GB2540657A

GB2540657A - Tracheal tubes, cuffs and their manufacture

Info

Publication number: GB2540657A
Application number: GB1608655.5A
Authority: GB
Inventors: Bateman Timothy; James Field Stephen; Andrew Graham Mark; Thomas Jeffrey Andrew
Original assignee: Smiths Medical International Ltd
Current assignee: Smiths Medical International Ltd
Priority date: 2015-05-23
Filing date: 2016-05-16
Publication date: 2017-01-25
Also published as: GB201509029D0; GB201608655D0

Abstract

A tracheal tube has an inflatable sealing cuff 21 with an attachment collar 11, 12 at each end. One collar 12 is moulded with reinforcing ribs 15. During manufacture of the cuff the ribs extend inwardly, but prior to assembly of the tracheal tube the cuff 21 is inverted. During assembly of the tracheal tube, the cuff is slid onto the shaft of the tube past inflating aperture 33. The other collar 11 and inflatable region 21 are then folded over the reinforced collar 12 (see arrows) and bonded in place, with the ribs 15 extending along and facing into the inflatable region. The reinforcing ribs 15 reinforce the wall of the shaft where it is exposed to pressure within the cuff 21, so that the tube shaft can be made thinner whilst still preventing it from being deformed inwardly by pressure from the cuff.

Description

TRACHEAL TUBES. CUFFS AND THEIR MANUFACTURE

This invention relates to tracheal tubes and cuffs, and to their manufacture.

Tracheal tubes are used to supply ventilation and anaesthetic gases to a patient, such as during surgery. The tracheal tube may be inserted via the mouth or nose, in the case of an endotracheal tube, or may be inserted via a surgically-made tracheostomy opening in the neck, in the case of a tracheostomy tube. Most, but not all, tracheal tubes have some form of a seal on their outside which forms a seal between the outside of the tube and the inside of the trachea so that gas flow is confined to the bore of the tube and cannot flow around the outside of the tube, between the tube and the trachea.

The most common form of seal is provided by an inflatable cuff that is inflated and deflated via a small bore lumen extending rearwardly along the tube and connected towards its rear end to an inflation line terminated by an inflation indicator, valve and connector. These inflatable cuffs may be of the high-volume/low-pressure kind where the cuff is formed of a flexible material moulded with a natural annular or doughnut shape that is inflated without stretching by relatively low-pressure gas supplied via the inflation line.

Alternatively, the cuff may be of the low-volume/high-pressure kind where the cuff is of an elastic material that lies close to the tube shaft when uninflated but is inflated and stretched to a larger diameter by relatively high pressure gas supplied via the inflation line.

One problem with cuffed tubes, especially of the higher pressure kind, is that the pressure within the cuff can be sufficient to deform slightly inwardly that part of the wall of the tube under the cuff. This effect is greatest in tubes having a thin or soft wall. This causes a problem because it can slightly restrict gas flow along the tube. It may also make it difficult to insert or remove devices into or from the bore of the tube. This can be a particular problem in tracheostomy tubes of the kind having an inner cannula since the constricting pressure from the cuff can increase friction between the inside of the tube and the outside of the inner cannula, making it more difficult to remove and replace the inner cannula. Ideally, the inner cannula is a close fit within the outer tube so as to minimise leakage between the outside of the cannula and the inside of the tube and so as to maximise die cross-section of the gas passage and minimise the restriction to flow. It has been proposed in GB1526286 to reinforce a cuffed tube by forming annular or helical reinforcing beads around the tube shaft.

It is an object of the present invention to provide an alternative tracheal tube and cuff, and an alternative method of manufacturing a cuff.

According to one aspect of the present invention there is provided a cuff for a tracheal tube, the cuff including an inflatable central region and two attachment portions at opposite ends by which the cuff is attached with a shaft of the tube, at least one of the attachment portions providing a reinforcement section adapted to extend within the inflatable region and reinforce that length of the shaft within the inflatable region under the attachment portion against inward deformation caused by elevated pressure inside the cuff.

