US20130325090A1 - Heating/cooling system for indwelling heat exchange catheter - Google Patents

Abstract

A cooling system for an indwelling heat exchange catheter includes a heat exchange bath that is configured to receive a conduit that carries saline to and from the catheter. A heating/cooling fluid is in the bath and exchanges heat with the saline. The heating/cooling fluid flows through a heat exchanger that includes a refrigerant and two variable speed DC compressor for removing heat from the refrigerant. A gear pump circulates the working fluid to and from the catheter and is removably engaged with a pump support platform.

Description

RELATED APPLICATIONS
• The present invention is a Continuation-in-Part of the U.S. patent application Ser. No. 09/965,560 filed on Sep. 25, 2001. This application claims priority from U.S. provisional patent application Ser. No. 60/492,818, filed Aug. 6, 2003.
BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates generally to methods and apparatus for exchanging heat with the body of a patient.
• 2. Description of the Related Art
• 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 improved if the patient is cooled below normal body temperature (37° 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'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 Radiant Medical of Portola Valley, Calif. 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 recognized herein, it is desirable that a heat exchange system for a heat exchange catheter consume minimal energy and space. Small size is desired because space is often at a premium in critical care units. Moreover, as also recognized herein, for patient comfort it is desirable that such a heat exchange system generate a minimum amount of noise. 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. It is the object of the present invention to still further address one or more of the above-noted considerations.
SUMMARY OF THE INVENTION
• A heat exchange system for an indwelling heat exchange catheter includes a heat exchange bath that is configured to receive a conduit that carries working fluid to and from the catheter. A heating/coolant fluid is disposed within the bath to exchange heat with the working fluid. The heating/coolant fluid flows through a heat exchanger that includes a refrigerant and two or more compressors that are connected in parallel to each other, Moreover, a heating/coolant fluid pump circulates the heating/coolant fluid between the heat exchanger and the heat exchange bath.
• In a preferred embodiment, the compressors are variable speed direct current (DC) compressors. Also, a positive displacement gear pump preferably pumps the working fluid, e.g., saline, to and from the catheter. In a preferred embodiment, the pump is removably engaged with a motor.
• In another aspect of the present invention, a heat exchange system for an indwelling heat exchange catheter includes a heat exchange bath that is configured to receive a conduit that carries working fluid to and from the catheter. A pump communicates with the conduit and pumps the working fluid to and from the catheter.
• In yet another aspect of the present invention, a fluid pump assembly includes a pump support platform. A pump is removably engaged with the pump support platform. In this aspect, the pump pumps working fluid to and from an intravascular catheter.
• In still another aspect of the present invention, a heat exchange system for an indwelling heat exchange catheter includes a heat exchange bath that is configured to receive a conduit that carries working fluid to and from the catheter. In this aspect of the present invention, a flow detector communicates with the conduit and detects when working fluid is flowing through the conduit.
• In yet still another aspect of the present invention, a fluid flow detector includes
• a clear housing and a paddle wheel that is rotatably disposed within the housing. The fluid flow detector further includes three infrared transmitter/receiver light emitting diode pairs. Each infrared transmitter/receiver light emitting diode pair establishes a signal path through the housing.
• The details of the present invention, both as to its construction and operation, can best be understood in reference to the accompanying drawings, in which like numerals refer to like parts, and which:
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a schematic diagram of a heating/cooling system in accordance with the present invention;
• FIG. 2 is a cross-sectional view of a heat exchange bath with the water glycol return line and level detector omitted for clarity;
• FIG. 3 is a cross-sectional view of a fluid level detector;
• FIG. 4 is a detailed cross-sectional view of a chiller/heater;
• FIG. 5 is a flow chart of the overall operation logic of the present invention;
• FIG. 6 is a flow chart of the linear mode operation logic of the present invention;
• FIG. 7 is a flow chart of a first portion of the compressor control logic;
• FIG. 8 is a flow chart of a second portion of the compressor control logic;
• FIG. 9 is a flow chart of a third portion of the compressor control logic;
• FIG. 10 is an exemplary graph of patient temperature and bath temperature versus time;
• FIG. 11 is a schematic diagram of an alternative heating/cooling system;
• FIG. 12 is a schematic diagram of an alternative refrigerating fluid circuit;
• FIG. 13 is a side plan view of a saline pump assembly;
• FIG. 14 is a top plan view of the saline pump assembly;
• FIG. 15 is a top plan view of a pump support platform;
• FIG. 16 is a bottom plan view of a pump;
• FIG. 17 is a perspective view of an alternative saline pump assembly;
• FIG. 18 is an exploded view of the alternative saline pump assembly;
• FIG. 19 is a side plan view of a preferred flow detector;
• FIG. 20 is flow chart of the saline flow detection logic; and
• FIG. 21 is flow chart of the glycol flow detection logic.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTDescription of the Heating/Cooling System
• Referring initially toFIG. 1, a patient heating/cooling system is shown and generally designated10. As shown, thesystem10 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 indwellingheat exchange catheter12 that can be inserted into a patient13 during an operation is connected to aheat exchange bath14 by a saline supply line16. The supply line16 is connected to a coiled or helicalheat exchange tube17 that is immersed in thebath14 fluid to exchange heat therewith. In turn, theheat exchange tube17 is connected to a peristaltictubing saline pump18 byfluid line20. Preferably, thesaline pump18 draws saline from asaline reservoir22 viafluid line24. As shown, thesaline reservoir22 is disposed within asaline level detector25 that, as described in detail below, helps control thesaline pump18 based on the level of saline in thelevel reservoir22. It is to be understood that in a preferred embodiment, thesaline pump18 has four modes: a standby or off mode, two treatment modes (i.e., two treatment speeds), and an idle mode wherein thesaline pump18 operates very slowly, but does not stop. In the idle mode, thepatient13 is effectively thermally decoupled from the heating/cooling system10.
• As further shown inFIG. 1, asaline source26 provides saline to thesaline reservoir22 viafluid line28. In a preferred embodiment, thesaline source26 is an intravenous (IV) bag and a line clamp27 is installed onfluid line28 between thesaline source26 and thesaline reservoir22. It is to be understood that after thesaline reservoir22 is filled the line clamp27 is clamped onfluid line28 to isolate thesaline source26 from thesaline reservoir22.FIG. 1 shows asaline return line29 communicates saline from thecatheter12 to thesaline reservoir22 to complete the saline circuit. It is to be appreciated that thetubes16,17,20,24, and29 can be provided as a disposable IV tubing set.
• FIG. 1 also shows asystem controller30 that is connected to thesaline level detector25 viaelectrical line32 andelectrical line34, i.e., one for each infrared detector that is associated with thesaline level detector25 as described below. Preferably, thesystem controller30 is also connected to asafety switch36 of thesaline pump18 viaelectrical line38. As described in further detail below, thesystem controller30 receives signals from thesaline level detector25 regarding the level of saline therein and uses this information to control thesaline pump18, including opening thesafety switch36 to de-energize thesaline pump18 under certain low saline level conditions.
