Laryngeal Impingement

Impingement of the endotracheal tube at the larynx when rail-roading over a fibreoptic scope is related to the relative sizes of tube and scope, as well as the shape of the tip of the tube. Posterior approach to larynx: Notice in this view (click here) from an observational scope that the intubating scope follows the posterior pharyngeal wall, flexes anteriorly to reach up to the laryngeal inlet and then is redirected posteriorly into the trachea. Sites of impingement: Given that the scope rests against the inter-arytenoid cleft or against the arytenoids and that the tip of a conventional tube lies to the right-hand side of the scope (when advanced in its normal orientation), the tube tip is likely to impinge on structures to the right and posterior of the glottis. Posterior impingment with conventional PVC tube: The longitudinal line (white on this tube) lies dorsally, at 6 o’clock. The tube tip initially impinges (partial posterior)the arytenoids, before being withdrawn to disempact, rotated 90 degrees anticlockwise and advanced without resistance. Lateral impingement: Here the tube tip overhangs the right ary-epiglottic fold.(click here)After the tube is disempacted and rotated appropriately, the tube tip passes posterior to the right arytenoid (complete posterior impingement)! This is the precursor to oesophageal intubation, which will pull the scope out of the trachea. There is a risk of damage to the laryngeal tissues as well as to the scope. Ease of passage of tube with ‘medialised’ tip: (click here) This tube (Intavent Fastrach) has a Tuohy-shaped soft tip which passes into the larynx with minimal resistance in any orientation. The incidence of difficulty at first pass (unrotated) is less with this type of tube than with conventional tip tubes. (see Anaesthesia, awaiting publication), though there is yet no study comparing pre-rotated tubes. Dr S.H.Scott, John Radcliffe Hospital, Oxford.