Abstract:
A critical care thermal therapy system incorporating a remote temperature sensor in association with a thermal module adapted for delivering a fluid to a patient in response to the sensed temperature thereof.

Description:
CROSS REFERENCE OF RELATED APPLICATIONS 
     The present application claims priority to and incorporates by reference the entirety of U.S. Provisional Patent Application Ser. No. 60/726,786 filed Oct. 14, 2005 and cross references and incorporates by reference U.S. Published Applications No. 2006/0034053 filed Aug. 12, 2005 and U.S. Published Applications No. 2005/0143797 filed Jul. 19, 2004. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to temperature control systems and methods and more particularly, but not by way of limitation, to critical care thermal therapy systems utilizing a temperature control module operated in conjunction with a remotely disposed monitoring system enhancing performance and reliability of the thermal control over a patient&#39;s body in a manner particularly suited for neonatal care and other critical care. 
     2. History of the Prior Art 
     Medical care providers have long recognized the need to provide warmth and/or cooling directly to patients as part of routine treatment and therapy. For example, faster and more efficient recoveries have been reported using cold therapy for orthopedic patients. Moreover, the benefits of warming patients undergoing surgery has been conclusively proven. 
     Several methods, devices, and systems have been developed that deliver temperature controlled fluids through pads or thermal blankets to achieve the above purpose. Typically these devices and systems have heating and/or cooling elements, a source for the temperature controlled fluid, a pump for forcing the temperature controlled fluid through the pad, blanket, or other patient cover and a thermal interface between the patient and the temperature controlled fluid. U.S. Pat. No. 4,884,304 to Elkins is directed to a mattress-cover device which contains liquid flow channels which provide the selective heating or cooling by conduction. 
     Cooling blankets have also been proposed such as the blanket disclosed in U.S. Pat. No. 4,660,388 to Greene. Greene discloses a cooling cover having an inflatable pad with plenum chambers at opposite ends thereof. Cool air is generated in a separate unit and directed to the pad and out a number of apertures on the underside of the pad and against the body of the person using the cover. 
     A disposable heating or cooling blanket is disclosed in U.S. Pat. No. 5,125,238 to Ragan, et al. which has three layers of flexible sheeting. Two of the layers form an air chamber and the third includes a comfortable layer for contact with the patient. Conditioned air is directed toward the covered person through a multiplicity of orifices in the bottom layers of the blanket. Another system is set forth and shown in U.S. Pat. No. 5,989,285, assigned to the assignee of the present invention. 
     More recently the advantages of thermal control have been realized for critical care patients such as neonatal babies and stroke victims. Accurate critical care with thermal therapy systems require not only a temperature controlled fluid, but also the monitoring of the body temperature of the patient. It is critical that a reliable thermal response is used to achieve the desired core body temperature. Several problems are inherent, however, in prior art systems which lack fast and accurate temperature control in response to monitored temperature values. Time delays can result in thermal overshoot by the system, reducing patient effectiveness. 
     The key issue in accurate temperature control is indeed providing a system which incorporates a monitoring system having real-time temperature reading and a system response in proportion to the thermal measurements taken for the patient being treated. In other words, a sensed temperature of the patient&#39;s body evokes a thermal response which is directly associated therewith and without a time delay therefrom. Time delays between the detection of a denied thermal deviation and the delivery of the necessary heat or cold can, as referenced above, be deleterious. A system which provides the delivery of the necessary heat or cold within a short response period is necessary for true critical care through thermal therapy. It is therefore important that modem thermal therapy systems reduce the time differential substantially in order to afford the delivery of the necessary heat or cold to the patient&#39;s body for the requisite therapeutic effect. 
     It should be further noted that thermal therapy in critical care situations may be required in mobile intensive care units. Strokes often occur away from hospitals and comprise the genesis of basic lifesaving scenarios of the type where thermal therapy may be a critical life, or quality of life, saving factor. If an effective critical care thermal therapy system is not provided in a mobile configuration operable with multiple forms of power (such as AC and/or DC current) the utilization of the system is limited. The availability of a critical care system should not be dependent upon a single form of power. 
