Utilisation of the method of Kalman filtering for performing the on-line computation of background metabolism in the free-moving, free-feeding rat.

Since 1984, we have utilized a metabolic device in which activity and food intake are measured at 10-second intervals, in relation to the respiratory exchanges in the rat (indirect calorimetry). To solve the problem of quantifying precisely the metabolic cost of activity, we have developed models of the diffusion of the cells' respiratory exchanges in the rat and in the metabolic chamber until they reached the gas analyzers. The predictions of these models have been used to feed a process of numerical filtering that computed an estimation of the energy cost of activity, and an estimation of the value of the part of the total metabolism that was not due to the cost of the muscular contractions. This later component of metabolism has been named background metabolism to be clearly distinguished from the true resting metabolism measured during resting periods. In this paper, two models of diffusion of the cell's respiratory exchanges are described, and examples of the computation of the background metabolism by the process of Kalman filtering are shown.