BACKGROUND Unpredicted difficult tracheal intubation (DTI) with Macintosh laryngoscopy occurs frequently in obese patients. We investigated the incidence of DTI using the GlideScope® videolaryngoscope (GVL) with an algorithm based on a pre-operative assessment with the El Ganzouri Risk Index (EGRI).

METHODS We prospectively enrolled morbidly obese patients (BMI>40 kg/m2) undergoing abdominal surgery. Patients were scheduled for flexible fibre optic bronchoscopic intubation (FFBI) or GVL intubation if the EGRI score was ≥7 or <7, respectively. The primary outcome was the occurrence of DTI that was defined as Cormack and Lehane (C&L) grades ≥III, Intubation Difficulty Scale (IDS)>5 and modified IDS (mIDS)>5. A numeric rating scale (NRS) was also used. Secondary outcomes included intubation success during the first attempt, the time to Cormack (TTC), the time to intubation (TTI), failure to intubate, oxygen desaturation and difficult ventilation.

The EGRI, a multivariate risk index that combines seven variables associated with DTI, was evaluated in all patients during the pre-anaesthesia visit. The results were reported in the clinical chart. All tracheal intubations in obese patients needing surgery were routinely performed using GVL. The intubations were performed or assisted by five board-certified anaesthesiologists who had prior experience with at least 20 GVL intubations, as well as at least two years of experience with anaesthesia in obese patients. In cases where the GVL intubation was performed by anaesthesiologists that were in training, the GVL expert was actively advising the operator during all of the intubating procedures. The standard equipment included a GVL with blade number three to five and an orotracheal hockey stick tube with a malleable single-use stylet (Fr 14, Intubating Stylet, DEAS). The standard anaesthesia induction started with 3-5 minutes of pre-oxygenation using 5 cm H2O PEEP in a 30° head-up position, as well as induction with fentanyl 3 μg kg -1 (LBW), propofol 2-3 mg kg -1 (LBW) and suxamethonium 1 mg Kg -1 (TBW). When spontaneous respiration ceased, the patient was mask ventilated with 100% oxygen. The tube was lubricated and advanced into the mouth under direct visual guidance to avoid complications, and then, under indirect visual guidance using the GVL monitor. The correct placement of the cuffed tube was verified using a capnograph and a stethoscope. The tube sizes were 7.0 for women and 7.5 for men. Each patient was monitored using an electrocardiogram, non-invasive arterial blood pressure measurement, and pulse oximetry before both tracheal intubation and anaesthesia induction. The basic demographic data and airway characteristics necessary to evaluate the primary outcome and to calculate the EGRI score were registered prior to anaesthesia. Patients with an EGRI score of 7 or higher were scheduled for elective fibre optic flexible bronchoscopic intubation (FFBI), while patients with an EGRI score of less than 7 underwent anaesthesia induction and GVL intubation, according to a predefined algorithm

Inclusion Criteria:

• Body Mass Index (BMI)>40 kg m-2.
• Surgery with tracheal intubation scheduled

Exclusion Criteria:

• age < 18 years
• severe psychological disorders that have the possibility of limiting the patient's comprehension of information
• previously impossible mask ventilation or intubation with GVL
• presence of pharyngo-laryngeal or neck tumours

Our patients population is the population of morbidly obese patients scheduled for bariatric surgery or other non-bariatric abdominal surgical interventions and referring to the University Division of Anaesthesia and Intensive Care at Spedali Civili of Brescia.