Kjetil G Ringdal1,2
, Timothy J Coats3
, Rolf Lefering4
, Stefano Di Bartolomeo5
, Petter Andreas Steen2
, Olav Røise6
, Lauri Handolin7
, Hans Morten Lossius1
and Utstein TCD expert panel 
1Department of Research, Norwegian Air Ambulance Foundation, Drøbak, Norway
2Faculty of Medicine, Faculty Division Ullevål University Hospital, University of Oslo, Norway
3Academic Unit of Emergency Medicine, Leicester University, UK
4Institute for Research in Operative Medicine, University of Witten/Herdecke, Cologne-Merheim Medical Centre, Cologne, Germany
5Unit of Hygiene and Epidemiology, DPMSC, School of Medicine, University of Udine, Italy
6Orthopaedic Centre, Ullevål University Hospital, Oslo, Norway
7Department of Orthopaedics and Traumatology, Helsinki University Central Hospital, Finland