• It is to be understood that within the saline circuit, saline is circulated to and from thecatheter12 through the helicalheat exchange tube17 in theheat exchange bath14. As described in detail below, theheat exchange bath14 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 patient13 into which thecatheter12 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/heater40 via a waterglycol supply line42 and a water glycol return line44. Awater glycol pump46 is installed in the water glycol return line44 to circulate water glycol through the water glycol circuit.FIG. 1 shows that theheat exchange bath14 is also in fluid communication with awater glycol reservoir47 installed within a water glycol level detector48 via fluid line50. In accordance with principles described below, the water glycol level detector48 is used to determine the level of water glycol within theheat exchange bath14.
• Further, thesystem controller30 is connected to the chiller/heater40 viaelectrical lines52 and54. Moreover, thesystem controller30 is connected to asafety switch55 at thewater glycol pump46 viaelectrical line56 and to the coolant level detector48 viaelectrical line58 andelectrical line60. Thus, thesystem controller30 can control the operation of the chiller/heater40 based on signals from a temperature monitor, described below, and control the operation of thewater glycol pump46 based on level signals from infrared detectors, also described below, that are disposed within the water glycol level detector48. As shown, thesystem controller300 is also connected to atemperature sensor57 placed at the outlet of the chiller/heater viaelectrical line59. Thecontroller30 uses input from thetemperature sensor57 to control the chiller/heater40 andother system10 components.
• It is to be understood that as the water glycol is pumped through the water/glycol circuit the chiller/heater40 can heat or cool the water glycol. Within theheat exchange bath14, 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 thecatheter12 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 variable speed direct current (DC)compressor62 is in fluid communication with the chiller/heater40 via arefrigerant supply line64 and arefrigerant return line66. It is to be understood that thecompressor62 is filled with refrigerant, e.g., R134a. Acompressor controller68 is connected to thecompressor62 via anelectrical line70. In turn, thesystem controller30 is connected to thecompressor controller68 via electrical line72. Thecompressor controller68 is also connected to a heater, described below, within the chiller/heater40 viaelectrical line73.
• It is to be understood that thesystem controller30 receives temperature signals from the temperature monitor, described below, and uses these signals to control the operation of thecompressor62 and the heater. Thecompressor62 is used to cool the water glycol that is pumped through the chiller/heater40 by thewater glycol pump46.
• Continuing to refer toFIG. 1, aDC power supply74 is connected to thesystem controller30 by anelectrical line76. In turn, theDC power supply74 preferably is connected to an isolation transformer (XFMR)78 byelectrical line80. TheXFMR78 can be connected to an alternating current (AC)input82, e.g., a standard one hundred and twenty volt (120V) wall outlet, via apower cord84. Thesystem10 can also be configured to work accommodate one hundred to two hundred and forty volts AC (100-240 VAC).
• As further shown inFIG. 1, atemperature monitor86 is connected to thesystem controller30 via anelectrical line88. A firstpatient temperature probe90 and a secondpatient temperature probe92 preferably are connected to the temperature monitor86 viaelectrical lines94 and96, respectively. As intended herein, the temperature monitor86 uses the temperature probes90,92 to monitor the temperature of thepatient13. Moreover, the temperature monitor86 sends signals to thesystem controller30 representing the temperature of thepatient13. These signals are used by thesystem controller30 to control the operation of the chiller/heater40, thesaline pump18, and theDC compressor62.
• FIG. 1 shows adisplay device98 that is connected to thesystem controller30 viaelectrical line100 andelectrical line102. Preferably, thedisplay device98 provides a visual indication of the patient's temperature and the bath temperature. For example, thedisplay device98 can be used to output graphs of minute by minute patient temperature (for, e.g., twenty one days) and water glycol bath temperature. thedisplay device98 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, thedisplay device98 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, thedisplay device98 also includes acontrol panel104 to allow a user, i.e., a doctor or a nurse, to input data, such as a target patient temperature, to thesystem10.
Description of the Heat Exchange Bath
• Referring now toFIG. 2, details of one preferred, non-limitingheat exchange bath14 are shown.FIG. 2 shows that the preferredheat exchange bath14 includes a bottom110 having a generally cylindricalcontinuous sidewall112 extending therefrom. As shown, thebottom110 of thebath14 is formed with ahole114 and the waterglycol supply line42 is connected thereto. A preferablyvertical standpipe116 extends from the end of the waterglycol supply line42 into the interior of thebath14. In a preferred embodiment, thestandpipe116 is perforated along its length with a series of four hole rings118 out of which water glycol flows into thebath14. These four hole rings118 ensure radial movement of the water glycol through theheat exchange tubing17, i.e., between and across the turns of the coil. It can be appreciated that in lieu of thestandpipe116, a small impeller (not shown) can be mounted on thebottom110 of thebath14 to circulate the water glycol therein.
• As shown inFIG. 2, the generally spiral-shapedheat exchange tubing17 is disposed within thebath14 such that when thebath14 is filled with water glycol theheat exchange tubing17 is fully immersed in the water glycol.FIG. 2 shows that the saline supply line16 is connected to one end of theheat exchange tubing17. Conversely, thefluid line20 from thesaline pump18 is connected to the other end of theheat exchange tubing17. As shown, to center and support the spiral-shaped tubing set120 around thestandpipe116, four vertical stanchions122 (only two shown inFIG. 2) extend up from thebottom110 of thebath14 and touch the outer surface of the tubing set120. In the alternative, theheat exchange tubing17 can rest against thesidewall112 of thebath14.
• FIG. 2 further shows that thebath14 is covered by alid124. Preferably, the bottom of thelid124 is spaced above the top of the water glycol within thebath14 in order to establish adead air space126 between thelid124 and the water glycol. Thisdead air space126 acts as an insulator to minimize parasitic heat loads, control the evaporation of the water glycol, and prevent progressive overfilling of thebath14 by condensation from the ambient air. Also, thelid124 can be sealed against thewall112 by a resilient, preferably silicone,gasket128.
Description of the Level Detector
• Referring now toFIG. 3, details of the preferred embodiment of thesaline level detector25 are shown. It is to be understood that the water glycol level detector48 operates using the same principles as thesaline level detector25. As shown inFIG. 3, thesaline level detector25 includes ahousing130 that is preferably made from acetal, e.g., Delrin® manufactured by E.I. Dupont De Nemours & Co. of Delaware. Thehousing130 is formed with a preferably “U” shapedcentral bore132 in which the preferablyclear saline reservoir22 is disposed.FIG. 3 shows that the housing is formed with a firsttransverse bore134, a secondtransverse bore136, and a thirdtransverse bore138 leading to thecentral bore132.
• As shown, thesaline level detector25 includes a light emitter, e.g., an infrared light emitting diode (IR LED)140, that is mounted in thefirst bore134 on one side of thelevel detector22. On the other hand, preferably two light detectors, such as afirst IR detector142 and asecond IR detector144, are placed on the opposite side of thesaline level detector25 from theLED140 within the second and thirdtransverse bores136,138. Preferably, thedetectors142,144 are photodiodes or phototransistors.
• In the presently preferred embodiment,IR LED140 and theIR detectors142,144 are coplanar. Preferably, theIR LED140 emits an IR light beam that can be detected by thefirst IR detector142 if the saline level is below a predetermined level, e.g., the level of theIR LED140 and theIR detectors142,144. In other words, if the saline is low, the IR light beam takes the path toward thefirst JR detector142 as indicated by the dashedline146. Conversely, if the saline is at the proper level within thesaline level detector25, the IR light beam is refracted so that it is detected by thesecond IR detector144. In this case, the IR light beam takes the path indicated byline148.
