WO2015130608A1

WO2015130608A1 - Medical dressing

Info

Publication number: WO2015130608A1
Application number: PCT/US2015/017089
Authority: WO
Inventors: Dean M. Remer; Deena M. CONRAD-VLASAK; Joseph P. Hensler; Richard L. Jacobson; Donald G. Peterson
Original assignee: 3M Innovative Properties Company
Priority date: 2014-02-25
Filing date: 2015-02-23
Publication date: 2015-09-03

Abstract

A medical dressing including a support material layer, a backing layer, and an adhesive. The adhesive forms a window. The backing layer extends over the window and is spatially affixed to the adhesive along an attachment region that surrounds, but is spatially offset from, an edge of the window. When used to cover an object on a patient's skin, the object bears against the backing layer and generates a lifting force onto the adhesive in a direction opposite the patient's skin. The off-set attachment region interior border dissipates the lifting force, transferring it to the adhesive as a shear-type force. The adhesive readily resists the shear-type force, providing the medical dressing with an elevated wear life.

Description

MEDICAL DRESSING

Background

The present disclosure relates to medical dressings. More particularly, it relates to medical dressings useful for covering and protecting a ported access site.

Transparent film dressings are widely used as protective layers over wounds because they facilitate healing in a moist environment while acting as a barrier to contaminating liquids and bacteria. The films are also used as surgical drapes because of their barrier properties. Dressings and drapes fitting the above description are available under a number of trade names such as TEGADERM™ (3M Company, St. Paul, MN) and OP-SITE™ (Smith & Nephew, Hull, England).

The polymeric films used in those dressings and drapes are conformable, i.e., the films are thin, flexible and supple. With medical dressing applications, an adhesive is coated onto or over a face of the film. The medical dressing is further typically supplied with a removable protective liner covering the adhesive coated surface of the film. When the liner is removed, the adhesive coated film tends to wrinkle and adhere to itself, interfering with the smooth, aseptic application of the dressing to a patient's skin. Various delivery systems have been proposed to address this problem such as those disclosed in U.S. Patent No. 6,685,682. The use of a removable carrier, which does not require tearing of the film after it has been placed on the patient, avoids the problems described above. The carrier also aids in accurate placement of the dressing on a patient.

Thin polymeric films that are flexible and resilient are beneficial when used on skin that flexes, stretches, and retracts. However, for some applications, such as securing devices such as tubing, ports, and catheters or other medical devices to a ported access installed to the patient, the high flexibility and resiliency of the thin polymeric film can cause too much movement of the secured medical device. Therefore, medical dressings have been developed that further incorporate areas having secured to the thin polymeric film, stiffer, less conformable materials such as adhesives, films, or fabrics. For example, U.S. Patent No. 5,088,483 discloses an adhesive composite that includes a conformable backing and a permanent adhesive reinforcement around the periphery of the adhesive composite. One example of a commercially available medical dressing with a reinforcement layer is TEGADERM™ IV Advanced Dressing (3M Company, St. Paul MN).

With ported access applications, the medical dressing thus not only protects the ported access site, but assists in securing the medical device relative to the patient. Users have expressed a strong preference for the medical dressing to provide an adhesive-free region that is placed in contact with the medical device (along with an adhesive border that adheres to the patient's skin). This allows for easier removal of the dressing while reducing the risk of medical device dislodgement or accidental injuries.

In some instances, ported access medical dressings are applied to a patient and remain in place for several days. When worn over time, the edge of the medical dressing can begin to lift or peel away from the patient, possibly resulting in contamination at the site or complete adhesive failure. In this regard, the ported access environment presents unique circumstances adverse to the useful wear time of the medical dressing. The medical dressing must accommodate a profile of the underlying medical device, and is thus tented over the medical device (e.g., a central portion of the medical dressing is displaced away from the patient's skin by the medical device). In other words, due to the presence of the medical device, the medical dressing cannot lay flat against the patient's skin, but instead a central portion of the medical dressing's film is forced or lifted away from the patient's skin. This tented condition generates a lifting force at the adhesive/skin interface, tending to pull the adhesive border away from the patient's skin.

In light of the above, a need exists for a medical dressing that will remain strongly secured to skin when applied over a medical device such as at a ported access site.

Summary

Some aspects of the present disclosure are directed toward a medical dressing including medical dressing structure having a support material layer, a backing layer, and an outer adhesive layer. The medical dressing structure defines opposing first and second major faces and a thickness direction. The backing layer is arranged over the support material layer. The outer adhesive layer defines the second major face. A window is formed in a thickness of the outer adhesive layer, defined by a window edge. The backing layer extends over the window and is spatially affixed relative to the outer adhesive layer at an attachment region terminating at an interior border that spatially surrounds the window edge. At least a portion of the interior border is spatially offset from the window edge such that a line extending at the portion and parallel with the thickness direction passes through the thickness of the outer adhesive layer. With this construction, when the medical dressing is used to cover an object located on the patient's skin (e.g., a ported access site), the object bears against the backing layer and ultimately generates a lifting force onto the outer adhesive layer in a direction opposite the patient's skin. By offsetting the attachment region interior border from the window edge, the lifting force is dissipated over a relatively large surface area, and exerts a shear-type force (as opposed to only a peel-type force) onto the outer adhesive layer at the adhesive/patient's skin interface. The outer adhesive layer readily resists the shear-type force, such that the medical dressing has an elevated wear life. In some embodiments, the attachment region interior border is spaced from an interior margin of the support material layer, such as when the interior margin is contiguous with the window edge or is spaced from the window edge. In other embodiments, the backing layer is a thin film and the support material layer is a nonwoven fabric. In yet other embodiments, the medical dressing is free of adhesive in the window.

Brief Description of the Drawings

FIG. 1A is a simplified bottom view of a medical dressing in accordance with principles of the present disclosure; FIG. IB is a cross-sectional view of the medical dressing of FIG. 1A, taken along the line IB-IB;

FIG. 1C is a simplified, exploded view of the medical dressing of FIG. 1A;

FIG. 2A is a front view of a support material layer component of the medical dressing of FIG.

1A;

FIG. 2B is a cross-sectional view of the support material layer of FIG. 2A, taken along the line

2B-2B;

FIG. 3A is a simplified bottom view of the medical dressing of FIG. 1A and illustrates a an attachment region;

FIG. 3B is a simplified, cross-sectional view of FIG. 3 A;

FIG. 4 is a bottom view of another medical dressing in accordance with principles of the present disclosure, schematically illustrating a relationship between an adhesive component and a bond region;

FIG. 5A is a simplified, cross-sectional view illustrating application of the medical dressing of FIG. 1 A to a patient's skin;

FIG. 5B is a simplified, cross-sectional view of the medical dressing of FIG. 1A applied to a patient's skin and over an object at the patient's skin;

FIG. 5C is a simplified, cross-sectional view of a prior medical dressing applied to a patient's skin and over an object at the patient's skin;

FIG. 6 is a simplified, cross-sectional view of another medical dressing in accordance with principles of the present disclosure;

FIG. 7 is a simplified, cross-sectional view of another medical dressing in accordance with principles of the present disclosure;

FIG. 8 is a simplified bottom view of another medical dressing in accordance with principles of the present disclosure; and

FIG. 9 is a simplified, cross-sectional view of another medical dressing in accordance with principles of the present disclosure.

