Dispensing system for use in cryogenic skin treatment

Abstract

The invention relates to a dispensing system for use in cryogenic skin treatment that is capable of targeted delivery of a cryogen at a high rate, thereby achieving rapid freezing of targeted skin tissue. The dispensing system of the present invention uses a cryogen that contains dimethyl ether and is designed to deliver the cryogen in an accurate and very effective manner.

Claims

1. A dispensing system for use in cryogenic skin treatment, the system comprising: (a) a container having an internal volume of 10-200 ml and comprising a liquid phase in direct contact and in equilibrium with a gas phase at a pressure of 2.5-8 bar, the liquid phase comprising at least 50 wt. % liquefied dimethyl ether; (b) an actuatable valve attached to the container, the valve comprising: (i) a mixing chamber having an operational internal volume of 10-600 μl and comprising an inlet and an outlet, wherein the inlet comprises a Venturi tube having an entry cone for receiving the gas phase from the container, an exit cone, and a constricted section that connects the entry cone with the exit cone, the constricted section or the exit cone comprising a liquid inlet for receiving the liquid phase from the container, the liquid inlet having a cross-sectional opening area of 8×10.sup.−3 to 100×10.sup.−3 mm.sup.2 and the constricted section having a cross-sectional opening area of 0.012 to not more than 0.5 mm.sup.2 and at least 150% larger than the cross-sectional opening area of the liquid inlet; (ii) a nozzle connected to the outlet of the mixing chamber, the nozzle comprising an orifice with a cross-sectional opening area in the range of 8×10.sup.−3 to 100×10.sup.−3 mm.sup.2; (c) a spacer attached to the container or to the valve, the spacer being adapted for defining a predetermined distance between the orifice of the nozzle and a skin surface to be treated; the distal end of the spacer being provided with a spray opening, the distance (h1) between the spray opening and the orifice of the nozzle being in the range of 2 to 25 mm; wherein the dispensing system is arranged to be used in a top-down position with the distal end of the spacer being placed in direct contact with skin around a skin surface to be treated and the nozzle being located below the container; and wherein the apparatus is configured such that upon actuation of the valve during such top-down use, the gas phase enters the mixing chamber through the Venturi tube thereby creating a Venturi effect that (i) draws the liquid phase into the Venturi tube via the liquid inlet and (ii) causes dispersal of the liquid phase into the gas phase; and the resulting cryogenic liquid-in-gas dispersion is expelled through the orifice of the nozzle and through the spray opening of the spacer to deliver the cryogenic dispersion to the skin surface to be treated at a rate of 30-200 mg/s.

2. The dispensing system according to claim 1, wherein the entry cone of the Venturi tube is connected to a drawing tube that extends into the container.

3. The dispensing system according to claim 1, wherein the liquid inlet of the Venturi tube connects the constricted section or the exit cone of the Venturi tube with the interior of the container adjacent to the valve.

4. The dispensing system according to claim 1, wherein the constricted section of the Venturi tube has a cross-sectional opening area of 0.12 to 0.5 mm.sup.2.

5. The dispensing system according to claim 1, wherein the Venturi tube has an entry cone of 30-90 degrees.

6. The dispensing system according to claim 1, wherein the Venturi tube has an exit cone of 10-40 degrees.

7. The dispensing system according to claim 1, wherein the cryogenic dispersion is expelled through the orifice of the nozzle forming a spray cone with an angle of not more than 40 degrees.

8. The dispensing system according to claim 1, wherein the liquid phase comprises at least 90 wt. % dimethyl ether.

9. The dispensing system according to claim 1, wherein the liquid phase comprises at least 90 wt. % of a mixture of dimethyl ether and one or more alkanes selected from propane, n-butane and isobutane.

10. The dispensing system according to claim 1, wherein the spray opening of the spacer has a minimum diameter of 2-10 mm.

11. The dispensing system according to claim 1, wherein the actuatable valve comprises a fixed part fixed to the container and comprising the Venturi tube and the liquid inlet and forming a circumferential sidewall of the mixing chamber, the valve further comprising a moveable part that is moveable with respect to the fixed part between a valve-open position and a valve-closed position and comprises the nozzle, wherein the nozzle has a circumferential side wall surrounding a channel for the liquid-in-gas dispersion and a through opening in the side wall, wherein the through opening is arranged such that in the valve-open position the through opening fluidly connects the mixing chamber and the orifice of the nozzle, and in the valve-closed position the moveable part and fixed part together seal off a passage between the mixing chamber and the through opening.

