The goal of this clinical trial is to compare three airway intubation devices in adult patients undergoing general anesthesia who require tracheal intubation. The main questions it aims to answer are:
* Does the SPHJ-II video-assisted adjustable red-light fluoroscopic tracheal intubation scope improve first-attempt intubation success compared with a visual lighted stylet and a visual intubation fiberscope? * How do the three devices compare in intubation efficiency, intubation-related complications, and peri-intubation physiological responses?
Researchers will compare the SPHJ-II, the visual lighted stylet, and the visual intubation fiberscope to evaluate their performance during tracheal intubation.
Participants will be randomly assigned to one of the three device groups and undergo tracheal intubation during general anesthesia using the assigned device.
Age 18 to 65 years, inclusive. American Society of Anesthesiologists (ASA) physical status I to III. Scheduled for surgery under general anesthesia requiring endotracheal intubation.
Anticipated severe difficulty with mask ventilation, such as severe obesity (BMI > 35 kg/m²) with obstructive sleep apnea syndrome, history of neck radiotherapy, craniofacial malformation, or other conditions judged by the attending anesthesiologist to confer high risk for mask ventilation, and patients requiring awake tracheal intubation.