Incisional absorbent dressing

Dressings, systems, and methods are disclosed, in some embodiments, that involve treating a tissue site with reduced pressure. In one embodiment, a reduced-pressure dressing may include a dressing bolster, a retention pouch, and a sealing member. The dressing bolster may be adapted to apply a compressive force to the tissue site capable of closing a wound or incision therein. The retention pouch may be adapted to retain and manage fluid extracted from the tissue site to keep the tissue site substantially free of fluid and to prevent clogging of the reduced-pressure dressing. The sealing member may provide a seal over the retention pouch, the dressing bolster, and a portion of the epidermis of the patient. Other dressings, systems, and methods are disclosed.

BACKGROUND

This disclosure relates generally to medical wound care systems, and more particularly, but not by way of limitation, to reduced-pressure incisional absorbent dressings, systems, and methods.

Depending on the medical circumstances, reduced pressure may be used for, among other things, reduced-pressure therapy to encourage granulation at a tissue site, draining fluids at a tissue site, closing a wound, reducing edema, promoting perfusion, or fluid management.

Common dressings, systems, and methods typically include tubing, external canisters, and other components for providing reduced-pressure therapy. These components may be cumbersome for the patient, expensive, and prone to leaking and blockages. Further, the dressing and associated components may require a particular orientation and installation in order for the patient to receive effective therapy. Thus, improvements that enhance patient comfort and usability while maintaining or exceeding current treatment capabilities are desirable.

SUMMARY

Shortcomings with certain aspects of tissue treatment methods, dressings, and systems are addressed by this disclosure as shown and described in a variety of illustrative, non-limiting embodiments herein.

According to an illustrative, non-limiting embodiment, a reduced-pressure dressing for treating a tissue site on a patient with reduced pressure includes a dressing bolster, a retention pouch, a sealing member, and a reduced-pressure interface. The dressing bolster is adapted to be positioned proximate to the tissue site, between the tissue site and the retention pouch. The retention pouch is adapted to retain a fluid. The sealing member is adapted to cover the retention pouch, the dressing bolster, and a portion of the epidermis of the patient that is proximate to the tissue site. The reduced-pressure interface is coupled to the sealing member for providing fluid communication to the reduced-pressure dressing.

According to another illustrative, non-limiting embodiment, a system for treating a tissue site on a patient with reduced pressure includes a reduced-pressure dressing, a reduced-pressure source, and a reduced-pressure delivery conduit. The reduced-pressure dressing includes a dressing bolster, a retention pouch, a sealing member, and a reduced-pressure interface. The dressing bolster has a first side and a second side. The first side of the dressing bolster faces opposite the second side and is adapted to be positioned facing the tissue site. The retention pouch is adapted to retain a fluid and is positioned proximate to the second side of the dressing bolster. The retention pouch includes a first permeable layer, a second permeable layer, and an absorbent core. The absorbent core is encapsulated between the first and the second permeable layers. The sealing member is adapted to cover the retention pouch, the dressing bolster, and a portion of the epidermis of the patient that is proximate to the tissue site. The reduced-pressure interface is coupled to the sealing member and provides fluid communication to the reduced-pressure dressing. The reduced-pressure delivery conduit fluidly couples the reduced-pressure source to the reduced-pressure interface.

According to another illustrative, non-limiting embodiment, a method of manufacturing a dressing for use with reduced pressure to treat a tissue site on a patient includes the steps of: providing a dressing bolster having a first side and a second side, the first side facing opposite the second side, wherein the dressing bolster is adapted to distribute reduced pressure to the tissue site and to contract upon application of reduced pressure; positioning a retention pouch proximate to the second side of the dressing bolster, wherein the retention pouch is adapted to retain a fluid; positioning a sealing member over the dressing bolster and the retention pouch, wherein a portion of the sealing member is adapted to sealingly engage the epidermis of a patient proximate to the tissue site; fluidly coupling a reduced-pressure source to the sealing member, wherein the reduced pressure source is in fluid communication with the dressing bolster and the retention pouch.

Other features and advantages of the illustrative embodiments will become apparent with reference to the drawings and detailed description that follow.

DETAILED DESCRIPTION

In the following Detailed Description of the non-limiting, illustrative embodiments, reference is made to the accompanying drawings that form a part hereof. Other embodiments may be utilized, and logical, structural, mechanical, electrical, and chemical changes may be made without departing from the scope of this disclosure. To avoid detail not necessary to enable those skilled in the art to practice the embodiments described herein, the Description may omit certain information known to those skilled in the art. Thus, the following Detailed Description is provided without limitation and with the scope of the illustrative embodiments being defined by the appended claims. Further, as used throughout the Description and unless otherwise indicated, “or” does not require mutual exclusivity.

Referring to the drawings,FIGS. 1-3depict an embodiment of a reduced-pressure treatment system100for treating a tissue site102, such as, for example, an incision104. The incision104may extend through or otherwise involve an epidermis106, a dermis108, and a subcutaneous tissue110. The reduced-pressure treatment system100may also be used at other tissue sites.

The tissue site102may be the bodily tissue of any human, animal, or other organism, including bone tissue, adipose tissue, muscle tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, ligaments, or any other tissue. The treatment of the tissue site102may include removal of fluids such as exudate or ascites.

The reduced-pressure treatment system100may include a reduced-pressure dressing112, a reduced-pressure subsystem113, and a reduced-pressure delivery conduit115. The reduced-pressure delivery conduit115may provide reduced pressure from the reduced-pressure subsystem113to the reduced-pressure dressing112.

