[1] Haukeland Hosp, Dept Pediat, N-5021 Bergen, Norway
[2] Univ Bergen, Dept Clin Sci, Bergen, Norway
[3] Royal Brompton Hosp, Dept Resp Med, London, England
[4] Bispebjerg Hosp, Resp Res Unit, Copenhagen, Denmark
[5] Univ Turin, Dept Med Sci, Turin, Italy
[6] Citta Salute & Sci, Resp Unit, Turin, Italy
[7] Imperial Coll, Paediat Resp Med, London, England
[8] Royal Brompton Hosp, London, England
[9] Fdn IRCCS Ca Granda Osped Maggiore Policlin, Dept Otolaryngol, Milan, Italy
[10] Med Univ Graz, ENT Hosp Graz, Dept Phoniatr Speech & Swallowing, Graz, Austria
[11] Heidelberg Univ, Dept Pneumol & Crit Care Med, Translat Lung Res Ctr Heidelberg, Thoraxklin, Heidelberg, Germany
[12] Hochgebirgsklin Davos, Davos, Switzerland
[13] Ropcke Zweers Hosp, Dept Otorhinolaryngol, Hardenberg, Netherlands
[14] Uppsala Univ, Dept Surg Sci Otorhinolaryngol & Head & Neck Surg, Uppsala, Sweden
[15] Louvain Univ Hosp Mt Godinne, Dept ORL Head & Neck Surg, Yvoir, Belgium
[16] Rigshosp, Dept Otolaryngol Head & Neck Surg, Copenhagen, Denmark
[17] Univ Copenhagen, Copenhagen, Denmark
[18] Newcastle Univ, Dept Otolaryngol Head & Neck Surg, Newcastle Upon Tyne, Tyne & Wear, England
[19] Freeman Rd Hosp, Newcastle Upon Tyne, Tyne & Wear, England
[20] Haukeland Hosp, Dept Surg, Bergen, Norway