• It is to be understood that the IR light beam can be modulated, i.e. pulsed, e.g., at nine and a half kiloHertz (9.5 kHz), to avoid false detections caused, e.g., by other light sources placed in the same room as thelevel detector25 and/or bubbles in thesaline reservoir22. For this purpose, thefirst IR detector142 andsecond IR detector144 can be connected to upper andlower tone detectors150,152, respectively, which output signals only when they receive an input of, e.g., 9.5 kHz. It can be appreciated that when the saline level within the level detector falls below a predetermined level, thecontroller30 can activate an alarm at thedisplay device98. The alarm can include a visible alarm, e.g., a light, or an audible alarm, e.g., a buzzer. Moreover, when the saline level drops below the predetermined level thecontroller30 can de-energize thesaline pump18 by opening thesafety switch36.
Description of the Chiller/Heater
• FIG. 4 shows the details regarding one preferred, non-limiting implementation of the chiller/heater40. As shown inFIG. 4, the chiller/heater40 is a shell-and-tube heat exchanger having alower chamber160, anupper chamber162, andplural tubes164 communicating water glycol therebetween. It is to be understood that water glycol flows into thelower chamber160, up thetubes164, into to theupper chamber162, and out of theupper chamber162 to theheat exchange bath14. Refrigerant, e.g., R134a, flows around thetubes164 to cool the water glycol therein. Aresistive heater element166 is disposed in thelower chamber160 and extends partially up anenlarged center tube168 for heating the water glycol in the chiller/heater60. As shown, theheater element166 can include a built-inthermocouple temperature sensor170 that can be used as described in detail below to determine if glycol is flowing through the chiller/heater60. It is to be appreciated that in a less preferred embodiment the chiller/heater40 and theheat exchange bath14 can be combined into a single unit. Moreover, it is to be appreciated that thetemperature sensor170 can be connected to the system controller.
Description of the Overall Operation Logic of the Present Invention
• Referring now toFIG. 5, the overall operation logic of the present invention is shown and commences at block200 wherein thecontroller30 is initialized and the patient temperature (T_pt), the patient target temperature (T_target), and the bath temperature (T_bath) are received. Preferably, T_ptis received from thetemperature monitor86, specifically from thesecond temperature probe92. Moving to block202, a temperature differential, ΔT, is determined by subtracting T_ptfrom T_target. Next, at decision diamond204 it is determined whether the absolute value of ΔT is less than a predetermined amount, e.g., one tenth of a degree Celsius (0.1° C.).
• If the absolute value of ΔT is greater than 0.1° C., the logic moves to block206 where thesystem10 enters maximum cooling mode or maximum warming mode. It is to be understood that if ΔT is negative thesaline pump18 is brought to full speed, thecompressor62 is turned on at high speed, and theheater166 is turned off to cool the patient. Conversely, if ΔT is positive, thesaline pump18 is brought to full speed, thecompressor62 is turned off, and theheater166 is turned on to warm the patient.
• Returning to decision diamond204, if the absolute value of ΔT is less than 0.1° C., the logic moves to block208 where the rate of change of T_ptwith respect to time, dT_pt/dt, is determined using the following equation:
• $\left[\sum _{i=1}^n\left(\frac{n+1}{2}\right)-i*T_{pt}\left(i\right)\right]/\left[n*\left(\frac{1-{\mathrm{<figure-callout\; label="n"\; filenames="US20130325090A1-20131205-D00016.png"\; state="\{\{state\}\}">n</figure-callout>}}^2}{12}\right)\right]$
• • where,
    • n=10 unless there has not yet been 10 minutes worth of patient temperature data
    • T_pt=Patient temperature
• From block208, the logic moves to decision diamond210 where it is determined whether the absolute value of dT_pt/dt is greater than thirty six hundredths of a degree Celsius per hour (0.36° C./hr). If not, the logic continues to block212 and a new T_bathis determined. The new T_bathis determined based on the rate of change of patient temperature. A higher rate of change results in a new T_baththat is further away from the current T_bathand a lower rate of change results in a new T_baththat is closer to the current T_bath. If dT_pt/dt is indeed greater than 0.36° C./hr and negative, meaning that thepatient13 is being rapidly cooled and does not require saline circulation through the catheter, the logic moves to block214 where thesaline pump18 is idled. Thereafter, the logic moves to212 and a new T_bathis determined.
• After block212, the logic proceeds to block216, wherein thecompressor62 and chiller/heater40 are operated in accordance with the rules set forth below to achieve the new T_bath. Continuing to block218, in a preferred embodiment, thesaline pump18 is selectively idled per the following rules:
• • 1. Condition: A warming treatment has just started and the water glycol temperature is lower than T_pt.
    • Rule: Thesaline pump18 idled until the water glycol temperature is at least as warm as T_pt.
  • 2. Condition: A controlled heating/cooling rate treatment has just started and the water glycol temperature is not within one degree Celsius (1° C.) of the water glycol reference temperature, T_ref, (T_pt−6° C. when cooling, T_pt+1° C. when heating).
    • Rule: Thesaline pump18 is idled until the water glycol temperature is within 1° C. of T_ref.
  • 3. Condition: T_ptis within 0.1° C. of T_targetand dT_pt/dt<0.36° C./hr.
    • Rule: Thesaline pump18 is idled at a very low rate until the water glycol temperature reaches T_ref.
  • 4. Condition: PID has been controlling the system, the error exceeds the overshoot threshold, and the water glycol temperature is warmer than T_pt.
    • Rule: Thesaline pump18 is idled until the water glycol temperature is lower than T_pt.
  • 5. Condition: PID has been controlling the system, the error exceeds the undershoot threshold, and the water glycol temperature is cooler than T_pt.
    • Rule: Thesaline pump18 is idled until the water glycol temperature is higher than T_pt.
• After thesaline pump18 is selectively idled as described above, the logic proceeds to block220 where the system enters the linear cooling mode, described below.
Description of the Linear Mode Operation Logic of the Present Invention
• FIG. 6 shows the linear mode operation logic of the present invention. Commencing at block230 a do loop is entered wherein while in the linear mode, the succeeding steps are performed. In the linear mode, several “fail safe” tests are monitored for to revert to maximum cooling or heating in the event that a rapid patient temperature change occurs. For instance, at decision diamond232, if it is determined that ΔT is greater than one half a degree Celsius (0.5° C.) and has a negative sign, the system exits linear mode and enters maximum cooling mode at block234. Also, if at decision diamond236 it is determined that ΔT is positive and greater than three tenths of a degree Celsius (0.3° C.), the logic moves to block238 where the linear mode is exited and the maximum warming mode is entered. Moreover, at block240, dT_pt/dt is determined using the equation described above.
• Proceeding to decision diamond242, it is determined whether dT_pt/dt is greater than seven tenths of a degree Celsius per hour (0.7° C./hr) for the last ten (10) minutes. If so, the logic moves to block234 where the linear mode is exited and the maximum cooling mode is entered. If dT_pt/dt is less than 0.7° C./hr for the last 10 minutes, the logic returns to decision diamond232 and continues as described above.
Description of the Compressor Control Logic of the Present Invention
• Referring now toFIG. 7, the control logic of the compressor is shown and commences atblock250 with a do loop, wherein after a new T_bathis determined, the following steps are performed. Atdecision diamond252, it is determined whether the new T_bathis greater than the current T_bath. If the new T_bathis lower than the current T_bath, the logic moves to block254 and theheater166 is deactivated while thecompressor62 is activated at maximum speed to cool the water glycol.
