WO2003022342A1

WO2003022342A1 - Anti-condensation sheath for breathing tube

Info

Publication number: WO2003022342A1
Application number: PCT/GB2002/004178
Authority: WO
Inventors: Richard Banfield Hicks
Original assignee: Intersurgical Limited
Priority date: 2001-09-13
Filing date: 2002-09-13
Publication date: 2003-03-20
Also published as: GB0122097D0

Abstract

A tube (10) which connects a patient connection (P) with a source (S) of a gaseous mixture used in patient ventilation is provided with a sheath (12) made from a transparent polymeric film laminate the greater part of which comprises vapour deposited aluminium. A central portion (13) of the sheath remains free of aluminium so that the accumulation of condensate in the tube (10) can be observed through the sheath (12) but the heat-reflective properties of the end regions of the sheath inhibit condensation in the tube (10).

Description

"ANTI-CONDENSATION SHEATH FOR BREATHING TUBE"

This invention relates to an anti-condensation sheath for a breathing tube of the kind used in patient ventilation to connect the patient to a source of a gaseous mixture.

In the case of forced or assisted breathing it is very important that the administered gases should be at approximately body temperature and should not have a drying effect. For this reason the inspiratory passageway or breathing tube of a breathing system is normally connected to a humidifier and the tube may be heated by an internal flexible heating element to maintain its internal temperature at about 37 degrees centigrade. The breathing tube normally has a corrugated or concertina wall. This increases flexibility and prevents crushing or pinching, but it also increases the surface area of the wall over which heat exchange can occur. This increases condensation within the tube, which is a serious problem in that the tube may be blocked with water which at best will interfere with the patient's breathing or at worst could drown him. The breathing tube should therefore be of a transparent material so that the accumulation of condensate can be observed and appropriate action taken to remove it.

It has been proposed to surround the breathing tube with a sheath, an air gap between the breathing tube and sheath providing heat insulation. A drawback of such a sheath is that it may prevent observation of the accumulation of condensate in the breathing tube. A wholly transparent sheath will be less efficient as a heat insulator than an opaque one.

It is therefore desirable to provide the sheath with one or more transparent "window" through which the breathing tube can be observed at a position where condensate will accumulate.

This will normally be in a central region of the tube and sheath which, in use, will be their lowermost region where the assembly sags between the humidifier and the breathing mask. The remainder of the surface of the sheath is preferably heat reflective. This will provide an efficient insulator which is more lightweight and flexible than a sheath of a more conventional insulating material.

A principal object of the present invention is to provide an efficient, lightweight sheath for a breathing tube the greater part of the surface area of which is heat reflective but which comprises one or more "windows" for the observation of the breathing tube and to provide such a sheath by a manufacturing technique enabling sheaths to be mass produced very economically. The technique permits the position and shape of the window or windows to be selectively varied to suit customer requirements without major alteration of the production equipment and consequent down time. A clear and accurate demarcation between transparent and opaque surface areas can be achieved using a simple metal deposition technique well proven in the field of food packaging, which is more cost effective than alternatives such as spraying, printing or painting.

In accordance with the present invention there is provided a sheath for a breathing tube for use in patient ventilation, the sheath being of greater internal diameter than the external diameter of the tube, characterised in that the sheath is of a transparent plastics material the greater part of which has been rendered heat reflective by the vapour deposition thereon of a metal, one or more selected areas of the sheath having no metal deposited thereon to permit observation of the tube through the sheath.

The said metal is preferably aluminium.

A central region of the sheath may remain transparent through the use of a metal mask during the vapour deposition process. Alternatively one or more selected areas of the sheath may remain transparent through the application of resist lacquer to said areas prior to the vapour deposition process.

The sheath is preferably manufactured by passing a first film of a transparent plastics material over a heated metal wire in a vacuum chamber and then laminating a second film of a transparent plastics material to the surface of the first film on which metal has been deposited.

Each of said films is preferably a transparent polymer from 10 to 100 microns in thickness.

