Extension of compartmental parameters to blocks of compartments with application to lipoprotein kinetics

Suppose that the compartments of a compartmental model are separated into blocks (sets of compartments). In general, the blocks can not be regarded as compartments but it may be possible to construct a "condensation model," the compartments of which correspond to the blocks, in such fashion so as to retain certain salient properties of the blocks. Condensation is a way of formally summarizing a large model by presenting a smaller one to emphasize certain characteristics of the larger model. Suppose that the parameters to be retained are the mean residence times through the blocks; this paper deals with the construction of the condensation model, the properties of the condensation model, and the possible applications of condensation to data analysis, particularly in regard to lipoprotein kinetics.