Abstract:
The invention relates to a test unit for wound drainage coverings comprising: a base body with at least one cavity; at least one supply line that runs through the base body and which connects an outer side of the base body to the cavity; a surface of the base body that is embodied as a support surface for supporting wound coverings and the wound drainage coverings thereof and several channels that run through the base body, the channels connecting the cavities to the support surface. Low pressure can be produced in the cavity and the channels when the support surface is covered in an air-tight manner. As a result, wound drainage applications are tested in different ways using simple and economical means.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to International Application Serial No. PCT/CH2008/000465 filed Nov. 4, 2008, which claims priority to Swiss Patent Application No. 01734/07 filed Nov. 8, 2007, the contents of which are incorporated by reference herein in their entirety. 
     TECHNICAL FIELD 
     The invention relates to a test unit for wound drainage dressings. 
     PRIOR ART 
     It is known to treat large or poorly healing wounds using a vacuum drainage device. WO 94/20041, for example, describes this. A cover, for example a film or a stiff cap, is placed over the wound, such that a wound space is obtained. A drainage tube is inserted into the wound space from the outside and is connected to a suction pump in order to suck wound secretions out of the wound. In order to fill the wound space and, in particular, to distribute the vacuum uniformly across the surface of the wound, a wound dressing is placed on the wound. This wound dressing is usually composed of a foam insert with suitably configured pores. This foam insert can at the same time serve as an absorption body for the wound secretions. 
     Corresponding wound drainage dressings are known, for example, from WO 2006/056294, U.S. Pat. No. 7,070,584, EP 1 284 777 and EP 0 620 720. A wound drainage dressing with a foam insert outside the airtight top layer is described in WO 2006/052839. Wound drainage dressings of more complicated configuration are disclosed, for example, in WO 03/086232 and US 2002/0065494. 
     Many suggestions have therefore been made as to how wound drainage dressings of this kind could be configured. However, it is difficult to establish which wound drainage dressing is best used on which wound and with which suction pressure. 
     DISCLOSURE OF THE INVENTION 
     It is therefore an object of the invention to make available a device which permits uniform testing and optimized use of wound drainage dressings under conditions as close as possible to those encountered in practice. 
     The test unit according to the invention for wound drainage dressings comprises:
         a main body with at least one cavity,   at least one supply line, which runs within the main body and which connects an outer face of the main body to the cavity,   a surface of the main body, which surface is designed as a support surface for supporting wound drainage dressings and the covers thereof, and   several channels, which run within the main body and which connect the cavity to the support surface,   wherein a vacuum is able to be generated in the cavity and the channels when the support surface is covered in an airtight manner.       

     The cavity and the channels simulate the wound. The cavity substantially simulates the wound bed, and the channels the pores in the wound floor. 
     Wound liquids of different compositions can be introduced into the simulated wound via the at least one supply line. It is possible to choose whether the wound liquid is supplied continuously, at predetermined time intervals or just once. The support surface permits easy and quick application of wound drainage dressings that are to be tested. These wound drainage dressings can be covered by an air-permeable, self-adhesive film, which is affixed to the support surface. However, they can also be used in the test unit along with the specific covers recommended by the manufacturer, for example rigid caps. In this case, the cap is simply affixed to the support surface, for example by means of an airtight, self-adhesive film. 
     The main body of the test unit preferably has a plane-parallel base plate, a supply plate and, arranged between these, a sealing plate, said supply plate having the channels and at least one recess for forming the cavity. The main body therefore has a relatively simple structure and can be produced inexpensively. It is also easy to clean, since the channels and the recess are easily accessible when the main body has been unscrewed. 
     Another advantage of the main body in this configuration is that several supply plates can be used with the same base plate and intermediate plate. In this way, the test unit is able to simulate a wide variety of sizes and arrangements of cavities and channels. 
     The test system according to the invention for wound drainage dressings has a test unit of this kind It further comprises at least one liquid reservoir, which is able to be connected to the at least one supply line, and a drainage container, which is able to be connected to the support surface via a vacuum line and a vacuum attachment. 
     The test system can be operated with a wide variety of suction pumps, in order also to take account of the effect of these suction pumps in the wound drainage. However, it is preferably used with a pump that comprises control and evaluation electronics or that can be connected to these. In this way, it is possible to control and document the degree of the applied vacuum, the duration of the applied vacuum, optionally any pressure changes or pulse sequences, and the supplied liquid. Of course, the volumetric flow and the flow rate of the suctioned drainage liquid are also measured and recorded and, if appropriate, additionally processed in the evaluation electronics. 
