Mechanical Ventilation in Ards: Good or Bad News?

Abstract

Despite an enormous progress in the technology of ventilators, the improvement in the diagnostic tools and in pharmacological treatment the Adult Respiratory Distress Syndrome (ARDS) is characterized by high mortality rate [1,2,3]. Although necessary, mechanical ventilation is commonly considered to be one of the main causes of further lung injury to diseased lungs, reducing the possibility of recovery. For this reason the iatrogenic effect of mechanical ventilation has been named ventilator-associated lung injury (VALI). VALI is the consequence of a sustained increase in alveolar pressure (‘barotrauma’), alveolar distension (‘volotrauma’) or alveolar collapse and decollapse with cycling during inspiration and expiration (‘shear stress trauma’). Recent clinical studies suggest that the optimal ventilatory treatment should combine the use of a reduced tidal volume with consequent permissive hypercapnia to reduce volotrauma, low inspiratory pressures to reduce barotrauma and an adequate level of positive end-expiratory pressure to recruit as much collapsed parenchyma as possible to reduce shear stress trauma [4,5]. However, different etiologies leading to ARDS and time may produce different alterations in the lung structure with consequent different responses to the ventilatory treatment.