Detailed Description

One embodiment of a medical dressing 20 in accordance with principles of the present disclosure is shown in FIGS. 1A-1C. The medical dressing 20 includes a dressing structure 22 defining opposing first and second major faces 24, 26. The dressing structure 22 includes a support material layer 30, a backing layer 32, and an outer adhesive layer 34. Details on the various components are provided below. In general terms, however, a window 36 is formed or defined in the outer adhesive layer 34. The support material layer 30 forms an opening 37 that can be commensurate with the window 36 (as in the non- limiting example of FIGS. 1A-1C and thus identified in FIG. 1A). The backing layer 32 extends over the window 36 (and the opening 37) and is thus visible in the rear view of FIG. 1A (otherwise depicting the second major face 26). The backing layer 32 is spatially affixed relative to the outer adhesive layer 34, for example by the backing layer 32 being secured to the support material layer 30 and the outer adhesive layer 34 being secure to the support material layer 30. An optional intermediate adhesive 38 can be employed to secure the support material layer 30 with the backing layer 32. Regardless, the backing layer 32 is not directly spatially affixed relative to the outer adhesive layer 34 (e.g., is not directly secured to the support material layer 30) in a region immediately surrounding the window 36. Stated otherwise, at the region immediately surrounding the window 36, the backing layer 32 is freely movable relative to the outer adhesive layer 34. At the region immediately surrounding the window 36, the backing layer 32 is spatially disconnected from the outer adhesive layer 34. The outer adhesive layer 34 is disposed over the support material layer 30 in some embodiments, defining the second major face 26 that is otherwise intended to be applied to a patient's skin. Alternatively, the arrangement of FIGS. 1A-1C can be reversed, with the outer adhesive 34 layer disposed over the backing layer 32 (opposite the support material layer 30). When applied over an object present on the patient's skin such as at a ported access site (e.g., to cover the site of an inserted needle, intravenous catheter or other medical device), the backing layer 32 will generally conform to and tent over the medical device in a region of the window 36, with spatial fixation of the backing layer 32 relative to the outer adhesive layer 34 (e.g., via bonding of the backing layer 32 to the support material layer 30) shifting the forces generated by the tented arrangement across a relatively large area of the outer adhesive layer 34. The backing layer 32 can be transparent or substantially transparent (e.g., 90% or greater transmission of visible light), affording a user the ability to see the underlying object (e.g., the patient's skin, port access, medical device coupled to the port access, etc.) through the window 36.

The stacked arrangement of the layers 30-34 establishes a thickness or thickness direction T for the dressing structure 22 (i.e., a distance or direction between the opposing major faces 24, 26). Features of the layers 30-34 relative to one another in space can be described with reference to the thickness direction T below. For purposes of this disclosure, when the dressing structure 22 is laid flat (on either of the major faces 24, 26), the major faces 24, 26 are substantially planar (e.g., with 10% of a truly planar arrangement) and substantially parallel to one another (e.g., within 10% of a truly parallel relationship), and the thickness direction T is substantially perpendicular (e.g., within 10% of a truly perpendicular relationship) to the planes of the first and second major faces 24, 26. Support Material Layer 30

As a point of reference, with embodiments in which the outer adhesive layer 34 is applied over an entirety of a major surface of the support material layer 30, geometries of the outer adhesive layer 34, including the window 36, can be dictated by geometries of the support material layer 30, including the opening 37. Thus, the following descriptions of the opening 37 geometries can be equally applicable to the window 36 in some embodiments. For ease of explanation, the support material layer 30 is shown in isolation in FIGS. 2A and 2B, it being understood that the surfaces and other features of the support material layer 30 are equally applicable to the support material layer 30 when provided as part of the medical dressing 20. The support material layer 30 provides strength to the medical dressing 20, and forms or defines opposing first and second major surfaces 40, 42 and an outer margin or perimeter 44. The support material layer 30 has a thickness between the opposing major surfaces 40, 42, with the opening 37 being formed entirely through the thickness. Thus, the opening 37 is open to or at both of the major surfaces 40, 42. An overall footprint or size and shape of the support material layer 30 is defined by the outer margin 44. In this regard, while the support material layer 30 is shown has having a generally square or rectangular shape, a wide variety of other shapes are equally applicable, such as circular, oval, or more complex shapes. With the one exemplary embodiment shown, the outer margin 44 can be described as being defined by four outer margin sections 44a-44d, it being understood that in other embodiments, the outer margin 44 can have a greater or lesser number of discernible edge sections, and one or more of the margin sections 44a-44d can be linear, curved, or have a complex shape.

In some embodiments, the opening 37 is sized and shaped for placement over a medical device sometimes used with ported access procedures, and thus can have a variety of shapes and sizes that may or may not differ from the shapes implicated by the FIGURES. Typically the opening 37 is off-set from the outer margin 44 and can optionally be generally centrally located relative to a footprint or shape of the support material layer 30. Regardless, a perimeter of the opening 37 is defined or circumscribed by an interior margin 50, with an entirety of the interior margin 50 being interiorly spaced from, or relative to, the outer margin 44 in some embodiments. In other embodiments, the opening 37 can extend to, or be open relative to, the outer margin 44. The interior margin 50 can have a simple or complex shape, and in some embodiments generally mimics a shape of the outer margin 44. For example, with the one exemplary embodiment shown, the interior margin 50 is defined by four interior margin sections 50a-50d that generally correspond with respective ones of the outer margin sections 44a-44d. The interior margin sections 50a-50d may or may not be generally identical in shape to the corresponding outer margin sections 44a-44d. Regardless, each of the interior margin sections 50a-50d is interiorly spaced from the corresponding outer margin section 44a-44d, with an available surface area of the support material layer 30 at both of the major surfaces 40, 42 being generated between the outer margin 44 and the interior margin 50.

In some embodiments, the support material layer 30 can incorporate or form one or more features that facilitate use at a ported access site. For example, one or more notches 52 can be formed through the thickness of the support material layer 30, extending inwardly from the outer margin 44. Where provided, the notch(es) 52 are sized and shaped to generally receive a medical device sometimes employed with ported access procedures, and can vary from the sizes and shapes implicated by the figures. In other embodiments, the notch(es) 52 can be omitted. In yet other embodiments, slits (not shown) can be formed in the support material layer 30, for example as described in US Patent Application Serial No. 61/775,805, filed March 1 1, 2013 and entitled "A Conformable Medical Dressing" (attorney docket number 71520US002), the entire teachings of which are incorporated herein by reference.

In some embodiments, the support material layer 30 has more stiffness and less elasticity than the backing layer 32 (FIG. 1 A). The support material layer 30 may be a coating, such as an adhesive, or may be a self-supporting substrate such as another film, foam, woven, knitted, or nonwoven fabric. For example, US Patent No. 5,088,483 discloses a permanent adhesive as a reinforcement that could be used as the support material layer 30.

