[1] Univ Murcia, Inst Resp Hlth, E-30001 Murcia, Spain
[2] Univ Santiago Chile, Sch Hlth Sci, Dept Pediat Resp Med, Santiago, Chile
[3] Univ Valencia, Publ & Environm Hlth Unit, E-46003 Valencia, Spain
[4] Torrecardenas Hosp, Pediat Resp Unit, Almeria, Spain
[5] 12 Octubre Childrens Hosp, Pediat Allergy & Resp Sect, Madrid, Spain