In one embodiment, the reduced-pressure dressing112may include a dressing bolster114, a retention pouch116, a sealing member118, and a reduced pressure interface119. While the reduced-pressure system100is shown inFIG. 3in the context of the reduced-pressure dressing112over an incision104, the reduced-pressure treatment system100may be used on other tissue sites, including open wounds. Further, the dressing bolster114and the retention pouch116described herein may be deployed in place of a fluid distribution manifold used in connection with other types of reduced-pressure treatment systems. Thus, this disclosure is not limited to the particular embodiments of the reduced-pressure treatment system100described herein.

The dressing bolster114has a first side120, a second side122, and edges123. The first side120and the second side122may terminate at edges123and face in opposite directions from one another. The first side120of the dressing bolster114may be adapted to face inward toward the tissue site102. The dressing bolster114may include a plurality of flexibility notches or recesses (not shown) that may be lateral cuts in the dressing bolster114. The dressing bolster114may include one or more longitudinal cuts or other cuts. The flexibility notches may enhance the flexibility of the dressing bolster114. The enhanced flexibility may be useful when the reduced-pressure dressing112is applied over a joint or other area of movement.

The dressing bolster114may be formed from any flexible bolster material or manifold material that provides a vacuum space or treatment space, such as, for example, a porous and permeable foam or foam-like material, a member formed with pathways, a graft, a gauze, or other similar material. As a more specific, non-limiting example, the dressing bolster114may be a reticulated, open-cell polyurethane or polyether foam that allows good permeability of wound fluids while under a reduced pressure. One such foam material is the VAC® GranuFoam® material available from Kinetic Concepts, Inc. (KCI) of San Antonio, Tex. Any material or combination of materials may be used as a manifold material for the dressing bolster114provided that the manifold material is operable to distribute reduced pressure. The term “manifold” as used herein generally refers to a substance or structure provided to assist in applying reduced pressure to, delivering fluids to, or removing fluids from a tissue site. A manifold may include a plurality of flow channels or pathways. The plurality of flow channels may be interconnected to improve the distribution of fluids provided to and removed from the area of tissue around the manifold. Examples of manifolds may include, without limitation, devices that have structural elements arranged to form flow channels, cellular foam, such as open-cell foam, porous tissue collections, and liquids, gels, and foams that include or cure to include flow channels.

A material with a higher or lower density, or a smaller or larger pore size than GranuFoam® material may be desirable for the dressing bolster114depending on the application. Among the many possible materials, the following may be used: GranuFoam® material; Foamex® technical foam (www.foamex.com); molded bed of nails structures; patterned grid material, such as those manufactured by Sercol Industrial Fabrics; 3D textiles, such as those manufactured by Baltex of Derby, U.K.; a gauze, a flexible channel-containing member; a graft; or similar material. Ionic silver may be added to the foam in a micro bonding process. Other substances may also be added to the foam, such as antimicrobial agents.

In one embodiment, the dressing bolster114may be a hydrophobic layer. The hydrophobic characteristics of the dressing bolster114may prevent the dressing bolster114from directly absorbing fluid, such as exudate, from the tissue site102, but allow the fluid to pass through. Thus, as depicted by the fluid communication arrows117inFIG. 3, the fluid may be drawn away from the tissue site102using a reduced pressure source, such as the reduced pressure subsystem113. Further, upon application of reduced pressure, the porous foam-like nature of the dressing bolster114as described above may permit the dressing bolster114to contract and apply a compressive force capable of closing a wound at a tissue site, such as the incision104at the tissue site102.

In one embodiment, a comfort layer124may be coupled to the first side120of the dressing bolster114. For example, the comfort layer124may be coupled to the dressing bolster114by a heat bond125, or any other suitable technique. The comfort layer124may provide for patient comfort when the dressing bolster114is placed adjacent to the epidermis106of the patient. The comfort layer124may be any material for preventing skin irritation and discomfort while allowing fluid transmission through the comfort layer124. As a non-limiting example, a woven elastic material or a polyester knit textile substrate may be used. As another non-limiting example, an InterDry™ textile material from Milliken Chemical of Spartanburg, S.C., may be used. The comfort layer124may include anti-microbial substances, such as silver.

As used herein, the term “coupled” may include coupling via a separate object and direct coupling. The term “coupled” may also encompass two or more components that are continuous with one another by virtue of each of the components being formed from the same piece of material. Also, the term “coupled” may include chemical, such as via a chemical bond, mechanical, thermal, or electrical coupling. Fluid coupling means that fluid may be in communication between the designated parts or locations.

Continuing withFIGS. 1-3, the retention pouch116may include a first permeable layer126, a second permeable layer127, and an absorbent core128. In one embodiment, the absorbent core128may be encapsulated between the first permeable layer126and the second permeable layer127. The first permeable layer126may have edges126a,bcoupled respectively to edges127a,bof the second permeable layer127around or otherwise encapsulating the absorbent core128. The edges126a,band127a,bof the first and the second permeable layers126,127may be secured or coupled to one another in any suitable manner, such as, for example, by the heat bond125described above.

