JP5421406B2 - Patient temperature control system - Google Patents

Description

  The present invention relates to a system and method for controlling a heat exchange function in a patient temperature control system, and more particularly to controlling heat exchange in a manner that avoids temperature overshoot and excessive temperature fluctuations.

  It is known to use contact pad systems to selectively cool and / or heat body tissue. In such a system, a fluid such as water or air circulates through one or more pads and affects the surface-to-surface thermal energy exchange with the patient. One highly effective contact pad and related system is disclosed in US Pat. No. 6,197,045, incorporated herein by reference. As noted in the '045 patent, the ability to establish and maintain intimate pad-patient contact is often very important to fully realize the medical effectiveness of the contact pad system. is there.

  Regarding the latter, the effect of temperature on the human body has been well documented. High temperature or hyperthermia can be harmful to the brain under normal conditions, and even more importantly during periods of physical tension such as illness or surgery. Conversely, lower body temperature or moderate hypothermia may provide some degree of neuroprotection. Moderate to severe hypothermia tends to be harmful to the body, specifically the cardiovascular system.

  Temperature management or temperature regulation can be viewed in two different ways. A first aspect of temperature management involves treating abnormal body temperature, ie, cooling a hot body or warming a cold body. The second aspect of thermoregulation is the development of using techniques to physically control the patient's body temperature to provide physiological benefits, such as cooling the patient who is having a seizure to gain some degree of neuroprotection Treatment.

  Hypothermia can occur for a variety of reasons, including exposure to a cooling environment, brain damage, or complex surgical procedures. During surgery, patients typically experience moderate hypothermia as a result of general anesthetic effects on the thermoregulatory system and prolonged exposure of the internal organs. Moderate hypothermia in medical or surgical patients has been thought to prolong the time to extubate, contribute to coagulation abnormalities, increase the chance of infection, and increase the burden on the heart as a result of shivering.

  Hyperthermia can occur as a result of a systemic inflammatory response, sepsis, seizures, or other brain damage. The mechanism of hyperthermic effects on the brain is not clearly understood, but there is evidence that even moderate increases in body temperature can contribute to neuropathy. High body temperature can also increase metabolic rate and drastically reduce the body's energy storage.

  In view of the above, it is possible to understand that the recognized medical application field of contact pad systems is expanding. As an example, a cooling pad system can be used in initial treatment to reduce nerve damage experienced by patients with stroke and head trauma. An additional field of application is the selective heating / cooling of patients during surgical procedures such as cardiopulmonary bypass surgery.

  As these and other medical application fields have evolved, the inventor has recognized that it is desirable to improve the predictability, responsiveness, adaptability, and portability of heat exchange pad systems. More specifically, while known heating / cooling contact pad systems have proven effective for many applications, the inventors have further improved the control system and associated control methods. Recognizes that additional performance objectives and potential application areas can be realized.

  Specifically, one object of the present invention is an improvement that provides rapid heating / cooling capability through one or more interconnectable contact pads, while also providing size, weight, and operational efficiency. To provide a patient temperature control system and method.

  It is another object of the present invention to provide an improved patient temperature control system and method that provides high heat exchange reliability while addressing application flexibility through the interoperability of one or more contact pads. There is.

It is another object of the present invention to provide an improved patient temperature control system and method that facilitates easy setup and portability.
It is another object of the present invention to provide an improved patient temperature control system that provides improved wearing and performance of one or more interconnectable contact pads.

It is another object of the present invention to provide an improved patient temperature control system and method that improves patient comfort.
One or more of the above objects and additional advantages may be achieved by using the features of the temperature control system and related methods disclosed below. System features include at least one heat exchanger to affect at least one of heating and cooling of the fluid, a circulation pump that circulates fluid through the heat exchanger, and heat transfer between the patient and the contact pad And at least one interconnectable patient contact pad that affects For the purposes of this specification, the term “contact pad” allows fluid to flow from an input port to an output port, otherwise it contacts the patient to affect heating or cooling. Refers to any type of pad that is adapted to.

  In one aspect, the system of the present invention may also include at least one first fluid reservoir or “make-up fluid reservoir” that is fluidly interconnectable with the contact pad. The first fluid reservoir can be used to contain fluid that can be removed from the reservoir to fill / circulate the pad during use. In this regard, the system establishes that during normal heating / cooling operations, fluid can be circulated through the pad and heat exchanger by a circulation pump without substantially passing through the first fluid reservoir. Is possible. With this arrangement, a rapid fluid temperature change can be achieved in the system because only the circulating fluid is temperature controlled (eg, remaining in the first fluid reservoir). Any additional fluid is not temperature controlled during fluid circulation). In this connection, it is possible to relax the heat exchanger requirements. In addition, compliance can be maintained by including sufficient fluid volume in the first reservoir to fill a plurality of interconnectable contact pads.

  The system preferably also comprises a second fluid reservoir or “circulating fluid reservoir” in which the fluid circulates during normal heating / cooling operations. In this regard, the first reservoir and the second reservoir are such that fluid can be removed from the first fluid reservoir by passing through the second fluid reservoir and flow again into the first fluid reservoir. Direct fluid interconnection is possible. In addition, the heat exchanger, the circulation pump, the first fluid reservoir, and the second fluid reservoir can be supported and disposed within a common housing, the system to facilitate portable use Almost self-contained.

  More specifically, all or at least a portion of the first fluid reservoir may be physically located above the second fluid reservoir to provide for fluid flow from the first reservoir to the second reservoir by gravity. It is. In this regard, it is possible to maintain the top of the first reservoir at approximately atmospheric pressure (eg, via a vent with a semi-permeable filter) to remove gas from / in the system. It is possible to pass through. Further, a sensor can be provided in the second fluid reservoir to sense the amount of fluid contacted by the second reservoir, providing a user output when / when the fluid amount falls below a predetermined amount. Is possible.

  For example, the sensor can provide an output signal to a control device (such as a microprocessor), which transmits the signal to a user output (such as a display device and / or an audible output device). Such user output can not only alert the user about the situation, but can also advise the user regarding the fluid refill procedure. In addition, the controller can automatically turn off the circulation pump and heat exchanger when / when the sensed fluid volume in the reservoir falls below a predetermined level.

  Further to the aspects described above, the first fluid volume includes a first fluid volume and a second fluid volume, respectively, of fluid present in the system (eg, when the system is fluidly separated from the interconnectable pad). A fluid reservoir and a second fluid reservoir can be provided, the first fluid volume being larger than the second fluid volume. The first fluid volume is preferably between about 3% and 50% of the first fluid volume. As can be appreciated, the interconnectable contact pad can have an internal volume that is greater than the second fluid volume, and at least some of the fluid contained in the first fluid reservoir is heated / It is possible to flow out of the first reservoir to circulate the pad during cooling. The amount of fluid removed from the first reservoir for such purposes depends on the number of interconnected pads.

  In connection with the foregoing, it should be understood that there is provided a body temperature control method of the present invention comprising the steps of including a fluid in a first fluid reservoir and at least a portion of the fluid flowing out of the first reservoir. Is possible. The removed portion circulates at least one interconnected contact pad and a heat exchanger fluidly interconnected to the contact pad without substantially passing through the first reservoir. The method then further includes contacting the pad with the patient to affect heat transfer between the pad and the patient. Typically, the fluid volume corresponding to the removed portion returns to the first fluid reservoir, for example upon completion of a given patient heating / cooling procedure.

  The method can further include selectively establishing a fluid interconnection of the contact pads. In this regard, the method selectively and easily interconnects to and from one or more contact pads, as deemed appropriate by a medical practitioner heating / cooling the patient in a given situation. It is anticipated that it can be implemented using a system that can be separated. For such purposes, the method may further comprise retaining the first fluid volume in the first fluid reservoir and retaining the second fluid volume in the second fluid reservoir, wherein the first fluid volume And the second fluid volume is combined to be sufficient to fill the plurality of contact pads. Preferably, the amount of fluid present in the second fluid reservoir can be sensed and the sensor output signal can be used to provide a user output, as noted above (eg, the fluid level is When falling below a preset amount).

  The described system and method can also provide for pumping circulating fluid through the interconnectable contact pads under negative pressure. Such negative pressure can be established by placing a circulation pump downstream of the pad, and fluid is pumped from the pad through the heat exchanger and into the second fluid reservoir. As mentioned, the second fluid reservoir can be maintained at approximately atmospheric pressure. Preferably, the method of the present invention can further comprise disposing interconnect contact pads above the first fluid reservoir and the second fluid reservoir. Such an arrangement facilitates fluid to flow out of the interconnectable contact pad and back into the system, for example if the pad leaks / pump stops.

  In another aspect, the patient body temperature of the present invention further includes a pressure sensor fluidly interconnected between the inlet side of the circulating pump and the outlet port of the interconnecting contact pad as well as the circulating pump and at least one heat exchanger. A control system is provided. The pressure sensor can provide an output pressure signal that can be used to control the circulation pump. Again, the circulation pump can be arranged to establish a negative pressure at the interconnectable contact pads. The output pressure signal can then be used to control the circulation pump to maintain the negative pressure within a predetermined range. Such a configuration facilitates maintaining a desired minimum pressure in each of the one or more interconnectable contact pads.

