Abstract:
Assemblies, systems, and methods convey fluid from an internal wound site or body cavity by applying negative pressure from a source outside the internal wound site or body cavity through a wound drain assembly that is placed directly inside the internal wound site or body cavity.

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/810,733, filed Jun. 2, 2006, and entitled “Foam Sponge Vacuum Assisted Internal Drainage System,” which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This application relates generally to the drainage of fluid from the body during the wound healing process, e.g., following surgery, trauma, or placement of implants or surgical devices. 
     BACKGROUND OF THE INVENTION 
     During surgery, or as a result of trauma, tissue volume can be removed or altered, and an open or dead space is created within the tissue that was previously attached to other tissue. The very small blood vessels that previously ran from the underlying tissue (i.e., muscle, connective tissue) to the overlying tissue (i.e., skin, muscle) can be cut or damaged. Although these vessels usually do not cause significant blood loss, they do allow escape of blood serum into the area. Human blood serum contains about ninety-three percent water and about seven percent protein (mostly albumin). 
     Following surgery or due to trauma, there can also be resulting tissue damage, regardless of how careful the surgeon is. This tissue damage results in cellular death, and the body&#39;s natural defense reaction is an inflammatory one. Because of the inflammation, cell death, and increased vascular permeability, fluid can also accumulate in the operative space. The larger the operative space, the greater is the potential for internal fluid collection. 
     The body can resolve the accumulation of fluid over time, if there is some form of natural drainage, and if there is not continued irritation to the area, and if circulation to the area is sufficient, and if the person is in good health or the volume of fluid collection is itself not too large. 
     If, for whatever reason, the body is unable to itself efficiently absorb the excess fluid, a seroma can occur. A seroma is defined as a sterile accumulation of blood serum in a circumscribed tissue location or operative space. A seroma is not by definition an “infection;” it does not necessarily involve the presence of white blood cells, bacteria, and the breakdown products of both. A seroma is fluid and blood serum that has accumulated in a dead space in the tissue. A seroma is the result of tissue insult and the product of tissue inflammation and the body&#39;s defense mechanisms. 
     Seromas commonly develop following drain removal or when fluid is produced at a greater rate than it is absorbed. Conventional wound management techniques are commonly applied when a seroma becomes a clinical concern. Placement of a seroma catheter or additional drain, as well as repeated or serial drainage of a seroma, may be required. A seroma or fluid collection is by far the most common complication in surgery today. Such complications result in a significant amount of lost income to patients, as well as expenses to insurers and physicians who have to care for these patients that require serial drainage. Such complications also delay wound healing, may entail additional surgical procedures, and ultimately delay the patient&#39;s return to work and routine functional activity. Seroma management can also be costly and, further, can place health care workers to additional needle exposure risks and related outcomes such as hepatitis, etc. 
     The aim of wound management in both chronic and acute situations is to assist the natural process and prevent further complications such as infection, slough, necrosis formation, and chronic seroma cavities. Maintenance of the optimum wound healing environment is essential, ensuring the wound is kept moist and warm. Wound care products strive to achieve these results and, in turn, help to promote rapid wound closure. 
     Fluid drainage can be as simple as creating an opening at the lowest edge of the seroma, and keeping this open and clean to allow continued drainage. A clinically accepted way to deal with a seroma that does not appear to be resolving on its own, is to install a continuous drain system, coupled with treatment with antibiotics to prevent infection while the continuous drain system is in use. There are currently numerous types of wound drains on the market, most of them utilizing some form of tubing to withdraw fluid from the wound until the body can resorb the fluid without assistance. A continuous drain system allows the fluid to continuously escape until the body can complete the healing process on its own. 
     A representative prior art continuous drain system can comprise an implanted device such as a piece of rubber tubing (Penrose drain) (as shown in  FIG. 1 ), which provides dependent gravity drainage or responds to a negative suction force generated by a manual closed suction bulb. These types of drains constitute the most common devices currently available. The problem with these devices is that, although they may drain fluid, fluid drainage is limited to fluid directly around the drain itself. As a result, current drains may manage fluid collection, but they do not effectively clear all of the fluid in the space and, more importantly, they do not clear enough fluid to effectively seal down and close off the dead space. 
     Another representative prior art continuous drain system, which is currently approved for external use only, can take the form of an externally applied device comprising a piece of foam with an open-cell structure, which coupled to one end of a drain tube (see  FIG. 2 ). The foam is placed externally on top of the wound or skin, and the entire external area is then covered with a transparent adhesive membrane, which is firmly secured to the healthy skin around the wound margin. The opposite end of the drain tube is connected to a vacuum source, and blood or serous fluid are drawn from the wound through the foam into a reservoir for subsequent disposal. Among the numerous names this prior art system is called are “Vacuum Assisted Closure device” or VAC devices. Conventional VAC devices, however, are only approved and used for external wounds only. Conventional VAC devices are not approved or used for internal wounds or operative sites. 