• Continuing todecision diamond256, it is determined whether the current bath temperature is within a predetermined range, e.g., two-tenths degrees Celsius (0.2° C.) of the new T_bath. If not, the logic moves to block258 where the cooling of the water glycol is continued. The logic then returns todecision diamond256. If the current bath temperature is within the predetermined range of the new T_bath, the logic moves to block260 wherein the compressor speed is progressively reduced.
• Fromblock260, the logic moves todecision diamond262 where it is determined whether the current temperature is stable at the new T_bath. If so, the logic moves to block264 and thecompressor62 is held at the current speed to maintain the temperature at the new T_bath. If, atdecision diamond262, the temperature has not stabilized at the new T_bath, the logic moves todecision diamond266 where it is determined whether the minimum compressor speed has been reached. If the minimum compressor speed has not been reached, the logic returns to block260 and continues as described above. Conversely, if the minimum compressor speed has been reached, the logic moves to block268 where the heater power is progressively increased.
• Next, the logic continues todecision diamond270 where it is determined if the current temperature has stabilized at the new T_bath. If not, the logic returns to block268 where the heater power continues to be progressively increased. If, on the other hand, the current temperature has stabilized at T_baththe logic moves to block272 where the current power is maintained. Thereafter, the logic moves to block264 where the compressor is idled at the current speed, in this case the lowest speed, in order to maintain the temperature at T_bath. In a preferred, non-limiting embodiment, the lowest temperature to which the bath can be commanded is one-half degree Celsius (0.5° C.).
• Returning todecision diamond252, if the new T_bathis greater than the current temperature, the logic proceeds todecision diamond274 where it is determined whether the new T_bathis less than or equal to a predetermined upper bath limit, e.g., forty two degrees Celsius (42° C.). If the new T_bathis less than the upper bath limit, the logic moves toFIG. 8. However, if the new T_bathis equal to the upper bath limit, the logic moves toFIG. 9.
• Proceeding toFIG. 8, if the new T_bathis less than the upper bath limit, the logic proceeds to block276 where thecompressor62 is activated at minimum speed and theheater166 is activated at maximum power. Fromblock276, the logic moves todecision diamond278 where it is determined if the current temperature is within a predetermined range, e.g., two-tenths degrees Celsius (0.2° C.) of the new T_bath. If not, the logic proceeds to block280 and the heating of the water glycol is continued. If the temperature is within the predetermined range, the logic continues to block282 where the heater power is progressively reduced.
• Next, atdecision diamond284, it is determined whether the current temperature has stabilized at the new T_bath. If the current temperature has stabilized at the new T_bath, the current heater power is maintained to maintain the temperature at the new T_bath. On the other hand, if the current temperature has not stabilized, the logic proceeds todecision diamond288 where it is determined if the heater duty cycle is equal to zero (0). If not, the logic returns to block282 where the progressive reduction of the heater power is continued.
• If, atdecision diamond288, the heater duty cycle is equal to zero, indicating that the lowest heating power has been reached, logic continues to block290 where the speed of thecompressor62 is progressively increased. Thereafter, atdecision diamond292, it is determined whether the current temperature has stabilized at the new T_bath. If the temperature has not stabilized, the logic moves to block290 where the reduction of the compressor speed is continued. On the other hand, if the temperature of the compressor speed has stabilized at T_bath, the logic continues to block294 where the current compressor speed is maintained. The logic then moves to block286 and ends.
• Returning to decision diamond274 (FIG. 7), if the new T_bathis equal to the upper bath limit, the logic moves toFIG. 9. Atblock296, the compressor is deactivated and the heater is activated at maximum power. Fromblock296, the logic moves todecision diamond298 where it is determined whether the temperature is within a predetermined range, e.g., two-tenths degrees Celsius (0.2° C.), of the new T_bath. If not, the heating of the water glycol is continued atblock300. If the current temperature is within 3° C. of the new T_bath, the logic proceeds to block302 where the power of theheater166 is progressively reduced. Then, atdecision diamond304, it is determined whether the temperature has stabilized at the new T_bath. If so, the current heater power is maintained to maintain the temperature at the new T_bath. Conversely, if the temperature has not stabilized at the new T_bath, the logic continues todecision diamond308 where it is determined whether the heater duty cycle has reached zero (0). If the heater duty cycle has not reached zero, the logic returns to block302 where the progressive reduction of the heater power is continued. On the other hand, if the heater duty cycle has reached zero, thecompressor62 is briefly cycled in order to cool the water glycol. Next, atdecision diamond312, it is again determined whether the temperature has stabilized at the new T_bath. If not, the logic returns to block310 and the compressor is again briefly cycled to cool the water glycol. If, atdecision diamond312, the temperature has stabilized at the new T_bath, the logic moves to block306 and ends.
• It is to be understood that the system described above has two nested closed-loop controllers: an outer loop and an inner loop. The outer loop is directly responsible for controlling the patient temperature and is driven by the temperature difference between T_targetand T_pt. On the other hand, the inner loop is directly responsible for the coolant temperature, i.e., T_bath, that is established by thesystem controller30. It is further to be understood that the outer loop logic, i.e., the overall operation logic and linear mode operation logic describe above, resides in thesystem controller30. The inner loop control logic, i.e., the compressor control logic described above, resides in thecompressor controller68. As intended by the present invention, when thecompressor controller68 receives a command to establish a new T_bath, thecompressor controller68 controls thecompressor62 and theheater166, as described above, in order to achieve the new T_bath.
• In a preferred, non-limiting embodiment, thecompressor controller68 has two means of control over thecompressor62. First, it can turn the power tocompressor62 on and off via a solid-state DC relay. Second, it can modulate the compressor speed between a maximum value, e.g., thirty five hundred revolutions per minute (3,500 RPM), and a minimum value, e.g., two thousand revolutions per minute (2,000 RPM).
• Also, in a non-limiting embodiment, thecompressor controller68 has only duty-cycle control over theheater166. Thecompressor controller68 can modulate the heater power anywhere between zero percent (0%), i.e., off, and one hundred percent (100%), i.e., on. Preferably, theheater166 has a fixed one second (1 s) pulse period. Also, in a preferred embodiment theheater166 has a maximum power of two hundred and forty watts (240 w). Thus, a fifty percent (50%) duty cycle corresponds to one hundred and twenty watts (120 w) of time-averaged input power to the water glycol and a twenty five percent (25%) duty cycle would correspond to sixty watts (60 w) of time-averaged input power.
Description of an Exemplary Graph of Patient Temperature and Bath Temperature Versus Time
• FIG. 10 shows one exemplary, non-limiting graph of T_pt, represented byline320, and T_bath, represented byline322, plotted versus time. As shown, the patient is initially in a hyperthermic state, i.e., the patient has a fever of thirty-nine degrees Celsius (39° C.). The patient is cooled from 39° C. toward a T_targetequal to thirty-six and one-half degrees Celsius (36.5° C.) preferably over a three hour period at a rate of eight tenths of a degree Celsius per hour (0.80° C./hr). This can be achieved by entering a maximum cooling mode where the T_bathis one-half a degree Celsius (0.5° C.).
