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