What is and how to Manage the Acute Respiratory Distress Syndrome?

Acute respiratory distress syndrome (ARDS) is an acute hypoxemic respiratory failure with lung oedema of non cardiac origin. Its primary treatment is mechanical ventilation. ARDS is under the spotlights with influenza A pandemic flu. An operating definition has been set out by an experts-consensus conference in order to include patients in clinical trials. However, this definition lacks diagnostic accuracy when compared with lung pathology. The conventional mechanical ventilation has two main objectives: firstly, preservation of arterial blood oxygenation, and secondly, protection of the lung from excessive volume or pressure at the end of inspiration. It has been demonstrated that high tidal volume can increase mortality as compared to low tidal volume. The setting of positive end-expiratory pressure (PEEP) is still not solved. Three large randomized controlled trials failed to demonstrate any benefit between a high and a low level of PEEP. A fascinating strategy of mechanical ventilation is lung recruitment, which is defined as an increase in aerated lung mass by reducing non-aerated or poorly aerated lung mass. Recruiting the lung is useful because it can improve oxygenation and limit ventilator-induced lung injury. Lung recruitment depends not only on the ventilatory settings but also on lung and patient. Several adjunct treatments can be used, as prone position or various pharmacological interventions (inhaled nitric oxide). There are several non conventional methods to deliver mechanical ventilation, such as non invasive mechanical ventilation, liquid ventilation, none of them being recommended to date. Finally, the use of extracorporeal lung support is gaining further interest.