Evaluation of Difficult Airway With Ultrasonography

Patients with BMI> 30, schedule elective surgery under general anesthesia, and give consent will be included in the study. In the preoperative evaluation, demographic data of the patients, airway physical examination results (mouth opening, Mallampati score, thyromental distance, neck circumference (from thyroid cartilage level), abnormal upper tooth presence, neck movement restriction], presence of sleep apnea and STOP-BANG score will be recorded. In the patients taken on the operation table with supine position, ultrasound-guided soft tissue distances will be measured using ultrasound 6-13 Hz linear probe. The distance between the hyoid bone-skin (DSHB), the vocal cord anterior commissura-skin distance (DSAC), the minimum distance of the trachea to the skin at the level of the suprasternal notch (DST), the distance between the thyroid isthmus and the skin (DSI), and the distance between the epiglottis and the skin (DSE) will be measured and recorded. After standard monitoring and anesthesia induction, difficult mask ventilation will be evaluated with Han Scale [(1) can be ventilated with a mask; 2) can be ventilated with the airway (with or without muscle relaxation); 3) difficult mask ventilation (insufficient, unstable, two practitioners are needed); 4) cannot be ventilated by mask] and grade 3-4 will be recorded as difficult mask ventilation. Difficult laryngoscopy will be evaluated with Cormack Lehane Scale [grade 1: vocal cords appear; grade-2: posterior commissura and epiglottis visible; grade-3: only epiglottis are seen; grade-4: glottic structures are not visible] and grade 3-4 will be recorded as difficult laryngoscopy. Difficult intubation will also be evaluated with the number and duration of intubation attempts with the Macintosh blade. Tracheal intubation will be performed by an anesthesiologist who has at least two years of experience and unaware of ultrasound measurements. The duration of intubation (the time from the first handling of the laryngoscope until the capnography trace appeared) and the number of trials will be recorded.

Inclusion criteria

• Patients planned to undergo general anesthesia for elective surgery
• American Anesthesiology Association physical classification (ASA) status I-III
• Body mass index (BMI) above 30

Exclusion criteria

• Patients with neck mass
• History of previous neck and thyroid surgery, trauma, arthritis, loss of teeth
• History of difficult intubation
• Bearded patients
• Pregnant women