PRESSURE-SENSING NEGATIVE PRESSURE THERAPY SPONGES AND METHODS FOR THE CREATION AND USE THEREOF

Abstract

Negative pressure wound therapy sponges that are custom-fabricated to fit a given wound to be treated, corresponding methods of creating said sponges in situ or external to a wound, and related systems for performing negative pressure wound therapy using said sponges. Exemplary sponge embodiments may have pressure-sensing capabilities.

Claims

1. A negative pressure therapy sponge with pressure-sensing capability, comprising: a sponge body that conforms to the size and contours of a given wound to be treated, the sponge body being of an open cell foam material having a pore size of between about 200 μm and about 1,000 μm; and a pressure-sensing mechanism located on at least a portion of the exterior surface of the sponge body.

2. The sponge of claim 1, wherein the pressure-sensing mechanism is a pressure-sensitive coating, a piezoelectric sensor, or an electroactive ink sensor such as a force sensing resistor, that is located and adapted to measure pressures within the sponge when in use.

3. A method for the in-situ creation of a negative pressure therapy sponge with pressure-sensing capability, comprising: providing a sponge material in a multi-component, unreacted form; dispensing the multi-component foam material into a wound to be treated; allowing the components of the foam material to react, expand and form an open cell foam sponge that fills the wound; and applying a pressure-sensing mechanism to at least a portion of the exterior surface of the sponge.

4. The method of claim 2, wherein a liner or bladder is placed in the wound prior to introduction of the unreacted foam components.

5. A method of pressure-sensing negative pressure wound therapy, comprising: creating a pressure-sensing negative pressure wound therapy sponge in situ or placing a pre-formed pressure-sensing negative pressure wound therapy sponge within a wound to be treated; connecting the pressure-sensing negative pressure wound therapy sponge to a pressure monitoring device; and monitoring pressures applied to the sponge during negative pressure wound therapy to optimize the procedure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the following descriptions of the drawings and exemplary embodiments, like reference numerals across the several views refer to identical or equivalent features, and:

[0026] FIG. 1 depicts the creation and placement of one exemplary negative pressure therapy sponge embodiment within an open wound of a patient;

[0027] FIG. 2 is a magnified view of one exemplary foam material from which an exemplary negative pressure therapy sponge embodiment may be manufactured;

[0028] FIG. 3 illustrates other techniques for creating an exemplary negative pressure therapy sponge embodiment;

[0029] FIG. 4 depicts the creation and placement of one exemplary negative pressure therapy sponge embodiment within an open wound of a patient using liner/bladder within the wound to receive the sponge material;

[0030] FIG. 5 represents a sensor placed on the surface of an exemplary negative pressure therapy sponge embodiment that is located in the wound of a patient, along with an associated exemplary monitor/controller for presenting sensor data to a user;

[0031] FIG. 6 is a magnified view of an exemplary wound pressure display, such as the pressure display shown in FIG. 5;

[0032] FIG. 7 depicts one exemplary embodiment of a force-sensing resistor (FSR) that may be utilized as a sensor for placement on the surface of an exemplary negative pressure therapy sponge embodiment;

[0033] FIG. 8 illustrates another exemplary monitor controller in the form of a smart phone for receiving data from a sponge-placed sensor, and for remotely controlling the negative pressure level produced by an associated NPWT device;

[0034] FIG. 9 is a magnified view of one exemplary film and sensor that may form an outer (exposed) surface of an exemplary negative pressure therapy sponge embodiment;

[0035] FIG. 10 illustrates another exemplary method of producing a custom negative pressure therapy sponge, wherein a sensor/film may be placed over a wound prior to injecting foam material into the wound;

[0036] FIG. 11 depicts the connection of suction hosing to a port on the sensor/film of FIG. 10, along with foam injection through another port on the sensor/film; and

