The following clinicians contributed to this briefing:
Dr Jonathan Ball, consultant and honorary senior lecturer in general and neuro intensive care, St George's University Hospital NHS Foundation Trust. Declared no interests.
Professor Gary H Mills, consultant in intensive care medicine and anaesthesia honorary professor in critical care medicine, University of Sheffield. Declared no interests.
Dr Peter Macnaughton, consultant in intensive care medicine, University of Plymouth Hospitals NHS Trust. Declared no interests.
Dr Alastair Glossop, consultant in critical care and anaesthesia, Sheffield Teaching Hospital NHS Foundation Trust. Dr Glossop is a paid consultant, public speaker and adviser to Armstrong Medical UK Ltd since 2014.