Ventilatory strategies for acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a severe condition that has a high mortality. Mechanical ventilation is required and concepts have evolved over the last few decades as to the methods and principles guiding such ventilatory support. In particular, volutrauma as a feature of ventilator-associated lung injury has been well documented, leading to pressure-limited strategies with consequent permissive hypercapnia. Such an approach is in direct contrast to traditional ventilatory teaching of high tidal volumes and normal PaCO2. Current strategies therefore emphasis lower tidal volumes, adequate positive end-expiratory pressure (PEEP), minimum FiO2, and the use of pressure-control modes (plus or minus inverse-ratio ventilation). Hypercapnia is allowed to develop, and adjunctive methods are employed to improve oxygenation in order to minimise the "pressure-cost" of maintaining adequate oxygenation. With such an approach, overall mortality is reported to be around 40%.