1. Department of Anesthesiology and Perioperative Medicine, Complejo Hospitalario Universitario de A Coruña, 15006 A Coruña, Spain
2. Anesthesiology, Perioperative Medicine and Pain Management Research Group, 15006 A Coruña, Spain
3. Spanish Difficult Airway Group (GEVAD), 15006 A Coruña, Spain
4. Department of Anaesthesiology, Salamanca University Hospital, 37007 Salamanca, Spain
5. Department of Anesthesiology and Intensive Therapy, Medical University of Lodz, 90-419 Lodz, Poland