COOLANT DEVICE

Abstract: A device, for use in the treatment of soft tissue injuries, delivers a refrigerant foam comprising a matrix of a topically acceptable material such as a paraffin wax, and a refrigerant as a foaming agent for the wax. Preferably, a mixture of different fluorinated hydrocarbons such as dichlorodifluoromethane, trichloromonofluoromethane and dichhlorotetrafluorethane is used as refrigerant. An adhesion-promoting agent such as glycerine may first be applied to the site of the injury to assist in ensuring that the refrigerant foam remains in intimate contact with the injured tissue.

Description: COOLANT DEVICE This invention relates to a coolant device, especi¬ ally for use in the emergency treatment of burns, and in the treatment of other soft tissue injuries, such as bruises or strains of muscles, ligaments and tendons. It is well known that both pain and tissue damage ( and, in particular, oedema) at a burn site can be substantially reduced if the burn site is cooled rapidly to a temperature which is below 30 C, and then maintained at that temperature for a substantial period of time. For example, it is suggested in an article by J.W.L. Davies in Burns, Vol. 9 (1982) pages 1 to 6, that burns should preferably be cooled in water at 20 to 25°C for an hour or more. -The selection of this temperature range is said to avoid the potential hazards of frost¬ bite or hypothermia induced by temperatures near 0°C. It is also known that pain and tissue damage in the case of bruises, sprains and the like can be reduced by cooling the site of the injury. For example, it- has been proposed in Japanese Patent Specification No. 54-86606 to provide cooling in such cases by means of a coolant aerosol comprising one or more organic chemical compounds with a molecular weight greater than 80, a latent heat of evaporation of 100 cal/g or less at 25 C and a boiling point of 20 to 100°C, together with a compressed gas as a propellant. Such an aerosol is said to provide rapid cooling down to -20°C or -30 C at 5 cm from the spray nozzle, and -10°C tp -25°C at 10 cm from the spray nozzle. Refrigerants such as R-12 (dichlorodifluoro- methane), which have a boiling point below 20 C, are said to be unsatisfactory by reason of providing only slight cooling of the object which is being sprayed, despite considerable cooling around the nozzle of the aerosol. The aerosol of Japanese Patent Specification No. 54-86606 suffers from the disadvantage that it is difficult to obtain a cooling effect which is of suffi¬ cient duration to give optimal pain relief and minimum tissue damage. A relatively long cooling effect is only obtained by choosing refrigerants which yield very low temperatures such as the temperatures mentioned above. This involves the risk of frostbite or hypo¬ thermia, especially to patients, who are in a state- of shock, such as burns patients. The aerosol disclosed in Japanese Patent Specification No. 54-86606 is there¬ fore believed to be wholly unsuitable for the emergency treatment of burns. We have now devised a means for cooling the site of a soft tissue injury, which avoids th -above described disadvantages and which is eminently suitable for use in the emergency treatment of burns, as well as sprains and the like. According to the present invention, there is pro¬ vided a device for delivering a refrigerant foam, said device comprising a vessel containing a topically acceptable foam-forming material and a topically acceptable refrigerant under pressure, and means for delivering from said device an intimate mixture of the foam-forming material and the refrigerant, the boiling point of the refrigerant being chosen such that on delivery from the device the refrigerant serves as a foaming agent for the foam-forming material. Also provided by the invention is a foam-forming mixture for use in the treament of soft tissue injuries, said mixture comprising at least one topically accept¬ able refrigerant and a topically acceptable foam-form¬ ing material. A refrigerant foam, as provided by the invention, produces very rapid cooling of any surface with which it comes into contact. Most importantly, however, it also has a low thermal conductivity. This means that prolonged cooling is obtained without the need to resort to very low initial temperatures. For example, the device of the present invention may produce a foam which will pro- vide cooling down to, say, 0°C, and maintain that temperature for from 15 to 30 minutes. The prolonged cooling effect ensures that maximum pain relief and minimum tissue damage is obtained, while the avoidance of very low initial temperatures substant- ially eliminates the danger of frostbite or hypothermia. The refrigerant used in the device of the invention preferably comprises one or more halogenated hydrocarbons. Particularly preferred are fluorinated hydrocarbons. If a single refrigerant is to be used, it should preferably have acoolingpoint below lO ϊ. It is greatly preferred, however, that two or more