Patent Application
20070021697
1. Field of the Invention
This invention relates in general to tissue treatment, and more particularly, but not by way of limitation, to an apparatus and process for the use of therapeutic and prophylactic agents, such as antimicrobial agents, in combination with the application of subatmospheric pressure tissue treatment.
2. Description of the Related Art
Subatmospheric pressure-induced healing of tissue, including but not limited to wounds, has been commercialized by KCI USA, Inc. of San Antonio, Tex., in the form of its “VACUUM ASSISTED CLOSURE®” (or “V.A.C.®”) subatmospheric pressure tissue treatment product line. The subatmospheric pressure-induced healing process in epithelial and subcutaneous tissues was first described in U.S. Pat. Nos. 5,636,643 and 5,645,081 issued to Argenta et al., on Jun. 10, 1997 and Jul. 8, 1997 respectively, the disclosures of which are incorporated by reference as though fully set forth herein. A dressing that was later found to be useful for subatmospheric pressure-induced healing has also been described in commonly assigned U.S. Pat. No. 4,969,880 issued on Nov. 13, 1990 to Zamierowski, as well as its continuations and continuations in part, U.S. Pat. No. 5,100,396, issued on Mar. 31, 1992, U.S. Pat. No. 5,261,893, issued Nov. 16, 1993, and U.S. Pat. No. 5,527,293, issued Jun. 18, 1996, the disclosures of which are incorporated herein by this reference. Further improvements and modifications of such a dressing are also described in U.S. Pat. No. 6,071,267, issued on Jun. 6, 2000 to Zamierowski. Additional improvements have also been described in U.S. Pat. No. 6,142,982, issued on May 13, 1998 to Hunt, et al., and U.S. Pat. No. 7,004,915 issued on February 28, 2006 to Boynton, et al., the disclosures of which are incorporated by reference as though fully set forth herein. Improvements in the use and operation of the connection and conduit components between the dressing and the source of subatmospheric pressure instrumentation have been described in the U.S. provisional patent application Ser. No. 60/765,548, entitled SYSTEMS AND METHODS FOR IMPROVED CONNECTION TO WOUND DRESSINGS IN CONJUNCTION WITH REDUCED PRESSURE WOUND TREATMENT SYSTEMS filed Feb. 6, 2006, disclosure of which is incorporated by reference as though fully set forth herein.
Subatmospheric pressure-induced tissue treatment involves applying subatmospheric pressure to a tissue site over an area, magnitude and time period sufficient to promote healing. In practice, application of the subatmospheric pressure to the tissue site, commercialized by Assignee or its parent under the designations VACUUM ASSISTED CLOSURE® or V.A.C.® therapy, typically involves the mechanical contraction of a wound site with simultaneous removal of excess and interstitial body-liquid. In this manner, V.A.C.® therapy cooperates with the body's natural inflammatory process while alleviating many of the known intrinsic side effects, such as edema caused by increased liquid delivery to the wound site absent the necessary vascular structure for proper removal of waste liquids. As a result, V.A.C.® therapy has been highly successful in the promotion of tissue site closure, healing many sites previously thought largely untreatable.
As is well known in the healing arts, application of certain therapeutic or prophylactic agents to the tissue site may facilitate patient comfort, tissue assessment or directly impact the rate of healing. For example, bacteria may contaminate tissue and interstitial or surface body-liquid at the tissue site. Application of indicating agents known in the art can cause a color change in the presence of a bacterial agent and allow a health care provider to easily and readily ascertain the presence of infection. Further, application of an antimicrobial agent directly to the tissue site may reduce or inhibit bacterial density. Still further, application of anesthetic agents may relieve a patient's discomfort, in those instances where discomfort occurs.
Application of these and other agents directly to the tissue site may be problematic and ineffective for patients receiving subatmospheric pressure tissue treatment. Because the very nature of subatmospheric pressure tissue treatment dictates an atmospherically sealed tissue site, delivery of agents directly to the tissue typically necessitates interrupting application of the subatmospheric pressure, breaking the subatmospheric pressure seal, and disturbing the tissue site. Not only is this a time consuming process for the caregiver, disturbance to the tissue site may increase the possibility of external- and cross-contamination. Disturbance to the tissue site may also cause the patient discomfort in some instances. Furthermore, any applied medicament may be evacuated when the application of subatmospheric pressure tissue treatment is resumed, so a long term, continuous effect from the applied agent may not be realized.
A wide variety of antimicrobial compounds combined with wound dressings can control microbial contamination and potentially lower the rate of infection. Uniform distribution of the antimicrobial can be key to the antimicrobial performance of the wound dressing. What is not known is a reliable method of coating medical wound dressings or foams with a polymer coating agent wherein the entire volume of the dressing is uniformly coated. This occurs for several reasons.
Particularly, some foam dressings are relatively thick, often in the range of about 1.25 inches. The thickness of these dressings limits the coating process, inasmuch as there is no way to insure a uniform coating throughout the entire structure such that the structure is capable of being severed omnidirectionally while still having the desired antimicrobial agent exposed for use in a wound.
Certain coating methods exist, such as vapor deposition (both physical and chemical), electrostatic coating, spraying and sputter coating. However, these coating methods are costly, and are not adaptable to uniformly coating three-dimensional surfaces of certain dressings, such as reticulated foam. In addition, these methods have extensive environmental issues that concern users of the dressings in the medical industry.
Other methods of adding antimicrobials to the dressing, such as additives in the foaming process itself or the use of adjunctive therapies or combination products (e.g. one thin antimicrobial dressing attached to the foam) exist, but are difficult to use and suffer other deficiencies. Particularly, these methods are known to mechanically impact the foam and to materially impact the permeability of the foam.
