RESUSCITATOR ARRANGEMENTS AND FILTER ASSEMBLIES

This invention relates to filter assemblies of the kind for use with breathing apparatus including a filter unit having a housing containing a filter element, the housing having a tubular gas coupling on an outlet, patient side and an inlet opening on the opposite side.

Ventilators or resuscitators are used to supply a breathing gas such as air, oxygen or a mixture of air and oxygen to a patient who needs assistance with breathing. The ventilator may be of the manual kind where a resilient bag is squeezed by hand to provide gas pressure to the patient, such ventilators are sold, for example by Smiths Medical under the Portex 1 ^st Response trade mark. Alternatively, the ventilator may be of the gas-powered kind such as sold by Smiths Medical under the Pneupac trade mark. The outlet of the ventilator is coupled to a breathing device, such as a face mask or tracheal tube, by which the gas is supplied to the patient. A filter may be coupled between the breathing device to prevent the resuscitator being contaminated by biological substances in exhaled gas from the patient.

In some emergency situations the patient may be exposed to hazard from biological or chemical substances in the air, or there may be concern that such substances are present or may be present in the near future. In the case of a gas-powered resuscitator operating in a pure oxygen mode, the patient is to some extent protected from any such hazardous substances in the air. However, most resuscitators have a safety feature that enables the patient to breath atmospheric air if the pressure of oxygen should fall. Also, in some situations it is undesirable for the patient to breath undiluted oxygen so it is preferable for the oxygen to be mixed with atmospheric air, this also has the advantage of extending the life of the oxygen cylinder. It can be seen, in these situations, and where manual squeeze-bag ventilators are used, that the patient would be exposed to inhale any contaminants present in the atmosphere. The conventional medical HEPA type filters presently used with resuscitators are not intended, and are not effective, to protect the patient against many of the hazardous substances to which he might be exposed, such as in a battlefield or chemical incident situation.

It is an object of the present invention to provide an alternative resuscitator arrangement and filter assembly.

According to one aspect of the present invention there is provided a resuscitator arrangement of the above-specified kind, characterised in that the filter assembly includes an inlet arrangement adapted to make a sealing connection with the housing of the filter unit, and that the inlet arrangement has a tubular gas coupling in sealing communication with the inlet opening such that gas can be supplied to the patient through the filter unit via the gas coupling on the inlet arrangement.

The filter unit is preferably adapted to filter biological and chemical hazardous substances and may contain a carbon material. The inlet arrangement preferably has a collar of a flexible, resilient material arranged to make a sealing connection with the housing of the filter unit. The inlet arrangement may be made substantially entirely of a flexible, resilient material. The collar preferably has a sealing bead around its inner surface adapted to engage the filter unit housing on one side of a projecting lip on the filter unit housing. The collar may include at least one projecting finger portion by which the collar can be folded back.

According to another aspect of the present invention there is provided a resuscitator arrangement with a patient outlet and a filter assembly according to the above one aspect of the present invention.

The resuscitator arrangement preferably includes a patient valve connected with the outlet of the filter assembly, the patient valve being arranged to enable the patient to exhale to atmosphere. The arrangement may include an exhaust collector fitted over an exhaust outlet of the patient valve, the exhaust collector including a one-way valve arranged to prevent atmospheric gas entering the patient valve. The resuscitator may be a gas-powered resuscitator or a squeeze-bag resuscitator.

A gas-powered resuscitator arrangement and a filter assembly according to the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows schematically the resuscitator arrangement with the filter assembly connected with a face mask;

Figure 2 is a perspective view of the inlet end of the filter assembly;

Figure 3 is a partly-sectional side elevation view of the filter assembly;

Figure 4 is a partly cut-away perspective view of the underside of the inlet fitment;

Figure 5 is a cross-sectional side elevation view of an alternative filter assembly; and

Figure 6 is a cross-sectional view of the patient valve assembly.

With reference first to Figures 1 to 4, the resuscitator arrangement includes a conventional gas-powered resuscitator 1 with an inlet 2 connected via tubing 3 to a cylinder 4 of pressurized oxygen. The patient outlet 5 of the resuscitator is connected via a short length of tubing 6 to the inlet 7 of a filter assembly 8. The outlet 9 of the filter assembly 8 connects with one end of a length of flexible tubing 10, the other end of which connects to a modified patient valve assembly 11, which has its outlet 12 connected to a conventional face mask 13. Several resuscitators could be supplied from a common gas cylinder via a suitable gas manifold. It will be appreciated that other sources of pressurized breathing gas could be used, such as from a hospital's gas supply system. The outlet could be connected to other breathing devices, such as a tracheal tube.

The resuscitator 1 is a conventional, compressed oxygen-powered resuscitator such as of the kind sold by Smiths Medical International Limited under the "PneuPac VRl" trade mark. (PneuPac VRl is a registered trade mark of Smiths Medical International Limited). The resuscitator has various features one of which enables it to be switched between supplying pure oxygen or a mixture of oxygen and entrained atmospheric air. Another

feature of the resuscitator 1 is that, if the pressure of the oxygen supply should drop and the patient is breathing spontaneously, a valve within the resuscitator opens to allow the patient to breath atmospheric air substantially unhindered. It can be seen, therefore, that there are several situations where, conventionally, the patient might receive atmospheric air, with any contaminants this might include, instead of pure oxygen. The resuscitator need not be of this kind but could, for example, be a manual squeeze-bag resuscitator, which supplies only atmospheric air to a patient, or predominantly air with a bleed of pure oxygen.