refriger¬ ants- be used, each having different boiling points. This has the advantage that rapid evaporation of the lower boiling component generates the foam and produces, the initial cooling effect, while subsequentslower evapora¬ tion of the higher boiling component or components serves to keep the foam at its low temperature. Thus, for example, the refrigerant may comprise a component having a boiling point in the range -60 C to 10 C, and more preferably in the range -40°C to -20°C . , and a component having a boiling point in the range 10 C to 40°C, for example 20°C to 30°C. In particularly pre¬ ferred embodiments, three refrigerants are used, namely a low boiling component having a boiling point in the range -40°C to -20°C, for example -30°C, a high boiling component having a boiling point in the range 10 C to 40°C, for example 24 C, and an intermediate component having a boiling point in the range -20°C to 10°C,- for example 4°C. When two refrigerants are used, the lower boiling OMPI component is preferably present in an amount of from 40 to 80% by weight of the foam-forming mixture, and more preferably from 50 to 70% by weight, for example 60% by weight. The higher boiling component is advantageously present in an amount of from 20 to 40% by weight of the foam-forming mixture, and preferably from 25 to 30% by weight, for example 30% by weight. When three refrigerants are used, the lowest boil¬ ing component is advantageously present in an amount of from 20 to 50% by weight,of the foam-forming mixture, and preferably in an amount of from 30 to 40% by weight, for example 35% by weight. The high boiling component is preferably present in an amount of from 20 to 40% by weight of the foam-forming mixture, and more preferably in an amount of from 25 to 35% by weight, for example 30% by weight. The intermediate boiling component is preferably present in an amount of from 15 to 30% by weight of the foam-forming mixture, and more preferably from 20 to 25% by weight, for-example 23% by weight. The refrigerant (or the lowest boiling component thereof if a mixture of refrigerants is used) prefer¬ ably has a latent heat of evaporation of at least 5000 kJ/mole, and more preferably at least 8000 kJ/mole, for example 9000 kJ/mole. Preferred refrigerants are dichlorodifluoromethane (R12), which has a boiling point of -29.8°C, trichloro¬ monofluoromethane (Rll), which has a boiling of 23.S C, and dichlorotetrafluoroethane (R114) , which has a boil¬ ing point of 4.1°C. The refrigerant can be used as the propellant for the device. That is to say, it is not necessary to use a compressed gas such as carbon dioxide or nitrogen, because the refrigerant has a sufficiently high vapour pressure at room temperature to drive the mixture of refrigerant and foam-forming material from the device. OMP ^ WIP While a compressed gas may be used if desired, its use has the disadvantage of adding to the expense of the device, and also means that pressure is steadily lost from the device during use. The foam-forming material is preferably present in an amount of from 5 to 30% by weight of the foam-forming mixture, and more preferably in amount of from 10 to 20% by weight. The foam-forming material should preferably have a high specific heat, so that the foam warms up only slowly on exposure to ambient temperatures. The foam- forming material must obviously be capable of intimate .. mixing with the refrigerant, so that a foam results from evaporation of the refrigerant. This will usually be achieved in one of two ways. On the one hand, the foam-forming material (which may be liquid or solid at room temperature) can be soluble in the refrigerant or mixture of refrigerants. On the other hand, the foam- forming material can be'a liquid or gel which is capable of forming an emulsion or similar dispersion with the refrigerant or refrigerants. It will be understood that if an aqueous medium such as an aqueous gel is used as the foam-forming material, it may be necessary to include a surface active agent to ensure adequate mixing of the aqueous medium with a hydrophobic refrigerant. Preferably, the foam-forming material is a wax, such as paraffin wax. Not only is paraffin wax soluble in the usual hydrocarbon refrigerants, but it also has a high specific heat, usually in the region of 0.5 cal/g. We have found that a wax-based refrigerant foam has very little tendency to adhere to tissue to which it is applied. In some cases, such as in the treatment of burns, this can be a great advantage, in that relatively little trauma is involved in removing such a wax-based foam from a burn site to which it has been applied. On ■ the other hand, there may be circumstances (such as in the treatment of sprains in human patients) , in which greater adhesiveness will be desired. In such a case, it may be desirable to apply an adhesion promoting substance to the tissue either before, or simultaneously with applying the refrigerant foam. Examples of suitable adhesion promoting substances are