Guided tracheal intubation over a flexible introducer in situ (railroading) is commonly used to manage difficult tracheal intubation, exchange of endotracheal tube, staged extubation, and retrograde (trans-laryngeal) intubation.

The difficulties with railroading, misplacement of the tube, device-related trauma, failed intubation, and the incidence of life-threatening hypoxia during the procedure, still lead to morbidities and mortalities^1-5.

The difficulties as the frictional resistance between the tube and the flexible introducer, failure to control the trajectory of the advancing tube and the iatrogenic airway trauma; all arise from the physical characters [rigidity, elasticity] of the devices used and their dynamic deformation (change in shape) during the railroading process^6.7.

On the other hand, issues as 'hold up' of the tube at the peri-glottic area and the difficulty with the safe delivery of oxygen into the lungs during the procedure is difficult asthe flexible introducer occupies the main lumen of the tube.

An airway trauma from impingement occurs when it has to give in to the advancing ends of the stiffer devices. Abrupt stretching of the narrower section of the airway by unyielding, semi-rigid devices also produce trauma⁸.