HETEROGENEOUS ORGAN MODELS

A theoretical study is made of three organ flow models with heterogeneity of capillary transit times. A new parametrization of Rose and Goresky''s Model II facilitates in many cases a reduction to Goresky''s Model II, accomplished by a special time shift. The shift parameter .tau.cz = .tau.cm - tAPP/b defined here is critical in this analysis of Model III. A new expression of the series for outflow concentration in Model III is given and proves useful in examining the model as an operator and in relating it to Models I and II. A result on parameter optimization is given: if .tau.cz .gtoreq. 0 then Model II cannot fit better than Model II. This is applied to some data from Rose and Goresky [Circulation Res. 39, 541-544 (1976)] and raises a new question about their model. A heart model of Levin and Bassingthwaighte based on regional flow measurement is shown to be a discretized generalization of Model II.