[0037] FIG. 12 shows a fully-formed exemplary negative pressure therapy sponge within the wound of FIGS. 10-11, in addition to a monitor/controller connected to the sensor of the sensor/film and a suction device connected to the port previously used to inject the foam.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0038] As described above, exemplary negative pressure therapy sponge embodiments are custom-fabricated to correspond to size, shape and contours of a given wound, and to evenly fill the wound. At least some exemplary negative pressure therapy sponge embodiments may be created by injecting foam components into a wound and allowing the foam components to react, expand, and fill the wound. Other exemplary negative pressure therapy sponge embodiments may be produced by creating a digital 3-D model of a wound (such as by imaging with a camera, laser or the like) and then 3-D printing a custom negative pressure therapy sponge.

[0039] Exemplary negative pressure therapy sponge embodiments may be comprised of materials such as, for example, open cell silicones. Such materials may have a density of between, for example, 0.18 and 0.25 g/cm.sup.3. Without limitation, one exemplary silicone-based material that may be used polydimethylsiloxane (PDMS) silicon rubber. Silicone-based products are well-suited as a custom negative pressure therapy sponge material due to their biocompatibility, and reduced skin irritation and cytotoxicity.

[0040] An alternative composition for producing an exemplary negative pressure therapy sponge embodiment may be polyurethane, polyester, polyether or a variant/combination. For example, an exemplary negative pressure therapy sponge embodiment may be comprised of a mixture of polymeric diphenylmethane diisocyanate (Iso, MDI), polyol (polyether glycerol, polyether glycol), and catalyst (33% triethylenediamine (TEDA), 66% dipropylene glycol (DPG)). The materials may be reticulated and may possess viseoelastic properties. One non-limiting example of suitable soft foam may be created with a relative density of about 5.2 lb/cubic ft. Such a mixture may comprise, for example and without limitation, 1.5 g catalyst and 43 g iso per 100 g polyol. Increasing concentrations of iso to polyol result in foams of increasing density and firmness.

[0041] As represented in FIG. 1, in one exemplary embodiment, the selected sponge material (e.g., silicone) is initially provided in multi-component liquid form, which liquid components are injected via a syringe-type applicator into a wound of interest and allowed to react to create a custom negative pressure therapy sponge with open cell pores that conforms to the exact shape and contours of the wound.

[0042] FIG. 1 also represents an alternative technique for creating an exemplary negative pressure therapy sponge. As illustrated in the upper left corner of FIG. 1, an aerosolized foam material may be employed instead of a foam dispensed from a syringe-type applicator. In this case, the aerosolized foam would be sprayed into a wound of interest and allowed to react to create a custom negative pressure therapy sponge with open cell pores that conforms to the exact shape and contours of the wound.

[0043] As illustrated in FIG. 2, the foam sponge resulting from either creation technique shown in FIG. 1 is preferably an open-cell solid structure with pore sizes ranging from, for example, 200-1,000 μm (FIG. 2). The pore size may be determined by the plastic bubble or cell formation with mechanical oscillation of the materials to arrive at the desired pores per inch (ppi).

[0044] As represented in FIG. 3, an exemplary negative pressure therapy sponge embodiment may also be created using a 3-D printer. More specifically, a wound of interest would first be imaged, such as through conventional 3-D reconstructions, a CT scan, 3-D photography, laser scanning, etc. In FIG. 3, a portable 3-D scanner (camera) is used to capture wound images from a patient's bedside. In any case, the imaging process is used to create a digital 3-D wound model that may be sent to a device such as, but not limited to, a 3-D printer. The 3-D printer or other sponge forming device is then used to create a custom negative pressure therapy sponge from the digital 3-D wound model, such that the sponge will precisely fit within and evenly fill the wound. When a device such as a 3-D printer is used to create an exemplary negative pressure therapy sponge embodiment, the desired pore size may be set with viseoelastic properties customized to the wound being treated. For example, a deep narrow wound may have more rigid compression properties and larger pore sizes to prevent debris and fluid from disrupting fluid removal capability.