One example of nonwoven useful as the support material layer 30 is a high strength nonwoven fabric available from E. I. Dupont de Nemours & Company of Wilmington, Delaware under the trademark Sontara, including Sontara 8010, a hydroengangled polyester fabric. Other suitable nonwoven webs include a hydroentangled polyester fabric available from Veratec, a division of International Paper of Walpole, Mass. Another suitable nonwoven web is the nonwoven elastomeric web described in U.S. Patent No. 5,230,701, herein incorporated by reference in its entirety. Backing Layer 32

Returning to FIGS. 1A-1C, the backing layer 32 is sized and shaped in accordance with a size and shape of at least the opening 37, and in some embodiments in accordance with a perimeter size and shape of the support material layer 30 (e.g., so as to extend over an entirety of the first major surface 40 of the support material layer 30). Regardless, the backing layer 32 can be constructed to be elastic and provide an impermeable barrier to the passage of liquids and at least some gases. Being elastic allows for the backing layer 32 to expand, contract, stretch and recover as the underlying substrate (e.g., the patient's skin) moves.

Elasticity can be measured in any number of commonly used means for evaluating stretch and recovery of a material. In one embodiment, the backing layer 32 (independent of the support material layer 30) has an elongation to break of at least 200%. In one embodiment, the backing layer 32 (independent of the support material layer 30) has an elongation to break of less than 500%. In one embodiment, the support material layer 30 (independent of the backing layer 32) has an elongation to break of at least 20%. In one embodiment, the support material layer 30 (independent of the backing layer 32) has an elongation to break of at least 100%, alternatively at least 200%. By way of comparison, in one embodiment the support material layer 30 has an elongation to break less than 500%, alternatively less than 200%.

Elasticity can be measured by an initial modulus of elasticity, which is the force require to apply a specified amount of stretch. In one embodiment, the backing layer 32 has a modulus, at 10% elongation, of less than 2 Newtons. In one embodiment, the backing layer 32 has a modulus, at 10% elongation, of less than 1.5 Newtons. Representative barrier materials useful as the backing layer 32 include nonwoven and woven fibrous webs, knits, films, foams, polymeric films and other familiar backing materials. In some embodiments, the backing layer 32 is a transparent substrate (e.g., a transparent film) to allow for viewing (through the window 36) of the underlying skin or medical device.

In one embodiment, the backing layer 32 has high moisture vapor permeability, but generally impermeable to liquid water so that microbes and other contaminants are sealed out from the area under the substrate. One example of a suitable material is a high moisture vapor permeable film such as described in U.S. Patent Nos. 3,645,835 and 4,595,001, the disclosures of which are herein incorporated by reference. In high moisture vapor permeable film/adhesive composites, the composite should transmit moisture vapor at a rate equal to or greater than human skin such as, for example, at a rate of at least 300 g/m² 124 hrs at 37°C/100-10% RH, or at least 700 g/m² 124 hrs at 37°C/100- 10% RH, or at least 2000 g/m² /24 hrs at 37°C/100-10% RH using the inverted cup method as described in U.S. Patent No. 4,595,001. Perforated substrates or films or pattern coated adhesives may be used to increase the moisture vapor transmission. In one embodiment, the backing layer 32 is an elastomeric polyurethane, polyester, or polyether block amide films. These films combine the desirable properties of resiliency, elasticity, high moisture vapor permeability, and transparency. A description of this characteristic of backing layers can be found in issued U.S. Patent Nos. 5,088,483 and 5,160,315, the teachings of which are hereby incorporated by reference.

Commercially available examples of potentially suitable backing layer materials may include the thin polymeric film backings sold under the trade names TEGADERM (3M Company), OPSITE (Smith & Nephew), etc. Many other materials can be employed as the backing layer 32, including those commonly used in the manufacture of surgical incise drapes (e.g., incise drapes manufactured by 3M Company under the trade names STERIDRAPE and IOBAN), etc.

Because fluids may be actively removed from the sealed environments defined by the medical dressings of the present disclosure, a relatively high moisture vapor permeable backing may not be required. As a result, some other materials potentially useful as the backing layer 32 may include, e.g., metallocene polyolefins and SBS and SIS block copolymer materials.

Regardless, however, it may be desirable that the backing layer 32 be kept relatively thin to, e.g., improve conformability. For example, the backing layer 32 may be formed of polymeric films with a thickness of 200 micrometers or less, or 100 micrometers or less, potentially 50 micrometers or less, or even 25 micrometers or less.

Outer Adhesive Layer 34

The outer adhesive layer 34 is disposed over (e.g., applied to) the second major surface 42 of the support material layer 30 in some embodiments. In some embodiments, the outer adhesive layer 34 covers (e.g., full coverage or pattern coated) an entirety of the second major surface 42 of the support material layer 30, although in other embodiments less than an entirety of the second major surface 42 of the support material layer 30 is encompassed by the outer adhesive layer 34. With the configuration of FIGS. 1A-1C, the outer adhesive layer 34 (that is otherwise disposed over the second major surface 42) is not applied to the "exposed" portion of the backing layer 32 at the opening 37. With this construction, the medical dressing 20 can be referred to as having or providing an "adhesive free window" (meaning that second major face 26 is free of the outer adhesive layer 34 in the area of the window 36). For ease of explanation, the outer adhesive layer 34 can be described as defining or terminating at an outer edge 60. Further, a perimeter of the window 36 is defined or circumscribed by a window edge 62. Relative the second major surface 42 of the support material layer 30, the outer adhesive layer 34 extends to, or in close proximity to, the outer margin 44 and the interior margin 50. In the embodiment shown, the outer edge 60 is contiguous with the outer margin 44 of the support material layer 30, and the window edge 62 is contiguous with the interior margin 50. Consistent with the above descriptions of the support material layer 30, then, the outer edge 60 can thus be viewed as defining outer edge segments 60a-60d and the window edge 62 as defining window edge segments 62a-62d in some embodiments. In other embodiments, the outer adhesive layer 34 can be formatted such that the outer edge 60 is spaced from the outer margin 44 (in a direction of the interior margin 50) and/or such that the window edge 62 is spaced from the interior margin 50 (in a direction of the outer margin 44). In other embodiments, the arrangement of FIGS. 1A- 1C is reversed and the outer adhesive layer 34 is disposed over a major face of the backing layer 32 opposite the support material layer 30 (so as to define the second major face 26 of the dressing structure 22) as described below.

The outer adhesive layer 34 can assume a wide variety of forms useful for temporarily securing the medical dressing 20 to skin. Suitable adhesive for use in medical dressings include any adhesive that provides acceptable adhesion to skin and is acceptable for use on skin (e.g., the adhesive should preferably be non-irritating and non-sensitizing). Suitable adhesives are pressure sensitive and in certain embodiments have a relatively high moisture vapor transmission rate to allow for moisture evaporation. Suitable pressure sensitive adhesives include those based on acrylates, urethane, hyrdogels, hydrocolloids, block copolymers, silicones, rubber based adhesives (including natural rubber, polyisoprene, polyisobutylene, butyl rubber etc.) as well as combinations of these adhesives. The adhesive component may contain tackifiers, plasticizers, rheology modifiers as well as active components including for example an antimicrobial agent.

