Abstract:
A portable cooler is provided for heat exchange catheters that is powered by one or more batteries. The cooler can include Rankine cycle compressor components or thermoelectric cooler (TEC) components. The cooler can be carried in an ambulance and used to support coolant to an indwelling heat exchange catheter that is placed in the patient&#39;s venous system to prevent fever and/or induce therapeutic moderate hypothermia in, e.g., stroke victims, heart attack victims, and cardiac arrest victims.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to coolers for heat exchange catheters. 
     BACKGROUND OF THE INVENTION 
     The present assignee has introduced heat exchangers that cool (and in some cases heat) saline that is sent in a closed loop through an indwelling heat exchange catheter for the purpose of maintaining patient temperature. The catheter can be used to prevent fever following ischemic insult or trauma or to induce therapeutic hypothermia for conditions such as stroke, heart attack (myocardial infarction), and cardiac arrest, as well as cooling for aneurysm surgery and warming after cardiac bypass operations, and other heating/cooling applications. 
     Of relevance to the present invention is the discovery that the medical outcome for a patient suffering from severe brain trauma or from ischemia caused by stroke, cardiac arrest, or heart attack is improved if the patient is cooled below normal body temperature (38° C.). As understood by the present invention, the medical outcome for many such patients might be significantly improved if the patients were to be moderately cooled to 32° C.-34° C. relatively quickly after an ischemic insult for a short period, e.g., 12-72 hours. It is believed that such cooling improves patient outcomes by improving the mortality rate, in that many organs can benefit from the cooling, and by improving the neurological outcome for those patients that survive. 
     As recognized in co-pending U.S. patent application Ser. No. 09/133,813, filed Aug. 13, 1998, owned by the present assignee and incorporated herein by reference, the above-mentioned advantages in treating ischemia by cooling can be realized by cooling the patient&#39;s entire body, i.e., by inducing systemic hypothermia. The advantage of systemic hypothermia is that, as recognized by the present assignee, to induce systemic hypothermia a cooling catheter or other cooling device need not be advanced into the blood supply of the brain, but rather can be easily and quickly placed into the relatively large vena cava of the central venous system. Moreover, since many patients already are intubated with central venous catheters for other clinically approved purposes anyway, providing a central venous catheter that can also cool the blood requires no additional surgical procedures for those patients. A cooling central venous catheter is disclosed in the present assignee&#39;s co-pending U.S. patent application Ser. Nos. 09/253,109, filed Feb. 19, 1999 and 09/305,613, filed May 5, 1999, both of which are incorporated herein by reference. 
     As mentioned above, it is believed that the sooner a patient is cooled after ischemic insult, the better the therapy. The present invention recognizes that many patients will have their first encounter with health care personnel in ambulances. Thus, it would be advantageous, as understood herein, to provide a means to cool these patients in the ambulance, with cooling continuing in the hospital. Heretofore, however, the heat exchangers that have been induced were not generally portable and in any case typically require AC power, both of which characteristics prevent their use in ambulances. With these recognitions in mind, the invention herein is provided. 
     SUMMARY OF THE INVENTION 
     A system for controlling patient temperature includes a portable housing and a heat exchanger in the housing and powered by at least one battery. A heat exchange element is in thermal contact with the heat exchanger, and the heat exchange element carries coolant. Also, a closed loop heat exchange catheter receives coolant from and sends coolant to the heat exchange element. The catheter is configured for placement in the circulatory system of a patient to exchange heat with the blood of the patient. The preferred heat exchanger may be based on compressor principles or on thermoelectric cooling principles. 
     In a preferred non-limiting embodiment, the catheter is configured for percutaneous advancement into the central venous system of the patient. The coolant preferably is not infused into the bloodstream of the patient. 
     If desired, a pump may be supported on the housing to pump coolant through the system. In further preferred non-limiting embodiments, tubing connects the catheter to the heat exchange element through a connector, and a quick disconnect assembly is engaged with the housing and is also engaged with at least a portion of the tubing connected to the catheter to disconnect the catheter from the housing when the housing moves past a limit of the disconnect assembly. The disconnect assembly may include a tether. 
     With respect to the heat exchange element, it may form an interior through which coolant flows and an exterior in thermal contact with the heat exchanger. Coolant flows through the heat exchange element through tortuous paths. The tortuous paths may be established at least in part by spheres disposed in the interior of the heat exchange element. 
