1 Complejo Hospitalario Universitario de A Coruña, Department of Anaesthesiology and Perioperative Medicine, A Coruña, Spain. Electronic address: magoris@hotmail.com.
2 Medical University of Pleven, Pleven, Bulgaria.
3 Jiangsu Cancer Hospital, Department of Anesthesiology, Nanjing, China.
4 Hospital General Universitario Morales Meseguer, Intensive Care Unit and Non Invasive Ventilatory Unit, Murcia, Spain.