Abstract:
A disposable esophageal probe having dual temperature elements is connected to a cooling catheter controller via a reusable interconnect line to provide redundancy in temperature feedback to the controller, namely, to provide both a control temperature feedback signal and an alarm temperature feedback signal to the controller.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to methods and apparatus for cooling patients for therapeutic purposes, and more particularly to systems for measuring temperature in a patient to provide a feedback control signal for controlling a cooling catheter. 
     BACKGROUND 
     It has been discovered that the medical outcome for a patient suffering from severe brain trauma or from ischemia caused by stroke or heart attack is degraded if the patient&#39;s body temperature rises above normal (38° C.). It is further believed that the medical outcome for many such patients might be significantly improved if the patients were to be cooled relatively quickly to around 32° C. for a short period, e.g., 24-72 hours. Apart from the therapeutic benefits of hypothermia, the outcomes for brain trauma or ischemia patients that develop fevers is worse than for patients that do not develop fevers. Consequently, temperature management for such patients is important, even when hypothermia is not to be used to treat the patients. 
     The affected organ, in any case, is the brain. Accordingly, systems and methods have been disclosed that propose cooling blood flowing to the brain through the carotid artery. An example of such systems and methods is disclosed in co-pending U.S. patent application Ser. No. 09/063,984, filed Apr. 21, 1998, owned by the present assignee and incorporated herein by reference. In the referenced application, various catheters are disclosed which can be advanced into a patient&#39;s carotid artery and through which coolant can be pumped in a closed circuit, to remove heat from the blood in the carotid artery and thereby cool the brain. The referenced devices have the advantage over other methods of cooling (e.g., wrapping patients in cold blankets) of being controllable, relatively easy to use, and of being capable of rapidly cooling and maintaining blood temperature at a desired set point. 
     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 brain trauma/ischemic patients by cooling can also 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, if only to manage temperature and thereby ameliorate fever spikes, 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. No. 09/253,109, filed Feb. 19, 1999 and incorporated herein by reference. 
     To supply coolant such as saline to the above-disclosed catheters, a cooling system such as the present assignee&#39;s system disclosed in co-pending U.S. patent application Ser. No. 09/220,897, filed Dec. 24, 1998 and incorporated herein by reference, can be used to remove heat from the coolant and return the coolant to the catheter in a closed loop heat exchange system. An alternate system is the thermoelectric cooler (TEC)-based system owned by the present assignee and disclosed in co-pending U.S. patent application Ser. No. 09/260,950, filed Mar. 2, 1999, also incorporated herein by reference. In any case, a cooling system controller preferably maintains temperature at a desired setpoint, be it normothermic or hypothermic. As recognized herein, to facilitate such temperature maintenance, it is necessary to measure patient temperature. 
     As understood by the present invention, esophageal temperature is a preferred parameter to use because it is more sensitive to body core temperature changes than, e.g., rectal temperature. As also understood by the present invention, for ease of use and to avoid burdensome sterilization procedures, the portion of an esophageal temperature sensor that is advanced into a patient should be disposable. Portions not in contact with the patient, however, need not be disposable. The present invention is provided with these considerations in mind. 
     SUMMARY OF THE INVENTION 
     A temperature probe for a therapeutic cooling catheter system includes an elongated probe body that has a distal end and a proximal end, and that is configured for being advanced into a patient with the distal end located in the patient&#39;s body and the proximal end located outside the patient&#39;s body. First and second temperature sensors, preferably thermistors, are located at or near the distal end of the probe body for generating respective first and second temperature signals. Also, a probe connector is located at or near the proximal end of the probe body, and a reusable interconnect cable has a cable connector configured for engaging the probe connector and at least one controller connector electrically connected to the cable connector and engageable with a controller. 
     In a preferred embodiment, the probe body is configured for advancement into a patient&#39;s esophagus. Also in the preferred embodiment, the probe connector snappingly engages the cable connector. One of the connectors preferably is a male telephone connector and the other connector is a female telephone connector. More specifically, the preferred probe connector includes an outwardly biased pivot arm and the cable connector includes a socket including at least one retainer rail, and the arm snappingly engages the rail when the probe connector is advanced into the cable connector. The arm of the probe connector extends beyond the cable connector when the probe connector is fully engaged with the cable connector, with the arm being manipulable to cause the arm to clear the rail and thereby permit disengagement of the probe connector from the cable connector. 
     As disclosed in greater detail below, the cable includes first and second controller segments terminating in respective first and second controller connectors. Each controller connector is engageable with the controller. The controller connectors can be phone plugs. 
