Patent Publication Number: US-9883900-B2

Title: Method of operating a medical cooling system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of patent application Ser. No. 12/913,281, filed Oct. 27, 2010, entitled COMPATIBLE CRYOGENIC COOLING SYSTEM, issued on Apr. 21, 2015, as U.S. Pat. No. 9,011,420, the entirety of which is related to and claims priority to and is incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     n/a 
     FIELD OF THE INVENTION 
     The present invention relates to a medical coolant system and methods of use thereof, and more particularly, towards a cryogenic coolant system for use with medical devices to treat or ablate tissue. 
     BACKGROUND OF THE INVENTION 
     A number of cooled catheter systems have been developed for treating patients. Such systems may provide a variety of cryogenic and/or cooling treatment or diagnostic procedures, including cooling a desired tissue region, such as a portion of the heart, to stun it and allow cold mapping of the heart and/or confirmation of a catheter position with respect to localized tissue lesions, or to apply a more severe level of cold to ablate tissue at the site of the catheter ending. 
     In general, when used for endovascular access to treat the cardiac wall, catheters of this type, in common with the corresponding earlier-developed radio frequency or electrothermal ablation catheter, must meet fairly demanding limitations regarding their size, flexibility, and the factors of strength, electrical conductivity and the like which affect their safety and may give rise to failure modes in use. These constraints generally require that the catheter be no larger than several millimeters in diameter so as to pass through the vascular system of the patient to the heart. Thus, any electrodes (in the case of mapping or RF/electrothermal ablation catheters), and any coolant passages (in the case of cryocatheters) must fit within a catheter body of small size. 
     A number of different fluids have been used for the coolant component of prior art cryotreatment catheters, such as a concentrated saline solution or other liquid of suitably low freezing point and viscosity, and of suitably high thermal conductivity and heat capacity, or a liquified gas such as liquid nitrogen. In all such constructions, the coolant must circulate through the catheter, thus necessitating multiple passages leading to the cooling area of the tip from the catheter handle. 
     Furthermore, conditions of patient safety must be considered, raising numerous problems or design constraints for each particular system. Thus for example, a high pressure may be required to circulate sufficient coolant through the catheter body to its tip and back, and the overall design of a catheter must be such that fracture of the catheter wall or leakage of the coolant either does not occur, or if it occurs, is harmless. Further, for an endovascular catheter construction, the presence of the coolant and circulation system should not substantially impair the flexibility or maneuverability of the catheter tip and body. 
     To some extent these considerations have been addressed by using a phase change material as the cryogenic fluid, and arranging the catheter such that the phase change, e.g., from a liquid to a gas, occurs in the treatment portion of the catheter tip. Another possible approach is to employ a pressurized gas, and configure the catheter for cooling by expansion of the gas in the tip structure. However, owing to the small size that such a catheter is required to assume for vascular insertion, or the awkwardness of handling a cryogenic treatment probe generally, the design of a safe and effective coolant circulation system which nonetheless dependably provides sufficient cooling capacity at a remote tip remains a difficult goal. 
     Moreover, when specialized fluids or coolants are selected for use, they are often available only in large, industrial-size containers that can take up a significant amount of space in an operating room or electrophysiology lab. In addition, if the coolant or tank provides for a limited number of procedures before needing to be re-filled or replaced, a hospital or treatment center may need to store numerous containers of the selected fluid or coolant to treat a steady stream of patients. Such storage and/or frequent replacement of one coolant tank with another can greatly increase the cost and reduce the efficiency of maintaining and operating a particular medical cooling system and associated devices. 
     Accordingly, it would be desirable to provide a coolant system that can be effectively and efficiently integrated into or otherwise used with existing fluid source systems within a hospital or treatment center to avoid the undesired costs and efforts associated with the frequent re-filling or replacing of coolant sources in medical cooling systems. 