The pressure sensitive adhesives that may be used in or as the outer adhesive layer 34 may include adhesives that are typically applied to the skin such as the acrylate copolymers described in U.S. Patent No. RE 24,906, particularly a 97:3 isooctyl acrylate :acrylamide copolymer. Another example may include a 70: 15: 15 isooctyl acrylate: ethyleneoxide acrylate: acrylic acid terpolymer, as described in U.S. Patent No. 4,737,410 (Example 31). Other potentially useful adhesives are described in U.S. Patent Nos. 3,389,827; 4,1 12,213; 4,310,509; and 4,323,557. Inclusion of medicaments or antimicrobial agents in the adhesive 34 is also contemplated, as described in U.S. Patent Nos. 4,310,509 and 4,323,557.

Silicone adhesive can also be used as the outer adhesive layer 34. Generally, silicone adhesives can provide suitable adhesion to skin while gently removing from skin. Suitable silicone adhesives are disclosed in PCT Publications WO2010/056541 and WO2010/056543, the teachings of which are herein incorporated by reference in their entireties.

The pressure sensitive adhesives useful as the outer adhesive layer 34 may, in some embodiments, transmit moisture vapor at a rate greater to or equal to that of human skin. While such a characteristic can be achieved through the selection of an appropriate adhesive, it is also contemplated that other methods of achieving a high relative rate of moisture vapor transmission may be used, such as pattern coating the adhesive on the backing, as described in U.S. Patent No. 4,595,001. Other potentially suitable pressure sensitive adhesives may include blown-micro-fiber (BMF) adhesives such as, for example, those described in U.S. Patent No. 6,994,904. The pressure sensitive adhesive used in the medical dressing may also include one or more areas in which the adhesive itself includes structures such as, e.g., the microreplicated structures described in U.S. Patent No. 6,893,655.

In some embodiments, different adhesives can be discretely applied along the second major face 26, such as disclosed in U.S. Patent Application Serial No. 61/664,246 filed June 26, 2012 and entitled "Medical Dressing with Multiple Adhesives." For example, a portion may include an acrylate adhesive while another portion may include a silicone adhesive. In one embodiment, to prevent edge separation, adjacent the outer margin 44 is acrylate adhesive, while near the interior margin 50 there is silicone adhesive. In one embodiment, to strongly secure with a device or tubing near the interior margin 50 there is acrylate adhesive, while near the outer margin 44 in contact with skin is silicone adhesive.

With alternative embodiments in which adhesive is applied to the backing layer 32 in a region of the opening 37, it may be desirable for the composite backing layer 32/adhesive to be permeable, including the backing layer 32 being provided as a film. U.S. Patent Nos. 3,645,835 and 4,595,001, the disclosures of which are hereby incorporated by reference, describe methods of making such composites and methods for testing their permeability. Preferably, the film/adhesive composite should transmit moisture vapor at a rate equal to or greater than human skin. Preferably, the adhesive coated film transmits moisture vapor at a rate of at least 300 g/m²/24 hrs/37 C/100-10% RH, more preferably at least 700 g/m²/24 hrs/37 C/100-10% RH, and most preferably at least 2000 g/m²/24 hrs/37 C/100- 10% RH using the inverted cup method as described in U.S. Patent No. 4,595,001.

Support Material Layer 30 - Backing Layer 32 Securement

In general terms, medical dressings of the present disclosure can be made by conventional techniques (e.g., extrusion, solvent casting, calendaring, laminating, adhesive coating, and the like) that are familiar to those skilled in the art. U.S. Patent No. 6,685,682, the entire teachings of which are incorporated herein by reference, discloses constructions and methods for making medical dressings with backing layers and support material layers.

Regardless of the exact manufacturing methodology employed, in one embodiment the backing layer 32 is secured to the support material layer 30, and in particular is bonded to the first major surface 40 of the support material layer 30. In this regard, the backing layer 32 can be secured or bonded to the support material layer 30 through adhesive, thermal bonding, lamination, or other commonly used securement techniques. The embodiment of FIGS. 1A-1C generally illustrates use of the intermediate adhesive 38 (a thickness of which is exaggerated for ease of understanding). With other securement or bonding techniques (e.g., heat lamination, ultrasonic welding, etc.), however, an additional material (otherwise bonding the support material layer 30 to the backing layer 32) is not necessary or present. With embodiments in which the intermediate adhesive 38 is employed, any of the adhesive compositions described above for the outer adhesive layer 34 are equally useful as the intermediate adhesive 38 (e.g., an acrylic adhesive) or any other biologically-safe adhesive selected to effectuate a robust bond with the materials of the support material layer 30 and the backing layer 32.

As mentioned above, in some embodiments the support material layer 30 and the backing layer

32 optionally have a substantially identical perimeter size and shape (e.g., within 10 percent of an identical size and shape), such that the backing layer 32 overlies a substantial entirety of the support material layer 30. In other embodiments, the backing layer 32 is smaller than the support material layer 30 (or vice-versa). Regardless, the backing layer 32 is arranged so as to extend over or across the opening 37 in the support material layer 30 (and thus across the window 36), with portions of the backing layer 32 directly over the support material layer 30 being bonded to the first major surface 40. This bonding, in turn, spatially affixes the backing layer 32 relative to the outer adhesive layer 34 (due to the outer adhesive layer 34 being bonded to the second major surface 42 of the support material layer 30). The backing layer 32 is not directly bonded to the support material layer 30 at the opening 37 (as a structure of the support material layer 30 does not exist at the opening 37). In addition, the backing layer 32 is not directly spatially affixed relative to the outer adhesive layer 34 (via the support material layer 30) immediately adjacent the window edge 62.

To better illustrate a relationship between bonding of the support material layer 30 and the backing layer 32 with the spatial affixment of the backing layer 32 relative to the outer adhesive layer 34 in accordance with principles of the present disclosure, FIG. 3A is a bottom view of the medical dressing 20, with an attachment region 80 between the support material layer 30 (FIG. 1C) and backing layer 32 shown with stippling. The attachment region 80 represents the area at which the backing layer 32 overlies the support material layer 30 and is directly bonded thereto (e.g., by, for example, the intermediate adhesive 38 (FIG. IB), lamination, heat seal, etc.), and thus the area where the backing layer 32 is spatially affixed relative to the outer adhesive layer 34. As a point of reference, with the non- limiting embodiment of FIG. 3A, the outer adhesive layer 34 covers an entirety of the support material layer 30; however because the outer edge 60 of the outer adhesive layer 34 is contiguous with the outer margin 44 of the support material layer 30 and the window edge 62 is contiguous with the interior margin 50, the outer and interior margins 44, 50 can be identified in the view of FIG. 3A. The attachment region 80 is continuous and can extend to, or nearly to, the outer margin 44 of the support material layer 30 with embodiments in which the support material layer 30 and the backing layer 32 are of identical, or nearly identical, perimeter size and shape. In other embodiments, an outer border of the attachment region 80 can be spaced from a portion or entirety of the outer margin 44 (e.g., where the backing layer 32 is smaller than the support material layer 30). Regardless, the attachment region 80 terminates at an interior border 82 that spatially surrounds, but is spaced or stepped back from, the window edge 62, for example by surrounding but being spaced or stepped back from the interior margin 50 of the support material layer 30. The interior border 82 can be continuous and completely spatially surround or encircle the window 36 in some embodiments. With this construction, a continuous attachment-free interface zone 84 (also labeled in FIG. IB) is established about the window 36 at which backing layer 32 directly overlies a structure of the support material layer 30 (e.g., the backing layer 32 can contact the first major surface 40) but is not directly bonded to the support material layer 30 and thus is not spatially affixed to the outer adhesive layer 34.