[0045] It should be realized that the above-described and shown exemplary techniques for producing an exemplary custom negative pressure therapy sponge allow for the creation of a custom sponge at each dressing change (if warranted). Consequently, as the size, shape and interior contours of a given wound change during the healing process, exemplary negative pressure therapy sponges may be easily custom-fabricated to accommodate such changes, thereby ensuring that the sponge used will always properly fit the wound during all stages of healing.

[0046] As illustrated in FIG. 4, a bladder or liner may be placed into a wound prior to foam application to permit the foam to harden prior to tissue contact while still achieving the desired wound-conforming, custom shape. The bladder/liner materials may be, for example, plastic, silicone, polyurethane, etc. For example, the bladder/liner may be a thin polyurethane, Mylar®, silicone-based, or other plastic based sheet material. The bladder/liner may be similar in thickness to a Tegaderm™ tape (available from 3M Healthcare in St. Paul, Minn.). After the foam hardens, the resulting custom negative pressure therapy sponge and the bladder/liner may be removed, the custom negative pressure therapy sponge may then be re-inserted into the wound. The foam chemicals may be aerated while being mixed within the bladder/liner to allow for proper creation of pores.

[0047] The foam used to form a given exemplary negative pressure therapy sponge embodiment may be compressible at −125 mmHg of negative pressure, but not compressible at −50 mmHg of negative pressure. The pore size employed may be selected based on the amount of microdeformation desired. More microdeformation will be produced when the pore size is between about 500-1,000 μm. Prevention of pore size closure will allow for fluid exudate removal.

[0048] When no pressure is applied to an exemplary negative pressure therapy sponge located within a wound, the foam of the sponge will remain in its resting state. An applied negative pressure using an appropriate NPWT device will cause the sponge material to collapse, but it will return to its resting state upon removal of the negative pressure. An exemplary negative pressure therapy sponge embodiment may be removed from a wound without pieces of the sponge breaking off and remaining as foreign bodies within the wound.

[0049] The pore size of an exemplary negative pressure therapy sponge embodiment may be predetermined to maximize the promotion of granulation tissue formation, cellular proliferation, and vascular in-growth. The pore size of an exemplary negative pressure therapy sponge embodiment may also be designed to mildly adhere to the wound bed such that debridement occurs at each sponge removal. An exemplary negative pressure therapy sponge embodiment may also be coated with antimicrobial materials such as, for example, silver, chlorhexidine, iodine, or other antimicrobial agents. To provide rigidity to the negative pressure therapy sponge structure, exemplary embodiments may be nano coated with materials such as, for example, carbon, anodized carbon, silicon dioxide, silicone, silica, fiberglass, PTFE or equivalent fortifying materials. Coating the open cell foam will generally not reduce the pore size.

[0050] In certain embodiments, the pressure sensing sponge is coated with wound modifying substances. For example, the sponge may be coated or bioprinted with growth factors or stem cells. Growth factor families such as Vascular Endothelial Growth Factor (VEGF), Insulin-like Growth Factor (IGF), Fibroblast Growth Factor (FGF), Platlet-derived Growth Factor (PDGF), Bone Morphogenetic Protein (BMP), Epidermal Growth Factor (EGF), transforming growth factor (TGF), Keratinocyte Growth Factor (KGF), Colony Stimulating Factors, Tropoelastin, Interleukins, Collagens or the like may be added both to the sponge or 2-part silicone preparation to improve wound healing capacity.

[0051] Also in accordance with alternative embodiments, Autogenous or Allograft stem cells such as embryonic stem cells, tissue specific stems cells including Mesenchymal Stem Cells (MSCs), Adipose-derived Stem Cells (ASCs), Pericyte-derived stem cells (PSCs), hematopoietic stem cells, or epithelial stem cells can be bioimprinted on to the sponge materials. Alternatively, chemical wound debriding substances can be added to the sponge materials to assist with necrotic tissue removal, harmful metalloproteinase breakdown and accelerate healing. Enzymatic debriding products can be added to the final sponge or 2-part system including collagenase based products, papain based products, papain-urea based products, hydrogels, or other equivalent autolytic debriders. Other possible autolytic agents include: elastase, myeloperoxidase, acid hydrolase, and lysosomal enzymes.