     The present invention addresses these considerations and affords an improvement over the prior art by providing an efficient thermal therapy system with real-time feedback monitored thermal response to uniformly heat or cool fluid delivered to a patient when and where the patient is in need. The present invention further includes a system that is operable on both AC and/or DC current and in an optionally portable configuration to facilitate use within automobile, care flight and other mobile configurations. 
     SUMMARY OF THE INVENTION 
     The present invention relates generally to a critical care thermal therapy system and method providing a patient with both recirculating temperature controlled fluid and real time monitoring and response to improve performance parameters and enhance patient care. 
     In one aspect, the present invention provides a portable critical care thermal therapy system, operable on multiple forms of electrical power for providing direct thermal therapy in response to a monitored temperature of the patient for accurate thermal control and treatment. 
     In yet another embodiment, the present invention provides a thermal therapy system combining Thermo Electric Components (TEC) for the generation of heat and cold as necessary for thermal therapy. TEC devices are assembled to run on DC current which may be provided by a battery or a converter from AC current. In this manner, the TEC system will support thermal therapy in mobile situations. 
     In yet another aspect, the present invention relates to a neonatal critical care thermal therapy system affording low noise and low vibration operation. 
     In yet another aspect, the present invention includes a system incorporating temperature monitoring of the patient through at least one of rectal temperature measurements, esophageal temperature measurements, skin temperature measurements, and/or deep brain temperature measurements. The system may be provided in a rack mount configuration or in a portable configuration while providing a treatment fluid having the necessary temperature and thermal capacitance to heat or cool large or small areas of a patient. The area of the patient can be limited to that of a specific region comprising a thermal wrap of limited size or a complete blanket such as that set forth as shown in above referenced U.S. Pat. No. 5,989,285 assigned to the assignee of the present invention and incorporated herein, in its entirety, by reference. Other thermal treatment units may be incorporated therewith in accordance with the principles of the present invention. 
     In a further aspect, the present invention includes a critical care, thermal therapy system utilizing a thermal fluid flow to which a patient is thermally exposed. The system comprises a recirculating, temperature controlled fluid flow network adapted for patient care, a temperature control module connectable in fluid communication with the temperature controlled fluid flow network for regulating the thermal fluid temperature and flow to the patient, a thermal therapy device adapted for the flow of the thermal fluid therethrough and thermal exposure to the patient, the device being connectable to the temperature control module through the temperature controlled fluid flow network, and at least one temperature sensor in thermal communication with the patient and remotely disposed from the temperature control module. In one embodiment, the at least one remotely disposed temperature sensor monitors a select body temperature and sends thermal measurement signals to the temperature control module and in another embodiment, the temperature control module is adapted to increase or decrease the control fluid temperature and flow rate in response to the thermal measurement signals from the at least one remotely disposed temperature sensor. 
     In yet a further embodiment, the above described embodiment, the thermal measurement signals sent by the at least one remotely disposed temperature sensor comprises real-time measurements, and further comprises a user interface coupled to the temperature control module for setting a desired temperature and tolerance boundaries wherein the tolerance boundaries represent upper and lower thermal fluid temperature limits. 
     In a preferred embodiment, the user interface is electrically isolated from the temperature control module and the temperature control module is adapted for continually adjusting the thermal fluid temperature such that the monitored temperature approaches the desired temperature. 
