GB2541082A

GB2541082A - Couplings and tracheal tubes

Info

Publication number: GB2541082A
Application number: GB1609664.6A
Authority: GB
Inventors: James Field Stephen
Original assignee: Smiths Medical International Ltd
Current assignee: Smiths Medical International Ltd
Priority date: 2015-07-07
Filing date: 2016-06-02
Publication date: 2017-02-08
Also published as: GB201511882D0; GB201609664D0

Abstract

A coupling is taught for connecting the machine end 4 of a tracheostomy tube 1 to a gas coupling. The coupling arrangement requiring that the machine end 4 of the tracheostomy tube 1 have a magnet 18, 19, that is arranged to attract and retain a cooperating magnet 28, 29 on the gas coupling. The coupling arrangement also comprises a mechanical advantage to separate the coupling from the tube and overcome the magnetic attraction. This could include an arrangement for rotating the coupling relative to the tube - preferably through the provision of a bayonet type coupling (Fig 2), complementary threads (76, Fig 6) etc. - or through the provision of wedge devices (55, 56, Fig 5) that can be squeezed together between the magnets on the tube and coupling to separate them.

Description

COUPLINGS AND TRACHEAL TUBES

This invention relates to couplings and tracheal tubes.

Tracheal tubes are used to enable ventilation or respiration of a patient Endotracheal tubes are inserted into the trachea via the mouth or nose. Tracheostomy tubes are inserted into the trachea via a surgically-formed opening in the neck so that one end locates in the trachea and the other end locates outside the patient adjacent the neck surface. Various types of different tracheostomy tubes are presently available to suit different needs. Tracheostomy tubes are also available with an inner cannula so that the inner cannula can be removed and replaced periodically to prevent the build-up of secretions and avoid the need to replace the tube itself. Tracheostomy tubes can also be inserted by different techniques, such as the surgical cut down procedure carried out in an operating theatre or a percutaneous dilatation procedure, which may 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 may have a 15mm tapered male coupling at its machine end for use in connection to a ventilator. Alternatively, the tube may have a low profile opening at its machine end so that it can be worn inconspicuously by a spontaneously breathing patient. It is an advantage to be able to connect a ventilator or other apparatus such as a filter, HME, speaking valve or the like, to such tubes when the patient needs therapy or assistance in breathing. Conventional couplings used to connect to such low profile tubes may result in forces being applied to the tube itself during connection and disconnection, causing forces to be exerted on the tissue of the tracheostomy or within the trachea. This can result in trauma and stenosis. It is important that couplings are not inadvertently disconnected during use because this may go undetected and prevent correct ventilation of the patient. This is particularly important where the patient is out of a clinical environment, such as at home, since there may be no supervision of the ventilation.

There are also other applications outside the medical field where couplings are used that would benefit from easier coupling and uncoupling.

It is an object of the present invention to provide an alternative coupling and tracheal tube including a coupling.

According to one aspect of the present invention there is provided a coupling including two parts arranged to be held together at least in part by a magnetic interaction, the coupling including means for applying a mechanical advantage to move the two parts relative to one another in order to reduce the magnetic interaction to facilitate uncoupling.

The means for applying a mechanical advantage may include a ramp on one part and a lug member on the other part that is slidable along the ramp. Alternatively, the means for applying a mechanical advantage may include a wedge member that is displaceable between surfaces of the two parts to force them apart. The wedge member s preferably supported on a resilient support that can be flexed to allow the wedge member to be moved between surfaces of the two parts. The means for applying a mechanical advantage may include two wedge members positioned on opposite sides of the two parts so that the two wedge members can be moved between the surfaces by squeezing them together. Alternatively, the means for applying a mechanical advantage may include cooperating screw threads on the two parts such that the two parts are displaced axially by twisting them relative to one another.

According to another aspect of the present invention there is provided a coupling including two parts that can be coupled with one another, each part including a magnet and a cooperating mechanical formation arranged such that the mechanical formations on the two parts are aligned with one another in a first position prior to locking engagement in which position the magnets on the two parts are out of alignment with one another, the two parts being rotatable relative to one another into a second position where the two magnets are aligned with one another and apply an attractive force between the two parts and where the mechanical formations are in locking engagement with one another.

