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With the advent and more widespread use of video-assisted laryngoscopy (VL), the incidence of difficult intubation has decreased. However, the optimal position for endotracheal intubation facilitated by VL is not yet determined. The objective of this study is to evaluate the effects of different patient positioning (neutral position versus sniffing position) on the glottic view and intubation time during orotracheal intubation facilitated by two video-assisted laryngoscopes (McGrath laryngoscope and C-MAC D-blade laryngoscope). A total of 252 patients who required orotracheal intubation for elective surgery were included in the study. Primary outcomes include airway difficulty score(ADS), intubation difficulty scale (IDS), the percentage of glottic opening (POGO) and intubation time. By the indexes above and crossover analysis, the study aimed to prove the ideal position for VL.

Endotracheal tube general anesthesia (ETGA) is required for a variety of surgeries. Traditionally, the patient is placed in a sniffing position to facilitate endotracheal intubation with a direct laryngoscope. Increased attempts in intubation or intubation failed may be encountered during direct laryngoscope, leading to hypoxemia or neurological sequelae. Injure to the teeth, gingiva or lips is also sometimes unavoidable. With the advent and more widespread use of video-assisted laryngoscopy (VL), the incidence of difficult intubation has decreased.

However, the optimal position for endotracheal intubation facilitated by VL is not yet determined. A previous study suggested that better glottic view is achieved when placing the patient in a neutral position than the sniffing position during orotracheal intubation by fiberoptic bronchoscopy. The objective of this study is to evaluate the effects of different patient positioning (neutral position versus sniffing position) on the glottic view and intubation time during orotracheal intubation facilitated by two video-assisted laryngoscopes (McGrath laryngoscope and C-MAC D-blade laryngoscope).

A total of 252 American Society of Anesthesiologists I-II patients, in the age above 20 years, who required orotracheal intubation for elective surgery were included in the study. Patients received nasotracheal intubation, awake tracheal intubation, emergency surgery, required rapid-sequence intubation (RSI), those in pregnancy, with possible difficult intubation(with oropharyngeal pathology, limited neck mobility, previous head and neck surgical history), anticipated difficult intubation assessed by preoperative Airway Difficult Score(ADS)(≥ 7), with allergy history of common anesthetics agents or any underlying comorbidities which refrain them from receiving common anesthetic agents were excluded.

The types of VL and the orders of position were randomly allocated by computer and the study take place in the operation room. Primary outcomes include airway difficulty (evaluated by ADS), ease of intubation (evaluated by intubation difficulty scale [IDS], the percentage of glottic opening [POGO]) and intubation time. By the indexes above and crossover analysis, the study aimed to prove the ideal position for VL, improve the efficiency of intubation and decrease the rate of difficult intubation by VL in the future.

Inclusion Criteria:

• age above 20 years
• Anesthesiologists I-II
• who required orotracheal intubation for elective surgery

Exclusion Criteria:

• nasotracheal intubation
• awake tracheal intubation
• emergency surgery
• required rapid-sequence intubation (RSI)
• those in pregnancy
• with possible difficult intubation(with oropharyngeal pathology, limited neck mobility, previous head and neck surgical history)
• anticipated difficult intubation assessed by preoperative Airway Difficult Score (≥ 7)
• with allergy history of common anesthetics agents
• any underlying comorbidities which refrain them from receiving common anesthetic agents