US 3696813 A
An improved method for cooling a probe tip of a cryosurgical instrument is provided by supplying a two phase refrigerant comprising a gaseous phase and a liquid phase to a restricted orifice adjacent an expansion chamber of the instrument, conveying the refrigerant through said orifice into said expansion chamber for expanding the gaseous phase into the chamber thereby providing a Joule-Thomson refrigeration effect and for providing additional cooling of the chamber by the evaporation of the liquid phase therein, and, conveying an effluent gas of the expansion chamber to atmosphere. A cryosurgical instrument comprises an expansion chamber formed of a high thermal conductivity material having an outer surface thereof which is adapted for contacting body tissue which is to be treated, a means for conveying a gaseous refrigerant from a source thereof to said expansion chamber, said means including a stationary body forming an orifice of fixed dimensions through which said gas expands into said chamber for cooling said chamber, and, a means for exhausting said gas to atmosphere, said exhaust means including a flow channel communicating between said chamber and a quick acting flow valve, said valve biased for interrupting a flow path through the valve between said exhaust conduit and atmosphere and selectively operable to establish the flow path through the valve.
Description (OCR text may contain errors)
United States Patent Wallach [451 Oct. 10, 1972  CRYOSURGICAL INSTRUMENT Ronald M. Wallach, Norwalk, Conn.
 Assignee: Cryomedics, lnc., Bridgeport, Conn.
 Filed: Oct. 6, 1971 ] Appl. No.: 189,469
Primary ExaminerMeyer Perlin Attorney-William Kaufman 1 1 ABSTRACT An improved method for cooling a probe tip of a crypsurgical instrument is provided by supplying a two phase refrigerant comprising a gaseous phase and a liquid phase to a restricted orifice adjacent an expansion chamber of the instrument, conveying the refrigerant through said orifice into said expansion chamber for expanding the gaseous phase into the chamber thereby providing a Joule-Thomson refrigeration effect and for providing additional cooling of the chamber by the evaporation of the liquid phase therein, and, conveying an effluent gas of the expansion chamber to atmosphere. A cryosurgical instrument comprises an expansion chamber formed of a high thermal conductivity material having an outer surface thereof which is adapted for contacting body tissue which is to be treated, a means for conveying a gaseous refrigerant from a source thereof to said expansion chamber, said means including a stationary body forming an orifice of fixed dimensions through which said gas expands into said chamber for cooling said chamber, and, a means for exhausting said gas to atmosphere, said exhaust means including a flow channel communicating between said chamber and a quick acting flow valve, said valve biased for interrupting a flow path through the valve between said exhaust conduit and atmosphere and selectively operable to establish the flow path through the valve.
12 Claims, 4 Drawing Figures LIL CRYOSURGICAL INSTRUMENT This invention relates to surgical apparatus utilizing cryosurgical techniques. The invention relates more particularly to an improved cryosurgical instrument.
Surgical techniques have been developed for treating defective or diseased body tissue by reducing the temperature of the tissue to relatively low values. Various cryosurgical instruments are known for aiding the medical practitioner in this form of treatment. Generally, these instruments include a probe tip which is initially placed in contact with the tissue to be treated and which is then cooled. The cooled probe tip is normally maintained in contact with the treated tissue for a short interval of time. In practice the cryosurgical instrument is required to provide a reduction in temperature of the probe tip to temperatures of less than --55 C. in order to achieve a useful heat exchange and lowering of tissue temperature. It is also necessary that these low temperatures be attained rapidly after the probe tip contacts the tissue so that the tissue freezing is localized and the patient is not subjected to prolonged cold treatment. Additionally, it has been found that body tissue undesirably adheres to a cooled treatment probe at these low temperatures and it is therefore necessary to provide means for rapidly warming the treatment probe in order to facilitate removal of the probe from the body tissue.
