SPECIFICATIONEndo-oesophageal tubeThe invention relates to devices for effecting intubation of strictures of the oesophagus and cardia.
In prior UK patent specification 1518654 there is described a device of this kind which is designed to be introduced endoscopically and pushed into position after the stricture has been dilated.
The device disclosed in SpecificationNo.1518654 includes a formation on the distal end thereof arranged to collapse towards the tubular main part of the device on insertion through a stricture, but to oppose reverse motion through the stricture by regaining its original shape once through the stricture. The particular formation disclosed takes the form of a conical "flap", which is liable to invert if violent reflux occurs, and hence the tube is able to move back up the oesophagus, leaving the stricture without its tubular protection.
This invention provides an endo-oesophageal tube comprising a tubular main part having a formation at each end thereof for preventing movement of the device through a stricture in the oesophagus in use, the formation at the distal end (i.e. the end which in use lies below the stricture) being in the form of an external formation broadening out away from the said distal end of the tube. This invention seeks to overcome the possible reverse motion of the tube in the oesophagus by providing at the distal end of the tubular main part a non-collapsible external formation, which cannot invert even if violent reflux occurs. The external formation broadens out away from the distal end of the tubular main part and does not collapse toward the tubular main part during insertion.The strictures for which such tubes are employed have been found to be resilient enough to enable passage of a solid external formation.
The formation may be substantially frusto-conical (i.e. of substantially circular crosssection) but it is preferred that two opposed sides of the formation should be somewhat flattened towards the tubular main part, whereby the formation has a somewhat oval or elliptical cross section. This shape leads to the minimum possibility of damage to the oesophagus during insertion of the tube. In a preferred embodiment, the distal tip of the tube is somewhat tapered in order to minimise trauma to the patient's oesophagus during insertion of the tube.
The formation at the upper or proximal end of the device is preferably a funnel-like formation to assist in directing food through the tube and avoid the likelihood of food being lodged above the tube.
In the preferred embodiment, it has the shape of the frustum of a cone, with a short length of circular, parallel-sided tube around the lip of the funnel.
The device disclosed in Specification No.
1518654 includes a barrel-shaped funnel having a re-entrant inner lip and a proximal opening smaller than the maximum inner diameter of the device, thus providing a shelf on which food particles can collect at the upper end of the device. The simple frusto-conical funnel described above minimises the risk of such collection.
For strictures high in the oesophagus, near the crico-pharynx, an alternative design of proximal formation may be necessary because of considerations of available space. In this case, the formation at the upper end of the device is preferably in the form of a disc or short solid frustum of a cone extending radially of the tube.
In a number of patients, the tube will be positioned such that its distal end is in the stomach, with the remainder of the tube in the oesophagus. In such cases, the cardia is by-passed by the tube, with the result that patient discomfort may result through reflux of gastric contents into the oesophagus. In order to minimise this discomfort, the tube may incorporate a valve, preferably at one or other, or both of its ends. The valve is designed such that food material will pass normally down the tube into the stomach, but gastic contents will be unable to pass back through the valve under normal conditions.
However, the valve is such that under extreme conditions, for example if the patient vomits, gastric contents are able to pass back up through the oesophagus thus ensuring that the tube remains in its correct position within the oesophagus.
Such a valve is preferably made of a thin membrane of silicone rubber which is able to invert under severe reflux. Such a membrane may be adhered to a moulded silicone rubber tube with a silicone adhesive, although other materials and methods could be employed.
The tube of the present invention may be constructed of any material sufficiently resilient to withstand the flexing necessary to introduce the device into the oesophagus, for example rubber latex, or polyethylene. Silicone rubber is particularly preferred because of its resistance to attack by gastric juices and low tendency to irritate human tissue.
A helical reinforcing element, preferably a nylon monofilament thread, may be incorporated within the wall of the tube to enhance its resistance to crushing, without adversely affecting its flexibility.
The tube may be formed by various methods.
For example, when the material used is rubber latex, the preferred method is by dip-forming. in this method, a simple latex tube is first formed, without the distal formation, and is preferably reinforced by having a helical reinforcing element as described above wound on its outer surface.