     Current wound drain devices assemblies at times do not remove a substantial amount of fluid from within a wound and have other performance issues. For example, external VAC devices clear fluid directly around external wounds(as  FIG. 3  shows), and they are limited to the application to external wounds only. They leave the remainder of the wound site or operating space open and filled with fluid. 
     Furthermore, the clinical use of external VAC devices may not make wound drainage more cost-effective, clinician-friendly, and patient-friendly. 
     For example, the foam structures and adhesive membranes associated with conventional practices of external VAC need to be periodically removed and replaced. Currently, dressing changes are recommended every 48 hours for adults with non-infected wounds, and daily for infants and adolescents. Current techniques place the foam material in direct contact with granulating tissue. Removal of the foam structures in the presence of granulating tissue and the force of pressure on the wound bed that this removal can cause pain or discomfort. The sponge can also de-particulate and remain in the wound. Furthermore, the multiple steps of the conventional external VAC procedure—removing the adhesive membrane, then removing the old foam structures, then inserting the new foam structures, and then reapplying the adhesive member along the entire periphery of the wound—are exacting, tedious and time consuming. They only prolong pain or discomfort, and cause further disruption to the patient, and also demand dedicated nursing time and resources. 
     Furthermore, to function correctly, the adhesive membrane applied over the foam wound structures must form an airtight seal with the skin. Obtaining such a seal can be difficult, particularly in body regions where the surrounding skin is tortuous, and/or mucosal and/or moist. 
     Furthermore, prolonged wearing of wet dressings can cause further breakdown and maceration of the surrounding skin thereby increasing the wound size. This can cause further discomfort to the patient, and the exudate can often be offensive in odor and color causing further embarrassment to the patient. This may, in turn, require more numerous dressing changes and re-padding throughout the day, which is disruptive to the patient and costly both in terms of nursing time and resources. 
     Furthermore, since the membrane and the material of the foam structures are both in direct contact with tissue, tissue reactions can occur. 
     There remains a need for improved drains, systems, devices, methods that are cost-effective, patient-friendly, and clinician-friendly. 
     SUMMARY OF THE INVENTION 
     The invention provides assemblies, systems, and methods that are cost-effective, patient-friendly, and clinician-friendly. The assemblies, systems, and methods convey fluid from an internal wound site or body cavity by applying negative pressure from a source that is outside the internal wound site or body cavity through a wound drain assembly that is placed directly inside the internal wound site or body cavity. Unlike conventional VAC devices, the assemblies, systems, and methods that embody the technical features of the invention are not a treatment modality that is limited to placement on an exterior wound or operational site following trauma or surgery, providing drainage in a reactive and localized fashion. Instead, the assemblies, systems, and methods that embody the technical features of the invention make possible a treatment modality that is sized and configured for placement directly inside an internal wound site or body cavity at the time of surgery, to provide direct and immediate drainage of any entire wound site in a proactive fashion. 
     One aspect of the invention provides a wound drain assembly comprising a housing enclosing an open interior. The housing is sized and configured for placement directly within an interior wound site or body cavity. Perforations in the housing communicate with the open interior. A foam sponge material is carried within the open interior. The foam sponge material absorbs fluid residing in the interior wound site or body cavity. Tubing is coupled to the housing in communication with the open interior of the housing. The tubing extends from within the interior wound site to outside the interior wound site or body cavity. The tubing outside the interior wound site or body cavity is sized and configured to be coupled to a source of negative pressure outside the body cavity. The negative pressure conveys through the tubing fluid that is absorbed by the foam sponge material inside the internal wound site or body cavity. 
     Another aspect of the invention provides a wound drain system comprising a wound drain assembly as just described, which is coupled to a source of negative pressure outside the body cavity. 
     Other aspects of the invention provide methods that provide the wound drain assembly or system as above described and that operate the assembly or system to convey fluid from an interior wound site or body cavity. 
     The assembly, system, and/or method apply a vacuum of significant pressure internally and directly in a wound area or body cavity for enhanced wound healing benefits. By applying a vacuum of significant consistent pressure internally and directly in the wound area or body cavity, the assembly, system, and/or method reduce the “dead-space” or open area inside the wound or cavity, and thereby aid in decreasing tissue edema and swelling of the overlying and underlying tissue. The assembly, system, and/or method increase the nature and extent of wound drainage, promote tissue adherence and closure of wounds, and thus decrease seroma formation and promote primary wound healing. The assembly, system, and/or method thereby decrease the costly and increased patient morbidity caused by seroma formation and the resultant delay in primary wound healing or need for additional surgical procedures or drainage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an anatomic side section prior art view of a human abdomen showing an interior wound area and a tube that is placed according to conventional techniques to drain fluid from a seroma at the wound site. 