In a known form of cryosurgical instrument, a refrigerant fluid under pressure is expanded into a chamber through a restricted orifice thus producing a cooling effect commonly known as the Joule-Thomson effect. The probe tip, which is formed by an outer surface of the chamber, is thereby rapidly cooled. The instrument also incorporates means for effecting the rapid warming of the probe tip in order to facilitate removal of the probe from the body tissue.
Various arrangements have been employed for cooling and for warming the probe tip. In one arrangement, the flow of a refrigerant gas to the expansion chamber is controlled by a valve located upstream from the chamber. Effluent gas from the chamber is exhausted to atmosphere. Cooling of the probe tip is accomplished by actuating the valve for enabling the flow of refrigerant gas to the expansion chamber and then to atmosphere. Warming of the probe tip is accomplished by interrupting the flow of gas to the expansion chamber and heating the probe tip by electrical means including a coil heater positioned in the probe tip.
In another cryosurgical instrument, probe tip cooling is provided by unseating a flow valve element located downstream of the expansion chamber and simultaneously forming a restrictive orifice at the chamber inlet by contacting an orifice seat with a moveable conduit. A refrigerant fluid then flows from a source, through the orifice and exhausts through the unseated downstream valve. Warming of the probe tip is accomplished by seating the downstream valve element and simultaneously separating the moveable conduit from the orifice seat thus permitting refrigerant fluid at ambient temperatures to flood the expansion chamber.
These arrangements as well as other various cryosurgical instrument arrangements are relatively complex and costly. At times they are relatively difficult for a medical practitioner to handle and do not provide him with the degree of manipulative facility necessary in a medical procedure where the practitioner must devote his close attention to the progress of the procedure. In addition, these known instruments do not attain the cooling and warming rates which are desirable with this medical procedure.
Accordingly, it is an object of this invention to provide an improved method and apparatus for cryosurgical treatment.
Another object of the invention is to provide an improved method for cooling a probe tip of a cryosurgical instrument.
Another object of the invention is to provide a cryosurgical instrument having a relatively non-complex refrigerant fluid flow arrangement for both cooling and warming the probe tip of the instrument.
Another object of the invention is to provide an improved cryosurgical instrument employing a gaseous refrigerant for both cooling and warming the probe.
Another object of this invention is to provide a cryosurgical instrument which extends to the medical practitioner a relatively greater degree of manipulative facility than has been permitted by prior instruments.
Another object of the invention is to provide a cryosurgical instrument of improved reliability.
Another object of the invention is to provide an improved cryosurgical instrument employing a refrigerant maintained under relatively high pressure.
A further object of the invention is to provide a relatively non-complex and a relatively low cost cryosurgical instrument.
In accordance with the general features of this invention, an improved method for cooling a probe tip of a cryosurgical instrument is provided by supplying a two phase refrigerant comprising a gaseous phase and a liquid phase to a restricted orifice adjacent an expansion chamber of the instrument, conveying the refrigerant through said orifice into said expansion chamber for expanding the gaseous phase into the chamber and providing a Joule-Thomson refrigeration effect and for providing additional cooling of the chamber by the evaporation of the liquid phase therein, and, conveying an effluent gas of the expansion chamber to atmosphere, In accordance with a more particular feature of the method of this invention, a two phase refrigerant is supplied for introduction into the evaporation chamber by conveying a saturated gas refrigerant toward the restrictive orifice and by precooling the saturated gas prior to introduction into the chamber thereby condensing a portion of the saturated gas. Precooling of the saturated gas phase refrigerant is accomplished in one embodiment by flowing the effluent gas of the chamber about the saturated gas which is supplied to the orifice.