Because wound sizes and shapes have almost infinite variations, a wound dressing must be adaptable to accommodate the wound and provide appropriate antimicrobial properties to control infection both in the dressing and in the wound. Accordingly, there have been needs to improve dressings for tissue and to develop a process for uniformly coating the dressing or foam with antimicrobial agents sufficient to decontaminate the wound yet simple to use and cost-effective, such that the foam will be adapted for in situ adjustment to match the wound shape and dimension.
These and other needs are fulfilled through the development of a process for uniformly coating a foam or other dressing, and a foam or dressing formed by this process with an antimicrobial polymer (i.e., a polymer-based coating incorporating an antimicrobial agent). Such foam or dressing is particularly useful in subatmospheric pressure wound therapy.
Also disclosed are a process for uniformly coating the foam or dressing with a metal, including but not limited to an antimicrobial metal, a foam or dressing formed by this process; its use with a subatmospheric pressure tissue treatment device; and a subatmospheric pressure tissue treatment system and dressing with antimicrobial effects. The foam or dressing formed by the polymer-based and metal-based coating processes discussed herein serves as a screen for use in delivering one or more therapeutic or prophylactic agents, such as antimicrobial agents, to a tissue site in combination with the application of subatmospheric pressure tissue treatment.
In one embodiment, the screen is placed in contact with tissue and a cover is positioned to enclose the screen. The cover also serves to define a space between the cover and the tissue. A pathway is provided between a source of subatmospheric pressure and the space defined by the cover, for application of a subatmospheric pressure within the space defined by the cover. A container is connected to the pathway between the source of subatmospheric pressure and the cover. The container receives the body-liquid drawn along the pathway from within the space defined by the cover.
At least a portion of the screen is a substrate that has been uniformly covered with a coating comprising one or more therapeutic or prophylactic agents. The coating releases at least a portion of the agents within the space defined by the cover. The exterior and interior surfaces of the substrate are covered with the coating to enable the user to expose at least one coated surface of the uniformly covered substrate portion of the screen when adjusting the size and shape of the screen to fit the tissue site.
During application of the subatmospheric pressure within the space defined by the cover, an area of contact between the tissue and the uniformly covered substrate portion of the screen is increased as the tissue microdeforms and the screen compresses and conforms to the surface of the tissue. The coating releases at least a portion of the agents directly to the area of contacted tissue.
In another embodiment, a process for adapting the substrate for treating the tissue during the application of subatmospheric pressure tissue treatment includes the steps of creating a coating solution comprising at least one therapeutic or prophylactic agent; uniformly coating the substrate with the coating comprising the agents, such that an upper surface, a lower surface, side surfaces, and interior surfaces of the screen are uniformly coated; and severing the uniformly coated screen to match the size and shape of the tissue site, such that all exposed surfaces of the screen are uniformly coated sufficient to treat the tissue site during application of the subatmospheric pressure.
The process may further include steps for positioning the screen in contact with the tissue; placing the cover over the screen; providing the pathway between the cover and the source of subatmospheric pressure for applying the subatmospheric pressure within the space defined by the cover; increasing the area of contact between the tissue and the screen by applying the subatmospheric pressure within the space defined by the cover; and releasing at least a portion of the at least one therapeutic or prophylactic agent to the area of contacted tissue.
Many other objects, features and aspects of the present invention will be evident to those of ordinary skill in the relevant arts, especially in light of the foregoing discussions and the following drawings, exemplary detailed description and appended claims.
A more complete understanding of the disclosed method and apparatus may be obtained by reference to the following Detailed Description of the Preferred Embodiments, with like reference numerals denoting like elements, when considered in conjunction with the accompanying Drawings, wherein:
One embodiment provides a method for uniformly coating a wound dressing with antimicrobial polymers incorporating agents, such as Au, utilizing a process and a wound dressing formed under the process. The method of uniform coating enables a user of the dressing to sever the dressing in any direction and still have all exposed surfaces uniformly coated with the antimicrobial agent sufficient to decontaminate the wound.
An alternative embodiment provides a method for uniformly coating a foam or dressing with a metal-based coating incorporating agents, such as Au, and a dressing formed under the process. As with the polymer-based coating process, the metal-based coating process enables the user to sever the dressing in any direction and still have all exposed surfaces uniformly coated with the agent sufficient to treat the wound.
Silver serves herein as an exemplary agent since the properties of silver allow it to be easily incorporated into both polymer-based coatings and into metal-based coatings. Other agents useful in alternative embodiments include, but are not limited to, therapeutic and prophylactic agents, such as antimicrobial agents, enzymatic debriders, anesthetic agents, chemotherapeutic agents, indicating agents, and growth factors. Antimicrobial agents include but are not limited to antibacterial agents such as antibiotic and bacteriostatic agents. A coating may incorporate single or multiple agents for release to the tissue and to the body-liquid drawn from the tissue. The coating contacts body-liquid and tissue, and releases the agent(s) in the presence of an aqueous environment.
The dressing or screen formed by the coating process is comprised of a substrate uniformly covered with the polymer-based or metal-based coating. The dressing or screen includes a plurality of flow ports or passages provided to allow gas and body-liquid to pass through for facilitating tissue healing. Surfaces of the plurality of ports or passages are also uniformly covered with the coating. The substrate may include, without limitation, material such as foam, yarn, film, filament, fiber, fabric, filler materials, or any combination thereof. The substrate material may be comprised of any substance capable of having the coating applied thereto, including without limitation, nylon, polyester, acrylic, rayon, cotton, polyurethane, other polymeric materials, cellulose materials, such as wood fiber, or any combination thereof. A foam portion of the dressing is preferably of open-celled, reticulated polyurethane, polyether, polyvinylacetate, or polyvinylalcohol construction, but other substitutions or modifications to the foam substrate are considered to be within the scope of this invention.