The desired outer contour and distal anti-reflux formation may then be produced by repeated dipping in rubber latex.
When silicone rubber is used, the preferred methods are injection or compression moulding. If it is desired to incorporate a helical reinforcing element, a two-stage moulding process may be used.
The tube is preferably manufactured of radio opaque material for example of one of the resilient materials mentioned above loaded with a radioopaque filler such as a barium compound, thus, in effect, making the whole tube visible during X-ray examination. This is preferable to the provision of only a single strip of radio-opaque material running the length of the tube. Such strips can render X-ray viewing of the tube difficult when a radio-opaque endo-oesophageal tube introducer is used to insert the tube, as the radio-opaque strip can be masked by the introducer, making the tube invisible on the X-ray screen.Several specific embodiments of the invention will now be described with reference to the accompanying drawings, in which:~Figure 1 is a side elevation partially in section of a tube according to the invention,Figure 2 is a plan view of the device of Figure 1,Figure 3 is a view similar to that of Figure 1 of an alternative embodiment of a tube according to the invention,Figure 4 is a plan view of the device of Figure 3,Figure 5 is a side elevation of a further embodiment of a tube according to the invention, with a disc-shaped formation at its proximal end,Figure 6 is a plan view of the device of Figure 5,Figure 7 is an enlarged side elevation showing a valve which may be incorporated into any of the tubes shown in Figures 1, 2, 3, 4, 5 and 6 above, andFigure 8 is a plan view of the valve shown inFigure 7, and Figure 9 shows an alternative valve arrangement which can be incorporated in the tube of Figures 1 and 2 or 3 and 4.
In the drawings, like references are used for like parts.
The tube illustrated in Figure 1 comprises a tubular main part 1 of circular cross-section having at its upper (or proximal) end a frustoconical funnel 2 which is integral with the tubular main part 1. The funnel 2 is provided with a short length of circular parallel-sided tube 3 at its proximal lip, integral with the funnel 2 and of the same diameter as the maximum diameter of the funnel 2. At the lower (or distal) end of the tubular main part 1 there is provided an external formation 4, which is solid and an integral part of the tubular main part 1. The external formation 4 is of frusto-conical shape, as shown in Figure 2.
The lower (distal) end 5 of the external formation 4 tapers slightly. This tapering serves the purpose of a lead-in for the tube, so that minimum trauma is caused to the patient during insertion of the tube.
Throughout the length of the device, embedded within the wall of the tubular main part 1 , the proximal funnel 2 and the distal external formation 4 is provided a helical nylon monofilament thread 6, to reinforce the tube and give enhanced resistance to collapse or crushing, whilst retaining flexibility.
The inner diameters of the tubular main part 1 and the external formation 4 are the same, so that no internal lip or cavity is formed between the two parts.
In the tube shown in Figures 3 and 4 the tubular main part 1 and proximal funnel 2 are substantially identical with those shown inFigures 1 and 2. The external formation 4, however, is substantially elliptical in cross-section, with a maximum major axis of approximately 17 mm.
In the tube shown in Figures 5 and 6, the tubular main part 1 and distal formation 4 and 5 are substantially identical to those shown inFigures 1 and 2 or 3 and 4. The proximal part, however, instead of being funnel-shaped, consists of a thin disc 7 integral to the tubular main part 1, the outer diameter of the disc being greater than the outer diameter of the tubular main part.
In the valve arrangement shown in Figures 7 and 8, the end 5 of the formation 4 is covered by; dome-shaped membrane of silicone rubber, having slits 8 meeting in the centre of the dome to form four cusps 9. The cusps open in response to the weight of food above them, but are closed to the normal passage of gastric contents in the reverse direction. Should the patient vomit, thus subjecting the valve to a higher than normal reverse pressure differential the cusps can invert to allow the passage of gastric contents.
The valve shown in Figure 9 is similar to that shown in Figures 7 and 8, except that it is formed inside the funnel at the proximal end of the tube.
In either case, the membrane is secured to the silicone tube with a suitable adhesive, such as silicone adhesive.