Abstract:
A method for cooling a medical device includes fluidly connecting a cooling fluid reservoir to a medical device. The fluid connection includes a fluid out-flow path and a fluid return path corresponding to the fluid reservoir. The cooling fluid is pumped from the fluid reservoir to the medical device. The medical device is energized and the heat generated by the energization is absorbed by the cooling fluid pumped to the medical device. The cooling fluid is received at the reservoir containing the absorbed heat. The cooling fluid transfers the absorbed heat to the cooling fluid in the reservoir and to the environment adjacent to the reservoir.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/835,808, filed Mar. 15, 2013, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to the use of energy delivery devices. More particularly, the present disclosure is directed to a method for cooling for energy delivery devices. 
         [0004]    2. Background of the Related Art 
         [0005]    Energy delivery procedures such as tissue ablation are used in numerous medical procedures to treat many conditions. Ablation can be performed to remove undesired tissue such as cancer cells. Ablation procedures may also involve the modification of the tissue without removal, such as to stop electrical propagation through the tissue in patients with an arrhythmia condition. Often the ablation is performed by passing energy, such as electrical energy, through one or more electrodes and causing the tissue in contact with the electrodes to heat up to an ablative temperature. 
         [0006]    Electromagnetic (EM) ablation may also be used instead of direct energy discharge into tissue. For example, microwave (MW) ablation is a common example of such EM ablation where energy is applied to tissue through microwave radiation. EM ablation devices may require cooling to operate within desired parameters without damaging the ablation device or causing unintended tissue damage. Examples of EM ablation medical devices include percutaneous needle ablation probes and flexible intraluminal ablation catheters. Some devices implement cooling systems including a peristaltic pump that forces saline or another fluid through a tubing system operably connected to an energy delivery device. The saline solution draws heat from the energy delivery device and is then pumped out into a receptacle or to a drain. However, these systems require constant supply of saline bags, can be wasteful, and can be inefficient. 
       SUMMARY 
       [0007]    Like reference numerals may refer to similar or identical elements throughout the description of the figures. As shown in the drawings and described throughout the following description, as is traditional when referring to relative positioning on a surgical instrument, the term “proximal” refers to the end of the apparatus that is closer to the user and the term “distal” refers to the end of the apparatus that is farther away from the user. The term “clinician” refers to any medical professional (e.g., doctor, surgeon, nurse, or the like) performing a medical procedure involving the use of embodiments described herein. 
         [0008]    According to aspects of the disclosure, a method of cooling a medical device is disclosed. The method includes providing a fluid reservoir, pumping a cooling fluid, and energizing a medical device. The method may also include providing a drip chamber, a fluid flow indicator, a tubing system, and/or an elbow. Pumping the cooling fluid may include pressurizing the cooling fluid before the fluid flow through the medical device. The method may also include measuring the temperature of the cooling fluid. In embodiments, a flow rate of fluid with the system is adjusted in response to the temperature of the cooling fluid. 
         [0009]    According to other aspects of the disclosure, a method of recirculating a cooling fluid for use with an energy delivery device is disclosed. The method includes providing an energy delivery device and a recirculating cooling system connected to the energy delivery device. The recirculating cooling system is configured to maintain the energy delivery device with a desired temperature range. The recirculating cooling system may include a tubing system and a fluid reservoir. The tubing system configured to interconnect the fluid reservoir with the energy delivery device and carry the cooling fluid from the fluid reservoir and through the energy delivery device before returning the cooling fluid to the fluid reservoir. The method may further include providing a thermocouple on a portion of the cooling system to measure a system temperature. The desired temperature range may include an upper limit. The flow rate of the fluid may be increased with the system temperature approaches the upper limit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which: 
           [0011]      FIG. 1  is a side view of a portion of a cooling system in accordance with the present disclosure; 
           [0012]      FIG. 2  is a cross-sectional view of a drip chamber and flow indicator, in accordance with the present disclosure; 
           [0013]      FIG. 3  is a perspective view of a flow indicator of a cooling system in accordance with the present disclosure; 
           [0014]      FIG. 4A  is an exploded view of a portion of the cooling system in accordance with the present disclosure; 
           [0015]      FIG. 4B  is a side view of the portion of the cooling system of  FIG. 4A ; 
           [0016]      FIG. 5A  is a cross-sectional view of a fluid return elbow member in accordance with the present disclosure; 
           [0017]      FIG. 5B  is a front view of the fluid return elbow of  FIG. 5A ; 
           [0018]      FIG. 5C  is a bottom view of the fluid return elbow of  FIG. 5A ; 
           [0019]      FIG. 6  is a side view of a cooling system in accordance with the present disclosure; 