  Further, the system can include a controller that receives the output pressure signal from the pressure sensor and responsively provides a control signal to the circulation pump. With respect to the latter, it is possible to provide a control signal to control the operating speed of the pump. More specifically, the controller can use the outlet pressure signal and a predetermined set of information to control the operating speed of the pump (eg, corresponding to the desired pressure range of the interconnectable contact pad). is there.

  The system of the present invention may also include a flow meter that measures the flow rate of fluid between the outlet side of the circulation pump and the inlet port of the interconnectable contact pad. The flow meter provides an output flow signal. Next, a user output device can be included that provides an output in response to identifying a predetermined relationship between the output flow signal and the pump operating speed and / or output pressure signal. As a major example, such a predetermined relationship may correspond to a situation that may indicate the presence of a potential fluid circuit obstruction (such as a piping kink used for pad interconnection). The user output can include treatment action information to assist the user in dealing with the situation.

  In the described system, the flow meter and heat exchanger, and any other pressure drop system components (such as a fluid reservoir) can be located downstream of the circulation pump and upstream of the interconnectable pad. preferable. By doing so, it is possible to more reliably maintain the desired negative pressure at the interconnectable pads. Again, the mentioned system components can be supported and arranged in a common housing so as to be a self-contained system.

  In connection with the system of the invention referred to above, operating the circulation pump to circulate a heat exchanger and at least one interconnect contact in the fluid, and at least one interconnect contact with the inlet side of the circulation pump It can be appreciated that a method of controlling patient temperature is provided that includes sensing the pressure of fluid between the outlet port of the pad. The sensed fluid pressure is used in the process of operating the pump. The step of operating can provide for establishing a negative pressure at the contact pad. In addition, an output pressure signal can be provided with respect to the sensed pressure, and the output pressure signal is used in the operating process to maintain the negative pressure within a predetermined range. Such a predetermined range ensures that sufficient fluid flow is maintained to affect the desired heat transfer, while avoiding high pressures that may overstress the contact pads. , Can be set with respect to the attributes of a given interconnect contact pad.

  The method of the present invention may further include the steps of including at least a portion of the circulating fluid in the fluid reservoir and maintaining the fluid reservoir at approximately atmospheric pressure. Next, the maintaining step can provide ventilation to the ambient atmosphere of the fluid reservoir and the like.

  Further, the method can include the step of providing a control signal to the circulating pump (eg, via a microprocessor controller) using the output pressure signal referred to above, such control. The signal controls the operating speed of the pump. In addition, the method can include measuring flow rate downstream of the circulation pump and upstream of the inlet port of the interconnect contact pad, and can provide an output flow signal (such as to a controller). is there. The method can then provide a user output in response to identifying a predetermined relationship between the output flow signal and the pump operating speed and / or output pressure signal. As mentioned, such a predetermined relationship may be established with respect to conditions indicative of an obstruction in the fluid circuit of the system. User output may be provided to identify at least one treatment response that the user may take.

  In an additional aspect, the heat exchanger for at least one of heating / cooling of the fluid, a circulation pump for circulating the heat exchanger and the interconnectable contact pad to the fluid, and the fluid interconnectable to the interconnectable pad And a fluid reservoir containing at least a portion of the circulating fluid. What is important in this aspect is that the interior of the fluid reservoir is maintained at approximately atmospheric pressure. For such purposes, it is possible to interconnect a vent to a fluid reservoir, such a vent allowing the passage of gas and limiting the passage of fluid so as to restrict the passage of fluid. Has a sex membrane. Furthermore, a circulation pump can be arranged to establish a negative pressure at the interconnectable pad. Such a configuration facilitates reliable passage of fluid through the contact pad and minimizes fluid leakage if the pad is pierced or torn.

  It is also possible to provide a vent line between the mentioned vent (eg in the fluid reservoir) and the outlet side of the fluid reservoir. In addition, a vent valve can be provided to open and close the vent line, and opening the vent line causes the gas to vent the vent line and interconnect contact pads in response to the negative pressure established therein. Pass freely. The vent line is preferably interconnected to the upper end of the fluid reservoir.

  It is also possible to provide a control device to open / close the vent valve. In that regard, a user interface may be included to receive user input instructions for operating the controller. That is, the user can operate the system in one mode of operation in which the vent valve is closed and fluid circulates through the interconnectable contact pads. In other modes of operation, the controller can be “commanded” to open the vent valve to pump gas through the at least one interconnectable contact pad and drain fluid from the contact pad. Such a mode of operation can be used upon completion of a given patient temperature control procedure. Again, various system components can be placed in support of a common housing.

  In view of the above, operating the circulation pump to circulate a heat exchanger through the fluid, the fluid reservoir, and at least one contact pad fluidly interconnected between them, and bringing the fluid reservoir to approximately atmospheric pressure Other methods of the invention are also provided, including the step of maintaining. The act of operating can provide for establishing a negative pressure at the interconnect contact pad. In that regard, the contact pad is preferably capable of being placed above the fluid reservoir.

  In order to drain fluid from the interconnect contact pad, the method can further comprise allowing gas to flow through the vent line into the interconnect contact pad. Such gas flow can be selectively achieved by opening / closing a vent valve located in the vent line in response to a control signal provided by the controller. Again, in response to an input command provided by the user, it is possible to provide such a control signal, draining fluid in one mode of operation and fluid for heating / cooling in another mode of operation. Can be circulated.

  In another aspect, a heat exchanger, a circulation pump for circulating the heat exchanger and interconnectable pad through the fluid, and a fluid bypass for flowing fluid from the outlet side of the heat exchanger back to the inlet side of the circulation pump A patient temperature control system and method using the wire is provided. Such a configuration, for example, heats / cools the circulating fluid without an interconnectable contact pad to achieve fluid preconditioning prior to interconnecting the pads or before the fluid flows through the pads. Expect to do. In connection with the system / method of the present invention, a bypass valve can be used to open and close the fluid bypass line. In addition, a controller can be provided to provide a control signal to open / close the valve. The system / method can then use a user interface to start / end fluid conditioning and thereby receive commands at the controller, such as a command to open / close the bypass valve. is there.

  In one configuration, the system of the present invention can also include a fluid reservoir containing at least a portion of the circulating fluid, and a fluid bypass line extends between the fluid reservoir and the inlet side of the circulation pump. Such a reservoir can be drained to remove gas from the system as described above.

  Further, it is possible to use a fluid temperature sensor that senses the temperature of the circulating fluid and provides an output temperature signal in response thereto. Such an output temperature sensor can then be used to control the heat exchanger. For example, the controller can receive a fluid output temperature signal to control the operation of the heat exchanger, and the fluid is adjusted to a temperature within a predetermined range. Such a range can be set in the user interface described above. Again, the system components described above can be placed in support of a common housing.

  In another aspect, a patient temperature control system and method using a first heat exchanger and a second heat exchanger that respectively heat and cool fluid and a circulation pump that circulates fluid to at least one interconnecting contact pad. Provided. A housing is also provided for supporting and housing the pump and the first heat exchanger and the second heat exchanger, wherein one of the heat exchangers is selectively connected to an external source that provides one of heating or cooling of the medium. Can be interconnected. The configurations mentioned can provide temperature control systems and associated methods with reduced components and weight, thereby increasing availability. As a prime example, one of the heat exchangers mentioned can be selectively interconnectable with an external fluid cooling system that provides cooling fluid for applications requiring significant fluid cooling.

  The system / method of the present invention may further use an auxiliary pump that pumps fluid through a heat exchanger interconnected with an external source. A fluid temperature sensor can then be provided that senses the temperature of the system fluid and provides an output temperature signal that can be used to control the operation of the auxiliary pump. In this regard, it is also possible to provide a controller that receives the output temperature signal and provides a control signal that sets the speed of the auxiliary pump, and a desired degree of heat transfer with an external source is achieved.

  In another additional aspect of the invention, a heat exchanger for one of heating and cooling of the fluid, a circulation pump for circulating the heat exchanger and at least one fluid interconnectable contact pad through the fluid; Patient temperature control systems and methods are provided that use a first fluid temperature sensor and a second fluid temperature sensor disposed upstream and downstream of the heat exchanger, respectively. Such a sensor senses the temperature of the circulating fluid and provides a first temperature output signal and a second temperature output signal. In addition, a controller can be used to provide a control signal to the heat exchanger using the first temperature output signal and the second temperature output signal. With the described configuration, the temperature of the fluid flowing to / from the pad is determined, so it is possible to determine the amount of heat exchange through the interconnectable contact pad to / from the patient. Thus, the heat exchanger can be more precisely controlled to achieve the target patient body temperature.

  Further in this regard, the system / method may use a flow meter that measures the flow rate of fluid between the circulation pump and the outlet port to the interconnectable contact pad. Such a flow meter can provide a flow output signal that can also be used by the controller in providing a heat exchanger control signal.

  Further, the mentioned system / method may include a controller adapted to receive an input signal indicative of the patient's body temperature and use such signal in providing a heat exchanger control signal. It is. As an example, the input signal can be received from one or more patient core temperature sensors. By way of example, such a patient core temperature sensor can compare nasopharynx, esophagus, bladder, tympanic membrane, and / or rectal probes.

  As can be appreciated, each of the various features described above can optionally be combined in a selection system. In addition, many user interface features can be implemented to provide a highly automatic and user-friendly system.

  The inventor has further recognized that it is advantageous to construct a temperature control system that provides precise control of the various heat exchange devices used herein. The inventor has further recognized that the system can include specially configured controllers that use a variety of temperature control modeling that significantly reduces temperature swings and overshoots.

