Introduction Endoracheal intubation (ETI) is a crucial but risky procedure, especially among patients with suspected difficult endotracheal intubation (DTI). Bronchoscopy, as an improved technique commonly used in DTI, might encounters the difficulties of visualization. The magnetic point-of-care ultrasound (MGPOCUS) not only provide an novel visualization from outside, but also enable the estimation of relative position and trajectory of bronchoscopy. The study aims to evaluate the efficiency of MGPOCUS assisted bronchoscopy in time taken to the first-attempt success, the first-attempt and overall success of ETI, complications and satisfaction of visualization among patients suspected with DTI.

Methods and analysis The current study is a randomized, parallel-group, single-blinded, single-center study. Participants (n=350) will be recruited by primary anesthesiologist and randomized to groups of ETI with bronchoscopy or MGPOCUS assisted bronchoscopy. The primary outcome is time taken to the first-attempt success ETI. Secondary outcomes include procedure time, the first-attempt and overall success, complications and satisfaction of visualization. Cox regression with the Bonferroni correction and the linear mixed regression will be used to analysis the outcomes.

Inclusion Criteria:

• Aged between 18 and 85 years old.
• Requiring ETI.
• Anticipated DTI meets one or more positive findings in the airway evaluation, including history, examination, and appropriate investigations of anatomy .
• Signed written informed consent.
• Willingness for the primary anesthesia team to participate.

Exclusion Criteria:

• Anterior neck lesions (masses, lacerations, or subcutaneous emphysema).
• A history of neck operation or tracheotomy.
• Allergies to ultrasound coupling gel.
• At risk of pulmonary or cardiovascular complications during intubation with flexible bronchoscope, including severe hypoxemia, severe pulmonary hypertension, unstable or severe obstructive airway disease.
• At risk of bleeding during bronchoscope, including anticoagulants or coagulopathy, renal insufficiency, and superior vena cava syndrome.
• High risk of aspiration.
• Current pregnancy.
• Patient unable to cooperate (for awake intubation).

Data is available upon request from the corresponding author after the completion of the study.