Abstract: Home-use applicators for non-invasively removing heat from subcutaneous, lipid-rich cells via phase change coolants, and associated devices, systems and methods. A device in accordance with a particular embodiment includes an applicator releasably positionable in thermal communication with human skin, and a coolant vessel having a coolant. The device further includes a heat transfer conduit operatively coupled to the applicator and housing a heat transfer fluid that is isolated from fluid contact with the coolant. A heat exchanger is operatively coupled between the coolant vessel and the heat transfer conduit to transfer heat between the heat transfer fluid and the coolant, and a fluid driver is operatively coupled to the heat transfer conduit to direct the heat transfer fluid between the applicator and the heat exchanger.

Abstract: Methods and systems for delivering electromagnetic energy to a patient's tissue with an attendant reduction in the pain experienced by the patient due to tissue heating. Electromagnetic energy is delivered from an electrode through a skin surface to heat a first region of tissue beneath the skin surface and a second region of the tissue between the first region and the skin surface. During the delivery of the electromagnetic energy, a temperature of the second region of the tissue is caused to oscillate between at least one maximum temperature and at least one minimum temperature. The temperature oscillation may be induced by a timed sequence of cryogen pulses delivered to the electrode, which in turn extracts thermal energy out of the second region of tissue through the contacting skin surface.

Abstract: During cryotherapy, using an endoscope that extends within a patient to a cold treatment site, the device of the invention vacuums gas from the site through radial intake ports to a cylindrical space in an evacuation chamber held elastically circumferentially about the distal end of the endoscope tube that carries the cryoprobe to the site.

Abstract: A method for tightening and rejuvenating skin utilizing a cryogenic applicator, which includes the steps of holding a handle of a barrel of the cryogenic applicator in a hand, fluidly communicating the barrel with a source of a biocompatible non-toxic cryogenic fluid to supply the biocompatible non-toxic cryogenic fluid through a hollow interior of the barrel, out through a plurality of openings in a distal portion of the barrel, and onto a head of the cryogenic applicator, rolling the head quickly, smoothly, and evenly over the skin being treated for a period of time in an order of hundredths or tenths of a second, and sparging the biocompatible non-toxic cryogenic fluid onto the skin quickly, evenly, and smoothly when the head is rolled on the skin, and thereby tightening and rejuvenating the skin.

Abstract: Low temperature lesion formation apparatus, systems and methods. The apparatus includes a base member and an inflatable element carried by the base member.

Abstract: Cryosurgical instruments and methods utilizing improved heat transfer characteristics. A cryosurgical device includes: a tubular housing; a cryogen supply passage; a heat exchange enhancing member in the housing, disposed along a longitudinal axis of the housing; an annular cooling passage between the heat exchange enhancing member and the tubular housing; a tip cooling and cryogen flow directing section that transmits a temperature of a cryogen flow to the tip, and an insulation element in the tubular housing.

Abstract: Self-contained disposable cryosurgical devices dispense a cryogenic fluid, such as a stream of liquid nitrous oxide, carbon dioxide or argon. The cryosurgical devices include a container, including a reservoir containing a cryogenic fluid, a flow passage configured to receive the cryogenic fluid from the reservoir, a valve assembly configured in an ergonomic housing, and a dispensing head. The device further includes at least one filter disposed in the flow passage configured to facilitate the flow of the cryogenic fluid. The valve assembly includes a valve body and valve slide that is actuated to effect the flow of the cryogenic fluid through the flow passage to patient target. The housing includes an activation lever with an eccentric hub that primes the device for use when a container is loaded into the housing and the activation lever is closed.

Abstract: Stabilizing an object in the body of a patient involves the injection of a lower critical solution temperature (LCST) material or other flowable material into the body of the patient so that the material contacts the object. The LCST material or other flowable material then forms a gel in the body such that the object is contained at least partially within the gel and thereby stabilized by the gel such that the object can then be easily fragmented within the body and/or retrieved from the body.

Abstract: An apparatus and methods for treating lesions on skin are presented. The apparatus collects information about a lesion and can automatically determine a course of treatment for the lesion. The device can include a controller that positions the nozzle proximate to a surface region of the lesion and automatically dispenses a pulse of the cryogenic fluid from the nozzle. The controller then positions the nozzle proximate to another surface region of the lesion and automatically dispenses a pulse of the cryogenic fluid from the nozzle.

