This invention relates to speaking valve assemblies of the kind having a patient end adapted for fitting with the machine end of a tracheostomy tube, the assembly having a first valve located towards the machine end of the assembly, the first valve being normally closed but being opened by a reduced pressure at the patient end of the assembly during patient inhalation to allow gas to flow through the first valve to the patient end of the assembly.
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. Also, 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. Both these ends can be achieved by deflating or partially deflating the sealing cuff on 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. 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, U.S. Pat. No. 4,325,366, GB2164424, GB2214089, GB2313317, EP78685, EP214243, EP18461, DE2505123 and DE3503874.
A problem arises when a speaking valve is used with an unfenestrated tracheostomy tube if the sealing cuff is inadvertently not deflated since there is no path for exhaled air from the patient. This can lead to the patient suffocating. PCT/GB2015/000212 and PCT/GB2015/000224 suggest alternative arrangements by which this problem can be addressed.
It is an object of the present invention to provide an alternative speaking valve assembly and a tracheostomy tube including such a speaking valve assembly.
According to one aspect of the present invention there is provided a speaking valve assembly of the above-specified kind, characterised in that the assembly further includes a pressure relief arrangement located between the first valve and the patient end of the assembly, that the pressure relief arrangement is normally closed to prevent gas escaping through the arrangement but is arranged to open and allow gas to escape when pressure inside the assembly rises above a level experienced during normal exhalation and vocalisation.
The pressure relief device may include a ball valve. The ball valve may include a circular opening in the wall of the valve, a spherical ball arranged to engage and seal the opening and a cage attached with the valve and surrounding the opening and the ball such that the ball can be moved away from the opening by pressure within the valve and falls back onto the opening when pressure falls.
Alternatively, the pressure relief device may include a slidable pressure relief member that is movable by increased pressure within the valve assembly above a level experienced during normal exhalation and vocalisation from a first position in which it covers a vent to a second position in which it reveals the vent to allow gas to escape through the assembly and via the vent. The pressure relief member is preferably arranged to remain in the second position following increased pressure when the pressure falls below the increased pressure. The vent may be provided by a plurality of apertures spaced around a housing of the assembly, the pressure relief member being provided by a cylindrical collar slidable along the housing over the apertures. The apertures may be elongated and inclined at an angle to the axis of the housing. The first valve is preferably mounted with the cylindrical collar. The slidable collar may have an outer surface region that is concealed within the housing in the first position and is visible externally in the second position. The outer surface region is preferably prominently marked to be visible externally of the speaking valve assembly.
According to another aspect of the present invention there is provided a tracheostomy tube assembly including a tracheostomy tube and a speaking valve assembly according to the above one aspect of the present invention fitted on the machine end of the tube.
A tracheostomy tube including two different forms of speaking valve assembly all according to the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
With reference first to
The tracheostomy tube 1 includes a curved shaft 10 of a plastics material and having a circular cross-section. The tube extends from a patient end 11 to a neck flange 12 and a machine end coupling 13 of the conventional 15 mm male tapered kind. A sealing member in the form of an inflatable cuff 14 encircles the shaft 10 towards the patient end 11, the interior of the cuff communicating with an inflation line 15 including an inflation indicator in the form of a pilot balloon 16 and, at its machine end, a sealing valve 17. The tube 1 also has several openings or fenestrations 18 about midway along its length in a location where they are positioned, in use, in the trachea above the sealing cuff 14.
The speaking valve assembly 2 is of cylindrical shape with an outer housing 20. The housing 20 has a support beam 21 extending laterally across its machine end 22 and supporting the centre of a membrane flap valve 23 on the patient side of the beam. The flap valve 23 normally lies flat against an annular sealing seat 24 to prevent any substantial flow of air around the valve during expiration. When the patient inhales, pressure inside the housing 20 falls and causes the membrane 23 to lift at its outer edge away from the seat 24, as shown by the broken line in
The speaking valve assembly 2 differs from conventional speaking valves in that it includes a pressure relief device 30 between the flap valve 23 and the patient end 26 of the housing 20. The purpose of the pressure relief device 30 is to allow air to flow out of the speaking valve assembly 2 to atmosphere when pressure rises inside the housing 20 above a level experienced during normal exhalation. In the present example, the pressure relief device 30 takes the form of a ball valve that is normally closed but is opened by pressure above a certain level. The ball valve 30 consists of a circular opening 31 with a frusto-conical profile in the upper side of the wall of the housing 20. A solid, spherical ball 32 having a diameter slightly larger than that of the opening 31 is seated in the opening to seal it closed. A cage 33 is attached to the housing 20 around the opening 31 and the ball 32, being inclined away from the vertical towards the machine end 22 of the housing 20 at an angle of about 30°. The dimensions of the cage 33 are such as to allow the ball 32 to be displaced away from the opening 31 and to fall back into the opening.