[0052] As represented in FIG. 5, the use of exemplary negative pressure therapy sponge embodiments may include wound monitoring. That is, whether a negative pressure therapy sponge embodiment is created in-situ as described above, prefabricated using, for example, a 3-D printing process, or even non-custom, the foam used to create the sponge will be pressure sensing in nature. To that end, an exemplary negative pressure therapy sponge embodiment may be coated with silver, zinc oxide, anodized carbon, copper, Au NPs, other carrier vehicles, other piezoelectric materials or pressure-sensing nanotechnology. When coated, such an exemplary sponge may be coated only along the circumference or on all material surfaces. In any case, the applied electroactive coating will have high electrical conductivity and be resistant to oxidation. The coating will also adhere well to the underlying sponge material.

[0053] FIG. 7 represents one type of pressure sensor that may be employed in a pressure-sensing exemplary negative pressure therapy sponge embodiment. In this particular example, the force sensor is a force-sensing resistor. However, other sensor types may be used in other embodiments.

[0054] As pressure-sensing negative pressure therapy sponge embodiment is compressed, a change in polarity, resistance and/or voltage will be captured by a monitor/controller, as shown. Associated monitor/controller software or other programming may apply an algorithm converting the sensed changes to pressures (e.g., mmHg) and may also display to a user wound pressures in or surrounding the sponge, such as but not limited to in the manner of a pressure heat map as shown in FIGS. 5-6.

[0055] Electrical power for the monitor/controller may be supplied by a portable battery, such as but not limited to coin batteries or lithium ion batteries to provide portability. The voltage (likely below around 5 V) will not be high enough to be sensed by the patient. The electroactive coating will be able to bend with the sponge without significantly altering the resistance in the system. If only the surface of the sponge is coated, a second coating may be applied to provide an encapsulation layer.

[0056] Pressure sensing may be continuous or intermittent as current is pulsed across the system. The electroactive coating may be connected to an adapter/controller. Non-limiting adapter/controller examples include a FFC-FPC (SMT) adapter to a micro PCB with Bluetooth capability. The adapter may also be directly connected to the pressure display monitor or pump display.

[0057] Sensing pressure within the sponge or wound provides, among other things, information that may be used to further customize the treatment of a given wound. The primary goal of the dressing design and suction pressure is to achieve a uniform distribution of tissue deformation in the surface of the wounded tissue. Larger sponge pore sizes may result in greater microdeformation and fluid removal. Smaller sponge pore sizes may lead to greater macrodeformation. Monitoring and presenting pressure data to a user will permit the user to adjust the negative pressure applied from the associated vacuum source during NWPT to create the most ideal negative and positive pressure balance to optimize wound healing.

[0058] When pressure monitoring/reporting is provided, there may be an alarm associated with the monitor/controller that prevents too much positive pressure (e.g., as indicated by red on the heat map of FIGS. 5-6) which may cause an excessive ischemic environment within the wound tissues. The alarm may also alert a user when too little negative pressure is in the sponge, as such a condition may result in less than adequate fluid removal and an increased infection risk. Each wound may have particular pressure parameters that will accelerate wound healing.

[0059] One important aspect of the exemplary pressure sensing negative pressure therapy sponge embodiments described and shown herein is that pressure is being sensed at the wound interface and not at a remote pump outside the wound. The heat map or other pressure indicating display will also allow a user to monitor the three dimensional size of the wound and monitor healing progress. Changes in wound size may be plotted against the pressures the wound faces to create the greatest rate of reduction in wound size.

[0060] As indicated in FIG. 8, a monitor/controller may be in the form of a smart phone or similar portable device provided with an appropriate application so that pressure information associated with a sponge in a wound may be observed remotely and/or by multiple personnel. In such a case, the monitor/controller may be equipped with Bluetooth® communication capability or may include some other communication protocol having low-power consumption.

