Introduction:
Endotracheal intubation is a standard method for the airway management in the patients undergoing general anaesthesia and in emergency medicine. Difficult intubation occurs in approximately 5% of the cases; when not predicted may cause threat to patient safety. The goal of our study was to evaluate preoperative methods of predicting difficult intubation.

Material and methods:
A group of 51 patients undergoing elective surgery under general anaesthesia were analysed. Before the operation the patients were interviewed and examined with different methods of predicting difficult intubation (the Mallampati test, the upper-lip bite test, the inter-incisor gap; thyro-mental, hyoido-mental and sterno-mental distance, movement of the cervical spine). During the induction of anaesthesia the anesthesiologist graded the
laryngeal view in the direct laryngoscopy using the Cormack-Lehane classification.

Results:
According to the Mallampati test, in case of 10 patients difficult intubation was expected. Difficult laryngoscopy (Cormack-Lehane grade 3 or 4) appeared in six patients, while difficult intubation (evaluated subjectively by the intubating anesthesiologist) in five patients. Four patients who experienced difficult intubation had the Mallampati score 1 or 2. There was a statistically significant correlation between the Cormack-Lehane scale and the inter-
incisor gap, hyoido-mental and sterno-mental distance and the flexion and extension of the cervical spine.

Conclusions:
The available methods of predicting difficult intubation have sensitivity varying from 16% (upper-lip bite test) to 33%(the Mallampati test, the inter-incisor gap, thyroido-mental and sterno-mental distance). The inter-incisor gap, the flexion and extension of the cervical spine, the hyoido-mental and sterno-mental distance are parameters which might increase the probability of predicting difficult laryngoscopy and intubation. However there is no combination of methods which can exclude any complications in securing the airway. A good direct laryngological view of the vocal cords does not exclude difficult intubation.