Abstract:
A heat exchange system for an indwelling catheter is tested for proper operation by observing whether a fluid temperature is within a command zone range and if not whether temperature moves toward the range or equalizes with it within predetermined parameters after a pump has stopped, and only if temperature exhibits none of the tested-for conditions indicating an error.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to systems and methods for effecting non-standard fluid line connections. 
     BACKGROUND OF THE INVENTION 
     It has been discovered that the medical outcome for a patient suffering from severe brain trauma or from isehemia caused by stroke or heart attack is improved if the patient is cooled below normal body temperature (37.degree. C.). Furthermore, it is also accepted that for such patients, it is important to prevent hyperthermia (fever) even if it is decided not to induce hypothermia. Moreover, in certain applications such as post-CABG surgery, it might be desirable to rewarm a hypothermic patient. 
     As recognized by the present invention, the above-mentioned advantages in regulating temperature can be realized by cooling or heating the patient&#39;s entire body. Moreover, the present invention understands that since many patients already are intubated with central venous catheters for other clinically approved purposes anyway such as drug delivery and blood monitoring, providing a central venous catheter that can also cool or heat the blood requires no additional surgical procedures for those patients. However, single purpose heat exchange catheters such as are made by Innercool Therapies of San Diego, Calif. and Zoll Medical Corp. can also be less optimally used. 
     Regardless of the particular catheter used, it is clear that heat must be removed from or added to the coolant that flows through the catheter. As still further understood by the present invention, it is desirable that the heat exchange system be easy to use by health care personnel, and provide for monitoring systems and convenient temperature control. U.S. Pat. No. 6,146,411, incorporated herein by reference, discloses one such heat exchange system. 
     As understood herein, it would be advantageous to test the heating/cooling system to ensure proper functionality regarding the ability of the system to cool or heat the glycol liquid that in turn will heat or cool the saline liquid being used in the catheter. 
     SUMMARY OF THE INVENTION 
     A computer-implemented method for testing for proper functioning of a heat exchange system engageable with an indwelling heat exchange catheter to circulate working fluid therein using a pump includes determining whether temperature of heat exchange fluid in a chamber through which the working fluid is circulated is within a range of a target temperature. If the temperature of the heat exchange fluid is not within the range, the method includes stopping the pump. Only if (1) the temperature is not within the range at the elapse of the predetermined period, or (2) the temperature has not changed during the predetermined period by at least a predetermined amount, is an error indication returned. 
     If it is determined that the temperature is not within the range, the method may include deciding whether the temperature is warmer than the range or cooler than the range. If the temperature is warmer than the range the method can further include measuring the temperature with the pump stopped during the predetermined period and returning an error only at the elapse of the predetermined period if the temperature is not within the range or if the temperature has not changed during the predetermined period by at least the predetermined amount. On the other hand, if the temperature is cooler than the range the method can further include measuring the temperature with the pump stopped during the predetermined period and, if the temperature has not changed by the predetermined amount since the pump was stopped, determining whether a compressor has started. The test can be delayed if the compressor has not started. 
     In another aspect, a heat exchanger for treating working fluid to be circulated through an indwelling heat exchange catheter includes a pump for pumping the working fluid in a fluid path, and a heat exchange chamber in the path and containing a heat exchange fluid having a temperature. A processor controls the pump. The processor executes logic that includes determining that the beat exchanger is not working properly if the temperature of the heat exchange fluid is not within an expected range only if (1) substantial equalization of heat exchange fluid temperature with working fluid temperature does not occur within a predetermined period after stopping the pump, or (2) temperature does not change by at least a predetermined amount within a predetermined period after stopping the pump. 
     In still another aspect, a processor for a heat exchange system for heating and cooling a working fluid circulated through a catheter by a pump is programmed to determine whether a fluid temperature is within a command zone range and if not, to determine whether temperature moves toward the range or equalizes with it within predetermined parameters after a pump has stopped. Only if temperature does not move toward the range or equalize with it within predetermined parameters after the pump has stopped does the processor indicate an error. 
