• Giacomo Bellani, Cristina Messa, Luca Guerra, Ester Spagnolli, Giuseppe Foti, Nicolò Patroniti, Roberto Fumagalli, Guido Musch, Ferruccio Fazio, and Antonio Pesenti.
• Department of Experimental Medicine, 'Centro Bioimmagini Molecolari', University of Milan-Bicocca, Monza (MI), Italy.
• Crit. Care Med. 2009 Jul 1;37(7):2216-22.

ObjectiveNeutrophilic inflammation plays a key role in the pathogenesis of acute respiratory distress syndrome (ARDS) and acute lung injury (ALI). Positron emission tomography (PET) with [F]-fluoro-2-deoxy-D-glucose (FDG) can be used to image cellular metabolism that, during lung inflammatory processes, likely reflects neutrophils activity. The aim of this study was to assess the magnitude and regional distribution of inflammatory metabolic activity in the lungs of patients with ALI/ARDS by PET with FDG.DesignProspective clinical investigation.PatientsTen patients with ALI/ARDS; four spontaneously breathing and two mechanically ventilated subjects, without known lung disease, served as controls.InterventionsIn each individual we performed an FDG PET/computed tomography of the thorax.Measurements And Main ResultsFDG cellular influx rate constant (Ki) was computed for the imaged lung field and for regions of interest, grouping voxels with similar density. In all patients with ALI/ARDS, Ki was higher than in controls, also after accounting for the increased lung density. Ki values differed greatly among patients, but in all patients Ki of the normally aerated regions was much higher (2- to 24-fold) than in controls. Whereas in some patients the highest Ki values corresponded to regions with the lowest aeration, in others these regions had lower Ki than normally and mildly hypoaerated regions.ConclusionIn patients with ALI/ARDS, undergoing mechanical ventilation since days, the metabolic activity of the lungs is markedly increased across the entire lung density spectrum. The intensity of this activation and its regional distribution, however, vary widely within and between patients.

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