           [0020]      FIGS. 7A and 7B  are cross-sectional views of a drip chamber and a flow indicator, in accordance with the present disclosure; and 
           [0021]      FIG. 8  is a side view of a cooling system in accordance with the present disclosure depicting locations of flow sensors and thermocouples. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Particular embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings; however, the disclosed embodiments are merely examples of the disclosure and may be embodied in various forms. Well known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure. 
         [0023]    In accordance with at least one aspect of the present disclosure, an energy delivery device cooling system is disclosed. Referring generally to  FIGS. 1-6 , the system  1000  includes a reservoir connector assembly  100  in communication with a reservoir  200 . The reservoir  200  is configured to contain or hold a cooling fluid. The reservoir connector assembly  100  may include an elongate member  101  configured to extend into the reservoir  200 . Tubing system  400  connects the reservoir  200  with a medical device having inlet and outlet ports and forming a closed loop cooling system  1000 , as will be described in greater detail below. Examples of medical devices to which the system  1000  may be connected can be found in commonly owned U.S. Pat. Nos. 8,334,812; 8,430,871; 9,247,992; and 9,459,770; each of which is incorporated herein by reference in its entirety. 
         [0024]    In some embodiments, the elongate member  101  can have any length and shape capable of being inserted into the reservoir  200 . For example, the elongate member  101  can be a spike with a penetrating tip. In other embodiments, the elongate member  101  can have a blunt or substantially flat tip. The elongate member  101  can be substantially cylindrical, and in the embodiments with a piercing tip, the tip can be symmetrically conical or non-symmetrically conical. 
         [0025]    Referring specifically to  FIG. 2 , the elongate member  101  has at least a first lumen  105  and a second lumen  107  defined therethrough. Each lumen  105 ,  107  is configured to be in fluid communication with the reservoir  200  shown in  FIG. 1  at openings  105   a  and  107   a  respectively. The first lumen  105  may act as an inflow lumen for drawing fluid from the reservoir  200  and the second lumen  107  may act as a return lumen for returning fluid to the reservoir  200 . 
         [0026]    Lumens  105 ,  107  and openings  105   a ,  107   a  may have the same or different diameters. The diameter of the lumens  105 ,  107  may be selected based on a desired volumetric flow rate and fluid velocity for a given medical device. For example, to promote mixing in the reservoir  200 , a smaller diameter lumen  107  can be chosen to achieve a higher velocity of the fluid for a given pressure. The increased velocity can increase turbulent flow within the reservoir  200  and/or the tubing system  400 , resulting in increased mixing of the fluid. This increased mixing can promote homogenization of the fluid temperature within the reservoir  200  and/or the tubing system  400 . The turbulent flow can also increase the efficiency of the transfer of heat from the fluid to the surrounding environment. 
         [0027]    At least one outflow port  109  is in fluid communication with the first lumen  105  and allows fluid to flow from the reservoir  200  into a drip chamber  300  or directly into the tubing system  400 . With continued reference to  FIG. 2  and added reference to  FIG. 4A , the reservoir connector assembly  100  includes a return port  103  configured to allow cooling fluid to return to the reservoir connector assembly  100  from the tubing system  400 . The return port  103  is in fluid communication with the second lumen  107  and may be configured to allow for direct or indirect fluid communication with tubing system  400 . It is also envisioned that the reservoir connector assembly  100  includes more than one return port  103 . 
         [0028]    In some embodiments, the elongate member  101  further includes a third lumen and a fourth lumen having third and fourth openings, respectively, and in fluid communication with the reservoir  200  and the outflow port  109 . Similarly, added lumens may also connect to the return port  103 . 
         [0029]    The elongate member  101  or the reservoir  200  may include a thermocouple  202  operably connected thereto to monitor a temperature of the fluid inside the reservoir  200 . Alternatively, the thermocouple  202  may be placed in various locations to measure the temperature of the fluid in the system  1000 , as shown in  FIG. 8 . For example, the thermocouple  202  may be placed near the opening of the second lumen  107  to measure the temperature of the fluid flowing into the reservoir  200 , near the first lumen  105  to measure the temperature of the fluid flowing out of the reservoir  200 , in a portion of the tubing system  400  to measure the temperature of fluid flowing therein, or any combination thereof. The thermocouple  202  may be connected to an energy source for the medical device, for example a microwave generator (not shown), and may be employed as a safety shut off for the energy source such that if the temperature of the fluid rises beyond a set threshold that indicates insufficient cooling, the energy source is shut off to prevent undesired damage to patient tissue during treatment. 
