System and method for determining and controlling core body temperature

A method for measuring body temperature while regulating the temperature of at least a portion of a patient, comprising:

• inserting into the patient a temperature probe having sensors to measure the temperature of the patient;
• providing a disposable heat transfer catheter and heat exchange unit coupled via conduits and a diverter unit that enable controlled circulation of a heat exchange medium therebetween;
• providing a master control unit housing a microprocessor and a heater/cooler unit within;
• installing the heat exchange unit into the master control unit and into thermal communication with the heater/cooler unit;
• inserting the heat transfer catheter into the patient;
• circulating fluid between the heat transfer catheter and heat exchange unit, therein transferring heat between the heat exchange unit and the heater/cooler unit so as to regulate the temperature of the patient via the heat transfer catheter;
• periodically interrupting fluid flow between the heat transfer catheter and the heat exchange unit by diverting the heat exchange medium between the heat exchange unit and heater/cooler unit and bypassing the heat transfer catheter;
• analyzing the signals received from the temperature probe while the flow of heat exchange medium is interrupted and determining an accurate core body temperature from the rate of change of the temperature while the heat exchange medium is interrupted;
• and
• re-starting the flow of heat exchange medium between the heat transfer catheter and the heat exchange unit.

A heat transfer catheter system, comprising:

• a heat transfer catheter insertable into a patient;
• a disposable heat exchange unit having a fluid pathway therewithin and incorporating an integral pump head adapted to move fluid through the fluid pathway;
• conduits coupled to the heat transfer catheter and heat exchange unit that enable circulation of a heat exchange medium therebetween upon operation of the pump head;
• a diverter unit that periodically redirects the fluid pathway, bypassing the heat transfer catheter;
• and
• a reusable master control unit having a heater/cooler and a pump driver, the disposable heat exchange unit being adapted to couple to the master control unit such that the pump driver engages the integral pump head and so that the fluid pathway is in thermal communication with the heater/cooler, the control unit controlling the diverter unit to periodically interrupt fluid circulation within the heat exchange unit and the heat transfer catheter, the control unit configured
• to receive a target temperature input and a sensor signal from a temperature sensor,
• to analyze the signals from the sensor during the fluid flow interruption to determine a rate of change of the temperature as a function of time,
• to compare the determined temperature to a target temperature,
• to restart the flow of heat exchange medium through the heat transfer catheter, and
• to control the rate at which the patient temperature approaches the target temperature by controlling the heating/cooling apparatus with proportional integrated differential (PID) responses.

A method for measuring body temperature while regulating the temperature of at least a portion of a patient using a heat exchange catheter inserted into a lumen of the patient's body, the heat exchange catheter having conduits that enable circulation of a heat exchange medium between a heat exchange portion of the catheter and a heating/cooling apparatus for adding or removing thermal energy from the heat exchange fluid, the heating/cooling apparatus controlled by a controller, comprising:

• measuring the temperature of the patient using a temperature probe, the temperature probe providing a signal representative of the temperature of the patient to the controller;
• circulating fluid under control of the controller between the heat transfer catheter and the heating/cooling apparatus so as to regulate the temperature of patient;
• sampling a plurality of temperature signals received by the controller during a selected interval;
• analyzing the plurality of temperature signals received from the temperature probe during the selected interval to determine a peak temperature occurring during the selected interval;
• comparing the determined peak temperature to a target temperature;
• and
• controlling the heating/cooling apparatus in accordance with the comparison to controllably add or remove thermal energy from the heat exchange fluid to heat or cool the fluid circulating through the lumen of the patient's body so that the determined peak temperature occurring during the selected interval approaches the target temperature.

A system for regulating the temperature of at least a portion of a patient's body, comprising:

• a heating/cooling apparatus;
• a heat exchange catheter for insertion into a lumen of the patient's body, the heat exchange catheter having conduits that enable circulation of a heat exchange medium between a heat exchange portion of the catheter and the heating/cooling apparatus for adding or removing thermal energy from the heat exchange medium;
• a temperature sensor disposed in the lumen downstream of the heat exchange catheter for providing temperature signals representative of the temperature of body fluid flowing through the lumen;
• and
• a controller including a processor and a memory, the processor capable of being programmed by software to
• sample the temperature signals at a selected interval,
• determine a selected temperature value sampled within a selected range of the selected intervals and store that determined value in a memory of the controller,
• increment the selected range of selected intervals a selected number of times and, after each increment, repeating determining the selected temperature value sampled within the incremented selected range of selected intervals and store that value, and
• calculate a peak temperature value from the stored determined values, the controller responsive to the calculated peak temperature value to control the heating/cooling apparatus to add or remove thermal energy from the heat exchange medium.