Description
An appreciation of the pathophysiology underlying acute respiratory failure is the key to understanding current strategies employed in managing patients with respiratory failure, particularly those suffering from acute lung injury. The realisation that previously aimed for goals of ventilation (a PaCO2 of 5 kPa) or oxygenation (a PaO2 of 13 kPa) were overcautious has allowed new strategies to be adopted with a degree of confidence. In selecting a mode of support, the need to limit ventilator induced lung injury (VILI) is the key objective. Some previously used modes of respiratory support may have lead to volume or shear stress. Strategies to maintain alveolar patency – open lung ventilation – or to redistribute blood or gas flow – redistributive therapy- using position (gravity), pharmacological manipulation of gas or blood flow, or both, are natural adjuncts to limiting VILI.
