Quantitative Assessment of Blood Lactate in Shock: Measure of Hypoxia or Beneficial Energy Source

Figure 2

Diagram of the microcirculatory supply of oxygen (O₂) to the tissue and the Krogh model of the local regulation of capillary blood flow. As the blood travels down the capillary, the O₂ partial pressure falls from the arterial (P_AO₂) to the venous (P_VO₂) value. The PO₂ falls as it diffuses from the capillary into the tissue as a result of the tissue oxygen consumption at the constant rate . Krogh hypothesized that there was a region (dotted) at the venous end of the tissue where the PO₂ fell to zero and that this hypoxic region produced a negative feedback signal that locally controlled the capillary flow. The position of the two O₂ microelectrodes (labeled “1” and “2”) refers to the measurements of Whalen and colleagues discussed in the text.