The stepped back spatial arrangement of the attachment region 80 relative to the window edge 62 can be described, for example, by the interior border 82 being spatially spaced from at least a portion of, and in some embodiments an entirety of, the window edge 62 in a direction of the outer edge 60. In some embodiments, no portion of the interior border 82 is spatially aligned with the window edge 62. In other embodiments of the present disclosure, the attachment-free interface zone 84 is provided at less than all sides of the window edge 62 (e.g., in alternative constructions, the interior border 82 spatially extends to or is spatially contiguous with a segment of the window edge 62). The interior border 82 can optionally be substantially uniformly spatially spaced from the window edge 62 in some or all directions (e.g., within 10% of a truly uniform spacing). Alternatively, the attachment- free interface zone 84 may not be substantially uniform relative to the window edge 62. With the exemplary embodiment of FIG. 3A, the interior border 82 can be described as defining border portions 82a- 82d that each correspond generally with a respective one of the window edge segments 62a-62d. The first border portion 82a is generally spatially aligned with the first window edge segment 62a, but is spaced from the first window edge segment 62a in a direction of the first outer edge section 60a by a spacing 90a; the second border portion 82b is generally spatially aligned with the second window edge segment 62b, but is spaced from the second window edge segment 62b in a direction of the second outer edge section 60b by a spacing 90b; etc. In some embodiments, a shape of each border portion 82a-82d mimics the shape of the corresponding window edge segment 62a-62d, such that the attachment- free interface zone 84 has a substantially uniform dimension between the corresponding border portion 82a-82d/window edge segment 62a-62d pair (e.g., the spacing 90a of the first border portion 82a from the first window edge segment 62a in a direction of the first outer edge segment 60a is substantially uniform, etc.). In related embodiments, the spacings 90a-90d are substantially identical (e.g., within 10%). Alternatively, one or more of the spacings 90a-90d can be non-uniform (e.g., a shape of the border portion 82a-82d can be linear, whereas a shape of the corresponding window edge segment 62a-62d is curved) and/or one or more of the spacings 90a-90d can differ from one or more of the other spacings 90-90d. Regardless, a minimum spatial spacing or off-set of the interior border 82 from the window edge 62 in all directions is established and is at least 1 mm in some embodiments, alternatively at least 2 mm, alternatively at least 3 mm.

The above-described spatial relationships between the interior border 82 of the attachment region 80 relative to the window 36 in the outer adhesive layer 34 are further identified in the cross-sectional view of FIG. 3B. As shown, the interior border 82 spatially surrounds, but is spatially offset from, the window edge 62 (e.g., the attachment region 80 at which the backing layer 32 is spatially affixed relative to the outer adhesive layer 34 is spaced from the outer adhesive layer 34 in the thickness direction T by the support material layer 30 and does not extend to the window edge 62). Stated otherwise, a hypothetical line H extending at or from the interior border 82 parallel with the thickness direction T passes through a thickness of the outer adhesive layer 34. As a point of clarification, the line H in FIG. 3B is shown along the first border portion 82a. A spatial offset S is established between the line H and the corresponding first window edge segment 62a (i.e., the window edge segment most proximate the border portion at which the hypothetical line H is taken). The spatial offset S of the interior border 82 is in a direction of the outer edge 60 and is perpendicular to the thickness direction T (i.e., relative to the identifications of FIG. 3B, the identified spatial offset S between the first interior border portion 82a and the first window edge segment 62a is perpendicular to the thickness direction T in a direction of the first outer edge segment 60a). While in some embodiments the hypothetical line H (and the corresponding relationships described above) can be taken at any location along the interior border 82, in other embodiments, the spatial offset S is provided at less than an entirety of the interior border 82.

The stepped back spatial arrangement of the attachment region 80 (and in particular the interior border 82) relative to the window edge 62 can alternatively be described in terms of area. For example, the area within or circumscribed by the interior border 82 is greater than the area circumscribed by the window edge 62 (the area within the interior border 82 is equal to the area of the window 36 plus the area of the attachment- free interface zone 84). The area within the interior border 82 is at least 5% greater than the area of the window 36 in some embodiments, alternatively at least 10% greater. By way of another example, the support material layer 30 (FIG. 1C) has or defines the available surface area at the first major surface 40 as described above and over which the outer adhesive layer 34 is applied. Even with embodiments in which the attachment region 80 extends to the outer margin 44, a surface area of the attachment region 80 is less than the area of the available surface area of the first major surface 40. The stepped back spatial arrangement of the attachment region 80 relative to the window edge 62 can alternatively be described in terms of perimeter. For example, the interior border 82 defines a perimeter that is greater than a perimeter defined by the window edge 62. The perimeter defined by the interior border 82 can be at least 5% greater than the perimeter defined by the window edge 62, alternatively 10% greater.

The stepped back spatial arrangement of the attachment region 80 relative to the window edge 62 can alternatively be described relative to the opening 37 (FIG. IB) in the support material layer 30. In general terms, some of the above explanations of an arrangement of the attachment region interior border 82 relative to the window edge 62 apply equally to the interior margin 50 of the opening 37 with embodiments in which the outer adhesive layer 34 extends to the interior margin 50 (i.e., the window edge 62 is contiguous with the interior margin 50). FIGS. 3A and 3B are indicative of this arrangement, with the attachment region interior border 82 being spaced or stepped back from the opening interior margin 50 (identified generally in FIG. 3A) in all directions. With other embodiments in which the outer adhesive layer 34 is stepped back from the interior margin 50, the extent to which the attachment region interior border 82 is stepped back from the interior margin 50 can be increased. For example, with the alternative embodiment dressing structure 22A of FIG. 4, the window edge 62A is spaced from the interior margin 50A, and the attachment region interior border 82A is interiorly spaced from the window edge 62A. The stepped back arrangement of the attachment region interior border 82A relative to the window edge 62A can have any of the geometry characteristics described above with respect to FIGS. 3A and 3B, and in particular of the attachment region interior border 82 relative to the window edge 62.

Performance of the Medical Dressing 20

The medical dressings of the present disclosure can be used to protect a wide variety of wound sites for relatively long periods of time, for example worn by (and viably adhesively secured to the skin of) a patient for in upwards of six or more days if desired. It will be understood that in some end use applications, a useful life of an applied medical dressing is characterized in terms of viable adhesive attachment of the medical dressing to the patient's skin. In other words, where the end use application does not otherwise entail absorption of fluids or other environmental conditions that would require replacement or changing of the medical dressing after a relatively short period of time, it is desired that the applied medical dressing remain in place for an extended period of time; under these circumstances, so long as the medical dressing remains adequately secured to the patient's skin, the medical dressing does not need to be replaced or changed.

