Patent Publication Number: US-2018043119-A1

Title: Speaking valve assemblies and tracheostomy tube assemblies

Description:
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&#39;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: 
         FIG. 1  is a perspective view of the tracheostomy tube and a first form of speaking valve assembly; 
         FIG. 2  is an enlarged cross-sectional side elevation view of the machine end of the tracheostomy tube and the speaking valve assembly during normal inspiration; 
         FIG. 3  is an enlarged cross-sectional side elevation view of the machine end of the tracheostomy tube and the speaking valve assembly when normal expiration is prevented; 
         FIG. 4  is an enlarged perspective view of a second, alternative form of speaking valve assembly in its normal condition; 
         FIG. 5  is an enlarged cross-sectional side elevation view of the second form of speaking valve assembly in its normal condition; 
         FIG. 6  is an enlarged perspective view of the second form of speaking valve assembly in its venting condition; and 
         FIG. 7  is an enlarged cross-sectional view of the second form of speaking valve assembly in its venting condition. 
     
    
    
     With reference first to  FIGS. 1 and 2 , the assembly comprises a tracheostomy tube  1  and a speaking valve assembly  2  of the first form fitted on the machine end  3  of the tube. 
     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  FIG. 2 , and thereby allows air to flow through the valve assembly  2  from its machine end  22  to its patient end  26 , and from there, to the patient via the interior of the tube  1 . The patient end  26  of the housing  20  has a female tapered internal surface  27  shaped to make a sealing fit on the outside of the machine end coupling  13  of the tracheostomy tube  1 . 
     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  FIG. 3 ) to be lifted away from sealing engagement with the opening  31  when gas pressure in the housing  20  rises above a level experienced during normal exhalation and vocalisation by an appropriate choice of mass of the ball  32 . When the patient inhales again, the pressure inside the housing  20  falls, allowing the ball  32  to fall back by gravity and reseat in the opening  31 . This arrangement is advantageous because the alternating movement of the ball  32  in the cage  33  is highly conspicuous and visible to clinicians in the immediate vicinity, giving a clear alarm signal that something is wrong. The rattling noise of the ball  32  moving in the cage  33  enhances the warning. By a suitable selection of hard materials for the ball  32  and cage  33  the noise can be increased. 
     A second, alternative form of speaking valve assembly  200  will now be described with reference to  FIGS. 4 to 7 . The speaking valve assembly is of cylindrical shape having an outer housing  220  with a tapered inner surface  221  at its patient end shaped to form a secure fit on the machine end coupling  13  of the tube  1 . Towards its opposite, machine end  222  the housing  220  has a ring of several vent apertures or openings  223  extending around the housing. Any number of one or more vent apertures may be used but typically there would be about eight apertures equally spaced from one another around the housing  220 . The apertures  223  shown take the form of short, elongated slots with rounded ends inclined at an angle of about 60° to the axis of the housing  220 . Apertures of other shapes could be used. 
     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  FIGS. 6 and 7 . As soon as the lip  227  at the patient end of the collar  226  starts to move over the vent apertures  223  exhaled air starts to escape from inside the housing  220  to atmosphere. The inclined shape of apertures  223  causes them to be exposed only gradually by the lip  227 , leading to a less sudden drop in pressure within the housing. The pressure needed to open the vent openings  223  are closed by an appropriate choice of friction between the sub-assembly  225  and the housing  220 . The sub-assembly  225  remains in the extended, venting position because of the friction between the sub-assembly and the housing  220 . In this position the patient can both exhale and inhale freely through the vent openings  223 . The outer surface  228  of the collar  226 , which is normally concealed within the housing  220  in the retracted position, is marked in a conspicuous manner, such as by being coloured bright red. This arrangement ensures that clinical staff immediately become aware that the speaking valve  200  has been moved to its extended state and that the patient is having difficulties exhaling. When the patient inhales again, the pressure inside the housing  220  falls but the sub-assembly  225  remains extended so as to give a warning to clinical staff that there is a problem. 
     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.