glycerine, and topically acceptable oils. A particularly convenient additive for increasing the adhesion of a wax-based refrigerant foam is petroleum jelly. A mixture of petroleum jelly and paraffin wax as the foam-forming material has the additional advan¬ tage of greater flexibility as compared with a foam . formed without petroleum jelly. The device of the present invention may contain other additives, such as antibacterial agents. A mixture of such agents may be used to achieve a broad spectrum of antibacterial activity. An example of such a mixture is a mixture of neomycin sulphate, polymyxin sulphate and bacitracin zinc. For certain applications, it may also be desirable to incorporate a local anaesthetic in the refrigerant foam. When the foam is to be used in the emergency treatment of burns, however, it is advisable to avoid the incorporation of an anaesthetic, because pain at a burn site is a useful indication that insufficient cooling has been achieved. This is because peripheral nerves are generally only active above 8°C. The device of the present invention is not only useful for the treatment of human patients, but also has numerous veterinary applications, for example in the treatment of soft tissue injuries of horses and other domestic animals. In such veterinary appli¬ cations, the use of an additive to promote adhesion of the refrigerant foam to the tissue being treated OMP will generally not be necessary, because the foam will form in intimate association with the animal's hair, which thereby serves to keep the foam in place. The device of the invention may be a conventional aerosol can containing a mixture of the foam-forming material and refrigerant. It will be appreciated, however, that other forms may be used. For example, the refrigerant and the foam-forming material may be kept in separate reservoirs, being mixed only immediately prior to release from the nozzle of the device. The device may also be arranged to deliver first a spray of an adhesion-promoting substance, followed by the refrigerant foam. A coolant device according to the present invention is now described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a schematic vertical section through an aerosol device according to the invention, and Figure 2 is a vertical section through an alternative embodiment. Referring to Figure 1, an aerosol device comprises a pressure-resistant metal container, formed from a generally cylindrical body 1, a base 2, and a cover 3. The container may be formed in one piece, or the body 1, the base 2, and the cover 3 may be formed separately and then assembled to form the container. A raised central portion 4 of the cover 3 forms a nozzle having an outlet 5. The container is divided into two compartments by means of an impervious flexible bag 6 located within the container, adjacent the base 2. During operation of the device, the space enclosed by the bag 6 communicates with the outlet 5 via a tubular element 7, which extends axially within the body 1. The tubular element 7 is sealingly connected at one end to a neck 8 formed in the OMPI flexible bag 6, and at the other end to the cover 3 around the periphery of the raised central portion 4. Communication of the interior of the container with the outlet 5 is controlled by means of a valve arrangement shown generally at 9. The valve arrange¬ ment comprises first, second and third valve members 10, 11 and 12 spaced a short distance apart on a rod 13 which is axially disposed in the tubular element 7. The rod 13 passes through a central aperture 14 in the raised portion 4 of the cover 3, to terminate in an actuating knob 15. A sealing ring 16 ensures that the contents of the container do not escape through the aperture 14 when the rod 13 is moved axially. A coil spring 17 is arranged axially in the tubular element 7 between an abutment 18 and the second valve member 11. The first valve member 10 is thus biassed against a seal 19 arranged in the raised portion 4 of the cover 3, to isolate the interior of the raised portion from t e remainder of the interior of the container. The second valve member .11 is in the form of a piston having channels 20 extending axially there¬ through. The second valve member 11 forms a sliding fit in a cylindrical region 21 of the tubular element 7, the wall of the tubular element in this region being pierced by vents 22. The vents 22 are closed by the second valve member 11 when the first valve member 10 bears against the seal 19. The third valve member 12 is arranged to engage against an annular rim 23, formed by a constriction 24 in the tubular element 7. when the rod 13 is fully depressed against the bias of the coil spring 17. The device, when ready for use, contains in the main body thereof, a foam-forming mixture 25 of a topically acceptable refrigerant and a topically accept- O PI able foam-forming material. The refrigerant has a suffi¬ ciently high vapour pressure at ambient temperatures that the contents of the device are under a pressure of . a few atmospheres. The bag 6 contains an adhesion promoting agent 26 such as glycerine. The adhesion promoting agent is also under pressure, because the bag 6 is flexible. The operation of the device is as follows: Partial depression of the actuating knob 15 causes the first valve member 10 to disengage from the seal 19. The vents 22, however, remain sealed by the second valve member 11, and the annular rim 23 is not yet engaged by the third valve member 12. The pressure on the bag 6 therefore causes the adhesion promoting agent 26 to rise up the tubular element 7 and be dis¬ pensed from the outlet 5 in a fine spray. - ■ Further depression of the actuating knob 15 causes the third valve element 12 to form a seal with the annular rim 23, thereby cutting off the supply of adhesion promoting agent. Simultaneously, the second valve member 11 moves to a position in which the vents 22 are no longer closed. The foam-forming mixture " 25 therefore passes through the vents 22 and thence out through the outlet 5. On release from the device, the refrigerant compon¬ ent of the foam-forming mixture, boils, causing the foam-forming mixture, to expand to form-a foam. Figure 2 shows a simplified device which does not deliver a preliminary spray of adhesion promoting agent. However, it includes a modification which assists in increasing the shelf-life of the device. The device of Figure 2 comprises a pressure-resist¬ ant container formed from a generally cylindrical body 101, a base 102 and a cover 103. The cover 103 has a centrally disposed raised portion 104 which defines an opening 130. Prior to use, the container is filled with a mixture 125 of a topically acceptable refrigerant and a topically acceptable foam-forming material. The open¬ ing 130 is then sealed with an impermeable disc 131 of frangible material such as a plastics film or metal foil. Sealingly surrounding the raised portion 104 is.' a cap 132 having a cylindrical side wall 133 and flat top plate 134. The top plate 134 has a centrally dis¬ posed outlet 135, through which passes a hollow tube 136, the tube 136 forming a sliding fit in an 0-ring 137 mounted at the outlet 135. Externally of the container, the tube 136 terminates ' in an actuating knob 115. The bore of the tube 136 communicates with a bore 138 in the actuating knob 115, leading to an outlet nozzle 105. Internally of the container, the tube 136 has a side opening 122 and terminates in a valve member 110. The valve member 110 is biassed by biassing means (not shown, for reasons of clarity) against a sealing- ring 116. The valve member 110 is provided on its underside with a spear 139, which has its point 140 adjacent the disc 131. When the actuating knob 115 is first depressed, the spear 139 breaks the seal formed by the disc 131, so that the foam-forming mixture. passes into the space defined by the cap 132. The mixture then passes into the tube 136 via opening 122, and thence out through the nozzle 105, whenever the actuating knob is depressed. This construction- has the advantage that reliance is not placed on the seal betwen the valve member and the sealing ring until after the device is first used. The generally more effective seal provided by the sealing disc means that the device has an improved shelf-life as compared with the embodiment of Figure 1. O PI Foam-forming mixtures for use in the device of the present invention are now illustrated in the following Examples:- EXAMPLE ' 1. An aerosol device such as that illustrated in Figure 2 was charged with a mixture of the following components: Component % by weight Paraffin wax 10 R12 refrigerant 60 Rll refrigerant 30 Release of the mixture from the aerosol device yielded a refrigerant foam which was eminently suited for use in the emergency treatment of burns. The foam was relatively non-adherent to skin, and maintained a temperature of approximately 0°C for about 20 minutes. EXAMPLE 2. An aerosol device was charged with the following mixture: Component % by weight Paraffin wax 8 Petroleum jelly 12 Refrigerant Rll 35 Refrigerant R12 30 Refrigerant R114 23 On release from the devic , the mixture yielded a refrigerant foam which was particularly well suited to equine veterinary use. The foam had a lower melting point than that obtained with the mixture of Example 1. O PI This had the advantage that it was able to wet the hair of the horse to which it was applied, allowing more rapid transfer of heat from the site of the injury. Also, the flow velocity of the foam-forming mixture in the nozzle of the aerosol device, (and therefore the frequency of the sound produced) was reduced. This had the advantage of being less disturbing to a tempera¬ mental animal, such as a race horse. The foam produced initial cooling to approximately 8°C, which is particularly beneficial to athletic injuries. It will be understood that the present invention has been described above purely by way of example, and modi- factions of detail can be made within the scope and spirit of the invention.

