Protective ventilation of patients with acute respiratory distress syndrome

The majority of patients with acute respiratory distress syndrome(ARDS) require mechanical ventilation. This support providestime for the lungs to heal, but the adverse effects of mechanicalventilation significantly influence patient outcome. Traditionally,these were ascribed to mechanical effects, such as haemodynamiccompromise from decreased venous return or gross air leaks inducedby large transpulmonary pressures. More recently, however, theARDS Network study has established the clinical importance oflowering the tidal volume to limit overdistension of the lungwhen ventilating patients with ARDS. This study suggests thatventilator-associated lung injury (VALI) caused by overdistensionof the lung contributes to the mortality of patients with ARDS.Moreover, the results from clinical and basic research haverevealed more subtle types of VALI, including upregulation ofthe inflammatory response in the injured and overdistended lung.This not only damages the lung, but the overflow of inflammatorymediators into the systemic circulation may explain why mostpatients who die with ARDS succumb to multi-organ failure ratherthan respiratory failure. The results of these studies, thepresent understanding of the pathophysiology of VALI, and protectiveventilatory strategies are reviewed. Br J Anaesth 2004; 92: 261–70