     SUMMARY OF THE INVENTION 
     The present invention advantageously provides a medical cooling system for use in association with a fluid distribution network having a plurality of fluid outlets in communication with a central supply, the medical cooling system including a fluid delivery conduit defining an inlet engageable with one of the fluid outlets and an outlet engageable with a medical device; a compressor in fluid communication with the fluid delivery conduit; an adsorbent element disposed in the fluid delivery conduit; and a subcooler in thermal communication with the fluid delivery conduit. The system may include a medical device coupled to the outlet of the fluid delivery conduit, where the medical device is a cryogenic treatment device. The compressor may operate to compress a fluid, such as nitrous oxide, received from the fluid outlet to a pressure between approximately 500 psig to 1,000 psig, and the adsorbent element may reduce a humidity level of a fluid received from the fluid outlet to approximately 60 ppm or less. The system may include a reservoir downstream of the compressor and in fluid communication with the fluid delivery conduit; a fluid return conduit engageable with the medical device; a vacuum pump coupled to the fluid return conduit; and/or a flow meter coupled to the fluid delivery conduit. 
     A method of operating a medical cooling system is provided, including coupling a medical cooling system to an outlet of a fluid distribution network having a plurality of fluid outlets in communication with a central supply; delivering fluid from the outlet to the medical cooling system; compressing the delivered fluid with the medical cooling system; and decreasing the moisture content of the delivered fluid with the medical cooling system. The method may include liquefying the fluid with the medical cooling system; storing the fluid in the medical cooling system for use in a medical procedure; delivering the fluid from the medical cooling system to a medical device; and/or removing the fluid from medical device with the medical cooling system. 
     A method of operating a medical system is provided, including coupling a medical system to an outlet of a fluid distribution network having a plurality of fluid outlets in a patient treatment center; delivering fluid from the outlet to the medical system; compressing the delivered fluid with the medical system; decreasing the moisture content of the delivered fluid with the medical system; cooling the fluid with the medical system; delivering the fluid from the medical system to a medical device; and removing the fluid from medical device with the medical system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIG. 1  is an illustration of an embodiment of a medical system constructed in accordance with the principles of the present invention; 
         FIG. 2  is a schematic of an embodiment of a medical coolant delivery system for the medical system of  FIG. 1 ; and 
         FIG. 3  is an additional schematic of an embodiment of a medical coolant delivery system for the medical system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a medical cooling system that can be effectively and efficiently integrated into or otherwise used with existing fluid source systems within a hospital or treatment center to avoid the undesired costs and efforts associated with the frequent re-filling or replacing of coolant sources in typical medical cooling systems. Referring now to the drawing figures in which like reference designations refer to like elements, an embodiment of a medical system constructed in accordance with principles of the present invention is shown in  FIG. 1  and generally designated as “ 10 .” The system  10  generally includes a medical device  12  that may be coupled to a coolant control and delivery system  14 . The medical device  12  may generally include one or more treatment regions for energetic or other therapeutic interaction between the medical device  12  and a treatment site. The treatment region(s) may deliver, for example, cryogenic therapy, radiofrequency energy, or other energetic transfer with a tissue area in proximity to the treatment region(s), including cardiac tissue. 
     Continuing to refer to  FIG. 1 , the medical device  12  may include an elongate body  16  passable through a patient&#39;s vasculature and/or proximate to a tissue region for diagnosis or treatment, such as a catheter, sheath, or intravascular introducer. The elongate body  16  may define a proximal portion  18  and a distal portion  20 , and may further include one or more lumens disposed within the elongate body  16  thereby providing mechanical, electrical, and/or fluid communication between the proximal portion of the elongate body  16  and the distal portion of the elongate body  16 , as discussed in more detail below. 
     The medical device  12  may include a shaft  22  at least partially disposed within a portion of the elongate body  16 . The shaft  22  may extend or otherwise protrude from a distal end of the elongate body  16 , and may be movable with respect to the elongate body  16  in longitudinal and rotational directions. That is, the shaft  22  may be slidably and/or rotatably moveable with respect to the elongate body  16 . The shaft  22  may further define a lumen  24  therein for the introduction and passage of a guide wire. The shaft  22  may include or otherwise be coupled to a distal tip  26  that defines an opening and passage therethrough for the guide wire. 