In one embodiment, a polyurethane foam is uniformly coated with a silver hydrogel polymer. The polymer coating itself contains PVP or Poly(vinyl-pyrrolidone), which is a water-soluble polymer with pyrrolidone side groups, typically used as a food additive, stabilizer, clarifying agent, tableting adjunct and dispersing agent. It is most commonly known as the polymer component of Betadine (a povidone-iodine formulation). In addition, the coating may contain Chitosan, which is a deacetylated derivative of chitin, a polysaccharide that is refined from shells of shrimps, crabs and other crustaceans. Chitosan has also been used in hemostatic dressings. The third optional component of the polymer is preferably Silver Sodium Aluminosilicate, which is silver salt powder with 20% active ionic silver by weight.
In a preferred embodiment, an apparatus and process for treating tissue is provided, wherein the foam or dressing formed by the polymer-based or metal-based coating processes discussed herein serves as a screen for use with a subatmospheric pressure tissue treatment device. The screen is placed in contact with the tissue and enclosed under a generally impermeable cover. The cover provides a substantially air-tight seal over the screen and the tissue, and defines a space over the tissue and under the cover. A liquid conduit is connected between a source of subatmospheric pressure and the cover to provide a pathway for applying a subatmospheric pressure within the space defined by the cover and for drawing interstitial and surface body-liquid therefrom.
When the subatmospheric pressure is applied to the tissue site, the screen compresses and conforms to the surface of the tissue as air is removed from within the space defined by the cover. Microdeformation of the tissue under the cover also occurs. These movements increase an area of contact between the screen and the tissue. In the aqueous environment within the space defined by the cover, the coating releases the agent, such as silver, directly to the increased area of contacted tissue. Increasing the area of contacted tissue brings the coating into direct contact with additional tissue, thereby maximizing the effectiveness of the agent release. In embodiments where the agent is silver, the coating releases silver ions directly to the contacted tissue to help-reduce bacterial density on the area of contacted tissue.
As used herein, references to “wound dressing,” “dressing,” and “foam” as a dressing, are understood to generally refer to the screen comprising the substrate uniformly covered with the coating. In a few instances, the terms have been used to refer to the substrate itself, but their meaning will obvious be to those skilled in the art. The screen is placed substantially over a tissue site to promote the growth of granulation tissue and also to prevent its overgrowth and to release at least one therapeutic or prophylactic agent to the tissue site via the coating. As will be understood by those skilled in the art, the substrate may include, without limitation, material such as foam, yarn, film, filament, fiber, fabric, filler materials, or any combination thereof. The substrate may be comprised of any substance capable of having the coating applied thereto including, without limitation, nylon, polyester, acrylic, rayon, cotton, polyurethane, other polymeric materials, cellulose materials, such as wood fiber, or a combination thereof. Individual fibers are worked (woven, knitted, crocheted, felted, blown, etc.) into a fabric dressing. Foam dressing is preferably of open-celled, reticulated polyurethane, polyvinylalcohol, or polyvinylacetate construction, but other modifications to the foam dressing are considered to be within the scope of this invention.
As used herein, references to “drape” are understood to generally refer to a flexible sheet of construction that is generally body-liquid-impermeable. For purposes of this discussion, use of the term “impermeable” without further qualification, should be understood to generally refer to material and construction that is generally impermeable to body-liquid. Most particular examples include drapes such as those comprising an impermeable elastomeric material, such as a film, the underside of which is at least peripherally covered with a pressure-sensitive adhesive for providing a substantially air-tight seal with a second region of tissue surrounding the tissue site. Alternatively, drapes may be substituted with other covers while still appreciating certain aspects of the invention.
As used herein, references to “subatmospheric pressure” are understood to generally refer to a pressure less than the ambient atmospheric pressure outside the covered tissue site receiving treatment. In most cases, this subatmospheric pressure will be less than the atmospheric pressure at which the patient is located. Subatmospheric pressure tissue treatment may comprise a substantially continuous application of the subatmospheric pressure, where the subatmospheric pressure is relieved only to change the screen, or it can be practiced with the use of a cyclic application of the subatmospheric pressure in alternate periods of application and non-application, or it can be practiced by oscillating the pressure over time.
As used herein, references to “tissue” are understood to generally refer to an aggregation of similar cells or types of cells, together with any associated intercellular materials adapted to perform one or more specific functions including, but not limited to bone tissue, adipose tissue, muscle tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, and ligaments.
As used herein, references to “wound” and “wound site” are understood to generally refer to the tissue site, wherein the term “tissue site” is understood to generally refer to a region of tissue including, but not limited to, a wound or defect located on or within any tissue. The term “tissue site” may further refer to the region of any tissue that is not necessarily wounded or defective, but is instead such as those in which it is desired to add or promote the growth of additional tissue. For example, the subatmospheric pressure tissue treatment may be used in certain tissue regions to grow additional tissue that may be harvested and transplanted to another tissue location.
As used herein, references to “wound fluids,” “wound exudates,” “fluid drainage,” or “fluids” or “liquid” related to the tissue site, are understood to generally refer to body-liquid, wherein the term “body-liquid” is understood to generally refer to any interstitial liquid in the tissues or liquid that has exuded from the tissue or its capillaries.
Referring first to
The foam is then placed in a convectional forced-air oven set to a predetermined temperature and time to completely dry the solution-coated foam, 114. Alternatively, to verify the dry condition of the foam, the weight of the foam may be checked again, 116. If light-sensitivity remains an issue, the foam can be packaged in a pouch with a low moisture vapor transmission rate (MVTR), which limits the exposure of the foam to light and to humidity, 118. The foam is now ready for use on such sites as partial thickness burns, traumatic wounds, surgical wounds, dehisced wounds, diabetic wounds, pressure ulcers, leg ulcers, flaps and grafts.
