GB2056285A - Tracheal tube assembly - Google Patents

Abstract

A tracheal tube assembly comprises an outer tube 1 for insertion within the trachea 3 of a patient, and an inner tube 2 that extends within the outer tube. The inner tube 2 is circumferentially corrugated so as to be flexible about its length and is formed with at least one groove 28, 29, or elongate reinforcing member traversing the corrugations 27. The inner tube 2 may have two grooves 28, 29 located on opposite sides of the tube and extending parallel to its length. The grooves 28, 29 may be separated from one another along the length of the inner tube 2. Alternatively, the inner tube 2 may have a groove extending helically about it, or several grooves parallel to the length of the inner tube separated from one another along its length in a helical fashion. <IMAGE>

Description

SPECIFICATION Tracheal tube assemblies This invention relates to tracheal tube assemblies.

The invention is more especially concerned with tracheal tube assemblies comprising an outer tube adapted for insertion within the trachea of a patient and an inner tube which extends within the outer tube and which can be removed from the assembly to facilitate cleaning of the gas passage through the assembly.

Tracheal tube and tracheal tube assemblies are commonly used during and following surgery to enable ventilation of the patient's lungs and administration of anaesthetic gases. These tubes and assemblies take two forms: the endotracheal tube, which extends out of the patient's trachea through his mouth, and the tracheostomy tube, which extends out of the trachea through an opening made by surgery in the patient's neck.

The end of the tube located within the trachea is generally sealed with the inner surface of the trachea by means of an inflatable cuff which encircles that end of the tube. In use, gases are administered to the patient by making suitable connection to the end of the tube which protrudes from the trachea.

In prolonged use these tubes suffer from the disadvantage that the gas passage through them can become blocked by bodily secretions which dry out and solidify within the gas passage through the tube. To avoid this the tracheal tube must periodically be removed and cleaned or replaced. This removal and replacement requires the presence of a skilled medical practitioner and can cause some discomfort to the patient. To overcome this disadvantage it has been proposed to use a flexible inner tube which is normally located within the outer tube and which can be readily removed and replaced without disturbing the outer tube which remains in position in the patient's trachea. The inner tubes proposed for such tracheal tube assemblies have been formed variously of a metal wire helix, a smooth-walled tube of rubber or synthetic material, or a corrugated plastics tube.Of these, the corrugated plastics tube has been found to be most suitable since it can be made with a thinner wall, and thereby only slightly reduces the diameter of the gas passage through the assembly, whilst still having sufficient rigidity.

Although such corrugated tubes are satisfactory to a certain extent, they suffer from the disadvantage that the walls must still be relatively thick in order to give them sufficient axial reigidity. Without sufficient axial rigidity, when the corrugated tube is pushed into the outer tube it will tend to buckle axially like a concertina or bellows thereby preventing the corrugated tube being pushed fully to the end of the outer tube.

The relatively thick walls necessary with such corrugated tubes have the disadvantages of further restricting gas flow through the tracheal tube assembly and also of making the corrugated tubes less flexible about their length. This reduction in flexibility is an especial disadvantage in tracheostomy tubes where the outer tube may be bent at an angle of between 900 and 1200 along its length since, when a relatively inflexible inner tube is inserted within such an outer tube the inner tube has a tendency to buckle at the curved section of the outer tube, flattening the normally circular cross-section of the inner tube to an oval shape and thereby reducing fluid flow through it.

Its an object of the present invention to provide a tracheal tube assembly which alleviates the above-mentioned disadvantages.

According to the present invention there is provided a tracheal tube assembly comprising an outer tubular member adapted for insertion within the trachea of a patient, and an inner tubular member arranged to extend within the outer member, wherein the inner member has at least a portion of its length formed with circumferential corrugations so as thereby to enable flexing of the portion about the length of the inner member, and wherein the inner member includes an elongate reinforcement member that is disposed to traverse some at least of said corrugations such as thereby to increase the axial rigidity of the inner member.

The reinforcement member may be arranged to extend parallel to the length of the inner member.

There may be a plurality of reinforcement members and they may be disposed on opposite sides of the inner member. The reinforcement members may be separated from one another along the length of the inner member. The reinforcement members may include a groove.

