Interpretation of Oxygen Disappearance Curves Measured in Blood Perfused Tissues

We have developed a two compartment (tissue and blood) lumped parameter model to interpret oxygen disappearance curves (O₂ DCs) measured in vivo with PO₂ microelectrodes in tissues which are perfused with blood. To include the properties of the oxyhemoglobin equilibrium curve (HEC), we used an algorithm we have recently developed for both standard and nonstandard conditions. The new blood and tissue model is more useful than a previous analysis using the Hill equation for blood and constant oxygen consumption (\( \mathop {\text{V}}\limits^ \bullet\ \)O₂). The model can be adapted for constant (zero-order) consumption, Michelis-Menten kinetics, or for double cytochrome systems. Examples for the former include brain, and for the latter, carotid body. The models are discussed in relationship to experimental microelectrode measurements in gerbil brain and in cat carotid body after blood flow occlusion.