The retention pouch116may be adapted to retain fluid, such as fluid extracted from the tissue site102. The first permeable layer126and the second permeable layer127may each have a fluid acquisition surface129facing in an opposite direction from a directional wicking surface130. The directional wicking surfaces130of the first and the second permeable layers126,127may each have a grain (not shown) oriented in a longitudinal direction along the length of the reduced-pressure dressing112. The orientation of the grain of the directional wicking surfaces130may facilitate the wicking of fluid, such as fluid extracted from the tissue site102, along the length of the reduced-pressure dressing112. The wicking of fluid in this manner may enhance the ability of the retention pouch116to retain and manage fluid efficiently for preventing clogs as will be described in further detail below. The retention pouch116may additionally include a recess131capable of receiving or otherwise accommodating a filter133. The filter133may be positioned in a gap135between the recess131and the sealing member118to further enhance the ability of the reduced-pressure dressing112to resist clogging. The recess131may be formed or defined, for example, by coupling the first permeable layer126to the second permeable layer127through the absorbent core128. In another embodiment, a portion of the absorbent core128may be removed to provide, for example, a notch138or other aperture, permitting the first permeable layer126to contact and to be coupled to the second permeable layer127. The first and the second permeable layer126,127may be coupled, for example, by the heat bond125or other suitable technique.

The first and the second permeable layers126,127may be any material exhibiting the fluid acquisition and wicking characteristics described above, such as, for example, Libeltex TDL2, manufactured by Libeltex. The filter133may be formed of any suitable hydrophobic material and may have a 3-dimensional shape.

The absorbent core128may be any material that retains liquids and may, for example, include one or more of the following: Luquafleece® material; BASF 402c; Technical Absorbents 2317, available from Technical Absorbents (www.techabsorbents.com); sodium polyacrylate super absorbers; cellulosics (carboxy methyl cellulose and salts such as sodium CMC); or alginates. The absorbent core128may allow fluids and exudate removed from the tissue site102to be stored within the retention pouch116rather than external to the reduced-pressure dressing112.

Similar to the dressing bolster114, the retention pouch116may include a plurality of flexibility notches121or recesses that may be lateral cuts in the retention pouch116. The retention pouch116may include one or more longitudinal cuts or other cuts. The flexibility notches may enhance the flexibility of the retention pouch116and increase the ability of the retention pouch116to conform to, for example, the joint of a patient. Further, the enhanced flexibility may assist in preventing any interference with the ability of the dressing bolster114to contract as described above.

The retention pouch116may have a maximum fluid capacity. At the maximum fluid capacity of the retention pouch116, fluid communication through the retention pouch116may be substantially precluded. The retention pouch116may have a maximum fluid capacity of any amount to suit a particular application. In one embodiment, for example, the retention pouch116may have a maximum fluid capacity of about 50 milliliters.

In one embodiment, the dressing bolster114may be positioned between the tissue site102and the retention pouch116with the first side120of the dressing bolster114facing the tissue site102. In this embodiment, the fluid acquisition surface129of the first permeable layer126may be positioned proximate to and facing the second side122of the dressing bolster114. Further, the fluid acquisition surface129of the second permeable layer127may be positioned facing the absorbent core128.

The sealing member118may provide a fluid seal over the dressing bolster114, the retention pouch116, and at least a portion of the epidermis106of the patient. As such, the sealing member118may be formed from any material that allows for a fluid seal. “Fluid seal,” or “seal,” means a seal adequate to maintain reduced pressure at a desired site given the particular reduced pressure source or subsystem involved. The sealing member118may be sealed against the epidermis106or against a gasket or drape by a sealing apparatus. The sealing apparatus may be, for example, an adhesive sealing tape, drape tape or strip, double-side drape tape, pressure-sensitive adhesive, paste, hydrocolloid, hydrogel, or similar material. If a tape is used, the tape may be formed of the same material as the sealing member118with a pre-applied, pressure-sensitive adhesive. The pressure-sensitive adhesive or other sealing apparatus may be applied, for example, on a patient-facing side of the sealing-member118, or portion thereof, for providing the fluid seal between the sealing member118and the epidermis106. Before the sealing member118is secured to the epidermis, removable strips covering and protecting the pressure-sensitive adhesive may be removed.

In one embodiment, the sealing member118may be an elastomeric material that provides the fluid seal described above. “Elastomeric” means having the properties of an elastomer and generally refers to a polymeric material that has rubber-like properties. More specifically, an elastomeric material may have an ultimate elongation greater than 100% and a significant amount of resilience. The resilience of a material refers to the ability of the material to recover from an elastic deformation. Examples of elastomers and elastomeric materials may include, without limitation, natural rubbers, polyisoprene, styrene butadiene rubber, chloroprene rubber, polybutadiene, nitrile rubber, butyl rubber, ethylene propylene rubber, ethylene propylene diene monomer, chlorosulfonated polyethylene, polysulfide rubber, polyurethane, EVA film, co-polyester, and silicones. Further, the sealing member118may be, for example, a silicone drape, a 3M Tegaderm® drape, an acrylic drape such as one available from Avery Dennison, or an incise drape.

The sealing member118may include a first sealing member portion132and a second sealing member portion134. The first sealing member portion132may extend over and beyond the retention pouch116and the dressing bolster114to form a sealing member extension136. The sealing member extension136has a first side (not shown) and a second side (not shown), and the first side may be adapted to face inward toward the tissue site102. The sealing member extension136may be, for example, a sealing member flange. A portion of the sealing member118may include a sealing member aperture137to allow fluid communication between the reduced-pressure dressing112and a reduced-pressure source, such as the reduced-pressure subsystem113.

