Evaluation of Anterior Neck Ultrasound in Predicting Difficult Airway in Obese Patients

Difficult airway management remains a major concern in anesthetic practice and is associated with increased morbidity, particularly in obese patients. Excess anterior neck soft tissue and altered upper airway anatomy contribute to challenges in mask ventilation, laryngoscopy, and tracheal intubation. Conventional clinical airway assessment tests have limited predictive accuracy in this population, highlighting the need for additional objective assessment tools.

This prospective observational study is designed to evaluate the predictive value of ultrasound-based assessment of anterior neck soft tissue thickness for difficult airway risk in overweight and obese adult patients undergoing elective surgery under general anesthesia. The study will be conducted at a single tertiary care center after ethics committee approval, and written informed consent will be obtained from all participants.

Eligible patients aged 18-70 years with a body mass index (BMI) greater than 25 kg/m² and classified as ASA physical status I-III will be included. Emergency surgeries, pregnant patients, individuals with known difficult airway history, maxillofacial anomalies, neck masses, or a BMI greater than 60 kg/m² will be excluded.

Preoperative airway assessment will include conventional clinical parameters such as modified Mallampati score, mouth opening, interincisor distance, thyromental distance, sternomental distance, neck circumference, neck mobility, upper lip bite test, and snoring history. In addition, anterior neck ultrasound measurements will be performed preoperatively in the supine position using a high-frequency linear probe by trained anesthesiologists following a standardized protocol. Ultrasound parameters will include tongue dimensions, hyomental distance, skin-to-hyoid distance, skin-to-epiglottis distance, skin-to-vocal cords distance, skin-to-thyroid isthmus distance, skin-to-suprasternal notch distance, and the pre-epiglottic space to epiglottis-vocal cords distance ratio (PE/E-VC). Anterior neck ultrasound measurements will performed preoperatively by trained anesthesiologists using a standardized protocol.

A single prospective cohort of overweight/obese surgical patients will undergo preoperative ultrasound and clinical airway assessments, and outcomes during induction will be recorded. After induction of general anesthesia, laryngoscopic view will be assessed using the Cormack-Lehane classification. Difficult laryngoscopy will be defined as Cormack-Lehane grade III or IV. Intubation difficulty will be evaluated using the Intubation Difficulty Scale (IDS), and mask ventilation difficulty will be assessed using the Han scale. Intraoperative airway management data, including number of intubation attempts, need for adjuncts, alternative techniques, and airway-related complications, will be recorded.

Statistical analysis will focus on determining the diagnostic accuracy of ultrasound and clinical airway parameters. Receiver operating characteristic (ROC) curve analysis will be used to calculate the area under the curve (AUC), sensitivity, specificity, positive predictive value, and negative predictive value for each parameter and selected combinations. The findings aim to clarify the role of anterior neck ultrasound as a complementary tool for preoperative airway risk stratification in obese patients.

• Ultrasound-derived anterior neck soft tissue measurements [Time frame: During anesthesia induction]
• Intubation Difficulty Scale (IDS) score [Time frame: during tracheal intubation]
• Han Scale [Time frame: during ventilation]