With reference now particularly to Figures 2 to 4, the filter assembly 8 includes a conventional NBC filter canister or unit 17 such as an AMF 12 filter canister sold by Avon Rubber pic. This has a drum shape housing 18 with a circular section and has a threaded tubular projection forming the assembly outlet 9 extending axially in the centre of the outlet end face 20, which provides a gas coupling. The threaded coupling 9 is intended to fit with the gas inlet on a standard NATO respirator facepiece. On the opposite end face 21 a circular inlet hole 22 lies flush with the surface of the face, that is, no gas coupling is provided at the inlet end of the filter canister 17. A shallow lip 23 projects outwardly circumferentially around the filter housing 18 at the inlet end. The filter canister 17 contains activated carbon in the form of extruded pelletised charcoal impregnated with metallic salts and triethylenediamine for hazardous gas absorption. The filter also contains a HEPA particle filter in the form of a pleated fabric made of glass fibre/vinyon copolymer co-pleated with polypropylene netting. Such filters are effective to remove a range of nerve agents, blister agents, tear agents and chemicals such as chlorine, phosgene, chloropicin and diphenylchloroarsine .

The filter assembly 8 also includes an inlet arrangement or fitment 30 by which a gas connection is established to the inlet 22. The fitment 30 is preferably moulded entirely from a flexible, resilient rubber-like material having a circular plate 31 , which may have a shallow taper to conform to the profile of the inlet end face 21 of the filter canister 17, and which has strengthening ribs 32 on its inner surface. Centrally, a smooth, tubular gas coupling 33 projects outwardly of the plate 31 having a passage 33' therethrough, which opens to the inner side of the plate 31. The material of the coupling 33 enables it to be fitted resiliently over a male connector 14 inserted within it. A short collar 34 projects axially from the inner

side of the plate 31, which is formed with an inturned sealing bead 35 around its edge. The juncture between the collar 34 and the plate 31 is profiled to form a flexure joint 36, which enables the collar to be pulled back and everted, as shown by the broken lines in Figure 3. The collar 34 can be pulled back to this everted state to enable it to be fitted onto the inlet end of the filter canister 17, after which the collar is pushed forwardly so that it snaps back into its original position about the outside of the canister. The bead 35 on the collar is located so that it engages the canister just below the lip 23 on the housing 18. The thickness, resilience and dimensions of the inlet fitment 30 are selected so that it provides a secure, gas- tight seal around the outside of the filter housing 18 towards the inlet end. Preferably, the shape is such as to minimize deadspace between the inside of the fitment 30 and the outside of the filter canister 17. The fitment 30 also has one or more forwardly-projecting fingers 37 moulded as an extension of the collar 34. The purpose of this finger 37 is to facilitate folding back the collar 34, particularly when the inlet fitment 30 needs to be removed from a filter canister 17, since it might otherwise be difficult to grip the edge of the collar when it lies close against the surface of the filter housing. The inlet fitment 30 can be made at relatively low cost, it can be fitted and removed from a filter canister easily without tools and it can have a low weight and bulk for storage. It will be appreciated that the entire fitment need not be of a resilient material. Instead, the main part of the fitment could be rigid and only the collar need be resilient. In this case, the fitment could be a two-shot injection moulding of two different materials providing the rigid and resilient parts. Where the main part of the fitment is rigid, the coupling 33 would typically have a tapered passage to receive and seal with a male tapered coupling.

Alternative inlet fitments are possible, as shown in Figure 5. This fitment 40 has two separate rigid parts 41 and 42 held together by screws 43. One part 41 is a flat, circular end plate with an inlet gas coupling 44 and the other part 42 is a cylindrical component with a outwardly-projecting flange 45 at. one end, with an O-ring seal 46. The cylindrical component 42 has a ledge 47 on its inner surface about halfway along its length, against which the lip 23 on the filter housing sits. An O-ring seal 48 close to the forward end of the cylindrical component is arranged to make a seal around the outside of the filter housing 18. The filter canister 17 is inserted in the cylindrical component 42 from the flange end and the end plate 41 is then fitted on with the screws 43 to effect a seal with the O-ring 46.

The patient valve assembly 11 may be provided by an entirely conventional patient valve 50, such as of the kind sold by Laerdal or Galemed, including a flexible valve element 51, which is opened by inlet gas pressure from the resuscitator to allow gas to pass from its inlet 52 to the patient. When the patient exhales, the valve element 51 is displaced to open an exhaust outlet 53 in the housing of the patient valve 50 so that exhaled gas passes to atmosphere. Although the exhaust port 53 is covered by a flap valve 54, this is relatively inefficient and there is some risk of a small leakage into the valve through the exhaust outlet, which risks exposing the patient to an air-bome hazard. To avoid this risk it is recommended that an exhaust collector 55 be fitted over the patient valve assembly. This collector 55 seals with the valve housing around the exhaust outlet 53 and has a tubular port 56 by which exhaust gas flows to atmosphere. To prevent gas entering the exhaust outlet 53, a high- efficiency non-return valve 57 such as a spring-loaded valve or a PEEP valve is fitted into the port 56,

The arrangement of the present invention enables a conventional resuscitator to be used in hazardous environments by making use of readily available, standard filters. The filters can be stored in their usual packaging so that they retain their effectiveness. When needed, the filter is readily removed from the packaging and connected with the inlet fitment so that it can be connected in the breathing circuit. Any hazardous material supplied from the resuscitator is effectively removed by the filter before the gas reaches the patient.