     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 block diagram of an example system in accordance with present principles; and 
         FIGS. 2 and 3  are flow charts showing example logic in accordance with present principles. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to  FIG. 1 , a patient heating/cooling system is shown and generally designated  10 . As shown, the system  10  includes three separate fluid circuits: a saline circuit (also referred to as the working fluid circuit), a water glycol circuit (also referred to as the heating/cooling fluid circuit), and a refrigerant circuit (also referred to as the refrigerating fluid circuit.) 
     Taking the saline circuit first, an indwelling heat exchange catheter  12  that can be inserted into a patient  13  during an operation is connected to a heat exchange bath  14  by a saline supply line  16 . The supply line  16  is connected to a coiled or helical heat exchange tube  17  that is immersed in the bath  14  fluid to exchange heat therewith. In turn, the heat exchange tube  17  is connected to a peristaltic tubing saline pump  18  by fluid line  20 . 
     It is to be understood that in a preferred embodiment, the saline pump  18  has three modes: a standby or off mode, a treatment mode, and an idle mode wherein the saline pump  18  operates very slowly, but does not stop. In the idle mode, the patient  13  is effectively thermally decoupled from the heating/cooling system  10 . 
     As further shown in  FIG. 1 , a saline return line  22  communicates saline from the catheter  12  to the saline pump  18  to complete the saline circuit. It is to be appreciated that the tubes  16 ,  17 ,  20 , and  22  can be provided as a disposable IV tubing set. 
       FIG. 1  also shows a system controller  24 . As described in further detail below, the system controller  24  receives signals from a saline level detector (not shown) regarding the level of saline therein and uses this information to control the saline pump  18 . 
     It is to be understood that within the saline circuit, saline is circulated to and from the catheter  12  through the helical heat exchange tube  17  in the heat exchange bath  14 . As described in detail below, the heat exchange bath  14  is filled with heating/cooling fluid, preferably water glycol. The water glycol can be heated or cooled in order to heat or cool the saline and thus, increase or decrease the temperature of the patient  13  into which the catheter  12  is inserted. Also, it is to be understood that the preferred working fluid is saline, but any similar fluid well known in the art can be used. 
     Now considering the water glycol circuit, the water glycol circuit communicates with a chiller/heater  26  via a water glycol supply line  28  and a water glycol return line  30 . A water glycol pump  32  is installed in the water glycol return line  30  to circulate water glycol through the water glycol circuit. 
     Further, the system controller  24  is connected to the chiller/heater  26  via electrical lines  34  and  36 . Moreover, the system controller  24  is connected to a safety switch  38  at the water glycol pump  32  via electrical line  40 . Thus, the system controller  24  can control the operation of the chiller/heater  26  based on signals from a temperature monitor, described below, and control the operation of the water glycol pump  32  based on level signals from infrared detectors (not shown) that are disposed within a water glycol level detector (not shown). 
     The system controller  24  is also connected to a temperature sensor  42  via electrical line  44  placed at the outlet of the chiller/beater  26 . The controller  24  uses input from the temperature sensor  42  to control the chiller/heater  26  and other system  10  components. 
     In one non-limiting embodiment, the water glycol may be pumped through the water/glycol circuit the chiller/heater  26  can heat or cool the water glycol. Within the heat exchange bath  14 , the water glycol exchanges heat with the saline. Thus, the water glycol can be used to heat or cool saline and in turn, heat or cool the patient in which the catheter  12  is intubated. It is to be further understood that water glycol is the preferred heating/cooling fluid. However, any other fluid with similar properties can be used. 
