Background Art Following chest surgery or injury, a patient may have an intercostal drainage catheter inserted to drain the pleural or cardiac cavity. The machine end of the catheter is usually connected to a drainage bottle having a chamber containing water and an inlet tube extending below the surface of the water, to provide an underwater seal preventing air being sucked into the patient. These drainage bottles are rigid, thereby enabling suction to be applied, to increase drainage. This drainage system, however, does have a number of disadvantages. The water in the bottle makes it difficult to manoeuvre, since care must be taken to ensure that it does not tip and allow air to be sucked into the chest. Also, when the bottle is lifted, the inlet tube must be clamped, to ensure that the liquid in the bottle does not siphon into the patient.

This restricts the activity of the patient and, in practice, limits use of the system to hospitals.

More recently, a flexible drainage bag has been developed, as described in GB2190355 and as sold by Portex Limited of Hythe, Kent, England. The bag does not contain water but, instead, has a flap valve inside the bag, at its inlet, which prevents flow of fluid back to the patient. This bag has various advantages because it can be used out of hospital and is considerably more portable. One problem, however, is that, because the bag is flexible, it is not possible to apply suction to increase drainage.

Disclosure of Invention It is an object of the present invention to provide improved drainage systems.

According to the present invention there is provided a drainage system of the above specified kind characterised in that the system includes a one-way valve connected to the catheter between the catheter and an inlet of the drainage container so that fluid can flow from the catheter into the container via the valve but cannot flow in the opposite direction.

The drainage container is preferably substantially rigid and has an outlet. The system may include a suction device connected to the outlet of the container. The drainage container may be divided by a dam wall into two chambers, one chamber being located beneath the inlet of the container so that liquid entering the container initially flows into the one chamber and then overflows the dam wall into the other chamber. The drainage container preferably has an inlet tube with a lower end through which liquid flows out of the tube into the container, the inlet tube being movable between a first position in which the lower end of the tube is above the surface of liquid in the container and a second position in which the lower end of the tube is below the liquid surface. The drainage container may have a seal that makes a sliding seal with the outside of the inlet tube. The drainage container may have a flexible sleeve attached with the inlet tube and with the container such as to prevent contamination to or from the inlet tube. The one-way valve is preferably a flutter valve and the valve preferably has a tapered male coupling adapted to receive the machine end of the drainage catheter as a push fit. The drainage system may include a T-coupling connected between the valve and the drainage container, the T-coupling having a side arm with a self sealing septum.

An intercostal drainage system including a drainage catheter, in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings Brief Description of Drawings Figure 1 is a side elevation view of the system showing the drainage container in section; and Figure 2 is an enlarged sectional side elevation of the one-way valve.

Best Mode for Carrying Out the Invention The chest drainage system includes an intercostal drainage catheter 1 connected to the inlet 2 of a drainage container 3 via a one-way valve 4 and drainage tubing 5. The outlet 6 of the container 3 is connected to a suction pump 7 via suction tubing 8.

The intercostal catheter 1 is of conventional construction, having an open patient end 10 and several side openings 11 close to the patient end. The machine end 12 of the catheter is a push fit onto a tapered male coupling 40 at the inlet end of the valve 4.

The valve 4 has a semi-rigid cylindrical housing 41 of a transparent plastics material, with rigid end flanges 42 and 43 bonded to the housing at opposite ends. The inlet coupling 40 extends through the inlet end flange 42 forming a short spigot 44 within the housing 41. A flutter valve element 45 is secured at its upper end to the outside of the spigot 44. The valve element 45 has a flat, flexible plastics sleeve, about 65mm long, which is open at its lower end 46 and is closed along its sides 47. The flat, flexible nature of the sleeve allows fluid flowing from the spigot 44 to open the valve element and flow through it. However, if pressure in the valve housing 41 is greater than that in the spigot 44, it will urge the valve element 45 closed, thereby preventing flow in the opposite direction. The outlet flange 43 has an outwardly-projecting male coupling 48 coupled to an optional T-piece coupling 49. The coupling 49 has a lateral arm 50 with a self-sealing septum provided by a rubber cap 51, which can be penetrated by a needle (not shown) connected to a gas sampling device, or to a pressure indicator, to enable gas sampling or pressure measurement close to the machine end 12 of the catheter 1.

The outlet arm 52 of the T-piece coupling 49 is connected to the patient end 53 of the drainage tubing 5, which is conventional flexible plastics tubing. The machine end 54 of the tubing 5 is connected to the inlet 2 of the drainage container 3. The inlet 2 includes a short, rigid, vertical tube 20, such as of glass, extending through a seal 21 on the top of the bottle.

The seal 21 has internal sealing rings 22 making a sliding, gas-tight seal with the outside of the tube 20, so that the tube can be slid into, or out of, the container 3. The length of the tube 20 is such that, when it is pushed fully down, its lower end is located just above the floor of the container 3. When the inlet tube 20 is pulled out, upward movement is limited by a stop 23 on the outside of the tube, which engages the underside of the seal 21, leaving about 50mm of tube projecting down from the seal. In order to prevent contamination to or from the outside of the inlet tube 20 when it is pulled up, it may be protected in a flexible sleeve (not shown) attached at its lower end to the seal 21 and at its upper end to the upper end of the tube 20.

The container 3 is a bottle moulded from a rigid plastics material and is of generally rectangular shape having a dam wall 34 extending between the front and rear walls of the bottle, and projecting from the floor to about half the height of the bottle. The wall 34 is located about one-third the way across the width of the bottle, closer to the inlet 2, so as to divide the bottle into a minor chamber 35, directly below the inlet 2, and a major chamber 36.

The minor chamber 35 contains a small volume of water 37. The front wall of the bottle has two vertical graduation scales (not shown) extending up the height of the minor and major chambers, respectively, to enable the volume of liquid in the bottle 3 to be measured. In some applications, such as thoracic drainage, there is no need for a double chamber bottle; a single chamber bottle is sufficient. The outlet 6 of the bottle 3 takes the form of a short tube 60 extending through the roof of the bottle, and may include a hydrophobic filter to prevent the escape of any liquid. Where suction is not required, the drainage container could be of a flexible material.

One end of the suction tubing 8 is connected to the tube 60, the other end being connected to the inlet of the suction pump 7.

Industrial Applicability In operation, the catheter 1 is introduced intercostally, in the usual way. The machine end 12 of the catheter 1 is then pushed onto the inlet coupling 40 of the valve 4, which is ready-assembled on the patient end 53 of the drainage tubing 5. Alternatively, the valve 4 could be ready-assembled and bonded onto the machine end of the catheter 1. Preferably, the machine end 54 of the drainage tubing 5 is ready-assembled on the inlet 2 of the bottle 3. In many applications, suction is not required, so the outlet 6 of the bottle 3 is left open to atmosphere, so that liquid in the pleural cavity can drain along the catheter 1, through the valve 4 and the drainage tubing 5, into the bottle. The inlet tube 20 may be pushed down below the water 37 so that leakage of air from the patient can be observed by the bubbles this produces form the lower end of the tube. When the end of the tube 20 is below the water surface, the water does provide some resistance to flow of fluid into the bottle 3, so, where observation of air leakage is not required, the end of the inlet tube is left above the water surface. The valve 4 prevents suction into the patient, so there is no risk that air or liquid would flow to the patient if the bottle 3 were tipped over or raised above the height of the patient.

It will be appreciated that there are various applications, other than intercostal drainage, where the invention can be used.