Underbody Warming Systems with Core Temperature Monitoring
Apparatus and methods related to a non-invasive core temperature monitor for monitoring the temperature of a patient. In certain embodiments, the monitor may include a heated underbody support for heating at least a portion of a patient. The heated underbody support may include a low thermal mass heater and a temperature sensor. The heater may heat the peripheral thermal compartment of the patient to a temperature that is greater than the core temperature of the patient. The monitor may reduce the temperature of the low thermal mass heater to a set-point temperature that is less than the core temperature, allowing the temperature of the low thermal mass heater to move towards being in thermal equilibrium with the core body temperature. The core temperature may be determined when the peripheral thermal compartment of the patient is in substantial thermal equilibrium with the temperature of the core thermal compartment of the patient.
1 . A non-invasive core temperature monitor for monitoring the temperature of a patient, the core temperature monitor comprising:
a heated underbody support for heating and supporting at least a portion of the patient, the heated underbody support including a low thermal mass heater that is configured to be in thermal contact with at least a portion of the patient during a core temperature measurement;
a temperature sensor configured to be interposed between an upper surface of the low thermal mass heater and the patient during temperature monitoring, the temperature sensor further configured to be in thermal contact with the patient's skin during temperature monitoring;
a switch that controls electric power to the low thermal mass heater;
wherein activation of the switch can rapidly reduce the electric power supplied to the low thermal mass heater allowing the low thermal mass heater to rapidly cool.
2 . The non-invasive core temperature monitor of claim 1 , wherein the low thermal mass heater is made of electrically conductive fabric, film or foil.
3 . The non-invasive core temperature monitor of claim 1 , wherein a small amount of thermal insulating material is interposed between the temperature sensor and the low thermal mass heater.
4 . The non-invasive core temperature monitor of claim 1 , wherein the temperature of the low thermal mass heater is controlled to a temperature that is greater than the core temperature of the patient, and then rapidly reduced to a temperature that is less than the core temperature of the patient when the switch is activated.
5 . The non-invasive core temperature monitor of claim 4 , wherein the activation of the switch also activates a timer that measures a predetermined amount of time to pass while the over-heated peripheral thermal compartment of the patient cools and comes into thermal equilibrium with the core thermal compartment at a predetermined thermal equilibrium time;
when the predetermined thermal equilibrium time is reached, the temperature sensor measures the skin temperature of the patient;
wherein the skin temperature reflects the temperature of the peripheral thermal compartment that is in thermal equilibrium with the temperature of the core thermal compartment and thus the measured skin temperature correlates with the core temperature of the patient.
6 . The non-invasive core temperature monitor of claim 5 , wherein the predetermined amount of time is in the range of 0.5-5 minutes.
7 . The non-invasive core temperature monitor of claim 4 , wherein the activation of the switch activates an algorithm that monitors the temperature-time curve of the measured skin temperatures following the rapid reduction in heater temperature.
8 . The non-invasive core temperature monitor of claim 7 , wherein core temperature corresponds to the temperature of the temperature-time curve at which a rapid decline in measured skin temperature transitions to a gradual decline in the measured skin temperature.
9 . The non-invasive core temperature monitor of claim 5 , wherein the measured skin temperature is compared to a desired patient temperature and the result of this comparison is used to automatically control a set-point operating temperature of the heated underbody support.
10 . The non-invasive core temperature monitor of claim 8 , wherein the measured skin temperature is compared to a desired patient temperature and the result of this comparison is used to automatically control the set-point operating temperature of the heated underbody support.
11 . A method for non-invasive core temperature monitoring, the method comprising:
providing a heated underbody support for heating at least a portion of a patient, the heated underbody support comprising:
a low thermal mass heater arranged to be in thermal contact with at least a portion of the patient during core temperature monitoring;
a temperature sensor configured to be in thermal contact with the patient's skin to measure the temperature of the peripheral thermal compartment of the patient during temperature monitoring;
a switch that can rapidly reduce the electric power supplied to the low thermal mass heater;
controlling the low thermal mass heater to a temperature that is greater than the core temperature of the patient;
activating the switch to rapidly reduce the temperature of the low thermal mass heater to a set-point temperature that is less than the core temperature of the patient; and
measuring the temperature of the peripheral thermal compartment that is in substantially thermal equilibrium with the temperature of the core thermal compartment.
12 . The method of claim 10 , wherein activating the switch activates a timer, and wherein measuring the temperature of the peripheral thermal compartment that is in thermal equilibrium with the temperature of the core thermal compartment comprises waiting a predetermined amount of time after activating the switch to allow the over-heated peripheral thermal compartment of the patient to cool and come into thermal equilibrium with the core thermal compartment.
13 . The method of claim 11 , wherein the predetermined amount of time is in the range of 0.5-5 minutes.
14 . The method of claim 11 , wherein the low thermal mass heater is made of electrically conductive fabric, film or foil.
15 . The method of claim 11 , wherein activating the switch activates an algorithm that monitors the temperature-time curve of the peripheral thermal compartment following the rapid reduction in heater temperature, and wherein measuring the temperature of the core thermal compartment comprises monitoring the temperature-time curve to determine when a rapid decline in measured skin temperature transitions to a gradual decline in measured skin temperature indicating that thermal equilibrium between the peripheral thermal compartment and the core thermal compartment has been reached and the temperature of the peripheral thermal compartment is substantially equal to the temperature of the core thermal compartment.
16 . The method of claim 15 , wherein the low thermal mass heater is made of electrically conductive fabric, film or foil.
17 . The method of claim 15 , wherein thermal insulating material is interposed between the temperature sensor and the low thermal mass heater.
18 . A non-invasive core temperature monitor for monitoring the temperature of a patient, the core temperature monitor comprising:
a heated underbody support for heating at least a portion of a patient;
the heated underbody support including a low thermal mass heater, the low thermal mass heater configured to be in thermal contact with at least a portion of the patient during temperature monitoring, the low thermal mass heater configured to heat the peripheral thermal compartment of the patient to a temperature that is greater than the core temperature of the patient;
a temperature sensor configured to be in thermal contact with the patient's skin during temperature monitoring;
a switch, or an algorithm of a processor, that is configured to reduce the temperature of the low thermal mass heater to a set-point temperature that is less than the core temperature of the patient allowing the temperature of the low thermal mass heater to move towards being in thermal equilibrium with the core body temperature of the patient, and wherein the algorithm monitors the temperature-time curve; and
wherein the core temperature of the patient corresponds to the temperature sensed by the temperature sensor when the peripheral thermal compartment of the patient is in substantial thermal equilibrium with the temperature of the core thermal compartment of the patient.
19 . The core temperature monitor of claim 18 , wherein the low thermal mass heater is made of electrically conductive fabric, film or foil.
20 . The support of claim 18 , wherein the switch, or the algorithm of the processor, is configured to discontinue or substantially reduce the power that is supplied to the heater assembly.
21 . The support of claim 18 , wherein the temperature of the peripheral thermal compartment that is in substantial thermal equilibrium with the temperature of the core thermal compartment is determined by waiting a predetermined amount of time.
22 . The support of claim 18 , wherein the temperature of the peripheral thermal compartment that is in substantial thermal equilibrium with the temperature of the core thermal compartment is determined by monitoring the temperature-time curve to determine when a rapid decline in measured skin temperature transitions to a gradual decline in measured skin temperature indicating that thermal equilibrium between the peripheral thermal compartment and the core thermal compartment has been reached and the temperature of the peripheral thermal compartment is substantially equal to the temperature of the core thermal compartment.