     The medical device  12  may further include a fluid injection tube  28  traversing at least a portion of the elongate body and towards the distal portion. The injection tube  28  may be coupled to or otherwise extend from the distal portion of the elongate body  16 , and may further be coupled to the shaft  22  and/or distal tip of the medical device  12 . The fluid injection tube  28  may be flexible, constructed from a shape memory material (such as Nitinol), and/or include other controllably deformable materials that allow the fluid injection tube  28  to be manipulated into a plurality of different geometric configurations, shapes, and/or dimensions. 
     The fluid injection tube  28  may define a lumen therein for the passage or delivery of a fluid from the proximal portion of the elongate body  16  and/or the coolant control and delivery system  14  to the distal portion and/or treatment region(s) of the medical device  12 . The fluid injection tube  28  may further include one or more apertures or openings therein to provide for the dispersion or directed ejection of fluid from the tube to an environment exterior to the fluid injection tube  28 . 
     The medical device may further include a thermal treatment region  30  at or near the distal portion of the device. The thermal treatment region  30  may include a thermally-transmissive section or area allowing thermal exchange with a targeted tissue or region external to the medical device using one or more thermal treatment modalities, such as radiofrequency energy delivery, cryogenic treatment of the tissue for example. As shown in  FIG. 1 , the thermal treatment region  30  may include an expandable element  32  at the distal portion of the elongate body  16 . The expandable element  32  may be coupled to a portion of the elongate body  16  and also coupled to a portion of the shaft  22  and/or distal tip  26  to contain a portion of the fluid injection tube  28  therein. The expandable element  32  defines an interior chamber or region that contains coolant or fluid dispersed from the fluid injection tube  28 , and may be in fluid communication with an exhaust lumen  34  defined by or included in the elongate body  16  for the removal of dispersed coolant from the interior of the expandable element  32 . The expandable element  32  may further include one or more material layers providing for puncture resistance, radiopacity, or the like. Of note, while the thermal treatment region  30  is described as including an expandable element, other configurations of the thermal treatment region are contemplated, including linear thermal segments, arcuate thermal segments, non-expandable cooling chambers, and the like. 
     The medical device  12  may include a handle  36  coupled to the proximal portion of the elongate body  16 . The handle  36  can include circuitry for identification and/or use in controlling of the medical device  12  or another component of the system. For example, the handle  36  may include one or more pressure sensors  38  to monitor the fluid pressure within the medical device  12 . Additionally, the handle  36  may be provided with a fitting  40  for receiving a guide wire that may be passed into the guide wire lumen  24 . The handle  36  may also include connectors  42  that are matable to the coolant control and delivery system  14  either directly or indirectly by way of one or more umbilicals. The handle  36  may further include blood detection circuitry in fluid and/or optical communication with the injection, exhaust and/or interstitial lumens. The handle  36  may also include a pressure relief valve in fluid communication with the fluid injection tube  28  and/or exhaust lumen  34  to automatically open under a predetermined threshold value in the event that value is exceeded. 
     The handle  36  may also include one or more actuation or control features that allow a user to control, deflect, steer, or otherwise manipulate a distal portion of the medical device from the proximal portion of the medical device. For example, the handle  36  may include one or more components such as a lever or knob  44  for manipulating the elongate body  16  and/or additional components of the medical device  12 , such as a pull wire  46  with a proximal end and a distal end anchored to the elongate body  16  at or near the distal portion. The medical device  12  may include an actuator element  48  that is movably coupled to the proximal portion of the elongate body  16  and/or the handle  36 . The actuator element  48  may further be coupled to a proximal portion of the shaft  22  such that manipulating the actuator element  48  in a longitudinal direction causes the shaft  22  to slide towards either of the proximal or distal portions of the elongate body  16 . The actuator element  48  may include a thumb-slide, a push-button, a rotating lever, or other mechanical structure for providing a movable coupling to the elongate body  16 , the handle  36 , and/or the shaft  22 . Moreover, the actuator element  48  may be movably coupled to the handle  36  such that the actuator element is movable into individual, distinct positions, and is able to be releasably secured in any one of the distinct positions. 