In a preferred embodiment of the invention said one or more selected areas is a central region of the sheath which is approximately one third of the length of the sheath. A preferred embodiment of the invention will now be described with reference to the accompanying drawing, which illustrates a sheathed breathing tube in accordance with the present invention in side elevation.

A corrugated breathing tube 10 can be connected at one end S to a source of a gas mixture, such as air and oxygen, whereby the gas mixture is supplied to a patient via the other end P of the tube. The tube 10 is of a transparent or at least translucent polymeric material so that the accumulation of condensate 14 within the tube can be observed and appropriate action taken. Within the tube 10 a flexible heating element 11 passes to and fro to maintain the gas mixture supplied to the patient at around 37 degrees centigrade.

In accordance with the present invention the tube 10 is surrounded by a sheath 12 of substantially greater internal diameter than the external diameter of the tube 10. This provides an insulative barrier of still air between the exterior of the tube 10 and ambience, having the effect of reducing the rate at which condensation 14 occurs within the tube 10.

The sheath 12 is made by wrapping around the tube 10 an appropriate length of a polymeric film laminate which corresponds generally to the length of the tube 10. A central portion of the film, representing approximately one third of its length, has had no metal applied to it. The central portion of the sheath thus formed, indicated by the broken lines at 13, thus remains at least semi-transparent.

Water will collect at the lowest point of the tube 10. When this is draped over bedding, and particularly if the patient moves, the lowest point of the tube 10 will not be exactly at its centre but will remain in a central region. The extent of the "window" 13 in the sheath 12 is sufficient to accommodate such changes.

In use whenever an accumulation of condensate 14 in the tube 10 is observed through the "window" 13 the tube 10 together with the sheath 12 is disconnected at one or the other of its ends either from the supply S or the patient connection P and lowered to drain the water out.

The sheath 12 has been manufactured by passing a first film of transparent polyamide, polyester, polypropylene or polyethylene between 10 and 100 microns in thickness over a heated aluminium wire in a vacuum chamber. Subsequent to the vapour deposition of aluminium on the first film a second, similar film is laminated to the first film with the deposited metal sandwiched between the films. This will prevent accidental removal of metal from the sheath.

The "window" 13 has been provided in one of two ways. Either a metal mask has been applied to the first film to prevent vapour deposition to a lengthwise strip of the film, or the first film has been treated with a resist lacquer to prevent vapour deposition on the treated area or areas. Subsequent to vapour deposition the resist lacquer is washed off before the lamination procedure. The use of resist lacquer has the advantage that the area or areas of the finished sheath which remain transparent can be varied in size and location and are not limited to lengthwise strips of uniform width. For example the sheath could be provided with a "window" along the whole or part of its length and this need not be straight but might pass spirally around the sheath. Several "windows" might be provided spaced along the length of the sheath.

Claims

CLAIMS:

1. A sheath for a breathing tube for use in patient ventilation, the sheath being of greater internal diameter than the external diameter of the tube, characterised in that the sheath is of a transparent plastics material the greater part of which has been rendered heat reflective by the vapour deposition thereon of a metal, one or more selected areas of the sheath having no metal deposited thereon to permit observation of the tube through the sheath.

2. A sheath as claimed in claim 1 , characterised in that the metal is aluminium.

3. A sheath as claimed in either preceding claim, characterised in that a central region of the sheath remains transparent through the use of a metal mask during the vapour deposition process.

4. A sheath as claimed in claim 1 or claim 2, characterised in that one or more selected areas of the sheath remain transparent through the application of resist lacquer to said areas prior to the vapour deposition process.

5. A sheath as claimed in any one of the preceding claims, characterised in that it is manufactured by passing a first film of a transparent plastics material over a heated metal wire in a vacuum chamber and then laminating a second film of a transparent plastics material to the surface of the first film on which metal has been deposited.

6. A sheath as claimed in claim 5, characterised in that each of said films is a transparent polymer from 10 to 100 microns in thickness.

7. A tube as claimed in any one of the preceding claims, characterised in that said one or more selected areas is a central region of the sheath which is approximately one third of the length of the sheath.