     The test unit according to the invention permits, among others, the following measurement possibilities:
         measuring the time that is needed, with the preselected vacuum, before a defined quantity of liquid is taken up by the wound drainage dressing being tested;   measuring the different behavior of the wound drainage dressing at different vacuums (e.g. degree, pulse sequence, duration);   comparing various liquids with different properties, for example water, secretion, blood, bacterially infected blood, acid or alkaline bacterial medium, saline solution;   testing the different behavior of the wound drainage dressing by applying liquids to sectors of the test unit;   testing the different behavior and the different degree of saturation of the wound drainage dressing in its individual zones, e.g. from the edge to the center.       

     The test unit according to the invention and the test system thus permit uniform testing of known wound drainage dressings. They permit more optimized use of these wound drainage dressings. Moreover, they are an important aid in the development of new wound drainage dressings and covers and also in the development of new suction pumps and new methods of wound drainage. 
     Other advantageous embodiments are set forth in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter of the invention is explained below on the basis of preferred illustrative embodiments and with reference to the attached drawings, in which: 
         FIG. 1  shows a schematic representation of a test system according to the invention; 
         FIG. 2  shows a detail according to  FIG. 1 , with test unit and liquid reservoir system; 
         FIG. 3  shows an exploded view of the test unit according to  FIG. 1 ; 
         FIG. 4  shows a bottom view of a supply plate of the test unit; 
         FIG. 5  shows an exploded view of the test unit and of the liquid reservoir system according to  FIG. 2 ; 
         FIG. 6   a  shows a view of the test unit in a first application; 
         FIG. 6   b  shows a graph of the measured volumetric values of the first application; 
         FIG. 7   a  shows a view of the test unit in a second application; 
         FIG. 7   b  shows a graph of the measured volumetric values of the second application; 
         FIG. 8   a  shows a view of the test unit in a third application; 
         FIG. 8   b  shows a graph of the measured volumetric values of the third application; 
         FIG. 9   a  shows a view of the test unit in a fourth application; 
         FIG. 9   b  shows a graph of the measured volumetric values of the fourth application; 
         FIG. 9   c  shows a graph of the volumetric values measured when using different wound covers; 
         FIG. 9   d  shows a graph of the volumetric values measured when using different wound liquids; 
         FIG. 9   e  shows a graph of the volumetric values measured when using different vacuums; 
         FIG. 9   f  shows a graph of the volumetric values measured when using different vacuums; 
         FIG. 10   a  shows a view of the test unit in a fifth application; 
         FIG. 10   b  shows a graph of the measured volumetric values of the fifth application; 
         FIG. 11   a  shows a view of the test unit in a sixth application; 
         FIG. 11   b  shows a graph of the measured volumetric values of the sixth application; 
         FIG. 12   a  shows a view of the test unit in a seventh application; 
         FIG. 12   b  shows a graph of the measured volumetric values of the seventh application; 
         FIG. 13   a  shows a view of the test unit in an eighth application; 
         FIG. 13   b  shows a graph of the measured volumetric values of the eighth application; 
         FIG. 14   a  shows a view of the test unit in a first arrangement of the wound cover; 
         FIG. 14   b  shows a view of the test unit in a second arrangement of the wound cover; 
         FIG. 14   c  shows a view of the test unit in a third arrangement of the wound cover; 
         FIG. 14   d  shows a graph of the volumetric values measured according to the three arrangements in  FIGS. 14   a  to  14   c;    
         FIG. 15   a  shows a view of the test unit with a suction bar in a first form; 
         FIG. 15   b  shows a view of the test unit with a suction bar in a second form; 
         FIG. 15   c  shows a view of the test unit with a suction bar in a third form, and 
         FIG. 15   d  shows a graph of the volumetric values measured according to the three arrangements in  FIGS. 15   a  to  15   c.    
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a schematic representation of a test system according to the invention. It has a main body  1  of a test unit, a vacuum attachment  2 , which is arranged on the main body  1  or can be connected thereto in an airtight manner via a wound cover A, a drainage line  3  connected to the vacuum attachment  2 , a drainage container  4 , into which the drainage line  3  opens, a pump line  5  leading from the drainage container  4 , and a suction pump  6  connected to the pump line  5 . 
     The main body  1  is also connected to a liquid reservoir system  8  via a connecting line system  7 , which has at least one connecting line  70 ,  71 ,  72 ,  73 . This liquid reservoir system  8  has at least one liquid reservoir  80 ,  81 ,  82 ,  83 . The reservoirs  80 ,  81 ,  82 ,  83  preferably have a level indicator, as can be seen in  FIG. 2 . 