     Now considering the third (refrigerant) circuit, a compressor  46 , which in non-limiting implementations may be a variable speed DC compressor, is in fluid communication with the chiller/heater  26  via a refrigerant supply line  48  and a refrigerant return line  50 . It is to be understood that the compressor  46  is filled with refrigerant, e.g., R134a. A compressor controller  52  is connected to the compressor  46  via an electrical line  54 . In turn, the system controller  24  is connected to the compressor controller  52  via electrical line  56 . The compressor controller  52  is also connected to a heater, described below, within the chiller/heater  26  via electrical line  73 . 
     It is to be understood that the system controller  24  receives temperature signals from the temperature monitor, described below, and uses these signals to control the operation of the compressor  46  and the heater. The compressor  46  is used to compress refrigerant which, when it expands in the chiller/heater  26 , cools the water glycol that is pumped through the chiller/heater  26  by the water glycol pump  32 . 
     As further shown in  FIG. 1 , a temperature monitor  70  is connected to the system controller  24  via an electrical line  72 . A first patient temperature probe  74  and a second patient temperature probe  76  preferably are connected to the temperature monitor  70  via electrical lines  78  and  80 , respectively. As intended herein, the temperature monitor  70  uses the temperature probes  74  and  76  to monitor the temperature of the patient  13 . Moreover, the temperature monitor  70  sends signals to the system controller  24  representing the temperature of the patient  13 . These signals are used by the system controller  24  to control the operation of the chiller/heater  26 , the saline pump  18 , and the compressor  46 . 
       FIG. 1  shows a display device  82  that is connected to the system controller  24  via electrical line  84  and electrical line  86 . Preferably, the display device  82  provides a visual indication of the patient&#39;s temperature and the bath temperature. For example, the display device  82  can be used to output graphs of minute by minute patient temperature (for, e.g., twenty one days) and water glycol bath temperature. The display device  82  can also be used to provide information regarding the cooling power required by the patient, whether the system is heating or cooling the bath, and at which rate, e.g., low, medium, or maximum, the system is heating or cooling the bath. Further, the display device  82  can display the current patient temperature and the patient target temperature. 
     It is to be understood that a user can scroll the graphs left or right with respect to a stationary cursor within the center of the display. As the graphs are scrolled, information corresponding thereto can be displayed. As shown, the display device  82  also includes a control panel  88  to allow a user, i.e., a doctor or a nurse, to input data, such as a target patient temperature, to the system  10 . 
     Now referencing  FIG. 2 , the beginning of the logic for testing the chiller/heater  26  of testing a cooling/heating system is shown, though it is understood that the present invention is not to be limited to only the current system. 
     Beginning with block  90  and before the catheter system engaged with a patient, a “power on self test” (POST) occurs. During the POST, an initial test is performed to ensure that certain basic features of the system  10  which are not central to present principles are functioning properly. Assuming the POST test passes, the catheter system is engaged with the patient. The logic next moves to block  92 . At block  92  a chiller/heater  26  test timer is set to a specified time interval from which it will count down. In one non-limiting implementation, the time interval can be sixty minutes, but a different time interval may be used. Then at block  94  the chiller/heater  26  test timer begins to count down. 
     At block  96  the chiller/heater  26  test timer expires. Block  96  hereinafter begins a logic subseries generally designated as Logic Flow A. The expiration of the timer indicates that a test of the functionality of the chiller/heater  26  should be performed. 
     At block  98  the chiller/heater  26  test begins. The chiller/heater  26  test determines whether the chiller/heater  26 , which cools glycol used in the heat exchange bath  14 , is properly functioning as follows. 
     At block  100  the logic determines the initial heat exchange bath  14  temperature. The logic then determines at diamond  102  whether the heat exchange bath  14  temperature determined at block  100  is within the intended temperature range, hereafter designated as the “Command Zone.” In one embodiment, the Command Zone can be a temperature range from one degree Celsius below commanded bath temperature to one degree above commanded bath temperature, although other ranges may be used. 
     If the heat exchange bath  14  temperature is within the Command Zone, the logic then moves to block  104  where another chiller/heater  26  test timer is set to count down. This time interval is preferably less than the first time interval determined at block  92 , preferably but not limited to a fifteen minute interval. 
