual wound.

One method of improving the attachment of living tissue to a wound comprises the steps of first binding the living tissue to the wound to form a wound-tissue complex, then applying a negative or reduced pressure of selected magnitude to the wound complex. -tissue over an area sufficient to promote the migration of epithelial and subcutaneous tissue into the complex, the negative pressure being maintained for a selected period of time sufficient to facilitate wound closure. Attaching living tissue to a wound is a common procedure that can take many forms. For example, a common technique is the use of a "flap," a technique in which skin tissue from an area adjacent to the wound is separated on three sides but remains attached on the fourth, and is then moved over the wound. Another frequently used technique is an open skin graft in which the skin is completely separated from another skin surface that is grafted onto the wound. The application of negative pressure to the wound-graft complex reduces the bacterial density in the complex and improves blood flow to the wound, thereby improving the attachment of the grafted tissue. Additional characteristics of the apparatus and methods for using the same may become apparent from the following examples.

Example 1

Treatment of open wounds

To demonstrate the use of a negative pressure implement in the treatment of open wounds, an animal study was conducted using pigs as subjects. Pigs are frequently used as subjects in wound healing studies as they have essentially the same skin and subcutaneous tissue structure as humans.

Five 15 kg Chester pigs were obtained and acclimatized for one week before use. The animals were sedated by an intramuscular injection of ketamine (25 mg / kg): xylazine (2.5 mg / kg): acepromazine (5 mg / kg). The backs and sides of the animals were shaved and washed for surgery. One percent halothane was administered via an endotracheal tube for maintenance of anesthesia. Two circular wounds were created in the midline of the animals. The wounds were 2.5 cm in diameter having a depth that reached, but did not include, the deep fascia over the spinal cord (approximately 1 cm). Wounds in pigs at this site do not contract during healing. Alginate impressions of each wound were made to determine wound volumes.

A reduced pressure implement of the type discussed in relation to Figures 2 and 11 was placed over each wound, and the cups were sealed to the skin with an Ioban sheet. A non-compressible silicone tube was attached to each pig's front tool and a reduced pressure of 16.9 kPa (5 inches Hg) below atmospheric pressure was supplied to the front tools. No reduced pressure was applied to the posterior wounds. Animals were allowed to recover from anesthesia and fed and fed ad libitum. The tubes were suspended from a pulley system over the top of each sty arranged to provide each animal with complete unrestricted access to their sty.

Animals were sedated 48 hours after surgery as described above, and then daily thereafter so that alginate impressions of each wound could be made. This pattern was continued until the wounded areas were filled with granulation tissue until they were coplanar with the tissue.

ES 2 151 925 T5 surrounding. The results of this experiment, including the time to complete filling of the wound space by granulation tissue and the rate of formation of the granulation tissue, are presented in Table 1. The data in the third column of Table 1 shows the number of days it takes for treated and untreated wounds to heal. To allow comparisons between the rate of healing of wounds of varying sizes, the data in the fourth column is expressed as a rate of healing in terms of cc of granulation tissue per day. As can be seen, the treated wounds exhibited higher healing rates than the untreated wounds. The reduced pressure treated wounds were filled with granulation tissue at an average rate that was 52.3% greater than the granulation rate of the control wounds. Animals numbered 1 and 2 experienced intermittent reduced pressure loss throughout the experiment, yet the treated wounds of these animals also healed significantly faster than their control wounds.

