title: Reply.
authors.affiliation: Department of Anaesthesia and Intensive Care, Papworth Hospital, Papworth Everard, Cambridge, United Kingdom.
authors.forename: Bilal M
authors.initials: BM
authors.lastname: Ansari
authors.affiliation: Department of Anaesthesia and Intensive Care, Papworth Hospital, Papworth Everard, Cambridge, United Kingdom.
authors.forename: Maurice P
authors.initials: MP
authors.lastname: Hogan
authors.affiliation: Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Collier
authors.affiliation: Department of Physiotherapy, Papworth Hospital, Papworth Everard, Cambridge, United Kingdom.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Baddeley
authors.affiliation: Department of Cardiothoracic Surgery, Papworth Hospital, Papworth Everard, Cambridge, United Kingdom.
authors.forename: Marco
authors.initials: M
authors.lastname: Scarci
authors.affiliation: Department of Cardiothoracic Surgery, Papworth Hospital, Papworth Everard, Cambridge, United Kingdom.
authors.forename: Aman S
authors.initials: AS
authors.lastname: Coonar
authors.affiliation: Department of Research and Development, Papworth Hospital, Papworth Everard, Cambridge, United Kingdom.
authors.forename: Fiona E
authors.initials: FE
authors.lastname: Bottrill
authors.affiliation: Department of Anaesthesia and Intensive Care, Papworth Hospital, Papworth Everard, Cambridge, United Kingdom.
authors.forename: Guillermo C
authors.initials: GC
authors.lastname: Martinez
authors.affiliation: Department of Anaesthesia and Intensive Care, Papworth Hospital, Papworth Everard, Cambridge, United Kingdom. Electronic address: andrew.klein@nhs.net.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Klein