Mechanical ventilation in adult respiratory distress syndrome: a good friend or a secret killer?

Adult respiratory distress syndrome is characterized by a high mortality rate despite enormous progress in the technology of ventilators, improvement in the diagnostic tools and in pharmacological treatment. Mechanical ventilation, although necessary, is generally considered to be one of the main causes of further injury to diseased lungs, reducing the possibility of recovery (ventilator-induced lung injury). Ventilator-induced lung injury 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). Experimental and 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 lung parenchyma as possible to reduce shear stress trauma. However, because adult respiratory distress syndrome is a syndrome of different aetiologies, a general optimal ventilatory strategy applicable to patients with adult respiratory distress syndrome probably does not exist. Indeed, it would be better to tailor it taking into account the pathophysiology of individual patients and the primitive cause of the disease itself. Only a better knowledge of the patients' underlying pathophysiology in the different kinds of adult respiratory distress syndrome will help in tailoring the least damaging ventilation programme for each individual patient.