Acute lung injury/acute respiratory distress syndrome pathophysiology : what we have learned from computed tomography scanning

PURPOSE OF REVIEW: Although many years have passed since its first application in acute respiratory distress syndrome, computed tomography remains widely employed for research and clinical purposes. Here, we review recent findings derived from computed tomography scanning during acute respiratory distress syndrome, particularly concerning setting positive end-expiratory pressure and mechanisms of ventilator-induced lung injury. RECENT FINDINGS: Several studies have provided evidence for the validity of monitoring dynamic mechanics of the respiratory system to estimate the balance between beneficial (i.e. reduction of alveolar derecruitment) and harmful (i.e. lung hyperinflation) effects, consequent to positive end-expiratory pressure increase. The combination of different respiratory variables to estimate lung recruitment has become a more accepted approach. Computed tomography scanning has provided important evidence of lung hyperinflation even after the use of low tidal volume in a specific category of patients. Alternative techniques, such as electrical impedance tomography and lung ultrasound, appear as promising tools potentially available at the bedside. SUMMARY: As far as setting positive end-expiratory pressure is concerned, further randomized clinical studies are warranted to verify the pathophysiologic findings recently observed with computed tomography scanning. Similarly, the safety of the widespread use of low tidal volume should be brought into question, possibly pointing out a category of patients who may benefit from alternative techniques of respiratory support.