The reinforcement section may have a plurality of reinforcement members extending along the attachment portion. The reinforcing members are preferably a plurality of longitudinally-extending ribs. The thickness of the cuff at the reinforcement members is preferably substantially twice the thickness of the cuff between adjacent reinforcement members. The reinforcement members are preferably ribs formed along a surface of the at least one attachment portion that face the interior of the inflatable region when the cuff is assembled on the shaft. The attachment portion with the reinforcing section is preferably towards the machine end of the cuff.

According to another aspect of the present invention there is provided a method of making a cuff according to the above one aspect of the present invention including the steps of providing a preform having a bore along its length, an attachment portion in the form of a collar at opposite ends at least one of which is formed along its inner surface with a plurality of reinforcing ribs and the preform including an intermediate portion between the collars having a thickness greater than the collars, placing the preform in a mould cavity, expanding the intermediate portion of the preform in the cavity to increase the diameter of the intermediate portion and reduce its wall thickness, subsequently removing the preform as a cuff from the mould cavity, and inverting the cuff so that the reinforcing ribs lie on the outside of the cuff.

According to a further aspect of the present invention there is provided a cuff made by a method according to the above other aspect of the present invention.

According to a fourth aspect of the present invention there is provided a tracheal tube including a shaft and a cuff according to the above one or further aspect of the present invention attached with the shaft.

The cuff may include one attachment portion having a reinforcing section, the attachment portion with the reinforcing section extending inside the inflatable region of the cuff, and the other attachment portion extending externally of the inflatable region. The tube shaft preferably has an inflation aperture opening on its external surface into the inflatable region of the cuff, the attachment portion with the reinforcing section being attached with the outside of the shaft within the inflatable region and being spaced just to one side of the inflation aperture. The tracheal tube may include an inner cannula extending along the inside of the shaft and removable therefrom.

According to a fifth aspect of the present invention there is provided a method of making a tracheal tube comprising the steps of providing a tube shaft, providing an inflatable sealing cuff having a collar at each end and an intermediate inflatable region between the collars, one of the collars having reinforcement members on its outer surface, sliding the cuff onto the shaft with the collar having the reinforcement members being towards the patient end of the shaft until the end of the collar is located adjacent an inflation aperture of the shaft, inverting the inflatable region and the other collar over the collar with the reinforcement members so that the inflatable region extends over the inflation aperture and the other collar is located on the opposite side of the aperture from the one collar, and bonding the two collars to the outside of the shaft so that the reinforcement members on the one collar face into the inflatable region.

According to a sixth aspect of the present invention there is provided a tracheal tube made by a method according to the above fifth aspect of the present invention. A tracheostomy tube, a cuff for the tube and their manufacture, 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 sectional side elevation view of the cuff at a preliminary stage of manufacture;

Figure 2 is a sectional side elevation view of the cuff at a later stage of manufacture;

Figure 3 is an end view of the cuff in Figure 2, along the arrow ΙΠ;

Figures 3 A and 3B show alternative arrangements for the cuff reinforcements;

Figure 4 is an enlarged side elevation view of the patient end of the tracheostomy tube with the cuff partly assembled on the tube; and

Figure 5 is a side elevation view of the completed tracheostomy tube.

With reference first to Figure 1 there is shown a preform or parison 1 from which the cuff is made. The preform 1 has an axial bore 10 along its length of a constant diameter although its diameter could vary along its length, such as being tapered. At opposite ends the preform 1 has attachment portions or collars 11 and 12 with an intermediate central portion 13 between the collars. As shown, the wall thickness of the intermediate portion 13 is thicker than that of the two collars 11 and 12 although the reinforcing collar could be thicker. The lower collar 11, which will be located at the patient end of the tube when assembled, has a smooth inner and external surface. The upper collar 12, which will be located at the machine end of the cuff, has a smooth external surface but its inner surface is formed with several longitudinally-extending reinforcing members or ribs 15 extending side-by-side along the length of the collar. The height of the ribs 15 is about equal to the thickness of the wall of the collar 12 so that the thickness of the collar in the region of the ribs 15 is about twice the thickness between the ribs. Typically, the collar 12 has about six ribs 15 and the width of the ribs is about equal to the width of the spacing between the ribs.

