WO2007028975A1

WO2007028975A1 - Improvements in or relating to cryogenic therapeutic treatments

Info

Publication number: WO2007028975A1
Application number: PCT/GB2006/003280
Authority: WO
Inventors: Mohammed Firoz Hussein
Original assignee: Mohammed Firoz Hussein
Priority date: 2005-09-07
Filing date: 2006-09-06
Publication date: 2007-03-15
Also published as: GB2431108A; GB0518219D0

Abstract

The present invention relates to cryogenic therapeutic treatments and, in particular provides a mechanism and device to facilitate in the application of cryogenic fluids for use in therapeutic treatments. Cryosurgery is the destruction of skin using cold. The use of liquified gas coolants to cool and freeze tissue has long been known. The main agent used in medical treatment is liquid nitrogen. This is conveniently applied via a cryospray at -196°C. Liquid nitrogen applied with a cotton bud is much less cold and less destructive. Cryogenic fluids such as liquid nitrogen, which pose little risk to the environment, have also been used extensively to cool surfaces. Unfortunately, for many applications and in particular cosmetic surgery this low temperature can seriously damage and kill human tissue. Extreme care must be taken. Given the disadvantages of current human epidermal and mucosal epidermal skin cooling techniques, a need exists for a device that provides a safe and economical alternative. The present invention seeks to provide a solution to the problems addressed above. The present invention seeks to provide an improved apparatus for the topical application of cryogenic substances in epidemiological, gynaecological and other histological treatments and the like. In one aspect, the invention provides an apparatus for the treatment of epidermal lesions by cryogenic substances or fluids, the apparatus comprising an applicator for the dispensing of cryogenic fluid in the treatment of lesions in epidermal tissue, the applicator comprising a generally cup shaped element.

Description

IMPROVEMENTS IN OR RELATING TO CRYOGENIC THERAPEUTIC TREATMENTS

Field of Invention

The present invention relates to cryogenic therapeutic treatments and, in particular provides an apparatus and device to facilitate in the application of cryogenic fluids for use in therapeutic treatments.

Background to the Invention

Cryosurgery is the destruction of tissues using the properties of freezing. The use of liquified gas coolants to cool and freeze tissue has long been known. The main agent used in medical treatment is liquid nitrogen. This is conveniently applied via the spraying of a cryogenic agent. Liquid nitrogen applied with a cotton bud is much less cold and less destructive. Commonly employed cryogenic fluids are liquid nitrogen and dimethyl ether/propane aerosol (this formulation has previously been employed by a product known as Histofreezer ™). This achieves a skin temperature of between zero and - 50⁰C. It is well known to produce a cooling effect by the evaporation of a liquid. For example, dichlorotetrafluoroethane (also known as Frigiderm™ or Freon 114) has been used extensively in cosmetic surgery to cool and stiffen skin. An advantage of dichlorotetrafluoroethane is that under normal conditions its maximum skin cooling temperature is -40⁰C, even though its boiling point is +3.80⁰C. Ethyl chloride is an efficient skin refrigerant but has the undesirable qualities of being explosive when mixed with air, toxic to the liver, as well as being capable of causing general anesthesia upon inhalation by the patient or doctor.

It has been proven that colder cryorefrigerants (Cryosthesia -60⁰C also known as dichlorodifluoromethane or Freon 12, boiling point -29.8⁰C) can produce maximum skin cooling temperatures of -66⁰C, but care needs to be taken in the application, since improper use can cause unwanted tissue damage and resulting in serious complications, such a scarring, depigmentation and infection. Unfortunately, all of these chlorofluorocarbon refrigerants have been shown to damage the ozone layer and their use is now strictly controlled if not banned in many countries. Dry ice or frozen carbon dioxide has also been used to cool the skin. However, applying dry ice to an epidermal surface can quickly produce temperatures of close to -78⁰C. "Dry ice" application has been shown to be destructive to the epithelium layer and is now more commonly used to improve the penetration of skin peeling chemicals by removing the epidermis just prior to peel-acid application. Because temperatures of -78⁰C. are rapidly approached with little room for manual control, direct solid state, "dry ice" contact is not a viable option for controlled cooling of skin prior to or during dermabrasion if the surgeon is to minimize thermal damage. Surgeons have reported that solid carbon dioxide contact produced scarring because it was applied under pressure that occluded the otherwise warming local blood supply.