     With further regard to the controller, the first temperature sensor generates a control feedback signal that is useful by the controller for controlling a heat exchanger. Also, the second temperature sensor generates an alarm feedback signal useful by the controller for generating an alarm signal. The system is disclosed in combination with a heat exchange catheter in closed loop fluid communication with the heat exchanger. 
     In another aspect, a controller includes a program of instructions for undertaking method acts for controlling a heat exchanger. These acts includes receiving, from first and second temperature sensors, respective first and second patient esophageal temperature signals. Also, the method acts includes controlling a heat exchanger for a cooling catheter in response to at least the first signal, and generating an alarm signal when the second signal reaches a predetermined setpoint. 
     In still another aspect, an esophageal temperature sensing apparatus includes first and second temperature sensors supported by a disposable probe body. The probe body is configured for advancing the sensors into a patient&#39;s esophagus, with the proximal end of the probe body remaining outside the patient&#39;s body at all times. A male or female telephone probe connector is at the proximal end, and an interconnect cable having a female or male telephone cable connector is selectively snappingly engageable with the probe connector. Moreover, a controller connector is engageable with a controller of a closed circuit cooling catheter heat exchange system. As set forth below, the interconnect cable establishes electrical connectivity between the cable connector and the controller connector. 
     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 schematic view of the present invention in its intended environment; 
     FIG. 2 is a top view of the probe body in an exploded relationship with the interconnect cable; 
     FIG. 3 is a cross-sectional view of the cable connector as seen along the line  3 — 3  in FIG. 2; 
     FIG. 4 is a cross-sectional view of the cable connector as seen along the line  4 — 4  in FIG. 2; and 
     FIG. 5 is a flow chart of the logic of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to FIG. 1, a therapeutic system, generally designated  10 , is shown for establishing and maintaining hypothermia in a patient  12 , or for attenuating a fever spike in a patient and then maintaining normal body temperature in the patient. As shown, the system  10  includes a cooling system  14  that can be a water-bath system or a TEC-based system such as either of the systems disclosed in the last two of the above-referenced applications. In any case, the cooling system  14  can be considered a source of coolant, preferably sterile saline, for the catheters of the present invention. 
     As set forth in the last two of the above-referenced applications, the cooling system  14  can include a heat exchange system  16  including a pump. The pump and/or heat exchange elements in the heat exchange system  16  are controlled by a controller  18 . The controller  18  can be implemented by a software-executing processor or by discrete logic circuits or other electronic circuitry device to establish a desired patient temperature by appropriately controlling the pump and/or heat exchanger in response to a temperature signal derived from one or more sensors in the patient  12 . 
     As shown in FIG. 1, a catheter  20  can communicate with the cooling system  14  via coolant supply and return lines  22 ,  23 . The coolant lines  22 ,  23  can be IV lines or tubes or other suitable fluid conduits, such as metal (steel) tubes. When the coolant lines  22 ,  23  are plastic tubes, they can be connected to the catheter  20  and the cooling system  14  by suitable connecting structure, such as Luer fittings, interference fits, solvent bonding, heat staking, ultrasonic welding, and the like. The catheter  20  can be any of the catheters disclosed in the first two of the above-referenced applications in which coolant is circulated in a closed fluid communication loop to remove heat from the patient  12 . The catheter  20  is advanced (preferably through an introducer sheath) into the patient  12  through a neck entry point or femoral entry point to establish hypothermia in the patient  12 , or to attenuate a fever back to normal body temperature. Preferably, the catheter  20  is advanced into the central venous system, and more preferably into the vena cava, either through the subclavian vein or jugular vein or femoral vein. 
     To enable the controller  18  to control the heat exchanger  16 , patient temperature feedback is required. As understood by the present invention, patient safety standards can dictate that the feedback be redundant, such that if one temperature sensor fails, the second sensor can still monitor temperature. As further understood by the present invention, while two sensors are desirable, it is also desirable to minimize the number of probes that are advanced into a patient. 
     Accordingly, a temperature feedback apparatus  24  including a probe body  26  and an interconnect cable  28  is provided herein to interconnect at least first and second temperature sensors (not shown in FIG. 1) that are positioned in the patient  12  to the controller  18 . Although the sensors can be positioned in, e.g., the rectum, bladder, or near the tympanic membrane of the patient  12 , they are preferably positioned in the esophagus. 