With reference now to Figure 2, the next step in the manufacture of the cuff is to place the preform 1 in a mould tool 20 and to blow mould the thicker central portion 13 outwardly to expand its diameter and reduce its wall thickness. The collars 11 and 12 may be left substantially unchanged by the blow moulding process.

Figure 3 is a plan view of the finished cuff 21 looking down on the upper, ribbed collar 12 and showing the arrangement of the ribs 15 around the inside of the collar.

Instead of having a continuous collar with ribs around its inside, the collar could have a castellated formation provided by a series of ribs 15’ and gaps 16’, as shown in Figure 3A. The collar could have ribs on the outer surface as well as, or instead of, the inside surface, as shown by the ribs 15” in Figure 3B.

The next step is to mount the cuff 21 onto the tracheostomy tube. There are several ways in which this can be done. Figure 4 shows a method that involves first turning the cuff 21 inside out so that the ribs 15 are facing outwardly. The cuff 21 is then slipped onto the patient end 30 of the shaft 31 of the tracheostomy tube 32 with the ribbed collar 12 lowermost, closer to the patient end of the shaft, and with the opposite collar 11 further from the patient end of the tube. The lower end of the ribbed collar 12 is positioned just above an inflation outlet opening 33 on the outside of the shaft 31, which opens into an inflation lumen 34 extending within and along the thickness of the wall of the shaft. It will be appreciated that the smooth (originally external) surface of the ribbed collar 12 is now in close contact with the outer surface of the shaft 31. The cuff 21 is positioned on the shaft 31 so that the ribbed collar 12 is at the desired final position along the shaft. An adhesive, solvent or other bonding agent may be placed between the ribbed collarl2 and the shaft 31.

The next step, as shown in Figures 4 and 5, is to fold the unribbed collar 11 down over the ribbed collar 12 so that the cuff 21 is turned inside out and the ribbed collar remains in position. The unribbed collar 11, which is now in the lower position close to the patient end 30 of the shaft 31, is secured with the outer surface of the shaft by any conventional means, such as using an adhesive, solvent or other bonding agent. It can be seen that the lower collar 11 is now attached to the tube shaft 31 below and outside the inflatable region 35 of the cuff 30. The upper, ribbed collar 12, by contrast, extends inside the inflatable region 35 of the cuff 30 with the reinforcing ribs 15 facing into the inflatable region. The length of the upper collar 12 is selected to be slightly shorter than that of the inflatable region 35 so that it extends along substantially the entire length of that part of the shaft 31 within the inflatable region whilst leaving the inflation opening 33 exposed to the interior of the inflatable region. The ribs 15 on the upper collar 12 form reinforcement members for that part of the shaft 31 under the collar and within the cuff 21 that will be exposed to pressure from the inflation air within the cuff. This is effective to reduce the amount by which the wall of the shaft 31 is deformed inwardly by the cuff pressure, enabling the wall of the shaft to be thinner than would otherwise be the case without the risk that the bore through the shaft would be constricted by the cuff pressure. This enables the tube 32 to be used with a close-fitting inner cannula 36 with a reduced risk of the cannula being difficult to remove and replace because of constriction of the shaft 31 of the tube caused by cuff pressure.

Instead of positioning the lower end of the ribbed collar just above the inflation aperture it would be possible to extend the ribbed collar over the inflation aperture and subsequently to form an opening through the collar into the inflation aperture.

The cuff need not be of the same shape as described with a central region of cylindrical shape but could have other conventional shapes, such as with a rounded or with a tapered profile. The present invention could be used on other tracheal tubes, not just on tracheostomy tubes. There are alternative methods by which the cuff could be assembled on the tube shaft. For example, the cuff need not be turned inside out before sliding onto the shaft but instead, just the reinforcing collar turned inside out. Instead of the reinforcement being provided by the rear, machine end collar it would be possible for the forward, patient end collar to be provided with reinforcing means and ne inverted within the inflatable part of the cuff. In another alternative arrangement, both cuffs could have reinforcement ribs or the like and be inverted within the cuff extending towards one another and spaced by a short gap sufficient to expose the opening into the inflation lumen.

