Difficult airway management is a major cause of perioperative complications. Standard bedside airway assessment tests may have limited ability to predict difficult intubation and difficult mask ventilation. This prospective observational study aims to evaluate whether preoperative ultrasound measurements of airway structures (such as skin-to-epiglottis distance, tongue thickness, and pre-epiglottic space) can predict difficult intubation and difficult mask ventilation in adult patients undergoing surgery under general anesthesia.

This prospective observational cohort study was conducted to evaluate the predictive value of preoperative ultrasonographic airway measurements for difficult intubation and difficult mask ventilation in adult patients undergoing elective surgery under general anesthesia. A total of 400 patients aged 18-70 years with ASA physical status I-III were included. Before induction of anesthesia, standard clinical airway assessment tests were recorded, and ultrasound measurements were performed to assess airway-related anatomical structures. Ultrasonographic parameters included skin-to-epiglottis distance, skin-to-thyroid cartilage distance, thyroid cartilage-to-epiglottis distance, pre-epiglottic space depth, tongue thickness, and hyomental distance measurements.

Intraoperatively, mask ventilation and intubation conditions were documented. Difficult intubation was defined as requiring two or more intubation attempts. Difficult mask ventilation was defined as the need for two-handed mask ventilation or inability to ventilate adequately using a face mask. The primary objective was to determine the association between ultrasonographic measurements and difficult intubation

Inclusion Criteria:

• Age 18-70 years

ASA physical status I-III

Elective surgery under general anesthesia requiring orotracheal intubation

Written informed consent

Exclusion Criteria:

• Refusal to participate

Emergency surgery

Pregnancy

Known upper airway pathology or previous airway surgery

Restricted mouth opening (<3 cm)

Cervical spine instability or significant limitation of neck mobility

Morbid obesity (BMI ≥40 kg/m²)

Obstructive upper airway masses (e.g., head and neck tumors)

Prior neck radiotherapy

Clinically relevant neck masses

Major facial/mandibular trauma or craniofacial anomalies

Adult patients aged 18-70 years (ASA I-III) scheduled for elective surgery under general anesthesia requiring orotracheal intubation

Individual participant data will not be shared due to institutional policies and to protect participant privacy and confidentiality.