Abstract: An apparatus for providing cryotherapy to an equine hoof for treatment or prevention of laminitis includes a housing configured to receive a hoof of the equine having laminitis such that at least a lower portion of the hoof is enclosed by the housing. The housing has a chamber within, in communication with a source of cooling fluid. The housing may be supported in a boot. A heat transfer surface of the housing delivers cooling to a sole area of the equine hoof, thereby treating or preventing laminitis, for example, without directly contacting the hoof with fluid. Tubing for flow of cooling fluid to and from the chamber extends upwardly along each of the legs of the equine being treated to prevent crimping or entanglement of the tubing due to movement of the equine.

Abstract: A cryosurgical system featuring both cooling and heating utilizing a single type of cryogen but from two different sources. The liquid cryogen cools the tip of a cryosurgical instrument in the cryosurgical system, such as a cryoprobe or cryocatheter. The gaseous cryogen is further heated by a heating element, preferably an electrical heating element, supplying the heating needed for the thaw and release parts of the cryo treatment procedure. Thus, the cryosurgical system supports the freeze/thaw cycle of the operation of the cryosurgical instrument.

Abstract: A cryogenic catheter includes an outer flexible member having at least one cryogenic fluid path through the flexible member. The at least one fluid path is defined by a plurality of flexible members disposed within the outer flexible member.

Abstract: A cryosurgical instrument for obtaining a tissue sample with a probe, including the probe including a probe head onto which the tissue sample is frozen and a probe shank for guiding the probe head to the tissue sample, a supply means for supplying a fluid into an expansion chamber configured such that supplied fluid expands therein for cooling the probe head, and a removal means connected to the expansion chamber for removing the expanded fluid therefrom via at least one opening on a distal end of the probe to remove the expanded fluid to an outer region outside the probe. A method for cooling a probe head of a cryosurgical probe including supplying a fluid to an expansion chamber near the probe head, expanding the fluid so that heat energy is withdrawn from the probe head, and removing the expanded fluid in a distal region of the probe.

Abstract: A cryocatheter system includes a first handle portion having a proximal end, a distal end, a first fluid flow path, and a second fluid flow path; a second handle portion having a proximal end, a distal end, a first fluid flow path, and a second fluid flow path; and a catheter having a proximal end, a distal end, a first fluid flow path, and a second fluid flow path. The distal end of the first handle portion is matable with the proximal end of the second handle portion to place the respective first and second fluid flow paths of each handle portion in fluid communication; and the distal end of the second handle portion is matable with the proximal end of the catheter to place the respective first and second fluid flow paths of the second handle portion and the catheter in fluid communication.

Abstract: A method of cryogenically treating a tissue region is provided, including positioning a treatment region of a medical device proximate the tissue region; transferring coolant in a substantially liquid phase from a coolant reservoir to a subcooler; transitioning the coolant from the liquid phase into a supercritical state; transferring the supercritical coolant to the treatment region; changing the coolant from the supercritical state to at least one of a liquid phase and a gaseous phase at the treatment region; ablating the tissue region; and evacuating coolant from the treatment region of the medical device.

Abstract: An instrument for use on a body site is provided comprising a bushing having portions, a coolant source, and a bore, wherein the instrument may be used to introduce an implant, instrument, or tool to a body site. After the implant, instrument, or tool is introduced to a body site, at least one portion of the bushing may be removed. A method of use for the instrument is also provided. A kit including the instrument is further provided.

Abstract: A catheter is adapted to exchange heat with a body fluid, such as blood, flowing in a body conduit, such as a blood vessel. The catheter includes a shaft with a heat exchange region disposed at its distal end. This region may include hollow fibers which are adapted to receive a remotely cooled heat exchange fluid preferably flowing in a direction counter to that of the body fluid. The hollow fibers enhance the surface area of contact, as well as the mixing of both the heat exchange fluid and the body fluid. The catheter can be positioned to produce hypothermia in a selective area of the body or alternatively positioned to systemically cool the entire body system.

