Wound dressing with advanced fluid handling

A wound dressing for managing wound fluids includes a porous contact layer for positioning adjacent a wound. An internal open window extends through the contact layer exposing a distal side of an absorbent member. The absorbent member is disposed in a superimposed relation to the window of the contact layer and is dimensioned to extend laterally beyond the window such that a portion of the absorbent member overlaps and is secured to the contact layer. A drape layer is disposed on a proximal side of the absorbent member, and is adhesively coated to fasten the drape layer to the absorbent member. A cover layer disposed over the drape layer defines an internal open window such that the open window is adjacent the absorbent member. A distal side of the cover layer is adhesively coated to secure the cover layer to the contact layer.

BACKGROUND

1. Technical Field

The present disclosure relates generally to wound dressings. In particular, the disclosure relates to a wound dressing adapted for receiving fluids that exude from a wound, and for directing and distributing the fluids within the dressing to promote healing of the wound.

2. Background of Related Art

Various techniques to promote healing of a wound involve covering the wound with a bandage or dressing. The dressing typically provides a barrier that inhibits bacterial migration from the ambient environment into the wound. Some dressings are equipped to absorb or receive “wound exudates,” e.g., the fluid produced by the body that tends to accumulate in a wound. Historically, such dressings have included an absorbent material attached to an adhesive backing layer that provides a margin around the absorbent material. Thus the backing layer may be employed to adhesively seal the dressing to the skin around the wound. In use, these dressings may remain in place to receive and maintain the exudates in the absorbent material for several days. Since wound exudates typically includes water, the exudates maintained may serve to promote a moist wound environment, which may be particularly beneficial for dermal burns, pressure ulcers, incised wounds, or similar ailments.

As a wound dressing receives exudates, the absorbent material may tend to swell and distort the shape of the dressing. This distortion may undermine the effectiveness of the bacterial barrier of the wound dressing by reducing the dressing's ability to adhere to the skin. Additionally the distortion may permit moisture that is drawn away from the wound by the absorbent material to settle in the periwound area, e.g. the area of skin laterally surrounding the wound. Moisture in the periwound area may induce further tissue deterioration.

SUMMARY

The present disclosure describes a wound dressing suitable for managing fluids such as wound exudates. The dressing includes a porous contact layer for positioning adjacent a wound. The porous contact layer defines a distal wound-facing surface, an opposed proximal surface, and an internal open window extending therethrough. An absorbent member is disposed in superimposed relation to the window of the contact layer, and is dimensioned to extend laterally beyond the window such that a portion of the absorbent member overlaps and is secured to the proximal surface of the contact layer. A drape layer is disposed on a proximal side of the absorbent member. A distal side of the drape layer is adhesively coated to fasten the drape layer to the absorbent member. A cover layer defines an internal open window, and is disposed over the drape layer such that the open window is adjacent the absorbent member. A distal side of the cover layer is adhesively coated to secure the cover layer to the contact layer.

At least about 50% of the surface area of a distal side of the absorbent member may be exposed to a distal side of the dressing through the internal open window of the contact layer. In some embodiments, at least about 85% of the surface area of the distal side of the absorbent member is exposed through the internal open window of the contact layer. The absorbent member may define a generally rectangular shape, and the internal open window of the contact layer may define a generally circular or oval shape. The absorbent member may be constructed of an open-celled polyurethane foam.

The contact layer may include a layer of a cross linked, acrylic-based construction adhesive on a proximal side thereof that adherers the absorbent member to the contact layer. The distal side of the drape layer may be adhesively coated with a patterned coating of the construction adhesive.

The porous contact layer may include a plurality of perforations extending therethrough that exhibit a diameter in the range of about 200 to about 1000 microns, and are spaced such that the contact layer exhibits a perforation density in the range of about 50 to about 300 perforations per square inch. The perforations may exhibit a diameter of about 500 microns, and the perforation density of the contact layer may be about 85 microns per square inch. The contact layer may be constructed as a composite including a thin film substrate component that is coated on a distal side with a pressure sensitive, wound-side adhesive component, and coated on a proximal side with a construction adhesive component. The plurality of perforations may extend through each of the component layers of the contact layer.

According to another aspect of the disclosure, a wound dressing includes an absorbent member defining a distal wound-facing surface and an opposed proximal surface. The distal wound facing surface defines a surface area. A porous contact layer defines an internal open window extending therethrough. The porous contact layer includes a thin film membrane having a pressure sensitive, wound-side adhesive on a distal side thereof and a continuous coating of a construction adhesive on a proximal side thereof. The proximal side of the porous contact layer is adhered to the distal wound facing surface of the absorbent member such that at least about 50 percent of the surface area of the distal side of the absorbent member is exposed to a distal side of the wound dressing through the internal open window. A backing layer includes a patterned coating of the construction adhesive on a distal side thereof, and is adhered to the proximal side of the absorbent member by the patterned coating of the construction adhesive.