12. The dispensing system according to claim 11, wherein the fixed part is provided with a gasket through which the moveable part extends, wherein when the moveable part is in the valve-closed position the gasket seals off the passage between the mixing chamber and the through opening.

13. The dispensing system according to claim 1, wherein at an end opposite from the nozzle the container has a top wall, the system further comprising a holder for moveably holding the container therein, wherein the spacer and the nozzle are fixed with respect to the holder and the holder surrounds a substantial portion of a circumferential outer wall of the container while leaving the top wall at least partially free for allowing the valve to be actuated by a user by pressing his or her finger on the top wall end of the container relative to the holder towards the spray opening.

14. A method of treating skin, the method comprising topically applying a cryogenic dispersion onto the skin of a person or animal using a dispensing system according to claim 1.

15. The method according to claim 14, wherein the cryogenic dispersion is applied to a wart, a mole, a freckle, a skin tag, an age spot or a lentigine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Below the present invention is further explained with reference to the drawings, in which

(2) FIGS. 1A, 1B, 1C, 1D, 1E: schematically show cross-sectional representations of a dispensing system, and details thereof, according to the present invention;

(3) FIGS. 2A, 2B, 2C: show representations of a dispensing system according to the present invention, provided with a holder around the container

(4) FIGS. 1A and 1B respectively show a dispensing system 1 according to the present invention, with an actuatable valve 20 closed so that fluid and gas from within the interior of the container are blocked from exiting the container through nozzle 30, and with the valve 20 open so that the nozzle is in fluid communication with the interior of the container 10. Though in the embodiments shown the nozzle comprises two parts, 32, 33 which are attached to each other, it will be appreciated that the nozzle may instead be formed as a single unit.

(5) The container has an internal volume of about 120 ml, for containing a liquid phase 11 and a gas phase 12 which are in direct contact with each other. In the embodiment shown, the liquid phase and gas phase are both at a pressure of around 4bar, and the liquid phase 11 consists of liquefied dimethyl ether. Alternatively, the liquid phase 11 may consist of a 3:1. (w/w) mixture liquefied dimethyl ether and liquefied propane.

(6) The nozzle 30 of the valve 20 is attached to the container 10. A spacer 40 is fixed to the container and ensures that orifice 31 of the nozzle 30 remains spaced apart from spray opening 41 of the spacer 40. The orifice of the nozzle has a relatively small cross-sectional opening area in the range of 0.018-0.07 mm.sup.2 through which a directed spray of liquid-in-gas dispersion 50 can be ejected towards the opening 41 of the spacer, which opening 41 has a larger cross-sectional opening area in a plane normal to the longitudinal direction of the nozzle. During use, e.g. when cryogenically treating a wart, the dispensing system is positioned such that a contact surface 48 of the spacer makes contact with the skin surrounding the skin area to be treated and such that the skin to be treated 80 is accessible through the opening 41. A view-port 46 in the sidewall 47 of the spacer allows a view of the skin to be treated from a side of the spacer facing away from the contact surface 48, thus facilitating positioning of the dispensing device as well as inspection of the skin during treatment. The view port preferably comprises an opening in the sidewall 47, so that condensation from the liquid-in-gas dispersion can leave the spacer without having to remove the spacer from the skin and without blocking view of the skin to be treated.

(7) The valve 20 comprises a fixed part 18 that is fixed to the container 10, and a moveable part 19 which is moveable relative to the container between a valve-closed position, shown in FIG. 1A, and a valve-open position, shown in FIG. 1B. FIG. 1C shows the valve of 20 in greater detail, in the valve open position, however with the space 40 not shown for reasons of clarity. The moveable part 19 and the fixed part 18 together form a mixing chamber 21 with an inlet 22 for supply of liquid phase 11 and phase 12 to the mixing chamber. The volume of the mixing chamber depends on the position of the moveable part 19 relative to the fixed part, and has a volume of about 200 μl when the upon full actuation of the valve to the valve-open position. For receiving gas phase 12 from the container, the inlet is provided with a Venturi tube 24 having an entry cone 25 that in turn is connected to a drawing tube 29 that extends into the container. The Venturi tube tapers towards a constricted section 26 to which it is connected, which section 26 in turn is connected to an exit cone 27 that debauches in the mixing chamber 21. The constricted section 26 further comprises a liquid inlet 28 for receiving liquid phase 11 from the container 10. When the device is in the top-down position and the moveable part 19 is moved in the valve-open position, as shown in FIGS. 1B and 1C, the propellant gas 12 flows through the Venturi tube 24, causing underpressure in the liquid inlet 28, as a result of which liquid 11 is drawn into the mixing chamber 21 together with the propellant gas 12, where the two phases are further mixed to form a liquid-in-gas dispersal. Also with reference to FIG. 1B, the liquid-in-gas dispersal 50 is ejected out of the mixing chamber 21, through a through-opening 15 in side wall 16 of the nozzle 30, and out of nozzle orifice 31 to the spray opening 41. The moveable part 19 can be held in the valve-open position for any desired amount of time, e.g. until the pressure within the container is substantially equal to the pressure outside of the dispenser system.

