Patent Publication Number: US-2023137005-A1

Title: Reinforced medico-surgical tubes and their manufacture

Description:
This invention relates to reinforced medico-surgical tubes of the kind having a shaft of a first, plastics material reinforced along at least a part of its length by a helical member of a second, stiffer material and embedded with the first material, 
     Tracheal tubes are used to enable ventilation, respiration, or spontaneous breathing of a patient. Endotracheal tubes are inserted via the mouth or nose so that one end locates in the trachea and the other end locates outside the patient. Tracheostomy tubes are inserted into the trachea via a surgically formed opening in the neck. Tracheostomy tubes can be inserted by different techniques, such as the surgical cut-down procedure carried out in an operating theatre or a cricothyroidotomy procedure, which may be carried out in emergency situations. 
     Tracheostomy tubes are generally used for more long-term ventilation or where it is not possible to insert an airway through the mouth or nose. The patient is often conscious while breathing through a tracheostomy tube, which may be open to atmosphere or connected by tubing to some form of ventilator. The tube is secured in position by means of a flange fixed with the machine end of the tube and positioned to extend outwardly on opposite sides of the tube. 
     Tracheostomy tubes can be made of various materials and are usually of a bendable plastics material such as PVC, polyurethane or silicone. Silicone tubes are particularly advantageous for long-term use because they can be highly flexible, making them less traumatic and damaging to tissue contacted by the tube. The silicone material is also highly compatible with patient tissue with a very low risk of granulation. Another advantage of silicone is that it is resistant to high temperatures, which enables it to be repeatedly autoclaved and reused. The soft nature of silicone tubes, however, means that they can be easily kinked and occluded by external pressure unless measures are taken to avoid this. Often, silicone tubes are reinforced by means of a stiff helical member extending along the tube, either along substantially their entire length or along only a part of the length. Typically, the reinforcement member is a metal wire although non-metallic helical reinforcement members, such as of stiff plastics can be used, although these do not have the same degree of kink and crush resistance as metal wires. 
     Examples of reinforced tracheal tubes are described in, for example, GB2552250, U.S. Pat. No. 5,906,036, WO2010/089523, EP1078645, WO2015075412, WO08083286, U.S. Pat. Nos. 6,148,818, 5,546,936, 5,429,127, EP0950424, EP2644221, U.S. Pat. Nos. 5,628,787, 4,737,153, US2012/0118294, U.S. Pat. Nos. 4,990,143, 5,181,509, US2007083132, U.S. Pat. Nos. 8,783,254, 6,130,406, 6,017,335 and DE867144. 
     One problem with helically-reinforced medico-surgical tubes arises where the tube needs to have a small-bore lumen or other elongate member extending along its length such as to inflate a sealing cuff or for gas sampling, irrigation or suctioning and the like. The presence of the helical reinforcement within the thickness of the wall means that it is not possible to incorporate such a small-bore lumen within the wall of the tube without increasing its thickness. Any increase in wall thickness makes the tube stiffer and, for a given outside diameter, reduces the internal diameter and thereby reduces flow along the bore of the tube. Accordingly, such helically reinforced tubes usually have any longitudinal small-bore lumen provided by a small diameter tube secured in a shallow channel along the outside of the tube. This, however, means that the otherwise smooth external surface of the tube is interrupted along its length by a projecting ridge. This is a particular disadvantage where the tube is used with delicate tissue, such as in paediatric tracheostomy tubes, since the ridge can cause damage to tissue. Similar problems exist in other reinforced medico-surgical tubes. 
     It is an object of the present invention to provide an alternative reinforced medico-surgical tube and a method of making such a tube. 
     According to one aspect of the present invention there is provided a reinforced medico-surgical tube of the above-specified kind, characterised in that the helical member has a longitudinal path along a part at least of its length extending transversely of the turns of the helical member, and that the tube includes an elongate member extended along a part at least of the length of the longitudinal path so that a part at least of the thickness of the elongate member is received in the longitudinal path. 
     The longitudinal path may be provided by an indentation in the helical member. Alternatively, the longitudinal path may be provided by notches in the helical member or by a gap in the helical member. The elongate member is preferably a small-bore tube extending longitudinally along a part at least of the length of the longitudinal path so that a part at least of the thickness of the small-bore tube is received in the longitudinal path. The tube preferably has an inflatable sealing cuff towards its patient end, the patient end of the small-bore tube opening into the sealing cuff. The helical member is preferably of a metal wire, such as of titanium. The plastics material may include silicone. The tube may be a tracheostomy tube. 