During normal respiration, when the tube 1 is used without the speaking valve assembly 2, the fenestrations 18 are closed by an inner cannula (not shown) inserted into the tube from its machine end 3 to extend beyond and cover the fenestrations 18. In this way, air flows into the tube 1 from its machine end 3 and flows out of its patient end 11 during inhalation. During exhalation, air flows in the opposite direction from the patient end 11 and flows out of the machine end 3. When the patient wishes to speak, the inner cannula is removed and the speaking valve assembly 2 is plugged onto the machine end coupling 13 of the tube 1. The speaking valve assembly 2 allows the patient to inhale fairly freely via the flap valve 23. The speaking valve assembly 2, however, prevents normal exhalation via the assembly because the flap valve 23 is closed by elevated pressure in the housing 20 and the mass of the ball 32 is chosen such that the pressure in the housing is insufficient to lift the ball and open the opening 31. Instead, exhaled air flows out of the tube 1 via the fenestrations 18 upwardly along the trachea to the vocal folds so that the patient can speak.
There are, however, situations where a conventional speaking valve assembly could allow the patient to inhale but prevent the patient exhaling. For example, a speaking valve might be fitted to a tube that did not have any fenestrations. This can be done safely if the tube does not have any sealing cuff, since the patient could exhale around the outside of the tube. Alternatively, the valve could be fitted safely to a tube with a sealing cuff providing that the cuff was fully deflated before this was done. It will be appreciated, however, that conventional speaking valve assemblies present a possible hazard if used with unfenestrated tubes if the clinical staff do not ensure the sealing cuff is fully deflated. By contrast, the speaking valve assemblies according to the present invention avoid this problem by providing a safety by-pass path for exhalation gas, such as via the ball valve 30. The ball valve 30, is arranged (as shown in
A second, alternative form of speaking valve assembly 200 will now be described with reference to
The speaking valve assembly 200 also includes a separate sub-assembly 225 having a collar 226 with an outwardly projecting sealing lip 227 at its patient end. In the normal condition of the valve assembly 200 the collar 226 extends internally of the housing 220 with its sealing lip 227 engaging the inside of the housing on the patient side of the apertures 223 so that these are covered and closed. The vent apertures 223 and the collar 226 together provide a pressure relief arrangement. At its machine end, the sub-assembly 225 is enlarged to form a ring portion 228, the ring portion and collar 226 defining between them an external step 229. The step 229 abuts the end face of an inwardly-extending lip 230 at the machine end of the housing 220, which makes a sliding seal with the outer surface 227 of the collar 226. A cross spar 231 extends diametrically across the sub-assembly 225 level with the step 229. A valve cap 232 is fitted on the outside of the ring portion 228. The valve cap 232 has a central aperture 233 across which a lateral support beam 234 extends. The support beam 234 has a central, forwardly-projecting peg 235 that locates on the rear surface of the spar 231 and supports the centre of a membrane flap valve 236 on the patient side of the beam. The flap valve 236 normally lies flat against an annular sealing seat 237 on the inside of the cap 232 to prevent any substantial flow of air around the valve during expiration. When the patient inhales, pressure inside the assembly 200 falls and causes the membrane 236 to lift at its outer edge away from the seat 237 and thereby allow air to flow through the valve assembly 200 from its machine end 238 to its patient end 239, and from there, to the patient via the interior of the tube 1.
The sub-assembly 225 and vent openings 223 act together as a pressure relief device between the flap valve 236 and the patient end 239 of the housing 220. If expiratory pressure inside the speaking valve assembly 200 should rise above a level experienced during normal exhalation and vocalisation, the flap valve 236 would be forced closed and pressure would rise sufficiently to force the sub-assembly 225 to be moved outwardly relative to the housing 220 as shown in
It is not essential that the pressure relief device be provided by one of the two arrangements described above. Instead, alternative relief valves could be used, such as those including a valve element actuated by a spring rather than relying on the gravity force acting on the mass of a ball.
Number | Date | Country | Kind |
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1503693.2 | Mar 2015 | GB | national |
1505371.3 | Mar 2015 | GB | national |
Filing Document | Filing Date | Country | Kind |
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PCT/GB2016/000032 | 2/15/2016 | WO | 00 |