GB2201097A

GB2201097A - Portable analgesia unit

Info

Publication number: GB2201097A
Application number: GB08800902A
Authority: GB
Inventors: Sarah Veronica Richards
Original assignee: LIFE SUPPORT ENG Ltd
Current assignee: LIFE SUPPORT ENG Ltd
Priority date: 1987-02-17
Filing date: 1988-01-15
Publication date: 1988-08-24
Anticipated expiration: 2008-01-15
Also published as: GB2201097B; GB8703584D0; GB8800902D0

Abstract

A portable analgesia unit comprises a cylinder 10 containing a mixture of oxygen and nitrous oxide, the cylinder being housed in an insulating jacket 12 which may in turn be secured within a carrying case. The cylinder 10 is connected by a regulator 16 and hose 24 to a face mask 26, to which a patient may self-administer the pain-relieving gas mixture by operating a demand valve 28. A re-usable heat pack 30, in the form of a crystallisable gel, is located in the jacket 12, and operation of the heat pack ensures that the temperature of the cylinder 10 does not drop below a dangerous level, i.e. a temperature below which the gases of the mixture separate out. <IMAGE>

Description

Title: Portable Analgesia Unit Field of the invention This invention relates to a portable analgesia unit particularly for the self-administration of Entonox (RTM), a gas composed of 50% nitrous oxide and 50% oxygen, premixed in a single cylinder.

Background to the invention Such units provide an answer to the problem of relieving pain almost immediately, without altering any vital signs or symptoms. The idea has been tried out successfully in county ambulance services, dental-a-aesthesia, obstetric analgesia and has been approved by the Central Midwives Board.

The clinical condition of a patient can deteriorate due to pain and therefore the use of Entonox can be of great benefit. It has the advantage that it provides a good degree of analgesia to patients in pain, with rapid reversal of effect on cessation of administration. It also provides an oxygen rich atmosphere for the patient to breathe. The gas is easily and quickly absorbed into the body, and the resulting effective and controllable pain relief does not interfere with medical assessment. It is self-administered and a problem of overdose cannot occur.

The patient opens the demand valve by inhaling through a face mask therefore when the patient becomes drowsy his or her hand holding the mask falls away from the face and the demand valve is automatically closed.

The unit allows self-adminstration through a mask assembly with a low resistance demand valve. Pain relief should occur 20 seconds after the onset of treatment. Entonox (RTM) has no reaction with other medications and does not alter- vital signs or symptoms. It also supplies 508 oxygen, which is beneficial especially after trauma.

The premixed gases, nitrous oxide (N2O) and oxygen (02)1 start to separate at an ambient temperature of -7 C. The oxygen is then drawn off first, and although this is not dangerous it will not provide pain relief. However, gradually the contents of the cylinder#becomes progressively more hypoxic until pure nitrous oxide is drawn off, and this is very dangerous.

One way of preventing this problem is by storing the Entonox cylinders at an ambient temperature above +50C and not leaving the cylinders in vehicles parked in cold environments. However, this may be impractical, and for some midwives and general practitioners is impossible.

It is an object therefore of this invention to overcome the above-mentioned problem.

Summary of the invention In accordance with this invention there is provided a portable analgesia unit comprising a cylinder for containing a mixture of oxygen and nitrous oxide, a regulator valve coupled to said cylinder, a face mask, a demand valve coupled to said mask, and a hose which couples said demand valve to said regulator valve, said cylinder being at least partially housed in an insulated jacket, and self-contained heating means being located in said jacket adjacent said cylinder.

One particular form of self-contained heating means which is suitable for this application is the re-usable heat pack described and claimed in European Patent Application No. 83304501.6, which is hereby incorporated into this patent specification by reference.

The heat pack basically comprises a plastic envelope containing a solution hose main ingredient is sodium acetate trihydrate to which is added a microbial polysaccharide known as Xantham Gum. The pack, which is in effect a heat battery, is charged by heating it to above 650C when the ingredients change from a crystallised solid to a gel form, absorbing latent heat as a result.

