Comparison of Glottic Views and Intubation Times in the Supine and 25 Degree Back-up Positions

The sniffing position has traditionally been considered the optimal head position for direct laryngoscopy and is the usual patient position preferred by most anaesthetists. In theory, neck flexion aligns the pharyngeal and laryngeal axes, and head extension at the atlanto-occipital joint aligns the oral axis with these two axes allowing the line of sight to fall on the glottis. It is recognized as the starting head position for direct laryngoscopy because it provides the best chance of adequate exposure.

However the sniffing position does not guarantee adequate exposure in all patients because many other anatomical factors control the final degree of visualization.

To achieve a proper sniffing position in obese patients, the "ramped" (or the back-up) position has been used as this produces better neck flexion and head extension in these patients when compared to the horizontal supine position. Also the forces required to elevate and move the tongue and other tissues out of the line of sight are less when the patients are ramped.

Our hypothesis is that the view of the glottis may be improved by putting all (ie not only obese) patients requiring intubation in the ramped or back up position while maintaining the classic sniffing position.

Inclusion criteria

• Adult surgical patients who required intubation as part of their routine anaesthesia

Exclusion criteria

• Patients less than 18 years old,
• Patients recognised to have difficult airways where an alternative method of intubation (e.g. fibre optic) was the method of choice,
• Patients undergoing emergency surgery where patient positioning and data collection might cause delay (e.g. exsanguinating patients) or where the supine position is not optimal (e.g. brisk bleeding into the upper airway),
• Patients requiring rapid sequence induction of anaesthesia