     In a still further aspect, the present invention includes a method of thermal therapy critical care with utilizing a thermal fluid flow to which a patient is thermally exposed, the method comprising the steps of recirculating a control fluid through a closed-loop fluid flow network adapted for patient care, adjusting the temperature of the thermal fluid with a temperature control module connectable to the fluid flow network controlling the flow of the thermal fluid with the temperature control module, thermally exposing an environment to the thermal fluid via a thermal therapy device connectable to the fluid flow network, monitoring a patient temperature with at least one temperature sensor remotely disposed from the temperature control module, and sending real-time signals from the at least one remotely disposed temperature sensor to the temperature control module indicating the patient temperature. In one embodiment, the at least one remotely disposed temperature sensor is electrically isolated from a main power supply of the temperature control module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages and features of the invention will become more apparent with reference to the following detailed description of a presently preferred embodiment thereof in connection with the accompanying drawings, wherein like reference numerals have been applied to like elements, in which: 
         FIG. 1  is a perspective view of a critical care thermal therapy system controller for use with one or more remote temperature sensors and a fluid flow network, including a thermal therapy cover, pad or wrap utilized as a thermal treatment device as described herein; 
         FIG. 2  is a functional block diagram of the thermal therapy system controller of  FIG. 1  illustrating the functionality thereof in conjunction with remote sensors used therewith; 
         FIG. 3  is a block diagram of the operational aspects of the thermal therapy system controller of  FIG. 1  illustrating the interactive functionality with a microcontroller incorporated therewith; 
         FIG. 4  is a perspective view of a DC power converter module for use in conjunction with the thermal therapy system controller of  FIG. 1 ; 
         FIG. 5  is a perspective view of two remote sensing modules facing in opposite directions for illustrating the utilization therewith in conjunction with the thermal therapy system controller of  FIG. 1 ; 
         FIG. 6  is a perspective view of one embodiment of the system of the present invention; 
         FIG. 7  is a chart presenting performance data; and 
         FIG. 8  is a chart of additional performance data related to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates to a critical care thermal therapy system having improved performance characteristics. Referring now specifically to the drawings, and in particular to  FIG. 1 , there is shown a thermal control unit  210  capable of providing a flow of liquid at the necessary flow rate to control the temperature of a thermal blanket or similar covering for the patient. For example, a temperature control blanket such as that set forth and shown in U.S. Pat. No. 5,989,285 could be incorporated for use herewith. It should be noted however that other patient coverings such as wraps, blankets and pad designs may be utilized in conjunction with the principles of the present invention. 
     Still referring to  FIG. 1 , the thermal control unit  210  of the present invention includes chassis  212  having control panel  214  disposed across a frontal portion thereof. The thermal control unit  210  is further constructed with a handle  216  disposed upon a side region therealong to facilitate handling. It should be noted that the thermal control unit  210  may be of the type set forth, shown, and described in U.S. patent application Ser. No. 11/202,885, the entirety of which is incorporated herein by reference. The 3U design of that particular invention is set forth and shown herein for reference purposes only and other size and operation configurations may be utilized. For purposes of reference, however, the teachings set forth shown and described in the above referenced U.S. patent application Ser. No. 11/202,885 are submitted to further enable one of ordinary skill in the art to construct the invention as hereinafter described. For example, the thermal capacity of the thermal control unit  210  may be selected in conjunction with temperature and flow conditions as shown in the specification sheet provided in the above-referenced patent application. The availability for select operation parameters for the thermal control unit  210  including, for example, up to six internal fan assemblies and an additional three internal fans with external fan trains and the like permit the designer and/or ultimate end-user the ability to specify the requisite operational parameters as well as AC or DC power source (or both) for the functional operation. 
     Still referring to the 3U system described above, multiple advantages are afforded for both customer and user in conjunction with the present invention. For example, the critical care thermal therapy system of the present invention may utilize, in certain embodiments, rack mounting configurations. One such configuration might include hospital applications. In other applications wherein portability is desirable, and DC power converter modules are available, the ability to utilize the system of the present invention and/or have the system upgraded for selective operation and selective emergency environments provide enumerable advantages over many prior art systems. 
