Diffusivity of oxygen in microvascular beds as determined from PO2 distribution maps

Dynamic changes in the distribution of PO2 in the rat mesentery were measured to determine the O2 diffusion coefficient (DO2) and consumption rate (VO2). The distribution of PO2 was obtained in two-dimensional maps by microscopic fluorometry on the basis of oxygen quenching. The corresponding vasculature was also recorded on a video recorder to analyze the PO2 distribution consistent with the arrangement of the microvessels. Anesthetized rats breathing room air were subjected to 100% O2 ventilation to induce dynamic changes in PO2 distribution. We assumed a homogenous and constant VO2 in the tissue, and a one-dimensional diffusion equation was applied to simulate oxygen transport. The PO2 data corresponded very well to the theoretical curves, and calculated DO2 was 1.04 +/- 0.78 X 10(-5) cm2/s (mean +/- SD, n = 38) and VO2 was 8.2 +/- 3.9 x 10(-6) cm3 O2.cm-3 tissue.s-1 (n = 27) at 37 degrees C. However, PO2 values at points remote from the arterioles remained higher than the theoretical prediction.