IE44244B1 - Venting device for stomas and other body openings - Google Patents

Abstract

The invention concerns a device for venting stomas and other discharge openings for metabolic products from the human body, the venting device being adapted to be placed in close direct or indirect relationship to the human body and stoma or other body opening, the venting device having a dimension perpendicular to the human body less than at least one dimension parallel to the body, the venting device containing an odor-removing filter material between gas- and liquid-tight walls with delimited passage for gaseous substances, the odor-removing filter material being passed by gases by a path longer than the dimension of the filter perpendicular to the body.

Description

This invention relates to improvements in devices such as the post surgical ostomy devices used for preventing the escape of gaseous, liquid, and solid waste materials from the stoma of 5 ostomy patients or from an anus with insufficient will control of the anus closing ring muscle.

More specifically, the invention relates to devices for venting stomas and other discharge openings for metabolic products from the human body.

A surgical procedure such as colostomy, ileostomy or ureteromy compromises the formation of an opening, or stoma, in the wall of the intestine or urethra so as to form a channel to the outer world through the body wall and skin of the patient. The stoma provides a means of communication between the intestine or urethra and the external world so as to permit the excretion of excretions suoh as fecal material or urine. As the excretion cannot be controlled by the will -in the same manner as excretions from the normal body openings, it is necessary for the patient to wear some sealing device which may comprise a collecting device. Actually, it is quite common for ostomy patients to wear some form of a 'stoma bag' or 'stoma pouch' for the rest of their life.

The most widely form for collecting receptacle is a bag or pouch made of film or foil of a transparent polymer material, affixed to the 4244 abdomen of the patient by means of a double-sided adhesive disc with a central opening t eg latering with the stoma; the stoma may be slightly projecting from the abdomen and passed through the central opening of the adhesive disc. In another embodiment a flange made of relatively stiff material such as a suitable polymer is secured to the back panel of the pouch, for instance by heat sealing; and a sealing gasket is affixed between the flange and the skin of the patient, whereby the pouch is held in position by means of a belt attached to the flange.

Fecal material is collected more or less constantly in the pouch and after a period, usually several hours, the pouch is discarded and replaced by another. The length of the period during which any given pouch may be used is strongly influenced, however, by the rate of production of flatus, i.e. of instestinal gases.

Several factors such as kind of food eaten, type of microflora and psychic condition affect the production rate and the composition of the intestinal gases. Over a 12 hours period the amount may vary between 50 and 1000 ml or even more. Generally the volume of flatus and intestinal gas passed via rectal tube ranges from about 400 to about 1200 ml per day. The commonly held belief that certain - 3 foods produce flatulence has been well documented. Ingestion of beans, fpr instance, may increase the mean flatus excretion rate from 15 ml to 176 ml per hr. The rate over shorter periods of time may show wide, variations, and it is particularly the flatus released at high rate which is difficult to: deodorize and also most likely to create problems for the patient. Thus, the variations in amounts and composition of flatus in themselves give great problems.

The composition :-.. -he inte2, 17% O2, 3% C02. Flatus in general contains less than 2% oxygen with the remainder of the gas consisting of varying proportions of nitrogen, carbon dioxide, hydrogen, methane and trace components. Keizo Kodama and Yoshiaki Miura in J.Japan Soc. Food Nutrition 2, pages. 149-152(1949) give the following composition: C02 13-34%, CH^ 19-26%, H2 20-27%, N2 17-48%. The odoriferous gases include indole, skatole, volatile amines, and hydrogen sulfide, and represent normally less than 1% of flatus.

Gf these gases hydrogen sulfide is by far the major component and presents the worst problem since it is readily detected by the nose in concentrations as low as 1 part in 100 million.

The gases enter the drainage pouch and expand it which gives rise to both practical and psychic problems for the patient. It has been practice to teach him to vent the gases from the pouch by puncturing the upper part of the pouch with a needle and after the exit of the gases seal the puncture anew with adhesive tape. However, because of the obnoxious nature of some of the gases and the frequency with which it is necessary to vent the pouch, this solution is quite unsatisfactory and may g.ive rise to embarrassing situations. Therefore, it is known to provide the pouch with some sort of filter to allow escape of gases.

Another manner of sealing the stoma of ostomy patients is to close it by a socalled stoma-cap, which is affixed to the body in much the same manner as the drainage pouch. A third and more important is to close the stoma by a plug or a stopper-like device inserted into the stoma and maintained in position by a flange or cover plate the inner face of which is in contact with the skin of the abdomen around the stoma.Such a stopper may be maintained in position by magnetic force, small permanent magnets being sewn into the body of the patient around the stoma by a surgical operation. There is no drainage pouch, but the fecal material is removed from time to time by irrigation, e.g. every two days, after removal of tho plug and subsequent re-insertion of it. To prevent pressure-build up behind the plug ωΐ behind the stoma cap), we have suggested to provide it with a venting opening covered vzith several layers of non-woven textile containing active carbon. In practice the gases are not, however, made non-odorous by the passage through this filter, possibly because the path passed by the gases through the filter >.s ”ei.y rhbrt. Accordingly, this device may also give rise to embarrassing situations.

