Diffusivity of oxygen in microvascular beds as determined from Po-2 distribution maps

Dynamic changes in the distribution of PO2 in the rat mesentery were measured to determine the O-2 diffusion coefficient (DO2) and consumption rate (Vover dot O-2). 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% O-2 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) cm(2)/s (mean +/- SD, n = 38) and Vover dot O-2 was 8.2 +/- 3.9 x 10(-6) cm(3) O-2 . 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.