The first side of the sealing member extension136may be placed on a second side (not shown) of the second sealing member portion134that is adapted to face away from the tissue site102. The sealing member extension136and the second side of the second sealing member portion134may be coupled, for example, by an adhesive, the previously described heat bond125, welding, cements, or other suitable devices. In another embodiment, the first sealing member portion132and the second sealing member portion134may be integrally formed. The first sealing member portion132may include a plurality of bellows142, folds, or stretch zones. The bellows142may provide additional material to enhance the ability of the sealing member118to stretch or to move. For example, if the reduced-pressure dressing112is used on a joint or other area of movement on a patient, additional material provided by the bellows142may enhance the ability of the sealing member118to move and conform to the joint.

One or more release members (not shown) may be releasably coupled to the second side of the second sealing member portion134. The release members may provide stiffness and assist in deployment of the reduced-pressure dressing112. The release members may be a casting paper or a film held on the second side of the second sealing member portion134.

The reduced-pressure interface119may be coupled to the sealing member118and may be in fluid communication with the sealing member aperture137in the sealing member118. The reduced-pressure interface119may provide fluid communication between the sealing member aperture137and the reduced-pressure delivery conduit115. The reduced-pressure interface119may be formed as a component of a reduced-pressure assembly140.

In one embodiment, the reduced-pressure interface119may include a membrane filter (not shown) in fluid communication with the sealing member aperture137for prevention of clogs and transmission of odors from the reduced-pressure dressing112during therapy. The membrane filter may be, for example, a hydrophobic or oleophobic filter. Additionally, the membrane filter may include a substance, such as, for example, charcoal for controlling odor. The membrane filter may be replaceable or formed integrally with the reduced-pressure interface119and the reduced-pressure assembly140, if so equipped. In another embodiment, the membrane filter may be positioned in any suitable location between the reduced-pressure dressing112and a reduced-pressure source144, described below.

The reduced-pressure subsystem113may include a reduced-pressure source144. The reduced-pressure source144may provide reduced pressure as a part of the system100. The reduced-pressure source144may be any suitable device for providing reduced pressure as described herein, such as, for example, a vacuum pump, wall suction, or other source. The reduced-pressure source144may be fluidly coupled to the reduced-pressure interface119by the reduced-pressure delivery conduit115. The reduced-pressure interface119may deliver the reduced pressure through the sealing member aperture137of the sealing member118to the reduced-pressure dressing112and the tissue site102.

As used herein, “reduced pressure” generally refers to a pressure less than the ambient pressure at the tissue site102being subjected to treatment. This reduced pressure may be less than the atmospheric pressure or less than a hydrostatic pressure at a tissue site. Unless otherwise indicated, values of pressure stated herein are gauge pressures. While the amount and nature of reduced pressure applied to a tissue site may vary according to the application, the reduced pressure may be between about −5 mm Hg to about −500 mm Hg, and more specifically, between about −100 mm Hg to about −200 mm Hg.

The reduced pressure delivered may be constant or varied, patterned or random, and may be delivered continuously or intermittently. Although the terms “vacuum” and “negative pressure” may be used to describe the pressure applied to a tissue site, the actual pressure applied to the tissue site may be more than the pressure normally associated with a complete vacuum. Consistent with the use herein, an increase in reduced pressure or vacuum pressure may refers to a relative reduction in absolute pressure.

In one embodiment, one or more monitoring devices (not shown) may be fluidly coupled to the reduced-pressure delivery conduit115. The monitoring devices may be, for example, a pressure-feedback device, a volume detection system, a blood detection system, an infection detection system, a flow monitoring system, a temperature monitoring system, or other device. In another embodiment, the monitoring devices may be formed integrally with the reduced-pressure subsystem113and/or the reduced-pressure source144.

The reduced-pressure treatment system100may include a fluid capacity indicator145capable of indicating whether the retention pouch116has reached maximum fluid capacity. The retention pouch116may communicates reduced pressure applied to the reduced-pressure dressing112to the fluid capacity indicator145. In one embodiment, the fluid capacity indicator145may be a component of the reduced-pressure assembly140. In another embodiment, the fluid capacity indicator145may be a separate unit in fluid communication with the retention pouch116.

Referring now toFIGS. 4-11, the fluid capacity indicator145may be formed with a moving member152and a visual indicator154associated with the moving member152. The moving member152may be adapted to move when reduced pressure communicated through the retention pouch116exceeds a threshold pressure (Pt).

In one embodiment, the visual indicator154is an indicator member162, such as, for example, a disk-shaped member164. The disk-shaped member164may also be a button or a member of any shape that indicates a changed state relative to pressure. The moving member152may be a collapsible wall156that has a first end158and a second end160. The first end158may be coupled to the indicator member162. The second end160may be coupled to a base166. The collapsible wall156and the indicator member162form a pressure vessel with the base166or with the retention pouch116. The collapsible wall156may have a convex interior surface157and may include baffles or other features to assist in collapsing the collapsible wall156.

When reduced pressure delivered to the dressing bolster114and communicated through the retention pouch116to the fluid capacity indicator145exceeds the threshold pressure (Pt), the collapsible wall156may collapse. When the collapsible wall156collapses, the visual indicator154may move from a first position, such as an extended position shown inFIG. 5A, to a second position, such as a retracted position shown inFIG. 5B. The collapsible wall156of the fluid capacity indicator145may be sized and shaped to collapse or move the indicator member162substantially flush against the base166at the threshold pressure (Pt). When the threshold pressure (Pt) no longer exists, the visual indicator154may return to the extended position. At maximum fluid capacity, or when the retention pouch116is otherwise substantially saturated with fluid, the retention pouch116may preclude the communication of reduced pressure to the fluid capacity indicator145. Thus, the threshold pressure may not exist, for example, when the retention pouch116is substantially saturated with fluid. Accordingly, when in the extended position during therapy, the visual indicator154may indicate that the retention pouch116and/or the reduced-pressure dressing112have reached the maximum fluid capacity.

