A key feature of ARDS is the systemic production of pro-inflammatory mediators and cytokines, such as tumour necrosis factor (TNF) α, interleukin (IL) 1β, IL-6 and IL-8, which have been found in the bronchoalveolar lavage fluid and plasma of patients with ARDS; and elevated concentrations have been associated with an unfavourable outcome [22-24]. Here, TNF is linked to acute respiratory distress syndrome.