[0061] By using an appropriately programmed monitor/controller, such as the exemplary monitor/controller shown in FIG. 8, a user could remotely alter sponge pressures by adjusting the negative pressure applied thereto by a connected NPWT pump. Additionally, since real time sponge pressures may be observed, the need for large and expensive pumps may be reduced as more cost effective sources of negative pressure (e.g., wall suction) may be implemented. Normal skin breakdown surrounding the wound being treated can also be monitored for excessive pressures to prevent skin breakdown.

[0062] In addition to pressure sensing capabilities, an exemplary negative pressure therapy sponge embodiment may also be capable of sensing other characteristics such as but not limited to temperature, pH, glucose and growth factor, which sensed characteristics may be used to, for example, notify a user of an increasing risk of infection, metalloproteinases presence, or other inhibitors to wound healing. An exemplary negative pressure therapy sponge embodiment may also be coated with microspheres to allow the sponge to be drug eluding and deliver growth factors such as VEGF, IGF, FGF or other angiogenic, fibroblastic, or tissue promoting agents.

[0063] In order to produce adequate negative pressure within a wound to be treated, a closed or substantially closed system must generally be provided. In one exemplary embodiment as represented in FIG. 9, a film such as a clear polyurethane, polyethylene, silicone, acrylate or combination film may be placed over an exemplary negative pressure therapy sponge embodiment while the sponge resides in a wound to be treated so as to crate closed system. The film may include an adhesive and may be similar to commercial products like Tegaderm™ tape. The film may also have semipermeable membranes.

[0064] Chlorhexidine or a similar antimicrobial substance(s) may be applied to an exemplary film and/or to the adhesive on the film in contact with the skin surrounding the wound. As shown in FIG. 9, an exemplary film may also include piezoelectric or other sensor elements. For example, a piezoelectric coating may be placed on the entire sheet of film or only on a central portion. The provided sensor may also be cut or trimmed so the sensor only covers the sponge surface area. The area of the film that overlies the sponge will then be capable of providing pressure readings from very close to the wound interface. Again, a display of pressures may be presented to a user to facilitate the optimization of NPWT pressure.

[0065] An alternative technique for creating an exemplary custom negative pressure therapy sponge within a wound to be treated is depicted in FIGS. 10-12. The typical process for placing a known negative pressure therapy sponge in a wound and then applying a wound vacuum thereto to create a negative pressure, involves first applying the polyurethane sponge after it is cut roughly to size. Upon placement in the wound, the sponge commonly sticks out in many places. Thus, a second person is usually required, such that one person can hold the sponge in place while the other person places the overlying tape/dressing. A hole is next cut in the dressing and a pump adapter and hose is applied (see circular disk with hose attached in FIGS. 5 and 9). Sometimes it is necessary to add multiple small pieces of tape to hold the sponges in place and it is a race against fluid seeping out the edges before the vacuum is turned on. This seepage ruins the seal and then one has to spend time finding where the leak is.

[0066] Consequently, the exemplary embodiment illustrated in FIGS. 10-12 is designed to overcome these problems by essentially reversing the typical steps involved in placing a negative pressure therapy sponge in a wound. More particularly, and as represented in FIGS. 10-12, an adhesive-backed film is first applied over the wound to produce a good seal on normal (non-wounded) skin, or a non-adhesive-backed film is taped to the normal skin. The film includes at least an injection port through which foam may be applied into the wound in a manner as described above. The film may also include a suction port.

[0067] With the film in place (see FIG. 10), foam may be applied through the injection port and into the wound (see FIG. 11), whereafter the foam components will react and expand to form a custom negative pressure therapy sponge that conforms to and fills the wound (see FIG. 12). Such an arrangement eliminates the need for multiple sponges and for the assistance an additional person during application, as well as the leaks common to known techniques and systems.