     Still referring to  FIG. 1 , the chassis  212  shown herein may also be of a different dimension than the 3U dimension described above. The dimension may vary dependent upon the quantity of cooling engines selected and utilized therewith. The cooling engines shown and described herein utilize a peltier effect and incorporate TEC thermal modules. TEC modules allow for portable DC use. With DC use, a power converter may be provided, such as that shown in  FIG. 4 . The unit is operable with a patient covering such as the blanket set forth and described in the patent application, while monitoring the temperature of the patient with remote modules  300  the type shown in  FIG. 5 . As discussed below, the remote modules  300  of  FIG. 5  are electrically isolated from the thermal control unit  210  to therein reduce the possibility of electric shock to the patient. This operational parameter is provided with both portable and rack mounted configurations. 
     Referring now to  FIG. 2  there is shown a functional block diagram of the thermal control unit  210 . This particular unit is powered by AC power  220 ′ allowing a peltier power supply (PPS)  222  and auxiliary power supply (APS)  224  to operate. The PPS  222  supplies current to a thermal engine  226 . An operation mode of cooling is shown herein but the thermal control unit  210  may also utilize heat. In operation, the thermal engine  226  takes fluid from a coolant pump  228  via a flow meter  230 . The coolant pump  228  pulls from reservoir  232 , which collects fluid returning from a thermal therapy cover pad or blanket hereinafter referred to as a Thermal Therapy Device (TTD)  236 . The output of engine  226  is coolant flow  234  that feeds the TTD  236 . 
     Still referring to  FIG. 2 , the coolant pump  228  may be powered by APS  224  as indicated. It may also supply micro-controller  240  with requisite power. The micro-controller  240  regulates the flow through the flow meter  230  via the pump  228 . With micro-controller  240  the speed of fans  242  is also regulated to control the flow of air thereacross and thus the heat transfer therefrom. The reading from the various sensors is then indicated on a control panel  214 . Ambient sensors  244  are also utilized with a buzzer  246  to alert attendants in the event of operational issues. 
     Still referring to  FIG. 2 , a sensor  255  is shown as an esophageal sensor which may be utilized. As described above, other sensors are contemplated in accordance with to the principles of the present invention. 
     Referring now to  FIG. 3 , there is shown a thermal control unit block diagram. The thermal control unit  210  is electrically isolated from the array  250  of sensors used to monitor temperature of the patient. Array  250  comprises TTD blanket sensor  251 , duraskin sensor  253  and esophageal sensor  255 . These sensors as well as others could be provided for direct communication with the controller. The communication link may be through direct connection, infrared, and/or other remote communication systems. For purpose of example, connections are illustrated by dotted lines  251 ′,  253 ′ and  255 ′. The data from the sensors are then received by the micro-controller  240  which may include an analog/digital converter  260 . The data is processed to determine patient temperature and fluid temperature. An illustrative algorithm for making these calculations is described below. 
     Core Temperature Adaptive Control 
     One of the primary functions of a control loop includes using the temperature data read from a sensor, for example an esophageal sensor, placed in proximity to the patient, to precisely control the cool down and warm up of the patient&#39;s core body temperature. The purpose of this exemplary algorithm is to reach the esophageal set point temperature (core body temperature) rapidly with minimum overshoot (&lt;0.5 deg C.) and control the temperature at set point to with +/−0.2 deg C. 
     The control algorithm may also be able to auto-tune and adapt for variables such as patient weight, probe placement, sensor artifacts due to movement by the patient, temperature spikes due to IV&#39;s or meds, acid reflux and variation in metabolic conditions of the patient. 
     Control Method: 
     For exemplary purposes, a control method utilizing an esophageal temperature sensor will be described, but other thermal sensors monitoring other temperatures could also be utilized. The esophageal temperature sensing module may use a moving average computation to determine the esophageal temperature. It may also calculate the rate and acceleration factors for the temperature (first and second derivatives respectively). 
     This information may be used by the esophageal control loop to determine the optimal coolant, for example a blanket, temperature to be delivered to the patient as to achieve the desired core temperature. 