Certain cryosurgery procedures are applied prior to mechanical dermabrasion. The hardness of the skin freeze has been shown to be critical in controlling the depth of dermabrasion and classified as either superficial (0.2-0.5 mm), moderate (0.5-1.0 mm), or deep (1.5-2.0 mm) according to Ayres {Ayres S III: Superficial chemosurgery, including combined technique, using dermabrasion, in Epstein E, Epstein E Jr, editors: Skin surgery. Springfield, 111., 1982, Charles C Thomas, Publisher.} The skin temperatures achieved and thus the hardness of the skin is dependent upon the type of freezing agent, skin temperature prior to treatment, operating room temperature and numerous other factors. A recent and particularly valuable therapeutic use of cryogenics is to provide localized freezing of a part of a human or animal body in order to remove a wart or other growth from epidermal tissue. In this use, a refrigerant is maintained under pressure in a can and is dispensed, via a valve and an outlet tube, through a cotton wool bud which surrounds the discharge end of the outlet tube and which is placed on or near the site to be treated. Handheld, liquid nitrogen cryosurgical devices and other refrigerant devices have been used to treat a wide range of common skin lesions. Conditions commonly treated in general practice are: Verruca (warts), Actinic Keratoses, Seborrheic Keratoses, Molluscum, Papilloma (skin tags), Lentigines (age spots), Condyloma (genital warts), and Basal Cell Carcinoma (skin cancer). EP057030 provides a hand-held device for the cryogenic treatment of a body, comprising a container for a cryogenic fluid and an application end, the container being in the form of an isothermal reservoir comprising at one of its ends a wide filler opening which can be sealed by a stopper while its other end has passing through it a channel or conduit for the flow of Equid, this other end being equipped with an adapted application nozzle, the sealing stopper of the reservoir being provided with a vent for the escape of the vaporised fraction of the cooling liquid and comprising, if appropriate, means for regulating the cross-section of this vent. WO2004042763 provides an applicator for an anti-microbial solution and includes an aerosol container and an applicator pad assembly having a hollow arm. The hollow arm has a proximal end attached to an aerosol cap and a distal end having a flanged arm plate to receive a foam applicator pad. The aerosol cap is removeably attached to the aerosol container. A solution flow control is in communication with the aerosol container for selectively dispensing the anti-microbial solution. The aerosol container holds the antimicrobial solution under pressure and flow is controlled by a pressure-sensitive flow control tab.

US6226996 provides a device that uniformly cools a surface to a specified temperature using a mist of cryogenic fluid. The device comprises a cryogenic fluid reservoir, a valve for controllably releasing the fluid through an atomizing nozzle, a non-contact temperature sensor, and a control unit to display the measured temperature. The control means can optionally pre-set the desired surface temperature and control the valve. The application of mist can be controlled. However, this device does not Limit the area of application of the cryogenic fluid.

One device which has been used to assist the physician in providing localised refrigerant comprises an acrylic plate having frusto-conical apertures: the plate is placed upon a patients skin such that an aperture surrounds a lesion; the plate will typically have several apertures of varying sizes such that an appropriate amount of refrigerant can be placed upon a lesion without damaging skin surrounding a lesion. These plates are typically employed with liquid nitrogen, since, in some cases, accurate dispensing of such fluid from an aerosol canister filled with refrigerant can be problematic. One such type of acrylic plate device is marketed by Brymill Cryogenic Systems having a trade name "Cryoplate".

Whilst this type of device can assist in an improved localisation of refrigerant fluid and protection of adjacent skin areas, it is a relatively expensive item and needs to be subjected a sterilisation treatment after each use; furthermore this type of plastics can be easily scratched, limiting the number of times that the device can be used: scratched and/or otherwise damaged plates do not inspire any patient confidence. A further disadvantage is that the plate, once placed upon a patient's skin may be susceptible to leakage of a refrigerant fluid since the edges of the frusto-conical opening may not be maintained in continuous circumferential contact with the skin because of the contours of the body, patient movement and the fact that the lips of the frusto-conical aperture are coplanar with the underside of the planar acrylic member. Furthermore, the absence of a. handle on a material having non-textured surface may lead to slippage in use. A still further problem is that the device needs to be held down manually, whereby the physician's hand or the hand of his assistant/ the patient is susceptible to intimate contact with cryogenic fluid in the event of a spillage. This application has neither been used nor advocated with aerosol based cryogenic products.

Given the disadvantages of current human epidermal and mucosal epidermal skin cooling techniques, a need exists for a device that provides a safe and economical alternative.

Object of the Invention

The present invention seeks to provide a solution to the problems addressed above. The present invention seeks to provide an improved apparatus for the topical application of cryogenic substances in epidemiological, gynaecological and other histological treatments and the like.