In one example, a foam made by the method described has achieved in-vitro efficacy on two common bacteria—staphylococcus aureus and pseudomonas aeruginosa, with a 20% silver salt load (4% silver by weight, though about 0.1% to about 6% has shown to be at least partially effective). The dressing maintains its effectiveness for 72 hours through a controlled and steady state release of ionic silver. Specifically, a diffusive gradient exists between the silver coating and the anionic rich outside environment that lead to disassociation and eventual transport of the silver ion. Using the above process, over a 6 log reduction or about 99.9999% of pathogenic bacteria have been eliminated between about 24 hours and about 72 hours.
The coating process can easily incorporate other additives, such as enzymatic debriders, anesthetic agents, growth factors and many other biopharmaceuticals. In addition, the coating can be formulated specific to coat thickness, although very thin coatings (about 2 to 10 micrometers) are preferable. The formulation can further be adapted to allow for large particle sizes and different release kinetics, such as concentration and rate and the duration of release.
The coating process can also easily incorporate other additives, singly or in combination. Those skilled in the art can easily adapt this process for polymer-coating other substrates previously listed, such as fiber or film, without undue experimentation.
The uniform and impregnated coating allows for delivery of silver ions both outside and within the foam. In this manner, not only is bacteria eliminated on the wound bed, but also within the dressing itself. As discussed below with reference to
Referring now to
The foam from the removal step 204 is subjected to a convection oven for drying, 212. During certain silver-solution coating experiments, when the temperature of the oven is set at about 90° C., 20 minutes has been found to be an effective drying time. However, it is preferable to dry the foam for about at least 6 minutes to minimize any breakdown of coating. The foam is next packaged in appropriate containers, such as the MVTR pouch or similar containers for shipment to the user, 214.
Referring now to
The uniform and impregnated coating allows for delivery of silver ions both outside and within the dressing 300. Silver ions release from the uniform coating in the aqueous environment and diffuse to the tissue and into the body-liquid. Pathogens on the tissue, on the underside of the drape, and in the body-liquid that come into contact with the silver ions released from the coating on the outside of the dressing 300 are effectively eliminated. Reduction of bacterial density also occurs as application of the subatmospheric pressure through the dressing 300 effectively pulls body-liquid and accompanying pathogens through the uniformly coated dressing 300, bringing the pathogens into contact with the coating and silver ions within the dressing 300. Additionally, bacterial density within the container is reduced as body-liquid and accompanying silver ions are drawn into the container.
The embodiment of
When used in combination with subatmospheric pressure therapeutic devices, such as those commercialized by KCI USA, Inc. (and its affiliates) of San Antonio, Tex. as part of the V.A.C.® product line, the dressing 300 is particularly effective.
In this embodiment, the subatmospheric pressure therapeutic device 400 preferably serves as the “V.A.C. ATS®” or the “V.A.C. Freedom®” subatmospheric pressure tissue treatment device commercially available from KCI USA, Inc. (and its affiliates) of San Antonio, TX. The “V.A.C. ATS®” device is designed for higher acuity wounds and patients in acute care and long-term care facilities. The V.A.C. ATS® device is illustrated and described below with reference to U.S. Pat. No. 7,004,915, issued to Boynton, et al., and set forth with reference to FIGS. 13 to 17. The “V.A.C. Freedom®” device is a portable subatmospheric pressure tissue treatment device that allows patients to return to daily activities while continuing to receive subatmospheric pressure tissue treatment. The V.A.C. Freedom® device is illustrated and described below with reference to U.S. Pat. No. 6,142,982, issued to Hunt, et al., and set forth with reference to FIGS. 6 to 12B. Suitable alternative subatmospheric pressure therapeutic devices may be the “V.A.C. Instill®” device, the “V.A.C.® Classic” device, the “Mini V.A.C.®” device, or any other “V.A.C.®” model device commercially available from KCI USA, Inc. (and its affiliates) of San Antonio, Tex. Additional suitable alternative devices, dressings and components may be those described in the provisional application previously cited in the Description of the Related Art, the disclosure of which is incorporated by reference as though fully set forth herein. Such alternative V.A.C.® devices, dressings and components also may be generally represented by the subatmospheric pressure therapeutic device 400 and its dressings and components.
Further, in this embodiment the drape 404 serves as a cover, and is preferably the “V.A.C.® Drape” commercially available from KCI USA, Inc. (and its affiliates) of San Antonio, Tex. The subatmospheric pressure hose 406 serves as a liquid conduit, which combined with the connector 408 is preferably the “V.A.C. T.R.A.C.® Pad,” also commercially available from KCI USA, Inc. of San Antonio, Tex.
Referring now to
One embodiment of the subatmospheric pressure therapeutic device 400 of
Referring to the drawings, the portable therapeutic apparatus comprises a housing 702 (best shown in
Within housing shell 901 is located a subatmospheric pressure pump 602 with associated electric motor 602A and the pump is connected by a silicon rubber tube 604 to a canister spigot 906A in a compartment 908 for the canister 606. Also connected to a second canister spigot 906B via a tube 608 is a pressure relief valve 610 and both tubes 604 and 608 are connected via T-connectors T to pressure transducers (not shown). A microprocessor 910 is mounted on a PCB board 912 and a membrane assembly 914 incorporates an LCD indicator and control buttons.
The apparatus may include means for recording pressures and treatment conditions given to a particular patient which may be printed out subsequently by the physician. Alternatively, the equipment may include a modem and a telephone jack so that the conditions under which the patient has been treated can be interrogated by the physician from a distant station.