• Once T_ptreaches thirty six and six tenth degrees (36.6° C.), thesaline pump18 preferably is idled to thermally de-couple the patient13 from thecooling system10 and the T_bathis increased, e.g., by energizing theheater166, to approximately twenty-five degrees Celsius (25° C.). By thermally de-coupling the patient13 from thecooling system10, T_ptwill discontinue the rapid decrease described above while T_bathis increased.
• After T_bathreaches 25° C., thesaline pump18 is returned to full speed to thermally couple the patient13 to thecooling system20. As intended by the present invention, the higher T_bathslows the rate at which thepatient13 is cooled and helps to maintain T_ptin a state of equilibrium near T_target, e.g., within one-tenth of a degree Celsius (0.1° C.) of T_target. If necessary, T_bathcan be slightly increased or decreased, e.g., less than five degrees Celsius (5° C.), as shown in order to maintain T_ptin the state of equilibrium described above.
Description of an Alternative Heating/Cooling System
• Referring now toFIG. 11, an alternative patient heating/cooling system is shown and generally designated410. Similar to the above-describedsystem10, thesystem410 shown inFIG. 11 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 indwellingheat exchange catheter412 that can be inserted into apatient413 during an operation is connected to aheat exchange bath414 by asaline supply line416. Thesupply line416 is connected to a coiled or helicalheat exchange tube417 that is immersed in the bath fluid to exchange heat therewith. In turn, theheat exchange tube417 is connected anair trap vessel418 byfluid line420. Theair trap vessel418 is surrounded by anair trap detector419. As shown, theair trap vessel418 is connected to asaline pump422 byfluid line424.
• It is to be understood that theair trap detector419 is identical in construction to thesaline level detector25 described above and shown inFIG. 3 and can be used to detect when air is introduced into the working fluid circuit downstream from thepump422, e.g., by thepump422 itself. Accordingly, if air is detected in theair trap vessel418, thepump422 is immediately shut down by a controller in accordance with the principles discussed earlier.
• As further shown inFIG. 11, asaline source426 provides saline to thepump422 viafluid line427.FIG. 11 shows asaline return line428 that communicates saline from thecatheter412 to the saline,reservoir426 to complete the saline circuit. Asaline flow detector429, described in detail below, is installed along thesaline return line428 between thecatheter412 and thesaline reservoir426.FIG. 11, shows that thesaline flow detector429 provides feedback to the system controller, described below, viaelectrical line425.
• FIG. 11 also shows asystem controller430 that is connected to theair trap detector419 viaelectrical line432 andelectrical line434, i.e., one for each infrared detector that is associated with theair trap detector419. Preferably, thesystem controller430 is also connected to asafety switch436 of thesaline pump422 viaelectrical line438. As described in further detail below, thesystem controller430 receives signals from theair trap detector419 regarding the level of saline therein and uses this information to control thesaline pump422, including opening thesafety switch436 to de-energize thesaline pump422 under certain low saline level conditions. It is to be understood that within the saline circuit, saline is circulated to and from thecatheter412 through the helicalheat exchange tube417 in theheat exchange bath414.
• Now considering the water glycol circuit, the water glycol circuit communicates with a chiller/heater440 via a waterglycol supply line442 and a water glycol return line444. Awater glycol pump446 is installed in the waterglycol supply line442 to circulate water glycol through the water glycol circuit.FIG. 11 shows that theheat exchange bath414 is also in fluid communication with awater glycol reservoir447 viafluid line450. As shown, the water glycol reservoir is installed within a waterglycol level detector448. In accordance with the principles described above, the waterglycol level detector448 can be used to determine the level of water glycol within theheat exchange bath414.
• Further, thesystem controller430 is connected to the chiller/heater440 viaelectrical lines452 and454. Moreover, thesystem controller430 is connected to thecoolant level detector448 viaelectrical line458 andelectrical line460. Thus, thesystem controller430 can control the operation of the chiller/heater440 based on signals from a temperature monitor, described below, and control the operation of thewater glycol pump446 based on level signals from the infrared detectors that are disposed within the waterglycol level detector448. As shown, thesystem controller430 is also connected to a temperature sensor457 placed at the outlet of the chiller/heater viaelectrical line459. Thecontroller430 uses input from the temperature sensor457 to control the chiller/heater440 andother system410 components.
• It is to be understood that as the water glycol is pumped through the water/glycol circuit the chiller/heater440 can heat or cool the water glycol. Within theheat exchange bath414, 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 thecatheter412 is installed. 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 variable speed direct current (DC)compressor462 is in fluid communication with the chiller/heater440 via arefrigerant supply line464 and arefrigerant return line466. It is to be understood that thecompressor462 is filled with refrigerant, e.g., R134a. Acompressor controller468 is connected to thecompressor462 via anelectrical line470. In turn, thesystem controller430 is connected to thecompressor controller468 viaelectrical line472. Thecompressor controller468 is also connected to a heater (FIG. 4) within the chiller/heater440 viaelectrical line473.
• It is to be understood that thesystem controller430 receives temperature signals from the temperature monitor, described below, and uses these signals to control the operation of thecompressor462 and the heater. Thecompressor462 is used to cool the water glycol that is pumped through the chiller/heater440 by thewater glycol pump446.
• Continuing to refer toFIG. 11, aDC power supply474 is connected to thesystem controller430 by anelectrical line476. In turn, theDC power supply474 preferably is connected to an isolation transformer (XFMR)478 byelectrical line480. TheXFMR478 can be connected to an alternating current (AC)input482, e.g., a standard one hundred and twenty volt (120V) wall outlet, via apower cord484. It can be appreciated that a power supply having a low current leakage can be used and if it is indeed used, theXFMR478 can be eliminated.
• As further shown inFIG. 11, atemperature monitor486 is connected to thesystem controller430 via anelectrical line488. A firstpatient temperature probe490 and a second patient temperature probe492 preferably are connected to the temperature monitor486 viaelectrical lines494 and496, respectively. As intended herein, the temperature monitor486 uses the temperature probes490,492 to monitor the temperature of thepatient413. Moreover, thetemperature monitor486 sends signals to thesystem controller430 representing the temperature of thepatient413. These signals are used by thesystem controller430 to control the operation of the chiller/heater440, thesaline pump418, and theDC compressor462.
• FIG. 11 shows adisplay device498 that is connected to thesystem controller430 viaelectrical line500 andelectrical line502. Preferably, thedisplay device498 can provide a visual indication of the patient's temperature and the bath temperature. For example, thedisplay device498 can be used to output graphs of minute by minute patient temperature (for, e.g., twenty one days) and water glycol bath temperature. Thedisplay device498 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, thedisplay device498 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, thedisplay device498 also includes acontrol panel504 to allow a user, i.e., a doctor or a nurse, to input data, such as a target patient temperature, to thesystem410.
Description of an Alternative Refrigerating Fluid Circuit