Statement of Invention

In accordance with a first aspect of the invention, there is provided an applicator for the dispensing of cryogenic fluid in the treatment of lesions in epidermal tissue, the applicator comprising a generally cup shaped element having side and base walls, the side wall defining a circumferential rim, the walls defining an inlet for a cryogenic fluid and a number of exhaust apertures to allow for the exhaust of evaporated cryogenic fluid from a treatment area about which the rim surrounds. In use, the cup is held against the skin over the area to be treated. Cryogenic material is supplied via a tube from a cryogenic source such as an aerosol equipped with a valve to effect a controlled release of cryogenic gas. When the liquid gas is released it collects within the 'cup' thereby affecting only the portion of the skin contained within the 'cup' area.

The inlet for the cryogenic fluid can be disposed within the base wall of the cup; furthermore, the inlet can comprise a tube which extends inwardly from the wall. The inlet can be centrally displaced. The inlet can be connected to an aerosol refrigerant by means of an intermediate tube.

A simple exhaust may be provided, which could vent by means of a small diameter integrally formed tube which can enable attachment with a flexible plastics exhaust tube, whereby to prevent the release of exhaust gases from occluding vision for a physician during treatment.

Two or more exhaust apertures, may be provided, which can be distributed symmetrically about the inlet. Conveniently, the exhaust apertures have a diameter of between 1 and 3 mm. The exhaust gases can be guided through an exhaust tube. Conveniently, the exhaust tube extends in a generally parallel fashion with intermediate tube

A handle can be provided, which enables the applicator to be correctly placed with a minimum of risk of injury to an operator of the applicator. Conveniently, the applicator is manufactured from a clear plastics material. Preferably, the cup is of a double walled construction, whereby accidental contact by a physician does not cause distress or affect procedure. The rim can have a diameter of between 5 and 35 mm. The walls of the cup can extend between 4 - 20 mm in height, or more if desired/required by clinical need, from the rim towards the base.

An endoscope can also be provided with a viewing lens within the cup, such that a view of the lesion may be obtained during treatment, as appropriate when treating lesions within orifices such as cervical lesion, oral or anal. Superficial lesions of the skin are ordinarily easily visualised and monitored since the cups are conveniently made of a clear transparent plastic.

Conveniently, the source of cryogenic fluid comprises an aerosol canister of freezer spray.

To assist in the containment of cryogenic fluid, it may be convenient if a cup has a resilient foam or elastomeric plastics element arranged around a peripheral rim thereof.

Brief Description of the Figures

For a better understanding of the present invention, reference will now be made, by way of example only, to the Figures as shown in the accompanying drawing sheets, wherein:- Figure 1 illustrate a first embodiment of the invention in perspective view; Figure 2 shows an example of a first embodiment in use; Figures 3a and 3b show in detail a large size cup in accordance with the invention;

Figure 4a and 4b show in detail a medium size cup in accordance with the invention; Figure 5a and 5b show in detail a small size cup in accordance with the invention; Figure 6 shows a first alternative type of cup; Figure 7 shows a second alternative type of cup;

Figures 8 and 8b show a third alternative type of cup; and,

Figure 9 shows a fourth alternative type of cup.

Detailed description of the Preferred Embodiments

There will now be described, by way of example only, the best mode contemplated by the inventor for carrying out the present invention. In the following description, numerous specific details are set out in order to provide a complete understanding to the present invention. It will be apparent to those skilled in the art, that the present invention may be put into practice with variations of the specific

With reference to Figure 1, there is shown a first embodiment of the invention, wherein an apparatus 10 comprises a cup element 12 which has an inlet 13 which receives a tube 16 for a supply of cryogenic fluid, for example from an aerosol canister 20 of cryogenic fluid. The inlet 13 can conveniently comprise a tube having a diameter corresponding to the inside diameter of the tube 16, to enable a push-fit connection. It is also possible to have a snap-fit connection configured. The inlet may extend for a few centimetres so that connection may be made with a supply tube outside of an internal cavity. Conveniently the canister of cryogenic fluid is an aerosol canister of "freezer spray", obtainable, for example, under the trade name Dermafreeze (TM).

An aerosol can, will have a valve through which the cryogen may be released. The valve is worked by manually depressing it using an actuator: Different types of actuator can be employed, depending on the particular technique being applied. It is preferable that the release of cryogenic fluid can be varied in a controlled fashion. In Figure 1, the actuator has a female opening into which a clear, translucent or opaque plastic tube is inserted. The other end of a plastic tube functions as a female opening to allow the insertion on the cup. A clip mechanism may be employed to ensure a secure fit although an alternative method may be utilised for this purpose. The plastic tube will be available in different sizes which may vary for example, to provide high levels of insulation or enable the flow rate to be increased.