Abstract: A method for tightening and rejuvenating skin utilizing a cryogenic applicator, which includes the steps of holding a handle of a barrel of the cryogenic applicator in a hand, fluidly communicating the barrel with a source of a biocompatible non-toxic cryogenic fluid to supply the biocompatible non-toxic cryogenic fluid through a hollow interior of the barrel, out through a plurality of openings in a distal portion of the barrel, and onto a head of the cryogenic applicator, rolling the head quickly, smoothly, and evenly over the skin being treated for a period of time in an order of hundredths or tenths of a second, and sparging the biocompatible non-toxic cryogenic fluid onto the skin quickly, evenly, and smoothly when the head is rolled on the skin, and thereby tightening and rejuvenating the skin.

Abstract: Devices, systems, and methods treat cosmetic defects, and often apply cooling with at least one tissue-penetrating probe inserted through of the skin of a patient. The cooling may remodel one or more target tissue so as to effect a desired change in a composition of the target tissue and/or a change in its behavior. Exemplary embodiments of the cooling treatments will interfere with the nerve/muscle contractile function chain so as to mitigate wrinkles of the skin. Related treatments may be used therapeutically for treatment of back and other muscle spasms, chronic pain, and the like. Some embodiments may remodel subcutaneous adipose tissue so as to alter a shape or appearance of the skin surface.

Abstract: The present invention is of systems and methods for MRI-guided cryosurgery. The systems enable a surgeon positioned next to a patient and within an MRI magnetic environment both to monitor progress of a cryosurgical intervention by observing MRI images of the intervention in real time, and to fully control aspects of operation of a cryosurgery apparatus by remotely controlling a fluid supply source positioned external to that magnetic environment, which fluid supply source supplies cryogenic fluids to cryoprobes operable within that magnetic environment, thereby enabling real-time MRI-guided control of a cryoablation process.

Abstract: Methods and systems for detecting fluid egress, assessing lesion quality, determining tissue composition or structure, determining ice coverage of catheter tip and providing tissue contact assessment, by providing a catheter having a shaft with a proximal end portion and a distal end portion, the proximal end portion and the distal end portion define at least one fluid pathway therebetween with the shaft having a plurality of electrodes, positioning the catheter at a tissue treatment site, applying an electrical current between at least two of the plurality of electrodes, measuring impedance voltage between the at least two of the plurality of electrodes and, processing the measured impedance voltage caused by the applied electrical current to determine if fluid egress is present, to assess lesion quality, to determine tissue composition, ice cover of catheter tip, and to provide contact assessment.

Abstract: A surgical instrument for treating a tissue includes a handpiece and a tissue engaging portion arranged to be received by the handpiece. The tissue engaging portion includes first and second opposed jaw members having an open position and a closed position for engaging the tissue therebetween, where the first and second jaw members are arranged to receive surgical energy from a surgical generator. The tissue engaging portion further includes at least one cooling member spaced from at least one of the first and second jaw members, where the cooling member has an open position and a closed position for engaging the tissue. Positioning the jaw members in their closed position and applying surgical energy to the tissue allows for treatment of the tissue, and positioning the cooling member in its closed position provides at least one of a pressure gradient or a thermal gradient between the jaw members and the cooling member.

Abstract: The present invention relates to Joule-Thomson cooling systems operable to achieve rapid-response extreme cooling utilizing krypton as a cooling gas. Devices presented do not require heat exchangers between gas input and output conduits, and consequently are characterized by rapid response, small diameters and enhanced flexibility.

Abstract: A cryogenic applicator for rejuvenating skin and a treatment for use of the applicator. A barrel is hand-held. A head is rotatably mounted to the barrel. A cryogenic interface fluidly connects the barrel to a source of a biocompatible non-toxic cryogenic fluid to supply the cryogenic fluid through the barrel to the head that in turn sparges the cryogenic fluid onto the skin quickly, evenly, and smoothly when the head is rolled on the skin, and thereby rejuvenate the skin. The treatment includes the step of rolling the head quickly, smoothly, and evenly over the skin being treated for a period of time in an order of hundredths or tenths of a second, and sparging the cryogenic fluid onto the skin quickly, evenly, and smoothly when the head is rolled on the skin, and thereby rejuvenate the skin.

Abstract: A cryogenic medical system includes a medical device and a console connectable to the medical device at a connection point. The console controls the temperature of the medical device. The console includes a first cooling system directing coolant to the medical device at a first temperature along a coolant supply line and a second cooling system chilling the coolant within the coolant supply line to a temperature below the first temperature before the coolant reaches the connection point.