According to a further aspect of the present invention there is provided a tracheal tube assembly including a tracheal tube and a separate gas coupling adapted for removable connection with the tracheal tube, the tracheal tube having a patient end adapted for location within the trachea and a machine end adapted to locate outside the body and including a machine end coupling by which gas connection can be made to the tube by the separate gas coupling, the machine end coupling and the separate gas coupling both including at least one magnet arranged to help retain the couplings together when opposite poles of the magnets interact with one another.

The magnets on the machine end coupling and the gas coupling may be arranged to be brought together or separated by relative rotational displacement of the two couplings.

According to yet another aspect of the present invention there is provided a tracheal tube for an assembly according to the above further aspect of the present invention.

According to a fifth aspect of the present invention there is provided a gas coupling for an assembly according to the above further aspect of the present invention. A tracheostomy tube assembly including a coupling, both 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 perspective view of a tracheostomy tube;

Figure 2 illustrates the gas coupling used with the tracheostomy tube;

Figure 3 illustrates operation of connecting the coupling with the tracheostomy tube;

Figure 4 is an end view of an alternative tracheostomy tube;

Figure 5 is a cross-sectional side elevation view of the alternative tracheostomy tube showing a gas coupling fitted in place;

Figure 6 is a side elevation view of a third form of tracheostomy; and

Figures 7A, 7B and 7C show schematically a modified form of the arrangement shown in Figure 6.

With reference first to Figure 1, there is shown a tracheostomy tube with a curved shaft 1 of circular section with a patient end 2 adapted to be located within the trachea of the patient. The shaft 1 has a conventional sealing cuff 3 towards its patient end. The shaft 1 is moulded or extruded and is bendable but relatively stiff, being made of a plastics material such as PVC or silicone. Alternatively, the tube could be rigid and could be made of a nonplastics material, such as a metal. The machine end 4 of the shaft 1 is adapted, during use to be located adjacent the tracheostomy opening formed in the patient’s neck. The machine end 4 of the shaft 1 supports a radially-extending support flange 5 that lies against the skin surface on either side of the tracheostomy opening. The flange 5 has openings 6 at opposite ends for attachment to a neck strap (not shown) used to support the tube with the patient’s neck.

Centrally, the flange 5 supports a magnetic coupling arrangement 7 around an opening 8 into the shaft 1. With reference also to Figure 3, the coupling arrangement 7 includes a generally circular plastics bayonet ring 9 projecting a short distance above the surface of the flange 5 and cut away to form two diametrically arranged keyways 10 and 11 at opposite sides. The bayonet ring 9 is undercut around a part of its inner circumference to form a first overhanging flange 12 that extends clockwise from the keyway 10 around the ring by about 90° and a second overhanging flange 13 extending clockwise around the ring from the other keyway 11 by about 90°. At the closed ends of the two flanges 12 and 13, that is, the ends away from the keyways 10 and 11, the lower surface of the coupling arrangement 7 is formed with a shallow recess 14 and 15 respectively each having an inclined ramp 16 and 17 on the side towards the respective keyway 10 or 11. Two small permanent rod magnets 18 and 19 are mounted in respective ones of the keyways 10 and 11, being bonded into recesses in the flange 5 so that their ends are level with the surface of the flange. The magnets need not be permanently fixed in the flange but could be removable, such as by being mounted on a removable frame clipped onto the flange, so that they can be removed when not wanted, such as during an MRI procedure. The axis of polarisation of the magnets 18 and 19 is orthogonal to the plane of the flange 5 and the magnets are oppositely arranged so that the magnet 18 in the keyway 10 presents its north pole outwardly and the magnet 19 in the keyway 11 presents its south pole outwardly. It will be appreciated that the orientations of the magnets could be reversed so long as their relative orientation is attractive.