A tracheostomy tube assembly and a method of manufacture, in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional elevation showing the tube assembly; Figure 2a is a perspective view to an enlarged scale showing a part of the inner tube of Figure 1; Figure 2b is an end view along the arrow II of the part of the inner tube of Figure 2a; Figures 3a and b to 5a and b are respectively perspectively and end views of a part of three alternative forms of inner tube; and Figures 6a and 6b illustrate steps in the manufacture of a part of the inner tube of Figures 2a and b.

With reference to Figure 1 there is shown a tracheostomy tube assembly comprising an outer tube 1 and an inner tube 2 that extends axially within the outer tube.

The outer tube 1 is of PVC and includes a tubular section 10 that is bent midway along its ~ length at an angle of about 1100. One end 1 1 of the tubular section 10, which will be called the "patient end" is arranged for location within the patient's trachea 3 and carries a cuff 12 which can be inflated to provide a seal with the trachea by means of an inflation line 13 and a lumen (not shown) extending through the wall of the tubular section. The other end 14 of the tubular section 10, which will be called the "machine end" carries a connector portion 15 which serves to make connection of the assembly with a ventilator machine (not shown). The connector portion 1 5 comprises a generally cylindrical body portion 16 having an axial opening 17 which is normally closed by cap 18.The body portion 16 also has a side-entry port 19 which is coupled to the ventilator machine by means of flexible tubing 20.

The inner tube 2 is in the form of a thin-walled flexible sleeve 21 (which will be described in greater detail later) that is terminated at its machine end 22 with a hollow cylindrical coupling member 23. The coupling member 23 embraces and is sealed to the flexible sleeve 21. The coupling member has two flanges 24 separated by an annular recess 25 around its outer surface that is engaged by a co-operating inwardly-directed annular projection 26 formed around the machine end of the tubular section 10. The recess 25 and projection 26 are arranged to be a snap-fit with one another. With the coupling member 23 in engagement with the tubular section 10, the flexible sleeve 21 extends along the entire length of the tubular section 10 in contact with its inner surface, terminating flush with the patient end 11 of the tubular section.

The inner tube 2 is inserted within the outer tube 1 through the axial opening 17 in the connector portion 15. The coupling member 23, at the machine end of the inner tube 2, may be grasped by an insertion tool (not shown) to facilitate insertion and removal of the inner tube through the opening 17. The insertion tool might take several different forms; it could, for example, be arranged to grip the outer surface of the coupling member 23 (which might additionally be provided with a suitable projection or indentation to improve the grip), alternatively, the tool could be arranged to be inserted within the coupling member and grip its inner surface.

The flexible sleeve 21 of the inner tube 2 may take several different forms. Essentially, the sleeve 21 is circumferentially corrugated along at least that part of the sleeve which is located within the bent portion of the outer tube 1, and is reinforced along at least a part of its length to resist axial compression of the sleeve by means of one or more reinforcement members that traverse some of the corrugations.

Four different forms of sleeve will be described below with reference to Figures 2a to 5b. In each of these the corrugations are described as being disposed along substantially the entire length of the sleeve and in each the corrugations are described as being of helical form. It will be appreciated, however, that it is only necessary for the corrugations to be disposed along that part of the sleeve which is to be curved along its length and that the corrugations could take the form of parallel annular rings rather than a helix.

Figures 2a and 2b show in greater detail the sleeve 21 of the inner tube 2 illustrated in Figure 1. The sleeve 21 is about 90mm long and about 8mm in diameter having a wall thickness of between 0.1 mm and 0.25mm. The sleeve 21 is corrugated from a point about 5mm from the coupling member along the remainder of its length by means of a single helical groove 27 between 0.5mm and 1 .Omm deep, although it will be appreciated that two or more helices could be used. The pitch of the helix is about 2mm, being sufficiently short such that separation between the adjacent turns of the groove 27 is substantially equal to the width of the groove. The sleeve 21 is made of a high density polythene or polypropylene and is conveniently manufactured by an extrusion blow-moulding process such as is described below.The sleeve 21 also has a forward and a rearward axial groove 28 and 29 respectively which are formed as indentations in its inner surface and which are of substantially the same depth and width as the helical groove 27. The grooves 28 and 29 are located diametrically opposite one anpther, the forward groove 28 extending 3.5cm rearwardly from the forward end of the sleeve 21, and the rearward groove 29 traversing the rear 2cm of corrugations. The wall thickness of the sleeve 21 is such that, without the axial grooves 28 and 29, the circumferential corrugations would enable the sleeve to be compressed axially in the manner of a concertina and it would therefore be difficult, when inserting the inner tube 2 within the outer tube 1, to ensure that the patient end of the inner tube terminated flush with the patient end 11 of the outer tube.