  Described herein is a temperature control device for use in a patient temperature control system. The controller includes a plurality of temperature sensors that measure temperature at the inlet and outlet of the system and a flow rate that monitors the flow of water to and from the body temperature control pad that can be placed on the patient to provide temperature control. It can be electrically connected to the meter. The signal received at the controller indicates the flow rate of the fluid circulating through the system, the output temperature of the fluid circulating to the at least one body temperature control pad, and the input temperature of the fluid circulating from the at least one body temperature control pad. .

  During operation of the temperature control system, the controller is configured to process signals received from various sensors to calculate a number of control terms. The control terms can further be used to calculate one or more power signals that can be transmitted to the one or more heat exchange devices. The control term may include a first control term that is proportional to the first difference in the temperature of the fluid circulating through the system for the fluid between the inlet temperature and the selected set point. The second control term, which can also be used by the controller, may be proportional to the difference between the outlet temperature and the selected temperature set point. The system controller can further use the first and second terms to generate a power signal that can be transmitted to one or more of the heat exchange devices. In response, the heat exchange device can influence the temperature of the circulation temperature accordingly.

  In one configuration of the invention, the heat exchange device usable by the system may include a first heat exchange device specially configured to heat the fluid in response to the power signal. The second heat exchange device can be configured to cool the circulating fluid in response to receiving the power signal. One or more auxiliary pumps can be used to pass the fluid through the heat exchange device.

  In other configurations of the present invention, the first control term can be modeled to the theoretical heat transfer rate required to raise or lower the circulating water from the measured inlet temperature to the selected temperature set point. More specifically, the first control term can be calculated by a combination of the gain term, the measured flow rate, the provided flow offset, and the temperature difference described above.

  The second control term can be specially configured to control the rate of temperature change when the outlet measured temperature reaches the temperature set point. Specifically, the matter addressed by the second term is output temperature fluctuation and overshoot in the vicinity of the set point. According to another configuration of the invention, the second control term can be based on a modified proportional integral derivative (PID) controller. As part of the PID control algorithm, it is possible to include a modified integral term and a modified derivative term. Also, a variable gain for the measured flow rate of the fluid flowing through the system can be used.

  With respect to the modified integral term, this can be approximated by the sum of measurement errors over time. The error is the measured temperature difference between the outlet temperature and the temperature set point. The measurement error may be usable in a controlled manner. For example, if the error is decreasing too slowly or increasing at any rate, the current error can be used for the summation. If the magnitude of the error is greater than a specified value, the integration can be further limited so that the integral does not change. The minimum and maximum values of the integral term can be further limited so as not to be a major part of the overall control of the temperature exchange device.

  With respect to the modified derivative term, this can be calculated by determining the slope of the “running least squares” line adapted to the most recent N data points (error). The magnitude of the modified derivative term can also be limited in certain circumstances to prevent response to noise.

  In accordance with the present invention, the system can be further configured to operate in one or more different modes depending on the measured temperature of the inlet or outlet. For example, temperatures that are too high or too low can be dangerous for the patient. Thus, the control model described herein can be configured to respond differently at a certain temperature. In one mode, the modified integral term can be changed to increase at a faster rate if it is detected that the temperature is too high. This can be done by multiplying the modified integral term by a weighting factor. In addition, the modified differential term can be disabled when the temperature is decreasing.

  According to the present invention, the control device can be configured as part of a body temperature control system. The body temperature control system may include one or more temperature sensors that monitor temperature at the inlet and outlet of the system. The outlet temperature sensor is specifically configured to measure the temperature of water flowing from any reservoir in the system to a body temperature control pad located on the patient. The inlet temperature sensor measures the fluid temperature flowing from the body temperature control pad to the system described herein. The system can further include one or more reservoirs for holding circulating fluid and one or more pumps that circulate the system through the fluid at a selected rate. Further, the system is configured to pump fluid flowing through the first heat exchanger or the second heat exchanger to affect heat exchange between the fluid disposed in the heat exchanger and the fluid. It is possible to include at least one auxiliary pump. Depending on the configuration of the system, the flow rate of the fluid flowing through the auxiliary pump can be a means to control the temperature. In addition, in conjunction with the control device, it can be a user interface device, which allows the system user to manually set the values used by the system, such as temperature set point and minimum and maximum temperature. It is possible to input with. A programmed sequence for controlling the temperature can also be entered. For example, controlled cooling or heating can be used at various parts of the procedure during surgery. These sequences can be programmed so that they can be started automatically or manually.

  With respect to system operation, a body temperature control pad can be connected to the temperature control system and body temperature control settings can be specified prior to performing a surgical procedure. After the procedure is started and the body temperature control system is started, periodic readings are taken at the inlet and outlet temperature sensors and from the flow meter. For each of these periodic readings, the values of the first and second control terms are calculated. As discussed above, the first control term is proportional to the measurement error at the temperature inlet between the measured fluid temperature and the set point. The second control term is proportional to the error between the outlet temperature and the set point.

  After the first control term and the second control term are calculated, a power signal is generated and transmitted to the heat exchange device identified to provide the desired type of heat exchange. Since the temperature is monitored, it is possible to detect that the measured temperature at the outlet or inlet exceeds the specified temperature range. In this situation, the controller automatically initiates an alternative mode of operation where the second term increases at a faster rate. After the temperature begins to move in an acceptable range, the derivative term can be set to zero so as not to slow down the adjustment process. Increasing the second term at a faster rate continues until it is detected that the outlet temperature is again within the desired range. At this point, the controller can start a normal operating mode. During operation, one or more temperature set points can be identified as part of the pre-program sequence so that the system changes the temperature of the fluid to the desired temperature set point.

  Additional aspects and advantages of the present invention will become apparent to those skilled in the art upon consideration of the further description provided below.

1 is a hydraulic schematic of one embodiment of a patient temperature control system comprising many aspects of the present invention. FIG. FIG. 2 is an electrical schematic diagram corresponding to the embodiment of FIG. 1. The disassembled perspective view of embodiment of FIG. The front view of embodiment of FIG. The side view of embodiment of FIG. The process flowchart of one Embodiment of the patient body temperature control method of this invention. FIG. 5 is a process flow diagram of fluid preconditioning in the embodiment of the method of FIG. The figure which shows the example use condition of this invention. 1 is a front view of one embodiment of a user interface that can be used in connection with the present invention. FIG. Flow chart describing patient temperature control function. Flow chart describing patient temperature control function. Flow chart describing patient temperature control function. Flow chart describing patient temperature control function.

  1, 2 and 3A-3C relate to one embodiment of a patient temperature control system comprising a number of aspects of the present invention. As will be apparent to those skilled in the art, such aspects can be implemented in a variety of other embodiments.

  According to the hydraulic schematic of FIG. 1, the illustrated patient temperature control system 10 can be selectively interconnected to one or more contact pads to heat / cool the patient. As an example, pad 1 can be of the type described in US Pat. No. 6,197,045. The system 10 includes a pad under negative pressure (eg, during normal operation, preferably at least about -11684 Pascals (about -3 psi), and most preferably at least about -48263 Pascals (about -7 psi) negative). A circulation pump 20 for pumping fluid (such as water) flowing through 1, a circulation reservoir 30 and a make-up reservoir 40 containing fluid, and a controllable heat exchange device for heating / cooling the fluid circulating in the system 10 62, 64 (eg, electric heater and radiator / temperature fluid cooling to heat fluid).

  A primary fluid line 50 (e.g., established by piping) fluidly interconnects the mentioned system components. To perform other selective fluid cooling / heating via the external interface, the secondary fluid line 52 (eg, established by the plumbing) is connected to the primary fluid line at each end by a built-in heat exchanger 66. 50 can be fluidly interconnected. Further, a fluid bypass line 54 (eg, established by piping) can be fluidly interconnected between the reservoir 40 and the circulation pump 20 to selectively condition the fluid.

  The reservoirs 30 and 40, the circulation pump 20, the heat exchange devices 62, 64, and 66 and the fluid lines 50, 52, and 54 referred to can all be placed inside the common housing 100. . The housing 100 includes a selectively openable / closable fluid output port 110 and fluid input port 120 between which the pad 1 can be selectively fluidly interconnected. With respect to the latter, an opposing piping 3 / manifold 5 assembly can be provided and interconnected to the outlet port 110 and the inlet port 120, with one or more pads being in fluid interconnection between the opposing manifolds 5. Is possible.

  As further described, while filling / emptying pad 1 (eg, after fluid conditioning and pad 1 interconnection), fluid is transferred from circulation reservoir 30 into pad 1 and to make-up. Flow from the up reservoir 40 to the circulation reservoir 30 / from the circulation reservoir 30 to the makeup reservoir 40. During normal patient heating / cooling operations, fluid circulates through the circulation reservoir 30, the pad 1, and the heat exchange devices 62 and 64 and / or 66 without substantially passing through the make-up reservoir 40.

  The fluid containment, handling, and heat exchange components of the system 10 are described in further detail with reference to FIGS. 1 and 3A-3C. The circulation reservoir 30 can be physically located below the make-up reservoir 40 and has a fluid interconnect line 32 extending therebetween. In the embodiment shown in FIGS. 3A-3C, the top of the circulation reservoir 30 is located below the bottom of the make-up reservoir 40. As will become apparent, such a configuration provides for gravity flow of fluid from the make-up reservoir 40 into the circulation reservoir 30. In this connection, the make-up reservoir 40 can be placed physically below the pad 1 when interconnected.

