Figure 3.

A conceptual model of capillary flow and oxygen diffusion. A cylinder represents the area of tissue surrounding an individual capillary. A markedly low value for the (global) mixed venous oxygen saturation (SvO₂) reflects markedly deoxygenated blood in the pooled post-capillary venules. Regardless of how well oxygenated the blood may be on the arteriolar side of the capillary (A), a very low SvO₂ indicates that tissues near the venous end of the capillary (V) are supplied by deoxygenated blood ('lethal corner'). This conceptual model explains how a low SvO₂ is associated with tissue dysoxia.