The thickness of the collapsible wall156, wall material stiffness, and wall geometry are examples of variables that may impact the pressure at which the collapsible wall156collapses. The rigidity of the base166may also be a factor. While the wall thickness of the collapsible wall156may be determined using finite element analysis, it may be necessary to empirically determine the wall thickness to achieve movement at the threshold pressure (Pt). In some embodiments, the collapsible wall156may be designed so that the collapsible wall156collapses by sudden buckling as the threshold pressure (Pt) is crossed, providing a binary indication of the fluid capacity within the reduced-pressure dressing112.

The fluid capacity indicator145may be formed on the base166with the reduced-pressure interface119as a component of the reduced-pressure assembly140. In such an embodiment, the fluid capacity indicator145may be in fluid communication with the retention pouch116through an indicator aperture167. The fluid capacity indicator145may also be a separate component from the reduced-pressure indicator119and reduced-pressure assembly140that is placed into fluid communication with the retention pouch116.

The fluid capacity indicator145, reduced-pressure interface119, and base166may be formed from a medical-grade, soft polymer or other pliable material. As non-limiting examples, the fluid capacity indicator145, reduced-pressure interface119, and base166may be formed from polyurethane, polyethylene, polyvinyl chloride (PVC), fluorosilicone, ethylene-propylene, or similar materials. In one illustrative, non-limiting embodiment, the fluid capacity indicator145, reduced-pressure interface119, and base166are molded from DEHP-free PVC. The fluid capacity indicator145, reduced-pressure interface119, and base166may be molded, casted, or extruded, and may be formed as an integral unit.

As previously described, the reduced-pressure interface119may be in fluid communication with the reduced-pressure delivery conduit115for delivering reduced pressure to the reduced-pressure dressing112. In the illustrative, non-limiting embodiments shown inFIGS. 4-11, the reduced-pressure interface119may include a housing wall176. The housing wall176may be dome-shaped or any shape that defines an interior space178that has an open portion, or interface aperture180, in fluid communication with the sealing member aperture137in the reduced-pressure dressing112.

The housing wall176may have a receptacle182for receiving and maintaining an end of the reduced-pressure delivery conduit115. As shown inFIGS. 9 and 10, the receptacle182may have a first aperture184and a second aperture186in fluid communication with one another. The first aperture184may be large enough to allow the reduced-pressure delivery conduit115to enter with an interference fit. The second aperture186may allow fluid to enter, but restrict the reduced-pressure delivery conduit115from entering. The first and the second apertures184,186may be in fluid communication with the interior space178.

Referring to the previously described embodiments ofFIGS. 1-11, in one illustrative embodiment of operation, a user may place the first side120of the dressing bolster114proximate the tissue site102. Further, the user may place the retention pouch116proximate the second side122of the dressing bolster114. Subsequently, the user may place the sealing member118over the retention pouch116, the dressing bolster114, and a portion of the epidermis106of the patient. The sealing member118may be sealingly secured to the portion of the epidermis106as described above. The reduced-pressure delivery conduit115may be coupled to the reduced-pressure interface119and to the reduced-pressure source144. In one embodiment, the reduced-pressure dressing112may be a pre-assembled component placed proximate to the tissue site102by the user.

The reduced-pressure source144may then be activated and for delivering reduced pressure to the reduced-pressure dressing112. Upon application of the reduced pressure to the reduced-pressure dressing112, the dressing bolster114may contract and distribute the reduced pressure to the tissue site102. The contraction of the dressing bolster114may apply a compressive force capable of closing a portion of the tissue site102, such as the incision104. For example, the compressive force may have a first force component directed downward toward the tissue site102and a second force component directed laterally across the tissue site102. The combination of the first and the second force components may cooperate, for example, to urge the sides of the incision104to a closed position.

As previously described, the dressing bolster114and the retention pouch116may be formed of permeable materials that act as a manifold for providing fluid communication between the sealing member aperture137and the tissue site102. Thus, the reduced pressure distributed to the tissue site102by the dressing bolster114may draw fluid away from the tissue site102toward the retention pouch116where the fluid may be retained. As depicted by the fluid communication arrows117inFIG. 3, the sealing member aperture137may be in fluid communication with the edges123of the dressing bolster114along the sides of the reduced-pressure dressing112. In this configuration, the reduced-pressure dressing112may not require fluid communication through the retention pouch116in order for reduced pressure applied the reduced-pressure dressing112to reach the tissue site102. Accordingly, when the retention pouch116has reached the maximum fluid capacity, the reduced-pressure interface119may remain in fluid communication with the tissue site102at least by virtue of the fluid communication with the edges123of the dressing bolster114. The fluid communication between the reduced-pressure interface119and the edges123may permit the dressing bolster114to distribute reduced pressure to the tissue site102if the retention pouch116becomes substantially saturated with fluid, or otherwise clogged. In such a configuration, the edges123of the dressing bolster114may provide an independent or direct fluid communication path between the reduced-pressure interface119and the tissue site102. Thus, when the retention pouch116has reached the maximum fluid capacity, the reduced-pressure interface119may be in fluid communication with the tissue site102at least through an edge123of the dressing bolster114.

