Volatile Sedation for Patients With the Acute Respiratory Distress Syndrome

This study will investigate how different types of routine sedation may affect patient's breathing whilst on a ventilator in the Intensive Care Unit (ICU). There are different approaches to sedation which may have advantages and disadvantages. During the study patients will receive both intravenous and inhaled volatile sedation (similar to anaesthetic 'gases' used for general anaesthesia) and the drive to breath, breathing efforts and function of the lung will be assessed.