TABLE 1

<td>Animal</td><td>Wound</td><td>Initial Wound Volume (cm³)</td><td>Days Until Complete Granulation</td><td>Granulation Speed ​​(cm³ /day)</td><td>% Speed ​​Increase Due to Treatment</td>

<td>N ° 1</td><td>Control</td><td> 4,9</td><td> 13</td><td> 0,38</td><td> 26,3</td>

<td></td><td>Treated</td><td> 5,3</td><td> 11</td><td> 0,48</td><td></td>

<td>N ° 2</td><td>Control</td><td> 7,2</td><td> 8</td><td> 0,90</td><td> 28,9</td>

<td></td><td>Treated</td><td> 9,3</td><td> 8</td><td> 1,16</td><td></td>

<td>N ° 3</td><td>Control</td><td> 4,0</td><td> 12</td><td> 0,33</td><td> 75,8</td>

<td></td><td>Treated</td><td> 3,5</td><td> 6</td><td> 0,58</td><td></td>

<td>N ° 4</td><td>Control</td><td> 4,7</td><td> 11</td><td> 0,43</td><td> 65,1</td>

<td></td><td>Treated</td><td> 5,0</td><td> 7</td><td> 0,71</td><td></td>

<td>N ° 5</td><td>Control</td><td> 4,7</td><td> 11</td><td> 0,43</td><td> 65,1</td>

<td></td><td>Treated</td><td> 5,1</td><td> 7</td><td> 0,71</td><td></td>

<td>Half</td><td> —</td><td> —</td><td> ---</td><td> —</td><td> 52,3</td>

Example 2

Reduction of infection

During the course of the experiment described as Example 1 above, the reduced pressure treated wounds were observed to be much cleaner and bleed more spontaneously than the untreated wounds. It was therefore undertaken to determine the relative rates of clearance of a known bacterial inoculum from treated and untreated wounds.

Five 15 kg pigs were obtained and the wounds were created as indicated in Example 1. Defects of 2.5 cm diameter were created on the back of each pig using sterile technique, with a 7.5 cm interval maintained between the edges of the defects. Hemostasis was obtained by electrocautery. Before the placement of the reduced pressure utensils, 10⁸ Staphylococcus aureus organisms in 1 ml of saline. Reduced pressure devices of the type shown in Figures 2 and 11 were then attached as in Example 1, and a reduced pressure of 16.9 kPa (5 inches Hg) was applied below atmospheric pressure at one of the wounds of each animal. No reduced pressure was applied to the other wound of each animal. T-shirts were worn over the animals and no antibiotics were administered during the course of the study. Animals were sedated as in Example 1 at 24 hour intervals and a 3 mm diameter full thickness biopsy was taken from each wound site daily. The devices were then reattached and reduced pressure was applied again. This rule was continued for a week.

The biopsy samples were weighed and sterile saline (99 times the weight of the biopsy) was added. Tissue samples were homogenized in a tissue grinder and serial dilutions were made in triplicate. 100 microliters of each dilution were grown on a blood agar plate and incubated overnight. The number of colonies was counted on each plate and thus the number of organisms per gram of tissue was calculated. Data were recorded as the common logarithm of the number of organisms / gram of tissue and are shown in Table 2.

IS 2 151 925 T5

TABLE 2

<td colspan="8">Logio (organisms / g) Medium</td>

<td></td><td>Day0</td><td>Day 1</td><td>Day 2</td><td>Day 3</td><td>Day 4</td><td>Day 5</td><td>Day 7</td>

<td>Control</td><td> 8,44</td><td> 8,04</td><td> 8,17</td><td> 7,13</td><td> 7,13</td><td> 8,82</td><td> 7,08</td>

<td>Treaty</td><td> 7,69</td><td> 7,36</td><td> 7,37</td><td> 6,79</td><td> 6,43</td><td> 3,98</td><td> 4,32</td>

As can be seen in Table 2, the common logarithm of the mean number of organisms per gram of tissue present in the treated and untreated wounds decreased slightly for the five animals during the first 4 days. In treated wounds, the mean log of organisms / g decreased dramatically between days 4 and 5. The mean log of organisms / g within the untreated wounds increased during the same period. Using the traditional baseline of 10⁵ organisms / g to define infection, the data in Table 2 shows that the average treated wound was disinfected after four days of treatment while the average untreated wound was still infected after 7 days.

