TUBE ASSEMBLY FOR USE IN A WOUND DRAINAGE SYSTEM
Technical field
The present invention generally relates to tubes, in particular tubes for use in negative pressure systems, i.e. suction systems, for removal of fluids from a wound and thus for enhancing wound healing. Such systems may comprise a wound enclosure which is attachable to a wound circumference of a living being to form an enclosure, and a suction source in fluid communication with the enclosure to provide a pressure difference between a negative pressure in the enclosure and an air pressure of an ambient space. Pressure detection within the wound enclosure is desirable in order to control and maintain an appropriate suction level within the wound enclosure.
Background of the invention
It has been found that fluid drainage of wounds promotes tissue growth and thereby facilitates a reduced healing time. The treatment has been exercised for many years, and various therapeutic apparatus for providing suction to a wound have been developed.
A wound cover may be fixed in a sealing manner to the skin of a living being so that an enclosure is formed around the wound. The cover is connected to a pump, and suction is applied. The suction forces exudate from the enclosure to a receptacle.
WO 01/34223 discloses a suction tube in the form of a multi-lumen tube having a central lumen for applying suction to a wound site and one or more peripheral lumens for sensing pressure at the wound site. The design of WO 01/34223 results in a rather large overall wall thickness and therefore a relatively hard and inflexible tubing system, which causes patient discomfort and is inconvenient for transportation purposes. Summary of the invention
It is an object of preferred embodiments of the present invention to provide a wound drainage system with an improved tubing system for draining fluid and detecting pressure at the wound site.
In a first aspect, the invention provides a system for draining fluid from a wound, comprising :
- an enclosure for enclosing the wound;
- a drainage conduit for connecting a wound site within the enclosure to a suction source;
- a pressure communication conduit providing a communication between the wound site and a pressure sensing element; wherein the drainage conduit and the pressure communication conduit extend coaxially, so that one of the conduits is in the form of an annular passage surrounding the other conduit. Preferably, one of the conduits is formed by an inner tube, and the other conduit is formed by an outer tube, which surrounds the inner tube.
In a second aspect, the invention also provides a tube assembly for use in the above system, the tube assembly comprising an inner tube and an outer tube, the inner and outer tube extending coaxially with the outer tube surrounding the inner tube. Though the tube according to the second aspect of the invention is primarily intended for the drainage system according to the first aspect of the invention, other applications are possible. In general, the tube assembly may be used is any setup, in which fluid flow and communication between two sites is required. One particular use is so-called night bags, in which urine may flow in one of the inner and outer tube, and pressure equalisation is made through the other tube.
Thanks to the provision of co-axial conduits, with one surrounding the other, the conduits may be accommodated in a tube assembly having a relatively small wall thickness. This results in a more flexible system and reduces the risk of kinking as compared to prior art systems having a central tube and peripheral tubes. Moreover, handling is rendered easier as compared to handling of tube systems including separate tubes extending in parallel. It is further achieved that one of the conduits may extend beyond the other one, so that, for example at one of the conduits, one may terminate at one face of an exudate collecting canister, whereas another conduit may extend further to a pressure sensing element, e.g. through the canister to a pressure sensing element arranged at another face of the canister. A further advantage of the present invention is that it allows for easy and inexpensive interconnection of the conduits to other conduits or tubes, or to connecting elements. This is described in further detail below.
In one embodiment, the stiffness of the inner tube is different from the stiffness of the outer tube. Particularly, the inner tube may be stiffer than the outer tube. This allows the inner tube to be made from a relatively thin-walled material and reduces the risk of kinking of the inner tube. The other tube may be made from a relatively soft material to increase patient comfort.
The risk of kinking may be further reduced by providing a corrugated wall along at least a portion of a length of one or both tubes. The corrugated tube wall may extend along the entire length of the tube wall or only along a part thereof. For example, corrugated sections may be provided, with non-corrugated sections extending between the corrugated sections. It has been found that corrugations are particularly beneficial in the wall of the inner tube.
Each of the tubes may be terminated by a conical wall portion at at least one end thereof. The conical wall sections provide the possibility of easily connecting the tube assembly to a connector, e.g. for connecting to another tube assembly or for connecting the tube assembly at the wound site. Sealing and/or locking may be accomplished by firmly pressing the tubes against the connector or by rotating respective male and female parts relative to each other. In order to hold the parts together, a bayonet clutch or an ordinary screw thread may be used. In a one embodiment, the drainage conduit surrounds the pressure communication conduit. This allows the drainage conduit to terminate before the pressure communication conduit terminates, allowing for convenient connection to, e.g., a suction unit including an exudate collecting canister and a pump unit.
Description of the drawings
Embodiments of the invention will now be described further with reference to the accompanying drawings.
Fig. 1 illustrates a tube assembly 100 comprising an inner tube 102 and an outer tube 104. In the upper sketch of Fig. 1, the tubes are concentric, whereas they are centrally offset in the lower sketch. The inner tube may move freely within the outer tube, except for its end points, which may be fixed at connectors or the like. As shown in Fig. 2, the tubes may form a conical male connector 106 at at least one end thereof.
Fig. 3 illustrates a system for draining fluid from a wound (not shown). A free end 103 of the tube assembly 100 is intended for connection to a wound site (not shown). The system includes a drive and collecting unit 110 comprising an exudate collecting canister 112 and a drive and control unit 114. The drive and control unit 114 comprises a pressure sensing element (not shown) for measuring a pressure at the wound site through the inner tube 102. The outer tube 104 terminates at an inlet to the canister 112, whereas the inner tube
(pressure communication conduit) extends through the canister. Fig. 4 shows a corrugated inner tube 102 surrounded by a non-corrugated outer tube 104.