Thermal Model

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The patient is modelled as a three-compartment thermal model (fast, medium, slow). The temperature of the fast compartment is reported to the monitoring system as the naso-pharyngeal temperature, whereas the metabolic rate is determined by the temperature of the medium compartment. The system constrains temperature in the range 15 - 40C.


The effect of temperature on basal metabolic rate (BMR) is modelled according to the data of Kirklin. In the figure below, the effect of temperature on BMR is shown in a patient with a nominal BMR at 37 centigrade of 200 ml/min.




The impact of simply cooling a patient on ECMO is shown in the figure below. In this case, a patient on stable VV ECMO at a flow rate of 5.0 lpm is cooled by 5 C from 38.8 to 33.8.  No other changes to the management of the patient or the ECMO system were made. The effect on PaO2 and SaO2 is shown.


Effect of Cooling


Kirklin JW and Barratt-Boyes BG. 'Cardiac Surgery'. New York: Churchill Livingstone, 1993:61-127.