Example 3

Treatment of burns

The use of reduced pressure burns has been found to retard the progression of partial thickness burns to full thickness burns. A partial thickness burn is a burn in which the depth of cell death due to thermal trauma does not extend below the level of the deeper epidermal structures (i.e., the base of hair follicles, sweat glands, sebaceous glands, etc.). A burn that is initially a partial thickness burn will often deepen and progress to a full thickness burn due to insufficient blood circulation to the epidermal cells below the partial burn.

Example 3A

The loins of five 15 kg pigs were shaved and washed for surgery. A 3.8 cm (1.5 inch) diameter brass roll was heated to 190 ° C in an oil bath. The roller was pressed onto the skin of the pig for 15 seconds following a well known technique of relating the depth of the burn to time and temperature. Three burns were created on the spine of each pig, separated by 5 cm intervals. The cups of the suction apparatus of the configuration shown in Figures 2 and 11 were placed over two of the burns, with silver sulfadiazine cream (Silvadine-Trade Mark), the standard antibiotic cream applied to human burns before excision of the burned tissue, applied to the third. Cefaxolin (Kefzol) (500 mg) was administered intramuscularly (antibiotic). Suction of 0.91 to 2.72 kg of vacuum (2-6 pounds of vacuum) was applied to one of the cups. A small (2 mm) puncture biopsy was taken from the injured area and examined histologically for the depth of the burn.

The biopsies were analyzed by a dermatologist who was unaware of the nature of the study. It was concluded that the suctioned tissue specimens were healthier and healed more quickly than the non-suctioned specimens.

Example 3B

A group of 2 cm diameter standardized depth partial thickness burns was created by pressing a heated metal roller on each side of five anesthetized pigs to create 16 burns on each side of each pig. Reduced pressure utensils of the type shown in Figures 2 and 11 were secured over each of the burns on the left side of each animal and a continuous pressure of 20.3 kPa (6 inches of Hg) was supplied to the pressure utensils. reduced. Animals were anesthetized daily, and elliptical full-thickness biopsies extending from uninjured tissue, through the center of each burn, and into uninjured tissue were collected, fixed in formalin, processed for histological analysis, and stained with hematoxylin / eosin and Gomori trichrome. The histological slides were then given to a dermatologist for blind determination of the depth of the burn according to the Local Breslow Scale of Maximum Depth of Cell Death below the skin surface.

The Breslow Level (maximum total depth) for burns treated by reduced pressure was 0.095 mm. The maximum depth of burns that were not treated by reduced pressure was 0.885 mm. The use of reduced pressure utensils thus resulted in a 112% reduction in the maximum depth of burn progression.

IS 2 151 925 T5

Example 3C

Treating a negative pressure burn

Patient B. is admitted with second and third degree burns on his face and upper extremities, including both hands, as a result of a house fire. A large mitten-shaped reduced pressure implement of the general type shown in Figures 1 and 10 is placed on the patient's right hand, with open cell foam inserts placed between the fingers to apply reduced pressure to the interdigital spaces. Three pounds of vacuum are applied cyclically in a five minute run, 5 minute stop pattern. The utensil is changed on a three-times-a-week schedule. Treatment is continued until necrotic tissue is shed or cut, followed by placement of a split-thickness skin graft.

Example 4

Flap treatment

To determine the effect of the application of reduced pressure on the survival of a skin flap, five 15 kg Chester pigs were obtained and acclimatized for 1 week as previously described. Two dorsally based 3 cm x 12 cm flap lines were drawn using indelible ink on each side of the pigs, leaving 6 cm between each flap. The flaps were assigned to one of four groups as follows:

(1) Double-treated flaps are flaps that were exposed to reduced pressure both before and after surgery;

(2) Pretreated flaps are flaps that were exposed to reduced pressure before surgery, but were not exposed to reduced pressure after surgery;

(3) Post-treated flaps are flaps that were exposed to reduced pressure after surgery; and (4) Control flaps are flaps that were not exposed to reduced pressure before or after surgery.

