Abstract:
A portable wound treatment apparatus, for stimulating the healing of superficial wounds, comprises a housing containing a suction pump and a canister for containing fluids drawn from the wound. The housing is supported on a harness or belt worn by the patient. The canister is connected to a porous wound dressing at the wound site via a plurality of tubes, a multi-lumen tube or a combination thereof. A rechargeable battery pack may be incorporated within the housing or externally thereto. The external battery pack may be shaped to balance the housing on the harness or belt. Pressure transducers are provided to monitor and report pressures at the wound site or internal to the canister. Monitored pressures may also be utilized to determine the filled state of the canister and, thereafter, either report this state to the operator or automatically discontinue suction from the wound, or both.

Description:
RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 09/078,223 filed May 13, 1998 now U.S. Pat. No. 6,142,982, which is a continuation of PCT international application Serial No. PCT/GB96/02802 filed Nov. 14, 1996, which designates the United States and claims priority to British patent application No. 9523253.4 filed Nov. 14, 1995. By this reference, the full disclosures, including the drawings and claims, of U.S. patent application Ser. No. 09/078,223; PCT international application Serial No. PCT/GB96/02802; and British patent application No. 9523253.4 are incorporated herein as though each were now set forth in their respective entirety. 

   FIELD OF THE INVENTION 
   The present invention relates to the healing of wounds. More particularly, the invention relates to an apparatus for stimulating the healing of superficial wounds. 
   BACKGROUND OF THE INVENTION 
   PCT Application No. GB95/01983 (WO 96/05873) describes apparatus for stimulating the healing of wounds comprising a porous pad which is permeable to fluids for introduction into the wound, a dressing for covering the wound and providing an air-tight seal around the wound, a drainage tube connecting the pad to a suction pump so that negative pressure can be applied to the wound to draw fluids therefrom and a canister for collecting fluids sucked from the wound. The apparatus described in the above application has proven to be clinically effective but there are some limitations in its use. 
   The apparatus described in the above PCT application is effective for treating a wide variety of different types and sizes of wounds. However, it may require the patient to undergo treatment on the apparatus for a long period. In cases where the patient is confined to bed this may not be a major problem, but where the patient is mobile it means that he or she would be confined for long periods while the treatment takes place. 
   An object of this invention is therefore to provide an apparatus which can be used more conveniently, especially by patients who are reasonably mobile, and which has certain further advantages which will become apparent from the following description. 
   SUMMARY OF THE INVENTION 
   In accordance with the foregoing object, there is provided in one aspect of the present invention a portable therapeutic apparatus for stimulating the healing of superficial wounds in a person, which comprises a housing containing a suction pump and a canister for containing fluids drawn from the wound by said pump, said canister including means for connection to a dressing in the region of the wound and a harness or belt for supporting the housing on the person. 
   Typically, the housing will have a curved surface on the side intended to be supported against the person&#39;s body so as to make the apparatus more comfortable to wear. In addition, controls and indicators indicating the status of the treatment being applied to the wound are preferably located on the upper side of the housing so that the patient can easily see, e.g., the level of suction pressure being applied and the program for such treatment. 
   The suction pump is conveniently driven by an electric motor and batteries for such motor may be contained within the housing. However, it is generally more convenient to provide a separate housing for the batteries since these can be placed on the belt or harness in such a way as to balance the weight of the housing, preferably in a housing shaped similarly to the housing for the pump and canister. The canister should be removably mounted within the housing, e.g. by means of a latch or release mechanism, so that the canister can be readily removed and replaced when full. 
   In a portable therapeutic apparatus (in contrast with a static apparatus of the kind described in the above PCT application which cannot be easily carried by the patient), it is less easy to determine the pressure prevailing at the wound site being treated. This is because the pressure will depend, in part, upon the hydrostatic height between the pump and the wound being treated and this height may vary during the treatment, depending upon the patient&#39;s movements. The apparatus in accordance with the invention overcomes this problem by providing an additional conduit connecting the wound site or an area close thereto to a pressure-detecting means, preferably located in the housing. The pressure-detecting means can be linked to a microprocessor programmed to maintain such pressure within a predetermined range irrespective of the movement of the patient. This can be done by, for example, signaling the pump to increase its speed where the hydrostatic pressure increases between the pump and the wound site or, conversely, reducing its speed where the hydrostatic pressure is reduced. This feature can also be used in a static therapeutic apparatus of the kind described in the above-mentioned PCT application. 
