Analysis of oxygen transport and oxygen utilization combined

We propose a model which combines oxygen transport system from blood to tissue with oxygen utilization system at the tissue.The model consists of 3 equations; the relationship between tissue P_{O 2} (Pts_{O 2}) and O₂ utilization (Vrc_{O 2}), diffusion from vessel to tissue, and Fick equation. This model has two advantages. First, it is self-consistent. Varying Vrc_{O 2} varies the oxygen transport. Second, it enables to analyze the effects of various factors of oxygen transport/utilization on other factors.We applied this model to the brain tissue. Following values were assumed. Critical tissue P_{O 2} (Pcrit_{O 2}) 2mmHg; oxygen utilization above this level 3ml·min^–1·100g^–1; diffusion coefficient from blood vessel to tissue (D) 0.2ml·min^–1·mmHg^–1·100g^–1; cerebral blood flow (CBF) 50ml·min^–1·100g^–1; hemoglobin 15g·100ml^–1. Hill equation was used for oxygen dissociation curve with n of 2.7 and P50 of 27.0mmHg.From these, the following values were obtained; Pv_{O 2}, Pts_{O 2} and Vrc_{O 2}. The changes were analyzed for the 5 input values, Pa_{O 2}, CBF, D, P50 and Hb, changing from zero to their respective normal values. A reduction of a single parameter down to 50% of normal barely affected oxygen utilization. A further reduction resulted in significant oxygen utilization. Under conditions studied, a decrease in P50 reduced oxygen utilization faster than that in any other parameters.(Suwa K: Analysis of oxygen transport and oxygen utilization combined. J Anesth 6: 51–56, 1992)