         [0030]    As shown in  FIG. 1 , a reservoir connector assembly  100  fluidly connects the reservoir  200  with a drip chamber  300 . The drip chamber  300  may include a top portion  301  ( FIG. 4A ) configured to receive a portion of the reservoir connector assembly  100  and a bottom portion  303  configured to connect the drip chamber  300  in fluid communication with the tubing system  400 . In embodiments, a fluid connector  305  connects the bottom portion  303  with the tubing system  400  and facilitates fluid communication therebetween. Between the top portion  301  and the bottom portion  303  is a central portion  307 , which may be formed as a cylinder. As shown in  FIGS. 2, 7, and 8 , the central portion  307  of the drip chamber  300  may also include a flow indicator  309  for indicating that a fluid is flowing from the reservoir  200  through the drip chamber  300  to the tubing system  400 . 
         [0031]    As shown in  FIG. 3 , the flow indicator  309  may be formed of a hollow cylinder  310  with hydrofoils  311  configured to rotate the hollow cylinder  310  in the drip chamber  300  when fluid flows through the flow indicator  309 . The flow indicator  309  may include a design  313  disposed on an outer surface thereof that visually indicates that the cylinder  309  is rotating, and thus that fluid is flowing therethrough. For example, the design  313  may resemble a barber-shop pole, however, other designs can be used to indicate fluid flow, for example a corporate logo COVIDIEN® or other graphic design. The cylinder  310  may be formed of a material with a specific gravity causing the cylinder  310  to either be neutrally buoyant in the cooling fluid or to float in the cooling fluid. Other embodiments of flow indicators  309  may be utilized that are suitable for indicating flow in the drip chamber  300  including but not limited to low density balls, floating material indicators, paddle wheel indicators, or the like. 
         [0032]    An alternative arrangement of a flow indicator  309   a  is depicted in  FIGS. 7A and 7B . As shown in  FIGS. 7A and 7B , the flow indicator  309   a  is generally in the shape of a cube, though other geometric shapes may be employed without departing from the scope of the present disclosure. The cube shape may be advantageous by eliminating the possibility of the flow indicator  309   a  occluding the bottom portion  303  of the drip chamber  300  when the system  1000  is initially primed with the fluid. The flow indicator  309   a  has a density related to the cooling fluid such that when fluid is not flowing through the drip container  300  the flow indicator  309   a  floats to the upper surface  700  of the fluid in the drip container  300  as shown in  FIG. 7A  and when fluid is flowing through the drip container  300  the flow indicator  309   a  partially submerges beneath the surface  700  and may also rotate to provide visual indicia of fluid flow as shown in  FIG. 7B . 
         [0033]    The tubing system  400  may include one or more return fluid flow indicators disposed thereon to indicate that a fluid is returning from the medical device to the reservoir  200  through tubing system  400 . Examples of such return flow indicator include bubble indicators and traps, Venturi-style indicators, Hall-effect fluid flow indicators, and the like. Indicators, such as bubble indicators and venturi devices, also have the dual purpose of removing any gas which may have entered the system or vapor from the liquid flow to prevent disruption in the flow. Other fluid flow indicators may also be employed to measure fluid velocity, pressure, or volumetric flow rate. Examples of the fluid flow indicators are currently sold by Introtek International under the name BDC and BER Ultrasonic Clamp-on Air Bubble, Air-in-line &amp; Liquid level Detection Systems as well as the Drip Chamber Ultrasonic Liquid Level Sensors. 
         [0034]      FIG. 8  illustrates numerous locations where flow indicators  309   b  and thermocouples  202 , as described above, may be employed within system  1000 . The flow indicators  309   b  are flow sensors that detect flow of a fluid between portions of the flow indicators  309   b . The flow indicators  309   b  and thermocouples  202  may be attached to various portions of the system  1000  and may be attached to devices (not shown) that provide audible and/or visual indicia of fluid flow within the system  1000 . Further, the devices themselves may provide audible and/or visual indicia when fluid is not flowing within portions of the system  1000 , e.g. when a tube is kinked or blocked. 
         [0035]    Referring now to  FIGS. 1 and 2 , the tubing system  400  includes one or more tubes  401  that allow a fluid to flow from the reservoir connector assembly  100 , through an energy delivery device (not shown) such as an ablation needle or catheter or an energy source, and back to the reservoir connector assembly  100 . The tubing system  400  may include a first end  403  and a second end  405 . 
         [0036]    In the illustrated embodiment, the first end  403  is in fluid communication with the outflow port  109 , either indirectly through the bottom portion  303  of drip chamber  300  or by direct connection to outflow port  109 , and is configured to allow fluid to flow into tubing system  400 . The second end  405  is in fluid communication with the return port  103 , and is configured to allow fluid to return to the reservoir  200  through the second lumen  107 . 
         [0037]    Tubing system  400  may also include one or more thermal diffusion devices  407  configured to draw heat from the fluid and diffuse the heat to the ambient environment. As shown in  FIG. 1 , the thermal diffusion device  407  includes a series of fins  409  in contact with the tube  401  returning from a medical device. A fan may be employed to direct airflow over the fins and increase the cooling effect. While shown connected to the tube  401 , a thermal diffusion device  409  could also or alternatively be employed on the reservoir  200 . A further alternative could employ passing the tube  401  returning from the medical device through a reservoir containing cold water or ice water in order to further draw heat out of the fluid flowing through the tubes  401 . 