As will be understood it is known in the three forms of sealing devices for stomas to insert a filter at some suitable part in the path of the gases. Several such filters are known. Thus, a preferred embodiment of a filter known from US Patent Specification No. 3,759,260 comprises a disc of matted fibres and activated granular carbon having one surface overlying the inner side of the vent aperture of the pouch and an area surrounding the aperture, and an impervious cover over the opposite surface of the disc, whereby the gases to be vented pass radially through the disc from the periphery to the vent aperture placed centrally relative the filter. This does not function quite satisfactory, 44344 which is believed to be due to the short path passed by the gases and, perhaps most important, a tendency; to a channelling effect to· be discussed later in this text.

A filter for venting gases from stoma pouches is described in Danish patent specification No. 130,277, and British Patent Specification No. 1,405,032.

The preferred embodiment of this comprises a square disc of matted fibres and activated carbon in granular form.

One surface is covered with a gas-tight material with a central venting aperture, whereas the other surface of the disc is covered with another cover of gas-tight material with several apertures displaced relative the centre, whereby the gases to be exhausted pass through an oblique, partly radial path through the filter. A similar filter is disclosed in Danish patent specification No. 133,080.

In this, one of the impervious covers has a central venting aperture and the opposite cover several venting apertures evenly distributed over the area of the filter disc.

The prior art filter devices described are similar in that they all comprise a flat disc of matted fibres and activated granular carbon, said disc having the two opposite faces covered with impervious materials with - 7 44344 apertures so that the gases to be exhausted are forced to pass in a more or less radial direction through tho niter, i.e, by a path longer than the thickness of the disc.

The purpose of this is to make more effective use of the capacity of the activated carbon for absorbing the odorous constituents of the intestine gases. However, in practice the known filter assemblies do not function as intended and the useful lifetime of filters are not satisfactory whereby despite of the use of filters there may arise embarrassing situations; also frequent removals and replacements of the filters are needed and the active carbon present is not utilized full, which means an extra financial burden.

We not? believe that one reason for the unsatisfactory function of the known filters described is that a considerable 'channelling' takes place during the passage of the gases. . The filter disc is made of comparatively stiff material. The gas-tight covers are made of thin films or foils of plastics materials with no special precautions to ensure a stable, gas-tight contact with the surfaces of the filter disc. As a result, the path axially through the filter and then along a channel between the filter disc and the cover to the vent aperture or apertures (or vice versa, first along a channel between the filter disc and cover and then axially 4 2 4 4 through the filter) will offer mUch less resistance than the path radially or obliquely through the filter disc and therefore will be preferably followed. We now believe that another reason for the unsatisfactory function of the known devices is the irregular production and composition of the intestinal waste gases. If the absolute amount of odoriferous substances to be removed were rather constant over the hours of the day, the filter material, for instance active carbon, could be provided in an amount corresponding to the rate of odoriferous gases and the geometry of the placing of the active carbon would be relatively unimportant. As, however, amounts and composition vary very much, a regular utilisation of the entire mass of active carbon is impossible and the geometry of the device becomes more important.

A device according to the invention for covering an opening for the discharge of metabolic products from the human body and which includes means for venting the opening comprises a disc of an odour removing filter material and gas tight cover material in gas tight contact with the filter material, the cover material being provided with inlet and outlet openings, at least one of the openings being located at the edge of the disc and the other being located such that gas being vented has to pass through the filter material a distance of at least 5 times the thickness of the disc of filter material.

There is often an opening through the disc of filter material and the inlet for gases to be vented is 2 4 4 around the edge of the opening, and the outlet is around the outer edge of the disc, there being means to prevent the direct escape of gases from the device across the opening. Generally the disc is circular and the opening positioned centrally.

As explained in more detail below, the means to prevent direct escape of gases may comprise the gas tight cover material extending across and hermetically sealing the central opening of the disc filter material.

This is suitable in, for instance, a plug or stopper device. When the device is to collect fecal material the means to precent direct escape of gases may comprise a pouch for collecting fecal material from the body opening.

In one pouch device, the cover material on the side of the disc distant from the pouch does not extend across the opening in the disc and there are means for holding the device in position with that side of the disc adjacent the skin. Thus the filter assembly is close to the skin, with the pouch extending beyond the filter assembly.

In another pouch device the cover material on the side of the disc distant from the pouch extends across and seals the opening and the pouch includes an inlet opening, distant from the disc, for receiving fecal matter from the body opening, and there are means for holding the device in position with the inlet opening in the pouch against the body opening. Thus in this pouch device the filter is distant from the body.

There are known means for holding devices such as those of the invention in position. The means may be magnetic or adhesive. - 10 44244 As a result of the invention it is now possible to ensure that unpurified gases do not pass through the device without being filtered and it is possible to ensure optimum utilisation of the active filter material. Thus without using more filter material than has been used previously it is possible to remove successfully odoriferous gases from the intestine gases even in periods with maximum production of such gases with maximum contents of malodorous components.

