evaluate the efficacy of the ultrasound approach in predicting difficult mask ventilation in a heterogeneous population of patients undergoing general anesthesia.

Preoperative ultrasound of the upper airway and detection of 5 ultrasound measurements:

Trachea-skin distance at the level of the thyroid isthmus; Trachea-skin distance at the jugular level Front commissure-skin distance; Distance from skin to the thyroid membrane Distance between hyoid bone and skin. Comparison of this measurement with HAN-scale for prediction of difficult mask ventilation during general anesthesia

Inclusion Criteria:

- all patient > 18years old undergoing general anesthesia for elective surgery

Exclusion Criteria:

• Patients with fractures of the bones of the facial mass;
• Patients with laryngeal tumors
• Patients previously undergoing demolition of the larynx or neck;
• Tracheostomized patients;
• Pregnancy;
• Inter-incisive distance <3 cm;
• severely limited cervical mobility;
• Patients who are not given muscle relaxants
• Patient rejection.

all patient > 18 ys undergoing general anesthesia for elective surgery