Surgery – Respiratory method or device – Respiratory gas supply means enters mouth or tracheotomy...
Patent
1992-04-29
1995-02-07
Burr, Edgar S.
Surgery
Respiratory method or device
Respiratory gas supply means enters mouth or tracheotomy...
12820023, 604282, A61M 1600
Patent
active
053868269
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to tracheal tube assemblies of the kind having an outer tube and an inner cannula that is insertable within and removable from the outer tube.
With such assemblies, the inner cannula is removed and replaced periodically when secretions have built up on the cannula to an extent that there is a risk of blockage. Tracheal tube assemblies are described, for example, in U.S. Pat. No. 3,948,274, GB 2056285B, GB 1099277, GB 125754, WO 90/04992, FR 2539998A, DE 72467, DE 1268313, EP 0107779A, U.S. Pat. Nos. 4,817,598, 3,659,612, 4,009,720, 3,088,466, 4,315,545, 2,765,792, 3,169,529, 3,263,684, 3,334,631, 3,587,589, 3,688,774, 3,731,692, 3,889,688, 3,948,273, 3,973,569, 3,987,798, 4,033,353, 4,045,058, 4,235,229, 4,471,776, 4,593,690.
In order to ensure as large as possible bore through the assembly, the wall of the inner cannula must be as thin as possible and the external diameter of the inner cannula must be as close as possible to the internal diameter of the outer tube. This, however, increases the risk of kinking of the cannula on insertion, especially where friction with the outer tube causes a greater axial force to be exerted on the cannula. A further problem arises because, if the cannula is made of a low-friction material, these tend not to enable respiratory secretions to cling to them readily, thereby increasing the risk that secretions will become dislodged and fall into the bronchi and lead to infection.
It is an object of the present invention to provide an improved inner cannula for a tracheal tube assembly.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a tracheal tube assembly of the above-specified kind, characterized in that the inner cannula has an inner surface to which respiratory secretions will cling, and an outer surface of a different material with a lower coefficient of friction than the inner surface.
The outer surface may be a continuous layer of a filament extending around the outside of the cannula. The filament may extend helically around the tube and may be of a metal. Alternatively, the outer surface may be provided by a low friction plastics material. The inner surface is preferably smooth and may be of a flexible plastics material such as PVC. The machine end of the inner cannula may project beyond the machine end of the outer tube and provide a flexible portion, the inner cannula having a coupling on its machine end.
BRIEF DESCRIPTION OF THE DRAWINGS
A tracheal tube assembly including an inner cannula, in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a partly sectional side elevation view of the assembly;
FIG. 2 is a cross-section to a larger scale of a part of the inner cannula; and
FIG. 3 is a cross-section of an alternative inner cannula.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference first to FIG. 1, the assembly comprises an outer tracheostomy tube 1 and an inner cannula 2.
The tracheostomy tube 1 is of conventional construction having a patient end 10 which, in use, is located in the patient's trachea and has an inflatable cuff 11 that seals the tube with the trachea. The machine end 12 of the tube 1 extends at approximately right angles to the patient end, there being an abrupt bend portion 13 between them. A flange 14 is located at the machine end 12 where it emerges from the tracheostomy at the surface of the patient's neck and to which it is secured by a tape (not shown).
With reference now also to FIG. 2, the inner cannula 2 comprises an inner flexible tube 20 of PVC which has a circular section and a smooth internal bore 15. Around the external surface of the tube 20 extends a filament in the form of a helical coil 21 of stainless steel wire. The coil 21 is secured to the external surface of the tube 20 and may be partly embedded in it, providing that the outer surface of the coil is exposed.
A filament of other low friction materials, such as a low-fric
REFERENCES:
patent: 2765792 (1956-10-01), Nichols
patent: 3039469 (1962-06-01), Fountain
patent: 3169529 (1965-02-01), Koenig
patent: 3225767 (1965-12-01), Smith
patent: 3498286 (1970-03-01), Polanyi
patent: 5078702 (1992-01-01), Pomeranz
patent: 5119811 (1992-06-01), Inglis
Inglis Timothy J. J.
Millar Michael R.
Burr Edgar S.
Raciti Eric P.
Smiths Industries Public Limited Company
University of Leeds Industrial Services Limited
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