• Referring toFIG. 12 an alternative refrigerating fluid circuit is shown and is generally designated600.FIG. 12 shows that the refrigeratingfluid circuit600 includes afirst compressor602 and asecond compressor604 that are connected in parallel to each other and connected in series to acondenser606 and anevaporator608. Anexpansion valve610 is also connected between thecondenser606 and theevaporator608 to complete the fluid circuit. As shown inFIG. 12, glycol is pumped to and from the evaporator608 from a glycol bath. In a preferred embodiment, thecompressors602,604 are variable speed direct current (dc) compressors that can be controlled by a controller, e.g., a computer or any other microprocessor. In order to prevent one or both of thecompressors602,604 from stalling during operation, the controller preferably includes an algorithm that can prevent either compressor from being energized when the other compressor is fully loaded. It can be appreciated that the twocompressors602,604 working in parallel with each other increase the cooling power of the refrigeratingfluid circuit600.
Description of a Saline Pump Assembly
• FIGS. 13 and 14 show an exemplary, non-limiting saline pump assembly, generally designated650. As shown inFIGS. 13 and 14, thepump assembly650 includes adiaphragm pump652 that is removably engaged with apump support platform654. In one non-limiting embodiment, thepump652 is similar to the high efficiency diaphragm pump disclosed in U.S. Pat. Nos. 5,791,882 and 5,800,136, incorporated herein by reference.
• FIG. 13 shows that thepump support platform654 includes anupper plate656 and alower plate658 that, in a preferred embodiment, are attached to each other, e.g., by threaded fasteners. As shown inFIG. 13,plural feet660 extend from thelower plate658 and provide stable support for thepump support platform654.FIG. 13 also shows that apump drive assembly662 is incorporated into thelower plate658 of thepump support platform654. Thepump drive assembly662 includes a motor and a drive shaft, described below, that extends through theupper plate656 of thepump support platform654 and engages thepump650.
• As shown inFIGS. 13 and 14, thepump support platform654 includes a quick-release locking arm664 that prevents thepump652 from being disengaged with thepump support platform654—unless thelocking arm664 is rotated to release thepump652.FIGS. 14 and 15 also show that thepump support platform654 includes anoverflow bore665 through which any saline that may leak from thepump652 can flow.FIG. 14 further shows that thepump652 includes aninlet666 and anoutlet668. As discussed above, thepump652, i.e., theoutlet668 thereof, can be connected to the air trap vessel418 (FIG. 11) that is downstream from thepump652.
• Referring now toFIG. 15, further details concerning thepump support platform654 are shown.FIG. 15 shows that theupper plate656 of thepump support platform654 is formed with a generally cylindrical pump locking bore672. The outer periphery of the pump locking bore672 is radially formed with a first,slot674, asecond slot676, and athird slot678. As shown, eachslot674,676,678 is equally spaced around the outer periphery of the pump locking bore672. Also, eachslot674,676,678 is curved to match the radius of curvature of the pump locking bore672 and eachslot674,676,678 terminates in asemi-cylindrical bay680,682,684.FIG. 15 also shows that adrive shaft686 extends from the pump drive assembly662 (FIG. 13) through theupper plate656. It is to be understood that thepump drive assembly662 includes amotor687 for rotating thedrive shaft686. Themotor687 can be directly connected to thedrive shaft686, as shown, or it can be geared thereto.
• FIG. 16 shows further details concerning the construction of thepump652. As shown, thepump652 includes a generally cylindricallower housing688. A first generallycylindrical leg690, a second generallycylindrical leg692, and a third generallycylindrical leg694 are equally spaced around the periphery of thelower housing688.FIG. 16 shows that thepump652 further includes adrive shaft receptacle696 into which the drive shaft686 (FIG. 15) extends when thepump652 is removably engaged with thepump support platform654. It is to be understood that thedrive shaft686 is keyed to thedrive shaft receptacle696.
• It can be appreciated that thepump652 can be engaged with thepump support platform654 by aligning thecylindrical legs690,692,694 with thesemi-cylindrical bays680,682,684 established by the pump locking bore672. Thedrive shaft686 is also aligned with thedrive shaft receptacle696. In this relationship, thepump652 can be slid toward thepump support platform654 until thelower housing688 of thepump652 contacts theupper plate656 of thepump support platform654. Thepump652 is then rotated within the pump locking bore672 until eachleg690,692,694 of thepump652 reaches a respective end of eachslot674,676,678 formed by the pump locking bore672. It is to be understood that during installation of thepump652 on thepump support platform654, oneleg690,692,694 of the pump652 (any leg, thereof) rides against and then past the quick-release locking arm664 until the quick-release locking arm664 clears theleg690,692,694 and snaps under spring bias to a position to prevent thepump652 from being removed from thepump support platform654.
• In accordance with the principles of the present invention, apump652 can be easily engaged and disengaged with thepump support platform654 during use. Thus, a first sterilized pump can be used in conjunction with the treatment of a first patient. After treatment has concluded, the now-used pump can be removed and replaced with a second sterilized pump to be used in conjunction with the treatment of a second patient. The pump support platform654 (and the motor therein) need not be replaced for each new pump and the costs of utilizing the heat/cooling system of the present invention are reduced.
Description of an Alternative Saline Pump Assembly
• In an alternative embodiment, as shown inFIGS. 17 and 18, asaline pump assembly700 includes apump support platform702 and a positivedisplacement gear pump704. In non-limiting embodiments, thegear pump704 can incorporate some or all of the features set forth in U.S. Pat. Nos. 6,270,324; 6,210,138; 6,158,994; 5,494,416; 5,219,274; 5,165,868; and 4,065,235, all of which are incorporated herein by reference. As shown inFIGS. 17 and 18, thepump support platform702 includes apump drive motor706 that is preferably a brushless, direct current motor.
• FIGS. 17 and 18 show that thepump support platform702 includes afirst support collar708 and asecond support collar710 that fit into a generally cylindrical pump locking bore712 formed in thesupport platform702.Plural fasteners714 can be used to affix thesupport collars708,710 to thesupport platform702. It is to be understood that thegear pump704 fits into the support collars, after they are inserted in thebore712. As shown inFIG. 18, a first spring loadedball plunger715 and a second spring loadedball plunger716 are provided and can be used to removably engage thegear pump704 with thesupport platform702. One or more alignment pins713 can be used to properly align thegear pump704 when it is engaged with thesupport platform702. When thegear pump704 is installed in thesupport platform702, theball plungers715,716 engage ametal flange717 around thegear pump704 and provide a downward force on themetal flange717 in order to keep thegear pump704 installed in thesupport platform702.
• As shown inFIGS. 17 and 18, a firstoptical sensor718 and a secondoptical sensor719 are installed on the upper surface of thesupport platform702 and can be used to detect the presence of thegear pump704 on thesupport platform702. It is to be understood that eachoptical sensor718,719 includes an emitter (not shown) and a detector (not shown) that are configured to transmit an optical signal toward the space in which thegear pump704 occupies when it is properly installed and detect reflection from thegear pump704 when it is, indeed, properly installed.
• FIG. 18 further shows that thegear pump704 includes acylindrical magnet720 that extends from thegear pump704. It is to be understood that thecylindrical magnet720 is attached to a drive shaft (not shown) within thegear pump704 and as thecylindrical magnet720 rotates it rotates the drive shaft. Further, themotor706 includes a cup-shapedmagnet722 that is sized and shaped to receive thecylindrical magnet720 and magnetically engage thecylindrical magnet720. The cup-shapedmagnet722 is coupled to a drive shaft (not shown) within themotor706 and themotor706 can be energized to rotate the cup-shapedmagnet722.
• With this structure, thegear pump704 can be removably engaged with thesupport platform702. When thegear pump704 is engaged with thesupport platform702, thecylindrical magnet720 is magnetically coupled to the cup-shapedmagnet722. Accordingly, as the cup-shapedmagnet722 is rotated by themotor706 it causes thecylindrical magnet720 to rotate and which, in turn, causes thegear pump704 to pump fluid therethrough.