(8) FIG. 1D schematically shows a cross-section isometric view of a portion of the dispensing system, with the moveable part 19 is in in the valve open position, which illustrates how liquid-in-gas dispersal can travel from the mixing chamber 21 along recessed portions 14 on the inner circumference of the fixed part 18 to the outlet 23 of the mixing chamber.

(9) Referring to FIG. 1D as well as to FIG. 1A, when the moveable part 19 is in the valve-closed position, the fluid communication between the mixing chamber 21 and the interior of the container 10 where the gas phase 12 and liquid phase 11 are contained remains open. However, fluid communication from the mixing chamber 21 to the nozzle 30 via through opening 15 is sealed off by gasket 60 through which the nozzle 30 extends, and which gasket sealingly abuts a shoulder 63 of the fixed part 18 that is urged against the gasket by spring 64. The gasket 60 is thus compressed between the shoulder 63 of the moveable part 19 and the bottom wall 62 of the container 10. An additional gasket 61 is attached to the moveable part 19 for preventing gas and/or liquid from escaping from the container 10 along the outer surface of the moveable part.

(10) FIG. 1E shows a detail of a portion of the nozzle 30 and the spacer 40. The nozzle orifice 31 has a relatively small diameter d1 of between 0.15-0.30 mm to ensure that the liquid-in-gas dispersal 50 is ejected from the orifice in a narrow spray cone. The angle α of the spray cone is about 30 degrees. The contacting surface 48 of the spacer 40 is in contact with a skin portion 80 while leaving skin to be treated free. The liquid-in gas dispersal 50 can thus reach the portion of skin to be treated that lies under the spray opening 41. The spray opening 41 lies at a fixed distance h1 of between 2 and 25 mm from the orifice 31, independent of whether the valve is in the valve-open or in the valve-closed position.

(11) FIGS. 2A, 2B and 2C respectively show a schematical cross-sectional side view, a side view and an isometric view of the dispensing system according to the present invention, further comprising a holder 70 for holding the container therein in such a manner that the container 10 can be moved relative to the holder along the longitudinal direction L of both. Though the container 10 typically comprises a metal, the holder may be made from a plastics material that is more flexible than the container. During use, position of the holder 70 relative to the nozzle 30 and the spacer 40 is fixed, regardless of whether the valve is open or closed. The spacer 40 is attached to holder at a bottom side 71 of the holder 70, while at its opposite topside 72 the holder leaves free a portion of the top wall 9 of container 10 which lies opposite to the bottom wall 62 of the container. When the spacer 40 is in contact with skin to be treated, a user can press the top wall 9 of the container 10 downwards relative to the holder and towards spray-opening 41, e.g. by pushing his finger or thumb against the top wall 9, in this manner also moving the moveable part 19 of the actuator valve 20 to the valve-open position.

(12) As can be seen more clearly in FIG. 2A, the length L1 of the container 10 is smaller than the length L2 of the holder 70 and space 40 combined. More in particular, the holder extends over a length greater than the length of the container held therein. Near its top side 72, the holder is provided with an opening 74 through which the container 10 can be inserted into and taken out of from the holder 70. The opening has an edge 73 which, when projected onto the top wall 9 of the container in a plane normal to the longitudinal direction of the container, overlaps a portion of the top wall 9 of the container 10. The edge 73 thus helps prevent the container from accidentally falling out of the holder 70. When the gas phase and/or liquid phase in the container has been used up, the container can be taken out of the holder to be replaced with another container.