With the above in mind and with reference to FIG. 5A (that otherwise reflects, in simplified form, application of the medical dressing 20 to a patient's skin 100), the outer adhesive layer 34 can be formulated as described above to achieve the desired long term securement to the patient's skin 100.

Under usage circumstances where the medical dressing 20 is allowed to lie generally flat relative to the patient's skin 100 (i.e., no overt external forces are placed on to the backing layer 32), the outer adhesive layer 34 readily remains in intimate contact with the patient's skin 100.

In other end use environments, the medical dressing 20 must accommodate structures associated with the patient's skin 100. For example, FIG. 5B generally reflects a ported access site end use environment in which the medical dressing 20 is placed over a medical device 102 (e.g., needle, catheter, etc.) that is otherwise raised above the patient's skin 100. The medical dressing 20 is arranged to locate the medical device 102 within the window 36, with the medical device 102 bearing against the backing layer 32. The outer adhesive layer 34 is again secured to the patient's skin 100. With this arrangement, then, presence of the medical device 102 forces the backing layer 32 away from the support material layer 30 in a region of the window 36 and the opening 37 (i.e., as compared to the arrangement of FIG. 5A in which the backing layer 32 naturally remains relatively flat or substantially parallel with support material layer 30). Because the backing layer 32 is bonded to the first major surface 40 of the support material layer 30, this tented condition effectively results in the backing layer 32 applying a constant lifting force L on to the support material layer 30, and thus on to the outer adhesive layer 34, in a direction away from the patient's skin 100. The lifting force L (due to presence of the medical device 102) can negatively affect long term securement of the outer adhesive layer 34 with the patient's skin 100 (or "wear time" of the medical dressing 20). However, with the medical dressings of the present disclosure, the stepped back arrangement of the attachment region 80 relative to the window edge 62 minimizes the effect of the lifting force L at the outer adhesive layer 34/patient's skin 100 interface.

As shown in FIG. 5B, the backing layer 32 freely lifts away from the support material layer 30

(and thus the outer adhesive layer 34) at the attachment-free interface zone 84. Thus, the lifting force L is transferred to the support material layer 30 primarily at the interior border 82 of the attachment region 80. The interior border 82 is spatially offset (in a direction of the outer perimeter margin 44) from the window edge 62 of the outer adhesive layer 34. For example, relative to the cross-sectional view of FIG. 5B, the medical dressing 20 can be described as having first and second segments 1 10, 1 12 at opposite sides of the window 36, respectively (e.g., the first segment 1 10 is defined between the first outer edge segment 60a and the first window edge segment 62a). With respect to the first segment 1 10, the interior border 82 of the attachment region 80 is not aligned with the window edge 62 of the outer adhesive layer 34 (in the thickness direction T), but instead is directly over a thickness of the outer adhesive layer 34. In other words, at the first segment 110 (and again, relative to the view of FIG. 5B), the outer adhesive layer 34 is continuously present from the first outer edge segment 60a (that is at or in close proximity to the first outer margin section 44a of the support material layer 30) to the first window edge segment 62a (that is at or in close proximity to the first interior margin segment 50a), and the attachment region interior border 82 is between the first outer edge segment 60a and the first window edge segment 62a. A similar relationship of the attachment region interior border 82 relative to the outer adhesive layer 34 is established along the second segment 1 12 (as well as along any other plane perpendicular to the medical dressing 20 and passing through the window 36). The lifting force L, as primarily applied at the attachment region interior border 82, is thus moved away from the adhesive window edge 62 and is shifted into more of a shear- like force at the outer adhesive layer 34/patient's skin 100 interface. Vectors F1-F3 in FIG. 5B illustrate the forces experienced by the outer adhesive layer 34 at the outer adhesive layer 34/patient's skin 100 interface (due to the lifting force L) and highlight that the forces F1-F3 are primarily focused at a location displaced from the adhesive window edge 62. It will be understood that this off set is generated in all directions (in the plane of the outer adhesive layer 34) in some embodiments.

By way of comparison, FIG. 5C is a simplified diagram of a conventional dressing structure 122 including an outer adhesive layer 134 forming a window edge 162 contiguous with an interior margin 150 of a support material layer 130. A backing layer 132 is bonded to the support material layer 130 at an interior border 182 that is contiguous with the interior margin 150 and thus the window edge 162. The backing layer 132 is thus spatially affixed to the outer adhesive layer 134 at the window edge 162. The view of FIG. 5C is akin to the view of FIG. 5B and illustrates forces F4, F5 that would be experienced by the outer adhesive layer 134 at the outer adhesive layer 134/patient's skin 100 interface (due to the lifting force L) with the attachment region interior border 182 aligned (or substantially aligned) with the adhesive window edge 162 (e.g., the bond region 180 extends to the interior margin 150 of the support material layer 130). Under these circumstances, the lifting force L primarily exerts a peel- like force (F4, F5) on to the outer adhesive layer 134/patient's skin 100 interface at the window edge 162 of the outer adhesive layer 134. As compared to the shear-like force F1-F3 of FIG. 5B, the peel-like force F4, F5 more readily or easily initiates lifting of the outer adhesive layer 134 away from the patient's skin 100. Moreover, a length or surface area of the attachment region interior border 182 is less than that of the bond region interior border 82 (FIG. 5B) associated with medical dressings of the present disclosure, thus increasing the area over which the lifting force L is dissipated. Thus, the medical dressings 20 of the present disclosure (for example the arrangement of FIG. 5B) are less likely to wear or otherwise experience failure at the outer adhesive layer 34/patient's skin 100 interface.

Alternative Embodiments

Spatial affixment of the backing layer 32 relative to the outer adhesive layer 34 at an attachment region forming an interior border that is spatially offset from an edge of a window in the outer adhesive layer 34 can be accomplished with various other configurations in accordance with principles of the present disclosure. For example, another medical dressing 20B, and in particular another dressing structure 22B, in accordance with principles of the present disclosure is shown in FIG. 6. The dressing structure 22B includes a support material layer 30B coated with an outer adhesive layer 34B that forms the window 36B (at least partially circumscribed by a window edge 62B) as described above. Further, the dressing structure 20B includes a backing layer 32B that can be highly akin to the backing layer 32 (FIG. 1C) described above. The backing layer 32B is secured to the support material layer 30B, for example via an intermediate adhesive layer 38B that can be highly akin to the intermediate adhesive layer 38 (FIG. 1C) described above. Once again, securement of the backing layer 32B to the material support layer 30B generates an attachment region 80B at which the backing layer 32B is spatially affixed relative to the outer adhesive layer 34B in the thickness direction T, with an interior border 82B of the attachment region 80B being spatially offset from the window edge 62B in the outer adhesive layer 34B. For example, a hypothetical line H extending at the interior border 82B parallel with the thickness direction T passes through a thickness of the outer adhesive layer 34B. With the construction of FIG. 6, an outer perimeter shape or footprint of the backing layer 32B (and thus of the optional intermediate support layer 38B) is smaller than that of support material layer 30B.

