1. Clinic for Anesthesiology and Intensive Therapy, University Clinical Center in Niš, 18000 Niš, Serbia
2. Clinic for Anesthesiology and Intensive Therapy, Military Medical Academy, 11000 Belgrade, Serbia
3. Faculty of Medicine of the Military Medical Academy, University of Defence, 11000 Belgrade, Serbia
4. Otolaryngology Clinic, University Clinical Center in Niš, 18000 Niš, Serbia
5. Department Otorhinolaryngology, Faculty of Medicine, Univeristy in Niš, 18000 Niš, Serbia
6. Department Surgery and Anesthesiology and Reanimatology, Faculty of Medicine, University in Niš, 18000 Niš, Serbia