The filter part of the devices according to the invention does not have to be formed integrally with the device and instead can be manufactured separately as a releasable member that can be used for a prolonged period of time and can be transferred from one stoma pouch, cap or plug to another.

Accordingly a filter assembly according to the invention comprises a disc of an odour removing filter material and gas tight cover material in gas tight contact with the filter material, the cover material being provided with inlet and outlet openings, at least one of the openings being located at the edge of the disc and the other being located such that gas passing between the inlet and outlet has to pass through the filter material a distance of at least 5 times the thickness of the disc of filter material.

The disc naturally has a dimension perpendicular to the body opening against which it is to be fitted less than at least one of its dimensions parallel to the body. - 11 4 42 4 4 The gas-tight contact between walls and filter material will prevent channeling and can be obtained both with a granular or powdery filter material such as for instance ' granules of activated carbon; and with a filter material in the form of a body, for instance of a foamed or paper-like, material impregnated with an odour-removing material such as activated carbon or some chemical compound; and with some porous substance in itself acting as odour-removing material. The geometry of the device, i.e. the provision that the path for the gases is at least five times as long as its smallest dimension ensures that the gases are forced to come into contact with a large bulk of the odour-removing filter material and this firstly means an efficient utilisation thereof and secondly ensures that a sudden increase in the amount of gases or their contents of malodorous components will not cause the escape of fetor to the surroundings and hence - not create embarrassment. 4 2 ‘14 In the invention the filter material is generally provided as a substantially flat disc provided with a hole in the middle. The flat sides of the odour-removing filter material are in gas-tight contact with gas-impervious walls or the like, whereas the edges of the inner hole and the outer periphery of the disc are at least partially free for the entrance and escape of the intestine gases, respectively. Here, the proper length of the gas path is ensured by the width of the ring, i.e. the radial distance from the hole to the outer periphery, being at least five times the thickness of the disc or ring of the filter material. Generally the gas inlet into the filter material is the edge of the central opening, and the discharge of purified gases the edge of the outer periphery of the ring, means being provided to prevent direct escape of gases through the central opening, the flat surfaces of the ring being in gas-tight contact with covers or walls, the radial width of the ring being at least 5 times its thickness. Such ring may be placed in a variety of manners. Very conveniently, the central opening in the ring has a diameter slightly above that of the stoma. The venting device can be placed around the stoma and connected with a sealing device, preferably a stoma bag or stoma plug. When used with a stoma bag, the inner ( i.e. nearest to the skin of the patient) cover or wall on the filter material may be adhesive or provided with an adhesive preventing leakage between the skin and filter when the device is glued to the body around the stoma. The outer wall or cover is similarly glued to or integral with the stoma bag having its entry opening in register with the central opening of the ring. Gases as well as solids and liquids may pass direct from the stoma into the pouch via the central opening. However, pressure-build up is prevented because the gases can escape via the filter material since its free outer edge is situated between the skin and the bag. The filter material removes the odoriferous substances and permits passage of the innocuous gases. If connected with the bag by adhesive, the venting device may be 'moved from one bag to another until the filter material is exhausted, vzhich involves a saving in cost. Also, the construction of this device is quite simple and it is built up of inexpensive materials.

This means that it is cheap in use, which is an important advantage because ostomy and similar patients must always use some sort of sealing device. The venting device may of course also be placed on the other side of the stoma bag that is. turned away from the torso; in such case the central hole of the filter may have any desired size and vzill often be smaller than the stoma opening.

This embodiment is particularly useful for stoma plugs held magnetically in place and is a very elegant solution of the problems connected with release of pressure built up in the intestine and stoma in cases where the stoma is closed with such plug. Herefore, a reliable filter for venting devices in such plugs have not been available and it has been necessary to some degree to vent unpurified intestine gases. Now, however, the ring embodiment of the present invention will allow a very reliable, continuous venting of purified, non-odoriferous intestine gases, even in oases of sudden increased production for instance in connection with a meal. A very useful stoma plug has a part inserted into the stoma and integral or connected therewith a flange the inner face of which is in engagement with the skin around the stoma and provides a hermetic sealing.

The ring of filter material can be situated with the central opening of the ring surrounding the plug proper with some clearance, whereby the gases can pass along the plug in the stoma, enter the filter through the edge of the opening and leave the filter through the circumferential edge thereof. The inner face of the filter (that closest to the body) is in gas-tight contact with a gas-tight cover; this may in itself be adhesive, or it may have an adhesive on the side facing the filter and possibly also the side facing the skin around the stoma. The outer face of the filter is directly or indirectly in gas-tight contact with the inner face Of the flange of the plug. By these means it is ensured that the intestine gases cannot escape without passing the odour-removing filter material.

The opening of' the ring may be eccentric provided that the shortest possible distance for the gases is still 5 times the thickness of the filter material. It is not strictly necessary but usually preferred that the entire edge of the opening admits the gases, or the entire outer edge permits their escape; part thereof may be blocked by a gas-impervious material.