The pretreated flaps were initially treated by covering an area surrounding one of the flap lines on the left side of each animal with a reduced pressure utensil of the type shown in Figures 1 and 10 that has a large piece of open-celled foam in it. which a tube was inserted. The foam was covered and sealed to the flap area with an impermeable adhesive sheet. A reduced pressure of 3.2 kg (7 pounds) was applied continuously to the area for 7 days.

On the day of surgery, each pig was sedated as previously described and anesthesia was maintained by 1% halothane. Two 3 cm x 12 cm dorsally based flaps were created on each side of the pig following the lines of the flaps. The flaps were created with a depth just below the panniculus carnosus (a subcutaneous muscle layer). The flaps were lifted and then sutured back into place with simple 3-0 interrupted sutures. The reduced pressure utensils were then placed on the anterior flaps on each side of the animal. A reduced pressure of 2.3-3.2 kg (5-7 pounds) was continuously applied to the anterior flaps. Each suction tube was raised from the utensils over the animals upward through a pulley suspended over the pens and downward into a vacuum separator bottle to collect any liquid exudate. A hose was connected from each vacuum separator bottle to a vacuum pump to supply the reduced pressure to the utensils. The animals had free access to all areas of the sty.

The animals were anesthetized 72 hours after surgery and the utensils were removed. Photographs were taken of each side of the animals, and copies of the flaps (and comprising any discolored areas) were made on acetate to allow planimetric calculation of percent survival. The utensils were then replaced and reduced pressure was reapplied. This rule was continued at 48 hour intervals until no further necrosis or healing of the flaps was observed.

The distal portions of all the flaps were discolored 72 hours after surgery, with the flaps exposed to reduced pressure being lighter in color. The distal ends of all the flaps appeared to be necrotic and a crust formed over the distal portion of each flap. During the time the scab spontaneously peeled off, exposing the original flap line. The scab on the control and pretreated flaps subsequently flaked earlier than the posttreated and doubly treated flaps. The control flaps had contracted to a Y-conformation that was evident after the scab had peeled off. The doubly treated flaps had contracted slightly and appeared as long thin rectangles after detachment of the scab. Pretreated flaps and posttreated flaps were intermediate between control and doubly treated flaps with respect to flap contraction.

The doubly treated flaps exhibited the longest survival in terms of retention percentage (72.2%) of the original flap size. Post-treated flaps had the second longest survival (67.4%). Pretreated flaps had the third longest flap survival (64.8%). The control flaps had the least super13

ES 2 151 925 T5 flap experience (51.2%). All treated flaps (doubly treated, pretreated, and posttreated) exhibited significantly greater surface area survival than control flaps. The doubly treated flaps had significantly longer surface area survival than the pretreated or posttreated flaps. Pretreated flaps were not significantly different from posttreated flaps with respect to flap survival.

Example 5

Treatment of pressure ulcers

The application of reduced pressure on chronic pressure ulcers was tested and found to be effective in treating them. Necrotic soft tissue was removed from the ulcers prior to placement on the treatment site of a reduced pressure implement of the type described in relation to Figures 1 and 10. Treatment of pressure ulcers was tested using both continuous and cyclical application. reduced pressure. Cyclical application of reduced pressure was found to be both more effective and less discomforting for patients than continuous application. The cyclic application of reduced pressure was carried out according to an application scheme of 5 minutes of suction followed by 5 minutes of no suction. In 15 patients tested, successful treatment required 2 to 13 weeks. Fifteen of the ulcers healed completely and each treated ulcer demonstrated a progressive decrease in size during treatment. The following case stories demonstrate how various pressure sores were treated:

Case 1

A 39-year-old male T4 paraplegic had suffered multiple recurrent pressure sores over a period of 8 years. He had been treated for a truncateric decubitus with a dentate fascia tensor flap that had developed a recurrent ulcer in the center of the flap 4 months before presentation. The ulcer underwent necrotic tissue detachment to the uninvolved periosteum resulting in a wound measuring 12 cm by 5 cm with a depth of 5 cm. During the course of 4 weeks of cyclical application of reduced pressure, the wound progressively closed and spontaneously re-epithelialized. A reduced pressure of 16.9 kPa (5 inches Hg) below atmospheric pressure was cyclically applied with 5 minute intervals of applied pressure followed by 5 minute intervals of no pressure applied. The wound was still healthy for more than 5 months after treatment.