  In operation, the gas in the circulation reservoir 30 can rise through the fluid interconnect line 32 and into the make-up reservoir 40. Further, a vent line 34 can be provided at the top of the circulation reservoir 30 to remove gas from the circulation reservoir 30. The vent line 34 can be vented to the atmosphere through a non-spill outlet to the atmosphere or can be vented into the make-up reservoir 40 as shown in FIG. The make-up reservoir 40 can then include a vent line 42 having a non-spill outlet 44 to the atmosphere. The vent 44 functions to maintain atmospheric pressure (eg, about 101353 Pascal (about 14.7 psi)) in the make-up reservoir 40. As an example, the vent 44 can comprise a porous hydrophobic membrane that restricts fluid flow and allows gas to pass through the membrane.

  As can be appreciated, including vent lines 34 and 42 is advantageous because it provides for the removal of air bubbles from the fluid circulating through pad 1. In this regard, if a leak occurs in a fluid circuit located outside of the system 10 (eg, a leak in the pad 1), due to the negative pressure operating conditions generated by the circulation pump 20, the air is leaked due to the leak. Please note that it is inhaled. Such air is then finally removed from the make-up reservoir 40 via a non-spill vent 44.

  To exclude fluid from the pad 1, the system 10 can include a vent line 46 that is interconnected at one end to a primary fluid line 50 downstream of the circulation reservoir 30. The other end of the vent line 46 can be interconnected to the top of the make-up reservoir 40. A controllable vent valve 90 can be inserted along the vent line 46 at a position physically above the make-up reservoir 40 to selectively flow gas into the reservoir 40. More specifically, vent valve 90 can be selectively opened while circulation pump 20 is operating to empty pad 1. Next, air passes through the pad 1, passes through the vent 44, the make-up reservoir 40, and the vent valve 90 in order to discharge the fluid in the pad 1. It is sucked in. At the same time, fluid in the pad 1 is pumped from the pad 1 by the circulation pump 20 and then collected in the make-up reservoir 40 through the circulation reservoir 30.

  The fluid can be removed from the system 10 via a drain 36 that is fluidly interconnected to and disposed below the circulation reservoir 30. When the pad 1 is separated from the system 10, fluid can be easily introduced into the system 10 via the outlet port 110.

  The heat exchange devices 62, 64, and 66 can all be located downstream of the circulation pump 20 and upstream of the circulation reservoir 30. Such an arrangement isolates the pressure drop associated with these components relative to the positive side of the circulation pump 20, thereby improving the ability of the pump 20 to maintain the desired negative pressure within the pad 1.

  As further shown in FIG. 1, a separately controllable auxiliary pump 68 can be inserted along the secondary fluid line 52 to selectively circulate fluid to the heat exchange device 66. The heat exchange device 66 can be placed in place within the housing 100 to facilitate convenient interconnection with external cooling and / or heating sources. In one configuration, the heat exchanging device 66 can consist of a double-sided exchanger located at the bottom of the housing 100, and the fluid can be cooled again from the external cooling device 200 through one side of the heat exchanger 66. Circulating through 200, fluid in system 10 passes through the other side of heat exchanger 66 to improve cooling. The speed of the auxiliary pump 68 can be selectively controlled to affect the desired degree of fluid cooling / heating in the exchanger 66. By providing the secondary fluid line 52 described above, large and heavy cooling or heating equipment is still physically separated from the system 10 but can be used in combination with the system 10. This makes the system 10 significantly smaller and lighter, improving portability.

  With further reference to the fluid bypass line 54, FIG. 1 shows the fluid interconnection between the make-up reservoir 40 and the primary fluid line 50 in a position downstream of the circulation pump 20 and upstream of the pad 1. The fluid bypass line 54 can be routed through the controllable bypass valve 92 to selectively control the flow of fluid through the fluid bypass line 54. Specifically, the bypass valve 92 can be opened to prepare for preconditioning the fluid of the system 10 prior to interconnecting the pads 1. For example, fluid can be circulated through the bypass fluid line 54 via the operation of the circulation pump 20 and heat exchange devices 62, 64, and / or 66, thereby allowing the pad 1 to be desired before interconnecting it. Fluid temperature is achieved. Thus, effective patient temperature control can be established more quickly, improving patient comfort.

  In addition to the fluid routing, containment, and heat exchange components described above, the system 10 shown in FIGS. 1, 2, and 3A-3C also includes several sensors for system control and improved performance. ing. Specifically, a level sensor 80 can be provided in the make-up reservoir 40 to sense the amount of fluid therein. In one configuration, the level sensor 80 can comprise a pressure sensor and can determine the amount of fluid in the reservoir 40 with respect to the sensed head pressure. Such fluid level sensing may be used in the system 10 to provide user alerts, system control, and / or system disablement when sensing fluid levels below and / or above a predetermined amount. Is possible.

  In order to establish the desired temperature of the fluid circulating through the pad 1, the system 10 can use one or more temperature sensors. Specifically, the outlet temperature sensor 70 can be disposed along the primary fluid line 50 at a location downstream of the heat exchange devices 62, 64, and 66. In the embodiment shown in FIG. 1, an outlet temperature sensor 70 is provided in the circulation reservoir 30 to sense the fluid temperature therein. Alternatively and / or additionally, an inlet temperature sensor 72 can be positioned along the primary fluid line 50 at a location downstream of the pad 1 and upstream of the heat exchange devices 62, 64, and 66. In the embodiment shown in FIG. 1, the inlet temperature sensor 72 is disposed upstream of the circulation pump 20. The temperature of the fluid sensed by the sensors 70 and / or 72 should be used in conjunction with one or more controls of the heat exchange devices 62, 64, and 66 to obtain the desired temperature of the circulating fluid. Is possible (eg by controlling the operation of the auxiliary pump 68). As will be further described, including both the outlet fluid temperature sensor 70 and the inlet temperature sensor 72 allows for a continuous calculation of the thermal energy exchange rate between the pad 1 and a given patient, thereby providing a system Information is available that can be used to improve performance (eg, control heat exchangers 62, 64, and pump 68 to quickly rise within a predetermined range of “target” patient body temperature).

  In addition to temperature sensors 70 and 72, system 10 can further include an alarm fluid temperature sensor 74 disposed along primary fluid line 50 downstream from heat exchange devices 62, 64, and 66. In the embodiment shown in FIG. 1, the alarm temperature sensor 74 is arranged in the circulation reservoir 30 to sense the fluid temperature therein. The alarm temperature sensor 74 provides temperature sensing that may be redundant to the temperature sensing of the outlet temperature sensor 70, and can substantially reduce any risk that the circulating fluid is outside a predetermined temperature range. . For example, the system 10 can cause either the sensor 70 or 74 to cause the circulation pump 20 to be automatically stopped when a fluid temperature outside a predetermined high / low range is sensed.

  The system 10 may further include an inlet pressure sensor 82 disposed downstream of the interconnectable pad 1 and upstream of the circulation pump 20. More specifically, the inlet pressure sensor 82 can be disposed along the primary fluid line 50 between the inlet port 120 and the inlet side of the circulation pump 20. Sensing the pressure of the fluid at the mentioned location facilitates maintaining a predetermined and desired negative pressure within the interconnectable pad 1. In this regard, the speed of the circulation pump 20 can be controlled with respect to the sensed fluid pressure at the sensor 82. Such functionality is provided by the described arrangement regardless of whether one or more pads 1 are interconnected to the system 10.

  The system 10 can further include a flow meter 94 disposed along the primary fluid line 50 downstream of the circulation pump 20. In the illustrated embodiment, the flow meter 94 is disposed between the circulation pump 20 and the heat exchange devices 62, 64, and 66. A flow meter 94 is provided for sensing the fluid flow through the primary fluid line 50, thereby facilitating monitoring of the expected fluid flow through the pad 1 versus the actual fluid flow. . Such a function then allows the system 10 to detect potential undesired fluid flow obstructions (eg, piping that interconnects pad 1 to inlet port 110 or outlet port 120). Kink in line 3). In addition, monitoring fluid flow facilitates patient thermal energy exchange and fluid heating / cooling control decisions.

  As noted above, the various heat exchange devices 62, 64, and 66, pumps 20 and 68, and valves 90 and 92 can all be selectively controlled. As also mentioned, the identified sensor can provide information that can be used to accomplish several system control functions. To further describe such functions, reference is now made specifically to the electrical schematic diagram of FIG. Importantly, the system 10 can include at least one controller or microprocessor 130 operatively interconnected to various referenced sensors via a signal conditioning interface 140. As an example, the signal conditional interface 140 may comprise hardware / software for filtering or shifting analog signals received from various sensors, for example. Further, an A / D converter can be provided at interface 140 or processor 130 to convert the conditional signal to a digital signal for processing.

  As will be appreciated, the processor 130 can be programmed to process the digital signals and provide various control functions described herein. More specifically, processor 130 may use control algorithms and associated preset / user defined control limits / ranges stored in memory 132 (such as non-volatile random access memory). To selectively modify the control limit set that can be used with the control algorithm, as well as to initiate / end system operation, the system 10 can include a user interface 150 interconnected to the processor 130. The user interface 150 may include one or more input devices (such as a keypad entry, touch screen, mouse with a pointer, etc.), as well as one or more display devices 152. The display device 152 displays system operating conditions, settings, and alarms to the user, and / or the user can set up and operate the system 10, and therapeutic actions that can be taken if the system conditions of interest are detected. Can be encouraged.