The thickness of the filter material may vary within wide limits. Usually it will be between 0.8 and 8,0 mm and typically 1.5-3 mm.

The ring is preferably substantially circular with a circular central opening. The outer diameter may expediently be 3-10 cm, a very convenient size is 6-7 cm diameter. The inner opening expediently has a diameter of 0.5-2 cm, very conveniently 1-1.5 cm. An expedient width of the ring (outer minus inner diameter) is 2-3 cm, especially about 2.5 cm.

If the embodiment with a channel is used, a convenient channel diameter is 2-5 mm, especially 3-4 mm.

When the venting device is constructed as just described with a ring-shaped filter material, this should have the nature of a body rather the more or less loose particles because it would be difficult to prevent such particles frcm falling out. It could, of course, be done by the aid of a membrane of some porous material, but this would increase the cost and give no particular advantage; in contradistinction, it will not increase the costs appreciably in the main embodiment first discussed to cover the ends of the channels by such porous material.

It may be convenient to use two or more different filter materials, placed concentrically, but usually this is not necessary. One very useful odor-removing principle of the filter material is activated carbon. In both main forms of the device the activated carbon may be distributed in granular form in a fibrous material.This preferably is a cellulose fibre material in the form of a woven or non-woven textile or a cottony or fleecy material.

However, it is belived that a still better form of the odor-removing filter material is a filter element consisting of an open-celled, elastic cellular matrix impregnated with a dispersion of activated carbon in a binder.

The elasticity helps to tighten the various contact surfaces so as to minimize the risk of leaking of unpurified gases. The binder ensures that there will never inside the filter element be formed channels without activated carbon; the element is easy to handle and can easily be given whichever shape desired. Such impregnated elastic foam is extremely suitable for all of the embodiments discussed and is especially ~ suitable for the filter rings described.

The binder may be an ethylene-vinyl acetate latex or dispersion, a styrene-butadiene latex or an acryl latex. It may also be a . * solution of a suitable polymer or copolymer.

The active carbon may' also be distributed in the polymer itself.

Instead of being impregnated with the activated carbon, the open-celled elastic cellular foam or matrix may be made of a polymer containing a large amount of amine grouping or be impregnated with an amine. Such amines, for instance in the form of urethanes, are efficient odour-removing substances.

In the ring-version of the device, the cover or wall on the side of the ring not in contact with the body may extend over and hermetically close the central opening of the ring; such embodiment can be placed directly on the outer wall of a stoma bag, or constitute the top and flange of a stoma plug. The gas-tight contact between the odor-removing filter material and the gas-tight covers or walls may be achieved by adhesion.Very expediently, both of the two gas-tight covers are adhesive on both sides, whereby they may serve as bonding members between body-filter element-stoma bag or stoma plug flange.

In the ring-embodiment of the device, the gas-tight cover on the inner surface (that facing the body) may have a larger central opening than the filter disc and the other 424 4 gas-tight cover; then, of course, the narrowest ring must be at least five times as wide as the thickness of the filter. Such embodiment has a larger inlet area for the gases and is particularly well fit for use in cases where a large volume is expected.

The gas-tight contact between the filter element and the flange, when the device is used in a stoma plug, may advantageously be ensured by magnetic elements as is explained more fully in connection with the drawings.The gas-tight contact between the various members may also be ensured by elastic forces as already explained. 44344 The venting device according to the invention will now be described moke in detail with reference to the drawings, it being understood that drawings only serve at illustrating the various principles involved as represented by the various embodiments shown, and must not be construed as a limitation of the invention.

In the drawing, Figure 1 is a cross section through the torso of a person wearing a stoma pouch provided with one embodiment of the venting device according to the invention.

Figure 2 is a part section through a person with a stoma bag with another embodiment of the venting device according to the invention, Figure 3 is a part section through a third embodiment 15 of a venting device according to the invention, Figure 4 is a section through a person and his stoma, a plug inserted into the stoma and provided with a venting device according to the invention, Figure 5 shows part of Figure 4 in larger scale, Figure 6 is a cross section through part of an embodiment of the venting device according to the invention, Figure 7 is a cross section through part of a still further embodiment of the venting device according to the invention, 4 2 4 4 Figures 1-7 for reasons of clarity are shown as slightly exploded views . In reality there will be no space between, eg., objects 1, 3, 4 and 5.