Abstract: Methods and apparatus for cryo-therapy are disclosed herein. This includes a hollow guidewire disposed within a catheter having helical loops contacting tissue. A coolant delivery tube disposed within can have a coolant delivered from a proximal end into the guidewire lumen. The coolant flows back proximally through the guidewire while cooling the guidewire surface and cooling or cryogenically ablating the contacting tissue. To minimize guidewire exposure to surrounding fluids or tissue, insulative barriers can be attached to the guidewire. A coolant delivery tube and return lumen can be integrated from a single extrusion in various configurations. Expandable balloons can also be used to expand the loops of the guidewire to contact the tissue. Also, helical loops with a coolant delivery tube or stem disposed longitudinally within the loops can be used and the loops can also have a variable collapsible cooling region.

Abstract: A cryogenic dispensing system has a cartridge containing a cryogenic material of limited dose and a housing to hold and dispense the cryogenic material at a controlled flow rate. The housing has a hollow interior and has an inlet opening adapted to receive a cartridge containing a cryogenic material and an outlet opening adapted to deliver cryogenic material from the interior to a wart, other tissue to be treated or the like. The hollow interior of the housing has an intermediate portion adapted to receive the insert member which has an engineered flow path therethrough and a method of starting the flow, where when opened, places the inlet in fluid communication through the flow path with the outlet. Preferably, the system includes a cartridge which contains liquid CO2. A masking ring may also be provided downstream of the flow path for applications of CO2 to selected dermatological areas such as a wart or the like.

Abstract: The invention proposes a cryosurgical instrument and its accessory system operating on the base of a refrigerant evaporation. The invention comprises combination of some technical solutions. Flow in a central lumen of the cryosurgical instrument has oscillating character; the refrigerant is provided on the internal surface of the distal cryotip in the form of separated portions. 2. The internal surface of the distal cryotip of the cryosurgical instrument is covered by a porous coating, which soaks completely one portion of the refrigerant. 3. Vapors obtained as a result of the refrigerant boiling on the porous coating of the cryotip are removed through the central lumen into the atmosphere. Combination of these technical solutions allows to construct a safely cryosurgical instrument with high freezing power and small outer diameter. The proposed cryosurgical instrument may be designed as a flexible cryocatheter or as a rigid cryoprobe.

Abstract: Devices, systems, and methods treat cosmetic defects, and often apply cooling with at least one tissue-penetrating probe inserted through of the skin of a patient. The cooling may remodel one or more target tissue so as to effect a desired change in a composition of the target tissue and/or a change in its behavior. Exemplary embodiments of the cooling treatments will interfere with the nerve/muscle contractile function chain so as to mitigate wrinkles of the skin. Related treatments may be used therapeutically for treatment of back and other muscle spasms, chronic pain, and the like. Some embodiments may remodel subcutaneous adipose tissue so as to alter a shape or appearance of the skin surface.

Abstract: Apparatus for applying thermotherapy to a part of the human or animal body comprising an applicator having a flexible enclosure in which thermal energy transfer fluid can circulate, a connector for connecting the applicator to a control system, an interface layer for providing a thermally conductive interface between the flexible enclosure and a treatment site and, an electrically conductive supporting layer for supporting the interface layer and capable of being energised by an electrical signal from the control system to improve the thermal conductivity of the interface layer. The apparatus also includes a valve unit for connecting the applicator to a control system, a heat exchanger for cooling a thermal energy transfer fluid and a control system for controlling the application of thermotherapy.

Abstract: An apparatus and methods for treating lesions on skin are presented. The apparatus collects information about a lesion and can automatically determine a course of treatment for the lesion. The device can include a controller that positions the nozzle proximate to a surface region of the lesion and automatically dispenses a pulse of the cryogenic fluid from the nozzle. The controller then positions the nozzle proximate to another surface region of the lesion and automatically dispenses a pulse of the cryogenic fluid from the nozzle.

Abstract: The invention relates to a new dispensing device for pressurized containers of coolants for cryotherapy, with a manual opening/closing valve, which includes a dispenser body suited to be permanently fixed to said container, a valve-opening element and a cap with teeth resting against said valve-opening element to cause the opening of the valve. In one embodiment, at least one tube or duct for application of the coolant, at one end of which at least one applicator pad or filter is partially and removably inserted, is permanently built in and integral with said dispenser body.