     According to another aspect of the present invention there is provided a method of making a reinforced medico-surgical tube including the steps of providing a helical reinforcing member of a relatively stiff material with a longitudinal path along a part at least of its length, extending an elongate member along the path, and overmoulding the reinforcing member and elongate member with a relatively flexible plastics material. 
     According to a further aspect of the present invention there is provided a method of making a reinforced medico-surgical tube including the steps of providing a helical reinforcing member of relatively stiff material, deforming the outside of the helical reinforcing member inwardly to form an elongate indented groove along a part at least of the length of the reinforcing member, extending an elongate member along the groove, and overmoulding the reinforcing member and elongate member with a relatively flexible plastics material. 
     The method may include the steps of providing an anvil extending through the helical reinforcing member, the anvil having a groove extending longitudinally on its outside along a part at least of its length, using a die to deform a part of the helical reinforcing member into the groove on the anvil so as to form the indented groove in the helical reinforcing member, and subsequently removing the anvil and die from the reinforcing member. 
     According to a fourth aspect of the present invention there is provided a reinforced medico-surgical tube made by a method according to the above other or further aspect of the present invention. 
     A reinforced tracheostomy tube and its method of manufacture 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; 
         FIG.  2    is a cross-sectional transverse view of the tube of  FIG.  1   ; 
         FIG.  2 A  is a cross-sectional transverse view of a modified tube: 
         FIG.  3    is a side view of the reinforcing wire at an initial stage of manufacture; 
         FIG.  4    illustrates a subsequent stage in the manufacturing process; 
         FIG.  5    is a perspective view of the reinforcing wire after forming a groove; 
         FIG.  6    is a perspective view of an alternative reinforcing wire; 
         FIG.  7    is a perspective view of a different configuration of reinforcement; and 
         FIG.  8    is an end view of an alternative tube. 
     
    
    
     With reference first to  FIGS.  1 ,  2  and  2 A  the tracheostomy tube  1  has a curved shaft  10  of circular section and with an outer diameter of around 12 mm. The shaft  10  has a moulded, tubular wall  110  of a relatively soft plastics material. The shaft  10  has a patient end  12  adapted to be located within the trachea of the patient and has a conventional inflatable sealing cuff  13  towards its patient end. The cuff  13  shown is of the high-pressure kind made of an elastic material that lies close to the shaft  10  when deflated and is stretched outwardly when inflated. The cuff  13  is attached to the outside of the shaft  10  by two collars  14  and  15  at opposite ends. The shaft  10  and cuff  13  are both moulded of a silicone material. It will be appreciated that the tube could be of a different sizes, shapes and materials according to the application and that the cuff could be of the low-pressure kind 
     The machine end  16  of the shaft  10  is adapted, during use, to extend externally through the tracheostomy opening formed in the patient&#39;s neck. The machine end  16  of the shaft  10  is bonded with a hub or connector  17  having a conventional 15 mm male tapered outer surface  18 . The connector  17  is adapted to make a removable push fit in a conventional 15 mm female connector (not shown) at one end of a breathing tube extending to a ventilator or anaesthetic machine. Alternatively, the machine end of the tube  1  could be left open to atmosphere when the patient is breathing spontaneously. The tracheostomy tube  1  also includes a radially extending support flange  20  adapted to lie against the skin surface of the neck on either side of the tracheostomy stoma. The flange  20  is moulded integrally as one part with the shaft  10  at its machine end  15 , although the flange and connector could be formed separately and be subsequently attached. The flange  20  has openings  21  at opposite ends for attachment to a neck strap (not shown) used to support the tube with the patient&#39;s neck. 
     The shaft  10  has a reinforcement member  30  that extends along and around the shaft and is embedded with the wall  110  of the shaft by overmoulding. More particularly, the reinforcing member  30  is a helically-wound metal wire such as of titanium or stainless steel. The reinforcing wire  30  is formed with a groove  31  extending longitudinally along one side of the curve of the shaft  10 , the groove being indented inwardly. A small-bore inflation line tube  32  extends along the groove  31  outside the helical reinforcement member  30  and opens at its patient end  33  beneath the trachea-sealing cuff  13  between the two collars  14  and  15 . The inflation line  32  and the reinforcement member  30  are both encased in the silicone material of the wall of the shaft. The groove  31  in the reinforcement member  30  receives the thickness of the inflation line  32  sufficiently to ensure that it does not form any projection, or only forms a shallow projection, on the outside of the shaft  10 .  FIG.  2 A  shows a modified tube  10 ′ where the silicone plastics of the tube wall extends over the inner surface of the reinforcement member  30 ′ as well as its external surface. 