     In another aspect, a method for cooling a patient while the patient is located in a vehicle includes disposing a dc-powered heat exchanger in the vehicle, and advancing a heat exchange catheter into the venous system of the patient. The system also includes establishing fluid communication between the catheter and heat exchanger. The heat exchanger is operated to circulate coolant through the catheter to cool the patient. 
     In yet another aspect, a heat exchange system that is configured for engaging, in fluid communication, an indwelling heat exchange catheter, includes a portable housing, a heat exchanger in the housing, and at least one battery electrically connected to the heat exchanger to power the heat exchanger. 
    
    
     
       The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the present portable cooler, showing the heat exchange catheter schematically; 
         FIG. 2  is a perspective view of a compressor components of a first embodiment of the cooler; 
         FIG. 3  is a perspective view of a thermoelectric cooler (TEC) components of a second embodiment of the cooler; 
         FIG. 4  is a perspective view of the disposable heat exchange element, with one of the edges turned up to expose the spacing spheres for illustration; 
         FIG. 5  is a cross-sectional view as seen along the line  5 — 5  in  FIG. 4 ; 
         FIG. 6  is a perspective view of the quick disconnect connector in the engaged configuration, with portions broken away and schematically showing the housing  16 ; and 
         FIG. 7  is a perspective view of the quick disconnect connector in the disengaged configuration, with portions broken away. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to  FIG. 1 , a system is shown, generally designated  10 , that includes a heat exchange catheter  12  that is in fluid communication with a cooler  14 . While the term “cooler” is used herein, it is to be understood that the cooler  14  can in some embodiments warm coolant as well as cool it. 
     In accordance with present principles, the system  10  can be used to induce therapeutic hypothermia in a patient using a catheter in which coolant circulates in a closed loop, such that no coolant enters the body. While certain preferred catheters are disclosed below, it is to be understood that other catheters can be used in accordance with present principles, including, without limitation, any of the catheters disclosed in the following U.S. patents, all incorporated herein by reference: U.S. Pat. Nos. 5,486,208, 5,837,003, 6,110,168, 6,149,673, 6,149,676, 6,231,594, 6,264,679, 6,306,161, 6,235,048, 6,238,428, 6,245,095, 6,251,129, 6,251,130, 6,245,626, 6,261,312, 6,312,452, 6,325,818, 6,409,747, 6,368,304, 6,338,727, 6,299,599, 6,287,326, 6,126,684. 
     As shown in  FIG. 1 , the cooler  14  includes a lightweight portable plastic or metal housing  16  that can include a handle  18 . One or more air intakes  20  can be provided on the housing  16 , as well as a series of air exhaust vents  22 . 
     A heat exchange element, described more fully below, can be received in a slot  24  of the housing  16 . As shown, an inlet tubing set  26  and an outlet tubing set  28  are connected to the heat exchange element in the slot  24 , and these tubes  26 ,  28  are connected to the catheter  12 . Thus, coolant such as but not limited to saline can circulate in a closed loop through the catheter  12  and heat exchange element without exiting the loop into, e.g., the patient&#39;s bloodstream, with the coolant being cooled as it passes through the heat exchange element. The coolant in turn cools the blood. 
     If desired, a temperature probe can be engaged with the patient to provide feedback to the system  10  to establish a predetermined temperature, but in the preferred embodiment that is not necessary. Specifically, the preferred embodiment seeks simply to start the cooling process as quickly as possible during the relatively short period that the patient is enroute to a hospital, with longer-term controlled cooling being undertaken at the hospital. Because many hours may be required to reach target temperature in the hypothermic range, the system  10  need only commence removing heat from the patient as quickly as possible, without requiring patient temperature feedback or sophisticated control algorithms that can be employed in hospital systems. 
     In one non-limiting embodiment the inlet tubing set  26  can include a dual lumen IV spike  30  that interconnects an IV bag  32  of coolant, e.g., saline, with the coolant circuit established in part by the inlet tubing set  26 . Also, in a non-limiting embodiment the inlet tubing set  26  can include a quick connect tubing pump  33  such as a peristaltic pump or diaphragm pump that can receive IV tubing and engage the tubing externally to pump fluid therethrough. Moreover, if desired the outlet tubing set  28  can include an air trap  34  to remove air from the saline entering the catheter  12  from the cooler  14 . 
