VivaSight-SL Versus Videolaryngoscopy in Expected Difficult Airway

Endotracheal intubation is required for different surgical procedures for mechanical ventilation and to prevent aspiration of secretions. Endotracheal intubation is usually performed by direct laryngoscopy (DL), but this technique may fail in patients with a difficult airway, i.e. during otorhinolaryngologic or oral and maxillofacial surgery. Besides fiberoptic intubation that is regarded as gold standard, videolaryngoscopy (VL) has evolved as a valuable alternative technique in patients with a difficult airway. However, VL has its limitations and may also fail due to insufficient visualization of the larynx. An endotracheal tube with an integrated camera (VST, VivaSight-SL, Ambu A/S, Ballerup, Denmark) may allow for direct guidance of the tube and may aid in endotracheal intubation in difficult airway patients. This tube has been evaluated in intensive care patients and in patients with morbid adiposity compared to DL, but there is a paucity of data in difficult airway patients, so far.

Therefore, we aim to test the VST in difficult airway patients compared to VL in a prospective randomized non-inferiority trial.

Patients will be assessed for eligibility in the Anesthesiology Pre-assessment Clinic of the University Medical Center Hamburg-Eppendorf prior to elective surgery.

All patients receive a structured preoperative airway assessment in accordance with standard operating procedure of the Department of Anesthesiology, University Medical Center Hamburg-Eppendorf using the implemented in-house algorithm for the prediction of difficult airway management and the Simplified Airway Risk Index (SARI).

Patients randomized to the intervention group will be intubated with a VST. Depending on gender and patient's size, tubes with inner diameters of 7.0, 7.5, and 8.0 are available. The tubes camera is connected to an Ambu aView monitor (Ambu A/S, Ballerup, Denmark). Patients randomized to the control group are intubated with a C-MAC videolaryngoscope (Karl Storz SE \& Co. KG, Tuttlingen, Germany) with a Macintosh type blade size 3 or 4 blade.

Anesthesia management, the choice of the blade and tube size, as well as the use of adjuncts like stylets, introducers or forceps or airway optimization maneuvers (e.g. backward upward rightward pressure [BURP] and optimum external laryngeal manipulation [OELM]) will be left to the discretion of the attending physician.

All intubations are recorded through the monitors for later review (e.g. Cormack-Lehane and POGO-score).

Based on an expected endtidal fraction of oxygen after intubation of 80% with a standard deviation of 8%, and a noninferiority margin of 10%, 2x 24 patients are required with errors of α=0.025 and β=0.2 (PASS version 08.0.6, NCSS, LLC. Kaysville, UT, USA).

All participating physicians are anesthesiology residents or fellows. To avoid a bias that may occur due to different skills for VL compared to the VST, physicians participating in this study take part in a structured manikin airway training. The age and months of work experience of the participating anesthetists will be assessed within a questionnaire. It has been shown that novice physicians are able to reliably intubate a manikin with the VST after a 30 min training session of DL and VST. For VL, it has been shown that novice physicians may intubate manikins set up to a difficult airway scenario after a brief introduction and five intubations with the VL and that anesthesiology residents may quickly adopt the use of the C-MAC VL.

Therefore, participating physicians are trained for 30 min under the supervision of an independent anesthetist before participating in this study.