     The machine end of the inflation line  32  extends through the flange  20  and continues unattached with the shaft  10  being terminated by a conventional combined inflation indicator and valve  36 . 
     In some cases it may be preferred for the reinforcement member  30  not to extend along the entire length of the shaft, such as when it is necessary to form a region that is softer, such as at the patient end  12 . In some cases, it may be necessary to form a region that is not malleable, so as to prevent the lumen being closed if the reinforced section of the tube is inadvertently compressed or pinched 
     The shaft  10  of the tube  1  is made using steps shown in  FIGS.  3  to  5   . First, as shown in  FIG.  3   , a metal wire  30 ″ is wound into a helical coil shape  30 . This coil  30  may be formed initially or it may be formed by winding directly onto an anvil or former  50  shown in  FIG.  4   . The wire  30 ″ is shown as having a circular section but it could have other shape cross sections. For example, a wire with a rectangular or oval section could enable the wall of the tube to be thinner if the wire is wound with its wider side aligned longitudinally of the length of the tube. The anvil  50  is of cylindrical shape and circular section having a diameter equal to the desired internal diameter of the helical coil  30 . The anvil  50  has a groove  51  extending along its length on its outer surface. A die  52  is positioned above the anvil  50  in alignment with the groove  51  and is mounted for reciprocating movement down into the groove and up out of the groove. With the coil  30  mounted around the anvil  50 , the action of moving the die  52  downwardly causes it to engage that part of the coil above the groove  51  and deform the coil down into the groove. The metal of the coil  30  is preferably malleable so that the coil is permanently deformed with the groove  31  along its length, as shown in  FIG.  5   . The coil  30  is then removed from the anvil  50  and placed on a suitable mould tool (not shown), the inflation line  32  being extended along the groove  31 . The silicone or other soft plastics material of the wall of the shaft  10  is then overmoulded about the coil  30 , flowing between its turns and covering the inflation line  32  to form a smooth outer surface of the shaft or both a smooth outer and inner surface. The flange  20  can also be integrally moulded with the shaft  10  at this stage. The sealing cuff  13  is then attached in the usual way, after forming the opening  33  to the patient end  33  of the inflation lumen  32 . The machine end of the inflation line  32  is joined with the combined inflation indicator, valve and connector  36 . 
     The arrangement of the present invention enables a tube of a relatively soft and flexible plastics material to be reinforced effectively against kinking and crushing without the inflation line or other elongate member protruding along the outer surface or protruding into the lumen of the tube. 
     The invention is not limited to cuffed tubes but could be used with tubes having, for example, a suction or irrigation lumen, or a lumen for gas-sampling or for supplying a therapeutic gas or liquid. Other elongate members could extend along the groove in the helical reinforcement instead of, or in addition to, a small-bore tube. The elongate member could, for example, be an electrical wire, such as for connection to an electrical sensor, or a fibre-optic cable, such as for viewing purposes or for supplying radiation to a body cavity. The invention is not limited to tracheal tubes but could be used in other medico-surgical tubes, such as urinary catheters or chest drainage tubes. 
     The helical reinforcement member need not be of a metal but could, for example, be of a stiff plastics material. With some materials it might be necessary to use a heated die to enable the coil to be deformed and to set in the groove shape. The reinforcement member need not extend along the entire length of the tube since in some tubes it might only be necessary to reinforce a part of the tube. In some tubes the small bore tube or other elongate member might only extend along a part of the length of the reinforced portion of the tube, in which case the groove in the outside of the coil need not extend along its entire length. 
     Instead of an indented notch in the reinforcement member, as shown in  FIGS.  1 ,  2 ,  4  and  5   , a longitudinal path could be provided along the reinforcement member in other ways. For example, a longitudinal path  130  could be provided by a cut-out notch  131 , as shown in  FIG.  6   . A path for receiving an elongate member could be provided in other ways, such as shown in  FIG.  7    where the turns of the reinforcement coil  230  are bent back on themselves in boustrophedon fashion to leave a path  231  extending longitudinally along the coil. The bent portions of the coil  230  would preferably have rounded corners and not the square corners shown in the Figure.  FIG.  8    shows how the wall thickness could vary around the circumference of the tube, being thickest in the region where the elongate member  332  extends and without any protrusion on the inner or outer surface.