  At this point, it should be noted that the system 10 may further include or be interconnectable with a power supply 160 (such as a 24 volt DC source) that powers internal drive circuitry (not shown). The drive circuit can then provide drive signals to the various sensors referred to above, as well as to the temperature simulator 180, calibration simulator 182, and control chip 172. In addition, power supply 160 provides drive signals to vent valve 90, bypass valve 92, circulation pump 20, and auxiliary pump 68 via switch 162, and to heater 62 via solid state relay 164 (SSR). Can be provided. Finally, the power supply 160 can provide drive signals directly to the radiator / fan 64 and the electronics fan 170.

  While power supply 160 provides drive signals to each of the fluid handling devices and heat exchange devices referred to above, processor 130 controls its operation. More specifically, the processor 130 can control the open / closed state of the vent valve 90 and the bypass valve 92. The processor 130 can also control the operation (speed, etc.) of the circulation pump 20 and the auxiliary pump 68. Further, the processor 130 can control the operation of the heater 62 and the radiator / fan 64 (eg, by fan control) to perform the desired amount of heating and cooling. In the embodiment shown in FIG. 2, a relay 166 is inserted between the processor 130 and the auxiliary pump 68 and the radiator / fan 64, and the control signal from the processor 130 is used when the external heat exchange device 200 is not in use. Control signals from the processor 130 directed to the radiator / fan 64 are directed to the auxiliary pump 68 when the external heat exchange device 200 is interconnected. In other configurations, it is possible to provide control signals to both the radiator / fan 64 and the auxiliary pump 68 in concert for their dual operation.

  Note that FIG. 2 illustrates the interconnection of one or more external patient temperature sensors 210 and signal conditioning interface 140. The patient temperature sensor 210 can comprise, for example, one or more body core temperature sensors (such as nasopharynx, esophagus, bladder, tympanic membrane, and rectal probe) that provide analog signals to the signal conditioning interface 140. is there. The interface 140 then provides a digital signal to the processor 130 for use in preset temperature control algorithm applications. As a major example, the temperature data received from the external sensor 210 may be used in the processor 130 to determine the amount and rate of heat exchange affected by the system 10 with respect to the preset / user defined patient “target” temperature. Is possible. The processor 130 can then provide appropriate control drive signals to the heater 62, radiator / fan 64, and / or auxiliary pump 68.

  In addition to the components, FIG. 2 is capable of selectively interconnecting the external operating room data logger (recorder) 220 and / or the external diagnostic processor 230 to the processor 130 via the data bus 174. It also shows that. As will be appreciated, the ability to connect the system 10 with the logger 220 and / or the processor 230 is used to process information collected from, or sensor information from, one or more of the sensors of the system 10 and the sensor. Allows digital information to be downloaded and uploaded, including digital information in response to the information.

  Reference is now made to FIG. 4, which shows a process flow diagram of one embodiment of a patient temperature control method. Such a method can be implemented in connection with the operation of the system embodiment of FIGS. 1-3, and to facilitate a better understanding of the various processes, the system of FIGS. The operation of the embodiment will be described. However, it should be understood that the methods described below can be implemented in a variety of different system embodiments.

  As shown in FIG. 4, the operation of the system 10 can be first performed for selective establishment of system control limits / ranges by the user (step 300). Setting limits / ranges can be accomplished by the user at the input device 154 (eg, by prompting the user on the display device 152 for ease of use). By way of example, the configurable limits / ranges may include target patient temperature, minimum / maximum patient body temperature, target temperature for circulating fluid, and maximum / minimum fluid temperature.

  The system test can then be completed to confirm / calibrate the critical operating capabilities of the system 10 (step 310). By way of example, such a test can be initiated automatically upon completion of process 300 and / or otherwise complies with prompting of display device 152 and user input of input device 154. It is possible to start selectively. The system test can include any number of automated procedures initiated by the processor 130 to verify the operation of the various sensors, fluid treatment devices, heat exchange devices, and associated circuitry of the system 10. .

  In particular, the processor 130 can automatically send a test signal to a temperature simulator 180 (eg, consisting of one or more resistors of known values) such that the temperature simulator 180 can The analog signal input is provided to the comparator 166 for testing. For example, a test signal provided by processor 130 may allow temperature simulator 180 to provide an analog signal input to comparator 166 that exceeds a predetermined value (eg, corresponding to a maximum temperature). Such a signal should cause comparator 166 to send a signal to open switch 162 as well as a response signal to processor 130. The processor 130 can then monitor the response of the switch 162 to confirm the operation of both the comparator 166 and the switch 162. The system test procedure may also include providing a test signal from the processor 130 to the calibration simulator 182 (eg, consisting of one or more resistors). The calibration simulator 182 can then provide a conditioned analog signal. This signal is used by the processor 130 to automatically calibrate the system 10 so that the signal received from the external sensor 210 during operation can be converted to the exact patient temperature displayed. .

  As shown in FIG. 4, if any of the system test procedures indicate that there is a problem with the system 10 (step 320), a user alert can be provided at the user interface 150 (step 320). . As an example, a visual alert can be provided on display device 152. Additionally and / or alternatively, an audible alert signal can be provided at the user interface 150. When an alarm output is provided, the user can take appropriate corrective action to address the alarm situation. In this regard, the user interface 150 displays treatment instructions to the user to allow user override in certain situations.

  The method embodiment of FIG. 4 provides for optional preconditioning of fluid by the system 10 (step 330). As previously mentioned, such preconditioning may require heating or cooling the fluid in the system 10 before interconnecting with the one or more contact pads 1. When time permits, such preconditioning may be desirable in terms of both patient comfort and rapid patient temperature changes. As an example, the preconditioning process can be selectively initiated by the user via input device 154.

  Following the initiation of fluid preconditioning (step 330), various components of the system 10 can be automatically and / or manually controlled (step 340). More specifically, referring now to FIG. 5, it is possible to open the bypass valve 92 of the system 10 by sending a control signal by the processor 130 (step 500). Next, the circulation pump 20 can be operated at a predetermined speed in accordance with the transmission of the control signal by the processor 130 (step 510). By opening the bypass valve 92 and the operation of the circulation pump 20, the fluid in the makeup reservoir 40 passes through the bypass fluid line 54, the circulation pump 20, the circulation reservoir 30, and the makeup reservoir 40 again. It flows in.

  As illustrated by FIG. 5, the fluid temperature can be sensed to determine if the fluid temperature is within a predetermined desired range (step 520). More specifically, the temperature sensor 70 can be used to sense the temperature of the fluid in the circulation reservoir 30, and the sensed temperature signal is provided to the processor 130 for comparison with a predetermined range. The With respect to the latter, the predetermined range can be preset or otherwise established by the user in connection with the setup operation. If the sensed temperature is not within the predetermined range, the processor 130 sends control signals to the heat exchange devices 62, 64 and / or the auxiliary pump 68 to achieve the desired degree of fluid heating / cooling (step 530). Is possible. As can be appreciated, temperature sensing by the sensor 70 and control of the heat exchange devices 62, 64 and the pump 68 by the processor 130 are continued as needed to establish the desired fluid temperature.

  Returning now to FIG. 4, the initiation of actual patient heating / cooling requires interconnecting one or more contact pads 1 to the system 10 (step 350). In connection with such interconnections, the system 10 may require a user to provide appropriate control inputs at the input device 154. After the contact pads 1 are interconnected, fluid circulation through the pads can be initiated (step 360). In this regard, appropriate user input may be required at the input device 154, in which case the circulation pump 20 can be operated according to a preset speed setting algorithm. In connection with steps 350 and 360 referred to above, pad 1 and the patient are preferably placed above system 10 as shown in FIG.

  At this point, further system testing can be provided (step 370). As a main example, the processor 130 uses the signals provided by the flow meter 94 and / or pressure sensor 82 and the known operating speed of the circulation pump 20 to ensure that the fluid is suitable for the system 10 and interconnect pad 1. It is possible to determine whether it is circulating. More specifically, for a given operating speed of the circulation pump 20, the pressure sensed by the sensor 82 and the fluid flow measured by the flow meter 94 are predicted within a predetermined range under normal operating conditions. Should be possible. If the signal received from the flow meter 94 indicates that the flow volume is outside the predetermined range, the processor 130 may indicate a situation of potential concern to the user as well as potential therapeutic actions to be taken at the user interface 150. It can be identified (step 380). By way of example, a message can be provided at the display device 152 that checks the kink of the pipeline 3 that was used to interconnect the pad 1 to the system 10. Further, if the system conditions are outside the predetermined range and / or are not corrected within the predetermined time, the operation of the circulation pump 20, the heat exchange devices 62, 64, and / or the auxiliary pump 68 is automatically terminated. As such, a processor 130 may be provided (step 190).