In use, with reference to Figure 2, the cup 12 will be held firmly against the epidermis of the skin EP, the rim of the cup surrounding a lesion to be treated. As the actuator is pressed the cryogen is released and it travels down the tube and is forced to make contact with the skin as the cups do not petmit it to escape. The effect of cryogen on the skin is to freeze it, in correspondence with the principles of thermodynamics. The dermis D will also be affected, to a certain extent, dependent upon the type of treatment being applied.

The cryogen is conveniently supplied by way of a cryogenic liquid retained within an aerosol can under pressure. As soon as it is released it rapidly expands to a gaseous state. In doing so it takes energy, in the form of heat, from the surrounding area. Therefore by taking the heat away from the skin it causes a cooling effect. The rapid nature of the expansion and the physical properties of the cryogen mean that it can cool to very low temperature and freeze down to -50⁰C. This effect can only be possible whilst the cryogen is in its liquid state. Therefore if it takes longer to travel to the site of action the less likely it is to have a more profound effect.

There have been several prior art techniques that have been widely employed: Direct spraying of the cryogen to the skin - this technique has a moderate effect but requires copious amounts of cryogen to be sprayed to the area for the freezing to take effect and the spraying needs to be continued. One drawback is that the area being treated can only be controlled by the distance of the spray nozzle from the skin. So therefore the further back one is, the larger the target area and the closer one is the smaller the area. Nevertheless even when held closely, the spray disperses over a large area and has the potential risk on bouncing/ splashing back off the skin and towards the user. The further away a spray nozzle is from a treatment area reduces the impact as the liquid has begun to expand or almost evaporated by the time it reaches the skin.

A further technique that has been employed is that of dripping a cryogen directly on the skin. By pressing the actuator of a spray element gently, the cryogen can be released at a slow rate and this has an effect of creating drips. Drips so produced can be allowed to fall on the skin but again there is a lack of control in the targeting of specific areas and also has the feature that the drip may evaporate or 'run/roll' away from the target area this potentially freezing a healthy area.

Another technique is to allow drips of the cryogen to pass on an adhesive pad which has been placed over the size and area of treatment. This improves on the direct dripping technique. However it has drawbacks in that it may evaporate before hitting the adhesive pad and that which does saturate the adhesive pad must first freeze the pad, as it is made of a conductive material, before it has any effect of freezing the skin. Furthermore the area of treatment is obscured and the extent of treatment and progress cannot be monitored. A still further technique has been to employ a foam (or cotton wool) tipped applicator. The cryogen is sprayed into the foam/bud until it starts to drip which indicates that it is saturated. The foam tip is then applied to the skin which allows the liquid to come into contact. This is an effective method but has two drawbacks. One is that the liquid will draw energy from the surrounding atmosphere and that the foam tip, which is made of a conductive material, has to be held very firmly, indenting the skin to allow sufficient contact area for an appreciable effect. Further the area of treatment is obscured.

In contrast, and in accordance with the invention, the use of cups enables a cryogen to make immediate contact with the skin and the cup is maintained in contact under some pressure which slows the rate of expansion of the cryogenic liquid, thereby increasing its effectiveness. The cup must be manufactured from a low thermal conductivity material, conveniently from a plastics material, whereby the cryogenic fluid is only able to draw energy from the skin as the cup is significantly less thermally conductive. The cup is also clear so the area of treatment is visible at all time as is the amount of cryogen sprayed onto the area. The diameter of the cup allows the user to choose the appropriate area of treatment. Furthermore the cup need only be held in position using light pressure so as not to allow leakage of liquid. By the provision of vents, as the gas expands it can flow out of the enclosure defined between the cup and the skin vent.

With reference to Figures 3 — 5, the cups can be of various sizes to accommodate different sizes of lesions. Elliptical cups can also be employed. The diameters of the rims of the cups can vary from 50mm to 5mm, although there will be a greater requirement for 15, 10 & 5mm cups. The cups are conveniently made from polyformaldehyde, organic glass although other types of plastics materials such as acrylic plastics can be used, such the cups are clear / transparent so as to allow a user to visually monitor the extent and progress of treatment. In contrast other systems currently being used for similar purposes obscure the area of treatment during the treatment period.