Figure 2 shows a gas coupling 20 used to make connection with the coupling arrangement 7 on the tracheostomy tube 1. It comprises a male tapered connector portion 21 with a machine end 22 shown as being open but could be connected to a breathing circuit via a cooperating female tapered connector. At its patient end 23 the gas coupling 20 has a magnetic locking ring 24 formed by an outwardly projecting collar 25 with two radially-projecting lugs or ears 26 and 27 arranged diametrically opposite one another. The width of the lugs 26 and 27 is slightly narrower than that of the keyways 10 and 11 on the tube coupling 7 and their thickness is just less than the height of the undercut beneath the flanges 12 and 13 on the bayonet ring 9. The gas coupling 20 also supports two permanent rod magnets 28 and 29 arranged to interact with the two magnets 18 and 19 on the coupling arrangement 7 on the flange 5. The magnets 28 and 29 are bonded into the collar 25 at locations midway between the two lugs 26 and 27 and diametrically opposite one another. The magnets 28 and 29 are aligned with their axes of polarisation parallel with the axis of the coupling 20 and with their polarity oriented in opposite senses so that the magnet 28 shown at the lower side of Figure 2 presents its south pole towards the patient side of the coupling and so that the other magnet 29 shown at the upper side of Figure 2 presents its north pole towards the patient side of the coupling. Alternatively, both magnets on the flange and both magnets on the coupling could be oriented with the same polarity but orienting them with opposite polarities, as described above, means that the coupling can only be attached with the flange when in one angular orientation - this may be an advantage or disadvantage depending on the nature of the coupling.

The magnets 18,19, 28 and 29 could be made entirely of a permanent magnet material or they could include one or more permanent magnets bonded on or moulded within a plastics body. The magnet material could be hard or flexible. Examples of permanent magnet materials include: nickel/iron/cobalt alloys, alnico, ceramic/ferrites, samarium cobalt, neodymium-iron-boron and others.

To interconnect the gas coupling 20 with the flange coupling 7 the gas coupling is oriented to a first position where its lugs 26 and 27 align with the keyways 10 and 11 on the flange coupling. The gas coupling 20 is then pushed towards the flange coupling 7 so that the lugs 26 and 27 enter the keyways 10 and 11. It can be seen that, in this first position, the magnets 28 and 29 on the gas coupling 20 are spaced from the magnets 18 and 19 on the flange coupling 7 so that there is little or no interaction between their fields. The gas coupling 20 is then twisted relative to the flange coupling 7 in a clockwise sense so that the lugs 26 and 27 slide along the tracks beneath the overhanging flanges 12 and 13. When the gas coupling 20 has been twisted through 90° to a second position the lugs 26 and 27 slide down the ramps 16 and 17 into the respective recesses 14 and 15. As the coupling 20 is twisted its magnets 28 and 29 move closer to the magnets 18 and 19 on the flange coupling 7. The orientation of the polarities of these magnets is such that they attract one another as they move closer together, thereby applying bodi an angular force tending to twist the gas coupling 20 in a clockwise sense and an axial force tending to pull the gas coupling forwardly into closer contact with the flange coupling 7. The magnetic interaction between the two pairs of magnets 18 and 19, and 28 and 29, therefore, acts to draw the lugs 26 and 27 down and into the recesses 14 and 15. Once the lugs 26 and 27 have moved fully into the recesses 14 and 15 the gas coupling 20 is in close contact with the flange coupling 7 and the magnets 28 and 29, and 18 and 19 are closest together, thereby exerting the maximum interactive force tending to hold the two coupling parts together. In this position, the two parts are locked together and retained by a combination of the magnets and the engagement of the lugs under the flanges 12 and 13. The coupling operation is also illustrated schematically in Figure 3.

To disconnect the gas coupling 20 from the flange coupling 7, the gas coupling is twisted anticlockwise relative to the flange coupling so that the lugs 26 and 27 ride up the ramps 16 and 17. This provides a mechanical advantage for the axial displacement, causing the gas coupling and its magnets 28 and 29 to be displaced axially slightly away from the flange coupling and its magnets 18 and 19. This axial and angular displacement moves the magnets apart, thereby weakening their interaction and making it progressively easier to rotate the gas coupling relative to the flange coupling. When the lugs 26 and 27 are back in alignment with the keyways 10 and 11 the magnetic interaction is minimal or non-existent allowing the gas coupling 20 to be pulled away from the flange coupling 7.

It can be seen that the coupling arrangement of the present invention is somewhat similar to a conventional bayonet coupling. However, whereas a conventional bayonet ( coupling relies on a combination of friction and resilience to hold the two parts of the coupling against separating rotational displacement the arrangement of the present invention instead relies on magnetic interaction. This enables a coupling of the present invention to be

I provided with a much freer, lower friction fit so that less force needs to be exerted between the two parts of the coupling at the initial stage of coupling and the final stage of uncoupling. i

This is particularly important when making connection to medical devices since it can be important to avoid exerting unnecessary forces where the device is in contact with the patient.