Claims

1. A cuff (21) for a tracheal tube (32), the cuff including an inflatable central region (35) and two attachment portions (11,12) at opposite ends by which the cuff is attached with a shaft (31) of the tube (32), wherein at least one of the attachment portions (12) provides a reinforcement section (15) adapted to extend within the inflatable region (35) and reinforce that length of the shaft (31) within die inflatable region (15) under the attachment portion (12) against inward deformation caused by elevated pressure inside the cuff (21).

2. A cuff (21) according to Claim 1, wherein the reinforcement section has a plurality of reinforcement members (15) extending along the attachment portion (12).

3. A cuff (21) according to Claim 2, wherein the reinforcing members are a plurality of longitudinally-extending ribs (15).

4. A cuff (21) according to Claim 2 or 3, wherein the thickness of the cuff (21) at the reinforcement members (15) is substantially twice the thickness of the cuff between adjacent reinforcement members.

5. A cuff (21) according to any one of Claims 2 to 4, wherein the reinforcement members are ribs (15) formed along a surface of the at least one attachment portion (12) that face the interior of the inflatable region (35) when the cuff is assembled on the shaft (31).

6. A cuff (21) according to any one of the preceding claims, wherein the attachment portion (12) with the reinforcing section is towards the machine end of the cuff.

7. A cuff (21) substantially as hereinbefore described with reference to the accompanying drawings.

8. A method of making a cuff (21) according to any one of the preceding claims including the steps of providing a preform (1) having a bore (10) along its length, an attachment portion in the form of a collar (11 and 12) at opposite ends at least one of which is formed along its inner surface with a plurality of reinforcing ribs (15) and the preform (1) including an intermediate portion (13) between the collars having a thickness greater than the collars, placing the preform (1) in a mould cavity (20), expanding the intermediate portion (13) of the preform in the cavity to increase the diameter of the intermediate portion and reduce its wall thickness, subsequently removing the preform as a cuff (21) from the mould cavity (20), and inverting the cuff (21) so that the reinforcing ribs (15) lie on the outside of the cuff.

9. A method of making a cuff (21) substantially as hereinbefore described with reference to the accompanying drawings.

10. A cuff (21) made by a method according to Claim 8 or 9.

11. A tracheal tube (32) including a shaft (31) and a cuff (21) according to any one of Claims 1 to 7 or Claim 10 attached with the shaft (31).

12. A tracheal tube (32) according to Claim 11, wherein the cuff (21) includes one attachment portion (12) having a reinforcing section (15), wherein the attachment portion (12) with the reinforcing section extends inside the inflatable region (35) of the cuff (21), and wherein the other attachment portion (11) extends externally of the inflatable region (35).

13. A tracheal tube (32) according to Claim 11 or 12, wherein the tube shaft (31) has an inflation aperture (33) opening on its external surface into the inflatable region (35) of the cuff (21), and wherein the attachment portion (12) with the reinforcing section (15) is attached with the outside of the shaft (31) within the inflatable region (35) and is spaced just to one side of the inflation aperture (33).

14. A tracheal tube according to any one of Claims 11 to 13 including an inner cannula (36) extending along the inside of the shaft (31) and removable therefrom.

15. A tracheal tube (32) substantially as hereinbefore described with reference to the accompanying drawings.

16. A method of making a tracheal tube (32) comprising the steps of providing a tube shaft (31), providing an inflatable sealing cuff (21) having a collar (11,12) at each end and an intermediate inflatable region (35) between the collars, one of the collars (12) having reinforcement members (15) on its outer surface, sliding the cuff (21) onto the shaft (31) with the collar (12) having the reinforcement members (15) being towards the patient end of the shaft (31) until the end of the collar is located adjacent an inflation aperture (33) of the shaft, inverting the inflatable region (35) and the other collar (11) over the collar (12) with the reinforcement members (15) so that the inflatable region (35) extends over the inflation aperture (33) and the other collar (11) is located on the opposite side of the aperture (33) from the one collar (12), and bonding the two collars (11 and 12) to the outside of the shaft (31) so that the reinforcement members (15) on the one collar (12) face into the inflatable region (35).

17. A method of making a tracheal tube (32) substantially as hereinbefore described with reference to the accompanying drawings.

18. A tracheal tube (32) made by a method according to Claim 16 or 17.