In accordancewith the features of the apparatus of this invention, a cryosurgical instrument comprises an expansion chamber formed of a high thermal conductivity material having an outer surface thereof which is adapted for contacting body tissue which is to be treated, a means for conveying a gaseous refrigerant from a source thereof to said expansion chamber, said means including a stationary body forming an orifice of fixed dimensions through which said gas expands into said chamber for cooling said chamber and a means for exhausting said gas to atmosphere, said exhaust means including a flow channel communicating between said chamber and a quick acting flow valve for completing a flow channel between said conduit to atmosphere. The flow valve is biased for normally interrupting the flow of effluent gas from the chamber thereby maintaining a refrigerant gas at ambient temperature within said expansion chamber and maintaining said chamber in a relatively warm state. The quick acting valve is selectively operable for completing a flow path from said exhaust conduit to atmosphere thereby effecting the continuous flow of refrigerant gas into said chamber and causing a cooling thereof. In accordance with other more particular features of the apparatus of this invention, the refrigerant gas comprises a gas under relatively high pressure and said quick acting valve means is adapted for automatically enabling the flow of gas from said expansion chamber to atmosphere when the pressure within said instrument exceeds a predetermined safe level.
The cryosurgical, apparatus of this invention is further advantageously constructed in a generally pistol shaped configuration having a hand grip thereof and a trigger mechanism providing for the actuation of the 1 quick acting valve,. and a probe tip supported at a distal segment of a flow conduit.
These and other objects and features of the invention will be apparent with reference to the following specification and to the drawings wherein:
FIG. 1 is a perspective view of an embodiment of a cryosurgical instrument for practicing the present invention;
FIG. 2 is a side view, partly in section and partly cut away, of the cryosurgical instrument of FIG. 1;
FIG. 3 is a view taken along lines 33 of FIG. 2; and
FIG. 4 is a sectional view of an alternative quick acting valve for use in the instrument of FIGS. 1 and 2.
Referring now to the drawings and particularly to FIG. 1, a cryosurgical instrument is shown arranged in a generally pistol shaped configuration. The instrument includes a gripping stock formed by stock members 9 and 10, a triggering lever arm 12 for actuating a quick acting valve, and an elongated tubular shaped body 13 which extends from the stock and supports a probe tip 14 near a distal segment thereof. A refrigerant is coupled to the pistol shaped instrument by a flexible con-v duit 18. As indicated in greater detail hereinafter, the tubing 18 is coupled to a rotary shut off valve 20 which interrupts the flow of refrigerant from a source 22 strument, the lever arm 12 is squeezed toward the stock thereby effecting the flow of refrigerant through the instrument and cooling of the probe tip 14. Release of this lever arm interrupts the flow of refrigerant and warming of the probe tip occurs. The general pistol shaped configuration of this instrument and the convenient trigger lever arm 12 for operating a quick acting valve of the instrument as well as the elongated tubular body 13 which supports the probe tip at a remote point from the stock provide a cryosurgical instrument for the medical practitioner which is easily handled and readily operated. The medical practitioner is thereby free to direct almost his complete attention to the progress of the surgical procedure.
Reference is now made to FIGS. 2 and 3 for a more detailed description of the construction and operation of this instrument. The probe 14 is formed into a generally conically shaped configuration having an outer surface 23 thereof which converges to a tip 24. The tip 24 is brought into physical contact with tissue to be treated during the cryosurgical procedure. Although a particular probe and probe shape are illustrated in the drawings, it is noted that the probe can assume various other particular configurations in order to satisfy the particular needs of the specific cryosurgical procedure which is practiced with the instrument. The probe 14 is fabricated of a high thermal conductivity material such as silver or other suitable material. A circular shoulder 26 is integrally formed in the probe 14 and a circular adapter plate 28 is positioned at this shoulder and secured thereto by silver soldering. The probe 14 and the adapter plate 28 define an internal volume 30 comprising an expansion chamber.v
A refrigerant which is conveyed toward the chamber 30 for cooling the chamber comprises in accordance with a feature of the invention a saturated gas which is maintained at a relatively high pressure at ambient temperature. A saturated gas exhibits a high thermal conductivity relative to unsaturated gas and is therefore an efficient heat transfer medium for removing heat from the chamber. Exemplary gases for use in the instrument comprise carbon dioxide and nitrous oxide. FIG. 2 illustrates the storage tank 22 which is partially filled with carbon dioxide 32 in the liquid phase and with saturated carbon dioxide gas. The gas is confined within the tank 22 above the level of the liquid phase carbon dioxide. This pressurized saturated gas is supplied to the instrument through a supply tank shut off valve 34, through a fluid coupling yoke 36, and through the flexible high pressure tabulation 18. A pressure regulator (not illustrated) may be attached to the yoke 36 when the cryosurgical instrument is utilized as an accessory which is coupled directly to the supply 22.