     The system  10  may further include one or more sensors to monitor the operating parameters throughout the system, including for example, pressure, temperature, flow rates, volume, or the like in the coolant control and delivery system  14  and/or the medical device  12 , in addition to monitoring, recording or otherwise conveying measurements or conditions within the medical device  12  or the ambient environment at the distal portion of the medical device  12 . The sensor(s) may be in communication with one or more components of the coolant control and delivery system  14  for initiating or triggering one or more alerts or therapeutic delivery modifications during operation of the medical device  12 . One or more valves, controllers, or the like may be in communication with the sensor(s) to provide for the controlled dispersion or circulation of fluid through the lumens/fluid paths of the medical device  12 . Such valves, controllers, or the like may be located in a portion of the medical device  12  and/or in the coolant control and delivery system  14 , as described in more detail below. 
     Turning now to  FIG. 2 , a schematic of the coolant control and delivery system  14  is shown. In general, the coolant control and delivery system  14  may include pumps, valves, controllers or the like to deliver, recover and/or re-circulate fluid delivered to the handle, the elongate body, and/or the fluid pathways of the medical device  12 . The control and delivery system  14  also includes various control mechanisms for the medical system  10 , such as one or more controllers, processors, and/or software modules containing instructions or algorithms to provide for the automated operation and performance of the features, sequences, or procedures described herein. 
     The coolant control and delivery system  14  may obtain a fluid or coolant from a fluid distribution network  50  having a plurality of fluid outlets  52  in fluid communication with a central source  54  to avoid the associated costs and other requirements of maintaining a medical system having a large tank storing fluid or coolant for use with a particular medical device. As used herein, the term “fluid” includes liquids, gases, and mixtures thereof. The fluid distribution network  50  may be integral with a hospital or patient treatment center that routes fluids to a plurality of outlets  52  in individual rooms or locations within the hospital or treatment center. For example, many hospitals include outlets throughout the building providing oxygen, nitrous oxide, or other fluids for on-demand use in the individual rooms or treatment areas, with the central fluid source  54  located in another area of the hospital or treatment center outside of the patient treatment areas. Although typically used for direct patient inhalation and/or treatment or anesthesia, such available fluids can be conditioned for use as a coolant during a thermal treatment procedure as described herein. 
     Particularly, the coolant control and delivery system  14  may generally include a fluid conditioning segment or subsystem  56  that manipulates the characteristics of a fluid provided by the fluid distribution network  50  to optimize its use in the medical system  10 . The fluid conditioning subsystem  56  may include a fluid inlet line  58  engageable with one of the outlets  52  of the fluid distribution network  50  using one or more connectors. A subcooler  60  may be coupled to the fluid inlet line in thermal communication with a fluid flowing therethrough to lower the temperature of the fluid in the fluid inlet line  58 . The subcooler  60  may include a heat exchange assembly or mechanism that transfers heat away from the fluid flowing through the subsystem  56 . Examples of such subcooling or heat exchange configurations may include a closed-loop fluid circuit that removes heat from the fluid inlet line using a compressor, condenser, and/or heat exchanger; a Peltier heat transfer device; or other thermal transfer mechanisms and/or temperature reduction components. 
     One or more adsorbent materials or elements  62  may be disposed within or otherwise coupled to the fluid inlet line to reduce the humidity or moisture content of the fluid flowing therethrough. While moisture or humidity in the fluid provided by the fluid distribution network  50  may be suitable or unproblematic for use as an inhalant for a patient, the moisture in the fluid can cause the creation of ice crystals in a medical system using the fluid as a coolant. The ice crystals can obstruct fluid flow paths within the medical system  10  and can also damage components of the system. Accordingly, the adsorbent element(s)  62  may remove moisture to a designated level to prevent or greatly reduce the formation of ice crystals, such as a moisture level less than 50 ppm for example. 