The patterned coating of the construction adhesive may be in the range of about 0.4 to about 0.6 grams of adhesive per 100 square inches of surface area of the backing layer. The backing layer may be constructed as a composite including a drape layer adhered to the absorbent member by the patterned coating of the construction adhesive on a distal side thereof, and a cover layer defining an internal open window. The cover layer may be adhered to a proximal side of the drape layer by a continuous or patterned coating of the construction adhesive. An outer edge of the cover layer may be coincident with an outer edge of the porous contact layer, and an outer edge of the drape layer may be coincident with an outer edge of the absorbent member.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The attached figures illustrate exemplary embodiments of the present disclosure and are referenced to describe the embodiments depicted therein. Hereinafter, the disclosure will be described in detail by explaining the figures wherein like reference numerals represent like parts throughout the several views.

Referring initially toFIG. 1, a wound dressing10includes a composite contact layer12, an intermediate absorbent member14and a backing layer16. These components12,14,16are superimposed and adhered with one another to form the unitary dressing10. The contact layer12is disposed on a distal or wound-facing side of the dressing10, and is adapted for contact with a patient to secure the dressing10over a wound “W” (seeFIG. 4). The backing layer16is disposed on a proximal, or non-wound facing side of the dressing10, and extends laterally beyond the absorbent member14. As described in greater detail below, the backing layer16may be adhesively coupled to a perimeter of the contact layer12such that the absorbent member14is sandwiched between the attachment and backing layers12,16.

The composite contact layer12is constructed of three distinct component layers including a wound-side adhesive layer20, a membrane or thin film layer22, and a construction adhesive layer24. The wound-side adhesive layer20is suitable for direct contact with a wound or the skin of a patient, and defines a distal surface of the contact layer12. A pressure sensitive, acrylic copolymer adhesive such Gelva® GMS 2495 provided by Cytec Industries of Woodland Park, N.J. may be suitable for use as the wound side-adhesive. Other suitable adhesives for the wound-side adhesive layer20include Gelva® GMS 737, silicone adhesives, and any other commercially available medical adhesives. The film layer22provides a substrate to which the adhesive layers20,24may be adhered. An extensible, 1.0 mm thermoplastic urethane (TPU) film such as the commercially available Vacuflex film 18411 manufactured by OMNIFLEX of Greenfield, Mass. may serve as the film layer22. Any thermoplastic film that can be perforated or otherwise made porous may be suitable for the construction of the film layer22. The construction adhesive layer24defines a proximal surface of the contact layer12and may be constructed of a continuous coating of an acrylic copolymer adhesive such Gelva® GMS 3101-03 provided Cytec Industries.

The three component layers20,22and24of the composite contact layer12are coextensive in that each of the component layers20,22and24share an outer lateral edge “E1” and an inner lateral edge “E2”. Laterally within the inner edge “E2”, the contact layer12defines an internal open distal window such as fluid access opening30extending through the contact layer12. The fluid access opening30is central to the contact layer12, as well as central to the dressing10. The shape of the central fluid access opening30may be generally round or oval as depicted, although alternative configurations and shapes, e.g., rectangular, may also be suitable.

A distal side of the absorbent member14is superimposed with and secured to the contact layer12by the construction adhesive layer24at a laterally interior portion “I” of the dressing10. The interior portion “I” circumscribes the fluid access opening30, and defines a boundary “B” that is coincident with an outer lateral edge “E3” of the absorbent member14. Thus, the location of the boundary “B” and the size of the interior portion “I” are both defined by the lateral extent of the absorbent member14. Only a fraction of the surface area of the distal side of the absorbent member14overlaps the construction adhesive layer24. For example, about 50% or less of the surface area may overlap the construction adhesive layer24such that 50% or more surface area of the distal side of the absorbent member14is exposed to a distal side of the dressing through the fluid access opening30. In some embodiments, about 15% of the surface area overlaps, while about 85% of the surface area of the distal side of the absorbent member14is exposed through the fluid access opening30. The portion of the absorbent member14exposed through the fluid access opening30is substantially devoid of any adhesive.