     The main body  1  has (see  FIGS. 1 and 2 ) a support surface  100 , which is preferably flat and has several channels  183 ,  186 ,  193 ,  196  leading into the interior of the main body  1 . A wound dressing D that is to be tested can be placed on this support surface  100  and cover at least some of the channels  183 ,  186 ,  193 ,  196 , and it can be covered by a standard wound cover A or by a wound cover A that is to be tested, and both are connected tightly to the vacuum attachment and to the main body  1 . A self-adhesive film is preferably used for this purpose. 
     The main body  1  of the test unit is shown in more detail in  FIGS. 3 to 5 . It has a preferably plane-parallel base plate  12 , a supply plate  10  and, arranged between these, a sealing plate  11 . The base plate  12  and the supply plate  10  are preferably made of a plastic, in particular Plexiglas, or of a metal, in particular steel or aluminum. The sealing plate  11  is preferably made of a flexible sealing material, in particular silicone or rubber. 
     The sealing plate  11  is likewise preferably plane-parallel and has through-openings. Connecting screws  14  are guided through these openings in order to screw the base plate  12  to the supply plate  10  in an airtight and liquid-tight manner. For this purpose, threaded holes are provided in the supply plate  10 , or threaded bushings  16  are let into the supply plate  10  flush with the lower surface thereof. 
     The base plate  12  preferably stands on feet  13 , which likewise can be screwed, for example, to the base plate  12  via fastening screws  15 . 
     The base plate  12  preferably has no elevations or depressions other than those for connection to feet  13  and to supply plate  10 , nor does it have any inner bores or channels. The supply plate  10  is preferably also plane-parallel and has the same shape and surface area as the base plate  12 . Both preferably comprise a generally rectangular shape. However, the supply plate  10  has recesses and bores. 
     As can be seen from  FIG. 3 , the supply plate  10  has bores at least on one end face, preferably specifically on one end face, which bores form supply openings  17  of the supply lines  181 ,  184 ,  191 ,  194  that can be seen in  FIGS. 4 and 5 . The abovementioned connecting lines  70 ,  71 ,  72 ,  73  open into these supply openings  17 . For this purpose, attachment pieces  70 ′,  71 ′,  72 ′,  73 ′ are preferably present, which can be plugged into the openings  17 . 
     According to the invention, the supply plate  10  has recesses which are closed at the top toward the support surface  100 , except for the channels described below, and are open at the bottom toward the sealing plate  11  and base plate  12 . These recesses are closed by the sealing plate  11  and the base plate  12  to form cavities  182 ,  185 ,  192 ,  195  completely separate from one another. They can have a wide variety of shapes. In the example shown here, a first cavity  182  and second cavity  185  have a constant rectangular longitudinal section and are adjacent to each other but spaced apart from each other. They here have the same surface area and preferably also the same depth, such that they have the same volume. A third cavity  192  and fourth cavity  195  are each designed so as to be spaced apart from and partially frame one of the first and second cavities  182 ,  185 , respectively. For this purpose, they have a C-shaped longitudinal section, which is again preferably constant. They too preferably have the same volume. However, these cavities can also have other shapes and volumes. It is also possible for more or fewer than these four cavities to the present. They can together have a geometric pattern or have another arrangement in the supply plate  10 . Moreover, they can have different depths in relation to the support surface  100  inside the supply plate  10 . 
     These recesses are open toward the outside via the abovementioned supply lines  181 ,  184 ,  191 ,  194 . These supply lines  181 ,  184 ,  191 ,  194  are also formed in the supply plate  10  by grooves that are open at the bottom and that merge into closed tubes only in the end-face edge area. These grooves are tightly closed off by virtue of the sealing plate  11  and the base plate  12 , except for the supply openings  17 . Since no cavities have to be formed and no bores have to be established, the production of the supply plate is made easier and it is also easier to clean. 
     These supply lines  181 ,  184 ,  191 ,  194  can be of the same length or of different lengths. They preferably extend parallel to the support surface  100 , such that the supply of liquid takes place parallel to the surface of the wound dressing. Each supply line preferably leads to a respective cavity and each supply line to a respective supply opening. However, they can also branch and serve several cavities, or a cavity can have several supply lines. All the supply lines preferably have the same internal diameter. However, they can also have different diameters. 