         FIG. 2  is an anatomic side section prior art view of an exterior wound area showing an external VAC device placed according to conventional techniques to drain fluid from a seroma only at an external wound site. 
         FIG. 3  is an anatomic, somewhat diagrammatic prior art view of the limited drainage area achieved by the external VAC device shown in  FIG. 2 . 
         FIG. 4  is an anatomic side section view of a human abdomen, like that shown in  FIG. 1 , but showing a drain system that embodies features of the invention, comprising an internally placed wound drain assembly coupled to an external source of negative pressure. 
         FIG. 5  is an anatomic, somewhat diagrammatic view of the enhanced drainage area achieved by the drain system shown in  FIG. 4 . 
         FIG. 6  is a perspective, exploded view of a representative embodiment of a wound drain assembly of the type shown in  FIG. 4 . 
         FIGS. 7A and 7B  are enlarged views of representative forms of foam sponge material that the wound drain assembly shown in  FIG. 6  carries. 
         FIG. 8  is a perspective, assembled view of the wound drain assembly shown in  FIG. 6 . 
         FIGS. 9 to 13  are perspective views of other representative embodiments of a wound drain assembly of the type shown in  FIG. 4 . 
         FIGS. 14 and 15  are representative views of various systems of a type shown in  FIG. 4 . 
         FIGS. 16 and 17  show, respectively, a wound drain assembly of the type shown in  FIG. 4  before and during the application of negative pressure. 
         FIG. 18  shows, in an anatomic view, a system like that shown in  FIG. 4 , comprising a wound drain assembly coupled to a portable source of negative pressure that can be carried by an individual, but also be fixed or attached to a wall section. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention that may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
       FIG. 4  shows a wound drainage system  10  comprising an internal drain assembly  12  that is sized and configured for surgical placement within a wound area W (or body cavity). The wound area W may be anywhere in a human or animal, e.g., within a body cavity, or beneath the skin, or in muscle, or within the soft tissues. As will be described in greater detail later (see  FIG. 6 ), the internal drain assembly  12  includes a housing  18  that encloses a foam sponge component  16 . The foam sponge component  16  communicates with the wound area W through one or more apertures  20  formed in the housing  18 . 
     The internal drain assembly  12  is coupled to drain tubing  14 , which is desirable flexible. The drain tubing  14  extends outside the wound area W. The drain tubing  14  can extend through a percutaneous incision in the skin overlying any wound area W. Alternatively, the drain tubing  14  can extend through an opening in a skin flap bounding the wound area. The flexible drain tubing  14  includes a terminal end  22  that extends outside the body. 
     The terminal end  22  desirably includes a quick release connector  24 . The connector  24  is sized and configured to be connected to a conventional external negative pressure suction device  26  (such as a V.A.C.® device made by KCI International, or a conventional wall suction or other regulated vacuum device.). 
     In use, the drain tubing  14  is connected to the suction device  26 , and the suction device  26  is operated to apply a requisite negative pressure through the internal drain assembly  12 . Blood or serous fluid absorbed by and passing through the foam sponge component  16  are drawn by the negative pressure from the wound area W. The drain tubing  14  desirably includes an inline reservoir  30  to collect the withdrawn fluid for disposal. 
     As  FIG. 5  shows, occupying the interior of the wound area W, the internal drain assembly  12  conveys negative pressure throughout the entire open volume of the wound space. The negative pressure applied by the internal drain assembly  12  clears fluid from the entire wound volume. The removal of fluid from the entire wound volume promotes tissue adherence within the wound space, to close the wound space and seal the wound. 
     As  FIGS. 6 and 8  show, the internal drain assembly  12  comprises a housing  18 . The housing  18  is made from an inert, biocompatible material that does not adhere to or activate the body&#39;s natural foreign body defense mechanism. The material can comprise, e.g., silicone rubber, polyurethane, or other biocompatible plastics. 
     The housing  18  can be formed. e.g., by extrusion, molding, or machining. As will be described in greater detail later, the housing  18  can be formed in various shapes and sizes, depending upon the requirements and morphology of the wound site and function and use of the drain. In the configuration shown in  FIG. 8 , a representative size measures about 5″ (length)×about ¾″ (width)×about ½″ (height). 
     The housing  18  is formed to include a hollow interior chamber  28 , which is enclosed by the side and end walls of the housing  18 . The housing  18  is also formed to include one or more through-slots, through-apertures, or through-perforations  20  in the side and/or end walls of the housing  18 . The through-slots, through-holes, or through-perforations  20  open the hollow interior chamber  28  to communication with the wound site environment outside the housing  18 . 
     An end of the flexible drain tubing  14  is coupled to the housing  18  and opens into the hollow interior chamber  28 . The flexible drain tubing  14  is made of medical grade, inert material. e.g., silicone rubber, polyurethane, or other biocompatible plastics. The tubing  14  is desirably sized and configured to accommodate sufficient fluid flow with a relatively small and tolerable incision size (e.g., about 2-3″ in diameter). 