The positioning of the dressing bolster114and the retention pouch116as a layer relative to one another, with the retention pouch116positioned above the dressing bolster114and away from the tissue site102, may permit the dressing bolster114to contract freely without any interference. Further, the thickness of the retention pouch116relative to the dressing bolster114may provide additional benefit for the operation of the dressing bolster114. For example,FIG. 3depicts the dressing bolster114as having a thickness greater than a thickness of the retention pouch116. Although the reduced-pressure dressing112does not require the retention pouch116to be thinner than the dressing bolster114, such a configuration may enhance the ability of the dressing bolster114to operate freely without interference from fluid being absorbed by the retention pouch116.

As described above, the retention pouch116may include the first and the second permeable layers126,127that encapsulate the absorbent core128for retaining fluid during treatment. As shown inFIG. 3, the first permeable layer126may be positioned proximate the dressing bolster114and the second permeable layer127may be positioned proximate the sealing member118. The fluid acquisition surface129of the first permeable layer126may face the dressing bolster114and the directional wicking surface130of the first permeable layer126may face the absorbent core128. Further, the fluid acquisition surface129of the second permeable layer127may face the absorbent core128and the directional wicking surface130of the second permeable layer127may face the sealing member118.

As fluid contacts the first and the second permeable layers126,127, the fluid may be distributed by each of the directional wicking surfaces130along the length of the reduced-pressure dressing112. The grain of each of the directional wicking surfaces130may be oriented along the length of the reduced-pressure dressing112such that the fluid will follow the direction of the grain by a wicking action without regard to the orientation of the reduced-pressure dressing112on the patient. As such, the fluid may be distributed and absorbed by the absorbent core128in a substantially even manner.

The configuration of the first and second permeable layers126,127may be particularly useful in managing fluid extracted from the tissue site102within the reduced-pressure dressing112. In one embodiment, as fluid contacts the fluid acquisition surface129of the first permeable layer126, the fluid may first be drawn into the retention pouch116and away from the dressing bolster114. Subsequently, the fluid may be wicked along the directional wicking surface130of the first permeable layer126for absorption by the absorbent core128. As fluid contacts the directional wicking surface130of the second permeable layer127, the fluid may first be wicked along the directional wicking surface130of the second permeable layer127, away from the sealing member aperture137. Fluid contacting the second permeable layer127may first be wicked away from the sealing member aperture137to preclude clogging of the sealing member aperture137. Clogging can occur, for example, from excess fluid near the sealing member aperture137. Subsequently, the fluid may be drawn into the retention pouch116through the second permeable layer127and absorbed by the absorbent core128. Thus, the configuration and positioning of the first and second permeable layers126,127relative to one another may direct fluid away from the tissue site102and away from the sealing member aperture137for storage in the retention pouch116. In this manner, the tissue site102may be kept substantially free of fluids, and the sealing member aperture137may be kept substantially free of clogs.

The recess131on the retention pouch116may further enhance the ability of the reduced-pressure dressing112to resist clogging. For example, the recess131may provide the gap135between the sealing member aperture137, which may be in fluid communication with the reduced-pressure interface119, and the retention pouch116. The gap135may substantially preclude excess fluid from becoming lodged between the sealing member118and the retention pouch116near the sealing member aperture137. As an additional precaution, the filter133may be positioned in the gap135to preclude excess fluids from reaching the sealing member aperture137.

The storage and management of extracted fluids in the reduced-pressure dressing112may provide many benefits. The potential for clogging as discussed above may be reduced and the storage of fluids within the reduced-pressure dressing112may eliminate the need for external storage components that could potentially leak or cause discomfort. Further, the reduction in the number of components may lowers the volume that must be maintained at reduced pressure, thereby increasing efficiency. Also, the reduced-pressure dressing112may be capable of managing fluids without regard to any particular orientation of the reduced-pressure dressing112on the patient. Thus, the reduced-pressure dressing112at least provides increased comfort, usability, efficiency, and confidence that the patient is receiving effective treatment.

For operation, the fluid capacity indicator145may require that the reduced pressure being applied to the reduced-pressure dressing112be communicated through the retention pouch116to the fluid capacity indicator145. The communication of reduced pressure through the retention pouch116to the fluid capacity indicator145may provide a pressure feedback signal to the fluid capacity indicator that is related to the fluid saturation of the retention pouch116. Once the reduced pressure is greater, or more negative with respect to ambient pressure, than the threshold pressure (Pt), the fluid capacity indicator145may give a visual indication that the pressure has passed the threshold pressure (Pt). In this embodiment, when the threshold pressure (Pt) has been reached, the visual indicator154may move to a position substantially flush with, or otherwise near, the base166. If reduced pressure is interrupted such that the threshold pressure (Pt) no longer persists, the visual indicator154may return to a position indicating a lack of adequate reduced pressure. Such an interruption in the reduced pressure could occur, for example, if the retention pouch116becomes substantially saturated with fluid, thereby precluding or otherwise inhibiting the communication of reduced pressure to the fluid capacity indicator145. Thus, the physical position of the visual indicator154provides an indication as to the level of fluid saturation or capacity within the retention pouch116that may be easily understood by the user.

Referring toFIG. 12, another embodiment is illustrated for the fluid capacity indicator145. As shown inFIG. 12, the moving member152may be an indicator sealing member170suspended over a convex member172. The convex member172may be formed in a base or body171having an aperture173in fluid communication with the retention pouch116. The indicator sealing member170may be coupled to the convex member172by an adhesive175or other sealing device. The broken lines show the indicator sealing member170in a first position before the threshold pressure (Pt) has been achieved, and the solid lines show the indicator sealing member170in a position approximating the convex member172after the threshold pressure (Pt) has been achieved.

