Acute respiratory distress syndrome (ARDS) is characterized by diffuse alveolar damage andresulting from an increased permeability of the alveolar-capillary membrane. Of notice, thereis an intense lung inflammation. Positron emission tomography (PET) and electricalimpedance tomography (EIT) allow noninvasive assessment of pulmonary ventilation,perfusion and inflammation. We use these techniques to decipher the impairments ofventilation and inflammation throughout the lungs in an experimental model of acute lunginjury by hydrochloric acid inhalation in pigs.In a first study, we compared EIT to PET in quantifying pulmonary aerated volume andventilation, using PET as a gold standard. We found that lung ventilation and volume wereaccurately measured with EIT over a wide range of lung volume and minute ventilation. Wehave then described and validated a new model to obtain lung aerated volume and ventilationwith PET, without the requirement of gas sampling in the respiratory circuit. Finally, weconducted a controlled study with PET to evaluate the effects of positive end-expiratorypressure and body position on regional lung inflammation, ventilation and perfusion.Inflammation was significantly higher in injured groups than in control. However, there wasno significant change in inflammation across ALI groups despite significant differencebetween ventilation and perfusion repartition.We have developed in this work a stable experimental model of acute lung injury andvalidated noninvasive imaging tools allowing studying of important physiologic parametersthat could help setting up mechanical ventilation.
