1 Department of Anaesthesiology, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand Auckland City Hospital, Auckland, New Zealand p.baker@auckland.ac.nz.
2 St James's Hospital, Dublin, Ireland.
3 Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
4 London's Air Ambulance, Royal London Hospital, London, UK University of Bristol, Bristol, UK.