• It is to be understood that for overpressure protection, thegear pump704 includes a bypass relief valve (not shown) that opens on high pressure. In lieu of a bypass relief valve, themagnets720,722 can be magnetized such that the magnetic coupling established therebetween can be broken under conditions of overpressure. Moreover, the speed of thepump704 can be established for the desired heat exchange rate.
Description of a Preferred Saline Flow Detector
• Referring now toFIG. 19, a preferred, non-limiting embodiment of a saline flow detector is shown and generally designated800. As shown inFIG. 19, theflow detector800 includes a preferably clear,plastic housing802 having aninlet804 and anoutlet806. A lightweight, preferablyplastic paddle wheel808 is installed within thehousing802 on anaxle810.FIG. 19 shows that thepaddle wheel808 includes acentral hub812 from which preferably three opaque,plastic paddles814 extend radially (it is to be understood that eachpaddle814 includes a pair of opposing paddle blades). As shown, thepaddles814 are positioned around thehub812 approximately one-hundred and twenty degrees (120°) from each other. It can be appreciated that fluid flowing from theinlet804 to theoutlet806 flows tangential to thepaddle wheel808 and causes it to spin. Moreover, three opaque walls815 are formed around thepaddle wheel808 between alternating pairs of adjacent paddle blades.
• As shown inFIG. 19, preferably three infrared transmitter/receiver light emitting diode (IR T/R LED) pairs816 can be placed such that thehousing802 is between each IR T/R LED pair816 and each IR T/R LED pair816 can send and receive a signal through thehousing802 across thepaddle wheel808 to detect rotation of thepaddle wheel808 when fluid flows through thehousing802. In a preferred embodiment, the IR T/R LED pairs816 are positioned on an imaginary circle concentric with theaxle810. Moreover, the IR T/R LED pairs are arranged so that acenter pair816 is aligned with theaxle810 and two side pairs816 flank thecenter pair816. Each side pair is approximately plus-or-minus sixty-four degrees (±64°) from thecenter pair816 on the imaginary circle. This arrangement insures that that regardless of the position of thepin wheel808, one of the three signal paths established by the IR T/R LED pairs816 through thehousing802 is always unblocked by thepaddle wheel808.
• FIG. 19 further shows that each IR T/R LED pair816 is connected to aprocessor818 that, in turn, is connected to asystem controller820. Theprocessor818 includes a program that, based on the signals received from the IR T/R LED pairs816, allows theprocessor818 to determine if thepaddle wheel808 is rotating and fluid is flowing through the housing and accordingly, the working fluid circuit. If not, an alarm can be activated.
Description of the Saline Flow Detection Logic
• FIG. 20 shows the saline flow detection logic that commences atblock850 wherein theflow detector800 is energized, i.e., its power is turned on. Moving todecision diamond852, it is determined whether pulses are being received at theprocessor818. The pulses represent motion of thepaddle wheel808, i.e., the motion of the paddles through the light beams established by the IR T/R LED pairs816. If there are indeed pulses, the logic moves todecision diamond854 where it is determined whether a timer has expired. If the timer has not expired, the logic loops back todecision diamond852 and continues as described above. If so, the logic moves to block856 and an “optics error” message is presented to the user. The logic then ends atstate858.
• Returning todecision diamond852, if pulses are not present, the logic moves todecision diamond860 where it is determined whether all three IR T/R LED pairs816 are on. If so, the logic moves todecision diamond862 where it is determined if all three IR T/R LED pairs816 are operating properly. This can be determined, e.g., by sequentially toggling the IR T/R LED pairs816 on and off. If it is determined that the IR T/R LED pairs816 are not operating properly, the logic moves to block856 where an “optics error” message is presented to the user. The logic then ends atstate858. Otherwise, an “optics ok, no pinwheel” message is presented to the user. The logic then ends atstate858.
• Atdecision diamond860, if all three IR T/R LED pairs816 are not on, the logic moves todecision diamond866 where it is determined if two out of three of the IR T/R LED pairs816 are on. If so, the logic moves todecision diamond868 where it is determined whether the two IR T/R LED pairs816 are operating properly, e.g., by toggling the two IR T/R LED pairs816 on and off. If the two IR T/R LED pairs816 are not operating properly, the logic moves to block856 where an “optics error” message is presented to the user. The logic then ends atstate858. Otherwise, if the two IR T/R LED pairs816 are operating properly, the logic moves todecision diamond870 where it is determined if signal pulses are present. If not, the logic moves to block872 where a “no flow” message is presented to the user. The logic then loops back todecision diamond870.
• Atdecision diamond870, if pulses are present, the logic moves todecision diamond874 where it is determined if all three IR T/R LED pairs816 are operating properly. If so, an “optics ok, flow” message is indicated to the user atblock876. Otherwise, an “optics warning, flow” message is indicated to the user atblock878. Fromblock876 or block878, the logic moves to block880 where it is determined if pulses are present. If pulses are indeed present, the logic returns todecision diamond874 and continues as described above. Conversely, if pulses are not present, the logic proceeds to block882 where a “no flow” message is presented to the user. The logic then ends atstate858.
• Returning todecision diamond866, if it is determined that two IR T/R LED pairs816 are not on, the logic continues todecision diamond884 where it is determined if one IR T/R LED pair816 is on. If not, the logic proceeds to block856 where an “optics error” is presented to the user. The logic then ends atstate858. If the IR T/R LED pair816 is on, the logic moves todecision diamond886 where it is determined whether the IR T/R LED pair816 is operational. If the IR T/R LED pair816 is not operational, the logic continues to block856 where an “optics error” is presented to the user. The logic then ends atstate858. If the IR T/R LED pair816 is operating properly, the logic moves todecision diamond870 and continues as described above.
• With the above logic, theflow detector800 can indicate flow through the working fluid circuit only if signal pulses are output by theflow detector800. Moreover, while thepaddle wheel808 is rotating, theprocessor818 is constantly testing each of the IR T/R LED pairs816 by sequentially toggling each of the IR T/R LED pairs816 on and off and reading the signals output thereby.
Description of the Glycol Flow Detection Logic
• Referring now toFIG. 21, the glycol flow detection logic is shown and commences atblock900 with a do loop wherein periodically, the following steps are performed. Atblock902, the heater166 (FIG. 4) is periodically pulsed. Moving todecision diamond904, it is determined if there is a sudden increase in temperature (e.g., above a predetermined quantity), as indicated by the thermocouple temperature sensor170 (FIG. 4). If not, the logic ends atstate906. Otherwise, the logic proceeds to block908 where it is indicated to a controller that there is a problem with the glycol circulation. It can be appreciated that in response to the indication of a problem, the controller can shut off power to the heater at block910.
Relevant Equations
• As described above, the power required to cool the patient can be viewed at thedisplay device98. It is to be understood that the power equation described below is most accurate for a patient having a weight of approximately seventy-five kilograms (75 kg). Accordingly, the power used to cool a patient can be determined using the following equation:
• $\left(\frac{t_{pt}/\mathrm{t°}C.\text{/}\min \times 60\min \text{/}\mathrm{hr}}{1.4°C.\text{/}\mathrm{hr}}\right)\times 100w\times \left(-1\right)$
• • where:
    • dT_pt/dt is determined by the equation disclosed above.
• While the particular HEATING/COOLING SYSTEM FOR INDWELLING HEAT EXCHANGE CATHETER as herein shown and described in detail is fully capable of attaining the above-described aspects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and thus, is 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 is 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.section 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”