Continuing with the embodiment ofFIG. 12, the visual indicator154may be a combination of elements. If the indicator sealing member170is a first color and a surface174is a second color, the combination may visually create a third color indicative of the threshold pressure (Pt) being achieved. In another embodiment, the indicator sealing member170may be slightly opaque at a distance, but when brought into contact with the surface174may allow visual indicia on the surface174to be read.

The color changes and indicia schemes for the visual indicator154mentioned in connection withFIG. 12may also be utilized as an aspect of the illustrative embodiment ofFIGS. 1-11. In addition or as an alternative, the moving member152may create an audible sound when going from a first position to a second position to signify audibly a change in state. For example, a “click” noise may be made as the moving member152goes from a retracted position to an extended position and vice-versa.

FIGS. 13-14Bdepict another illustrative embodiment of a reduced-pressure assembly240that may be used with a reduced-pressure system, such as the reduced-pressure treatment system100ofFIG. 1. As shown inFIG. 13, the reduced-pressure assembly240may include a base266having a reduced-pressure interface219and a fluid capacity indicator245. The reduced-pressure assembly240may be similar to the reduced-pressure assembly140ofFIGS. 1-11. However, the fluid capacity indicator245associated with the reduced-pressure assembly240may be an electro-mechanical indicator203. The electro-mechanical indicator203may provide a visual indication if the threshold pressure (Pt) does not exist, and may also provide a powered visual alert, an audible alert, or an output signal for other use. AlthoughFIG. 13depicts the electro-mechanical indicator203as a component of the reduced-pressure assembly240, the electro-mechanical indicator203may be a separate component.

The electro-mechanical indicator203may be formed with a moving member252and a visual indicator254associated with the moving member252. Similar to the embodiments ofFIGS. 1-11, the moving member252may be adapted to move when reduced pressure communicated through the retention pouch116exceeds a threshold pressure (Pt). The visual indicator254may help a user to visualize the movement of the moving member252. In one embodiment, the visual indicator254may be an indicator member262, such as, for example, a disk-shaped member264. The disk-shaped member264may also be a button or a member of any shape that signifies a changed state relative to pressure. The moving member252may be a collapsible wall256that has a first end258and a second end260. The first end258may be coupled to the indicator member262. The second end260may be coupled to the base266. The collapsible wall256and the indicator member262may form a pressure vessel with the base266or with the retention pouch116. The collapsible wall256may have a convex interior surface257and may include baffles or other features to assist in collapsing the collapsible wall256.

The electro-mechanical indicator203may additionally include a thin, tactile pressure transducer290associated with the moving member252and the visual indicator254. When the moving member252collapses under reduced pressure, the tactile pressure transducer290may receive adequate physical pressure or contact to create an indication signal indicating that the reduced pressure has met or exceeded the threshold pressure (Pt). The tactile pressure transducer290may function to give a binary signal or may give a graduated signal, such as a voltage that varies with the magnitude of the force or pressure.

The tactile pressure transducer290may communicate with a detector circuit292. One or more electrical leads293may be used to electrically couple the tactile pressure transducer290to the detector circuit292. The detector circuit292may use the indication signal to provide an alert when appropriate. The detector circuit292may be a battery-powered electrical circuit that has been miniaturized. Numerous other circuits are possible.

When the reduced pressure is at the threshold pressure (Pt), or more negative relative to ambient pressure than the threshold pressure (Pt), the moving member252may move or collapse, causing a physical force to impinge on the tactile pressure transducer290. The physical force on the tactile pressure transducer290may cause the indication signal to change states. The change in the indication signal may then be used to energize or de-energize an LED294or other powered visual device to provide a visual or audible signal to a user. In addition or as an alternative, the change in the indication signal may cause a speaker296, or other transducer, such as a piezo-electric device, to be energized or de-energized to give a visual or an audible alert.

The tactile pressure transducer290may be any transducer or device that can detect that the moving member252has moved. The tactile pressure transducer290may be, as non-limiting examples, a piezoresistive strain gage, capacitive device, electromagnetic device, piezoelectric device, optical device, potentiometric device, or similar device. The tactile pressure transducer290may also include an integrated contact switch and a circuit that detects an open or closed state in response to movement of the moving member252. In one illustrative, non-limiting embodiment, a thin-film resistive force sensor may be used, such as, for example, a FlexiForce® load sensor, available from Tekscan, Inc. of Boston, Mass. (www.tekscan.com).

Any suitable circuit design may be used as the detector circuit292. For example, in one illustrative, non-limiting embodiment, the detector circuit292may use a P-channel MOSFET (PFET). In this illustrative embodiment, when the tactile pressure transducer290is exposed to pressure, the impedance of the tactile pressure transducer290may drop to a low value. Without pressure, the tactile pressure transducer290may have a high impedance. The LED294may be tied to the drain of the PFET so that when the PFET is off, there is no current through the LED. Thus, the PFET may act as an open switch. The tactile pressure transducer290may be used as part of a voltage divider to drive the gate of the PFET. When the tactile pressure transducer290is exposed to pressure, the impedance of the tactile pressure transducer290may be low and the voltage divider may change to a high voltage, which biases the PFET off. In the absence of pressure, the impedance of the tactile pressure transducer290may be high and the voltage divider may change to a low voltage, which biases the PFET on such that the LED will illuminate. A coin cell battery (not shown) may be mounted on the base266to power the detector circuit292. The detector circuit292may be a flexible member to facilitate comfort of the patient. Other circuits may be readily used, and the components may be sterilized.