The absorbent member14is intended to allow wound dressing12to absorb, capture, or transport wound exudates, and may be constructed of materials such as non-woven gauze, reticulated foam, or alginate fibers. In one embodiment, the absorbent member14may include a generally rectangular pad of Covidien™ AMD Antimicrobial Foam dressing. The Covidien™ AMD Foam dressing is polyurethane-based foam including the antiseptic agent polyhexamethylene biguanide (PHMB). A microstructured open-celled surface on the foam pad promotes absorption of exudates, and the added PHMB attacks bacteria on and within the dressing10. The generally rectangular shape of the absorbent member14facilitates adhesion of the absorbent member to the contact layer12when the fluid access opening30defines a generally circular or oval shape.

A distal side of the backing layer16is coupled to the absorbent member14, and is also coupled to a perimeter region “P” of the dressing10by the construction adhesive layer24. The perimeter region “P” extends laterally between the boundary “B” and the outer edge “E1” of the contact layer12. An outer edge “E4” of the backing layer16may be coincident with the outer edge “E1” of the contact layer12. The backing layer16may be constructed of a moisture vapor permeable membrane to promote the exchange of oxygen and moisture between the wound “W” and the ambient atmosphere. Membranes that provide a sufficient moisture vapor transmission rate (MVTR) include the transparent membranes sold under the trade names NOVOTEX AB5454, and also POLYSKIN®II by Tyco Healthcare Group LP (d/b/a Covidien), for example. A thin, tinted urethane film that promotes moisture vapor transmission therethrough may also be suitable for use as the backing layer16. Higher rates of moisture vapor transmission between have been demonstrated to generally promote wound healing.

Referring now toFIG. 2, the contact layer12is porous to permit the transmission of wound fluids and moisture vapor therethrough. The contact layer12includes a plurality of perforations32extending through each of the component layers20,22and24. In the embodiment depicted inFIG. 2, the perforations32provide the porosity to the contact layer32. Other embodiments are contemplated in which other structures such as a non-woven web or fabric (not shown) provides the porosity to the contact layer32, and any type of porous membrane may also be suitable. The perforations32are generally circular in shape, and have a diameter in the range of about 200 to about 1000 microns. The perforations are spaced such that the contact layer12exhibits a perforation density in the range of about 50 to about 300 perforations32per square inch. In some embodiments, the perforations32exhibit a diameter of about 500 microns, and the perforation density of the contact layer12is about 85 microns per square inch. The perforations32permit transmission of wound exudates through the contact layer12, and promote moisture vapor transmission through the dressing10, particularly at the perimeter region “P” (FIG. 1) of the dressing10.

Referring now toFIG. 3, the distal side of the backing layer16includes a patterned adhesive coating38disposed thereon. The adhesive coating38may be constructed of the same adhesive as the construction adhesive layer24, e.g. the acrylic based Gelva® GMS 3101-03 adhesive discussed above. The patterned adhesive coating38is applied such that adhesive free areas40of the backing layer16form stretched or elongated diamond shapes. Alternatively, generally round, square or any other shape or pattern (not shown) of adhesive free areas on the backing layer16may be employed. The adhesive free areas40promote breathability and moisture vapor transmission through the backing layer16. The adhesive coating38is relatively light, e.g. in the range of about 0.4 to about 0.6 grams of adhesive per 100 square inches of surface area. The light adhesive coating facilitates a controlled detachment of the backing layer16from the absorbent member14as described below with reference toFIG. 5.

When the wound dressing10is assembled, the continuous construction adhesive layer24and the patterned adhesive coating38adhere the various layers12,14,16of the wound dressing10to one another. The shear strength of the adhesive bond generated between the layers12,14and16may be enhanced by subjecting the dressing10to a radiation sterilization procedure such as electron beam, X-ray or gamma radiation. The acrylic based construction adhesive cross links when exposed to radiation, and thus the shear strength is enhanced. The shear strength of the adhesive bond generated generally increases with radiation dosage. The enhanced shear strength enables the adhesive to become more resistant to de-bonding forces applied in a lateral direction. Lateral de-bonding forces may be generated by swelling of the absorbent member14as exudates are absorbed as discussed below with reference toFIG. 5. As discussed below, the enhanced shear strength of the construction adhesive discourages swelling of the absorbent member14in the lateral direction and promotes swelling of the absorbent member12in a vertical direction.