     The fluid conditioning subsystem  56  may also include one or more compressors  64  coupled to the fluid inlet line downstream of the subcooler  60  to increase the pressure of fluid received from the fluid distribution network  50  to a level for sufficient use as a coolant in a thermal treatment procedure. For example, the outlet pressure of a fluid, such as nitrous oxide, in a hospital network may be in the range of approximately 20 to 50 psi, while a suitable pressure for use as a cryogenic coolant may be in the range of approximately 500 to 1,000 psig. Accordingly, the compressor(s)  64  may operate to compress a fluid to a pressure level between approximately 500 to 1,000 psig, or otherwise have a compression factor of approximately 15 to 30, or higher. 
     Now turning to  FIG. 3 , an alternative configuration for the fluid conditioning subsystem  56  is shown. A first subcooler  65  is coupled to a fluid conduit receiving a fluid from the outlet  54 . An adsorbent element  66  may also be disposed on or about the fluid conduit to remove moisture as described above, and a compressor  67  is also included to increase the pressure of the fluid in the conduit or inlet line for use by system  10 . A radiator or heat exchanger  68  may be located downstream of one or more compressors  68  to allow the compressed fluid to be cooled through thermal exchange with the surrounding air (or another thermal dissipation fluid or material). The fluid conditioning subsystem  56  may also include a second subcooler  69  downstream of the compressor and/or radiator to further cool or otherwise reduce the temperature of the fluid passing through the subsystem  56 . 
     In compressing the fluid received from the outlet  52  by a factor of 15 to 30 (e.g., from approximately 50 psi to 500-1,000 psig), the fluid is heated considerably. For example, if the fluid dispersed by the outlet  52  is at room temperature (or about 20° C., for example), and the fluid is compressed or otherwise has its pressure raised by a factor of 10 to 20, its resulting temperature at the outlet of a compressor will be approximately 280° C. to 300° C. To subsequently use the compressed fluid as a cryogenic coolant to thermally treat tissue with the medical device, the temperature must be lowered, and the fluid may be liquefied. In  FIGS. 2-3 , the subcooler  60 ,  65  upstream of the compressor  64 ,  67  can primarily reduce the temperature of the fluid provided by the outlet from a temperature of approximately 20° C. to a cooled temperature between approximately −80° C. to −20° C. Due to the high compression factor, the compressor  67  may still have an outlet fluid temperature of approximately 200° C. The heated temperature of the fluid exiting the compressor  67  can be passively dissipated by the radiator  68  into the surrounding air or other medium (as shown in  FIG. 3 ). The second subcooler  69  can then reduce the temperature of the fluid even further, which may include inducing a phase change of the fluid from a gaseous or partly-gaseous state to a liquid state, prior to delivering or transferring the coolant to the other segments of the system for later use in the medical device  10 . Variations in the placement and quantity of thermal exchange components such as subcoolers or radiators about one or more compressors may be implemented to achieve the increased compression of the fluid while maintaining or achieving a desired operating temperature of the fluid after compression. 
     Referring again to  FIG. 2 , the coolant control and delivery system  14  may include a fluid delivery subsystem  72  that selectively controls the circulation and/or delivery of fluid received from the fluid conditioning subsystem  56  to the medical device  12 . The fluid delivery subsystem  72  may receive fluid from an outlet line  74  of the conditioning subsystem, and may be coupled to the medical device  12  through a connector  76 , which places a supply lumen  78  and an exhaust lumen  80  of the fluid delivery subsystem  72  in fluid communication with the fluid injection tube  28  and exhaust lumen  34  of the medical device  12 . 