The grooves 28 and 29 serve as reinforcement members to reduce such axial compression.

The grooves 28 and 29 do not extend over the central portion along the length of the inner tube 2 which is bent when the inner tube is in position within the outer tube 1. For this reason, the inner tube 2 can take up any orientation within the outer tube 1, without the grooves 28 and 29 providing any resistance to bending of the central portion.

It will be appreciated that the grooves 28 and 29 could extend the entire length of the sleeve 21 in which case the sleeve would be more flexible in a a plane which contains the axis of the sleeve and which is at right angles to the plane containing the reinforcing grooves 28 and 29, since flexing in this plane would not bring about any change in the length of the reinforcing grooves. For this reason, if such an inner tube 2 was inserted within the outer tube 1 it would have a tendency to take up an angular position in which the two reinforcing grooves 28 and 29 lie in a plane at right angles to the plane of curvature of the outer tube.

An alternative sleeve 31 is shown in Figures 3a and 3b, this sleeve being similar to the sleeve 21 shown in Figure 2a and 2b in that it also has a helical groove 32 giving the sleeve a corrugated surface, and two axial reinforcement members 33 and 34. The reinforcement members 33 and 34, however, differ from those of Figure 2a and 2b in that they each comprise several parallel grooves 35 that extend axially the entire len length of the sleeve 31. The reinforcement members 33 and 34, in this way, themselves have corrugated surfaces which act in a bellows-like fashion to enable the sleeve 31 to be radially compressed to a certain extent along the line 36, that is, in a direction at right angles to a diameter joining the two reinforcement members 33 and 34.The compressibility of the axially corrugated reinforcement members 33 and 34 enables the same sleeve 31 to be fitted within outer tubes having a range of different internal diameters whilst still retaining close contact between the outer surface of the sleeve and the inner surface of the outer tube.

It is not essential that the reinforcement member of members extend axially of the corrugated sleeve. In another embodiment shown in Figures 4a and 4b a sleeve 41 has a short-pitch helical groove 42 extending around it providing a corrugated surface, in the same manner as with the sleeves 21 and 31 of Figures 2 and 3, and also has two relatively long-pitch helical reinforcement grooves 43 and 44. The long-pitch grooves 43 and 44 make between one and two turns along the sleeve 41 in opposite senses, traversing the short-pitch groove 42 and thereby increasing the axial rigidity to the sleeve, A further different form of sleeve 51 is shown in Figures 5a and 5b, this sleeve again being provided with a short-pitch helical groove 52 giving the sleeve a corrugated surface.Axial rigidity of the sleeve 51 is increased by means of a number of relatively short, straight, indented reinforcement grooves 53 which extend parallel to the axis of the sleeve and which are disposed about its surface. Each of the reinforcement grooves 53 traverses three or four turns of the helical groove 52, each reinforcement groove being spaced a short distance about the circumference of the sleeve 51 from an adjacent groove and also being displaced axially relative to the adjacent groove. The axial reinforcement grooves 53 are arranged to overlap one another such that one end of one axial groove traverses the same turn of the helical groove 52 as the other end of an adjacent axial groove. In this way, the grooves 53 are disposed in a helical fashion around the sleeve 51.The sleeves 41 and 51 have the advantage as compared with sleeves 21 and 31 in that they are equally flexible in all directions about their entire length.