     In one exemplary embodiment, the esophageal adaptive control uses the esoph_error (defined as esophageal temp—esophageal set temp) to as the primary factor in determining the controller output computation. If the esoph_error is positive, the control output will apply cooling and if negative heating will be provided. 
     For both COOL and HEAT modes, there are four states: 
     STABLE State: If the esoph_error is within 0.25 deg C. of esophageal set point. 
     SLOW State: This state is applied when the esoph_error is &gt;0.25 deg C. but&lt;=1.00 deg C. 
     MEDIUM State: This is applied when the esoph_error is &gt;1.00 deg C. but&lt;=2.00 deg C. 
     FAST State: If the esoph_error is &gt;2.00 deg C. 
     Within each state, the algorithm uses the temperature rate and second derivative information to adjust the coolant set temperature of the therapy unit. By using the esophageal temperature characteristics this algorithm changes the set temperature of the coolant (UP or DOWN) and lets the Supply Temperature Adaptive Control algorithm control the fluid temperature delivered to the patient. 
     The rate information may be used to determine the magnitude of coolant set temperature adjustment. This adjustment can be, for example, from +/−0.01 deg C. to 1.00 deg C. The second derivative gives useful information of change of temperature rate; this may be used to detect sudden temperature artifacts such as administration of meds or patient movement. If such events are detected, the control algorithm maintains the previous control parameters until the transient event has passed. Use of the second derivative allows the controller to not react to transients, thus minimizing temperature oscillations of core body temperature. 
     Supply Temperature Adaptive Control 
     This control loop maintains the coolant (supply) temperature of the therapy unit to within +/−0.1 deg C. of coolant set temperature. 
     The control loop calculates the control error by subtracting the measured temperature from the set temperature. If the error is positive the Proportional-Integral (PI) control will be in COOL mode and if negative it will operate in HEAT mode. 
     For both COOL and HEAT modes, these are three fuzzy stages for each mode. 
     Stage 1—MAX Drive: If the control error is greater than or equal to 2.00 deg C. then the Tec&#39;s are driven at maximum power to achieve setpoint condition. This mode is primarily to provide rapid response to changing set points or thermal conditions. 
     Stage 2—CONTROL Drive: If the control error is greater than 0.1 deg C. but less than 2.00 deg C., the TEC drive is proportional to the control error. This is a unique way to achieve quick settling time as the coolant temperature nears the set point, the magnitude of the control error will also decrease. Due to the linear relationship between the control error and TEC drive, the drive level will also reduce. This method dampens any temperature overshot, and minimizes temperature oscillations at set point. 
     Stage 3—STABLE Drive: If the control error is less than 0.1 deg C., the Tec&#39;s drive is turned OFF and the temperature is allowed to coast at or near set point. 
     Supply Temperature Adaptive Control (Optimization Loop) 
     If the PI control is in stage 2 or 3, this module may look at the average control error over a given time interval, and update the PI loop to drive the error to less then 0.05 deg C. The level of adjustment may be determined by the magnitude of the error and rate of change of the error (first derivative). 
     Information may be displayed on LCD  262  where keys and input controls  264  are connected to the micro-controller  240  through digital input/output ports  266 . A communication port  268  provides control of heating/cooling engine  226  and flow meter  230 . 
     Referring now to  FIG. 4  there is shown a DC power converter module  100  as referenced above for use in conjunction with a portable aspect of the present invention. Likewise,  FIG. 5  illustrates two remote sensing modules  300  of the type utilized to detect critical patient temperature and communicate with the control unit  210  of  FIG. 1  to control the flow of fluid as described in  FIGS. 2 and 3 . 
     In operation, the individual operating the control unit  210  turns it on, chooses heat or cold and inputs the desired temperature via the input controls  264  on control panel  214 . Control signals from control unit  210  are input to engine  226  and to pump  228  for control thereof. Temperature feedback from sensor array  250  is transmitted to micro-controller  240  as described above. 