Canister 606 is a push fit into the cavity 908 and its lower end is supported in a cover 916. The cover 916 incorporates fingers 918 which are releasably engageable with lips 920 to hold the canister in position. The canister and the latch mechanism is arranged so that when the latch is engaged, the spigots 906A and 906B are in sealing engagement or abutment with tubular protrusions 922 and 924 formed in the top of the canister.
The method of operation of the apparatus can be appreciated from the schematic layout in
A second tube 614 is connected to the wound site 302 at one end, and also to a pressure relief valve 610 and to a second transducer 616. Tubes 614 and 615 can be combined in a multi-partitioned tube in manner to be described later. By means of tube 614 and transducer 616 the pressure at the wound site can be measured or monitored. A filter 618 is placed at or close to the outlet end of the canister 606 to prevent liquid or solid particles from entering the tube 604. The filter is a bacterial filter which is hydrophobic and preferably also lipophobic. Thus, aqueous and oily liquids will bead on the surface of the filter. During normal use there is sufficient air flow through the filter such that the pressure drop across the filter is not substantial.
As soon as the liquid in the canister reaches a level where the filter is occluded, a much increased subatmospheric pressure occurs in tube 604 and this is detected by transducer 612. Transducer 612 is connected to circuitry which interprets such a pressure change as a filled canister and signals this by means of a message on the LCD and/or buzzer that the canister requires replacement. It may also automatically shut off the working of the pump.
In the event that it is desired to apply intermittent subatmospheric pressure to the wound site, a pressure relief valve 610 enables the pressure at the wound site to be brought to atmospheric pressure rapidly. Thus, if the apparatus is programmed, for example, to relieve pressure at 10 minute intervals, at these intervals valve 610 will open for a specified period, allow the pressure to equalize at the wound site and then close to restore the subatmospheric pressure. It will be appreciated that when constant subatmospheric pressure is being applied to the wound site, valve 610 remains closed and there is no leakage from atmosphere. In this state, it is possible to maintain subatmospheric pressure at the wound site without running the pump continuously, but only from time to time, to maintain a desired level of subatmospheric pressure (i.e. a desired pressure below atmospheric), which is detected by the transducer 612. This saves power and enables the appliance to operate for long periods on its battery power supply.
Instead of running two separate tubes to the wound site, it is preferable to contain tubes 614 and 615 in a single tube which is connected through the canister. Thus, for example, tubes 604 and 615 may comprise an internal tube surrounded by an annularg space represented by tube 614. This is illustrated in
In an alternative embodiment, the multi-lumen tube may be constructed as shown in
The partitioned tube need not continue all the way to the wound site 302, but can be connected to a short section of single bore tube close to the wound site.
In the event of an air leak in the dressing at the wound site 302, this can be detected by both transducers 612 and 616 reading insufficient subatmospheric pressure for a specific time period, and then triggering a leak alarm, i.e. a message on the LCD, preferably also with an audible warning.
Typically, the pump 602 is a diaphragm pump but other types of pump and equivalent components to those specifically employed may be substituted.
In an alternative form, the drape can be made in two parts, e.g. by cutting along the line X-X in
The surgical drape may include a protective film 1206, e.g. of polyethylene, and a liner 1208 that is stripped off prior to use to expose the pressure-sensitive adhesive layer. The polyurethane film may also include handling bars 1210, 1212, which are not coated with adhesive, to facilitate stretching of the film over the wound site. The dressing is preferably a pad of porous, flexible plastics foam, e.g. reticulated, open intercommunicating cellular flexible polyurethane foam, especially of the kind described in the above-mentioned PCT application WO 96/05873.
Alternatively, a reticulated intercommunicating cellular foam made from flexible polyvinylacetate or polyvinylalcohol foam may be used. The latter is advantageous because it is hydrophilic. Other hydrophilic open celled foams may be used.
In another method of therapy, the foam dressing may be sutured into a wound after surgery and the foam dressing connected to the pump unit by the multi-lumen catheter. Subatmospheric pressure can then be applied continuously or intermittently for a period determined by the surgeon, e.g. from about 6 hours to 4 to 5 days. After this period, the dressing is removed and the wound re-sutured. This therapy improves the rate of granulation and healing of wounds after surgery.
In the foregoing embodiments described with reference to Hunt, et al., the LCD screen 708, microprocessor 910, and PCB board 912 combine to serve as a controller; the subatmospheric pressure pump 602 serves as the source of subatmospheric pressure; the tubes 604 and 615 together serve as the liquid conduit; the transducer 612 serves as the pump pressure transducer; the tubes 608 and 614 together serve as the pressure detection conduit, and the transducer 616 serves as the tissue pressure transducer.
As described above, the tubes 614 and 615 may be contained in one tube to serve as the multi-lumen conduit, wherein the internal bore 1102 serves as a liquid lumen and conduits 1104 serve as pressure detection lumen. Further, the canister 606 serves at the container; the surgical drape serves as the cover; the dressing 300 serves as the screen; and the wound site 302 serves as the tissue site. After the screen is placed in contact with the tissue site, the cover is positioned to enclose the screen, defining the space under the cover and over the tissue site for application of the subatmospheric pressure. It is contemplated that the device may also include wireless communication equipment to allow physicians to remotely access records of the conditions under which the patient has been treated.
An alternative embodiment of the subatmospheric pressure therapeutic device 400 of
A preferred apparatus and process for detecting whether a container is filled with the body-liquid drawn from within the space defined by the cover, and for preventing the body-liquid from contaminating the source of subatmospheric pressure is set forth below with reference to Boynton et al. A preferred apparatus and process for oscillating application of the subatmospheric pressure over time is also described below with reference to Boynton et al.
