INCORPORATING O-2-HB REACTION-KINETICS AND THE FAHRAEUS EFFECT INTO AMICROCIRCULATORY O-2-CO2 TRANSPORT MODEL

The influence of O-2-Hb reaction kinetics and the Fahraeus effect on s teady state O-2 and CO2 transport in cat brain microcirculation was in vestigated using our refined multicompartmental model, The most import ant model predictions include: 1) capillaries are the sites in the mic rocirculation where the effect of O-2-Hb kinetics is most pronounced; 2),while there is only a small difference between equilibrium and actu al oxygen saturation, this effect is not negligible; 3) O-2-Hb kinetic s tends to make the PO2 level at the venous entrance higher than in ve nules; 4) the influence of the Fahraeus effect leads to a lower tissue PO2 level than in venules and the outlet vein. The resultant decline in tissue PO2 may lead to a decrease in O-2 consumption rate and extra ction ratio; 5) although the Fahraeus effect changes the ratio between arteriolar flux and capillary flux, incorporating the fahraeus effect and O-2-Hb kinetics into the simulation does not change our previous conclusion that most of the O-2 and CO2 exchange takes place at the ca pillary level; 6) in general, influences of O-2-Hb kinetics and Fahrae us effect are synergistic; 7) a model that excludes these two mechanis ms might overestimate the tissue oxygenation level especially during s evere hypoxia.