Fig. 1

Microcirculatory alterations that underlie the loss of hemodynamic coherence between the macro- and microcirculations resulting in tissue hypoxia. Type 1 comprises a condition with a heterogeneous perfusion of the microcirculation as exhibited by septic patients with obstructed capillaries next to perfused capillaries, which results in a heterogeneous oxygenation of the tissue cells. Type 2 occurs as a consequence of hemodilution, with the dilution of microcirculatory blood resulting in the loss of RBC-filled capillaries and increasing the diffusion distance between oxygen carrying RBCs and tissue cells. Type 3 alterations result in a stasis of microcirculatory RBC flow induced by an increased arterial vascular resistance, vasopressor therapy, increased venous pressure, or hyperoxia. Type 4 alterations involve edema caused by capillary leak syndrome and results in an increased diffusive distance and reduced ability of oxygen to reach tissue cells. Adapted from [1]