   In the apparatus described in the above PCT application, the level of liquid in the canister is monitored by capacitance measurement. It has now been found that a simpler way of determining when the canister is filled is by measuring or detecting the pressure drop across the canister. The pressure drop can be increased by providing a filter barrier in the region of the outlet end of the canister. Thus, when the liquid reaches a level within the canister so as to substantially occlude the filter, a sharp pressure change occurs in the conduit between the canister and the pump. By monitoring this pressure change, the point at which the canister is filled can be accurately determined. 
   Finally, many other features, objects and advantages of the present invention will be apparent 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. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Although the scope of the present invention is much broader than any particular embodiment, a detailed description of the preferred embodiment follows together with illustrative figures, wherein like reference numerals refer to like components, and wherein: 
       FIG. 1  is a schematic layout of the apparatus in accordance with the invention; 
       FIGS. 2A and 2B  are pictorial representations of the housing of the pump and canister; 
       FIGS. 3A and 3B  are pictorial representations of the apparatus supported on a belt and harness respectively; 
       FIG. 4  is an exploded view of the housing showing the contents; 
       FIGS. 5A to 5F  show various views of a preferred form of the canister and a section of a multi-lumen tube; 
       FIGS. 6A to 6D  show various views of a foam dressing connector for connecting the housing to the dressing; 
       FIG. 6E  shows a section of a modified multi-lumen tube; and 
       FIGS. 7A and 7B  show a plan and perspective view of a surgical drape for use with the apparatus. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Although those of ordinary skill in the art will readily recognize many alternative embodiments, especially in light of the illustrations provided herein, this detailed description is exemplary of the preferred embodiment of the present invention, the scope of which is limited only by the claims appended hereto. 
   Referring to the drawings, the portable therapeutic apparatus comprises a housing  210  (best shown in  FIGS. 2A and 2B ), having rounded corners and a side  211  which is concavely curved in order to fit comfortably to the wearer&#39;s body. The shaping of the housing with curved surfaces is to avoid sharp corners or edges that could dig in to the user or his caregiver. The upper surface  212  is generally flat and has an LCD screen  213  on which details such as applied pressure can be displayed. Control buttons  214  are provided to adjust pressures and treatment intervals. Provision is made for housing a canister within the housing and a snap release cover  215  is arranged for removing or introducing the canister. 
     FIGS. 3A and 3B  show schematically ways in which the housing  210  may be supported on the patient&#39;s body. In  FIG. 3A  the housing  210  is supported on a belt  216  and its weight is balanced by a similarly rounded casing  217  containing a rechargeable battery pack.  FIG. 3B  shows an alternative arrangement in which the housing is supported on a harness  218  and again a battery pack is contained in a housing  219 , also supported on the harness. 
     FIG. 4  shows an exploded view of the housing  210  indicating the main components within the housing. The housing consists of front and rear shell moldings  1  and  2  having an external belt clip  21  for attachment to a belt or harness. 
   Within housing shell  1  is located a suction pump  6  with associated electric motor  6 A and the pump is connected by a silicon rubber tube  103  to a canister spigot  7 A in a cavity  20  for the canister  100 . Also connected to a second canister spigot  7 B via a tube  10  is a pressure relief valve  8  and both tubes  103  and  10  are connected via T-connectors T to pressure transducers (not shown). A microprocessor  4  is mounted on a PCB board  5  and a membrane assembly  3  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  100  is a push fit into the cavity  20  and its lower end is supported in a cover  30 . The cover  30  incorporates fingers  31  which are releasably engageable with lips  32  to hold the canister in position. The canister and the latch mechanism is arranged so that when the latch is engaged, the spigots  7 A and  7 B are in sealing engagement or abutment with tubular protrusions  33  and  34  formed in the top of the canister. 
   The method of operation of the apparatus can be appreciated from the schematic layout in  FIG. 1 , in which the canister  100  is connected via tube  101  to a porous dressing  102  at the wound site. Suction is applied to the wound site via the canister by a tube  103 , connected to the pump  6 . The pressure in the tube  103  is detected by the transducer  105 . 
