1 Department of Anesthesia and Perioperative Medicine, Complejo Hospitalario Universitario de A Coruña, A Coruña, Galicia, Spain; Anesthesiology and Pain Management Research Group, Institute for Biomedical Research of A Coruña (INIBIC), A Coruña, Spain; Spanish Difficult Airway Group (GEVAD), Spain. Electronic address: magoris@hotmail.com.
2 Department of Anesthesia, Hospital Universitario Infanta Elena, Valdemoro, Madrid, Spain.
3 Department of Anesthesia, Hospital Universitario Infanta Leonor, Madrid, Spain.
4 Department of Anesthesia, Complejo Asistencial Universitario de Salamanca, Universidad de Salamanca (CAUSA), Salamanca, Spain.