GB2316872A

GB2316872A - Cooling cuff

Info

Publication number: GB2316872A
Application number: GB9618818A
Authority: GB
Inventors: James Reginald House; Matthew Robert Humphris Clarke; Ian Roberts
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1996-09-10
Filing date: 1996-09-10
Publication date: 1998-03-11
Also published as: GB9618818D0

Abstract

A cooling cuff for wear around the lower part of a limb, comprising an impermeable sleeve 1 which provides a sealed channel around the limb. The sleeve 1 having an inlet 3 and an outlet 4 to facilitate circulation of cooling fluid within the sealed channel.

Description

COOLING CUFF The present invention relates to a means of reducing the core temperature of a person who is either suffering from, or is at risk of suffering from heat strain.

Normally, heat produced by metabolism is balanced by heat loss to maintain a constant body temperature. However, when heat loss through normal physiological mechanisms is severely limited (for example, due to increased environmental temperature and humidity or the wearing of protective clothing), heat loss may become insufficient, causing the body temperature to rise and heat strain to result.

A known device for reducing heat strain is an ice vest which increases the heat flux from the body. Known ice vests comprise a cotton waistcoat into which packs of frozen gel are inserted. The efficiency of this device depends upon the conductive temperature gradient between the skin and the gel packs, the surface area of the packs in contact with the body and the specific heat capacity and volume of the gel.

A disadvantage of known ice vests is that the cold gel packs reduce the skin temperature, thereby reducing the blood flow in the skin (vasoconstriction). Consequently, warm blood from the core of the body is restricted from perfusing the skin and the most effective method of transferring heat from the body core to the skin is lost. As ice vests rely upon heat transfer from the body core to the skin to function effectively, their cooling ability is thereby reduced.

Another known and effective method of reducing core temperature and thereby reducing the effects of heat strain, requires immersion of the hands in cold water. This method of cooling relies on the principle of increasing the convective heat loss from the body by utilising the rich perfusion of blood in the hands. The person being treated must take regular rest intervals during which their hands are immersed in cold water.

A disadvantage of the hand immersion method of cooling is the requirement for regular rest intervals to enable the core temperature to reduce to safe levels. Also, hand immersion may prove impractical in circumstances where the maintenance of full mobility and manual dexterity are essential. In certain situations, this problem may be overcome by using foot immersion.

The control of blood flow within the feet has been shown to be analogous to that within the hands and hence a similar effect to hand cooling may be obtained by cooling the feet.

Accordingly, the present invention provides a cooling cuff to be worn around the lower part of a limb, comprising an impermeable sleeve, which provides a sealed channel around the limb, and an inlet and outlet for the provision and removal of cooling fluid tc the channel.

With this arrangement, cooling fluid passes through the channel and is maintained in thermal contact with the skin of the limb.

This provides a device which implements the hand or foot cooling method but allows the benefits of the method to be obtained continuously, without the need for regular rest intervals.

The cooling cuff will also be suitable for use in environments where water is considered to be a hazard (i.e. when dealing with electrical supplies) as the cooling fluid is retained within a closed channel.

It has been found in experiments using the hand cooling method that cooling is achieved more quickly where the water into which the hands are placed is maintained at a constant cooled temperature. When the hands are placed in water where the temperature is not controlled, the ambient temperature and heat loss from the hands, warms the water, thereby reducing the cooling effect. A simple method of maintaining the water at a constant temperature is achieved by placing ice cubes in the water. The present invention ensures that the cooling fluid is continuously circulated around the arm and can be provided from a chilled source so that it remains at a constant temperature. Furthermore, this temperature can be accurately controlled at a predetermined level.

As with ice vests, it is thought that where the temperature of the water into which the hands are immersed is reduced below 25 c, vasoconstriction will start to restrict the peripheral blood flow in individuals with normal deep body temperatures, with maximum vasoconstriction occuring at temperatures of around 150c. The reduction in skin temperature will diminish the cooling effect of the water. However, this phenomenon is overcome when the deep body temperature of the individual has been raised. This will be the case where the individual has carried out a work shift prior to immersing the hands during the rest period. The present invention can be adapted such that the temperature of the chilled fluid passing over the forearm or lower leg is varied depending upon the length of time that the subject has been exposed to heat strain.