Another embodiment medical dressing 20C in accordance with principles of the present disclosure is shown in FIG. 7, and includes a dressing structure 22C. The dressing structure 22C defines opposing first and second major faces 24C, 26C, and includes a support material layer 30C, a backing layer 32C and an outer adhesive layer 34C. A window 36C is formed through the outer adhesive layer 34C, and is at least partially circumscribed by a window edge 62C. The support material layer 30C and the outer adhesive layer 34C are disposed over opposite major surfaces of the backing layer 32C, with the backing layer 32C extending over the window 36C. As compared to other embodiments, then, the outer adhesive layer 34C is more directly secured to the backing layer 32C, and the support material layer 30C forms the first major face 24C. In other related embodiments, the support material 30C is omitted.

Securement of the outer adhesive layer 34C to a surface of the backing layer 32C establishes an attachment region 80C at which the backing layer 32C is spatially affixed to the outer adhesive layer 34C in the thickness direction T. For example, the outer adhesive layer 34C can be coated (e.g., full coverage or pattern coated) to the backing layer 32C. Regardless, an interior border 82C of the attachment region 80C is spatially offset or spaced from a window edge 62C of the window 36C commensurate with the above descriptions. For example, a hypothetical line H extending at the interior border 82C parallel with the thickness direction T passes through a thickness of the outer adhesive layer 34C.

In some embodiments, the spatial offset of the attachment region interior border 82C relative to the window edge 62C can be effectuated by a bond blocking material 190 applied between a portion of the backing layer 32C/outer adhesive layer 34C interface as shown. The bond blocking material 190 can assume various forms appropriate for preventing robust securement or attachment between the layers 32C, 34C, for example a low adhesion backsize or other coating, a laminated film, etc.

During use, the medical dressing 20C is applied to a patient as described above, including the outer adhesive layer 34C being adhesively secured to the patient's skin. Under circumstances where the end use environment exerts an upward lifting force on to the backing layer 32C in a region of the window 36C, the backing layer 32C will freely lift away from the outer adhesive layer 34C at an attachment-free zone 84C (e.g., along the bond blocking material 190). The lifting force is thus primarily transferred to the outer adhesive layer 34C at a location spaced from the window edge 62C as described above.

Another embodiment medical dressing 20D in accordance with principles of the present disclosure is shown in FIG. 8 and includes a dressing structure 22D. The dressing structure 22D can be highly akin to the dressing structure 22 described above, with the view of FIG. 8 being comparable to the view of FIG. 3A. Thus, the dressing structure 22D includes a backing layer 32D spatially affixed to an outer adhesive layer 34D, for example via a support material layer (hidden), at an attachment region 80D (represented by stippling in FIG. 8). A window 36D is formed in the outer adhesive layer 34D that is spatially contiguous with an opening 37D in the support material layer. The window 36D is open at an outer edge 60D of the outer adhesive layer 34D. In other words, the window edge 60D is discontinuous. An interior border 82D of the attachment region 80D is spatially off set from the window edge 60D as described above, and similarly is "open" at a side of the dressing structure 22D.

Optional Components

Medical dressings of the present disclosure can optionally include one or more additional components, several of which are shown in simplified form relative to the alternative medical dressing 200 of FIG. 9. The medical dressing 200 includes the dressing structure 22 (or any other dressing structure described above), and thus has the support material layer 30, the backing layer 32, the outer adhesive layer 34, and the optional intermediate adhesive 38. In addition, the medical dressing 200 includes an optional release liner 202, an optional carrier 204 and an optional low adhesion coating 206.

Where provided, the carrier 204 and the release liner 202 define opposing major faces 208, 210, respectively, of the medical dressing 200. During use, the release liner 202 and the carrier 204 can be removed, with the dressing structure 22 being applied to a patient's skin (not shown) in accordance with previous explanations. In other embodiment medical dressings of the present disclosure, one or more or all of the release liner 202, the carrier 204 and the low adhesion coating 206 can be omitted.

The optional release liner 202 may be included that covers all or a portion of the outer adhesive layer(s) 34 to prevent contamination of the outer adhesive layers(s) 34. In one embodiment, the packaging (not shown) that contains the medical dressing may serve as a release liner. Suitable release liners can be made of kraft papers, polyethylene, polypropylene, polyester or composites of any of these materials. In one embodiment, the release liner 202 is coated with release agents such as fluorochemicals or silicones. For example, U.S. Pat. No. 4,472,480, the entire teachings of which are hereby incorporated by reference, describes low surface energy perfluorochemical liners. In one embodiment, the release liner 202 is a paper, polyolefin film, or polyester film coated with silicone release materials.

The optional carrier 204 may be included that covers a portion (optionally all) of the dressing structure 22, providing structural support if the dressing structure 22 is thin and highly flexible (e.g., where the backing layer 32 is a thin film). The carrier 204 may be removable from the dressing structure 22 once the outer adhesive layer 34 is placed on skin. The carrier 204 can be constructed of a variety of materials such as fabrics that are woven or kitted, nonwoven material, papers, or film. In one embodiment, the carrier 204 is along the perimeter of the dressing structure 22 and is removable from the dressing structure 22, similar to the carrier used the 3M Tegaderm™ Transparent Film Dressing, available from 3M Company, St. Paul, MN.

The carrier 204 may include frames, handles, stiffening strips, etc., as disclosed, for example, in U.S. Patent Nos. 6,742,522; 5,979,450; 6, 169,224; 5,088,483; 4,598,044; D493,230, the entire teachings of each of which are hereby incorporated by reference. The carrier material used to supply the carrier 204 is optionally more rigid than the backing layer 32 to prevent the backing layer 32 from wrinkling during application. The carrier 204 can be heat-sealable to the backing layer 32, with or without the low adhesion coating 206 described below, for the purpose of manufacturing the medical dressing 200. In general, optional materials for the carrier 204 can include, but are not limited to, ethylene vinyl acetate copolymer or ethylene acrylic acid coating papers and polyester films.

With embodiments including the carrier 204, the backing layer 32 is optionally coated with the low adhesion coating 206 (at a face of the backing layer 32 opposite the support material layer 30). The low adhesion coating 206 can be coated as a solution of polyvinyl N-octadecyl carbamate and a blend of silicone resins, as describe in U.S. Patent No. 5,803,086, the entire teachings of which are incorporated herein by reference. It will be understood that other coatings providing the low adhesion characteristics can be substituted. The primary considerations in choosing any low adhesion coating are their release characteristics and their compatibility with the attachment means between the carrier 204 and the backing layer 32.

When the carrier 204 is heat seal-bonded to the backing layer 32, the low adhesion coating 206 (where provided) is compatible with the heat seal bond between the carrier 204 and the backing layer 32, and also retains its low adhesion characteristic after heat sealing. In other embodiments, the low adhesion coating 206 can be omitted.

An absorbent material (not shown) may also be used in conjunction with the medical dressings described herein. For example, the absorbent material can be attached to or carried by the backing layer 32 in a region of the opening 37 (and thus the window 36) or may be a separate element applied to the patient's skin in conjunction with application of the dressing structure 22. The absorbent materials can be manufactured of any of a variety of materials including, but not limited to, woven or nonwoven cotton or rayon. The optional absorbent material or absorbent pad is useful for containing a number of substances, optionally including antimicrobial agents, drugs for transdermal drug delivery, chemical indicators to monitor hormones or other substances in a patient, etc.

