Bougie-guided Tracheal Tube Placement Through the Air-Q® Intubating Laryngeal Airway: Clinical Evaluation

After ethical committee approval and written informed consent, 140 patients of either sex, > 18 years old, ASA physical status I and II scheduled to receive general anesthesia with tracheal intubation for an elective surgical procedure will be enrolled in the study. They will be randomly allocated to one of two groups according to a computer generated list of 70 patients each. Blind endotracheal intubation will be performed through the air-Q with bougie assisted (Group B) or without assistance (Group Q). Patients ASA physical status >III, mouth opening <2 cm, increased risk of aspiration, those with poor lung compliance, with lesions of the oropharynx or epiglottis and known or anticipated difficult tracheal intubation or facemask ventilation will be excluded from the study.

In the operating room, the following monitors will be attached to the patients: five leads ECG, noninvasive blood pressure, pulse oximetry, ETCO2, anesthetic gas analyzer and neuromuscular monitoring (Infinity Kappa, Dräger, Lübeck, Germany). After adequate oxygenation, general anesthesia will be induced with 2 mg kg-1 propofol, 1-2 µg kg-1 fentanyl and 0.6 mg kg-1 rocuronium. Mask-ventilation with a mixture of oxygen and sevoflurane for an end-tidal concentration of 2% will be followed. The air-Q/ILA will be inserted once ulnar nerve train-of-four stimulation produced no visually detectable response while the patient's head in a neutral position. All airway manipulations (device insertion and tracheal intubation) will be performed by a senior anesthesiology staff member. The size of the air-Q will be selected on the basis of the patient's weight, in accordance with the corresponding manufacturer's recommendations. If ventilation with the device is unsatisfactory, the "Klein maneuver" corrects downfolding of the epiglottis by using a jaw thrust and an up-down maneuver of the ILA. During tracheal intubation through the air-Q/ILA, the tracheal tube is advanced to a depth of 12 to 15 cm so that the tip of the tube is close to the air-Q/ILA opening. Intubation through these supraglottic devices will be facilitated using a water-based lubricant. Then removal of the ILA immediately after tracheal intubation can be assisted by a stylet produced by the manufacturer. Tracheal intubation will be successful if ventilation through the tracheal tube produced an adequate chest expansion and a capnographic curve is obtained.

In group B, the operator gently inserts the bougie through the air-Q/ILA while looking at any bulges in the neck to judge the approximate positioning of the bougie. As soon as the bougie enters the trachea, a characteristic click is felt by the assistant and the operator feels the bougie entering in a hallow space. Another sign for intra tracheal bougie insertion when the bougie reaches the small bronchus between 30 and 40 cm marks (distal hold up sign). The air-Q/ILA is then removed and a tracheal tube is railroaded over the bougie.

Conventional single-use polyvinyl chloride (PVC) tracheal tubes (Mallinckrodt Company, Juarez, Chihuahua, Mexico) will be used for blind tracheal intubation in both groups: size 7.0 mm ID tracheal tubes for patients weighing ≥50 kg and 6.0 mm ID tubes for patients <50 kg. In both study groups, 3 attempts at device insertion and intubation will be allowed. Intubation will be only attempted if appropriate ventilation is obtained. Lung ventilation through the supraglottic device is permitted between intubation attempts. If tracheal intubation through the device is unsuccessful, it is performed by direct laryngoscopy.

The following parameters will be measured: