Awake fibrecapnic intubation

Abstract

We read with interest the report of awake fibrecapnic intubation by Huitink, Buitelaar and Schutte [1]. Whilst new techniques which enable us to deal with the difficult airway are always welcome, we feel that one of the assumptions that this technique relies upon is not always valid. The method, as described, involves passing a catheter through the working channel of the fibrescope and then through the laryngeal inlet whilst monitoring through the catheter for carbon dioxide by standard capnography. The fibrescope is then ‘rail-roaded’ over the catheter and the tracheal tube over the fibrescope. Whilst this was usually done under direct vision, in cases with poor visibility (suggested as five of 14 cases), this was done ‘blind’, relying on the presence of a capnogram to guide the operator. Additionally, it was not always possible to confirm the location of the fibrescope by visualisation of either tracheal rings or the carina, prior to introducing the tracheal tube. The authors assume that four consecutive capnograph traces will reliably predict that the catheter lies within the trachea. Whereas this may be true if it were passed under direct vision, this is not necessarily true if passed blindly, as in the spontaneously breathing patient a capnograph trace will be readily recordable throughout the oropharynx. The possibility exists, therefore, that the catheter may be in the oropharynx, perhaps obscured from vision by tumour mass, yet still able to detect carbon dioxide. The presence of a trace in these circumstances is not, in itself, confirmation of final placement. Furthermore, in the presence of a friable tumour, blind probing of the airway or ‘rail-roading’ of the fibrescope over a misplaced catheter may risk producing trauma and bleeding. The authors suggest that the catheter could be used for jet ventilation in patients with severe upper airway obstruction. Although jet ventilation is possible via a catheter, these are usually specifically provided for this purpose, and of a much shorter length. Using the suction catheter described in this study for jet ventilation may be difficult or unwise. Additionally, jet ventilation in patients with severe upper airway obstruction should be performed with extreme caution; there is a risk of barotrauma unless a sufficient outflow tract exists or has been provided to allow gas to escape between insufflations.