Alterations in endotracheal tube position during general anaesthesia

The effect of head and neck movement and Trendelenburg tilt on endotracheal tube position, relative to the carina, was studied in fifty adult patients requiring intubation for elective surgery. On average, inward movement, that is shortening of the distance between the endotracheal tube tip and the carina, resulted from neck flexion (mean = -5.5 mm), whereas outward movement occurred with neck extension (mean = 6.3 mm). Neck rotation, to right and left, and Trendelenburg tilt did not show any trend towards inward nor outward movement (mean = 0.3 mm/1.7 mm/-0.6 mm, respectively). Whilst these mean positional changes for flexion and extension confirm the findings of earlier investigations, our range of maximum inward and outward displacement for flexion (23 mm in/19 mm out), extension (21 mm in/33 mm out), rotation to right (19 mm in/17 mm out), to left (22 mm in/19 mm out) and Trendelenburg tilt (22 mm in/16 mm out) indicate that for any given postural change in any one patient, the direction and magnitude of endotracheal tube displacement is not readily predictable.