     As shown in  FIG. 1 , the housing  16  can contain or otherwise support one or more, preferably two, batteries  36 . The batteries  36  may be twelve volt lead acid rechargeable vehicle batteries. The batteries  36 , when disconnected from their charger, can be if desired the sole source of power for the system  10 , powering both the heat exchange components within the housing  16  and the pump  33 . 
       FIG. 2  shows heat exchange components that can be included within the housing  16  in one non-limiting exemplary embodiment. As show, a Rankine cycle compressor  40  can compress refrigerant such as freon and send the freon to a condenser  42  with cooling fans  43 , which receive air through the air intake  20  and exhaust air through the vents  22  (FIG.  1 ). The compressor  40  may be a Danfoss BD35F compressor. From the condenser  42  the freon flows through freon lines  44  to preferably two heat exchange plates  46  made of, e.g., copper or steel or other metal. A heat exchange element  48 , mentioned above as being disposable in the slot  24  of the housing  16  and discussed further below, is sandwiched between the plates  46  in thermal contact therewith to cool the heat exchange element. After passing through the plates  46  freon is sent back to the compressor through return freon lines  50 . 
       FIG. 3  shows that instead of a compressor-based system, the housing  16  of the system  10  can hold thermoelectric coolers (TEC)  52  that are thermally coupled with heat exchange cold plates  54  that sandwich the heat exchange element  48  and that consequently cool the element  48 . Opposite the cold plates  54 , the TEC  52  are thermally coupled to heat sink plates  56  in accordance with TEC principles known in the art, which may include cooling fins  58 . Axial cooling fans  60  remove heat from the heat sink plates  56 . The fans  60  can receive air through the air intake  20  and exhaust air through the vents  22  (FIG.  1 ). 
       FIGS. 4 and 5  show a preferred non-limiting heat exchange element  48 , which can be configured to have opposed flat flexible plastic layers  62  that form a coolant space  64  therebetween. A semi-rigid plastic receiving edge  66  may extend between the layers  62  and be formed with tubing receptacles  68  that receive respective segments  70 ,  72  of the inlet tubing set  26  and outlet tubing set  28  (segments  70 ,  72  also shown in FIG.  1 ). A tortuous path is established through which coolant can flow from the inlet receptacle  68  to the outlet. In a preferred non-limiting embodiment the tortuous paths are provided by hard plastic spheres  74 , although other objects, such as egg-shaped objects, rectilinear objects and channels, and so on may be used. 
     The present recognizes that because the present system  10  is intended to be carried in an ambulance, the housing  16  may move suddenly, and that such movement could pose a risk of pulling the catheter  12 , which is attached to the housing  16  by means of the tubing sets  26 ,  28 , out of the patient. Accordingly, if desired a quick disconnect connector assembly, generally designated  80  in  FIGS. 6 and 7 , can be provided. The assembly  80  can have a first rigid half connector  82  that mates with a second rigid half connector  84  in fluid communication therewith, with the second rigid half connector  84  being connected to the inlet and outlet tubing sets  26 ,  28 . In contrast, the first half connector  82  is connected to supply and return tubes  86 ,  88  that are in turn connected to the catheter  12 . 
     A tether  90  may be connected to the first half connector  82  preferably by means of a pin  92 , it being understood that the pin  92  engages and may hold together the half connectors  82 ,  84 . The tether  90  is also connected to the housing  16 , whereas the second half connector  84  preferably is attached, e.g., by means of a strap  94 , to an object such as a gurney that is separate from the housing  16 . With this structure, should the housing  16  move within the ambulance a sufficient amount, the tether  90  dislocates the pin  92  as indicated by the arrow  96  to decouple the half connectors  82 ,  84  (and, hence, the catheter  12  and housing  16 ) from each other, to prevent pulling the catheter  12  out of the patient. If desired one or both half connectors  82 ,  84  can be included with self-sealing valves that automatically close upon decoupling. 
     While the particular PORTABLE COOLER FOR HEAT EXCHANGE CATHETER as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more”. All structural and functional equivalents to the elements of the above-described preferred embodiment that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited as a “step” instead of an “act”.