Case 2

A 45-year-old male paraplegic suffered a recurrent pressure sore in the ischial fossa and abscess prior to treatment. Debridement of the wound was carried out with partial ischial resection. One week later, a VY biceps femoris flap was re-advanced and a rotational gluteal flap was performed. Six days later, the wound dehisced and the patient developed bilateral pneumonia requiring respiratory support. The flap became progressively edematous and firm and resisted all efforts in mobilization. At this point, a reduced pressure treatment was initiated by providing continuous non-cyclic suction or a vacuum approximately 16.9 kPa (5 inches Hg) below atmospheric pressure. A total of 2 liters of fluid was withdrawn by the reduced pressure tool during the first 72 hours of treatment. Intravenous fluids were administered to replace the fluid withdrawn from the wound. The utensil was replaced and the wound was examined three times a week. Treatment was continued for a total of 6 weeks during which the flap became progressively less hard, the formation of granulation tissue progressed rapidly, the wound edges approached and the wound healed completely.

Case 3

A 51-year-old T1 paraplegic had multiple previous pressure sores culminating in bilateral asynchronous hip disarticulations and bilateral total thigh flaps. Seven months before administration, she developed a 7 cm by 23 cm pressure sore on the rest of both hips. The bone was exposed and there was no tissue available for wound closure. Bandage changes over a 3-month period had not improved the wound. A reduced pressure implement was then secured to the wound. During the first 3 weeks of treatment, a reduced pressure of 16.9 kPa (5 inches Hg) was applied below atmospheric pressure. During the next 9 weeks, reduced pressure was applied cyclically at 5 minute intervals. The utensil was replaced every 3 days during the treatment. In the course of treatment, the wound was first granulated to cover the bone completely and then the wound was re-epithelialized from the margins. After 12 weeks of treatment, a 2 cm by 5 cm scrotal flap was used to cover the midline area of ​​the wound. The wound has remained stable for more than 6 months after treatment.

Example 6

Treatment of dehiscent incisions

A debilitated 50-year-old white male who had undergone a colostomy via a midline laparotomy was readmitted to the hospital for wound dehiscence and evisceration after infection

ES 2 151 925 T5 upper respiratory. He was immediately taken to the operating room and the abdominal wall was closed with Prolene mesh. Six weeks after Prolene mesh placement, the wound was still open and measured 28 cm by 23 cm. Only scattered granulation tissue had grown through the Prolene mesh during the six weeks. At this time, a large reduced pressure implement of the type shown in Figure 5 was placed on an underlying porous Aquaplast sheet (WFR / Aquaplast Corp. Vycoff, Nj 07481) on top of the Prolene mesh / surface of the wound and the space was closed with an Ioban cover tent. A continuous vacuum of 16.9 kPa (5 inches Hg) was applied below atmospheric pressure. The utensil was changed three times a week. After 8 days of treatment, granulation tissue had grown and fully covered the Prolene mesh. Two days later, the patient was taken to the operating room, where the surrounding tissue was undermined and used to close 75% of the wound. Split thickness skin grafts were used to cover the remainder of the wound, and placed on the granulation tissue bed. There was 80% graft seizure, and the remaining areas healed spontaneously with dressing changes from wet to dry. The wound has remained stable 16 months after surgery.

