This invention relates to assemblies of the kind of a fenestrated tracheostomy tube and a speaking valve fitted on the machine end of the tracheostomy tube.

Tracheostomy tubes are used to ventilate patients during and after surgery. As the patient begins to recover, it is preferable for him to be gradually weaned off breathing through the tube before it is completely removed. In order to enable the patient to speak it is necessary to allow at least a part of the air exhaled by the patient to flow up past the tracheostomy tube to the vocal folds instead of out through the machine end of the tube. This can be done by partially deflating the cuff of the tube. Alternatively, a fenestrated

tracheostomy tube can be used having one or more small openings in its side wall, so that a part of the patient's breathing passes through these openings and via his nose or mouth, instead of through the machine end of the tracheostomy tube. The fenestration openings can be closed by means of an inner cannula, which is removed when it is desired to allow gas to flow through the openings. The inner cannula could be replaced by an inner cannula with openings that align with the openings in the outer tube. Examples of fenestrated tubes are described in GB1522632, US4852565, US5771888, US6722367, US5957978 and

US7987851. When the patient needs to speak it is common practice to fit a speaking valve to the machine end of the tube. The speaking valve includes a one-way valve that enables air to be inhaled by the patient through the valve but prevents or limits flow out through the valve so that air instead flows to the larynx via the fenestrations or around the outside of a tube with a deflated cuff. Examples of speaking valves are described in, for example, US4325366, GB2164424, GB2214089, GB2313317, EP78685, EP214243, EP18461, DE2505123 and DE3503874.

A problem arises with the use of speaking valves in that, if a speaking valve is attached in error to an unfenestrated tracheostomy tube, and if the sealing cuff is not deflated, it prevents the patient exhaling. This can lead to the patient being suffocated. It is an object of the present invention to provide an alternative speaking valve, tracheostomy tube and assembly.

According to one aspect of the present invention there is provided an assembly of the above-specified kind, characterised in that the speaking valve and machine end of the tracheostomy tube have cooperating connecting surfaces providing keying formations of non- circular section such that the speaking valve cannot be fitted to tracheostomy tubes with a machine end having a connection surface of circular section.

The keying formations of the tube and speaking valve preferably have a part-circular section interrupted by at least one flat section. The keying formations of the tube and speaking valve preferably have a part-circular section interrupted by two flat sections on opposite sides of the circular section. The tracheostomy tube may include an outer fenestrated tube and an inner fenestrated cannula extending within the outer tube. The inner cannula may have a machine end portion with cooperating keying formations of non-circular section adapted to receive the speaking valve. The speaking valve may have an internal formation adapted to extend within the interior of the machine end of the fenestrated inner cannula. The outer surface of the internal formation is preferably a close fit within the machine end of the fenestrated inner cannula.

According to another aspect of the present invention there is provided a tracheostomy tube for an assembly according to the above one aspect of the present invention.

According to a further aspect of the present invention there is provided a speaking valve for an assembly according to the above one aspect of the present invention.

An assembly of a tracheostomy tube and speaking valve according to the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a side elevation view of the assembly with the speaking valve

separated from the tube; Figure 2 is a perspective view of the assembly with the speaking valve

separated from the tube and with the outer tube removed to show the inner cannula; and

Figure 3 is an enlarged sectional side elevation view of the speaking valve and the machine end of the tracheostomy tube.

The assembly comprises a tracheostomy tube 1 and a speaking valve 3, shown separated in the drawings but, in use, fitted on to the machine end of the tube.

The tracheostomy tube includes a curved shaft 10 of a plastics material and having a circular cross-section. The patient end region 12 of the tube is straight and communicates with a curved intermediate region 13, which extends to a neck flange 14 and a machine end coupling 15. A sealing member in the form of an inflatable cuff 16 (shown deflated) encircles the patient end region 12, the interior of the cuff communicating with an inflation line 17 extending along a groove 18 formed along one side of the shaft 1. The inflation line 17 extends through the neck flange 14 and is terminated at its machine end by a connector and inflation indicator 19. The tracheostomy tube could be of other materials and of other shapes.

The tube shaft 10 includes a fenestrated region 20 formed substantially midway along the curved region 13 at a location where it lies centrally of the trachea airway "T" during use. The fenestrated region 20 has eight fenestrations, openings or holes 21 through the wall of the shaft 10 arranged in two rows of four holes each extending longitudinally side-by-side on opposite sides of the centre line of the shaft. Spacing the holes 21 away from the centre line of the shaft in this way reduces the risk that a suction catheter, endoscope or the like inserted in the tube will snag on the holes. It also reduces the risk that a small diameter catheter or instrument inserted in the tube could inadvertently pass through a fenestration hole and possibly cause trauma to the patient. Typically, the holes 21 are about 3mm in diameter although the size and number of holes will vary according to the size of the tube. The total area of the holes 21 is preferably about 10% greater than the cross-sectional area of the interior of the shaft 10. The holes 21 are located on the external or convex, outer side of the curved region 13 so that, in use, they face upwards along the trachea T, that is, towards the larynx. Alternative arrangements of one or more fenestrations could be used.