The regulator will avoid excess pressure in relatively warm climates. The tubulation 18 extends through an aperture 38 formed in a rear surface 40 of the pistol grip.
The gripping stock members 9 and 10 are formed for example of a plastic material. Each member has a pistol grip shape and a flange formed along a periphery thereof. The pistol grip members are butted together at these flanges and form an internal volume in an upper portion of the stock which encloses the shut off valve 20, a portion of the inlet and exhaust flow chamber and a quick acting control valve 42 for the instrument. The members 9 and 10 define an exhaust chamber 43 which extends between the valve and an outlet aperture 44 in the stock. Screws 46 extend between the pistol grip members and secure the members together. I
The instrument includes a means for conveying a refrigerant from an inlet thereof to the expansion chamber. This means comprises the shut off valve 20, an inlet conduit 51 and a body 52 forming a restricted orifice. The flexible refrigerant supply line 18 is coupled to the shutoff valve 20 which comprises a rotary operated ball valve assembly, the details of which are known in the art. For purposes of clarity in FIG. 2 of the drawing, the shut off valve assembly 20 is shown in FIG. 2 to be rotated by from its preferred position as illustrated generally in FIG. 1. The valve is mounted to the stock member 9 by a threaded shoulder which extends through an aperture in grip member 9 and a nut 50 which engages the threaded shoulder. The tubuduit 51 which comprises an elongated tubular body for conveying refrigerant from an outlet of the shut off valve to the expansion chamber 30 is seated at one end at an outlet aperture 55 of the valve 50 and extends to the expansion chamber 30 at a distal segment thereof. This refrigeration inlet tubulation 51 is coupled to the valve by a conventional coupling for high pressure use including a conically flared end segment and a ferrule positioned about the body 51 near the flared segment (not illustrated). The tube 51 is locked to the threaded body of the valve 20 by a locking nut 56.
The inlet tubulation body 51 extends along its length successively through an adapter coupling 58 and through a T fitting 60. The outer diameter of the tubular body 51 and the inner diameter of the adapter 58 are selected to provide for support of the body 51 by the adapter 58. The tubular body 51 is therefore supported at its seated position at the outlet aperture 55 of the valve 20 and by the inner surfaces of the adapter member 58; The outer diameter of the tubular body 51 and the inner diameter of the T fitting 60 are selected for providing an annular space between these bodies within the T fitting 60. Adapter 58 is locked to the T fitting 60 by a locking nut 62 which engages the threaded body of the T fitting at one end thereof and is engaged by a locking nut 64 which is rotably coupled to the ball valve locking nut 56.
A restrictive orifice is provided for the instrument by the plug body 52 which is supported at an outlet aperture of the tubular body 51 adjacent the expansion chamber 30. The plug body 52 is shown positioned within the tubular body and is secured therein by silver soldering. The body 52 includes a centrally formed bore 66 extending axially therethrough for providing a restricted orifice through which the two phase refrigerant which is supplied'to the orifice is conveyed to the expansion chamber 30. Orifice 66 establishes a pressure drop between the pressure of the refrigerant upstream of the expansion volume and the pressure of the expansion chamber. A relatively large bore may be utilized as the orifice thereby greatly reducing plugging and interruption of refrigerant flow.