The following embodiment is a vacuum assisted system for stimulating the healing of tissue.
Referring now to
Addition of an indicating agent, such as crystal violet, methylene blue, or similar agents known in the art causes a color change in the foam 300′ when in the presence of a bacterial agent. As such, a user or health care provider can easily and readily ascertain if an infection is present at the wound site 302′. It is contemplated that the indicating agent may also be placed in line of the conduit 1302, between the wound site 302′ and the canister 606. In such a configuration (not shown), the presence of bacterial contaminants in the wound site 302′, could be easily and readily ascertained without disturbing the wound bed, as there would be a nearly immediate color change as bacterially infected wound exudates are drawn from the wound site 302′ and through the conduit 1302 during application of subatmospheric pressure.
It is also contemplated that the foam pad 300′ may be coated with a bacteriostatic agent. Addition of such an agent, would serve to limit or reduce the bacterial density present at the wound site 302′. The agent may be coated or bonded to the foam pad 300′ prior to insertion in the wound site, such as during a sterile packaging process. Alternatively, the agent may be injected into the foam pad 300′ after insertion in the wound site 302′.
After insertion into the wound site 302′ and sealing with the wound drape 404, the foam pad 300′ is placed in fluid communication with a subatmospheric pressure source 602 for promotion of wound healing and secondarily, fluid drainage, as known to those of ordinary skill in the art. The subatmospheric pressure source 602 may be a portable electrically powered pump, or other suitable subatmospheric pressure source.
According to one embodiment, the foam pad 300′, wound drape 404, and subatmospheric pressure source 602 are implemented as known in the prior art, with the exception of those modifications detailed further herein.
The foam pad 300′ preferably comprises a highly reticulated, open-cell polyurethane or polyether foam for effective permeability of wound fluids while under subatmospheric pressure. The pad 300′ is preferably placed in fluid communication, via a plastic or like material conduit 1302, with a canister 606 and a subatmospheric pressure source 602. A first hydrophobic membrane filter 618 is interposed between the canister 606 and the subatmospheric pressure source 602, in order to prevent wound exudates from contaminating the subatmospheric pressure source 602. The first filter 618 may also serve as a fill-sensor for canister 606. As fluid contacts the first filter 618, a signal is sent to the subatmospheric pressure source 602, causing it to shut down. The wound drape 404 preferably comprises an elastomeric material at least peripherally covered with a pressure sensitive adhesive for sealing application over the wound site 302′, such that a subatmospheric pressure seal is maintained over the wound site 302′. The conduit 1302 may be placed in fluidic communication with the foam 300′ by means of an appendage 408 that can be adhered to the drape 404.
According to a preferred embodiment, a second hydrophobic filter 1304 is interposed between the first filter 618 and the subatmospheric pressure source 602. The addition of the second filter 1304 is advantageous when the first filter 618 is also used as a fill sensor for the canister 606. In such a situation, the first filter 618 may act as a fill sensor, while the second filter 1304 further inhibits contamination of wound exudates into the subatmospheric pressure source 602. This separation of functions into a safety device and a control (or limiting) device, allows for each device to be independently engineered. An odor vapor filter 1306, which may be a charcoal filter, may be interposed between the first filter 618 and the second filter 1304, in order to counteract the production of malodorous vapors present in the wound exudates. In an alternate embodiment (not shown), the odor vapor filter 1306 may be interposed between the second hydrophobic filter 1306 and the subatmospheric pressure source 602. A second odor filter 1308 may be interposed between the subatmospheric pressure source 602 and an external exhaust port 1310, in order to further reduce the escape of malodorous vapors. A further embodiment allows for first 618 and second filters 1304 to be incorporated as an integral part of the canister 606 to ensure that the filters 618, 1304, at least one of which are likely to become contaminated during normal use, are automatically disposed of in order to reduce the exposure of the system to any contaminants that may be trapped by the filters 618 and 1304.
A means for sampling fluids may also be utilized by providing a resealable access port 1312 from the conduit 1302. The port 1312 is positioned between the distal end 1302a of the conduit 1302 and the proximal end 1302b of the conduit 1302. The port 1312, as further detailed in
The process by which wound fluids are sampled comprises penetrating the membrane 1402 with a fluid sampler 1404, such as a hypodermic needle or syringe. The sampler 1404 is inserted through the membrane 1402 and into the port 1312 until it is in contact with wound fluids flowing through the inner lumen 1406 of the conduit 1302. As illustrated in
The subatmospheric pressure source 602 may consist of a portable pump housed within a housing 1502, as illustrated in
According to one embodiment, a means for securing the housing 1502 to a stationary object, such as an intravenous fluid support pole for example, is provided in the form of a clamp 1506. The clamp 1506, which may be a G-clamp as known in the art, is retractable, such that when not in use is in a stored position within a recess 1508 of the housing 1502. A hinging mechanism 1510 is provided to allow the clamp 1506 to extend outward from the housing 1502, to up to a 90 degree angle from its stored position. An alternative embodiment (not shown) allows the clamp 1506 to be positioned at up to a 180 degree angle from its stored position. The hinging mechanism 1510 is such that when the clamp 1506 is fully extended, it is locked in position, such that the housing 1502 is suspended by the clamp 1506. A securing device 1512, such as a threaded bolt, penetrates through an aperture 1514 of the clamp 1506, to allow the clamp 1506 to be adjustably secured to various stationary objects of varying thickness.
Alternatively, the securing device 1512, may be comprised of a spring actuated bolt or pin, that is capable of automatically adjusting to various objects, such as intravenous fluid support poles, having varying cross-sectional thicknesses.
