acute respiratory distress syndrome

- diagnostic criteria
  i) acute onset
  ii)widespread bilateral CXR infiltrates
  iii)refractory hypoxemia (PaO2/FiO2< 200mmHg)
  iv)PCWP < 18mmHg

- causes
   direct: pneumonia, aspiration of gastric contents, inhalational injury, fat embolism
   indirect: sepsis, severe trauma with shock, pancreatitis, cardiopulmonary bypass
- first sign is often unexplained tachypnea, followed by increasing hypoxaemia with central cyanosis and breathlessness
- management is supportive and based on treatment of underlying cause.