Thus, at the start of the first work period, the fluid could be relatively warm (i.e. around 250c) to reduce the effects of vasoconstriction. As the core body temperature rises during subsequent work periods, the fluid passing through the cooling cuff can be progressively chilled to improve the cooling effect.

The cooling cuffs may be provided in either a single layer or a double layer configuration. In both cases, two sizes may be provided. One for use around the forearm (or lower leg) and the other for use around the wrist (or ankle). The double layer cuff has the advantage that the cooling fluid passes through a self contained, closed channel. Thus, the requirement for sealing the cuff around the limb, as required in the single layer configuration, is removed and the cuff is less prone to leaks.

The single layer cuff is usefully formed from closed cell neoprene fabric coated on both sides which is formed to provide a tube or sleeve. The sleeve provides the outer wall of a channel through which the cooling fluid flows and the inner wall of the channel is provided by the skin of the limb. Latex seals are provided at either end of the sleeve to seal around the wrist and elbow (or ankle and knee).

Preferably, the wrist and elbow seals are provided by a tapering section of latex tube which can be cut to provide a water tight seal at the wrist or elbow but does not restrict the peripheral blood flow in these areas. Desirably, the latex tubes are formed with parallel ribs to provide a stronger edge to cut to. This helps prevent tearing of the latex seals when the user is donning or doffing the cuff.

The double layer cuffs are formed from two waterproof layers which provide the inner and outer walls of a channel through which the cooling fluid flows. Preferably, the layer in contact with the skin is provided by a material of low thermal insulation (high thermal conductivity) to ensure maximum heat transfer from the skin to the cooling fluid. Furthermore, this layer is preferably smooth and in close contact with the skin to minimise insulation due to trapped air between the skin and the waterproof layer.

The performance of the double layer cuff can be further improved by the provision of a number of perpendicular bars formed by sealing the two waterproof layers together either by heat sealing, stitching or similar methods. The perpendicular bars are arranged such that they define a reversing channel across the entire surface area of the cuff.

In both the single layer and double layer cuff configurations, the flow of cooling fluid and efficiency of drainage should be such that distortion of the sleeve is minimised. In use, the cuff should not form a large fluid filled balloon around the arm or leg.

Three embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, wherein Fig 1. shows a single layer cuff provided by a neoprene rubber tube with latex seals at each end to seal against the wrist and elbow.

Fig 2. shows a double layer cuff provided by a sealed bag of metallised polymer film which is provided with a velcro fastening so that the bag can be wrapped around the forearm (or lower leg) and fastened to form a sleeve.

Fig 3. shows a double layer cuff of the type shown in Figure 2 but with the addition of perpendicular bars to define a reversing flow channel for the cooling fluid.

Referring to Figure 1, the single layer cooling cuff comprises a waterproof sleeve 1 with seals 2 at each end to seal against the forearm or lower leg. Cooling fluid is provided under pressure through the inlet 3, moves through the cavity between the sleeve 1 and the limb and exits from the outlet 4. The seals 2 are provided by a tapered section of latex tube which can be cut to size to adapt the sleeve to fit different users.

The single layer cuffs are manufactured as follows. The sleeve 1 is provided by a sheet of 4mm closed cell neoprene fabric coated on both sides which has been marked and cut out, with holes provided for the inlet 3 and outlet 4. The inlet and outlet 3,4 are produced by vacuum casting 60/70 polyurethane resin and are bonded to the neoprene sheet using waterproof adhesive. The inlet and outlet 3,4 are sealed to the neoprene sheet on both sides using latex sections 5. The neoprene sheet is stitched to form the sleeve 1 and the stitch line is sealed on both sides of the sleeve 1 with latex tape. The tapered latex seals 2 are bonded to each end of the sleeve 1 using waterproof adhesive with the adhesive joint being sealed on the inside of the sleeve 1 with latex tape and on the outside of the sleeve 1 using Seam Grip polyurethane seam sealant.

Referring to Figure 2, the double layer cooling cuff comprises a sealed bag 6 to which a fastening 7 (such as a zip, button or velcro) is attached. The sealed bag 6 is provided with an inlet 3 and an outlet 4. Cooling fluid is provided under pressure to the inlet 3, circulates around the sealed bag 6 and exits from the outlet 4. In use, the sealed bag 6 is loosely fitted around the forearm or lower leg and secured using the fastening 7. The cooling fluid then inflates the sealed bag 6, providing close contact with the arm or leg, enabling one size of cuff to be worn by different users.