One embodiment also allows for management of a power supply to the subatmospheric pressure source 602, in order to maximize battery life when a direct current is utilized as a power supply. In a preferred embodiment, as illustrated in the flow chart of
Battery life is further extended, as illustrated in the flow chart shown in
Referring now back to
The use of the variable frequency pump drive system 1314 allows the pressure of the pump 602 to be maximized. In tests on sample oscillating pumps, the maximum pressure achieved was doubled by varying the drive frequency by only 30%. Additionally, the system 1314 maximizes flow rate over the extended frequency range. As a result, performance of the pump 602 is significantly improved over existing fixed frequency drive system pumps without increasing the pump size or weight. Consequently, battery life is further extended, thus giving the user greater mobility by not having to be tethered to a stationary power source. Alternatively, a similar performance level to the prior art fixed frequency drive system pumps can be achieved with a smaller pump. As a result, patient mobility is improved by improving the portability of the unit.
Another embodiment also increases the stimulation of cellular growth by oscillating the pressure over time, as illustrated in the flow chart of
If the actual pressure is increasing in test 1708, a determination is then made as to whether a variable target pressure is still less than the maximum target pressure 1710. If the variable target pressure is still less than the maximum target pressure the software next determines whether the actual pressure has equaled (risen to) the ascending target pressure 1712. If the actual pressure has attained the ascending target pressure, the software increments the variable target pressure by one interval 1714. Otherwise, it refrains from doing so until the actual pressure has equaled the ascending target pressure. If the variable target pressure has reached the maximum target pressure in the test of block 1710 the software sets the pressure direction to “decreasing” 1716 and the variable target pressure begins to move into the downward part of its oscillatory cycle.
The interval may be measured in mmHg or any other common unit of pressure measurement. The magnitude of the interval is preferably in the range of about 1 to 10 mmHg, according to the preference of the user.
If the actual pressure is decreasing in test 1708, a determination is then made as to whether the variable target pressure is still greater than the minimum target pressure 1718. If the variable target pressure is still greater than the minimum target pressure the software next determines whether the actual pressure has attained (fallen to) the descending target pressure 1720. If the actual pressure has equaled the descending target pressure the software decrements the variable target pressure by one interval 1722. Otherwise it refrains from doing so until the actual pressure has equaled the descending target pressure. If the variable target pressure has reached the minimum target pressure in the test of block 1718, the software sets the pressure direction to “increasing” 1724 and the variable target pressure begins to move into the upward part of its oscillatory cycle. This oscillatory process continues until the user de-selects the pulsing mode.
In the foregoing embodiments described with reference to Boynton, et al., the foam pad 300′ serves as the screen; the wound site 302′ serves as the tissue site; the wound drape 404 serves as the cover; the conduit 1302 serves as the liquid conduit; the canister 606 serves as the container; and the electrically powered pump 602 serves as the source of subatmospheric pressure. The appendage 408 serves as the connector interposed between the liquid conduit and the space defined by the cover to secure the liquid conduit to the cover. It is contemplated that the equipment may include wireless communication equipment to allow physicians to remotely access records of the conditions under which the patient has been treated.
Alternate embodiments of the cover are contemplated including, but not limited to, semi-rigid covers that protect the tissue site 320′.
The metallic properties of certain therapeutic or prophylactic agents, such as the antimicrobial silver, also lend themselves to metal-coating the dressing 300. Referring now to
Next, a silver oxide precipitate is combined in a solvent, such as ammonia, to create a silver-solvent complex, 1918. Any solvent capable of dissolving the metal and/or forming a metal-solvent complex may be used. The silver-solvent complex is then placed in a third holding tank and continuously agitated, 1920. The foam is placed in the third holding tank, 1922. The foam is then saturated with the silver-solvent complex, 1924.
Next, a surfactant is completely dissolved in deionized water and placed in a fourth holding tank, 1926. The foam is removed from the third holding tank and placed in the fourth holding tank, 1928. A reducing agent, such as formaldehyde, is added to the surfactant solution and agitated, and the foam is saturated in the solution, 1930. Any reducing agent that is capable of causing the metal to precipitate onto the substrate may be used in this embodiment. The reducing agent precipitates the silver onto the foam to form the metal-coated foam, 1932. The foam is removed from the fourth holding tank and excess solution is removed from the foam, 1934. A rinse solution is prepared in a fifth holding tank, 1936. The foam is immersed and thoroughly rinsed, 1938. The foam is removed from the fifth holding tank and excess rinse is removed from the foam, 1940.
Next, a mild caustic soda solution is prepared and placed in a sixth holding tank, 1942. The foam is immersed in the sixth holding tank and saturated in the caustic soda solution, 1944. The foam is removed from the sixth holding tank and excess caustic solution is removed from the foam, 1946. A rinse solution is prepared in a seventh holding tank, 1948. The foam is immersed and thoroughly rinsed, 1950. Next, the foam is removed from the seventh holding tank and excess rinse is removed from the foam, 1952. Optionally, the weight of the saturated foam, while still wet, may be calculated, 1954.
The foam is then placed in a convectional forced-air oven set to a predetermined temperature and time to completely dry the metal-coated foam, 1956. Alternatively, to verify the dry condition of the foam, the weight of the foam may be checked again, 1958. The foam is then packaged in a moisture vapor transmission rate pouch, if preferred, 1960. The foam is now ready for use on the tissue site, which may include without limitation, any site that may benefit from subatmospheric pressure tissue treatment, such as partial thickness burns, traumatic wounds, surgical wounds, dehisced wounds, diabetic wounds, pressure ulcers, leg ulcers, flaps and grafts.
It is understood that the foregoing coating-process steps, components, component proportions, the amount of time the substrate is immersed in the solutions, and the process for applying the solution to the substrate may vary to accommodate the substrate material and the agent to be coated on the substrate. Such variations are considered to be within the scope of this invention. Those skilled in the art can easily adapt the foregoing coating process for metal-coating other substrates, such as fiber or film, without undue experimentation.