As shown in Figure 1, a stoma bag or pouch 6 is 5 fastened to the torso 1 of a person having a stoma 2, for instance made by a surgical operation. A venting device according to the invention is situated between the skin of the patient and the bag. The venting device comprises a ring-shaped, gas-tight disc 3 of an adhesive polymer composition. The disc has a central hole fitting more or less closely around the outer opening of the stoma. One side of disc 3 adheres to the skin of the person and thereby acts as a means or part of the means for carrying the stoma bag. The other side of the disc adheres to a ring-shaped filter element 4 comprising an odorremoving material. Filter element 4 has a radial width at least 5 times its thickness (in the embodiment shown about 20 times its thickness) and may for instance consist of a commercial filter paper impregnated with activated carbon. in a preferred embodiment, the ring-shaped filter element is made of an open-celled, elastic cellular polymer foam impregnated with or containing activated carbon. On the other flat surface of filter element 4 a further ringshaped, gas-tight disc 5 of an adhesive polymer composition 44344 is affixed; it bonds together filter element 4 and stoma bag 5 the inlet opening of which is aligned with central openings in adhesive rings 3 and 5 and filter element 4 as well as stoma 2 when Situated in operative place. In use, liquids and solids from stoma 2 can enter bag 6 via the openings in ring-shaped elements 3, 4, and 5.

Intestine gases or gases.produced by the liquids and solids can escape via the venting device; they enter the ring-shaped filter element through the inner periphery, pass radially through the filter element and leave through the outer periphery. As ring-shaped discs 3 and 5 are adhesive, there is ensured gas-tight contact between them and the filter element, as well as gas-tight contact to the skin of person 1 and to bag 6. Accordingly, the gases can only escape through the filter element; as this filter element contains an odor-removing filter material, and as its dimensions ensure a long path for the gases through this filter material, it will effectively ensure the removal of malodorous components of the gases whereby only innocuous gases actually leave the device.

In Figure 1, the filtering element is situated between the bag and the skin of the person. It may alternatively be'placed at the outer side of the bag 6, away from the patient's body. Thereby suitable means would be provided to affix the bag direct to the body with its inlet aligning the stoma; the opposite side of the bag would have an opening aligning with the central hole in the filter element 4, the latter being affixed to the bag. The outer face of the filter element would be in gas-tight contact With an entire disc of a gas-tight material e.g. a gas tight plastics film, covering both the ring-shaped filter element and the central opening thereof. 4 2 4 4 However, the position shown in Figure 1 is the most advantageous because it has been found that although the intestine gases are saturated with water vapour, no condensation of water vapour occurs inside the filter element. Such condensation is difficult to avoid in a filter placed at the outer, cooler surface of the stoma bag and would, when formed, seriously interfere with the function of the filter.

Although no special means are provided to prevent liquid collected in the stoma bag from entering the filter element, it has surprisingly been found that the latter remains dry and active for long periods.

Nevertheless, if the material collected in the bag contains large amounts of water, or other special conditions exist, it may be advantageous to use the embodiment shown in Figure 2. Here, again, 1 is the torso of a person with a stoma 2. Again, an inner ring-shaped adhesive disc 3, a ring-shaped filter disc 4 and an outer ring-shaped adhesive disc 5 form a connection between torso 1 and bag 6, the connection being gas-tight except for the possibility of gases escaping through the odorremoving filter material from inner edge to outer edge of the disc. Here, however, the inner edge of filter element 4 is covered by a film 7 of a gas-permeable hydrophobic material (e.g. the material sold by E.i. du Pont de Nemours and Company under the trade mark Tyvec). The film 7 is secured by glueing or welding to the inner part of the adhesive rings 3 and 5.

As actually shown, the stoma bag 6 in Figure 2 is adapted to be secured to the filter assembly 3, 4, 5, 7 via flange 14. Such a flange 14 may be used to ensure greater freedom of movement of the stoma bag. Xt may also 44344 be used when the stoma bag is fastened to the tor$o by means of a belt. The embodiment of venting device shown in Figure 2 may well be used without this flange 14.

Figure 3 shows a cross section of another embodi5 ment of a venting device having a filter for use under conditions of large amount of water in the bag, or other special conditions. Reference numerals 3, 4 and 5 have the same meanings as in Figures 1 and 2,and 8 is an inner ring of a gas-permeable hydrophobic material such as Tyvec or of an open-celled hydrophobic foam plastics material.

Figure 4 is a cross section through the torso 1 of a patient with a stoma 2 closed by a so-called magnetic plug 11. By a surgical operation a permanent magnet in the form of a ring enclosed in a suitable plastics material has been placed around stoma 2. This ring attracts and holds the plug 11 which contains another magnet or set of magnets (not shown). By the attractive forces between the magnet(s) in 12 and 11, a cover plate 10, which is part of plug 11, is pressed against a gasket 9 which prevents leakage from the stoma. With this type of closure for the stoma the build up of pressure from intestine gas collected in the stoma is a particularly severe problem. The gas pressure lifts the plug away from the gasket even if the gasket is adhesive, and leakage results. For this type of stoma closure our invention is particularly useful.

Figure 5 shows a detailed half cross-section of gasket 9 which is made according to our invention and comprises a filter allowing the intestine gases to leave the stoma without discharging malodorous gases to the free. A ring-shaped inner disc 3 of gas-impervious material is adapted to be held in gas-tight contact with the skin under the influence of the magnetic forces. Ring 3 is in gas-tight contact with a ring-shaped filter disc 4, e.g. of similar construction as the disc used in connection with Figures 1 and 2, and thus again in gas-tight contact with an outer gas-impervious disc 13 which is made of adhesive material or provided with an adhesive on both sides.

