1. Department of Anaesthesia and Intensive Medicine, Military University Hospital, 1st Medical Faculty, Charles University in Prague, 160 00 Prague, Czech Republic
2. Department of Anaesthesia and Intensive Medicine, General University Hospital, 1st Medical Faculty, Charles University in Prague, 120 21 Prague, Czech Republic
3. Department of Anaesthesia, Craigavon Area Hospital, BT63 5QQ Portadown, Northern Ireland, UK