     Temperature controlled liquid flows from the heating/cooling engine  226  to the TTD  236 . TTD  236  and flow system which may be used with the present applications may be seen in U.S. patent application Ser. No. 10/894,369 incorporated herein by reference. It will be appreciated that the flow of temperature control liquid is therefore provided to a patient in need of thermal therapy care. 
     The following operational aspects are specifically referenced herein relative to the subject application. The present invention provides portability, accuracy, and temperature monitoring with increased real response time to provide improved patient care. Prior art systems attempting to provide thermal therapy to patients often manifested overshoot inefficiency problems. Overshoot is one of the more critical aspects from the standpoint of patient care under thermal therapy. With both stroke and neonatal patients, the need for real-time temperature control and the requisite thermal therapy within predefined tolerance boundaries is critical. For this reason, multiple aspects of temperature measurement of the patient is anticipated with the remote modules of the present invention affording doctors the ability to take temperatures such as rectal as well as esophageal and/or deep brain in addition to dermal. The remote sensing protects the patients and insulates the patient from any risks relative to power being supplied thereto, in this way, the patient is not exposed to the power supply. In one embodiment referred to above with a rack mount, the patient is able to experience the benefits of the system and thermal therapy in a low-noise, low-vibration environment. This may be very critical in neonatal units. 
     In summary, the AC/DC options of the present invention, as well as the size and weight of the thermal control unit  210 , provide great benefits in association with the low noise and possibility for MICU ambulance/helicopter care. 
     With regard to neonatal applications it is important to note that premature infants typically cannot regulate their own body temperature and therefore the ability to accurately control thermal therapy systems with immediate response is a market advantage over the prior art. Feedback with multiple remote sensors is thus critical to the operation of the thermal engine  226  and the ability to provide larger thermal capacity by modifying the number and/or size of the thermal engine within the chassis  212  is of distinct importance. While particular embodiments of the present invention have been described, it will be appreciated by those skilled in the art that various modifications, alternatives, variations, etc., may be made without departing from the spirit and scope of the invention as defined in the appended claims. 
     Referring now to  FIG. 6 , there is shown a perspective view of the control unit  210  of  FIG. 1  and the critical care system described above connected thereto. The control unit  210  is shown coupled to a tubular array providing the flow of fluid to a thermal blanket (TTD). In this particular test embodiment, a sensor is illustrated with direct connection to the controller. In actual operation, the sensor or sensors may be remote so that the patient does not have any direct electrical connectivity to the control unit  210  or a direct connection with appropriate safety isolation may be used. In this manner the possibility of shock should be substantially eliminated. 
       FIG. 7  comprises neo-thermo performance data bench testing information relative to the principles of the present invention. The neo-thermo test set up utilized a stainless steel reservoir is used with a crib blanket. An immersion heating element was used as the thermal load and an esophageal temperature sensor was used to monitor the fluid temperature within the reservoir. The reservoir was filled with liquid detergent, which was found to conduct heat at a slower rate than water and perhaps provide a better test relative to data to be applied to human testing parameters. Temperature stability charts illustrating the relationship between the esophageal set temperature, the measured esophageal temperature, the supply fluid temperature and the esophageal rate are shown. 
     Still referring to  FIG. 7 , the chart provided illustrate the improved efficiency relative to thermal therapy treatment afforded by the present invention. The stability charts illustrate the fact that the present invention maintains the desired temperature in a uniform and stable fashion. The chart relative to the test set-up for the neo-thermo temperature system illustrate an esophageal temperature that is very stable and accurately maintained. 
       FIG. 8  comprises a chart illustrating additional temperature stability readings relative to the supply temperature, the esophageal temperature as well as the esophageal rate. The Figure shows a temperature spike or transient event and the response thereto. 
     It is believed that the operation and construction of the present invention will be apparent from the foregoing description of a preferred embodiment. While the device shown is described as being preferred, it will be obvious to a person of ordinary skill in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the following claims. Therefore, the spirit and the scope of the appended claims should not be limited to the description of the preferred embodiments contained herein.