Endotracheal intubation (ETI) is one of the safest means of securing the airway and a fundamental step for this vital procedure is successful laryngoscopy. Proper positioning of the head and neck is essential for optimal laryngeal visualization during laryngoscopy and improper positioning may result in inability to visualize the larynx optimally which may lead to unacceptably long time or even failed intubation.

Sniffing position in a patient is traditionally described as achieving neck flexion by head elevation and head extension at atlanto-occipital joint. This position is recommended as a standard head and neck position for optimal glottis exposure for direct laryngoscopy (DL) as it is said to help in the alignment of pharyngeal, laryngeal and oral axes to facilitate directing the line-of-vision towards laryngeal inlet.^1,2 Of late, concerns have been raised about the anatomical alignment of the three axes alignment theory (TAAT) and even for sniffing position also for DL resulting in this concept as becoming a matter of controversy.³

Video-laryngoscopes have been one of the latest additions to the resources of Anaesthesiologists which have been found to be more useful than DL for glottic visualization and tracheal intubation in normal and difficult clinical situations related to management of airway.⁴ Impressed by the utility of this device, some authors have even recommended videolaryngoscopy (VL) as the first choice for even routine ETIs ahead of DL.⁵ However, role of VL as a rescue method especially when DL proves difficult or fails goes unabated during induction of anaesthesia in every day practice. In these scenarios, most anaesthesiologists are habitual of keeping the head and neck position same as that used with DL without any change, to proceed with VL and many times result in ‘wasted and failed attempts’ for intubation.⁶ This may be because no optimal position of head and neck has been recommended till date for achieving best outcomes with VL.

Though plenty of literature is available related to various head and neck positions and head elevations by different pillow heights and also by inflatable devices like pressure infusion bags during DL, but they offer dissimilar recommendations^7,8 without any universal consistency. More importantly, there are no studies which recommend any specific head and neck positions for achieving most favourable glottic views and best intubating conditions during videolaryngoscopy.

During the last decade, another secondary parameter of horizontal alignment of external auditory meatus (EAM) and supra-sternal notch (SN) line came into light which is not directly related to the airway anatomy but has been suggested as a good end-point while making the positions for DL in both obese as well as non-obese patients. This parameter has been found to demonstrate a closer alignment of pharyngeal, laryngeal and oral axes to provide a better line of vision for DL.⁵ However, there are no studies to provide any information on the relationship of EAM-SN line in terms of the angle with horizontal axis during various head elevations during video laryngoscopy and nor are there any recommendations on this issue.

The difference in the geometric design of the Macintosh laryngoscope in comparison to video-laryngoscopes in terms of angle of the blade and the required line-of-sight due to location of the camera just a few millimetres prior to the vocal cords in the video-laryngoscopes providing image of the glottis on an external monitor, TAAT theory also gets unconvincing during VL.⁹

Inflatable head pillows which can offer sequential increase in head elevation by inflation of a gas can be a good option to have continuous and uninterrupted views of glottis with serial elevations of head and neck during laryngoscopy.

Extensive search of literature revealed that there are no studies using DL as well as VL, which have used the method of sequential raising of pillow height by using inflatable pillows to achieve best glottic views and intubating conditions at any particular pillow height.

In view of the above and the undeniable need to improve upon the methods for best glottic views to decrease the incidence of difficult or failed intubations with VL, the present pilot study was designed in Indian non-obese adult patients to evaluate and compare the usefulness of the head-flat and minimum head elevation position that would provide the best glottic views in terms of Percentage of Glottic Opening (POGO) score. The respective positions would be achieved one after another, sequentially with the help of a simple, self-customised inflatable head pillow which would be able to provide variable head elevations between 0 cm to 10 cm. Ease of insertion of the blade of video-laryngoscope, need of optimization manoeuvres for facilitating ease of intubation, intubation difficulty score (IDS), time to successful intubation, number of Intubation attempts, incidence of failure to intubate and angles of ‘EAM-SN line vs. horizontal’ in the head-flat and minimum pillow height position identified for best POGO score will also be assessed and if possible, the most optimal position of patient’s head and neck for best outcomes would be recommended.

Lacunae in the existing knowledge

Extensive search of literature reveals that the usefulness of sniffing position for the videolaryngoscopy is not established, importance of the TAAT is doubtful, reports mentioning optimal head elevation and angle of flexion of neck are not available for getting the optimal glottic views and intubating conditions and relevant relationship of EAM-SN line angle with horizontal axis for VL in different head and neck positions is not available, hence the present study.