  Assuming that the system 10 is operating within normal predictive ranges, the system 10 can be automatically controlled to provide the desired patient heating / cooling at the interconnect pad 1. In this regard, the inlet pressure of the inlet port 120 can be maintained in a predetermined operating range, and the temperature of the circulating fluid is established to affect the desired heating / cooling of the patient through the pad 1. Is possible (step 400). In order to maintain the desired negative pressure at the interconnect pad 1, the processor 130 can use the sensed pressure signal provided by the inlet pressure sensor 82 to control the speed of the operational pump 20. In order to establish the temperature of the circulating fluid, the processor 130 may use one or both of the output signals from the temperature sensors 72, 70 of the system 10 as well as the sensed temperature signal provided by the external temperature sensor 210. Is possible. Note that it is particularly advantageous to use all such sensed temperature signals. More specifically, using all of these signals allows for the calculation of heat exchange with the patient. Therefore, it is possible to set the control of the heat exchange device. In one configuration, such a setting can be provided using the following algorithm.

_{W = KQ (T i -T t} ) -MCdT avg / dt
Where W = transmission of heat exchangers 62, 64 and 66,
K = conversion from calories / minute to watts,
Q = water flow rate (eg, measured by flow meter 94),
Ti = water inlet temperature (eg, measured by sensor 72),
Tt = target temperature of water (e.g. set by user),
M = mass of circulating water (eg, entered or determined by system 10),
C = heat capacity of water, and
dT _avg / dt = average rate of change in the temperature of the circulating water (determined using measurement by sensor 70 for example)

  Returning now to FIG. 4, the output signals from sensors 70, 72, 74, 82, and 94 can be used periodically to ensure system operation within a preset tolerance (steps). 410). If the monitoring action is outside acceptable limits, a user alert can be provided for corrective action (step 420) and the action can be automatically terminated if the condition of concern persists. (Step 390).

  With respect to the heat exchanger algorithm described above, the system described herein is further configured to use an additional algorithm that controls the manner in which the system approaches and maintains a particular patient temperature set point. It is possible. Referring again to FIG. 2, the processor 130 can access and use one or more of these water temperature control algorithms during operation, thereby affecting the water temperature in a controlled manner. It is possible.

  In accordance with the present invention, the water temperature control algorithm used is the power applied to the circulating water (energy per unit time) so that the water temperature quickly approaches the desired set point temperature and then is maintained in its vicinity. To decide. The temperature control algorithm used herein reduces significant temperature fluctuations near the selected patient temperature set point and reduces the water temperature when one or more of the monitored temperatures of the system are outside the preset range. Further configured to include the ability to rapidly change.

  According to one embodiment of the invention, the supplied power can be calculated using a combination of at least two control terms. The first term is based on the water temperature measured at the inlet of the system, and the second term is based on the outlet water temperature. As part of this temperature control process, the outlet water temperature is the temperature driven to the set point. The first control term may be proportional to the calculated difference between the inlet water temperature and the patient body temperature set point. More specifically, the first control term can be the product of the gain, the measured flow rate with the offset term subtracted from it, and the difference between the water temperature set point and the measured inlet water temperature. This can be calculated by the following equation.

Control term 1 = gain × (measured flow rate−flow offset) × (water temperature set point−measurement inlet temperature).
According to the above equation, if the measured flow rate is less than the flow offset, control term 1 is set to zero. If the flow offset is set to zero, the gain can be selected so that control term 1 is equal to the heat transfer rate required to raise or lower the circulating water from the measured inlet temperature to the water temperature set point. is there. Control term 1 provides a theoretical temperature change that changes the water temperature to the temperature set point, but the algorithm can be further refined to take into account the realistic characteristics of the system described herein. It is.

  One specific characteristic is that in practice, the actual heat input rate or applied power may not exactly match the command value. This is especially true in situations where two or more heat effect devices are used to provide heat transfer. In essence, the heater can only apply heat, and a radiator, cooling device, ice, or some other device can only be used to cool. Further, the actual power provided by the heater may vary from the command value due to changes in line voltage, heater electrical resistance, and heat loss to the environment. The power removed by the cooling device can be affected by ambient air temperature, partial blockage of airflow, and various other factors.

  A second property that can be taken into account is that it is not instantaneous to add or remove heat from the water. It is not possible to apply the required heat transfer rate determined at a moment in time at that moment. More specifically, even in the fastest systems, the time at which a command is initiated and the amount of time that the heat exchanger cools or heats to a specified level, and thus it takes to add heat to / remove heat from the water. Some delay occurs between the amount of time.

  A third property that can be taken into account is the limit on the amount of heat that can be added to or removed from a particular amount of water. For example, a radiator cannot operate below a certain flow rate and cannot reach a certain minimum temperature.

  In order to take into account the characteristics described above, the gain can be set to a value lower than that which would theoretically require the heat transfer rate, and can include non-zero flow offsets. The flow offset term reduces the value of control term 1 at low flow rates and reduces the effects of the heat transfer delay described above.

  The second control term is mainly intended to control the rate of change of the water temperature and the shaking braking near the temperature set point. The second term is calculated using the difference between the water temperature set point and the measurement outlet temperature. As described above, the measured outlet temperature is measured at the outlet of the system before water circulates through the body temperature control pad. In accordance with the present invention, the algorithm for calculating the second term can be based on a proportional, integral, and derivative (PID) controller with some modifications.

The PID control device that can be used in this specification can be expressed by the following equation.
PID control = K _p × error + K _I × integration (error) + K _d × differentiation (error)
here,
K _p = proportional gain,
K _I = integral gain,
K _d = differential gain,
Error = measured temperature between outlet temperature and set point.

The equation used by the water temperature control algorithm to calculate the second term is as follows:
Control term 2 = variable gain × (K _p × error + K _I × (corrected integration (error)) + K _d × (corrected derivative (error))).

The variable error is calculated using the measured flow rate of water flowing through the system. As described above, the flow rate is calculated using a flow meter. The variable gain is calculated by the following formula:
Variable gain = K ₀ + K ₁ × measured flow rate.

This is just one representation of the equation for calculating the gain, but those skilled in the art will appreciate that other forms can be used.
Looking at the above equation, it can be seen that the variable gain increases as the measured flow rate increases. As will be understood by further study of the system, the heat transfer rate required to increase the water temperature by a given amount must increase as the flow rate increases. Also, since the outlet water temperature is measured downstream of the heater and cooling device, there is a time delay between the time to apply heat to a given water bolus and the time to measure that temperature. This time delay increases as the flow rate decreases.

As is understood when analyzing a control system, time delays tend to induce wobble and overshoot in the control system. As the time delay increases, the response of the control system must be slowed to reduce overshoot. This reduces the proportional gain Kp and the integral gain K _I, it can be accomplished by increasing the differential term Kd. In the presence of measurement noise, large differentials can make the control system uneasy. Therefore, variable gain is used to reduce the proportional gain and integral part of the control term, while the derivative remains unchanged. As a result, the derivative term contributes to a larger portion of the control term at lower flow rates.

  The flow rate of water flowing through the system described herein is related to the number of body temperature control pads connected to the system. The number of pads is directly related to the heat transfer surface area, which is related to the heat transfer load on the machine. As the flow rate increases, the heat load generally increases. The control system described herein is configured to increase responsiveness as the load increases.

  The integral term described herein is configured to eliminate steady state errors. According to the system described herein, if there is a small and slowly changing error, the error integration will gradually increase over time to bring the error to zero. However, if there is a time delay in the system, it can lead to overshoot and wobble.

  It is important to minimize temperature overshoot to avoid temperature limits that may affect system operation. The modified integral term described above is adapted to reduce overshoot and sway by limiting the conditions under which integration is possible. In a sampled data system, the integral is approximated by the sum of errors over time. According to the control system described herein, the current error is added to the modified integral term only if the magnitude of the error decreases very slowly or increases at any rate. The integration can be further limited so that the integration does not change if the magnitude of the error is greater than a predetermined value (such as 5 ° C.). The maximum and minimum values of the modified integral term are also limited so that they do not become a major part of the overall control.

  The derivative is usually approximated by the difference between two consecutive measurements divided by the sampling time. In systems with measurement noise, this can be a large change in the approximate derivative, which can cause a significant change in the control term. This can be addressed with digital filtering, but the result of filtering is not a good approximation since the signal-to-noise ratio can be very large.

The modified differential term used herein can be calculated by determining the slope of the “running least squares” line applied to the most recent N data points. The derivation of this approximation can be performed as follows:
To determine the derivative, fit a line through the most recent N data points. Given a point (Ti, Ti), a least-squares line adapted to pass through the point T = A + Bt
Is determined from:

The estimate of the derivative is the slope B. To maintain a running least square slope, estimate the following:

If it is assumed that a series of first data points are on the line, then:

In estimating the tilt, the “slide” T-axis is used and the following equation is set:

By these estimations, the following equation is established.

If T _h-N-1 = A _old ,

As the set point is filtered, the temperature error is used in the above calculation instead of the temperature so that the controller responds appropriately to changes in the set point.

For the least square slope calculation, the following example constants can be used:
Total time = 45; \ * (0 + 1 + 2 ... 9) Not total time Squared time sum = 285; * (1 + 4 + 9 + ... + 8)
Delta = 825; \ * 10 ^-num- sample * squared time ^total- (total-time) 2
Tau = 1; \ * Sampling period Number of samples = 10 \ * Number of samples used Variables can include:
Sum of time error \ * Sum of time temperature error Error sum \ * Sum of error Error intercept \ * Least square intercept term Error slope \ * Least square slope Initially, all variables are set to zero.