Claims: CLAIMS 1. A device for delivering a refrigerant foam, said device comprising a vessel containing a topically acceptable foam-forming material and a topically accept- able refrigerant under pressure, and means for delivering from said device an intimate mixture of the foam-forming material and the refrigerant, the boiling point of the refrigerant being chosen such that on delivery from the device the refrigerant serves as a foaming agent for the foam-forming material. 2. A device according to claim 1, wherein the refrig¬ erant comprises one or more fluorinated hydrocarbons. 3. A device according to claim l.or claim 2, wherein the refrigerant comprises a low boiling component having a boiling point in the range -60°C to 10°C, and a high boiling component having a boiling point in the range 10°C to 40°C. 4. A device according to claim 3 wherein the low boiling component constitutes from 40 to 80% by v/eight of the foam-forming mixture, and the high boiling component constitutes from 10 to 40% by weight of said mixture. 5. A device according to claim 1 or claim 2, wherein the refrigerant comprises a low boiling component having a boiling point in the range -40°C to -20°C, a high boiling component having a boiling point in the range 10°C to 40°C, and an intermediate boiling com¬ ponent having a boiling point in the range -20°C to 10°C. 6. A device according to claim 5 wherein the low boiling component constitutes from 20 to 50% by weight of the foam-forming mixture, and the high boiling compo¬ nent constitutes from 20 to 40% by weight of said mixture, and the intermediate boiling component constitutes from 15 to 30% by wei ght of sai d mixture. OMPI • 7. A device according to any of claims 3 to 6 wherein the low boiling component is dichlorodi luoromethane, the high boiling component is trichloromonofluoro¬ methane, and the intermediate boiling component, if present, is dichlorotetrafluoroethane. 8. A. device according to any preceding claim wherein the foam-forming material constitutes from 5 to 30% by weight of the foam-forming mixture. 9. A device according to any preceding claim, wherein the foam-forming material comprises a paraffin wax. 10. A device according to claim 9 wherein the foam- forming material is a mixture of a paraffin wax and petroleum jelly. 11. A device according to any preceding claim, wherein said device being arranged to deliver first an adhesion promoting agent, and then said foam-forming mixture. 12. A foam-forming mixture for use in the treatment of soft-tissue injuries, said mixture comprising a topi¬ cally acceptable refrigerant and a topically acceptable foam-forming material. 13. A foam-forming mixture according to claim 12, where¬ in said refrigerant is as defined in any of claims 2 to 7. 14. A foam-forming mixture according to claim 12 or claim 13, wherein the foam-forming material is as defined in any of claims 8 to 10. O PI

Inventors: BRIGGS JOSEPH HODGSON, TURNER STANLEY BERRY, BRIGGS, JOSEPH, HODGSON, TURNER, STANLEY, BERRY
Applicants: BRIGGS JOSEPH HODGSON, TURNER STANLEY BERRY, BRIGGS, JOSEPH, HODGSON, TURNER, STANLEY, BERRY
Application year: 1984
Main classification: A61F7
IPC codes: A61D1, A61F7, A61K9, A61L26, B65D83, B65D85, C09K3