Abnormalities in Lung Computed Tomography and Physiological Alterations in Patients With Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) involves respiratory failure from different causes, but with a common pathologic manifestation in the form of inflammatory pulmonary edema. Histopathological examination of tissue obtained from patients with ARDS suggests that the pathology is heterogeneous and involves 3 phases: exudative, inflammatory, and fibroproliferative. Such alterations are associated with a decreased lung compliance leading to an increased pressure in the airways under mechanical ventilation (MV) that becomes more pronounced with increasing severity of ARDS, so that the consequent respiratory mechanics has thus been shown to be determinant of patient outcomes. In addition, computed tomography (CT) has revealed a heterogeneous pattern of lung injury, with areas of normal lung interspersed with morphologically altered regions, among which abnormalities the ground-glass opacification and consolidation are the most frequent. It has been performed quantitative assessments of ARDS by means of CT, thus enabling a correlation of such pathologic details with physiologic and clinical parameters as well as with patient outcomes. From the above, the investigators hypothesize that in patients with ARDS, a greater involvement in oxygenation and higher mechanical alterations will be correlated with a more advanced consolidation in the CT scan. Therefore, the primary objective of the study will be to determine the correlation between the extent of oxygenation (assessed by the PaO2/FiO2 ratio) and the degree of consolidation (total CO) in the CT scan. The secondary objectives will be: (1) to determine the correlation between the driving pressure and the total CO as evidenced by CT; (2) to determine the correlation between the static pressure and the total CO; (3) to determine the correlation between the static compliance and the total CO; (4) to determine the correlation between oxygenation index and the total CO; (5) to determine the correlation between the lung injury score (LIS) and the total CO; (6) to determine the correlation between ventilator free days and the total CO; (7) to determine the independent variables associated with total CO; (8) to determine differences in the CT with respect to the total lung-disease score [total CO plus total value of ground-glass opacification (total GC)] between survivors and nonsurvivors.