Fig. 1. Representative images of gas fraction, perfusion, and net 18F-fluorodeoxyglucose uptake rate (Ki) in supine sheep after 2 h of mechanical ventilation with positive end-expiratory pressure = 0 cm H2O and plateau pressure of 30-32 cm H2O in the control (A -C ) and after mild endotoxemia (D -F ). There is a clear vertical dependence of aeration and perfusion in both groups. No significant change in mean gas fraction or perfusion redistribution was observed with endotoxemia. In contrast, the increase in magnitude and degree of heterogeneity of the net 18F-fluorodeoxyglucose uptake is apparent in the endotoxin group when compared with the control group. FDG = fluorodeoxyglucose.