Ventilator-associated lung injury: a search for better therapeutic targets

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) represent a continuum of injury that may arise from a number of primary insults. Localised injury may progress due to trauma from mechanical ventilation, a finding that has led to intense debate in the clinical and experimental literature over optimal ventilator management. The implementation of low tidal volume strategies has led to an improvement in outcomes; however, mortality remains unacceptably high. In the current review, ventilator-associated lung injury is examined, as it relates to the pathophysiological changes beyond direct airway trauma in ALI and ARDS, and an attempt is made to provide a historical perspective to outline potential current and future pitfalls in the use of surrogate end-points and the discovery of potential biomarkers. The systemic responses that lead to multi-organ dysfunction, the leading causes of morbidity and mortality in ALI and ARDS, are caused by pro-inflammatory signalling cascades and the activation of such diverse mediators as reactive oxygen species, immune response elements, apoptotic constituents and coagulation proteins. These areas are examined, including key mediators, and possible future areas of interest are discussed, including the potential of an "acute lung injury chip" to integrate measured surrogate biomarkers with real-time clinical information to improve patient outcomes.