     The fluid delivery subsystem  72  may include a first reservoir  82  for the storage of conditioned fluid received from the conditioning subsystem. The first reservoir  82  may have sufficient volume to store enough coolant to complete a designated procedure with the medical device  12 , and/or may act as a safeguard or buffer if fluid is drawn continuously from the outlet  52  and conditioning subsystem  56  during a designated procedure. For example, the first reservoir may have a capacity of approximately 1.5 to 2 lbs of fluid or coolant, rather than the large, industrial size reservoirs having a typical capacity of 10 to 20 lbs. The first reservoir  82  can thus allow the conditioning subsystem  56  to operate intermittently or periodically while maintaining or storing enough coolant for a procedure, thereby increasing the efficiency of the medical system  10 . 
     The delivery subsystem  72  may also include a second reservoir  84  having a volumetric capacity smaller than the volumetric capacity of the first reservoir. For example, the second reservoir  84  may have a volumetric capacity of approximately 20 cm 3 , which has been shown to reduce the likelihood of cardiac abnormalities and/or failure due to coolant egress from a medical device into the vascular system. 
     A vacuum source  86  in the fluid delivery subsystem  72  may create a low-pressure environment in one or more conduits within the medical system  10  and/or medical device  12  so that fluid is drawn into the conduit(s)/lumen(s) of the elongate body  16 , away from the distal portion and towards the proximal portion of the elongate body  16 . The vacuum source  86  may include any structure and/or apparatus able to provide a negative pressure gradient for providing fluid flow, including pumps, plunger devices, or the like. 
     One or more valves may be disposed about the fluid delivery subsystem in fluid communication with the supply lumen  78  and/or the exhaust lumen  80  for manipulating and/or providing fluid flow along a desired path. For example, the fluid delivery subsystem  72  may include a pair of valves,  88  and  90 , in fluid communication with the first reservoir  82  such that the first reservoir  82  may be selectively switched from being in fluid communication with the second reservoir  84  to being in fluid communication with the supply lumen  78 . Moreover, a valve  92  may be disposed on the exhaust lumen  80  such that the exhaust lumen  80  may be selectively switched from being in fluid communication with the second reservoir  84  to being in fluid communication with the vacuum source  86 . In addition, the fluid delivery subsystem may include one or more check valves and/or pressure relief valves CV configured to open to atmosphere or to a recovery tank should a pressure level and/or flow rate within a portion of the medical system  10  exceed a desired or predetermined level. 
     The fluid delivery subsystem  72  may include a valve  94  in fluid communication with both the supply lumen  78  and the exhaust lumen  80 . In particular, the valve  94  may be in fluid communication with the supply lumen at a position upstream of the connector  76 , while being in fluid communication with the exhaust lumen downstream from the connector  76 . The valve  94  may further be placed in fluid communication with the surrounding atmosphere to equalize pressure in both the exhaust and supply lumens. During operation, the fluid delivery subsystem  72  may detect a failure of the medical device  12 , such as an indication of the presence of blood or bodily fluid being entrained into the medical system  10 . Upon such detection, coolant flow may be terminated. However, despite the termination of fluid flow, due to the built-up pressure levels in the supply and exhaust lumens, bodily fluid may continue to be siphoned into the medical device and thus into portions of the fluid delivery subsystem. To reduce the likelihood that siphoning occurs, the valve  94  may be actuated to place both the supply lumen  78  and the exhaust lumen  80  into fluid communication with the atmosphere. By doing so, the pressure in either lumen will be substantially equalized and thus will prevent the further ingress of bodily fluids into the medical device and thus the console. Of course, the equalization and/or subjection of both the supply and exhaust lumens may be achieved by using one or more valves in various configuration. 
     The fluid delivery subsystem  72  may also include a subcooler  96  disposed about a portion of the supply lumen  78  for achieving a desired temperature and/or coolant phase (e.g., liquid) of fluid flowing therethrough. The subcooler  96  may include a compressor, condenser and the like placed in thermal communication with the supply lumen  78 . 