The radial width of gasket 9 is at least 5 times the thickness of filter ring 4.

Tt is an advantage to use the adhesive disc 13 which positions and keeps the filter disc in place when the plug is opened and closed for removal of faecal material.

Ring 3 may be a soft flexible gasket and if desired may also be adhesive to obtain maximum security against leakage.

Figure 6 shows a cross-section of another gasket suitable for use with the magnetic plug 10, 11. Reference numerals 3, 4, and 13 have the same meaning as in Figure 5. Reference 7 is a ring of Tyvec which extends over the inner edge of the filter disc 4. This disc of Tyvec or other hydrophobic gas-permeable material must have an outer diameter smaller than the filter disc; the radial distance from its Inner periphery to the outer periphery of the filter ring must be at least 5 times the thickness of the filter discs. It goes without saying that there must be gas-tight direct contact 42 44 between filter ring 4 and ring 3 where the Tyvec ring 7 is not present.

Figure 7 shows a cross-section of another filter assembly suitable for use both with a magnetic plug and a stoma bag. Here one of the gas-impervious covers (3) has a larger central opening than filter element 4, thereby increasing the effective area through which the gas may enter the interior of the filter element. Again, the three rings- must be in gas-tight contact with each other and the radial width of the cover ring (3) having the larger central opening must be at least 5 times the thickness of the filter ring.

If desired the filter element may be impregnated partly or wholly with a hydrophobing agent such as a fluoropolymer or a silicone.

It is also understood that if desired the filter need not be symmetric with respect to dimensions or other properties around the stoma, but may for instance be gas-impervious around a fraction of the stoma periphery. 4 1 2 1 J Example 1 A stoma bag made from polyvinylidene ohlorids and having a flange on the rear side was fitted with a filter element of the general construction shown in Eigure 2. The active filter element (4) was made from 3 mm thick open ceiled polyurethane foam of density 17 kg/m impregnated with a slurry of activated carbon powder in a binder comprising an ethylene-vinylacetate polymer dispersion. The impregnated polyurethane foam had a density of 48 kg/m and contained 37% b.w. of activated carbon.

The ring-shaped gas-tight discs (3) and {5) were made from a double sided self-adhesive polymer composition which adhered firmly to the filter element (4) and this prevented channelling.

The stoma bag was tested on a male patient having severe problems with large volumes of intestine gas. The bag was used over 28 hours and during this time the intestine gas was released continuously and was completely free of odor. When using a stoma bag with a filter device according to USP 3,759.260 the patient complained that the venting device was not able to deodorise the intestine gas as fast as it was produced and he had to change back to a venting device according to the invention.

Example 2 A patient having a stoma closed by a magnetic plug as shown in figure 4 complains of leakage around the plug. Various gasket materials and known gaskets constructions are tried, but the seal is never tight for more than a short period, after which time faecal material starts to leak out. The magnetic plug is now fitted with a filter device of a 4 2 4 4 construction as shown in Figure 7. The active filter element is made from an open celled flexible polyurethane foam impregnated with activated carbon. The overall density is 60 kg/m^ and the filter contains 29% b.w. of carbon.

' The outer gas-tight disc (13) is made from a double-sided self-adhesive polymer composition and the inner gas-tight disc is made from a sealing material comprising about 50% of a viscous polyisobutylene matrix and about 50% of a hydrophilic powdery filter comprising gelatin sodium carboxymethyl cellulose and powdery pectin . The outer diameter of the filter device is 60 millimeters and the diameter;of the central hole in ring (4) and adhesive disc '13) is 10 mm and in the inner cover (3) the hole diameter is 14 mm.

With this filter device the plug remains tight for hours. The intestine gas is completely deodorized and vented as fast as it is produced and there is no leakage of faecal material. The plug is opened three times during this period and faecal material is removed by irrigation of the intestine. When the plug is reinserted the seal is still perfect.

Example 3. in an investigation at the University Clinic at Erlangen, Germany, nine stoma patients, Who all had severe problems with leakage of obnoxious material around their magnetic stoma plugs when using known gaskets were given venting devices according to the invention. With a venting device as shown in Figure 7, eight of the nine patients became free of problems, i.e., the intestine gas was removed in a controlled manner through the filter and there was no problem with leakage or odour.

In a similar investigation made by Dr. H. Feustel at - 28 4 4 2 4 4 the University Clinic at Giessen, Germany, nine out of ten patients were relieved cf problems with their stoma.