Abstract: An apparatus and methods for treating lesions on skin are presented. The apparatus collects information about a lesion and can automatically determine a course of treatment for the lesion. The device can include a controller that positions the nozzle proximate to a surface region of the lesion and automatically dispenses a pulse of the cryogenic fluid from the nozzle. The controller then positions the nozzle proximate to another surface region of the lesion and automatically dispenses a pulse of the cryogenic fluid from the nozzle.

Abstract: The device of the invention takes the form of a catheter/probe and is a closed loop system in which cryogen is delivered along the length of the catheter/probe to the tip where freezing occurs, and then is recirculated. The device is a tube within a tube and comprises a number of parts including supply and return tubes (internal tubes), outer sheath (external tube) sealed to the inner tubes at one or both ends with a gas filled lumen between the internal and external tubes. The lumen of the external tube is filled with a saturated gas which solidifies upon cooling, thereby creating a vacuum along the length of the catheter and providing for insulation between the inner and outer tubes, and preventing freezing along the length of the probe shaft. Further, the outside surface of the internal tubes is modified to potentiate gas nucleation on the outer surfaces of the internal tubes when cooled.

Abstract: A cryosurgical device and system is provided comprising a pressurized container, a metered valve that regulates the retrieval of a coolant solution stored in the pressurized container and regulates the volume of coolant solution dispensed with each actuation of the device, an actuator that engages the metered valve when engaged, and directs the coolant solution to an extension tube, which directs the coolant solution away from the pressurized container, and an applicator head configuring an open-ended enclosure attached to a distal end of the extension tube.

Abstract: The invention relates to a cryosurgical instrument and a method for separating a tissue sample from surrounding tissue of a biological tissue that is to be treated. The cryosurgical instrument comprises a probe for guiding a probe head on to a biological tissue to be treated, and gas conduits for delivering coolant gas, wherein the probe head is designed in such a way that, in order to collect a tissue sample, a limited region of the tissue can be cooled by means of the gas delivered and can be separated from the surrounding tissue in a state in which it is frozen on the probe head. The instrument is intended to permit reliable removal of a tissue sample without damaging the tissue and to ensure a high degree of safety for the patient. To this end, the instrument has a support means in which the probe is guided and which can be moved relative to the probe in such a way that the surrounding tissue can be counter-supported during separation of the tissue sample.

Abstract: A cryosurgical probe assembly that includes a gas delivery assembly, including a stem and a fluid conduit subassembly bonded to the stem. The fluid conduit subassembly delivers and returns cooling fluid used for cryogenic cooling. The fluid conduit subassembly, comprises a shaft for providing a heat exchange surface for cryogenic ablation; a housing securely connected to said shaft; and, an insulation element slideably engaged with an inner surface of the shaft and slideably engaged with the stem. The cryosurgical probe assembly includes an adjustable sliding apparatus that includes a slider assembly securely attached to said insulation tube for slideably guiding the insulation tube along said shaft; and, a button assembly operatively connected to the slider assembly for allowing a user to actuate the slider assembly to provide a desired adjustment of the insulation tube relative to the shaft. A handle assembly is positioned about the housing.

Abstract: A catheter having an extended treatment zone for cooling tissue is provided. The catheter includes an elongate catheter body having a distal tip, and a fluid injection conduit disposed inside the catheter body defining a return lumen therein. The fluid injection conduit further defines two or more injection orifices including a first distal orifice near the distal tip, and a second orifice longitudinally offset along the fluid injection conduit to be less proximate the distal tip than the first orifice. Fluid cryogen flowing through the orifices creates an extended tissue cooling contour about the distal end portion of the catheter. At least one ECG ring electrode is provided about the catheter body near the second orifice. The catheter may thus provide for electrocardiographic mapping of tissue nodes lying transversely between the distal tip and the ECG ring electrode.

Abstract: The invention relates to a device for cold treating a tissue. The invention also relates to an assembly of such a device and a container comprising a cryogenic liquid, such as a spray can. The invention further relates to a method for cold treating a tissue.

Abstract: The present invention relates to a tissue warming device for use with an ultrasound probe having top and bottom sides located diametrically opposite to each other viewed from a frontal cross-section of the probe. The device includes a sheath configured and dimensioned to receive at least a portion of the probe. A first sack, which is associated with the sheath, covers at least a portion of the top side of the probe. The sack includes first and second passages. The first passage allows warm fluid to be directed into the first sack for expansion thereof. The second passage allows fluid to be removed from the first sack. When expanded with warm fluid, the first sack warms body tissue disposed adjacent thereto. The warm fluid may be a warm liquid, such as an aqueous liquid.