     By determining that the heat exchange bath  14  temperature is within the Command Zone, the logic may conclude that the chiller/heater  26  is functioning properly. Then at block  106  the timer begins another countdown and the logic then reverts back to the beginning of Logic Flow A. 
     Referring back to diamond  102 , should the logic determine that the heat exchange bath  14  temperature is not within the Command Zone, the logic then moves to block  108  where the chiller/heater  26  test timer is set to a specified time interval that may if desired be substantially similar to the interval used at block  92 . 
     Then at block  110  the chiller/heater  26  test timer begins to count down from the given time interval. The bath  14  temperature may not have been within the Command Zone when the initial bath temp  100  was determined. Thus the timer that begins at block  110  provides an opportunity for the chiller/heater  26  to beat or cool the glycol used in the heat exchange bath  14  so that the temperature of the bath  14  reaches the Command Zone. 
     At block  112  the chiller/heater  26  test timer expires and the logic moves to block  114 , where the coolant pump  18  is stopped. Moving to decision diamond  116 , the logic determines whether the heat exchange bath  14  temperature is above the Command Zone. 
     If the heat exchange bath  14  temperature is not above the Command Zone, the logic moves to Logic Flow B which is referenced in  FIG. 3 . If the heat exchange bath  14  temperature is above the Command Zone, the logic instead diverts to Logic Flow C, also referenced in  FIG. 3 . 
     First assuming that the temperature is not above the Command Zone, reference is now made to Logic Flow B in  FIG. 3 . At block  118  a chiller/heater  26  timer is set to a specified period of time, preferably but not limited to three minutes. At block  120  the chiller/heater  26  test timer begins. During the expiration of the timer that began at block  120 , the coolant pump  18  that was stopped at block  114  remains stopped. With the pump  18  stopped, the chiller/heater  26  is able to reach the targeted Command Zone in the bath  14  more quickly since no heat transfer takes place in the bath when the pump is stopped. 
     Moving to block  122 , the logic determines the current bath  14  temperature. Then at diamond  124 , the logic subtracts the current temperature from the temperature at which the bath was when the pump was stopped at block  114 , as measured at state  116  in  FIG. 2 . Remaining at diamond  124 , the logic takes the current bath  14  temperature and subtracts the initial temperature. The logic then determines whether the difference between the current and initial temperature is greater than a threshold, which in one non-limiting embodiment may be half a degree Celsius. 
     If at decision diamond  124  the logic determines that the difference in temperature is greater than half a degree Celsius, the logic reverts back to the beginning of Logic Flow A, meaning that the system test has passed in that the system is attempting to regain the command zone at an acceptably fast rate of temperature change. That is, if the difference is greater than half a degree Celsius, this indicates that the chiller/heater  26  is functioning properly. 
     However, if it is determined that the temperature of the bath has changed less than the threshold (e.g., less than one-half of one degree) during the period in which the pump is stopped, the logic then continues to decision diamond  126 , wherein the logic determines whether the current heat exchange bath  14  temperature is within the Command Zone range. If the logic determines that the current temperature is within the Command Zone, the logic reverts back to the beginning of Logic Flow A. 
     On the other hand, if the logic determines that the current temperature is not within the Command Zone, the logic continues to decision diamond  128 . At diamond  128  the logic determines whether the chiller/heater  26  test timer has expired. If it has not expired, the logic reverts back to block  122  where the logic executes the same process until the timer that began at block  120  expires. 
     In contrast, if the timer has expired while the bath  14  temperature is neither within the Command Zone or heated at least a predetermined amount, an error is returned at block  130 . The error, which may be indicated aurally or visually on, e+g., the display device  82 , is reported because, after the relatively short timer period (three minutes being an example time), the system bath  14  temperature should have either reached the Command Zone or heated at least half a degree Celsius. If it has not, then the chiller/heater  26  is not functioning properly and an error is reported. 
