Optimal Head and Neck Position for Intubation During Videolaryngoscopy: Comparison Between "Sniffing" and Neutral Position Using Channelled and Non-channelled Videolaryngoscopes

The optimum patient head and neck position for direct laryngoscopy (when the anaesthetist views the larynx with a curved metallic blade before passing a tube for ventilation of the lungs) is traditionally considered to be the "sniffing the morning air" (neck flexion and head extension) position. This has been questioned previously as there is no randomized controlled study to date to explore this statement. The patient should be optimally positioned prior to induction of anaesthesia, especially because in the event of an unexpected difficult intubation, the Difficult Airway Society guidelines suggest the use of an alternative laryngoscope. In current clinical practice a videolaryngoscope (a curved blade with a camera attached to it that allows the anaesthetist to see around corners) has been used as an alternative laryngoscope. To the best of our knowledge, the ideal patient position for videolaryngoscopy has not yet been described. The intubation time and rate of success at intubation using a C-Mac D-Blade videolaryngoscope was previously assessed by Serocki et al, but only in the sniffing position. It is possible that adopting a different position when using the C-Mac D- Blade might result in a superior view of the larynx. Furthermore, the optimal patient position has not yet been assessed for intubation with the King Vision videolaryngoscope.

This key information could gain precious seconds in a difficult airway scenario (when securing the airway with a tube for ventilation proves difficult) and has obvious implications for patient management. The answer to this question could also help the anaesthetists take informed decisions when using videolaryngoscopy to intubate the trachea in elective settings. The investigators aim to assess the effect of two different positions on the laryngeal view obtained during videolaryngoscopy with two commercially available and well established videolaryngoscopes to try and answer this question.