Referring to Figure 3, the cuff shown in Figure 2 is additionally provided with perpendicular bars 9 which define a reversing flow channel 10 for the cooling fluid. Cooling fluid is provided under pressure to the inlet 3, circulates around the sealed bag 6 within the reversing flow channel 10 and exits from the outlet 4.

The double layer cuffs are manufactured as follows: The sealed bag 6 is provided by 70 micron thick Melinex (trade name) film, which consists of a biaxially orientated polyethylene terephthalate (PET) film 12 microns thick, metallised on one surface by aluminium deposition and laminated with polyethylene (PE). This metallised film has a shiny side (PET) and a matt side (PE) and can be heat sealed together provided contact is between two matt sides. The metallised film is marked and cut out, with holes provided on one side for the inlet 3 and outlet 4. The inlet and outlets 3,4 are produced as previously described for the single layer cuff. The metallised film is heat sealed into a bag 6, using a heat sealing machine set at 2000c for 2 seconds. The inlet and outlet 3,4 are bonded to the sealed bag 6 using waterproof adhesive and sealed to the bag 6 using latex sections 5. The sealed bag 6 is stitched to a backing sheet 8 of 2mm thick closed cell neoprene fabric coated on both sides. Finally, velcro fastening strips 7 are attached to the backing sheet 8.

Further improvement of the single layer cuff can be achieved by producing the cuff from a one piece rubber sleeve with seals at each end. This construction eliminates the requirement for seams and hence reduces the potential for leakage of the cooling fluid.

Such a cuff can be produced by latex dipping a specially designed former.

Claims

1. A cooling cuff to be worn around the lower part of a limb,

comprising an impermeable sleeve, which provides a sealed channel around the limb, and an inlet and outlet for the provision and removal of cooling fluid to the channel.

2. A cooling cuff as claimed in claim 1 wherein the sealed channel is defined between the impermeable sleeve and the skin of the limb, the sleeve having circumferential seals capable of sealing to the limb at both ends.

3. A cooling cuff as claimed in claim 2 wherein the seals are provided by a flexible tapered portion of the sleeve, suitable for cutting to the appropriate size to form a seal around the limb.

4. A cooling cuff as claimed in claim 3 wherein the tapered seals are provided with parallel ribs to provide a plurality of strengthened cutting edges to facilitate fitting of the cuff to a limb.

5. A cooling cuff as claimed in claim 1 wherein the sleeve is provided by two impermeable layers which are sealed together at their edges, the channel being defined between the two impermeable layers.

6. A cooling cuff as claimed in claim 5 wherein the two impermeable layers are sealed together at multiple locations to define a channel which ensures flow of the cooling fluid across the entire surface area of the cooling cuff.

7. A cooling cuff as claimed in claim 5 or claim 6 wherein the two impermeable layers are formed as a flat bag and provided with a fastening such that the bag can be wrapped around the limb and fastened to form the sleeve.

8. A cooling cuff as claimed in claims 5, 6 or 7 wherein the impermeable layer in contact with the skin comprises a material of high thermal conductivity.

9. A cooling cuff as claimed in any of the preceding claims wherein the sleeve comprises a flexible material.

10. A cooling cuff as claimed in any of the preceding claims wherein the sleeve is adapted to be worn around the lower arm.

11. A cooling cuff as hereinbefore described with reference to the accompanying drawings.

12. A cooling system comprising a cooling cuff as described in any of the preceding claims and a circulator adapted to supply cooling fluid to the cuff.

13. A cooling system as claimed in claim 12 wherein the circulator is adapted to provide the cooling fluid at a constant chilled temperature.

14. A cooling system as claimed in claim 12 wherein the circulator is programmable and is programmed to provide cooling fluid at multiple fixed temperatures.

Amendments to the claims have been filed as follows 1. A cooling cuff to be worn around the lower part of a limb, comprising an impermeable sleeve, which provides a sealed channel around the limb, and an inlet and outlet sized for the provision and removal of cooling fluid to the channel without significant distortion of the cuff in use.