Heat and mass transfer of a thermal indicator in pulsatile flow through the cardio-pulmonary system. I. Modeling.

The construction of a physico-mathematical model which describes the mechanism of indicator dispersion in the circulation and which fits the thermal dilution curves (TDC) is presented. Because of its more evident physical meaning, formulation of the problem in terms of heat and mass transfer is preferred to stochastic theory. Hypotheses necessary to simplify the general system of governing equations are clearly defined and discussed. This deductive method leads to a one-dimensional convective heat transfer model in which pulsatility and form of injection appear naturally. Simulations of TDC in constant and pulsatile flow cases are performed on a digital mini-computer which demonstrates the model's ability to represent different experimental or clinical observations. This will facilitate hemodynamic parameter identification from TD techniques and will increase the accuracy of this identification.