Hypoxaemic rescue therapies in acute respiratory distress syndrome: Why, when, what and which one?

Acute respiratory distress syndrome (ARDS) is an inflammatory condition of the lungs which can result in refractory and life-threatening hypoxaemic respiratory failure. The risk factors for the development of ARDS are many but include trauma, multiple blood transfusions, burns and major surgery, therefore this condition is not uncommon in the severely injured patient. When ARDS is severe, high-inspired oxygen concentrations are frequently required to minimise hypoxaemia. In these situations clinicians commonly utilise interventions termed 'hypoxaemic rescue therapies' in an attempt to improve oxygenation, as without these, conventional mechanical ventilation can be associated with high mortality. However, their lack of efficacy on mortality when used prophylactically in generalised ARDS cohorts has resulted in their use being confined to clinical trials and the subset of ARDS patients with refractory hypoxaemia. First line hypoxaemic rescue therapies include inhaled nitric oxide, prone positioning, alveolar recruitment manoeuvres and high frequency oscillatory ventilation, which have all been shown to be effective in improving oxygenation. In situations where these first line rescue therapies are inadequate extra-corporeal membrane oxygenation has emerged as a lifesaving second line rescue therapy. Rescue therapies in critically ill patients with traumatic injuries presents specific challenges and requires careful assessment of both the short and longer term benefits, therapeutic limitations, and specific adverse effects before their use.