     A foam sponge component  16  is housed within the hollow interior chamber  28 . The foam sponge component  16  is characterized in that it does not particulate in the presence of fluid and pressure. The foam sponge material can comprise, e.g., an open-cell porous structure (see  FIG. 7A ) or a granulated foam construction (see  FIG. 7B ). The foam sponge component  16  can be variously constructed from a biocompatible material that does not adhere to or activate the body&#39;s natural foreign body defense mechanism, e.g., sponge materials used with conventional VAC devices. As stated later, the foam sponge component  16  can be impregnated with antibacterial products or solutions. 
     In use (as  FIGS. 4 and 5  show), the internal drain assembly  12  is placed within an interior of the wound area W (or body cavity). Fluids collecting in the wound or body cavity are absorbed by and pass through the foam sponge component  16  through the perforations  20  in the housing  18 . Fluid absorbed by the foam sponge component  16  is siphoned away by the drain tubing  14  when a requisite negative pressure is applied. 
     The negative pressure can be, e.g., 125 to 200 mmHg, and is desirably about 125 mmHg, below ambient pressure. The amount of negative vacuum pressure can be regulated in a continuous, discontinuous, or otherwise variable manner, to maximize wound healing and closure and thereby reduce overlying soft tissue edema and swelling. In this way, the system  10  promotes primary wound healing while also decreasing or minimizing seroma formation. 
     As  FIGS. 16 and 17  show, the introduction of negative pressure into the housing  18  can cause the housing  18  to collapse against the foam sponge component  16  (as  FIG. 17  shows), while the through-perforations  20  of the housing  18  maintain open paths for fluid to be absorbed by the foam sponge component  16 . 
     The foam sponge component  16  is desirably compressible for easy insertion into and removal from the housing  18  for replacement. The configuration of the housing  18  can also provide a contour that facilitates sliding of the internal drain assembly  12 , easing removal from the body. 
     The foam sponge component  16  may also be impregnated with components such as silver or antibacterials or other growth factors that may decrease infection and promote wound healing. 
     As  FIGS. 9 to 13  show, the housing  18  can be formed in various dimensions, shapes, and sizes, and the foam sponge component  16  cut to corresponding dimensions, shapes, and sizes. These dimensions, shapes, and sizes can comprise, e.g., square ( FIG. 9 ); oval ( FIG. 10 ); hexagonal ( FIG. 11 ); round ( FIG. 12 ); or rectangular ( FIG. 13 ); or any linear or curvilinear shape or combinations thereof. The ends of the housing  18  can be tapered or not tapered (as  FIGS. 9 to 13  demonstrate). The through-perforations  20  can also be variously shaped and sized (as  FIGS. 9 to 13  demonstrate). The through-perforations  20  can also be tapered or not tapered along their axes. 
     The wound drainage system  10  can be variously configured and assembled. For example, as shown in  FIG. 14 , the in-line reservoir  30  is intended, in use, to be placed at a gravity position at or below the drain assembly  12  and includes separate fluid inlet and vacuum outlet paths arranged along the top of the reservoir  20 , coupled, respectively, to the internal drain assembly  12  and the external negative pressure suction device  26 . As  FIG. 15  shows, the reservoir  30  is intended, in use, to be placed at a gravity position above the drain assembly  12  and includes an fluid inlet path arranged along the bottom of the reservoir  30  (coupled to the drain assembly  12 ) and a vacuum outlet port arranged along the top of the reservoir  30  (coupled to the external negative pressure suction device  26 ). 
     As  FIG. 18 , the system  10  may include a battery powered external negative pressure suction device  26 ′ that can be carried by the individual. The system  10  can therefore be operated while the individual ambulates, so that the individual need not be bed-bound during the recovery period. 
     It is believed that applying a vacuum of significant pressure internally and directly in a wound area or body cavity removes chronic edema and leads to increased localized blood flow. It is also believed that the applied forces applied internally and directly in a wound area result in the enhanced formation of tissue adherence. It is further believed that applying a vacuum of significant pressure internally and directly in a wound area or body cavity will accelerate healing by the application of a universal negative force to the entire wound volume, drawing the wound edges together, assisting closure, enhancing wound healing, and decreasing dead space and seroma. Presumed mechanisms responsible for achieving these objectives include: (i) changes in microvascular blood flow dynamic; (ii) changes in interstital fluid; (iii) removal of wound exudates; (iv) stimulation of growth factors and collagen formation; (iv) reduction in bacterial colonization; (v) mechanical closure of wound by “reverse tissue expansion;” (vi) increasing adherence of the soft tissue and internal wound healing; and (vii) decreasing dead space and seroma formation. 
     The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.