A means for exhausting gases to the atmosphere from the expansion chamber is provided and includes an annular flow channel 67 formed between the tubular bodies 13 and 51, and, the quick acting flow control valve means 42 adapted for establishing and interrupting the flow of effiuent gas from this conduit to atmosphere. The tubular body 13 is seated at an outlet aperture 68 of the T fitting 60. A seated segment thereof is conically flared and the tube is secured to the T fitting by a ferrule (not illustrated) and a locking nut 70. The body 13 thus extends from and is supported by the T fitting 60. An aperture 72 is provided in the pistol grip from which the tube 13 extends. The tube 13 is concentrically positioned with respect to the tubular body 51 and has an inner diameter greater than the outer diameter of the tubular body 51 thereby establishing an annular shaped exhaust flow channel 67 between these bodies. The adapter plate 28 includes an integral cylindrically shaped extension 73 having a bore 74 therein and into which the tubular body 13 extends. The adapter plate 28 is secured to the body 13 by silver soldering for example. Probe 14 is thereby supported at a distal position from the pistol grip. Effluent gases of the chamber 30 will flow through the exhaust channel 67 to an outlet aperture 75 of the T fitting 60. The direction of refrigerant flow in the instrument is indicated in FIG. 2 by the arrows.
An inlet of the manually operable quick acting valve means 42 is coupled to the outlet aperture 75 of the T fitting 60. This valve includes a flow path extending therethrough and is adapted for alternatively establishing and interrupting the flow of effiuent gas from the expansion chamber 30 and through the exhaust channel 67 to atmosphere. The quick acting valve 42 includes a core body 82 having a cyclindrically shaped inlet segment 84 which is internally threaded and which engages a threaded segment on an outer surface of the T fitting 60. The core body 82 includes a similar cyclindrically shaped internally threaded outlet segment 86 which engages a threaded muffler body 88 having a disc 90 positioned in an aperture thereof and operating to muffle the sound of effiuent gas flowing from the valve 42. The disc 90 is formed of sintered bronze or stainless steel or other suitable material. The core body 82 further includes a bore 92, a channel 94 and a channel 96. A flow passage through the valve is provided by the channel 94 which communicates between the inlet segment 84 by the volume of the bore 92, and by the channel 96 which communicates between the bore 92 and the outlet segment 84 and muffler element 88. The bore 92 is concentrically aligned with a bore 98 of relatively larger diameter which is formed in the core body 82. A valve element 100 extends into the bores 98 and 92. A coil spring 102 is positioned about the valve element 100 and is compressed between a nut 106 and a shoulder segment of the valve element 100. A groove 110 is formed in the shoulder segment for receiving an O ring 112. The O ring provides a seal between the valve shoulder and the inner surface of the bore 98.
The valve element 100 includes an inner segment 113 thereof having a face 114 which seats against an inlet aperture of the channel 96 and interrupts the flow path through the valve. The valve actuating lever 12 is pivotally coupled by a pin 116 to a segment of the valve element 100 which extends through an aperture in the nut 106. As the lever 12 is squeezed counterclockwise by finger pressure as viewed in FIG. 2, the lever 12 pivots about an outer edge of the nut 106 and forces the valve element 100 to travel to the left against the biasing action of the coil spring 102. The face 114 is thereby unseated from the entrance aperture of channel 96 and a flow passage is provided through the valve. As the lever 12 is released, the spring 102 immediately causes the face 114 to reseat and interrupts the flow path.
An upper edge of the lever 112 is beveled and an aperture which is formed in lever 12 for receiving the pin 116 is spaced from an edge of the lever by a distance sufficient for providing that lever 12 is rotable about the pin in a clockwise direction as viewed in FIG. 2. Clockwise rotation will translate the location of the pin 16 to the left thereby unseating the face 114. As the lever is rotated 90 clockwise as viewed in FIG. 2, an end segment of the lever will contact the nut 116 thereby biasing the valve in a locked open position. Rotation of the lever 12 by applying finger pressure thereto for causing counterclockwise motion of the lever will release the valve from this locked open position.