         [0038]    The system  1000  may further include an elbow member  500  connected to the second end  405  of the tubing system  400  as shown in  FIGS. 5A-C . The second end  405  of the tubing system  400  in fluid communication with the return port  103  through the elbow member  500 . 
         [0039]    The elbow member  500  may include a body  501  defining a lumen  503 , an inflow port  505  in fluid communication with the lumen  503 , and an outflow port  507  in fluid communication with the lumen  503 . The inflow port  505  is configured to connect to a return section or second end  405  of a tubing system  400 , and the outflow port  507  is configured to connect to or accept the return port  103  of the reservoir connection assembly  100 . 
         [0040]    The elbow member  500  may further have a flange  509  disposed around the outflow port  507  to ensure proper alignment of the elbow  500  with the reservoir connection assembly  100  as shown in  FIGS. 4A and 4B . For example, as shown, flange  509  has a tombstone shape with a flat portion on a bottom portion thereof to allowing for connection with return port  103  in only one orientation of the elbow  500 . 
         [0041]    In at least some embodiments, the elbow  500  is formed of molded plastic. The elbow  500  may be injection molded, blow molded, or formed in any other suitable manner known in the art. The elbow  500  may be made of one solid piece or a conglomeration of subparts. 
         [0042]    In one embodiment, one or more pumps may be used to control fluid flow through the cooling system  1000 . Referring to  FIG. 6 , a pump  600  may be connected to the tubing system  400  to pressurize a fluid in the tubing  401 . While any pump known in the art can be used, as shown  FIG. 6 , the type of pump  600  used is a peristaltic pump which applies pressure to compress the outside of a pump tubing  602  forcing fluid downstream towards the medical device. The pump tubing  602  may be made of a thicker gauge of the same material or a different material than the tubing  401 , thus allowing it to withstand the repetitive stresses of the peristaltic pump for the duration of a medical procedure. Connectors  604  may be used to fluidly connect the pump tubing  602  to the tubing  401 . Further, a protective slip cover  606  may alternatively be used to protect either the pump tubing  602 , or the tubing  401 , if no pump tubing  602  is utilized. Though described herein with respect to a peristaltic pump, any device suitable to create a pressure to advance fluid through the tubing  401  in the cooling system  1000  may be used. 
         [0043]    As an alternative to using a peristaltic pump  600 , the entire system  1000  may rely on gravity and the change in density of the fluid as it is heated to allow the fluid to circulate through the system  1000 . For example, as water heats, its density at 1 atm (sea level) decreases from about 62.4 lb/ft 3  at 60° F. to about 60 lb/ft 3  at 212° F. This difference in density may in some circumstances promote sufficient circulation of the fluid through the system  1000  to maintain proper cooling of the medical device. 
         [0044]    The fluid used in cooling system  1000  may be any suitable liquid such as saline solution, de-ionized water, sugar water, and combinations thereof, or the like. For example, the reservoir  200  may be a saline bag traditionally used in medicine. 
         [0045]    In use, the tubing system  400  is connected to a medical device (not shown) to cool the medical device. The medical device may have cooling lumens such as those found in microwave ablation probes and microwave ablation catheters. The tubing system  400  connects to an inflow port of the medical device allowing cooling fluid to flow through the lumens of the medical device to and flow out of an outflow port on the medical device. The cooling fluid may pumped from the reservoir  200  through the medical device, as described above, or alternatively, the cooling fluid may be gravity fed to the medical device. The cooling system  1000  may include the reservoir connection assembly  100  and the drip chamber  300  in fluid communication with the tubing system  400 , as described above. The cooling fluid flows from the reservoir  200  through the reservoir connection assembly  100 , drip chamber  300 , and the tubing system  400  into the inflow port of the medical device. The fluid returns to the reservoir  200  flowing from the outflow port of the medical device through tubing system  400 , the return port  103 , and the second lumen  107  of reservoir connection assembly  100 . The fluid extracts or absorbs heat from the medical device to cool the device. As the fluid is traveling through system  1000 , it releases some heat into the environment surrounding the tubing system  400 . If thermal diffusion devices  407  are connected to the system  1000 , heat may be released from the fluid more efficiently, allowing for a reduced operating temperature of the system  1000 . 
         [0046]    Temperatures maintained in the system  1000  and the energy delivery device should be within a range to avoid injury to the patient and adequate to allow flow through the system. For example, the temperature should be below approximately 113° F. to avoid injury to the patient and above the freezing temperature of the fluid. Pressures and flow rates within the system  1000  and the components thereof may be varied through variations in pump speed, and through design of the system  1000  and the components thereof. 
         [0047]    Some example performance parameters include: 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 Microwave Needle 
                 Microwave 
               