Example 7

Treating an infected wound

Infected wounds have been successfully treated through the application of reduced pressure as described in the following cases:

Case 1

A 39-year-old white male sustained severe avulsive trauma to his left lower limb in a motor vehicle accident ten years prior to presentation. He had a 10-year history of chronic osteomyelitis and an open ulcer 3 cm in diameter with bone exposure of his left lateral malleolus. He had previously undergone 7 local surgeries to attempt wound closure. An arteriogram showed a vessel foot with diffuse atherosclerosis and post-traumatic changes. The limb underwent necrotic soft tissue debridement and all involved bone was saucerized. The patient underwent a 5-week course of antibiotics. The day after debridement, a reduced pressure device of the type shown in Figures 2 and 11 was applied to the wound and a reduced pressure of 16.9 kPa (5 inches Hg) was applied below atmospheric pressure. The device was changed on a three-times-a-week schedule. After 14 days of treatment, the wound was smaller and filled with granulation tissue that completely covered the previously exposed bone. A split thickness skin graft was placed over the wound and healed first. The wound has been stable for 13 months with no recurrence of osteomyelitis or tissue degradation.

Case 2

A 51-year-old white male T8 paraplegic was admitted to the hospital for an infected left trunk pressure sore that had been present for one year and measured 4 cm by 6 cm. The patient had previously undergone multiple interventions for the treatment of this condition including a VY advancement flap 4 months prior to presentation. A scan revealed possible chronic osteomyelitis of the left femur. It was decided to treat the potential osteomyelitis with a 5-week course of IV antibiotics. The wound was debrided, then treated using a reduced pressure utensil of the type shown in Figures 1 and 10 for 6 weeks with cyclic reduced pressure [16.9 kPa (5 inches Hg) below atmospheric pressure ;

minutes running / 5 minutes stopped]. The wound was rapidly granulating and diminishing in size. After weeks the wound had closed and the patient was discharged. The patient was readmitted one month later with a draining sinic tract to the bone. The previously scanned left femoral head was resected and the wound was closed first over the drains. The wound healed without further problem.

Example 8

Chronic open wound secondary to stasis ulcers

A 45-year-old black patient with a 10-year history of bilateral stasis ulcers of the pretibial area presented with infected bilateral 10 cm by 15 cm ulcers with exposed fascia. Two previous skin graft attempts in the past year had failed. The patient was treated using a reduced pressure utensil of the type shown in Figures 1 and 10 for 14 days with cyclical reduced pressure (5 minutes walking / 5 minutes stopping) of approximately 16.9 kPa (5 inches Hg) per below atmospheric pressure. After 14 days of treatment, the quantitative bacterial counts of both ulcers were below 102 bacteria / granular tissue and both ulcers appeared as healthy granulation beds. Split thickness skin grafts were then applied and exhibited 100% seizure. The patient is ambulant and the wounds have been healthy for 2 months, which is the longest time the wounds have been healthy in the last 10 years.

IS 2 151 925 T5

Example 9

Improved blood flow

It is believed that the effectiveness of the reduced pressure implements in such treatments that have been described is due at least in part to the improvement of blood circulation within the treated wounds. To determine the effect of applying pressure on blood flow, a Doppler laser needle probe was inserted into the tissue adjacent to a pressure sore. A baseline flow level was recorded for 30 minutes. Next, the relative blood flow level was measured while continuously applying a reduced pressure corresponding to 16.9 kPa (5 inches Hg) below atmospheric pressure to the wound for 30 minutes using a reduced pressure instrument of the type shown in Figures 1 and 10. During continuous reduced pressure application, the relative blood flow level was only slightly higher than the baseline level.

The reduced pressure supply to the implement was then cycled on and off at 5 minute intervals. During the "gait" portions of the cycle, the relative blood flow level was twice as high as the baseline level. It is postulated that the increased blood flow during the "stop" cycle is probably due to a "rebound" phenomenon. During the "narcha" cycle, blood is drawn through the injured tissue from both the venous and arterial vessels of the vascular network in the vicinity of the wound. During the "stop" cycle, this blood is transported into the venous vessel of the vascular network at a rate that is greater than that which would have been observed in the absence of the preceding "go" cycle.

The terms and expressions that have been used are used as terms of description and not of limitation and there is no intention in the use of such terms and expressions to exclude any equivalences of the features shown and described, or portions thereof, but is recognizes that various modifications are possible within the scope of the claimed invention.