Effects of TCAV and Volume Control Ventilation on the Distribution of Aerated Lung Parenchyma in ARDS Patients

Acute respiratory distress syndrome (ARDS) is a severe form of acute respiratory failure with mortality rates reaching as high as 35%. Management of ARDS is based on the treatment (if possible) of the underlying cause of ARDS and on invasive mechanical ventilation with positive expiratory pressure (PEEP). Another strategy of invasive ventilation, Time-Controlled Adaptative Ventilation (TCAV), is the application of specific settings to the airway pressure release ventilation (APRV) mode. TCAV is based on a prolonged time at plateau pressure, creating a phase of continuous positive pressure, associated with brief release phases allowing the elimination of carbon dioxide. In prospective and retrospective clinical reviews, as well as in experimental animal studies, TCAV has demonstrated improvements in oxygenation and lung function, with the ability to prevent ARDS. The thoracic computed tomography (CT) scan evaluates lung recruitment (re-aeration by positive pressure of non-ventilated lung territories) and the adverse effects of positive pressure on the parenchyma (hyperinflation). The objective of this study is to evaluate, with CT scans performed to assess lungs of patients with ARDS, the effects of TCAV compared to a standard volumetric controlled ventilation, by measuring alveolar recruitment and over-distension.