With reference to Figure 6, there is shown a cup 62, wherein the inlet tube 66 extends within the cup by a distance X to ensure that the fluid makes good initial contact with the lesion. In addition to having specific vents as disclosed above, it would also be possible to have a valve which enables cryogenic fluids to pass into the cup through an inlet, which inlet subsequently acts as an outlet after the cryogenic fluid supply ceases and the pressure within the cup due to the presence of evaporating cryogenic fluid causes the valve to enable such evaporating gaseous fluid to flow out. This has the advantage that only one aperture is required in the cup and thus the cup can be manufactured in a relatively simple manufacturing process. Alternatively, the cup may have single or multiple vent holes, as discussed above, which will allow immediate venting. The beneficial features described in relation to the single aperture cup are equally applicable, except that there is no initial build up of pressure. The rim of the cup may be fitted with a soft circumferential contact pad to assist in retention of cryogenic fluid without the need for significant pressure against the skin, once applied.

Other embodiments are shown in Figures 7, 8a and 8b. In Figure 7, a cup 70 is provided with a concentric inlet/outlet tube arrangement 60, 67. Figures 8a shows a sectional view through an embodiment 80 with a vent pipe 87 integrally formed with the cup, wherein the vent can be connected to a flexible plastics tube. By having a vent extension enables areas not previously as having been considered to be treated as being capable of being treated, since internal parts may be treated vent; To have a vented extension which in itself directs the venting away from a particular are or user or which may be used by attaching a flexible or other tube which takes the vent further away from the area of treatment. One particular advantage of this would be in the treatment of cervical warts (intra-vaginal lesions). Current systems do not allow a safe method of applying cryogen to this part of the female anatomy and the method just described would safely fulfil the objectives.

A further advantage provided by the present invention is that mucosal epidermal tissue such as ENT tissue, anal tissue (in particular the perinium) and cervical tissue can be readily treated. The treatment of petinium, mucosal oral and cervical lesion has not been noted in previous aerosol cryogen product as their delivery mechanisms did not permit controlled treatments of these areas. In the treatment of internal tissues, the use of a cup with an elongate inlet, corresponding to a 10-20cm portion of inlet tube may be indicated. A still further advantage provided by the present invention arises with the treatment of warts, especially elongate warts including those commonly referred to as tag warts. Many warts extend outwardly from the epidermis; previous treatments have resulted in cryogenic fluids being applied to one side of the wart and the treatment is not effective. In contrast and in accordance with the present invention, the use of a fluid cryogen enables the fluid to surround the base, walls and tip of the wart, whereby removal of the wart is ensured and can be accomplished in a straightforward fashion. Referring now to Figure 9, a handle 99 is shown attached to the cup 90. The Figure is shown in plan view, with an inlet 92 and an outlet 97. Specific advantages of having a handle are numerous, allowing increased control in delivery of a cryogenic fluid.

Claims

CLAMS:

1. An applicator for the dispensing of cryogenic fluid in the treatment of lesions in epidermal tissue, die applicator comprising a generally cup shaped element having side and base walls, the side wall defining a circumferential rim, the walls defining an inlet for a cryogenic fluid and a number of exhaust apertures to allow for the exhaust of evaporated cryogenic fluid from a treatment area about which the rim surrounds.

2. An applicator according to claim 1 wherein the inlet for the cryogenic fluid is disposed within the base wall of the cup.

3. An applicator according to claim lor 2, wherein inlet comprises a tube which extends inwardly from the wall.

4. An applicator according to claim 1, wherein there is a single aperture iα the cup and the inlet has a valve associated therewith whereby inlet and exhaust gases can flow through the same aperture.

5. An applicator according to any one of claims 1- 4, wherein there is provided two or more exhaust apertures, which are distributed symmetrically about the inlet.

6. An applicator according to any one of claims 1 — 5 wherein the inlet is connected to an aerosol refrigerant by means of an intermediate tube.

7. An applicator according to any one of claims 1- 6 wherein there is provided a handle which enables the applicator to be correctly placed with a minimum of risk of injury to an operator of the applicator.

8. An applicator according to any one of claims 1- 7, wherein the applicator is manufactured from a clear plastics material.

9. An applicator according to any one of claims 1 - 8, wherein the exhaust apertures have a diameter of between 1 and 3 mm.

10. An applicator according to any one of claims 1 — 9, wherein the rim has a diameter of between 5 and 35 mrn.

11. An applicator according to any one of claims 1- 10, wherein the walls of the cup extend 4 — 20 mm from the rim towards the base.

12. An applicator according to any one of claims 1 - 11, wherein the cup has a double walled construction.

13. An applicator according to any one of claims 1 - 12, wherein, the exhaust gases are guided through an exhaust tube.

14. An applicator according to claim 13, wherein exhaust tube extends in a generally parallel fashion with intermediate tube.

15. An applicator according to any one of claims 1 - 14, wherein there is provided an endoscope.

16. An applicator according to any one of claims 1- 15, wherein there is provided a foam/elastomeric material about the circumferential rim of the cup.