   A second tube  106  is connected to the wound site  102  at one end, and also to a pressure relief valve  8  and to a second transducer  108 . Tubes  106  and  101  can be combined in a multi-partitioned tube in manner to be described later. By means of tube  106  and transducer  108  the pressure at the wound site can be measured or monitored. A filter  109  is placed at or close to the outlet end of the canister  100  to prevent liquid or solid particles from entering the tube  103 . 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 negative pressure occurs in tube  103  and this is detected by transducer  105 . Transducer  105  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 suction to the wound site, a pressure relief valve  8  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  8  will open for a specified period, allow the pressure to equalize at the wound site and then close to restore the suction. It will be appreciated that when constant suction (or negative pressure) is being applied to the wound site, valve  8  remains closed and there is no leakage from atmosphere. In this state, it is possible to maintain negative pressure at the wound site without running the pump continuously, but only from time to time, to maintain a desired level of negative pressure (i.e. a desired pressure below atmospheric), which is detected by the transducer  105 . 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  106  and  101  in a single tube which is connected through the canister. Thus, for example, tubes  103  and  101  may comprise an internal tube surrounded by an annular space represented by tube  106 . This is illustrated in  FIGS. 5A to 5F  and in a modified form in  FIG. 6E . 
   In an alternative embodiment, the multi-lumen tube may be constructed as shown in  FIG. 6E . In this embodiment, the internal bore  606  comprises the line  101  (see  FIG. 1 ) and is used to extract fluids from the wound site. Air flow (represented by line  106  in  FIG. 1 ) passes down conduits  607  located within the walls of the tube. By spacing the conduits  607  at 90° intervals around the tube, the risk of arresting the air flow by kinking or twisting the multi-lumen tube is minimized. 
     FIG. 5E  is a plan view of the top of a preferred shape of the canister, the generally triangular shape in section being chosen to fit better the space within cavity  20  (see  FIG. 4 ). Tubular protrusions on the top of the canister are connected internally of the canister with respectively conduits  124  and  121  (see sectional view of  FIG. 5B ), thus maintaining a separation between the tubes which are represented by lines  103  and  106  in  FIG. 1 . At the base of the canister, a molding  125  facilitates connection to a multi-partitioned tube  126  shown in  FIG. 5F . Tube  126  has a central bore  127  that is sized to fit over a spigot  128  in molding  125 . At the same time, the external wall of tube  126  seals against the inner wall  129  of molding  125 . Thus, compartment  124  will connect with central bore  127  and the compartment  121  will connect with the annular spaces  130  of tube  126 . In this way, a conduit  130  corresponds with line  106  and central bore  127  with line  101  as shown in  FIG. 1 . 
   The partitioned tube need not continue all the way to the wound site  102 , 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  102 , this can be detected by both transducers  105  and  108  reading insufficient negative 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  6  is a diaphragm pump but other types of pumps and equivalent components to those specifically employed may be substituted. 
     FIGS. 6A–6D  show various views of a connector for attaching the multi-lumen tube at the wound site.  FIGS. 7A and 7B  show a plan and perspective view of a surgical drape for attaching the connector to a porous dressing at the wound site. The connector comprises a molded plastics disc-like cup  601  having a centrally positioned spout  602 . The spout  602  is sized to accept, as a closely sliding fit, the end of a multi-lumen tube, e.g. of the kind shown in  FIG. 5F  or  6 E. In use, a porous dressing is cut to correspond with the extent of the wound and pressed onto the wound as shown in  FIG. 10  of our above-cited PCT application WO 96/05873. Instead of introducing the lumen into the foam dressing, the cup  601  is pressed onto the porous dressing and secured by a surgical drape. However, if desired, the end of the lumen can be passed into the spout and additionally pressed into the foam. A surgical drape, such as shown in  FIGS. 7A and 7B , can be used to secure the connector, lumen and dressing. The drape comprises a polyurethane film  701  coated on one side with a pressure-sensitive acrylic resin adhesive. A hole  702  is cut through all layers of the drape and the hole is dimensioned to correspond approximately with the outer cross-section of the spout  602 . Film  701  has an overall size that allows it to be adhered to the patient&#39;s skin around the wound site while, at the same time, securing the connector to the porous dressing. A sufficient overlap around the wound is provided so that an airtight cavity is formed around the wound. 
   In an alternative form, the drape can be made in two parts, e.g. by cutting along the line X—X in  FIG. 7A . With this arrangement, the wound can be sealed by overlapping two pieces of surgical drape so that they overlap each other along a line Y—Y as shown in  FIG. 6D . 
   The surgical drape may include a protective film  703 , e.g. of polyethylene, and a liner  704  that is stripped off prior to use to expose the pressure-sensitive adhesive layer. The polyurethane film may also include handling bars  705 ,  706 , 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. Negative 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. 
   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 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.