     Now reverting back to diamond  116  and assuming that the temperature is above the Command Zone, reference is made to Logic Flow C in  FIG. 3 . At block  132 , the logic determines the current bath  14  temperature. 
     Moving to diamond  134 , the logic subtracts the initial temperature from the current temperature determined at block  132 . Remaining at diamond  134 , the logic takes the number just determined by subtracting the current temperature from the initial temperature and determines whether the difference is greater than a predetermined temperature change, e.g., half a degree Celsius. 
     If at decision diamond  134  it is determined that the difference in temperature is greater than half a degree Celsius, the logic reverts back to the beginning of Logic Flow A. A difference in temperature that is greater than half a degree Celsius indicates that the chiller/heater  26  is functioning properly and cooling the bath  1 . 4  temperature to bring it to within the Command Zone. 
     However, if it is determined that the difference in temperature is less than half a degree Celsius, the logic then continues to decision diamond  136 . At diamond  136 , the logic determines whether the current heat exchange bath temperature is within the Command Zone. If the logic determines that the current temperature has already been brought to within the Command Zone, the logic reverts back to the beginning of Logic Flow A. 
     If the logic determines that the current temperature is still not within the Command Zone, however, the logic continues again to diamond  138 . At diamond  138  the logic determines whether the compressor  46  has started. If the compressor  46  has started, it should be cooling the glycol being pumped to the bath  14 . However, if the compressor  46  has not started, the logic reverts back to the beginning of Logic Flow C and proceeds again. The logic is thus waiting for the compressor  46  to start. 
     If the logic determines that the compressor  46  has started, the logic may proceed to block  140 . At block  140 , a chiller/heater  26  test delay timer is set to a short period of time, preferably but not limited to three minutes. At block  142  the chiller/heater  26  test delay timer begins. 
     At the expiration of the delay the logic then moves to block  144  where the logic determines the current bath  14  temperature. Moving to diamond  146 , the logic subtracts the initial temperature determined at block  100  from the current temperature determined at block  144 . Remaining at diamond  146 , the logic takes the number just determined by subtracting the current temperature from the initial temperature and determines whether the difference is greater than half a degree Celsius. 
     If at decision diamond  146  it is determined that the difference in temperature is greater than a predetermined delta, e.g., half a degree Celsius, the logic reverts back to the beginning of Logic Flow A. A difference in temperature that is greater than the predetermined delta indicates that the chiller/heater  26  is functioning properly. 
     However, if it is determined that the difference in temperature is less than the predetermined delta, the logic then continues to decision diamond  148 . At diamond  148 , the logic determines whether the current heat exchange bath  14  temperature is within the Command Zone. If the logic determines that the current temperature is already within the Command Zone, the logic reverts back to the beginning of Logic Flow A. 
     However, if the logic determines that the current temperature is still not within the Command Zone, the logic continues again to decision diamond  150 . At diamond  150 , the logic determines whether the chiller/heater  26  test timer has expired. If it has not expired, the logic reverts back to block  144  where the logic executes the same process. 
     However, if the timer has expired while the bath  14  temperature is neither within the Command Zone or cooled to at least half a degree Celsius, an error is reported at block  152 . 
     After the relatively short timer period, three minutes being an example time, the system bath  14  temperature should have either reached the Command Zone or changed at least by the predetermined delta. If it has not, then the chiller/heater  26  is not functioning properly and an error will be reported. 
     The above test may be performed when the system is in “operate” or “standby”. Also, no changes are made by the test to the patient target temperature set by the operator, and in the event that the operator changes target temperature, the test is delayed by an additional period (e.g., fifteen minutes) to allow the system to slew toward target temperature before testing it. 
     While the particular SYSTEM AND METHOD FOR TESTING HEAT EXCHANGE SYSTEM FOR HEAT EXCHANGE CATHETER is herein shown and described in detail, it is to be understood that the subject matter which is encompassed by the present invention is limited only by the claims.