In operation, the refrigerant is conveyed through the conduit 51 to the body orifice 52 at relatively high pressure wherein it expands to'a lower pressure within the expansion chamber 30. This expansion is accompanied by a refrigerant effect commonly known as the Joule- Thomson effect which cools the probe 14 and rapidly lowers the temperature of the tip 24. The gases which thus expand, flow from the expansion chamber 30 through the annular exhaust channel 67, through the flow path of the quick acting valve 42, and through the muffler 88 and channel 43 to atmosphere. Cooling of the probe is accomplished by squeezing the triggering lever 12 thereby causing the flow of refrigerant through the instrument. The refrigerant will continuously flow from the reservoir 22, through the inlet means, through the orifice 66, and from the expansion chamber 30 to atmosphere. Release of the trigger lever 12 interrupts the flow path in the valve 42. As a result, a back pressure immediately develops. within the channel 67 and the pressure in chamber 30 rapidly rises to the pressure maintained in the source 22 thereby interrupting the further flow of refrigerant. When the flow is thus interrupted, the gases which occupy the tubular body 51, the chamber 30 and the annular exhaust conduit space 67 is substantially at ambient temperature and operates to rapidly raise the temperature of the probe 14 for safe removal of the probe tip from thetissue being treated.
Control of the temperature of the probe tip 14 to desired intermediate temperatures between ambient temperature and maximum low temperature can be effected by a repetitive actuation and release of the lever 12. However, this form of temperature control requires continuous attention by the medical practitioner for regulating the temperature. In accordance with another feature of the invention, an adjustable temperature control is provided by a flow valve means 42 which is adapted for establishing a metered flow of refrigerant. FIG. 4 illustrates an alternative arrangement of the valve of FIG. 1 which is adapted for metering the flow of refrigerant. The valve includes a threaded body 134 having an internally threaded segment thereof which engages the valve core 82. A valve element 152 is positioned within the body 134 and a tapered seating segment 146 is positioned adjacent the channel 96 for interrupting the flow channel when fully seated and for establishing an orifice with the valve seat when displaced from the seat. A lever arm 130 is coupled to a segment of the element 152 which extends'through a -cap 142. The cap 142 is threaded internally and engages an externally threaded outer segment of the body 134. A biasing spring 150 is provided and establishes a force on the element 152 which maintains the element in a normally seated position for interrupting flow through the valve. Rotation of the lever arm 130 in a clockwise direction will cause the element 152 to travel to the left asviewed in FIG. 4 against the compressive force of the spring 150. The tapered face of the segment 146 will thus unseat and establish a flow path through the valve. The distance traveled by the valve element 152 toward the left will establish the size of the flow orifice between the tapered segment 146 and its seat formed in the core body 82 at the inlet of channel 96. This distance is in turn established by the position of the cap 142 on the body 134. The cap 142 is rotable to different axial positions along the length of the body 134 and an inner surface thereof functions as a stop for the element. Thus by adjusting the position of the cap 134, the amount of unseating of the valve element 146 can be accurately controlled. After this position is located, a locking nut 140 is rotated against the collar thereby, locking the collar in a fixed position. Thus by squeezing the lever 130 in a clockwise direction, the valve can be caused to unseat by a predetermined amount corresponding to a refrigerant flow rate which will establish a desired probe tip temperature. The medical practitioner need only squeeze the lever 130 for unseating the valve element and the need for repetitively unseating and seating the valve is eliminated.
In accordance with another feature of this invention, a saturated gas refrigerant is utilized and the effluent gas from the expansion chamber 30 flows over a portion of the refrigerant inlet means. By this technique, portions of the inflowing saturated refrigerant gas condense within the tubular body 51 to supply a liquid phase which is conveyed'along with the vapor phase of the refrigerant into the expansion chamber 30. The orifice diameter employed with the gas herein is suitably larger than could be used with a wholly liquid refrigerant. As a result, both the gas and liquid phases are sprayed into the expansion chamber. This liquid phase refrigerant remains within the expansion chamber for a short interval of time during which time it absorbs latent heat of vaporization. Thus, a double cooling action is provided. By pre-cooling the saturated refrigerant gas which is flowing tothe restrictive orifice, there is provided both a vapor and liquid phase refrigerant. The vapor phase expands through the orifice and in accordance with the Joule-Thomson effect provides a refrigerating effect thereby cooling the applicator head 14. In cooperation with this cooling effect, the liquid phase which has been provided by precooling is sprayed into the expansion chamber 30 and absorbs a quantity of heat over a period of time equivalent to its latent heat of vaporization. It has been found that the combined cooling established by this combination of Joule-Thomson effect and the latent heat of vaporization rapidly lowers the temperature of the probe 14 and provides very rapid cooling of the tip 24.