The absorbent material may include a hydrocolloid composition, including the hydrocolloid compositions described in U.S. Patent Nos. 5,622,71 1 and 5,633,010, the entire teachings of which are hereby incorporated by reference. The hydrocolloid absorbent may comprise, for example, a natural hydrocolloid, such as pectin, gelatin, or carboxymethylcellulose (CMC) (Aqualon Corp., Wilmington, Del.), a semi-synthetic hydrocolloid, such as cross-linked carboxymethylcellulose (X4ink CMC) (e.g. Ac-Di-Sol; FMC Corp., Philadelphia, Pa.), a synthetic hydrocolloid, such as cross-linked polyacrylic acid (PAA) (e.g., CARBOPOL™ No. 974P; B.F. Goodrich, Brecksville, Ohio), or a combination thereof. Absorbent materials may also be chosen from other synthetic and natural hydrophilic materials including polymer gels and foams.

An optional antimicrobial component (not shown) may be included that is either separate from the medical dressing or may be integral with the dressing. The antimicrobial component is placed near or adjacent to the insertion site of the medical device 102 (FIG. 5B) to inhibit microbial growth in and around the insertion site. The antimicrobial component can be an absorbent foam or gel, such as used in a 3M Tegaderm™ CHG I.V. Securement Dressing, available from 3M Company. Non-limiting examples of useful antimicrobial materials formatted as a hydrogel are provided in U.S. Application Publication No. 2013/0274667, the entire teachings of which are hereby incorporated by reference.

Although specific embodiments of the present disclosure have been shown and described herein, it is understood that these embodiments are merely illustrative of the many possible specific arrangements that can be devised in application of the principles of the present disclosure. Numerous and varied other arrangements can be devised in accordance with these principles by those of ordinary skill in the art without departing from the spirit and scope of the present disclosure. Thus, the scope of the present disclosure should not be limited to the structures described in this application, but only by the structures described by the language of the claims and the equivalents of those structures.

Claims

What is claimed is:

1. A medical dressing comprising:

a medical dressing structure defining opposing, first and second major faces and a thickness direction, the medical dressing structure including:

a support material layer,

a backing layer arranged over the support material layer,

an outer adhesive layer defining the second major face;

wherein a window is formed through a thickness of the outer adhesive layer and a perimeter of the window is defined by a window edge;

and further wherein the backing layer extends over the window and is spatially affixed relative to the outer adhesive layer at an attachment region terminating at an interior border that spatially surrounds the window edge;

and even further wherein at least a portion of the interior border is spatially offset from the window edge such that a line extending at the portion and parallel with the thickness direction passes through the thickness of the outer adhesive layer.

2. The medical dressing of claim 1, wherein the support material layer defines an outer margin, and further wherein the interior border of the attachment region is spatially spaced from the window edge in a direction of the outer margin.

3. The medical dressing of claim 1, wherein a spacing between the interior border and the window edge is such that a section of the backing layer directly overlies, but is not spatially affixed relative to, the outer adhesive layer.

4. The medical dressing of claim 3, wherein the section is continuous about a shape of the widow edge.

5. The medical dressing of claim 3, wherein the backing layer defines an inner face facing the outer adhesive layer and an outer face opposite the inner face, and further wherein the medical dressing is configured such that in response to a force applied to the inner face in a region of the window and in a direction perpendicular to a major plane defined by the outer adhesive layer, the backing layer freely lifts away from the outer adhesive layer along the section.

6. The medical dressing of claim 3, wherein the section spatially surrounds less than an entirety of a shape of the window edge.

7. The medical dressing of claim 1, wherein the interior border defines and circumscribes an attachment-free zone along the backing layer, and further wherein an area of the attachment-free zone is greater than an area of the window.

8. The medical dressing of claim 7, wherein the area of the attachment- free zone is at least 5% greater than the area of the window.

9. The medical dressing of claim 1, wherein the interior border is continuous, and further wherein a perimeter of the interior border is greater than a perimeter of the window edge.

10. The medical dressing of claim 1, wherein the interior border is spaced from the window edge by a distance of not less than 1 mm.

1 1. The medical dressing of claim 1 , wherein the support material layer defines opposing first and second major surfaces, the outer adhesive layer disposed over the second major face, the medical dressing further comprising:

an intermediate adhesive layer bonding the backing layer to the first major surface of the support material layer at the attachment region.

12. The medical dressing of claim 1 1, wherein a surface area of the intermediate adhesive layer is less than a surface area of the first major surface of the support material layer.

13. The medical dressing of claim 12, wherein the support material layer defines an outer margin, and further wherein the intermediate adhesive layer is contiguous with the outer margin.

14. The medical dressing of claim 1, wherein the outer adhesive layer defines an outer edge adjacent an outer margin of the support material layer and opposite the window edge, and further wherein the interior border is spatially offset from the window edge in a direction of the outer edge.

15. The medical dressing of claim 1, wherein an opening is formed through a thickness of the support material layer, the opening being aligned with the window in the outer adhesive layer, wherein a perimeter of the opening is defined by an interior margin, and further wherein the window edge spatially surrounds the interior margin.

16. The medical dressing of claim 15, wherein the backing layer is bonded to the support material layer opposite the outer adhesive layer such that the backing layer defines the first major face of the medical dressing structure.

17. The medical dressing of claim 15, wherein the interior margin is spatially aligned with the window edge.

18. The medical dressing of claim 1, wherein the backing layer is a film.

19. The medical dressing of claim 1, wherein the backing layer includes a film selected from the group consisting of a polyurethane film, a polyester film, and a polyether block amide film.

20. The medical dressing of claim 1, wherein the support material layer is a nonwoven fabric.

21. The medical dressing of claim 1, wherein the outer adhesive layer is applied to the support material layer.

22. The medical dressing of claim 21, wherein the second major face of the medical dressing structure is free of adhesive in the window.

23. The medical dressing of claim 1, further comprising:

a release liner removably disposed over the outer adhesive layer.

24. The medical dressing of claim 1, further comprising:

a carrier disposed over the first major face of the medical dressing structure.

25. A medical dressing comprising:

an adhesive structure including an adhesive layer and forming a window, wherein the window is defined by a window edge located within an outer edge of the outer adhesive layer; and a backing layer extending over the window and attached to the adhesive structure at an

attachment region terminating at an interior border that at least partially surrounds the window and is spaced from the window edge in a direction of the outer edge.

26. The medical dressing of claim 25, wherein the adhesive structure further includes a support material layer disposed between the backing layer and the outer adhesive layer.

27. The medical dressing of claim 25, further comprising:

a support material layer disposed over the backing layer opposite the adhesive structure.

28. A medical dressing comprising:

a medical dressing structure defining opposing, first and second major faces, the medical dressing structure including:

a support material layer,

a backing layer arranged over the support material layer,

an outer adhesive layer defining the second major face;

wherein a window is formed through a thickness of the outer adhesive layer, a perimeter of the window being defined by a window edge;

and further wherein the backing layer extends over the window and is spatially affixed relative to the outer adhesive layer at an attachment region terminating at an interior border;

and even further wherein the interior border is spaced from the window edge to establish an attachment free zone at which the backing layer is freely movable relative to the outer adhesive layer.