[1] James Cook Univ Hosp, Dept Otolaryngol, Middlesbrough TS4 3BW, Cleveland, England
[2] Royal Hosp Sick Children, Dept Paediat Otolaryngol, Glasgow G3 8SJ, Lanark, Scotland
[3] Royal Victoria Infirm, Dept Paediat Resp Med, Newcastle Upon Tyne NE1 4LP, Tyne & Wear, England
[4] James Cook Univ Hosp, Dept Anaesthesia, Middlesbrough TS4 3BW, Cleveland, England