Another form of magnetic coupling for a tracheostomy tube is illustrated in Figures 4 and S where the flange 50 supports an annular, ring magnet 51 that is magnetically polarised along its axis so that its forward, upper surface 52 has a north polarity and its lower surface 53 has a south polarity. Instead of a ring magnet it would be possible to use a circular row of separate magnets. The flange 50 also supports a release mechanism 54 provided by two sprung wedge devices 55 and 56 on diametrically opposite sides of the ring magnet 51. Each wedge device 55 and 56 includes a resilient support 57 and 58 fixed with the flange 50 and projecting upwardly, the supports being capable of being resiliently flexed in a vertical plane that includes both supports. The wedge devices 55 and 56 also include a horizontallyextending wedge 59 and 60 supported at the upper end of respective supports 57 and 58 and projecting parallel with the surface of the flange 50 level with the upper surface of the magnet 51. The wedges 59 and 60 taper in thickness, being thicker at their respective supports 57 and 58 and with their thinner ends projecting from the supports and aligned diametrically with one another just outside the edge of the ring magnet 51. Operation of the release mechanism 54 will be described later.

The magnetic coupling also includes a gas coupling 65 having a male tapered connector portion 66 with an open machine end 67. At its patient end 68 the gas coupling 65 has a magnetic locking ring formed by an annular ring magnet 69 of the same shape and size as the ring magnet 51 mounted on the flange 50 and similarly polarised along its axis with its upper surface 70 having a north polarity and its lower surface 71 having a south polarity.

The mating ring magnets need not be of the same size and shape so long as they cooperate to hold the two parts together. The ring magnet 69 on the lower surface of the gas coupling 65 makes a secure magnetic bond with the ring magnet 51 on the upper surface of the flange 50 to hold the two parts of the coupling together.

Modem permanent magnets can produce a very strong field sufficient securely to hold together the two parts of the coupling. The bond can be so strong that it can be difficult to separate unaided or the high force necessary to separate may cause the tube to move and cause discomfort or trauma to the patient. The release mechanism 54 described above facilitates uncoupling without disturbing the tube. To release the coupling the two supports 57 and 58 are squeezed together in a direction parallel to the plane of the flange 50. This pushes the two wedges 55 and 56 inwards towards one another and between the two ring magnets 51 and 69. The tapered shape of the wedges 55 and 56 achieves a mechanical advantage in applying a force to separate the two magnets 51 and 69 in a direction parallel with the axis of the two ring magnets. As they move apart, the magnetic interaction between the two magnets 51 and 59 drops allowing the gas coupling 65 to be lifted away from the flange coupling 51 without difficulty.

Instead of ring magnets, the arrangement described above could include a number of short rod magnets polarised along axes parallel to the axis of the coupling.

Figure 6 shows another alternative magnetic coupling arrangement with a flange 70 supporting a coupling provided by a ring magnet 71 polarised along its axis so that its upper surface has a north polarity and its lower surface has a south polarity. The gas coupling 72 has a male tapered connector portion 73 with an open, upper machine end 74. The lower end patient end of the connector portion supports a ring magnet 75 that is also polarised along its axis so that its upper surface has a north polarity and its lower surface has a south polarity. A sleeve 76 with a half turn thread extends between the gas coupling 72 and the flange coupling 71 and may either extend from the gas coupling or from the flange coupling. The threaded sleeve 76 engages a cooperating thread on the other component so that the gas coupling 72 is screwed fully down into mating engagement with the flange coupling 71 by twisting the gas coupling through 180° relative to the flange coupling. It will be appreciated that the interaction between the two magnets 71 and 75 will apply a force tending to urge the two parts together and to hold them together once fully engaged. The screw threaded sleeve 76 provides a mechanical advantage that enables the magnetic holding force to be overcome readily when it is necessary to uncouple the two components without the need to apply an excessive manual pulling force that could disturb the tube.