[0068] As indicated in FIG. 10, a pressure sensor may be a part of the film, for any of the purposes described above. As indicated in FIG. 12, an adapter and associated suction hosing may be attached to the suction port that passes through the film to permit the subsequent application of negative pressure to the wound and the formed sponge during the NPWT process. The injection port may be used multiple times and may also act as an irrigation port to allow removal of debris from the sponge, or as a conduit for delivering medications/therapies (e.g., for antibiotic irrigation).

[0069] In addition to wound therapy as previously described, it is contemplated that exemplary negative pressure therapy sponge and system embodiments may be used in the treatment of burn scar reduction, and hypertrophic or keloid scarring where pressure is a main source of treatment. An exemplary pressure-sensing negative pressure therapy sponge may also be placed on top of an incision to take tension off the repair and optimize aesthetic outcomes. Applying the correct amount of pressure while limiting patient discomfort can be customized to each individual. Pressure-sensing negative pressure therapy sponge embodiments may also be used in custom orthotics such as prosthesis, shoes, inserts, and padding. In such applications, an exemplary pressure-sensing negative pressure therapy sponge may alert a user when excessive pressures leading to skin breakdown might occur. Such a use of an exemplary pressure-sensing negative pressure therapy sponge may also optimize comfort or wear-ability of a prosthetic or orthotic device.

[0070] The pressure-sensing foam used to create an exemplary pressure-sensing negative pressure therapy sponge may also be used in the treatment of deformational or positional plagiocephaly. Such a foam may replace existing foams on market and allow for custom application of a molding helmet at the time of patient evaluation. The pressure sensing capability of such a foam inside the helmet could alert the treating individual of excessive pressures during the head molding/shaping process as the calvarium enlarges. The pressure sensing capability of such a foam may also notify a user when the head shape is optimal or when the foam needs to be adjusted. The use of such a foam may also reduce discomfort, ulceration and erythema, and may optimize fit to the underlying tissue/bone.

[0071] Larger custom open cell memory foam applications may be used in the operating theater for patients along areas prone to break down such as elbows, hips, knees and head during surgery. The custom foam may be placed in splints and casts with pressure reading to prevent skin breakdown, ulceration, or compartment syndrome. There may be applications in the veterinary environment such as the treatment of equine wounds.

[0072] In addition to the foregoing, in alternative embodiments the sensor or sensing element is included in a layer within the sponge (not necessarily on surface, circumference or coated within). The sensor or sensing element may also be in the form of one or more columns under the port that can be cut to varying length corresponding to the depth of the wound. Such a column preferably has a different rigidity than the surrounding sponge to help assess the pressure being observed at various depths of the wound (sort of like a tsunami buoy system). In yet further alternative embodiments, the pump automatically or dynamically changes the ‘flow’ within the system to ensure that the pressure seen at or near the bottom of the sensor is sufficient or ideal for wound healing specific to the wound being treated. In such embodiments, the number of ‘alerts’ and ‘stoppages’ of the pump is reduced as compared with conventional wound vac pumps, as such alerts and stoppages tend to lead to patient dissatisfaction (e.g., disrupted sleep) and device failure (e.g., from overlying tape getting too saturated and leaking from pump inactivity).

[0073] Although the invention has been described in conjunction with specific preferred and other embodiments, it is evident that many substitutions, alternatives and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, the invention is intended to embrace all of the alternatives and variations that fall within the spirit and scope of the appended claims. For example, it should be understood that, in accordance with the various alternative embodiments described herein, various systems, and uses and methods based on such systems, may be obtained. The various refinements and alternative and additional features also described may be combined to provide additional advantageous combinations and the like in accordance with the present invention. Also as will be understood by those skilled in the art based on the foregoing description, various aspects of the preferred embodiments may be used in various subcombinations to achieve at least certain of the benefits and attributes described herein, and such subcombinations also are within the scope of the present invention. All such refinements, enhancements and further uses of the present invention are within the scope of the present invention.