     FIGS. 2-4 show the details of the temperature feedback apparatus  24 . As can be appreciated in reference to FIG. 2, the probe body  26  is a disposable elongated probe body having a distal end  30  and a proximal end  32 . In the preferred embodiment, the probe body  26  is configured for advancing the probe body into a patient&#39;s esophagus with the distal end  30  located in the patient&#39;s body and the proximal end  32  located outside the patient&#39;s body. 
     At least first and second temperature sensors  34 ,  36  are located at or near the distal end  30  of the probe body  26 . The sensors are preferably YSI400 series thermistors that generate respective first and second temperature signals. Each thermistor is electrically connected to two electrical leads in accordance with means known in the art, and the leads extend through the probe body  26  to the proximal end  32  of the body  26 . Surrounding the leads and the sensors  34 ,  36  is a plastic biocompatible sheath  38  that can be coated with antimicrobial coatings and/or antithrombogenic coatings. Also, the sensors  34 ,  36  are isolated from each other by placing the first sensor  34  inside a first insulative sheath and then placing the first sheath and second sensor  36  inside a second sheath. Sensors other than thermistors, such as thermocouples, resistance temperature detectors (RTDs), and the like can be used. 
     A probe connector  40  is located at or near the proximal end  32  of the probe body  26 . The interconnect cable  28 , which preferably is reusable, has a cable connector  42  that is configured for easily and quickly engaging and disengaging the probe connector  40 , preferably in a snapping or interference fit. In one preferred embodiment, the probe connector  40  is a male telephone connector and cable connector is a female telephone connector, although these structures can be reversed. 
     Accordingly, in the preferred embodiment shown in FIGS. 2-4, the probe connector  40  includes an outwardly biased pivot arm  44  that is formed with transverse ears  44   a  and a narrow extension  44   b . The cable connector  42 , on the other hand, includes a socket  46  that in turn includes at least one retainer rail  48 . The arm  44  of the probe connector  40  rides against the rail  48  when the probe connector  40  is advanced into the cable connector  42  to overcome the outward bias of the arm  44 . When the probe connector  40  has been advanced a sufficient distance into the cable connector  42 , the ears  44   a  clear the rail  48 , causing the pivot arm  44  to snap outwardly under the influence of its material bias, thereby engaging the connectors  40 ,  42 . Electrical contact between the connectors  40 ,  42  is established between a connector ramp  50  in the cable connector  42  and complimentarily-formed structure (not shown) on the probe connector  40 . 
     When the connectors  40 ,  42  are fully engaged, the extension  44   b  of the probe connector  40  extends beyond the cable connector  42 . The extension  44   b  can be manipulated to cause the arm  44  to clear the rail  48  and thereby permit the connectors  40 ,  42  to be disengaged by pulling the probe connector  40  out of the cable connector  42 . 
     In the embodiment shown in FIG. 2, the cable  28  includes first and second controller segments  52 ,  54  that terminate in respective first and second controller connectors  56 ,  58 . It is to be understood that the first controller connector  56  is electrically connected to the first sensor  34  via the first segment  52  and probe body  26  when the connectors  40 ,  42  are engaged, and the second controller connector  58  is electrically connected to the second sensor  36  via the second segment  54  and probe body  26  under these circumstances. In accordance with the present invention, each controller connector  56 ,  58  is engageable with the controller  18  (FIG. 1) to thereby establish an electrical path between the sensors  34 ,  36  and the controller  18 . Preferably, the controller connectors  56 ,  58  are phone plugs. 
     Per the present invention the first temperature sensor  34  generates a control feedback signal that is useful by the controller  18  for controlling the heat exchanger  16 . Also, the second temperature sensor  36  generates an alarm feedback signal that is useful by the controller  18  for generating an alarm signal. 
     FIG. 5 shows the logic of the present controller  18  in treating the signals from the sensors  34 ,  36 . Commencing at decision diamond  60 , it is determined whether two valid signals have been received. If not, indicating an undesirable loss of redundancy, the process moves to block  62  to return an error signal or alarm. Otherwise, the logic moves to block  64 . 
     At block  64 , the controller  18  uses the control signal from the first sensor  34  to control the heat exchanger  16  as set forth in the latter two of the above-disclosed patent applications. Proceeding to decision diamond  66 , it is determined whether the second signal, i.e., the signal from the second sensor  36 , has reached a high temperature or low temperature setpoint. If not, the process ends at state  68 , but if a setpoint has been reached an alarm is generated at block  70 . The process, although shown in flow chart format for ease of disclosure, can be a continuous state process. 
     While the particular TEMPERATURE PROBE AND INTERCONNECT CABLE FOR HYPOTHERMIA CATHETER TEMPERATURE FEEDBACK 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”.