In such thoracic drainage apparatus, to prevent air/fluid re-entering the thoracic cavity, a valve mechanism is inserted into the collection system. As illustrated diagrammatically in FIGURE I of the accompanying drawings, the traditional system employs a submerged seal-drain valve 5.

This system, however, is difficult to transport. Traditional glass collecting vessels are fragile, and also tilting the collecting vessel can allow fluid to re-enter the thoracic cavity. Although newer plastics containers do not break so readily as glass, with the design of FIGURE 1 they still allow fluid to re-enter the chest when tilted.

More recently, soft, tlexible, expandable plastic bags have been employed for collecting body fluids. In FIGURE 2 of the accompanying drawings there is illustrated for example a standard plastic urine collection bag which has a valve"A"to prevent retrograde flow and which has been used to transport patients with drainage tubes in situ. However, if used for thoracic drainage apparatus the absence of an additional vent or air release valve renders the patient vulnerable to life threatening build up of air pressure in the thoracic cavity-tension pneumothorax. Without an air escape vent or valve, air that is drained from the chest through valve"A"will build up in the bag and may eventually reach a pressure that unseals valve"A". The beneficial effect of a thoracostomy tube in relieving and/or preventing pneumothorax would then be lost.

For thoracic drainage apparatus it has therefore been proposed to provide an additional air release valve in a flexible plastic collection bag, especially for use during transport of patients and in systems for those patients who require a thoracostomy tube to be in place while they remain ambulatory.

This arrangement is illustrated in the diagram of FIGURE 3 which shows the additional valve-controlled vent"B". The problem of possible spillage of blood/fluid through valve"B"remains, however, with the arrangement of FIGURE 3 which can pose a risk of contamination of personnel and/or the environment; also spillage can make it difficult or impossible to determine accurately the amount of blood which the patients have lost.

In order to overcome the related problems of spillage of fluid and its effects on the fluid (blood) loss determination the present invention provides a drainage bag device, for medical use, comprising or including a flexible bag container provided with a non-return inlet valve and an air release valve, together with a liquid absorbent mass located in the bag so as to be spaced apart from the valves.

More particularly, the invention provides body cavity drainage apparatus for medical use comprising a flexible body fluid collection bag having an inlet with non-return inlet valve means for entry of said body fluid and having a vent for the escape of air, said bag also containing a mass of liquid absorbent material which is located therein so as to be separated from said inlet and from said vent by an air space that is maintained even when said mass has absorbed liquid to its maximum absorption capacity.

In preferred embodiments the dry weight of the bag with the mass of liquid absorbent material in situ is known and is preferably marked on the bag.

Also, the bags are preferably produced so as to have a predetermined standard weight.

The mass preferably comprises what is commonly referred to as "super-absorbent material", such as is used in disposable baby-nappies and tampons, to absorb blood/fluid rapidly and to retain the fluid. This is a polymer based material well-known in the art. The mass of this liquid absorbent material is preferably fixed to the bag or is otherwise restrained so as to prevent migration of the mass towards the inlet or the air release valve.

Changes in colour and expansion of the bag can alert the physician to continued/increased blood/fluid loss, and measurement of the change in weight of the bag can enable blood/fluid volumetric loss to be calculated accurately and simply.

In some embodiments, the mass may be made up of granules or lumps, e. g. of a hydrogel, contained in a porous pouch located in a fixed position in the bag.

The device of the invention is not necessarily confined to thoracic drainage apparatus and ambulatory chest drainage. A similar bag device can also be employed in other circumstances where blood and body fluids have to be drained and collecte, e. g. from surgical or other wounds, or during peritoneal dialysis or during vacuum or suction drainage.

The invention will be described further, by way of example, with reference to FIGURE 4 of the accompanying diagrammatic drawings which FIGURE is a diagram showing an example of a device of the invention.

The device shown includes a body fluid collection bag 10 formed of flexible substantially inelastic plastics material having, at its upper end 11 (in the orientation shown in FIGURE 4), an inlet 12 fitted with an inlet valve 13 which, at least insofar as liquids are concerned, is of non-return form; and having also an air vent opening 14 provided with an air release valve 15.

The bag device 10 further includes a mass 20 of highly absorbent fibrous material, located in a lower portion 20A of the bag 10 so as to be spaced from the topmost or upper end 11. The mass 20 is confined mechanically in the bag 10 by fixing means (not shown) so as to be held spaced apart from said upper end 11. The fixing means can be of any suitable form, e. g. a layer of adhesive bonding the mass to one wall of the bag, a flexible insert acting as a spring to hold down the mass, a porous or perforate membrane or sheath welded to the bag to encompass the mass 20 or to partition the bag, bonds between the walls 22 of the bag above the mass 20, or the formation of a pocket in the bag, this pocket containing the mass 20 and being open to receive liquid for absorption.

The volume of the mass 20 is determined by the amount of liquid to be absorbed, but in preferred embodiments the full volume of the bag is preferably at least 10% greater than the volume of the mass when it has absorbed fluid to its maximum absorption capacity, thereby to ensure that the air space 23 above the mass is maintained.

The mass 20 may be made up of several layers or parts of absorbent material or materials, or of a granular material contained in baglets, a pouch or a wrapping of porous, perforate, fibrous or woven material.

The bag 10 is preferably formed from a flexible impervious transparent or translucent inelastic material, although it may have relatively stiff walls, especially in those forms intended for use in suction drainage.

The valves may be of any suitable form.

In preferred embodiments, the collection bag devices are manufactured so that the weights thereof are standardized, or are within a specified range, for a given nominal capacity which will be known for any particular bag.

Alternatively, the bags may be weighed individually and the dry weight thereof, marked on the device or on its packing or on a label.

It will of course be appreciated that the invention is not confined to details of the foregoing disclosure and many variations, mechanical equivalents and modifications are possible within the scope of the invention as defined in the appended claims.