A preferred embodiment uses a metallic coating process provided by Noble Fibers Technologies, Inc., of Clarks Summit, Pa., for producing the “V.A.C. GranuFoam® Silver” antimicrobial silver-coated foam dressing product commercialized by KCI USA, Inc. (and its affiliates) of San Antonio, Tex., for use in combination with their V.A.C.® subatmospheric pressure tissue treatment devices. Although portions of the metallic coating process used by Noble Fibers are proprietary and may not be publicly known, similar techniques will be known to those skilled in the art without undue experimentation.
The V.A.C. GranuFoam® Silver antimicrobial silver-coated foam dressing has achieved in-vitro efficacy on two common bacteria-staphylococcus aureus and pseudomonas aeruginosa, with a uniformly coated 99.9% pure silver metallic coating (4-12% silver by weight, though as little as 0.1% has shown to be at least partially effective). The coating is approximately 1-3 micrometers thick. The dressing maintains its effectiveness for at least 72 hours through a controlled and steady state release of ionic silver, providing over a 4 log reduction or about 99.99% of pathogenic bacteria have been eliminated between about 24 hours and about 72 hours. The coated dressing maintains the physical properties of the foam dressing substrate, which allows for direct and complete contact with the tissue site under application of the subatmospheric pressure.
An alternate embodiment includes uniformly coating a fiber substrate with a metallic agent, such as silver, wherein all fibers are circumferentially covered with the metallic coating. In this embodiment, the fiber is worked (woven, knitted, crocheted, felted, blown, etc.) to construct the dressing 300 subsequent the coating process. The uniform coating of the fiber substrate may be accomplished utilizing a metal-based coating process similar to the process 1900 of
A similar process is used by Argentum Medical, LLC. of Chicago, Ill., for coating their “Silverlon®” antibacterial woven dressing product line. Although portions of the process are proprietary and may not be publicly known, similar techniques for metal-coating fiber, will be known to those skilled in the art.
While the foregoing description is exemplary of the preferred embodiments, those of ordinary skill in the relevant arts will recognize the many variations, alterations, modifications, substitutions and the like that are readily possible. It is contemplated that the components and additives for the polymer-based or metal-based coating solution may vary widely to accommodate the various substrate materials and agent(s) to be released. The coating can be formulated specific to coat thickness. It may be formulated to allow for various particle sizes. The coating may be formulated to provide various release kinetics, including but not limited to concentration, rate and the duration of agent release. For example, the release profile may be engineered such that release occurs in a matter of hours for up to several weeks. Concentration of delivery can be engineered to release from a low concentration of parts-per-billion (ppb) to several hundred parts-per-million (ppm) of agent within minutes. In the case where multiple agents are to be released, the coating may be formulated to provide scheduled and alternating agent releases.
Further, it is contemplated that the method of coating application or deposition may also vary widely, based on the various potential substrate materials and agent(s) to be released. The substrate material may vary beyond that set forth. Examples of the substrate useful in these embodiments include, but are not limited to foam, yarns, films, filaments, fibers, fabrics, filler materials, and a combination thereof that can be formed into the dressing 300.
It is also contemplated that the coating may incorporate single or multiple agents for release. Agents useful in these embodiments include, but are not limited to therapeutic and prophylactic agents, such as antimicrobial agents, enzymatic debriders, anesthetic agents, chemotherapeutic agents, indicating agents, and growth factors. Antimicrobial agents include, but are not limited to antibacterial agents, such as antibiotic and bacteriostatic agents. Useful indicating agents include, but are not limited to crystal violet, methylene blue, and similar agents known to cause a color change in tissue and/or body-liquid, for example, when in the presence of a bacterial agent, acidity, and alkalinity. Growth factors useful in embodiments discussed herein include, but are not limited to transforming growth factor, epidermal growth factor, platelet derived growth factor, insulin-like growth factor, keratinocyte growth factor, fibroblast growth factor, granulocyte macrophage colony stimulating factor, and granulocyte colony stimulating factor.
It is further contemplated that the screen 300 may comprise a plurality of portions, such as layers, only one of which comprises the uniformly covered substrate portion of the screen. In one embodiment, the screen 300 may be comprised of a lower uniformly covered substrate portion and an upper impermeable film portion of the screen, wherein the upper film portion of the screen may include an aperture or plurality of flow ports to provide fluid communication between the uniformly covered substrate portion of screen and the source of subatmospheric pressure. In an alternative embodiment, each of the plurality of portions of the screen may be comprised of substrate covered with different or alternating coatings for releasing a plurality of therapeutic or prophylactic agents to the tissue site 302.
While the foregoing description is exemplary of the preferred embodiments of the present invention, those of ordinary skill in the relevant arts will recognize the many other alternatives, variations, alterations, modifications, substitutions and the like as are readily possible, especially in light of this description, the accompanying drawings and claims drawn thereto. In any case, because the scope of the present invention is much broader than any particular embodiment, the foregoing detailed description should not be construed as a limitation of the scope of the present invention, which is limited only by the claims appended hereto.
The present application is a continuation-in-part of U.S. patent application Ser. No. 11/189,195 entitled METHOD FOR COATING SUBSTRATE WITH ANTIMICROBIAL AGENT AND PRODUCT FORMED THEREBY filed Jul. 26, 2005, which claims priority to U.S. Provisional Patent Application No. 60/591,014, filed Jul. 26, 2004, assigned to the assignee of the present application, the disclosure of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60591014 | Jul 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11189195 | Jul 2005 | US |
| Child | 11494171 | Jul 2006 | US |
