[1] Department of Anaesthesia and Critical Care,
[2] Northampton General Hospital Trust,undefined
[3] Billing Road,undefined
[4] Northampton NN1 5BD,undefined
[5] United Kingdom e-mail: tordoff@sleepngh.demon.co.uk Tel.: + 44-16 04-63 47 00 Fax: + 44-16 04-54 56 72,undefined