Referring now toFIG. 4, the wound dressing10is depicted in an initial configuration as applied over a wound “W” prior to the receipt of wound exudates into the absorbent member14. The wound-side adhesive layer20of the composite contact layer12adheres the dressing10to the skin “S”. A portion of the composite contact layer12may extend laterally into the wound “W” as depicted, or alternatively, the fluid access opening30may be dimensioned to circumscribe the entire wound “W”. The continuously coated construction adhesive layer24forms a sturdy bond between the backing layer16and the contact layer12. The absorbent member14is laterally constrained within the interior region “I” of the dressing10by the bond generated between the backing layer16and the contact layer12in the perimeter region “P”. The patterned coating38(FIG. 3) on the distal, wound-facing side of the backing layer16maintains the absorbent member14in intimate contact with the backing layer16.

In the initial configuration, a void44may be established between the absorbent member14and the wound “W”. The void44provides an area into which the absorbent absorbent member14may swell as exudates are absorbed. Unconstrained, the absorbent member14may have a tendency to swell uniformly in every direction. However, as assembled in the wound dressing10, the swelling of the absorbent member14is constrained by the backing layer16and the contact layer12. The fluid access opening30permits the absorbent member14to migrate or swell unobstructed, primarily in a vertical direction into the void44.

Referring now toFIG. 5, the wound dressing10is depicted in a second configuration wherein wound exudates have been received into the absorbent member14. As the wound “W” produces exudates, the exudates are directed through the perforations32in the contact layer12, and/or are directly received into the absorbent member14. As indicated by arrows “A”, the exudates move into a central area of the dressing10as the absorbent member14swells. The absorbent member14swells primarily in a vertical direction, and moves into the area previously occupied by the void44(FIG. 4). The swelling occurs primarily in the vertical direction since the force required for swelling in any other constrained direction is significantly greater than the force required for swelling in the unconstrained direction through the fluid access opening30. The swelling draws the absorbent member14into intimate contact with the wound “W”, and thus, maintains the wound “W” in a moist condition.

The absorbent member14also swells in a lateral direction as indicated by arrows “B”. The lateral swelling stretches the absorbent member14laterally outward, which generates a buckling force in the absorbent member14. The bucking force induces the central regions of the absorbent member14to move in the vertical direction, and assists in the movement of the absorbent member14through the fluid access opening30. This swelling of the absorbent member14draws backing layer16toward the wound “W”. A dimple or depression forms in backing layer16that begins in the central region of the dressing10and expands laterally outward as the absorbent member14becomes saturated with exudates. The patterned adhesive coating38(FIG. 3) is sufficiently light to permit separation of backing layer16from the absorbent member14such that a proximal reservoir48develops in the dressing10. The proximal reservoir48provides a space into additional vertical swelling may occur, or into which exudates may flow. Thus, the configuration of the dressing10permits the dressing10to remain attached to the skin even after the absorbent member14is saturated.

Exudates in the proximal reservoir48exchange moisture vapor through the backing layer16at a higher rate than the portions of a moist pad layer attached to the backing layer16. Also, since the proximal reservoir48may freely receive exudates when the absorbent member14is saturated, the proximal reservoir48discourages pooling of the exudates at the periwoud area, which might otherwise cause further tissue deterioration and undermine the adhesive bond of the contact layer12with the skin “S”. Thus, the configuration of the dressing10promotes healing of the wound “W”.

Referring now toFIG. 6, an alternate embodiment of a dressing50includes the composite contact layer12and the intermediate absorbent member14as described above with reference toFIGS. 1 through 6, and also includes a composite backing layer52. The composite backing layer52is constructed of two distinct component layers including a drape layer56and a proximal cover layer58. Both the drape layer56and the cover layer58may be constructed of a thin film substrate and a patterned adhesive coating38in the manner of the backing layer16described above. Alternatively, the cover layer58may include a continuous coating of the construction adhesive.

The drape layer56adheres to the absorbent member14such that an outer edge “E5” of the drape layer56is coincident with the outer edge “E3” of the absorbent member14. Alternatively, the drape layer56may extend laterally beyond the outer edge “E3” of the absorbent member14. The cover layer58adheres to the drape layer56and to the contact layer12. An outer edge “E6” of the cover layer58is coincident with the outer edge “E1” of the composite contact layer12, and an inner edge “E7” of the cover layer58is disposed laterally inward with respect to the outer edge “E5” of the drape layer56. An internal proximal window60is defined in the cover layer58such that the proximal window60is disposed adjacent the absorbent member14when the dressing50is assembled.

The composite backing layer52provides rigidity to a lateral perimeter of the dressing50, and thus, may prohibit lateral swelling of the absorbent member14. The rigidity at the lateral perimeter also aids in maintaining the integrity of the dressing50as the absorbent member becomes saturated, and facilitates application of the dressing50.

Although the foregoing disclosure has been described in some detail by way of illustration and example, for purposes of clarity or understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.