Total time error = Total time error = τ * Total error + Number of samples * τ * Error + Error intercept Total error = Total error-Total error + Error;
Error intercept = (time square sum * error sum-time sum * time error sum) / delta;
Error slope = (number of samples * total time error−total time * total error) / delta The magnitude of the modified differential term can also be limited to prevent response to noise.

  Various safety features can also be incorporated into the system when using the processes described above. More specifically, if a monitoring condition is detected, one or more alternative processing modes can be used. For example, if the water temperature is very high or very low, an alternative mode of operation can bring the water temperature into the safe area as quickly as possible. Prior to operation, a maximum allowable water temperature set point can be set (eg, 42 ° C.). Temperatures above this value can be dangerous for the patient. The algorithm described herein can be configured to respond differently at temperatures above 42 ° C. so as to quickly drop the water temperature again to a safer level. To implement in this mode, the modified integral term can be increased at a faster rate. This can be done by multiplying the modified integral term by a weighting factor. In addition, the derivative term is disabled (set to zero) while the temperature is decreasing. Non-zero integral terms may tend to slow the rate of temperature drop. Conversely, in situations where the system described herein is used to induce hypothermia, the modified integral and modified derivative terms provide a rapid temperature rise when the temperature falls below a specified minimum temperature. Further modifications are possible.

  The normal mode of operation of the system described herein is disclosed in the flowcharts of FIGS. Depending on the specific operating mode of the temperature control system, the water temperature set point is selected by the user of the system prior to preparation or specified as part of a pre-programmed sequence. For example, in situations where the body temperature control pad induces hypothermia, the temperature set point is selected to cool accordingly. Conversely, when the temperature control system is in the heating mode, the temperature set point is selected to provide the desired amount of body heating. Also at this point, a flow offset setpoint is established. During system operation, water temperatures at both the inlet and outlet of the system are measured periodically.

  As an initial step in calculating the power signal, it can first be determined whether the current measured flow rate is greater than the selected flow offset. If the measured flow is less than the flow offset, the first control term is set to zero and the calculation process continues. If the measured flow rate is not less than the flow offset, the first control term is calculated from above using equations with readings from various sensors.

  If the first control term is calculated for a specific period, processing continues with the calculation of the second control term. At this point, the outlet temperature is measured. A current error value, which is the difference between the measured outlet temperature and the set point temperature, is then calculated.

  The current error is then combined with the previous data to calculate the rate of change. The last N errors are identified and a “running least squares” line fitted as described above is calculated. This rate of change is used to identify the modified integral. If less than N errors are available, calculate using only available points.

  The current error value is then compared to an integration band that is a predetermined error range. If the error value is not within the integration band, the error value is not added to the sum used as an estimate of the error integral over time. This effectively disables the integral part of the control term until the measured temperature approaches the set point temperature. This helps to reduce overshoot and swing. The integral term is intended to reduce or eliminate steady state errors. When the error is large, it is driven quickly towards the set point and not in steady state. Adding the error to the integral term only when the error is small prevents the integral part of the controller from responding to unsteady state errors.

  If the error is within the integration band, a determination is made as to whether the magnitude of the error is rapidly decreasing. If the error magnitude has not decreased by more than a predetermined percentage, it is added to the integral term. Otherwise, the integral term is not changed. By definition, the steady state error does not change, so using the rate of change of error to determine whether to add to the integral term ensures that the integral term responds only to the steady state error. This prevents the integral term from making excessive guarantees that may induce overshoot and wobble.

  After the step of calculating the integral sum is completed, it can be further determined whether the outlet temperature has exceeded the upper limit. As previously described, in situations where the measured temperature exceeds the maximum temperature or falls below the minimum temperature, the system initiates an operating mode that can be configured to rapidly decrease or increase the temperature, respectively. . In this situation, it is possible to add a weighting factor to the current measurement error (in this case, multiply the error by 2) and this correction error is added to the integral sum.

  Further inquiries can be made as to whether the slope calculated for the least squares adaptation of the accumulated error is negative. If negative, this means that the temperature is dropping, so the slope can be set to zero, which effectively disables the derivative term and increases the rate of temperature change. To do.

  At this point, the corrected integral term and the corrected differential term have been calculated, and both terms can be limited so that they are not outside the predetermined range. These ranges are established so that the modified integral term is not a major part of the overall control term. The final component of the calculated second control term is the flow change gain. As mentioned above, this can be done using the signal received from the flow meter.

  Since the variable gain and modified derivative term and modified integral term are calculated, the control term 2 can be calculated and added to the control term 1 to generate the entire control term. All control terms can also be limited within a predetermined range. Finally, a determination can be made as to whether heat exchange should be used. A command signal is generated and transmitted based on the selected device. The control process described above is repeated periodically in response to manual actions by the system program and / or system user.

  Reference is now made to FIG. 6 illustrating one embodiment of a user interface 150. Such an interface 150 will be described with respect to an exemplary application of various features of the system 10 described above. The user interface 150 includes user operation keys 502 to 518, a message screen 530, and a patient temperature display device 540. Message screen 530 displays parameter settings, warnings, and alarms during operation.

  When the patient temperature sensor 210 is used in a given procedure, the display device 540 provides the measured patient temperature. In one configuration, the indicated temperature should be in the range of 25 ° C to 42 ° C. When patient temperature sensor 210 is in place, icon 542 indicates a trend or change in patient temperature. As shown, the icon 542 can consist of a plurality of upward and downward arrows, with a circle between the upward and downward arrows. The illuminated upward yellow arrow indicates that the patient's body temperature is rising. An illuminated down yellow arrow indicates that the patient's temperature is falling. The higher or lower the illuminated arrow, the faster the temperature change. When only the yellow circle is illuminated, the patient's body temperature is almost constant.

The four main automatic operating modes of the system 10 can be set using the keys 502-508:
1. “Patient temperature control mode” —set by pressing key 502,
2. "Water temperature control mode"-set by pressing key 504,
3. “Eject mode” —set by pressing key 506,
4). “Stop Mode” —set by pressing key 508,
Additional information regarding the modification of a particular mode and corresponding parameter settings is achieved by pressing the “Up Arrow” key 510 or the “Down Arrow” key 512 while in a given mode, as further described. It is possible.

  In the patient temperature control mode, the system 10 automatically functions to monitor the patient's temperature and control it to the set target temperature. To achieve the target temperature, the water is cooled or heated as necessary and pumped through the pad 1. In one configuration, patient temperature can be controlled and monitored between 33 ° C and 37 ° C. When activated, the yellow indicator light on the key 502 is illuminated. The water flow rate is displayed on message screen 530 in liters per minute (ie, “lpm”).

  In the water temperature control mode, the system 10 automatically functions so that temperature-controlled water flows through the pad 1. The water is controlled to a specific target temperature set by the operator. In one configuration, the target water temperature can be set between 4 ° C and 42 ° C. When activated, the yellow indicator light on the key 504 is illuminated. When this mode is active, the water temperature and flow rate are displayed on the message screen 530 unless an alarm condition occurs.

  In the drain mode, the system 10 automatically functions to drain water from the pad 1. When the mode is activated, the yellow light on the key 506 is illuminated. When this mode is active, a message (such as “drain water”) is displayed on the message display screen 530. It is possible to provide the system 10 to automatically return to the stop mode when the pad 1 is empty.

  By pressing the stop mode key 508 at any time, one of three other modes (ie, patient temperature control, water temperature control mode, or drain mode) is stopped. When activated, the yellow light above the stop mode key 508 is illuminated. Any other mode can be activated from the stop mode by pressing the corresponding mode key.

Various system settings and other information can be reached from the displayed menu and information list on message screen 530 in stop mode, water temperature control mode, and patient temperature mode, including, for example:
1. 1. Set patient target temperature 2. Set target water temperature Measurement water level 4. Maximum / minimum water temperature setting 5. Set high and low patient temperature warning settings Other setup parameters (data output interval, etc.)
As can be appreciated, the settings mentioned can be changed for each procedure. The system 10 can provide settings to return to default parameters after the system 10 is disabled. New default parameters can also be saved permanently if desired.

  As mentioned above, “up arrow” key 510 and “down arrow” key 512 allow the user to scroll through menus and information lists on message screen 530. In that regard, the “input key” 514 allows the operator to select and change parameter settings. For example, the arrow keys 510, 512 can be used to select a given parameter listed in the message screen 530, and then the input key 514 can be pressed to publish the published method (lighten or different It is possible to display parameters (such as lighting with color). The arrow keys 510, 512 can then be used to increase or decrease the setpoint. When the desired value is displayed, the user can press the input key 514 to establish the setting again. “Return to Main Menu Key” 516 exits the given menu and returns the user to the main menu. An “alarm / warning” icon 520 is automatically illuminated when a warning or alarm condition is detected. By pressing the “Cancel key” 520, the warning or alarm is released.

  Prior to use of the system 10, the reservoirs 30 and 40 should be filled with a fluid such as distilled or sterile water. In order to do this, the system 10 should be connected to a power source 160, such as a suitable power outlet, such as via a plug-in. After being turned on, the system 10 can be provided to perform a brief self-test and enter a stop mode. The yellow light above the stop mode key 508 is illuminated. Using the “down arrow” key 512, the user can scroll through the menu until the display reads “water level“ XX ”use—press enter to fill”. The user can then connect the filling tube into one of the inlet connectors on the block manifold 5. The other end of the filling tube can be placed in a water container. The enter key 514 can then be pressed to cause the system 10 to begin filling and automatically stop when filling is complete. The system 10 then returns to the stop mode.