Claims (22)

We claim:

1. A heat exchange system for a heat exchange catheter, comprising:

a heat exchange receptacle configured to receive a conduit carrying fluid to and from the catheter when the fluid is at a temperature different from normal mammal body temperature to exchange heat with a mammal in whom the catheter is disposed; and

a pump in communication with the conduit for pumping the working fluid to and from the catheter.

2. The system ofclaim 1, wherein the pump is detachably engaged with the conduit and a pump support platform.

3. The system ofclaim 2, wherein the pump support platform comprises:

a pump locking bore, the pump removably engaging the pump locking bore.

4. The system ofclaim 3, wherein the pump support platform further comprises:

at least one spring loaded ball plunger, the spring loaded ball plunger removably engaging the pump with the pump support platform.

5. The system ofclaim 4, wherein the pump support platform further comprises:

a motor, the motor engaging the pump to provide power to the pump when the pump is engaged with the pump support platform.

6. The system ofclaim 4, wherein the pump support platform further comprises:

at least one sensor for detecting the presence of the pump when it is engaged with the pump support platform.

7. The system ofclaim 1, further comprising:

at least one air trap vessel downstream from the pump; and

at least one air trap detector at least partially surrounding the air trap vessel.

8-22. (canceled)

23. A system for a heat exchange catheter, comprising:

a heat exchange receptacle configured to receive a conduit carrying fluid to and from the catheter when the fluid is at a temperature different from normal human body temperature to exchange heat with a patient in whom the catheter is disposed; and

a pump support platform supporting a pump for pumping fluid to the catheter, the pump support platform further comprising at least one sensor for detecting the presence of the pump when the pump is engaged with the pump support platform.

24. The system ofclaim 23, wherein the pump is a gear pump in communication with the conduit for pumping the fluid to and from the catheter.

25. The system ofclaim 23, wherein the pump is detachably engaged with the conduit and a pump support platform.

26. The system ofclaim 25, wherein the pump support platform comprises:

a pump locking bore, the pump removably engaging the pump locking bore.

27. The system ofclaim 26, wherein the pump support platform further comprises:

at least one spring loaded ball plunger, the spring loaded ball plunger removably engaging the pump with the pump support platform.

28. The system ofclaim 27, wherein the pump support platform further comprises:

a motor, the motor engaging the pump to provide power to the pump when the pump is engaged with the pump support platform.

29. The system ofclaim 23, further comprising:

at least one air trap vessel downstream from the pump; and

at least one air trap detector at least partially surrounding the air trap vessel.

30. A system for a heat exchange catheter, comprising:

a heat exchange receptacle configured to receive a conduit carrying fluid to and from the catheter when the fluid is at a temperature different from normal human body temperature to exchange heat with a patient in whom the catheter is disposed;

a pump support platform supporting a pump for pumping working fluid to the catheter;

at least one air trap vessel downstream from the pump; and

at least one air trap detector at least partially surrounding the air trap vessel.

31. The system ofclaim 30, wherein the pump is a gear pump in communication with the conduit for pumping the fluid to and from the catheter.

32. The system ofclaim 30, wherein the pump is detachably engaged with the conduit and a pump support platform.

33. The system ofclaim 32, wherein the pump support platform comprises:

a pump locking bore, the pump removably engaging the pump locking bore.

34. The system ofclaim 33, wherein the pump support platform further comprises:

at least one spring loaded ball plunger, the spring loaded ball plunger removably engaging the pump with the pump support platform.

35. The system ofclaim 34, wherein the pump support platform further comprises:

a motor, the motor engaging the pump to provide power to the pump when the pump is engaged with the pump support platform.

36. The system ofclaim 30, wherein the pump support platform further comprises at least one sensor for detecting the presence of the pump when it is engaged with the pump support platform.

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