In another illustrative, non-limiting embodiment, the tactile pressure transducer290may develop an analog voltage signal. In this embodiment, the detector circuit292may be a comparator circuit to drive the previously described visual alert or audio alert. In another illustrative, non-limiting embodiment, the tactile pressure transducer290may develop an analog voltage signal and the detector circuit292may provide a number of alerts based on the sensed analog voltage. For example, a green light may be displayed when the reduced pressure is greater than the threshold pressure (Pt), and a yellow light may be displayed when the reduced pressure is lower than the threshold pressure (Pt), but not lower than an alarm pressure. A red light may be displayed when the reduced pressure is lower than an alarm pressure. As the level of fluid saturation in the retention pouch116increases, the communication of reduced pressure may decrease through the retention pouch116to the fluid capacity indicator254associated with the tactile pressure transducer290. Thus, the decrease in communication of reduced pressure may correspond to an increase in pressure, or a pressure that is less negative relative to ambient pressure, that permits the fluid capacity indicator254to return to an extended position as described above. Thus, the state of pressure indicated by each of the alerts may indicate different degrees of fluid saturation of the retention pouch116.

The use of the electro-mechanical indicator203may be particularly helpful in certain circumstances. For example, the electro-mechanical indicator203may alert a patient who is sleeping of a problem that might otherwise not be apparent. The electro-mechanical indicator203may simplify the visual reading or interpretation of the visual indicator254.

Referring toFIGS. 15A-15E, charts are provided that illustrate reduced pressure measured over a 24 hour period (1440 minutes) at four locations in the reduced pressure dressing112during an experimental treatment session for simulating extraction of fluid from a simulated tissue site. Reduced pressure (measured in mm HG) is plotted on the vertical axis and time (measured in minutes) is plotted on the horizontal axis.FIGS. 15A-15Eprovide plot lines depicting a different location302,304,306, and308in the reduced-pressure dressing112at which reduced pressure was measured during the treatment session.FIG. 15Adepicts each location302,304,306, and308plotted together andFIGS. 15B-15Eeach depict one location302,304,306, and308, respectively. Thus,FIGS. 15A-15Eillustrate the application of reduced pressure to a simulated tissue site during operation of the reduced-pressure dressing112.

Beginning with a dry, unsaturated reduced-pressure dressing112, fluid was instilled at a rate of at 2.083 milliliters per hour in the reduced-pressure dressing112. A maximum volume of 50 milliliters of fluid was instilled in the reduced-pressure dressing112and ultimately absorbed by the retention pouch116, described above, during the simulation. Reduced pressure was applied to the reduced-pressure dressing112while the fluid was being instilled in a central location on the underside of the reduced-pressure dressing112. For a 1440 minute time frame, reduced pressure in the reduce-pressure dressing112was monitored at the locations302,304,306, and308equidistantly spaced on the underside of the reduced-pressure dressing112.

Variations in reduced pressure measured at the locations302,304,306, and308are based, in part, on the effect of the fluid entering the reduced-pressure dressing112. Each of the locations302,304,306, and308for up to the 1440 minutes plotted maintained a reduced pressure ranging between about 110 mmHg and 130 mmHg. Thus,FIGS. 15A-15Eshow that the reduced-pressure dressing112effectively maintained reduced pressure to the locations302,304,306, and308even when the retention pouch116reached a maximum fluid saturation of 50 milliliters near the end of the simulation. Accordingly, the retention of fluid in the reduced-pressure dressing112will not interfere with the application of reduced pressure to a tissue site, such as the tissue site102, or with the operation of the reduced-pressure dressing112.

Provided herein is also a method of manufacturing a dressing for use with reduced pressure to treat a tissue site on a patient. In one illustrative, non-limiting embodiment, a method of manufacturing the reduced-pressure dressing112may include the steps of providing the previously described dressing bolster114. Further, the method may include the step of positioning the previously described retention pouch116proximate to the second side122of the dressing bolster114. Subsequently, the method may include the step of positioning the sealing member118over the dressing bolster114and the retention pouch116. The sealing member118may be adapted as previously described to sealingly engage the epidermis106of a patient that is proximate to the tissue site102. Additionally, the method may include the step of fluidly coupling the reduced-pressure source144to the sealing member118such that the reduced pressure source144is in fluid communication with the dressing bolster114and the retention pouch116.

In another embodiment, the step of positioning the retention pouch116may include the steps of positioning the first permeable layer126proximate to the second side122of the dressing bolster114, providing the absorbent core128, providing the second permeable layer127, and encapsulating the absorbent core128between the first and second permeable layers126,127.

In another embodiment, the method may additionally include the step of forming the recess131on the retention pouch116. The recess131may provide a gap135between the sealing member118and the retention pouch116that is proximate to the sealing member aperture137. The reduced-pressure source144may be in fluid communication with the reduced-pressure dressing112through the sealing member aperture137. Thus, the gap135may be proximate to the coupling of the reduced-pressure source144to the sealing member118. The method may additionally include the step of positioning a filter133in the gap135.

In another embodiment, the method may additionally include the step of fluidly coupling the previously described fluid capacity indicator145to the sealing member118.

In another embodiment, the method may additionally include the step of providing a tactile pressure transducer290associated with the collapsible wall156and operable to provide a signal indicative of contact with the collapsible wall156.

Although this disclosure has been provided in the context of certain illustrative, non-limiting embodiments, various changes, substitutions, permutations, and alterations may be made without departing from the scope of this disclosure as defined by the appended claims. Further, any feature described in connection with any one embodiment may also be applicable to any other embodiment.