     One or more sensors may be disposed about the supply and exhaust lumens of the fluid delivery subsystem  72  for detecting temperature, pressure, and/or flow rates through a particular portion of the fluid delivery subsystem. For example, a first pressure sensor  98  may be disposed about the exhaust lumen proximate to the connector  76 . In addition, a second pressure sensor  100  may be disposed about the supply lumen  78 . Of course, additional sensors SS may be included throughout the fluid delivery subsystem  72  for monitoring and/or controlling particular portions of the medical system and operation thereof. 
     In addition to the one or more sensors, one or more controllers may be coupled to the sensors, and in turn, coupled to one or more of the valves situated throughout the fluid delivery subsystem  72  such that the valves may be controllably manipulated in response to information obtained by the sensors. For example, a first controller  102  may be coupled to the first pressure sensor  98 , wherein the first controller  102  is further coupled to a valve  104  disposed on a portion of the exhaust line, and where the valve  104  may also be in fluid communication with the vacuum source  86 . In addition, a second controller  130  may be coupled to the second pressure sensor  100 , where the second controller  130  is further coupled to a valve  108  disposed about the supply lumen  78 . Accordingly, fluid flow through portions of the exhaust and/or supply lumens may be controllably manipulated in direct response to the information obtained by sensors contained therein. In addition to the one or more sensors, one or more controllers may be coupled to the sensors, and in turn, coupled to one or more of the valves situated throughout the fluid delivery subsystem  72  such that the valves may be controllably manipulated in response to information obtained by the sensors. For example, a first controller  102  may be coupled to the first pressure sensor  98 , wherein the first controller  102  is further coupled to a valve  104  disposed on a portion of the exhaust line, and where the valve  104  may also be in fluid communication with the vacuum source  86 . In addition, a second controller  130  may be coupled to the second pressure sensor  100 , where the second controller  130  is further coupled to a valve  108  disposed about the supply lumen  78 . Accordingly, fluid flow through portions of the exhaust and/or supply lumens may be controllably manipulated in direct response to the information obtained by sensors contained therein. 
     Of note, while the coolant control and delivery system (including its subsystems and components described herein) are illustrated in  FIG. 1  as having a single housing, it is contemplated that the components and subsystems described herein may be configured in one or more housings or other enclosures to reduce the amount of space taken up by the system, to reduce operating noise or sound levels produced by the system, to ease installation and/or transport of the system, and/or to selectively couple one or more of the components or subsystems disclosed herein to one or more pre-existing systems or facilities for use (e.g., to retrofit a previously-installed, tank-based fluid delivery system with a fluid conditioning subsystem to allow use of the pre-existing system with an available fluid distribution network). 
     In an exemplary use, the medical system  10  may be used to thermally treat a targeted tissue region of a patient. In a particular example, the coolant control and delivery system  14  may obtain a fluid flow from the fluid distribution network  50 , modify the characteristics of the fluid output of the delivery network  50 , deliver the conditioned fluid to the medical device  12 , and ablate tissue in proximity to the distal portion  20  of the medical device  12 . More particularly, the fluid inlet line  58  of the conditioning subsystem  56  may be connected to an outlet  52  of the fluid distribution network  50  supplying nitrous oxide throughout the network. The conditioning subsystem  56  may cool, compress, de-humidify, or otherwise treat and condition the received fluid (e.g., nitrous oxide) for subsequent use in the thermal procedure by the medical device  12 . The conditioning subsystem  56  may be operated continuously during a designated medical procedure or may be run intermittently for a predetermined time period in order to supply sufficient coolant to the first reservoir  82  of the fluid delivery subsystem  72  and/or the medical device  12  for the duration of the selected procedure. The fluid delivery subsystem  72  may then be operated to selectively and controllably deliver the conditioned fluid to the medical device  14 . In a particular example, the fluid delivery subsystem  72  may circulate or otherwise deliver the fluid to the medical device through one or more evacuation or flushing phases, inflation phases, transition phases, ablation phases, and/or deflation phases as described in U.S. patent application Ser. No. 12/603,250, filed on Oct. 21, 2009, entitled “DEFLATION MECHANISM FOR A MEDICAL DEVICE,” the entirety of which is hereby incorporated by reference. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.