As indicated hereinbefore, a typical saturated gaseous refrigerant for use with the described cryosurgical instrument comprises saturated carbon dioxide gas. At
ambient temperatures, the saturated gaseous phase of this refrigerant is maintained at a pressure generally on the order of 800 psi. If this pressure is greatly exceeded as might occur due to a malfunction in the system, a hazard to safety could then exist. In accordance with another feature of this invention, the cryogenic instrument includes means for automatically providing a flow path between the source 22 and atmosphere at a predetermined pressure in excess of safe operating pressures. Referring once again to FIG. 2, the shoulder 112 of the valve element includes a face thereof which seats against a shouldersurface of the bore 98. The valve face 1 14 has a diameter which is less than the diameter of the bore 92 thereby defining an annular space about the valve element within this bore.
Pressure within the instrument is continuously applied through the channel 94 to this annular space and this pressure will be exerted against the face 120 on the shoulder of the valve element. When this pressure becomes excessive, it exerts a force on the face 120 which causes the valve element to move toward the left as viewed in FIG. 2 and unseat the valve face 114'. A flow path is thereby automatically established within the valve which relieves the pressure within the instru ment. The pressure at which the valve element will automatically unseat is determined by the surface area of the valve face 120 exposed to the pressure and the spring constant of the spring 102. These factors can be selected to provide a desired pressure release when the pressure within the instrument exceeds a predetermined safe level. As a secondary safety feature, the flexible inlet line 18, which is formed of nylon for example, is selected to have a burst strength at a predetermined value greater than the pressure at which the valve element unseats automatically.
In one embodiment of the invention which is not deemed limiting in any respect the following parameters were employed. A refrigerant comprising saturated CO gas at 840 psi was applied to a cryosurgical instrument of the type shown in H0. 2 wherein the tubular member 51 was formed of an 11% inches length of stainless steel tubing having a A; inch outside diameter and a 0.028 inch wall thickness. The tubular body 13 was formed of a 9 inches length of stainless steel having a A inch outside diameter and a 0.035 inch wall thickness. The body includes a 0.013 inch bore 66 forming a restrictive orifice. The volume of the expansion chamber 30 was selected to provide a 70 to 1 expansion in the volume of the gas phase. Under these conditions, the probe tip 24 which was formed of silver reduced from ambient temperature to 50 C. in about five seconds when the probe was suspended in air under ambient conditions. Release of the lever 12 interrupted the flow of refrigerant gas and resulted in a warming of the probe tip which was effected for a safe removal of the probe tip from body temperature within a period of about five seconds.
Thus an improved cryosurgical method and apparatus have been described which enhance the practice of cryosurgery. The described process and apparatus facilitate the handling and operation of a cryosurgical instrument as well as provide enhanced cooling and warming of the applicator tip.
While I have described a particular embodiment of my invention, various modifications may be made thereto by practitioners in the art without departing from the spirit of the invention and the scope of the appended claims.
What is claimed is:
1. A cryosurgical instrument adapted for operation in a cooling mode and in a rapid warming mode comprising:
means defining an expansion chamber; said means including a body formed of a high thermal conductivity material and having a surface thereof shaped for contacting body tissue and providing heat transfer with the tissue; refrigerant supply means for conveying a gaseous refrigerant from a source to said expansion chamber, said means including a stationary body defining a flow restriction through which said gas is introduced into said chamber for effecting a Joule Thomson expansion of said gas thereby cooling said chamber; and,
means for conveying an effluent gas from said chamber to atmosphere during said cooling mode, said means including a quick acting two position flow valve having means for positioning said valve in an open position to enable flow and means for positioning said valve in a closed position to interrupt flow and an exhaust flow channel communicating between said chamber, said quick acting flow valve and atmosphere, said valve including means for selectively opening said flow channel during said cooling mode and closing said flow channel during said warming mode.