The reinforcement members of the sleeves described above are each formed by grooves indented in the inner surface of the sleeve. It will be appreciated that the grooves could instead be formed by indentations on the outer surface of the sleeve. Alternatively, the reinforcement members could be provided by elements of increased thickness, or by elements of a material differing from that of the remainder of the sleeve; such alternative arrangements, however,-might be more difficult to make by a blow-moulding process.

The extrusion blow-moulding process by which the above-described sleeves are made will now be described in more detail with reference to Figures 6a and 6b. A parison 61, in the form of a smoothsurfaced sleeve of plastics material, is extruded downwards from a vertically mounted extruding machine 62. When the required length has been extruded, two halves 63 and 64 of a mould 65 are clamped about the parison 61 which is still in a hot, molten state. The mould 65, when closed has a cylindrical cavity 66 the diameter of which is greater than the outer diameter of the parison 61, the surface of the cavity being formed with a configuration of grooves 67 corresponding with that to be formed on the sleeve. In operation, clamping of the mould 65 about the parison 61 causes it to be pinched closed at its lower end 68, thereby sealing the parison.The other end 69 of the parison 61 is cut close to the upper surface of the mould 65 and the nozzle 70 of an air line 71 is inserted in the manner shown in Figure 6b. High pressure air, from a source 72, is blown into the parison 61 thereby forcing the wall of the parison outward into contact with the wall of cavity 66.

Air trapped between the parison 61 and the cavity 66 escapes through the joint between the two halves 63 and 64 of the mould 65. As soon as the molten material of the parison 61 contacts the wall of the cavity 66 it quenches and becomes hard, taking up the shape and configuration of the cavity. The mould 65 is then opened and the corrugated sleeve is removed after which it may be trimmed of any surplus material and joined to the coupling member 23 to complete the inner tube 2.

It will be appreciated that various other methods could be used to form the corrugated sleeve and the complete inner tube.

Claims (14)

1. A tracheal tube assembly comprising an outer tubular member adapted for insertion within the trachea of a patient, and an inner tubular member arranged to extend within the outer member, wherein the inner member has at least a portion of its length formed with circumferential corrugations so as thereby to enable flexing of the portion about the length of the inner member, and wherein the inner member includes an elongate reinforcement member that is disposed to traverse some at least of said corrugations such as thereby to increase the axial rigidity of the inner member.

2. A tracheal tube asse,mbly according to Claim 1, wherein the reinforcement member is arranged to extend parallel to the length of the inner member.

3. A tracheal tube assembly according to Claim 1 or 2, wherein the inner member has a plurality of reinforcement members disposed to traverse some at least of said corrugations.

4. A tracheal tube assembly according to Claim 3, wherein the inner member has two reinforcement members disposed on opposite sides of the inner member.

5. A tracheal tube assembly according to Claim 4, wherein the inner member has two reinforcement members extending axially on the opposite sides of the inner member, and wherein each reinforcement member includes a plurality of parallel grooves arranged to increase the compressibility of the inner member in a direction at right angles to a line joining said reinforcement members and at right angles to the axis of the inner member.

6. A tracheal tube assembly according to Claim 3 or 4, wherein the inner member has two reinforcement members separated from one another along the length of the inner member.

7. A tracheal tube assembly according to Claim 1, wherein the reinforcement member is arranged to extend helically around the inner member.

8. A tracheal tube assembly according to Claim 1, wherein the inner member has a plurality of reinforcement members that are arranged to extend parallel to the length of the inner member and that are spaced apart around its circumference and along its length such as to overlap one another along its length.

9. A tracheal tube assembly according to any one of the preceding claims, wherein the or each reinforcement member includes a groove.

10. A tracheal tube assembly according to Claim 9, wherein the depth of the or each groove is substantially equal to the depth of the corrugations.

11. A tracheal tube assembly according to Claim 9 or 10, wherein the or each groove is formed as an indentation in the inner surface of said inner member.

12. A tracheal tube assembly according to any one of the preceding claims, wherein a part at least of the inner member is formed by blow moulding.

13. A tracheal tube assembly substantially as hereinbefore described with reference to Figure 1 and any one of Figures 2 to 5b of the accompanying drawings.

14. An inner member for a tracheal tube assembly according to any one of the preceding claims.