  The filling process can be interrupted at any time by pressing the stop mode key 508. However, the reservoirs 30, 40 may not be fully filled for the maximum number of uses. To determine the number of procedures that can be performed before refilling (eg, assuming a predetermined number of pad design limits), the user uses the up arrow key 510 and the down arrow key 512 The menu can then be scrolled until the message screen 530 displays the water level and the remaining usage count.

  It should be noted that many parameters that control temperature in the system 10 can be changed and / or adapted and stored for future use. Before using the system 10 for a given patient, it is possible to determine which settings the user will use. All parameters revert to default settings unless new settings are saved.

While the stop mode key 508 is illuminated, it is possible to reach the temperature parameter. The user can scroll through various menu options by pressing the up arrow key 510 or the down arrow key 512. In one configuration, the default settings and the range of options can be set as follows:
User-selected operation settings:
Parameter Default Option Data output interval 1 minute Off, 5 seconds to 10 minutes
Interval 5-60 seconds --5 seconds
Interval 1 to 10 minutes-1 minute Data output format Compact Compact or detailed User-selected processing mode:
Parameter Default Range Incremental change Patient temperature 37 ° C 33 ° C to 37 ° C 0.1 ° C increment Water target temperature 37 ° C 4.0 ° C to 42.0 ° C 1.0 ° C increment Maximum water temperature 42 ° C 32.0 ° C to 42. 0 ° C 1.0 ° C increment Minimum water temperature 4 ° C 4.0 ° C to 32 ° C 1.0 ° C increment User adjustable warning:
Parameter Default range Incremental change Patient hyperthermia warning 42 ° C 25.1 ° C to 42.0 ° C 0.1 ° C
Patient hypothermia warning 25 ° C 25.0 ° C to 41.9 ° C 0.1 ° C
Parameter Default Incremental change Cooling device connected for cooling No Yes or no.

To change any of the default settings from stop mode, the user can use the following procedure:
1. The up arrow key 510 and the down arrow key 512 are used to access settings displayed on the message screen 530.

2. Press enter key 514 to highlight parameters that can be modified.
3. Press the up arrow key 510 or the down arrow key 512 to reach the desired setting. Press enter key 514 to save.

4). To change additional settings, continue to scroll through the menu and press the up arrow key 510 or the down arrow key 512 to reach the appropriate screen.
5. Repeat the procedure to highlight, select, and save display parameters.

6). The newly configured parameters remain through a given procedure until the system 10 is turned off.
All adapted parameters can be saved permanently or until the user decides to change them. To save newly set parameters as default settings, the user can use the following procedure:
1. Scroll through the menu screen until the "Setup" screen is displayed.

2. Press the enter key 514 to scroll through the menu until “Save current settings” is displayed.
3. Press enter key 514 to save the settings.

The temperature sensor 210 can then be placed on the patient and connected to the system 10. The patient's body temperature can then be monitored and controlled.
To continue the patient's treatment, as described above, the user presses the stop mode key 508 and uses the menu provided when the stop mode key 508 is activated and all of the parameters are It is possible to verify that it is programmed to the desired setting. The following settings should be noted first:
1. Patient target temperature: Determine the temperature set point for the patient. The temperature setting range can be limited to 33 ° C to 37 ° C.

2. Maximum water temperature: Allows the user to determine the maximum water temperature that circulates the pad during the patient treatment mode.
3. Patient temperature maximum or minimum warning: Allows the user to determine the patient's temperature at which the system 10 should provide an alert.

The user can then press the patient temperature control mode key 502. The message screen 530 then indicates the system 10 set patient target body temperature, current water temperature, and current water flow rate. It is possible to initiate a heating or cooling cycle for a procedure or before temperature sensor 210 is deployed without controlling the temperature. Without automatically controlling the patient's body temperature, it is possible to circulate temperature controlled water using the water temperature control mode. This mode can be used regardless of whether the temperature probe is arranged. To do this, the user can access the water target temperature screen by pressing the up arrow key 510 or the down arrow key 512 while in stop mode or water temperature control mode. The user can then adjust the water temperature to the desired setting as follows:
1. Press the up arrow key 510 or the down arrow key 512 until “water target temperature 37 ° C., entering change” appears on the message screen 530.

  2. If a new water target temperature is desired, the enter key 514 is pressed to highlight the temperature. 3. Press the up arrow key 510 or the down arrow key 514 until the desired temperature is displayed. It is possible to change between 4.0 ° C and 42 ° C in 1.0 ° C / F increments.

  After the water target temperature is set and the mode key 502 is pressed, the system starts to adjust the water temperature to the desired setting. The flow rate is shown in message screen 530. The flow rate can vary depending on the size of the patient, the style of pad used, and the number of pads applied.

As mentioned, the system 10 includes: 1. Patient temperature warning Features that allow the user to pre-program certain alerts, including water temperature alerts, can be incorporated into the system 10.

  Specifically, the system 10 can provide a default alert that warns when a patient's body temperature exceeds a set level if the water temperature rises or stays above that set level. There is also a default alert that alerts the user when the patient's body temperature falls below a set level if the water temperature decreases or stays below that set level.

High and low patient set temperature alerts can be established by the user as follows:
1. While in the stop mode, the up arrow key 510 or the down arrow key until the screen displays “Patient high temperature warning 42 ° C., enter for change” or “Patient low temperature warning 25.0 ° C., enter for change” Use 512 to scroll through the menu.

  2. Press the enter key and use the up arrow key 510 or the down arrow key 512 to select a new temperature. The high temperature range can be provided to be adjusted in increments of 0.1 ° C. between 25.1 ° C. and 52.0 ° C. The low temperature range can be provided to be adjusted in increments of 0.1 ° C. between 25.0 ° C. and 51.9 degrees.

3. Press the Enter key to save.
As can be appreciated, many additional warnings and alarms can be provided. More generally in this regard, the above description is strictly intended to facilitate understanding of the present invention. It is intended and is not intended to limit the scope otherwise determined by the following claims.

Claims (11)

A patient temperature control system,
A first heat exchanger for one of heating and cooling of the fluid;
A circulation pump for circulating fluid first through a primary fluid line through a heat exchanger and then through at least one fluid interconnectable contact pad, the outlet of the at least one interconnectable contact pad A circulating pump having an inlet side interconnectable with a port and operative to establish a negative pressure at said at least one interconnectable contact pad;
A pressure sensor interconnected between an inlet side of the circulation pump and an interconnectable outlet port of the at least one interconnectable contact pad, the output pressure signal being usable for controlling the circulation pump; A pressure sensor to provide,
A flow meter for measuring a flow rate of fluid between a circulation pump and an outlet port to the at least one interconnectable contact pad, the flow meter providing a flow output signal;
Upstream and downstream of the first heat exchanger to sense the temperature of the fluid flowing into and out of the first heat exchanger and providing a first temperature output signal and a second temperature output signal A first fluid temperature sensor and a second fluid temperature sensor respectively disposed in
An input signal indicative of the measured patient temperature is received and used in conjunction with the first temperature output signal , the second temperature output signal, and the flow rate output signal , and the first control signal is used as the first heat exchanger. The control device further uses the output pressure signal to provide a second control signal for controlling the operation speed of the circulation pump to maintain the negative pressure within a predetermined range. System. Further comprising a fluid bypass line interconnected with the primary fluid line such that fluid flows from the outlet side of the first heat exchanger to the inlet side of the circulation pump without passing through the at least one interconnectable contact pad. Item 4. The system according to Item 1. The system of claim 2, further comprising a bypass valve that opens and closes the fluid bypass line. A first fluid reservoir for containing fluid;
A second fluid reservoir interconnected with the first fluid reservoir and containing a fluid;
The first heat exchanger is interconnected with the second fluid reservoir and the first heat exchanger, the second fluid reservoir, and the at least one interconnect without a fluid portion circulating through the first fluid reservoir. contactable pads Ri cyclable der through, the second fluid temperature sensor system according to claim 1 that is provided in the second fluid reservoir. The system of claim 4, wherein the second fluid reservoir is directly interconnected with the first fluid reservoir, and the interior of the first fluid reservoir and the second fluid reservoir is maintained at approximately atmospheric pressure. At least an upper portion of the first fluid reservoir is physically disposed above the second fluid reservoir and is a vent that allows gas to pass but restricts passage of fluid and is interconnected with the upper portion of the first fluid reservoir. The system of claim 5, further comprising a vent. The system of claim 1, further comprising a user output device that provides an output in response to identifying a predetermined relationship between a flow output signal and at least one of an output pressure signal and the operating speed . The controller provides a first control signal to the first heat exchanger that affects heating or cooling the patient to a temperature within a predetermined range, and the system receives a user input and receives the user input. The system of claim 1 , further comprising a user interface for establishing. The system of claim 8, wherein the predetermined temperature range is settable by the user as a function of time. The user interface is
9. The user output comprising: a measured patient body temperature corresponding to the input signal; and a fluid temperature corresponding to at least one of the first temperature output signal and the second temperature output signal. system. The apparatus further includes a second heat exchanger for the other of heating and cooling the fluid, and the controller uses both the first temperature control signal and the second temperature control signal to convert the third control signal to the second heat exchange. The system of claim 1, wherein the system is provided to a vessel.