Figures 7A, 7B and 7C illustrate schematically a modification of the arrangement of Figure 6 where the ring magnets 71 and 75 of Figure 6 are each divided into two halves so that the facing surfaces of the magnets 7Γ and 75’ have one half of one polarity and the other half of the opposite polarity. Figure 7A shows the arrangement where the gas coupling 75’ is fully engaged with the flange coupling 71 ’ and is in its lowest position. In this state the north half of the lower magnet 71 ’ is aligned with the south half of the upper magnet 75’ and the south half of the lower magnet is aligned with the north half of the upper magnet. In this state the magnets 71’ and 75’ exert the maximum force to hold the two parts of the coupling together. If one part is now rotated clockwise relative to the other through 90°, as shown in Figure 7B, it moves to a neutral position where each pole of the two magnets overlaps both poles of the other magnet and there is no overall force applied between the two parts of the coupling. It can be seen that further rotation clockwise to the position shown in Figure 7C progressively brings a greater proportion of the same poles into alignment so that a force gradually increases tending to separate the two magnets 71’ and 75’ and hence the two parts of the coupling.

It will be appreciated that such magnetic couplings might not be suitable for use in an MRI environment. Another issue with the magnetic couplings is that care would have to be taken if the tracheostomy tube were fitted with a speaking valve having a valve element of a magnetic material since the presence of the magnetic coupling might affect operation of the valve.

Although the invention has particular application with tracheostomy tubes in order to enable forces applied to the patient during coupling and uncoupling to be reduced, it could also be used on other tracheal, medico-surgical or non medico-surgical couplings.

Claims

1. A coupling including two parts arranged to be held together at least in part by a magnetic interaction, wherein the coupling includes means for applying a mechanical advantage to move the two parts relative to one another in order to reduce the magnetic interaction to facilitate uncoupling.

2. A coupling according to Claim 1, wherein the means for applying a mechanical advantage includes a ramp on one part and a lug member on the other part that is slidable along the ramp.

3. A coupling according to Claim 1, wherein the means for applying a mechanical advantage may include a wedge member that is displaceable between surfaces of the two parts to force them apart.

4. A coupling according to Claim 3, wherein the wedge member is supported on a resilient support that can be flexed to allow the wedge member to be moved between surfaces of the two parts.

5. A coupling according to Claim 3 or 4, wherein the means for applying a mechanical advantage includes two wedge members positioned on opposite sides of the two parts so that the two wedge members can be moved between the surfaces by squeezing them together.

6. A coupling according to Claim 1, wherein the means for applying a mechanical advantage includes cooperating screw threads on the two parts such that the two parts are displaced axially by twisting them relative to one another.

7. A coupling including two parts that can be coupled with one another, wherein each part includes a magnet and a cooperating mechanical formation arranged such that the mechanical formations on the two parts are aligned with one another in a first position prior to locking engagement in which position the magnets on the two parts are out of alignment with one another, and wherein the two parts are rotatable relative to one another into a second position where the two magnets are aligned with one another and apply an attractive force between the two parts and where the mechanical formations are in locking engagement with one another.

8. A tracheal tube assembly including a tracheal tube and a separate gas coupling adapted for removable connection with the tracheal tube, the tracheal tube having a patient end adapted for location within the trachea and a machine end adapted to locate outside the body and including a machine end coupling by which gas connection can be made to the tube by the separate gas coupling, wherein the machine end coupling and the separate gas coupling both include at least one magnet arranged to help retain the couplings together when opposite poles of the magnets interact with one another.

9. A tracheal tube assembly according to Claim 8, wherein the magnets on the machine end coupling and the gas coupling are arranged to be brought together or separated by relative rotational displacement of the two couplings.

10. An assembly substantially as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.

11. An assembly substantially as hereinbefore described with reference to Figures 1 to 3 as modified by Figures 4 and 5 of the accompanying drawings

12. An assembly substantially as hereinbefore described with reference to Figures 1 to 3 as modified by Figure 6 of the accompanying drawings.

13. An assembly substantially as hereinbefore described with reference to Figures 1 to 3 as modified by Figure 6 and as further modified by Figures 7A to 7C of the accompanying drawings.

14. A tracheal tube for an assembly according to any one of Claims 8 to 13.

15. A gas coupling for an assembly according to any one of Claims 8 to 13.

16. Any novel and inventive feature or combination of features as hereinbefore described with reference to the accompanying drawings.