The gel is slowly coupled and remains staL~- down to and below normal room temperature.

Preferably the re-usable heat pack is formed as a hollow cylinder to encompass at least part of the gas cylinder.

Alternatively the pack may be in arcuate form to encompass a portion of the cylinder surface of the gas cylinder.

The pack is activated to release the stored latent heat, which results in the pack reaching a temperature of about 58 C over a period of one or two hours depending on the size and thickness of the pack and the insulation value of the jacket.

This is sufficient to raise the temperature of the gas cylinder to a value which prevents the gases separating out.

Description of embodiment An embodiment of a portable analgesia unit in accordance with the invention will now be described, by way of example, with reference to the single figure of the accompanying drawing, which is a perspective view of such a unit with some parts cut away to show the inside.

Referring to the single figure of the drawing, the unit comprises a gas cylinder 10 of approximately two litres capacity and containing the nitrous oxide and oxygen mixture. The cylinder is surrounded by an insulating jacket 12 of generally cylindrical shape, but forming an apex along a line 14 where the jacket may be conveniently secured to the inside of a carrying case (not shown). An instruction label 15 is shown attached to the jacket 15.

The cylinder 10 includes a pressure regulator assembly 16 attached to it by an A-clamp 18 and incorporating a pressure gauge 20. A pin index valve 22 of the cylinder is openable by a key (not shown) to allow gas to flow to the regulator 16.

Connected to the regulator 16 is a medium pressure hose 24, whose other end is connected to face mask 26 via a demand valve 28.

Positioned in the double lining of the insulating jacket 12 is a re-usable heat pack 30, only one corner of which is shown at the cut out. The heat pack is of the type above-described, and its ingredient is in a gel form ready for use.

In use of the analgesia unit, the valve 22 of the cylinder is opened with the key (supplied with each unit) and the gas mixture is admitted to the regulator 16 which supplies a reduced pressure to the demand valve 28. Due to the low resistance of the valve 28 when breathing, a gentle inhalation from the patient is all that is required to deliver the gas mixture. When the pressure indicated by the pressure gauge 20 falls to a level of 20 bar, the cylinder 10 should be exchanged for a freshly charged unit.

Should the ambient temperature of the cylinder 10 fall below -7 C the heat pack 30 is activated by pressing against a metal starter disc 32 in the gel, thereby raising temperature of the cylinder 10 and prevent the gases separating out before the unit is used by a patient.

After use the pack 30 can readily be removed from the jacket 12 and replaced with another pack, while the spent pack is recharged by heating to 650C, as above described.

Clearly the shape of the pack 30 in the jacket 12 could, alternatively, be in the form of a hollow cylinder to encompass part of the cylinder.

Claims

1. A portable analgesia unit comprising a cylinder for containing a mixture of oxygen and nitrous oxide, a regulator valve coupled to said cylinder, a face mask, a demand valve coupled to said mask and a hose which couples said demand valve to said regulator valve, said cylinder being at least partially housed in an insulated jacket, and self-contained heating means being located in said jacket adjacent said cylinder.

2. A portable analgesia unit according to claim 1 in which said self-contained heating means is a re-usable eat pack.

3. A portable analgesia unit according to claim 1 or claim 2 in which said self-contained heating means comprises a plastic envelope containing sodium acetate trihydrate to which is added a microbial polysaccharide.

4. A portable analgesia unit according to any one of claims 1 to 3 in which said heating means is formed as a hollow cylinder to encompass at least part of the gas cylinder.

5. A portable analgesia unit according to any one of claims 1 to 3 in which said heating means is in arcuate form to encompass a portion of the cylindrical surface of the gas cylinder.

6. A portable analgesia unit substantially as herein described with reference to, and a shown in, the accompanying drawing.