               
                   
                 Pump 
                 Ablation Probe 
                 Ablation Catheter 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Pressure 
                 35-45 
                 psi 
                 45-55 
                 psi 
                 50-70 
                 psi 
               
               
                   
                 Up to 60 
                 psi 
               
               
                 Flow Rate 
                 4.8-6.1 
                 in 3 /min 
                 4.2-5.5 
                 in 3 /min 
                 1.4-1.8 
                 in 3 /min 
               
               
                   
               
             
          
         
       
     
         [0048]    One of the advantages of the cooling system  1000  described herein is that it can employ standard sterile saline bags as the fluid reservoir, which eliminates the need for a specialized fluid source. Further the system  1000  recirculates fluid as opposed to simply dumping the cooling fluid after one pass through the medical device, thereby conserving cooling fluid and eliminating the need for a collection bucket or bag. 
         [0049]    Methods are also disclosed herein. In an embodiment, a method may include providing a saline bag or other fluid reservoir and a saline bag elongate member having multiple lumens defined therein. The saline bag elongate member includes at least one return port connected to at least one of the lumens. The method may also include providing a drip container such as the drip container  300  disclosed herein. 
         [0050]    The method may further include providing an elbow  500  as disclosed herein. The method further includes connecting the elbow  500  to the return port of the saline bag elongate member to allow fluid flow to return into the saline bag through the return port. The method also includes the step of connecting a return portion of the tubing system  400  to the elbow  500 . 
         [0051]    Also disclosed is a method for recirculating a cooling fluid for use with an energy delivery device. The method includes providing an energy delivery device, providing a recirculating cooling system connected to the energy delivery device, and recirculating a fluid through the cooling system and energy delivery device to maintain the energy delivery device at a desired temperature or within a desired temperature range to prevent undesired damage to tissue. The desired temperature range may include an upper limit corresponding to a temperature above which tissue is damaged and a lower limit below which the fluid will not flow within the system. The flow rate of fluid within the system may be adjusted as the temperature approaches the upper limit or the lower limit. For example, when the temperature approaches the upper limit the flow rate may be increased to increase the cooling of the medical device. The system may include visual or audible indicia when the temperature approaches the upper or lower limit. 
         [0052]    It should be understood that the foregoing description is only illustrative of the present disclosure. Various alternatives and modifications can be devised by those skilled in the art without departing from the disclosure. Accordingly, the present disclosure is intended to embrace all such alternatives, modifications, and variances. The embodiments described with reference to the attached drawing figs. are presented only to demonstrate certain examples of the disclosure. Other elements, steps, methods, and techniques that are insubstantially different from those described above and/or in the appended claims are also intended to be within the scope of the disclosure.