Inert gas wash-out from tissue: model analysis.
Model simulations on variously arranged two-compartment models are performed to provide a basis for interpreting the observed non-monoexponential (or non-linear logarithmic) wash-out time courses of inert gases from tissue. The variables considered are: blood flow, tissue volume, solubility of gas in tissue and blood, and diffusive conductances (diffusing capacities) for tissue/blood gas transfer and for gas transfer between tissue compartments. The wash-out is studied in terms of both mean tissue partial pressure and effluent venous blood partial pressure. Diffusion limitation within a tissue-blood capillary unit is shown to produce logarithmic wash-out rates which increase or decrease during wash-out, depending on the functional structure of the unit. On the other hand, in a system consisting of dissimilar tissue-blood capillary units arranged in parallel, the logarithmic wash-out rate decreases with wash-out time. It is shown that the conventional analysis of nonlinear logarithmic wash-out may overestimate or underestimate tissue perfusion or the extent of its inhomogeneity.
D000818:Animals; D002196:Capillaries / Q000502:physiology; D005740:Gases / Q000378:metabolism*; D007700:Kinetics; D008433:Mathematics; D008954:Models, Biological; D012039:Regional Blood Flow
D005740:Gases