Example 4 A magnetic stoma plug was fitted with a venting device of the construction shown in Figure 6. The filter element (4) was made from filter paper impregnated with active carbon. The outer gas-impervious disc (13) was made from a styrene-isoprene-styrene rubber sheet, and the inner disc (35 was made from sealing material comprising a viscous polyisobutylene matrix with a hydrophilic filter comprising a blend of starch, gelatin and pectin. The gas-tight contact between disc (13) and the filter element (4) was obtained by the magnetic forces holding the plug in place in the stoma. This plug was tested on a patient who had never been free of leakage and odours from his stoma. With the new venting device he had no problems with leakage and the intestine gas leaving the filter element was completely free of odour. After 29 hours the plug was removed. The filter element was still active, but the inner gas-impervious disc (3) had swollen so much from intestine fluids that the passage between the inner rim of the disc and the plug (11 in Figure 4) was blocked. The function of this venting device could be further improved by increasing the diameter of the central hole of disc (3) as shown in figure 7. The ratio between thickness of filter element and radial path from the central hole to the outer rim was in this experiment 1:40.

Example 5 In order to investigate the influence of the physical - 29 4 4 3 4 4 dimensions upon the performances of the active filter element the following experiment was made.

A flexible open-celled polyurethane foam was cut into sheets Of a thickness of 3 mm. The sheets were impregnated with active carbon in a binder comprising a vinyl copolymer dispersion. The dried sheets contained 28% b.w. of carbon and had a density of 55 kg/m3.

Rectangular discs were cut from a sheet. The area of 2 the discs were in all cases 4,5 cm and the length and width were as shown in table 1. These discs were each covered with adhesive gas impervious tape on top, bottom and the two sides, whereas the remaining two sides were sealed to small plastic tubes to allow the passage of gas through the inlet tube into the disc through its lengthwise direction, and then out through the exit tube. The inlet tube could be connected to a gas tank filled with a test gas at atmospheric pressure. The exit tube could be connected to a detector tube containing a plumbous salt and calibrated to show the amount of H^S in the gas passing the tube. The other end of the detector tube was connected to a calibrated suction pump which could pump precisely known volumes of test gas from the gas tank, through the filter element and the detector tube. The test gas consisted of a blend of 80% nitrogen and about 20% methane with 25 p.p.m. H-,S added. During the experiment any II not being absorbed by the filter element would react with the plumbous salt in the detector tube from which a direct reading of the amount could be obtained.

Since in practice the stoma patients have the greatest problems when large volumes cf intestine gas is suddenly released the gas rates were varied to find the filter dimensions most effective at the high gas rates corresponding to this situation. - . ' - 3o Table i. Dimensions of Filter Elements 44344 Filter No. Length nun ' .......' Width mm . . ...--------.-- ....... Thickness mm Length Thickness 1 3 22,4 22,4 0,1 2 10 15 9 1,1 3 15 30 3 5 4 30 15 3 10 5 45 10 3 15 Table 2. Efficiency of Filter Elements versus Flow Rate Rate of gas flow ml/min 10 20 1 j 50 1 100 1 200 Filter No. Total vol. ml. Efficiency % Efficiency % Efficiency % Efficiency % Efficiency % 100 98 90 77 60 20 200 25 1 300 97 84 66 47 27 400 30 500 95 69 55 44 32 100 99 94 91 80 58 2 300 99 92 78 59 42 500 98 85 70 55 40 100 100 100 96 89 60 200 100 100 92 80 55 3 300 100 98 84 70 50 400 100 98 79 . 67 45 500 100 96 78 67 44 100 100 100 100 96 80 200 100 100 100 90 70 4 300 100 100 93 83 60 400 100 100 90 77 56 500 100 99 89 72 52 100 100 100 100 100 86 200 100 100 100 91 70 5 300 100 100 98 83 65 400 100 100 90 77 55 500 100 99 90 . 72 55 4424 4 The results of the experiment are shown in table 2.

It will be seen that filter No. 1, where the gas passes perpendicularly to the plane of the filter element is the least efficient. Even at the lowest gas flow rate 100% efficiency is never reached and as the flow rate increases the efficiency drops rapidly. (Efficiency is the percentage of H2S absorbed by the filter).

The filters Nos. 3, 4, and 5 are all highly efficient at the lower flow rates even after a total of 500 ml of test gas has passed the filter elements. At higher flow rates the filters drop off in efficiency, but even at a rate of 100 ml/min filters Nos. 4 and 5 retain an efficiency of 83% after the first 300 ml of test gas and 72 % after 500 ml.

Filter No. 2 is, although clearly better than No. 1, never 100% efficient and is more sensitive to an increase in flow rate and volume than filters 3, 4, and 5.

It Is thus seen that in order to combine efficiency at high flow rates with large total capacity the venting device should be designed with a gas path through the filter element which is considerably longer (at least 5 times) than the smallest dimension of the filter element.

Example 6 A test gas comprising nitrogen, methane, hydrogen ., carbon dioxide and 25 p.p.m. H2S was passed into a commercial stoma cap manufactured by Hollister Incorporated and broadly as described in Danish Patent Specification No. 133080.