2. The cryosurgical instrument of claim 1 wherein said exhaust flow channel is arranged for conveying the effluent gas from said chamber about a portion of said refrigerant supply means for pre-cooling said gaseous refrigerant prior to introducing said refringerant through said flow restricting means into said chamber, and said gaseous refrigerant comprises a saturated gas.
3. The cryosurgical instrument of claim 1 wherein said refrigerant supply means includes an elongated supply conduit, said flow restricting means is positioned near a-distal end of said supply conduit, means are provided for supplying a gaseous refrigerant to an inlet end of said supply conduit, said exhaust channel means is formed by an exhaust conduit which is positioned with relation to said supply conduit for forming an annular space therebetween, and said quick acting valve is coupled in a flow path between said outlet conduit and atmosphere.
4. The cryosurgical instrument of claim 3 wherein said quick acting valve includes a valve seat and a valve element, means for biasing said valve for causing said valve element to seat and thereby interrupt said valve flow path and an operating lever for unseating said valve element.
5. The cryosurgical instrument of claim 4 wherein said quick acting valve includes means for establishing the flow of a metered amount of gas less than an amount of maximum flow through said valve.
6. The cryosurgical instrument of claim 4 wherein said valve includes means for automatically unseating said valve element and providing a flow path to atmosphere when the pressure within said instrument exceeds a predetermined safe pressure.
7. The cryosurgical instrument of claim 6 wherein said valve includes a channel formed therein which communicates with said exhaust channel, said valve includes means exposed to the pressure of said valve channel for establishing a force on said valve element which counteracts the force established by said biasing means and unseats saidvalve face thereby establishing a flow path through said valve to atmosphere from said channel when the pressure in said instrument exceeds a predetermined safe level.
8. The cryosurgical instrument of claim 7 wherein said lever arm includes means for enabling said arm to be rotated in a first direction for unseating said valve element and said lever arm further includes means for enabling said arm to be rotated in a second opposite direction for establishing a force on said valve element which operates against the force of said biasing means thereby locking said-valve element in an unseated position.
9. The cryosurgical instrument of claim 3 wherein said supply and exhaust conduits are concentrically orientated and said quick acting valve means is posi tioned near an end of said exhaust conduit and is spaced radially therefrom, a hand gripping support member formedabout said valve thereby providing a pistol shaped hand grip for said instrument, said valve actuating lever positioned for quick acting operation by drawing the lever arm towards said hand grip.
10. An improved method for cooling and warming an applicator head of a cryosurgical instrument in contact with body tissue comprising the steps of:
conveying a saturated gaseous refrigerant at substantially ambient temperature and relatively high pressure toward a stationary flow restricting means communicating with an expansion chamber in the head of the instrument;
cooling said refrigerant prior to introduction into said chamber by effecting heat exchange with an effluent gas emanating from said chamber thereby condensing a portion of said refrigerant forming a two phase refrigerant comprising a major amount of a gaseous phase and a minor amount of a liquid phase;
introducing the two phase refrigerant through said stationary flow restricting means into the-relatively low pressure expansion chamber, said chamber being in contact with body tissue, effecting a Joule-Thomson expansion of said gaseous phase and'boiling of said liquid phase, thereby cooling said expansion chamber; and,
conveying an effluent from said expansion chamber to atmosphere during cooling of said chamber and then cutting off the flow of said effluent gas trapping a sufficient body of gaseous refrigerant at substantially ambient temperature within said expansion chamber to effect rapid warming of said chamber.
11. An improved method as defined in claim 10 wherein the saturated gaseous refrigerant is carbon dioxide.
12. An improved method as defined in claim 10 wherein the saturated gaseous refrigerant is nitrous oxide.