Abstract: Systems and methods for controllably delivering liquid coolant such as nitrous oxide to an ablation device for cryogenically ablating tissue. A cooling element liquefies gaseous coolant released from a coolant supply or tank. An actuator in fluid communication with and between the cooling element and the ablation device defines a chamber. Liquid coolant is controllably drawn into and controllably expelled from the chamber for delivery to the cryo-ablation device. Liquid coolant can be controllably drawn into the chamber from the cooling element or from a container or reservoir that stores liquid coolant generated by the cooling element.

Abstract: A cryosurgical system with a cryoprobe, with a bypass valve communicating between the cryogen supply line and the cryogen exhaust line. The bypass valve is located in the cryoprobe, close to the distal tip of the cryoprobe, and is operable to open upon cryogen flow to purge gasses in the supply pathway and then close automatically when cooled by passing flow of liquid nitrogen.

Abstract: A medical device includes a steering element defining a passage for a guide wire. A fluid injection tube defining a proximal and a distal end is also included, wherein a portion of the fluid injection tube is contoured about a portion of the steering element. A plurality of injection ports may be disposed in the portion of the fluid injection tube contoured about the steering element.

Abstract: A system and method for controlling the inflation, ablation, and deflation of a balloon catheter. The system includes a balloon catheter, a console, a pressurized gas or liquid inflation source, and an umbilical system to deliver pressurized coolant to the balloon catheter. The system may include controller that monitors the amount of pressure and volume within the balloon catheter. During inflation, the pressure and/or volume of fluid within the balloon is maintained at a target amount in order to provide sufficient mechanized pressure against the desired target region. The system limits the inflation pressure such that a safe quantity of gas would be released should a leak occur. If the amount falls below a certain threshold level, gas or fluid egress is presumed and the inflation process is halted.

Abstract: A cryosurgical instrument, in which a separator is installed in a central feeding lumen and/or in a cryotip to separate gaseous and liquid components of a cryogen.

Abstract: A method and apparatus is provided for heating or cooling at least a selected portion of a patient's body. The method begins by inserting a catheter having a balloon into the colon or stomach of the patient. A heated or chilled fluid is conducted through a supply lumen of the catheter and into the balloon. The fluid is evacuated from the balloon through a return lumen of the catheter.

Abstract: Cryogenic tissue ablation instruments for treating body tissue include an elongate flexible body with a proximal supply port for coupling with a pressurized coolant (e.g., liquid N2O), a supply lumen in fluid communication with the proximal supply port, and an expandable cryogenic balloon carried on a distal portion of the elongate body, the balloon having a wall defining an interior of the balloon.

Abstract: An apparatus for compressing a gas and its uses are disclosed. The apparatus comprises a fixed-volume container having a hollow and a moveable element subdividing said hollow into a first variable-volume portion and a second variable-volume portion, the second variable-volume portion having an opening for introducing therein a hydraulic and/or pneumatic fluid under pressure, for causing an increase in the volume of said second variable-portion by moving said moveable element, thereby, consequently, decreasing the volume of the first variable-volume portion and compressing a gas contained therein.

Abstract: An apparatus and method for automatic operation of a refrigeration system to provide refrigeration power to a catheter for tissue ablation or mapping. The primary refrigeration system can be open loop or closed loop, and a precool loop will typically be closed loop. Equipment and procedures are disclosed for bringing the system to the desired operational state, for controlling the operation by controlling refrigerant flow rate, for performing safety checks, and for achieving safe shutdown.

Abstract: A catheter-based system for performing a cryoablation procedure uses a precooler to lower the temperature of a fluid refrigerant to a sub-cool temperature (?40° C.) at a working pressure (400 psi). The sub-cooled fluid is then introduced into a supply line of the catheter. Upon outflow of the primary fluid from the supply line, and into a tip section of the catheter, the fluid refrigerant boils at an outflow pressure of approximately one atmosphere, at a temperature of about ?88° C. In operation, the working pressure is computer controlled to obtain an appropriate outflow pressure for the coldest possible temperature in the tip section.