The machine end coupling 15 differs from conventional couplings in that its outer surface 50 is of cylindrical shape with a circular section that is interrupted by two flat keying surfaces 51 extending longitudinally on opposite sides of the coupling from its machine end along about two thirds the length of the coupling. This gives the external surface of the machine end of the coupling 15 an overall non-circular configuration.

The tracheostomy tube includes an optional inner cannula 40 (Figures 2 and 3) having a curved shaft 41 that is a close sliding fit within the shaft 10 of the tube. The shaft 41 of the inner cannula 40 has fenestrations 42 formed in its wall and positioned to align with the fenestrations 21 in the shaft 10. At its machine end 43 the inner cannula 40 is formed with an enlarged hub 44 that is a close sliding fit within the machine end coupling 15 of the outer rube l.

There are two features on the fenestrated inner cannula 40 that enable the speaking valve to be fitted with it and prevent the speaking valve being fitted with conventional inner cannulae. These features can be used together for maximum safety or may be alternatives. One feature is provided by making the wall of the hub 44 thinner than in conventional inner cannulae so that the internal diameter of the hub is greater than in convention inner cannulae. The second feature is provided by an integral radial flange 45 at the machine end of the hub 44 that is arranged to abut the end face of the outer tube coupling 15 and has an outer surface the same diameter and shape as the outer surface of the coupling, with two opposite flat regions 46 that align with the flat surfaces 51 on the coupling. The machine end of the hub 44 also has a ring-pull formation 47 that locates outside the machine end coupling 15 on the outer tube 1 so as to enable the inner cannula 40 to be pulled out of the outer tube when necessary by folding down and gripping the ring-pull formation. The external diameter of the ring-pull formation 47 is the same as that of the flange 45 and the coupling 15 and it also has two flats 48 located to align with the flats 46 on the flange and the flats 51 on the coupling 5. The speaking valve 3 includes an outer housing 30 of cylindrical shape and circular section. The rear, machine end 31 of the housing 30 supports a circular, flexible valve element 32 extending laterally of the housing on the inner face of six radially-extending support struts 33. The valve element 32 is fixed centrally to the struts 33 so that its outer edge can be deflected inwardly by a reduced gas pressure within the housing (during inhalation) to allow air to flow through the valve. An elevated pressure within the speaking valve 3 (during exhalation) forces the valve element 32 into closer contact with the struts 33, preventing any significant flow of air out of the valve, so that it is diverted through the fenestrations 21. The opposite, coupling end 34 of the housing 30 has a female tapered internal surface 35 of generally circular section apart from two flat surfaces 36 that are positioned and shaped to match with the flat surfaces 51 on the outside of the tracheostomy tube coupling 15. The speaking valve 3 also has an internal formation in the form of a ring 38 extending axially within the housing 30 and spaced from its internal wall. The ring 38 extends level with the coupling end 34 of the housing 30 and its external diameter is selected to be a close sliding fit within the interior of the hub 44 of the fenestrated inner cannula 40. The ring 38 has openings 39 towards its rear end so that air can flow to and from the centre of the ring into the surrounding volume of the housing 30.

The two flat surfaces 36 on the inside of the speaking valve 3 enable it to be fitted onto the machine end coupling 15 of the tracheostomy tube 1 since the flat surfaces on the valve locate with the flat surfaces 51 on the outside of the machine end coupling. Where a fenestrated inner cannula is also used, the speaking valve 3 fits over the flange 45 with its flats 46 and over the ring-pull formation 47 with its flats 48. It can be seen that the speaking valve 3 cannot be fitted to conventional tracheostomy tubes without the keying flats, thereby avoiding the risk that the speaking valve be fitted to tubes without fenestrations. The tracheostomy tube 1 could be used with an unfenestrated inner cannula since this may be necessary, such as if the patient needs to be ventilated and the fenestrations in the outer tube need to be covered and closed. However, when such an unfenestrated inner cannula is in place, the speaking valve 3 cannot be fitted because the machine end of the hub on such an inner cannula would lack the flat surfaces necessary to allow the speaking valve to be fitted. When the speaking valve 3 is fitted onto the machine end coupling 15 with the inner cannula 40 in place air can flow into the tracheostomy tube 1 when the patient inhales via the speaking valve and through the centre of the ring 38 and its openings 39. The internal diameter of the fenestrated inner cannula hub 44 is selected to be larger than in conventional unfenestrated inner cannulae so that the ring 38 on the speaking valve 3 prevents this being inserted in conventional inner cannulae hubs. This ensures that, when the speaking valve 3 is used in conjunction with an inner cannula it can only be fitted in a fenestrated inner cannula having the larger inner diameter to its hub.

The flat surfaces 51 on the outside of the tracheostomy tube coupling 15 do not extend along the entire length of the coupling so that there is a portion at the patient end of the coupling that has a completely circular section. This enables a conventional connector with a circular female coupling to be fitted onto the tracheostomy tube coupling in a sealing fashion. However, the speaking valves of the present invention with the non-circular section can only be fitted on specially shaped fenestrated tracheostomy tube couplings.