The gases leaving the exit hole in the venting device were passed through a detector tube and the total amount of H2S passing the venting device was measured. After 400 ml of 4 2 4 4 test gas had passsed a reading of 5 was obtained. After 600 ml the reading had increased to 15 and the experiment was stopped. In a similar stoma cap the filter element was brought into gas-tight contact with enclosing gas-tight plastic foils by the use of an adhesive, so that the gas had to pass from the rim to the venting hole through the filter element and channelling was effectively prevented.

Test gas was now passed through the venting device. After 400 ml the reading was zero. After 600 ml the reading was 7.5 and the experiment was stopped.

Example 7 A stoma bag made from two rectangular sheets of plastics foil sealed around the edges is fitted with a venting device consisting of a flat filter element measuring 15 x 30 x 3 mm made from felted cellulosic fibers and containing finely granulated active carbon. The filter element is placed into a small pocket made by sealing of a 22 x 40 mm sheet of a similar plastics foil onto one of the sheets forming the stoma bag. An entry hole and an exit hole is made in the two sheets enclosing the filter element so that the gas to be vented is forced to pass through the length of the filter element.

In another stoma bag of a similar construction a gastight contact between the filter element and the enclosing walls is obtained by means of an adhesive.

The capacity and efficiency of the two venting devices is compared by passing a test gas containing II2S through them. The results are shown in table 3.

Volume Efficiency % of Test without gas- -tight contact with gas-tight contact Gas 5o ml/min 100 ml/min 50 ml/min 100 ml/min 100 100 100 100 100 200 100 90 100 96 300 93 66 95 84 400 83 53 92 80 500 66 52 89 72 The results clearly show that efficiency can be considerably improved by bringing the filter element into gas-tight contact with the enclosing walls.

Example 8 In another experiment the venting device described in the above example was fitted, onto a stoma bag by a self-adhesive disc , so that intestine gases collected in the bag could be vented through the venting device into the atmosphere. In use the stoma bag would collect the solid and liquid faecal material produced in the intestine while the intestine gas was deodorized and released through the venting device. After a period of the normally 5-10 hours the bag with the collected material would be removed and discharged, while the venting device was transferred onto a new bag, which was placed over the stoma. After three weeks of continuous use in this manner the venting device still performed satisfactory and the patient had no problems with odours.

Claims (16)

1. CLAIMS :1. A device for covering an opening for the discharge of metabolic products from the human body and which includes means for venting the opening, the device comprising a disc of an odour removing filter material and gas tight cover material in gas tight contact with the filter material, the cover material being provided with inlet and outlet openings, at least one of the openings being located at the edge of the disc and the other being located such that gas being vented has to pass through the filter material a distance of at least 5 times the thickness of the disc of filter material.

2. A device according to claim 1 in which there is an opening through the disc, the inlet for gases to be vented is around the edge of the opening, the outlet is around the outer edge of the disc, and there are means to prevent the direct escape of gases from the device across the opening

3. A device according to claim 2 in which the disc is circular and the opening is central.

4. A device according to claim 2 or claim 3 in which the means to prevent the direct escape of gases comprises the gas tight cover material extending across and hermetically sealing the central opening of the disc.

5. A device according to claim 2 or claim 3 in which the means to prevent the direct escape of gases comprises a pouch for collecting fecal matter from the body opening. 4 4 244

6. A device according to claim 5 in which the cover material on one side of the disc distant from the pouch does not extend across the opening in the disc and there are means for holding the device in position with that 5 side of the disc adjacent the skin.

7. A device according to claim 5 in which cover material on the side of the disc distant from the pouch extends across and seals the opening and the pouch includes an inlet opening, distant from the disc, for receiving fecal 10 matter from the body opening, and means for holding the device in position with the inlet opening of the pouch against the body opening.

8. A device according to claim 6 or claim 7 in which the means for holding the device in position comprise 15 adhesive material.

9. A device according to any of olaims 5 to 7 in which the pouch is adhesively bonded to the cover material covering the disc on the pouch side of the disc.

10. A device according to any of claims 2 to 9 in which 20 the cover material on each side of the disc carries, on its surface distant from the disc, an adhesive material.

11. A device according to any of claims 2 to 10 in which the inlet opening for the cover material is covered by a hydrophobic gas pervious material. 25

12. A device according to any preceding claim in which 4 4 244 the gas tight contact between the cover material and the disc of filter material has been provided by adhesive bonding.

13. A device according to any preceding claim in which 5 the filter material comprises an open-celled, elastic, cellular matrix that has been impregnated with a dispersion of activated carbon in a binder.

14. A device according to claim 1 substantially as herein described with reference to any of the accompanying 10 drawings.

15. A filter assembly suitable for use in a device according to any preceding claim and comprising a disc of an odour removing filter material and gas tight cover material in gas tight contact with the filter material, the cover 15 material being provided with inlet and outlet openings, at least one of the openings being located at the edge of the disc and the other being located such that gas passing between the inlet and outlet has to pass through the filter material a distance of at least 5 times the thickness of 20 the disc of filter material.

16. A filter assembly according to claim 15 in which there is an opening through the disc, the inlet for gases to be vented is around the edge of the opening and the outlet is around the outer edge of the disc.