     From the cavities  182 ,  185 ,  192 ,  195 , capillaries or channels  183 ,  186 ,  193 ,  196  lead outward to the support surface  100 . Each cavity has several such channels. The channels of the same cavity can have the same internal diameter or different internal diameters. Similarly, channels of different cavities can have the same diameter or different diameters. They preferably extend in a direction perpendicular to the support surface  100 , although they can also extend at an angle thereto. The channels of a cavity preferably form, on the support surface, a geometric pattern, and the latter can be differently configured for each cavity. The channels are preferably distributed as uniformly as possible across the surface area or at least over an area of the respective cavity. 
     The cavities preferably have a volume of 2 cm 3  to 4 cm 3 . The channels are preferably 3 mm to 8 mm long and have an internal diameter of preferably 1 mm to 1.5 mm. The supply lines preferably have an internal diameter of 2 mm to 4 mm. 
     In a preferred embodiment, the test unit is heatable, such that the temperatures of the patient can be simulated. 
     By virtue of this test unit and this test system, it is now possible to test drainage applications. Thus, different test liquids can be introduced in a targeted manner from the liquid reservoirs into individual cavities. These test liquids can simulate wound liquids or treatment liquids. 
     Different wound dressings can be placed on the support surface and can be covered with different wound covers. Moreover, differently designed vacuum attachments (drains) can be used, which can also be arranged at different locations in relation to the wound dressing and to the filled cavities. By virtue of cavities of different shapes and different sizes, it is possible to simulate different types of wound bed. Moreover, the behavior of the same wound dressings, wound covers and drains can be tested with different suction pumps, different vacuums, suction sequences and different drainage duration. 
     Such applications are shown in the figures described below. These are to be understood only as examples and are not exhaustive: 
       FIG. 6   a  shows a vacuum attachment (drain)  2  in the form of a rectangular bar which has a plurality of suction openings distributed uniformly along the length thereof and which is arranged over a rectangular wound dressing D. This wound dressing D covers the entire channel area of the support surface  100 . The same wound liquid is supplied to the four cavities in succession via all of the supply openings, here designated as E 1 , E 2 , I 1  and  12 . In this example, no further liquid is supplied during the suction procedure. In other examples, however, this would be possible. Each individual supply is subjected to a vacuum and the flow behavior is measured. For all four cavities in succession, the same suction sequence is used (i.e., among other things, duration, degree of vacuum, possible variations in the pressure during the suction procedure). 
       FIG. 6   b  shows the measured values. The y-axis shows the time, the x-axis shows the volume converted during the suction. This volume is preferably measured in the drainage container. As can be seen, therefore, the distance at which the drain  2  is arranged from the suctioned cavity has an important role. 
     The same procedure was followed in  FIG. 7   a , and the same drain  2 , the same wound dressing D and the same test liquid were used. Here, the drain  2  was arranged at the opposite end of the hollow chambers. 
     The measured values were again plotted in  FIG. 7   b.    
     The same procedure was again followed in the example according to  FIGS. 8   a  and  8   b . Here, the drain  2  is arranged in the lower area. 
     In the example according to  FIGS. 9   a  and  9   b , it will be seen that with the same procedure as in the other examples, but with the drain  2  placed across the center of the hollow chambers, the least variation occurs in the behavior of the four hollow chambers. Therefore, in the figures that follow, this arrangement is once again used in order to vary other parameters. 
     Thus, in the measurement shown in  FIG. 9   c , four different wound dressings were used in succession, but with the same test liquid and the same suction sequence. In  FIG. 9   d , with the same wound dressing and suction sequence, four different test liquids were supplied in succession. In  FIG. 9   e , with the same wound dressing and the same test liquid, different suction sequences were used. In  FIG. 9   f , another wound dressing was used, but with the same test liquid. Here too, the suction frequency was varied. 
       FIGS. 10   a  and  10   b  show an experiment in which three drains  2  arranged at different sites were used in succession, but always the same cavity.  FIGS. 11   a  and  11   b  show the experiment using a different cavity than in the abovementioned example. The same applies to  FIGS. 12   a  and  12   b  and  FIGS. 13   a  and  13   b.    
     In  FIG. 14   a , the drain  2  is arranged underneath the wound dressing D. It is arranged inside the wound dressing D in  FIG. 14   b  and above the wound dressing D in  FIG. 14   c . The measured results are shown in  FIG. 14   d.    
     Differently configured drains  2  are used in  FIGS. 15   a  to  15   c . The measurement result is shown in turn in  FIG. 15   d.    
     As will be seen from these examples, wound drainage applications can be tested in a wide variety of ways by simple and inexpensive means.